Mercurial > hg > truffle
annotate src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp @ 10372:e72f7eecc96d
8013895: G1: G1SummarizeRSetStats output on Linux needs improvemen
Summary: Fixed the output of G1SummarizeRSetStats: too small datatype for the number of concurrently processed cards, added concurrent remembered set thread time retrieval for Linux and Windows (BSD uses os::elapsedTime() now), and other cleanup. The information presented during VM operation is now relative to the previous output, not always cumulative if G1SummarizeRSetStatsPeriod > 0. At VM exit, the code prints a cumulative summary.
Reviewed-by: johnc, jwilhelm
author | tschatzl |
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date | Tue, 28 May 2013 09:32:06 +0200 |
parents | 7c5a1b62f53d |
children | f2110083203d |
rev | line source |
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0 | 1 /* |
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2 * Copyright (c) 2001, 2013, 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" | |
40 #include "gc_implementation/shared/isGCActiveMark.hpp" | |
41 #include "gc_interface/collectedHeap.inline.hpp" | |
42 #include "memory/cardTableRS.hpp" | |
43 #include "memory/collectorPolicy.hpp" | |
44 #include "memory/gcLocker.inline.hpp" | |
45 #include "memory/genCollectedHeap.hpp" | |
46 #include "memory/genMarkSweep.hpp" | |
47 #include "memory/genOopClosures.inline.hpp" | |
48 #include "memory/iterator.hpp" | |
49 #include "memory/referencePolicy.hpp" | |
50 #include "memory/resourceArea.hpp" | |
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51 #include "memory/tenuredGeneration.hpp" |
1972 | 52 #include "oops/oop.inline.hpp" |
53 #include "prims/jvmtiExport.hpp" | |
54 #include "runtime/globals_extension.hpp" | |
55 #include "runtime/handles.inline.hpp" | |
56 #include "runtime/java.hpp" | |
57 #include "runtime/vmThread.hpp" | |
58 #include "services/memoryService.hpp" | |
59 #include "services/runtimeService.hpp" | |
0 | 60 |
61 // statics | |
62 CMSCollector* ConcurrentMarkSweepGeneration::_collector = NULL; | |
63 bool CMSCollector::_full_gc_requested = false; | |
64 | |
65 ////////////////////////////////////////////////////////////////// | |
66 // In support of CMS/VM thread synchronization | |
67 ////////////////////////////////////////////////////////////////// | |
68 // We split use of the CGC_lock into 2 "levels". | |
69 // The low-level locking is of the usual CGC_lock monitor. We introduce | |
70 // a higher level "token" (hereafter "CMS token") built on top of the | |
71 // low level monitor (hereafter "CGC lock"). | |
72 // The token-passing protocol gives priority to the VM thread. The | |
73 // CMS-lock doesn't provide any fairness guarantees, but clients | |
74 // should ensure that it is only held for very short, bounded | |
75 // durations. | |
76 // | |
77 // When either of the CMS thread or the VM thread is involved in | |
78 // collection operations during which it does not want the other | |
79 // thread to interfere, it obtains the CMS token. | |
80 // | |
81 // If either thread tries to get the token while the other has | |
82 // it, that thread waits. However, if the VM thread and CMS thread | |
83 // both want the token, then the VM thread gets priority while the | |
84 // CMS thread waits. This ensures, for instance, that the "concurrent" | |
85 // phases of the CMS thread's work do not block out the VM thread | |
86 // for long periods of time as the CMS thread continues to hog | |
87 // the token. (See bug 4616232). | |
88 // | |
89 // The baton-passing functions are, however, controlled by the | |
90 // flags _foregroundGCShouldWait and _foregroundGCIsActive, | |
91 // and here the low-level CMS lock, not the high level token, | |
92 // ensures mutual exclusion. | |
93 // | |
94 // Two important conditions that we have to satisfy: | |
95 // 1. if a thread does a low-level wait on the CMS lock, then it | |
96 // relinquishes the CMS token if it were holding that token | |
97 // when it acquired the low-level CMS lock. | |
98 // 2. any low-level notifications on the low-level lock | |
99 // should only be sent when a thread has relinquished the token. | |
100 // | |
101 // In the absence of either property, we'd have potential deadlock. | |
102 // | |
103 // We protect each of the CMS (concurrent and sequential) phases | |
104 // with the CMS _token_, not the CMS _lock_. | |
105 // | |
106 // The only code protected by CMS lock is the token acquisition code | |
107 // itself, see ConcurrentMarkSweepThread::[de]synchronize(), and the | |
108 // baton-passing code. | |
109 // | |
110 // Unfortunately, i couldn't come up with a good abstraction to factor and | |
111 // hide the naked CGC_lock manipulation in the baton-passing code | |
112 // further below. That's something we should try to do. Also, the proof | |
113 // of correctness of this 2-level locking scheme is far from obvious, | |
114 // and potentially quite slippery. We have an uneasy supsicion, for instance, | |
115 // that there may be a theoretical possibility of delay/starvation in the | |
116 // low-level lock/wait/notify scheme used for the baton-passing because of | |
117 // potential intereference with the priority scheme embodied in the | |
118 // CMS-token-passing protocol. See related comments at a CGC_lock->wait() | |
119 // invocation further below and marked with "XXX 20011219YSR". | |
120 // Indeed, as we note elsewhere, this may become yet more slippery | |
121 // in the presence of multiple CMS and/or multiple VM threads. XXX | |
122 | |
123 class CMSTokenSync: public StackObj { | |
124 private: | |
125 bool _is_cms_thread; | |
126 public: | |
127 CMSTokenSync(bool is_cms_thread): | |
128 _is_cms_thread(is_cms_thread) { | |
129 assert(is_cms_thread == Thread::current()->is_ConcurrentGC_thread(), | |
130 "Incorrect argument to constructor"); | |
131 ConcurrentMarkSweepThread::synchronize(_is_cms_thread); | |
132 } | |
133 | |
134 ~CMSTokenSync() { | |
135 assert(_is_cms_thread ? | |
136 ConcurrentMarkSweepThread::cms_thread_has_cms_token() : | |
137 ConcurrentMarkSweepThread::vm_thread_has_cms_token(), | |
138 "Incorrect state"); | |
139 ConcurrentMarkSweepThread::desynchronize(_is_cms_thread); | |
140 } | |
141 }; | |
142 | |
143 // Convenience class that does a CMSTokenSync, and then acquires | |
144 // upto three locks. | |
145 class CMSTokenSyncWithLocks: public CMSTokenSync { | |
146 private: | |
147 // Note: locks are acquired in textual declaration order | |
148 // and released in the opposite order | |
149 MutexLockerEx _locker1, _locker2, _locker3; | |
150 public: | |
151 CMSTokenSyncWithLocks(bool is_cms_thread, Mutex* mutex1, | |
152 Mutex* mutex2 = NULL, Mutex* mutex3 = NULL): | |
153 CMSTokenSync(is_cms_thread), | |
154 _locker1(mutex1, Mutex::_no_safepoint_check_flag), | |
155 _locker2(mutex2, Mutex::_no_safepoint_check_flag), | |
156 _locker3(mutex3, Mutex::_no_safepoint_check_flag) | |
157 { } | |
158 }; | |
159 | |
160 | |
161 // Wrapper class to temporarily disable icms during a foreground cms collection. | |
162 class ICMSDisabler: public StackObj { | |
163 public: | |
164 // The ctor disables icms and wakes up the thread so it notices the change; | |
165 // the dtor re-enables icms. Note that the CMSCollector methods will check | |
166 // CMSIncrementalMode. | |
167 ICMSDisabler() { CMSCollector::disable_icms(); CMSCollector::start_icms(); } | |
168 ~ICMSDisabler() { CMSCollector::enable_icms(); } | |
169 }; | |
170 | |
171 ////////////////////////////////////////////////////////////////// | |
172 // Concurrent Mark-Sweep Generation ///////////////////////////// | |
173 ////////////////////////////////////////////////////////////////// | |
174 | |
175 NOT_PRODUCT(CompactibleFreeListSpace* debug_cms_space;) | |
176 | |
177 // This struct contains per-thread things necessary to support parallel | |
178 // young-gen collection. | |
6197 | 179 class CMSParGCThreadState: public CHeapObj<mtGC> { |
0 | 180 public: |
181 CFLS_LAB lab; | |
182 PromotionInfo promo; | |
183 | |
184 // Constructor. | |
185 CMSParGCThreadState(CompactibleFreeListSpace* cfls) : lab(cfls) { | |
186 promo.setSpace(cfls); | |
187 } | |
188 }; | |
189 | |
190 ConcurrentMarkSweepGeneration::ConcurrentMarkSweepGeneration( | |
191 ReservedSpace rs, size_t initial_byte_size, int level, | |
192 CardTableRS* ct, bool use_adaptive_freelists, | |
6026 | 193 FreeBlockDictionary<FreeChunk>::DictionaryChoice dictionaryChoice) : |
0 | 194 CardGeneration(rs, initial_byte_size, level, ct), |
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195 _dilatation_factor(((double)MinChunkSize)/((double)(CollectedHeap::min_fill_size()))), |
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196 _debug_collection_type(Concurrent_collection_type), |
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197 _did_compact(false) |
0 | 198 { |
199 HeapWord* bottom = (HeapWord*) _virtual_space.low(); | |
200 HeapWord* end = (HeapWord*) _virtual_space.high(); | |
201 | |
202 _direct_allocated_words = 0; | |
203 NOT_PRODUCT( | |
204 _numObjectsPromoted = 0; | |
205 _numWordsPromoted = 0; | |
206 _numObjectsAllocated = 0; | |
207 _numWordsAllocated = 0; | |
208 ) | |
209 | |
210 _cmsSpace = new CompactibleFreeListSpace(_bts, MemRegion(bottom, end), | |
211 use_adaptive_freelists, | |
212 dictionaryChoice); | |
213 NOT_PRODUCT(debug_cms_space = _cmsSpace;) | |
214 if (_cmsSpace == NULL) { | |
215 vm_exit_during_initialization( | |
216 "CompactibleFreeListSpace allocation failure"); | |
217 } | |
218 _cmsSpace->_gen = this; | |
219 | |
220 _gc_stats = new CMSGCStats(); | |
221 | |
222 // Verify the assumption that FreeChunk::_prev and OopDesc::_klass | |
223 // offsets match. The ability to tell free chunks from objects | |
224 // depends on this property. | |
225 debug_only( | |
226 FreeChunk* junk = NULL; | |
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227 assert(UseCompressedKlassPointers || |
187 | 228 junk->prev_addr() == (void*)(oop(junk)->klass_addr()), |
0 | 229 "Offset of FreeChunk::_prev within FreeChunk must match" |
230 " that of OopDesc::_klass within OopDesc"); | |
231 ) | |
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232 if (CollectedHeap::use_parallel_gc_threads()) { |
0 | 233 typedef CMSParGCThreadState* CMSParGCThreadStatePtr; |
234 _par_gc_thread_states = | |
6197 | 235 NEW_C_HEAP_ARRAY(CMSParGCThreadStatePtr, ParallelGCThreads, mtGC); |
0 | 236 if (_par_gc_thread_states == NULL) { |
237 vm_exit_during_initialization("Could not allocate par gc structs"); | |
238 } | |
239 for (uint i = 0; i < ParallelGCThreads; i++) { | |
240 _par_gc_thread_states[i] = new CMSParGCThreadState(cmsSpace()); | |
241 if (_par_gc_thread_states[i] == NULL) { | |
242 vm_exit_during_initialization("Could not allocate par gc structs"); | |
243 } | |
244 } | |
245 } else { | |
246 _par_gc_thread_states = NULL; | |
247 } | |
248 _incremental_collection_failed = false; | |
249 // The "dilatation_factor" is the expansion that can occur on | |
250 // account of the fact that the minimum object size in the CMS | |
251 // generation may be larger than that in, say, a contiguous young | |
252 // generation. | |
253 // Ideally, in the calculation below, we'd compute the dilatation | |
254 // factor as: MinChunkSize/(promoting_gen's min object size) | |
255 // Since we do not have such a general query interface for the | |
256 // promoting generation, we'll instead just use the mimimum | |
257 // object size (which today is a header's worth of space); | |
258 // note that all arithmetic is in units of HeapWords. | |
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259 assert(MinChunkSize >= CollectedHeap::min_fill_size(), "just checking"); |
0 | 260 assert(_dilatation_factor >= 1.0, "from previous assert"); |
261 } | |
262 | |
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263 |
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264 // The field "_initiating_occupancy" represents the occupancy percentage |
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265 // at which we trigger a new collection cycle. Unless explicitly specified |
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266 // via CMSInitiatingOccupancyFraction (argument "io" below), it |
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267 // is calculated by: |
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268 // |
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269 // Let "f" be MinHeapFreeRatio in |
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270 // |
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271 // _intiating_occupancy = 100-f + |
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272 // f * (CMSTriggerRatio/100) |
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273 // where CMSTriggerRatio is the argument "tr" below. |
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274 // |
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275 // That is, if we assume the heap is at its desired maximum occupancy at the |
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276 // end of a collection, we let CMSTriggerRatio of the (purported) free |
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277 // space be allocated before initiating a new collection cycle. |
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278 // |
8035 | 279 void ConcurrentMarkSweepGeneration::init_initiating_occupancy(intx io, uintx tr) { |
280 assert(io <= 100 && tr <= 100, "Check the arguments"); | |
94
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281 if (io >= 0) { |
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282 _initiating_occupancy = (double)io / 100.0; |
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283 } else { |
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284 _initiating_occupancy = ((100 - MinHeapFreeRatio) + |
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285 (double)(tr * MinHeapFreeRatio) / 100.0) |
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286 / 100.0; |
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287 } |
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288 } |
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289 |
0 | 290 void ConcurrentMarkSweepGeneration::ref_processor_init() { |
291 assert(collector() != NULL, "no collector"); | |
292 collector()->ref_processor_init(); | |
293 } | |
294 | |
295 void CMSCollector::ref_processor_init() { | |
296 if (_ref_processor == NULL) { | |
297 // Allocate and initialize a reference processor | |
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298 _ref_processor = |
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299 new ReferenceProcessor(_span, // span |
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300 (ParallelGCThreads > 1) && ParallelRefProcEnabled, // mt processing |
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301 (int) ParallelGCThreads, // mt processing degree |
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302 _cmsGen->refs_discovery_is_mt(), // mt discovery |
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303 (int) MAX2(ConcGCThreads, ParallelGCThreads), // mt discovery degree |
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304 _cmsGen->refs_discovery_is_atomic(), // discovery is not atomic |
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305 &_is_alive_closure, // closure for liveness info |
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306 false); // next field updates do not need write barrier |
0 | 307 // Initialize the _ref_processor field of CMSGen |
308 _cmsGen->set_ref_processor(_ref_processor); | |
309 | |
310 } | |
311 } | |
312 | |
313 CMSAdaptiveSizePolicy* CMSCollector::size_policy() { | |
314 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
315 assert(gch->kind() == CollectedHeap::GenCollectedHeap, | |
316 "Wrong type of heap"); | |
317 CMSAdaptiveSizePolicy* sp = (CMSAdaptiveSizePolicy*) | |
318 gch->gen_policy()->size_policy(); | |
319 assert(sp->is_gc_cms_adaptive_size_policy(), | |
320 "Wrong type of size policy"); | |
321 return sp; | |
322 } | |
323 | |
324 CMSGCAdaptivePolicyCounters* CMSCollector::gc_adaptive_policy_counters() { | |
325 CMSGCAdaptivePolicyCounters* results = | |
326 (CMSGCAdaptivePolicyCounters*) collector_policy()->counters(); | |
327 assert( | |
328 results->kind() == GCPolicyCounters::CMSGCAdaptivePolicyCountersKind, | |
329 "Wrong gc policy counter kind"); | |
330 return results; | |
331 } | |
332 | |
333 | |
334 void ConcurrentMarkSweepGeneration::initialize_performance_counters() { | |
335 | |
336 const char* gen_name = "old"; | |
337 | |
338 // Generation Counters - generation 1, 1 subspace | |
339 _gen_counters = new GenerationCounters(gen_name, 1, 1, &_virtual_space); | |
340 | |
341 _space_counters = new GSpaceCounters(gen_name, 0, | |
342 _virtual_space.reserved_size(), | |
343 this, _gen_counters); | |
344 } | |
345 | |
346 CMSStats::CMSStats(ConcurrentMarkSweepGeneration* cms_gen, unsigned int alpha): | |
347 _cms_gen(cms_gen) | |
348 { | |
349 assert(alpha <= 100, "bad value"); | |
350 _saved_alpha = alpha; | |
351 | |
352 // Initialize the alphas to the bootstrap value of 100. | |
353 _gc0_alpha = _cms_alpha = 100; | |
354 | |
355 _cms_begin_time.update(); | |
356 _cms_end_time.update(); | |
357 | |
358 _gc0_duration = 0.0; | |
359 _gc0_period = 0.0; | |
360 _gc0_promoted = 0; | |
361 | |
362 _cms_duration = 0.0; | |
363 _cms_period = 0.0; | |
364 _cms_allocated = 0; | |
365 | |
366 _cms_used_at_gc0_begin = 0; | |
367 _cms_used_at_gc0_end = 0; | |
368 _allow_duty_cycle_reduction = false; | |
369 _valid_bits = 0; | |
370 _icms_duty_cycle = CMSIncrementalDutyCycle; | |
371 } | |
372 | |
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373 double CMSStats::cms_free_adjustment_factor(size_t free) const { |
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374 // TBD: CR 6909490 |
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375 return 1.0; |
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376 } |
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377 |
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378 void CMSStats::adjust_cms_free_adjustment_factor(bool fail, size_t free) { |
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379 } |
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380 |
0 | 381 // If promotion failure handling is on use |
382 // the padded average size of the promotion for each | |
383 // young generation collection. | |
384 double CMSStats::time_until_cms_gen_full() const { | |
385 size_t cms_free = _cms_gen->cmsSpace()->free(); | |
386 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
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387 size_t expected_promotion = MIN2(gch->get_gen(0)->capacity(), |
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388 (size_t) _cms_gen->gc_stats()->avg_promoted()->padded_average()); |
0 | 389 if (cms_free > expected_promotion) { |
390 // Start a cms collection if there isn't enough space to promote | |
391 // for the next minor collection. Use the padded average as | |
392 // a safety factor. | |
393 cms_free -= expected_promotion; | |
394 | |
395 // Adjust by the safety factor. | |
396 double cms_free_dbl = (double)cms_free; | |
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397 double cms_adjustment = (100.0 - CMSIncrementalSafetyFactor)/100.0; |
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398 // Apply a further correction factor which tries to adjust |
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399 // for recent occurance of concurrent mode failures. |
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400 cms_adjustment = cms_adjustment * cms_free_adjustment_factor(cms_free); |
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401 cms_free_dbl = cms_free_dbl * cms_adjustment; |
0 | 402 |
403 if (PrintGCDetails && Verbose) { | |
404 gclog_or_tty->print_cr("CMSStats::time_until_cms_gen_full: cms_free " | |
405 SIZE_FORMAT " expected_promotion " SIZE_FORMAT, | |
406 cms_free, expected_promotion); | |
407 gclog_or_tty->print_cr(" cms_free_dbl %f cms_consumption_rate %f", | |
408 cms_free_dbl, cms_consumption_rate() + 1.0); | |
409 } | |
410 // Add 1 in case the consumption rate goes to zero. | |
411 return cms_free_dbl / (cms_consumption_rate() + 1.0); | |
412 } | |
413 return 0.0; | |
414 } | |
415 | |
416 // Compare the duration of the cms collection to the | |
417 // time remaining before the cms generation is empty. | |
418 // Note that the time from the start of the cms collection | |
419 // to the start of the cms sweep (less than the total | |
420 // duration of the cms collection) can be used. This | |
421 // has been tried and some applications experienced | |
422 // promotion failures early in execution. This was | |
423 // possibly because the averages were not accurate | |
424 // enough at the beginning. | |
425 double CMSStats::time_until_cms_start() const { | |
426 // We add "gc0_period" to the "work" calculation | |
427 // below because this query is done (mostly) at the | |
428 // end of a scavenge, so we need to conservatively | |
429 // account for that much possible delay | |
430 // in the query so as to avoid concurrent mode failures | |
431 // due to starting the collection just a wee bit too | |
432 // late. | |
433 double work = cms_duration() + gc0_period(); | |
434 double deadline = time_until_cms_gen_full(); | |
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435 // If a concurrent mode failure occurred recently, we want to be |
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436 // more conservative and halve our expected time_until_cms_gen_full() |
0 | 437 if (work > deadline) { |
438 if (Verbose && PrintGCDetails) { | |
439 gclog_or_tty->print( | |
440 " CMSCollector: collect because of anticipated promotion " | |
441 "before full %3.7f + %3.7f > %3.7f ", cms_duration(), | |
442 gc0_period(), time_until_cms_gen_full()); | |
443 } | |
444 return 0.0; | |
445 } | |
446 return work - deadline; | |
447 } | |
448 | |
449 // Return a duty cycle based on old_duty_cycle and new_duty_cycle, limiting the | |
450 // amount of change to prevent wild oscillation. | |
451 unsigned int CMSStats::icms_damped_duty_cycle(unsigned int old_duty_cycle, | |
452 unsigned int new_duty_cycle) { | |
453 assert(old_duty_cycle <= 100, "bad input value"); | |
454 assert(new_duty_cycle <= 100, "bad input value"); | |
455 | |
456 // Note: use subtraction with caution since it may underflow (values are | |
457 // unsigned). Addition is safe since we're in the range 0-100. | |
458 unsigned int damped_duty_cycle = new_duty_cycle; | |
459 if (new_duty_cycle < old_duty_cycle) { | |
460 const unsigned int largest_delta = MAX2(old_duty_cycle / 4, 5U); | |
461 if (new_duty_cycle + largest_delta < old_duty_cycle) { | |
462 damped_duty_cycle = old_duty_cycle - largest_delta; | |
463 } | |
464 } else if (new_duty_cycle > old_duty_cycle) { | |
465 const unsigned int largest_delta = MAX2(old_duty_cycle / 4, 15U); | |
466 if (new_duty_cycle > old_duty_cycle + largest_delta) { | |
467 damped_duty_cycle = MIN2(old_duty_cycle + largest_delta, 100U); | |
468 } | |
469 } | |
470 assert(damped_duty_cycle <= 100, "invalid duty cycle computed"); | |
471 | |
472 if (CMSTraceIncrementalPacing) { | |
473 gclog_or_tty->print(" [icms_damped_duty_cycle(%d,%d) = %d] ", | |
474 old_duty_cycle, new_duty_cycle, damped_duty_cycle); | |
475 } | |
476 return damped_duty_cycle; | |
477 } | |
478 | |
479 unsigned int CMSStats::icms_update_duty_cycle_impl() { | |
480 assert(CMSIncrementalPacing && valid(), | |
481 "should be handled in icms_update_duty_cycle()"); | |
482 | |
483 double cms_time_so_far = cms_timer().seconds(); | |
484 double scaled_duration = cms_duration_per_mb() * _cms_used_at_gc0_end / M; | |
485 double scaled_duration_remaining = fabsd(scaled_duration - cms_time_so_far); | |
486 | |
487 // Avoid division by 0. | |
488 double time_until_full = MAX2(time_until_cms_gen_full(), 0.01); | |
489 double duty_cycle_dbl = 100.0 * scaled_duration_remaining / time_until_full; | |
490 | |
491 unsigned int new_duty_cycle = MIN2((unsigned int)duty_cycle_dbl, 100U); | |
492 if (new_duty_cycle > _icms_duty_cycle) { | |
493 // Avoid very small duty cycles (1 or 2); 0 is allowed. | |
494 if (new_duty_cycle > 2) { | |
495 _icms_duty_cycle = icms_damped_duty_cycle(_icms_duty_cycle, | |
496 new_duty_cycle); | |
497 } | |
498 } else if (_allow_duty_cycle_reduction) { | |
499 // The duty cycle is reduced only once per cms cycle (see record_cms_end()). | |
500 new_duty_cycle = icms_damped_duty_cycle(_icms_duty_cycle, new_duty_cycle); | |
501 // Respect the minimum duty cycle. | |
502 unsigned int min_duty_cycle = (unsigned int)CMSIncrementalDutyCycleMin; | |
503 _icms_duty_cycle = MAX2(new_duty_cycle, min_duty_cycle); | |
504 } | |
505 | |
506 if (PrintGCDetails || CMSTraceIncrementalPacing) { | |
507 gclog_or_tty->print(" icms_dc=%d ", _icms_duty_cycle); | |
508 } | |
509 | |
510 _allow_duty_cycle_reduction = false; | |
511 return _icms_duty_cycle; | |
512 } | |
513 | |
514 #ifndef PRODUCT | |
515 void CMSStats::print_on(outputStream *st) const { | |
516 st->print(" gc0_alpha=%d,cms_alpha=%d", _gc0_alpha, _cms_alpha); | |
517 st->print(",gc0_dur=%g,gc0_per=%g,gc0_promo=" SIZE_FORMAT, | |
518 gc0_duration(), gc0_period(), gc0_promoted()); | |
519 st->print(",cms_dur=%g,cms_dur_per_mb=%g,cms_per=%g,cms_alloc=" SIZE_FORMAT, | |
520 cms_duration(), cms_duration_per_mb(), | |
521 cms_period(), cms_allocated()); | |
522 st->print(",cms_since_beg=%g,cms_since_end=%g", | |
523 cms_time_since_begin(), cms_time_since_end()); | |
524 st->print(",cms_used_beg=" SIZE_FORMAT ",cms_used_end=" SIZE_FORMAT, | |
525 _cms_used_at_gc0_begin, _cms_used_at_gc0_end); | |
526 if (CMSIncrementalMode) { | |
527 st->print(",dc=%d", icms_duty_cycle()); | |
528 } | |
529 | |
530 if (valid()) { | |
531 st->print(",promo_rate=%g,cms_alloc_rate=%g", | |
532 promotion_rate(), cms_allocation_rate()); | |
533 st->print(",cms_consumption_rate=%g,time_until_full=%g", | |
534 cms_consumption_rate(), time_until_cms_gen_full()); | |
535 } | |
536 st->print(" "); | |
537 } | |
538 #endif // #ifndef PRODUCT | |
539 | |
540 CMSCollector::CollectorState CMSCollector::_collectorState = | |
541 CMSCollector::Idling; | |
542 bool CMSCollector::_foregroundGCIsActive = false; | |
543 bool CMSCollector::_foregroundGCShouldWait = false; | |
544 | |
545 CMSCollector::CMSCollector(ConcurrentMarkSweepGeneration* cmsGen, | |
546 CardTableRS* ct, | |
547 ConcurrentMarkSweepPolicy* cp): | |
548 _cmsGen(cmsGen), | |
549 _ct(ct), | |
550 _ref_processor(NULL), // will be set later | |
551 _conc_workers(NULL), // may be set later | |
552 _abort_preclean(false), | |
553 _start_sampling(false), | |
554 _between_prologue_and_epilogue(false), | |
555 _markBitMap(0, Mutex::leaf + 1, "CMS_markBitMap_lock"), | |
556 _modUnionTable((CardTableModRefBS::card_shift - LogHeapWordSize), | |
557 -1 /* lock-free */, "No_lock" /* dummy */), | |
558 _modUnionClosure(&_modUnionTable), | |
559 _modUnionClosurePar(&_modUnionTable), | |
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560 // Adjust my span to cover old (cms) gen |
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561 _span(cmsGen->reserved()), |
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562 // Construct the is_alive_closure with _span & markBitMap |
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563 _is_alive_closure(_span, &_markBitMap), |
0 | 564 _restart_addr(NULL), |
565 _overflow_list(NULL), | |
566 _stats(cmsGen), | |
567 _eden_chunk_array(NULL), // may be set in ctor body | |
568 _eden_chunk_capacity(0), // -- ditto -- | |
569 _eden_chunk_index(0), // -- ditto -- | |
570 _survivor_plab_array(NULL), // -- ditto -- | |
571 _survivor_chunk_array(NULL), // -- ditto -- | |
572 _survivor_chunk_capacity(0), // -- ditto -- | |
573 _survivor_chunk_index(0), // -- ditto -- | |
574 _ser_pmc_preclean_ovflw(0), | |
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575 _ser_kac_preclean_ovflw(0), |
0 | 576 _ser_pmc_remark_ovflw(0), |
577 _par_pmc_remark_ovflw(0), | |
578 _ser_kac_ovflw(0), | |
579 _par_kac_ovflw(0), | |
580 #ifndef PRODUCT | |
581 _num_par_pushes(0), | |
582 #endif | |
583 _collection_count_start(0), | |
584 _verifying(false), | |
585 _icms_start_limit(NULL), | |
586 _icms_stop_limit(NULL), | |
587 _verification_mark_bm(0, Mutex::leaf + 1, "CMS_verification_mark_bm_lock"), | |
588 _completed_initialization(false), | |
589 _collector_policy(cp), | |
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590 _should_unload_classes(false), |
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591 _concurrent_cycles_since_last_unload(0), |
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592 _roots_scanning_options(0), |
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593 _inter_sweep_estimate(CMS_SweepWeight, CMS_SweepPadding), |
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594 _intra_sweep_estimate(CMS_SweepWeight, CMS_SweepPadding) |
0 | 595 { |
596 if (ExplicitGCInvokesConcurrentAndUnloadsClasses) { | |
597 ExplicitGCInvokesConcurrent = true; | |
598 } | |
599 // Now expand the span and allocate the collection support structures | |
600 // (MUT, marking bit map etc.) to cover both generations subject to | |
601 // collection. | |
602 | |
603 // For use by dirty card to oop closures. | |
604 _cmsGen->cmsSpace()->set_collector(this); | |
605 | |
606 // Allocate MUT and marking bit map | |
607 { | |
608 MutexLockerEx x(_markBitMap.lock(), Mutex::_no_safepoint_check_flag); | |
609 if (!_markBitMap.allocate(_span)) { | |
610 warning("Failed to allocate CMS Bit Map"); | |
611 return; | |
612 } | |
613 assert(_markBitMap.covers(_span), "_markBitMap inconsistency?"); | |
614 } | |
615 { | |
616 _modUnionTable.allocate(_span); | |
617 assert(_modUnionTable.covers(_span), "_modUnionTable inconsistency?"); | |
618 } | |
619 | |
1284 | 620 if (!_markStack.allocate(MarkStackSize)) { |
0 | 621 warning("Failed to allocate CMS Marking Stack"); |
622 return; | |
623 } | |
624 | |
625 // Support for multi-threaded concurrent phases | |
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626 if (CMSConcurrentMTEnabled) { |
1284 | 627 if (FLAG_IS_DEFAULT(ConcGCThreads)) { |
0 | 628 // just for now |
1284 | 629 FLAG_SET_DEFAULT(ConcGCThreads, (ParallelGCThreads + 3)/4); |
630 } | |
631 if (ConcGCThreads > 1) { | |
0 | 632 _conc_workers = new YieldingFlexibleWorkGang("Parallel CMS Threads", |
1284 | 633 ConcGCThreads, true); |
0 | 634 if (_conc_workers == NULL) { |
635 warning("GC/CMS: _conc_workers allocation failure: " | |
636 "forcing -CMSConcurrentMTEnabled"); | |
637 CMSConcurrentMTEnabled = false; | |
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638 } else { |
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639 _conc_workers->initialize_workers(); |
0 | 640 } |
641 } else { | |
642 CMSConcurrentMTEnabled = false; | |
643 } | |
644 } | |
645 if (!CMSConcurrentMTEnabled) { | |
1284 | 646 ConcGCThreads = 0; |
0 | 647 } else { |
648 // Turn off CMSCleanOnEnter optimization temporarily for | |
649 // the MT case where it's not fixed yet; see 6178663. | |
650 CMSCleanOnEnter = false; | |
651 } | |
1284 | 652 assert((_conc_workers != NULL) == (ConcGCThreads > 1), |
0 | 653 "Inconsistency"); |
654 | |
655 // Parallel task queues; these are shared for the | |
656 // concurrent and stop-world phases of CMS, but | |
657 // are not shared with parallel scavenge (ParNew). | |
658 { | |
659 uint i; | |
1284 | 660 uint num_queues = (uint) MAX2(ParallelGCThreads, ConcGCThreads); |
0 | 661 |
662 if ((CMSParallelRemarkEnabled || CMSConcurrentMTEnabled | |
663 || ParallelRefProcEnabled) | |
664 && num_queues > 0) { | |
665 _task_queues = new OopTaskQueueSet(num_queues); | |
666 if (_task_queues == NULL) { | |
667 warning("task_queues allocation failure."); | |
668 return; | |
669 } | |
6197 | 670 _hash_seed = NEW_C_HEAP_ARRAY(int, num_queues, mtGC); |
0 | 671 if (_hash_seed == NULL) { |
672 warning("_hash_seed array allocation failure"); | |
673 return; | |
674 } | |
675 | |
1665 | 676 typedef Padded<OopTaskQueue> PaddedOopTaskQueue; |
0 | 677 for (i = 0; i < num_queues; i++) { |
1665 | 678 PaddedOopTaskQueue *q = new PaddedOopTaskQueue(); |
679 if (q == NULL) { | |
0 | 680 warning("work_queue allocation failure."); |
681 return; | |
682 } | |
1665 | 683 _task_queues->register_queue(i, q); |
0 | 684 } |
685 for (i = 0; i < num_queues; i++) { | |
686 _task_queues->queue(i)->initialize(); | |
687 _hash_seed[i] = 17; // copied from ParNew | |
688 } | |
689 } | |
690 } | |
691 | |
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692 _cmsGen ->init_initiating_occupancy(CMSInitiatingOccupancyFraction, CMSTriggerRatio); |
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693 |
0 | 694 // Clip CMSBootstrapOccupancy between 0 and 100. |
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695 _bootstrap_occupancy = ((double)CMSBootstrapOccupancy)/(double)100; |
0 | 696 |
697 _full_gcs_since_conc_gc = 0; | |
698 | |
699 // Now tell CMS generations the identity of their collector | |
700 ConcurrentMarkSweepGeneration::set_collector(this); | |
701 | |
702 // Create & start a CMS thread for this CMS collector | |
703 _cmsThread = ConcurrentMarkSweepThread::start(this); | |
704 assert(cmsThread() != NULL, "CMS Thread should have been created"); | |
705 assert(cmsThread()->collector() == this, | |
706 "CMS Thread should refer to this gen"); | |
707 assert(CGC_lock != NULL, "Where's the CGC_lock?"); | |
708 | |
709 // Support for parallelizing young gen rescan | |
710 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
711 _young_gen = gch->prev_gen(_cmsGen); | |
712 if (gch->supports_inline_contig_alloc()) { | |
713 _top_addr = gch->top_addr(); | |
714 _end_addr = gch->end_addr(); | |
715 assert(_young_gen != NULL, "no _young_gen"); | |
716 _eden_chunk_index = 0; | |
717 _eden_chunk_capacity = (_young_gen->max_capacity()+CMSSamplingGrain)/CMSSamplingGrain; | |
6197 | 718 _eden_chunk_array = NEW_C_HEAP_ARRAY(HeapWord*, _eden_chunk_capacity, mtGC); |
0 | 719 if (_eden_chunk_array == NULL) { |
720 _eden_chunk_capacity = 0; | |
721 warning("GC/CMS: _eden_chunk_array allocation failure"); | |
722 } | |
723 } | |
724 assert(_eden_chunk_array != NULL || _eden_chunk_capacity == 0, "Error"); | |
725 | |
726 // Support for parallelizing survivor space rescan | |
727 if (CMSParallelRemarkEnabled && CMSParallelSurvivorRemarkEnabled) { | |
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728 const size_t max_plab_samples = |
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729 ((DefNewGeneration*)_young_gen)->max_survivor_size()/MinTLABSize; |
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730 |
6197 | 731 _survivor_plab_array = NEW_C_HEAP_ARRAY(ChunkArray, ParallelGCThreads, mtGC); |
732 _survivor_chunk_array = NEW_C_HEAP_ARRAY(HeapWord*, 2*max_plab_samples, mtGC); | |
733 _cursor = NEW_C_HEAP_ARRAY(size_t, ParallelGCThreads, mtGC); | |
0 | 734 if (_survivor_plab_array == NULL || _survivor_chunk_array == NULL |
735 || _cursor == NULL) { | |
736 warning("Failed to allocate survivor plab/chunk array"); | |
737 if (_survivor_plab_array != NULL) { | |
6197 | 738 FREE_C_HEAP_ARRAY(ChunkArray, _survivor_plab_array, mtGC); |
0 | 739 _survivor_plab_array = NULL; |
740 } | |
741 if (_survivor_chunk_array != NULL) { | |
6197 | 742 FREE_C_HEAP_ARRAY(HeapWord*, _survivor_chunk_array, mtGC); |
0 | 743 _survivor_chunk_array = NULL; |
744 } | |
745 if (_cursor != NULL) { | |
6197 | 746 FREE_C_HEAP_ARRAY(size_t, _cursor, mtGC); |
0 | 747 _cursor = NULL; |
748 } | |
749 } else { | |
750 _survivor_chunk_capacity = 2*max_plab_samples; | |
751 for (uint i = 0; i < ParallelGCThreads; i++) { | |
6197 | 752 HeapWord** vec = NEW_C_HEAP_ARRAY(HeapWord*, max_plab_samples, mtGC); |
0 | 753 if (vec == NULL) { |
754 warning("Failed to allocate survivor plab array"); | |
755 for (int j = i; j > 0; j--) { | |
6197 | 756 FREE_C_HEAP_ARRAY(HeapWord*, _survivor_plab_array[j-1].array(), mtGC); |
0 | 757 } |
6197 | 758 FREE_C_HEAP_ARRAY(ChunkArray, _survivor_plab_array, mtGC); |
759 FREE_C_HEAP_ARRAY(HeapWord*, _survivor_chunk_array, mtGC); | |
0 | 760 _survivor_plab_array = NULL; |
761 _survivor_chunk_array = NULL; | |
762 _survivor_chunk_capacity = 0; | |
763 break; | |
764 } else { | |
765 ChunkArray* cur = | |
766 ::new (&_survivor_plab_array[i]) ChunkArray(vec, | |
767 max_plab_samples); | |
768 assert(cur->end() == 0, "Should be 0"); | |
769 assert(cur->array() == vec, "Should be vec"); | |
770 assert(cur->capacity() == max_plab_samples, "Error"); | |
771 } | |
772 } | |
773 } | |
774 } | |
775 assert( ( _survivor_plab_array != NULL | |
776 && _survivor_chunk_array != NULL) | |
777 || ( _survivor_chunk_capacity == 0 | |
778 && _survivor_chunk_index == 0), | |
779 "Error"); | |
780 | |
781 // Choose what strong roots should be scanned depending on verification options | |
782 if (!CMSClassUnloadingEnabled) { | |
783 // If class unloading is disabled we want to include all classes into the root set. | |
784 add_root_scanning_option(SharedHeap::SO_AllClasses); | |
785 } else { | |
786 add_root_scanning_option(SharedHeap::SO_SystemClasses); | |
787 } | |
788 | |
789 NOT_PRODUCT(_overflow_counter = CMSMarkStackOverflowInterval;) | |
790 _gc_counters = new CollectorCounters("CMS", 1); | |
791 _completed_initialization = true; | |
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792 _inter_sweep_timer.start(); // start of time |
0 | 793 } |
794 | |
795 const char* ConcurrentMarkSweepGeneration::name() const { | |
796 return "concurrent mark-sweep generation"; | |
797 } | |
798 void ConcurrentMarkSweepGeneration::update_counters() { | |
799 if (UsePerfData) { | |
800 _space_counters->update_all(); | |
801 _gen_counters->update_all(); | |
802 } | |
803 } | |
804 | |
805 // this is an optimized version of update_counters(). it takes the | |
806 // used value as a parameter rather than computing it. | |
807 // | |
808 void ConcurrentMarkSweepGeneration::update_counters(size_t used) { | |
809 if (UsePerfData) { | |
810 _space_counters->update_used(used); | |
811 _space_counters->update_capacity(); | |
812 _gen_counters->update_all(); | |
813 } | |
814 } | |
815 | |
816 void ConcurrentMarkSweepGeneration::print() const { | |
817 Generation::print(); | |
818 cmsSpace()->print(); | |
819 } | |
820 | |
821 #ifndef PRODUCT | |
822 void ConcurrentMarkSweepGeneration::print_statistics() { | |
823 cmsSpace()->printFLCensus(0); | |
824 } | |
825 #endif | |
826 | |
827 void ConcurrentMarkSweepGeneration::printOccupancy(const char *s) { | |
828 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
829 if (PrintGCDetails) { | |
830 if (Verbose) { | |
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831 gclog_or_tty->print("[%d %s-%s: "SIZE_FORMAT"("SIZE_FORMAT")]", |
0 | 832 level(), short_name(), s, used(), capacity()); |
833 } else { | |
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834 gclog_or_tty->print("[%d %s-%s: "SIZE_FORMAT"K("SIZE_FORMAT"K)]", |
0 | 835 level(), short_name(), s, used() / K, capacity() / K); |
836 } | |
837 } | |
838 if (Verbose) { | |
839 gclog_or_tty->print(" "SIZE_FORMAT"("SIZE_FORMAT")", | |
840 gch->used(), gch->capacity()); | |
841 } else { | |
842 gclog_or_tty->print(" "SIZE_FORMAT"K("SIZE_FORMAT"K)", | |
843 gch->used() / K, gch->capacity() / K); | |
844 } | |
845 } | |
846 | |
847 size_t | |
848 ConcurrentMarkSweepGeneration::contiguous_available() const { | |
849 // dld proposes an improvement in precision here. If the committed | |
850 // part of the space ends in a free block we should add that to | |
851 // uncommitted size in the calculation below. Will make this | |
852 // change later, staying with the approximation below for the | |
853 // time being. -- ysr. | |
854 return MAX2(_virtual_space.uncommitted_size(), unsafe_max_alloc_nogc()); | |
855 } | |
856 | |
857 size_t | |
858 ConcurrentMarkSweepGeneration::unsafe_max_alloc_nogc() const { | |
859 return _cmsSpace->max_alloc_in_words() * HeapWordSize; | |
860 } | |
861 | |
862 size_t ConcurrentMarkSweepGeneration::max_available() const { | |
863 return free() + _virtual_space.uncommitted_size(); | |
864 } | |
865 | |
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866 bool ConcurrentMarkSweepGeneration::promotion_attempt_is_safe(size_t max_promotion_in_bytes) const { |
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867 size_t available = max_available(); |
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868 size_t av_promo = (size_t)gc_stats()->avg_promoted()->padded_average(); |
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869 bool res = (available >= av_promo) || (available >= max_promotion_in_bytes); |
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870 if (Verbose && PrintGCDetails) { |
1888
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871 gclog_or_tty->print_cr( |
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872 "CMS: promo attempt is%s safe: available("SIZE_FORMAT") %s av_promo("SIZE_FORMAT")," |
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873 "max_promo("SIZE_FORMAT")", |
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874 res? "":" not", available, res? ">=":"<", |
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875 av_promo, max_promotion_in_bytes); |
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876 } |
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877 return res; |
0 | 878 } |
879 | |
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880 // At a promotion failure dump information on block layout in heap |
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881 // (cms old generation). |
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882 void ConcurrentMarkSweepGeneration::promotion_failure_occurred() { |
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883 if (CMSDumpAtPromotionFailure) { |
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884 cmsSpace()->dump_at_safepoint_with_locks(collector(), gclog_or_tty); |
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885 } |
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886 } |
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887 |
0 | 888 CompactibleSpace* |
889 ConcurrentMarkSweepGeneration::first_compaction_space() const { | |
890 return _cmsSpace; | |
891 } | |
892 | |
893 void ConcurrentMarkSweepGeneration::reset_after_compaction() { | |
894 // Clear the promotion information. These pointers can be adjusted | |
895 // along with all the other pointers into the heap but | |
896 // compaction is expected to be a rare event with | |
897 // a heap using cms so don't do it without seeing the need. | |
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898 if (CollectedHeap::use_parallel_gc_threads()) { |
0 | 899 for (uint i = 0; i < ParallelGCThreads; i++) { |
900 _par_gc_thread_states[i]->promo.reset(); | |
901 } | |
902 } | |
903 } | |
904 | |
905 void ConcurrentMarkSweepGeneration::space_iterate(SpaceClosure* blk, bool usedOnly) { | |
906 blk->do_space(_cmsSpace); | |
907 } | |
908 | |
909 void ConcurrentMarkSweepGeneration::compute_new_size() { | |
910 assert_locked_or_safepoint(Heap_lock); | |
911 | |
912 // If incremental collection failed, we just want to expand | |
913 // to the limit. | |
914 if (incremental_collection_failed()) { | |
915 clear_incremental_collection_failed(); | |
916 grow_to_reserved(); | |
917 return; | |
918 } | |
919 | |
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920 // The heap has been compacted but not reset yet. |
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921 // Any metric such as free() or used() will be incorrect. |
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922 |
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923 CardGeneration::compute_new_size(); |
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924 |
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925 // Reset again after a possible resizing |
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926 if (did_compact()) { |
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927 cmsSpace()->reset_after_compaction(); |
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928 } |
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929 } |
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930 |
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931 void ConcurrentMarkSweepGeneration::compute_new_size_free_list() { |
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932 assert_locked_or_safepoint(Heap_lock); |
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933 |
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934 // If incremental collection failed, we just want to expand |
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935 // to the limit. |
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936 if (incremental_collection_failed()) { |
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937 clear_incremental_collection_failed(); |
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938 grow_to_reserved(); |
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939 return; |
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940 } |
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941 |
0 | 942 double free_percentage = ((double) free()) / capacity(); |
943 double desired_free_percentage = (double) MinHeapFreeRatio / 100; | |
944 double maximum_free_percentage = (double) MaxHeapFreeRatio / 100; | |
945 | |
946 // compute expansion delta needed for reaching desired free percentage | |
947 if (free_percentage < desired_free_percentage) { | |
948 size_t desired_capacity = (size_t)(used() / ((double) 1 - desired_free_percentage)); | |
949 assert(desired_capacity >= capacity(), "invalid expansion size"); | |
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950 size_t expand_bytes = MAX2(desired_capacity - capacity(), MinHeapDeltaBytes); |
0 | 951 if (PrintGCDetails && Verbose) { |
952 size_t desired_capacity = (size_t)(used() / ((double) 1 - desired_free_percentage)); | |
953 gclog_or_tty->print_cr("\nFrom compute_new_size: "); | |
954 gclog_or_tty->print_cr(" Free fraction %f", free_percentage); | |
955 gclog_or_tty->print_cr(" Desired free fraction %f", | |
956 desired_free_percentage); | |
957 gclog_or_tty->print_cr(" Maximum free fraction %f", | |
958 maximum_free_percentage); | |
959 gclog_or_tty->print_cr(" Capactiy "SIZE_FORMAT, capacity()/1000); | |
960 gclog_or_tty->print_cr(" Desired capacity "SIZE_FORMAT, | |
961 desired_capacity/1000); | |
962 int prev_level = level() - 1; | |
963 if (prev_level >= 0) { | |
964 size_t prev_size = 0; | |
965 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
966 Generation* prev_gen = gch->_gens[prev_level]; | |
967 prev_size = prev_gen->capacity(); | |
968 gclog_or_tty->print_cr(" Younger gen size "SIZE_FORMAT, | |
969 prev_size/1000); | |
970 } | |
971 gclog_or_tty->print_cr(" unsafe_max_alloc_nogc "SIZE_FORMAT, | |
972 unsafe_max_alloc_nogc()/1000); | |
973 gclog_or_tty->print_cr(" contiguous available "SIZE_FORMAT, | |
974 contiguous_available()/1000); | |
975 gclog_or_tty->print_cr(" Expand by "SIZE_FORMAT" (bytes)", | |
976 expand_bytes); | |
977 } | |
978 // safe if expansion fails | |
979 expand(expand_bytes, 0, CMSExpansionCause::_satisfy_free_ratio); | |
980 if (PrintGCDetails && Verbose) { | |
981 gclog_or_tty->print_cr(" Expanded free fraction %f", | |
982 ((double) free()) / capacity()); | |
983 } | |
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984 } else { |
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985 size_t desired_capacity = (size_t)(used() / ((double) 1 - desired_free_percentage)); |
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986 assert(desired_capacity <= capacity(), "invalid expansion size"); |
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987 size_t shrink_bytes = capacity() - desired_capacity; |
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988 // Don't shrink unless the delta is greater than the minimum shrink we want |
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989 if (shrink_bytes >= MinHeapDeltaBytes) { |
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990 shrink_free_list_by(shrink_bytes); |
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991 } |
0 | 992 } |
993 } | |
994 | |
995 Mutex* ConcurrentMarkSweepGeneration::freelistLock() const { | |
996 return cmsSpace()->freelistLock(); | |
997 } | |
998 | |
999 HeapWord* ConcurrentMarkSweepGeneration::allocate(size_t size, | |
1000 bool tlab) { | |
1001 CMSSynchronousYieldRequest yr; | |
1002 MutexLockerEx x(freelistLock(), | |
1003 Mutex::_no_safepoint_check_flag); | |
1004 return have_lock_and_allocate(size, tlab); | |
1005 } | |
1006 | |
1007 HeapWord* ConcurrentMarkSweepGeneration::have_lock_and_allocate(size_t size, | |
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1008 bool tlab /* ignored */) { |
0 | 1009 assert_lock_strong(freelistLock()); |
1010 size_t adjustedSize = CompactibleFreeListSpace::adjustObjectSize(size); | |
1011 HeapWord* res = cmsSpace()->allocate(adjustedSize); | |
1012 // Allocate the object live (grey) if the background collector has | |
1013 // started marking. This is necessary because the marker may | |
1014 // have passed this address and consequently this object will | |
1015 // not otherwise be greyed and would be incorrectly swept up. | |
1016 // Note that if this object contains references, the writing | |
1017 // of those references will dirty the card containing this object | |
1018 // allowing the object to be blackened (and its references scanned) | |
1019 // either during a preclean phase or at the final checkpoint. | |
1020 if (res != NULL) { | |
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1021 // We may block here with an uninitialized object with |
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1022 // its mark-bit or P-bits not yet set. Such objects need |
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1023 // to be safely navigable by block_start(). |
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1024 assert(oop(res)->klass_or_null() == NULL, "Object should be uninitialized here."); |
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1025 assert(!((FreeChunk*)res)->is_free(), "Error, block will look free but show wrong size"); |
0 | 1026 collector()->direct_allocated(res, adjustedSize); |
1027 _direct_allocated_words += adjustedSize; | |
1028 // allocation counters | |
1029 NOT_PRODUCT( | |
1030 _numObjectsAllocated++; | |
1031 _numWordsAllocated += (int)adjustedSize; | |
1032 ) | |
1033 } | |
1034 return res; | |
1035 } | |
1036 | |
1037 // In the case of direct allocation by mutators in a generation that | |
1038 // is being concurrently collected, the object must be allocated | |
1039 // live (grey) if the background collector has started marking. | |
1040 // This is necessary because the marker may | |
1041 // have passed this address and consequently this object will | |
1042 // not otherwise be greyed and would be incorrectly swept up. | |
1043 // Note that if this object contains references, the writing | |
1044 // of those references will dirty the card containing this object | |
1045 // allowing the object to be blackened (and its references scanned) | |
1046 // either during a preclean phase or at the final checkpoint. | |
1047 void CMSCollector::direct_allocated(HeapWord* start, size_t size) { | |
1048 assert(_markBitMap.covers(start, size), "Out of bounds"); | |
1049 if (_collectorState >= Marking) { | |
1050 MutexLockerEx y(_markBitMap.lock(), | |
1051 Mutex::_no_safepoint_check_flag); | |
1052 // [see comments preceding SweepClosure::do_blk() below for details] | |
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1053 // |
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1054 // Can the P-bits be deleted now? JJJ |
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1055 // |
0 | 1056 // 1. need to mark the object as live so it isn't collected |
1057 // 2. need to mark the 2nd bit to indicate the object may be uninitialized | |
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1058 // 3. need to mark the end of the object so marking, precleaning or sweeping |
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1059 // can skip over uninitialized or unparsable objects. An allocated |
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1060 // object is considered uninitialized for our purposes as long as |
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1061 // its klass word is NULL. All old gen objects are parsable |
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1062 // as soon as they are initialized.) |
0 | 1063 _markBitMap.mark(start); // object is live |
1064 _markBitMap.mark(start + 1); // object is potentially uninitialized? | |
1065 _markBitMap.mark(start + size - 1); | |
1066 // mark end of object | |
1067 } | |
1068 // check that oop looks uninitialized | |
187 | 1069 assert(oop(start)->klass_or_null() == NULL, "_klass should be NULL"); |
0 | 1070 } |
1071 | |
1072 void CMSCollector::promoted(bool par, HeapWord* start, | |
1073 bool is_obj_array, size_t obj_size) { | |
1074 assert(_markBitMap.covers(start), "Out of bounds"); | |
1075 // See comment in direct_allocated() about when objects should | |
1076 // be allocated live. | |
1077 if (_collectorState >= Marking) { | |
1078 // we already hold the marking bit map lock, taken in | |
1079 // the prologue | |
1080 if (par) { | |
1081 _markBitMap.par_mark(start); | |
1082 } else { | |
1083 _markBitMap.mark(start); | |
1084 } | |
1085 // We don't need to mark the object as uninitialized (as | |
1086 // in direct_allocated above) because this is being done with the | |
1087 // world stopped and the object will be initialized by the | |
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1088 // time the marking, precleaning or sweeping get to look at it. |
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1089 // But see the code for copying objects into the CMS generation, |
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1090 // where we need to ensure that concurrent readers of the |
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1091 // block offset table are able to safely navigate a block that |
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1092 // is in flux from being free to being allocated (and in |
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1093 // transition while being copied into) and subsequently |
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1094 // becoming a bona-fide object when the copy/promotion is complete. |
0 | 1095 assert(SafepointSynchronize::is_at_safepoint(), |
1096 "expect promotion only at safepoints"); | |
1097 | |
1098 if (_collectorState < Sweeping) { | |
1099 // Mark the appropriate cards in the modUnionTable, so that | |
1100 // this object gets scanned before the sweep. If this is | |
1101 // not done, CMS generation references in the object might | |
1102 // not get marked. | |
1103 // For the case of arrays, which are otherwise precisely | |
1104 // marked, we need to dirty the entire array, not just its head. | |
1105 if (is_obj_array) { | |
1106 // The [par_]mark_range() method expects mr.end() below to | |
1107 // be aligned to the granularity of a bit's representation | |
1108 // in the heap. In the case of the MUT below, that's a | |
1109 // card size. | |
1110 MemRegion mr(start, | |
1111 (HeapWord*)round_to((intptr_t)(start + obj_size), | |
1112 CardTableModRefBS::card_size /* bytes */)); | |
1113 if (par) { | |
1114 _modUnionTable.par_mark_range(mr); | |
1115 } else { | |
1116 _modUnionTable.mark_range(mr); | |
1117 } | |
1118 } else { // not an obj array; we can just mark the head | |
1119 if (par) { | |
1120 _modUnionTable.par_mark(start); | |
1121 } else { | |
1122 _modUnionTable.mark(start); | |
1123 } | |
1124 } | |
1125 } | |
1126 } | |
1127 } | |
1128 | |
1129 static inline size_t percent_of_space(Space* space, HeapWord* addr) | |
1130 { | |
1131 size_t delta = pointer_delta(addr, space->bottom()); | |
1132 return (size_t)(delta * 100.0 / (space->capacity() / HeapWordSize)); | |
1133 } | |
1134 | |
1135 void CMSCollector::icms_update_allocation_limits() | |
1136 { | |
1137 Generation* gen0 = GenCollectedHeap::heap()->get_gen(0); | |
1138 EdenSpace* eden = gen0->as_DefNewGeneration()->eden(); | |
1139 | |
1140 const unsigned int duty_cycle = stats().icms_update_duty_cycle(); | |
1141 if (CMSTraceIncrementalPacing) { | |
1142 stats().print(); | |
1143 } | |
1144 | |
1145 assert(duty_cycle <= 100, "invalid duty cycle"); | |
1146 if (duty_cycle != 0) { | |
1147 // The duty_cycle is a percentage between 0 and 100; convert to words and | |
1148 // then compute the offset from the endpoints of the space. | |
1149 size_t free_words = eden->free() / HeapWordSize; | |
1150 double free_words_dbl = (double)free_words; | |
1151 size_t duty_cycle_words = (size_t)(free_words_dbl * duty_cycle / 100.0); | |
1152 size_t offset_words = (free_words - duty_cycle_words) / 2; | |
1153 | |
1154 _icms_start_limit = eden->top() + offset_words; | |
1155 _icms_stop_limit = eden->end() - offset_words; | |
1156 | |
1157 // The limits may be adjusted (shifted to the right) by | |
1158 // CMSIncrementalOffset, to allow the application more mutator time after a | |
1159 // young gen gc (when all mutators were stopped) and before CMS starts and | |
1160 // takes away one or more cpus. | |
1161 if (CMSIncrementalOffset != 0) { | |
1162 double adjustment_dbl = free_words_dbl * CMSIncrementalOffset / 100.0; | |
1163 size_t adjustment = (size_t)adjustment_dbl; | |
1164 HeapWord* tmp_stop = _icms_stop_limit + adjustment; | |
1165 if (tmp_stop > _icms_stop_limit && tmp_stop < eden->end()) { | |
1166 _icms_start_limit += adjustment; | |
1167 _icms_stop_limit = tmp_stop; | |
1168 } | |
1169 } | |
1170 } | |
1171 if (duty_cycle == 0 || (_icms_start_limit == _icms_stop_limit)) { | |
1172 _icms_start_limit = _icms_stop_limit = eden->end(); | |
1173 } | |
1174 | |
1175 // Install the new start limit. | |
1176 eden->set_soft_end(_icms_start_limit); | |
1177 | |
1178 if (CMSTraceIncrementalMode) { | |
1179 gclog_or_tty->print(" icms alloc limits: " | |
