Mercurial > hg > truffle
annotate src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp @ 19083:09292c24d555
LSStackSlotAllocator: hide inner class.
author | Josef Eisl <josef.eisl@jku.at> |
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date | Sat, 31 Jan 2015 11:07:15 +0100 |
parents | 52b4284cb496 |
children | 7848fc12602b |
rev | line source |
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0 | 1 /* |
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2 * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved. |
0 | 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
4 * | |
5 * This code is free software; you can redistribute it and/or modify it | |
6 * under the terms of the GNU General Public License version 2 only, as | |
7 * published by the Free Software Foundation. | |
8 * | |
9 * This code is distributed in the hope that it will be useful, but WITHOUT | |
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
12 * version 2 for more details (a copy is included in the LICENSE file that | |
13 * accompanied this code). | |
14 * | |
15 * You should have received a copy of the GNU General Public License version | |
16 * 2 along with this work; if not, write to the Free Software Foundation, | |
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | |
18 * | |
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
0 | 22 * |
23 */ | |
24 | |
1972 | 25 #include "precompiled.hpp" |
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26 #include "classfile/classLoaderData.hpp" |
1972 | 27 #include "classfile/symbolTable.hpp" |
28 #include "classfile/systemDictionary.hpp" | |
29 #include "code/codeCache.hpp" | |
30 #include "gc_implementation/concurrentMarkSweep/cmsAdaptiveSizePolicy.hpp" | |
31 #include "gc_implementation/concurrentMarkSweep/cmsCollectorPolicy.hpp" | |
32 #include "gc_implementation/concurrentMarkSweep/cmsGCAdaptivePolicyCounters.hpp" | |
33 #include "gc_implementation/concurrentMarkSweep/cmsOopClosures.inline.hpp" | |
34 #include "gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.hpp" | |
35 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.inline.hpp" | |
36 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp" | |
37 #include "gc_implementation/concurrentMarkSweep/vmCMSOperations.hpp" | |
38 #include "gc_implementation/parNew/parNewGeneration.hpp" | |
39 #include "gc_implementation/shared/collectorCounters.hpp" | |
10405 | 40 #include "gc_implementation/shared/gcTimer.hpp" |
41 #include "gc_implementation/shared/gcTrace.hpp" | |
42 #include "gc_implementation/shared/gcTraceTime.hpp" | |
1972 | 43 #include "gc_implementation/shared/isGCActiveMark.hpp" |
44 #include "gc_interface/collectedHeap.inline.hpp" | |
10405 | 45 #include "memory/allocation.hpp" |
1972 | 46 #include "memory/cardTableRS.hpp" |
47 #include "memory/collectorPolicy.hpp" | |
48 #include "memory/gcLocker.inline.hpp" | |
49 #include "memory/genCollectedHeap.hpp" | |
50 #include "memory/genMarkSweep.hpp" | |
51 #include "memory/genOopClosures.inline.hpp" | |
52 #include "memory/iterator.hpp" | |
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53 #include "memory/padded.hpp" |
1972 | 54 #include "memory/referencePolicy.hpp" |
55 #include "memory/resourceArea.hpp" | |
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56 #include "memory/tenuredGeneration.hpp" |
1972 | 57 #include "oops/oop.inline.hpp" |
58 #include "prims/jvmtiExport.hpp" | |
59 #include "runtime/globals_extension.hpp" | |
60 #include "runtime/handles.inline.hpp" | |
61 #include "runtime/java.hpp" | |
62 #include "runtime/vmThread.hpp" | |
63 #include "services/memoryService.hpp" | |
64 #include "services/runtimeService.hpp" | |
0 | 65 |
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66 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC |
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67 |
0 | 68 // statics |
69 CMSCollector* ConcurrentMarkSweepGeneration::_collector = NULL; | |
10405 | 70 bool CMSCollector::_full_gc_requested = false; |
71 GCCause::Cause CMSCollector::_full_gc_cause = GCCause::_no_gc; | |
0 | 72 |
73 ////////////////////////////////////////////////////////////////// | |
74 // In support of CMS/VM thread synchronization | |
75 ////////////////////////////////////////////////////////////////// | |
76 // We split use of the CGC_lock into 2 "levels". | |
77 // The low-level locking is of the usual CGC_lock monitor. We introduce | |
78 // a higher level "token" (hereafter "CMS token") built on top of the | |
79 // low level monitor (hereafter "CGC lock"). | |
80 // The token-passing protocol gives priority to the VM thread. The | |
81 // CMS-lock doesn't provide any fairness guarantees, but clients | |
82 // should ensure that it is only held for very short, bounded | |
83 // durations. | |
84 // | |
85 // When either of the CMS thread or the VM thread is involved in | |
86 // collection operations during which it does not want the other | |
87 // thread to interfere, it obtains the CMS token. | |
88 // | |
89 // If either thread tries to get the token while the other has | |
90 // it, that thread waits. However, if the VM thread and CMS thread | |
91 // both want the token, then the VM thread gets priority while the | |
92 // CMS thread waits. This ensures, for instance, that the "concurrent" | |
93 // phases of the CMS thread's work do not block out the VM thread | |
94 // for long periods of time as the CMS thread continues to hog | |
95 // the token. (See bug 4616232). | |
96 // | |
97 // The baton-passing functions are, however, controlled by the | |
98 // flags _foregroundGCShouldWait and _foregroundGCIsActive, | |
99 // and here the low-level CMS lock, not the high level token, | |
100 // ensures mutual exclusion. | |
101 // | |
102 // Two important conditions that we have to satisfy: | |
103 // 1. if a thread does a low-level wait on the CMS lock, then it | |
104 // relinquishes the CMS token if it were holding that token | |
105 // when it acquired the low-level CMS lock. | |
106 // 2. any low-level notifications on the low-level lock | |
107 // should only be sent when a thread has relinquished the token. | |
108 // | |
109 // In the absence of either property, we'd have potential deadlock. | |
110 // | |
111 // We protect each of the CMS (concurrent and sequential) phases | |
112 // with the CMS _token_, not the CMS _lock_. | |
113 // | |
114 // The only code protected by CMS lock is the token acquisition code | |
115 // itself, see ConcurrentMarkSweepThread::[de]synchronize(), and the | |
116 // baton-passing code. | |
117 // | |
118 // Unfortunately, i couldn't come up with a good abstraction to factor and | |
119 // hide the naked CGC_lock manipulation in the baton-passing code | |
120 // further below. That's something we should try to do. Also, the proof | |
121 // of correctness of this 2-level locking scheme is far from obvious, | |
122 // and potentially quite slippery. We have an uneasy supsicion, for instance, | |
123 // that there may be a theoretical possibility of delay/starvation in the | |
124 // low-level lock/wait/notify scheme used for the baton-passing because of | |
125 // potential intereference with the priority scheme embodied in the | |
126 // CMS-token-passing protocol. See related comments at a CGC_lock->wait() | |
127 // invocation further below and marked with "XXX 20011219YSR". | |
128 // Indeed, as we note elsewhere, this may become yet more slippery | |
129 // in the presence of multiple CMS and/or multiple VM threads. XXX | |
130 | |
131 class CMSTokenSync: public StackObj { | |
132 private: | |
133 bool _is_cms_thread; | |
134 public: | |
135 CMSTokenSync(bool is_cms_thread): | |
136 _is_cms_thread(is_cms_thread) { | |
137 assert(is_cms_thread == Thread::current()->is_ConcurrentGC_thread(), | |
138 "Incorrect argument to constructor"); | |
139 ConcurrentMarkSweepThread::synchronize(_is_cms_thread); | |
140 } | |
141 | |
142 ~CMSTokenSync() { | |
143 assert(_is_cms_thread ? | |
144 ConcurrentMarkSweepThread::cms_thread_has_cms_token() : | |
145 ConcurrentMarkSweepThread::vm_thread_has_cms_token(), | |
146 "Incorrect state"); | |
147 ConcurrentMarkSweepThread::desynchronize(_is_cms_thread); | |
148 } | |
149 }; | |
150 | |
151 // Convenience class that does a CMSTokenSync, and then acquires | |
152 // upto three locks. | |
153 class CMSTokenSyncWithLocks: public CMSTokenSync { | |
154 private: | |
155 // Note: locks are acquired in textual declaration order | |
156 // and released in the opposite order | |
157 MutexLockerEx _locker1, _locker2, _locker3; | |
158 public: | |
159 CMSTokenSyncWithLocks(bool is_cms_thread, Mutex* mutex1, | |
160 Mutex* mutex2 = NULL, Mutex* mutex3 = NULL): | |
161 CMSTokenSync(is_cms_thread), | |
162 _locker1(mutex1, Mutex::_no_safepoint_check_flag), | |
163 _locker2(mutex2, Mutex::_no_safepoint_check_flag), | |
164 _locker3(mutex3, Mutex::_no_safepoint_check_flag) | |
165 { } | |
166 }; | |
167 | |
168 | |
169 // Wrapper class to temporarily disable icms during a foreground cms collection. | |
170 class ICMSDisabler: public StackObj { | |
171 public: | |
172 // The ctor disables icms and wakes up the thread so it notices the change; | |
173 // the dtor re-enables icms. Note that the CMSCollector methods will check | |
174 // CMSIncrementalMode. | |
175 ICMSDisabler() { CMSCollector::disable_icms(); CMSCollector::start_icms(); } | |
176 ~ICMSDisabler() { CMSCollector::enable_icms(); } | |
177 }; | |
178 | |
179 ////////////////////////////////////////////////////////////////// | |
180 // Concurrent Mark-Sweep Generation ///////////////////////////// | |
181 ////////////////////////////////////////////////////////////////// | |
182 | |
183 NOT_PRODUCT(CompactibleFreeListSpace* debug_cms_space;) | |
184 | |
185 // This struct contains per-thread things necessary to support parallel | |
186 // young-gen collection. | |
6197 | 187 class CMSParGCThreadState: public CHeapObj<mtGC> { |
0 | 188 public: |
189 CFLS_LAB lab; | |
190 PromotionInfo promo; | |
191 | |
192 // Constructor. | |
193 CMSParGCThreadState(CompactibleFreeListSpace* cfls) : lab(cfls) { | |
194 promo.setSpace(cfls); | |
195 } | |
196 }; | |
197 | |
198 ConcurrentMarkSweepGeneration::ConcurrentMarkSweepGeneration( | |
199 ReservedSpace rs, size_t initial_byte_size, int level, | |
200 CardTableRS* ct, bool use_adaptive_freelists, | |
6026 | 201 FreeBlockDictionary<FreeChunk>::DictionaryChoice dictionaryChoice) : |
0 | 202 CardGeneration(rs, initial_byte_size, level, ct), |
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203 _dilatation_factor(((double)MinChunkSize)/((double)(CollectedHeap::min_fill_size()))), |
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204 _debug_collection_type(Concurrent_collection_type), |
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205 _did_compact(false) |
0 | 206 { |
207 HeapWord* bottom = (HeapWord*) _virtual_space.low(); | |
208 HeapWord* end = (HeapWord*) _virtual_space.high(); | |
209 | |
210 _direct_allocated_words = 0; | |
211 NOT_PRODUCT( | |
212 _numObjectsPromoted = 0; | |
213 _numWordsPromoted = 0; | |
214 _numObjectsAllocated = 0; | |
215 _numWordsAllocated = 0; | |
216 ) | |
217 | |
218 _cmsSpace = new CompactibleFreeListSpace(_bts, MemRegion(bottom, end), | |
219 use_adaptive_freelists, | |
220 dictionaryChoice); | |
221 NOT_PRODUCT(debug_cms_space = _cmsSpace;) | |
222 if (_cmsSpace == NULL) { | |
223 vm_exit_during_initialization( | |
224 "CompactibleFreeListSpace allocation failure"); | |
225 } | |
226 _cmsSpace->_gen = this; | |
227 | |
228 _gc_stats = new CMSGCStats(); | |
229 | |
230 // Verify the assumption that FreeChunk::_prev and OopDesc::_klass | |
231 // offsets match. The ability to tell free chunks from objects | |
232 // depends on this property. | |
233 debug_only( | |
234 FreeChunk* junk = NULL; | |
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235 assert(UseCompressedClassPointers || |
187 | 236 junk->prev_addr() == (void*)(oop(junk)->klass_addr()), |
0 | 237 "Offset of FreeChunk::_prev within FreeChunk must match" |
238 " that of OopDesc::_klass within OopDesc"); | |
239 ) | |
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240 if (CollectedHeap::use_parallel_gc_threads()) { |
0 | 241 typedef CMSParGCThreadState* CMSParGCThreadStatePtr; |
242 _par_gc_thread_states = | |
6197 | 243 NEW_C_HEAP_ARRAY(CMSParGCThreadStatePtr, ParallelGCThreads, mtGC); |
0 | 244 if (_par_gc_thread_states == NULL) { |
245 vm_exit_during_initialization("Could not allocate par gc structs"); | |
246 } | |
247 for (uint i = 0; i < ParallelGCThreads; i++) { | |
248 _par_gc_thread_states[i] = new CMSParGCThreadState(cmsSpace()); | |
249 if (_par_gc_thread_states[i] == NULL) { | |
250 vm_exit_during_initialization("Could not allocate par gc structs"); | |
251 } | |
252 } | |
253 } else { | |
254 _par_gc_thread_states = NULL; | |
255 } | |
256 _incremental_collection_failed = false; | |
257 // The "dilatation_factor" is the expansion that can occur on | |
258 // account of the fact that the minimum object size in the CMS | |
259 // generation may be larger than that in, say, a contiguous young | |
260 // generation. | |
261 // Ideally, in the calculation below, we'd compute the dilatation | |
262 // factor as: MinChunkSize/(promoting_gen's min object size) | |
263 // Since we do not have such a general query interface for the | |
264 // promoting generation, we'll instead just use the mimimum | |
265 // object size (which today is a header's worth of space); | |
266 // note that all arithmetic is in units of HeapWords. | |
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267 assert(MinChunkSize >= CollectedHeap::min_fill_size(), "just checking"); |
0 | 268 assert(_dilatation_factor >= 1.0, "from previous assert"); |
269 } | |
270 | |
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271 |
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272 // The field "_initiating_occupancy" represents the occupancy percentage |
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273 // at which we trigger a new collection cycle. Unless explicitly specified |
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274 // via CMSInitiatingOccupancyFraction (argument "io" below), it |
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275 // is calculated by: |
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276 // |
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277 // Let "f" be MinHeapFreeRatio in |
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278 // |
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279 // _intiating_occupancy = 100-f + |
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280 // f * (CMSTriggerRatio/100) |
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281 // where CMSTriggerRatio is the argument "tr" below. |
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282 // |
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283 // That is, if we assume the heap is at its desired maximum occupancy at the |
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284 // end of a collection, we let CMSTriggerRatio of the (purported) free |
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285 // space be allocated before initiating a new collection cycle. |
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286 // |
8035 | 287 void ConcurrentMarkSweepGeneration::init_initiating_occupancy(intx io, uintx tr) { |
288 assert(io <= 100 && tr <= 100, "Check the arguments"); | |
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289 if (io >= 0) { |
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290 _initiating_occupancy = (double)io / 100.0; |
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291 } else { |
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292 _initiating_occupancy = ((100 - MinHeapFreeRatio) + |
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293 (double)(tr * MinHeapFreeRatio) / 100.0) |
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294 / 100.0; |
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295 } |
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296 } |
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297 |
0 | 298 void ConcurrentMarkSweepGeneration::ref_processor_init() { |
299 assert(collector() != NULL, "no collector"); | |
300 collector()->ref_processor_init(); | |
301 } | |
302 | |
303 void CMSCollector::ref_processor_init() { | |
304 if (_ref_processor == NULL) { | |
305 // Allocate and initialize a reference processor | |
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306 _ref_processor = |
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307 new ReferenceProcessor(_span, // span |
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308 (ParallelGCThreads > 1) && ParallelRefProcEnabled, // mt processing |
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309 (int) ParallelGCThreads, // mt processing degree |
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310 _cmsGen->refs_discovery_is_mt(), // mt discovery |
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311 (int) MAX2(ConcGCThreads, ParallelGCThreads), // mt discovery degree |
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312 _cmsGen->refs_discovery_is_atomic(), // discovery is not atomic |
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313 &_is_alive_closure); // closure for liveness info |
0 | 314 // Initialize the _ref_processor field of CMSGen |
315 _cmsGen->set_ref_processor(_ref_processor); | |
316 | |
317 } | |
318 } | |
319 | |
320 CMSAdaptiveSizePolicy* CMSCollector::size_policy() { | |
321 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
322 assert(gch->kind() == CollectedHeap::GenCollectedHeap, | |
323 "Wrong type of heap"); | |
324 CMSAdaptiveSizePolicy* sp = (CMSAdaptiveSizePolicy*) | |
325 gch->gen_policy()->size_policy(); | |
326 assert(sp->is_gc_cms_adaptive_size_policy(), | |
327 "Wrong type of size policy"); | |
328 return sp; | |
329 } | |
330 | |
331 CMSGCAdaptivePolicyCounters* CMSCollector::gc_adaptive_policy_counters() { | |
332 CMSGCAdaptivePolicyCounters* results = | |
333 (CMSGCAdaptivePolicyCounters*) collector_policy()->counters(); | |
334 assert( | |
335 results->kind() == GCPolicyCounters::CMSGCAdaptivePolicyCountersKind, | |
336 "Wrong gc policy counter kind"); | |
337 return results; | |
338 } | |
339 | |
340 | |
341 void ConcurrentMarkSweepGeneration::initialize_performance_counters() { | |
342 | |
343 const char* gen_name = "old"; | |
344 | |
345 // Generation Counters - generation 1, 1 subspace | |
346 _gen_counters = new GenerationCounters(gen_name, 1, 1, &_virtual_space); | |
347 | |
348 _space_counters = new GSpaceCounters(gen_name, 0, | |
349 _virtual_space.reserved_size(), | |
350 this, _gen_counters); | |
351 } | |
352 | |
353 CMSStats::CMSStats(ConcurrentMarkSweepGeneration* cms_gen, unsigned int alpha): | |
354 _cms_gen(cms_gen) | |
355 { | |
356 assert(alpha <= 100, "bad value"); | |
357 _saved_alpha = alpha; | |
358 | |
359 // Initialize the alphas to the bootstrap value of 100. | |
360 _gc0_alpha = _cms_alpha = 100; | |
361 | |
362 _cms_begin_time.update(); | |
363 _cms_end_time.update(); | |
364 | |
365 _gc0_duration = 0.0; | |
366 _gc0_period = 0.0; | |
367 _gc0_promoted = 0; | |
368 | |
369 _cms_duration = 0.0; | |
370 _cms_period = 0.0; | |
371 _cms_allocated = 0; | |
372 | |
373 _cms_used_at_gc0_begin = 0; | |
374 _cms_used_at_gc0_end = 0; | |
375 _allow_duty_cycle_reduction = false; | |
376 _valid_bits = 0; | |
377 _icms_duty_cycle = CMSIncrementalDutyCycle; | |
378 } | |
379 | |
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380 double CMSStats::cms_free_adjustment_factor(size_t free) const { |
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381 // TBD: CR 6909490 |
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382 return 1.0; |
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383 } |
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384 |
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385 void CMSStats::adjust_cms_free_adjustment_factor(bool fail, size_t free) { |
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386 } |
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387 |
0 | 388 // If promotion failure handling is on use |
389 // the padded average size of the promotion for each | |
390 // young generation collection. | |
391 double CMSStats::time_until_cms_gen_full() const { | |
392 size_t cms_free = _cms_gen->cmsSpace()->free(); | |
393 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
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394 size_t expected_promotion = MIN2(gch->get_gen(0)->capacity(), |
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395 (size_t) _cms_gen->gc_stats()->avg_promoted()->padded_average()); |
0 | 396 if (cms_free > expected_promotion) { |
397 // Start a cms collection if there isn't enough space to promote | |
398 // for the next minor collection. Use the padded average as | |
399 // a safety factor. | |
400 cms_free -= expected_promotion; | |
401 | |
402 // Adjust by the safety factor. | |
403 double cms_free_dbl = (double)cms_free; | |
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404 double cms_adjustment = (100.0 - CMSIncrementalSafetyFactor)/100.0; |
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405 // Apply a further correction factor which tries to adjust |
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406 // for recent occurance of concurrent mode failures. |
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407 cms_adjustment = cms_adjustment * cms_free_adjustment_factor(cms_free); |
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408 cms_free_dbl = cms_free_dbl * cms_adjustment; |
0 | 409 |
410 if (PrintGCDetails && Verbose) { | |
411 gclog_or_tty->print_cr("CMSStats::time_until_cms_gen_full: cms_free " | |
412 SIZE_FORMAT " expected_promotion " SIZE_FORMAT, | |
413 cms_free, expected_promotion); | |
414 gclog_or_tty->print_cr(" cms_free_dbl %f cms_consumption_rate %f", | |
415 cms_free_dbl, cms_consumption_rate() + 1.0); | |
416 } | |
417 // Add 1 in case the consumption rate goes to zero. | |
418 return cms_free_dbl / (cms_consumption_rate() + 1.0); | |
419 } | |
420 return 0.0; | |
421 } | |
422 | |
423 // Compare the duration of the cms collection to the | |
424 // time remaining before the cms generation is empty. | |
425 // Note that the time from the start of the cms collection | |
426 // to the start of the cms sweep (less than the total | |
427 // duration of the cms collection) can be used. This | |
428 // has been tried and some applications experienced | |
429 // promotion failures early in execution. This was | |
430 // possibly because the averages were not accurate | |
431 // enough at the beginning. | |
432 double CMSStats::time_until_cms_start() const { | |
433 // We add "gc0_period" to the "work" calculation | |
434 // below because this query is done (mostly) at the | |
435 // end of a scavenge, so we need to conservatively | |
436 // account for that much possible delay | |
437 // in the query so as to avoid concurrent mode failures | |
438 // due to starting the collection just a wee bit too | |
439 // late. | |
440 double work = cms_duration() + gc0_period(); | |
441 double deadline = time_until_cms_gen_full(); | |
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442 // If a concurrent mode failure occurred recently, we want to be |
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443 // more conservative and halve our expected time_until_cms_gen_full() |
0 | 444 if (work > deadline) { |
445 if (Verbose && PrintGCDetails) { | |
446 gclog_or_tty->print( | |
447 " CMSCollector: collect because of anticipated promotion " | |
448 "before full %3.7f + %3.7f > %3.7f ", cms_duration(), | |
449 gc0_period(), time_until_cms_gen_full()); | |
450 } | |
451 return 0.0; | |
452 } | |
453 return work - deadline; | |
454 } | |
455 | |
456 // Return a duty cycle based on old_duty_cycle and new_duty_cycle, limiting the | |
457 // amount of change to prevent wild oscillation. | |
458 unsigned int CMSStats::icms_damped_duty_cycle(unsigned int old_duty_cycle, | |
459 unsigned int new_duty_cycle) { | |
460 assert(old_duty_cycle <= 100, "bad input value"); | |
461 assert(new_duty_cycle <= 100, "bad input value"); | |
462 | |
463 // Note: use subtraction with caution since it may underflow (values are | |
464 // unsigned). Addition is safe since we're in the range 0-100. | |
465 unsigned int damped_duty_cycle = new_duty_cycle; | |
466 if (new_duty_cycle < old_duty_cycle) { | |
467 const unsigned int largest_delta = MAX2(old_duty_cycle / 4, 5U); | |
468 if (new_duty_cycle + largest_delta < old_duty_cycle) { | |
469 damped_duty_cycle = old_duty_cycle - largest_delta; | |
470 } | |
471 } else if (new_duty_cycle > old_duty_cycle) { | |
472 const unsigned int largest_delta = MAX2(old_duty_cycle / 4, 15U); | |
473 if (new_duty_cycle > old_duty_cycle + largest_delta) { | |
474 damped_duty_cycle = MIN2(old_duty_cycle + largest_delta, 100U); | |
475 } | |
476 } | |
477 assert(damped_duty_cycle <= 100, "invalid duty cycle computed"); | |
478 | |
479 if (CMSTraceIncrementalPacing) { | |
480 gclog_or_tty->print(" [icms_damped_duty_cycle(%d,%d) = %d] ", | |
481 old_duty_cycle, new_duty_cycle, damped_duty_cycle); | |
482 } | |
483 return damped_duty_cycle; | |
484 } | |
485 | |
486 unsigned int CMSStats::icms_update_duty_cycle_impl() { | |
487 assert(CMSIncrementalPacing && valid(), | |
488 "should be handled in icms_update_duty_cycle()"); | |
489 | |
490 double cms_time_so_far = cms_timer().seconds(); | |
491 double scaled_duration = cms_duration_per_mb() * _cms_used_at_gc0_end / M; | |
492 double scaled_duration_remaining = fabsd(scaled_duration - cms_time_so_far); | |
493 | |
494 // Avoid division by 0. | |
495 double time_until_full = MAX2(time_until_cms_gen_full(), 0.01); | |
496 double duty_cycle_dbl = 100.0 * scaled_duration_remaining / time_until_full; | |
497 | |
498 unsigned int new_duty_cycle = MIN2((unsigned int)duty_cycle_dbl, 100U); | |
499 if (new_duty_cycle > _icms_duty_cycle) { | |
500 // Avoid very small duty cycles (1 or 2); 0 is allowed. | |
501 if (new_duty_cycle > 2) { | |
502 _icms_duty_cycle = icms_damped_duty_cycle(_icms_duty_cycle, | |
503 new_duty_cycle); | |
504 } | |
505 } else if (_allow_duty_cycle_reduction) { | |
506 // The duty cycle is reduced only once per cms cycle (see record_cms_end()). | |
507 new_duty_cycle = icms_damped_duty_cycle(_icms_duty_cycle, new_duty_cycle); | |
508 // Respect the minimum duty cycle. | |
509 unsigned int min_duty_cycle = (unsigned int)CMSIncrementalDutyCycleMin; | |
510 _icms_duty_cycle = MAX2(new_duty_cycle, min_duty_cycle); | |
511 } | |
512 | |
513 if (PrintGCDetails || CMSTraceIncrementalPacing) { | |
514 gclog_or_tty->print(" icms_dc=%d ", _icms_duty_cycle); | |
515 } | |
516 | |
517 _allow_duty_cycle_reduction = false; | |
518 return _icms_duty_cycle; | |
519 } | |
520 | |
521 #ifndef PRODUCT | |
522 void CMSStats::print_on(outputStream *st) const { | |
523 st->print(" gc0_alpha=%d,cms_alpha=%d", _gc0_alpha, _cms_alpha); | |
524 st->print(",gc0_dur=%g,gc0_per=%g,gc0_promo=" SIZE_FORMAT, | |
525 gc0_duration(), gc0_period(), gc0_promoted()); | |
526 st->print(",cms_dur=%g,cms_dur_per_mb=%g,cms_per=%g,cms_alloc=" SIZE_FORMAT, | |
527 cms_duration(), cms_duration_per_mb(), | |
528 cms_period(), cms_allocated()); | |
529 st->print(",cms_since_beg=%g,cms_since_end=%g", | |
530 cms_time_since_begin(), cms_time_since_end()); | |
531 st->print(",cms_used_beg=" SIZE_FORMAT ",cms_used_end=" SIZE_FORMAT, | |
532 _cms_used_at_gc0_begin, _cms_used_at_gc0_end); | |
533 if (CMSIncrementalMode) { | |
534 st->print(",dc=%d", icms_duty_cycle()); | |
535 } | |
536 | |
537 if (valid()) { | |
538 st->print(",promo_rate=%g,cms_alloc_rate=%g", | |
539 promotion_rate(), cms_allocation_rate()); | |
540 st->print(",cms_consumption_rate=%g,time_until_full=%g", | |
541 cms_consumption_rate(), time_until_cms_gen_full()); | |
542 } | |
543 st->print(" "); | |
544 } | |
545 #endif // #ifndef PRODUCT | |
546 | |
547 CMSCollector::CollectorState CMSCollector::_collectorState = | |
548 CMSCollector::Idling; | |
549 bool CMSCollector::_foregroundGCIsActive = false; | |
550 bool CMSCollector::_foregroundGCShouldWait = false; | |
551 | |
552 CMSCollector::CMSCollector(ConcurrentMarkSweepGeneration* cmsGen, | |
553 CardTableRS* ct, | |
554 ConcurrentMarkSweepPolicy* cp): | |
555 _cmsGen(cmsGen), | |
556 _ct(ct), | |
557 _ref_processor(NULL), // will be set later | |
558 _conc_workers(NULL), // may be set later | |
559 _abort_preclean(false), | |
560 _start_sampling(false), | |
561 _between_prologue_and_epilogue(false), | |
562 _markBitMap(0, Mutex::leaf + 1, "CMS_markBitMap_lock"), | |
563 _modUnionTable((CardTableModRefBS::card_shift - LogHeapWordSize), | |
564 -1 /* lock-free */, "No_lock" /* dummy */), | |
565 _modUnionClosure(&_modUnionTable), | |
566 _modUnionClosurePar(&_modUnionTable), | |
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567 // Adjust my span to cover old (cms) gen |
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568 _span(cmsGen->reserved()), |
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569 // Construct the is_alive_closure with _span & markBitMap |
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570 _is_alive_closure(_span, &_markBitMap), |
0 | 571 _restart_addr(NULL), |
572 _overflow_list(NULL), | |
573 _stats(cmsGen), | |
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574 _eden_chunk_lock(new Mutex(Mutex::leaf + 1, "CMS_eden_chunk_lock", true)), |
0 | 575 _eden_chunk_array(NULL), // may be set in ctor body |
576 _eden_chunk_capacity(0), // -- ditto -- | |
577 _eden_chunk_index(0), // -- ditto -- | |
578 _survivor_plab_array(NULL), // -- ditto -- | |
579 _survivor_chunk_array(NULL), // -- ditto -- | |
580 _survivor_chunk_capacity(0), // -- ditto -- | |
581 _survivor_chunk_index(0), // -- ditto -- | |
582 _ser_pmc_preclean_ovflw(0), | |
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583 _ser_kac_preclean_ovflw(0), |
0 | 584 _ser_pmc_remark_ovflw(0), |
585 _par_pmc_remark_ovflw(0), | |
586 _ser_kac_ovflw(0), | |
587 _par_kac_ovflw(0), | |
588 #ifndef PRODUCT | |
589 _num_par_pushes(0), | |
590 #endif | |
591 _collection_count_start(0), | |
592 _verifying(false), | |
593 _icms_start_limit(NULL), | |
594 _icms_stop_limit(NULL), | |
595 _verification_mark_bm(0, Mutex::leaf + 1, "CMS_verification_mark_bm_lock"), | |
596 _completed_initialization(false), | |
597 _collector_policy(cp), | |
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598 _should_unload_classes(CMSClassUnloadingEnabled), |
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599 _concurrent_cycles_since_last_unload(0), |
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600 _roots_scanning_options(SharedHeap::SO_None), |
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601 _inter_sweep_estimate(CMS_SweepWeight, CMS_SweepPadding), |
10405 | 602 _intra_sweep_estimate(CMS_SweepWeight, CMS_SweepPadding), |
603 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) CMSTracer()), | |
604 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()), | |
605 _cms_start_registered(false) | |
0 | 606 { |
607 if (ExplicitGCInvokesConcurrentAndUnloadsClasses) { | |
608 ExplicitGCInvokesConcurrent = true; | |
609 } | |
610 // Now expand the span and allocate the collection support structures | |
611 // (MUT, marking bit map etc.) to cover both generations subject to | |
612 // collection. | |
613 | |
614 // For use by dirty card to oop closures. | |
615 _cmsGen->cmsSpace()->set_collector(this); | |
616 | |
617 // Allocate MUT and marking bit map | |
618 { | |
619 MutexLockerEx x(_markBitMap.lock(), Mutex::_no_safepoint_check_flag); | |
620 if (!_markBitMap.allocate(_span)) { | |
621 warning("Failed to allocate CMS Bit Map"); | |
622 return; | |
623 } | |
624 assert(_markBitMap.covers(_span), "_markBitMap inconsistency?"); | |
625 } | |
626 { | |
627 _modUnionTable.allocate(_span); | |
628 assert(_modUnionTable.covers(_span), "_modUnionTable inconsistency?"); | |
629 } | |
630 | |
1284 | 631 if (!_markStack.allocate(MarkStackSize)) { |
0 | 632 warning("Failed to allocate CMS Marking Stack"); |
633 return; | |
634 } | |
635 | |
636 // Support for multi-threaded concurrent phases | |
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637 if (CMSConcurrentMTEnabled) { |
1284 | 638 if (FLAG_IS_DEFAULT(ConcGCThreads)) { |
0 | 639 // just for now |
1284 | 640 FLAG_SET_DEFAULT(ConcGCThreads, (ParallelGCThreads + 3)/4); |
641 } | |
642 if (ConcGCThreads > 1) { | |
0 | 643 _conc_workers = new YieldingFlexibleWorkGang("Parallel CMS Threads", |
1284 | 644 ConcGCThreads, true); |
0 | 645 if (_conc_workers == NULL) { |
646 warning("GC/CMS: _conc_workers allocation failure: " | |
647 "forcing -CMSConcurrentMTEnabled"); | |
648 CMSConcurrentMTEnabled = false; | |
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649 } else { |
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650 _conc_workers->initialize_workers(); |
0 | 651 } |
652 } else { | |
653 CMSConcurrentMTEnabled = false; | |
654 } | |
655 } | |
656 if (!CMSConcurrentMTEnabled) { | |
1284 | 657 ConcGCThreads = 0; |
0 | 658 } else { |
659 // Turn off CMSCleanOnEnter optimization temporarily for | |
660 // the MT case where it's not fixed yet; see 6178663. | |
661 CMSCleanOnEnter = false; | |
662 } | |
1284 | 663 assert((_conc_workers != NULL) == (ConcGCThreads > 1), |
0 | 664 "Inconsistency"); |
665 | |
666 // Parallel task queues; these are shared for the | |
667 // concurrent and stop-world phases of CMS, but | |
668 // are not shared with parallel scavenge (ParNew). | |
669 { | |
670 uint i; | |
1284 | 671 uint num_queues = (uint) MAX2(ParallelGCThreads, ConcGCThreads); |
0 | 672 |
673 if ((CMSParallelRemarkEnabled || CMSConcurrentMTEnabled | |
674 || ParallelRefProcEnabled) | |
675 && num_queues > 0) { | |
676 _task_queues = new OopTaskQueueSet(num_queues); | |
677 if (_task_queues == NULL) { | |
678 warning("task_queues allocation failure."); | |
679 return; | |
680 } | |
6197 | 681 _hash_seed = NEW_C_HEAP_ARRAY(int, num_queues, mtGC); |
0 | 682 if (_hash_seed == NULL) { |
683 warning("_hash_seed array allocation failure"); | |
684 return; | |
685 } | |
686 | |
1665 | 687 typedef Padded<OopTaskQueue> PaddedOopTaskQueue; |
0 | 688 for (i = 0; i < num_queues; i++) { |
1665 | 689 PaddedOopTaskQueue *q = new PaddedOopTaskQueue(); |
690 if (q == NULL) { | |
0 | 691 warning("work_queue allocation failure."); |
692 return; | |
693 } | |
1665 | 694 _task_queues->register_queue(i, q); |
0 | 695 } |
696 for (i = 0; i < num_queues; i++) { | |
697 _task_queues->queue(i)->initialize(); | |
698 _hash_seed[i] = 17; // copied from ParNew | |
699 } | |
700 } | |
701 } | |
702 | |
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703 _cmsGen ->init_initiating_occupancy(CMSInitiatingOccupancyFraction, CMSTriggerRatio); |
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704 |
0 | 705 // Clip CMSBootstrapOccupancy between 0 and 100. |
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706 _bootstrap_occupancy = ((double)CMSBootstrapOccupancy)/(double)100; |
0 | 707 |
708 _full_gcs_since_conc_gc = 0; | |
709 | |
710 // Now tell CMS generations the identity of their collector | |
711 ConcurrentMarkSweepGeneration::set_collector(this); | |
712 | |
713 // Create & start a CMS thread for this CMS collector | |
714 _cmsThread = ConcurrentMarkSweepThread::start(this); | |
715 assert(cmsThread() != NULL, "CMS Thread should have been created"); | |
716 assert(cmsThread()->collector() == this, | |
717 "CMS Thread should refer to this gen"); | |
718 assert(CGC_lock != NULL, "Where's the CGC_lock?"); | |
719 | |
720 // Support for parallelizing young gen rescan | |
721 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
722 _young_gen = gch->prev_gen(_cmsGen); | |
723 if (gch->supports_inline_contig_alloc()) { | |
724 _top_addr = gch->top_addr(); | |
725 _end_addr = gch->end_addr(); | |
726 assert(_young_gen != NULL, "no _young_gen"); | |
727 _eden_chunk_index = 0; | |
728 _eden_chunk_capacity = (_young_gen->max_capacity()+CMSSamplingGrain)/CMSSamplingGrain; | |
6197 | 729 _eden_chunk_array = NEW_C_HEAP_ARRAY(HeapWord*, _eden_chunk_capacity, mtGC); |
0 | 730 if (_eden_chunk_array == NULL) { |
731 _eden_chunk_capacity = 0; | |
732 warning("GC/CMS: _eden_chunk_array allocation failure"); | |
733 } | |
734 } | |
735 assert(_eden_chunk_array != NULL || _eden_chunk_capacity == 0, "Error"); | |
736 | |
737 // Support for parallelizing survivor space rescan | |
11975 | 738 if ((CMSParallelRemarkEnabled && CMSParallelSurvivorRemarkEnabled) || CMSParallelInitialMarkEnabled) { |
1289
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739 const size_t max_plab_samples = |
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740 ((DefNewGeneration*)_young_gen)->max_survivor_size()/MinTLABSize; |
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741 |
6197 | 742 _survivor_plab_array = NEW_C_HEAP_ARRAY(ChunkArray, ParallelGCThreads, mtGC); |
743 _survivor_chunk_array = NEW_C_HEAP_ARRAY(HeapWord*, 2*max_plab_samples, mtGC); | |
744 _cursor = NEW_C_HEAP_ARRAY(size_t, ParallelGCThreads, mtGC); | |
0 | 745 if (_survivor_plab_array == NULL || _survivor_chunk_array == NULL |
746 || _cursor == NULL) { | |
747 warning("Failed to allocate survivor plab/chunk array"); | |
748 if (_survivor_plab_array != NULL) { | |
6197 | 749 FREE_C_HEAP_ARRAY(ChunkArray, _survivor_plab_array, mtGC); |
0 | 750 _survivor_plab_array = NULL; |
751 } | |
752 if (_survivor_chunk_array != NULL) { | |
6197 | 753 FREE_C_HEAP_ARRAY(HeapWord*, _survivor_chunk_array, mtGC); |
0 | 754 _survivor_chunk_array = NULL; |
755 } | |
756 if (_cursor != NULL) { | |
6197 | 757 FREE_C_HEAP_ARRAY(size_t, _cursor, mtGC); |
0 | 758 _cursor = NULL; |
759 } | |
760 } else { | |
761 _survivor_chunk_capacity = 2*max_plab_samples; | |
762 for (uint i = 0; i < ParallelGCThreads; i++) { | |
6197 | 763 HeapWord** vec = NEW_C_HEAP_ARRAY(HeapWord*, max_plab_samples, mtGC); |
0 | 764 if (vec == NULL) { |
765 warning("Failed to allocate survivor plab array"); | |
766 for (int j = i; j > 0; j--) { | |
6197 | 767 FREE_C_HEAP_ARRAY(HeapWord*, _survivor_plab_array[j-1].array(), mtGC); |
0 | 768 } |
6197 | 769 FREE_C_HEAP_ARRAY(ChunkArray, _survivor_plab_array, mtGC); |
770 FREE_C_HEAP_ARRAY(HeapWord*, _survivor_chunk_array, mtGC); | |
0 | 771 _survivor_plab_array = NULL; |
772 _survivor_chunk_array = NULL; | |
773 _survivor_chunk_capacity = 0; | |
774 break; | |
775 } else { | |
776 ChunkArray* cur = | |
777 ::new (&_survivor_plab_array[i]) ChunkArray(vec, | |
778 max_plab_samples); | |
779 assert(cur->end() == 0, "Should be 0"); | |
780 assert(cur->array() == vec, "Should be vec"); | |
781 assert(cur->capacity() == max_plab_samples, "Error"); | |
782 } | |
783 } | |
784 } | |
785 } | |
786 assert( ( _survivor_plab_array != NULL | |
787 && _survivor_chunk_array != NULL) | |
788 || ( _survivor_chunk_capacity == 0 | |
789 && _survivor_chunk_index == 0), | |
790 "Error"); | |
791 | |
792 NOT_PRODUCT(_overflow_counter = CMSMarkStackOverflowInterval;) | |
793 _gc_counters = new CollectorCounters("CMS", 1); | |
794 _completed_initialization = true; | |
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795 _inter_sweep_timer.start(); // start of time |
0 | 796 } |
797 | |
798 const char* ConcurrentMarkSweepGeneration::name() const { | |
799 return "concurrent mark-sweep generation"; | |
800 } | |
801 void ConcurrentMarkSweepGeneration::update_counters() { | |
802 if (UsePerfData) { | |
803 _space_counters->update_all(); | |
804 _gen_counters->update_all(); | |
805 } | |
806 } | |
807 | |
808 // this is an optimized version of update_counters(). it takes the | |
809 // used value as a parameter rather than computing it. | |
810 // | |
811 void ConcurrentMarkSweepGeneration::update_counters(size_t used) { | |
812 if (UsePerfData) { | |
813 _space_counters->update_used(used); | |
814 _space_counters->update_capacity(); | |
815 _gen_counters->update_all(); | |
816 } | |
817 } | |
818 | |
819 void ConcurrentMarkSweepGeneration::print() const { | |
820 Generation::print(); | |
821 cmsSpace()->print(); | |
822 } | |
823 | |
824 #ifndef PRODUCT | |
825 void ConcurrentMarkSweepGeneration::print_statistics() { | |
826 cmsSpace()->printFLCensus(0); | |
827 } | |
828 #endif | |
829 | |
830 void ConcurrentMarkSweepGeneration::printOccupancy(const char *s) { | |
831 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
832 if (PrintGCDetails) { | |
833 if (Verbose) { | |
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834 gclog_or_tty->print("[%d %s-%s: "SIZE_FORMAT"("SIZE_FORMAT")]", |
0 | 835 level(), short_name(), s, used(), capacity()); |
836 } else { | |
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837 gclog_or_tty->print("[%d %s-%s: "SIZE_FORMAT"K("SIZE_FORMAT"K)]", |
0 | 838 level(), short_name(), s, used() / K, capacity() / K); |
839 } | |
840 } | |
841 if (Verbose) { | |
842 gclog_or_tty->print(" "SIZE_FORMAT"("SIZE_FORMAT")", | |
843 gch->used(), gch->capacity()); | |
844 } else { | |
845 gclog_or_tty->print(" "SIZE_FORMAT"K("SIZE_FORMAT"K)", | |
846 gch->used() / K, gch->capacity() / K); | |
847 } | |
848 } | |
849 | |
850 size_t | |
851 ConcurrentMarkSweepGeneration::contiguous_available() const { | |
852 // dld proposes an improvement in precision here. If the committed | |
853 // part of the space ends in a free block we should add that to | |
854 // uncommitted size in the calculation below. Will make this | |
855 // change later, staying with the approximation below for the | |
856 // time being. -- ysr. | |
857 return MAX2(_virtual_space.uncommitted_size(), unsafe_max_alloc_nogc()); | |
858 } | |
859 | |
860 size_t | |
861 ConcurrentMarkSweepGeneration::unsafe_max_alloc_nogc() const { | |
862 return _cmsSpace->max_alloc_in_words() * HeapWordSize; | |
863 } | |
864 | |
865 size_t ConcurrentMarkSweepGeneration::max_available() const { | |
866 return free() + _virtual_space.uncommitted_size(); | |
867 } | |
868 | |
1888
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869 bool ConcurrentMarkSweepGeneration::promotion_attempt_is_safe(size_t max_promotion_in_bytes) const { |
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870 size_t available = max_available(); |
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871 size_t av_promo = (size_t)gc_stats()->avg_promoted()->padded_average(); |
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872 bool res = (available >= av_promo) || (available >= max_promotion_in_bytes); |
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873 if (Verbose && PrintGCDetails) { |
1888
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874 gclog_or_tty->print_cr( |
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875 "CMS: promo attempt is%s safe: available("SIZE_FORMAT") %s av_promo("SIZE_FORMAT")," |
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876 "max_promo("SIZE_FORMAT")", |
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877 res? "":" not", available, res? ">=":"<", |
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878 av_promo, max_promotion_in_bytes); |
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879 } |
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880 return res; |
0 | 881 } |
882 | |
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883 // At a promotion failure dump information on block layout in heap |
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884 // (cms old generation). |
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885 void ConcurrentMarkSweepGeneration::promotion_failure_occurred() { |
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886 if (CMSDumpAtPromotionFailure) { |
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887 cmsSpace()->dump_at_safepoint_with_locks(collector(), gclog_or_tty); |
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888 } |
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889 } |
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890 |
0 | 891 CompactibleSpace* |
892 ConcurrentMarkSweepGeneration::first_compaction_space() const { | |
893 return _cmsSpace; | |
894 } | |
895 | |
896 void ConcurrentMarkSweepGeneration::reset_after_compaction() { | |
897 // Clear the promotion information. These pointers can be adjusted | |
898 // along with all the other pointers into the heap but | |
899 // compaction is expected to be a rare event with | |
900 // a heap using cms so don't do it without seeing the need. | |
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901 if (CollectedHeap::use_parallel_gc_threads()) { |
0 | 902 for (uint i = 0; i < ParallelGCThreads; i++) { |
903 _par_gc_thread_states[i]->promo.reset(); | |
904 } | |
905 } | |
906 } | |
907 | |
908 void ConcurrentMarkSweepGeneration::space_iterate(SpaceClosure* blk, bool usedOnly) { | |
909 blk->do_space(_cmsSpace); | |
910 } | |
911 | |
912 void ConcurrentMarkSweepGeneration::compute_new_size() { | |
913 assert_locked_or_safepoint(Heap_lock); | |
914 | |
915 // If incremental collection failed, we just want to expand | |
916 // to the limit. | |
917 if (incremental_collection_failed()) { | |
918 clear_incremental_collection_failed(); | |
919 grow_to_reserved(); | |
920 return; | |
921 } | |
922 | |
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923 // The heap has been compacted but not reset yet. |
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924 // Any metric such as free() or used() will be incorrect. |
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925 |
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926 CardGeneration::compute_new_size(); |
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927 |
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928 // Reset again after a possible resizing |
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929 if (did_compact()) { |
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930 cmsSpace()->reset_after_compaction(); |
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931 } |
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932 } |
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933 |
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934 void ConcurrentMarkSweepGeneration::compute_new_size_free_list() { |
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935 assert_locked_or_safepoint(Heap_lock); |
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936 |
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937 // If incremental collection failed, we just want to expand |
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938 // to the limit. |
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939 if (incremental_collection_failed()) { |
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940 clear_incremental_collection_failed(); |
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941 grow_to_reserved(); |
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942 return; |
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943 } |
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944 |
0 | 945 double free_percentage = ((double) free()) / capacity(); |
946 double desired_free_percentage = (double) MinHeapFreeRatio / 100; | |
947 double maximum_free_percentage = (double) MaxHeapFreeRatio / 100; | |
948 | |
949 // compute expansion delta needed for reaching desired free percentage | |
950 if (free_percentage < desired_free_percentage) { | |
951 size_t desired_capacity = (size_t)(used() / ((double) 1 - desired_free_percentage)); | |
952 assert(desired_capacity >= capacity(), "invalid expansion size"); | |
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953 size_t expand_bytes = MAX2(desired_capacity - capacity(), MinHeapDeltaBytes); |
0 | 954 if (PrintGCDetails && Verbose) { |
955 size_t desired_capacity = (size_t)(used() / ((double) 1 - desired_free_percentage)); | |
956 gclog_or_tty->print_cr("\nFrom compute_new_size: "); | |
957 gclog_or_tty->print_cr(" Free fraction %f", free_percentage); | |
958 gclog_or_tty->print_cr(" Desired free fraction %f", | |
959 desired_free_percentage); | |
960 gclog_or_tty->print_cr(" Maximum free fraction %f", | |
961 maximum_free_percentage); | |
962 gclog_or_tty->print_cr(" Capactiy "SIZE_FORMAT, capacity()/1000); | |
963 gclog_or_tty->print_cr(" Desired capacity "SIZE_FORMAT, | |
964 desired_capacity/1000); | |
965 int prev_level = level() - 1; | |
966 if (prev_level >= 0) { | |
967 size_t prev_size = 0; | |
968 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
969 Generation* prev_gen = gch->_gens[prev_level]; | |
970 prev_size = prev_gen->capacity(); | |
971 gclog_or_tty->print_cr(" Younger gen size "SIZE_FORMAT, | |
972 prev_size/1000); | |
973 } | |
974 gclog_or_tty->print_cr(" unsafe_max_alloc_nogc "SIZE_FORMAT, | |
975 unsafe_max_alloc_nogc()/1000); | |
976 gclog_or_tty->print_cr(" contiguous available "SIZE_FORMAT, | |
977 contiguous_available()/1000); | |
978 gclog_or_tty->print_cr(" Expand by "SIZE_FORMAT" (bytes)", | |
979 expand_bytes); | |
980 } | |
981 // safe if expansion fails | |
982 expand(expand_bytes, 0, CMSExpansionCause::_satisfy_free_ratio); | |
983 if (PrintGCDetails && Verbose) { | |
984 gclog_or_tty->print_cr(" Expanded free fraction %f", | |
985 ((double) free()) / capacity()); | |
986 } | |
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987 } else { |
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988 size_t desired_capacity = (size_t)(used() / ((double) 1 - desired_free_percentage)); |
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989 assert(desired_capacity <= capacity(), "invalid expansion size"); |
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990 size_t shrink_bytes = capacity() - desired_capacity; |
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991 // Don't shrink unless the delta is greater than the minimum shrink we want |
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992 if (shrink_bytes >= MinHeapDeltaBytes) { |
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993 shrink_free_list_by(shrink_bytes); |
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994 } |
0 | 995 } |
996 } | |
997 | |
998 Mutex* ConcurrentMarkSweepGeneration::freelistLock() const { | |
999 return cmsSpace()->freelistLock(); | |
1000 } | |
1001 | |
1002 HeapWord* ConcurrentMarkSweepGeneration::allocate(size_t size, | |
1003 bool tlab) { | |
1004 CMSSynchronousYieldRequest yr; | |
1005 MutexLockerEx x(freelistLock(), | |
1006 Mutex::_no_safepoint_check_flag); | |
1007 return have_lock_and_allocate(size, tlab); | |
1008 } | |
1009 | |
1010 HeapWord* ConcurrentMarkSweepGeneration::have_lock_and_allocate(size_t size, | |
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1011 bool tlab /* ignored */) { |
0 | 1012 assert_lock_strong(freelistLock()); |
1013 size_t adjustedSize = CompactibleFreeListSpace::adjustObjectSize(size); | |
1014 HeapWord* res = cmsSpace()->allocate(adjustedSize); | |
1015 // Allocate the object live (grey) if the background collector has | |
1016 // started marking. This is necessary because the marker may | |
1017 // have passed this address and consequently this object will | |
1018 // not otherwise be greyed and would be incorrectly swept up. | |
1019 // Note that if this object contains references, the writing | |
1020 // of those references will dirty the card containing this object | |
1021 // allowing the object to be blackened (and its references scanned) | |
1022 // either during a preclean phase or at the final checkpoint. | |
1023 if (res != NULL) { | |
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1024 // We may block here with an uninitialized object with |
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1025 // its mark-bit or P-bits not yet set. Such objects need |
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1026 // to be safely navigable by block_start(). |
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1027 assert(oop(res)->klass_or_null() == NULL, "Object should be uninitialized here."); |
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1028 assert(!((FreeChunk*)res)->is_free(), "Error, block will look free but show wrong size"); |
0 | 1029 collector()->direct_allocated(res, adjustedSize); |
1030 _direct_allocated_words += adjustedSize; | |
1031 // allocation counters | |
1032 NOT_PRODUCT( | |
1033 _numObjectsAllocated++; | |
1034 _numWordsAllocated += (int)adjustedSize; | |
1035 ) | |
1036 } | |
1037 return res; | |
1038 } | |
1039 | |
1040 // In the case of direct allocation by mutators in a generation that | |
1041 // is being concurrently collected, the object must be allocated | |
1042 // live (grey) if the background collector has started marking. | |
1043 // This is necessary because the marker may | |
1044 // have passed this address and consequently this object will | |
1045 // not otherwise be greyed and would be incorrectly swept up. | |
1046 // Note that if this object contains references, the writing | |
1047 // of those references will dirty the card containing this object | |
1048 // allowing the object to be blackened (and its references scanned) | |
1049 // either during a preclean phase or at the final checkpoint. | |
1050 void CMSCollector::direct_allocated(HeapWord* start, size_t size) { | |
1051 assert(_markBitMap.covers(start, size), "Out of bounds"); | |
1052 if (_collectorState >= Marking) { | |
1053 MutexLockerEx y(_markBitMap.lock(), | |
1054 Mutex::_no_safepoint_check_flag); | |
1055 // [see comments preceding SweepClosure::do_blk() below for details] | |
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1056 // |
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1057 // Can the P-bits be deleted now? JJJ |
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1058 // |
0 | 1059 // 1. need to mark the object as live so it isn't collected |
1060 // 2. need to mark the 2nd bit to indicate the object may be uninitialized | |
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1061 // 3. need to mark the end of the object so marking, precleaning or sweeping |
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1062 // can skip over uninitialized or unparsable objects. An allocated |
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1063 // object is considered uninitialized for our purposes as long as |
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1064 // its klass word is NULL. All old gen objects are parsable |
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1065 // as soon as they are initialized.) |
0 | 1066 _markBitMap.mark(start); // object is live |
1067 _markBitMap.mark(start + 1); // object is potentially uninitialized? | |
1068 _markBitMap.mark(start + size - 1); | |
1069 // mark end of object | |
1070 } | |
1071 // check that oop looks uninitialized | |
187 | 1072 assert(oop(start)->klass_or_null() == NULL, "_klass should be NULL"); |
0 | 1073 } |
1074 | |
1075 void CMSCollector::promoted(bool par, HeapWord* start, | |
1076 bool is_obj_array, size_t obj_size) { | |
1077 assert(_markBitMap.covers(start), "Out of bounds"); | |
1078 // See comment in direct_allocated() about when objects should | |
1079 // be allocated live. | |
1080 if (_collectorState >= Marking) { | |
1081 // we already hold the marking bit map lock, taken in | |
1082 // the prologue | |
1083 if (par) { | |
1084 _markBitMap.par_mark(start); | |
1085 } else { | |
1086 _markBitMap.mark(start); | |
1087 } | |
1088 // We don't need to mark the object as uninitialized (as | |
1089 // in direct_allocated above) because this is being done with the | |
1090 // world stopped and the object will be initialized by the | |
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1091 // time the marking, precleaning or sweeping get to look at it. |
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1092 // But see the code for copying objects into the CMS generation, |
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1093 // where we need to ensure that concurrent readers of the |
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1094 // block offset table are able to safely navigate a block that |
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1095 // is in flux from being free to being allocated (and in |
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1096 // transition while being copied into) and subsequently |
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1097 // becoming a bona-fide object when the copy/promotion is complete. |
0 | 1098 assert(SafepointSynchronize::is_at_safepoint(), |
1099 "expect promotion only at safepoints"); | |
1100 | |
1101 if (_collectorState < Sweeping) { | |
1102 // Mark the appropriate cards in the modUnionTable, so that | |
1103 // this object gets scanned before the sweep. If this is | |
1104 // not done, CMS generation references in the object might | |
1105 // not get marked. | |
1106 // For the case of arrays, which are otherwise precisely | |
1107 // marked, we need to dirty the entire array, not just its head. | |
1108 if (is_obj_array) { | |
1109 // The [par_]mark_range() method expects mr.end() below to | |
1110 // be aligned to the granularity of a bit's representation | |
1111 // in the heap. In the case of the MUT below, that's a | |
1112 // card size. | |
1113 MemRegion mr(start, | |
1114 (HeapWord*)round_to((intptr_t)(start + obj_size), | |
1115 CardTableModRefBS::card_size /* bytes */)); | |
1116 if (par) { | |
1117 _modUnionTable.par_mark_range(mr); | |
1118 } else { | |
1119 _modUnionTable.mark_range(mr); | |
1120 } | |
1121 } else { // not an obj array; we can just mark the head | |
1122 if (par) { | |
1123 _modUnionTable.par_mark(start); | |
1124 } else { | |
1125 _modUnionTable.mark(start); | |
1126 } | |
1127 } | |
1128 } | |
1129 } | |
1130 } | |
1131 | |
1132 static inline size_t percent_of_space(Space* space, HeapWord* addr) | |
1133 { | |
1134 size_t delta = pointer_delta(addr, space->bottom()); | |
1135 return (size_t)(delta * 100.0 / (space->capacity() / HeapWordSize)); | |
1136 } | |
1137 | |
1138 void CMSCollector::icms_update_allocation_limits() | |
1139 { | |
1140 Generation* gen0 = GenCollectedHeap::heap()->get_gen(0); | |
1141 EdenSpace* eden = gen0->as_DefNewGeneration()->eden(); | |
1142 | |
1143 const unsigned int duty_cycle = stats().icms_update_duty_cycle(); | |
1144 if (CMSTraceIncrementalPacing) { | |
1145 stats().print(); | |
1146 } | |
1147 | |
1148 assert(duty_cycle <= 100, "invalid duty cycle"); | |
1149 if (duty_cycle != 0) { | |
1150 // The duty_cycle is a percentage between 0 and 100; convert to words and | |
1151 // then compute the offset from the endpoints of the space. | |
1152 size_t free_words = eden->free() / HeapWordSize; | |
1153 double free_words_dbl = (double)free_words; | |
1154 size_t duty_cycle_words = (size_t)(free_words_dbl * duty_cycle / 100.0); | |
1155 size_t offset_words = (free_words - duty_cycle_words) / 2; | |
1156 | |
1157 _icms_start_limit = eden->top() + offset_words; | |
1158 _icms_stop_limit = eden->end() - offset_words; | |
1159 | |
1160 // The limits may be adjusted (shifted to the right) by | |
1161 // CMSIncrementalOffset, to allow the application more mutator time after a | |
1162 // young gen gc (when all mutators were stopped) and before CMS starts and | |
1163 // takes away one or more cpus. | |
1164 if (CMSIncrementalOffset != 0) { | |
1165 double adjustment_dbl = free_words_dbl * CMSIncrementalOffset / 100.0; | |
1166 size_t adjustment = (size_t)adjustment_dbl; | |
1167 HeapWord* tmp_stop = _icms_stop_limit + adjustment; | |
1168 if (tmp_stop > _icms_stop_limit && tmp_stop < eden->end()) { | |
1169 _icms_start_limit += adjustment; | |
1170 _icms_stop_limit = tmp_stop; | |
1171 } | |
1172 } | |
1173 } | |
1174 if (duty_cycle == 0 || (_icms_start_limit == _icms_stop_limit)) { | |
1175 _icms_start_limit = _icms_stop_limit = eden->end(); | |
1176 } | |
1177 | |
1178 // Install the new start limit. | |
1179 eden->set_soft_end(_icms_start_limit); | |
1180 | |
1181 if (CMSTraceIncrementalMode) { | |
1182 gclog_or_tty->print(" icms alloc limits: " | |
1183 PTR_FORMAT "," PTR_FORMAT | |
1184 " (" SIZE_FORMAT "%%," SIZE_FORMAT "%%) ", | |
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1185 p2i(_icms_start_limit), p2i(_icms_stop_limit), |
0 | 1186 percent_of_space(eden, _icms_start_limit), |
1187 percent_of_space(eden, _icms_stop_limit)); | |
1188 if (Verbose) { | |
1189 gclog_or_tty->print("eden: "); | |
1190 eden->print_on(gclog_or_tty); | |
1191 } | |
1192 } | |
1193 } | |
1194 | |
1195 // Any changes here should try to maintain the invariant | |
1196 // that if this method is called with _icms_start_limit | |
1197 // and _icms_stop_limit both NULL, then it should return NULL | |
1198 // and not notify the icms thread. | |
1199 HeapWord* | |
1200 CMSCollector::allocation_limit_reached(Space* space, HeapWord* top, | |
1201 size_t word_size) | |
1202 { | |
1203 // A start_limit equal to end() means the duty cycle is 0, so treat that as a | |
1204 // nop. | |
1205 if (CMSIncrementalMode && _icms_start_limit != space->end()) { | |
1206 if (top <= _icms_start_limit) { | |
1207 if (CMSTraceIncrementalMode) { | |
1208 space->print_on(gclog_or_tty); | |
1209 gclog_or_tty->stamp(); | |
1210 gclog_or_tty->print_cr(" start limit top=" PTR_FORMAT | |
1211 ", new limit=" PTR_FORMAT | |
1212 " (" SIZE_FORMAT "%%)", | |
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1213 p2i(top), p2i(_icms_stop_limit), |
0 | 1214 percent_of_space(space, _icms_stop_limit)); |
1215 } | |
1216 ConcurrentMarkSweepThread::start_icms(); | |
1217 assert(top < _icms_stop_limit, "Tautology"); | |
1218 if (word_size < pointer_delta(_icms_stop_limit, top)) { | |
1219 return _icms_stop_limit; | |
1220 } | |
1221 | |
1222 // The allocation will cross both the _start and _stop limits, so do the | |
1223 // stop notification also and return end(). | |
1224 if (CMSTraceIncrementalMode) { | |
1225 space->print_on(gclog_or_tty); | |
1226 gclog_or_tty->stamp(); | |
1227 gclog_or_tty->print_cr(" +stop limit top=" PTR_FORMAT | |
1228 ", new limit=" PTR_FORMAT | |
1229 " (" SIZE_FORMAT "%%)", | |
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1230 p2i(top), p2i(space->end()), |
