Mercurial > hg > truffle
annotate src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp @ 2226:c5a923563727
6912621: iCMS: Error: assert(_markBitMap.isMarked(addr + 1),"Missing Printezis bit?")
Summary: Fix block_size_if_printezis_bits() so it does not expect the bits, only uses them when available. Fix block_size_no_stall() so it does not stall when the bits are missing such cases, letting the caller deal with zero size returns. Constant pool cache oops do not need to be unparsable or conc_unsafe after their klass pointer is installed. Some cosmetic clean-ups and some assertion checking for conc-usafety which, in the presence of class file redefinition, has no a-priori time boundedness, so all GCs must be able to safely deal with putatively conc-unsafe objects in a stop-world pause.
Reviewed-by: jmasa, johnc
author | ysr |
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date | Mon, 07 Feb 2011 22:19:57 -0800 |
parents | 3582bf76420e |
children | a181f3a124dd |
rev | line source |
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0 | 1 /* |
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2 * Copyright (c) 2001, 2010, 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" |
26 #include "classfile/symbolTable.hpp" | |
27 #include "classfile/systemDictionary.hpp" | |
28 #include "code/codeCache.hpp" | |
29 #include "gc_implementation/concurrentMarkSweep/cmsAdaptiveSizePolicy.hpp" | |
30 #include "gc_implementation/concurrentMarkSweep/cmsCollectorPolicy.hpp" | |
31 #include "gc_implementation/concurrentMarkSweep/cmsGCAdaptivePolicyCounters.hpp" | |
32 #include "gc_implementation/concurrentMarkSweep/cmsOopClosures.inline.hpp" | |
33 #include "gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.hpp" | |
34 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.inline.hpp" | |
35 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp" | |
36 #include "gc_implementation/concurrentMarkSweep/vmCMSOperations.hpp" | |
37 #include "gc_implementation/parNew/parNewGeneration.hpp" | |
38 #include "gc_implementation/shared/collectorCounters.hpp" | |
39 #include "gc_implementation/shared/isGCActiveMark.hpp" | |
40 #include "gc_interface/collectedHeap.inline.hpp" | |
41 #include "memory/cardTableRS.hpp" | |
42 #include "memory/collectorPolicy.hpp" | |
43 #include "memory/gcLocker.inline.hpp" | |
44 #include "memory/genCollectedHeap.hpp" | |
45 #include "memory/genMarkSweep.hpp" | |
46 #include "memory/genOopClosures.inline.hpp" | |
47 #include "memory/iterator.hpp" | |
48 #include "memory/referencePolicy.hpp" | |
49 #include "memory/resourceArea.hpp" | |
50 #include "oops/oop.inline.hpp" | |
51 #include "prims/jvmtiExport.hpp" | |
52 #include "runtime/globals_extension.hpp" | |
53 #include "runtime/handles.inline.hpp" | |
54 #include "runtime/java.hpp" | |
55 #include "runtime/vmThread.hpp" | |
56 #include "services/memoryService.hpp" | |
57 #include "services/runtimeService.hpp" | |
0 | 58 |
59 // statics | |
60 CMSCollector* ConcurrentMarkSweepGeneration::_collector = NULL; | |
61 bool CMSCollector::_full_gc_requested = false; | |
62 | |
63 ////////////////////////////////////////////////////////////////// | |
64 // In support of CMS/VM thread synchronization | |
65 ////////////////////////////////////////////////////////////////// | |
66 // We split use of the CGC_lock into 2 "levels". | |
67 // The low-level locking is of the usual CGC_lock monitor. We introduce | |
68 // a higher level "token" (hereafter "CMS token") built on top of the | |
69 // low level monitor (hereafter "CGC lock"). | |
70 // The token-passing protocol gives priority to the VM thread. The | |
71 // CMS-lock doesn't provide any fairness guarantees, but clients | |
72 // should ensure that it is only held for very short, bounded | |
73 // durations. | |
74 // | |
75 // When either of the CMS thread or the VM thread is involved in | |
76 // collection operations during which it does not want the other | |
77 // thread to interfere, it obtains the CMS token. | |
78 // | |
79 // If either thread tries to get the token while the other has | |
80 // it, that thread waits. However, if the VM thread and CMS thread | |
81 // both want the token, then the VM thread gets priority while the | |
82 // CMS thread waits. This ensures, for instance, that the "concurrent" | |
83 // phases of the CMS thread's work do not block out the VM thread | |
84 // for long periods of time as the CMS thread continues to hog | |
85 // the token. (See bug 4616232). | |
86 // | |
87 // The baton-passing functions are, however, controlled by the | |
88 // flags _foregroundGCShouldWait and _foregroundGCIsActive, | |
89 // and here the low-level CMS lock, not the high level token, | |
90 // ensures mutual exclusion. | |
91 // | |
92 // Two important conditions that we have to satisfy: | |
93 // 1. if a thread does a low-level wait on the CMS lock, then it | |
94 // relinquishes the CMS token if it were holding that token | |
95 // when it acquired the low-level CMS lock. | |
96 // 2. any low-level notifications on the low-level lock | |
97 // should only be sent when a thread has relinquished the token. | |
98 // | |
99 // In the absence of either property, we'd have potential deadlock. | |
100 // | |
101 // We protect each of the CMS (concurrent and sequential) phases | |
102 // with the CMS _token_, not the CMS _lock_. | |
103 // | |
104 // The only code protected by CMS lock is the token acquisition code | |
105 // itself, see ConcurrentMarkSweepThread::[de]synchronize(), and the | |
106 // baton-passing code. | |
107 // | |
108 // Unfortunately, i couldn't come up with a good abstraction to factor and | |
109 // hide the naked CGC_lock manipulation in the baton-passing code | |
110 // further below. That's something we should try to do. Also, the proof | |
111 // of correctness of this 2-level locking scheme is far from obvious, | |
112 // and potentially quite slippery. We have an uneasy supsicion, for instance, | |
113 // that there may be a theoretical possibility of delay/starvation in the | |
114 // low-level lock/wait/notify scheme used for the baton-passing because of | |
115 // potential intereference with the priority scheme embodied in the | |
116 // CMS-token-passing protocol. See related comments at a CGC_lock->wait() | |
117 // invocation further below and marked with "XXX 20011219YSR". | |
118 // Indeed, as we note elsewhere, this may become yet more slippery | |
119 // in the presence of multiple CMS and/or multiple VM threads. XXX | |
120 | |
121 class CMSTokenSync: public StackObj { | |
122 private: | |
123 bool _is_cms_thread; | |
124 public: | |
125 CMSTokenSync(bool is_cms_thread): | |
126 _is_cms_thread(is_cms_thread) { | |
127 assert(is_cms_thread == Thread::current()->is_ConcurrentGC_thread(), | |
128 "Incorrect argument to constructor"); | |
129 ConcurrentMarkSweepThread::synchronize(_is_cms_thread); | |
130 } | |
131 | |
132 ~CMSTokenSync() { | |
133 assert(_is_cms_thread ? | |
134 ConcurrentMarkSweepThread::cms_thread_has_cms_token() : | |
135 ConcurrentMarkSweepThread::vm_thread_has_cms_token(), | |
136 "Incorrect state"); | |
137 ConcurrentMarkSweepThread::desynchronize(_is_cms_thread); | |
138 } | |
139 }; | |
140 | |
141 // Convenience class that does a CMSTokenSync, and then acquires | |
142 // upto three locks. | |
143 class CMSTokenSyncWithLocks: public CMSTokenSync { | |
144 private: | |
145 // Note: locks are acquired in textual declaration order | |
146 // and released in the opposite order | |
147 MutexLockerEx _locker1, _locker2, _locker3; | |
148 public: | |
149 CMSTokenSyncWithLocks(bool is_cms_thread, Mutex* mutex1, | |
150 Mutex* mutex2 = NULL, Mutex* mutex3 = NULL): | |
151 CMSTokenSync(is_cms_thread), | |
152 _locker1(mutex1, Mutex::_no_safepoint_check_flag), | |
153 _locker2(mutex2, Mutex::_no_safepoint_check_flag), | |
154 _locker3(mutex3, Mutex::_no_safepoint_check_flag) | |
155 { } | |
156 }; | |
157 | |
158 | |
159 // Wrapper class to temporarily disable icms during a foreground cms collection. | |
160 class ICMSDisabler: public StackObj { | |
161 public: | |
162 // The ctor disables icms and wakes up the thread so it notices the change; | |
163 // the dtor re-enables icms. Note that the CMSCollector methods will check | |
164 // CMSIncrementalMode. | |
165 ICMSDisabler() { CMSCollector::disable_icms(); CMSCollector::start_icms(); } | |
166 ~ICMSDisabler() { CMSCollector::enable_icms(); } | |
167 }; | |
168 | |
169 ////////////////////////////////////////////////////////////////// | |
170 // Concurrent Mark-Sweep Generation ///////////////////////////// | |
171 ////////////////////////////////////////////////////////////////// | |
172 | |
173 NOT_PRODUCT(CompactibleFreeListSpace* debug_cms_space;) | |
174 | |
175 // This struct contains per-thread things necessary to support parallel | |
176 // young-gen collection. | |
177 class CMSParGCThreadState: public CHeapObj { | |
178 public: | |
179 CFLS_LAB lab; | |
180 PromotionInfo promo; | |
181 | |
182 // Constructor. | |
183 CMSParGCThreadState(CompactibleFreeListSpace* cfls) : lab(cfls) { | |
184 promo.setSpace(cfls); | |
185 } | |
186 }; | |
187 | |
188 ConcurrentMarkSweepGeneration::ConcurrentMarkSweepGeneration( | |
189 ReservedSpace rs, size_t initial_byte_size, int level, | |
190 CardTableRS* ct, bool use_adaptive_freelists, | |
191 FreeBlockDictionary::DictionaryChoice dictionaryChoice) : | |
192 CardGeneration(rs, initial_byte_size, level, ct), | |
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193 _dilatation_factor(((double)MinChunkSize)/((double)(CollectedHeap::min_fill_size()))), |
0 | 194 _debug_collection_type(Concurrent_collection_type) |
195 { | |
196 HeapWord* bottom = (HeapWord*) _virtual_space.low(); | |
197 HeapWord* end = (HeapWord*) _virtual_space.high(); | |
198 | |
199 _direct_allocated_words = 0; | |
200 NOT_PRODUCT( | |
201 _numObjectsPromoted = 0; | |
202 _numWordsPromoted = 0; | |
203 _numObjectsAllocated = 0; | |
204 _numWordsAllocated = 0; | |
205 ) | |
206 | |
207 _cmsSpace = new CompactibleFreeListSpace(_bts, MemRegion(bottom, end), | |
208 use_adaptive_freelists, | |
209 dictionaryChoice); | |
210 NOT_PRODUCT(debug_cms_space = _cmsSpace;) | |
211 if (_cmsSpace == NULL) { | |
212 vm_exit_during_initialization( | |
213 "CompactibleFreeListSpace allocation failure"); | |
214 } | |
215 _cmsSpace->_gen = this; | |
216 | |
217 _gc_stats = new CMSGCStats(); | |
218 | |
219 // Verify the assumption that FreeChunk::_prev and OopDesc::_klass | |
220 // offsets match. The ability to tell free chunks from objects | |
221 // depends on this property. | |
222 debug_only( | |
223 FreeChunk* junk = NULL; | |
187 | 224 assert(UseCompressedOops || |
225 junk->prev_addr() == (void*)(oop(junk)->klass_addr()), | |
0 | 226 "Offset of FreeChunk::_prev within FreeChunk must match" |
227 " that of OopDesc::_klass within OopDesc"); | |
228 ) | |
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229 if (CollectedHeap::use_parallel_gc_threads()) { |
0 | 230 typedef CMSParGCThreadState* CMSParGCThreadStatePtr; |
231 _par_gc_thread_states = | |
232 NEW_C_HEAP_ARRAY(CMSParGCThreadStatePtr, ParallelGCThreads); | |
233 if (_par_gc_thread_states == NULL) { | |
234 vm_exit_during_initialization("Could not allocate par gc structs"); | |
235 } | |
236 for (uint i = 0; i < ParallelGCThreads; i++) { | |
237 _par_gc_thread_states[i] = new CMSParGCThreadState(cmsSpace()); | |
238 if (_par_gc_thread_states[i] == NULL) { | |
239 vm_exit_during_initialization("Could not allocate par gc structs"); | |
240 } | |
241 } | |
242 } else { | |
243 _par_gc_thread_states = NULL; | |
244 } | |
245 _incremental_collection_failed = false; | |
246 // The "dilatation_factor" is the expansion that can occur on | |
247 // account of the fact that the minimum object size in the CMS | |
248 // generation may be larger than that in, say, a contiguous young | |
249 // generation. | |
250 // Ideally, in the calculation below, we'd compute the dilatation | |
251 // factor as: MinChunkSize/(promoting_gen's min object size) | |
252 // Since we do not have such a general query interface for the | |
253 // promoting generation, we'll instead just use the mimimum | |
254 // object size (which today is a header's worth of space); | |
255 // note that all arithmetic is in units of HeapWords. | |
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256 assert(MinChunkSize >= CollectedHeap::min_fill_size(), "just checking"); |
0 | 257 assert(_dilatation_factor >= 1.0, "from previous assert"); |
258 } | |
259 | |
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260 |
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261 // The field "_initiating_occupancy" represents the occupancy percentage |
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262 // at which we trigger a new collection cycle. Unless explicitly specified |
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263 // via CMSInitiating[Perm]OccupancyFraction (argument "io" below), it |
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264 // is calculated by: |
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265 // |
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266 // Let "f" be MinHeapFreeRatio in |
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267 // |
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268 // _intiating_occupancy = 100-f + |
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269 // f * (CMSTrigger[Perm]Ratio/100) |
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270 // where CMSTrigger[Perm]Ratio is the argument "tr" below. |
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271 // |
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272 // That is, if we assume the heap is at its desired maximum occupancy at the |
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273 // end of a collection, we let CMSTrigger[Perm]Ratio of the (purported) free |
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274 // space be allocated before initiating a new collection cycle. |
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275 // |
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276 void ConcurrentMarkSweepGeneration::init_initiating_occupancy(intx io, intx tr) { |
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277 assert(io <= 100 && tr >= 0 && tr <= 100, "Check the arguments"); |
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278 if (io >= 0) { |
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279 _initiating_occupancy = (double)io / 100.0; |
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280 } else { |
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281 _initiating_occupancy = ((100 - MinHeapFreeRatio) + |
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282 (double)(tr * MinHeapFreeRatio) / 100.0) |
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283 / 100.0; |
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284 } |
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285 } |
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286 |
0 | 287 void ConcurrentMarkSweepGeneration::ref_processor_init() { |
288 assert(collector() != NULL, "no collector"); | |
289 collector()->ref_processor_init(); | |
290 } | |
291 | |
292 void CMSCollector::ref_processor_init() { | |
293 if (_ref_processor == NULL) { | |
294 // Allocate and initialize a reference processor | |
295 _ref_processor = ReferenceProcessor::create_ref_processor( | |
296 _span, // span | |
297 _cmsGen->refs_discovery_is_atomic(), // atomic_discovery | |
298 _cmsGen->refs_discovery_is_mt(), // mt_discovery | |
299 &_is_alive_closure, | |
300 ParallelGCThreads, | |
301 ParallelRefProcEnabled); | |
302 // Initialize the _ref_processor field of CMSGen | |
303 _cmsGen->set_ref_processor(_ref_processor); | |
304 | |
305 // Allocate a dummy ref processor for perm gen. | |
306 ReferenceProcessor* rp2 = new ReferenceProcessor(); | |
307 if (rp2 == NULL) { | |
308 vm_exit_during_initialization("Could not allocate ReferenceProcessor object"); | |
309 } | |
310 _permGen->set_ref_processor(rp2); | |
311 } | |
312 } | |
313 | |
314 CMSAdaptiveSizePolicy* CMSCollector::size_policy() { | |
315 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
316 assert(gch->kind() == CollectedHeap::GenCollectedHeap, | |
317 "Wrong type of heap"); | |
318 CMSAdaptiveSizePolicy* sp = (CMSAdaptiveSizePolicy*) | |
319 gch->gen_policy()->size_policy(); | |
320 assert(sp->is_gc_cms_adaptive_size_policy(), | |
321 "Wrong type of size policy"); | |
322 return sp; | |
323 } | |
324 | |
325 CMSGCAdaptivePolicyCounters* CMSCollector::gc_adaptive_policy_counters() { | |
326 CMSGCAdaptivePolicyCounters* results = | |
327 (CMSGCAdaptivePolicyCounters*) collector_policy()->counters(); | |
328 assert( | |
329 results->kind() == GCPolicyCounters::CMSGCAdaptivePolicyCountersKind, | |
330 "Wrong gc policy counter kind"); | |
331 return results; | |
332 } | |
333 | |
334 | |
335 void ConcurrentMarkSweepGeneration::initialize_performance_counters() { | |
336 | |
337 const char* gen_name = "old"; | |
338 | |
339 // Generation Counters - generation 1, 1 subspace | |
340 _gen_counters = new GenerationCounters(gen_name, 1, 1, &_virtual_space); | |
341 | |
342 _space_counters = new GSpaceCounters(gen_name, 0, | |
343 _virtual_space.reserved_size(), | |
344 this, _gen_counters); | |
345 } | |
346 | |
347 CMSStats::CMSStats(ConcurrentMarkSweepGeneration* cms_gen, unsigned int alpha): | |
348 _cms_gen(cms_gen) | |
349 { | |
350 assert(alpha <= 100, "bad value"); | |
351 _saved_alpha = alpha; | |
352 | |
353 // Initialize the alphas to the bootstrap value of 100. | |
354 _gc0_alpha = _cms_alpha = 100; | |
355 | |
356 _cms_begin_time.update(); | |
357 _cms_end_time.update(); | |
358 | |
359 _gc0_duration = 0.0; | |
360 _gc0_period = 0.0; | |
361 _gc0_promoted = 0; | |
362 | |
363 _cms_duration = 0.0; | |
364 _cms_period = 0.0; | |
365 _cms_allocated = 0; | |
366 | |
367 _cms_used_at_gc0_begin = 0; | |
368 _cms_used_at_gc0_end = 0; | |
369 _allow_duty_cycle_reduction = false; | |
370 _valid_bits = 0; | |
371 _icms_duty_cycle = CMSIncrementalDutyCycle; | |
372 } | |
373 | |
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374 double CMSStats::cms_free_adjustment_factor(size_t free) const { |
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375 // TBD: CR 6909490 |
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376 return 1.0; |
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377 } |
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378 |
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379 void CMSStats::adjust_cms_free_adjustment_factor(bool fail, size_t free) { |
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380 } |
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381 |
0 | 382 // If promotion failure handling is on use |
383 // the padded average size of the promotion for each | |
384 // young generation collection. | |
385 double CMSStats::time_until_cms_gen_full() const { | |
386 size_t cms_free = _cms_gen->cmsSpace()->free(); | |
387 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
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388 size_t expected_promotion = MIN2(gch->get_gen(0)->capacity(), |
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389 (size_t) _cms_gen->gc_stats()->avg_promoted()->padded_average()); |
0 | 390 if (cms_free > expected_promotion) { |
391 // Start a cms collection if there isn't enough space to promote | |
392 // for the next minor collection. Use the padded average as | |
393 // a safety factor. | |
394 cms_free -= expected_promotion; | |
395 | |
396 // Adjust by the safety factor. | |
397 double cms_free_dbl = (double)cms_free; | |
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398 double cms_adjustment = (100.0 - CMSIncrementalSafetyFactor)/100.0; |
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399 // Apply a further correction factor which tries to adjust |
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400 // for recent occurance of concurrent mode failures. |
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401 cms_adjustment = cms_adjustment * cms_free_adjustment_factor(cms_free); |
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402 cms_free_dbl = cms_free_dbl * cms_adjustment; |
0 | 403 |
404 if (PrintGCDetails && Verbose) { | |
405 gclog_or_tty->print_cr("CMSStats::time_until_cms_gen_full: cms_free " | |
406 SIZE_FORMAT " expected_promotion " SIZE_FORMAT, | |
407 cms_free, expected_promotion); | |
408 gclog_or_tty->print_cr(" cms_free_dbl %f cms_consumption_rate %f", | |
409 cms_free_dbl, cms_consumption_rate() + 1.0); | |
410 } | |
411 // Add 1 in case the consumption rate goes to zero. | |
412 return cms_free_dbl / (cms_consumption_rate() + 1.0); | |
413 } | |
414 return 0.0; | |
415 } | |
416 | |
417 // Compare the duration of the cms collection to the | |
418 // time remaining before the cms generation is empty. | |
419 // Note that the time from the start of the cms collection | |
420 // to the start of the cms sweep (less than the total | |
421 // duration of the cms collection) can be used. This | |
422 // has been tried and some applications experienced | |
423 // promotion failures early in execution. This was | |
424 // possibly because the averages were not accurate | |
425 // enough at the beginning. | |
426 double CMSStats::time_until_cms_start() const { | |
427 // We add "gc0_period" to the "work" calculation | |
428 // below because this query is done (mostly) at the | |
429 // end of a scavenge, so we need to conservatively | |
430 // account for that much possible delay | |
431 // in the query so as to avoid concurrent mode failures | |
432 // due to starting the collection just a wee bit too | |
433 // late. | |
434 double work = cms_duration() + gc0_period(); | |
435 double deadline = time_until_cms_gen_full(); | |
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436 // If a concurrent mode failure occurred recently, we want to be |
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437 // more conservative and halve our expected time_until_cms_gen_full() |
0 | 438 if (work > deadline) { |
439 if (Verbose && PrintGCDetails) { | |
440 gclog_or_tty->print( | |
441 " CMSCollector: collect because of anticipated promotion " | |
442 "before full %3.7f + %3.7f > %3.7f ", cms_duration(), | |
443 gc0_period(), time_until_cms_gen_full()); | |
444 } | |
445 return 0.0; | |
446 } | |
447 return work - deadline; | |
448 } | |
449 | |
450 // Return a duty cycle based on old_duty_cycle and new_duty_cycle, limiting the | |
451 // amount of change to prevent wild oscillation. | |
452 unsigned int CMSStats::icms_damped_duty_cycle(unsigned int old_duty_cycle, | |
453 unsigned int new_duty_cycle) { | |
454 assert(old_duty_cycle <= 100, "bad input value"); | |
455 assert(new_duty_cycle <= 100, "bad input value"); | |
456 | |
457 // Note: use subtraction with caution since it may underflow (values are | |
458 // unsigned). Addition is safe since we're in the range 0-100. | |
459 unsigned int damped_duty_cycle = new_duty_cycle; | |
460 if (new_duty_cycle < old_duty_cycle) { | |
461 const unsigned int largest_delta = MAX2(old_duty_cycle / 4, 5U); | |
462 if (new_duty_cycle + largest_delta < old_duty_cycle) { | |
463 damped_duty_cycle = old_duty_cycle - largest_delta; | |
464 } | |
465 } else if (new_duty_cycle > old_duty_cycle) { | |
466 const unsigned int largest_delta = MAX2(old_duty_cycle / 4, 15U); | |
467 if (new_duty_cycle > old_duty_cycle + largest_delta) { | |
468 damped_duty_cycle = MIN2(old_duty_cycle + largest_delta, 100U); | |
469 } | |
470 } | |
471 assert(damped_duty_cycle <= 100, "invalid duty cycle computed"); | |
472 | |
473 if (CMSTraceIncrementalPacing) { | |
474 gclog_or_tty->print(" [icms_damped_duty_cycle(%d,%d) = %d] ", | |
475 old_duty_cycle, new_duty_cycle, damped_duty_cycle); | |
476 } | |
477 return damped_duty_cycle; | |
478 } | |
479 | |
480 unsigned int CMSStats::icms_update_duty_cycle_impl() { | |
481 assert(CMSIncrementalPacing && valid(), | |
482 "should be handled in icms_update_duty_cycle()"); | |
483 | |
484 double cms_time_so_far = cms_timer().seconds(); | |
485 double scaled_duration = cms_duration_per_mb() * _cms_used_at_gc0_end / M; | |
486 double scaled_duration_remaining = fabsd(scaled_duration - cms_time_so_far); | |
487 | |
488 // Avoid division by 0. | |
489 double time_until_full = MAX2(time_until_cms_gen_full(), 0.01); | |
490 double duty_cycle_dbl = 100.0 * scaled_duration_remaining / time_until_full; | |
491 | |
492 unsigned int new_duty_cycle = MIN2((unsigned int)duty_cycle_dbl, 100U); | |
493 if (new_duty_cycle > _icms_duty_cycle) { | |
494 // Avoid very small duty cycles (1 or 2); 0 is allowed. | |
495 if (new_duty_cycle > 2) { | |
496 _icms_duty_cycle = icms_damped_duty_cycle(_icms_duty_cycle, | |
497 new_duty_cycle); | |
498 } | |
499 } else if (_allow_duty_cycle_reduction) { | |
500 // The duty cycle is reduced only once per cms cycle (see record_cms_end()). | |
501 new_duty_cycle = icms_damped_duty_cycle(_icms_duty_cycle, new_duty_cycle); | |
502 // Respect the minimum duty cycle. | |
503 unsigned int min_duty_cycle = (unsigned int)CMSIncrementalDutyCycleMin; | |
504 _icms_duty_cycle = MAX2(new_duty_cycle, min_duty_cycle); | |
505 } | |
506 | |
507 if (PrintGCDetails || CMSTraceIncrementalPacing) { | |
508 gclog_or_tty->print(" icms_dc=%d ", _icms_duty_cycle); | |
509 } | |
510 | |
511 _allow_duty_cycle_reduction = false; | |
512 return _icms_duty_cycle; | |
513 } | |
514 | |
515 #ifndef PRODUCT | |
516 void CMSStats::print_on(outputStream *st) const { | |
517 st->print(" gc0_alpha=%d,cms_alpha=%d", _gc0_alpha, _cms_alpha); | |
518 st->print(",gc0_dur=%g,gc0_per=%g,gc0_promo=" SIZE_FORMAT, | |
519 gc0_duration(), gc0_period(), gc0_promoted()); | |
520 st->print(",cms_dur=%g,cms_dur_per_mb=%g,cms_per=%g,cms_alloc=" SIZE_FORMAT, | |
521 cms_duration(), cms_duration_per_mb(), | |
522 cms_period(), cms_allocated()); | |
523 st->print(",cms_since_beg=%g,cms_since_end=%g", | |
524 cms_time_since_begin(), cms_time_since_end()); | |
525 st->print(",cms_used_beg=" SIZE_FORMAT ",cms_used_end=" SIZE_FORMAT, | |
526 _cms_used_at_gc0_begin, _cms_used_at_gc0_end); | |
527 if (CMSIncrementalMode) { | |
528 st->print(",dc=%d", icms_duty_cycle()); | |
529 } | |
530 | |
531 if (valid()) { | |
532 st->print(",promo_rate=%g,cms_alloc_rate=%g", | |
533 promotion_rate(), cms_allocation_rate()); | |
534 st->print(",cms_consumption_rate=%g,time_until_full=%g", | |
535 cms_consumption_rate(), time_until_cms_gen_full()); | |
536 } | |
537 st->print(" "); | |
538 } | |
539 #endif // #ifndef PRODUCT | |
540 | |
541 CMSCollector::CollectorState CMSCollector::_collectorState = | |
542 CMSCollector::Idling; | |
543 bool CMSCollector::_foregroundGCIsActive = false; | |
544 bool CMSCollector::_foregroundGCShouldWait = false; | |
545 | |
546 CMSCollector::CMSCollector(ConcurrentMarkSweepGeneration* cmsGen, | |
547 ConcurrentMarkSweepGeneration* permGen, | |
548 CardTableRS* ct, | |
549 ConcurrentMarkSweepPolicy* cp): | |
550 _cmsGen(cmsGen), | |
551 _permGen(permGen), | |
552 _ct(ct), | |
553 _ref_processor(NULL), // will be set later | |
554 _conc_workers(NULL), // may be set later | |
555 _abort_preclean(false), | |
556 _start_sampling(false), | |
557 _between_prologue_and_epilogue(false), | |
558 _markBitMap(0, Mutex::leaf + 1, "CMS_markBitMap_lock"), | |
559 _perm_gen_verify_bit_map(0, -1 /* no mutex */, "No_lock"), | |
560 _modUnionTable((CardTableModRefBS::card_shift - LogHeapWordSize), | |
561 -1 /* lock-free */, "No_lock" /* dummy */), | |
562 _modUnionClosure(&_modUnionTable), | |
563 _modUnionClosurePar(&_modUnionTable), | |
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564 // Adjust my span to cover old (cms) gen and perm gen |
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565 _span(cmsGen->reserved()._union(permGen->reserved())), |
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566 // Construct the is_alive_closure with _span & markBitMap |
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567 _is_alive_closure(_span, &_markBitMap), |
0 | 568 _restart_addr(NULL), |
569 _overflow_list(NULL), | |
570 _stats(cmsGen), | |
571 _eden_chunk_array(NULL), // may be set in ctor body | |
572 _eden_chunk_capacity(0), // -- ditto -- | |
573 _eden_chunk_index(0), // -- ditto -- | |
574 _survivor_plab_array(NULL), // -- ditto -- | |
575 _survivor_chunk_array(NULL), // -- ditto -- | |
576 _survivor_chunk_capacity(0), // -- ditto -- | |
577 _survivor_chunk_index(0), // -- ditto -- | |
578 _ser_pmc_preclean_ovflw(0), | |
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579 _ser_kac_preclean_ovflw(0), |
0 | 580 _ser_pmc_remark_ovflw(0), |
581 _par_pmc_remark_ovflw(0), | |
582 _ser_kac_ovflw(0), | |
583 _par_kac_ovflw(0), | |
584 #ifndef PRODUCT | |
585 _num_par_pushes(0), | |
586 #endif | |
587 _collection_count_start(0), | |
588 _verifying(false), | |
589 _icms_start_limit(NULL), | |
590 _icms_stop_limit(NULL), | |
591 _verification_mark_bm(0, Mutex::leaf + 1, "CMS_verification_mark_bm_lock"), | |
592 _completed_initialization(false), | |
593 _collector_policy(cp), | |
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594 _should_unload_classes(false), |
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595 _concurrent_cycles_since_last_unload(0), |
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596 _roots_scanning_options(0), |
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597 _inter_sweep_estimate(CMS_SweepWeight, CMS_SweepPadding), |
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598 _intra_sweep_estimate(CMS_SweepWeight, CMS_SweepPadding) |
0 | 599 { |
600 if (ExplicitGCInvokesConcurrentAndUnloadsClasses) { | |
601 ExplicitGCInvokesConcurrent = true; | |
602 } | |
603 // Now expand the span and allocate the collection support structures | |
604 // (MUT, marking bit map etc.) to cover both generations subject to | |
605 // collection. | |
606 | |
607 // First check that _permGen is adjacent to _cmsGen and above it. | |
608 assert( _cmsGen->reserved().word_size() > 0 | |
609 && _permGen->reserved().word_size() > 0, | |
610 "generations should not be of zero size"); | |
611 assert(_cmsGen->reserved().intersection(_permGen->reserved()).is_empty(), | |
612 "_cmsGen and _permGen should not overlap"); | |
613 assert(_cmsGen->reserved().end() == _permGen->reserved().start(), | |
614 "_cmsGen->end() different from _permGen->start()"); | |
615 | |
616 // For use by dirty card to oop closures. | |
617 _cmsGen->cmsSpace()->set_collector(this); | |
618 _permGen->cmsSpace()->set_collector(this); | |
619 | |
620 // Allocate MUT and marking bit map | |
621 { | |
622 MutexLockerEx x(_markBitMap.lock(), Mutex::_no_safepoint_check_flag); | |
623 if (!_markBitMap.allocate(_span)) { | |
624 warning("Failed to allocate CMS Bit Map"); | |
625 return; | |
626 } | |
627 assert(_markBitMap.covers(_span), "_markBitMap inconsistency?"); | |
628 } | |
629 { | |
630 _modUnionTable.allocate(_span); | |
631 assert(_modUnionTable.covers(_span), "_modUnionTable inconsistency?"); | |
632 } | |
633 | |
1284 | 634 if (!_markStack.allocate(MarkStackSize)) { |
0 | 635 warning("Failed to allocate CMS Marking Stack"); |
636 return; | |
637 } | |
638 if (!_revisitStack.allocate(CMSRevisitStackSize)) { | |
639 warning("Failed to allocate CMS Revisit Stack"); | |
640 return; | |
641 } | |
642 | |
643 // Support for multi-threaded concurrent phases | |
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644 if (CollectedHeap::use_parallel_gc_threads() && CMSConcurrentMTEnabled) { |
1284 | 645 if (FLAG_IS_DEFAULT(ConcGCThreads)) { |
0 | 646 // just for now |
1284 | 647 FLAG_SET_DEFAULT(ConcGCThreads, (ParallelGCThreads + 3)/4); |
648 } | |
649 if (ConcGCThreads > 1) { | |
0 | 650 _conc_workers = new YieldingFlexibleWorkGang("Parallel CMS Threads", |
1284 | 651 ConcGCThreads, true); |
0 | 652 if (_conc_workers == NULL) { |
653 warning("GC/CMS: _conc_workers allocation failure: " | |
654 "forcing -CMSConcurrentMTEnabled"); | |
655 CMSConcurrentMTEnabled = false; | |
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656 } else { |
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657 _conc_workers->initialize_workers(); |
0 | 658 } |
659 } else { | |
660 CMSConcurrentMTEnabled = false; | |
661 } | |
662 } | |
663 if (!CMSConcurrentMTEnabled) { | |
1284 | 664 ConcGCThreads = 0; |
0 | 665 } else { |
666 // Turn off CMSCleanOnEnter optimization temporarily for | |
667 // the MT case where it's not fixed yet; see 6178663. | |
668 CMSCleanOnEnter = false; | |
669 } | |
1284 | 670 assert((_conc_workers != NULL) == (ConcGCThreads > 1), |
0 | 671 "Inconsistency"); |
672 | |
673 // Parallel task queues; these are shared for the | |
674 // concurrent and stop-world phases of CMS, but | |
675 // are not shared with parallel scavenge (ParNew). | |
676 { | |
677 uint i; | |
1284 | 678 uint num_queues = (uint) MAX2(ParallelGCThreads, ConcGCThreads); |
0 | 679 |
680 if ((CMSParallelRemarkEnabled || CMSConcurrentMTEnabled | |
681 || ParallelRefProcEnabled) | |
682 && num_queues > 0) { | |
683 _task_queues = new OopTaskQueueSet(num_queues); | |
684 if (_task_queues == NULL) { | |
685 warning("task_queues allocation failure."); | |
686 return; | |
687 } | |
688 _hash_seed = NEW_C_HEAP_ARRAY(int, num_queues); | |
689 if (_hash_seed == NULL) { | |
690 warning("_hash_seed array allocation failure"); | |
691 return; | |
692 } | |
693 | |
1665 | 694 typedef Padded<OopTaskQueue> PaddedOopTaskQueue; |
0 | 695 for (i = 0; i < num_queues; i++) { |
1665 | 696 PaddedOopTaskQueue *q = new PaddedOopTaskQueue(); |
697 if (q == NULL) { | |
0 | 698 warning("work_queue allocation failure."); |
699 return; | |
700 } | |
1665 | 701 _task_queues->register_queue(i, q); |
0 | 702 } |
703 for (i = 0; i < num_queues; i++) { | |
704 _task_queues->queue(i)->initialize(); | |
705 _hash_seed[i] = 17; // copied from ParNew | |
706 } | |
707 } | |
708 } | |
709 | |
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710 _cmsGen ->init_initiating_occupancy(CMSInitiatingOccupancyFraction, CMSTriggerRatio); |
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711 _permGen->init_initiating_occupancy(CMSInitiatingPermOccupancyFraction, CMSTriggerPermRatio); |
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712 |
0 | 713 // Clip CMSBootstrapOccupancy between 0 and 100. |
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714 _bootstrap_occupancy = ((double)MIN2((uintx)100, MAX2((uintx)0, CMSBootstrapOccupancy))) |
0 | 715 /(double)100; |
716 | |
717 _full_gcs_since_conc_gc = 0; | |
718 | |
719 // Now tell CMS generations the identity of their collector | |
720 ConcurrentMarkSweepGeneration::set_collector(this); | |
721 | |
722 // Create & start a CMS thread for this CMS collector | |
723 _cmsThread = ConcurrentMarkSweepThread::start(this); | |
724 assert(cmsThread() != NULL, "CMS Thread should have been created"); | |
725 assert(cmsThread()->collector() == this, | |
726 "CMS Thread should refer to this gen"); | |
727 assert(CGC_lock != NULL, "Where's the CGC_lock?"); | |
728 | |
729 // Support for parallelizing young gen rescan | |
730 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
731 _young_gen = gch->prev_gen(_cmsGen); | |
732 if (gch->supports_inline_contig_alloc()) { | |
733 _top_addr = gch->top_addr(); | |
734 _end_addr = gch->end_addr(); | |
735 assert(_young_gen != NULL, "no _young_gen"); | |
736 _eden_chunk_index = 0; | |
737 _eden_chunk_capacity = (_young_gen->max_capacity()+CMSSamplingGrain)/CMSSamplingGrain; | |
738 _eden_chunk_array = NEW_C_HEAP_ARRAY(HeapWord*, _eden_chunk_capacity); | |
739 if (_eden_chunk_array == NULL) { | |
740 _eden_chunk_capacity = 0; | |
741 warning("GC/CMS: _eden_chunk_array allocation failure"); | |
742 } | |
743 } | |
744 assert(_eden_chunk_array != NULL || _eden_chunk_capacity == 0, "Error"); | |
745 | |
746 // Support for parallelizing survivor space rescan | |
747 if (CMSParallelRemarkEnabled && CMSParallelSurvivorRemarkEnabled) { | |
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748 const size_t max_plab_samples = |
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749 ((DefNewGeneration*)_young_gen)->max_survivor_size()/MinTLABSize; |
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750 |
0 | 751 _survivor_plab_array = NEW_C_HEAP_ARRAY(ChunkArray, ParallelGCThreads); |
752 _survivor_chunk_array = NEW_C_HEAP_ARRAY(HeapWord*, 2*max_plab_samples); | |
753 _cursor = NEW_C_HEAP_ARRAY(size_t, ParallelGCThreads); | |
754 if (_survivor_plab_array == NULL || _survivor_chunk_array == NULL | |
755 || _cursor == NULL) { | |
756 warning("Failed to allocate survivor plab/chunk array"); | |
757 if (_survivor_plab_array != NULL) { | |
758 FREE_C_HEAP_ARRAY(ChunkArray, _survivor_plab_array); | |
759 _survivor_plab_array = NULL; | |
760 } | |
761 if (_survivor_chunk_array != NULL) { | |
762 FREE_C_HEAP_ARRAY(HeapWord*, _survivor_chunk_array); | |
763 _survivor_chunk_array = NULL; | |
764 } | |
765 if (_cursor != NULL) { | |
766 FREE_C_HEAP_ARRAY(size_t, _cursor); | |
767 _cursor = NULL; | |
768 } | |
769 } else { | |
770 _survivor_chunk_capacity = 2*max_plab_samples; | |
771 for (uint i = 0; i < ParallelGCThreads; i++) { | |
772 HeapWord** vec = NEW_C_HEAP_ARRAY(HeapWord*, max_plab_samples); | |
773 if (vec == NULL) { | |
774 warning("Failed to allocate survivor plab array"); | |
775 for (int j = i; j > 0; j--) { | |
776 FREE_C_HEAP_ARRAY(HeapWord*, _survivor_plab_array[j-1].array()); | |
777 } | |
778 FREE_C_HEAP_ARRAY(ChunkArray, _survivor_plab_array); | |
779 FREE_C_HEAP_ARRAY(HeapWord*, _survivor_chunk_array); | |
780 _survivor_plab_array = NULL; | |
781 _survivor_chunk_array = NULL; | |
782 _survivor_chunk_capacity = 0; | |
783 break; | |
784 } else { | |
785 ChunkArray* cur = | |
786 ::new (&_survivor_plab_array[i]) ChunkArray(vec, | |
787 max_plab_samples); | |
788 assert(cur->end() == 0, "Should be 0"); | |
789 assert(cur->array() == vec, "Should be vec"); | |
790 assert(cur->capacity() == max_plab_samples, "Error"); | |
791 } | |
792 } | |
793 } | |
794 } | |
795 assert( ( _survivor_plab_array != NULL | |
796 && _survivor_chunk_array != NULL) | |
797 || ( _survivor_chunk_capacity == 0 | |
798 && _survivor_chunk_index == 0), | |
799 "Error"); | |
800 | |
801 // Choose what strong roots should be scanned depending on verification options | |
802 // and perm gen collection mode. | |
803 if (!CMSClassUnloadingEnabled) { | |
804 // If class unloading is disabled we want to include all classes into the root set. | |
805 add_root_scanning_option(SharedHeap::SO_AllClasses); | |
806 } else { | |
807 add_root_scanning_option(SharedHeap::SO_SystemClasses); | |
808 } | |
809 | |
810 NOT_PRODUCT(_overflow_counter = CMSMarkStackOverflowInterval;) | |
811 _gc_counters = new CollectorCounters("CMS", 1); | |
812 _completed_initialization = true; | |
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813 _inter_sweep_timer.start(); // start of time |
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814 #ifdef SPARC |
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815 // Issue a stern warning, but allow use for experimentation and debugging. |
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816 if (VM_Version::is_sun4v() && UseMemSetInBOT) { |
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817 assert(!FLAG_IS_DEFAULT(UseMemSetInBOT), "Error"); |
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818 warning("Experimental flag -XX:+UseMemSetInBOT is known to cause instability" |
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819 " on sun4v; please understand that you are using at your own risk!"); |
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820 } |
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821 #endif |
0 | 822 } |
823 | |
824 const char* ConcurrentMarkSweepGeneration::name() const { | |
825 return "concurrent mark-sweep generation"; | |
826 } | |
827 void ConcurrentMarkSweepGeneration::update_counters() { | |
828 if (UsePerfData) { | |
829 _space_counters->update_all(); | |
830 _gen_counters->update_all(); | |
831 } | |
832 } | |
833 | |
834 // this is an optimized version of update_counters(). it takes the | |
835 // used value as a parameter rather than computing it. | |
836 // | |
837 void ConcurrentMarkSweepGeneration::update_counters(size_t used) { | |
838 if (UsePerfData) { | |
839 _space_counters->update_used(used); | |
840 _space_counters->update_capacity(); | |
841 _gen_counters->update_all(); | |
842 } | |
843 } | |
844 | |
845 void ConcurrentMarkSweepGeneration::print() const { | |
846 Generation::print(); | |
847 cmsSpace()->print(); | |
848 } | |
849 | |
850 #ifndef PRODUCT | |
851 void ConcurrentMarkSweepGeneration::print_statistics() { | |
852 cmsSpace()->printFLCensus(0); | |
853 } | |
854 #endif | |
855 | |
856 void ConcurrentMarkSweepGeneration::printOccupancy(const char *s) { | |
857 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
858 if (PrintGCDetails) { | |
859 if (Verbose) { | |
860 gclog_or_tty->print(" [%d %s-%s: "SIZE_FORMAT"("SIZE_FORMAT")]", | |
861 level(), short_name(), s, used(), capacity()); | |
862 } else { | |
863 gclog_or_tty->print(" [%d %s-%s: "SIZE_FORMAT"K("SIZE_FORMAT"K)]", | |
864 level(), short_name(), s, used() / K, capacity() / K); | |
865 } | |
866 } | |
867 if (Verbose) { | |
868 gclog_or_tty->print(" "SIZE_FORMAT"("SIZE_FORMAT")", | |
869 gch->used(), gch->capacity()); | |
870 } else { | |
871 gclog_or_tty->print(" "SIZE_FORMAT"K("SIZE_FORMAT"K)", | |
872 gch->used() / K, gch->capacity() / K); | |
873 } | |
874 } | |
875 | |
876 size_t | |
877 ConcurrentMarkSweepGeneration::contiguous_available() const { | |
878 // dld proposes an improvement in precision here. If the committed | |
879 // part of the space ends in a free block we should add that to | |
880 // uncommitted size in the calculation below. Will make this | |
881 // change later, staying with the approximation below for the | |
882 // time being. -- ysr. | |
883 return MAX2(_virtual_space.uncommitted_size(), unsafe_max_alloc_nogc()); | |
884 } | |
885 | |
886 size_t | |
887 ConcurrentMarkSweepGeneration::unsafe_max_alloc_nogc() const { | |
888 return _cmsSpace->max_alloc_in_words() * HeapWordSize; | |
889 } | |
890 | |
891 size_t ConcurrentMarkSweepGeneration::max_available() const { | |
892 return free() + _virtual_space.uncommitted_size(); | |
893 } | |
894 | |
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895 bool ConcurrentMarkSweepGeneration::promotion_attempt_is_safe(size_t max_promotion_in_bytes) const { |
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896 size_t available = max_available(); |
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897 size_t av_promo = (size_t)gc_stats()->avg_promoted()->padded_average(); |
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898 bool res = (available >= av_promo) || (available >= max_promotion_in_bytes); |
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899 if (Verbose && PrintGCDetails) { |
1888
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900 gclog_or_tty->print_cr( |
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901 "CMS: promo attempt is%s safe: available("SIZE_FORMAT") %s av_promo("SIZE_FORMAT")," |
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902 "max_promo("SIZE_FORMAT")", |
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903 res? "":" not", available, res? ">=":"<", |
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904 av_promo, max_promotion_in_bytes); |
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905 } |
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906 return res; |
0 | 907 } |
908 | |
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909 // At a promotion failure dump information on block layout in heap |
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910 // (cms old generation). |
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911 void ConcurrentMarkSweepGeneration::promotion_failure_occurred() { |
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912 if (CMSDumpAtPromotionFailure) { |
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913 cmsSpace()->dump_at_safepoint_with_locks(collector(), gclog_or_tty); |
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914 } |
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915 } |
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916 |
0 | 917 CompactibleSpace* |
918 ConcurrentMarkSweepGeneration::first_compaction_space() const { | |
919 return _cmsSpace; | |
920 } | |
921 | |
922 void ConcurrentMarkSweepGeneration::reset_after_compaction() { | |
923 // Clear the promotion information. These pointers can be adjusted | |
924 // along with all the other pointers into the heap but | |
925 // compaction is expected to be a rare event with | |
926 // a heap using cms so don't do it without seeing the need. | |
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927 if (CollectedHeap::use_parallel_gc_threads()) { |
0 | 928 for (uint i = 0; i < ParallelGCThreads; i++) { |
929 _par_gc_thread_states[i]->promo.reset(); | |
930 } | |
931 } | |
932 } | |
933 | |
934 void ConcurrentMarkSweepGeneration::space_iterate(SpaceClosure* blk, bool usedOnly) { | |
935 blk->do_space(_cmsSpace); | |
936 } | |
937 | |
938 void ConcurrentMarkSweepGeneration::compute_new_size() { | |
939 assert_locked_or_safepoint(Heap_lock); | |
940 | |
941 // If incremental collection failed, we just want to expand | |
942 // to the limit. | |
943 if (incremental_collection_failed()) { | |
944 clear_incremental_collection_failed(); | |
945 grow_to_reserved(); | |
946 return; | |
947 } | |
948 | |
949 size_t expand_bytes = 0; | |
950 double free_percentage = ((double) free()) / capacity(); | |
951 double desired_free_percentage = (double) MinHeapFreeRatio / 100; | |
952 double maximum_free_percentage = (double) MaxHeapFreeRatio / 100; | |
953 | |
954 // compute expansion delta needed for reaching desired free percentage | |
955 if (free_percentage < desired_free_percentage) { | |
956 size_t desired_capacity = (size_t)(used() / ((double) 1 - desired_free_percentage)); | |
957 assert(desired_capacity >= capacity(), "invalid expansion size"); | |
958 expand_bytes = MAX2(desired_capacity - capacity(), MinHeapDeltaBytes); | |
959 } | |
960 if (expand_bytes > 0) { | |
961 if (PrintGCDetails && Verbose) { | |
962 size_t desired_capacity = (size_t)(used() / ((double) 1 - desired_free_percentage)); | |
963 gclog_or_tty->print_cr("\nFrom compute_new_size: "); | |
964 gclog_or_tty->print_cr(" Free fraction %f", free_percentage); | |
965 gclog_or_tty->print_cr(" Desired free fraction %f", | |
966 desired_free_percentage); | |
967 gclog_or_tty->print_cr(" Maximum free fraction %f", | |
968 maximum_free_percentage); | |
969 gclog_or_tty->print_cr(" Capactiy "SIZE_FORMAT, capacity()/1000); | |
970 gclog_or_tty->print_cr(" Desired capacity "SIZE_FORMAT, | |
971 desired_capacity/1000); | |
972 int prev_level = level() - 1; | |
973 if (prev_level >= 0) { | |
974 size_t prev_size = 0; | |
975 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
976 Generation* prev_gen = gch->_gens[prev_level]; | |
977 prev_size = prev_gen->capacity(); | |
978 gclog_or_tty->print_cr(" Younger gen size "SIZE_FORMAT, | |
979 prev_size/1000); | |
980 } | |
981 gclog_or_tty->print_cr(" unsafe_max_alloc_nogc "SIZE_FORMAT, | |
982 unsafe_max_alloc_nogc()/1000); | |
983 gclog_or_tty->print_cr(" contiguous available "SIZE_FORMAT, | |
984 contiguous_available()/1000); | |
985 gclog_or_tty->print_cr(" Expand by "SIZE_FORMAT" (bytes)", | |
986 expand_bytes); | |
987 } | |
988 // safe if expansion fails | |
989 expand(expand_bytes, 0, CMSExpansionCause::_satisfy_free_ratio); | |
990 if (PrintGCDetails && Verbose) { | |
991 gclog_or_tty->print_cr(" Expanded free fraction %f", | |
992 ((double) free()) / capacity()); | |
993 } | |
994 } | |
995 } | |
996 | |
997 Mutex* ConcurrentMarkSweepGeneration::freelistLock() const { | |
998 return cmsSpace()->freelistLock(); | |
999 } | |
1000 | |
1001 HeapWord* ConcurrentMarkSweepGeneration::allocate(size_t size, | |
1002 bool tlab) { | |
1003 CMSSynchronousYieldRequest yr; | |
1004 MutexLockerEx x(freelistLock(), | |
1005 Mutex::_no_safepoint_check_flag); | |
1006 return have_lock_and_allocate(size, tlab); | |
1007 } | |
1008 | |
1009 HeapWord* ConcurrentMarkSweepGeneration::have_lock_and_allocate(size_t size, | |
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1010 bool tlab /* ignored */) { |
0 | 1011 assert_lock_strong(freelistLock()); |
1012 size_t adjustedSize = CompactibleFreeListSpace::adjustObjectSize(size); | |
1013 HeapWord* res = cmsSpace()->allocate(adjustedSize); | |
1014 // Allocate the object live (grey) if the background collector has | |
1015 // started marking. This is necessary because the marker may | |
1016 // have passed this address and consequently this object will | |
1017 // not otherwise be greyed and would be incorrectly swept up. | |
1018 // Note that if this object contains references, the writing | |
1019 // of those references will dirty the card containing this object | |
1020 // allowing the object to be blackened (and its references scanned) | |
1021 // either during a preclean phase or at the final checkpoint. | |
1022 if (res != NULL) { | |
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1023 // We may block here with an uninitialized object with |
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1024 // its mark-bit or P-bits not yet set. Such objects need |
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1025 // to be safely navigable by block_start(). |
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1026 assert(oop(res)->klass_or_null() == NULL, "Object should be uninitialized here."); |
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1027 assert(!((FreeChunk*)res)->isFree(), "Error, block will look free but show wrong size"); |
0 | 1028 collector()->direct_allocated(res, adjustedSize); |
1029 _direct_allocated_words += adjustedSize; | |
1030 // allocation counters | |
1031 NOT_PRODUCT( | |
1032 _numObjectsAllocated++; | |
1033 _numWordsAllocated += (int)adjustedSize; | |
1034 ) | |
1035 } | |
1036 return res; | |
1037 } | |
1038 | |
1039 // In the case of direct allocation by mutators in a generation that | |
1040 // is being concurrently collected, the object must be allocated | |
1041 // live (grey) if the background collector has started marking. | |
1042 // This is necessary because the marker may | |
1043 // have passed this address and consequently this object will | |
1044 // not otherwise be greyed and would be incorrectly swept up. | |
1045 // Note that if this object contains references, the writing | |
1046 // of those references will dirty the card containing this object | |
1047 // allowing the object to be blackened (and its references scanned) | |
1048 // either during a preclean phase or at the final checkpoint. | |
1049 void CMSCollector::direct_allocated(HeapWord* start, size_t size) { | |
1050 assert(_markBitMap.covers(start, size), "Out of bounds"); | |
1051 if (_collectorState >= Marking) { | |
1052 MutexLockerEx y(_markBitMap.lock(), | |
1053 Mutex::_no_safepoint_check_flag); | |
1054 // [see comments preceding SweepClosure::do_blk() below for details] | |
1055 // 1. need to mark the object as live so it isn't collected | |
1056 // 2. need to mark the 2nd bit to indicate the object may be uninitialized | |
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1057 // 3. need to mark the end of the object so marking, precleaning or sweeping |
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1058 // can skip over uninitialized or unparsable objects. An allocated |
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1059 // object is considered uninitialized for our purposes as long as |
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1060 // its klass word is NULL. (Unparsable objects are those which are |
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1061 // initialized in the sense just described, but whose sizes can still |
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1062 // not be correctly determined. Note that the class of unparsable objects |
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1063 // can only occur in the perm gen. All old gen objects are parsable |
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1064 // as soon as they are initialized.) |
0 | 1065 _markBitMap.mark(start); // object is live |
1066 _markBitMap.mark(start + 1); // object is potentially uninitialized? | |
1067 _markBitMap.mark(start + size - 1); | |
1068 // mark end of object | |
1069 } | |
1070 // check that oop looks uninitialized | |
187 | 1071 assert(oop(start)->klass_or_null() == NULL, "_klass should be NULL"); |
0 | 1072 } |
1073 | |
1074 void CMSCollector::promoted(bool par, HeapWord* start, | |
1075 bool is_obj_array, size_t obj_size) { | |
1076 assert(_markBitMap.covers(start), "Out of bounds"); | |
1077 // See comment in direct_allocated() about when objects should | |
1078 // be allocated live. | |
1079 if (_collectorState >= Marking) { | |
1080 // we already hold the marking bit map lock, taken in | |
1081 // the prologue | |
1082 if (par) { | |
1083 _markBitMap.par_mark(start); | |
1084 } else { | |
1085 _markBitMap.mark(start); | |
1086 } | |
1087 // We don't need to mark the object as uninitialized (as | |
1088 // in direct_allocated above) because this is being done with the | |
1089 // world stopped and the object will be initialized by the | |
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1090 // time the marking, precleaning or sweeping get to look at it. |
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1091 // But see the code for copying objects into the CMS generation, |
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1092 // where we need to ensure that concurrent readers of the |
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1093 // block offset table are able to safely navigate a block that |
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1094 // is in flux from being free to being allocated (and in |
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1095 // transition while being copied into) and subsequently |
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1096 // becoming a bona-fide object when the copy/promotion is complete. |
0 | 1097 assert(SafepointSynchronize::is_at_safepoint(), |
1098 "expect promotion only at safepoints"); | |
1099 | |
1100 if (_collectorState < Sweeping) { | |
1101 // Mark the appropriate cards in the modUnionTable, so that | |
1102 // this object gets scanned before the sweep. If this is | |
1103 // not done, CMS generation references in the object might | |
1104 // not get marked. | |
1105 // For the case of arrays, which are otherwise precisely | |
1106 // marked, we need to dirty the entire array, not just its head. | |
1107 if (is_obj_array) { | |
1108 // The [par_]mark_range() method expects mr.end() below to | |
1109 // be aligned to the granularity of a bit's representation | |
1110 // in the heap. In the case of the MUT below, that's a | |
1111 // card size. | |
1112 MemRegion mr(start, | |
1113 (HeapWord*)round_to((intptr_t)(start + obj_size), | |
1114 CardTableModRefBS::card_size /* bytes */)); | |
1115 if (par) { | |
1116 _modUnionTable.par_mark_range(mr); | |
1117 } else { | |
1118 _modUnionTable.mark_range(mr); | |
1119 } | |
1120 } else { // not an obj array; we can just mark the head | |
1121 if (par) { | |
1122 _modUnionTable.par_mark(start); | |
1123 } else { | |
1124 _modUnionTable.mark(start); | |
1125 } | |
1126 } | |
1127 } | |
1128 } | |
1129 } | |
1130 | |
1131 static inline size_t percent_of_space(Space* space, HeapWord* addr) | |
1132 { | |
1133 size_t delta = pointer_delta(addr, space->bottom()); | |
1134 return (size_t)(delta * 100.0 / (space->capacity() / HeapWordSize)); | |
1135 } | |
1136 | |
1137 void CMSCollector::icms_update_allocation_limits() | |
1138 { | |
1139 Generation* gen0 = GenCollectedHeap::heap()->get_gen(0); | |
1140 EdenSpace* eden = gen0->as_DefNewGeneration()->eden(); | |
1141 | |
1142 const unsigned int duty_cycle = stats().icms_update_duty_cycle(); | |
1143 if (CMSTraceIncrementalPacing) { | |
1144 stats().print(); | |
1145 } | |
1146 | |
1147 assert(duty_cycle <= 100, "invalid duty cycle"); | |
1148 if (duty_cycle != 0) { | |
1149 // The duty_cycle is a percentage between 0 and 100; convert to words and | |
1150 // then compute the offset from the endpoints of the space. | |
1151 size_t free_words = eden->free() / HeapWordSize; | |
1152 double free_words_dbl = (double)free_words; | |
1153 size_t duty_cycle_words = (size_t)(free_words_dbl * duty_cycle / 100.0); | |
1154 size_t offset_words = (free_words - duty_cycle_words) / 2; | |
1155 | |
1156 _icms_start_limit = eden->top() + offset_words; | |
1157 _icms_stop_limit = eden->end() - offset_words; | |
1158 | |
1159 // The limits may be adjusted (shifted to the right) by | |
1160 // CMSIncrementalOffset, to allow the application more mutator time after a | |
1161 // young gen gc (when all mutators were stopped) and before CMS starts and | |
1162 // takes away one or more cpus. | |
1163 if (CMSIncrementalOffset != 0) { | |
1164 double adjustment_dbl = free_words_dbl * CMSIncrementalOffset / 100.0; | |
1165 size_t adjustment = (size_t)adjustment_dbl; | |
1166 HeapWord* tmp_stop = _icms_stop_limit + adjustment; | |
1167 if (tmp_stop > _icms_stop_limit && tmp_stop < eden->end()) { | |
1168 _icms_start_limit += adjustment; | |
1169 _icms_stop_limit = tmp_stop; | |
1170 } | |
1171 } | |
1172 } | |
1173 if (duty_cycle == 0 || (_icms_start_limit == _icms_stop_limit)) { | |
1174 _icms_start_limit = _icms_stop_limit = eden->end(); | |
1175 } | |
1176 | |
1177 // Install the new start limit. | |
1178 eden->set_soft_end(_icms_start_limit); | |
1179 | |
1180 if (CMSTraceIncrementalMode) { | |
1181 gclog_or_tty->print(" icms alloc limits: " | |
1182 PTR_FORMAT "," PTR_FORMAT | |
1183 " (" SIZE_FORMAT "%%," SIZE_FORMAT "%%) ", | |
1184 _icms_start_limit, _icms_stop_limit, | |
1185 percent_of_space(eden, _icms_start_limit), | |
1186 percent_of_space(eden, _icms_stop_limit)); | |
1187 if (Verbose) { | |
1188 gclog_or_tty->print("eden: "); | |
1189 eden->print_on(gclog_or_tty); | |
1190 } | |
1191 } | |
1192 } | |
1193 | |
1194 // Any changes here should try to maintain the invariant | |
1195 // that if this method is called with _icms_start_limit | |
1196 // and _icms_stop_limit both NULL, then it should return NULL | |
1197 // and not notify the icms thread. | |
1198 HeapWord* | |