1180 PTR_FORMAT "," PTR_FORMAT | |
1181 " (" SIZE_FORMAT "%%," SIZE_FORMAT "%%) ", | |
1182 _icms_start_limit, _icms_stop_limit, | |
1183 percent_of_space(eden, _icms_start_limit), | |
1184 percent_of_space(eden, _icms_stop_limit)); | |
1185 if (Verbose) { | |
1186 gclog_or_tty->print("eden: "); | |
1187 eden->print_on(gclog_or_tty); | |
1188 } | |
1189 } | |
1190 } | |
1191 | |
1192 // Any changes here should try to maintain the invariant | |
1193 // that if this method is called with _icms_start_limit | |
1194 // and _icms_stop_limit both NULL, then it should return NULL | |
1195 // and not notify the icms thread. | |
1196 HeapWord* | |
1197 CMSCollector::allocation_limit_reached(Space* space, HeapWord* top, | |
1198 size_t word_size) | |
1199 { | |
1200 // A start_limit equal to end() means the duty cycle is 0, so treat that as a | |
1201 // nop. | |
1202 if (CMSIncrementalMode && _icms_start_limit != space->end()) { | |
1203 if (top <= _icms_start_limit) { | |
1204 if (CMSTraceIncrementalMode) { | |
1205 space->print_on(gclog_or_tty); | |
1206 gclog_or_tty->stamp(); | |
1207 gclog_or_tty->print_cr(" start limit top=" PTR_FORMAT | |
1208 ", new limit=" PTR_FORMAT | |
1209 " (" SIZE_FORMAT "%%)", | |
1210 top, _icms_stop_limit, | |
1211 percent_of_space(space, _icms_stop_limit)); | |
1212 } | |
1213 ConcurrentMarkSweepThread::start_icms(); | |
1214 assert(top < _icms_stop_limit, "Tautology"); | |
1215 if (word_size < pointer_delta(_icms_stop_limit, top)) { | |
1216 return _icms_stop_limit; | |
1217 } | |
1218 | |
1219 // The allocation will cross both the _start and _stop limits, so do the | |
1220 // stop notification also and return end(). | |
1221 if (CMSTraceIncrementalMode) { | |
1222 space->print_on(gclog_or_tty); | |
1223 gclog_or_tty->stamp(); | |
1224 gclog_or_tty->print_cr(" +stop limit top=" PTR_FORMAT | |
1225 ", new limit=" PTR_FORMAT | |
1226 " (" SIZE_FORMAT "%%)", | |
1227 top, space->end(), | |
1228 percent_of_space(space, space->end())); | |
1229 } | |
1230 ConcurrentMarkSweepThread::stop_icms(); | |
1231 return space->end(); | |
1232 } | |
1233 | |
1234 if (top <= _icms_stop_limit) { | |
1235 if (CMSTraceIncrementalMode) { | |
1236 space->print_on(gclog_or_tty); | |
1237 gclog_or_tty->stamp(); | |
1238 gclog_or_tty->print_cr(" stop limit top=" PTR_FORMAT | |
1239 ", new limit=" PTR_FORMAT | |
1240 " (" SIZE_FORMAT "%%)", | |
1241 top, space->end(), | |
1242 percent_of_space(space, space->end())); | |
1243 } | |
1244 ConcurrentMarkSweepThread::stop_icms(); | |
1245 return space->end(); | |
1246 } | |
1247 | |
1248 if (CMSTraceIncrementalMode) { | |
1249 space->print_on(gclog_or_tty); | |
1250 gclog_or_tty->stamp(); | |
1251 gclog_or_tty->print_cr(" end limit top=" PTR_FORMAT | |
1252 ", new limit=" PTR_FORMAT, | |
1253 top, NULL); | |
1254 } | |
1255 } | |
1256 | |
1257 return NULL; | |
1258 } | |
1259 | |
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1260 oop ConcurrentMarkSweepGeneration::promote(oop obj, size_t obj_size) { |
0 | 1261 assert(obj_size == (size_t)obj->size(), "bad obj_size passed in"); |
1262 // allocate, copy and if necessary update promoinfo -- | |
1263 // delegate to underlying space. | |
1264 assert_lock_strong(freelistLock()); | |
1265 | |
1266 #ifndef PRODUCT | |
1267 if (Universe::heap()->promotion_should_fail()) { | |
1268 return NULL; | |
1269 } | |
1270 #endif // #ifndef PRODUCT | |
1271 | |
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1272 oop res = _cmsSpace->promote(obj, obj_size); |
0 | 1273 if (res == NULL) { |
1274 // expand and retry | |
1275 size_t s = _cmsSpace->expansionSpaceRequired(obj_size); // HeapWords | |
1276 expand(s*HeapWordSize, MinHeapDeltaBytes, | |
1277 CMSExpansionCause::_satisfy_promotion); | |
1278 // Since there's currently no next generation, we don't try to promote | |
1279 // into a more senior generation. | |
1280 assert(next_gen() == NULL, "assumption, based upon which no attempt " | |
1281 "is made to pass on a possibly failing " | |
1282 "promotion to next generation"); | |
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1283 res = _cmsSpace->promote(obj, obj_size); |
0 | 1284 } |
1285 if (res != NULL) { | |
1286 // See comment in allocate() about when objects should | |
1287 // be allocated live. | |
1288 assert(obj->is_oop(), "Will dereference klass pointer below"); | |
1289 collector()->promoted(false, // Not parallel | |
1290 (HeapWord*)res, obj->is_objArray(), obj_size); | |
1291 // promotion counters | |
1292 NOT_PRODUCT( | |
1293 _numObjectsPromoted++; | |
1294 _numWordsPromoted += | |
1295 (int)(CompactibleFreeListSpace::adjustObjectSize(obj->size())); | |
1296 ) | |
1297 } | |
1298 return res; | |
1299 } | |
1300 | |
1301 | |
1302 HeapWord* | |
1303 ConcurrentMarkSweepGeneration::allocation_limit_reached(Space* space, | |
1304 HeapWord* top, | |
1305 size_t word_sz) | |
1306 { | |
1307 return collector()->allocation_limit_reached(space, top, word_sz); | |
1308 } | |
1309 | |
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1310 // IMPORTANT: Notes on object size recognition in CMS. |
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1311 // --------------------------------------------------- |
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1312 // A block of storage in the CMS generation is always in |
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1313 // one of three states. A free block (FREE), an allocated |
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1314 // object (OBJECT) whose size() method reports the correct size, |
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1315 // and an intermediate state (TRANSIENT) in which its size cannot |
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1316 // be accurately determined. |
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1317 // STATE IDENTIFICATION: (32 bit and 64 bit w/o COOPS) |
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1318 // ----------------------------------------------------- |
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1319 // FREE: klass_word & 1 == 1; mark_word holds block size |
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1320 // |
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1321 // OBJECT: klass_word installed; klass_word != 0 && klass_word & 1 == 0; |
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1322 // obj->size() computes correct size |
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1323 // |
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1324 // TRANSIENT: klass_word == 0; size is indeterminate until we become an OBJECT |
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1325 // |
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1326 // STATE IDENTIFICATION: (64 bit+COOPS) |
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1327 // ------------------------------------ |
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1328 // FREE: mark_word & CMS_FREE_BIT == 1; mark_word & ~CMS_FREE_BIT gives block_size |
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1329 // |
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1330 // OBJECT: klass_word installed; klass_word != 0; |
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1331 // obj->size() computes correct size |
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1332 // |
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1333 // TRANSIENT: klass_word == 0; size is indeterminate until we become an OBJECT |
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1334 // |
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1335 // |
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1336 // STATE TRANSITION DIAGRAM |
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1337 // |
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1338 // mut / parnew mut / parnew |
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1339 // FREE --------------------> TRANSIENT ---------------------> OBJECT --| |
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1340 // ^ | |
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1341 // |------------------------ DEAD <------------------------------------| |
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1342 // sweep mut |
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1343 // |
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1344 // While a block is in TRANSIENT state its size cannot be determined |
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1345 // so readers will either need to come back later or stall until |
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1346 // the size can be determined. Note that for the case of direct |
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1347 // allocation, P-bits, when available, may be used to determine the |
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1348 // size of an object that may not yet have been initialized. |
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1349 |
0 | 1350 // Things to support parallel young-gen collection. |
1351 oop | |
1352 ConcurrentMarkSweepGeneration::par_promote(int thread_num, | |
1353 oop old, markOop m, | |
1354 size_t word_sz) { | |
1355 #ifndef PRODUCT | |
1356 if (Universe::heap()->promotion_should_fail()) { | |
1357 return NULL; | |
1358 } | |
1359 #endif // #ifndef PRODUCT | |
1360 | |
1361 CMSParGCThreadState* ps = _par_gc_thread_states[thread_num]; | |
1362 PromotionInfo* promoInfo = &ps->promo; | |
1363 // if we are tracking promotions, then first ensure space for | |
1364 // promotion (including spooling space for saving header if necessary). | |
1365 // then allocate and copy, then track promoted info if needed. | |
1366 // When tracking (see PromotionInfo::track()), the mark word may | |
1367 // be displaced and in this case restoration of the mark word | |
1368 // occurs in the (oop_since_save_marks_)iterate phase. | |
1369 if (promoInfo->tracking() && !promoInfo->ensure_spooling_space()) { | |
1370 // Out of space for allocating spooling buffers; | |
1371 // try expanding and allocating spooling buffers. | |
1372 if (!expand_and_ensure_spooling_space(promoInfo)) { | |
1373 return NULL; | |
1374 } | |
1375 } | |
1376 assert(promoInfo->has_spooling_space(), "Control point invariant"); | |
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1377 const size_t alloc_sz = CompactibleFreeListSpace::adjustObjectSize(word_sz); |
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1378 HeapWord* obj_ptr = ps->lab.alloc(alloc_sz); |
0 | 1379 if (obj_ptr == NULL) { |
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1380 obj_ptr = expand_and_par_lab_allocate(ps, alloc_sz); |
0 | 1381 if (obj_ptr == NULL) { |
1382 return NULL; | |
1383 } | |
1384 } | |
1385 oop obj = oop(obj_ptr); | |
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1386 OrderAccess::storestore(); |
187 | 1387 assert(obj->klass_or_null() == NULL, "Object should be uninitialized here."); |
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1388 assert(!((FreeChunk*)obj_ptr)->is_free(), "Error, block will look free but show wrong size"); |
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1389 // IMPORTANT: See note on object initialization for CMS above. |
0 | 1390 // Otherwise, copy the object. Here we must be careful to insert the |
1391 // klass pointer last, since this marks the block as an allocated object. | |
187 | 1392 // Except with compressed oops it's the mark word. |
0 | 1393 HeapWord* old_ptr = (HeapWord*)old; |
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1394 // Restore the mark word copied above. |
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1395 obj->set_mark(m); |
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1396 assert(obj->klass_or_null() == NULL, "Object should be uninitialized here."); |
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1397 assert(!((FreeChunk*)obj_ptr)->is_free(), "Error, block will look free but show wrong size"); |
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1398 OrderAccess::storestore(); |
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1399 |
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1400 if (UseCompressedKlassPointers) { |
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1401 // Copy gap missed by (aligned) header size calculation below |
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1402 obj->set_klass_gap(old->klass_gap()); |
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1403 } |
0 | 1404 if (word_sz > (size_t)oopDesc::header_size()) { |
1405 Copy::aligned_disjoint_words(old_ptr + oopDesc::header_size(), | |
1406 obj_ptr + oopDesc::header_size(), | |
1407 word_sz - oopDesc::header_size()); | |
1408 } | |
187 | 1409 |
0 | 1410 // Now we can track the promoted object, if necessary. We take care |
1521 | 1411 // to delay the transition from uninitialized to full object |
0 | 1412 // (i.e., insertion of klass pointer) until after, so that it |
1413 // atomically becomes a promoted object. | |
1414 if (promoInfo->tracking()) { | |
1415 promoInfo->track((PromotedObject*)obj, old->klass()); | |
1416 } | |
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1417 assert(obj->klass_or_null() == NULL, "Object should be uninitialized here."); |
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1418 assert(!((FreeChunk*)obj_ptr)->is_free(), "Error, block will look free but show wrong size"); |
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1419 assert(old->is_oop(), "Will use and dereference old klass ptr below"); |
187 | 1420 |
1421 // Finally, install the klass pointer (this should be volatile). | |
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1422 OrderAccess::storestore(); |
0 | 1423 obj->set_klass(old->klass()); |
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1424 // We should now be able to calculate the right size for this object |
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1425 assert(obj->is_oop() && obj->size() == (int)word_sz, "Error, incorrect size computed for promoted object"); |
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1426 |
0 | 1427 collector()->promoted(true, // parallel |
1428 obj_ptr, old->is_objArray(), word_sz); | |
1429 | |
1430 NOT_PRODUCT( | |
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1431 Atomic::inc_ptr(&_numObjectsPromoted); |
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1432 Atomic::add_ptr(alloc_sz, &_numWordsPromoted); |
0 | 1433 ) |
1434 | |
1435 return obj; | |
1436 } | |
1437 | |
1438 void | |
1439 ConcurrentMarkSweepGeneration:: | |
1440 par_promote_alloc_undo(int thread_num, | |
1441 HeapWord* obj, size_t word_sz) { | |
1442 // CMS does not support promotion undo. | |
1443 ShouldNotReachHere(); | |
1444 } | |
1445 | |
1446 void | |
1447 ConcurrentMarkSweepGeneration:: | |
1448 par_promote_alloc_done(int thread_num) { | |
1449 CMSParGCThreadState* ps = _par_gc_thread_states[thread_num]; | |
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1450 ps->lab.retire(thread_num); |
0 | 1451 } |
1452 | |
1453 void | |
1454 ConcurrentMarkSweepGeneration:: | |
1455 par_oop_since_save_marks_iterate_done(int thread_num) { | |
1456 CMSParGCThreadState* ps = _par_gc_thread_states[thread_num]; | |
1457 ParScanWithoutBarrierClosure* dummy_cl = NULL; | |
1458 ps->promo.promoted_oops_iterate_nv(dummy_cl); | |
1459 } | |
1460 | |
1461 bool ConcurrentMarkSweepGeneration::should_collect(bool full, | |
1462 size_t size, | |
1463 bool tlab) | |
1464 { | |
1465 // We allow a STW collection only if a full | |
1466 // collection was requested. | |
1467 return full || should_allocate(size, tlab); // FIX ME !!! | |
1468 // This and promotion failure handling are connected at the | |
1469 // hip and should be fixed by untying them. | |
1470 } | |
1471 | |
1472 bool CMSCollector::shouldConcurrentCollect() { | |
1473 if (_full_gc_requested) { | |
1474 if (Verbose && PrintGCDetails) { | |
1475 gclog_or_tty->print_cr("CMSCollector: collect because of explicit " | |
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1476 " gc request (or gc_locker)"); |
0 | 1477 } |
1478 return true; | |
1479 } | |
1480 | |
1481 // For debugging purposes, change the type of collection. | |
1482 // If the rotation is not on the concurrent collection | |
1483 // type, don't start a concurrent collection. | |
1484 NOT_PRODUCT( | |
1485 if (RotateCMSCollectionTypes && | |
1486 (_cmsGen->debug_collection_type() != | |
1487 ConcurrentMarkSweepGeneration::Concurrent_collection_type)) { | |
1488 assert(_cmsGen->debug_collection_type() != | |
1489 ConcurrentMarkSweepGeneration::Unknown_collection_type, | |
1490 "Bad cms collection type"); | |
1491 return false; | |
1492 } | |
1493 ) | |
1494 | |
1495 FreelistLocker x(this); | |
1496 // ------------------------------------------------------------------ | |
1497 // Print out lots of information which affects the initiation of | |
1498 // a collection. | |
1499 if (PrintCMSInitiationStatistics && stats().valid()) { | |
1500 gclog_or_tty->print("CMSCollector shouldConcurrentCollect: "); | |
1501 gclog_or_tty->stamp(); | |
1502 gclog_or_tty->print_cr(""); | |
1503 stats().print_on(gclog_or_tty); | |
1504 gclog_or_tty->print_cr("time_until_cms_gen_full %3.7f", | |
1505 stats().time_until_cms_gen_full()); | |
1506 gclog_or_tty->print_cr("free="SIZE_FORMAT, _cmsGen->free()); | |
1507 gclog_or_tty->print_cr("contiguous_available="SIZE_FORMAT, | |
1508 _cmsGen->contiguous_available()); | |
1509 gclog_or_tty->print_cr("promotion_rate=%g", stats().promotion_rate()); | |
1510 gclog_or_tty->print_cr("cms_allocation_rate=%g", stats().cms_allocation_rate()); | |
1511 gclog_or_tty->print_cr("occupancy=%3.7f", _cmsGen->occupancy()); | |
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1512 gclog_or_tty->print_cr("initiatingOccupancy=%3.7f", _cmsGen->initiating_occupancy()); |
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1513 gclog_or_tty->print_cr("metadata initialized %d", |
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1514 MetaspaceGC::should_concurrent_collect()); |
0 | 1515 } |
1516 // ------------------------------------------------------------------ | |
1517 | |
1518 // If the estimated time to complete a cms collection (cms_duration()) | |
1519 // is less than the estimated time remaining until the cms generation | |
1520 // is full, start a collection. | |
1521 if (!UseCMSInitiatingOccupancyOnly) { | |
1522 if (stats().valid()) { | |
1523 if (stats().time_until_cms_start() == 0.0) { | |
1524 return true; | |
1525 } | |
1526 } else { | |
1527 // We want to conservatively collect somewhat early in order | |
1528 // to try and "bootstrap" our CMS/promotion statistics; | |
1529 // this branch will not fire after the first successful CMS | |
1530 // collection because the stats should then be valid. | |
1531 if (_cmsGen->occupancy() >= _bootstrap_occupancy) { | |
1532 if (Verbose && PrintGCDetails) { | |
1533 gclog_or_tty->print_cr( | |
1534 " CMSCollector: collect for bootstrapping statistics:" | |
1535 " occupancy = %f, boot occupancy = %f", _cmsGen->occupancy(), | |
1536 _bootstrap_occupancy); | |
1537 } | |
1538 return true; | |
1539 } | |
1540 } | |
1541 } | |
1542 | |
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1543 // Otherwise, we start a collection cycle if |
0 | 1544 // old gen want a collection cycle started. Each may use |
1545 // an appropriate criterion for making this decision. | |
1546 // XXX We need to make sure that the gen expansion | |
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1547 // criterion dovetails well with this. XXX NEED TO FIX THIS |
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1548 if (_cmsGen->should_concurrent_collect()) { |
0 | 1549 if (Verbose && PrintGCDetails) { |
1550 gclog_or_tty->print_cr("CMS old gen initiated"); | |
1551 } | |
1552 return true; | |
1553 } | |
1554 | |
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1555 // We start a collection if we believe an incremental collection may fail; |
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1556 // this is not likely to be productive in practice because it's probably too |
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1557 // late anyway. |
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1558 GenCollectedHeap* gch = GenCollectedHeap::heap(); |
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1559 assert(gch->collector_policy()->is_two_generation_policy(), |
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1560 "You may want to check the correctness of the following"); |
1994
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1561 if (gch->incremental_collection_will_fail(true /* consult_young */)) { |
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1562 if (Verbose && PrintGCDetails) { |
94
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1563 gclog_or_tty->print("CMSCollector: collect because incremental collection will fail "); |
0 | 1564 } |
1565 return true; | |
1566 } | |
1567 | |
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1568 if (MetaspaceGC::should_concurrent_collect()) { |
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1569 if (Verbose && PrintGCDetails) { |
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1570 gclog_or_tty->print("CMSCollector: collect for metadata allocation "); |
94
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1571 } |
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1572 return true; |
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1573 } |
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1574 |
0 | 1575 return false; |
1576 } | |
1577 | |
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1578 void CMSCollector::set_did_compact(bool v) { _cmsGen->set_did_compact(v); } |
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1579 |
0 | 1580 // Clear _expansion_cause fields of constituent generations |
1581 void CMSCollector::clear_expansion_cause() { | |
1582 _cmsGen->clear_expansion_cause(); | |
1583 } | |
1584 | |
94
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1585 // We should be conservative in starting a collection cycle. To |
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1586 // start too eagerly runs the risk of collecting too often in the |
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1587 // extreme. To collect too rarely falls back on full collections, |
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1588 // which works, even if not optimum in terms of concurrent work. |
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1589 // As a work around for too eagerly collecting, use the flag |
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1590 // UseCMSInitiatingOccupancyOnly. This also has the advantage of |
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1591 // giving the user an easily understandable way of controlling the |
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1592 // collections. |
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1593 // We want to start a new collection cycle if any of the following |
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1594 // conditions hold: |
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1595 // . our current occupancy exceeds the configured initiating occupancy |
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1596 // for this generation, or |
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1597 // . we recently needed to expand this space and have not, since that |
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1598 // expansion, done a collection of this generation, or |
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1599 // . the underlying space believes that it may be a good idea to initiate |
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1600 // a concurrent collection (this may be based on criteria such as the |
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1601 // following: the space uses linear allocation and linear allocation is |
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1602 // going to fail, or there is believed to be excessive fragmentation in |
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1603 // the generation, etc... or ... |
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1604 // [.(currently done by CMSCollector::shouldConcurrentCollect() only for |
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1605 // the case of the old generation; see CR 6543076): |
94
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1606 // we may be approaching a point at which allocation requests may fail because |
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1607 // we will be out of sufficient free space given allocation rate estimates.] |
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1608 bool ConcurrentMarkSweepGeneration::should_concurrent_collect() const { |
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1609 |
0 | 1610 assert_lock_strong(freelistLock()); |
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1611 if (occupancy() > initiating_occupancy()) { |
0 | 1612 if (PrintGCDetails && Verbose) { |
1613 gclog_or_tty->print(" %s: collect because of occupancy %f / %f ", | |
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1614 short_name(), occupancy(), initiating_occupancy()); |
0 | 1615 } |
1616 return true; | |
1617 } | |
1618 if (UseCMSInitiatingOccupancyOnly) { | |
1619 return false; | |
1620 } | |
1621 if (expansion_cause() == CMSExpansionCause::_satisfy_allocation) { | |
1622 if (PrintGCDetails && Verbose) { | |
1623 gclog_or_tty->print(" %s: collect because expanded for allocation ", | |
1624 short_name()); | |
1625 } | |
1626 return true; | |
1627 } | |
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1628 if (_cmsSpace->should_concurrent_collect()) { |
0 | 1629 if (PrintGCDetails && Verbose) { |
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1630 gclog_or_tty->print(" %s: collect because cmsSpace says so ", |
0 | 1631 short_name()); |
1632 } | |
1633 return true; | |
1634 } | |
1635 return false; | |
1636 } | |
1637 | |
1638 void ConcurrentMarkSweepGeneration::collect(bool full, | |
1639 bool clear_all_soft_refs, | |
1640 size_t size, | |
1641 bool tlab) | |
1642 { | |
1643 collector()->collect(full, clear_all_soft_refs, size, tlab); | |
1644 } | |
1645 | |
1646 void CMSCollector::collect(bool full, | |
1647 bool clear_all_soft_refs, | |
1648 size_t size, | |
1649 bool tlab) | |
1650 { | |
1651 if (!UseCMSCollectionPassing && _collectorState > Idling) { | |
1652 // For debugging purposes skip the collection if the state | |
1653 // is not currently idle | |
1654 if (TraceCMSState) { | |
1655 gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " skipped full:%d CMS state %d", | |
1656 Thread::current(), full, _collectorState); | |
1657 } | |
1658 return; | |
1659 } | |
1660 | |
1661 // The following "if" branch is present for defensive reasons. | |
1662 // In the current uses of this interface, it can be replaced with: | |
1663 // assert(!GC_locker.is_active(), "Can't be called otherwise"); | |
1664 // But I am not placing that assert here to allow future | |
1665 // generality in invoking this interface. | |
1666 if (GC_locker::is_active()) { | |
1667 // A consistency test for GC_locker | |
1668 assert(GC_locker::needs_gc(), "Should have been set already"); | |
1669 // Skip this foreground collection, instead | |
1670 // expanding the heap if necessary. | |
1671 // Need the free list locks for the call to free() in compute_new_size() | |
1672 compute_new_size(); | |
1673 return; | |
1674 } | |
1675 acquire_control_and_collect(full, clear_all_soft_refs); | |
1676 _full_gcs_since_conc_gc++; | |
1677 } | |
1678 | |
1679 void CMSCollector::request_full_gc(unsigned int full_gc_count) { | |
1680 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
1681 unsigned int gc_count = gch->total_full_collections(); | |
1682 if (gc_count == full_gc_count) { | |
1683 MutexLockerEx y(CGC_lock, Mutex::_no_safepoint_check_flag); | |
1684 _full_gc_requested = true; | |
1685 CGC_lock->notify(); // nudge CMS thread | |
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1686 } else { |
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1687 assert(gc_count > full_gc_count, "Error: causal loop"); |
0 | 1688 } |
1689 } | |
1690 | |
1691 | |
1692 // The foreground and background collectors need to coordinate in order | |
1693 // to make sure that they do not mutually interfere with CMS collections. | |
1694 // When a background collection is active, | |
1695 // the foreground collector may need to take over (preempt) and | |
1696 // synchronously complete an ongoing collection. Depending on the | |
1697 // frequency of the background collections and the heap usage | |
1698 // of the application, this preemption can be seldom or frequent. | |
1699 // There are only certain | |
1700 // points in the background collection that the "collection-baton" | |
1701 // can be passed to the foreground collector. | |
1702 // | |
1703 // The foreground collector will wait for the baton before | |
1704 // starting any part of the collection. The foreground collector | |
1705 // will only wait at one location. | |
1706 // | |
1707 // The background collector will yield the baton before starting a new | |
1708 // phase of the collection (e.g., before initial marking, marking from roots, | |
1709 // precleaning, final re-mark, sweep etc.) This is normally done at the head | |
1710 // of the loop which switches the phases. The background collector does some | |
1711 // of the phases (initial mark, final re-mark) with the world stopped. | |
1712 // Because of locking involved in stopping the world, | |
1713 // the foreground collector should not block waiting for the background | |
1714 // collector when it is doing a stop-the-world phase. The background | |
1715 // collector will yield the baton at an additional point just before | |
1716 // it enters a stop-the-world phase. Once the world is stopped, the | |
1717 // background collector checks the phase of the collection. If the | |
1718 // phase has not changed, it proceeds with the collection. If the | |
1719 // phase has changed, it skips that phase of the collection. See | |
1720 // the comments on the use of the Heap_lock in collect_in_background(). | |
1721 // | |
1722 // Variable used in baton passing. | |
1723 // _foregroundGCIsActive - Set to true by the foreground collector when | |
1724 // it wants the baton. The foreground clears it when it has finished | |
1725 // the collection. | |
1726 // _foregroundGCShouldWait - Set to true by the background collector | |
1727 // when it is running. The foreground collector waits while | |
1728 // _foregroundGCShouldWait is true. | |
1729 // CGC_lock - monitor used to protect access to the above variables | |
1730 // and to notify the foreground and background collectors. | |
1731 // _collectorState - current state of the CMS collection. | |
1732 // | |
1733 // The foreground collector | |
1734 // acquires the CGC_lock | |
1735 // sets _foregroundGCIsActive | |
1736 // waits on the CGC_lock for _foregroundGCShouldWait to be false | |
1737 // various locks acquired in preparation for the collection | |
1738 // are released so as not to block the background collector | |
1739 // that is in the midst of a collection | |
1740 // proceeds with the collection | |
1741 // clears _foregroundGCIsActive | |
1742 // returns | |
1743 // | |
1744 // The background collector in a loop iterating on the phases of the | |
1745 // collection | |
1746 // acquires the CGC_lock | |
1747 // sets _foregroundGCShouldWait | |
1748 // if _foregroundGCIsActive is set | |
1749 // clears _foregroundGCShouldWait, notifies _CGC_lock | |
1750 // waits on _CGC_lock for _foregroundGCIsActive to become false | |
1751 // and exits the loop. | |
1752 // otherwise | |
1753 // proceed with that phase of the collection | |
1754 // if the phase is a stop-the-world phase, | |
1755 // yield the baton once more just before enqueueing | |
1756 // the stop-world CMS operation (executed by the VM thread). | |
1757 // returns after all phases of the collection are done | |
1758 // | |
1759 | |
1760 void CMSCollector::acquire_control_and_collect(bool full, | |
1761 bool clear_all_soft_refs) { | |
1762 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint"); | |
1763 assert(!Thread::current()->is_ConcurrentGC_thread(), | |
1764 "shouldn't try to acquire control from self!"); | |
1765 | |
1766 // Start the protocol for acquiring control of the | |
1767 // collection from the background collector (aka CMS thread). | |
1768 assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(), | |
1769 "VM thread should have CMS token"); | |
1770 // Remember the possibly interrupted state of an ongoing | |
1771 // concurrent collection | |
1772 CollectorState first_state = _collectorState; | |
1773 | |
1774 // Signal to a possibly ongoing concurrent collection that | |
1775 // we want to do a foreground collection. | |
1776 _foregroundGCIsActive = true; | |
1777 | |
1778 // Disable incremental mode during a foreground collection. | |
1779 ICMSDisabler icms_disabler; | |
1780 | |
1781 // release locks and wait for a notify from the background collector | |
1782 // releasing the locks in only necessary for phases which | |
1783 // do yields to improve the granularity of the collection. | |
1784 assert_lock_strong(bitMapLock()); | |
1785 // We need to lock the Free list lock for the space that we are | |
1786 // currently collecting. | |
1787 assert(haveFreelistLocks(), "Must be holding free list locks"); | |
1788 bitMapLock()->unlock(); | |
1789 releaseFreelistLocks(); | |
1790 { | |
1791 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
1792 if (_foregroundGCShouldWait) { | |
1793 // We are going to be waiting for action for the CMS thread; | |
1794 // it had better not be gone (for instance at shutdown)! | |
1795 assert(ConcurrentMarkSweepThread::cmst() != NULL, | |
1796 "CMS thread must be running"); | |
1797 // Wait here until the background collector gives us the go-ahead | |
1798 ConcurrentMarkSweepThread::clear_CMS_flag( | |
1799 ConcurrentMarkSweepThread::CMS_vm_has_token); // release token | |
1800 // Get a possibly blocked CMS thread going: | |
1801 // Note that we set _foregroundGCIsActive true above, | |
1802 // without protection of the CGC_lock. | |
1803 CGC_lock->notify(); | |
1804 assert(!ConcurrentMarkSweepThread::vm_thread_wants_cms_token(), | |
1805 "Possible deadlock"); | |
1806 while (_foregroundGCShouldWait) { | |
1807 // wait for notification | |
1808 CGC_lock->wait(Mutex::_no_safepoint_check_flag); | |
1809 // Possibility of delay/starvation here, since CMS token does | |
1810 // not know to give priority to VM thread? Actually, i think | |
1811 // there wouldn't be any delay/starvation, but the proof of | |
1812 // that "fact" (?) appears non-trivial. XXX 20011219YSR | |
1813 } | |
1814 ConcurrentMarkSweepThread::set_CMS_flag( | |
1815 ConcurrentMarkSweepThread::CMS_vm_has_token); | |
1816 } | |
1817 } | |
1818 // The CMS_token is already held. Get back the other locks. | |
1819 assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(), | |
1820 "VM thread should have CMS token"); | |
1821 getFreelistLocks(); | |
1822 bitMapLock()->lock_without_safepoint_check(); | |
1823 if (TraceCMSState) { | |
1824 gclog_or_tty->print_cr("CMS foreground collector has asked for control " | |
1825 INTPTR_FORMAT " with first state %d", Thread::current(), first_state); | |
1826 gclog_or_tty->print_cr(" gets control with state %d", _collectorState); | |
1827 } | |
1828 | |
1829 // Check if we need to do a compaction, or if not, whether | |
1830 // we need to start the mark-sweep from scratch. | |
1831 bool should_compact = false; | |
1832 bool should_start_over = false; | |
1833 decide_foreground_collection_type(clear_all_soft_refs, | |
1834 &should_compact, &should_start_over); | |
1835 | |
1836 NOT_PRODUCT( | |
1837 if (RotateCMSCollectionTypes) { | |
1838 if (_cmsGen->debug_collection_type() == | |
1839 ConcurrentMarkSweepGeneration::MSC_foreground_collection_type) { | |
1840 should_compact = true; | |
1841 } else if (_cmsGen->debug_collection_type() == | |
1842 ConcurrentMarkSweepGeneration::MS_foreground_collection_type) { | |
1843 should_compact = false; | |
1844 } | |
1845 } | |
1846 ) | |
1847 | |
1848 if (PrintGCDetails && first_state > Idling) { | |
1849 GCCause::Cause cause = GenCollectedHeap::heap()->gc_cause(); | |
1850 if (GCCause::is_user_requested_gc(cause) || | |
1851 GCCause::is_serviceability_requested_gc(cause)) { | |
1852 gclog_or_tty->print(" (concurrent mode interrupted)"); | |
1853 } else { | |
1854 gclog_or_tty->print(" (concurrent mode failure)"); | |
1855 } | |
1856 } | |
1857 | |
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1858 set_did_compact(should_compact); |
0 | 1859 if (should_compact) { |
1860 // If the collection is being acquired from the background | |
1861 // collector, there may be references on the discovered | |
1862 // references lists that have NULL referents (being those | |
1863 // that were concurrently cleared by a mutator) or | |
1864 // that are no longer active (having been enqueued concurrently | |
1865 // by the mutator). | |
1866 // Scrub the list of those references because Mark-Sweep-Compact | |
1867 // code assumes referents are not NULL and that all discovered | |
1868 // Reference objects are active. | |
1869 ref_processor()->clean_up_discovered_references(); | |
1870 | |
1871 do_compaction_work(clear_all_soft_refs); | |
1872 | |
1873 // Has the GC time limit been exceeded? | |
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1874 DefNewGeneration* young_gen = _young_gen->as_DefNewGeneration(); |
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1875 size_t max_eden_size = young_gen->max_capacity() - |
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1876 young_gen->to()->capacity() - |
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1877 young_gen->from()->capacity(); |
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1878 GenCollectedHeap* gch = GenCollectedHeap::heap(); |
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1879 GCCause::Cause gc_cause = gch->gc_cause(); |
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1880 size_policy()->check_gc_overhead_limit(_young_gen->used(), |
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1881 young_gen->eden()->used(), |
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1882 _cmsGen->max_capacity(), |
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1883 max_eden_size, |
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1884 full, |
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1885 gc_cause, |
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1886 gch->collector_policy()); |
0 | 1887 } else { |
1888 do_mark_sweep_work(clear_all_soft_refs, first_state, | |
1889 should_start_over); | |
1890 } | |
1891 // Reset the expansion cause, now that we just completed | |
1892 // a collection cycle. | |
1893 clear_expansion_cause(); | |
1894 _foregroundGCIsActive = false; | |
1895 return; | |
1896 } | |
1897 | |
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1898 // Resize the tenured generation |
0 | 1899 // after obtaining the free list locks for the |
1900 // two generations. | |
1901 void CMSCollector::compute_new_size() { | |
1902 assert_locked_or_safepoint(Heap_lock); | |
1903 FreelistLocker z(this); | |
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1904 MetaspaceGC::compute_new_size(); |
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1905 _cmsGen->compute_new_size_free_list(); |
0 | 1906 } |
1907 | |
1908 // A work method used by foreground collection to determine | |
1909 // what type of collection (compacting or not, continuing or fresh) | |
1910 // it should do. | |
1911 // NOTE: the intent is to make UseCMSCompactAtFullCollection | |
1912 // and CMSCompactWhenClearAllSoftRefs the default in the future | |
1913 // and do away with the flags after a suitable period. | |
1914 void CMSCollector::decide_foreground_collection_type( | |
1915 bool clear_all_soft_refs, bool* should_compact, | |
1916 bool* should_start_over) { | |
1917 // Normally, we'll compact only if the UseCMSCompactAtFullCollection | |
1918 // flag is set, and we have either requested a System.gc() or | |
1919 // the number of full gc's since the last concurrent cycle | |
1920 // has exceeded the threshold set by CMSFullGCsBeforeCompaction, | |
1921 // or if an incremental collection has failed | |
1922 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
1923 assert(gch->collector_policy()->is_two_generation_policy(), | |
1924 "You may want to check the correctness of the following"); | |
1925 // Inform cms gen if this was due to partial collection failing. | |
1926 // The CMS gen may use this fact to determine its expansion policy. | |
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1927 if (gch->incremental_collection_will_fail(false /* don't consult_young */)) { |
0 | 1928 assert(!_cmsGen->incremental_collection_failed(), |
1929 "Should have been noticed, reacted to and cleared"); | |
1930 _cmsGen->set_incremental_collection_failed(); | |
1931 } | |
1932 *should_compact = | |
1933 UseCMSCompactAtFullCollection && | |
1934 ((_full_gcs_since_conc_gc >= CMSFullGCsBeforeCompaction) || | |
1935 GCCause::is_user_requested_gc(gch->gc_cause()) || | |
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1936 gch->incremental_collection_will_fail(true /* consult_young */)); |
0 | 1937 *should_start_over = false; |
1938 if (clear_all_soft_refs && !*should_compact) { | |
1939 // We are about to do a last ditch collection attempt | |
1940 // so it would normally make sense to do a compaction | |
1941 // to reclaim as much space as possible. | |
1942 if (CMSCompactWhenClearAllSoftRefs) { | |
1943 // Default: The rationale is that in this case either | |
1944 // we are past the final marking phase, in which case | |
1945 // we'd have to start over, or so little has been done | |
1946 // that there's little point in saving that work. Compaction | |
1947 // appears to be the sensible choice in either case. | |
1948 *should_compact = true; | |
1949 } else { | |
1950 // We have been asked to clear all soft refs, but not to | |
1951 // compact. Make sure that we aren't past the final checkpoint | |
1952 // phase, for that is where we process soft refs. If we are already | |
1953 // past that phase, we'll need to redo the refs discovery phase and | |
1954 // if necessary clear soft refs that weren't previously | |
1955 // cleared. We do so by remembering the phase in which | |
1956 // we came in, and if we are past the refs processing | |
1957 // phase, we'll choose to just redo the mark-sweep | |
1958 // collection from scratch. | |
1959 if (_collectorState > FinalMarking) { | |
1960 // We are past the refs processing phase; | |
1961 // start over and do a fresh synchronous CMS cycle | |
1962 _collectorState = Resetting; // skip to reset to start new cycle | |
1963 reset(false /* == !asynch */); | |
1964 *should_start_over = true; | |
1965 } // else we can continue a possibly ongoing current cycle | |
1966 } | |
1967 } | |
1968 } | |
1969 | |
1970 // A work method used by the foreground collector to do | |
1971 // a mark-sweep-compact. | |
1972 void CMSCollector::do_compaction_work(bool clear_all_soft_refs) { | |
1973 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
1974 TraceTime t("CMS:MSC ", PrintGCDetails && Verbose, true, gclog_or_tty); | |
1975 if (PrintGC && Verbose && !(GCCause::is_user_requested_gc(gch->gc_cause()))) { | |
1976 gclog_or_tty->print_cr("Compact ConcurrentMarkSweepGeneration after %d " | |
1977 "collections passed to foreground collector", _full_gcs_since_conc_gc); | |
1978 } | |
1979 | |
1980 // Sample collection interval time and reset for collection pause. | |
1981 if (UseAdaptiveSizePolicy) { | |
1982 size_policy()->msc_collection_begin(); | |
1983 } | |
1984 | |
1985 // Temporarily widen the span of the weak reference processing to | |
1986 // the entire heap. | |
1987 MemRegion new_span(GenCollectedHeap::heap()->reserved_region()); | |
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1988 ReferenceProcessorSpanMutator rp_mut_span(ref_processor(), new_span); |
0 | 1989 // Temporarily, clear the "is_alive_non_header" field of the |
1990 // reference processor. | |
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1991 ReferenceProcessorIsAliveMutator rp_mut_closure(ref_processor(), NULL); |
0 | 1992 // Temporarily make reference _processing_ single threaded (non-MT). |
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1993 ReferenceProcessorMTProcMutator rp_mut_mt_processing(ref_processor(), false); |
0 | 1994 // Temporarily make refs discovery atomic |
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1995 ReferenceProcessorAtomicMutator rp_mut_atomic(ref_processor(), true); |
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1996 // Temporarily make reference _discovery_ single threaded (non-MT) |
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1997 ReferenceProcessorMTDiscoveryMutator rp_mut_discovery(ref_processor(), false); |
0 | 1998 |
1999 ref_processor()->set_enqueuing_is_done(false); | |
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2000 ref_processor()->enable_discovery(false /*verify_disabled*/, false /*check_no_refs*/); |
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2001 ref_processor()->setup_policy(clear_all_soft_refs); |
0 | 2002 // If an asynchronous collection finishes, the _modUnionTable is |
2003 // all clear. If we are assuming the collection from an asynchronous | |
2004 // collection, clear the _modUnionTable. | |
2005 assert(_collectorState != Idling || _modUnionTable.isAllClear(), | |
2006 "_modUnionTable should be clear if the baton was not passed"); | |
2007 _modUnionTable.clear_all(); | |
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2008 assert(_collectorState != Idling || _ct->klass_rem_set()->mod_union_is_clear(), |
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2009 "mod union for klasses should be clear if the baton was passed"); |
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2010 _ct->klass_rem_set()->clear_mod_union(); |
0 | 2011 |
2012 // We must adjust the allocation statistics being maintained | |
2013 // in the free list space. We do so by reading and clearing | |
2014 // the sweep timer and updating the block flux rate estimates below. | |
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2015 assert(!_intra_sweep_timer.is_active(), "_intra_sweep_timer should be inactive"); |
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2016 if (_inter_sweep_timer.is_active()) { |
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2017 _inter_sweep_timer.stop(); |
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2018 // Note that we do not use this sample to update the _inter_sweep_estimate. |
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2019 _cmsGen->cmsSpace()->beginSweepFLCensus((float)(_inter_sweep_timer.seconds()), |
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2020 _inter_sweep_estimate.padded_average(), |
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2021 _intra_sweep_estimate.padded_average()); |
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2022 } |
0 | 2023 |
2024 GenMarkSweep::invoke_at_safepoint(_cmsGen->level(), | |
2025 ref_processor(), clear_all_soft_refs); | |
2026 #ifdef ASSERT | |
2027 CompactibleFreeListSpace* cms_space = _cmsGen->cmsSpace(); | |
2028 size_t free_size = cms_space->free(); | |
2029 assert(free_size == | |
2030 pointer_delta(cms_space->end(), cms_space->compaction_top()) | |
2031 * HeapWordSize, | |
2032 "All the free space should be compacted into one chunk at top"); | |
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2033 assert(cms_space->dictionary()->total_chunk_size( |
0 | 2034 debug_only(cms_space->freelistLock())) == 0 || |
2035 cms_space->totalSizeInIndexedFreeLists() == 0, | |
2036 "All the free space should be in a single chunk"); | |
2037 size_t num = cms_space->totalCount(); | |
2038 assert((free_size == 0 && num == 0) || | |
2039 (free_size > 0 && (num == 1 || num == 2)), | |
2040 "There should be at most 2 free chunks after compaction"); | |
2041 #endif // ASSERT | |
2042 _collectorState = Resetting; | |
2043 assert(_restart_addr == NULL, | |
2044 "Should have been NULL'd before baton was passed"); | |
2045 reset(false /* == !asynch */); | |
2046 _cmsGen->reset_after_compaction(); | |
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2047 _concurrent_cycles_since_last_unload = 0; |
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2048 |
0 | 2049 // Clear any data recorded in the PLAB chunk arrays. |
2050 if (_survivor_plab_array != NULL) { | |
2051 reset_survivor_plab_arrays(); | |
2052 } | |
2053 | |
2054 // Adjust the per-size allocation stats for the next epoch. | |
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2055 _cmsGen->cmsSpace()->endSweepFLCensus(sweep_count() /* fake */); |
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2056 // Restart the "inter sweep timer" for the next epoch. |
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2057 _inter_sweep_timer.reset(); |
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2058 _inter_sweep_timer.start(); |
0 | 2059 |
2060 // Sample collection pause time and reset for collection interval. | |
2061 if (UseAdaptiveSizePolicy) { | |
2062 size_policy()->msc_collection_end(gch->gc_cause()); | |
2063 } | |
2064 | |
2065 // For a mark-sweep-compact, compute_new_size() will be called | |
2066 // in the heap's do_collection() method. | |
2067 } | |
2068 | |
2069 // A work method used by the foreground collector to do | |
2070 // a mark-sweep, after taking over from a possibly on-going | |
2071 // concurrent mark-sweep collection. | |
2072 void CMSCollector::do_mark_sweep_work(bool clear_all_soft_refs, | |
2073 CollectorState first_state, bool should_start_over) { | |
2074 if (PrintGC && Verbose) { | |
2075 gclog_or_tty->print_cr("Pass concurrent collection to foreground " | |
2076 "collector with count %d", | |
2077 _full_gcs_since_conc_gc); | |
2078 } | |
2079 switch (_collectorState) { | |
2080 case Idling: | |
2081 if (first_state == Idling || should_start_over) { | |
2082 // The background GC was not active, or should | |
2083 // restarted from scratch; start the cycle. | |
2084 _collectorState = InitialMarking; | |
2085 } | |
2086 // If first_state was not Idling, then a background GC | |
2087 // was in progress and has now finished. No need to do it | |
2088 // again. Leave the state as Idling. | |
2089 break; | |
2090 case Precleaning: | |
2091 // In the foreground case don't do the precleaning since | |
2092 // it is not done concurrently and there is extra work | |
2093 // required. | |
2094 _collectorState = FinalMarking; | |
2095 } | |
2096 collect_in_foreground(clear_all_soft_refs); | |
2097 | |
2098 // For a mark-sweep, compute_new_size() will be called | |
2099 // in the heap's do_collection() method. | |
2100 } | |
2101 | |
2102 | |
2103 void CMSCollector::getFreelistLocks() const { | |
2104 // Get locks for all free lists in all generations that this | |
2105 // collector is responsible for | |
2106 _cmsGen->freelistLock()->lock_without_safepoint_check(); | |
2107 } | |
2108 | |
2109 void CMSCollector::releaseFreelistLocks() const { | |
2110 // Release locks for all free lists in all generations that this | |
2111 // collector is responsible for | |
2112 _cmsGen->freelistLock()->unlock(); | |
2113 } | |
2114 | |
2115 bool CMSCollector::haveFreelistLocks() const { | |
2116 // Check locks for all free lists in all generations that this | |
2117 // collector is responsible for | |
2118 assert_lock_strong(_cmsGen->freelistLock()); | |
2119 PRODUCT_ONLY(ShouldNotReachHere()); | |
2120 return true; | |
2121 } | |
2122 | |
2123 // A utility class that is used by the CMS collector to | |
2124 // temporarily "release" the foreground collector from its | |
2125 // usual obligation to wait for the background collector to | |
2126 // complete an ongoing phase before proceeding. | |
2127 class ReleaseForegroundGC: public StackObj { | |
2128 private: | |
2129 CMSCollector* _c; | |
2130 public: | |
2131 ReleaseForegroundGC(CMSCollector* c) : _c(c) { | |
2132 assert(_c->_foregroundGCShouldWait, "Else should not need to call"); | |
2133 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
2134 // allow a potentially blocked foreground collector to proceed | |
2135 _c->_foregroundGCShouldWait = false; | |
2136 if (_c->_foregroundGCIsActive) { | |
2137 CGC_lock->notify(); | |
2138 } | |
2139 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
2140 "Possible deadlock"); | |
2141 } | |
2142 | |
2143 ~ReleaseForegroundGC() { | |
2144 assert(!_c->_foregroundGCShouldWait, "Usage protocol violation?"); | |
2145 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
2146 _c->_foregroundGCShouldWait = true; | |
2147 } | |
2148 }; | |
2149 | |
2150 // There are separate collect_in_background and collect_in_foreground because of | |
2151 // the different locking requirements of the background collector and the | |
2152 // foreground collector. There was originally an attempt to share | |
2153 // one "collect" method between the background collector and the foreground | |
2154 // collector but the if-then-else required made it cleaner to have | |
2155 // separate methods. | |
2156 void CMSCollector::collect_in_background(bool clear_all_soft_refs) { | |
2157 assert(Thread::current()->is_ConcurrentGC_thread(), | |
2158 "A CMS asynchronous collection is only allowed on a CMS thread."); | |
2159 | |
2160 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
2161 { | |
2162 bool safepoint_check = Mutex::_no_safepoint_check_flag; | |
2163 MutexLockerEx hl(Heap_lock, safepoint_check); | |
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2164 FreelistLocker fll(this); |
0 | 2165 MutexLockerEx x(CGC_lock, safepoint_check); |
2166 if (_foregroundGCIsActive || !UseAsyncConcMarkSweepGC) { | |
2167 // The foreground collector is active or we're | |
2168 // not using asynchronous collections. Skip this | |
2169 // background collection. | |
2170 assert(!_foregroundGCShouldWait, "Should be clear"); | |
2171 return; | |
2172 } else { | |
2173 assert(_collectorState == Idling, "Should be idling before start."); | |
2174 _collectorState = InitialMarking; | |
2175 // Reset the expansion cause, now that we are about to begin | |
2176 // a new cycle. | |
2177 clear_expansion_cause(); | |
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2178 |
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2179 // Clear the MetaspaceGC flag since a concurrent collection |
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2180 // is starting but also clear it after the collection. |
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2181 MetaspaceGC::set_should_concurrent_collect(false); |
0 | 2182 } |
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2183 // Decide if we want to enable class unloading as part of the |
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2184 // ensuing concurrent GC cycle. |
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2185 update_should_unload_classes(); |
0 | 2186 _full_gc_requested = false; // acks all outstanding full gc requests |
2187 // Signal that we are about to start a collection | |
2188 gch->increment_total_full_collections(); // ... starting a collection cycle | |
2189 _collection_count_start = gch->total_full_collections(); | |
2190 } | |
2191 | |
2192 // Used for PrintGC | |
2193 size_t prev_used; | |
2194 if (PrintGC && Verbose) { | |
2195 prev_used = _cmsGen->used(); // XXXPERM | |
2196 } | |
2197 | |
2198 // The change of the collection state is normally done at this level; | |
2199 // the exceptions are phases that are executed while the world is | |
2200 // stopped. For those phases the change of state is done while the | |
2201 // world is stopped. For baton passing purposes this allows the | |
2202 // background collector to finish the phase and change state atomically. | |
2203 // The foreground collector cannot wait on a phase that is done | |
2204 // while the world is stopped because the foreground collector already | |
2205 // has the world stopped and would deadlock. | |
2206 while (_collectorState != Idling) { | |
2207 if (TraceCMSState) { | |
2208 gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " in CMS state %d", | |
2209 Thread::current(), _collectorState); | |
2210 } | |
2211 // The foreground collector | |
2212 // holds the Heap_lock throughout its collection. | |
2213 // holds the CMS token (but not the lock) | |
2214 // except while it is waiting for the background collector to yield. | |
2215 // | |
2216 // The foreground collector should be blocked (not for long) | |
2217 // if the background collector is about to start a phase | |
2218 // executed with world stopped. If the background | |
2219 // collector has already started such a phase, the | |
2220 // foreground collector is blocked waiting for the | |
2221 // Heap_lock. The stop-world phases (InitialMarking and FinalMarking) | |
2222 // are executed in the VM thread. | |
2223 // | |
2224 // The locking order is | |
2225 // PendingListLock (PLL) -- if applicable (FinalMarking) | |
2226 // Heap_lock (both this & PLL locked in VM_CMS_Operation::prologue()) | |
2227 // CMS token (claimed in | |
2228 // stop_world_and_do() --> | |
2229 // safepoint_synchronize() --> | |
2230 // CMSThread::synchronize()) | |
2231 | |
2232 { | |
2233 // Check if the FG collector wants us to yield. | |
2234 CMSTokenSync x(true); // is cms thread | |
2235 if (waitForForegroundGC()) { | |
2236 // We yielded to a foreground GC, nothing more to be | |
2237 // done this round. | |
2238 assert(_foregroundGCShouldWait == false, "We set it to false in " | |
2239 "waitForForegroundGC()"); | |
2240 if (TraceCMSState) { | |
2241 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT | |
2242 " exiting collection CMS state %d", | |
2243 Thread::current(), _collectorState); | |
2244 } | |
2245 return; | |
2246 } else { | |
2247 // The background collector can run but check to see if the | |
2248 // foreground collector has done a collection while the | |
