Mercurial > hg > graal-compiler
annotate src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp @ 1836:894b1d7c7e01
6423256: GC stacks should use a better data structure
6942771: SEGV in ParScanThreadState::take_from_overflow_stack
Reviewed-by: apetrusenko, ysr, pbk
| author | jcoomes |
|---|---|
| date | Tue, 28 Sep 2010 15:56:15 -0700 |
| parents | 8b10f48633dc |
| children | c99c53f07c14 |
| rev | line source |
|---|---|
| 0 | 1 /* |
|
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2 * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved. |
| 0 | 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| 4 * | |
| 5 * This code is free software; you can redistribute it and/or modify it | |
| 6 * under the terms of the GNU General Public License version 2 only, as | |
| 7 * published by the Free Software Foundation. | |
| 8 * | |
| 9 * This code is distributed in the hope that it will be useful, but WITHOUT | |
| 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
| 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
| 12 * version 2 for more details (a copy is included in the LICENSE file that | |
| 13 * accompanied this code). | |
| 14 * | |
| 15 * You should have received a copy of the GNU General Public License version | |
| 16 * 2 along with this work; if not, write to the Free Software Foundation, | |
| 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | |
| 18 * | |
|
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
| 0 | 22 * |
| 23 */ | |
| 24 | |
| 25 # include "incls/_precompiled.incl" | |
| 26 # include "incls/_concurrentMarkSweepGeneration.cpp.incl" | |
| 27 | |
| 28 // statics | |
| 29 CMSCollector* ConcurrentMarkSweepGeneration::_collector = NULL; | |
| 30 bool CMSCollector::_full_gc_requested = false; | |
| 31 | |
| 32 ////////////////////////////////////////////////////////////////// | |
| 33 // In support of CMS/VM thread synchronization | |
| 34 ////////////////////////////////////////////////////////////////// | |
| 35 // We split use of the CGC_lock into 2 "levels". | |
| 36 // The low-level locking is of the usual CGC_lock monitor. We introduce | |
| 37 // a higher level "token" (hereafter "CMS token") built on top of the | |
| 38 // low level monitor (hereafter "CGC lock"). | |
| 39 // The token-passing protocol gives priority to the VM thread. The | |
| 40 // CMS-lock doesn't provide any fairness guarantees, but clients | |
| 41 // should ensure that it is only held for very short, bounded | |
| 42 // durations. | |
| 43 // | |
| 44 // When either of the CMS thread or the VM thread is involved in | |
| 45 // collection operations during which it does not want the other | |
| 46 // thread to interfere, it obtains the CMS token. | |
| 47 // | |
| 48 // If either thread tries to get the token while the other has | |
| 49 // it, that thread waits. However, if the VM thread and CMS thread | |
| 50 // both want the token, then the VM thread gets priority while the | |
| 51 // CMS thread waits. This ensures, for instance, that the "concurrent" | |
| 52 // phases of the CMS thread's work do not block out the VM thread | |
| 53 // for long periods of time as the CMS thread continues to hog | |
| 54 // the token. (See bug 4616232). | |
| 55 // | |
| 56 // The baton-passing functions are, however, controlled by the | |
| 57 // flags _foregroundGCShouldWait and _foregroundGCIsActive, | |
| 58 // and here the low-level CMS lock, not the high level token, | |
| 59 // ensures mutual exclusion. | |
| 60 // | |
| 61 // Two important conditions that we have to satisfy: | |
| 62 // 1. if a thread does a low-level wait on the CMS lock, then it | |
| 63 // relinquishes the CMS token if it were holding that token | |
| 64 // when it acquired the low-level CMS lock. | |
| 65 // 2. any low-level notifications on the low-level lock | |
| 66 // should only be sent when a thread has relinquished the token. | |
| 67 // | |
| 68 // In the absence of either property, we'd have potential deadlock. | |
| 69 // | |
| 70 // We protect each of the CMS (concurrent and sequential) phases | |
| 71 // with the CMS _token_, not the CMS _lock_. | |
| 72 // | |
| 73 // The only code protected by CMS lock is the token acquisition code | |
| 74 // itself, see ConcurrentMarkSweepThread::[de]synchronize(), and the | |
| 75 // baton-passing code. | |
| 76 // | |
| 77 // Unfortunately, i couldn't come up with a good abstraction to factor and | |
| 78 // hide the naked CGC_lock manipulation in the baton-passing code | |
| 79 // further below. That's something we should try to do. Also, the proof | |
| 80 // of correctness of this 2-level locking scheme is far from obvious, | |
| 81 // and potentially quite slippery. We have an uneasy supsicion, for instance, | |
| 82 // that there may be a theoretical possibility of delay/starvation in the | |
| 83 // low-level lock/wait/notify scheme used for the baton-passing because of | |
| 84 // potential intereference with the priority scheme embodied in the | |
| 85 // CMS-token-passing protocol. See related comments at a CGC_lock->wait() | |
| 86 // invocation further below and marked with "XXX 20011219YSR". | |
| 87 // Indeed, as we note elsewhere, this may become yet more slippery | |
| 88 // in the presence of multiple CMS and/or multiple VM threads. XXX | |
| 89 | |
| 90 class CMSTokenSync: public StackObj { | |
| 91 private: | |
| 92 bool _is_cms_thread; | |
| 93 public: | |
| 94 CMSTokenSync(bool is_cms_thread): | |
| 95 _is_cms_thread(is_cms_thread) { | |
| 96 assert(is_cms_thread == Thread::current()->is_ConcurrentGC_thread(), | |
| 97 "Incorrect argument to constructor"); | |
| 98 ConcurrentMarkSweepThread::synchronize(_is_cms_thread); | |
| 99 } | |
| 100 | |
| 101 ~CMSTokenSync() { | |
| 102 assert(_is_cms_thread ? | |
| 103 ConcurrentMarkSweepThread::cms_thread_has_cms_token() : | |
| 104 ConcurrentMarkSweepThread::vm_thread_has_cms_token(), | |
| 105 "Incorrect state"); | |
| 106 ConcurrentMarkSweepThread::desynchronize(_is_cms_thread); | |
| 107 } | |
| 108 }; | |
| 109 | |
| 110 // Convenience class that does a CMSTokenSync, and then acquires | |
| 111 // upto three locks. | |
| 112 class CMSTokenSyncWithLocks: public CMSTokenSync { | |
| 113 private: | |
| 114 // Note: locks are acquired in textual declaration order | |
| 115 // and released in the opposite order | |
| 116 MutexLockerEx _locker1, _locker2, _locker3; | |
| 117 public: | |
| 118 CMSTokenSyncWithLocks(bool is_cms_thread, Mutex* mutex1, | |
| 119 Mutex* mutex2 = NULL, Mutex* mutex3 = NULL): | |
| 120 CMSTokenSync(is_cms_thread), | |
| 121 _locker1(mutex1, Mutex::_no_safepoint_check_flag), | |
| 122 _locker2(mutex2, Mutex::_no_safepoint_check_flag), | |
| 123 _locker3(mutex3, Mutex::_no_safepoint_check_flag) | |
| 124 { } | |
| 125 }; | |
| 126 | |
| 127 | |