1199 CMSCollector::allocation_limit_reached(Space* space, HeapWord* top, | |
1200 size_t word_size) | |
1201 { | |
1202 // A start_limit equal to end() means the duty cycle is 0, so treat that as a | |
1203 // nop. | |
1204 if (CMSIncrementalMode && _icms_start_limit != space->end()) { | |
1205 if (top <= _icms_start_limit) { | |
1206 if (CMSTraceIncrementalMode) { | |
1207 space->print_on(gclog_or_tty); | |
1208 gclog_or_tty->stamp(); | |
1209 gclog_or_tty->print_cr(" start limit top=" PTR_FORMAT | |
1210 ", new limit=" PTR_FORMAT | |
1211 " (" SIZE_FORMAT "%%)", | |
1212 top, _icms_stop_limit, | |
1213 percent_of_space(space, _icms_stop_limit)); | |
1214 } | |
1215 ConcurrentMarkSweepThread::start_icms(); | |
1216 assert(top < _icms_stop_limit, "Tautology"); | |
1217 if (word_size < pointer_delta(_icms_stop_limit, top)) { | |
1218 return _icms_stop_limit; | |
1219 } | |
1220 | |
1221 // The allocation will cross both the _start and _stop limits, so do the | |
1222 // stop notification also and return end(). | |
1223 if (CMSTraceIncrementalMode) { | |
1224 space->print_on(gclog_or_tty); | |
1225 gclog_or_tty->stamp(); | |
1226 gclog_or_tty->print_cr(" +stop limit top=" PTR_FORMAT | |
1227 ", new limit=" PTR_FORMAT | |
1228 " (" SIZE_FORMAT "%%)", | |
1229 top, space->end(), | |
1230 percent_of_space(space, space->end())); | |
1231 } | |
1232 ConcurrentMarkSweepThread::stop_icms(); | |
1233 return space->end(); | |
1234 } | |
1235 | |
1236 if (top <= _icms_stop_limit) { | |
1237 if (CMSTraceIncrementalMode) { | |
1238 space->print_on(gclog_or_tty); | |
1239 gclog_or_tty->stamp(); | |
1240 gclog_or_tty->print_cr(" stop limit top=" PTR_FORMAT | |
1241 ", new limit=" PTR_FORMAT | |
1242 " (" SIZE_FORMAT "%%)", | |
1243 top, space->end(), | |
1244 percent_of_space(space, space->end())); | |
1245 } | |
1246 ConcurrentMarkSweepThread::stop_icms(); | |
1247 return space->end(); | |
1248 } | |
1249 | |
1250 if (CMSTraceIncrementalMode) { | |
1251 space->print_on(gclog_or_tty); | |
1252 gclog_or_tty->stamp(); | |
1253 gclog_or_tty->print_cr(" end limit top=" PTR_FORMAT | |
1254 ", new limit=" PTR_FORMAT, | |
1255 top, NULL); | |
1256 } | |
1257 } | |
1258 | |
1259 return NULL; | |
1260 } | |
1261 | |
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1262 oop ConcurrentMarkSweepGeneration::promote(oop obj, size_t obj_size) { |
0 | 1263 assert(obj_size == (size_t)obj->size(), "bad obj_size passed in"); |
1264 // allocate, copy and if necessary update promoinfo -- | |
1265 // delegate to underlying space. | |
1266 assert_lock_strong(freelistLock()); | |
1267 | |
1268 #ifndef PRODUCT | |
1269 if (Universe::heap()->promotion_should_fail()) { | |
1270 return NULL; | |
1271 } | |
1272 #endif // #ifndef PRODUCT | |
1273 | |
113
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1274 oop res = _cmsSpace->promote(obj, obj_size); |
0 | 1275 if (res == NULL) { |
1276 // expand and retry | |
1277 size_t s = _cmsSpace->expansionSpaceRequired(obj_size); // HeapWords | |
1278 expand(s*HeapWordSize, MinHeapDeltaBytes, | |
1279 CMSExpansionCause::_satisfy_promotion); | |
1280 // Since there's currently no next generation, we don't try to promote | |
1281 // into a more senior generation. | |
1282 assert(next_gen() == NULL, "assumption, based upon which no attempt " | |
1283 "is made to pass on a possibly failing " | |
1284 "promotion to next generation"); | |
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1285 res = _cmsSpace->promote(obj, obj_size); |
0 | 1286 } |
1287 if (res != NULL) { | |
1288 // See comment in allocate() about when objects should | |
1289 // be allocated live. | |
1290 assert(obj->is_oop(), "Will dereference klass pointer below"); | |
1291 collector()->promoted(false, // Not parallel | |
1292 (HeapWord*)res, obj->is_objArray(), obj_size); | |
1293 // promotion counters | |
1294 NOT_PRODUCT( | |
1295 _numObjectsPromoted++; | |
1296 _numWordsPromoted += | |
1297 (int)(CompactibleFreeListSpace::adjustObjectSize(obj->size())); | |
1298 ) | |
1299 } | |
1300 return res; | |
1301 } | |
1302 | |
1303 | |
1304 HeapWord* | |
1305 ConcurrentMarkSweepGeneration::allocation_limit_reached(Space* space, | |
1306 HeapWord* top, | |
1307 size_t word_sz) | |
1308 { | |
1309 return collector()->allocation_limit_reached(space, top, word_sz); | |
1310 } | |
1311 | |
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1312 // IMPORTANT: Notes on object size recognition in CMS. |
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1313 // --------------------------------------------------- |
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1314 // A block of storage in the CMS generation is always in |
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1315 // one of three states. A free block (FREE), an allocated |
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1316 // object (OBJECT) whose size() method reports the correct size, |
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1317 // and an intermediate state (TRANSIENT) in which its size cannot |
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1318 // be accurately determined. |
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1319 // STATE IDENTIFICATION: (32 bit and 64 bit w/o COOPS) |
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1320 // ----------------------------------------------------- |
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1321 // FREE: klass_word & 1 == 1; mark_word holds block size |
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1322 // |
1777
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1323 // OBJECT: klass_word installed; klass_word != 0 && klass_word & 1 == 0; |
1716
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1324 // obj->size() computes correct size |
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1325 // [Perm Gen objects needs to be "parsable" before they can be navigated] |
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1326 // |
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1327 // TRANSIENT: klass_word == 0; size is indeterminate until we become an OBJECT |
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1328 // |
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1329 // STATE IDENTIFICATION: (64 bit+COOPS) |
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1330 // ------------------------------------ |
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1331 // FREE: mark_word & CMS_FREE_BIT == 1; mark_word & ~CMS_FREE_BIT gives block_size |
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1332 // |
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1333 // OBJECT: klass_word installed; klass_word != 0; |
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1334 // obj->size() computes correct size |
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1335 // [Perm Gen comment above continues to hold] |
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1336 // |
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1337 // TRANSIENT: klass_word == 0; size is indeterminate until we become an OBJECT |
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1338 // |
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1339 // |
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1340 // STATE TRANSITION DIAGRAM |
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1341 // |
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1342 // mut / parnew mut / parnew |
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1343 // FREE --------------------> TRANSIENT ---------------------> OBJECT --| |
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1344 // ^ | |
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1345 // |------------------------ DEAD <------------------------------------| |
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1346 // sweep mut |
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1347 // |
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1348 // While a block is in TRANSIENT state its size cannot be determined |
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1349 // so readers will either need to come back later or stall until |
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1350 // the size can be determined. Note that for the case of direct |
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1351 // allocation, P-bits, when available, may be used to determine the |
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1352 // size of an object that may not yet have been initialized. |
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1353 |
0 | 1354 // Things to support parallel young-gen collection. |
1355 oop | |
1356 ConcurrentMarkSweepGeneration::par_promote(int thread_num, | |
1357 oop old, markOop m, | |
1358 size_t word_sz) { | |
1359 #ifndef PRODUCT | |
1360 if (Universe::heap()->promotion_should_fail()) { | |
1361 return NULL; | |
1362 } | |
1363 #endif // #ifndef PRODUCT | |
1364 | |
1365 CMSParGCThreadState* ps = _par_gc_thread_states[thread_num]; | |
1366 PromotionInfo* promoInfo = &ps->promo; | |
1367 // if we are tracking promotions, then first ensure space for | |
1368 // promotion (including spooling space for saving header if necessary). | |
1369 // then allocate and copy, then track promoted info if needed. | |
1370 // When tracking (see PromotionInfo::track()), the mark word may | |
1371 // be displaced and in this case restoration of the mark word | |
1372 // occurs in the (oop_since_save_marks_)iterate phase. | |
1373 if (promoInfo->tracking() && !promoInfo->ensure_spooling_space()) { | |
1374 // Out of space for allocating spooling buffers; | |
1375 // try expanding and allocating spooling buffers. | |
1376 if (!expand_and_ensure_spooling_space(promoInfo)) { | |
1377 return NULL; | |
1378 } | |
1379 } | |
1380 assert(promoInfo->has_spooling_space(), "Control point invariant"); | |
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1381 const size_t alloc_sz = CompactibleFreeListSpace::adjustObjectSize(word_sz); |
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1382 HeapWord* obj_ptr = ps->lab.alloc(alloc_sz); |
0 | 1383 if (obj_ptr == NULL) { |
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1384 obj_ptr = expand_and_par_lab_allocate(ps, alloc_sz); |
0 | 1385 if (obj_ptr == NULL) { |
1386 return NULL; | |
1387 } | |
1388 } | |
1389 oop obj = oop(obj_ptr); | |
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1390 OrderAccess::storestore(); |
187 | 1391 assert(obj->klass_or_null() == NULL, "Object should be uninitialized here."); |
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1392 assert(!((FreeChunk*)obj_ptr)->isFree(), "Error, block will look free but show wrong size"); |
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1393 // IMPORTANT: See note on object initialization for CMS above. |
0 | 1394 // Otherwise, copy the object. Here we must be careful to insert the |
1395 // klass pointer last, since this marks the block as an allocated object. | |
187 | 1396 // Except with compressed oops it's the mark word. |
0 | 1397 HeapWord* old_ptr = (HeapWord*)old; |
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1398 // Restore the mark word copied above. |
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1399 obj->set_mark(m); |
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1400 assert(obj->klass_or_null() == NULL, "Object should be uninitialized here."); |
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1401 assert(!((FreeChunk*)obj_ptr)->isFree(), "Error, block will look free but show wrong size"); |
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1402 OrderAccess::storestore(); |
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1403 |
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1404 if (UseCompressedOops) { |
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1405 // Copy gap missed by (aligned) header size calculation below |
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1406 obj->set_klass_gap(old->klass_gap()); |
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1407 } |
0 | 1408 if (word_sz > (size_t)oopDesc::header_size()) { |
1409 Copy::aligned_disjoint_words(old_ptr + oopDesc::header_size(), | |
1410 obj_ptr + oopDesc::header_size(), | |
1411 word_sz - oopDesc::header_size()); | |
1412 } | |
187 | 1413 |
0 | 1414 // Now we can track the promoted object, if necessary. We take care |
1521 | 1415 // to delay the transition from uninitialized to full object |
0 | 1416 // (i.e., insertion of klass pointer) until after, so that it |
1417 // atomically becomes a promoted object. | |
1418 if (promoInfo->tracking()) { | |
1419 promoInfo->track((PromotedObject*)obj, old->klass()); | |
1420 } | |
1716
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1421 assert(obj->klass_or_null() == NULL, "Object should be uninitialized here."); |
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1422 assert(!((FreeChunk*)obj_ptr)->isFree(), "Error, block will look free but show wrong size"); |
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1423 assert(old->is_oop(), "Will use and dereference old klass ptr below"); |
187 | 1424 |
1425 // Finally, install the klass pointer (this should be volatile). | |
1716
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1426 OrderAccess::storestore(); |
0 | 1427 obj->set_klass(old->klass()); |
1716
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1428 // We should now be able to calculate the right size for this object |
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1429 assert(obj->is_oop() && obj->size() == (int)word_sz, "Error, incorrect size computed for promoted object"); |
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1430 |
0 | 1431 collector()->promoted(true, // parallel |
1432 obj_ptr, old->is_objArray(), word_sz); | |
1433 | |
1434 NOT_PRODUCT( | |
1716
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1435 Atomic::inc_ptr(&_numObjectsPromoted); |
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1436 Atomic::add_ptr(alloc_sz, &_numWordsPromoted); |
0 | 1437 ) |
1438 | |
1439 return obj; | |
1440 } | |
1441 | |
1442 void | |
1443 ConcurrentMarkSweepGeneration:: | |
1444 par_promote_alloc_undo(int thread_num, | |
1445 HeapWord* obj, size_t word_sz) { | |
1446 // CMS does not support promotion undo. | |
1447 ShouldNotReachHere(); | |
1448 } | |
1449 | |
1450 void | |
1451 ConcurrentMarkSweepGeneration:: | |
1452 par_promote_alloc_done(int thread_num) { | |
1453 CMSParGCThreadState* ps = _par_gc_thread_states[thread_num]; | |
1145
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1454 ps->lab.retire(thread_num); |
0 | 1455 } |
1456 | |
1457 void | |
1458 ConcurrentMarkSweepGeneration:: | |
1459 par_oop_since_save_marks_iterate_done(int thread_num) { | |
1460 CMSParGCThreadState* ps = _par_gc_thread_states[thread_num]; | |
1461 ParScanWithoutBarrierClosure* dummy_cl = NULL; | |
1462 ps->promo.promoted_oops_iterate_nv(dummy_cl); | |
1463 } | |
1464 | |
1465 // XXXPERM | |
1466 bool ConcurrentMarkSweepGeneration::should_collect(bool full, | |
1467 size_t size, | |
1468 bool tlab) | |
1469 { | |
1470 // We allow a STW collection only if a full | |
1471 // collection was requested. | |
1472 return full || should_allocate(size, tlab); // FIX ME !!! | |
1473 // This and promotion failure handling are connected at the | |
1474 // hip and should be fixed by untying them. | |
1475 } | |
1476 | |
1477 bool CMSCollector::shouldConcurrentCollect() { | |
1478 if (_full_gc_requested) { | |
1479 if (Verbose && PrintGCDetails) { | |
1480 gclog_or_tty->print_cr("CMSCollector: collect because of explicit " | |
1520
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1481 " gc request (or gc_locker)"); |
0 | 1482 } |
1483 return true; | |
1484 } | |
1485 | |
1486 // For debugging purposes, change the type of collection. | |
1487 // If the rotation is not on the concurrent collection | |
1488 // type, don't start a concurrent collection. | |
1489 NOT_PRODUCT( | |
1490 if (RotateCMSCollectionTypes && | |
1491 (_cmsGen->debug_collection_type() != | |
1492 ConcurrentMarkSweepGeneration::Concurrent_collection_type)) { | |
1493 assert(_cmsGen->debug_collection_type() != | |
1494 ConcurrentMarkSweepGeneration::Unknown_collection_type, | |
1495 "Bad cms collection type"); | |
1496 return false; | |
1497 } | |
1498 ) | |
1499 | |
1500 FreelistLocker x(this); | |
1501 // ------------------------------------------------------------------ | |
1502 // Print out lots of information which affects the initiation of | |
1503 // a collection. | |
1504 if (PrintCMSInitiationStatistics && stats().valid()) { | |
1505 gclog_or_tty->print("CMSCollector shouldConcurrentCollect: "); | |
1506 gclog_or_tty->stamp(); | |
1507 gclog_or_tty->print_cr(""); | |
1508 stats().print_on(gclog_or_tty); | |
1509 gclog_or_tty->print_cr("time_until_cms_gen_full %3.7f", | |
1510 stats().time_until_cms_gen_full()); | |
1511 gclog_or_tty->print_cr("free="SIZE_FORMAT, _cmsGen->free()); | |
1512 gclog_or_tty->print_cr("contiguous_available="SIZE_FORMAT, | |
1513 _cmsGen->contiguous_available()); | |
1514 gclog_or_tty->print_cr("promotion_rate=%g", stats().promotion_rate()); | |
1515 gclog_or_tty->print_cr("cms_allocation_rate=%g", stats().cms_allocation_rate()); | |
1516 gclog_or_tty->print_cr("occupancy=%3.7f", _cmsGen->occupancy()); | |
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1517 gclog_or_tty->print_cr("initiatingOccupancy=%3.7f", _cmsGen->initiating_occupancy()); |
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1518 gclog_or_tty->print_cr("initiatingPermOccupancy=%3.7f", _permGen->initiating_occupancy()); |
0 | 1519 } |
1520 // ------------------------------------------------------------------ | |
1521 | |
1522 // If the estimated time to complete a cms collection (cms_duration()) | |
1523 // is less than the estimated time remaining until the cms generation | |
1524 // is full, start a collection. | |
1525 if (!UseCMSInitiatingOccupancyOnly) { | |
1526 if (stats().valid()) { | |
1527 if (stats().time_until_cms_start() == 0.0) { | |
1528 return true; | |
1529 } | |
1530 } else { | |
1531 // We want to conservatively collect somewhat early in order | |
1532 // to try and "bootstrap" our CMS/promotion statistics; | |
1533 // this branch will not fire after the first successful CMS | |
1534 // collection because the stats should then be valid. | |
1535 if (_cmsGen->occupancy() >= _bootstrap_occupancy) { | |
1536 if (Verbose && PrintGCDetails) { | |
1537 gclog_or_tty->print_cr( | |
1538 " CMSCollector: collect for bootstrapping statistics:" | |
1539 " occupancy = %f, boot occupancy = %f", _cmsGen->occupancy(), | |
1540 _bootstrap_occupancy); | |
1541 } | |
1542 return true; | |
1543 } | |
1544 } | |
1545 } | |
1546 | |
1547 // Otherwise, we start a collection cycle if either the perm gen or | |
1548 // old gen want a collection cycle started. Each may use | |
1549 // an appropriate criterion for making this decision. | |
1550 // XXX We need to make sure that the gen expansion | |
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1551 // criterion dovetails well with this. XXX NEED TO FIX THIS |
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1552 if (_cmsGen->should_concurrent_collect()) { |
0 | 1553 if (Verbose && PrintGCDetails) { |
1554 gclog_or_tty->print_cr("CMS old gen initiated"); | |
1555 } | |
1556 return true; | |
1557 } | |
1558 | |
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1559 // We start a collection if we believe an incremental collection may fail; |
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1560 // this is not likely to be productive in practice because it's probably too |
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1561 // late anyway. |
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1562 GenCollectedHeap* gch = GenCollectedHeap::heap(); |
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1563 assert(gch->collector_policy()->is_two_generation_policy(), |
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1564 "You may want to check the correctness of the following"); |
1994
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1565 if (gch->incremental_collection_will_fail(true /* consult_young */)) { |
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1566 if (Verbose && PrintGCDetails) { |
94
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1567 gclog_or_tty->print("CMSCollector: collect because incremental collection will fail "); |
0 | 1568 } |
1569 return true; | |
1570 } | |
1571 | |
94
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1572 if (CMSClassUnloadingEnabled && _permGen->should_concurrent_collect()) { |
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1573 bool res = update_should_unload_classes(); |
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1574 if (res) { |
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1575 if (Verbose && PrintGCDetails) { |
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1576 gclog_or_tty->print_cr("CMS perm gen initiated"); |
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1577 } |
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1578 return true; |
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1579 } |
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1580 } |
0 | 1581 return false; |
1582 } | |
1583 | |
1584 // Clear _expansion_cause fields of constituent generations | |
1585 void CMSCollector::clear_expansion_cause() { | |
1586 _cmsGen->clear_expansion_cause(); | |
1587 _permGen->clear_expansion_cause(); | |
1588 } | |
1589 | |
94
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1590 // We should be conservative in starting a collection cycle. To |
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1591 // start too eagerly runs the risk of collecting too often in the |
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1592 // extreme. To collect too rarely falls back on full collections, |
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1593 // which works, even if not optimum in terms of concurrent work. |
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1594 // As a work around for too eagerly collecting, use the flag |
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1595 // UseCMSInitiatingOccupancyOnly. This also has the advantage of |
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1596 // giving the user an easily understandable way of controlling the |
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1597 // collections. |
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1598 // We want to start a new collection cycle if any of the following |
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1599 // conditions hold: |
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1600 // . our current occupancy exceeds the configured initiating occupancy |
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1601 // for this generation, or |
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1602 // . we recently needed to expand this space and have not, since that |
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1603 // expansion, done a collection of this generation, or |
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1604 // . the underlying space believes that it may be a good idea to initiate |
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1605 // a concurrent collection (this may be based on criteria such as the |
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1606 // following: the space uses linear allocation and linear allocation is |
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1607 // going to fail, or there is believed to be excessive fragmentation in |
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1608 // the generation, etc... or ... |
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1609 // [.(currently done by CMSCollector::shouldConcurrentCollect() only for |
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1610 // the case of the old generation, not the perm generation; see CR 6543076): |
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1611 // we may be approaching a point at which allocation requests may fail because |
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1612 // we will be out of sufficient free space given allocation rate estimates.] |
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1613 bool ConcurrentMarkSweepGeneration::should_concurrent_collect() const { |
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1614 |
0 | 1615 assert_lock_strong(freelistLock()); |
94
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1616 if (occupancy() > initiating_occupancy()) { |
0 | 1617 if (PrintGCDetails && Verbose) { |
1618 gclog_or_tty->print(" %s: collect because of occupancy %f / %f ", | |
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1619 short_name(), occupancy(), initiating_occupancy()); |
0 | 1620 } |
1621 return true; | |
1622 } | |
1623 if (UseCMSInitiatingOccupancyOnly) { | |
1624 return false; | |
1625 } | |
1626 if (expansion_cause() == CMSExpansionCause::_satisfy_allocation) { | |
1627 if (PrintGCDetails && Verbose) { | |
1628 gclog_or_tty->print(" %s: collect because expanded for allocation ", | |
1629 short_name()); | |
1630 } | |
1631 return true; | |
1632 } | |
94
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1633 if (_cmsSpace->should_concurrent_collect()) { |
0 | 1634 if (PrintGCDetails && Verbose) { |
94
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1635 gclog_or_tty->print(" %s: collect because cmsSpace says so ", |
0 | 1636 short_name()); |
1637 } | |
1638 return true; | |
1639 } | |
1640 return false; | |
1641 } | |
1642 | |
1643 void ConcurrentMarkSweepGeneration::collect(bool full, | |
1644 bool clear_all_soft_refs, | |
1645 size_t size, | |
1646 bool tlab) | |
1647 { | |
1648 collector()->collect(full, clear_all_soft_refs, size, tlab); | |
1649 } | |
1650 | |
1651 void CMSCollector::collect(bool full, | |
1652 bool clear_all_soft_refs, | |
1653 size_t size, | |
1654 bool tlab) | |
1655 { | |
1656 if (!UseCMSCollectionPassing && _collectorState > Idling) { | |
1657 // For debugging purposes skip the collection if the state | |
1658 // is not currently idle | |
1659 if (TraceCMSState) { | |
1660 gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " skipped full:%d CMS state %d", | |
1661 Thread::current(), full, _collectorState); | |
1662 } | |
1663 return; | |
1664 } | |
1665 | |
1666 // The following "if" branch is present for defensive reasons. | |
1667 // In the current uses of this interface, it can be replaced with: | |
1668 // assert(!GC_locker.is_active(), "Can't be called otherwise"); | |
1669 // But I am not placing that assert here to allow future | |
1670 // generality in invoking this interface. | |
1671 if (GC_locker::is_active()) { | |
1672 // A consistency test for GC_locker | |
1673 assert(GC_locker::needs_gc(), "Should have been set already"); | |
1674 // Skip this foreground collection, instead | |
1675 // expanding the heap if necessary. | |
1676 // Need the free list locks for the call to free() in compute_new_size() | |
1677 compute_new_size(); | |
1678 return; | |
1679 } | |
1680 acquire_control_and_collect(full, clear_all_soft_refs); | |
1681 _full_gcs_since_conc_gc++; | |
1682 | |
1683 } | |
1684 | |
1685 void CMSCollector::request_full_gc(unsigned int full_gc_count) { | |
1686 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
1687 unsigned int gc_count = gch->total_full_collections(); | |
1688 if (gc_count == full_gc_count) { | |
1689 MutexLockerEx y(CGC_lock, Mutex::_no_safepoint_check_flag); | |
1690 _full_gc_requested = true; | |
1691 CGC_lock->notify(); // nudge CMS thread | |
1692 } | |
1693 } | |
1694 | |
1695 | |
1696 // The foreground and background collectors need to coordinate in order | |
1697 // to make sure that they do not mutually interfere with CMS collections. | |
1698 // When a background collection is active, | |
1699 // the foreground collector may need to take over (preempt) and | |
1700 // synchronously complete an ongoing collection. Depending on the | |
1701 // frequency of the background collections and the heap usage | |
1702 // of the application, this preemption can be seldom or frequent. | |
1703 // There are only certain | |
1704 // points in the background collection that the "collection-baton" | |
1705 // can be passed to the foreground collector. | |
1706 // | |
1707 // The foreground collector will wait for the baton before | |
1708 // starting any part of the collection. The foreground collector | |
1709 // will only wait at one location. | |
1710 // | |
1711 // The background collector will yield the baton before starting a new | |
1712 // phase of the collection (e.g., before initial marking, marking from roots, | |
1713 // precleaning, final re-mark, sweep etc.) This is normally done at the head | |
1714 // of the loop which switches the phases. The background collector does some | |
1715 // of the phases (initial mark, final re-mark) with the world stopped. | |
1716 // Because of locking involved in stopping the world, | |
1717 // the foreground collector should not block waiting for the background | |
1718 // collector when it is doing a stop-the-world phase. The background | |
1719 // collector will yield the baton at an additional point just before | |
1720 // it enters a stop-the-world phase. Once the world is stopped, the | |
1721 // background collector checks the phase of the collection. If the | |
1722 // phase has not changed, it proceeds with the collection. If the | |
1723 // phase has changed, it skips that phase of the collection. See | |
1724 // the comments on the use of the Heap_lock in collect_in_background(). | |
1725 // | |
1726 // Variable used in baton passing. | |
1727 // _foregroundGCIsActive - Set to true by the foreground collector when | |
1728 // it wants the baton. The foreground clears it when it has finished | |
1729 // the collection. | |
1730 // _foregroundGCShouldWait - Set to true by the background collector | |
1731 // when it is running. The foreground collector waits while | |
1732 // _foregroundGCShouldWait is true. | |
1733 // CGC_lock - monitor used to protect access to the above variables | |
1734 // and to notify the foreground and background collectors. | |
1735 // _collectorState - current state of the CMS collection. | |
1736 // | |
1737 // The foreground collector | |
1738 // acquires the CGC_lock | |
1739 // sets _foregroundGCIsActive | |
1740 // waits on the CGC_lock for _foregroundGCShouldWait to be false | |
1741 // various locks acquired in preparation for the collection | |
1742 // are released so as not to block the background collector | |
1743 // that is in the midst of a collection | |
1744 // proceeds with the collection | |
1745 // clears _foregroundGCIsActive | |
1746 // returns | |
1747 // | |
1748 // The background collector in a loop iterating on the phases of the | |
1749 // collection | |
1750 // acquires the CGC_lock | |
1751 // sets _foregroundGCShouldWait | |
1752 // if _foregroundGCIsActive is set | |
1753 // clears _foregroundGCShouldWait, notifies _CGC_lock | |
1754 // waits on _CGC_lock for _foregroundGCIsActive to become false | |
1755 // and exits the loop. | |
1756 // otherwise | |
1757 // proceed with that phase of the collection | |
1758 // if the phase is a stop-the-world phase, | |
1759 // yield the baton once more just before enqueueing | |
1760 // the stop-world CMS operation (executed by the VM thread). | |
1761 // returns after all phases of the collection are done | |
1762 // | |
1763 | |
1764 void CMSCollector::acquire_control_and_collect(bool full, | |
1765 bool clear_all_soft_refs) { | |
1766 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint"); | |
1767 assert(!Thread::current()->is_ConcurrentGC_thread(), | |
1768 "shouldn't try to acquire control from self!"); | |
1769 | |
1770 // Start the protocol for acquiring control of the | |
1771 // collection from the background collector (aka CMS thread). | |
1772 assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(), | |
1773 "VM thread should have CMS token"); | |
1774 // Remember the possibly interrupted state of an ongoing | |
1775 // concurrent collection | |
1776 CollectorState first_state = _collectorState; | |
1777 | |
1778 // Signal to a possibly ongoing concurrent collection that | |
1779 // we want to do a foreground collection. | |
1780 _foregroundGCIsActive = true; | |
1781 | |
1782 // Disable incremental mode during a foreground collection. | |
1783 ICMSDisabler icms_disabler; | |
1784 | |
1785 // release locks and wait for a notify from the background collector | |
1786 // releasing the locks in only necessary for phases which | |
1787 // do yields to improve the granularity of the collection. | |
1788 assert_lock_strong(bitMapLock()); | |
1789 // We need to lock the Free list lock for the space that we are | |
1790 // currently collecting. | |
1791 assert(haveFreelistLocks(), "Must be holding free list locks"); | |
1792 bitMapLock()->unlock(); | |
1793 releaseFreelistLocks(); | |
1794 { | |
1795 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
1796 if (_foregroundGCShouldWait) { | |
1797 // We are going to be waiting for action for the CMS thread; | |
1798 // it had better not be gone (for instance at shutdown)! | |
1799 assert(ConcurrentMarkSweepThread::cmst() != NULL, | |
1800 "CMS thread must be running"); | |
1801 // Wait here until the background collector gives us the go-ahead | |
1802 ConcurrentMarkSweepThread::clear_CMS_flag( | |
1803 ConcurrentMarkSweepThread::CMS_vm_has_token); // release token | |
1804 // Get a possibly blocked CMS thread going: | |
1805 // Note that we set _foregroundGCIsActive true above, | |
1806 // without protection of the CGC_lock. | |
1807 CGC_lock->notify(); | |
1808 assert(!ConcurrentMarkSweepThread::vm_thread_wants_cms_token(), | |
1809 "Possible deadlock"); | |
1810 while (_foregroundGCShouldWait) { | |
1811 // wait for notification | |
1812 CGC_lock->wait(Mutex::_no_safepoint_check_flag); | |
1813 // Possibility of delay/starvation here, since CMS token does | |
1814 // not know to give priority to VM thread? Actually, i think | |
1815 // there wouldn't be any delay/starvation, but the proof of | |
1816 // that "fact" (?) appears non-trivial. XXX 20011219YSR | |
1817 } | |
1818 ConcurrentMarkSweepThread::set_CMS_flag( | |
1819 ConcurrentMarkSweepThread::CMS_vm_has_token); | |
1820 } | |
1821 } | |
1822 // The CMS_token is already held. Get back the other locks. | |
1823 assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(), | |
1824 "VM thread should have CMS token"); | |
1825 getFreelistLocks(); | |
1826 bitMapLock()->lock_without_safepoint_check(); | |
1827 if (TraceCMSState) { | |
1828 gclog_or_tty->print_cr("CMS foreground collector has asked for control " | |
1829 INTPTR_FORMAT " with first state %d", Thread::current(), first_state); | |
1830 gclog_or_tty->print_cr(" gets control with state %d", _collectorState); | |
1831 } | |
1832 | |
1833 // Check if we need to do a compaction, or if not, whether | |
1834 // we need to start the mark-sweep from scratch. | |
1835 bool should_compact = false; | |
1836 bool should_start_over = false; | |
1837 decide_foreground_collection_type(clear_all_soft_refs, | |
1838 &should_compact, &should_start_over); | |
1839 | |
1840 NOT_PRODUCT( | |
1841 if (RotateCMSCollectionTypes) { | |
1842 if (_cmsGen->debug_collection_type() == | |
1843 ConcurrentMarkSweepGeneration::MSC_foreground_collection_type) { | |
1844 should_compact = true; | |
1845 } else if (_cmsGen->debug_collection_type() == | |
1846 ConcurrentMarkSweepGeneration::MS_foreground_collection_type) { | |
1847 should_compact = false; | |
1848 } | |
1849 } | |
1850 ) | |
1851 | |
1852 if (PrintGCDetails && first_state > Idling) { | |
1853 GCCause::Cause cause = GenCollectedHeap::heap()->gc_cause(); | |
1854 if (GCCause::is_user_requested_gc(cause) || | |
1855 GCCause::is_serviceability_requested_gc(cause)) { | |
1856 gclog_or_tty->print(" (concurrent mode interrupted)"); | |
1857 } else { | |
1858 gclog_or_tty->print(" (concurrent mode failure)"); | |
1859 } | |
1860 } | |
1861 | |
1862 if (should_compact) { | |
1863 // If the collection is being acquired from the background | |
1864 // collector, there may be references on the discovered | |
1865 // references lists that have NULL referents (being those | |
1866 // that were concurrently cleared by a mutator) or | |
1867 // that are no longer active (having been enqueued concurrently | |
1868 // by the mutator). | |
1869 // Scrub the list of those references because Mark-Sweep-Compact | |
1870 // code assumes referents are not NULL and that all discovered | |
1871 // Reference objects are active. | |
1872 ref_processor()->clean_up_discovered_references(); | |
1873 | |
1874 do_compaction_work(clear_all_soft_refs); | |
1875 | |
1876 // Has the GC time limit been exceeded? | |
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1877 DefNewGeneration* young_gen = _young_gen->as_DefNewGeneration(); |
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1878 size_t max_eden_size = young_gen->max_capacity() - |
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1879 young_gen->to()->capacity() - |
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1880 young_gen->from()->capacity(); |
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1881 GenCollectedHeap* gch = GenCollectedHeap::heap(); |
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1882 GCCause::Cause gc_cause = gch->gc_cause(); |
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1883 size_policy()->check_gc_overhead_limit(_young_gen->used(), |
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1884 young_gen->eden()->used(), |
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1885 _cmsGen->max_capacity(), |
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1886 max_eden_size, |
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1887 full, |
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1888 gc_cause, |
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1889 gch->collector_policy()); |
0 | 1890 } else { |
1891 do_mark_sweep_work(clear_all_soft_refs, first_state, | |
1892 should_start_over); | |
1893 } | |
1894 // Reset the expansion cause, now that we just completed | |
1895 // a collection cycle. | |
1896 clear_expansion_cause(); | |
1897 _foregroundGCIsActive = false; | |
1898 return; | |
1899 } | |
1900 | |
1901 // Resize the perm generation and the tenured generation | |
1902 // after obtaining the free list locks for the | |
1903 // two generations. | |
1904 void CMSCollector::compute_new_size() { | |
1905 assert_locked_or_safepoint(Heap_lock); | |
1906 FreelistLocker z(this); | |
1907 _permGen->compute_new_size(); | |
1908 _cmsGen->compute_new_size(); | |
1909 } | |
1910 | |
1911 // A work method used by foreground collection to determine | |
1912 // what type of collection (compacting or not, continuing or fresh) | |
1913 // it should do. | |
1914 // NOTE: the intent is to make UseCMSCompactAtFullCollection | |
1915 // and CMSCompactWhenClearAllSoftRefs the default in the future | |
1916 // and do away with the flags after a suitable period. | |
1917 void CMSCollector::decide_foreground_collection_type( | |
1918 bool clear_all_soft_refs, bool* should_compact, | |
1919 bool* should_start_over) { | |
1920 // Normally, we'll compact only if the UseCMSCompactAtFullCollection | |
1921 // flag is set, and we have either requested a System.gc() or | |
1922 // the number of full gc's since the last concurrent cycle | |
1923 // has exceeded the threshold set by CMSFullGCsBeforeCompaction, | |
1924 // or if an incremental collection has failed | |
1925 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
1926 assert(gch->collector_policy()->is_two_generation_policy(), | |
1927 "You may want to check the correctness of the following"); | |
1928 // Inform cms gen if this was due to partial collection failing. | |
1929 // The CMS gen may use this fact to determine its expansion policy. | |
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1930 if (gch->incremental_collection_will_fail(false /* don't consult_young */)) { |
0 | 1931 assert(!_cmsGen->incremental_collection_failed(), |
1932 "Should have been noticed, reacted to and cleared"); | |
1933 _cmsGen->set_incremental_collection_failed(); | |
1934 } | |
1935 *should_compact = | |
1936 UseCMSCompactAtFullCollection && | |
1937 ((_full_gcs_since_conc_gc >= CMSFullGCsBeforeCompaction) || | |
1938 GCCause::is_user_requested_gc(gch->gc_cause()) || | |
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1939 gch->incremental_collection_will_fail(true /* consult_young */)); |
0 | 1940 *should_start_over = false; |
1941 if (clear_all_soft_refs && !*should_compact) { | |
1942 // We are about to do a last ditch collection attempt | |
1943 // so it would normally make sense to do a compaction | |
1944 // to reclaim as much space as possible. | |
1945 if (CMSCompactWhenClearAllSoftRefs) { | |
1946 // Default: The rationale is that in this case either | |
1947 // we are past the final marking phase, in which case | |
1948 // we'd have to start over, or so little has been done | |
1949 // that there's little point in saving that work. Compaction | |
1950 // appears to be the sensible choice in either case. | |
1951 *should_compact = true; | |
1952 } else { | |
1953 // We have been asked to clear all soft refs, but not to | |
1954 // compact. Make sure that we aren't past the final checkpoint | |
1955 // phase, for that is where we process soft refs. If we are already | |
1956 // past that phase, we'll need to redo the refs discovery phase and | |
1957 // if necessary clear soft refs that weren't previously | |
1958 // cleared. We do so by remembering the phase in which | |
1959 // we came in, and if we are past the refs processing | |
1960 // phase, we'll choose to just redo the mark-sweep | |
1961 // collection from scratch. | |
1962 if (_collectorState > FinalMarking) { | |
1963 // We are past the refs processing phase; | |
1964 // start over and do a fresh synchronous CMS cycle | |
1965 _collectorState = Resetting; // skip to reset to start new cycle | |
1966 reset(false /* == !asynch */); | |
1967 *should_start_over = true; | |
1968 } // else we can continue a possibly ongoing current cycle | |
1969 } | |
1970 } | |
1971 } | |
1972 | |
1973 // A work method used by the foreground collector to do | |
1974 // a mark-sweep-compact. | |
1975 void CMSCollector::do_compaction_work(bool clear_all_soft_refs) { | |
1976 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
1977 TraceTime t("CMS:MSC ", PrintGCDetails && Verbose, true, gclog_or_tty); | |
1978 if (PrintGC && Verbose && !(GCCause::is_user_requested_gc(gch->gc_cause()))) { | |
1979 gclog_or_tty->print_cr("Compact ConcurrentMarkSweepGeneration after %d " | |
1980 "collections passed to foreground collector", _full_gcs_since_conc_gc); | |
1981 } | |
1982 | |
1983 // Sample collection interval time and reset for collection pause. | |
1984 if (UseAdaptiveSizePolicy) { | |
1985 size_policy()->msc_collection_begin(); | |
1986 } | |
1987 | |
1988 // Temporarily widen the span of the weak reference processing to | |
1989 // the entire heap. | |
1990 MemRegion new_span(GenCollectedHeap::heap()->reserved_region()); | |
1991 ReferenceProcessorSpanMutator x(ref_processor(), new_span); | |
1992 | |
1993 // Temporarily, clear the "is_alive_non_header" field of the | |
1994 // reference processor. | |
1995 ReferenceProcessorIsAliveMutator y(ref_processor(), NULL); | |
1996 | |
1997 // Temporarily make reference _processing_ single threaded (non-MT). | |
1998 ReferenceProcessorMTProcMutator z(ref_processor(), false); | |
1999 | |
2000 // Temporarily make refs discovery atomic | |
2001 ReferenceProcessorAtomicMutator w(ref_processor(), true); | |
2002 | |
2003 ref_processor()->set_enqueuing_is_done(false); | |
2004 ref_processor()->enable_discovery(); | |
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2005 ref_processor()->setup_policy(clear_all_soft_refs); |
0 | 2006 // If an asynchronous collection finishes, the _modUnionTable is |
2007 // all clear. If we are assuming the collection from an asynchronous | |
2008 // collection, clear the _modUnionTable. | |
2009 assert(_collectorState != Idling || _modUnionTable.isAllClear(), | |
2010 "_modUnionTable should be clear if the baton was not passed"); | |
2011 _modUnionTable.clear_all(); | |
2012 | |
2013 // We must adjust the allocation statistics being maintained | |
2014 // in the free list space. We do so by reading and clearing | |
2015 // the sweep timer and updating the block flux rate estimates below. | |
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2016 assert(!_intra_sweep_timer.is_active(), "_intra_sweep_timer should be inactive"); |
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2017 if (_inter_sweep_timer.is_active()) { |
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2018 _inter_sweep_timer.stop(); |
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2019 // Note that we do not use this sample to update the _inter_sweep_estimate. |
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2020 _cmsGen->cmsSpace()->beginSweepFLCensus((float)(_inter_sweep_timer.seconds()), |
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2021 _inter_sweep_estimate.padded_average(), |
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2022 _intra_sweep_estimate.padded_average()); |
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2023 } |
0 | 2024 |
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2025 { |
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2026 TraceCMSMemoryManagerStats(); |
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2027 } |
0 | 2028 GenMarkSweep::invoke_at_safepoint(_cmsGen->level(), |
2029 ref_processor(), clear_all_soft_refs); | |
2030 #ifdef ASSERT | |
2031 CompactibleFreeListSpace* cms_space = _cmsGen->cmsSpace(); | |
2032 size_t free_size = cms_space->free(); | |
2033 assert(free_size == | |
2034 pointer_delta(cms_space->end(), cms_space->compaction_top()) | |
2035 * HeapWordSize, | |
2036 "All the free space should be compacted into one chunk at top"); | |
2037 assert(cms_space->dictionary()->totalChunkSize( | |
2038 debug_only(cms_space->freelistLock())) == 0 || | |
2039 cms_space->totalSizeInIndexedFreeLists() == 0, | |
2040 "All the free space should be in a single chunk"); | |
2041 size_t num = cms_space->totalCount(); | |
2042 assert((free_size == 0 && num == 0) || | |
2043 (free_size > 0 && (num == 1 || num == 2)), | |
2044 "There should be at most 2 free chunks after compaction"); | |
2045 #endif // ASSERT | |
2046 _collectorState = Resetting; | |
2047 assert(_restart_addr == NULL, | |
2048 "Should have been NULL'd before baton was passed"); | |
2049 reset(false /* == !asynch */); | |
2050 _cmsGen->reset_after_compaction(); | |
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2051 _concurrent_cycles_since_last_unload = 0; |
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2052 |
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2053 if (verifying() && !should_unload_classes()) { |
0 | 2054 perm_gen_verify_bit_map()->clear_all(); |
2055 } | |
2056 | |
2057 // Clear any data recorded in the PLAB chunk arrays. | |
2058 if (_survivor_plab_array != NULL) { | |
2059 reset_survivor_plab_arrays(); | |
2060 } | |
2061 | |
2062 // Adjust the per-size allocation stats for the next epoch. | |
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2063 _cmsGen->cmsSpace()->endSweepFLCensus(sweep_count() /* fake */); |
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2064 // Restart the "inter sweep timer" for the next epoch. |
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2065 _inter_sweep_timer.reset(); |
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2066 _inter_sweep_timer.start(); |
0 | 2067 |
2068 // Sample collection pause time and reset for collection interval. | |
2069 if (UseAdaptiveSizePolicy) { | |
2070 size_policy()->msc_collection_end(gch->gc_cause()); | |
2071 } | |
2072 | |
2073 // For a mark-sweep-compact, compute_new_size() will be called | |
2074 // in the heap's do_collection() method. | |
2075 } | |
2076 | |
2077 // A work method used by the foreground collector to do | |
2078 // a mark-sweep, after taking over from a possibly on-going | |
2079 // concurrent mark-sweep collection. | |
2080 void CMSCollector::do_mark_sweep_work(bool clear_all_soft_refs, | |
2081 CollectorState first_state, bool should_start_over) { | |
2082 if (PrintGC && Verbose) { | |
2083 gclog_or_tty->print_cr("Pass concurrent collection to foreground " | |
2084 "collector with count %d", | |
2085 _full_gcs_since_conc_gc); | |
2086 } | |
2087 switch (_collectorState) { | |
2088 case Idling: | |
2089 if (first_state == Idling || should_start_over) { | |
2090 // The background GC was not active, or should | |
2091 // restarted from scratch; start the cycle. | |
2092 _collectorState = InitialMarking; | |
2093 } | |
2094 // If first_state was not Idling, then a background GC | |
2095 // was in progress and has now finished. No need to do it | |
2096 // again. Leave the state as Idling. | |
2097 break; | |
2098 case Precleaning: | |
2099 // In the foreground case don't do the precleaning since | |
2100 // it is not done concurrently and there is extra work | |
2101 // required. | |
2102 _collectorState = FinalMarking; | |
2103 } | |
2104 if (PrintGCDetails && | |
2105 (_collectorState > Idling || | |
2106 !GCCause::is_user_requested_gc(GenCollectedHeap::heap()->gc_cause()))) { | |
2107 gclog_or_tty->print(" (concurrent mode failure)"); | |
2108 } | |
2109 collect_in_foreground(clear_all_soft_refs); | |
2110 | |
2111 // For a mark-sweep, compute_new_size() will be called | |
2112 // in the heap's do_collection() method. | |
2113 } | |
2114 | |
2115 | |
2116 void CMSCollector::getFreelistLocks() const { | |
2117 // Get locks for all free lists in all generations that this | |
2118 // collector is responsible for | |
2119 _cmsGen->freelistLock()->lock_without_safepoint_check(); | |
2120 _permGen->freelistLock()->lock_without_safepoint_check(); | |
2121 } | |
2122 | |
2123 void CMSCollector::releaseFreelistLocks() const { | |
2124 // Release locks for all free lists in all generations that this | |
2125 // collector is responsible for | |
2126 _cmsGen->freelistLock()->unlock(); | |
2127 _permGen->freelistLock()->unlock(); | |
2128 } | |
2129 | |
2130 bool CMSCollector::haveFreelistLocks() const { | |
2131 // Check locks for all free lists in all generations that this | |
2132 // collector is responsible for | |
2133 assert_lock_strong(_cmsGen->freelistLock()); | |
2134 assert_lock_strong(_permGen->freelistLock()); | |
2135 PRODUCT_ONLY(ShouldNotReachHere()); | |
2136 return true; | |
2137 } | |
2138 | |
2139 // A utility class that is used by the CMS collector to | |
2140 // temporarily "release" the foreground collector from its | |
2141 // usual obligation to wait for the background collector to | |
2142 // complete an ongoing phase before proceeding. | |
2143 class ReleaseForegroundGC: public StackObj { | |
2144 private: | |
2145 CMSCollector* _c; | |
2146 public: | |
2147 ReleaseForegroundGC(CMSCollector* c) : _c(c) { | |
2148 assert(_c->_foregroundGCShouldWait, "Else should not need to call"); | |
2149 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
2150 // allow a potentially blocked foreground collector to proceed | |
2151 _c->_foregroundGCShouldWait = false; | |
2152 if (_c->_foregroundGCIsActive) { | |
2153 CGC_lock->notify(); | |
2154 } | |
2155 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
2156 "Possible deadlock"); | |
2157 } | |
2158 | |
2159 ~ReleaseForegroundGC() { | |
2160 assert(!_c->_foregroundGCShouldWait, "Usage protocol violation?"); | |
2161 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
2162 _c->_foregroundGCShouldWait = true; | |
2163 } | |
2164 }; | |
2165 | |
2166 // There are separate collect_in_background and collect_in_foreground because of | |
2167 // the different locking requirements of the background collector and the | |
2168 // foreground collector. There was originally an attempt to share | |
2169 // one "collect" method between the background collector and the foreground | |
2170 // collector but the if-then-else required made it cleaner to have | |
2171 // separate methods. | |
2172 void CMSCollector::collect_in_background(bool clear_all_soft_refs) { | |
2173 assert(Thread::current()->is_ConcurrentGC_thread(), | |
2174 "A CMS asynchronous collection is only allowed on a CMS thread."); | |
2175 | |
2176 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
2177 { | |
2178 bool safepoint_check = Mutex::_no_safepoint_check_flag; | |
2179 MutexLockerEx hl(Heap_lock, safepoint_check); | |
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2180 FreelistLocker fll(this); |
0 | 2181 MutexLockerEx x(CGC_lock, safepoint_check); |
2182 if (_foregroundGCIsActive || !UseAsyncConcMarkSweepGC) { | |
2183 // The foreground collector is active or we're | |
2184 // not using asynchronous collections. Skip this | |
2185 // background collection. | |
2186 assert(!_foregroundGCShouldWait, "Should be clear"); | |
2187 return; | |
2188 } else { | |
2189 assert(_collectorState == Idling, "Should be idling before start."); | |
2190 _collectorState = InitialMarking; | |
2191 // Reset the expansion cause, now that we are about to begin | |
2192 // a new cycle. | |
2193 clear_expansion_cause(); | |
2194 } | |
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2195 // Decide if we want to enable class unloading as part of the |
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2196 // ensuing concurrent GC cycle. |
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2197 update_should_unload_classes(); |
0 | 2198 _full_gc_requested = false; // acks all outstanding full gc requests |
2199 // Signal that we are about to start a collection | |
2200 gch->increment_total_full_collections(); // ... starting a collection cycle | |
2201 _collection_count_start = gch->total_full_collections(); | |
2202 } | |
2203 | |
2204 // Used for PrintGC | |
2205 size_t prev_used; | |
2206 if (PrintGC && Verbose) { | |
2207 prev_used = _cmsGen->used(); // XXXPERM | |
2208 } | |
2209 | |
2210 // The change of the collection state is normally done at this level; | |
2211 // the exceptions are phases that are executed while the world is | |
2212 // stopped. For those phases the change of state is done while the | |
2213 // world is stopped. For baton passing purposes this allows the | |
2214 // background collector to finish the phase and change state atomically. | |
2215 // The foreground collector cannot wait on a phase that is done | |
2216 // while the world is stopped because the foreground collector already | |
2217 // has the world stopped and would deadlock. | |
2218 while (_collectorState != Idling) { | |
2219 if (TraceCMSState) { | |
2220 gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " in CMS state %d", | |
2221 Thread::current(), _collectorState); | |
2222 } | |
2223 // The foreground collector | |
2224 // holds the Heap_lock throughout its collection. | |
2225 // holds the CMS token (but not the lock) | |
2226 // except while it is waiting for the background collector to yield. | |
2227 // | |
2228 // The foreground collector should be blocked (not for long) | |
2229 // if the background collector is about to start a phase | |
2230 // executed with world stopped. If the background | |
2231 // collector has already started such a phase, the | |
2232 // foreground collector is blocked waiting for the | |
2233 // Heap_lock. The stop-world phases (InitialMarking and FinalMarking) | |
2234 // are executed in the VM thread. | |
2235 // | |
2236 // The locking order is | |
2237 // PendingListLock (PLL) -- if applicable (FinalMarking) | |
2238 // Heap_lock (both this & PLL locked in VM_CMS_Operation::prologue()) | |
2239 // CMS token (claimed in | |
2240 // stop_world_and_do() --> | |
2241 // safepoint_synchronize() --> | |
2242 // CMSThread::synchronize()) | |
2243 | |
2244 { | |
2245 // Check if the FG collector wants us to yield. | |
2246 CMSTokenSync x(true); // is cms thread | |
2247 if (waitForForegroundGC()) { | |
2248 // We yielded to a foreground GC, nothing more to be | |
2249 // done this round. | |
2250 assert(_foregroundGCShouldWait == false, "We set it to false in " | |
2251 "waitForForegroundGC()"); | |
2252 if (TraceCMSState) { | |
2253 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT | |
2254 " exiting collection CMS state %d", | |
2255 Thread::current(), _collectorState); | |
2256 } | |
2257 return; | |
2258 } else { | |
2259 // The background collector can run but check to see if the | |
2260 // foreground collector has done a collection while the | |
2261 // background collector was waiting to get the CGC_lock | |
2262 // above. If yes, break so that _foregroundGCShouldWait | |
2263 // is cleared before returning. | |
2264 if (_collectorState == Idling) { | |
2265 break; | |
2266 } | |
2267 } | |
2268 } | |
2269 | |
2270 assert(_foregroundGCShouldWait, "Foreground collector, if active, " | |
2271 "should be waiting"); | |
2272 | |
2273 switch (_collectorState) { | |
2274 case InitialMarking: | |
2275 { | |
2276 ReleaseForegroundGC x(this); | |
2277 stats().record_cms_begin(); | |
2278 | |
2279 VM_CMS_Initial_Mark initial_mark_op(this); | |
2280 VMThread::execute(&initial_mark_op); | |
2281 } | |
2282 // The collector state may be any legal state at this point | |
2283 // since the background collector may have yielded to the | |
2284 // foreground collector. | |
2285 break; | |
2286 case Marking: | |
2287 // initial marking in checkpointRootsInitialWork has been completed | |
2288 if (markFromRoots(true)) { // we were successful | |
2289 assert(_collectorState == Precleaning, "Collector state should " | |
2290 "have changed"); | |
2291 } else { | |
2292 assert(_foregroundGCIsActive, "Internal state inconsistency"); | |
2293 } | |
2294 break; | |
2295 case Precleaning: | |
2296 if (UseAdaptiveSizePolicy) { | |
2297 size_policy()->concurrent_precleaning_begin(); | |
2298 } | |
2299 // marking from roots in markFromRoots has been completed | |
2300 preclean(); | |
2301 if (UseAdaptiveSizePolicy) { | |
2302 size_policy()->concurrent_precleaning_end(); | |
2303 } | |
2304 assert(_collectorState == AbortablePreclean || | |
2305 _collectorState == FinalMarking, | |
2306 "Collector state should have changed"); | |
2307 break; | |
2308 case AbortablePreclean: | |
