Mercurial > hg > truffle
annotate src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp @ 6796:b31471cdc53e
7200163: add CodeComments functionality to assember stubs
Summary: Pass the codeBuffer to the Stub constructor, and adapts the disassembler to print the comments.
Reviewed-by: jrose, kvn, twisti
Contributed-by: goetz.lindenmaier@sap.com
author | kvn |
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date | Mon, 24 Sep 2012 10:30:14 -0700 |
parents | da91efe96a93 |
children | 9646b7ff4d14 |
rev | line source |
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0 | 1 /* |
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2 * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved. |
0 | 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
4 * | |
5 * This code is free software; you can redistribute it and/or modify it | |
6 * under the terms of the GNU General Public License version 2 only, as | |
7 * published by the Free Software Foundation. | |
8 * | |
9 * This code is distributed in the hope that it will be useful, but WITHOUT | |
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
12 * version 2 for more details (a copy is included in the LICENSE file that | |
13 * accompanied this code). | |
14 * | |
15 * You should have received a copy of the GNU General Public License version | |
16 * 2 along with this work; if not, write to the Free Software Foundation, | |
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | |
18 * | |
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
0 | 22 * |
23 */ | |
24 | |
1972 | 25 #include "precompiled.hpp" |
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26 #include "classfile/classLoaderData.hpp" |
1972 | 27 #include "classfile/symbolTable.hpp" |
28 #include "classfile/systemDictionary.hpp" | |
29 #include "code/codeCache.hpp" | |
30 #include "gc_implementation/concurrentMarkSweep/cmsAdaptiveSizePolicy.hpp" | |
31 #include "gc_implementation/concurrentMarkSweep/cmsCollectorPolicy.hpp" | |
32 #include "gc_implementation/concurrentMarkSweep/cmsGCAdaptivePolicyCounters.hpp" | |
33 #include "gc_implementation/concurrentMarkSweep/cmsOopClosures.inline.hpp" | |
34 #include "gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.hpp" | |
35 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.inline.hpp" | |
36 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp" | |
37 #include "gc_implementation/concurrentMarkSweep/vmCMSOperations.hpp" | |
38 #include "gc_implementation/parNew/parNewGeneration.hpp" | |
39 #include "gc_implementation/shared/collectorCounters.hpp" | |
40 #include "gc_implementation/shared/isGCActiveMark.hpp" | |
41 #include "gc_interface/collectedHeap.inline.hpp" | |
42 #include "memory/cardTableRS.hpp" | |
43 #include "memory/collectorPolicy.hpp" | |
44 #include "memory/gcLocker.inline.hpp" | |
45 #include "memory/genCollectedHeap.hpp" | |
46 #include "memory/genMarkSweep.hpp" | |
47 #include "memory/genOopClosures.inline.hpp" | |
48 #include "memory/iterator.hpp" | |
49 #include "memory/referencePolicy.hpp" | |
50 #include "memory/resourceArea.hpp" | |
51 #include "oops/oop.inline.hpp" | |
52 #include "prims/jvmtiExport.hpp" | |
53 #include "runtime/globals_extension.hpp" | |
54 #include "runtime/handles.inline.hpp" | |
55 #include "runtime/java.hpp" | |
56 #include "runtime/vmThread.hpp" | |
57 #include "services/memoryService.hpp" | |
58 #include "services/runtimeService.hpp" | |
0 | 59 |
60 // statics | |
61 CMSCollector* ConcurrentMarkSweepGeneration::_collector = NULL; | |
62 bool CMSCollector::_full_gc_requested = false; | |
63 | |
64 ////////////////////////////////////////////////////////////////// | |
65 // In support of CMS/VM thread synchronization | |
66 ////////////////////////////////////////////////////////////////// | |
67 // We split use of the CGC_lock into 2 "levels". | |
68 // The low-level locking is of the usual CGC_lock monitor. We introduce | |
69 // a higher level "token" (hereafter "CMS token") built on top of the | |
70 // low level monitor (hereafter "CGC lock"). | |
71 // The token-passing protocol gives priority to the VM thread. The | |
72 // CMS-lock doesn't provide any fairness guarantees, but clients | |
73 // should ensure that it is only held for very short, bounded | |
74 // durations. | |
75 // | |
76 // When either of the CMS thread or the VM thread is involved in | |
77 // collection operations during which it does not want the other | |
78 // thread to interfere, it obtains the CMS token. | |
79 // | |
80 // If either thread tries to get the token while the other has | |
81 // it, that thread waits. However, if the VM thread and CMS thread | |
82 // both want the token, then the VM thread gets priority while the | |
83 // CMS thread waits. This ensures, for instance, that the "concurrent" | |
84 // phases of the CMS thread's work do not block out the VM thread | |
85 // for long periods of time as the CMS thread continues to hog | |
86 // the token. (See bug 4616232). | |
87 // | |
88 // The baton-passing functions are, however, controlled by the | |
89 // flags _foregroundGCShouldWait and _foregroundGCIsActive, | |
90 // and here the low-level CMS lock, not the high level token, | |
91 // ensures mutual exclusion. | |
92 // | |
93 // Two important conditions that we have to satisfy: | |
94 // 1. if a thread does a low-level wait on the CMS lock, then it | |
95 // relinquishes the CMS token if it were holding that token | |
96 // when it acquired the low-level CMS lock. | |
97 // 2. any low-level notifications on the low-level lock | |
98 // should only be sent when a thread has relinquished the token. | |
99 // | |
100 // In the absence of either property, we'd have potential deadlock. | |
101 // | |
102 // We protect each of the CMS (concurrent and sequential) phases | |
103 // with the CMS _token_, not the CMS _lock_. | |
104 // | |
105 // The only code protected by CMS lock is the token acquisition code | |
106 // itself, see ConcurrentMarkSweepThread::[de]synchronize(), and the | |
107 // baton-passing code. | |
108 // | |
109 // Unfortunately, i couldn't come up with a good abstraction to factor and | |
110 // hide the naked CGC_lock manipulation in the baton-passing code | |
111 // further below. That's something we should try to do. Also, the proof | |
112 // of correctness of this 2-level locking scheme is far from obvious, | |
113 // and potentially quite slippery. We have an uneasy supsicion, for instance, | |
114 // that there may be a theoretical possibility of delay/starvation in the | |
115 // low-level lock/wait/notify scheme used for the baton-passing because of | |
116 // potential intereference with the priority scheme embodied in the | |
117 // CMS-token-passing protocol. See related comments at a CGC_lock->wait() | |
118 // invocation further below and marked with "XXX 20011219YSR". | |
119 // Indeed, as we note elsewhere, this may become yet more slippery | |
120 // in the presence of multiple CMS and/or multiple VM threads. XXX | |
121 | |
122 class CMSTokenSync: public StackObj { | |
123 private: | |
124 bool _is_cms_thread; | |
125 public: | |
126 CMSTokenSync(bool is_cms_thread): | |
127 _is_cms_thread(is_cms_thread) { | |
128 assert(is_cms_thread == Thread::current()->is_ConcurrentGC_thread(), | |
129 "Incorrect argument to constructor"); | |
130 ConcurrentMarkSweepThread::synchronize(_is_cms_thread); | |
131 } | |
132 | |
133 ~CMSTokenSync() { | |
134 assert(_is_cms_thread ? | |
135 ConcurrentMarkSweepThread::cms_thread_has_cms_token() : | |
136 ConcurrentMarkSweepThread::vm_thread_has_cms_token(), | |
137 "Incorrect state"); | |
138 ConcurrentMarkSweepThread::desynchronize(_is_cms_thread); | |
139 } | |
140 }; | |
141 | |
142 // Convenience class that does a CMSTokenSync, and then acquires | |
143 // upto three locks. | |
144 class CMSTokenSyncWithLocks: public CMSTokenSync { | |
145 private: | |
146 // Note: locks are acquired in textual declaration order | |
147 // and released in the opposite order | |
148 MutexLockerEx _locker1, _locker2, _locker3; | |
149 public: | |
150 CMSTokenSyncWithLocks(bool is_cms_thread, Mutex* mutex1, | |
151 Mutex* mutex2 = NULL, Mutex* mutex3 = NULL): | |
152 CMSTokenSync(is_cms_thread), | |
153 _locker1(mutex1, Mutex::_no_safepoint_check_flag), | |
154 _locker2(mutex2, Mutex::_no_safepoint_check_flag), | |
155 _locker3(mutex3, Mutex::_no_safepoint_check_flag) | |
156 { } | |
157 }; | |
158 | |
159 | |
160 // Wrapper class to temporarily disable icms during a foreground cms collection. | |
161 class ICMSDisabler: public StackObj { | |
162 public: | |
163 // The ctor disables icms and wakes up the thread so it notices the change; | |
164 // the dtor re-enables icms. Note that the CMSCollector methods will check | |
165 // CMSIncrementalMode. | |
166 ICMSDisabler() { CMSCollector::disable_icms(); CMSCollector::start_icms(); } | |
167 ~ICMSDisabler() { CMSCollector::enable_icms(); } | |
168 }; | |
169 | |
170 ////////////////////////////////////////////////////////////////// | |
171 // Concurrent Mark-Sweep Generation ///////////////////////////// | |
172 ////////////////////////////////////////////////////////////////// | |
173 | |
174 NOT_PRODUCT(CompactibleFreeListSpace* debug_cms_space;) | |
175 | |
176 // This struct contains per-thread things necessary to support parallel | |
177 // young-gen collection. | |
6197 | 178 class CMSParGCThreadState: public CHeapObj<mtGC> { |
0 | 179 public: |
180 CFLS_LAB lab; | |
181 PromotionInfo promo; | |
182 | |
183 // Constructor. | |
184 CMSParGCThreadState(CompactibleFreeListSpace* cfls) : lab(cfls) { | |
185 promo.setSpace(cfls); | |
186 } | |
187 }; | |
188 | |
189 ConcurrentMarkSweepGeneration::ConcurrentMarkSweepGeneration( | |
190 ReservedSpace rs, size_t initial_byte_size, int level, | |
191 CardTableRS* ct, bool use_adaptive_freelists, | |
6026 | 192 FreeBlockDictionary<FreeChunk>::DictionaryChoice dictionaryChoice) : |
0 | 193 CardGeneration(rs, initial_byte_size, level, ct), |
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194 _dilatation_factor(((double)MinChunkSize)/((double)(CollectedHeap::min_fill_size()))), |
0 | 195 _debug_collection_type(Concurrent_collection_type) |
196 { | |
197 HeapWord* bottom = (HeapWord*) _virtual_space.low(); | |
198 HeapWord* end = (HeapWord*) _virtual_space.high(); | |
199 | |
200 _direct_allocated_words = 0; | |
201 NOT_PRODUCT( | |
202 _numObjectsPromoted = 0; | |
203 _numWordsPromoted = 0; | |
204 _numObjectsAllocated = 0; | |
205 _numWordsAllocated = 0; | |
206 ) | |
207 | |
208 _cmsSpace = new CompactibleFreeListSpace(_bts, MemRegion(bottom, end), | |
209 use_adaptive_freelists, | |
210 dictionaryChoice); | |
211 NOT_PRODUCT(debug_cms_space = _cmsSpace;) | |
212 if (_cmsSpace == NULL) { | |
213 vm_exit_during_initialization( | |
214 "CompactibleFreeListSpace allocation failure"); | |
215 } | |
216 _cmsSpace->_gen = this; | |
217 | |
218 _gc_stats = new CMSGCStats(); | |
219 | |
220 // Verify the assumption that FreeChunk::_prev and OopDesc::_klass | |
221 // offsets match. The ability to tell free chunks from objects | |
222 // depends on this property. | |
223 debug_only( | |
224 FreeChunk* junk = NULL; | |
187 | 225 assert(UseCompressedOops || |
226 junk->prev_addr() == (void*)(oop(junk)->klass_addr()), | |
0 | 227 "Offset of FreeChunk::_prev within FreeChunk must match" |
228 " that of OopDesc::_klass within OopDesc"); | |
229 ) | |
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230 if (CollectedHeap::use_parallel_gc_threads()) { |
0 | 231 typedef CMSParGCThreadState* CMSParGCThreadStatePtr; |
232 _par_gc_thread_states = | |
6197 | 233 NEW_C_HEAP_ARRAY(CMSParGCThreadStatePtr, ParallelGCThreads, mtGC); |
0 | 234 if (_par_gc_thread_states == NULL) { |
235 vm_exit_during_initialization("Could not allocate par gc structs"); | |
236 } | |
237 for (uint i = 0; i < ParallelGCThreads; i++) { | |
238 _par_gc_thread_states[i] = new CMSParGCThreadState(cmsSpace()); | |
239 if (_par_gc_thread_states[i] == NULL) { | |
240 vm_exit_during_initialization("Could not allocate par gc structs"); | |
241 } | |
242 } | |
243 } else { | |
244 _par_gc_thread_states = NULL; | |
245 } | |
246 _incremental_collection_failed = false; | |
247 // The "dilatation_factor" is the expansion that can occur on | |
248 // account of the fact that the minimum object size in the CMS | |
249 // generation may be larger than that in, say, a contiguous young | |
250 // generation. | |
251 // Ideally, in the calculation below, we'd compute the dilatation | |
252 // factor as: MinChunkSize/(promoting_gen's min object size) | |
253 // Since we do not have such a general query interface for the | |
254 // promoting generation, we'll instead just use the mimimum | |
255 // object size (which today is a header's worth of space); | |
256 // note that all arithmetic is in units of HeapWords. | |
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257 assert(MinChunkSize >= CollectedHeap::min_fill_size(), "just checking"); |
0 | 258 assert(_dilatation_factor >= 1.0, "from previous assert"); |
259 } | |
260 | |
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261 |
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262 // The field "_initiating_occupancy" represents the occupancy percentage |
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263 // at which we trigger a new collection cycle. Unless explicitly specified |
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264 // via CMSInitiatingOccupancyFraction (argument "io" below), it |
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265 // is calculated by: |
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266 // |
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267 // Let "f" be MinHeapFreeRatio in |
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268 // |
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269 // _intiating_occupancy = 100-f + |
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270 // f * (CMSTriggerRatio/100) |
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271 // where CMSTriggerRatio is the argument "tr" below. |
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272 // |
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273 // That is, if we assume the heap is at its desired maximum occupancy at the |
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274 // end of a collection, we let CMSTriggerRatio of the (purported) free |
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275 // space be allocated before initiating a new collection cycle. |
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276 // |
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277 void ConcurrentMarkSweepGeneration::init_initiating_occupancy(intx io, intx tr) { |
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278 assert(io <= 100 && tr >= 0 && tr <= 100, "Check the arguments"); |
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279 if (io >= 0) { |
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280 _initiating_occupancy = (double)io / 100.0; |
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281 } else { |
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282 _initiating_occupancy = ((100 - MinHeapFreeRatio) + |
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283 (double)(tr * MinHeapFreeRatio) / 100.0) |
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284 / 100.0; |
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285 } |
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286 } |
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287 |
0 | 288 void ConcurrentMarkSweepGeneration::ref_processor_init() { |
289 assert(collector() != NULL, "no collector"); | |
290 collector()->ref_processor_init(); | |
291 } | |
292 | |
293 void CMSCollector::ref_processor_init() { | |
294 if (_ref_processor == NULL) { | |
295 // Allocate and initialize a reference processor | |
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296 _ref_processor = |
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297 new ReferenceProcessor(_span, // span |
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298 (ParallelGCThreads > 1) && ParallelRefProcEnabled, // mt processing |
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299 (int) ParallelGCThreads, // mt processing degree |
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300 _cmsGen->refs_discovery_is_mt(), // mt discovery |
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301 (int) MAX2(ConcGCThreads, ParallelGCThreads), // mt discovery degree |
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302 _cmsGen->refs_discovery_is_atomic(), // discovery is not atomic |
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303 &_is_alive_closure, // closure for liveness info |
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304 false); // next field updates do not need write barrier |
0 | 305 // Initialize the _ref_processor field of CMSGen |
306 _cmsGen->set_ref_processor(_ref_processor); | |
307 | |
308 } | |
309 } | |
310 | |
311 CMSAdaptiveSizePolicy* CMSCollector::size_policy() { | |
312 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
313 assert(gch->kind() == CollectedHeap::GenCollectedHeap, | |
314 "Wrong type of heap"); | |
315 CMSAdaptiveSizePolicy* sp = (CMSAdaptiveSizePolicy*) | |
316 gch->gen_policy()->size_policy(); | |
317 assert(sp->is_gc_cms_adaptive_size_policy(), | |
318 "Wrong type of size policy"); | |
319 return sp; | |
320 } | |
321 | |
322 CMSGCAdaptivePolicyCounters* CMSCollector::gc_adaptive_policy_counters() { | |
323 CMSGCAdaptivePolicyCounters* results = | |
324 (CMSGCAdaptivePolicyCounters*) collector_policy()->counters(); | |
325 assert( | |
326 results->kind() == GCPolicyCounters::CMSGCAdaptivePolicyCountersKind, | |
327 "Wrong gc policy counter kind"); | |
328 return results; | |
329 } | |
330 | |
331 | |
332 void ConcurrentMarkSweepGeneration::initialize_performance_counters() { | |
333 | |
334 const char* gen_name = "old"; | |
335 | |
336 // Generation Counters - generation 1, 1 subspace | |
337 _gen_counters = new GenerationCounters(gen_name, 1, 1, &_virtual_space); | |
338 | |
339 _space_counters = new GSpaceCounters(gen_name, 0, | |
340 _virtual_space.reserved_size(), | |
341 this, _gen_counters); | |
342 } | |
343 | |
344 CMSStats::CMSStats(ConcurrentMarkSweepGeneration* cms_gen, unsigned int alpha): | |
345 _cms_gen(cms_gen) | |
346 { | |
347 assert(alpha <= 100, "bad value"); | |
348 _saved_alpha = alpha; | |
349 | |
350 // Initialize the alphas to the bootstrap value of 100. | |
351 _gc0_alpha = _cms_alpha = 100; | |
352 | |
353 _cms_begin_time.update(); | |
354 _cms_end_time.update(); | |
355 | |
356 _gc0_duration = 0.0; | |
357 _gc0_period = 0.0; | |
358 _gc0_promoted = 0; | |
359 | |
360 _cms_duration = 0.0; | |
361 _cms_period = 0.0; | |
362 _cms_allocated = 0; | |
363 | |
364 _cms_used_at_gc0_begin = 0; | |
365 _cms_used_at_gc0_end = 0; | |
366 _allow_duty_cycle_reduction = false; | |
367 _valid_bits = 0; | |
368 _icms_duty_cycle = CMSIncrementalDutyCycle; | |
369 } | |
370 | |
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371 double CMSStats::cms_free_adjustment_factor(size_t free) const { |
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372 // TBD: CR 6909490 |
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373 return 1.0; |
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374 } |
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375 |
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376 void CMSStats::adjust_cms_free_adjustment_factor(bool fail, size_t free) { |
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377 } |
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378 |
0 | 379 // If promotion failure handling is on use |
380 // the padded average size of the promotion for each | |
381 // young generation collection. | |
382 double CMSStats::time_until_cms_gen_full() const { | |
383 size_t cms_free = _cms_gen->cmsSpace()->free(); | |
384 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
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385 size_t expected_promotion = MIN2(gch->get_gen(0)->capacity(), |
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386 (size_t) _cms_gen->gc_stats()->avg_promoted()->padded_average()); |
0 | 387 if (cms_free > expected_promotion) { |
388 // Start a cms collection if there isn't enough space to promote | |
389 // for the next minor collection. Use the padded average as | |
390 // a safety factor. | |
391 cms_free -= expected_promotion; | |
392 | |
393 // Adjust by the safety factor. | |
394 double cms_free_dbl = (double)cms_free; | |
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395 double cms_adjustment = (100.0 - CMSIncrementalSafetyFactor)/100.0; |
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396 // Apply a further correction factor which tries to adjust |
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397 // for recent occurance of concurrent mode failures. |
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398 cms_adjustment = cms_adjustment * cms_free_adjustment_factor(cms_free); |
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399 cms_free_dbl = cms_free_dbl * cms_adjustment; |
0 | 400 |
401 if (PrintGCDetails && Verbose) { | |
402 gclog_or_tty->print_cr("CMSStats::time_until_cms_gen_full: cms_free " | |
403 SIZE_FORMAT " expected_promotion " SIZE_FORMAT, | |
404 cms_free, expected_promotion); | |
405 gclog_or_tty->print_cr(" cms_free_dbl %f cms_consumption_rate %f", | |
406 cms_free_dbl, cms_consumption_rate() + 1.0); | |
407 } | |
408 // Add 1 in case the consumption rate goes to zero. | |
409 return cms_free_dbl / (cms_consumption_rate() + 1.0); | |
410 } | |
411 return 0.0; | |
412 } | |
413 | |
414 // Compare the duration of the cms collection to the | |
415 // time remaining before the cms generation is empty. | |
416 // Note that the time from the start of the cms collection | |
417 // to the start of the cms sweep (less than the total | |
418 // duration of the cms collection) can be used. This | |
419 // has been tried and some applications experienced | |
420 // promotion failures early in execution. This was | |
421 // possibly because the averages were not accurate | |
422 // enough at the beginning. | |
423 double CMSStats::time_until_cms_start() const { | |
424 // We add "gc0_period" to the "work" calculation | |
425 // below because this query is done (mostly) at the | |
426 // end of a scavenge, so we need to conservatively | |
427 // account for that much possible delay | |
428 // in the query so as to avoid concurrent mode failures | |
429 // due to starting the collection just a wee bit too | |
430 // late. | |
431 double work = cms_duration() + gc0_period(); | |
432 double deadline = time_until_cms_gen_full(); | |
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433 // If a concurrent mode failure occurred recently, we want to be |
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434 // more conservative and halve our expected time_until_cms_gen_full() |
0 | 435 if (work > deadline) { |
436 if (Verbose && PrintGCDetails) { | |
437 gclog_or_tty->print( | |
438 " CMSCollector: collect because of anticipated promotion " | |
439 "before full %3.7f + %3.7f > %3.7f ", cms_duration(), | |
440 gc0_period(), time_until_cms_gen_full()); | |
441 } | |
442 return 0.0; | |
443 } | |
444 return work - deadline; | |
445 } | |
446 | |
447 // Return a duty cycle based on old_duty_cycle and new_duty_cycle, limiting the | |
448 // amount of change to prevent wild oscillation. | |
449 unsigned int CMSStats::icms_damped_duty_cycle(unsigned int old_duty_cycle, | |
450 unsigned int new_duty_cycle) { | |
451 assert(old_duty_cycle <= 100, "bad input value"); | |
452 assert(new_duty_cycle <= 100, "bad input value"); | |
453 | |
454 // Note: use subtraction with caution since it may underflow (values are | |
455 // unsigned). Addition is safe since we're in the range 0-100. | |
456 unsigned int damped_duty_cycle = new_duty_cycle; | |
457 if (new_duty_cycle < old_duty_cycle) { | |
458 const unsigned int largest_delta = MAX2(old_duty_cycle / 4, 5U); | |
459 if (new_duty_cycle + largest_delta < old_duty_cycle) { | |
460 damped_duty_cycle = old_duty_cycle - largest_delta; | |
461 } | |
462 } else if (new_duty_cycle > old_duty_cycle) { | |
463 const unsigned int largest_delta = MAX2(old_duty_cycle / 4, 15U); | |
464 if (new_duty_cycle > old_duty_cycle + largest_delta) { | |
465 damped_duty_cycle = MIN2(old_duty_cycle + largest_delta, 100U); | |
466 } | |
467 } | |
468 assert(damped_duty_cycle <= 100, "invalid duty cycle computed"); | |
469 | |
470 if (CMSTraceIncrementalPacing) { | |
471 gclog_or_tty->print(" [icms_damped_duty_cycle(%d,%d) = %d] ", | |
472 old_duty_cycle, new_duty_cycle, damped_duty_cycle); | |
473 } | |
474 return damped_duty_cycle; | |
475 } | |
476 | |
477 unsigned int CMSStats::icms_update_duty_cycle_impl() { | |
478 assert(CMSIncrementalPacing && valid(), | |
479 "should be handled in icms_update_duty_cycle()"); | |
480 | |
481 double cms_time_so_far = cms_timer().seconds(); | |
482 double scaled_duration = cms_duration_per_mb() * _cms_used_at_gc0_end / M; | |
483 double scaled_duration_remaining = fabsd(scaled_duration - cms_time_so_far); | |
484 | |
485 // Avoid division by 0. | |
486 double time_until_full = MAX2(time_until_cms_gen_full(), 0.01); | |
487 double duty_cycle_dbl = 100.0 * scaled_duration_remaining / time_until_full; | |
488 | |
489 unsigned int new_duty_cycle = MIN2((unsigned int)duty_cycle_dbl, 100U); | |
490 if (new_duty_cycle > _icms_duty_cycle) { | |
491 // Avoid very small duty cycles (1 or 2); 0 is allowed. | |
492 if (new_duty_cycle > 2) { | |
493 _icms_duty_cycle = icms_damped_duty_cycle(_icms_duty_cycle, | |
494 new_duty_cycle); | |
495 } | |
496 } else if (_allow_duty_cycle_reduction) { | |
497 // The duty cycle is reduced only once per cms cycle (see record_cms_end()). | |
498 new_duty_cycle = icms_damped_duty_cycle(_icms_duty_cycle, new_duty_cycle); | |
499 // Respect the minimum duty cycle. | |
500 unsigned int min_duty_cycle = (unsigned int)CMSIncrementalDutyCycleMin; | |
501 _icms_duty_cycle = MAX2(new_duty_cycle, min_duty_cycle); | |
502 } | |
503 | |
504 if (PrintGCDetails || CMSTraceIncrementalPacing) { | |
505 gclog_or_tty->print(" icms_dc=%d ", _icms_duty_cycle); | |
506 } | |
507 | |
508 _allow_duty_cycle_reduction = false; | |
509 return _icms_duty_cycle; | |
510 } | |
511 | |
512 #ifndef PRODUCT | |
513 void CMSStats::print_on(outputStream *st) const { | |
514 st->print(" gc0_alpha=%d,cms_alpha=%d", _gc0_alpha, _cms_alpha); | |
515 st->print(",gc0_dur=%g,gc0_per=%g,gc0_promo=" SIZE_FORMAT, | |
516 gc0_duration(), gc0_period(), gc0_promoted()); | |
517 st->print(",cms_dur=%g,cms_dur_per_mb=%g,cms_per=%g,cms_alloc=" SIZE_FORMAT, | |
518 cms_duration(), cms_duration_per_mb(), | |
519 cms_period(), cms_allocated()); | |
520 st->print(",cms_since_beg=%g,cms_since_end=%g", | |
521 cms_time_since_begin(), cms_time_since_end()); | |
522 st->print(",cms_used_beg=" SIZE_FORMAT ",cms_used_end=" SIZE_FORMAT, | |
523 _cms_used_at_gc0_begin, _cms_used_at_gc0_end); | |
524 if (CMSIncrementalMode) { | |
525 st->print(",dc=%d", icms_duty_cycle()); | |
526 } | |
527 | |
528 if (valid()) { | |
529 st->print(",promo_rate=%g,cms_alloc_rate=%g", | |
530 promotion_rate(), cms_allocation_rate()); | |
531 st->print(",cms_consumption_rate=%g,time_until_full=%g", | |
532 cms_consumption_rate(), time_until_cms_gen_full()); | |
533 } | |
534 st->print(" "); | |
535 } | |
536 #endif // #ifndef PRODUCT | |
537 | |
538 CMSCollector::CollectorState CMSCollector::_collectorState = | |
539 CMSCollector::Idling; | |
540 bool CMSCollector::_foregroundGCIsActive = false; | |
541 bool CMSCollector::_foregroundGCShouldWait = false; | |
542 | |
543 CMSCollector::CMSCollector(ConcurrentMarkSweepGeneration* cmsGen, | |
544 CardTableRS* ct, | |
545 ConcurrentMarkSweepPolicy* cp): | |
546 _cmsGen(cmsGen), | |
547 _ct(ct), | |
548 _ref_processor(NULL), // will be set later | |
549 _conc_workers(NULL), // may be set later | |
550 _abort_preclean(false), | |
551 _start_sampling(false), | |
552 _between_prologue_and_epilogue(false), | |
553 _markBitMap(0, Mutex::leaf + 1, "CMS_markBitMap_lock"), | |
554 _modUnionTable((CardTableModRefBS::card_shift - LogHeapWordSize), | |
555 -1 /* lock-free */, "No_lock" /* dummy */), | |
556 _modUnionClosure(&_modUnionTable), | |
557 _modUnionClosurePar(&_modUnionTable), | |
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558 // Adjust my span to cover old (cms) gen |
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559 _span(cmsGen->reserved()), |
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560 // Construct the is_alive_closure with _span & markBitMap |
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561 _is_alive_closure(_span, &_markBitMap), |
0 | 562 _restart_addr(NULL), |
563 _overflow_list(NULL), | |
564 _stats(cmsGen), | |
565 _eden_chunk_array(NULL), // may be set in ctor body | |
566 _eden_chunk_capacity(0), // -- ditto -- | |
567 _eden_chunk_index(0), // -- ditto -- | |
568 _survivor_plab_array(NULL), // -- ditto -- | |
569 _survivor_chunk_array(NULL), // -- ditto -- | |
570 _survivor_chunk_capacity(0), // -- ditto -- | |
571 _survivor_chunk_index(0), // -- ditto -- | |
572 _ser_pmc_preclean_ovflw(0), | |
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573 _ser_kac_preclean_ovflw(0), |
0 | 574 _ser_pmc_remark_ovflw(0), |
575 _par_pmc_remark_ovflw(0), | |
576 _ser_kac_ovflw(0), | |
577 _par_kac_ovflw(0), | |
578 #ifndef PRODUCT | |
579 _num_par_pushes(0), | |
580 #endif | |
581 _collection_count_start(0), | |
582 _verifying(false), | |
583 _icms_start_limit(NULL), | |
584 _icms_stop_limit(NULL), | |
585 _verification_mark_bm(0, Mutex::leaf + 1, "CMS_verification_mark_bm_lock"), | |
586 _completed_initialization(false), | |
587 _collector_policy(cp), | |
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588 _should_unload_classes(false), |
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589 _concurrent_cycles_since_last_unload(0), |
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590 _roots_scanning_options(0), |
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591 _inter_sweep_estimate(CMS_SweepWeight, CMS_SweepPadding), |
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592 _intra_sweep_estimate(CMS_SweepWeight, CMS_SweepPadding) |
0 | 593 { |
594 if (ExplicitGCInvokesConcurrentAndUnloadsClasses) { | |
595 ExplicitGCInvokesConcurrent = true; | |
596 } | |
597 // Now expand the span and allocate the collection support structures | |
598 // (MUT, marking bit map etc.) to cover both generations subject to | |
599 // collection. | |
600 | |
601 // For use by dirty card to oop closures. | |
602 _cmsGen->cmsSpace()->set_collector(this); | |
603 | |
604 // Allocate MUT and marking bit map | |
605 { | |
606 MutexLockerEx x(_markBitMap.lock(), Mutex::_no_safepoint_check_flag); | |
607 if (!_markBitMap.allocate(_span)) { | |
608 warning("Failed to allocate CMS Bit Map"); | |
609 return; | |
610 } | |
611 assert(_markBitMap.covers(_span), "_markBitMap inconsistency?"); | |
612 } | |
613 { | |
614 _modUnionTable.allocate(_span); | |
615 assert(_modUnionTable.covers(_span), "_modUnionTable inconsistency?"); | |
616 } | |
617 | |
1284 | 618 if (!_markStack.allocate(MarkStackSize)) { |
0 | 619 warning("Failed to allocate CMS Marking Stack"); |
620 return; | |
621 } | |
622 | |
623 // Support for multi-threaded concurrent phases | |
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624 if (CMSConcurrentMTEnabled) { |
1284 | 625 if (FLAG_IS_DEFAULT(ConcGCThreads)) { |
0 | 626 // just for now |
1284 | 627 FLAG_SET_DEFAULT(ConcGCThreads, (ParallelGCThreads + 3)/4); |
628 } | |
629 if (ConcGCThreads > 1) { | |
0 | 630 _conc_workers = new YieldingFlexibleWorkGang("Parallel CMS Threads", |
1284 | 631 ConcGCThreads, true); |
0 | 632 if (_conc_workers == NULL) { |
633 warning("GC/CMS: _conc_workers allocation failure: " | |
634 "forcing -CMSConcurrentMTEnabled"); | |
635 CMSConcurrentMTEnabled = false; | |
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636 } else { |
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637 _conc_workers->initialize_workers(); |
0 | 638 } |
639 } else { | |
640 CMSConcurrentMTEnabled = false; | |
641 } | |
642 } | |
643 if (!CMSConcurrentMTEnabled) { | |
1284 | 644 ConcGCThreads = 0; |
0 | 645 } else { |
646 // Turn off CMSCleanOnEnter optimization temporarily for | |
647 // the MT case where it's not fixed yet; see 6178663. | |
648 CMSCleanOnEnter = false; | |
649 } | |
1284 | 650 assert((_conc_workers != NULL) == (ConcGCThreads > 1), |
0 | 651 "Inconsistency"); |
652 | |
653 // Parallel task queues; these are shared for the | |
654 // concurrent and stop-world phases of CMS, but | |
655 // are not shared with parallel scavenge (ParNew). | |
656 { | |
657 uint i; | |
1284 | 658 uint num_queues = (uint) MAX2(ParallelGCThreads, ConcGCThreads); |
0 | 659 |
660 if ((CMSParallelRemarkEnabled || CMSConcurrentMTEnabled | |
661 || ParallelRefProcEnabled) | |
662 && num_queues > 0) { | |
663 _task_queues = new OopTaskQueueSet(num_queues); | |
664 if (_task_queues == NULL) { | |
665 warning("task_queues allocation failure."); | |
666 return; | |
667 } | |
6197 | 668 _hash_seed = NEW_C_HEAP_ARRAY(int, num_queues, mtGC); |
0 | 669 if (_hash_seed == NULL) { |
670 warning("_hash_seed array allocation failure"); | |
671 return; | |
672 } | |
673 | |
1665 | 674 typedef Padded<OopTaskQueue> PaddedOopTaskQueue; |
0 | 675 for (i = 0; i < num_queues; i++) { |
1665 | 676 PaddedOopTaskQueue *q = new PaddedOopTaskQueue(); |
677 if (q == NULL) { | |
0 | 678 warning("work_queue allocation failure."); |
679 return; | |
680 } | |
1665 | 681 _task_queues->register_queue(i, q); |
0 | 682 } |
683 for (i = 0; i < num_queues; i++) { | |
684 _task_queues->queue(i)->initialize(); | |
685 _hash_seed[i] = 17; // copied from ParNew | |
686 } | |
687 } | |
688 } | |
689 | |
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690 _cmsGen ->init_initiating_occupancy(CMSInitiatingOccupancyFraction, CMSTriggerRatio); |
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691 |
0 | 692 // Clip CMSBootstrapOccupancy between 0 and 100. |
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693 _bootstrap_occupancy = ((double)MIN2((uintx)100, MAX2((uintx)0, CMSBootstrapOccupancy))) |
0 | 694 /(double)100; |
695 | |
696 _full_gcs_since_conc_gc = 0; | |
697 | |
698 // Now tell CMS generations the identity of their collector | |
699 ConcurrentMarkSweepGeneration::set_collector(this); | |
700 | |
701 // Create & start a CMS thread for this CMS collector | |
702 _cmsThread = ConcurrentMarkSweepThread::start(this); | |
703 assert(cmsThread() != NULL, "CMS Thread should have been created"); | |
704 assert(cmsThread()->collector() == this, | |
705 "CMS Thread should refer to this gen"); | |
706 assert(CGC_lock != NULL, "Where's the CGC_lock?"); | |
707 | |
708 // Support for parallelizing young gen rescan | |
709 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
710 _young_gen = gch->prev_gen(_cmsGen); | |
711 if (gch->supports_inline_contig_alloc()) { | |
712 _top_addr = gch->top_addr(); | |
713 _end_addr = gch->end_addr(); | |
714 assert(_young_gen != NULL, "no _young_gen"); | |
715 _eden_chunk_index = 0; | |
716 _eden_chunk_capacity = (_young_gen->max_capacity()+CMSSamplingGrain)/CMSSamplingGrain; | |
6197 | 717 _eden_chunk_array = NEW_C_HEAP_ARRAY(HeapWord*, _eden_chunk_capacity, mtGC); |
0 | 718 if (_eden_chunk_array == NULL) { |
719 _eden_chunk_capacity = 0; | |
720 warning("GC/CMS: _eden_chunk_array allocation failure"); | |
721 } | |
722 } | |
723 assert(_eden_chunk_array != NULL || _eden_chunk_capacity == 0, "Error"); | |
724 | |
725 // Support for parallelizing survivor space rescan | |
726 if (CMSParallelRemarkEnabled && CMSParallelSurvivorRemarkEnabled) { | |
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727 const size_t max_plab_samples = |
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728 ((DefNewGeneration*)_young_gen)->max_survivor_size()/MinTLABSize; |
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729 |
6197 | 730 _survivor_plab_array = NEW_C_HEAP_ARRAY(ChunkArray, ParallelGCThreads, mtGC); |
731 _survivor_chunk_array = NEW_C_HEAP_ARRAY(HeapWord*, 2*max_plab_samples, mtGC); | |
732 _cursor = NEW_C_HEAP_ARRAY(size_t, ParallelGCThreads, mtGC); | |
0 | 733 if (_survivor_plab_array == NULL || _survivor_chunk_array == NULL |
734 || _cursor == NULL) { | |
735 warning("Failed to allocate survivor plab/chunk array"); | |
736 if (_survivor_plab_array != NULL) { | |
6197 | 737 FREE_C_HEAP_ARRAY(ChunkArray, _survivor_plab_array, mtGC); |
0 | 738 _survivor_plab_array = NULL; |
739 } | |
740 if (_survivor_chunk_array != NULL) { | |
6197 | 741 FREE_C_HEAP_ARRAY(HeapWord*, _survivor_chunk_array, mtGC); |
0 | 742 _survivor_chunk_array = NULL; |
743 } | |
744 if (_cursor != NULL) { | |
6197 | 745 FREE_C_HEAP_ARRAY(size_t, _cursor, mtGC); |
0 | 746 _cursor = NULL; |
747 } | |
748 } else { | |
749 _survivor_chunk_capacity = 2*max_plab_samples; | |
750 for (uint i = 0; i < ParallelGCThreads; i++) { | |
6197 | 751 HeapWord** vec = NEW_C_HEAP_ARRAY(HeapWord*, max_plab_samples, mtGC); |
0 | 752 if (vec == NULL) { |
753 warning("Failed to allocate survivor plab array"); | |
754 for (int j = i; j > 0; j--) { | |
6197 | 755 FREE_C_HEAP_ARRAY(HeapWord*, _survivor_plab_array[j-1].array(), mtGC); |
0 | 756 } |
6197 | 757 FREE_C_HEAP_ARRAY(ChunkArray, _survivor_plab_array, mtGC); |
758 FREE_C_HEAP_ARRAY(HeapWord*, _survivor_chunk_array, mtGC); | |
0 | 759 _survivor_plab_array = NULL; |
760 _survivor_chunk_array = NULL; | |
761 _survivor_chunk_capacity = 0; | |
762 break; | |
763 } else { | |
764 ChunkArray* cur = | |
765 ::new (&_survivor_plab_array[i]) ChunkArray(vec, | |
766 max_plab_samples); | |
767 assert(cur->end() == 0, "Should be 0"); | |
768 assert(cur->array() == vec, "Should be vec"); | |
769 assert(cur->capacity() == max_plab_samples, "Error"); | |
770 } | |
771 } | |
772 } | |
773 } | |
774 assert( ( _survivor_plab_array != NULL | |
775 && _survivor_chunk_array != NULL) | |
776 || ( _survivor_chunk_capacity == 0 | |
777 && _survivor_chunk_index == 0), | |
778 "Error"); | |
779 | |
780 // Choose what strong roots should be scanned depending on verification options | |
781 if (!CMSClassUnloadingEnabled) { | |
782 // If class unloading is disabled we want to include all classes into the root set. | |
783 add_root_scanning_option(SharedHeap::SO_AllClasses); | |
784 } else { | |
785 add_root_scanning_option(SharedHeap::SO_SystemClasses); | |
786 } | |
787 | |
788 NOT_PRODUCT(_overflow_counter = CMSMarkStackOverflowInterval;) | |
789 _gc_counters = new CollectorCounters("CMS", 1); | |
790 _completed_initialization = true; | |
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791 _inter_sweep_timer.start(); // start of time |
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792 #ifdef SPARC |
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793 // Issue a stern warning, but allow use for experimentation and debugging. |
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794 if (VM_Version::is_sun4v() && UseMemSetInBOT) { |
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795 assert(!FLAG_IS_DEFAULT(UseMemSetInBOT), "Error"); |
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796 warning("Experimental flag -XX:+UseMemSetInBOT is known to cause instability" |
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797 " on sun4v; please understand that you are using at your own risk!"); |
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798 } |
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799 #endif |
0 | 800 } |
801 | |
802 const char* ConcurrentMarkSweepGeneration::name() const { | |
803 return "concurrent mark-sweep generation"; | |
804 } | |
805 void ConcurrentMarkSweepGeneration::update_counters() { | |
806 if (UsePerfData) { | |
807 _space_counters->update_all(); | |
808 _gen_counters->update_all(); | |
809 } | |
810 } | |
811 | |
812 // this is an optimized version of update_counters(). it takes the | |
813 // used value as a parameter rather than computing it. | |
814 // | |
815 void ConcurrentMarkSweepGeneration::update_counters(size_t used) { | |
816 if (UsePerfData) { | |
817 _space_counters->update_used(used); | |
818 _space_counters->update_capacity(); | |
819 _gen_counters->update_all(); | |
820 } | |
821 } | |
822 | |
823 void ConcurrentMarkSweepGeneration::print() const { | |
824 Generation::print(); | |
825 cmsSpace()->print(); | |
826 } | |
827 | |
828 #ifndef PRODUCT | |
829 void ConcurrentMarkSweepGeneration::print_statistics() { | |
830 cmsSpace()->printFLCensus(0); | |
831 } | |
832 #endif | |
833 | |
834 void ConcurrentMarkSweepGeneration::printOccupancy(const char *s) { | |
835 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
836 if (PrintGCDetails) { | |
837 if (Verbose) { | |
838 gclog_or_tty->print(" [%d %s-%s: "SIZE_FORMAT"("SIZE_FORMAT")]", | |
839 level(), short_name(), s, used(), capacity()); | |
840 } else { | |
841 gclog_or_tty->print(" [%d %s-%s: "SIZE_FORMAT"K("SIZE_FORMAT"K)]", | |
842 level(), short_name(), s, used() / K, capacity() / K); | |
843 } | |
844 } | |
845 if (Verbose) { | |
846 gclog_or_tty->print(" "SIZE_FORMAT"("SIZE_FORMAT")", | |
847 gch->used(), gch->capacity()); | |
848 } else { | |
849 gclog_or_tty->print(" "SIZE_FORMAT"K("SIZE_FORMAT"K)", | |
850 gch->used() / K, gch->capacity() / K); | |
851 } | |
852 } | |
853 | |
854 size_t | |
855 ConcurrentMarkSweepGeneration::contiguous_available() const { | |
856 // dld proposes an improvement in precision here. If the committed | |
857 // part of the space ends in a free block we should add that to | |
858 // uncommitted size in the calculation below. Will make this | |
859 // change later, staying with the approximation below for the | |
860 // time being. -- ysr. | |
861 return MAX2(_virtual_space.uncommitted_size(), unsafe_max_alloc_nogc()); | |
862 } | |
863 | |
864 size_t | |
865 ConcurrentMarkSweepGeneration::unsafe_max_alloc_nogc() const { | |
866 return _cmsSpace->max_alloc_in_words() * HeapWordSize; | |
867 } | |
868 | |
869 size_t ConcurrentMarkSweepGeneration::max_available() const { | |
870 return free() + _virtual_space.uncommitted_size(); | |
871 } | |
872 | |
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873 bool ConcurrentMarkSweepGeneration::promotion_attempt_is_safe(size_t max_promotion_in_bytes) const { |
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874 size_t available = max_available(); |
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875 size_t av_promo = (size_t)gc_stats()->avg_promoted()->padded_average(); |
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876 bool res = (available >= av_promo) || (available >= max_promotion_in_bytes); |
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877 if (Verbose && PrintGCDetails) { |
1888
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878 gclog_or_tty->print_cr( |
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879 "CMS: promo attempt is%s safe: available("SIZE_FORMAT") %s av_promo("SIZE_FORMAT")," |
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880 "max_promo("SIZE_FORMAT")", |
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881 res? "":" not", available, res? ">=":"<", |
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882 av_promo, max_promotion_in_bytes); |
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883 } |
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884 return res; |
0 | 885 } |
886 | |
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887 // At a promotion failure dump information on block layout in heap |
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888 // (cms old generation). |
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889 void ConcurrentMarkSweepGeneration::promotion_failure_occurred() { |
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890 if (CMSDumpAtPromotionFailure) { |
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891 cmsSpace()->dump_at_safepoint_with_locks(collector(), gclog_or_tty); |
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892 } |
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893 } |
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894 |
0 | 895 CompactibleSpace* |
896 ConcurrentMarkSweepGeneration::first_compaction_space() const { | |
897 return _cmsSpace; | |
898 } | |
899 | |
900 void ConcurrentMarkSweepGeneration::reset_after_compaction() { | |
901 // Clear the promotion information. These pointers can be adjusted | |
902 // along with all the other pointers into the heap but | |
903 // compaction is expected to be a rare event with | |
904 // a heap using cms so don't do it without seeing the need. | |
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905 if (CollectedHeap::use_parallel_gc_threads()) { |
0 | 906 for (uint i = 0; i < ParallelGCThreads; i++) { |
907 _par_gc_thread_states[i]->promo.reset(); | |
908 } | |
909 } | |
910 } | |
911 | |
912 void ConcurrentMarkSweepGeneration::space_iterate(SpaceClosure* blk, bool usedOnly) { | |
913 blk->do_space(_cmsSpace); | |
914 } | |
915 | |
916 void ConcurrentMarkSweepGeneration::compute_new_size() { | |
917 assert_locked_or_safepoint(Heap_lock); | |
918 | |
919 // If incremental collection failed, we just want to expand | |
920 // to the limit. | |
921 if (incremental_collection_failed()) { | |
922 clear_incremental_collection_failed(); | |
923 grow_to_reserved(); | |
924 return; | |
925 } | |
926 | |
927 size_t expand_bytes = 0; | |
928 double free_percentage = ((double) free()) / capacity(); | |
929 double desired_free_percentage = (double) MinHeapFreeRatio / 100; | |
930 double maximum_free_percentage = (double) MaxHeapFreeRatio / 100; | |
931 | |
932 // compute expansion delta needed for reaching desired free percentage | |
933 if (free_percentage < desired_free_percentage) { | |
934 size_t desired_capacity = (size_t)(used() / ((double) 1 - desired_free_percentage)); | |
935 assert(desired_capacity >= capacity(), "invalid expansion size"); | |
936 expand_bytes = MAX2(desired_capacity - capacity(), MinHeapDeltaBytes); | |
937 } | |
938 if (expand_bytes > 0) { | |
939 if (PrintGCDetails && Verbose) { | |
940 size_t desired_capacity = (size_t)(used() / ((double) 1 - desired_free_percentage)); | |
941 gclog_or_tty->print_cr("\nFrom compute_new_size: "); | |
942 gclog_or_tty->print_cr(" Free fraction %f", free_percentage); | |
943 gclog_or_tty->print_cr(" Desired free fraction %f", | |
944 desired_free_percentage); | |
945 gclog_or_tty->print_cr(" Maximum free fraction %f", | |
946 maximum_free_percentage); | |
947 gclog_or_tty->print_cr(" Capactiy "SIZE_FORMAT, capacity()/1000); | |
948 gclog_or_tty->print_cr(" Desired capacity "SIZE_FORMAT, | |
949 desired_capacity/1000); | |
950 int prev_level = level() - 1; | |
951 if (prev_level >= 0) { | |
952 size_t prev_size = 0; | |
953 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
954 Generation* prev_gen = gch->_gens[prev_level]; | |
955 prev_size = prev_gen->capacity(); | |
956 gclog_or_tty->print_cr(" Younger gen size "SIZE_FORMAT, | |
957 prev_size/1000); | |
958 } | |
959 gclog_or_tty->print_cr(" unsafe_max_alloc_nogc "SIZE_FORMAT, | |
960 unsafe_max_alloc_nogc()/1000); | |
961 gclog_or_tty->print_cr(" contiguous available "SIZE_FORMAT, | |
962 contiguous_available()/1000); | |
963 gclog_or_tty->print_cr(" Expand by "SIZE_FORMAT" (bytes)", | |
964 expand_bytes); | |
965 } | |
966 // safe if expansion fails | |
967 expand(expand_bytes, 0, CMSExpansionCause::_satisfy_free_ratio); | |
968 if (PrintGCDetails && Verbose) { | |
969 gclog_or_tty->print_cr(" Expanded free fraction %f", | |
970 ((double) free()) / capacity()); | |
971 } | |
972 } | |
973 } | |
974 | |
975 Mutex* ConcurrentMarkSweepGeneration::freelistLock() const { | |
976 return cmsSpace()->freelistLock(); | |
977 } | |
978 | |
979 HeapWord* ConcurrentMarkSweepGeneration::allocate(size_t size, | |
980 bool tlab) { | |
981 CMSSynchronousYieldRequest yr; | |
982 MutexLockerEx x(freelistLock(), | |
983 Mutex::_no_safepoint_check_flag); | |
984 return have_lock_and_allocate(size, tlab); | |
985 } | |
986 | |
987 HeapWord* ConcurrentMarkSweepGeneration::have_lock_and_allocate(size_t size, | |
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988 bool tlab /* ignored */) { |
0 | 989 assert_lock_strong(freelistLock()); |
990 size_t adjustedSize = CompactibleFreeListSpace::adjustObjectSize(size); | |
991 HeapWord* res = cmsSpace()->allocate(adjustedSize); | |
992 // Allocate the object live (grey) if the background collector has | |
993 // started marking. This is necessary because the marker may | |
994 // have passed this address and consequently this object will | |
995 // not otherwise be greyed and would be incorrectly swept up. | |
996 // Note that if this object contains references, the writing | |
997 // of those references will dirty the card containing this object | |
998 // allowing the object to be blackened (and its references scanned) | |
999 // either during a preclean phase or at the final checkpoint. | |
1000 if (res != NULL) { | |
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1001 // We may block here with an uninitialized object with |
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1002 // its mark-bit or P-bits not yet set. Such objects need |
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1003 // to be safely navigable by block_start(). |
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1004 assert(oop(res)->klass_or_null() == NULL, "Object should be uninitialized here."); |
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1005 assert(!((FreeChunk*)res)->is_free(), "Error, block will look free but show wrong size"); |
0 | 1006 collector()->direct_allocated(res, adjustedSize); |
1007 _direct_allocated_words += adjustedSize; | |
1008 // allocation counters | |
1009 NOT_PRODUCT( | |
1010 _numObjectsAllocated++; | |
1011 _numWordsAllocated += (int)adjustedSize; | |
1012 ) | |
1013 } | |
1014 return res; | |
1015 } | |
1016 | |
1017 // In the case of direct allocation by mutators in a generation that | |
1018 // is being concurrently collected, the object must be allocated | |
1019 // live (grey) if the background collector has started marking. | |
1020 // This is necessary because the marker may | |
1021 // have passed this address and consequently this object will | |
1022 // not otherwise be greyed and would be incorrectly swept up. | |
1023 // Note that if this object contains references, the writing | |
1024 // of those references will dirty the card containing this object | |
1025 // allowing the object to be blackened (and its references scanned) | |
1026 // either during a preclean phase or at the final checkpoint. | |
1027 void CMSCollector::direct_allocated(HeapWord* start, size_t size) { | |
1028 assert(_markBitMap.covers(start, size), "Out of bounds"); | |
1029 if (_collectorState >= Marking) { | |
1030 MutexLockerEx y(_markBitMap.lock(), | |
1031 Mutex::_no_safepoint_check_flag); | |
1032 // [see comments preceding SweepClosure::do_blk() below for details] | |
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1033 // |
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1034 // Can the P-bits be deleted now? JJJ |
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1035 // |
0 | 1036 // 1. need to mark the object as live so it isn't collected |
1037 // 2. need to mark the 2nd bit to indicate the object may be uninitialized | |
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1038 // 3. need to mark the end of the object so marking, precleaning or sweeping |
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1039 // can skip over uninitialized or unparsable objects. An allocated |
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1040 // object is considered uninitialized for our purposes as long as |
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1041 // its klass word is NULL. All old gen objects are parsable |
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1042 // as soon as they are initialized.) |
0 | 1043 _markBitMap.mark(start); // object is live |
1044 _markBitMap.mark(start + 1); // object is potentially uninitialized? | |
1045 _markBitMap.mark(start + size - 1); | |
1046 // mark end of object | |
1047 } | |
1048 // check that oop looks uninitialized | |
187 | 1049 assert(oop(start)->klass_or_null() == NULL, "_klass should be NULL"); |
0 | 1050 } |
1051 | |
1052 void CMSCollector::promoted(bool par, HeapWord* start, | |
1053 bool is_obj_array, size_t obj_size) { | |
1054 assert(_markBitMap.covers(start), "Out of bounds"); | |
1055 // See comment in direct_allocated() about when objects should | |
1056 // be allocated live. | |
1057 if (_collectorState >= Marking) { | |
1058 // we already hold the marking bit map lock, taken in | |
1059 // the prologue | |
1060 if (par) { | |
1061 _markBitMap.par_mark(start); | |
1062 } else { | |
1063 _markBitMap.mark(start); | |
1064 } | |
1065 // We don't need to mark the object as uninitialized (as | |
1066 // in direct_allocated above) because this is being done with the | |
1067 // world stopped and the object will be initialized by the | |
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1068 // time the marking, precleaning or sweeping get to look at it. |
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1069 // But see the code for copying objects into the CMS generation, |
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1070 // where we need to ensure that concurrent readers of the |
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1071 // block offset table are able to safely navigate a block that |
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1072 // is in flux from being free to being allocated (and in |
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1073 // transition while being copied into) and subsequently |
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1074 // becoming a bona-fide object when the copy/promotion is complete. |
0 | 1075 assert(SafepointSynchronize::is_at_safepoint(), |
1076 "expect promotion only at safepoints"); | |
1077 | |
1078 if (_collectorState < Sweeping) { | |
1079 // Mark the appropriate cards in the modUnionTable, so that | |
1080 // this object gets scanned before the sweep. If this is | |
1081 // not done, CMS generation references in the object might | |
1082 // not get marked. | |
1083 // For the case of arrays, which are otherwise precisely | |
1084 // marked, we need to dirty the entire array, not just its head. | |
1085 if (is_obj_array) { | |
1086 // The [par_]mark_range() method expects mr.end() below to | |
1087 // be aligned to the granularity of a bit's representation | |
1088 // in the heap. In the case of the MUT below, that's a | |
1089 // card size. | |
1090 MemRegion mr(start, | |
1091 (HeapWord*)round_to((intptr_t)(start + obj_size), | |
1092 CardTableModRefBS::card_size /* bytes */)); | |
1093 if (par) { | |
1094 _modUnionTable.par_mark_range(mr); | |
1095 } else { | |
1096 _modUnionTable.mark_range(mr); | |
1097 } | |
1098 } else { // not an obj array; we can just mark the head | |
1099 if (par) { | |
1100 _modUnionTable.par_mark(start); | |
1101 } else { | |
1102 _modUnionTable.mark(start); | |
1103 } | |
1104 } | |
1105 } | |
1106 } | |
1107 } | |
1108 | |
1109 static inline size_t percent_of_space(Space* space, HeapWord* addr) | |
1110 { | |
1111 size_t delta = pointer_delta(addr, space->bottom()); | |
1112 return (size_t)(delta * 100.0 / (space->capacity() / HeapWordSize)); | |
1113 } | |
1114 | |
1115 void CMSCollector::icms_update_allocation_limits() | |
1116 { | |
1117 Generation* gen0 = GenCollectedHeap::heap()->get_gen(0); | |
1118 EdenSpace* eden = gen0->as_DefNewGeneration()->eden(); | |
1119 | |
1120 const unsigned int duty_cycle = stats().icms_update_duty_cycle(); | |
1121 if (CMSTraceIncrementalPacing) { | |
1122 stats().print(); | |
1123 } | |
1124 | |
1125 assert(duty_cycle <= 100, "invalid duty cycle"); | |
1126 if (duty_cycle != 0) { | |
1127 // The duty_cycle is a percentage between 0 and 100; convert to words and | |
1128 // then compute the offset from the endpoints of the space. | |
1129 size_t free_words = eden->free() / HeapWordSize; | |
1130 double free_words_dbl = (double)free_words; | |
1131 size_t duty_cycle_words = (size_t)(free_words_dbl * duty_cycle / 100.0); | |
1132 size_t offset_words = (free_words - duty_cycle_words) / 2; | |
1133 | |
1134 _icms_start_limit = eden->top() + offset_words; | |
1135 _icms_stop_limit = eden->end() - offset_words; | |
1136 | |
1137 // The limits may be adjusted (shifted to the right) by | |
1138 // CMSIncrementalOffset, to allow the application more mutator time after a | |
1139 // young gen gc (when all mutators were stopped) and before CMS starts and | |
1140 // takes away one or more cpus. | |
1141 if (CMSIncrementalOffset != 0) { | |
1142 double adjustment_dbl = free_words_dbl * CMSIncrementalOffset / 100.0; | |
1143 size_t adjustment = (size_t)adjustment_dbl; | |
1144 HeapWord* tmp_stop = _icms_stop_limit + adjustment; | |
1145 if (tmp_stop > _icms_stop_limit && tmp_stop < eden->end()) { | |
1146 _icms_start_limit += adjustment; | |
1147 _icms_stop_limit = tmp_stop; | |
1148 } | |
1149 } | |
1150 } | |
1151 if (duty_cycle == 0 || (_icms_start_limit == _icms_stop_limit)) { | |
1152 _icms_start_limit = _icms_stop_limit = eden->end(); | |
1153 } | |
1154 | |
1155 // Install the new start limit. | |
1156 eden->set_soft_end(_icms_start_limit); | |
1157 | |
1158 if (CMSTraceIncrementalMode) { | |
1159 gclog_or_tty->print(" icms alloc limits: " | |
1160 PTR_FORMAT "," PTR_FORMAT | |
1161 " (" SIZE_FORMAT "%%," SIZE_FORMAT "%%) ", | |
1162 _icms_start_limit, _icms_stop_limit, | |
1163 percent_of_space(eden, _icms_start_limit), | |
1164 percent_of_space(eden, _icms_stop_limit)); | |
1165 if (Verbose) { | |
1166 gclog_or_tty->print("eden: "); | |
1167 eden->print_on(gclog_or_tty); | |
1168 } | |
1169 } | |
1170 } | |
1171 | |
1172 // Any changes here should try to maintain the invariant | |
1173 // that if this method is called with _icms_start_limit | |
1174 // and _icms_stop_limit both NULL, then it should return NULL | |
1175 // and not notify the icms thread. | |
1176 HeapWord* | |
1177 CMSCollector::allocation_limit_reached(Space* space, HeapWord* top, | |
1178 size_t word_size) | |
1179 { | |
1180 // A start_limit equal to end() means the duty cycle is 0, so treat that as a | |
1181 // nop. | |
1182 if (CMSIncrementalMode && _icms_start_limit != space->end()) { | |
1183 if (top <= _icms_start_limit) { | |
1184 if (CMSTraceIncrementalMode) { | |
1185 space->print_on(gclog_or_tty); | |
1186 gclog_or_tty->stamp(); | |
1187 gclog_or_tty->print_cr(" start limit top=" PTR_FORMAT | |
1188 ", new limit=" PTR_FORMAT | |
1189 " (" SIZE_FORMAT "%%)", | |
1190 top, _icms_stop_limit, | |
1191 percent_of_space(space, _icms_stop_limit)); | |
1192 } | |
1193 ConcurrentMarkSweepThread::start_icms(); | |
1194 assert(top < _icms_stop_limit, "Tautology"); | |
1195 if (word_size < pointer_delta(_icms_stop_limit, top)) { | |
1196 return _icms_stop_limit; | |
1197 } | |
1198 | |
1199 // The allocation will cross both the _start and _stop limits, so do the | |
1200 // stop notification also and return end(). | |
1201 if (CMSTraceIncrementalMode) { | |
1202 space->print_on(gclog_or_tty); | |
1203 gclog_or_tty->stamp(); | |
1204 gclog_or_tty->print_cr(" +stop limit top=" PTR_FORMAT | |
1205 ", new limit=" PTR_FORMAT | |
1206 " (" SIZE_FORMAT "%%)", | |
1207 top, space->end(), | |
1208 percent_of_space(space, space->end())); | |
1209 } | |
1210 ConcurrentMarkSweepThread::stop_icms(); | |
1211 return space->end(); | |
1212 } | |
1213 | |
1214 if (top <= _icms_stop_limit) { | |
1215 if (CMSTraceIncrementalMode) { | |
1216 space->print_on(gclog_or_tty); | |
1217 gclog_or_tty->stamp(); | |
1218 gclog_or_tty->print_cr(" stop limit top=" PTR_FORMAT | |
1219 ", new limit=" PTR_FORMAT | |
1220 " (" SIZE_FORMAT "%%)", | |
1221 top, space->end(), | |
1222 percent_of_space(space, space->end())); | |
1223 } | |
1224 ConcurrentMarkSweepThread::stop_icms(); | |
1225 return space->end(); | |
1226 } | |
1227 | |
1228 if (CMSTraceIncrementalMode) { | |
1229 space->print_on(gclog_or_tty); | |
1230 gclog_or_tty->stamp(); | |
1231 gclog_or_tty->print_cr(" end limit top=" PTR_FORMAT | |
1232 ", new limit=" PTR_FORMAT, | |
1233 top, NULL); | |
1234 } | |
1235 } | |
1236 | |
1237 return NULL; | |
1238 } | |
1239 | |
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1240 oop ConcurrentMarkSweepGeneration::promote(oop obj, size_t obj_size) { |
0 | 1241 assert(obj_size == (size_t)obj->size(), "bad obj_size passed in"); |
1242 // allocate, copy and if necessary update promoinfo -- | |
1243 // delegate to underlying space. | |
1244 assert_lock_strong(freelistLock()); | |
1245 | |
1246 #ifndef PRODUCT | |
1247 if (Universe::heap()->promotion_should_fail()) { | |
1248 return NULL; | |
1249 } | |
1250 #endif // #ifndef PRODUCT | |
1251 | |
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1252 oop res = _cmsSpace->promote(obj, obj_size); |
0 | 1253 if (res == NULL) { |
1254 // expand and retry | |
1255 size_t s = _cmsSpace->expansionSpaceRequired(obj_size); // HeapWords | |
1256 expand(s*HeapWordSize, MinHeapDeltaBytes, | |
1257 CMSExpansionCause::_satisfy_promotion); | |
1258 // Since there's currently no next generation, we don't try to promote | |
1259 // into a more senior generation. | |
1260 assert(next_gen() == NULL, "assumption, based upon which no attempt " | |
1261 "is made to pass on a possibly failing " | |
1262 "promotion to next generation"); | |
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1263 res = _cmsSpace->promote(obj, obj_size); |
0 | 1264 } |
1265 if (res != NULL) { | |
1266 // See comment in allocate() about when objects should | |
1267 // be allocated live. | |
1268 assert(obj->is_oop(), "Will dereference klass pointer below"); | |
1269 collector()->promoted(false, // Not parallel | |
1270 (HeapWord*)res, obj->is_objArray(), obj_size); | |
1271 // promotion counters | |
1272 NOT_PRODUCT( | |
1273 _numObjectsPromoted++; | |
1274 _numWordsPromoted += | |
1275 (int)(CompactibleFreeListSpace::adjustObjectSize(obj->size())); | |
1276 ) | |
1277 } | |