0 | 1231 percent_of_space(space, space->end())); |
1232 } | |
1233 ConcurrentMarkSweepThread::stop_icms(); | |
1234 return space->end(); | |
1235 } | |
1236 | |
1237 if (top <= _icms_stop_limit) { | |
1238 if (CMSTraceIncrementalMode) { | |
1239 space->print_on(gclog_or_tty); | |
1240 gclog_or_tty->stamp(); | |
1241 gclog_or_tty->print_cr(" stop limit top=" PTR_FORMAT | |
1242 ", new limit=" PTR_FORMAT | |
1243 " (" SIZE_FORMAT "%%)", | |
1244 top, space->end(), | |
1245 percent_of_space(space, space->end())); | |
1246 } | |
1247 ConcurrentMarkSweepThread::stop_icms(); | |
1248 return space->end(); | |
1249 } | |
1250 | |
1251 if (CMSTraceIncrementalMode) { | |
1252 space->print_on(gclog_or_tty); | |
1253 gclog_or_tty->stamp(); | |
1254 gclog_or_tty->print_cr(" end limit top=" PTR_FORMAT | |
1255 ", new limit=" PTR_FORMAT, | |
1256 top, NULL); | |
1257 } | |
1258 } | |
1259 | |
1260 return NULL; | |
1261 } | |
1262 | |
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1263 oop ConcurrentMarkSweepGeneration::promote(oop obj, size_t obj_size) { |
0 | 1264 assert(obj_size == (size_t)obj->size(), "bad obj_size passed in"); |
1265 // allocate, copy and if necessary update promoinfo -- | |
1266 // delegate to underlying space. | |
1267 assert_lock_strong(freelistLock()); | |
1268 | |
1269 #ifndef PRODUCT | |
1270 if (Universe::heap()->promotion_should_fail()) { | |
1271 return NULL; | |
1272 } | |
1273 #endif // #ifndef PRODUCT | |
1274 | |
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1275 oop res = _cmsSpace->promote(obj, obj_size); |
0 | 1276 if (res == NULL) { |
1277 // expand and retry | |
1278 size_t s = _cmsSpace->expansionSpaceRequired(obj_size); // HeapWords | |
1279 expand(s*HeapWordSize, MinHeapDeltaBytes, | |
1280 CMSExpansionCause::_satisfy_promotion); | |
1281 // Since there's currently no next generation, we don't try to promote | |
1282 // into a more senior generation. | |
1283 assert(next_gen() == NULL, "assumption, based upon which no attempt " | |
1284 "is made to pass on a possibly failing " | |
1285 "promotion to next generation"); | |
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1286 res = _cmsSpace->promote(obj, obj_size); |
0 | 1287 } |
1288 if (res != NULL) { | |
1289 // See comment in allocate() about when objects should | |
1290 // be allocated live. | |
1291 assert(obj->is_oop(), "Will dereference klass pointer below"); | |
1292 collector()->promoted(false, // Not parallel | |
1293 (HeapWord*)res, obj->is_objArray(), obj_size); | |
1294 // promotion counters | |
1295 NOT_PRODUCT( | |
1296 _numObjectsPromoted++; | |
1297 _numWordsPromoted += | |
1298 (int)(CompactibleFreeListSpace::adjustObjectSize(obj->size())); | |
1299 ) | |
1300 } | |
1301 return res; | |
1302 } | |
1303 | |
1304 | |
1305 HeapWord* | |
1306 ConcurrentMarkSweepGeneration::allocation_limit_reached(Space* space, | |
1307 HeapWord* top, | |
1308 size_t word_sz) | |
1309 { | |
1310 return collector()->allocation_limit_reached(space, top, word_sz); | |
1311 } | |
1312 | |
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1313 // IMPORTANT: Notes on object size recognition in CMS. |
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1314 // --------------------------------------------------- |
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1315 // A block of storage in the CMS generation is always in |
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1316 // one of three states. A free block (FREE), an allocated |
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1317 // object (OBJECT) whose size() method reports the correct size, |
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1318 // and an intermediate state (TRANSIENT) in which its size cannot |
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1319 // be accurately determined. |
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1320 // STATE IDENTIFICATION: (32 bit and 64 bit w/o COOPS) |
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1321 // ----------------------------------------------------- |
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1322 // FREE: klass_word & 1 == 1; mark_word holds block size |
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1323 // |
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1324 // OBJECT: klass_word installed; klass_word != 0 && klass_word & 1 == 0; |
1716
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1325 // obj->size() computes correct size |
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1326 // |
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1327 // TRANSIENT: klass_word == 0; size is indeterminate until we become an OBJECT |
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1328 // |
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1329 // STATE IDENTIFICATION: (64 bit+COOPS) |
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1330 // ------------------------------------ |
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1331 // FREE: mark_word & CMS_FREE_BIT == 1; mark_word & ~CMS_FREE_BIT gives block_size |
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1332 // |
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1333 // OBJECT: klass_word installed; klass_word != 0; |
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1334 // obj->size() computes correct size |
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1335 // |
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1336 // TRANSIENT: klass_word == 0; size is indeterminate until we become an OBJECT |
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1337 // |
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1338 // |
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1339 // STATE TRANSITION DIAGRAM |
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1340 // |
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1341 // mut / parnew mut / parnew |
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1342 // FREE --------------------> TRANSIENT ---------------------> OBJECT --| |
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1343 // ^ | |
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1344 // |------------------------ DEAD <------------------------------------| |
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1345 // sweep mut |
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1346 // |
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1347 // While a block is in TRANSIENT state its size cannot be determined |
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1348 // so readers will either need to come back later or stall until |
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1349 // the size can be determined. Note that for the case of direct |
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1350 // allocation, P-bits, when available, may be used to determine the |
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1351 // size of an object that may not yet have been initialized. |
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1352 |
0 | 1353 // Things to support parallel young-gen collection. |
1354 oop | |
1355 ConcurrentMarkSweepGeneration::par_promote(int thread_num, | |
1356 oop old, markOop m, | |
1357 size_t word_sz) { | |
1358 #ifndef PRODUCT | |
1359 if (Universe::heap()->promotion_should_fail()) { | |
1360 return NULL; | |
1361 } | |
1362 #endif // #ifndef PRODUCT | |
1363 | |
1364 CMSParGCThreadState* ps = _par_gc_thread_states[thread_num]; | |
1365 PromotionInfo* promoInfo = &ps->promo; | |
1366 // if we are tracking promotions, then first ensure space for | |
1367 // promotion (including spooling space for saving header if necessary). | |
1368 // then allocate and copy, then track promoted info if needed. | |
1369 // When tracking (see PromotionInfo::track()), the mark word may | |
1370 // be displaced and in this case restoration of the mark word | |
1371 // occurs in the (oop_since_save_marks_)iterate phase. | |
1372 if (promoInfo->tracking() && !promoInfo->ensure_spooling_space()) { | |
1373 // Out of space for allocating spooling buffers; | |
1374 // try expanding and allocating spooling buffers. | |
1375 if (!expand_and_ensure_spooling_space(promoInfo)) { | |
1376 return NULL; | |
1377 } | |
1378 } | |
1379 assert(promoInfo->has_spooling_space(), "Control point invariant"); | |
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1380 const size_t alloc_sz = CompactibleFreeListSpace::adjustObjectSize(word_sz); |
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1381 HeapWord* obj_ptr = ps->lab.alloc(alloc_sz); |
0 | 1382 if (obj_ptr == NULL) { |
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1383 obj_ptr = expand_and_par_lab_allocate(ps, alloc_sz); |
0 | 1384 if (obj_ptr == NULL) { |
1385 return NULL; | |
1386 } | |
1387 } | |
1388 oop obj = oop(obj_ptr); | |
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1389 OrderAccess::storestore(); |
187 | 1390 assert(obj->klass_or_null() == NULL, "Object should be uninitialized here."); |
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1391 assert(!((FreeChunk*)obj_ptr)->is_free(), "Error, block will look free but show wrong size"); |
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1392 // IMPORTANT: See note on object initialization for CMS above. |
0 | 1393 // Otherwise, copy the object. Here we must be careful to insert the |
1394 // klass pointer last, since this marks the block as an allocated object. | |
187 | 1395 // Except with compressed oops it's the mark word. |
0 | 1396 HeapWord* old_ptr = (HeapWord*)old; |
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1397 // Restore the mark word copied above. |
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1398 obj->set_mark(m); |
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1399 assert(obj->klass_or_null() == NULL, "Object should be uninitialized here."); |
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1400 assert(!((FreeChunk*)obj_ptr)->is_free(), "Error, block will look free but show wrong size"); |
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1401 OrderAccess::storestore(); |
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1402 |
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1403 if (UseCompressedClassPointers) { |
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1404 // Copy gap missed by (aligned) header size calculation below |
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1405 obj->set_klass_gap(old->klass_gap()); |
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1406 } |
0 | 1407 if (word_sz > (size_t)oopDesc::header_size()) { |
1408 Copy::aligned_disjoint_words(old_ptr + oopDesc::header_size(), | |
1409 obj_ptr + oopDesc::header_size(), | |
1410 word_sz - oopDesc::header_size()); | |
1411 } | |
187 | 1412 |
0 | 1413 // Now we can track the promoted object, if necessary. We take care |
1521 | 1414 // to delay the transition from uninitialized to full object |
0 | 1415 // (i.e., insertion of klass pointer) until after, so that it |
1416 // atomically becomes a promoted object. | |
1417 if (promoInfo->tracking()) { | |
1418 promoInfo->track((PromotedObject*)obj, old->klass()); | |
1419 } | |
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1420 assert(obj->klass_or_null() == NULL, "Object should be uninitialized here."); |
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1421 assert(!((FreeChunk*)obj_ptr)->is_free(), "Error, block will look free but show wrong size"); |
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1422 assert(old->is_oop(), "Will use and dereference old klass ptr below"); |
187 | 1423 |
1424 // Finally, install the klass pointer (this should be volatile). | |
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1425 OrderAccess::storestore(); |
0 | 1426 obj->set_klass(old->klass()); |
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1427 // We should now be able to calculate the right size for this object |
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1428 assert(obj->is_oop() && obj->size() == (int)word_sz, "Error, incorrect size computed for promoted object"); |
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1429 |
0 | 1430 collector()->promoted(true, // parallel |
1431 obj_ptr, old->is_objArray(), word_sz); | |
1432 | |
1433 NOT_PRODUCT( | |
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1434 Atomic::inc_ptr(&_numObjectsPromoted); |
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1435 Atomic::add_ptr(alloc_sz, &_numWordsPromoted); |
0 | 1436 ) |
1437 | |
1438 return obj; | |
1439 } | |
1440 | |
1441 void | |
1442 ConcurrentMarkSweepGeneration:: | |
1443 par_promote_alloc_undo(int thread_num, | |
1444 HeapWord* obj, size_t word_sz) { | |
1445 // CMS does not support promotion undo. | |
1446 ShouldNotReachHere(); | |
1447 } | |
1448 | |
1449 void | |
1450 ConcurrentMarkSweepGeneration:: | |
1451 par_promote_alloc_done(int thread_num) { | |
1452 CMSParGCThreadState* ps = _par_gc_thread_states[thread_num]; | |
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1453 ps->lab.retire(thread_num); |
0 | 1454 } |
1455 | |
1456 void | |
1457 ConcurrentMarkSweepGeneration:: | |
1458 par_oop_since_save_marks_iterate_done(int thread_num) { | |
1459 CMSParGCThreadState* ps = _par_gc_thread_states[thread_num]; | |
1460 ParScanWithoutBarrierClosure* dummy_cl = NULL; | |
1461 ps->promo.promoted_oops_iterate_nv(dummy_cl); | |
1462 } | |
1463 | |
1464 bool ConcurrentMarkSweepGeneration::should_collect(bool full, | |
1465 size_t size, | |
1466 bool tlab) | |
1467 { | |
1468 // We allow a STW collection only if a full | |
1469 // collection was requested. | |
1470 return full || should_allocate(size, tlab); // FIX ME !!! | |
1471 // This and promotion failure handling are connected at the | |
1472 // hip and should be fixed by untying them. | |
1473 } | |
1474 | |
1475 bool CMSCollector::shouldConcurrentCollect() { | |
1476 if (_full_gc_requested) { | |
1477 if (Verbose && PrintGCDetails) { | |
1478 gclog_or_tty->print_cr("CMSCollector: collect because of explicit " | |
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1479 " gc request (or gc_locker)"); |
0 | 1480 } |
1481 return true; | |
1482 } | |
1483 | |
1484 // For debugging purposes, change the type of collection. | |
1485 // If the rotation is not on the concurrent collection | |
1486 // type, don't start a concurrent collection. | |
1487 NOT_PRODUCT( | |
1488 if (RotateCMSCollectionTypes && | |
1489 (_cmsGen->debug_collection_type() != | |
1490 ConcurrentMarkSweepGeneration::Concurrent_collection_type)) { | |
1491 assert(_cmsGen->debug_collection_type() != | |
1492 ConcurrentMarkSweepGeneration::Unknown_collection_type, | |
1493 "Bad cms collection type"); | |
1494 return false; | |
1495 } | |
1496 ) | |
1497 | |
1498 FreelistLocker x(this); | |
1499 // ------------------------------------------------------------------ | |
1500 // Print out lots of information which affects the initiation of | |
1501 // a collection. | |
1502 if (PrintCMSInitiationStatistics && stats().valid()) { | |
1503 gclog_or_tty->print("CMSCollector shouldConcurrentCollect: "); | |
1504 gclog_or_tty->stamp(); | |
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1505 gclog_or_tty->cr(); |
0 | 1506 stats().print_on(gclog_or_tty); |
1507 gclog_or_tty->print_cr("time_until_cms_gen_full %3.7f", | |
1508 stats().time_until_cms_gen_full()); | |
1509 gclog_or_tty->print_cr("free="SIZE_FORMAT, _cmsGen->free()); | |
1510 gclog_or_tty->print_cr("contiguous_available="SIZE_FORMAT, | |
1511 _cmsGen->contiguous_available()); | |
1512 gclog_or_tty->print_cr("promotion_rate=%g", stats().promotion_rate()); | |
1513 gclog_or_tty->print_cr("cms_allocation_rate=%g", stats().cms_allocation_rate()); | |
1514 gclog_or_tty->print_cr("occupancy=%3.7f", _cmsGen->occupancy()); | |
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1515 gclog_or_tty->print_cr("initiatingOccupancy=%3.7f", _cmsGen->initiating_occupancy()); |
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1516 gclog_or_tty->print_cr("metadata initialized %d", |
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1517 MetaspaceGC::should_concurrent_collect()); |
0 | 1518 } |
1519 // ------------------------------------------------------------------ | |
1520 | |
1521 // If the estimated time to complete a cms collection (cms_duration()) | |
1522 // is less than the estimated time remaining until the cms generation | |
1523 // is full, start a collection. | |
1524 if (!UseCMSInitiatingOccupancyOnly) { | |
1525 if (stats().valid()) { | |
1526 if (stats().time_until_cms_start() == 0.0) { | |
1527 return true; | |
1528 } | |
1529 } else { | |
1530 // We want to conservatively collect somewhat early in order | |
1531 // to try and "bootstrap" our CMS/promotion statistics; | |
1532 // this branch will not fire after the first successful CMS | |
1533 // collection because the stats should then be valid. | |
1534 if (_cmsGen->occupancy() >= _bootstrap_occupancy) { | |
1535 if (Verbose && PrintGCDetails) { | |
1536 gclog_or_tty->print_cr( | |
1537 " CMSCollector: collect for bootstrapping statistics:" | |
1538 " occupancy = %f, boot occupancy = %f", _cmsGen->occupancy(), | |
1539 _bootstrap_occupancy); | |
1540 } | |
1541 return true; | |
1542 } | |
1543 } | |
1544 } | |
1545 | |
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1546 // Otherwise, we start a collection cycle if |
0 | 1547 // old gen want a collection cycle started. Each may use |
1548 // an appropriate criterion for making this decision. | |
1549 // XXX We need to make sure that the gen expansion | |
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1550 // criterion dovetails well with this. XXX NEED TO FIX THIS |
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1551 if (_cmsGen->should_concurrent_collect()) { |
0 | 1552 if (Verbose && PrintGCDetails) { |
1553 gclog_or_tty->print_cr("CMS old gen initiated"); | |
1554 } | |
1555 return true; | |
1556 } | |
1557 | |
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1558 // We start a collection if we believe an incremental collection may fail; |
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1559 // this is not likely to be productive in practice because it's probably too |
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1560 // late anyway. |
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1561 GenCollectedHeap* gch = GenCollectedHeap::heap(); |
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1562 assert(gch->collector_policy()->is_two_generation_policy(), |
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1563 "You may want to check the correctness of the following"); |
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1564 if (gch->incremental_collection_will_fail(true /* consult_young */)) { |
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1565 if (Verbose && PrintGCDetails) { |
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1566 gclog_or_tty->print("CMSCollector: collect because incremental collection will fail "); |
0 | 1567 } |
1568 return true; | |
1569 } | |
1570 | |
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1571 if (MetaspaceGC::should_concurrent_collect()) { |
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1572 if (Verbose && PrintGCDetails) { |
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1573 gclog_or_tty->print("CMSCollector: collect for metadata allocation "); |
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1574 } |
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1575 return true; |
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1576 } |
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1577 |
0 | 1578 return false; |
1579 } | |
1580 | |
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1581 void CMSCollector::set_did_compact(bool v) { _cmsGen->set_did_compact(v); } |
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1582 |
0 | 1583 // Clear _expansion_cause fields of constituent generations |
1584 void CMSCollector::clear_expansion_cause() { | |
1585 _cmsGen->clear_expansion_cause(); | |
1586 } | |
1587 | |
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1588 // We should be conservative in starting a collection cycle. To |
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1589 // start too eagerly runs the risk of collecting too often in the |
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1590 // extreme. To collect too rarely falls back on full collections, |
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1591 // which works, even if not optimum in terms of concurrent work. |
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1592 // As a work around for too eagerly collecting, use the flag |
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1593 // UseCMSInitiatingOccupancyOnly. This also has the advantage of |
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1594 // giving the user an easily understandable way of controlling the |
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1595 // collections. |
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1596 // We want to start a new collection cycle if any of the following |
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1597 // conditions hold: |
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1598 // . our current occupancy exceeds the configured initiating occupancy |
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1599 // for this generation, or |
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1600 // . we recently needed to expand this space and have not, since that |
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1601 // expansion, done a collection of this generation, or |
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1602 // . the underlying space believes that it may be a good idea to initiate |
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1603 // a concurrent collection (this may be based on criteria such as the |
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1604 // following: the space uses linear allocation and linear allocation is |
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1605 // going to fail, or there is believed to be excessive fragmentation in |
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1606 // the generation, etc... or ... |
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1607 // [.(currently done by CMSCollector::shouldConcurrentCollect() only for |
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1608 // the case of the old generation; see CR 6543076): |
94
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1609 // we may be approaching a point at which allocation requests may fail because |
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1610 // we will be out of sufficient free space given allocation rate estimates.] |
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1611 bool ConcurrentMarkSweepGeneration::should_concurrent_collect() const { |
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1612 |
0 | 1613 assert_lock_strong(freelistLock()); |
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1614 if (occupancy() > initiating_occupancy()) { |
0 | 1615 if (PrintGCDetails && Verbose) { |
1616 gclog_or_tty->print(" %s: collect because of occupancy %f / %f ", | |
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1617 short_name(), occupancy(), initiating_occupancy()); |
0 | 1618 } |
1619 return true; | |
1620 } | |
1621 if (UseCMSInitiatingOccupancyOnly) { | |
1622 return false; | |
1623 } | |
1624 if (expansion_cause() == CMSExpansionCause::_satisfy_allocation) { | |
1625 if (PrintGCDetails && Verbose) { | |
1626 gclog_or_tty->print(" %s: collect because expanded for allocation ", | |
1627 short_name()); | |
1628 } | |
1629 return true; | |
1630 } | |
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1631 if (_cmsSpace->should_concurrent_collect()) { |
0 | 1632 if (PrintGCDetails && Verbose) { |
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1633 gclog_or_tty->print(" %s: collect because cmsSpace says so ", |
0 | 1634 short_name()); |
1635 } | |
1636 return true; | |
1637 } | |
1638 return false; | |
1639 } | |
1640 | |
1641 void ConcurrentMarkSweepGeneration::collect(bool full, | |
1642 bool clear_all_soft_refs, | |
1643 size_t size, | |
1644 bool tlab) | |
1645 { | |
1646 collector()->collect(full, clear_all_soft_refs, size, tlab); | |
1647 } | |
1648 | |
1649 void CMSCollector::collect(bool full, | |
1650 bool clear_all_soft_refs, | |
1651 size_t size, | |
1652 bool tlab) | |
1653 { | |
1654 if (!UseCMSCollectionPassing && _collectorState > Idling) { | |
1655 // For debugging purposes skip the collection if the state | |
1656 // is not currently idle | |
1657 if (TraceCMSState) { | |
1658 gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " skipped full:%d CMS state %d", | |
1659 Thread::current(), full, _collectorState); | |
1660 } | |
1661 return; | |
1662 } | |
1663 | |
1664 // The following "if" branch is present for defensive reasons. | |
1665 // In the current uses of this interface, it can be replaced with: | |
1666 // assert(!GC_locker.is_active(), "Can't be called otherwise"); | |
1667 // But I am not placing that assert here to allow future | |
1668 // generality in invoking this interface. | |
1669 if (GC_locker::is_active()) { | |
1670 // A consistency test for GC_locker | |
1671 assert(GC_locker::needs_gc(), "Should have been set already"); | |
1672 // Skip this foreground collection, instead | |
1673 // expanding the heap if necessary. | |
1674 // Need the free list locks for the call to free() in compute_new_size() | |
1675 compute_new_size(); | |
1676 return; | |
1677 } | |
1678 acquire_control_and_collect(full, clear_all_soft_refs); | |
1679 _full_gcs_since_conc_gc++; | |
1680 } | |
1681 | |
10405 | 1682 void CMSCollector::request_full_gc(unsigned int full_gc_count, GCCause::Cause cause) { |
0 | 1683 GenCollectedHeap* gch = GenCollectedHeap::heap(); |
1684 unsigned int gc_count = gch->total_full_collections(); | |
1685 if (gc_count == full_gc_count) { | |
1686 MutexLockerEx y(CGC_lock, Mutex::_no_safepoint_check_flag); | |
1687 _full_gc_requested = true; | |
10405 | 1688 _full_gc_cause = cause; |
0 | 1689 CGC_lock->notify(); // nudge CMS thread |
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1690 } else { |
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1691 assert(gc_count > full_gc_count, "Error: causal loop"); |
0 | 1692 } |
1693 } | |
1694 | |
10405 | 1695 bool CMSCollector::is_external_interruption() { |
1696 GCCause::Cause cause = GenCollectedHeap::heap()->gc_cause(); | |
1697 return GCCause::is_user_requested_gc(cause) || | |
1698 GCCause::is_serviceability_requested_gc(cause); | |
1699 } | |
1700 | |
1701 void CMSCollector::report_concurrent_mode_interruption() { | |
1702 if (is_external_interruption()) { | |
1703 if (PrintGCDetails) { | |
1704 gclog_or_tty->print(" (concurrent mode interrupted)"); | |
1705 } | |
1706 } else { | |
1707 if (PrintGCDetails) { | |
1708 gclog_or_tty->print(" (concurrent mode failure)"); | |
1709 } | |
1710 _gc_tracer_cm->report_concurrent_mode_failure(); | |
1711 } | |
1712 } | |
1713 | |
0 | 1714 |
1715 // The foreground and background collectors need to coordinate in order | |
1716 // to make sure that they do not mutually interfere with CMS collections. | |
1717 // When a background collection is active, | |
1718 // the foreground collector may need to take over (preempt) and | |
1719 // synchronously complete an ongoing collection. Depending on the | |
1720 // frequency of the background collections and the heap usage | |
1721 // of the application, this preemption can be seldom or frequent. | |
1722 // There are only certain | |
1723 // points in the background collection that the "collection-baton" | |
1724 // can be passed to the foreground collector. | |
1725 // | |
1726 // The foreground collector will wait for the baton before | |
1727 // starting any part of the collection. The foreground collector | |
1728 // will only wait at one location. | |
1729 // | |
1730 // The background collector will yield the baton before starting a new | |
1731 // phase of the collection (e.g., before initial marking, marking from roots, | |
1732 // precleaning, final re-mark, sweep etc.) This is normally done at the head | |
1733 // of the loop which switches the phases. The background collector does some | |
1734 // of the phases (initial mark, final re-mark) with the world stopped. | |
1735 // Because of locking involved in stopping the world, | |
1736 // the foreground collector should not block waiting for the background | |
1737 // collector when it is doing a stop-the-world phase. The background | |
1738 // collector will yield the baton at an additional point just before | |
1739 // it enters a stop-the-world phase. Once the world is stopped, the | |
1740 // background collector checks the phase of the collection. If the | |
1741 // phase has not changed, it proceeds with the collection. If the | |
1742 // phase has changed, it skips that phase of the collection. See | |
1743 // the comments on the use of the Heap_lock in collect_in_background(). | |
1744 // | |
1745 // Variable used in baton passing. | |
1746 // _foregroundGCIsActive - Set to true by the foreground collector when | |
1747 // it wants the baton. The foreground clears it when it has finished | |
1748 // the collection. | |
1749 // _foregroundGCShouldWait - Set to true by the background collector | |
1750 // when it is running. The foreground collector waits while | |
1751 // _foregroundGCShouldWait is true. | |
1752 // CGC_lock - monitor used to protect access to the above variables | |
1753 // and to notify the foreground and background collectors. | |
1754 // _collectorState - current state of the CMS collection. | |
1755 // | |
1756 // The foreground collector | |
1757 // acquires the CGC_lock | |
1758 // sets _foregroundGCIsActive | |
1759 // waits on the CGC_lock for _foregroundGCShouldWait to be false | |
1760 // various locks acquired in preparation for the collection | |
1761 // are released so as not to block the background collector | |
1762 // that is in the midst of a collection | |
1763 // proceeds with the collection | |
1764 // clears _foregroundGCIsActive | |
1765 // returns | |
1766 // | |
1767 // The background collector in a loop iterating on the phases of the | |
1768 // collection | |
1769 // acquires the CGC_lock | |
1770 // sets _foregroundGCShouldWait | |
1771 // if _foregroundGCIsActive is set | |
1772 // clears _foregroundGCShouldWait, notifies _CGC_lock | |
1773 // waits on _CGC_lock for _foregroundGCIsActive to become false | |
1774 // and exits the loop. | |
1775 // otherwise | |
1776 // proceed with that phase of the collection | |
1777 // if the phase is a stop-the-world phase, | |
1778 // yield the baton once more just before enqueueing | |
1779 // the stop-world CMS operation (executed by the VM thread). | |
1780 // returns after all phases of the collection are done | |
1781 // | |
1782 | |
1783 void CMSCollector::acquire_control_and_collect(bool full, | |
1784 bool clear_all_soft_refs) { | |
1785 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint"); | |
1786 assert(!Thread::current()->is_ConcurrentGC_thread(), | |
1787 "shouldn't try to acquire control from self!"); | |
1788 | |
1789 // Start the protocol for acquiring control of the | |
1790 // collection from the background collector (aka CMS thread). | |
1791 assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(), | |
1792 "VM thread should have CMS token"); | |
1793 // Remember the possibly interrupted state of an ongoing | |
1794 // concurrent collection | |
1795 CollectorState first_state = _collectorState; | |
1796 | |
1797 // Signal to a possibly ongoing concurrent collection that | |
1798 // we want to do a foreground collection. | |
1799 _foregroundGCIsActive = true; | |
1800 | |
1801 // Disable incremental mode during a foreground collection. | |
1802 ICMSDisabler icms_disabler; | |
1803 | |
1804 // release locks and wait for a notify from the background collector | |
1805 // releasing the locks in only necessary for phases which | |
1806 // do yields to improve the granularity of the collection. | |
1807 assert_lock_strong(bitMapLock()); | |
1808 // We need to lock the Free list lock for the space that we are | |
1809 // currently collecting. | |
1810 assert(haveFreelistLocks(), "Must be holding free list locks"); | |
1811 bitMapLock()->unlock(); | |
1812 releaseFreelistLocks(); | |
1813 { | |
1814 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
1815 if (_foregroundGCShouldWait) { | |
1816 // We are going to be waiting for action for the CMS thread; | |
1817 // it had better not be gone (for instance at shutdown)! | |
1818 assert(ConcurrentMarkSweepThread::cmst() != NULL, | |
1819 "CMS thread must be running"); | |
1820 // Wait here until the background collector gives us the go-ahead | |
1821 ConcurrentMarkSweepThread::clear_CMS_flag( | |
1822 ConcurrentMarkSweepThread::CMS_vm_has_token); // release token | |
1823 // Get a possibly blocked CMS thread going: | |
1824 // Note that we set _foregroundGCIsActive true above, | |
1825 // without protection of the CGC_lock. | |
1826 CGC_lock->notify(); | |
1827 assert(!ConcurrentMarkSweepThread::vm_thread_wants_cms_token(), | |
1828 "Possible deadlock"); | |
1829 while (_foregroundGCShouldWait) { | |
1830 // wait for notification | |
1831 CGC_lock->wait(Mutex::_no_safepoint_check_flag); | |
1832 // Possibility of delay/starvation here, since CMS token does | |
1833 // not know to give priority to VM thread? Actually, i think | |
1834 // there wouldn't be any delay/starvation, but the proof of | |
1835 // that "fact" (?) appears non-trivial. XXX 20011219YSR | |
1836 } | |
1837 ConcurrentMarkSweepThread::set_CMS_flag( | |
1838 ConcurrentMarkSweepThread::CMS_vm_has_token); | |
1839 } | |
1840 } | |
1841 // The CMS_token is already held. Get back the other locks. | |
1842 assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(), | |
1843 "VM thread should have CMS token"); | |
1844 getFreelistLocks(); | |
1845 bitMapLock()->lock_without_safepoint_check(); | |
1846 if (TraceCMSState) { | |
1847 gclog_or_tty->print_cr("CMS foreground collector has asked for control " | |
1848 INTPTR_FORMAT " with first state %d", Thread::current(), first_state); | |
1849 gclog_or_tty->print_cr(" gets control with state %d", _collectorState); | |
1850 } | |
1851 | |
1852 // Check if we need to do a compaction, or if not, whether | |
1853 // we need to start the mark-sweep from scratch. | |
1854 bool should_compact = false; | |
1855 bool should_start_over = false; | |
1856 decide_foreground_collection_type(clear_all_soft_refs, | |
1857 &should_compact, &should_start_over); | |
1858 | |
1859 NOT_PRODUCT( | |
1860 if (RotateCMSCollectionTypes) { | |
1861 if (_cmsGen->debug_collection_type() == | |
1862 ConcurrentMarkSweepGeneration::MSC_foreground_collection_type) { | |
1863 should_compact = true; | |
1864 } else if (_cmsGen->debug_collection_type() == | |
1865 ConcurrentMarkSweepGeneration::MS_foreground_collection_type) { | |
1866 should_compact = false; | |
1867 } | |
1868 } | |
1869 ) | |
1870 | |
10405 | 1871 if (first_state > Idling) { |
1872 report_concurrent_mode_interruption(); | |
0 | 1873 } |
1874 | |
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1875 set_did_compact(should_compact); |
0 | 1876 if (should_compact) { |
1877 // If the collection is being acquired from the background | |
1878 // collector, there may be references on the discovered | |
1879 // references lists that have NULL referents (being those | |
1880 // that were concurrently cleared by a mutator) or | |
1881 // that are no longer active (having been enqueued concurrently | |
1882 // by the mutator). | |
1883 // Scrub the list of those references because Mark-Sweep-Compact | |
1884 // code assumes referents are not NULL and that all discovered | |
1885 // Reference objects are active. | |
1886 ref_processor()->clean_up_discovered_references(); | |
1887 | |
10405 | 1888 if (first_state > Idling) { |
1889 save_heap_summary(); | |
1890 } | |
1891 | |
0 | 1892 do_compaction_work(clear_all_soft_refs); |
1893 | |
1894 // Has the GC time limit been exceeded? | |
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1895 DefNewGeneration* young_gen = _young_gen->as_DefNewGeneration(); |
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1896 size_t max_eden_size = young_gen->max_capacity() - |
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1897 young_gen->to()->capacity() - |
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1898 young_gen->from()->capacity(); |
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1899 GenCollectedHeap* gch = GenCollectedHeap::heap(); |
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1900 GCCause::Cause gc_cause = gch->gc_cause(); |
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1901 size_policy()->check_gc_overhead_limit(_young_gen->used(), |
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1902 young_gen->eden()->used(), |
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1903 _cmsGen->max_capacity(), |
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1904 max_eden_size, |
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1905 full, |
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1906 gc_cause, |
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1907 gch->collector_policy()); |
0 | 1908 } else { |
1909 do_mark_sweep_work(clear_all_soft_refs, first_state, | |
1910 should_start_over); | |
1911 } | |
1912 // Reset the expansion cause, now that we just completed | |
1913 // a collection cycle. | |
1914 clear_expansion_cause(); | |
1915 _foregroundGCIsActive = false; | |
1916 return; | |
1917 } | |
1918 | |
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1919 // Resize the tenured generation |
0 | 1920 // after obtaining the free list locks for the |
1921 // two generations. | |
1922 void CMSCollector::compute_new_size() { | |
1923 assert_locked_or_safepoint(Heap_lock); | |
1924 FreelistLocker z(this); | |
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1925 MetaspaceGC::compute_new_size(); |
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1926 _cmsGen->compute_new_size_free_list(); |
0 | 1927 } |
1928 | |
1929 // A work method used by foreground collection to determine | |
1930 // what type of collection (compacting or not, continuing or fresh) | |
1931 // it should do. | |
1932 // NOTE: the intent is to make UseCMSCompactAtFullCollection | |
1933 // and CMSCompactWhenClearAllSoftRefs the default in the future | |
1934 // and do away with the flags after a suitable period. | |
1935 void CMSCollector::decide_foreground_collection_type( | |
1936 bool clear_all_soft_refs, bool* should_compact, | |
1937 bool* should_start_over) { | |
1938 // Normally, we'll compact only if the UseCMSCompactAtFullCollection | |
1939 // flag is set, and we have either requested a System.gc() or | |
1940 // the number of full gc's since the last concurrent cycle | |
1941 // has exceeded the threshold set by CMSFullGCsBeforeCompaction, | |
1942 // or if an incremental collection has failed | |
1943 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
1944 assert(gch->collector_policy()->is_two_generation_policy(), | |
1945 "You may want to check the correctness of the following"); | |
1946 // Inform cms gen if this was due to partial collection failing. | |
1947 // The CMS gen may use this fact to determine its expansion policy. | |
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1948 if (gch->incremental_collection_will_fail(false /* don't consult_young */)) { |
0 | 1949 assert(!_cmsGen->incremental_collection_failed(), |
1950 "Should have been noticed, reacted to and cleared"); | |
1951 _cmsGen->set_incremental_collection_failed(); | |
1952 } | |
1953 *should_compact = | |
1954 UseCMSCompactAtFullCollection && | |
1955 ((_full_gcs_since_conc_gc >= CMSFullGCsBeforeCompaction) || | |
1956 GCCause::is_user_requested_gc(gch->gc_cause()) || | |
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1957 gch->incremental_collection_will_fail(true /* consult_young */)); |
0 | 1958 *should_start_over = false; |
1959 if (clear_all_soft_refs && !*should_compact) { | |
1960 // We are about to do a last ditch collection attempt | |
1961 // so it would normally make sense to do a compaction | |
1962 // to reclaim as much space as possible. | |
1963 if (CMSCompactWhenClearAllSoftRefs) { | |
1964 // Default: The rationale is that in this case either | |
1965 // we are past the final marking phase, in which case | |
1966 // we'd have to start over, or so little has been done | |
1967 // that there's little point in saving that work. Compaction | |
1968 // appears to be the sensible choice in either case. | |
1969 *should_compact = true; | |
1970 } else { | |
1971 // We have been asked to clear all soft refs, but not to | |
1972 // compact. Make sure that we aren't past the final checkpoint | |
1973 // phase, for that is where we process soft refs. If we are already | |
1974 // past that phase, we'll need to redo the refs discovery phase and | |
1975 // if necessary clear soft refs that weren't previously | |
1976 // cleared. We do so by remembering the phase in which | |
1977 // we came in, and if we are past the refs processing | |
1978 // phase, we'll choose to just redo the mark-sweep | |
1979 // collection from scratch. | |
1980 if (_collectorState > FinalMarking) { | |
1981 // We are past the refs processing phase; | |
1982 // start over and do a fresh synchronous CMS cycle | |
1983 _collectorState = Resetting; // skip to reset to start new cycle | |
1984 reset(false /* == !asynch */); | |
1985 *should_start_over = true; | |
1986 } // else we can continue a possibly ongoing current cycle | |
1987 } | |
1988 } | |
1989 } | |
1990 | |
1991 // A work method used by the foreground collector to do | |
1992 // a mark-sweep-compact. | |
1993 void CMSCollector::do_compaction_work(bool clear_all_soft_refs) { | |
1994 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
10405 | 1995 |
1996 STWGCTimer* gc_timer = GenMarkSweep::gc_timer(); | |
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1997 gc_timer->register_gc_start(); |
10405 | 1998 |
1999 SerialOldTracer* gc_tracer = GenMarkSweep::gc_tracer(); | |
2000 gc_tracer->report_gc_start(gch->gc_cause(), gc_timer->gc_start()); | |
2001 | |
2002 GCTraceTime t("CMS:MSC ", PrintGCDetails && Verbose, true, NULL); | |
0 | 2003 if (PrintGC && Verbose && !(GCCause::is_user_requested_gc(gch->gc_cause()))) { |
2004 gclog_or_tty->print_cr("Compact ConcurrentMarkSweepGeneration after %d " | |
2005 "collections passed to foreground collector", _full_gcs_since_conc_gc); | |
2006 } | |
2007 | |
2008 // Sample collection interval time and reset for collection pause. | |
2009 if (UseAdaptiveSizePolicy) { | |
2010 size_policy()->msc_collection_begin(); | |
2011 } | |
2012 | |
2013 // Temporarily widen the span of the weak reference processing to | |
2014 // the entire heap. | |
2015 MemRegion new_span(GenCollectedHeap::heap()->reserved_region()); | |
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2016 ReferenceProcessorSpanMutator rp_mut_span(ref_processor(), new_span); |
0 | 2017 // Temporarily, clear the "is_alive_non_header" field of the |
2018 // reference processor. | |
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2019 ReferenceProcessorIsAliveMutator rp_mut_closure(ref_processor(), NULL); |
0 | 2020 // Temporarily make reference _processing_ single threaded (non-MT). |
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2021 ReferenceProcessorMTProcMutator rp_mut_mt_processing(ref_processor(), false); |
0 | 2022 // Temporarily make refs discovery atomic |
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2023 ReferenceProcessorAtomicMutator rp_mut_atomic(ref_processor(), true); |
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2024 // Temporarily make reference _discovery_ single threaded (non-MT) |
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2025 ReferenceProcessorMTDiscoveryMutator rp_mut_discovery(ref_processor(), false); |
0 | 2026 |
2027 ref_processor()->set_enqueuing_is_done(false); | |
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2028 ref_processor()->enable_discovery(false /*verify_disabled*/, false /*check_no_refs*/); |
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2029 ref_processor()->setup_policy(clear_all_soft_refs); |
0 | 2030 // If an asynchronous collection finishes, the _modUnionTable is |
2031 // all clear. If we are assuming the collection from an asynchronous | |
2032 // collection, clear the _modUnionTable. | |
2033 assert(_collectorState != Idling || _modUnionTable.isAllClear(), | |
2034 "_modUnionTable should be clear if the baton was not passed"); | |
2035 _modUnionTable.clear_all(); | |
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2036 assert(_collectorState != Idling || _ct->klass_rem_set()->mod_union_is_clear(), |
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2037 "mod union for klasses should be clear if the baton was passed"); |
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2038 _ct->klass_rem_set()->clear_mod_union(); |
0 | 2039 |
2040 // We must adjust the allocation statistics being maintained | |
2041 // in the free list space. We do so by reading and clearing | |
2042 // the sweep timer and updating the block flux rate estimates below. | |
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2043 assert(!_intra_sweep_timer.is_active(), "_intra_sweep_timer should be inactive"); |
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2044 if (_inter_sweep_timer.is_active()) { |
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2045 _inter_sweep_timer.stop(); |
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2046 // Note that we do not use this sample to update the _inter_sweep_estimate. |
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2047 _cmsGen->cmsSpace()->beginSweepFLCensus((float)(_inter_sweep_timer.seconds()), |
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2048 _inter_sweep_estimate.padded_average(), |
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2049 _intra_sweep_estimate.padded_average()); |
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2050 } |
0 | 2051 |
2052 GenMarkSweep::invoke_at_safepoint(_cmsGen->level(), | |
2053 ref_processor(), clear_all_soft_refs); | |
2054 #ifdef ASSERT | |
2055 CompactibleFreeListSpace* cms_space = _cmsGen->cmsSpace(); | |
2056 size_t free_size = cms_space->free(); | |
2057 assert(free_size == | |
2058 pointer_delta(cms_space->end(), cms_space->compaction_top()) | |
2059 * HeapWordSize, | |
2060 "All the free space should be compacted into one chunk at top"); | |
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2061 assert(cms_space->dictionary()->total_chunk_size( |
0 | 2062 debug_only(cms_space->freelistLock())) == 0 || |
2063 cms_space->totalSizeInIndexedFreeLists() == 0, | |
2064 "All the free space should be in a single chunk"); | |
2065 size_t num = cms_space->totalCount(); | |
2066 assert((free_size == 0 && num == 0) || | |
2067 (free_size > 0 && (num == 1 || num == 2)), | |
2068 "There should be at most 2 free chunks after compaction"); | |
2069 #endif // ASSERT | |
2070 _collectorState = Resetting; | |
2071 assert(_restart_addr == NULL, | |
2072 "Should have been NULL'd before baton was passed"); | |
2073 reset(false /* == !asynch */); | |
2074 _cmsGen->reset_after_compaction(); | |
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2075 _concurrent_cycles_since_last_unload = 0; |
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2076 |
0 | 2077 // Clear any data recorded in the PLAB chunk arrays. |
2078 if (_survivor_plab_array != NULL) { | |
2079 reset_survivor_plab_arrays(); | |
2080 } | |
2081 | |
2082 // Adjust the per-size allocation stats for the next epoch. | |
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2083 _cmsGen->cmsSpace()->endSweepFLCensus(sweep_count() /* fake */); |
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2084 // Restart the "inter sweep timer" for the next epoch. |
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2085 _inter_sweep_timer.reset(); |
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2086 _inter_sweep_timer.start(); |
0 | 2087 |
2088 // Sample collection pause time and reset for collection interval. | |
2089 if (UseAdaptiveSizePolicy) { | |
2090 size_policy()->msc_collection_end(gch->gc_cause()); | |
2091 } | |
2092 | |
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2093 gc_timer->register_gc_end(); |
10405 | 2094 |
2095 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions()); | |
2096 | |
0 | 2097 // For a mark-sweep-compact, compute_new_size() will be called |
2098 // in the heap's do_collection() method. | |
2099 } | |
2100 | |
2101 // A work method used by the foreground collector to do | |
2102 // a mark-sweep, after taking over from a possibly on-going | |
2103 // concurrent mark-sweep collection. | |
2104 void CMSCollector::do_mark_sweep_work(bool clear_all_soft_refs, | |
2105 CollectorState first_state, bool should_start_over) { | |
2106 if (PrintGC && Verbose) { | |
2107 gclog_or_tty->print_cr("Pass concurrent collection to foreground " | |
2108 "collector with count %d", | |
2109 _full_gcs_since_conc_gc); | |
2110 } | |
2111 switch (_collectorState) { | |
2112 case Idling: | |
2113 if (first_state == Idling || should_start_over) { | |
2114 // The background GC was not active, or should | |
2115 // restarted from scratch; start the cycle. | |
2116 _collectorState = InitialMarking; | |
2117 } | |
2118 // If first_state was not Idling, then a background GC | |
2119 // was in progress and has now finished. No need to do it | |
2120 // again. Leave the state as Idling. | |
2121 break; | |
2122 case Precleaning: | |
2123 // In the foreground case don't do the precleaning since | |
2124 // it is not done concurrently and there is extra work | |
2125 // required. | |
2126 _collectorState = FinalMarking; | |
2127 } | |
10405 | 2128 collect_in_foreground(clear_all_soft_refs, GenCollectedHeap::heap()->gc_cause()); |
0 | 2129 |
2130 // For a mark-sweep, compute_new_size() will be called | |
2131 // in the heap's do_collection() method. | |
2132 } | |
2133 | |
2134 | |
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2135 void CMSCollector::print_eden_and_survivor_chunk_arrays() { |
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2136 DefNewGeneration* dng = _young_gen->as_DefNewGeneration(); |
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2137 EdenSpace* eden_space = dng->eden(); |
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2138 ContiguousSpace* from_space = dng->from(); |
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2139 ContiguousSpace* to_space = dng->to(); |
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2140 // Eden |
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2141 if (_eden_chunk_array != NULL) { |
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2142 gclog_or_tty->print_cr("eden " PTR_FORMAT "-" PTR_FORMAT "-" PTR_FORMAT "(" SIZE_FORMAT ")", |
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2143 eden_space->bottom(), eden_space->top(), |
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2144 eden_space->end(), eden_space->capacity()); |
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2145 gclog_or_tty->print_cr("_eden_chunk_index=" SIZE_FORMAT ", " |
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2146 "_eden_chunk_capacity=" SIZE_FORMAT, |
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2147 _eden_chunk_index, _eden_chunk_capacity); |
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2148 for (size_t i = 0; i < _eden_chunk_index; i++) { |
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2149 gclog_or_tty->print_cr("_eden_chunk_array[" SIZE_FORMAT "]=" PTR_FORMAT, |
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2150 i, _eden_chunk_array[i]); |
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2151 } |
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2152 } |
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2153 // Survivor |
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2154 if (_survivor_chunk_array != NULL) { |
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2155 gclog_or_tty->print_cr("survivor " PTR_FORMAT "-" PTR_FORMAT "-" PTR_FORMAT "(" SIZE_FORMAT ")", |
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2156 from_space->bottom(), from_space->top(), |
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2157 from_space->end(), from_space->capacity()); |
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2158 gclog_or_tty->print_cr("_survivor_chunk_index=" SIZE_FORMAT ", " |
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2159 "_survivor_chunk_capacity=" SIZE_FORMAT, |
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2160 _survivor_chunk_index, _survivor_chunk_capacity); |
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2161 for (size_t i = 0; i < _survivor_chunk_index; i++) { |
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2162 gclog_or_tty->print_cr("_survivor_chunk_array[" SIZE_FORMAT "]=" PTR_FORMAT, |
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2163 i, _survivor_chunk_array[i]); |
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2164 } |
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2165 } |
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2166 } |
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2167 |
0 | 2168 void CMSCollector::getFreelistLocks() const { |
2169 // Get locks for all free lists in all generations that this | |
2170 // collector is responsible for | |
2171 _cmsGen->freelistLock()->lock_without_safepoint_check(); | |
2172 } | |
2173 | |
2174 void CMSCollector::releaseFreelistLocks() const { | |
2175 // Release locks for all free lists in all generations that this | |
2176 // collector is responsible for | |
2177 _cmsGen->freelistLock()->unlock(); | |
2178 } | |
2179 | |
2180 bool CMSCollector::haveFreelistLocks() const { | |
2181 // Check locks for all free lists in all generations that this | |
2182 // collector is responsible for | |
2183 assert_lock_strong(_cmsGen->freelistLock()); | |
2184 PRODUCT_ONLY(ShouldNotReachHere()); | |
2185 return true; | |
2186 } | |
2187 | |
2188 // A utility class that is used by the CMS collector to | |
2189 // temporarily "release" the foreground collector from its | |
2190 // usual obligation to wait for the background collector to | |
2191 // complete an ongoing phase before proceeding. | |
2192 class ReleaseForegroundGC: public StackObj { | |
2193 private: | |
2194 CMSCollector* _c; | |
2195 public: | |
2196 ReleaseForegroundGC(CMSCollector* c) : _c(c) { | |
2197 assert(_c->_foregroundGCShouldWait, "Else should not need to call"); | |
2198 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
2199 // allow a potentially blocked foreground collector to proceed | |
2200 _c->_foregroundGCShouldWait = false; | |
2201 if (_c->_foregroundGCIsActive) { | |
2202 CGC_lock->notify(); | |
2203 } | |
2204 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
2205 "Possible deadlock"); | |
2206 } | |
2207 | |
2208 ~ReleaseForegroundGC() { | |
2209 assert(!_c->_foregroundGCShouldWait, "Usage protocol violation?"); | |
2210 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
2211 _c->_foregroundGCShouldWait = true; | |
2212 } | |
2213 }; | |
2214 | |
2215 // There are separate collect_in_background and collect_in_foreground because of | |
2216 // the different locking requirements of the background collector and the | |
2217 // foreground collector. There was originally an attempt to share | |
2218 // one "collect" method between the background collector and the foreground | |
2219 // collector but the if-then-else required made it cleaner to have | |
2220 // separate methods. | |
10405 | 2221 void CMSCollector::collect_in_background(bool clear_all_soft_refs, GCCause::Cause cause) { |
0 | 2222 assert(Thread::current()->is_ConcurrentGC_thread(), |
2223 "A CMS asynchronous collection is only allowed on a CMS thread."); | |
2224 | |
2225 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
2226 { | |
2227 bool safepoint_check = Mutex::_no_safepoint_check_flag; | |
2228 MutexLockerEx hl(Heap_lock, safepoint_check); | |
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2229 FreelistLocker fll(this); |
0 | 2230 MutexLockerEx x(CGC_lock, safepoint_check); |
2231 if (_foregroundGCIsActive || !UseAsyncConcMarkSweepGC) { | |
2232 // The foreground collector is active or we're | |
2233 // not using asynchronous collections. Skip this | |
2234 // background collection. | |
2235 assert(!_foregroundGCShouldWait, "Should be clear"); | |
2236 return; | |
2237 } else { | |
2238 assert(_collectorState == Idling, "Should be idling before start."); | |
2239 _collectorState = InitialMarking; | |
10405 | 2240 register_gc_start(cause); |
0 | 2241 // Reset the expansion cause, now that we are about to begin |
2242 // a new cycle. | |
2243 clear_expansion_cause(); | |
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2244 |
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2245 // Clear the MetaspaceGC flag since a concurrent collection |
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2246 // is starting but also clear it after the collection. |
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2247 MetaspaceGC::set_should_concurrent_collect(false); |
0 | 2248 } |
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2249 // Decide if we want to enable class unloading as part of the |
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2250 // ensuing concurrent GC cycle. |
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2251 update_should_unload_classes(); |
0 | 2252 _full_gc_requested = false; // acks all outstanding full gc requests |
10405 | 2253 _full_gc_cause = GCCause::_no_gc; |
0 | 2254 // Signal that we are about to start a collection |
2255 gch->increment_total_full_collections(); // ... starting a collection cycle | |
2256 _collection_count_start = gch->total_full_collections(); | |
2257 } | |
2258 | |
2259 // Used for PrintGC | |
2260 size_t prev_used; | |
2261 if (PrintGC && Verbose) { | |
2262 prev_used = _cmsGen->used(); // XXXPERM | |
2263 } | |
2264 | |
2265 // The change of the collection state is normally done at this level; | |
2266 // the exceptions are phases that are executed while the world is | |
2267 // stopped. For those phases the change of state is done while the | |
2268 // world is stopped. For baton passing purposes this allows the | |
2269 // background collector to finish the phase and change state atomically. | |
2270 // The foreground collector cannot wait on a phase that is done | |
2271 // while the world is stopped because the foreground collector already | |
2272 // has the world stopped and would deadlock. | |
2273 while (_collectorState != Idling) { | |
2274 if (TraceCMSState) { | |
2275 gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " in CMS state %d", | |
2276 Thread::current(), _collectorState); | |
2277 } | |
2278 // The foreground collector | |
2279 // holds the Heap_lock throughout its collection. | |
2280 // holds the CMS token (but not the lock) | |
2281 // except while it is waiting for the background collector to yield. | |
2282 // | |
2283 // The foreground collector should be blocked (not for long) | |
2284 // if the background collector is about to start a phase | |
2285 // executed with world stopped. If the background | |
2286 // collector has already started such a phase, the | |
2287 // foreground collector is blocked waiting for the | |
2288 // Heap_lock. The stop-world phases (InitialMarking and FinalMarking) | |
2289 // are executed in the VM thread. | |
2290 // | |
2291 // The locking order is | |
2292 // PendingListLock (PLL) -- if applicable (FinalMarking) | |
2293 // Heap_lock (both this & PLL locked in VM_CMS_Operation::prologue()) | |
2294 // CMS token (claimed in | |
2295 // stop_world_and_do() --> | |
2296 // safepoint_synchronize() --> | |
2297 // CMSThread::synchronize()) | |
2298 | |
2299 { | |
2300 // Check if the FG collector wants us to yield. | |
2301 CMSTokenSync x(true); // is cms thread | |
2302 if (waitForForegroundGC()) { | |
2303 // We yielded to a foreground GC, nothing more to be | |
2304 // done this round. | |
2305 assert(_foregroundGCShouldWait == false, "We set it to false in " | |
2306 "waitForForegroundGC()"); | |
2307 if (TraceCMSState) { | |
2308 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT | |
2309 " exiting collection CMS state %d", | |
2310 Thread::current(), _collectorState); | |
2311 } | |
2312 return; | |
2313 } else { | |
2314 // The background collector can run but check to see if the | |
2315 // foreground collector has done a collection while the | |
2316 // background collector was waiting to get the CGC_lock | |
2317 // above. If yes, break so that _foregroundGCShouldWait | |
2318 // is cleared before returning. | |
2319 if (_collectorState == Idling) { | |
2320 break; | |
2321 } | |
2322 } | |
2323 } | |
2324 | |
2325 assert(_foregroundGCShouldWait, "Foreground collector, if active, " | |
2326 "should be waiting"); | |
2327 | |
2328 switch (_collectorState) { | |
2329 case InitialMarking: | |
2330 { | |
2331 ReleaseForegroundGC x(this); | |
2332 stats().record_cms_begin(); | |
2333 VM_CMS_Initial_Mark initial_mark_op(this); | |
2334 VMThread::execute(&initial_mark_op); | |
2335 } | |
2336 // The collector state may be any legal state at this point | |
2337 // since the background collector may have yielded to the | |
2338 // foreground collector. | |
2339 break; | |
2340 case Marking: | |
2341 // initial marking in checkpointRootsInitialWork has been completed | |
2342 if (markFromRoots(true)) { // we were successful | |
2343 assert(_collectorState == Precleaning, "Collector state should " | |
2344 "have changed"); | |
2345 } else { | |
2346 assert(_foregroundGCIsActive, "Internal state inconsistency"); | |
2347 } | |
2348 break; | |
2349 case Precleaning: | |
2350 if (UseAdaptiveSizePolicy) { | |
2351 size_policy()->concurrent_precleaning_begin(); | |
2352 } | |