2309 if (UseAdaptiveSizePolicy) { | |
2310 size_policy()->concurrent_phases_resume(); | |
2311 } | |
2312 abortable_preclean(); | |
2313 if (UseAdaptiveSizePolicy) { | |
2314 size_policy()->concurrent_precleaning_end(); | |
2315 } | |
2316 assert(_collectorState == FinalMarking, "Collector state should " | |
2317 "have changed"); | |
2318 break; | |
2319 case FinalMarking: | |
2320 { | |
2321 ReleaseForegroundGC x(this); | |
2322 | |
2323 VM_CMS_Final_Remark final_remark_op(this); | |
2324 VMThread::execute(&final_remark_op); | |
935 | 2325 } |
0 | 2326 assert(_foregroundGCShouldWait, "block post-condition"); |
2327 break; | |
2328 case Sweeping: | |
2329 if (UseAdaptiveSizePolicy) { | |
2330 size_policy()->concurrent_sweeping_begin(); | |
2331 } | |
2332 // final marking in checkpointRootsFinal has been completed | |
2333 sweep(true); | |
2334 assert(_collectorState == Resizing, "Collector state change " | |
2335 "to Resizing must be done under the free_list_lock"); | |
2336 _full_gcs_since_conc_gc = 0; | |
2337 | |
2338 // Stop the timers for adaptive size policy for the concurrent phases | |
2339 if (UseAdaptiveSizePolicy) { | |
2340 size_policy()->concurrent_sweeping_end(); | |
2341 size_policy()->concurrent_phases_end(gch->gc_cause(), | |
2342 gch->prev_gen(_cmsGen)->capacity(), | |
2343 _cmsGen->free()); | |
2344 } | |
2345 | |
2346 case Resizing: { | |
2347 // Sweeping has been completed... | |
2348 // At this point the background collection has completed. | |
2349 // Don't move the call to compute_new_size() down | |
2350 // into code that might be executed if the background | |
2351 // collection was preempted. | |
2352 { | |
2353 ReleaseForegroundGC x(this); // unblock FG collection | |
2354 MutexLockerEx y(Heap_lock, Mutex::_no_safepoint_check_flag); | |
2355 CMSTokenSync z(true); // not strictly needed. | |
2356 if (_collectorState == Resizing) { | |
2357 compute_new_size(); | |
2358 _collectorState = Resetting; | |
2359 } else { | |
2360 assert(_collectorState == Idling, "The state should only change" | |
2361 " because the foreground collector has finished the collection"); | |
2362 } | |
2363 } | |
2364 break; | |
2365 } | |
2366 case Resetting: | |
2367 // CMS heap resizing has been completed | |
2368 reset(true); | |
2369 assert(_collectorState == Idling, "Collector state should " | |
2370 "have changed"); | |
2371 stats().record_cms_end(); | |
2372 // Don't move the concurrent_phases_end() and compute_new_size() | |
2373 // calls to here because a preempted background collection | |
2374 // has it's state set to "Resetting". | |
2375 break; | |
2376 case Idling: | |
2377 default: | |
2378 ShouldNotReachHere(); | |
2379 break; | |
2380 } | |
2381 if (TraceCMSState) { | |
2382 gclog_or_tty->print_cr(" Thread " INTPTR_FORMAT " done - next CMS state %d", | |
2383 Thread::current(), _collectorState); | |
2384 } | |
2385 assert(_foregroundGCShouldWait, "block post-condition"); | |
2386 } | |
2387 | |
2388 // Should this be in gc_epilogue? | |
2389 collector_policy()->counters()->update_counters(); | |
2390 | |
2391 { | |
2392 // Clear _foregroundGCShouldWait and, in the event that the | |
2393 // foreground collector is waiting, notify it, before | |
2394 // returning. | |
2395 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
2396 _foregroundGCShouldWait = false; | |
2397 if (_foregroundGCIsActive) { | |
2398 CGC_lock->notify(); | |
2399 } | |
2400 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
2401 "Possible deadlock"); | |
2402 } | |
2403 if (TraceCMSState) { | |
2404 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT | |
2405 " exiting collection CMS state %d", | |
2406 Thread::current(), _collectorState); | |
2407 } | |
2408 if (PrintGC && Verbose) { | |
2409 _cmsGen->print_heap_change(prev_used); | |
2410 } | |
2411 } | |
2412 | |
2413 void CMSCollector::collect_in_foreground(bool clear_all_soft_refs) { | |
2414 assert(_foregroundGCIsActive && !_foregroundGCShouldWait, | |
2415 "Foreground collector should be waiting, not executing"); | |
2416 assert(Thread::current()->is_VM_thread(), "A foreground collection" | |
2417 "may only be done by the VM Thread with the world stopped"); | |
2418 assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(), | |
2419 "VM thread should have CMS token"); | |
2420 | |
2421 NOT_PRODUCT(TraceTime t("CMS:MS (foreground) ", PrintGCDetails && Verbose, | |
2422 true, gclog_or_tty);) | |
2423 if (UseAdaptiveSizePolicy) { | |
2424 size_policy()->ms_collection_begin(); | |
2425 } | |
2426 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact); | |
2427 | |
2428 HandleMark hm; // Discard invalid handles created during verification | |
2429 | |
2430 if (VerifyBeforeGC && | |
2431 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
2432 Universe::verify(true); | |
2433 } | |
2434 | |
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2435 // Snapshot the soft reference policy to be used in this collection cycle. |
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2436 ref_processor()->setup_policy(clear_all_soft_refs); |
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2437 |
0 | 2438 bool init_mark_was_synchronous = false; // until proven otherwise |
2439 while (_collectorState != Idling) { | |
2440 if (TraceCMSState) { | |
2441 gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " in CMS state %d", | |
2442 Thread::current(), _collectorState); | |
2443 } | |
2444 switch (_collectorState) { | |
2445 case InitialMarking: | |
2446 init_mark_was_synchronous = true; // fact to be exploited in re-mark | |
2447 checkpointRootsInitial(false); | |
2448 assert(_collectorState == Marking, "Collector state should have changed" | |
2449 " within checkpointRootsInitial()"); | |
2450 break; | |
2451 case Marking: | |
2452 // initial marking in checkpointRootsInitialWork has been completed | |
2453 if (VerifyDuringGC && | |
2454 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
2455 gclog_or_tty->print("Verify before initial mark: "); | |
2456 Universe::verify(true); | |
2457 } | |
2458 { | |
2459 bool res = markFromRoots(false); | |
2460 assert(res && _collectorState == FinalMarking, "Collector state should " | |
2461 "have changed"); | |
2462 break; | |
2463 } | |
2464 case FinalMarking: | |
2465 if (VerifyDuringGC && | |
2466 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
2467 gclog_or_tty->print("Verify before re-mark: "); | |
2468 Universe::verify(true); | |
2469 } | |
2470 checkpointRootsFinal(false, clear_all_soft_refs, | |
2471 init_mark_was_synchronous); | |
2472 assert(_collectorState == Sweeping, "Collector state should not " | |
2473 "have changed within checkpointRootsFinal()"); | |
2474 break; | |
2475 case Sweeping: | |
2476 // final marking in checkpointRootsFinal has been completed | |
2477 if (VerifyDuringGC && | |
2478 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
2479 gclog_or_tty->print("Verify before sweep: "); | |
2480 Universe::verify(true); | |
2481 } | |
2482 sweep(false); | |
2483 assert(_collectorState == Resizing, "Incorrect state"); | |
2484 break; | |
2485 case Resizing: { | |
2486 // Sweeping has been completed; the actual resize in this case | |
2487 // is done separately; nothing to be done in this state. | |
2488 _collectorState = Resetting; | |
2489 break; | |
2490 } | |
2491 case Resetting: | |
2492 // The heap has been resized. | |
2493 if (VerifyDuringGC && | |
2494 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
2495 gclog_or_tty->print("Verify before reset: "); | |
2496 Universe::verify(true); | |
2497 } | |
2498 reset(false); | |
2499 assert(_collectorState == Idling, "Collector state should " | |
2500 "have changed"); | |
2501 break; | |
2502 case Precleaning: | |
2503 case AbortablePreclean: | |
2504 // Elide the preclean phase | |
2505 _collectorState = FinalMarking; | |
2506 break; | |
2507 default: | |
2508 ShouldNotReachHere(); | |
2509 } | |
2510 if (TraceCMSState) { | |
2511 gclog_or_tty->print_cr(" Thread " INTPTR_FORMAT " done - next CMS state %d", | |
2512 Thread::current(), _collectorState); | |
2513 } | |
2514 } | |
2515 | |
2516 if (UseAdaptiveSizePolicy) { | |
2517 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
2518 size_policy()->ms_collection_end(gch->gc_cause()); | |
2519 } | |
2520 | |
2521 if (VerifyAfterGC && | |
2522 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
2523 Universe::verify(true); | |
2524 } | |
2525 if (TraceCMSState) { | |
2526 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT | |
2527 " exiting collection CMS state %d", | |
2528 Thread::current(), _collectorState); | |
2529 } | |
2530 } | |
2531 | |
2532 bool CMSCollector::waitForForegroundGC() { | |
2533 bool res = false; | |
2534 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
2535 "CMS thread should have CMS token"); | |
2536 // Block the foreground collector until the | |
2537 // background collectors decides whether to | |
2538 // yield. | |
2539 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
2540 _foregroundGCShouldWait = true; | |
2541 if (_foregroundGCIsActive) { | |
2542 // The background collector yields to the | |
2543 // foreground collector and returns a value | |
2544 // indicating that it has yielded. The foreground | |
2545 // collector can proceed. | |
2546 res = true; | |
2547 _foregroundGCShouldWait = false; | |
2548 ConcurrentMarkSweepThread::clear_CMS_flag( | |
2549 ConcurrentMarkSweepThread::CMS_cms_has_token); | |
2550 ConcurrentMarkSweepThread::set_CMS_flag( | |
2551 ConcurrentMarkSweepThread::CMS_cms_wants_token); | |
2552 // Get a possibly blocked foreground thread going | |
2553 CGC_lock->notify(); | |
2554 if (TraceCMSState) { | |
2555 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT " waiting at CMS state %d", | |
2556 Thread::current(), _collectorState); | |
2557 } | |
2558 while (_foregroundGCIsActive) { | |
2559 CGC_lock->wait(Mutex::_no_safepoint_check_flag); | |
2560 } | |
2561 ConcurrentMarkSweepThread::set_CMS_flag( | |
2562 ConcurrentMarkSweepThread::CMS_cms_has_token); | |
2563 ConcurrentMarkSweepThread::clear_CMS_flag( | |
2564 ConcurrentMarkSweepThread::CMS_cms_wants_token); | |
2565 } | |
2566 if (TraceCMSState) { | |
2567 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT " continuing at CMS state %d", | |
2568 Thread::current(), _collectorState); | |
2569 } | |
2570 return res; | |
2571 } | |
2572 | |
2573 // Because of the need to lock the free lists and other structures in | |
2574 // the collector, common to all the generations that the collector is | |
2575 // collecting, we need the gc_prologues of individual CMS generations | |
2576 // delegate to their collector. It may have been simpler had the | |
2577 // current infrastructure allowed one to call a prologue on a | |
2578 // collector. In the absence of that we have the generation's | |
2579 // prologue delegate to the collector, which delegates back | |
2580 // some "local" work to a worker method in the individual generations | |
2581 // that it's responsible for collecting, while itself doing any | |
2582 // work common to all generations it's responsible for. A similar | |
2583 // comment applies to the gc_epilogue()'s. | |
2584 // The role of the varaible _between_prologue_and_epilogue is to | |
2585 // enforce the invocation protocol. | |
2586 void CMSCollector::gc_prologue(bool full) { | |
2587 // Call gc_prologue_work() for each CMSGen and PermGen that | |
2588 // we are responsible for. | |
2589 | |
2590 // The following locking discipline assumes that we are only called | |
2591 // when the world is stopped. | |
2592 assert(SafepointSynchronize::is_at_safepoint(), "world is stopped assumption"); | |
2593 | |
2594 // The CMSCollector prologue must call the gc_prologues for the | |
2595 // "generations" (including PermGen if any) that it's responsible | |
2596 // for. | |
2597 | |
2598 assert( Thread::current()->is_VM_thread() | |
2599 || ( CMSScavengeBeforeRemark | |
2600 && Thread::current()->is_ConcurrentGC_thread()), | |
2601 "Incorrect thread type for prologue execution"); | |
2602 | |
2603 if (_between_prologue_and_epilogue) { | |
2604 // We have already been invoked; this is a gc_prologue delegation | |
2605 // from yet another CMS generation that we are responsible for, just | |
2606 // ignore it since all relevant work has already been done. | |
2607 return; | |
2608 } | |
2609 | |
2610 // set a bit saying prologue has been called; cleared in epilogue | |
2611 _between_prologue_and_epilogue = true; | |
2612 // Claim locks for common data structures, then call gc_prologue_work() | |
2613 // for each CMSGen and PermGen that we are responsible for. | |
2614 | |
2615 getFreelistLocks(); // gets free list locks on constituent spaces | |
2616 bitMapLock()->lock_without_safepoint_check(); | |
2617 | |
2618 // Should call gc_prologue_work() for all cms gens we are responsible for | |
2619 bool registerClosure = _collectorState >= Marking | |
2620 && _collectorState < Sweeping; | |
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2621 ModUnionClosure* muc = CollectedHeap::use_parallel_gc_threads() ? |
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2622 &_modUnionClosurePar |
0 | 2623 : &_modUnionClosure; |
2624 _cmsGen->gc_prologue_work(full, registerClosure, muc); | |
2625 _permGen->gc_prologue_work(full, registerClosure, muc); | |
2626 | |
2627 if (!full) { | |
2628 stats().record_gc0_begin(); | |
2629 } | |
2630 } | |
2631 | |
2632 void ConcurrentMarkSweepGeneration::gc_prologue(bool full) { | |
2633 // Delegate to CMScollector which knows how to coordinate between | |
2634 // this and any other CMS generations that it is responsible for | |
2635 // collecting. | |
2636 collector()->gc_prologue(full); | |
2637 } | |
2638 | |
2639 // This is a "private" interface for use by this generation's CMSCollector. | |
2640 // Not to be called directly by any other entity (for instance, | |
2641 // GenCollectedHeap, which calls the "public" gc_prologue method above). | |
2642 void ConcurrentMarkSweepGeneration::gc_prologue_work(bool full, | |
2643 bool registerClosure, ModUnionClosure* modUnionClosure) { | |
2644 assert(!incremental_collection_failed(), "Shouldn't be set yet"); | |
2645 assert(cmsSpace()->preconsumptionDirtyCardClosure() == NULL, | |
2646 "Should be NULL"); | |
2647 if (registerClosure) { | |
2648 cmsSpace()->setPreconsumptionDirtyCardClosure(modUnionClosure); | |
2649 } | |
2650 cmsSpace()->gc_prologue(); | |
2651 // Clear stat counters | |
2652 NOT_PRODUCT( | |
2653 assert(_numObjectsPromoted == 0, "check"); | |
2654 assert(_numWordsPromoted == 0, "check"); | |
2655 if (Verbose && PrintGC) { | |
2656 gclog_or_tty->print("Allocated "SIZE_FORMAT" objects, " | |
2657 SIZE_FORMAT" bytes concurrently", | |
2658 _numObjectsAllocated, _numWordsAllocated*sizeof(HeapWord)); | |
2659 } | |
2660 _numObjectsAllocated = 0; | |
2661 _numWordsAllocated = 0; | |
2662 ) | |
2663 } | |
2664 | |
2665 void CMSCollector::gc_epilogue(bool full) { | |
2666 // The following locking discipline assumes that we are only called | |
2667 // when the world is stopped. | |
2668 assert(SafepointSynchronize::is_at_safepoint(), | |
2669 "world is stopped assumption"); | |
2670 | |
2671 // Currently the CMS epilogue (see CompactibleFreeListSpace) merely checks | |
2672 // if linear allocation blocks need to be appropriately marked to allow the | |
2673 // the blocks to be parsable. We also check here whether we need to nudge the | |
2674 // CMS collector thread to start a new cycle (if it's not already active). | |
2675 assert( Thread::current()->is_VM_thread() | |
2676 || ( CMSScavengeBeforeRemark | |
2677 && Thread::current()->is_ConcurrentGC_thread()), | |
2678 "Incorrect thread type for epilogue execution"); | |
2679 | |
2680 if (!_between_prologue_and_epilogue) { | |
2681 // We have already been invoked; this is a gc_epilogue delegation | |
2682 // from yet another CMS generation that we are responsible for, just | |
2683 // ignore it since all relevant work has already been done. | |
2684 return; | |
2685 } | |
2686 assert(haveFreelistLocks(), "must have freelist locks"); | |
2687 assert_lock_strong(bitMapLock()); | |
2688 | |
2689 _cmsGen->gc_epilogue_work(full); | |
2690 _permGen->gc_epilogue_work(full); | |
2691 | |
2692 if (_collectorState == AbortablePreclean || _collectorState == Precleaning) { | |
2693 // in case sampling was not already enabled, enable it | |
2694 _start_sampling = true; | |
2695 } | |
2696 // reset _eden_chunk_array so sampling starts afresh | |
2697 _eden_chunk_index = 0; | |
2698 | |
2699 size_t cms_used = _cmsGen->cmsSpace()->used(); | |
2700 size_t perm_used = _permGen->cmsSpace()->used(); | |
2701 | |
2702 // update performance counters - this uses a special version of | |
2703 // update_counters() that allows the utilization to be passed as a | |
2704 // parameter, avoiding multiple calls to used(). | |
2705 // | |
2706 _cmsGen->update_counters(cms_used); | |
2707 _permGen->update_counters(perm_used); | |
2708 | |
2709 if (CMSIncrementalMode) { | |
2710 icms_update_allocation_limits(); | |
2711 } | |
2712 | |
2713 bitMapLock()->unlock(); | |
2714 releaseFreelistLocks(); | |
2715 | |
2716 _between_prologue_and_epilogue = false; // ready for next cycle | |
2717 } | |
2718 | |
2719 void ConcurrentMarkSweepGeneration::gc_epilogue(bool full) { | |
2720 collector()->gc_epilogue(full); | |
2721 | |
2722 // Also reset promotion tracking in par gc thread states. | |
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2723 if (CollectedHeap::use_parallel_gc_threads()) { |
0 | 2724 for (uint i = 0; i < ParallelGCThreads; i++) { |
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2725 _par_gc_thread_states[i]->promo.stopTrackingPromotions(i); |
0 | 2726 } |
2727 } | |
2728 } | |
2729 | |
2730 void ConcurrentMarkSweepGeneration::gc_epilogue_work(bool full) { | |
2731 assert(!incremental_collection_failed(), "Should have been cleared"); | |
2732 cmsSpace()->setPreconsumptionDirtyCardClosure(NULL); | |
2733 cmsSpace()->gc_epilogue(); | |
2734 // Print stat counters | |
2735 NOT_PRODUCT( | |
2736 assert(_numObjectsAllocated == 0, "check"); | |
2737 assert(_numWordsAllocated == 0, "check"); | |
2738 if (Verbose && PrintGC) { | |
2739 gclog_or_tty->print("Promoted "SIZE_FORMAT" objects, " | |
2740 SIZE_FORMAT" bytes", | |
2741 _numObjectsPromoted, _numWordsPromoted*sizeof(HeapWord)); | |
2742 } | |
2743 _numObjectsPromoted = 0; | |
2744 _numWordsPromoted = 0; | |
2745 ) | |
2746 | |
2747 if (PrintGC && Verbose) { | |
2748 // Call down the chain in contiguous_available needs the freelistLock | |
2749 // so print this out before releasing the freeListLock. | |
2750 gclog_or_tty->print(" Contiguous available "SIZE_FORMAT" bytes ", | |
2751 contiguous_available()); | |
2752 } | |
2753 } | |
2754 | |
2755 #ifndef PRODUCT | |
2756 bool CMSCollector::have_cms_token() { | |
2757 Thread* thr = Thread::current(); | |
2758 if (thr->is_VM_thread()) { | |
2759 return ConcurrentMarkSweepThread::vm_thread_has_cms_token(); | |
2760 } else if (thr->is_ConcurrentGC_thread()) { | |
2761 return ConcurrentMarkSweepThread::cms_thread_has_cms_token(); | |
2762 } else if (thr->is_GC_task_thread()) { | |
2763 return ConcurrentMarkSweepThread::vm_thread_has_cms_token() && | |
2764 ParGCRareEvent_lock->owned_by_self(); | |
2765 } | |
2766 return false; | |
2767 } | |
2768 #endif | |
2769 | |
2770 // Check reachability of the given heap address in CMS generation, | |
2771 // treating all other generations as roots. | |
2772 bool CMSCollector::is_cms_reachable(HeapWord* addr) { | |
2773 // We could "guarantee" below, rather than assert, but i'll | |
2774 // leave these as "asserts" so that an adventurous debugger | |
2775 // could try this in the product build provided some subset of | |
2776 // the conditions were met, provided they were intersted in the | |
2777 // results and knew that the computation below wouldn't interfere | |
2778 // with other concurrent computations mutating the structures | |
2779 // being read or written. | |
2780 assert(SafepointSynchronize::is_at_safepoint(), | |
2781 "Else mutations in object graph will make answer suspect"); | |
2782 assert(have_cms_token(), "Should hold cms token"); | |
2783 assert(haveFreelistLocks(), "must hold free list locks"); | |
2784 assert_lock_strong(bitMapLock()); | |
2785 | |
2786 // Clear the marking bit map array before starting, but, just | |
2787 // for kicks, first report if the given address is already marked | |
2788 gclog_or_tty->print_cr("Start: Address 0x%x is%s marked", addr, | |
2789 _markBitMap.isMarked(addr) ? "" : " not"); | |
2790 | |
2791 if (verify_after_remark()) { | |
2792 MutexLockerEx x(verification_mark_bm()->lock(), Mutex::_no_safepoint_check_flag); | |
2793 bool result = verification_mark_bm()->isMarked(addr); | |
2794 gclog_or_tty->print_cr("TransitiveMark: Address 0x%x %s marked", addr, | |
2795 result ? "IS" : "is NOT"); | |
2796 return result; | |
2797 } else { | |
2798 gclog_or_tty->print_cr("Could not compute result"); | |
2799 return false; | |
2800 } | |
2801 } | |
2802 | |
2803 //////////////////////////////////////////////////////// | |
2804 // CMS Verification Support | |
2805 //////////////////////////////////////////////////////// | |
2806 // Following the remark phase, the following invariant | |
2807 // should hold -- each object in the CMS heap which is | |
2808 // marked in markBitMap() should be marked in the verification_mark_bm(). | |
2809 | |
2810 class VerifyMarkedClosure: public BitMapClosure { | |
2811 CMSBitMap* _marks; | |
2812 bool _failed; | |
2813 | |
2814 public: | |
2815 VerifyMarkedClosure(CMSBitMap* bm): _marks(bm), _failed(false) {} | |
2816 | |
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2817 bool do_bit(size_t offset) { |
0 | 2818 HeapWord* addr = _marks->offsetToHeapWord(offset); |
2819 if (!_marks->isMarked(addr)) { | |
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2820 oop(addr)->print_on(gclog_or_tty); |
0 | 2821 gclog_or_tty->print_cr(" ("INTPTR_FORMAT" should have been marked)", addr); |
2822 _failed = true; | |
2823 } | |
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2824 return true; |
0 | 2825 } |
2826 | |
2827 bool failed() { return _failed; } | |
2828 }; | |
2829 | |
2830 bool CMSCollector::verify_after_remark() { | |
2831 gclog_or_tty->print(" [Verifying CMS Marking... "); | |
2832 MutexLockerEx ml(verification_mark_bm()->lock(), Mutex::_no_safepoint_check_flag); | |
2833 static bool init = false; | |
2834 | |
2835 assert(SafepointSynchronize::is_at_safepoint(), | |
2836 "Else mutations in object graph will make answer suspect"); | |
2837 assert(have_cms_token(), | |
2838 "Else there may be mutual interference in use of " | |
2839 " verification data structures"); | |
2840 assert(_collectorState > Marking && _collectorState <= Sweeping, | |
2841 "Else marking info checked here may be obsolete"); | |
2842 assert(haveFreelistLocks(), "must hold free list locks"); | |
2843 assert_lock_strong(bitMapLock()); | |
2844 | |
2845 | |
2846 // Allocate marking bit map if not already allocated | |
2847 if (!init) { // first time | |
2848 if (!verification_mark_bm()->allocate(_span)) { | |
2849 return false; | |
2850 } | |
2851 init = true; | |
2852 } | |
2853 | |
2854 assert(verification_mark_stack()->isEmpty(), "Should be empty"); | |
2855 | |
2856 // Turn off refs discovery -- so we will be tracing through refs. | |
2857 // This is as intended, because by this time | |
2858 // GC must already have cleared any refs that need to be cleared, | |
2859 // and traced those that need to be marked; moreover, | |
2860 // the marking done here is not going to intefere in any | |
2861 // way with the marking information used by GC. | |
2862 NoRefDiscovery no_discovery(ref_processor()); | |
2863 | |
2864 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;) | |
2865 | |
2866 // Clear any marks from a previous round | |
2867 verification_mark_bm()->clear_all(); | |
2868 assert(verification_mark_stack()->isEmpty(), "markStack should be empty"); | |
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2869 verify_work_stacks_empty(); |
0 | 2870 |
2871 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
2872 gch->ensure_parsability(false); // fill TLABs, but no need to retire them | |
2873 // Update the saved marks which may affect the root scans. | |
2874 gch->save_marks(); | |
2875 | |
2876 if (CMSRemarkVerifyVariant == 1) { | |
2877 // In this first variant of verification, we complete | |
2878 // all marking, then check if the new marks-verctor is | |
2879 // a subset of the CMS marks-vector. | |
2880 verify_after_remark_work_1(); | |
2881 } else if (CMSRemarkVerifyVariant == 2) { | |
2882 // In this second variant of verification, we flag an error | |
2883 // (i.e. an object reachable in the new marks-vector not reachable | |
2884 // in the CMS marks-vector) immediately, also indicating the | |
2885 // identify of an object (A) that references the unmarked object (B) -- | |
2886 // presumably, a mutation to A failed to be picked up by preclean/remark? | |
2887 verify_after_remark_work_2(); | |
2888 } else { | |
2889 warning("Unrecognized value %d for CMSRemarkVerifyVariant", | |
2890 CMSRemarkVerifyVariant); | |
2891 } | |
2892 gclog_or_tty->print(" done] "); | |
2893 return true; | |
2894 } | |
2895 | |
2896 void CMSCollector::verify_after_remark_work_1() { | |
2897 ResourceMark rm; | |
2898 HandleMark hm; | |
2899 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
2900 | |
2901 // Mark from roots one level into CMS | |
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2902 MarkRefsIntoClosure notOlder(_span, verification_mark_bm()); |
0 | 2903 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. |
2904 | |
2905 gch->gen_process_strong_roots(_cmsGen->level(), | |
2906 true, // younger gens are roots | |
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2907 true, // activate StrongRootsScope |
0 | 2908 true, // collecting perm gen |
2909 SharedHeap::ScanningOption(roots_scanning_options()), | |
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2910 ¬Older, |
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2911 true, // walk code active on stacks |
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2912 NULL); |
0 | 2913 |
2914 // Now mark from the roots | |
2915 assert(_revisitStack.isEmpty(), "Should be empty"); | |
2916 MarkFromRootsClosure markFromRootsClosure(this, _span, | |
2917 verification_mark_bm(), verification_mark_stack(), &_revisitStack, | |
2918 false /* don't yield */, true /* verifying */); | |
2919 assert(_restart_addr == NULL, "Expected pre-condition"); | |
2920 verification_mark_bm()->iterate(&markFromRootsClosure); | |
2921 while (_restart_addr != NULL) { | |
2922 // Deal with stack overflow: by restarting at the indicated | |
2923 // address. | |
2924 HeapWord* ra = _restart_addr; | |
2925 markFromRootsClosure.reset(ra); | |
2926 _restart_addr = NULL; | |
2927 verification_mark_bm()->iterate(&markFromRootsClosure, ra, _span.end()); | |
2928 } | |
2929 assert(verification_mark_stack()->isEmpty(), "Should have been drained"); | |
2930 verify_work_stacks_empty(); | |
2931 // Should reset the revisit stack above, since no class tree | |
2932 // surgery is forthcoming. | |
2933 _revisitStack.reset(); // throwing away all contents | |
2934 | |
2935 // Marking completed -- now verify that each bit marked in | |
2936 // verification_mark_bm() is also marked in markBitMap(); flag all | |
2937 // errors by printing corresponding objects. | |
2938 VerifyMarkedClosure vcl(markBitMap()); | |
2939 verification_mark_bm()->iterate(&vcl); | |
2940 if (vcl.failed()) { | |
2941 gclog_or_tty->print("Verification failed"); | |
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2942 Universe::heap()->print_on(gclog_or_tty); |
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2943 fatal("CMS: failed marking verification after remark"); |
0 | 2944 } |
2945 } | |
2946 | |
2947 void CMSCollector::verify_after_remark_work_2() { | |
2948 ResourceMark rm; | |
2949 HandleMark hm; | |
2950 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
2951 | |
2952 // Mark from roots one level into CMS | |
2953 MarkRefsIntoVerifyClosure notOlder(_span, verification_mark_bm(), | |
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2954 markBitMap()); |
0 | 2955 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. |
2956 gch->gen_process_strong_roots(_cmsGen->level(), | |
2957 true, // younger gens are roots | |
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2958 true, // activate StrongRootsScope |
0 | 2959 true, // collecting perm gen |
2960 SharedHeap::ScanningOption(roots_scanning_options()), | |
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2961 ¬Older, |
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2962 true, // walk code active on stacks |
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2963 NULL); |
0 | 2964 |
2965 // Now mark from the roots | |
2966 assert(_revisitStack.isEmpty(), "Should be empty"); | |
2967 MarkFromRootsVerifyClosure markFromRootsClosure(this, _span, | |
2968 verification_mark_bm(), markBitMap(), verification_mark_stack()); | |
2969 assert(_restart_addr == NULL, "Expected pre-condition"); | |
2970 verification_mark_bm()->iterate(&markFromRootsClosure); | |
2971 while (_restart_addr != NULL) { | |
2972 // Deal with stack overflow: by restarting at the indicated | |
2973 // address. | |
2974 HeapWord* ra = _restart_addr; | |
2975 markFromRootsClosure.reset(ra); | |
2976 _restart_addr = NULL; | |
2977 verification_mark_bm()->iterate(&markFromRootsClosure, ra, _span.end()); | |
2978 } | |
2979 assert(verification_mark_stack()->isEmpty(), "Should have been drained"); | |
2980 verify_work_stacks_empty(); | |
2981 // Should reset the revisit stack above, since no class tree | |
2982 // surgery is forthcoming. | |
2983 _revisitStack.reset(); // throwing away all contents | |
2984 | |
2985 // Marking completed -- now verify that each bit marked in | |
2986 // verification_mark_bm() is also marked in markBitMap(); flag all | |
2987 // errors by printing corresponding objects. | |
2988 VerifyMarkedClosure vcl(markBitMap()); | |
2989 verification_mark_bm()->iterate(&vcl); | |
2990 assert(!vcl.failed(), "Else verification above should not have succeeded"); | |
2991 } | |
2992 | |
2993 void ConcurrentMarkSweepGeneration::save_marks() { | |
2994 // delegate to CMS space | |
2995 cmsSpace()->save_marks(); | |
2996 for (uint i = 0; i < ParallelGCThreads; i++) { | |
2997 _par_gc_thread_states[i]->promo.startTrackingPromotions(); | |
2998 } | |
2999 } | |
3000 | |
3001 bool ConcurrentMarkSweepGeneration::no_allocs_since_save_marks() { | |
3002 return cmsSpace()->no_allocs_since_save_marks(); | |
3003 } | |
3004 | |
3005 #define CMS_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \ | |
3006 \ | |
3007 void ConcurrentMarkSweepGeneration:: \ | |
3008 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \ | |
3009 cl->set_generation(this); \ | |
3010 cmsSpace()->oop_since_save_marks_iterate##nv_suffix(cl); \ | |
3011 cl->reset_generation(); \ | |
3012 save_marks(); \ | |
3013 } | |
3014 | |
3015 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DEFN) | |
3016 | |
3017 void | |
3018 ConcurrentMarkSweepGeneration::object_iterate_since_last_GC(ObjectClosure* blk) | |
3019 { | |
3020 // Not currently implemented; need to do the following. -- ysr. | |
3021 // dld -- I think that is used for some sort of allocation profiler. So it | |
3022 // really means the objects allocated by the mutator since the last | |
3023 // GC. We could potentially implement this cheaply by recording only | |
3024 // the direct allocations in a side data structure. | |
3025 // | |
3026 // I think we probably ought not to be required to support these | |
3027 // iterations at any arbitrary point; I think there ought to be some | |
3028 // call to enable/disable allocation profiling in a generation/space, | |
3029 // and the iterator ought to return the objects allocated in the | |
3030 // gen/space since the enable call, or the last iterator call (which | |
3031 // will probably be at a GC.) That way, for gens like CM&S that would | |
3032 // require some extra data structure to support this, we only pay the | |
3033 // cost when it's in use... | |
3034 cmsSpace()->object_iterate_since_last_GC(blk); | |
3035 } | |
3036 | |
3037 void | |
3038 ConcurrentMarkSweepGeneration::younger_refs_iterate(OopsInGenClosure* cl) { | |
3039 cl->set_generation(this); | |
3040 younger_refs_in_space_iterate(_cmsSpace, cl); | |
3041 cl->reset_generation(); | |
3042 } | |
3043 | |
3044 void | |
3045 ConcurrentMarkSweepGeneration::oop_iterate(MemRegion mr, OopClosure* cl) { | |
3046 if (freelistLock()->owned_by_self()) { | |
3047 Generation::oop_iterate(mr, cl); | |
3048 } else { | |
3049 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
3050 Generation::oop_iterate(mr, cl); | |
3051 } | |
3052 } | |
3053 | |
3054 void | |
3055 ConcurrentMarkSweepGeneration::oop_iterate(OopClosure* cl) { | |
3056 if (freelistLock()->owned_by_self()) { | |
3057 Generation::oop_iterate(cl); | |
3058 } else { | |
3059 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
3060 Generation::oop_iterate(cl); | |
3061 } | |
3062 } | |
3063 | |
3064 void | |
3065 ConcurrentMarkSweepGeneration::object_iterate(ObjectClosure* cl) { | |
3066 if (freelistLock()->owned_by_self()) { | |
3067 Generation::object_iterate(cl); | |
3068 } else { | |
3069 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
3070 Generation::object_iterate(cl); | |
3071 } | |
3072 } | |
3073 | |
3074 void | |
517
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3075 ConcurrentMarkSweepGeneration::safe_object_iterate(ObjectClosure* cl) { |
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3076 if (freelistLock()->owned_by_self()) { |
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3077 Generation::safe_object_iterate(cl); |
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3078 } else { |
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3079 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); |
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3080 Generation::safe_object_iterate(cl); |
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3081 } |
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3082 } |
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3083 |
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3084 void |
0 | 3085 ConcurrentMarkSweepGeneration::pre_adjust_pointers() { |
3086 } | |
3087 | |
3088 void | |
3089 ConcurrentMarkSweepGeneration::post_compact() { | |
3090 } | |
3091 | |
3092 void | |
3093 ConcurrentMarkSweepGeneration::prepare_for_verify() { | |
3094 // Fix the linear allocation blocks to look like free blocks. | |
3095 | |
3096 // Locks are normally acquired/released in gc_prologue/gc_epilogue, but those | |
3097 // are not called when the heap is verified during universe initialization and | |
3098 // at vm shutdown. | |
3099 if (freelistLock()->owned_by_self()) { | |
3100 cmsSpace()->prepare_for_verify(); | |
3101 } else { | |
3102 MutexLockerEx fll(freelistLock(), Mutex::_no_safepoint_check_flag); | |
3103 cmsSpace()->prepare_for_verify(); | |
3104 } | |
3105 } | |
3106 | |
3107 void | |
3108 ConcurrentMarkSweepGeneration::verify(bool allow_dirty /* ignored */) { | |
3109 // Locks are normally acquired/released in gc_prologue/gc_epilogue, but those | |
3110 // are not called when the heap is verified during universe initialization and | |
3111 // at vm shutdown. | |
3112 if (freelistLock()->owned_by_self()) { | |
3113 cmsSpace()->verify(false /* ignored */); | |
3114 } else { | |
3115 MutexLockerEx fll(freelistLock(), Mutex::_no_safepoint_check_flag); | |
3116 cmsSpace()->verify(false /* ignored */); | |
3117 } | |
3118 } | |
3119 | |
3120 void CMSCollector::verify(bool allow_dirty /* ignored */) { | |
3121 _cmsGen->verify(allow_dirty); | |
3122 _permGen->verify(allow_dirty); | |
3123 } | |
3124 | |
3125 #ifndef PRODUCT | |
3126 bool CMSCollector::overflow_list_is_empty() const { | |
3127 assert(_num_par_pushes >= 0, "Inconsistency"); | |
3128 if (_overflow_list == NULL) { | |
3129 assert(_num_par_pushes == 0, "Inconsistency"); | |
3130 } | |
3131 return _overflow_list == NULL; | |
3132 } | |
3133 | |
3134 // The methods verify_work_stacks_empty() and verify_overflow_empty() | |
3135 // merely consolidate assertion checks that appear to occur together frequently. | |
3136 void CMSCollector::verify_work_stacks_empty() const { | |
3137 assert(_markStack.isEmpty(), "Marking stack should be empty"); | |
3138 assert(overflow_list_is_empty(), "Overflow list should be empty"); | |
3139 } | |
3140 | |
3141 void CMSCollector::verify_overflow_empty() const { | |
3142 assert(overflow_list_is_empty(), "Overflow list should be empty"); | |
3143 assert(no_preserved_marks(), "No preserved marks"); | |
3144 } | |
3145 #endif // PRODUCT | |
3146 | |
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3147 // Decide if we want to enable class unloading as part of the |
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3148 // ensuing concurrent GC cycle. We will collect the perm gen and |
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3149 // unload classes if it's the case that: |
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3150 // (1) an explicit gc request has been made and the flag |
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3151 // ExplicitGCInvokesConcurrentAndUnloadsClasses is set, OR |
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3152 // (2) (a) class unloading is enabled at the command line, and |
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3153 // (b) (i) perm gen threshold has been crossed, or |
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3154 // (ii) old gen is getting really full, or |
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3155 // (iii) the previous N CMS collections did not collect the |
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3156 // perm gen |
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3157 // NOTE: Provided there is no change in the state of the heap between |
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3158 // calls to this method, it should have idempotent results. Moreover, |
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3159 // its results should be monotonically increasing (i.e. going from 0 to 1, |
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3160 // but not 1 to 0) between successive calls between which the heap was |
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3161 // not collected. For the implementation below, it must thus rely on |
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3162 // the property that concurrent_cycles_since_last_unload() |
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3163 // will not decrease unless a collection cycle happened and that |
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3164 // _permGen->should_concurrent_collect() and _cmsGen->is_too_full() are |
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3165 // themselves also monotonic in that sense. See check_monotonicity() |
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3166 // below. |
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3167 bool CMSCollector::update_should_unload_classes() { |
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3168 _should_unload_classes = false; |
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3169 // Condition 1 above |
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3170 if (_full_gc_requested && ExplicitGCInvokesConcurrentAndUnloadsClasses) { |
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3171 _should_unload_classes = true; |
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3172 } else if (CMSClassUnloadingEnabled) { // Condition 2.a above |
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3173 // Disjuncts 2.b.(i,ii,iii) above |
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3174 _should_unload_classes = (concurrent_cycles_since_last_unload() >= |
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3175 CMSClassUnloadingMaxInterval) |
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3176 || _permGen->should_concurrent_collect() |
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3177 || _cmsGen->is_too_full(); |
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3178 } |
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3179 return _should_unload_classes; |
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3180 } |
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3181 |
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3182 bool ConcurrentMarkSweepGeneration::is_too_full() const { |
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3183 bool res = should_concurrent_collect(); |
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3184 res = res && (occupancy() > (double)CMSIsTooFullPercentage/100.0); |
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3185 return res; |
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3186 } |
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3187 |
0 | 3188 void CMSCollector::setup_cms_unloading_and_verification_state() { |
3189 const bool should_verify = VerifyBeforeGC || VerifyAfterGC || VerifyDuringGC | |
3190 || VerifyBeforeExit; | |
3191 const int rso = SharedHeap::SO_Symbols | SharedHeap::SO_Strings | |
3192 | SharedHeap::SO_CodeCache; | |
3193 | |
94
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3194 if (should_unload_classes()) { // Should unload classes this cycle |
0 | 3195 remove_root_scanning_option(rso); // Shrink the root set appropriately |
3196 set_verifying(should_verify); // Set verification state for this cycle | |
3197 return; // Nothing else needs to be done at this time | |
3198 } | |
3199 | |
3200 // Not unloading classes this cycle | |
94
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3201 assert(!should_unload_classes(), "Inconsitency!"); |
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3202 if ((!verifying() || unloaded_classes_last_cycle()) && should_verify) { |
0 | 3203 // We were not verifying, or we _were_ unloading classes in the last cycle, |
3204 // AND some verification options are enabled this cycle; in this case, | |
3205 // we must make sure that the deadness map is allocated if not already so, | |
3206 // and cleared (if already allocated previously -- | |
3207 // CMSBitMap::sizeInBits() is used to determine if it's allocated). | |
3208 if (perm_gen_verify_bit_map()->sizeInBits() == 0) { | |
3209 if (!perm_gen_verify_bit_map()->allocate(_permGen->reserved())) { | |
3210 warning("Failed to allocate permanent generation verification CMS Bit Map;\n" | |
3211 "permanent generation verification disabled"); | |
3212 return; // Note that we leave verification disabled, so we'll retry this | |
3213 // allocation next cycle. We _could_ remember this failure | |
3214 // and skip further attempts and permanently disable verification | |
3215 // attempts if that is considered more desirable. | |
3216 } | |
3217 assert(perm_gen_verify_bit_map()->covers(_permGen->reserved()), | |
3218 "_perm_gen_ver_bit_map inconsistency?"); | |
3219 } else { | |
3220 perm_gen_verify_bit_map()->clear_all(); | |
3221 } | |
3222 // Include symbols, strings and code cache elements to prevent their resurrection. | |
3223 add_root_scanning_option(rso); | |
3224 set_verifying(true); | |
3225 } else if (verifying() && !should_verify) { | |
3226 // We were verifying, but some verification flags got disabled. | |
3227 set_verifying(false); | |
3228 // Exclude symbols, strings and code cache elements from root scanning to | |
3229 // reduce IM and RM pauses. | |
3230 remove_root_scanning_option(rso); | |
3231 } | |
3232 } | |
3233 | |
3234 | |
3235 #ifndef PRODUCT | |
3236 HeapWord* CMSCollector::block_start(const void* p) const { | |
3237 const HeapWord* addr = (HeapWord*)p; | |
3238 if (_span.contains(p)) { | |
3239 if (_cmsGen->cmsSpace()->is_in_reserved(addr)) { | |
3240 return _cmsGen->cmsSpace()->block_start(p); | |
3241 } else { | |
3242 assert(_permGen->cmsSpace()->is_in_reserved(addr), | |
3243 "Inconsistent _span?"); | |
3244 return _permGen->cmsSpace()->block_start(p); | |
3245 } | |
3246 } | |
3247 return NULL; | |
3248 } | |
3249 #endif | |
3250 | |
3251 HeapWord* | |
3252 ConcurrentMarkSweepGeneration::expand_and_allocate(size_t word_size, | |
3253 bool tlab, | |
3254 bool parallel) { | |
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3255 CMSSynchronousYieldRequest yr; |
0 | 3256 assert(!tlab, "Can't deal with TLAB allocation"); |
3257 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
3258 expand(word_size*HeapWordSize, MinHeapDeltaBytes, | |
3259 CMSExpansionCause::_satisfy_allocation); | |
3260 if (GCExpandToAllocateDelayMillis > 0) { | |
3261 os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false); | |
3262 } | |
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3263 return have_lock_and_allocate(word_size, tlab); |
0 | 3264 } |
3265 | |
3266 // YSR: All of this generation expansion/shrinking stuff is an exact copy of | |
3267 // OneContigSpaceCardGeneration, which makes me wonder if we should move this | |
3268 // to CardGeneration and share it... | |
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3269 bool ConcurrentMarkSweepGeneration::expand(size_t bytes, size_t expand_bytes) { |
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3270 return CardGeneration::expand(bytes, expand_bytes); |
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3271 } |
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3272 |
0 | 3273 void ConcurrentMarkSweepGeneration::expand(size_t bytes, size_t expand_bytes, |
3274 CMSExpansionCause::Cause cause) | |
3275 { | |
271
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3276 |
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3277 bool success = expand(bytes, expand_bytes); |
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3278 |
0 | 3279 // remember why we expanded; this information is used |
3280 // by shouldConcurrentCollect() when making decisions on whether to start | |
3281 // a new CMS cycle. | |
3282 if (success) { | |
3283 set_expansion_cause(cause); | |
3284 if (PrintGCDetails && Verbose) { | |
3285 gclog_or_tty->print_cr("Expanded CMS gen for %s", | |
3286 CMSExpansionCause::to_string(cause)); | |
3287 } | |
3288 } | |
3289 } | |
3290 | |
3291 HeapWord* ConcurrentMarkSweepGeneration::expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz) { | |
3292 HeapWord* res = NULL; | |
3293 MutexLocker x(ParGCRareEvent_lock); | |
3294 while (true) { | |
3295 // Expansion by some other thread might make alloc OK now: | |
3296 res = ps->lab.alloc(word_sz); | |
3297 if (res != NULL) return res; | |
3298 // If there's not enough expansion space available, give up. | |
3299 if (_virtual_space.uncommitted_size() < (word_sz * HeapWordSize)) { | |
3300 return NULL; | |
3301 } | |
3302 // Otherwise, we try expansion. | |
3303 expand(word_sz*HeapWordSize, MinHeapDeltaBytes, | |
3304 CMSExpansionCause::_allocate_par_lab); | |
3305 // Now go around the loop and try alloc again; | |
3306 // A competing par_promote might beat us to the expansion space, | |
3307 // so we may go around the loop again if promotion fails agaion. | |
3308 if (GCExpandToAllocateDelayMillis > 0) { | |
3309 os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false); | |
3310 } | |
3311 } | |
3312 } | |
3313 | |
3314 | |
3315 bool ConcurrentMarkSweepGeneration::expand_and_ensure_spooling_space( | |
3316 PromotionInfo* promo) { | |
3317 MutexLocker x(ParGCRareEvent_lock); | |
3318 size_t refill_size_bytes = promo->refillSize() * HeapWordSize; | |
3319 while (true) { | |
3320 // Expansion by some other thread might make alloc OK now: | |
3321 if (promo->ensure_spooling_space()) { | |
3322 assert(promo->has_spooling_space(), | |
3323 "Post-condition of successful ensure_spooling_space()"); | |
3324 return true; | |
3325 } | |
3326 // If there's not enough expansion space available, give up. | |
3327 if (_virtual_space.uncommitted_size() < refill_size_bytes) { | |
3328 return false; | |
3329 } | |
3330 // Otherwise, we try expansion. | |
3331 expand(refill_size_bytes, MinHeapDeltaBytes, | |
3332 CMSExpansionCause::_allocate_par_spooling_space); | |
3333 // Now go around the loop and try alloc again; | |
3334 // A competing allocation might beat us to the expansion space, | |
3335 // so we may go around the loop again if allocation fails again. | |
3336 if (GCExpandToAllocateDelayMillis > 0) { | |
3337 os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false); | |
3338 } | |
3339 } | |
3340 } | |
3341 | |
3342 | |
3343 | |
3344 void ConcurrentMarkSweepGeneration::shrink(size_t bytes) { | |
3345 assert_locked_or_safepoint(Heap_lock); | |
3346 size_t size = ReservedSpace::page_align_size_down(bytes); | |
3347 if (size > 0) { | |
3348 shrink_by(size); | |
3349 } | |
3350 } | |
3351 | |
3352 bool ConcurrentMarkSweepGeneration::grow_by(size_t bytes) { | |
3353 assert_locked_or_safepoint(Heap_lock); | |
3354 bool result = _virtual_space.expand_by(bytes); | |
3355 if (result) { | |
3356 HeapWord* old_end = _cmsSpace->end(); | |
3357 size_t new_word_size = | |
3358 heap_word_size(_virtual_space.committed_size()); | |
3359 MemRegion mr(_cmsSpace->bottom(), new_word_size); | |
3360 _bts->resize(new_word_size); // resize the block offset shared array | |
3361 Universe::heap()->barrier_set()->resize_covered_region(mr); | |
3362 // Hmmmm... why doesn't CFLS::set_end verify locking? | |
3363 // This is quite ugly; FIX ME XXX | |
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3364 _cmsSpace->assert_locked(freelistLock()); |
0 | 3365 _cmsSpace->set_end((HeapWord*)_virtual_space.high()); |
3366 | |
3367 // update the space and generation capacity counters | |
3368 if (UsePerfData) { | |
3369 _space_counters->update_capacity(); | |
3370 _gen_counters->update_all(); | |
3371 } | |
3372 | |
3373 if (Verbose && PrintGC) { | |
3374 size_t new_mem_size = _virtual_space.committed_size(); | |
3375 size_t old_mem_size = new_mem_size - bytes; | |
3376 gclog_or_tty->print_cr("Expanding %s from %ldK by %ldK to %ldK", | |
3377 name(), old_mem_size/K, bytes/K, new_mem_size/K); | |
3378 } | |
3379 } | |
3380 return result; | |
3381 } | |
3382 | |
3383 bool ConcurrentMarkSweepGeneration::grow_to_reserved() { | |
3384 assert_locked_or_safepoint(Heap_lock); | |
3385 bool success = true; | |
3386 const size_t remaining_bytes = _virtual_space.uncommitted_size(); | |
3387 if (remaining_bytes > 0) { | |
3388 success = grow_by(remaining_bytes); | |
3389 DEBUG_ONLY(if (!success) warning("grow to reserved failed");) | |
3390 } | |
3391 return success; | |
3392 } | |
3393 | |
3394 void ConcurrentMarkSweepGeneration::shrink_by(size_t bytes) { | |
3395 assert_locked_or_safepoint(Heap_lock); | |
3396 assert_lock_strong(freelistLock()); | |
3397 // XXX Fix when compaction is implemented. | |
3398 warning("Shrinking of CMS not yet implemented"); | |
3399 return; | |
3400 } | |
3401 | |
3402 | |
3403 // Simple ctor/dtor wrapper for accounting & timer chores around concurrent | |
3404 // phases. | |
3405 class CMSPhaseAccounting: public StackObj { | |
3406 public: | |
3407 CMSPhaseAccounting(CMSCollector *collector, | |
3408 const char *phase, | |
3409 bool print_cr = true); | |
3410 ~CMSPhaseAccounting(); | |
3411 | |
3412 private: | |
3413 CMSCollector *_collector; | |
3414 const char *_phase; | |
3415 elapsedTimer _wallclock; | |
3416 bool _print_cr; | |
3417 | |
3418 public: | |
3419 // Not MT-safe; so do not pass around these StackObj's | |
3420 // where they may be accessed by other threads. | |
3421 jlong wallclock_millis() { | |
3422 assert(_wallclock.is_active(), "Wall clock should not stop"); | |
3423 _wallclock.stop(); // to record time | |
3424 jlong ret = _wallclock.milliseconds(); | |
3425 _wallclock.start(); // restart | |
3426 return ret; | |
3427 } | |
3428 }; | |
3429 | |
3430 CMSPhaseAccounting::CMSPhaseAccounting(CMSCollector *collector, | |
3431 const char *phase, | |
3432 bool print_cr) : | |
3433 _collector(collector), _phase(phase), _print_cr(print_cr) { | |
3434 | |
3435 if (PrintCMSStatistics != 0) { | |
3436 _collector->resetYields(); | |
3437 } | |
3438 if (PrintGCDetails && PrintGCTimeStamps) { | |
3439 gclog_or_tty->date_stamp(PrintGCDateStamps); | |
3440 gclog_or_tty->stamp(); | |
3441 gclog_or_tty->print_cr(": [%s-concurrent-%s-start]", | |
3442 _collector->cmsGen()->short_name(), _phase); | |
3443 } | |
3444 _collector->resetTimer(); | |
3445 _wallclock.start(); | |
3446 _collector->startTimer(); | |
3447 } | |
3448 | |
3449 CMSPhaseAccounting::~CMSPhaseAccounting() { | |
3450 assert(_wallclock.is_active(), "Wall clock should not have stopped"); | |
3451 _collector->stopTimer(); | |
3452 _wallclock.stop(); | |
3453 if (PrintGCDetails) { | |
3454 gclog_or_tty->date_stamp(PrintGCDateStamps); | |
3455 if (PrintGCTimeStamps) { | |
3456 gclog_or_tty->stamp(); | |
3457 gclog_or_tty->print(": "); | |
3458 } | |
3459 gclog_or_tty->print("[%s-concurrent-%s: %3.3f/%3.3f secs]", | |
3460 _collector->cmsGen()->short_name(), | |
3461 _phase, _collector->timerValue(), _wallclock.seconds()); | |
3462 if (_print_cr) { | |
3463 gclog_or_tty->print_cr(""); | |
3464 } | |
3465 if (PrintCMSStatistics != 0) { | |
3466 gclog_or_tty->print_cr(" (CMS-concurrent-%s yielded %d times)", _phase, | |
3467 _collector->yields()); | |
3468 } | |
3469 } | |
3470 } | |
3471 | |
3472 // CMS work | |
3473 | |
3474 // Checkpoint the roots into this generation from outside | |
3475 // this generation. [Note this initial checkpoint need only | |
3476 // be approximate -- we'll do a catch up phase subsequently.] | |
3477 void CMSCollector::checkpointRootsInitial(bool asynch) { | |
3478 assert(_collectorState == InitialMarking, "Wrong collector state"); | |
3479 check_correct_thread_executing(); | |
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3480 TraceCMSMemoryManagerStats tms(_collectorState); |
2125
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3481 |
0 | 3482 ReferenceProcessor* rp = ref_processor(); |
3483 SpecializationStats::clear(); | |
3484 assert(_restart_addr == NULL, "Control point invariant"); | |
3485 if (asynch) { | |
3486 // acquire locks for subsequent manipulations | |
3487 MutexLockerEx x(bitMapLock(), | |
3488 Mutex::_no_safepoint_check_flag); | |
3489 checkpointRootsInitialWork(asynch); | |
3490 rp->verify_no_references_recorded(); | |
3491 rp->enable_discovery(); // enable ("weak") refs discovery | |
3492 _collectorState = Marking; | |
3493 } else { | |
3494 // (Weak) Refs discovery: this is controlled from genCollectedHeap::do_collection | |
3495 // which recognizes if we are a CMS generation, and doesn't try to turn on | |
3496 // discovery; verify that they aren't meddling. | |
3497 assert(!rp->discovery_is_atomic(), | |
3498 "incorrect setting of discovery predicate"); | |
3499 assert(!rp->discovery_enabled(), "genCollectedHeap shouldn't control " | |
3500 "ref discovery for this generation kind"); | |
3501 // already have locks | |
3502 checkpointRootsInitialWork(asynch); | |
3503 rp->enable_discovery(); // now enable ("weak") refs discovery | |
3504 _collectorState = Marking; | |
3505 } | |
3506 SpecializationStats::print(); | |
3507 } | |
3508 | |
3509 void CMSCollector::checkpointRootsInitialWork(bool asynch) { | |
3510 assert(SafepointSynchronize::is_at_safepoint(), "world should be stopped"); | |
3511 assert(_collectorState == InitialMarking, "just checking"); | |
3512 | |
3513 // If there has not been a GC[n-1] since last GC[n] cycle completed, | |
3514 // precede our marking with a collection of all | |
3515 // younger generations to keep floating garbage to a minimum. | |
3516 // XXX: we won't do this for now -- it's an optimization to be done later. | |
3517 | |
3518 // already have locks | |
3519 assert_lock_strong(bitMapLock()); | |
3520 assert(_markBitMap.isAllClear(), "was reset at end of previous cycle"); | |
3521 | |
3522 // Setup the verification and class unloading state for this | |
3523 // CMS collection cycle. | |
3524 setup_cms_unloading_and_verification_state(); | |
3525 | |
3526 NOT_PRODUCT(TraceTime t("\ncheckpointRootsInitialWork", | |
3527 PrintGCDetails && Verbose, true, gclog_or_tty);) | |
3528 if (UseAdaptiveSizePolicy) { | |
3529 size_policy()->checkpoint_roots_initial_begin(); | |
3530 } | |
3531 | |
3532 // Reset all the PLAB chunk arrays if necessary. | |
3533 if (_survivor_plab_array != NULL && !CMSPLABRecordAlways) { | |
3534 reset_survivor_plab_arrays(); | |
3535 } | |
3536 | |
3537 ResourceMark rm; | |
3538 HandleMark hm; | |
3539 | |
3540 FalseClosure falseClosure; | |
3541 // In the case of a synchronous collection, we will elide the | |
3542 // remark step, so it's important to catch all the nmethod oops | |
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3543 // in this step. |
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3544 // The final 'true' flag to gen_process_strong_roots will ensure this. |
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3545 // If 'async' is true, we can relax the nmethod tracing. |
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3546 MarkRefsIntoClosure notOlder(_span, &_markBitMap); |
0 | 3547 GenCollectedHeap* gch = GenCollectedHeap::heap(); |
3548 | |
3549 verify_work_stacks_empty(); | |
3550 verify_overflow_empty(); | |
3551 | |
3552 gch->ensure_parsability(false); // fill TLABs, but no need to retire them | |
3553 // Update the saved marks which may affect the root scans. | |
3554 gch->save_marks(); | |
3555 | |
3556 // weak reference processing has not started yet. | |
3557 ref_processor()->set_enqueuing_is_done(false); | |
3558 | |
3559 { | |
935 | 3560 // This is not needed. DEBUG_ONLY(RememberKlassesChecker imx(true);) |
0 | 3561 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;) |
3562 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. | |
3563 gch->gen_process_strong_roots(_cmsGen->level(), | |
3564 true, // younger gens are roots | |
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3565 true, // activate StrongRootsScope |
0 | 3566 true, // collecting perm gen |
3567 SharedHeap::ScanningOption(roots_scanning_options()), | |
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3568 ¬Older, |
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3569 true, // walk all of code cache if (so & SO_CodeCache) |
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3570 NULL); |
0 | 3571 } |
3572 | |
3573 // Clear mod-union table; it will be dirtied in the prologue of | |