| 128 // Wrapper class to temporarily disable icms during a foreground cms collection. | |
| 129 class ICMSDisabler: public StackObj { | |
| 130 public: | |
| 131 // The ctor disables icms and wakes up the thread so it notices the change; | |
| 132 // the dtor re-enables icms. Note that the CMSCollector methods will check | |
| 133 // CMSIncrementalMode. | |
| 134 ICMSDisabler() { CMSCollector::disable_icms(); CMSCollector::start_icms(); } | |
| 135 ~ICMSDisabler() { CMSCollector::enable_icms(); } | |
| 136 }; | |
| 137 | |
| 138 ////////////////////////////////////////////////////////////////// | |
| 139 // Concurrent Mark-Sweep Generation ///////////////////////////// | |
| 140 ////////////////////////////////////////////////////////////////// | |
| 141 | |
| 142 NOT_PRODUCT(CompactibleFreeListSpace* debug_cms_space;) | |
| 143 | |
| 144 // This struct contains per-thread things necessary to support parallel | |
| 145 // young-gen collection. | |
| 146 class CMSParGCThreadState: public CHeapObj { | |
| 147 public: | |
| 148 CFLS_LAB lab; | |
| 149 PromotionInfo promo; | |
| 150 | |
| 151 // Constructor. | |
| 152 CMSParGCThreadState(CompactibleFreeListSpace* cfls) : lab(cfls) { | |
| 153 promo.setSpace(cfls); | |
| 154 } | |
| 155 }; | |
| 156 | |
| 157 ConcurrentMarkSweepGeneration::ConcurrentMarkSweepGeneration( | |
| 158 ReservedSpace rs, size_t initial_byte_size, int level, | |
| 159 CardTableRS* ct, bool use_adaptive_freelists, | |
| 160 FreeBlockDictionary::DictionaryChoice dictionaryChoice) : | |
| 161 CardGeneration(rs, initial_byte_size, level, ct), | |
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162 _dilatation_factor(((double)MinChunkSize)/((double)(CollectedHeap::min_fill_size()))), |
| 0 | 163 _debug_collection_type(Concurrent_collection_type) |
| 164 { | |
| 165 HeapWord* bottom = (HeapWord*) _virtual_space.low(); | |
| 166 HeapWord* end = (HeapWord*) _virtual_space.high(); | |
| 167 | |
| 168 _direct_allocated_words = 0; | |
| 169 NOT_PRODUCT( | |
| 170 _numObjectsPromoted = 0; | |
| 171 _numWordsPromoted = 0; | |
| 172 _numObjectsAllocated = 0; | |
| 173 _numWordsAllocated = 0; | |
| 174 ) | |
| 175 | |
| 176 _cmsSpace = new CompactibleFreeListSpace(_bts, MemRegion(bottom, end), | |
| 177 use_adaptive_freelists, | |
| 178 dictionaryChoice); | |
| 179 NOT_PRODUCT(debug_cms_space = _cmsSpace;) | |
| 180 if (_cmsSpace == NULL) { | |
| 181 vm_exit_during_initialization( | |
| 182 "CompactibleFreeListSpace allocation failure"); | |
| 183 } | |
| 184 _cmsSpace->_gen = this; | |
| 185 | |
| 186 _gc_stats = new CMSGCStats(); | |
| 187 | |
| 188 // Verify the assumption that FreeChunk::_prev and OopDesc::_klass | |
| 189 // offsets match. The ability to tell free chunks from objects | |
| 190 // depends on this property. | |
| 191 debug_only( | |
| 192 FreeChunk* junk = NULL; | |
| 187 | 193 assert(UseCompressedOops || |
| 194 junk->prev_addr() == (void*)(oop(junk)->klass_addr()), | |
| 0 | 195 "Offset of FreeChunk::_prev within FreeChunk must match" |
| 196 " that of OopDesc::_klass within OopDesc"); | |
| 197 ) | |
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198 if (CollectedHeap::use_parallel_gc_threads()) { |
| 0 | 199 typedef CMSParGCThreadState* CMSParGCThreadStatePtr; |
| 200 _par_gc_thread_states = | |
| 201 NEW_C_HEAP_ARRAY(CMSParGCThreadStatePtr, ParallelGCThreads); | |
| 202 if (_par_gc_thread_states == NULL) { | |
| 203 vm_exit_during_initialization("Could not allocate par gc structs"); | |
| 204 } | |
| 205 for (uint i = 0; i < ParallelGCThreads; i++) { | |
| 206 _par_gc_thread_states[i] = new CMSParGCThreadState(cmsSpace()); | |
| 207 if (_par_gc_thread_states[i] == NULL) { | |
| 208 vm_exit_during_initialization("Could not allocate par gc structs"); | |
| 209 } | |
| 210 } | |
| 211 } else { | |
| 212 _par_gc_thread_states = NULL; | |
| 213 } | |
| 214 _incremental_collection_failed = false; | |
| 215 // The "dilatation_factor" is the expansion that can occur on | |
| 216 // account of the fact that the minimum object size in the CMS | |
| 217 // generation may be larger than that in, say, a contiguous young | |
| 218 // generation. | |
| 219 // Ideally, in the calculation below, we'd compute the dilatation | |
| 220 // factor as: MinChunkSize/(promoting_gen's min object size) | |
| 221 // Since we do not have such a general query interface for the | |
| 222 // promoting generation, we'll instead just use the mimimum | |
| 223 // object size (which today is a header's worth of space); | |
| 224 // note that all arithmetic is in units of HeapWords. | |
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225 assert(MinChunkSize >= CollectedHeap::min_fill_size(), "just checking"); |
| 0 | 226 assert(_dilatation_factor >= 1.0, "from previous assert"); |
| 227 } | |
| 228 | |
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229 |
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230 // The field "_initiating_occupancy" represents the occupancy percentage |
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231 // at which we trigger a new collection cycle. Unless explicitly specified |
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232 // via CMSInitiating[Perm]OccupancyFraction (argument "io" below), it |
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233 // is calculated by: |
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234 // |
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235 // Let "f" be MinHeapFreeRatio in |
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236 // |
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237 // _intiating_occupancy = 100-f + |
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238 // f * (CMSTrigger[Perm]Ratio/100) |
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239 // where CMSTrigger[Perm]Ratio is the argument "tr" below. |
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240 // |
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241 // That is, if we assume the heap is at its desired maximum occupancy at the |
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242 // end of a collection, we let CMSTrigger[Perm]Ratio of the (purported) free |
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243 // space be allocated before initiating a new collection cycle. |
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244 // |
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245 void ConcurrentMarkSweepGeneration::init_initiating_occupancy(intx io, intx tr) { |
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246 assert(io <= 100 && tr >= 0 && tr <= 100, "Check the arguments"); |
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247 if (io >= 0) { |
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248 _initiating_occupancy = (double)io / 100.0; |
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249 } else { |