2353 // marking from roots in markFromRoots has been completed | |
2354 preclean(); | |
2355 if (UseAdaptiveSizePolicy) { | |
2356 size_policy()->concurrent_precleaning_end(); | |
2357 } | |
2358 assert(_collectorState == AbortablePreclean || | |
2359 _collectorState == FinalMarking, | |
2360 "Collector state should have changed"); | |
2361 break; | |
2362 case AbortablePreclean: | |
2363 if (UseAdaptiveSizePolicy) { | |
2364 size_policy()->concurrent_phases_resume(); | |
2365 } | |
2366 abortable_preclean(); | |
2367 if (UseAdaptiveSizePolicy) { | |
2368 size_policy()->concurrent_precleaning_end(); | |
2369 } | |
2370 assert(_collectorState == FinalMarking, "Collector state should " | |
2371 "have changed"); | |
2372 break; | |
2373 case FinalMarking: | |
2374 { | |
2375 ReleaseForegroundGC x(this); | |
2376 | |
2377 VM_CMS_Final_Remark final_remark_op(this); | |
2378 VMThread::execute(&final_remark_op); | |
935 | 2379 } |
0 | 2380 assert(_foregroundGCShouldWait, "block post-condition"); |
2381 break; | |
2382 case Sweeping: | |
2383 if (UseAdaptiveSizePolicy) { | |
2384 size_policy()->concurrent_sweeping_begin(); | |
2385 } | |
2386 // final marking in checkpointRootsFinal has been completed | |
2387 sweep(true); | |
2388 assert(_collectorState == Resizing, "Collector state change " | |
2389 "to Resizing must be done under the free_list_lock"); | |
2390 _full_gcs_since_conc_gc = 0; | |
2391 | |
2392 // Stop the timers for adaptive size policy for the concurrent phases | |
2393 if (UseAdaptiveSizePolicy) { | |
2394 size_policy()->concurrent_sweeping_end(); | |
2395 size_policy()->concurrent_phases_end(gch->gc_cause(), | |
2396 gch->prev_gen(_cmsGen)->capacity(), | |
2397 _cmsGen->free()); | |
2398 } | |
2399 | |
2400 case Resizing: { | |
2401 // Sweeping has been completed... | |
2402 // At this point the background collection has completed. | |
2403 // Don't move the call to compute_new_size() down | |
2404 // into code that might be executed if the background | |
2405 // collection was preempted. | |
2406 { | |
2407 ReleaseForegroundGC x(this); // unblock FG collection | |
2408 MutexLockerEx y(Heap_lock, Mutex::_no_safepoint_check_flag); | |
2409 CMSTokenSync z(true); // not strictly needed. | |
2410 if (_collectorState == Resizing) { | |
2411 compute_new_size(); | |
10405 | 2412 save_heap_summary(); |
0 | 2413 _collectorState = Resetting; |
2414 } else { | |
2415 assert(_collectorState == Idling, "The state should only change" | |
2416 " because the foreground collector has finished the collection"); | |
2417 } | |
2418 } | |
2419 break; | |
2420 } | |
2421 case Resetting: | |
2422 // CMS heap resizing has been completed | |
2423 reset(true); | |
2424 assert(_collectorState == Idling, "Collector state should " | |
2425 "have changed"); | |
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2426 |
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2427 MetaspaceGC::set_should_concurrent_collect(false); |
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2428 |
0 | 2429 stats().record_cms_end(); |
2430 // Don't move the concurrent_phases_end() and compute_new_size() | |
2431 // calls to here because a preempted background collection | |
2432 // has it's state set to "Resetting". | |
2433 break; | |
2434 case Idling: | |
2435 default: | |
2436 ShouldNotReachHere(); | |
2437 break; | |
2438 } | |
2439 if (TraceCMSState) { | |
2440 gclog_or_tty->print_cr(" Thread " INTPTR_FORMAT " done - next CMS state %d", | |
2441 Thread::current(), _collectorState); | |
2442 } | |
2443 assert(_foregroundGCShouldWait, "block post-condition"); | |
2444 } | |
2445 | |
2446 // Should this be in gc_epilogue? | |
2447 collector_policy()->counters()->update_counters(); | |
2448 | |
2449 { | |
2450 // Clear _foregroundGCShouldWait and, in the event that the | |
2451 // foreground collector is waiting, notify it, before | |
2452 // returning. | |
2453 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
2454 _foregroundGCShouldWait = false; | |
2455 if (_foregroundGCIsActive) { | |
2456 CGC_lock->notify(); | |
2457 } | |
2458 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
2459 "Possible deadlock"); | |
2460 } | |
2461 if (TraceCMSState) { | |
2462 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT | |
2463 " exiting collection CMS state %d", | |
2464 Thread::current(), _collectorState); | |
2465 } | |
2466 if (PrintGC && Verbose) { | |
2467 _cmsGen->print_heap_change(prev_used); | |
2468 } | |
2469 } | |
2470 | |
10405 | 2471 void CMSCollector::register_foreground_gc_start(GCCause::Cause cause) { |
2472 if (!_cms_start_registered) { | |
2473 register_gc_start(cause); | |
2474 } | |
2475 } | |
2476 | |
2477 void CMSCollector::register_gc_start(GCCause::Cause cause) { | |
2478 _cms_start_registered = true; | |
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2479 _gc_timer_cm->register_gc_start(); |
10405 | 2480 _gc_tracer_cm->report_gc_start(cause, _gc_timer_cm->gc_start()); |
2481 } | |
2482 | |
2483 void CMSCollector::register_gc_end() { | |
2484 if (_cms_start_registered) { | |
2485 report_heap_summary(GCWhen::AfterGC); | |
2486 | |
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2487 _gc_timer_cm->register_gc_end(); |
10405 | 2488 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions()); |
2489 _cms_start_registered = false; | |
2490 } | |
2491 } | |
2492 | |
2493 void CMSCollector::save_heap_summary() { | |
2494 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
2495 _last_heap_summary = gch->create_heap_summary(); | |
2496 _last_metaspace_summary = gch->create_metaspace_summary(); | |
2497 } | |
2498 | |
2499 void CMSCollector::report_heap_summary(GCWhen::Type when) { | |
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2500 _gc_tracer_cm->report_gc_heap_summary(when, _last_heap_summary); |
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2501 _gc_tracer_cm->report_metaspace_summary(when, _last_metaspace_summary); |
10405 | 2502 } |
2503 | |
2504 void CMSCollector::collect_in_foreground(bool clear_all_soft_refs, GCCause::Cause cause) { | |
0 | 2505 assert(_foregroundGCIsActive && !_foregroundGCShouldWait, |
2506 "Foreground collector should be waiting, not executing"); | |
2507 assert(Thread::current()->is_VM_thread(), "A foreground collection" | |
2508 "may only be done by the VM Thread with the world stopped"); | |
2509 assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(), | |
2510 "VM thread should have CMS token"); | |
2511 | |
10405 | 2512 NOT_PRODUCT(GCTraceTime t("CMS:MS (foreground) ", PrintGCDetails && Verbose, |
2513 true, NULL);) | |
0 | 2514 if (UseAdaptiveSizePolicy) { |
2515 size_policy()->ms_collection_begin(); | |
2516 } | |
2517 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact); | |
2518 | |
2519 HandleMark hm; // Discard invalid handles created during verification | |
2520 | |
2521 if (VerifyBeforeGC && | |
2522 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
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2523 Universe::verify(); |
0 | 2524 } |
2525 | |
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2526 // Snapshot the soft reference policy to be used in this collection cycle. |
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2527 ref_processor()->setup_policy(clear_all_soft_refs); |
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2528 |
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2529 // Decide if class unloading should be done |
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2530 update_should_unload_classes(); |
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2531 |
0 | 2532 bool init_mark_was_synchronous = false; // until proven otherwise |
2533 while (_collectorState != Idling) { | |
2534 if (TraceCMSState) { | |
2535 gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " in CMS state %d", | |
2536 Thread::current(), _collectorState); | |
2537 } | |
2538 switch (_collectorState) { | |
2539 case InitialMarking: | |
10405 | 2540 register_foreground_gc_start(cause); |
0 | 2541 init_mark_was_synchronous = true; // fact to be exploited in re-mark |
2542 checkpointRootsInitial(false); | |
2543 assert(_collectorState == Marking, "Collector state should have changed" | |
2544 " within checkpointRootsInitial()"); | |
2545 break; | |
2546 case Marking: | |
2547 // initial marking in checkpointRootsInitialWork has been completed | |
2548 if (VerifyDuringGC && | |
2549 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
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2550 Universe::verify("Verify before initial mark: "); |
0 | 2551 } |
2552 { | |
2553 bool res = markFromRoots(false); | |
2554 assert(res && _collectorState == FinalMarking, "Collector state should " | |
2555 "have changed"); | |
2556 break; | |
2557 } | |
2558 case FinalMarking: | |
2559 if (VerifyDuringGC && | |
2560 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
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2561 Universe::verify("Verify before re-mark: "); |
0 | 2562 } |
2563 checkpointRootsFinal(false, clear_all_soft_refs, | |
2564 init_mark_was_synchronous); | |
2565 assert(_collectorState == Sweeping, "Collector state should not " | |
2566 "have changed within checkpointRootsFinal()"); | |
2567 break; | |
2568 case Sweeping: | |
2569 // final marking in checkpointRootsFinal has been completed | |
2570 if (VerifyDuringGC && | |
2571 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
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2572 Universe::verify("Verify before sweep: "); |
0 | 2573 } |
2574 sweep(false); | |
2575 assert(_collectorState == Resizing, "Incorrect state"); | |
2576 break; | |
2577 case Resizing: { | |
2578 // Sweeping has been completed; the actual resize in this case | |
2579 // is done separately; nothing to be done in this state. | |
2580 _collectorState = Resetting; | |
2581 break; | |
2582 } | |
2583 case Resetting: | |
2584 // The heap has been resized. | |
2585 if (VerifyDuringGC && | |
2586 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
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2587 Universe::verify("Verify before reset: "); |
0 | 2588 } |
10405 | 2589 save_heap_summary(); |
0 | 2590 reset(false); |
2591 assert(_collectorState == Idling, "Collector state should " | |
2592 "have changed"); | |
2593 break; | |
2594 case Precleaning: | |
2595 case AbortablePreclean: | |
2596 // Elide the preclean phase | |
2597 _collectorState = FinalMarking; | |
2598 break; | |
2599 default: | |
2600 ShouldNotReachHere(); | |
2601 } | |
2602 if (TraceCMSState) { | |
2603 gclog_or_tty->print_cr(" Thread " INTPTR_FORMAT " done - next CMS state %d", | |
2604 Thread::current(), _collectorState); | |
2605 } | |
2606 } | |
2607 | |
2608 if (UseAdaptiveSizePolicy) { | |
2609 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
2610 size_policy()->ms_collection_end(gch->gc_cause()); | |
2611 } | |
2612 | |
2613 if (VerifyAfterGC && | |
2614 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
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2615 Universe::verify(); |
0 | 2616 } |
2617 if (TraceCMSState) { | |
2618 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT | |
2619 " exiting collection CMS state %d", | |
2620 Thread::current(), _collectorState); | |
2621 } | |
2622 } | |
2623 | |
2624 bool CMSCollector::waitForForegroundGC() { | |
2625 bool res = false; | |
2626 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
2627 "CMS thread should have CMS token"); | |
2628 // Block the foreground collector until the | |
2629 // background collectors decides whether to | |
2630 // yield. | |
2631 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
2632 _foregroundGCShouldWait = true; | |
2633 if (_foregroundGCIsActive) { | |
2634 // The background collector yields to the | |
2635 // foreground collector and returns a value | |
2636 // indicating that it has yielded. The foreground | |
2637 // collector can proceed. | |
2638 res = true; | |
2639 _foregroundGCShouldWait = false; | |
2640 ConcurrentMarkSweepThread::clear_CMS_flag( | |
2641 ConcurrentMarkSweepThread::CMS_cms_has_token); | |
2642 ConcurrentMarkSweepThread::set_CMS_flag( | |
2643 ConcurrentMarkSweepThread::CMS_cms_wants_token); | |
2644 // Get a possibly blocked foreground thread going | |
2645 CGC_lock->notify(); | |
2646 if (TraceCMSState) { | |
2647 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT " waiting at CMS state %d", | |
2648 Thread::current(), _collectorState); | |
2649 } | |
2650 while (_foregroundGCIsActive) { | |
2651 CGC_lock->wait(Mutex::_no_safepoint_check_flag); | |
2652 } | |
2653 ConcurrentMarkSweepThread::set_CMS_flag( | |
2654 ConcurrentMarkSweepThread::CMS_cms_has_token); | |
2655 ConcurrentMarkSweepThread::clear_CMS_flag( | |
2656 ConcurrentMarkSweepThread::CMS_cms_wants_token); | |
2657 } | |
2658 if (TraceCMSState) { | |
2659 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT " continuing at CMS state %d", | |
2660 Thread::current(), _collectorState); | |
2661 } | |
2662 return res; | |
2663 } | |
2664 | |
2665 // Because of the need to lock the free lists and other structures in | |
2666 // the collector, common to all the generations that the collector is | |
2667 // collecting, we need the gc_prologues of individual CMS generations | |
2668 // delegate to their collector. It may have been simpler had the | |
2669 // current infrastructure allowed one to call a prologue on a | |
2670 // collector. In the absence of that we have the generation's | |
2671 // prologue delegate to the collector, which delegates back | |
2672 // some "local" work to a worker method in the individual generations | |
2673 // that it's responsible for collecting, while itself doing any | |
2674 // work common to all generations it's responsible for. A similar | |
2675 // comment applies to the gc_epilogue()'s. | |
2676 // The role of the varaible _between_prologue_and_epilogue is to | |
2677 // enforce the invocation protocol. | |
2678 void CMSCollector::gc_prologue(bool full) { | |
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2679 // Call gc_prologue_work() for the CMSGen |
0 | 2680 // we are responsible for. |
2681 | |
2682 // The following locking discipline assumes that we are only called | |
2683 // when the world is stopped. | |
2684 assert(SafepointSynchronize::is_at_safepoint(), "world is stopped assumption"); | |
2685 | |
2686 // The CMSCollector prologue must call the gc_prologues for the | |
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2687 // "generations" that it's responsible |
0 | 2688 // for. |
2689 | |
2690 assert( Thread::current()->is_VM_thread() | |
2691 || ( CMSScavengeBeforeRemark | |
2692 && Thread::current()->is_ConcurrentGC_thread()), | |
2693 "Incorrect thread type for prologue execution"); | |
2694 | |
2695 if (_between_prologue_and_epilogue) { | |
2696 // We have already been invoked; this is a gc_prologue delegation | |
2697 // from yet another CMS generation that we are responsible for, just | |
2698 // ignore it since all relevant work has already been done. | |
2699 return; | |
2700 } | |
2701 | |
2702 // set a bit saying prologue has been called; cleared in epilogue | |
2703 _between_prologue_and_epilogue = true; | |
2704 // Claim locks for common data structures, then call gc_prologue_work() | |
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2705 // for each CMSGen. |
0 | 2706 |
2707 getFreelistLocks(); // gets free list locks on constituent spaces | |
2708 bitMapLock()->lock_without_safepoint_check(); | |
2709 | |
2710 // Should call gc_prologue_work() for all cms gens we are responsible for | |
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2711 bool duringMarking = _collectorState >= Marking |
0 | 2712 && _collectorState < Sweeping; |
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2713 |
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2714 // The young collections clear the modified oops state, which tells if |
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2715 // there are any modified oops in the class. The remark phase also needs |
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2716 // that information. Tell the young collection to save the union of all |
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2717 // modified klasses. |
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2718 if (duringMarking) { |
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2719 _ct->klass_rem_set()->set_accumulate_modified_oops(true); |
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2720 } |
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2721 |
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2722 bool registerClosure = duringMarking; |
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2723 |
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2724 ModUnionClosure* muc = CollectedHeap::use_parallel_gc_threads() ? |
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2725 &_modUnionClosurePar |
0 | 2726 : &_modUnionClosure; |
2727 _cmsGen->gc_prologue_work(full, registerClosure, muc); | |
2728 | |
2729 if (!full) { | |
2730 stats().record_gc0_begin(); | |
2731 } | |
2732 } | |
2733 | |
2734 void ConcurrentMarkSweepGeneration::gc_prologue(bool full) { | |
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2735 |
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2736 _capacity_at_prologue = capacity(); |
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2737 _used_at_prologue = used(); |
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2738 |
0 | 2739 // Delegate to CMScollector which knows how to coordinate between |
2740 // this and any other CMS generations that it is responsible for | |
2741 // collecting. | |
2742 collector()->gc_prologue(full); | |
2743 } | |
2744 | |
2745 // This is a "private" interface for use by this generation's CMSCollector. | |
2746 // Not to be called directly by any other entity (for instance, | |
2747 // GenCollectedHeap, which calls the "public" gc_prologue method above). | |
2748 void ConcurrentMarkSweepGeneration::gc_prologue_work(bool full, | |
2749 bool registerClosure, ModUnionClosure* modUnionClosure) { | |
2750 assert(!incremental_collection_failed(), "Shouldn't be set yet"); | |
2751 assert(cmsSpace()->preconsumptionDirtyCardClosure() == NULL, | |
2752 "Should be NULL"); | |
2753 if (registerClosure) { | |
2754 cmsSpace()->setPreconsumptionDirtyCardClosure(modUnionClosure); | |
2755 } | |
2756 cmsSpace()->gc_prologue(); | |
2757 // Clear stat counters | |
2758 NOT_PRODUCT( | |
2759 assert(_numObjectsPromoted == 0, "check"); | |
2760 assert(_numWordsPromoted == 0, "check"); | |
2761 if (Verbose && PrintGC) { | |
2762 gclog_or_tty->print("Allocated "SIZE_FORMAT" objects, " | |
2763 SIZE_FORMAT" bytes concurrently", | |
2764 _numObjectsAllocated, _numWordsAllocated*sizeof(HeapWord)); | |
2765 } | |
2766 _numObjectsAllocated = 0; | |
2767 _numWordsAllocated = 0; | |
2768 ) | |
2769 } | |
2770 | |
2771 void CMSCollector::gc_epilogue(bool full) { | |
2772 // The following locking discipline assumes that we are only called | |
2773 // when the world is stopped. | |
2774 assert(SafepointSynchronize::is_at_safepoint(), | |
2775 "world is stopped assumption"); | |
2776 | |
2777 // Currently the CMS epilogue (see CompactibleFreeListSpace) merely checks | |
2778 // if linear allocation blocks need to be appropriately marked to allow the | |
2779 // the blocks to be parsable. We also check here whether we need to nudge the | |
2780 // CMS collector thread to start a new cycle (if it's not already active). | |
2781 assert( Thread::current()->is_VM_thread() | |
2782 || ( CMSScavengeBeforeRemark | |
2783 && Thread::current()->is_ConcurrentGC_thread()), | |
2784 "Incorrect thread type for epilogue execution"); | |
2785 | |
2786 if (!_between_prologue_and_epilogue) { | |
2787 // We have already been invoked; this is a gc_epilogue delegation | |
2788 // from yet another CMS generation that we are responsible for, just | |
2789 // ignore it since all relevant work has already been done. | |
2790 return; | |
2791 } | |
2792 assert(haveFreelistLocks(), "must have freelist locks"); | |
2793 assert_lock_strong(bitMapLock()); | |
2794 | |
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2795 _ct->klass_rem_set()->set_accumulate_modified_oops(false); |
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2796 |
0 | 2797 _cmsGen->gc_epilogue_work(full); |
2798 | |
2799 if (_collectorState == AbortablePreclean || _collectorState == Precleaning) { | |
2800 // in case sampling was not already enabled, enable it | |
2801 _start_sampling = true; | |
2802 } | |
2803 // reset _eden_chunk_array so sampling starts afresh | |
2804 _eden_chunk_index = 0; | |
2805 | |
2806 size_t cms_used = _cmsGen->cmsSpace()->used(); | |
2807 | |
2808 // update performance counters - this uses a special version of | |
2809 // update_counters() that allows the utilization to be passed as a | |
2810 // parameter, avoiding multiple calls to used(). | |
2811 // | |
2812 _cmsGen->update_counters(cms_used); | |
2813 | |
2814 if (CMSIncrementalMode) { | |
2815 icms_update_allocation_limits(); | |
2816 } | |
2817 | |
2818 bitMapLock()->unlock(); | |
2819 releaseFreelistLocks(); | |
2820 | |
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2821 if (!CleanChunkPoolAsync) { |
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2822 Chunk::clean_chunk_pool(); |
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2823 } |
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2824 |
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2825 set_did_compact(false); |
0 | 2826 _between_prologue_and_epilogue = false; // ready for next cycle |
2827 } | |
2828 | |
2829 void ConcurrentMarkSweepGeneration::gc_epilogue(bool full) { | |
2830 collector()->gc_epilogue(full); | |
2831 | |
2832 // Also reset promotion tracking in par gc thread states. | |
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2833 if (CollectedHeap::use_parallel_gc_threads()) { |
0 | 2834 for (uint i = 0; i < ParallelGCThreads; i++) { |
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2835 _par_gc_thread_states[i]->promo.stopTrackingPromotions(i); |
0 | 2836 } |
2837 } | |
2838 } | |
2839 | |
2840 void ConcurrentMarkSweepGeneration::gc_epilogue_work(bool full) { | |
2841 assert(!incremental_collection_failed(), "Should have been cleared"); | |
2842 cmsSpace()->setPreconsumptionDirtyCardClosure(NULL); | |
2843 cmsSpace()->gc_epilogue(); | |
2844 // Print stat counters | |
2845 NOT_PRODUCT( | |
2846 assert(_numObjectsAllocated == 0, "check"); | |
2847 assert(_numWordsAllocated == 0, "check"); | |
2848 if (Verbose && PrintGC) { | |
2849 gclog_or_tty->print("Promoted "SIZE_FORMAT" objects, " | |
2850 SIZE_FORMAT" bytes", | |
2851 _numObjectsPromoted, _numWordsPromoted*sizeof(HeapWord)); | |
2852 } | |
2853 _numObjectsPromoted = 0; | |
2854 _numWordsPromoted = 0; | |
2855 ) | |
2856 | |
2857 if (PrintGC && Verbose) { | |
2858 // Call down the chain in contiguous_available needs the freelistLock | |
2859 // so print this out before releasing the freeListLock. | |
2860 gclog_or_tty->print(" Contiguous available "SIZE_FORMAT" bytes ", | |
2861 contiguous_available()); | |
2862 } | |
2863 } | |
2864 | |
2865 #ifndef PRODUCT | |
2866 bool CMSCollector::have_cms_token() { | |
2867 Thread* thr = Thread::current(); | |
2868 if (thr->is_VM_thread()) { | |
2869 return ConcurrentMarkSweepThread::vm_thread_has_cms_token(); | |
2870 } else if (thr->is_ConcurrentGC_thread()) { | |
2871 return ConcurrentMarkSweepThread::cms_thread_has_cms_token(); | |
2872 } else if (thr->is_GC_task_thread()) { | |
2873 return ConcurrentMarkSweepThread::vm_thread_has_cms_token() && | |
2874 ParGCRareEvent_lock->owned_by_self(); | |
2875 } | |
2876 return false; | |
2877 } | |
2878 #endif | |
2879 | |
2880 // Check reachability of the given heap address in CMS generation, | |
2881 // treating all other generations as roots. | |
2882 bool CMSCollector::is_cms_reachable(HeapWord* addr) { | |
2883 // We could "guarantee" below, rather than assert, but i'll | |
2884 // leave these as "asserts" so that an adventurous debugger | |
2885 // could try this in the product build provided some subset of | |
2886 // the conditions were met, provided they were intersted in the | |
2887 // results and knew that the computation below wouldn't interfere | |
2888 // with other concurrent computations mutating the structures | |
2889 // being read or written. | |
2890 assert(SafepointSynchronize::is_at_safepoint(), | |
2891 "Else mutations in object graph will make answer suspect"); | |
2892 assert(have_cms_token(), "Should hold cms token"); | |
2893 assert(haveFreelistLocks(), "must hold free list locks"); | |
2894 assert_lock_strong(bitMapLock()); | |
2895 | |
2896 // Clear the marking bit map array before starting, but, just | |
2897 // for kicks, first report if the given address is already marked | |
2898 gclog_or_tty->print_cr("Start: Address 0x%x is%s marked", addr, | |
2899 _markBitMap.isMarked(addr) ? "" : " not"); | |
2900 | |
2901 if (verify_after_remark()) { | |
2902 MutexLockerEx x(verification_mark_bm()->lock(), Mutex::_no_safepoint_check_flag); | |
2903 bool result = verification_mark_bm()->isMarked(addr); | |
2904 gclog_or_tty->print_cr("TransitiveMark: Address 0x%x %s marked", addr, | |
2905 result ? "IS" : "is NOT"); | |
2906 return result; | |
2907 } else { | |
2908 gclog_or_tty->print_cr("Could not compute result"); | |
2909 return false; | |
2910 } | |
2911 } | |
2912 | |
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2913 |
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2914 void |
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2915 CMSCollector::print_on_error(outputStream* st) { |
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2916 CMSCollector* collector = ConcurrentMarkSweepGeneration::_collector; |
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2917 if (collector != NULL) { |
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2918 CMSBitMap* bitmap = &collector->_markBitMap; |
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2919 st->print_cr("Marking Bits: (CMSBitMap*) " PTR_FORMAT, bitmap); |
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2920 bitmap->print_on_error(st, " Bits: "); |
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2921 |
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2922 st->cr(); |
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2923 |
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2924 CMSBitMap* mut_bitmap = &collector->_modUnionTable; |
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2925 st->print_cr("Mod Union Table: (CMSBitMap*) " PTR_FORMAT, mut_bitmap); |
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2926 mut_bitmap->print_on_error(st, " Bits: "); |
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2927 } |
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2928 } |
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2929 |
0 | 2930 //////////////////////////////////////////////////////// |
2931 // CMS Verification Support | |
2932 //////////////////////////////////////////////////////// | |
2933 // Following the remark phase, the following invariant | |
2934 // should hold -- each object in the CMS heap which is | |
2935 // marked in markBitMap() should be marked in the verification_mark_bm(). | |
2936 | |
2937 class VerifyMarkedClosure: public BitMapClosure { | |
2938 CMSBitMap* _marks; | |
2939 bool _failed; | |
2940 | |
2941 public: | |
2942 VerifyMarkedClosure(CMSBitMap* bm): _marks(bm), _failed(false) {} | |
2943 | |
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2944 bool do_bit(size_t offset) { |
0 | 2945 HeapWord* addr = _marks->offsetToHeapWord(offset); |
2946 if (!_marks->isMarked(addr)) { | |
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2947 oop(addr)->print_on(gclog_or_tty); |
0 | 2948 gclog_or_tty->print_cr(" ("INTPTR_FORMAT" should have been marked)", addr); |
2949 _failed = true; | |
2950 } | |
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2951 return true; |
0 | 2952 } |
2953 | |
2954 bool failed() { return _failed; } | |
2955 }; | |
2956 | |
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2957 bool CMSCollector::verify_after_remark(bool silent) { |
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2958 if (!silent) gclog_or_tty->print(" [Verifying CMS Marking... "); |
0 | 2959 MutexLockerEx ml(verification_mark_bm()->lock(), Mutex::_no_safepoint_check_flag); |
2960 static bool init = false; | |
2961 | |
2962 assert(SafepointSynchronize::is_at_safepoint(), | |
2963 "Else mutations in object graph will make answer suspect"); | |
2964 assert(have_cms_token(), | |
2965 "Else there may be mutual interference in use of " | |
2966 " verification data structures"); | |
2967 assert(_collectorState > Marking && _collectorState <= Sweeping, | |
2968 "Else marking info checked here may be obsolete"); | |
2969 assert(haveFreelistLocks(), "must hold free list locks"); | |
2970 assert_lock_strong(bitMapLock()); | |
2971 | |
2972 | |
2973 // Allocate marking bit map if not already allocated | |
2974 if (!init) { // first time | |
2975 if (!verification_mark_bm()->allocate(_span)) { | |
2976 return false; | |
2977 } | |
2978 init = true; | |
2979 } | |
2980 | |
2981 assert(verification_mark_stack()->isEmpty(), "Should be empty"); | |
2982 | |
2983 // Turn off refs discovery -- so we will be tracing through refs. | |
2984 // This is as intended, because by this time | |
2985 // GC must already have cleared any refs that need to be cleared, | |
2986 // and traced those that need to be marked; moreover, | |
2987 // the marking done here is not going to intefere in any | |
2988 // way with the marking information used by GC. | |
2989 NoRefDiscovery no_discovery(ref_processor()); | |
2990 | |
2991 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;) | |
2992 | |
2993 // Clear any marks from a previous round | |
2994 verification_mark_bm()->clear_all(); | |
2995 assert(verification_mark_stack()->isEmpty(), "markStack should be empty"); | |
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2996 verify_work_stacks_empty(); |
0 | 2997 |
2998 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
2999 gch->ensure_parsability(false); // fill TLABs, but no need to retire them | |
3000 // Update the saved marks which may affect the root scans. | |
3001 gch->save_marks(); | |
3002 | |
3003 if (CMSRemarkVerifyVariant == 1) { | |
3004 // In this first variant of verification, we complete | |
3005 // all marking, then check if the new marks-verctor is | |
3006 // a subset of the CMS marks-vector. | |
3007 verify_after_remark_work_1(); | |
3008 } else if (CMSRemarkVerifyVariant == 2) { | |
3009 // In this second variant of verification, we flag an error | |
3010 // (i.e. an object reachable in the new marks-vector not reachable | |
3011 // in the CMS marks-vector) immediately, also indicating the | |
3012 // identify of an object (A) that references the unmarked object (B) -- | |
3013 // presumably, a mutation to A failed to be picked up by preclean/remark? | |
3014 verify_after_remark_work_2(); | |
3015 } else { | |
3016 warning("Unrecognized value %d for CMSRemarkVerifyVariant", | |
3017 CMSRemarkVerifyVariant); | |
3018 } | |
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3019 if (!silent) gclog_or_tty->print(" done] "); |
0 | 3020 return true; |
3021 } | |
3022 | |
3023 void CMSCollector::verify_after_remark_work_1() { | |
3024 ResourceMark rm; | |
3025 HandleMark hm; | |
3026 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
3027 | |
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3028 // Get a clear set of claim bits for the strong roots processing to work with. |
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3029 ClassLoaderDataGraph::clear_claimed_marks(); |
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3030 |
0 | 3031 // Mark from roots one level into CMS |
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3032 MarkRefsIntoClosure notOlder(_span, verification_mark_bm()); |
0 | 3033 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. |
3034 | |
3035 gch->gen_process_strong_roots(_cmsGen->level(), | |
3036 true, // younger gens are roots | |
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3037 true, // activate StrongRootsScope |
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3038 false, // not scavenging |
0 | 3039 SharedHeap::ScanningOption(roots_scanning_options()), |
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3040 ¬Older, |
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3041 true, // walk code active on stacks |
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3042 NULL, |
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3043 NULL); // SSS: Provide correct closure |
0 | 3044 |
3045 // Now mark from the roots | |
3046 MarkFromRootsClosure markFromRootsClosure(this, _span, | |
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3047 verification_mark_bm(), verification_mark_stack(), |
0 | 3048 false /* don't yield */, true /* verifying */); |
3049 assert(_restart_addr == NULL, "Expected pre-condition"); | |
3050 verification_mark_bm()->iterate(&markFromRootsClosure); | |
3051 while (_restart_addr != NULL) { | |
3052 // Deal with stack overflow: by restarting at the indicated | |
3053 // address. | |
3054 HeapWord* ra = _restart_addr; | |
3055 markFromRootsClosure.reset(ra); | |
3056 _restart_addr = NULL; | |
3057 verification_mark_bm()->iterate(&markFromRootsClosure, ra, _span.end()); | |
3058 } | |
3059 assert(verification_mark_stack()->isEmpty(), "Should have been drained"); | |
3060 verify_work_stacks_empty(); | |
3061 | |
3062 // Marking completed -- now verify that each bit marked in | |
3063 // verification_mark_bm() is also marked in markBitMap(); flag all | |
3064 // errors by printing corresponding objects. | |
3065 VerifyMarkedClosure vcl(markBitMap()); | |
3066 verification_mark_bm()->iterate(&vcl); | |
3067 if (vcl.failed()) { | |
3068 gclog_or_tty->print("Verification failed"); | |
1145
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3069 Universe::heap()->print_on(gclog_or_tty); |
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3070 fatal("CMS: failed marking verification after remark"); |
0 | 3071 } |
3072 } | |
3073 | |
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3074 class VerifyKlassOopsKlassClosure : public KlassClosure { |
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3075 class VerifyKlassOopsClosure : public OopClosure { |
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3076 CMSBitMap* _bitmap; |
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3077 public: |
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3078 VerifyKlassOopsClosure(CMSBitMap* bitmap) : _bitmap(bitmap) { } |
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3079 void do_oop(oop* p) { guarantee(*p == NULL || _bitmap->isMarked((HeapWord*) *p), "Should be marked"); } |
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3080 void do_oop(narrowOop* p) { ShouldNotReachHere(); } |
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3081 } _oop_closure; |
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3082 public: |
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3083 VerifyKlassOopsKlassClosure(CMSBitMap* bitmap) : _oop_closure(bitmap) {} |
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3084 void do_klass(Klass* k) { |
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3085 k->oops_do(&_oop_closure); |
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3086 } |
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3087 }; |
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3088 |
0 | 3089 void CMSCollector::verify_after_remark_work_2() { |
3090 ResourceMark rm; | |
3091 HandleMark hm; | |
3092 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
3093 | |
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3094 // Get a clear set of claim bits for the strong roots processing to work with. |
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3095 ClassLoaderDataGraph::clear_claimed_marks(); |
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3096 |
0 | 3097 // Mark from roots one level into CMS |
3098 MarkRefsIntoVerifyClosure notOlder(_span, verification_mark_bm(), | |
994
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3099 markBitMap()); |
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3100 CMKlassClosure klass_closure(¬Older); |
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3101 |
0 | 3102 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. |
3103 gch->gen_process_strong_roots(_cmsGen->level(), | |
3104 true, // younger gens are roots | |
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3105 true, // activate StrongRootsScope |
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3106 false, // not scavenging |
0 | 3107 SharedHeap::ScanningOption(roots_scanning_options()), |
989
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3108 ¬Older, |
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3109 true, // walk code active on stacks |
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3110 NULL, |
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3111 &klass_closure); |
0 | 3112 |
3113 // Now mark from the roots | |
3114 MarkFromRootsVerifyClosure markFromRootsClosure(this, _span, | |
3115 verification_mark_bm(), markBitMap(), verification_mark_stack()); | |
3116 assert(_restart_addr == NULL, "Expected pre-condition"); | |
3117 verification_mark_bm()->iterate(&markFromRootsClosure); | |
3118 while (_restart_addr != NULL) { | |
3119 // Deal with stack overflow: by restarting at the indicated | |
3120 // address. | |
3121 HeapWord* ra = _restart_addr; | |
3122 markFromRootsClosure.reset(ra); | |
3123 _restart_addr = NULL; | |
3124 verification_mark_bm()->iterate(&markFromRootsClosure, ra, _span.end()); | |
3125 } | |
3126 assert(verification_mark_stack()->isEmpty(), "Should have been drained"); | |
3127 verify_work_stacks_empty(); | |
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3128 |
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3129 VerifyKlassOopsKlassClosure verify_klass_oops(verification_mark_bm()); |
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3130 ClassLoaderDataGraph::classes_do(&verify_klass_oops); |
0 | 3131 |
3132 // Marking completed -- now verify that each bit marked in | |
3133 // verification_mark_bm() is also marked in markBitMap(); flag all | |
3134 // errors by printing corresponding objects. | |
3135 VerifyMarkedClosure vcl(markBitMap()); | |
3136 verification_mark_bm()->iterate(&vcl); | |
3137 assert(!vcl.failed(), "Else verification above should not have succeeded"); | |
3138 } | |
3139 | |
3140 void ConcurrentMarkSweepGeneration::save_marks() { | |
3141 // delegate to CMS space | |
3142 cmsSpace()->save_marks(); | |
3143 for (uint i = 0; i < ParallelGCThreads; i++) { | |
3144 _par_gc_thread_states[i]->promo.startTrackingPromotions(); | |
3145 } | |
3146 } | |
3147 | |
3148 bool ConcurrentMarkSweepGeneration::no_allocs_since_save_marks() { | |
3149 return cmsSpace()->no_allocs_since_save_marks(); | |
3150 } | |
3151 | |
3152 #define CMS_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \ | |
3153 \ | |
3154 void ConcurrentMarkSweepGeneration:: \ | |
3155 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \ | |
3156 cl->set_generation(this); \ | |
3157 cmsSpace()->oop_since_save_marks_iterate##nv_suffix(cl); \ | |
3158 cl->reset_generation(); \ | |
3159 save_marks(); \ | |
3160 } | |
3161 | |
3162 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DEFN) | |
3163 | |
3164 void | |
3165 ConcurrentMarkSweepGeneration::younger_refs_iterate(OopsInGenClosure* cl) { | |
3166 cl->set_generation(this); | |
3167 younger_refs_in_space_iterate(_cmsSpace, cl); | |
3168 cl->reset_generation(); | |
3169 } | |
3170 | |
3171 void | |
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3172 ConcurrentMarkSweepGeneration::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) { |
0 | 3173 if (freelistLock()->owned_by_self()) { |
3174 Generation::oop_iterate(mr, cl); | |
3175 } else { | |
3176 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
3177 Generation::oop_iterate(mr, cl); | |
3178 } | |
3179 } | |
3180 | |
3181 void | |
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3182 ConcurrentMarkSweepGeneration::oop_iterate(ExtendedOopClosure* cl) { |
0 | 3183 if (freelistLock()->owned_by_self()) { |
3184 Generation::oop_iterate(cl); | |
3185 } else { | |
3186 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
3187 Generation::oop_iterate(cl); | |
3188 } | |
3189 } | |
3190 | |
3191 void | |
3192 ConcurrentMarkSweepGeneration::object_iterate(ObjectClosure* cl) { | |
3193 if (freelistLock()->owned_by_self()) { | |
3194 Generation::object_iterate(cl); | |
3195 } else { | |
3196 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
3197 Generation::object_iterate(cl); | |
3198 } | |
3199 } | |
3200 | |
3201 void | |
517
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3202 ConcurrentMarkSweepGeneration::safe_object_iterate(ObjectClosure* cl) { |
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3203 if (freelistLock()->owned_by_self()) { |
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3204 Generation::safe_object_iterate(cl); |
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3205 } else { |
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3206 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); |
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3207 Generation::safe_object_iterate(cl); |
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3208 } |
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3209 } |
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3210 |
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3211 void |
0 | 3212 ConcurrentMarkSweepGeneration::post_compact() { |
3213 } | |
3214 | |
3215 void | |
3216 ConcurrentMarkSweepGeneration::prepare_for_verify() { | |
3217 // Fix the linear allocation blocks to look like free blocks. | |
3218 | |
3219 // Locks are normally acquired/released in gc_prologue/gc_epilogue, but those | |
3220 // are not called when the heap is verified during universe initialization and | |
3221 // at vm shutdown. | |
3222 if (freelistLock()->owned_by_self()) { | |
3223 cmsSpace()->prepare_for_verify(); | |
3224 } else { | |
3225 MutexLockerEx fll(freelistLock(), Mutex::_no_safepoint_check_flag); | |
3226 cmsSpace()->prepare_for_verify(); | |
3227 } | |
3228 } | |
3229 | |
3230 void | |
6008 | 3231 ConcurrentMarkSweepGeneration::verify() { |
0 | 3232 // Locks are normally acquired/released in gc_prologue/gc_epilogue, but those |
3233 // are not called when the heap is verified during universe initialization and | |
3234 // at vm shutdown. | |
3235 if (freelistLock()->owned_by_self()) { | |
6008 | 3236 cmsSpace()->verify(); |
0 | 3237 } else { |
3238 MutexLockerEx fll(freelistLock(), Mutex::_no_safepoint_check_flag); | |
6008 | 3239 cmsSpace()->verify(); |
3240 } | |
3241 } | |
3242 | |
3243 void CMSCollector::verify() { | |
3244 _cmsGen->verify(); | |
0 | 3245 } |
3246 | |
3247 #ifndef PRODUCT | |
3248 bool CMSCollector::overflow_list_is_empty() const { | |
3249 assert(_num_par_pushes >= 0, "Inconsistency"); | |
3250 if (_overflow_list == NULL) { | |
3251 assert(_num_par_pushes == 0, "Inconsistency"); | |
3252 } | |
3253 return _overflow_list == NULL; | |
3254 } | |
3255 | |
3256 // The methods verify_work_stacks_empty() and verify_overflow_empty() | |
3257 // merely consolidate assertion checks that appear to occur together frequently. | |
3258 void CMSCollector::verify_work_stacks_empty() const { | |
3259 assert(_markStack.isEmpty(), "Marking stack should be empty"); | |
3260 assert(overflow_list_is_empty(), "Overflow list should be empty"); | |
3261 } | |
3262 | |
3263 void CMSCollector::verify_overflow_empty() const { | |
3264 assert(overflow_list_is_empty(), "Overflow list should be empty"); | |
3265 assert(no_preserved_marks(), "No preserved marks"); | |
3266 } | |
3267 #endif // PRODUCT | |
3268 | |
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3269 // Decide if we want to enable class unloading as part of the |
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3270 // ensuing concurrent GC cycle. We will collect and |
94
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3271 // unload classes if it's the case that: |
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3272 // (1) an explicit gc request has been made and the flag |
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3273 // ExplicitGCInvokesConcurrentAndUnloadsClasses is set, OR |
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3274 // (2) (a) class unloading is enabled at the command line, and |
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3275 // (b) old gen is getting really full |
94
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3276 // NOTE: Provided there is no change in the state of the heap between |
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3277 // calls to this method, it should have idempotent results. Moreover, |
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3278 // its results should be monotonically increasing (i.e. going from 0 to 1, |
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3279 // but not 1 to 0) between successive calls between which the heap was |
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3280 // not collected. For the implementation below, it must thus rely on |
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3281 // the property that concurrent_cycles_since_last_unload() |
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3282 // will not decrease unless a collection cycle happened and that |
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3283 // _cmsGen->is_too_full() are |
94
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3284 // themselves also monotonic in that sense. See check_monotonicity() |
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3285 // below. |
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3286 void CMSCollector::update_should_unload_classes() { |
94
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3287 _should_unload_classes = false; |
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3288 // Condition 1 above |
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3289 if (_full_gc_requested && ExplicitGCInvokesConcurrentAndUnloadsClasses) { |
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3290 _should_unload_classes = true; |
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3291 } else if (CMSClassUnloadingEnabled) { // Condition 2.a above |
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3292 // Disjuncts 2.b.(i,ii,iii) above |
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3293 _should_unload_classes = (concurrent_cycles_since_last_unload() >= |
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3294 CMSClassUnloadingMaxInterval) |
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3295 || _cmsGen->is_too_full(); |
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3296 } |
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3297 } |
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3298 |
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3299 bool ConcurrentMarkSweepGeneration::is_too_full() const { |
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|
3300 bool res = should_concurrent_collect(); |
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6634032: CMS: Need CMSInitiatingPermOccupancyFraction for perm, divorcing from CMSInitiatingOccupancyFraction
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3301 res = res && (occupancy() > (double)CMSIsTooFullPercentage/100.0); |
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3302 return res; |
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|
3303 } |
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3304 |
0 | 3305 void CMSCollector::setup_cms_unloading_and_verification_state() { |
3293
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3306 const bool should_verify = VerifyBeforeGC || VerifyAfterGC || VerifyDuringGC |
0 | 3307 || VerifyBeforeExit; |
3293
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|
3308 const int rso = SharedHeap::SO_Strings | SharedHeap::SO_CodeCache; |
0 | 3309 |
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3310 // We set the proper root for this CMS cycle here. |
94
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3311 if (should_unload_classes()) { // Should unload classes this cycle |
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3312 remove_root_scanning_option(SharedHeap::SO_AllClasses); |
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3313 add_root_scanning_option(SharedHeap::SO_SystemClasses); |
0 | 3314 remove_root_scanning_option(rso); // Shrink the root set appropriately |
3315 set_verifying(should_verify); // Set verification state for this cycle | |
3316 return; // Nothing else needs to be done at this time | |
3317 } | |
3318 | |
3319 // Not unloading classes this cycle | |
94
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3320 assert(!should_unload_classes(), "Inconsitency!"); |
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3321 remove_root_scanning_option(SharedHeap::SO_SystemClasses); |
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3322 add_root_scanning_option(SharedHeap::SO_AllClasses); |
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3323 |
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|
3324 if ((!verifying() || unloaded_classes_last_cycle()) && should_verify) { |
0 | 3325 // Include symbols, strings and code cache elements to prevent their resurrection. |
3326 add_root_scanning_option(rso); | |
3327 set_verifying(true); | |
3328 } else if (verifying() && !should_verify) { | |
3329 // We were verifying, but some verification flags got disabled. | |
3330 set_verifying(false); | |
3331 // Exclude symbols, strings and code cache elements from root scanning to | |
3332 // reduce IM and RM pauses. | |
3333 remove_root_scanning_option(rso); | |
3334 } | |
3335 } | |
3336 | |
3337 | |
3338 #ifndef PRODUCT | |
3339 HeapWord* CMSCollector::block_start(const void* p) const { | |
3340 const HeapWord* addr = (HeapWord*)p; | |
3341 if (_span.contains(p)) { | |
3342 if (_cmsGen->cmsSpace()->is_in_reserved(addr)) { | |
3343 return _cmsGen->cmsSpace()->block_start(p); | |
3344 } | |
3345 } | |
3346 return NULL; | |
3347 } | |
3348 #endif | |
3349 | |
3350 HeapWord* | |
3351 ConcurrentMarkSweepGeneration::expand_and_allocate(size_t word_size, | |
3352 bool tlab, | |
3353 bool parallel) { | |
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3354 CMSSynchronousYieldRequest yr; |
0 | 3355 assert(!tlab, "Can't deal with TLAB allocation"); |
3356 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
3357 expand(word_size*HeapWordSize, MinHeapDeltaBytes, | |
3358 CMSExpansionCause::_satisfy_allocation); | |
3359 if (GCExpandToAllocateDelayMillis > 0) { | |
3360 os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false); | |
3361 } | |
9
173195ff483a
6642634: Test nsk/regression/b6186200 crashed with SIGSEGV
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3362 return have_lock_and_allocate(word_size, tlab); |
0 | 3363 } |
3364 | |
3365 // YSR: All of this generation expansion/shrinking stuff is an exact copy of | |
3366 // OneContigSpaceCardGeneration, which makes me wonder if we should move this | |
3367 // to CardGeneration and share it... | |
271
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3368 bool ConcurrentMarkSweepGeneration::expand(size_t bytes, size_t expand_bytes) { |
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3369 return CardGeneration::expand(bytes, expand_bytes); |
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|
3370 } |
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3371 |
0 | 3372 void ConcurrentMarkSweepGeneration::expand(size_t bytes, size_t expand_bytes, |
3373 CMSExpansionCause::Cause cause) | |
3374 { | |
271
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3375 |
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3376 bool success = expand(bytes, expand_bytes); |
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3377 |
0 | 3378 // remember why we expanded; this information is used |
3379 // by shouldConcurrentCollect() when making decisions on whether to start | |
3380 // a new CMS cycle. | |
3381 if (success) { | |
3382 set_expansion_cause(cause); | |
3383 if (PrintGCDetails && Verbose) { | |
3384 gclog_or_tty->print_cr("Expanded CMS gen for %s", | |
3385 CMSExpansionCause::to_string(cause)); | |
3386 } | |
3387 } | |
3388 } | |
3389 | |
3390 HeapWord* ConcurrentMarkSweepGeneration::expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz) { | |
3391 HeapWord* res = NULL; | |
3392 MutexLocker x(ParGCRareEvent_lock); | |
3393 while (true) { | |
3394 // Expansion by some other thread might make alloc OK now: | |
3395 res = ps->lab.alloc(word_sz); | |
3396 if (res != NULL) return res; | |
3397 // If there's not enough expansion space available, give up. | |
3398 if (_virtual_space.uncommitted_size() < (word_sz * HeapWordSize)) { | |
3399 return NULL; | |
3400 } | |
3401 // Otherwise, we try expansion. | |
3402 expand(word_sz*HeapWordSize, MinHeapDeltaBytes, | |
3403 CMSExpansionCause::_allocate_par_lab); | |
3404 // Now go around the loop and try alloc again; | |
3405 // A competing par_promote might beat us to the expansion space, | |
3406 // so we may go around the loop again if promotion fails agaion. | |
3407 if (GCExpandToAllocateDelayMillis > 0) { | |
3408 os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false); | |
3409 } | |
3410 } | |
3411 } | |
3412 | |
3413 | |
3414 bool ConcurrentMarkSweepGeneration::expand_and_ensure_spooling_space( | |
3415 PromotionInfo* promo) { | |
3416 MutexLocker x(ParGCRareEvent_lock); | |
3417 size_t refill_size_bytes = promo->refillSize() * HeapWordSize; | |
3418 while (true) { | |
3419 // Expansion by some other thread might make alloc OK now: | |
3420 if (promo->ensure_spooling_space()) { | |
3421 assert(promo->has_spooling_space(), | |
3422 "Post-condition of successful ensure_spooling_space()"); | |
3423 return true; | |
3424 } | |
3425 // If there's not enough expansion space available, give up. | |
3426 if (_virtual_space.uncommitted_size() < refill_size_bytes) { | |
3427 return false; | |
3428 } | |
3429 // Otherwise, we try expansion. | |
3430 expand(refill_size_bytes, MinHeapDeltaBytes, | |
3431 CMSExpansionCause::_allocate_par_spooling_space); | |
3432 // Now go around the loop and try alloc again; | |
3433 // A competing allocation might beat us to the expansion space, | |
3434 // so we may go around the loop again if allocation fails again. | |
3435 if (GCExpandToAllocateDelayMillis > 0) { | |
3436 os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false); | |
3437 } | |
3438 } | |
3439 } | |
3440 | |
3441 | |
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3442 void ConcurrentMarkSweepGeneration::shrink_by(size_t bytes) { |
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3443 assert_locked_or_safepoint(ExpandHeap_lock); |
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|
3444 // Shrink committed space |
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|
3445 _virtual_space.shrink_by(bytes); |
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8008508: CMS does not correctly reduce heap size after a Full GC
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|
3446 // Shrink space; this also shrinks the space's BOT |
8617e38bb4cb
8008508: CMS does not correctly reduce heap size after a Full GC
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|
3447 _cmsSpace->set_end((HeapWord*) _virtual_space.high()); |
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|
3448 size_t new_word_size = heap_word_size(_cmsSpace->capacity()); |
8617e38bb4cb
8008508: CMS does not correctly reduce heap size after a Full GC
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|
3449 // Shrink the shared block offset array |
8617e38bb4cb
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|
3450 _bts->resize(new_word_size); |
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diff
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|
3451 MemRegion mr(_cmsSpace->bottom(), new_word_size); |
8617e38bb4cb
8008508: CMS does not correctly reduce heap size after a Full GC
jmasa
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8784
diff
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|
3452 // Shrink the card table |
8617e38bb4cb
8008508: CMS does not correctly reduce heap size after a Full GC
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diff
changeset
|
3453 Universe::heap()->barrier_set()->resize_covered_region(mr); |
8617e38bb4cb
8008508: CMS does not correctly reduce heap size after a Full GC
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|
3454 |
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8008508: CMS does not correctly reduce heap size after a Full GC
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diff
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|
3455 if (Verbose && PrintGC) { |
8617e38bb4cb
8008508: CMS does not correctly reduce heap size after a Full GC
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8784
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changeset
|
3456 size_t new_mem_size = _virtual_space.committed_size(); |
8617e38bb4cb
8008508: CMS does not correctly reduce heap size after a Full GC
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diff
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|
3457 size_t old_mem_size = new_mem_size + bytes; |
8617e38bb4cb
8008508: CMS does not correctly reduce heap size after a Full GC
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diff
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|
3458 gclog_or_tty->print_cr("Shrinking %s from " SIZE_FORMAT "K to " SIZE_FORMAT "K", |
8617e38bb4cb
8008508: CMS does not correctly reduce heap size after a Full GC
jmasa
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diff
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|
3459 name(), old_mem_size/K, new_mem_size/K); |
8617e38bb4cb
8008508: CMS does not correctly reduce heap size after a Full GC
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|
3460 } |
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|
3461 } |
0 | 3462 |
3463 void ConcurrentMarkSweepGeneration::shrink(size_t bytes) { | |
3464 assert_locked_or_safepoint(Heap_lock); | |
3465 size_t size = ReservedSpace::page_align_size_down(bytes); | |
12112
1bb10d3170fa
8022817: CMS should not shrink if compaction was not done
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diff
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|
3466 // Only shrink if a compaction was done so that all the free space |
1bb10d3170fa
8022817: CMS should not shrink if compaction was not done
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diff
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|
3467 // in the generation is in a contiguous block at the end. |
1bb10d3170fa
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jmasa
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diff
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|
3468 if (size > 0 && did_compact()) { |
0 | 3469 shrink_by(size); |
3470 } | |
3471 } | |
3472 | |
3473 bool ConcurrentMarkSweepGeneration::grow_by(size_t bytes) { | |
3474 assert_locked_or_safepoint(Heap_lock); | |
3475 bool result = _virtual_space.expand_by(bytes); | |
3476 if (result) { | |
3477 size_t new_word_size = | |
3478 heap_word_size(_virtual_space.committed_size()); | |
3479 MemRegion mr(_cmsSpace->bottom(), new_word_size); | |
3480 _bts->resize(new_word_size); // resize the block offset shared array | |
3481 Universe::heap()->barrier_set()->resize_covered_region(mr); | |
3482 // Hmmmm... why doesn't CFLS::set_end verify locking? | |
3483 // This is quite ugly; FIX ME XXX | |
1145
e018e6884bd8
6631166: CMS: better heuristics when combatting fragmentation
ysr
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1085
diff
changeset
|
3484 _cmsSpace->assert_locked(freelistLock()); |
0 | 3485 _cmsSpace->set_end((HeapWord*)_virtual_space.high()); |
3486 | |
3487 // update the space and generation capacity counters | |
3488 if (UsePerfData) { | |
3489 _space_counters->update_capacity(); | |
3490 _gen_counters->update_all(); | |
3491 } | |
3492 | |
3493 if (Verbose && PrintGC) { | |
3494 size_t new_mem_size = _virtual_space.committed_size(); | |
3495 size_t old_mem_size = new_mem_size - bytes; | |
7623
203f64878aab
7102489: RFE: cleanup jlong typedef on __APPLE__and _LLP64 systems.
hseigel
parents:
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diff
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|
3496 gclog_or_tty->print_cr("Expanding %s from " SIZE_FORMAT "K by " SIZE_FORMAT "K to " SIZE_FORMAT "K", |
0 | 3497 name(), old_mem_size/K, bytes/K, new_mem_size/K); |
3498 } | |
3499 } | |
3500 return result; | |
3501 } | |
3502 | |
3503 bool ConcurrentMarkSweepGeneration::grow_to_reserved() { | |
3504 assert_locked_or_safepoint(Heap_lock); | |
3505 bool success = true; | |
3506 const size_t remaining_bytes = _virtual_space.uncommitted_size(); | |
3507 if (remaining_bytes > 0) { | |
3508 success = grow_by(remaining_bytes); | |
3509 DEBUG_ONLY(if (!success) warning("grow to reserved failed");) | |
3510 } | |
3511 return success; | |
3512 } | |
3513 | |
9072
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8008508: CMS does not correctly reduce heap size after a Full GC
jmasa
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8784
diff
changeset
|
3514 void ConcurrentMarkSweepGeneration::shrink_free_list_by(size_t bytes) { |
0 | 3515 assert_locked_or_safepoint(Heap_lock); |
3516 assert_lock_strong(freelistLock()); | |
10180
ebded0261dfc
8012111: Remove warning about CMS generation shrinking.
jmasa
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9152
diff
changeset
|
3517 if (PrintGCDetails && Verbose) { |
ebded0261dfc
8012111: Remove warning about CMS generation shrinking.