1278 return res; | |
1279 } | |
1280 | |
1281 | |
1282 HeapWord* | |
1283 ConcurrentMarkSweepGeneration::allocation_limit_reached(Space* space, | |
1284 HeapWord* top, | |
1285 size_t word_sz) | |
1286 { | |
1287 return collector()->allocation_limit_reached(space, top, word_sz); | |
1288 } | |
1289 | |
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1290 // IMPORTANT: Notes on object size recognition in CMS. |
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1291 // --------------------------------------------------- |
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1292 // A block of storage in the CMS generation is always in |
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1293 // one of three states. A free block (FREE), an allocated |
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1294 // object (OBJECT) whose size() method reports the correct size, |
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1295 // and an intermediate state (TRANSIENT) in which its size cannot |
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1296 // be accurately determined. |
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1297 // STATE IDENTIFICATION: (32 bit and 64 bit w/o COOPS) |
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1298 // ----------------------------------------------------- |
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1299 // FREE: klass_word & 1 == 1; mark_word holds block size |
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1300 // |
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1301 // OBJECT: klass_word installed; klass_word != 0 && klass_word & 1 == 0; |
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1302 // obj->size() computes correct size |
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1303 // |
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1304 // TRANSIENT: klass_word == 0; size is indeterminate until we become an OBJECT |
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1305 // |
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1306 // STATE IDENTIFICATION: (64 bit+COOPS) |
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1307 // ------------------------------------ |
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1308 // FREE: mark_word & CMS_FREE_BIT == 1; mark_word & ~CMS_FREE_BIT gives block_size |
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1309 // |
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1310 // OBJECT: klass_word installed; klass_word != 0; |
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1311 // obj->size() computes correct size |
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1312 // |
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1313 // TRANSIENT: klass_word == 0; size is indeterminate until we become an OBJECT |
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1314 // |
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1315 // |
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1316 // STATE TRANSITION DIAGRAM |
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1317 // |
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1318 // mut / parnew mut / parnew |
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1319 // FREE --------------------> TRANSIENT ---------------------> OBJECT --| |
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1320 // ^ | |
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1321 // |------------------------ DEAD <------------------------------------| |
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1322 // sweep mut |
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1323 // |
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1324 // While a block is in TRANSIENT state its size cannot be determined |
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1325 // so readers will either need to come back later or stall until |
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1326 // the size can be determined. Note that for the case of direct |
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1327 // allocation, P-bits, when available, may be used to determine the |
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1328 // size of an object that may not yet have been initialized. |
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1329 |
0 | 1330 // Things to support parallel young-gen collection. |
1331 oop | |
1332 ConcurrentMarkSweepGeneration::par_promote(int thread_num, | |
1333 oop old, markOop m, | |
1334 size_t word_sz) { | |
1335 #ifndef PRODUCT | |
1336 if (Universe::heap()->promotion_should_fail()) { | |
1337 return NULL; | |
1338 } | |
1339 #endif // #ifndef PRODUCT | |
1340 | |
1341 CMSParGCThreadState* ps = _par_gc_thread_states[thread_num]; | |
1342 PromotionInfo* promoInfo = &ps->promo; | |
1343 // if we are tracking promotions, then first ensure space for | |
1344 // promotion (including spooling space for saving header if necessary). | |
1345 // then allocate and copy, then track promoted info if needed. | |
1346 // When tracking (see PromotionInfo::track()), the mark word may | |
1347 // be displaced and in this case restoration of the mark word | |
1348 // occurs in the (oop_since_save_marks_)iterate phase. | |
1349 if (promoInfo->tracking() && !promoInfo->ensure_spooling_space()) { | |
1350 // Out of space for allocating spooling buffers; | |
1351 // try expanding and allocating spooling buffers. | |
1352 if (!expand_and_ensure_spooling_space(promoInfo)) { | |
1353 return NULL; | |
1354 } | |
1355 } | |
1356 assert(promoInfo->has_spooling_space(), "Control point invariant"); | |
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1357 const size_t alloc_sz = CompactibleFreeListSpace::adjustObjectSize(word_sz); |
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1358 HeapWord* obj_ptr = ps->lab.alloc(alloc_sz); |
0 | 1359 if (obj_ptr == NULL) { |
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1360 obj_ptr = expand_and_par_lab_allocate(ps, alloc_sz); |
0 | 1361 if (obj_ptr == NULL) { |
1362 return NULL; | |
1363 } | |
1364 } | |
1365 oop obj = oop(obj_ptr); | |
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1366 OrderAccess::storestore(); |
187 | 1367 assert(obj->klass_or_null() == NULL, "Object should be uninitialized here."); |
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1368 assert(!((FreeChunk*)obj_ptr)->is_free(), "Error, block will look free but show wrong size"); |
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1369 // IMPORTANT: See note on object initialization for CMS above. |
0 | 1370 // Otherwise, copy the object. Here we must be careful to insert the |
1371 // klass pointer last, since this marks the block as an allocated object. | |
187 | 1372 // Except with compressed oops it's the mark word. |
0 | 1373 HeapWord* old_ptr = (HeapWord*)old; |
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1374 // Restore the mark word copied above. |
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1375 obj->set_mark(m); |
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1376 assert(obj->klass_or_null() == NULL, "Object should be uninitialized here."); |
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1377 assert(!((FreeChunk*)obj_ptr)->is_free(), "Error, block will look free but show wrong size"); |
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1378 OrderAccess::storestore(); |
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1379 |
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1380 if (UseCompressedKlassPointers) { |
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1381 // Copy gap missed by (aligned) header size calculation below |
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1382 obj->set_klass_gap(old->klass_gap()); |
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1383 } |
0 | 1384 if (word_sz > (size_t)oopDesc::header_size()) { |
1385 Copy::aligned_disjoint_words(old_ptr + oopDesc::header_size(), | |
1386 obj_ptr + oopDesc::header_size(), | |
1387 word_sz - oopDesc::header_size()); | |
1388 } | |
187 | 1389 |
0 | 1390 // Now we can track the promoted object, if necessary. We take care |
1521 | 1391 // to delay the transition from uninitialized to full object |
0 | 1392 // (i.e., insertion of klass pointer) until after, so that it |
1393 // atomically becomes a promoted object. | |
1394 if (promoInfo->tracking()) { | |
1395 promoInfo->track((PromotedObject*)obj, old->klass()); | |
1396 } | |
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1397 assert(obj->klass_or_null() == NULL, "Object should be uninitialized here."); |
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1398 assert(!((FreeChunk*)obj_ptr)->is_free(), "Error, block will look free but show wrong size"); |
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1399 assert(old->is_oop(), "Will use and dereference old klass ptr below"); |
187 | 1400 |
1401 // Finally, install the klass pointer (this should be volatile). | |
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1402 OrderAccess::storestore(); |
0 | 1403 obj->set_klass(old->klass()); |
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1404 // We should now be able to calculate the right size for this object |
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1405 assert(obj->is_oop() && obj->size() == (int)word_sz, "Error, incorrect size computed for promoted object"); |
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1406 |
0 | 1407 collector()->promoted(true, // parallel |
1408 obj_ptr, old->is_objArray(), word_sz); | |
1409 | |
1410 NOT_PRODUCT( | |
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1411 Atomic::inc_ptr(&_numObjectsPromoted); |
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1412 Atomic::add_ptr(alloc_sz, &_numWordsPromoted); |
0 | 1413 ) |
1414 | |
1415 return obj; | |
1416 } | |
1417 | |
1418 void | |
1419 ConcurrentMarkSweepGeneration:: | |
1420 par_promote_alloc_undo(int thread_num, | |
1421 HeapWord* obj, size_t word_sz) { | |
1422 // CMS does not support promotion undo. | |
1423 ShouldNotReachHere(); | |
1424 } | |
1425 | |
1426 void | |
1427 ConcurrentMarkSweepGeneration:: | |
1428 par_promote_alloc_done(int thread_num) { | |
1429 CMSParGCThreadState* ps = _par_gc_thread_states[thread_num]; | |
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1430 ps->lab.retire(thread_num); |
0 | 1431 } |
1432 | |
1433 void | |
1434 ConcurrentMarkSweepGeneration:: | |
1435 par_oop_since_save_marks_iterate_done(int thread_num) { | |
1436 CMSParGCThreadState* ps = _par_gc_thread_states[thread_num]; | |
1437 ParScanWithoutBarrierClosure* dummy_cl = NULL; | |
1438 ps->promo.promoted_oops_iterate_nv(dummy_cl); | |
1439 } | |
1440 | |
1441 bool ConcurrentMarkSweepGeneration::should_collect(bool full, | |
1442 size_t size, | |
1443 bool tlab) | |
1444 { | |
1445 // We allow a STW collection only if a full | |
1446 // collection was requested. | |
1447 return full || should_allocate(size, tlab); // FIX ME !!! | |
1448 // This and promotion failure handling are connected at the | |
1449 // hip and should be fixed by untying them. | |
1450 } | |
1451 | |
1452 bool CMSCollector::shouldConcurrentCollect() { | |
1453 if (_full_gc_requested) { | |
1454 if (Verbose && PrintGCDetails) { | |
1455 gclog_or_tty->print_cr("CMSCollector: collect because of explicit " | |
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1456 " gc request (or gc_locker)"); |
0 | 1457 } |
1458 return true; | |
1459 } | |
1460 | |
1461 // For debugging purposes, change the type of collection. | |
1462 // If the rotation is not on the concurrent collection | |
1463 // type, don't start a concurrent collection. | |
1464 NOT_PRODUCT( | |
1465 if (RotateCMSCollectionTypes && | |
1466 (_cmsGen->debug_collection_type() != | |
1467 ConcurrentMarkSweepGeneration::Concurrent_collection_type)) { | |
1468 assert(_cmsGen->debug_collection_type() != | |
1469 ConcurrentMarkSweepGeneration::Unknown_collection_type, | |
1470 "Bad cms collection type"); | |
1471 return false; | |
1472 } | |
1473 ) | |
1474 | |
1475 FreelistLocker x(this); | |
1476 // ------------------------------------------------------------------ | |
1477 // Print out lots of information which affects the initiation of | |
1478 // a collection. | |
1479 if (PrintCMSInitiationStatistics && stats().valid()) { | |
1480 gclog_or_tty->print("CMSCollector shouldConcurrentCollect: "); | |
1481 gclog_or_tty->stamp(); | |
1482 gclog_or_tty->print_cr(""); | |
1483 stats().print_on(gclog_or_tty); | |
1484 gclog_or_tty->print_cr("time_until_cms_gen_full %3.7f", | |
1485 stats().time_until_cms_gen_full()); | |
1486 gclog_or_tty->print_cr("free="SIZE_FORMAT, _cmsGen->free()); | |
1487 gclog_or_tty->print_cr("contiguous_available="SIZE_FORMAT, | |
1488 _cmsGen->contiguous_available()); | |
1489 gclog_or_tty->print_cr("promotion_rate=%g", stats().promotion_rate()); | |
1490 gclog_or_tty->print_cr("cms_allocation_rate=%g", stats().cms_allocation_rate()); | |
1491 gclog_or_tty->print_cr("occupancy=%3.7f", _cmsGen->occupancy()); | |
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1492 gclog_or_tty->print_cr("initiatingOccupancy=%3.7f", _cmsGen->initiating_occupancy()); |
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1493 gclog_or_tty->print_cr("metadata initialized %d", |
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1494 MetaspaceGC::should_concurrent_collect()); |
0 | 1495 } |
1496 // ------------------------------------------------------------------ | |
1497 | |
1498 // If the estimated time to complete a cms collection (cms_duration()) | |
1499 // is less than the estimated time remaining until the cms generation | |
1500 // is full, start a collection. | |
1501 if (!UseCMSInitiatingOccupancyOnly) { | |
1502 if (stats().valid()) { | |
1503 if (stats().time_until_cms_start() == 0.0) { | |
1504 return true; | |
1505 } | |
1506 } else { | |
1507 // We want to conservatively collect somewhat early in order | |
1508 // to try and "bootstrap" our CMS/promotion statistics; | |
1509 // this branch will not fire after the first successful CMS | |
1510 // collection because the stats should then be valid. | |
1511 if (_cmsGen->occupancy() >= _bootstrap_occupancy) { | |
1512 if (Verbose && PrintGCDetails) { | |
1513 gclog_or_tty->print_cr( | |
1514 " CMSCollector: collect for bootstrapping statistics:" | |
1515 " occupancy = %f, boot occupancy = %f", _cmsGen->occupancy(), | |
1516 _bootstrap_occupancy); | |
1517 } | |
1518 return true; | |
1519 } | |
1520 } | |
1521 } | |
1522 | |
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1523 // Otherwise, we start a collection cycle if |
0 | 1524 // old gen want a collection cycle started. Each may use |
1525 // an appropriate criterion for making this decision. | |
1526 // XXX We need to make sure that the gen expansion | |
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1527 // criterion dovetails well with this. XXX NEED TO FIX THIS |
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1528 if (_cmsGen->should_concurrent_collect()) { |
0 | 1529 if (Verbose && PrintGCDetails) { |
1530 gclog_or_tty->print_cr("CMS old gen initiated"); | |
1531 } | |
1532 return true; | |
1533 } | |
1534 | |
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1535 // We start a collection if we believe an incremental collection may fail; |
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1536 // this is not likely to be productive in practice because it's probably too |
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1537 // late anyway. |
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1538 GenCollectedHeap* gch = GenCollectedHeap::heap(); |
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1539 assert(gch->collector_policy()->is_two_generation_policy(), |
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1540 "You may want to check the correctness of the following"); |
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1541 if (gch->incremental_collection_will_fail(true /* consult_young */)) { |
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1542 if (Verbose && PrintGCDetails) { |
94
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1543 gclog_or_tty->print("CMSCollector: collect because incremental collection will fail "); |
0 | 1544 } |
1545 return true; | |
1546 } | |
1547 | |
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1548 if (MetaspaceGC::should_concurrent_collect()) { |
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1549 if (Verbose && PrintGCDetails) { |
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1550 gclog_or_tty->print("CMSCollector: collect for metadata allocation "); |
94
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1551 } |
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1552 return true; |
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1553 } |
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1554 |
0 | 1555 return false; |
1556 } | |
1557 | |
1558 // Clear _expansion_cause fields of constituent generations | |
1559 void CMSCollector::clear_expansion_cause() { | |
1560 _cmsGen->clear_expansion_cause(); | |
1561 } | |
1562 | |
94
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1563 // We should be conservative in starting a collection cycle. To |
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1564 // start too eagerly runs the risk of collecting too often in the |
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1565 // extreme. To collect too rarely falls back on full collections, |
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1566 // which works, even if not optimum in terms of concurrent work. |
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1567 // As a work around for too eagerly collecting, use the flag |
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1568 // UseCMSInitiatingOccupancyOnly. This also has the advantage of |
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1569 // giving the user an easily understandable way of controlling the |
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1570 // collections. |
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1571 // We want to start a new collection cycle if any of the following |
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1572 // conditions hold: |
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1573 // . our current occupancy exceeds the configured initiating occupancy |
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1574 // for this generation, or |
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1575 // . we recently needed to expand this space and have not, since that |
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1576 // expansion, done a collection of this generation, or |
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1577 // . the underlying space believes that it may be a good idea to initiate |
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1578 // a concurrent collection (this may be based on criteria such as the |
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1579 // following: the space uses linear allocation and linear allocation is |
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1580 // going to fail, or there is believed to be excessive fragmentation in |
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1581 // the generation, etc... or ... |
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1582 // [.(currently done by CMSCollector::shouldConcurrentCollect() only for |
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1583 // the case of the old generation; see CR 6543076): |
94
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1584 // we may be approaching a point at which allocation requests may fail because |
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1585 // we will be out of sufficient free space given allocation rate estimates.] |
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1586 bool ConcurrentMarkSweepGeneration::should_concurrent_collect() const { |
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1587 |
0 | 1588 assert_lock_strong(freelistLock()); |
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1589 if (occupancy() > initiating_occupancy()) { |
0 | 1590 if (PrintGCDetails && Verbose) { |
1591 gclog_or_tty->print(" %s: collect because of occupancy %f / %f ", | |
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1592 short_name(), occupancy(), initiating_occupancy()); |
0 | 1593 } |
1594 return true; | |
1595 } | |
1596 if (UseCMSInitiatingOccupancyOnly) { | |
1597 return false; | |
1598 } | |
1599 if (expansion_cause() == CMSExpansionCause::_satisfy_allocation) { | |
1600 if (PrintGCDetails && Verbose) { | |
1601 gclog_or_tty->print(" %s: collect because expanded for allocation ", | |
1602 short_name()); | |
1603 } | |
1604 return true; | |
1605 } | |
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1606 if (_cmsSpace->should_concurrent_collect()) { |
0 | 1607 if (PrintGCDetails && Verbose) { |
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1608 gclog_or_tty->print(" %s: collect because cmsSpace says so ", |
0 | 1609 short_name()); |
1610 } | |
1611 return true; | |
1612 } | |
1613 return false; | |
1614 } | |
1615 | |
1616 void ConcurrentMarkSweepGeneration::collect(bool full, | |
1617 bool clear_all_soft_refs, | |
1618 size_t size, | |
1619 bool tlab) | |
1620 { | |
1621 collector()->collect(full, clear_all_soft_refs, size, tlab); | |
1622 } | |
1623 | |
1624 void CMSCollector::collect(bool full, | |
1625 bool clear_all_soft_refs, | |
1626 size_t size, | |
1627 bool tlab) | |
1628 { | |
1629 if (!UseCMSCollectionPassing && _collectorState > Idling) { | |
1630 // For debugging purposes skip the collection if the state | |
1631 // is not currently idle | |
1632 if (TraceCMSState) { | |
1633 gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " skipped full:%d CMS state %d", | |
1634 Thread::current(), full, _collectorState); | |
1635 } | |
1636 return; | |
1637 } | |
1638 | |
1639 // The following "if" branch is present for defensive reasons. | |
1640 // In the current uses of this interface, it can be replaced with: | |
1641 // assert(!GC_locker.is_active(), "Can't be called otherwise"); | |
1642 // But I am not placing that assert here to allow future | |
1643 // generality in invoking this interface. | |
1644 if (GC_locker::is_active()) { | |
1645 // A consistency test for GC_locker | |
1646 assert(GC_locker::needs_gc(), "Should have been set already"); | |
1647 // Skip this foreground collection, instead | |
1648 // expanding the heap if necessary. | |
1649 // Need the free list locks for the call to free() in compute_new_size() | |
1650 compute_new_size(); | |
1651 return; | |
1652 } | |
1653 acquire_control_and_collect(full, clear_all_soft_refs); | |
1654 _full_gcs_since_conc_gc++; | |
1655 | |
1656 } | |
1657 | |
1658 void CMSCollector::request_full_gc(unsigned int full_gc_count) { | |
1659 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
1660 unsigned int gc_count = gch->total_full_collections(); | |
1661 if (gc_count == full_gc_count) { | |
1662 MutexLockerEx y(CGC_lock, Mutex::_no_safepoint_check_flag); | |
1663 _full_gc_requested = true; | |
1664 CGC_lock->notify(); // nudge CMS thread | |
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1665 } else { |
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1666 assert(gc_count > full_gc_count, "Error: causal loop"); |
0 | 1667 } |
1668 } | |
1669 | |
1670 | |
1671 // The foreground and background collectors need to coordinate in order | |
1672 // to make sure that they do not mutually interfere with CMS collections. | |
1673 // When a background collection is active, | |
1674 // the foreground collector may need to take over (preempt) and | |
1675 // synchronously complete an ongoing collection. Depending on the | |
1676 // frequency of the background collections and the heap usage | |
1677 // of the application, this preemption can be seldom or frequent. | |
1678 // There are only certain | |
1679 // points in the background collection that the "collection-baton" | |
1680 // can be passed to the foreground collector. | |
1681 // | |
1682 // The foreground collector will wait for the baton before | |
1683 // starting any part of the collection. The foreground collector | |
1684 // will only wait at one location. | |
1685 // | |
1686 // The background collector will yield the baton before starting a new | |
1687 // phase of the collection (e.g., before initial marking, marking from roots, | |
1688 // precleaning, final re-mark, sweep etc.) This is normally done at the head | |
1689 // of the loop which switches the phases. The background collector does some | |
1690 // of the phases (initial mark, final re-mark) with the world stopped. | |
1691 // Because of locking involved in stopping the world, | |
1692 // the foreground collector should not block waiting for the background | |
1693 // collector when it is doing a stop-the-world phase. The background | |
1694 // collector will yield the baton at an additional point just before | |
1695 // it enters a stop-the-world phase. Once the world is stopped, the | |
1696 // background collector checks the phase of the collection. If the | |
1697 // phase has not changed, it proceeds with the collection. If the | |
1698 // phase has changed, it skips that phase of the collection. See | |
1699 // the comments on the use of the Heap_lock in collect_in_background(). | |
1700 // | |
1701 // Variable used in baton passing. | |
1702 // _foregroundGCIsActive - Set to true by the foreground collector when | |
1703 // it wants the baton. The foreground clears it when it has finished | |
1704 // the collection. | |
1705 // _foregroundGCShouldWait - Set to true by the background collector | |
1706 // when it is running. The foreground collector waits while | |
1707 // _foregroundGCShouldWait is true. | |
1708 // CGC_lock - monitor used to protect access to the above variables | |
1709 // and to notify the foreground and background collectors. | |
1710 // _collectorState - current state of the CMS collection. | |
1711 // | |
1712 // The foreground collector | |
1713 // acquires the CGC_lock | |
1714 // sets _foregroundGCIsActive | |
1715 // waits on the CGC_lock for _foregroundGCShouldWait to be false | |
1716 // various locks acquired in preparation for the collection | |
1717 // are released so as not to block the background collector | |
1718 // that is in the midst of a collection | |
1719 // proceeds with the collection | |
1720 // clears _foregroundGCIsActive | |
1721 // returns | |
1722 // | |
1723 // The background collector in a loop iterating on the phases of the | |
1724 // collection | |
1725 // acquires the CGC_lock | |
1726 // sets _foregroundGCShouldWait | |
1727 // if _foregroundGCIsActive is set | |
1728 // clears _foregroundGCShouldWait, notifies _CGC_lock | |
1729 // waits on _CGC_lock for _foregroundGCIsActive to become false | |
1730 // and exits the loop. | |
1731 // otherwise | |
1732 // proceed with that phase of the collection | |
1733 // if the phase is a stop-the-world phase, | |
1734 // yield the baton once more just before enqueueing | |
1735 // the stop-world CMS operation (executed by the VM thread). | |
1736 // returns after all phases of the collection are done | |
1737 // | |
1738 | |
1739 void CMSCollector::acquire_control_and_collect(bool full, | |
1740 bool clear_all_soft_refs) { | |
1741 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint"); | |
1742 assert(!Thread::current()->is_ConcurrentGC_thread(), | |
1743 "shouldn't try to acquire control from self!"); | |
1744 | |
1745 // Start the protocol for acquiring control of the | |
1746 // collection from the background collector (aka CMS thread). | |
1747 assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(), | |
1748 "VM thread should have CMS token"); | |
1749 // Remember the possibly interrupted state of an ongoing | |
1750 // concurrent collection | |
1751 CollectorState first_state = _collectorState; | |
1752 | |
1753 // Signal to a possibly ongoing concurrent collection that | |
1754 // we want to do a foreground collection. | |
1755 _foregroundGCIsActive = true; | |
1756 | |
1757 // Disable incremental mode during a foreground collection. | |
1758 ICMSDisabler icms_disabler; | |
1759 | |
1760 // release locks and wait for a notify from the background collector | |
1761 // releasing the locks in only necessary for phases which | |
1762 // do yields to improve the granularity of the collection. | |
1763 assert_lock_strong(bitMapLock()); | |
1764 // We need to lock the Free list lock for the space that we are | |
1765 // currently collecting. | |
1766 assert(haveFreelistLocks(), "Must be holding free list locks"); | |
1767 bitMapLock()->unlock(); | |
1768 releaseFreelistLocks(); | |
1769 { | |
1770 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
1771 if (_foregroundGCShouldWait) { | |
1772 // We are going to be waiting for action for the CMS thread; | |
1773 // it had better not be gone (for instance at shutdown)! | |
1774 assert(ConcurrentMarkSweepThread::cmst() != NULL, | |
1775 "CMS thread must be running"); | |
1776 // Wait here until the background collector gives us the go-ahead | |
1777 ConcurrentMarkSweepThread::clear_CMS_flag( | |
1778 ConcurrentMarkSweepThread::CMS_vm_has_token); // release token | |
1779 // Get a possibly blocked CMS thread going: | |
1780 // Note that we set _foregroundGCIsActive true above, | |
1781 // without protection of the CGC_lock. | |
1782 CGC_lock->notify(); | |
1783 assert(!ConcurrentMarkSweepThread::vm_thread_wants_cms_token(), | |
1784 "Possible deadlock"); | |
1785 while (_foregroundGCShouldWait) { | |
1786 // wait for notification | |
1787 CGC_lock->wait(Mutex::_no_safepoint_check_flag); | |
1788 // Possibility of delay/starvation here, since CMS token does | |
1789 // not know to give priority to VM thread? Actually, i think | |
1790 // there wouldn't be any delay/starvation, but the proof of | |
1791 // that "fact" (?) appears non-trivial. XXX 20011219YSR | |
1792 } | |
1793 ConcurrentMarkSweepThread::set_CMS_flag( | |
1794 ConcurrentMarkSweepThread::CMS_vm_has_token); | |
1795 } | |
1796 } | |
1797 // The CMS_token is already held. Get back the other locks. | |
1798 assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(), | |
1799 "VM thread should have CMS token"); | |
1800 getFreelistLocks(); | |
1801 bitMapLock()->lock_without_safepoint_check(); | |
1802 if (TraceCMSState) { | |
1803 gclog_or_tty->print_cr("CMS foreground collector has asked for control " | |
1804 INTPTR_FORMAT " with first state %d", Thread::current(), first_state); | |
1805 gclog_or_tty->print_cr(" gets control with state %d", _collectorState); | |
1806 } | |
1807 | |
1808 // Check if we need to do a compaction, or if not, whether | |
1809 // we need to start the mark-sweep from scratch. | |
1810 bool should_compact = false; | |
1811 bool should_start_over = false; | |
1812 decide_foreground_collection_type(clear_all_soft_refs, | |
1813 &should_compact, &should_start_over); | |
1814 | |
1815 NOT_PRODUCT( | |
1816 if (RotateCMSCollectionTypes) { | |
1817 if (_cmsGen->debug_collection_type() == | |
1818 ConcurrentMarkSweepGeneration::MSC_foreground_collection_type) { | |
1819 should_compact = true; | |
1820 } else if (_cmsGen->debug_collection_type() == | |
1821 ConcurrentMarkSweepGeneration::MS_foreground_collection_type) { | |
1822 should_compact = false; | |
1823 } | |
1824 } | |
1825 ) | |
1826 | |
1827 if (PrintGCDetails && first_state > Idling) { | |
1828 GCCause::Cause cause = GenCollectedHeap::heap()->gc_cause(); | |
1829 if (GCCause::is_user_requested_gc(cause) || | |
1830 GCCause::is_serviceability_requested_gc(cause)) { | |
1831 gclog_or_tty->print(" (concurrent mode interrupted)"); | |
1832 } else { | |
1833 gclog_or_tty->print(" (concurrent mode failure)"); | |
1834 } | |
1835 } | |
1836 | |
1837 if (should_compact) { | |
1838 // If the collection is being acquired from the background | |
1839 // collector, there may be references on the discovered | |
1840 // references lists that have NULL referents (being those | |
1841 // that were concurrently cleared by a mutator) or | |
1842 // that are no longer active (having been enqueued concurrently | |
1843 // by the mutator). | |
1844 // Scrub the list of those references because Mark-Sweep-Compact | |
1845 // code assumes referents are not NULL and that all discovered | |
1846 // Reference objects are active. | |
1847 ref_processor()->clean_up_discovered_references(); | |
1848 | |
1849 do_compaction_work(clear_all_soft_refs); | |
1850 | |
1851 // Has the GC time limit been exceeded? | |
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1852 DefNewGeneration* young_gen = _young_gen->as_DefNewGeneration(); |
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1853 size_t max_eden_size = young_gen->max_capacity() - |
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1854 young_gen->to()->capacity() - |
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1855 young_gen->from()->capacity(); |
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1856 GenCollectedHeap* gch = GenCollectedHeap::heap(); |
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1857 GCCause::Cause gc_cause = gch->gc_cause(); |
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1858 size_policy()->check_gc_overhead_limit(_young_gen->used(), |
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1859 young_gen->eden()->used(), |
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1860 _cmsGen->max_capacity(), |
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1861 max_eden_size, |
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1862 full, |
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1863 gc_cause, |
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1864 gch->collector_policy()); |
0 | 1865 } else { |
1866 do_mark_sweep_work(clear_all_soft_refs, first_state, | |
1867 should_start_over); | |
1868 } | |
1869 // Reset the expansion cause, now that we just completed | |
1870 // a collection cycle. | |
1871 clear_expansion_cause(); | |
1872 _foregroundGCIsActive = false; | |
1873 return; | |
1874 } | |
1875 | |
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1876 // Resize the tenured generation |
0 | 1877 // after obtaining the free list locks for the |
1878 // two generations. | |
1879 void CMSCollector::compute_new_size() { | |
1880 assert_locked_or_safepoint(Heap_lock); | |
1881 FreelistLocker z(this); | |
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1882 MetaspaceGC::compute_new_size(); |
0 | 1883 _cmsGen->compute_new_size(); |
1884 } | |
1885 | |
1886 // A work method used by foreground collection to determine | |
1887 // what type of collection (compacting or not, continuing or fresh) | |
1888 // it should do. | |
1889 // NOTE: the intent is to make UseCMSCompactAtFullCollection | |
1890 // and CMSCompactWhenClearAllSoftRefs the default in the future | |
1891 // and do away with the flags after a suitable period. | |
1892 void CMSCollector::decide_foreground_collection_type( | |
1893 bool clear_all_soft_refs, bool* should_compact, | |
1894 bool* should_start_over) { | |
1895 // Normally, we'll compact only if the UseCMSCompactAtFullCollection | |
1896 // flag is set, and we have either requested a System.gc() or | |
1897 // the number of full gc's since the last concurrent cycle | |
1898 // has exceeded the threshold set by CMSFullGCsBeforeCompaction, | |
1899 // or if an incremental collection has failed | |
1900 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
1901 assert(gch->collector_policy()->is_two_generation_policy(), | |
1902 "You may want to check the correctness of the following"); | |
1903 // Inform cms gen if this was due to partial collection failing. | |
1904 // The CMS gen may use this fact to determine its expansion policy. | |
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1905 if (gch->incremental_collection_will_fail(false /* don't consult_young */)) { |
0 | 1906 assert(!_cmsGen->incremental_collection_failed(), |
1907 "Should have been noticed, reacted to and cleared"); | |
1908 _cmsGen->set_incremental_collection_failed(); | |
1909 } | |
1910 *should_compact = | |
1911 UseCMSCompactAtFullCollection && | |
1912 ((_full_gcs_since_conc_gc >= CMSFullGCsBeforeCompaction) || | |
1913 GCCause::is_user_requested_gc(gch->gc_cause()) || | |
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1914 gch->incremental_collection_will_fail(true /* consult_young */)); |
0 | 1915 *should_start_over = false; |
1916 if (clear_all_soft_refs && !*should_compact) { | |
1917 // We are about to do a last ditch collection attempt | |
1918 // so it would normally make sense to do a compaction | |
1919 // to reclaim as much space as possible. | |
1920 if (CMSCompactWhenClearAllSoftRefs) { | |
1921 // Default: The rationale is that in this case either | |
1922 // we are past the final marking phase, in which case | |
1923 // we'd have to start over, or so little has been done | |
1924 // that there's little point in saving that work. Compaction | |
1925 // appears to be the sensible choice in either case. | |
1926 *should_compact = true; | |
1927 } else { | |
1928 // We have been asked to clear all soft refs, but not to | |
1929 // compact. Make sure that we aren't past the final checkpoint | |
1930 // phase, for that is where we process soft refs. If we are already | |
1931 // past that phase, we'll need to redo the refs discovery phase and | |
1932 // if necessary clear soft refs that weren't previously | |
1933 // cleared. We do so by remembering the phase in which | |
1934 // we came in, and if we are past the refs processing | |
1935 // phase, we'll choose to just redo the mark-sweep | |
1936 // collection from scratch. | |
1937 if (_collectorState > FinalMarking) { | |
1938 // We are past the refs processing phase; | |
1939 // start over and do a fresh synchronous CMS cycle | |
1940 _collectorState = Resetting; // skip to reset to start new cycle | |
1941 reset(false /* == !asynch */); | |
1942 *should_start_over = true; | |
1943 } // else we can continue a possibly ongoing current cycle | |
1944 } | |
1945 } | |
1946 } | |
1947 | |
1948 // A work method used by the foreground collector to do | |
1949 // a mark-sweep-compact. | |
1950 void CMSCollector::do_compaction_work(bool clear_all_soft_refs) { | |
1951 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
1952 TraceTime t("CMS:MSC ", PrintGCDetails && Verbose, true, gclog_or_tty); | |
1953 if (PrintGC && Verbose && !(GCCause::is_user_requested_gc(gch->gc_cause()))) { | |
1954 gclog_or_tty->print_cr("Compact ConcurrentMarkSweepGeneration after %d " | |
1955 "collections passed to foreground collector", _full_gcs_since_conc_gc); | |
1956 } | |
1957 | |
1958 // Sample collection interval time and reset for collection pause. | |
1959 if (UseAdaptiveSizePolicy) { | |
1960 size_policy()->msc_collection_begin(); | |
1961 } | |
1962 | |
1963 // Temporarily widen the span of the weak reference processing to | |
1964 // the entire heap. | |
1965 MemRegion new_span(GenCollectedHeap::heap()->reserved_region()); | |
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1966 ReferenceProcessorSpanMutator rp_mut_span(ref_processor(), new_span); |
0 | 1967 // Temporarily, clear the "is_alive_non_header" field of the |
1968 // reference processor. | |
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1969 ReferenceProcessorIsAliveMutator rp_mut_closure(ref_processor(), NULL); |
0 | 1970 // Temporarily make reference _processing_ single threaded (non-MT). |
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1971 ReferenceProcessorMTProcMutator rp_mut_mt_processing(ref_processor(), false); |
0 | 1972 // Temporarily make refs discovery atomic |
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1973 ReferenceProcessorAtomicMutator rp_mut_atomic(ref_processor(), true); |
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1974 // Temporarily make reference _discovery_ single threaded (non-MT) |
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1975 ReferenceProcessorMTDiscoveryMutator rp_mut_discovery(ref_processor(), false); |
0 | 1976 |
1977 ref_processor()->set_enqueuing_is_done(false); | |
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1978 ref_processor()->enable_discovery(false /*verify_disabled*/, false /*check_no_refs*/); |
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1979 ref_processor()->setup_policy(clear_all_soft_refs); |
0 | 1980 // If an asynchronous collection finishes, the _modUnionTable is |
1981 // all clear. If we are assuming the collection from an asynchronous | |
1982 // collection, clear the _modUnionTable. | |
1983 assert(_collectorState != Idling || _modUnionTable.isAllClear(), | |
1984 "_modUnionTable should be clear if the baton was not passed"); | |
1985 _modUnionTable.clear_all(); | |
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1986 assert(_collectorState != Idling || _ct->klass_rem_set()->mod_union_is_clear(), |
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1987 "mod union for klasses should be clear if the baton was passed"); |
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1988 _ct->klass_rem_set()->clear_mod_union(); |
0 | 1989 |
1990 // We must adjust the allocation statistics being maintained | |
1991 // in the free list space. We do so by reading and clearing | |
1992 // the sweep timer and updating the block flux rate estimates below. | |
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1993 assert(!_intra_sweep_timer.is_active(), "_intra_sweep_timer should be inactive"); |
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1994 if (_inter_sweep_timer.is_active()) { |
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1995 _inter_sweep_timer.stop(); |
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1996 // Note that we do not use this sample to update the _inter_sweep_estimate. |
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1997 _cmsGen->cmsSpace()->beginSweepFLCensus((float)(_inter_sweep_timer.seconds()), |
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1998 _inter_sweep_estimate.padded_average(), |
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1999 _intra_sweep_estimate.padded_average()); |
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2000 } |
0 | 2001 |
2002 GenMarkSweep::invoke_at_safepoint(_cmsGen->level(), | |
2003 ref_processor(), clear_all_soft_refs); | |
2004 #ifdef ASSERT | |
2005 CompactibleFreeListSpace* cms_space = _cmsGen->cmsSpace(); | |
2006 size_t free_size = cms_space->free(); | |
2007 assert(free_size == | |
2008 pointer_delta(cms_space->end(), cms_space->compaction_top()) | |
2009 * HeapWordSize, | |
2010 "All the free space should be compacted into one chunk at top"); | |
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2011 assert(cms_space->dictionary()->total_chunk_size( |
0 | 2012 debug_only(cms_space->freelistLock())) == 0 || |
2013 cms_space->totalSizeInIndexedFreeLists() == 0, | |
2014 "All the free space should be in a single chunk"); | |
2015 size_t num = cms_space->totalCount(); | |
2016 assert((free_size == 0 && num == 0) || | |
2017 (free_size > 0 && (num == 1 || num == 2)), | |
2018 "There should be at most 2 free chunks after compaction"); | |
2019 #endif // ASSERT | |
2020 _collectorState = Resetting; | |
2021 assert(_restart_addr == NULL, | |
2022 "Should have been NULL'd before baton was passed"); | |
2023 reset(false /* == !asynch */); | |
2024 _cmsGen->reset_after_compaction(); | |
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2025 _concurrent_cycles_since_last_unload = 0; |
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2026 |
0 | 2027 // Clear any data recorded in the PLAB chunk arrays. |
2028 if (_survivor_plab_array != NULL) { | |
2029 reset_survivor_plab_arrays(); | |
2030 } | |
2031 | |
2032 // Adjust the per-size allocation stats for the next epoch. | |
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2033 _cmsGen->cmsSpace()->endSweepFLCensus(sweep_count() /* fake */); |
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2034 // Restart the "inter sweep timer" for the next epoch. |
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2035 _inter_sweep_timer.reset(); |
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2036 _inter_sweep_timer.start(); |
0 | 2037 |
2038 // Sample collection pause time and reset for collection interval. | |
2039 if (UseAdaptiveSizePolicy) { | |
2040 size_policy()->msc_collection_end(gch->gc_cause()); | |
2041 } | |
2042 | |
2043 // For a mark-sweep-compact, compute_new_size() will be called | |
2044 // in the heap's do_collection() method. | |
2045 } | |
2046 | |
2047 // A work method used by the foreground collector to do | |
2048 // a mark-sweep, after taking over from a possibly on-going | |
2049 // concurrent mark-sweep collection. | |
2050 void CMSCollector::do_mark_sweep_work(bool clear_all_soft_refs, | |
2051 CollectorState first_state, bool should_start_over) { | |
2052 if (PrintGC && Verbose) { | |
2053 gclog_or_tty->print_cr("Pass concurrent collection to foreground " | |
2054 "collector with count %d", | |
2055 _full_gcs_since_conc_gc); | |
2056 } | |
2057 switch (_collectorState) { | |
2058 case Idling: | |
2059 if (first_state == Idling || should_start_over) { | |
2060 // The background GC was not active, or should | |
2061 // restarted from scratch; start the cycle. | |
2062 _collectorState = InitialMarking; | |
2063 } | |
2064 // If first_state was not Idling, then a background GC | |
2065 // was in progress and has now finished. No need to do it | |
2066 // again. Leave the state as Idling. | |
2067 break; | |
2068 case Precleaning: | |
2069 // In the foreground case don't do the precleaning since | |
2070 // it is not done concurrently and there is extra work | |
2071 // required. | |
2072 _collectorState = FinalMarking; | |
2073 } | |
2074 if (PrintGCDetails && | |
2075 (_collectorState > Idling || | |
2076 !GCCause::is_user_requested_gc(GenCollectedHeap::heap()->gc_cause()))) { | |
2077 gclog_or_tty->print(" (concurrent mode failure)"); | |
2078 } | |
2079 collect_in_foreground(clear_all_soft_refs); | |
2080 | |
2081 // For a mark-sweep, compute_new_size() will be called | |
2082 // in the heap's do_collection() method. | |
2083 } | |
2084 | |
2085 | |
2086 void CMSCollector::getFreelistLocks() const { | |
2087 // Get locks for all free lists in all generations that this | |
2088 // collector is responsible for | |
2089 _cmsGen->freelistLock()->lock_without_safepoint_check(); | |
2090 } | |
2091 | |
2092 void CMSCollector::releaseFreelistLocks() const { | |
2093 // Release locks for all free lists in all generations that this | |
2094 // collector is responsible for | |
2095 _cmsGen->freelistLock()->unlock(); | |
2096 } | |
2097 | |
2098 bool CMSCollector::haveFreelistLocks() const { | |
2099 // Check locks for all free lists in all generations that this | |
2100 // collector is responsible for | |
2101 assert_lock_strong(_cmsGen->freelistLock()); | |
2102 PRODUCT_ONLY(ShouldNotReachHere()); | |
2103 return true; | |
2104 } | |
2105 | |
2106 // A utility class that is used by the CMS collector to | |
2107 // temporarily "release" the foreground collector from its | |
2108 // usual obligation to wait for the background collector to | |
2109 // complete an ongoing phase before proceeding. | |
2110 class ReleaseForegroundGC: public StackObj { | |
2111 private: | |
2112 CMSCollector* _c; | |
2113 public: | |
2114 ReleaseForegroundGC(CMSCollector* c) : _c(c) { | |
2115 assert(_c->_foregroundGCShouldWait, "Else should not need to call"); | |
2116 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
2117 // allow a potentially blocked foreground collector to proceed | |
2118 _c->_foregroundGCShouldWait = false; | |
2119 if (_c->_foregroundGCIsActive) { | |
2120 CGC_lock->notify(); | |
2121 } | |
2122 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
2123 "Possible deadlock"); | |
2124 } | |
2125 | |
2126 ~ReleaseForegroundGC() { | |
2127 assert(!_c->_foregroundGCShouldWait, "Usage protocol violation?"); | |
2128 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
2129 _c->_foregroundGCShouldWait = true; | |
2130 } | |
2131 }; | |
2132 | |
2133 // There are separate collect_in_background and collect_in_foreground because of | |
2134 // the different locking requirements of the background collector and the | |
2135 // foreground collector. There was originally an attempt to share | |
2136 // one "collect" method between the background collector and the foreground | |
2137 // collector but the if-then-else required made it cleaner to have | |
2138 // separate methods. | |
2139 void CMSCollector::collect_in_background(bool clear_all_soft_refs) { | |
2140 assert(Thread::current()->is_ConcurrentGC_thread(), | |
2141 "A CMS asynchronous collection is only allowed on a CMS thread."); | |
2142 | |
2143 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
2144 { | |
2145 bool safepoint_check = Mutex::_no_safepoint_check_flag; | |
2146 MutexLockerEx hl(Heap_lock, safepoint_check); | |
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2147 FreelistLocker fll(this); |
0 | 2148 MutexLockerEx x(CGC_lock, safepoint_check); |
2149 if (_foregroundGCIsActive || !UseAsyncConcMarkSweepGC) { | |
2150 // The foreground collector is active or we're | |
2151 // not using asynchronous collections. Skip this | |
2152 // background collection. | |
2153 assert(!_foregroundGCShouldWait, "Should be clear"); | |
2154 return; | |
2155 } else { | |
2156 assert(_collectorState == Idling, "Should be idling before start."); | |
2157 _collectorState = InitialMarking; | |
2158 // Reset the expansion cause, now that we are about to begin | |
2159 // a new cycle. | |
2160 clear_expansion_cause(); | |
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2161 |
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2162 // Clear the MetaspaceGC flag since a concurrent collection |
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2163 // is starting but also clear it after the collection. |
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2164 MetaspaceGC::set_should_concurrent_collect(false); |
0 | 2165 } |
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2166 // Decide if we want to enable class unloading as part of the |
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2167 // ensuing concurrent GC cycle. |
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2168 update_should_unload_classes(); |
0 | 2169 _full_gc_requested = false; // acks all outstanding full gc requests |
2170 // Signal that we are about to start a collection | |
2171 gch->increment_total_full_collections(); // ... starting a collection cycle | |
2172 _collection_count_start = gch->total_full_collections(); | |
2173 } | |
2174 | |
2175 // Used for PrintGC | |
2176 size_t prev_used; | |
2177 if (PrintGC && Verbose) { | |
2178 prev_used = _cmsGen->used(); // XXXPERM | |
2179 } | |
2180 | |
2181 // The change of the collection state is normally done at this level; | |
2182 // the exceptions are phases that are executed while the world is | |
2183 // stopped. For those phases the change of state is done while the | |
2184 // world is stopped. For baton passing purposes this allows the | |
2185 // background collector to finish the phase and change state atomically. | |
2186 // The foreground collector cannot wait on a phase that is done | |
2187 // while the world is stopped because the foreground collector already | |
2188 // has the world stopped and would deadlock. | |
2189 while (_collectorState != Idling) { | |
2190 if (TraceCMSState) { | |
2191 gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " in CMS state %d", | |
2192 Thread::current(), _collectorState); | |
2193 } | |
2194 // The foreground collector | |
2195 // holds the Heap_lock throughout its collection. | |
2196 // holds the CMS token (but not the lock) | |
2197 // except while it is waiting for the background collector to yield. | |
2198 // | |
2199 // The foreground collector should be blocked (not for long) | |
2200 // if the background collector is about to start a phase | |
2201 // executed with world stopped. If the background | |
2202 // collector has already started such a phase, the | |
2203 // foreground collector is blocked waiting for the | |
2204 // Heap_lock. The stop-world phases (InitialMarking and FinalMarking) | |
2205 // are executed in the VM thread. | |
2206 // | |
2207 // The locking order is | |
2208 // PendingListLock (PLL) -- if applicable (FinalMarking) | |
2209 // Heap_lock (both this & PLL locked in VM_CMS_Operation::prologue()) | |
2210 // CMS token (claimed in | |
2211 // stop_world_and_do() --> | |
2212 // safepoint_synchronize() --> | |
2213 // CMSThread::synchronize()) | |
2214 | |
2215 { | |
2216 // Check if the FG collector wants us to yield. | |
2217 CMSTokenSync x(true); // is cms thread | |
2218 if (waitForForegroundGC()) { | |
2219 // We yielded to a foreground GC, nothing more to be | |
2220 // done this round. | |
2221 assert(_foregroundGCShouldWait == false, "We set it to false in " | |
2222 "waitForForegroundGC()"); | |
2223 if (TraceCMSState) { | |
2224 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT | |
2225 " exiting collection CMS state %d", | |
2226 Thread::current(), _collectorState); | |
2227 } | |
2228 return; | |
2229 } else { | |
2230 // The background collector can run but check to see if the | |
2231 // foreground collector has done a collection while the | |
2232 // background collector was waiting to get the CGC_lock | |
2233 // above. If yes, break so that _foregroundGCShouldWait | |
2234 // is cleared before returning. | |
2235 if (_collectorState == Idling) { | |
2236 break; | |
2237 } | |
2238 } | |
2239 } | |
2240 | |
2241 assert(_foregroundGCShouldWait, "Foreground collector, if active, " | |
2242 "should be waiting"); | |
2243 | |
2244 switch (_collectorState) { | |
2245 case InitialMarking: | |
2246 { | |
2247 ReleaseForegroundGC x(this); | |
2248 stats().record_cms_begin(); | |
2249 | |
2250 VM_CMS_Initial_Mark initial_mark_op(this); | |
2251 VMThread::execute(&initial_mark_op); | |
2252 } | |
2253 // The collector state may be any legal state at this point | |
2254 // since the background collector may have yielded to the | |
2255 // foreground collector. | |
2256 break; | |
2257 case Marking: | |
2258 // initial marking in checkpointRootsInitialWork has been completed | |
2259 if (markFromRoots(true)) { // we were successful | |
2260 assert(_collectorState == Precleaning, "Collector state should " | |
2261 "have changed"); | |
2262 } else { | |
2263 assert(_foregroundGCIsActive, "Internal state inconsistency"); | |
2264 } | |
2265 break; | |
2266 case Precleaning: | |
2267 if (UseAdaptiveSizePolicy) { | |
2268 size_policy()->concurrent_precleaning_begin(); | |
2269 } | |
2270 // marking from roots in markFromRoots has been completed | |
2271 preclean(); | |
2272 if (UseAdaptiveSizePolicy) { | |
2273 size_policy()->concurrent_precleaning_end(); | |
2274 } | |
2275 assert(_collectorState == AbortablePreclean || | |
2276 _collectorState == FinalMarking, | |
2277 "Collector state should have changed"); | |
2278 break; | |
2279 case AbortablePreclean: | |
2280 if (UseAdaptiveSizePolicy) { | |
2281 size_policy()->concurrent_phases_resume(); | |
2282 } | |
2283 abortable_preclean(); | |
2284 if (UseAdaptiveSizePolicy) { | |
2285 size_policy()->concurrent_precleaning_end(); | |
2286 } | |
2287 assert(_collectorState == FinalMarking, "Collector state should " | |
2288 "have changed"); | |
2289 break; | |
2290 case FinalMarking: | |
2291 { | |
2292 ReleaseForegroundGC x(this); | |
2293 | |
2294 VM_CMS_Final_Remark final_remark_op(this); | |
2295 VMThread::execute(&final_remark_op); | |
935 | 2296 } |
0 | 2297 assert(_foregroundGCShouldWait, "block post-condition"); |
2298 break; | |
2299 case Sweeping: | |
2300 if (UseAdaptiveSizePolicy) { | |
2301 size_policy()->concurrent_sweeping_begin(); | |
2302 } | |
2303 // final marking in checkpointRootsFinal has been completed | |
2304 sweep(true); | |
2305 assert(_collectorState == Resizing, "Collector state change " | |
2306 "to Resizing must be done under the free_list_lock"); | |
2307 _full_gcs_since_conc_gc = 0; | |
2308 | |
2309 // Stop the timers for adaptive size policy for the concurrent phases | |
2310 if (UseAdaptiveSizePolicy) { | |
2311 size_policy()->concurrent_sweeping_end(); | |
2312 size_policy()->concurrent_phases_end(gch->gc_cause(), | |
2313 gch->prev_gen(_cmsGen)->capacity(), | |
2314 _cmsGen->free()); | |
2315 } | |
2316 | |
2317 case Resizing: { | |
2318 // Sweeping has been completed... | |
2319 // At this point the background collection has completed. | |
2320 // Don't move the call to compute_new_size() down | |
2321 // into code that might be executed if the background | |
2322 // collection was preempted. | |
2323 { | |
2324 ReleaseForegroundGC x(this); // unblock FG collection | |
2325 MutexLockerEx y(Heap_lock, Mutex::_no_safepoint_check_flag); | |
2326 CMSTokenSync z(true); // not strictly needed. | |
2327 if (_collectorState == Resizing) { | |
2328 compute_new_size(); | |
2329 _collectorState = Resetting; | |
2330 } else { | |
2331 assert(_collectorState == Idling, "The state should only change" | |
2332 " because the foreground collector has finished the collection"); | |
2333 } | |
2334 } | |
2335 break; | |
2336 } | |
2337 case Resetting: | |
2338 // CMS heap resizing has been completed | |
2339 reset(true); | |
2340 assert(_collectorState == Idling, "Collector state should " | |
2341 "have changed"); | |
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2342 |
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2343 MetaspaceGC::set_should_concurrent_collect(false); |
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2344 |
0 | 2345 stats().record_cms_end(); |
2346 // Don't move the concurrent_phases_end() and compute_new_size() | |
2347 // calls to here because a preempted background collection | |
2348 // has it's state set to "Resetting". | |
2349 break; | |
2350 case Idling: | |
2351 default: | |
2352 ShouldNotReachHere(); | |
2353 break; | |
2354 } | |
2355 if (TraceCMSState) { | |
2356 gclog_or_tty->print_cr(" Thread " INTPTR_FORMAT " done - next CMS state %d", | |
2357 Thread::current(), _collectorState); | |
2358 } | |
2359 assert(_foregroundGCShouldWait, "block post-condition"); | |
2360 } | |
2361 | |
2362 // Should this be in gc_epilogue? | |
2363 collector_policy()->counters()->update_counters(); | |
2364 | |
2365 { | |
2366 // Clear _foregroundGCShouldWait and, in the event that the | |
2367 // foreground collector is waiting, notify it, before | |
2368 // returning. | |
2369 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
2370 _foregroundGCShouldWait = false; | |
2371 if (_foregroundGCIsActive) { | |
2372 CGC_lock->notify(); | |
2373 } | |
2374 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
2375 "Possible deadlock"); | |
2376 } | |
2377 if (TraceCMSState) { | |
2378 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT | |
2379 " exiting collection CMS state %d", | |
2380 Thread::current(), _collectorState); | |
2381 } | |
2382 if (PrintGC && Verbose) { | |
2383 _cmsGen->print_heap_change(prev_used); | |
2384 } | |
2385 } | |
2386 | |
2387 void CMSCollector::collect_in_foreground(bool clear_all_soft_refs) { | |
2388 assert(_foregroundGCIsActive && !_foregroundGCShouldWait, | |
2389 "Foreground collector should be waiting, not executing"); | |
2390 assert(Thread::current()->is_VM_thread(), "A foreground collection" | |
2391 "may only be done by the VM Thread with the world stopped"); | |
2392 assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(), | |
2393 "VM thread should have CMS token"); | |
2394 | |
2395 NOT_PRODUCT(TraceTime t("CMS:MS (foreground) ", PrintGCDetails && Verbose, | |
2396 true, gclog_or_tty);) | |
2397 if (UseAdaptiveSizePolicy) { | |
2398 size_policy()->ms_collection_begin(); | |
2399 } | |
2400 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact); | |
2401 | |
2402 HandleMark hm; // Discard invalid handles created during verification | |
2403 | |
2404 if (VerifyBeforeGC && | |
2405 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
2406 Universe::verify(true); | |
2407 } | |
2408 | |
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2409 // Snapshot the soft reference policy to be used in this collection cycle. |
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2410 ref_processor()->setup_policy(clear_all_soft_refs); |
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2411 |
0 | 2412 bool init_mark_was_synchronous = false; // until proven otherwise |
2413 while (_collectorState != Idling) { | |
2414 if (TraceCMSState) { | |
2415 gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " in CMS state %d", | |
2416 Thread::current(), _collectorState); | |
2417 } | |
2418 switch (_collectorState) { | |
2419 case InitialMarking: | |
2420 init_mark_was_synchronous = true; // fact to be exploited in re-mark | |
2421 checkpointRootsInitial(false); | |
2422 assert(_collectorState == Marking, "Collector state should have changed" | |
2423 " within checkpointRootsInitial()"); | |
2424 break; | |
2425 case Marking: | |
2426 // initial marking in checkpointRootsInitialWork has been completed | |
2427 if (VerifyDuringGC && | |
2428 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
2429 gclog_or_tty->print("Verify before initial mark: "); | |
2430 Universe::verify(true); | |
2431 } | |
2432 { | |
2433 bool res = markFromRoots(false); | |
2434 assert(res && _collectorState == FinalMarking, "Collector state should " | |
2435 "have changed"); | |
2436 break; | |
2437 } | |
2438 case FinalMarking: | |
2439 if (VerifyDuringGC && | |
2440 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
2441 gclog_or_tty->print("Verify before re-mark: "); | |
2442 Universe::verify(true); | |
2443 } | |
2444 checkpointRootsFinal(false, clear_all_soft_refs, | |
2445 init_mark_was_synchronous); | |
2446 assert(_collectorState == Sweeping, "Collector state should not " | |
2447 "have changed within checkpointRootsFinal()"); | |
2448 break; | |
2449 case Sweeping: | |
2450 // final marking in checkpointRootsFinal has been completed | |
2451 if (VerifyDuringGC && | |
2452 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