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250 _initiating_occupancy = ((100 - MinHeapFreeRatio) + |
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251 (double)(tr * MinHeapFreeRatio) / 100.0) |
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252 / 100.0; |
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253 } |
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254 } |
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255 |
| 0 | 256 void ConcurrentMarkSweepGeneration::ref_processor_init() { |
| 257 assert(collector() != NULL, "no collector"); | |
| 258 collector()->ref_processor_init(); | |
| 259 } | |
| 260 | |
| 261 void CMSCollector::ref_processor_init() { | |
| 262 if (_ref_processor == NULL) { | |
| 263 // Allocate and initialize a reference processor | |
| 264 _ref_processor = ReferenceProcessor::create_ref_processor( | |
| 265 _span, // span | |
| 266 _cmsGen->refs_discovery_is_atomic(), // atomic_discovery | |
| 267 _cmsGen->refs_discovery_is_mt(), // mt_discovery | |
| 268 &_is_alive_closure, | |
| 269 ParallelGCThreads, | |
| 270 ParallelRefProcEnabled); | |
| 271 // Initialize the _ref_processor field of CMSGen | |
| 272 _cmsGen->set_ref_processor(_ref_processor); | |
| 273 | |
| 274 // Allocate a dummy ref processor for perm gen. | |
| 275 ReferenceProcessor* rp2 = new ReferenceProcessor(); | |
| 276 if (rp2 == NULL) { | |
| 277 vm_exit_during_initialization("Could not allocate ReferenceProcessor object"); | |
| 278 } | |
| 279 _permGen->set_ref_processor(rp2); | |
| 280 } | |
| 281 } | |
| 282 | |
| 283 CMSAdaptiveSizePolicy* CMSCollector::size_policy() { | |
| 284 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 285 assert(gch->kind() == CollectedHeap::GenCollectedHeap, | |
| 286 "Wrong type of heap"); | |
| 287 CMSAdaptiveSizePolicy* sp = (CMSAdaptiveSizePolicy*) | |
| 288 gch->gen_policy()->size_policy(); | |
| 289 assert(sp->is_gc_cms_adaptive_size_policy(), | |
| 290 "Wrong type of size policy"); | |
| 291 return sp; | |
| 292 } | |
| 293 | |
| 294 CMSGCAdaptivePolicyCounters* CMSCollector::gc_adaptive_policy_counters() { | |
| 295 CMSGCAdaptivePolicyCounters* results = | |
| 296 (CMSGCAdaptivePolicyCounters*) collector_policy()->counters(); | |
| 297 assert( | |
| 298 results->kind() == GCPolicyCounters::CMSGCAdaptivePolicyCountersKind, | |
| 299 "Wrong gc policy counter kind"); | |
| 300 return results; | |
| 301 } | |
| 302 | |
| 303 | |
| 304 void ConcurrentMarkSweepGeneration::initialize_performance_counters() { | |
| 305 | |
| 306 const char* gen_name = "old"; | |
| 307 | |
| 308 // Generation Counters - generation 1, 1 subspace | |
| 309 _gen_counters = new GenerationCounters(gen_name, 1, 1, &_virtual_space); | |
| 310 | |
| 311 _space_counters = new GSpaceCounters(gen_name, 0, | |
| 312 _virtual_space.reserved_size(), | |
| 313 this, _gen_counters); | |
| 314 } | |
| 315 | |
| 316 CMSStats::CMSStats(ConcurrentMarkSweepGeneration* cms_gen, unsigned int alpha): | |
| 317 _cms_gen(cms_gen) | |
| 318 { | |
| 319 assert(alpha <= 100, "bad value"); | |
| 320 _saved_alpha = alpha; | |
| 321 | |
| 322 // Initialize the alphas to the bootstrap value of 100. | |
| 323 _gc0_alpha = _cms_alpha = 100; | |
| 324 | |
| 325 _cms_begin_time.update(); | |
| 326 _cms_end_time.update(); | |
| 327 | |
| 328 _gc0_duration = 0.0; | |
| 329 _gc0_period = 0.0; | |
| 330 _gc0_promoted = 0; | |
| 331 | |
| 332 _cms_duration = 0.0; | |
| 333 _cms_period = 0.0; | |
| 334 _cms_allocated = 0; | |
| 335 | |
| 336 _cms_used_at_gc0_begin = 0; | |
| 337 _cms_used_at_gc0_end = 0; | |
| 338 _allow_duty_cycle_reduction = false; | |
| 339 _valid_bits = 0; | |
| 340 _icms_duty_cycle = CMSIncrementalDutyCycle; | |
| 341 } | |
| 342 | |
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343 double CMSStats::cms_free_adjustment_factor(size_t free) const { |
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344 // TBD: CR 6909490 |
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345 return 1.0; |
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346 } |
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347 |
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348 void CMSStats::adjust_cms_free_adjustment_factor(bool fail, size_t free) { |
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349 } |
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350 |
| 0 | 351 // If promotion failure handling is on use |
| 352 // the padded average size of the promotion for each | |
| 353 // young generation collection. | |
| 354 double CMSStats::time_until_cms_gen_full() const { | |
| 355 size_t cms_free = _cms_gen->cmsSpace()->free(); | |
| 356 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 357 size_t expected_promotion = gch->get_gen(0)->capacity(); | |
| 358 if (HandlePromotionFailure) { | |
| 359 expected_promotion = MIN2( | |
| 360 (size_t) _cms_gen->gc_stats()->avg_promoted()->padded_average(), | |
| 361 expected_promotion); | |
| 362 } | |
| 363 if (cms_free > expected_promotion) { | |
| 364 // Start a cms collection if there isn't enough space to promote | |
| 365 // for the next minor collection. Use the padded average as | |
| 366 // a safety factor. | |
| 367 cms_free -= expected_promotion; | |
| 368 | |
| 369 // Adjust by the safety factor. | |
| 370 double cms_free_dbl = (double)cms_free; | |
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371 double cms_adjustment = (100.0 - CMSIncrementalSafetyFactor)/100.0; |
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372 // Apply a further correction factor which tries to adjust |
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373 // for recent occurance of concurrent mode failures. |
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374 cms_adjustment = cms_adjustment * cms_free_adjustment_factor(cms_free); |
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375 cms_free_dbl = cms_free_dbl * cms_adjustment; |
| 0 | 376 |
| 377 if (PrintGCDetails && Verbose) { | |
| 378 gclog_or_tty->print_cr("CMSStats::time_until_cms_gen_full: cms_free " | |
| 379 SIZE_FORMAT " expected_promotion " SIZE_FORMAT, | |
| 380 cms_free, expected_promotion); | |
| 381 gclog_or_tty->print_cr(" cms_free_dbl %f cms_consumption_rate %f", | |
| 382 cms_free_dbl, cms_consumption_rate() + 1.0); | |
| 383 } | |
| 384 // Add 1 in case the consumption rate goes to zero. | |
| 385 return cms_free_dbl / (cms_consumption_rate() + 1.0); | |
| 386 } | |
| 387 return 0.0; | |
| 388 } | |
| 389 | |
| 390 // Compare the duration of the cms collection to the | |
| 391 // time remaining before the cms generation is empty. | |
| 392 // Note that the time from the start of the cms collection | |
| 393 // to the start of the cms sweep (less than the total | |
| 394 // duration of the cms collection) can be used. This | |