jmasa
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diff
changeset
|
3518 warning("Shrinking of CMS not yet implemented"); |
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|
3519 } |
0 | 3520 return; |
3521 } | |
3522 | |
3523 | |
3524 // Simple ctor/dtor wrapper for accounting & timer chores around concurrent | |
3525 // phases. | |
3526 class CMSPhaseAccounting: public StackObj { | |
3527 public: | |
3528 CMSPhaseAccounting(CMSCollector *collector, | |
3529 const char *phase, | |
3530 bool print_cr = true); | |
3531 ~CMSPhaseAccounting(); | |
3532 | |
3533 private: | |
3534 CMSCollector *_collector; | |
3535 const char *_phase; | |
3536 elapsedTimer _wallclock; | |
3537 bool _print_cr; | |
3538 | |
3539 public: | |
3540 // Not MT-safe; so do not pass around these StackObj's | |
3541 // where they may be accessed by other threads. | |
3542 jlong wallclock_millis() { | |
3543 assert(_wallclock.is_active(), "Wall clock should not stop"); | |
3544 _wallclock.stop(); // to record time | |
3545 jlong ret = _wallclock.milliseconds(); | |
3546 _wallclock.start(); // restart | |
3547 return ret; | |
3548 } | |
3549 }; | |
3550 | |
3551 CMSPhaseAccounting::CMSPhaseAccounting(CMSCollector *collector, | |
3552 const char *phase, | |
3553 bool print_cr) : | |
3554 _collector(collector), _phase(phase), _print_cr(print_cr) { | |
3555 | |
3556 if (PrintCMSStatistics != 0) { | |
3557 _collector->resetYields(); | |
3558 } | |
8740
62609ffa2fc6
8008684: CMS: concurrent phase start markers should always be printed
tschatzl
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8736
diff
changeset
|
3559 if (PrintGCDetails) { |
0 | 3560 gclog_or_tty->date_stamp(PrintGCDateStamps); |
8740
62609ffa2fc6
8008684: CMS: concurrent phase start markers should always be printed
tschatzl
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diff
changeset
|
3561 gclog_or_tty->stamp(PrintGCTimeStamps); |
62609ffa2fc6
8008684: CMS: concurrent phase start markers should always be printed
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8736
diff
changeset
|
3562 gclog_or_tty->print_cr("[%s-concurrent-%s-start]", |
0 | 3563 _collector->cmsGen()->short_name(), _phase); |
3564 } | |
3565 _collector->resetTimer(); | |
3566 _wallclock.start(); | |
3567 _collector->startTimer(); | |
3568 } | |
3569 | |
3570 CMSPhaseAccounting::~CMSPhaseAccounting() { | |
3571 assert(_wallclock.is_active(), "Wall clock should not have stopped"); | |
3572 _collector->stopTimer(); | |
3573 _wallclock.stop(); | |
3574 if (PrintGCDetails) { | |
3575 gclog_or_tty->date_stamp(PrintGCDateStamps); | |
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9646b7ff4d14
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diff
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|
3576 gclog_or_tty->stamp(PrintGCTimeStamps); |
0 | 3577 gclog_or_tty->print("[%s-concurrent-%s: %3.3f/%3.3f secs]", |
3578 _collector->cmsGen()->short_name(), | |
3579 _phase, _collector->timerValue(), _wallclock.seconds()); | |
3580 if (_print_cr) { | |
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diff
changeset
|
3581 gclog_or_tty->cr(); |
0 | 3582 } |
3583 if (PrintCMSStatistics != 0) { | |
3584 gclog_or_tty->print_cr(" (CMS-concurrent-%s yielded %d times)", _phase, | |
3585 _collector->yields()); | |
3586 } | |
3587 } | |
3588 } | |
3589 | |
3590 // CMS work | |
3591 | |
11975 | 3592 // The common parts of CMSParInitialMarkTask and CMSParRemarkTask. |
3593 class CMSParMarkTask : public AbstractGangTask { | |
3594 protected: | |
3595 CMSCollector* _collector; | |
3596 int _n_workers; | |
3597 CMSParMarkTask(const char* name, CMSCollector* collector, int n_workers) : | |
3598 AbstractGangTask(name), | |
3599 _collector(collector), | |
3600 _n_workers(n_workers) {} | |
3601 // Work method in support of parallel rescan ... of young gen spaces | |
3602 void do_young_space_rescan(uint worker_id, OopsInGenClosure* cl, | |
3603 ContiguousSpace* space, | |
3604 HeapWord** chunk_array, size_t chunk_top); | |
3605 void work_on_young_gen_roots(uint worker_id, OopsInGenClosure* cl); | |
3606 }; | |
3607 | |
3608 // Parallel initial mark task | |
3609 class CMSParInitialMarkTask: public CMSParMarkTask { | |
3610 public: | |
3611 CMSParInitialMarkTask(CMSCollector* collector, int n_workers) : | |
3612 CMSParMarkTask("Scan roots and young gen for initial mark in parallel", | |
3613 collector, n_workers) {} | |
3614 void work(uint worker_id); | |
3615 }; | |
3616 | |
0 | 3617 // Checkpoint the roots into this generation from outside |
3618 // this generation. [Note this initial checkpoint need only | |
3619 // be approximate -- we'll do a catch up phase subsequently.] | |
3620 void CMSCollector::checkpointRootsInitial(bool asynch) { | |
3621 assert(_collectorState == InitialMarking, "Wrong collector state"); | |
3622 check_correct_thread_executing(); | |
3356
78542e2b5e35
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3623 TraceCMSMemoryManagerStats tms(_collectorState,GenCollectedHeap::heap()->gc_cause()); |
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3624 |
10405 | 3625 save_heap_summary(); |
3626 report_heap_summary(GCWhen::BeforeGC); | |
3627 | |
0 | 3628 ReferenceProcessor* rp = ref_processor(); |
3629 SpecializationStats::clear(); | |
3630 assert(_restart_addr == NULL, "Control point invariant"); | |
3631 if (asynch) { | |
3632 // acquire locks for subsequent manipulations | |
3633 MutexLockerEx x(bitMapLock(), | |
3634 Mutex::_no_safepoint_check_flag); | |
3635 checkpointRootsInitialWork(asynch); | |
3979
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3636 // enable ("weak") refs discovery |
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3637 rp->enable_discovery(true /*verify_disabled*/, true /*check_no_refs*/); |
0 | 3638 _collectorState = Marking; |
3639 } else { | |
3640 // (Weak) Refs discovery: this is controlled from genCollectedHeap::do_collection | |
3641 // which recognizes if we are a CMS generation, and doesn't try to turn on | |
3642 // discovery; verify that they aren't meddling. | |
3643 assert(!rp->discovery_is_atomic(), | |
3644 "incorrect setting of discovery predicate"); | |
3645 assert(!rp->discovery_enabled(), "genCollectedHeap shouldn't control " | |
3646 "ref discovery for this generation kind"); | |
3647 // already have locks | |
3648 checkpointRootsInitialWork(asynch); | |
3979
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3649 // now enable ("weak") refs discovery |
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3650 rp->enable_discovery(true /*verify_disabled*/, false /*verify_no_refs*/); |
0 | 3651 _collectorState = Marking; |
3652 } | |
3653 SpecializationStats::print(); | |
3654 } | |
3655 | |
3656 void CMSCollector::checkpointRootsInitialWork(bool asynch) { | |
3657 assert(SafepointSynchronize::is_at_safepoint(), "world should be stopped"); | |
3658 assert(_collectorState == InitialMarking, "just checking"); | |
3659 | |
3660 // If there has not been a GC[n-1] since last GC[n] cycle completed, | |
3661 // precede our marking with a collection of all | |
3662 // younger generations to keep floating garbage to a minimum. | |
3663 // XXX: we won't do this for now -- it's an optimization to be done later. | |
3664 | |
3665 // already have locks | |
3666 assert_lock_strong(bitMapLock()); | |
3667 assert(_markBitMap.isAllClear(), "was reset at end of previous cycle"); | |
3668 | |
3669 // Setup the verification and class unloading state for this | |
3670 // CMS collection cycle. | |
3671 setup_cms_unloading_and_verification_state(); | |
3672 | |
10405 | 3673 NOT_PRODUCT(GCTraceTime t("\ncheckpointRootsInitialWork", |
3674 PrintGCDetails && Verbose, true, _gc_timer_cm);) | |
0 | 3675 if (UseAdaptiveSizePolicy) { |
3676 size_policy()->checkpoint_roots_initial_begin(); | |
3677 } | |
3678 | |
3679 // Reset all the PLAB chunk arrays if necessary. | |
3680 if (_survivor_plab_array != NULL && !CMSPLABRecordAlways) { | |
3681 reset_survivor_plab_arrays(); | |
3682 } | |
3683 | |
3684 ResourceMark rm; | |
3685 HandleMark hm; | |
3686 | |
3687 FalseClosure falseClosure; | |
3688 // In the case of a synchronous collection, we will elide the | |
3689 // remark step, so it's important to catch all the nmethod oops | |
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3690 // in this step. |
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3691 // The final 'true' flag to gen_process_strong_roots will ensure this. |
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3692 // If 'async' is true, we can relax the nmethod tracing. |
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3693 MarkRefsIntoClosure notOlder(_span, &_markBitMap); |
0 | 3694 GenCollectedHeap* gch = GenCollectedHeap::heap(); |
3695 | |
3696 verify_work_stacks_empty(); | |
3697 verify_overflow_empty(); | |
3698 | |
3699 gch->ensure_parsability(false); // fill TLABs, but no need to retire them | |
3700 // Update the saved marks which may affect the root scans. | |
3701 gch->save_marks(); | |
3702 | |
3703 // weak reference processing has not started yet. | |
3704 ref_processor()->set_enqueuing_is_done(false); | |
3705 | |
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3706 // Need to remember all newly created CLDs, |
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3707 // so that we can guarantee that the remark finds them. |
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3708 ClassLoaderDataGraph::remember_new_clds(true); |
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3709 |
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3710 // Whenever a CLD is found, it will be claimed before proceeding to mark |
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3711 // the klasses. The claimed marks need to be cleared before marking starts. |
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3712 ClassLoaderDataGraph::clear_claimed_marks(); |
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3713 |
11973
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3714 if (CMSPrintEdenSurvivorChunks) { |
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3715 print_eden_and_survivor_chunk_arrays(); |
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3716 } |
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3717 |
0 | 3718 { |
3719 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;) | |
11975 | 3720 if (CMSParallelInitialMarkEnabled && CollectedHeap::use_parallel_gc_threads()) { |
3721 // The parallel version. | |
3722 FlexibleWorkGang* workers = gch->workers(); | |
3723 assert(workers != NULL, "Need parallel worker threads."); | |
3724 int n_workers = workers->active_workers(); | |
3725 CMSParInitialMarkTask tsk(this, n_workers); | |
3726 gch->set_par_threads(n_workers); | |
3727 initialize_sequential_subtasks_for_young_gen_rescan(n_workers); | |
3728 if (n_workers > 1) { | |
3729 GenCollectedHeap::StrongRootsScope srs(gch); | |
3730 workers->run_task(&tsk); | |
3731 } else { | |
3732 GenCollectedHeap::StrongRootsScope srs(gch); | |
3733 tsk.work(0); | |
3734 } | |
3735 gch->set_par_threads(0); | |
3736 } else { | |
3737 // The serial version. | |
3738 CMKlassClosure klass_closure(¬Older); | |
3739 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. | |
3740 gch->gen_process_strong_roots(_cmsGen->level(), | |
3741 true, // younger gens are roots | |
3742 true, // activate StrongRootsScope | |
3743 false, // not scavenging | |
3744 SharedHeap::ScanningOption(roots_scanning_options()), | |
3745 ¬Older, | |
3746 true, // walk all of code cache if (so & SO_CodeCache) | |
3747 NULL, | |
3748 &klass_closure); | |
3749 } | |
0 | 3750 } |
3751 | |
3752 // Clear mod-union table; it will be dirtied in the prologue of | |
3753 // CMS generation per each younger generation collection. | |
3754 | |
3755 assert(_modUnionTable.isAllClear(), | |
3756 "Was cleared in most recent final checkpoint phase" | |
3757 " or no bits are set in the gc_prologue before the start of the next " | |
3758 "subsequent marking phase."); | |
3759 | |
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3760 assert(_ct->klass_rem_set()->mod_union_is_clear(), "Must be"); |
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3761 |
0 | 3762 // Save the end of the used_region of the constituent generations |
3763 // to be used to limit the extent of sweep in each generation. | |
3764 save_sweep_limits(); | |
3765 if (UseAdaptiveSizePolicy) { | |
3766 size_policy()->checkpoint_roots_initial_end(gch->gc_cause()); | |
3767 } | |
3768 verify_overflow_empty(); | |
3769 } | |
3770 | |
3771 bool CMSCollector::markFromRoots(bool asynch) { | |
3772 // we might be tempted to assert that: | |
3773 // assert(asynch == !SafepointSynchronize::is_at_safepoint(), | |
3774 // "inconsistent argument?"); | |
3775 // However that wouldn't be right, because it's possible that | |
3776 // a safepoint is indeed in progress as a younger generation | |
3777 // stop-the-world GC happens even as we mark in this generation. | |
3778 assert(_collectorState == Marking, "inconsistent state?"); | |
3779 check_correct_thread_executing(); | |
3780 verify_overflow_empty(); | |
3781 | |
3782 bool res; | |
3783 if (asynch) { | |
3784 | |
3785 // Start the timers for adaptive size policy for the concurrent phases | |
3786 // Do it here so that the foreground MS can use the concurrent | |
3787 // timer since a foreground MS might has the sweep done concurrently | |
3788 // or STW. | |
3789 if (UseAdaptiveSizePolicy) { | |
3790 size_policy()->concurrent_marking_begin(); | |
3791 } | |
3792 | |
3793 // Weak ref discovery note: We may be discovering weak | |
3794 // refs in this generation concurrent (but interleaved) with | |
3795 // weak ref discovery by a younger generation collector. | |
3796 | |
3797 CMSTokenSyncWithLocks ts(true, bitMapLock()); | |
3798 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
3799 CMSPhaseAccounting pa(this, "mark", !PrintGCDetails); | |
3800 res = markFromRootsWork(asynch); | |
3801 if (res) { | |
3802 _collectorState = Precleaning; | |
3803 } else { // We failed and a foreground collection wants to take over | |
3804 assert(_foregroundGCIsActive, "internal state inconsistency"); | |
3805 assert(_restart_addr == NULL, "foreground will restart from scratch"); | |
3806 if (PrintGCDetails) { | |
3807 gclog_or_tty->print_cr("bailing out to foreground collection"); | |
3808 } | |
3809 } | |
3810 if (UseAdaptiveSizePolicy) { | |
3811 size_policy()->concurrent_marking_end(); | |
3812 } | |
3813 } else { | |
3814 assert(SafepointSynchronize::is_at_safepoint(), | |
3815 "inconsistent with asynch == false"); | |
3816 if (UseAdaptiveSizePolicy) { | |
3817 size_policy()->ms_collection_marking_begin(); | |
3818 } | |
3819 // already have locks | |
3820 res = markFromRootsWork(asynch); | |
3821 _collectorState = FinalMarking; | |
3822 if (UseAdaptiveSizePolicy) { | |
3823 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
3824 size_policy()->ms_collection_marking_end(gch->gc_cause()); | |
3825 } | |
3826 } | |
3827 verify_overflow_empty(); | |
3828 return res; | |
3829 } | |
3830 | |
3831 bool CMSCollector::markFromRootsWork(bool asynch) { | |
3832 // iterate over marked bits in bit map, doing a full scan and mark | |
3833 // from these roots using the following algorithm: | |
3834 // . if oop is to the right of the current scan pointer, | |
3835 // mark corresponding bit (we'll process it later) | |
3836 // . else (oop is to left of current scan pointer) | |
3837 // push oop on marking stack | |
3838 // . drain the marking stack | |
3839 | |
3840 // Note that when we do a marking step we need to hold the | |
3841 // bit map lock -- recall that direct allocation (by mutators) | |
3842 // and promotion (by younger generation collectors) is also | |
3843 // marking the bit map. [the so-called allocate live policy.] | |
3844 // Because the implementation of bit map marking is not | |
3845 // robust wrt simultaneous marking of bits in the same word, | |
3846 // we need to make sure that there is no such interference | |
3847 // between concurrent such updates. | |
3848 | |
3849 // already have locks | |
3850 assert_lock_strong(bitMapLock()); | |
3851 | |
3852 verify_work_stacks_empty(); | |
3853 verify_overflow_empty(); | |
3854 bool result = false; | |
1284 | 3855 if (CMSConcurrentMTEnabled && ConcGCThreads > 0) { |
0 | 3856 result = do_marking_mt(asynch); |
3857 } else { | |
3858 result = do_marking_st(asynch); | |
3859 } | |
3860 return result; | |
3861 } | |
3862 | |
3863 // Forward decl | |
3864 class CMSConcMarkingTask; | |
3865 | |
3866 class CMSConcMarkingTerminator: public ParallelTaskTerminator { | |
3867 CMSCollector* _collector; | |
3868 CMSConcMarkingTask* _task; | |
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3869 public: |
0 | 3870 virtual void yield(); |
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3871 |
0 | 3872 // "n_threads" is the number of threads to be terminated. |
3873 // "queue_set" is a set of work queues of other threads. | |
3874 // "collector" is the CMS collector associated with this task terminator. | |
3875 // "yield" indicates whether we need the gang as a whole to yield. | |
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3876 CMSConcMarkingTerminator(int n_threads, TaskQueueSetSuper* queue_set, CMSCollector* collector) : |
0 | 3877 ParallelTaskTerminator(n_threads, queue_set), |
1837
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3878 _collector(collector) { } |
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3879 |
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3880 void set_task(CMSConcMarkingTask* task) { |
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3881 _task = task; |
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3882 } |
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3883 }; |
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3884 |
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3885 class CMSConcMarkingTerminatorTerminator: public TerminatorTerminator { |
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3886 CMSConcMarkingTask* _task; |
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3887 public: |
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3888 bool should_exit_termination(); |
0 | 3889 void set_task(CMSConcMarkingTask* task) { |
3890 _task = task; | |
3891 } | |
3892 }; | |
3893 | |
3894 // MT Concurrent Marking Task | |
3895 class CMSConcMarkingTask: public YieldingFlexibleGangTask { | |
3896 CMSCollector* _collector; | |
3897 int _n_workers; // requested/desired # workers | |
3898 bool _asynch; | |
3899 bool _result; | |
3900 CompactibleFreeListSpace* _cms_space; | |
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3901 char _pad_front[64]; // padding to ... |
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3902 HeapWord* _global_finger; // ... avoid sharing cache line |
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3903 char _pad_back[64]; |
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3904 HeapWord* _restart_addr; |
0 | 3905 |
3906 // Exposed here for yielding support | |
3907 Mutex* const _bit_map_lock; | |
3908 | |
3909 // The per thread work queues, available here for stealing | |
3910 OopTaskQueueSet* _task_queues; | |
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3911 |
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3912 // Termination (and yielding) support |
0 | 3913 CMSConcMarkingTerminator _term; |
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3914 CMSConcMarkingTerminatorTerminator _term_term; |
0 | 3915 |
3916 public: | |
3917 CMSConcMarkingTask(CMSCollector* collector, | |
3918 CompactibleFreeListSpace* cms_space, | |
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3919 bool asynch, |
0 | 3920 YieldingFlexibleWorkGang* workers, |
3921 OopTaskQueueSet* task_queues): | |
3922 YieldingFlexibleGangTask("Concurrent marking done multi-threaded"), | |
3923 _collector(collector), | |
3924 _cms_space(cms_space), | |
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3925 _asynch(asynch), _n_workers(0), _result(true), |
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3926 _task_queues(task_queues), |
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3927 _term(_n_workers, task_queues, _collector), |
0 | 3928 _bit_map_lock(collector->bitMapLock()) |
3929 { | |
1833
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3930 _requested_size = _n_workers; |
0 | 3931 _term.set_task(this); |
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3932 _term_term.set_task(this); |
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3933 _restart_addr = _global_finger = _cms_space->bottom(); |
0 | 3934 } |
3935 | |
3936 | |
3937 OopTaskQueueSet* task_queues() { return _task_queues; } | |
3938 | |
3939 OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); } | |
3940 | |
3941 HeapWord** global_finger_addr() { return &_global_finger; } | |
3942 | |
3943 CMSConcMarkingTerminator* terminator() { return &_term; } | |
3944 | |
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3945 virtual void set_for_termination(int active_workers) { |
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3946 terminator()->reset_for_reuse(active_workers); |
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3947 } |
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3948 |
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3949 void work(uint worker_id); |
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3950 bool should_yield() { |
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3951 return ConcurrentMarkSweepThread::should_yield() |
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3952 && !_collector->foregroundGCIsActive() |
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3953 && _asynch; |
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3954 } |
0 | 3955 |
3956 virtual void coordinator_yield(); // stuff done by coordinator | |
3957 bool result() { return _result; } | |
3958 | |
3959 void reset(HeapWord* ra) { | |
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3960 assert(_global_finger >= _cms_space->end(), "Postcondition of ::work(i)"); |
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3961 _restart_addr = _global_finger = ra; |
0 | 3962 _term.reset_for_reuse(); |
3963 } | |
3964 | |
3965 static bool get_work_from_overflow_stack(CMSMarkStack* ovflw_stk, | |
3966 OopTaskQueue* work_q); | |
3967 | |
3968 private: | |
3969 void do_scan_and_mark(int i, CompactibleFreeListSpace* sp); | |
3970 void do_work_steal(int i); | |
3971 void bump_global_finger(HeapWord* f); | |
3972 }; | |
3973 | |
1837
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3974 bool CMSConcMarkingTerminatorTerminator::should_exit_termination() { |
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3975 assert(_task != NULL, "Error"); |
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3976 return _task->yielding(); |
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3977 // Note that we do not need the disjunct || _task->should_yield() above |
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3978 // because we want terminating threads to yield only if the task |
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3979 // is already in the midst of yielding, which happens only after at least one |
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3980 // thread has yielded. |
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3981 } |
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3982 |
0 | 3983 void CMSConcMarkingTerminator::yield() { |
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3984 if (_task->should_yield()) { |
0 | 3985 _task->yield(); |
3986 } else { | |
3987 ParallelTaskTerminator::yield(); | |
3988 } | |
3989 } | |
3990 | |
3991 //////////////////////////////////////////////////////////////// | |
3992 // Concurrent Marking Algorithm Sketch | |
3993 //////////////////////////////////////////////////////////////// | |
3994 // Until all tasks exhausted (both spaces): | |
3995 // -- claim next available chunk | |
3996 // -- bump global finger via CAS | |
3997 // -- find first object that starts in this chunk | |
3998 // and start scanning bitmap from that position | |
3999 // -- scan marked objects for oops | |
4000 // -- CAS-mark target, and if successful: | |
4001 // . if target oop is above global finger (volatile read) | |
4002 // nothing to do | |
4003 // . if target oop is in chunk and above local finger | |
4004 // then nothing to do | |
4005 // . else push on work-queue | |
4006 // -- Deal with possible overflow issues: | |
4007 // . local work-queue overflow causes stuff to be pushed on | |
4008 // global (common) overflow queue | |
4009 // . always first empty local work queue | |
4010 // . then get a batch of oops from global work queue if any | |
4011 // . then do work stealing | |
4012 // -- When all tasks claimed (both spaces) | |
4013 // and local work queue empty, | |
4014 // then in a loop do: | |
4015 // . check global overflow stack; steal a batch of oops and trace | |
4016 // . try to steal from other threads oif GOS is empty | |
4017 // . if neither is available, offer termination | |
4018 // -- Terminate and return result | |
4019 // | |
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4020 void CMSConcMarkingTask::work(uint worker_id) { |
0 | 4021 elapsedTimer _timer; |
4022 ResourceMark rm; | |
4023 HandleMark hm; | |
4024 | |
4025 DEBUG_ONLY(_collector->verify_overflow_empty();) | |
4026 | |
4027 // Before we begin work, our work queue should be empty | |
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4028 assert(work_queue(worker_id)->size() == 0, "Expected to be empty"); |
0 | 4029 // Scan the bitmap covering _cms_space, tracing through grey objects. |
4030 _timer.start(); | |
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4031 do_scan_and_mark(worker_id, _cms_space); |
0 | 4032 _timer.stop(); |
4033 if (PrintCMSStatistics != 0) { | |
4034 gclog_or_tty->print_cr("Finished cms space scanning in %dth thread: %3.3f sec", | |
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4035 worker_id, _timer.seconds()); |
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4036 // XXX: need xxx/xxx type of notation, two timers |
0 | 4037 } |
4038 | |
4039 // ... do work stealing | |
4040 _timer.reset(); | |
4041 _timer.start(); | |
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4042 do_work_steal(worker_id); |
0 | 4043 _timer.stop(); |
4044 if (PrintCMSStatistics != 0) { | |
4045 gclog_or_tty->print_cr("Finished work stealing in %dth thread: %3.3f sec", | |
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4046 worker_id, _timer.seconds()); |
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4047 // XXX: need xxx/xxx type of notation, two timers |
0 | 4048 } |
4049 assert(_collector->_markStack.isEmpty(), "Should have been emptied"); | |
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4050 assert(work_queue(worker_id)->size() == 0, "Should have been emptied"); |
0 | 4051 // Note that under the current task protocol, the |
4052 // following assertion is true even of the spaces | |
4053 // expanded since the completion of the concurrent | |
4054 // marking. XXX This will likely change under a strict | |
4055 // ABORT semantics. | |
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4056 // After perm removal the comparison was changed to |
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4057 // greater than or equal to from strictly greater than. |
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4058 // Before perm removal the highest address sweep would |
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4059 // have been at the end of perm gen but now is at the |
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4060 // end of the tenured gen. |
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4061 assert(_global_finger >= _cms_space->end(), |
0 | 4062 "All tasks have been completed"); |
4063 DEBUG_ONLY(_collector->verify_overflow_empty();) | |
4064 } | |
4065 | |
4066 void CMSConcMarkingTask::bump_global_finger(HeapWord* f) { | |
4067 HeapWord* read = _global_finger; | |
4068 HeapWord* cur = read; | |
4069 while (f > read) { | |
4070 cur = read; | |
4071 read = (HeapWord*) Atomic::cmpxchg_ptr(f, &_global_finger, cur); | |
4072 if (cur == read) { | |
4073 // our cas succeeded | |
4074 assert(_global_finger >= f, "protocol consistency"); | |
4075 break; | |
4076 } | |
4077 } | |
4078 } | |
4079 | |
4080 // This is really inefficient, and should be redone by | |
4081 // using (not yet available) block-read and -write interfaces to the | |
4082 // stack and the work_queue. XXX FIX ME !!! | |
4083 bool CMSConcMarkingTask::get_work_from_overflow_stack(CMSMarkStack* ovflw_stk, | |
4084 OopTaskQueue* work_q) { | |
4085 // Fast lock-free check | |
4086 if (ovflw_stk->length() == 0) { | |
4087 return false; | |
4088 } | |
4089 assert(work_q->size() == 0, "Shouldn't steal"); | |
4090 MutexLockerEx ml(ovflw_stk->par_lock(), | |
4091 Mutex::_no_safepoint_check_flag); | |
4092 // Grab up to 1/4 the size of the work queue | |
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4093 size_t num = MIN2((size_t)(work_q->max_elems() - work_q->size())/4, |
0 | 4094 (size_t)ParGCDesiredObjsFromOverflowList); |
4095 num = MIN2(num, ovflw_stk->length()); | |
4096 for (int i = (int) num; i > 0; i--) { | |
4097 oop cur = ovflw_stk->pop(); | |
4098 assert(cur != NULL, "Counted wrong?"); | |
4099 work_q->push(cur); | |
4100 } | |
4101 return num > 0; | |
4102 } | |
4103 | |
4104 void CMSConcMarkingTask::do_scan_and_mark(int i, CompactibleFreeListSpace* sp) { | |
4105 SequentialSubTasksDone* pst = sp->conc_par_seq_tasks(); | |
4106 int n_tasks = pst->n_tasks(); | |
4107 // We allow that there may be no tasks to do here because | |
4108 // we are restarting after a stack overflow. | |
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4109 assert(pst->valid() || n_tasks == 0, "Uninitialized use?"); |
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4110 uint nth_task = 0; |
0 | 4111 |
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4112 HeapWord* aligned_start = sp->bottom(); |
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4113 if (sp->used_region().contains(_restart_addr)) { |
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4114 // Align down to a card boundary for the start of 0th task |
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4115 // for this space. |
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4116 aligned_start = |
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4117 (HeapWord*)align_size_down((uintptr_t)_restart_addr, |
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4118 CardTableModRefBS::card_size); |
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4119 } |
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4120 |
0 | 4121 size_t chunk_size = sp->marking_task_size(); |
4122 while (!pst->is_task_claimed(/* reference */ nth_task)) { | |
4123 // Having claimed the nth task in this space, | |
4124 // compute the chunk that it corresponds to: | |
340
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4125 MemRegion span = MemRegion(aligned_start + nth_task*chunk_size, |
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4126 aligned_start + (nth_task+1)*chunk_size); |
0 | 4127 // Try and bump the global finger via a CAS; |
4128 // note that we need to do the global finger bump | |
4129 // _before_ taking the intersection below, because | |
4130 // the task corresponding to that region will be | |
4131 // deemed done even if the used_region() expands | |
4132 // because of allocation -- as it almost certainly will | |
4133 // during start-up while the threads yield in the | |
4134 // closure below. | |
4135 HeapWord* finger = span.end(); | |
4136 bump_global_finger(finger); // atomically | |
4137 // There are null tasks here corresponding to chunks | |
4138 // beyond the "top" address of the space. | |
4139 span = span.intersection(sp->used_region()); | |
4140 if (!span.is_empty()) { // Non-null task | |
340
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4141 HeapWord* prev_obj; |
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4142 assert(!span.contains(_restart_addr) || nth_task == 0, |
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4143 "Inconsistency"); |
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4144 if (nth_task == 0) { |
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4145 // For the 0th task, we'll not need to compute a block_start. |
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4146 if (span.contains(_restart_addr)) { |
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4147 // In the case of a restart because of stack overflow, |
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4148 // we might additionally skip a chunk prefix. |
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4149 prev_obj = _restart_addr; |
0 | 4150 } else { |
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4151 prev_obj = span.start(); |
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4152 } |
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4153 } else { |
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4154 // We want to skip the first object because |
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4155 // the protocol is to scan any object in its entirety |
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4156 // that _starts_ in this span; a fortiori, any |
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4157 // object starting in an earlier span is scanned |
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4158 // as part of an earlier claimed task. |
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4159 // Below we use the "careful" version of block_start |
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4160 // so we do not try to navigate uninitialized objects. |
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4161 prev_obj = sp->block_start_careful(span.start()); |
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4162 // Below we use a variant of block_size that uses the |
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4163 // Printezis bits to avoid waiting for allocated |
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4164 // objects to become initialized/parsable. |
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4165 while (prev_obj < span.start()) { |
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4166 size_t sz = sp->block_size_no_stall(prev_obj, _collector); |
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4167 if (sz > 0) { |
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4168 prev_obj += sz; |
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4169 } else { |
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4170 // In this case we may end up doing a bit of redundant |
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4171 // scanning, but that appears unavoidable, short of |
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4172 // locking the free list locks; see bug 6324141. |
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4173 break; |
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4174 } |
0 | 4175 } |
4176 } | |
4177 if (prev_obj < span.end()) { | |
4178 MemRegion my_span = MemRegion(prev_obj, span.end()); | |
4179 // Do the marking work within a non-empty span -- | |
4180 // the last argument to the constructor indicates whether the | |
4181 // iteration should be incremental with periodic yields. | |
4182 Par_MarkFromRootsClosure cl(this, _collector, my_span, | |
4183 &_collector->_markBitMap, | |
4184 work_queue(i), | |
4185 &_collector->_markStack, | |
4186 _asynch); | |
4187 _collector->_markBitMap.iterate(&cl, my_span.start(), my_span.end()); | |
4188 } // else nothing to do for this task | |
4189 } // else nothing to do for this task | |
4190 } | |
4191 // We'd be tempted to assert here that since there are no | |
4192 // more tasks left to claim in this space, the global_finger | |
4193 // must exceed space->top() and a fortiori space->end(). However, | |
4194 // that would not quite be correct because the bumping of | |
4195 // global_finger occurs strictly after the claiming of a task, | |
4196 // so by the time we reach here the global finger may not yet | |
4197 // have been bumped up by the thread that claimed the last | |
4198 // task. | |
4199 pst->all_tasks_completed(); | |
4200 } | |
4201 | |
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4202 class Par_ConcMarkingClosure: public CMSOopClosure { |
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4203 private: |
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4204 CMSCollector* _collector; |
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4205 CMSConcMarkingTask* _task; |
0 | 4206 MemRegion _span; |
4207 CMSBitMap* _bit_map; | |
4208 CMSMarkStack* _overflow_stack; | |
4209 OopTaskQueue* _work_queue; | |
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4210 protected: |
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4211 DO_OOP_WORK_DEFN |
0 | 4212 public: |
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4213 Par_ConcMarkingClosure(CMSCollector* collector, CMSConcMarkingTask* task, OopTaskQueue* work_queue, |
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4214 CMSBitMap* bit_map, CMSMarkStack* overflow_stack): |
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4215 CMSOopClosure(collector->ref_processor()), |
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4216 _collector(collector), |
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4217 _task(task), |
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4218 _span(collector->_span), |
0 | 4219 _work_queue(work_queue), |
4220 _bit_map(bit_map), | |
935 | 4221 _overflow_stack(overflow_stack) |
4222 { } | |
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4223 virtual void do_oop(oop* p); |
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4224 virtual void do_oop(narrowOop* p); |
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4225 |
0 | 4226 void trim_queue(size_t max); |
4227 void handle_stack_overflow(HeapWord* lost); | |
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4228 void do_yield_check() { |
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4229 if (_task->should_yield()) { |
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4230 _task->yield(); |
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4231 } |
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4232 } |
0 | 4233 }; |
4234 | |
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4235 // Grey object scanning during work stealing phase -- |
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4236 // the salient assumption here is that any references |
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4237 // that are in these stolen objects being scanned must |
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4238 // already have been initialized (else they would not have |
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4239 // been published), so we do not need to check for |
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4240 // uninitialized objects before pushing here. |
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4241 void Par_ConcMarkingClosure::do_oop(oop obj) { |
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4242 assert(obj->is_oop_or_null(true), "expected an oop or NULL"); |
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4243 HeapWord* addr = (HeapWord*)obj; |
0 | 4244 // Check if oop points into the CMS generation |
4245 // and is not marked | |
4246 if (_span.contains(addr) && !_bit_map->isMarked(addr)) { | |
4247 // a white object ... | |
4248 // If we manage to "claim" the object, by being the | |
4249 // first thread to mark it, then we push it on our | |
4250 // marking stack | |
4251 if (_bit_map->par_mark(addr)) { // ... now grey | |
4252 // push on work queue (grey set) | |
4253 bool simulate_overflow = false; | |
4254 NOT_PRODUCT( | |
4255 if (CMSMarkStackOverflowALot && | |
4256 _collector->simulate_overflow()) { | |
4257 // simulate a stack overflow | |
4258 simulate_overflow = true; | |
4259 } | |
4260 ) | |
4261 if (simulate_overflow || | |
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4262 !(_work_queue->push(obj) || _overflow_stack->par_push(obj))) { |
0 | 4263 // stack overflow |
4264 if (PrintCMSStatistics != 0) { | |
4265 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
4266 SIZE_FORMAT, _overflow_stack->capacity()); | |
4267 } | |
4268 // We cannot assert that the overflow stack is full because | |
4269 // it may have been emptied since. | |
4270 assert(simulate_overflow || | |
4271 _work_queue->size() == _work_queue->max_elems(), | |
4272 "Else push should have succeeded"); | |
4273 handle_stack_overflow(addr); | |
4274 } | |
4275 } // Else, some other thread got there first | |
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4276 do_yield_check(); |
0 | 4277 } |
4278 } | |
4279 | |
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4280 void Par_ConcMarkingClosure::do_oop(oop* p) { Par_ConcMarkingClosure::do_oop_work(p); } |
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4281 void Par_ConcMarkingClosure::do_oop(narrowOop* p) { Par_ConcMarkingClosure::do_oop_work(p); } |
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4282 |
0 | 4283 void Par_ConcMarkingClosure::trim_queue(size_t max) { |
4284 while (_work_queue->size() > max) { | |
4285 oop new_oop; | |
4286 if (_work_queue->pop_local(new_oop)) { | |
4287 assert(new_oop->is_oop(), "Should be an oop"); | |
4288 assert(_bit_map->isMarked((HeapWord*)new_oop), "Grey object"); | |
4289 assert(_span.contains((HeapWord*)new_oop), "Not in span"); | |
4290 new_oop->oop_iterate(this); // do_oop() above | |
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4291 do_yield_check(); |
0 | 4292 } |
4293 } | |
4294 } | |
4295 | |
4296 // Upon stack overflow, we discard (part of) the stack, | |
4297 // remembering the least address amongst those discarded | |
4298 // in CMSCollector's _restart_address. | |
4299 void Par_ConcMarkingClosure::handle_stack_overflow(HeapWord* lost) { | |
4300 // We need to do this under a mutex to prevent other | |
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4301 // workers from interfering with the work done below. |
0 | 4302 MutexLockerEx ml(_overflow_stack->par_lock(), |
4303 Mutex::_no_safepoint_check_flag); | |
4304 // Remember the least grey address discarded | |
4305 HeapWord* ra = (HeapWord*)_overflow_stack->least_value(lost); | |
4306 _collector->lower_restart_addr(ra); | |
4307 _overflow_stack->reset(); // discard stack contents | |
4308 _overflow_stack->expand(); // expand the stack if possible | |
4309 } | |
4310 | |
4311 | |
4312 void CMSConcMarkingTask::do_work_steal(int i) { | |
4313 OopTaskQueue* work_q = work_queue(i); | |
4314 oop obj_to_scan; | |
4315 CMSBitMap* bm = &(_collector->_markBitMap); | |
4316 CMSMarkStack* ovflw = &(_collector->_markStack); | |
4317 int* seed = _collector->hash_seed(i); | |
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4318 Par_ConcMarkingClosure cl(_collector, this, work_q, bm, ovflw); |
0 | 4319 while (true) { |
4320 cl.trim_queue(0); | |
4321 assert(work_q->size() == 0, "Should have been emptied above"); | |
4322 if (get_work_from_overflow_stack(ovflw, work_q)) { | |
4323 // Can't assert below because the work obtained from the | |
4324 // overflow stack may already have been stolen from us. | |
4325 // assert(work_q->size() > 0, "Work from overflow stack"); | |
4326 continue; | |
4327 } else if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) { | |
4328 assert(obj_to_scan->is_oop(), "Should be an oop"); | |
4329 assert(bm->isMarked((HeapWord*)obj_to_scan), "Grey object"); | |
4330 obj_to_scan->oop_iterate(&cl); | |
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4331 } else if (terminator()->offer_termination(&_term_term)) { |
0 | 4332 assert(work_q->size() == 0, "Impossible!"); |
4333 break; | |
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4334 } else if (yielding() || should_yield()) { |
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4335 yield(); |
0 | 4336 } |
4337 } | |
4338 } | |
4339 | |
4340 // This is run by the CMS (coordinator) thread. | |
4341 void CMSConcMarkingTask::coordinator_yield() { | |
4342 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
4343 "CMS thread should hold CMS token"); | |
4344 // First give up the locks, then yield, then re-lock | |
4345 // We should probably use a constructor/destructor idiom to | |
4346 // do this unlock/lock or modify the MutexUnlocker class to | |
4347 // serve our purpose. XXX | |
4348 assert_lock_strong(_bit_map_lock); | |
4349 _bit_map_lock->unlock(); | |
4350 ConcurrentMarkSweepThread::desynchronize(true); | |
4351 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
4352 _collector->stopTimer(); | |
4353 if (PrintCMSStatistics != 0) { | |
4354 _collector->incrementYields(); | |
4355 } | |
4356 _collector->icms_wait(); | |
4357 | |
4358 // It is possible for whichever thread initiated the yield request | |
4359 // not to get a chance to wake up and take the bitmap lock between | |
4360 // this thread releasing it and reacquiring it. So, while the | |
4361 // should_yield() flag is on, let's sleep for a bit to give the | |
4362 // other thread a chance to wake up. The limit imposed on the number | |
4363 // of iterations is defensive, to avoid any unforseen circumstances | |
4364 // putting us into an infinite loop. Since it's always been this | |
4365 // (coordinator_yield()) method that was observed to cause the | |
4366 // problem, we are using a parameter (CMSCoordinatorYieldSleepCount) | |
4367 // which is by default non-zero. For the other seven methods that | |
4368 // also perform the yield operation, as are using a different | |
4369 // parameter (CMSYieldSleepCount) which is by default zero. This way we | |
4370 // can enable the sleeping for those methods too, if necessary. | |
4371 // See 6442774. | |
4372 // | |
4373 // We really need to reconsider the synchronization between the GC | |
4374 // thread and the yield-requesting threads in the future and we | |
4375 // should really use wait/notify, which is the recommended | |
4376 // way of doing this type of interaction. Additionally, we should | |
4377 // consolidate the eight methods that do the yield operation and they | |
4378 // are almost identical into one for better maintenability and | |
4379 // readability. See 6445193. | |
4380 // | |
4381 // Tony 2006.06.29 | |
4382 for (unsigned i = 0; i < CMSCoordinatorYieldSleepCount && | |
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4383 ConcurrentMarkSweepThread::should_yield() && |
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4384 !CMSCollector::foregroundGCIsActive(); ++i) { |
0 | 4385 os::sleep(Thread::current(), 1, false); |
4386 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
4387 } | |
4388 | |
4389 ConcurrentMarkSweepThread::synchronize(true); | |
4390 _bit_map_lock->lock_without_safepoint_check(); | |
4391 _collector->startTimer(); | |
4392 } | |
4393 | |
4394 bool CMSCollector::do_marking_mt(bool asynch) { | |
1284 | 4395 assert(ConcGCThreads > 0 && conc_workers() != NULL, "precondition"); |
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4396 int num_workers = AdaptiveSizePolicy::calc_active_conc_workers( |
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4397 conc_workers()->total_workers(), |
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4398 conc_workers()->active_workers(), |
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4399 Threads::number_of_non_daemon_threads()); |
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4400 conc_workers()->set_active_workers(num_workers); |
0 | 4401 |
4402 CompactibleFreeListSpace* cms_space = _cmsGen->cmsSpace(); | |
4403 | |
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4404 CMSConcMarkingTask tsk(this, |
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4405 cms_space, |
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4406 asynch, |
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4407 conc_workers(), |
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4408 task_queues()); |
0 | 4409 |
4410 // Since the actual number of workers we get may be different | |
4411 // from the number we requested above, do we need to do anything different | |
4412 // below? In particular, may be we need to subclass the SequantialSubTasksDone | |
4413 // class?? XXX | |
4414 cms_space ->initialize_sequential_subtasks_for_marking(num_workers); | |
4415 | |
4416 // Refs discovery is already non-atomic. | |
4417 assert(!ref_processor()->discovery_is_atomic(), "Should be non-atomic"); | |
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4418 assert(ref_processor()->discovery_is_mt(), "Discovery should be MT"); |
0 | 4419 conc_workers()->start_task(&tsk); |
4420 while (tsk.yielded()) { | |
4421 tsk.coordinator_yield(); | |
4422 conc_workers()->continue_task(&tsk); | |
4423 } | |
4424 // If the task was aborted, _restart_addr will be non-NULL | |
4425 assert(tsk.completed() || _restart_addr != NULL, "Inconsistency"); | |
4426 while (_restart_addr != NULL) { | |
4427 // XXX For now we do not make use of ABORTED state and have not | |
4428 // yet implemented the right abort semantics (even in the original | |
4429 // single-threaded CMS case). That needs some more investigation | |
4430 // and is deferred for now; see CR# TBF. 07252005YSR. XXX | |
4431 assert(!CMSAbortSemantics || tsk.aborted(), "Inconsistency"); | |
4432 // If _restart_addr is non-NULL, a marking stack overflow | |
605 | 4433 // occurred; we need to do a fresh marking iteration from the |
0 | 4434 // indicated restart address. |
4435 if (_foregroundGCIsActive && asynch) { | |
4436 // We may be running into repeated stack overflows, having | |
4437 // reached the limit of the stack size, while making very | |
4438 // slow forward progress. It may be best to bail out and | |
4439 // let the foreground collector do its job. | |
4440 // Clear _restart_addr, so that foreground GC | |
4441 // works from scratch. This avoids the headache of | |
4442 // a "rescan" which would otherwise be needed because | |
4443 // of the dirty mod union table & card table. | |
4444 _restart_addr = NULL; | |
4445 return false; | |
4446 } | |
4447 // Adjust the task to restart from _restart_addr | |
4448 tsk.reset(_restart_addr); | |
4449 cms_space ->initialize_sequential_subtasks_for_marking(num_workers, | |
4450 _restart_addr); | |
4451 _restart_addr = NULL; | |
4452 // Get the workers going again | |
4453 conc_workers()->start_task(&tsk); | |
4454 while (tsk.yielded()) { | |
4455 tsk.coordinator_yield(); | |
4456 conc_workers()->continue_task(&tsk); | |
4457 } | |
4458 } | |
4459 assert(tsk.completed(), "Inconsistency"); | |
4460 assert(tsk.result() == true, "Inconsistency"); | |
4461 return true; | |
4462 } | |
4463 | |
4464 bool CMSCollector::do_marking_st(bool asynch) { | |
4465 ResourceMark rm; | |
4466 HandleMark hm; | |
4467 | |
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4468 // Temporarily make refs discovery single threaded (non-MT) |
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4469 ReferenceProcessorMTDiscoveryMutator rp_mut_discovery(ref_processor(), false); |
0 | 4470 MarkFromRootsClosure markFromRootsClosure(this, _span, &_markBitMap, |
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4471 &_markStack, CMSYield && asynch); |
0 | 4472 // the last argument to iterate indicates whether the iteration |
4473 // should be incremental with periodic yields. | |
4474 _markBitMap.iterate(&markFromRootsClosure); | |
4475 // If _restart_addr is non-NULL, a marking stack overflow | |
605 | 4476 // occurred; we need to do a fresh iteration from the |
0 | 4477 // indicated restart address. |
4478 while (_restart_addr != NULL) { | |
4479 if (_foregroundGCIsActive && asynch) { | |
4480 // We may be running into repeated stack overflows, having | |
4481 // reached the limit of the stack size, while making very | |
4482 // slow forward progress. It may be best to bail out and | |
4483 // let the foreground collector do its job. | |
4484 // Clear _restart_addr, so that foreground GC | |
4485 // works from scratch. This avoids the headache of | |
4486 // a "rescan" which would otherwise be needed because | |
4487 // of the dirty mod union table & card table. | |
4488 _restart_addr = NULL; | |
4489 return false; // indicating failure to complete marking | |
4490 } | |
4491 // Deal with stack overflow: | |
4492 // we restart marking from _restart_addr | |
4493 HeapWord* ra = _restart_addr; | |
4494 markFromRootsClosure.reset(ra); | |
4495 _restart_addr = NULL; | |
4496 _markBitMap.iterate(&markFromRootsClosure, ra, _span.end()); | |
4497 } | |
4498 return true; | |
4499 } | |
4500 | |
4501 void CMSCollector::preclean() { | |
4502 check_correct_thread_executing(); | |
4503 assert(Thread::current()->is_ConcurrentGC_thread(), "Wrong thread"); | |
4504 verify_work_stacks_empty(); | |
4505 verify_overflow_empty(); | |
4506 _abort_preclean = false; | |
4507 if (CMSPrecleaningEnabled) { | |
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4508 if (!CMSEdenChunksRecordAlways) { |
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4509 _eden_chunk_index = 0; |
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4510 } |
0 | 4511 size_t used = get_eden_used(); |
4512 size_t capacity = get_eden_capacity(); | |
4513 // Don't start sampling unless we will get sufficiently | |
4514 // many samples. | |
4515 if (used < (capacity/(CMSScheduleRemarkSamplingRatio * 100) | |
4516 * CMSScheduleRemarkEdenPenetration)) { | |
4517 _start_sampling = true; | |
4518 } else { | |
4519 _start_sampling = false; | |
4520 } | |
4521 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
4522 CMSPhaseAccounting pa(this, "preclean", !PrintGCDetails); | |
4523 preclean_work(CMSPrecleanRefLists1, CMSPrecleanSurvivors1); | |
4524 } | |
4525 CMSTokenSync x(true); // is cms thread | |
4526 if (CMSPrecleaningEnabled) { | |
4527 sample_eden(); | |
4528 _collectorState = AbortablePreclean; | |
4529 } else { | |
4530 _collectorState = FinalMarking; | |
4531 } | |
4532 verify_work_stacks_empty(); | |
4533 verify_overflow_empty(); | |
4534 } | |
4535 | |
4536 // Try and schedule the remark such that young gen | |
4537 // occupancy is CMSScheduleRemarkEdenPenetration %. | |
4538 void CMSCollector::abortable_preclean() { | |
4539 check_correct_thread_executing(); | |
4540 assert(CMSPrecleaningEnabled, "Inconsistent control state"); | |
4541 assert(_collectorState == AbortablePreclean, "Inconsistent control state"); | |
4542 | |
4543 // If Eden's current occupancy is below this threshold, | |
4544 // immediately schedule the remark; else preclean | |
4545 // past the next scavenge in an effort to | |
4546 // schedule the pause as described avove. By choosing | |
4547 // CMSScheduleRemarkEdenSizeThreshold >= max eden size | |
4548 // we will never do an actual abortable preclean cycle. | |
4549 if (get_eden_used() > CMSScheduleRemarkEdenSizeThreshold) { | |
4550 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
4551 CMSPhaseAccounting pa(this, "abortable-preclean", !PrintGCDetails); | |
4552 // We need more smarts in the abortable preclean | |
4553 // loop below to deal with cases where allocation | |
4554 // in young gen is very very slow, and our precleaning | |
4555 // is running a losing race against a horde of | |
4556 // mutators intent on flooding us with CMS updates | |
4557 // (dirty cards). | |
4558 // One, admittedly dumb, strategy is to give up | |
4559 // after a certain number of abortable precleaning loops | |
4560 // or after a certain maximum time. We want to make | |
4561 // this smarter in the next iteration. | |
4562 // XXX FIX ME!!! YSR | |
4563 size_t loops = 0, workdone = 0, cumworkdone = 0, waited = 0; | |
4564 while (!(should_abort_preclean() || | |
4565 ConcurrentMarkSweepThread::should_terminate())) { | |
4566 workdone = preclean_work(CMSPrecleanRefLists2, CMSPrecleanSurvivors2); | |
4567 cumworkdone += workdone; | |
4568 loops++; | |
4569 // Voluntarily terminate abortable preclean phase if we have | |
4570 // been at it for too long. | |
4571 if ((CMSMaxAbortablePrecleanLoops != 0) && | |
4572 loops >= CMSMaxAbortablePrecleanLoops) { | |
4573 if (PrintGCDetails) { | |
4574 gclog_or_tty->print(" CMS: abort preclean due to loops "); | |
4575 } | |
4576 break; | |
4577 } | |
4578 if (pa.wallclock_millis() > CMSMaxAbortablePrecleanTime) { | |
4579 if (PrintGCDetails) { | |
4580 gclog_or_tty->print(" CMS: abort preclean due to time "); | |
4581 } | |
4582 break; | |
4583 } | |
4584 // If we are doing little work each iteration, we should | |
4585 // take a short break. | |
4586 if (workdone < CMSAbortablePrecleanMinWorkPerIteration) { | |
4587 // Sleep for some time, waiting for work to accumulate | |
4588 stopTimer(); | |
4589 cmsThread()->wait_on_cms_lock(CMSAbortablePrecleanWaitMillis); | |
4590 startTimer(); | |
4591 waited++; | |
4592 } | |
4593 } | |
4594 if (PrintCMSStatistics > 0) { | |
4595 gclog_or_tty->print(" [%d iterations, %d waits, %d cards)] ", | |
4596 loops, waited, cumworkdone); | |
4597 } | |
4598 } | |
4599 CMSTokenSync x(true); // is cms thread | |
4600 if (_collectorState != Idling) { | |
4601 assert(_collectorState == AbortablePreclean, | |
4602 "Spontaneous state transition?"); | |
4603 _collectorState = FinalMarking; | |
4604 } // Else, a foreground collection completed this CMS cycle. | |
4605 return; | |
4606 } | |
4607 | |
4608 // Respond to an Eden sampling opportunity | |
4609 void CMSCollector::sample_eden() { | |
4610 // Make sure a young gc cannot sneak in between our | |
4611 // reading and recording of a sample. | |
4612 assert(Thread::current()->is_ConcurrentGC_thread(), | |
4613 "Only the cms thread may collect Eden samples"); | |
4614 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
4615 "Should collect samples while holding CMS token"); | |
4616 if (!_start_sampling) { | |
4617 return; | |
4618 } | |
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4619 // When CMSEdenChunksRecordAlways is true, the eden chunk array |
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4620 // is populated by the young generation. |
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4621 if (_eden_chunk_array != NULL && !CMSEdenChunksRecordAlways) { |
0 | 4622 if (_eden_chunk_index < _eden_chunk_capacity) { |
4623 _eden_chunk_array[_eden_chunk_index] = *_top_addr; // take sample | |
4624 assert(_eden_chunk_array[_eden_chunk_index] <= *_end_addr, | |
4625 "Unexpected state of Eden"); | |
4626 // We'd like to check that what we just sampled is an oop-start address; | |
4627 // however, we cannot do that here since the object may not yet have been | |
4628 // initialized. So we'll instead do the check when we _use_ this sample | |
4629 // later. | |
4630 if (_eden_chunk_index == 0 || | |
4631 (pointer_delta(_eden_chunk_array[_eden_chunk_index], | |
4632 _eden_chunk_array[_eden_chunk_index-1]) | |
4633 >= CMSSamplingGrain)) { | |
4634 _eden_chunk_index++; // commit sample | |
4635 } | |
4636 } | |
4637 } | |
4638 if ((_collectorState == AbortablePreclean) && !_abort_preclean) { | |
4639 size_t used = get_eden_used(); | |
4640 size_t capacity = get_eden_capacity(); | |
4641 assert(used <= capacity, "Unexpected state of Eden"); | |
4642 if (used > (capacity/100 * CMSScheduleRemarkEdenPenetration)) { | |
4643 _abort_preclean = true; | |
4644 } | |
4645 } | |
4646 } | |
4647 | |
4648 | |
4649 size_t CMSCollector::preclean_work(bool clean_refs, bool clean_survivor) { | |
4650 assert(_collectorState == Precleaning || | |
4651 _collectorState == AbortablePreclean, "incorrect state"); | |
4652 ResourceMark rm; | |
4653 HandleMark hm; | |
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4654 |
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4655 // Precleaning is currently not MT but the reference processor |
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4656 // may be set for MT. Disable it temporarily here. |
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4657 ReferenceProcessor* rp = ref_processor(); |
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4658 ReferenceProcessorMTDiscoveryMutator rp_mut_discovery(rp, false); |
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4659 |
0 | 4660 // Do one pass of scrubbing the discovered reference lists |
4661 // to remove any reference objects with strongly-reachable | |
4662 // referents. | |
4663 if (clean_refs) { | |
4664 CMSPrecleanRefsYieldClosure yield_cl(this); | |
4665 assert(rp->span().equals(_span), "Spans should be equal"); | |
4666 CMSKeepAliveClosure keep_alive(this, _span, &_markBitMap, | |
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4667 &_markStack, true /* preclean */); |
0 | 4668 CMSDrainMarkingStackClosure complete_trace(this, |
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4669 _span, &_markBitMap, &_markStack, |
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4670 &keep_alive, true /* preclean */); |
0 | 4671 |
4672 // We don't want this step to interfere with a young | |
4673 // collection because we don't want to take CPU | |
4674 // or memory bandwidth away from the young GC threads | |
4675 // (which may be as many as there are CPUs). | |
4676 // Note that we don't need to protect ourselves from | |
4677 // interference with mutators because they can't | |
4678 // manipulate the discovered reference lists nor affect | |
4679 // the computed reachability of the referents, the | |
4680 // only properties manipulated by the precleaning | |
4681 // of these reference lists. | |
4682 stopTimer(); | |
4683 CMSTokenSyncWithLocks x(true /* is cms thread */, | |
4684 bitMapLock()); | |
4685 startTimer(); | |
4686 sample_eden(); | |
935 | 4687 |
0 | 4688 // The following will yield to allow foreground |
4689 // collection to proceed promptly. XXX YSR: | |
4690 // The code in this method may need further | |
4691 // tweaking for better performance and some restructuring | |
4692 // for cleaner interfaces. | |
10405 | 4693 GCTimer *gc_timer = NULL; // Currently not tracing concurrent phases |
0 | 4694 rp->preclean_discovered_references( |
10405 | 4695 rp->is_alive_non_header(), &keep_alive, &complete_trace, &yield_cl, |
4696 gc_timer); | |
0 | 4697 } |
4698 | |
4699 if (clean_survivor) { // preclean the active survivor space(s) | |
4700 assert(_young_gen->kind() == Generation::DefNew || | |
4701 _young_gen->kind() == Generation::ParNew || | |
4702 _young_gen->kind() == Generation::ASParNew, | |
4703 "incorrect type for cast"); | |
4704 DefNewGeneration* dng = (DefNewGeneration*)_young_gen; | |
4705 PushAndMarkClosure pam_cl(this, _span, ref_processor(), | |
4706 &_markBitMap, &_modUnionTable, | |
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4707 &_markStack, true /* precleaning phase */); |
0 | 4708 stopTimer(); |
4709 CMSTokenSyncWithLocks ts(true /* is cms thread */, | |
4710 bitMapLock()); | |
4711 startTimer(); | |
4712 unsigned int before_count = | |
4713 GenCollectedHeap::heap()->total_collections(); | |
4714 SurvivorSpacePrecleanClosure | |
4715 sss_cl(this, _span, &_markBitMap, &_markStack, | |
4716 &pam_cl, before_count, CMSYield); | |
4717 dng->from()->object_iterate_careful(&sss_cl); | |
4718 dng->to()->object_iterate_careful(&sss_cl); | |
4719 } | |
4720 MarkRefsIntoAndScanClosure | |
4721 mrias_cl(_span, ref_processor(), &_markBitMap, &_modUnionTable, | |
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4722 &_markStack, this, CMSYield, |
0 | 4723 true /* precleaning phase */); |
4724 // CAUTION: The following closure has persistent state that may need to | |
4725 // be reset upon a decrease in the sequence of addresses it | |
4726 // processes. | |
4727 ScanMarkedObjectsAgainCarefullyClosure | |
4728 smoac_cl(this, _span, | |
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4729 &_markBitMap, &_markStack, &mrias_cl, CMSYield); |
0 | 4730 |
4731 // Preclean dirty cards in ModUnionTable and CardTable using | |
4732 // appropriate convergence criterion; | |
4733 // repeat CMSPrecleanIter times unless we find that | |
4734 // we are losing. | |
4735 assert(CMSPrecleanIter < 10, "CMSPrecleanIter is too large"); | |
4736 assert(CMSPrecleanNumerator < CMSPrecleanDenominator, | |
4737 "Bad convergence multiplier"); | |
4738 assert(CMSPrecleanThreshold >= 100, | |
4739 "Unreasonably low CMSPrecleanThreshold"); | |
4740 | |
4741 size_t numIter, cumNumCards, lastNumCards, curNumCards; | |
4742 for (numIter = 0, cumNumCards = lastNumCards = curNumCards = 0; | |
4743 numIter < CMSPrecleanIter; | |
4744 numIter++, lastNumCards = curNumCards, cumNumCards += curNumCards) { | |
4745 curNumCards = preclean_mod_union_table(_cmsGen, &smoac_cl); | |
4746 if (Verbose && PrintGCDetails) { | |
4747 gclog_or_tty->print(" (modUnionTable: %d cards)", curNumCards); | |
4748 } | |
4749 // Either there are very few dirty cards, so re-mark | |
4750 // pause will be small anyway, or our pre-cleaning isn't | |
4751 // that much faster than the rate at which cards are being | |
4752 // dirtied, so we might as well stop and re-mark since | |
4753 // precleaning won't improve our re-mark time by much. | |
4754 if (curNumCards <= CMSPrecleanThreshold || | |
4755 (numIter > 0 && | |
4756 (curNumCards * CMSPrecleanDenominator > | |
4757 lastNumCards * CMSPrecleanNumerator))) { | |
4758 numIter++; | |
4759 cumNumCards += curNumCards; | |
4760 break; | |
4761 } | |
4762 } | |
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4763 |
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4764 preclean_klasses(&mrias_cl, _cmsGen->freelistLock()); |
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4765 |
0 | 4766 curNumCards = preclean_card_table(_cmsGen, &smoac_cl); |
4767 cumNumCards += curNumCards; | |
4768 if (PrintGCDetails && PrintCMSStatistics != 0) { | |
4769 gclog_or_tty->print_cr(" (cardTable: %d cards, re-scanned %d cards, %d iterations)", | |
4770 curNumCards, cumNumCards, numIter); | |
4771 } | |
4772 return cumNumCards; // as a measure of useful work done | |
4773 } | |
4774 | |
4775 // PRECLEANING NOTES: | |
4776 // Precleaning involves: | |
4777 // . reading the bits of the modUnionTable and clearing the set bits. | |
4778 // . For the cards corresponding to the set bits, we scan the | |
4779 // objects on those cards. This means we need the free_list_lock | |
4780 // so that we can safely iterate over the CMS space when scanning | |
4781 // for oops. | |
4782 // . When we scan the objects, we'll be both reading and setting | |
4783 // marks in the marking bit map, so we'll need the marking bit map. | |
4784 // . For protecting _collector_state transitions, we take the CGC_lock. | |
4785 // Note that any races in the reading of of card table entries by the | |
4786 // CMS thread on the one hand and the clearing of those entries by the | |
4787 // VM thread or the setting of those entries by the mutator threads on the | |
4788 // other are quite benign. However, for efficiency it makes sense to keep | |
4789 // the VM thread from racing with the CMS thread while the latter is | |
4790 // dirty card info to the modUnionTable. We therefore also use the | |
4791 // CGC_lock to protect the reading of the card table and the mod union | |
4792 // table by the CM thread. | |
4793 // . We run concurrently with mutator updates, so scanning | |
4794 // needs to be done carefully -- we should not try to scan | |