2249 // background collector was waiting to get the CGC_lock | |
2250 // above. If yes, break so that _foregroundGCShouldWait | |
2251 // is cleared before returning. | |
2252 if (_collectorState == Idling) { | |
2253 break; | |
2254 } | |
2255 } | |
2256 } | |
2257 | |
2258 assert(_foregroundGCShouldWait, "Foreground collector, if active, " | |
2259 "should be waiting"); | |
2260 | |
2261 switch (_collectorState) { | |
2262 case InitialMarking: | |
2263 { | |
2264 ReleaseForegroundGC x(this); | |
2265 stats().record_cms_begin(); | |
2266 | |
2267 VM_CMS_Initial_Mark initial_mark_op(this); | |
2268 VMThread::execute(&initial_mark_op); | |
2269 } | |
2270 // The collector state may be any legal state at this point | |
2271 // since the background collector may have yielded to the | |
2272 // foreground collector. | |
2273 break; | |
2274 case Marking: | |
2275 // initial marking in checkpointRootsInitialWork has been completed | |
2276 if (markFromRoots(true)) { // we were successful | |
2277 assert(_collectorState == Precleaning, "Collector state should " | |
2278 "have changed"); | |
2279 } else { | |
2280 assert(_foregroundGCIsActive, "Internal state inconsistency"); | |
2281 } | |
2282 break; | |
2283 case Precleaning: | |
2284 if (UseAdaptiveSizePolicy) { | |
2285 size_policy()->concurrent_precleaning_begin(); | |
2286 } | |
2287 // marking from roots in markFromRoots has been completed | |
2288 preclean(); | |
2289 if (UseAdaptiveSizePolicy) { | |
2290 size_policy()->concurrent_precleaning_end(); | |
2291 } | |
2292 assert(_collectorState == AbortablePreclean || | |
2293 _collectorState == FinalMarking, | |
2294 "Collector state should have changed"); | |
2295 break; | |
2296 case AbortablePreclean: | |
2297 if (UseAdaptiveSizePolicy) { | |
2298 size_policy()->concurrent_phases_resume(); | |
2299 } | |
2300 abortable_preclean(); | |
2301 if (UseAdaptiveSizePolicy) { | |
2302 size_policy()->concurrent_precleaning_end(); | |
2303 } | |
2304 assert(_collectorState == FinalMarking, "Collector state should " | |
2305 "have changed"); | |
2306 break; | |
2307 case FinalMarking: | |
2308 { | |
2309 ReleaseForegroundGC x(this); | |
2310 | |
2311 VM_CMS_Final_Remark final_remark_op(this); | |
2312 VMThread::execute(&final_remark_op); | |
935 | 2313 } |
0 | 2314 assert(_foregroundGCShouldWait, "block post-condition"); |
2315 break; | |
2316 case Sweeping: | |
2317 if (UseAdaptiveSizePolicy) { | |
2318 size_policy()->concurrent_sweeping_begin(); | |
2319 } | |
2320 // final marking in checkpointRootsFinal has been completed | |
2321 sweep(true); | |
2322 assert(_collectorState == Resizing, "Collector state change " | |
2323 "to Resizing must be done under the free_list_lock"); | |
2324 _full_gcs_since_conc_gc = 0; | |
2325 | |
2326 // Stop the timers for adaptive size policy for the concurrent phases | |
2327 if (UseAdaptiveSizePolicy) { | |
2328 size_policy()->concurrent_sweeping_end(); | |
2329 size_policy()->concurrent_phases_end(gch->gc_cause(), | |
2330 gch->prev_gen(_cmsGen)->capacity(), | |
2331 _cmsGen->free()); | |
2332 } | |
2333 | |
2334 case Resizing: { | |
2335 // Sweeping has been completed... | |
2336 // At this point the background collection has completed. | |
2337 // Don't move the call to compute_new_size() down | |
2338 // into code that might be executed if the background | |
2339 // collection was preempted. | |
2340 { | |
2341 ReleaseForegroundGC x(this); // unblock FG collection | |
2342 MutexLockerEx y(Heap_lock, Mutex::_no_safepoint_check_flag); | |
2343 CMSTokenSync z(true); // not strictly needed. | |
2344 if (_collectorState == Resizing) { | |
2345 compute_new_size(); | |
2346 _collectorState = Resetting; | |
2347 } else { | |
2348 assert(_collectorState == Idling, "The state should only change" | |
2349 " because the foreground collector has finished the collection"); | |
2350 } | |
2351 } | |
2352 break; | |
2353 } | |
2354 case Resetting: | |
2355 // CMS heap resizing has been completed | |
2356 reset(true); | |
2357 assert(_collectorState == Idling, "Collector state should " | |
2358 "have changed"); | |
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2359 |
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2360 MetaspaceGC::set_should_concurrent_collect(false); |
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2361 |
0 | 2362 stats().record_cms_end(); |
2363 // Don't move the concurrent_phases_end() and compute_new_size() | |
2364 // calls to here because a preempted background collection | |
2365 // has it's state set to "Resetting". | |
2366 break; | |
2367 case Idling: | |
2368 default: | |
2369 ShouldNotReachHere(); | |
2370 break; | |
2371 } | |
2372 if (TraceCMSState) { | |
2373 gclog_or_tty->print_cr(" Thread " INTPTR_FORMAT " done - next CMS state %d", | |
2374 Thread::current(), _collectorState); | |
2375 } | |
2376 assert(_foregroundGCShouldWait, "block post-condition"); | |
2377 } | |
2378 | |
2379 // Should this be in gc_epilogue? | |
2380 collector_policy()->counters()->update_counters(); | |
2381 | |
2382 { | |
2383 // Clear _foregroundGCShouldWait and, in the event that the | |
2384 // foreground collector is waiting, notify it, before | |
2385 // returning. | |
2386 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
2387 _foregroundGCShouldWait = false; | |
2388 if (_foregroundGCIsActive) { | |
2389 CGC_lock->notify(); | |
2390 } | |
2391 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
2392 "Possible deadlock"); | |
2393 } | |
2394 if (TraceCMSState) { | |
2395 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT | |
2396 " exiting collection CMS state %d", | |
2397 Thread::current(), _collectorState); | |
2398 } | |
2399 if (PrintGC && Verbose) { | |
2400 _cmsGen->print_heap_change(prev_used); | |
2401 } | |
2402 } | |
2403 | |
2404 void CMSCollector::collect_in_foreground(bool clear_all_soft_refs) { | |
2405 assert(_foregroundGCIsActive && !_foregroundGCShouldWait, | |
2406 "Foreground collector should be waiting, not executing"); | |
2407 assert(Thread::current()->is_VM_thread(), "A foreground collection" | |
2408 "may only be done by the VM Thread with the world stopped"); | |
2409 assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(), | |
2410 "VM thread should have CMS token"); | |
2411 | |
2412 NOT_PRODUCT(TraceTime t("CMS:MS (foreground) ", PrintGCDetails && Verbose, | |
2413 true, gclog_or_tty);) | |
2414 if (UseAdaptiveSizePolicy) { | |
2415 size_policy()->ms_collection_begin(); | |
2416 } | |
2417 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact); | |
2418 | |
2419 HandleMark hm; // Discard invalid handles created during verification | |
2420 | |
2421 if (VerifyBeforeGC && | |
2422 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
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|
2423 Universe::verify(); |
0 | 2424 } |
2425 | |
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2426 // Snapshot the soft reference policy to be used in this collection cycle. |
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2427 ref_processor()->setup_policy(clear_all_soft_refs); |
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2428 |
0 | 2429 bool init_mark_was_synchronous = false; // until proven otherwise |
2430 while (_collectorState != Idling) { | |
2431 if (TraceCMSState) { | |
2432 gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " in CMS state %d", | |
2433 Thread::current(), _collectorState); | |
2434 } | |
2435 switch (_collectorState) { | |
2436 case InitialMarking: | |
2437 init_mark_was_synchronous = true; // fact to be exploited in re-mark | |
2438 checkpointRootsInitial(false); | |
2439 assert(_collectorState == Marking, "Collector state should have changed" | |
2440 " within checkpointRootsInitial()"); | |
2441 break; | |
2442 case Marking: | |
2443 // initial marking in checkpointRootsInitialWork has been completed | |
2444 if (VerifyDuringGC && | |
2445 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
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2446 Universe::verify("Verify before initial mark: "); |
0 | 2447 } |
2448 { | |
2449 bool res = markFromRoots(false); | |
2450 assert(res && _collectorState == FinalMarking, "Collector state should " | |
2451 "have changed"); | |
2452 break; | |
2453 } | |
2454 case FinalMarking: | |
2455 if (VerifyDuringGC && | |
2456 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
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2457 Universe::verify("Verify before re-mark: "); |
0 | 2458 } |
2459 checkpointRootsFinal(false, clear_all_soft_refs, | |
2460 init_mark_was_synchronous); | |
2461 assert(_collectorState == Sweeping, "Collector state should not " | |
2462 "have changed within checkpointRootsFinal()"); | |
2463 break; | |
2464 case Sweeping: | |
2465 // final marking in checkpointRootsFinal has been completed | |
2466 if (VerifyDuringGC && | |
2467 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
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2468 Universe::verify("Verify before sweep: "); |
0 | 2469 } |
2470 sweep(false); | |
2471 assert(_collectorState == Resizing, "Incorrect state"); | |
2472 break; | |
2473 case Resizing: { | |
2474 // Sweeping has been completed; the actual resize in this case | |
2475 // is done separately; nothing to be done in this state. | |
2476 _collectorState = Resetting; | |
2477 break; | |
2478 } | |
2479 case Resetting: | |
2480 // The heap has been resized. | |
2481 if (VerifyDuringGC && | |
2482 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
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2483 Universe::verify("Verify before reset: "); |
0 | 2484 } |
2485 reset(false); | |
2486 assert(_collectorState == Idling, "Collector state should " | |
2487 "have changed"); | |
2488 break; | |
2489 case Precleaning: | |
2490 case AbortablePreclean: | |
2491 // Elide the preclean phase | |
2492 _collectorState = FinalMarking; | |
2493 break; | |
2494 default: | |
2495 ShouldNotReachHere(); | |
2496 } | |
2497 if (TraceCMSState) { | |
2498 gclog_or_tty->print_cr(" Thread " INTPTR_FORMAT " done - next CMS state %d", | |
2499 Thread::current(), _collectorState); | |
2500 } | |
2501 } | |
2502 | |
2503 if (UseAdaptiveSizePolicy) { | |
2504 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
2505 size_policy()->ms_collection_end(gch->gc_cause()); | |
2506 } | |
2507 | |
2508 if (VerifyAfterGC && | |
2509 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
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2510 Universe::verify(); |
0 | 2511 } |
2512 if (TraceCMSState) { | |
2513 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT | |
2514 " exiting collection CMS state %d", | |
2515 Thread::current(), _collectorState); | |
2516 } | |
2517 } | |
2518 | |
2519 bool CMSCollector::waitForForegroundGC() { | |
2520 bool res = false; | |
2521 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
2522 "CMS thread should have CMS token"); | |
2523 // Block the foreground collector until the | |
2524 // background collectors decides whether to | |
2525 // yield. | |
2526 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
2527 _foregroundGCShouldWait = true; | |
2528 if (_foregroundGCIsActive) { | |
2529 // The background collector yields to the | |
2530 // foreground collector and returns a value | |
2531 // indicating that it has yielded. The foreground | |
2532 // collector can proceed. | |
2533 res = true; | |
2534 _foregroundGCShouldWait = false; | |
2535 ConcurrentMarkSweepThread::clear_CMS_flag( | |
2536 ConcurrentMarkSweepThread::CMS_cms_has_token); | |
2537 ConcurrentMarkSweepThread::set_CMS_flag( | |
2538 ConcurrentMarkSweepThread::CMS_cms_wants_token); | |
2539 // Get a possibly blocked foreground thread going | |
2540 CGC_lock->notify(); | |
2541 if (TraceCMSState) { | |
2542 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT " waiting at CMS state %d", | |
2543 Thread::current(), _collectorState); | |
2544 } | |
2545 while (_foregroundGCIsActive) { | |
2546 CGC_lock->wait(Mutex::_no_safepoint_check_flag); | |
2547 } | |
2548 ConcurrentMarkSweepThread::set_CMS_flag( | |
2549 ConcurrentMarkSweepThread::CMS_cms_has_token); | |
2550 ConcurrentMarkSweepThread::clear_CMS_flag( | |
2551 ConcurrentMarkSweepThread::CMS_cms_wants_token); | |
2552 } | |
2553 if (TraceCMSState) { | |
2554 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT " continuing at CMS state %d", | |
2555 Thread::current(), _collectorState); | |
2556 } | |
2557 return res; | |
2558 } | |
2559 | |
2560 // Because of the need to lock the free lists and other structures in | |
2561 // the collector, common to all the generations that the collector is | |
2562 // collecting, we need the gc_prologues of individual CMS generations | |
2563 // delegate to their collector. It may have been simpler had the | |
2564 // current infrastructure allowed one to call a prologue on a | |
2565 // collector. In the absence of that we have the generation's | |
2566 // prologue delegate to the collector, which delegates back | |
2567 // some "local" work to a worker method in the individual generations | |
2568 // that it's responsible for collecting, while itself doing any | |
2569 // work common to all generations it's responsible for. A similar | |
2570 // comment applies to the gc_epilogue()'s. | |
2571 // The role of the varaible _between_prologue_and_epilogue is to | |
2572 // enforce the invocation protocol. | |
2573 void CMSCollector::gc_prologue(bool full) { | |
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2574 // Call gc_prologue_work() for the CMSGen |
0 | 2575 // we are responsible for. |
2576 | |
2577 // The following locking discipline assumes that we are only called | |
2578 // when the world is stopped. | |
2579 assert(SafepointSynchronize::is_at_safepoint(), "world is stopped assumption"); | |
2580 | |
2581 // The CMSCollector prologue must call the gc_prologues for the | |
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2582 // "generations" that it's responsible |
0 | 2583 // for. |
2584 | |
2585 assert( Thread::current()->is_VM_thread() | |
2586 || ( CMSScavengeBeforeRemark | |
2587 && Thread::current()->is_ConcurrentGC_thread()), | |
2588 "Incorrect thread type for prologue execution"); | |
2589 | |
2590 if (_between_prologue_and_epilogue) { | |
2591 // We have already been invoked; this is a gc_prologue delegation | |
2592 // from yet another CMS generation that we are responsible for, just | |
2593 // ignore it since all relevant work has already been done. | |
2594 return; | |
2595 } | |
2596 | |
2597 // set a bit saying prologue has been called; cleared in epilogue | |
2598 _between_prologue_and_epilogue = true; | |
2599 // Claim locks for common data structures, then call gc_prologue_work() | |
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2600 // for each CMSGen. |
0 | 2601 |
2602 getFreelistLocks(); // gets free list locks on constituent spaces | |
2603 bitMapLock()->lock_without_safepoint_check(); | |
2604 | |
2605 // Should call gc_prologue_work() for all cms gens we are responsible for | |
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2606 bool duringMarking = _collectorState >= Marking |
0 | 2607 && _collectorState < Sweeping; |
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2608 |
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2609 // The young collections clear the modified oops state, which tells if |
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2610 // there are any modified oops in the class. The remark phase also needs |
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2611 // that information. Tell the young collection to save the union of all |
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2612 // modified klasses. |
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2613 if (duringMarking) { |
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2614 _ct->klass_rem_set()->set_accumulate_modified_oops(true); |
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2615 } |
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2616 |
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2617 bool registerClosure = duringMarking; |
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2618 |
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2619 ModUnionClosure* muc = CollectedHeap::use_parallel_gc_threads() ? |
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2620 &_modUnionClosurePar |
0 | 2621 : &_modUnionClosure; |
2622 _cmsGen->gc_prologue_work(full, registerClosure, muc); | |
2623 | |
2624 if (!full) { | |
2625 stats().record_gc0_begin(); | |
2626 } | |
2627 } | |
2628 | |
2629 void ConcurrentMarkSweepGeneration::gc_prologue(bool full) { | |
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2630 |
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2631 _capacity_at_prologue = capacity(); |
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2632 _used_at_prologue = used(); |
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2633 |
0 | 2634 // Delegate to CMScollector which knows how to coordinate between |
2635 // this and any other CMS generations that it is responsible for | |
2636 // collecting. | |
2637 collector()->gc_prologue(full); | |
2638 } | |
2639 | |
2640 // This is a "private" interface for use by this generation's CMSCollector. | |
2641 // Not to be called directly by any other entity (for instance, | |
2642 // GenCollectedHeap, which calls the "public" gc_prologue method above). | |
2643 void ConcurrentMarkSweepGeneration::gc_prologue_work(bool full, | |
2644 bool registerClosure, ModUnionClosure* modUnionClosure) { | |
2645 assert(!incremental_collection_failed(), "Shouldn't be set yet"); | |
2646 assert(cmsSpace()->preconsumptionDirtyCardClosure() == NULL, | |
2647 "Should be NULL"); | |
2648 if (registerClosure) { | |
2649 cmsSpace()->setPreconsumptionDirtyCardClosure(modUnionClosure); | |
2650 } | |
2651 cmsSpace()->gc_prologue(); | |
2652 // Clear stat counters | |
2653 NOT_PRODUCT( | |
2654 assert(_numObjectsPromoted == 0, "check"); | |
2655 assert(_numWordsPromoted == 0, "check"); | |
2656 if (Verbose && PrintGC) { | |
2657 gclog_or_tty->print("Allocated "SIZE_FORMAT" objects, " | |
2658 SIZE_FORMAT" bytes concurrently", | |
2659 _numObjectsAllocated, _numWordsAllocated*sizeof(HeapWord)); | |
2660 } | |
2661 _numObjectsAllocated = 0; | |
2662 _numWordsAllocated = 0; | |
2663 ) | |
2664 } | |
2665 | |
2666 void CMSCollector::gc_epilogue(bool full) { | |
2667 // The following locking discipline assumes that we are only called | |
2668 // when the world is stopped. | |
2669 assert(SafepointSynchronize::is_at_safepoint(), | |
2670 "world is stopped assumption"); | |
2671 | |
2672 // Currently the CMS epilogue (see CompactibleFreeListSpace) merely checks | |
2673 // if linear allocation blocks need to be appropriately marked to allow the | |
2674 // the blocks to be parsable. We also check here whether we need to nudge the | |
2675 // CMS collector thread to start a new cycle (if it's not already active). | |
2676 assert( Thread::current()->is_VM_thread() | |
2677 || ( CMSScavengeBeforeRemark | |
2678 && Thread::current()->is_ConcurrentGC_thread()), | |
2679 "Incorrect thread type for epilogue execution"); | |
2680 | |
2681 if (!_between_prologue_and_epilogue) { | |
2682 // We have already been invoked; this is a gc_epilogue delegation | |
2683 // from yet another CMS generation that we are responsible for, just | |
2684 // ignore it since all relevant work has already been done. | |
2685 return; | |
2686 } | |
2687 assert(haveFreelistLocks(), "must have freelist locks"); | |
2688 assert_lock_strong(bitMapLock()); | |
2689 | |
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2690 _ct->klass_rem_set()->set_accumulate_modified_oops(false); |
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2691 |
0 | 2692 _cmsGen->gc_epilogue_work(full); |
2693 | |
2694 if (_collectorState == AbortablePreclean || _collectorState == Precleaning) { | |
2695 // in case sampling was not already enabled, enable it | |
2696 _start_sampling = true; | |
2697 } | |
2698 // reset _eden_chunk_array so sampling starts afresh | |
2699 _eden_chunk_index = 0; | |
2700 | |
2701 size_t cms_used = _cmsGen->cmsSpace()->used(); | |
2702 | |
2703 // update performance counters - this uses a special version of | |
2704 // update_counters() that allows the utilization to be passed as a | |
2705 // parameter, avoiding multiple calls to used(). | |
2706 // | |
2707 _cmsGen->update_counters(cms_used); | |
2708 | |
2709 if (CMSIncrementalMode) { | |
2710 icms_update_allocation_limits(); | |
2711 } | |
2712 | |
2713 bitMapLock()->unlock(); | |
2714 releaseFreelistLocks(); | |
2715 | |
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2716 if (!CleanChunkPoolAsync) { |
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2717 Chunk::clean_chunk_pool(); |
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2718 } |
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2719 |
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2720 set_did_compact(false); |
0 | 2721 _between_prologue_and_epilogue = false; // ready for next cycle |
2722 } | |
2723 | |
2724 void ConcurrentMarkSweepGeneration::gc_epilogue(bool full) { | |
2725 collector()->gc_epilogue(full); | |
2726 | |
2727 // Also reset promotion tracking in par gc thread states. | |
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2728 if (CollectedHeap::use_parallel_gc_threads()) { |
0 | 2729 for (uint i = 0; i < ParallelGCThreads; i++) { |
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2730 _par_gc_thread_states[i]->promo.stopTrackingPromotions(i); |
0 | 2731 } |
2732 } | |
2733 } | |
2734 | |
2735 void ConcurrentMarkSweepGeneration::gc_epilogue_work(bool full) { | |
2736 assert(!incremental_collection_failed(), "Should have been cleared"); | |
2737 cmsSpace()->setPreconsumptionDirtyCardClosure(NULL); | |
2738 cmsSpace()->gc_epilogue(); | |
2739 // Print stat counters | |
2740 NOT_PRODUCT( | |
2741 assert(_numObjectsAllocated == 0, "check"); | |
2742 assert(_numWordsAllocated == 0, "check"); | |
2743 if (Verbose && PrintGC) { | |
2744 gclog_or_tty->print("Promoted "SIZE_FORMAT" objects, " | |
2745 SIZE_FORMAT" bytes", | |
2746 _numObjectsPromoted, _numWordsPromoted*sizeof(HeapWord)); | |
2747 } | |
2748 _numObjectsPromoted = 0; | |
2749 _numWordsPromoted = 0; | |
2750 ) | |
2751 | |
2752 if (PrintGC && Verbose) { | |
2753 // Call down the chain in contiguous_available needs the freelistLock | |
2754 // so print this out before releasing the freeListLock. | |
2755 gclog_or_tty->print(" Contiguous available "SIZE_FORMAT" bytes ", | |
2756 contiguous_available()); | |
2757 } | |
2758 } | |
2759 | |
2760 #ifndef PRODUCT | |
2761 bool CMSCollector::have_cms_token() { | |
2762 Thread* thr = Thread::current(); | |
2763 if (thr->is_VM_thread()) { | |
2764 return ConcurrentMarkSweepThread::vm_thread_has_cms_token(); | |
2765 } else if (thr->is_ConcurrentGC_thread()) { | |
2766 return ConcurrentMarkSweepThread::cms_thread_has_cms_token(); | |
2767 } else if (thr->is_GC_task_thread()) { | |
2768 return ConcurrentMarkSweepThread::vm_thread_has_cms_token() && | |
2769 ParGCRareEvent_lock->owned_by_self(); | |
2770 } | |
2771 return false; | |
2772 } | |
2773 #endif | |
2774 | |
2775 // Check reachability of the given heap address in CMS generation, | |
2776 // treating all other generations as roots. | |
2777 bool CMSCollector::is_cms_reachable(HeapWord* addr) { | |
2778 // We could "guarantee" below, rather than assert, but i'll | |
2779 // leave these as "asserts" so that an adventurous debugger | |
2780 // could try this in the product build provided some subset of | |
2781 // the conditions were met, provided they were intersted in the | |
2782 // results and knew that the computation below wouldn't interfere | |
2783 // with other concurrent computations mutating the structures | |
2784 // being read or written. | |
2785 assert(SafepointSynchronize::is_at_safepoint(), | |
2786 "Else mutations in object graph will make answer suspect"); | |
2787 assert(have_cms_token(), "Should hold cms token"); | |
2788 assert(haveFreelistLocks(), "must hold free list locks"); | |
2789 assert_lock_strong(bitMapLock()); | |
2790 | |
2791 // Clear the marking bit map array before starting, but, just | |
2792 // for kicks, first report if the given address is already marked | |
2793 gclog_or_tty->print_cr("Start: Address 0x%x is%s marked", addr, | |
2794 _markBitMap.isMarked(addr) ? "" : " not"); | |
2795 | |
2796 if (verify_after_remark()) { | |
2797 MutexLockerEx x(verification_mark_bm()->lock(), Mutex::_no_safepoint_check_flag); | |
2798 bool result = verification_mark_bm()->isMarked(addr); | |
2799 gclog_or_tty->print_cr("TransitiveMark: Address 0x%x %s marked", addr, | |
2800 result ? "IS" : "is NOT"); | |
2801 return result; | |
2802 } else { | |
2803 gclog_or_tty->print_cr("Could not compute result"); | |
2804 return false; | |
2805 } | |
2806 } | |
2807 | |
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2808 |
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2809 void |
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2810 CMSCollector::print_on_error(outputStream* st) { |
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2811 CMSCollector* collector = ConcurrentMarkSweepGeneration::_collector; |
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2812 if (collector != NULL) { |
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2813 CMSBitMap* bitmap = &collector->_markBitMap; |
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2814 st->print_cr("Marking Bits: (CMSBitMap*) " PTR_FORMAT, bitmap); |
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2815 bitmap->print_on_error(st, " Bits: "); |
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2816 |
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2817 st->cr(); |
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2818 |
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2819 CMSBitMap* mut_bitmap = &collector->_modUnionTable; |
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2820 st->print_cr("Mod Union Table: (CMSBitMap*) " PTR_FORMAT, mut_bitmap); |
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2821 mut_bitmap->print_on_error(st, " Bits: "); |
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2822 } |
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2823 } |
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2824 |
0 | 2825 //////////////////////////////////////////////////////// |
2826 // CMS Verification Support | |
2827 //////////////////////////////////////////////////////// | |
2828 // Following the remark phase, the following invariant | |
2829 // should hold -- each object in the CMS heap which is | |
2830 // marked in markBitMap() should be marked in the verification_mark_bm(). | |
2831 | |
2832 class VerifyMarkedClosure: public BitMapClosure { | |
2833 CMSBitMap* _marks; | |
2834 bool _failed; | |
2835 | |
2836 public: | |
2837 VerifyMarkedClosure(CMSBitMap* bm): _marks(bm), _failed(false) {} | |
2838 | |
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2839 bool do_bit(size_t offset) { |
0 | 2840 HeapWord* addr = _marks->offsetToHeapWord(offset); |
2841 if (!_marks->isMarked(addr)) { | |
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2842 oop(addr)->print_on(gclog_or_tty); |
0 | 2843 gclog_or_tty->print_cr(" ("INTPTR_FORMAT" should have been marked)", addr); |
2844 _failed = true; | |
2845 } | |
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2846 return true; |
0 | 2847 } |
2848 | |
2849 bool failed() { return _failed; } | |
2850 }; | |
2851 | |
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2852 bool CMSCollector::verify_after_remark(bool silent) { |
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2853 if (!silent) gclog_or_tty->print(" [Verifying CMS Marking... "); |
0 | 2854 MutexLockerEx ml(verification_mark_bm()->lock(), Mutex::_no_safepoint_check_flag); |
2855 static bool init = false; | |
2856 | |
2857 assert(SafepointSynchronize::is_at_safepoint(), | |
2858 "Else mutations in object graph will make answer suspect"); | |
2859 assert(have_cms_token(), | |
2860 "Else there may be mutual interference in use of " | |
2861 " verification data structures"); | |
2862 assert(_collectorState > Marking && _collectorState <= Sweeping, | |
2863 "Else marking info checked here may be obsolete"); | |
2864 assert(haveFreelistLocks(), "must hold free list locks"); | |
2865 assert_lock_strong(bitMapLock()); | |
2866 | |
2867 | |
2868 // Allocate marking bit map if not already allocated | |
2869 if (!init) { // first time | |
2870 if (!verification_mark_bm()->allocate(_span)) { | |
2871 return false; | |
2872 } | |
2873 init = true; | |
2874 } | |
2875 | |
2876 assert(verification_mark_stack()->isEmpty(), "Should be empty"); | |
2877 | |
2878 // Turn off refs discovery -- so we will be tracing through refs. | |
2879 // This is as intended, because by this time | |
2880 // GC must already have cleared any refs that need to be cleared, | |
2881 // and traced those that need to be marked; moreover, | |
2882 // the marking done here is not going to intefere in any | |
2883 // way with the marking information used by GC. | |
2884 NoRefDiscovery no_discovery(ref_processor()); | |
2885 | |
2886 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;) | |
2887 | |
2888 // Clear any marks from a previous round | |
2889 verification_mark_bm()->clear_all(); | |
2890 assert(verification_mark_stack()->isEmpty(), "markStack should be empty"); | |
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2891 verify_work_stacks_empty(); |
0 | 2892 |
2893 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
2894 gch->ensure_parsability(false); // fill TLABs, but no need to retire them | |
2895 // Update the saved marks which may affect the root scans. | |
2896 gch->save_marks(); | |
2897 | |
2898 if (CMSRemarkVerifyVariant == 1) { | |
2899 // In this first variant of verification, we complete | |
2900 // all marking, then check if the new marks-verctor is | |
2901 // a subset of the CMS marks-vector. | |
2902 verify_after_remark_work_1(); | |
2903 } else if (CMSRemarkVerifyVariant == 2) { | |
2904 // In this second variant of verification, we flag an error | |
2905 // (i.e. an object reachable in the new marks-vector not reachable | |
2906 // in the CMS marks-vector) immediately, also indicating the | |
2907 // identify of an object (A) that references the unmarked object (B) -- | |
2908 // presumably, a mutation to A failed to be picked up by preclean/remark? | |
2909 verify_after_remark_work_2(); | |
2910 } else { | |
2911 warning("Unrecognized value %d for CMSRemarkVerifyVariant", | |
2912 CMSRemarkVerifyVariant); | |
2913 } | |
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2914 if (!silent) gclog_or_tty->print(" done] "); |
0 | 2915 return true; |
2916 } | |
2917 | |
2918 void CMSCollector::verify_after_remark_work_1() { | |
2919 ResourceMark rm; | |
2920 HandleMark hm; | |
2921 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
2922 | |
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2923 // Get a clear set of claim bits for the strong roots processing to work with. |
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2924 ClassLoaderDataGraph::clear_claimed_marks(); |
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2925 |
0 | 2926 // Mark from roots one level into CMS |
994
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2927 MarkRefsIntoClosure notOlder(_span, verification_mark_bm()); |
0 | 2928 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. |
2929 | |
2930 gch->gen_process_strong_roots(_cmsGen->level(), | |
2931 true, // younger gens are roots | |
989
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2932 true, // activate StrongRootsScope |
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2933 false, // not scavenging |
0 | 2934 SharedHeap::ScanningOption(roots_scanning_options()), |
989
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2935 ¬Older, |
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2936 true, // walk code active on stacks |
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2937 NULL, |
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2938 NULL); // SSS: Provide correct closure |
0 | 2939 |
2940 // Now mark from the roots | |
2941 MarkFromRootsClosure markFromRootsClosure(this, _span, | |
6725
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2942 verification_mark_bm(), verification_mark_stack(), |
0 | 2943 false /* don't yield */, true /* verifying */); |
2944 assert(_restart_addr == NULL, "Expected pre-condition"); | |
2945 verification_mark_bm()->iterate(&markFromRootsClosure); | |
2946 while (_restart_addr != NULL) { | |
2947 // Deal with stack overflow: by restarting at the indicated | |
2948 // address. | |
2949 HeapWord* ra = _restart_addr; | |
2950 markFromRootsClosure.reset(ra); | |
2951 _restart_addr = NULL; | |
2952 verification_mark_bm()->iterate(&markFromRootsClosure, ra, _span.end()); | |
2953 } | |
2954 assert(verification_mark_stack()->isEmpty(), "Should have been drained"); | |
2955 verify_work_stacks_empty(); | |
2956 | |
2957 // Marking completed -- now verify that each bit marked in | |
2958 // verification_mark_bm() is also marked in markBitMap(); flag all | |
2959 // errors by printing corresponding objects. | |
2960 VerifyMarkedClosure vcl(markBitMap()); | |
2961 verification_mark_bm()->iterate(&vcl); | |
2962 if (vcl.failed()) { | |
2963 gclog_or_tty->print("Verification failed"); | |
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2964 Universe::heap()->print_on(gclog_or_tty); |
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2965 fatal("CMS: failed marking verification after remark"); |
0 | 2966 } |
2967 } | |
2968 | |
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2969 class VerifyKlassOopsKlassClosure : public KlassClosure { |
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2970 class VerifyKlassOopsClosure : public OopClosure { |
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2971 CMSBitMap* _bitmap; |
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2972 public: |
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2973 VerifyKlassOopsClosure(CMSBitMap* bitmap) : _bitmap(bitmap) { } |
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2974 void do_oop(oop* p) { guarantee(*p == NULL || _bitmap->isMarked((HeapWord*) *p), "Should be marked"); } |
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2975 void do_oop(narrowOop* p) { ShouldNotReachHere(); } |
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2976 } _oop_closure; |
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2977 public: |
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2978 VerifyKlassOopsKlassClosure(CMSBitMap* bitmap) : _oop_closure(bitmap) {} |
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2979 void do_klass(Klass* k) { |
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2980 k->oops_do(&_oop_closure); |
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2981 } |
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2982 }; |
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2983 |
0 | 2984 void CMSCollector::verify_after_remark_work_2() { |
2985 ResourceMark rm; | |
2986 HandleMark hm; | |
2987 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
2988 | |
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2989 // Get a clear set of claim bits for the strong roots processing to work with. |
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2990 ClassLoaderDataGraph::clear_claimed_marks(); |
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2991 |
0 | 2992 // Mark from roots one level into CMS |
2993 MarkRefsIntoVerifyClosure notOlder(_span, verification_mark_bm(), | |
994
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2994 markBitMap()); |
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2995 CMKlassClosure klass_closure(¬Older); |
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2996 |
0 | 2997 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. |
2998 gch->gen_process_strong_roots(_cmsGen->level(), | |
2999 true, // younger gens are roots | |
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3000 true, // activate StrongRootsScope |
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3001 false, // not scavenging |
0 | 3002 SharedHeap::ScanningOption(roots_scanning_options()), |
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3003 ¬Older, |
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3004 true, // walk code active on stacks |
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3005 NULL, |
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3006 &klass_closure); |
0 | 3007 |
3008 // Now mark from the roots | |
3009 MarkFromRootsVerifyClosure markFromRootsClosure(this, _span, | |
3010 verification_mark_bm(), markBitMap(), verification_mark_stack()); | |
3011 assert(_restart_addr == NULL, "Expected pre-condition"); | |
3012 verification_mark_bm()->iterate(&markFromRootsClosure); | |
3013 while (_restart_addr != NULL) { | |
3014 // Deal with stack overflow: by restarting at the indicated | |
3015 // address. | |
3016 HeapWord* ra = _restart_addr; | |
3017 markFromRootsClosure.reset(ra); | |
3018 _restart_addr = NULL; | |
3019 verification_mark_bm()->iterate(&markFromRootsClosure, ra, _span.end()); | |
3020 } | |
3021 assert(verification_mark_stack()->isEmpty(), "Should have been drained"); | |
3022 verify_work_stacks_empty(); | |
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3023 |
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3024 VerifyKlassOopsKlassClosure verify_klass_oops(verification_mark_bm()); |
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3025 ClassLoaderDataGraph::classes_do(&verify_klass_oops); |
0 | 3026 |
3027 // Marking completed -- now verify that each bit marked in | |
3028 // verification_mark_bm() is also marked in markBitMap(); flag all | |
3029 // errors by printing corresponding objects. | |
3030 VerifyMarkedClosure vcl(markBitMap()); | |
3031 verification_mark_bm()->iterate(&vcl); | |
3032 assert(!vcl.failed(), "Else verification above should not have succeeded"); | |
3033 } | |
3034 | |
3035 void ConcurrentMarkSweepGeneration::save_marks() { | |
3036 // delegate to CMS space | |
3037 cmsSpace()->save_marks(); | |
3038 for (uint i = 0; i < ParallelGCThreads; i++) { | |
3039 _par_gc_thread_states[i]->promo.startTrackingPromotions(); | |
3040 } | |
3041 } | |
3042 | |
3043 bool ConcurrentMarkSweepGeneration::no_allocs_since_save_marks() { | |
3044 return cmsSpace()->no_allocs_since_save_marks(); | |
3045 } | |
3046 | |
3047 #define CMS_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \ | |
3048 \ | |
3049 void ConcurrentMarkSweepGeneration:: \ | |
3050 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \ | |
3051 cl->set_generation(this); \ | |
3052 cmsSpace()->oop_since_save_marks_iterate##nv_suffix(cl); \ | |
3053 cl->reset_generation(); \ | |
3054 save_marks(); \ | |
3055 } | |
3056 | |
3057 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DEFN) | |
3058 | |
3059 void | |
3060 ConcurrentMarkSweepGeneration::object_iterate_since_last_GC(ObjectClosure* blk) | |
3061 { | |
3062 // Not currently implemented; need to do the following. -- ysr. | |
3063 // dld -- I think that is used for some sort of allocation profiler. So it | |
3064 // really means the objects allocated by the mutator since the last | |
3065 // GC. We could potentially implement this cheaply by recording only | |
3066 // the direct allocations in a side data structure. | |
3067 // | |
3068 // I think we probably ought not to be required to support these | |
3069 // iterations at any arbitrary point; I think there ought to be some | |
3070 // call to enable/disable allocation profiling in a generation/space, | |
3071 // and the iterator ought to return the objects allocated in the | |
3072 // gen/space since the enable call, or the last iterator call (which | |
3073 // will probably be at a GC.) That way, for gens like CM&S that would | |
3074 // require some extra data structure to support this, we only pay the | |
3075 // cost when it's in use... | |
3076 cmsSpace()->object_iterate_since_last_GC(blk); | |
3077 } | |
3078 | |
3079 void | |
3080 ConcurrentMarkSweepGeneration::younger_refs_iterate(OopsInGenClosure* cl) { | |
3081 cl->set_generation(this); | |
3082 younger_refs_in_space_iterate(_cmsSpace, cl); | |
3083 cl->reset_generation(); | |
3084 } | |
3085 | |
3086 void | |
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3087 ConcurrentMarkSweepGeneration::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) { |
0 | 3088 if (freelistLock()->owned_by_self()) { |
3089 Generation::oop_iterate(mr, cl); | |
3090 } else { | |
3091 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
3092 Generation::oop_iterate(mr, cl); | |
3093 } | |
3094 } | |
3095 | |
3096 void | |
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3097 ConcurrentMarkSweepGeneration::oop_iterate(ExtendedOopClosure* cl) { |
0 | 3098 if (freelistLock()->owned_by_self()) { |
3099 Generation::oop_iterate(cl); | |
3100 } else { | |
3101 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
3102 Generation::oop_iterate(cl); | |
3103 } | |
3104 } | |
3105 | |
3106 void | |
3107 ConcurrentMarkSweepGeneration::object_iterate(ObjectClosure* cl) { | |
3108 if (freelistLock()->owned_by_self()) { | |
3109 Generation::object_iterate(cl); | |
3110 } else { | |
3111 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
3112 Generation::object_iterate(cl); | |
3113 } | |
3114 } | |
3115 | |
3116 void | |
517
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3117 ConcurrentMarkSweepGeneration::safe_object_iterate(ObjectClosure* cl) { |
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3118 if (freelistLock()->owned_by_self()) { |
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3119 Generation::safe_object_iterate(cl); |
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3120 } else { |
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3121 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); |
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3122 Generation::safe_object_iterate(cl); |
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3123 } |
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3124 } |
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3125 |
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3126 void |
0 | 3127 ConcurrentMarkSweepGeneration::post_compact() { |
3128 } | |
3129 | |
3130 void | |
3131 ConcurrentMarkSweepGeneration::prepare_for_verify() { | |
3132 // Fix the linear allocation blocks to look like free blocks. | |
3133 | |
3134 // Locks are normally acquired/released in gc_prologue/gc_epilogue, but those | |
3135 // are not called when the heap is verified during universe initialization and | |
3136 // at vm shutdown. | |
3137 if (freelistLock()->owned_by_self()) { | |
3138 cmsSpace()->prepare_for_verify(); | |
3139 } else { | |
3140 MutexLockerEx fll(freelistLock(), Mutex::_no_safepoint_check_flag); | |
3141 cmsSpace()->prepare_for_verify(); | |
3142 } | |
3143 } | |
3144 | |
3145 void | |
6008 | 3146 ConcurrentMarkSweepGeneration::verify() { |
0 | 3147 // Locks are normally acquired/released in gc_prologue/gc_epilogue, but those |
3148 // are not called when the heap is verified during universe initialization and | |
3149 // at vm shutdown. | |
3150 if (freelistLock()->owned_by_self()) { | |
6008 | 3151 cmsSpace()->verify(); |
0 | 3152 } else { |
3153 MutexLockerEx fll(freelistLock(), Mutex::_no_safepoint_check_flag); | |
6008 | 3154 cmsSpace()->verify(); |
3155 } | |
3156 } | |
3157 | |
3158 void CMSCollector::verify() { | |
3159 _cmsGen->verify(); | |
0 | 3160 } |
3161 | |
3162 #ifndef PRODUCT | |
3163 bool CMSCollector::overflow_list_is_empty() const { | |
3164 assert(_num_par_pushes >= 0, "Inconsistency"); | |
3165 if (_overflow_list == NULL) { | |
3166 assert(_num_par_pushes == 0, "Inconsistency"); | |
3167 } | |
3168 return _overflow_list == NULL; | |
3169 } | |
3170 | |
3171 // The methods verify_work_stacks_empty() and verify_overflow_empty() | |
3172 // merely consolidate assertion checks that appear to occur together frequently. | |
3173 void CMSCollector::verify_work_stacks_empty() const { | |
3174 assert(_markStack.isEmpty(), "Marking stack should be empty"); | |
3175 assert(overflow_list_is_empty(), "Overflow list should be empty"); | |
3176 } | |
3177 | |
3178 void CMSCollector::verify_overflow_empty() const { | |
3179 assert(overflow_list_is_empty(), "Overflow list should be empty"); | |
3180 assert(no_preserved_marks(), "No preserved marks"); | |
3181 } | |
3182 #endif // PRODUCT | |
3183 | |
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3184 // Decide if we want to enable class unloading as part of the |
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3185 // ensuing concurrent GC cycle. We will collect and |
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3186 // unload classes if it's the case that: |
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3187 // (1) an explicit gc request has been made and the flag |
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3188 // ExplicitGCInvokesConcurrentAndUnloadsClasses is set, OR |
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3189 // (2) (a) class unloading is enabled at the command line, and |
6725
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3190 // (b) old gen is getting really full |
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3191 // NOTE: Provided there is no change in the state of the heap between |
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3192 // calls to this method, it should have idempotent results. Moreover, |
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3193 // its results should be monotonically increasing (i.e. going from 0 to 1, |
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3194 // but not 1 to 0) between successive calls between which the heap was |
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3195 // not collected. For the implementation below, it must thus rely on |
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3196 // the property that concurrent_cycles_since_last_unload() |
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3197 // will not decrease unless a collection cycle happened and that |
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3198 // _cmsGen->is_too_full() are |
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3199 // themselves also monotonic in that sense. See check_monotonicity() |
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3200 // below. |
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3201 void CMSCollector::update_should_unload_classes() { |
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3202 _should_unload_classes = false; |
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3203 // Condition 1 above |
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3204 if (_full_gc_requested && ExplicitGCInvokesConcurrentAndUnloadsClasses) { |
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3205 _should_unload_classes = true; |
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3206 } else if (CMSClassUnloadingEnabled) { // Condition 2.a above |
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3207 // Disjuncts 2.b.(i,ii,iii) above |
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3208 _should_unload_classes = (concurrent_cycles_since_last_unload() >= |
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3209 CMSClassUnloadingMaxInterval) |
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3210 || _cmsGen->is_too_full(); |
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3211 } |
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3212 } |
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3213 |
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3214 bool ConcurrentMarkSweepGeneration::is_too_full() const { |
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3215 bool res = should_concurrent_collect(); |
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3216 res = res && (occupancy() > (double)CMSIsTooFullPercentage/100.0); |
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3217 return res; |
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3218 } |
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3219 |
0 | 3220 void CMSCollector::setup_cms_unloading_and_verification_state() { |
3293
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3221 const bool should_verify = VerifyBeforeGC || VerifyAfterGC || VerifyDuringGC |
0 | 3222 || VerifyBeforeExit; |
3293
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3223 const int rso = SharedHeap::SO_Strings | SharedHeap::SO_CodeCache; |
0 | 3224 |
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3225 if (should_unload_classes()) { // Should unload classes this cycle |
0 | 3226 remove_root_scanning_option(rso); // Shrink the root set appropriately |
3227 set_verifying(should_verify); // Set verification state for this cycle | |
3228 return; // Nothing else needs to be done at this time | |
3229 } | |
3230 | |
3231 // Not unloading classes this cycle | |
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3232 assert(!should_unload_classes(), "Inconsitency!"); |
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3233 if ((!verifying() || unloaded_classes_last_cycle()) && should_verify) { |
0 | 3234 // Include symbols, strings and code cache elements to prevent their resurrection. |
3235 add_root_scanning_option(rso); | |
3236 set_verifying(true); | |
3237 } else if (verifying() && !should_verify) { | |
3238 // We were verifying, but some verification flags got disabled. | |
3239 set_verifying(false); | |
3240 // Exclude symbols, strings and code cache elements from root scanning to | |
3241 // reduce IM and RM pauses. | |
3242 remove_root_scanning_option(rso); | |
3243 } | |
3244 } | |
3245 | |
3246 | |
3247 #ifndef PRODUCT | |
3248 HeapWord* CMSCollector::block_start(const void* p) const { | |
3249 const HeapWord* addr = (HeapWord*)p; | |
3250 if (_span.contains(p)) { | |
3251 if (_cmsGen->cmsSpace()->is_in_reserved(addr)) { | |
3252 return _cmsGen->cmsSpace()->block_start(p); | |
3253 } | |
3254 } | |
3255 return NULL; | |
3256 } | |
3257 #endif | |
3258 | |
3259 HeapWord* | |
3260 ConcurrentMarkSweepGeneration::expand_and_allocate(size_t word_size, | |
3261 bool tlab, | |
3262 bool parallel) { | |
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3263 CMSSynchronousYieldRequest yr; |
0 | 3264 assert(!tlab, "Can't deal with TLAB allocation"); |
3265 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
3266 expand(word_size*HeapWordSize, MinHeapDeltaBytes, | |
3267 CMSExpansionCause::_satisfy_allocation); | |
3268 if (GCExpandToAllocateDelayMillis > 0) { | |
3269 os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false); | |
3270 } | |
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3271 return have_lock_and_allocate(word_size, tlab); |
0 | 3272 } |
3273 | |
3274 // YSR: All of this generation expansion/shrinking stuff is an exact copy of | |
3275 // OneContigSpaceCardGeneration, which makes me wonder if we should move this | |
3276 // to CardGeneration and share it... | |
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3277 bool ConcurrentMarkSweepGeneration::expand(size_t bytes, size_t expand_bytes) { |
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3278 return CardGeneration::expand(bytes, expand_bytes); |
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3279 } |
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3280 |
0 | 3281 void ConcurrentMarkSweepGeneration::expand(size_t bytes, size_t expand_bytes, |
3282 CMSExpansionCause::Cause cause) | |
3283 { | |
271
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3284 |
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3285 bool success = expand(bytes, expand_bytes); |
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3286 |
0 | 3287 // remember why we expanded; this information is used |
3288 // by shouldConcurrentCollect() when making decisions on whether to start | |
3289 // a new CMS cycle. | |
3290 if (success) { | |
3291 set_expansion_cause(cause); | |
3292 if (PrintGCDetails && Verbose) { | |
3293 gclog_or_tty->print_cr("Expanded CMS gen for %s", | |
3294 CMSExpansionCause::to_string(cause)); | |
3295 } | |
3296 } | |
3297 } | |
3298 | |
3299 HeapWord* ConcurrentMarkSweepGeneration::expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz) { | |
3300 HeapWord* res = NULL; | |
3301 MutexLocker x(ParGCRareEvent_lock); | |
3302 while (true) { | |
3303 // Expansion by some other thread might make alloc OK now: | |
3304 res = ps->lab.alloc(word_sz); | |
3305 if (res != NULL) return res; | |
3306 // If there's not enough expansion space available, give up. | |
3307 if (_virtual_space.uncommitted_size() < (word_sz * HeapWordSize)) { | |
3308 return NULL; | |
3309 } | |
3310 // Otherwise, we try expansion. | |
3311 expand(word_sz*HeapWordSize, MinHeapDeltaBytes, | |
3312 CMSExpansionCause::_allocate_par_lab); | |
3313 // Now go around the loop and try alloc again; | |
3314 // A competing par_promote might beat us to the expansion space, | |
3315 // so we may go around the loop again if promotion fails agaion. | |
3316 if (GCExpandToAllocateDelayMillis > 0) { | |
3317 os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false); | |
3318 } | |
3319 } | |
3320 } | |
3321 | |
3322 | |
3323 bool ConcurrentMarkSweepGeneration::expand_and_ensure_spooling_space( | |
3324 PromotionInfo* promo) { | |
3325 MutexLocker x(ParGCRareEvent_lock); | |
3326 size_t refill_size_bytes = promo->refillSize() * HeapWordSize; | |
3327 while (true) { | |
3328 // Expansion by some other thread might make alloc OK now: | |
3329 if (promo->ensure_spooling_space()) { | |
3330 assert(promo->has_spooling_space(), | |
3331 "Post-condition of successful ensure_spooling_space()"); | |
3332 return true; | |
3333 } | |
3334 // If there's not enough expansion space available, give up. | |
3335 if (_virtual_space.uncommitted_size() < refill_size_bytes) { | |
3336 return false; | |
3337 } | |
3338 // Otherwise, we try expansion. | |
3339 expand(refill_size_bytes, MinHeapDeltaBytes, | |
3340 CMSExpansionCause::_allocate_par_spooling_space); | |
3341 // Now go around the loop and try alloc again; | |
3342 // A competing allocation might beat us to the expansion space, | |
3343 // so we may go around the loop again if allocation fails again. | |
3344 if (GCExpandToAllocateDelayMillis > 0) { | |
3345 os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false); | |
3346 } | |
3347 } | |
3348 } | |
3349 | |
3350 | |
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3351 void ConcurrentMarkSweepGeneration::shrink_by(size_t bytes) { |
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3352 assert_locked_or_safepoint(ExpandHeap_lock); |
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3353 // Shrink committed space |
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3354 _virtual_space.shrink_by(bytes); |
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3355 // Shrink space; this also shrinks the space's BOT |
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3356 _cmsSpace->set_end((HeapWord*) _virtual_space.high()); |
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3357 size_t new_word_size = heap_word_size(_cmsSpace->capacity()); |
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3358 // Shrink the shared block offset array |
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3359 _bts->resize(new_word_size); |
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3360 MemRegion mr(_cmsSpace->bottom(), new_word_size); |
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3361 // Shrink the card table |
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3362 Universe::heap()->barrier_set()->resize_covered_region(mr); |
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3363 |
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3364 if (Verbose && PrintGC) { |
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3365 size_t new_mem_size = _virtual_space.committed_size(); |
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3366 size_t old_mem_size = new_mem_size + bytes; |
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3367 gclog_or_tty->print_cr("Shrinking %s from " SIZE_FORMAT "K to " SIZE_FORMAT "K", |
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3368 name(), old_mem_size/K, new_mem_size/K); |
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|
3369 } |
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3370 } |
0 | 3371 |
3372 void ConcurrentMarkSweepGeneration::shrink(size_t bytes) { | |
3373 assert_locked_or_safepoint(Heap_lock); | |
3374 size_t size = ReservedSpace::page_align_size_down(bytes); | |
3375 if (size > 0) { | |
3376 shrink_by(size); | |
3377 } | |
3378 } | |
3379 | |
3380 bool ConcurrentMarkSweepGeneration::grow_by(size_t bytes) { | |
3381 assert_locked_or_safepoint(Heap_lock); | |
3382 bool result = _virtual_space.expand_by(bytes); | |
3383 if (result) { | |
3384 size_t new_word_size = | |
3385 heap_word_size(_virtual_space.committed_size()); | |
3386 MemRegion mr(_cmsSpace->bottom(), new_word_size); | |
3387 _bts->resize(new_word_size); // resize the block offset shared array | |
3388 Universe::heap()->barrier_set()->resize_covered_region(mr); | |
3389 // Hmmmm... why doesn't CFLS::set_end verify locking? | |
3390 // This is quite ugly; FIX ME XXX | |
1145
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3391 _cmsSpace->assert_locked(freelistLock()); |
0 | 3392 _cmsSpace->set_end((HeapWord*)_virtual_space.high()); |
3393 | |
3394 // update the space and generation capacity counters | |
3395 if (UsePerfData) { | |
3396 _space_counters->update_capacity(); | |
3397 _gen_counters->update_all(); | |
3398 } | |
3399 | |
3400 if (Verbose && PrintGC) { | |
3401 size_t new_mem_size = _virtual_space.committed_size(); | |
3402 size_t old_mem_size = new_mem_size - bytes; | |
7623
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7102489: RFE: cleanup jlong typedef on __APPLE__and _LLP64 systems.