| 395 // has been tried and some applications experienced | |
| 396 // promotion failures early in execution. This was | |
| 397 // possibly because the averages were not accurate | |
| 398 // enough at the beginning. | |
| 399 double CMSStats::time_until_cms_start() const { | |
| 400 // We add "gc0_period" to the "work" calculation | |
| 401 // below because this query is done (mostly) at the | |
| 402 // end of a scavenge, so we need to conservatively | |
| 403 // account for that much possible delay | |
| 404 // in the query so as to avoid concurrent mode failures | |
| 405 // due to starting the collection just a wee bit too | |
| 406 // late. | |
| 407 double work = cms_duration() + gc0_period(); | |
| 408 double deadline = time_until_cms_gen_full(); | |
|
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409 // If a concurrent mode failure occurred recently, we want to be |
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410 // more conservative and halve our expected time_until_cms_gen_full() |
| 0 | 411 if (work > deadline) { |
| 412 if (Verbose && PrintGCDetails) { | |
| 413 gclog_or_tty->print( | |
| 414 " CMSCollector: collect because of anticipated promotion " | |
| 415 "before full %3.7f + %3.7f > %3.7f ", cms_duration(), | |
| 416 gc0_period(), time_until_cms_gen_full()); | |
| 417 } | |
| 418 return 0.0; | |
| 419 } | |
| 420 return work - deadline; | |
| 421 } | |
| 422 | |
| 423 // Return a duty cycle based on old_duty_cycle and new_duty_cycle, limiting the | |
| 424 // amount of change to prevent wild oscillation. | |
| 425 unsigned int CMSStats::icms_damped_duty_cycle(unsigned int old_duty_cycle, | |
| 426 unsigned int new_duty_cycle) { | |
| 427 assert(old_duty_cycle <= 100, "bad input value"); | |
| 428 assert(new_duty_cycle <= 100, "bad input value"); | |
| 429 | |
| 430 // Note: use subtraction with caution since it may underflow (values are | |
| 431 // unsigned). Addition is safe since we're in the range 0-100. | |
| 432 unsigned int damped_duty_cycle = new_duty_cycle; | |
| 433 if (new_duty_cycle < old_duty_cycle) { | |
| 434 const unsigned int largest_delta = MAX2(old_duty_cycle / 4, 5U); | |
| 435 if (new_duty_cycle + largest_delta < old_duty_cycle) { | |
| 436 damped_duty_cycle = old_duty_cycle - largest_delta; | |
| 437 } | |
| 438 } else if (new_duty_cycle > old_duty_cycle) { | |
| 439 const unsigned int largest_delta = MAX2(old_duty_cycle / 4, 15U); | |
| 440 if (new_duty_cycle > old_duty_cycle + largest_delta) { | |
| 441 damped_duty_cycle = MIN2(old_duty_cycle + largest_delta, 100U); | |
| 442 } | |
| 443 } | |
| 444 assert(damped_duty_cycle <= 100, "invalid duty cycle computed"); | |
| 445 | |
| 446 if (CMSTraceIncrementalPacing) { | |
| 447 gclog_or_tty->print(" [icms_damped_duty_cycle(%d,%d) = %d] ", | |
| 448 old_duty_cycle, new_duty_cycle, damped_duty_cycle); | |
| 449 } | |
| 450 return damped_duty_cycle; | |
| 451 } | |
| 452 | |
| 453 unsigned int CMSStats::icms_update_duty_cycle_impl() { | |
| 454 assert(CMSIncrementalPacing && valid(), | |
| 455 "should be handled in icms_update_duty_cycle()"); | |
| 456 | |
| 457 double cms_time_so_far = cms_timer().seconds(); | |
| 458 double scaled_duration = cms_duration_per_mb() * _cms_used_at_gc0_end / M; | |
| 459 double scaled_duration_remaining = fabsd(scaled_duration - cms_time_so_far); | |
| 460 | |
| 461 // Avoid division by 0. | |
| 462 double time_until_full = MAX2(time_until_cms_gen_full(), 0.01); | |
| 463 double duty_cycle_dbl = 100.0 * scaled_duration_remaining / time_until_full; | |
| 464 | |
| 465 unsigned int new_duty_cycle = MIN2((unsigned int)duty_cycle_dbl, 100U); | |
| 466 if (new_duty_cycle > _icms_duty_cycle) { | |
| 467 // Avoid very small duty cycles (1 or 2); 0 is allowed. | |
| 468 if (new_duty_cycle > 2) { | |
| 469 _icms_duty_cycle = icms_damped_duty_cycle(_icms_duty_cycle, | |
| 470 new_duty_cycle); | |
| 471 } | |
| 472 } else if (_allow_duty_cycle_reduction) { | |
| 473 // The duty cycle is reduced only once per cms cycle (see record_cms_end()). | |
| 474 new_duty_cycle = icms_damped_duty_cycle(_icms_duty_cycle, new_duty_cycle); | |
| 475 // Respect the minimum duty cycle. | |
| 476 unsigned int min_duty_cycle = (unsigned int)CMSIncrementalDutyCycleMin; | |
| 477 _icms_duty_cycle = MAX2(new_duty_cycle, min_duty_cycle); | |
| 478 } | |
| 479 | |
| 480 if (PrintGCDetails || CMSTraceIncrementalPacing) { | |
| 481 gclog_or_tty->print(" icms_dc=%d ", _icms_duty_cycle); | |
| 482 } | |
| 483 | |
| 484 _allow_duty_cycle_reduction = false; | |
| 485 return _icms_duty_cycle; | |
| 486 } | |
| 487 | |
| 488 #ifndef PRODUCT | |
| 489 void CMSStats::print_on(outputStream *st) const { | |
| 490 st->print(" gc0_alpha=%d,cms_alpha=%d", _gc0_alpha, _cms_alpha); | |
| 491 st->print(",gc0_dur=%g,gc0_per=%g,gc0_promo=" SIZE_FORMAT, | |
| 492 gc0_duration(), gc0_period(), gc0_promoted()); | |
| 493 st->print(",cms_dur=%g,cms_dur_per_mb=%g,cms_per=%g,cms_alloc=" SIZE_FORMAT, | |
| 494 cms_duration(), cms_duration_per_mb(), | |
| 495 cms_period(), cms_allocated()); | |
| 496 st->print(",cms_since_beg=%g,cms_since_end=%g", | |
| 497 cms_time_since_begin(), cms_time_since_end()); | |
| 498 st->print(",cms_used_beg=" SIZE_FORMAT ",cms_used_end=" SIZE_FORMAT, | |
| 499 _cms_used_at_gc0_begin, _cms_used_at_gc0_end); | |
| 500 if (CMSIncrementalMode) { | |
| 501 st->print(",dc=%d", icms_duty_cycle()); | |
| 502 } | |
| 503 | |
| 504 if (valid()) { | |
| 505 st->print(",promo_rate=%g,cms_alloc_rate=%g", | |
| 506 promotion_rate(), cms_allocation_rate()); | |
| 507 st->print(",cms_consumption_rate=%g,time_until_full=%g", | |
| 508 cms_consumption_rate(), time_until_cms_gen_full()); | |
| 509 } | |
| 510 st->print(" "); | |
| 511 } | |
| 512 #endif // #ifndef PRODUCT | |
| 513 | |
| 514 CMSCollector::CollectorState CMSCollector::_collectorState = | |
| 515 CMSCollector::Idling; | |
| 516 bool CMSCollector::_foregroundGCIsActive = false; | |
| 517 bool CMSCollector::_foregroundGCShouldWait = false; | |
| 518 | |
| 519 CMSCollector::CMSCollector(ConcurrentMarkSweepGeneration* cmsGen, | |
| 520 ConcurrentMarkSweepGeneration* permGen, | |
| 521 CardTableRS* ct, | |
| 522 ConcurrentMarkSweepPolicy* cp): | |
| 523 _cmsGen(cmsGen), | |
| 524 _permGen(permGen), | |
| 525 _ct(ct), | |
| 526 _ref_processor(NULL), // will be set later | |
| 527 _conc_workers(NULL), // may be set later | |
| 528 _abort_preclean(false), | |
| 529 _start_sampling(false), | |
| 530 _between_prologue_and_epilogue(false), | |
| 531 _markBitMap(0, Mutex::leaf + 1, "CMS_markBitMap_lock"), | |
| 532 _perm_gen_verify_bit_map(0, -1 /* no mutex */, "No_lock"), | |
| 533 _modUnionTable((CardTableModRefBS::card_shift - LogHeapWordSize), | |
| 534 -1 /* lock-free */, "No_lock" /* dummy */), | |
| 535 _modUnionClosure(&_modUnionTable), | |
| 536 _modUnionClosurePar(&_modUnionTable), | |