4795 // potentially uninitialized objects. | |
4796 // | |
4797 // Locking strategy: While holding the CGC_lock, we scan over and | |
4798 // reset a maximal dirty range of the mod union / card tables, then lock | |
4799 // the free_list_lock and bitmap lock to do a full marking, then | |
4800 // release these locks; and repeat the cycle. This allows for a | |
4801 // certain amount of fairness in the sharing of these locks between | |
4802 // the CMS collector on the one hand, and the VM thread and the | |
4803 // mutators on the other. | |
4804 | |
4805 // NOTE: preclean_mod_union_table() and preclean_card_table() | |
4806 // further below are largely identical; if you need to modify | |
4807 // one of these methods, please check the other method too. | |
4808 | |
4809 size_t CMSCollector::preclean_mod_union_table( | |
4810 ConcurrentMarkSweepGeneration* gen, | |
4811 ScanMarkedObjectsAgainCarefullyClosure* cl) { | |
4812 verify_work_stacks_empty(); | |
4813 verify_overflow_empty(); | |
4814 | |
4815 // strategy: starting with the first card, accumulate contiguous | |
4816 // ranges of dirty cards; clear these cards, then scan the region | |
4817 // covered by these cards. | |
4818 | |
4819 // Since all of the MUT is committed ahead, we can just use | |
4820 // that, in case the generations expand while we are precleaning. | |
4821 // It might also be fine to just use the committed part of the | |
4822 // generation, but we might potentially miss cards when the | |
4823 // generation is rapidly expanding while we are in the midst | |
4824 // of precleaning. | |
4825 HeapWord* startAddr = gen->reserved().start(); | |
4826 HeapWord* endAddr = gen->reserved().end(); | |
4827 | |
4828 cl->setFreelistLock(gen->freelistLock()); // needed for yielding | |
4829 | |
4830 size_t numDirtyCards, cumNumDirtyCards; | |
4831 HeapWord *nextAddr, *lastAddr; | |
4832 for (cumNumDirtyCards = numDirtyCards = 0, | |
4833 nextAddr = lastAddr = startAddr; | |
4834 nextAddr < endAddr; | |
4835 nextAddr = lastAddr, cumNumDirtyCards += numDirtyCards) { | |
4836 | |
4837 ResourceMark rm; | |
4838 HandleMark hm; | |
4839 | |
4840 MemRegion dirtyRegion; | |
4841 { | |
4842 stopTimer(); | |
935 | 4843 // Potential yield point |
0 | 4844 CMSTokenSync ts(true); |
4845 startTimer(); | |
4846 sample_eden(); | |
4847 // Get dirty region starting at nextOffset (inclusive), | |
4848 // simultaneously clearing it. | |
4849 dirtyRegion = | |
4850 _modUnionTable.getAndClearMarkedRegion(nextAddr, endAddr); | |
4851 assert(dirtyRegion.start() >= nextAddr, | |
4852 "returned region inconsistent?"); | |
4853 } | |
4854 // Remember where the next search should begin. | |
4855 // The returned region (if non-empty) is a right open interval, | |
4856 // so lastOffset is obtained from the right end of that | |
4857 // interval. | |
4858 lastAddr = dirtyRegion.end(); | |
4859 // Should do something more transparent and less hacky XXX | |
4860 numDirtyCards = | |
4861 _modUnionTable.heapWordDiffToOffsetDiff(dirtyRegion.word_size()); | |
4862 | |
4863 // We'll scan the cards in the dirty region (with periodic | |
4864 // yields for foreground GC as needed). | |
4865 if (!dirtyRegion.is_empty()) { | |
4866 assert(numDirtyCards > 0, "consistency check"); | |
4867 HeapWord* stop_point = NULL; | |
453
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4868 stopTimer(); |
935 | 4869 // Potential yield point |
453
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4870 CMSTokenSyncWithLocks ts(true, gen->freelistLock(), |
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4871 bitMapLock()); |
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4872 startTimer(); |
0 | 4873 { |
4874 verify_work_stacks_empty(); | |
4875 verify_overflow_empty(); | |
4876 sample_eden(); | |
4877 stop_point = | |
4878 gen->cmsSpace()->object_iterate_careful_m(dirtyRegion, cl); | |
4879 } | |
4880 if (stop_point != NULL) { | |
4881 // The careful iteration stopped early either because it found an | |
4882 // uninitialized object, or because we were in the midst of an | |
4883 // "abortable preclean", which should now be aborted. Redirty | |
4884 // the bits corresponding to the partially-scanned or unscanned | |
4885 // cards. We'll either restart at the next block boundary or | |
4886 // abort the preclean. | |
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4887 assert((_collectorState == AbortablePreclean && should_abort_preclean()), |
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4888 "Should only be AbortablePreclean."); |
0 | 4889 _modUnionTable.mark_range(MemRegion(stop_point, dirtyRegion.end())); |
4890 if (should_abort_preclean()) { | |
4891 break; // out of preclean loop | |
4892 } else { | |
4893 // Compute the next address at which preclean should pick up; | |
4894 // might need bitMapLock in order to read P-bits. | |
4895 lastAddr = next_card_start_after_block(stop_point); | |
4896 } | |
4897 } | |
4898 } else { | |
4899 assert(lastAddr == endAddr, "consistency check"); | |
4900 assert(numDirtyCards == 0, "consistency check"); | |
4901 break; | |
4902 } | |
4903 } | |
4904 verify_work_stacks_empty(); | |
4905 verify_overflow_empty(); | |
4906 return cumNumDirtyCards; | |
4907 } | |
4908 | |
4909 // NOTE: preclean_mod_union_table() above and preclean_card_table() | |
4910 // below are largely identical; if you need to modify | |
4911 // one of these methods, please check the other method too. | |
4912 | |
4913 size_t CMSCollector::preclean_card_table(ConcurrentMarkSweepGeneration* gen, | |
4914 ScanMarkedObjectsAgainCarefullyClosure* cl) { | |
4915 // strategy: it's similar to precleamModUnionTable above, in that | |
4916 // we accumulate contiguous ranges of dirty cards, mark these cards | |
4917 // precleaned, then scan the region covered by these cards. | |
4918 HeapWord* endAddr = (HeapWord*)(gen->_virtual_space.high()); | |
4919 HeapWord* startAddr = (HeapWord*)(gen->_virtual_space.low()); | |
4920 | |
4921 cl->setFreelistLock(gen->freelistLock()); // needed for yielding | |
4922 | |
4923 size_t numDirtyCards, cumNumDirtyCards; | |
4924 HeapWord *lastAddr, *nextAddr; | |
4925 | |
4926 for (cumNumDirtyCards = numDirtyCards = 0, | |
4927 nextAddr = lastAddr = startAddr; | |
4928 nextAddr < endAddr; | |
4929 nextAddr = lastAddr, cumNumDirtyCards += numDirtyCards) { | |
4930 | |
4931 ResourceMark rm; | |
4932 HandleMark hm; | |
4933 | |
4934 MemRegion dirtyRegion; | |
4935 { | |
4936 // See comments in "Precleaning notes" above on why we | |
4937 // do this locking. XXX Could the locking overheads be | |
4938 // too high when dirty cards are sparse? [I don't think so.] | |
4939 stopTimer(); | |
4940 CMSTokenSync x(true); // is cms thread | |
4941 startTimer(); | |
4942 sample_eden(); | |
4943 // Get and clear dirty region from card table | |
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4944 dirtyRegion = _ct->ct_bs()->dirty_card_range_after_reset( |
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4945 MemRegion(nextAddr, endAddr), |
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4946 true, |
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4947 CardTableModRefBS::precleaned_card_val()); |
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4948 |
0 | 4949 assert(dirtyRegion.start() >= nextAddr, |
4950 "returned region inconsistent?"); | |
4951 } | |
4952 lastAddr = dirtyRegion.end(); | |
4953 numDirtyCards = | |
4954 dirtyRegion.word_size()/CardTableModRefBS::card_size_in_words; | |
4955 | |
4956 if (!dirtyRegion.is_empty()) { | |
4957 stopTimer(); | |
4958 CMSTokenSyncWithLocks ts(true, gen->freelistLock(), bitMapLock()); | |
4959 startTimer(); | |
4960 sample_eden(); | |
4961 verify_work_stacks_empty(); | |
4962 verify_overflow_empty(); | |
4963 HeapWord* stop_point = | |
4964 gen->cmsSpace()->object_iterate_careful_m(dirtyRegion, cl); | |
4965 if (stop_point != NULL) { | |
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4966 assert((_collectorState == AbortablePreclean && should_abort_preclean()), |
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4967 "Should only be AbortablePreclean."); |
0 | 4968 _ct->ct_bs()->invalidate(MemRegion(stop_point, dirtyRegion.end())); |
4969 if (should_abort_preclean()) { | |
4970 break; // out of preclean loop | |
4971 } else { | |
4972 // Compute the next address at which preclean should pick up. | |
4973 lastAddr = next_card_start_after_block(stop_point); | |
4974 } | |
4975 } | |
4976 } else { | |
4977 break; | |
4978 } | |
4979 } | |
4980 verify_work_stacks_empty(); | |
4981 verify_overflow_empty(); | |
4982 return cumNumDirtyCards; | |
4983 } | |
4984 | |
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4985 class PrecleanKlassClosure : public KlassClosure { |
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4986 CMKlassClosure _cm_klass_closure; |
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4987 public: |
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4988 PrecleanKlassClosure(OopClosure* oop_closure) : _cm_klass_closure(oop_closure) {} |
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4989 void do_klass(Klass* k) { |
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4990 if (k->has_accumulated_modified_oops()) { |
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4991 k->clear_accumulated_modified_oops(); |
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4992 |
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4993 _cm_klass_closure.do_klass(k); |
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4994 } |
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4995 } |
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4996 }; |
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4997 |
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4998 // The freelist lock is needed to prevent asserts, is it really needed? |
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4999 void CMSCollector::preclean_klasses(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock) { |
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5000 |
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5001 cl->set_freelistLock(freelistLock); |
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5002 |
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5003 CMSTokenSyncWithLocks ts(true, freelistLock, bitMapLock()); |
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5004 |
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5005 // SSS: Add equivalent to ScanMarkedObjectsAgainCarefullyClosure::do_yield_check and should_abort_preclean? |
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5006 // SSS: We should probably check if precleaning should be aborted, at suitable intervals? |
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5007 PrecleanKlassClosure preclean_klass_closure(cl); |
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5008 ClassLoaderDataGraph::classes_do(&preclean_klass_closure); |
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5009 |
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5010 verify_work_stacks_empty(); |
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5011 verify_overflow_empty(); |
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5012 } |
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5013 |
0 | 5014 void CMSCollector::checkpointRootsFinal(bool asynch, |
5015 bool clear_all_soft_refs, bool init_mark_was_synchronous) { | |
5016 assert(_collectorState == FinalMarking, "incorrect state transition?"); | |
5017 check_correct_thread_executing(); | |
5018 // world is stopped at this checkpoint | |
5019 assert(SafepointSynchronize::is_at_safepoint(), | |
5020 "world should be stopped"); | |
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5021 TraceCMSMemoryManagerStats tms(_collectorState,GenCollectedHeap::heap()->gc_cause()); |
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5022 |
0 | 5023 verify_work_stacks_empty(); |
5024 verify_overflow_empty(); | |
5025 | |
5026 SpecializationStats::clear(); | |
5027 if (PrintGCDetails) { | |
5028 gclog_or_tty->print("[YG occupancy: "SIZE_FORMAT" K ("SIZE_FORMAT" K)]", | |
5029 _young_gen->used() / K, | |
5030 _young_gen->capacity() / K); | |
5031 } | |
5032 if (asynch) { | |
5033 if (CMSScavengeBeforeRemark) { | |
5034 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
5035 // Temporarily set flag to false, GCH->do_collection will | |
5036 // expect it to be false and set to true | |
5037 FlagSetting fl(gch->_is_gc_active, false); | |
10405 | 5038 NOT_PRODUCT(GCTraceTime t("Scavenge-Before-Remark", |
5039 PrintGCDetails && Verbose, true, _gc_timer_cm);) | |
0 | 5040 int level = _cmsGen->level() - 1; |
5041 if (level >= 0) { | |
5042 gch->do_collection(true, // full (i.e. force, see below) | |
5043 false, // !clear_all_soft_refs | |
5044 0, // size | |
5045 false, // is_tlab | |
5046 level // max_level | |
5047 ); | |
5048 } | |
5049 } | |
5050 FreelistLocker x(this); | |
5051 MutexLockerEx y(bitMapLock(), | |
5052 Mutex::_no_safepoint_check_flag); | |
5053 assert(!init_mark_was_synchronous, "but that's impossible!"); | |
5054 checkpointRootsFinalWork(asynch, clear_all_soft_refs, false); | |
5055 } else { | |
5056 // already have all the locks | |
5057 checkpointRootsFinalWork(asynch, clear_all_soft_refs, | |
5058 init_mark_was_synchronous); | |
5059 } | |
5060 verify_work_stacks_empty(); | |
5061 verify_overflow_empty(); | |
5062 SpecializationStats::print(); | |
5063 } | |
5064 | |
5065 void CMSCollector::checkpointRootsFinalWork(bool asynch, | |
5066 bool clear_all_soft_refs, bool init_mark_was_synchronous) { | |
5067 | |
10405 | 5068 NOT_PRODUCT(GCTraceTime tr("checkpointRootsFinalWork", PrintGCDetails, false, _gc_timer_cm);) |
0 | 5069 |
5070 assert(haveFreelistLocks(), "must have free list locks"); | |
5071 assert_lock_strong(bitMapLock()); | |
5072 | |
5073 if (UseAdaptiveSizePolicy) { | |
5074 size_policy()->checkpoint_roots_final_begin(); | |
5075 } | |
5076 | |
5077 ResourceMark rm; | |
5078 HandleMark hm; | |
5079 | |
5080 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
5081 | |
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5082 if (should_unload_classes()) { |
0 | 5083 CodeCache::gc_prologue(); |
5084 } | |
5085 assert(haveFreelistLocks(), "must have free list locks"); | |
5086 assert_lock_strong(bitMapLock()); | |
5087 | |
5088 if (!init_mark_was_synchronous) { | |
5089 // We might assume that we need not fill TLAB's when | |
5090 // CMSScavengeBeforeRemark is set, because we may have just done | |
5091 // a scavenge which would have filled all TLAB's -- and besides | |
5092 // Eden would be empty. This however may not always be the case -- | |
5093 // for instance although we asked for a scavenge, it may not have | |
5094 // happened because of a JNI critical section. We probably need | |
5095 // a policy for deciding whether we can in that case wait until | |
5096 // the critical section releases and then do the remark following | |
5097 // the scavenge, and skip it here. In the absence of that policy, | |
5098 // or of an indication of whether the scavenge did indeed occur, | |
5099 // we cannot rely on TLAB's having been filled and must do | |
5100 // so here just in case a scavenge did not happen. | |
5101 gch->ensure_parsability(false); // fill TLAB's, but no need to retire them | |
5102 // Update the saved marks which may affect the root scans. | |
5103 gch->save_marks(); | |
5104 | |
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5105 if (CMSPrintEdenSurvivorChunks) { |
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5106 print_eden_and_survivor_chunk_arrays(); |
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5107 } |
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5108 |
0 | 5109 { |
5110 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;) | |
5111 | |
5112 // Note on the role of the mod union table: | |
5113 // Since the marker in "markFromRoots" marks concurrently with | |
5114 // mutators, it is possible for some reachable objects not to have been | |
5115 // scanned. For instance, an only reference to an object A was | |
5116 // placed in object B after the marker scanned B. Unless B is rescanned, | |
5117 // A would be collected. Such updates to references in marked objects | |
5118 // are detected via the mod union table which is the set of all cards | |
5119 // dirtied since the first checkpoint in this GC cycle and prior to | |
5120 // the most recent young generation GC, minus those cleaned up by the | |
5121 // concurrent precleaning. | |
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5122 if (CMSParallelRemarkEnabled && CollectedHeap::use_parallel_gc_threads()) { |
10405 | 5123 GCTraceTime t("Rescan (parallel) ", PrintGCDetails, false, _gc_timer_cm); |
0 | 5124 do_remark_parallel(); |
5125 } else { | |
10405 | 5126 GCTraceTime t("Rescan (non-parallel) ", PrintGCDetails, false, |
5127 _gc_timer_cm); | |
0 | 5128 do_remark_non_parallel(); |
5129 } | |
5130 } | |
5131 } else { | |
5132 assert(!asynch, "Can't have init_mark_was_synchronous in asynch mode"); | |
5133 // The initial mark was stop-world, so there's no rescanning to | |
5134 // do; go straight on to the next step below. | |
5135 } | |
5136 verify_work_stacks_empty(); | |
5137 verify_overflow_empty(); | |
5138 | |
5139 { | |
10405 | 5140 NOT_PRODUCT(GCTraceTime ts("refProcessingWork", PrintGCDetails, false, _gc_timer_cm);) |
0 | 5141 refProcessingWork(asynch, clear_all_soft_refs); |
5142 } | |
5143 verify_work_stacks_empty(); | |
5144 verify_overflow_empty(); | |
5145 | |
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5146 if (should_unload_classes()) { |
0 | 5147 CodeCache::gc_epilogue(); |
5148 } | |
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5149 JvmtiExport::gc_epilogue(); |
0 | 5150 |
5151 // If we encountered any (marking stack / work queue) overflow | |
5152 // events during the current CMS cycle, take appropriate | |
5153 // remedial measures, where possible, so as to try and avoid | |
5154 // recurrence of that condition. | |
5155 assert(_markStack.isEmpty(), "No grey objects"); | |
5156 size_t ser_ovflw = _ser_pmc_remark_ovflw + _ser_pmc_preclean_ovflw + | |
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5157 _ser_kac_ovflw + _ser_kac_preclean_ovflw; |
0 | 5158 if (ser_ovflw > 0) { |
5159 if (PrintCMSStatistics != 0) { | |
5160 gclog_or_tty->print_cr("Marking stack overflow (benign) " | |
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5161 "(pmc_pc="SIZE_FORMAT", pmc_rm="SIZE_FORMAT", kac="SIZE_FORMAT |
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5162 ", kac_preclean="SIZE_FORMAT")", |
0 | 5163 _ser_pmc_preclean_ovflw, _ser_pmc_remark_ovflw, |
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5164 _ser_kac_ovflw, _ser_kac_preclean_ovflw); |
0 | 5165 } |
5166 _markStack.expand(); | |
5167 _ser_pmc_remark_ovflw = 0; | |
5168 _ser_pmc_preclean_ovflw = 0; | |
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5169 _ser_kac_preclean_ovflw = 0; |
0 | 5170 _ser_kac_ovflw = 0; |
5171 } | |
5172 if (_par_pmc_remark_ovflw > 0 || _par_kac_ovflw > 0) { | |
5173 if (PrintCMSStatistics != 0) { | |
5174 gclog_or_tty->print_cr("Work queue overflow (benign) " | |
5175 "(pmc_rm="SIZE_FORMAT", kac="SIZE_FORMAT")", | |
5176 _par_pmc_remark_ovflw, _par_kac_ovflw); | |
5177 } | |
5178 _par_pmc_remark_ovflw = 0; | |
5179 _par_kac_ovflw = 0; | |
5180 } | |
5181 if (PrintCMSStatistics != 0) { | |
5182 if (_markStack._hit_limit > 0) { | |
5183 gclog_or_tty->print_cr(" (benign) Hit max stack size limit ("SIZE_FORMAT")", | |
5184 _markStack._hit_limit); | |
5185 } | |
5186 if (_markStack._failed_double > 0) { | |
5187 gclog_or_tty->print_cr(" (benign) Failed stack doubling ("SIZE_FORMAT")," | |
5188 " current capacity "SIZE_FORMAT, | |
5189 _markStack._failed_double, | |
5190 _markStack.capacity()); | |
5191 } | |
5192 } | |
5193 _markStack._hit_limit = 0; | |
5194 _markStack._failed_double = 0; | |
5195 | |
5196 if ((VerifyAfterGC || VerifyDuringGC) && | |
5197 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
5198 verify_after_remark(); | |
5199 } | |
5200 | |
10405 | 5201 _gc_tracer_cm->report_object_count_after_gc(&_is_alive_closure); |
5202 | |
0 | 5203 // Change under the freelistLocks. |
5204 _collectorState = Sweeping; | |
5205 // Call isAllClear() under bitMapLock | |
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5206 assert(_modUnionTable.isAllClear(), |
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5207 "Should be clear by end of the final marking"); |
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5208 assert(_ct->klass_rem_set()->mod_union_is_clear(), |
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5209 "Should be clear by end of the final marking"); |
0 | 5210 if (UseAdaptiveSizePolicy) { |
5211 size_policy()->checkpoint_roots_final_end(gch->gc_cause()); | |
5212 } | |
5213 } | |
5214 | |
11975 | 5215 void CMSParInitialMarkTask::work(uint worker_id) { |
5216 elapsedTimer _timer; | |
5217 ResourceMark rm; | |
5218 HandleMark hm; | |
5219 | |
5220 // ---------- scan from roots -------------- | |
5221 _timer.start(); | |
5222 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
5223 Par_MarkRefsIntoClosure par_mri_cl(_collector->_span, &(_collector->_markBitMap)); | |
5224 CMKlassClosure klass_closure(&par_mri_cl); | |
5225 | |
5226 // ---------- young gen roots -------------- | |
5227 { | |
5228 work_on_young_gen_roots(worker_id, &par_mri_cl); | |
5229 _timer.stop(); | |
5230 if (PrintCMSStatistics != 0) { | |
5231 gclog_or_tty->print_cr( | |
5232 "Finished young gen initial mark scan work in %dth thread: %3.3f sec", | |
5233 worker_id, _timer.seconds()); | |
5234 } | |
5235 } | |
5236 | |
5237 // ---------- remaining roots -------------- | |
5238 _timer.reset(); | |
5239 _timer.start(); | |
5240 gch->gen_process_strong_roots(_collector->_cmsGen->level(), | |
5241 false, // yg was scanned above | |
5242 false, // this is parallel code | |
5243 false, // not scavenging | |
5244 SharedHeap::ScanningOption(_collector->CMSCollector::roots_scanning_options()), | |
5245 &par_mri_cl, | |
5246 true, // walk all of code cache if (so & SO_CodeCache) | |
5247 NULL, | |
5248 &klass_closure); | |
5249 assert(_collector->should_unload_classes() | |
5250 || (_collector->CMSCollector::roots_scanning_options() & SharedHeap::SO_CodeCache), | |
5251 "if we didn't scan the code cache, we have to be ready to drop nmethods with expired weak oops"); | |
5252 _timer.stop(); | |
5253 if (PrintCMSStatistics != 0) { | |
5254 gclog_or_tty->print_cr( | |
5255 "Finished remaining root initial mark scan work in %dth thread: %3.3f sec", | |
5256 worker_id, _timer.seconds()); | |
5257 } | |
5258 } | |
5259 | |
0 | 5260 // Parallel remark task |
11975 | 5261 class CMSParRemarkTask: public CMSParMarkTask { |
0 | 5262 CompactibleFreeListSpace* _cms_space; |
5263 | |
5264 // The per-thread work queues, available here for stealing. | |
5265 OopTaskQueueSet* _task_queues; | |
5266 ParallelTaskTerminator _term; | |
5267 | |
5268 public: | |
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5269 // A value of 0 passed to n_workers will cause the number of |
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5270 // workers to be taken from the active workers in the work gang. |
0 | 5271 CMSParRemarkTask(CMSCollector* collector, |
5272 CompactibleFreeListSpace* cms_space, | |
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5273 int n_workers, FlexibleWorkGang* workers, |
0 | 5274 OopTaskQueueSet* task_queues): |
11975 | 5275 CMSParMarkTask("Rescan roots and grey objects in parallel", |
5276 collector, n_workers), | |
6725
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5277 _cms_space(cms_space), |
0 | 5278 _task_queues(task_queues), |
1833
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5279 _term(n_workers, task_queues) { } |
0 | 5280 |
5281 OopTaskQueueSet* task_queues() { return _task_queues; } | |
5282 | |
5283 OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); } | |
5284 | |
5285 ParallelTaskTerminator* terminator() { return &_term; } | |
1833
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5286 int n_workers() { return _n_workers; } |
0 | 5287 |
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5288 void work(uint worker_id); |
0 | 5289 |
5290 private: | |
5291 // ... of dirty cards in old space | |
5292 void do_dirty_card_rescan_tasks(CompactibleFreeListSpace* sp, int i, | |
5293 Par_MarkRefsIntoAndScanClosure* cl); | |
5294 | |
5295 // ... work stealing for the above | |
5296 void do_work_steal(int i, Par_MarkRefsIntoAndScanClosure* cl, int* seed); | |
5297 }; | |
5298 | |
6725
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5299 class RemarkKlassClosure : public KlassClosure { |
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5300 CMKlassClosure _cm_klass_closure; |
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5301 public: |
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5302 RemarkKlassClosure(OopClosure* oop_closure) : _cm_klass_closure(oop_closure) {} |
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5303 void do_klass(Klass* k) { |
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5304 // Check if we have modified any oops in the Klass during the concurrent marking. |
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5305 if (k->has_accumulated_modified_oops()) { |
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5306 k->clear_accumulated_modified_oops(); |
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5307 |
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5308 // We could have transfered the current modified marks to the accumulated marks, |
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5309 // like we do with the Card Table to Mod Union Table. But it's not really necessary. |
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5310 } else if (k->has_modified_oops()) { |
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5311 // Don't clear anything, this info is needed by the next young collection. |
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5312 } else { |
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5313 // No modified oops in the Klass. |
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5314 return; |
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5315 } |
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5316 |
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5317 // The klass has modified fields, need to scan the klass. |
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5318 _cm_klass_closure.do_klass(k); |
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5319 } |
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5320 }; |
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5321 |
11975 | 5322 void CMSParMarkTask::work_on_young_gen_roots(uint worker_id, OopsInGenClosure* cl) { |
5323 DefNewGeneration* dng = _collector->_young_gen->as_DefNewGeneration(); | |
5324 EdenSpace* eden_space = dng->eden(); | |
5325 ContiguousSpace* from_space = dng->from(); | |
5326 ContiguousSpace* to_space = dng->to(); | |
5327 | |
5328 HeapWord** eca = _collector->_eden_chunk_array; | |
5329 size_t ect = _collector->_eden_chunk_index; | |
5330 HeapWord** sca = _collector->_survivor_chunk_array; | |
5331 size_t sct = _collector->_survivor_chunk_index; | |
5332 | |
5333 assert(ect <= _collector->_eden_chunk_capacity, "out of bounds"); | |
5334 assert(sct <= _collector->_survivor_chunk_capacity, "out of bounds"); | |
5335 | |
5336 do_young_space_rescan(worker_id, cl, to_space, NULL, 0); | |
5337 do_young_space_rescan(worker_id, cl, from_space, sca, sct); | |
5338 do_young_space_rescan(worker_id, cl, eden_space, eca, ect); | |
5339 } | |
5340 | |
1833
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5341 // work_queue(i) is passed to the closure |
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5342 // Par_MarkRefsIntoAndScanClosure. The "i" parameter |
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5343 // also is passed to do_dirty_card_rescan_tasks() and to |
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5344 // do_work_steal() to select the i-th task_queue. |
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5345 |
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5346 void CMSParRemarkTask::work(uint worker_id) { |
0 | 5347 elapsedTimer _timer; |
5348 ResourceMark rm; | |
5349 HandleMark hm; | |
5350 | |
5351 // ---------- rescan from roots -------------- | |
5352 _timer.start(); | |
5353 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
5354 Par_MarkRefsIntoAndScanClosure par_mrias_cl(_collector, | |
5355 _collector->_span, _collector->ref_processor(), | |
5356 &(_collector->_markBitMap), | |
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5357 work_queue(worker_id)); |
0 | 5358 |
5359 // Rescan young gen roots first since these are likely | |
5360 // coarsely partitioned and may, on that account, constitute | |
5361 // the critical path; thus, it's best to start off that | |
5362 // work first. | |
5363 // ---------- young gen roots -------------- | |
5364 { | |
11975 | 5365 work_on_young_gen_roots(worker_id, &par_mrias_cl); |
0 | 5366 _timer.stop(); |
5367 if (PrintCMSStatistics != 0) { | |
5368 gclog_or_tty->print_cr( | |
5369 "Finished young gen rescan work in %dth thread: %3.3f sec", | |
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5370 worker_id, _timer.seconds()); |
0 | 5371 } |
5372 } | |
5373 | |
5374 // ---------- remaining roots -------------- | |
5375 _timer.reset(); | |
5376 _timer.start(); | |
5377 gch->gen_process_strong_roots(_collector->_cmsGen->level(), | |
5378 false, // yg was scanned above | |
989
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5379 false, // this is parallel code |
6725
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5380 false, // not scavenging |
0 | 5381 SharedHeap::ScanningOption(_collector->CMSCollector::roots_scanning_options()), |
989
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5382 &par_mrias_cl, |
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5383 true, // walk all of code cache if (so & SO_CodeCache) |
6725
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5384 NULL, |
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5385 NULL); // The dirty klasses will be handled below |
989
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5386 assert(_collector->should_unload_classes() |
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5387 || (_collector->CMSCollector::roots_scanning_options() & SharedHeap::SO_CodeCache), |
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5388 "if we didn't scan the code cache, we have to be ready to drop nmethods with expired weak oops"); |
0 | 5389 _timer.stop(); |
5390 if (PrintCMSStatistics != 0) { | |
5391 gclog_or_tty->print_cr( | |
5392 "Finished remaining root rescan work in %dth thread: %3.3f sec", | |
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5393 worker_id, _timer.seconds()); |
0 | 5394 } |
5395 | |
6725
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5396 // ---------- unhandled CLD scanning ---------- |
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5397 if (worker_id == 0) { // Single threaded at the moment. |
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5398 _timer.reset(); |
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5399 _timer.start(); |
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5400 |
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5401 // Scan all new class loader data objects and new dependencies that were |
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5402 // introduced during concurrent marking. |
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5403 ResourceMark rm; |
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5404 GrowableArray<ClassLoaderData*>* array = ClassLoaderDataGraph::new_clds(); |
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5405 for (int i = 0; i < array->length(); i++) { |
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5406 par_mrias_cl.do_class_loader_data(array->at(i)); |
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5407 } |
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5408 |
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5409 // We don't need to keep track of new CLDs anymore. |
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5410 ClassLoaderDataGraph::remember_new_clds(false); |
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5411 |
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5412 _timer.stop(); |
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5413 if (PrintCMSStatistics != 0) { |
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5414 gclog_or_tty->print_cr( |
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5415 "Finished unhandled CLD scanning work in %dth thread: %3.3f sec", |
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5416 worker_id, _timer.seconds()); |
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5417 } |
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5418 } |
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5419 |
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5420 // ---------- dirty klass scanning ---------- |
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5421 if (worker_id == 0) { // Single threaded at the moment. |
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5422 _timer.reset(); |
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5423 _timer.start(); |
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5424 |
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5425 // Scan all classes that was dirtied during the concurrent marking phase. |
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5426 RemarkKlassClosure remark_klass_closure(&par_mrias_cl); |
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5427 ClassLoaderDataGraph::classes_do(&remark_klass_closure); |
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5428 |
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5429 _timer.stop(); |
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5430 if (PrintCMSStatistics != 0) { |
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5431 gclog_or_tty->print_cr( |
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5432 "Finished dirty klass scanning work in %dth thread: %3.3f sec", |
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5433 worker_id, _timer.seconds()); |
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5434 } |
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5435 } |
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5436 |
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5437 // We might have added oops to ClassLoaderData::_handles during the |
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5438 // concurrent marking phase. These oops point to newly allocated objects |
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5439 // that are guaranteed to be kept alive. Either by the direct allocation |
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5440 // code, or when the young collector processes the strong roots. Hence, |
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5441 // we don't have to revisit the _handles block during the remark phase. |
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5442 |
0 | 5443 // ---------- rescan dirty cards ------------ |
5444 _timer.reset(); | |
5445 _timer.start(); | |
5446 | |
5447 // Do the rescan tasks for each of the two spaces | |
6725
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5448 // (cms_space) in turn. |
4728
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5449 // "worker_id" is passed to select the task_queue for "worker_id" |
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5450 do_dirty_card_rescan_tasks(_cms_space, worker_id, &par_mrias_cl); |
0 | 5451 _timer.stop(); |
5452 if (PrintCMSStatistics != 0) { | |
5453 gclog_or_tty->print_cr( | |
5454 "Finished dirty card rescan work in %dth thread: %3.3f sec", | |
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5455 worker_id, _timer.seconds()); |
0 | 5456 } |
5457 | |
5458 // ---------- steal work from other threads ... | |
5459 // ---------- ... and drain overflow list. | |
5460 _timer.reset(); | |
5461 _timer.start(); | |
4728
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5462 do_work_steal(worker_id, &par_mrias_cl, _collector->hash_seed(worker_id)); |
0 | 5463 _timer.stop(); |
5464 if (PrintCMSStatistics != 0) { | |
5465 gclog_or_tty->print_cr( | |
5466 "Finished work stealing in %dth thread: %3.3f sec", | |
4728
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5467 worker_id, _timer.seconds()); |
0 | 5468 } |
5469 } | |
5470 | |
1833
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5471 // Note that parameter "i" is not used. |
0 | 5472 void |
11975 | 5473 CMSParMarkTask::do_young_space_rescan(uint worker_id, |
5474 OopsInGenClosure* cl, ContiguousSpace* space, | |
0 | 5475 HeapWord** chunk_array, size_t chunk_top) { |
5476 // Until all tasks completed: | |
5477 // . claim an unclaimed task | |
5478 // . compute region boundaries corresponding to task claimed | |
5479 // using chunk_array | |
5480 // . par_oop_iterate(cl) over that region | |
5481 | |
5482 ResourceMark rm; | |
5483 HandleMark hm; | |
5484 | |
5485 SequentialSubTasksDone* pst = space->par_seq_tasks(); | |
5486 | |
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5487 uint nth_task = 0; |
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5488 uint n_tasks = pst->n_tasks(); |
0 | 5489 |
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5490 if (n_tasks > 0) { |
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5491 assert(pst->valid(), "Uninitialized use?"); |
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5492 HeapWord *start, *end; |
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5493 while (!pst->is_task_claimed(/* reference */ nth_task)) { |
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5494 // We claimed task # nth_task; compute its boundaries. |
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5495 if (chunk_top == 0) { // no samples were taken |
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5496 assert(nth_task == 0 && n_tasks == 1, "Can have only 1 EdenSpace task"); |
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5497 start = space->bottom(); |
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5498 end = space->top(); |
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5499 } else if (nth_task == 0) { |
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5500 start = space->bottom(); |
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5501 end = chunk_array[nth_task]; |
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5502 } else if (nth_task < (uint)chunk_top) { |
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5503 assert(nth_task >= 1, "Control point invariant"); |
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5504 start = chunk_array[nth_task - 1]; |
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5505 end = chunk_array[nth_task]; |
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5506 } else { |
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5507 assert(nth_task == (uint)chunk_top, "Control point invariant"); |
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5508 start = chunk_array[chunk_top - 1]; |
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5509 end = space->top(); |
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5510 } |
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5511 MemRegion mr(start, end); |
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5512 // Verify that mr is in space |
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5513 assert(mr.is_empty() || space->used_region().contains(mr), |
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5514 "Should be in space"); |
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5515 // Verify that "start" is an object boundary |
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5516 assert(mr.is_empty() || oop(mr.start())->is_oop(), |
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5517 "Should be an oop"); |
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5518 space->par_oop_iterate(mr, cl); |
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5519 } |
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5520 pst->all_tasks_completed(); |
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5521 } |
0 | 5522 } |
5523 | |
5524 void | |
5525 CMSParRemarkTask::do_dirty_card_rescan_tasks( | |
5526 CompactibleFreeListSpace* sp, int i, | |
5527 Par_MarkRefsIntoAndScanClosure* cl) { | |
5528 // Until all tasks completed: | |
5529 // . claim an unclaimed task | |
5530 // . compute region boundaries corresponding to task claimed | |
5531 // . transfer dirty bits ct->mut for that region | |
5532 // . apply rescanclosure to dirty mut bits for that region | |
5533 | |
5534 ResourceMark rm; | |
5535 HandleMark hm; | |
5536 | |
5537 OopTaskQueue* work_q = work_queue(i); | |
5538 ModUnionClosure modUnionClosure(&(_collector->_modUnionTable)); | |
5539 // CAUTION! CAUTION! CAUTION! CAUTION! CAUTION! CAUTION! CAUTION! | |
5540 // CAUTION: This closure has state that persists across calls to | |
5541 // the work method dirty_range_iterate_clear() in that it has | |
5542 // imbedded in it a (subtype of) UpwardsObjectClosure. The | |
5543 // use of that state in the imbedded UpwardsObjectClosure instance | |
5544 // assumes that the cards are always iterated (even if in parallel | |
5545 // by several threads) in monotonically increasing order per each | |
5546 // thread. This is true of the implementation below which picks | |
5547 // card ranges (chunks) in monotonically increasing order globally | |
5548 // and, a-fortiori, in monotonically increasing order per thread | |
5549 // (the latter order being a subsequence of the former). | |
5550 // If the work code below is ever reorganized into a more chaotic | |
5551 // work-partitioning form than the current "sequential tasks" | |
5552 // paradigm, the use of that persistent state will have to be | |
5553 // revisited and modified appropriately. See also related | |
5554 // bug 4756801 work on which should examine this code to make | |
5555 // sure that the changes there do not run counter to the | |
5556 // assumptions made here and necessary for correctness and | |
5557 // efficiency. Note also that this code might yield inefficient | |
5558 // behaviour in the case of very large objects that span one or | |
5559 // more work chunks. Such objects would potentially be scanned | |
5560 // several times redundantly. Work on 4756801 should try and | |
5561 // address that performance anomaly if at all possible. XXX | |
5562 MemRegion full_span = _collector->_span; | |
5563 CMSBitMap* bm = &(_collector->_markBitMap); // shared | |
5564 MarkFromDirtyCardsClosure | |
5565 greyRescanClosure(_collector, full_span, // entire span of interest | |
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5566 sp, bm, work_q, cl); |
0 | 5567 |
5568 SequentialSubTasksDone* pst = sp->conc_par_seq_tasks(); | |
5569 assert(pst->valid(), "Uninitialized use?"); | |
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5570 uint nth_task = 0; |
0 | 5571 const int alignment = CardTableModRefBS::card_size * BitsPerWord; |
5572 MemRegion span = sp->used_region(); | |
5573 HeapWord* start_addr = span.start(); | |
5574 HeapWord* end_addr = (HeapWord*)round_to((intptr_t)span.end(), | |
5575 alignment); | |
5576 const size_t chunk_size = sp->rescan_task_size(); // in HeapWord units | |
5577 assert((HeapWord*)round_to((intptr_t)start_addr, alignment) == | |
5578 start_addr, "Check alignment"); | |
5579 assert((size_t)round_to((intptr_t)chunk_size, alignment) == | |
5580 chunk_size, "Check alignment"); | |
5581 | |
5582 while (!pst->is_task_claimed(/* reference */ nth_task)) { | |
5583 // Having claimed the nth_task, compute corresponding mem-region, | |
5584 // which is a-fortiori aligned correctly (i.e. at a MUT bopundary). | |
5585 // The alignment restriction ensures that we do not need any | |
5586 // synchronization with other gang-workers while setting or | |
5587 // clearing bits in thus chunk of the MUT. | |
5588 MemRegion this_span = MemRegion(start_addr + nth_task*chunk_size, | |
5589 start_addr + (nth_task+1)*chunk_size); | |
5590 // The last chunk's end might be way beyond end of the | |
5591 // used region. In that case pull back appropriately. | |
5592 if (this_span.end() > end_addr) { | |
5593 this_span.set_end(end_addr); | |
5594 assert(!this_span.is_empty(), "Program logic (calculation of n_tasks)"); | |
5595 } | |
5596 // Iterate over the dirty cards covering this chunk, marking them | |
5597 // precleaned, and setting the corresponding bits in the mod union | |
5598 // table. Since we have been careful to partition at Card and MUT-word | |
5599 // boundaries no synchronization is needed between parallel threads. | |
5600 _collector->_ct->ct_bs()->dirty_card_iterate(this_span, | |
5601 &modUnionClosure); | |
5602 | |
5603 // Having transferred these marks into the modUnionTable, | |
5604 // rescan the marked objects on the dirty cards in the modUnionTable. | |
5605 // Even if this is at a synchronous collection, the initial marking | |
5606 // may have been done during an asynchronous collection so there | |
5607 // may be dirty bits in the mod-union table. | |
5608 _collector->_modUnionTable.dirty_range_iterate_clear( | |
5609 this_span, &greyRescanClosure); | |
5610 _collector->_modUnionTable.verifyNoOneBitsInRange( | |
5611 this_span.start(), | |
5612 this_span.end()); | |
5613 } | |
5614 pst->all_tasks_completed(); // declare that i am done | |
5615 } | |
5616 | |
5617 // . see if we can share work_queues with ParNew? XXX | |
5618 void | |
5619 CMSParRemarkTask::do_work_steal(int i, Par_MarkRefsIntoAndScanClosure* cl, | |
5620 int* seed) { | |
5621 OopTaskQueue* work_q = work_queue(i); | |
5622 NOT_PRODUCT(int num_steals = 0;) | |
5623 oop obj_to_scan; | |
5624 CMSBitMap* bm = &(_collector->_markBitMap); | |
5625 | |
5626 while (true) { | |
5627 // Completely finish any left over work from (an) earlier round(s) | |
5628 cl->trim_queue(0); | |
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5629 size_t num_from_overflow_list = MIN2((size_t)(work_q->max_elems() - work_q->size())/4, |
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5630 (size_t)ParGCDesiredObjsFromOverflowList); |
0 | 5631 // Now check if there's any work in the overflow list |
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5632 // Passing ParallelGCThreads as the third parameter, no_of_gc_threads, |
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5633 // only affects the number of attempts made to get work from the |
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5634 // overflow list and does not affect the number of workers. Just |
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5635 // pass ParallelGCThreads so this behavior is unchanged. |
0 | 5636 if (_collector->par_take_from_overflow_list(num_from_overflow_list, |
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|
5637 work_q, |
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5638 ParallelGCThreads)) { |
0 | 5639 // found something in global overflow list; |
5640 // not yet ready to go stealing work from others. | |
5641 // We'd like to assert(work_q->size() != 0, ...) | |
5642 // because we just took work from the overflow list, | |
5643 // but of course we can't since all of that could have | |
5644 // been already stolen from us. | |
5645 // "He giveth and He taketh away." | |
5646 continue; | |
5647 } | |
5648 // Verify that we have no work before we resort to stealing | |
5649 assert(work_q->size() == 0, "Have work, shouldn't steal"); | |
5650 // Try to steal from other queues that have work | |
5651 if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) { | |
5652 NOT_PRODUCT(num_steals++;) | |
5653 assert(obj_to_scan->is_oop(), "Oops, not an oop!"); | |
5654 assert(bm->isMarked((HeapWord*)obj_to_scan), "Stole an unmarked oop?"); | |
5655 // Do scanning work | |
5656 obj_to_scan->oop_iterate(cl); | |
5657 // Loop around, finish this work, and try to steal some more | |
5658 } else if (terminator()->offer_termination()) { | |
5659 break; // nirvana from the infinite cycle | |
5660 } | |
5661 } | |
5662 NOT_PRODUCT( | |
5663 if (PrintCMSStatistics != 0) { | |
5664 gclog_or_tty->print("\n\t(%d: stole %d oops)", i, num_steals); | |
5665 } | |
5666 ) | |
5667 assert(work_q->size() == 0 && _collector->overflow_list_is_empty(), | |
5668 "Else our work is not yet done"); | |
5669 } | |
5670 | |
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5671 // Record object boundaries in _eden_chunk_array by sampling the eden |
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5672 // top in the slow-path eden object allocation code path and record |
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5673 // the boundaries, if CMSEdenChunksRecordAlways is true. If |
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5674 // CMSEdenChunksRecordAlways is false, we use the other asynchronous |
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5675 // sampling in sample_eden() that activates during the part of the |
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5676 // preclean phase. |
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5677 void CMSCollector::sample_eden_chunk() { |
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5678 if (CMSEdenChunksRecordAlways && _eden_chunk_array != NULL) { |
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5679 if (_eden_chunk_lock->try_lock()) { |
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5680 // Record a sample. This is the critical section. The contents |
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5681 // of the _eden_chunk_array have to be non-decreasing in the |
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5682 // address order. |
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5683 _eden_chunk_array[_eden_chunk_index] = *_top_addr; |
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5684 assert(_eden_chunk_array[_eden_chunk_index] <= *_end_addr, |
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5685 "Unexpected state of Eden"); |
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5686 if (_eden_chunk_index == 0 || |
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5687 ((_eden_chunk_array[_eden_chunk_index] > _eden_chunk_array[_eden_chunk_index-1]) && |
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5688 (pointer_delta(_eden_chunk_array[_eden_chunk_index], |
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5689 _eden_chunk_array[_eden_chunk_index-1]) >= CMSSamplingGrain))) { |
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5690 _eden_chunk_index++; // commit sample |
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5691 } |
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5692 _eden_chunk_lock->unlock(); |
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5693 } |
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5694 } |
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5695 } |
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5696 |
0 | 5697 // Return a thread-local PLAB recording array, as appropriate. |
5698 void* CMSCollector::get_data_recorder(int thr_num) { | |
5699 if (_survivor_plab_array != NULL && | |
5700 (CMSPLABRecordAlways || | |
5701 (_collectorState > Marking && _collectorState < FinalMarking))) { | |
5702 assert(thr_num < (int)ParallelGCThreads, "thr_num is out of bounds"); | |
5703 ChunkArray* ca = &_survivor_plab_array[thr_num]; | |
5704 ca->reset(); // clear it so that fresh data is recorded | |
5705 return (void*) ca; | |
5706 } else { | |
5707 return NULL; | |
5708 } | |
5709 } | |
5710 | |
5711 // Reset all the thread-local PLAB recording arrays | |
5712 void CMSCollector::reset_survivor_plab_arrays() { | |
5713 for (uint i = 0; i < ParallelGCThreads; i++) { | |
5714 _survivor_plab_array[i].reset(); | |
5715 } | |
5716 } | |
5717 | |
5718 // Merge the per-thread plab arrays into the global survivor chunk | |
5719 // array which will provide the partitioning of the survivor space | |
11975 | 5720 // for CMS initial scan and rescan. |
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5721 void CMSCollector::merge_survivor_plab_arrays(ContiguousSpace* surv, |
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5722 int no_of_gc_threads) { |
0 | 5723 assert(_survivor_plab_array != NULL, "Error"); |
5724 assert(_survivor_chunk_array != NULL, "Error"); | |
11975 | 5725 assert(_collectorState == FinalMarking || |
5726 (CMSParallelInitialMarkEnabled && _collectorState == InitialMarking), "Error"); | |
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5727 for (int j = 0; j < no_of_gc_threads; j++) { |
0 | 5728 _cursor[j] = 0; |
5729 } | |
5730 HeapWord* top = surv->top(); | |
5731 size_t i; | |
5732 for (i = 0; i < _survivor_chunk_capacity; i++) { // all sca entries | |
5733 HeapWord* min_val = top; // Higher than any PLAB address | |
5734 uint min_tid = 0; // position of min_val this round | |
1833
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5735 for (int j = 0; j < no_of_gc_threads; j++) { |
0 | 5736 ChunkArray* cur_sca = &_survivor_plab_array[j]; |
5737 if (_cursor[j] == cur_sca->end()) { | |
5738 continue; | |
5739 } | |
5740 assert(_cursor[j] < cur_sca->end(), "ctl pt invariant"); | |
5741 HeapWord* cur_val = cur_sca->nth(_cursor[j]); | |
5742 assert(surv->used_region().contains(cur_val), "Out of bounds value"); | |
5743 if (cur_val < min_val) { | |
5744 min_tid = j; | |
5745 min_val = cur_val; | |
5746 } else { | |
5747 assert(cur_val < top, "All recorded addresses should be less"); | |
5748 } | |
5749 } | |
5750 // At this point min_val and min_tid are respectively | |
5751 // the least address in _survivor_plab_array[j]->nth(_cursor[j]) | |
5752 // and the thread (j) that witnesses that address. | |
5753 // We record this address in the _survivor_chunk_array[i] | |
5754 // and increment _cursor[min_tid] prior to the next round i. | |
5755 if (min_val == top) { | |
5756 break; | |
5757 } | |
5758 _survivor_chunk_array[i] = min_val; | |
5759 _cursor[min_tid]++; | |
5760 } | |
5761 // We are all done; record the size of the _survivor_chunk_array | |
5762 _survivor_chunk_index = i; // exclusive: [0, i) | |
5763 if (PrintCMSStatistics > 0) { | |
5764 gclog_or_tty->print(" (Survivor:" SIZE_FORMAT "chunks) ", i); | |
5765 } | |
5766 // Verify that we used up all the recorded entries | |
5767 #ifdef ASSERT | |
5768 size_t total = 0; | |
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5769 for (int j = 0; j < no_of_gc_threads; j++) { |
0 | 5770 assert(_cursor[j] == _survivor_plab_array[j].end(), "Ctl pt invariant"); |
5771 total += _cursor[j]; | |
5772 } | |
5773 assert(total == _survivor_chunk_index, "Ctl Pt Invariant"); | |
5774 // Check that the merged array is in sorted order | |
5775 if (total > 0) { | |
5776 for (size_t i = 0; i < total - 1; i++) { | |
5777 if (PrintCMSStatistics > 0) { | |
5778 gclog_or_tty->print(" (chunk" SIZE_FORMAT ":" INTPTR_FORMAT ") ", | |
5779 i, _survivor_chunk_array[i]); | |
5780 } | |
5781 assert(_survivor_chunk_array[i] < _survivor_chunk_array[i+1], | |
5782 "Not sorted"); | |
5783 } | |
5784 } | |
5785 #endif // ASSERT | |
5786 } | |
5787 | |
5788 // Set up the space's par_seq_tasks structure for work claiming | |
11975 | 5789 // for parallel initial scan and rescan of young gen. |
0 | 5790 // See ParRescanTask where this is currently used. |
5791 void | |
5792 CMSCollector:: | |
5793 initialize_sequential_subtasks_for_young_gen_rescan(int n_threads) { | |
5794 assert(n_threads > 0, "Unexpected n_threads argument"); | |
5795 DefNewGeneration* dng = (DefNewGeneration*)_young_gen; | |
5796 | |
5797 // Eden space | |
12088
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5798 if (!dng->eden()->is_empty()) { |
0 | 5799 SequentialSubTasksDone* pst = dng->eden()->par_seq_tasks(); |
5800 assert(!pst->valid(), "Clobbering existing data?"); | |
5801 // Each valid entry in [0, _eden_chunk_index) represents a task. | |
5802 size_t n_tasks = _eden_chunk_index + 1; | |
5803 assert(n_tasks == 1 || _eden_chunk_array != NULL, "Error"); | |
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5804 // Sets the condition for completion of the subtask (how many threads |
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5805 // need to finish in order to be done). |
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5806 pst->set_n_threads(n_threads); |
0 | 5807 pst->set_n_tasks((int)n_tasks); |
5808 } | |
5809 | |
5810 // Merge the survivor plab arrays into _survivor_chunk_array | |
5811 if (_survivor_plab_array != NULL) { | |
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5812 merge_survivor_plab_arrays(dng->from(), n_threads); |
0 | 5813 } else { |
5814 assert(_survivor_chunk_index == 0, "Error"); | |
5815 } | |
5816 | |
5817 // To space | |
5818 { | |
5819 SequentialSubTasksDone* pst = dng->to()->par_seq_tasks(); | |
5820 assert(!pst->valid(), "Clobbering existing data?"); | |
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5821 // Sets the condition for completion of the subtask (how many threads |
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5822 // need to finish in order to be done). |
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5823 pst->set_n_threads(n_threads); |
0 | 5824 pst->set_n_tasks(1); |
5825 assert(pst->valid(), "Error"); | |
5826 } | |
5827 | |
5828 // From space | |
5829 { | |
5830 SequentialSubTasksDone* pst = dng->from()->par_seq_tasks(); | |
5831 assert(!pst->valid(), "Clobbering existing data?"); | |
5832 size_t n_tasks = _survivor_chunk_index + 1; | |
5833 assert(n_tasks == 1 || _survivor_chunk_array != NULL, "Error"); | |
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5834 // Sets the condition for completion of the subtask (how many threads |
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5835 // need to finish in order to be done). |
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5836 pst->set_n_threads(n_threads); |
0 | 5837 pst->set_n_tasks((int)n_tasks); |
5838 assert(pst->valid(), "Error"); | |
5839 } | |
5840 } | |
5841 | |
5842 // Parallel version of remark | |
5843 void CMSCollector::do_remark_parallel() { | |
5844 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
1833
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5845 FlexibleWorkGang* workers = gch->workers(); |
0 | 5846 assert(workers != NULL, "Need parallel worker threads."); |
4095
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5847 // Choose to use the number of GC workers most recently set |
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5848 // into "active_workers". If active_workers is not set, set it |
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5849 // to ParallelGCThreads. |
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5850 int n_workers = workers->active_workers(); |
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5851 if (n_workers == 0) { |
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5852 assert(n_workers > 0, "Should have been set during scavenge"); |
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5853 n_workers = ParallelGCThreads; |
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5854 workers->set_active_workers(n_workers); |
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5855 } |
0 | 5856 CompactibleFreeListSpace* cms_space = _cmsGen->cmsSpace(); |
5857 | |
5858 CMSParRemarkTask tsk(this, | |
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5859 cms_space, |
0 | 5860 n_workers, workers, task_queues()); |
5861 | |
5862 // Set up for parallel process_strong_roots work. | |
5863 gch->set_par_threads(n_workers); | |
5864 // We won't be iterating over the cards in the card table updating | |
5865 // the younger_gen cards, so we shouldn't call the following else | |
5866 // the verification code as well as subsequent younger_refs_iterate | |
5867 // code would get confused. XXX | |
5868 // gch->rem_set()->prepare_for_younger_refs_iterate(true); // parallel | |
5869 | |
5870 // The young gen rescan work will not be done as part of | |
5871 // process_strong_roots (which currently doesn't knw how to | |
5872 // parallelize such a scan), but rather will be broken up into | |
5873 // a set of parallel tasks (via the sampling that the [abortable] | |
5874 // preclean phase did of EdenSpace, plus the [two] tasks of | |
5875 // scanning the [two] survivor spaces. Further fine-grain | |
5876 // parallelization of the scanning of the survivor spaces | |
5877 // themselves, and of precleaning of the younger gen itself | |
5878 // is deferred to the future. | |
5879 initialize_sequential_subtasks_for_young_gen_rescan(n_workers); | |
5880 | |
5881 // The dirty card rescan work is broken up into a "sequence" | |
5882 // of parallel tasks (per constituent space) that are dynamically | |
5883 // claimed by the parallel threads. | |
5884 cms_space->initialize_sequential_subtasks_for_rescan(n_workers); | |
5885 | |
5886 // It turns out that even when we're using 1 thread, doing the work in a | |
5887 // separate thread causes wide variance in run times. We can't help this | |
5888 // in the multi-threaded case, but we special-case n=1 here to get | |
5889 // repeatable measurements of the 1-thread overhead of the parallel code. | |
5890 if (n_workers > 1) { | |
2369
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5891 // Make refs discovery MT-safe, if it isn't already: it may not |
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5892 // necessarily be so, since it's possible that we are doing |
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5893 // ST marking. |
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5894 ReferenceProcessorMTDiscoveryMutator mt(ref_processor(), true); |
989
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5895 GenCollectedHeap::StrongRootsScope srs(gch); |
0 | 5896 workers->run_task(&tsk); |
5897 } else { | |
4876
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5898 ReferenceProcessorMTDiscoveryMutator mt(ref_processor(), false); |
989
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5899 GenCollectedHeap::StrongRootsScope srs(gch); |
0 | 5900 tsk.work(0); |
5901 } | |
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5902 |
0 | 5903 gch->set_par_threads(0); // 0 ==> non-parallel. |
5904 // restore, single-threaded for now, any preserved marks | |
5905 // as a result of work_q overflow | |
5906 restore_preserved_marks_if_any(); | |
5907 } | |
5908 | |
5909 // Non-parallel version of remark | |
5910 void CMSCollector::do_remark_non_parallel() { | |
5911 ResourceMark rm; | |
5912 HandleMark hm; | |
5913 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
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5914 ReferenceProcessorMTDiscoveryMutator mt(ref_processor(), false); |
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5915 |
0 | 5916 MarkRefsIntoAndScanClosure |
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5917 mrias_cl(_span, ref_processor(), &_markBitMap, NULL /* not precleaning */, |
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5918 &_markStack, this, |
0 | 5919 false /* should_yield */, false /* not precleaning */); |
5920 MarkFromDirtyCardsClosure | |
5921 markFromDirtyCardsClosure(this, _span, | |
5922 NULL, // space is set further below | |
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5923 &_markBitMap, &_markStack, &mrias_cl); |
0 | 5924 { |
10405 | 5925 GCTraceTime t("grey object rescan", PrintGCDetails, false, _gc_timer_cm); |
342
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5926 // Iterate over the dirty cards, setting the corresponding bits in the |
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|
5927 // mod union table. |
0 | 5928 { |
5929 ModUnionClosure modUnionClosure(&_modUnionTable); | |
5930 _ct->ct_bs()->dirty_card_iterate( | |
5931 _cmsGen->used_region(), | |
5932 &modUnionClosure); | |
5933 } | |
5934 // Having transferred these marks into the modUnionTable, we just need | |
5935 // to rescan the marked objects on the dirty cards in the modUnionTable. | |
5936 // The initial marking may have been done during an asynchronous | |
5937 // collection so there may be dirty bits in the mod-union table. | |
5938 const int alignment = | |
5939 CardTableModRefBS::card_size * BitsPerWord; | |
5940 { | |
5941 // ... First handle dirty cards in CMS gen | |
5942 markFromDirtyCardsClosure.set_space(_cmsGen->cmsSpace()); | |
5943 MemRegion ur = _cmsGen->used_region(); | |
5944 HeapWord* lb = ur.start(); | |
5945 HeapWord* ub = (HeapWord*)round_to((intptr_t)ur.end(), alignment); | |
5946 MemRegion cms_span(lb, ub); | |
5947 _modUnionTable.dirty_range_iterate_clear(cms_span, | |
5948 &markFromDirtyCardsClosure); | |
5949 verify_work_stacks_empty(); | |
5950 if (PrintCMSStatistics != 0) { | |
5951 gclog_or_tty->print(" (re-scanned "SIZE_FORMAT" dirty cards in cms gen) ", | |
5952 markFromDirtyCardsClosure.num_dirty_cards()); | |
5953 } | |
5954 } | |
5955 } | |
5956 if (VerifyDuringGC && | |
5957 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
5958 HandleMark hm; // Discard invalid handles created during verification | |
6865
4202510ee0fe
8000831: Heap verification output incorrect/incomplete
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|
5959 Universe::verify(); |
0 | 5960 } |
5961 { | |
10405 | 5962 GCTraceTime t("root rescan", PrintGCDetails, false, _gc_timer_cm); |
0 | 5963 |
5964 verify_work_stacks_empty(); | |
5965 | |
5966 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. | |
989
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5967 GenCollectedHeap::StrongRootsScope srs(gch); |
0 | 5968 gch->gen_process_strong_roots(_cmsGen->level(), |
5969 true, // younger gens as roots | |
989
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5970 false, // use the local StrongRootsScope |
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5971 false, // not scavenging |
0 | 5972 SharedHeap::ScanningOption(roots_scanning_options()), |
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|
5973 &mrias_cl, |
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|
5974 true, // walk code active on stacks |
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5975 NULL, |
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5976 NULL); // The dirty klasses will be handled below |
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5977 |
989
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|
5978 assert(should_unload_classes() |
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|
5979 || (roots_scanning_options() & SharedHeap::SO_CodeCache), |
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5980 "if we didn't scan the code cache, we have to be ready to drop nmethods with expired weak oops"); |
0 | 5981 } |
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5982 |
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5983 { |
10405 | 5984 GCTraceTime t("visit unhandled CLDs", PrintGCDetails, false, _gc_timer_cm); |
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|
5985 |
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5986 verify_work_stacks_empty(); |
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5987 |
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5988 // Scan all class loader data objects that might have been introduced |