2453 gclog_or_tty->print("Verify before sweep: "); | |
2454 Universe::verify(true); | |
2455 } | |
2456 sweep(false); | |
2457 assert(_collectorState == Resizing, "Incorrect state"); | |
2458 break; | |
2459 case Resizing: { | |
2460 // Sweeping has been completed; the actual resize in this case | |
2461 // is done separately; nothing to be done in this state. | |
2462 _collectorState = Resetting; | |
2463 break; | |
2464 } | |
2465 case Resetting: | |
2466 // The heap has been resized. | |
2467 if (VerifyDuringGC && | |
2468 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
2469 gclog_or_tty->print("Verify before reset: "); | |
2470 Universe::verify(true); | |
2471 } | |
2472 reset(false); | |
2473 assert(_collectorState == Idling, "Collector state should " | |
2474 "have changed"); | |
2475 break; | |
2476 case Precleaning: | |
2477 case AbortablePreclean: | |
2478 // Elide the preclean phase | |
2479 _collectorState = FinalMarking; | |
2480 break; | |
2481 default: | |
2482 ShouldNotReachHere(); | |
2483 } | |
2484 if (TraceCMSState) { | |
2485 gclog_or_tty->print_cr(" Thread " INTPTR_FORMAT " done - next CMS state %d", | |
2486 Thread::current(), _collectorState); | |
2487 } | |
2488 } | |
2489 | |
2490 if (UseAdaptiveSizePolicy) { | |
2491 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
2492 size_policy()->ms_collection_end(gch->gc_cause()); | |
2493 } | |
2494 | |
2495 if (VerifyAfterGC && | |
2496 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
2497 Universe::verify(true); | |
2498 } | |
2499 if (TraceCMSState) { | |
2500 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT | |
2501 " exiting collection CMS state %d", | |
2502 Thread::current(), _collectorState); | |
2503 } | |
2504 } | |
2505 | |
2506 bool CMSCollector::waitForForegroundGC() { | |
2507 bool res = false; | |
2508 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
2509 "CMS thread should have CMS token"); | |
2510 // Block the foreground collector until the | |
2511 // background collectors decides whether to | |
2512 // yield. | |
2513 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
2514 _foregroundGCShouldWait = true; | |
2515 if (_foregroundGCIsActive) { | |
2516 // The background collector yields to the | |
2517 // foreground collector and returns a value | |
2518 // indicating that it has yielded. The foreground | |
2519 // collector can proceed. | |
2520 res = true; | |
2521 _foregroundGCShouldWait = false; | |
2522 ConcurrentMarkSweepThread::clear_CMS_flag( | |
2523 ConcurrentMarkSweepThread::CMS_cms_has_token); | |
2524 ConcurrentMarkSweepThread::set_CMS_flag( | |
2525 ConcurrentMarkSweepThread::CMS_cms_wants_token); | |
2526 // Get a possibly blocked foreground thread going | |
2527 CGC_lock->notify(); | |
2528 if (TraceCMSState) { | |
2529 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT " waiting at CMS state %d", | |
2530 Thread::current(), _collectorState); | |
2531 } | |
2532 while (_foregroundGCIsActive) { | |
2533 CGC_lock->wait(Mutex::_no_safepoint_check_flag); | |
2534 } | |
2535 ConcurrentMarkSweepThread::set_CMS_flag( | |
2536 ConcurrentMarkSweepThread::CMS_cms_has_token); | |
2537 ConcurrentMarkSweepThread::clear_CMS_flag( | |
2538 ConcurrentMarkSweepThread::CMS_cms_wants_token); | |
2539 } | |
2540 if (TraceCMSState) { | |
2541 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT " continuing at CMS state %d", | |
2542 Thread::current(), _collectorState); | |
2543 } | |
2544 return res; | |
2545 } | |
2546 | |
2547 // Because of the need to lock the free lists and other structures in | |
2548 // the collector, common to all the generations that the collector is | |
2549 // collecting, we need the gc_prologues of individual CMS generations | |
2550 // delegate to their collector. It may have been simpler had the | |
2551 // current infrastructure allowed one to call a prologue on a | |
2552 // collector. In the absence of that we have the generation's | |
2553 // prologue delegate to the collector, which delegates back | |
2554 // some "local" work to a worker method in the individual generations | |
2555 // that it's responsible for collecting, while itself doing any | |
2556 // work common to all generations it's responsible for. A similar | |
2557 // comment applies to the gc_epilogue()'s. | |
2558 // The role of the varaible _between_prologue_and_epilogue is to | |
2559 // enforce the invocation protocol. | |
2560 void CMSCollector::gc_prologue(bool full) { | |
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2561 // Call gc_prologue_work() for the CMSGen |
0 | 2562 // we are responsible for. |
2563 | |
2564 // The following locking discipline assumes that we are only called | |
2565 // when the world is stopped. | |
2566 assert(SafepointSynchronize::is_at_safepoint(), "world is stopped assumption"); | |
2567 | |
2568 // The CMSCollector prologue must call the gc_prologues for the | |
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2569 // "generations" that it's responsible |
0 | 2570 // for. |
2571 | |
2572 assert( Thread::current()->is_VM_thread() | |
2573 || ( CMSScavengeBeforeRemark | |
2574 && Thread::current()->is_ConcurrentGC_thread()), | |
2575 "Incorrect thread type for prologue execution"); | |
2576 | |
2577 if (_between_prologue_and_epilogue) { | |
2578 // We have already been invoked; this is a gc_prologue delegation | |
2579 // from yet another CMS generation that we are responsible for, just | |
2580 // ignore it since all relevant work has already been done. | |
2581 return; | |
2582 } | |
2583 | |
2584 // set a bit saying prologue has been called; cleared in epilogue | |
2585 _between_prologue_and_epilogue = true; | |
2586 // Claim locks for common data structures, then call gc_prologue_work() | |
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2587 // for each CMSGen. |
0 | 2588 |
2589 getFreelistLocks(); // gets free list locks on constituent spaces | |
2590 bitMapLock()->lock_without_safepoint_check(); | |
2591 | |
2592 // Should call gc_prologue_work() for all cms gens we are responsible for | |
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2593 bool duringMarking = _collectorState >= Marking |
0 | 2594 && _collectorState < Sweeping; |
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2595 |
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2596 // The young collections clear the modified oops state, which tells if |
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2597 // there are any modified oops in the class. The remark phase also needs |
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2598 // that information. Tell the young collection to save the union of all |
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2599 // modified klasses. |
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2600 if (duringMarking) { |
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2601 _ct->klass_rem_set()->set_accumulate_modified_oops(true); |
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2602 } |
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2603 |
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2604 bool registerClosure = duringMarking; |
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2605 |
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2606 ModUnionClosure* muc = CollectedHeap::use_parallel_gc_threads() ? |
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2607 &_modUnionClosurePar |
0 | 2608 : &_modUnionClosure; |
2609 _cmsGen->gc_prologue_work(full, registerClosure, muc); | |
2610 | |
2611 if (!full) { | |
2612 stats().record_gc0_begin(); | |
2613 } | |
2614 } | |
2615 | |
2616 void ConcurrentMarkSweepGeneration::gc_prologue(bool full) { | |
2617 // Delegate to CMScollector which knows how to coordinate between | |
2618 // this and any other CMS generations that it is responsible for | |
2619 // collecting. | |
2620 collector()->gc_prologue(full); | |
2621 } | |
2622 | |
2623 // This is a "private" interface for use by this generation's CMSCollector. | |
2624 // Not to be called directly by any other entity (for instance, | |
2625 // GenCollectedHeap, which calls the "public" gc_prologue method above). | |
2626 void ConcurrentMarkSweepGeneration::gc_prologue_work(bool full, | |
2627 bool registerClosure, ModUnionClosure* modUnionClosure) { | |
2628 assert(!incremental_collection_failed(), "Shouldn't be set yet"); | |
2629 assert(cmsSpace()->preconsumptionDirtyCardClosure() == NULL, | |
2630 "Should be NULL"); | |
2631 if (registerClosure) { | |
2632 cmsSpace()->setPreconsumptionDirtyCardClosure(modUnionClosure); | |
2633 } | |
2634 cmsSpace()->gc_prologue(); | |
2635 // Clear stat counters | |
2636 NOT_PRODUCT( | |
2637 assert(_numObjectsPromoted == 0, "check"); | |
2638 assert(_numWordsPromoted == 0, "check"); | |
2639 if (Verbose && PrintGC) { | |
2640 gclog_or_tty->print("Allocated "SIZE_FORMAT" objects, " | |
2641 SIZE_FORMAT" bytes concurrently", | |
2642 _numObjectsAllocated, _numWordsAllocated*sizeof(HeapWord)); | |
2643 } | |
2644 _numObjectsAllocated = 0; | |
2645 _numWordsAllocated = 0; | |
2646 ) | |
2647 } | |
2648 | |
2649 void CMSCollector::gc_epilogue(bool full) { | |
2650 // The following locking discipline assumes that we are only called | |
2651 // when the world is stopped. | |
2652 assert(SafepointSynchronize::is_at_safepoint(), | |
2653 "world is stopped assumption"); | |
2654 | |
2655 // Currently the CMS epilogue (see CompactibleFreeListSpace) merely checks | |
2656 // if linear allocation blocks need to be appropriately marked to allow the | |
2657 // the blocks to be parsable. We also check here whether we need to nudge the | |
2658 // CMS collector thread to start a new cycle (if it's not already active). | |
2659 assert( Thread::current()->is_VM_thread() | |
2660 || ( CMSScavengeBeforeRemark | |
2661 && Thread::current()->is_ConcurrentGC_thread()), | |
2662 "Incorrect thread type for epilogue execution"); | |
2663 | |
2664 if (!_between_prologue_and_epilogue) { | |
2665 // We have already been invoked; this is a gc_epilogue delegation | |
2666 // from yet another CMS generation that we are responsible for, just | |
2667 // ignore it since all relevant work has already been done. | |
2668 return; | |
2669 } | |
2670 assert(haveFreelistLocks(), "must have freelist locks"); | |
2671 assert_lock_strong(bitMapLock()); | |
2672 | |
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2673 _ct->klass_rem_set()->set_accumulate_modified_oops(false); |
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2674 |
0 | 2675 _cmsGen->gc_epilogue_work(full); |
2676 | |
2677 if (_collectorState == AbortablePreclean || _collectorState == Precleaning) { | |
2678 // in case sampling was not already enabled, enable it | |
2679 _start_sampling = true; | |
2680 } | |
2681 // reset _eden_chunk_array so sampling starts afresh | |
2682 _eden_chunk_index = 0; | |
2683 | |
2684 size_t cms_used = _cmsGen->cmsSpace()->used(); | |
2685 | |
2686 // update performance counters - this uses a special version of | |
2687 // update_counters() that allows the utilization to be passed as a | |
2688 // parameter, avoiding multiple calls to used(). | |
2689 // | |
2690 _cmsGen->update_counters(cms_used); | |
2691 | |
2692 if (CMSIncrementalMode) { | |
2693 icms_update_allocation_limits(); | |
2694 } | |
2695 | |
2696 bitMapLock()->unlock(); | |
2697 releaseFreelistLocks(); | |
2698 | |
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2699 if (!CleanChunkPoolAsync) { |
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2700 Chunk::clean_chunk_pool(); |
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2701 } |
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2702 |
0 | 2703 _between_prologue_and_epilogue = false; // ready for next cycle |
2704 } | |
2705 | |
2706 void ConcurrentMarkSweepGeneration::gc_epilogue(bool full) { | |
2707 collector()->gc_epilogue(full); | |
2708 | |
2709 // Also reset promotion tracking in par gc thread states. | |
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2710 if (CollectedHeap::use_parallel_gc_threads()) { |
0 | 2711 for (uint i = 0; i < ParallelGCThreads; i++) { |
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2712 _par_gc_thread_states[i]->promo.stopTrackingPromotions(i); |
0 | 2713 } |
2714 } | |
2715 } | |
2716 | |
2717 void ConcurrentMarkSweepGeneration::gc_epilogue_work(bool full) { | |
2718 assert(!incremental_collection_failed(), "Should have been cleared"); | |
2719 cmsSpace()->setPreconsumptionDirtyCardClosure(NULL); | |
2720 cmsSpace()->gc_epilogue(); | |
2721 // Print stat counters | |
2722 NOT_PRODUCT( | |
2723 assert(_numObjectsAllocated == 0, "check"); | |
2724 assert(_numWordsAllocated == 0, "check"); | |
2725 if (Verbose && PrintGC) { | |
2726 gclog_or_tty->print("Promoted "SIZE_FORMAT" objects, " | |
2727 SIZE_FORMAT" bytes", | |
2728 _numObjectsPromoted, _numWordsPromoted*sizeof(HeapWord)); | |
2729 } | |
2730 _numObjectsPromoted = 0; | |
2731 _numWordsPromoted = 0; | |
2732 ) | |
2733 | |
2734 if (PrintGC && Verbose) { | |
2735 // Call down the chain in contiguous_available needs the freelistLock | |
2736 // so print this out before releasing the freeListLock. | |
2737 gclog_or_tty->print(" Contiguous available "SIZE_FORMAT" bytes ", | |
2738 contiguous_available()); | |
2739 } | |
2740 } | |
2741 | |
2742 #ifndef PRODUCT | |
2743 bool CMSCollector::have_cms_token() { | |
2744 Thread* thr = Thread::current(); | |
2745 if (thr->is_VM_thread()) { | |
2746 return ConcurrentMarkSweepThread::vm_thread_has_cms_token(); | |
2747 } else if (thr->is_ConcurrentGC_thread()) { | |
2748 return ConcurrentMarkSweepThread::cms_thread_has_cms_token(); | |
2749 } else if (thr->is_GC_task_thread()) { | |
2750 return ConcurrentMarkSweepThread::vm_thread_has_cms_token() && | |
2751 ParGCRareEvent_lock->owned_by_self(); | |
2752 } | |
2753 return false; | |
2754 } | |
2755 #endif | |
2756 | |
2757 // Check reachability of the given heap address in CMS generation, | |
2758 // treating all other generations as roots. | |
2759 bool CMSCollector::is_cms_reachable(HeapWord* addr) { | |
2760 // We could "guarantee" below, rather than assert, but i'll | |
2761 // leave these as "asserts" so that an adventurous debugger | |
2762 // could try this in the product build provided some subset of | |
2763 // the conditions were met, provided they were intersted in the | |
2764 // results and knew that the computation below wouldn't interfere | |
2765 // with other concurrent computations mutating the structures | |
2766 // being read or written. | |
2767 assert(SafepointSynchronize::is_at_safepoint(), | |
2768 "Else mutations in object graph will make answer suspect"); | |
2769 assert(have_cms_token(), "Should hold cms token"); | |
2770 assert(haveFreelistLocks(), "must hold free list locks"); | |
2771 assert_lock_strong(bitMapLock()); | |
2772 | |
2773 // Clear the marking bit map array before starting, but, just | |
2774 // for kicks, first report if the given address is already marked | |
2775 gclog_or_tty->print_cr("Start: Address 0x%x is%s marked", addr, | |
2776 _markBitMap.isMarked(addr) ? "" : " not"); | |
2777 | |
2778 if (verify_after_remark()) { | |
2779 MutexLockerEx x(verification_mark_bm()->lock(), Mutex::_no_safepoint_check_flag); | |
2780 bool result = verification_mark_bm()->isMarked(addr); | |
2781 gclog_or_tty->print_cr("TransitiveMark: Address 0x%x %s marked", addr, | |
2782 result ? "IS" : "is NOT"); | |
2783 return result; | |
2784 } else { | |
2785 gclog_or_tty->print_cr("Could not compute result"); | |
2786 return false; | |
2787 } | |
2788 } | |
2789 | |
2790 //////////////////////////////////////////////////////// | |
2791 // CMS Verification Support | |
2792 //////////////////////////////////////////////////////// | |
2793 // Following the remark phase, the following invariant | |
2794 // should hold -- each object in the CMS heap which is | |
2795 // marked in markBitMap() should be marked in the verification_mark_bm(). | |
2796 | |
2797 class VerifyMarkedClosure: public BitMapClosure { | |
2798 CMSBitMap* _marks; | |
2799 bool _failed; | |
2800 | |
2801 public: | |
2802 VerifyMarkedClosure(CMSBitMap* bm): _marks(bm), _failed(false) {} | |
2803 | |
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2804 bool do_bit(size_t offset) { |
0 | 2805 HeapWord* addr = _marks->offsetToHeapWord(offset); |
2806 if (!_marks->isMarked(addr)) { | |
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2807 oop(addr)->print_on(gclog_or_tty); |
0 | 2808 gclog_or_tty->print_cr(" ("INTPTR_FORMAT" should have been marked)", addr); |
2809 _failed = true; | |
2810 } | |
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2811 return true; |
0 | 2812 } |
2813 | |
2814 bool failed() { return _failed; } | |
2815 }; | |
2816 | |
2817 bool CMSCollector::verify_after_remark() { | |
2818 gclog_or_tty->print(" [Verifying CMS Marking... "); | |
2819 MutexLockerEx ml(verification_mark_bm()->lock(), Mutex::_no_safepoint_check_flag); | |
2820 static bool init = false; | |
2821 | |
2822 assert(SafepointSynchronize::is_at_safepoint(), | |
2823 "Else mutations in object graph will make answer suspect"); | |
2824 assert(have_cms_token(), | |
2825 "Else there may be mutual interference in use of " | |
2826 " verification data structures"); | |
2827 assert(_collectorState > Marking && _collectorState <= Sweeping, | |
2828 "Else marking info checked here may be obsolete"); | |
2829 assert(haveFreelistLocks(), "must hold free list locks"); | |
2830 assert_lock_strong(bitMapLock()); | |
2831 | |
2832 | |
2833 // Allocate marking bit map if not already allocated | |
2834 if (!init) { // first time | |
2835 if (!verification_mark_bm()->allocate(_span)) { | |
2836 return false; | |
2837 } | |
2838 init = true; | |
2839 } | |
2840 | |
2841 assert(verification_mark_stack()->isEmpty(), "Should be empty"); | |
2842 | |
2843 // Turn off refs discovery -- so we will be tracing through refs. | |
2844 // This is as intended, because by this time | |
2845 // GC must already have cleared any refs that need to be cleared, | |
2846 // and traced those that need to be marked; moreover, | |
2847 // the marking done here is not going to intefere in any | |
2848 // way with the marking information used by GC. | |
2849 NoRefDiscovery no_discovery(ref_processor()); | |
2850 | |
2851 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;) | |
2852 | |
2853 // Clear any marks from a previous round | |
2854 verification_mark_bm()->clear_all(); | |
2855 assert(verification_mark_stack()->isEmpty(), "markStack should be empty"); | |
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2856 verify_work_stacks_empty(); |
0 | 2857 |
2858 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
2859 gch->ensure_parsability(false); // fill TLABs, but no need to retire them | |
2860 // Update the saved marks which may affect the root scans. | |
2861 gch->save_marks(); | |
2862 | |
2863 if (CMSRemarkVerifyVariant == 1) { | |
2864 // In this first variant of verification, we complete | |
2865 // all marking, then check if the new marks-verctor is | |
2866 // a subset of the CMS marks-vector. | |
2867 verify_after_remark_work_1(); | |
2868 } else if (CMSRemarkVerifyVariant == 2) { | |
2869 // In this second variant of verification, we flag an error | |
2870 // (i.e. an object reachable in the new marks-vector not reachable | |
2871 // in the CMS marks-vector) immediately, also indicating the | |
2872 // identify of an object (A) that references the unmarked object (B) -- | |
2873 // presumably, a mutation to A failed to be picked up by preclean/remark? | |
2874 verify_after_remark_work_2(); | |
2875 } else { | |
2876 warning("Unrecognized value %d for CMSRemarkVerifyVariant", | |
2877 CMSRemarkVerifyVariant); | |
2878 } | |
2879 gclog_or_tty->print(" done] "); | |
2880 return true; | |
2881 } | |
2882 | |
2883 void CMSCollector::verify_after_remark_work_1() { | |
2884 ResourceMark rm; | |
2885 HandleMark hm; | |
2886 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
2887 | |
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2888 // Get a clear set of claim bits for the strong roots processing to work with. |
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2889 ClassLoaderDataGraph::clear_claimed_marks(); |
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2890 |
0 | 2891 // Mark from roots one level into CMS |
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2892 MarkRefsIntoClosure notOlder(_span, verification_mark_bm()); |
0 | 2893 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. |
2894 | |
2895 gch->gen_process_strong_roots(_cmsGen->level(), | |
2896 true, // younger gens are roots | |
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2897 true, // activate StrongRootsScope |
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2898 false, // not scavenging |
0 | 2899 SharedHeap::ScanningOption(roots_scanning_options()), |
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2900 ¬Older, |
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2901 true, // walk code active on stacks |
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2902 NULL, |
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2903 NULL); // SSS: Provide correct closure |
0 | 2904 |
2905 // Now mark from the roots | |
2906 MarkFromRootsClosure markFromRootsClosure(this, _span, | |
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2907 verification_mark_bm(), verification_mark_stack(), |
0 | 2908 false /* don't yield */, true /* verifying */); |
2909 assert(_restart_addr == NULL, "Expected pre-condition"); | |
2910 verification_mark_bm()->iterate(&markFromRootsClosure); | |
2911 while (_restart_addr != NULL) { | |
2912 // Deal with stack overflow: by restarting at the indicated | |
2913 // address. | |
2914 HeapWord* ra = _restart_addr; | |
2915 markFromRootsClosure.reset(ra); | |
2916 _restart_addr = NULL; | |
2917 verification_mark_bm()->iterate(&markFromRootsClosure, ra, _span.end()); | |
2918 } | |
2919 assert(verification_mark_stack()->isEmpty(), "Should have been drained"); | |
2920 verify_work_stacks_empty(); | |
2921 | |
2922 // Marking completed -- now verify that each bit marked in | |
2923 // verification_mark_bm() is also marked in markBitMap(); flag all | |
2924 // errors by printing corresponding objects. | |
2925 VerifyMarkedClosure vcl(markBitMap()); | |
2926 verification_mark_bm()->iterate(&vcl); | |
2927 if (vcl.failed()) { | |
2928 gclog_or_tty->print("Verification failed"); | |
1145
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2929 Universe::heap()->print_on(gclog_or_tty); |
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2930 fatal("CMS: failed marking verification after remark"); |
0 | 2931 } |
2932 } | |
2933 | |
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2934 class VerifyKlassOopsKlassClosure : public KlassClosure { |
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2935 class VerifyKlassOopsClosure : public OopClosure { |
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2936 CMSBitMap* _bitmap; |
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2937 public: |
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2938 VerifyKlassOopsClosure(CMSBitMap* bitmap) : _bitmap(bitmap) { } |
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2939 void do_oop(oop* p) { guarantee(*p == NULL || _bitmap->isMarked((HeapWord*) *p), "Should be marked"); } |
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2940 void do_oop(narrowOop* p) { ShouldNotReachHere(); } |
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2941 } _oop_closure; |
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2942 public: |
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2943 VerifyKlassOopsKlassClosure(CMSBitMap* bitmap) : _oop_closure(bitmap) {} |
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2944 void do_klass(Klass* k) { |
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2945 k->oops_do(&_oop_closure); |
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2946 } |
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2947 }; |
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2948 |
0 | 2949 void CMSCollector::verify_after_remark_work_2() { |
2950 ResourceMark rm; | |
2951 HandleMark hm; | |
2952 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
2953 | |
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2954 // Get a clear set of claim bits for the strong roots processing to work with. |
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2955 ClassLoaderDataGraph::clear_claimed_marks(); |
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2956 |
0 | 2957 // Mark from roots one level into CMS |
2958 MarkRefsIntoVerifyClosure notOlder(_span, verification_mark_bm(), | |
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2959 markBitMap()); |
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2960 CMKlassClosure klass_closure(¬Older); |
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2961 |
0 | 2962 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. |
2963 gch->gen_process_strong_roots(_cmsGen->level(), | |
2964 true, // younger gens are roots | |
989
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2965 true, // activate StrongRootsScope |
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2966 false, // not scavenging |
0 | 2967 SharedHeap::ScanningOption(roots_scanning_options()), |
989
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2968 ¬Older, |
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2969 true, // walk code active on stacks |
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2970 NULL, |
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2971 &klass_closure); |
0 | 2972 |
2973 // Now mark from the roots | |
2974 MarkFromRootsVerifyClosure markFromRootsClosure(this, _span, | |
2975 verification_mark_bm(), markBitMap(), verification_mark_stack()); | |
2976 assert(_restart_addr == NULL, "Expected pre-condition"); | |
2977 verification_mark_bm()->iterate(&markFromRootsClosure); | |
2978 while (_restart_addr != NULL) { | |
2979 // Deal with stack overflow: by restarting at the indicated | |
2980 // address. | |
2981 HeapWord* ra = _restart_addr; | |
2982 markFromRootsClosure.reset(ra); | |
2983 _restart_addr = NULL; | |
2984 verification_mark_bm()->iterate(&markFromRootsClosure, ra, _span.end()); | |
2985 } | |
2986 assert(verification_mark_stack()->isEmpty(), "Should have been drained"); | |
2987 verify_work_stacks_empty(); | |
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2988 |
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2989 VerifyKlassOopsKlassClosure verify_klass_oops(verification_mark_bm()); |
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2990 ClassLoaderDataGraph::classes_do(&verify_klass_oops); |
0 | 2991 |
2992 // Marking completed -- now verify that each bit marked in | |
2993 // verification_mark_bm() is also marked in markBitMap(); flag all | |
2994 // errors by printing corresponding objects. | |
2995 VerifyMarkedClosure vcl(markBitMap()); | |
2996 verification_mark_bm()->iterate(&vcl); | |
2997 assert(!vcl.failed(), "Else verification above should not have succeeded"); | |
2998 } | |
2999 | |
3000 void ConcurrentMarkSweepGeneration::save_marks() { | |
3001 // delegate to CMS space | |
3002 cmsSpace()->save_marks(); | |
3003 for (uint i = 0; i < ParallelGCThreads; i++) { | |
3004 _par_gc_thread_states[i]->promo.startTrackingPromotions(); | |
3005 } | |
3006 } | |
3007 | |
3008 bool ConcurrentMarkSweepGeneration::no_allocs_since_save_marks() { | |
3009 return cmsSpace()->no_allocs_since_save_marks(); | |
3010 } | |
3011 | |
3012 #define CMS_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \ | |
3013 \ | |
3014 void ConcurrentMarkSweepGeneration:: \ | |
3015 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \ | |
3016 cl->set_generation(this); \ | |
3017 cmsSpace()->oop_since_save_marks_iterate##nv_suffix(cl); \ | |
3018 cl->reset_generation(); \ | |
3019 save_marks(); \ | |
3020 } | |
3021 | |
3022 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DEFN) | |
3023 | |
3024 void | |
3025 ConcurrentMarkSweepGeneration::object_iterate_since_last_GC(ObjectClosure* blk) | |
3026 { | |
3027 // Not currently implemented; need to do the following. -- ysr. | |
3028 // dld -- I think that is used for some sort of allocation profiler. So it | |
3029 // really means the objects allocated by the mutator since the last | |
3030 // GC. We could potentially implement this cheaply by recording only | |
3031 // the direct allocations in a side data structure. | |
3032 // | |
3033 // I think we probably ought not to be required to support these | |
3034 // iterations at any arbitrary point; I think there ought to be some | |
3035 // call to enable/disable allocation profiling in a generation/space, | |
3036 // and the iterator ought to return the objects allocated in the | |
3037 // gen/space since the enable call, or the last iterator call (which | |
3038 // will probably be at a GC.) That way, for gens like CM&S that would | |
3039 // require some extra data structure to support this, we only pay the | |
3040 // cost when it's in use... | |
3041 cmsSpace()->object_iterate_since_last_GC(blk); | |
3042 } | |
3043 | |
3044 void | |
3045 ConcurrentMarkSweepGeneration::younger_refs_iterate(OopsInGenClosure* cl) { | |
3046 cl->set_generation(this); | |
3047 younger_refs_in_space_iterate(_cmsSpace, cl); | |
3048 cl->reset_generation(); | |
3049 } | |
3050 | |
3051 void | |
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3052 ConcurrentMarkSweepGeneration::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) { |
0 | 3053 if (freelistLock()->owned_by_self()) { |
3054 Generation::oop_iterate(mr, cl); | |
3055 } else { | |
3056 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
3057 Generation::oop_iterate(mr, cl); | |
3058 } | |
3059 } | |
3060 | |
3061 void | |
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3062 ConcurrentMarkSweepGeneration::oop_iterate(ExtendedOopClosure* cl) { |
0 | 3063 if (freelistLock()->owned_by_self()) { |
3064 Generation::oop_iterate(cl); | |
3065 } else { | |
3066 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
3067 Generation::oop_iterate(cl); | |
3068 } | |
3069 } | |
3070 | |
3071 void | |
3072 ConcurrentMarkSweepGeneration::object_iterate(ObjectClosure* cl) { | |
3073 if (freelistLock()->owned_by_self()) { | |
3074 Generation::object_iterate(cl); | |
3075 } else { | |
3076 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
3077 Generation::object_iterate(cl); | |
3078 } | |
3079 } | |
3080 | |
3081 void | |
517
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3082 ConcurrentMarkSweepGeneration::safe_object_iterate(ObjectClosure* cl) { |
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3083 if (freelistLock()->owned_by_self()) { |
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3084 Generation::safe_object_iterate(cl); |
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3085 } else { |
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3086 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); |
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3087 Generation::safe_object_iterate(cl); |
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3088 } |
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3089 } |
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3090 |
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3091 void |
0 | 3092 ConcurrentMarkSweepGeneration::post_compact() { |
3093 } | |
3094 | |
3095 void | |
3096 ConcurrentMarkSweepGeneration::prepare_for_verify() { | |
3097 // Fix the linear allocation blocks to look like free blocks. | |
3098 | |
3099 // Locks are normally acquired/released in gc_prologue/gc_epilogue, but those | |
3100 // are not called when the heap is verified during universe initialization and | |
3101 // at vm shutdown. | |
3102 if (freelistLock()->owned_by_self()) { | |
3103 cmsSpace()->prepare_for_verify(); | |
3104 } else { | |
3105 MutexLockerEx fll(freelistLock(), Mutex::_no_safepoint_check_flag); | |
3106 cmsSpace()->prepare_for_verify(); | |
3107 } | |
3108 } | |
3109 | |
3110 void | |
6008 | 3111 ConcurrentMarkSweepGeneration::verify() { |
0 | 3112 // Locks are normally acquired/released in gc_prologue/gc_epilogue, but those |
3113 // are not called when the heap is verified during universe initialization and | |
3114 // at vm shutdown. | |
3115 if (freelistLock()->owned_by_self()) { | |
6008 | 3116 cmsSpace()->verify(); |
0 | 3117 } else { |
3118 MutexLockerEx fll(freelistLock(), Mutex::_no_safepoint_check_flag); | |
6008 | 3119 cmsSpace()->verify(); |
3120 } | |
3121 } | |
3122 | |
3123 void CMSCollector::verify() { | |
3124 _cmsGen->verify(); | |
0 | 3125 } |
3126 | |
3127 #ifndef PRODUCT | |
3128 bool CMSCollector::overflow_list_is_empty() const { | |
3129 assert(_num_par_pushes >= 0, "Inconsistency"); | |
3130 if (_overflow_list == NULL) { | |
3131 assert(_num_par_pushes == 0, "Inconsistency"); | |
3132 } | |
3133 return _overflow_list == NULL; | |
3134 } | |
3135 | |
3136 // The methods verify_work_stacks_empty() and verify_overflow_empty() | |
3137 // merely consolidate assertion checks that appear to occur together frequently. | |
3138 void CMSCollector::verify_work_stacks_empty() const { | |
3139 assert(_markStack.isEmpty(), "Marking stack should be empty"); | |
3140 assert(overflow_list_is_empty(), "Overflow list should be empty"); | |
3141 } | |
3142 | |
3143 void CMSCollector::verify_overflow_empty() const { | |
3144 assert(overflow_list_is_empty(), "Overflow list should be empty"); | |
3145 assert(no_preserved_marks(), "No preserved marks"); | |
3146 } | |
3147 #endif // PRODUCT | |
3148 | |
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3149 // Decide if we want to enable class unloading as part of the |
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3150 // ensuing concurrent GC cycle. We will collect and |
94
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3151 // unload classes if it's the case that: |
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3152 // (1) an explicit gc request has been made and the flag |
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3153 // ExplicitGCInvokesConcurrentAndUnloadsClasses is set, OR |
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3154 // (2) (a) class unloading is enabled at the command line, and |
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3155 // (b) old gen is getting really full |
94
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3156 // NOTE: Provided there is no change in the state of the heap between |
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|
3157 // calls to this method, it should have idempotent results. Moreover, |
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|
3158 // its results should be monotonically increasing (i.e. going from 0 to 1, |
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3159 // but not 1 to 0) between successive calls between which the heap was |
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3160 // not collected. For the implementation below, it must thus rely on |
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3161 // the property that concurrent_cycles_since_last_unload() |
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3162 // will not decrease unless a collection cycle happened and that |
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3163 // _cmsGen->is_too_full() are |
94
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3164 // themselves also monotonic in that sense. See check_monotonicity() |
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3165 // below. |
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3166 void CMSCollector::update_should_unload_classes() { |
94
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3167 _should_unload_classes = false; |
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3168 // Condition 1 above |
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3169 if (_full_gc_requested && ExplicitGCInvokesConcurrentAndUnloadsClasses) { |
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3170 _should_unload_classes = true; |
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3171 } else if (CMSClassUnloadingEnabled) { // Condition 2.a above |
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3172 // Disjuncts 2.b.(i,ii,iii) above |
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3173 _should_unload_classes = (concurrent_cycles_since_last_unload() >= |
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3174 CMSClassUnloadingMaxInterval) |
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3175 || _cmsGen->is_too_full(); |
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3176 } |
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3177 } |
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3178 |
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3179 bool ConcurrentMarkSweepGeneration::is_too_full() const { |
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3180 bool res = should_concurrent_collect(); |
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3181 res = res && (occupancy() > (double)CMSIsTooFullPercentage/100.0); |
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3182 return res; |
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3183 } |
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3184 |
0 | 3185 void CMSCollector::setup_cms_unloading_and_verification_state() { |
3293
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3186 const bool should_verify = VerifyBeforeGC || VerifyAfterGC || VerifyDuringGC |
0 | 3187 || VerifyBeforeExit; |
3293
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3188 const int rso = SharedHeap::SO_Strings | SharedHeap::SO_CodeCache; |
0 | 3189 |
94
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3190 if (should_unload_classes()) { // Should unload classes this cycle |
0 | 3191 remove_root_scanning_option(rso); // Shrink the root set appropriately |
3192 set_verifying(should_verify); // Set verification state for this cycle | |
3193 return; // Nothing else needs to be done at this time | |
3194 } | |
3195 | |
3196 // Not unloading classes this cycle | |
94
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3197 assert(!should_unload_classes(), "Inconsitency!"); |
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3198 if ((!verifying() || unloaded_classes_last_cycle()) && should_verify) { |
0 | 3199 // Include symbols, strings and code cache elements to prevent their resurrection. |
3200 add_root_scanning_option(rso); | |
3201 set_verifying(true); | |
3202 } else if (verifying() && !should_verify) { | |
3203 // We were verifying, but some verification flags got disabled. | |
3204 set_verifying(false); | |
3205 // Exclude symbols, strings and code cache elements from root scanning to | |
3206 // reduce IM and RM pauses. | |
3207 remove_root_scanning_option(rso); | |
3208 } | |
3209 } | |
3210 | |
3211 | |
3212 #ifndef PRODUCT | |
3213 HeapWord* CMSCollector::block_start(const void* p) const { | |
3214 const HeapWord* addr = (HeapWord*)p; | |
3215 if (_span.contains(p)) { | |
3216 if (_cmsGen->cmsSpace()->is_in_reserved(addr)) { | |
3217 return _cmsGen->cmsSpace()->block_start(p); | |
3218 } | |
3219 } | |
3220 return NULL; | |
3221 } | |
3222 #endif | |
3223 | |
3224 HeapWord* | |
3225 ConcurrentMarkSweepGeneration::expand_and_allocate(size_t word_size, | |
3226 bool tlab, | |
3227 bool parallel) { | |
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3228 CMSSynchronousYieldRequest yr; |
0 | 3229 assert(!tlab, "Can't deal with TLAB allocation"); |
3230 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
3231 expand(word_size*HeapWordSize, MinHeapDeltaBytes, | |
3232 CMSExpansionCause::_satisfy_allocation); | |
3233 if (GCExpandToAllocateDelayMillis > 0) { | |
3234 os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false); | |
3235 } | |
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3236 return have_lock_and_allocate(word_size, tlab); |
0 | 3237 } |
3238 | |
3239 // YSR: All of this generation expansion/shrinking stuff is an exact copy of | |
3240 // OneContigSpaceCardGeneration, which makes me wonder if we should move this | |
3241 // to CardGeneration and share it... | |
271
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3242 bool ConcurrentMarkSweepGeneration::expand(size_t bytes, size_t expand_bytes) { |
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3243 return CardGeneration::expand(bytes, expand_bytes); |
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3244 } |
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3245 |
0 | 3246 void ConcurrentMarkSweepGeneration::expand(size_t bytes, size_t expand_bytes, |
3247 CMSExpansionCause::Cause cause) | |
3248 { | |
271
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3249 |
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3250 bool success = expand(bytes, expand_bytes); |
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3251 |
0 | 3252 // remember why we expanded; this information is used |
3253 // by shouldConcurrentCollect() when making decisions on whether to start | |
3254 // a new CMS cycle. | |
3255 if (success) { | |
3256 set_expansion_cause(cause); | |
3257 if (PrintGCDetails && Verbose) { | |
3258 gclog_or_tty->print_cr("Expanded CMS gen for %s", | |
3259 CMSExpansionCause::to_string(cause)); | |
3260 } | |
3261 } | |
3262 } | |
3263 | |
3264 HeapWord* ConcurrentMarkSweepGeneration::expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz) { | |
3265 HeapWord* res = NULL; | |
3266 MutexLocker x(ParGCRareEvent_lock); | |
3267 while (true) { | |
3268 // Expansion by some other thread might make alloc OK now: | |
3269 res = ps->lab.alloc(word_sz); | |
3270 if (res != NULL) return res; | |
3271 // If there's not enough expansion space available, give up. | |
3272 if (_virtual_space.uncommitted_size() < (word_sz * HeapWordSize)) { | |
3273 return NULL; | |
3274 } | |
3275 // Otherwise, we try expansion. | |
3276 expand(word_sz*HeapWordSize, MinHeapDeltaBytes, | |
3277 CMSExpansionCause::_allocate_par_lab); | |
3278 // Now go around the loop and try alloc again; | |
3279 // A competing par_promote might beat us to the expansion space, | |
3280 // so we may go around the loop again if promotion fails agaion. | |
3281 if (GCExpandToAllocateDelayMillis > 0) { | |
3282 os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false); | |
3283 } | |
3284 } | |
3285 } | |
3286 | |
3287 | |
3288 bool ConcurrentMarkSweepGeneration::expand_and_ensure_spooling_space( | |
3289 PromotionInfo* promo) { | |
3290 MutexLocker x(ParGCRareEvent_lock); | |
3291 size_t refill_size_bytes = promo->refillSize() * HeapWordSize; | |
3292 while (true) { | |
3293 // Expansion by some other thread might make alloc OK now: | |
3294 if (promo->ensure_spooling_space()) { | |
3295 assert(promo->has_spooling_space(), | |
3296 "Post-condition of successful ensure_spooling_space()"); | |
3297 return true; | |
3298 } | |
3299 // If there's not enough expansion space available, give up. | |
3300 if (_virtual_space.uncommitted_size() < refill_size_bytes) { | |
3301 return false; | |
3302 } | |
3303 // Otherwise, we try expansion. | |
3304 expand(refill_size_bytes, MinHeapDeltaBytes, | |
3305 CMSExpansionCause::_allocate_par_spooling_space); | |
3306 // Now go around the loop and try alloc again; | |
3307 // A competing allocation might beat us to the expansion space, | |
3308 // so we may go around the loop again if allocation fails again. | |
3309 if (GCExpandToAllocateDelayMillis > 0) { | |
3310 os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false); | |
3311 } | |
3312 } | |
3313 } | |
3314 | |
3315 | |
3316 | |
3317 void ConcurrentMarkSweepGeneration::shrink(size_t bytes) { | |
3318 assert_locked_or_safepoint(Heap_lock); | |
3319 size_t size = ReservedSpace::page_align_size_down(bytes); | |
3320 if (size > 0) { | |
3321 shrink_by(size); | |
3322 } | |
3323 } | |
3324 | |
3325 bool ConcurrentMarkSweepGeneration::grow_by(size_t bytes) { | |
3326 assert_locked_or_safepoint(Heap_lock); | |
3327 bool result = _virtual_space.expand_by(bytes); | |
3328 if (result) { | |
3329 HeapWord* old_end = _cmsSpace->end(); | |
3330 size_t new_word_size = | |
3331 heap_word_size(_virtual_space.committed_size()); | |
3332 MemRegion mr(_cmsSpace->bottom(), new_word_size); | |
3333 _bts->resize(new_word_size); // resize the block offset shared array | |
3334 Universe::heap()->barrier_set()->resize_covered_region(mr); | |
3335 // Hmmmm... why doesn't CFLS::set_end verify locking? | |
3336 // This is quite ugly; FIX ME XXX | |
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3337 _cmsSpace->assert_locked(freelistLock()); |
0 | 3338 _cmsSpace->set_end((HeapWord*)_virtual_space.high()); |
3339 | |
3340 // update the space and generation capacity counters | |
3341 if (UsePerfData) { | |
3342 _space_counters->update_capacity(); | |
3343 _gen_counters->update_all(); | |
3344 } | |
3345 | |
3346 if (Verbose && PrintGC) { | |
3347 size_t new_mem_size = _virtual_space.committed_size(); | |
3348 size_t old_mem_size = new_mem_size - bytes; | |
3349 gclog_or_tty->print_cr("Expanding %s from %ldK by %ldK to %ldK", | |
3350 name(), old_mem_size/K, bytes/K, new_mem_size/K); | |
3351 } | |
3352 } | |
3353 return result; | |
3354 } | |
3355 | |
3356 bool ConcurrentMarkSweepGeneration::grow_to_reserved() { | |
3357 assert_locked_or_safepoint(Heap_lock); | |
3358 bool success = true; | |
3359 const size_t remaining_bytes = _virtual_space.uncommitted_size(); | |
3360 if (remaining_bytes > 0) { | |
3361 success = grow_by(remaining_bytes); | |
3362 DEBUG_ONLY(if (!success) warning("grow to reserved failed");) | |
3363 } | |
3364 return success; | |
3365 } | |
3366 | |
3367 void ConcurrentMarkSweepGeneration::shrink_by(size_t bytes) { | |
3368 assert_locked_or_safepoint(Heap_lock); | |
3369 assert_lock_strong(freelistLock()); | |
3370 // XXX Fix when compaction is implemented. | |
3371 warning("Shrinking of CMS not yet implemented"); | |
3372 return; | |
3373 } | |
3374 | |
3375 | |
3376 // Simple ctor/dtor wrapper for accounting & timer chores around concurrent | |
3377 // phases. | |
3378 class CMSPhaseAccounting: public StackObj { | |
3379 public: | |
3380 CMSPhaseAccounting(CMSCollector *collector, | |
3381 const char *phase, | |
3382 bool print_cr = true); | |
3383 ~CMSPhaseAccounting(); | |
3384 | |
3385 private: | |
3386 CMSCollector *_collector; | |
3387 const char *_phase; | |
3388 elapsedTimer _wallclock; | |
3389 bool _print_cr; | |
3390 | |
3391 public: | |
3392 // Not MT-safe; so do not pass around these StackObj's | |
3393 // where they may be accessed by other threads. | |
3394 jlong wallclock_millis() { | |
3395 assert(_wallclock.is_active(), "Wall clock should not stop"); | |
3396 _wallclock.stop(); // to record time | |
3397 jlong ret = _wallclock.milliseconds(); | |
3398 _wallclock.start(); // restart | |
3399 return ret; | |
3400 } | |
3401 }; | |
3402 | |
3403 CMSPhaseAccounting::CMSPhaseAccounting(CMSCollector *collector, | |
3404 const char *phase, | |
3405 bool print_cr) : | |
3406 _collector(collector), _phase(phase), _print_cr(print_cr) { | |
3407 | |
3408 if (PrintCMSStatistics != 0) { | |
3409 _collector->resetYields(); | |
3410 } | |
3411 if (PrintGCDetails && PrintGCTimeStamps) { | |
3412 gclog_or_tty->date_stamp(PrintGCDateStamps); | |
3413 gclog_or_tty->stamp(); | |
3414 gclog_or_tty->print_cr(": [%s-concurrent-%s-start]", | |
3415 _collector->cmsGen()->short_name(), _phase); | |
3416 } | |
3417 _collector->resetTimer(); | |
3418 _wallclock.start(); | |
3419 _collector->startTimer(); | |
3420 } | |
3421 | |
3422 CMSPhaseAccounting::~CMSPhaseAccounting() { | |
3423 assert(_wallclock.is_active(), "Wall clock should not have stopped"); | |
3424 _collector->stopTimer(); | |
3425 _wallclock.stop(); | |
3426 if (PrintGCDetails) { | |
3427 gclog_or_tty->date_stamp(PrintGCDateStamps); | |
3428 if (PrintGCTimeStamps) { | |
3429 gclog_or_tty->stamp(); | |
3430 gclog_or_tty->print(": "); | |
3431 } | |
3432 gclog_or_tty->print("[%s-concurrent-%s: %3.3f/%3.3f secs]", | |
3433 _collector->cmsGen()->short_name(), | |
3434 _phase, _collector->timerValue(), _wallclock.seconds()); | |
3435 if (_print_cr) { | |
3436 gclog_or_tty->print_cr(""); | |
3437 } | |
3438 if (PrintCMSStatistics != 0) { | |
3439 gclog_or_tty->print_cr(" (CMS-concurrent-%s yielded %d times)", _phase, | |
3440 _collector->yields()); | |
3441 } | |
3442 } | |
3443 } | |
3444 | |
3445 // CMS work | |
3446 | |
3447 // Checkpoint the roots into this generation from outside | |
3448 // this generation. [Note this initial checkpoint need only | |
3449 // be approximate -- we'll do a catch up phase subsequently.] | |
3450 void CMSCollector::checkpointRootsInitial(bool asynch) { | |
3451 assert(_collectorState == InitialMarking, "Wrong collector state"); | |
3452 check_correct_thread_executing(); | |
3356
78542e2b5e35
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3453 TraceCMSMemoryManagerStats tms(_collectorState,GenCollectedHeap::heap()->gc_cause()); |
2125
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3454 |
0 | 3455 ReferenceProcessor* rp = ref_processor(); |
3456 SpecializationStats::clear(); | |
3457 assert(_restart_addr == NULL, "Control point invariant"); | |
3458 if (asynch) { | |
3459 // acquire locks for subsequent manipulations | |
3460 MutexLockerEx x(bitMapLock(), | |
3461 Mutex::_no_safepoint_check_flag); | |
3462 checkpointRootsInitialWork(asynch); | |
3979
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3463 // enable ("weak") refs discovery |
4dfb2df418f2
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3464 rp->enable_discovery(true /*verify_disabled*/, true /*check_no_refs*/); |
0 | 3465 _collectorState = Marking; |
3466 } else { | |
3467 // (Weak) Refs discovery: this is controlled from genCollectedHeap::do_collection | |
3468 // which recognizes if we are a CMS generation, and doesn't try to turn on | |
3469 // discovery; verify that they aren't meddling. | |
3470 assert(!rp->discovery_is_atomic(), | |
3471 "incorrect setting of discovery predicate"); | |
3472 assert(!rp->discovery_enabled(), "genCollectedHeap shouldn't control " | |
3473 "ref discovery for this generation kind"); | |
3474 // already have locks | |
3475 checkpointRootsInitialWork(asynch); | |
3979
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3476 // now enable ("weak") refs discovery |
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|
3477 rp->enable_discovery(true /*verify_disabled*/, false /*verify_no_refs*/); |
0 | 3478 _collectorState = Marking; |
3479 } | |
3480 SpecializationStats::print(); | |
3481 } | |
3482 | |
3483 void CMSCollector::checkpointRootsInitialWork(bool asynch) { | |
3484 assert(SafepointSynchronize::is_at_safepoint(), "world should be stopped"); | |
3485 assert(_collectorState == InitialMarking, "just checking"); | |
3486 | |
3487 // If there has not been a GC[n-1] since last GC[n] cycle completed, | |
3488 // precede our marking with a collection of all | |
3489 // younger generations to keep floating garbage to a minimum. | |
3490 // XXX: we won't do this for now -- it's an optimization to be done later. | |
3491 | |
3492 // already have locks | |
3493 assert_lock_strong(bitMapLock()); | |
3494 assert(_markBitMap.isAllClear(), "was reset at end of previous cycle"); | |
3495 | |
3496 // Setup the verification and class unloading state for this | |
3497 // CMS collection cycle. | |
3498 setup_cms_unloading_and_verification_state(); | |
3499 | |
3500 NOT_PRODUCT(TraceTime t("\ncheckpointRootsInitialWork", | |
3501 PrintGCDetails && Verbose, true, gclog_or_tty);) | |
3502 if (UseAdaptiveSizePolicy) { | |
3503 size_policy()->checkpoint_roots_initial_begin(); | |
3504 } | |
3505 | |
3506 // Reset all the PLAB chunk arrays if necessary. | |
3507 if (_survivor_plab_array != NULL && !CMSPLABRecordAlways) { | |
3508 reset_survivor_plab_arrays(); | |
3509 } | |
3510 | |
3511 ResourceMark rm; | |
3512 HandleMark hm; | |
3513 | |
3514 FalseClosure falseClosure; | |
3515 // In the case of a synchronous collection, we will elide the | |
3516 // remark step, so it's important to catch all the nmethod oops | |
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3517 // in this step. |
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3518 // The final 'true' flag to gen_process_strong_roots will ensure this. |
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3519 // If 'async' is true, we can relax the nmethod tracing. |
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3520 MarkRefsIntoClosure notOlder(_span, &_markBitMap); |
0 | 3521 GenCollectedHeap* gch = GenCollectedHeap::heap(); |
3522 | |
3523 verify_work_stacks_empty(); | |
3524 verify_overflow_empty(); | |
3525 | |
3526 gch->ensure_parsability(false); // fill TLABs, but no need to retire them | |
3527 // Update the saved marks which may affect the root scans. | |
3528 gch->save_marks(); | |
3529 | |
3530 // weak reference processing has not started yet. | |
3531 ref_processor()->set_enqueuing_is_done(false); | |
3532 | |
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3533 // Need to remember all newly created CLDs, |
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3534 // so that we can guarantee that the remark finds them. |
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3535 ClassLoaderDataGraph::remember_new_clds(true); |
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3536 |
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3537 // Whenever a CLD is found, it will be claimed before proceeding to mark |
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3538 // the klasses. The claimed marks need to be cleared before marking starts. |
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3539 ClassLoaderDataGraph::clear_claimed_marks(); |
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3540 |
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3541 CMKlassClosure klass_closure(¬Older); |
0 | 3542 { |
3543 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;) | |
3544 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. | |
3545 gch->gen_process_strong_roots(_cmsGen->level(), | |
3546 true, // younger gens are roots | |
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3547 true, // activate StrongRootsScope |
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3548 false, // not scavenging |
0 | 3549 SharedHeap::ScanningOption(roots_scanning_options()), |
989
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3550 ¬Older, |
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3551 true, // walk all of code cache if (so & SO_CodeCache) |
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3552 NULL, |
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3553 &klass_closure); |
0 | 3554 } |
3555 | |
3556 // Clear mod-union table; it will be dirtied in the prologue of | |
3557 // CMS generation per each younger generation collection. | |
3558 | |
3559 assert(_modUnionTable.isAllClear(), | |
3560 "Was cleared in most recent final checkpoint phase" | |
3561 " or no bits are set in the gc_prologue before the start of the next " | |
3562 "subsequent marking phase."); | |
3563 | |
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3564 assert(_ct->klass_rem_set()->mod_union_is_clear(), "Must be"); |
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3565 |
0 | 3566 // Save the end of the used_region of the constituent generations |
3567 // to be used to limit the extent of sweep in each generation. | |
3568 save_sweep_limits(); | |
3569 if (UseAdaptiveSizePolicy) { | |
3570 size_policy()->checkpoint_roots_initial_end(gch->gc_cause()); | |
3571 } | |
3572 verify_overflow_empty(); | |
3573 } | |
3574 | |
3575 bool CMSCollector::markFromRoots(bool asynch) { | |
3576 // we might be tempted to assert that: | |
3577 // assert(asynch == !SafepointSynchronize::is_at_safepoint(), | |
3578 // "inconsistent argument?"); | |
3579 // However that wouldn't be right, because it's possible that | |
3580 // a safepoint is indeed in progress as a younger generation | |
3581 // stop-the-world GC happens even as we mark in this generation. | |
3582 assert(_collectorState == Marking, "inconsistent state?"); | |
3583 check_correct_thread_executing(); | |
3584 verify_overflow_empty(); | |
3585 | |
3586 bool res; | |
3587 if (asynch) { | |
3588 | |
3589 // Start the timers for adaptive size policy for the concurrent phases | |
3590 // Do it here so that the foreground MS can use the concurrent | |
3591 // timer since a foreground MS might has the sweep done concurrently | |
3592 // or STW. | |
3593 if (UseAdaptiveSizePolicy) { | |
3594 size_policy()->concurrent_marking_begin(); | |
3595 } | |
3596 | |
3597 // Weak ref discovery note: We may be discovering weak | |
3598 // refs in this generation concurrent (but interleaved) with | |
3599 // weak ref discovery by a younger generation collector. | |
3600 | |
3601 CMSTokenSyncWithLocks ts(true, bitMapLock()); | |
3602 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
3603 CMSPhaseAccounting pa(this, "mark", !PrintGCDetails); | |
3604 res = markFromRootsWork(asynch); | |
3605 if (res) { | |
3606 _collectorState = Precleaning; | |
3607 } else { // We failed and a foreground collection wants to take over | |
3608 assert(_foregroundGCIsActive, "internal state inconsistency"); | |
3609 assert(_restart_addr == NULL, "foreground will restart from scratch"); | |
3610 if (PrintGCDetails) { | |
3611 gclog_or_tty->print_cr("bailing out to foreground collection"); | |
3612 } | |
3613 } | |
3614 if (UseAdaptiveSizePolicy) { | |
3615 size_policy()->concurrent_marking_end(); | |
3616 } | |
3617 } else { | |
3618 assert(SafepointSynchronize::is_at_safepoint(), | |
3619 "inconsistent with asynch == false"); | |
3620 if (UseAdaptiveSizePolicy) { | |
3621 size_policy()->ms_collection_marking_begin(); | |
3622 } | |
3623 // already have locks | |
3624 res = markFromRootsWork(asynch); | |
3625 _collectorState = FinalMarking; | |
3626 if (UseAdaptiveSizePolicy) { | |
3627 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
3628 size_policy()->ms_collection_marking_end(gch->gc_cause()); | |
3629 } | |
3630 } | |
3631 verify_overflow_empty(); | |
3632 return res; | |
3633 } | |
3634 | |
3635 bool CMSCollector::markFromRootsWork(bool asynch) { | |
3636 // iterate over marked bits in bit map, doing a full scan and mark | |
3637 // from these roots using the following algorithm: | |
3638 // . if oop is to the right of the current scan pointer, | |
3639 // mark corresponding bit (we'll process it later) | |
3640 // . else (oop is to left of current scan pointer) | |
3641 // push oop on marking stack | |
3642 // . drain the marking stack | |
3643 | |
3644 // Note that when we do a marking step we need to hold the | |
3645 // bit map lock -- recall that direct allocation (by mutators) | |
3646 // and promotion (by younger generation collectors) is also | |
3647 // marking the bit map. [the so-called allocate live policy.] | |
3648 // Because the implementation of bit map marking is not | |
3649 // robust wrt simultaneous marking of bits in the same word, | |
3650 // we need to make sure that there is no such interference | |
3651 // between concurrent such updates. | |
3652 | |
3653 // already have locks | |
3654 assert_lock_strong(bitMapLock()); | |
3655 | |
3656 verify_work_stacks_empty(); | |
3657 verify_overflow_empty(); | |
3658 bool result = false; | |
1284 | 3659 if (CMSConcurrentMTEnabled && ConcGCThreads > 0) { |
0 | 3660 result = do_marking_mt(asynch); |
3661 } else { | |
3662 result = do_marking_st(asynch); | |
3663 } | |
3664 return result; | |
3665 } | |
3666 | |
3667 // Forward decl | |
3668 class CMSConcMarkingTask; | |
3669 | |
3670 class CMSConcMarkingTerminator: public ParallelTaskTerminator { | |
3671 CMSCollector* _collector; | |
3672 CMSConcMarkingTask* _task; | |
1837
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3673 public: |
0 | 3674 virtual void yield(); |
1837
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3675 |
0 | 3676 // "n_threads" is the number of threads to be terminated. |
3677 // "queue_set" is a set of work queues of other threads. | |
3678 // "collector" is the CMS collector associated with this task terminator. | |
3679 // "yield" indicates whether we need the gang as a whole to yield. | |
1837
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3680 CMSConcMarkingTerminator(int n_threads, TaskQueueSetSuper* queue_set, CMSCollector* collector) : |
0 | 3681 ParallelTaskTerminator(n_threads, queue_set), |
1837
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3682 _collector(collector) { } |
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3683 |
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3684 void set_task(CMSConcMarkingTask* task) { |
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3685 _task = task; |
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3686 } |
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3687 }; |
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3688 |
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3689 class CMSConcMarkingTerminatorTerminator: public TerminatorTerminator { |
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3690 CMSConcMarkingTask* _task; |
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3691 public: |
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3692 bool should_exit_termination(); |
0 | 3693 void set_task(CMSConcMarkingTask* task) { |
3694 _task = task; | |
3695 } | |
3696 }; | |
3697 | |
3698 // MT Concurrent Marking Task | |
3699 class CMSConcMarkingTask: public YieldingFlexibleGangTask { | |
3700 CMSCollector* _collector; | |
3701 int _n_workers; // requested/desired # workers | |
3702 bool _asynch; | |
3703 bool _result; | |
3704 CompactibleFreeListSpace* _cms_space; | |
1837
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3705 char _pad_front[64]; // padding to ... |
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3706 HeapWord* _global_finger; // ... avoid sharing cache line |
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3707 char _pad_back[64]; |
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3708 HeapWord* _restart_addr; |
0 | 3709 |
3710 // Exposed here for yielding support | |
3711 Mutex* const _bit_map_lock; | |