|
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537 // Adjust my span to cover old (cms) gen and perm gen |
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538 _span(cmsGen->reserved()._union(permGen->reserved())), |
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539 // Construct the is_alive_closure with _span & markBitMap |
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540 _is_alive_closure(_span, &_markBitMap), |
| 0 | 541 _restart_addr(NULL), |
| 542 _overflow_list(NULL), | |
| 543 _stats(cmsGen), | |
| 544 _eden_chunk_array(NULL), // may be set in ctor body | |
| 545 _eden_chunk_capacity(0), // -- ditto -- | |
| 546 _eden_chunk_index(0), // -- ditto -- | |
| 547 _survivor_plab_array(NULL), // -- ditto -- | |
| 548 _survivor_chunk_array(NULL), // -- ditto -- | |
| 549 _survivor_chunk_capacity(0), // -- ditto -- | |
| 550 _survivor_chunk_index(0), // -- ditto -- | |
| 551 _ser_pmc_preclean_ovflw(0), | |
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552 _ser_kac_preclean_ovflw(0), |
| 0 | 553 _ser_pmc_remark_ovflw(0), |
| 554 _par_pmc_remark_ovflw(0), | |
| 555 _ser_kac_ovflw(0), | |
| 556 _par_kac_ovflw(0), | |
| 557 #ifndef PRODUCT | |
| 558 _num_par_pushes(0), | |
| 559 #endif | |
| 560 _collection_count_start(0), | |
| 561 _verifying(false), | |
| 562 _icms_start_limit(NULL), | |
| 563 _icms_stop_limit(NULL), | |
| 564 _verification_mark_bm(0, Mutex::leaf + 1, "CMS_verification_mark_bm_lock"), | |
| 565 _completed_initialization(false), | |
| 566 _collector_policy(cp), | |
|
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567 _should_unload_classes(false), |
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568 _concurrent_cycles_since_last_unload(0), |
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569 _roots_scanning_options(0), |
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570 _inter_sweep_estimate(CMS_SweepWeight, CMS_SweepPadding), |
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571 _intra_sweep_estimate(CMS_SweepWeight, CMS_SweepPadding) |
| 0 | 572 { |
| 573 if (ExplicitGCInvokesConcurrentAndUnloadsClasses) { | |
| 574 ExplicitGCInvokesConcurrent = true; | |
| 575 } | |
| 576 // Now expand the span and allocate the collection support structures | |
| 577 // (MUT, marking bit map etc.) to cover both generations subject to | |
| 578 // collection. | |
| 579 | |
| 580 // First check that _permGen is adjacent to _cmsGen and above it. | |
| 581 assert( _cmsGen->reserved().word_size() > 0 | |
| 582 && _permGen->reserved().word_size() > 0, | |
| 583 "generations should not be of zero size"); | |
| 584 assert(_cmsGen->reserved().intersection(_permGen->reserved()).is_empty(), | |
| 585 "_cmsGen and _permGen should not overlap"); | |
| 586 assert(_cmsGen->reserved().end() == _permGen->reserved().start(), | |
| 587 "_cmsGen->end() different from _permGen->start()"); | |
| 588 | |
| 589 // For use by dirty card to oop closures. | |
| 590 _cmsGen->cmsSpace()->set_collector(this); | |
| 591 _permGen->cmsSpace()->set_collector(this); | |
| 592 | |
| 593 // Allocate MUT and marking bit map | |
| 594 { | |
| 595 MutexLockerEx x(_markBitMap.lock(), Mutex::_no_safepoint_check_flag); | |
| 596 if (!_markBitMap.allocate(_span)) { | |
| 597 warning("Failed to allocate CMS Bit Map"); | |
| 598 return; | |
| 599 } | |
| 600 assert(_markBitMap.covers(_span), "_markBitMap inconsistency?"); | |
| 601 } | |
| 602 { | |
| 603 _modUnionTable.allocate(_span); | |
| 604 assert(_modUnionTable.covers(_span), "_modUnionTable inconsistency?"); | |
| 605 } | |
| 606 | |
| 1284 | 607 if (!_markStack.allocate(MarkStackSize)) { |
| 0 | 608 warning("Failed to allocate CMS Marking Stack"); |
| 609 return; | |
| 610 } | |
| 611 if (!_revisitStack.allocate(CMSRevisitStackSize)) { | |
| 612 warning("Failed to allocate CMS Revisit Stack"); | |
| 613 return; | |
| 614 } | |
| 615 | |
| 616 // Support for multi-threaded concurrent phases | |
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617 if (CollectedHeap::use_parallel_gc_threads() && CMSConcurrentMTEnabled) { |
| 1284 | 618 if (FLAG_IS_DEFAULT(ConcGCThreads)) { |
| 0 | 619 // just for now |
| 1284 | 620 FLAG_SET_DEFAULT(ConcGCThreads, (ParallelGCThreads + 3)/4); |
| 621 } | |
| 622 if (ConcGCThreads > 1) { | |
| 0 | 623 _conc_workers = new YieldingFlexibleWorkGang("Parallel CMS Threads", |
| 1284 | 624 ConcGCThreads, true); |
| 0 | 625 if (_conc_workers == NULL) { |
| 626 warning("GC/CMS: _conc_workers allocation failure: " | |
| 627 "forcing -CMSConcurrentMTEnabled"); | |
| 628 CMSConcurrentMTEnabled = false; | |
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629 } else { |
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630 _conc_workers->initialize_workers(); |
| 0 | 631 } |
| 632 } else { | |
| 633 CMSConcurrentMTEnabled = false; | |
| 634 } | |
| 635 } | |
| 636 if (!CMSConcurrentMTEnabled) { | |
| 1284 | 637 ConcGCThreads = 0; |
| 0 | 638 } else { |
| 639 // Turn off CMSCleanOnEnter optimization temporarily for | |
| 640 // the MT case where it's not fixed yet; see 6178663. | |
| 641 CMSCleanOnEnter = false; | |
| 642 } | |
| 1284 | 643 assert((_conc_workers != NULL) == (ConcGCThreads > 1), |
| 0 | 644 "Inconsistency"); |
| 645 | |
| 646 // Parallel task queues; these are shared for the | |
| 647 // concurrent and stop-world phases of CMS, but | |
| 648 // are not shared with parallel scavenge (ParNew). | |
| 649 { | |
| 650 uint i; | |
| 1284 | 651 uint num_queues = (uint) MAX2(ParallelGCThreads, ConcGCThreads); |
| 0 | 652 |
| 653 if ((CMSParallelRemarkEnabled || CMSConcurrentMTEnabled | |
| 654 || ParallelRefProcEnabled) | |
| 655 && num_queues > 0) { | |
| 656 _task_queues = new OopTaskQueueSet(num_queues); | |
| 657 if (_task_queues == NULL) { | |
| 658 warning("task_queues allocation failure."); | |
| 659 return; | |
| 660 } | |
| 661 _hash_seed = NEW_C_HEAP_ARRAY(int, num_queues); | |
| 662 if (_hash_seed == NULL) { | |
| 663 warning("_hash_seed array allocation failure"); | |
| 664 return; | |
| 665 } | |
| 666 | |
| 1665 | 667 typedef Padded<OopTaskQueue> PaddedOopTaskQueue; |
| 0 | 668 for (i = 0; i < num_queues; i++) { |
| 1665 | 669 PaddedOopTaskQueue *q = new PaddedOopTaskQueue(); |
| 670 if (q == NULL) { | |
| 0 | 671 warning("work_queue allocation failure."); |
| 672 return; | |
| 673 } | |
| 1665 | 674 _task_queues->register_queue(i, q); |
| 0 | 675 } |
| 676 for (i = 0; i < num_queues; i++) { | |
| 677 _task_queues->queue(i)->initialize(); | |
| 678 _hash_seed[i] = 17; // copied from ParNew | |
| 679 } | |
| 680 } | |
| 681 } | |
| 682 | |
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683 _cmsGen ->init_initiating_occupancy(CMSInitiatingOccupancyFraction, CMSTriggerRatio); |
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684 _permGen->init_initiating_occupancy(CMSInitiatingPermOccupancyFraction, CMSTriggerPermRatio); |