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|
5989 // during concurrent marking. |
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|
5990 ResourceMark rm; |
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|
5991 GrowableArray<ClassLoaderData*>* array = ClassLoaderDataGraph::new_clds(); |
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5992 for (int i = 0; i < array->length(); i++) { |
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5993 mrias_cl.do_class_loader_data(array->at(i)); |
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5994 } |
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5995 |
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5996 // We don't need to keep track of new CLDs anymore. |
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|
5997 ClassLoaderDataGraph::remember_new_clds(false); |
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5998 |
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5999 verify_work_stacks_empty(); |
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6000 } |
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6001 |
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|
6002 { |
10405 | 6003 GCTraceTime t("dirty klass scan", PrintGCDetails, false, _gc_timer_cm); |
6725
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6004 |
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6005 verify_work_stacks_empty(); |
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6006 |
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6007 RemarkKlassClosure remark_klass_closure(&mrias_cl); |
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6008 ClassLoaderDataGraph::classes_do(&remark_klass_closure); |
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6009 |
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6010 verify_work_stacks_empty(); |
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6011 } |
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6012 |
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6013 // We might have added oops to ClassLoaderData::_handles during the |
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6014 // concurrent marking phase. These oops point to newly allocated objects |
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6015 // that are guaranteed to be kept alive. Either by the direct allocation |
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6016 // code, or when the young collector processes the strong roots. Hence, |
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6017 // we don't have to revisit the _handles block during the remark phase. |
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6018 |
0 | 6019 verify_work_stacks_empty(); |
6020 // Restore evacuated mark words, if any, used for overflow list links | |
6021 if (!CMSOverflowEarlyRestoration) { | |
6022 restore_preserved_marks_if_any(); | |
6023 } | |
6024 verify_overflow_empty(); | |
6025 } | |
6026 | |
6027 //////////////////////////////////////////////////////// | |
6028 // Parallel Reference Processing Task Proxy Class | |
6029 //////////////////////////////////////////////////////// | |
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6030 class CMSRefProcTaskProxy: public AbstractGangTaskWOopQueues { |
0 | 6031 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; |
6032 CMSCollector* _collector; | |
6033 CMSBitMap* _mark_bit_map; | |
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6034 const MemRegion _span; |
0 | 6035 ProcessTask& _task; |
6036 | |
6037 public: | |
6038 CMSRefProcTaskProxy(ProcessTask& task, | |
6039 CMSCollector* collector, | |
6040 const MemRegion& span, | |
6041 CMSBitMap* mark_bit_map, | |
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6042 AbstractWorkGang* workers, |
0 | 6043 OopTaskQueueSet* task_queues): |
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6044 // XXX Should superclass AGTWOQ also know about AWG since it knows |
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6045 // about the task_queues used by the AWG? Then it could initialize |
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6046 // the terminator() object. See 6984287. The set_for_termination() |
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6047 // below is a temporary band-aid for the regression in 6984287. |
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6048 AbstractGangTaskWOopQueues("Process referents by policy in parallel", |
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6049 task_queues), |
0 | 6050 _task(task), |
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6051 _collector(collector), _span(span), _mark_bit_map(mark_bit_map) |
2369
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6052 { |
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6053 assert(_collector->_span.equals(_span) && !_span.is_empty(), |
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6054 "Inconsistency in _span"); |
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6055 set_for_termination(workers->active_workers()); |
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6056 } |
0 | 6057 |
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6058 OopTaskQueueSet* task_queues() { return queues(); } |
0 | 6059 |
6060 OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); } | |
6061 | |
6062 void do_work_steal(int i, | |
6063 CMSParDrainMarkingStackClosure* drain, | |
6064 CMSParKeepAliveClosure* keep_alive, | |
6065 int* seed); | |
6066 | |
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6067 virtual void work(uint worker_id); |
0 | 6068 }; |
6069 | |
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6070 void CMSRefProcTaskProxy::work(uint worker_id) { |
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6071 assert(_collector->_span.equals(_span), "Inconsistency in _span"); |
0 | 6072 CMSParKeepAliveClosure par_keep_alive(_collector, _span, |
935 | 6073 _mark_bit_map, |
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|
6074 work_queue(worker_id)); |
0 | 6075 CMSParDrainMarkingStackClosure par_drain_stack(_collector, _span, |
935 | 6076 _mark_bit_map, |
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|
6077 work_queue(worker_id)); |
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6078 CMSIsAliveClosure is_alive_closure(_span, _mark_bit_map); |
4728
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|
6079 _task.work(worker_id, is_alive_closure, par_keep_alive, par_drain_stack); |
0 | 6080 if (_task.marks_oops_alive()) { |
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|
6081 do_work_steal(worker_id, &par_drain_stack, &par_keep_alive, |
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|
6082 _collector->hash_seed(worker_id)); |
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|
6083 } |
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|
6084 assert(work_queue(worker_id)->size() == 0, "work_queue should be empty"); |
0 | 6085 assert(_collector->_overflow_list == NULL, "non-empty _overflow_list"); |
6086 } | |
6087 | |
6088 class CMSRefEnqueueTaskProxy: public AbstractGangTask { | |
6089 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; | |
6090 EnqueueTask& _task; | |
6091 | |
6092 public: | |
6093 CMSRefEnqueueTaskProxy(EnqueueTask& task) | |
6094 : AbstractGangTask("Enqueue reference objects in parallel"), | |
6095 _task(task) | |
6096 { } | |
6097 | |
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|
6098 virtual void work(uint worker_id) |
0 | 6099 { |
4728
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|
6100 _task.work(worker_id); |
0 | 6101 } |
6102 }; | |
6103 | |
6104 CMSParKeepAliveClosure::CMSParKeepAliveClosure(CMSCollector* collector, | |
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6105 MemRegion span, CMSBitMap* bit_map, OopTaskQueue* work_queue): |
0 | 6106 _span(span), |
6107 _bit_map(bit_map), | |
6108 _work_queue(work_queue), | |
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6109 _mark_and_push(collector, span, bit_map, work_queue), |
0 | 6110 _low_water_mark(MIN2((uint)(work_queue->max_elems()/4), |
6111 (uint)(CMSWorkQueueDrainThreshold * ParallelGCThreads))) | |
6112 { } | |
6113 | |
6114 // . see if we can share work_queues with ParNew? XXX | |
6115 void CMSRefProcTaskProxy::do_work_steal(int i, | |
6116 CMSParDrainMarkingStackClosure* drain, | |
6117 CMSParKeepAliveClosure* keep_alive, | |
6118 int* seed) { | |
6119 OopTaskQueue* work_q = work_queue(i); | |
6120 NOT_PRODUCT(int num_steals = 0;) | |
6121 oop obj_to_scan; | |
6122 | |
6123 while (true) { | |
6124 // Completely finish any left over work from (an) earlier round(s) | |
6125 drain->trim_queue(0); | |
679
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6819891: ParNew: Fix work queue overflow code to deal correctly with +UseCompressedOops
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|
6126 size_t num_from_overflow_list = MIN2((size_t)(work_q->max_elems() - work_q->size())/4, |
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6819891: ParNew: Fix work queue overflow code to deal correctly with +UseCompressedOops
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|
6127 (size_t)ParGCDesiredObjsFromOverflowList); |
0 | 6128 // Now check if there's any work in the overflow list |
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6129 // Passing ParallelGCThreads as the third parameter, no_of_gc_threads, |
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|
6130 // only affects the number of attempts made to get work from the |
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|
6131 // overflow list and does not affect the number of workers. Just |
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|
6132 // pass ParallelGCThreads so this behavior is unchanged. |
0 | 6133 if (_collector->par_take_from_overflow_list(num_from_overflow_list, |
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|
6134 work_q, |
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|
6135 ParallelGCThreads)) { |
0 | 6136 // Found something in global overflow list; |
6137 // not yet ready to go stealing work from others. | |
6138 // We'd like to assert(work_q->size() != 0, ...) | |
6139 // because we just took work from the overflow list, | |
6140 // but of course we can't, since all of that might have | |
6141 // been already stolen from us. | |
6142 continue; | |
6143 } | |
6144 // Verify that we have no work before we resort to stealing | |
6145 assert(work_q->size() == 0, "Have work, shouldn't steal"); | |
6146 // Try to steal from other queues that have work | |
6147 if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) { | |
6148 NOT_PRODUCT(num_steals++;) | |
6149 assert(obj_to_scan->is_oop(), "Oops, not an oop!"); | |
6150 assert(_mark_bit_map->isMarked((HeapWord*)obj_to_scan), "Stole an unmarked oop?"); | |
6151 // Do scanning work | |
6152 obj_to_scan->oop_iterate(keep_alive); | |
6153 // Loop around, finish this work, and try to steal some more | |
6154 } else if (terminator()->offer_termination()) { | |
6155 break; // nirvana from the infinite cycle | |
6156 } | |
6157 } | |
6158 NOT_PRODUCT( | |
6159 if (PrintCMSStatistics != 0) { | |
6160 gclog_or_tty->print("\n\t(%d: stole %d oops)", i, num_steals); | |
6161 } | |
6162 ) | |
6163 } | |
6164 | |
6165 void CMSRefProcTaskExecutor::execute(ProcessTask& task) | |
6166 { | |
6167 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
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6168 FlexibleWorkGang* workers = gch->workers(); |
0 | 6169 assert(workers != NULL, "Need parallel worker threads."); |
6170 CMSRefProcTaskProxy rp_task(task, &_collector, | |
6171 _collector.ref_processor()->span(), | |
6172 _collector.markBitMap(), | |
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|
6173 workers, _collector.task_queues()); |
0 | 6174 workers->run_task(&rp_task); |
6175 } | |
6176 | |
6177 void CMSRefProcTaskExecutor::execute(EnqueueTask& task) | |
6178 { | |
6179 | |
6180 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
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6181 FlexibleWorkGang* workers = gch->workers(); |
0 | 6182 assert(workers != NULL, "Need parallel worker threads."); |
6183 CMSRefEnqueueTaskProxy enq_task(task); | |
6184 workers->run_task(&enq_task); | |
6185 } | |
6186 | |
6187 void CMSCollector::refProcessingWork(bool asynch, bool clear_all_soft_refs) { | |
6188 | |
6189 ResourceMark rm; | |
6190 HandleMark hm; | |
6191 | |
6192 ReferenceProcessor* rp = ref_processor(); | |
6193 assert(rp->span().equals(_span), "Spans should be equal"); | |
453
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6194 assert(!rp->enqueuing_is_done(), "Enqueuing should not be complete"); |
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diff
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|
6195 // Process weak references. |
457
27a80744a83b
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|
6196 rp->setup_policy(clear_all_soft_refs); |
453
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|
6197 verify_work_stacks_empty(); |
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|
6198 |
0 | 6199 CMSKeepAliveClosure cmsKeepAliveClosure(this, _span, &_markBitMap, |
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6200 &_markStack, false /* !preclean */); |
0 | 6201 CMSDrainMarkingStackClosure cmsDrainMarkingStackClosure(this, |
6202 _span, &_markBitMap, &_markStack, | |
452
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|
6203 &cmsKeepAliveClosure, false /* !preclean */); |
0 | 6204 { |
10405 | 6205 GCTraceTime t("weak refs processing", PrintGCDetails, false, _gc_timer_cm); |
6206 | |
6207 ReferenceProcessorStats stats; | |
0 | 6208 if (rp->processing_is_mt()) { |
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6209 // Set the degree of MT here. If the discovery is done MT, there |
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|
6210 // may have been a different number of threads doing the discovery |
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|
6211 // and a different number of discovered lists may have Ref objects. |
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6212 // That is OK as long as the Reference lists are balanced (see |
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|
6213 // balance_all_queues() and balance_queues()). |
4095
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6214 GenCollectedHeap* gch = GenCollectedHeap::heap(); |
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6215 int active_workers = ParallelGCThreads; |
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6216 FlexibleWorkGang* workers = gch->workers(); |
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6217 if (workers != NULL) { |
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|
6218 active_workers = workers->active_workers(); |
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6219 // The expectation is that active_workers will have already |
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|
6220 // been set to a reasonable value. If it has not been set, |
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|
6221 // investigate. |
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|
6222 assert(active_workers > 0, "Should have been set during scavenge"); |
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|
6223 } |
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|
6224 rp->set_active_mt_degree(active_workers); |
0 | 6225 CMSRefProcTaskExecutor task_executor(*this); |
10405 | 6226 stats = rp->process_discovered_references(&_is_alive_closure, |
0 | 6227 &cmsKeepAliveClosure, |
6228 &cmsDrainMarkingStackClosure, | |
10405 | 6229 &task_executor, |
6230 _gc_timer_cm); | |
0 | 6231 } else { |
10405 | 6232 stats = rp->process_discovered_references(&_is_alive_closure, |
0 | 6233 &cmsKeepAliveClosure, |
6234 &cmsDrainMarkingStackClosure, | |
10405 | 6235 NULL, |
6236 _gc_timer_cm); | |
6237 } | |
6238 _gc_tracer_cm->report_gc_reference_stats(stats); | |
6239 | |
10188
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6240 } |
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|
6241 |
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6242 // This is the point where the entire marking should have completed. |
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|
6243 verify_work_stacks_empty(); |
0 | 6244 |
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|
6245 if (should_unload_classes()) { |
0 | 6246 { |
10405 | 6247 GCTraceTime t("class unloading", PrintGCDetails, false, _gc_timer_cm); |
0 | 6248 |
10188
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6249 // Unload classes and purge the SystemDictionary. |
0 | 6250 bool purged_class = SystemDictionary::do_unloading(&_is_alive_closure); |
6251 | |
10188
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6252 // Unload nmethods. |
6787
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|
6253 CodeCache::do_unloading(&_is_alive_closure, purged_class); |
0 | 6254 |
10188
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6255 // Prune dead klasses from subklass/sibling/implementor lists. |
6725
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6256 Klass::clean_weak_klass_links(&_is_alive_closure); |
0 | 6257 } |
6258 | |
6259 { | |
10405 | 6260 GCTraceTime t("scrub symbol table", PrintGCDetails, false, _gc_timer_cm); |
2177
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6261 // Clean up unreferenced symbols in symbol table. |
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6262 SymbolTable::unlink(); |
0 | 6263 } |
6264 } | |
6265 | |
6725
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6266 // CMS doesn't use the StringTable as hard roots when class unloading is turned off. |
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6267 // Need to check if we really scanned the StringTable. |
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6268 if ((roots_scanning_options() & SharedHeap::SO_Strings) == 0) { |
10405 | 6269 GCTraceTime t("scrub string table", PrintGCDetails, false, _gc_timer_cm); |
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6270 // Delete entries for dead interned strings. |
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6271 StringTable::unlink(&_is_alive_closure); |
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6272 } |
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6273 |
0 | 6274 // Restore any preserved marks as a result of mark stack or |
6275 // work queue overflow | |
6276 restore_preserved_marks_if_any(); // done single-threaded for now | |
6277 | |
6278 rp->set_enqueuing_is_done(true); | |
6279 if (rp->processing_is_mt()) { | |
1833
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6280 rp->balance_all_queues(); |
0 | 6281 CMSRefProcTaskExecutor task_executor(*this); |
6282 rp->enqueue_discovered_references(&task_executor); | |
6283 } else { | |
6284 rp->enqueue_discovered_references(NULL); | |
6285 } | |
6286 rp->verify_no_references_recorded(); | |
6287 assert(!rp->discovery_enabled(), "should have been disabled"); | |
6288 } | |
6289 | |
6290 #ifndef PRODUCT | |
6291 void CMSCollector::check_correct_thread_executing() { | |
6292 Thread* t = Thread::current(); | |
6293 // Only the VM thread or the CMS thread should be here. | |
6294 assert(t->is_ConcurrentGC_thread() || t->is_VM_thread(), | |
6295 "Unexpected thread type"); | |
6296 // If this is the vm thread, the foreground process | |
6297 // should not be waiting. Note that _foregroundGCIsActive is | |
6298 // true while the foreground collector is waiting. | |
6299 if (_foregroundGCShouldWait) { | |
6300 // We cannot be the VM thread | |
6301 assert(t->is_ConcurrentGC_thread(), | |
6302 "Should be CMS thread"); | |
6303 } else { | |
6304 // We can be the CMS thread only if we are in a stop-world | |
6305 // phase of CMS collection. | |
6306 if (t->is_ConcurrentGC_thread()) { | |
6307 assert(_collectorState == InitialMarking || | |
6308 _collectorState == FinalMarking, | |
6309 "Should be a stop-world phase"); | |
6310 // The CMS thread should be holding the CMS_token. | |
6311 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
6312 "Potential interference with concurrently " | |
6313 "executing VM thread"); | |
6314 } | |
6315 } | |
6316 } | |
6317 #endif | |
6318 | |
6319 void CMSCollector::sweep(bool asynch) { | |
6320 assert(_collectorState == Sweeping, "just checking"); | |
6321 check_correct_thread_executing(); | |
6322 verify_work_stacks_empty(); | |
6323 verify_overflow_empty(); | |
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6324 increment_sweep_count(); |
3356
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6325 TraceCMSMemoryManagerStats tms(_collectorState,GenCollectedHeap::heap()->gc_cause()); |
1703
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6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
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|
6326 |
1145
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6327 _inter_sweep_timer.stop(); |
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6328 _inter_sweep_estimate.sample(_inter_sweep_timer.seconds()); |
0 | 6329 size_policy()->avg_cms_free_at_sweep()->sample(_cmsGen->free()); |
6330 | |
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6331 assert(!_intra_sweep_timer.is_active(), "Should not be active"); |
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6332 _intra_sweep_timer.reset(); |
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6333 _intra_sweep_timer.start(); |
0 | 6334 if (asynch) { |
6335 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
6336 CMSPhaseAccounting pa(this, "sweep", !PrintGCDetails); | |
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6337 // First sweep the old gen |
0 | 6338 { |
6339 CMSTokenSyncWithLocks ts(true, _cmsGen->freelistLock(), | |
6340 bitMapLock()); | |
6341 sweepWork(_cmsGen, asynch); | |
6342 } | |
6343 | |
6344 // Update Universe::_heap_*_at_gc figures. | |
6345 // We need all the free list locks to make the abstract state | |
6346 // transition from Sweeping to Resetting. See detailed note | |
6347 // further below. | |
6348 { | |
6725
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6349 CMSTokenSyncWithLocks ts(true, _cmsGen->freelistLock()); |
0 | 6350 // Update heap occupancy information which is used as |
6351 // input to soft ref clearing policy at the next gc. | |
6352 Universe::update_heap_info_at_gc(); | |
6353 _collectorState = Resizing; | |
6354 } | |
6355 } else { | |
6356 // already have needed locks | |
6357 sweepWork(_cmsGen, asynch); | |
6358 // Update heap occupancy information which is used as | |
6359 // input to soft ref clearing policy at the next gc. | |
6360 Universe::update_heap_info_at_gc(); | |
6361 _collectorState = Resizing; | |
6362 } | |
6363 verify_work_stacks_empty(); | |
6364 verify_overflow_empty(); | |
6365 | |
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|
6366 if (should_unload_classes()) { |
17935
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|
6367 // Delay purge to the beginning of the next safepoint. Metaspace::contains |
7384f6a12fc1
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|
6368 // requires that the virtual spaces are stable and not deleted. |
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|
6369 ClassLoaderDataGraph::set_should_purge(true); |
8784
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|
6370 } |
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|
6371 |
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6372 _intra_sweep_timer.stop(); |
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6373 _intra_sweep_estimate.sample(_intra_sweep_timer.seconds()); |
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6374 |
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|
6375 _inter_sweep_timer.reset(); |
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|
6376 _inter_sweep_timer.start(); |
0 | 6377 |
4911 | 6378 // We need to use a monotonically non-deccreasing time in ms |
6379 // or we will see time-warp warnings and os::javaTimeMillis() | |
6380 // does not guarantee monotonicity. | |
6381 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; | |
6382 update_time_of_last_gc(now); | |
0 | 6383 |
6384 // NOTE on abstract state transitions: | |
6385 // Mutators allocate-live and/or mark the mod-union table dirty | |
6386 // based on the state of the collection. The former is done in | |
6387 // the interval [Marking, Sweeping] and the latter in the interval | |
6388 // [Marking, Sweeping). Thus the transitions into the Marking state | |
6389 // and out of the Sweeping state must be synchronously visible | |
6390 // globally to the mutators. | |
6391 // The transition into the Marking state happens with the world | |
6392 // stopped so the mutators will globally see it. Sweeping is | |
6393 // done asynchronously by the background collector so the transition | |
6394 // from the Sweeping state to the Resizing state must be done | |
6395 // under the freelistLock (as is the check for whether to | |
6396 // allocate-live and whether to dirty the mod-union table). | |
6397 assert(_collectorState == Resizing, "Change of collector state to" | |
6398 " Resizing must be done under the freelistLocks (plural)"); | |
6399 | |
1888
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diff
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|
6400 // Now that sweeping has been completed, we clear |
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diff
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|
6401 // the incremental_collection_failed flag, |
0 | 6402 // thus inviting a younger gen collection to promote into |
6403 // this generation. If such a promotion may still fail, | |
6404 // the flag will be set again when a young collection is | |
6405 // attempted. | |
6406 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
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|
6407 gch->clear_incremental_collection_failed(); // Worth retrying as fresh space may have been freed up |
0 | 6408 gch->update_full_collections_completed(_collection_count_start); |
6409 } | |
6410 | |
6411 // FIX ME!!! Looks like this belongs in CFLSpace, with | |
6412 // CMSGen merely delegating to it. | |
6413 void ConcurrentMarkSweepGeneration::setNearLargestChunk() { | |
1145
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|
6414 double nearLargestPercent = FLSLargestBlockCoalesceProximity; |
0 | 6415 HeapWord* minAddr = _cmsSpace->bottom(); |
6416 HeapWord* largestAddr = | |
6028
f69a5d43dc19
7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
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diff
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|
6417 (HeapWord*) _cmsSpace->dictionary()->find_largest_dict(); |
1145
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|
6418 if (largestAddr == NULL) { |
0 | 6419 // The dictionary appears to be empty. In this case |
6420 // try to coalesce at the end of the heap. | |
6421 largestAddr = _cmsSpace->end(); | |
6422 } | |
6423 size_t largestOffset = pointer_delta(largestAddr, minAddr); | |
6424 size_t nearLargestOffset = | |
6425 (size_t)((double)largestOffset * nearLargestPercent) - MinChunkSize; | |
1145
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|
6426 if (PrintFLSStatistics != 0) { |
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|
6427 gclog_or_tty->print_cr( |
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diff
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|
6428 "CMS: Large Block: " PTR_FORMAT ";" |
e018e6884bd8
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|
6429 " Proximity: " PTR_FORMAT " -> " PTR_FORMAT, |
e018e6884bd8
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|
6430 largestAddr, |
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|
6431 _cmsSpace->nearLargestChunk(), minAddr + nearLargestOffset); |
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|
6432 } |
0 | 6433 _cmsSpace->set_nearLargestChunk(minAddr + nearLargestOffset); |
6434 } | |
6435 | |
6436 bool ConcurrentMarkSweepGeneration::isNearLargestChunk(HeapWord* addr) { | |
6437 return addr >= _cmsSpace->nearLargestChunk(); | |
6438 } | |
6439 | |
6440 FreeChunk* ConcurrentMarkSweepGeneration::find_chunk_at_end() { | |
6441 return _cmsSpace->find_chunk_at_end(); | |
6442 } | |
6443 | |
6444 void ConcurrentMarkSweepGeneration::update_gc_stats(int current_level, | |
6445 bool full) { | |
6446 // The next lower level has been collected. Gather any statistics | |
6447 // that are of interest at this point. | |
6448 if (!full && (current_level + 1) == level()) { | |
6449 // Gather statistics on the young generation collection. | |
6450 collector()->stats().record_gc0_end(used()); | |
6451 } | |
6452 } | |
6453 | |
6454 CMSAdaptiveSizePolicy* ConcurrentMarkSweepGeneration::size_policy() { | |
6455 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
6456 assert(gch->kind() == CollectedHeap::GenCollectedHeap, | |
6457 "Wrong type of heap"); | |
6458 CMSAdaptiveSizePolicy* sp = (CMSAdaptiveSizePolicy*) | |
6459 gch->gen_policy()->size_policy(); | |
6460 assert(sp->is_gc_cms_adaptive_size_policy(), | |
6461 "Wrong type of size policy"); | |
6462 return sp; | |
6463 } | |
6464 | |
6465 void ConcurrentMarkSweepGeneration::rotate_debug_collection_type() { | |
6466 if (PrintGCDetails && Verbose) { | |
6467 gclog_or_tty->print("Rotate from %d ", _debug_collection_type); | |
6468 } | |
6469 _debug_collection_type = (CollectionTypes) (_debug_collection_type + 1); | |
6470 _debug_collection_type = | |
6471 (CollectionTypes) (_debug_collection_type % Unknown_collection_type); | |
6472 if (PrintGCDetails && Verbose) { | |
6473 gclog_or_tty->print_cr("to %d ", _debug_collection_type); | |
6474 } | |
6475 } | |
6476 | |
6477 void CMSCollector::sweepWork(ConcurrentMarkSweepGeneration* gen, | |
6478 bool asynch) { | |
6479 // We iterate over the space(s) underlying this generation, | |
6480 // checking the mark bit map to see if the bits corresponding | |
6481 // to specific blocks are marked or not. Blocks that are | |
6482 // marked are live and are not swept up. All remaining blocks | |
6483 // are swept up, with coalescing on-the-fly as we sweep up | |
6484 // contiguous free and/or garbage blocks: | |
6485 // We need to ensure that the sweeper synchronizes with allocators | |
6486 // and stop-the-world collectors. In particular, the following | |
6487 // locks are used: | |
6488 // . CMS token: if this is held, a stop the world collection cannot occur | |
6489 // . freelistLock: if this is held no allocation can occur from this | |
6490 // generation by another thread | |
6491 // . bitMapLock: if this is held, no other thread can access or update | |
6492 // | |
6493 | |
6494 // Note that we need to hold the freelistLock if we use | |
6495 // block iterate below; else the iterator might go awry if | |
6496 // a mutator (or promotion) causes block contents to change | |
6497 // (for instance if the allocator divvies up a block). | |
6498 // If we hold the free list lock, for all practical purposes | |
6499 // young generation GC's can't occur (they'll usually need to | |
6500 // promote), so we might as well prevent all young generation | |
6501 // GC's while we do a sweeping step. For the same reason, we might | |
6502 // as well take the bit map lock for the entire duration | |
6503 | |
6504 // check that we hold the requisite locks | |
6505 assert(have_cms_token(), "Should hold cms token"); | |
6506 assert( (asynch && ConcurrentMarkSweepThread::cms_thread_has_cms_token()) | |
6507 || (!asynch && ConcurrentMarkSweepThread::vm_thread_has_cms_token()), | |
6508 "Should possess CMS token to sweep"); | |
6509 assert_lock_strong(gen->freelistLock()); | |
6510 assert_lock_strong(bitMapLock()); | |
6511 | |
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6512 assert(!_inter_sweep_timer.is_active(), "Was switched off in an outer context"); |
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6513 assert(_intra_sweep_timer.is_active(), "Was switched on in an outer context"); |
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|
6514 gen->cmsSpace()->beginSweepFLCensus((float)(_inter_sweep_timer.seconds()), |
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|
6515 _inter_sweep_estimate.padded_average(), |
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|
6516 _intra_sweep_estimate.padded_average()); |
0 | 6517 gen->setNearLargestChunk(); |
6518 | |
6519 { | |
6520 SweepClosure sweepClosure(this, gen, &_markBitMap, | |
6521 CMSYield && asynch); | |
6522 gen->cmsSpace()->blk_iterate_careful(&sweepClosure); | |
6523 // We need to free-up/coalesce garbage/blocks from a | |
6524 // co-terminal free run. This is done in the SweepClosure | |
6525 // destructor; so, do not remove this scope, else the | |
6526 // end-of-sweep-census below will be off by a little bit. | |
6527 } | |
6528 gen->cmsSpace()->sweep_completed(); | |
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|
6529 gen->cmsSpace()->endSweepFLCensus(sweep_count()); |
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|
6530 if (should_unload_classes()) { // unloaded classes this cycle, |
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|
6531 _concurrent_cycles_since_last_unload = 0; // ... reset count |
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6532 } else { // did not unload classes, |
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|
6533 _concurrent_cycles_since_last_unload++; // ... increment count |
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|
6534 } |
0 | 6535 } |
6536 | |
6537 // Reset CMS data structures (for now just the marking bit map) | |
6538 // preparatory for the next cycle. | |
6539 void CMSCollector::reset(bool asynch) { | |
6540 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
6541 CMSAdaptiveSizePolicy* sp = size_policy(); | |
6542 AdaptiveSizePolicyOutput(sp, gch->total_collections()); | |
6543 if (asynch) { | |
6544 CMSTokenSyncWithLocks ts(true, bitMapLock()); | |
6545 | |
6546 // If the state is not "Resetting", the foreground thread | |
6547 // has done a collection and the resetting. | |
6548 if (_collectorState != Resetting) { | |
6549 assert(_collectorState == Idling, "The state should only change" | |
6550 " because the foreground collector has finished the collection"); | |
6551 return; | |
6552 } | |
6553 | |
6554 // Clear the mark bitmap (no grey objects to start with) | |
6555 // for the next cycle. | |
6556 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
6557 CMSPhaseAccounting cmspa(this, "reset", !PrintGCDetails); | |
6558 | |
6559 HeapWord* curAddr = _markBitMap.startWord(); | |
6560 while (curAddr < _markBitMap.endWord()) { | |
6561 size_t remaining = pointer_delta(_markBitMap.endWord(), curAddr); | |
6562 MemRegion chunk(curAddr, MIN2(CMSBitMapYieldQuantum, remaining)); | |
6563 _markBitMap.clear_large_range(chunk); | |
6564 if (ConcurrentMarkSweepThread::should_yield() && | |
6565 !foregroundGCIsActive() && | |
6566 CMSYield) { | |
6567 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
6568 "CMS thread should hold CMS token"); | |
6569 assert_lock_strong(bitMapLock()); | |
6570 bitMapLock()->unlock(); | |
6571 ConcurrentMarkSweepThread::desynchronize(true); | |
6572 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
6573 stopTimer(); | |
6574 if (PrintCMSStatistics != 0) { | |
6575 incrementYields(); | |
6576 } | |
6577 icms_wait(); | |
6578 | |
6579 // See the comment in coordinator_yield() | |
6580 for (unsigned i = 0; i < CMSYieldSleepCount && | |
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6581 ConcurrentMarkSweepThread::should_yield() && |
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6582 !CMSCollector::foregroundGCIsActive(); ++i) { |
0 | 6583 os::sleep(Thread::current(), 1, false); |
6584 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
6585 } | |
6586 | |
6587 ConcurrentMarkSweepThread::synchronize(true); | |
6588 bitMapLock()->lock_without_safepoint_check(); | |
6589 startTimer(); | |
6590 } | |
6591 curAddr = chunk.end(); | |
6592 } | |
1387
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|
6593 // A successful mostly concurrent collection has been done. |
0bfd3fb24150
6858496: Clear all SoftReferences before an out-of-memory due to GC overhead limit.
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6594 // Because only the full (i.e., concurrent mode failure) collections |
0bfd3fb24150
6858496: Clear all SoftReferences before an out-of-memory due to GC overhead limit.
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6595 // are being measured for gc overhead limits, clean the "near" flag |
0bfd3fb24150
6858496: Clear all SoftReferences before an out-of-memory due to GC overhead limit.
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6596 // and count. |
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|
6597 sp->reset_gc_overhead_limit_count(); |
0 | 6598 _collectorState = Idling; |
6599 } else { | |
6600 // already have the lock | |
6601 assert(_collectorState == Resetting, "just checking"); | |
6602 assert_lock_strong(bitMapLock()); | |
6603 _markBitMap.clear_all(); | |
6604 _collectorState = Idling; | |
6605 } | |
6606 | |
6607 // Stop incremental mode after a cycle completes, so that any future cycles | |
6608 // are triggered by allocation. | |
6609 stop_icms(); | |
6610 | |
6611 NOT_PRODUCT( | |
6612 if (RotateCMSCollectionTypes) { | |
6613 _cmsGen->rotate_debug_collection_type(); | |
6614 } | |
6615 ) | |
10405 | 6616 |
6617 register_gc_end(); | |
0 | 6618 } |
6619 | |
6064
9d679effd28c
7166894: Add gc cause to GC logging for all collectors
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6028
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|
6620 void CMSCollector::do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause) { |
0 | 6621 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps); |
6622 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
10405 | 6623 GCTraceTime t(GCCauseString("GC", gc_cause), PrintGC, !PrintGCDetails, NULL); |
0 | 6624 TraceCollectorStats tcs(counters()); |
6625 | |
6626 switch (op) { | |
6627 case CMS_op_checkpointRootsInitial: { | |
2125
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6458402: 3 jvmti tests fail with CMS and +ExplicitGCInvokesConcurrent
kamg
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changeset
|
6628 SvcGCMarker sgcm(SvcGCMarker::OTHER); |
0 | 6629 checkpointRootsInitial(true); // asynch |
6630 if (PrintGC) { | |
6631 _cmsGen->printOccupancy("initial-mark"); | |
6632 } | |
6633 break; | |
6634 } | |
6635 case CMS_op_checkpointRootsFinal: { | |
2125
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|
6636 SvcGCMarker sgcm(SvcGCMarker::OTHER); |
0 | 6637 checkpointRootsFinal(true, // asynch |
6638 false, // !clear_all_soft_refs | |
6639 false); // !init_mark_was_synchronous | |
6640 if (PrintGC) { | |
6641 _cmsGen->printOccupancy("remark"); | |
6642 } | |
6643 break; | |
6644 } | |
6645 default: | |
6646 fatal("No such CMS_op"); | |
6647 } | |
6648 } | |
6649 | |
6650 #ifndef PRODUCT | |
6651 size_t const CMSCollector::skip_header_HeapWords() { | |
6652 return FreeChunk::header_size(); | |
6653 } | |
6654 | |
6655 // Try and collect here conditions that should hold when | |
6656 // CMS thread is exiting. The idea is that the foreground GC | |
6657 // thread should not be blocked if it wants to terminate | |
6658 // the CMS thread and yet continue to run the VM for a while | |
6659 // after that. | |
6660 void CMSCollector::verify_ok_to_terminate() const { | |
6661 assert(Thread::current()->is_ConcurrentGC_thread(), | |
6662 "should be called by CMS thread"); | |
6663 assert(!_foregroundGCShouldWait, "should be false"); | |
6664 // We could check here that all the various low-level locks | |
6665 // are not held by the CMS thread, but that is overkill; see | |
6666 // also CMSThread::verify_ok_to_terminate() where the CGC_lock | |
6667 // is checked. | |
6668 } | |
6669 #endif | |
6670 | |
6671 size_t CMSCollector::block_size_using_printezis_bits(HeapWord* addr) const { | |
453
c96030fff130
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6672 assert(_markBitMap.isMarked(addr) && _markBitMap.isMarked(addr + 1), |
c96030fff130
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6673 "missing Printezis mark?"); |
0 | 6674 HeapWord* nextOneAddr = _markBitMap.getNextMarkedWordAddress(addr + 2); |
6675 size_t size = pointer_delta(nextOneAddr + 1, addr); | |
6676 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
6677 "alignment problem"); | |
6678 assert(size >= 3, "Necessary for Printezis marks to work"); | |
6679 return size; | |
6680 } | |
6681 | |
6682 // A variant of the above (block_size_using_printezis_bits()) except | |
6683 // that we return 0 if the P-bits are not yet set. | |
6684 size_t CMSCollector::block_size_if_printezis_bits(HeapWord* addr) const { | |
2226
c5a923563727
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2177
diff
changeset
|
6685 if (_markBitMap.isMarked(addr + 1)) { |
c5a923563727
6912621: iCMS: Error: assert(_markBitMap.isMarked(addr + 1),"Missing Printezis bit?")
ysr
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2177
diff
changeset
|
6686 assert(_markBitMap.isMarked(addr), "P-bit can be set only for marked objects"); |
0 | 6687 HeapWord* nextOneAddr = _markBitMap.getNextMarkedWordAddress(addr + 2); |
6688 size_t size = pointer_delta(nextOneAddr + 1, addr); | |
6689 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
6690 "alignment problem"); | |
6691 assert(size >= 3, "Necessary for Printezis marks to work"); | |
6692 return size; | |
2226
c5a923563727
6912621: iCMS: Error: assert(_markBitMap.isMarked(addr + 1),"Missing Printezis bit?")
ysr
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2177
diff
changeset
|
6693 } |
c5a923563727
6912621: iCMS: Error: assert(_markBitMap.isMarked(addr + 1),"Missing Printezis bit?")
ysr
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2177
diff
changeset
|
6694 return 0; |
0 | 6695 } |
6696 | |
6697 HeapWord* CMSCollector::next_card_start_after_block(HeapWord* addr) const { | |
6698 size_t sz = 0; | |
6699 oop p = (oop)addr; | |
6725
da91efe96a93
6964458: Reimplement class meta-data storage to use native memory
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diff
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|
6700 if (p->klass_or_null() != NULL) { |
0 | 6701 sz = CompactibleFreeListSpace::adjustObjectSize(p->size()); |
6702 } else { | |
6703 sz = block_size_using_printezis_bits(addr); | |
6704 } | |
6705 assert(sz > 0, "size must be nonzero"); | |
6706 HeapWord* next_block = addr + sz; | |
6707 HeapWord* next_card = (HeapWord*)round_to((uintptr_t)next_block, | |
6708 CardTableModRefBS::card_size); | |
6709 assert(round_down((uintptr_t)addr, CardTableModRefBS::card_size) < | |
6710 round_down((uintptr_t)next_card, CardTableModRefBS::card_size), | |
6711 "must be different cards"); | |
6712 return next_card; | |
6713 } | |
6714 | |
6715 | |
6716 // CMS Bit Map Wrapper ///////////////////////////////////////// | |
6717 | |
6718 // Construct a CMS bit map infrastructure, but don't create the | |
6719 // bit vector itself. That is done by a separate call CMSBitMap::allocate() | |
6720 // further below. | |
6721 CMSBitMap::CMSBitMap(int shifter, int mutex_rank, const char* mutex_name): | |
342
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|
6722 _bm(), |
0 | 6723 _shifter(shifter), |
6724 _lock(mutex_rank >= 0 ? new Mutex(mutex_rank, mutex_name, true) : NULL) | |
6725 { | |
6726 _bmStartWord = 0; | |
6727 _bmWordSize = 0; | |
6728 } | |
6729 | |
6730 bool CMSBitMap::allocate(MemRegion mr) { | |
6731 _bmStartWord = mr.start(); | |
6732 _bmWordSize = mr.word_size(); | |
6733 ReservedSpace brs(ReservedSpace::allocation_align_size_up( | |
6734 (_bmWordSize >> (_shifter + LogBitsPerByte)) + 1)); | |
6735 if (!brs.is_reserved()) { | |
6736 warning("CMS bit map allocation failure"); | |
6737 return false; | |
6738 } | |
6739 // For now we'll just commit all of the bit map up fromt. | |
6740 // Later on we'll try to be more parsimonious with swap. | |
6741 if (!_virtual_space.initialize(brs, brs.size())) { | |
6742 warning("CMS bit map backing store failure"); | |
6743 return false; | |
6744 } | |
6745 assert(_virtual_space.committed_size() == brs.size(), | |
6746 "didn't reserve backing store for all of CMS bit map?"); | |
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6747 _bm.set_map((BitMap::bm_word_t*)_virtual_space.low()); |
0 | 6748 assert(_virtual_space.committed_size() << (_shifter + LogBitsPerByte) >= |
6749 _bmWordSize, "inconsistency in bit map sizing"); | |
6750 _bm.set_size(_bmWordSize >> _shifter); | |
6751 | |
6752 // bm.clear(); // can we rely on getting zero'd memory? verify below | |
6753 assert(isAllClear(), | |
6754 "Expected zero'd memory from ReservedSpace constructor"); | |
6755 assert(_bm.size() == heapWordDiffToOffsetDiff(sizeInWords()), | |
6756 "consistency check"); | |
6757 return true; | |
6758 } | |
6759 | |
6760 void CMSBitMap::dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl) { | |
6761 HeapWord *next_addr, *end_addr, *last_addr; | |
6762 assert_locked(); | |
6763 assert(covers(mr), "out-of-range error"); | |
6764 // XXX assert that start and end are appropriately aligned | |
6765 for (next_addr = mr.start(), end_addr = mr.end(); | |
6766 next_addr < end_addr; next_addr = last_addr) { | |
6767 MemRegion dirty_region = getAndClearMarkedRegion(next_addr, end_addr); | |
6768 last_addr = dirty_region.end(); | |
6769 if (!dirty_region.is_empty()) { | |
6770 cl->do_MemRegion(dirty_region); | |
6771 } else { | |
6772 assert(last_addr == end_addr, "program logic"); | |
6773 return; | |
6774 } | |
6775 } | |
6776 } | |
6777 | |
9076
7b835924c31c
8011872: Include Bit Map addresses in the hs_err files
stefank
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9072
diff
changeset
|
6778 void CMSBitMap::print_on_error(outputStream* st, const char* prefix) const { |
7b835924c31c
8011872: Include Bit Map addresses in the hs_err files
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9072
diff
changeset
|
6779 _bm.print_on_error(st, prefix); |
7b835924c31c
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9072
diff
changeset
|
6780 } |
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|
6781 |
0 | 6782 #ifndef PRODUCT |
6783 void CMSBitMap::assert_locked() const { | |
6784 CMSLockVerifier::assert_locked(lock()); | |
6785 } | |
6786 | |
6787 bool CMSBitMap::covers(MemRegion mr) const { | |
6788 // assert(_bm.map() == _virtual_space.low(), "map inconsistency"); | |
6789 assert((size_t)_bm.size() == (_bmWordSize >> _shifter), | |
6790 "size inconsistency"); | |
6791 return (mr.start() >= _bmStartWord) && | |
6792 (mr.end() <= endWord()); | |
6793 } | |
6794 | |
6795 bool CMSBitMap::covers(HeapWord* start, size_t size) const { | |
6796 return (start >= _bmStartWord && (start + size) <= endWord()); | |
6797 } | |
6798 | |
6799 void CMSBitMap::verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) { | |
6800 // verify that there are no 1 bits in the interval [left, right) | |
6801 FalseBitMapClosure falseBitMapClosure; | |
6802 iterate(&falseBitMapClosure, left, right); | |
6803 } | |
6804 | |
6805 void CMSBitMap::region_invariant(MemRegion mr) | |
6806 { | |
6807 assert_locked(); | |
6808 // mr = mr.intersection(MemRegion(_bmStartWord, _bmWordSize)); | |
6809 assert(!mr.is_empty(), "unexpected empty region"); | |
6810 assert(covers(mr), "mr should be covered by bit map"); | |
6811 // convert address range into offset range | |
6812 size_t start_ofs = heapWordToOffset(mr.start()); | |
6813 // Make sure that end() is appropriately aligned | |
6814 assert(mr.end() == (HeapWord*)round_to((intptr_t)mr.end(), | |
6815 (1 << (_shifter+LogHeapWordSize))), | |
6816 "Misaligned mr.end()"); | |
6817 size_t end_ofs = heapWordToOffset(mr.end()); | |
6818 assert(end_ofs > start_ofs, "Should mark at least one bit"); | |
6819 } | |
6820 | |
6821 #endif | |
6822 | |
6823 bool CMSMarkStack::allocate(size_t size) { | |
6824 // allocate a stack of the requisite depth | |
6825 ReservedSpace rs(ReservedSpace::allocation_align_size_up( | |
6826 size * sizeof(oop))); | |
6827 if (!rs.is_reserved()) { | |
6828 warning("CMSMarkStack allocation failure"); | |
6829 return false; | |
6830 } | |
6831 if (!_virtual_space.initialize(rs, rs.size())) { | |
6832 warning("CMSMarkStack backing store failure"); | |
6833 return false; | |
6834 } | |
6835 assert(_virtual_space.committed_size() == rs.size(), | |
6836 "didn't reserve backing store for all of CMS stack?"); | |
6837 _base = (oop*)(_virtual_space.low()); | |
6838 _index = 0; | |
6839 _capacity = size; | |
6840 NOT_PRODUCT(_max_depth = 0); | |
6841 return true; | |
6842 } | |
6843 | |
6844 // XXX FIX ME !!! In the MT case we come in here holding a | |
6845 // leaf lock. For printing we need to take a further lock | |
6846 // which has lower rank. We need to recallibrate the two | |
6847 // lock-ranks involved in order to be able to rpint the | |
6848 // messages below. (Or defer the printing to the caller. | |
6849 // For now we take the expedient path of just disabling the | |
6850 // messages for the problematic case.) | |
6851 void CMSMarkStack::expand() { | |
1284 | 6852 assert(_capacity <= MarkStackSizeMax, "stack bigger than permitted"); |
6853 if (_capacity == MarkStackSizeMax) { | |
0 | 6854 if (_hit_limit++ == 0 && !CMSConcurrentMTEnabled && PrintGCDetails) { |
6855 // We print a warning message only once per CMS cycle. | |
6856 gclog_or_tty->print_cr(" (benign) Hit CMSMarkStack max size limit"); | |
6857 } | |
6858 return; | |
6859 } | |
6860 // Double capacity if possible | |
1284 | 6861 size_t new_capacity = MIN2(_capacity*2, MarkStackSizeMax); |
0 | 6862 // Do not give up existing stack until we have managed to |
6863 // get the double capacity that we desired. | |
6864 ReservedSpace rs(ReservedSpace::allocation_align_size_up( | |
6865 new_capacity * sizeof(oop))); | |
6866 if (rs.is_reserved()) { | |
6867 // Release the backing store associated with old stack | |
6868 _virtual_space.release(); | |
6869 // Reinitialize virtual space for new stack | |
6870 if (!_virtual_space.initialize(rs, rs.size())) { | |
6871 fatal("Not enough swap for expanded marking stack"); | |
6872 } | |
6873 _base = (oop*)(_virtual_space.low()); | |
6874 _index = 0; | |
6875 _capacity = new_capacity; | |
6876 } else if (_failed_double++ == 0 && !CMSConcurrentMTEnabled && PrintGCDetails) { | |
6877 // Failed to double capacity, continue; | |
6878 // we print a detail message only once per CMS cycle. | |
6879 gclog_or_tty->print(" (benign) Failed to expand marking stack from "SIZE_FORMAT"K to " | |
6880 SIZE_FORMAT"K", | |
6881 _capacity / K, new_capacity / K); | |
6882 } | |
6883 } | |
6884 | |
6885 | |
6886 // Closures | |
6887 // XXX: there seems to be a lot of code duplication here; | |
6888 // should refactor and consolidate common code. | |
6889 | |
6890 // This closure is used to mark refs into the CMS generation in | |
6891 // the CMS bit map. Called at the first checkpoint. This closure | |
6892 // assumes that we do not need to re-mark dirty cards; if the CMS | |
6725
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6197
diff
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|
6893 // generation on which this is used is not an oldest |
0 | 6894 // generation then this will lose younger_gen cards! |
6895 | |
6896 MarkRefsIntoClosure::MarkRefsIntoClosure( | |
994
753cf9794df9
6885169: merge of 4957990 and 6863023 causes conflict on do_nmethods
jrose
parents:
993
diff
changeset
|
6897 MemRegion span, CMSBitMap* bitMap): |
0 | 6898 _span(span), |
994
753cf9794df9
6885169: merge of 4957990 and 6863023 causes conflict on do_nmethods
jrose
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993
diff
changeset
|
6899 _bitMap(bitMap) |
0 | 6900 { |
6901 assert(_ref_processor == NULL, "deliberately left NULL"); | |
6902 assert(_bitMap->covers(_span), "_bitMap/_span mismatch"); | |
6903 } | |
6904 | |
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94
diff
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|
6905 void MarkRefsIntoClosure::do_oop(oop obj) { |
0 | 6906 // if p points into _span, then mark corresponding bit in _markBitMap |
113
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6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
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94
diff
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|
6907 assert(obj->is_oop(), "expected an oop"); |
ba764ed4b6f2
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coleenp
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94
diff
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|
6908 HeapWord* addr = (HeapWord*)obj; |
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
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94
diff
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|
6909 if (_span.contains(addr)) { |
ba764ed4b6f2
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coleenp
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94
diff
changeset
|
6910 // this should be made more efficient |
ba764ed4b6f2
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coleenp
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94
diff
changeset
|
6911 _bitMap->mark(addr); |
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
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94
diff
changeset
|
6912 } |
ba764ed4b6f2
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94
diff
changeset
|
6913 } |
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
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94
diff
changeset
|
6914 |
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
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94
diff
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|
6915 void MarkRefsIntoClosure::do_oop(oop* p) { MarkRefsIntoClosure::do_oop_work(p); } |
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6916 void MarkRefsIntoClosure::do_oop(narrowOop* p) { MarkRefsIntoClosure::do_oop_work(p); } |
0 | 6917 |
11975 | 6918 Par_MarkRefsIntoClosure::Par_MarkRefsIntoClosure( |
6919 MemRegion span, CMSBitMap* bitMap): | |
6920 _span(span), | |
6921 _bitMap(bitMap) | |
6922 { | |
6923 assert(_ref_processor == NULL, "deliberately left NULL"); | |
6924 assert(_bitMap->covers(_span), "_bitMap/_span mismatch"); | |
6925 } | |
6926 | |
6927 void Par_MarkRefsIntoClosure::do_oop(oop obj) { | |
6928 // if p points into _span, then mark corresponding bit in _markBitMap | |
6929 assert(obj->is_oop(), "expected an oop"); | |
6930 HeapWord* addr = (HeapWord*)obj; | |
6931 if (_span.contains(addr)) { | |
6932 // this should be made more efficient | |
6933 _bitMap->par_mark(addr); | |
6934 } | |
6935 } | |
6936 | |
6937 void Par_MarkRefsIntoClosure::do_oop(oop* p) { Par_MarkRefsIntoClosure::do_oop_work(p); } | |
6938 void Par_MarkRefsIntoClosure::do_oop(narrowOop* p) { Par_MarkRefsIntoClosure::do_oop_work(p); } | |
6939 | |
0 | 6940 // A variant of the above, used for CMS marking verification. |
6941 MarkRefsIntoVerifyClosure::MarkRefsIntoVerifyClosure( | |
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6942 MemRegion span, CMSBitMap* verification_bm, CMSBitMap* cms_bm): |
0 | 6943 _span(span), |
6944 _verification_bm(verification_bm), | |
994
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6945 _cms_bm(cms_bm) |
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6946 { |
0 | 6947 assert(_ref_processor == NULL, "deliberately left NULL"); |
6948 assert(_verification_bm->covers(_span), "_verification_bm/_span mismatch"); | |
6949 } | |
6950 | |
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6951 void MarkRefsIntoVerifyClosure::do_oop(oop obj) { |
0 | 6952 // if p points into _span, then mark corresponding bit in _markBitMap |
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6953 assert(obj->is_oop(), "expected an oop"); |
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6954 HeapWord* addr = (HeapWord*)obj; |
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6955 if (_span.contains(addr)) { |
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6956 _verification_bm->mark(addr); |
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6957 if (!_cms_bm->isMarked(addr)) { |
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6958 oop(addr)->print(); |
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6959 gclog_or_tty->print_cr(" (" INTPTR_FORMAT " should have been marked)", addr); |
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6960 fatal("... aborting"); |
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6961 } |
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6962 } |
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6963 } |
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6964 |
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6965 void MarkRefsIntoVerifyClosure::do_oop(oop* p) { MarkRefsIntoVerifyClosure::do_oop_work(p); } |
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6966 void MarkRefsIntoVerifyClosure::do_oop(narrowOop* p) { MarkRefsIntoVerifyClosure::do_oop_work(p); } |
0 | 6967 |
6968 ////////////////////////////////////////////////// | |
6969 // MarkRefsIntoAndScanClosure | |
6970 ////////////////////////////////////////////////// | |
6971 | |
6972 MarkRefsIntoAndScanClosure::MarkRefsIntoAndScanClosure(MemRegion span, | |
6973 ReferenceProcessor* rp, | |
6974 CMSBitMap* bit_map, | |
6975 CMSBitMap* mod_union_table, | |
6976 CMSMarkStack* mark_stack, | |
6977 CMSCollector* collector, | |
6978 bool should_yield, | |
6979 bool concurrent_precleaning): | |
6980 _collector(collector), | |
6981 _span(span), | |
6982 _bit_map(bit_map), | |
6983 _mark_stack(mark_stack), | |
6984 _pushAndMarkClosure(collector, span, rp, bit_map, mod_union_table, | |
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6985 mark_stack, concurrent_precleaning), |
0 | 6986 _yield(should_yield), |
6987 _concurrent_precleaning(concurrent_precleaning), | |
6988 _freelistLock(NULL) | |
6989 { | |
6990 _ref_processor = rp; | |
6991 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
6992 } | |
6993 | |
6994 // This closure is used to mark refs into the CMS generation at the | |
6995 // second (final) checkpoint, and to scan and transitively follow | |
6996 // the unmarked oops. It is also used during the concurrent precleaning | |
6997 // phase while scanning objects on dirty cards in the CMS generation. | |
6998 // The marks are made in the marking bit map and the marking stack is | |
6999 // used for keeping the (newly) grey objects during the scan. | |
7000 // The parallel version (Par_...) appears further below. | |
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7001 void MarkRefsIntoAndScanClosure::do_oop(oop obj) { |
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7002 if (obj != NULL) { |
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7003 assert(obj->is_oop(), "expected an oop"); |
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7004 HeapWord* addr = (HeapWord*)obj; |
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7005 assert(_mark_stack->isEmpty(), "pre-condition (eager drainage)"); |
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7006 assert(_collector->overflow_list_is_empty(), |
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7007 "overflow list should be empty"); |
0 | 7008 if (_span.contains(addr) && |
7009 !_bit_map->isMarked(addr)) { | |
7010 // mark bit map (object is now grey) | |
7011 _bit_map->mark(addr); | |
7012 // push on marking stack (stack should be empty), and drain the | |
7013 // stack by applying this closure to the oops in the oops popped | |
7014 // from the stack (i.e. blacken the grey objects) | |
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7015 bool res = _mark_stack->push(obj); |
0 | 7016 assert(res, "Should have space to push on empty stack"); |
7017 do { | |
7018 oop new_oop = _mark_stack->pop(); | |
7019 assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop"); | |
7020 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
7021 "only grey objects on this stack"); | |
7022 // iterate over the oops in this oop, marking and pushing | |
7023 // the ones in CMS heap (i.e. in _span). | |
7024 new_oop->oop_iterate(&_pushAndMarkClosure); | |
7025 // check if it's time to yield | |
7026 do_yield_check(); | |
7027 } while (!_mark_stack->isEmpty() || | |
7028 (!_concurrent_precleaning && take_from_overflow_list())); | |
7029 // if marking stack is empty, and we are not doing this | |
7030 // during precleaning, then check the overflow list | |
7031 } | |
7032 assert(_mark_stack->isEmpty(), "post-condition (eager drainage)"); | |
7033 assert(_collector->overflow_list_is_empty(), | |
7034 "overflow list was drained above"); | |
7035 // We could restore evacuated mark words, if any, used for | |
7036 // overflow list links here because the overflow list is | |
7037 // provably empty here. That would reduce the maximum | |
7038 // size requirements for preserved_{oop,mark}_stack. | |
7039 // But we'll just postpone it until we are all done | |
7040 // so we can just stream through. | |
7041 if (!_concurrent_precleaning && CMSOverflowEarlyRestoration) { | |
7042 _collector->restore_preserved_marks_if_any(); | |
7043 assert(_collector->no_preserved_marks(), "No preserved marks"); | |
7044 } | |
7045 assert(!CMSOverflowEarlyRestoration || _collector->no_preserved_marks(), | |
7046 "All preserved marks should have been restored above"); | |
7047 } | |
7048 } | |
7049 | |
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7050 void MarkRefsIntoAndScanClosure::do_oop(oop* p) { MarkRefsIntoAndScanClosure::do_oop_work(p); } |
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7051 void MarkRefsIntoAndScanClosure::do_oop(narrowOop* p) { MarkRefsIntoAndScanClosure::do_oop_work(p); } |
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7052 |
0 | 7053 void MarkRefsIntoAndScanClosure::do_yield_work() { |
7054 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
7055 "CMS thread should hold CMS token"); | |
7056 assert_lock_strong(_freelistLock); | |
7057 assert_lock_strong(_bit_map->lock()); | |
7058 // relinquish the free_list_lock and bitMaplock() | |
7059 _bit_map->lock()->unlock(); | |
7060 _freelistLock->unlock(); | |
7061 ConcurrentMarkSweepThread::desynchronize(true); | |
7062 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
7063 _collector->stopTimer(); | |
7064 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
7065 if (PrintCMSStatistics != 0) { | |
7066 _collector->incrementYields(); | |
7067 } | |
7068 _collector->icms_wait(); | |
7069 | |
7070 // See the comment in coordinator_yield() | |
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7071 for (unsigned i = 0; |
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7072 i < CMSYieldSleepCount && |
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7073 ConcurrentMarkSweepThread::should_yield() && |
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7074 !CMSCollector::foregroundGCIsActive(); |
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7075 ++i) { |
0 | 7076 os::sleep(Thread::current(), 1, false); |
7077 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
7078 } | |
7079 | |
7080 ConcurrentMarkSweepThread::synchronize(true); | |
7081 _freelistLock->lock_without_safepoint_check(); | |
7082 _bit_map->lock()->lock_without_safepoint_check(); | |
7083 _collector->startTimer(); | |
7084 } | |
7085 | |
7086 /////////////////////////////////////////////////////////// | |
7087 // Par_MarkRefsIntoAndScanClosure: a parallel version of | |
7088 // MarkRefsIntoAndScanClosure | |
7089 /////////////////////////////////////////////////////////// | |
7090 Par_MarkRefsIntoAndScanClosure::Par_MarkRefsIntoAndScanClosure( | |
7091 CMSCollector* collector, MemRegion span, ReferenceProcessor* rp, | |
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7092 CMSBitMap* bit_map, OopTaskQueue* work_queue): |
0 | 7093 _span(span), |
7094 _bit_map(bit_map), | |
7095 _work_queue(work_queue), | |
7096 _low_water_mark(MIN2((uint)(work_queue->max_elems()/4), | |
7097 (uint)(CMSWorkQueueDrainThreshold * ParallelGCThreads))), | |
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7098 _par_pushAndMarkClosure(collector, span, rp, bit_map, work_queue) |
0 | 7099 { |
7100 _ref_processor = rp; | |
7101 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
7102 } | |
7103 | |
7104 // This closure is used to mark refs into the CMS generation at the | |
7105 // second (final) checkpoint, and to scan and transitively follow | |
7106 // the unmarked oops. The marks are made in the marking bit map and | |
7107 // the work_queue is used for keeping the (newly) grey objects during | |
7108 // the scan phase whence they are also available for stealing by parallel | |
7109 // threads. Since the marking bit map is shared, updates are | |
7110 // synchronized (via CAS). | |
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7111 void Par_MarkRefsIntoAndScanClosure::do_oop(oop obj) { |
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7112 if (obj != NULL) { |
0 | 7113 // Ignore mark word because this could be an already marked oop |
7114 // that may be chained at the end of the overflow list. | |
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7115 assert(obj->is_oop(true), "expected an oop"); |
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7116 HeapWord* addr = (HeapWord*)obj; |
0 | 7117 if (_span.contains(addr) && |
7118 !_bit_map->isMarked(addr)) { | |
7119 // mark bit map (object will become grey): | |
7120 // It is possible for several threads to be | |
7121 // trying to "claim" this object concurrently; | |
7122 // the unique thread that succeeds in marking the | |
7123 // object first will do the subsequent push on | |
7124 // to the work queue (or overflow list). | |
7125 if (_bit_map->par_mark(addr)) { | |
7126 // push on work_queue (which may not be empty), and trim the | |
7127 // queue to an appropriate length by applying this closure to | |
7128 // the oops in the oops popped from the stack (i.e. blacken the | |
7129 // grey objects) | |
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7130 bool res = _work_queue->push(obj); |
0 | 7131 assert(res, "Low water mark should be less than capacity?"); |
7132 trim_queue(_low_water_mark); | |
7133 } // Else, another thread claimed the object | |
7134 } | |
7135 } | |
7136 } | |
7137 | |
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7138 void Par_MarkRefsIntoAndScanClosure::do_oop(oop* p) { Par_MarkRefsIntoAndScanClosure::do_oop_work(p); } |
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7139 void Par_MarkRefsIntoAndScanClosure::do_oop(narrowOop* p) { Par_MarkRefsIntoAndScanClosure::do_oop_work(p); } |
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7140 |
0 | 7141 // This closure is used to rescan the marked objects on the dirty cards |
7142 // in the mod union table and the card table proper. | |
7143 size_t ScanMarkedObjectsAgainCarefullyClosure::do_object_careful_m( | |
7144 oop p, MemRegion mr) { | |
7145 | |
7146 size_t size = 0; | |
7147 HeapWord* addr = (HeapWord*)p; | |
7148 DEBUG_ONLY(_collector->verify_work_stacks_empty();) | |
7149 assert(_span.contains(addr), "we are scanning the CMS generation"); | |
7150 // check if it's time to yield | |
7151 if (do_yield_check()) { | |
7152 // We yielded for some foreground stop-world work, | |
7153 // and we have been asked to abort this ongoing preclean cycle. | |