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3403 gclog_or_tty->print_cr("Expanding %s from " SIZE_FORMAT "K by " SIZE_FORMAT "K to " SIZE_FORMAT "K", |
0 | 3404 name(), old_mem_size/K, bytes/K, new_mem_size/K); |
3405 } | |
3406 } | |
3407 return result; | |
3408 } | |
3409 | |
3410 bool ConcurrentMarkSweepGeneration::grow_to_reserved() { | |
3411 assert_locked_or_safepoint(Heap_lock); | |
3412 bool success = true; | |
3413 const size_t remaining_bytes = _virtual_space.uncommitted_size(); | |
3414 if (remaining_bytes > 0) { | |
3415 success = grow_by(remaining_bytes); | |
3416 DEBUG_ONLY(if (!success) warning("grow to reserved failed");) | |
3417 } | |
3418 return success; | |
3419 } | |
3420 | |
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3421 void ConcurrentMarkSweepGeneration::shrink_free_list_by(size_t bytes) { |
0 | 3422 assert_locked_or_safepoint(Heap_lock); |
3423 assert_lock_strong(freelistLock()); | |
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3424 if (PrintGCDetails && Verbose) { |
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|
3425 warning("Shrinking of CMS not yet implemented"); |
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3426 } |
0 | 3427 return; |
3428 } | |
3429 | |
3430 | |
3431 // Simple ctor/dtor wrapper for accounting & timer chores around concurrent | |
3432 // phases. | |
3433 class CMSPhaseAccounting: public StackObj { | |
3434 public: | |
3435 CMSPhaseAccounting(CMSCollector *collector, | |
3436 const char *phase, | |
3437 bool print_cr = true); | |
3438 ~CMSPhaseAccounting(); | |
3439 | |
3440 private: | |
3441 CMSCollector *_collector; | |
3442 const char *_phase; | |
3443 elapsedTimer _wallclock; | |
3444 bool _print_cr; | |
3445 | |
3446 public: | |
3447 // Not MT-safe; so do not pass around these StackObj's | |
3448 // where they may be accessed by other threads. | |
3449 jlong wallclock_millis() { | |
3450 assert(_wallclock.is_active(), "Wall clock should not stop"); | |
3451 _wallclock.stop(); // to record time | |
3452 jlong ret = _wallclock.milliseconds(); | |
3453 _wallclock.start(); // restart | |
3454 return ret; | |
3455 } | |
3456 }; | |
3457 | |
3458 CMSPhaseAccounting::CMSPhaseAccounting(CMSCollector *collector, | |
3459 const char *phase, | |
3460 bool print_cr) : | |
3461 _collector(collector), _phase(phase), _print_cr(print_cr) { | |
3462 | |
3463 if (PrintCMSStatistics != 0) { | |
3464 _collector->resetYields(); | |
3465 } | |
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|
3466 if (PrintGCDetails) { |
0 | 3467 gclog_or_tty->date_stamp(PrintGCDateStamps); |
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3468 gclog_or_tty->stamp(PrintGCTimeStamps); |
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3469 gclog_or_tty->print_cr("[%s-concurrent-%s-start]", |
0 | 3470 _collector->cmsGen()->short_name(), _phase); |
3471 } | |
3472 _collector->resetTimer(); | |
3473 _wallclock.start(); | |
3474 _collector->startTimer(); | |
3475 } | |
3476 | |
3477 CMSPhaseAccounting::~CMSPhaseAccounting() { | |
3478 assert(_wallclock.is_active(), "Wall clock should not have stopped"); | |
3479 _collector->stopTimer(); | |
3480 _wallclock.stop(); | |
3481 if (PrintGCDetails) { | |
3482 gclog_or_tty->date_stamp(PrintGCDateStamps); | |
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3483 gclog_or_tty->stamp(PrintGCTimeStamps); |
0 | 3484 gclog_or_tty->print("[%s-concurrent-%s: %3.3f/%3.3f secs]", |
3485 _collector->cmsGen()->short_name(), | |
3486 _phase, _collector->timerValue(), _wallclock.seconds()); | |
3487 if (_print_cr) { | |
3488 gclog_or_tty->print_cr(""); | |
3489 } | |
3490 if (PrintCMSStatistics != 0) { | |
3491 gclog_or_tty->print_cr(" (CMS-concurrent-%s yielded %d times)", _phase, | |
3492 _collector->yields()); | |
3493 } | |
3494 } | |
3495 } | |
3496 | |
3497 // CMS work | |
3498 | |
3499 // Checkpoint the roots into this generation from outside | |
3500 // this generation. [Note this initial checkpoint need only | |
3501 // be approximate -- we'll do a catch up phase subsequently.] | |
3502 void CMSCollector::checkpointRootsInitial(bool asynch) { | |
3503 assert(_collectorState == InitialMarking, "Wrong collector state"); | |
3504 check_correct_thread_executing(); | |
3356
78542e2b5e35
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|
3505 TraceCMSMemoryManagerStats tms(_collectorState,GenCollectedHeap::heap()->gc_cause()); |
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|
3506 |
0 | 3507 ReferenceProcessor* rp = ref_processor(); |
3508 SpecializationStats::clear(); | |
3509 assert(_restart_addr == NULL, "Control point invariant"); | |
3510 if (asynch) { | |
3511 // acquire locks for subsequent manipulations | |
3512 MutexLockerEx x(bitMapLock(), | |
3513 Mutex::_no_safepoint_check_flag); | |
3514 checkpointRootsInitialWork(asynch); | |
3979
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3515 // enable ("weak") refs discovery |
4dfb2df418f2
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|
3516 rp->enable_discovery(true /*verify_disabled*/, true /*check_no_refs*/); |
0 | 3517 _collectorState = Marking; |
3518 } else { | |
3519 // (Weak) Refs discovery: this is controlled from genCollectedHeap::do_collection | |
3520 // which recognizes if we are a CMS generation, and doesn't try to turn on | |
3521 // discovery; verify that they aren't meddling. | |
3522 assert(!rp->discovery_is_atomic(), | |
3523 "incorrect setting of discovery predicate"); | |
3524 assert(!rp->discovery_enabled(), "genCollectedHeap shouldn't control " | |
3525 "ref discovery for this generation kind"); | |
3526 // already have locks | |
3527 checkpointRootsInitialWork(asynch); | |
3979
4dfb2df418f2
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3528 // now enable ("weak") refs discovery |
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|
3529 rp->enable_discovery(true /*verify_disabled*/, false /*verify_no_refs*/); |
0 | 3530 _collectorState = Marking; |
3531 } | |
3532 SpecializationStats::print(); | |
3533 } | |
3534 | |
3535 void CMSCollector::checkpointRootsInitialWork(bool asynch) { | |
3536 assert(SafepointSynchronize::is_at_safepoint(), "world should be stopped"); | |
3537 assert(_collectorState == InitialMarking, "just checking"); | |
3538 | |
3539 // If there has not been a GC[n-1] since last GC[n] cycle completed, | |
3540 // precede our marking with a collection of all | |
3541 // younger generations to keep floating garbage to a minimum. | |
3542 // XXX: we won't do this for now -- it's an optimization to be done later. | |
3543 | |
3544 // already have locks | |
3545 assert_lock_strong(bitMapLock()); | |
3546 assert(_markBitMap.isAllClear(), "was reset at end of previous cycle"); | |
3547 | |
3548 // Setup the verification and class unloading state for this | |
3549 // CMS collection cycle. | |
3550 setup_cms_unloading_and_verification_state(); | |
3551 | |
3552 NOT_PRODUCT(TraceTime t("\ncheckpointRootsInitialWork", | |
3553 PrintGCDetails && Verbose, true, gclog_or_tty);) | |
3554 if (UseAdaptiveSizePolicy) { | |
3555 size_policy()->checkpoint_roots_initial_begin(); | |
3556 } | |
3557 | |
3558 // Reset all the PLAB chunk arrays if necessary. | |
3559 if (_survivor_plab_array != NULL && !CMSPLABRecordAlways) { | |
3560 reset_survivor_plab_arrays(); | |
3561 } | |
3562 | |
3563 ResourceMark rm; | |
3564 HandleMark hm; | |
3565 | |
3566 FalseClosure falseClosure; | |
3567 // In the case of a synchronous collection, we will elide the | |
3568 // remark step, so it's important to catch all the nmethod oops | |
994
753cf9794df9
6885169: merge of 4957990 and 6863023 causes conflict on do_nmethods
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3569 // in this step. |
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3570 // The final 'true' flag to gen_process_strong_roots will ensure this. |
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3571 // If 'async' is true, we can relax the nmethod tracing. |
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3572 MarkRefsIntoClosure notOlder(_span, &_markBitMap); |
0 | 3573 GenCollectedHeap* gch = GenCollectedHeap::heap(); |
3574 | |
3575 verify_work_stacks_empty(); | |
3576 verify_overflow_empty(); | |
3577 | |
3578 gch->ensure_parsability(false); // fill TLABs, but no need to retire them | |
3579 // Update the saved marks which may affect the root scans. | |
3580 gch->save_marks(); | |
3581 | |
3582 // weak reference processing has not started yet. | |
3583 ref_processor()->set_enqueuing_is_done(false); | |
3584 | |
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6964458: Reimplement class meta-data storage to use native memory
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3585 // Need to remember all newly created CLDs, |
da91efe96a93
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3586 // so that we can guarantee that the remark finds them. |
da91efe96a93
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diff
changeset
|
3587 ClassLoaderDataGraph::remember_new_clds(true); |
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diff
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|
3588 |
da91efe96a93
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|
3589 // Whenever a CLD is found, it will be claimed before proceeding to mark |
da91efe96a93
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diff
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3590 // the klasses. The claimed marks need to be cleared before marking starts. |
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6964458: Reimplement class meta-data storage to use native memory
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|
3591 ClassLoaderDataGraph::clear_claimed_marks(); |
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|
3592 |
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|
3593 CMKlassClosure klass_closure(¬Older); |
0 | 3594 { |
3595 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;) | |
3596 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. | |
3597 gch->gen_process_strong_roots(_cmsGen->level(), | |
3598 true, // younger gens are roots | |
989
148e5441d916
6863023: need non-perm oops in code cache for JSR 292
jrose
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diff
changeset
|
3599 true, // activate StrongRootsScope |
6725
da91efe96a93
6964458: Reimplement class meta-data storage to use native memory
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diff
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|
3600 false, // not scavenging |
0 | 3601 SharedHeap::ScanningOption(roots_scanning_options()), |
989
148e5441d916
6863023: need non-perm oops in code cache for JSR 292
jrose
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|
3602 ¬Older, |
148e5441d916
6863023: need non-perm oops in code cache for JSR 292
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diff
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|
3603 true, // walk all of code cache if (so & SO_CodeCache) |
6725
da91efe96a93
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|
3604 NULL, |
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|
3605 &klass_closure); |
0 | 3606 } |
3607 | |
3608 // Clear mod-union table; it will be dirtied in the prologue of | |
3609 // CMS generation per each younger generation collection. | |
3610 | |
3611 assert(_modUnionTable.isAllClear(), | |
3612 "Was cleared in most recent final checkpoint phase" | |
3613 " or no bits are set in the gc_prologue before the start of the next " | |
3614 "subsequent marking phase."); | |
3615 | |
6725
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|
3616 assert(_ct->klass_rem_set()->mod_union_is_clear(), "Must be"); |
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|
3617 |
0 | 3618 // Save the end of the used_region of the constituent generations |
3619 // to be used to limit the extent of sweep in each generation. | |
3620 save_sweep_limits(); | |
3621 if (UseAdaptiveSizePolicy) { | |
3622 size_policy()->checkpoint_roots_initial_end(gch->gc_cause()); | |
3623 } | |
3624 verify_overflow_empty(); | |
3625 } | |
3626 | |
3627 bool CMSCollector::markFromRoots(bool asynch) { | |
3628 // we might be tempted to assert that: | |
3629 // assert(asynch == !SafepointSynchronize::is_at_safepoint(), | |
3630 // "inconsistent argument?"); | |
3631 // However that wouldn't be right, because it's possible that | |
3632 // a safepoint is indeed in progress as a younger generation | |
3633 // stop-the-world GC happens even as we mark in this generation. | |
3634 assert(_collectorState == Marking, "inconsistent state?"); | |
3635 check_correct_thread_executing(); | |
3636 verify_overflow_empty(); | |
3637 | |
3638 bool res; | |
3639 if (asynch) { | |
3640 | |
3641 // Start the timers for adaptive size policy for the concurrent phases | |
3642 // Do it here so that the foreground MS can use the concurrent | |
3643 // timer since a foreground MS might has the sweep done concurrently | |
3644 // or STW. | |
3645 if (UseAdaptiveSizePolicy) { | |
3646 size_policy()->concurrent_marking_begin(); | |
3647 } | |
3648 | |
3649 // Weak ref discovery note: We may be discovering weak | |
3650 // refs in this generation concurrent (but interleaved) with | |
3651 // weak ref discovery by a younger generation collector. | |
3652 | |
3653 CMSTokenSyncWithLocks ts(true, bitMapLock()); | |
3654 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
3655 CMSPhaseAccounting pa(this, "mark", !PrintGCDetails); | |
3656 res = markFromRootsWork(asynch); | |
3657 if (res) { | |
3658 _collectorState = Precleaning; | |
3659 } else { // We failed and a foreground collection wants to take over | |
3660 assert(_foregroundGCIsActive, "internal state inconsistency"); | |
3661 assert(_restart_addr == NULL, "foreground will restart from scratch"); | |
3662 if (PrintGCDetails) { | |
3663 gclog_or_tty->print_cr("bailing out to foreground collection"); | |
3664 } | |
3665 } | |
3666 if (UseAdaptiveSizePolicy) { | |
3667 size_policy()->concurrent_marking_end(); | |
3668 } | |
3669 } else { | |
3670 assert(SafepointSynchronize::is_at_safepoint(), | |
3671 "inconsistent with asynch == false"); | |
3672 if (UseAdaptiveSizePolicy) { | |
3673 size_policy()->ms_collection_marking_begin(); | |
3674 } | |
3675 // already have locks | |
3676 res = markFromRootsWork(asynch); | |
3677 _collectorState = FinalMarking; | |
3678 if (UseAdaptiveSizePolicy) { | |
3679 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
3680 size_policy()->ms_collection_marking_end(gch->gc_cause()); | |
3681 } | |
3682 } | |
3683 verify_overflow_empty(); | |
3684 return res; | |
3685 } | |
3686 | |
3687 bool CMSCollector::markFromRootsWork(bool asynch) { | |
3688 // iterate over marked bits in bit map, doing a full scan and mark | |
3689 // from these roots using the following algorithm: | |
3690 // . if oop is to the right of the current scan pointer, | |
3691 // mark corresponding bit (we'll process it later) | |
3692 // . else (oop is to left of current scan pointer) | |
3693 // push oop on marking stack | |
3694 // . drain the marking stack | |
3695 | |
3696 // Note that when we do a marking step we need to hold the | |
3697 // bit map lock -- recall that direct allocation (by mutators) | |
3698 // and promotion (by younger generation collectors) is also | |
3699 // marking the bit map. [the so-called allocate live policy.] | |
3700 // Because the implementation of bit map marking is not | |
3701 // robust wrt simultaneous marking of bits in the same word, | |
3702 // we need to make sure that there is no such interference | |
3703 // between concurrent such updates. | |
3704 | |
3705 // already have locks | |
3706 assert_lock_strong(bitMapLock()); | |
3707 | |
3708 verify_work_stacks_empty(); | |
3709 verify_overflow_empty(); | |
3710 bool result = false; | |
1284 | 3711 if (CMSConcurrentMTEnabled && ConcGCThreads > 0) { |
0 | 3712 result = do_marking_mt(asynch); |
3713 } else { | |
3714 result = do_marking_st(asynch); | |
3715 } | |
3716 return result; | |
3717 } | |
3718 | |
3719 // Forward decl | |
3720 class CMSConcMarkingTask; | |
3721 | |
3722 class CMSConcMarkingTerminator: public ParallelTaskTerminator { | |
3723 CMSCollector* _collector; | |
3724 CMSConcMarkingTask* _task; | |
1837
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3725 public: |
0 | 3726 virtual void yield(); |
1837
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3727 |
0 | 3728 // "n_threads" is the number of threads to be terminated. |
3729 // "queue_set" is a set of work queues of other threads. | |
3730 // "collector" is the CMS collector associated with this task terminator. | |
3731 // "yield" indicates whether we need the gang as a whole to yield. | |
1837
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|
3732 CMSConcMarkingTerminator(int n_threads, TaskQueueSetSuper* queue_set, CMSCollector* collector) : |
0 | 3733 ParallelTaskTerminator(n_threads, queue_set), |
1837
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|
3734 _collector(collector) { } |
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3735 |
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3736 void set_task(CMSConcMarkingTask* task) { |
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3737 _task = task; |
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6692906: CMS: parallel concurrent marking may be prone to hanging or stalling mutators for periods of time
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|
3738 } |
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6692906: CMS: parallel concurrent marking may be prone to hanging or stalling mutators for periods of time
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|
3739 }; |
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3740 |
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3741 class CMSConcMarkingTerminatorTerminator: public TerminatorTerminator { |
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3742 CMSConcMarkingTask* _task; |
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3743 public: |
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3744 bool should_exit_termination(); |
0 | 3745 void set_task(CMSConcMarkingTask* task) { |
3746 _task = task; | |
3747 } | |
3748 }; | |
3749 | |
3750 // MT Concurrent Marking Task | |
3751 class CMSConcMarkingTask: public YieldingFlexibleGangTask { | |
3752 CMSCollector* _collector; | |
3753 int _n_workers; // requested/desired # workers | |
3754 bool _asynch; | |
3755 bool _result; | |
3756 CompactibleFreeListSpace* _cms_space; | |
1837
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3757 char _pad_front[64]; // padding to ... |
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3758 HeapWord* _global_finger; // ... avoid sharing cache line |
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3759 char _pad_back[64]; |
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3760 HeapWord* _restart_addr; |
0 | 3761 |
3762 // Exposed here for yielding support | |
3763 Mutex* const _bit_map_lock; | |
3764 | |
3765 // The per thread work queues, available here for stealing | |
3766 OopTaskQueueSet* _task_queues; | |
1837
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3767 |
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3768 // Termination (and yielding) support |
0 | 3769 CMSConcMarkingTerminator _term; |
1837
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3770 CMSConcMarkingTerminatorTerminator _term_term; |
0 | 3771 |
3772 public: | |
3773 CMSConcMarkingTask(CMSCollector* collector, | |
3774 CompactibleFreeListSpace* cms_space, | |
1833
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3775 bool asynch, |
0 | 3776 YieldingFlexibleWorkGang* workers, |
3777 OopTaskQueueSet* task_queues): | |
3778 YieldingFlexibleGangTask("Concurrent marking done multi-threaded"), | |
3779 _collector(collector), | |
3780 _cms_space(cms_space), | |
1833
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3781 _asynch(asynch), _n_workers(0), _result(true), |
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3782 _task_queues(task_queues), |
1837
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3783 _term(_n_workers, task_queues, _collector), |
0 | 3784 _bit_map_lock(collector->bitMapLock()) |
3785 { | |
1833
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3786 _requested_size = _n_workers; |
0 | 3787 _term.set_task(this); |
1837
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3788 _term_term.set_task(this); |
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3789 _restart_addr = _global_finger = _cms_space->bottom(); |
0 | 3790 } |
3791 | |
3792 | |
3793 OopTaskQueueSet* task_queues() { return _task_queues; } | |
3794 | |
3795 OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); } | |
3796 | |
3797 HeapWord** global_finger_addr() { return &_global_finger; } | |
3798 | |
3799 CMSConcMarkingTerminator* terminator() { return &_term; } | |
3800 | |
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3801 virtual void set_for_termination(int active_workers) { |
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3802 terminator()->reset_for_reuse(active_workers); |
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3803 } |
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3804 |
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3805 void work(uint worker_id); |
1837
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3806 bool should_yield() { |
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3807 return ConcurrentMarkSweepThread::should_yield() |
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3808 && !_collector->foregroundGCIsActive() |
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3809 && _asynch; |
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3810 } |
0 | 3811 |
3812 virtual void coordinator_yield(); // stuff done by coordinator | |
3813 bool result() { return _result; } | |
3814 | |
3815 void reset(HeapWord* ra) { | |
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3816 assert(_global_finger >= _cms_space->end(), "Postcondition of ::work(i)"); |
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3817 _restart_addr = _global_finger = ra; |
0 | 3818 _term.reset_for_reuse(); |
3819 } | |
3820 | |
3821 static bool get_work_from_overflow_stack(CMSMarkStack* ovflw_stk, | |
3822 OopTaskQueue* work_q); | |
3823 | |
3824 private: | |
3825 void do_scan_and_mark(int i, CompactibleFreeListSpace* sp); | |
3826 void do_work_steal(int i); | |
3827 void bump_global_finger(HeapWord* f); | |
3828 }; | |
3829 | |
1837
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3830 bool CMSConcMarkingTerminatorTerminator::should_exit_termination() { |
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3831 assert(_task != NULL, "Error"); |
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3832 return _task->yielding(); |
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3833 // Note that we do not need the disjunct || _task->should_yield() above |
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3834 // because we want terminating threads to yield only if the task |
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3835 // is already in the midst of yielding, which happens only after at least one |
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3836 // thread has yielded. |
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3837 } |
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3838 |
0 | 3839 void CMSConcMarkingTerminator::yield() { |
1837
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3840 if (_task->should_yield()) { |
0 | 3841 _task->yield(); |
3842 } else { | |
3843 ParallelTaskTerminator::yield(); | |
3844 } | |
3845 } | |
3846 | |
3847 //////////////////////////////////////////////////////////////// | |
3848 // Concurrent Marking Algorithm Sketch | |
3849 //////////////////////////////////////////////////////////////// | |
3850 // Until all tasks exhausted (both spaces): | |
3851 // -- claim next available chunk | |
3852 // -- bump global finger via CAS | |
3853 // -- find first object that starts in this chunk | |
3854 // and start scanning bitmap from that position | |
3855 // -- scan marked objects for oops | |
3856 // -- CAS-mark target, and if successful: | |
3857 // . if target oop is above global finger (volatile read) | |
3858 // nothing to do | |
3859 // . if target oop is in chunk and above local finger | |
3860 // then nothing to do | |
3861 // . else push on work-queue | |
3862 // -- Deal with possible overflow issues: | |
3863 // . local work-queue overflow causes stuff to be pushed on | |
3864 // global (common) overflow queue | |
3865 // . always first empty local work queue | |
3866 // . then get a batch of oops from global work queue if any | |
3867 // . then do work stealing | |
3868 // -- When all tasks claimed (both spaces) | |
3869 // and local work queue empty, | |
3870 // then in a loop do: | |
3871 // . check global overflow stack; steal a batch of oops and trace | |
3872 // . try to steal from other threads oif GOS is empty | |
3873 // . if neither is available, offer termination | |
3874 // -- Terminate and return result | |
3875 // | |
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3876 void CMSConcMarkingTask::work(uint worker_id) { |
0 | 3877 elapsedTimer _timer; |
3878 ResourceMark rm; | |
3879 HandleMark hm; | |
3880 | |
3881 DEBUG_ONLY(_collector->verify_overflow_empty();) | |
3882 | |
3883 // Before we begin work, our work queue should be empty | |
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3884 assert(work_queue(worker_id)->size() == 0, "Expected to be empty"); |
0 | 3885 // Scan the bitmap covering _cms_space, tracing through grey objects. |
3886 _timer.start(); | |
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3887 do_scan_and_mark(worker_id, _cms_space); |
0 | 3888 _timer.stop(); |
3889 if (PrintCMSStatistics != 0) { | |
3890 gclog_or_tty->print_cr("Finished cms space scanning in %dth thread: %3.3f sec", | |
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3891 worker_id, _timer.seconds()); |
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3892 // XXX: need xxx/xxx type of notation, two timers |
0 | 3893 } |
3894 | |
3895 // ... do work stealing | |
3896 _timer.reset(); | |
3897 _timer.start(); | |
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3898 do_work_steal(worker_id); |
0 | 3899 _timer.stop(); |
3900 if (PrintCMSStatistics != 0) { | |
3901 gclog_or_tty->print_cr("Finished work stealing in %dth thread: %3.3f sec", | |
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3902 worker_id, _timer.seconds()); |
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3903 // XXX: need xxx/xxx type of notation, two timers |
0 | 3904 } |
3905 assert(_collector->_markStack.isEmpty(), "Should have been emptied"); | |
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3906 assert(work_queue(worker_id)->size() == 0, "Should have been emptied"); |
0 | 3907 // Note that under the current task protocol, the |
3908 // following assertion is true even of the spaces | |
3909 // expanded since the completion of the concurrent | |
3910 // marking. XXX This will likely change under a strict | |
3911 // ABORT semantics. | |
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3912 // After perm removal the comparison was changed to |
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3913 // greater than or equal to from strictly greater than. |
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3914 // Before perm removal the highest address sweep would |
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3915 // have been at the end of perm gen but now is at the |
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3916 // end of the tenured gen. |
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3917 assert(_global_finger >= _cms_space->end(), |
0 | 3918 "All tasks have been completed"); |
3919 DEBUG_ONLY(_collector->verify_overflow_empty();) | |
3920 } | |
3921 | |
3922 void CMSConcMarkingTask::bump_global_finger(HeapWord* f) { | |
3923 HeapWord* read = _global_finger; | |
3924 HeapWord* cur = read; | |
3925 while (f > read) { | |
3926 cur = read; | |
3927 read = (HeapWord*) Atomic::cmpxchg_ptr(f, &_global_finger, cur); | |
3928 if (cur == read) { | |
3929 // our cas succeeded | |
3930 assert(_global_finger >= f, "protocol consistency"); | |
3931 break; | |
3932 } | |
3933 } | |
3934 } | |
3935 | |
3936 // This is really inefficient, and should be redone by | |
3937 // using (not yet available) block-read and -write interfaces to the | |
3938 // stack and the work_queue. XXX FIX ME !!! | |
3939 bool CMSConcMarkingTask::get_work_from_overflow_stack(CMSMarkStack* ovflw_stk, | |
3940 OopTaskQueue* work_q) { | |
3941 // Fast lock-free check | |
3942 if (ovflw_stk->length() == 0) { | |
3943 return false; | |
3944 } | |
3945 assert(work_q->size() == 0, "Shouldn't steal"); | |
3946 MutexLockerEx ml(ovflw_stk->par_lock(), | |
3947 Mutex::_no_safepoint_check_flag); | |
3948 // Grab up to 1/4 the size of the work queue | |
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3949 size_t num = MIN2((size_t)(work_q->max_elems() - work_q->size())/4, |
0 | 3950 (size_t)ParGCDesiredObjsFromOverflowList); |
3951 num = MIN2(num, ovflw_stk->length()); | |
3952 for (int i = (int) num; i > 0; i--) { | |
3953 oop cur = ovflw_stk->pop(); | |
3954 assert(cur != NULL, "Counted wrong?"); | |
3955 work_q->push(cur); | |
3956 } | |
3957 return num > 0; | |
3958 } | |
3959 | |
3960 void CMSConcMarkingTask::do_scan_and_mark(int i, CompactibleFreeListSpace* sp) { | |
3961 SequentialSubTasksDone* pst = sp->conc_par_seq_tasks(); | |
3962 int n_tasks = pst->n_tasks(); | |
3963 // We allow that there may be no tasks to do here because | |
3964 // we are restarting after a stack overflow. | |
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3965 assert(pst->valid() || n_tasks == 0, "Uninitialized use?"); |
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3966 uint nth_task = 0; |
0 | 3967 |
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3968 HeapWord* aligned_start = sp->bottom(); |
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3969 if (sp->used_region().contains(_restart_addr)) { |
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3970 // Align down to a card boundary for the start of 0th task |
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3971 // for this space. |
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3972 aligned_start = |
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3973 (HeapWord*)align_size_down((uintptr_t)_restart_addr, |
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3974 CardTableModRefBS::card_size); |
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3975 } |
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3976 |
0 | 3977 size_t chunk_size = sp->marking_task_size(); |
3978 while (!pst->is_task_claimed(/* reference */ nth_task)) { | |
3979 // Having claimed the nth task in this space, | |
3980 // compute the chunk that it corresponds to: | |
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3981 MemRegion span = MemRegion(aligned_start + nth_task*chunk_size, |
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3982 aligned_start + (nth_task+1)*chunk_size); |
0 | 3983 // Try and bump the global finger via a CAS; |
3984 // note that we need to do the global finger bump | |
3985 // _before_ taking the intersection below, because | |
3986 // the task corresponding to that region will be | |
3987 // deemed done even if the used_region() expands | |
3988 // because of allocation -- as it almost certainly will | |
3989 // during start-up while the threads yield in the | |
3990 // closure below. | |
3991 HeapWord* finger = span.end(); | |
3992 bump_global_finger(finger); // atomically | |
3993 // There are null tasks here corresponding to chunks | |
3994 // beyond the "top" address of the space. | |
3995 span = span.intersection(sp->used_region()); | |
3996 if (!span.is_empty()) { // Non-null task | |
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3997 HeapWord* prev_obj; |
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3998 assert(!span.contains(_restart_addr) || nth_task == 0, |
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3999 "Inconsistency"); |
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4000 if (nth_task == 0) { |
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4001 // For the 0th task, we'll not need to compute a block_start. |
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4002 if (span.contains(_restart_addr)) { |
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4003 // In the case of a restart because of stack overflow, |
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4004 // we might additionally skip a chunk prefix. |
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4005 prev_obj = _restart_addr; |
0 | 4006 } else { |
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4007 prev_obj = span.start(); |
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4008 } |
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4009 } else { |
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4010 // We want to skip the first object because |
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4011 // the protocol is to scan any object in its entirety |
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4012 // that _starts_ in this span; a fortiori, any |
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4013 // object starting in an earlier span is scanned |
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4014 // as part of an earlier claimed task. |
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4015 // Below we use the "careful" version of block_start |
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4016 // so we do not try to navigate uninitialized objects. |
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4017 prev_obj = sp->block_start_careful(span.start()); |
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4018 // Below we use a variant of block_size that uses the |
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4019 // Printezis bits to avoid waiting for allocated |
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4020 // objects to become initialized/parsable. |
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4021 while (prev_obj < span.start()) { |
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4022 size_t sz = sp->block_size_no_stall(prev_obj, _collector); |
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4023 if (sz > 0) { |
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4024 prev_obj += sz; |
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4025 } else { |
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4026 // In this case we may end up doing a bit of redundant |
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4027 // scanning, but that appears unavoidable, short of |
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4028 // locking the free list locks; see bug 6324141. |
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4029 break; |
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4030 } |
0 | 4031 } |
4032 } | |
4033 if (prev_obj < span.end()) { | |
4034 MemRegion my_span = MemRegion(prev_obj, span.end()); | |
4035 // Do the marking work within a non-empty span -- | |
4036 // the last argument to the constructor indicates whether the | |
4037 // iteration should be incremental with periodic yields. | |
4038 Par_MarkFromRootsClosure cl(this, _collector, my_span, | |
4039 &_collector->_markBitMap, | |
4040 work_queue(i), | |
4041 &_collector->_markStack, | |
4042 _asynch); | |
4043 _collector->_markBitMap.iterate(&cl, my_span.start(), my_span.end()); | |
4044 } // else nothing to do for this task | |
4045 } // else nothing to do for this task | |
4046 } | |
4047 // We'd be tempted to assert here that since there are no | |
4048 // more tasks left to claim in this space, the global_finger | |
4049 // must exceed space->top() and a fortiori space->end(). However, | |
4050 // that would not quite be correct because the bumping of | |
4051 // global_finger occurs strictly after the claiming of a task, | |
4052 // so by the time we reach here the global finger may not yet | |
4053 // have been bumped up by the thread that claimed the last | |
4054 // task. | |
4055 pst->all_tasks_completed(); | |
4056 } | |
4057 | |
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4058 class Par_ConcMarkingClosure: public CMSOopClosure { |
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4059 private: |
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4060 CMSCollector* _collector; |
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4061 CMSConcMarkingTask* _task; |
0 | 4062 MemRegion _span; |
4063 CMSBitMap* _bit_map; | |
4064 CMSMarkStack* _overflow_stack; | |
4065 OopTaskQueue* _work_queue; | |
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4066 protected: |
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4067 DO_OOP_WORK_DEFN |
0 | 4068 public: |
1837
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4069 Par_ConcMarkingClosure(CMSCollector* collector, CMSConcMarkingTask* task, OopTaskQueue* work_queue, |
6725
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4070 CMSBitMap* bit_map, CMSMarkStack* overflow_stack): |
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4071 CMSOopClosure(collector->ref_processor()), |
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4072 _collector(collector), |
1837
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4073 _task(task), |
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4074 _span(collector->_span), |
0 | 4075 _work_queue(work_queue), |
4076 _bit_map(bit_map), | |
935 | 4077 _overflow_stack(overflow_stack) |
4078 { } | |
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4079 virtual void do_oop(oop* p); |
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4080 virtual void do_oop(narrowOop* p); |
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4081 |
0 | 4082 void trim_queue(size_t max); |
4083 void handle_stack_overflow(HeapWord* lost); | |
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4084 void do_yield_check() { |
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4085 if (_task->should_yield()) { |
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4086 _task->yield(); |
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4087 } |
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4088 } |
0 | 4089 }; |
4090 | |
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4091 // Grey object scanning during work stealing phase -- |
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4092 // the salient assumption here is that any references |
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4093 // that are in these stolen objects being scanned must |
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4094 // already have been initialized (else they would not have |
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4095 // been published), so we do not need to check for |
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4096 // uninitialized objects before pushing here. |
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4097 void Par_ConcMarkingClosure::do_oop(oop obj) { |
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4098 assert(obj->is_oop_or_null(true), "expected an oop or NULL"); |
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4099 HeapWord* addr = (HeapWord*)obj; |
0 | 4100 // Check if oop points into the CMS generation |
4101 // and is not marked | |
4102 if (_span.contains(addr) && !_bit_map->isMarked(addr)) { | |
4103 // a white object ... | |
4104 // If we manage to "claim" the object, by being the | |
4105 // first thread to mark it, then we push it on our | |
4106 // marking stack | |
4107 if (_bit_map->par_mark(addr)) { // ... now grey | |
4108 // push on work queue (grey set) | |
4109 bool simulate_overflow = false; | |
4110 NOT_PRODUCT( | |
4111 if (CMSMarkStackOverflowALot && | |
4112 _collector->simulate_overflow()) { | |
4113 // simulate a stack overflow | |
4114 simulate_overflow = true; | |
4115 } | |
4116 ) | |
4117 if (simulate_overflow || | |
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4118 !(_work_queue->push(obj) || _overflow_stack->par_push(obj))) { |
0 | 4119 // stack overflow |
4120 if (PrintCMSStatistics != 0) { | |
4121 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
4122 SIZE_FORMAT, _overflow_stack->capacity()); | |
4123 } | |
4124 // We cannot assert that the overflow stack is full because | |
4125 // it may have been emptied since. | |
4126 assert(simulate_overflow || | |
4127 _work_queue->size() == _work_queue->max_elems(), | |
4128 "Else push should have succeeded"); | |
4129 handle_stack_overflow(addr); | |
4130 } | |
4131 } // Else, some other thread got there first | |
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4132 do_yield_check(); |
0 | 4133 } |
4134 } | |
4135 | |
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4136 void Par_ConcMarkingClosure::do_oop(oop* p) { Par_ConcMarkingClosure::do_oop_work(p); } |
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4137 void Par_ConcMarkingClosure::do_oop(narrowOop* p) { Par_ConcMarkingClosure::do_oop_work(p); } |
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4138 |
0 | 4139 void Par_ConcMarkingClosure::trim_queue(size_t max) { |
4140 while (_work_queue->size() > max) { | |
4141 oop new_oop; | |
4142 if (_work_queue->pop_local(new_oop)) { | |
4143 assert(new_oop->is_oop(), "Should be an oop"); | |
4144 assert(_bit_map->isMarked((HeapWord*)new_oop), "Grey object"); | |
4145 assert(_span.contains((HeapWord*)new_oop), "Not in span"); | |
4146 new_oop->oop_iterate(this); // do_oop() above | |
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4147 do_yield_check(); |
0 | 4148 } |
4149 } | |
4150 } | |
4151 | |
4152 // Upon stack overflow, we discard (part of) the stack, | |
4153 // remembering the least address amongst those discarded | |
4154 // in CMSCollector's _restart_address. | |
4155 void Par_ConcMarkingClosure::handle_stack_overflow(HeapWord* lost) { | |
4156 // We need to do this under a mutex to prevent other | |
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4157 // workers from interfering with the work done below. |
0 | 4158 MutexLockerEx ml(_overflow_stack->par_lock(), |
4159 Mutex::_no_safepoint_check_flag); | |
4160 // Remember the least grey address discarded | |
4161 HeapWord* ra = (HeapWord*)_overflow_stack->least_value(lost); | |
4162 _collector->lower_restart_addr(ra); | |
4163 _overflow_stack->reset(); // discard stack contents | |
4164 _overflow_stack->expand(); // expand the stack if possible | |
4165 } | |
4166 | |
4167 | |
4168 void CMSConcMarkingTask::do_work_steal(int i) { | |
4169 OopTaskQueue* work_q = work_queue(i); | |
4170 oop obj_to_scan; | |
4171 CMSBitMap* bm = &(_collector->_markBitMap); | |
4172 CMSMarkStack* ovflw = &(_collector->_markStack); | |
4173 int* seed = _collector->hash_seed(i); | |
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4174 Par_ConcMarkingClosure cl(_collector, this, work_q, bm, ovflw); |
0 | 4175 while (true) { |
4176 cl.trim_queue(0); | |
4177 assert(work_q->size() == 0, "Should have been emptied above"); | |
4178 if (get_work_from_overflow_stack(ovflw, work_q)) { | |
4179 // Can't assert below because the work obtained from the | |
4180 // overflow stack may already have been stolen from us. | |
4181 // assert(work_q->size() > 0, "Work from overflow stack"); | |
4182 continue; | |
4183 } else if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) { | |
4184 assert(obj_to_scan->is_oop(), "Should be an oop"); | |
4185 assert(bm->isMarked((HeapWord*)obj_to_scan), "Grey object"); | |
4186 obj_to_scan->oop_iterate(&cl); | |
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4187 } else if (terminator()->offer_termination(&_term_term)) { |
0 | 4188 assert(work_q->size() == 0, "Impossible!"); |
4189 break; | |
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4190 } else if (yielding() || should_yield()) { |
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4191 yield(); |
0 | 4192 } |
4193 } | |
4194 } | |
4195 | |
4196 // This is run by the CMS (coordinator) thread. | |
4197 void CMSConcMarkingTask::coordinator_yield() { | |
4198 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
4199 "CMS thread should hold CMS token"); | |
4200 // First give up the locks, then yield, then re-lock | |
4201 // We should probably use a constructor/destructor idiom to | |
4202 // do this unlock/lock or modify the MutexUnlocker class to | |
4203 // serve our purpose. XXX | |
4204 assert_lock_strong(_bit_map_lock); | |
4205 _bit_map_lock->unlock(); | |
4206 ConcurrentMarkSweepThread::desynchronize(true); | |
4207 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
4208 _collector->stopTimer(); | |
4209 if (PrintCMSStatistics != 0) { | |
4210 _collector->incrementYields(); | |
4211 } | |
4212 _collector->icms_wait(); | |
4213 | |
4214 // It is possible for whichever thread initiated the yield request | |
4215 // not to get a chance to wake up and take the bitmap lock between | |
4216 // this thread releasing it and reacquiring it. So, while the | |
4217 // should_yield() flag is on, let's sleep for a bit to give the | |
4218 // other thread a chance to wake up. The limit imposed on the number | |
4219 // of iterations is defensive, to avoid any unforseen circumstances | |
4220 // putting us into an infinite loop. Since it's always been this | |
4221 // (coordinator_yield()) method that was observed to cause the | |
4222 // problem, we are using a parameter (CMSCoordinatorYieldSleepCount) | |
4223 // which is by default non-zero. For the other seven methods that | |
4224 // also perform the yield operation, as are using a different | |
4225 // parameter (CMSYieldSleepCount) which is by default zero. This way we | |
4226 // can enable the sleeping for those methods too, if necessary. | |
4227 // See 6442774. | |
4228 // | |
4229 // We really need to reconsider the synchronization between the GC | |
4230 // thread and the yield-requesting threads in the future and we | |
4231 // should really use wait/notify, which is the recommended | |
4232 // way of doing this type of interaction. Additionally, we should | |
4233 // consolidate the eight methods that do the yield operation and they | |
4234 // are almost identical into one for better maintenability and | |
4235 // readability. See 6445193. | |
4236 // | |
4237 // Tony 2006.06.29 | |
4238 for (unsigned i = 0; i < CMSCoordinatorYieldSleepCount && | |
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4239 ConcurrentMarkSweepThread::should_yield() && |
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4240 !CMSCollector::foregroundGCIsActive(); ++i) { |
0 | 4241 os::sleep(Thread::current(), 1, false); |
4242 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
4243 } | |
4244 | |
4245 ConcurrentMarkSweepThread::synchronize(true); | |
4246 _bit_map_lock->lock_without_safepoint_check(); | |
4247 _collector->startTimer(); | |
4248 } | |
4249 | |
4250 bool CMSCollector::do_marking_mt(bool asynch) { | |
1284 | 4251 assert(ConcGCThreads > 0 && conc_workers() != NULL, "precondition"); |
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4252 int num_workers = AdaptiveSizePolicy::calc_active_conc_workers( |
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4253 conc_workers()->total_workers(), |
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4254 conc_workers()->active_workers(), |
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4255 Threads::number_of_non_daemon_threads()); |
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4256 conc_workers()->set_active_workers(num_workers); |
0 | 4257 |
4258 CompactibleFreeListSpace* cms_space = _cmsGen->cmsSpace(); | |
4259 | |
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4260 CMSConcMarkingTask tsk(this, |
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4261 cms_space, |
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4262 asynch, |
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4263 conc_workers(), |
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4264 task_queues()); |
0 | 4265 |
4266 // Since the actual number of workers we get may be different | |
4267 // from the number we requested above, do we need to do anything different | |
4268 // below? In particular, may be we need to subclass the SequantialSubTasksDone | |
4269 // class?? XXX | |
4270 cms_space ->initialize_sequential_subtasks_for_marking(num_workers); | |
4271 | |
4272 // Refs discovery is already non-atomic. | |
4273 assert(!ref_processor()->discovery_is_atomic(), "Should be non-atomic"); | |
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4274 assert(ref_processor()->discovery_is_mt(), "Discovery should be MT"); |
0 | 4275 conc_workers()->start_task(&tsk); |
4276 while (tsk.yielded()) { | |
4277 tsk.coordinator_yield(); | |
4278 conc_workers()->continue_task(&tsk); | |
4279 } | |
4280 // If the task was aborted, _restart_addr will be non-NULL | |
4281 assert(tsk.completed() || _restart_addr != NULL, "Inconsistency"); | |
4282 while (_restart_addr != NULL) { | |
4283 // XXX For now we do not make use of ABORTED state and have not | |
4284 // yet implemented the right abort semantics (even in the original | |
4285 // single-threaded CMS case). That needs some more investigation | |
4286 // and is deferred for now; see CR# TBF. 07252005YSR. XXX | |
4287 assert(!CMSAbortSemantics || tsk.aborted(), "Inconsistency"); | |
4288 // If _restart_addr is non-NULL, a marking stack overflow | |
605 | 4289 // occurred; we need to do a fresh marking iteration from the |
0 | 4290 // indicated restart address. |
4291 if (_foregroundGCIsActive && asynch) { | |
4292 // We may be running into repeated stack overflows, having | |
4293 // reached the limit of the stack size, while making very | |
4294 // slow forward progress. It may be best to bail out and | |
4295 // let the foreground collector do its job. | |
4296 // Clear _restart_addr, so that foreground GC | |
4297 // works from scratch. This avoids the headache of | |
4298 // a "rescan" which would otherwise be needed because | |
4299 // of the dirty mod union table & card table. | |
4300 _restart_addr = NULL; | |
4301 return false; | |
4302 } | |
4303 // Adjust the task to restart from _restart_addr | |
4304 tsk.reset(_restart_addr); | |
4305 cms_space ->initialize_sequential_subtasks_for_marking(num_workers, | |
4306 _restart_addr); | |
4307 _restart_addr = NULL; | |
4308 // Get the workers going again | |
4309 conc_workers()->start_task(&tsk); | |
4310 while (tsk.yielded()) { | |
4311 tsk.coordinator_yield(); | |
4312 conc_workers()->continue_task(&tsk); | |
4313 } | |
4314 } | |
4315 assert(tsk.completed(), "Inconsistency"); | |
4316 assert(tsk.result() == true, "Inconsistency"); | |
4317 return true; | |
4318 } | |
4319 | |
4320 bool CMSCollector::do_marking_st(bool asynch) { | |
4321 ResourceMark rm; | |
4322 HandleMark hm; | |
4323 | |
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4324 // Temporarily make refs discovery single threaded (non-MT) |
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4325 ReferenceProcessorMTDiscoveryMutator rp_mut_discovery(ref_processor(), false); |
0 | 4326 MarkFromRootsClosure markFromRootsClosure(this, _span, &_markBitMap, |
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4327 &_markStack, CMSYield && asynch); |
0 | 4328 // the last argument to iterate indicates whether the iteration |
4329 // should be incremental with periodic yields. | |
4330 _markBitMap.iterate(&markFromRootsClosure); | |
4331 // If _restart_addr is non-NULL, a marking stack overflow | |
605 | 4332 // occurred; we need to do a fresh iteration from the |
0 | 4333 // indicated restart address. |
4334 while (_restart_addr != NULL) { | |
4335 if (_foregroundGCIsActive && asynch) { | |
4336 // We may be running into repeated stack overflows, having | |
4337 // reached the limit of the stack size, while making very | |
4338 // slow forward progress. It may be best to bail out and | |
4339 // let the foreground collector do its job. | |
4340 // Clear _restart_addr, so that foreground GC | |
4341 // works from scratch. This avoids the headache of | |
4342 // a "rescan" which would otherwise be needed because | |
4343 // of the dirty mod union table & card table. | |
4344 _restart_addr = NULL; | |
4345 return false; // indicating failure to complete marking | |
4346 } | |
4347 // Deal with stack overflow: | |
4348 // we restart marking from _restart_addr | |
4349 HeapWord* ra = _restart_addr; | |
4350 markFromRootsClosure.reset(ra); | |
4351 _restart_addr = NULL; | |
4352 _markBitMap.iterate(&markFromRootsClosure, ra, _span.end()); | |
4353 } | |
4354 return true; | |
4355 } | |
4356 | |
4357 void CMSCollector::preclean() { | |
4358 check_correct_thread_executing(); | |
4359 assert(Thread::current()->is_ConcurrentGC_thread(), "Wrong thread"); | |
4360 verify_work_stacks_empty(); | |
4361 verify_overflow_empty(); | |
4362 _abort_preclean = false; | |
4363 if (CMSPrecleaningEnabled) { | |
4364 _eden_chunk_index = 0; | |
4365 size_t used = get_eden_used(); | |
4366 size_t capacity = get_eden_capacity(); | |
4367 // Don't start sampling unless we will get sufficiently | |
4368 // many samples. | |
4369 if (used < (capacity/(CMSScheduleRemarkSamplingRatio * 100) | |
4370 * CMSScheduleRemarkEdenPenetration)) { | |
4371 _start_sampling = true; | |
4372 } else { | |
4373 _start_sampling = false; | |
4374 } | |
4375 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
4376 CMSPhaseAccounting pa(this, "preclean", !PrintGCDetails); | |
4377 preclean_work(CMSPrecleanRefLists1, CMSPrecleanSurvivors1); | |
4378 } | |
4379 CMSTokenSync x(true); // is cms thread | |
4380 if (CMSPrecleaningEnabled) { | |
4381 sample_eden(); | |
4382 _collectorState = AbortablePreclean; | |
4383 } else { | |
4384 _collectorState = FinalMarking; | |
4385 } | |
4386 verify_work_stacks_empty(); | |
4387 verify_overflow_empty(); | |
4388 } | |
4389 | |
4390 // Try and schedule the remark such that young gen | |
4391 // occupancy is CMSScheduleRemarkEdenPenetration %. | |
4392 void CMSCollector::abortable_preclean() { | |
4393 check_correct_thread_executing(); | |
4394 assert(CMSPrecleaningEnabled, "Inconsistent control state"); | |
4395 assert(_collectorState == AbortablePreclean, "Inconsistent control state"); | |
4396 | |
4397 // If Eden's current occupancy is below this threshold, | |
4398 // immediately schedule the remark; else preclean | |
4399 // past the next scavenge in an effort to | |
4400 // schedule the pause as described avove. By choosing | |
4401 // CMSScheduleRemarkEdenSizeThreshold >= max eden size | |
4402 // we will never do an actual abortable preclean cycle. | |
4403 if (get_eden_used() > CMSScheduleRemarkEdenSizeThreshold) { | |
4404 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
4405 CMSPhaseAccounting pa(this, "abortable-preclean", !PrintGCDetails); | |
4406 // We need more smarts in the abortable preclean | |
4407 // loop below to deal with cases where allocation | |
4408 // in young gen is very very slow, and our precleaning | |
4409 // is running a losing race against a horde of | |
4410 // mutators intent on flooding us with CMS updates | |
4411 // (dirty cards). | |
4412 // One, admittedly dumb, strategy is to give up | |
4413 // after a certain number of abortable precleaning loops | |
4414 // or after a certain maximum time. We want to make | |
4415 // this smarter in the next iteration. | |
4416 // XXX FIX ME!!! YSR | |
4417 size_t loops = 0, workdone = 0, cumworkdone = 0, waited = 0; | |
4418 while (!(should_abort_preclean() || | |
4419 ConcurrentMarkSweepThread::should_terminate())) { | |
4420 workdone = preclean_work(CMSPrecleanRefLists2, CMSPrecleanSurvivors2); | |
4421 cumworkdone += workdone; | |
4422 loops++; | |
4423 // Voluntarily terminate abortable preclean phase if we have | |
4424 // been at it for too long. | |
4425 if ((CMSMaxAbortablePrecleanLoops != 0) && | |
4426 loops >= CMSMaxAbortablePrecleanLoops) { | |
4427 if (PrintGCDetails) { | |
4428 gclog_or_tty->print(" CMS: abort preclean due to loops "); | |
4429 } | |
4430 break; | |
4431 } | |
4432 if (pa.wallclock_millis() > CMSMaxAbortablePrecleanTime) { | |
4433 if (PrintGCDetails) { | |
4434 gclog_or_tty->print(" CMS: abort preclean due to time "); | |
4435 } | |
4436 break; | |
4437 } | |
4438 // If we are doing little work each iteration, we should | |
4439 // take a short break. | |
4440 if (workdone < CMSAbortablePrecleanMinWorkPerIteration) { | |
4441 // Sleep for some time, waiting for work to accumulate | |
4442 stopTimer(); | |
4443 cmsThread()->wait_on_cms_lock(CMSAbortablePrecleanWaitMillis); | |
4444 startTimer(); | |
4445 waited++; | |
4446 } | |
4447 } | |
4448 if (PrintCMSStatistics > 0) { | |
4449 gclog_or_tty->print(" [%d iterations, %d waits, %d cards)] ", | |
4450 loops, waited, cumworkdone); | |
4451 } | |
4452 } | |
4453 CMSTokenSync x(true); // is cms thread | |
4454 if (_collectorState != Idling) { | |
4455 assert(_collectorState == AbortablePreclean, | |
4456 "Spontaneous state transition?"); | |
4457 _collectorState = FinalMarking; | |
4458 } // Else, a foreground collection completed this CMS cycle. | |
4459 return; | |
4460 } | |
4461 | |
4462 // Respond to an Eden sampling opportunity | |
4463 void CMSCollector::sample_eden() { | |
4464 // Make sure a young gc cannot sneak in between our | |
4465 // reading and recording of a sample. | |
4466 assert(Thread::current()->is_ConcurrentGC_thread(), | |
4467 "Only the cms thread may collect Eden samples"); | |
4468 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
4469 "Should collect samples while holding CMS token"); | |
4470 if (!_start_sampling) { | |
4471 return; | |
4472 } | |
4473 if (_eden_chunk_array) { | |
4474 if (_eden_chunk_index < _eden_chunk_capacity) { | |
4475 _eden_chunk_array[_eden_chunk_index] = *_top_addr; // take sample | |
4476 assert(_eden_chunk_array[_eden_chunk_index] <= *_end_addr, | |
4477 "Unexpected state of Eden"); | |
4478 // We'd like to check that what we just sampled is an oop-start address; | |
4479 // however, we cannot do that here since the object may not yet have been | |
4480 // initialized. So we'll instead do the check when we _use_ this sample | |
4481 // later. | |
4482 if (_eden_chunk_index == 0 || | |
4483 (pointer_delta(_eden_chunk_array[_eden_chunk_index], | |
4484 _eden_chunk_array[_eden_chunk_index-1]) | |
4485 >= CMSSamplingGrain)) { | |
4486 _eden_chunk_index++; // commit sample | |
4487 } | |
4488 } | |
4489 } | |
4490 if ((_collectorState == AbortablePreclean) && !_abort_preclean) { | |
4491 size_t used = get_eden_used(); | |
4492 size_t capacity = get_eden_capacity(); | |
4493 assert(used <= capacity, "Unexpected state of Eden"); | |
4494 if (used > (capacity/100 * CMSScheduleRemarkEdenPenetration)) { | |
4495 _abort_preclean = true; | |
4496 } | |
4497 } | |
4498 } | |
4499 | |
4500 | |
4501 size_t CMSCollector::preclean_work(bool clean_refs, bool clean_survivor) { | |
4502 assert(_collectorState == Precleaning || | |
4503 _collectorState == AbortablePreclean, "incorrect state"); | |
4504 ResourceMark rm; | |
4505 HandleMark hm; | |
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4506 |
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4507 // Precleaning is currently not MT but the reference processor |
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4508 // may be set for MT. Disable it temporarily here. |
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4509 ReferenceProcessor* rp = ref_processor(); |
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4510 ReferenceProcessorMTDiscoveryMutator rp_mut_discovery(rp, false); |
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4511 |
0 | 4512 // Do one pass of scrubbing the discovered reference lists |
4513 // to remove any reference objects with strongly-reachable | |
4514 // referents. | |
4515 if (clean_refs) { | |
4516 CMSPrecleanRefsYieldClosure yield_cl(this); | |
4517 assert(rp->span().equals(_span), "Spans should be equal"); | |
4518 CMSKeepAliveClosure keep_alive(this, _span, &_markBitMap, | |
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4519 &_markStack, true /* preclean */); |
0 | 4520 CMSDrainMarkingStackClosure complete_trace(this, |
452
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4521 _span, &_markBitMap, &_markStack, |
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4522 &keep_alive, true /* preclean */); |
0 | 4523 |
4524 // We don't want this step to interfere with a young | |
4525 // collection because we don't want to take CPU | |
4526 // or memory bandwidth away from the young GC threads | |
4527 // (which may be as many as there are CPUs). | |
4528 // Note that we don't need to protect ourselves from | |
4529 // interference with mutators because they can't | |
4530 // manipulate the discovered reference lists nor affect | |
4531 // the computed reachability of the referents, the | |
4532 // only properties manipulated by the precleaning | |
4533 // of these reference lists. | |
4534 stopTimer(); | |
4535 CMSTokenSyncWithLocks x(true /* is cms thread */, | |
4536 bitMapLock()); | |
4537 startTimer(); | |
4538 sample_eden(); | |
935 | 4539 |
0 | 4540 // The following will yield to allow foreground |
4541 // collection to proceed promptly. XXX YSR: | |
4542 // The code in this method may need further | |
4543 // tweaking for better performance and some restructuring | |
4544 // for cleaner interfaces. | |
4545 rp->preclean_discovered_references( | |
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4546 rp->is_alive_non_header(), &keep_alive, &complete_trace, &yield_cl); |
0 | 4547 } |
4548 | |
4549 if (clean_survivor) { // preclean the active survivor space(s) | |
4550 assert(_young_gen->kind() == Generation::DefNew || | |
4551 _young_gen->kind() == Generation::ParNew || | |
4552 _young_gen->kind() == Generation::ASParNew, | |
4553 "incorrect type for cast"); | |
4554 DefNewGeneration* dng = (DefNewGeneration*)_young_gen; | |
4555 PushAndMarkClosure pam_cl(this, _span, ref_processor(), | |
4556 &_markBitMap, &_modUnionTable, | |
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4557 &_markStack, true /* precleaning phase */); |
0 | 4558 stopTimer(); |
4559 CMSTokenSyncWithLocks ts(true /* is cms thread */, | |
4560 bitMapLock()); | |
4561 startTimer(); | |
4562 unsigned int before_count = | |
4563 GenCollectedHeap::heap()->total_collections(); | |
4564 SurvivorSpacePrecleanClosure | |
4565 sss_cl(this, _span, &_markBitMap, &_markStack, | |
4566 &pam_cl, before_count, CMSYield); | |
4567 dng->from()->object_iterate_careful(&sss_cl); | |
4568 dng->to()->object_iterate_careful(&sss_cl); | |
4569 } | |
4570 MarkRefsIntoAndScanClosure | |
4571 mrias_cl(_span, ref_processor(), &_markBitMap, &_modUnionTable, | |
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4572 &_markStack, this, CMSYield, |
0 | 4573 true /* precleaning phase */); |
4574 // CAUTION: The following closure has persistent state that may need to | |
4575 // be reset upon a decrease in the sequence of addresses it | |
4576 // processes. | |
4577 ScanMarkedObjectsAgainCarefullyClosure | |
4578 smoac_cl(this, _span, | |
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4579 &_markBitMap, &_markStack, &mrias_cl, CMSYield); |
0 | 4580 |
4581 // Preclean dirty cards in ModUnionTable and CardTable using | |
4582 // appropriate convergence criterion; | |
4583 // repeat CMSPrecleanIter times unless we find that | |
4584 // we are losing. | |
4585 assert(CMSPrecleanIter < 10, "CMSPrecleanIter is too large"); | |
4586 assert(CMSPrecleanNumerator < CMSPrecleanDenominator, | |
4587 "Bad convergence multiplier"); | |
4588 assert(CMSPrecleanThreshold >= 100, | |
4589 "Unreasonably low CMSPrecleanThreshold"); | |
4590 | |
4591 size_t numIter, cumNumCards, lastNumCards, curNumCards; | |
4592 for (numIter = 0, cumNumCards = lastNumCards = curNumCards = 0; | |
4593 numIter < CMSPrecleanIter; | |
4594 numIter++, lastNumCards = curNumCards, cumNumCards += curNumCards) { | |
4595 curNumCards = preclean_mod_union_table(_cmsGen, &smoac_cl); | |
4596 if (Verbose && PrintGCDetails) { | |
4597 gclog_or_tty->print(" (modUnionTable: %d cards)", curNumCards); | |
4598 } | |
4599 // Either there are very few dirty cards, so re-mark | |
4600 // pause will be small anyway, or our pre-cleaning isn't | |
4601 // that much faster than the rate at which cards are being | |
4602 // dirtied, so we might as well stop and re-mark since | |
4603 // precleaning won't improve our re-mark time by much. | |
4604 if (curNumCards <= CMSPrecleanThreshold || | |
4605 (numIter > 0 && | |
4606 (curNumCards * CMSPrecleanDenominator > | |
4607 lastNumCards * CMSPrecleanNumerator))) { | |
4608 numIter++; | |
4609 cumNumCards += curNumCards; | |
4610 break; | |
4611 } | |
4612 } | |
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4613 |
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4614 preclean_klasses(&mrias_cl, _cmsGen->freelistLock()); |
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4615 |
0 | 4616 curNumCards = preclean_card_table(_cmsGen, &smoac_cl); |
4617 cumNumCards += curNumCards; | |
4618 if (PrintGCDetails && PrintCMSStatistics != 0) { | |
4619 gclog_or_tty->print_cr(" (cardTable: %d cards, re-scanned %d cards, %d iterations)", | |
4620 curNumCards, cumNumCards, numIter); | |
4621 } | |
4622 return cumNumCards; // as a measure of useful work done | |
4623 } | |
4624 | |
4625 // PRECLEANING NOTES: | |
4626 // Precleaning involves: | |
4627 // . reading the bits of the modUnionTable and clearing the set bits. | |
4628 // . For the cards corresponding to the set bits, we scan the | |
4629 // objects on those cards. This means we need the free_list_lock | |
4630 // so that we can safely iterate over the CMS space when scanning | |
4631 // for oops. | |
4632 // . When we scan the objects, we'll be both reading and setting | |
4633 // marks in the marking bit map, so we'll need the marking bit map. | |
4634 // . For protecting _collector_state transitions, we take the CGC_lock. | |
4635 // Note that any races in the reading of of card table entries by the | |
4636 // CMS thread on the one hand and the clearing of those entries by the | |
4637 // VM thread or the setting of those entries by the mutator threads on the | |
4638 // other are quite benign. However, for efficiency it makes sense to keep | |
4639 // the VM thread from racing with the CMS thread while the latter is | |
4640 // dirty card info to the modUnionTable. We therefore also use the | |
4641 // CGC_lock to protect the reading of the card table and the mod union | |
4642 // table by the CM thread. | |
4643 // . We run concurrently with mutator updates, so scanning | |
4644 // needs to be done carefully -- we should not try to scan | |
4645 // potentially uninitialized objects. | |
4646 // | |
4647 // Locking strategy: While holding the CGC_lock, we scan over and | |
4648 // reset a maximal dirty range of the mod union / card tables, then lock | |
4649 // the free_list_lock and bitmap lock to do a full marking, then | |
4650 // release these locks; and repeat the cycle. This allows for a | |
4651 // certain amount of fairness in the sharing of these locks between | |
4652 // the CMS collector on the one hand, and the VM thread and the | |
4653 // mutators on the other. | |
4654 | |
4655 // NOTE: preclean_mod_union_table() and preclean_card_table() | |
4656 // further below are largely identical; if you need to modify | |
4657 // one of these methods, please check the other method too. | |
4658 | |
4659 size_t CMSCollector::preclean_mod_union_table( | |
4660 ConcurrentMarkSweepGeneration* gen, | |
4661 ScanMarkedObjectsAgainCarefullyClosure* cl) { | |
4662 verify_work_stacks_empty(); | |
4663 verify_overflow_empty(); | |
4664 | |
4665 // strategy: starting with the first card, accumulate contiguous | |
4666 // ranges of dirty cards; clear these cards, then scan the region | |
4667 // covered by these cards. | |
4668 | |
4669 // Since all of the MUT is committed ahead, we can just use | |
4670 // that, in case the generations expand while we are precleaning. | |
4671 // It might also be fine to just use the committed part of the | |
4672 // generation, but we might potentially miss cards when the | |
4673 // generation is rapidly expanding while we are in the midst | |
4674 // of precleaning. | |
4675 HeapWord* startAddr = gen->reserved().start(); | |
4676 HeapWord* endAddr = gen->reserved().end(); | |
4677 | |
4678 cl->setFreelistLock(gen->freelistLock()); // needed for yielding | |
4679 | |
4680 size_t numDirtyCards, cumNumDirtyCards; | |
4681 HeapWord *nextAddr, *lastAddr; | |
4682 for (cumNumDirtyCards = numDirtyCards = 0, | |
4683 nextAddr = lastAddr = startAddr; | |
4684 nextAddr < endAddr; | |
4685 nextAddr = lastAddr, cumNumDirtyCards += numDirtyCards) { | |
4686 | |
4687 ResourceMark rm; | |
4688 HandleMark hm; | |
4689 | |
4690 MemRegion dirtyRegion; | |
4691 { | |
4692 stopTimer(); | |
935 | 4693 // Potential yield point |
0 | 4694 CMSTokenSync ts(true); |
4695 startTimer(); | |
4696 sample_eden(); | |
4697 // Get dirty region starting at nextOffset (inclusive), | |
4698 // simultaneously clearing it. | |
4699 dirtyRegion = | |
4700 _modUnionTable.getAndClearMarkedRegion(nextAddr, endAddr); | |
4701 assert(dirtyRegion.start() >= nextAddr, | |
4702 "returned region inconsistent?"); | |
4703 } | |
4704 // Remember where the next search should begin. | |
4705 // The returned region (if non-empty) is a right open interval, | |
4706 // so lastOffset is obtained from the right end of that | |
4707 // interval. | |
4708 lastAddr = dirtyRegion.end(); | |
4709 // Should do something more transparent and less hacky XXX | |
4710 numDirtyCards = | |
4711 _modUnionTable.heapWordDiffToOffsetDiff(dirtyRegion.word_size()); | |
4712 | |
4713 // We'll scan the cards in the dirty region (with periodic | |
4714 // yields for foreground GC as needed). | |
4715 if (!dirtyRegion.is_empty()) { | |
4716 assert(numDirtyCards > 0, "consistency check"); | |
4717 HeapWord* stop_point = NULL; | |
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4718 stopTimer(); |
935 | 4719 // Potential yield point |
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4720 CMSTokenSyncWithLocks ts(true, gen->freelistLock(), |
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4721 bitMapLock()); |
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4722 startTimer(); |
0 | 4723 { |
4724 verify_work_stacks_empty(); | |
4725 verify_overflow_empty(); | |
4726 sample_eden(); | |
4727 stop_point = | |
4728 gen->cmsSpace()->object_iterate_careful_m(dirtyRegion, cl); | |
4729 } | |
4730 if (stop_point != NULL) { | |
4731 // The careful iteration stopped early either because it found an | |
4732 // uninitialized object, or because we were in the midst of an | |
4733 // "abortable preclean", which should now be aborted. Redirty | |
4734 // the bits corresponding to the partially-scanned or unscanned | |
4735 // cards. We'll either restart at the next block boundary or | |
4736 // abort the preclean. | |
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4737 assert((_collectorState == AbortablePreclean && should_abort_preclean()), |
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4738 "Should only be AbortablePreclean."); |
0 | 4739 _modUnionTable.mark_range(MemRegion(stop_point, dirtyRegion.end())); |
4740 if (should_abort_preclean()) { | |
4741 break; // out of preclean loop | |
4742 } else { | |
4743 // Compute the next address at which preclean should pick up; | |
4744 // might need bitMapLock in order to read P-bits. | |
4745 lastAddr = next_card_start_after_block(stop_point); | |
4746 } | |
4747 } | |
4748 } else { | |
4749 assert(lastAddr == endAddr, "consistency check"); | |
4750 assert(numDirtyCards == 0, "consistency check"); | |
4751 break; | |
4752 } | |
4753 } | |
4754 verify_work_stacks_empty(); | |
4755 verify_overflow_empty(); | |
4756 return cumNumDirtyCards; | |
4757 } | |
4758 | |
4759 // NOTE: preclean_mod_union_table() above and preclean_card_table() | |
4760 // below are largely identical; if you need to modify | |
4761 // one of these methods, please check the other method too. | |
4762 | |
4763 size_t CMSCollector::preclean_card_table(ConcurrentMarkSweepGeneration* gen, | |
4764 ScanMarkedObjectsAgainCarefullyClosure* cl) { | |
4765 // strategy: it's similar to precleamModUnionTable above, in that | |
4766 // we accumulate contiguous ranges of dirty cards, mark these cards | |
4767 // precleaned, then scan the region covered by these cards. | |
4768 HeapWord* endAddr = (HeapWord*)(gen->_virtual_space.high()); | |