3574 // CMS generation per each younger generation collection. | |
3575 | |
3576 assert(_modUnionTable.isAllClear(), | |
3577 "Was cleared in most recent final checkpoint phase" | |
3578 " or no bits are set in the gc_prologue before the start of the next " | |
3579 "subsequent marking phase."); | |
3580 | |
3581 // Temporarily disabled, since pre/post-consumption closures don't | |
3582 // care about precleaned cards | |
3583 #if 0 | |
3584 { | |
3585 MemRegion mr = MemRegion((HeapWord*)_virtual_space.low(), | |
3586 (HeapWord*)_virtual_space.high()); | |
3587 _ct->ct_bs()->preclean_dirty_cards(mr); | |
3588 } | |
3589 #endif | |
3590 | |
3591 // Save the end of the used_region of the constituent generations | |
3592 // to be used to limit the extent of sweep in each generation. | |
3593 save_sweep_limits(); | |
3594 if (UseAdaptiveSizePolicy) { | |
3595 size_policy()->checkpoint_roots_initial_end(gch->gc_cause()); | |
3596 } | |
3597 verify_overflow_empty(); | |
3598 } | |
3599 | |
3600 bool CMSCollector::markFromRoots(bool asynch) { | |
3601 // we might be tempted to assert that: | |
3602 // assert(asynch == !SafepointSynchronize::is_at_safepoint(), | |
3603 // "inconsistent argument?"); | |
3604 // However that wouldn't be right, because it's possible that | |
3605 // a safepoint is indeed in progress as a younger generation | |
3606 // stop-the-world GC happens even as we mark in this generation. | |
3607 assert(_collectorState == Marking, "inconsistent state?"); | |
3608 check_correct_thread_executing(); | |
3609 verify_overflow_empty(); | |
3610 | |
3611 bool res; | |
3612 if (asynch) { | |
3613 | |
3614 // Start the timers for adaptive size policy for the concurrent phases | |
3615 // Do it here so that the foreground MS can use the concurrent | |
3616 // timer since a foreground MS might has the sweep done concurrently | |
3617 // or STW. | |
3618 if (UseAdaptiveSizePolicy) { | |
3619 size_policy()->concurrent_marking_begin(); | |
3620 } | |
3621 | |
3622 // Weak ref discovery note: We may be discovering weak | |
3623 // refs in this generation concurrent (but interleaved) with | |
3624 // weak ref discovery by a younger generation collector. | |
3625 | |
3626 CMSTokenSyncWithLocks ts(true, bitMapLock()); | |
3627 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
3628 CMSPhaseAccounting pa(this, "mark", !PrintGCDetails); | |
3629 res = markFromRootsWork(asynch); | |
3630 if (res) { | |
3631 _collectorState = Precleaning; | |
3632 } else { // We failed and a foreground collection wants to take over | |
3633 assert(_foregroundGCIsActive, "internal state inconsistency"); | |
3634 assert(_restart_addr == NULL, "foreground will restart from scratch"); | |
3635 if (PrintGCDetails) { | |
3636 gclog_or_tty->print_cr("bailing out to foreground collection"); | |
3637 } | |
3638 } | |
3639 if (UseAdaptiveSizePolicy) { | |
3640 size_policy()->concurrent_marking_end(); | |
3641 } | |
3642 } else { | |
3643 assert(SafepointSynchronize::is_at_safepoint(), | |
3644 "inconsistent with asynch == false"); | |
3645 if (UseAdaptiveSizePolicy) { | |
3646 size_policy()->ms_collection_marking_begin(); | |
3647 } | |
3648 // already have locks | |
3649 res = markFromRootsWork(asynch); | |
3650 _collectorState = FinalMarking; | |
3651 if (UseAdaptiveSizePolicy) { | |
3652 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
3653 size_policy()->ms_collection_marking_end(gch->gc_cause()); | |
3654 } | |
3655 } | |
3656 verify_overflow_empty(); | |
3657 return res; | |
3658 } | |
3659 | |
3660 bool CMSCollector::markFromRootsWork(bool asynch) { | |
3661 // iterate over marked bits in bit map, doing a full scan and mark | |
3662 // from these roots using the following algorithm: | |
3663 // . if oop is to the right of the current scan pointer, | |
3664 // mark corresponding bit (we'll process it later) | |
3665 // . else (oop is to left of current scan pointer) | |
3666 // push oop on marking stack | |
3667 // . drain the marking stack | |
3668 | |
3669 // Note that when we do a marking step we need to hold the | |
3670 // bit map lock -- recall that direct allocation (by mutators) | |
3671 // and promotion (by younger generation collectors) is also | |
3672 // marking the bit map. [the so-called allocate live policy.] | |
3673 // Because the implementation of bit map marking is not | |
3674 // robust wrt simultaneous marking of bits in the same word, | |
3675 // we need to make sure that there is no such interference | |
3676 // between concurrent such updates. | |
3677 | |
3678 // already have locks | |
3679 assert_lock_strong(bitMapLock()); | |
3680 | |
3681 // Clear the revisit stack, just in case there are any | |
3682 // obsolete contents from a short-circuited previous CMS cycle. | |
3683 _revisitStack.reset(); | |
3684 verify_work_stacks_empty(); | |
3685 verify_overflow_empty(); | |
3686 assert(_revisitStack.isEmpty(), "tabula rasa"); | |
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3687 DEBUG_ONLY(RememberKlassesChecker cmx(should_unload_classes());) |
0 | 3688 bool result = false; |
1284 | 3689 if (CMSConcurrentMTEnabled && ConcGCThreads > 0) { |
0 | 3690 result = do_marking_mt(asynch); |
3691 } else { | |
3692 result = do_marking_st(asynch); | |
3693 } | |
3694 return result; | |
3695 } | |
3696 | |
3697 // Forward decl | |
3698 class CMSConcMarkingTask; | |
3699 | |
3700 class CMSConcMarkingTerminator: public ParallelTaskTerminator { | |
3701 CMSCollector* _collector; | |
3702 CMSConcMarkingTask* _task; | |
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3703 public: |
0 | 3704 virtual void yield(); |
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3705 |
0 | 3706 // "n_threads" is the number of threads to be terminated. |
3707 // "queue_set" is a set of work queues of other threads. | |
3708 // "collector" is the CMS collector associated with this task terminator. | |
3709 // "yield" indicates whether we need the gang as a whole to yield. | |
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3710 CMSConcMarkingTerminator(int n_threads, TaskQueueSetSuper* queue_set, CMSCollector* collector) : |
0 | 3711 ParallelTaskTerminator(n_threads, queue_set), |
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3712 _collector(collector) { } |
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3713 |
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3714 void set_task(CMSConcMarkingTask* task) { |
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3715 _task = task; |
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3716 } |
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3717 }; |
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3718 |
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3719 class CMSConcMarkingTerminatorTerminator: public TerminatorTerminator { |
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3720 CMSConcMarkingTask* _task; |
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3721 public: |
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3722 bool should_exit_termination(); |
0 | 3723 void set_task(CMSConcMarkingTask* task) { |
3724 _task = task; | |
3725 } | |
3726 }; | |
3727 | |
3728 // MT Concurrent Marking Task | |
3729 class CMSConcMarkingTask: public YieldingFlexibleGangTask { | |
3730 CMSCollector* _collector; | |
3731 int _n_workers; // requested/desired # workers | |
3732 bool _asynch; | |
3733 bool _result; | |
3734 CompactibleFreeListSpace* _cms_space; | |
3735 CompactibleFreeListSpace* _perm_space; | |
1837
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3736 char _pad_front[64]; // padding to ... |
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3737 HeapWord* _global_finger; // ... avoid sharing cache line |
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3738 char _pad_back[64]; |
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3739 HeapWord* _restart_addr; |
0 | 3740 |
3741 // Exposed here for yielding support | |
3742 Mutex* const _bit_map_lock; | |
3743 | |
3744 // The per thread work queues, available here for stealing | |
3745 OopTaskQueueSet* _task_queues; | |
1837
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3746 |
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3747 // Termination (and yielding) support |
0 | 3748 CMSConcMarkingTerminator _term; |
1837
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3749 CMSConcMarkingTerminatorTerminator _term_term; |
0 | 3750 |
3751 public: | |
3752 CMSConcMarkingTask(CMSCollector* collector, | |
3753 CompactibleFreeListSpace* cms_space, | |
3754 CompactibleFreeListSpace* perm_space, | |
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3755 bool asynch, |
0 | 3756 YieldingFlexibleWorkGang* workers, |
3757 OopTaskQueueSet* task_queues): | |
3758 YieldingFlexibleGangTask("Concurrent marking done multi-threaded"), | |
3759 _collector(collector), | |
3760 _cms_space(cms_space), | |
3761 _perm_space(perm_space), | |
1833
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3762 _asynch(asynch), _n_workers(0), _result(true), |
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3763 _task_queues(task_queues), |
1837
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3764 _term(_n_workers, task_queues, _collector), |
0 | 3765 _bit_map_lock(collector->bitMapLock()) |
3766 { | |
1833
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3767 _requested_size = _n_workers; |
0 | 3768 _term.set_task(this); |
1837
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3769 _term_term.set_task(this); |
0 | 3770 assert(_cms_space->bottom() < _perm_space->bottom(), |
3771 "Finger incorrectly initialized below"); | |
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3772 _restart_addr = _global_finger = _cms_space->bottom(); |
0 | 3773 } |
3774 | |
3775 | |
3776 OopTaskQueueSet* task_queues() { return _task_queues; } | |
3777 | |
3778 OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); } | |
3779 | |
3780 HeapWord** global_finger_addr() { return &_global_finger; } | |
3781 | |
3782 CMSConcMarkingTerminator* terminator() { return &_term; } | |
3783 | |
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3784 virtual void set_for_termination(int active_workers) { |
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3785 terminator()->reset_for_reuse(active_workers); |
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3786 } |
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3787 |
0 | 3788 void work(int i); |
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3789 bool should_yield() { |
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3790 return ConcurrentMarkSweepThread::should_yield() |
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3791 && !_collector->foregroundGCIsActive() |
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3792 && _asynch; |
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3793 } |
0 | 3794 |
3795 virtual void coordinator_yield(); // stuff done by coordinator | |
3796 bool result() { return _result; } | |
3797 | |
3798 void reset(HeapWord* ra) { | |
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3799 assert(_global_finger >= _cms_space->end(), "Postcondition of ::work(i)"); |
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3800 assert(_global_finger >= _perm_space->end(), "Postcondition of ::work(i)"); |
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3801 assert(ra < _perm_space->end(), "ra too large"); |
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3802 _restart_addr = _global_finger = ra; |
0 | 3803 _term.reset_for_reuse(); |
3804 } | |
3805 | |
3806 static bool get_work_from_overflow_stack(CMSMarkStack* ovflw_stk, | |
3807 OopTaskQueue* work_q); | |
3808 | |
3809 private: | |
3810 void do_scan_and_mark(int i, CompactibleFreeListSpace* sp); | |
3811 void do_work_steal(int i); | |
3812 void bump_global_finger(HeapWord* f); | |
3813 }; | |
3814 | |
1837
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3815 bool CMSConcMarkingTerminatorTerminator::should_exit_termination() { |
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3816 assert(_task != NULL, "Error"); |
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3817 return _task->yielding(); |
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3818 // Note that we do not need the disjunct || _task->should_yield() above |
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3819 // because we want terminating threads to yield only if the task |
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3820 // is already in the midst of yielding, which happens only after at least one |
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3821 // thread has yielded. |
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3822 } |
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3823 |
0 | 3824 void CMSConcMarkingTerminator::yield() { |
1837
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3825 if (_task->should_yield()) { |
0 | 3826 _task->yield(); |
3827 } else { | |
3828 ParallelTaskTerminator::yield(); | |
3829 } | |
3830 } | |
3831 | |
3832 //////////////////////////////////////////////////////////////// | |
3833 // Concurrent Marking Algorithm Sketch | |
3834 //////////////////////////////////////////////////////////////// | |
3835 // Until all tasks exhausted (both spaces): | |
3836 // -- claim next available chunk | |
3837 // -- bump global finger via CAS | |
3838 // -- find first object that starts in this chunk | |
3839 // and start scanning bitmap from that position | |
3840 // -- scan marked objects for oops | |
3841 // -- CAS-mark target, and if successful: | |
3842 // . if target oop is above global finger (volatile read) | |
3843 // nothing to do | |
3844 // . if target oop is in chunk and above local finger | |
3845 // then nothing to do | |
3846 // . else push on work-queue | |
3847 // -- Deal with possible overflow issues: | |
3848 // . local work-queue overflow causes stuff to be pushed on | |
3849 // global (common) overflow queue | |
3850 // . always first empty local work queue | |
3851 // . then get a batch of oops from global work queue if any | |
3852 // . then do work stealing | |
3853 // -- When all tasks claimed (both spaces) | |
3854 // and local work queue empty, | |
3855 // then in a loop do: | |
3856 // . check global overflow stack; steal a batch of oops and trace | |
3857 // . try to steal from other threads oif GOS is empty | |
3858 // . if neither is available, offer termination | |
3859 // -- Terminate and return result | |
3860 // | |
3861 void CMSConcMarkingTask::work(int i) { | |
3862 elapsedTimer _timer; | |
3863 ResourceMark rm; | |
3864 HandleMark hm; | |
3865 | |
3866 DEBUG_ONLY(_collector->verify_overflow_empty();) | |
3867 | |
3868 // Before we begin work, our work queue should be empty | |
3869 assert(work_queue(i)->size() == 0, "Expected to be empty"); | |
3870 // Scan the bitmap covering _cms_space, tracing through grey objects. | |
3871 _timer.start(); | |
3872 do_scan_and_mark(i, _cms_space); | |
3873 _timer.stop(); | |
3874 if (PrintCMSStatistics != 0) { | |
3875 gclog_or_tty->print_cr("Finished cms space scanning in %dth thread: %3.3f sec", | |
3876 i, _timer.seconds()); // XXX: need xxx/xxx type of notation, two timers | |
3877 } | |
3878 | |
3879 // ... do the same for the _perm_space | |
3880 _timer.reset(); | |
3881 _timer.start(); | |
3882 do_scan_and_mark(i, _perm_space); | |
3883 _timer.stop(); | |
3884 if (PrintCMSStatistics != 0) { | |
3885 gclog_or_tty->print_cr("Finished perm space scanning in %dth thread: %3.3f sec", | |
3886 i, _timer.seconds()); // XXX: need xxx/xxx type of notation, two timers | |
3887 } | |
3888 | |
3889 // ... do work stealing | |
3890 _timer.reset(); | |
3891 _timer.start(); | |
3892 do_work_steal(i); | |
3893 _timer.stop(); | |
3894 if (PrintCMSStatistics != 0) { | |
3895 gclog_or_tty->print_cr("Finished work stealing in %dth thread: %3.3f sec", | |
3896 i, _timer.seconds()); // XXX: need xxx/xxx type of notation, two timers | |
3897 } | |
3898 assert(_collector->_markStack.isEmpty(), "Should have been emptied"); | |
3899 assert(work_queue(i)->size() == 0, "Should have been emptied"); | |
3900 // Note that under the current task protocol, the | |
3901 // following assertion is true even of the spaces | |
3902 // expanded since the completion of the concurrent | |
3903 // marking. XXX This will likely change under a strict | |
3904 // ABORT semantics. | |
3905 assert(_global_finger > _cms_space->end() && | |
3906 _global_finger >= _perm_space->end(), | |
3907 "All tasks have been completed"); | |
3908 DEBUG_ONLY(_collector->verify_overflow_empty();) | |
3909 } | |
3910 | |
3911 void CMSConcMarkingTask::bump_global_finger(HeapWord* f) { | |
3912 HeapWord* read = _global_finger; | |
3913 HeapWord* cur = read; | |
3914 while (f > read) { | |
3915 cur = read; | |
3916 read = (HeapWord*) Atomic::cmpxchg_ptr(f, &_global_finger, cur); | |
3917 if (cur == read) { | |
3918 // our cas succeeded | |
3919 assert(_global_finger >= f, "protocol consistency"); | |
3920 break; | |
3921 } | |
3922 } | |
3923 } | |
3924 | |
3925 // This is really inefficient, and should be redone by | |
3926 // using (not yet available) block-read and -write interfaces to the | |
3927 // stack and the work_queue. XXX FIX ME !!! | |
3928 bool CMSConcMarkingTask::get_work_from_overflow_stack(CMSMarkStack* ovflw_stk, | |
3929 OopTaskQueue* work_q) { | |
3930 // Fast lock-free check | |
3931 if (ovflw_stk->length() == 0) { | |
3932 return false; | |
3933 } | |
3934 assert(work_q->size() == 0, "Shouldn't steal"); | |
3935 MutexLockerEx ml(ovflw_stk->par_lock(), | |
3936 Mutex::_no_safepoint_check_flag); | |
3937 // Grab up to 1/4 the size of the work queue | |
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3938 size_t num = MIN2((size_t)(work_q->max_elems() - work_q->size())/4, |
0 | 3939 (size_t)ParGCDesiredObjsFromOverflowList); |
3940 num = MIN2(num, ovflw_stk->length()); | |
3941 for (int i = (int) num; i > 0; i--) { | |
3942 oop cur = ovflw_stk->pop(); | |
3943 assert(cur != NULL, "Counted wrong?"); | |
3944 work_q->push(cur); | |
3945 } | |
3946 return num > 0; | |
3947 } | |
3948 | |
3949 void CMSConcMarkingTask::do_scan_and_mark(int i, CompactibleFreeListSpace* sp) { | |
3950 SequentialSubTasksDone* pst = sp->conc_par_seq_tasks(); | |
3951 int n_tasks = pst->n_tasks(); | |
3952 // We allow that there may be no tasks to do here because | |
3953 // we are restarting after a stack overflow. | |
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3954 assert(pst->valid() || n_tasks == 0, "Uninitialized use?"); |
0 | 3955 int nth_task = 0; |
3956 | |
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3957 HeapWord* aligned_start = sp->bottom(); |
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3958 if (sp->used_region().contains(_restart_addr)) { |
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3959 // Align down to a card boundary for the start of 0th task |
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3960 // for this space. |
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3961 aligned_start = |
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3962 (HeapWord*)align_size_down((uintptr_t)_restart_addr, |
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3963 CardTableModRefBS::card_size); |
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3964 } |
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3965 |
0 | 3966 size_t chunk_size = sp->marking_task_size(); |
3967 while (!pst->is_task_claimed(/* reference */ nth_task)) { | |
3968 // Having claimed the nth task in this space, | |
3969 // compute the chunk that it corresponds to: | |
340
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3970 MemRegion span = MemRegion(aligned_start + nth_task*chunk_size, |
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3971 aligned_start + (nth_task+1)*chunk_size); |
0 | 3972 // Try and bump the global finger via a CAS; |
3973 // note that we need to do the global finger bump | |
3974 // _before_ taking the intersection below, because | |
3975 // the task corresponding to that region will be | |
3976 // deemed done even if the used_region() expands | |
3977 // because of allocation -- as it almost certainly will | |
3978 // during start-up while the threads yield in the | |
3979 // closure below. | |
3980 HeapWord* finger = span.end(); | |
3981 bump_global_finger(finger); // atomically | |
3982 // There are null tasks here corresponding to chunks | |
3983 // beyond the "top" address of the space. | |
3984 span = span.intersection(sp->used_region()); | |
3985 if (!span.is_empty()) { // Non-null task | |
340
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3986 HeapWord* prev_obj; |
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3987 assert(!span.contains(_restart_addr) || nth_task == 0, |
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3988 "Inconsistency"); |
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3989 if (nth_task == 0) { |
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3990 // For the 0th task, we'll not need to compute a block_start. |
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3991 if (span.contains(_restart_addr)) { |
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3992 // In the case of a restart because of stack overflow, |
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3993 // we might additionally skip a chunk prefix. |
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3994 prev_obj = _restart_addr; |
0 | 3995 } else { |
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3996 prev_obj = span.start(); |
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3997 } |
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3998 } else { |
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3999 // We want to skip the first object because |
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4000 // the protocol is to scan any object in its entirety |
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4001 // that _starts_ in this span; a fortiori, any |
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4002 // object starting in an earlier span is scanned |
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4003 // as part of an earlier claimed task. |
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4004 // Below we use the "careful" version of block_start |
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4005 // so we do not try to navigate uninitialized objects. |
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4006 prev_obj = sp->block_start_careful(span.start()); |
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4007 // Below we use a variant of block_size that uses the |
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4008 // Printezis bits to avoid waiting for allocated |
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4009 // objects to become initialized/parsable. |
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4010 while (prev_obj < span.start()) { |
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4011 size_t sz = sp->block_size_no_stall(prev_obj, _collector); |
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4012 if (sz > 0) { |
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4013 prev_obj += sz; |
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4014 } else { |
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4015 // In this case we may end up doing a bit of redundant |
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4016 // scanning, but that appears unavoidable, short of |
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4017 // locking the free list locks; see bug 6324141. |
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4018 break; |
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4019 } |
0 | 4020 } |
4021 } | |
4022 if (prev_obj < span.end()) { | |
4023 MemRegion my_span = MemRegion(prev_obj, span.end()); | |
4024 // Do the marking work within a non-empty span -- | |
4025 // the last argument to the constructor indicates whether the | |
4026 // iteration should be incremental with periodic yields. | |
4027 Par_MarkFromRootsClosure cl(this, _collector, my_span, | |
4028 &_collector->_markBitMap, | |
4029 work_queue(i), | |
4030 &_collector->_markStack, | |
4031 &_collector->_revisitStack, | |
4032 _asynch); | |
4033 _collector->_markBitMap.iterate(&cl, my_span.start(), my_span.end()); | |
4034 } // else nothing to do for this task | |
4035 } // else nothing to do for this task | |
4036 } | |
4037 // We'd be tempted to assert here that since there are no | |
4038 // more tasks left to claim in this space, the global_finger | |
4039 // must exceed space->top() and a fortiori space->end(). However, | |
4040 // that would not quite be correct because the bumping of | |
4041 // global_finger occurs strictly after the claiming of a task, | |
4042 // so by the time we reach here the global finger may not yet | |
4043 // have been bumped up by the thread that claimed the last | |
4044 // task. | |
4045 pst->all_tasks_completed(); | |
4046 } | |
4047 | |
935 | 4048 class Par_ConcMarkingClosure: public Par_KlassRememberingOopClosure { |
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4049 private: |
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4050 CMSConcMarkingTask* _task; |
0 | 4051 MemRegion _span; |
4052 CMSBitMap* _bit_map; | |
4053 CMSMarkStack* _overflow_stack; | |
4054 OopTaskQueue* _work_queue; | |
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4055 protected: |
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4056 DO_OOP_WORK_DEFN |
0 | 4057 public: |
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4058 Par_ConcMarkingClosure(CMSCollector* collector, CMSConcMarkingTask* task, OopTaskQueue* work_queue, |
935 | 4059 CMSBitMap* bit_map, CMSMarkStack* overflow_stack, |
4060 CMSMarkStack* revisit_stack): | |
4061 Par_KlassRememberingOopClosure(collector, NULL, revisit_stack), | |
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4062 _task(task), |
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4063 _span(collector->_span), |
0 | 4064 _work_queue(work_queue), |
4065 _bit_map(bit_map), | |
935 | 4066 _overflow_stack(overflow_stack) |
4067 { } | |
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4068 virtual void do_oop(oop* p); |
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4069 virtual void do_oop(narrowOop* p); |
0 | 4070 void trim_queue(size_t max); |
4071 void handle_stack_overflow(HeapWord* lost); | |
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4072 void do_yield_check() { |
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4073 if (_task->should_yield()) { |
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4074 _task->yield(); |
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4075 } |
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4076 } |
0 | 4077 }; |
4078 | |
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4079 // Grey object scanning during work stealing phase -- |
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4080 // the salient assumption here is that any references |
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4081 // that are in these stolen objects being scanned must |
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4082 // already have been initialized (else they would not have |
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4083 // been published), so we do not need to check for |
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4084 // uninitialized objects before pushing here. |
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4085 void Par_ConcMarkingClosure::do_oop(oop obj) { |
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4086 assert(obj->is_oop_or_null(true), "expected an oop or NULL"); |
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4087 HeapWord* addr = (HeapWord*)obj; |
0 | 4088 // Check if oop points into the CMS generation |
4089 // and is not marked | |
4090 if (_span.contains(addr) && !_bit_map->isMarked(addr)) { | |
4091 // a white object ... | |
4092 // If we manage to "claim" the object, by being the | |
4093 // first thread to mark it, then we push it on our | |
4094 // marking stack | |
4095 if (_bit_map->par_mark(addr)) { // ... now grey | |
4096 // push on work queue (grey set) | |
4097 bool simulate_overflow = false; | |
4098 NOT_PRODUCT( | |
4099 if (CMSMarkStackOverflowALot && | |
4100 _collector->simulate_overflow()) { | |
4101 // simulate a stack overflow | |
4102 simulate_overflow = true; | |
4103 } | |
4104 ) | |
4105 if (simulate_overflow || | |
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4106 !(_work_queue->push(obj) || _overflow_stack->par_push(obj))) { |
0 | 4107 // stack overflow |
4108 if (PrintCMSStatistics != 0) { | |
4109 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
4110 SIZE_FORMAT, _overflow_stack->capacity()); | |
4111 } | |
4112 // We cannot assert that the overflow stack is full because | |
4113 // it may have been emptied since. | |
4114 assert(simulate_overflow || | |
4115 _work_queue->size() == _work_queue->max_elems(), | |
4116 "Else push should have succeeded"); | |
4117 handle_stack_overflow(addr); | |
4118 } | |
4119 } // Else, some other thread got there first | |
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4120 do_yield_check(); |
0 | 4121 } |
4122 } | |
4123 | |
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4124 void Par_ConcMarkingClosure::do_oop(oop* p) { Par_ConcMarkingClosure::do_oop_work(p); } |
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4125 void Par_ConcMarkingClosure::do_oop(narrowOop* p) { Par_ConcMarkingClosure::do_oop_work(p); } |
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4126 |
0 | 4127 void Par_ConcMarkingClosure::trim_queue(size_t max) { |
4128 while (_work_queue->size() > max) { | |
4129 oop new_oop; | |
4130 if (_work_queue->pop_local(new_oop)) { | |
4131 assert(new_oop->is_oop(), "Should be an oop"); | |
4132 assert(_bit_map->isMarked((HeapWord*)new_oop), "Grey object"); | |
4133 assert(_span.contains((HeapWord*)new_oop), "Not in span"); | |
4134 assert(new_oop->is_parsable(), "Should be parsable"); | |
4135 new_oop->oop_iterate(this); // do_oop() above | |
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4136 do_yield_check(); |
0 | 4137 } |
4138 } | |
4139 } | |
4140 | |
4141 // Upon stack overflow, we discard (part of) the stack, | |
4142 // remembering the least address amongst those discarded | |
4143 // in CMSCollector's _restart_address. | |
4144 void Par_ConcMarkingClosure::handle_stack_overflow(HeapWord* lost) { | |
4145 // We need to do this under a mutex to prevent other | |
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4146 // workers from interfering with the work done below. |
0 | 4147 MutexLockerEx ml(_overflow_stack->par_lock(), |
4148 Mutex::_no_safepoint_check_flag); | |
4149 // Remember the least grey address discarded | |
4150 HeapWord* ra = (HeapWord*)_overflow_stack->least_value(lost); | |
4151 _collector->lower_restart_addr(ra); | |
4152 _overflow_stack->reset(); // discard stack contents | |
4153 _overflow_stack->expand(); // expand the stack if possible | |
4154 } | |
4155 | |
4156 | |
4157 void CMSConcMarkingTask::do_work_steal(int i) { | |
4158 OopTaskQueue* work_q = work_queue(i); | |
4159 oop obj_to_scan; | |
4160 CMSBitMap* bm = &(_collector->_markBitMap); | |
4161 CMSMarkStack* ovflw = &(_collector->_markStack); | |
935 | 4162 CMSMarkStack* revisit = &(_collector->_revisitStack); |
0 | 4163 int* seed = _collector->hash_seed(i); |
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4164 Par_ConcMarkingClosure cl(_collector, this, work_q, bm, ovflw, revisit); |
0 | 4165 while (true) { |
4166 cl.trim_queue(0); | |
4167 assert(work_q->size() == 0, "Should have been emptied above"); | |
4168 if (get_work_from_overflow_stack(ovflw, work_q)) { | |
4169 // Can't assert below because the work obtained from the | |
4170 // overflow stack may already have been stolen from us. | |
4171 // assert(work_q->size() > 0, "Work from overflow stack"); | |
4172 continue; | |
4173 } else if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) { | |
4174 assert(obj_to_scan->is_oop(), "Should be an oop"); | |
4175 assert(bm->isMarked((HeapWord*)obj_to_scan), "Grey object"); | |
4176 obj_to_scan->oop_iterate(&cl); | |
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4177 } else if (terminator()->offer_termination(&_term_term)) { |
0 | 4178 assert(work_q->size() == 0, "Impossible!"); |
4179 break; | |
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4180 } else if (yielding() || should_yield()) { |
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4181 yield(); |
0 | 4182 } |
4183 } | |
4184 } | |
4185 | |
4186 // This is run by the CMS (coordinator) thread. | |
4187 void CMSConcMarkingTask::coordinator_yield() { | |
4188 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
4189 "CMS thread should hold CMS token"); | |
935 | 4190 DEBUG_ONLY(RememberKlassesChecker mux(false);) |
0 | 4191 // First give up the locks, then yield, then re-lock |
4192 // We should probably use a constructor/destructor idiom to | |
4193 // do this unlock/lock or modify the MutexUnlocker class to | |
4194 // serve our purpose. XXX | |
4195 assert_lock_strong(_bit_map_lock); | |
4196 _bit_map_lock->unlock(); | |
4197 ConcurrentMarkSweepThread::desynchronize(true); | |
4198 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
4199 _collector->stopTimer(); | |
4200 if (PrintCMSStatistics != 0) { | |
4201 _collector->incrementYields(); | |
4202 } | |
4203 _collector->icms_wait(); | |
4204 | |
4205 // It is possible for whichever thread initiated the yield request | |
4206 // not to get a chance to wake up and take the bitmap lock between | |
4207 // this thread releasing it and reacquiring it. So, while the | |
4208 // should_yield() flag is on, let's sleep for a bit to give the | |
4209 // other thread a chance to wake up. The limit imposed on the number | |
4210 // of iterations is defensive, to avoid any unforseen circumstances | |
4211 // putting us into an infinite loop. Since it's always been this | |
4212 // (coordinator_yield()) method that was observed to cause the | |
4213 // problem, we are using a parameter (CMSCoordinatorYieldSleepCount) | |
4214 // which is by default non-zero. For the other seven methods that | |
4215 // also perform the yield operation, as are using a different | |
4216 // parameter (CMSYieldSleepCount) which is by default zero. This way we | |
4217 // can enable the sleeping for those methods too, if necessary. | |
4218 // See 6442774. | |
4219 // | |
4220 // We really need to reconsider the synchronization between the GC | |
4221 // thread and the yield-requesting threads in the future and we | |
4222 // should really use wait/notify, which is the recommended | |
4223 // way of doing this type of interaction. Additionally, we should | |
4224 // consolidate the eight methods that do the yield operation and they | |
4225 // are almost identical into one for better maintenability and | |
4226 // readability. See 6445193. | |
4227 // | |
4228 // Tony 2006.06.29 | |
4229 for (unsigned i = 0; i < CMSCoordinatorYieldSleepCount && | |
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4230 ConcurrentMarkSweepThread::should_yield() && |
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4231 !CMSCollector::foregroundGCIsActive(); ++i) { |
0 | 4232 os::sleep(Thread::current(), 1, false); |
4233 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
4234 } | |
4235 | |
4236 ConcurrentMarkSweepThread::synchronize(true); | |
4237 _bit_map_lock->lock_without_safepoint_check(); | |
4238 _collector->startTimer(); | |
4239 } | |
4240 | |
4241 bool CMSCollector::do_marking_mt(bool asynch) { | |
1284 | 4242 assert(ConcGCThreads > 0 && conc_workers() != NULL, "precondition"); |
0 | 4243 // In the future this would be determined ergonomically, based |
4244 // on #cpu's, # active mutator threads (and load), and mutation rate. | |
1284 | 4245 int num_workers = ConcGCThreads; |
0 | 4246 |
4247 CompactibleFreeListSpace* cms_space = _cmsGen->cmsSpace(); | |
4248 CompactibleFreeListSpace* perm_space = _permGen->cmsSpace(); | |
4249 | |
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4250 CMSConcMarkingTask tsk(this, |
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4251 cms_space, |
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4252 perm_space, |
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4253 asynch, |
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4254 conc_workers(), |
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4255 task_queues()); |
0 | 4256 |
4257 // Since the actual number of workers we get may be different | |
4258 // from the number we requested above, do we need to do anything different | |
4259 // below? In particular, may be we need to subclass the SequantialSubTasksDone | |
4260 // class?? XXX | |
4261 cms_space ->initialize_sequential_subtasks_for_marking(num_workers); | |
4262 perm_space->initialize_sequential_subtasks_for_marking(num_workers); | |
4263 | |
4264 // Refs discovery is already non-atomic. | |
4265 assert(!ref_processor()->discovery_is_atomic(), "Should be non-atomic"); | |
4266 // Mutate the Refs discovery so it is MT during the | |
4267 // multi-threaded marking phase. | |
4268 ReferenceProcessorMTMutator mt(ref_processor(), num_workers > 1); | |
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4269 DEBUG_ONLY(RememberKlassesChecker cmx(should_unload_classes());) |
0 | 4270 conc_workers()->start_task(&tsk); |
4271 while (tsk.yielded()) { | |
4272 tsk.coordinator_yield(); | |
4273 conc_workers()->continue_task(&tsk); | |
4274 } | |
4275 // If the task was aborted, _restart_addr will be non-NULL | |
4276 assert(tsk.completed() || _restart_addr != NULL, "Inconsistency"); | |
4277 while (_restart_addr != NULL) { | |
4278 // XXX For now we do not make use of ABORTED state and have not | |
4279 // yet implemented the right abort semantics (even in the original | |
4280 // single-threaded CMS case). That needs some more investigation | |
4281 // and is deferred for now; see CR# TBF. 07252005YSR. XXX | |
4282 assert(!CMSAbortSemantics || tsk.aborted(), "Inconsistency"); | |
4283 // If _restart_addr is non-NULL, a marking stack overflow | |
605 | 4284 // occurred; we need to do a fresh marking iteration from the |
0 | 4285 // indicated restart address. |
4286 if (_foregroundGCIsActive && asynch) { | |
4287 // We may be running into repeated stack overflows, having | |
4288 // reached the limit of the stack size, while making very | |
4289 // slow forward progress. It may be best to bail out and | |
4290 // let the foreground collector do its job. | |
4291 // Clear _restart_addr, so that foreground GC | |
4292 // works from scratch. This avoids the headache of | |
4293 // a "rescan" which would otherwise be needed because | |
4294 // of the dirty mod union table & card table. | |
4295 _restart_addr = NULL; | |
4296 return false; | |
4297 } | |
4298 // Adjust the task to restart from _restart_addr | |
4299 tsk.reset(_restart_addr); | |
4300 cms_space ->initialize_sequential_subtasks_for_marking(num_workers, | |
4301 _restart_addr); | |
4302 perm_space->initialize_sequential_subtasks_for_marking(num_workers, | |
4303 _restart_addr); | |
4304 _restart_addr = NULL; | |
4305 // Get the workers going again | |
4306 conc_workers()->start_task(&tsk); | |
4307 while (tsk.yielded()) { | |
4308 tsk.coordinator_yield(); | |
4309 conc_workers()->continue_task(&tsk); | |
4310 } | |
4311 } | |
4312 assert(tsk.completed(), "Inconsistency"); | |
4313 assert(tsk.result() == true, "Inconsistency"); | |
4314 return true; | |
4315 } | |
4316 | |
4317 bool CMSCollector::do_marking_st(bool asynch) { | |
4318 ResourceMark rm; | |
4319 HandleMark hm; | |
4320 | |
4321 MarkFromRootsClosure markFromRootsClosure(this, _span, &_markBitMap, | |
4322 &_markStack, &_revisitStack, CMSYield && asynch); | |
4323 // the last argument to iterate indicates whether the iteration | |
4324 // should be incremental with periodic yields. | |
4325 _markBitMap.iterate(&markFromRootsClosure); | |
4326 // If _restart_addr is non-NULL, a marking stack overflow | |
605 | 4327 // occurred; we need to do a fresh iteration from the |
0 | 4328 // indicated restart address. |
4329 while (_restart_addr != NULL) { | |
4330 if (_foregroundGCIsActive && asynch) { | |
4331 // We may be running into repeated stack overflows, having | |
4332 // reached the limit of the stack size, while making very | |
4333 // slow forward progress. It may be best to bail out and | |
4334 // let the foreground collector do its job. | |
4335 // Clear _restart_addr, so that foreground GC | |
4336 // works from scratch. This avoids the headache of | |
4337 // a "rescan" which would otherwise be needed because | |
4338 // of the dirty mod union table & card table. | |
4339 _restart_addr = NULL; | |
4340 return false; // indicating failure to complete marking | |
4341 } | |
4342 // Deal with stack overflow: | |
4343 // we restart marking from _restart_addr | |
4344 HeapWord* ra = _restart_addr; | |
4345 markFromRootsClosure.reset(ra); | |
4346 _restart_addr = NULL; | |
4347 _markBitMap.iterate(&markFromRootsClosure, ra, _span.end()); | |
4348 } | |
4349 return true; | |
4350 } | |
4351 | |
4352 void CMSCollector::preclean() { | |
4353 check_correct_thread_executing(); | |
4354 assert(Thread::current()->is_ConcurrentGC_thread(), "Wrong thread"); | |
4355 verify_work_stacks_empty(); | |
4356 verify_overflow_empty(); | |
4357 _abort_preclean = false; | |
4358 if (CMSPrecleaningEnabled) { | |
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4359 // Precleaning is currently not MT but the reference processor |
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4360 // may be set for MT. Disable it temporarily here. |
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4361 ReferenceProcessor* rp = ref_processor(); |
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4362 ReferenceProcessorMTProcMutator z(rp, false); |
0 | 4363 _eden_chunk_index = 0; |
4364 size_t used = get_eden_used(); | |
4365 size_t capacity = get_eden_capacity(); | |
4366 // Don't start sampling unless we will get sufficiently | |
4367 // many samples. | |
4368 if (used < (capacity/(CMSScheduleRemarkSamplingRatio * 100) | |
4369 * CMSScheduleRemarkEdenPenetration)) { | |
4370 _start_sampling = true; | |
4371 } else { | |
4372 _start_sampling = false; | |
4373 } | |
4374 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
4375 CMSPhaseAccounting pa(this, "preclean", !PrintGCDetails); | |
4376 preclean_work(CMSPrecleanRefLists1, CMSPrecleanSurvivors1); | |
4377 } | |
4378 CMSTokenSync x(true); // is cms thread | |
4379 if (CMSPrecleaningEnabled) { | |
4380 sample_eden(); | |
4381 _collectorState = AbortablePreclean; | |
4382 } else { | |
4383 _collectorState = FinalMarking; | |
4384 } | |
4385 verify_work_stacks_empty(); | |
4386 verify_overflow_empty(); | |
4387 } | |
4388 | |
4389 // Try and schedule the remark such that young gen | |
4390 // occupancy is CMSScheduleRemarkEdenPenetration %. | |
4391 void CMSCollector::abortable_preclean() { | |
4392 check_correct_thread_executing(); | |
4393 assert(CMSPrecleaningEnabled, "Inconsistent control state"); | |
4394 assert(_collectorState == AbortablePreclean, "Inconsistent control state"); | |
4395 | |
4396 // If Eden's current occupancy is below this threshold, | |
4397 // immediately schedule the remark; else preclean | |
4398 // past the next scavenge in an effort to | |
4399 // schedule the pause as described avove. By choosing | |
4400 // CMSScheduleRemarkEdenSizeThreshold >= max eden size | |
4401 // we will never do an actual abortable preclean cycle. | |
4402 if (get_eden_used() > CMSScheduleRemarkEdenSizeThreshold) { | |
4403 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
4404 CMSPhaseAccounting pa(this, "abortable-preclean", !PrintGCDetails); | |
4405 // We need more smarts in the abortable preclean | |
4406 // loop below to deal with cases where allocation | |
4407 // in young gen is very very slow, and our precleaning | |
4408 // is running a losing race against a horde of | |
4409 // mutators intent on flooding us with CMS updates | |
4410 // (dirty cards). | |
4411 // One, admittedly dumb, strategy is to give up | |
4412 // after a certain number of abortable precleaning loops | |
4413 // or after a certain maximum time. We want to make | |
4414 // this smarter in the next iteration. | |
4415 // XXX FIX ME!!! YSR | |
4416 size_t loops = 0, workdone = 0, cumworkdone = 0, waited = 0; | |
4417 while (!(should_abort_preclean() || | |
4418 ConcurrentMarkSweepThread::should_terminate())) { | |
4419 workdone = preclean_work(CMSPrecleanRefLists2, CMSPrecleanSurvivors2); | |
4420 cumworkdone += workdone; | |
4421 loops++; | |
4422 // Voluntarily terminate abortable preclean phase if we have | |
4423 // been at it for too long. | |
4424 if ((CMSMaxAbortablePrecleanLoops != 0) && | |
4425 loops >= CMSMaxAbortablePrecleanLoops) { | |
4426 if (PrintGCDetails) { | |
4427 gclog_or_tty->print(" CMS: abort preclean due to loops "); | |
4428 } | |
4429 break; | |
4430 } | |
4431 if (pa.wallclock_millis() > CMSMaxAbortablePrecleanTime) { | |
4432 if (PrintGCDetails) { | |
4433 gclog_or_tty->print(" CMS: abort preclean due to time "); | |
4434 } | |
4435 break; | |
4436 } | |
4437 // If we are doing little work each iteration, we should | |
4438 // take a short break. | |
4439 if (workdone < CMSAbortablePrecleanMinWorkPerIteration) { | |
4440 // Sleep for some time, waiting for work to accumulate | |
4441 stopTimer(); | |
4442 cmsThread()->wait_on_cms_lock(CMSAbortablePrecleanWaitMillis); | |
4443 startTimer(); | |
4444 waited++; | |
4445 } | |
4446 } | |
4447 if (PrintCMSStatistics > 0) { | |
4448 gclog_or_tty->print(" [%d iterations, %d waits, %d cards)] ", | |
4449 loops, waited, cumworkdone); | |
4450 } | |
4451 } | |
4452 CMSTokenSync x(true); // is cms thread | |
4453 if (_collectorState != Idling) { | |
4454 assert(_collectorState == AbortablePreclean, | |
4455 "Spontaneous state transition?"); | |
4456 _collectorState = FinalMarking; | |
4457 } // Else, a foreground collection completed this CMS cycle. | |
4458 return; | |
4459 } | |
4460 | |
4461 // Respond to an Eden sampling opportunity | |
4462 void CMSCollector::sample_eden() { | |
4463 // Make sure a young gc cannot sneak in between our | |
4464 // reading and recording of a sample. | |
4465 assert(Thread::current()->is_ConcurrentGC_thread(), | |
4466 "Only the cms thread may collect Eden samples"); | |
4467 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
4468 "Should collect samples while holding CMS token"); | |
4469 if (!_start_sampling) { | |
4470 return; | |
4471 } | |
4472 if (_eden_chunk_array) { | |
4473 if (_eden_chunk_index < _eden_chunk_capacity) { | |
4474 _eden_chunk_array[_eden_chunk_index] = *_top_addr; // take sample | |
4475 assert(_eden_chunk_array[_eden_chunk_index] <= *_end_addr, | |
4476 "Unexpected state of Eden"); | |
4477 // We'd like to check that what we just sampled is an oop-start address; | |
4478 // however, we cannot do that here since the object may not yet have been | |
4479 // initialized. So we'll instead do the check when we _use_ this sample | |
4480 // later. | |
4481 if (_eden_chunk_index == 0 || | |
4482 (pointer_delta(_eden_chunk_array[_eden_chunk_index], | |
4483 _eden_chunk_array[_eden_chunk_index-1]) | |
4484 >= CMSSamplingGrain)) { | |
4485 _eden_chunk_index++; // commit sample | |
4486 } | |
4487 } | |
4488 } | |
4489 if ((_collectorState == AbortablePreclean) && !_abort_preclean) { | |
4490 size_t used = get_eden_used(); | |
4491 size_t capacity = get_eden_capacity(); | |
4492 assert(used <= capacity, "Unexpected state of Eden"); | |
4493 if (used > (capacity/100 * CMSScheduleRemarkEdenPenetration)) { | |
4494 _abort_preclean = true; | |
4495 } | |
4496 } | |
4497 } | |
4498 | |
4499 | |
4500 size_t CMSCollector::preclean_work(bool clean_refs, bool clean_survivor) { | |
4501 assert(_collectorState == Precleaning || | |
4502 _collectorState == AbortablePreclean, "incorrect state"); | |
4503 ResourceMark rm; | |
4504 HandleMark hm; | |
4505 // Do one pass of scrubbing the discovered reference lists | |
4506 // to remove any reference objects with strongly-reachable | |
4507 // referents. | |
4508 if (clean_refs) { | |
4509 ReferenceProcessor* rp = ref_processor(); | |
4510 CMSPrecleanRefsYieldClosure yield_cl(this); | |
4511 assert(rp->span().equals(_span), "Spans should be equal"); | |
4512 CMSKeepAliveClosure keep_alive(this, _span, &_markBitMap, | |
935 | 4513 &_markStack, &_revisitStack, |
4514 true /* preclean */); | |
0 | 4515 CMSDrainMarkingStackClosure complete_trace(this, |
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4516 _span, &_markBitMap, &_markStack, |
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4517 &keep_alive, true /* preclean */); |
0 | 4518 |
4519 // We don't want this step to interfere with a young | |
4520 // collection because we don't want to take CPU | |
4521 // or memory bandwidth away from the young GC threads | |
4522 // (which may be as many as there are CPUs). | |
4523 // Note that we don't need to protect ourselves from | |
4524 // interference with mutators because they can't | |
4525 // manipulate the discovered reference lists nor affect | |
4526 // the computed reachability of the referents, the | |
4527 // only properties manipulated by the precleaning | |
4528 // of these reference lists. | |
4529 stopTimer(); | |
4530 CMSTokenSyncWithLocks x(true /* is cms thread */, | |
4531 bitMapLock()); | |
4532 startTimer(); | |
4533 sample_eden(); | |
935 | 4534 |
0 | 4535 // The following will yield to allow foreground |
4536 // collection to proceed promptly. XXX YSR: | |
4537 // The code in this method may need further | |
4538 // tweaking for better performance and some restructuring | |
4539 // for cleaner interfaces. | |
4540 rp->preclean_discovered_references( | |
4541 rp->is_alive_non_header(), &keep_alive, &complete_trace, | |
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4542 &yield_cl, should_unload_classes()); |
0 | 4543 } |
4544 | |
4545 if (clean_survivor) { // preclean the active survivor space(s) | |
4546 assert(_young_gen->kind() == Generation::DefNew || | |
4547 _young_gen->kind() == Generation::ParNew || | |
4548 _young_gen->kind() == Generation::ASParNew, | |
4549 "incorrect type for cast"); | |
4550 DefNewGeneration* dng = (DefNewGeneration*)_young_gen; | |
4551 PushAndMarkClosure pam_cl(this, _span, ref_processor(), | |
4552 &_markBitMap, &_modUnionTable, | |
4553 &_markStack, &_revisitStack, | |
4554 true /* precleaning phase */); | |
4555 stopTimer(); | |
4556 CMSTokenSyncWithLocks ts(true /* is cms thread */, | |
4557 bitMapLock()); | |
4558 startTimer(); | |
4559 unsigned int before_count = | |
4560 GenCollectedHeap::heap()->total_collections(); | |
4561 SurvivorSpacePrecleanClosure | |
4562 sss_cl(this, _span, &_markBitMap, &_markStack, | |
4563 &pam_cl, before_count, CMSYield); | |
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4564 DEBUG_ONLY(RememberKlassesChecker mx(should_unload_classes());) |
0 | 4565 dng->from()->object_iterate_careful(&sss_cl); |
4566 dng->to()->object_iterate_careful(&sss_cl); | |
4567 } | |
4568 MarkRefsIntoAndScanClosure | |
4569 mrias_cl(_span, ref_processor(), &_markBitMap, &_modUnionTable, | |
4570 &_markStack, &_revisitStack, this, CMSYield, | |
4571 true /* precleaning phase */); | |
4572 // CAUTION: The following closure has persistent state that may need to | |
4573 // be reset upon a decrease in the sequence of addresses it | |
4574 // processes. | |
4575 ScanMarkedObjectsAgainCarefullyClosure | |
4576 smoac_cl(this, _span, | |
4577 &_markBitMap, &_markStack, &_revisitStack, &mrias_cl, CMSYield); | |
4578 | |
4579 // Preclean dirty cards in ModUnionTable and CardTable using | |
4580 // appropriate convergence criterion; | |
4581 // repeat CMSPrecleanIter times unless we find that | |
4582 // we are losing. | |
4583 assert(CMSPrecleanIter < 10, "CMSPrecleanIter is too large"); | |
4584 assert(CMSPrecleanNumerator < CMSPrecleanDenominator, | |
4585 "Bad convergence multiplier"); | |
4586 assert(CMSPrecleanThreshold >= 100, | |
4587 "Unreasonably low CMSPrecleanThreshold"); | |
4588 | |
4589 size_t numIter, cumNumCards, lastNumCards, curNumCards; | |
4590 for (numIter = 0, cumNumCards = lastNumCards = curNumCards = 0; | |
4591 numIter < CMSPrecleanIter; | |
4592 numIter++, lastNumCards = curNumCards, cumNumCards += curNumCards) { | |
4593 curNumCards = preclean_mod_union_table(_cmsGen, &smoac_cl); | |
4594 if (CMSPermGenPrecleaningEnabled) { | |
4595 curNumCards += preclean_mod_union_table(_permGen, &smoac_cl); | |
4596 } | |
4597 if (Verbose && PrintGCDetails) { | |
4598 gclog_or_tty->print(" (modUnionTable: %d cards)", curNumCards); | |
4599 } | |
4600 // Either there are very few dirty cards, so re-mark | |
4601 // pause will be small anyway, or our pre-cleaning isn't | |
4602 // that much faster than the rate at which cards are being | |
4603 // dirtied, so we might as well stop and re-mark since | |
4604 // precleaning won't improve our re-mark time by much. | |
4605 if (curNumCards <= CMSPrecleanThreshold || | |
4606 (numIter > 0 && | |
4607 (curNumCards * CMSPrecleanDenominator > | |
4608 lastNumCards * CMSPrecleanNumerator))) { | |
4609 numIter++; | |
4610 cumNumCards += curNumCards; | |
4611 break; | |
4612 } | |
4613 } | |
4614 curNumCards = preclean_card_table(_cmsGen, &smoac_cl); | |
4615 if (CMSPermGenPrecleaningEnabled) { | |
4616 curNumCards += preclean_card_table(_permGen, &smoac_cl); | |
4617 } | |
4618 cumNumCards += curNumCards; | |
4619 if (PrintGCDetails && PrintCMSStatistics != 0) { | |
4620 gclog_or_tty->print_cr(" (cardTable: %d cards, re-scanned %d cards, %d iterations)", | |
4621 curNumCards, cumNumCards, numIter); | |
4622 } | |
4623 return cumNumCards; // as a measure of useful work done | |
4624 } | |
4625 | |
4626 // PRECLEANING NOTES: | |
4627 // Precleaning involves: | |
4628 // . reading the bits of the modUnionTable and clearing the set bits. | |
4629 // . For the cards corresponding to the set bits, we scan the | |
4630 // objects on those cards. This means we need the free_list_lock | |
4631 // so that we can safely iterate over the CMS space when scanning | |
4632 // for oops. | |
4633 // . When we scan the objects, we'll be both reading and setting | |
4634 // marks in the marking bit map, so we'll need the marking bit map. | |
4635 // . For protecting _collector_state transitions, we take the CGC_lock. | |
4636 // Note that any races in the reading of of card table entries by the | |
4637 // CMS thread on the one hand and the clearing of those entries by the | |
4638 // VM thread or the setting of those entries by the mutator threads on the | |
4639 // other are quite benign. However, for efficiency it makes sense to keep | |
4640 // the VM thread from racing with the CMS thread while the latter is | |
4641 // dirty card info to the modUnionTable. We therefore also use the | |
4642 // CGC_lock to protect the reading of the card table and the mod union | |
4643 // table by the CM thread. | |
4644 // . We run concurrently with mutator updates, so scanning | |
4645 // needs to be done carefully -- we should not try to scan | |
4646 // potentially uninitialized objects. | |
4647 // | |
4648 // Locking strategy: While holding the CGC_lock, we scan over and | |
4649 // reset a maximal dirty range of the mod union / card tables, then lock | |
4650 // the free_list_lock and bitmap lock to do a full marking, then | |
4651 // release these locks; and repeat the cycle. This allows for a | |
4652 // certain amount of fairness in the sharing of these locks between | |
4653 // the CMS collector on the one hand, and the VM thread and the | |
4654 // mutators on the other. | |
4655 | |
4656 // NOTE: preclean_mod_union_table() and preclean_card_table() | |
4657 // further below are largely identical; if you need to modify | |
4658 // one of these methods, please check the other method too. | |
4659 | |
4660 size_t CMSCollector::preclean_mod_union_table( | |
4661 ConcurrentMarkSweepGeneration* gen, | |
4662 ScanMarkedObjectsAgainCarefullyClosure* cl) { | |
4663 verify_work_stacks_empty(); | |
4664 verify_overflow_empty(); | |
4665 | |
935 | 4666 // Turn off checking for this method but turn it back on |
4667 // selectively. There are yield points in this method | |
4668 // but it is difficult to turn the checking off just around | |
4669 // the yield points. It is simpler to selectively turn | |
4670 // it on. | |
4671 DEBUG_ONLY(RememberKlassesChecker mux(false);) | |
4672 | |
0 | 4673 // strategy: starting with the first card, accumulate contiguous |
4674 // ranges of dirty cards; clear these cards, then scan the region | |
4675 // covered by these cards. | |
4676 | |
4677 // Since all of the MUT is committed ahead, we can just use | |
4678 // that, in case the generations expand while we are precleaning. | |
4679 // It might also be fine to just use the committed part of the | |
4680 // generation, but we might potentially miss cards when the | |
4681 // generation is rapidly expanding while we are in the midst | |
4682 // of precleaning. | |
4683 HeapWord* startAddr = gen->reserved().start(); | |
4684 HeapWord* endAddr = gen->reserved().end(); | |
4685 | |
4686 cl->setFreelistLock(gen->freelistLock()); // needed for yielding | |
4687 | |
4688 size_t numDirtyCards, cumNumDirtyCards; | |
4689 HeapWord *nextAddr, *lastAddr; | |
4690 for (cumNumDirtyCards = numDirtyCards = 0, | |
4691 nextAddr = lastAddr = startAddr; | |
4692 nextAddr < endAddr; | |
4693 nextAddr = lastAddr, cumNumDirtyCards += numDirtyCards) { | |
4694 | |
4695 ResourceMark rm; | |
4696 HandleMark hm; | |
4697 | |
4698 MemRegion dirtyRegion; | |
4699 { | |
4700 stopTimer(); | |
935 | 4701 // Potential yield point |
0 | 4702 CMSTokenSync ts(true); |
4703 startTimer(); | |
4704 sample_eden(); | |
4705 // Get dirty region starting at nextOffset (inclusive), | |
4706 // simultaneously clearing it. | |
4707 dirtyRegion = | |
4708 _modUnionTable.getAndClearMarkedRegion(nextAddr, endAddr); | |
4709 assert(dirtyRegion.start() >= nextAddr, | |
4710 "returned region inconsistent?"); | |
4711 } | |
4712 // Remember where the next search should begin. | |
4713 // The returned region (if non-empty) is a right open interval, | |
4714 // so lastOffset is obtained from the right end of that | |
4715 // interval. | |
4716 lastAddr = dirtyRegion.end(); | |