7154 return 0; | |
7155 } | |
7156 if (_bitMap->isMarked(addr)) { | |
7157 // it's marked; is it potentially uninitialized? | |
187 | 7158 if (p->klass_or_null() != NULL) { |
0 | 7159 // an initialized object; ignore mark word in verification below |
7160 // since we are running concurrent with mutators | |
7161 assert(p->is_oop(true), "should be an oop"); | |
7162 if (p->is_objArray()) { | |
7163 // objArrays are precisely marked; restrict scanning | |
7164 // to dirty cards only. | |
187 | 7165 size = CompactibleFreeListSpace::adjustObjectSize( |
7166 p->oop_iterate(_scanningClosure, mr)); | |
0 | 7167 } else { |
7168 // A non-array may have been imprecisely marked; we need | |
7169 // to scan object in its entirety. | |
7170 size = CompactibleFreeListSpace::adjustObjectSize( | |
7171 p->oop_iterate(_scanningClosure)); | |
7172 } | |
9152 | 7173 #ifdef ASSERT |
0 | 7174 size_t direct_size = |
7175 CompactibleFreeListSpace::adjustObjectSize(p->size()); | |
7176 assert(size == direct_size, "Inconsistency in size"); | |
7177 assert(size >= 3, "Necessary for Printezis marks to work"); | |
7178 if (!_bitMap->isMarked(addr+1)) { | |
7179 _bitMap->verifyNoOneBitsInRange(addr+2, addr+size); | |
7180 } else { | |
7181 _bitMap->verifyNoOneBitsInRange(addr+2, addr+size-1); | |
7182 assert(_bitMap->isMarked(addr+size-1), | |
7183 "inconsistent Printezis mark"); | |
7184 } | |
9152 | 7185 #endif // ASSERT |
0 | 7186 } else { |
7187 // an unitialized object | |
7188 assert(_bitMap->isMarked(addr+1), "missing Printezis mark?"); | |
7189 HeapWord* nextOneAddr = _bitMap->getNextMarkedWordAddress(addr + 2); | |
7190 size = pointer_delta(nextOneAddr + 1, addr); | |
7191 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
7192 "alignment problem"); | |
7193 // Note that pre-cleaning needn't redirty the card. OopDesc::set_klass() | |
7194 // will dirty the card when the klass pointer is installed in the | |
7195 // object (signalling the completion of initialization). | |
7196 } | |
7197 } else { | |
7198 // Either a not yet marked object or an uninitialized object | |
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7199 if (p->klass_or_null() == NULL) { |
0 | 7200 // An uninitialized object, skip to the next card, since |
7201 // we may not be able to read its P-bits yet. | |
7202 assert(size == 0, "Initial value"); | |
7203 } else { | |
7204 // An object not (yet) reached by marking: we merely need to | |
7205 // compute its size so as to go look at the next block. | |
7206 assert(p->is_oop(true), "should be an oop"); | |
7207 size = CompactibleFreeListSpace::adjustObjectSize(p->size()); | |
7208 } | |
7209 } | |
7210 DEBUG_ONLY(_collector->verify_work_stacks_empty();) | |
7211 return size; | |
7212 } | |
7213 | |
7214 void ScanMarkedObjectsAgainCarefullyClosure::do_yield_work() { | |
7215 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
7216 "CMS thread should hold CMS token"); | |
7217 assert_lock_strong(_freelistLock); | |
7218 assert_lock_strong(_bitMap->lock()); | |
7219 // relinquish the free_list_lock and bitMaplock() | |
7220 _bitMap->lock()->unlock(); | |
7221 _freelistLock->unlock(); | |
7222 ConcurrentMarkSweepThread::desynchronize(true); | |
7223 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
7224 _collector->stopTimer(); | |
7225 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
7226 if (PrintCMSStatistics != 0) { | |
7227 _collector->incrementYields(); | |
7228 } | |
7229 _collector->icms_wait(); | |
7230 | |
7231 // See the comment in coordinator_yield() | |
7232 for (unsigned i = 0; i < CMSYieldSleepCount && | |
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7233 ConcurrentMarkSweepThread::should_yield() && |
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7234 !CMSCollector::foregroundGCIsActive(); ++i) { |
0 | 7235 os::sleep(Thread::current(), 1, false); |
7236 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
7237 } | |
7238 | |
7239 ConcurrentMarkSweepThread::synchronize(true); | |
7240 _freelistLock->lock_without_safepoint_check(); | |
7241 _bitMap->lock()->lock_without_safepoint_check(); | |
7242 _collector->startTimer(); | |
7243 } | |
7244 | |
7245 | |
7246 ////////////////////////////////////////////////////////////////// | |
7247 // SurvivorSpacePrecleanClosure | |
7248 ////////////////////////////////////////////////////////////////// | |
7249 // This (single-threaded) closure is used to preclean the oops in | |
7250 // the survivor spaces. | |
7251 size_t SurvivorSpacePrecleanClosure::do_object_careful(oop p) { | |
7252 | |
7253 HeapWord* addr = (HeapWord*)p; | |
7254 DEBUG_ONLY(_collector->verify_work_stacks_empty();) | |
7255 assert(!_span.contains(addr), "we are scanning the survivor spaces"); | |
187 | 7256 assert(p->klass_or_null() != NULL, "object should be initializd"); |
0 | 7257 // an initialized object; ignore mark word in verification below |
7258 // since we are running concurrent with mutators | |
7259 assert(p->is_oop(true), "should be an oop"); | |
7260 // Note that we do not yield while we iterate over | |
7261 // the interior oops of p, pushing the relevant ones | |
7262 // on our marking stack. | |
7263 size_t size = p->oop_iterate(_scanning_closure); | |
7264 do_yield_check(); | |
7265 // Observe that below, we do not abandon the preclean | |
7266 // phase as soon as we should; rather we empty the | |
7267 // marking stack before returning. This is to satisfy | |
7268 // some existing assertions. In general, it may be a | |
7269 // good idea to abort immediately and complete the marking | |
7270 // from the grey objects at a later time. | |
7271 while (!_mark_stack->isEmpty()) { | |
7272 oop new_oop = _mark_stack->pop(); | |
7273 assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop"); | |
7274 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
7275 "only grey objects on this stack"); | |
7276 // iterate over the oops in this oop, marking and pushing | |
7277 // the ones in CMS heap (i.e. in _span). | |
7278 new_oop->oop_iterate(_scanning_closure); | |
7279 // check if it's time to yield | |
7280 do_yield_check(); | |
7281 } | |
7282 unsigned int after_count = | |
7283 GenCollectedHeap::heap()->total_collections(); | |
7284 bool abort = (_before_count != after_count) || | |
7285 _collector->should_abort_preclean(); | |
7286 return abort ? 0 : size; | |
7287 } | |
7288 | |
7289 void SurvivorSpacePrecleanClosure::do_yield_work() { | |
7290 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
7291 "CMS thread should hold CMS token"); | |
7292 assert_lock_strong(_bit_map->lock()); | |
7293 // Relinquish the bit map lock | |
7294 _bit_map->lock()->unlock(); | |
7295 ConcurrentMarkSweepThread::desynchronize(true); | |
7296 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
7297 _collector->stopTimer(); | |
7298 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
7299 if (PrintCMSStatistics != 0) { | |
7300 _collector->incrementYields(); | |
7301 } | |
7302 _collector->icms_wait(); | |
7303 | |
7304 // See the comment in coordinator_yield() | |
7305 for (unsigned i = 0; i < CMSYieldSleepCount && | |
7306 ConcurrentMarkSweepThread::should_yield() && | |
7307 !CMSCollector::foregroundGCIsActive(); ++i) { | |
7308 os::sleep(Thread::current(), 1, false); | |
7309 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
7310 } | |
7311 | |
7312 ConcurrentMarkSweepThread::synchronize(true); | |
7313 _bit_map->lock()->lock_without_safepoint_check(); | |
7314 _collector->startTimer(); | |
7315 } | |
7316 | |
7317 // This closure is used to rescan the marked objects on the dirty cards | |
7318 // in the mod union table and the card table proper. In the parallel | |
7319 // case, although the bitMap is shared, we do a single read so the | |
7320 // isMarked() query is "safe". | |
7321 bool ScanMarkedObjectsAgainClosure::do_object_bm(oop p, MemRegion mr) { | |
7322 // Ignore mark word because we are running concurrent with mutators | |
7323 assert(p->is_oop_or_null(true), "expected an oop or null"); | |
7324 HeapWord* addr = (HeapWord*)p; | |
7325 assert(_span.contains(addr), "we are scanning the CMS generation"); | |
7326 bool is_obj_array = false; | |
9152 | 7327 #ifdef ASSERT |
0 | 7328 if (!_parallel) { |
7329 assert(_mark_stack->isEmpty(), "pre-condition (eager drainage)"); | |
7330 assert(_collector->overflow_list_is_empty(), | |
7331 "overflow list should be empty"); | |
7332 | |
7333 } | |
9152 | 7334 #endif // ASSERT |
0 | 7335 if (_bit_map->isMarked(addr)) { |
7336 // Obj arrays are precisely marked, non-arrays are not; | |
7337 // so we scan objArrays precisely and non-arrays in their | |
7338 // entirety. | |
7339 if (p->is_objArray()) { | |
7340 is_obj_array = true; | |
7341 if (_parallel) { | |
7342 p->oop_iterate(_par_scan_closure, mr); | |
7343 } else { | |
7344 p->oop_iterate(_scan_closure, mr); | |
7345 } | |
7346 } else { | |
7347 if (_parallel) { | |
7348 p->oop_iterate(_par_scan_closure); | |
7349 } else { | |
7350 p->oop_iterate(_scan_closure); | |
7351 } | |
7352 } | |
7353 } | |
9152 | 7354 #ifdef ASSERT |
0 | 7355 if (!_parallel) { |
7356 assert(_mark_stack->isEmpty(), "post-condition (eager drainage)"); | |
7357 assert(_collector->overflow_list_is_empty(), | |
7358 "overflow list should be empty"); | |
7359 | |
7360 } | |
9152 | 7361 #endif // ASSERT |
0 | 7362 return is_obj_array; |
7363 } | |
7364 | |
7365 MarkFromRootsClosure::MarkFromRootsClosure(CMSCollector* collector, | |
7366 MemRegion span, | |
7367 CMSBitMap* bitMap, CMSMarkStack* markStack, | |
7368 bool should_yield, bool verifying): | |
7369 _collector(collector), | |
7370 _span(span), | |
7371 _bitMap(bitMap), | |
7372 _mut(&collector->_modUnionTable), | |
7373 _markStack(markStack), | |
7374 _yield(should_yield), | |
7375 _skipBits(0) | |
7376 { | |
7377 assert(_markStack->isEmpty(), "stack should be empty"); | |
7378 _finger = _bitMap->startWord(); | |
7379 _threshold = _finger; | |
7380 assert(_collector->_restart_addr == NULL, "Sanity check"); | |
7381 assert(_span.contains(_finger), "Out of bounds _finger?"); | |
7382 DEBUG_ONLY(_verifying = verifying;) | |
7383 } | |
7384 | |
7385 void MarkFromRootsClosure::reset(HeapWord* addr) { | |
7386 assert(_markStack->isEmpty(), "would cause duplicates on stack"); | |
7387 assert(_span.contains(addr), "Out of bounds _finger?"); | |
7388 _finger = addr; | |
7389 _threshold = (HeapWord*)round_to( | |
7390 (intptr_t)_finger, CardTableModRefBS::card_size); | |
7391 } | |
7392 | |
7393 // Should revisit to see if this should be restructured for | |
7394 // greater efficiency. | |
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7395 bool MarkFromRootsClosure::do_bit(size_t offset) { |
0 | 7396 if (_skipBits > 0) { |
7397 _skipBits--; | |
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7398 return true; |
0 | 7399 } |
7400 // convert offset into a HeapWord* | |
7401 HeapWord* addr = _bitMap->startWord() + offset; | |
7402 assert(_bitMap->endWord() && addr < _bitMap->endWord(), | |
7403 "address out of range"); | |
7404 assert(_bitMap->isMarked(addr), "tautology"); | |
7405 if (_bitMap->isMarked(addr+1)) { | |
7406 // this is an allocated but not yet initialized object | |
7407 assert(_skipBits == 0, "tautology"); | |
7408 _skipBits = 2; // skip next two marked bits ("Printezis-marks") | |
7409 oop p = oop(addr); | |
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7410 if (p->klass_or_null() == NULL) { |
0 | 7411 DEBUG_ONLY(if (!_verifying) {) |
7412 // We re-dirty the cards on which this object lies and increase | |
7413 // the _threshold so that we'll come back to scan this object | |
7414 // during the preclean or remark phase. (CMSCleanOnEnter) | |
7415 if (CMSCleanOnEnter) { | |
7416 size_t sz = _collector->block_size_using_printezis_bits(addr); | |
7417 HeapWord* end_card_addr = (HeapWord*)round_to( | |
7418 (intptr_t)(addr+sz), CardTableModRefBS::card_size); | |
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7419 MemRegion redirty_range = MemRegion(addr, end_card_addr); |
0 | 7420 assert(!redirty_range.is_empty(), "Arithmetical tautology"); |
7421 // Bump _threshold to end_card_addr; note that | |
7422 // _threshold cannot possibly exceed end_card_addr, anyhow. | |
7423 // This prevents future clearing of the card as the scan proceeds | |
7424 // to the right. | |
7425 assert(_threshold <= end_card_addr, | |
7426 "Because we are just scanning into this object"); | |
7427 if (_threshold < end_card_addr) { | |
7428 _threshold = end_card_addr; | |
7429 } | |
187 | 7430 if (p->klass_or_null() != NULL) { |
0 | 7431 // Redirty the range of cards... |
7432 _mut->mark_range(redirty_range); | |
7433 } // ...else the setting of klass will dirty the card anyway. | |
7434 } | |
7435 DEBUG_ONLY(}) | |
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7436 return true; |
0 | 7437 } |
7438 } | |
7439 scanOopsInOop(addr); | |
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7440 return true; |
0 | 7441 } |
7442 | |
7443 // We take a break if we've been at this for a while, | |
7444 // so as to avoid monopolizing the locks involved. | |
7445 void MarkFromRootsClosure::do_yield_work() { | |
7446 // First give up the locks, then yield, then re-lock | |
7447 // We should probably use a constructor/destructor idiom to | |
7448 // do this unlock/lock or modify the MutexUnlocker class to | |
7449 // serve our purpose. XXX | |
7450 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
7451 "CMS thread should hold CMS token"); | |
7452 assert_lock_strong(_bitMap->lock()); | |
7453 _bitMap->lock()->unlock(); | |
7454 ConcurrentMarkSweepThread::desynchronize(true); | |
7455 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
7456 _collector->stopTimer(); | |
7457 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
7458 if (PrintCMSStatistics != 0) { | |
7459 _collector->incrementYields(); | |
7460 } | |
7461 _collector->icms_wait(); | |
7462 | |
7463 // See the comment in coordinator_yield() | |
7464 for (unsigned i = 0; i < CMSYieldSleepCount && | |
7465 ConcurrentMarkSweepThread::should_yield() && | |
7466 !CMSCollector::foregroundGCIsActive(); ++i) { | |
7467 os::sleep(Thread::current(), 1, false); | |
7468 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
7469 } | |
7470 | |
7471 ConcurrentMarkSweepThread::synchronize(true); | |
7472 _bitMap->lock()->lock_without_safepoint_check(); | |
7473 _collector->startTimer(); | |
7474 } | |
7475 | |
7476 void MarkFromRootsClosure::scanOopsInOop(HeapWord* ptr) { | |
7477 assert(_bitMap->isMarked(ptr), "expected bit to be set"); | |
7478 assert(_markStack->isEmpty(), | |
7479 "should drain stack to limit stack usage"); | |
7480 // convert ptr to an oop preparatory to scanning | |
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7481 oop obj = oop(ptr); |
0 | 7482 // Ignore mark word in verification below, since we |
7483 // may be running concurrent with mutators. | |
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7484 assert(obj->is_oop(true), "should be an oop"); |
0 | 7485 assert(_finger <= ptr, "_finger runneth ahead"); |
7486 // advance the finger to right end of this object | |
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7487 _finger = ptr + obj->size(); |
0 | 7488 assert(_finger > ptr, "we just incremented it above"); |
7489 // On large heaps, it may take us some time to get through | |
7490 // the marking phase (especially if running iCMS). During | |
7491 // this time it's possible that a lot of mutations have | |
7492 // accumulated in the card table and the mod union table -- | |
7493 // these mutation records are redundant until we have | |
7494 // actually traced into the corresponding card. | |
7495 // Here, we check whether advancing the finger would make | |
7496 // us cross into a new card, and if so clear corresponding | |
7497 // cards in the MUT (preclean them in the card-table in the | |
7498 // future). | |
7499 | |
7500 DEBUG_ONLY(if (!_verifying) {) | |
7501 // The clean-on-enter optimization is disabled by default, | |
7502 // until we fix 6178663. | |
7503 if (CMSCleanOnEnter && (_finger > _threshold)) { | |
7504 // [_threshold, _finger) represents the interval | |
7505 // of cards to be cleared in MUT (or precleaned in card table). | |
7506 // The set of cards to be cleared is all those that overlap | |
7507 // with the interval [_threshold, _finger); note that | |
7508 // _threshold is always kept card-aligned but _finger isn't | |
7509 // always card-aligned. | |
7510 HeapWord* old_threshold = _threshold; | |
7511 assert(old_threshold == (HeapWord*)round_to( | |
7512 (intptr_t)old_threshold, CardTableModRefBS::card_size), | |
7513 "_threshold should always be card-aligned"); | |
7514 _threshold = (HeapWord*)round_to( | |
7515 (intptr_t)_finger, CardTableModRefBS::card_size); | |
7516 MemRegion mr(old_threshold, _threshold); | |
7517 assert(!mr.is_empty(), "Control point invariant"); | |
7518 assert(_span.contains(mr), "Should clear within span"); | |
7519 _mut->clear_range(mr); | |
7520 } | |
7521 DEBUG_ONLY(}) | |
7522 // Note: the finger doesn't advance while we drain | |
7523 // the stack below. | |
7524 PushOrMarkClosure pushOrMarkClosure(_collector, | |
7525 _span, _bitMap, _markStack, | |
7526 _finger, this); | |
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7527 bool res = _markStack->push(obj); |
0 | 7528 assert(res, "Empty non-zero size stack should have space for single push"); |
7529 while (!_markStack->isEmpty()) { | |
7530 oop new_oop = _markStack->pop(); | |
7531 // Skip verifying header mark word below because we are | |
7532 // running concurrent with mutators. | |
7533 assert(new_oop->is_oop(true), "Oops! expected to pop an oop"); | |
7534 // now scan this oop's oops | |
7535 new_oop->oop_iterate(&pushOrMarkClosure); | |
7536 do_yield_check(); | |
7537 } | |
7538 assert(_markStack->isEmpty(), "tautology, emphasizing post-condition"); | |
7539 } | |
7540 | |
7541 Par_MarkFromRootsClosure::Par_MarkFromRootsClosure(CMSConcMarkingTask* task, | |
7542 CMSCollector* collector, MemRegion span, | |
7543 CMSBitMap* bit_map, | |
7544 OopTaskQueue* work_queue, | |
7545 CMSMarkStack* overflow_stack, | |
7546 bool should_yield): | |
7547 _collector(collector), | |
7548 _whole_span(collector->_span), | |
7549 _span(span), | |
7550 _bit_map(bit_map), | |
7551 _mut(&collector->_modUnionTable), | |
7552 _work_queue(work_queue), | |
7553 _overflow_stack(overflow_stack), | |
7554 _yield(should_yield), | |
7555 _skip_bits(0), | |
7556 _task(task) | |
7557 { | |
7558 assert(_work_queue->size() == 0, "work_queue should be empty"); | |
7559 _finger = span.start(); | |
7560 _threshold = _finger; // XXX Defer clear-on-enter optimization for now | |
7561 assert(_span.contains(_finger), "Out of bounds _finger?"); | |
7562 } | |
7563 | |
7564 // Should revisit to see if this should be restructured for | |
7565 // greater efficiency. | |
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7566 bool Par_MarkFromRootsClosure::do_bit(size_t offset) { |
0 | 7567 if (_skip_bits > 0) { |
7568 _skip_bits--; | |
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7569 return true; |
0 | 7570 } |
7571 // convert offset into a HeapWord* | |
7572 HeapWord* addr = _bit_map->startWord() + offset; | |
7573 assert(_bit_map->endWord() && addr < _bit_map->endWord(), | |
7574 "address out of range"); | |
7575 assert(_bit_map->isMarked(addr), "tautology"); | |
7576 if (_bit_map->isMarked(addr+1)) { | |
7577 // this is an allocated object that might not yet be initialized | |
7578 assert(_skip_bits == 0, "tautology"); | |
7579 _skip_bits = 2; // skip next two marked bits ("Printezis-marks") | |
7580 oop p = oop(addr); | |
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7581 if (p->klass_or_null() == NULL) { |
0 | 7582 // in the case of Clean-on-Enter optimization, redirty card |
7583 // and avoid clearing card by increasing the threshold. | |
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7584 return true; |
0 | 7585 } |
7586 } | |
7587 scan_oops_in_oop(addr); | |
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7588 return true; |
0 | 7589 } |
7590 | |
7591 void Par_MarkFromRootsClosure::scan_oops_in_oop(HeapWord* ptr) { | |
7592 assert(_bit_map->isMarked(ptr), "expected bit to be set"); | |
7593 // Should we assert that our work queue is empty or | |
7594 // below some drain limit? | |
7595 assert(_work_queue->size() == 0, | |
7596 "should drain stack to limit stack usage"); | |
7597 // convert ptr to an oop preparatory to scanning | |
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7598 oop obj = oop(ptr); |
0 | 7599 // Ignore mark word in verification below, since we |
7600 // may be running concurrent with mutators. | |
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7601 assert(obj->is_oop(true), "should be an oop"); |
0 | 7602 assert(_finger <= ptr, "_finger runneth ahead"); |
7603 // advance the finger to right end of this object | |
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7604 _finger = ptr + obj->size(); |
0 | 7605 assert(_finger > ptr, "we just incremented it above"); |
7606 // On large heaps, it may take us some time to get through | |
7607 // the marking phase (especially if running iCMS). During | |
7608 // this time it's possible that a lot of mutations have | |
7609 // accumulated in the card table and the mod union table -- | |
7610 // these mutation records are redundant until we have | |
7611 // actually traced into the corresponding card. | |
7612 // Here, we check whether advancing the finger would make | |
7613 // us cross into a new card, and if so clear corresponding | |
7614 // cards in the MUT (preclean them in the card-table in the | |
7615 // future). | |
7616 | |
7617 // The clean-on-enter optimization is disabled by default, | |
7618 // until we fix 6178663. | |
7619 if (CMSCleanOnEnter && (_finger > _threshold)) { | |
7620 // [_threshold, _finger) represents the interval | |
7621 // of cards to be cleared in MUT (or precleaned in card table). | |
7622 // The set of cards to be cleared is all those that overlap | |
7623 // with the interval [_threshold, _finger); note that | |
7624 // _threshold is always kept card-aligned but _finger isn't | |
7625 // always card-aligned. | |
7626 HeapWord* old_threshold = _threshold; | |
7627 assert(old_threshold == (HeapWord*)round_to( | |
7628 (intptr_t)old_threshold, CardTableModRefBS::card_size), | |
7629 "_threshold should always be card-aligned"); | |
7630 _threshold = (HeapWord*)round_to( | |
7631 (intptr_t)_finger, CardTableModRefBS::card_size); | |
7632 MemRegion mr(old_threshold, _threshold); | |
7633 assert(!mr.is_empty(), "Control point invariant"); | |
7634 assert(_span.contains(mr), "Should clear within span"); // _whole_span ?? | |
7635 _mut->clear_range(mr); | |
7636 } | |
7637 | |
7638 // Note: the local finger doesn't advance while we drain | |
7639 // the stack below, but the global finger sure can and will. | |
7640 HeapWord** gfa = _task->global_finger_addr(); | |
7641 Par_PushOrMarkClosure pushOrMarkClosure(_collector, | |
7642 _span, _bit_map, | |
7643 _work_queue, | |
7644 _overflow_stack, | |
7645 _finger, | |
7646 gfa, this); | |
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7647 bool res = _work_queue->push(obj); // overflow could occur here |
0 | 7648 assert(res, "Will hold once we use workqueues"); |
7649 while (true) { | |
7650 oop new_oop; | |
7651 if (!_work_queue->pop_local(new_oop)) { | |
7652 // We emptied our work_queue; check if there's stuff that can | |
7653 // be gotten from the overflow stack. | |
7654 if (CMSConcMarkingTask::get_work_from_overflow_stack( | |
7655 _overflow_stack, _work_queue)) { | |
7656 do_yield_check(); | |
7657 continue; | |
7658 } else { // done | |
7659 break; | |
7660 } | |
7661 } | |
7662 // Skip verifying header mark word below because we are | |
7663 // running concurrent with mutators. | |
7664 assert(new_oop->is_oop(true), "Oops! expected to pop an oop"); | |
7665 // now scan this oop's oops | |
7666 new_oop->oop_iterate(&pushOrMarkClosure); | |
7667 do_yield_check(); | |
7668 } | |
7669 assert(_work_queue->size() == 0, "tautology, emphasizing post-condition"); | |
7670 } | |
7671 | |
7672 // Yield in response to a request from VM Thread or | |
7673 // from mutators. | |
7674 void Par_MarkFromRootsClosure::do_yield_work() { | |
7675 assert(_task != NULL, "sanity"); | |
7676 _task->yield(); | |
7677 } | |
7678 | |
7679 // A variant of the above used for verifying CMS marking work. | |
7680 MarkFromRootsVerifyClosure::MarkFromRootsVerifyClosure(CMSCollector* collector, | |
7681 MemRegion span, | |
7682 CMSBitMap* verification_bm, CMSBitMap* cms_bm, | |
7683 CMSMarkStack* mark_stack): | |
7684 _collector(collector), | |
7685 _span(span), | |
7686 _verification_bm(verification_bm), | |
7687 _cms_bm(cms_bm), | |
7688 _mark_stack(mark_stack), | |
7689 _pam_verify_closure(collector, span, verification_bm, cms_bm, | |
7690 mark_stack) | |
7691 { | |
7692 assert(_mark_stack->isEmpty(), "stack should be empty"); | |
7693 _finger = _verification_bm->startWord(); | |
7694 assert(_collector->_restart_addr == NULL, "Sanity check"); | |
7695 assert(_span.contains(_finger), "Out of bounds _finger?"); | |
7696 } | |
7697 | |
7698 void MarkFromRootsVerifyClosure::reset(HeapWord* addr) { | |
7699 assert(_mark_stack->isEmpty(), "would cause duplicates on stack"); | |
7700 assert(_span.contains(addr), "Out of bounds _finger?"); | |
7701 _finger = addr; | |
7702 } | |
7703 | |
7704 // Should revisit to see if this should be restructured for | |
7705 // greater efficiency. | |
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7706 bool MarkFromRootsVerifyClosure::do_bit(size_t offset) { |
0 | 7707 // convert offset into a HeapWord* |
7708 HeapWord* addr = _verification_bm->startWord() + offset; | |
7709 assert(_verification_bm->endWord() && addr < _verification_bm->endWord(), | |
7710 "address out of range"); | |
7711 assert(_verification_bm->isMarked(addr), "tautology"); | |
7712 assert(_cms_bm->isMarked(addr), "tautology"); | |
7713 | |
7714 assert(_mark_stack->isEmpty(), | |
7715 "should drain stack to limit stack usage"); | |
7716 // convert addr to an oop preparatory to scanning | |
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7717 oop obj = oop(addr); |
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7718 assert(obj->is_oop(), "should be an oop"); |
0 | 7719 assert(_finger <= addr, "_finger runneth ahead"); |
7720 // advance the finger to right end of this object | |
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7721 _finger = addr + obj->size(); |
0 | 7722 assert(_finger > addr, "we just incremented it above"); |
7723 // Note: the finger doesn't advance while we drain | |
7724 // the stack below. | |
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7725 bool res = _mark_stack->push(obj); |
0 | 7726 assert(res, "Empty non-zero size stack should have space for single push"); |
7727 while (!_mark_stack->isEmpty()) { | |
7728 oop new_oop = _mark_stack->pop(); | |
7729 assert(new_oop->is_oop(), "Oops! expected to pop an oop"); | |
7730 // now scan this oop's oops | |
7731 new_oop->oop_iterate(&_pam_verify_closure); | |
7732 } | |
7733 assert(_mark_stack->isEmpty(), "tautology, emphasizing post-condition"); | |
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7734 return true; |
0 | 7735 } |
7736 | |
7737 PushAndMarkVerifyClosure::PushAndMarkVerifyClosure( | |
7738 CMSCollector* collector, MemRegion span, | |
7739 CMSBitMap* verification_bm, CMSBitMap* cms_bm, | |
7740 CMSMarkStack* mark_stack): | |
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7741 CMSOopClosure(collector->ref_processor()), |
0 | 7742 _collector(collector), |
7743 _span(span), | |
7744 _verification_bm(verification_bm), | |
7745 _cms_bm(cms_bm), | |
7746 _mark_stack(mark_stack) | |
7747 { } | |
7748 | |
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7749 void PushAndMarkVerifyClosure::do_oop(oop* p) { PushAndMarkVerifyClosure::do_oop_work(p); } |
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7750 void PushAndMarkVerifyClosure::do_oop(narrowOop* p) { PushAndMarkVerifyClosure::do_oop_work(p); } |
0 | 7751 |
7752 // Upon stack overflow, we discard (part of) the stack, | |
7753 // remembering the least address amongst those discarded | |
7754 // in CMSCollector's _restart_address. | |
7755 void PushAndMarkVerifyClosure::handle_stack_overflow(HeapWord* lost) { | |
7756 // Remember the least grey address discarded | |
7757 HeapWord* ra = (HeapWord*)_mark_stack->least_value(lost); | |
7758 _collector->lower_restart_addr(ra); | |
7759 _mark_stack->reset(); // discard stack contents | |
7760 _mark_stack->expand(); // expand the stack if possible | |
7761 } | |
7762 | |
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7763 void PushAndMarkVerifyClosure::do_oop(oop obj) { |
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7764 assert(obj->is_oop_or_null(), "expected an oop or NULL"); |
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7765 HeapWord* addr = (HeapWord*)obj; |
0 | 7766 if (_span.contains(addr) && !_verification_bm->isMarked(addr)) { |
7767 // Oop lies in _span and isn't yet grey or black | |
7768 _verification_bm->mark(addr); // now grey | |
7769 if (!_cms_bm->isMarked(addr)) { | |
7770 oop(addr)->print(); | |
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7771 gclog_or_tty->print_cr(" (" INTPTR_FORMAT " should have been marked)", |
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7772 addr); |
0 | 7773 fatal("... aborting"); |
7774 } | |
7775 | |
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7776 if (!_mark_stack->push(obj)) { // stack overflow |
0 | 7777 if (PrintCMSStatistics != 0) { |
7778 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
7779 SIZE_FORMAT, _mark_stack->capacity()); | |
7780 } | |
7781 assert(_mark_stack->isFull(), "Else push should have succeeded"); | |
7782 handle_stack_overflow(addr); | |
7783 } | |
7784 // anything including and to the right of _finger | |
7785 // will be scanned as we iterate over the remainder of the | |
7786 // bit map | |
7787 } | |
7788 } | |
7789 | |
7790 PushOrMarkClosure::PushOrMarkClosure(CMSCollector* collector, | |
7791 MemRegion span, | |
7792 CMSBitMap* bitMap, CMSMarkStack* markStack, | |
7793 HeapWord* finger, MarkFromRootsClosure* parent) : | |
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7794 CMSOopClosure(collector->ref_processor()), |
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7795 _collector(collector), |
0 | 7796 _span(span), |
7797 _bitMap(bitMap), | |
7798 _markStack(markStack), | |
7799 _finger(finger), | |
935 | 7800 _parent(parent) |
0 | 7801 { } |
7802 | |
7803 Par_PushOrMarkClosure::Par_PushOrMarkClosure(CMSCollector* collector, | |
7804 MemRegion span, | |
7805 CMSBitMap* bit_map, | |
7806 OopTaskQueue* work_queue, | |
7807 CMSMarkStack* overflow_stack, | |
7808 HeapWord* finger, | |
7809 HeapWord** global_finger_addr, | |
7810 Par_MarkFromRootsClosure* parent) : | |
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7811 CMSOopClosure(collector->ref_processor()), |
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7812 _collector(collector), |
0 | 7813 _whole_span(collector->_span), |
7814 _span(span), | |
7815 _bit_map(bit_map), | |
7816 _work_queue(work_queue), | |
7817 _overflow_stack(overflow_stack), | |
7818 _finger(finger), | |
7819 _global_finger_addr(global_finger_addr), | |
935 | 7820 _parent(parent) |
0 | 7821 { } |
7822 | |
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7823 // Assumes thread-safe access by callers, who are |
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7824 // responsible for mutual exclusion. |
0 | 7825 void CMSCollector::lower_restart_addr(HeapWord* low) { |
7826 assert(_span.contains(low), "Out of bounds addr"); | |
7827 if (_restart_addr == NULL) { | |
7828 _restart_addr = low; | |
7829 } else { | |
7830 _restart_addr = MIN2(_restart_addr, low); | |
7831 } | |
7832 } | |
7833 | |
7834 // Upon stack overflow, we discard (part of) the stack, | |
7835 // remembering the least address amongst those discarded | |
7836 // in CMSCollector's _restart_address. | |
7837 void PushOrMarkClosure::handle_stack_overflow(HeapWord* lost) { | |
7838 // Remember the least grey address discarded | |
7839 HeapWord* ra = (HeapWord*)_markStack->least_value(lost); | |
7840 _collector->lower_restart_addr(ra); | |
7841 _markStack->reset(); // discard stack contents | |
7842 _markStack->expand(); // expand the stack if possible | |
7843 } | |
7844 | |
7845 // Upon stack overflow, we discard (part of) the stack, | |
7846 // remembering the least address amongst those discarded | |
7847 // in CMSCollector's _restart_address. | |
7848 void Par_PushOrMarkClosure::handle_stack_overflow(HeapWord* lost) { | |
7849 // We need to do this under a mutex to prevent other | |
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7850 // workers from interfering with the work done below. |
0 | 7851 MutexLockerEx ml(_overflow_stack->par_lock(), |
7852 Mutex::_no_safepoint_check_flag); | |
7853 // Remember the least grey address discarded | |
7854 HeapWord* ra = (HeapWord*)_overflow_stack->least_value(lost); | |
7855 _collector->lower_restart_addr(ra); | |
7856 _overflow_stack->reset(); // discard stack contents | |
7857 _overflow_stack->expand(); // expand the stack if possible | |
7858 } | |
7859 | |
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7860 void CMKlassClosure::do_klass(Klass* k) { |
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7861 assert(_oop_closure != NULL, "Not initialized?"); |
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7862 k->oops_do(_oop_closure); |
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7863 } |
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7864 |
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7865 void PushOrMarkClosure::do_oop(oop obj) { |
0 | 7866 // Ignore mark word because we are running concurrent with mutators. |
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7867 assert(obj->is_oop_or_null(true), "expected an oop or NULL"); |
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7868 HeapWord* addr = (HeapWord*)obj; |
0 | 7869 if (_span.contains(addr) && !_bitMap->isMarked(addr)) { |
7870 // Oop lies in _span and isn't yet grey or black | |
7871 _bitMap->mark(addr); // now grey | |
7872 if (addr < _finger) { | |
7873 // the bit map iteration has already either passed, or | |
7874 // sampled, this bit in the bit map; we'll need to | |
7875 // use the marking stack to scan this oop's oops. | |
7876 bool simulate_overflow = false; | |
7877 NOT_PRODUCT( | |
7878 if (CMSMarkStackOverflowALot && | |
7879 _collector->simulate_overflow()) { | |
7880 // simulate a stack overflow | |
7881 simulate_overflow = true; | |
7882 } | |
7883 ) | |
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7884 if (simulate_overflow || !_markStack->push(obj)) { // stack overflow |
0 | 7885 if (PrintCMSStatistics != 0) { |
7886 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
7887 SIZE_FORMAT, _markStack->capacity()); | |
7888 } | |
7889 assert(simulate_overflow || _markStack->isFull(), "Else push should have succeeded"); | |
7890 handle_stack_overflow(addr); | |
7891 } | |
7892 } | |
7893 // anything including and to the right of _finger | |
7894 // will be scanned as we iterate over the remainder of the | |
7895 // bit map | |
7896 do_yield_check(); | |
7897 } | |
7898 } | |
7899 | |
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7900 void PushOrMarkClosure::do_oop(oop* p) { PushOrMarkClosure::do_oop_work(p); } |
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7901 void PushOrMarkClosure::do_oop(narrowOop* p) { PushOrMarkClosure::do_oop_work(p); } |
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7902 |
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7903 void Par_PushOrMarkClosure::do_oop(oop obj) { |
0 | 7904 // Ignore mark word because we are running concurrent with mutators. |
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7905 assert(obj->is_oop_or_null(true), "expected an oop or NULL"); |
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7906 HeapWord* addr = (HeapWord*)obj; |
0 | 7907 if (_whole_span.contains(addr) && !_bit_map->isMarked(addr)) { |
7908 // Oop lies in _span and isn't yet grey or black | |
7909 // We read the global_finger (volatile read) strictly after marking oop | |
7910 bool res = _bit_map->par_mark(addr); // now grey | |
7911 volatile HeapWord** gfa = (volatile HeapWord**)_global_finger_addr; | |
7912 // Should we push this marked oop on our stack? | |
7913 // -- if someone else marked it, nothing to do | |
7914 // -- if target oop is above global finger nothing to do | |
7915 // -- if target oop is in chunk and above local finger | |
7916 // then nothing to do | |
7917 // -- else push on work queue | |
7918 if ( !res // someone else marked it, they will deal with it | |
7919 || (addr >= *gfa) // will be scanned in a later task | |
7920 || (_span.contains(addr) && addr >= _finger)) { // later in this chunk | |
7921 return; | |
7922 } | |
7923 // the bit map iteration has already either passed, or | |
7924 // sampled, this bit in the bit map; we'll need to | |
7925 // use the marking stack to scan this oop's oops. | |
7926 bool simulate_overflow = false; | |
7927 NOT_PRODUCT( | |
7928 if (CMSMarkStackOverflowALot && | |
7929 _collector->simulate_overflow()) { | |
7930 // simulate a stack overflow | |
7931 simulate_overflow = true; | |
7932 } | |
7933 ) | |
7934 if (simulate_overflow || | |
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7935 !(_work_queue->push(obj) || _overflow_stack->par_push(obj))) { |
0 | 7936 // stack overflow |
7937 if (PrintCMSStatistics != 0) { | |
7938 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
7939 SIZE_FORMAT, _overflow_stack->capacity()); | |
7940 } | |
7941 // We cannot assert that the overflow stack is full because | |
7942 // it may have been emptied since. | |
7943 assert(simulate_overflow || | |
7944 _work_queue->size() == _work_queue->max_elems(), | |
7945 "Else push should have succeeded"); | |
7946 handle_stack_overflow(addr); | |
7947 } | |
7948 do_yield_check(); | |
7949 } | |
7950 } | |
7951 | |
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7952 void Par_PushOrMarkClosure::do_oop(oop* p) { Par_PushOrMarkClosure::do_oop_work(p); } |
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7953 void Par_PushOrMarkClosure::do_oop(narrowOop* p) { Par_PushOrMarkClosure::do_oop_work(p); } |
0 | 7954 |
7955 PushAndMarkClosure::PushAndMarkClosure(CMSCollector* collector, | |
7956 MemRegion span, | |
7957 ReferenceProcessor* rp, | |
7958 CMSBitMap* bit_map, | |
7959 CMSBitMap* mod_union_table, | |
7960 CMSMarkStack* mark_stack, | |
7961 bool concurrent_precleaning): | |
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7962 CMSOopClosure(rp), |
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7963 _collector(collector), |
0 | 7964 _span(span), |
7965 _bit_map(bit_map), | |
7966 _mod_union_table(mod_union_table), | |
7967 _mark_stack(mark_stack), | |
935 | 7968 _concurrent_precleaning(concurrent_precleaning) |
0 | 7969 { |
7970 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
7971 } | |
7972 | |
7973 // Grey object rescan during pre-cleaning and second checkpoint phases -- | |
7974 // the non-parallel version (the parallel version appears further below.) | |
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7975 void PushAndMarkClosure::do_oop(oop obj) { |
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7976 // Ignore mark word verification. If during concurrent precleaning, |
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7977 // the object monitor may be locked. If during the checkpoint |
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7978 // phases, the object may already have been reached by a different |
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7979 // path and may be at the end of the global overflow list (so |
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7980 // the mark word may be NULL). |
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7981 assert(obj->is_oop_or_null(true /* ignore mark word */), |
0 | 7982 "expected an oop or NULL"); |
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7983 HeapWord* addr = (HeapWord*)obj; |
0 | 7984 // Check if oop points into the CMS generation |
7985 // and is not marked | |
7986 if (_span.contains(addr) && !_bit_map->isMarked(addr)) { | |
7987 // a white object ... | |
7988 _bit_map->mark(addr); // ... now grey | |
7989 // push on the marking stack (grey set) | |
7990 bool simulate_overflow = false; | |
7991 NOT_PRODUCT( | |
7992 if (CMSMarkStackOverflowALot && | |
7993 _collector->simulate_overflow()) { | |
7994 // simulate a stack overflow | |
7995 simulate_overflow = true; | |
7996 } | |
7997 ) | |
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7998 if (simulate_overflow || !_mark_stack->push(obj)) { |
0 | 7999 if (_concurrent_precleaning) { |
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8000 // During precleaning we can just dirty the appropriate card(s) |
0 | 8001 // in the mod union table, thus ensuring that the object remains |
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8002 // in the grey set and continue. In the case of object arrays |
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8003 // we need to dirty all of the cards that the object spans, |
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8004 // since the rescan of object arrays will be limited to the |
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8005 // dirty cards. |
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8006 // Note that no one can be intefering with us in this action |
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8007 // of dirtying the mod union table, so no locking or atomics |
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8008 // are required. |
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8009 if (obj->is_objArray()) { |
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8010 size_t sz = obj->size(); |
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8011 HeapWord* end_card_addr = (HeapWord*)round_to( |
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8012 (intptr_t)(addr+sz), CardTableModRefBS::card_size); |
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8013 MemRegion redirty_range = MemRegion(addr, end_card_addr); |
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8014 assert(!redirty_range.is_empty(), "Arithmetical tautology"); |
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8015 _mod_union_table->mark_range(redirty_range); |
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8016 } else { |
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8017 _mod_union_table->mark(addr); |
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8018 } |
0 | 8019 _collector->_ser_pmc_preclean_ovflw++; |
8020 } else { | |
8021 // During the remark phase, we need to remember this oop | |
8022 // in the overflow list. | |
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8023 _collector->push_on_overflow_list(obj); |
0 | 8024 _collector->_ser_pmc_remark_ovflw++; |
8025 } | |
8026 } | |
8027 } | |
8028 } | |
8029 | |
8030 Par_PushAndMarkClosure::Par_PushAndMarkClosure(CMSCollector* collector, | |
8031 MemRegion span, | |
8032 ReferenceProcessor* rp, | |
8033 CMSBitMap* bit_map, | |
6725
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8034 OopTaskQueue* work_queue): |
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8035 CMSOopClosure(rp), |
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8036 _collector(collector), |
0 | 8037 _span(span), |
8038 _bit_map(bit_map), | |
935 | 8039 _work_queue(work_queue) |
0 | 8040 { |
8041 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
8042 } | |
8043 | |
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8044 void PushAndMarkClosure::do_oop(oop* p) { PushAndMarkClosure::do_oop_work(p); } |
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8045 void PushAndMarkClosure::do_oop(narrowOop* p) { PushAndMarkClosure::do_oop_work(p); } |
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8046 |
0 | 8047 // Grey object rescan during second checkpoint phase -- |
8048 // the parallel version. | |
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8049 void Par_PushAndMarkClosure::do_oop(oop obj) { |
0 | 8050 // In the assert below, we ignore the mark word because |
8051 // this oop may point to an already visited object that is | |
8052 // on the overflow stack (in which case the mark word has | |
8053 // been hijacked for chaining into the overflow stack -- | |
8054 // if this is the last object in the overflow stack then | |
8055 // its mark word will be NULL). Because this object may | |
8056 // have been subsequently popped off the global overflow | |
8057 // stack, and the mark word possibly restored to the prototypical | |
8058 // value, by the time we get to examined this failing assert in | |
8059 // the debugger, is_oop_or_null(false) may subsequently start | |
8060 // to hold. | |
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8061 assert(obj->is_oop_or_null(true), |
0 | 8062 "expected an oop or NULL"); |
113
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8063 HeapWord* addr = (HeapWord*)obj; |
0 | 8064 // Check if oop points into the CMS generation |
8065 // and is not marked | |
8066 if (_span.contains(addr) && !_bit_map->isMarked(addr)) { | |
8067 // a white object ... | |
8068 // If we manage to "claim" the object, by being the | |
8069 // first thread to mark it, then we push it on our | |
8070 // marking stack | |
8071 if (_bit_map->par_mark(addr)) { // ... now grey | |
8072 // push on work queue (grey set) | |
8073 bool simulate_overflow = false; | |
8074 NOT_PRODUCT( | |
8075 if (CMSMarkStackOverflowALot && | |
8076 _collector->par_simulate_overflow()) { | |
8077 // simulate a stack overflow | |
8078 simulate_overflow = true; | |
8079 } | |
8080 ) | |
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8081 if (simulate_overflow || !_work_queue->push(obj)) { |
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8082 _collector->par_push_on_overflow_list(obj); |
0 | 8083 _collector->_par_pmc_remark_ovflw++; // imprecise OK: no need to CAS |
8084 } | |
8085 } // Else, some other thread got there first | |
8086 } | |
8087 } | |
8088 | |
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8089 void Par_PushAndMarkClosure::do_oop(oop* p) { Par_PushAndMarkClosure::do_oop_work(p); } |
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8090 void Par_PushAndMarkClosure::do_oop(narrowOop* p) { Par_PushAndMarkClosure::do_oop_work(p); } |
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8091 |
0 | 8092 void CMSPrecleanRefsYieldClosure::do_yield_work() { |
8093 Mutex* bml = _collector->bitMapLock(); | |
8094 assert_lock_strong(bml); | |
8095 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
8096 "CMS thread should hold CMS token"); | |
8097 | |
8098 bml->unlock(); | |
8099 ConcurrentMarkSweepThread::desynchronize(true); | |
8100 | |
8101 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
8102 | |
8103 _collector->stopTimer(); | |
8104 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
8105 if (PrintCMSStatistics != 0) { | |
8106 _collector->incrementYields(); | |
8107 } | |
8108 _collector->icms_wait(); | |
8109 | |
8110 // See the comment in coordinator_yield() | |
8111 for (unsigned i = 0; i < CMSYieldSleepCount && | |
8112 ConcurrentMarkSweepThread::should_yield() && | |
8113 !CMSCollector::foregroundGCIsActive(); ++i) { | |
8114 os::sleep(Thread::current(), 1, false); | |
8115 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
8116 } | |
8117 | |
8118 ConcurrentMarkSweepThread::synchronize(true); | |
8119 bml->lock(); | |
8120 | |
8121 _collector->startTimer(); | |
8122 } | |
8123 | |
8124 bool CMSPrecleanRefsYieldClosure::should_return() { | |
8125 if (ConcurrentMarkSweepThread::should_yield()) { | |
8126 do_yield_work(); | |
8127 } | |
8128 return _collector->foregroundGCIsActive(); | |
8129 } | |
8130 | |
8131 void MarkFromDirtyCardsClosure::do_MemRegion(MemRegion mr) { | |
8132 assert(((size_t)mr.start())%CardTableModRefBS::card_size_in_words == 0, | |
8133 "mr should be aligned to start at a card boundary"); | |
8134 // We'd like to assert: | |
8135 // assert(mr.word_size()%CardTableModRefBS::card_size_in_words == 0, | |
8136 // "mr should be a range of cards"); | |
8137 // However, that would be too strong in one case -- the last | |
8138 // partition ends at _unallocated_block which, in general, can be | |
8139 // an arbitrary boundary, not necessarily card aligned. | |
8140 if (PrintCMSStatistics != 0) { | |
8141 _num_dirty_cards += | |
8142 mr.word_size()/CardTableModRefBS::card_size_in_words; | |
8143 } | |
8144 _space->object_iterate_mem(mr, &_scan_cl); | |
8145 } | |
8146 | |
8147 SweepClosure::SweepClosure(CMSCollector* collector, | |
8148 ConcurrentMarkSweepGeneration* g, | |
8149 CMSBitMap* bitMap, bool should_yield) : | |
8150 _collector(collector), | |
8151 _g(g), | |
8152 _sp(g->cmsSpace()), | |
8153 _limit(_sp->sweep_limit()), | |
8154 _freelistLock(_sp->freelistLock()), | |
8155 _bitMap(bitMap), | |
8156 _yield(should_yield), | |
8157 _inFreeRange(false), // No free range at beginning of sweep | |
8158 _freeRangeInFreeLists(false), // No free range at beginning of sweep | |
8159 _lastFreeRangeCoalesced(false), | |
8160 _freeFinger(g->used_region().start()) | |
8161 { | |
8162 NOT_PRODUCT( | |
8163 _numObjectsFreed = 0; | |
8164 _numWordsFreed = 0; | |
8165 _numObjectsLive = 0; | |
8166 _numWordsLive = 0; | |
8167 _numObjectsAlreadyFree = 0; | |
8168 _numWordsAlreadyFree = 0; | |
8169 _last_fc = NULL; | |
8170 | |
8171 _sp->initializeIndexedFreeListArrayReturnedBytes(); | |
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8172 _sp->dictionary()->initialize_dict_returned_bytes(); |
0 | 8173 ) |
8174 assert(_limit >= _sp->bottom() && _limit <= _sp->end(), | |
8175 "sweep _limit out of bounds"); | |
8176 if (CMSTraceSweeper) { | |
3405
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8177 gclog_or_tty->print_cr("\n====================\nStarting new sweep with limit " PTR_FORMAT, |
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8178 _limit); |
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8179 } |
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8180 } |
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8181 |
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8182 void SweepClosure::print_on(outputStream* st) const { |
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8183 tty->print_cr("_sp = [" PTR_FORMAT "," PTR_FORMAT ")", |
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8184 _sp->bottom(), _sp->end()); |
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8185 tty->print_cr("_limit = " PTR_FORMAT, _limit); |
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8186 tty->print_cr("_freeFinger = " PTR_FORMAT, _freeFinger); |
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8187 NOT_PRODUCT(tty->print_cr("_last_fc = " PTR_FORMAT, _last_fc);) |
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8188 tty->print_cr("_inFreeRange = %d, _freeRangeInFreeLists = %d, _lastFreeRangeCoalesced = %d", |
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8189 _inFreeRange, _freeRangeInFreeLists, _lastFreeRangeCoalesced); |
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8190 } |
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8191 |
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8192 #ifndef PRODUCT |
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8193 // Assertion checking only: no useful work in product mode -- |
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8194 // however, if any of the flags below become product flags, |
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8195 // you may need to review this code to see if it needs to be |
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8196 // enabled in product mode. |
0 | 8197 SweepClosure::~SweepClosure() { |
8198 assert_lock_strong(_freelistLock); | |
2132
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8199 assert(_limit >= _sp->bottom() && _limit <= _sp->end(), |
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8200 "sweep _limit out of bounds"); |
0 | 8201 if (inFreeRange()) { |
3405
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8202 warning("inFreeRange() should have been reset; dumping state of SweepClosure"); |
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8203 print(); |
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8204 ShouldNotReachHere(); |
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8205 } |
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8206 if (Verbose && PrintGC) { |
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8207 gclog_or_tty->print("Collected "SIZE_FORMAT" objects, " SIZE_FORMAT " bytes", |
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8208 _numObjectsFreed, _numWordsFreed*sizeof(HeapWord)); |
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8209 gclog_or_tty->print_cr("\nLive "SIZE_FORMAT" objects, " |
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8210 SIZE_FORMAT" bytes " |
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8211 "Already free "SIZE_FORMAT" objects, "SIZE_FORMAT" bytes", |
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8212 _numObjectsLive, _numWordsLive*sizeof(HeapWord), |
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8213 _numObjectsAlreadyFree, _numWordsAlreadyFree*sizeof(HeapWord)); |
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8214 size_t totalBytes = (_numWordsFreed + _numWordsLive + _numWordsAlreadyFree) |
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8215 * sizeof(HeapWord); |
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8216 gclog_or_tty->print_cr("Total sweep: "SIZE_FORMAT" bytes", totalBytes); |
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8217 |
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8218 if (PrintCMSStatistics && CMSVerifyReturnedBytes) { |
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8219 size_t indexListReturnedBytes = _sp->sumIndexedFreeListArrayReturnedBytes(); |
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8220 size_t dict_returned_bytes = _sp->dictionary()->sum_dict_returned_bytes(); |
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8221 size_t returned_bytes = indexListReturnedBytes + dict_returned_bytes; |
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8222 gclog_or_tty->print("Returned "SIZE_FORMAT" bytes", returned_bytes); |
3405
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8223 gclog_or_tty->print(" Indexed List Returned "SIZE_FORMAT" bytes", |
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8224 indexListReturnedBytes); |
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8225 gclog_or_tty->print_cr(" Dictionary Returned "SIZE_FORMAT" bytes", |
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8226 dict_returned_bytes); |
3405
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7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
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3356
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changeset
|
8227 } |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8228 } |
0 | 8229 if (CMSTraceSweeper) { |
3405
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8230 gclog_or_tty->print_cr("end of sweep with _limit = " PTR_FORMAT "\n================", |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
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changeset
|
8231 _limit); |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8232 } |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8233 } |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
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changeset
|
8234 #endif // PRODUCT |
0 | 8235 |
8236 void SweepClosure::initialize_free_range(HeapWord* freeFinger, | |
8237 bool freeRangeInFreeLists) { | |
8238 if (CMSTraceSweeper) { | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8239 gclog_or_tty->print("---- Start free range at 0x%x with free block (%d)\n", |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8240 freeFinger, freeRangeInFreeLists); |
0 | 8241 } |
8242 assert(!inFreeRange(), "Trampling existing free range"); | |
8243 set_inFreeRange(true); | |
8244 set_lastFreeRangeCoalesced(false); | |
8245 | |
8246 set_freeFinger(freeFinger); | |
8247 set_freeRangeInFreeLists(freeRangeInFreeLists); | |
8248 if (CMSTestInFreeList) { | |
8249 if (freeRangeInFreeLists) { | |
8250 FreeChunk* fc = (FreeChunk*) freeFinger; | |
6028
f69a5d43dc19
7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
jmasa
parents:
6026
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|
8251 assert(fc->is_free(), "A chunk on the free list should be free."); |
0 | 8252 assert(fc->size() > 0, "Free range should have a size"); |
6028
f69a5d43dc19
7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
jmasa
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6026
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changeset
|
8253 assert(_sp->verify_chunk_in_free_list(fc), "Chunk is not in free lists"); |
0 | 8254 } |
8255 } | |
8256 } | |
8257 | |
8258 // Note that the sweeper runs concurrently with mutators. Thus, | |
8259 // it is possible for direct allocation in this generation to happen | |
8260 // in the middle of the sweep. Note that the sweeper also coalesces | |
8261 // contiguous free blocks. Thus, unless the sweeper and the allocator | |
8262 // synchronize appropriately freshly allocated blocks may get swept up. | |
8263 // This is accomplished by the sweeper locking the free lists while | |
8264 // it is sweeping. Thus blocks that are determined to be free are | |
8265 // indeed free. There is however one additional complication: | |
8266 // blocks that have been allocated since the final checkpoint and | |
8267 // mark, will not have been marked and so would be treated as | |
8268 // unreachable and swept up. To prevent this, the allocator marks | |
8269 // the bit map when allocating during the sweep phase. This leads, | |
8270 // however, to a further complication -- objects may have been allocated | |
8271 // but not yet initialized -- in the sense that the header isn't yet | |
8272 // installed. The sweeper can not then determine the size of the block | |
8273 // in order to skip over it. To deal with this case, we use a technique | |
8274 // (due to Printezis) to encode such uninitialized block sizes in the | |
8275 // bit map. Since the bit map uses a bit per every HeapWord, but the | |
8276 // CMS generation has a minimum object size of 3 HeapWords, it follows | |
8277 // that "normal marks" won't be adjacent in the bit map (there will | |
8278 // always be at least two 0 bits between successive 1 bits). We make use | |
8279 // of these "unused" bits to represent uninitialized blocks -- the bit | |
8280 // corresponding to the start of the uninitialized object and the next | |
8281 // bit are both set. Finally, a 1 bit marks the end of the object that | |
8282 // started with the two consecutive 1 bits to indicate its potentially | |
8283 // uninitialized state. | |
8284 | |
8285 size_t SweepClosure::do_blk_careful(HeapWord* addr) { | |
8286 FreeChunk* fc = (FreeChunk*)addr; | |
8287 size_t res; | |
8288 | |
1720
5ed703250bff
6977970: CMS: concurrentMarkSweepGeneration.cpp:7947 assert(addr <= _limit) failed: sweep invariant
ysr
parents:
1716
diff
changeset
|
8289 // Check if we are done sweeping. Below we check "addr >= _limit" rather |
5ed703250bff
6977970: CMS: concurrentMarkSweepGeneration.cpp:7947 assert(addr <= _limit) failed: sweep invariant
ysr
parents:
1716
diff
changeset
|
8290 // than "addr == _limit" because although _limit was a block boundary when |
5ed703250bff
6977970: CMS: concurrentMarkSweepGeneration.cpp:7947 assert(addr <= _limit) failed: sweep invariant
ysr
parents:
1716
diff
changeset
|
8291 // we started the sweep, it may no longer be one because heap expansion |
5ed703250bff
6977970: CMS: concurrentMarkSweepGeneration.cpp:7947 assert(addr <= _limit) failed: sweep invariant
ysr
parents:
1716
diff
changeset
|
8292 // may have caused us to coalesce the block ending at the address _limit |
5ed703250bff
6977970: CMS: concurrentMarkSweepGeneration.cpp:7947 assert(addr <= _limit) failed: sweep invariant
ysr
parents:
1716
diff
changeset
|
8293 // with a newly expanded chunk (this happens when _limit was set to the |
3405
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
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changeset
|
8294 // previous _end of the space), so we may have stepped past _limit: |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
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changeset
|
8295 // see the following Zeno-like trail of CRs 6977970, 7008136, 7042740. |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8296 if (addr >= _limit) { // we have swept up to or past the limit: finish up |
0 | 8297 assert(_limit >= _sp->bottom() && _limit <= _sp->end(), |
8298 "sweep _limit out of bounds"); | |
1720
5ed703250bff
6977970: CMS: concurrentMarkSweepGeneration.cpp:7947 assert(addr <= _limit) failed: sweep invariant
ysr
parents:
1716
diff
changeset
|
8299 assert(addr < _sp->end(), "addr out of bounds"); |
3405
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8300 // Flush any free range we might be holding as a single |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8301 // coalesced chunk to the appropriate free list. |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8302 if (inFreeRange()) { |
3405
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8303 assert(freeFinger() >= _sp->bottom() && freeFinger() < _limit, |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8304 err_msg("freeFinger() " PTR_FORMAT" is out-of-bounds", freeFinger())); |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8305 flush_cur_free_chunk(freeFinger(), |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8306 pointer_delta(addr, freeFinger())); |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8307 if (CMSTraceSweeper) { |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8308 gclog_or_tty->print("Sweep: last chunk: "); |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8309 gclog_or_tty->print("put_free_blk 0x%x ("SIZE_FORMAT") " |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8310 "[coalesced:"SIZE_FORMAT"]\n", |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8311 freeFinger(), pointer_delta(addr, freeFinger()), |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8312 lastFreeRangeCoalesced()); |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8313 } |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8314 } |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8315 |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8316 // help the iterator loop finish |
1720
5ed703250bff
6977970: CMS: concurrentMarkSweepGeneration.cpp:7947 assert(addr <= _limit) failed: sweep invariant
ysr
parents:
1716
diff
changeset
|
8317 return pointer_delta(_sp->end(), addr); |
5ed703250bff
6977970: CMS: concurrentMarkSweepGeneration.cpp:7947 assert(addr <= _limit) failed: sweep invariant
ysr
parents:
1716
diff
changeset
|
8318 } |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8319 |
1720
5ed703250bff
6977970: CMS: concurrentMarkSweepGeneration.cpp:7947 assert(addr <= _limit) failed: sweep invariant
ysr
parents:
1716
diff
changeset
|
8320 assert(addr < _limit, "sweep invariant"); |
0 | 8321 // check if we should yield |
8322 do_yield_check(addr); | |
6028
f69a5d43dc19
7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
jmasa
parents:
6026
diff
changeset
|
8323 if (fc->is_free()) { |
0 | 8324 // Chunk that is already free |
8325 res = fc->size(); | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8326 do_already_free_chunk(fc); |
0 | 8327 debug_only(_sp->verifyFreeLists()); |
3405
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8328 // If we flush the chunk at hand in lookahead_and_flush() |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8329 // and it's coalesced with a preceding chunk, then the |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8330 // process of "mangling" the payload of the coalesced block |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8331 // will cause erasure of the size information from the |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8332 // (erstwhile) header of all the coalesced blocks but the |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8333 // first, so the first disjunct in the assert will not hold |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8334 // in that specific case (in which case the second disjunct |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8335 // will hold). |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8336 assert(res == fc->size() || ((HeapWord*)fc) + res >= _limit, |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8337 "Otherwise the size info doesn't change at this step"); |
0 | 8338 NOT_PRODUCT( |
8339 _numObjectsAlreadyFree++; | |
8340 _numWordsAlreadyFree += res; | |
8341 ) | |
8342 NOT_PRODUCT(_last_fc = fc;) | |
8343 } else if (!_bitMap->isMarked(addr)) { | |
8344 // Chunk is fresh garbage | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8345 res = do_garbage_chunk(fc); |
0 | 8346 debug_only(_sp->verifyFreeLists()); |
8347 NOT_PRODUCT( | |
8348 _numObjectsFreed++; | |
8349 _numWordsFreed += res; | |
8350 ) | |
8351 } else { | |
8352 // Chunk that is alive. | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8353 res = do_live_chunk(fc); |
0 | 8354 debug_only(_sp->verifyFreeLists()); |
8355 NOT_PRODUCT( | |
8356 _numObjectsLive++; | |
8357 _numWordsLive += res; | |
8358 ) | |
8359 } | |
8360 return res; | |
8361 } | |
8362 | |
8363 // For the smart allocation, record following | |
8364 // split deaths - a free chunk is removed from its free list because | |
8365 // it is being split into two or more chunks. | |
8366 // split birth - a free chunk is being added to its free list because | |
8367 // a larger free chunk has been split and resulted in this free chunk. | |
8368 // coal death - a free chunk is being removed from its free list because | |
8369 // it is being coalesced into a large free chunk. | |
8370 // coal birth - a free chunk is being added to its free list because | |
8371 // it was created when two or more free chunks where coalesced into | |
8372 // this free chunk. | |
8373 // | |
8374 // These statistics are used to determine the desired number of free | |
8375 // chunks of a given size. The desired number is chosen to be relative | |
8376 // to the end of a CMS sweep. The desired number at the end of a sweep | |
8377 // is the | |
8378 // count-at-end-of-previous-sweep (an amount that was enough) | |
8379 // - count-at-beginning-of-current-sweep (the excess) | |
8380 // + split-births (gains in this size during interval) | |
8381 // - split-deaths (demands on this size during interval) | |
8382 // where the interval is from the end of one sweep to the end of the | |
8383 // next. | |
8384 // | |
8385 // When sweeping the sweeper maintains an accumulated chunk which is | |
8386 // the chunk that is made up of chunks that have been coalesced. That | |
8387 // will be termed the left-hand chunk. A new chunk of garbage that | |
8388 // is being considered for coalescing will be referred to as the | |
8389 // right-hand chunk. | |
8390 // | |