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685 |
| 0 | 686 // Clip CMSBootstrapOccupancy between 0 and 100. |
|
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687 _bootstrap_occupancy = ((double)MIN2((uintx)100, MAX2((uintx)0, CMSBootstrapOccupancy))) |
| 0 | 688 /(double)100; |
| 689 | |
| 690 _full_gcs_since_conc_gc = 0; | |
| 691 | |
| 692 // Now tell CMS generations the identity of their collector | |
| 693 ConcurrentMarkSweepGeneration::set_collector(this); | |
| 694 | |
| 695 // Create & start a CMS thread for this CMS collector | |
| 696 _cmsThread = ConcurrentMarkSweepThread::start(this); | |
| 697 assert(cmsThread() != NULL, "CMS Thread should have been created"); | |
| 698 assert(cmsThread()->collector() == this, | |
| 699 "CMS Thread should refer to this gen"); | |
| 700 assert(CGC_lock != NULL, "Where's the CGC_lock?"); | |
| 701 | |
| 702 // Support for parallelizing young gen rescan | |
| 703 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 704 _young_gen = gch->prev_gen(_cmsGen); | |
| 705 if (gch->supports_inline_contig_alloc()) { | |
| 706 _top_addr = gch->top_addr(); | |
| 707 _end_addr = gch->end_addr(); | |
| 708 assert(_young_gen != NULL, "no _young_gen"); | |
| 709 _eden_chunk_index = 0; | |
| 710 _eden_chunk_capacity = (_young_gen->max_capacity()+CMSSamplingGrain)/CMSSamplingGrain; | |
| 711 _eden_chunk_array = NEW_C_HEAP_ARRAY(HeapWord*, _eden_chunk_capacity); | |
| 712 if (_eden_chunk_array == NULL) { | |
| 713 _eden_chunk_capacity = 0; | |
| 714 warning("GC/CMS: _eden_chunk_array allocation failure"); | |
| 715 } | |
| 716 } | |
| 717 assert(_eden_chunk_array != NULL || _eden_chunk_capacity == 0, "Error"); | |
| 718 | |
| 719 // Support for parallelizing survivor space rescan | |
| 720 if (CMSParallelRemarkEnabled && CMSParallelSurvivorRemarkEnabled) { | |
|
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721 const size_t max_plab_samples = |
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722 ((DefNewGeneration*)_young_gen)->max_survivor_size()/MinTLABSize; |
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723 |
| 0 | 724 _survivor_plab_array = NEW_C_HEAP_ARRAY(ChunkArray, ParallelGCThreads); |
| 725 _survivor_chunk_array = NEW_C_HEAP_ARRAY(HeapWord*, 2*max_plab_samples); | |
| 726 _cursor = NEW_C_HEAP_ARRAY(size_t, ParallelGCThreads); | |
| 727 if (_survivor_plab_array == NULL || _survivor_chunk_array == NULL | |
| 728 || _cursor == NULL) { | |
| 729 warning("Failed to allocate survivor plab/chunk array"); | |
| 730 if (_survivor_plab_array != NULL) { | |
| 731 FREE_C_HEAP_ARRAY(ChunkArray, _survivor_plab_array); | |
| 732 _survivor_plab_array = NULL; | |
| 733 } | |
| 734 if (_survivor_chunk_array != NULL) { | |
| 735 FREE_C_HEAP_ARRAY(HeapWord*, _survivor_chunk_array); | |
| 736 _survivor_chunk_array = NULL; | |
| 737 } | |
| 738 if (_cursor != NULL) { | |
| 739 FREE_C_HEAP_ARRAY(size_t, _cursor); | |
| 740 _cursor = NULL; | |
| 741 } | |
| 742 } else { | |
| 743 _survivor_chunk_capacity = 2*max_plab_samples; | |
| 744 for (uint i = 0; i < ParallelGCThreads; i++) { | |
| 745 HeapWord** vec = NEW_C_HEAP_ARRAY(HeapWord*, max_plab_samples); | |
| 746 if (vec == NULL) { | |
| 747 warning("Failed to allocate survivor plab array"); | |
| 748 for (int j = i; j > 0; j--) { | |
| 749 FREE_C_HEAP_ARRAY(HeapWord*, _survivor_plab_array[j-1].array()); | |
| 750 } | |
| 751 FREE_C_HEAP_ARRAY(ChunkArray, _survivor_plab_array); | |
| 752 FREE_C_HEAP_ARRAY(HeapWord*, _survivor_chunk_array); | |
| 753 _survivor_plab_array = NULL; | |
| 754 _survivor_chunk_array = NULL; | |
| 755 _survivor_chunk_capacity = 0; | |
| 756 break; | |
| 757 } else { | |
| 758 ChunkArray* cur = | |
| 759 ::new (&_survivor_plab_array[i]) ChunkArray(vec, | |
| 760 max_plab_samples); | |
| 761 assert(cur->end() == 0, "Should be 0"); | |
| 762 assert(cur->array() == vec, "Should be vec"); | |
| 763 assert(cur->capacity() == max_plab_samples, "Error"); | |
| 764 } | |
| 765 } | |
| 766 } | |
| 767 } | |
| 768 assert( ( _survivor_plab_array != NULL | |
| 769 && _survivor_chunk_array != NULL) | |
| 770 || ( _survivor_chunk_capacity == 0 | |
| 771 && _survivor_chunk_index == 0), | |
| 772 "Error"); | |
| 773 | |
| 774 // Choose what strong roots should be scanned depending on verification options | |
| 775 // and perm gen collection mode. | |
| 776 if (!CMSClassUnloadingEnabled) { | |
| 777 // If class unloading is disabled we want to include all classes into the root set. | |
| 778 add_root_scanning_option(SharedHeap::SO_AllClasses); | |
| 779 } else { | |
| 780 add_root_scanning_option(SharedHeap::SO_SystemClasses); | |
| 781 } | |
| 782 | |
| 783 NOT_PRODUCT(_overflow_counter = CMSMarkStackOverflowInterval;) | |
| 784 _gc_counters = new CollectorCounters("CMS", 1); | |
| 785 _completed_initialization = true; | |
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786 _inter_sweep_timer.start(); // start of time |
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787 #ifdef SPARC |
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788 // Issue a stern warning, but allow use for experimentation and debugging. |
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789 if (VM_Version::is_sun4v() && UseMemSetInBOT) { |
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790 assert(!FLAG_IS_DEFAULT(UseMemSetInBOT), "Error"); |
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791 warning("Experimental flag -XX:+UseMemSetInBOT is known to cause instability" |
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792 " on sun4v; please understand that you are using at your own risk!"); |
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793 } |
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794 #endif |
| 0 | 795 } |
| 796 | |
| 797 const char* ConcurrentMarkSweepGeneration::name() const { | |
| 798 return "concurrent mark-sweep generation"; | |
| 799 } | |
| 800 void ConcurrentMarkSweepGeneration::update_counters() { | |
| 801 if (UsePerfData) { | |
| 802 _space_counters->update_all(); | |
| 803 _gen_counters->update_all(); | |
| 804 } | |
| 805 } | |
| 806 | |
| 807 // this is an optimized version of update_counters(). it takes the | |
| 808 // used value as a parameter rather than computing it. | |
| 809 // | |
| 810 void ConcurrentMarkSweepGeneration::update_counters(size_t used) { | |
| 811 if (UsePerfData) { | |
| 812 _space_counters->update_used(used); | |
| 813 _space_counters->update_capacity(); | |
| 814 _gen_counters->update_all(); | |
| 815 } | |
| 816 } | |
| 817 | |
| 818 void ConcurrentMarkSweepGeneration::print() const { | |
| 819 Generation::print(); | |
| 820 cmsSpace()->print(); | |
| 821 } | |
| 822 | |
| 823 #ifndef PRODUCT | |
| 824 void ConcurrentMarkSweepGeneration::print_statistics() { | |
| 825 cmsSpace()->printFLCensus(0); | |