4717 // Should do something more transparent and less hacky XXX | |
4718 numDirtyCards = | |
4719 _modUnionTable.heapWordDiffToOffsetDiff(dirtyRegion.word_size()); | |
4720 | |
4721 // We'll scan the cards in the dirty region (with periodic | |
4722 // yields for foreground GC as needed). | |
4723 if (!dirtyRegion.is_empty()) { | |
4724 assert(numDirtyCards > 0, "consistency check"); | |
4725 HeapWord* stop_point = NULL; | |
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4726 stopTimer(); |
935 | 4727 // Potential yield point |
453
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4728 CMSTokenSyncWithLocks ts(true, gen->freelistLock(), |
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4729 bitMapLock()); |
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4730 startTimer(); |
0 | 4731 { |
4732 verify_work_stacks_empty(); | |
4733 verify_overflow_empty(); | |
4734 sample_eden(); | |
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4735 DEBUG_ONLY(RememberKlassesChecker mx(should_unload_classes());) |
0 | 4736 stop_point = |
4737 gen->cmsSpace()->object_iterate_careful_m(dirtyRegion, cl); | |
4738 } | |
4739 if (stop_point != NULL) { | |
4740 // The careful iteration stopped early either because it found an | |
4741 // uninitialized object, or because we were in the midst of an | |
4742 // "abortable preclean", which should now be aborted. Redirty | |
4743 // the bits corresponding to the partially-scanned or unscanned | |
4744 // cards. We'll either restart at the next block boundary or | |
4745 // abort the preclean. | |
4746 assert((CMSPermGenPrecleaningEnabled && (gen == _permGen)) || | |
4747 (_collectorState == AbortablePreclean && should_abort_preclean()), | |
4748 "Unparsable objects should only be in perm gen."); | |
4749 _modUnionTable.mark_range(MemRegion(stop_point, dirtyRegion.end())); | |
4750 if (should_abort_preclean()) { | |
4751 break; // out of preclean loop | |
4752 } else { | |
4753 // Compute the next address at which preclean should pick up; | |
4754 // might need bitMapLock in order to read P-bits. | |
4755 lastAddr = next_card_start_after_block(stop_point); | |
4756 } | |
4757 } | |
4758 } else { | |
4759 assert(lastAddr == endAddr, "consistency check"); | |
4760 assert(numDirtyCards == 0, "consistency check"); | |
4761 break; | |
4762 } | |
4763 } | |
4764 verify_work_stacks_empty(); | |
4765 verify_overflow_empty(); | |
4766 return cumNumDirtyCards; | |
4767 } | |
4768 | |
4769 // NOTE: preclean_mod_union_table() above and preclean_card_table() | |
4770 // below are largely identical; if you need to modify | |
4771 // one of these methods, please check the other method too. | |
4772 | |
4773 size_t CMSCollector::preclean_card_table(ConcurrentMarkSweepGeneration* gen, | |
4774 ScanMarkedObjectsAgainCarefullyClosure* cl) { | |
4775 // strategy: it's similar to precleamModUnionTable above, in that | |
4776 // we accumulate contiguous ranges of dirty cards, mark these cards | |
4777 // precleaned, then scan the region covered by these cards. | |
4778 HeapWord* endAddr = (HeapWord*)(gen->_virtual_space.high()); | |
4779 HeapWord* startAddr = (HeapWord*)(gen->_virtual_space.low()); | |
4780 | |
4781 cl->setFreelistLock(gen->freelistLock()); // needed for yielding | |
4782 | |
4783 size_t numDirtyCards, cumNumDirtyCards; | |
4784 HeapWord *lastAddr, *nextAddr; | |
4785 | |
4786 for (cumNumDirtyCards = numDirtyCards = 0, | |
4787 nextAddr = lastAddr = startAddr; | |
4788 nextAddr < endAddr; | |
4789 nextAddr = lastAddr, cumNumDirtyCards += numDirtyCards) { | |
4790 | |
4791 ResourceMark rm; | |
4792 HandleMark hm; | |
4793 | |
4794 MemRegion dirtyRegion; | |
4795 { | |
4796 // See comments in "Precleaning notes" above on why we | |
4797 // do this locking. XXX Could the locking overheads be | |
4798 // too high when dirty cards are sparse? [I don't think so.] | |
4799 stopTimer(); | |
4800 CMSTokenSync x(true); // is cms thread | |
4801 startTimer(); | |
4802 sample_eden(); | |
4803 // Get and clear dirty region from card table | |
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4804 dirtyRegion = _ct->ct_bs()->dirty_card_range_after_reset( |
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4805 MemRegion(nextAddr, endAddr), |
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4806 true, |
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4807 CardTableModRefBS::precleaned_card_val()); |
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4808 |
0 | 4809 assert(dirtyRegion.start() >= nextAddr, |
4810 "returned region inconsistent?"); | |
4811 } | |
4812 lastAddr = dirtyRegion.end(); | |
4813 numDirtyCards = | |
4814 dirtyRegion.word_size()/CardTableModRefBS::card_size_in_words; | |
4815 | |
4816 if (!dirtyRegion.is_empty()) { | |
4817 stopTimer(); | |
4818 CMSTokenSyncWithLocks ts(true, gen->freelistLock(), bitMapLock()); | |
4819 startTimer(); | |
4820 sample_eden(); | |
4821 verify_work_stacks_empty(); | |
4822 verify_overflow_empty(); | |
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4823 DEBUG_ONLY(RememberKlassesChecker mx(should_unload_classes());) |
0 | 4824 HeapWord* stop_point = |
4825 gen->cmsSpace()->object_iterate_careful_m(dirtyRegion, cl); | |
4826 if (stop_point != NULL) { | |
4827 // The careful iteration stopped early because it found an | |
4828 // uninitialized object. Redirty the bits corresponding to the | |
4829 // partially-scanned or unscanned cards, and start again at the | |
4830 // next block boundary. | |
4831 assert(CMSPermGenPrecleaningEnabled || | |
4832 (_collectorState == AbortablePreclean && should_abort_preclean()), | |
4833 "Unparsable objects should only be in perm gen."); | |
4834 _ct->ct_bs()->invalidate(MemRegion(stop_point, dirtyRegion.end())); | |
4835 if (should_abort_preclean()) { | |
4836 break; // out of preclean loop | |
4837 } else { | |
4838 // Compute the next address at which preclean should pick up. | |
4839 lastAddr = next_card_start_after_block(stop_point); | |
4840 } | |
4841 } | |
4842 } else { | |
4843 break; | |
4844 } | |
4845 } | |
4846 verify_work_stacks_empty(); | |
4847 verify_overflow_empty(); | |
4848 return cumNumDirtyCards; | |
4849 } | |
4850 | |
4851 void CMSCollector::checkpointRootsFinal(bool asynch, | |
4852 bool clear_all_soft_refs, bool init_mark_was_synchronous) { | |
4853 assert(_collectorState == FinalMarking, "incorrect state transition?"); | |
4854 check_correct_thread_executing(); | |
4855 // world is stopped at this checkpoint | |
4856 assert(SafepointSynchronize::is_at_safepoint(), | |
4857 "world should be stopped"); | |
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4858 TraceCMSMemoryManagerStats tms(_collectorState); |
0 | 4859 verify_work_stacks_empty(); |
4860 verify_overflow_empty(); | |
4861 | |
4862 SpecializationStats::clear(); | |
4863 if (PrintGCDetails) { | |
4864 gclog_or_tty->print("[YG occupancy: "SIZE_FORMAT" K ("SIZE_FORMAT" K)]", | |
4865 _young_gen->used() / K, | |
4866 _young_gen->capacity() / K); | |
4867 } | |
4868 if (asynch) { | |
4869 if (CMSScavengeBeforeRemark) { | |
4870 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
4871 // Temporarily set flag to false, GCH->do_collection will | |
4872 // expect it to be false and set to true | |
4873 FlagSetting fl(gch->_is_gc_active, false); | |
4874 NOT_PRODUCT(TraceTime t("Scavenge-Before-Remark", | |
4875 PrintGCDetails && Verbose, true, gclog_or_tty);) | |
4876 int level = _cmsGen->level() - 1; | |
4877 if (level >= 0) { | |
4878 gch->do_collection(true, // full (i.e. force, see below) | |
4879 false, // !clear_all_soft_refs | |
4880 0, // size | |
4881 false, // is_tlab | |
4882 level // max_level | |
4883 ); | |
4884 } | |
4885 } | |
4886 FreelistLocker x(this); | |
4887 MutexLockerEx y(bitMapLock(), | |
4888 Mutex::_no_safepoint_check_flag); | |
4889 assert(!init_mark_was_synchronous, "but that's impossible!"); | |
4890 checkpointRootsFinalWork(asynch, clear_all_soft_refs, false); | |
4891 } else { | |
4892 // already have all the locks | |
4893 checkpointRootsFinalWork(asynch, clear_all_soft_refs, | |
4894 init_mark_was_synchronous); | |
4895 } | |
4896 verify_work_stacks_empty(); | |
4897 verify_overflow_empty(); | |
4898 SpecializationStats::print(); | |
4899 } | |
4900 | |
4901 void CMSCollector::checkpointRootsFinalWork(bool asynch, | |
4902 bool clear_all_soft_refs, bool init_mark_was_synchronous) { | |
4903 | |
4904 NOT_PRODUCT(TraceTime tr("checkpointRootsFinalWork", PrintGCDetails, false, gclog_or_tty);) | |
4905 | |
4906 assert(haveFreelistLocks(), "must have free list locks"); | |
4907 assert_lock_strong(bitMapLock()); | |
4908 | |
4909 if (UseAdaptiveSizePolicy) { | |
4910 size_policy()->checkpoint_roots_final_begin(); | |
4911 } | |
4912 | |
4913 ResourceMark rm; | |
4914 HandleMark hm; | |
4915 | |
4916 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
4917 | |
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4918 if (should_unload_classes()) { |
0 | 4919 CodeCache::gc_prologue(); |
4920 } | |
4921 assert(haveFreelistLocks(), "must have free list locks"); | |
4922 assert_lock_strong(bitMapLock()); | |
4923 | |
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4924 DEBUG_ONLY(RememberKlassesChecker fmx(should_unload_classes());) |
0 | 4925 if (!init_mark_was_synchronous) { |
4926 // We might assume that we need not fill TLAB's when | |
4927 // CMSScavengeBeforeRemark is set, because we may have just done | |
4928 // a scavenge which would have filled all TLAB's -- and besides | |
4929 // Eden would be empty. This however may not always be the case -- | |
4930 // for instance although we asked for a scavenge, it may not have | |
4931 // happened because of a JNI critical section. We probably need | |
4932 // a policy for deciding whether we can in that case wait until | |
4933 // the critical section releases and then do the remark following | |
4934 // the scavenge, and skip it here. In the absence of that policy, | |
4935 // or of an indication of whether the scavenge did indeed occur, | |
4936 // we cannot rely on TLAB's having been filled and must do | |
4937 // so here just in case a scavenge did not happen. | |
4938 gch->ensure_parsability(false); // fill TLAB's, but no need to retire them | |
4939 // Update the saved marks which may affect the root scans. | |
4940 gch->save_marks(); | |
4941 | |
4942 { | |
4943 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;) | |
4944 | |
4945 // Note on the role of the mod union table: | |
4946 // Since the marker in "markFromRoots" marks concurrently with | |
4947 // mutators, it is possible for some reachable objects not to have been | |
4948 // scanned. For instance, an only reference to an object A was | |
4949 // placed in object B after the marker scanned B. Unless B is rescanned, | |
4950 // A would be collected. Such updates to references in marked objects | |
4951 // are detected via the mod union table which is the set of all cards | |
4952 // dirtied since the first checkpoint in this GC cycle and prior to | |
4953 // the most recent young generation GC, minus those cleaned up by the | |
4954 // concurrent precleaning. | |
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4955 if (CMSParallelRemarkEnabled && CollectedHeap::use_parallel_gc_threads()) { |
0 | 4956 TraceTime t("Rescan (parallel) ", PrintGCDetails, false, gclog_or_tty); |
4957 do_remark_parallel(); | |
4958 } else { | |
4959 TraceTime t("Rescan (non-parallel) ", PrintGCDetails, false, | |
4960 gclog_or_tty); | |
4961 do_remark_non_parallel(); | |
4962 } | |
4963 } | |
4964 } else { | |
4965 assert(!asynch, "Can't have init_mark_was_synchronous in asynch mode"); | |
4966 // The initial mark was stop-world, so there's no rescanning to | |
4967 // do; go straight on to the next step below. | |
4968 } | |
4969 verify_work_stacks_empty(); | |
4970 verify_overflow_empty(); | |
4971 | |
4972 { | |
4973 NOT_PRODUCT(TraceTime ts("refProcessingWork", PrintGCDetails, false, gclog_or_tty);) | |
4974 refProcessingWork(asynch, clear_all_soft_refs); | |
4975 } | |
4976 verify_work_stacks_empty(); | |
4977 verify_overflow_empty(); | |
4978 | |
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4979 if (should_unload_classes()) { |
0 | 4980 CodeCache::gc_epilogue(); |
4981 } | |
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4982 JvmtiExport::gc_epilogue(); |
0 | 4983 |
4984 // If we encountered any (marking stack / work queue) overflow | |
4985 // events during the current CMS cycle, take appropriate | |
4986 // remedial measures, where possible, so as to try and avoid | |
4987 // recurrence of that condition. | |
4988 assert(_markStack.isEmpty(), "No grey objects"); | |
4989 size_t ser_ovflw = _ser_pmc_remark_ovflw + _ser_pmc_preclean_ovflw + | |
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4990 _ser_kac_ovflw + _ser_kac_preclean_ovflw; |
0 | 4991 if (ser_ovflw > 0) { |
4992 if (PrintCMSStatistics != 0) { | |
4993 gclog_or_tty->print_cr("Marking stack overflow (benign) " | |
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4994 "(pmc_pc="SIZE_FORMAT", pmc_rm="SIZE_FORMAT", kac="SIZE_FORMAT |
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4995 ", kac_preclean="SIZE_FORMAT")", |
0 | 4996 _ser_pmc_preclean_ovflw, _ser_pmc_remark_ovflw, |
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4997 _ser_kac_ovflw, _ser_kac_preclean_ovflw); |
0 | 4998 } |
4999 _markStack.expand(); | |
5000 _ser_pmc_remark_ovflw = 0; | |
5001 _ser_pmc_preclean_ovflw = 0; | |
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5002 _ser_kac_preclean_ovflw = 0; |
0 | 5003 _ser_kac_ovflw = 0; |
5004 } | |
5005 if (_par_pmc_remark_ovflw > 0 || _par_kac_ovflw > 0) { | |
5006 if (PrintCMSStatistics != 0) { | |
5007 gclog_or_tty->print_cr("Work queue overflow (benign) " | |
5008 "(pmc_rm="SIZE_FORMAT", kac="SIZE_FORMAT")", | |
5009 _par_pmc_remark_ovflw, _par_kac_ovflw); | |
5010 } | |
5011 _par_pmc_remark_ovflw = 0; | |
5012 _par_kac_ovflw = 0; | |
5013 } | |
5014 if (PrintCMSStatistics != 0) { | |
5015 if (_markStack._hit_limit > 0) { | |
5016 gclog_or_tty->print_cr(" (benign) Hit max stack size limit ("SIZE_FORMAT")", | |
5017 _markStack._hit_limit); | |
5018 } | |
5019 if (_markStack._failed_double > 0) { | |
5020 gclog_or_tty->print_cr(" (benign) Failed stack doubling ("SIZE_FORMAT")," | |
5021 " current capacity "SIZE_FORMAT, | |
5022 _markStack._failed_double, | |
5023 _markStack.capacity()); | |
5024 } | |
5025 } | |
5026 _markStack._hit_limit = 0; | |
5027 _markStack._failed_double = 0; | |
5028 | |
935 | 5029 // Check that all the klasses have been checked |
5030 assert(_revisitStack.isEmpty(), "Not all klasses revisited"); | |
5031 | |
0 | 5032 if ((VerifyAfterGC || VerifyDuringGC) && |
5033 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
5034 verify_after_remark(); | |
5035 } | |
5036 | |
5037 // Change under the freelistLocks. | |
5038 _collectorState = Sweeping; | |
5039 // Call isAllClear() under bitMapLock | |
5040 assert(_modUnionTable.isAllClear(), "Should be clear by end of the" | |
5041 " final marking"); | |
5042 if (UseAdaptiveSizePolicy) { | |
5043 size_policy()->checkpoint_roots_final_end(gch->gc_cause()); | |
5044 } | |
5045 } | |
5046 | |
5047 // Parallel remark task | |
5048 class CMSParRemarkTask: public AbstractGangTask { | |
5049 CMSCollector* _collector; | |
5050 int _n_workers; | |
5051 CompactibleFreeListSpace* _cms_space; | |
5052 CompactibleFreeListSpace* _perm_space; | |
5053 | |
5054 // The per-thread work queues, available here for stealing. | |
5055 OopTaskQueueSet* _task_queues; | |
5056 ParallelTaskTerminator _term; | |
5057 | |
5058 public: | |
5059 CMSParRemarkTask(CMSCollector* collector, | |
5060 CompactibleFreeListSpace* cms_space, | |
5061 CompactibleFreeListSpace* perm_space, | |
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5062 int n_workers, FlexibleWorkGang* workers, |
0 | 5063 OopTaskQueueSet* task_queues): |
5064 AbstractGangTask("Rescan roots and grey objects in parallel"), | |
5065 _collector(collector), | |
5066 _cms_space(cms_space), _perm_space(perm_space), | |
5067 _n_workers(n_workers), | |
5068 _task_queues(task_queues), | |
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5069 _term(n_workers, task_queues) { } |
0 | 5070 |
5071 OopTaskQueueSet* task_queues() { return _task_queues; } | |
5072 | |
5073 OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); } | |
5074 | |
5075 ParallelTaskTerminator* terminator() { return &_term; } | |
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5076 int n_workers() { return _n_workers; } |
0 | 5077 |
5078 void work(int i); | |
5079 | |
5080 private: | |
5081 // Work method in support of parallel rescan ... of young gen spaces | |
5082 void do_young_space_rescan(int i, Par_MarkRefsIntoAndScanClosure* cl, | |
5083 ContiguousSpace* space, | |
5084 HeapWord** chunk_array, size_t chunk_top); | |
5085 | |
5086 // ... of dirty cards in old space | |
5087 void do_dirty_card_rescan_tasks(CompactibleFreeListSpace* sp, int i, | |
5088 Par_MarkRefsIntoAndScanClosure* cl); | |
5089 | |
5090 // ... work stealing for the above | |
5091 void do_work_steal(int i, Par_MarkRefsIntoAndScanClosure* cl, int* seed); | |
5092 }; | |
5093 | |
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5094 // work_queue(i) is passed to the closure |
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5095 // Par_MarkRefsIntoAndScanClosure. The "i" parameter |
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5096 // also is passed to do_dirty_card_rescan_tasks() and to |
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5097 // do_work_steal() to select the i-th task_queue. |
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5098 |
0 | 5099 void CMSParRemarkTask::work(int i) { |
5100 elapsedTimer _timer; | |
5101 ResourceMark rm; | |
5102 HandleMark hm; | |
5103 | |
5104 // ---------- rescan from roots -------------- | |
5105 _timer.start(); | |
5106 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
5107 Par_MarkRefsIntoAndScanClosure par_mrias_cl(_collector, | |
5108 _collector->_span, _collector->ref_processor(), | |
5109 &(_collector->_markBitMap), | |
5110 work_queue(i), &(_collector->_revisitStack)); | |
5111 | |
5112 // Rescan young gen roots first since these are likely | |
5113 // coarsely partitioned and may, on that account, constitute | |
5114 // the critical path; thus, it's best to start off that | |
5115 // work first. | |
5116 // ---------- young gen roots -------------- | |
5117 { | |
5118 DefNewGeneration* dng = _collector->_young_gen->as_DefNewGeneration(); | |
5119 EdenSpace* eden_space = dng->eden(); | |
5120 ContiguousSpace* from_space = dng->from(); | |
5121 ContiguousSpace* to_space = dng->to(); | |
5122 | |
5123 HeapWord** eca = _collector->_eden_chunk_array; | |
5124 size_t ect = _collector->_eden_chunk_index; | |
5125 HeapWord** sca = _collector->_survivor_chunk_array; | |
5126 size_t sct = _collector->_survivor_chunk_index; | |
5127 | |
5128 assert(ect <= _collector->_eden_chunk_capacity, "out of bounds"); | |
5129 assert(sct <= _collector->_survivor_chunk_capacity, "out of bounds"); | |
5130 | |
5131 do_young_space_rescan(i, &par_mrias_cl, to_space, NULL, 0); | |
5132 do_young_space_rescan(i, &par_mrias_cl, from_space, sca, sct); | |
5133 do_young_space_rescan(i, &par_mrias_cl, eden_space, eca, ect); | |
5134 | |
5135 _timer.stop(); | |
5136 if (PrintCMSStatistics != 0) { | |
5137 gclog_or_tty->print_cr( | |
5138 "Finished young gen rescan work in %dth thread: %3.3f sec", | |
5139 i, _timer.seconds()); | |
5140 } | |
5141 } | |
5142 | |
5143 // ---------- remaining roots -------------- | |
5144 _timer.reset(); | |
5145 _timer.start(); | |
5146 gch->gen_process_strong_roots(_collector->_cmsGen->level(), | |
5147 false, // yg was scanned above | |
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|
5148 false, // this is parallel code |
0 | 5149 true, // collecting perm gen |
5150 SharedHeap::ScanningOption(_collector->CMSCollector::roots_scanning_options()), | |
989
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5151 &par_mrias_cl, |
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5152 true, // walk all of code cache if (so & SO_CodeCache) |
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|
5153 NULL); |
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|
5154 assert(_collector->should_unload_classes() |
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|
5155 || (_collector->CMSCollector::roots_scanning_options() & SharedHeap::SO_CodeCache), |
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5156 "if we didn't scan the code cache, we have to be ready to drop nmethods with expired weak oops"); |
0 | 5157 _timer.stop(); |
5158 if (PrintCMSStatistics != 0) { | |
5159 gclog_or_tty->print_cr( | |
5160 "Finished remaining root rescan work in %dth thread: %3.3f sec", | |
5161 i, _timer.seconds()); | |
5162 } | |
5163 | |
5164 // ---------- rescan dirty cards ------------ | |
5165 _timer.reset(); | |
5166 _timer.start(); | |
5167 | |
5168 // Do the rescan tasks for each of the two spaces | |
5169 // (cms_space and perm_space) in turn. | |
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|
5170 // "i" is passed to select the "i-th" task_queue |
0 | 5171 do_dirty_card_rescan_tasks(_cms_space, i, &par_mrias_cl); |
5172 do_dirty_card_rescan_tasks(_perm_space, i, &par_mrias_cl); | |
5173 _timer.stop(); | |
5174 if (PrintCMSStatistics != 0) { | |
5175 gclog_or_tty->print_cr( | |
5176 "Finished dirty card rescan work in %dth thread: %3.3f sec", | |
5177 i, _timer.seconds()); | |
5178 } | |
5179 | |
5180 // ---------- steal work from other threads ... | |
5181 // ---------- ... and drain overflow list. | |
5182 _timer.reset(); | |
5183 _timer.start(); | |
5184 do_work_steal(i, &par_mrias_cl, _collector->hash_seed(i)); | |
5185 _timer.stop(); | |
5186 if (PrintCMSStatistics != 0) { | |
5187 gclog_or_tty->print_cr( | |
5188 "Finished work stealing in %dth thread: %3.3f sec", | |
5189 i, _timer.seconds()); | |
5190 } | |
5191 } | |
5192 | |
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5193 // Note that parameter "i" is not used. |
0 | 5194 void |
5195 CMSParRemarkTask::do_young_space_rescan(int i, | |
5196 Par_MarkRefsIntoAndScanClosure* cl, ContiguousSpace* space, | |
5197 HeapWord** chunk_array, size_t chunk_top) { | |
5198 // Until all tasks completed: | |
5199 // . claim an unclaimed task | |
5200 // . compute region boundaries corresponding to task claimed | |
5201 // using chunk_array | |
5202 // . par_oop_iterate(cl) over that region | |
5203 | |
5204 ResourceMark rm; | |
5205 HandleMark hm; | |
5206 | |
5207 SequentialSubTasksDone* pst = space->par_seq_tasks(); | |
5208 assert(pst->valid(), "Uninitialized use?"); | |
5209 | |
5210 int nth_task = 0; | |
5211 int n_tasks = pst->n_tasks(); | |
5212 | |
5213 HeapWord *start, *end; | |
5214 while (!pst->is_task_claimed(/* reference */ nth_task)) { | |
5215 // We claimed task # nth_task; compute its boundaries. | |
5216 if (chunk_top == 0) { // no samples were taken | |
5217 assert(nth_task == 0 && n_tasks == 1, "Can have only 1 EdenSpace task"); | |
5218 start = space->bottom(); | |
5219 end = space->top(); | |
5220 } else if (nth_task == 0) { | |
5221 start = space->bottom(); | |
5222 end = chunk_array[nth_task]; | |
5223 } else if (nth_task < (jint)chunk_top) { | |
5224 assert(nth_task >= 1, "Control point invariant"); | |
5225 start = chunk_array[nth_task - 1]; | |
5226 end = chunk_array[nth_task]; | |
5227 } else { | |
5228 assert(nth_task == (jint)chunk_top, "Control point invariant"); | |
5229 start = chunk_array[chunk_top - 1]; | |
5230 end = space->top(); | |
5231 } | |
5232 MemRegion mr(start, end); | |
5233 // Verify that mr is in space | |
5234 assert(mr.is_empty() || space->used_region().contains(mr), | |
5235 "Should be in space"); | |
5236 // Verify that "start" is an object boundary | |
5237 assert(mr.is_empty() || oop(mr.start())->is_oop(), | |
5238 "Should be an oop"); | |
5239 space->par_oop_iterate(mr, cl); | |
5240 } | |
5241 pst->all_tasks_completed(); | |
5242 } | |
5243 | |
5244 void | |
5245 CMSParRemarkTask::do_dirty_card_rescan_tasks( | |
5246 CompactibleFreeListSpace* sp, int i, | |
5247 Par_MarkRefsIntoAndScanClosure* cl) { | |
5248 // Until all tasks completed: | |
5249 // . claim an unclaimed task | |
5250 // . compute region boundaries corresponding to task claimed | |
5251 // . transfer dirty bits ct->mut for that region | |
5252 // . apply rescanclosure to dirty mut bits for that region | |
5253 | |
5254 ResourceMark rm; | |
5255 HandleMark hm; | |
5256 | |
5257 OopTaskQueue* work_q = work_queue(i); | |
5258 ModUnionClosure modUnionClosure(&(_collector->_modUnionTable)); | |
5259 // CAUTION! CAUTION! CAUTION! CAUTION! CAUTION! CAUTION! CAUTION! | |
5260 // CAUTION: This closure has state that persists across calls to | |
5261 // the work method dirty_range_iterate_clear() in that it has | |
5262 // imbedded in it a (subtype of) UpwardsObjectClosure. The | |
5263 // use of that state in the imbedded UpwardsObjectClosure instance | |
5264 // assumes that the cards are always iterated (even if in parallel | |
5265 // by several threads) in monotonically increasing order per each | |
5266 // thread. This is true of the implementation below which picks | |
5267 // card ranges (chunks) in monotonically increasing order globally | |
5268 // and, a-fortiori, in monotonically increasing order per thread | |
5269 // (the latter order being a subsequence of the former). | |
5270 // If the work code below is ever reorganized into a more chaotic | |
5271 // work-partitioning form than the current "sequential tasks" | |
5272 // paradigm, the use of that persistent state will have to be | |
5273 // revisited and modified appropriately. See also related | |
5274 // bug 4756801 work on which should examine this code to make | |
5275 // sure that the changes there do not run counter to the | |
5276 // assumptions made here and necessary for correctness and | |
5277 // efficiency. Note also that this code might yield inefficient | |
5278 // behaviour in the case of very large objects that span one or | |
5279 // more work chunks. Such objects would potentially be scanned | |
5280 // several times redundantly. Work on 4756801 should try and | |
5281 // address that performance anomaly if at all possible. XXX | |
5282 MemRegion full_span = _collector->_span; | |
5283 CMSBitMap* bm = &(_collector->_markBitMap); // shared | |
5284 CMSMarkStack* rs = &(_collector->_revisitStack); // shared | |
5285 MarkFromDirtyCardsClosure | |
5286 greyRescanClosure(_collector, full_span, // entire span of interest | |
5287 sp, bm, work_q, rs, cl); | |
5288 | |
5289 SequentialSubTasksDone* pst = sp->conc_par_seq_tasks(); | |
5290 assert(pst->valid(), "Uninitialized use?"); | |
5291 int nth_task = 0; | |
5292 const int alignment = CardTableModRefBS::card_size * BitsPerWord; | |
5293 MemRegion span = sp->used_region(); | |
5294 HeapWord* start_addr = span.start(); | |
5295 HeapWord* end_addr = (HeapWord*)round_to((intptr_t)span.end(), | |
5296 alignment); | |
5297 const size_t chunk_size = sp->rescan_task_size(); // in HeapWord units | |
5298 assert((HeapWord*)round_to((intptr_t)start_addr, alignment) == | |
5299 start_addr, "Check alignment"); | |
5300 assert((size_t)round_to((intptr_t)chunk_size, alignment) == | |
5301 chunk_size, "Check alignment"); | |
5302 | |
5303 while (!pst->is_task_claimed(/* reference */ nth_task)) { | |
5304 // Having claimed the nth_task, compute corresponding mem-region, | |
5305 // which is a-fortiori aligned correctly (i.e. at a MUT bopundary). | |
5306 // The alignment restriction ensures that we do not need any | |
5307 // synchronization with other gang-workers while setting or | |
5308 // clearing bits in thus chunk of the MUT. | |
5309 MemRegion this_span = MemRegion(start_addr + nth_task*chunk_size, | |
5310 start_addr + (nth_task+1)*chunk_size); | |
5311 // The last chunk's end might be way beyond end of the | |
5312 // used region. In that case pull back appropriately. | |
5313 if (this_span.end() > end_addr) { | |
5314 this_span.set_end(end_addr); | |
5315 assert(!this_span.is_empty(), "Program logic (calculation of n_tasks)"); | |
5316 } | |
5317 // Iterate over the dirty cards covering this chunk, marking them | |
5318 // precleaned, and setting the corresponding bits in the mod union | |
5319 // table. Since we have been careful to partition at Card and MUT-word | |
5320 // boundaries no synchronization is needed between parallel threads. | |
5321 _collector->_ct->ct_bs()->dirty_card_iterate(this_span, | |
5322 &modUnionClosure); | |
5323 | |
5324 // Having transferred these marks into the modUnionTable, | |
5325 // rescan the marked objects on the dirty cards in the modUnionTable. | |
5326 // Even if this is at a synchronous collection, the initial marking | |
5327 // may have been done during an asynchronous collection so there | |
5328 // may be dirty bits in the mod-union table. | |
5329 _collector->_modUnionTable.dirty_range_iterate_clear( | |
5330 this_span, &greyRescanClosure); | |
5331 _collector->_modUnionTable.verifyNoOneBitsInRange( | |
5332 this_span.start(), | |
5333 this_span.end()); | |
5334 } | |
5335 pst->all_tasks_completed(); // declare that i am done | |
5336 } | |
5337 | |
5338 // . see if we can share work_queues with ParNew? XXX | |
5339 void | |
5340 CMSParRemarkTask::do_work_steal(int i, Par_MarkRefsIntoAndScanClosure* cl, | |
5341 int* seed) { | |
5342 OopTaskQueue* work_q = work_queue(i); | |
5343 NOT_PRODUCT(int num_steals = 0;) | |
5344 oop obj_to_scan; | |
5345 CMSBitMap* bm = &(_collector->_markBitMap); | |
5346 | |
5347 while (true) { | |
5348 // Completely finish any left over work from (an) earlier round(s) | |
5349 cl->trim_queue(0); | |
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5350 size_t num_from_overflow_list = MIN2((size_t)(work_q->max_elems() - work_q->size())/4, |
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5351 (size_t)ParGCDesiredObjsFromOverflowList); |
0 | 5352 // Now check if there's any work in the overflow list |
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5353 // Passing ParallelGCThreads as the third parameter, no_of_gc_threads, |
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5354 // only affects the number of attempts made to get work from the |
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5355 // overflow list and does not affect the number of workers. Just |
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5356 // pass ParallelGCThreads so this behavior is unchanged. |
0 | 5357 if (_collector->par_take_from_overflow_list(num_from_overflow_list, |
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5358 work_q, |
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5359 ParallelGCThreads)) { |
0 | 5360 // found something in global overflow list; |
5361 // not yet ready to go stealing work from others. | |
5362 // We'd like to assert(work_q->size() != 0, ...) | |
5363 // because we just took work from the overflow list, | |
5364 // but of course we can't since all of that could have | |
5365 // been already stolen from us. | |
5366 // "He giveth and He taketh away." | |
5367 continue; | |
5368 } | |
5369 // Verify that we have no work before we resort to stealing | |
5370 assert(work_q->size() == 0, "Have work, shouldn't steal"); | |
5371 // Try to steal from other queues that have work | |
5372 if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) { | |
5373 NOT_PRODUCT(num_steals++;) | |
5374 assert(obj_to_scan->is_oop(), "Oops, not an oop!"); | |
5375 assert(bm->isMarked((HeapWord*)obj_to_scan), "Stole an unmarked oop?"); | |
5376 // Do scanning work | |
5377 obj_to_scan->oop_iterate(cl); | |
5378 // Loop around, finish this work, and try to steal some more | |
5379 } else if (terminator()->offer_termination()) { | |
5380 break; // nirvana from the infinite cycle | |
5381 } | |
5382 } | |
5383 NOT_PRODUCT( | |
5384 if (PrintCMSStatistics != 0) { | |
5385 gclog_or_tty->print("\n\t(%d: stole %d oops)", i, num_steals); | |
5386 } | |
5387 ) | |
5388 assert(work_q->size() == 0 && _collector->overflow_list_is_empty(), | |
5389 "Else our work is not yet done"); | |
5390 } | |
5391 | |
5392 // Return a thread-local PLAB recording array, as appropriate. | |
5393 void* CMSCollector::get_data_recorder(int thr_num) { | |
5394 if (_survivor_plab_array != NULL && | |
5395 (CMSPLABRecordAlways || | |
5396 (_collectorState > Marking && _collectorState < FinalMarking))) { | |
5397 assert(thr_num < (int)ParallelGCThreads, "thr_num is out of bounds"); | |
5398 ChunkArray* ca = &_survivor_plab_array[thr_num]; | |
5399 ca->reset(); // clear it so that fresh data is recorded | |
5400 return (void*) ca; | |
5401 } else { | |
5402 return NULL; | |
5403 } | |
5404 } | |
5405 | |
5406 // Reset all the thread-local PLAB recording arrays | |
5407 void CMSCollector::reset_survivor_plab_arrays() { | |
5408 for (uint i = 0; i < ParallelGCThreads; i++) { | |
5409 _survivor_plab_array[i].reset(); | |
5410 } | |
5411 } | |
5412 | |
5413 // Merge the per-thread plab arrays into the global survivor chunk | |
5414 // array which will provide the partitioning of the survivor space | |
5415 // for CMS rescan. | |
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5416 void CMSCollector::merge_survivor_plab_arrays(ContiguousSpace* surv, |
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5417 int no_of_gc_threads) { |
0 | 5418 assert(_survivor_plab_array != NULL, "Error"); |
5419 assert(_survivor_chunk_array != NULL, "Error"); | |
5420 assert(_collectorState == FinalMarking, "Error"); | |
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5421 for (int j = 0; j < no_of_gc_threads; j++) { |
0 | 5422 _cursor[j] = 0; |
5423 } | |
5424 HeapWord* top = surv->top(); | |
5425 size_t i; | |
5426 for (i = 0; i < _survivor_chunk_capacity; i++) { // all sca entries | |
5427 HeapWord* min_val = top; // Higher than any PLAB address | |
5428 uint min_tid = 0; // position of min_val this round | |
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5429 for (int j = 0; j < no_of_gc_threads; j++) { |
0 | 5430 ChunkArray* cur_sca = &_survivor_plab_array[j]; |
5431 if (_cursor[j] == cur_sca->end()) { | |
5432 continue; | |
5433 } | |
5434 assert(_cursor[j] < cur_sca->end(), "ctl pt invariant"); | |
5435 HeapWord* cur_val = cur_sca->nth(_cursor[j]); | |
5436 assert(surv->used_region().contains(cur_val), "Out of bounds value"); | |
5437 if (cur_val < min_val) { | |
5438 min_tid = j; | |
5439 min_val = cur_val; | |
5440 } else { | |
5441 assert(cur_val < top, "All recorded addresses should be less"); | |
5442 } | |
5443 } | |
5444 // At this point min_val and min_tid are respectively | |
5445 // the least address in _survivor_plab_array[j]->nth(_cursor[j]) | |
5446 // and the thread (j) that witnesses that address. | |
5447 // We record this address in the _survivor_chunk_array[i] | |
5448 // and increment _cursor[min_tid] prior to the next round i. | |
5449 if (min_val == top) { | |
5450 break; | |
5451 } | |
5452 _survivor_chunk_array[i] = min_val; | |
5453 _cursor[min_tid]++; | |
5454 } | |
5455 // We are all done; record the size of the _survivor_chunk_array | |
5456 _survivor_chunk_index = i; // exclusive: [0, i) | |
5457 if (PrintCMSStatistics > 0) { | |
5458 gclog_or_tty->print(" (Survivor:" SIZE_FORMAT "chunks) ", i); | |
5459 } | |
5460 // Verify that we used up all the recorded entries | |
5461 #ifdef ASSERT | |
5462 size_t total = 0; | |
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5463 for (int j = 0; j < no_of_gc_threads; j++) { |
0 | 5464 assert(_cursor[j] == _survivor_plab_array[j].end(), "Ctl pt invariant"); |
5465 total += _cursor[j]; | |
5466 } | |
5467 assert(total == _survivor_chunk_index, "Ctl Pt Invariant"); | |
5468 // Check that the merged array is in sorted order | |
5469 if (total > 0) { | |
5470 for (size_t i = 0; i < total - 1; i++) { | |
5471 if (PrintCMSStatistics > 0) { | |
5472 gclog_or_tty->print(" (chunk" SIZE_FORMAT ":" INTPTR_FORMAT ") ", | |
5473 i, _survivor_chunk_array[i]); | |
5474 } | |
5475 assert(_survivor_chunk_array[i] < _survivor_chunk_array[i+1], | |
5476 "Not sorted"); | |
5477 } | |
5478 } | |
5479 #endif // ASSERT | |
5480 } | |
5481 | |
5482 // Set up the space's par_seq_tasks structure for work claiming | |
5483 // for parallel rescan of young gen. | |
5484 // See ParRescanTask where this is currently used. | |
5485 void | |
5486 CMSCollector:: | |
5487 initialize_sequential_subtasks_for_young_gen_rescan(int n_threads) { | |
5488 assert(n_threads > 0, "Unexpected n_threads argument"); | |
5489 DefNewGeneration* dng = (DefNewGeneration*)_young_gen; | |
5490 | |
5491 // Eden space | |
5492 { | |
5493 SequentialSubTasksDone* pst = dng->eden()->par_seq_tasks(); | |
5494 assert(!pst->valid(), "Clobbering existing data?"); | |
5495 // Each valid entry in [0, _eden_chunk_index) represents a task. | |
5496 size_t n_tasks = _eden_chunk_index + 1; | |
5497 assert(n_tasks == 1 || _eden_chunk_array != NULL, "Error"); | |
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5498 // Sets the condition for completion of the subtask (how many threads |
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5499 // need to finish in order to be done). |
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5500 pst->set_n_threads(n_threads); |
0 | 5501 pst->set_n_tasks((int)n_tasks); |
5502 } | |
5503 | |
5504 // Merge the survivor plab arrays into _survivor_chunk_array | |
5505 if (_survivor_plab_array != NULL) { | |
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5506 merge_survivor_plab_arrays(dng->from(), n_threads); |
0 | 5507 } else { |
5508 assert(_survivor_chunk_index == 0, "Error"); | |
5509 } | |
5510 | |
5511 // To space | |
5512 { | |
5513 SequentialSubTasksDone* pst = dng->to()->par_seq_tasks(); | |
5514 assert(!pst->valid(), "Clobbering existing data?"); | |
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5515 // Sets the condition for completion of the subtask (how many threads |
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5516 // need to finish in order to be done). |
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5517 pst->set_n_threads(n_threads); |
0 | 5518 pst->set_n_tasks(1); |
5519 assert(pst->valid(), "Error"); | |
5520 } | |
5521 | |
5522 // From space | |
5523 { | |
5524 SequentialSubTasksDone* pst = dng->from()->par_seq_tasks(); | |
5525 assert(!pst->valid(), "Clobbering existing data?"); | |
5526 size_t n_tasks = _survivor_chunk_index + 1; | |
5527 assert(n_tasks == 1 || _survivor_chunk_array != NULL, "Error"); | |
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5528 // Sets the condition for completion of the subtask (how many threads |
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5529 // need to finish in order to be done). |
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5530 pst->set_n_threads(n_threads); |
0 | 5531 pst->set_n_tasks((int)n_tasks); |
5532 assert(pst->valid(), "Error"); | |
5533 } | |
5534 } | |
5535 | |
5536 // Parallel version of remark | |
5537 void CMSCollector::do_remark_parallel() { | |
5538 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
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5539 FlexibleWorkGang* workers = gch->workers(); |
0 | 5540 assert(workers != NULL, "Need parallel worker threads."); |
5541 int n_workers = workers->total_workers(); | |
5542 CompactibleFreeListSpace* cms_space = _cmsGen->cmsSpace(); | |
5543 CompactibleFreeListSpace* perm_space = _permGen->cmsSpace(); | |
5544 | |
5545 CMSParRemarkTask tsk(this, | |
5546 cms_space, perm_space, | |
5547 n_workers, workers, task_queues()); | |
5548 | |
5549 // Set up for parallel process_strong_roots work. | |
5550 gch->set_par_threads(n_workers); | |
5551 // We won't be iterating over the cards in the card table updating | |
5552 // the younger_gen cards, so we shouldn't call the following else | |
5553 // the verification code as well as subsequent younger_refs_iterate | |
5554 // code would get confused. XXX | |
5555 // gch->rem_set()->prepare_for_younger_refs_iterate(true); // parallel | |
5556 | |
5557 // The young gen rescan work will not be done as part of | |
5558 // process_strong_roots (which currently doesn't knw how to | |
5559 // parallelize such a scan), but rather will be broken up into | |
5560 // a set of parallel tasks (via the sampling that the [abortable] | |
5561 // preclean phase did of EdenSpace, plus the [two] tasks of | |
5562 // scanning the [two] survivor spaces. Further fine-grain | |
5563 // parallelization of the scanning of the survivor spaces | |
5564 // themselves, and of precleaning of the younger gen itself | |
5565 // is deferred to the future. | |
5566 initialize_sequential_subtasks_for_young_gen_rescan(n_workers); | |
5567 | |
5568 // The dirty card rescan work is broken up into a "sequence" | |
5569 // of parallel tasks (per constituent space) that are dynamically | |
5570 // claimed by the parallel threads. | |
5571 cms_space->initialize_sequential_subtasks_for_rescan(n_workers); | |
5572 perm_space->initialize_sequential_subtasks_for_rescan(n_workers); | |
5573 | |
5574 // It turns out that even when we're using 1 thread, doing the work in a | |
5575 // separate thread causes wide variance in run times. We can't help this | |
5576 // in the multi-threaded case, but we special-case n=1 here to get | |
5577 // repeatable measurements of the 1-thread overhead of the parallel code. | |
5578 if (n_workers > 1) { | |
5579 // Make refs discovery MT-safe | |
5580 ReferenceProcessorMTMutator mt(ref_processor(), true); | |
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5581 GenCollectedHeap::StrongRootsScope srs(gch); |
0 | 5582 workers->run_task(&tsk); |
5583 } else { | |
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5584 GenCollectedHeap::StrongRootsScope srs(gch); |
0 | 5585 tsk.work(0); |
5586 } | |
5587 gch->set_par_threads(0); // 0 ==> non-parallel. | |
5588 // restore, single-threaded for now, any preserved marks | |
5589 // as a result of work_q overflow | |
5590 restore_preserved_marks_if_any(); | |
5591 } | |
5592 | |
5593 // Non-parallel version of remark | |
5594 void CMSCollector::do_remark_non_parallel() { | |
5595 ResourceMark rm; | |
5596 HandleMark hm; | |
5597 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
5598 MarkRefsIntoAndScanClosure | |
5599 mrias_cl(_span, ref_processor(), &_markBitMap, &_modUnionTable, | |
5600 &_markStack, &_revisitStack, this, | |
5601 false /* should_yield */, false /* not precleaning */); | |
5602 MarkFromDirtyCardsClosure | |
5603 markFromDirtyCardsClosure(this, _span, | |
5604 NULL, // space is set further below | |
5605 &_markBitMap, &_markStack, &_revisitStack, | |
5606 &mrias_cl); | |
5607 { | |
5608 TraceTime t("grey object rescan", PrintGCDetails, false, gclog_or_tty); | |
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5609 // Iterate over the dirty cards, setting the corresponding bits in the |
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5610 // mod union table. |
0 | 5611 { |
5612 ModUnionClosure modUnionClosure(&_modUnionTable); | |
5613 _ct->ct_bs()->dirty_card_iterate( | |
5614 _cmsGen->used_region(), | |
5615 &modUnionClosure); | |
5616 _ct->ct_bs()->dirty_card_iterate( | |
5617 _permGen->used_region(), | |
5618 &modUnionClosure); | |
5619 } | |
5620 // Having transferred these marks into the modUnionTable, we just need | |
5621 // to rescan the marked objects on the dirty cards in the modUnionTable. | |
5622 // The initial marking may have been done during an asynchronous | |
5623 // collection so there may be dirty bits in the mod-union table. | |
5624 const int alignment = | |
5625 CardTableModRefBS::card_size * BitsPerWord; | |
5626 { | |
5627 // ... First handle dirty cards in CMS gen | |
5628 markFromDirtyCardsClosure.set_space(_cmsGen->cmsSpace()); | |
5629 MemRegion ur = _cmsGen->used_region(); | |
5630 HeapWord* lb = ur.start(); | |
5631 HeapWord* ub = (HeapWord*)round_to((intptr_t)ur.end(), alignment); | |
5632 MemRegion cms_span(lb, ub); | |
5633 _modUnionTable.dirty_range_iterate_clear(cms_span, | |
5634 &markFromDirtyCardsClosure); | |
5635 verify_work_stacks_empty(); | |
5636 if (PrintCMSStatistics != 0) { | |
5637 gclog_or_tty->print(" (re-scanned "SIZE_FORMAT" dirty cards in cms gen) ", | |
5638 markFromDirtyCardsClosure.num_dirty_cards()); | |
5639 } | |
5640 } | |
5641 { | |
5642 // .. and then repeat for dirty cards in perm gen | |
5643 markFromDirtyCardsClosure.set_space(_permGen->cmsSpace()); | |
5644 MemRegion ur = _permGen->used_region(); | |
5645 HeapWord* lb = ur.start(); | |
5646 HeapWord* ub = (HeapWord*)round_to((intptr_t)ur.end(), alignment); | |
5647 MemRegion perm_span(lb, ub); | |
5648 _modUnionTable.dirty_range_iterate_clear(perm_span, | |
5649 &markFromDirtyCardsClosure); | |
5650 verify_work_stacks_empty(); | |
5651 if (PrintCMSStatistics != 0) { | |
5652 gclog_or_tty->print(" (re-scanned "SIZE_FORMAT" dirty cards in perm gen) ", | |
5653 markFromDirtyCardsClosure.num_dirty_cards()); | |
5654 } | |
5655 } | |
5656 } | |
5657 if (VerifyDuringGC && | |
5658 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
5659 HandleMark hm; // Discard invalid handles created during verification | |
5660 Universe::verify(true); | |
5661 } | |
5662 { | |
5663 TraceTime t("root rescan", PrintGCDetails, false, gclog_or_tty); | |
5664 | |
5665 verify_work_stacks_empty(); | |
5666 | |
5667 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. | |
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|
5668 GenCollectedHeap::StrongRootsScope srs(gch); |
0 | 5669 gch->gen_process_strong_roots(_cmsGen->level(), |
5670 true, // younger gens as roots | |
989
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|
5671 false, // use the local StrongRootsScope |
0 | 5672 true, // collecting perm gen |
5673 SharedHeap::ScanningOption(roots_scanning_options()), | |
989
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|
5674 &mrias_cl, |
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diff
changeset
|
5675 true, // walk code active on stacks |
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diff
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|
5676 NULL); |
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diff
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|
5677 assert(should_unload_classes() |
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diff
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|
5678 || (roots_scanning_options() & SharedHeap::SO_CodeCache), |
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|
5679 "if we didn't scan the code cache, we have to be ready to drop nmethods with expired weak oops"); |
0 | 5680 } |
5681 verify_work_stacks_empty(); | |
5682 // Restore evacuated mark words, if any, used for overflow list links | |
5683 if (!CMSOverflowEarlyRestoration) { | |
5684 restore_preserved_marks_if_any(); | |
5685 } | |
5686 verify_overflow_empty(); | |
5687 } | |
5688 | |
5689 //////////////////////////////////////////////////////// | |
5690 // Parallel Reference Processing Task Proxy Class | |
5691 //////////////////////////////////////////////////////// | |
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5692 class CMSRefProcTaskProxy: public AbstractGangTaskWOopQueues { |
0 | 5693 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; |
5694 CMSCollector* _collector; | |
5695 CMSBitMap* _mark_bit_map; | |
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5696 const MemRegion _span; |
0 | 5697 ProcessTask& _task; |
5698 | |
5699 public: | |
5700 CMSRefProcTaskProxy(ProcessTask& task, | |
5701 CMSCollector* collector, | |
5702 const MemRegion& span, | |
5703 CMSBitMap* mark_bit_map, | |
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5704 AbstractWorkGang* workers, |
0 | 5705 OopTaskQueueSet* task_queues): |
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5706 AbstractGangTaskWOopQueues("Process referents by policy in parallel", |
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|
5707 task_queues), |
0 | 5708 _task(task), |
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5709 _collector(collector), _span(span), _mark_bit_map(mark_bit_map) |
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5710 { |
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5711 assert(_collector->_span.equals(_span) && !_span.is_empty(), |
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5712 "Inconsistency in _span"); |
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5713 } |
0 | 5714 |
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5715 OopTaskQueueSet* task_queues() { return queues(); } |
0 | 5716 |
5717 OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); } | |
5718 | |
5719 void do_work_steal(int i, | |
5720 CMSParDrainMarkingStackClosure* drain, | |
5721 CMSParKeepAliveClosure* keep_alive, | |
5722 int* seed); | |
5723 | |
5724 virtual void work(int i); | |
5725 }; | |
5726 | |
5727 void CMSRefProcTaskProxy::work(int i) { | |
143
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5728 assert(_collector->_span.equals(_span), "Inconsistency in _span"); |
0 | 5729 CMSParKeepAliveClosure par_keep_alive(_collector, _span, |
935 | 5730 _mark_bit_map, |
5731 &_collector->_revisitStack, | |
5732 work_queue(i)); | |
0 | 5733 CMSParDrainMarkingStackClosure par_drain_stack(_collector, _span, |
935 | 5734 _mark_bit_map, |
5735 &_collector->_revisitStack, | |
5736 work_queue(i)); | |
143
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|
5737 CMSIsAliveClosure is_alive_closure(_span, _mark_bit_map); |
0 | 5738 _task.work(i, is_alive_closure, par_keep_alive, par_drain_stack); |
5739 if (_task.marks_oops_alive()) { | |
5740 do_work_steal(i, &par_drain_stack, &par_keep_alive, | |
5741 _collector->hash_seed(i)); | |
5742 } | |
5743 assert(work_queue(i)->size() == 0, "work_queue should be empty"); | |
5744 assert(_collector->_overflow_list == NULL, "non-empty _overflow_list"); | |
5745 } | |
5746 | |
5747 class CMSRefEnqueueTaskProxy: public AbstractGangTask { | |
5748 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; | |
5749 EnqueueTask& _task; | |
5750 | |
5751 public: | |
5752 CMSRefEnqueueTaskProxy(EnqueueTask& task) | |
5753 : AbstractGangTask("Enqueue reference objects in parallel"), | |
5754 _task(task) | |
5755 { } | |
5756 | |
5757 virtual void work(int i) | |
5758 { | |
5759 _task.work(i); | |
5760 } | |
5761 }; | |
5762 | |
5763 CMSParKeepAliveClosure::CMSParKeepAliveClosure(CMSCollector* collector, | |
935 | 5764 MemRegion span, CMSBitMap* bit_map, CMSMarkStack* revisit_stack, |
5765 OopTaskQueue* work_queue): | |
5766 Par_KlassRememberingOopClosure(collector, NULL, revisit_stack), | |
0 | 5767 _span(span), |
5768 _bit_map(bit_map), | |
5769 _work_queue(work_queue), | |
935 | 5770 _mark_and_push(collector, span, bit_map, revisit_stack, work_queue), |
0 | 5771 _low_water_mark(MIN2((uint)(work_queue->max_elems()/4), |
5772 (uint)(CMSWorkQueueDrainThreshold * ParallelGCThreads))) | |
5773 { } | |
5774 | |
5775 // . see if we can share work_queues with ParNew? XXX | |
5776 void CMSRefProcTaskProxy::do_work_steal(int i, | |
5777 CMSParDrainMarkingStackClosure* drain, | |
5778 CMSParKeepAliveClosure* keep_alive, | |
5779 int* seed) { | |
5780 OopTaskQueue* work_q = work_queue(i); | |
5781 NOT_PRODUCT(int num_steals = 0;) | |
5782 oop obj_to_scan; | |
5783 | |
5784 while (true) { | |
5785 // Completely finish any left over work from (an) earlier round(s) | |
5786 drain->trim_queue(0); | |
679
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6819891: ParNew: Fix work queue overflow code to deal correctly with +UseCompressedOops
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changeset
|
5787 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
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|
5788 (size_t)ParGCDesiredObjsFromOverflowList); |
0 | 5789 // Now check if there's any work in the overflow list |
1833
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5790 // Passing ParallelGCThreads as the third parameter, no_of_gc_threads, |
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|
5791 // only affects the number of attempts made to get work from the |
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changeset
|
5792 // overflow list and does not affect the number of workers. Just |
8b10f48633dc
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jmasa
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changeset
|
5793 // pass ParallelGCThreads so this behavior is unchanged. |
0 | 5794 if (_collector->par_take_from_overflow_list(num_from_overflow_list, |
1833
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jmasa
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|
5795 work_q, |
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diff
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|
5796 ParallelGCThreads)) { |
0 | 5797 // Found something in global overflow list; |
5798 // not yet ready to go stealing work from others. | |
5799 // We'd like to assert(work_q->size() != 0, ...) | |
5800 // because we just took work from the overflow list, | |
5801 // but of course we can't, since all of that might have | |
5802 // been already stolen from us. | |
5803 continue; | |
5804 } | |
5805 // Verify that we have no work before we resort to stealing | |
5806 assert(work_q->size() == 0, "Have work, shouldn't steal"); | |
5807 // Try to steal from other queues that have work | |
5808 if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) { | |
5809 NOT_PRODUCT(num_steals++;) | |
5810 assert(obj_to_scan->is_oop(), "Oops, not an oop!"); | |
5811 assert(_mark_bit_map->isMarked((HeapWord*)obj_to_scan), "Stole an unmarked oop?"); | |
5812 // Do scanning work | |
5813 obj_to_scan->oop_iterate(keep_alive); | |
5814 // Loop around, finish this work, and try to steal some more | |
5815 } else if (terminator()->offer_termination()) { | |
5816 break; // nirvana from the infinite cycle | |
5817 } | |
5818 } | |
5819 NOT_PRODUCT( | |
5820 if (PrintCMSStatistics != 0) { | |
5821 gclog_or_tty->print("\n\t(%d: stole %d oops)", i, num_steals); | |
5822 } | |
5823 ) | |
5824 } | |
5825 | |
5826 void CMSRefProcTaskExecutor::execute(ProcessTask& task) | |
5827 { | |
5828 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
1833
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jmasa
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|
5829 FlexibleWorkGang* workers = gch->workers(); |
0 | 5830 assert(workers != NULL, "Need parallel worker threads."); |
5831 CMSRefProcTaskProxy rp_task(task, &_collector, | |
5832 _collector.ref_processor()->span(), | |
5833 _collector.markBitMap(), | |
1833
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jmasa
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changeset
|
5834 workers, _collector.task_queues()); |
0 | 5835 workers->run_task(&rp_task); |
5836 } | |
5837 | |
5838 void CMSRefProcTaskExecutor::execute(EnqueueTask& task) | |
5839 { | |
5840 | |
5841 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
1833
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jmasa
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|
5842 FlexibleWorkGang* workers = gch->workers(); |
0 | 5843 assert(workers != NULL, "Need parallel worker threads."); |
5844 CMSRefEnqueueTaskProxy enq_task(task); | |
5845 workers->run_task(&enq_task); | |
5846 } | |
5847 | |
5848 void CMSCollector::refProcessingWork(bool asynch, bool clear_all_soft_refs) { | |
5849 | |
5850 ResourceMark rm; | |
5851 HandleMark hm; | |
5852 | |
5853 ReferenceProcessor* rp = ref_processor(); | |
5854 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
|
5855 assert(!rp->enqueuing_is_done(), "Enqueuing should not be complete"); |
c96030fff130
6684579: SoftReference processing can be made more efficient
ysr
parents:
452
diff
changeset
|
5856 // Process weak references. |
457
27a80744a83b
6778647: snap(), snap_policy() should be renamed setup(), setup_policy()
ysr
parents:
453
diff
changeset
|
5857 rp->setup_policy(clear_all_soft_refs); |
453
c96030fff130
6684579: SoftReference processing can be made more efficient
ysr
parents:
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diff
changeset
|
5858 verify_work_stacks_empty(); |
c96030fff130
6684579: SoftReference processing can be made more efficient
ysr
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diff
changeset
|
5859 |
0 | 5860 CMSKeepAliveClosure cmsKeepAliveClosure(this, _span, &_markBitMap, |
935 | 5861 &_markStack, &_revisitStack, |
5862 false /* !preclean */); | |
0 | 5863 CMSDrainMarkingStackClosure cmsDrainMarkingStackClosure(this, |
5864 _span, &_markBitMap, &_markStack, | |
452
00b023ae2d78
6722113: CMS: Incorrect overflow handling during precleaning of Reference lists
ysr
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360
diff
changeset
|
5865 &cmsKeepAliveClosure, false /* !preclean */); |
0 | 5866 { |
5867 TraceTime t("weak refs processing", PrintGCDetails, false, gclog_or_tty); | |
5868 if (rp->processing_is_mt()) { | |
1833
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|
5869 // Set the degree of MT here. If the discovery is done MT, there |
8b10f48633dc
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jmasa
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diff
changeset
|
5870 // may have been a different number of threads doing the discovery |
8b10f48633dc
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1777
diff
changeset
|
5871 // and a different number of discovered lists may have Ref objects. |
8b10f48633dc
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jmasa
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diff
changeset
|
5872 // That is OK as long as the Reference lists are balanced (see |
8b10f48633dc
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jmasa
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diff
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|
5873 // balance_all_queues() and balance_queues()). |
8b10f48633dc
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jmasa
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diff
changeset
|
5874 |
8b10f48633dc
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jmasa
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|
5875 |
8b10f48633dc
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|
5876 rp->set_mt_degree(ParallelGCThreads); |
0 | 5877 CMSRefProcTaskExecutor task_executor(*this); |
453
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ysr
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diff
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|
5878 rp->process_discovered_references(&_is_alive_closure, |
0 | 5879 &cmsKeepAliveClosure, |