4769 HeapWord* startAddr = (HeapWord*)(gen->_virtual_space.low()); | |
4770 | |
4771 cl->setFreelistLock(gen->freelistLock()); // needed for yielding | |
4772 | |
4773 size_t numDirtyCards, cumNumDirtyCards; | |
4774 HeapWord *lastAddr, *nextAddr; | |
4775 | |
4776 for (cumNumDirtyCards = numDirtyCards = 0, | |
4777 nextAddr = lastAddr = startAddr; | |
4778 nextAddr < endAddr; | |
4779 nextAddr = lastAddr, cumNumDirtyCards += numDirtyCards) { | |
4780 | |
4781 ResourceMark rm; | |
4782 HandleMark hm; | |
4783 | |
4784 MemRegion dirtyRegion; | |
4785 { | |
4786 // See comments in "Precleaning notes" above on why we | |
4787 // do this locking. XXX Could the locking overheads be | |
4788 // too high when dirty cards are sparse? [I don't think so.] | |
4789 stopTimer(); | |
4790 CMSTokenSync x(true); // is cms thread | |
4791 startTimer(); | |
4792 sample_eden(); | |
4793 // Get and clear dirty region from card table | |
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4794 dirtyRegion = _ct->ct_bs()->dirty_card_range_after_reset( |
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4795 MemRegion(nextAddr, endAddr), |
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4796 true, |
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4797 CardTableModRefBS::precleaned_card_val()); |
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4798 |
0 | 4799 assert(dirtyRegion.start() >= nextAddr, |
4800 "returned region inconsistent?"); | |
4801 } | |
4802 lastAddr = dirtyRegion.end(); | |
4803 numDirtyCards = | |
4804 dirtyRegion.word_size()/CardTableModRefBS::card_size_in_words; | |
4805 | |
4806 if (!dirtyRegion.is_empty()) { | |
4807 stopTimer(); | |
4808 CMSTokenSyncWithLocks ts(true, gen->freelistLock(), bitMapLock()); | |
4809 startTimer(); | |
4810 sample_eden(); | |
4811 verify_work_stacks_empty(); | |
4812 verify_overflow_empty(); | |
4813 HeapWord* stop_point = | |
4814 gen->cmsSpace()->object_iterate_careful_m(dirtyRegion, cl); | |
4815 if (stop_point != NULL) { | |
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4816 assert((_collectorState == AbortablePreclean && should_abort_preclean()), |
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4817 "Should only be AbortablePreclean."); |
0 | 4818 _ct->ct_bs()->invalidate(MemRegion(stop_point, dirtyRegion.end())); |
4819 if (should_abort_preclean()) { | |
4820 break; // out of preclean loop | |
4821 } else { | |
4822 // Compute the next address at which preclean should pick up. | |
4823 lastAddr = next_card_start_after_block(stop_point); | |
4824 } | |
4825 } | |
4826 } else { | |
4827 break; | |
4828 } | |
4829 } | |
4830 verify_work_stacks_empty(); | |
4831 verify_overflow_empty(); | |
4832 return cumNumDirtyCards; | |
4833 } | |
4834 | |
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4835 class PrecleanKlassClosure : public KlassClosure { |
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4836 CMKlassClosure _cm_klass_closure; |
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4837 public: |
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4838 PrecleanKlassClosure(OopClosure* oop_closure) : _cm_klass_closure(oop_closure) {} |
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4839 void do_klass(Klass* k) { |
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4840 if (k->has_accumulated_modified_oops()) { |
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4841 k->clear_accumulated_modified_oops(); |
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4842 |
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4843 _cm_klass_closure.do_klass(k); |
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4844 } |
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4845 } |
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4846 }; |
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4847 |
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4848 // The freelist lock is needed to prevent asserts, is it really needed? |
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4849 void CMSCollector::preclean_klasses(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock) { |
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4850 |
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4851 cl->set_freelistLock(freelistLock); |
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4852 |
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4853 CMSTokenSyncWithLocks ts(true, freelistLock, bitMapLock()); |
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4854 |
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4855 // SSS: Add equivalent to ScanMarkedObjectsAgainCarefullyClosure::do_yield_check and should_abort_preclean? |
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4856 // SSS: We should probably check if precleaning should be aborted, at suitable intervals? |
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4857 PrecleanKlassClosure preclean_klass_closure(cl); |
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4858 ClassLoaderDataGraph::classes_do(&preclean_klass_closure); |
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4859 |
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4860 verify_work_stacks_empty(); |
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4861 verify_overflow_empty(); |
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4862 } |
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4863 |
0 | 4864 void CMSCollector::checkpointRootsFinal(bool asynch, |
4865 bool clear_all_soft_refs, bool init_mark_was_synchronous) { | |
4866 assert(_collectorState == FinalMarking, "incorrect state transition?"); | |
4867 check_correct_thread_executing(); | |
4868 // world is stopped at this checkpoint | |
4869 assert(SafepointSynchronize::is_at_safepoint(), | |
4870 "world should be stopped"); | |
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4871 TraceCMSMemoryManagerStats tms(_collectorState,GenCollectedHeap::heap()->gc_cause()); |
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4872 |
0 | 4873 verify_work_stacks_empty(); |
4874 verify_overflow_empty(); | |
4875 | |
4876 SpecializationStats::clear(); | |
4877 if (PrintGCDetails) { | |
4878 gclog_or_tty->print("[YG occupancy: "SIZE_FORMAT" K ("SIZE_FORMAT" K)]", | |
4879 _young_gen->used() / K, | |
4880 _young_gen->capacity() / K); | |
4881 } | |
4882 if (asynch) { | |
4883 if (CMSScavengeBeforeRemark) { | |
4884 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
4885 // Temporarily set flag to false, GCH->do_collection will | |
4886 // expect it to be false and set to true | |
4887 FlagSetting fl(gch->_is_gc_active, false); | |
4888 NOT_PRODUCT(TraceTime t("Scavenge-Before-Remark", | |
4889 PrintGCDetails && Verbose, true, gclog_or_tty);) | |
4890 int level = _cmsGen->level() - 1; | |
4891 if (level >= 0) { | |
4892 gch->do_collection(true, // full (i.e. force, see below) | |
4893 false, // !clear_all_soft_refs | |
4894 0, // size | |
4895 false, // is_tlab | |
4896 level // max_level | |
4897 ); | |
4898 } | |
4899 } | |
4900 FreelistLocker x(this); | |
4901 MutexLockerEx y(bitMapLock(), | |
4902 Mutex::_no_safepoint_check_flag); | |
4903 assert(!init_mark_was_synchronous, "but that's impossible!"); | |
4904 checkpointRootsFinalWork(asynch, clear_all_soft_refs, false); | |
4905 } else { | |
4906 // already have all the locks | |
4907 checkpointRootsFinalWork(asynch, clear_all_soft_refs, | |
4908 init_mark_was_synchronous); | |
4909 } | |
4910 verify_work_stacks_empty(); | |
4911 verify_overflow_empty(); | |
4912 SpecializationStats::print(); | |
4913 } | |
4914 | |
4915 void CMSCollector::checkpointRootsFinalWork(bool asynch, | |
4916 bool clear_all_soft_refs, bool init_mark_was_synchronous) { | |
4917 | |
4918 NOT_PRODUCT(TraceTime tr("checkpointRootsFinalWork", PrintGCDetails, false, gclog_or_tty);) | |
4919 | |
4920 assert(haveFreelistLocks(), "must have free list locks"); | |
4921 assert_lock_strong(bitMapLock()); | |
4922 | |
4923 if (UseAdaptiveSizePolicy) { | |
4924 size_policy()->checkpoint_roots_final_begin(); | |
4925 } | |
4926 | |
4927 ResourceMark rm; | |
4928 HandleMark hm; | |
4929 | |
4930 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
4931 | |
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4932 if (should_unload_classes()) { |
0 | 4933 CodeCache::gc_prologue(); |
4934 } | |
4935 assert(haveFreelistLocks(), "must have free list locks"); | |
4936 assert_lock_strong(bitMapLock()); | |
4937 | |
4938 if (!init_mark_was_synchronous) { | |
4939 // We might assume that we need not fill TLAB's when | |
4940 // CMSScavengeBeforeRemark is set, because we may have just done | |
4941 // a scavenge which would have filled all TLAB's -- and besides | |
4942 // Eden would be empty. This however may not always be the case -- | |
4943 // for instance although we asked for a scavenge, it may not have | |
4944 // happened because of a JNI critical section. We probably need | |
4945 // a policy for deciding whether we can in that case wait until | |
4946 // the critical section releases and then do the remark following | |
4947 // the scavenge, and skip it here. In the absence of that policy, | |
4948 // or of an indication of whether the scavenge did indeed occur, | |
4949 // we cannot rely on TLAB's having been filled and must do | |
4950 // so here just in case a scavenge did not happen. | |
4951 gch->ensure_parsability(false); // fill TLAB's, but no need to retire them | |
4952 // Update the saved marks which may affect the root scans. | |
4953 gch->save_marks(); | |
4954 | |
4955 { | |
4956 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;) | |
4957 | |
4958 // Note on the role of the mod union table: | |
4959 // Since the marker in "markFromRoots" marks concurrently with | |
4960 // mutators, it is possible for some reachable objects not to have been | |
4961 // scanned. For instance, an only reference to an object A was | |
4962 // placed in object B after the marker scanned B. Unless B is rescanned, | |
4963 // A would be collected. Such updates to references in marked objects | |
4964 // are detected via the mod union table which is the set of all cards | |
4965 // dirtied since the first checkpoint in this GC cycle and prior to | |
4966 // the most recent young generation GC, minus those cleaned up by the | |
4967 // concurrent precleaning. | |
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4968 if (CMSParallelRemarkEnabled && CollectedHeap::use_parallel_gc_threads()) { |
0 | 4969 TraceTime t("Rescan (parallel) ", PrintGCDetails, false, gclog_or_tty); |
4970 do_remark_parallel(); | |
4971 } else { | |
4972 TraceTime t("Rescan (non-parallel) ", PrintGCDetails, false, | |
4973 gclog_or_tty); | |
4974 do_remark_non_parallel(); | |
4975 } | |
4976 } | |
4977 } else { | |
4978 assert(!asynch, "Can't have init_mark_was_synchronous in asynch mode"); | |
4979 // The initial mark was stop-world, so there's no rescanning to | |
4980 // do; go straight on to the next step below. | |
4981 } | |
4982 verify_work_stacks_empty(); | |
4983 verify_overflow_empty(); | |
4984 | |
4985 { | |
4986 NOT_PRODUCT(TraceTime ts("refProcessingWork", PrintGCDetails, false, gclog_or_tty);) | |
4987 refProcessingWork(asynch, clear_all_soft_refs); | |
4988 } | |
4989 verify_work_stacks_empty(); | |
4990 verify_overflow_empty(); | |
4991 | |
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4992 if (should_unload_classes()) { |
0 | 4993 CodeCache::gc_epilogue(); |
4994 } | |
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4995 JvmtiExport::gc_epilogue(); |
0 | 4996 |
4997 // If we encountered any (marking stack / work queue) overflow | |
4998 // events during the current CMS cycle, take appropriate | |
4999 // remedial measures, where possible, so as to try and avoid | |
5000 // recurrence of that condition. | |
5001 assert(_markStack.isEmpty(), "No grey objects"); | |
5002 size_t ser_ovflw = _ser_pmc_remark_ovflw + _ser_pmc_preclean_ovflw + | |
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5003 _ser_kac_ovflw + _ser_kac_preclean_ovflw; |
0 | 5004 if (ser_ovflw > 0) { |
5005 if (PrintCMSStatistics != 0) { | |
5006 gclog_or_tty->print_cr("Marking stack overflow (benign) " | |
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5007 "(pmc_pc="SIZE_FORMAT", pmc_rm="SIZE_FORMAT", kac="SIZE_FORMAT |
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5008 ", kac_preclean="SIZE_FORMAT")", |
0 | 5009 _ser_pmc_preclean_ovflw, _ser_pmc_remark_ovflw, |
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5010 _ser_kac_ovflw, _ser_kac_preclean_ovflw); |
0 | 5011 } |
5012 _markStack.expand(); | |
5013 _ser_pmc_remark_ovflw = 0; | |
5014 _ser_pmc_preclean_ovflw = 0; | |
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5015 _ser_kac_preclean_ovflw = 0; |
0 | 5016 _ser_kac_ovflw = 0; |
5017 } | |
5018 if (_par_pmc_remark_ovflw > 0 || _par_kac_ovflw > 0) { | |
5019 if (PrintCMSStatistics != 0) { | |
5020 gclog_or_tty->print_cr("Work queue overflow (benign) " | |
5021 "(pmc_rm="SIZE_FORMAT", kac="SIZE_FORMAT")", | |
5022 _par_pmc_remark_ovflw, _par_kac_ovflw); | |
5023 } | |
5024 _par_pmc_remark_ovflw = 0; | |
5025 _par_kac_ovflw = 0; | |
5026 } | |
5027 if (PrintCMSStatistics != 0) { | |
5028 if (_markStack._hit_limit > 0) { | |
5029 gclog_or_tty->print_cr(" (benign) Hit max stack size limit ("SIZE_FORMAT")", | |
5030 _markStack._hit_limit); | |
5031 } | |
5032 if (_markStack._failed_double > 0) { | |
5033 gclog_or_tty->print_cr(" (benign) Failed stack doubling ("SIZE_FORMAT")," | |
5034 " current capacity "SIZE_FORMAT, | |
5035 _markStack._failed_double, | |
5036 _markStack.capacity()); | |
5037 } | |
5038 } | |
5039 _markStack._hit_limit = 0; | |
5040 _markStack._failed_double = 0; | |
5041 | |
5042 if ((VerifyAfterGC || VerifyDuringGC) && | |
5043 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
5044 verify_after_remark(); | |
5045 } | |
5046 | |
5047 // Change under the freelistLocks. | |
5048 _collectorState = Sweeping; | |
5049 // Call isAllClear() under bitMapLock | |
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5050 assert(_modUnionTable.isAllClear(), |
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5051 "Should be clear by end of the final marking"); |
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5052 assert(_ct->klass_rem_set()->mod_union_is_clear(), |
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5053 "Should be clear by end of the final marking"); |
0 | 5054 if (UseAdaptiveSizePolicy) { |
5055 size_policy()->checkpoint_roots_final_end(gch->gc_cause()); | |
5056 } | |
5057 } | |
5058 | |
5059 // Parallel remark task | |
5060 class CMSParRemarkTask: public AbstractGangTask { | |
5061 CMSCollector* _collector; | |
5062 int _n_workers; | |
5063 CompactibleFreeListSpace* _cms_space; | |
5064 | |
5065 // The per-thread work queues, available here for stealing. | |
5066 OopTaskQueueSet* _task_queues; | |
5067 ParallelTaskTerminator _term; | |
5068 | |
5069 public: | |
4095
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5070 // A value of 0 passed to n_workers will cause the number of |
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5071 // workers to be taken from the active workers in the work gang. |
0 | 5072 CMSParRemarkTask(CMSCollector* collector, |
5073 CompactibleFreeListSpace* cms_space, | |
1833
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5074 int n_workers, FlexibleWorkGang* workers, |
0 | 5075 OopTaskQueueSet* task_queues): |
5076 AbstractGangTask("Rescan roots and grey objects in parallel"), | |
5077 _collector(collector), | |
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5078 _cms_space(cms_space), |
0 | 5079 _n_workers(n_workers), |
5080 _task_queues(task_queues), | |
1833
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5081 _term(n_workers, task_queues) { } |
0 | 5082 |
5083 OopTaskQueueSet* task_queues() { return _task_queues; } | |
5084 | |
5085 OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); } | |
5086 | |
5087 ParallelTaskTerminator* terminator() { return &_term; } | |
1833
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5088 int n_workers() { return _n_workers; } |
0 | 5089 |
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5090 void work(uint worker_id); |
0 | 5091 |
5092 private: | |
5093 // Work method in support of parallel rescan ... of young gen spaces | |
5094 void do_young_space_rescan(int i, Par_MarkRefsIntoAndScanClosure* cl, | |
5095 ContiguousSpace* space, | |
5096 HeapWord** chunk_array, size_t chunk_top); | |
5097 | |
5098 // ... of dirty cards in old space | |
5099 void do_dirty_card_rescan_tasks(CompactibleFreeListSpace* sp, int i, | |
5100 Par_MarkRefsIntoAndScanClosure* cl); | |
5101 | |
5102 // ... work stealing for the above | |
5103 void do_work_steal(int i, Par_MarkRefsIntoAndScanClosure* cl, int* seed); | |
5104 }; | |
5105 | |
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5106 class RemarkKlassClosure : public KlassClosure { |
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5107 CMKlassClosure _cm_klass_closure; |
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5108 public: |
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5109 RemarkKlassClosure(OopClosure* oop_closure) : _cm_klass_closure(oop_closure) {} |
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5110 void do_klass(Klass* k) { |
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5111 // Check if we have modified any oops in the Klass during the concurrent marking. |
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5112 if (k->has_accumulated_modified_oops()) { |
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5113 k->clear_accumulated_modified_oops(); |
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5114 |
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5115 // We could have transfered the current modified marks to the accumulated marks, |
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5116 // like we do with the Card Table to Mod Union Table. But it's not really necessary. |
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5117 } else if (k->has_modified_oops()) { |
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5118 // Don't clear anything, this info is needed by the next young collection. |
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5119 } else { |
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5120 // No modified oops in the Klass. |
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5121 return; |
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5122 } |
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5123 |
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5124 // The klass has modified fields, need to scan the klass. |
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5125 _cm_klass_closure.do_klass(k); |
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5126 } |
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5127 }; |
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5128 |
1833
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5129 // work_queue(i) is passed to the closure |
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5130 // Par_MarkRefsIntoAndScanClosure. The "i" parameter |
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5131 // also is passed to do_dirty_card_rescan_tasks() and to |
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5132 // do_work_steal() to select the i-th task_queue. |
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5133 |
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5134 void CMSParRemarkTask::work(uint worker_id) { |
0 | 5135 elapsedTimer _timer; |
5136 ResourceMark rm; | |
5137 HandleMark hm; | |
5138 | |
5139 // ---------- rescan from roots -------------- | |
5140 _timer.start(); | |
5141 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
5142 Par_MarkRefsIntoAndScanClosure par_mrias_cl(_collector, | |
5143 _collector->_span, _collector->ref_processor(), | |
5144 &(_collector->_markBitMap), | |
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5145 work_queue(worker_id)); |
0 | 5146 |
5147 // Rescan young gen roots first since these are likely | |
5148 // coarsely partitioned and may, on that account, constitute | |
5149 // the critical path; thus, it's best to start off that | |
5150 // work first. | |
5151 // ---------- young gen roots -------------- | |
5152 { | |
5153 DefNewGeneration* dng = _collector->_young_gen->as_DefNewGeneration(); | |
5154 EdenSpace* eden_space = dng->eden(); | |
5155 ContiguousSpace* from_space = dng->from(); | |
5156 ContiguousSpace* to_space = dng->to(); | |
5157 | |
5158 HeapWord** eca = _collector->_eden_chunk_array; | |
5159 size_t ect = _collector->_eden_chunk_index; | |
5160 HeapWord** sca = _collector->_survivor_chunk_array; | |
5161 size_t sct = _collector->_survivor_chunk_index; | |
5162 | |
5163 assert(ect <= _collector->_eden_chunk_capacity, "out of bounds"); | |
5164 assert(sct <= _collector->_survivor_chunk_capacity, "out of bounds"); | |
5165 | |
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5166 do_young_space_rescan(worker_id, &par_mrias_cl, to_space, NULL, 0); |
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5167 do_young_space_rescan(worker_id, &par_mrias_cl, from_space, sca, sct); |
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5168 do_young_space_rescan(worker_id, &par_mrias_cl, eden_space, eca, ect); |
0 | 5169 |
5170 _timer.stop(); | |
5171 if (PrintCMSStatistics != 0) { | |
5172 gclog_or_tty->print_cr( | |
5173 "Finished young gen rescan work in %dth thread: %3.3f sec", | |
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5174 worker_id, _timer.seconds()); |
0 | 5175 } |
5176 } | |
5177 | |
5178 // ---------- remaining roots -------------- | |
5179 _timer.reset(); | |
5180 _timer.start(); | |
5181 gch->gen_process_strong_roots(_collector->_cmsGen->level(), | |
5182 false, // yg was scanned above | |
989
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5183 false, // this is parallel code |
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5184 false, // not scavenging |
0 | 5185 SharedHeap::ScanningOption(_collector->CMSCollector::roots_scanning_options()), |
989
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5186 &par_mrias_cl, |
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5187 true, // walk all of code cache if (so & SO_CodeCache) |
6725
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5188 NULL, |
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5189 NULL); // The dirty klasses will be handled below |
989
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|
5190 assert(_collector->should_unload_classes() |
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5191 || (_collector->CMSCollector::roots_scanning_options() & SharedHeap::SO_CodeCache), |
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5192 "if we didn't scan the code cache, we have to be ready to drop nmethods with expired weak oops"); |
0 | 5193 _timer.stop(); |
5194 if (PrintCMSStatistics != 0) { | |
5195 gclog_or_tty->print_cr( | |
5196 "Finished remaining root rescan work in %dth thread: %3.3f sec", | |
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5197 worker_id, _timer.seconds()); |
0 | 5198 } |
5199 | |
6725
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5200 // ---------- unhandled CLD scanning ---------- |
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5201 if (worker_id == 0) { // Single threaded at the moment. |
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5202 _timer.reset(); |
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5203 _timer.start(); |
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5204 |
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5205 // Scan all new class loader data objects and new dependencies that were |
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5206 // introduced during concurrent marking. |
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5207 ResourceMark rm; |
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5208 GrowableArray<ClassLoaderData*>* array = ClassLoaderDataGraph::new_clds(); |
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5209 for (int i = 0; i < array->length(); i++) { |
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5210 par_mrias_cl.do_class_loader_data(array->at(i)); |
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5211 } |
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5212 |
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5213 // We don't need to keep track of new CLDs anymore. |
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5214 ClassLoaderDataGraph::remember_new_clds(false); |
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5215 |
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5216 _timer.stop(); |
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5217 if (PrintCMSStatistics != 0) { |
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5218 gclog_or_tty->print_cr( |
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5219 "Finished unhandled CLD scanning work in %dth thread: %3.3f sec", |
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5220 worker_id, _timer.seconds()); |
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5221 } |
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5222 } |
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5223 |
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5224 // ---------- dirty klass scanning ---------- |
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5225 if (worker_id == 0) { // Single threaded at the moment. |
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5226 _timer.reset(); |
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5227 _timer.start(); |
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5228 |
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5229 // Scan all classes that was dirtied during the concurrent marking phase. |
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5230 RemarkKlassClosure remark_klass_closure(&par_mrias_cl); |
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5231 ClassLoaderDataGraph::classes_do(&remark_klass_closure); |
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5232 |
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5233 _timer.stop(); |
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5234 if (PrintCMSStatistics != 0) { |
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5235 gclog_or_tty->print_cr( |
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5236 "Finished dirty klass scanning work in %dth thread: %3.3f sec", |
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5237 worker_id, _timer.seconds()); |
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5238 } |
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5239 } |
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5240 |
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5241 // We might have added oops to ClassLoaderData::_handles during the |
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5242 // concurrent marking phase. These oops point to newly allocated objects |
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5243 // that are guaranteed to be kept alive. Either by the direct allocation |
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5244 // code, or when the young collector processes the strong roots. Hence, |
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5245 // we don't have to revisit the _handles block during the remark phase. |
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5246 |
0 | 5247 // ---------- rescan dirty cards ------------ |
5248 _timer.reset(); | |
5249 _timer.start(); | |
5250 | |
5251 // Do the rescan tasks for each of the two spaces | |
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5252 // (cms_space) in turn. |
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5253 // "worker_id" is passed to select the task_queue for "worker_id" |
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5254 do_dirty_card_rescan_tasks(_cms_space, worker_id, &par_mrias_cl); |
0 | 5255 _timer.stop(); |
5256 if (PrintCMSStatistics != 0) { | |
5257 gclog_or_tty->print_cr( | |
5258 "Finished dirty card rescan work in %dth thread: %3.3f sec", | |
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5259 worker_id, _timer.seconds()); |
0 | 5260 } |
5261 | |
5262 // ---------- steal work from other threads ... | |
5263 // ---------- ... and drain overflow list. | |
5264 _timer.reset(); | |
5265 _timer.start(); | |
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5266 do_work_steal(worker_id, &par_mrias_cl, _collector->hash_seed(worker_id)); |
0 | 5267 _timer.stop(); |
5268 if (PrintCMSStatistics != 0) { | |
5269 gclog_or_tty->print_cr( | |
5270 "Finished work stealing in %dth thread: %3.3f sec", | |
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5271 worker_id, _timer.seconds()); |
0 | 5272 } |
5273 } | |
5274 | |
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5275 // Note that parameter "i" is not used. |
0 | 5276 void |
5277 CMSParRemarkTask::do_young_space_rescan(int i, | |
5278 Par_MarkRefsIntoAndScanClosure* cl, ContiguousSpace* space, | |
5279 HeapWord** chunk_array, size_t chunk_top) { | |
5280 // Until all tasks completed: | |
5281 // . claim an unclaimed task | |
5282 // . compute region boundaries corresponding to task claimed | |
5283 // using chunk_array | |
5284 // . par_oop_iterate(cl) over that region | |
5285 | |
5286 ResourceMark rm; | |
5287 HandleMark hm; | |
5288 | |
5289 SequentialSubTasksDone* pst = space->par_seq_tasks(); | |
5290 assert(pst->valid(), "Uninitialized use?"); | |
5291 | |
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5292 uint nth_task = 0; |
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5293 uint n_tasks = pst->n_tasks(); |
0 | 5294 |
5295 HeapWord *start, *end; | |
5296 while (!pst->is_task_claimed(/* reference */ nth_task)) { | |
5297 // We claimed task # nth_task; compute its boundaries. | |
5298 if (chunk_top == 0) { // no samples were taken | |
5299 assert(nth_task == 0 && n_tasks == 1, "Can have only 1 EdenSpace task"); | |
5300 start = space->bottom(); | |
5301 end = space->top(); | |
5302 } else if (nth_task == 0) { | |
5303 start = space->bottom(); | |
5304 end = chunk_array[nth_task]; | |
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5305 } else if (nth_task < (uint)chunk_top) { |
0 | 5306 assert(nth_task >= 1, "Control point invariant"); |
5307 start = chunk_array[nth_task - 1]; | |
5308 end = chunk_array[nth_task]; | |
5309 } else { | |
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5310 assert(nth_task == (uint)chunk_top, "Control point invariant"); |
0 | 5311 start = chunk_array[chunk_top - 1]; |
5312 end = space->top(); | |
5313 } | |
5314 MemRegion mr(start, end); | |
5315 // Verify that mr is in space | |
5316 assert(mr.is_empty() || space->used_region().contains(mr), | |
5317 "Should be in space"); | |
5318 // Verify that "start" is an object boundary | |
5319 assert(mr.is_empty() || oop(mr.start())->is_oop(), | |
5320 "Should be an oop"); | |
5321 space->par_oop_iterate(mr, cl); | |
5322 } | |
5323 pst->all_tasks_completed(); | |
5324 } | |
5325 | |
5326 void | |
5327 CMSParRemarkTask::do_dirty_card_rescan_tasks( | |
5328 CompactibleFreeListSpace* sp, int i, | |
5329 Par_MarkRefsIntoAndScanClosure* cl) { | |
5330 // Until all tasks completed: | |
5331 // . claim an unclaimed task | |
5332 // . compute region boundaries corresponding to task claimed | |
5333 // . transfer dirty bits ct->mut for that region | |
5334 // . apply rescanclosure to dirty mut bits for that region | |
5335 | |
5336 ResourceMark rm; | |
5337 HandleMark hm; | |
5338 | |
5339 OopTaskQueue* work_q = work_queue(i); | |
5340 ModUnionClosure modUnionClosure(&(_collector->_modUnionTable)); | |
5341 // CAUTION! CAUTION! CAUTION! CAUTION! CAUTION! CAUTION! CAUTION! | |
5342 // CAUTION: This closure has state that persists across calls to | |
5343 // the work method dirty_range_iterate_clear() in that it has | |
5344 // imbedded in it a (subtype of) UpwardsObjectClosure. The | |
5345 // use of that state in the imbedded UpwardsObjectClosure instance | |
5346 // assumes that the cards are always iterated (even if in parallel | |
5347 // by several threads) in monotonically increasing order per each | |
5348 // thread. This is true of the implementation below which picks | |
5349 // card ranges (chunks) in monotonically increasing order globally | |
5350 // and, a-fortiori, in monotonically increasing order per thread | |
5351 // (the latter order being a subsequence of the former). | |
5352 // If the work code below is ever reorganized into a more chaotic | |
5353 // work-partitioning form than the current "sequential tasks" | |
5354 // paradigm, the use of that persistent state will have to be | |
5355 // revisited and modified appropriately. See also related | |
5356 // bug 4756801 work on which should examine this code to make | |
5357 // sure that the changes there do not run counter to the | |
5358 // assumptions made here and necessary for correctness and | |
5359 // efficiency. Note also that this code might yield inefficient | |
5360 // behaviour in the case of very large objects that span one or | |
5361 // more work chunks. Such objects would potentially be scanned | |
5362 // several times redundantly. Work on 4756801 should try and | |
5363 // address that performance anomaly if at all possible. XXX | |
5364 MemRegion full_span = _collector->_span; | |
5365 CMSBitMap* bm = &(_collector->_markBitMap); // shared | |
5366 MarkFromDirtyCardsClosure | |
5367 greyRescanClosure(_collector, full_span, // entire span of interest | |
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5368 sp, bm, work_q, cl); |
0 | 5369 |
5370 SequentialSubTasksDone* pst = sp->conc_par_seq_tasks(); | |
5371 assert(pst->valid(), "Uninitialized use?"); | |
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5372 uint nth_task = 0; |
0 | 5373 const int alignment = CardTableModRefBS::card_size * BitsPerWord; |
5374 MemRegion span = sp->used_region(); | |
5375 HeapWord* start_addr = span.start(); | |
5376 HeapWord* end_addr = (HeapWord*)round_to((intptr_t)span.end(), | |
5377 alignment); | |
5378 const size_t chunk_size = sp->rescan_task_size(); // in HeapWord units | |
5379 assert((HeapWord*)round_to((intptr_t)start_addr, alignment) == | |
5380 start_addr, "Check alignment"); | |
5381 assert((size_t)round_to((intptr_t)chunk_size, alignment) == | |
5382 chunk_size, "Check alignment"); | |
5383 | |
5384 while (!pst->is_task_claimed(/* reference */ nth_task)) { | |
5385 // Having claimed the nth_task, compute corresponding mem-region, | |
5386 // which is a-fortiori aligned correctly (i.e. at a MUT bopundary). | |
5387 // The alignment restriction ensures that we do not need any | |
5388 // synchronization with other gang-workers while setting or | |
5389 // clearing bits in thus chunk of the MUT. | |
5390 MemRegion this_span = MemRegion(start_addr + nth_task*chunk_size, | |
5391 start_addr + (nth_task+1)*chunk_size); | |
5392 // The last chunk's end might be way beyond end of the | |
5393 // used region. In that case pull back appropriately. | |
5394 if (this_span.end() > end_addr) { | |
5395 this_span.set_end(end_addr); | |
5396 assert(!this_span.is_empty(), "Program logic (calculation of n_tasks)"); | |
5397 } | |
5398 // Iterate over the dirty cards covering this chunk, marking them | |
5399 // precleaned, and setting the corresponding bits in the mod union | |
5400 // table. Since we have been careful to partition at Card and MUT-word | |
5401 // boundaries no synchronization is needed between parallel threads. | |
5402 _collector->_ct->ct_bs()->dirty_card_iterate(this_span, | |
5403 &modUnionClosure); | |
5404 | |
5405 // Having transferred these marks into the modUnionTable, | |
5406 // rescan the marked objects on the dirty cards in the modUnionTable. | |
5407 // Even if this is at a synchronous collection, the initial marking | |
5408 // may have been done during an asynchronous collection so there | |
5409 // may be dirty bits in the mod-union table. | |
5410 _collector->_modUnionTable.dirty_range_iterate_clear( | |
5411 this_span, &greyRescanClosure); | |
5412 _collector->_modUnionTable.verifyNoOneBitsInRange( | |
5413 this_span.start(), | |
5414 this_span.end()); | |
5415 } | |
5416 pst->all_tasks_completed(); // declare that i am done | |
5417 } | |
5418 | |
5419 // . see if we can share work_queues with ParNew? XXX | |
5420 void | |
5421 CMSParRemarkTask::do_work_steal(int i, Par_MarkRefsIntoAndScanClosure* cl, | |
5422 int* seed) { | |
5423 OopTaskQueue* work_q = work_queue(i); | |
5424 NOT_PRODUCT(int num_steals = 0;) | |
5425 oop obj_to_scan; | |
5426 CMSBitMap* bm = &(_collector->_markBitMap); | |
5427 | |
5428 while (true) { | |
5429 // Completely finish any left over work from (an) earlier round(s) | |
5430 cl->trim_queue(0); | |
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5431 size_t num_from_overflow_list = MIN2((size_t)(work_q->max_elems() - work_q->size())/4, |
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5432 (size_t)ParGCDesiredObjsFromOverflowList); |
0 | 5433 // Now check if there's any work in the overflow list |
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5434 // Passing ParallelGCThreads as the third parameter, no_of_gc_threads, |
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5435 // only affects the number of attempts made to get work from the |
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5436 // overflow list and does not affect the number of workers. Just |
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5437 // pass ParallelGCThreads so this behavior is unchanged. |
0 | 5438 if (_collector->par_take_from_overflow_list(num_from_overflow_list, |
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5439 work_q, |
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5440 ParallelGCThreads)) { |
0 | 5441 // found something in global overflow list; |
5442 // not yet ready to go stealing work from others. | |
5443 // We'd like to assert(work_q->size() != 0, ...) | |
5444 // because we just took work from the overflow list, | |
5445 // but of course we can't since all of that could have | |
5446 // been already stolen from us. | |
5447 // "He giveth and He taketh away." | |
5448 continue; | |
5449 } | |
5450 // Verify that we have no work before we resort to stealing | |
5451 assert(work_q->size() == 0, "Have work, shouldn't steal"); | |
5452 // Try to steal from other queues that have work | |
5453 if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) { | |
5454 NOT_PRODUCT(num_steals++;) | |
5455 assert(obj_to_scan->is_oop(), "Oops, not an oop!"); | |
5456 assert(bm->isMarked((HeapWord*)obj_to_scan), "Stole an unmarked oop?"); | |
5457 // Do scanning work | |
5458 obj_to_scan->oop_iterate(cl); | |
5459 // Loop around, finish this work, and try to steal some more | |
5460 } else if (terminator()->offer_termination()) { | |
5461 break; // nirvana from the infinite cycle | |
5462 } | |
5463 } | |
5464 NOT_PRODUCT( | |
5465 if (PrintCMSStatistics != 0) { | |
5466 gclog_or_tty->print("\n\t(%d: stole %d oops)", i, num_steals); | |
5467 } | |
5468 ) | |
5469 assert(work_q->size() == 0 && _collector->overflow_list_is_empty(), | |
5470 "Else our work is not yet done"); | |
5471 } | |
5472 | |
5473 // Return a thread-local PLAB recording array, as appropriate. | |
5474 void* CMSCollector::get_data_recorder(int thr_num) { | |
5475 if (_survivor_plab_array != NULL && | |
5476 (CMSPLABRecordAlways || | |
5477 (_collectorState > Marking && _collectorState < FinalMarking))) { | |
5478 assert(thr_num < (int)ParallelGCThreads, "thr_num is out of bounds"); | |
5479 ChunkArray* ca = &_survivor_plab_array[thr_num]; | |
5480 ca->reset(); // clear it so that fresh data is recorded | |
5481 return (void*) ca; | |
5482 } else { | |
5483 return NULL; | |
5484 } | |
5485 } | |
5486 | |
5487 // Reset all the thread-local PLAB recording arrays | |
5488 void CMSCollector::reset_survivor_plab_arrays() { | |
5489 for (uint i = 0; i < ParallelGCThreads; i++) { | |
5490 _survivor_plab_array[i].reset(); | |
5491 } | |
5492 } | |
5493 | |
5494 // Merge the per-thread plab arrays into the global survivor chunk | |
5495 // array which will provide the partitioning of the survivor space | |
5496 // for CMS rescan. | |
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5497 void CMSCollector::merge_survivor_plab_arrays(ContiguousSpace* surv, |
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5498 int no_of_gc_threads) { |
0 | 5499 assert(_survivor_plab_array != NULL, "Error"); |
5500 assert(_survivor_chunk_array != NULL, "Error"); | |
5501 assert(_collectorState == FinalMarking, "Error"); | |
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5502 for (int j = 0; j < no_of_gc_threads; j++) { |
0 | 5503 _cursor[j] = 0; |
5504 } | |
5505 HeapWord* top = surv->top(); | |
5506 size_t i; | |
5507 for (i = 0; i < _survivor_chunk_capacity; i++) { // all sca entries | |
5508 HeapWord* min_val = top; // Higher than any PLAB address | |
5509 uint min_tid = 0; // position of min_val this round | |
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5510 for (int j = 0; j < no_of_gc_threads; j++) { |
0 | 5511 ChunkArray* cur_sca = &_survivor_plab_array[j]; |
5512 if (_cursor[j] == cur_sca->end()) { | |
5513 continue; | |
5514 } | |
5515 assert(_cursor[j] < cur_sca->end(), "ctl pt invariant"); | |
5516 HeapWord* cur_val = cur_sca->nth(_cursor[j]); | |
5517 assert(surv->used_region().contains(cur_val), "Out of bounds value"); | |
5518 if (cur_val < min_val) { | |
5519 min_tid = j; | |
5520 min_val = cur_val; | |
5521 } else { | |
5522 assert(cur_val < top, "All recorded addresses should be less"); | |
5523 } | |
5524 } | |
5525 // At this point min_val and min_tid are respectively | |
5526 // the least address in _survivor_plab_array[j]->nth(_cursor[j]) | |
5527 // and the thread (j) that witnesses that address. | |
5528 // We record this address in the _survivor_chunk_array[i] | |
5529 // and increment _cursor[min_tid] prior to the next round i. | |
5530 if (min_val == top) { | |
5531 break; | |
5532 } | |
5533 _survivor_chunk_array[i] = min_val; | |
5534 _cursor[min_tid]++; | |
5535 } | |
5536 // We are all done; record the size of the _survivor_chunk_array | |
5537 _survivor_chunk_index = i; // exclusive: [0, i) | |
5538 if (PrintCMSStatistics > 0) { | |
5539 gclog_or_tty->print(" (Survivor:" SIZE_FORMAT "chunks) ", i); | |
5540 } | |
5541 // Verify that we used up all the recorded entries | |
5542 #ifdef ASSERT | |
5543 size_t total = 0; | |
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5544 for (int j = 0; j < no_of_gc_threads; j++) { |
0 | 5545 assert(_cursor[j] == _survivor_plab_array[j].end(), "Ctl pt invariant"); |
5546 total += _cursor[j]; | |
5547 } | |
5548 assert(total == _survivor_chunk_index, "Ctl Pt Invariant"); | |
5549 // Check that the merged array is in sorted order | |
5550 if (total > 0) { | |
5551 for (size_t i = 0; i < total - 1; i++) { | |
5552 if (PrintCMSStatistics > 0) { | |
5553 gclog_or_tty->print(" (chunk" SIZE_FORMAT ":" INTPTR_FORMAT ") ", | |
5554 i, _survivor_chunk_array[i]); | |
5555 } | |
5556 assert(_survivor_chunk_array[i] < _survivor_chunk_array[i+1], | |
5557 "Not sorted"); | |
5558 } | |
5559 } | |
5560 #endif // ASSERT | |
5561 } | |
5562 | |
5563 // Set up the space's par_seq_tasks structure for work claiming | |
5564 // for parallel rescan of young gen. | |
5565 // See ParRescanTask where this is currently used. | |
5566 void | |
5567 CMSCollector:: | |
5568 initialize_sequential_subtasks_for_young_gen_rescan(int n_threads) { | |
5569 assert(n_threads > 0, "Unexpected n_threads argument"); | |
5570 DefNewGeneration* dng = (DefNewGeneration*)_young_gen; | |
5571 | |
5572 // Eden space | |
5573 { | |
5574 SequentialSubTasksDone* pst = dng->eden()->par_seq_tasks(); | |
5575 assert(!pst->valid(), "Clobbering existing data?"); | |
5576 // Each valid entry in [0, _eden_chunk_index) represents a task. | |
5577 size_t n_tasks = _eden_chunk_index + 1; | |
5578 assert(n_tasks == 1 || _eden_chunk_array != NULL, "Error"); | |
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5579 // Sets the condition for completion of the subtask (how many threads |
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5580 // need to finish in order to be done). |
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5581 pst->set_n_threads(n_threads); |
0 | 5582 pst->set_n_tasks((int)n_tasks); |
5583 } | |
5584 | |
5585 // Merge the survivor plab arrays into _survivor_chunk_array | |
5586 if (_survivor_plab_array != NULL) { | |
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5587 merge_survivor_plab_arrays(dng->from(), n_threads); |
0 | 5588 } else { |
5589 assert(_survivor_chunk_index == 0, "Error"); | |
5590 } | |
5591 | |
5592 // To space | |
5593 { | |
5594 SequentialSubTasksDone* pst = dng->to()->par_seq_tasks(); | |
5595 assert(!pst->valid(), "Clobbering existing data?"); | |
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5596 // Sets the condition for completion of the subtask (how many threads |
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5597 // need to finish in order to be done). |
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5598 pst->set_n_threads(n_threads); |
0 | 5599 pst->set_n_tasks(1); |
5600 assert(pst->valid(), "Error"); | |
5601 } | |
5602 | |
5603 // From space | |
5604 { | |
5605 SequentialSubTasksDone* pst = dng->from()->par_seq_tasks(); | |
5606 assert(!pst->valid(), "Clobbering existing data?"); | |
5607 size_t n_tasks = _survivor_chunk_index + 1; | |
5608 assert(n_tasks == 1 || _survivor_chunk_array != NULL, "Error"); | |
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5609 // Sets the condition for completion of the subtask (how many threads |
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|
5610 // need to finish in order to be done). |
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5611 pst->set_n_threads(n_threads); |
0 | 5612 pst->set_n_tasks((int)n_tasks); |
5613 assert(pst->valid(), "Error"); | |
5614 } | |
5615 } | |
5616 | |
5617 // Parallel version of remark | |
5618 void CMSCollector::do_remark_parallel() { | |
5619 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
1833
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5620 FlexibleWorkGang* workers = gch->workers(); |
0 | 5621 assert(workers != NULL, "Need parallel worker threads."); |
4095
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5622 // Choose to use the number of GC workers most recently set |
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5623 // into "active_workers". If active_workers is not set, set it |
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|
5624 // to ParallelGCThreads. |
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5625 int n_workers = workers->active_workers(); |
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5626 if (n_workers == 0) { |
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|
5627 assert(n_workers > 0, "Should have been set during scavenge"); |
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5628 n_workers = ParallelGCThreads; |
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5629 workers->set_active_workers(n_workers); |
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5630 } |
0 | 5631 CompactibleFreeListSpace* cms_space = _cmsGen->cmsSpace(); |
5632 | |
5633 CMSParRemarkTask tsk(this, | |
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5634 cms_space, |
0 | 5635 n_workers, workers, task_queues()); |
5636 | |
5637 // Set up for parallel process_strong_roots work. | |
5638 gch->set_par_threads(n_workers); | |
5639 // We won't be iterating over the cards in the card table updating | |
5640 // the younger_gen cards, so we shouldn't call the following else | |
5641 // the verification code as well as subsequent younger_refs_iterate | |
5642 // code would get confused. XXX | |
5643 // gch->rem_set()->prepare_for_younger_refs_iterate(true); // parallel | |
5644 | |
5645 // The young gen rescan work will not be done as part of | |
5646 // process_strong_roots (which currently doesn't knw how to | |
5647 // parallelize such a scan), but rather will be broken up into | |
5648 // a set of parallel tasks (via the sampling that the [abortable] | |
5649 // preclean phase did of EdenSpace, plus the [two] tasks of | |
5650 // scanning the [two] survivor spaces. Further fine-grain | |
5651 // parallelization of the scanning of the survivor spaces | |
5652 // themselves, and of precleaning of the younger gen itself | |
5653 // is deferred to the future. | |
5654 initialize_sequential_subtasks_for_young_gen_rescan(n_workers); | |
5655 | |
5656 // The dirty card rescan work is broken up into a "sequence" | |
5657 // of parallel tasks (per constituent space) that are dynamically | |
5658 // claimed by the parallel threads. | |
5659 cms_space->initialize_sequential_subtasks_for_rescan(n_workers); | |
5660 | |
5661 // It turns out that even when we're using 1 thread, doing the work in a | |
5662 // separate thread causes wide variance in run times. We can't help this | |
5663 // in the multi-threaded case, but we special-case n=1 here to get | |
5664 // repeatable measurements of the 1-thread overhead of the parallel code. | |
5665 if (n_workers > 1) { | |
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5666 // Make refs discovery MT-safe, if it isn't already: it may not |
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5667 // necessarily be so, since it's possible that we are doing |
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5668 // ST marking. |
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5669 ReferenceProcessorMTDiscoveryMutator mt(ref_processor(), true); |
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5670 GenCollectedHeap::StrongRootsScope srs(gch); |
0 | 5671 workers->run_task(&tsk); |
5672 } else { | |
4876
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5673 ReferenceProcessorMTDiscoveryMutator mt(ref_processor(), false); |
989
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5674 GenCollectedHeap::StrongRootsScope srs(gch); |
0 | 5675 tsk.work(0); |
5676 } | |
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5677 |
0 | 5678 gch->set_par_threads(0); // 0 ==> non-parallel. |
5679 // restore, single-threaded for now, any preserved marks | |
5680 // as a result of work_q overflow | |
5681 restore_preserved_marks_if_any(); | |
5682 } | |
5683 | |
5684 // Non-parallel version of remark | |
5685 void CMSCollector::do_remark_non_parallel() { | |
5686 ResourceMark rm; | |
5687 HandleMark hm; | |
5688 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
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5689 ReferenceProcessorMTDiscoveryMutator mt(ref_processor(), false); |
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5690 |
0 | 5691 MarkRefsIntoAndScanClosure |
6725
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5692 mrias_cl(_span, ref_processor(), &_markBitMap, NULL /* not precleaning */, |
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5693 &_markStack, this, |
0 | 5694 false /* should_yield */, false /* not precleaning */); |
5695 MarkFromDirtyCardsClosure | |
5696 markFromDirtyCardsClosure(this, _span, | |
5697 NULL, // space is set further below | |
6725
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|
5698 &_markBitMap, &_markStack, &mrias_cl); |
0 | 5699 { |
5700 TraceTime t("grey object rescan", PrintGCDetails, false, gclog_or_tty); | |
342
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|
5701 // Iterate over the dirty cards, setting the corresponding bits in the |
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|
5702 // mod union table. |
0 | 5703 { |
5704 ModUnionClosure modUnionClosure(&_modUnionTable); | |
5705 _ct->ct_bs()->dirty_card_iterate( | |
5706 _cmsGen->used_region(), | |
5707 &modUnionClosure); | |
5708 } | |
5709 // Having transferred these marks into the modUnionTable, we just need | |
5710 // to rescan the marked objects on the dirty cards in the modUnionTable. | |
5711 // The initial marking may have been done during an asynchronous | |
5712 // collection so there may be dirty bits in the mod-union table. | |
5713 const int alignment = | |
5714 CardTableModRefBS::card_size * BitsPerWord; | |
5715 { | |
5716 // ... First handle dirty cards in CMS gen | |
5717 markFromDirtyCardsClosure.set_space(_cmsGen->cmsSpace()); | |
5718 MemRegion ur = _cmsGen->used_region(); | |
5719 HeapWord* lb = ur.start(); | |
5720 HeapWord* ub = (HeapWord*)round_to((intptr_t)ur.end(), alignment); | |
5721 MemRegion cms_span(lb, ub); | |
5722 _modUnionTable.dirty_range_iterate_clear(cms_span, | |
5723 &markFromDirtyCardsClosure); | |
5724 verify_work_stacks_empty(); | |
5725 if (PrintCMSStatistics != 0) { | |
5726 gclog_or_tty->print(" (re-scanned "SIZE_FORMAT" dirty cards in cms gen) ", | |
5727 markFromDirtyCardsClosure.num_dirty_cards()); | |
5728 } | |
5729 } | |
5730 } | |
5731 if (VerifyDuringGC && | |
5732 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
5733 HandleMark hm; // Discard invalid handles created during verification | |
6865
4202510ee0fe
8000831: Heap verification output incorrect/incomplete
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6787
diff
changeset
|
5734 Universe::verify(); |
0 | 5735 } |
5736 { | |
5737 TraceTime t("root rescan", PrintGCDetails, false, gclog_or_tty); | |
5738 | |
5739 verify_work_stacks_empty(); | |
5740 | |
5741 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. | |
989
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|
5742 GenCollectedHeap::StrongRootsScope srs(gch); |
0 | 5743 gch->gen_process_strong_roots(_cmsGen->level(), |
5744 true, // younger gens as roots | |
989
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|
5745 false, // use the local StrongRootsScope |
6725
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5746 false, // not scavenging |
0 | 5747 SharedHeap::ScanningOption(roots_scanning_options()), |
989
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|
5748 &mrias_cl, |
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|
5749 true, // walk code active on stacks |
6725
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|
5750 NULL, |
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|
5751 NULL); // The dirty klasses will be handled below |
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|
5752 |
989
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|
5753 assert(should_unload_classes() |
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|
5754 || (roots_scanning_options() & SharedHeap::SO_CodeCache), |
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|
5755 "if we didn't scan the code cache, we have to be ready to drop nmethods with expired weak oops"); |
0 | 5756 } |
6725
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|
5757 |
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|
5758 { |
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|
5759 TraceTime t("visit unhandled CLDs", PrintGCDetails, false, gclog_or_tty); |
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|
5760 |
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|
5761 verify_work_stacks_empty(); |
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|
5762 |
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|
5763 // Scan all class loader data objects that might have been introduced |
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diff
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|
5764 // during concurrent marking. |
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|
5765 ResourceMark rm; |
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|
5766 GrowableArray<ClassLoaderData*>* array = ClassLoaderDataGraph::new_clds(); |
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|
5767 for (int i = 0; i < array->length(); i++) { |
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|
5768 mrias_cl.do_class_loader_data(array->at(i)); |
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|
5769 } |
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|
5770 |
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|
5771 // We don't need to keep track of new CLDs anymore. |
da91efe96a93
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|
5772 ClassLoaderDataGraph::remember_new_clds(false); |
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|
5773 |
da91efe96a93
6964458: Reimplement class meta-data storage to use native memory
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|
5774 verify_work_stacks_empty(); |
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|
5775 } |
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|
5776 |
da91efe96a93
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|
5777 { |
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diff
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|
5778 TraceTime t("dirty klass scan", PrintGCDetails, false, gclog_or_tty); |
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|
5779 |
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|
5780 verify_work_stacks_empty(); |
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|
5781 |
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|
5782 RemarkKlassClosure remark_klass_closure(&mrias_cl); |
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|
5783 ClassLoaderDataGraph::classes_do(&remark_klass_closure); |
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|
5784 |
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|
5785 verify_work_stacks_empty(); |
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|
5786 } |
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|
5787 |
da91efe96a93
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|
5788 // We might have added oops to ClassLoaderData::_handles during the |
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|
5789 // concurrent marking phase. These oops point to newly allocated objects |
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|
5790 // that are guaranteed to be kept alive. Either by the direct allocation |
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|
5791 // code, or when the young collector processes the strong roots. Hence, |
da91efe96a93
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|
5792 // we don't have to revisit the _handles block during the remark phase. |
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|
5793 |
0 | 5794 verify_work_stacks_empty(); |
5795 // Restore evacuated mark words, if any, used for overflow list links | |
5796 if (!CMSOverflowEarlyRestoration) { | |
5797 restore_preserved_marks_if_any(); | |
5798 } | |
5799 verify_overflow_empty(); | |
5800 } | |
5801 | |
5802 //////////////////////////////////////////////////////// | |
5803 // Parallel Reference Processing Task Proxy Class | |
5804 //////////////////////////////////////////////////////// | |
1833
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6984287: Regularize how GC parallel workers are specified.
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|
5805 class CMSRefProcTaskProxy: public AbstractGangTaskWOopQueues { |
0 | 5806 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; |
5807 CMSCollector* _collector; | |
5808 CMSBitMap* _mark_bit_map; | |
143
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6662086: 6u4+, 7b11+: CMS never clears referents when -XX:+ParallelRefProcEnabled
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113
diff
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|
5809 const MemRegion _span; |
0 | 5810 ProcessTask& _task; |
5811 | |
5812 public: | |
5813 CMSRefProcTaskProxy(ProcessTask& task, | |
5814 CMSCollector* collector, | |
5815 const MemRegion& span, | |
5816 CMSBitMap* mark_bit_map, | |
1833
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jmasa
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|
5817 AbstractWorkGang* workers, |
0 | 5818 OopTaskQueueSet* task_queues): |
2369
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|
5819 // XXX Should superclass AGTWOQ also know about AWG since it knows |
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diff
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|
5820 // about the task_queues used by the AWG? Then it could initialize |
92da084fefc9
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|
5821 // the terminator() object. See 6984287. The set_for_termination() |
92da084fefc9
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|
5822 // below is a temporary band-aid for the regression in 6984287. |
1833
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|
5823 AbstractGangTaskWOopQueues("Process referents by policy in parallel", |
8b10f48633dc
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|
5824 task_queues), |
0 | 5825 _task(task), |
1833
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1777
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|
5826 _collector(collector), _span(span), _mark_bit_map(mark_bit_map) |
2369
92da084fefc9
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|
5827 { |
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diff
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|
5828 assert(_collector->_span.equals(_span) && !_span.is_empty(), |
92da084fefc9
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|
5829 "Inconsistency in _span"); |
92da084fefc9
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|
5830 set_for_termination(workers->active_workers()); |
92da084fefc9
6668573: CMS: reference processing crash if ParallelCMSThreads > ParallelGCThreads
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diff
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|
5831 } |
0 | 5832 |
1833
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|
5833 OopTaskQueueSet* task_queues() { return queues(); } |
0 | 5834 |
5835 OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); } | |
5836 | |
5837 void do_work_steal(int i, | |
5838 CMSParDrainMarkingStackClosure* drain, | |
5839 CMSParKeepAliveClosure* keep_alive, | |
5840 int* seed); | |
5841 | |
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|
5842 virtual void work(uint worker_id); |
0 | 5843 }; |
5844 | |
4728
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jmasa
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diff
changeset
|
5845 void CMSRefProcTaskProxy::work(uint worker_id) { |
143
b5489bb705c9
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diff
changeset
|
5846 assert(_collector->_span.equals(_span), "Inconsistency in _span"); |
0 | 5847 CMSParKeepAliveClosure par_keep_alive(_collector, _span, |
935 | 5848 _mark_bit_map, |
4728
441e946dc1af
7121618: Change type of number of GC workers to unsigned int.
jmasa
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diff
changeset
|
5849 work_queue(worker_id)); |
0 | 5850 CMSParDrainMarkingStackClosure par_drain_stack(_collector, _span, |
935 | 5851 _mark_bit_map, |
4728
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jmasa
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4128
diff
changeset
|
5852 work_queue(worker_id)); |
143
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|
5853 CMSIsAliveClosure is_alive_closure(_span, _mark_bit_map); |
4728
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7121618: Change type of number of GC workers to unsigned int.
jmasa
parents:
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diff
changeset
|
5854 _task.work(worker_id, is_alive_closure, par_keep_alive, par_drain_stack); |
0 | 5855 if (_task.marks_oops_alive()) { |
4728
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jmasa
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diff
changeset
|
5856 do_work_steal(worker_id, &par_drain_stack, &par_keep_alive, |
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jmasa
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diff
changeset
|
5857 _collector->hash_seed(worker_id)); |
441e946dc1af
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jmasa
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diff
changeset
|
5858 } |
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jmasa
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diff
changeset
|
5859 assert(work_queue(worker_id)->size() == 0, "work_queue should be empty"); |
0 | 5860 assert(_collector->_overflow_list == NULL, "non-empty _overflow_list"); |
5861 } | |
5862 | |
5863 class CMSRefEnqueueTaskProxy: public AbstractGangTask { | |
5864 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; | |
5865 EnqueueTask& _task; | |
5866 | |
5867 public: | |
5868 CMSRefEnqueueTaskProxy(EnqueueTask& task) | |
5869 : AbstractGangTask("Enqueue reference objects in parallel"), | |
5870 _task(task) | |
5871 { } | |
5872 | |
4728
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jmasa
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diff
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|
5873 virtual void work(uint worker_id) |
0 | 5874 { |
4728
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jmasa
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diff
changeset
|
5875 _task.work(worker_id); |
0 | 5876 } |
5877 }; | |
5878 | |
5879 CMSParKeepAliveClosure::CMSParKeepAliveClosure(CMSCollector* collector, | |
6725
da91efe96a93
6964458: Reimplement class meta-data storage to use native memory
coleenp
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diff
changeset
|
5880 MemRegion span, CMSBitMap* bit_map, OopTaskQueue* work_queue): |
0 | 5881 _span(span), |
5882 _bit_map(bit_map), | |
5883 _work_queue(work_queue), | |
6725
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diff
changeset
|
5884 _mark_and_push(collector, span, bit_map, work_queue), |
0 | 5885 _low_water_mark(MIN2((uint)(work_queue->max_elems()/4), |
5886 (uint)(CMSWorkQueueDrainThreshold * ParallelGCThreads))) | |
5887 { } | |
5888 | |
5889 // . see if we can share work_queues with ParNew? XXX | |
5890 void CMSRefProcTaskProxy::do_work_steal(int i, | |
5891 CMSParDrainMarkingStackClosure* drain, | |
5892 CMSParKeepAliveClosure* keep_alive, | |
5893 int* seed) { | |
5894 OopTaskQueue* work_q = work_queue(i); | |
5895 NOT_PRODUCT(int num_steals = 0;) | |
5896 oop obj_to_scan; | |
5897 | |
5898 while (true) { | |
5899 // Completely finish any left over work from (an) earlier round(s) | |
5900 drain->trim_queue(0); | |
679
cea947c8a988
6819891: ParNew: Fix work queue overflow code to deal correctly with +UseCompressedOops
ysr
parents:
628
diff
changeset
|
5901 size_t num_from_overflow_list = MIN2((size_t)(work_q->max_elems() - work_q->size())/4, |
cea947c8a988
6819891: ParNew: Fix work queue overflow code to deal correctly with +UseCompressedOops
ysr
parents:
628
diff
changeset
|
5902 (size_t)ParGCDesiredObjsFromOverflowList); |
0 | 5903 // Now check if there's any work in the overflow list |
1833
8b10f48633dc
6984287: Regularize how GC parallel workers are specified.
jmasa
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1777
diff
changeset
|
5904 // Passing ParallelGCThreads as the third parameter, no_of_gc_threads, |
8b10f48633dc
6984287: Regularize how GC parallel workers are specified.
jmasa
parents:
1777
diff
changeset
|
5905 // only affects the number of attempts made to get work from the |
8b10f48633dc
6984287: Regularize how GC parallel workers are specified.
jmasa
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1777
diff
changeset
|
5906 // overflow list and does not affect the number of workers. Just |
8b10f48633dc
6984287: Regularize how GC parallel workers are specified.
jmasa
parents:
1777
diff
changeset
|
5907 // pass ParallelGCThreads so this behavior is unchanged. |
0 | 5908 if (_collector->par_take_from_overflow_list(num_from_overflow_list, |
1833
8b10f48633dc
6984287: Regularize how GC parallel workers are specified.
jmasa
parents:
1777
diff
changeset
|
5909 work_q, |
8b10f48633dc
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diff
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|
5910 ParallelGCThreads)) { |
0 | 5911 // Found something in global overflow list; |
5912 // not yet ready to go stealing work from others. | |
5913 // We'd like to assert(work_q->size() != 0, ...) | |
5914 // because we just took work from the overflow list, | |
5915 // but of course we can't, since all of that might have | |
5916 // been already stolen from us. | |
5917 continue; | |
5918 } | |
5919 // Verify that we have no work before we resort to stealing | |
5920 assert(work_q->size() == 0, "Have work, shouldn't steal"); | |
5921 // Try to steal from other queues that have work | |
5922 if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) { | |
5923 NOT_PRODUCT(num_steals++;) | |
5924 assert(obj_to_scan->is_oop(), "Oops, not an oop!"); | |
5925 assert(_mark_bit_map->isMarked((HeapWord*)obj_to_scan), "Stole an unmarked oop?"); | |
5926 // Do scanning work | |
5927 obj_to_scan->oop_iterate(keep_alive); | |
5928 // Loop around, finish this work, and try to steal some more | |
5929 } else if (terminator()->offer_termination()) { | |
5930 break; // nirvana from the infinite cycle | |
5931 } | |
5932 } | |
5933 NOT_PRODUCT( | |
5934 if (PrintCMSStatistics != 0) { | |
5935 gclog_or_tty->print("\n\t(%d: stole %d oops)", i, num_steals); | |
5936 } | |
5937 ) | |
5938 } | |
5939 | |
5940 void CMSRefProcTaskExecutor::execute(ProcessTask& task) | |
5941 { | |
5942 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
1833
8b10f48633dc
6984287: Regularize how GC parallel workers are specified.
jmasa
parents:
1777
diff
changeset
|
5943 FlexibleWorkGang* workers = gch->workers(); |
0 | 5944 assert(workers != NULL, "Need parallel worker threads."); |
5945 CMSRefProcTaskProxy rp_task(task, &_collector, | |
5946 _collector.ref_processor()->span(), | |
5947 _collector.markBitMap(), | |
1833
8b10f48633dc
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jmasa
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1777
diff
changeset
|
5948 workers, _collector.task_queues()); |
0 | 5949 workers->run_task(&rp_task); |
5950 } | |
5951 | |
5952 void CMSRefProcTaskExecutor::execute(EnqueueTask& task) | |
5953 { | |
5954 | |
5955 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
1833
8b10f48633dc
6984287: Regularize how GC parallel workers are specified.
jmasa
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1777
diff
changeset
|
5956 FlexibleWorkGang* workers = gch->workers(); |
0 | 5957 assert(workers != NULL, "Need parallel worker threads."); |
5958 CMSRefEnqueueTaskProxy enq_task(task); | |
5959 workers->run_task(&enq_task); | |
5960 } | |
5961 | |
5962 void CMSCollector::refProcessingWork(bool asynch, bool clear_all_soft_refs) { | |
5963 | |
5964 ResourceMark rm; | |
5965 HandleMark hm; | |
5966 | |
5967 ReferenceProcessor* rp = ref_processor(); | |
5968 assert(rp->span().equals(_span), "Spans should be equal"); | |
453
c96030fff130
6684579: SoftReference processing can be made more efficient
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452
diff
changeset
|
5969 assert(!rp->enqueuing_is_done(), "Enqueuing should not be complete"); |
c96030fff130
6684579: SoftReference processing can be made more efficient
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452
diff
changeset
|
5970 // Process weak references. |
457
27a80744a83b
6778647: snap(), snap_policy() should be renamed setup(), setup_policy()
ysr
parents:
453
diff
changeset
|
5971 rp->setup_policy(clear_all_soft_refs); |
453
c96030fff130
6684579: SoftReference processing can be made more efficient
ysr
parents:
452
diff
changeset
|
5972 verify_work_stacks_empty(); |
c96030fff130
6684579: SoftReference processing can be made more efficient
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452
diff
changeset
|
5973 |
0 | 5974 CMSKeepAliveClosure cmsKeepAliveClosure(this, _span, &_markBitMap, |
6725
da91efe96a93
6964458: Reimplement class meta-data storage to use native memory
coleenp
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6197
diff
changeset
|
5975 &_markStack, false /* !preclean */); |
0 | 5976 CMSDrainMarkingStackClosure cmsDrainMarkingStackClosure(this, |
5977 _span, &_markBitMap, &_markStack, | |
452
00b023ae2d78
6722113: CMS: Incorrect overflow handling during precleaning of Reference lists
ysr
parents:
360
diff
changeset
|
5978 &cmsKeepAliveClosure, false /* !preclean */); |
0 | 5979 { |
5980 TraceTime t("weak refs processing", PrintGCDetails, false, gclog_or_tty); | |
5981 if (rp->processing_is_mt()) { | |
1833
8b10f48633dc
6984287: Regularize how GC parallel workers are specified.
jmasa
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1777
diff
changeset
|
5982 // Set the degree of MT here. If the discovery is done MT, there |
8b10f48633dc
6984287: Regularize how GC parallel workers are specified.