| 826 } | |
| 827 #endif | |
| 828 | |
| 829 void ConcurrentMarkSweepGeneration::printOccupancy(const char *s) { | |
| 830 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 831 if (PrintGCDetails) { | |
| 832 if (Verbose) { | |
| 833 gclog_or_tty->print(" [%d %s-%s: "SIZE_FORMAT"("SIZE_FORMAT")]", | |
| 834 level(), short_name(), s, used(), capacity()); | |
| 835 } else { | |
| 836 gclog_or_tty->print(" [%d %s-%s: "SIZE_FORMAT"K("SIZE_FORMAT"K)]", | |
| 837 level(), short_name(), s, used() / K, capacity() / K); | |
| 838 } | |
| 839 } | |
| 840 if (Verbose) { | |
| 841 gclog_or_tty->print(" "SIZE_FORMAT"("SIZE_FORMAT")", | |
| 842 gch->used(), gch->capacity()); | |
| 843 } else { | |
| 844 gclog_or_tty->print(" "SIZE_FORMAT"K("SIZE_FORMAT"K)", | |
| 845 gch->used() / K, gch->capacity() / K); | |
| 846 } | |
| 847 } | |
| 848 | |
| 849 size_t | |
| 850 ConcurrentMarkSweepGeneration::contiguous_available() const { | |
| 851 // dld proposes an improvement in precision here. If the committed | |
| 852 // part of the space ends in a free block we should add that to | |
| 853 // uncommitted size in the calculation below. Will make this | |
| 854 // change later, staying with the approximation below for the | |
| 855 // time being. -- ysr. | |
| 856 return MAX2(_virtual_space.uncommitted_size(), unsafe_max_alloc_nogc()); | |
| 857 } | |
| 858 | |
| 859 size_t | |
| 860 ConcurrentMarkSweepGeneration::unsafe_max_alloc_nogc() const { | |
| 861 return _cmsSpace->max_alloc_in_words() * HeapWordSize; | |
| 862 } | |
| 863 | |
| 864 size_t ConcurrentMarkSweepGeneration::max_available() const { | |
| 865 return free() + _virtual_space.uncommitted_size(); | |
| 866 } | |
| 867 | |
| 868 bool ConcurrentMarkSweepGeneration::promotion_attempt_is_safe( | |
| 869 size_t max_promotion_in_bytes, | |
| 870 bool younger_handles_promotion_failure) const { | |
| 871 | |
| 872 // This is the most conservative test. Full promotion is | |
| 873 // guaranteed if this is used. The multiplicative factor is to | |
| 874 // account for the worst case "dilatation". | |
| 875 double adjusted_max_promo_bytes = _dilatation_factor * max_promotion_in_bytes; | |
| 876 if (adjusted_max_promo_bytes > (double)max_uintx) { // larger than size_t | |
| 877 adjusted_max_promo_bytes = (double)max_uintx; | |
| 878 } | |
| 879 bool result = (max_contiguous_available() >= (size_t)adjusted_max_promo_bytes); | |
| 880 | |
| 881 if (younger_handles_promotion_failure && !result) { | |
| 882 // Full promotion is not guaranteed because fragmentation | |
| 883 // of the cms generation can prevent the full promotion. | |
| 884 result = (max_available() >= (size_t)adjusted_max_promo_bytes); | |
| 885 | |
| 886 if (!result) { | |
| 887 // With promotion failure handling the test for the ability | |
| 888 // to support the promotion does not have to be guaranteed. | |
| 889 // Use an average of the amount promoted. | |
| 890 result = max_available() >= (size_t) | |
| 891 gc_stats()->avg_promoted()->padded_average(); | |
| 892 if (PrintGC && Verbose && result) { | |
| 893 gclog_or_tty->print_cr( | |
| 894 "\nConcurrentMarkSweepGeneration::promotion_attempt_is_safe" | |
| 895 " max_available: " SIZE_FORMAT | |
| 896 " avg_promoted: " SIZE_FORMAT, | |
| 897 max_available(), (size_t) | |
| 898 gc_stats()->avg_promoted()->padded_average()); | |
| 899 } | |
| 900 } else { | |
| 901 if (PrintGC && Verbose) { | |
| 902 gclog_or_tty->print_cr( | |
| 903 "\nConcurrentMarkSweepGeneration::promotion_attempt_is_safe" | |
| 904 " max_available: " SIZE_FORMAT | |
| 905 " adj_max_promo_bytes: " SIZE_FORMAT, | |
| 906 max_available(), (size_t)adjusted_max_promo_bytes); | |
| 907 } | |
| 908 } | |
| 909 } else { | |
| 910 if (PrintGC && Verbose) { | |
| 911 gclog_or_tty->print_cr( | |
| 912 "\nConcurrentMarkSweepGeneration::promotion_attempt_is_safe" | |
| 913 " contiguous_available: " SIZE_FORMAT | |
| 914 " adj_max_promo_bytes: " SIZE_FORMAT, | |
| 915 max_contiguous_available(), (size_t)adjusted_max_promo_bytes); | |
| 916 } | |
| 917 } | |
| 918 return result; | |
| 919 } | |
| 920 | |
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921 // At a promotion failure dump information on block layout in heap |
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922 // (cms old generation). |
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923 void ConcurrentMarkSweepGeneration::promotion_failure_occurred() { |
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924 if (CMSDumpAtPromotionFailure) { |
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925 cmsSpace()->dump_at_safepoint_with_locks(collector(), gclog_or_tty); |
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926 } |
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927 } |
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928 |
| 0 | 929 CompactibleSpace* |
| 930 ConcurrentMarkSweepGeneration::first_compaction_space() const { | |
| 931 return _cmsSpace; | |
| 932 } | |
| 933 | |
| 934 void ConcurrentMarkSweepGeneration::reset_after_compaction() { | |
| 935 // Clear the promotion information. These pointers can be adjusted | |
| 936 // along with all the other pointers into the heap but | |
| 937 // compaction is expected to be a rare event with | |
| 938 // a heap using cms so don't do it without seeing the need. | |
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939 if (CollectedHeap::use_parallel_gc_threads()) { |
| 0 | 940 for (uint i = 0; i < ParallelGCThreads; i++) { |
| 941 _par_gc_thread_states[i]->promo.reset(); | |
| 942 } | |
| 943 } | |
| 944 } | |
| 945 | |
| 946 void ConcurrentMarkSweepGeneration::space_iterate(SpaceClosure* blk, bool usedOnly) { | |
| 947 blk->do_space(_cmsSpace); | |
| 948 } | |
| 949 | |
| 950 void ConcurrentMarkSweepGeneration::compute_new_size() { | |
| 951 assert_locked_or_safepoint(Heap_lock); | |
| 952 | |
| 953 // If incremental collection failed, we just want to expand | |
| 954 // to the limit. | |
| 955 if (incremental_collection_failed()) { | |
| 956 clear_incremental_collection_failed(); | |
| 957 grow_to_reserved(); | |
| 958 return; | |
| 959 } | |
| 960 | |
| 961 size_t expand_bytes = 0; | |
| 962 double free_percentage = ((double) free()) / capacity(); | |
| 963 double desired_free_percentage = (double) MinHeapFreeRatio / 100; | |
| 964 double maximum_free_percentage = (double) MaxHeapFreeRatio / 100; | |
| 965 | |
| 966 // compute expansion delta needed for reaching desired free percentage | |
| 967 if (free_percentage < desired_free_percentage) { | |
| 968 size_t desired_capacity = (size_t)(used() / ((double) 1 - desired_free_percentage)); | |
| 969 assert(desired_capacity >= capacity(), "invalid expansion size"); | |
| 970 expand_bytes = MAX2(desired_capacity - capacity(), MinHeapDeltaBytes); | |
| 971 } | |
| 972 if (expand_bytes > 0) { | |