5880 &cmsDrainMarkingStackClosure, | |
5881 &task_executor); | |
5882 } else { | |
453
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diff
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|
5883 rp->process_discovered_references(&_is_alive_closure, |
0 | 5884 &cmsKeepAliveClosure, |
5885 &cmsDrainMarkingStackClosure, | |
5886 NULL); | |
5887 } | |
5888 verify_work_stacks_empty(); | |
5889 } | |
5890 | |
94
0834225a7916
6634032: CMS: Need CMSInitiatingPermOccupancyFraction for perm, divorcing from CMSInitiatingOccupancyFraction
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diff
changeset
|
5891 if (should_unload_classes()) { |
0 | 5892 { |
5893 TraceTime t("class unloading", PrintGCDetails, false, gclog_or_tty); | |
5894 | |
5895 // Follow SystemDictionary roots and unload classes | |
5896 bool purged_class = SystemDictionary::do_unloading(&_is_alive_closure); | |
5897 | |
5898 // Follow CodeCache roots and unload any methods marked for unloading | |
5899 CodeCache::do_unloading(&_is_alive_closure, | |
5900 &cmsKeepAliveClosure, | |
5901 purged_class); | |
5902 | |
5903 cmsDrainMarkingStackClosure.do_void(); | |
5904 verify_work_stacks_empty(); | |
5905 | |
5906 // Update subklass/sibling/implementor links in KlassKlass descendants | |
5907 assert(!_revisitStack.isEmpty(), "revisit stack should not be empty"); | |
5908 oop k; | |
5909 while ((k = _revisitStack.pop()) != NULL) { | |
5910 ((Klass*)(oopDesc*)k)->follow_weak_klass_links( | |
5911 &_is_alive_closure, | |
5912 &cmsKeepAliveClosure); | |
5913 } | |
5914 assert(!ClassUnloading || | |
5915 (_markStack.isEmpty() && overflow_list_is_empty()), | |
5916 "Should not have found new reachable objects"); | |
5917 assert(_revisitStack.isEmpty(), "revisit stack should have been drained"); | |
5918 cmsDrainMarkingStackClosure.do_void(); | |
5919 verify_work_stacks_empty(); | |
5920 } | |
5921 | |
5922 { | |
5923 TraceTime t("scrub symbol & string tables", PrintGCDetails, false, gclog_or_tty); | |
2177
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6990754: Use native memory and reference counting to implement SymbolTable
coleenp
parents:
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changeset
|
5924 // Now clean up stale oops in StringTable |
0 | 5925 StringTable::unlink(&_is_alive_closure); |
2177
3582bf76420e
6990754: Use native memory and reference counting to implement SymbolTable
coleenp
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diff
changeset
|
5926 // Clean up unreferenced symbols in symbol table. |
3582bf76420e
6990754: Use native memory and reference counting to implement SymbolTable
coleenp
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diff
changeset
|
5927 SymbolTable::unlink(); |
0 | 5928 } |
5929 } | |
5930 | |
5931 verify_work_stacks_empty(); | |
5932 // Restore any preserved marks as a result of mark stack or | |
5933 // work queue overflow | |
5934 restore_preserved_marks_if_any(); // done single-threaded for now | |
5935 | |
5936 rp->set_enqueuing_is_done(true); | |
5937 if (rp->processing_is_mt()) { | |
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|
5938 rp->balance_all_queues(); |
0 | 5939 CMSRefProcTaskExecutor task_executor(*this); |
5940 rp->enqueue_discovered_references(&task_executor); | |
5941 } else { | |
5942 rp->enqueue_discovered_references(NULL); | |
5943 } | |
5944 rp->verify_no_references_recorded(); | |
5945 assert(!rp->discovery_enabled(), "should have been disabled"); | |
5946 } | |
5947 | |
5948 #ifndef PRODUCT | |
5949 void CMSCollector::check_correct_thread_executing() { | |
5950 Thread* t = Thread::current(); | |
5951 // Only the VM thread or the CMS thread should be here. | |
5952 assert(t->is_ConcurrentGC_thread() || t->is_VM_thread(), | |
5953 "Unexpected thread type"); | |
5954 // If this is the vm thread, the foreground process | |
5955 // should not be waiting. Note that _foregroundGCIsActive is | |
5956 // true while the foreground collector is waiting. | |
5957 if (_foregroundGCShouldWait) { | |
5958 // We cannot be the VM thread | |
5959 assert(t->is_ConcurrentGC_thread(), | |
5960 "Should be CMS thread"); | |
5961 } else { | |
5962 // We can be the CMS thread only if we are in a stop-world | |
5963 // phase of CMS collection. | |
5964 if (t->is_ConcurrentGC_thread()) { | |
5965 assert(_collectorState == InitialMarking || | |
5966 _collectorState == FinalMarking, | |
5967 "Should be a stop-world phase"); | |
5968 // The CMS thread should be holding the CMS_token. | |
5969 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
5970 "Potential interference with concurrently " | |
5971 "executing VM thread"); | |
5972 } | |
5973 } | |
5974 } | |
5975 #endif | |
5976 | |
5977 void CMSCollector::sweep(bool asynch) { | |
5978 assert(_collectorState == Sweeping, "just checking"); | |
5979 check_correct_thread_executing(); | |
5980 verify_work_stacks_empty(); | |
5981 verify_overflow_empty(); | |
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5982 increment_sweep_count(); |
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5983 TraceCMSMemoryManagerStats tms(_collectorState); |
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5984 |
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5985 _inter_sweep_timer.stop(); |
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5986 _inter_sweep_estimate.sample(_inter_sweep_timer.seconds()); |
0 | 5987 size_policy()->avg_cms_free_at_sweep()->sample(_cmsGen->free()); |
5988 | |
5989 // PermGen verification support: If perm gen sweeping is disabled in | |
5990 // this cycle, we preserve the perm gen object "deadness" information | |
5991 // in the perm_gen_verify_bit_map. In order to do that we traverse | |
5992 // all blocks in perm gen and mark all dead objects. | |
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5993 if (verifying() && !should_unload_classes()) { |
0 | 5994 assert(perm_gen_verify_bit_map()->sizeInBits() != 0, |
5995 "Should have already been allocated"); | |
5996 MarkDeadObjectsClosure mdo(this, _permGen->cmsSpace(), | |
5997 markBitMap(), perm_gen_verify_bit_map()); | |
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5998 if (asynch) { |
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5999 CMSTokenSyncWithLocks ts(true, _permGen->freelistLock(), |
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6000 bitMapLock()); |
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6001 _permGen->cmsSpace()->blk_iterate(&mdo); |
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6002 } else { |
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6003 // In the case of synchronous sweep, we already have |
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6004 // the requisite locks/tokens. |
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6005 _permGen->cmsSpace()->blk_iterate(&mdo); |
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6006 } |
0 | 6007 } |
6008 | |
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6009 assert(!_intra_sweep_timer.is_active(), "Should not be active"); |
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6010 _intra_sweep_timer.reset(); |
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6011 _intra_sweep_timer.start(); |
0 | 6012 if (asynch) { |
6013 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
6014 CMSPhaseAccounting pa(this, "sweep", !PrintGCDetails); | |
6015 // First sweep the old gen then the perm gen | |
6016 { | |
6017 CMSTokenSyncWithLocks ts(true, _cmsGen->freelistLock(), | |
6018 bitMapLock()); | |
6019 sweepWork(_cmsGen, asynch); | |
6020 } | |
6021 | |
6022 // Now repeat for perm gen | |
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6023 if (should_unload_classes()) { |
0 | 6024 CMSTokenSyncWithLocks ts(true, _permGen->freelistLock(), |
6025 bitMapLock()); | |
6026 sweepWork(_permGen, asynch); | |
6027 } | |
6028 | |
6029 // Update Universe::_heap_*_at_gc figures. | |
6030 // We need all the free list locks to make the abstract state | |
6031 // transition from Sweeping to Resetting. See detailed note | |
6032 // further below. | |
6033 { | |
6034 CMSTokenSyncWithLocks ts(true, _cmsGen->freelistLock(), | |
6035 _permGen->freelistLock()); | |
6036 // Update heap occupancy information which is used as | |
6037 // input to soft ref clearing policy at the next gc. | |
6038 Universe::update_heap_info_at_gc(); | |
6039 _collectorState = Resizing; | |
6040 } | |
6041 } else { | |
6042 // already have needed locks | |
6043 sweepWork(_cmsGen, asynch); | |
6044 | |
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6045 if (should_unload_classes()) { |
0 | 6046 sweepWork(_permGen, asynch); |
6047 } | |
6048 // Update heap occupancy information which is used as | |
6049 // input to soft ref clearing policy at the next gc. | |
6050 Universe::update_heap_info_at_gc(); | |
6051 _collectorState = Resizing; | |
6052 } | |
6053 verify_work_stacks_empty(); | |
6054 verify_overflow_empty(); | |
6055 | |
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6056 _intra_sweep_timer.stop(); |
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6057 _intra_sweep_estimate.sample(_intra_sweep_timer.seconds()); |
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6058 |
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6059 _inter_sweep_timer.reset(); |
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6060 _inter_sweep_timer.start(); |
0 | 6061 |
6062 update_time_of_last_gc(os::javaTimeMillis()); | |
6063 | |
6064 // NOTE on abstract state transitions: | |
6065 // Mutators allocate-live and/or mark the mod-union table dirty | |
6066 // based on the state of the collection. The former is done in | |
6067 // the interval [Marking, Sweeping] and the latter in the interval | |
6068 // [Marking, Sweeping). Thus the transitions into the Marking state | |
6069 // and out of the Sweeping state must be synchronously visible | |
6070 // globally to the mutators. | |
6071 // The transition into the Marking state happens with the world | |
6072 // stopped so the mutators will globally see it. Sweeping is | |
6073 // done asynchronously by the background collector so the transition | |
6074 // from the Sweeping state to the Resizing state must be done | |
6075 // under the freelistLock (as is the check for whether to | |
6076 // allocate-live and whether to dirty the mod-union table). | |
6077 assert(_collectorState == Resizing, "Change of collector state to" | |
6078 " Resizing must be done under the freelistLocks (plural)"); | |
6079 | |
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6080 // Now that sweeping has been completed, we clear |
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6081 // the incremental_collection_failed flag, |
0 | 6082 // thus inviting a younger gen collection to promote into |
6083 // this generation. If such a promotion may still fail, | |
6084 // the flag will be set again when a young collection is | |
6085 // attempted. | |
6086 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
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6087 gch->clear_incremental_collection_failed(); // Worth retrying as fresh space may have been freed up |
0 | 6088 gch->update_full_collections_completed(_collection_count_start); |
6089 } | |
6090 | |
6091 // FIX ME!!! Looks like this belongs in CFLSpace, with | |
6092 // CMSGen merely delegating to it. | |
6093 void ConcurrentMarkSweepGeneration::setNearLargestChunk() { | |
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6094 double nearLargestPercent = FLSLargestBlockCoalesceProximity; |
0 | 6095 HeapWord* minAddr = _cmsSpace->bottom(); |
6096 HeapWord* largestAddr = | |
6097 (HeapWord*) _cmsSpace->dictionary()->findLargestDict(); | |
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6098 if (largestAddr == NULL) { |
0 | 6099 // The dictionary appears to be empty. In this case |
6100 // try to coalesce at the end of the heap. | |
6101 largestAddr = _cmsSpace->end(); | |
6102 } | |
6103 size_t largestOffset = pointer_delta(largestAddr, minAddr); | |
6104 size_t nearLargestOffset = | |
6105 (size_t)((double)largestOffset * nearLargestPercent) - MinChunkSize; | |
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6106 if (PrintFLSStatistics != 0) { |
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6107 gclog_or_tty->print_cr( |
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6108 "CMS: Large Block: " PTR_FORMAT ";" |
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6109 " Proximity: " PTR_FORMAT " -> " PTR_FORMAT, |
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6110 largestAddr, |
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6111 _cmsSpace->nearLargestChunk(), minAddr + nearLargestOffset); |
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6112 } |
0 | 6113 _cmsSpace->set_nearLargestChunk(minAddr + nearLargestOffset); |
6114 } | |
6115 | |
6116 bool ConcurrentMarkSweepGeneration::isNearLargestChunk(HeapWord* addr) { | |
6117 return addr >= _cmsSpace->nearLargestChunk(); | |
6118 } | |
6119 | |
6120 FreeChunk* ConcurrentMarkSweepGeneration::find_chunk_at_end() { | |
6121 return _cmsSpace->find_chunk_at_end(); | |
6122 } | |
6123 | |
6124 void ConcurrentMarkSweepGeneration::update_gc_stats(int current_level, | |
6125 bool full) { | |
6126 // The next lower level has been collected. Gather any statistics | |
6127 // that are of interest at this point. | |
6128 if (!full && (current_level + 1) == level()) { | |
6129 // Gather statistics on the young generation collection. | |
6130 collector()->stats().record_gc0_end(used()); | |
6131 } | |
6132 } | |
6133 | |
6134 CMSAdaptiveSizePolicy* ConcurrentMarkSweepGeneration::size_policy() { | |
6135 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
6136 assert(gch->kind() == CollectedHeap::GenCollectedHeap, | |
6137 "Wrong type of heap"); | |
6138 CMSAdaptiveSizePolicy* sp = (CMSAdaptiveSizePolicy*) | |
6139 gch->gen_policy()->size_policy(); | |
6140 assert(sp->is_gc_cms_adaptive_size_policy(), | |
6141 "Wrong type of size policy"); | |
6142 return sp; | |
6143 } | |
6144 | |
6145 void ConcurrentMarkSweepGeneration::rotate_debug_collection_type() { | |
6146 if (PrintGCDetails && Verbose) { | |
6147 gclog_or_tty->print("Rotate from %d ", _debug_collection_type); | |
6148 } | |
6149 _debug_collection_type = (CollectionTypes) (_debug_collection_type + 1); | |
6150 _debug_collection_type = | |
6151 (CollectionTypes) (_debug_collection_type % Unknown_collection_type); | |
6152 if (PrintGCDetails && Verbose) { | |
6153 gclog_or_tty->print_cr("to %d ", _debug_collection_type); | |
6154 } | |
6155 } | |
6156 | |
6157 void CMSCollector::sweepWork(ConcurrentMarkSweepGeneration* gen, | |
6158 bool asynch) { | |
6159 // We iterate over the space(s) underlying this generation, | |
6160 // checking the mark bit map to see if the bits corresponding | |
6161 // to specific blocks are marked or not. Blocks that are | |
6162 // marked are live and are not swept up. All remaining blocks | |
6163 // are swept up, with coalescing on-the-fly as we sweep up | |
6164 // contiguous free and/or garbage blocks: | |
6165 // We need to ensure that the sweeper synchronizes with allocators | |
6166 // and stop-the-world collectors. In particular, the following | |
6167 // locks are used: | |
6168 // . CMS token: if this is held, a stop the world collection cannot occur | |
6169 // . freelistLock: if this is held no allocation can occur from this | |
6170 // generation by another thread | |
6171 // . bitMapLock: if this is held, no other thread can access or update | |
6172 // | |
6173 | |
6174 // Note that we need to hold the freelistLock if we use | |
6175 // block iterate below; else the iterator might go awry if | |
6176 // a mutator (or promotion) causes block contents to change | |
6177 // (for instance if the allocator divvies up a block). | |
6178 // If we hold the free list lock, for all practical purposes | |
6179 // young generation GC's can't occur (they'll usually need to | |
6180 // promote), so we might as well prevent all young generation | |
6181 // GC's while we do a sweeping step. For the same reason, we might | |
6182 // as well take the bit map lock for the entire duration | |
6183 | |
6184 // check that we hold the requisite locks | |
6185 assert(have_cms_token(), "Should hold cms token"); | |
6186 assert( (asynch && ConcurrentMarkSweepThread::cms_thread_has_cms_token()) | |
6187 || (!asynch && ConcurrentMarkSweepThread::vm_thread_has_cms_token()), | |
6188 "Should possess CMS token to sweep"); | |
6189 assert_lock_strong(gen->freelistLock()); | |
6190 assert_lock_strong(bitMapLock()); | |
6191 | |
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6192 assert(!_inter_sweep_timer.is_active(), "Was switched off in an outer context"); |
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6193 assert(_intra_sweep_timer.is_active(), "Was switched on in an outer context"); |
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6194 gen->cmsSpace()->beginSweepFLCensus((float)(_inter_sweep_timer.seconds()), |
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6195 _inter_sweep_estimate.padded_average(), |
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6196 _intra_sweep_estimate.padded_average()); |
0 | 6197 gen->setNearLargestChunk(); |
6198 | |
6199 { | |
6200 SweepClosure sweepClosure(this, gen, &_markBitMap, | |
6201 CMSYield && asynch); | |
6202 gen->cmsSpace()->blk_iterate_careful(&sweepClosure); | |
6203 // We need to free-up/coalesce garbage/blocks from a | |
6204 // co-terminal free run. This is done in the SweepClosure | |
6205 // destructor; so, do not remove this scope, else the | |
6206 // end-of-sweep-census below will be off by a little bit. | |
6207 } | |
6208 gen->cmsSpace()->sweep_completed(); | |
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6209 gen->cmsSpace()->endSweepFLCensus(sweep_count()); |
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6210 if (should_unload_classes()) { // unloaded classes this cycle, |
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6211 _concurrent_cycles_since_last_unload = 0; // ... reset count |
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6212 } else { // did not unload classes, |
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6213 _concurrent_cycles_since_last_unload++; // ... increment count |
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6214 } |
0 | 6215 } |
6216 | |
6217 // Reset CMS data structures (for now just the marking bit map) | |
6218 // preparatory for the next cycle. | |
6219 void CMSCollector::reset(bool asynch) { | |
6220 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
6221 CMSAdaptiveSizePolicy* sp = size_policy(); | |
6222 AdaptiveSizePolicyOutput(sp, gch->total_collections()); | |
6223 if (asynch) { | |
6224 CMSTokenSyncWithLocks ts(true, bitMapLock()); | |
6225 | |
6226 // If the state is not "Resetting", the foreground thread | |
6227 // has done a collection and the resetting. | |
6228 if (_collectorState != Resetting) { | |
6229 assert(_collectorState == Idling, "The state should only change" | |
6230 " because the foreground collector has finished the collection"); | |
6231 return; | |
6232 } | |
6233 | |
6234 // Clear the mark bitmap (no grey objects to start with) | |
6235 // for the next cycle. | |
6236 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
6237 CMSPhaseAccounting cmspa(this, "reset", !PrintGCDetails); | |
6238 | |
6239 HeapWord* curAddr = _markBitMap.startWord(); | |
6240 while (curAddr < _markBitMap.endWord()) { | |
6241 size_t remaining = pointer_delta(_markBitMap.endWord(), curAddr); | |
6242 MemRegion chunk(curAddr, MIN2(CMSBitMapYieldQuantum, remaining)); | |
6243 _markBitMap.clear_large_range(chunk); | |
6244 if (ConcurrentMarkSweepThread::should_yield() && | |
6245 !foregroundGCIsActive() && | |
6246 CMSYield) { | |
6247 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
6248 "CMS thread should hold CMS token"); | |
6249 assert_lock_strong(bitMapLock()); | |
6250 bitMapLock()->unlock(); | |
6251 ConcurrentMarkSweepThread::desynchronize(true); | |
6252 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
6253 stopTimer(); | |
6254 if (PrintCMSStatistics != 0) { | |
6255 incrementYields(); | |
6256 } | |
6257 icms_wait(); | |
6258 | |
6259 // See the comment in coordinator_yield() | |
6260 for (unsigned i = 0; i < CMSYieldSleepCount && | |
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6261 ConcurrentMarkSweepThread::should_yield() && |
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6262 !CMSCollector::foregroundGCIsActive(); ++i) { |
0 | 6263 os::sleep(Thread::current(), 1, false); |
6264 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
6265 } | |
6266 | |
6267 ConcurrentMarkSweepThread::synchronize(true); | |
6268 bitMapLock()->lock_without_safepoint_check(); | |
6269 startTimer(); | |
6270 } | |
6271 curAddr = chunk.end(); | |
6272 } | |
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6273 // A successful mostly concurrent collection has been done. |
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6274 // Because only the full (i.e., concurrent mode failure) collections |
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6275 // are being measured for gc overhead limits, clean the "near" flag |
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6276 // and count. |
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6277 sp->reset_gc_overhead_limit_count(); |
0 | 6278 _collectorState = Idling; |
6279 } else { | |
6280 // already have the lock | |
6281 assert(_collectorState == Resetting, "just checking"); | |
6282 assert_lock_strong(bitMapLock()); | |
6283 _markBitMap.clear_all(); | |
6284 _collectorState = Idling; | |
6285 } | |
6286 | |
6287 // Stop incremental mode after a cycle completes, so that any future cycles | |
6288 // are triggered by allocation. | |
6289 stop_icms(); | |
6290 | |
6291 NOT_PRODUCT( | |
6292 if (RotateCMSCollectionTypes) { | |
6293 _cmsGen->rotate_debug_collection_type(); | |
6294 } | |
6295 ) | |
6296 } | |
6297 | |
6298 void CMSCollector::do_CMS_operation(CMS_op_type op) { | |
6299 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps); | |
6300 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
6301 TraceTime t("GC", PrintGC, !PrintGCDetails, gclog_or_tty); | |
6302 TraceCollectorStats tcs(counters()); | |
6303 | |
6304 switch (op) { | |
6305 case CMS_op_checkpointRootsInitial: { | |
2125
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|
6306 SvcGCMarker sgcm(SvcGCMarker::OTHER); |
0 | 6307 checkpointRootsInitial(true); // asynch |
6308 if (PrintGC) { | |
6309 _cmsGen->printOccupancy("initial-mark"); | |
6310 } | |
6311 break; | |
6312 } | |
6313 case CMS_op_checkpointRootsFinal: { | |
2125
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|
6314 SvcGCMarker sgcm(SvcGCMarker::OTHER); |
0 | 6315 checkpointRootsFinal(true, // asynch |
6316 false, // !clear_all_soft_refs | |
6317 false); // !init_mark_was_synchronous | |
6318 if (PrintGC) { | |
6319 _cmsGen->printOccupancy("remark"); | |
6320 } | |
6321 break; | |
6322 } | |
6323 default: | |
6324 fatal("No such CMS_op"); | |
6325 } | |
6326 } | |
6327 | |
6328 #ifndef PRODUCT | |
6329 size_t const CMSCollector::skip_header_HeapWords() { | |
6330 return FreeChunk::header_size(); | |
6331 } | |
6332 | |
6333 // Try and collect here conditions that should hold when | |
6334 // CMS thread is exiting. The idea is that the foreground GC | |
6335 // thread should not be blocked if it wants to terminate | |
6336 // the CMS thread and yet continue to run the VM for a while | |
6337 // after that. | |
6338 void CMSCollector::verify_ok_to_terminate() const { | |
6339 assert(Thread::current()->is_ConcurrentGC_thread(), | |
6340 "should be called by CMS thread"); | |
6341 assert(!_foregroundGCShouldWait, "should be false"); | |
6342 // We could check here that all the various low-level locks | |
6343 // are not held by the CMS thread, but that is overkill; see | |
6344 // also CMSThread::verify_ok_to_terminate() where the CGC_lock | |
6345 // is checked. | |
6346 } | |
6347 #endif | |
6348 | |
6349 size_t CMSCollector::block_size_using_printezis_bits(HeapWord* addr) const { | |
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6350 assert(_markBitMap.isMarked(addr) && _markBitMap.isMarked(addr + 1), |
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6351 "missing Printezis mark?"); |
0 | 6352 HeapWord* nextOneAddr = _markBitMap.getNextMarkedWordAddress(addr + 2); |
6353 size_t size = pointer_delta(nextOneAddr + 1, addr); | |
6354 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
6355 "alignment problem"); | |
6356 assert(size >= 3, "Necessary for Printezis marks to work"); | |
6357 return size; | |
6358 } | |
6359 | |
6360 // A variant of the above (block_size_using_printezis_bits()) except | |
6361 // that we return 0 if the P-bits are not yet set. | |
6362 size_t CMSCollector::block_size_if_printezis_bits(HeapWord* addr) const { | |
2226
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6363 if (_markBitMap.isMarked(addr + 1)) { |
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6364 assert(_markBitMap.isMarked(addr), "P-bit can be set only for marked objects"); |
0 | 6365 HeapWord* nextOneAddr = _markBitMap.getNextMarkedWordAddress(addr + 2); |
6366 size_t size = pointer_delta(nextOneAddr + 1, addr); | |
6367 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
6368 "alignment problem"); | |
6369 assert(size >= 3, "Necessary for Printezis marks to work"); | |
6370 return size; | |
2226
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6371 } |
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|
6372 return 0; |
0 | 6373 } |
6374 | |
6375 HeapWord* CMSCollector::next_card_start_after_block(HeapWord* addr) const { | |
6376 size_t sz = 0; | |
6377 oop p = (oop)addr; | |
187 | 6378 if (p->klass_or_null() != NULL && p->is_parsable()) { |
0 | 6379 sz = CompactibleFreeListSpace::adjustObjectSize(p->size()); |
6380 } else { | |
6381 sz = block_size_using_printezis_bits(addr); | |
6382 } | |
6383 assert(sz > 0, "size must be nonzero"); | |
6384 HeapWord* next_block = addr + sz; | |
6385 HeapWord* next_card = (HeapWord*)round_to((uintptr_t)next_block, | |
6386 CardTableModRefBS::card_size); | |
6387 assert(round_down((uintptr_t)addr, CardTableModRefBS::card_size) < | |
6388 round_down((uintptr_t)next_card, CardTableModRefBS::card_size), | |
6389 "must be different cards"); | |
6390 return next_card; | |
6391 } | |
6392 | |
6393 | |
6394 // CMS Bit Map Wrapper ///////////////////////////////////////// | |
6395 | |
6396 // Construct a CMS bit map infrastructure, but don't create the | |
6397 // bit vector itself. That is done by a separate call CMSBitMap::allocate() | |
6398 // further below. | |
6399 CMSBitMap::CMSBitMap(int shifter, int mutex_rank, const char* mutex_name): | |
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6400 _bm(), |
0 | 6401 _shifter(shifter), |
6402 _lock(mutex_rank >= 0 ? new Mutex(mutex_rank, mutex_name, true) : NULL) | |
6403 { | |
6404 _bmStartWord = 0; | |
6405 _bmWordSize = 0; | |
6406 } | |
6407 | |
6408 bool CMSBitMap::allocate(MemRegion mr) { | |
6409 _bmStartWord = mr.start(); | |
6410 _bmWordSize = mr.word_size(); | |
6411 ReservedSpace brs(ReservedSpace::allocation_align_size_up( | |
6412 (_bmWordSize >> (_shifter + LogBitsPerByte)) + 1)); | |
6413 if (!brs.is_reserved()) { | |
6414 warning("CMS bit map allocation failure"); | |
6415 return false; | |
6416 } | |
6417 // For now we'll just commit all of the bit map up fromt. | |
6418 // Later on we'll try to be more parsimonious with swap. | |
6419 if (!_virtual_space.initialize(brs, brs.size())) { | |
6420 warning("CMS bit map backing store failure"); | |
6421 return false; | |
6422 } | |
6423 assert(_virtual_space.committed_size() == brs.size(), | |
6424 "didn't reserve backing store for all of CMS bit map?"); | |
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6425 _bm.set_map((BitMap::bm_word_t*)_virtual_space.low()); |
0 | 6426 assert(_virtual_space.committed_size() << (_shifter + LogBitsPerByte) >= |
6427 _bmWordSize, "inconsistency in bit map sizing"); | |
6428 _bm.set_size(_bmWordSize >> _shifter); | |
6429 | |
6430 // bm.clear(); // can we rely on getting zero'd memory? verify below | |
6431 assert(isAllClear(), | |
6432 "Expected zero'd memory from ReservedSpace constructor"); | |
6433 assert(_bm.size() == heapWordDiffToOffsetDiff(sizeInWords()), | |
6434 "consistency check"); | |
6435 return true; | |
6436 } | |
6437 | |
6438 void CMSBitMap::dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl) { | |
6439 HeapWord *next_addr, *end_addr, *last_addr; | |
6440 assert_locked(); | |
6441 assert(covers(mr), "out-of-range error"); | |
6442 // XXX assert that start and end are appropriately aligned | |
6443 for (next_addr = mr.start(), end_addr = mr.end(); | |
6444 next_addr < end_addr; next_addr = last_addr) { | |
6445 MemRegion dirty_region = getAndClearMarkedRegion(next_addr, end_addr); | |
6446 last_addr = dirty_region.end(); | |
6447 if (!dirty_region.is_empty()) { | |
6448 cl->do_MemRegion(dirty_region); | |
6449 } else { | |
6450 assert(last_addr == end_addr, "program logic"); | |
6451 return; | |
6452 } | |
6453 } | |
6454 } | |
6455 | |
6456 #ifndef PRODUCT | |
6457 void CMSBitMap::assert_locked() const { | |
6458 CMSLockVerifier::assert_locked(lock()); | |
6459 } | |
6460 | |
6461 bool CMSBitMap::covers(MemRegion mr) const { | |
6462 // assert(_bm.map() == _virtual_space.low(), "map inconsistency"); | |
6463 assert((size_t)_bm.size() == (_bmWordSize >> _shifter), | |
6464 "size inconsistency"); | |
6465 return (mr.start() >= _bmStartWord) && | |
6466 (mr.end() <= endWord()); | |
6467 } | |
6468 | |
6469 bool CMSBitMap::covers(HeapWord* start, size_t size) const { | |
6470 return (start >= _bmStartWord && (start + size) <= endWord()); | |
6471 } | |
6472 | |
6473 void CMSBitMap::verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) { | |
6474 // verify that there are no 1 bits in the interval [left, right) | |
6475 FalseBitMapClosure falseBitMapClosure; | |
6476 iterate(&falseBitMapClosure, left, right); | |
6477 } | |
6478 | |
6479 void CMSBitMap::region_invariant(MemRegion mr) | |
6480 { | |
6481 assert_locked(); | |
6482 // mr = mr.intersection(MemRegion(_bmStartWord, _bmWordSize)); | |
6483 assert(!mr.is_empty(), "unexpected empty region"); | |
6484 assert(covers(mr), "mr should be covered by bit map"); | |
6485 // convert address range into offset range | |
6486 size_t start_ofs = heapWordToOffset(mr.start()); | |
6487 // Make sure that end() is appropriately aligned | |
6488 assert(mr.end() == (HeapWord*)round_to((intptr_t)mr.end(), | |
6489 (1 << (_shifter+LogHeapWordSize))), | |
6490 "Misaligned mr.end()"); | |
6491 size_t end_ofs = heapWordToOffset(mr.end()); | |
6492 assert(end_ofs > start_ofs, "Should mark at least one bit"); | |
6493 } | |
6494 | |
6495 #endif | |
6496 | |
6497 bool CMSMarkStack::allocate(size_t size) { | |
6498 // allocate a stack of the requisite depth | |
6499 ReservedSpace rs(ReservedSpace::allocation_align_size_up( | |
6500 size * sizeof(oop))); | |
6501 if (!rs.is_reserved()) { | |
6502 warning("CMSMarkStack allocation failure"); | |
6503 return false; | |
6504 } | |
6505 if (!_virtual_space.initialize(rs, rs.size())) { | |
6506 warning("CMSMarkStack backing store failure"); | |
6507 return false; | |
6508 } | |
6509 assert(_virtual_space.committed_size() == rs.size(), | |
6510 "didn't reserve backing store for all of CMS stack?"); | |
6511 _base = (oop*)(_virtual_space.low()); | |
6512 _index = 0; | |
6513 _capacity = size; | |
6514 NOT_PRODUCT(_max_depth = 0); | |
6515 return true; | |
6516 } | |
6517 | |
6518 // XXX FIX ME !!! In the MT case we come in here holding a | |
6519 // leaf lock. For printing we need to take a further lock | |
6520 // which has lower rank. We need to recallibrate the two | |
6521 // lock-ranks involved in order to be able to rpint the | |
6522 // messages below. (Or defer the printing to the caller. | |
6523 // For now we take the expedient path of just disabling the | |
6524 // messages for the problematic case.) | |
6525 void CMSMarkStack::expand() { | |
1284 | 6526 assert(_capacity <= MarkStackSizeMax, "stack bigger than permitted"); |
6527 if (_capacity == MarkStackSizeMax) { | |
0 | 6528 if (_hit_limit++ == 0 && !CMSConcurrentMTEnabled && PrintGCDetails) { |
6529 // We print a warning message only once per CMS cycle. | |
6530 gclog_or_tty->print_cr(" (benign) Hit CMSMarkStack max size limit"); | |
6531 } | |
6532 return; | |
6533 } | |
6534 // Double capacity if possible | |
1284 | 6535 size_t new_capacity = MIN2(_capacity*2, MarkStackSizeMax); |
0 | 6536 // Do not give up existing stack until we have managed to |
6537 // get the double capacity that we desired. | |
6538 ReservedSpace rs(ReservedSpace::allocation_align_size_up( | |
6539 new_capacity * sizeof(oop))); | |
6540 if (rs.is_reserved()) { | |
6541 // Release the backing store associated with old stack | |
6542 _virtual_space.release(); | |
6543 // Reinitialize virtual space for new stack | |
6544 if (!_virtual_space.initialize(rs, rs.size())) { | |
6545 fatal("Not enough swap for expanded marking stack"); | |
6546 } | |
6547 _base = (oop*)(_virtual_space.low()); | |
6548 _index = 0; | |
6549 _capacity = new_capacity; | |
6550 } else if (_failed_double++ == 0 && !CMSConcurrentMTEnabled && PrintGCDetails) { | |
6551 // Failed to double capacity, continue; | |
6552 // we print a detail message only once per CMS cycle. | |
6553 gclog_or_tty->print(" (benign) Failed to expand marking stack from "SIZE_FORMAT"K to " | |
6554 SIZE_FORMAT"K", | |
6555 _capacity / K, new_capacity / K); | |
6556 } | |
6557 } | |
6558 | |
6559 | |
6560 // Closures | |
6561 // XXX: there seems to be a lot of code duplication here; | |
6562 // should refactor and consolidate common code. | |
6563 | |
6564 // This closure is used to mark refs into the CMS generation in | |
6565 // the CMS bit map. Called at the first checkpoint. This closure | |
6566 // assumes that we do not need to re-mark dirty cards; if the CMS | |
6567 // generation on which this is used is not an oldest (modulo perm gen) | |
6568 // generation then this will lose younger_gen cards! | |
6569 | |
6570 MarkRefsIntoClosure::MarkRefsIntoClosure( | |
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|
6571 MemRegion span, CMSBitMap* bitMap): |
0 | 6572 _span(span), |
994
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|
6573 _bitMap(bitMap) |
0 | 6574 { |
6575 assert(_ref_processor == NULL, "deliberately left NULL"); | |
6576 assert(_bitMap->covers(_span), "_bitMap/_span mismatch"); | |
6577 } | |
6578 | |
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6579 void MarkRefsIntoClosure::do_oop(oop obj) { |
0 | 6580 // if p points into _span, then mark corresponding bit in _markBitMap |
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6581 assert(obj->is_oop(), "expected an oop"); |
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6582 HeapWord* addr = (HeapWord*)obj; |
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6583 if (_span.contains(addr)) { |
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6584 // this should be made more efficient |
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6585 _bitMap->mark(addr); |
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6586 } |
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|
6587 } |
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|
6588 |
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6589 void MarkRefsIntoClosure::do_oop(oop* p) { MarkRefsIntoClosure::do_oop_work(p); } |
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6590 void MarkRefsIntoClosure::do_oop(narrowOop* p) { MarkRefsIntoClosure::do_oop_work(p); } |
0 | 6591 |
6592 // A variant of the above, used for CMS marking verification. | |
6593 MarkRefsIntoVerifyClosure::MarkRefsIntoVerifyClosure( | |
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|
6594 MemRegion span, CMSBitMap* verification_bm, CMSBitMap* cms_bm): |
0 | 6595 _span(span), |
6596 _verification_bm(verification_bm), | |
994
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6597 _cms_bm(cms_bm) |
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|
6598 { |
0 | 6599 assert(_ref_processor == NULL, "deliberately left NULL"); |
6600 assert(_verification_bm->covers(_span), "_verification_bm/_span mismatch"); | |
6601 } | |
6602 | |
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6603 void MarkRefsIntoVerifyClosure::do_oop(oop obj) { |
0 | 6604 // if p points into _span, then mark corresponding bit in _markBitMap |
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6605 assert(obj->is_oop(), "expected an oop"); |
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6606 HeapWord* addr = (HeapWord*)obj; |
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6607 if (_span.contains(addr)) { |
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6608 _verification_bm->mark(addr); |
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6609 if (!_cms_bm->isMarked(addr)) { |
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6610 oop(addr)->print(); |
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6611 gclog_or_tty->print_cr(" (" INTPTR_FORMAT " should have been marked)", addr); |
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6612 fatal("... aborting"); |
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6613 } |
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6614 } |
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|
6615 } |
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6616 |
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6617 void MarkRefsIntoVerifyClosure::do_oop(oop* p) { MarkRefsIntoVerifyClosure::do_oop_work(p); } |
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6618 void MarkRefsIntoVerifyClosure::do_oop(narrowOop* p) { MarkRefsIntoVerifyClosure::do_oop_work(p); } |
0 | 6619 |
6620 ////////////////////////////////////////////////// | |
6621 // MarkRefsIntoAndScanClosure | |
6622 ////////////////////////////////////////////////// | |
6623 | |
6624 MarkRefsIntoAndScanClosure::MarkRefsIntoAndScanClosure(MemRegion span, | |
6625 ReferenceProcessor* rp, | |
6626 CMSBitMap* bit_map, | |
6627 CMSBitMap* mod_union_table, | |
6628 CMSMarkStack* mark_stack, | |
6629 CMSMarkStack* revisit_stack, | |
6630 CMSCollector* collector, | |
6631 bool should_yield, | |
6632 bool concurrent_precleaning): | |
6633 _collector(collector), | |
6634 _span(span), | |
6635 _bit_map(bit_map), | |
6636 _mark_stack(mark_stack), | |
6637 _pushAndMarkClosure(collector, span, rp, bit_map, mod_union_table, | |
6638 mark_stack, revisit_stack, concurrent_precleaning), | |
6639 _yield(should_yield), | |
6640 _concurrent_precleaning(concurrent_precleaning), | |
6641 _freelistLock(NULL) | |
6642 { | |
6643 _ref_processor = rp; | |
6644 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
6645 } | |
6646 | |
6647 // This closure is used to mark refs into the CMS generation at the | |
6648 // second (final) checkpoint, and to scan and transitively follow | |
6649 // the unmarked oops. It is also used during the concurrent precleaning | |
6650 // phase while scanning objects on dirty cards in the CMS generation. | |
6651 // The marks are made in the marking bit map and the marking stack is | |
6652 // used for keeping the (newly) grey objects during the scan. | |
6653 // The parallel version (Par_...) appears further below. | |
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6654 void MarkRefsIntoAndScanClosure::do_oop(oop obj) { |
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6655 if (obj != NULL) { |
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6656 assert(obj->is_oop(), "expected an oop"); |
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6657 HeapWord* addr = (HeapWord*)obj; |
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6658 assert(_mark_stack->isEmpty(), "pre-condition (eager drainage)"); |
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6659 assert(_collector->overflow_list_is_empty(), |
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6660 "overflow list should be empty"); |
0 | 6661 if (_span.contains(addr) && |
6662 !_bit_map->isMarked(addr)) { | |
6663 // mark bit map (object is now grey) | |
6664 _bit_map->mark(addr); | |
6665 // push on marking stack (stack should be empty), and drain the | |
6666 // stack by applying this closure to the oops in the oops popped | |
6667 // from the stack (i.e. blacken the grey objects) | |
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6668 bool res = _mark_stack->push(obj); |
0 | 6669 assert(res, "Should have space to push on empty stack"); |
6670 do { | |
6671 oop new_oop = _mark_stack->pop(); | |
6672 assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop"); | |
6673 assert(new_oop->is_parsable(), "Found unparsable oop"); | |
6674 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
6675 "only grey objects on this stack"); | |
6676 // iterate over the oops in this oop, marking and pushing | |
6677 // the ones in CMS heap (i.e. in _span). | |
6678 new_oop->oop_iterate(&_pushAndMarkClosure); | |
6679 // check if it's time to yield | |
6680 do_yield_check(); | |
6681 } while (!_mark_stack->isEmpty() || | |
6682 (!_concurrent_precleaning && take_from_overflow_list())); | |
6683 // if marking stack is empty, and we are not doing this | |
6684 // during precleaning, then check the overflow list | |
6685 } | |
6686 assert(_mark_stack->isEmpty(), "post-condition (eager drainage)"); | |
6687 assert(_collector->overflow_list_is_empty(), | |
6688 "overflow list was drained above"); | |
6689 // We could restore evacuated mark words, if any, used for | |
6690 // overflow list links here because the overflow list is | |
6691 // provably empty here. That would reduce the maximum | |
6692 // size requirements for preserved_{oop,mark}_stack. | |
6693 // But we'll just postpone it until we are all done | |
6694 // so we can just stream through. | |
6695 if (!_concurrent_precleaning && CMSOverflowEarlyRestoration) { | |
6696 _collector->restore_preserved_marks_if_any(); | |
6697 assert(_collector->no_preserved_marks(), "No preserved marks"); | |
6698 } | |
6699 assert(!CMSOverflowEarlyRestoration || _collector->no_preserved_marks(), | |
6700 "All preserved marks should have been restored above"); | |
6701 } | |
6702 } | |
6703 | |
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6704 void MarkRefsIntoAndScanClosure::do_oop(oop* p) { MarkRefsIntoAndScanClosure::do_oop_work(p); } |
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6705 void MarkRefsIntoAndScanClosure::do_oop(narrowOop* p) { MarkRefsIntoAndScanClosure::do_oop_work(p); } |
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6706 |
0 | 6707 void MarkRefsIntoAndScanClosure::do_yield_work() { |
6708 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
6709 "CMS thread should hold CMS token"); | |
6710 assert_lock_strong(_freelistLock); | |
6711 assert_lock_strong(_bit_map->lock()); | |
6712 // relinquish the free_list_lock and bitMaplock() | |
935 | 6713 DEBUG_ONLY(RememberKlassesChecker mux(false);) |
0 | 6714 _bit_map->lock()->unlock(); |
6715 _freelistLock->unlock(); | |
6716 ConcurrentMarkSweepThread::desynchronize(true); | |
6717 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
6718 _collector->stopTimer(); | |
6719 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
6720 if (PrintCMSStatistics != 0) { | |
6721 _collector->incrementYields(); | |
6722 } | |
6723 _collector->icms_wait(); | |
6724 | |
6725 // See the comment in coordinator_yield() | |
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6726 for (unsigned i = 0; |
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6727 i < CMSYieldSleepCount && |
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6728 ConcurrentMarkSweepThread::should_yield() && |
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6729 !CMSCollector::foregroundGCIsActive(); |
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6730 ++i) { |
0 | 6731 os::sleep(Thread::current(), 1, false); |
6732 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
6733 } | |
6734 | |
6735 ConcurrentMarkSweepThread::synchronize(true); | |
6736 _freelistLock->lock_without_safepoint_check(); | |
6737 _bit_map->lock()->lock_without_safepoint_check(); | |
6738 _collector->startTimer(); | |
6739 } | |
6740 | |
6741 /////////////////////////////////////////////////////////// | |
6742 // Par_MarkRefsIntoAndScanClosure: a parallel version of | |
6743 // MarkRefsIntoAndScanClosure | |
6744 /////////////////////////////////////////////////////////// | |
6745 Par_MarkRefsIntoAndScanClosure::Par_MarkRefsIntoAndScanClosure( | |
6746 CMSCollector* collector, MemRegion span, ReferenceProcessor* rp, | |
6747 CMSBitMap* bit_map, OopTaskQueue* work_queue, CMSMarkStack* revisit_stack): | |
6748 _span(span), | |
6749 _bit_map(bit_map), | |
6750 _work_queue(work_queue), | |
6751 _low_water_mark(MIN2((uint)(work_queue->max_elems()/4), | |
6752 (uint)(CMSWorkQueueDrainThreshold * ParallelGCThreads))), | |
6753 _par_pushAndMarkClosure(collector, span, rp, bit_map, work_queue, | |
6754 revisit_stack) | |
6755 { | |
6756 _ref_processor = rp; | |
6757 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
6758 } | |
6759 | |
6760 // This closure is used to mark refs into the CMS generation at the | |
6761 // second (final) checkpoint, and to scan and transitively follow | |
6762 // the unmarked oops. The marks are made in the marking bit map and | |
6763 // the work_queue is used for keeping the (newly) grey objects during | |
6764 // the scan phase whence they are also available for stealing by parallel | |
6765 // threads. Since the marking bit map is shared, updates are | |
6766 // synchronized (via CAS). | |
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6767 void Par_MarkRefsIntoAndScanClosure::do_oop(oop obj) { |
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6768 if (obj != NULL) { |
0 | 6769 // Ignore mark word because this could be an already marked oop |
6770 // that may be chained at the end of the overflow list. | |
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6771 assert(obj->is_oop(true), "expected an oop"); |
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6772 HeapWord* addr = (HeapWord*)obj; |
0 | 6773 if (_span.contains(addr) && |
6774 !_bit_map->isMarked(addr)) { | |
6775 // mark bit map (object will become grey): | |
6776 // It is possible for several threads to be | |
6777 // trying to "claim" this object concurrently; | |
6778 // the unique thread that succeeds in marking the | |
6779 // object first will do the subsequent push on | |
6780 // to the work queue (or overflow list). | |
6781 if (_bit_map->par_mark(addr)) { | |
6782 // push on work_queue (which may not be empty), and trim the | |
6783 // queue to an appropriate length by applying this closure to | |
6784 // the oops in the oops popped from the stack (i.e. blacken the | |
6785 // grey objects) | |
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6786 bool res = _work_queue->push(obj); |
0 | 6787 assert(res, "Low water mark should be less than capacity?"); |
6788 trim_queue(_low_water_mark); | |
6789 } // Else, another thread claimed the object | |
6790 } | |
6791 } | |
6792 } | |
6793 | |
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6794 void Par_MarkRefsIntoAndScanClosure::do_oop(oop* p) { Par_MarkRefsIntoAndScanClosure::do_oop_work(p); } |
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6795 void Par_MarkRefsIntoAndScanClosure::do_oop(narrowOop* p) { Par_MarkRefsIntoAndScanClosure::do_oop_work(p); } |
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6796 |
0 | 6797 // This closure is used to rescan the marked objects on the dirty cards |
6798 // in the mod union table and the card table proper. | |
6799 size_t ScanMarkedObjectsAgainCarefullyClosure::do_object_careful_m( | |
6800 oop p, MemRegion mr) { | |
6801 | |
6802 size_t size = 0; | |
6803 HeapWord* addr = (HeapWord*)p; | |
6804 DEBUG_ONLY(_collector->verify_work_stacks_empty();) | |
6805 assert(_span.contains(addr), "we are scanning the CMS generation"); | |
6806 // check if it's time to yield | |
6807 if (do_yield_check()) { | |
6808 // We yielded for some foreground stop-world work, | |
6809 // and we have been asked to abort this ongoing preclean cycle. | |
6810 return 0; | |
6811 } | |
6812 if (_bitMap->isMarked(addr)) { | |
6813 // it's marked; is it potentially uninitialized? | |
187 | 6814 if (p->klass_or_null() != NULL) { |
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6815 // If is_conc_safe is false, the object may be undergoing |
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6816 // change by the VM outside a safepoint. Don't try to |
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6817 // scan it, but rather leave it for the remark phase. |
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6818 if (CMSPermGenPrecleaningEnabled && |
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6819 (!p->is_conc_safe() || !p->is_parsable())) { |
0 | 6820 // Signal precleaning to redirty the card since |
6821 // the klass pointer is already installed. | |
6822 assert(size == 0, "Initial value"); | |
6823 } else { | |
6824 assert(p->is_parsable(), "must be parsable."); | |
6825 // an initialized object; ignore mark word in verification below | |
6826 // since we are running concurrent with mutators | |
6827 assert(p->is_oop(true), "should be an oop"); | |
6828 if (p->is_objArray()) { | |
6829 // objArrays are precisely marked; restrict scanning | |
6830 // to dirty cards only. | |
187 | 6831 size = CompactibleFreeListSpace::adjustObjectSize( |
6832 p->oop_iterate(_scanningClosure, mr)); | |
0 | 6833 } else { |
6834 // A non-array may have been imprecisely marked; we need | |
6835 // to scan object in its entirety. | |
6836 size = CompactibleFreeListSpace::adjustObjectSize( | |
6837 p->oop_iterate(_scanningClosure)); | |
6838 } | |
6839 #ifdef DEBUG | |
6840 size_t direct_size = | |
6841 CompactibleFreeListSpace::adjustObjectSize(p->size()); | |
6842 assert(size == direct_size, "Inconsistency in size"); | |
6843 assert(size >= 3, "Necessary for Printezis marks to work"); | |
6844 if (!_bitMap->isMarked(addr+1)) { | |
6845 _bitMap->verifyNoOneBitsInRange(addr+2, addr+size); | |
6846 } else { | |
6847 _bitMap->verifyNoOneBitsInRange(addr+2, addr+size-1); | |
6848 assert(_bitMap->isMarked(addr+size-1), | |
6849 "inconsistent Printezis mark"); | |
6850 } | |
6851 #endif // DEBUG | |
6852 } | |
6853 } else { | |
6854 // an unitialized object | |
6855 assert(_bitMap->isMarked(addr+1), "missing Printezis mark?"); | |
6856 HeapWord* nextOneAddr = _bitMap->getNextMarkedWordAddress(addr + 2); | |
6857 size = pointer_delta(nextOneAddr + 1, addr); | |
6858 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
6859 "alignment problem"); | |
6860 // Note that pre-cleaning needn't redirty the card. OopDesc::set_klass() | |
6861 // will dirty the card when the klass pointer is installed in the | |
6862 // object (signalling the completion of initialization). | |
6863 } | |
6864 } else { | |
6865 // Either a not yet marked object or an uninitialized object | |
187 | 6866 if (p->klass_or_null() == NULL || !p->is_parsable()) { |
0 | 6867 // An uninitialized object, skip to the next card, since |
6868 // we may not be able to read its P-bits yet. | |
6869 assert(size == 0, "Initial value"); | |
6870 } else { | |
6871 // An object not (yet) reached by marking: we merely need to | |
6872 // compute its size so as to go look at the next block. | |
6873 assert(p->is_oop(true), "should be an oop"); | |
6874 size = CompactibleFreeListSpace::adjustObjectSize(p->size()); | |
6875 } | |
6876 } | |
6877 DEBUG_ONLY(_collector->verify_work_stacks_empty();) | |
6878 return size; | |
6879 } | |
6880 | |
6881 void ScanMarkedObjectsAgainCarefullyClosure::do_yield_work() { | |
6882 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
6883 "CMS thread should hold CMS token"); | |
6884 assert_lock_strong(_freelistLock); | |
6885 assert_lock_strong(_bitMap->lock()); | |
935 | 6886 DEBUG_ONLY(RememberKlassesChecker mux(false);) |
0 | 6887 // relinquish the free_list_lock and bitMaplock() |
6888 _bitMap->lock()->unlock(); | |
6889 _freelistLock->unlock(); | |
6890 ConcurrentMarkSweepThread::desynchronize(true); | |
6891 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
6892 _collector->stopTimer(); | |
6893 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
6894 if (PrintCMSStatistics != 0) { | |
6895 _collector->incrementYields(); | |
6896 } | |
6897 _collector->icms_wait(); | |
6898 | |
6899 // See the comment in coordinator_yield() | |
6900 for (unsigned i = 0; i < CMSYieldSleepCount && | |
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6901 ConcurrentMarkSweepThread::should_yield() && |
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6902 !CMSCollector::foregroundGCIsActive(); ++i) { |
0 | 6903 os::sleep(Thread::current(), 1, false); |
6904 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
6905 } | |
6906 | |
6907 ConcurrentMarkSweepThread::synchronize(true); | |
6908 _freelistLock->lock_without_safepoint_check(); | |
6909 _bitMap->lock()->lock_without_safepoint_check(); | |
6910 _collector->startTimer(); | |
6911 } | |
6912 | |
6913 | |
6914 ////////////////////////////////////////////////////////////////// | |
6915 // SurvivorSpacePrecleanClosure | |
6916 ////////////////////////////////////////////////////////////////// | |
6917 // This (single-threaded) closure is used to preclean the oops in | |
6918 // the survivor spaces. | |
6919 size_t SurvivorSpacePrecleanClosure::do_object_careful(oop p) { | |
6920 | |
6921 HeapWord* addr = (HeapWord*)p; | |
6922 DEBUG_ONLY(_collector->verify_work_stacks_empty();) | |
6923 assert(!_span.contains(addr), "we are scanning the survivor spaces"); | |
187 | 6924 assert(p->klass_or_null() != NULL, "object should be initializd"); |
0 | 6925 assert(p->is_parsable(), "must be parsable."); |
6926 // an initialized object; ignore mark word in verification below | |
6927 // since we are running concurrent with mutators | |
6928 assert(p->is_oop(true), "should be an oop"); | |
6929 // Note that we do not yield while we iterate over | |
6930 // the interior oops of p, pushing the relevant ones | |
6931 // on our marking stack. | |
6932 size_t size = p->oop_iterate(_scanning_closure); | |
6933 do_yield_check(); | |
6934 // Observe that below, we do not abandon the preclean | |
6935 // phase as soon as we should; rather we empty the | |
6936 // marking stack before returning. This is to satisfy | |
6937 // some existing assertions. In general, it may be a | |
6938 // good idea to abort immediately and complete the marking | |
6939 // from the grey objects at a later time. | |
6940 while (!_mark_stack->isEmpty()) { | |
6941 oop new_oop = _mark_stack->pop(); | |
6942 assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop"); | |
6943 assert(new_oop->is_parsable(), "Found unparsable oop"); | |
6944 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
6945 "only grey objects on this stack"); | |
6946 // iterate over the oops in this oop, marking and pushing | |
6947 // the ones in CMS heap (i.e. in _span). | |
6948 new_oop->oop_iterate(_scanning_closure); | |
6949 // check if it's time to yield | |
6950 do_yield_check(); | |
6951 } | |
6952 unsigned int after_count = | |
6953 GenCollectedHeap::heap()->total_collections(); | |
6954 bool abort = (_before_count != after_count) || | |
6955 _collector->should_abort_preclean(); | |
6956 return abort ? 0 : size; | |
6957 } | |
6958 | |
6959 void SurvivorSpacePrecleanClosure::do_yield_work() { | |
6960 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
6961 "CMS thread should hold CMS token"); | |
6962 assert_lock_strong(_bit_map->lock()); | |
935 | 6963 DEBUG_ONLY(RememberKlassesChecker smx(false);) |
0 | 6964 // Relinquish the bit map lock |
6965 _bit_map->lock()->unlock(); | |
6966 ConcurrentMarkSweepThread::desynchronize(true); | |
6967 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
6968 _collector->stopTimer(); | |
6969 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
6970 if (PrintCMSStatistics != 0) { | |
6971 _collector->incrementYields(); | |
6972 } | |
6973 _collector->icms_wait(); | |
6974 | |
6975 // See the comment in coordinator_yield() | |
6976 for (unsigned i = 0; i < CMSYieldSleepCount && | |
6977 ConcurrentMarkSweepThread::should_yield() && | |
6978 !CMSCollector::foregroundGCIsActive(); ++i) { | |
6979 os::sleep(Thread::current(), 1, false); | |
6980 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
6981 } | |
6982 | |
6983 ConcurrentMarkSweepThread::synchronize(true); | |
6984 _bit_map->lock()->lock_without_safepoint_check(); | |
6985 _collector->startTimer(); | |
6986 } | |
6987 | |
6988 // This closure is used to rescan the marked objects on the dirty cards | |
6989 // in the mod union table and the card table proper. In the parallel | |
6990 // case, although the bitMap is shared, we do a single read so the | |
6991 // isMarked() query is "safe". | |
6992 bool ScanMarkedObjectsAgainClosure::do_object_bm(oop p, MemRegion mr) { | |
6993 // Ignore mark word because we are running concurrent with mutators | |
6994 assert(p->is_oop_or_null(true), "expected an oop or null"); | |
6995 HeapWord* addr = (HeapWord*)p; | |
6996 assert(_span.contains(addr), "we are scanning the CMS generation"); | |
6997 bool is_obj_array = false; | |
6998 #ifdef DEBUG | |
6999 if (!_parallel) { | |
7000 assert(_mark_stack->isEmpty(), "pre-condition (eager drainage)"); | |
7001 assert(_collector->overflow_list_is_empty(), | |
7002 "overflow list should be empty"); | |
7003 | |
7004 } | |
7005 #endif // DEBUG | |
7006 if (_bit_map->isMarked(addr)) { | |
7007 // Obj arrays are precisely marked, non-arrays are not; | |
7008 // so we scan objArrays precisely and non-arrays in their | |
7009 // entirety. | |
7010 if (p->is_objArray()) { | |
7011 is_obj_array = true; | |
7012 if (_parallel) { | |
7013 p->oop_iterate(_par_scan_closure, mr); | |
7014 } else { | |
7015 p->oop_iterate(_scan_closure, mr); | |
7016 } | |
7017 } else { | |
7018 if (_parallel) { | |
7019 p->oop_iterate(_par_scan_closure); | |
7020 } else { | |
7021 p->oop_iterate(_scan_closure); | |
7022 } | |
7023 } | |
7024 } | |
7025 #ifdef DEBUG | |
7026 if (!_parallel) { | |
7027 assert(_mark_stack->isEmpty(), "post-condition (eager drainage)"); | |
7028 assert(_collector->overflow_list_is_empty(), | |
7029 "overflow list should be empty"); | |
7030 | |
7031 } | |
7032 #endif // DEBUG | |