3712 | |
3713 // The per thread work queues, available here for stealing | |
3714 OopTaskQueueSet* _task_queues; | |
1837
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3715 |
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3716 // Termination (and yielding) support |
0 | 3717 CMSConcMarkingTerminator _term; |
1837
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3718 CMSConcMarkingTerminatorTerminator _term_term; |
0 | 3719 |
3720 public: | |
3721 CMSConcMarkingTask(CMSCollector* collector, | |
3722 CompactibleFreeListSpace* cms_space, | |
1833
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3723 bool asynch, |
0 | 3724 YieldingFlexibleWorkGang* workers, |
3725 OopTaskQueueSet* task_queues): | |
3726 YieldingFlexibleGangTask("Concurrent marking done multi-threaded"), | |
3727 _collector(collector), | |
3728 _cms_space(cms_space), | |
1833
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3729 _asynch(asynch), _n_workers(0), _result(true), |
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3730 _task_queues(task_queues), |
1837
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3731 _term(_n_workers, task_queues, _collector), |
0 | 3732 _bit_map_lock(collector->bitMapLock()) |
3733 { | |
1833
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3734 _requested_size = _n_workers; |
0 | 3735 _term.set_task(this); |
1837
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3736 _term_term.set_task(this); |
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3737 _restart_addr = _global_finger = _cms_space->bottom(); |
0 | 3738 } |
3739 | |
3740 | |
3741 OopTaskQueueSet* task_queues() { return _task_queues; } | |
3742 | |
3743 OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); } | |
3744 | |
3745 HeapWord** global_finger_addr() { return &_global_finger; } | |
3746 | |
3747 CMSConcMarkingTerminator* terminator() { return &_term; } | |
3748 | |
1833
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3749 virtual void set_for_termination(int active_workers) { |
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3750 terminator()->reset_for_reuse(active_workers); |
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3751 } |
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3752 |
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3753 void work(uint worker_id); |
1837
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3754 bool should_yield() { |
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3755 return ConcurrentMarkSweepThread::should_yield() |
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3756 && !_collector->foregroundGCIsActive() |
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3757 && _asynch; |
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3758 } |
0 | 3759 |
3760 virtual void coordinator_yield(); // stuff done by coordinator | |
3761 bool result() { return _result; } | |
3762 | |
3763 void reset(HeapWord* ra) { | |
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3764 assert(_global_finger >= _cms_space->end(), "Postcondition of ::work(i)"); |
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3765 _restart_addr = _global_finger = ra; |
0 | 3766 _term.reset_for_reuse(); |
3767 } | |
3768 | |
3769 static bool get_work_from_overflow_stack(CMSMarkStack* ovflw_stk, | |
3770 OopTaskQueue* work_q); | |
3771 | |
3772 private: | |
3773 void do_scan_and_mark(int i, CompactibleFreeListSpace* sp); | |
3774 void do_work_steal(int i); | |
3775 void bump_global_finger(HeapWord* f); | |
3776 }; | |
3777 | |
1837
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3778 bool CMSConcMarkingTerminatorTerminator::should_exit_termination() { |
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3779 assert(_task != NULL, "Error"); |
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3780 return _task->yielding(); |
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3781 // Note that we do not need the disjunct || _task->should_yield() above |
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3782 // because we want terminating threads to yield only if the task |
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3783 // is already in the midst of yielding, which happens only after at least one |
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3784 // thread has yielded. |
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3785 } |
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3786 |
0 | 3787 void CMSConcMarkingTerminator::yield() { |
1837
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3788 if (_task->should_yield()) { |
0 | 3789 _task->yield(); |
3790 } else { | |
3791 ParallelTaskTerminator::yield(); | |
3792 } | |
3793 } | |
3794 | |
3795 //////////////////////////////////////////////////////////////// | |
3796 // Concurrent Marking Algorithm Sketch | |
3797 //////////////////////////////////////////////////////////////// | |
3798 // Until all tasks exhausted (both spaces): | |
3799 // -- claim next available chunk | |
3800 // -- bump global finger via CAS | |
3801 // -- find first object that starts in this chunk | |
3802 // and start scanning bitmap from that position | |
3803 // -- scan marked objects for oops | |
3804 // -- CAS-mark target, and if successful: | |
3805 // . if target oop is above global finger (volatile read) | |
3806 // nothing to do | |
3807 // . if target oop is in chunk and above local finger | |
3808 // then nothing to do | |
3809 // . else push on work-queue | |
3810 // -- Deal with possible overflow issues: | |
3811 // . local work-queue overflow causes stuff to be pushed on | |
3812 // global (common) overflow queue | |
3813 // . always first empty local work queue | |
3814 // . then get a batch of oops from global work queue if any | |
3815 // . then do work stealing | |
3816 // -- When all tasks claimed (both spaces) | |
3817 // and local work queue empty, | |
3818 // then in a loop do: | |
3819 // . check global overflow stack; steal a batch of oops and trace | |
3820 // . try to steal from other threads oif GOS is empty | |
3821 // . if neither is available, offer termination | |
3822 // -- Terminate and return result | |
3823 // | |
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3824 void CMSConcMarkingTask::work(uint worker_id) { |
0 | 3825 elapsedTimer _timer; |
3826 ResourceMark rm; | |
3827 HandleMark hm; | |
3828 | |
3829 DEBUG_ONLY(_collector->verify_overflow_empty();) | |
3830 | |
3831 // Before we begin work, our work queue should be empty | |
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3832 assert(work_queue(worker_id)->size() == 0, "Expected to be empty"); |
0 | 3833 // Scan the bitmap covering _cms_space, tracing through grey objects. |
3834 _timer.start(); | |
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3835 do_scan_and_mark(worker_id, _cms_space); |
0 | 3836 _timer.stop(); |
3837 if (PrintCMSStatistics != 0) { | |
3838 gclog_or_tty->print_cr("Finished cms space scanning in %dth thread: %3.3f sec", | |
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3839 worker_id, _timer.seconds()); |
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3840 // XXX: need xxx/xxx type of notation, two timers |
0 | 3841 } |
3842 | |
3843 // ... do work stealing | |
3844 _timer.reset(); | |
3845 _timer.start(); | |
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3846 do_work_steal(worker_id); |
0 | 3847 _timer.stop(); |
3848 if (PrintCMSStatistics != 0) { | |
3849 gclog_or_tty->print_cr("Finished work stealing in %dth thread: %3.3f sec", | |
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3850 worker_id, _timer.seconds()); |
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3851 // XXX: need xxx/xxx type of notation, two timers |
0 | 3852 } |
3853 assert(_collector->_markStack.isEmpty(), "Should have been emptied"); | |
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3854 assert(work_queue(worker_id)->size() == 0, "Should have been emptied"); |
0 | 3855 // Note that under the current task protocol, the |
3856 // following assertion is true even of the spaces | |
3857 // expanded since the completion of the concurrent | |
3858 // marking. XXX This will likely change under a strict | |
3859 // ABORT semantics. | |
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3860 // After perm removal the comparison was changed to |
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3861 // greater than or equal to from strictly greater than. |
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3862 // Before perm removal the highest address sweep would |
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3863 // have been at the end of perm gen but now is at the |
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3864 // end of the tenured gen. |
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3865 assert(_global_finger >= _cms_space->end(), |
0 | 3866 "All tasks have been completed"); |
3867 DEBUG_ONLY(_collector->verify_overflow_empty();) | |
3868 } | |
3869 | |
3870 void CMSConcMarkingTask::bump_global_finger(HeapWord* f) { | |
3871 HeapWord* read = _global_finger; | |
3872 HeapWord* cur = read; | |
3873 while (f > read) { | |
3874 cur = read; | |
3875 read = (HeapWord*) Atomic::cmpxchg_ptr(f, &_global_finger, cur); | |
3876 if (cur == read) { | |
3877 // our cas succeeded | |
3878 assert(_global_finger >= f, "protocol consistency"); | |
3879 break; | |
3880 } | |
3881 } | |
3882 } | |
3883 | |
3884 // This is really inefficient, and should be redone by | |
3885 // using (not yet available) block-read and -write interfaces to the | |
3886 // stack and the work_queue. XXX FIX ME !!! | |
3887 bool CMSConcMarkingTask::get_work_from_overflow_stack(CMSMarkStack* ovflw_stk, | |
3888 OopTaskQueue* work_q) { | |
3889 // Fast lock-free check | |
3890 if (ovflw_stk->length() == 0) { | |
3891 return false; | |
3892 } | |
3893 assert(work_q->size() == 0, "Shouldn't steal"); | |
3894 MutexLockerEx ml(ovflw_stk->par_lock(), | |
3895 Mutex::_no_safepoint_check_flag); | |
3896 // Grab up to 1/4 the size of the work queue | |
679
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3897 size_t num = MIN2((size_t)(work_q->max_elems() - work_q->size())/4, |
0 | 3898 (size_t)ParGCDesiredObjsFromOverflowList); |
3899 num = MIN2(num, ovflw_stk->length()); | |
3900 for (int i = (int) num; i > 0; i--) { | |
3901 oop cur = ovflw_stk->pop(); | |
3902 assert(cur != NULL, "Counted wrong?"); | |
3903 work_q->push(cur); | |
3904 } | |
3905 return num > 0; | |
3906 } | |
3907 | |
3908 void CMSConcMarkingTask::do_scan_and_mark(int i, CompactibleFreeListSpace* sp) { | |
3909 SequentialSubTasksDone* pst = sp->conc_par_seq_tasks(); | |
3910 int n_tasks = pst->n_tasks(); | |
3911 // We allow that there may be no tasks to do here because | |
3912 // we are restarting after a stack overflow. | |
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3913 assert(pst->valid() || n_tasks == 0, "Uninitialized use?"); |
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3914 uint nth_task = 0; |
0 | 3915 |
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3916 HeapWord* aligned_start = sp->bottom(); |
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3917 if (sp->used_region().contains(_restart_addr)) { |
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3918 // Align down to a card boundary for the start of 0th task |
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3919 // for this space. |
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3920 aligned_start = |
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3921 (HeapWord*)align_size_down((uintptr_t)_restart_addr, |
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3922 CardTableModRefBS::card_size); |
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3923 } |
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3924 |
0 | 3925 size_t chunk_size = sp->marking_task_size(); |
3926 while (!pst->is_task_claimed(/* reference */ nth_task)) { | |
3927 // Having claimed the nth task in this space, | |
3928 // compute the chunk that it corresponds to: | |
340
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3929 MemRegion span = MemRegion(aligned_start + nth_task*chunk_size, |
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3930 aligned_start + (nth_task+1)*chunk_size); |
0 | 3931 // Try and bump the global finger via a CAS; |
3932 // note that we need to do the global finger bump | |
3933 // _before_ taking the intersection below, because | |
3934 // the task corresponding to that region will be | |
3935 // deemed done even if the used_region() expands | |
3936 // because of allocation -- as it almost certainly will | |
3937 // during start-up while the threads yield in the | |
3938 // closure below. | |
3939 HeapWord* finger = span.end(); | |
3940 bump_global_finger(finger); // atomically | |
3941 // There are null tasks here corresponding to chunks | |
3942 // beyond the "top" address of the space. | |
3943 span = span.intersection(sp->used_region()); | |
3944 if (!span.is_empty()) { // Non-null task | |
340
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3945 HeapWord* prev_obj; |
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3946 assert(!span.contains(_restart_addr) || nth_task == 0, |
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3947 "Inconsistency"); |
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3948 if (nth_task == 0) { |
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3949 // For the 0th task, we'll not need to compute a block_start. |
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3950 if (span.contains(_restart_addr)) { |
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3951 // In the case of a restart because of stack overflow, |
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3952 // we might additionally skip a chunk prefix. |
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3953 prev_obj = _restart_addr; |
0 | 3954 } else { |
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3955 prev_obj = span.start(); |
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3956 } |
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3957 } else { |
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3958 // We want to skip the first object because |
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3959 // the protocol is to scan any object in its entirety |
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3960 // that _starts_ in this span; a fortiori, any |
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3961 // object starting in an earlier span is scanned |
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3962 // as part of an earlier claimed task. |
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3963 // Below we use the "careful" version of block_start |
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3964 // so we do not try to navigate uninitialized objects. |
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3965 prev_obj = sp->block_start_careful(span.start()); |
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3966 // Below we use a variant of block_size that uses the |
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3967 // Printezis bits to avoid waiting for allocated |
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3968 // objects to become initialized/parsable. |
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3969 while (prev_obj < span.start()) { |
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3970 size_t sz = sp->block_size_no_stall(prev_obj, _collector); |
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3971 if (sz > 0) { |
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3972 prev_obj += sz; |
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3973 } else { |
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3974 // In this case we may end up doing a bit of redundant |
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3975 // scanning, but that appears unavoidable, short of |
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3976 // locking the free list locks; see bug 6324141. |
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3977 break; |
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3978 } |
0 | 3979 } |
3980 } | |
3981 if (prev_obj < span.end()) { | |
3982 MemRegion my_span = MemRegion(prev_obj, span.end()); | |
3983 // Do the marking work within a non-empty span -- | |
3984 // the last argument to the constructor indicates whether the | |
3985 // iteration should be incremental with periodic yields. | |
3986 Par_MarkFromRootsClosure cl(this, _collector, my_span, | |
3987 &_collector->_markBitMap, | |
3988 work_queue(i), | |
3989 &_collector->_markStack, | |
3990 _asynch); | |
3991 _collector->_markBitMap.iterate(&cl, my_span.start(), my_span.end()); | |
3992 } // else nothing to do for this task | |
3993 } // else nothing to do for this task | |
3994 } | |
3995 // We'd be tempted to assert here that since there are no | |
3996 // more tasks left to claim in this space, the global_finger | |
3997 // must exceed space->top() and a fortiori space->end(). However, | |
3998 // that would not quite be correct because the bumping of | |
3999 // global_finger occurs strictly after the claiming of a task, | |
4000 // so by the time we reach here the global finger may not yet | |
4001 // have been bumped up by the thread that claimed the last | |
4002 // task. | |
4003 pst->all_tasks_completed(); | |
4004 } | |
4005 | |
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4006 class Par_ConcMarkingClosure: public CMSOopClosure { |
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4007 private: |
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4008 CMSCollector* _collector; |
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4009 CMSConcMarkingTask* _task; |
0 | 4010 MemRegion _span; |
4011 CMSBitMap* _bit_map; | |
4012 CMSMarkStack* _overflow_stack; | |
4013 OopTaskQueue* _work_queue; | |
113
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4014 protected: |
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4015 DO_OOP_WORK_DEFN |
0 | 4016 public: |
1837
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4017 Par_ConcMarkingClosure(CMSCollector* collector, CMSConcMarkingTask* task, OopTaskQueue* work_queue, |
6725
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4018 CMSBitMap* bit_map, CMSMarkStack* overflow_stack): |
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4019 CMSOopClosure(collector->ref_processor()), |
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4020 _collector(collector), |
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4021 _task(task), |
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4022 _span(collector->_span), |
0 | 4023 _work_queue(work_queue), |
4024 _bit_map(bit_map), | |
935 | 4025 _overflow_stack(overflow_stack) |
4026 { } | |
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4027 virtual void do_oop(oop* p); |
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4028 virtual void do_oop(narrowOop* p); |
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4029 |
0 | 4030 void trim_queue(size_t max); |
4031 void handle_stack_overflow(HeapWord* lost); | |
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4032 void do_yield_check() { |
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4033 if (_task->should_yield()) { |
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4034 _task->yield(); |
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4035 } |
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4036 } |
0 | 4037 }; |
4038 | |
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4039 // Grey object scanning during work stealing phase -- |
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4040 // the salient assumption here is that any references |
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4041 // that are in these stolen objects being scanned must |
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4042 // already have been initialized (else they would not have |
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4043 // been published), so we do not need to check for |
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4044 // uninitialized objects before pushing here. |
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4045 void Par_ConcMarkingClosure::do_oop(oop obj) { |
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4046 assert(obj->is_oop_or_null(true), "expected an oop or NULL"); |
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4047 HeapWord* addr = (HeapWord*)obj; |
0 | 4048 // Check if oop points into the CMS generation |
4049 // and is not marked | |
4050 if (_span.contains(addr) && !_bit_map->isMarked(addr)) { | |
4051 // a white object ... | |
4052 // If we manage to "claim" the object, by being the | |
4053 // first thread to mark it, then we push it on our | |
4054 // marking stack | |
4055 if (_bit_map->par_mark(addr)) { // ... now grey | |
4056 // push on work queue (grey set) | |
4057 bool simulate_overflow = false; | |
4058 NOT_PRODUCT( | |
4059 if (CMSMarkStackOverflowALot && | |
4060 _collector->simulate_overflow()) { | |
4061 // simulate a stack overflow | |
4062 simulate_overflow = true; | |
4063 } | |
4064 ) | |
4065 if (simulate_overflow || | |
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4066 !(_work_queue->push(obj) || _overflow_stack->par_push(obj))) { |
0 | 4067 // stack overflow |
4068 if (PrintCMSStatistics != 0) { | |
4069 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
4070 SIZE_FORMAT, _overflow_stack->capacity()); | |
4071 } | |
4072 // We cannot assert that the overflow stack is full because | |
4073 // it may have been emptied since. | |
4074 assert(simulate_overflow || | |
4075 _work_queue->size() == _work_queue->max_elems(), | |
4076 "Else push should have succeeded"); | |
4077 handle_stack_overflow(addr); | |
4078 } | |
4079 } // Else, some other thread got there first | |
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4080 do_yield_check(); |
0 | 4081 } |
4082 } | |
4083 | |
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4084 void Par_ConcMarkingClosure::do_oop(oop* p) { Par_ConcMarkingClosure::do_oop_work(p); } |
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4085 void Par_ConcMarkingClosure::do_oop(narrowOop* p) { Par_ConcMarkingClosure::do_oop_work(p); } |
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4086 |
0 | 4087 void Par_ConcMarkingClosure::trim_queue(size_t max) { |
4088 while (_work_queue->size() > max) { | |
4089 oop new_oop; | |
4090 if (_work_queue->pop_local(new_oop)) { | |
4091 assert(new_oop->is_oop(), "Should be an oop"); | |
4092 assert(_bit_map->isMarked((HeapWord*)new_oop), "Grey object"); | |
4093 assert(_span.contains((HeapWord*)new_oop), "Not in span"); | |
4094 new_oop->oop_iterate(this); // do_oop() above | |
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|
4095 do_yield_check(); |
0 | 4096 } |
4097 } | |
4098 } | |
4099 | |
4100 // Upon stack overflow, we discard (part of) the stack, | |
4101 // remembering the least address amongst those discarded | |
4102 // in CMSCollector's _restart_address. | |
4103 void Par_ConcMarkingClosure::handle_stack_overflow(HeapWord* lost) { | |
4104 // We need to do this under a mutex to prevent other | |
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4105 // workers from interfering with the work done below. |
0 | 4106 MutexLockerEx ml(_overflow_stack->par_lock(), |
4107 Mutex::_no_safepoint_check_flag); | |
4108 // Remember the least grey address discarded | |
4109 HeapWord* ra = (HeapWord*)_overflow_stack->least_value(lost); | |
4110 _collector->lower_restart_addr(ra); | |
4111 _overflow_stack->reset(); // discard stack contents | |
4112 _overflow_stack->expand(); // expand the stack if possible | |
4113 } | |
4114 | |
4115 | |
4116 void CMSConcMarkingTask::do_work_steal(int i) { | |
4117 OopTaskQueue* work_q = work_queue(i); | |
4118 oop obj_to_scan; | |
4119 CMSBitMap* bm = &(_collector->_markBitMap); | |
4120 CMSMarkStack* ovflw = &(_collector->_markStack); | |
4121 int* seed = _collector->hash_seed(i); | |
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4122 Par_ConcMarkingClosure cl(_collector, this, work_q, bm, ovflw); |
0 | 4123 while (true) { |
4124 cl.trim_queue(0); | |
4125 assert(work_q->size() == 0, "Should have been emptied above"); | |
4126 if (get_work_from_overflow_stack(ovflw, work_q)) { | |
4127 // Can't assert below because the work obtained from the | |
4128 // overflow stack may already have been stolen from us. | |
4129 // assert(work_q->size() > 0, "Work from overflow stack"); | |
4130 continue; | |
4131 } else if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) { | |
4132 assert(obj_to_scan->is_oop(), "Should be an oop"); | |
4133 assert(bm->isMarked((HeapWord*)obj_to_scan), "Grey object"); | |
4134 obj_to_scan->oop_iterate(&cl); | |
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4135 } else if (terminator()->offer_termination(&_term_term)) { |
0 | 4136 assert(work_q->size() == 0, "Impossible!"); |
4137 break; | |
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4138 } else if (yielding() || should_yield()) { |
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4139 yield(); |
0 | 4140 } |
4141 } | |
4142 } | |
4143 | |
4144 // This is run by the CMS (coordinator) thread. | |
4145 void CMSConcMarkingTask::coordinator_yield() { | |
4146 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
4147 "CMS thread should hold CMS token"); | |
4148 // First give up the locks, then yield, then re-lock | |
4149 // We should probably use a constructor/destructor idiom to | |
4150 // do this unlock/lock or modify the MutexUnlocker class to | |
4151 // serve our purpose. XXX | |
4152 assert_lock_strong(_bit_map_lock); | |
4153 _bit_map_lock->unlock(); | |
4154 ConcurrentMarkSweepThread::desynchronize(true); | |
4155 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
4156 _collector->stopTimer(); | |
4157 if (PrintCMSStatistics != 0) { | |
4158 _collector->incrementYields(); | |
4159 } | |
4160 _collector->icms_wait(); | |
4161 | |
4162 // It is possible for whichever thread initiated the yield request | |
4163 // not to get a chance to wake up and take the bitmap lock between | |
4164 // this thread releasing it and reacquiring it. So, while the | |
4165 // should_yield() flag is on, let's sleep for a bit to give the | |
4166 // other thread a chance to wake up. The limit imposed on the number | |
4167 // of iterations is defensive, to avoid any unforseen circumstances | |
4168 // putting us into an infinite loop. Since it's always been this | |
4169 // (coordinator_yield()) method that was observed to cause the | |
4170 // problem, we are using a parameter (CMSCoordinatorYieldSleepCount) | |
4171 // which is by default non-zero. For the other seven methods that | |
4172 // also perform the yield operation, as are using a different | |
4173 // parameter (CMSYieldSleepCount) which is by default zero. This way we | |
4174 // can enable the sleeping for those methods too, if necessary. | |
4175 // See 6442774. | |
4176 // | |
4177 // We really need to reconsider the synchronization between the GC | |
4178 // thread and the yield-requesting threads in the future and we | |
4179 // should really use wait/notify, which is the recommended | |
4180 // way of doing this type of interaction. Additionally, we should | |
4181 // consolidate the eight methods that do the yield operation and they | |
4182 // are almost identical into one for better maintenability and | |
4183 // readability. See 6445193. | |
4184 // | |
4185 // Tony 2006.06.29 | |
4186 for (unsigned i = 0; i < CMSCoordinatorYieldSleepCount && | |
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4187 ConcurrentMarkSweepThread::should_yield() && |
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4188 !CMSCollector::foregroundGCIsActive(); ++i) { |
0 | 4189 os::sleep(Thread::current(), 1, false); |
4190 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
4191 } | |
4192 | |
4193 ConcurrentMarkSweepThread::synchronize(true); | |
4194 _bit_map_lock->lock_without_safepoint_check(); | |
4195 _collector->startTimer(); | |
4196 } | |
4197 | |
4198 bool CMSCollector::do_marking_mt(bool asynch) { | |
1284 | 4199 assert(ConcGCThreads > 0 && conc_workers() != NULL, "precondition"); |
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4200 int num_workers = AdaptiveSizePolicy::calc_active_conc_workers( |
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4201 conc_workers()->total_workers(), |
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4202 conc_workers()->active_workers(), |
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4203 Threads::number_of_non_daemon_threads()); |
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4204 conc_workers()->set_active_workers(num_workers); |
0 | 4205 |
4206 CompactibleFreeListSpace* cms_space = _cmsGen->cmsSpace(); | |
4207 | |
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4208 CMSConcMarkingTask tsk(this, |
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4209 cms_space, |
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4210 asynch, |
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4211 conc_workers(), |
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4212 task_queues()); |
0 | 4213 |
4214 // Since the actual number of workers we get may be different | |
4215 // from the number we requested above, do we need to do anything different | |
4216 // below? In particular, may be we need to subclass the SequantialSubTasksDone | |
4217 // class?? XXX | |
4218 cms_space ->initialize_sequential_subtasks_for_marking(num_workers); | |
4219 | |
4220 // Refs discovery is already non-atomic. | |
4221 assert(!ref_processor()->discovery_is_atomic(), "Should be non-atomic"); | |
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4222 assert(ref_processor()->discovery_is_mt(), "Discovery should be MT"); |
0 | 4223 conc_workers()->start_task(&tsk); |
4224 while (tsk.yielded()) { | |
4225 tsk.coordinator_yield(); | |
4226 conc_workers()->continue_task(&tsk); | |
4227 } | |
4228 // If the task was aborted, _restart_addr will be non-NULL | |
4229 assert(tsk.completed() || _restart_addr != NULL, "Inconsistency"); | |
4230 while (_restart_addr != NULL) { | |
4231 // XXX For now we do not make use of ABORTED state and have not | |
4232 // yet implemented the right abort semantics (even in the original | |
4233 // single-threaded CMS case). That needs some more investigation | |
4234 // and is deferred for now; see CR# TBF. 07252005YSR. XXX | |
4235 assert(!CMSAbortSemantics || tsk.aborted(), "Inconsistency"); | |
4236 // If _restart_addr is non-NULL, a marking stack overflow | |
605 | 4237 // occurred; we need to do a fresh marking iteration from the |
0 | 4238 // indicated restart address. |
4239 if (_foregroundGCIsActive && asynch) { | |
4240 // We may be running into repeated stack overflows, having | |
4241 // reached the limit of the stack size, while making very | |
4242 // slow forward progress. It may be best to bail out and | |
4243 // let the foreground collector do its job. | |
4244 // Clear _restart_addr, so that foreground GC | |
4245 // works from scratch. This avoids the headache of | |
4246 // a "rescan" which would otherwise be needed because | |
4247 // of the dirty mod union table & card table. | |
4248 _restart_addr = NULL; | |
4249 return false; | |
4250 } | |
4251 // Adjust the task to restart from _restart_addr | |
4252 tsk.reset(_restart_addr); | |
4253 cms_space ->initialize_sequential_subtasks_for_marking(num_workers, | |
4254 _restart_addr); | |
4255 _restart_addr = NULL; | |
4256 // Get the workers going again | |
4257 conc_workers()->start_task(&tsk); | |
4258 while (tsk.yielded()) { | |
4259 tsk.coordinator_yield(); | |
4260 conc_workers()->continue_task(&tsk); | |
4261 } | |
4262 } | |
4263 assert(tsk.completed(), "Inconsistency"); | |
4264 assert(tsk.result() == true, "Inconsistency"); | |
4265 return true; | |
4266 } | |
4267 | |
4268 bool CMSCollector::do_marking_st(bool asynch) { | |
4269 ResourceMark rm; | |
4270 HandleMark hm; | |
4271 | |
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4272 // Temporarily make refs discovery single threaded (non-MT) |
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4273 ReferenceProcessorMTDiscoveryMutator rp_mut_discovery(ref_processor(), false); |
0 | 4274 MarkFromRootsClosure markFromRootsClosure(this, _span, &_markBitMap, |
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4275 &_markStack, CMSYield && asynch); |
0 | 4276 // the last argument to iterate indicates whether the iteration |
4277 // should be incremental with periodic yields. | |
4278 _markBitMap.iterate(&markFromRootsClosure); | |
4279 // If _restart_addr is non-NULL, a marking stack overflow | |
605 | 4280 // occurred; we need to do a fresh iteration from the |
0 | 4281 // indicated restart address. |
4282 while (_restart_addr != NULL) { | |
4283 if (_foregroundGCIsActive && asynch) { | |
4284 // We may be running into repeated stack overflows, having | |
4285 // reached the limit of the stack size, while making very | |
4286 // slow forward progress. It may be best to bail out and | |
4287 // let the foreground collector do its job. | |
4288 // Clear _restart_addr, so that foreground GC | |
4289 // works from scratch. This avoids the headache of | |
4290 // a "rescan" which would otherwise be needed because | |
4291 // of the dirty mod union table & card table. | |
4292 _restart_addr = NULL; | |
4293 return false; // indicating failure to complete marking | |
4294 } | |
4295 // Deal with stack overflow: | |
4296 // we restart marking from _restart_addr | |
4297 HeapWord* ra = _restart_addr; | |
4298 markFromRootsClosure.reset(ra); | |
4299 _restart_addr = NULL; | |
4300 _markBitMap.iterate(&markFromRootsClosure, ra, _span.end()); | |
4301 } | |
4302 return true; | |
4303 } | |
4304 | |
4305 void CMSCollector::preclean() { | |
4306 check_correct_thread_executing(); | |
4307 assert(Thread::current()->is_ConcurrentGC_thread(), "Wrong thread"); | |
4308 verify_work_stacks_empty(); | |
4309 verify_overflow_empty(); | |
4310 _abort_preclean = false; | |
4311 if (CMSPrecleaningEnabled) { | |
4312 _eden_chunk_index = 0; | |
4313 size_t used = get_eden_used(); | |
4314 size_t capacity = get_eden_capacity(); | |
4315 // Don't start sampling unless we will get sufficiently | |
4316 // many samples. | |
4317 if (used < (capacity/(CMSScheduleRemarkSamplingRatio * 100) | |
4318 * CMSScheduleRemarkEdenPenetration)) { | |
4319 _start_sampling = true; | |
4320 } else { | |
4321 _start_sampling = false; | |
4322 } | |
4323 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
4324 CMSPhaseAccounting pa(this, "preclean", !PrintGCDetails); | |
4325 preclean_work(CMSPrecleanRefLists1, CMSPrecleanSurvivors1); | |
4326 } | |
4327 CMSTokenSync x(true); // is cms thread | |
4328 if (CMSPrecleaningEnabled) { | |
4329 sample_eden(); | |
4330 _collectorState = AbortablePreclean; | |
4331 } else { | |
4332 _collectorState = FinalMarking; | |
4333 } | |
4334 verify_work_stacks_empty(); | |
4335 verify_overflow_empty(); | |
4336 } | |
4337 | |
4338 // Try and schedule the remark such that young gen | |
4339 // occupancy is CMSScheduleRemarkEdenPenetration %. | |
4340 void CMSCollector::abortable_preclean() { | |
4341 check_correct_thread_executing(); | |
4342 assert(CMSPrecleaningEnabled, "Inconsistent control state"); | |
4343 assert(_collectorState == AbortablePreclean, "Inconsistent control state"); | |
4344 | |
4345 // If Eden's current occupancy is below this threshold, | |
4346 // immediately schedule the remark; else preclean | |
4347 // past the next scavenge in an effort to | |
4348 // schedule the pause as described avove. By choosing | |
4349 // CMSScheduleRemarkEdenSizeThreshold >= max eden size | |
4350 // we will never do an actual abortable preclean cycle. | |
4351 if (get_eden_used() > CMSScheduleRemarkEdenSizeThreshold) { | |
4352 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
4353 CMSPhaseAccounting pa(this, "abortable-preclean", !PrintGCDetails); | |
4354 // We need more smarts in the abortable preclean | |
4355 // loop below to deal with cases where allocation | |
4356 // in young gen is very very slow, and our precleaning | |
4357 // is running a losing race against a horde of | |
4358 // mutators intent on flooding us with CMS updates | |
4359 // (dirty cards). | |
4360 // One, admittedly dumb, strategy is to give up | |
4361 // after a certain number of abortable precleaning loops | |
4362 // or after a certain maximum time. We want to make | |
4363 // this smarter in the next iteration. | |
4364 // XXX FIX ME!!! YSR | |
4365 size_t loops = 0, workdone = 0, cumworkdone = 0, waited = 0; | |
4366 while (!(should_abort_preclean() || | |
4367 ConcurrentMarkSweepThread::should_terminate())) { | |
4368 workdone = preclean_work(CMSPrecleanRefLists2, CMSPrecleanSurvivors2); | |
4369 cumworkdone += workdone; | |
4370 loops++; | |
4371 // Voluntarily terminate abortable preclean phase if we have | |
4372 // been at it for too long. | |
4373 if ((CMSMaxAbortablePrecleanLoops != 0) && | |
4374 loops >= CMSMaxAbortablePrecleanLoops) { | |
4375 if (PrintGCDetails) { | |
4376 gclog_or_tty->print(" CMS: abort preclean due to loops "); | |
4377 } | |
4378 break; | |
4379 } | |
4380 if (pa.wallclock_millis() > CMSMaxAbortablePrecleanTime) { | |
4381 if (PrintGCDetails) { | |
4382 gclog_or_tty->print(" CMS: abort preclean due to time "); | |
4383 } | |
4384 break; | |
4385 } | |
4386 // If we are doing little work each iteration, we should | |
4387 // take a short break. | |
4388 if (workdone < CMSAbortablePrecleanMinWorkPerIteration) { | |
4389 // Sleep for some time, waiting for work to accumulate | |
4390 stopTimer(); | |
4391 cmsThread()->wait_on_cms_lock(CMSAbortablePrecleanWaitMillis); | |
4392 startTimer(); | |
4393 waited++; | |
4394 } | |
4395 } | |
4396 if (PrintCMSStatistics > 0) { | |
4397 gclog_or_tty->print(" [%d iterations, %d waits, %d cards)] ", | |
4398 loops, waited, cumworkdone); | |
4399 } | |
4400 } | |
4401 CMSTokenSync x(true); // is cms thread | |
4402 if (_collectorState != Idling) { | |
4403 assert(_collectorState == AbortablePreclean, | |
4404 "Spontaneous state transition?"); | |
4405 _collectorState = FinalMarking; | |
4406 } // Else, a foreground collection completed this CMS cycle. | |
4407 return; | |
4408 } | |
4409 | |
4410 // Respond to an Eden sampling opportunity | |
4411 void CMSCollector::sample_eden() { | |
4412 // Make sure a young gc cannot sneak in between our | |
4413 // reading and recording of a sample. | |
4414 assert(Thread::current()->is_ConcurrentGC_thread(), | |
4415 "Only the cms thread may collect Eden samples"); | |
4416 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
4417 "Should collect samples while holding CMS token"); | |
4418 if (!_start_sampling) { | |
4419 return; | |
4420 } | |
4421 if (_eden_chunk_array) { | |
4422 if (_eden_chunk_index < _eden_chunk_capacity) { | |
4423 _eden_chunk_array[_eden_chunk_index] = *_top_addr; // take sample | |
4424 assert(_eden_chunk_array[_eden_chunk_index] <= *_end_addr, | |
4425 "Unexpected state of Eden"); | |
4426 // We'd like to check that what we just sampled is an oop-start address; | |
4427 // however, we cannot do that here since the object may not yet have been | |
4428 // initialized. So we'll instead do the check when we _use_ this sample | |
4429 // later. | |
4430 if (_eden_chunk_index == 0 || | |
4431 (pointer_delta(_eden_chunk_array[_eden_chunk_index], | |
4432 _eden_chunk_array[_eden_chunk_index-1]) | |
4433 >= CMSSamplingGrain)) { | |
4434 _eden_chunk_index++; // commit sample | |
4435 } | |
4436 } | |
4437 } | |
4438 if ((_collectorState == AbortablePreclean) && !_abort_preclean) { | |
4439 size_t used = get_eden_used(); | |
4440 size_t capacity = get_eden_capacity(); | |
4441 assert(used <= capacity, "Unexpected state of Eden"); | |
4442 if (used > (capacity/100 * CMSScheduleRemarkEdenPenetration)) { | |
4443 _abort_preclean = true; | |
4444 } | |
4445 } | |
4446 } | |
4447 | |
4448 | |
4449 size_t CMSCollector::preclean_work(bool clean_refs, bool clean_survivor) { | |
4450 assert(_collectorState == Precleaning || | |
4451 _collectorState == AbortablePreclean, "incorrect state"); | |
4452 ResourceMark rm; | |
4453 HandleMark hm; | |
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4454 |
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4455 // Precleaning is currently not MT but the reference processor |
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4456 // may be set for MT. Disable it temporarily here. |
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4457 ReferenceProcessor* rp = ref_processor(); |
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4458 ReferenceProcessorMTDiscoveryMutator rp_mut_discovery(rp, false); |
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4459 |
0 | 4460 // Do one pass of scrubbing the discovered reference lists |
4461 // to remove any reference objects with strongly-reachable | |
4462 // referents. | |
4463 if (clean_refs) { | |
4464 CMSPrecleanRefsYieldClosure yield_cl(this); | |
4465 assert(rp->span().equals(_span), "Spans should be equal"); | |
4466 CMSKeepAliveClosure keep_alive(this, _span, &_markBitMap, | |
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4467 &_markStack, true /* preclean */); |
0 | 4468 CMSDrainMarkingStackClosure complete_trace(this, |
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4469 _span, &_markBitMap, &_markStack, |
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4470 &keep_alive, true /* preclean */); |
0 | 4471 |
4472 // We don't want this step to interfere with a young | |
4473 // collection because we don't want to take CPU | |
4474 // or memory bandwidth away from the young GC threads | |
4475 // (which may be as many as there are CPUs). | |
4476 // Note that we don't need to protect ourselves from | |
4477 // interference with mutators because they can't | |
4478 // manipulate the discovered reference lists nor affect | |
4479 // the computed reachability of the referents, the | |
4480 // only properties manipulated by the precleaning | |
4481 // of these reference lists. | |
4482 stopTimer(); | |
4483 CMSTokenSyncWithLocks x(true /* is cms thread */, | |
4484 bitMapLock()); | |
4485 startTimer(); | |
4486 sample_eden(); | |
935 | 4487 |
0 | 4488 // The following will yield to allow foreground |
4489 // collection to proceed promptly. XXX YSR: | |
4490 // The code in this method may need further | |
4491 // tweaking for better performance and some restructuring | |
4492 // for cleaner interfaces. | |
4493 rp->preclean_discovered_references( | |
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4494 rp->is_alive_non_header(), &keep_alive, &complete_trace, &yield_cl); |
0 | 4495 } |
4496 | |
4497 if (clean_survivor) { // preclean the active survivor space(s) | |
4498 assert(_young_gen->kind() == Generation::DefNew || | |
4499 _young_gen->kind() == Generation::ParNew || | |
4500 _young_gen->kind() == Generation::ASParNew, | |
4501 "incorrect type for cast"); | |
4502 DefNewGeneration* dng = (DefNewGeneration*)_young_gen; | |
4503 PushAndMarkClosure pam_cl(this, _span, ref_processor(), | |
4504 &_markBitMap, &_modUnionTable, | |
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4505 &_markStack, true /* precleaning phase */); |
0 | 4506 stopTimer(); |
4507 CMSTokenSyncWithLocks ts(true /* is cms thread */, | |
4508 bitMapLock()); | |
4509 startTimer(); | |
4510 unsigned int before_count = | |
4511 GenCollectedHeap::heap()->total_collections(); | |
4512 SurvivorSpacePrecleanClosure | |
4513 sss_cl(this, _span, &_markBitMap, &_markStack, | |
4514 &pam_cl, before_count, CMSYield); | |
4515 dng->from()->object_iterate_careful(&sss_cl); | |
4516 dng->to()->object_iterate_careful(&sss_cl); | |
4517 } | |
4518 MarkRefsIntoAndScanClosure | |
4519 mrias_cl(_span, ref_processor(), &_markBitMap, &_modUnionTable, | |
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4520 &_markStack, this, CMSYield, |
0 | 4521 true /* precleaning phase */); |
4522 // CAUTION: The following closure has persistent state that may need to | |
4523 // be reset upon a decrease in the sequence of addresses it | |
4524 // processes. | |
4525 ScanMarkedObjectsAgainCarefullyClosure | |
4526 smoac_cl(this, _span, | |
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4527 &_markBitMap, &_markStack, &mrias_cl, CMSYield); |
0 | 4528 |
4529 // Preclean dirty cards in ModUnionTable and CardTable using | |
4530 // appropriate convergence criterion; | |
4531 // repeat CMSPrecleanIter times unless we find that | |
4532 // we are losing. | |
4533 assert(CMSPrecleanIter < 10, "CMSPrecleanIter is too large"); | |
4534 assert(CMSPrecleanNumerator < CMSPrecleanDenominator, | |
4535 "Bad convergence multiplier"); | |
4536 assert(CMSPrecleanThreshold >= 100, | |
4537 "Unreasonably low CMSPrecleanThreshold"); | |
4538 | |
4539 size_t numIter, cumNumCards, lastNumCards, curNumCards; | |
4540 for (numIter = 0, cumNumCards = lastNumCards = curNumCards = 0; | |
4541 numIter < CMSPrecleanIter; | |
4542 numIter++, lastNumCards = curNumCards, cumNumCards += curNumCards) { | |
4543 curNumCards = preclean_mod_union_table(_cmsGen, &smoac_cl); | |
4544 if (Verbose && PrintGCDetails) { | |
4545 gclog_or_tty->print(" (modUnionTable: %d cards)", curNumCards); | |
4546 } | |
4547 // Either there are very few dirty cards, so re-mark | |
4548 // pause will be small anyway, or our pre-cleaning isn't | |
4549 // that much faster than the rate at which cards are being | |
4550 // dirtied, so we might as well stop and re-mark since | |
4551 // precleaning won't improve our re-mark time by much. | |
4552 if (curNumCards <= CMSPrecleanThreshold || | |
4553 (numIter > 0 && | |
4554 (curNumCards * CMSPrecleanDenominator > | |
4555 lastNumCards * CMSPrecleanNumerator))) { | |
4556 numIter++; | |
4557 cumNumCards += curNumCards; | |
4558 break; | |
4559 } | |
4560 } | |
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4561 |
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4562 preclean_klasses(&mrias_cl, _cmsGen->freelistLock()); |
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4563 |
0 | 4564 curNumCards = preclean_card_table(_cmsGen, &smoac_cl); |
4565 cumNumCards += curNumCards; | |
4566 if (PrintGCDetails && PrintCMSStatistics != 0) { | |
4567 gclog_or_tty->print_cr(" (cardTable: %d cards, re-scanned %d cards, %d iterations)", | |
4568 curNumCards, cumNumCards, numIter); | |
4569 } | |
4570 return cumNumCards; // as a measure of useful work done | |
4571 } | |
4572 | |
4573 // PRECLEANING NOTES: | |
4574 // Precleaning involves: | |
4575 // . reading the bits of the modUnionTable and clearing the set bits. | |
4576 // . For the cards corresponding to the set bits, we scan the | |
4577 // objects on those cards. This means we need the free_list_lock | |
4578 // so that we can safely iterate over the CMS space when scanning | |
4579 // for oops. | |
4580 // . When we scan the objects, we'll be both reading and setting | |
4581 // marks in the marking bit map, so we'll need the marking bit map. | |
4582 // . For protecting _collector_state transitions, we take the CGC_lock. | |
4583 // Note that any races in the reading of of card table entries by the | |
4584 // CMS thread on the one hand and the clearing of those entries by the | |
4585 // VM thread or the setting of those entries by the mutator threads on the | |
4586 // other are quite benign. However, for efficiency it makes sense to keep | |
4587 // the VM thread from racing with the CMS thread while the latter is | |
4588 // dirty card info to the modUnionTable. We therefore also use the | |
4589 // CGC_lock to protect the reading of the card table and the mod union | |
4590 // table by the CM thread. | |
4591 // . We run concurrently with mutator updates, so scanning | |
4592 // needs to be done carefully -- we should not try to scan | |
4593 // potentially uninitialized objects. | |
4594 // | |
4595 // Locking strategy: While holding the CGC_lock, we scan over and | |
4596 // reset a maximal dirty range of the mod union / card tables, then lock | |
4597 // the free_list_lock and bitmap lock to do a full marking, then | |
4598 // release these locks; and repeat the cycle. This allows for a | |
4599 // certain amount of fairness in the sharing of these locks between | |
4600 // the CMS collector on the one hand, and the VM thread and the | |
4601 // mutators on the other. | |
4602 | |
4603 // NOTE: preclean_mod_union_table() and preclean_card_table() | |
4604 // further below are largely identical; if you need to modify | |
4605 // one of these methods, please check the other method too. | |
4606 | |
4607 size_t CMSCollector::preclean_mod_union_table( | |
4608 ConcurrentMarkSweepGeneration* gen, | |
4609 ScanMarkedObjectsAgainCarefullyClosure* cl) { | |
4610 verify_work_stacks_empty(); | |
4611 verify_overflow_empty(); | |
4612 | |
4613 // strategy: starting with the first card, accumulate contiguous | |
4614 // ranges of dirty cards; clear these cards, then scan the region | |
4615 // covered by these cards. | |
4616 | |
4617 // Since all of the MUT is committed ahead, we can just use | |
4618 // that, in case the generations expand while we are precleaning. | |
4619 // It might also be fine to just use the committed part of the | |
4620 // generation, but we might potentially miss cards when the | |
4621 // generation is rapidly expanding while we are in the midst | |
4622 // of precleaning. | |
4623 HeapWord* startAddr = gen->reserved().start(); | |
4624 HeapWord* endAddr = gen->reserved().end(); | |
4625 | |
4626 cl->setFreelistLock(gen->freelistLock()); // needed for yielding | |
4627 | |
4628 size_t numDirtyCards, cumNumDirtyCards; | |
4629 HeapWord *nextAddr, *lastAddr; | |
4630 for (cumNumDirtyCards = numDirtyCards = 0, | |
4631 nextAddr = lastAddr = startAddr; | |
4632 nextAddr < endAddr; | |
4633 nextAddr = lastAddr, cumNumDirtyCards += numDirtyCards) { | |
4634 | |
4635 ResourceMark rm; | |
4636 HandleMark hm; | |
4637 | |
4638 MemRegion dirtyRegion; | |
4639 { | |
4640 stopTimer(); | |
935 | 4641 // Potential yield point |
0 | 4642 CMSTokenSync ts(true); |
4643 startTimer(); | |
4644 sample_eden(); | |
4645 // Get dirty region starting at nextOffset (inclusive), | |
4646 // simultaneously clearing it. | |
4647 dirtyRegion = | |
4648 _modUnionTable.getAndClearMarkedRegion(nextAddr, endAddr); | |
4649 assert(dirtyRegion.start() >= nextAddr, | |
4650 "returned region inconsistent?"); | |
4651 } | |
4652 // Remember where the next search should begin. | |
4653 // The returned region (if non-empty) is a right open interval, | |
4654 // so lastOffset is obtained from the right end of that | |
4655 // interval. | |
4656 lastAddr = dirtyRegion.end(); | |
4657 // Should do something more transparent and less hacky XXX | |
4658 numDirtyCards = | |
4659 _modUnionTable.heapWordDiffToOffsetDiff(dirtyRegion.word_size()); | |
4660 | |
4661 // We'll scan the cards in the dirty region (with periodic | |
4662 // yields for foreground GC as needed). | |
4663 if (!dirtyRegion.is_empty()) { | |
4664 assert(numDirtyCards > 0, "consistency check"); | |
4665 HeapWord* stop_point = NULL; | |
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4666 stopTimer(); |
935 | 4667 // Potential yield point |
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4668 CMSTokenSyncWithLocks ts(true, gen->freelistLock(), |
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4669 bitMapLock()); |
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4670 startTimer(); |
0 | 4671 { |
4672 verify_work_stacks_empty(); | |
4673 verify_overflow_empty(); | |
4674 sample_eden(); | |
4675 stop_point = | |
4676 gen->cmsSpace()->object_iterate_careful_m(dirtyRegion, cl); | |
4677 } | |
4678 if (stop_point != NULL) { | |
4679 // The careful iteration stopped early either because it found an | |
4680 // uninitialized object, or because we were in the midst of an | |
4681 // "abortable preclean", which should now be aborted. Redirty | |
4682 // the bits corresponding to the partially-scanned or unscanned | |
4683 // cards. We'll either restart at the next block boundary or | |
4684 // abort the preclean. | |
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4685 assert((_collectorState == AbortablePreclean && should_abort_preclean()), |
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4686 "Should only be AbortablePreclean."); |
0 | 4687 _modUnionTable.mark_range(MemRegion(stop_point, dirtyRegion.end())); |
4688 if (should_abort_preclean()) { | |
4689 break; // out of preclean loop | |
4690 } else { | |
4691 // Compute the next address at which preclean should pick up; | |
4692 // might need bitMapLock in order to read P-bits. | |
4693 lastAddr = next_card_start_after_block(stop_point); | |
4694 } | |
4695 } | |
4696 } else { | |
4697 assert(lastAddr == endAddr, "consistency check"); | |
4698 assert(numDirtyCards == 0, "consistency check"); | |
4699 break; | |
4700 } | |
4701 } | |
4702 verify_work_stacks_empty(); | |
4703 verify_overflow_empty(); | |
4704 return cumNumDirtyCards; | |
4705 } | |
4706 | |
4707 // NOTE: preclean_mod_union_table() above and preclean_card_table() | |
4708 // below are largely identical; if you need to modify | |
4709 // one of these methods, please check the other method too. | |
4710 | |
4711 size_t CMSCollector::preclean_card_table(ConcurrentMarkSweepGeneration* gen, | |
4712 ScanMarkedObjectsAgainCarefullyClosure* cl) { | |
4713 // strategy: it's similar to precleamModUnionTable above, in that | |
4714 // we accumulate contiguous ranges of dirty cards, mark these cards | |
4715 // precleaned, then scan the region covered by these cards. | |
4716 HeapWord* endAddr = (HeapWord*)(gen->_virtual_space.high()); | |
4717 HeapWord* startAddr = (HeapWord*)(gen->_virtual_space.low()); | |
4718 | |
4719 cl->setFreelistLock(gen->freelistLock()); // needed for yielding | |
4720 | |
4721 size_t numDirtyCards, cumNumDirtyCards; | |
4722 HeapWord *lastAddr, *nextAddr; | |
4723 | |
4724 for (cumNumDirtyCards = numDirtyCards = 0, | |
4725 nextAddr = lastAddr = startAddr; | |
4726 nextAddr < endAddr; | |
4727 nextAddr = lastAddr, cumNumDirtyCards += numDirtyCards) { | |
4728 | |
4729 ResourceMark rm; | |
4730 HandleMark hm; | |
4731 | |
4732 MemRegion dirtyRegion; | |
4733 { | |
4734 // See comments in "Precleaning notes" above on why we | |
4735 // do this locking. XXX Could the locking overheads be | |
4736 // too high when dirty cards are sparse? [I don't think so.] | |
4737 stopTimer(); | |
4738 CMSTokenSync x(true); // is cms thread | |
4739 startTimer(); | |
4740 sample_eden(); | |
4741 // Get and clear dirty region from card table | |
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4742 dirtyRegion = _ct->ct_bs()->dirty_card_range_after_reset( |
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4743 MemRegion(nextAddr, endAddr), |
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4744 true, |
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4745 CardTableModRefBS::precleaned_card_val()); |
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4746 |
0 | 4747 assert(dirtyRegion.start() >= nextAddr, |
4748 "returned region inconsistent?"); | |
4749 } | |
4750 lastAddr = dirtyRegion.end(); | |
4751 numDirtyCards = | |
4752 dirtyRegion.word_size()/CardTableModRefBS::card_size_in_words; | |
4753 | |
4754 if (!dirtyRegion.is_empty()) { | |
4755 stopTimer(); | |
4756 CMSTokenSyncWithLocks ts(true, gen->freelistLock(), bitMapLock()); | |
4757 startTimer(); | |
4758 sample_eden(); | |
4759 verify_work_stacks_empty(); | |
4760 verify_overflow_empty(); | |
4761 HeapWord* stop_point = | |
4762 gen->cmsSpace()->object_iterate_careful_m(dirtyRegion, cl); | |
4763 if (stop_point != NULL) { | |
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4764 assert((_collectorState == AbortablePreclean && should_abort_preclean()), |
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4765 "Should only be AbortablePreclean."); |
0 | 4766 _ct->ct_bs()->invalidate(MemRegion(stop_point, dirtyRegion.end())); |
4767 if (should_abort_preclean()) { | |
4768 break; // out of preclean loop | |
4769 } else { | |
4770 // Compute the next address at which preclean should pick up. | |
4771 lastAddr = next_card_start_after_block(stop_point); | |
4772 } | |
4773 } | |
4774 } else { | |
4775 break; | |
4776 } | |
4777 } | |
4778 verify_work_stacks_empty(); | |
4779 verify_overflow_empty(); | |
4780 return cumNumDirtyCards; | |
4781 } | |
4782 | |
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4783 class PrecleanKlassClosure : public KlassClosure { |
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4784 CMKlassClosure _cm_klass_closure; |
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4785 public: |
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4786 PrecleanKlassClosure(OopClosure* oop_closure) : _cm_klass_closure(oop_closure) {} |
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4787 void do_klass(Klass* k) { |
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4788 if (k->has_accumulated_modified_oops()) { |
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4789 k->clear_accumulated_modified_oops(); |
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4790 |
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4791 _cm_klass_closure.do_klass(k); |
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4792 } |
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4793 } |
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4794 }; |
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4795 |
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4796 // The freelist lock is needed to prevent asserts, is it really needed? |
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4797 void CMSCollector::preclean_klasses(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock) { |
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4798 |
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4799 cl->set_freelistLock(freelistLock); |
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4800 |
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4801 CMSTokenSyncWithLocks ts(true, freelistLock, bitMapLock()); |
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4802 |
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4803 // SSS: Add equivalent to ScanMarkedObjectsAgainCarefullyClosure::do_yield_check and should_abort_preclean? |
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4804 // SSS: We should probably check if precleaning should be aborted, at suitable intervals? |
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4805 PrecleanKlassClosure preclean_klass_closure(cl); |
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4806 ClassLoaderDataGraph::classes_do(&preclean_klass_closure); |
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4807 |
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4808 verify_work_stacks_empty(); |
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4809 verify_overflow_empty(); |
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4810 } |
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4811 |
0 | 4812 void CMSCollector::checkpointRootsFinal(bool asynch, |
4813 bool clear_all_soft_refs, bool init_mark_was_synchronous) { | |
4814 assert(_collectorState == FinalMarking, "incorrect state transition?"); | |
4815 check_correct_thread_executing(); | |
4816 // world is stopped at this checkpoint | |
4817 assert(SafepointSynchronize::is_at_safepoint(), | |
4818 "world should be stopped"); | |
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4819 TraceCMSMemoryManagerStats tms(_collectorState,GenCollectedHeap::heap()->gc_cause()); |
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4820 |
0 | 4821 verify_work_stacks_empty(); |
4822 verify_overflow_empty(); | |
4823 | |
4824 SpecializationStats::clear(); | |
4825 if (PrintGCDetails) { | |
4826 gclog_or_tty->print("[YG occupancy: "SIZE_FORMAT" K ("SIZE_FORMAT" K)]", | |
4827 _young_gen->used() / K, | |
4828 _young_gen->capacity() / K); | |
4829 } | |
4830 if (asynch) { | |
4831 if (CMSScavengeBeforeRemark) { | |
4832 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
4833 // Temporarily set flag to false, GCH->do_collection will | |
4834 // expect it to be false and set to true | |
4835 FlagSetting fl(gch->_is_gc_active, false); | |
4836 NOT_PRODUCT(TraceTime t("Scavenge-Before-Remark", | |
4837 PrintGCDetails && Verbose, true, gclog_or_tty);) | |
4838 int level = _cmsGen->level() - 1; | |
4839 if (level >= 0) { | |
4840 gch->do_collection(true, // full (i.e. force, see below) | |
4841 false, // !clear_all_soft_refs | |
4842 0, // size | |
4843 false, // is_tlab | |
4844 level // max_level | |
4845 ); | |
4846 } | |
4847 } | |
4848 FreelistLocker x(this); | |
4849 MutexLockerEx y(bitMapLock(), | |
4850 Mutex::_no_safepoint_check_flag); | |
4851 assert(!init_mark_was_synchronous, "but that's impossible!"); | |
4852 checkpointRootsFinalWork(asynch, clear_all_soft_refs, false); | |
4853 } else { | |
4854 // already have all the locks | |
4855 checkpointRootsFinalWork(asynch, clear_all_soft_refs, | |
4856 init_mark_was_synchronous); | |
4857 } | |
4858 verify_work_stacks_empty(); | |
4859 verify_overflow_empty(); | |
4860 SpecializationStats::print(); | |
4861 } | |
4862 | |
4863 void CMSCollector::checkpointRootsFinalWork(bool asynch, | |
4864 bool clear_all_soft_refs, bool init_mark_was_synchronous) { | |
4865 | |
4866 NOT_PRODUCT(TraceTime tr("checkpointRootsFinalWork", PrintGCDetails, false, gclog_or_tty);) | |
4867 | |
4868 assert(haveFreelistLocks(), "must have free list locks"); | |
4869 assert_lock_strong(bitMapLock()); | |
4870 | |
4871 if (UseAdaptiveSizePolicy) { | |
4872 size_policy()->checkpoint_roots_final_begin(); | |
4873 } | |
4874 | |
4875 ResourceMark rm; | |
4876 HandleMark hm; | |
4877 | |
4878 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
4879 | |
94
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4880 if (should_unload_classes()) { |
0 | 4881 CodeCache::gc_prologue(); |
4882 } | |
4883 assert(haveFreelistLocks(), "must have free list locks"); | |
4884 assert_lock_strong(bitMapLock()); | |
4885 | |
4886 if (!init_mark_was_synchronous) { | |