jmasa
parents:
1777
diff
changeset
|
5983 // may have been a different number of threads doing the discovery |
8b10f48633dc
6984287: Regularize how GC parallel workers are specified.
jmasa
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1777
diff
changeset
|
5984 // and a different number of discovered lists may have Ref objects. |
8b10f48633dc
6984287: Regularize how GC parallel workers are specified.
jmasa
parents:
1777
diff
changeset
|
5985 // That is OK as long as the Reference lists are balanced (see |
8b10f48633dc
6984287: Regularize how GC parallel workers are specified.
jmasa
parents:
1777
diff
changeset
|
5986 // balance_all_queues() and balance_queues()). |
4095
bca17e38de00
6593758: RFE: Enhance GC ergonomics to dynamically choose ParallelGCThreads
jmasa
parents:
3979
diff
changeset
|
5987 GenCollectedHeap* gch = GenCollectedHeap::heap(); |
bca17e38de00
6593758: RFE: Enhance GC ergonomics to dynamically choose ParallelGCThreads
jmasa
parents:
3979
diff
changeset
|
5988 int active_workers = ParallelGCThreads; |
bca17e38de00
6593758: RFE: Enhance GC ergonomics to dynamically choose ParallelGCThreads
jmasa
parents:
3979
diff
changeset
|
5989 FlexibleWorkGang* workers = gch->workers(); |
bca17e38de00
6593758: RFE: Enhance GC ergonomics to dynamically choose ParallelGCThreads
jmasa
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3979
diff
changeset
|
5990 if (workers != NULL) { |
bca17e38de00
6593758: RFE: Enhance GC ergonomics to dynamically choose ParallelGCThreads
jmasa
parents:
3979
diff
changeset
|
5991 active_workers = workers->active_workers(); |
bca17e38de00
6593758: RFE: Enhance GC ergonomics to dynamically choose ParallelGCThreads
jmasa
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3979
diff
changeset
|
5992 // The expectation is that active_workers will have already |
bca17e38de00
6593758: RFE: Enhance GC ergonomics to dynamically choose ParallelGCThreads
jmasa
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3979
diff
changeset
|
5993 // been set to a reasonable value. If it has not been set, |
bca17e38de00
6593758: RFE: Enhance GC ergonomics to dynamically choose ParallelGCThreads
jmasa
parents:
3979
diff
changeset
|
5994 // investigate. |
bca17e38de00
6593758: RFE: Enhance GC ergonomics to dynamically choose ParallelGCThreads
jmasa
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3979
diff
changeset
|
5995 assert(active_workers > 0, "Should have been set during scavenge"); |
bca17e38de00
6593758: RFE: Enhance GC ergonomics to dynamically choose ParallelGCThreads
jmasa
parents:
3979
diff
changeset
|
5996 } |
bca17e38de00
6593758: RFE: Enhance GC ergonomics to dynamically choose ParallelGCThreads
jmasa
parents:
3979
diff
changeset
|
5997 rp->set_active_mt_degree(active_workers); |
0 | 5998 CMSRefProcTaskExecutor task_executor(*this); |
453
c96030fff130
6684579: SoftReference processing can be made more efficient
ysr
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diff
changeset
|
5999 rp->process_discovered_references(&_is_alive_closure, |
0 | 6000 &cmsKeepAliveClosure, |
6001 &cmsDrainMarkingStackClosure, | |
6002 &task_executor); | |
6003 } else { | |
453
c96030fff130
6684579: SoftReference processing can be made more efficient
ysr
parents:
452
diff
changeset
|
6004 rp->process_discovered_references(&_is_alive_closure, |
0 | 6005 &cmsKeepAliveClosure, |
6006 &cmsDrainMarkingStackClosure, | |
6007 NULL); | |
6008 } | |
10188
2f50bc369470
8013160: NPG: Remove unnecessary mark stack draining after CodeCache::do_unloading
stefank
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10186
diff
changeset
|
6009 } |
2f50bc369470
8013160: NPG: Remove unnecessary mark stack draining after CodeCache::do_unloading
stefank
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10186
diff
changeset
|
6010 |
2f50bc369470
8013160: NPG: Remove unnecessary mark stack draining after CodeCache::do_unloading
stefank
parents:
10186
diff
changeset
|
6011 // This is the point where the entire marking should have completed. |
2f50bc369470
8013160: NPG: Remove unnecessary mark stack draining after CodeCache::do_unloading
stefank
parents:
10186
diff
changeset
|
6012 verify_work_stacks_empty(); |
0 | 6013 |
94
0834225a7916
6634032: CMS: Need CMSInitiatingPermOccupancyFraction for perm, divorcing from CMSInitiatingOccupancyFraction
ysr
parents:
9
diff
changeset
|
6014 if (should_unload_classes()) { |
0 | 6015 { |
6016 TraceTime t("class unloading", PrintGCDetails, false, gclog_or_tty); | |
6017 | |
10188
2f50bc369470
8013160: NPG: Remove unnecessary mark stack draining after CodeCache::do_unloading
stefank
parents:
10186
diff
changeset
|
6018 // Unload classes and purge the SystemDictionary. |
0 | 6019 bool purged_class = SystemDictionary::do_unloading(&_is_alive_closure); |
6020 | |
10188
2f50bc369470
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stefank
parents:
10186
diff
changeset
|
6021 // Unload nmethods. |
6787
8966c2d65d96
7200470: KeepAliveClosure not needed in CodeCache::do_unloading
brutisso
parents:
6755
diff
changeset
|
6022 CodeCache::do_unloading(&_is_alive_closure, purged_class); |
0 | 6023 |
10188
2f50bc369470
8013160: NPG: Remove unnecessary mark stack draining after CodeCache::do_unloading
stefank
parents:
10186
diff
changeset
|
6024 // Prune dead klasses from subklass/sibling/implementor lists. |
6725
da91efe96a93
6964458: Reimplement class meta-data storage to use native memory
coleenp
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6197
diff
changeset
|
6025 Klass::clean_weak_klass_links(&_is_alive_closure); |
0 | 6026 } |
6027 | |
6028 { | |
2379
b099aaf51bf8
6962931: move interned strings out of the perm gen
jcoomes
parents:
2369
diff
changeset
|
6029 TraceTime t("scrub symbol table", PrintGCDetails, false, gclog_or_tty); |
2177
3582bf76420e
6990754: Use native memory and reference counting to implement SymbolTable
coleenp
parents:
2147
diff
changeset
|
6030 // Clean up unreferenced symbols in symbol table. |
3582bf76420e
6990754: Use native memory and reference counting to implement SymbolTable
coleenp
parents:
2147
diff
changeset
|
6031 SymbolTable::unlink(); |
0 | 6032 } |
6033 } | |
6034 | |
6725
da91efe96a93
6964458: Reimplement class meta-data storage to use native memory
coleenp
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6197
diff
changeset
|
6035 // CMS doesn't use the StringTable as hard roots when class unloading is turned off. |
da91efe96a93
6964458: Reimplement class meta-data storage to use native memory
coleenp
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6197
diff
changeset
|
6036 // Need to check if we really scanned the StringTable. |
da91efe96a93
6964458: Reimplement class meta-data storage to use native memory
coleenp
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6197
diff
changeset
|
6037 if ((roots_scanning_options() & SharedHeap::SO_Strings) == 0) { |
2379
b099aaf51bf8
6962931: move interned strings out of the perm gen
jcoomes
parents:
2369
diff
changeset
|
6038 TraceTime t("scrub string table", PrintGCDetails, false, gclog_or_tty); |
10188
2f50bc369470
8013160: NPG: Remove unnecessary mark stack draining after CodeCache::do_unloading
stefank
parents:
10186
diff
changeset
|
6039 // Delete entries for dead interned strings. |
2379
b099aaf51bf8
6962931: move interned strings out of the perm gen
jcoomes
parents:
2369
diff
changeset
|
6040 StringTable::unlink(&_is_alive_closure); |
b099aaf51bf8
6962931: move interned strings out of the perm gen
jcoomes
parents:
2369
diff
changeset
|
6041 } |
b099aaf51bf8
6962931: move interned strings out of the perm gen
jcoomes
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2369
diff
changeset
|
6042 |
0 | 6043 // Restore any preserved marks as a result of mark stack or |
6044 // work queue overflow | |
6045 restore_preserved_marks_if_any(); // done single-threaded for now | |
6046 | |
6047 rp->set_enqueuing_is_done(true); | |
6048 if (rp->processing_is_mt()) { | |
1833
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6984287: Regularize how GC parallel workers are specified.
jmasa
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1777
diff
changeset
|
6049 rp->balance_all_queues(); |
0 | 6050 CMSRefProcTaskExecutor task_executor(*this); |
6051 rp->enqueue_discovered_references(&task_executor); | |
6052 } else { | |
6053 rp->enqueue_discovered_references(NULL); | |
6054 } | |
6055 rp->verify_no_references_recorded(); | |
6056 assert(!rp->discovery_enabled(), "should have been disabled"); | |
6057 } | |
6058 | |
6059 #ifndef PRODUCT | |
6060 void CMSCollector::check_correct_thread_executing() { | |
6061 Thread* t = Thread::current(); | |
6062 // Only the VM thread or the CMS thread should be here. | |
6063 assert(t->is_ConcurrentGC_thread() || t->is_VM_thread(), | |
6064 "Unexpected thread type"); | |
6065 // If this is the vm thread, the foreground process | |
6066 // should not be waiting. Note that _foregroundGCIsActive is | |
6067 // true while the foreground collector is waiting. | |
6068 if (_foregroundGCShouldWait) { | |
6069 // We cannot be the VM thread | |
6070 assert(t->is_ConcurrentGC_thread(), | |
6071 "Should be CMS thread"); | |
6072 } else { | |
6073 // We can be the CMS thread only if we are in a stop-world | |
6074 // phase of CMS collection. | |
6075 if (t->is_ConcurrentGC_thread()) { | |
6076 assert(_collectorState == InitialMarking || | |
6077 _collectorState == FinalMarking, | |
6078 "Should be a stop-world phase"); | |
6079 // The CMS thread should be holding the CMS_token. | |
6080 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
6081 "Potential interference with concurrently " | |
6082 "executing VM thread"); | |
6083 } | |
6084 } | |
6085 } | |
6086 #endif | |
6087 | |
6088 void CMSCollector::sweep(bool asynch) { | |
6089 assert(_collectorState == Sweeping, "just checking"); | |
6090 check_correct_thread_executing(); | |
6091 verify_work_stacks_empty(); | |
6092 verify_overflow_empty(); | |
1145
e018e6884bd8
6631166: CMS: better heuristics when combatting fragmentation
ysr
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1085
diff
changeset
|
6093 increment_sweep_count(); |
3356
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6094 TraceCMSMemoryManagerStats tms(_collectorState,GenCollectedHeap::heap()->gc_cause()); |
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6095 |
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6096 _inter_sweep_timer.stop(); |
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6097 _inter_sweep_estimate.sample(_inter_sweep_timer.seconds()); |
0 | 6098 size_policy()->avg_cms_free_at_sweep()->sample(_cmsGen->free()); |
6099 | |
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6100 assert(!_intra_sweep_timer.is_active(), "Should not be active"); |
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6101 _intra_sweep_timer.reset(); |
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6102 _intra_sweep_timer.start(); |
0 | 6103 if (asynch) { |
6104 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
6105 CMSPhaseAccounting pa(this, "sweep", !PrintGCDetails); | |
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6106 // First sweep the old gen |
0 | 6107 { |
6108 CMSTokenSyncWithLocks ts(true, _cmsGen->freelistLock(), | |
6109 bitMapLock()); | |
6110 sweepWork(_cmsGen, asynch); | |
6111 } | |
6112 | |
6113 // Update Universe::_heap_*_at_gc figures. | |
6114 // We need all the free list locks to make the abstract state | |
6115 // transition from Sweeping to Resetting. See detailed note | |
6116 // further below. | |
6117 { | |
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6118 CMSTokenSyncWithLocks ts(true, _cmsGen->freelistLock()); |
0 | 6119 // Update heap occupancy information which is used as |
6120 // input to soft ref clearing policy at the next gc. | |
6121 Universe::update_heap_info_at_gc(); | |
6122 _collectorState = Resizing; | |
6123 } | |
6124 } else { | |
6125 // already have needed locks | |
6126 sweepWork(_cmsGen, asynch); | |
6127 // Update heap occupancy information which is used as | |
6128 // input to soft ref clearing policy at the next gc. | |
6129 Universe::update_heap_info_at_gc(); | |
6130 _collectorState = Resizing; | |
6131 } | |
6132 verify_work_stacks_empty(); | |
6133 verify_overflow_empty(); | |
6134 | |
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6135 if (should_unload_classes()) { |
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8005602: NPG: classunloading does not happen while CMS GC with -XX:+CMSClassUnloadingEnabled is used
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|
6136 ClassLoaderDataGraph::purge(); |
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6137 } |
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6138 |
1145
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6139 _intra_sweep_timer.stop(); |
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6140 _intra_sweep_estimate.sample(_intra_sweep_timer.seconds()); |
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6141 |
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6142 _inter_sweep_timer.reset(); |
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6143 _inter_sweep_timer.start(); |
0 | 6144 |
4911 | 6145 // We need to use a monotonically non-deccreasing time in ms |
6146 // or we will see time-warp warnings and os::javaTimeMillis() | |
6147 // does not guarantee monotonicity. | |
6148 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; | |
6149 update_time_of_last_gc(now); | |
0 | 6150 |
6151 // NOTE on abstract state transitions: | |
6152 // Mutators allocate-live and/or mark the mod-union table dirty | |
6153 // based on the state of the collection. The former is done in | |
6154 // the interval [Marking, Sweeping] and the latter in the interval | |
6155 // [Marking, Sweeping). Thus the transitions into the Marking state | |
6156 // and out of the Sweeping state must be synchronously visible | |
6157 // globally to the mutators. | |
6158 // The transition into the Marking state happens with the world | |
6159 // stopped so the mutators will globally see it. Sweeping is | |
6160 // done asynchronously by the background collector so the transition | |
6161 // from the Sweeping state to the Resizing state must be done | |
6162 // under the freelistLock (as is the check for whether to | |
6163 // allocate-live and whether to dirty the mod-union table). | |
6164 assert(_collectorState == Resizing, "Change of collector state to" | |
6165 " Resizing must be done under the freelistLocks (plural)"); | |
6166 | |
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6167 // Now that sweeping has been completed, we clear |
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6168 // the incremental_collection_failed flag, |
0 | 6169 // thus inviting a younger gen collection to promote into |
6170 // this generation. If such a promotion may still fail, | |
6171 // the flag will be set again when a young collection is | |
6172 // attempted. | |
6173 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
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6174 gch->clear_incremental_collection_failed(); // Worth retrying as fresh space may have been freed up |
0 | 6175 gch->update_full_collections_completed(_collection_count_start); |
6176 } | |
6177 | |
6178 // FIX ME!!! Looks like this belongs in CFLSpace, with | |
6179 // CMSGen merely delegating to it. | |
6180 void ConcurrentMarkSweepGeneration::setNearLargestChunk() { | |
1145
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6181 double nearLargestPercent = FLSLargestBlockCoalesceProximity; |
0 | 6182 HeapWord* minAddr = _cmsSpace->bottom(); |
6183 HeapWord* largestAddr = | |
6028
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6184 (HeapWord*) _cmsSpace->dictionary()->find_largest_dict(); |
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6185 if (largestAddr == NULL) { |
0 | 6186 // The dictionary appears to be empty. In this case |
6187 // try to coalesce at the end of the heap. | |
6188 largestAddr = _cmsSpace->end(); | |
6189 } | |
6190 size_t largestOffset = pointer_delta(largestAddr, minAddr); | |
6191 size_t nearLargestOffset = | |
6192 (size_t)((double)largestOffset * nearLargestPercent) - MinChunkSize; | |
1145
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6193 if (PrintFLSStatistics != 0) { |
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6194 gclog_or_tty->print_cr( |
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6195 "CMS: Large Block: " PTR_FORMAT ";" |
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6196 " Proximity: " PTR_FORMAT " -> " PTR_FORMAT, |
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6197 largestAddr, |
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6198 _cmsSpace->nearLargestChunk(), minAddr + nearLargestOffset); |
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6199 } |
0 | 6200 _cmsSpace->set_nearLargestChunk(minAddr + nearLargestOffset); |
6201 } | |
6202 | |
6203 bool ConcurrentMarkSweepGeneration::isNearLargestChunk(HeapWord* addr) { | |
6204 return addr >= _cmsSpace->nearLargestChunk(); | |
6205 } | |
6206 | |
6207 FreeChunk* ConcurrentMarkSweepGeneration::find_chunk_at_end() { | |
6208 return _cmsSpace->find_chunk_at_end(); | |
6209 } | |
6210 | |
6211 void ConcurrentMarkSweepGeneration::update_gc_stats(int current_level, | |
6212 bool full) { | |
6213 // The next lower level has been collected. Gather any statistics | |
6214 // that are of interest at this point. | |
6215 if (!full && (current_level + 1) == level()) { | |
6216 // Gather statistics on the young generation collection. | |
6217 collector()->stats().record_gc0_end(used()); | |
6218 } | |
6219 } | |
6220 | |
6221 CMSAdaptiveSizePolicy* ConcurrentMarkSweepGeneration::size_policy() { | |
6222 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
6223 assert(gch->kind() == CollectedHeap::GenCollectedHeap, | |
6224 "Wrong type of heap"); | |
6225 CMSAdaptiveSizePolicy* sp = (CMSAdaptiveSizePolicy*) | |
6226 gch->gen_policy()->size_policy(); | |
6227 assert(sp->is_gc_cms_adaptive_size_policy(), | |
6228 "Wrong type of size policy"); | |
6229 return sp; | |
6230 } | |
6231 | |
6232 void ConcurrentMarkSweepGeneration::rotate_debug_collection_type() { | |
6233 if (PrintGCDetails && Verbose) { | |
6234 gclog_or_tty->print("Rotate from %d ", _debug_collection_type); | |
6235 } | |
6236 _debug_collection_type = (CollectionTypes) (_debug_collection_type + 1); | |
6237 _debug_collection_type = | |
6238 (CollectionTypes) (_debug_collection_type % Unknown_collection_type); | |
6239 if (PrintGCDetails && Verbose) { | |
6240 gclog_or_tty->print_cr("to %d ", _debug_collection_type); | |
6241 } | |
6242 } | |
6243 | |
6244 void CMSCollector::sweepWork(ConcurrentMarkSweepGeneration* gen, | |
6245 bool asynch) { | |
6246 // We iterate over the space(s) underlying this generation, | |
6247 // checking the mark bit map to see if the bits corresponding | |
6248 // to specific blocks are marked or not. Blocks that are | |
6249 // marked are live and are not swept up. All remaining blocks | |
6250 // are swept up, with coalescing on-the-fly as we sweep up | |
6251 // contiguous free and/or garbage blocks: | |
6252 // We need to ensure that the sweeper synchronizes with allocators | |
6253 // and stop-the-world collectors. In particular, the following | |
6254 // locks are used: | |
6255 // . CMS token: if this is held, a stop the world collection cannot occur | |
6256 // . freelistLock: if this is held no allocation can occur from this | |
6257 // generation by another thread | |
6258 // . bitMapLock: if this is held, no other thread can access or update | |
6259 // | |
6260 | |
6261 // Note that we need to hold the freelistLock if we use | |
6262 // block iterate below; else the iterator might go awry if | |
6263 // a mutator (or promotion) causes block contents to change | |
6264 // (for instance if the allocator divvies up a block). | |
6265 // If we hold the free list lock, for all practical purposes | |
6266 // young generation GC's can't occur (they'll usually need to | |
6267 // promote), so we might as well prevent all young generation | |
6268 // GC's while we do a sweeping step. For the same reason, we might | |
6269 // as well take the bit map lock for the entire duration | |
6270 | |
6271 // check that we hold the requisite locks | |
6272 assert(have_cms_token(), "Should hold cms token"); | |
6273 assert( (asynch && ConcurrentMarkSweepThread::cms_thread_has_cms_token()) | |
6274 || (!asynch && ConcurrentMarkSweepThread::vm_thread_has_cms_token()), | |
6275 "Should possess CMS token to sweep"); | |
6276 assert_lock_strong(gen->freelistLock()); | |
6277 assert_lock_strong(bitMapLock()); | |
6278 | |
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6279 assert(!_inter_sweep_timer.is_active(), "Was switched off in an outer context"); |
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6280 assert(_intra_sweep_timer.is_active(), "Was switched on in an outer context"); |
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6281 gen->cmsSpace()->beginSweepFLCensus((float)(_inter_sweep_timer.seconds()), |
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|
6282 _inter_sweep_estimate.padded_average(), |
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|
6283 _intra_sweep_estimate.padded_average()); |
0 | 6284 gen->setNearLargestChunk(); |
6285 | |
6286 { | |
6287 SweepClosure sweepClosure(this, gen, &_markBitMap, | |
6288 CMSYield && asynch); | |
6289 gen->cmsSpace()->blk_iterate_careful(&sweepClosure); | |
6290 // We need to free-up/coalesce garbage/blocks from a | |
6291 // co-terminal free run. This is done in the SweepClosure | |
6292 // destructor; so, do not remove this scope, else the | |
6293 // end-of-sweep-census below will be off by a little bit. | |
6294 } | |
6295 gen->cmsSpace()->sweep_completed(); | |
1145
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6296 gen->cmsSpace()->endSweepFLCensus(sweep_count()); |
94
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6634032: CMS: Need CMSInitiatingPermOccupancyFraction for perm, divorcing from CMSInitiatingOccupancyFraction
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diff
changeset
|
6297 if (should_unload_classes()) { // unloaded classes this cycle, |
0834225a7916
6634032: CMS: Need CMSInitiatingPermOccupancyFraction for perm, divorcing from CMSInitiatingOccupancyFraction
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diff
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|
6298 _concurrent_cycles_since_last_unload = 0; // ... reset count |
0834225a7916
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diff
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6299 } else { // did not unload classes, |
0834225a7916
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|
6300 _concurrent_cycles_since_last_unload++; // ... increment count |
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|
6301 } |
0 | 6302 } |
6303 | |
6304 // Reset CMS data structures (for now just the marking bit map) | |
6305 // preparatory for the next cycle. | |
6306 void CMSCollector::reset(bool asynch) { | |
6307 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
6308 CMSAdaptiveSizePolicy* sp = size_policy(); | |
6309 AdaptiveSizePolicyOutput(sp, gch->total_collections()); | |
6310 if (asynch) { | |
6311 CMSTokenSyncWithLocks ts(true, bitMapLock()); | |
6312 | |
6313 // If the state is not "Resetting", the foreground thread | |
6314 // has done a collection and the resetting. | |
6315 if (_collectorState != Resetting) { | |
6316 assert(_collectorState == Idling, "The state should only change" | |
6317 " because the foreground collector has finished the collection"); | |
6318 return; | |
6319 } | |
6320 | |
6321 // Clear the mark bitmap (no grey objects to start with) | |
6322 // for the next cycle. | |
6323 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
6324 CMSPhaseAccounting cmspa(this, "reset", !PrintGCDetails); | |
6325 | |
6326 HeapWord* curAddr = _markBitMap.startWord(); | |
6327 while (curAddr < _markBitMap.endWord()) { | |
6328 size_t remaining = pointer_delta(_markBitMap.endWord(), curAddr); | |
6329 MemRegion chunk(curAddr, MIN2(CMSBitMapYieldQuantum, remaining)); | |
6330 _markBitMap.clear_large_range(chunk); | |
6331 if (ConcurrentMarkSweepThread::should_yield() && | |
6332 !foregroundGCIsActive() && | |
6333 CMSYield) { | |
6334 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
6335 "CMS thread should hold CMS token"); | |
6336 assert_lock_strong(bitMapLock()); | |
6337 bitMapLock()->unlock(); | |
6338 ConcurrentMarkSweepThread::desynchronize(true); | |
6339 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
6340 stopTimer(); | |
6341 if (PrintCMSStatistics != 0) { | |
6342 incrementYields(); | |
6343 } | |
6344 icms_wait(); | |
6345 | |
6346 // See the comment in coordinator_yield() | |
6347 for (unsigned i = 0; i < CMSYieldSleepCount && | |
113
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6348 ConcurrentMarkSweepThread::should_yield() && |
ba764ed4b6f2
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|
6349 !CMSCollector::foregroundGCIsActive(); ++i) { |
0 | 6350 os::sleep(Thread::current(), 1, false); |
6351 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
6352 } | |
6353 | |
6354 ConcurrentMarkSweepThread::synchronize(true); | |
6355 bitMapLock()->lock_without_safepoint_check(); | |
6356 startTimer(); | |
6357 } | |
6358 curAddr = chunk.end(); | |
6359 } | |
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6360 // 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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6361 // Because only the full (i.e., concurrent mode failure) collections |
0bfd3fb24150
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6362 // are being measured for gc overhead limits, clean the "near" flag |
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6363 // and count. |
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|
6364 sp->reset_gc_overhead_limit_count(); |
0 | 6365 _collectorState = Idling; |
6366 } else { | |
6367 // already have the lock | |
6368 assert(_collectorState == Resetting, "just checking"); | |
6369 assert_lock_strong(bitMapLock()); | |
6370 _markBitMap.clear_all(); | |
6371 _collectorState = Idling; | |
6372 } | |
6373 | |
6374 // Stop incremental mode after a cycle completes, so that any future cycles | |
6375 // are triggered by allocation. | |
6376 stop_icms(); | |
6377 | |
6378 NOT_PRODUCT( | |
6379 if (RotateCMSCollectionTypes) { | |
6380 _cmsGen->rotate_debug_collection_type(); | |
6381 } | |
6382 ) | |
6383 } | |
6384 | |
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|
6385 void CMSCollector::do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause) { |
0 | 6386 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps); |
6387 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
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|
6388 TraceTime t(GCCauseString("GC", gc_cause), PrintGC, !PrintGCDetails, gclog_or_tty); |
0 | 6389 TraceCollectorStats tcs(counters()); |
6390 | |
6391 switch (op) { | |
6392 case CMS_op_checkpointRootsInitial: { | |
2125
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|
6393 SvcGCMarker sgcm(SvcGCMarker::OTHER); |
0 | 6394 checkpointRootsInitial(true); // asynch |
6395 if (PrintGC) { | |
6396 _cmsGen->printOccupancy("initial-mark"); | |
6397 } | |
6398 break; | |
6399 } | |
6400 case CMS_op_checkpointRootsFinal: { | |
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|
6401 SvcGCMarker sgcm(SvcGCMarker::OTHER); |
0 | 6402 checkpointRootsFinal(true, // asynch |
6403 false, // !clear_all_soft_refs | |
6404 false); // !init_mark_was_synchronous | |
6405 if (PrintGC) { | |
6406 _cmsGen->printOccupancy("remark"); | |
6407 } | |
6408 break; | |
6409 } | |
6410 default: | |
6411 fatal("No such CMS_op"); | |
6412 } | |
6413 } | |
6414 | |
6415 #ifndef PRODUCT | |
6416 size_t const CMSCollector::skip_header_HeapWords() { | |
6417 return FreeChunk::header_size(); | |
6418 } | |
6419 | |
6420 // Try and collect here conditions that should hold when | |
6421 // CMS thread is exiting. The idea is that the foreground GC | |
6422 // thread should not be blocked if it wants to terminate | |
6423 // the CMS thread and yet continue to run the VM for a while | |
6424 // after that. | |
6425 void CMSCollector::verify_ok_to_terminate() const { | |
6426 assert(Thread::current()->is_ConcurrentGC_thread(), | |
6427 "should be called by CMS thread"); | |
6428 assert(!_foregroundGCShouldWait, "should be false"); | |
6429 // We could check here that all the various low-level locks | |
6430 // are not held by the CMS thread, but that is overkill; see | |
6431 // also CMSThread::verify_ok_to_terminate() where the CGC_lock | |
6432 // is checked. | |
6433 } | |
6434 #endif | |
6435 | |
6436 size_t CMSCollector::block_size_using_printezis_bits(HeapWord* addr) const { | |
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6437 assert(_markBitMap.isMarked(addr) && _markBitMap.isMarked(addr + 1), |
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6438 "missing Printezis mark?"); |
0 | 6439 HeapWord* nextOneAddr = _markBitMap.getNextMarkedWordAddress(addr + 2); |
6440 size_t size = pointer_delta(nextOneAddr + 1, addr); | |
6441 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
6442 "alignment problem"); | |
6443 assert(size >= 3, "Necessary for Printezis marks to work"); | |
6444 return size; | |
6445 } | |
6446 | |
6447 // A variant of the above (block_size_using_printezis_bits()) except | |
6448 // that we return 0 if the P-bits are not yet set. | |
6449 size_t CMSCollector::block_size_if_printezis_bits(HeapWord* addr) const { | |
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6450 if (_markBitMap.isMarked(addr + 1)) { |
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6451 assert(_markBitMap.isMarked(addr), "P-bit can be set only for marked objects"); |
0 | 6452 HeapWord* nextOneAddr = _markBitMap.getNextMarkedWordAddress(addr + 2); |
6453 size_t size = pointer_delta(nextOneAddr + 1, addr); | |
6454 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
6455 "alignment problem"); | |
6456 assert(size >= 3, "Necessary for Printezis marks to work"); | |
6457 return size; | |
2226
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6458 } |
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6459 return 0; |
0 | 6460 } |
6461 | |
6462 HeapWord* CMSCollector::next_card_start_after_block(HeapWord* addr) const { | |
6463 size_t sz = 0; | |
6464 oop p = (oop)addr; | |
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6465 if (p->klass_or_null() != NULL) { |
0 | 6466 sz = CompactibleFreeListSpace::adjustObjectSize(p->size()); |
6467 } else { | |
6468 sz = block_size_using_printezis_bits(addr); | |
6469 } | |
6470 assert(sz > 0, "size must be nonzero"); | |
6471 HeapWord* next_block = addr + sz; | |
6472 HeapWord* next_card = (HeapWord*)round_to((uintptr_t)next_block, | |
6473 CardTableModRefBS::card_size); | |
6474 assert(round_down((uintptr_t)addr, CardTableModRefBS::card_size) < | |
6475 round_down((uintptr_t)next_card, CardTableModRefBS::card_size), | |
6476 "must be different cards"); | |
6477 return next_card; | |
6478 } | |
6479 | |
6480 | |
6481 // CMS Bit Map Wrapper ///////////////////////////////////////// | |
6482 | |
6483 // Construct a CMS bit map infrastructure, but don't create the | |
6484 // bit vector itself. That is done by a separate call CMSBitMap::allocate() | |
6485 // further below. | |
6486 CMSBitMap::CMSBitMap(int shifter, int mutex_rank, const char* mutex_name): | |
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6487 _bm(), |
0 | 6488 _shifter(shifter), |
6489 _lock(mutex_rank >= 0 ? new Mutex(mutex_rank, mutex_name, true) : NULL) | |
6490 { | |
6491 _bmStartWord = 0; | |
6492 _bmWordSize = 0; | |
6493 } | |
6494 | |
6495 bool CMSBitMap::allocate(MemRegion mr) { | |
6496 _bmStartWord = mr.start(); | |
6497 _bmWordSize = mr.word_size(); | |
6498 ReservedSpace brs(ReservedSpace::allocation_align_size_up( | |
6499 (_bmWordSize >> (_shifter + LogBitsPerByte)) + 1)); | |
6500 if (!brs.is_reserved()) { | |
6501 warning("CMS bit map allocation failure"); | |
6502 return false; | |
6503 } | |
6504 // For now we'll just commit all of the bit map up fromt. | |
6505 // Later on we'll try to be more parsimonious with swap. | |
6506 if (!_virtual_space.initialize(brs, brs.size())) { | |
6507 warning("CMS bit map backing store failure"); | |
6508 return false; | |
6509 } | |
6510 assert(_virtual_space.committed_size() == brs.size(), | |
6511 "didn't reserve backing store for all of CMS bit map?"); | |
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6512 _bm.set_map((BitMap::bm_word_t*)_virtual_space.low()); |
0 | 6513 assert(_virtual_space.committed_size() << (_shifter + LogBitsPerByte) >= |
6514 _bmWordSize, "inconsistency in bit map sizing"); | |
6515 _bm.set_size(_bmWordSize >> _shifter); | |
6516 | |
6517 // bm.clear(); // can we rely on getting zero'd memory? verify below | |
6518 assert(isAllClear(), | |
6519 "Expected zero'd memory from ReservedSpace constructor"); | |
6520 assert(_bm.size() == heapWordDiffToOffsetDiff(sizeInWords()), | |
6521 "consistency check"); | |
6522 return true; | |
6523 } | |
6524 | |
6525 void CMSBitMap::dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl) { | |
6526 HeapWord *next_addr, *end_addr, *last_addr; | |
6527 assert_locked(); | |
6528 assert(covers(mr), "out-of-range error"); | |
6529 // XXX assert that start and end are appropriately aligned | |
6530 for (next_addr = mr.start(), end_addr = mr.end(); | |
6531 next_addr < end_addr; next_addr = last_addr) { | |
6532 MemRegion dirty_region = getAndClearMarkedRegion(next_addr, end_addr); | |
6533 last_addr = dirty_region.end(); | |
6534 if (!dirty_region.is_empty()) { | |
6535 cl->do_MemRegion(dirty_region); | |
6536 } else { | |
6537 assert(last_addr == end_addr, "program logic"); | |
6538 return; | |
6539 } | |
6540 } | |
6541 } | |
6542 | |
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6543 void CMSBitMap::print_on_error(outputStream* st, const char* prefix) const { |
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6544 _bm.print_on_error(st, prefix); |
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6545 } |
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6546 |
0 | 6547 #ifndef PRODUCT |
6548 void CMSBitMap::assert_locked() const { | |
6549 CMSLockVerifier::assert_locked(lock()); | |
6550 } | |
6551 | |
6552 bool CMSBitMap::covers(MemRegion mr) const { | |
6553 // assert(_bm.map() == _virtual_space.low(), "map inconsistency"); | |
6554 assert((size_t)_bm.size() == (_bmWordSize >> _shifter), | |
6555 "size inconsistency"); | |
6556 return (mr.start() >= _bmStartWord) && | |
6557 (mr.end() <= endWord()); | |
6558 } | |
6559 | |
6560 bool CMSBitMap::covers(HeapWord* start, size_t size) const { | |
6561 return (start >= _bmStartWord && (start + size) <= endWord()); | |
6562 } | |
6563 | |
6564 void CMSBitMap::verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) { | |
6565 // verify that there are no 1 bits in the interval [left, right) | |
6566 FalseBitMapClosure falseBitMapClosure; | |
6567 iterate(&falseBitMapClosure, left, right); | |
6568 } | |
6569 | |
6570 void CMSBitMap::region_invariant(MemRegion mr) | |
6571 { | |
6572 assert_locked(); | |
6573 // mr = mr.intersection(MemRegion(_bmStartWord, _bmWordSize)); | |
6574 assert(!mr.is_empty(), "unexpected empty region"); | |
6575 assert(covers(mr), "mr should be covered by bit map"); | |
6576 // convert address range into offset range | |
6577 size_t start_ofs = heapWordToOffset(mr.start()); | |
6578 // Make sure that end() is appropriately aligned | |
6579 assert(mr.end() == (HeapWord*)round_to((intptr_t)mr.end(), | |
6580 (1 << (_shifter+LogHeapWordSize))), | |
6581 "Misaligned mr.end()"); | |
6582 size_t end_ofs = heapWordToOffset(mr.end()); | |
6583 assert(end_ofs > start_ofs, "Should mark at least one bit"); | |
6584 } | |
6585 | |
6586 #endif | |
6587 | |
6588 bool CMSMarkStack::allocate(size_t size) { | |
6589 // allocate a stack of the requisite depth | |
6590 ReservedSpace rs(ReservedSpace::allocation_align_size_up( | |
6591 size * sizeof(oop))); | |
6592 if (!rs.is_reserved()) { | |
6593 warning("CMSMarkStack allocation failure"); | |
6594 return false; | |
6595 } | |
6596 if (!_virtual_space.initialize(rs, rs.size())) { | |
6597 warning("CMSMarkStack backing store failure"); | |
6598 return false; | |
6599 } | |
6600 assert(_virtual_space.committed_size() == rs.size(), | |
6601 "didn't reserve backing store for all of CMS stack?"); | |
6602 _base = (oop*)(_virtual_space.low()); | |
6603 _index = 0; | |
6604 _capacity = size; | |
6605 NOT_PRODUCT(_max_depth = 0); | |
6606 return true; | |
6607 } | |
6608 | |
6609 // XXX FIX ME !!! In the MT case we come in here holding a | |
6610 // leaf lock. For printing we need to take a further lock | |
6611 // which has lower rank. We need to recallibrate the two | |
6612 // lock-ranks involved in order to be able to rpint the | |
6613 // messages below. (Or defer the printing to the caller. | |
6614 // For now we take the expedient path of just disabling the | |
6615 // messages for the problematic case.) | |
6616 void CMSMarkStack::expand() { | |
1284 | 6617 assert(_capacity <= MarkStackSizeMax, "stack bigger than permitted"); |
6618 if (_capacity == MarkStackSizeMax) { | |
0 | 6619 if (_hit_limit++ == 0 && !CMSConcurrentMTEnabled && PrintGCDetails) { |
6620 // We print a warning message only once per CMS cycle. | |
6621 gclog_or_tty->print_cr(" (benign) Hit CMSMarkStack max size limit"); | |
6622 } | |
6623 return; | |
6624 } | |
6625 // Double capacity if possible | |
1284 | 6626 size_t new_capacity = MIN2(_capacity*2, MarkStackSizeMax); |
0 | 6627 // Do not give up existing stack until we have managed to |
6628 // get the double capacity that we desired. | |
6629 ReservedSpace rs(ReservedSpace::allocation_align_size_up( | |
6630 new_capacity * sizeof(oop))); | |
6631 if (rs.is_reserved()) { | |
6632 // Release the backing store associated with old stack | |
6633 _virtual_space.release(); | |
6634 // Reinitialize virtual space for new stack | |
6635 if (!_virtual_space.initialize(rs, rs.size())) { | |
6636 fatal("Not enough swap for expanded marking stack"); | |
6637 } | |
6638 _base = (oop*)(_virtual_space.low()); | |
6639 _index = 0; | |
6640 _capacity = new_capacity; | |
6641 } else if (_failed_double++ == 0 && !CMSConcurrentMTEnabled && PrintGCDetails) { | |
6642 // Failed to double capacity, continue; | |
6643 // we print a detail message only once per CMS cycle. | |
6644 gclog_or_tty->print(" (benign) Failed to expand marking stack from "SIZE_FORMAT"K to " | |
6645 SIZE_FORMAT"K", | |
6646 _capacity / K, new_capacity / K); | |
6647 } | |
6648 } | |
6649 | |
6650 | |
6651 // Closures | |
6652 // XXX: there seems to be a lot of code duplication here; | |
6653 // should refactor and consolidate common code. | |
6654 | |
6655 // This closure is used to mark refs into the CMS generation in | |
6656 // the CMS bit map. Called at the first checkpoint. This closure | |
6657 // assumes that we do not need to re-mark dirty cards; if the CMS | |
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6658 // generation on which this is used is not an oldest |
0 | 6659 // generation then this will lose younger_gen cards! |
6660 | |
6661 MarkRefsIntoClosure::MarkRefsIntoClosure( | |
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6662 MemRegion span, CMSBitMap* bitMap): |
0 | 6663 _span(span), |
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6664 _bitMap(bitMap) |
0 | 6665 { |
6666 assert(_ref_processor == NULL, "deliberately left NULL"); | |
6667 assert(_bitMap->covers(_span), "_bitMap/_span mismatch"); | |
6668 } | |
6669 | |
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6670 void MarkRefsIntoClosure::do_oop(oop obj) { |
0 | 6671 // if p points into _span, then mark corresponding bit in _markBitMap |
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6672 assert(obj->is_oop(), "expected an oop"); |
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6673 HeapWord* addr = (HeapWord*)obj; |
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6674 if (_span.contains(addr)) { |
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6675 // this should be made more efficient |
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6676 _bitMap->mark(addr); |
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6677 } |
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6678 } |
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6679 |
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6680 void MarkRefsIntoClosure::do_oop(oop* p) { MarkRefsIntoClosure::do_oop_work(p); } |
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6681 void MarkRefsIntoClosure::do_oop(narrowOop* p) { MarkRefsIntoClosure::do_oop_work(p); } |
0 | 6682 |
6683 // A variant of the above, used for CMS marking verification. | |
6684 MarkRefsIntoVerifyClosure::MarkRefsIntoVerifyClosure( | |
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6685 MemRegion span, CMSBitMap* verification_bm, CMSBitMap* cms_bm): |
0 | 6686 _span(span), |
6687 _verification_bm(verification_bm), | |
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6688 _cms_bm(cms_bm) |
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6689 { |
0 | 6690 assert(_ref_processor == NULL, "deliberately left NULL"); |
6691 assert(_verification_bm->covers(_span), "_verification_bm/_span mismatch"); | |
6692 } | |
6693 | |
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6694 void MarkRefsIntoVerifyClosure::do_oop(oop obj) { |
0 | 6695 // if p points into _span, then mark corresponding bit in _markBitMap |
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6696 assert(obj->is_oop(), "expected an oop"); |
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6697 HeapWord* addr = (HeapWord*)obj; |
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6698 if (_span.contains(addr)) { |
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6699 _verification_bm->mark(addr); |
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6700 if (!_cms_bm->isMarked(addr)) { |
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6701 oop(addr)->print(); |
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6702 gclog_or_tty->print_cr(" (" INTPTR_FORMAT " should have been marked)", addr); |
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6703 fatal("... aborting"); |
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6704 } |
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6705 } |
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6706 } |
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6707 |
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6708 void MarkRefsIntoVerifyClosure::do_oop(oop* p) { MarkRefsIntoVerifyClosure::do_oop_work(p); } |
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6709 void MarkRefsIntoVerifyClosure::do_oop(narrowOop* p) { MarkRefsIntoVerifyClosure::do_oop_work(p); } |
0 | 6710 |
6711 ////////////////////////////////////////////////// | |
6712 // MarkRefsIntoAndScanClosure | |
6713 ////////////////////////////////////////////////// | |
6714 | |
6715 MarkRefsIntoAndScanClosure::MarkRefsIntoAndScanClosure(MemRegion span, | |
6716 ReferenceProcessor* rp, | |
6717 CMSBitMap* bit_map, | |
6718 CMSBitMap* mod_union_table, | |
6719 CMSMarkStack* mark_stack, | |
6720 CMSCollector* collector, | |
6721 bool should_yield, | |
6722 bool concurrent_precleaning): | |
6723 _collector(collector), | |
6724 _span(span), | |
6725 _bit_map(bit_map), | |
6726 _mark_stack(mark_stack), | |
6727 _pushAndMarkClosure(collector, span, rp, bit_map, mod_union_table, | |
6725
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6728 mark_stack, concurrent_precleaning), |
0 | 6729 _yield(should_yield), |
6730 _concurrent_precleaning(concurrent_precleaning), | |
6731 _freelistLock(NULL) | |
6732 { | |
6733 _ref_processor = rp; | |
6734 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
6735 } | |
6736 | |
6737 // This closure is used to mark refs into the CMS generation at the | |
6738 // second (final) checkpoint, and to scan and transitively follow | |
6739 // the unmarked oops. It is also used during the concurrent precleaning | |
6740 // phase while scanning objects on dirty cards in the CMS generation. | |
6741 // The marks are made in the marking bit map and the marking stack is | |
6742 // used for keeping the (newly) grey objects during the scan. | |
6743 // The parallel version (Par_...) appears further below. | |
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6744 void MarkRefsIntoAndScanClosure::do_oop(oop obj) { |
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6745 if (obj != NULL) { |
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6746 assert(obj->is_oop(), "expected an oop"); |
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6747 HeapWord* addr = (HeapWord*)obj; |
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6748 assert(_mark_stack->isEmpty(), "pre-condition (eager drainage)"); |
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6749 assert(_collector->overflow_list_is_empty(), |
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6750 "overflow list should be empty"); |
0 | 6751 if (_span.contains(addr) && |
6752 !_bit_map->isMarked(addr)) { | |
6753 // mark bit map (object is now grey) | |
6754 _bit_map->mark(addr); | |
6755 // push on marking stack (stack should be empty), and drain the | |
6756 // stack by applying this closure to the oops in the oops popped | |
6757 // from the stack (i.e. blacken the grey objects) | |
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6758 bool res = _mark_stack->push(obj); |
0 | 6759 assert(res, "Should have space to push on empty stack"); |
6760 do { | |
6761 oop new_oop = _mark_stack->pop(); | |
6762 assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop"); | |
6763 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
6764 "only grey objects on this stack"); | |
6765 // iterate over the oops in this oop, marking and pushing | |
6766 // the ones in CMS heap (i.e. in _span). | |
6767 new_oop->oop_iterate(&_pushAndMarkClosure); | |
6768 // check if it's time to yield | |
6769 do_yield_check(); | |
6770 } while (!_mark_stack->isEmpty() || | |
6771 (!_concurrent_precleaning && take_from_overflow_list())); | |
6772 // if marking stack is empty, and we are not doing this | |
6773 // during precleaning, then check the overflow list | |
6774 } | |
6775 assert(_mark_stack->isEmpty(), "post-condition (eager drainage)"); | |
6776 assert(_collector->overflow_list_is_empty(), | |
6777 "overflow list was drained above"); | |
6778 // We could restore evacuated mark words, if any, used for | |
6779 // overflow list links here because the overflow list is | |
6780 // provably empty here. That would reduce the maximum | |
6781 // size requirements for preserved_{oop,mark}_stack. | |
6782 // But we'll just postpone it until we are all done | |
6783 // so we can just stream through. | |
6784 if (!_concurrent_precleaning && CMSOverflowEarlyRestoration) { | |
6785 _collector->restore_preserved_marks_if_any(); | |
6786 assert(_collector->no_preserved_marks(), "No preserved marks"); | |
6787 } | |
6788 assert(!CMSOverflowEarlyRestoration || _collector->no_preserved_marks(), | |
6789 "All preserved marks should have been restored above"); | |
6790 } | |
6791 } | |
6792 | |
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6793 void MarkRefsIntoAndScanClosure::do_oop(oop* p) { MarkRefsIntoAndScanClosure::do_oop_work(p); } |
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6794 void MarkRefsIntoAndScanClosure::do_oop(narrowOop* p) { MarkRefsIntoAndScanClosure::do_oop_work(p); } |
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6795 |
0 | 6796 void MarkRefsIntoAndScanClosure::do_yield_work() { |
6797 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
6798 "CMS thread should hold CMS token"); | |
6799 assert_lock_strong(_freelistLock); | |
6800 assert_lock_strong(_bit_map->lock()); | |
6801 // relinquish the free_list_lock and bitMaplock() | |
6802 _bit_map->lock()->unlock(); | |
6803 _freelistLock->unlock(); | |
6804 ConcurrentMarkSweepThread::desynchronize(true); | |
6805 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
6806 _collector->stopTimer(); | |
6807 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
6808 if (PrintCMSStatistics != 0) { | |
6809 _collector->incrementYields(); | |
6810 } | |
6811 _collector->icms_wait(); | |
6812 | |
6813 // See the comment in coordinator_yield() | |
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6814 for (unsigned i = 0; |
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6815 i < CMSYieldSleepCount && |
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6816 ConcurrentMarkSweepThread::should_yield() && |
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6817 !CMSCollector::foregroundGCIsActive(); |
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6818 ++i) { |
0 | 6819 os::sleep(Thread::current(), 1, false); |
6820 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
6821 } | |
6822 | |
6823 ConcurrentMarkSweepThread::synchronize(true); | |
6824 _freelistLock->lock_without_safepoint_check(); | |
6825 _bit_map->lock()->lock_without_safepoint_check(); | |
6826 _collector->startTimer(); | |
6827 } | |
6828 | |
6829 /////////////////////////////////////////////////////////// | |
6830 // Par_MarkRefsIntoAndScanClosure: a parallel version of | |
6831 // MarkRefsIntoAndScanClosure | |
6832 /////////////////////////////////////////////////////////// | |
6833 Par_MarkRefsIntoAndScanClosure::Par_MarkRefsIntoAndScanClosure( | |
6834 CMSCollector* collector, MemRegion span, ReferenceProcessor* rp, | |
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6835 CMSBitMap* bit_map, OopTaskQueue* work_queue): |
0 | 6836 _span(span), |
6837 _bit_map(bit_map), | |
6838 _work_queue(work_queue), | |
6839 _low_water_mark(MIN2((uint)(work_queue->max_elems()/4), | |
6840 (uint)(CMSWorkQueueDrainThreshold * ParallelGCThreads))), | |
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6841 _par_pushAndMarkClosure(collector, span, rp, bit_map, work_queue) |
0 | 6842 { |
6843 _ref_processor = rp; | |
6844 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
6845 } | |
6846 | |
6847 // This closure is used to mark refs into the CMS generation at the | |
6848 // second (final) checkpoint, and to scan and transitively follow | |
6849 // the unmarked oops. The marks are made in the marking bit map and | |
6850 // the work_queue is used for keeping the (newly) grey objects during | |
6851 // the scan phase whence they are also available for stealing by parallel | |
6852 // threads. Since the marking bit map is shared, updates are | |
6853 // synchronized (via CAS). | |
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6854 void Par_MarkRefsIntoAndScanClosure::do_oop(oop obj) { |
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6855 if (obj != NULL) { |
0 | 6856 // Ignore mark word because this could be an already marked oop |
6857 // that may be chained at the end of the overflow list. | |
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6858 assert(obj->is_oop(true), "expected an oop"); |
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6859 HeapWord* addr = (HeapWord*)obj; |
0 | 6860 if (_span.contains(addr) && |
6861 !_bit_map->isMarked(addr)) { | |
6862 // mark bit map (object will become grey): | |
6863 // It is possible for several threads to be | |
6864 // trying to "claim" this object concurrently; | |
6865 // the unique thread that succeeds in marking the | |
6866 // object first will do the subsequent push on | |
6867 // to the work queue (or overflow list). | |
6868 if (_bit_map->par_mark(addr)) { | |
6869 // push on work_queue (which may not be empty), and trim the | |
6870 // queue to an appropriate length by applying this closure to | |
6871 // the oops in the oops popped from the stack (i.e. blacken the | |
6872 // grey objects) | |
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6873 bool res = _work_queue->push(obj); |
0 | 6874 assert(res, "Low water mark should be less than capacity?"); |
6875 trim_queue(_low_water_mark); | |
6876 } // Else, another thread claimed the object | |
6877 } | |
6878 } | |
6879 } | |
6880 | |
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6881 void Par_MarkRefsIntoAndScanClosure::do_oop(oop* p) { Par_MarkRefsIntoAndScanClosure::do_oop_work(p); } |
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6882 void Par_MarkRefsIntoAndScanClosure::do_oop(narrowOop* p) { Par_MarkRefsIntoAndScanClosure::do_oop_work(p); } |
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6883 |
0 | 6884 // This closure is used to rescan the marked objects on the dirty cards |
6885 // in the mod union table and the card table proper. | |
6886 size_t ScanMarkedObjectsAgainCarefullyClosure::do_object_careful_m( | |
6887 oop p, MemRegion mr) { | |
6888 | |
6889 size_t size = 0; | |
6890 HeapWord* addr = (HeapWord*)p; | |
6891 DEBUG_ONLY(_collector->verify_work_stacks_empty();) | |
6892 assert(_span.contains(addr), "we are scanning the CMS generation"); | |
6893 // check if it's time to yield | |
6894 if (do_yield_check()) { | |
6895 // We yielded for some foreground stop-world work, | |
6896 // and we have been asked to abort this ongoing preclean cycle. | |
6897 return 0; | |
6898 } | |
6899 if (_bitMap->isMarked(addr)) { | |
6900 // it's marked; is it potentially uninitialized? | |
187 | 6901 if (p->klass_or_null() != NULL) { |
0 | 6902 // an initialized object; ignore mark word in verification below |
6903 // since we are running concurrent with mutators | |
6904 assert(p->is_oop(true), "should be an oop"); | |
6905 if (p->is_objArray()) { | |
6906 // objArrays are precisely marked; restrict scanning | |
6907 // to dirty cards only. | |
187 | 6908 size = CompactibleFreeListSpace::adjustObjectSize( |
6909 p->oop_iterate(_scanningClosure, mr)); | |
0 | 6910 } else { |
6911 // A non-array may have been imprecisely marked; we need | |
6912 // to scan object in its entirety. | |
6913 size = CompactibleFreeListSpace::adjustObjectSize( | |
6914 p->oop_iterate(_scanningClosure)); | |
6915 } | |
9152 | 6916 #ifdef ASSERT |
0 | 6917 size_t direct_size = |
6918 CompactibleFreeListSpace::adjustObjectSize(p->size()); | |
6919 assert(size == direct_size, "Inconsistency in size"); | |
6920 assert(size >= 3, "Necessary for Printezis marks to work"); | |
6921 if (!_bitMap->isMarked(addr+1)) { | |
6922 _bitMap->verifyNoOneBitsInRange(addr+2, addr+size); | |
6923 } else { | |
6924 _bitMap->verifyNoOneBitsInRange(addr+2, addr+size-1); | |
6925 assert(_bitMap->isMarked(addr+size-1), | |
6926 "inconsistent Printezis mark"); | |
6927 } | |
9152 | 6928 #endif // ASSERT |
0 | 6929 } else { |
6930 // an unitialized object | |
6931 assert(_bitMap->isMarked(addr+1), "missing Printezis mark?"); | |
6932 HeapWord* nextOneAddr = _bitMap->getNextMarkedWordAddress(addr + 2); | |
6933 size = pointer_delta(nextOneAddr + 1, addr); | |
6934 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
6935 "alignment problem"); | |
6936 // Note that pre-cleaning needn't redirty the card. OopDesc::set_klass() | |
6937 // will dirty the card when the klass pointer is installed in the | |
6938 // object (signalling the completion of initialization). | |
6939 } | |
6940 } else { | |
6941 // Either a not yet marked object or an uninitialized object | |
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6942 if (p->klass_or_null() == NULL) { |
0 | 6943 // An uninitialized object, skip to the next card, since |
6944 // we may not be able to read its P-bits yet. | |
6945 assert(size == 0, "Initial value"); | |
6946 } else { | |
6947 // An object not (yet) reached by marking: we merely need to | |
6948 // compute its size so as to go look at the next block. | |
6949 assert(p->is_oop(true), "should be an oop"); | |
6950 size = CompactibleFreeListSpace::adjustObjectSize(p->size()); | |
6951 } | |
6952 } | |
6953 DEBUG_ONLY(_collector->verify_work_stacks_empty();) | |
6954 return size; | |
6955 } | |
6956 | |
6957 void ScanMarkedObjectsAgainCarefullyClosure::do_yield_work() { | |
6958 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
6959 "CMS thread should hold CMS token"); | |
6960 assert_lock_strong(_freelistLock); | |
6961 assert_lock_strong(_bitMap->lock()); | |
6962 // relinquish the free_list_lock and bitMaplock() | |
6963 _bitMap->lock()->unlock(); | |
6964 _freelistLock->unlock(); | |
6965 ConcurrentMarkSweepThread::desynchronize(true); | |
6966 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
6967 _collector->stopTimer(); | |
6968 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
6969 if (PrintCMSStatistics != 0) { | |
6970 _collector->incrementYields(); | |
6971 } | |
6972 _collector->icms_wait(); | |
6973 | |
6974 // See the comment in coordinator_yield() | |
6975 for (unsigned i = 0; i < CMSYieldSleepCount && | |
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6976 ConcurrentMarkSweepThread::should_yield() && |
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6977 !CMSCollector::foregroundGCIsActive(); ++i) { |
0 | 6978 os::sleep(Thread::current(), 1, false); |
6979 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
6980 } | |
6981 | |
6982 ConcurrentMarkSweepThread::synchronize(true); | |
6983 _freelistLock->lock_without_safepoint_check(); | |
6984 _bitMap->lock()->lock_without_safepoint_check(); | |
6985 _collector->startTimer(); | |
6986 } | |
6987 | |
6988 | |
6989 ////////////////////////////////////////////////////////////////// | |
6990 // SurvivorSpacePrecleanClosure | |
6991 ////////////////////////////////////////////////////////////////// | |
6992 // This (single-threaded) closure is used to preclean the oops in | |
6993 // the survivor spaces. | |
6994 size_t SurvivorSpacePrecleanClosure::do_object_careful(oop p) { | |
6995 | |
6996 HeapWord* addr = (HeapWord*)p; | |
6997 DEBUG_ONLY(_collector->verify_work_stacks_empty();) | |
6998 assert(!_span.contains(addr), "we are scanning the survivor spaces"); | |
187 | 6999 assert(p->klass_or_null() != NULL, "object should be initializd"); |
0 | 7000 // an initialized object; ignore mark word in verification below |
7001 // since we are running concurrent with mutators | |
7002 assert(p->is_oop(true), "should be an oop"); | |
7003 // Note that we do not yield while we iterate over | |
7004 // the interior oops of p, pushing the relevant ones | |
7005 // on our marking stack. | |
7006 size_t size = p->oop_iterate(_scanning_closure); | |
7007 do_yield_check(); | |
7008 // Observe that below, we do not abandon the preclean | |
7009 // phase as soon as we should; rather we empty the | |
7010 // marking stack before returning. This is to satisfy | |
7011 // some existing assertions. In general, it may be a | |
7012 // good idea to abort immediately and complete the marking | |
7013 // from the grey objects at a later time. | |
7014 while (!_mark_stack->isEmpty()) { | |
7015 oop new_oop = _mark_stack->pop(); | |
7016 assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop"); | |
7017 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
7018 "only grey objects on this stack"); | |
7019 // iterate over the oops in this oop, marking and pushing | |
7020 // the ones in CMS heap (i.e. in _span). | |
7021 new_oop->oop_iterate(_scanning_closure); | |
7022 // check if it's time to yield | |
7023 do_yield_check(); | |
7024 } | |
7025 unsigned int after_count = | |
7026 GenCollectedHeap::heap()->total_collections(); | |
7027 bool abort = (_before_count != after_count) || | |
7028 _collector->should_abort_preclean(); | |
7029 return abort ? 0 : size; | |
7030 } | |
7031 | |
7032 void SurvivorSpacePrecleanClosure::do_yield_work() { | |
7033 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
7034 "CMS thread should hold CMS token"); | |
7035 assert_lock_strong(_bit_map->lock()); | |
7036 // Relinquish the bit map lock | |
7037 _bit_map->lock()->unlock(); | |
7038 ConcurrentMarkSweepThread::desynchronize(true); | |
7039 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
7040 _collector->stopTimer(); | |
7041 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
7042 if (PrintCMSStatistics != 0) { | |
7043 _collector->incrementYields(); | |
7044 } | |
7045 _collector->icms_wait(); | |
7046 | |
7047 // See the comment in coordinator_yield() | |
7048 for (unsigned i = 0; i < CMSYieldSleepCount && | |
7049 ConcurrentMarkSweepThread::should_yield() && | |
7050 !CMSCollector::foregroundGCIsActive(); ++i) { | |
7051 os::sleep(Thread::current(), 1, false); | |
7052 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
7053 } | |
7054 | |
7055 ConcurrentMarkSweepThread::synchronize(true); | |
7056 _bit_map->lock()->lock_without_safepoint_check(); | |
7057 _collector->startTimer(); | |
7058 } | |
7059 | |
7060 // This closure is used to rescan the marked objects on the dirty cards | |
7061 // in the mod union table and the card table proper. In the parallel | |
7062 // case, although the bitMap is shared, we do a single read so the | |
7063 // isMarked() query is "safe". | |
7064 bool ScanMarkedObjectsAgainClosure::do_object_bm(oop p, MemRegion mr) { | |
7065 // Ignore mark word because we are running concurrent with mutators | |
7066 assert(p->is_oop_or_null(true), "expected an oop or null"); | |
7067 HeapWord* addr = (HeapWord*)p; | |
7068 assert(_span.contains(addr), "we are scanning the CMS generation"); | |
7069 bool is_obj_array = false; | |
9152 | 7070 #ifdef ASSERT |
0 | 7071 if (!_parallel) { |
7072 assert(_mark_stack->isEmpty(), "pre-condition (eager drainage)"); | |
7073 assert(_collector->overflow_list_is_empty(), | |
7074 "overflow list should be empty"); | |
7075 | |
7076 } | |
9152 | 7077 #endif // ASSERT |
0 | 7078 if (_bit_map->isMarked(addr)) { |
7079 // Obj arrays are precisely marked, non-arrays are not; | |
7080 // so we scan objArrays precisely and non-arrays in their | |
7081 // entirety. | |
7082 if (p->is_objArray()) { | |
7083 is_obj_array = true; | |
7084 if (_parallel) { | |
7085 p->oop_iterate(_par_scan_closure, mr); | |
7086 } else { | |
7087 p->oop_iterate(_scan_closure, mr); | |
7088 } | |
7089 } else { | |
7090 if (_parallel) { | |
7091 p->oop_iterate(_par_scan_closure); | |
7092 } else { | |
7093 p->oop_iterate(_scan_closure); | |
7094 } | |
7095 } | |
7096 } | |
9152 | 7097 #ifdef ASSERT |
0 | 7098 if (!_parallel) { |
7099 assert(_mark_stack->isEmpty(), "post-condition (eager drainage)"); | |
7100 assert(_collector->overflow_list_is_empty(), | |
7101 "overflow list should be empty"); | |
7102 | |
7103 } | |
9152 | 7104 #endif // ASSERT |
0 | 7105 return is_obj_array; |
7106 } | |
7107 | |
7108 MarkFromRootsClosure::MarkFromRootsClosure(CMSCollector* collector, | |
7109 MemRegion span, | |
7110 CMSBitMap* bitMap, CMSMarkStack* markStack, | |
7111 bool should_yield, bool verifying): | |
7112 _collector(collector), | |
7113 _span(span), | |
7114 _bitMap(bitMap), | |
7115 _mut(&collector->_modUnionTable), | |
7116 _markStack(markStack), | |
7117 _yield(should_yield), | |
7118 _skipBits(0) | |
7119 { | |
7120 assert(_markStack->isEmpty(), "stack should be empty"); | |
7121 _finger = _bitMap->startWord(); | |
7122 _threshold = _finger; | |
7123 assert(_collector->_restart_addr == NULL, "Sanity check"); | |
7124 assert(_span.contains(_finger), "Out of bounds _finger?"); | |