7033 return is_obj_array; | |
7034 } | |
7035 | |
7036 MarkFromRootsClosure::MarkFromRootsClosure(CMSCollector* collector, | |
7037 MemRegion span, | |
7038 CMSBitMap* bitMap, CMSMarkStack* markStack, | |
7039 CMSMarkStack* revisitStack, | |
7040 bool should_yield, bool verifying): | |
7041 _collector(collector), | |
7042 _span(span), | |
7043 _bitMap(bitMap), | |
7044 _mut(&collector->_modUnionTable), | |
7045 _markStack(markStack), | |
7046 _revisitStack(revisitStack), | |
7047 _yield(should_yield), | |
7048 _skipBits(0) | |
7049 { | |
7050 assert(_markStack->isEmpty(), "stack should be empty"); | |
7051 _finger = _bitMap->startWord(); | |
7052 _threshold = _finger; | |
7053 assert(_collector->_restart_addr == NULL, "Sanity check"); | |
7054 assert(_span.contains(_finger), "Out of bounds _finger?"); | |
7055 DEBUG_ONLY(_verifying = verifying;) | |
7056 } | |
7057 | |
7058 void MarkFromRootsClosure::reset(HeapWord* addr) { | |
7059 assert(_markStack->isEmpty(), "would cause duplicates on stack"); | |
7060 assert(_span.contains(addr), "Out of bounds _finger?"); | |
7061 _finger = addr; | |
7062 _threshold = (HeapWord*)round_to( | |
7063 (intptr_t)_finger, CardTableModRefBS::card_size); | |
7064 } | |
7065 | |
7066 // Should revisit to see if this should be restructured for | |
7067 // greater efficiency. | |
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7068 bool MarkFromRootsClosure::do_bit(size_t offset) { |
0 | 7069 if (_skipBits > 0) { |
7070 _skipBits--; | |
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7071 return true; |
0 | 7072 } |
7073 // convert offset into a HeapWord* | |
7074 HeapWord* addr = _bitMap->startWord() + offset; | |
7075 assert(_bitMap->endWord() && addr < _bitMap->endWord(), | |
7076 "address out of range"); | |
7077 assert(_bitMap->isMarked(addr), "tautology"); | |
7078 if (_bitMap->isMarked(addr+1)) { | |
7079 // this is an allocated but not yet initialized object | |
7080 assert(_skipBits == 0, "tautology"); | |
7081 _skipBits = 2; // skip next two marked bits ("Printezis-marks") | |
7082 oop p = oop(addr); | |
187 | 7083 if (p->klass_or_null() == NULL || !p->is_parsable()) { |
0 | 7084 DEBUG_ONLY(if (!_verifying) {) |
7085 // We re-dirty the cards on which this object lies and increase | |
7086 // the _threshold so that we'll come back to scan this object | |
7087 // during the preclean or remark phase. (CMSCleanOnEnter) | |
7088 if (CMSCleanOnEnter) { | |
7089 size_t sz = _collector->block_size_using_printezis_bits(addr); | |
7090 HeapWord* end_card_addr = (HeapWord*)round_to( | |
7091 (intptr_t)(addr+sz), CardTableModRefBS::card_size); | |
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7092 MemRegion redirty_range = MemRegion(addr, end_card_addr); |
0 | 7093 assert(!redirty_range.is_empty(), "Arithmetical tautology"); |
7094 // Bump _threshold to end_card_addr; note that | |
7095 // _threshold cannot possibly exceed end_card_addr, anyhow. | |
7096 // This prevents future clearing of the card as the scan proceeds | |
7097 // to the right. | |
7098 assert(_threshold <= end_card_addr, | |
7099 "Because we are just scanning into this object"); | |
7100 if (_threshold < end_card_addr) { | |
7101 _threshold = end_card_addr; | |
7102 } | |
187 | 7103 if (p->klass_or_null() != NULL) { |
0 | 7104 // Redirty the range of cards... |
7105 _mut->mark_range(redirty_range); | |
7106 } // ...else the setting of klass will dirty the card anyway. | |
7107 } | |
7108 DEBUG_ONLY(}) | |
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7109 return true; |
0 | 7110 } |
7111 } | |
7112 scanOopsInOop(addr); | |
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7113 return true; |
0 | 7114 } |
7115 | |
7116 // We take a break if we've been at this for a while, | |
7117 // so as to avoid monopolizing the locks involved. | |
7118 void MarkFromRootsClosure::do_yield_work() { | |
7119 // First give up the locks, then yield, then re-lock | |
7120 // We should probably use a constructor/destructor idiom to | |
7121 // do this unlock/lock or modify the MutexUnlocker class to | |
7122 // serve our purpose. XXX | |
7123 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
7124 "CMS thread should hold CMS token"); | |
7125 assert_lock_strong(_bitMap->lock()); | |
935 | 7126 DEBUG_ONLY(RememberKlassesChecker mux(false);) |
0 | 7127 _bitMap->lock()->unlock(); |
7128 ConcurrentMarkSweepThread::desynchronize(true); | |
7129 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
7130 _collector->stopTimer(); | |
7131 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
7132 if (PrintCMSStatistics != 0) { | |
7133 _collector->incrementYields(); | |
7134 } | |
7135 _collector->icms_wait(); | |
7136 | |
7137 // See the comment in coordinator_yield() | |
7138 for (unsigned i = 0; i < CMSYieldSleepCount && | |
7139 ConcurrentMarkSweepThread::should_yield() && | |
7140 !CMSCollector::foregroundGCIsActive(); ++i) { | |
7141 os::sleep(Thread::current(), 1, false); | |
7142 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
7143 } | |
7144 | |
7145 ConcurrentMarkSweepThread::synchronize(true); | |
7146 _bitMap->lock()->lock_without_safepoint_check(); | |
7147 _collector->startTimer(); | |
7148 } | |
7149 | |
7150 void MarkFromRootsClosure::scanOopsInOop(HeapWord* ptr) { | |
7151 assert(_bitMap->isMarked(ptr), "expected bit to be set"); | |
7152 assert(_markStack->isEmpty(), | |
7153 "should drain stack to limit stack usage"); | |
7154 // convert ptr to an oop preparatory to scanning | |
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7155 oop obj = oop(ptr); |
0 | 7156 // Ignore mark word in verification below, since we |
7157 // may be running concurrent with mutators. | |
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7158 assert(obj->is_oop(true), "should be an oop"); |
0 | 7159 assert(_finger <= ptr, "_finger runneth ahead"); |
7160 // advance the finger to right end of this object | |
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7161 _finger = ptr + obj->size(); |
0 | 7162 assert(_finger > ptr, "we just incremented it above"); |
7163 // On large heaps, it may take us some time to get through | |
7164 // the marking phase (especially if running iCMS). During | |
7165 // this time it's possible that a lot of mutations have | |
7166 // accumulated in the card table and the mod union table -- | |
7167 // these mutation records are redundant until we have | |
7168 // actually traced into the corresponding card. | |
7169 // Here, we check whether advancing the finger would make | |
7170 // us cross into a new card, and if so clear corresponding | |
7171 // cards in the MUT (preclean them in the card-table in the | |
7172 // future). | |
7173 | |
7174 DEBUG_ONLY(if (!_verifying) {) | |
7175 // The clean-on-enter optimization is disabled by default, | |
7176 // until we fix 6178663. | |
7177 if (CMSCleanOnEnter && (_finger > _threshold)) { | |
7178 // [_threshold, _finger) represents the interval | |
7179 // of cards to be cleared in MUT (or precleaned in card table). | |
7180 // The set of cards to be cleared is all those that overlap | |
7181 // with the interval [_threshold, _finger); note that | |
7182 // _threshold is always kept card-aligned but _finger isn't | |
7183 // always card-aligned. | |
7184 HeapWord* old_threshold = _threshold; | |
7185 assert(old_threshold == (HeapWord*)round_to( | |
7186 (intptr_t)old_threshold, CardTableModRefBS::card_size), | |
7187 "_threshold should always be card-aligned"); | |
7188 _threshold = (HeapWord*)round_to( | |
7189 (intptr_t)_finger, CardTableModRefBS::card_size); | |
7190 MemRegion mr(old_threshold, _threshold); | |
7191 assert(!mr.is_empty(), "Control point invariant"); | |
7192 assert(_span.contains(mr), "Should clear within span"); | |
7193 // XXX When _finger crosses from old gen into perm gen | |
7194 // we may be doing unnecessary cleaning; do better in the | |
7195 // future by detecting that condition and clearing fewer | |
7196 // MUT/CT entries. | |
7197 _mut->clear_range(mr); | |
7198 } | |
7199 DEBUG_ONLY(}) | |
7200 // Note: the finger doesn't advance while we drain | |
7201 // the stack below. | |
7202 PushOrMarkClosure pushOrMarkClosure(_collector, | |
7203 _span, _bitMap, _markStack, | |
7204 _revisitStack, | |
7205 _finger, this); | |
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7206 bool res = _markStack->push(obj); |
0 | 7207 assert(res, "Empty non-zero size stack should have space for single push"); |
7208 while (!_markStack->isEmpty()) { | |
7209 oop new_oop = _markStack->pop(); | |
7210 // Skip verifying header mark word below because we are | |
7211 // running concurrent with mutators. | |
7212 assert(new_oop->is_oop(true), "Oops! expected to pop an oop"); | |
7213 // now scan this oop's oops | |
7214 new_oop->oop_iterate(&pushOrMarkClosure); | |
7215 do_yield_check(); | |
7216 } | |
7217 assert(_markStack->isEmpty(), "tautology, emphasizing post-condition"); | |
7218 } | |
7219 | |
7220 Par_MarkFromRootsClosure::Par_MarkFromRootsClosure(CMSConcMarkingTask* task, | |
7221 CMSCollector* collector, MemRegion span, | |
7222 CMSBitMap* bit_map, | |
7223 OopTaskQueue* work_queue, | |
7224 CMSMarkStack* overflow_stack, | |
7225 CMSMarkStack* revisit_stack, | |
7226 bool should_yield): | |
7227 _collector(collector), | |
7228 _whole_span(collector->_span), | |
7229 _span(span), | |
7230 _bit_map(bit_map), | |
7231 _mut(&collector->_modUnionTable), | |
7232 _work_queue(work_queue), | |
7233 _overflow_stack(overflow_stack), | |
7234 _revisit_stack(revisit_stack), | |
7235 _yield(should_yield), | |
7236 _skip_bits(0), | |
7237 _task(task) | |
7238 { | |
7239 assert(_work_queue->size() == 0, "work_queue should be empty"); | |
7240 _finger = span.start(); | |
7241 _threshold = _finger; // XXX Defer clear-on-enter optimization for now | |
7242 assert(_span.contains(_finger), "Out of bounds _finger?"); | |
7243 } | |
7244 | |
7245 // Should revisit to see if this should be restructured for | |
7246 // greater efficiency. | |
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7247 bool Par_MarkFromRootsClosure::do_bit(size_t offset) { |
0 | 7248 if (_skip_bits > 0) { |
7249 _skip_bits--; | |
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7250 return true; |
0 | 7251 } |
7252 // convert offset into a HeapWord* | |
7253 HeapWord* addr = _bit_map->startWord() + offset; | |
7254 assert(_bit_map->endWord() && addr < _bit_map->endWord(), | |
7255 "address out of range"); | |
7256 assert(_bit_map->isMarked(addr), "tautology"); | |
7257 if (_bit_map->isMarked(addr+1)) { | |
7258 // this is an allocated object that might not yet be initialized | |
7259 assert(_skip_bits == 0, "tautology"); | |
7260 _skip_bits = 2; // skip next two marked bits ("Printezis-marks") | |
7261 oop p = oop(addr); | |
187 | 7262 if (p->klass_or_null() == NULL || !p->is_parsable()) { |
0 | 7263 // in the case of Clean-on-Enter optimization, redirty card |
7264 // and avoid clearing card by increasing the threshold. | |
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7265 return true; |
0 | 7266 } |
7267 } | |
7268 scan_oops_in_oop(addr); | |
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7269 return true; |
0 | 7270 } |
7271 | |
7272 void Par_MarkFromRootsClosure::scan_oops_in_oop(HeapWord* ptr) { | |
7273 assert(_bit_map->isMarked(ptr), "expected bit to be set"); | |
7274 // Should we assert that our work queue is empty or | |
7275 // below some drain limit? | |
7276 assert(_work_queue->size() == 0, | |
7277 "should drain stack to limit stack usage"); | |
7278 // convert ptr to an oop preparatory to scanning | |
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7279 oop obj = oop(ptr); |
0 | 7280 // Ignore mark word in verification below, since we |
7281 // may be running concurrent with mutators. | |
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7282 assert(obj->is_oop(true), "should be an oop"); |
0 | 7283 assert(_finger <= ptr, "_finger runneth ahead"); |
7284 // advance the finger to right end of this object | |
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7285 _finger = ptr + obj->size(); |
0 | 7286 assert(_finger > ptr, "we just incremented it above"); |
7287 // On large heaps, it may take us some time to get through | |
7288 // the marking phase (especially if running iCMS). During | |
7289 // this time it's possible that a lot of mutations have | |
7290 // accumulated in the card table and the mod union table -- | |
7291 // these mutation records are redundant until we have | |
7292 // actually traced into the corresponding card. | |
7293 // Here, we check whether advancing the finger would make | |
7294 // us cross into a new card, and if so clear corresponding | |
7295 // cards in the MUT (preclean them in the card-table in the | |
7296 // future). | |
7297 | |
7298 // The clean-on-enter optimization is disabled by default, | |
7299 // until we fix 6178663. | |
7300 if (CMSCleanOnEnter && (_finger > _threshold)) { | |
7301 // [_threshold, _finger) represents the interval | |
7302 // of cards to be cleared in MUT (or precleaned in card table). | |
7303 // The set of cards to be cleared is all those that overlap | |
7304 // with the interval [_threshold, _finger); note that | |
7305 // _threshold is always kept card-aligned but _finger isn't | |
7306 // always card-aligned. | |
7307 HeapWord* old_threshold = _threshold; | |
7308 assert(old_threshold == (HeapWord*)round_to( | |
7309 (intptr_t)old_threshold, CardTableModRefBS::card_size), | |
7310 "_threshold should always be card-aligned"); | |
7311 _threshold = (HeapWord*)round_to( | |
7312 (intptr_t)_finger, CardTableModRefBS::card_size); | |
7313 MemRegion mr(old_threshold, _threshold); | |
7314 assert(!mr.is_empty(), "Control point invariant"); | |
7315 assert(_span.contains(mr), "Should clear within span"); // _whole_span ?? | |
7316 // XXX When _finger crosses from old gen into perm gen | |
7317 // we may be doing unnecessary cleaning; do better in the | |
7318 // future by detecting that condition and clearing fewer | |
7319 // MUT/CT entries. | |
7320 _mut->clear_range(mr); | |
7321 } | |
7322 | |
7323 // Note: the local finger doesn't advance while we drain | |
7324 // the stack below, but the global finger sure can and will. | |
7325 HeapWord** gfa = _task->global_finger_addr(); | |
7326 Par_PushOrMarkClosure pushOrMarkClosure(_collector, | |
7327 _span, _bit_map, | |
7328 _work_queue, | |
7329 _overflow_stack, | |
7330 _revisit_stack, | |
7331 _finger, | |
7332 gfa, this); | |
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7333 bool res = _work_queue->push(obj); // overflow could occur here |
0 | 7334 assert(res, "Will hold once we use workqueues"); |
7335 while (true) { | |
7336 oop new_oop; | |
7337 if (!_work_queue->pop_local(new_oop)) { | |
7338 // We emptied our work_queue; check if there's stuff that can | |
7339 // be gotten from the overflow stack. | |
7340 if (CMSConcMarkingTask::get_work_from_overflow_stack( | |
7341 _overflow_stack, _work_queue)) { | |
7342 do_yield_check(); | |
7343 continue; | |
7344 } else { // done | |
7345 break; | |
7346 } | |
7347 } | |
7348 // Skip verifying header mark word below because we are | |
7349 // running concurrent with mutators. | |
7350 assert(new_oop->is_oop(true), "Oops! expected to pop an oop"); | |
7351 // now scan this oop's oops | |
7352 new_oop->oop_iterate(&pushOrMarkClosure); | |
7353 do_yield_check(); | |
7354 } | |
7355 assert(_work_queue->size() == 0, "tautology, emphasizing post-condition"); | |
7356 } | |
7357 | |
7358 // Yield in response to a request from VM Thread or | |
7359 // from mutators. | |
7360 void Par_MarkFromRootsClosure::do_yield_work() { | |
7361 assert(_task != NULL, "sanity"); | |
7362 _task->yield(); | |
7363 } | |
7364 | |
7365 // A variant of the above used for verifying CMS marking work. | |
7366 MarkFromRootsVerifyClosure::MarkFromRootsVerifyClosure(CMSCollector* collector, | |
7367 MemRegion span, | |
7368 CMSBitMap* verification_bm, CMSBitMap* cms_bm, | |
7369 CMSMarkStack* mark_stack): | |
7370 _collector(collector), | |
7371 _span(span), | |
7372 _verification_bm(verification_bm), | |
7373 _cms_bm(cms_bm), | |
7374 _mark_stack(mark_stack), | |
7375 _pam_verify_closure(collector, span, verification_bm, cms_bm, | |
7376 mark_stack) | |
7377 { | |
7378 assert(_mark_stack->isEmpty(), "stack should be empty"); | |
7379 _finger = _verification_bm->startWord(); | |
7380 assert(_collector->_restart_addr == NULL, "Sanity check"); | |
7381 assert(_span.contains(_finger), "Out of bounds _finger?"); | |
7382 } | |
7383 | |
7384 void MarkFromRootsVerifyClosure::reset(HeapWord* addr) { | |
7385 assert(_mark_stack->isEmpty(), "would cause duplicates on stack"); | |
7386 assert(_span.contains(addr), "Out of bounds _finger?"); | |
7387 _finger = addr; | |
7388 } | |
7389 | |
7390 // Should revisit to see if this should be restructured for | |
7391 // greater efficiency. | |
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7392 bool MarkFromRootsVerifyClosure::do_bit(size_t offset) { |
0 | 7393 // convert offset into a HeapWord* |
7394 HeapWord* addr = _verification_bm->startWord() + offset; | |
7395 assert(_verification_bm->endWord() && addr < _verification_bm->endWord(), | |
7396 "address out of range"); | |
7397 assert(_verification_bm->isMarked(addr), "tautology"); | |
7398 assert(_cms_bm->isMarked(addr), "tautology"); | |
7399 | |
7400 assert(_mark_stack->isEmpty(), | |
7401 "should drain stack to limit stack usage"); | |
7402 // convert addr to an oop preparatory to scanning | |
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7403 oop obj = oop(addr); |
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7404 assert(obj->is_oop(), "should be an oop"); |
0 | 7405 assert(_finger <= addr, "_finger runneth ahead"); |
7406 // advance the finger to right end of this object | |
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7407 _finger = addr + obj->size(); |
0 | 7408 assert(_finger > addr, "we just incremented it above"); |
7409 // Note: the finger doesn't advance while we drain | |
7410 // the stack below. | |
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7411 bool res = _mark_stack->push(obj); |
0 | 7412 assert(res, "Empty non-zero size stack should have space for single push"); |
7413 while (!_mark_stack->isEmpty()) { | |
7414 oop new_oop = _mark_stack->pop(); | |
7415 assert(new_oop->is_oop(), "Oops! expected to pop an oop"); | |
7416 // now scan this oop's oops | |
7417 new_oop->oop_iterate(&_pam_verify_closure); | |
7418 } | |
7419 assert(_mark_stack->isEmpty(), "tautology, emphasizing post-condition"); | |
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7420 return true; |
0 | 7421 } |
7422 | |
7423 PushAndMarkVerifyClosure::PushAndMarkVerifyClosure( | |
7424 CMSCollector* collector, MemRegion span, | |
7425 CMSBitMap* verification_bm, CMSBitMap* cms_bm, | |
7426 CMSMarkStack* mark_stack): | |
7427 OopClosure(collector->ref_processor()), | |
7428 _collector(collector), | |
7429 _span(span), | |
7430 _verification_bm(verification_bm), | |
7431 _cms_bm(cms_bm), | |
7432 _mark_stack(mark_stack) | |
7433 { } | |
7434 | |
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7435 void PushAndMarkVerifyClosure::do_oop(oop* p) { PushAndMarkVerifyClosure::do_oop_work(p); } |
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7436 void PushAndMarkVerifyClosure::do_oop(narrowOop* p) { PushAndMarkVerifyClosure::do_oop_work(p); } |
0 | 7437 |
7438 // Upon stack overflow, we discard (part of) the stack, | |
7439 // remembering the least address amongst those discarded | |
7440 // in CMSCollector's _restart_address. | |
7441 void PushAndMarkVerifyClosure::handle_stack_overflow(HeapWord* lost) { | |
7442 // Remember the least grey address discarded | |
7443 HeapWord* ra = (HeapWord*)_mark_stack->least_value(lost); | |
7444 _collector->lower_restart_addr(ra); | |
7445 _mark_stack->reset(); // discard stack contents | |
7446 _mark_stack->expand(); // expand the stack if possible | |
7447 } | |
7448 | |
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7449 void PushAndMarkVerifyClosure::do_oop(oop obj) { |
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7450 assert(obj->is_oop_or_null(), "expected an oop or NULL"); |
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7451 HeapWord* addr = (HeapWord*)obj; |
0 | 7452 if (_span.contains(addr) && !_verification_bm->isMarked(addr)) { |
7453 // Oop lies in _span and isn't yet grey or black | |
7454 _verification_bm->mark(addr); // now grey | |
7455 if (!_cms_bm->isMarked(addr)) { | |
7456 oop(addr)->print(); | |
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7457 gclog_or_tty->print_cr(" (" INTPTR_FORMAT " should have been marked)", |
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7458 addr); |
0 | 7459 fatal("... aborting"); |
7460 } | |
7461 | |
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7462 if (!_mark_stack->push(obj)) { // stack overflow |
0 | 7463 if (PrintCMSStatistics != 0) { |
7464 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
7465 SIZE_FORMAT, _mark_stack->capacity()); | |
7466 } | |
7467 assert(_mark_stack->isFull(), "Else push should have succeeded"); | |
7468 handle_stack_overflow(addr); | |
7469 } | |
7470 // anything including and to the right of _finger | |
7471 // will be scanned as we iterate over the remainder of the | |
7472 // bit map | |
7473 } | |
7474 } | |
7475 | |
7476 PushOrMarkClosure::PushOrMarkClosure(CMSCollector* collector, | |
7477 MemRegion span, | |
7478 CMSBitMap* bitMap, CMSMarkStack* markStack, | |
7479 CMSMarkStack* revisitStack, | |
7480 HeapWord* finger, MarkFromRootsClosure* parent) : | |
935 | 7481 KlassRememberingOopClosure(collector, collector->ref_processor(), revisitStack), |
0 | 7482 _span(span), |
7483 _bitMap(bitMap), | |
7484 _markStack(markStack), | |
7485 _finger(finger), | |
935 | 7486 _parent(parent) |
0 | 7487 { } |
7488 | |
7489 Par_PushOrMarkClosure::Par_PushOrMarkClosure(CMSCollector* collector, | |
7490 MemRegion span, | |
7491 CMSBitMap* bit_map, | |
7492 OopTaskQueue* work_queue, | |
7493 CMSMarkStack* overflow_stack, | |
7494 CMSMarkStack* revisit_stack, | |
7495 HeapWord* finger, | |
7496 HeapWord** global_finger_addr, | |
7497 Par_MarkFromRootsClosure* parent) : | |
935 | 7498 Par_KlassRememberingOopClosure(collector, |
7499 collector->ref_processor(), | |
7500 revisit_stack), | |
0 | 7501 _whole_span(collector->_span), |
7502 _span(span), | |
7503 _bit_map(bit_map), | |
7504 _work_queue(work_queue), | |
7505 _overflow_stack(overflow_stack), | |
7506 _finger(finger), | |
7507 _global_finger_addr(global_finger_addr), | |
935 | 7508 _parent(parent) |
0 | 7509 { } |
7510 | |
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7511 // Assumes thread-safe access by callers, who are |
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7512 // responsible for mutual exclusion. |
0 | 7513 void CMSCollector::lower_restart_addr(HeapWord* low) { |
7514 assert(_span.contains(low), "Out of bounds addr"); | |
7515 if (_restart_addr == NULL) { | |
7516 _restart_addr = low; | |
7517 } else { | |
7518 _restart_addr = MIN2(_restart_addr, low); | |
7519 } | |
7520 } | |
7521 | |
7522 // Upon stack overflow, we discard (part of) the stack, | |
7523 // remembering the least address amongst those discarded | |
7524 // in CMSCollector's _restart_address. | |
7525 void PushOrMarkClosure::handle_stack_overflow(HeapWord* lost) { | |
7526 // Remember the least grey address discarded | |
7527 HeapWord* ra = (HeapWord*)_markStack->least_value(lost); | |
7528 _collector->lower_restart_addr(ra); | |
7529 _markStack->reset(); // discard stack contents | |
7530 _markStack->expand(); // expand the stack if possible | |
7531 } | |
7532 | |
7533 // Upon stack overflow, we discard (part of) the stack, | |
7534 // remembering the least address amongst those discarded | |
7535 // in CMSCollector's _restart_address. | |
7536 void Par_PushOrMarkClosure::handle_stack_overflow(HeapWord* lost) { | |
7537 // We need to do this under a mutex to prevent other | |
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7538 // workers from interfering with the work done below. |
0 | 7539 MutexLockerEx ml(_overflow_stack->par_lock(), |
7540 Mutex::_no_safepoint_check_flag); | |
7541 // Remember the least grey address discarded | |
7542 HeapWord* ra = (HeapWord*)_overflow_stack->least_value(lost); | |
7543 _collector->lower_restart_addr(ra); | |
7544 _overflow_stack->reset(); // discard stack contents | |
7545 _overflow_stack->expand(); // expand the stack if possible | |
7546 } | |
7547 | |
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7548 void PushOrMarkClosure::do_oop(oop obj) { |
0 | 7549 // Ignore mark word because we are running concurrent with mutators. |
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7550 assert(obj->is_oop_or_null(true), "expected an oop or NULL"); |
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7551 HeapWord* addr = (HeapWord*)obj; |
0 | 7552 if (_span.contains(addr) && !_bitMap->isMarked(addr)) { |
7553 // Oop lies in _span and isn't yet grey or black | |
7554 _bitMap->mark(addr); // now grey | |
7555 if (addr < _finger) { | |
7556 // the bit map iteration has already either passed, or | |
7557 // sampled, this bit in the bit map; we'll need to | |
7558 // use the marking stack to scan this oop's oops. | |
7559 bool simulate_overflow = false; | |
7560 NOT_PRODUCT( | |
7561 if (CMSMarkStackOverflowALot && | |
7562 _collector->simulate_overflow()) { | |
7563 // simulate a stack overflow | |
7564 simulate_overflow = true; | |
7565 } | |
7566 ) | |
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7567 if (simulate_overflow || !_markStack->push(obj)) { // stack overflow |
0 | 7568 if (PrintCMSStatistics != 0) { |
7569 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
7570 SIZE_FORMAT, _markStack->capacity()); | |
7571 } | |
7572 assert(simulate_overflow || _markStack->isFull(), "Else push should have succeeded"); | |
7573 handle_stack_overflow(addr); | |
7574 } | |
7575 } | |
7576 // anything including and to the right of _finger | |
7577 // will be scanned as we iterate over the remainder of the | |
7578 // bit map | |
7579 do_yield_check(); | |
7580 } | |
7581 } | |
7582 | |
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7583 void PushOrMarkClosure::do_oop(oop* p) { PushOrMarkClosure::do_oop_work(p); } |
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7584 void PushOrMarkClosure::do_oop(narrowOop* p) { PushOrMarkClosure::do_oop_work(p); } |
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7585 |
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7586 void Par_PushOrMarkClosure::do_oop(oop obj) { |
0 | 7587 // Ignore mark word because we are running concurrent with mutators. |
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7588 assert(obj->is_oop_or_null(true), "expected an oop or NULL"); |
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7589 HeapWord* addr = (HeapWord*)obj; |
0 | 7590 if (_whole_span.contains(addr) && !_bit_map->isMarked(addr)) { |
7591 // Oop lies in _span and isn't yet grey or black | |
7592 // We read the global_finger (volatile read) strictly after marking oop | |
7593 bool res = _bit_map->par_mark(addr); // now grey | |
7594 volatile HeapWord** gfa = (volatile HeapWord**)_global_finger_addr; | |
7595 // Should we push this marked oop on our stack? | |
7596 // -- if someone else marked it, nothing to do | |
7597 // -- if target oop is above global finger nothing to do | |
7598 // -- if target oop is in chunk and above local finger | |
7599 // then nothing to do | |
7600 // -- else push on work queue | |
7601 if ( !res // someone else marked it, they will deal with it | |
7602 || (addr >= *gfa) // will be scanned in a later task | |
7603 || (_span.contains(addr) && addr >= _finger)) { // later in this chunk | |
7604 return; | |
7605 } | |
7606 // the bit map iteration has already either passed, or | |
7607 // sampled, this bit in the bit map; we'll need to | |
7608 // use the marking stack to scan this oop's oops. | |
7609 bool simulate_overflow = false; | |
7610 NOT_PRODUCT( | |
7611 if (CMSMarkStackOverflowALot && | |
7612 _collector->simulate_overflow()) { | |
7613 // simulate a stack overflow | |
7614 simulate_overflow = true; | |
7615 } | |
7616 ) | |
7617 if (simulate_overflow || | |
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7618 !(_work_queue->push(obj) || _overflow_stack->par_push(obj))) { |
0 | 7619 // stack overflow |
7620 if (PrintCMSStatistics != 0) { | |
7621 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
7622 SIZE_FORMAT, _overflow_stack->capacity()); | |
7623 } | |
7624 // We cannot assert that the overflow stack is full because | |
7625 // it may have been emptied since. | |
7626 assert(simulate_overflow || | |
7627 _work_queue->size() == _work_queue->max_elems(), | |
7628 "Else push should have succeeded"); | |
7629 handle_stack_overflow(addr); | |
7630 } | |
7631 do_yield_check(); | |
7632 } | |
7633 } | |
7634 | |
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7635 void Par_PushOrMarkClosure::do_oop(oop* p) { Par_PushOrMarkClosure::do_oop_work(p); } |
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7636 void Par_PushOrMarkClosure::do_oop(narrowOop* p) { Par_PushOrMarkClosure::do_oop_work(p); } |
0 | 7637 |
935 | 7638 KlassRememberingOopClosure::KlassRememberingOopClosure(CMSCollector* collector, |
7639 ReferenceProcessor* rp, | |
7640 CMSMarkStack* revisit_stack) : | |
7641 OopClosure(rp), | |
7642 _collector(collector), | |
7643 _revisit_stack(revisit_stack), | |
7644 _should_remember_klasses(collector->should_unload_classes()) {} | |
7645 | |
0 | 7646 PushAndMarkClosure::PushAndMarkClosure(CMSCollector* collector, |
7647 MemRegion span, | |
7648 ReferenceProcessor* rp, | |
7649 CMSBitMap* bit_map, | |
7650 CMSBitMap* mod_union_table, | |
7651 CMSMarkStack* mark_stack, | |
7652 CMSMarkStack* revisit_stack, | |
7653 bool concurrent_precleaning): | |
935 | 7654 KlassRememberingOopClosure(collector, rp, revisit_stack), |
0 | 7655 _span(span), |
7656 _bit_map(bit_map), | |
7657 _mod_union_table(mod_union_table), | |
7658 _mark_stack(mark_stack), | |
935 | 7659 _concurrent_precleaning(concurrent_precleaning) |
0 | 7660 { |
7661 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
7662 } | |
7663 | |
7664 // Grey object rescan during pre-cleaning and second checkpoint phases -- | |
7665 // the non-parallel version (the parallel version appears further below.) | |
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7666 void PushAndMarkClosure::do_oop(oop obj) { |
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7667 // Ignore mark word verification. If during concurrent precleaning, |
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7668 // the object monitor may be locked. If during the checkpoint |
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7669 // phases, the object may already have been reached by a different |
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7670 // path and may be at the end of the global overflow list (so |
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7671 // the mark word may be NULL). |
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7672 assert(obj->is_oop_or_null(true /* ignore mark word */), |
0 | 7673 "expected an oop or NULL"); |
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7674 HeapWord* addr = (HeapWord*)obj; |
0 | 7675 // Check if oop points into the CMS generation |
7676 // and is not marked | |
7677 if (_span.contains(addr) && !_bit_map->isMarked(addr)) { | |
7678 // a white object ... | |
7679 _bit_map->mark(addr); // ... now grey | |
7680 // push on the marking stack (grey set) | |
7681 bool simulate_overflow = false; | |
7682 NOT_PRODUCT( | |
7683 if (CMSMarkStackOverflowALot && | |
7684 _collector->simulate_overflow()) { | |
7685 // simulate a stack overflow | |
7686 simulate_overflow = true; | |
7687 } | |
7688 ) | |
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7689 if (simulate_overflow || !_mark_stack->push(obj)) { |
0 | 7690 if (_concurrent_precleaning) { |
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7691 // During precleaning we can just dirty the appropriate card(s) |
0 | 7692 // in the mod union table, thus ensuring that the object remains |
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7693 // in the grey set and continue. In the case of object arrays |
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7694 // we need to dirty all of the cards that the object spans, |
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7695 // since the rescan of object arrays will be limited to the |
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7696 // dirty cards. |
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7697 // Note that no one can be intefering with us in this action |
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7698 // of dirtying the mod union table, so no locking or atomics |
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7699 // are required. |
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7700 if (obj->is_objArray()) { |
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7701 size_t sz = obj->size(); |
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7702 HeapWord* end_card_addr = (HeapWord*)round_to( |
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7703 (intptr_t)(addr+sz), CardTableModRefBS::card_size); |
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7704 MemRegion redirty_range = MemRegion(addr, end_card_addr); |
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7705 assert(!redirty_range.is_empty(), "Arithmetical tautology"); |
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7706 _mod_union_table->mark_range(redirty_range); |
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7707 } else { |
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7708 _mod_union_table->mark(addr); |
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7709 } |
0 | 7710 _collector->_ser_pmc_preclean_ovflw++; |
7711 } else { | |
7712 // During the remark phase, we need to remember this oop | |
7713 // in the overflow list. | |
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7714 _collector->push_on_overflow_list(obj); |
0 | 7715 _collector->_ser_pmc_remark_ovflw++; |
7716 } | |
7717 } | |
7718 } | |
7719 } | |
7720 | |
7721 Par_PushAndMarkClosure::Par_PushAndMarkClosure(CMSCollector* collector, | |
7722 MemRegion span, | |
7723 ReferenceProcessor* rp, | |
7724 CMSBitMap* bit_map, | |
7725 OopTaskQueue* work_queue, | |
7726 CMSMarkStack* revisit_stack): | |
935 | 7727 Par_KlassRememberingOopClosure(collector, rp, revisit_stack), |
0 | 7728 _span(span), |
7729 _bit_map(bit_map), | |
935 | 7730 _work_queue(work_queue) |
0 | 7731 { |
7732 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
7733 } | |
7734 | |
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7735 void PushAndMarkClosure::do_oop(oop* p) { PushAndMarkClosure::do_oop_work(p); } |
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7736 void PushAndMarkClosure::do_oop(narrowOop* p) { PushAndMarkClosure::do_oop_work(p); } |
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7737 |
0 | 7738 // Grey object rescan during second checkpoint phase -- |
7739 // the parallel version. | |
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7740 void Par_PushAndMarkClosure::do_oop(oop obj) { |
0 | 7741 // In the assert below, we ignore the mark word because |
7742 // this oop may point to an already visited object that is | |
7743 // on the overflow stack (in which case the mark word has | |
7744 // been hijacked for chaining into the overflow stack -- | |
7745 // if this is the last object in the overflow stack then | |
7746 // its mark word will be NULL). Because this object may | |
7747 // have been subsequently popped off the global overflow | |
7748 // stack, and the mark word possibly restored to the prototypical | |
7749 // value, by the time we get to examined this failing assert in | |
7750 // the debugger, is_oop_or_null(false) may subsequently start | |
7751 // to hold. | |
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7752 assert(obj->is_oop_or_null(true), |
0 | 7753 "expected an oop or NULL"); |
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7754 HeapWord* addr = (HeapWord*)obj; |
0 | 7755 // Check if oop points into the CMS generation |
7756 // and is not marked | |
7757 if (_span.contains(addr) && !_bit_map->isMarked(addr)) { | |
7758 // a white object ... | |
7759 // If we manage to "claim" the object, by being the | |
7760 // first thread to mark it, then we push it on our | |
7761 // marking stack | |
7762 if (_bit_map->par_mark(addr)) { // ... now grey | |
7763 // push on work queue (grey set) | |
7764 bool simulate_overflow = false; | |
7765 NOT_PRODUCT( | |
7766 if (CMSMarkStackOverflowALot && | |
7767 _collector->par_simulate_overflow()) { | |
7768 // simulate a stack overflow | |
7769 simulate_overflow = true; | |
7770 } | |
7771 ) | |
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7772 if (simulate_overflow || !_work_queue->push(obj)) { |
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|
7773 _collector->par_push_on_overflow_list(obj); |
0 | 7774 _collector->_par_pmc_remark_ovflw++; // imprecise OK: no need to CAS |
7775 } | |
7776 } // Else, some other thread got there first | |
7777 } | |
7778 } | |
7779 | |
113
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7780 void Par_PushAndMarkClosure::do_oop(oop* p) { Par_PushAndMarkClosure::do_oop_work(p); } |
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7781 void Par_PushAndMarkClosure::do_oop(narrowOop* p) { Par_PushAndMarkClosure::do_oop_work(p); } |
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7782 |
941 | 7783 void PushAndMarkClosure::remember_mdo(DataLayout* v) { |
7784 // TBD | |
7785 } | |
7786 | |
7787 void Par_PushAndMarkClosure::remember_mdo(DataLayout* v) { | |
7788 // TBD | |
7789 } | |
7790 | |
0 | 7791 void CMSPrecleanRefsYieldClosure::do_yield_work() { |
935 | 7792 DEBUG_ONLY(RememberKlassesChecker mux(false);) |
0 | 7793 Mutex* bml = _collector->bitMapLock(); |
7794 assert_lock_strong(bml); | |
7795 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
7796 "CMS thread should hold CMS token"); | |
7797 | |
7798 bml->unlock(); | |
7799 ConcurrentMarkSweepThread::desynchronize(true); | |
7800 | |
7801 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
7802 | |
7803 _collector->stopTimer(); | |
7804 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
7805 if (PrintCMSStatistics != 0) { | |
7806 _collector->incrementYields(); | |
7807 } | |
7808 _collector->icms_wait(); | |
7809 | |
7810 // See the comment in coordinator_yield() | |
7811 for (unsigned i = 0; i < CMSYieldSleepCount && | |
7812 ConcurrentMarkSweepThread::should_yield() && | |
7813 !CMSCollector::foregroundGCIsActive(); ++i) { | |
7814 os::sleep(Thread::current(), 1, false); | |
7815 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
7816 } | |
7817 | |
7818 ConcurrentMarkSweepThread::synchronize(true); | |
7819 bml->lock(); | |
7820 | |
7821 _collector->startTimer(); | |
7822 } | |
7823 | |
7824 bool CMSPrecleanRefsYieldClosure::should_return() { | |
7825 if (ConcurrentMarkSweepThread::should_yield()) { | |
7826 do_yield_work(); | |
7827 } | |
7828 return _collector->foregroundGCIsActive(); | |
7829 } | |
7830 | |
7831 void MarkFromDirtyCardsClosure::do_MemRegion(MemRegion mr) { | |
7832 assert(((size_t)mr.start())%CardTableModRefBS::card_size_in_words == 0, | |
7833 "mr should be aligned to start at a card boundary"); | |
7834 // We'd like to assert: | |
7835 // assert(mr.word_size()%CardTableModRefBS::card_size_in_words == 0, | |
7836 // "mr should be a range of cards"); | |
7837 // However, that would be too strong in one case -- the last | |
7838 // partition ends at _unallocated_block which, in general, can be | |
7839 // an arbitrary boundary, not necessarily card aligned. | |
7840 if (PrintCMSStatistics != 0) { | |
7841 _num_dirty_cards += | |
7842 mr.word_size()/CardTableModRefBS::card_size_in_words; | |
7843 } | |
7844 _space->object_iterate_mem(mr, &_scan_cl); | |
7845 } | |
7846 | |
7847 SweepClosure::SweepClosure(CMSCollector* collector, | |
7848 ConcurrentMarkSweepGeneration* g, | |
7849 CMSBitMap* bitMap, bool should_yield) : | |
7850 _collector(collector), | |
7851 _g(g), | |
7852 _sp(g->cmsSpace()), | |
7853 _limit(_sp->sweep_limit()), | |
7854 _freelistLock(_sp->freelistLock()), | |
7855 _bitMap(bitMap), | |
7856 _yield(should_yield), | |
7857 _inFreeRange(false), // No free range at beginning of sweep | |
7858 _freeRangeInFreeLists(false), // No free range at beginning of sweep | |
7859 _lastFreeRangeCoalesced(false), | |
7860 _freeFinger(g->used_region().start()) | |
7861 { | |
7862 NOT_PRODUCT( | |
7863 _numObjectsFreed = 0; | |
7864 _numWordsFreed = 0; | |
7865 _numObjectsLive = 0; | |
7866 _numWordsLive = 0; | |
7867 _numObjectsAlreadyFree = 0; | |
7868 _numWordsAlreadyFree = 0; | |
7869 _last_fc = NULL; | |
7870 | |
7871 _sp->initializeIndexedFreeListArrayReturnedBytes(); | |
7872 _sp->dictionary()->initializeDictReturnedBytes(); | |
7873 ) | |
7874 assert(_limit >= _sp->bottom() && _limit <= _sp->end(), | |
7875 "sweep _limit out of bounds"); | |
7876 if (CMSTraceSweeper) { | |
7877 gclog_or_tty->print("\n====================\nStarting new sweep\n"); | |
7878 } | |
7879 } | |
7880 | |
7881 // We need this destructor to reclaim any space at the end | |
2132
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7882 // of the space, which do_blk below may not yet have added back to |
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7883 // the free lists. |
0 | 7884 SweepClosure::~SweepClosure() { |
7885 assert_lock_strong(_freelistLock); | |
2132
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7886 assert(_limit >= _sp->bottom() && _limit <= _sp->end(), |
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7887 "sweep _limit out of bounds"); |
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7888 // Flush any remaining coterminal free run as a single |
4947ee68d19c
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7889 // coalesced chunk to the appropriate free list. |
0 | 7890 if (inFreeRange()) { |
2132
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7891 assert(freeFinger() < _limit, "freeFinger points too high"); |
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7892 flush_cur_free_chunk(freeFinger(), pointer_delta(_limit, freeFinger())); |
0 | 7893 if (CMSTraceSweeper) { |
2132
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7894 gclog_or_tty->print("Sweep: last chunk: "); |
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7895 gclog_or_tty->print("put_free_blk 0x%x ("SIZE_FORMAT") [coalesced:"SIZE_FORMAT"]\n", |
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7896 freeFinger(), pointer_delta(_limit, freeFinger()), lastFreeRangeCoalesced()); |
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7897 } |
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7898 } // else nothing to flush |
0 | 7899 NOT_PRODUCT( |
7900 if (Verbose && PrintGC) { | |
7901 gclog_or_tty->print("Collected "SIZE_FORMAT" objects, " | |
7902 SIZE_FORMAT " bytes", | |
7903 _numObjectsFreed, _numWordsFreed*sizeof(HeapWord)); | |
7904 gclog_or_tty->print_cr("\nLive "SIZE_FORMAT" objects, " | |
7905 SIZE_FORMAT" bytes " | |
7906 "Already free "SIZE_FORMAT" objects, "SIZE_FORMAT" bytes", | |
7907 _numObjectsLive, _numWordsLive*sizeof(HeapWord), | |
7908 _numObjectsAlreadyFree, _numWordsAlreadyFree*sizeof(HeapWord)); | |
7909 size_t totalBytes = (_numWordsFreed + _numWordsLive + _numWordsAlreadyFree) * | |
7910 sizeof(HeapWord); | |
7911 gclog_or_tty->print_cr("Total sweep: "SIZE_FORMAT" bytes", totalBytes); | |
7912 | |
7913 if (PrintCMSStatistics && CMSVerifyReturnedBytes) { | |
7914 size_t indexListReturnedBytes = _sp->sumIndexedFreeListArrayReturnedBytes(); | |
7915 size_t dictReturnedBytes = _sp->dictionary()->sumDictReturnedBytes(); | |
7916 size_t returnedBytes = indexListReturnedBytes + dictReturnedBytes; | |
7917 gclog_or_tty->print("Returned "SIZE_FORMAT" bytes", returnedBytes); | |
7918 gclog_or_tty->print(" Indexed List Returned "SIZE_FORMAT" bytes", | |
7919 indexListReturnedBytes); | |
7920 gclog_or_tty->print_cr(" Dictionary Returned "SIZE_FORMAT" bytes", | |
7921 dictReturnedBytes); | |
7922 } | |
7923 } | |
7924 ) | |
7925 // Now, in debug mode, just null out the sweep_limit | |
7926 NOT_PRODUCT(_sp->clear_sweep_limit();) | |
7927 if (CMSTraceSweeper) { | |
7928 gclog_or_tty->print("end of sweep\n================\n"); | |
7929 } | |
7930 } | |
7931 | |
7932 void SweepClosure::initialize_free_range(HeapWord* freeFinger, | |
7933 bool freeRangeInFreeLists) { | |
7934 if (CMSTraceSweeper) { | |
2132
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7935 gclog_or_tty->print("---- Start free range at 0x%x with free block (%d)\n", |
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7936 freeFinger, freeRangeInFreeLists); |
0 | 7937 } |
7938 assert(!inFreeRange(), "Trampling existing free range"); | |
7939 set_inFreeRange(true); | |
7940 set_lastFreeRangeCoalesced(false); | |
7941 | |
7942 set_freeFinger(freeFinger); | |
7943 set_freeRangeInFreeLists(freeRangeInFreeLists); | |
7944 if (CMSTestInFreeList) { | |
7945 if (freeRangeInFreeLists) { | |
7946 FreeChunk* fc = (FreeChunk*) freeFinger; | |
7947 assert(fc->isFree(), "A chunk on the free list should be free."); | |
7948 assert(fc->size() > 0, "Free range should have a size"); | |
7949 assert(_sp->verifyChunkInFreeLists(fc), "Chunk is not in free lists"); | |
7950 } | |
7951 } | |
7952 } | |
7953 | |
7954 // Note that the sweeper runs concurrently with mutators. Thus, | |
7955 // it is possible for direct allocation in this generation to happen | |
7956 // in the middle of the sweep. Note that the sweeper also coalesces | |
7957 // contiguous free blocks. Thus, unless the sweeper and the allocator | |
7958 // synchronize appropriately freshly allocated blocks may get swept up. | |
7959 // This is accomplished by the sweeper locking the free lists while | |
7960 // it is sweeping. Thus blocks that are determined to be free are | |
7961 // indeed free. There is however one additional complication: | |
7962 // blocks that have been allocated since the final checkpoint and | |
7963 // mark, will not have been marked and so would be treated as | |
7964 // unreachable and swept up. To prevent this, the allocator marks | |
7965 // the bit map when allocating during the sweep phase. This leads, | |
7966 // however, to a further complication -- objects may have been allocated | |
7967 // but not yet initialized -- in the sense that the header isn't yet | |
7968 // installed. The sweeper can not then determine the size of the block | |
7969 // in order to skip over it. To deal with this case, we use a technique | |
7970 // (due to Printezis) to encode such uninitialized block sizes in the | |
7971 // bit map. Since the bit map uses a bit per every HeapWord, but the | |
7972 // CMS generation has a minimum object size of 3 HeapWords, it follows | |
7973 // that "normal marks" won't be adjacent in the bit map (there will | |
7974 // always be at least two 0 bits between successive 1 bits). We make use | |
7975 // of these "unused" bits to represent uninitialized blocks -- the bit | |
7976 // corresponding to the start of the uninitialized object and the next | |
7977 // bit are both set. Finally, a 1 bit marks the end of the object that | |
7978 // started with the two consecutive 1 bits to indicate its potentially | |
7979 // uninitialized state. | |
7980 | |
7981 size_t SweepClosure::do_blk_careful(HeapWord* addr) { | |
7982 FreeChunk* fc = (FreeChunk*)addr; | |
7983 size_t res; | |
7984 | |
1720
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7985 // 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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7986 // 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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7987 // we started the sweep, it may no longer be one because heap expansion |
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6977970: CMS: concurrentMarkSweepGeneration.cpp:7947 assert(addr <= _limit) failed: sweep invariant
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7988 // may have caused us to coalesce the block ending at the address _limit |
5ed703250bff
6977970: CMS: concurrentMarkSweepGeneration.cpp:7947 assert(addr <= _limit) failed: sweep invariant
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7989 // with a newly expanded chunk (this happens when _limit was set to the |
5ed703250bff
6977970: CMS: concurrentMarkSweepGeneration.cpp:7947 assert(addr <= _limit) failed: sweep invariant
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7990 // previous _end of the space), so we may have stepped past _limit; see CR 6977970. |
2132
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7991 if (addr >= _limit) { // we have swept up to or past the limit: finish up |
0 | 7992 assert(_limit >= _sp->bottom() && _limit <= _sp->end(), |
7993 "sweep _limit out of bounds"); | |
1720
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7994 assert(addr < _sp->end(), "addr out of bounds"); |
2132
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7995 // Flush any remaining coterminal free run as a single |
4947ee68d19c
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7996 // coalesced chunk to the appropriate free list. |
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7997 if (inFreeRange()) { |
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7998 assert(freeFinger() < _limit, "finger points too high"); |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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7999 flush_cur_free_chunk(freeFinger(), |
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8000 pointer_delta(addr, freeFinger())); |
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8001 if (CMSTraceSweeper) { |
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7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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8002 gclog_or_tty->print("Sweep: last chunk: "); |
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8003 gclog_or_tty->print("put_free_blk 0x%x ("SIZE_FORMAT") " |
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8004 "[coalesced:"SIZE_FORMAT"]\n", |
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8005 freeFinger(), pointer_delta(addr, freeFinger()), |
4947ee68d19c
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8006 lastFreeRangeCoalesced()); |
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|
8007 } |
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|
8008 } |
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|
8009 |
4947ee68d19c
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|
8010 // help the iterator loop finish |
1720
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6977970: CMS: concurrentMarkSweepGeneration.cpp:7947 assert(addr <= _limit) failed: sweep invariant
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|
8011 return pointer_delta(_sp->end(), addr); |
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6977970: CMS: concurrentMarkSweepGeneration.cpp:7947 assert(addr <= _limit) failed: sweep invariant
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|
8012 } |
2132
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|
8013 |
1720
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|
8014 assert(addr < _limit, "sweep invariant"); |
0 | 8015 // check if we should yield |
8016 do_yield_check(addr); | |
8017 if (fc->isFree()) { | |
8018 // Chunk that is already free | |
8019 res = fc->size(); | |
2132
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|
8020 do_already_free_chunk(fc); |
0 | 8021 debug_only(_sp->verifyFreeLists()); |
8022 assert(res == fc->size(), "Don't expect the size to change"); | |
8023 NOT_PRODUCT( | |
8024 _numObjectsAlreadyFree++; | |
8025 _numWordsAlreadyFree += res; | |
8026 ) | |
8027 NOT_PRODUCT(_last_fc = fc;) | |
8028 } else if (!_bitMap->isMarked(addr)) { | |
8029 // Chunk is fresh garbage | |
2132
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|
8030 res = do_garbage_chunk(fc); |
0 | 8031 debug_only(_sp->verifyFreeLists()); |
8032 NOT_PRODUCT( | |
8033 _numObjectsFreed++; | |
8034 _numWordsFreed += res; | |
8035 ) | |
8036 } else { | |
8037 // Chunk that is alive. | |
2132
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|
8038 res = do_live_chunk(fc); |
0 | 8039 debug_only(_sp->verifyFreeLists()); |
8040 NOT_PRODUCT( | |
8041 _numObjectsLive++; | |
8042 _numWordsLive += res; | |
8043 ) | |
8044 } | |
8045 return res; | |
8046 } | |
8047 | |
8048 // For the smart allocation, record following | |
8049 // split deaths - a free chunk is removed from its free list because | |
8050 // it is being split into two or more chunks. | |
8051 // split birth - a free chunk is being added to its free list because | |
8052 // a larger free chunk has been split and resulted in this free chunk. | |
8053 // coal death - a free chunk is being removed from its free list because | |
8054 // it is being coalesced into a large free chunk. | |
8055 // coal birth - a free chunk is being added to its free list because | |
8056 // it was created when two or more free chunks where coalesced into | |
8057 // this free chunk. | |
8058 // | |
8059 // These statistics are used to determine the desired number of free | |
8060 // chunks of a given size. The desired number is chosen to be relative | |
8061 // to the end of a CMS sweep. The desired number at the end of a sweep | |
8062 // is the | |
8063 // count-at-end-of-previous-sweep (an amount that was enough) | |
8064 // - count-at-beginning-of-current-sweep (the excess) | |
8065 // + split-births (gains in this size during interval) | |
8066 // - split-deaths (demands on this size during interval) | |
8067 // where the interval is from the end of one sweep to the end of the | |
8068 // next. | |
8069 // | |
8070 // When sweeping the sweeper maintains an accumulated chunk which is | |
8071 // the chunk that is made up of chunks that have been coalesced. That | |
8072 // will be termed the left-hand chunk. A new chunk of garbage that | |
8073 // is being considered for coalescing will be referred to as the | |
8074 // right-hand chunk. | |
8075 // | |
8076 // When making a decision on whether to coalesce a right-hand chunk with | |
8077 // the current left-hand chunk, the current count vs. the desired count | |
8078 // of the left-hand chunk is considered. Also if the right-hand chunk | |
8079 // is near the large chunk at the end of the heap (see | |
8080 // ConcurrentMarkSweepGeneration::isNearLargestChunk()), then the | |
8081 // left-hand chunk is coalesced. | |
8082 // | |
8083 // When making a decision about whether to split a chunk, the desired count | |
8084 // vs. the current count of the candidate to be split is also considered. | |
8085 // If the candidate is underpopulated (currently fewer chunks than desired) | |
8086 // a chunk of an overpopulated (currently more chunks than desired) size may | |
8087 // be chosen. The "hint" associated with a free list, if non-null, points | |
8088 // to a free list which may be overpopulated. | |
8089 // | |
8090 | |
2132
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|
8091 void SweepClosure::do_already_free_chunk(FreeChunk* fc) { |
0 | 8092 size_t size = fc->size(); |
8093 // Chunks that cannot be coalesced are not in the | |
8094 // free lists. | |
8095 if (CMSTestInFreeList && !fc->cantCoalesce()) { | |
8096 assert(_sp->verifyChunkInFreeLists(fc), | |
8097 "free chunk should be in free lists"); | |
8098 } | |
8099 // a chunk that is already free, should not have been | |
8100 // marked in the bit map | |
8101 HeapWord* addr = (HeapWord*) fc; | |
8102 assert(!_bitMap->isMarked(addr), "free chunk should be unmarked"); | |
8103 // Verify that the bit map has no bits marked between | |
8104 // addr and purported end of this block. | |
8105 _bitMap->verifyNoOneBitsInRange(addr + 1, addr + size); | |
8106 | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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1994
diff
changeset
|
8107 // Some chunks cannot be coalesced under any circumstances. |
0 | 8108 // See the definition of cantCoalesce(). |
8109 if (!fc->cantCoalesce()) { | |
8110 // This chunk can potentially be coalesced. | |
8111 if (_sp->adaptive_freelists()) { | |
8112 // All the work is done in | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
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|
8113 do_post_free_or_garbage_chunk(fc, size); |
0 | 8114 } else { // Not adaptive free lists |
8115 // this is a free chunk that can potentially be coalesced by the sweeper; | |
8116 if (!inFreeRange()) { | |
8117 // if the next chunk is a free block that can't be coalesced | |
8118 // it doesn't make sense to remove this chunk from the free lists | |
8119 FreeChunk* nextChunk = (FreeChunk*)(addr + size); | |
2136
c91cc404ca46
7011940: iCMS: SIGSEGV in SweepClosure::do_already_free_chunk(FreeChunk*)+0x360
ysr
parents:
2132
diff
changeset
|
8120 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
|
8121 if ((HeapWord*)nextChunk < _sp->end() && // There is another free chunk to the right ... |
c91cc404ca46
7011940: iCMS: SIGSEGV in SweepClosure::do_already_free_chunk(FreeChunk*)+0x360
ysr
parents:
2132
diff
changeset
|
8122 nextChunk->isFree() && // ... which is free... |
c91cc404ca46
7011940: iCMS: SIGSEGV in SweepClosure::do_already_free_chunk(FreeChunk*)+0x360
ysr
parents:
2132
diff
changeset
|
8123 nextChunk->cantCoalesce()) { // ... but can't be coalesced |
0 | 8124 // nothing to do |
8125 } else { | |
8126 // Potentially the start of a new free range: | |
8127 // Don't eagerly remove it from the free lists. | |
8128 // No need to remove it if it will just be put | |
8129 // back again. (Also from a pragmatic point of view | |
8130 // if it is a free block in a region that is beyond | |
8131 // any allocated blocks, an assertion will fail) | |
8132 // Remember the start of a free run. | |
8133 initialize_free_range(addr, true); | |
8134 // end - can coalesce with next chunk | |
8135 } | |
8136 } else { | |
8137 // the midst of a free range, we are coalescing | |
8138 debug_only(record_free_block_coalesced(fc);) | |
8139 if (CMSTraceSweeper) { | |
8140 gclog_or_tty->print(" -- pick up free block 0x%x (%d)\n", fc, size); | |
8141 } | |
8142 // remove it from the free lists | |
8143 _sp->removeFreeChunkFromFreeLists(fc); | |