4887 // We might assume that we need not fill TLAB's when | |
4888 // CMSScavengeBeforeRemark is set, because we may have just done | |
4889 // a scavenge which would have filled all TLAB's -- and besides | |
4890 // Eden would be empty. This however may not always be the case -- | |
4891 // for instance although we asked for a scavenge, it may not have | |
4892 // happened because of a JNI critical section. We probably need | |
4893 // a policy for deciding whether we can in that case wait until | |
4894 // the critical section releases and then do the remark following | |
4895 // the scavenge, and skip it here. In the absence of that policy, | |
4896 // or of an indication of whether the scavenge did indeed occur, | |
4897 // we cannot rely on TLAB's having been filled and must do | |
4898 // so here just in case a scavenge did not happen. | |
4899 gch->ensure_parsability(false); // fill TLAB's, but no need to retire them | |
4900 // Update the saved marks which may affect the root scans. | |
4901 gch->save_marks(); | |
4902 | |
4903 { | |
4904 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;) | |
4905 | |
4906 // Note on the role of the mod union table: | |
4907 // Since the marker in "markFromRoots" marks concurrently with | |
4908 // mutators, it is possible for some reachable objects not to have been | |
4909 // scanned. For instance, an only reference to an object A was | |
4910 // placed in object B after the marker scanned B. Unless B is rescanned, | |
4911 // A would be collected. Such updates to references in marked objects | |
4912 // are detected via the mod union table which is the set of all cards | |
4913 // dirtied since the first checkpoint in this GC cycle and prior to | |
4914 // the most recent young generation GC, minus those cleaned up by the | |
4915 // concurrent precleaning. | |
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4916 if (CMSParallelRemarkEnabled && CollectedHeap::use_parallel_gc_threads()) { |
0 | 4917 TraceTime t("Rescan (parallel) ", PrintGCDetails, false, gclog_or_tty); |
4918 do_remark_parallel(); | |
4919 } else { | |
4920 TraceTime t("Rescan (non-parallel) ", PrintGCDetails, false, | |
4921 gclog_or_tty); | |
4922 do_remark_non_parallel(); | |
4923 } | |
4924 } | |
4925 } else { | |
4926 assert(!asynch, "Can't have init_mark_was_synchronous in asynch mode"); | |
4927 // The initial mark was stop-world, so there's no rescanning to | |
4928 // do; go straight on to the next step below. | |
4929 } | |
4930 verify_work_stacks_empty(); | |
4931 verify_overflow_empty(); | |
4932 | |
4933 { | |
4934 NOT_PRODUCT(TraceTime ts("refProcessingWork", PrintGCDetails, false, gclog_or_tty);) | |
4935 refProcessingWork(asynch, clear_all_soft_refs); | |
4936 } | |
4937 verify_work_stacks_empty(); | |
4938 verify_overflow_empty(); | |
4939 | |
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4940 if (should_unload_classes()) { |
0 | 4941 CodeCache::gc_epilogue(); |
4942 } | |
2147
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4943 JvmtiExport::gc_epilogue(); |
0 | 4944 |
4945 // If we encountered any (marking stack / work queue) overflow | |
4946 // events during the current CMS cycle, take appropriate | |
4947 // remedial measures, where possible, so as to try and avoid | |
4948 // recurrence of that condition. | |
4949 assert(_markStack.isEmpty(), "No grey objects"); | |
4950 size_t ser_ovflw = _ser_pmc_remark_ovflw + _ser_pmc_preclean_ovflw + | |
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4951 _ser_kac_ovflw + _ser_kac_preclean_ovflw; |
0 | 4952 if (ser_ovflw > 0) { |
4953 if (PrintCMSStatistics != 0) { | |
4954 gclog_or_tty->print_cr("Marking stack overflow (benign) " | |
452
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4955 "(pmc_pc="SIZE_FORMAT", pmc_rm="SIZE_FORMAT", kac="SIZE_FORMAT |
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4956 ", kac_preclean="SIZE_FORMAT")", |
0 | 4957 _ser_pmc_preclean_ovflw, _ser_pmc_remark_ovflw, |
452
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4958 _ser_kac_ovflw, _ser_kac_preclean_ovflw); |
0 | 4959 } |
4960 _markStack.expand(); | |
4961 _ser_pmc_remark_ovflw = 0; | |
4962 _ser_pmc_preclean_ovflw = 0; | |
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4963 _ser_kac_preclean_ovflw = 0; |
0 | 4964 _ser_kac_ovflw = 0; |
4965 } | |
4966 if (_par_pmc_remark_ovflw > 0 || _par_kac_ovflw > 0) { | |
4967 if (PrintCMSStatistics != 0) { | |
4968 gclog_or_tty->print_cr("Work queue overflow (benign) " | |
4969 "(pmc_rm="SIZE_FORMAT", kac="SIZE_FORMAT")", | |
4970 _par_pmc_remark_ovflw, _par_kac_ovflw); | |
4971 } | |
4972 _par_pmc_remark_ovflw = 0; | |
4973 _par_kac_ovflw = 0; | |
4974 } | |
4975 if (PrintCMSStatistics != 0) { | |
4976 if (_markStack._hit_limit > 0) { | |
4977 gclog_or_tty->print_cr(" (benign) Hit max stack size limit ("SIZE_FORMAT")", | |
4978 _markStack._hit_limit); | |
4979 } | |
4980 if (_markStack._failed_double > 0) { | |
4981 gclog_or_tty->print_cr(" (benign) Failed stack doubling ("SIZE_FORMAT")," | |
4982 " current capacity "SIZE_FORMAT, | |
4983 _markStack._failed_double, | |
4984 _markStack.capacity()); | |
4985 } | |
4986 } | |
4987 _markStack._hit_limit = 0; | |
4988 _markStack._failed_double = 0; | |
4989 | |
4990 if ((VerifyAfterGC || VerifyDuringGC) && | |
4991 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
4992 verify_after_remark(); | |
4993 } | |
4994 | |
4995 // Change under the freelistLocks. | |
4996 _collectorState = Sweeping; | |
4997 // Call isAllClear() under bitMapLock | |
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4998 assert(_modUnionTable.isAllClear(), |
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4999 "Should be clear by end of the final marking"); |
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5000 assert(_ct->klass_rem_set()->mod_union_is_clear(), |
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5001 "Should be clear by end of the final marking"); |
0 | 5002 if (UseAdaptiveSizePolicy) { |
5003 size_policy()->checkpoint_roots_final_end(gch->gc_cause()); | |
5004 } | |
5005 } | |
5006 | |
5007 // Parallel remark task | |
5008 class CMSParRemarkTask: public AbstractGangTask { | |
5009 CMSCollector* _collector; | |
5010 int _n_workers; | |
5011 CompactibleFreeListSpace* _cms_space; | |
5012 | |
5013 // The per-thread work queues, available here for stealing. | |
5014 OopTaskQueueSet* _task_queues; | |
5015 ParallelTaskTerminator _term; | |
5016 | |
5017 public: | |
4095
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5018 // A value of 0 passed to n_workers will cause the number of |
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5019 // workers to be taken from the active workers in the work gang. |
0 | 5020 CMSParRemarkTask(CMSCollector* collector, |
5021 CompactibleFreeListSpace* cms_space, | |
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5022 int n_workers, FlexibleWorkGang* workers, |
0 | 5023 OopTaskQueueSet* task_queues): |
5024 AbstractGangTask("Rescan roots and grey objects in parallel"), | |
5025 _collector(collector), | |
6725
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5026 _cms_space(cms_space), |
0 | 5027 _n_workers(n_workers), |
5028 _task_queues(task_queues), | |
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5029 _term(n_workers, task_queues) { } |
0 | 5030 |
5031 OopTaskQueueSet* task_queues() { return _task_queues; } | |
5032 | |
5033 OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); } | |
5034 | |
5035 ParallelTaskTerminator* terminator() { return &_term; } | |
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5036 int n_workers() { return _n_workers; } |
0 | 5037 |
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5038 void work(uint worker_id); |
0 | 5039 |
5040 private: | |
5041 // Work method in support of parallel rescan ... of young gen spaces | |
5042 void do_young_space_rescan(int i, Par_MarkRefsIntoAndScanClosure* cl, | |
5043 ContiguousSpace* space, | |
5044 HeapWord** chunk_array, size_t chunk_top); | |
5045 | |
5046 // ... of dirty cards in old space | |
5047 void do_dirty_card_rescan_tasks(CompactibleFreeListSpace* sp, int i, | |
5048 Par_MarkRefsIntoAndScanClosure* cl); | |
5049 | |
5050 // ... work stealing for the above | |
5051 void do_work_steal(int i, Par_MarkRefsIntoAndScanClosure* cl, int* seed); | |
5052 }; | |
5053 | |
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5054 class RemarkKlassClosure : public KlassClosure { |
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5055 CMKlassClosure _cm_klass_closure; |
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5056 public: |
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5057 RemarkKlassClosure(OopClosure* oop_closure) : _cm_klass_closure(oop_closure) {} |
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5058 void do_klass(Klass* k) { |
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5059 // Check if we have modified any oops in the Klass during the concurrent marking. |
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5060 if (k->has_accumulated_modified_oops()) { |
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5061 k->clear_accumulated_modified_oops(); |
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5062 |
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5063 // We could have transfered the current modified marks to the accumulated marks, |
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5064 // like we do with the Card Table to Mod Union Table. But it's not really necessary. |
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5065 } else if (k->has_modified_oops()) { |
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5066 // Don't clear anything, this info is needed by the next young collection. |
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5067 } else { |
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5068 // No modified oops in the Klass. |
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5069 return; |
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|
5070 } |
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5071 |
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5072 // The klass has modified fields, need to scan the klass. |
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5073 _cm_klass_closure.do_klass(k); |
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5074 } |
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5075 }; |
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5076 |
1833
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|
5077 // work_queue(i) is passed to the closure |
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5078 // Par_MarkRefsIntoAndScanClosure. The "i" parameter |
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5079 // also is passed to do_dirty_card_rescan_tasks() and to |
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|
5080 // do_work_steal() to select the i-th task_queue. |
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5081 |
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5082 void CMSParRemarkTask::work(uint worker_id) { |
0 | 5083 elapsedTimer _timer; |
5084 ResourceMark rm; | |
5085 HandleMark hm; | |
5086 | |
5087 // ---------- rescan from roots -------------- | |
5088 _timer.start(); | |
5089 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
5090 Par_MarkRefsIntoAndScanClosure par_mrias_cl(_collector, | |
5091 _collector->_span, _collector->ref_processor(), | |
5092 &(_collector->_markBitMap), | |
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5093 work_queue(worker_id)); |
0 | 5094 |
5095 // Rescan young gen roots first since these are likely | |
5096 // coarsely partitioned and may, on that account, constitute | |
5097 // the critical path; thus, it's best to start off that | |
5098 // work first. | |
5099 // ---------- young gen roots -------------- | |
5100 { | |
5101 DefNewGeneration* dng = _collector->_young_gen->as_DefNewGeneration(); | |
5102 EdenSpace* eden_space = dng->eden(); | |
5103 ContiguousSpace* from_space = dng->from(); | |
5104 ContiguousSpace* to_space = dng->to(); | |
5105 | |
5106 HeapWord** eca = _collector->_eden_chunk_array; | |
5107 size_t ect = _collector->_eden_chunk_index; | |
5108 HeapWord** sca = _collector->_survivor_chunk_array; | |
5109 size_t sct = _collector->_survivor_chunk_index; | |
5110 | |
5111 assert(ect <= _collector->_eden_chunk_capacity, "out of bounds"); | |
5112 assert(sct <= _collector->_survivor_chunk_capacity, "out of bounds"); | |
5113 | |
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5114 do_young_space_rescan(worker_id, &par_mrias_cl, to_space, NULL, 0); |
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5115 do_young_space_rescan(worker_id, &par_mrias_cl, from_space, sca, sct); |
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|
5116 do_young_space_rescan(worker_id, &par_mrias_cl, eden_space, eca, ect); |
0 | 5117 |
5118 _timer.stop(); | |
5119 if (PrintCMSStatistics != 0) { | |
5120 gclog_or_tty->print_cr( | |
5121 "Finished young gen rescan work in %dth thread: %3.3f sec", | |
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|
5122 worker_id, _timer.seconds()); |
0 | 5123 } |
5124 } | |
5125 | |
5126 // ---------- remaining roots -------------- | |
5127 _timer.reset(); | |
5128 _timer.start(); | |
5129 gch->gen_process_strong_roots(_collector->_cmsGen->level(), | |
5130 false, // yg was scanned above | |
989
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5131 false, // this is parallel code |
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5132 false, // not scavenging |
0 | 5133 SharedHeap::ScanningOption(_collector->CMSCollector::roots_scanning_options()), |
989
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|
5134 &par_mrias_cl, |
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5135 true, // walk all of code cache if (so & SO_CodeCache) |
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5136 NULL, |
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5137 NULL); // The dirty klasses will be handled below |
989
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diff
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|
5138 assert(_collector->should_unload_classes() |
148e5441d916
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5139 || (_collector->CMSCollector::roots_scanning_options() & SharedHeap::SO_CodeCache), |
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5140 "if we didn't scan the code cache, we have to be ready to drop nmethods with expired weak oops"); |
0 | 5141 _timer.stop(); |
5142 if (PrintCMSStatistics != 0) { | |
5143 gclog_or_tty->print_cr( | |
5144 "Finished remaining root rescan work in %dth thread: %3.3f sec", | |
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5145 worker_id, _timer.seconds()); |
0 | 5146 } |
5147 | |
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5148 // ---------- unhandled CLD scanning ---------- |
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5149 if (worker_id == 0) { // Single threaded at the moment. |
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5150 _timer.reset(); |
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5151 _timer.start(); |
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5152 |
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5153 // Scan all new class loader data objects and new dependencies that were |
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5154 // introduced during concurrent marking. |
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5155 ResourceMark rm; |
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5156 GrowableArray<ClassLoaderData*>* array = ClassLoaderDataGraph::new_clds(); |
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5157 for (int i = 0; i < array->length(); i++) { |
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5158 par_mrias_cl.do_class_loader_data(array->at(i)); |
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5159 } |
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5160 |
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5161 // We don't need to keep track of new CLDs anymore. |
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5162 ClassLoaderDataGraph::remember_new_clds(false); |
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5163 |
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5164 _timer.stop(); |
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5165 if (PrintCMSStatistics != 0) { |
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5166 gclog_or_tty->print_cr( |
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5167 "Finished unhandled CLD scanning work in %dth thread: %3.3f sec", |
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5168 worker_id, _timer.seconds()); |
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5169 } |
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5170 } |
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5171 |
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5172 // ---------- dirty klass scanning ---------- |
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5173 if (worker_id == 0) { // Single threaded at the moment. |
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5174 _timer.reset(); |
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5175 _timer.start(); |
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5176 |
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5177 // Scan all classes that was dirtied during the concurrent marking phase. |
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5178 RemarkKlassClosure remark_klass_closure(&par_mrias_cl); |
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5179 ClassLoaderDataGraph::classes_do(&remark_klass_closure); |
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5180 |
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5181 _timer.stop(); |
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5182 if (PrintCMSStatistics != 0) { |
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5183 gclog_or_tty->print_cr( |
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5184 "Finished dirty klass scanning work in %dth thread: %3.3f sec", |
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5185 worker_id, _timer.seconds()); |
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5186 } |
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5187 } |
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5188 |
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5189 // We might have added oops to ClassLoaderData::_handles during the |
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5190 // concurrent marking phase. These oops point to newly allocated objects |
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5191 // that are guaranteed to be kept alive. Either by the direct allocation |
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5192 // code, or when the young collector processes the strong roots. Hence, |
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5193 // we don't have to revisit the _handles block during the remark phase. |
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5194 |
0 | 5195 // ---------- rescan dirty cards ------------ |
5196 _timer.reset(); | |
5197 _timer.start(); | |
5198 | |
5199 // Do the rescan tasks for each of the two spaces | |
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5200 // (cms_space) in turn. |
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5201 // "worker_id" is passed to select the task_queue for "worker_id" |
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5202 do_dirty_card_rescan_tasks(_cms_space, worker_id, &par_mrias_cl); |
0 | 5203 _timer.stop(); |
5204 if (PrintCMSStatistics != 0) { | |
5205 gclog_or_tty->print_cr( | |
5206 "Finished dirty card rescan work in %dth thread: %3.3f sec", | |
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5207 worker_id, _timer.seconds()); |
0 | 5208 } |
5209 | |
5210 // ---------- steal work from other threads ... | |
5211 // ---------- ... and drain overflow list. | |
5212 _timer.reset(); | |
5213 _timer.start(); | |
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5214 do_work_steal(worker_id, &par_mrias_cl, _collector->hash_seed(worker_id)); |
0 | 5215 _timer.stop(); |
5216 if (PrintCMSStatistics != 0) { | |
5217 gclog_or_tty->print_cr( | |
5218 "Finished work stealing in %dth thread: %3.3f sec", | |
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5219 worker_id, _timer.seconds()); |
0 | 5220 } |
5221 } | |
5222 | |
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5223 // Note that parameter "i" is not used. |
0 | 5224 void |
5225 CMSParRemarkTask::do_young_space_rescan(int i, | |
5226 Par_MarkRefsIntoAndScanClosure* cl, ContiguousSpace* space, | |
5227 HeapWord** chunk_array, size_t chunk_top) { | |
5228 // Until all tasks completed: | |
5229 // . claim an unclaimed task | |
5230 // . compute region boundaries corresponding to task claimed | |
5231 // using chunk_array | |
5232 // . par_oop_iterate(cl) over that region | |
5233 | |
5234 ResourceMark rm; | |
5235 HandleMark hm; | |
5236 | |
5237 SequentialSubTasksDone* pst = space->par_seq_tasks(); | |
5238 assert(pst->valid(), "Uninitialized use?"); | |
5239 | |
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5240 uint nth_task = 0; |
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5241 uint n_tasks = pst->n_tasks(); |
0 | 5242 |
5243 HeapWord *start, *end; | |
5244 while (!pst->is_task_claimed(/* reference */ nth_task)) { | |
5245 // We claimed task # nth_task; compute its boundaries. | |
5246 if (chunk_top == 0) { // no samples were taken | |
5247 assert(nth_task == 0 && n_tasks == 1, "Can have only 1 EdenSpace task"); | |
5248 start = space->bottom(); | |
5249 end = space->top(); | |
5250 } else if (nth_task == 0) { | |
5251 start = space->bottom(); | |
5252 end = chunk_array[nth_task]; | |
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5253 } else if (nth_task < (uint)chunk_top) { |
0 | 5254 assert(nth_task >= 1, "Control point invariant"); |
5255 start = chunk_array[nth_task - 1]; | |
5256 end = chunk_array[nth_task]; | |
5257 } else { | |
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5258 assert(nth_task == (uint)chunk_top, "Control point invariant"); |
0 | 5259 start = chunk_array[chunk_top - 1]; |
5260 end = space->top(); | |
5261 } | |
5262 MemRegion mr(start, end); | |
5263 // Verify that mr is in space | |
5264 assert(mr.is_empty() || space->used_region().contains(mr), | |
5265 "Should be in space"); | |
5266 // Verify that "start" is an object boundary | |
5267 assert(mr.is_empty() || oop(mr.start())->is_oop(), | |
5268 "Should be an oop"); | |
5269 space->par_oop_iterate(mr, cl); | |
5270 } | |
5271 pst->all_tasks_completed(); | |
5272 } | |
5273 | |
5274 void | |
5275 CMSParRemarkTask::do_dirty_card_rescan_tasks( | |
5276 CompactibleFreeListSpace* sp, int i, | |
5277 Par_MarkRefsIntoAndScanClosure* cl) { | |
5278 // Until all tasks completed: | |
5279 // . claim an unclaimed task | |
5280 // . compute region boundaries corresponding to task claimed | |
5281 // . transfer dirty bits ct->mut for that region | |
5282 // . apply rescanclosure to dirty mut bits for that region | |
5283 | |
5284 ResourceMark rm; | |
5285 HandleMark hm; | |
5286 | |
5287 OopTaskQueue* work_q = work_queue(i); | |
5288 ModUnionClosure modUnionClosure(&(_collector->_modUnionTable)); | |
5289 // CAUTION! CAUTION! CAUTION! CAUTION! CAUTION! CAUTION! CAUTION! | |
5290 // CAUTION: This closure has state that persists across calls to | |
5291 // the work method dirty_range_iterate_clear() in that it has | |
5292 // imbedded in it a (subtype of) UpwardsObjectClosure. The | |
5293 // use of that state in the imbedded UpwardsObjectClosure instance | |
5294 // assumes that the cards are always iterated (even if in parallel | |
5295 // by several threads) in monotonically increasing order per each | |
5296 // thread. This is true of the implementation below which picks | |
5297 // card ranges (chunks) in monotonically increasing order globally | |
5298 // and, a-fortiori, in monotonically increasing order per thread | |
5299 // (the latter order being a subsequence of the former). | |
5300 // If the work code below is ever reorganized into a more chaotic | |
5301 // work-partitioning form than the current "sequential tasks" | |
5302 // paradigm, the use of that persistent state will have to be | |
5303 // revisited and modified appropriately. See also related | |
5304 // bug 4756801 work on which should examine this code to make | |
5305 // sure that the changes there do not run counter to the | |
5306 // assumptions made here and necessary for correctness and | |
5307 // efficiency. Note also that this code might yield inefficient | |
5308 // behaviour in the case of very large objects that span one or | |
5309 // more work chunks. Such objects would potentially be scanned | |
5310 // several times redundantly. Work on 4756801 should try and | |
5311 // address that performance anomaly if at all possible. XXX | |
5312 MemRegion full_span = _collector->_span; | |
5313 CMSBitMap* bm = &(_collector->_markBitMap); // shared | |
5314 MarkFromDirtyCardsClosure | |
5315 greyRescanClosure(_collector, full_span, // entire span of interest | |
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5316 sp, bm, work_q, cl); |
0 | 5317 |
5318 SequentialSubTasksDone* pst = sp->conc_par_seq_tasks(); | |
5319 assert(pst->valid(), "Uninitialized use?"); | |
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5320 uint nth_task = 0; |
0 | 5321 const int alignment = CardTableModRefBS::card_size * BitsPerWord; |
5322 MemRegion span = sp->used_region(); | |
5323 HeapWord* start_addr = span.start(); | |
5324 HeapWord* end_addr = (HeapWord*)round_to((intptr_t)span.end(), | |
5325 alignment); | |
5326 const size_t chunk_size = sp->rescan_task_size(); // in HeapWord units | |
5327 assert((HeapWord*)round_to((intptr_t)start_addr, alignment) == | |
5328 start_addr, "Check alignment"); | |
5329 assert((size_t)round_to((intptr_t)chunk_size, alignment) == | |
5330 chunk_size, "Check alignment"); | |
5331 | |
5332 while (!pst->is_task_claimed(/* reference */ nth_task)) { | |
5333 // Having claimed the nth_task, compute corresponding mem-region, | |
5334 // which is a-fortiori aligned correctly (i.e. at a MUT bopundary). | |
5335 // The alignment restriction ensures that we do not need any | |
5336 // synchronization with other gang-workers while setting or | |
5337 // clearing bits in thus chunk of the MUT. | |
5338 MemRegion this_span = MemRegion(start_addr + nth_task*chunk_size, | |
5339 start_addr + (nth_task+1)*chunk_size); | |
5340 // The last chunk's end might be way beyond end of the | |
5341 // used region. In that case pull back appropriately. | |
5342 if (this_span.end() > end_addr) { | |
5343 this_span.set_end(end_addr); | |
5344 assert(!this_span.is_empty(), "Program logic (calculation of n_tasks)"); | |
5345 } | |
5346 // Iterate over the dirty cards covering this chunk, marking them | |
5347 // precleaned, and setting the corresponding bits in the mod union | |
5348 // table. Since we have been careful to partition at Card and MUT-word | |
5349 // boundaries no synchronization is needed between parallel threads. | |
5350 _collector->_ct->ct_bs()->dirty_card_iterate(this_span, | |
5351 &modUnionClosure); | |
5352 | |
5353 // Having transferred these marks into the modUnionTable, | |
5354 // rescan the marked objects on the dirty cards in the modUnionTable. | |
5355 // Even if this is at a synchronous collection, the initial marking | |
5356 // may have been done during an asynchronous collection so there | |
5357 // may be dirty bits in the mod-union table. | |
5358 _collector->_modUnionTable.dirty_range_iterate_clear( | |
5359 this_span, &greyRescanClosure); | |
5360 _collector->_modUnionTable.verifyNoOneBitsInRange( | |
5361 this_span.start(), | |
5362 this_span.end()); | |
5363 } | |
5364 pst->all_tasks_completed(); // declare that i am done | |
5365 } | |
5366 | |
5367 // . see if we can share work_queues with ParNew? XXX | |
5368 void | |
5369 CMSParRemarkTask::do_work_steal(int i, Par_MarkRefsIntoAndScanClosure* cl, | |
5370 int* seed) { | |
5371 OopTaskQueue* work_q = work_queue(i); | |
5372 NOT_PRODUCT(int num_steals = 0;) | |
5373 oop obj_to_scan; | |
5374 CMSBitMap* bm = &(_collector->_markBitMap); | |
5375 | |
5376 while (true) { | |
5377 // Completely finish any left over work from (an) earlier round(s) | |
5378 cl->trim_queue(0); | |
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5379 size_t num_from_overflow_list = MIN2((size_t)(work_q->max_elems() - work_q->size())/4, |
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5380 (size_t)ParGCDesiredObjsFromOverflowList); |
0 | 5381 // Now check if there's any work in the overflow list |
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5382 // Passing ParallelGCThreads as the third parameter, no_of_gc_threads, |
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5383 // only affects the number of attempts made to get work from the |
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5384 // overflow list and does not affect the number of workers. Just |
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5385 // pass ParallelGCThreads so this behavior is unchanged. |
0 | 5386 if (_collector->par_take_from_overflow_list(num_from_overflow_list, |
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5387 work_q, |
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5388 ParallelGCThreads)) { |
0 | 5389 // found something in global overflow list; |
5390 // not yet ready to go stealing work from others. | |
5391 // We'd like to assert(work_q->size() != 0, ...) | |
5392 // because we just took work from the overflow list, | |
5393 // but of course we can't since all of that could have | |
5394 // been already stolen from us. | |
5395 // "He giveth and He taketh away." | |
5396 continue; | |
5397 } | |
5398 // Verify that we have no work before we resort to stealing | |
5399 assert(work_q->size() == 0, "Have work, shouldn't steal"); | |
5400 // Try to steal from other queues that have work | |
5401 if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) { | |
5402 NOT_PRODUCT(num_steals++;) | |
5403 assert(obj_to_scan->is_oop(), "Oops, not an oop!"); | |
5404 assert(bm->isMarked((HeapWord*)obj_to_scan), "Stole an unmarked oop?"); | |
5405 // Do scanning work | |
5406 obj_to_scan->oop_iterate(cl); | |
5407 // Loop around, finish this work, and try to steal some more | |
5408 } else if (terminator()->offer_termination()) { | |
5409 break; // nirvana from the infinite cycle | |
5410 } | |
5411 } | |
5412 NOT_PRODUCT( | |
5413 if (PrintCMSStatistics != 0) { | |
5414 gclog_or_tty->print("\n\t(%d: stole %d oops)", i, num_steals); | |
5415 } | |
5416 ) | |
5417 assert(work_q->size() == 0 && _collector->overflow_list_is_empty(), | |
5418 "Else our work is not yet done"); | |
5419 } | |
5420 | |
5421 // Return a thread-local PLAB recording array, as appropriate. | |
5422 void* CMSCollector::get_data_recorder(int thr_num) { | |
5423 if (_survivor_plab_array != NULL && | |
5424 (CMSPLABRecordAlways || | |
5425 (_collectorState > Marking && _collectorState < FinalMarking))) { | |
5426 assert(thr_num < (int)ParallelGCThreads, "thr_num is out of bounds"); | |
5427 ChunkArray* ca = &_survivor_plab_array[thr_num]; | |
5428 ca->reset(); // clear it so that fresh data is recorded | |
5429 return (void*) ca; | |
5430 } else { | |
5431 return NULL; | |
5432 } | |
5433 } | |
5434 | |
5435 // Reset all the thread-local PLAB recording arrays | |
5436 void CMSCollector::reset_survivor_plab_arrays() { | |
5437 for (uint i = 0; i < ParallelGCThreads; i++) { | |
5438 _survivor_plab_array[i].reset(); | |
5439 } | |
5440 } | |
5441 | |
5442 // Merge the per-thread plab arrays into the global survivor chunk | |
5443 // array which will provide the partitioning of the survivor space | |
5444 // for CMS rescan. | |
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5445 void CMSCollector::merge_survivor_plab_arrays(ContiguousSpace* surv, |
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5446 int no_of_gc_threads) { |
0 | 5447 assert(_survivor_plab_array != NULL, "Error"); |
5448 assert(_survivor_chunk_array != NULL, "Error"); | |
5449 assert(_collectorState == FinalMarking, "Error"); | |
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5450 for (int j = 0; j < no_of_gc_threads; j++) { |
0 | 5451 _cursor[j] = 0; |
5452 } | |
5453 HeapWord* top = surv->top(); | |
5454 size_t i; | |
5455 for (i = 0; i < _survivor_chunk_capacity; i++) { // all sca entries | |
5456 HeapWord* min_val = top; // Higher than any PLAB address | |
5457 uint min_tid = 0; // position of min_val this round | |
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5458 for (int j = 0; j < no_of_gc_threads; j++) { |
0 | 5459 ChunkArray* cur_sca = &_survivor_plab_array[j]; |
5460 if (_cursor[j] == cur_sca->end()) { | |
5461 continue; | |
5462 } | |
5463 assert(_cursor[j] < cur_sca->end(), "ctl pt invariant"); | |
5464 HeapWord* cur_val = cur_sca->nth(_cursor[j]); | |
5465 assert(surv->used_region().contains(cur_val), "Out of bounds value"); | |
5466 if (cur_val < min_val) { | |
5467 min_tid = j; | |
5468 min_val = cur_val; | |
5469 } else { | |
5470 assert(cur_val < top, "All recorded addresses should be less"); | |
5471 } | |
5472 } | |
5473 // At this point min_val and min_tid are respectively | |
5474 // the least address in _survivor_plab_array[j]->nth(_cursor[j]) | |
5475 // and the thread (j) that witnesses that address. | |
5476 // We record this address in the _survivor_chunk_array[i] | |
5477 // and increment _cursor[min_tid] prior to the next round i. | |
5478 if (min_val == top) { | |
5479 break; | |
5480 } | |
5481 _survivor_chunk_array[i] = min_val; | |
5482 _cursor[min_tid]++; | |
5483 } | |
5484 // We are all done; record the size of the _survivor_chunk_array | |
5485 _survivor_chunk_index = i; // exclusive: [0, i) | |
5486 if (PrintCMSStatistics > 0) { | |
5487 gclog_or_tty->print(" (Survivor:" SIZE_FORMAT "chunks) ", i); | |
5488 } | |
5489 // Verify that we used up all the recorded entries | |
5490 #ifdef ASSERT | |
5491 size_t total = 0; | |
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5492 for (int j = 0; j < no_of_gc_threads; j++) { |
0 | 5493 assert(_cursor[j] == _survivor_plab_array[j].end(), "Ctl pt invariant"); |
5494 total += _cursor[j]; | |
5495 } | |
5496 assert(total == _survivor_chunk_index, "Ctl Pt Invariant"); | |
5497 // Check that the merged array is in sorted order | |
5498 if (total > 0) { | |
5499 for (size_t i = 0; i < total - 1; i++) { | |
5500 if (PrintCMSStatistics > 0) { | |
5501 gclog_or_tty->print(" (chunk" SIZE_FORMAT ":" INTPTR_FORMAT ") ", | |
5502 i, _survivor_chunk_array[i]); | |
5503 } | |
5504 assert(_survivor_chunk_array[i] < _survivor_chunk_array[i+1], | |
5505 "Not sorted"); | |
5506 } | |
5507 } | |
5508 #endif // ASSERT | |
5509 } | |
5510 | |
5511 // Set up the space's par_seq_tasks structure for work claiming | |
5512 // for parallel rescan of young gen. | |
5513 // See ParRescanTask where this is currently used. | |
5514 void | |
5515 CMSCollector:: | |
5516 initialize_sequential_subtasks_for_young_gen_rescan(int n_threads) { | |
5517 assert(n_threads > 0, "Unexpected n_threads argument"); | |
5518 DefNewGeneration* dng = (DefNewGeneration*)_young_gen; | |
5519 | |
5520 // Eden space | |
5521 { | |
5522 SequentialSubTasksDone* pst = dng->eden()->par_seq_tasks(); | |
5523 assert(!pst->valid(), "Clobbering existing data?"); | |
5524 // Each valid entry in [0, _eden_chunk_index) represents a task. | |
5525 size_t n_tasks = _eden_chunk_index + 1; | |
5526 assert(n_tasks == 1 || _eden_chunk_array != NULL, "Error"); | |
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5527 // Sets the condition for completion of the subtask (how many threads |
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5528 // need to finish in order to be done). |
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5529 pst->set_n_threads(n_threads); |
0 | 5530 pst->set_n_tasks((int)n_tasks); |
5531 } | |
5532 | |
5533 // Merge the survivor plab arrays into _survivor_chunk_array | |
5534 if (_survivor_plab_array != NULL) { | |
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5535 merge_survivor_plab_arrays(dng->from(), n_threads); |
0 | 5536 } else { |
5537 assert(_survivor_chunk_index == 0, "Error"); | |
5538 } | |
5539 | |
5540 // To space | |
5541 { | |
5542 SequentialSubTasksDone* pst = dng->to()->par_seq_tasks(); | |
5543 assert(!pst->valid(), "Clobbering existing data?"); | |
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5544 // Sets the condition for completion of the subtask (how many threads |
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5545 // need to finish in order to be done). |
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5546 pst->set_n_threads(n_threads); |
0 | 5547 pst->set_n_tasks(1); |
5548 assert(pst->valid(), "Error"); | |
5549 } | |
5550 | |
5551 // From space | |
5552 { | |
5553 SequentialSubTasksDone* pst = dng->from()->par_seq_tasks(); | |
5554 assert(!pst->valid(), "Clobbering existing data?"); | |
5555 size_t n_tasks = _survivor_chunk_index + 1; | |
5556 assert(n_tasks == 1 || _survivor_chunk_array != NULL, "Error"); | |
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5557 // Sets the condition for completion of the subtask (how many threads |
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5558 // need to finish in order to be done). |
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5559 pst->set_n_threads(n_threads); |
0 | 5560 pst->set_n_tasks((int)n_tasks); |
5561 assert(pst->valid(), "Error"); | |
5562 } | |
5563 } | |
5564 | |
5565 // Parallel version of remark | |
5566 void CMSCollector::do_remark_parallel() { | |
5567 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
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5568 FlexibleWorkGang* workers = gch->workers(); |
0 | 5569 assert(workers != NULL, "Need parallel worker threads."); |
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5570 // Choose to use the number of GC workers most recently set |
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5571 // into "active_workers". If active_workers is not set, set it |
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5572 // to ParallelGCThreads. |
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5573 int n_workers = workers->active_workers(); |
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5574 if (n_workers == 0) { |
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5575 assert(n_workers > 0, "Should have been set during scavenge"); |
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5576 n_workers = ParallelGCThreads; |
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5577 workers->set_active_workers(n_workers); |
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5578 } |
0 | 5579 CompactibleFreeListSpace* cms_space = _cmsGen->cmsSpace(); |
5580 | |
5581 CMSParRemarkTask tsk(this, | |
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5582 cms_space, |
0 | 5583 n_workers, workers, task_queues()); |
5584 | |
5585 // Set up for parallel process_strong_roots work. | |
5586 gch->set_par_threads(n_workers); | |
5587 // We won't be iterating over the cards in the card table updating | |
5588 // the younger_gen cards, so we shouldn't call the following else | |
5589 // the verification code as well as subsequent younger_refs_iterate | |
5590 // code would get confused. XXX | |
5591 // gch->rem_set()->prepare_for_younger_refs_iterate(true); // parallel | |
5592 | |
5593 // The young gen rescan work will not be done as part of | |
5594 // process_strong_roots (which currently doesn't knw how to | |
5595 // parallelize such a scan), but rather will be broken up into | |
5596 // a set of parallel tasks (via the sampling that the [abortable] | |
5597 // preclean phase did of EdenSpace, plus the [two] tasks of | |
5598 // scanning the [two] survivor spaces. Further fine-grain | |
5599 // parallelization of the scanning of the survivor spaces | |
5600 // themselves, and of precleaning of the younger gen itself | |
5601 // is deferred to the future. | |
5602 initialize_sequential_subtasks_for_young_gen_rescan(n_workers); | |
5603 | |
5604 // The dirty card rescan work is broken up into a "sequence" | |
5605 // of parallel tasks (per constituent space) that are dynamically | |
5606 // claimed by the parallel threads. | |
5607 cms_space->initialize_sequential_subtasks_for_rescan(n_workers); | |
5608 | |
5609 // It turns out that even when we're using 1 thread, doing the work in a | |
5610 // separate thread causes wide variance in run times. We can't help this | |
5611 // in the multi-threaded case, but we special-case n=1 here to get | |
5612 // repeatable measurements of the 1-thread overhead of the parallel code. | |
5613 if (n_workers > 1) { | |
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5614 // Make refs discovery MT-safe, if it isn't already: it may not |
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5615 // necessarily be so, since it's possible that we are doing |
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5616 // ST marking. |
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5617 ReferenceProcessorMTDiscoveryMutator mt(ref_processor(), true); |
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5618 GenCollectedHeap::StrongRootsScope srs(gch); |
0 | 5619 workers->run_task(&tsk); |
5620 } else { | |
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5621 ReferenceProcessorMTDiscoveryMutator mt(ref_processor(), false); |
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5622 GenCollectedHeap::StrongRootsScope srs(gch); |
0 | 5623 tsk.work(0); |
5624 } | |
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5625 |
0 | 5626 gch->set_par_threads(0); // 0 ==> non-parallel. |
5627 // restore, single-threaded for now, any preserved marks | |
5628 // as a result of work_q overflow | |
5629 restore_preserved_marks_if_any(); | |
5630 } | |
5631 | |
5632 // Non-parallel version of remark | |
5633 void CMSCollector::do_remark_non_parallel() { | |
5634 ResourceMark rm; | |
5635 HandleMark hm; | |
5636 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
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5637 ReferenceProcessorMTDiscoveryMutator mt(ref_processor(), false); |
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5638 |
0 | 5639 MarkRefsIntoAndScanClosure |
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5640 mrias_cl(_span, ref_processor(), &_markBitMap, NULL /* not precleaning */, |
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5641 &_markStack, this, |
0 | 5642 false /* should_yield */, false /* not precleaning */); |
5643 MarkFromDirtyCardsClosure | |
5644 markFromDirtyCardsClosure(this, _span, | |
5645 NULL, // space is set further below | |
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5646 &_markBitMap, &_markStack, &mrias_cl); |
0 | 5647 { |
5648 TraceTime t("grey object rescan", PrintGCDetails, false, gclog_or_tty); | |
342
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5649 // Iterate over the dirty cards, setting the corresponding bits in the |
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5650 // mod union table. |
0 | 5651 { |
5652 ModUnionClosure modUnionClosure(&_modUnionTable); | |
5653 _ct->ct_bs()->dirty_card_iterate( | |
5654 _cmsGen->used_region(), | |
5655 &modUnionClosure); | |
5656 } | |
5657 // Having transferred these marks into the modUnionTable, we just need | |
5658 // to rescan the marked objects on the dirty cards in the modUnionTable. | |
5659 // The initial marking may have been done during an asynchronous | |
5660 // collection so there may be dirty bits in the mod-union table. | |
5661 const int alignment = | |
5662 CardTableModRefBS::card_size * BitsPerWord; | |
5663 { | |
5664 // ... First handle dirty cards in CMS gen | |
5665 markFromDirtyCardsClosure.set_space(_cmsGen->cmsSpace()); | |
5666 MemRegion ur = _cmsGen->used_region(); | |
5667 HeapWord* lb = ur.start(); | |
5668 HeapWord* ub = (HeapWord*)round_to((intptr_t)ur.end(), alignment); | |
5669 MemRegion cms_span(lb, ub); | |
5670 _modUnionTable.dirty_range_iterate_clear(cms_span, | |
5671 &markFromDirtyCardsClosure); | |
5672 verify_work_stacks_empty(); | |
5673 if (PrintCMSStatistics != 0) { | |
5674 gclog_or_tty->print(" (re-scanned "SIZE_FORMAT" dirty cards in cms gen) ", | |
5675 markFromDirtyCardsClosure.num_dirty_cards()); | |
5676 } | |
5677 } | |
5678 } | |
5679 if (VerifyDuringGC && | |
5680 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
5681 HandleMark hm; // Discard invalid handles created during verification | |
5682 Universe::verify(true); | |
5683 } | |
5684 { | |
5685 TraceTime t("root rescan", PrintGCDetails, false, gclog_or_tty); | |
5686 | |
5687 verify_work_stacks_empty(); | |
5688 | |
5689 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. | |
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5690 GenCollectedHeap::StrongRootsScope srs(gch); |
0 | 5691 gch->gen_process_strong_roots(_cmsGen->level(), |
5692 true, // younger gens as roots | |
989
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5693 false, // use the local StrongRootsScope |
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5694 false, // not scavenging |
0 | 5695 SharedHeap::ScanningOption(roots_scanning_options()), |
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5696 &mrias_cl, |
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5697 true, // walk code active on stacks |
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5698 NULL, |
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5699 NULL); // The dirty klasses will be handled below |
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5700 |
989
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|
5701 assert(should_unload_classes() |
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5702 || (roots_scanning_options() & SharedHeap::SO_CodeCache), |
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5703 "if we didn't scan the code cache, we have to be ready to drop nmethods with expired weak oops"); |
0 | 5704 } |
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5705 |
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5706 { |
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5707 TraceTime t("visit unhandled CLDs", PrintGCDetails, false, gclog_or_tty); |
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5708 |
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5709 verify_work_stacks_empty(); |
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5710 |
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5711 // Scan all class loader data objects that might have been introduced |
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5712 // during concurrent marking. |
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5713 ResourceMark rm; |
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5714 GrowableArray<ClassLoaderData*>* array = ClassLoaderDataGraph::new_clds(); |
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5715 for (int i = 0; i < array->length(); i++) { |
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5716 mrias_cl.do_class_loader_data(array->at(i)); |
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5717 } |
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5718 |
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5719 // We don't need to keep track of new CLDs anymore. |
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5720 ClassLoaderDataGraph::remember_new_clds(false); |
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5721 |
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5722 verify_work_stacks_empty(); |
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5723 } |
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5724 |
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5725 { |
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5726 TraceTime t("dirty klass scan", PrintGCDetails, false, gclog_or_tty); |
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5727 |
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5728 verify_work_stacks_empty(); |
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5729 |
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5730 RemarkKlassClosure remark_klass_closure(&mrias_cl); |
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5731 ClassLoaderDataGraph::classes_do(&remark_klass_closure); |
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5732 |
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5733 verify_work_stacks_empty(); |
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5734 } |
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5735 |
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5736 // We might have added oops to ClassLoaderData::_handles during the |
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5737 // concurrent marking phase. These oops point to newly allocated objects |
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5738 // that are guaranteed to be kept alive. Either by the direct allocation |
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5739 // code, or when the young collector processes the strong roots. Hence, |
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5740 // we don't have to revisit the _handles block during the remark phase. |
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5741 |
0 | 5742 verify_work_stacks_empty(); |
5743 // Restore evacuated mark words, if any, used for overflow list links | |
5744 if (!CMSOverflowEarlyRestoration) { | |
5745 restore_preserved_marks_if_any(); | |
5746 } | |
5747 verify_overflow_empty(); | |
5748 } | |
5749 | |
5750 //////////////////////////////////////////////////////// | |
5751 // Parallel Reference Processing Task Proxy Class | |
5752 //////////////////////////////////////////////////////// | |
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5753 class CMSRefProcTaskProxy: public AbstractGangTaskWOopQueues { |
0 | 5754 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; |
5755 CMSCollector* _collector; | |
5756 CMSBitMap* _mark_bit_map; | |
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5757 const MemRegion _span; |
0 | 5758 ProcessTask& _task; |
5759 | |
5760 public: | |
5761 CMSRefProcTaskProxy(ProcessTask& task, | |
5762 CMSCollector* collector, | |
5763 const MemRegion& span, | |
5764 CMSBitMap* mark_bit_map, | |
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5765 AbstractWorkGang* workers, |
0 | 5766 OopTaskQueueSet* task_queues): |
2369
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5767 // XXX Should superclass AGTWOQ also know about AWG since it knows |
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5768 // about the task_queues used by the AWG? Then it could initialize |
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5769 // the terminator() object. See 6984287. The set_for_termination() |
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5770 // below is a temporary band-aid for the regression in 6984287. |
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5771 AbstractGangTaskWOopQueues("Process referents by policy in parallel", |
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5772 task_queues), |
0 | 5773 _task(task), |
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5774 _collector(collector), _span(span), _mark_bit_map(mark_bit_map) |
2369
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5775 { |
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5776 assert(_collector->_span.equals(_span) && !_span.is_empty(), |
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5777 "Inconsistency in _span"); |
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5778 set_for_termination(workers->active_workers()); |
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5779 } |
0 | 5780 |
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5781 OopTaskQueueSet* task_queues() { return queues(); } |
0 | 5782 |
5783 OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); } | |
5784 | |
5785 void do_work_steal(int i, | |
5786 CMSParDrainMarkingStackClosure* drain, | |
5787 CMSParKeepAliveClosure* keep_alive, | |
5788 int* seed); | |
5789 | |
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5790 virtual void work(uint worker_id); |
0 | 5791 }; |
5792 | |
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5793 void CMSRefProcTaskProxy::work(uint worker_id) { |
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5794 assert(_collector->_span.equals(_span), "Inconsistency in _span"); |
0 | 5795 CMSParKeepAliveClosure par_keep_alive(_collector, _span, |
935 | 5796 _mark_bit_map, |
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5797 work_queue(worker_id)); |
0 | 5798 CMSParDrainMarkingStackClosure par_drain_stack(_collector, _span, |
935 | 5799 _mark_bit_map, |
4728
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5800 work_queue(worker_id)); |
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5801 CMSIsAliveClosure is_alive_closure(_span, _mark_bit_map); |
4728
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5802 _task.work(worker_id, is_alive_closure, par_keep_alive, par_drain_stack); |
0 | 5803 if (_task.marks_oops_alive()) { |
4728
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|
5804 do_work_steal(worker_id, &par_drain_stack, &par_keep_alive, |
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5805 _collector->hash_seed(worker_id)); |
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|
5806 } |
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|
5807 assert(work_queue(worker_id)->size() == 0, "work_queue should be empty"); |
0 | 5808 assert(_collector->_overflow_list == NULL, "non-empty _overflow_list"); |
5809 } | |
5810 | |
5811 class CMSRefEnqueueTaskProxy: public AbstractGangTask { | |
5812 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; | |
5813 EnqueueTask& _task; | |
5814 | |
5815 public: | |
5816 CMSRefEnqueueTaskProxy(EnqueueTask& task) | |
5817 : AbstractGangTask("Enqueue reference objects in parallel"), | |
5818 _task(task) | |
5819 { } | |
5820 | |
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|
5821 virtual void work(uint worker_id) |
0 | 5822 { |
4728
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|
5823 _task.work(worker_id); |
0 | 5824 } |
5825 }; | |
5826 | |
5827 CMSParKeepAliveClosure::CMSParKeepAliveClosure(CMSCollector* collector, | |
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5828 MemRegion span, CMSBitMap* bit_map, OopTaskQueue* work_queue): |
0 | 5829 _span(span), |
5830 _bit_map(bit_map), | |
5831 _work_queue(work_queue), | |
6725
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5832 _mark_and_push(collector, span, bit_map, work_queue), |
0 | 5833 _low_water_mark(MIN2((uint)(work_queue->max_elems()/4), |
5834 (uint)(CMSWorkQueueDrainThreshold * ParallelGCThreads))) | |
5835 { } | |
5836 | |
5837 // . see if we can share work_queues with ParNew? XXX | |
5838 void CMSRefProcTaskProxy::do_work_steal(int i, | |
5839 CMSParDrainMarkingStackClosure* drain, | |
5840 CMSParKeepAliveClosure* keep_alive, | |
5841 int* seed) { | |
5842 OopTaskQueue* work_q = work_queue(i); | |
5843 NOT_PRODUCT(int num_steals = 0;) | |
5844 oop obj_to_scan; | |
5845 | |
5846 while (true) { | |
5847 // Completely finish any left over work from (an) earlier round(s) | |
5848 drain->trim_queue(0); | |
679
cea947c8a988
6819891: ParNew: Fix work queue overflow code to deal correctly with +UseCompressedOops
ysr
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|
5849 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
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|
5850 (size_t)ParGCDesiredObjsFromOverflowList); |
0 | 5851 // Now check if there's any work in the overflow list |
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|
5852 // Passing ParallelGCThreads as the third parameter, no_of_gc_threads, |
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|
5853 // only affects the number of attempts made to get work from the |
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|
5854 // overflow list and does not affect the number of workers. Just |
8b10f48633dc
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|
5855 // pass ParallelGCThreads so this behavior is unchanged. |
0 | 5856 if (_collector->par_take_from_overflow_list(num_from_overflow_list, |
1833
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|
5857 work_q, |
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|
5858 ParallelGCThreads)) { |
0 | 5859 // Found something in global overflow list; |
5860 // not yet ready to go stealing work from others. | |
5861 // We'd like to assert(work_q->size() != 0, ...) | |
5862 // because we just took work from the overflow list, | |
5863 // but of course we can't, since all of that might have | |
5864 // been already stolen from us. | |
5865 continue; | |
5866 } | |
5867 // Verify that we have no work before we resort to stealing | |
5868 assert(work_q->size() == 0, "Have work, shouldn't steal"); | |
5869 // Try to steal from other queues that have work | |
5870 if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) { | |
5871 NOT_PRODUCT(num_steals++;) | |
5872 assert(obj_to_scan->is_oop(), "Oops, not an oop!"); | |
5873 assert(_mark_bit_map->isMarked((HeapWord*)obj_to_scan), "Stole an unmarked oop?"); | |
5874 // Do scanning work | |
5875 obj_to_scan->oop_iterate(keep_alive); | |
5876 // Loop around, finish this work, and try to steal some more | |
5877 } else if (terminator()->offer_termination()) { | |
5878 break; // nirvana from the infinite cycle | |
5879 } | |
5880 } | |
5881 NOT_PRODUCT( | |
5882 if (PrintCMSStatistics != 0) { | |
5883 gclog_or_tty->print("\n\t(%d: stole %d oops)", i, num_steals); | |
5884 } | |
5885 ) | |
5886 } | |
5887 | |
5888 void CMSRefProcTaskExecutor::execute(ProcessTask& task) | |
5889 { | |
5890 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
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|
5891 FlexibleWorkGang* workers = gch->workers(); |
0 | 5892 assert(workers != NULL, "Need parallel worker threads."); |
5893 CMSRefProcTaskProxy rp_task(task, &_collector, | |
5894 _collector.ref_processor()->span(), | |
5895 _collector.markBitMap(), | |
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|
5896 workers, _collector.task_queues()); |
0 | 5897 workers->run_task(&rp_task); |
5898 } | |
5899 | |
5900 void CMSRefProcTaskExecutor::execute(EnqueueTask& task) | |
5901 { | |
5902 | |
5903 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
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|
5904 FlexibleWorkGang* workers = gch->workers(); |
0 | 5905 assert(workers != NULL, "Need parallel worker threads."); |
5906 CMSRefEnqueueTaskProxy enq_task(task); | |
5907 workers->run_task(&enq_task); | |
5908 } | |
5909 | |
5910 void CMSCollector::refProcessingWork(bool asynch, bool clear_all_soft_refs) { | |
5911 | |
5912 ResourceMark rm; | |
5913 HandleMark hm; | |
5914 | |
5915 ReferenceProcessor* rp = ref_processor(); | |
5916 assert(rp->span().equals(_span), "Spans should be equal"); | |
453
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|
5917 assert(!rp->enqueuing_is_done(), "Enqueuing should not be complete"); |
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diff
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|
5918 // Process weak references. |
457
27a80744a83b
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diff
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|
5919 rp->setup_policy(clear_all_soft_refs); |
453
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|
5920 verify_work_stacks_empty(); |
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|
5921 |
0 | 5922 CMSKeepAliveClosure cmsKeepAliveClosure(this, _span, &_markBitMap, |
6725
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5923 &_markStack, false /* !preclean */); |
0 | 5924 CMSDrainMarkingStackClosure cmsDrainMarkingStackClosure(this, |
5925 _span, &_markBitMap, &_markStack, | |
452
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6722113: CMS: Incorrect overflow handling during precleaning of Reference lists
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diff
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|
5926 &cmsKeepAliveClosure, false /* !preclean */); |
0 | 5927 { |
5928 TraceTime t("weak refs processing", PrintGCDetails, false, gclog_or_tty); | |
5929 if (rp->processing_is_mt()) { | |
1833
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|
5930 // Set the degree of MT here. If the discovery is done MT, there |
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|
5931 // may have been a different number of threads doing the discovery |
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|
5932 // and a different number of discovered lists may have Ref objects. |
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|
5933 // That is OK as long as the Reference lists are balanced (see |
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|
5934 // balance_all_queues() and balance_queues()). |
4095
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|
5935 GenCollectedHeap* gch = GenCollectedHeap::heap(); |
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|
5936 int active_workers = ParallelGCThreads; |
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|
5937 FlexibleWorkGang* workers = gch->workers(); |
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|
5938 if (workers != NULL) { |
bca17e38de00
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|
5939 active_workers = workers->active_workers(); |
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|
5940 // The expectation is that active_workers will have already |
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|
5941 // been set to a reasonable value. If it has not been set, |
bca17e38de00
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|
5942 // investigate. |
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|
5943 assert(active_workers > 0, "Should have been set during scavenge"); |
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|
5944 } |