7125 DEBUG_ONLY(_verifying = verifying;) | |
7126 } | |
7127 | |
7128 void MarkFromRootsClosure::reset(HeapWord* addr) { | |
7129 assert(_markStack->isEmpty(), "would cause duplicates on stack"); | |
7130 assert(_span.contains(addr), "Out of bounds _finger?"); | |
7131 _finger = addr; | |
7132 _threshold = (HeapWord*)round_to( | |
7133 (intptr_t)_finger, CardTableModRefBS::card_size); | |
7134 } | |
7135 | |
7136 // Should revisit to see if this should be restructured for | |
7137 // greater efficiency. | |
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7138 bool MarkFromRootsClosure::do_bit(size_t offset) { |
0 | 7139 if (_skipBits > 0) { |
7140 _skipBits--; | |
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7141 return true; |
0 | 7142 } |
7143 // convert offset into a HeapWord* | |
7144 HeapWord* addr = _bitMap->startWord() + offset; | |
7145 assert(_bitMap->endWord() && addr < _bitMap->endWord(), | |
7146 "address out of range"); | |
7147 assert(_bitMap->isMarked(addr), "tautology"); | |
7148 if (_bitMap->isMarked(addr+1)) { | |
7149 // this is an allocated but not yet initialized object | |
7150 assert(_skipBits == 0, "tautology"); | |
7151 _skipBits = 2; // skip next two marked bits ("Printezis-marks") | |
7152 oop p = oop(addr); | |
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7153 if (p->klass_or_null() == NULL) { |
0 | 7154 DEBUG_ONLY(if (!_verifying) {) |
7155 // We re-dirty the cards on which this object lies and increase | |
7156 // the _threshold so that we'll come back to scan this object | |
7157 // during the preclean or remark phase. (CMSCleanOnEnter) | |
7158 if (CMSCleanOnEnter) { | |
7159 size_t sz = _collector->block_size_using_printezis_bits(addr); | |
7160 HeapWord* end_card_addr = (HeapWord*)round_to( | |
7161 (intptr_t)(addr+sz), CardTableModRefBS::card_size); | |
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7162 MemRegion redirty_range = MemRegion(addr, end_card_addr); |
0 | 7163 assert(!redirty_range.is_empty(), "Arithmetical tautology"); |
7164 // Bump _threshold to end_card_addr; note that | |
7165 // _threshold cannot possibly exceed end_card_addr, anyhow. | |
7166 // This prevents future clearing of the card as the scan proceeds | |
7167 // to the right. | |
7168 assert(_threshold <= end_card_addr, | |
7169 "Because we are just scanning into this object"); | |
7170 if (_threshold < end_card_addr) { | |
7171 _threshold = end_card_addr; | |
7172 } | |
187 | 7173 if (p->klass_or_null() != NULL) { |
0 | 7174 // Redirty the range of cards... |
7175 _mut->mark_range(redirty_range); | |
7176 } // ...else the setting of klass will dirty the card anyway. | |
7177 } | |
7178 DEBUG_ONLY(}) | |
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7179 return true; |
0 | 7180 } |
7181 } | |
7182 scanOopsInOop(addr); | |
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7183 return true; |
0 | 7184 } |
7185 | |
7186 // We take a break if we've been at this for a while, | |
7187 // so as to avoid monopolizing the locks involved. | |
7188 void MarkFromRootsClosure::do_yield_work() { | |
7189 // First give up the locks, then yield, then re-lock | |
7190 // We should probably use a constructor/destructor idiom to | |
7191 // do this unlock/lock or modify the MutexUnlocker class to | |
7192 // serve our purpose. XXX | |
7193 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
7194 "CMS thread should hold CMS token"); | |
7195 assert_lock_strong(_bitMap->lock()); | |
7196 _bitMap->lock()->unlock(); | |
7197 ConcurrentMarkSweepThread::desynchronize(true); | |
7198 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
7199 _collector->stopTimer(); | |
7200 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
7201 if (PrintCMSStatistics != 0) { | |
7202 _collector->incrementYields(); | |
7203 } | |
7204 _collector->icms_wait(); | |
7205 | |
7206 // See the comment in coordinator_yield() | |
7207 for (unsigned i = 0; i < CMSYieldSleepCount && | |
7208 ConcurrentMarkSweepThread::should_yield() && | |
7209 !CMSCollector::foregroundGCIsActive(); ++i) { | |
7210 os::sleep(Thread::current(), 1, false); | |
7211 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
7212 } | |
7213 | |
7214 ConcurrentMarkSweepThread::synchronize(true); | |
7215 _bitMap->lock()->lock_without_safepoint_check(); | |
7216 _collector->startTimer(); | |
7217 } | |
7218 | |
7219 void MarkFromRootsClosure::scanOopsInOop(HeapWord* ptr) { | |
7220 assert(_bitMap->isMarked(ptr), "expected bit to be set"); | |
7221 assert(_markStack->isEmpty(), | |
7222 "should drain stack to limit stack usage"); | |
7223 // convert ptr to an oop preparatory to scanning | |
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7224 oop obj = oop(ptr); |
0 | 7225 // Ignore mark word in verification below, since we |
7226 // may be running concurrent with mutators. | |
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7227 assert(obj->is_oop(true), "should be an oop"); |
0 | 7228 assert(_finger <= ptr, "_finger runneth ahead"); |
7229 // advance the finger to right end of this object | |
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7230 _finger = ptr + obj->size(); |
0 | 7231 assert(_finger > ptr, "we just incremented it above"); |
7232 // On large heaps, it may take us some time to get through | |
7233 // the marking phase (especially if running iCMS). During | |
7234 // this time it's possible that a lot of mutations have | |
7235 // accumulated in the card table and the mod union table -- | |
7236 // these mutation records are redundant until we have | |
7237 // actually traced into the corresponding card. | |
7238 // Here, we check whether advancing the finger would make | |
7239 // us cross into a new card, and if so clear corresponding | |
7240 // cards in the MUT (preclean them in the card-table in the | |
7241 // future). | |
7242 | |
7243 DEBUG_ONLY(if (!_verifying) {) | |
7244 // The clean-on-enter optimization is disabled by default, | |
7245 // until we fix 6178663. | |
7246 if (CMSCleanOnEnter && (_finger > _threshold)) { | |
7247 // [_threshold, _finger) represents the interval | |
7248 // of cards to be cleared in MUT (or precleaned in card table). | |
7249 // The set of cards to be cleared is all those that overlap | |
7250 // with the interval [_threshold, _finger); note that | |
7251 // _threshold is always kept card-aligned but _finger isn't | |
7252 // always card-aligned. | |
7253 HeapWord* old_threshold = _threshold; | |
7254 assert(old_threshold == (HeapWord*)round_to( | |
7255 (intptr_t)old_threshold, CardTableModRefBS::card_size), | |
7256 "_threshold should always be card-aligned"); | |
7257 _threshold = (HeapWord*)round_to( | |
7258 (intptr_t)_finger, CardTableModRefBS::card_size); | |
7259 MemRegion mr(old_threshold, _threshold); | |
7260 assert(!mr.is_empty(), "Control point invariant"); | |
7261 assert(_span.contains(mr), "Should clear within span"); | |
7262 _mut->clear_range(mr); | |
7263 } | |
7264 DEBUG_ONLY(}) | |
7265 // Note: the finger doesn't advance while we drain | |
7266 // the stack below. | |
7267 PushOrMarkClosure pushOrMarkClosure(_collector, | |
7268 _span, _bitMap, _markStack, | |
7269 _finger, this); | |
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7270 bool res = _markStack->push(obj); |
0 | 7271 assert(res, "Empty non-zero size stack should have space for single push"); |
7272 while (!_markStack->isEmpty()) { | |
7273 oop new_oop = _markStack->pop(); | |
7274 // Skip verifying header mark word below because we are | |
7275 // running concurrent with mutators. | |
7276 assert(new_oop->is_oop(true), "Oops! expected to pop an oop"); | |
7277 // now scan this oop's oops | |
7278 new_oop->oop_iterate(&pushOrMarkClosure); | |
7279 do_yield_check(); | |
7280 } | |
7281 assert(_markStack->isEmpty(), "tautology, emphasizing post-condition"); | |
7282 } | |
7283 | |
7284 Par_MarkFromRootsClosure::Par_MarkFromRootsClosure(CMSConcMarkingTask* task, | |
7285 CMSCollector* collector, MemRegion span, | |
7286 CMSBitMap* bit_map, | |
7287 OopTaskQueue* work_queue, | |
7288 CMSMarkStack* overflow_stack, | |
7289 bool should_yield): | |
7290 _collector(collector), | |
7291 _whole_span(collector->_span), | |
7292 _span(span), | |
7293 _bit_map(bit_map), | |
7294 _mut(&collector->_modUnionTable), | |
7295 _work_queue(work_queue), | |
7296 _overflow_stack(overflow_stack), | |
7297 _yield(should_yield), | |
7298 _skip_bits(0), | |
7299 _task(task) | |
7300 { | |
7301 assert(_work_queue->size() == 0, "work_queue should be empty"); | |
7302 _finger = span.start(); | |
7303 _threshold = _finger; // XXX Defer clear-on-enter optimization for now | |
7304 assert(_span.contains(_finger), "Out of bounds _finger?"); | |
7305 } | |
7306 | |
7307 // Should revisit to see if this should be restructured for | |
7308 // greater efficiency. | |
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7309 bool Par_MarkFromRootsClosure::do_bit(size_t offset) { |
0 | 7310 if (_skip_bits > 0) { |
7311 _skip_bits--; | |
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7312 return true; |
0 | 7313 } |
7314 // convert offset into a HeapWord* | |
7315 HeapWord* addr = _bit_map->startWord() + offset; | |
7316 assert(_bit_map->endWord() && addr < _bit_map->endWord(), | |
7317 "address out of range"); | |
7318 assert(_bit_map->isMarked(addr), "tautology"); | |
7319 if (_bit_map->isMarked(addr+1)) { | |
7320 // this is an allocated object that might not yet be initialized | |
7321 assert(_skip_bits == 0, "tautology"); | |
7322 _skip_bits = 2; // skip next two marked bits ("Printezis-marks") | |
7323 oop p = oop(addr); | |
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7324 if (p->klass_or_null() == NULL) { |
0 | 7325 // in the case of Clean-on-Enter optimization, redirty card |
7326 // and avoid clearing card by increasing the threshold. | |
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7327 return true; |
0 | 7328 } |
7329 } | |
7330 scan_oops_in_oop(addr); | |
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7331 return true; |
0 | 7332 } |
7333 | |
7334 void Par_MarkFromRootsClosure::scan_oops_in_oop(HeapWord* ptr) { | |
7335 assert(_bit_map->isMarked(ptr), "expected bit to be set"); | |
7336 // Should we assert that our work queue is empty or | |
7337 // below some drain limit? | |
7338 assert(_work_queue->size() == 0, | |
7339 "should drain stack to limit stack usage"); | |
7340 // convert ptr to an oop preparatory to scanning | |
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7341 oop obj = oop(ptr); |
0 | 7342 // Ignore mark word in verification below, since we |
7343 // may be running concurrent with mutators. | |
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7344 assert(obj->is_oop(true), "should be an oop"); |
0 | 7345 assert(_finger <= ptr, "_finger runneth ahead"); |
7346 // advance the finger to right end of this object | |
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7347 _finger = ptr + obj->size(); |
0 | 7348 assert(_finger > ptr, "we just incremented it above"); |
7349 // On large heaps, it may take us some time to get through | |
7350 // the marking phase (especially if running iCMS). During | |
7351 // this time it's possible that a lot of mutations have | |
7352 // accumulated in the card table and the mod union table -- | |
7353 // these mutation records are redundant until we have | |
7354 // actually traced into the corresponding card. | |
7355 // Here, we check whether advancing the finger would make | |
7356 // us cross into a new card, and if so clear corresponding | |
7357 // cards in the MUT (preclean them in the card-table in the | |
7358 // future). | |
7359 | |
7360 // The clean-on-enter optimization is disabled by default, | |
7361 // until we fix 6178663. | |
7362 if (CMSCleanOnEnter && (_finger > _threshold)) { | |
7363 // [_threshold, _finger) represents the interval | |
7364 // of cards to be cleared in MUT (or precleaned in card table). | |
7365 // The set of cards to be cleared is all those that overlap | |
7366 // with the interval [_threshold, _finger); note that | |
7367 // _threshold is always kept card-aligned but _finger isn't | |
7368 // always card-aligned. | |
7369 HeapWord* old_threshold = _threshold; | |
7370 assert(old_threshold == (HeapWord*)round_to( | |
7371 (intptr_t)old_threshold, CardTableModRefBS::card_size), | |
7372 "_threshold should always be card-aligned"); | |
7373 _threshold = (HeapWord*)round_to( | |
7374 (intptr_t)_finger, CardTableModRefBS::card_size); | |
7375 MemRegion mr(old_threshold, _threshold); | |
7376 assert(!mr.is_empty(), "Control point invariant"); | |
7377 assert(_span.contains(mr), "Should clear within span"); // _whole_span ?? | |
7378 _mut->clear_range(mr); | |
7379 } | |
7380 | |
7381 // Note: the local finger doesn't advance while we drain | |
7382 // the stack below, but the global finger sure can and will. | |
7383 HeapWord** gfa = _task->global_finger_addr(); | |
7384 Par_PushOrMarkClosure pushOrMarkClosure(_collector, | |
7385 _span, _bit_map, | |
7386 _work_queue, | |
7387 _overflow_stack, | |
7388 _finger, | |
7389 gfa, this); | |
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7390 bool res = _work_queue->push(obj); // overflow could occur here |
0 | 7391 assert(res, "Will hold once we use workqueues"); |
7392 while (true) { | |
7393 oop new_oop; | |
7394 if (!_work_queue->pop_local(new_oop)) { | |
7395 // We emptied our work_queue; check if there's stuff that can | |
7396 // be gotten from the overflow stack. | |
7397 if (CMSConcMarkingTask::get_work_from_overflow_stack( | |
7398 _overflow_stack, _work_queue)) { | |
7399 do_yield_check(); | |
7400 continue; | |
7401 } else { // done | |
7402 break; | |
7403 } | |
7404 } | |
7405 // Skip verifying header mark word below because we are | |
7406 // running concurrent with mutators. | |
7407 assert(new_oop->is_oop(true), "Oops! expected to pop an oop"); | |
7408 // now scan this oop's oops | |
7409 new_oop->oop_iterate(&pushOrMarkClosure); | |
7410 do_yield_check(); | |
7411 } | |
7412 assert(_work_queue->size() == 0, "tautology, emphasizing post-condition"); | |
7413 } | |
7414 | |
7415 // Yield in response to a request from VM Thread or | |
7416 // from mutators. | |
7417 void Par_MarkFromRootsClosure::do_yield_work() { | |
7418 assert(_task != NULL, "sanity"); | |
7419 _task->yield(); | |
7420 } | |
7421 | |
7422 // A variant of the above used for verifying CMS marking work. | |
7423 MarkFromRootsVerifyClosure::MarkFromRootsVerifyClosure(CMSCollector* collector, | |
7424 MemRegion span, | |
7425 CMSBitMap* verification_bm, CMSBitMap* cms_bm, | |
7426 CMSMarkStack* mark_stack): | |
7427 _collector(collector), | |
7428 _span(span), | |
7429 _verification_bm(verification_bm), | |
7430 _cms_bm(cms_bm), | |
7431 _mark_stack(mark_stack), | |
7432 _pam_verify_closure(collector, span, verification_bm, cms_bm, | |
7433 mark_stack) | |
7434 { | |
7435 assert(_mark_stack->isEmpty(), "stack should be empty"); | |
7436 _finger = _verification_bm->startWord(); | |
7437 assert(_collector->_restart_addr == NULL, "Sanity check"); | |
7438 assert(_span.contains(_finger), "Out of bounds _finger?"); | |
7439 } | |
7440 | |
7441 void MarkFromRootsVerifyClosure::reset(HeapWord* addr) { | |
7442 assert(_mark_stack->isEmpty(), "would cause duplicates on stack"); | |
7443 assert(_span.contains(addr), "Out of bounds _finger?"); | |
7444 _finger = addr; | |
7445 } | |
7446 | |
7447 // Should revisit to see if this should be restructured for | |
7448 // greater efficiency. | |
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7449 bool MarkFromRootsVerifyClosure::do_bit(size_t offset) { |
0 | 7450 // convert offset into a HeapWord* |
7451 HeapWord* addr = _verification_bm->startWord() + offset; | |
7452 assert(_verification_bm->endWord() && addr < _verification_bm->endWord(), | |
7453 "address out of range"); | |
7454 assert(_verification_bm->isMarked(addr), "tautology"); | |
7455 assert(_cms_bm->isMarked(addr), "tautology"); | |
7456 | |
7457 assert(_mark_stack->isEmpty(), | |
7458 "should drain stack to limit stack usage"); | |
7459 // convert addr to an oop preparatory to scanning | |
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7460 oop obj = oop(addr); |
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7461 assert(obj->is_oop(), "should be an oop"); |
0 | 7462 assert(_finger <= addr, "_finger runneth ahead"); |
7463 // advance the finger to right end of this object | |
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7464 _finger = addr + obj->size(); |
0 | 7465 assert(_finger > addr, "we just incremented it above"); |
7466 // Note: the finger doesn't advance while we drain | |
7467 // the stack below. | |
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7468 bool res = _mark_stack->push(obj); |
0 | 7469 assert(res, "Empty non-zero size stack should have space for single push"); |
7470 while (!_mark_stack->isEmpty()) { | |
7471 oop new_oop = _mark_stack->pop(); | |
7472 assert(new_oop->is_oop(), "Oops! expected to pop an oop"); | |
7473 // now scan this oop's oops | |
7474 new_oop->oop_iterate(&_pam_verify_closure); | |
7475 } | |
7476 assert(_mark_stack->isEmpty(), "tautology, emphasizing post-condition"); | |
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7477 return true; |
0 | 7478 } |
7479 | |
7480 PushAndMarkVerifyClosure::PushAndMarkVerifyClosure( | |
7481 CMSCollector* collector, MemRegion span, | |
7482 CMSBitMap* verification_bm, CMSBitMap* cms_bm, | |
7483 CMSMarkStack* mark_stack): | |
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7484 CMSOopClosure(collector->ref_processor()), |
0 | 7485 _collector(collector), |
7486 _span(span), | |
7487 _verification_bm(verification_bm), | |
7488 _cms_bm(cms_bm), | |
7489 _mark_stack(mark_stack) | |
7490 { } | |
7491 | |
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7492 void PushAndMarkVerifyClosure::do_oop(oop* p) { PushAndMarkVerifyClosure::do_oop_work(p); } |
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7493 void PushAndMarkVerifyClosure::do_oop(narrowOop* p) { PushAndMarkVerifyClosure::do_oop_work(p); } |
0 | 7494 |
7495 // Upon stack overflow, we discard (part of) the stack, | |
7496 // remembering the least address amongst those discarded | |
7497 // in CMSCollector's _restart_address. | |
7498 void PushAndMarkVerifyClosure::handle_stack_overflow(HeapWord* lost) { | |
7499 // Remember the least grey address discarded | |
7500 HeapWord* ra = (HeapWord*)_mark_stack->least_value(lost); | |
7501 _collector->lower_restart_addr(ra); | |
7502 _mark_stack->reset(); // discard stack contents | |
7503 _mark_stack->expand(); // expand the stack if possible | |
7504 } | |
7505 | |
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7506 void PushAndMarkVerifyClosure::do_oop(oop obj) { |
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7507 assert(obj->is_oop_or_null(), "expected an oop or NULL"); |
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7508 HeapWord* addr = (HeapWord*)obj; |
0 | 7509 if (_span.contains(addr) && !_verification_bm->isMarked(addr)) { |
7510 // Oop lies in _span and isn't yet grey or black | |
7511 _verification_bm->mark(addr); // now grey | |
7512 if (!_cms_bm->isMarked(addr)) { | |
7513 oop(addr)->print(); | |
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7514 gclog_or_tty->print_cr(" (" INTPTR_FORMAT " should have been marked)", |
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7515 addr); |
0 | 7516 fatal("... aborting"); |
7517 } | |
7518 | |
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7519 if (!_mark_stack->push(obj)) { // stack overflow |
0 | 7520 if (PrintCMSStatistics != 0) { |
7521 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
7522 SIZE_FORMAT, _mark_stack->capacity()); | |
7523 } | |
7524 assert(_mark_stack->isFull(), "Else push should have succeeded"); | |
7525 handle_stack_overflow(addr); | |
7526 } | |
7527 // anything including and to the right of _finger | |
7528 // will be scanned as we iterate over the remainder of the | |
7529 // bit map | |
7530 } | |
7531 } | |
7532 | |
7533 PushOrMarkClosure::PushOrMarkClosure(CMSCollector* collector, | |
7534 MemRegion span, | |
7535 CMSBitMap* bitMap, CMSMarkStack* markStack, | |
7536 HeapWord* finger, MarkFromRootsClosure* parent) : | |
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7537 CMSOopClosure(collector->ref_processor()), |
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7538 _collector(collector), |
0 | 7539 _span(span), |
7540 _bitMap(bitMap), | |
7541 _markStack(markStack), | |
7542 _finger(finger), | |
935 | 7543 _parent(parent) |
0 | 7544 { } |
7545 | |
7546 Par_PushOrMarkClosure::Par_PushOrMarkClosure(CMSCollector* collector, | |
7547 MemRegion span, | |
7548 CMSBitMap* bit_map, | |
7549 OopTaskQueue* work_queue, | |
7550 CMSMarkStack* overflow_stack, | |
7551 HeapWord* finger, | |
7552 HeapWord** global_finger_addr, | |
7553 Par_MarkFromRootsClosure* parent) : | |
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7554 CMSOopClosure(collector->ref_processor()), |
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7555 _collector(collector), |
0 | 7556 _whole_span(collector->_span), |
7557 _span(span), | |
7558 _bit_map(bit_map), | |
7559 _work_queue(work_queue), | |
7560 _overflow_stack(overflow_stack), | |
7561 _finger(finger), | |
7562 _global_finger_addr(global_finger_addr), | |
935 | 7563 _parent(parent) |
0 | 7564 { } |
7565 | |
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7566 // Assumes thread-safe access by callers, who are |
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7567 // responsible for mutual exclusion. |
0 | 7568 void CMSCollector::lower_restart_addr(HeapWord* low) { |
7569 assert(_span.contains(low), "Out of bounds addr"); | |
7570 if (_restart_addr == NULL) { | |
7571 _restart_addr = low; | |
7572 } else { | |
7573 _restart_addr = MIN2(_restart_addr, low); | |
7574 } | |
7575 } | |
7576 | |
7577 // Upon stack overflow, we discard (part of) the stack, | |
7578 // remembering the least address amongst those discarded | |
7579 // in CMSCollector's _restart_address. | |
7580 void PushOrMarkClosure::handle_stack_overflow(HeapWord* lost) { | |
7581 // Remember the least grey address discarded | |
7582 HeapWord* ra = (HeapWord*)_markStack->least_value(lost); | |
7583 _collector->lower_restart_addr(ra); | |
7584 _markStack->reset(); // discard stack contents | |
7585 _markStack->expand(); // expand the stack if possible | |
7586 } | |
7587 | |
7588 // Upon stack overflow, we discard (part of) the stack, | |
7589 // remembering the least address amongst those discarded | |
7590 // in CMSCollector's _restart_address. | |
7591 void Par_PushOrMarkClosure::handle_stack_overflow(HeapWord* lost) { | |
7592 // We need to do this under a mutex to prevent other | |
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7593 // workers from interfering with the work done below. |
0 | 7594 MutexLockerEx ml(_overflow_stack->par_lock(), |
7595 Mutex::_no_safepoint_check_flag); | |
7596 // Remember the least grey address discarded | |
7597 HeapWord* ra = (HeapWord*)_overflow_stack->least_value(lost); | |
7598 _collector->lower_restart_addr(ra); | |
7599 _overflow_stack->reset(); // discard stack contents | |
7600 _overflow_stack->expand(); // expand the stack if possible | |
7601 } | |
7602 | |
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7603 void CMKlassClosure::do_klass(Klass* k) { |
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7604 assert(_oop_closure != NULL, "Not initialized?"); |
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7605 k->oops_do(_oop_closure); |
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7606 } |
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7607 |
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7608 void PushOrMarkClosure::do_oop(oop obj) { |
0 | 7609 // Ignore mark word because we are running concurrent with mutators. |
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7610 assert(obj->is_oop_or_null(true), "expected an oop or NULL"); |
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7611 HeapWord* addr = (HeapWord*)obj; |
0 | 7612 if (_span.contains(addr) && !_bitMap->isMarked(addr)) { |
7613 // Oop lies in _span and isn't yet grey or black | |
7614 _bitMap->mark(addr); // now grey | |
7615 if (addr < _finger) { | |
7616 // the bit map iteration has already either passed, or | |
7617 // sampled, this bit in the bit map; we'll need to | |
7618 // use the marking stack to scan this oop's oops. | |
7619 bool simulate_overflow = false; | |
7620 NOT_PRODUCT( | |
7621 if (CMSMarkStackOverflowALot && | |
7622 _collector->simulate_overflow()) { | |
7623 // simulate a stack overflow | |
7624 simulate_overflow = true; | |
7625 } | |
7626 ) | |
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7627 if (simulate_overflow || !_markStack->push(obj)) { // stack overflow |
0 | 7628 if (PrintCMSStatistics != 0) { |
7629 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
7630 SIZE_FORMAT, _markStack->capacity()); | |
7631 } | |
7632 assert(simulate_overflow || _markStack->isFull(), "Else push should have succeeded"); | |
7633 handle_stack_overflow(addr); | |
7634 } | |
7635 } | |
7636 // anything including and to the right of _finger | |
7637 // will be scanned as we iterate over the remainder of the | |
7638 // bit map | |
7639 do_yield_check(); | |
7640 } | |
7641 } | |
7642 | |
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7643 void PushOrMarkClosure::do_oop(oop* p) { PushOrMarkClosure::do_oop_work(p); } |
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7644 void PushOrMarkClosure::do_oop(narrowOop* p) { PushOrMarkClosure::do_oop_work(p); } |
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7645 |
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7646 void Par_PushOrMarkClosure::do_oop(oop obj) { |
0 | 7647 // Ignore mark word because we are running concurrent with mutators. |
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7648 assert(obj->is_oop_or_null(true), "expected an oop or NULL"); |
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7649 HeapWord* addr = (HeapWord*)obj; |
0 | 7650 if (_whole_span.contains(addr) && !_bit_map->isMarked(addr)) { |
7651 // Oop lies in _span and isn't yet grey or black | |
7652 // We read the global_finger (volatile read) strictly after marking oop | |
7653 bool res = _bit_map->par_mark(addr); // now grey | |
7654 volatile HeapWord** gfa = (volatile HeapWord**)_global_finger_addr; | |
7655 // Should we push this marked oop on our stack? | |
7656 // -- if someone else marked it, nothing to do | |
7657 // -- if target oop is above global finger nothing to do | |
7658 // -- if target oop is in chunk and above local finger | |
7659 // then nothing to do | |
7660 // -- else push on work queue | |
7661 if ( !res // someone else marked it, they will deal with it | |
7662 || (addr >= *gfa) // will be scanned in a later task | |
7663 || (_span.contains(addr) && addr >= _finger)) { // later in this chunk | |
7664 return; | |
7665 } | |
7666 // the bit map iteration has already either passed, or | |
7667 // sampled, this bit in the bit map; we'll need to | |
7668 // use the marking stack to scan this oop's oops. | |
7669 bool simulate_overflow = false; | |
7670 NOT_PRODUCT( | |
7671 if (CMSMarkStackOverflowALot && | |
7672 _collector->simulate_overflow()) { | |
7673 // simulate a stack overflow | |
7674 simulate_overflow = true; | |
7675 } | |
7676 ) | |
7677 if (simulate_overflow || | |
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7678 !(_work_queue->push(obj) || _overflow_stack->par_push(obj))) { |
0 | 7679 // stack overflow |
7680 if (PrintCMSStatistics != 0) { | |
7681 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
7682 SIZE_FORMAT, _overflow_stack->capacity()); | |
7683 } | |
7684 // We cannot assert that the overflow stack is full because | |
7685 // it may have been emptied since. | |
7686 assert(simulate_overflow || | |
7687 _work_queue->size() == _work_queue->max_elems(), | |
7688 "Else push should have succeeded"); | |
7689 handle_stack_overflow(addr); | |
7690 } | |
7691 do_yield_check(); | |
7692 } | |
7693 } | |
7694 | |
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7695 void Par_PushOrMarkClosure::do_oop(oop* p) { Par_PushOrMarkClosure::do_oop_work(p); } |
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7696 void Par_PushOrMarkClosure::do_oop(narrowOop* p) { Par_PushOrMarkClosure::do_oop_work(p); } |
0 | 7697 |
7698 PushAndMarkClosure::PushAndMarkClosure(CMSCollector* collector, | |
7699 MemRegion span, | |
7700 ReferenceProcessor* rp, | |
7701 CMSBitMap* bit_map, | |
7702 CMSBitMap* mod_union_table, | |
7703 CMSMarkStack* mark_stack, | |
7704 bool concurrent_precleaning): | |
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7705 CMSOopClosure(rp), |
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7706 _collector(collector), |
0 | 7707 _span(span), |
7708 _bit_map(bit_map), | |
7709 _mod_union_table(mod_union_table), | |
7710 _mark_stack(mark_stack), | |
935 | 7711 _concurrent_precleaning(concurrent_precleaning) |
0 | 7712 { |
7713 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
7714 } | |
7715 | |
7716 // Grey object rescan during pre-cleaning and second checkpoint phases -- | |
7717 // the non-parallel version (the parallel version appears further below.) | |
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7718 void PushAndMarkClosure::do_oop(oop obj) { |
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7719 // Ignore mark word verification. If during concurrent precleaning, |
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7720 // the object monitor may be locked. If during the checkpoint |
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7721 // phases, the object may already have been reached by a different |
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7722 // path and may be at the end of the global overflow list (so |
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7723 // the mark word may be NULL). |
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7724 assert(obj->is_oop_or_null(true /* ignore mark word */), |
0 | 7725 "expected an oop or NULL"); |
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7726 HeapWord* addr = (HeapWord*)obj; |
0 | 7727 // Check if oop points into the CMS generation |
7728 // and is not marked | |
7729 if (_span.contains(addr) && !_bit_map->isMarked(addr)) { | |
7730 // a white object ... | |
7731 _bit_map->mark(addr); // ... now grey | |
7732 // push on the marking stack (grey set) | |
7733 bool simulate_overflow = false; | |
7734 NOT_PRODUCT( | |
7735 if (CMSMarkStackOverflowALot && | |
7736 _collector->simulate_overflow()) { | |
7737 // simulate a stack overflow | |
7738 simulate_overflow = true; | |
7739 } | |
7740 ) | |
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7741 if (simulate_overflow || !_mark_stack->push(obj)) { |
0 | 7742 if (_concurrent_precleaning) { |
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7743 // During precleaning we can just dirty the appropriate card(s) |
0 | 7744 // in the mod union table, thus ensuring that the object remains |
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7745 // in the grey set and continue. In the case of object arrays |
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7746 // we need to dirty all of the cards that the object spans, |
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7747 // since the rescan of object arrays will be limited to the |
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7748 // dirty cards. |
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7749 // Note that no one can be intefering with us in this action |
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7750 // of dirtying the mod union table, so no locking or atomics |
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7751 // are required. |
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7752 if (obj->is_objArray()) { |
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7753 size_t sz = obj->size(); |
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7754 HeapWord* end_card_addr = (HeapWord*)round_to( |
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7755 (intptr_t)(addr+sz), CardTableModRefBS::card_size); |
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7756 MemRegion redirty_range = MemRegion(addr, end_card_addr); |
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7757 assert(!redirty_range.is_empty(), "Arithmetical tautology"); |
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7758 _mod_union_table->mark_range(redirty_range); |
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7759 } else { |
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7760 _mod_union_table->mark(addr); |
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7761 } |
0 | 7762 _collector->_ser_pmc_preclean_ovflw++; |
7763 } else { | |
7764 // During the remark phase, we need to remember this oop | |
7765 // in the overflow list. | |
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7766 _collector->push_on_overflow_list(obj); |
0 | 7767 _collector->_ser_pmc_remark_ovflw++; |
7768 } | |
7769 } | |
7770 } | |
7771 } | |
7772 | |
7773 Par_PushAndMarkClosure::Par_PushAndMarkClosure(CMSCollector* collector, | |
7774 MemRegion span, | |
7775 ReferenceProcessor* rp, | |
7776 CMSBitMap* bit_map, | |
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7777 OopTaskQueue* work_queue): |
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7778 CMSOopClosure(rp), |
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7779 _collector(collector), |
0 | 7780 _span(span), |
7781 _bit_map(bit_map), | |
935 | 7782 _work_queue(work_queue) |
0 | 7783 { |
7784 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
7785 } | |
7786 | |
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7787 void PushAndMarkClosure::do_oop(oop* p) { PushAndMarkClosure::do_oop_work(p); } |
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7788 void PushAndMarkClosure::do_oop(narrowOop* p) { PushAndMarkClosure::do_oop_work(p); } |
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7789 |
0 | 7790 // Grey object rescan during second checkpoint phase -- |
7791 // the parallel version. | |
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7792 void Par_PushAndMarkClosure::do_oop(oop obj) { |
0 | 7793 // In the assert below, we ignore the mark word because |
7794 // this oop may point to an already visited object that is | |
7795 // on the overflow stack (in which case the mark word has | |
7796 // been hijacked for chaining into the overflow stack -- | |
7797 // if this is the last object in the overflow stack then | |
7798 // its mark word will be NULL). Because this object may | |
7799 // have been subsequently popped off the global overflow | |
7800 // stack, and the mark word possibly restored to the prototypical | |
7801 // value, by the time we get to examined this failing assert in | |
7802 // the debugger, is_oop_or_null(false) may subsequently start | |
7803 // to hold. | |
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7804 assert(obj->is_oop_or_null(true), |
0 | 7805 "expected an oop or NULL"); |
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7806 HeapWord* addr = (HeapWord*)obj; |
0 | 7807 // Check if oop points into the CMS generation |
7808 // and is not marked | |
7809 if (_span.contains(addr) && !_bit_map->isMarked(addr)) { | |
7810 // a white object ... | |
7811 // If we manage to "claim" the object, by being the | |
7812 // first thread to mark it, then we push it on our | |
7813 // marking stack | |
7814 if (_bit_map->par_mark(addr)) { // ... now grey | |
7815 // push on work queue (grey set) | |
7816 bool simulate_overflow = false; | |
7817 NOT_PRODUCT( | |
7818 if (CMSMarkStackOverflowALot && | |
7819 _collector->par_simulate_overflow()) { | |
7820 // simulate a stack overflow | |
7821 simulate_overflow = true; | |
7822 } | |
7823 ) | |
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7824 if (simulate_overflow || !_work_queue->push(obj)) { |
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7825 _collector->par_push_on_overflow_list(obj); |
0 | 7826 _collector->_par_pmc_remark_ovflw++; // imprecise OK: no need to CAS |
7827 } | |
7828 } // Else, some other thread got there first | |
7829 } | |
7830 } | |
7831 | |
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7832 void Par_PushAndMarkClosure::do_oop(oop* p) { Par_PushAndMarkClosure::do_oop_work(p); } |
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7833 void Par_PushAndMarkClosure::do_oop(narrowOop* p) { Par_PushAndMarkClosure::do_oop_work(p); } |
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7834 |
0 | 7835 void CMSPrecleanRefsYieldClosure::do_yield_work() { |
7836 Mutex* bml = _collector->bitMapLock(); | |
7837 assert_lock_strong(bml); | |
7838 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
7839 "CMS thread should hold CMS token"); | |
7840 | |
7841 bml->unlock(); | |
7842 ConcurrentMarkSweepThread::desynchronize(true); | |
7843 | |
7844 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
7845 | |
7846 _collector->stopTimer(); | |
7847 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
7848 if (PrintCMSStatistics != 0) { | |
7849 _collector->incrementYields(); | |
7850 } | |
7851 _collector->icms_wait(); | |
7852 | |
7853 // See the comment in coordinator_yield() | |
7854 for (unsigned i = 0; i < CMSYieldSleepCount && | |
7855 ConcurrentMarkSweepThread::should_yield() && | |
7856 !CMSCollector::foregroundGCIsActive(); ++i) { | |
7857 os::sleep(Thread::current(), 1, false); | |
7858 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
7859 } | |
7860 | |
7861 ConcurrentMarkSweepThread::synchronize(true); | |
7862 bml->lock(); | |
7863 | |
7864 _collector->startTimer(); | |
7865 } | |
7866 | |
7867 bool CMSPrecleanRefsYieldClosure::should_return() { | |
7868 if (ConcurrentMarkSweepThread::should_yield()) { | |
7869 do_yield_work(); | |
7870 } | |
7871 return _collector->foregroundGCIsActive(); | |
7872 } | |
7873 | |
7874 void MarkFromDirtyCardsClosure::do_MemRegion(MemRegion mr) { | |
7875 assert(((size_t)mr.start())%CardTableModRefBS::card_size_in_words == 0, | |
7876 "mr should be aligned to start at a card boundary"); | |
7877 // We'd like to assert: | |
7878 // assert(mr.word_size()%CardTableModRefBS::card_size_in_words == 0, | |
7879 // "mr should be a range of cards"); | |
7880 // However, that would be too strong in one case -- the last | |
7881 // partition ends at _unallocated_block which, in general, can be | |
7882 // an arbitrary boundary, not necessarily card aligned. | |
7883 if (PrintCMSStatistics != 0) { | |
7884 _num_dirty_cards += | |
7885 mr.word_size()/CardTableModRefBS::card_size_in_words; | |
7886 } | |
7887 _space->object_iterate_mem(mr, &_scan_cl); | |
7888 } | |
7889 | |
7890 SweepClosure::SweepClosure(CMSCollector* collector, | |
7891 ConcurrentMarkSweepGeneration* g, | |
7892 CMSBitMap* bitMap, bool should_yield) : | |
7893 _collector(collector), | |
7894 _g(g), | |
7895 _sp(g->cmsSpace()), | |
7896 _limit(_sp->sweep_limit()), | |
7897 _freelistLock(_sp->freelistLock()), | |
7898 _bitMap(bitMap), | |
7899 _yield(should_yield), | |
7900 _inFreeRange(false), // No free range at beginning of sweep | |
7901 _freeRangeInFreeLists(false), // No free range at beginning of sweep | |
7902 _lastFreeRangeCoalesced(false), | |
7903 _freeFinger(g->used_region().start()) | |
7904 { | |
7905 NOT_PRODUCT( | |
7906 _numObjectsFreed = 0; | |
7907 _numWordsFreed = 0; | |
7908 _numObjectsLive = 0; | |
7909 _numWordsLive = 0; | |
7910 _numObjectsAlreadyFree = 0; | |
7911 _numWordsAlreadyFree = 0; | |
7912 _last_fc = NULL; | |
7913 | |
7914 _sp->initializeIndexedFreeListArrayReturnedBytes(); | |
6028
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7915 _sp->dictionary()->initialize_dict_returned_bytes(); |
0 | 7916 ) |
7917 assert(_limit >= _sp->bottom() && _limit <= _sp->end(), | |
7918 "sweep _limit out of bounds"); | |
7919 if (CMSTraceSweeper) { | |
3746
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7920 gclog_or_tty->print_cr("\n====================\nStarting new sweep with limit " PTR_FORMAT, |
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|
7921 _limit); |
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7922 } |
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7923 } |
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7924 |
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7925 void SweepClosure::print_on(outputStream* st) const { |
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7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
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7926 tty->print_cr("_sp = [" PTR_FORMAT "," PTR_FORMAT ")", |
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7927 _sp->bottom(), _sp->end()); |
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7928 tty->print_cr("_limit = " PTR_FORMAT, _limit); |
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7929 tty->print_cr("_freeFinger = " PTR_FORMAT, _freeFinger); |
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|
7930 NOT_PRODUCT(tty->print_cr("_last_fc = " PTR_FORMAT, _last_fc);) |
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7931 tty->print_cr("_inFreeRange = %d, _freeRangeInFreeLists = %d, _lastFreeRangeCoalesced = %d", |
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|
7932 _inFreeRange, _freeRangeInFreeLists, _lastFreeRangeCoalesced); |
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|
7933 } |
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7934 |
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|
7935 #ifndef PRODUCT |
537a4053b0f9
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|
7936 // Assertion checking only: no useful work in product mode -- |
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|
7937 // however, if any of the flags below become product flags, |
537a4053b0f9
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7938 // you may need to review this code to see if it needs to be |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
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|
7939 // enabled in product mode. |
0 | 7940 SweepClosure::~SweepClosure() { |
7941 assert_lock_strong(_freelistLock); | |
2132
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7942 assert(_limit >= _sp->bottom() && _limit <= _sp->end(), |
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7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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|
7943 "sweep _limit out of bounds"); |
0 | 7944 if (inFreeRange()) { |
3746
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
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|
7945 warning("inFreeRange() should have been reset; dumping state of SweepClosure"); |
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|
7946 print(); |
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|
7947 ShouldNotReachHere(); |
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|
7948 } |
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|
7949 if (Verbose && PrintGC) { |
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|
7950 gclog_or_tty->print("Collected "SIZE_FORMAT" objects, " SIZE_FORMAT " bytes", |
537a4053b0f9
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|
7951 _numObjectsFreed, _numWordsFreed*sizeof(HeapWord)); |
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|
7952 gclog_or_tty->print_cr("\nLive "SIZE_FORMAT" objects, " |
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|
7953 SIZE_FORMAT" bytes " |
537a4053b0f9
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|
7954 "Already free "SIZE_FORMAT" objects, "SIZE_FORMAT" bytes", |
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|
7955 _numObjectsLive, _numWordsLive*sizeof(HeapWord), |
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7956 _numObjectsAlreadyFree, _numWordsAlreadyFree*sizeof(HeapWord)); |
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7957 size_t totalBytes = (_numWordsFreed + _numWordsLive + _numWordsAlreadyFree) |
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7958 * sizeof(HeapWord); |
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|
7959 gclog_or_tty->print_cr("Total sweep: "SIZE_FORMAT" bytes", totalBytes); |
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7960 |
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|
7961 if (PrintCMSStatistics && CMSVerifyReturnedBytes) { |
537a4053b0f9
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|
7962 size_t indexListReturnedBytes = _sp->sumIndexedFreeListArrayReturnedBytes(); |
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7963 size_t dict_returned_bytes = _sp->dictionary()->sum_dict_returned_bytes(); |
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7964 size_t returned_bytes = indexListReturnedBytes + dict_returned_bytes; |
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7965 gclog_or_tty->print("Returned "SIZE_FORMAT" bytes", returned_bytes); |
3746
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|
7966 gclog_or_tty->print(" Indexed List Returned "SIZE_FORMAT" bytes", |
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|
7967 indexListReturnedBytes); |
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|
7968 gclog_or_tty->print_cr(" Dictionary Returned "SIZE_FORMAT" bytes", |
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|
7969 dict_returned_bytes); |
3746
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|
7970 } |
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|
7971 } |
0 | 7972 if (CMSTraceSweeper) { |
3746
537a4053b0f9
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|
7973 gclog_or_tty->print_cr("end of sweep with _limit = " PTR_FORMAT "\n================", |
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|
7974 _limit); |
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|
7975 } |
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|
7976 } |
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|
7977 #endif // PRODUCT |
0 | 7978 |
7979 void SweepClosure::initialize_free_range(HeapWord* freeFinger, | |
7980 bool freeRangeInFreeLists) { | |
7981 if (CMSTraceSweeper) { | |
2132
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|
7982 gclog_or_tty->print("---- Start free range at 0x%x with free block (%d)\n", |
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7983 freeFinger, freeRangeInFreeLists); |
0 | 7984 } |
7985 assert(!inFreeRange(), "Trampling existing free range"); | |
7986 set_inFreeRange(true); | |
7987 set_lastFreeRangeCoalesced(false); | |
7988 | |
7989 set_freeFinger(freeFinger); | |
7990 set_freeRangeInFreeLists(freeRangeInFreeLists); | |
7991 if (CMSTestInFreeList) { | |
7992 if (freeRangeInFreeLists) { | |
7993 FreeChunk* fc = (FreeChunk*) freeFinger; | |
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7994 assert(fc->is_free(), "A chunk on the free list should be free."); |
0 | 7995 assert(fc->size() > 0, "Free range should have a size"); |
6028
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|
7996 assert(_sp->verify_chunk_in_free_list(fc), "Chunk is not in free lists"); |
0 | 7997 } |
7998 } | |
7999 } | |
8000 | |
8001 // Note that the sweeper runs concurrently with mutators. Thus, | |
8002 // it is possible for direct allocation in this generation to happen | |
8003 // in the middle of the sweep. Note that the sweeper also coalesces | |
8004 // contiguous free blocks. Thus, unless the sweeper and the allocator | |
8005 // synchronize appropriately freshly allocated blocks may get swept up. | |
8006 // This is accomplished by the sweeper locking the free lists while | |
8007 // it is sweeping. Thus blocks that are determined to be free are | |
8008 // indeed free. There is however one additional complication: | |
8009 // blocks that have been allocated since the final checkpoint and | |
8010 // mark, will not have been marked and so would be treated as | |
8011 // unreachable and swept up. To prevent this, the allocator marks | |
8012 // the bit map when allocating during the sweep phase. This leads, | |
8013 // however, to a further complication -- objects may have been allocated | |
8014 // but not yet initialized -- in the sense that the header isn't yet | |
8015 // installed. The sweeper can not then determine the size of the block | |
8016 // in order to skip over it. To deal with this case, we use a technique | |
8017 // (due to Printezis) to encode such uninitialized block sizes in the | |
8018 // bit map. Since the bit map uses a bit per every HeapWord, but the | |
8019 // CMS generation has a minimum object size of 3 HeapWords, it follows | |
8020 // that "normal marks" won't be adjacent in the bit map (there will | |
8021 // always be at least two 0 bits between successive 1 bits). We make use | |
8022 // of these "unused" bits to represent uninitialized blocks -- the bit | |
8023 // corresponding to the start of the uninitialized object and the next | |
8024 // bit are both set. Finally, a 1 bit marks the end of the object that | |
8025 // started with the two consecutive 1 bits to indicate its potentially | |
8026 // uninitialized state. | |
8027 | |
8028 size_t SweepClosure::do_blk_careful(HeapWord* addr) { | |
8029 FreeChunk* fc = (FreeChunk*)addr; | |
8030 size_t res; | |
8031 | |
1720
5ed703250bff
6977970: CMS: concurrentMarkSweepGeneration.cpp:7947 assert(addr <= _limit) failed: sweep invariant
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|
8032 // Check if we are done sweeping. Below we check "addr >= _limit" rather |
5ed703250bff
6977970: CMS: concurrentMarkSweepGeneration.cpp:7947 assert(addr <= _limit) failed: sweep invariant
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|
8033 // than "addr == _limit" because although _limit was a block boundary when |
5ed703250bff
6977970: CMS: concurrentMarkSweepGeneration.cpp:7947 assert(addr <= _limit) failed: sweep invariant
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|
8034 // 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
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|
8035 // may have caused us to coalesce the block ending at the address _limit |
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6977970: CMS: concurrentMarkSweepGeneration.cpp:7947 assert(addr <= _limit) failed: sweep invariant
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|
8036 // with a newly expanded chunk (this happens when _limit was set to the |
3746
537a4053b0f9
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|
8037 // previous _end of the space), so we may have stepped past _limit: |
537a4053b0f9
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|
8038 // see the following Zeno-like trail of CRs 6977970, 7008136, 7042740. |
2132
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|
8039 if (addr >= _limit) { // we have swept up to or past the limit: finish up |
0 | 8040 assert(_limit >= _sp->bottom() && _limit <= _sp->end(), |
8041 "sweep _limit out of bounds"); | |
1720
5ed703250bff
6977970: CMS: concurrentMarkSweepGeneration.cpp:7947 assert(addr <= _limit) failed: sweep invariant
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|
8042 assert(addr < _sp->end(), "addr out of bounds"); |
3746
537a4053b0f9
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|
8043 // Flush any free range we might be holding as a single |
2132
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|
8044 // coalesced chunk to the appropriate free list. |
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|
8045 if (inFreeRange()) { |
3746
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|
8046 assert(freeFinger() >= _sp->bottom() && freeFinger() < _limit, |
537a4053b0f9
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|
8047 err_msg("freeFinger() " PTR_FORMAT" is out-of-bounds", freeFinger())); |
2132
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|
8048 flush_cur_free_chunk(freeFinger(), |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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1994
diff
changeset
|
8049 pointer_delta(addr, freeFinger())); |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
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|
8050 if (CMSTraceSweeper) { |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
changeset
|
8051 gclog_or_tty->print("Sweep: last chunk: "); |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
changeset
|
8052 gclog_or_tty->print("put_free_blk 0x%x ("SIZE_FORMAT") " |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
changeset
|
8053 "[coalesced:"SIZE_FORMAT"]\n", |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
changeset
|
8054 freeFinger(), pointer_delta(addr, freeFinger()), |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
changeset
|
8055 lastFreeRangeCoalesced()); |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
changeset
|
8056 } |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
changeset
|
8057 } |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
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|
8058 |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
changeset
|
8059 // help the iterator loop finish |
1720
5ed703250bff
6977970: CMS: concurrentMarkSweepGeneration.cpp:7947 assert(addr <= _limit) failed: sweep invariant
ysr
parents:
1716
diff
changeset
|
8060 return pointer_delta(_sp->end(), addr); |
5ed703250bff
6977970: CMS: concurrentMarkSweepGeneration.cpp:7947 assert(addr <= _limit) failed: sweep invariant
ysr
parents:
1716
diff
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|
8061 } |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
changeset
|
8062 |
1720
5ed703250bff
6977970: CMS: concurrentMarkSweepGeneration.cpp:7947 assert(addr <= _limit) failed: sweep invariant
ysr
parents:
1716
diff
changeset
|
8063 assert(addr < _limit, "sweep invariant"); |
0 | 8064 // check if we should yield |
8065 do_yield_check(addr); | |
6028
f69a5d43dc19
7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
jmasa
parents:
6026
diff
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|
8066 if (fc->is_free()) { |
0 | 8067 // Chunk that is already free |
8068 res = fc->size(); | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
changeset
|
8069 do_already_free_chunk(fc); |
0 | 8070 debug_only(_sp->verifyFreeLists()); |
3746
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8071 // If we flush the chunk at hand in lookahead_and_flush() |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8072 // and it's coalesced with a preceding chunk, then the |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8073 // process of "mangling" the payload of the coalesced block |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
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changeset
|
8074 // will cause erasure of the size information from the |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8075 // (erstwhile) header of all the coalesced blocks but the |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8076 // first, so the first disjunct in the assert will not hold |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8077 // in that specific case (in which case the second disjunct |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8078 // will hold). |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8079 assert(res == fc->size() || ((HeapWord*)fc) + res >= _limit, |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8080 "Otherwise the size info doesn't change at this step"); |
0 | 8081 NOT_PRODUCT( |
8082 _numObjectsAlreadyFree++; | |
8083 _numWordsAlreadyFree += res; | |
8084 ) | |
8085 NOT_PRODUCT(_last_fc = fc;) | |
8086 } else if (!_bitMap->isMarked(addr)) { | |
8087 // Chunk is fresh garbage | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8088 res = do_garbage_chunk(fc); |
0 | 8089 debug_only(_sp->verifyFreeLists()); |
8090 NOT_PRODUCT( | |
8091 _numObjectsFreed++; | |
8092 _numWordsFreed += res; | |
8093 ) | |
8094 } else { | |
8095 // Chunk that is alive. | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8096 res = do_live_chunk(fc); |
0 | 8097 debug_only(_sp->verifyFreeLists()); |
8098 NOT_PRODUCT( | |
8099 _numObjectsLive++; | |
8100 _numWordsLive += res; | |
8101 ) | |
8102 } | |
8103 return res; | |
8104 } | |
8105 | |
8106 // For the smart allocation, record following | |
8107 // split deaths - a free chunk is removed from its free list because | |
8108 // it is being split into two or more chunks. | |
8109 // split birth - a free chunk is being added to its free list because | |
8110 // a larger free chunk has been split and resulted in this free chunk. | |
8111 // coal death - a free chunk is being removed from its free list because | |
8112 // it is being coalesced into a large free chunk. | |
8113 // coal birth - a free chunk is being added to its free list because | |
8114 // it was created when two or more free chunks where coalesced into | |
8115 // this free chunk. | |
8116 // | |
8117 // These statistics are used to determine the desired number of free | |
8118 // chunks of a given size. The desired number is chosen to be relative | |
8119 // to the end of a CMS sweep. The desired number at the end of a sweep | |
8120 // is the | |
8121 // count-at-end-of-previous-sweep (an amount that was enough) | |
8122 // - count-at-beginning-of-current-sweep (the excess) | |
8123 // + split-births (gains in this size during interval) | |
8124 // - split-deaths (demands on this size during interval) | |
8125 // where the interval is from the end of one sweep to the end of the | |
8126 // next. | |
8127 // | |
8128 // When sweeping the sweeper maintains an accumulated chunk which is | |
8129 // the chunk that is made up of chunks that have been coalesced. That | |
8130 // will be termed the left-hand chunk. A new chunk of garbage that | |
8131 // is being considered for coalescing will be referred to as the | |
8132 // right-hand chunk. | |
8133 // | |
8134 // When making a decision on whether to coalesce a right-hand chunk with | |
8135 // the current left-hand chunk, the current count vs. the desired count | |
8136 // of the left-hand chunk is considered. Also if the right-hand chunk | |
8137 // is near the large chunk at the end of the heap (see | |
8138 // ConcurrentMarkSweepGeneration::isNearLargestChunk()), then the | |
8139 // left-hand chunk is coalesced. | |
8140 // | |
8141 // When making a decision about whether to split a chunk, the desired count | |
8142 // vs. the current count of the candidate to be split is also considered. | |
8143 // If the candidate is underpopulated (currently fewer chunks than desired) | |
8144 // a chunk of an overpopulated (currently more chunks than desired) size may | |
8145 // be chosen. The "hint" associated with a free list, if non-null, points | |
8146 // to a free list which may be overpopulated. | |
8147 // | |
8148 | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
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|
8149 void SweepClosure::do_already_free_chunk(FreeChunk* fc) { |
3746
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8150 const size_t size = fc->size(); |
0 | 8151 // Chunks that cannot be coalesced are not in the |
8152 // free lists. | |
8153 if (CMSTestInFreeList && !fc->cantCoalesce()) { | |
6028
f69a5d43dc19
7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
jmasa
parents:
6026
diff
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|
8154 assert(_sp->verify_chunk_in_free_list(fc), |
0 | 8155 "free chunk should be in free lists"); |
8156 } | |
8157 // a chunk that is already free, should not have been | |
8158 // marked in the bit map | |
3746
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8159 HeapWord* const addr = (HeapWord*) fc; |
0 | 8160 assert(!_bitMap->isMarked(addr), "free chunk should be unmarked"); |
8161 // Verify that the bit map has no bits marked between | |
8162 // addr and purported end of this block. | |
8163 _bitMap->verifyNoOneBitsInRange(addr + 1, addr + size); | |
8164 | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
changeset
|
8165 // Some chunks cannot be coalesced under any circumstances. |
0 | 8166 // See the definition of cantCoalesce(). |
8167 if (!fc->cantCoalesce()) { | |
8168 // This chunk can potentially be coalesced. | |
8169 if (_sp->adaptive_freelists()) { | |
8170 // All the work is done in | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8171 do_post_free_or_garbage_chunk(fc, size); |
0 | 8172 } else { // Not adaptive free lists |
8173 // this is a free chunk that can potentially be coalesced by the sweeper; | |
8174 if (!inFreeRange()) { | |
8175 // if the next chunk is a free block that can't be coalesced | |
8176 // it doesn't make sense to remove this chunk from the free lists | |
8177 FreeChunk* nextChunk = (FreeChunk*)(addr + size); | |
2136
c91cc404ca46
7011940: iCMS: SIGSEGV in SweepClosure::do_already_free_chunk(FreeChunk*)+0x360
ysr
parents:
2132
diff
changeset
|
8178 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
|
8179 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
|
8180 nextChunk->is_free() && // ... which is free... |
2136
c91cc404ca46
7011940: iCMS: SIGSEGV in SweepClosure::do_already_free_chunk(FreeChunk*)+0x360
ysr
parents:
2132
diff
changeset
|
8181 nextChunk->cantCoalesce()) { // ... but can't be coalesced |
0 | 8182 // nothing to do |
8183 } else { | |
8184 // Potentially the start of a new free range: | |
8185 // Don't eagerly remove it from the free lists. | |
8186 // No need to remove it if it will just be put | |
8187 // back again. (Also from a pragmatic point of view | |
8188 // if it is a free block in a region that is beyond | |
8189 // any allocated blocks, an assertion will fail) | |
8190 // Remember the start of a free run. | |
8191 initialize_free_range(addr, true); | |
8192 // end - can coalesce with next chunk | |
8193 } | |
8194 } else { | |
8195 // the midst of a free range, we are coalescing | |
3746
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8196 print_free_block_coalesced(fc); |
0 | 8197 if (CMSTraceSweeper) { |
8198 gclog_or_tty->print(" -- pick up free block 0x%x (%d)\n", fc, size); | |
8199 } | |
8200 // remove it from the free lists | |
8201 _sp->removeFreeChunkFromFreeLists(fc); | |
8202 set_lastFreeRangeCoalesced(true); | |
8203 // If the chunk is being coalesced and the current free range is | |
8204 // in the free lists, remove the current free range so that it | |
8205 // will be returned to the free lists in its entirety - all | |
8206 // the coalesced pieces included. | |
8207 if (freeRangeInFreeLists()) { | |
8208 FreeChunk* ffc = (FreeChunk*) freeFinger(); | |
8209 assert(ffc->size() == pointer_delta(addr, freeFinger()), | |
8210 "Size of free range is inconsistent with chunk size."); | |
8211 if (CMSTestInFreeList) { | |
6028
f69a5d43dc19
7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
jmasa
parents:
6026
diff
changeset
|
8212 assert(_sp->verify_chunk_in_free_list(ffc), |
0 | 8213 "free range is not in free lists"); |
8214 } | |
8215 _sp->removeFreeChunkFromFreeLists(ffc); | |
8216 set_freeRangeInFreeLists(false); | |
8217 } | |
8218 } | |
8219 } | |
3746
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8220 // Note that if the chunk is not coalescable (the else arm |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8221 // below), we unconditionally flush, without needing to do |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8222 // a "lookahead," as we do below. |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8223 if (inFreeRange()) lookahead_and_flush(fc, size); |