8144 set_lastFreeRangeCoalesced(true); | |
8145 // If the chunk is being coalesced and the current free range is | |
8146 // in the free lists, remove the current free range so that it | |
8147 // will be returned to the free lists in its entirety - all | |
8148 // the coalesced pieces included. | |
8149 if (freeRangeInFreeLists()) { | |
8150 FreeChunk* ffc = (FreeChunk*) freeFinger(); | |
8151 assert(ffc->size() == pointer_delta(addr, freeFinger()), | |
8152 "Size of free range is inconsistent with chunk size."); | |
8153 if (CMSTestInFreeList) { | |
8154 assert(_sp->verifyChunkInFreeLists(ffc), | |
8155 "free range is not in free lists"); | |
8156 } | |
8157 _sp->removeFreeChunkFromFreeLists(ffc); | |
8158 set_freeRangeInFreeLists(false); | |
8159 } | |
8160 } | |
8161 } | |
8162 } else { | |
8163 // Code path common to both original and adaptive free lists. | |
8164 | |
8165 // cant coalesce with previous block; this should be treated | |
8166 // as the end of a free run if any | |
8167 if (inFreeRange()) { | |
8168 // 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
|
8169 assert(freeFinger() < addr, "freeFinger points too high"); |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
changeset
|
8170 flush_cur_free_chunk(freeFinger(), pointer_delta(addr, freeFinger())); |
0 | 8171 } |
8172 // else, nothing to do, just continue | |
8173 } | |
8174 } | |
8175 | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8176 size_t SweepClosure::do_garbage_chunk(FreeChunk* fc) { |
0 | 8177 // This is a chunk of garbage. It is not in any free list. |
8178 // Add it to a free list or let it possibly be coalesced into | |
8179 // a larger chunk. | |
8180 HeapWord* addr = (HeapWord*) fc; | |
8181 size_t size = CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size()); | |
8182 | |
8183 if (_sp->adaptive_freelists()) { | |
8184 // Verify that the bit map has no bits marked between | |
8185 // addr and purported end of just dead object. | |
8186 _bitMap->verifyNoOneBitsInRange(addr + 1, addr + size); | |
8187 | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8188 do_post_free_or_garbage_chunk(fc, size); |
0 | 8189 } else { |
8190 if (!inFreeRange()) { | |
8191 // start of a new free range | |
8192 assert(size > 0, "A free range should have a size"); | |
8193 initialize_free_range(addr, false); | |
8194 | |
8195 } else { | |
8196 // this will be swept up when we hit the end of the | |
8197 // free range | |
8198 if (CMSTraceSweeper) { | |
8199 gclog_or_tty->print(" -- pick up garbage 0x%x (%d) \n", fc, size); | |
8200 } | |
8201 // If the chunk is being coalesced and the current free range is | |
8202 // in the free lists, remove the current free range so that it | |
8203 // will be returned to the free lists in its entirety - all | |
8204 // the coalesced pieces included. | |
8205 if (freeRangeInFreeLists()) { | |
8206 FreeChunk* ffc = (FreeChunk*)freeFinger(); | |
8207 assert(ffc->size() == pointer_delta(addr, freeFinger()), | |
8208 "Size of free range is inconsistent with chunk size."); | |
8209 if (CMSTestInFreeList) { | |
8210 assert(_sp->verifyChunkInFreeLists(ffc), | |
8211 "free range is not in free lists"); | |
8212 } | |
8213 _sp->removeFreeChunkFromFreeLists(ffc); | |
8214 set_freeRangeInFreeLists(false); | |
8215 } | |
8216 set_lastFreeRangeCoalesced(true); | |
8217 } | |
8218 // this will be swept up when we hit the end of the free range | |
8219 | |
8220 // Verify that the bit map has no bits marked between | |
8221 // addr and purported end of just dead object. | |
8222 _bitMap->verifyNoOneBitsInRange(addr + 1, addr + size); | |
8223 } | |
8224 return size; | |
8225 } | |
8226 | |
2132
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7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8227 size_t SweepClosure::do_live_chunk(FreeChunk* fc) { |
0 | 8228 HeapWord* addr = (HeapWord*) fc; |
8229 // The sweeper has just found a live object. Return any accumulated | |
8230 // left hand chunk to the free lists. | |
8231 if (inFreeRange()) { | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8232 assert(freeFinger() < addr, "freeFinger points too high"); |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8233 flush_cur_free_chunk(freeFinger(), pointer_delta(addr, freeFinger())); |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8234 } |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8235 |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
changeset
|
8236 // This object is live: we'd normally expect this to be |
0 | 8237 // an oop, and like to assert the following: |
8238 // assert(oop(addr)->is_oop(), "live block should be an oop"); | |
8239 // However, as we commented above, this may be an object whose | |
8240 // header hasn't yet been initialized. | |
8241 size_t size; | |
8242 assert(_bitMap->isMarked(addr), "Tautology for this control point"); | |
8243 if (_bitMap->isMarked(addr + 1)) { | |
8244 // Determine the size from the bit map, rather than trying to | |
8245 // compute it from the object header. | |
8246 HeapWord* nextOneAddr = _bitMap->getNextMarkedWordAddress(addr + 2); | |
8247 size = pointer_delta(nextOneAddr + 1, addr); | |
8248 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
8249 "alignment problem"); | |
8250 | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8251 #ifdef DEBUG |
187 | 8252 if (oop(addr)->klass_or_null() != NULL && |
94
0834225a7916
6634032: CMS: Need CMSInitiatingPermOccupancyFraction for perm, divorcing from CMSInitiatingOccupancyFraction
ysr
parents:
9
diff
changeset
|
8253 ( !_collector->should_unload_classes() |
518
0af8b0718fc9
6692899: CMS: many vm.parallel_class_loading tests fail with assert "missing Printezis mark"
jmasa
parents:
517
diff
changeset
|
8254 || (oop(addr)->is_parsable()) && |
0af8b0718fc9
6692899: CMS: many vm.parallel_class_loading tests fail with assert "missing Printezis mark"
jmasa
parents:
517
diff
changeset
|
8255 oop(addr)->is_conc_safe())) { |
0 | 8256 // Ignore mark word because we are running concurrent with mutators |
8257 assert(oop(addr)->is_oop(true), "live block should be an oop"); | |
518
0af8b0718fc9
6692899: CMS: many vm.parallel_class_loading tests fail with assert "missing Printezis mark"
jmasa
parents:
517
diff
changeset
|
8258 // is_conc_safe is checked before performing this assertion |
0af8b0718fc9
6692899: CMS: many vm.parallel_class_loading tests fail with assert "missing Printezis mark"
jmasa
parents:
517
diff
changeset
|
8259 // because an object that is not is_conc_safe may yet have |
0af8b0718fc9
6692899: CMS: many vm.parallel_class_loading tests fail with assert "missing Printezis mark"
jmasa
parents:
517
diff
changeset
|
8260 // the return from size() correct. |
0 | 8261 assert(size == |
8262 CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size()), | |
8263 "P-mark and computed size do not agree"); | |
8264 } | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8265 #endif |
0 | 8266 |
8267 } else { | |
8268 // This should be an initialized object that's alive. | |
187 | 8269 assert(oop(addr)->klass_or_null() != NULL && |
94
0834225a7916
6634032: CMS: Need CMSInitiatingPermOccupancyFraction for perm, divorcing from CMSInitiatingOccupancyFraction
ysr
parents:
9
diff
changeset
|
8270 (!_collector->should_unload_classes() |
0 | 8271 || oop(addr)->is_parsable()), |
8272 "Should be an initialized object"); | |
518
0af8b0718fc9
6692899: CMS: many vm.parallel_class_loading tests fail with assert "missing Printezis mark"
jmasa
parents:
517
diff
changeset
|
8273 // Note that there are objects used during class redefinition |
0af8b0718fc9
6692899: CMS: many vm.parallel_class_loading tests fail with assert "missing Printezis mark"
jmasa
parents:
517
diff
changeset
|
8274 // (e.g., merge_cp in VM_RedefineClasses::merge_cp_and_rewrite() |
0af8b0718fc9
6692899: CMS: many vm.parallel_class_loading tests fail with assert "missing Printezis mark"
jmasa
parents:
517
diff
changeset
|
8275 // which are discarded with their is_conc_safe state still |
0af8b0718fc9
6692899: CMS: many vm.parallel_class_loading tests fail with assert "missing Printezis mark"
jmasa
parents:
517
diff
changeset
|
8276 // false. These object may be floating garbage so may be |
0af8b0718fc9
6692899: CMS: many vm.parallel_class_loading tests fail with assert "missing Printezis mark"
jmasa
parents:
517
diff
changeset
|
8277 // seen here. If they are floating garbage their size |
0af8b0718fc9
6692899: CMS: many vm.parallel_class_loading tests fail with assert "missing Printezis mark"
jmasa
parents:
517
diff
changeset
|
8278 // should be attainable from their klass. Do not that |
0af8b0718fc9
6692899: CMS: many vm.parallel_class_loading tests fail with assert "missing Printezis mark"
jmasa
parents:
517
diff
changeset
|
8279 // is_conc_safe() is true for oop(addr). |
0 | 8280 // Ignore mark word because we are running concurrent with mutators |
8281 assert(oop(addr)->is_oop(true), "live block should be an oop"); | |
8282 // Verify that the bit map has no bits marked between | |
8283 // addr and purported end of this block. | |
8284 size = CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size()); | |
8285 assert(size >= 3, "Necessary for Printezis marks to work"); | |
8286 assert(!_bitMap->isMarked(addr+1), "Tautology for this control point"); | |
8287 DEBUG_ONLY(_bitMap->verifyNoOneBitsInRange(addr+2, addr+size);) | |
8288 } | |
8289 return size; | |
8290 } | |
8291 | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8292 void SweepClosure::do_post_free_or_garbage_chunk(FreeChunk* fc, |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8293 size_t chunkSize) { |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8294 // do_post_free_or_garbage_chunk() should only be called in the case |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8295 // of the adaptive free list allocator. |
0 | 8296 bool fcInFreeLists = fc->isFree(); |
8297 assert(_sp->adaptive_freelists(), "Should only be used in this case."); | |
8298 assert((HeapWord*)fc <= _limit, "sweep invariant"); | |
8299 if (CMSTestInFreeList && fcInFreeLists) { | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8300 assert(_sp->verifyChunkInFreeLists(fc), "free chunk is not in free lists"); |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8301 } |
0 | 8302 |
8303 if (CMSTraceSweeper) { | |
8304 gclog_or_tty->print_cr(" -- pick up another chunk at 0x%x (%d)", fc, chunkSize); | |
8305 } | |
8306 | |
8307 HeapWord* addr = (HeapWord*) fc; | |
8308 | |
8309 bool coalesce; | |
8310 size_t left = pointer_delta(addr, freeFinger()); | |
8311 size_t right = chunkSize; | |
8312 switch (FLSCoalescePolicy) { | |
8313 // numeric value forms a coalition aggressiveness metric | |
8314 case 0: { // never coalesce | |
8315 coalesce = false; | |
8316 break; | |
8317 } | |
8318 case 1: { // coalesce if left & right chunks on overpopulated lists | |
8319 coalesce = _sp->coalOverPopulated(left) && | |
8320 _sp->coalOverPopulated(right); | |
8321 break; | |
8322 } | |
8323 case 2: { // coalesce if left chunk on overpopulated list (default) | |
8324 coalesce = _sp->coalOverPopulated(left); | |
8325 break; | |
8326 } | |
8327 case 3: { // coalesce if left OR right chunk on overpopulated list | |
8328 coalesce = _sp->coalOverPopulated(left) || | |
8329 _sp->coalOverPopulated(right); | |
8330 break; | |
8331 } | |
8332 case 4: { // always coalesce | |
8333 coalesce = true; | |
8334 break; | |
8335 } | |
8336 default: | |
8337 ShouldNotReachHere(); | |
8338 } | |
8339 | |
8340 // Should the current free range be coalesced? | |
8341 // If the chunk is in a free range and either we decided to coalesce above | |
8342 // or the chunk is near the large block at the end of the heap | |
8343 // (isNearLargestChunk() returns true), then coalesce this chunk. | |
8344 bool doCoalesce = inFreeRange() && | |
8345 (coalesce || _g->isNearLargestChunk((HeapWord*)fc)); | |
8346 if (doCoalesce) { | |
8347 // Coalesce the current free range on the left with the new | |
8348 // chunk on the right. If either is on a free list, | |
8349 // it must be removed from the list and stashed in the closure. | |
8350 if (freeRangeInFreeLists()) { | |
8351 FreeChunk* ffc = (FreeChunk*)freeFinger(); | |
8352 assert(ffc->size() == pointer_delta(addr, freeFinger()), | |
8353 "Size of free range is inconsistent with chunk size."); | |
8354 if (CMSTestInFreeList) { | |
8355 assert(_sp->verifyChunkInFreeLists(ffc), | |
8356 "Chunk is not in free lists"); | |
8357 } | |
8358 _sp->coalDeath(ffc->size()); | |
8359 _sp->removeFreeChunkFromFreeLists(ffc); | |
8360 set_freeRangeInFreeLists(false); | |
8361 } | |
8362 if (fcInFreeLists) { | |
8363 _sp->coalDeath(chunkSize); | |
8364 assert(fc->size() == chunkSize, | |
8365 "The chunk has the wrong size or is not in the free lists"); | |
8366 _sp->removeFreeChunkFromFreeLists(fc); | |
8367 } | |
8368 set_lastFreeRangeCoalesced(true); | |
8369 } else { // not in a free range and/or should not coalesce | |
8370 // Return the current free range and start a new one. | |
8371 if (inFreeRange()) { | |
8372 // In a free range but cannot coalesce with the right hand chunk. | |
8373 // Put the current free range into the free lists. | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8374 flush_cur_free_chunk(freeFinger(), |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8375 pointer_delta(addr, freeFinger())); |
0 | 8376 } |
8377 // Set up for new free range. Pass along whether the right hand | |
8378 // chunk is in the free lists. | |
8379 initialize_free_range((HeapWord*)fc, fcInFreeLists); | |
8380 } | |
8381 } | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8382 |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8383 void SweepClosure::flush_cur_free_chunk(HeapWord* chunk, size_t size) { |
0 | 8384 assert(inFreeRange(), "Should only be called if currently in a free range."); |
8385 assert(size > 0, | |
8386 "A zero sized chunk cannot be added to the free lists."); | |
8387 if (!freeRangeInFreeLists()) { | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8388 if (CMSTestInFreeList) { |
0 | 8389 FreeChunk* fc = (FreeChunk*) chunk; |
8390 fc->setSize(size); | |
8391 assert(!_sp->verifyChunkInFreeLists(fc), | |
8392 "chunk should not be in free lists yet"); | |
8393 } | |
8394 if (CMSTraceSweeper) { | |
8395 gclog_or_tty->print_cr(" -- add free block 0x%x (%d) to free lists", | |
8396 chunk, size); | |
8397 } | |
8398 // A new free range is going to be starting. The current | |
8399 // free range has not been added to the free lists yet or | |
8400 // was removed so add it back. | |
8401 // If the current free range was coalesced, then the death | |
8402 // of the free range was recorded. Record a birth now. | |
8403 if (lastFreeRangeCoalesced()) { | |
8404 _sp->coalBirth(size); | |
8405 } | |
8406 _sp->addChunkAndRepairOffsetTable(chunk, size, | |
8407 lastFreeRangeCoalesced()); | |
8408 } | |
8409 set_inFreeRange(false); | |
8410 set_freeRangeInFreeLists(false); | |
8411 } | |
8412 | |
8413 // We take a break if we've been at this for a while, | |
8414 // so as to avoid monopolizing the locks involved. | |
8415 void SweepClosure::do_yield_work(HeapWord* addr) { | |
8416 // Return current free chunk being used for coalescing (if any) | |
8417 // to the appropriate freelist. After yielding, the next | |
8418 // free block encountered will start a coalescing range of | |
8419 // free blocks. If the next free block is adjacent to the | |
8420 // chunk just flushed, they will need to wait for the next | |
8421 // sweep to be coalesced. | |
8422 if (inFreeRange()) { | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8423 flush_cur_free_chunk(freeFinger(), pointer_delta(addr, freeFinger())); |
0 | 8424 } |
8425 | |
8426 // First give up the locks, then yield, then re-lock. | |
8427 // We should probably use a constructor/destructor idiom to | |
8428 // do this unlock/lock or modify the MutexUnlocker class to | |
8429 // serve our purpose. XXX | |
8430 assert_lock_strong(_bitMap->lock()); | |
8431 assert_lock_strong(_freelistLock); | |
8432 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
8433 "CMS thread should hold CMS token"); | |
8434 _bitMap->lock()->unlock(); | |
8435 _freelistLock->unlock(); | |
8436 ConcurrentMarkSweepThread::desynchronize(true); | |
8437 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
8438 _collector->stopTimer(); | |
8439 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
8440 if (PrintCMSStatistics != 0) { | |
8441 _collector->incrementYields(); | |
8442 } | |
8443 _collector->icms_wait(); | |
8444 | |
8445 // See the comment in coordinator_yield() | |
8446 for (unsigned i = 0; i < CMSYieldSleepCount && | |
8447 ConcurrentMarkSweepThread::should_yield() && | |
8448 !CMSCollector::foregroundGCIsActive(); ++i) { | |
8449 os::sleep(Thread::current(), 1, false); | |
8450 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
8451 } | |
8452 | |
8453 ConcurrentMarkSweepThread::synchronize(true); | |
8454 _freelistLock->lock(); | |
8455 _bitMap->lock()->lock_without_safepoint_check(); | |
8456 _collector->startTimer(); | |
8457 } | |
8458 | |
8459 #ifndef PRODUCT | |
8460 // This is actually very useful in a product build if it can | |
8461 // be called from the debugger. Compile it into the product | |
8462 // as needed. | |
8463 bool debug_verifyChunkInFreeLists(FreeChunk* fc) { | |
8464 return debug_cms_space->verifyChunkInFreeLists(fc); | |
8465 } | |
8466 | |
8467 void SweepClosure::record_free_block_coalesced(FreeChunk* fc) const { | |
8468 if (CMSTraceSweeper) { | |
8469 gclog_or_tty->print("Sweep:coal_free_blk 0x%x (%d)\n", fc, fc->size()); | |
8470 } | |
8471 } | |
8472 #endif | |
8473 | |
8474 // CMSIsAliveClosure | |
8475 bool CMSIsAliveClosure::do_object_b(oop obj) { | |
8476 HeapWord* addr = (HeapWord*)obj; | |
8477 return addr != NULL && | |
8478 (!_span.contains(addr) || _bit_map->isMarked(addr)); | |
8479 } | |
8480 | |
935 | 8481 CMSKeepAliveClosure::CMSKeepAliveClosure( CMSCollector* collector, |
8482 MemRegion span, | |
8483 CMSBitMap* bit_map, CMSMarkStack* mark_stack, | |
8484 CMSMarkStack* revisit_stack, bool cpc): | |
8485 KlassRememberingOopClosure(collector, NULL, revisit_stack), | |
8486 _span(span), | |
8487 _bit_map(bit_map), | |
8488 _mark_stack(mark_stack), | |
8489 _concurrent_precleaning(cpc) { | |
8490 assert(!_span.is_empty(), "Empty span could spell trouble"); | |
8491 } | |
8492 | |
8493 | |
0 | 8494 // CMSKeepAliveClosure: the serial version |
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8495 void CMSKeepAliveClosure::do_oop(oop obj) { |
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8496 HeapWord* addr = (HeapWord*)obj; |
0 | 8497 if (_span.contains(addr) && |
8498 !_bit_map->isMarked(addr)) { | |
8499 _bit_map->mark(addr); | |
8500 bool simulate_overflow = false; | |
8501 NOT_PRODUCT( | |
8502 if (CMSMarkStackOverflowALot && | |
8503 _collector->simulate_overflow()) { | |
8504 // simulate a stack overflow | |
8505 simulate_overflow = true; | |
8506 } | |
8507 ) | |
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8508 if (simulate_overflow || !_mark_stack->push(obj)) { |
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8509 if (_concurrent_precleaning) { |
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8510 // We dirty the overflown object and let the remark |
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8511 // phase deal with it. |
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8512 assert(_collector->overflow_list_is_empty(), "Error"); |
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8513 // In the case of object arrays, we need to dirty all of |
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8514 // the cards that the object spans. No locking or atomics |
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8515 // are needed since no one else can be mutating the mod union |
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8516 // table. |
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8517 if (obj->is_objArray()) { |
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8518 size_t sz = obj->size(); |
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8519 HeapWord* end_card_addr = |
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8520 (HeapWord*)round_to((intptr_t)(addr+sz), CardTableModRefBS::card_size); |
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8521 MemRegion redirty_range = MemRegion(addr, end_card_addr); |
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8522 assert(!redirty_range.is_empty(), "Arithmetical tautology"); |
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8523 _collector->_modUnionTable.mark_range(redirty_range); |
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8524 } else { |
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8525 _collector->_modUnionTable.mark(addr); |
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8526 } |
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8527 _collector->_ser_kac_preclean_ovflw++; |
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8528 } else { |
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8529 _collector->push_on_overflow_list(obj); |
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8530 _collector->_ser_kac_ovflw++; |
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8531 } |
0 | 8532 } |
8533 } | |
8534 } | |
8535 | |
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8536 void CMSKeepAliveClosure::do_oop(oop* p) { CMSKeepAliveClosure::do_oop_work(p); } |
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8537 void CMSKeepAliveClosure::do_oop(narrowOop* p) { CMSKeepAliveClosure::do_oop_work(p); } |
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8538 |
0 | 8539 // CMSParKeepAliveClosure: a parallel version of the above. |
8540 // The work queues are private to each closure (thread), | |
8541 // but (may be) available for stealing by other threads. | |
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8542 void CMSParKeepAliveClosure::do_oop(oop obj) { |
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8543 HeapWord* addr = (HeapWord*)obj; |
0 | 8544 if (_span.contains(addr) && |
8545 !_bit_map->isMarked(addr)) { | |
8546 // In general, during recursive tracing, several threads | |
8547 // may be concurrently getting here; the first one to | |
8548 // "tag" it, claims it. | |
8549 if (_bit_map->par_mark(addr)) { | |
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8550 bool res = _work_queue->push(obj); |
0 | 8551 assert(res, "Low water mark should be much less than capacity"); |
8552 // Do a recursive trim in the hope that this will keep | |
8553 // stack usage lower, but leave some oops for potential stealers | |
8554 trim_queue(_low_water_mark); | |
8555 } // Else, another thread got there first | |
8556 } | |
8557 } | |
8558 | |
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8559 void CMSParKeepAliveClosure::do_oop(oop* p) { CMSParKeepAliveClosure::do_oop_work(p); } |
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8560 void CMSParKeepAliveClosure::do_oop(narrowOop* p) { CMSParKeepAliveClosure::do_oop_work(p); } |
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8561 |
0 | 8562 void CMSParKeepAliveClosure::trim_queue(uint max) { |
8563 while (_work_queue->size() > max) { | |
8564 oop new_oop; | |
8565 if (_work_queue->pop_local(new_oop)) { | |
8566 assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop"); | |
8567 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
8568 "no white objects on this stack!"); | |
8569 assert(_span.contains((HeapWord*)new_oop), "Out of bounds oop"); | |
8570 // iterate over the oops in this oop, marking and pushing | |
8571 // the ones in CMS heap (i.e. in _span). | |
8572 new_oop->oop_iterate(&_mark_and_push); | |
8573 } | |
8574 } | |
8575 } | |
8576 | |
935 | 8577 CMSInnerParMarkAndPushClosure::CMSInnerParMarkAndPushClosure( |
8578 CMSCollector* collector, | |
8579 MemRegion span, CMSBitMap* bit_map, | |
8580 CMSMarkStack* revisit_stack, | |
8581 OopTaskQueue* work_queue): | |
8582 Par_KlassRememberingOopClosure(collector, NULL, revisit_stack), | |
8583 _span(span), | |
8584 _bit_map(bit_map), | |
8585 _work_queue(work_queue) { } | |
8586 | |
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8587 void CMSInnerParMarkAndPushClosure::do_oop(oop obj) { |
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8588 HeapWord* addr = (HeapWord*)obj; |
0 | 8589 if (_span.contains(addr) && |
8590 !_bit_map->isMarked(addr)) { | |
8591 if (_bit_map->par_mark(addr)) { | |
8592 bool simulate_overflow = false; | |
8593 NOT_PRODUCT( | |
8594 if (CMSMarkStackOverflowALot && | |
8595 _collector->par_simulate_overflow()) { | |
8596 // simulate a stack overflow | |
8597 simulate_overflow = true; | |
8598 } | |
8599 ) | |
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8600 if (simulate_overflow || !_work_queue->push(obj)) { |
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8601 _collector->par_push_on_overflow_list(obj); |
0 | 8602 _collector->_par_kac_ovflw++; |
8603 } | |
8604 } // Else another thread got there already | |
8605 } | |
8606 } | |
8607 | |
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8608 void CMSInnerParMarkAndPushClosure::do_oop(oop* p) { CMSInnerParMarkAndPushClosure::do_oop_work(p); } |
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8609 void CMSInnerParMarkAndPushClosure::do_oop(narrowOop* p) { CMSInnerParMarkAndPushClosure::do_oop_work(p); } |
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8610 |
0 | 8611 ////////////////////////////////////////////////////////////////// |
8612 // CMSExpansionCause ///////////////////////////// | |
8613 ////////////////////////////////////////////////////////////////// | |
8614 const char* CMSExpansionCause::to_string(CMSExpansionCause::Cause cause) { | |
8615 switch (cause) { | |
8616 case _no_expansion: | |
8617 return "No expansion"; | |
8618 case _satisfy_free_ratio: | |
8619 return "Free ratio"; | |
8620 case _satisfy_promotion: | |
8621 return "Satisfy promotion"; | |
8622 case _satisfy_allocation: | |
8623 return "allocation"; | |
8624 case _allocate_par_lab: | |
8625 return "Par LAB"; | |
8626 case _allocate_par_spooling_space: | |
8627 return "Par Spooling Space"; | |
8628 case _adaptive_size_policy: | |
8629 return "Ergonomics"; | |
8630 default: | |
8631 return "unknown"; | |
8632 } | |
8633 } | |
8634 | |
8635 void CMSDrainMarkingStackClosure::do_void() { | |
8636 // the max number to take from overflow list at a time | |
8637 const size_t num = _mark_stack->capacity()/4; | |
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8638 assert(!_concurrent_precleaning || _collector->overflow_list_is_empty(), |
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8639 "Overflow list should be NULL during concurrent phases"); |
0 | 8640 while (!_mark_stack->isEmpty() || |
8641 // if stack is empty, check the overflow list | |
8642 _collector->take_from_overflow_list(num, _mark_stack)) { | |
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8643 oop obj = _mark_stack->pop(); |
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8644 HeapWord* addr = (HeapWord*)obj; |
0 | 8645 assert(_span.contains(addr), "Should be within span"); |
8646 assert(_bit_map->isMarked(addr), "Should be marked"); | |
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8647 assert(obj->is_oop(), "Should be an oop"); |
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8648 obj->oop_iterate(_keep_alive); |
0 | 8649 } |
8650 } | |
8651 | |
8652 void CMSParDrainMarkingStackClosure::do_void() { | |
8653 // drain queue | |
8654 trim_queue(0); | |
8655 } | |
8656 | |
8657 // Trim our work_queue so its length is below max at return | |
8658 void CMSParDrainMarkingStackClosure::trim_queue(uint max) { | |
8659 while (_work_queue->size() > max) { | |
8660 oop new_oop; | |
8661 if (_work_queue->pop_local(new_oop)) { | |
8662 assert(new_oop->is_oop(), "Expected an oop"); | |
8663 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
8664 "no white objects on this stack!"); | |
8665 assert(_span.contains((HeapWord*)new_oop), "Out of bounds oop"); | |
8666 // iterate over the oops in this oop, marking and pushing | |
8667 // the ones in CMS heap (i.e. in _span). | |
8668 new_oop->oop_iterate(&_mark_and_push); | |
8669 } | |
8670 } | |
8671 } | |
8672 | |
8673 //////////////////////////////////////////////////////////////////// | |
8674 // Support for Marking Stack Overflow list handling and related code | |
8675 //////////////////////////////////////////////////////////////////// | |
8676 // Much of the following code is similar in shape and spirit to the | |
8677 // code used in ParNewGC. We should try and share that code | |
8678 // as much as possible in the future. | |
8679 | |
8680 #ifndef PRODUCT | |
8681 // Debugging support for CMSStackOverflowALot | |
8682 | |
8683 // It's OK to call this multi-threaded; the worst thing | |
8684 // that can happen is that we'll get a bunch of closely | |
8685 // spaced simulated oveflows, but that's OK, in fact | |
8686 // probably good as it would exercise the overflow code | |
8687 // under contention. | |
8688 bool CMSCollector::simulate_overflow() { | |
8689 if (_overflow_counter-- <= 0) { // just being defensive | |
8690 _overflow_counter = CMSMarkStackOverflowInterval; | |
8691 return true; | |
8692 } else { | |
8693 return false; | |
8694 } | |
8695 } | |
8696 | |
8697 bool CMSCollector::par_simulate_overflow() { | |
8698 return simulate_overflow(); | |
8699 } | |
8700 #endif | |
8701 | |
8702 // Single-threaded | |
8703 bool CMSCollector::take_from_overflow_list(size_t num, CMSMarkStack* stack) { | |
8704 assert(stack->isEmpty(), "Expected precondition"); | |
8705 assert(stack->capacity() > num, "Shouldn't bite more than can chew"); | |
8706 size_t i = num; | |
8707 oop cur = _overflow_list; | |
8708 const markOop proto = markOopDesc::prototype(); | |
534 | 8709 NOT_PRODUCT(ssize_t n = 0;) |
0 | 8710 for (oop next; i > 0 && cur != NULL; cur = next, i--) { |
8711 next = oop(cur->mark()); | |
8712 cur->set_mark(proto); // until proven otherwise | |
8713 assert(cur->is_oop(), "Should be an oop"); | |
8714 bool res = stack->push(cur); | |
8715 assert(res, "Bit off more than can chew?"); | |
8716 NOT_PRODUCT(n++;) | |
8717 } | |
8718 _overflow_list = cur; | |
8719 #ifndef PRODUCT | |
8720 assert(_num_par_pushes >= n, "Too many pops?"); | |
8721 _num_par_pushes -=n; | |
8722 #endif | |
8723 return !stack->isEmpty(); | |
8724 } | |
8725 | |
534 | 8726 #define BUSY (oop(0x1aff1aff)) |
8727 // (MT-safe) Get a prefix of at most "num" from the list. | |
8728 // The overflow list is chained through the mark word of | |
8729 // each object in the list. We fetch the entire list, | |
8730 // break off a prefix of the right size and return the | |
8731 // remainder. If other threads try to take objects from | |
8732 // the overflow list at that time, they will wait for | |
8733 // some time to see if data becomes available. If (and | |
8734 // only if) another thread places one or more object(s) | |
8735 // on the global list before we have returned the suffix | |
8736 // to the global list, we will walk down our local list | |
8737 // to find its end and append the global list to | |
8738 // our suffix before returning it. This suffix walk can | |
8739 // prove to be expensive (quadratic in the amount of traffic) | |
8740 // when there are many objects in the overflow list and | |
8741 // there is much producer-consumer contention on the list. | |
8742 // *NOTE*: The overflow list manipulation code here and | |
8743 // in ParNewGeneration:: are very similar in shape, | |
8744 // except that in the ParNew case we use the old (from/eden) | |
8745 // copy of the object to thread the list via its klass word. | |
8746 // Because of the common code, if you make any changes in | |
8747 // the code below, please check the ParNew version to see if | |
8748 // similar changes might be needed. | |
8749 // CR 6797058 has been filed to consolidate the common code. | |
0 | 8750 bool CMSCollector::par_take_from_overflow_list(size_t num, |
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8751 OopTaskQueue* work_q, |
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8752 int no_of_gc_threads) { |
534 | 8753 assert(work_q->size() == 0, "First empty local work queue"); |
0 | 8754 assert(num < work_q->max_elems(), "Can't bite more than we can chew"); |
8755 if (_overflow_list == NULL) { | |
8756 return false; | |
8757 } | |
8758 // Grab the entire list; we'll put back a suffix | |
534 | 8759 oop prefix = (oop)Atomic::xchg_ptr(BUSY, &_overflow_list); |
8760 Thread* tid = Thread::current(); | |
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8761 // Before "no_of_gc_threads" was introduced CMSOverflowSpinCount was |
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8762 // set to ParallelGCThreads. |
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8763 size_t CMSOverflowSpinCount = (size_t) no_of_gc_threads; // was ParallelGCThreads; |
534 | 8764 size_t sleep_time_millis = MAX2((size_t)1, num/100); |
8765 // If the list is busy, we spin for a short while, | |
8766 // sleeping between attempts to get the list. | |
8767 for (size_t spin = 0; prefix == BUSY && spin < CMSOverflowSpinCount; spin++) { | |
8768 os::sleep(tid, sleep_time_millis, false); | |
8769 if (_overflow_list == NULL) { | |
8770 // Nothing left to take | |
8771 return false; | |
8772 } else if (_overflow_list != BUSY) { | |
8773 // Try and grab the prefix | |
8774 prefix = (oop)Atomic::xchg_ptr(BUSY, &_overflow_list); | |
8775 } | |
8776 } | |
8777 // If the list was found to be empty, or we spun long | |
8778 // enough, we give up and return empty-handed. If we leave | |
8779 // the list in the BUSY state below, it must be the case that | |
8780 // some other thread holds the overflow list and will set it | |
8781 // to a non-BUSY state in the future. | |
8782 if (prefix == NULL || prefix == BUSY) { | |
8783 // Nothing to take or waited long enough | |
8784 if (prefix == NULL) { | |
8785 // Write back the NULL in case we overwrote it with BUSY above | |
8786 // and it is still the same value. | |
8787 (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY); | |
8788 } | |
8789 return false; | |
8790 } | |
8791 assert(prefix != NULL && prefix != BUSY, "Error"); | |
0 | 8792 size_t i = num; |
8793 oop cur = prefix; | |
534 | 8794 // Walk down the first "num" objects, unless we reach the end. |
0 | 8795 for (; i > 1 && cur->mark() != NULL; cur = oop(cur->mark()), i--); |
534 | 8796 if (cur->mark() == NULL) { |
8797 // We have "num" or fewer elements in the list, so there | |
8798 // is nothing to return to the global list. | |
8799 // Write back the NULL in lieu of the BUSY we wrote | |
8800 // above, if it is still the same value. | |
8801 if (_overflow_list == BUSY) { | |
8802 (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY); | |
8803 } | |
8804 } else { | |
8805 // Chop off the suffix and rerturn it to the global list. | |
8806 assert(cur->mark() != BUSY, "Error"); | |
0 | 8807 oop suffix_head = cur->mark(); // suffix will be put back on global list |
8808 cur->set_mark(NULL); // break off suffix | |
534 | 8809 // It's possible that the list is still in the empty(busy) state |
8810 // we left it in a short while ago; in that case we may be | |
8811 // able to place back the suffix without incurring the cost | |
8812 // of a walk down the list. | |
0 | 8813 oop observed_overflow_list = _overflow_list; |
534 | 8814 oop cur_overflow_list = observed_overflow_list; |
8815 bool attached = false; | |
8816 while (observed_overflow_list == BUSY || observed_overflow_list == NULL) { | |
0 | 8817 observed_overflow_list = |
534 | 8818 (oop) Atomic::cmpxchg_ptr(suffix_head, &_overflow_list, cur_overflow_list); |
8819 if (cur_overflow_list == observed_overflow_list) { | |
8820 attached = true; | |
8821 break; | |
8822 } else cur_overflow_list = observed_overflow_list; | |
8823 } | |
8824 if (!attached) { | |
8825 // Too bad, someone else sneaked in (at least) an element; we'll need | |
8826 // to do a splice. Find tail of suffix so we can prepend suffix to global | |
8827 // list. | |
8828 for (cur = suffix_head; cur->mark() != NULL; cur = (oop)(cur->mark())); | |
8829 oop suffix_tail = cur; | |
8830 assert(suffix_tail != NULL && suffix_tail->mark() == NULL, | |
8831 "Tautology"); | |
8832 observed_overflow_list = _overflow_list; | |
8833 do { | |
8834 cur_overflow_list = observed_overflow_list; | |
8835 if (cur_overflow_list != BUSY) { | |
8836 // Do the splice ... | |
8837 suffix_tail->set_mark(markOop(cur_overflow_list)); | |
8838 } else { // cur_overflow_list == BUSY | |
8839 suffix_tail->set_mark(NULL); | |
8840 } | |
8841 // ... and try to place spliced list back on overflow_list ... | |
8842 observed_overflow_list = | |
8843 (oop) Atomic::cmpxchg_ptr(suffix_head, &_overflow_list, cur_overflow_list); | |
8844 } while (cur_overflow_list != observed_overflow_list); | |
8845 // ... until we have succeeded in doing so. | |
8846 } | |
0 | 8847 } |
8848 | |
8849 // Push the prefix elements on work_q | |
8850 assert(prefix != NULL, "control point invariant"); | |
8851 const markOop proto = markOopDesc::prototype(); | |
8852 oop next; | |
534 | 8853 NOT_PRODUCT(ssize_t n = 0;) |
0 | 8854 for (cur = prefix; cur != NULL; cur = next) { |
8855 next = oop(cur->mark()); | |
8856 cur->set_mark(proto); // until proven otherwise | |
8857 assert(cur->is_oop(), "Should be an oop"); | |
8858 bool res = work_q->push(cur); | |
8859 assert(res, "Bit off more than we can chew?"); | |
8860 NOT_PRODUCT(n++;) | |
8861 } | |
8862 #ifndef PRODUCT | |
8863 assert(_num_par_pushes >= n, "Too many pops?"); | |
8864 Atomic::add_ptr(-(intptr_t)n, &_num_par_pushes); | |
8865 #endif | |
8866 return true; | |
8867 } | |
8868 | |
8869 // Single-threaded | |
8870 void CMSCollector::push_on_overflow_list(oop p) { | |
8871 NOT_PRODUCT(_num_par_pushes++;) | |
8872 assert(p->is_oop(), "Not an oop"); | |
8873 preserve_mark_if_necessary(p); | |
8874 p->set_mark((markOop)_overflow_list); | |
8875 _overflow_list = p; | |
8876 } | |
8877 | |
8878 // Multi-threaded; use CAS to prepend to overflow list | |
8879 void CMSCollector::par_push_on_overflow_list(oop p) { | |
8880 NOT_PRODUCT(Atomic::inc_ptr(&_num_par_pushes);) | |
8881 assert(p->is_oop(), "Not an oop"); | |
8882 par_preserve_mark_if_necessary(p); | |
8883 oop observed_overflow_list = _overflow_list; | |
8884 oop cur_overflow_list; | |
8885 do { | |
8886 cur_overflow_list = observed_overflow_list; | |
534 | 8887 if (cur_overflow_list != BUSY) { |
8888 p->set_mark(markOop(cur_overflow_list)); | |
8889 } else { | |
8890 p->set_mark(NULL); | |
8891 } | |
0 | 8892 observed_overflow_list = |
8893 (oop) Atomic::cmpxchg_ptr(p, &_overflow_list, cur_overflow_list); | |
8894 } while (cur_overflow_list != observed_overflow_list); | |
8895 } | |
534 | 8896 #undef BUSY |
0 | 8897 |
8898 // Single threaded | |
8899 // General Note on GrowableArray: pushes may silently fail | |
8900 // because we are (temporarily) out of C-heap for expanding | |
8901 // the stack. The problem is quite ubiquitous and affects | |
8902 // a lot of code in the JVM. The prudent thing for GrowableArray | |
8903 // to do (for now) is to exit with an error. However, that may | |
8904 // be too draconian in some cases because the caller may be | |
534 | 8905 // able to recover without much harm. For such cases, we |
0 | 8906 // should probably introduce a "soft_push" method which returns |
8907 // an indication of success or failure with the assumption that | |
8908 // the caller may be able to recover from a failure; code in | |
8909 // the VM can then be changed, incrementally, to deal with such | |
8910 // failures where possible, thus, incrementally hardening the VM | |
8911 // in such low resource situations. | |
8912 void CMSCollector::preserve_mark_work(oop p, markOop m) { | |
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8913 _preserved_oop_stack.push(p); |
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8914 _preserved_mark_stack.push(m); |
0 | 8915 assert(m == p->mark(), "Mark word changed"); |
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8916 assert(_preserved_oop_stack.size() == _preserved_mark_stack.size(), |
0 | 8917 "bijection"); |
8918 } | |
8919 | |
8920 // Single threaded | |
8921 void CMSCollector::preserve_mark_if_necessary(oop p) { | |
8922 markOop m = p->mark(); | |
8923 if (m->must_be_preserved(p)) { | |
8924 preserve_mark_work(p, m); | |
8925 } | |
8926 } | |
8927 | |
8928 void CMSCollector::par_preserve_mark_if_necessary(oop p) { | |
8929 markOop m = p->mark(); | |
8930 if (m->must_be_preserved(p)) { | |
8931 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); | |
8932 // Even though we read the mark word without holding | |
8933 // the lock, we are assured that it will not change | |
8934 // because we "own" this oop, so no other thread can | |
8935 // be trying to push it on the overflow list; see | |
8936 // the assertion in preserve_mark_work() that checks | |
8937 // that m == p->mark(). | |
8938 preserve_mark_work(p, m); | |
8939 } | |
8940 } | |
8941 | |
8942 // We should be able to do this multi-threaded, | |
8943 // a chunk of stack being a task (this is | |
8944 // correct because each oop only ever appears | |
8945 // once in the overflow list. However, it's | |
8946 // not very easy to completely overlap this with | |
8947 // other operations, so will generally not be done | |
8948 // until all work's been completed. Because we | |
8949 // expect the preserved oop stack (set) to be small, | |
8950 // it's probably fine to do this single-threaded. | |
8951 // We can explore cleverer concurrent/overlapped/parallel | |
8952 // processing of preserved marks if we feel the | |
8953 // need for this in the future. Stack overflow should | |
8954 // be so rare in practice and, when it happens, its | |
8955 // effect on performance so great that this will | |
8956 // likely just be in the noise anyway. | |
8957 void CMSCollector::restore_preserved_marks_if_any() { | |
8958 assert(SafepointSynchronize::is_at_safepoint(), | |
8959 "world should be stopped"); | |
8960 assert(Thread::current()->is_ConcurrentGC_thread() || | |
8961 Thread::current()->is_VM_thread(), | |
8962 "should be single-threaded"); | |
1836
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8963 assert(_preserved_oop_stack.size() == _preserved_mark_stack.size(), |
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8964 "bijection"); |
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8965 |
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8966 while (!_preserved_oop_stack.is_empty()) { |
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8967 oop p = _preserved_oop_stack.pop(); |
0 | 8968 assert(p->is_oop(), "Should be an oop"); |
8969 assert(_span.contains(p), "oop should be in _span"); | |
8970 assert(p->mark() == markOopDesc::prototype(), | |
8971 "Set when taken from overflow list"); | |
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8972 markOop m = _preserved_mark_stack.pop(); |
0 | 8973 p->set_mark(m); |
8974 } | |
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8975 assert(_preserved_mark_stack.is_empty() && _preserved_oop_stack.is_empty(), |
0 | 8976 "stacks were cleared above"); |
8977 } | |
8978 | |
8979 #ifndef PRODUCT | |
8980 bool CMSCollector::no_preserved_marks() const { | |
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8981 return _preserved_mark_stack.is_empty() && _preserved_oop_stack.is_empty(); |
0 | 8982 } |
8983 #endif | |
8984 | |
8985 CMSAdaptiveSizePolicy* ASConcurrentMarkSweepGeneration::cms_size_policy() const | |
8986 { | |
8987 GenCollectedHeap* gch = (GenCollectedHeap*) GenCollectedHeap::heap(); | |
8988 CMSAdaptiveSizePolicy* size_policy = | |
8989 (CMSAdaptiveSizePolicy*) gch->gen_policy()->size_policy(); | |
8990 assert(size_policy->is_gc_cms_adaptive_size_policy(), | |
8991 "Wrong type for size policy"); | |
8992 return size_policy; | |
8993 } | |
8994 | |
8995 void ASConcurrentMarkSweepGeneration::resize(size_t cur_promo_size, | |
8996 size_t desired_promo_size) { | |
8997 if (cur_promo_size < desired_promo_size) { | |
8998 size_t expand_bytes = desired_promo_size - cur_promo_size; | |
8999 if (PrintAdaptiveSizePolicy && Verbose) { | |
9000 gclog_or_tty->print_cr(" ASConcurrentMarkSweepGeneration::resize " | |
9001 "Expanding tenured generation by " SIZE_FORMAT " (bytes)", | |
9002 expand_bytes); | |
9003 } | |
9004 expand(expand_bytes, | |
9005 MinHeapDeltaBytes, | |
9006 CMSExpansionCause::_adaptive_size_policy); | |
9007 } else if (desired_promo_size < cur_promo_size) { | |
9008 size_t shrink_bytes = cur_promo_size - desired_promo_size; | |
9009 if (PrintAdaptiveSizePolicy && Verbose) { | |
9010 gclog_or_tty->print_cr(" ASConcurrentMarkSweepGeneration::resize " | |
9011 "Shrinking tenured generation by " SIZE_FORMAT " (bytes)", | |
9012 shrink_bytes); | |
9013 } | |
9014 shrink(shrink_bytes); | |
9015 } | |
9016 } | |
9017 | |
9018 CMSGCAdaptivePolicyCounters* ASConcurrentMarkSweepGeneration::gc_adaptive_policy_counters() { | |
9019 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
9020 CMSGCAdaptivePolicyCounters* counters = | |
9021 (CMSGCAdaptivePolicyCounters*) gch->collector_policy()->counters(); | |
9022 assert(counters->kind() == GCPolicyCounters::CMSGCAdaptivePolicyCountersKind, | |
9023 "Wrong kind of counters"); | |
9024 return counters; | |
9025 } | |
9026 | |
9027 | |
9028 void ASConcurrentMarkSweepGeneration::update_counters() { | |
9029 if (UsePerfData) { | |
9030 _space_counters->update_all(); | |
9031 _gen_counters->update_all(); | |
9032 CMSGCAdaptivePolicyCounters* counters = gc_adaptive_policy_counters(); | |
9033 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
9034 CMSGCStats* gc_stats_l = (CMSGCStats*) gc_stats(); | |
9035 assert(gc_stats_l->kind() == GCStats::CMSGCStatsKind, | |
9036 "Wrong gc statistics type"); | |
9037 counters->update_counters(gc_stats_l); | |
9038 } | |
9039 } | |
9040 | |
9041 void ASConcurrentMarkSweepGeneration::update_counters(size_t used) { | |
9042 if (UsePerfData) { | |
9043 _space_counters->update_used(used); | |
9044 _space_counters->update_capacity(); | |
9045 _gen_counters->update_all(); | |
9046 | |
9047 CMSGCAdaptivePolicyCounters* counters = gc_adaptive_policy_counters(); | |
9048 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
9049 CMSGCStats* gc_stats_l = (CMSGCStats*) gc_stats(); | |
9050 assert(gc_stats_l->kind() == GCStats::CMSGCStatsKind, | |
9051 "Wrong gc statistics type"); | |
9052 counters->update_counters(gc_stats_l); | |
9053 } | |
9054 } | |
9055 | |
9056 // The desired expansion delta is computed so that: | |
9057 // . desired free percentage or greater is used | |
9058 void ASConcurrentMarkSweepGeneration::compute_new_size() { | |
9059 assert_locked_or_safepoint(Heap_lock); | |
9060 | |
9061 GenCollectedHeap* gch = (GenCollectedHeap*) GenCollectedHeap::heap(); | |
9062 | |
9063 // If incremental collection failed, we just want to expand | |
9064 // to the limit. | |
9065 if (incremental_collection_failed()) { | |
9066 clear_incremental_collection_failed(); | |
9067 grow_to_reserved(); | |
9068 return; | |
9069 } | |
9070 | |
9071 assert(UseAdaptiveSizePolicy, "Should be using adaptive sizing"); | |
9072 | |
9073 assert(gch->kind() == CollectedHeap::GenCollectedHeap, | |
9074 "Wrong type of heap"); | |
9075 int prev_level = level() - 1; | |
9076 assert(prev_level >= 0, "The cms generation is the lowest generation"); | |
9077 Generation* prev_gen = gch->get_gen(prev_level); | |
9078 assert(prev_gen->kind() == Generation::ASParNew, | |
9079 "Wrong type of young generation"); | |
9080 ParNewGeneration* younger_gen = (ParNewGeneration*) prev_gen; | |
9081 size_t cur_eden = younger_gen->eden()->capacity(); | |
9082 CMSAdaptiveSizePolicy* size_policy = cms_size_policy(); | |
9083 size_t cur_promo = free(); | |
9084 size_policy->compute_tenured_generation_free_space(cur_promo, | |
9085 max_available(), | |
9086 cur_eden); | |
9087 resize(cur_promo, size_policy->promo_size()); | |
9088 | |
9089 // Record the new size of the space in the cms generation | |
9090 // that is available for promotions. This is temporary. | |
9091 // It should be the desired promo size. | |
9092 size_policy->avg_cms_promo()->sample(free()); | |
9093 size_policy->avg_old_live()->sample(used()); | |
9094 | |
9095 if (UsePerfData) { | |
9096 CMSGCAdaptivePolicyCounters* counters = gc_adaptive_policy_counters(); | |
9097 counters->update_cms_capacity_counter(capacity()); | |
9098 } | |
9099 } | |
9100 | |
9101 void ASConcurrentMarkSweepGeneration::shrink_by(size_t desired_bytes) { | |
9102 assert_locked_or_safepoint(Heap_lock); | |
9103 assert_lock_strong(freelistLock()); | |
9104 HeapWord* old_end = _cmsSpace->end(); | |
9105 HeapWord* unallocated_start = _cmsSpace->unallocated_block(); | |
9106 assert(old_end >= unallocated_start, "Miscalculation of unallocated_start"); | |
9107 FreeChunk* chunk_at_end = find_chunk_at_end(); | |
9108 if (chunk_at_end == NULL) { | |
9109 // No room to shrink | |
9110 if (PrintGCDetails && Verbose) { | |
9111 gclog_or_tty->print_cr("No room to shrink: old_end " | |
9112 PTR_FORMAT " unallocated_start " PTR_FORMAT | |
9113 " chunk_at_end " PTR_FORMAT, | |
9114 old_end, unallocated_start, chunk_at_end); | |
9115 } | |
9116 return; | |
9117 } else { | |
9118 | |
9119 // Find the chunk at the end of the space and determine | |
9120 // how much it can be shrunk. | |
9121 size_t shrinkable_size_in_bytes = chunk_at_end->size(); | |
9122 size_t aligned_shrinkable_size_in_bytes = | |
9123 align_size_down(shrinkable_size_in_bytes, os::vm_page_size()); | |
9124 assert(unallocated_start <= chunk_at_end->end(), | |
9125 "Inconsistent chunk at end of space"); | |
9126 size_t bytes = MIN2(desired_bytes, aligned_shrinkable_size_in_bytes); | |
9127 size_t word_size_before = heap_word_size(_virtual_space.committed_size()); | |
9128 | |
9129 // Shrink the underlying space | |
9130 _virtual_space.shrink_by(bytes); | |
9131 if (PrintGCDetails && Verbose) { | |
9132 gclog_or_tty->print_cr("ConcurrentMarkSweepGeneration::shrink_by:" | |
9133 " desired_bytes " SIZE_FORMAT | |
9134 " shrinkable_size_in_bytes " SIZE_FORMAT | |
9135 " aligned_shrinkable_size_in_bytes " SIZE_FORMAT | |
9136 " bytes " SIZE_FORMAT, | |
9137 desired_bytes, shrinkable_size_in_bytes, | |
9138 aligned_shrinkable_size_in_bytes, bytes); | |
9139 gclog_or_tty->print_cr(" old_end " SIZE_FORMAT | |
9140 " unallocated_start " SIZE_FORMAT, | |
9141 old_end, unallocated_start); | |
9142 } | |
9143 | |
9144 // If the space did shrink (shrinking is not guaranteed), | |
9145 // shrink the chunk at the end by the appropriate amount. | |
9146 if (((HeapWord*)_virtual_space.high()) < old_end) { | |
9147 size_t new_word_size = | |
9148 heap_word_size(_virtual_space.committed_size()); | |
9149 | |
9150 // Have to remove the chunk from the dictionary because it is changing | |
9151 // size and might be someplace elsewhere in the dictionary. | |
9152 | |
9153 // Get the chunk at end, shrink it, and put it | |
9154 // back. | |
9155 _cmsSpace->removeChunkFromDictionary(chunk_at_end); | |
9156 size_t word_size_change = word_size_before - new_word_size; | |
9157 size_t chunk_at_end_old_size = chunk_at_end->size(); | |
9158 assert(chunk_at_end_old_size >= word_size_change, | |
9159 "Shrink is too large"); | |
9160 chunk_at_end->setSize(chunk_at_end_old_size - | |
9161 word_size_change); | |
9162 _cmsSpace->freed((HeapWord*) chunk_at_end->end(), | |
9163 word_size_change); | |
9164 | |
9165 _cmsSpace->returnChunkToDictionary(chunk_at_end); | |
9166 | |
9167 MemRegion mr(_cmsSpace->bottom(), new_word_size); | |
9168 _bts->resize(new_word_size); // resize the block offset shared array | |
9169 Universe::heap()->barrier_set()->resize_covered_region(mr); | |
9170 _cmsSpace->assert_locked(); | |
9171 _cmsSpace->set_end((HeapWord*)_virtual_space.high()); | |
9172 | |
9173 NOT_PRODUCT(_cmsSpace->dictionary()->verify()); | |
9174 | |
9175 // update the space and generation capacity counters | |
9176 if (UsePerfData) { | |
9177 _space_counters->update_capacity(); | |
9178 _gen_counters->update_all(); | |
9179 } | |
9180 | |
9181 if (Verbose && PrintGCDetails) { | |
9182 size_t new_mem_size = _virtual_space.committed_size(); | |
9183 size_t old_mem_size = new_mem_size + bytes; | |
9184 gclog_or_tty->print_cr("Shrinking %s from %ldK by %ldK to %ldK", | |
9185 name(), old_mem_size/K, bytes/K, new_mem_size/K); | |
9186 } | |
9187 } | |
9188 | |
9189 assert(_cmsSpace->unallocated_block() <= _cmsSpace->end(), | |
9190 "Inconsistency at end of space"); | |
9191 assert(chunk_at_end->end() == _cmsSpace->end(), | |
9192 "Shrinking is inconsistent"); | |
9193 return; | |
9194 } | |
9195 } | |
9196 | |
9197 // Transfer some number of overflown objects to usual marking | |
9198 // stack. Return true if some objects were transferred. | |
9199 bool MarkRefsIntoAndScanClosure::take_from_overflow_list() { | |
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9200 size_t num = MIN2((size_t)(_mark_stack->capacity() - _mark_stack->length())/4, |
0 | 9201 (size_t)ParGCDesiredObjsFromOverflowList); |
9202 | |
9203 bool res = _collector->take_from_overflow_list(num, _mark_stack); | |
9204 assert(_collector->overflow_list_is_empty() || res, | |
9205 "If list is not empty, we should have taken something"); | |
9206 assert(!res || !_mark_stack->isEmpty(), | |
9207 "If we took something, it should now be on our stack"); | |
9208 return res; | |
9209 } | |
9210 | |
9211 size_t MarkDeadObjectsClosure::do_blk(HeapWord* addr) { | |
9212 size_t res = _sp->block_size_no_stall(addr, _collector); | |
9213 if (_sp->block_is_obj(addr)) { | |
9214 if (_live_bit_map->isMarked(addr)) { | |
9215 // It can't have been dead in a previous cycle | |
9216 guarantee(!_dead_bit_map->isMarked(addr), "No resurrection!"); | |
9217 } else { | |
9218 _dead_bit_map->mark(addr); // mark the dead object | |
9219 } | |
9220 } | |
2226
c5a923563727
6912621: iCMS: Error: assert(_markBitMap.isMarked(addr + 1),"Missing Printezis bit?")
ysr
parents:
2177
diff
changeset
|
9221 // Could be 0, if the block size could not be computed without stalling. |
0 | 9222 return res; |
9223 } | |
1703
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9224 |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9225 TraceCMSMemoryManagerStats::TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase): TraceMemoryManagerStats() { |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9226 |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9227 switch (phase) { |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9228 case CMSCollector::InitialMarking: |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9229 initialize(true /* fullGC */ , |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9230 true /* recordGCBeginTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9231 true /* recordPreGCUsage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9232 false /* recordPeakUsage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9233 false /* recordPostGCusage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9234 true /* recordAccumulatedGCTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9235 false /* recordGCEndTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9236 false /* countCollection */ ); |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9237 break; |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9238 |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9239 case CMSCollector::FinalMarking: |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9240 initialize(true /* fullGC */ , |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9241 false /* recordGCBeginTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9242 false /* recordPreGCUsage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9243 false /* recordPeakUsage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9244 false /* recordPostGCusage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9245 true /* recordAccumulatedGCTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9246 false /* recordGCEndTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9247 false /* countCollection */ ); |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9248 break; |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9249 |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9250 case CMSCollector::Sweeping: |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9251 initialize(true /* fullGC */ , |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9252 false /* recordGCBeginTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9253 false /* recordPreGCUsage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9254 true /* recordPeakUsage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9255 true /* recordPostGCusage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9256 false /* recordAccumulatedGCTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9257 true /* recordGCEndTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9258 true /* countCollection */ ); |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9259 break; |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9260 |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9261 default: |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9262 ShouldNotReachHere(); |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9263 } |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9264 } |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9265 |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9266 // when bailing out of cms in concurrent mode failure |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9267 TraceCMSMemoryManagerStats::TraceCMSMemoryManagerStats(): TraceMemoryManagerStats() { |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9268 initialize(true /* fullGC */ , |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9269 true /* recordGCBeginTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9270 true /* recordPreGCUsage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9271 true /* recordPeakUsage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9272 true /* recordPostGCusage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9273 true /* recordAccumulatedGCTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9274 true /* recordGCEndTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9275 true /* countCollection */ ); |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9276 } |