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5945 rp->set_active_mt_degree(active_workers); |
0 | 5946 CMSRefProcTaskExecutor task_executor(*this); |
453
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5947 rp->process_discovered_references(&_is_alive_closure, |
0 | 5948 &cmsKeepAliveClosure, |
5949 &cmsDrainMarkingStackClosure, | |
5950 &task_executor); | |
5951 } else { | |
453
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5952 rp->process_discovered_references(&_is_alive_closure, |
0 | 5953 &cmsKeepAliveClosure, |
5954 &cmsDrainMarkingStackClosure, | |
5955 NULL); | |
5956 } | |
5957 verify_work_stacks_empty(); | |
5958 } | |
5959 | |
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5960 if (should_unload_classes()) { |
0 | 5961 { |
5962 TraceTime t("class unloading", PrintGCDetails, false, gclog_or_tty); | |
5963 | |
5964 // Follow SystemDictionary roots and unload classes | |
5965 bool purged_class = SystemDictionary::do_unloading(&_is_alive_closure); | |
5966 | |
5967 // Follow CodeCache roots and unload any methods marked for unloading | |
5968 CodeCache::do_unloading(&_is_alive_closure, | |
5969 &cmsKeepAliveClosure, | |
5970 purged_class); | |
5971 | |
5972 cmsDrainMarkingStackClosure.do_void(); | |
5973 verify_work_stacks_empty(); | |
5974 | |
5975 // Update subklass/sibling/implementor links in KlassKlass descendants | |
6725
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5976 Klass::clean_weak_klass_links(&_is_alive_closure); |
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5977 // Nothing should have been pushed onto the working stacks. |
0 | 5978 verify_work_stacks_empty(); |
5979 } | |
5980 | |
5981 { | |
2379
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5982 TraceTime t("scrub symbol table", PrintGCDetails, false, gclog_or_tty); |
2177
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5983 // Clean up unreferenced symbols in symbol table. |
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5984 SymbolTable::unlink(); |
0 | 5985 } |
5986 } | |
5987 | |
6725
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5988 // CMS doesn't use the StringTable as hard roots when class unloading is turned off. |
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5989 // Need to check if we really scanned the StringTable. |
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5990 if ((roots_scanning_options() & SharedHeap::SO_Strings) == 0) { |
2379
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5991 TraceTime t("scrub string table", PrintGCDetails, false, gclog_or_tty); |
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5992 // Now clean up stale oops in StringTable |
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5993 StringTable::unlink(&_is_alive_closure); |
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5994 } |
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5995 |
0 | 5996 verify_work_stacks_empty(); |
5997 // Restore any preserved marks as a result of mark stack or | |
5998 // work queue overflow | |
5999 restore_preserved_marks_if_any(); // done single-threaded for now | |
6000 | |
6001 rp->set_enqueuing_is_done(true); | |
6002 if (rp->processing_is_mt()) { | |
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6003 rp->balance_all_queues(); |
0 | 6004 CMSRefProcTaskExecutor task_executor(*this); |
6005 rp->enqueue_discovered_references(&task_executor); | |
6006 } else { | |
6007 rp->enqueue_discovered_references(NULL); | |
6008 } | |
6009 rp->verify_no_references_recorded(); | |
6010 assert(!rp->discovery_enabled(), "should have been disabled"); | |
6011 } | |
6012 | |
6013 #ifndef PRODUCT | |
6014 void CMSCollector::check_correct_thread_executing() { | |
6015 Thread* t = Thread::current(); | |
6016 // Only the VM thread or the CMS thread should be here. | |
6017 assert(t->is_ConcurrentGC_thread() || t->is_VM_thread(), | |
6018 "Unexpected thread type"); | |
6019 // If this is the vm thread, the foreground process | |
6020 // should not be waiting. Note that _foregroundGCIsActive is | |
6021 // true while the foreground collector is waiting. | |
6022 if (_foregroundGCShouldWait) { | |
6023 // We cannot be the VM thread | |
6024 assert(t->is_ConcurrentGC_thread(), | |
6025 "Should be CMS thread"); | |
6026 } else { | |
6027 // We can be the CMS thread only if we are in a stop-world | |
6028 // phase of CMS collection. | |
6029 if (t->is_ConcurrentGC_thread()) { | |
6030 assert(_collectorState == InitialMarking || | |
6031 _collectorState == FinalMarking, | |
6032 "Should be a stop-world phase"); | |
6033 // The CMS thread should be holding the CMS_token. | |
6034 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
6035 "Potential interference with concurrently " | |
6036 "executing VM thread"); | |
6037 } | |
6038 } | |
6039 } | |
6040 #endif | |
6041 | |
6042 void CMSCollector::sweep(bool asynch) { | |
6043 assert(_collectorState == Sweeping, "just checking"); | |
6044 check_correct_thread_executing(); | |
6045 verify_work_stacks_empty(); | |
6046 verify_overflow_empty(); | |
1145
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6047 increment_sweep_count(); |
3356
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6048 TraceCMSMemoryManagerStats tms(_collectorState,GenCollectedHeap::heap()->gc_cause()); |
1703
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6049 |
1145
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6050 _inter_sweep_timer.stop(); |
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6051 _inter_sweep_estimate.sample(_inter_sweep_timer.seconds()); |
0 | 6052 size_policy()->avg_cms_free_at_sweep()->sample(_cmsGen->free()); |
6053 | |
1145
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6054 assert(!_intra_sweep_timer.is_active(), "Should not be active"); |
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6055 _intra_sweep_timer.reset(); |
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6056 _intra_sweep_timer.start(); |
0 | 6057 if (asynch) { |
6058 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
6059 CMSPhaseAccounting pa(this, "sweep", !PrintGCDetails); | |
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6060 // First sweep the old gen |
0 | 6061 { |
6062 CMSTokenSyncWithLocks ts(true, _cmsGen->freelistLock(), | |
6063 bitMapLock()); | |
6064 sweepWork(_cmsGen, asynch); | |
6065 } | |
6066 | |
6067 // Update Universe::_heap_*_at_gc figures. | |
6068 // We need all the free list locks to make the abstract state | |
6069 // transition from Sweeping to Resetting. See detailed note | |
6070 // further below. | |
6071 { | |
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6072 CMSTokenSyncWithLocks ts(true, _cmsGen->freelistLock()); |
0 | 6073 // Update heap occupancy information which is used as |
6074 // input to soft ref clearing policy at the next gc. | |
6075 Universe::update_heap_info_at_gc(); | |
6076 _collectorState = Resizing; | |
6077 } | |
6078 } else { | |
6079 // already have needed locks | |
6080 sweepWork(_cmsGen, asynch); | |
6081 // Update heap occupancy information which is used as | |
6082 // input to soft ref clearing policy at the next gc. | |
6083 Universe::update_heap_info_at_gc(); | |
6084 _collectorState = Resizing; | |
6085 } | |
6086 verify_work_stacks_empty(); | |
6087 verify_overflow_empty(); | |
6088 | |
1145
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6089 _intra_sweep_timer.stop(); |
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6090 _intra_sweep_estimate.sample(_intra_sweep_timer.seconds()); |
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6091 |
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6092 _inter_sweep_timer.reset(); |
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6093 _inter_sweep_timer.start(); |
0 | 6094 |
4911 | 6095 // We need to use a monotonically non-deccreasing time in ms |
6096 // or we will see time-warp warnings and os::javaTimeMillis() | |
6097 // does not guarantee monotonicity. | |
6098 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; | |
6099 update_time_of_last_gc(now); | |
0 | 6100 |
6101 // NOTE on abstract state transitions: | |
6102 // Mutators allocate-live and/or mark the mod-union table dirty | |
6103 // based on the state of the collection. The former is done in | |
6104 // the interval [Marking, Sweeping] and the latter in the interval | |
6105 // [Marking, Sweeping). Thus the transitions into the Marking state | |
6106 // and out of the Sweeping state must be synchronously visible | |
6107 // globally to the mutators. | |
6108 // The transition into the Marking state happens with the world | |
6109 // stopped so the mutators will globally see it. Sweeping is | |
6110 // done asynchronously by the background collector so the transition | |
6111 // from the Sweeping state to the Resizing state must be done | |
6112 // under the freelistLock (as is the check for whether to | |
6113 // allocate-live and whether to dirty the mod-union table). | |
6114 assert(_collectorState == Resizing, "Change of collector state to" | |
6115 " Resizing must be done under the freelistLocks (plural)"); | |
6116 | |
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6117 // Now that sweeping has been completed, we clear |
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6118 // the incremental_collection_failed flag, |
0 | 6119 // thus inviting a younger gen collection to promote into |
6120 // this generation. If such a promotion may still fail, | |
6121 // the flag will be set again when a young collection is | |
6122 // attempted. | |
6123 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
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6124 gch->clear_incremental_collection_failed(); // Worth retrying as fresh space may have been freed up |
0 | 6125 gch->update_full_collections_completed(_collection_count_start); |
6126 } | |
6127 | |
6128 // FIX ME!!! Looks like this belongs in CFLSpace, with | |
6129 // CMSGen merely delegating to it. | |
6130 void ConcurrentMarkSweepGeneration::setNearLargestChunk() { | |
1145
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6131 double nearLargestPercent = FLSLargestBlockCoalesceProximity; |
0 | 6132 HeapWord* minAddr = _cmsSpace->bottom(); |
6133 HeapWord* largestAddr = | |
6028
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6134 (HeapWord*) _cmsSpace->dictionary()->find_largest_dict(); |
1145
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6135 if (largestAddr == NULL) { |
0 | 6136 // The dictionary appears to be empty. In this case |
6137 // try to coalesce at the end of the heap. | |
6138 largestAddr = _cmsSpace->end(); | |
6139 } | |
6140 size_t largestOffset = pointer_delta(largestAddr, minAddr); | |
6141 size_t nearLargestOffset = | |
6142 (size_t)((double)largestOffset * nearLargestPercent) - MinChunkSize; | |
1145
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6143 if (PrintFLSStatistics != 0) { |
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|
6144 gclog_or_tty->print_cr( |
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|
6145 "CMS: Large Block: " PTR_FORMAT ";" |
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|
6146 " Proximity: " PTR_FORMAT " -> " PTR_FORMAT, |
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|
6147 largestAddr, |
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6148 _cmsSpace->nearLargestChunk(), minAddr + nearLargestOffset); |
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6149 } |
0 | 6150 _cmsSpace->set_nearLargestChunk(minAddr + nearLargestOffset); |
6151 } | |
6152 | |
6153 bool ConcurrentMarkSweepGeneration::isNearLargestChunk(HeapWord* addr) { | |
6154 return addr >= _cmsSpace->nearLargestChunk(); | |
6155 } | |
6156 | |
6157 FreeChunk* ConcurrentMarkSweepGeneration::find_chunk_at_end() { | |
6158 return _cmsSpace->find_chunk_at_end(); | |
6159 } | |
6160 | |
6161 void ConcurrentMarkSweepGeneration::update_gc_stats(int current_level, | |
6162 bool full) { | |
6163 // The next lower level has been collected. Gather any statistics | |
6164 // that are of interest at this point. | |
6165 if (!full && (current_level + 1) == level()) { | |
6166 // Gather statistics on the young generation collection. | |
6167 collector()->stats().record_gc0_end(used()); | |
6168 } | |
6169 } | |
6170 | |
6171 CMSAdaptiveSizePolicy* ConcurrentMarkSweepGeneration::size_policy() { | |
6172 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
6173 assert(gch->kind() == CollectedHeap::GenCollectedHeap, | |
6174 "Wrong type of heap"); | |
6175 CMSAdaptiveSizePolicy* sp = (CMSAdaptiveSizePolicy*) | |
6176 gch->gen_policy()->size_policy(); | |
6177 assert(sp->is_gc_cms_adaptive_size_policy(), | |
6178 "Wrong type of size policy"); | |
6179 return sp; | |
6180 } | |
6181 | |
6182 void ConcurrentMarkSweepGeneration::rotate_debug_collection_type() { | |
6183 if (PrintGCDetails && Verbose) { | |
6184 gclog_or_tty->print("Rotate from %d ", _debug_collection_type); | |
6185 } | |
6186 _debug_collection_type = (CollectionTypes) (_debug_collection_type + 1); | |
6187 _debug_collection_type = | |
6188 (CollectionTypes) (_debug_collection_type % Unknown_collection_type); | |
6189 if (PrintGCDetails && Verbose) { | |
6190 gclog_or_tty->print_cr("to %d ", _debug_collection_type); | |
6191 } | |
6192 } | |
6193 | |
6194 void CMSCollector::sweepWork(ConcurrentMarkSweepGeneration* gen, | |
6195 bool asynch) { | |
6196 // We iterate over the space(s) underlying this generation, | |
6197 // checking the mark bit map to see if the bits corresponding | |
6198 // to specific blocks are marked or not. Blocks that are | |
6199 // marked are live and are not swept up. All remaining blocks | |
6200 // are swept up, with coalescing on-the-fly as we sweep up | |
6201 // contiguous free and/or garbage blocks: | |
6202 // We need to ensure that the sweeper synchronizes with allocators | |
6203 // and stop-the-world collectors. In particular, the following | |
6204 // locks are used: | |
6205 // . CMS token: if this is held, a stop the world collection cannot occur | |
6206 // . freelistLock: if this is held no allocation can occur from this | |
6207 // generation by another thread | |
6208 // . bitMapLock: if this is held, no other thread can access or update | |
6209 // | |
6210 | |
6211 // Note that we need to hold the freelistLock if we use | |
6212 // block iterate below; else the iterator might go awry if | |
6213 // a mutator (or promotion) causes block contents to change | |
6214 // (for instance if the allocator divvies up a block). | |
6215 // If we hold the free list lock, for all practical purposes | |
6216 // young generation GC's can't occur (they'll usually need to | |
6217 // promote), so we might as well prevent all young generation | |
6218 // GC's while we do a sweeping step. For the same reason, we might | |
6219 // as well take the bit map lock for the entire duration | |
6220 | |
6221 // check that we hold the requisite locks | |
6222 assert(have_cms_token(), "Should hold cms token"); | |
6223 assert( (asynch && ConcurrentMarkSweepThread::cms_thread_has_cms_token()) | |
6224 || (!asynch && ConcurrentMarkSweepThread::vm_thread_has_cms_token()), | |
6225 "Should possess CMS token to sweep"); | |
6226 assert_lock_strong(gen->freelistLock()); | |
6227 assert_lock_strong(bitMapLock()); | |
6228 | |
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6229 assert(!_inter_sweep_timer.is_active(), "Was switched off in an outer context"); |
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6230 assert(_intra_sweep_timer.is_active(), "Was switched on in an outer context"); |
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6231 gen->cmsSpace()->beginSweepFLCensus((float)(_inter_sweep_timer.seconds()), |
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6232 _inter_sweep_estimate.padded_average(), |
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6233 _intra_sweep_estimate.padded_average()); |
0 | 6234 gen->setNearLargestChunk(); |
6235 | |
6236 { | |
6237 SweepClosure sweepClosure(this, gen, &_markBitMap, | |
6238 CMSYield && asynch); | |
6239 gen->cmsSpace()->blk_iterate_careful(&sweepClosure); | |
6240 // We need to free-up/coalesce garbage/blocks from a | |
6241 // co-terminal free run. This is done in the SweepClosure | |
6242 // destructor; so, do not remove this scope, else the | |
6243 // end-of-sweep-census below will be off by a little bit. | |
6244 } | |
6245 gen->cmsSpace()->sweep_completed(); | |
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6246 gen->cmsSpace()->endSweepFLCensus(sweep_count()); |
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6247 if (should_unload_classes()) { // unloaded classes this cycle, |
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6248 _concurrent_cycles_since_last_unload = 0; // ... reset count |
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6249 } else { // did not unload classes, |
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6250 _concurrent_cycles_since_last_unload++; // ... increment count |
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6251 } |
0 | 6252 } |
6253 | |
6254 // Reset CMS data structures (for now just the marking bit map) | |
6255 // preparatory for the next cycle. | |
6256 void CMSCollector::reset(bool asynch) { | |
6257 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
6258 CMSAdaptiveSizePolicy* sp = size_policy(); | |
6259 AdaptiveSizePolicyOutput(sp, gch->total_collections()); | |
6260 if (asynch) { | |
6261 CMSTokenSyncWithLocks ts(true, bitMapLock()); | |
6262 | |
6263 // If the state is not "Resetting", the foreground thread | |
6264 // has done a collection and the resetting. | |
6265 if (_collectorState != Resetting) { | |
6266 assert(_collectorState == Idling, "The state should only change" | |
6267 " because the foreground collector has finished the collection"); | |
6268 return; | |
6269 } | |
6270 | |
6271 // Clear the mark bitmap (no grey objects to start with) | |
6272 // for the next cycle. | |
6273 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
6274 CMSPhaseAccounting cmspa(this, "reset", !PrintGCDetails); | |
6275 | |
6276 HeapWord* curAddr = _markBitMap.startWord(); | |
6277 while (curAddr < _markBitMap.endWord()) { | |
6278 size_t remaining = pointer_delta(_markBitMap.endWord(), curAddr); | |
6279 MemRegion chunk(curAddr, MIN2(CMSBitMapYieldQuantum, remaining)); | |
6280 _markBitMap.clear_large_range(chunk); | |
6281 if (ConcurrentMarkSweepThread::should_yield() && | |
6282 !foregroundGCIsActive() && | |
6283 CMSYield) { | |
6284 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
6285 "CMS thread should hold CMS token"); | |
6286 assert_lock_strong(bitMapLock()); | |
6287 bitMapLock()->unlock(); | |
6288 ConcurrentMarkSweepThread::desynchronize(true); | |
6289 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
6290 stopTimer(); | |
6291 if (PrintCMSStatistics != 0) { | |
6292 incrementYields(); | |
6293 } | |
6294 icms_wait(); | |
6295 | |
6296 // See the comment in coordinator_yield() | |
6297 for (unsigned i = 0; i < CMSYieldSleepCount && | |
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6298 ConcurrentMarkSweepThread::should_yield() && |
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6299 !CMSCollector::foregroundGCIsActive(); ++i) { |
0 | 6300 os::sleep(Thread::current(), 1, false); |
6301 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
6302 } | |
6303 | |
6304 ConcurrentMarkSweepThread::synchronize(true); | |
6305 bitMapLock()->lock_without_safepoint_check(); | |
6306 startTimer(); | |
6307 } | |
6308 curAddr = chunk.end(); | |
6309 } | |
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6310 // A successful mostly concurrent collection has been done. |
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6311 // Because only the full (i.e., concurrent mode failure) collections |
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6312 // are being measured for gc overhead limits, clean the "near" flag |
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6313 // and count. |
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6314 sp->reset_gc_overhead_limit_count(); |
0 | 6315 _collectorState = Idling; |
6316 } else { | |
6317 // already have the lock | |
6318 assert(_collectorState == Resetting, "just checking"); | |
6319 assert_lock_strong(bitMapLock()); | |
6320 _markBitMap.clear_all(); | |
6321 _collectorState = Idling; | |
6322 } | |
6323 | |
6324 // Stop incremental mode after a cycle completes, so that any future cycles | |
6325 // are triggered by allocation. | |
6326 stop_icms(); | |
6327 | |
6328 NOT_PRODUCT( | |
6329 if (RotateCMSCollectionTypes) { | |
6330 _cmsGen->rotate_debug_collection_type(); | |
6331 } | |
6332 ) | |
6333 } | |
6334 | |
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6335 void CMSCollector::do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause) { |
0 | 6336 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps); |
6337 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
6064
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6338 TraceTime t(GCCauseString("GC", gc_cause), PrintGC, !PrintGCDetails, gclog_or_tty); |
0 | 6339 TraceCollectorStats tcs(counters()); |
6340 | |
6341 switch (op) { | |
6342 case CMS_op_checkpointRootsInitial: { | |
2125
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|
6343 SvcGCMarker sgcm(SvcGCMarker::OTHER); |
0 | 6344 checkpointRootsInitial(true); // asynch |
6345 if (PrintGC) { | |
6346 _cmsGen->printOccupancy("initial-mark"); | |
6347 } | |
6348 break; | |
6349 } | |
6350 case CMS_op_checkpointRootsFinal: { | |
2125
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6351 SvcGCMarker sgcm(SvcGCMarker::OTHER); |
0 | 6352 checkpointRootsFinal(true, // asynch |
6353 false, // !clear_all_soft_refs | |
6354 false); // !init_mark_was_synchronous | |
6355 if (PrintGC) { | |
6356 _cmsGen->printOccupancy("remark"); | |
6357 } | |
6358 break; | |
6359 } | |
6360 default: | |
6361 fatal("No such CMS_op"); | |
6362 } | |
6363 } | |
6364 | |
6365 #ifndef PRODUCT | |
6366 size_t const CMSCollector::skip_header_HeapWords() { | |
6367 return FreeChunk::header_size(); | |
6368 } | |
6369 | |
6370 // Try and collect here conditions that should hold when | |
6371 // CMS thread is exiting. The idea is that the foreground GC | |
6372 // thread should not be blocked if it wants to terminate | |
6373 // the CMS thread and yet continue to run the VM for a while | |
6374 // after that. | |
6375 void CMSCollector::verify_ok_to_terminate() const { | |
6376 assert(Thread::current()->is_ConcurrentGC_thread(), | |
6377 "should be called by CMS thread"); | |
6378 assert(!_foregroundGCShouldWait, "should be false"); | |
6379 // We could check here that all the various low-level locks | |
6380 // are not held by the CMS thread, but that is overkill; see | |
6381 // also CMSThread::verify_ok_to_terminate() where the CGC_lock | |
6382 // is checked. | |
6383 } | |
6384 #endif | |
6385 | |
6386 size_t CMSCollector::block_size_using_printezis_bits(HeapWord* addr) const { | |
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6387 assert(_markBitMap.isMarked(addr) && _markBitMap.isMarked(addr + 1), |
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6388 "missing Printezis mark?"); |
0 | 6389 HeapWord* nextOneAddr = _markBitMap.getNextMarkedWordAddress(addr + 2); |
6390 size_t size = pointer_delta(nextOneAddr + 1, addr); | |
6391 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
6392 "alignment problem"); | |
6393 assert(size >= 3, "Necessary for Printezis marks to work"); | |
6394 return size; | |
6395 } | |
6396 | |
6397 // A variant of the above (block_size_using_printezis_bits()) except | |
6398 // that we return 0 if the P-bits are not yet set. | |
6399 size_t CMSCollector::block_size_if_printezis_bits(HeapWord* addr) const { | |
2226
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|
6400 if (_markBitMap.isMarked(addr + 1)) { |
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|
6401 assert(_markBitMap.isMarked(addr), "P-bit can be set only for marked objects"); |
0 | 6402 HeapWord* nextOneAddr = _markBitMap.getNextMarkedWordAddress(addr + 2); |
6403 size_t size = pointer_delta(nextOneAddr + 1, addr); | |
6404 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
6405 "alignment problem"); | |
6406 assert(size >= 3, "Necessary for Printezis marks to work"); | |
6407 return size; | |
2226
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|
6408 } |
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|
6409 return 0; |
0 | 6410 } |
6411 | |
6412 HeapWord* CMSCollector::next_card_start_after_block(HeapWord* addr) const { | |
6413 size_t sz = 0; | |
6414 oop p = (oop)addr; | |
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6415 if (p->klass_or_null() != NULL) { |
0 | 6416 sz = CompactibleFreeListSpace::adjustObjectSize(p->size()); |
6417 } else { | |
6418 sz = block_size_using_printezis_bits(addr); | |
6419 } | |
6420 assert(sz > 0, "size must be nonzero"); | |
6421 HeapWord* next_block = addr + sz; | |
6422 HeapWord* next_card = (HeapWord*)round_to((uintptr_t)next_block, | |
6423 CardTableModRefBS::card_size); | |
6424 assert(round_down((uintptr_t)addr, CardTableModRefBS::card_size) < | |
6425 round_down((uintptr_t)next_card, CardTableModRefBS::card_size), | |
6426 "must be different cards"); | |
6427 return next_card; | |
6428 } | |
6429 | |
6430 | |
6431 // CMS Bit Map Wrapper ///////////////////////////////////////// | |
6432 | |
6433 // Construct a CMS bit map infrastructure, but don't create the | |
6434 // bit vector itself. That is done by a separate call CMSBitMap::allocate() | |
6435 // further below. | |
6436 CMSBitMap::CMSBitMap(int shifter, int mutex_rank, const char* mutex_name): | |
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6437 _bm(), |
0 | 6438 _shifter(shifter), |
6439 _lock(mutex_rank >= 0 ? new Mutex(mutex_rank, mutex_name, true) : NULL) | |
6440 { | |
6441 _bmStartWord = 0; | |
6442 _bmWordSize = 0; | |
6443 } | |
6444 | |
6445 bool CMSBitMap::allocate(MemRegion mr) { | |
6446 _bmStartWord = mr.start(); | |
6447 _bmWordSize = mr.word_size(); | |
6448 ReservedSpace brs(ReservedSpace::allocation_align_size_up( | |
6449 (_bmWordSize >> (_shifter + LogBitsPerByte)) + 1)); | |
6450 if (!brs.is_reserved()) { | |
6451 warning("CMS bit map allocation failure"); | |
6452 return false; | |
6453 } | |
6454 // For now we'll just commit all of the bit map up fromt. | |
6455 // Later on we'll try to be more parsimonious with swap. | |
6456 if (!_virtual_space.initialize(brs, brs.size())) { | |
6457 warning("CMS bit map backing store failure"); | |
6458 return false; | |
6459 } | |
6460 assert(_virtual_space.committed_size() == brs.size(), | |
6461 "didn't reserve backing store for all of CMS bit map?"); | |
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6462 _bm.set_map((BitMap::bm_word_t*)_virtual_space.low()); |
0 | 6463 assert(_virtual_space.committed_size() << (_shifter + LogBitsPerByte) >= |
6464 _bmWordSize, "inconsistency in bit map sizing"); | |
6465 _bm.set_size(_bmWordSize >> _shifter); | |
6466 | |
6467 // bm.clear(); // can we rely on getting zero'd memory? verify below | |
6468 assert(isAllClear(), | |
6469 "Expected zero'd memory from ReservedSpace constructor"); | |
6470 assert(_bm.size() == heapWordDiffToOffsetDiff(sizeInWords()), | |
6471 "consistency check"); | |
6472 return true; | |
6473 } | |
6474 | |
6475 void CMSBitMap::dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl) { | |
6476 HeapWord *next_addr, *end_addr, *last_addr; | |
6477 assert_locked(); | |
6478 assert(covers(mr), "out-of-range error"); | |
6479 // XXX assert that start and end are appropriately aligned | |
6480 for (next_addr = mr.start(), end_addr = mr.end(); | |
6481 next_addr < end_addr; next_addr = last_addr) { | |
6482 MemRegion dirty_region = getAndClearMarkedRegion(next_addr, end_addr); | |
6483 last_addr = dirty_region.end(); | |
6484 if (!dirty_region.is_empty()) { | |
6485 cl->do_MemRegion(dirty_region); | |
6486 } else { | |
6487 assert(last_addr == end_addr, "program logic"); | |
6488 return; | |
6489 } | |
6490 } | |
6491 } | |
6492 | |
6493 #ifndef PRODUCT | |
6494 void CMSBitMap::assert_locked() const { | |
6495 CMSLockVerifier::assert_locked(lock()); | |
6496 } | |
6497 | |
6498 bool CMSBitMap::covers(MemRegion mr) const { | |
6499 // assert(_bm.map() == _virtual_space.low(), "map inconsistency"); | |
6500 assert((size_t)_bm.size() == (_bmWordSize >> _shifter), | |
6501 "size inconsistency"); | |
6502 return (mr.start() >= _bmStartWord) && | |
6503 (mr.end() <= endWord()); | |
6504 } | |
6505 | |
6506 bool CMSBitMap::covers(HeapWord* start, size_t size) const { | |
6507 return (start >= _bmStartWord && (start + size) <= endWord()); | |
6508 } | |
6509 | |
6510 void CMSBitMap::verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) { | |
6511 // verify that there are no 1 bits in the interval [left, right) | |
6512 FalseBitMapClosure falseBitMapClosure; | |
6513 iterate(&falseBitMapClosure, left, right); | |
6514 } | |
6515 | |
6516 void CMSBitMap::region_invariant(MemRegion mr) | |
6517 { | |
6518 assert_locked(); | |
6519 // mr = mr.intersection(MemRegion(_bmStartWord, _bmWordSize)); | |
6520 assert(!mr.is_empty(), "unexpected empty region"); | |
6521 assert(covers(mr), "mr should be covered by bit map"); | |
6522 // convert address range into offset range | |
6523 size_t start_ofs = heapWordToOffset(mr.start()); | |
6524 // Make sure that end() is appropriately aligned | |
6525 assert(mr.end() == (HeapWord*)round_to((intptr_t)mr.end(), | |
6526 (1 << (_shifter+LogHeapWordSize))), | |
6527 "Misaligned mr.end()"); | |
6528 size_t end_ofs = heapWordToOffset(mr.end()); | |
6529 assert(end_ofs > start_ofs, "Should mark at least one bit"); | |
6530 } | |
6531 | |
6532 #endif | |
6533 | |
6534 bool CMSMarkStack::allocate(size_t size) { | |
6535 // allocate a stack of the requisite depth | |
6536 ReservedSpace rs(ReservedSpace::allocation_align_size_up( | |
6537 size * sizeof(oop))); | |
6538 if (!rs.is_reserved()) { | |
6539 warning("CMSMarkStack allocation failure"); | |
6540 return false; | |
6541 } | |
6542 if (!_virtual_space.initialize(rs, rs.size())) { | |
6543 warning("CMSMarkStack backing store failure"); | |
6544 return false; | |
6545 } | |
6546 assert(_virtual_space.committed_size() == rs.size(), | |
6547 "didn't reserve backing store for all of CMS stack?"); | |
6548 _base = (oop*)(_virtual_space.low()); | |
6549 _index = 0; | |
6550 _capacity = size; | |
6551 NOT_PRODUCT(_max_depth = 0); | |
6552 return true; | |
6553 } | |
6554 | |
6555 // XXX FIX ME !!! In the MT case we come in here holding a | |
6556 // leaf lock. For printing we need to take a further lock | |
6557 // which has lower rank. We need to recallibrate the two | |
6558 // lock-ranks involved in order to be able to rpint the | |
6559 // messages below. (Or defer the printing to the caller. | |
6560 // For now we take the expedient path of just disabling the | |
6561 // messages for the problematic case.) | |
6562 void CMSMarkStack::expand() { | |
1284 | 6563 assert(_capacity <= MarkStackSizeMax, "stack bigger than permitted"); |
6564 if (_capacity == MarkStackSizeMax) { | |
0 | 6565 if (_hit_limit++ == 0 && !CMSConcurrentMTEnabled && PrintGCDetails) { |
6566 // We print a warning message only once per CMS cycle. | |
6567 gclog_or_tty->print_cr(" (benign) Hit CMSMarkStack max size limit"); | |
6568 } | |
6569 return; | |
6570 } | |
6571 // Double capacity if possible | |
1284 | 6572 size_t new_capacity = MIN2(_capacity*2, MarkStackSizeMax); |
0 | 6573 // Do not give up existing stack until we have managed to |
6574 // get the double capacity that we desired. | |
6575 ReservedSpace rs(ReservedSpace::allocation_align_size_up( | |
6576 new_capacity * sizeof(oop))); | |
6577 if (rs.is_reserved()) { | |
6578 // Release the backing store associated with old stack | |
6579 _virtual_space.release(); | |
6580 // Reinitialize virtual space for new stack | |
6581 if (!_virtual_space.initialize(rs, rs.size())) { | |
6582 fatal("Not enough swap for expanded marking stack"); | |
6583 } | |
6584 _base = (oop*)(_virtual_space.low()); | |
6585 _index = 0; | |
6586 _capacity = new_capacity; | |
6587 } else if (_failed_double++ == 0 && !CMSConcurrentMTEnabled && PrintGCDetails) { | |
6588 // Failed to double capacity, continue; | |
6589 // we print a detail message only once per CMS cycle. | |
6590 gclog_or_tty->print(" (benign) Failed to expand marking stack from "SIZE_FORMAT"K to " | |
6591 SIZE_FORMAT"K", | |
6592 _capacity / K, new_capacity / K); | |
6593 } | |
6594 } | |
6595 | |
6596 | |
6597 // Closures | |
6598 // XXX: there seems to be a lot of code duplication here; | |
6599 // should refactor and consolidate common code. | |
6600 | |
6601 // This closure is used to mark refs into the CMS generation in | |
6602 // the CMS bit map. Called at the first checkpoint. This closure | |
6603 // assumes that we do not need to re-mark dirty cards; if the CMS | |
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6604 // generation on which this is used is not an oldest |
0 | 6605 // generation then this will lose younger_gen cards! |
6606 | |
6607 MarkRefsIntoClosure::MarkRefsIntoClosure( | |
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|
6608 MemRegion span, CMSBitMap* bitMap): |
0 | 6609 _span(span), |
994
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|
6610 _bitMap(bitMap) |
0 | 6611 { |
6612 assert(_ref_processor == NULL, "deliberately left NULL"); | |
6613 assert(_bitMap->covers(_span), "_bitMap/_span mismatch"); | |
6614 } | |
6615 | |
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6616 void MarkRefsIntoClosure::do_oop(oop obj) { |
0 | 6617 // if p points into _span, then mark corresponding bit in _markBitMap |
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6618 assert(obj->is_oop(), "expected an oop"); |
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6619 HeapWord* addr = (HeapWord*)obj; |
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6620 if (_span.contains(addr)) { |
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6621 // this should be made more efficient |
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|
6622 _bitMap->mark(addr); |
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6623 } |
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|
6624 } |
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|
6625 |
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|
6626 void MarkRefsIntoClosure::do_oop(oop* p) { MarkRefsIntoClosure::do_oop_work(p); } |
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6627 void MarkRefsIntoClosure::do_oop(narrowOop* p) { MarkRefsIntoClosure::do_oop_work(p); } |
0 | 6628 |
6629 // A variant of the above, used for CMS marking verification. | |
6630 MarkRefsIntoVerifyClosure::MarkRefsIntoVerifyClosure( | |
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|
6631 MemRegion span, CMSBitMap* verification_bm, CMSBitMap* cms_bm): |
0 | 6632 _span(span), |
6633 _verification_bm(verification_bm), | |
994
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|
6634 _cms_bm(cms_bm) |
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|
6635 { |
0 | 6636 assert(_ref_processor == NULL, "deliberately left NULL"); |
6637 assert(_verification_bm->covers(_span), "_verification_bm/_span mismatch"); | |
6638 } | |
6639 | |
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6640 void MarkRefsIntoVerifyClosure::do_oop(oop obj) { |
0 | 6641 // if p points into _span, then mark corresponding bit in _markBitMap |
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|
6642 assert(obj->is_oop(), "expected an oop"); |
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6643 HeapWord* addr = (HeapWord*)obj; |
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6644 if (_span.contains(addr)) { |
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6645 _verification_bm->mark(addr); |
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6646 if (!_cms_bm->isMarked(addr)) { |
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6647 oop(addr)->print(); |
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6648 gclog_or_tty->print_cr(" (" INTPTR_FORMAT " should have been marked)", addr); |
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6649 fatal("... aborting"); |
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6650 } |
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6651 } |
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6652 } |
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6653 |
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6654 void MarkRefsIntoVerifyClosure::do_oop(oop* p) { MarkRefsIntoVerifyClosure::do_oop_work(p); } |
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6655 void MarkRefsIntoVerifyClosure::do_oop(narrowOop* p) { MarkRefsIntoVerifyClosure::do_oop_work(p); } |
0 | 6656 |
6657 ////////////////////////////////////////////////// | |
6658 // MarkRefsIntoAndScanClosure | |
6659 ////////////////////////////////////////////////// | |
6660 | |
6661 MarkRefsIntoAndScanClosure::MarkRefsIntoAndScanClosure(MemRegion span, | |
6662 ReferenceProcessor* rp, | |
6663 CMSBitMap* bit_map, | |
6664 CMSBitMap* mod_union_table, | |
6665 CMSMarkStack* mark_stack, | |
6666 CMSCollector* collector, | |
6667 bool should_yield, | |
6668 bool concurrent_precleaning): | |
6669 _collector(collector), | |
6670 _span(span), | |
6671 _bit_map(bit_map), | |
6672 _mark_stack(mark_stack), | |
6673 _pushAndMarkClosure(collector, span, rp, bit_map, mod_union_table, | |
6725
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6674 mark_stack, concurrent_precleaning), |
0 | 6675 _yield(should_yield), |
6676 _concurrent_precleaning(concurrent_precleaning), | |
6677 _freelistLock(NULL) | |
6678 { | |
6679 _ref_processor = rp; | |
6680 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
6681 } | |
6682 | |
6683 // This closure is used to mark refs into the CMS generation at the | |
6684 // second (final) checkpoint, and to scan and transitively follow | |
6685 // the unmarked oops. It is also used during the concurrent precleaning | |
6686 // phase while scanning objects on dirty cards in the CMS generation. | |
6687 // The marks are made in the marking bit map and the marking stack is | |
6688 // used for keeping the (newly) grey objects during the scan. | |
6689 // The parallel version (Par_...) appears further below. | |
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6690 void MarkRefsIntoAndScanClosure::do_oop(oop obj) { |
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6691 if (obj != NULL) { |
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6692 assert(obj->is_oop(), "expected an oop"); |
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6693 HeapWord* addr = (HeapWord*)obj; |
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6694 assert(_mark_stack->isEmpty(), "pre-condition (eager drainage)"); |
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6695 assert(_collector->overflow_list_is_empty(), |
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6696 "overflow list should be empty"); |
0 | 6697 if (_span.contains(addr) && |
6698 !_bit_map->isMarked(addr)) { | |
6699 // mark bit map (object is now grey) | |
6700 _bit_map->mark(addr); | |
6701 // push on marking stack (stack should be empty), and drain the | |
6702 // stack by applying this closure to the oops in the oops popped | |
6703 // from the stack (i.e. blacken the grey objects) | |
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6704 bool res = _mark_stack->push(obj); |
0 | 6705 assert(res, "Should have space to push on empty stack"); |
6706 do { | |
6707 oop new_oop = _mark_stack->pop(); | |
6708 assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop"); | |
6709 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
6710 "only grey objects on this stack"); | |
6711 // iterate over the oops in this oop, marking and pushing | |
6712 // the ones in CMS heap (i.e. in _span). | |
6713 new_oop->oop_iterate(&_pushAndMarkClosure); | |
6714 // check if it's time to yield | |
6715 do_yield_check(); | |
6716 } while (!_mark_stack->isEmpty() || | |
6717 (!_concurrent_precleaning && take_from_overflow_list())); | |
6718 // if marking stack is empty, and we are not doing this | |
6719 // during precleaning, then check the overflow list | |
6720 } | |
6721 assert(_mark_stack->isEmpty(), "post-condition (eager drainage)"); | |
6722 assert(_collector->overflow_list_is_empty(), | |
6723 "overflow list was drained above"); | |
6724 // We could restore evacuated mark words, if any, used for | |
6725 // overflow list links here because the overflow list is | |
6726 // provably empty here. That would reduce the maximum | |
6727 // size requirements for preserved_{oop,mark}_stack. | |
6728 // But we'll just postpone it until we are all done | |
6729 // so we can just stream through. | |
6730 if (!_concurrent_precleaning && CMSOverflowEarlyRestoration) { | |
6731 _collector->restore_preserved_marks_if_any(); | |
6732 assert(_collector->no_preserved_marks(), "No preserved marks"); | |
6733 } | |
6734 assert(!CMSOverflowEarlyRestoration || _collector->no_preserved_marks(), | |
6735 "All preserved marks should have been restored above"); | |
6736 } | |
6737 } | |
6738 | |
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6739 void MarkRefsIntoAndScanClosure::do_oop(oop* p) { MarkRefsIntoAndScanClosure::do_oop_work(p); } |
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6740 void MarkRefsIntoAndScanClosure::do_oop(narrowOop* p) { MarkRefsIntoAndScanClosure::do_oop_work(p); } |
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6741 |
0 | 6742 void MarkRefsIntoAndScanClosure::do_yield_work() { |
6743 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
6744 "CMS thread should hold CMS token"); | |
6745 assert_lock_strong(_freelistLock); | |
6746 assert_lock_strong(_bit_map->lock()); | |
6747 // relinquish the free_list_lock and bitMaplock() | |
6748 _bit_map->lock()->unlock(); | |
6749 _freelistLock->unlock(); | |
6750 ConcurrentMarkSweepThread::desynchronize(true); | |
6751 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
6752 _collector->stopTimer(); | |
6753 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
6754 if (PrintCMSStatistics != 0) { | |
6755 _collector->incrementYields(); | |
6756 } | |
6757 _collector->icms_wait(); | |
6758 | |
6759 // See the comment in coordinator_yield() | |
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6760 for (unsigned i = 0; |
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6761 i < CMSYieldSleepCount && |
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6762 ConcurrentMarkSweepThread::should_yield() && |
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6763 !CMSCollector::foregroundGCIsActive(); |
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6764 ++i) { |
0 | 6765 os::sleep(Thread::current(), 1, false); |
6766 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
6767 } | |
6768 | |
6769 ConcurrentMarkSweepThread::synchronize(true); | |
6770 _freelistLock->lock_without_safepoint_check(); | |
6771 _bit_map->lock()->lock_without_safepoint_check(); | |
6772 _collector->startTimer(); | |
6773 } | |
6774 | |
6775 /////////////////////////////////////////////////////////// | |
6776 // Par_MarkRefsIntoAndScanClosure: a parallel version of | |
6777 // MarkRefsIntoAndScanClosure | |
6778 /////////////////////////////////////////////////////////// | |
6779 Par_MarkRefsIntoAndScanClosure::Par_MarkRefsIntoAndScanClosure( | |
6780 CMSCollector* collector, MemRegion span, ReferenceProcessor* rp, | |
6725
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6781 CMSBitMap* bit_map, OopTaskQueue* work_queue): |
0 | 6782 _span(span), |
6783 _bit_map(bit_map), | |
6784 _work_queue(work_queue), | |
6785 _low_water_mark(MIN2((uint)(work_queue->max_elems()/4), | |
6786 (uint)(CMSWorkQueueDrainThreshold * ParallelGCThreads))), | |
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6787 _par_pushAndMarkClosure(collector, span, rp, bit_map, work_queue) |
0 | 6788 { |
6789 _ref_processor = rp; | |
6790 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
6791 } | |
6792 | |
6793 // This closure is used to mark refs into the CMS generation at the | |
6794 // second (final) checkpoint, and to scan and transitively follow | |
6795 // the unmarked oops. The marks are made in the marking bit map and | |
6796 // the work_queue is used for keeping the (newly) grey objects during | |
6797 // the scan phase whence they are also available for stealing by parallel | |
6798 // threads. Since the marking bit map is shared, updates are | |
6799 // synchronized (via CAS). | |
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6800 void Par_MarkRefsIntoAndScanClosure::do_oop(oop obj) { |
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6801 if (obj != NULL) { |
0 | 6802 // Ignore mark word because this could be an already marked oop |
6803 // that may be chained at the end of the overflow list. | |
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6804 assert(obj->is_oop(true), "expected an oop"); |
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6805 HeapWord* addr = (HeapWord*)obj; |
0 | 6806 if (_span.contains(addr) && |
6807 !_bit_map->isMarked(addr)) { | |
6808 // mark bit map (object will become grey): | |
6809 // It is possible for several threads to be | |
6810 // trying to "claim" this object concurrently; | |
6811 // the unique thread that succeeds in marking the | |
6812 // object first will do the subsequent push on | |
6813 // to the work queue (or overflow list). | |
6814 if (_bit_map->par_mark(addr)) { | |
6815 // push on work_queue (which may not be empty), and trim the | |
6816 // queue to an appropriate length by applying this closure to | |
6817 // the oops in the oops popped from the stack (i.e. blacken the | |
6818 // grey objects) | |
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6819 bool res = _work_queue->push(obj); |
0 | 6820 assert(res, "Low water mark should be less than capacity?"); |
6821 trim_queue(_low_water_mark); | |
6822 } // Else, another thread claimed the object | |
6823 } | |
6824 } | |
6825 } | |
6826 | |
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6827 void Par_MarkRefsIntoAndScanClosure::do_oop(oop* p) { Par_MarkRefsIntoAndScanClosure::do_oop_work(p); } |
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6828 void Par_MarkRefsIntoAndScanClosure::do_oop(narrowOop* p) { Par_MarkRefsIntoAndScanClosure::do_oop_work(p); } |
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6829 |
0 | 6830 // This closure is used to rescan the marked objects on the dirty cards |
6831 // in the mod union table and the card table proper. | |
6832 size_t ScanMarkedObjectsAgainCarefullyClosure::do_object_careful_m( | |
6833 oop p, MemRegion mr) { | |
6834 | |
6835 size_t size = 0; | |
6836 HeapWord* addr = (HeapWord*)p; | |
6837 DEBUG_ONLY(_collector->verify_work_stacks_empty();) | |
6838 assert(_span.contains(addr), "we are scanning the CMS generation"); | |
6839 // check if it's time to yield | |
6840 if (do_yield_check()) { | |
6841 // We yielded for some foreground stop-world work, | |
6842 // and we have been asked to abort this ongoing preclean cycle. | |
6843 return 0; | |
6844 } | |
6845 if (_bitMap->isMarked(addr)) { | |
6846 // it's marked; is it potentially uninitialized? | |
187 | 6847 if (p->klass_or_null() != NULL) { |
0 | 6848 // an initialized object; ignore mark word in verification below |
6849 // since we are running concurrent with mutators | |
6850 assert(p->is_oop(true), "should be an oop"); | |
6851 if (p->is_objArray()) { | |
6852 // objArrays are precisely marked; restrict scanning | |
6853 // to dirty cards only. | |
187 | 6854 size = CompactibleFreeListSpace::adjustObjectSize( |
6855 p->oop_iterate(_scanningClosure, mr)); | |
0 | 6856 } else { |
6857 // A non-array may have been imprecisely marked; we need | |
6858 // to scan object in its entirety. | |
6859 size = CompactibleFreeListSpace::adjustObjectSize( | |
6860 p->oop_iterate(_scanningClosure)); | |
6861 } | |
6862 #ifdef DEBUG | |
6863 size_t direct_size = | |
6864 CompactibleFreeListSpace::adjustObjectSize(p->size()); | |
6865 assert(size == direct_size, "Inconsistency in size"); | |
6866 assert(size >= 3, "Necessary for Printezis marks to work"); | |
6867 if (!_bitMap->isMarked(addr+1)) { | |
6868 _bitMap->verifyNoOneBitsInRange(addr+2, addr+size); | |
6869 } else { | |
6870 _bitMap->verifyNoOneBitsInRange(addr+2, addr+size-1); | |
6871 assert(_bitMap->isMarked(addr+size-1), | |
6872 "inconsistent Printezis mark"); | |
6873 } | |
6874 #endif // DEBUG | |
6875 } else { | |
6876 // an unitialized object | |
6877 assert(_bitMap->isMarked(addr+1), "missing Printezis mark?"); | |
6878 HeapWord* nextOneAddr = _bitMap->getNextMarkedWordAddress(addr + 2); | |
6879 size = pointer_delta(nextOneAddr + 1, addr); | |
6880 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
6881 "alignment problem"); | |
6882 // Note that pre-cleaning needn't redirty the card. OopDesc::set_klass() | |
6883 // will dirty the card when the klass pointer is installed in the | |
6884 // object (signalling the completion of initialization). | |
6885 } | |
6886 } else { | |
6887 // Either a not yet marked object or an uninitialized object | |
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6888 if (p->klass_or_null() == NULL) { |
0 | 6889 // An uninitialized object, skip to the next card, since |
6890 // we may not be able to read its P-bits yet. | |
6891 assert(size == 0, "Initial value"); | |
6892 } else { | |
6893 // An object not (yet) reached by marking: we merely need to | |
6894 // compute its size so as to go look at the next block. | |
6895 assert(p->is_oop(true), "should be an oop"); | |
6896 size = CompactibleFreeListSpace::adjustObjectSize(p->size()); | |
6897 } | |
6898 } | |
6899 DEBUG_ONLY(_collector->verify_work_stacks_empty();) | |
6900 return size; | |
6901 } | |
6902 | |
6903 void ScanMarkedObjectsAgainCarefullyClosure::do_yield_work() { | |
6904 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
6905 "CMS thread should hold CMS token"); | |
6906 assert_lock_strong(_freelistLock); | |
6907 assert_lock_strong(_bitMap->lock()); | |
6908 // relinquish the free_list_lock and bitMaplock() | |
6909 _bitMap->lock()->unlock(); | |
6910 _freelistLock->unlock(); | |
6911 ConcurrentMarkSweepThread::desynchronize(true); | |
6912 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
6913 _collector->stopTimer(); | |
6914 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
6915 if (PrintCMSStatistics != 0) { | |
6916 _collector->incrementYields(); | |
6917 } | |
6918 _collector->icms_wait(); | |
6919 | |
6920 // See the comment in coordinator_yield() | |
6921 for (unsigned i = 0; i < CMSYieldSleepCount && | |
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6922 ConcurrentMarkSweepThread::should_yield() && |
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6923 !CMSCollector::foregroundGCIsActive(); ++i) { |
0 | 6924 os::sleep(Thread::current(), 1, false); |
6925 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
6926 } | |
6927 | |
6928 ConcurrentMarkSweepThread::synchronize(true); | |
6929 _freelistLock->lock_without_safepoint_check(); | |
6930 _bitMap->lock()->lock_without_safepoint_check(); | |
6931 _collector->startTimer(); | |
6932 } | |
6933 | |
6934 | |
6935 ////////////////////////////////////////////////////////////////// | |
6936 // SurvivorSpacePrecleanClosure | |
6937 ////////////////////////////////////////////////////////////////// | |
6938 // This (single-threaded) closure is used to preclean the oops in | |
6939 // the survivor spaces. | |
6940 size_t SurvivorSpacePrecleanClosure::do_object_careful(oop p) { | |
6941 | |
6942 HeapWord* addr = (HeapWord*)p; | |
6943 DEBUG_ONLY(_collector->verify_work_stacks_empty();) | |
6944 assert(!_span.contains(addr), "we are scanning the survivor spaces"); | |
187 | 6945 assert(p->klass_or_null() != NULL, "object should be initializd"); |
0 | 6946 // an initialized object; ignore mark word in verification below |
6947 // since we are running concurrent with mutators | |
6948 assert(p->is_oop(true), "should be an oop"); | |
6949 // Note that we do not yield while we iterate over | |
6950 // the interior oops of p, pushing the relevant ones | |
6951 // on our marking stack. | |
6952 size_t size = p->oop_iterate(_scanning_closure); | |
6953 do_yield_check(); | |
6954 // Observe that below, we do not abandon the preclean | |
6955 // phase as soon as we should; rather we empty the | |
6956 // marking stack before returning. This is to satisfy | |
6957 // some existing assertions. In general, it may be a | |
6958 // good idea to abort immediately and complete the marking | |
6959 // from the grey objects at a later time. | |
6960 while (!_mark_stack->isEmpty()) { | |
6961 oop new_oop = _mark_stack->pop(); | |
6962 assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop"); | |
6963 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
6964 "only grey objects on this stack"); | |
6965 // iterate over the oops in this oop, marking and pushing | |
6966 // the ones in CMS heap (i.e. in _span). | |
6967 new_oop->oop_iterate(_scanning_closure); | |
6968 // check if it's time to yield | |
6969 do_yield_check(); | |
6970 } | |
6971 unsigned int after_count = | |
6972 GenCollectedHeap::heap()->total_collections(); | |
6973 bool abort = (_before_count != after_count) || | |
6974 _collector->should_abort_preclean(); | |
6975 return abort ? 0 : size; | |
6976 } | |
6977 | |
6978 void SurvivorSpacePrecleanClosure::do_yield_work() { | |
6979 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
6980 "CMS thread should hold CMS token"); | |
6981 assert_lock_strong(_bit_map->lock()); | |
6982 // Relinquish the bit map lock | |
6983 _bit_map->lock()->unlock(); | |
6984 ConcurrentMarkSweepThread::desynchronize(true); | |
6985 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
6986 _collector->stopTimer(); | |
6987 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
6988 if (PrintCMSStatistics != 0) { | |
6989 _collector->incrementYields(); | |
6990 } | |
6991 _collector->icms_wait(); | |
6992 | |
6993 // See the comment in coordinator_yield() | |
6994 for (unsigned i = 0; i < CMSYieldSleepCount && | |
6995 ConcurrentMarkSweepThread::should_yield() && | |
6996 !CMSCollector::foregroundGCIsActive(); ++i) { | |
6997 os::sleep(Thread::current(), 1, false); | |
6998 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
6999 } | |
7000 | |
7001 ConcurrentMarkSweepThread::synchronize(true); | |
7002 _bit_map->lock()->lock_without_safepoint_check(); | |
7003 _collector->startTimer(); | |
7004 } | |
7005 | |
7006 // This closure is used to rescan the marked objects on the dirty cards | |
7007 // in the mod union table and the card table proper. In the parallel | |
7008 // case, although the bitMap is shared, we do a single read so the | |
7009 // isMarked() query is "safe". | |
7010 bool ScanMarkedObjectsAgainClosure::do_object_bm(oop p, MemRegion mr) { | |
7011 // Ignore mark word because we are running concurrent with mutators | |
7012 assert(p->is_oop_or_null(true), "expected an oop or null"); | |
7013 HeapWord* addr = (HeapWord*)p; | |
7014 assert(_span.contains(addr), "we are scanning the CMS generation"); | |
7015 bool is_obj_array = false; | |
7016 #ifdef DEBUG | |
7017 if (!_parallel) { | |
7018 assert(_mark_stack->isEmpty(), "pre-condition (eager drainage)"); | |
7019 assert(_collector->overflow_list_is_empty(), | |
7020 "overflow list should be empty"); | |
7021 | |
7022 } | |
7023 #endif // DEBUG | |
7024 if (_bit_map->isMarked(addr)) { | |
7025 // Obj arrays are precisely marked, non-arrays are not; | |
7026 // so we scan objArrays precisely and non-arrays in their | |
7027 // entirety. | |
7028 if (p->is_objArray()) { | |
7029 is_obj_array = true; | |
7030 if (_parallel) { | |
7031 p->oop_iterate(_par_scan_closure, mr); | |
7032 } else { | |
7033 p->oop_iterate(_scan_closure, mr); | |
7034 } | |
7035 } else { | |
7036 if (_parallel) { | |
7037 p->oop_iterate(_par_scan_closure); | |
7038 } else { | |
7039 p->oop_iterate(_scan_closure); | |
7040 } | |
7041 } | |
7042 } | |
7043 #ifdef DEBUG | |
7044 if (!_parallel) { | |
7045 assert(_mark_stack->isEmpty(), "post-condition (eager drainage)"); | |
7046 assert(_collector->overflow_list_is_empty(), | |
7047 "overflow list should be empty"); | |
7048 | |
7049 } | |
7050 #endif // DEBUG | |
7051 return is_obj_array; | |
7052 } | |
7053 | |
7054 MarkFromRootsClosure::MarkFromRootsClosure(CMSCollector* collector, | |
7055 MemRegion span, | |
7056 CMSBitMap* bitMap, CMSMarkStack* markStack, | |
7057 bool should_yield, bool verifying): | |
7058 _collector(collector), | |
7059 _span(span), | |
7060 _bitMap(bitMap), | |
7061 _mut(&collector->_modUnionTable), | |
7062 _markStack(markStack), | |
7063 _yield(should_yield), | |
7064 _skipBits(0) | |
7065 { | |
7066 assert(_markStack->isEmpty(), "stack should be empty"); | |
7067 _finger = _bitMap->startWord(); | |
7068 _threshold = _finger; | |
7069 assert(_collector->_restart_addr == NULL, "Sanity check"); | |
7070 assert(_span.contains(_finger), "Out of bounds _finger?"); | |
7071 DEBUG_ONLY(_verifying = verifying;) | |
7072 } | |
7073 | |
7074 void MarkFromRootsClosure::reset(HeapWord* addr) { | |
7075 assert(_markStack->isEmpty(), "would cause duplicates on stack"); | |
7076 assert(_span.contains(addr), "Out of bounds _finger?"); | |
7077 _finger = addr; | |
7078 _threshold = (HeapWord*)round_to( | |
7079 (intptr_t)_finger, CardTableModRefBS::card_size); | |
7080 } | |
7081 | |
7082 // Should revisit to see if this should be restructured for | |
7083 // greater efficiency. | |
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7084 bool MarkFromRootsClosure::do_bit(size_t offset) { |
0 | 7085 if (_skipBits > 0) { |
7086 _skipBits--; | |
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7087 return true; |
0 | 7088 } |
7089 // convert offset into a HeapWord* | |
7090 HeapWord* addr = _bitMap->startWord() + offset; | |
7091 assert(_bitMap->endWord() && addr < _bitMap->endWord(), | |
7092 "address out of range"); | |
7093 assert(_bitMap->isMarked(addr), "tautology"); | |
7094 if (_bitMap->isMarked(addr+1)) { | |
7095 // this is an allocated but not yet initialized object | |
7096 assert(_skipBits == 0, "tautology"); | |
7097 _skipBits = 2; // skip next two marked bits ("Printezis-marks") | |
7098 oop p = oop(addr); | |
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7099 if (p->klass_or_null() == NULL) { |
0 | 7100 DEBUG_ONLY(if (!_verifying) {) |
7101 // We re-dirty the cards on which this object lies and increase | |
7102 // the _threshold so that we'll come back to scan this object | |
7103 // during the preclean or remark phase. (CMSCleanOnEnter) | |
7104 if (CMSCleanOnEnter) { | |
7105 size_t sz = _collector->block_size_using_printezis_bits(addr); | |
7106 HeapWord* end_card_addr = (HeapWord*)round_to( | |
7107 (intptr_t)(addr+sz), CardTableModRefBS::card_size); | |
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7108 MemRegion redirty_range = MemRegion(addr, end_card_addr); |
0 | 7109 assert(!redirty_range.is_empty(), "Arithmetical tautology"); |
7110 // Bump _threshold to end_card_addr; note that | |
7111 // _threshold cannot possibly exceed end_card_addr, anyhow. | |
7112 // This prevents future clearing of the card as the scan proceeds | |
7113 // to the right. | |
7114 assert(_threshold <= end_card_addr, | |
7115 "Because we are just scanning into this object"); | |
7116 if (_threshold < end_card_addr) { | |
7117 _threshold = end_card_addr; | |
7118 } | |
187 | 7119 if (p->klass_or_null() != NULL) { |
0 | 7120 // Redirty the range of cards... |
7121 _mut->mark_range(redirty_range); | |
7122 } // ...else the setting of klass will dirty the card anyway. | |
7123 } | |
7124 DEBUG_ONLY(}) | |
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7125 return true; |
0 | 7126 } |
7127 } | |
7128 scanOopsInOop(addr); | |
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7129 return true; |
0 | 7130 } |
7131 | |
7132 // We take a break if we've been at this for a while, | |
7133 // so as to avoid monopolizing the locks involved. | |
7134 void MarkFromRootsClosure::do_yield_work() { | |
7135 // First give up the locks, then yield, then re-lock | |
7136 // We should probably use a constructor/destructor idiom to | |
7137 // do this unlock/lock or modify the MutexUnlocker class to | |
7138 // serve our purpose. XXX | |
7139 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
7140 "CMS thread should hold CMS token"); | |
7141 assert_lock_strong(_bitMap->lock()); | |
7142 _bitMap->lock()->unlock(); | |
7143 ConcurrentMarkSweepThread::desynchronize(true); | |
7144 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
7145 _collector->stopTimer(); | |
7146 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
7147 if (PrintCMSStatistics != 0) { | |
7148 _collector->incrementYields(); | |
7149 } | |
7150 _collector->icms_wait(); | |
7151 | |
7152 // See the comment in coordinator_yield() | |
7153 for (unsigned i = 0; i < CMSYieldSleepCount && | |
7154 ConcurrentMarkSweepThread::should_yield() && | |
7155 !CMSCollector::foregroundGCIsActive(); ++i) { | |
7156 os::sleep(Thread::current(), 1, false); | |
7157 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
7158 } | |
7159 | |
7160 ConcurrentMarkSweepThread::synchronize(true); | |
7161 _bitMap->lock()->lock_without_safepoint_check(); | |
7162 _collector->startTimer(); | |
7163 } | |
7164 | |
7165 void MarkFromRootsClosure::scanOopsInOop(HeapWord* ptr) { | |
7166 assert(_bitMap->isMarked(ptr), "expected bit to be set"); | |
7167 assert(_markStack->isEmpty(), | |
7168 "should drain stack to limit stack usage"); | |
7169 // convert ptr to an oop preparatory to scanning | |
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7170 oop obj = oop(ptr); |
0 | 7171 // Ignore mark word in verification below, since we |
7172 // may be running concurrent with mutators. | |
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7173 assert(obj->is_oop(true), "should be an oop"); |
0 | 7174 assert(_finger <= ptr, "_finger runneth ahead"); |
7175 // advance the finger to right end of this object | |
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7176 _finger = ptr + obj->size(); |
0 | 7177 assert(_finger > ptr, "we just incremented it above"); |