0 | 8224 } else { |
8225 // Code path common to both original and adaptive free lists. | |
8226 | |
8227 // cant coalesce with previous block; this should be treated | |
8228 // as the end of a free run if any | |
8229 if (inFreeRange()) { | |
8230 // we kicked some butt; time to pick up the garbage | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8231 assert(freeFinger() < addr, "freeFinger points too high"); |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8232 flush_cur_free_chunk(freeFinger(), pointer_delta(addr, freeFinger())); |
0 | 8233 } |
8234 // else, nothing to do, just continue | |
8235 } | |
8236 } | |
8237 | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8238 size_t SweepClosure::do_garbage_chunk(FreeChunk* fc) { |
0 | 8239 // This is a chunk of garbage. It is not in any free list. |
8240 // Add it to a free list or let it possibly be coalesced into | |
8241 // a larger chunk. | |
3746
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8242 HeapWord* const addr = (HeapWord*) fc; |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8243 const size_t size = CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size()); |
0 | 8244 |
8245 if (_sp->adaptive_freelists()) { | |
8246 // Verify that the bit map has no bits marked between | |
8247 // addr and purported end of just dead object. | |
8248 _bitMap->verifyNoOneBitsInRange(addr + 1, addr + size); | |
8249 | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
changeset
|
8250 do_post_free_or_garbage_chunk(fc, size); |
0 | 8251 } else { |
8252 if (!inFreeRange()) { | |
8253 // start of a new free range | |
8254 assert(size > 0, "A free range should have a size"); | |
8255 initialize_free_range(addr, false); | |
8256 } else { | |
8257 // this will be swept up when we hit the end of the | |
8258 // free range | |
8259 if (CMSTraceSweeper) { | |
8260 gclog_or_tty->print(" -- pick up garbage 0x%x (%d) \n", fc, size); | |
8261 } | |
8262 // If the chunk is being coalesced and the current free range is | |
8263 // in the free lists, remove the current free range so that it | |
8264 // will be returned to the free lists in its entirety - all | |
8265 // the coalesced pieces included. | |
8266 if (freeRangeInFreeLists()) { | |
8267 FreeChunk* ffc = (FreeChunk*)freeFinger(); | |
8268 assert(ffc->size() == pointer_delta(addr, freeFinger()), | |
8269 "Size of free range is inconsistent with chunk size."); | |
8270 if (CMSTestInFreeList) { | |
6028
f69a5d43dc19
7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
jmasa
parents:
6026
diff
changeset
|
8271 assert(_sp->verify_chunk_in_free_list(ffc), |
0 | 8272 "free range is not in free lists"); |
8273 } | |
8274 _sp->removeFreeChunkFromFreeLists(ffc); | |
8275 set_freeRangeInFreeLists(false); | |
8276 } | |
8277 set_lastFreeRangeCoalesced(true); | |
8278 } | |
8279 // this will be swept up when we hit the end of the free range | |
8280 | |
8281 // Verify that the bit map has no bits marked between | |
8282 // addr and purported end of just dead object. | |
8283 _bitMap->verifyNoOneBitsInRange(addr + 1, addr + size); | |
8284 } | |
3746
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8285 assert(_limit >= addr + size, |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8286 "A freshly garbage chunk can't possibly straddle over _limit"); |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8287 if (inFreeRange()) lookahead_and_flush(fc, size); |
0 | 8288 return size; |
8289 } | |
8290 | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
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|
8291 size_t SweepClosure::do_live_chunk(FreeChunk* fc) { |
0 | 8292 HeapWord* addr = (HeapWord*) fc; |
8293 // The sweeper has just found a live object. Return any accumulated | |
8294 // left hand chunk to the free lists. | |
8295 if (inFreeRange()) { | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8296 assert(freeFinger() < addr, "freeFinger points too high"); |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8297 flush_cur_free_chunk(freeFinger(), pointer_delta(addr, freeFinger())); |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
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|
8298 } |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
changeset
|
8299 |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
changeset
|
8300 // This object is live: we'd normally expect this to be |
0 | 8301 // an oop, and like to assert the following: |
8302 // assert(oop(addr)->is_oop(), "live block should be an oop"); | |
8303 // However, as we commented above, this may be an object whose | |
8304 // header hasn't yet been initialized. | |
8305 size_t size; | |
8306 assert(_bitMap->isMarked(addr), "Tautology for this control point"); | |
8307 if (_bitMap->isMarked(addr + 1)) { | |
8308 // Determine the size from the bit map, rather than trying to | |
8309 // compute it from the object header. | |
8310 HeapWord* nextOneAddr = _bitMap->getNextMarkedWordAddress(addr + 2); | |
8311 size = pointer_delta(nextOneAddr + 1, addr); | |
8312 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
8313 "alignment problem"); | |
8314 | |
9152 | 8315 #ifdef ASSERT |
6725
da91efe96a93
6964458: Reimplement class meta-data storage to use native memory
coleenp
parents:
6197
diff
changeset
|
8316 if (oop(addr)->klass_or_null() != NULL) { |
0 | 8317 // Ignore mark word because we are running concurrent with mutators |
8318 assert(oop(addr)->is_oop(true), "live block should be an oop"); | |
8319 assert(size == | |
8320 CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size()), | |
8321 "P-mark and computed size do not agree"); | |
8322 } | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
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|
8323 #endif |
0 | 8324 |
8325 } else { | |
8326 // 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
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|
8327 assert(oop(addr)->klass_or_null() != NULL, |
0 | 8328 "Should be an initialized object"); |
8329 // Ignore mark word because we are running concurrent with mutators | |
8330 assert(oop(addr)->is_oop(true), "live block should be an oop"); | |
8331 // Verify that the bit map has no bits marked between | |
8332 // addr and purported end of this block. | |
8333 size = CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size()); | |
8334 assert(size >= 3, "Necessary for Printezis marks to work"); | |
8335 assert(!_bitMap->isMarked(addr+1), "Tautology for this control point"); | |
8336 DEBUG_ONLY(_bitMap->verifyNoOneBitsInRange(addr+2, addr+size);) | |
8337 } | |
8338 return size; | |
8339 } | |
8340 | |
2132
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7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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1994
diff
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|
8341 void SweepClosure::do_post_free_or_garbage_chunk(FreeChunk* fc, |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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1994
diff
changeset
|
8342 size_t chunkSize) { |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
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|
8343 // do_post_free_or_garbage_chunk() should only be called in the case |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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1994
diff
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|
8344 // of the adaptive free list allocator. |
6028
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7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
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6026
diff
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|
8345 const bool fcInFreeLists = fc->is_free(); |
0 | 8346 assert(_sp->adaptive_freelists(), "Should only be used in this case."); |
8347 assert((HeapWord*)fc <= _limit, "sweep invariant"); | |
8348 if (CMSTestInFreeList && fcInFreeLists) { | |
6028
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|
8349 assert(_sp->verify_chunk_in_free_list(fc), "free chunk is not in free lists"); |
2132
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7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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|
8350 } |
0 | 8351 |
8352 if (CMSTraceSweeper) { | |
8353 gclog_or_tty->print_cr(" -- pick up another chunk at 0x%x (%d)", fc, chunkSize); | |
8354 } | |
8355 | |
3746
537a4053b0f9
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|
8356 HeapWord* const fc_addr = (HeapWord*) fc; |
0 | 8357 |
8358 bool coalesce; | |
3746
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7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
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|
8359 const size_t left = pointer_delta(fc_addr, freeFinger()); |
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7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
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changeset
|
8360 const size_t right = chunkSize; |
0 | 8361 switch (FLSCoalescePolicy) { |
8362 // numeric value forms a coalition aggressiveness metric | |
8363 case 0: { // never coalesce | |
8364 coalesce = false; | |
8365 break; | |
8366 } | |
8367 case 1: { // coalesce if left & right chunks on overpopulated lists | |
8368 coalesce = _sp->coalOverPopulated(left) && | |
8369 _sp->coalOverPopulated(right); | |
8370 break; | |
8371 } | |
8372 case 2: { // coalesce if left chunk on overpopulated list (default) | |
8373 coalesce = _sp->coalOverPopulated(left); | |
8374 break; | |
8375 } | |
8376 case 3: { // coalesce if left OR right chunk on overpopulated list | |
8377 coalesce = _sp->coalOverPopulated(left) || | |
8378 _sp->coalOverPopulated(right); | |
8379 break; | |
8380 } | |
8381 case 4: { // always coalesce | |
8382 coalesce = true; | |
8383 break; | |
8384 } | |
8385 default: | |
8386 ShouldNotReachHere(); | |
8387 } | |
8388 | |
8389 // Should the current free range be coalesced? | |
8390 // If the chunk is in a free range and either we decided to coalesce above | |
8391 // or the chunk is near the large block at the end of the heap | |
8392 // (isNearLargestChunk() returns true), then coalesce this chunk. | |
3746
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|
8393 const bool doCoalesce = inFreeRange() |
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7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
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changeset
|
8394 && (coalesce || _g->isNearLargestChunk(fc_addr)); |
0 | 8395 if (doCoalesce) { |
8396 // Coalesce the current free range on the left with the new | |
8397 // chunk on the right. If either is on a free list, | |
8398 // it must be removed from the list and stashed in the closure. | |
8399 if (freeRangeInFreeLists()) { | |
3746
537a4053b0f9
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|
8400 FreeChunk* const ffc = (FreeChunk*)freeFinger(); |
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7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
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changeset
|
8401 assert(ffc->size() == pointer_delta(fc_addr, freeFinger()), |
0 | 8402 "Size of free range is inconsistent with chunk size."); |
8403 if (CMSTestInFreeList) { | |
6028
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jmasa
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6026
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|
8404 assert(_sp->verify_chunk_in_free_list(ffc), |
0 | 8405 "Chunk is not in free lists"); |
8406 } | |
8407 _sp->coalDeath(ffc->size()); | |
8408 _sp->removeFreeChunkFromFreeLists(ffc); | |
8409 set_freeRangeInFreeLists(false); | |
8410 } | |
8411 if (fcInFreeLists) { | |
8412 _sp->coalDeath(chunkSize); | |
8413 assert(fc->size() == chunkSize, | |
8414 "The chunk has the wrong size or is not in the free lists"); | |
8415 _sp->removeFreeChunkFromFreeLists(fc); | |
8416 } | |
8417 set_lastFreeRangeCoalesced(true); | |
3746
537a4053b0f9
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3356
diff
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|
8418 print_free_block_coalesced(fc); |
0 | 8419 } else { // not in a free range and/or should not coalesce |
8420 // Return the current free range and start a new one. | |
8421 if (inFreeRange()) { | |
8422 // In a free range but cannot coalesce with the right hand chunk. | |
8423 // Put the current free range into the free lists. | |
2132
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7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
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|
8424 flush_cur_free_chunk(freeFinger(), |
3746
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8425 pointer_delta(fc_addr, freeFinger())); |
0 | 8426 } |
8427 // Set up for new free range. Pass along whether the right hand | |
8428 // chunk is in the free lists. | |
8429 initialize_free_range((HeapWord*)fc, fcInFreeLists); | |
8430 } | |
8431 } | |
2132
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7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
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|
8432 |
3746
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8433 // Lookahead flush: |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
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3356
diff
changeset
|
8434 // If we are tracking a free range, and this is the last chunk that |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8435 // we'll look at because its end crosses past _limit, we'll preemptively |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8436 // flush it along with any free range we may be holding on to. Note that |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
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|
8437 // this can be the case only for an already free or freshly garbage |
537a4053b0f9
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ysr
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3356
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|
8438 // chunk. If this block is an object, it can never straddle |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
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3356
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|
8439 // over _limit. The "straddling" occurs when _limit is set at |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
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|
8440 // the previous end of the space when this cycle started, and |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
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|
8441 // a subsequent heap expansion caused the previously co-terminal |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
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|
8442 // free block to be coalesced with the newly expanded portion, |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
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3356
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|
8443 // thus rendering _limit a non-block-boundary making it dangerous |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
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3356
diff
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|
8444 // for the sweeper to step over and examine. |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8445 void SweepClosure::lookahead_and_flush(FreeChunk* fc, size_t chunk_size) { |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8446 assert(inFreeRange(), "Should only be called if currently in a free range."); |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8447 HeapWord* const eob = ((HeapWord*)fc) + chunk_size; |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
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|
8448 assert(_sp->used_region().contains(eob - 1), |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8449 err_msg("eob = " PTR_FORMAT " out of bounds wrt _sp = [" PTR_FORMAT "," PTR_FORMAT ")" |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8450 " when examining fc = " PTR_FORMAT "(" SIZE_FORMAT ")", |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8451 _limit, _sp->bottom(), _sp->end(), fc, chunk_size)); |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8452 if (eob >= _limit) { |
6028
f69a5d43dc19
7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
jmasa
parents:
6026
diff
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|
8453 assert(eob == _limit || fc->is_free(), "Only a free chunk should allow us to cross over the limit"); |
3746
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8454 if (CMSTraceSweeper) { |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8455 gclog_or_tty->print_cr("_limit " PTR_FORMAT " reached or crossed by block " |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8456 "[" PTR_FORMAT "," PTR_FORMAT ") in space " |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8457 "[" PTR_FORMAT "," PTR_FORMAT ")", |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8458 _limit, fc, eob, _sp->bottom(), _sp->end()); |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
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|
8459 } |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8460 // Return the storage we are tracking back into the free lists. |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8461 if (CMSTraceSweeper) { |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8462 gclog_or_tty->print_cr("Flushing ... "); |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
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|
8463 } |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8464 assert(freeFinger() < eob, "Error"); |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
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|
8465 flush_cur_free_chunk( freeFinger(), pointer_delta(eob, freeFinger())); |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
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3356
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|
8466 } |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
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3356
diff
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|
8467 } |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
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3356
diff
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|
8468 |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
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|
8469 void SweepClosure::flush_cur_free_chunk(HeapWord* chunk, size_t size) { |
0 | 8470 assert(inFreeRange(), "Should only be called if currently in a free range."); |
8471 assert(size > 0, | |
8472 "A zero sized chunk cannot be added to the free lists."); | |
8473 if (!freeRangeInFreeLists()) { | |
2132
4947ee68d19c
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ysr
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1994
diff
changeset
|
8474 if (CMSTestInFreeList) { |
0 | 8475 FreeChunk* fc = (FreeChunk*) chunk; |
6028
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7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
jmasa
parents:
6026
diff
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|
8476 fc->set_size(size); |
f69a5d43dc19
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jmasa
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6026
diff
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|
8477 assert(!_sp->verify_chunk_in_free_list(fc), |
0 | 8478 "chunk should not be in free lists yet"); |
8479 } | |
8480 if (CMSTraceSweeper) { | |
8481 gclog_or_tty->print_cr(" -- add free block 0x%x (%d) to free lists", | |
8482 chunk, size); | |
8483 } | |
8484 // A new free range is going to be starting. The current | |
8485 // free range has not been added to the free lists yet or | |
8486 // was removed so add it back. | |
8487 // If the current free range was coalesced, then the death | |
8488 // of the free range was recorded. Record a birth now. | |
8489 if (lastFreeRangeCoalesced()) { | |
8490 _sp->coalBirth(size); | |
8491 } | |
8492 _sp->addChunkAndRepairOffsetTable(chunk, size, | |
8493 lastFreeRangeCoalesced()); | |
3746
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
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3356
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|
8494 } else if (CMSTraceSweeper) { |
537a4053b0f9
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ysr
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3356
diff
changeset
|
8495 gclog_or_tty->print_cr("Already in free list: nothing to flush"); |
0 | 8496 } |
8497 set_inFreeRange(false); | |
8498 set_freeRangeInFreeLists(false); | |
8499 } | |
8500 | |
8501 // We take a break if we've been at this for a while, | |
8502 // so as to avoid monopolizing the locks involved. | |
8503 void SweepClosure::do_yield_work(HeapWord* addr) { | |
8504 // Return current free chunk being used for coalescing (if any) | |
8505 // to the appropriate freelist. After yielding, the next | |
8506 // free block encountered will start a coalescing range of | |
8507 // free blocks. If the next free block is adjacent to the | |
8508 // chunk just flushed, they will need to wait for the next | |
8509 // sweep to be coalesced. | |
8510 if (inFreeRange()) { | |
2132
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ysr
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1994
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changeset
|
8511 flush_cur_free_chunk(freeFinger(), pointer_delta(addr, freeFinger())); |
0 | 8512 } |
8513 | |
8514 // First give up the locks, then yield, then re-lock. | |
8515 // We should probably use a constructor/destructor idiom to | |
8516 // do this unlock/lock or modify the MutexUnlocker class to | |
8517 // serve our purpose. XXX | |
8518 assert_lock_strong(_bitMap->lock()); | |
8519 assert_lock_strong(_freelistLock); | |
8520 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
8521 "CMS thread should hold CMS token"); | |
8522 _bitMap->lock()->unlock(); | |
8523 _freelistLock->unlock(); | |
8524 ConcurrentMarkSweepThread::desynchronize(true); | |
8525 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
8526 _collector->stopTimer(); | |
8527 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
8528 if (PrintCMSStatistics != 0) { | |
8529 _collector->incrementYields(); | |
8530 } | |
8531 _collector->icms_wait(); | |
8532 | |
8533 // See the comment in coordinator_yield() | |
8534 for (unsigned i = 0; i < CMSYieldSleepCount && | |
8535 ConcurrentMarkSweepThread::should_yield() && | |
8536 !CMSCollector::foregroundGCIsActive(); ++i) { | |
8537 os::sleep(Thread::current(), 1, false); | |
8538 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
8539 } | |
8540 | |
8541 ConcurrentMarkSweepThread::synchronize(true); | |
8542 _freelistLock->lock(); | |
8543 _bitMap->lock()->lock_without_safepoint_check(); | |
8544 _collector->startTimer(); | |
8545 } | |
8546 | |
8547 #ifndef PRODUCT | |
8548 // This is actually very useful in a product build if it can | |
8549 // be called from the debugger. Compile it into the product | |
8550 // as needed. | |
6028
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|
8551 bool debug_verify_chunk_in_free_list(FreeChunk* fc) { |
f69a5d43dc19
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jmasa
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6026
diff
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|
8552 return debug_cms_space->verify_chunk_in_free_list(fc); |
0 | 8553 } |
3746
537a4053b0f9
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ysr
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|
8554 #endif |
537a4053b0f9
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|
8555 |
537a4053b0f9
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ysr
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|
8556 void SweepClosure::print_free_block_coalesced(FreeChunk* fc) const { |
0 | 8557 if (CMSTraceSweeper) { |
3746
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3356
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|
8558 gclog_or_tty->print_cr("Sweep:coal_free_blk " PTR_FORMAT " (" SIZE_FORMAT ")", |
537a4053b0f9
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|
8559 fc, fc->size()); |
537a4053b0f9
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ysr
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3356
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|
8560 } |
537a4053b0f9
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8561 } |
0 | 8562 |
8563 // CMSIsAliveClosure | |
8564 bool CMSIsAliveClosure::do_object_b(oop obj) { | |
8565 HeapWord* addr = (HeapWord*)obj; | |
8566 return addr != NULL && | |
8567 (!_span.contains(addr) || _bit_map->isMarked(addr)); | |
8568 } | |
8569 | |
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8570 |
935 | 8571 CMSKeepAliveClosure::CMSKeepAliveClosure( CMSCollector* collector, |
8572 MemRegion span, | |
8573 CMSBitMap* bit_map, CMSMarkStack* mark_stack, | |
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8574 bool cpc): |
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8575 _collector(collector), |
935 | 8576 _span(span), |
8577 _bit_map(bit_map), | |
8578 _mark_stack(mark_stack), | |
8579 _concurrent_precleaning(cpc) { | |
8580 assert(!_span.is_empty(), "Empty span could spell trouble"); | |
8581 } | |
8582 | |
8583 | |
0 | 8584 // CMSKeepAliveClosure: the serial version |
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8585 void CMSKeepAliveClosure::do_oop(oop obj) { |
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8586 HeapWord* addr = (HeapWord*)obj; |
0 | 8587 if (_span.contains(addr) && |
8588 !_bit_map->isMarked(addr)) { | |
8589 _bit_map->mark(addr); | |
8590 bool simulate_overflow = false; | |
8591 NOT_PRODUCT( | |
8592 if (CMSMarkStackOverflowALot && | |
8593 _collector->simulate_overflow()) { | |
8594 // simulate a stack overflow | |
8595 simulate_overflow = true; | |
8596 } | |
8597 ) | |
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8598 if (simulate_overflow || !_mark_stack->push(obj)) { |
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8599 if (_concurrent_precleaning) { |
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8600 // We dirty the overflown object and let the remark |
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8601 // phase deal with it. |
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8602 assert(_collector->overflow_list_is_empty(), "Error"); |
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8603 // In the case of object arrays, we need to dirty all of |
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8604 // the cards that the object spans. No locking or atomics |
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8605 // are needed since no one else can be mutating the mod union |
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8606 // table. |
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8607 if (obj->is_objArray()) { |
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8608 size_t sz = obj->size(); |
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8609 HeapWord* end_card_addr = |
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8610 (HeapWord*)round_to((intptr_t)(addr+sz), CardTableModRefBS::card_size); |
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8611 MemRegion redirty_range = MemRegion(addr, end_card_addr); |
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8612 assert(!redirty_range.is_empty(), "Arithmetical tautology"); |
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8613 _collector->_modUnionTable.mark_range(redirty_range); |
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8614 } else { |
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8615 _collector->_modUnionTable.mark(addr); |
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8616 } |
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8617 _collector->_ser_kac_preclean_ovflw++; |
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8618 } else { |
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8619 _collector->push_on_overflow_list(obj); |
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8620 _collector->_ser_kac_ovflw++; |
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8621 } |
0 | 8622 } |
8623 } | |
8624 } | |
8625 | |
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8626 void CMSKeepAliveClosure::do_oop(oop* p) { CMSKeepAliveClosure::do_oop_work(p); } |
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8627 void CMSKeepAliveClosure::do_oop(narrowOop* p) { CMSKeepAliveClosure::do_oop_work(p); } |
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8628 |
0 | 8629 // CMSParKeepAliveClosure: a parallel version of the above. |
8630 // The work queues are private to each closure (thread), | |
8631 // but (may be) available for stealing by other threads. | |
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8632 void CMSParKeepAliveClosure::do_oop(oop obj) { |
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8633 HeapWord* addr = (HeapWord*)obj; |
0 | 8634 if (_span.contains(addr) && |
8635 !_bit_map->isMarked(addr)) { | |
8636 // In general, during recursive tracing, several threads | |
8637 // may be concurrently getting here; the first one to | |
8638 // "tag" it, claims it. | |
8639 if (_bit_map->par_mark(addr)) { | |
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8640 bool res = _work_queue->push(obj); |
0 | 8641 assert(res, "Low water mark should be much less than capacity"); |
8642 // Do a recursive trim in the hope that this will keep | |
8643 // stack usage lower, but leave some oops for potential stealers | |
8644 trim_queue(_low_water_mark); | |
8645 } // Else, another thread got there first | |
8646 } | |
8647 } | |
8648 | |
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8649 void CMSParKeepAliveClosure::do_oop(oop* p) { CMSParKeepAliveClosure::do_oop_work(p); } |
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8650 void CMSParKeepAliveClosure::do_oop(narrowOop* p) { CMSParKeepAliveClosure::do_oop_work(p); } |
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8651 |
0 | 8652 void CMSParKeepAliveClosure::trim_queue(uint max) { |
8653 while (_work_queue->size() > max) { | |
8654 oop new_oop; | |
8655 if (_work_queue->pop_local(new_oop)) { | |
8656 assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop"); | |
8657 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
8658 "no white objects on this stack!"); | |
8659 assert(_span.contains((HeapWord*)new_oop), "Out of bounds oop"); | |
8660 // iterate over the oops in this oop, marking and pushing | |
8661 // the ones in CMS heap (i.e. in _span). | |
8662 new_oop->oop_iterate(&_mark_and_push); | |
8663 } | |
8664 } | |
8665 } | |
8666 | |
935 | 8667 CMSInnerParMarkAndPushClosure::CMSInnerParMarkAndPushClosure( |
8668 CMSCollector* collector, | |
8669 MemRegion span, CMSBitMap* bit_map, | |
8670 OopTaskQueue* work_queue): | |
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8671 _collector(collector), |
935 | 8672 _span(span), |
8673 _bit_map(bit_map), | |
8674 _work_queue(work_queue) { } | |
8675 | |
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8676 void CMSInnerParMarkAndPushClosure::do_oop(oop obj) { |
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8677 HeapWord* addr = (HeapWord*)obj; |
0 | 8678 if (_span.contains(addr) && |
8679 !_bit_map->isMarked(addr)) { | |
8680 if (_bit_map->par_mark(addr)) { | |
8681 bool simulate_overflow = false; | |
8682 NOT_PRODUCT( | |
8683 if (CMSMarkStackOverflowALot && | |
8684 _collector->par_simulate_overflow()) { | |
8685 // simulate a stack overflow | |
8686 simulate_overflow = true; | |
8687 } | |
8688 ) | |
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8689 if (simulate_overflow || !_work_queue->push(obj)) { |
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8690 _collector->par_push_on_overflow_list(obj); |
0 | 8691 _collector->_par_kac_ovflw++; |
8692 } | |
8693 } // Else another thread got there already | |
8694 } | |
8695 } | |
8696 | |
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8697 void CMSInnerParMarkAndPushClosure::do_oop(oop* p) { CMSInnerParMarkAndPushClosure::do_oop_work(p); } |
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8698 void CMSInnerParMarkAndPushClosure::do_oop(narrowOop* p) { CMSInnerParMarkAndPushClosure::do_oop_work(p); } |
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8699 |
0 | 8700 ////////////////////////////////////////////////////////////////// |
8701 // CMSExpansionCause ///////////////////////////// | |
8702 ////////////////////////////////////////////////////////////////// | |
8703 const char* CMSExpansionCause::to_string(CMSExpansionCause::Cause cause) { | |
8704 switch (cause) { | |
8705 case _no_expansion: | |
8706 return "No expansion"; | |
8707 case _satisfy_free_ratio: | |
8708 return "Free ratio"; | |
8709 case _satisfy_promotion: | |
8710 return "Satisfy promotion"; | |
8711 case _satisfy_allocation: | |
8712 return "allocation"; | |
8713 case _allocate_par_lab: | |
8714 return "Par LAB"; | |
8715 case _allocate_par_spooling_space: | |
8716 return "Par Spooling Space"; | |
8717 case _adaptive_size_policy: | |
8718 return "Ergonomics"; | |
8719 default: | |
8720 return "unknown"; | |
8721 } | |
8722 } | |
8723 | |
8724 void CMSDrainMarkingStackClosure::do_void() { | |
8725 // the max number to take from overflow list at a time | |
8726 const size_t num = _mark_stack->capacity()/4; | |
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8727 assert(!_concurrent_precleaning || _collector->overflow_list_is_empty(), |
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8728 "Overflow list should be NULL during concurrent phases"); |
0 | 8729 while (!_mark_stack->isEmpty() || |
8730 // if stack is empty, check the overflow list | |
8731 _collector->take_from_overflow_list(num, _mark_stack)) { | |
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8732 oop obj = _mark_stack->pop(); |
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8733 HeapWord* addr = (HeapWord*)obj; |
0 | 8734 assert(_span.contains(addr), "Should be within span"); |
8735 assert(_bit_map->isMarked(addr), "Should be marked"); | |
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8736 assert(obj->is_oop(), "Should be an oop"); |
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8737 obj->oop_iterate(_keep_alive); |
0 | 8738 } |
8739 } | |
8740 | |
8741 void CMSParDrainMarkingStackClosure::do_void() { | |
8742 // drain queue | |
8743 trim_queue(0); | |
8744 } | |
8745 | |
8746 // Trim our work_queue so its length is below max at return | |
8747 void CMSParDrainMarkingStackClosure::trim_queue(uint max) { | |
8748 while (_work_queue->size() > max) { | |
8749 oop new_oop; | |
8750 if (_work_queue->pop_local(new_oop)) { | |
8751 assert(new_oop->is_oop(), "Expected an oop"); | |
8752 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
8753 "no white objects on this stack!"); | |
8754 assert(_span.contains((HeapWord*)new_oop), "Out of bounds oop"); | |
8755 // iterate over the oops in this oop, marking and pushing | |
8756 // the ones in CMS heap (i.e. in _span). | |
8757 new_oop->oop_iterate(&_mark_and_push); | |
8758 } | |
8759 } | |
8760 } | |
8761 | |
8762 //////////////////////////////////////////////////////////////////// | |
8763 // Support for Marking Stack Overflow list handling and related code | |
8764 //////////////////////////////////////////////////////////////////// | |
8765 // Much of the following code is similar in shape and spirit to the | |
8766 // code used in ParNewGC. We should try and share that code | |
8767 // as much as possible in the future. | |
8768 | |
8769 #ifndef PRODUCT | |
8770 // Debugging support for CMSStackOverflowALot | |
8771 | |
8772 // It's OK to call this multi-threaded; the worst thing | |
8773 // that can happen is that we'll get a bunch of closely | |
8774 // spaced simulated oveflows, but that's OK, in fact | |
8775 // probably good as it would exercise the overflow code | |
8776 // under contention. | |
8777 bool CMSCollector::simulate_overflow() { | |
8778 if (_overflow_counter-- <= 0) { // just being defensive | |
8779 _overflow_counter = CMSMarkStackOverflowInterval; | |
8780 return true; | |
8781 } else { | |
8782 return false; | |
8783 } | |
8784 } | |
8785 | |
8786 bool CMSCollector::par_simulate_overflow() { | |
8787 return simulate_overflow(); | |
8788 } | |
8789 #endif | |
8790 | |
8791 // Single-threaded | |
8792 bool CMSCollector::take_from_overflow_list(size_t num, CMSMarkStack* stack) { | |
8793 assert(stack->isEmpty(), "Expected precondition"); | |
8794 assert(stack->capacity() > num, "Shouldn't bite more than can chew"); | |
8795 size_t i = num; | |
8796 oop cur = _overflow_list; | |
8797 const markOop proto = markOopDesc::prototype(); | |
534 | 8798 NOT_PRODUCT(ssize_t n = 0;) |
0 | 8799 for (oop next; i > 0 && cur != NULL; cur = next, i--) { |
8800 next = oop(cur->mark()); | |
8801 cur->set_mark(proto); // until proven otherwise | |
8802 assert(cur->is_oop(), "Should be an oop"); | |
8803 bool res = stack->push(cur); | |
8804 assert(res, "Bit off more than can chew?"); | |
8805 NOT_PRODUCT(n++;) | |
8806 } | |
8807 _overflow_list = cur; | |
8808 #ifndef PRODUCT | |
8809 assert(_num_par_pushes >= n, "Too many pops?"); | |
8810 _num_par_pushes -=n; | |
8811 #endif | |
8812 return !stack->isEmpty(); | |
8813 } | |
8814 | |
534 | 8815 #define BUSY (oop(0x1aff1aff)) |
8816 // (MT-safe) Get a prefix of at most "num" from the list. | |
8817 // The overflow list is chained through the mark word of | |
8818 // each object in the list. We fetch the entire list, | |
8819 // break off a prefix of the right size and return the | |
8820 // remainder. If other threads try to take objects from | |
8821 // the overflow list at that time, they will wait for | |
8822 // some time to see if data becomes available. If (and | |
8823 // only if) another thread places one or more object(s) | |
8824 // on the global list before we have returned the suffix | |
8825 // to the global list, we will walk down our local list | |
8826 // to find its end and append the global list to | |
8827 // our suffix before returning it. This suffix walk can | |
8828 // prove to be expensive (quadratic in the amount of traffic) | |
8829 // when there are many objects in the overflow list and | |
8830 // there is much producer-consumer contention on the list. | |
8831 // *NOTE*: The overflow list manipulation code here and | |
8832 // in ParNewGeneration:: are very similar in shape, | |
8833 // except that in the ParNew case we use the old (from/eden) | |
8834 // copy of the object to thread the list via its klass word. | |
8835 // Because of the common code, if you make any changes in | |
8836 // the code below, please check the ParNew version to see if | |
8837 // similar changes might be needed. | |
8838 // CR 6797058 has been filed to consolidate the common code. | |
0 | 8839 bool CMSCollector::par_take_from_overflow_list(size_t num, |
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8840 OopTaskQueue* work_q, |
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8841 int no_of_gc_threads) { |
534 | 8842 assert(work_q->size() == 0, "First empty local work queue"); |
0 | 8843 assert(num < work_q->max_elems(), "Can't bite more than we can chew"); |
8844 if (_overflow_list == NULL) { | |
8845 return false; | |
8846 } | |
8847 // Grab the entire list; we'll put back a suffix | |
534 | 8848 oop prefix = (oop)Atomic::xchg_ptr(BUSY, &_overflow_list); |
8849 Thread* tid = Thread::current(); | |
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8850 // Before "no_of_gc_threads" was introduced CMSOverflowSpinCount was |
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8851 // set to ParallelGCThreads. |
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8852 size_t CMSOverflowSpinCount = (size_t) no_of_gc_threads; // was ParallelGCThreads; |
534 | 8853 size_t sleep_time_millis = MAX2((size_t)1, num/100); |
8854 // If the list is busy, we spin for a short while, | |
8855 // sleeping between attempts to get the list. | |
8856 for (size_t spin = 0; prefix == BUSY && spin < CMSOverflowSpinCount; spin++) { | |
8857 os::sleep(tid, sleep_time_millis, false); | |
8858 if (_overflow_list == NULL) { | |
8859 // Nothing left to take | |
8860 return false; | |
8861 } else if (_overflow_list != BUSY) { | |
8862 // Try and grab the prefix | |
8863 prefix = (oop)Atomic::xchg_ptr(BUSY, &_overflow_list); | |
8864 } | |
8865 } | |
8866 // If the list was found to be empty, or we spun long | |
8867 // enough, we give up and return empty-handed. If we leave | |
8868 // the list in the BUSY state below, it must be the case that | |
8869 // some other thread holds the overflow list and will set it | |
8870 // to a non-BUSY state in the future. | |
8871 if (prefix == NULL || prefix == BUSY) { | |
8872 // Nothing to take or waited long enough | |
8873 if (prefix == NULL) { | |
8874 // Write back the NULL in case we overwrote it with BUSY above | |
8875 // and it is still the same value. | |
8876 (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY); | |
8877 } | |
8878 return false; | |
8879 } | |
8880 assert(prefix != NULL && prefix != BUSY, "Error"); | |
0 | 8881 size_t i = num; |
8882 oop cur = prefix; | |
534 | 8883 // Walk down the first "num" objects, unless we reach the end. |
0 | 8884 for (; i > 1 && cur->mark() != NULL; cur = oop(cur->mark()), i--); |
534 | 8885 if (cur->mark() == NULL) { |
8886 // We have "num" or fewer elements in the list, so there | |
8887 // is nothing to return to the global list. | |
8888 // Write back the NULL in lieu of the BUSY we wrote | |
8889 // above, if it is still the same value. | |
8890 if (_overflow_list == BUSY) { | |
8891 (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY); | |
8892 } | |
8893 } else { | |
8894 // Chop off the suffix and rerturn it to the global list. | |
8895 assert(cur->mark() != BUSY, "Error"); | |
0 | 8896 oop suffix_head = cur->mark(); // suffix will be put back on global list |
8897 cur->set_mark(NULL); // break off suffix | |
534 | 8898 // It's possible that the list is still in the empty(busy) state |
8899 // we left it in a short while ago; in that case we may be | |
8900 // able to place back the suffix without incurring the cost | |
8901 // of a walk down the list. | |
0 | 8902 oop observed_overflow_list = _overflow_list; |
534 | 8903 oop cur_overflow_list = observed_overflow_list; |
8904 bool attached = false; | |
8905 while (observed_overflow_list == BUSY || observed_overflow_list == NULL) { | |
0 | 8906 observed_overflow_list = |
534 | 8907 (oop) Atomic::cmpxchg_ptr(suffix_head, &_overflow_list, cur_overflow_list); |
8908 if (cur_overflow_list == observed_overflow_list) { | |
8909 attached = true; | |
8910 break; | |
8911 } else cur_overflow_list = observed_overflow_list; | |
8912 } | |
8913 if (!attached) { | |
8914 // Too bad, someone else sneaked in (at least) an element; we'll need | |
8915 // to do a splice. Find tail of suffix so we can prepend suffix to global | |
8916 // list. | |
8917 for (cur = suffix_head; cur->mark() != NULL; cur = (oop)(cur->mark())); | |
8918 oop suffix_tail = cur; | |
8919 assert(suffix_tail != NULL && suffix_tail->mark() == NULL, | |
8920 "Tautology"); | |
8921 observed_overflow_list = _overflow_list; | |
8922 do { | |
8923 cur_overflow_list = observed_overflow_list; | |
8924 if (cur_overflow_list != BUSY) { | |
8925 // Do the splice ... | |
8926 suffix_tail->set_mark(markOop(cur_overflow_list)); | |
8927 } else { // cur_overflow_list == BUSY | |
8928 suffix_tail->set_mark(NULL); | |
8929 } | |
8930 // ... and try to place spliced list back on overflow_list ... | |
8931 observed_overflow_list = | |
8932 (oop) Atomic::cmpxchg_ptr(suffix_head, &_overflow_list, cur_overflow_list); | |
8933 } while (cur_overflow_list != observed_overflow_list); | |
8934 // ... until we have succeeded in doing so. | |
8935 } | |
0 | 8936 } |
8937 | |
8938 // Push the prefix elements on work_q | |
8939 assert(prefix != NULL, "control point invariant"); | |
8940 const markOop proto = markOopDesc::prototype(); | |
8941 oop next; | |
534 | 8942 NOT_PRODUCT(ssize_t n = 0;) |
0 | 8943 for (cur = prefix; cur != NULL; cur = next) { |
8944 next = oop(cur->mark()); | |
8945 cur->set_mark(proto); // until proven otherwise | |
8946 assert(cur->is_oop(), "Should be an oop"); | |
8947 bool res = work_q->push(cur); | |
8948 assert(res, "Bit off more than we can chew?"); | |
8949 NOT_PRODUCT(n++;) | |
8950 } | |
8951 #ifndef PRODUCT | |
8952 assert(_num_par_pushes >= n, "Too many pops?"); | |
8953 Atomic::add_ptr(-(intptr_t)n, &_num_par_pushes); | |
8954 #endif | |
8955 return true; | |
8956 } | |
8957 | |
8958 // Single-threaded | |
8959 void CMSCollector::push_on_overflow_list(oop p) { | |
8960 NOT_PRODUCT(_num_par_pushes++;) | |
8961 assert(p->is_oop(), "Not an oop"); | |
8962 preserve_mark_if_necessary(p); | |
8963 p->set_mark((markOop)_overflow_list); | |
8964 _overflow_list = p; | |
8965 } | |
8966 | |
8967 // Multi-threaded; use CAS to prepend to overflow list | |
8968 void CMSCollector::par_push_on_overflow_list(oop p) { | |
8969 NOT_PRODUCT(Atomic::inc_ptr(&_num_par_pushes);) | |
8970 assert(p->is_oop(), "Not an oop"); | |
8971 par_preserve_mark_if_necessary(p); | |
8972 oop observed_overflow_list = _overflow_list; | |
8973 oop cur_overflow_list; | |
8974 do { | |
8975 cur_overflow_list = observed_overflow_list; | |
534 | 8976 if (cur_overflow_list != BUSY) { |
8977 p->set_mark(markOop(cur_overflow_list)); | |
8978 } else { | |
8979 p->set_mark(NULL); | |
8980 } | |
0 | 8981 observed_overflow_list = |
8982 (oop) Atomic::cmpxchg_ptr(p, &_overflow_list, cur_overflow_list); | |
8983 } while (cur_overflow_list != observed_overflow_list); | |
8984 } | |
534 | 8985 #undef BUSY |
0 | 8986 |
8987 // Single threaded | |
8988 // General Note on GrowableArray: pushes may silently fail | |
8989 // because we are (temporarily) out of C-heap for expanding | |
8990 // the stack. The problem is quite ubiquitous and affects | |
8991 // a lot of code in the JVM. The prudent thing for GrowableArray | |
8992 // to do (for now) is to exit with an error. However, that may | |
8993 // be too draconian in some cases because the caller may be | |
534 | 8994 // able to recover without much harm. For such cases, we |
0 | 8995 // should probably introduce a "soft_push" method which returns |
8996 // an indication of success or failure with the assumption that | |
8997 // the caller may be able to recover from a failure; code in | |
8998 // the VM can then be changed, incrementally, to deal with such | |
8999 // failures where possible, thus, incrementally hardening the VM | |
9000 // in such low resource situations. | |
9001 void CMSCollector::preserve_mark_work(oop p, markOop m) { | |
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9002 _preserved_oop_stack.push(p); |
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9003 _preserved_mark_stack.push(m); |
0 | 9004 assert(m == p->mark(), "Mark word changed"); |
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9005 assert(_preserved_oop_stack.size() == _preserved_mark_stack.size(), |
0 | 9006 "bijection"); |
9007 } | |
9008 | |
9009 // Single threaded | |
9010 void CMSCollector::preserve_mark_if_necessary(oop p) { | |
9011 markOop m = p->mark(); | |
9012 if (m->must_be_preserved(p)) { | |
9013 preserve_mark_work(p, m); | |
9014 } | |
9015 } | |
9016 | |
9017 void CMSCollector::par_preserve_mark_if_necessary(oop p) { | |
9018 markOop m = p->mark(); | |
9019 if (m->must_be_preserved(p)) { | |
9020 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); | |
9021 // Even though we read the mark word without holding | |
9022 // the lock, we are assured that it will not change | |
9023 // because we "own" this oop, so no other thread can | |
9024 // be trying to push it on the overflow list; see | |
9025 // the assertion in preserve_mark_work() that checks | |
9026 // that m == p->mark(). | |
9027 preserve_mark_work(p, m); | |
9028 } | |
9029 } | |
9030 | |
9031 // We should be able to do this multi-threaded, | |
9032 // a chunk of stack being a task (this is | |
9033 // correct because each oop only ever appears | |
9034 // once in the overflow list. However, it's | |
9035 // not very easy to completely overlap this with | |
9036 // other operations, so will generally not be done | |
9037 // until all work's been completed. Because we | |
9038 // expect the preserved oop stack (set) to be small, | |
9039 // it's probably fine to do this single-threaded. | |
9040 // We can explore cleverer concurrent/overlapped/parallel | |
9041 // processing of preserved marks if we feel the | |
9042 // need for this in the future. Stack overflow should | |
9043 // be so rare in practice and, when it happens, its | |
9044 // effect on performance so great that this will | |
9045 // likely just be in the noise anyway. | |
9046 void CMSCollector::restore_preserved_marks_if_any() { | |
9047 assert(SafepointSynchronize::is_at_safepoint(), | |
9048 "world should be stopped"); | |
9049 assert(Thread::current()->is_ConcurrentGC_thread() || | |
9050 Thread::current()->is_VM_thread(), | |
9051 "should be single-threaded"); | |
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9052 assert(_preserved_oop_stack.size() == _preserved_mark_stack.size(), |
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9053 "bijection"); |
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9054 |
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9055 while (!_preserved_oop_stack.is_empty()) { |
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9056 oop p = _preserved_oop_stack.pop(); |
0 | 9057 assert(p->is_oop(), "Should be an oop"); |
9058 assert(_span.contains(p), "oop should be in _span"); | |
9059 assert(p->mark() == markOopDesc::prototype(), | |
9060 "Set when taken from overflow list"); | |
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9061 markOop m = _preserved_mark_stack.pop(); |
0 | 9062 p->set_mark(m); |
9063 } | |
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9064 assert(_preserved_mark_stack.is_empty() && _preserved_oop_stack.is_empty(), |
0 | 9065 "stacks were cleared above"); |
9066 } | |
9067 | |
9068 #ifndef PRODUCT | |
9069 bool CMSCollector::no_preserved_marks() const { | |
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9070 return _preserved_mark_stack.is_empty() && _preserved_oop_stack.is_empty(); |
0 | 9071 } |
9072 #endif | |
9073 | |
9074 CMSAdaptiveSizePolicy* ASConcurrentMarkSweepGeneration::cms_size_policy() const | |
9075 { | |
9076 GenCollectedHeap* gch = (GenCollectedHeap*) GenCollectedHeap::heap(); | |
9077 CMSAdaptiveSizePolicy* size_policy = | |
9078 (CMSAdaptiveSizePolicy*) gch->gen_policy()->size_policy(); | |
9079 assert(size_policy->is_gc_cms_adaptive_size_policy(), | |
9080 "Wrong type for size policy"); | |
9081 return size_policy; | |
9082 } | |
9083 | |
9084 void ASConcurrentMarkSweepGeneration::resize(size_t cur_promo_size, | |
9085 size_t desired_promo_size) { | |
9086 if (cur_promo_size < desired_promo_size) { | |
9087 size_t expand_bytes = desired_promo_size - cur_promo_size; | |
9088 if (PrintAdaptiveSizePolicy && Verbose) { | |
9089 gclog_or_tty->print_cr(" ASConcurrentMarkSweepGeneration::resize " | |
9090 "Expanding tenured generation by " SIZE_FORMAT " (bytes)", | |
9091 expand_bytes); | |
9092 } | |
9093 expand(expand_bytes, | |
9094 MinHeapDeltaBytes, | |
9095 CMSExpansionCause::_adaptive_size_policy); | |
9096 } else if (desired_promo_size < cur_promo_size) { | |
9097 size_t shrink_bytes = cur_promo_size - desired_promo_size; | |
9098 if (PrintAdaptiveSizePolicy && Verbose) { | |
9099 gclog_or_tty->print_cr(" ASConcurrentMarkSweepGeneration::resize " | |
9100 "Shrinking tenured generation by " SIZE_FORMAT " (bytes)", | |
9101 shrink_bytes); | |
9102 } | |
9103 shrink(shrink_bytes); | |
9104 } | |
9105 } | |
9106 | |
9107 CMSGCAdaptivePolicyCounters* ASConcurrentMarkSweepGeneration::gc_adaptive_policy_counters() { | |
9108 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
9109 CMSGCAdaptivePolicyCounters* counters = | |
9110 (CMSGCAdaptivePolicyCounters*) gch->collector_policy()->counters(); | |
9111 assert(counters->kind() == GCPolicyCounters::CMSGCAdaptivePolicyCountersKind, | |
9112 "Wrong kind of counters"); | |
9113 return counters; | |
9114 } | |
9115 | |
9116 | |
9117 void ASConcurrentMarkSweepGeneration::update_counters() { | |
9118 if (UsePerfData) { | |
9119 _space_counters->update_all(); | |
9120 _gen_counters->update_all(); | |
9121 CMSGCAdaptivePolicyCounters* counters = gc_adaptive_policy_counters(); | |
9122 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
9123 CMSGCStats* gc_stats_l = (CMSGCStats*) gc_stats(); | |
9124 assert(gc_stats_l->kind() == GCStats::CMSGCStatsKind, | |
9125 "Wrong gc statistics type"); | |
9126 counters->update_counters(gc_stats_l); | |
9127 } | |
9128 } | |
9129 | |
9130 void ASConcurrentMarkSweepGeneration::update_counters(size_t used) { | |
9131 if (UsePerfData) { | |
9132 _space_counters->update_used(used); | |
9133 _space_counters->update_capacity(); | |
9134 _gen_counters->update_all(); | |
9135 | |
9136 CMSGCAdaptivePolicyCounters* counters = gc_adaptive_policy_counters(); | |
9137 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
9138 CMSGCStats* gc_stats_l = (CMSGCStats*) gc_stats(); | |
9139 assert(gc_stats_l->kind() == GCStats::CMSGCStatsKind, | |
9140 "Wrong gc statistics type"); | |
9141 counters->update_counters(gc_stats_l); | |
9142 } | |
9143 } | |
9144 | |
9145 void ASConcurrentMarkSweepGeneration::shrink_by(size_t desired_bytes) { | |
9146 assert_locked_or_safepoint(Heap_lock); | |
9147 assert_lock_strong(freelistLock()); | |
9148 HeapWord* old_end = _cmsSpace->end(); | |
9149 HeapWord* unallocated_start = _cmsSpace->unallocated_block(); | |
9150 assert(old_end >= unallocated_start, "Miscalculation of unallocated_start"); | |
9151 FreeChunk* chunk_at_end = find_chunk_at_end(); | |
9152 if (chunk_at_end == NULL) { | |
9153 // No room to shrink | |
9154 if (PrintGCDetails && Verbose) { | |
9155 gclog_or_tty->print_cr("No room to shrink: old_end " | |
9156 PTR_FORMAT " unallocated_start " PTR_FORMAT | |
9157 " chunk_at_end " PTR_FORMAT, | |
9158 old_end, unallocated_start, chunk_at_end); | |
9159 } | |
9160 return; | |
9161 } else { | |
9162 | |
9163 // Find the chunk at the end of the space and determine | |
9164 // how much it can be shrunk. | |
9165 size_t shrinkable_size_in_bytes = chunk_at_end->size(); | |
9166 size_t aligned_shrinkable_size_in_bytes = | |
9167 align_size_down(shrinkable_size_in_bytes, os::vm_page_size()); | |
6885 | 9168 assert(unallocated_start <= (HeapWord*) chunk_at_end->end(), |
0 | 9169 "Inconsistent chunk at end of space"); |
9170 size_t bytes = MIN2(desired_bytes, aligned_shrinkable_size_in_bytes); | |
9171 size_t word_size_before = heap_word_size(_virtual_space.committed_size()); | |
9172 | |
9173 // Shrink the underlying space | |
9174 _virtual_space.shrink_by(bytes); | |
9175 if (PrintGCDetails && Verbose) { | |
9176 gclog_or_tty->print_cr("ConcurrentMarkSweepGeneration::shrink_by:" | |
9177 " desired_bytes " SIZE_FORMAT | |
9178 " shrinkable_size_in_bytes " SIZE_FORMAT | |
9179 " aligned_shrinkable_size_in_bytes " SIZE_FORMAT | |
9180 " bytes " SIZE_FORMAT, | |
9181 desired_bytes, shrinkable_size_in_bytes, | |
9182 aligned_shrinkable_size_in_bytes, bytes); | |
9183 gclog_or_tty->print_cr(" old_end " SIZE_FORMAT | |
9184 " unallocated_start " SIZE_FORMAT, | |
9185 old_end, unallocated_start); | |
9186 } | |
9187 | |
9188 // If the space did shrink (shrinking is not guaranteed), | |
9189 // shrink the chunk at the end by the appropriate amount. | |
9190 if (((HeapWord*)_virtual_space.high()) < old_end) { | |
9191 size_t new_word_size = | |
9192 heap_word_size(_virtual_space.committed_size()); | |
9193 | |
9194 // Have to remove the chunk from the dictionary because it is changing | |
9195 // size and might be someplace elsewhere in the dictionary. | |
9196 | |
9197 // Get the chunk at end, shrink it, and put it | |
9198 // back. | |
9199 _cmsSpace->removeChunkFromDictionary(chunk_at_end); | |
9200 size_t word_size_change = word_size_before - new_word_size; | |
9201 size_t chunk_at_end_old_size = chunk_at_end->size(); | |
9202 assert(chunk_at_end_old_size >= word_size_change, | |
9203 "Shrink is too large"); | |
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9204 chunk_at_end->set_size(chunk_at_end_old_size - |
0 | 9205 word_size_change); |
9206 _cmsSpace->freed((HeapWord*) chunk_at_end->end(), | |
9207 word_size_change); | |
9208 | |
9209 _cmsSpace->returnChunkToDictionary(chunk_at_end); | |
9210 | |
9211 MemRegion mr(_cmsSpace->bottom(), new_word_size); | |
9212 _bts->resize(new_word_size); // resize the block offset shared array | |
9213 Universe::heap()->barrier_set()->resize_covered_region(mr); | |
9214 _cmsSpace->assert_locked(); | |
9215 _cmsSpace->set_end((HeapWord*)_virtual_space.high()); | |
9216 | |
9217 NOT_PRODUCT(_cmsSpace->dictionary()->verify()); | |
9218 | |
9219 // update the space and generation capacity counters | |
9220 if (UsePerfData) { | |
9221 _space_counters->update_capacity(); | |
9222 _gen_counters->update_all(); | |
9223 } | |
9224 | |
9225 if (Verbose && PrintGCDetails) { | |
9226 size_t new_mem_size = _virtual_space.committed_size(); | |
9227 size_t old_mem_size = new_mem_size + bytes; | |
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9228 gclog_or_tty->print_cr("Shrinking %s from " SIZE_FORMAT "K by " SIZE_FORMAT "K to " SIZE_FORMAT "K", |
0 | 9229 name(), old_mem_size/K, bytes/K, new_mem_size/K); |
9230 } | |
9231 } | |
9232 | |
9233 assert(_cmsSpace->unallocated_block() <= _cmsSpace->end(), | |
9234 "Inconsistency at end of space"); | |
6885 | 9235 assert(chunk_at_end->end() == (uintptr_t*) _cmsSpace->end(), |
0 | 9236 "Shrinking is inconsistent"); |
9237 return; | |
9238 } | |
9239 } | |
9240 | |
9241 // Transfer some number of overflown objects to usual marking | |
9242 // stack. Return true if some objects were transferred. | |
9243 bool MarkRefsIntoAndScanClosure::take_from_overflow_list() { | |
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9244 size_t num = MIN2((size_t)(_mark_stack->capacity() - _mark_stack->length())/4, |
0 | 9245 (size_t)ParGCDesiredObjsFromOverflowList); |
9246 | |
9247 bool res = _collector->take_from_overflow_list(num, _mark_stack); | |
9248 assert(_collector->overflow_list_is_empty() || res, | |
9249 "If list is not empty, we should have taken something"); | |
9250 assert(!res || !_mark_stack->isEmpty(), | |
9251 "If we took something, it should now be on our stack"); | |
9252 return res; | |
9253 } | |
9254 | |
9255 size_t MarkDeadObjectsClosure::do_blk(HeapWord* addr) { | |
9256 size_t res = _sp->block_size_no_stall(addr, _collector); | |
9257 if (_sp->block_is_obj(addr)) { | |
9258 if (_live_bit_map->isMarked(addr)) { | |
9259 // It can't have been dead in a previous cycle | |
9260 guarantee(!_dead_bit_map->isMarked(addr), "No resurrection!"); | |
9261 } else { | |
9262 _dead_bit_map->mark(addr); // mark the dead object | |
9263 } | |
9264 } | |
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9265 // Could be 0, if the block size could not be computed without stalling. |
0 | 9266 return res; |
9267 } | |
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9268 |
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9269 TraceCMSMemoryManagerStats::TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause): TraceMemoryManagerStats() { |
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9270 |
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9271 switch (phase) { |
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9272 case CMSCollector::InitialMarking: |
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9273 initialize(true /* fullGC */ , |
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9274 cause /* cause of the GC */, |
1703
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9275 true /* recordGCBeginTime */, |
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9276 true /* recordPreGCUsage */, |
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9277 false /* recordPeakUsage */, |
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9278 false /* recordPostGCusage */, |
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changeset
|
9279 true /* recordAccumulatedGCTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9280 false /* recordGCEndTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9281 false /* countCollection */ ); |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9282 break; |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9283 |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9284 case CMSCollector::FinalMarking: |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9285 initialize(true /* fullGC */ , |
3356
78542e2b5e35
7036199: Adding a notification to the implementation of GarbageCollectorMXBeans
fparain
parents:
3293
diff
changeset
|
9286 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
|
9287 false /* recordGCBeginTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9288 false /* recordPreGCUsage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9289 false /* recordPeakUsage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9290 false /* recordPostGCusage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9291 true /* recordAccumulatedGCTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9292 false /* recordGCEndTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9293 false /* countCollection */ ); |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9294 break; |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9295 |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9296 case CMSCollector::Sweeping: |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9297 initialize(true /* fullGC */ , |
3356
78542e2b5e35
7036199: Adding a notification to the implementation of GarbageCollectorMXBeans
fparain
parents:
3293
diff
changeset
|
9298 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
|
9299 false /* recordGCBeginTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9300 false /* recordPreGCUsage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9301 true /* recordPeakUsage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9302 true /* recordPostGCusage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9303 false /* recordAccumulatedGCTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9304 true /* recordGCEndTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9305 true /* countCollection */ ); |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9306 break; |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9307 |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9308 default: |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9309 ShouldNotReachHere(); |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9310 } |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9311 } |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9312 |