8391 // When making a decision on whether to coalesce a right-hand chunk with | |
8392 // the current left-hand chunk, the current count vs. the desired count | |
8393 // of the left-hand chunk is considered. Also if the right-hand chunk | |
8394 // is near the large chunk at the end of the heap (see | |
8395 // ConcurrentMarkSweepGeneration::isNearLargestChunk()), then the | |
8396 // left-hand chunk is coalesced. | |
8397 // | |
8398 // When making a decision about whether to split a chunk, the desired count | |
8399 // vs. the current count of the candidate to be split is also considered. | |
8400 // If the candidate is underpopulated (currently fewer chunks than desired) | |
8401 // a chunk of an overpopulated (currently more chunks than desired) size may | |
8402 // be chosen. The "hint" associated with a free list, if non-null, points | |
8403 // to a free list which may be overpopulated. | |
8404 // | |
8405 | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8406 void SweepClosure::do_already_free_chunk(FreeChunk* fc) { |
3405
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8407 const size_t size = fc->size(); |
0 | 8408 // Chunks that cannot be coalesced are not in the |
8409 // free lists. | |
8410 if (CMSTestInFreeList && !fc->cantCoalesce()) { | |
6028
f69a5d43dc19
7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
jmasa
parents:
6026
diff
changeset
|
8411 assert(_sp->verify_chunk_in_free_list(fc), |
0 | 8412 "free chunk should be in free lists"); |
8413 } | |
8414 // a chunk that is already free, should not have been | |
8415 // marked in the bit map | |
3405
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8416 HeapWord* const addr = (HeapWord*) fc; |
0 | 8417 assert(!_bitMap->isMarked(addr), "free chunk should be unmarked"); |
8418 // Verify that the bit map has no bits marked between | |
8419 // addr and purported end of this block. | |
8420 _bitMap->verifyNoOneBitsInRange(addr + 1, addr + size); | |
8421 | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
changeset
|
8422 // Some chunks cannot be coalesced under any circumstances. |
0 | 8423 // See the definition of cantCoalesce(). |
8424 if (!fc->cantCoalesce()) { | |
8425 // This chunk can potentially be coalesced. | |
8426 if (_sp->adaptive_freelists()) { | |
8427 // All the work is done in | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8428 do_post_free_or_garbage_chunk(fc, size); |
0 | 8429 } else { // Not adaptive free lists |
8430 // this is a free chunk that can potentially be coalesced by the sweeper; | |
8431 if (!inFreeRange()) { | |
8432 // if the next chunk is a free block that can't be coalesced | |
8433 // it doesn't make sense to remove this chunk from the free lists | |
8434 FreeChunk* nextChunk = (FreeChunk*)(addr + size); | |
2136
c91cc404ca46
7011940: iCMS: SIGSEGV in SweepClosure::do_already_free_chunk(FreeChunk*)+0x360
ysr
parents:
2132
diff
changeset
|
8435 assert((HeapWord*)nextChunk <= _sp->end(), "Chunk size out of bounds?"); |
c91cc404ca46
7011940: iCMS: SIGSEGV in SweepClosure::do_already_free_chunk(FreeChunk*)+0x360
ysr
parents:
2132
diff
changeset
|
8436 if ((HeapWord*)nextChunk < _sp->end() && // There is another free chunk to the right ... |
6028
f69a5d43dc19
7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
jmasa
parents:
6026
diff
changeset
|
8437 nextChunk->is_free() && // ... which is free... |
2136
c91cc404ca46
7011940: iCMS: SIGSEGV in SweepClosure::do_already_free_chunk(FreeChunk*)+0x360
ysr
parents:
2132
diff
changeset
|
8438 nextChunk->cantCoalesce()) { // ... but can't be coalesced |
0 | 8439 // nothing to do |
8440 } else { | |
8441 // Potentially the start of a new free range: | |
8442 // Don't eagerly remove it from the free lists. | |
8443 // No need to remove it if it will just be put | |
8444 // back again. (Also from a pragmatic point of view | |
8445 // if it is a free block in a region that is beyond | |
8446 // any allocated blocks, an assertion will fail) | |
8447 // Remember the start of a free run. | |
8448 initialize_free_range(addr, true); | |
8449 // end - can coalesce with next chunk | |
8450 } | |
8451 } else { | |
8452 // the midst of a free range, we are coalescing | |
3405
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8453 print_free_block_coalesced(fc); |
0 | 8454 if (CMSTraceSweeper) { |
8455 gclog_or_tty->print(" -- pick up free block 0x%x (%d)\n", fc, size); | |
8456 } | |
8457 // remove it from the free lists | |
8458 _sp->removeFreeChunkFromFreeLists(fc); | |
8459 set_lastFreeRangeCoalesced(true); | |
8460 // If the chunk is being coalesced and the current free range is | |
8461 // in the free lists, remove the current free range so that it | |
8462 // will be returned to the free lists in its entirety - all | |
8463 // the coalesced pieces included. | |
8464 if (freeRangeInFreeLists()) { | |
8465 FreeChunk* ffc = (FreeChunk*) freeFinger(); | |
8466 assert(ffc->size() == pointer_delta(addr, freeFinger()), | |
8467 "Size of free range is inconsistent with chunk size."); | |
8468 if (CMSTestInFreeList) { | |
6028
f69a5d43dc19
7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
jmasa
parents:
6026
diff
changeset
|
8469 assert(_sp->verify_chunk_in_free_list(ffc), |
0 | 8470 "free range is not in free lists"); |
8471 } | |
8472 _sp->removeFreeChunkFromFreeLists(ffc); | |
8473 set_freeRangeInFreeLists(false); | |
8474 } | |
8475 } | |
8476 } | |
3405
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
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3356
diff
changeset
|
8477 // Note that if the chunk is not coalescable (the else arm |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
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changeset
|
8478 // below), we unconditionally flush, without needing to do |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
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3356
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changeset
|
8479 // a "lookahead," as we do below. |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8480 if (inFreeRange()) lookahead_and_flush(fc, size); |
0 | 8481 } else { |
8482 // Code path common to both original and adaptive free lists. | |
8483 | |
8484 // cant coalesce with previous block; this should be treated | |
8485 // as the end of a free run if any | |
8486 if (inFreeRange()) { | |
8487 // we kicked some butt; time to pick up the garbage | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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1994
diff
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|
8488 assert(freeFinger() < addr, "freeFinger points too high"); |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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1994
diff
changeset
|
8489 flush_cur_free_chunk(freeFinger(), pointer_delta(addr, freeFinger())); |
0 | 8490 } |
8491 // else, nothing to do, just continue | |
8492 } | |
8493 } | |
8494 | |
2132
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7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
changeset
|
8495 size_t SweepClosure::do_garbage_chunk(FreeChunk* fc) { |
0 | 8496 // This is a chunk of garbage. It is not in any free list. |
8497 // Add it to a free list or let it possibly be coalesced into | |
8498 // a larger chunk. | |
3405
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
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changeset
|
8499 HeapWord* const addr = (HeapWord*) fc; |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
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parents:
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|
8500 const size_t size = CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size()); |
0 | 8501 |
8502 if (_sp->adaptive_freelists()) { | |
8503 // Verify that the bit map has no bits marked between | |
8504 // addr and purported end of just dead object. | |
8505 _bitMap->verifyNoOneBitsInRange(addr + 1, addr + size); | |
8506 | |
2132
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7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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1994
diff
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|
8507 do_post_free_or_garbage_chunk(fc, size); |
0 | 8508 } else { |
8509 if (!inFreeRange()) { | |
8510 // start of a new free range | |
8511 assert(size > 0, "A free range should have a size"); | |
8512 initialize_free_range(addr, false); | |
8513 } else { | |
8514 // this will be swept up when we hit the end of the | |
8515 // free range | |
8516 if (CMSTraceSweeper) { | |
8517 gclog_or_tty->print(" -- pick up garbage 0x%x (%d) \n", fc, size); | |
8518 } | |
8519 // If the chunk is being coalesced and the current free range is | |
8520 // in the free lists, remove the current free range so that it | |
8521 // will be returned to the free lists in its entirety - all | |
8522 // the coalesced pieces included. | |
8523 if (freeRangeInFreeLists()) { | |
8524 FreeChunk* ffc = (FreeChunk*)freeFinger(); | |
8525 assert(ffc->size() == pointer_delta(addr, freeFinger()), | |
8526 "Size of free range is inconsistent with chunk size."); | |
8527 if (CMSTestInFreeList) { | |
6028
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7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
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6026
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|
8528 assert(_sp->verify_chunk_in_free_list(ffc), |
0 | 8529 "free range is not in free lists"); |
8530 } | |
8531 _sp->removeFreeChunkFromFreeLists(ffc); | |
8532 set_freeRangeInFreeLists(false); | |
8533 } | |
8534 set_lastFreeRangeCoalesced(true); | |
8535 } | |
8536 // this will be swept up when we hit the end of the free range | |
8537 | |
8538 // Verify that the bit map has no bits marked between | |
8539 // addr and purported end of just dead object. | |
8540 _bitMap->verifyNoOneBitsInRange(addr + 1, addr + size); | |
8541 } | |
3405
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
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parents:
3356
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changeset
|
8542 assert(_limit >= addr + size, |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
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parents:
3356
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changeset
|
8543 "A freshly garbage chunk can't possibly straddle over _limit"); |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
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parents:
3356
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changeset
|
8544 if (inFreeRange()) lookahead_and_flush(fc, size); |
0 | 8545 return size; |
8546 } | |
8547 | |
2132
4947ee68d19c
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1994
diff
changeset
|
8548 size_t SweepClosure::do_live_chunk(FreeChunk* fc) { |
0 | 8549 HeapWord* addr = (HeapWord*) fc; |
8550 // The sweeper has just found a live object. Return any accumulated | |
8551 // left hand chunk to the free lists. | |
8552 if (inFreeRange()) { | |
2132
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7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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1994
diff
changeset
|
8553 assert(freeFinger() < addr, "freeFinger points too high"); |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8554 flush_cur_free_chunk(freeFinger(), pointer_delta(addr, freeFinger())); |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8555 } |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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1994
diff
changeset
|
8556 |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
changeset
|
8557 // This object is live: we'd normally expect this to be |
0 | 8558 // an oop, and like to assert the following: |
8559 // assert(oop(addr)->is_oop(), "live block should be an oop"); | |
8560 // However, as we commented above, this may be an object whose | |
8561 // header hasn't yet been initialized. | |
8562 size_t size; | |
8563 assert(_bitMap->isMarked(addr), "Tautology for this control point"); | |
8564 if (_bitMap->isMarked(addr + 1)) { | |
8565 // Determine the size from the bit map, rather than trying to | |
8566 // compute it from the object header. | |
8567 HeapWord* nextOneAddr = _bitMap->getNextMarkedWordAddress(addr + 2); | |
8568 size = pointer_delta(nextOneAddr + 1, addr); | |
8569 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
8570 "alignment problem"); | |
8571 | |
9152 | 8572 #ifdef ASSERT |
6725
da91efe96a93
6964458: Reimplement class meta-data storage to use native memory
coleenp
parents:
6197
diff
changeset
|
8573 if (oop(addr)->klass_or_null() != NULL) { |
0 | 8574 // Ignore mark word because we are running concurrent with mutators |
8575 assert(oop(addr)->is_oop(true), "live block should be an oop"); | |
8576 assert(size == | |
8577 CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size()), | |
8578 "P-mark and computed size do not agree"); | |
8579 } | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8580 #endif |
0 | 8581 |
8582 } else { | |
8583 // This should be an initialized object that's alive. | |
6725
da91efe96a93
6964458: Reimplement class meta-data storage to use native memory
coleenp
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6197
diff
changeset
|
8584 assert(oop(addr)->klass_or_null() != NULL, |
0 | 8585 "Should be an initialized object"); |
8586 // Ignore mark word because we are running concurrent with mutators | |
8587 assert(oop(addr)->is_oop(true), "live block should be an oop"); | |
8588 // Verify that the bit map has no bits marked between | |
8589 // addr and purported end of this block. | |
8590 size = CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size()); | |
8591 assert(size >= 3, "Necessary for Printezis marks to work"); | |
8592 assert(!_bitMap->isMarked(addr+1), "Tautology for this control point"); | |
8593 DEBUG_ONLY(_bitMap->verifyNoOneBitsInRange(addr+2, addr+size);) | |
8594 } | |
8595 return size; | |
8596 } | |
8597 | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
changeset
|
8598 void SweepClosure::do_post_free_or_garbage_chunk(FreeChunk* fc, |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8599 size_t chunkSize) { |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8600 // do_post_free_or_garbage_chunk() should only be called in the case |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8601 // of the adaptive free list allocator. |
6028
f69a5d43dc19
7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
jmasa
parents:
6026
diff
changeset
|
8602 const bool fcInFreeLists = fc->is_free(); |
0 | 8603 assert(_sp->adaptive_freelists(), "Should only be used in this case."); |
8604 assert((HeapWord*)fc <= _limit, "sweep invariant"); | |
8605 if (CMSTestInFreeList && fcInFreeLists) { | |
6028
f69a5d43dc19
7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
jmasa
parents:
6026
diff
changeset
|
8606 assert(_sp->verify_chunk_in_free_list(fc), "free chunk is not in free lists"); |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
changeset
|
8607 } |
0 | 8608 |
8609 if (CMSTraceSweeper) { | |
8610 gclog_or_tty->print_cr(" -- pick up another chunk at 0x%x (%d)", fc, chunkSize); | |
8611 } | |
8612 | |
3405
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
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changeset
|
8613 HeapWord* const fc_addr = (HeapWord*) fc; |
0 | 8614 |
8615 bool coalesce; | |
3405
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8616 const size_t left = pointer_delta(fc_addr, freeFinger()); |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8617 const size_t right = chunkSize; |
0 | 8618 switch (FLSCoalescePolicy) { |
8619 // numeric value forms a coalition aggressiveness metric | |
8620 case 0: { // never coalesce | |
8621 coalesce = false; | |
8622 break; | |
8623 } | |
8624 case 1: { // coalesce if left & right chunks on overpopulated lists | |
8625 coalesce = _sp->coalOverPopulated(left) && | |
8626 _sp->coalOverPopulated(right); | |
8627 break; | |
8628 } | |
8629 case 2: { // coalesce if left chunk on overpopulated list (default) | |
8630 coalesce = _sp->coalOverPopulated(left); | |
8631 break; | |
8632 } | |
8633 case 3: { // coalesce if left OR right chunk on overpopulated list | |
8634 coalesce = _sp->coalOverPopulated(left) || | |
8635 _sp->coalOverPopulated(right); | |
8636 break; | |
8637 } | |
8638 case 4: { // always coalesce | |
8639 coalesce = true; | |
8640 break; | |
8641 } | |
8642 default: | |
8643 ShouldNotReachHere(); | |
8644 } | |
8645 | |
8646 // Should the current free range be coalesced? | |
8647 // If the chunk is in a free range and either we decided to coalesce above | |
8648 // or the chunk is near the large block at the end of the heap | |
8649 // (isNearLargestChunk() returns true), then coalesce this chunk. | |
3405
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8650 const bool doCoalesce = inFreeRange() |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8651 && (coalesce || _g->isNearLargestChunk(fc_addr)); |
0 | 8652 if (doCoalesce) { |
8653 // Coalesce the current free range on the left with the new | |
8654 // chunk on the right. If either is on a free list, | |
8655 // it must be removed from the list and stashed in the closure. | |
8656 if (freeRangeInFreeLists()) { | |
3405
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8657 FreeChunk* const ffc = (FreeChunk*)freeFinger(); |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8658 assert(ffc->size() == pointer_delta(fc_addr, freeFinger()), |
0 | 8659 "Size of free range is inconsistent with chunk size."); |
8660 if (CMSTestInFreeList) { | |
6028
f69a5d43dc19
7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
jmasa
parents:
6026
diff
changeset
|
8661 assert(_sp->verify_chunk_in_free_list(ffc), |
0 | 8662 "Chunk is not in free lists"); |
8663 } | |
8664 _sp->coalDeath(ffc->size()); | |
8665 _sp->removeFreeChunkFromFreeLists(ffc); | |
8666 set_freeRangeInFreeLists(false); | |
8667 } | |
8668 if (fcInFreeLists) { | |
8669 _sp->coalDeath(chunkSize); | |
8670 assert(fc->size() == chunkSize, | |
8671 "The chunk has the wrong size or is not in the free lists"); | |
8672 _sp->removeFreeChunkFromFreeLists(fc); | |
8673 } | |
8674 set_lastFreeRangeCoalesced(true); | |
3405
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8675 print_free_block_coalesced(fc); |
0 | 8676 } else { // not in a free range and/or should not coalesce |
8677 // Return the current free range and start a new one. | |
8678 if (inFreeRange()) { | |
8679 // In a free range but cannot coalesce with the right hand chunk. | |
8680 // Put the current free range into the free lists. | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8681 flush_cur_free_chunk(freeFinger(), |
3405
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8682 pointer_delta(fc_addr, freeFinger())); |
0 | 8683 } |
8684 // Set up for new free range. Pass along whether the right hand | |
8685 // chunk is in the free lists. | |
8686 initialize_free_range((HeapWord*)fc, fcInFreeLists); | |
8687 } | |
8688 } | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8689 |
3405
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8690 // Lookahead flush: |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8691 // If we are tracking a free range, and this is the last chunk that |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8692 // we'll look at because its end crosses past _limit, we'll preemptively |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8693 // flush it along with any free range we may be holding on to. Note that |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8694 // this can be the case only for an already free or freshly garbage |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8695 // chunk. If this block is an object, it can never straddle |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8696 // over _limit. The "straddling" occurs when _limit is set at |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8697 // the previous end of the space when this cycle started, and |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8698 // a subsequent heap expansion caused the previously co-terminal |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8699 // free block to be coalesced with the newly expanded portion, |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8700 // thus rendering _limit a non-block-boundary making it dangerous |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8701 // for the sweeper to step over and examine. |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8702 void SweepClosure::lookahead_and_flush(FreeChunk* fc, size_t chunk_size) { |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8703 assert(inFreeRange(), "Should only be called if currently in a free range."); |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8704 HeapWord* const eob = ((HeapWord*)fc) + chunk_size; |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8705 assert(_sp->used_region().contains(eob - 1), |
12112
1bb10d3170fa
8022817: CMS should not shrink if compaction was not done
jmasa
parents:
12088
diff
changeset
|
8706 err_msg("eob = " PTR_FORMAT " eob-1 = " PTR_FORMAT " _limit = " PTR_FORMAT |
1bb10d3170fa
8022817: CMS should not shrink if compaction was not done
jmasa
parents:
12088
diff
changeset
|
8707 " out of bounds wrt _sp = [" PTR_FORMAT "," PTR_FORMAT ")" |
3405
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8708 " when examining fc = " PTR_FORMAT "(" SIZE_FORMAT ")", |
12112
1bb10d3170fa
8022817: CMS should not shrink if compaction was not done
jmasa
parents:
12088
diff
changeset
|
8709 eob, eob-1, _limit, _sp->bottom(), _sp->end(), fc, chunk_size)); |
3405
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8710 if (eob >= _limit) { |
6028
f69a5d43dc19
7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
jmasa
parents:
6026
diff
changeset
|
8711 assert(eob == _limit || fc->is_free(), "Only a free chunk should allow us to cross over the limit"); |
3405
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8712 if (CMSTraceSweeper) { |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8713 gclog_or_tty->print_cr("_limit " PTR_FORMAT " reached or crossed by block " |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8714 "[" PTR_FORMAT "," PTR_FORMAT ") in space " |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8715 "[" PTR_FORMAT "," PTR_FORMAT ")", |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8716 _limit, fc, eob, _sp->bottom(), _sp->end()); |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8717 } |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8718 // Return the storage we are tracking back into the free lists. |
8cbcd406c42e
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
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8719 if (CMSTraceSweeper) { |
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8720 gclog_or_tty->print_cr("Flushing ... "); |
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8721 } |
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|
8722 assert(freeFinger() < eob, "Error"); |
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8723 flush_cur_free_chunk( freeFinger(), pointer_delta(eob, freeFinger())); |
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8724 } |
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8725 } |
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8726 |
2132
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|
8727 void SweepClosure::flush_cur_free_chunk(HeapWord* chunk, size_t size) { |
0 | 8728 assert(inFreeRange(), "Should only be called if currently in a free range."); |
8729 assert(size > 0, | |
8730 "A zero sized chunk cannot be added to the free lists."); | |
8731 if (!freeRangeInFreeLists()) { | |
2132
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|
8732 if (CMSTestInFreeList) { |
0 | 8733 FreeChunk* fc = (FreeChunk*) chunk; |
6028
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8734 fc->set_size(size); |
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8735 assert(!_sp->verify_chunk_in_free_list(fc), |
0 | 8736 "chunk should not be in free lists yet"); |
8737 } | |
8738 if (CMSTraceSweeper) { | |
8739 gclog_or_tty->print_cr(" -- add free block 0x%x (%d) to free lists", | |
8740 chunk, size); | |
8741 } | |
8742 // A new free range is going to be starting. The current | |
8743 // free range has not been added to the free lists yet or | |
8744 // was removed so add it back. | |
8745 // If the current free range was coalesced, then the death | |
8746 // of the free range was recorded. Record a birth now. | |
8747 if (lastFreeRangeCoalesced()) { | |
8748 _sp->coalBirth(size); | |
8749 } | |
8750 _sp->addChunkAndRepairOffsetTable(chunk, size, | |
8751 lastFreeRangeCoalesced()); | |
3405
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8752 } else if (CMSTraceSweeper) { |
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|
8753 gclog_or_tty->print_cr("Already in free list: nothing to flush"); |
0 | 8754 } |
8755 set_inFreeRange(false); | |
8756 set_freeRangeInFreeLists(false); | |
8757 } | |
8758 | |
8759 // We take a break if we've been at this for a while, | |
8760 // so as to avoid monopolizing the locks involved. | |
8761 void SweepClosure::do_yield_work(HeapWord* addr) { | |
8762 // Return current free chunk being used for coalescing (if any) | |
8763 // to the appropriate freelist. After yielding, the next | |
8764 // free block encountered will start a coalescing range of | |
8765 // free blocks. If the next free block is adjacent to the | |
8766 // chunk just flushed, they will need to wait for the next | |
8767 // sweep to be coalesced. | |
8768 if (inFreeRange()) { | |
2132
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|
8769 flush_cur_free_chunk(freeFinger(), pointer_delta(addr, freeFinger())); |
0 | 8770 } |
8771 | |
8772 // First give up the locks, then yield, then re-lock. | |
8773 // We should probably use a constructor/destructor idiom to | |
8774 // do this unlock/lock or modify the MutexUnlocker class to | |
8775 // serve our purpose. XXX | |
8776 assert_lock_strong(_bitMap->lock()); | |
8777 assert_lock_strong(_freelistLock); | |
8778 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
8779 "CMS thread should hold CMS token"); | |
8780 _bitMap->lock()->unlock(); | |
8781 _freelistLock->unlock(); | |
8782 ConcurrentMarkSweepThread::desynchronize(true); | |
8783 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
8784 _collector->stopTimer(); | |
8785 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
8786 if (PrintCMSStatistics != 0) { | |
8787 _collector->incrementYields(); | |
8788 } | |
8789 _collector->icms_wait(); | |
8790 | |
8791 // See the comment in coordinator_yield() | |
8792 for (unsigned i = 0; i < CMSYieldSleepCount && | |
8793 ConcurrentMarkSweepThread::should_yield() && | |
8794 !CMSCollector::foregroundGCIsActive(); ++i) { | |
8795 os::sleep(Thread::current(), 1, false); | |
8796 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
8797 } | |
8798 | |
8799 ConcurrentMarkSweepThread::synchronize(true); | |
8800 _freelistLock->lock(); | |
8801 _bitMap->lock()->lock_without_safepoint_check(); | |
8802 _collector->startTimer(); | |
8803 } | |
8804 | |
8805 #ifndef PRODUCT | |
8806 // This is actually very useful in a product build if it can | |
8807 // be called from the debugger. Compile it into the product | |
8808 // as needed. | |
6028
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8809 bool debug_verify_chunk_in_free_list(FreeChunk* fc) { |
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8810 return debug_cms_space->verify_chunk_in_free_list(fc); |
0 | 8811 } |
3405
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8812 #endif |
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8813 |
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|
8814 void SweepClosure::print_free_block_coalesced(FreeChunk* fc) const { |
0 | 8815 if (CMSTraceSweeper) { |
3405
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|
8816 gclog_or_tty->print_cr("Sweep:coal_free_blk " PTR_FORMAT " (" SIZE_FORMAT ")", |
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8817 fc, fc->size()); |
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8818 } |
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8819 } |
0 | 8820 |
8821 // CMSIsAliveClosure | |
8822 bool CMSIsAliveClosure::do_object_b(oop obj) { | |
8823 HeapWord* addr = (HeapWord*)obj; | |
8824 return addr != NULL && | |
8825 (!_span.contains(addr) || _bit_map->isMarked(addr)); | |
8826 } | |
8827 | |
6725
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8828 |
935 | 8829 CMSKeepAliveClosure::CMSKeepAliveClosure( CMSCollector* collector, |
8830 MemRegion span, | |
8831 CMSBitMap* bit_map, CMSMarkStack* mark_stack, | |
6725
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8832 bool cpc): |
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8833 _collector(collector), |
935 | 8834 _span(span), |
8835 _bit_map(bit_map), | |
8836 _mark_stack(mark_stack), | |
8837 _concurrent_precleaning(cpc) { | |
8838 assert(!_span.is_empty(), "Empty span could spell trouble"); | |
8839 } | |
8840 | |
8841 | |
0 | 8842 // CMSKeepAliveClosure: the serial version |
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8843 void CMSKeepAliveClosure::do_oop(oop obj) { |
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8844 HeapWord* addr = (HeapWord*)obj; |
0 | 8845 if (_span.contains(addr) && |
8846 !_bit_map->isMarked(addr)) { | |
8847 _bit_map->mark(addr); | |
8848 bool simulate_overflow = false; | |
8849 NOT_PRODUCT( | |
8850 if (CMSMarkStackOverflowALot && | |
8851 _collector->simulate_overflow()) { | |
8852 // simulate a stack overflow | |
8853 simulate_overflow = true; | |
8854 } | |
8855 ) | |
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8856 if (simulate_overflow || !_mark_stack->push(obj)) { |
452
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8857 if (_concurrent_precleaning) { |
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8858 // We dirty the overflown object and let the remark |
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8859 // phase deal with it. |
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8860 assert(_collector->overflow_list_is_empty(), "Error"); |
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8861 // In the case of object arrays, we need to dirty all of |
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8862 // the cards that the object spans. No locking or atomics |
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8863 // are needed since no one else can be mutating the mod union |
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8864 // table. |
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8865 if (obj->is_objArray()) { |
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8866 size_t sz = obj->size(); |
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|
8867 HeapWord* end_card_addr = |
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|
8868 (HeapWord*)round_to((intptr_t)(addr+sz), CardTableModRefBS::card_size); |
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8869 MemRegion redirty_range = MemRegion(addr, end_card_addr); |
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8870 assert(!redirty_range.is_empty(), "Arithmetical tautology"); |
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8871 _collector->_modUnionTable.mark_range(redirty_range); |
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|
8872 } else { |
00b023ae2d78
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|
8873 _collector->_modUnionTable.mark(addr); |
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|
8874 } |
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8875 _collector->_ser_kac_preclean_ovflw++; |
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|
8876 } else { |
00b023ae2d78
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|
8877 _collector->push_on_overflow_list(obj); |
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8878 _collector->_ser_kac_ovflw++; |
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8879 } |
0 | 8880 } |
8881 } | |
8882 } | |
8883 | |
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8884 void CMSKeepAliveClosure::do_oop(oop* p) { CMSKeepAliveClosure::do_oop_work(p); } |
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8885 void CMSKeepAliveClosure::do_oop(narrowOop* p) { CMSKeepAliveClosure::do_oop_work(p); } |
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8886 |
0 | 8887 // CMSParKeepAliveClosure: a parallel version of the above. |
8888 // The work queues are private to each closure (thread), | |
8889 // but (may be) available for stealing by other threads. | |
113
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8890 void CMSParKeepAliveClosure::do_oop(oop obj) { |
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8891 HeapWord* addr = (HeapWord*)obj; |
0 | 8892 if (_span.contains(addr) && |
8893 !_bit_map->isMarked(addr)) { | |
8894 // In general, during recursive tracing, several threads | |
8895 // may be concurrently getting here; the first one to | |
8896 // "tag" it, claims it. | |
8897 if (_bit_map->par_mark(addr)) { | |
113
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8898 bool res = _work_queue->push(obj); |
0 | 8899 assert(res, "Low water mark should be much less than capacity"); |
8900 // Do a recursive trim in the hope that this will keep | |
8901 // stack usage lower, but leave some oops for potential stealers | |
8902 trim_queue(_low_water_mark); | |
8903 } // Else, another thread got there first | |
8904 } | |
8905 } | |
8906 | |
113
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8907 void CMSParKeepAliveClosure::do_oop(oop* p) { CMSParKeepAliveClosure::do_oop_work(p); } |
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8908 void CMSParKeepAliveClosure::do_oop(narrowOop* p) { CMSParKeepAliveClosure::do_oop_work(p); } |
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8909 |
0 | 8910 void CMSParKeepAliveClosure::trim_queue(uint max) { |
8911 while (_work_queue->size() > max) { | |
8912 oop new_oop; | |
8913 if (_work_queue->pop_local(new_oop)) { | |
8914 assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop"); | |
8915 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
8916 "no white objects on this stack!"); | |
8917 assert(_span.contains((HeapWord*)new_oop), "Out of bounds oop"); | |
8918 // iterate over the oops in this oop, marking and pushing | |
8919 // the ones in CMS heap (i.e. in _span). | |
8920 new_oop->oop_iterate(&_mark_and_push); | |
8921 } | |
8922 } | |
8923 } | |
8924 | |
935 | 8925 CMSInnerParMarkAndPushClosure::CMSInnerParMarkAndPushClosure( |
8926 CMSCollector* collector, | |
8927 MemRegion span, CMSBitMap* bit_map, | |
8928 OopTaskQueue* work_queue): | |
6725
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8929 _collector(collector), |
935 | 8930 _span(span), |
8931 _bit_map(bit_map), | |
8932 _work_queue(work_queue) { } | |
8933 | |
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8934 void CMSInnerParMarkAndPushClosure::do_oop(oop obj) { |
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8935 HeapWord* addr = (HeapWord*)obj; |
0 | 8936 if (_span.contains(addr) && |
8937 !_bit_map->isMarked(addr)) { | |
8938 if (_bit_map->par_mark(addr)) { | |
8939 bool simulate_overflow = false; | |
8940 NOT_PRODUCT( | |
8941 if (CMSMarkStackOverflowALot && | |
8942 _collector->par_simulate_overflow()) { | |
8943 // simulate a stack overflow | |
8944 simulate_overflow = true; | |
8945 } | |
8946 ) | |
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8947 if (simulate_overflow || !_work_queue->push(obj)) { |
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8948 _collector->par_push_on_overflow_list(obj); |
0 | 8949 _collector->_par_kac_ovflw++; |
8950 } | |
8951 } // Else another thread got there already | |
8952 } | |
8953 } | |
8954 | |
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8955 void CMSInnerParMarkAndPushClosure::do_oop(oop* p) { CMSInnerParMarkAndPushClosure::do_oop_work(p); } |
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8956 void CMSInnerParMarkAndPushClosure::do_oop(narrowOop* p) { CMSInnerParMarkAndPushClosure::do_oop_work(p); } |
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8957 |
0 | 8958 ////////////////////////////////////////////////////////////////// |
8959 // CMSExpansionCause ///////////////////////////// | |
8960 ////////////////////////////////////////////////////////////////// | |
8961 const char* CMSExpansionCause::to_string(CMSExpansionCause::Cause cause) { | |
8962 switch (cause) { | |
8963 case _no_expansion: | |
8964 return "No expansion"; | |
8965 case _satisfy_free_ratio: | |
8966 return "Free ratio"; | |
8967 case _satisfy_promotion: | |
8968 return "Satisfy promotion"; | |
8969 case _satisfy_allocation: | |
8970 return "allocation"; | |
8971 case _allocate_par_lab: | |
8972 return "Par LAB"; | |
8973 case _allocate_par_spooling_space: | |
8974 return "Par Spooling Space"; | |
8975 case _adaptive_size_policy: | |
8976 return "Ergonomics"; | |
8977 default: | |
8978 return "unknown"; | |
8979 } | |
8980 } | |
8981 | |
8982 void CMSDrainMarkingStackClosure::do_void() { | |
8983 // the max number to take from overflow list at a time | |
8984 const size_t num = _mark_stack->capacity()/4; | |
452
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8985 assert(!_concurrent_precleaning || _collector->overflow_list_is_empty(), |
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8986 "Overflow list should be NULL during concurrent phases"); |
0 | 8987 while (!_mark_stack->isEmpty() || |
8988 // if stack is empty, check the overflow list | |
8989 _collector->take_from_overflow_list(num, _mark_stack)) { | |
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8990 oop obj = _mark_stack->pop(); |
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8991 HeapWord* addr = (HeapWord*)obj; |
0 | 8992 assert(_span.contains(addr), "Should be within span"); |
8993 assert(_bit_map->isMarked(addr), "Should be marked"); | |
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8994 assert(obj->is_oop(), "Should be an oop"); |
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8995 obj->oop_iterate(_keep_alive); |
0 | 8996 } |
8997 } | |
8998 | |
8999 void CMSParDrainMarkingStackClosure::do_void() { | |
9000 // drain queue | |
9001 trim_queue(0); | |
9002 } | |
9003 | |
9004 // Trim our work_queue so its length is below max at return | |
9005 void CMSParDrainMarkingStackClosure::trim_queue(uint max) { | |
9006 while (_work_queue->size() > max) { | |
9007 oop new_oop; | |
9008 if (_work_queue->pop_local(new_oop)) { | |
9009 assert(new_oop->is_oop(), "Expected an oop"); | |
9010 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
9011 "no white objects on this stack!"); | |
9012 assert(_span.contains((HeapWord*)new_oop), "Out of bounds oop"); | |
9013 // iterate over the oops in this oop, marking and pushing | |
9014 // the ones in CMS heap (i.e. in _span). | |
9015 new_oop->oop_iterate(&_mark_and_push); | |
9016 } | |
9017 } | |
9018 } | |
9019 | |
9020 //////////////////////////////////////////////////////////////////// | |
9021 // Support for Marking Stack Overflow list handling and related code | |
9022 //////////////////////////////////////////////////////////////////// | |
9023 // Much of the following code is similar in shape and spirit to the | |
9024 // code used in ParNewGC. We should try and share that code | |
9025 // as much as possible in the future. | |
9026 | |
9027 #ifndef PRODUCT | |
9028 // Debugging support for CMSStackOverflowALot | |
9029 | |
9030 // It's OK to call this multi-threaded; the worst thing | |
9031 // that can happen is that we'll get a bunch of closely | |
9032 // spaced simulated oveflows, but that's OK, in fact | |
9033 // probably good as it would exercise the overflow code | |
9034 // under contention. | |
9035 bool CMSCollector::simulate_overflow() { | |
9036 if (_overflow_counter-- <= 0) { // just being defensive | |
9037 _overflow_counter = CMSMarkStackOverflowInterval; | |
9038 return true; | |
9039 } else { | |
9040 return false; | |
9041 } | |
9042 } | |
9043 | |
9044 bool CMSCollector::par_simulate_overflow() { | |
9045 return simulate_overflow(); | |
9046 } | |
9047 #endif | |
9048 | |
9049 // Single-threaded | |
9050 bool CMSCollector::take_from_overflow_list(size_t num, CMSMarkStack* stack) { | |
9051 assert(stack->isEmpty(), "Expected precondition"); | |
9052 assert(stack->capacity() > num, "Shouldn't bite more than can chew"); | |
9053 size_t i = num; | |
9054 oop cur = _overflow_list; | |
9055 const markOop proto = markOopDesc::prototype(); | |
534 | 9056 NOT_PRODUCT(ssize_t n = 0;) |
0 | 9057 for (oop next; i > 0 && cur != NULL; cur = next, i--) { |
9058 next = oop(cur->mark()); | |
9059 cur->set_mark(proto); // until proven otherwise | |
9060 assert(cur->is_oop(), "Should be an oop"); | |
9061 bool res = stack->push(cur); | |
9062 assert(res, "Bit off more than can chew?"); | |
9063 NOT_PRODUCT(n++;) | |
9064 } | |
9065 _overflow_list = cur; | |
9066 #ifndef PRODUCT | |
9067 assert(_num_par_pushes >= n, "Too many pops?"); | |
9068 _num_par_pushes -=n; | |
9069 #endif | |
9070 return !stack->isEmpty(); | |
9071 } | |
9072 | |
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9073 #define BUSY (cast_to_oop<intptr_t>(0x1aff1aff)) |
534 | 9074 // (MT-safe) Get a prefix of at most "num" from the list. |
9075 // The overflow list is chained through the mark word of | |
9076 // each object in the list. We fetch the entire list, | |
9077 // break off a prefix of the right size and return the | |
9078 // remainder. If other threads try to take objects from | |
9079 // the overflow list at that time, they will wait for | |
9080 // some time to see if data becomes available. If (and | |
9081 // only if) another thread places one or more object(s) | |
9082 // on the global list before we have returned the suffix | |
9083 // to the global list, we will walk down our local list | |
9084 // to find its end and append the global list to | |
9085 // our suffix before returning it. This suffix walk can | |
9086 // prove to be expensive (quadratic in the amount of traffic) | |
9087 // when there are many objects in the overflow list and | |
9088 // there is much producer-consumer contention on the list. | |
9089 // *NOTE*: The overflow list manipulation code here and | |
9090 // in ParNewGeneration:: are very similar in shape, | |
9091 // except that in the ParNew case we use the old (from/eden) | |
9092 // copy of the object to thread the list via its klass word. | |
9093 // Because of the common code, if you make any changes in | |
9094 // the code below, please check the ParNew version to see if | |
9095 // similar changes might be needed. | |
9096 // CR 6797058 has been filed to consolidate the common code. | |
0 | 9097 bool CMSCollector::par_take_from_overflow_list(size_t num, |
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9098 OopTaskQueue* work_q, |
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9099 int no_of_gc_threads) { |
534 | 9100 assert(work_q->size() == 0, "First empty local work queue"); |
0 | 9101 assert(num < work_q->max_elems(), "Can't bite more than we can chew"); |
9102 if (_overflow_list == NULL) { | |
9103 return false; | |
9104 } | |
9105 // Grab the entire list; we'll put back a suffix | |
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9106 oop prefix = cast_to_oop(Atomic::xchg_ptr(BUSY, &_overflow_list)); |
534 | 9107 Thread* tid = Thread::current(); |
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9108 // Before "no_of_gc_threads" was introduced CMSOverflowSpinCount was |
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9109 // set to ParallelGCThreads. |
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9110 size_t CMSOverflowSpinCount = (size_t) no_of_gc_threads; // was ParallelGCThreads; |
534 | 9111 size_t sleep_time_millis = MAX2((size_t)1, num/100); |
9112 // If the list is busy, we spin for a short while, | |
9113 // sleeping between attempts to get the list. | |
9114 for (size_t spin = 0; prefix == BUSY && spin < CMSOverflowSpinCount; spin++) { | |
9115 os::sleep(tid, sleep_time_millis, false); | |
9116 if (_overflow_list == NULL) { | |
9117 // Nothing left to take | |
9118 return false; | |
9119 } else if (_overflow_list != BUSY) { | |
9120 // Try and grab the prefix | |
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9121 prefix = cast_to_oop(Atomic::xchg_ptr(BUSY, &_overflow_list)); |
534 | 9122 } |
9123 } | |
9124 // If the list was found to be empty, or we spun long | |
9125 // enough, we give up and return empty-handed. If we leave | |
9126 // the list in the BUSY state below, it must be the case that | |
9127 // some other thread holds the overflow list and will set it | |
9128 // to a non-BUSY state in the future. | |
9129 if (prefix == NULL || prefix == BUSY) { | |
9130 // Nothing to take or waited long enough | |
9131 if (prefix == NULL) { | |
9132 // Write back the NULL in case we overwrote it with BUSY above | |
9133 // and it is still the same value. | |
9134 (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY); | |
9135 } | |
9136 return false; | |
9137 } | |
9138 assert(prefix != NULL && prefix != BUSY, "Error"); | |
0 | 9139 size_t i = num; |
9140 oop cur = prefix; | |
534 | 9141 // Walk down the first "num" objects, unless we reach the end. |
0 | 9142 for (; i > 1 && cur->mark() != NULL; cur = oop(cur->mark()), i--); |
534 | 9143 if (cur->mark() == NULL) { |
9144 // We have "num" or fewer elements in the list, so there | |
9145 // is nothing to return to the global list. | |
9146 // Write back the NULL in lieu of the BUSY we wrote | |
9147 // above, if it is still the same value. | |
9148 if (_overflow_list == BUSY) { | |
9149 (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY); | |
9150 } | |
9151 } else { | |
9152 // Chop off the suffix and rerturn it to the global list. | |
9153 assert(cur->mark() != BUSY, "Error"); | |
0 | 9154 oop suffix_head = cur->mark(); // suffix will be put back on global list |
9155 cur->set_mark(NULL); // break off suffix | |
534 | 9156 // It's possible that the list is still in the empty(busy) state |
9157 // we left it in a short while ago; in that case we may be | |
9158 // able to place back the suffix without incurring the cost | |
9159 // of a walk down the list. | |
0 | 9160 oop observed_overflow_list = _overflow_list; |
534 | 9161 oop cur_overflow_list = observed_overflow_list; |
9162 bool attached = false; | |
9163 while (observed_overflow_list == BUSY || observed_overflow_list == NULL) { | |
0 | 9164 observed_overflow_list = |
534 | 9165 (oop) Atomic::cmpxchg_ptr(suffix_head, &_overflow_list, cur_overflow_list); |
9166 if (cur_overflow_list == observed_overflow_list) { | |
9167 attached = true; | |
9168 break; | |
9169 } else cur_overflow_list = observed_overflow_list; | |
9170 } | |
9171 if (!attached) { | |
9172 // Too bad, someone else sneaked in (at least) an element; we'll need | |
9173 // to do a splice. Find tail of suffix so we can prepend suffix to global | |
9174 // list. | |
9175 for (cur = suffix_head; cur->mark() != NULL; cur = (oop)(cur->mark())); | |
9176 oop suffix_tail = cur; | |
9177 assert(suffix_tail != NULL && suffix_tail->mark() == NULL, | |
9178 "Tautology"); | |
9179 observed_overflow_list = _overflow_list; | |
9180 do { | |
9181 cur_overflow_list = observed_overflow_list; | |
9182 if (cur_overflow_list != BUSY) { | |
9183 // Do the splice ... | |
9184 suffix_tail->set_mark(markOop(cur_overflow_list)); | |
9185 } else { // cur_overflow_list == BUSY | |
9186 suffix_tail->set_mark(NULL); | |
9187 } | |
9188 // ... and try to place spliced list back on overflow_list ... | |
9189 observed_overflow_list = | |
9190 (oop) Atomic::cmpxchg_ptr(suffix_head, &_overflow_list, cur_overflow_list); | |
9191 } while (cur_overflow_list != observed_overflow_list); | |
9192 // ... until we have succeeded in doing so. | |
9193 } | |
0 | 9194 } |
9195 | |
9196 // Push the prefix elements on work_q | |
9197 assert(prefix != NULL, "control point invariant"); | |
9198 const markOop proto = markOopDesc::prototype(); | |
9199 oop next; | |
534 | 9200 NOT_PRODUCT(ssize_t n = 0;) |
0 | 9201 for (cur = prefix; cur != NULL; cur = next) { |
9202 next = oop(cur->mark()); | |
9203 cur->set_mark(proto); // until proven otherwise | |
9204 assert(cur->is_oop(), "Should be an oop"); | |
9205 bool res = work_q->push(cur); | |
9206 assert(res, "Bit off more than we can chew?"); | |
9207 NOT_PRODUCT(n++;) | |
9208 } | |
9209 #ifndef PRODUCT | |
9210 assert(_num_par_pushes >= n, "Too many pops?"); | |
9211 Atomic::add_ptr(-(intptr_t)n, &_num_par_pushes); | |
9212 #endif | |
9213 return true; | |
9214 } | |
9215 | |
9216 // Single-threaded | |
9217 void CMSCollector::push_on_overflow_list(oop p) { | |
9218 NOT_PRODUCT(_num_par_pushes++;) | |
9219 assert(p->is_oop(), "Not an oop"); | |
9220 preserve_mark_if_necessary(p); | |
9221 p->set_mark((markOop)_overflow_list); | |
9222 _overflow_list = p; | |
9223 } | |
9224 | |
9225 // Multi-threaded; use CAS to prepend to overflow list | |
9226 void CMSCollector::par_push_on_overflow_list(oop p) { | |
9227 NOT_PRODUCT(Atomic::inc_ptr(&_num_par_pushes);) | |
9228 assert(p->is_oop(), "Not an oop"); | |
9229 par_preserve_mark_if_necessary(p); | |
9230 oop observed_overflow_list = _overflow_list; | |
9231 oop cur_overflow_list; | |
9232 do { | |
9233 cur_overflow_list = observed_overflow_list; | |
534 | 9234 if (cur_overflow_list != BUSY) { |
9235 p->set_mark(markOop(cur_overflow_list)); | |
9236 } else { | |
9237 p->set_mark(NULL); | |
9238 } | |
0 | 9239 observed_overflow_list = |
9240 (oop) Atomic::cmpxchg_ptr(p, &_overflow_list, cur_overflow_list); | |
9241 } while (cur_overflow_list != observed_overflow_list); | |
9242 } | |
534 | 9243 #undef BUSY |
0 | 9244 |
9245 // Single threaded | |
9246 // General Note on GrowableArray: pushes may silently fail | |
9247 // because we are (temporarily) out of C-heap for expanding | |
9248 // the stack. The problem is quite ubiquitous and affects | |
9249 // a lot of code in the JVM. The prudent thing for GrowableArray | |
9250 // to do (for now) is to exit with an error. However, that may | |
9251 // be too draconian in some cases because the caller may be | |
534 | 9252 // able to recover without much harm. For such cases, we |
0 | 9253 // should probably introduce a "soft_push" method which returns |
9254 // an indication of success or failure with the assumption that | |
9255 // the caller may be able to recover from a failure; code in | |
9256 // the VM can then be changed, incrementally, to deal with such | |
9257 // failures where possible, thus, incrementally hardening the VM | |
9258 // in such low resource situations. | |
9259 void CMSCollector::preserve_mark_work(oop p, markOop m) { | |
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9260 _preserved_oop_stack.push(p); |
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9261 _preserved_mark_stack.push(m); |
0 | 9262 assert(m == p->mark(), "Mark word changed"); |
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9263 assert(_preserved_oop_stack.size() == _preserved_mark_stack.size(), |
0 | 9264 "bijection"); |
9265 } | |
9266 | |
9267 // Single threaded | |
9268 void CMSCollector::preserve_mark_if_necessary(oop p) { | |
9269 markOop m = p->mark(); | |
9270 if (m->must_be_preserved(p)) { | |
9271 preserve_mark_work(p, m); | |
9272 } | |
9273 } | |
9274 | |
9275 void CMSCollector::par_preserve_mark_if_necessary(oop p) { | |
9276 markOop m = p->mark(); | |
9277 if (m->must_be_preserved(p)) { | |
9278 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); | |
9279 // Even though we read the mark word without holding | |
9280 // the lock, we are assured that it will not change | |
9281 // because we "own" this oop, so no other thread can | |
9282 // be trying to push it on the overflow list; see | |
9283 // the assertion in preserve_mark_work() that checks | |
9284 // that m == p->mark(). | |
9285 preserve_mark_work(p, m); | |
9286 } | |
9287 } | |
9288 | |
9289 // We should be able to do this multi-threaded, | |
9290 // a chunk of stack being a task (this is | |
9291 // correct because each oop only ever appears | |
9292 // once in the overflow list. However, it's | |
9293 // not very easy to completely overlap this with | |
9294 // other operations, so will generally not be done | |
9295 // until all work's been completed. Because we | |
9296 // expect the preserved oop stack (set) to be small, | |
9297 // it's probably fine to do this single-threaded. | |
9298 // We can explore cleverer concurrent/overlapped/parallel | |
9299 // processing of preserved marks if we feel the | |
9300 // need for this in the future. Stack overflow should | |
9301 // be so rare in practice and, when it happens, its | |
9302 // effect on performance so great that this will | |
9303 // likely just be in the noise anyway. | |
9304 void CMSCollector::restore_preserved_marks_if_any() { | |
9305 assert(SafepointSynchronize::is_at_safepoint(), | |
9306 "world should be stopped"); | |
9307 assert(Thread::current()->is_ConcurrentGC_thread() || | |
9308 Thread::current()->is_VM_thread(), | |
9309 "should be single-threaded"); | |
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9310 assert(_preserved_oop_stack.size() == _preserved_mark_stack.size(), |
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9311 "bijection"); |
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9312 |
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9313 while (!_preserved_oop_stack.is_empty()) { |
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9314 oop p = _preserved_oop_stack.pop(); |
0 | 9315 assert(p->is_oop(), "Should be an oop"); |
9316 assert(_span.contains(p), "oop should be in _span"); | |
9317 assert(p->mark() == markOopDesc::prototype(), | |
9318 "Set when taken from overflow list"); | |
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9319 markOop m = _preserved_mark_stack.pop(); |
0 | 9320 p->set_mark(m); |
9321 } | |
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9322 assert(_preserved_mark_stack.is_empty() && _preserved_oop_stack.is_empty(), |
0 | 9323 "stacks were cleared above"); |
9324 } | |
9325 | |
9326 #ifndef PRODUCT | |
9327 bool CMSCollector::no_preserved_marks() const { | |
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9328 return _preserved_mark_stack.is_empty() && _preserved_oop_stack.is_empty(); |
0 | 9329 } |
9330 #endif | |
9331 | |
9332 CMSAdaptiveSizePolicy* ASConcurrentMarkSweepGeneration::cms_size_policy() const | |
9333 { | |
9334 GenCollectedHeap* gch = (GenCollectedHeap*) GenCollectedHeap::heap(); | |
9335 CMSAdaptiveSizePolicy* size_policy = | |
9336 (CMSAdaptiveSizePolicy*) gch->gen_policy()->size_policy(); | |
9337 assert(size_policy->is_gc_cms_adaptive_size_policy(), | |
9338 "Wrong type for size policy"); | |
9339 return size_policy; | |
9340 } | |
9341 | |
9342 void ASConcurrentMarkSweepGeneration::resize(size_t cur_promo_size, | |
9343 size_t desired_promo_size) { | |
9344 if (cur_promo_size < desired_promo_size) { | |
9345 size_t expand_bytes = desired_promo_size - cur_promo_size; | |
9346 if (PrintAdaptiveSizePolicy && Verbose) { | |
9347 gclog_or_tty->print_cr(" ASConcurrentMarkSweepGeneration::resize " | |
9348 "Expanding tenured generation by " SIZE_FORMAT " (bytes)", | |
9349 expand_bytes); | |
9350 } | |
9351 expand(expand_bytes, | |
9352 MinHeapDeltaBytes, | |
9353 CMSExpansionCause::_adaptive_size_policy); | |
9354 } else if (desired_promo_size < cur_promo_size) { | |
9355 size_t shrink_bytes = cur_promo_size - desired_promo_size; | |
9356 if (PrintAdaptiveSizePolicy && Verbose) { | |
9357 gclog_or_tty->print_cr(" ASConcurrentMarkSweepGeneration::resize " | |
9358 "Shrinking tenured generation by " SIZE_FORMAT " (bytes)", | |
9359 shrink_bytes); | |
9360 } | |
9361 shrink(shrink_bytes); | |
9362 } | |
9363 } | |
9364 | |
9365 CMSGCAdaptivePolicyCounters* ASConcurrentMarkSweepGeneration::gc_adaptive_policy_counters() { | |
9366 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
9367 CMSGCAdaptivePolicyCounters* counters = | |
9368 (CMSGCAdaptivePolicyCounters*) gch->collector_policy()->counters(); | |
9369 assert(counters->kind() == GCPolicyCounters::CMSGCAdaptivePolicyCountersKind, | |
9370 "Wrong kind of counters"); | |
9371 return counters; | |
9372 } | |
9373 | |
9374 | |
9375 void ASConcurrentMarkSweepGeneration::update_counters() { | |
9376 if (UsePerfData) { | |
9377 _space_counters->update_all(); | |
9378 _gen_counters->update_all(); | |
9379 CMSGCAdaptivePolicyCounters* counters = gc_adaptive_policy_counters(); | |
9380 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
9381 CMSGCStats* gc_stats_l = (CMSGCStats*) gc_stats(); | |
9382 assert(gc_stats_l->kind() == GCStats::CMSGCStatsKind, | |
9383 "Wrong gc statistics type"); | |
9384 counters->update_counters(gc_stats_l); | |
9385 } | |
9386 } | |
9387 | |
9388 void ASConcurrentMarkSweepGeneration::update_counters(size_t used) { | |
9389 if (UsePerfData) { | |
9390 _space_counters->update_used(used); | |
9391 _space_counters->update_capacity(); | |
9392 _gen_counters->update_all(); | |
9393 | |
9394 CMSGCAdaptivePolicyCounters* counters = gc_adaptive_policy_counters(); | |
9395 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
9396 CMSGCStats* gc_stats_l = (CMSGCStats*) gc_stats(); | |
9397 assert(gc_stats_l->kind() == GCStats::CMSGCStatsKind, | |
9398 "Wrong gc statistics type"); | |
9399 counters->update_counters(gc_stats_l); | |
9400 } | |
9401 } | |
9402 | |
9403 void ASConcurrentMarkSweepGeneration::shrink_by(size_t desired_bytes) { | |
9404 assert_locked_or_safepoint(Heap_lock); | |
9405 assert_lock_strong(freelistLock()); | |
9406 HeapWord* old_end = _cmsSpace->end(); | |
9407 HeapWord* unallocated_start = _cmsSpace->unallocated_block(); | |
9408 assert(old_end >= unallocated_start, "Miscalculation of unallocated_start"); | |
9409 FreeChunk* chunk_at_end = find_chunk_at_end(); | |
9410 if (chunk_at_end == NULL) { | |
9411 // No room to shrink | |
9412 if (PrintGCDetails && Verbose) { | |
9413 gclog_or_tty->print_cr("No room to shrink: old_end " | |
9414 PTR_FORMAT " unallocated_start " PTR_FORMAT | |
9415 " chunk_at_end " PTR_FORMAT, | |
9416 old_end, unallocated_start, chunk_at_end); | |
9417 } | |
9418 return; | |
9419 } else { | |
9420 | |
9421 // Find the chunk at the end of the space and determine | |
9422 // how much it can be shrunk. | |
9423 size_t shrinkable_size_in_bytes = chunk_at_end->size(); | |
9424 size_t aligned_shrinkable_size_in_bytes = | |
9425 align_size_down(shrinkable_size_in_bytes, os::vm_page_size()); | |
6885 | 9426 assert(unallocated_start <= (HeapWord*) chunk_at_end->end(), |
0 | 9427 "Inconsistent chunk at end of space"); |
9428 size_t bytes = MIN2(desired_bytes, aligned_shrinkable_size_in_bytes); | |
9429 size_t word_size_before = heap_word_size(_virtual_space.committed_size()); | |
9430 | |
9431 // Shrink the underlying space | |
9432 _virtual_space.shrink_by(bytes); | |
9433 if (PrintGCDetails && Verbose) { | |
9434 gclog_or_tty->print_cr("ConcurrentMarkSweepGeneration::shrink_by:" | |
9435 " desired_bytes " SIZE_FORMAT | |
9436 " shrinkable_size_in_bytes " SIZE_FORMAT | |
9437 " aligned_shrinkable_size_in_bytes " SIZE_FORMAT | |
9438 " bytes " SIZE_FORMAT, | |
9439 desired_bytes, shrinkable_size_in_bytes, | |
9440 aligned_shrinkable_size_in_bytes, bytes); | |
9441 gclog_or_tty->print_cr(" old_end " SIZE_FORMAT | |
9442 " unallocated_start " SIZE_FORMAT, | |
9443 old_end, unallocated_start); | |
9444 } | |
9445 | |
9446 // If the space did shrink (shrinking is not guaranteed), | |
9447 // shrink the chunk at the end by the appropriate amount. | |
9448 if (((HeapWord*)_virtual_space.high()) < old_end) { | |
9449 size_t new_word_size = | |
9450 heap_word_size(_virtual_space.committed_size()); | |
9451 | |
9452 // Have to remove the chunk from the dictionary because it is changing | |
9453 // size and might be someplace elsewhere in the dictionary. | |
9454 | |
9455 // Get the chunk at end, shrink it, and put it | |
9456 // back. | |
9457 _cmsSpace->removeChunkFromDictionary(chunk_at_end); | |
9458 size_t word_size_change = word_size_before - new_word_size; | |
9459 size_t chunk_at_end_old_size = chunk_at_end->size(); | |
9460 assert(chunk_at_end_old_size >= word_size_change, | |
9461 "Shrink is too large"); | |
6028
f69a5d43dc19
7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
jmasa
parents:
6026
diff
changeset
|
9462 chunk_at_end->set_size(chunk_at_end_old_size - |
0 | 9463 word_size_change); |
9464 _cmsSpace->freed((HeapWord*) chunk_at_end->end(), | |
9465 word_size_change); | |
9466 | |
9467 _cmsSpace->returnChunkToDictionary(chunk_at_end); | |
9468 | |
9469 MemRegion mr(_cmsSpace->bottom(), new_word_size); | |
9470 _bts->resize(new_word_size); // resize the block offset shared array | |
9471 Universe::heap()->barrier_set()->resize_covered_region(mr); | |
9472 _cmsSpace->assert_locked(); | |
9473 _cmsSpace->set_end((HeapWord*)_virtual_space.high()); | |
9474 | |
9475 NOT_PRODUCT(_cmsSpace->dictionary()->verify()); | |
9476 | |
9477 // update the space and generation capacity counters | |
9478 if (UsePerfData) { | |
9479 _space_counters->update_capacity(); | |
9480 _gen_counters->update_all(); | |
9481 } | |
9482 | |
9483 if (Verbose && PrintGCDetails) { | |
9484 size_t new_mem_size = _virtual_space.committed_size(); | |
9485 size_t old_mem_size = new_mem_size + bytes; | |
7623
203f64878aab
7102489: RFE: cleanup jlong typedef on __APPLE__and _LLP64 systems.
hseigel
parents:
6885
diff
changeset
|
9486 gclog_or_tty->print_cr("Shrinking %s from " SIZE_FORMAT "K by " SIZE_FORMAT "K to " SIZE_FORMAT "K", |
0 | 9487 name(), old_mem_size/K, bytes/K, new_mem_size/K); |
9488 } | |
9489 } | |
9490 | |
9491 assert(_cmsSpace->unallocated_block() <= _cmsSpace->end(), | |
9492 "Inconsistency at end of space"); | |
6885 | 9493 assert(chunk_at_end->end() == (uintptr_t*) _cmsSpace->end(), |
0 | 9494 "Shrinking is inconsistent"); |
9495 return; | |
9496 } | |
9497 } | |
9498 // Transfer some number of overflown objects to usual marking | |
9499 // stack. Return true if some objects were transferred. | |
9500 bool MarkRefsIntoAndScanClosure::take_from_overflow_list() { | |
679
cea947c8a988
6819891: ParNew: Fix work queue overflow code to deal correctly with +UseCompressedOops
ysr
parents:
628
diff
changeset
|
9501 size_t num = MIN2((size_t)(_mark_stack->capacity() - _mark_stack->length())/4, |
0 | 9502 (size_t)ParGCDesiredObjsFromOverflowList); |
9503 | |
9504 bool res = _collector->take_from_overflow_list(num, _mark_stack); | |
9505 assert(_collector->overflow_list_is_empty() || res, | |
9506 "If list is not empty, we should have taken something"); | |
9507 assert(!res || !_mark_stack->isEmpty(), | |
9508 "If we took something, it should now be on our stack"); | |
9509 return res; | |
9510 } | |
9511 | |
9512 size_t MarkDeadObjectsClosure::do_blk(HeapWord* addr) { | |
9513 size_t res = _sp->block_size_no_stall(addr, _collector); | |
9514 if (_sp->block_is_obj(addr)) { | |
9515 if (_live_bit_map->isMarked(addr)) { | |
9516 // It can't have been dead in a previous cycle | |
9517 guarantee(!_dead_bit_map->isMarked(addr), "No resurrection!"); | |
9518 } else { | |
9519 _dead_bit_map->mark(addr); // mark the dead object | |
9520 } | |
9521 } | |
2226
c5a923563727
6912621: iCMS: Error: assert(_markBitMap.isMarked(addr + 1),"Missing Printezis bit?")
ysr
parents:
2177
diff
changeset
|
9522 // Could be 0, if the block size could not be computed without stalling. |
0 | 9523 return res; |
9524 } | |
1703
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9525 |
3356
78542e2b5e35
7036199: Adding a notification to the implementation of GarbageCollectorMXBeans
fparain
parents:
3293
diff
changeset
|
9526 TraceCMSMemoryManagerStats::TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause): TraceMemoryManagerStats() { |
1703
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9527 |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9528 switch (phase) { |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9529 case CMSCollector::InitialMarking: |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9530 initialize(true /* fullGC */ , |
3356
78542e2b5e35
7036199: Adding a notification to the implementation of GarbageCollectorMXBeans
fparain
parents:
3293
diff
changeset
|
9531 cause /* cause of the GC */, |
1703
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9532 true /* recordGCBeginTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9533 true /* recordPreGCUsage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9534 false /* recordPeakUsage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9535 false /* recordPostGCusage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9536 true /* recordAccumulatedGCTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9537 false /* recordGCEndTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9538 false /* countCollection */ ); |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9539 break; |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9540 |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9541 case CMSCollector::FinalMarking: |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9542 initialize(true /* fullGC */ , |
3356
78542e2b5e35
7036199: Adding a notification to the implementation of GarbageCollectorMXBeans
fparain
parents:
3293
diff
changeset
|
9543 cause /* cause of the GC */, |
1703
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9544 false /* recordGCBeginTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9545 false /* recordPreGCUsage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9546 false /* recordPeakUsage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9547 false /* recordPostGCusage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9548 true /* recordAccumulatedGCTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9549 false /* recordGCEndTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9550 false /* countCollection */ ); |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9551 break; |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9552 |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9553 case CMSCollector::Sweeping: |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9554 initialize(true /* fullGC */ , |
3356
78542e2b5e35
7036199: Adding a notification to the implementation of GarbageCollectorMXBeans
fparain
parents:
3293
diff
changeset
|
9555 cause /* cause of the GC */, |
1703
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9556 false /* recordGCBeginTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9557 false /* recordPreGCUsage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9558 true /* recordPeakUsage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9559 true /* recordPostGCusage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9560 false /* recordAccumulatedGCTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9561 true /* recordGCEndTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9562 true /* countCollection */ ); |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9563 break; |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9564 |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9565 default: |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9566 ShouldNotReachHere(); |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9567 } |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9568 } |