7178 // On large heaps, it may take us some time to get through | |
7179 // the marking phase (especially if running iCMS). During | |
7180 // this time it's possible that a lot of mutations have | |
7181 // accumulated in the card table and the mod union table -- | |
7182 // these mutation records are redundant until we have | |
7183 // actually traced into the corresponding card. | |
7184 // Here, we check whether advancing the finger would make | |
7185 // us cross into a new card, and if so clear corresponding | |
7186 // cards in the MUT (preclean them in the card-table in the | |
7187 // future). | |
7188 | |
7189 DEBUG_ONLY(if (!_verifying) {) | |
7190 // The clean-on-enter optimization is disabled by default, | |
7191 // until we fix 6178663. | |
7192 if (CMSCleanOnEnter && (_finger > _threshold)) { | |
7193 // [_threshold, _finger) represents the interval | |
7194 // of cards to be cleared in MUT (or precleaned in card table). | |
7195 // The set of cards to be cleared is all those that overlap | |
7196 // with the interval [_threshold, _finger); note that | |
7197 // _threshold is always kept card-aligned but _finger isn't | |
7198 // always card-aligned. | |
7199 HeapWord* old_threshold = _threshold; | |
7200 assert(old_threshold == (HeapWord*)round_to( | |
7201 (intptr_t)old_threshold, CardTableModRefBS::card_size), | |
7202 "_threshold should always be card-aligned"); | |
7203 _threshold = (HeapWord*)round_to( | |
7204 (intptr_t)_finger, CardTableModRefBS::card_size); | |
7205 MemRegion mr(old_threshold, _threshold); | |
7206 assert(!mr.is_empty(), "Control point invariant"); | |
7207 assert(_span.contains(mr), "Should clear within span"); | |
7208 _mut->clear_range(mr); | |
7209 } | |
7210 DEBUG_ONLY(}) | |
7211 // Note: the finger doesn't advance while we drain | |
7212 // the stack below. | |
7213 PushOrMarkClosure pushOrMarkClosure(_collector, | |
7214 _span, _bitMap, _markStack, | |
7215 _finger, this); | |
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7216 bool res = _markStack->push(obj); |
0 | 7217 assert(res, "Empty non-zero size stack should have space for single push"); |
7218 while (!_markStack->isEmpty()) { | |
7219 oop new_oop = _markStack->pop(); | |
7220 // Skip verifying header mark word below because we are | |
7221 // running concurrent with mutators. | |
7222 assert(new_oop->is_oop(true), "Oops! expected to pop an oop"); | |
7223 // now scan this oop's oops | |
7224 new_oop->oop_iterate(&pushOrMarkClosure); | |
7225 do_yield_check(); | |
7226 } | |
7227 assert(_markStack->isEmpty(), "tautology, emphasizing post-condition"); | |
7228 } | |
7229 | |
7230 Par_MarkFromRootsClosure::Par_MarkFromRootsClosure(CMSConcMarkingTask* task, | |
7231 CMSCollector* collector, MemRegion span, | |
7232 CMSBitMap* bit_map, | |
7233 OopTaskQueue* work_queue, | |
7234 CMSMarkStack* overflow_stack, | |
7235 bool should_yield): | |
7236 _collector(collector), | |
7237 _whole_span(collector->_span), | |
7238 _span(span), | |
7239 _bit_map(bit_map), | |
7240 _mut(&collector->_modUnionTable), | |
7241 _work_queue(work_queue), | |
7242 _overflow_stack(overflow_stack), | |
7243 _yield(should_yield), | |
7244 _skip_bits(0), | |
7245 _task(task) | |
7246 { | |
7247 assert(_work_queue->size() == 0, "work_queue should be empty"); | |
7248 _finger = span.start(); | |
7249 _threshold = _finger; // XXX Defer clear-on-enter optimization for now | |
7250 assert(_span.contains(_finger), "Out of bounds _finger?"); | |
7251 } | |
7252 | |
7253 // Should revisit to see if this should be restructured for | |
7254 // greater efficiency. | |
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7255 bool Par_MarkFromRootsClosure::do_bit(size_t offset) { |
0 | 7256 if (_skip_bits > 0) { |
7257 _skip_bits--; | |
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7258 return true; |
0 | 7259 } |
7260 // convert offset into a HeapWord* | |
7261 HeapWord* addr = _bit_map->startWord() + offset; | |
7262 assert(_bit_map->endWord() && addr < _bit_map->endWord(), | |
7263 "address out of range"); | |
7264 assert(_bit_map->isMarked(addr), "tautology"); | |
7265 if (_bit_map->isMarked(addr+1)) { | |
7266 // this is an allocated object that might not yet be initialized | |
7267 assert(_skip_bits == 0, "tautology"); | |
7268 _skip_bits = 2; // skip next two marked bits ("Printezis-marks") | |
7269 oop p = oop(addr); | |
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7270 if (p->klass_or_null() == NULL) { |
0 | 7271 // in the case of Clean-on-Enter optimization, redirty card |
7272 // and avoid clearing card by increasing the threshold. | |
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7273 return true; |
0 | 7274 } |
7275 } | |
7276 scan_oops_in_oop(addr); | |
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7277 return true; |
0 | 7278 } |
7279 | |
7280 void Par_MarkFromRootsClosure::scan_oops_in_oop(HeapWord* ptr) { | |
7281 assert(_bit_map->isMarked(ptr), "expected bit to be set"); | |
7282 // Should we assert that our work queue is empty or | |
7283 // below some drain limit? | |
7284 assert(_work_queue->size() == 0, | |
7285 "should drain stack to limit stack usage"); | |
7286 // convert ptr to an oop preparatory to scanning | |
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7287 oop obj = oop(ptr); |
0 | 7288 // Ignore mark word in verification below, since we |
7289 // may be running concurrent with mutators. | |
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7290 assert(obj->is_oop(true), "should be an oop"); |
0 | 7291 assert(_finger <= ptr, "_finger runneth ahead"); |
7292 // advance the finger to right end of this object | |
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7293 _finger = ptr + obj->size(); |
0 | 7294 assert(_finger > ptr, "we just incremented it above"); |
7295 // On large heaps, it may take us some time to get through | |
7296 // the marking phase (especially if running iCMS). During | |
7297 // this time it's possible that a lot of mutations have | |
7298 // accumulated in the card table and the mod union table -- | |
7299 // these mutation records are redundant until we have | |
7300 // actually traced into the corresponding card. | |
7301 // Here, we check whether advancing the finger would make | |
7302 // us cross into a new card, and if so clear corresponding | |
7303 // cards in the MUT (preclean them in the card-table in the | |
7304 // future). | |
7305 | |
7306 // The clean-on-enter optimization is disabled by default, | |
7307 // until we fix 6178663. | |
7308 if (CMSCleanOnEnter && (_finger > _threshold)) { | |
7309 // [_threshold, _finger) represents the interval | |
7310 // of cards to be cleared in MUT (or precleaned in card table). | |
7311 // The set of cards to be cleared is all those that overlap | |
7312 // with the interval [_threshold, _finger); note that | |
7313 // _threshold is always kept card-aligned but _finger isn't | |
7314 // always card-aligned. | |
7315 HeapWord* old_threshold = _threshold; | |
7316 assert(old_threshold == (HeapWord*)round_to( | |
7317 (intptr_t)old_threshold, CardTableModRefBS::card_size), | |
7318 "_threshold should always be card-aligned"); | |
7319 _threshold = (HeapWord*)round_to( | |
7320 (intptr_t)_finger, CardTableModRefBS::card_size); | |
7321 MemRegion mr(old_threshold, _threshold); | |
7322 assert(!mr.is_empty(), "Control point invariant"); | |
7323 assert(_span.contains(mr), "Should clear within span"); // _whole_span ?? | |
7324 _mut->clear_range(mr); | |
7325 } | |
7326 | |
7327 // Note: the local finger doesn't advance while we drain | |
7328 // the stack below, but the global finger sure can and will. | |
7329 HeapWord** gfa = _task->global_finger_addr(); | |
7330 Par_PushOrMarkClosure pushOrMarkClosure(_collector, | |
7331 _span, _bit_map, | |
7332 _work_queue, | |
7333 _overflow_stack, | |
7334 _finger, | |
7335 gfa, this); | |
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7336 bool res = _work_queue->push(obj); // overflow could occur here |
0 | 7337 assert(res, "Will hold once we use workqueues"); |
7338 while (true) { | |
7339 oop new_oop; | |
7340 if (!_work_queue->pop_local(new_oop)) { | |
7341 // We emptied our work_queue; check if there's stuff that can | |
7342 // be gotten from the overflow stack. | |
7343 if (CMSConcMarkingTask::get_work_from_overflow_stack( | |
7344 _overflow_stack, _work_queue)) { | |
7345 do_yield_check(); | |
7346 continue; | |
7347 } else { // done | |
7348 break; | |
7349 } | |
7350 } | |
7351 // Skip verifying header mark word below because we are | |
7352 // running concurrent with mutators. | |
7353 assert(new_oop->is_oop(true), "Oops! expected to pop an oop"); | |
7354 // now scan this oop's oops | |
7355 new_oop->oop_iterate(&pushOrMarkClosure); | |
7356 do_yield_check(); | |
7357 } | |
7358 assert(_work_queue->size() == 0, "tautology, emphasizing post-condition"); | |
7359 } | |
7360 | |
7361 // Yield in response to a request from VM Thread or | |
7362 // from mutators. | |
7363 void Par_MarkFromRootsClosure::do_yield_work() { | |
7364 assert(_task != NULL, "sanity"); | |
7365 _task->yield(); | |
7366 } | |
7367 | |
7368 // A variant of the above used for verifying CMS marking work. | |
7369 MarkFromRootsVerifyClosure::MarkFromRootsVerifyClosure(CMSCollector* collector, | |
7370 MemRegion span, | |
7371 CMSBitMap* verification_bm, CMSBitMap* cms_bm, | |
7372 CMSMarkStack* mark_stack): | |
7373 _collector(collector), | |
7374 _span(span), | |
7375 _verification_bm(verification_bm), | |
7376 _cms_bm(cms_bm), | |
7377 _mark_stack(mark_stack), | |
7378 _pam_verify_closure(collector, span, verification_bm, cms_bm, | |
7379 mark_stack) | |
7380 { | |
7381 assert(_mark_stack->isEmpty(), "stack should be empty"); | |
7382 _finger = _verification_bm->startWord(); | |
7383 assert(_collector->_restart_addr == NULL, "Sanity check"); | |
7384 assert(_span.contains(_finger), "Out of bounds _finger?"); | |
7385 } | |
7386 | |
7387 void MarkFromRootsVerifyClosure::reset(HeapWord* addr) { | |
7388 assert(_mark_stack->isEmpty(), "would cause duplicates on stack"); | |
7389 assert(_span.contains(addr), "Out of bounds _finger?"); | |
7390 _finger = addr; | |
7391 } | |
7392 | |
7393 // Should revisit to see if this should be restructured for | |
7394 // greater efficiency. | |
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7395 bool MarkFromRootsVerifyClosure::do_bit(size_t offset) { |
0 | 7396 // convert offset into a HeapWord* |
7397 HeapWord* addr = _verification_bm->startWord() + offset; | |
7398 assert(_verification_bm->endWord() && addr < _verification_bm->endWord(), | |
7399 "address out of range"); | |
7400 assert(_verification_bm->isMarked(addr), "tautology"); | |
7401 assert(_cms_bm->isMarked(addr), "tautology"); | |
7402 | |
7403 assert(_mark_stack->isEmpty(), | |
7404 "should drain stack to limit stack usage"); | |
7405 // convert addr to an oop preparatory to scanning | |
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7406 oop obj = oop(addr); |
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7407 assert(obj->is_oop(), "should be an oop"); |
0 | 7408 assert(_finger <= addr, "_finger runneth ahead"); |
7409 // advance the finger to right end of this object | |
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7410 _finger = addr + obj->size(); |
0 | 7411 assert(_finger > addr, "we just incremented it above"); |
7412 // Note: the finger doesn't advance while we drain | |
7413 // the stack below. | |
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7414 bool res = _mark_stack->push(obj); |
0 | 7415 assert(res, "Empty non-zero size stack should have space for single push"); |
7416 while (!_mark_stack->isEmpty()) { | |
7417 oop new_oop = _mark_stack->pop(); | |
7418 assert(new_oop->is_oop(), "Oops! expected to pop an oop"); | |
7419 // now scan this oop's oops | |
7420 new_oop->oop_iterate(&_pam_verify_closure); | |
7421 } | |
7422 assert(_mark_stack->isEmpty(), "tautology, emphasizing post-condition"); | |
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7423 return true; |
0 | 7424 } |
7425 | |
7426 PushAndMarkVerifyClosure::PushAndMarkVerifyClosure( | |
7427 CMSCollector* collector, MemRegion span, | |
7428 CMSBitMap* verification_bm, CMSBitMap* cms_bm, | |
7429 CMSMarkStack* mark_stack): | |
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7430 CMSOopClosure(collector->ref_processor()), |
0 | 7431 _collector(collector), |
7432 _span(span), | |
7433 _verification_bm(verification_bm), | |
7434 _cms_bm(cms_bm), | |
7435 _mark_stack(mark_stack) | |
7436 { } | |
7437 | |
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7438 void PushAndMarkVerifyClosure::do_oop(oop* p) { PushAndMarkVerifyClosure::do_oop_work(p); } |
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7439 void PushAndMarkVerifyClosure::do_oop(narrowOop* p) { PushAndMarkVerifyClosure::do_oop_work(p); } |
0 | 7440 |
7441 // Upon stack overflow, we discard (part of) the stack, | |
7442 // remembering the least address amongst those discarded | |
7443 // in CMSCollector's _restart_address. | |
7444 void PushAndMarkVerifyClosure::handle_stack_overflow(HeapWord* lost) { | |
7445 // Remember the least grey address discarded | |
7446 HeapWord* ra = (HeapWord*)_mark_stack->least_value(lost); | |
7447 _collector->lower_restart_addr(ra); | |
7448 _mark_stack->reset(); // discard stack contents | |
7449 _mark_stack->expand(); // expand the stack if possible | |
7450 } | |
7451 | |
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7452 void PushAndMarkVerifyClosure::do_oop(oop obj) { |
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7453 assert(obj->is_oop_or_null(), "expected an oop or NULL"); |
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7454 HeapWord* addr = (HeapWord*)obj; |
0 | 7455 if (_span.contains(addr) && !_verification_bm->isMarked(addr)) { |
7456 // Oop lies in _span and isn't yet grey or black | |
7457 _verification_bm->mark(addr); // now grey | |
7458 if (!_cms_bm->isMarked(addr)) { | |
7459 oop(addr)->print(); | |
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7460 gclog_or_tty->print_cr(" (" INTPTR_FORMAT " should have been marked)", |
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7461 addr); |
0 | 7462 fatal("... aborting"); |
7463 } | |
7464 | |
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7465 if (!_mark_stack->push(obj)) { // stack overflow |
0 | 7466 if (PrintCMSStatistics != 0) { |
7467 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
7468 SIZE_FORMAT, _mark_stack->capacity()); | |
7469 } | |
7470 assert(_mark_stack->isFull(), "Else push should have succeeded"); | |
7471 handle_stack_overflow(addr); | |
7472 } | |
7473 // anything including and to the right of _finger | |
7474 // will be scanned as we iterate over the remainder of the | |
7475 // bit map | |
7476 } | |
7477 } | |
7478 | |
7479 PushOrMarkClosure::PushOrMarkClosure(CMSCollector* collector, | |
7480 MemRegion span, | |
7481 CMSBitMap* bitMap, CMSMarkStack* markStack, | |
7482 HeapWord* finger, MarkFromRootsClosure* parent) : | |
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7483 CMSOopClosure(collector->ref_processor()), |
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7484 _collector(collector), |
0 | 7485 _span(span), |
7486 _bitMap(bitMap), | |
7487 _markStack(markStack), | |
7488 _finger(finger), | |
935 | 7489 _parent(parent) |
0 | 7490 { } |
7491 | |
7492 Par_PushOrMarkClosure::Par_PushOrMarkClosure(CMSCollector* collector, | |
7493 MemRegion span, | |
7494 CMSBitMap* bit_map, | |
7495 OopTaskQueue* work_queue, | |
7496 CMSMarkStack* overflow_stack, | |
7497 HeapWord* finger, | |
7498 HeapWord** global_finger_addr, | |
7499 Par_MarkFromRootsClosure* parent) : | |
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7500 CMSOopClosure(collector->ref_processor()), |
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7501 _collector(collector), |
0 | 7502 _whole_span(collector->_span), |
7503 _span(span), | |
7504 _bit_map(bit_map), | |
7505 _work_queue(work_queue), | |
7506 _overflow_stack(overflow_stack), | |
7507 _finger(finger), | |
7508 _global_finger_addr(global_finger_addr), | |
935 | 7509 _parent(parent) |
0 | 7510 { } |
7511 | |
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7512 // Assumes thread-safe access by callers, who are |
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7513 // responsible for mutual exclusion. |
0 | 7514 void CMSCollector::lower_restart_addr(HeapWord* low) { |
7515 assert(_span.contains(low), "Out of bounds addr"); | |
7516 if (_restart_addr == NULL) { | |
7517 _restart_addr = low; | |
7518 } else { | |
7519 _restart_addr = MIN2(_restart_addr, low); | |
7520 } | |
7521 } | |
7522 | |
7523 // Upon stack overflow, we discard (part of) the stack, | |
7524 // remembering the least address amongst those discarded | |
7525 // in CMSCollector's _restart_address. | |
7526 void PushOrMarkClosure::handle_stack_overflow(HeapWord* lost) { | |
7527 // Remember the least grey address discarded | |
7528 HeapWord* ra = (HeapWord*)_markStack->least_value(lost); | |
7529 _collector->lower_restart_addr(ra); | |
7530 _markStack->reset(); // discard stack contents | |
7531 _markStack->expand(); // expand the stack if possible | |
7532 } | |
7533 | |
7534 // Upon stack overflow, we discard (part of) the stack, | |
7535 // remembering the least address amongst those discarded | |
7536 // in CMSCollector's _restart_address. | |
7537 void Par_PushOrMarkClosure::handle_stack_overflow(HeapWord* lost) { | |
7538 // We need to do this under a mutex to prevent other | |
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7539 // workers from interfering with the work done below. |
0 | 7540 MutexLockerEx ml(_overflow_stack->par_lock(), |
7541 Mutex::_no_safepoint_check_flag); | |
7542 // Remember the least grey address discarded | |
7543 HeapWord* ra = (HeapWord*)_overflow_stack->least_value(lost); | |
7544 _collector->lower_restart_addr(ra); | |
7545 _overflow_stack->reset(); // discard stack contents | |
7546 _overflow_stack->expand(); // expand the stack if possible | |
7547 } | |
7548 | |
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7549 void CMKlassClosure::do_klass(Klass* k) { |
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7550 assert(_oop_closure != NULL, "Not initialized?"); |
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7551 k->oops_do(_oop_closure); |
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7552 } |
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7553 |
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7554 void PushOrMarkClosure::do_oop(oop obj) { |
0 | 7555 // Ignore mark word because we are running concurrent with mutators. |
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7556 assert(obj->is_oop_or_null(true), "expected an oop or NULL"); |
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7557 HeapWord* addr = (HeapWord*)obj; |
0 | 7558 if (_span.contains(addr) && !_bitMap->isMarked(addr)) { |
7559 // Oop lies in _span and isn't yet grey or black | |
7560 _bitMap->mark(addr); // now grey | |
7561 if (addr < _finger) { | |
7562 // the bit map iteration has already either passed, or | |
7563 // sampled, this bit in the bit map; we'll need to | |
7564 // use the marking stack to scan this oop's oops. | |
7565 bool simulate_overflow = false; | |
7566 NOT_PRODUCT( | |
7567 if (CMSMarkStackOverflowALot && | |
7568 _collector->simulate_overflow()) { | |
7569 // simulate a stack overflow | |
7570 simulate_overflow = true; | |
7571 } | |
7572 ) | |
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7573 if (simulate_overflow || !_markStack->push(obj)) { // stack overflow |
0 | 7574 if (PrintCMSStatistics != 0) { |
7575 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
7576 SIZE_FORMAT, _markStack->capacity()); | |
7577 } | |
7578 assert(simulate_overflow || _markStack->isFull(), "Else push should have succeeded"); | |
7579 handle_stack_overflow(addr); | |
7580 } | |
7581 } | |
7582 // anything including and to the right of _finger | |
7583 // will be scanned as we iterate over the remainder of the | |
7584 // bit map | |
7585 do_yield_check(); | |
7586 } | |
7587 } | |
7588 | |
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7589 void PushOrMarkClosure::do_oop(oop* p) { PushOrMarkClosure::do_oop_work(p); } |
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7590 void PushOrMarkClosure::do_oop(narrowOop* p) { PushOrMarkClosure::do_oop_work(p); } |
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7591 |
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7592 void Par_PushOrMarkClosure::do_oop(oop obj) { |
0 | 7593 // Ignore mark word because we are running concurrent with mutators. |
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7594 assert(obj->is_oop_or_null(true), "expected an oop or NULL"); |
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7595 HeapWord* addr = (HeapWord*)obj; |
0 | 7596 if (_whole_span.contains(addr) && !_bit_map->isMarked(addr)) { |
7597 // Oop lies in _span and isn't yet grey or black | |
7598 // We read the global_finger (volatile read) strictly after marking oop | |
7599 bool res = _bit_map->par_mark(addr); // now grey | |
7600 volatile HeapWord** gfa = (volatile HeapWord**)_global_finger_addr; | |
7601 // Should we push this marked oop on our stack? | |
7602 // -- if someone else marked it, nothing to do | |
7603 // -- if target oop is above global finger nothing to do | |
7604 // -- if target oop is in chunk and above local finger | |
7605 // then nothing to do | |
7606 // -- else push on work queue | |
7607 if ( !res // someone else marked it, they will deal with it | |
7608 || (addr >= *gfa) // will be scanned in a later task | |
7609 || (_span.contains(addr) && addr >= _finger)) { // later in this chunk | |
7610 return; | |
7611 } | |
7612 // the bit map iteration has already either passed, or | |
7613 // sampled, this bit in the bit map; we'll need to | |
7614 // use the marking stack to scan this oop's oops. | |
7615 bool simulate_overflow = false; | |
7616 NOT_PRODUCT( | |
7617 if (CMSMarkStackOverflowALot && | |
7618 _collector->simulate_overflow()) { | |
7619 // simulate a stack overflow | |
7620 simulate_overflow = true; | |
7621 } | |
7622 ) | |
7623 if (simulate_overflow || | |
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7624 !(_work_queue->push(obj) || _overflow_stack->par_push(obj))) { |
0 | 7625 // stack overflow |
7626 if (PrintCMSStatistics != 0) { | |
7627 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
7628 SIZE_FORMAT, _overflow_stack->capacity()); | |
7629 } | |
7630 // We cannot assert that the overflow stack is full because | |
7631 // it may have been emptied since. | |
7632 assert(simulate_overflow || | |
7633 _work_queue->size() == _work_queue->max_elems(), | |
7634 "Else push should have succeeded"); | |
7635 handle_stack_overflow(addr); | |
7636 } | |
7637 do_yield_check(); | |
7638 } | |
7639 } | |
7640 | |
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7641 void Par_PushOrMarkClosure::do_oop(oop* p) { Par_PushOrMarkClosure::do_oop_work(p); } |
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7642 void Par_PushOrMarkClosure::do_oop(narrowOop* p) { Par_PushOrMarkClosure::do_oop_work(p); } |
0 | 7643 |
7644 PushAndMarkClosure::PushAndMarkClosure(CMSCollector* collector, | |
7645 MemRegion span, | |
7646 ReferenceProcessor* rp, | |
7647 CMSBitMap* bit_map, | |
7648 CMSBitMap* mod_union_table, | |
7649 CMSMarkStack* mark_stack, | |
7650 bool concurrent_precleaning): | |
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7651 CMSOopClosure(rp), |
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7652 _collector(collector), |
0 | 7653 _span(span), |
7654 _bit_map(bit_map), | |
7655 _mod_union_table(mod_union_table), | |
7656 _mark_stack(mark_stack), | |
935 | 7657 _concurrent_precleaning(concurrent_precleaning) |
0 | 7658 { |
7659 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
7660 } | |
7661 | |
7662 // Grey object rescan during pre-cleaning and second checkpoint phases -- | |
7663 // the non-parallel version (the parallel version appears further below.) | |
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7664 void PushAndMarkClosure::do_oop(oop obj) { |
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7665 // Ignore mark word verification. If during concurrent precleaning, |
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7666 // the object monitor may be locked. If during the checkpoint |
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7667 // phases, the object may already have been reached by a different |
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7668 // path and may be at the end of the global overflow list (so |
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7669 // the mark word may be NULL). |
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7670 assert(obj->is_oop_or_null(true /* ignore mark word */), |
0 | 7671 "expected an oop or NULL"); |
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7672 HeapWord* addr = (HeapWord*)obj; |
0 | 7673 // Check if oop points into the CMS generation |
7674 // and is not marked | |
7675 if (_span.contains(addr) && !_bit_map->isMarked(addr)) { | |
7676 // a white object ... | |
7677 _bit_map->mark(addr); // ... now grey | |
7678 // push on the marking stack (grey set) | |
7679 bool simulate_overflow = false; | |
7680 NOT_PRODUCT( | |
7681 if (CMSMarkStackOverflowALot && | |
7682 _collector->simulate_overflow()) { | |
7683 // simulate a stack overflow | |
7684 simulate_overflow = true; | |
7685 } | |
7686 ) | |
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7687 if (simulate_overflow || !_mark_stack->push(obj)) { |
0 | 7688 if (_concurrent_precleaning) { |
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7689 // During precleaning we can just dirty the appropriate card(s) |
0 | 7690 // in the mod union table, thus ensuring that the object remains |
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7691 // in the grey set and continue. In the case of object arrays |
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7692 // we need to dirty all of the cards that the object spans, |
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7693 // since the rescan of object arrays will be limited to the |
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7694 // dirty cards. |
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7695 // Note that no one can be intefering with us in this action |
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7696 // of dirtying the mod union table, so no locking or atomics |
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7697 // are required. |
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7698 if (obj->is_objArray()) { |
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7699 size_t sz = obj->size(); |
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7700 HeapWord* end_card_addr = (HeapWord*)round_to( |
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7701 (intptr_t)(addr+sz), CardTableModRefBS::card_size); |
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7702 MemRegion redirty_range = MemRegion(addr, end_card_addr); |
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7703 assert(!redirty_range.is_empty(), "Arithmetical tautology"); |
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7704 _mod_union_table->mark_range(redirty_range); |
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7705 } else { |
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7706 _mod_union_table->mark(addr); |
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7707 } |
0 | 7708 _collector->_ser_pmc_preclean_ovflw++; |
7709 } else { | |
7710 // During the remark phase, we need to remember this oop | |
7711 // in the overflow list. | |
113
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7712 _collector->push_on_overflow_list(obj); |
0 | 7713 _collector->_ser_pmc_remark_ovflw++; |
7714 } | |
7715 } | |
7716 } | |
7717 } | |
7718 | |
7719 Par_PushAndMarkClosure::Par_PushAndMarkClosure(CMSCollector* collector, | |
7720 MemRegion span, | |
7721 ReferenceProcessor* rp, | |
7722 CMSBitMap* bit_map, | |
6725
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7723 OopTaskQueue* work_queue): |
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7724 CMSOopClosure(rp), |
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7725 _collector(collector), |
0 | 7726 _span(span), |
7727 _bit_map(bit_map), | |
935 | 7728 _work_queue(work_queue) |
0 | 7729 { |
7730 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
7731 } | |
7732 | |
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7733 void PushAndMarkClosure::do_oop(oop* p) { PushAndMarkClosure::do_oop_work(p); } |
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7734 void PushAndMarkClosure::do_oop(narrowOop* p) { PushAndMarkClosure::do_oop_work(p); } |
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7735 |
0 | 7736 // Grey object rescan during second checkpoint phase -- |
7737 // the parallel version. | |
113
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7738 void Par_PushAndMarkClosure::do_oop(oop obj) { |
0 | 7739 // In the assert below, we ignore the mark word because |
7740 // this oop may point to an already visited object that is | |
7741 // on the overflow stack (in which case the mark word has | |
7742 // been hijacked for chaining into the overflow stack -- | |
7743 // if this is the last object in the overflow stack then | |
7744 // its mark word will be NULL). Because this object may | |
7745 // have been subsequently popped off the global overflow | |
7746 // stack, and the mark word possibly restored to the prototypical | |
7747 // value, by the time we get to examined this failing assert in | |
7748 // the debugger, is_oop_or_null(false) may subsequently start | |
7749 // to hold. | |
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7750 assert(obj->is_oop_or_null(true), |
0 | 7751 "expected an oop or NULL"); |
113
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7752 HeapWord* addr = (HeapWord*)obj; |
0 | 7753 // Check if oop points into the CMS generation |
7754 // and is not marked | |
7755 if (_span.contains(addr) && !_bit_map->isMarked(addr)) { | |
7756 // a white object ... | |
7757 // If we manage to "claim" the object, by being the | |
7758 // first thread to mark it, then we push it on our | |
7759 // marking stack | |
7760 if (_bit_map->par_mark(addr)) { // ... now grey | |
7761 // push on work queue (grey set) | |
7762 bool simulate_overflow = false; | |
7763 NOT_PRODUCT( | |
7764 if (CMSMarkStackOverflowALot && | |
7765 _collector->par_simulate_overflow()) { | |
7766 // simulate a stack overflow | |
7767 simulate_overflow = true; | |
7768 } | |
7769 ) | |
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7770 if (simulate_overflow || !_work_queue->push(obj)) { |
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7771 _collector->par_push_on_overflow_list(obj); |
0 | 7772 _collector->_par_pmc_remark_ovflw++; // imprecise OK: no need to CAS |
7773 } | |
7774 } // Else, some other thread got there first | |
7775 } | |
7776 } | |
7777 | |
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7778 void Par_PushAndMarkClosure::do_oop(oop* p) { Par_PushAndMarkClosure::do_oop_work(p); } |
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7779 void Par_PushAndMarkClosure::do_oop(narrowOop* p) { Par_PushAndMarkClosure::do_oop_work(p); } |
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7780 |
0 | 7781 void CMSPrecleanRefsYieldClosure::do_yield_work() { |
7782 Mutex* bml = _collector->bitMapLock(); | |
7783 assert_lock_strong(bml); | |
7784 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
7785 "CMS thread should hold CMS token"); | |
7786 | |
7787 bml->unlock(); | |
7788 ConcurrentMarkSweepThread::desynchronize(true); | |
7789 | |
7790 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
7791 | |
7792 _collector->stopTimer(); | |
7793 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
7794 if (PrintCMSStatistics != 0) { | |
7795 _collector->incrementYields(); | |
7796 } | |
7797 _collector->icms_wait(); | |
7798 | |
7799 // See the comment in coordinator_yield() | |
7800 for (unsigned i = 0; i < CMSYieldSleepCount && | |
7801 ConcurrentMarkSweepThread::should_yield() && | |
7802 !CMSCollector::foregroundGCIsActive(); ++i) { | |
7803 os::sleep(Thread::current(), 1, false); | |
7804 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
7805 } | |
7806 | |
7807 ConcurrentMarkSweepThread::synchronize(true); | |
7808 bml->lock(); | |
7809 | |
7810 _collector->startTimer(); | |
7811 } | |
7812 | |
7813 bool CMSPrecleanRefsYieldClosure::should_return() { | |
7814 if (ConcurrentMarkSweepThread::should_yield()) { | |
7815 do_yield_work(); | |
7816 } | |
7817 return _collector->foregroundGCIsActive(); | |
7818 } | |
7819 | |
7820 void MarkFromDirtyCardsClosure::do_MemRegion(MemRegion mr) { | |
7821 assert(((size_t)mr.start())%CardTableModRefBS::card_size_in_words == 0, | |
7822 "mr should be aligned to start at a card boundary"); | |
7823 // We'd like to assert: | |
7824 // assert(mr.word_size()%CardTableModRefBS::card_size_in_words == 0, | |
7825 // "mr should be a range of cards"); | |
7826 // However, that would be too strong in one case -- the last | |
7827 // partition ends at _unallocated_block which, in general, can be | |
7828 // an arbitrary boundary, not necessarily card aligned. | |
7829 if (PrintCMSStatistics != 0) { | |
7830 _num_dirty_cards += | |
7831 mr.word_size()/CardTableModRefBS::card_size_in_words; | |
7832 } | |
7833 _space->object_iterate_mem(mr, &_scan_cl); | |
7834 } | |
7835 | |
7836 SweepClosure::SweepClosure(CMSCollector* collector, | |
7837 ConcurrentMarkSweepGeneration* g, | |
7838 CMSBitMap* bitMap, bool should_yield) : | |
7839 _collector(collector), | |
7840 _g(g), | |
7841 _sp(g->cmsSpace()), | |
7842 _limit(_sp->sweep_limit()), | |
7843 _freelistLock(_sp->freelistLock()), | |
7844 _bitMap(bitMap), | |
7845 _yield(should_yield), | |
7846 _inFreeRange(false), // No free range at beginning of sweep | |
7847 _freeRangeInFreeLists(false), // No free range at beginning of sweep | |
7848 _lastFreeRangeCoalesced(false), | |
7849 _freeFinger(g->used_region().start()) | |
7850 { | |
7851 NOT_PRODUCT( | |
7852 _numObjectsFreed = 0; | |
7853 _numWordsFreed = 0; | |
7854 _numObjectsLive = 0; | |
7855 _numWordsLive = 0; | |
7856 _numObjectsAlreadyFree = 0; | |
7857 _numWordsAlreadyFree = 0; | |
7858 _last_fc = NULL; | |
7859 | |
7860 _sp->initializeIndexedFreeListArrayReturnedBytes(); | |
6028
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7861 _sp->dictionary()->initialize_dict_returned_bytes(); |
0 | 7862 ) |
7863 assert(_limit >= _sp->bottom() && _limit <= _sp->end(), | |
7864 "sweep _limit out of bounds"); | |
7865 if (CMSTraceSweeper) { | |
3746
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7866 gclog_or_tty->print_cr("\n====================\nStarting new sweep with limit " PTR_FORMAT, |
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7867 _limit); |
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7868 } |
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7869 } |
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7870 |
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7871 void SweepClosure::print_on(outputStream* st) const { |
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7872 tty->print_cr("_sp = [" PTR_FORMAT "," PTR_FORMAT ")", |
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7873 _sp->bottom(), _sp->end()); |
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7874 tty->print_cr("_limit = " PTR_FORMAT, _limit); |
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7875 tty->print_cr("_freeFinger = " PTR_FORMAT, _freeFinger); |
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7876 NOT_PRODUCT(tty->print_cr("_last_fc = " PTR_FORMAT, _last_fc);) |
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7877 tty->print_cr("_inFreeRange = %d, _freeRangeInFreeLists = %d, _lastFreeRangeCoalesced = %d", |
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7878 _inFreeRange, _freeRangeInFreeLists, _lastFreeRangeCoalesced); |
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7879 } |
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7880 |
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7881 #ifndef PRODUCT |
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7882 // Assertion checking only: no useful work in product mode -- |
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7883 // however, if any of the flags below become product flags, |
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7884 // you may need to review this code to see if it needs to be |
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7885 // enabled in product mode. |
0 | 7886 SweepClosure::~SweepClosure() { |
7887 assert_lock_strong(_freelistLock); | |
2132
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7888 assert(_limit >= _sp->bottom() && _limit <= _sp->end(), |
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|
7889 "sweep _limit out of bounds"); |
0 | 7890 if (inFreeRange()) { |
3746
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|
7891 warning("inFreeRange() should have been reset; dumping state of SweepClosure"); |
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|
7892 print(); |
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7893 ShouldNotReachHere(); |
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7894 } |
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7895 if (Verbose && PrintGC) { |
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|
7896 gclog_or_tty->print("Collected "SIZE_FORMAT" objects, " SIZE_FORMAT " bytes", |
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7897 _numObjectsFreed, _numWordsFreed*sizeof(HeapWord)); |
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|
7898 gclog_or_tty->print_cr("\nLive "SIZE_FORMAT" objects, " |
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|
7899 SIZE_FORMAT" bytes " |
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|
7900 "Already free "SIZE_FORMAT" objects, "SIZE_FORMAT" bytes", |
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7901 _numObjectsLive, _numWordsLive*sizeof(HeapWord), |
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7902 _numObjectsAlreadyFree, _numWordsAlreadyFree*sizeof(HeapWord)); |
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7903 size_t totalBytes = (_numWordsFreed + _numWordsLive + _numWordsAlreadyFree) |
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7904 * sizeof(HeapWord); |
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7905 gclog_or_tty->print_cr("Total sweep: "SIZE_FORMAT" bytes", totalBytes); |
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7906 |
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7907 if (PrintCMSStatistics && CMSVerifyReturnedBytes) { |
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7908 size_t indexListReturnedBytes = _sp->sumIndexedFreeListArrayReturnedBytes(); |
6028
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7909 size_t dict_returned_bytes = _sp->dictionary()->sum_dict_returned_bytes(); |
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7910 size_t returned_bytes = indexListReturnedBytes + dict_returned_bytes; |
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7911 gclog_or_tty->print("Returned "SIZE_FORMAT" bytes", returned_bytes); |
3746
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7912 gclog_or_tty->print(" Indexed List Returned "SIZE_FORMAT" bytes", |
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7913 indexListReturnedBytes); |
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|
7914 gclog_or_tty->print_cr(" Dictionary Returned "SIZE_FORMAT" bytes", |
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7915 dict_returned_bytes); |
3746
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7916 } |
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7917 } |
0 | 7918 if (CMSTraceSweeper) { |
3746
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7919 gclog_or_tty->print_cr("end of sweep with _limit = " PTR_FORMAT "\n================", |
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7920 _limit); |
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7921 } |
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7922 } |
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7923 #endif // PRODUCT |
0 | 7924 |
7925 void SweepClosure::initialize_free_range(HeapWord* freeFinger, | |
7926 bool freeRangeInFreeLists) { | |
7927 if (CMSTraceSweeper) { | |
2132
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7928 gclog_or_tty->print("---- Start free range at 0x%x with free block (%d)\n", |
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7929 freeFinger, freeRangeInFreeLists); |
0 | 7930 } |
7931 assert(!inFreeRange(), "Trampling existing free range"); | |
7932 set_inFreeRange(true); | |
7933 set_lastFreeRangeCoalesced(false); | |
7934 | |
7935 set_freeFinger(freeFinger); | |
7936 set_freeRangeInFreeLists(freeRangeInFreeLists); | |
7937 if (CMSTestInFreeList) { | |
7938 if (freeRangeInFreeLists) { | |
7939 FreeChunk* fc = (FreeChunk*) freeFinger; | |
6028
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7940 assert(fc->is_free(), "A chunk on the free list should be free."); |
0 | 7941 assert(fc->size() > 0, "Free range should have a size"); |
6028
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|
7942 assert(_sp->verify_chunk_in_free_list(fc), "Chunk is not in free lists"); |
0 | 7943 } |
7944 } | |
7945 } | |
7946 | |
7947 // Note that the sweeper runs concurrently with mutators. Thus, | |
7948 // it is possible for direct allocation in this generation to happen | |
7949 // in the middle of the sweep. Note that the sweeper also coalesces | |
7950 // contiguous free blocks. Thus, unless the sweeper and the allocator | |
7951 // synchronize appropriately freshly allocated blocks may get swept up. | |
7952 // This is accomplished by the sweeper locking the free lists while | |
7953 // it is sweeping. Thus blocks that are determined to be free are | |
7954 // indeed free. There is however one additional complication: | |
7955 // blocks that have been allocated since the final checkpoint and | |
7956 // mark, will not have been marked and so would be treated as | |
7957 // unreachable and swept up. To prevent this, the allocator marks | |
7958 // the bit map when allocating during the sweep phase. This leads, | |
7959 // however, to a further complication -- objects may have been allocated | |
7960 // but not yet initialized -- in the sense that the header isn't yet | |
7961 // installed. The sweeper can not then determine the size of the block | |
7962 // in order to skip over it. To deal with this case, we use a technique | |
7963 // (due to Printezis) to encode such uninitialized block sizes in the | |
7964 // bit map. Since the bit map uses a bit per every HeapWord, but the | |
7965 // CMS generation has a minimum object size of 3 HeapWords, it follows | |
7966 // that "normal marks" won't be adjacent in the bit map (there will | |
7967 // always be at least two 0 bits between successive 1 bits). We make use | |
7968 // of these "unused" bits to represent uninitialized blocks -- the bit | |
7969 // corresponding to the start of the uninitialized object and the next | |
7970 // bit are both set. Finally, a 1 bit marks the end of the object that | |
7971 // started with the two consecutive 1 bits to indicate its potentially | |
7972 // uninitialized state. | |
7973 | |
7974 size_t SweepClosure::do_blk_careful(HeapWord* addr) { | |
7975 FreeChunk* fc = (FreeChunk*)addr; | |
7976 size_t res; | |
7977 | |
1720
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6977970: CMS: concurrentMarkSweepGeneration.cpp:7947 assert(addr <= _limit) failed: sweep invariant
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|
7978 // 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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|
7979 // 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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|
7980 // we started the sweep, it may no longer be one because heap expansion |
5ed703250bff
6977970: CMS: concurrentMarkSweepGeneration.cpp:7947 assert(addr <= _limit) failed: sweep invariant
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1716
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|
7981 // 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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|
7982 // with a newly expanded chunk (this happens when _limit was set to the |
3746
537a4053b0f9
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|
7983 // previous _end of the space), so we may have stepped past _limit: |
537a4053b0f9
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|
7984 // see the following Zeno-like trail of CRs 6977970, 7008136, 7042740. |
2132
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|
7985 if (addr >= _limit) { // we have swept up to or past the limit: finish up |
0 | 7986 assert(_limit >= _sp->bottom() && _limit <= _sp->end(), |
7987 "sweep _limit out of bounds"); | |
1720
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|
7988 assert(addr < _sp->end(), "addr out of bounds"); |
3746
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|
7989 // Flush any free range we might be holding as a single |
2132
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|
7990 // coalesced chunk to the appropriate free list. |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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|
7991 if (inFreeRange()) { |
3746
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|
7992 assert(freeFinger() >= _sp->bottom() && freeFinger() < _limit, |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
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|
7993 err_msg("freeFinger() " PTR_FORMAT" is out-of-bounds", freeFinger())); |
2132
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|
7994 flush_cur_free_chunk(freeFinger(), |
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|
7995 pointer_delta(addr, freeFinger())); |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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|
7996 if (CMSTraceSweeper) { |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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1994
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|
7997 gclog_or_tty->print("Sweep: last chunk: "); |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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|
7998 gclog_or_tty->print("put_free_blk 0x%x ("SIZE_FORMAT") " |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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|
7999 "[coalesced:"SIZE_FORMAT"]\n", |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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|
8000 freeFinger(), pointer_delta(addr, freeFinger()), |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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|
8001 lastFreeRangeCoalesced()); |
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7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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|
8002 } |
4947ee68d19c
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|
8003 } |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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|
8004 |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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|
8005 // help the iterator loop finish |
1720
5ed703250bff
6977970: CMS: concurrentMarkSweepGeneration.cpp:7947 assert(addr <= _limit) failed: sweep invariant
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|
8006 return pointer_delta(_sp->end(), addr); |
5ed703250bff
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|
8007 } |
2132
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|
8008 |
1720
5ed703250bff
6977970: CMS: concurrentMarkSweepGeneration.cpp:7947 assert(addr <= _limit) failed: sweep invariant
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|
8009 assert(addr < _limit, "sweep invariant"); |
0 | 8010 // check if we should yield |
8011 do_yield_check(addr); | |
6028
f69a5d43dc19
7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
jmasa
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|
8012 if (fc->is_free()) { |
0 | 8013 // Chunk that is already free |
8014 res = fc->size(); | |
2132
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7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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|
8015 do_already_free_chunk(fc); |
0 | 8016 debug_only(_sp->verifyFreeLists()); |
3746
537a4053b0f9
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ysr
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|
8017 // If we flush the chunk at hand in lookahead_and_flush() |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
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|
8018 // and it's coalesced with a preceding chunk, then the |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
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|
8019 // process of "mangling" the payload of the coalesced block |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
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|
8020 // will cause erasure of the size information from the |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
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|
8021 // (erstwhile) header of all the coalesced blocks but the |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
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|
8022 // first, so the first disjunct in the assert will not hold |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
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|
8023 // in that specific case (in which case the second disjunct |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
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|
8024 // will hold). |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
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|
8025 assert(res == fc->size() || ((HeapWord*)fc) + res >= _limit, |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
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changeset
|
8026 "Otherwise the size info doesn't change at this step"); |
0 | 8027 NOT_PRODUCT( |
8028 _numObjectsAlreadyFree++; | |
8029 _numWordsAlreadyFree += res; | |
8030 ) | |
8031 NOT_PRODUCT(_last_fc = fc;) | |
8032 } else if (!_bitMap->isMarked(addr)) { | |
8033 // Chunk is fresh garbage | |
2132
4947ee68d19c
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|
8034 res = do_garbage_chunk(fc); |
0 | 8035 debug_only(_sp->verifyFreeLists()); |
8036 NOT_PRODUCT( | |
8037 _numObjectsFreed++; | |
8038 _numWordsFreed += res; | |
8039 ) | |
8040 } else { | |
8041 // Chunk that is alive. | |
2132
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7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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|
8042 res = do_live_chunk(fc); |
0 | 8043 debug_only(_sp->verifyFreeLists()); |
8044 NOT_PRODUCT( | |
8045 _numObjectsLive++; | |
8046 _numWordsLive += res; | |
8047 ) | |
8048 } | |
8049 return res; | |
8050 } | |
8051 | |
8052 // For the smart allocation, record following | |
8053 // split deaths - a free chunk is removed from its free list because | |
8054 // it is being split into two or more chunks. | |
8055 // split birth - a free chunk is being added to its free list because | |
8056 // a larger free chunk has been split and resulted in this free chunk. | |
8057 // coal death - a free chunk is being removed from its free list because | |
8058 // it is being coalesced into a large free chunk. | |
8059 // coal birth - a free chunk is being added to its free list because | |
8060 // it was created when two or more free chunks where coalesced into | |
8061 // this free chunk. | |
8062 // | |
8063 // These statistics are used to determine the desired number of free | |
8064 // chunks of a given size. The desired number is chosen to be relative | |
8065 // to the end of a CMS sweep. The desired number at the end of a sweep | |
8066 // is the | |
8067 // count-at-end-of-previous-sweep (an amount that was enough) | |
8068 // - count-at-beginning-of-current-sweep (the excess) | |
8069 // + split-births (gains in this size during interval) | |
8070 // - split-deaths (demands on this size during interval) | |
8071 // where the interval is from the end of one sweep to the end of the | |
8072 // next. | |
8073 // | |
8074 // When sweeping the sweeper maintains an accumulated chunk which is | |
8075 // the chunk that is made up of chunks that have been coalesced. That | |
8076 // will be termed the left-hand chunk. A new chunk of garbage that | |
8077 // is being considered for coalescing will be referred to as the | |
8078 // right-hand chunk. | |
8079 // | |
8080 // When making a decision on whether to coalesce a right-hand chunk with | |
8081 // the current left-hand chunk, the current count vs. the desired count | |
8082 // of the left-hand chunk is considered. Also if the right-hand chunk | |
8083 // is near the large chunk at the end of the heap (see | |
8084 // ConcurrentMarkSweepGeneration::isNearLargestChunk()), then the | |
8085 // left-hand chunk is coalesced. | |
8086 // | |
8087 // When making a decision about whether to split a chunk, the desired count | |
8088 // vs. the current count of the candidate to be split is also considered. | |
8089 // If the candidate is underpopulated (currently fewer chunks than desired) | |
8090 // a chunk of an overpopulated (currently more chunks than desired) size may | |
8091 // be chosen. The "hint" associated with a free list, if non-null, points | |
8092 // to a free list which may be overpopulated. | |
8093 // | |
8094 | |
2132
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7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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|
8095 void SweepClosure::do_already_free_chunk(FreeChunk* fc) { |
3746
537a4053b0f9
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|
8096 const size_t size = fc->size(); |
0 | 8097 // Chunks that cannot be coalesced are not in the |
8098 // free lists. | |
8099 if (CMSTestInFreeList && !fc->cantCoalesce()) { | |
6028
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7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
jmasa
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6026
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|
8100 assert(_sp->verify_chunk_in_free_list(fc), |
0 | 8101 "free chunk should be in free lists"); |
8102 } | |
8103 // a chunk that is already free, should not have been | |
8104 // marked in the bit map | |
3746
537a4053b0f9
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ysr
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3356
diff
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|
8105 HeapWord* const addr = (HeapWord*) fc; |
0 | 8106 assert(!_bitMap->isMarked(addr), "free chunk should be unmarked"); |
8107 // Verify that the bit map has no bits marked between | |
8108 // addr and purported end of this block. | |
8109 _bitMap->verifyNoOneBitsInRange(addr + 1, addr + size); | |
8110 | |
2132
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7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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1994
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|
8111 // Some chunks cannot be coalesced under any circumstances. |
0 | 8112 // See the definition of cantCoalesce(). |
8113 if (!fc->cantCoalesce()) { | |
8114 // This chunk can potentially be coalesced. | |
8115 if (_sp->adaptive_freelists()) { | |
8116 // 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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|
8117 do_post_free_or_garbage_chunk(fc, size); |
0 | 8118 } else { // Not adaptive free lists |
8119 // this is a free chunk that can potentially be coalesced by the sweeper; | |
8120 if (!inFreeRange()) { | |
8121 // if the next chunk is a free block that can't be coalesced | |
8122 // it doesn't make sense to remove this chunk from the free lists | |
8123 FreeChunk* nextChunk = (FreeChunk*)(addr + size); | |
2136
c91cc404ca46
7011940: iCMS: SIGSEGV in SweepClosure::do_already_free_chunk(FreeChunk*)+0x360
ysr
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2132
diff
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|
8124 assert((HeapWord*)nextChunk <= _sp->end(), "Chunk size out of bounds?"); |
c91cc404ca46
7011940: iCMS: SIGSEGV in SweepClosure::do_already_free_chunk(FreeChunk*)+0x360
ysr
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2132
diff
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|
8125 if ((HeapWord*)nextChunk < _sp->end() && // There is another free chunk to the right ... |
6028
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jmasa
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6026
diff
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|
8126 nextChunk->is_free() && // ... which is free... |
2136
c91cc404ca46
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ysr
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2132
diff
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|
8127 nextChunk->cantCoalesce()) { // ... but can't be coalesced |
0 | 8128 // nothing to do |
8129 } else { | |
8130 // Potentially the start of a new free range: | |
8131 // Don't eagerly remove it from the free lists. | |
8132 // No need to remove it if it will just be put | |
8133 // back again. (Also from a pragmatic point of view | |
8134 // if it is a free block in a region that is beyond | |
8135 // any allocated blocks, an assertion will fail) | |
8136 // Remember the start of a free run. | |
8137 initialize_free_range(addr, true); | |
8138 // end - can coalesce with next chunk | |
8139 } | |
8140 } else { | |
8141 // the midst of a free range, we are coalescing | |
3746
537a4053b0f9
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|
8142 print_free_block_coalesced(fc); |
0 | 8143 if (CMSTraceSweeper) { |
8144 gclog_or_tty->print(" -- pick up free block 0x%x (%d)\n", fc, size); | |
8145 } | |
8146 // remove it from the free lists | |
8147 _sp->removeFreeChunkFromFreeLists(fc); | |
8148 set_lastFreeRangeCoalesced(true); | |
8149 // If the chunk is being coalesced and the current free range is | |
8150 // in the free lists, remove the current free range so that it | |
8151 // will be returned to the free lists in its entirety - all | |
8152 // the coalesced pieces included. | |
8153 if (freeRangeInFreeLists()) { | |
8154 FreeChunk* ffc = (FreeChunk*) freeFinger(); | |
8155 assert(ffc->size() == pointer_delta(addr, freeFinger()), | |
8156 "Size of free range is inconsistent with chunk size."); | |
8157 if (CMSTestInFreeList) { | |
6028
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6026
diff
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|
8158 assert(_sp->verify_chunk_in_free_list(ffc), |
0 | 8159 "free range is not in free lists"); |
8160 } | |
8161 _sp->removeFreeChunkFromFreeLists(ffc); | |
8162 set_freeRangeInFreeLists(false); | |
8163 } | |
8164 } | |
8165 } | |
3746
537a4053b0f9
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ysr
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|
8166 // Note that if the chunk is not coalescable (the else arm |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
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3356
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|
8167 // below), we unconditionally flush, without needing to do |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
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|
8168 // a "lookahead," as we do below. |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
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3356
diff
changeset
|
8169 if (inFreeRange()) lookahead_and_flush(fc, size); |
0 | 8170 } else { |
8171 // Code path common to both original and adaptive free lists. | |
8172 | |
8173 // cant coalesce with previous block; this should be treated | |
8174 // as the end of a free run if any | |
8175 if (inFreeRange()) { | |
8176 // we kicked some butt; time to pick up the garbage | |
2132
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1994
diff
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|
8177 assert(freeFinger() < addr, "freeFinger points too high"); |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
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|
8178 flush_cur_free_chunk(freeFinger(), pointer_delta(addr, freeFinger())); |
0 | 8179 } |
8180 // else, nothing to do, just continue | |
8181 } | |
8182 } | |
8183 | |
2132
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diff
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|
8184 size_t SweepClosure::do_garbage_chunk(FreeChunk* fc) { |
0 | 8185 // This is a chunk of garbage. It is not in any free list. |
8186 // Add it to a free list or let it possibly be coalesced into | |
8187 // a larger chunk. | |
3746
537a4053b0f9
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ysr
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3356
diff
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|
8188 HeapWord* const addr = (HeapWord*) fc; |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
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3356
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|
8189 const size_t size = CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size()); |
0 | 8190 |
8191 if (_sp->adaptive_freelists()) { | |
8192 // Verify that the bit map has no bits marked between | |
8193 // addr and purported end of just dead object. | |
8194 _bitMap->verifyNoOneBitsInRange(addr + 1, addr + size); | |
8195 | |
2132
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diff
changeset
|
8196 do_post_free_or_garbage_chunk(fc, size); |
0 | 8197 } else { |
8198 if (!inFreeRange()) { | |
8199 // start of a new free range | |
8200 assert(size > 0, "A free range should have a size"); | |
8201 initialize_free_range(addr, false); | |
8202 } else { | |
8203 // this will be swept up when we hit the end of the | |
8204 // free range | |
8205 if (CMSTraceSweeper) { | |
8206 gclog_or_tty->print(" -- pick up garbage 0x%x (%d) \n", fc, size); | |
8207 } | |
8208 // If the chunk is being coalesced and the current free range is | |
8209 // in the free lists, remove the current free range so that it | |
8210 // will be returned to the free lists in its entirety - all | |
8211 // the coalesced pieces included. | |
8212 if (freeRangeInFreeLists()) { | |
8213 FreeChunk* ffc = (FreeChunk*)freeFinger(); | |
8214 assert(ffc->size() == pointer_delta(addr, freeFinger()), | |
8215 "Size of free range is inconsistent with chunk size."); | |
8216 if (CMSTestInFreeList) { | |
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|
8217 assert(_sp->verify_chunk_in_free_list(ffc), |
0 | 8218 "free range is not in free lists"); |
8219 } | |
8220 _sp->removeFreeChunkFromFreeLists(ffc); | |
8221 set_freeRangeInFreeLists(false); | |
8222 } | |
8223 set_lastFreeRangeCoalesced(true); | |
8224 } | |
8225 // this will be swept up when we hit the end of the free range | |
8226 | |
8227 // Verify that the bit map has no bits marked between | |
8228 // addr and purported end of just dead object. | |
8229 _bitMap->verifyNoOneBitsInRange(addr + 1, addr + size); | |
8230 } | |
3746
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|
8231 assert(_limit >= addr + size, |
537a4053b0f9
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|
8232 "A freshly garbage chunk can't possibly straddle over _limit"); |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
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|
8233 if (inFreeRange()) lookahead_and_flush(fc, size); |
0 | 8234 return size; |
8235 } | |
8236 | |
2132
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7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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diff
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|
8237 size_t SweepClosure::do_live_chunk(FreeChunk* fc) { |
0 | 8238 HeapWord* addr = (HeapWord*) fc; |
8239 // The sweeper has just found a live object. Return any accumulated | |
8240 // left hand chunk to the free lists. | |
8241 if (inFreeRange()) { | |
2132
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7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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1994
diff
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|
8242 assert(freeFinger() < addr, "freeFinger points too high"); |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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1994
diff
changeset
|
8243 flush_cur_free_chunk(freeFinger(), pointer_delta(addr, freeFinger())); |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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|
8244 } |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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1994
diff
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|
8245 |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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changeset
|
8246 // This object is live: we'd normally expect this to be |
0 | 8247 // an oop, and like to assert the following: |
8248 // assert(oop(addr)->is_oop(), "live block should be an oop"); | |
8249 // However, as we commented above, this may be an object whose | |
8250 // header hasn't yet been initialized. | |
8251 size_t size; | |
8252 assert(_bitMap->isMarked(addr), "Tautology for this control point"); | |
8253 if (_bitMap->isMarked(addr + 1)) { | |
8254 // Determine the size from the bit map, rather than trying to | |
8255 // compute it from the object header. | |
8256 HeapWord* nextOneAddr = _bitMap->getNextMarkedWordAddress(addr + 2); | |
8257 size = pointer_delta(nextOneAddr + 1, addr); | |
8258 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
8259 "alignment problem"); | |
8260 | |
2132
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7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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1994
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|
8261 #ifdef DEBUG |
6725
da91efe96a93
6964458: Reimplement class meta-data storage to use native memory
coleenp
parents:
6197
diff
changeset
|
8262 if (oop(addr)->klass_or_null() != NULL) { |
0 | 8263 // Ignore mark word because we are running concurrent with mutators |
8264 assert(oop(addr)->is_oop(true), "live block should be an oop"); | |
8265 assert(size == | |
8266 CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size()), | |
8267 "P-mark and computed size do not agree"); | |
8268 } | |
2132
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7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
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diff
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|
8269 #endif |
0 | 8270 |
8271 } else { | |
8272 // This should be an initialized object that's alive. | |
6725
da91efe96a93
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coleenp
parents:
6197
diff
changeset
|
8273 assert(oop(addr)->klass_or_null() != NULL, |
0 | 8274 "Should be an initialized object"); |
8275 // Ignore mark word because we are running concurrent with mutators | |
8276 assert(oop(addr)->is_oop(true), "live block should be an oop"); | |
8277 // Verify that the bit map has no bits marked between | |
8278 // addr and purported end of this block. | |
8279 size = CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size()); | |
8280 assert(size >= 3, "Necessary for Printezis marks to work"); | |
8281 assert(!_bitMap->isMarked(addr+1), "Tautology for this control point"); | |
8282 DEBUG_ONLY(_bitMap->verifyNoOneBitsInRange(addr+2, addr+size);) | |
8283 } | |
8284 return size; | |
8285 } | |
8286 | |
2132
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7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
changeset
|
8287 void SweepClosure::do_post_free_or_garbage_chunk(FreeChunk* fc, |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
changeset
|
8288 size_t chunkSize) { |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
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|
8289 // do_post_free_or_garbage_chunk() should only be called in the case |
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
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|
8290 // of the adaptive free list allocator. |
6028
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7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
jmasa
parents:
6026
diff
changeset
|
8291 const bool fcInFreeLists = fc->is_free(); |
0 | 8292 assert(_sp->adaptive_freelists(), "Should only be used in this case."); |
8293 assert((HeapWord*)fc <= _limit, "sweep invariant"); | |
8294 if (CMSTestInFreeList && fcInFreeLists) { | |
6028
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7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
jmasa
parents:
6026
diff
changeset
|
8295 assert(_sp->verify_chunk_in_free_list(fc), "free chunk is not in free lists"); |
2132
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7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
changeset
|
8296 } |
0 | 8297 |
8298 if (CMSTraceSweeper) { | |
8299 gclog_or_tty->print_cr(" -- pick up another chunk at 0x%x (%d)", fc, chunkSize); | |
8300 } | |
8301 | |
3746
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
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|
8302 HeapWord* const fc_addr = (HeapWord*) fc; |
0 | 8303 |
8304 bool coalesce; | |
3746
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
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changeset
|
8305 const size_t left = pointer_delta(fc_addr, freeFinger()); |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
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parents:
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changeset
|
8306 const size_t right = chunkSize; |
0 | 8307 switch (FLSCoalescePolicy) { |
8308 // numeric value forms a coalition aggressiveness metric | |
8309 case 0: { // never coalesce | |
8310 coalesce = false; | |
8311 break; | |
8312 } | |
8313 case 1: { // coalesce if left & right chunks on overpopulated lists | |
8314 coalesce = _sp->coalOverPopulated(left) && | |
8315 _sp->coalOverPopulated(right); | |
8316 break; | |
8317 } | |
8318 case 2: { // coalesce if left chunk on overpopulated list (default) | |
8319 coalesce = _sp->coalOverPopulated(left); | |
8320 break; | |
8321 } | |
8322 case 3: { // coalesce if left OR right chunk on overpopulated list | |
8323 coalesce = _sp->coalOverPopulated(left) || | |
8324 _sp->coalOverPopulated(right); | |
8325 break; | |
8326 } | |
8327 case 4: { // always coalesce | |
8328 coalesce = true; | |
8329 break; | |
8330 } | |
8331 default: | |
8332 ShouldNotReachHere(); | |
8333 } | |
8334 | |
8335 // Should the current free range be coalesced? | |
8336 // If the chunk is in a free range and either we decided to coalesce above | |
8337 // or the chunk is near the large block at the end of the heap | |
8338 // (isNearLargestChunk() returns true), then coalesce this chunk. | |
3746
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
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|
8339 const bool doCoalesce = inFreeRange() |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
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changeset
|
8340 && (coalesce || _g->isNearLargestChunk(fc_addr)); |
0 | 8341 if (doCoalesce) { |
8342 // Coalesce the current free range on the left with the new | |
8343 // chunk on the right. If either is on a free list, | |
8344 // it must be removed from the list and stashed in the closure. | |
8345 if (freeRangeInFreeLists()) { | |
3746
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
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|
8346 FreeChunk* const ffc = (FreeChunk*)freeFinger(); |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
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3356
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|
8347 assert(ffc->size() == pointer_delta(fc_addr, freeFinger()), |
0 | 8348 "Size of free range is inconsistent with chunk size."); |
8349 if (CMSTestInFreeList) { | |
6028
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7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
jmasa
parents:
6026
diff
changeset
|
8350 assert(_sp->verify_chunk_in_free_list(ffc), |
0 | 8351 "Chunk is not in free lists"); |
8352 } | |
8353 _sp->coalDeath(ffc->size()); | |
8354 _sp->removeFreeChunkFromFreeLists(ffc); | |
8355 set_freeRangeInFreeLists(false); | |
8356 } | |
8357 if (fcInFreeLists) { | |
8358 _sp->coalDeath(chunkSize); | |
8359 assert(fc->size() == chunkSize, | |
8360 "The chunk has the wrong size or is not in the free lists"); | |
8361 _sp->removeFreeChunkFromFreeLists(fc); | |
8362 } | |
8363 set_lastFreeRangeCoalesced(true); | |
3746
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8364 print_free_block_coalesced(fc); |
0 | 8365 } else { // not in a free range and/or should not coalesce |
8366 // Return the current free range and start a new one. | |
8367 if (inFreeRange()) { | |
8368 // In a free range but cannot coalesce with the right hand chunk. | |
8369 // 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
|
8370 flush_cur_free_chunk(freeFinger(), |
3746
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8371 pointer_delta(fc_addr, freeFinger())); |
0 | 8372 } |
8373 // Set up for new free range. Pass along whether the right hand | |
8374 // chunk is in the free lists. | |
8375 initialize_free_range((HeapWord*)fc, fcInFreeLists); | |
8376 } | |
8377 } | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8378 |
3746
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8379 // Lookahead flush: |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8380 // If we are tracking a free range, and this is the last chunk that |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8381 // we'll look at because its end crosses past _limit, we'll preemptively |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8382 // flush it along with any free range we may be holding on to. Note that |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8383 // this can be the case only for an already free or freshly garbage |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8384 // chunk. If this block is an object, it can never straddle |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
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|
8385 // over _limit. The "straddling" occurs when _limit is set at |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
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|
8386 // the previous end of the space when this cycle started, and |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8387 // a subsequent heap expansion caused the previously co-terminal |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8388 // free block to be coalesced with the newly expanded portion, |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8389 // thus rendering _limit a non-block-boundary making it dangerous |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8390 // for the sweeper to step over and examine. |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8391 void SweepClosure::lookahead_and_flush(FreeChunk* fc, size_t chunk_size) { |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8392 assert(inFreeRange(), "Should only be called if currently in a free range."); |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8393 HeapWord* const eob = ((HeapWord*)fc) + chunk_size; |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8394 assert(_sp->used_region().contains(eob - 1), |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8395 err_msg("eob = " PTR_FORMAT " out of bounds wrt _sp = [" PTR_FORMAT "," PTR_FORMAT ")" |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8396 " when examining fc = " PTR_FORMAT "(" SIZE_FORMAT ")", |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8397 _limit, _sp->bottom(), _sp->end(), fc, chunk_size)); |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8398 if (eob >= _limit) { |
6028
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7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
jmasa
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6026
diff
changeset
|
8399 assert(eob == _limit || fc->is_free(), "Only a free chunk should allow us to cross over the limit"); |
3746
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8400 if (CMSTraceSweeper) { |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8401 gclog_or_tty->print_cr("_limit " PTR_FORMAT " reached or crossed by block " |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8402 "[" PTR_FORMAT "," PTR_FORMAT ") in space " |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8403 "[" PTR_FORMAT "," PTR_FORMAT ")", |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8404 _limit, fc, eob, _sp->bottom(), _sp->end()); |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
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|
8405 } |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8406 // Return the storage we are tracking back into the free lists. |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8407 if (CMSTraceSweeper) { |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8408 gclog_or_tty->print_cr("Flushing ... "); |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
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|
8409 } |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8410 assert(freeFinger() < eob, "Error"); |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
changeset
|
8411 flush_cur_free_chunk( freeFinger(), pointer_delta(eob, freeFinger())); |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
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|
8412 } |
537a4053b0f9
7042740: CMS: assert(n> q) failed: Looping at: ... blockOffsetTable.cpp:557
ysr
parents:
3356
diff
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|
8413 } |
537a4053b0f9
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ysr
parents:
3356
diff
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|
8414 |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
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1994
diff
changeset
|
8415 void SweepClosure::flush_cur_free_chunk(HeapWord* chunk, size_t size) { |
0 | 8416 assert(inFreeRange(), "Should only be called if currently in a free range."); |
8417 assert(size > 0, | |
8418 "A zero sized chunk cannot be added to the free lists."); | |
8419 if (!freeRangeInFreeLists()) { | |
2132
4947ee68d19c
7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
ysr
parents:
1994
diff
changeset
|
8420 if (CMSTestInFreeList) { |
0 | 8421 FreeChunk* fc = (FreeChunk*) chunk; |
6028
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7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
jmasa
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6026
diff
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|
8422 fc->set_size(size); |
f69a5d43dc19
7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
jmasa
parents:
6026
diff
changeset
|
8423 assert(!_sp->verify_chunk_in_free_list(fc), |
0 | 8424 "chunk should not be in free lists yet"); |
8425 } | |
8426 if (CMSTraceSweeper) { | |
8427 gclog_or_tty->print_cr(" -- add free block 0x%x (%d) to free lists", | |
8428 chunk, size); | |
8429 } | |
8430 // A new free range is going to be starting. The current | |
8431 // free range has not been added to the free lists yet or | |
8432 // was removed so add it back. | |
8433 // If the current free range was coalesced, then the death | |
8434 // of the free range was recorded. Record a birth now. | |
8435 if (lastFreeRangeCoalesced()) { | |
8436 _sp->coalBirth(size); | |
8437 } | |
8438 _sp->addChunkAndRepairOffsetTable(chunk, size, | |
8439 lastFreeRangeCoalesced()); | |
3746
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8440 } else if (CMSTraceSweeper) { |
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8441 gclog_or_tty->print_cr("Already in free list: nothing to flush"); |
0 | 8442 } |
8443 set_inFreeRange(false); | |
8444 set_freeRangeInFreeLists(false); | |
8445 } | |
8446 | |
8447 // We take a break if we've been at this for a while, | |
8448 // so as to avoid monopolizing the locks involved. | |
8449 void SweepClosure::do_yield_work(HeapWord* addr) { | |
8450 // Return current free chunk being used for coalescing (if any) | |
8451 // to the appropriate freelist. After yielding, the next | |
8452 // free block encountered will start a coalescing range of | |
8453 // free blocks. If the next free block is adjacent to the | |
8454 // chunk just flushed, they will need to wait for the next | |
8455 // sweep to be coalesced. | |
8456 if (inFreeRange()) { | |
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8457 flush_cur_free_chunk(freeFinger(), pointer_delta(addr, freeFinger())); |
0 | 8458 } |
8459 | |
8460 // First give up the locks, then yield, then re-lock. | |
8461 // We should probably use a constructor/destructor idiom to | |
8462 // do this unlock/lock or modify the MutexUnlocker class to | |
8463 // serve our purpose. XXX | |
8464 assert_lock_strong(_bitMap->lock()); | |
8465 assert_lock_strong(_freelistLock); | |
8466 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
8467 "CMS thread should hold CMS token"); | |
8468 _bitMap->lock()->unlock(); | |
8469 _freelistLock->unlock(); | |
8470 ConcurrentMarkSweepThread::desynchronize(true); | |
8471 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
8472 _collector->stopTimer(); | |
8473 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
8474 if (PrintCMSStatistics != 0) { | |
8475 _collector->incrementYields(); | |
8476 } | |
8477 _collector->icms_wait(); | |
8478 | |
8479 // See the comment in coordinator_yield() | |
8480 for (unsigned i = 0; i < CMSYieldSleepCount && | |
8481 ConcurrentMarkSweepThread::should_yield() && | |
8482 !CMSCollector::foregroundGCIsActive(); ++i) { | |
8483 os::sleep(Thread::current(), 1, false); | |
8484 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
8485 } | |
8486 | |
8487 ConcurrentMarkSweepThread::synchronize(true); | |
8488 _freelistLock->lock(); | |
8489 _bitMap->lock()->lock_without_safepoint_check(); | |
8490 _collector->startTimer(); | |
8491 } | |
8492 | |
8493 #ifndef PRODUCT | |
8494 // This is actually very useful in a product build if it can | |
8495 // be called from the debugger. Compile it into the product | |
8496 // as needed. | |
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8497 bool debug_verify_chunk_in_free_list(FreeChunk* fc) { |
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8498 return debug_cms_space->verify_chunk_in_free_list(fc); |
0 | 8499 } |
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8500 #endif |
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8501 |
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8502 void SweepClosure::print_free_block_coalesced(FreeChunk* fc) const { |
0 | 8503 if (CMSTraceSweeper) { |
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8504 gclog_or_tty->print_cr("Sweep:coal_free_blk " PTR_FORMAT " (" SIZE_FORMAT ")", |
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8505 fc, fc->size()); |
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8506 } |
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8507 } |
0 | 8508 |
8509 // CMSIsAliveClosure | |
8510 bool CMSIsAliveClosure::do_object_b(oop obj) { | |
8511 HeapWord* addr = (HeapWord*)obj; | |
8512 return addr != NULL && | |
8513 (!_span.contains(addr) || _bit_map->isMarked(addr)); | |
8514 } | |
8515 | |
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8516 |
935 | 8517 CMSKeepAliveClosure::CMSKeepAliveClosure( CMSCollector* collector, |
8518 MemRegion span, | |
8519 CMSBitMap* bit_map, CMSMarkStack* mark_stack, | |
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8520 bool cpc): |
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8521 _collector(collector), |
935 | 8522 _span(span), |
8523 _bit_map(bit_map), | |
8524 _mark_stack(mark_stack), | |
8525 _concurrent_precleaning(cpc) { | |
8526 assert(!_span.is_empty(), "Empty span could spell trouble"); | |
8527 } | |
8528 | |
8529 | |
0 | 8530 // CMSKeepAliveClosure: the serial version |
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8531 void CMSKeepAliveClosure::do_oop(oop obj) { |
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8532 HeapWord* addr = (HeapWord*)obj; |
0 | 8533 if (_span.contains(addr) && |
8534 !_bit_map->isMarked(addr)) { | |
8535 _bit_map->mark(addr); | |
8536 bool simulate_overflow = false; | |
8537 NOT_PRODUCT( | |
8538 if (CMSMarkStackOverflowALot && | |
8539 _collector->simulate_overflow()) { | |
8540 // simulate a stack overflow | |
8541 simulate_overflow = true; | |
8542 } | |
8543 ) | |
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8544 if (simulate_overflow || !_mark_stack->push(obj)) { |
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8545 if (_concurrent_precleaning) { |
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8546 // We dirty the overflown object and let the remark |
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8547 // phase deal with it. |
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8548 assert(_collector->overflow_list_is_empty(), "Error"); |
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8549 // In the case of object arrays, we need to dirty all of |
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8550 // the cards that the object spans. No locking or atomics |
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8551 // are needed since no one else can be mutating the mod union |
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8552 // table. |
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8553 if (obj->is_objArray()) { |
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8554 size_t sz = obj->size(); |
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8555 HeapWord* end_card_addr = |
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8556 (HeapWord*)round_to((intptr_t)(addr+sz), CardTableModRefBS::card_size); |
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8557 MemRegion redirty_range = MemRegion(addr, end_card_addr); |
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8558 assert(!redirty_range.is_empty(), "Arithmetical tautology"); |
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8559 _collector->_modUnionTable.mark_range(redirty_range); |
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8560 } else { |
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8561 _collector->_modUnionTable.mark(addr); |
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8562 } |
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8563 _collector->_ser_kac_preclean_ovflw++; |
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8564 } else { |
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8565 _collector->push_on_overflow_list(obj); |
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8566 _collector->_ser_kac_ovflw++; |
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8567 } |
0 | 8568 } |
8569 } | |
8570 } | |
8571 | |
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8572 void CMSKeepAliveClosure::do_oop(oop* p) { CMSKeepAliveClosure::do_oop_work(p); } |
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8573 void CMSKeepAliveClosure::do_oop(narrowOop* p) { CMSKeepAliveClosure::do_oop_work(p); } |
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8574 |
0 | 8575 // CMSParKeepAliveClosure: a parallel version of the above. |
8576 // The work queues are private to each closure (thread), | |
8577 // but (may be) available for stealing by other threads. | |
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8578 void CMSParKeepAliveClosure::do_oop(oop obj) { |
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8579 HeapWord* addr = (HeapWord*)obj; |
0 | 8580 if (_span.contains(addr) && |
8581 !_bit_map->isMarked(addr)) { | |
8582 // In general, during recursive tracing, several threads | |
8583 // may be concurrently getting here; the first one to | |
8584 // "tag" it, claims it. | |
8585 if (_bit_map->par_mark(addr)) { | |
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8586 bool res = _work_queue->push(obj); |
0 | 8587 assert(res, "Low water mark should be much less than capacity"); |
8588 // Do a recursive trim in the hope that this will keep | |
8589 // stack usage lower, but leave some oops for potential stealers | |
8590 trim_queue(_low_water_mark); | |
8591 } // Else, another thread got there first | |
8592 } | |
8593 } | |
8594 | |
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8595 void CMSParKeepAliveClosure::do_oop(oop* p) { CMSParKeepAliveClosure::do_oop_work(p); } |
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8596 void CMSParKeepAliveClosure::do_oop(narrowOop* p) { CMSParKeepAliveClosure::do_oop_work(p); } |
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8597 |
0 | 8598 void CMSParKeepAliveClosure::trim_queue(uint max) { |
8599 while (_work_queue->size() > max) { | |
8600 oop new_oop; | |
8601 if (_work_queue->pop_local(new_oop)) { | |
8602 assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop"); | |
8603 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
8604 "no white objects on this stack!"); | |
8605 assert(_span.contains((HeapWord*)new_oop), "Out of bounds oop"); | |
8606 // iterate over the oops in this oop, marking and pushing | |
8607 // the ones in CMS heap (i.e. in _span). | |
8608 new_oop->oop_iterate(&_mark_and_push); | |
8609 } | |
8610 } | |
8611 } | |
8612 | |
935 | 8613 CMSInnerParMarkAndPushClosure::CMSInnerParMarkAndPushClosure( |
8614 CMSCollector* collector, | |
8615 MemRegion span, CMSBitMap* bit_map, | |
8616 OopTaskQueue* work_queue): | |
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8617 _collector(collector), |
935 | 8618 _span(span), |
8619 _bit_map(bit_map), | |
8620 _work_queue(work_queue) { } | |
8621 | |
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8622 void CMSInnerParMarkAndPushClosure::do_oop(oop obj) { |
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8623 HeapWord* addr = (HeapWord*)obj; |
0 | 8624 if (_span.contains(addr) && |
8625 !_bit_map->isMarked(addr)) { | |
8626 if (_bit_map->par_mark(addr)) { | |
8627 bool simulate_overflow = false; | |
8628 NOT_PRODUCT( | |
8629 if (CMSMarkStackOverflowALot && | |
8630 _collector->par_simulate_overflow()) { | |
8631 // simulate a stack overflow | |
8632 simulate_overflow = true; | |
8633 } | |
8634 ) | |
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8635 if (simulate_overflow || !_work_queue->push(obj)) { |
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8636 _collector->par_push_on_overflow_list(obj); |
0 | 8637 _collector->_par_kac_ovflw++; |
8638 } | |
8639 } // Else another thread got there already | |
8640 } | |
8641 } | |
8642 | |
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8643 void CMSInnerParMarkAndPushClosure::do_oop(oop* p) { CMSInnerParMarkAndPushClosure::do_oop_work(p); } |
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8644 void CMSInnerParMarkAndPushClosure::do_oop(narrowOop* p) { CMSInnerParMarkAndPushClosure::do_oop_work(p); } |
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8645 |
0 | 8646 ////////////////////////////////////////////////////////////////// |
8647 // CMSExpansionCause ///////////////////////////// | |
8648 ////////////////////////////////////////////////////////////////// | |
8649 const char* CMSExpansionCause::to_string(CMSExpansionCause::Cause cause) { | |
8650 switch (cause) { | |
8651 case _no_expansion: | |
8652 return "No expansion"; | |
8653 case _satisfy_free_ratio: | |
8654 return "Free ratio"; | |
8655 case _satisfy_promotion: | |
8656 return "Satisfy promotion"; | |
8657 case _satisfy_allocation: | |
8658 return "allocation"; | |
8659 case _allocate_par_lab: | |
8660 return "Par LAB"; | |
8661 case _allocate_par_spooling_space: | |
8662 return "Par Spooling Space"; | |
8663 case _adaptive_size_policy: | |
8664 return "Ergonomics"; | |
8665 default: | |
8666 return "unknown"; | |
8667 } | |
8668 } | |
8669 | |
8670 void CMSDrainMarkingStackClosure::do_void() { | |
8671 // the max number to take from overflow list at a time | |
8672 const size_t num = _mark_stack->capacity()/4; | |
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8673 assert(!_concurrent_precleaning || _collector->overflow_list_is_empty(), |
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8674 "Overflow list should be NULL during concurrent phases"); |
0 | 8675 while (!_mark_stack->isEmpty() || |
8676 // if stack is empty, check the overflow list | |
8677 _collector->take_from_overflow_list(num, _mark_stack)) { | |
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8678 oop obj = _mark_stack->pop(); |
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8679 HeapWord* addr = (HeapWord*)obj; |
0 | 8680 assert(_span.contains(addr), "Should be within span"); |
8681 assert(_bit_map->isMarked(addr), "Should be marked"); | |
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8682 assert(obj->is_oop(), "Should be an oop"); |
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8683 obj->oop_iterate(_keep_alive); |
0 | 8684 } |
8685 } | |
8686 | |
8687 void CMSParDrainMarkingStackClosure::do_void() { | |
8688 // drain queue | |
8689 trim_queue(0); | |
8690 } | |
8691 | |
8692 // Trim our work_queue so its length is below max at return | |
8693 void CMSParDrainMarkingStackClosure::trim_queue(uint max) { | |
8694 while (_work_queue->size() > max) { | |
8695 oop new_oop; | |
8696 if (_work_queue->pop_local(new_oop)) { | |
8697 assert(new_oop->is_oop(), "Expected an oop"); | |
8698 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
8699 "no white objects on this stack!"); | |
8700 assert(_span.contains((HeapWord*)new_oop), "Out of bounds oop"); | |
8701 // iterate over the oops in this oop, marking and pushing | |
8702 // the ones in CMS heap (i.e. in _span). | |
8703 new_oop->oop_iterate(&_mark_and_push); | |
8704 } | |
8705 } | |
8706 } | |
8707 | |
8708 //////////////////////////////////////////////////////////////////// | |
8709 // Support for Marking Stack Overflow list handling and related code | |
8710 //////////////////////////////////////////////////////////////////// | |
8711 // Much of the following code is similar in shape and spirit to the | |
8712 // code used in ParNewGC. We should try and share that code | |
8713 // as much as possible in the future. | |
8714 | |
8715 #ifndef PRODUCT | |
8716 // Debugging support for CMSStackOverflowALot | |
8717 | |
8718 // It's OK to call this multi-threaded; the worst thing | |
8719 // that can happen is that we'll get a bunch of closely | |
8720 // spaced simulated oveflows, but that's OK, in fact | |
8721 // probably good as it would exercise the overflow code | |
8722 // under contention. | |
8723 bool CMSCollector::simulate_overflow() { | |
8724 if (_overflow_counter-- <= 0) { // just being defensive | |
8725 _overflow_counter = CMSMarkStackOverflowInterval; | |
8726 return true; | |
8727 } else { | |
8728 return false; | |
8729 } | |
8730 } | |
8731 | |
8732 bool CMSCollector::par_simulate_overflow() { | |
8733 return simulate_overflow(); | |
8734 } | |
8735 #endif | |
8736 | |
8737 // Single-threaded | |
8738 bool CMSCollector::take_from_overflow_list(size_t num, CMSMarkStack* stack) { | |
8739 assert(stack->isEmpty(), "Expected precondition"); | |
8740 assert(stack->capacity() > num, "Shouldn't bite more than can chew"); | |
8741 size_t i = num; | |
8742 oop cur = _overflow_list; | |
8743 const markOop proto = markOopDesc::prototype(); | |
534 | 8744 NOT_PRODUCT(ssize_t n = 0;) |
0 | 8745 for (oop next; i > 0 && cur != NULL; cur = next, i--) { |
8746 next = oop(cur->mark()); | |
8747 cur->set_mark(proto); // until proven otherwise | |
8748 assert(cur->is_oop(), "Should be an oop"); | |
8749 bool res = stack->push(cur); | |
8750 assert(res, "Bit off more than can chew?"); | |
8751 NOT_PRODUCT(n++;) | |
8752 } | |
8753 _overflow_list = cur; | |
8754 #ifndef PRODUCT | |
8755 assert(_num_par_pushes >= n, "Too many pops?"); | |
8756 _num_par_pushes -=n; | |
8757 #endif | |
8758 return !stack->isEmpty(); | |
8759 } | |
8760 | |
534 | 8761 #define BUSY (oop(0x1aff1aff)) |
8762 // (MT-safe) Get a prefix of at most "num" from the list. | |
8763 // The overflow list is chained through the mark word of | |
8764 // each object in the list. We fetch the entire list, | |
8765 // break off a prefix of the right size and return the | |
8766 // remainder. If other threads try to take objects from | |
8767 // the overflow list at that time, they will wait for | |
8768 // some time to see if data becomes available. If (and | |
8769 // only if) another thread places one or more object(s) | |
8770 // on the global list before we have returned the suffix | |
8771 // to the global list, we will walk down our local list | |
8772 // to find its end and append the global list to | |
8773 // our suffix before returning it. This suffix walk can | |
8774 // prove to be expensive (quadratic in the amount of traffic) | |
8775 // when there are many objects in the overflow list and | |
8776 // there is much producer-consumer contention on the list. | |
8777 // *NOTE*: The overflow list manipulation code here and | |
8778 // in ParNewGeneration:: are very similar in shape, | |
8779 // except that in the ParNew case we use the old (from/eden) | |
8780 // copy of the object to thread the list via its klass word. | |
8781 // Because of the common code, if you make any changes in | |
8782 // the code below, please check the ParNew version to see if | |
8783 // similar changes might be needed. | |
8784 // CR 6797058 has been filed to consolidate the common code. | |
0 | 8785 bool CMSCollector::par_take_from_overflow_list(size_t num, |
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8786 OopTaskQueue* work_q, |
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8787 int no_of_gc_threads) { |
534 | 8788 assert(work_q->size() == 0, "First empty local work queue"); |
0 | 8789 assert(num < work_q->max_elems(), "Can't bite more than we can chew"); |
8790 if (_overflow_list == NULL) { | |
8791 return false; | |
8792 } | |
8793 // Grab the entire list; we'll put back a suffix | |
534 | 8794 oop prefix = (oop)Atomic::xchg_ptr(BUSY, &_overflow_list); |
8795 Thread* tid = Thread::current(); | |
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8796 // Before "no_of_gc_threads" was introduced CMSOverflowSpinCount was |
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8797 // set to ParallelGCThreads. |
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8798 size_t CMSOverflowSpinCount = (size_t) no_of_gc_threads; // was ParallelGCThreads; |
534 | 8799 size_t sleep_time_millis = MAX2((size_t)1, num/100); |
8800 // If the list is busy, we spin for a short while, | |
8801 // sleeping between attempts to get the list. | |
8802 for (size_t spin = 0; prefix == BUSY && spin < CMSOverflowSpinCount; spin++) { | |
8803 os::sleep(tid, sleep_time_millis, false); | |
8804 if (_overflow_list == NULL) { | |
8805 // Nothing left to take | |
8806 return false; | |
8807 } else if (_overflow_list != BUSY) { | |
8808 // Try and grab the prefix | |
8809 prefix = (oop)Atomic::xchg_ptr(BUSY, &_overflow_list); | |
8810 } | |
8811 } | |
8812 // If the list was found to be empty, or we spun long | |
8813 // enough, we give up and return empty-handed. If we leave | |
8814 // the list in the BUSY state below, it must be the case that | |
8815 // some other thread holds the overflow list and will set it | |
8816 // to a non-BUSY state in the future. | |
8817 if (prefix == NULL || prefix == BUSY) { | |
8818 // Nothing to take or waited long enough | |
8819 if (prefix == NULL) { | |
8820 // Write back the NULL in case we overwrote it with BUSY above | |
8821 // and it is still the same value. | |
8822 (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY); | |
8823 } | |
8824 return false; | |
8825 } | |
8826 assert(prefix != NULL && prefix != BUSY, "Error"); | |
0 | 8827 size_t i = num; |
8828 oop cur = prefix; | |
534 | 8829 // Walk down the first "num" objects, unless we reach the end. |
0 | 8830 for (; i > 1 && cur->mark() != NULL; cur = oop(cur->mark()), i--); |
534 | 8831 if (cur->mark() == NULL) { |
8832 // We have "num" or fewer elements in the list, so there | |
8833 // is nothing to return to the global list. | |
8834 // Write back the NULL in lieu of the BUSY we wrote | |
8835 // above, if it is still the same value. | |
8836 if (_overflow_list == BUSY) { | |
8837 (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY); | |
8838 } | |
8839 } else { | |
8840 // Chop off the suffix and rerturn it to the global list. | |
8841 assert(cur->mark() != BUSY, "Error"); | |
0 | 8842 oop suffix_head = cur->mark(); // suffix will be put back on global list |
8843 cur->set_mark(NULL); // break off suffix | |
534 | 8844 // It's possible that the list is still in the empty(busy) state |
8845 // we left it in a short while ago; in that case we may be | |
8846 // able to place back the suffix without incurring the cost | |
8847 // of a walk down the list. | |
0 | 8848 oop observed_overflow_list = _overflow_list; |
534 | 8849 oop cur_overflow_list = observed_overflow_list; |
8850 bool attached = false; | |
8851 while (observed_overflow_list == BUSY || observed_overflow_list == NULL) { | |
0 | 8852 observed_overflow_list = |
534 | 8853 (oop) Atomic::cmpxchg_ptr(suffix_head, &_overflow_list, cur_overflow_list); |
8854 if (cur_overflow_list == observed_overflow_list) { | |
8855 attached = true; | |
8856 break; | |
8857 } else cur_overflow_list = observed_overflow_list; | |
8858 } | |
8859 if (!attached) { | |
8860 // Too bad, someone else sneaked in (at least) an element; we'll need | |
8861 // to do a splice. Find tail of suffix so we can prepend suffix to global | |
8862 // list. | |
8863 for (cur = suffix_head; cur->mark() != NULL; cur = (oop)(cur->mark())); | |
8864 oop suffix_tail = cur; | |
8865 assert(suffix_tail != NULL && suffix_tail->mark() == NULL, | |
8866 "Tautology"); | |
8867 observed_overflow_list = _overflow_list; | |
8868 do { | |
8869 cur_overflow_list = observed_overflow_list; | |
8870 if (cur_overflow_list != BUSY) { | |
8871 // Do the splice ... | |
8872 suffix_tail->set_mark(markOop(cur_overflow_list)); | |
8873 } else { // cur_overflow_list == BUSY | |
8874 suffix_tail->set_mark(NULL); | |
8875 } | |
8876 // ... and try to place spliced list back on overflow_list ... | |
8877 observed_overflow_list = | |
8878 (oop) Atomic::cmpxchg_ptr(suffix_head, &_overflow_list, cur_overflow_list); | |
8879 } while (cur_overflow_list != observed_overflow_list); | |
8880 // ... until we have succeeded in doing so. | |
8881 } | |
0 | 8882 } |
8883 | |
8884 // Push the prefix elements on work_q | |
8885 assert(prefix != NULL, "control point invariant"); | |
8886 const markOop proto = markOopDesc::prototype(); | |
8887 oop next; | |
534 | 8888 NOT_PRODUCT(ssize_t n = 0;) |
0 | 8889 for (cur = prefix; cur != NULL; cur = next) { |
8890 next = oop(cur->mark()); | |
8891 cur->set_mark(proto); // until proven otherwise | |
8892 assert(cur->is_oop(), "Should be an oop"); | |
8893 bool res = work_q->push(cur); | |
8894 assert(res, "Bit off more than we can chew?"); | |
8895 NOT_PRODUCT(n++;) | |
8896 } | |
8897 #ifndef PRODUCT | |
8898 assert(_num_par_pushes >= n, "Too many pops?"); | |
8899 Atomic::add_ptr(-(intptr_t)n, &_num_par_pushes); | |
8900 #endif | |
8901 return true; | |
8902 } | |
8903 | |
8904 // Single-threaded | |
8905 void CMSCollector::push_on_overflow_list(oop p) { | |
8906 NOT_PRODUCT(_num_par_pushes++;) | |
8907 assert(p->is_oop(), "Not an oop"); | |
8908 preserve_mark_if_necessary(p); | |
8909 p->set_mark((markOop)_overflow_list); | |
8910 _overflow_list = p; | |
8911 } | |
8912 | |
8913 // Multi-threaded; use CAS to prepend to overflow list | |
8914 void CMSCollector::par_push_on_overflow_list(oop p) { | |
8915 NOT_PRODUCT(Atomic::inc_ptr(&_num_par_pushes);) | |
8916 assert(p->is_oop(), "Not an oop"); | |
8917 par_preserve_mark_if_necessary(p); | |
8918 oop observed_overflow_list = _overflow_list; | |
8919 oop cur_overflow_list; | |
8920 do { | |
8921 cur_overflow_list = observed_overflow_list; | |
534 | 8922 if (cur_overflow_list != BUSY) { |
8923 p->set_mark(markOop(cur_overflow_list)); | |
8924 } else { | |
8925 p->set_mark(NULL); | |
8926 } | |
0 | 8927 observed_overflow_list = |
8928 (oop) Atomic::cmpxchg_ptr(p, &_overflow_list, cur_overflow_list); | |
8929 } while (cur_overflow_list != observed_overflow_list); | |
8930 } | |
534 | 8931 #undef BUSY |
0 | 8932 |
8933 // Single threaded | |
8934 // General Note on GrowableArray: pushes may silently fail | |
8935 // because we are (temporarily) out of C-heap for expanding | |
8936 // the stack. The problem is quite ubiquitous and affects | |
8937 // a lot of code in the JVM. The prudent thing for GrowableArray | |
8938 // to do (for now) is to exit with an error. However, that may | |
8939 // be too draconian in some cases because the caller may be | |
534 | 8940 // able to recover without much harm. For such cases, we |
0 | 8941 // should probably introduce a "soft_push" method which returns |
8942 // an indication of success or failure with the assumption that | |
8943 // the caller may be able to recover from a failure; code in | |
8944 // the VM can then be changed, incrementally, to deal with such | |
8945 // failures where possible, thus, incrementally hardening the VM | |
8946 // in such low resource situations. | |
8947 void CMSCollector::preserve_mark_work(oop p, markOop m) { | |
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8948 _preserved_oop_stack.push(p); |
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8949 _preserved_mark_stack.push(m); |
0 | 8950 assert(m == p->mark(), "Mark word changed"); |
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8951 assert(_preserved_oop_stack.size() == _preserved_mark_stack.size(), |
0 | 8952 "bijection"); |
8953 } | |
8954 | |
8955 // Single threaded | |
8956 void CMSCollector::preserve_mark_if_necessary(oop p) { | |
8957 markOop m = p->mark(); | |
8958 if (m->must_be_preserved(p)) { | |
8959 preserve_mark_work(p, m); | |
8960 } | |
8961 } | |
8962 | |
8963 void CMSCollector::par_preserve_mark_if_necessary(oop p) { | |
8964 markOop m = p->mark(); | |
8965 if (m->must_be_preserved(p)) { | |
8966 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); | |
8967 // Even though we read the mark word without holding | |
8968 // the lock, we are assured that it will not change | |
8969 // because we "own" this oop, so no other thread can | |
8970 // be trying to push it on the overflow list; see | |
8971 // the assertion in preserve_mark_work() that checks | |
8972 // that m == p->mark(). | |
8973 preserve_mark_work(p, m); | |
8974 } | |
8975 } | |
8976 | |
8977 // We should be able to do this multi-threaded, | |
8978 // a chunk of stack being a task (this is | |
8979 // correct because each oop only ever appears | |
8980 // once in the overflow list. However, it's | |
8981 // not very easy to completely overlap this with | |
8982 // other operations, so will generally not be done | |
8983 // until all work's been completed. Because we | |
8984 // expect the preserved oop stack (set) to be small, | |
8985 // it's probably fine to do this single-threaded. | |
8986 // We can explore cleverer concurrent/overlapped/parallel | |
8987 // processing of preserved marks if we feel the | |
8988 // need for this in the future. Stack overflow should | |
8989 // be so rare in practice and, when it happens, its | |
8990 // effect on performance so great that this will | |
8991 // likely just be in the noise anyway. | |
8992 void CMSCollector::restore_preserved_marks_if_any() { | |
8993 assert(SafepointSynchronize::is_at_safepoint(), | |
8994 "world should be stopped"); | |
8995 assert(Thread::current()->is_ConcurrentGC_thread() || | |
8996 Thread::current()->is_VM_thread(), | |
8997 "should be single-threaded"); | |
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8998 assert(_preserved_oop_stack.size() == _preserved_mark_stack.size(), |
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8999 "bijection"); |
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9000 |
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9001 while (!_preserved_oop_stack.is_empty()) { |
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9002 oop p = _preserved_oop_stack.pop(); |
0 | 9003 assert(p->is_oop(), "Should be an oop"); |
9004 assert(_span.contains(p), "oop should be in _span"); | |
9005 assert(p->mark() == markOopDesc::prototype(), | |
9006 "Set when taken from overflow list"); | |
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9007 markOop m = _preserved_mark_stack.pop(); |
0 | 9008 p->set_mark(m); |
9009 } | |
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9010 assert(_preserved_mark_stack.is_empty() && _preserved_oop_stack.is_empty(), |
0 | 9011 "stacks were cleared above"); |
9012 } | |
9013 | |
9014 #ifndef PRODUCT | |
9015 bool CMSCollector::no_preserved_marks() const { | |
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9016 return _preserved_mark_stack.is_empty() && _preserved_oop_stack.is_empty(); |
0 | 9017 } |
9018 #endif | |
9019 | |
9020 CMSAdaptiveSizePolicy* ASConcurrentMarkSweepGeneration::cms_size_policy() const | |
9021 { | |
9022 GenCollectedHeap* gch = (GenCollectedHeap*) GenCollectedHeap::heap(); | |
9023 CMSAdaptiveSizePolicy* size_policy = | |
9024 (CMSAdaptiveSizePolicy*) gch->gen_policy()->size_policy(); | |
9025 assert(size_policy->is_gc_cms_adaptive_size_policy(), | |
9026 "Wrong type for size policy"); | |
9027 return size_policy; | |
9028 } | |
9029 | |
9030 void ASConcurrentMarkSweepGeneration::resize(size_t cur_promo_size, | |
9031 size_t desired_promo_size) { | |
9032 if (cur_promo_size < desired_promo_size) { | |
9033 size_t expand_bytes = desired_promo_size - cur_promo_size; | |
9034 if (PrintAdaptiveSizePolicy && Verbose) { | |
9035 gclog_or_tty->print_cr(" ASConcurrentMarkSweepGeneration::resize " | |
9036 "Expanding tenured generation by " SIZE_FORMAT " (bytes)", | |
9037 expand_bytes); | |
9038 } | |
9039 expand(expand_bytes, | |
9040 MinHeapDeltaBytes, | |
9041 CMSExpansionCause::_adaptive_size_policy); | |
9042 } else if (desired_promo_size < cur_promo_size) { | |
9043 size_t shrink_bytes = cur_promo_size - desired_promo_size; | |
9044 if (PrintAdaptiveSizePolicy && Verbose) { | |
9045 gclog_or_tty->print_cr(" ASConcurrentMarkSweepGeneration::resize " | |
9046 "Shrinking tenured generation by " SIZE_FORMAT " (bytes)", | |
9047 shrink_bytes); | |
9048 } | |
9049 shrink(shrink_bytes); | |
9050 } | |
9051 } | |
9052 | |
9053 CMSGCAdaptivePolicyCounters* ASConcurrentMarkSweepGeneration::gc_adaptive_policy_counters() { | |
9054 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
9055 CMSGCAdaptivePolicyCounters* counters = | |
9056 (CMSGCAdaptivePolicyCounters*) gch->collector_policy()->counters(); | |
9057 assert(counters->kind() == GCPolicyCounters::CMSGCAdaptivePolicyCountersKind, | |
9058 "Wrong kind of counters"); | |
9059 return counters; | |
9060 } | |
9061 | |
9062 | |
9063 void ASConcurrentMarkSweepGeneration::update_counters() { | |
9064 if (UsePerfData) { | |
9065 _space_counters->update_all(); | |
9066 _gen_counters->update_all(); | |
9067 CMSGCAdaptivePolicyCounters* counters = gc_adaptive_policy_counters(); | |
9068 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
9069 CMSGCStats* gc_stats_l = (CMSGCStats*) gc_stats(); | |
9070 assert(gc_stats_l->kind() == GCStats::CMSGCStatsKind, | |
9071 "Wrong gc statistics type"); | |
9072 counters->update_counters(gc_stats_l); | |
9073 } | |
9074 } | |
9075 | |
9076 void ASConcurrentMarkSweepGeneration::update_counters(size_t used) { | |
9077 if (UsePerfData) { | |
9078 _space_counters->update_used(used); | |
9079 _space_counters->update_capacity(); | |
9080 _gen_counters->update_all(); | |
9081 | |
9082 CMSGCAdaptivePolicyCounters* counters = gc_adaptive_policy_counters(); | |
9083 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
9084 CMSGCStats* gc_stats_l = (CMSGCStats*) gc_stats(); | |
9085 assert(gc_stats_l->kind() == GCStats::CMSGCStatsKind, | |
9086 "Wrong gc statistics type"); | |
9087 counters->update_counters(gc_stats_l); | |
9088 } | |
9089 } | |
9090 | |
9091 // The desired expansion delta is computed so that: | |
9092 // . desired free percentage or greater is used | |
9093 void ASConcurrentMarkSweepGeneration::compute_new_size() { | |
9094 assert_locked_or_safepoint(Heap_lock); | |
9095 | |
9096 GenCollectedHeap* gch = (GenCollectedHeap*) GenCollectedHeap::heap(); | |
9097 | |
9098 // If incremental collection failed, we just want to expand | |
9099 // to the limit. | |
9100 if (incremental_collection_failed()) { | |
9101 clear_incremental_collection_failed(); | |
9102 grow_to_reserved(); | |
9103 return; | |
9104 } | |
9105 | |
9106 assert(UseAdaptiveSizePolicy, "Should be using adaptive sizing"); | |
9107 | |
9108 assert(gch->kind() == CollectedHeap::GenCollectedHeap, | |
9109 "Wrong type of heap"); | |
9110 int prev_level = level() - 1; | |
9111 assert(prev_level >= 0, "The cms generation is the lowest generation"); | |
9112 Generation* prev_gen = gch->get_gen(prev_level); | |
9113 assert(prev_gen->kind() == Generation::ASParNew, | |
9114 "Wrong type of young generation"); | |
9115 ParNewGeneration* younger_gen = (ParNewGeneration*) prev_gen; | |
9116 size_t cur_eden = younger_gen->eden()->capacity(); | |
9117 CMSAdaptiveSizePolicy* size_policy = cms_size_policy(); | |
9118 size_t cur_promo = free(); | |
9119 size_policy->compute_tenured_generation_free_space(cur_promo, | |
9120 max_available(), | |
9121 cur_eden); | |
9122 resize(cur_promo, size_policy->promo_size()); | |
9123 | |
9124 // Record the new size of the space in the cms generation | |
9125 // that is available for promotions. This is temporary. | |
9126 // It should be the desired promo size. | |
9127 size_policy->avg_cms_promo()->sample(free()); | |
9128 size_policy->avg_old_live()->sample(used()); | |
9129 | |
9130 if (UsePerfData) { | |
9131 CMSGCAdaptivePolicyCounters* counters = gc_adaptive_policy_counters(); | |
9132 counters->update_cms_capacity_counter(capacity()); | |
9133 } | |
9134 } | |
9135 | |
9136 void ASConcurrentMarkSweepGeneration::shrink_by(size_t desired_bytes) { | |
9137 assert_locked_or_safepoint(Heap_lock); | |
9138 assert_lock_strong(freelistLock()); | |
9139 HeapWord* old_end = _cmsSpace->end(); | |
9140 HeapWord* unallocated_start = _cmsSpace->unallocated_block(); | |
9141 assert(old_end >= unallocated_start, "Miscalculation of unallocated_start"); | |
9142 FreeChunk* chunk_at_end = find_chunk_at_end(); | |
9143 if (chunk_at_end == NULL) { | |
9144 // No room to shrink | |
9145 if (PrintGCDetails && Verbose) { | |
9146 gclog_or_tty->print_cr("No room to shrink: old_end " | |
9147 PTR_FORMAT " unallocated_start " PTR_FORMAT | |
9148 " chunk_at_end " PTR_FORMAT, | |
9149 old_end, unallocated_start, chunk_at_end); | |
9150 } | |
9151 return; | |
9152 } else { | |
9153 | |
9154 // Find the chunk at the end of the space and determine | |
9155 // how much it can be shrunk. | |
9156 size_t shrinkable_size_in_bytes = chunk_at_end->size(); | |
9157 size_t aligned_shrinkable_size_in_bytes = | |
9158 align_size_down(shrinkable_size_in_bytes, os::vm_page_size()); | |
9159 assert(unallocated_start <= chunk_at_end->end(), | |
9160 "Inconsistent chunk at end of space"); | |
9161 size_t bytes = MIN2(desired_bytes, aligned_shrinkable_size_in_bytes); | |
9162 size_t word_size_before = heap_word_size(_virtual_space.committed_size()); | |
9163 | |
9164 // Shrink the underlying space | |
9165 _virtual_space.shrink_by(bytes); | |
9166 if (PrintGCDetails && Verbose) { | |
9167 gclog_or_tty->print_cr("ConcurrentMarkSweepGeneration::shrink_by:" | |
9168 " desired_bytes " SIZE_FORMAT | |
9169 " shrinkable_size_in_bytes " SIZE_FORMAT | |
9170 " aligned_shrinkable_size_in_bytes " SIZE_FORMAT | |
9171 " bytes " SIZE_FORMAT, | |
9172 desired_bytes, shrinkable_size_in_bytes, | |
9173 aligned_shrinkable_size_in_bytes, bytes); | |
9174 gclog_or_tty->print_cr(" old_end " SIZE_FORMAT | |
9175 " unallocated_start " SIZE_FORMAT, | |
9176 old_end, unallocated_start); | |
9177 } | |
9178 | |
9179 // If the space did shrink (shrinking is not guaranteed), | |
9180 // shrink the chunk at the end by the appropriate amount. | |
9181 if (((HeapWord*)_virtual_space.high()) < old_end) { | |
9182 size_t new_word_size = | |
9183 heap_word_size(_virtual_space.committed_size()); | |
9184 | |
9185 // Have to remove the chunk from the dictionary because it is changing | |
9186 // size and might be someplace elsewhere in the dictionary. | |
9187 | |
9188 // Get the chunk at end, shrink it, and put it | |
9189 // back. | |
9190 _cmsSpace->removeChunkFromDictionary(chunk_at_end); | |
9191 size_t word_size_change = word_size_before - new_word_size; | |
9192 size_t chunk_at_end_old_size = chunk_at_end->size(); | |
9193 assert(chunk_at_end_old_size >= word_size_change, | |
9194 "Shrink is too large"); | |
6028
f69a5d43dc19
7164144: Fix variable naming style in freeBlockDictionary.* and binaryTreeDictionary*
jmasa
parents:
6026
diff
changeset
|
9195 chunk_at_end->set_size(chunk_at_end_old_size - |
0 | 9196 word_size_change); |
9197 _cmsSpace->freed((HeapWord*) chunk_at_end->end(), | |
9198 word_size_change); | |
9199 | |
9200 _cmsSpace->returnChunkToDictionary(chunk_at_end); | |
9201 | |
9202 MemRegion mr(_cmsSpace->bottom(), new_word_size); | |
9203 _bts->resize(new_word_size); // resize the block offset shared array | |
9204 Universe::heap()->barrier_set()->resize_covered_region(mr); | |
9205 _cmsSpace->assert_locked(); | |
9206 _cmsSpace->set_end((HeapWord*)_virtual_space.high()); | |
9207 | |
9208 NOT_PRODUCT(_cmsSpace->dictionary()->verify()); | |
9209 | |
9210 // update the space and generation capacity counters | |
9211 if (UsePerfData) { | |
9212 _space_counters->update_capacity(); | |
9213 _gen_counters->update_all(); | |
9214 } | |
9215 | |
9216 if (Verbose && PrintGCDetails) { | |
9217 size_t new_mem_size = _virtual_space.committed_size(); | |
9218 size_t old_mem_size = new_mem_size + bytes; | |
9219 gclog_or_tty->print_cr("Shrinking %s from %ldK by %ldK to %ldK", | |
9220 name(), old_mem_size/K, bytes/K, new_mem_size/K); | |
9221 } | |
9222 } | |
9223 | |
9224 assert(_cmsSpace->unallocated_block() <= _cmsSpace->end(), | |
9225 "Inconsistency at end of space"); | |
9226 assert(chunk_at_end->end() == _cmsSpace->end(), | |
9227 "Shrinking is inconsistent"); | |
9228 return; | |
9229 } | |
9230 } | |
9231 | |
9232 // Transfer some number of overflown objects to usual marking | |
9233 // stack. Return true if some objects were transferred. | |
9234 bool MarkRefsIntoAndScanClosure::take_from_overflow_list() { | |
679
cea947c8a988
6819891: ParNew: Fix work queue overflow code to deal correctly with +UseCompressedOops
ysr
parents:
628
diff
changeset
|
9235 size_t num = MIN2((size_t)(_mark_stack->capacity() - _mark_stack->length())/4, |
0 | 9236 (size_t)ParGCDesiredObjsFromOverflowList); |
9237 | |
9238 bool res = _collector->take_from_overflow_list(num, _mark_stack); | |
9239 assert(_collector->overflow_list_is_empty() || res, | |
9240 "If list is not empty, we should have taken something"); | |
9241 assert(!res || !_mark_stack->isEmpty(), | |
9242 "If we took something, it should now be on our stack"); | |
9243 return res; | |
9244 } | |
9245 | |
9246 size_t MarkDeadObjectsClosure::do_blk(HeapWord* addr) { | |
9247 size_t res = _sp->block_size_no_stall(addr, _collector); | |
9248 if (_sp->block_is_obj(addr)) { | |
9249 if (_live_bit_map->isMarked(addr)) { | |
9250 // It can't have been dead in a previous cycle | |
9251 guarantee(!_dead_bit_map->isMarked(addr), "No resurrection!"); | |
9252 } else { | |
9253 _dead_bit_map->mark(addr); // mark the dead object | |
9254 } | |
9255 } | |
2226
c5a923563727
6912621: iCMS: Error: assert(_markBitMap.isMarked(addr + 1),"Missing Printezis bit?")
ysr
parents:
2177
diff
changeset
|
9256 // Could be 0, if the block size could not be computed without stalling. |
0 | 9257 return res; |
9258 } | |
1703
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9259 |
3356
78542e2b5e35
7036199: Adding a notification to the implementation of GarbageCollectorMXBeans
fparain
parents:
3293
diff
changeset
|
9260 TraceCMSMemoryManagerStats::TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause): TraceMemoryManagerStats() { |
1703
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9261 |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9262 switch (phase) { |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9263 case CMSCollector::InitialMarking: |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9264 initialize(true /* fullGC */ , |
3356
78542e2b5e35
7036199: Adding a notification to the implementation of GarbageCollectorMXBeans
fparain
parents:
3293
diff
changeset
|
9265 cause /* cause of the GC */, |
1703
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9266 true /* recordGCBeginTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9267 true /* recordPreGCUsage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9268 false /* recordPeakUsage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9269 false /* recordPostGCusage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9270 true /* recordAccumulatedGCTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9271 false /* recordGCEndTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9272 false /* countCollection */ ); |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9273 break; |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9274 |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9275 case CMSCollector::FinalMarking: |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9276 initialize(true /* fullGC */ , |
3356
78542e2b5e35
7036199: Adding a notification to the implementation of GarbageCollectorMXBeans
fparain
parents:
3293
diff
changeset
|
9277 cause /* cause of the GC */, |
1703
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9278 false /* recordGCBeginTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9279 false /* recordPreGCUsage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9280 false /* recordPeakUsage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9281 false /* recordPostGCusage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9282 true /* recordAccumulatedGCTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9283 false /* recordGCEndTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9284 false /* countCollection */ ); |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9285 break; |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9286 |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9287 case CMSCollector::Sweeping: |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9288 initialize(true /* fullGC */ , |
3356
78542e2b5e35
7036199: Adding a notification to the implementation of GarbageCollectorMXBeans
fparain
parents:
3293
diff
changeset
|
9289 cause /* cause of the GC */, |
1703
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9290 false /* recordGCBeginTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9291 false /* recordPreGCUsage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9292 true /* recordPeakUsage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9293 true /* recordPostGCusage */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9294 false /* recordAccumulatedGCTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9295 true /* recordGCEndTime */, |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9296 true /* countCollection */ ); |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9297 break; |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9298 |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9299 default: |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9300 ShouldNotReachHere(); |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9301 } |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9302 } |
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9303 |