| 973 if (PrintGCDetails && Verbose) { | |
| 974 size_t desired_capacity = (size_t)(used() / ((double) 1 - desired_free_percentage)); | |
| 975 gclog_or_tty->print_cr("\nFrom compute_new_size: "); | |
| 976 gclog_or_tty->print_cr(" Free fraction %f", free_percentage); | |
| 977 gclog_or_tty->print_cr(" Desired free fraction %f", | |
| 978 desired_free_percentage); | |
| 979 gclog_or_tty->print_cr(" Maximum free fraction %f", | |
| 980 maximum_free_percentage); | |
| 981 gclog_or_tty->print_cr(" Capactiy "SIZE_FORMAT, capacity()/1000); | |
| 982 gclog_or_tty->print_cr(" Desired capacity "SIZE_FORMAT, | |
| 983 desired_capacity/1000); | |
| 984 int prev_level = level() - 1; | |
| 985 if (prev_level >= 0) { | |
| 986 size_t prev_size = 0; | |
| 987 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 988 Generation* prev_gen = gch->_gens[prev_level]; | |
| 989 prev_size = prev_gen->capacity(); | |
| 990 gclog_or_tty->print_cr(" Younger gen size "SIZE_FORMAT, | |
| 991 prev_size/1000); | |
| 992 } | |
| 993 gclog_or_tty->print_cr(" unsafe_max_alloc_nogc "SIZE_FORMAT, | |
| 994 unsafe_max_alloc_nogc()/1000); | |
| 995 gclog_or_tty->print_cr(" contiguous available "SIZE_FORMAT, | |
| 996 contiguous_available()/1000); | |
| 997 gclog_or_tty->print_cr(" Expand by "SIZE_FORMAT" (bytes)", | |
| 998 expand_bytes); | |
| 999 } | |
| 1000 // safe if expansion fails | |
| 1001 expand(expand_bytes, 0, CMSExpansionCause::_satisfy_free_ratio); | |
| 1002 if (PrintGCDetails && Verbose) { | |
| 1003 gclog_or_tty->print_cr(" Expanded free fraction %f", | |
| 1004 ((double) free()) / capacity()); | |
| 1005 } | |
| 1006 } | |
| 1007 } | |
| 1008 | |
| 1009 Mutex* ConcurrentMarkSweepGeneration::freelistLock() const { | |
| 1010 return cmsSpace()->freelistLock(); | |
| 1011 } | |
| 1012 | |
| 1013 HeapWord* ConcurrentMarkSweepGeneration::allocate(size_t size, | |
| 1014 bool tlab) { | |
| 1015 CMSSynchronousYieldRequest yr; | |
| 1016 MutexLockerEx x(freelistLock(), | |
| 1017 Mutex::_no_safepoint_check_flag); | |
| 1018 return have_lock_and_allocate(size, tlab); | |
| 1019 } | |
| 1020 | |
| 1021 HeapWord* ConcurrentMarkSweepGeneration::have_lock_and_allocate(size_t size, | |
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1022 bool tlab /* ignored */) { |
| 0 | 1023 assert_lock_strong(freelistLock()); |
| 1024 size_t adjustedSize = CompactibleFreeListSpace::adjustObjectSize(size); | |
| 1025 HeapWord* res = cmsSpace()->allocate(adjustedSize); | |
| 1026 // Allocate the object live (grey) if the background collector has | |
| 1027 // started marking. This is necessary because the marker may | |
| 1028 // have passed this address and consequently this object will | |
| 1029 // not otherwise be greyed and would be incorrectly swept up. | |
| 1030 // Note that if this object contains references, the writing | |
| 1031 // of those references will dirty the card containing this object | |
| 1032 // allowing the object to be blackened (and its references scanned) | |
| 1033 // either during a preclean phase or at the final checkpoint. | |
| 1034 if (res != NULL) { | |
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1035 // We may block here with an uninitialized object with |
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1036 // its mark-bit or P-bits not yet set. Such objects need |
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1037 // to be safely navigable by block_start(). |
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1038 assert(oop(res)->klass_or_null() == NULL, "Object should be uninitialized here."); |
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1039 assert(!((FreeChunk*)res)->isFree(), "Error, block will look free but show wrong size"); |
| 0 | 1040 collector()->direct_allocated(res, adjustedSize); |
| 1041 _direct_allocated_words += adjustedSize; | |
| 1042 // allocation counters | |
| 1043 NOT_PRODUCT( | |
| 1044 _numObjectsAllocated++; | |
| 1045 _numWordsAllocated += (int)adjustedSize; | |
| 1046 ) | |
| 1047 } | |
| 1048 return res; | |
| 1049 } | |
| 1050 | |
| 1051 // In the case of direct allocation by mutators in a generation that | |
| 1052 // is being concurrently collected, the object must be allocated | |
| 1053 // live (grey) if the background collector has started marking. | |
| 1054 // This is necessary because the marker may | |
| 1055 // have passed this address and consequently this object will | |
| 1056 // not otherwise be greyed and would be incorrectly swept up. | |
| 1057 // Note that if this object contains references, the writing | |
| 1058 // of those references will dirty the card containing this object | |
| 1059 // allowing the object to be blackened (and its references scanned) | |
| 1060 // either during a preclean phase or at the final checkpoint. | |
| 1061 void CMSCollector::direct_allocated(HeapWord* start, size_t size) { | |
| 1062 assert(_markBitMap.covers(start, size), "Out of bounds"); | |
| 1063 if (_collectorState >= Marking) { | |
| 1064 MutexLockerEx y(_markBitMap.lock(), | |
| 1065 Mutex::_no_safepoint_check_flag); | |
| 1066 // [see comments preceding SweepClosure::do_blk() below for details] | |
| 1067 // 1. need to mark the object as live so it isn't collected | |
| 1068 // 2. need to mark the 2nd bit to indicate the object may be uninitialized | |
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1069 // 3. need to mark the end of the object so marking, precleaning or sweeping |
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1070 // can skip over uninitialized or unparsable objects. An allocated |
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1071 // object is considered uninitialized for our purposes as long as |
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1072 // its klass word is NULL. (Unparsable objects are those which are |
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1073 // initialized in the sense just described, but whose sizes can still |
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1074 // not be correctly determined. Note that the class of unparsable objects |
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1075 // can only occur in the perm gen. All old gen objects are parsable |
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1076 // as soon as they are initialized.) |
| 0 | 1077 _markBitMap.mark(start); // object is live |
| 1078 _markBitMap.mark(start + 1); // object is potentially uninitialized? | |
| 1079 _markBitMap.mark(start + size - 1); | |
| 1080 // mark end of object | |
| 1081 } | |
| 1082 // check that oop looks uninitialized | |
| 187 | 1083 assert(oop(start)->klass_or_null() == NULL, "_klass should be NULL"); |
| 0 | 1084 } |
| 1085 | |
| 1086 void CMSCollector::promoted(bool par, HeapWord* start, | |
| 1087 bool is_obj_array, size_t obj_size) { | |
| 1088 assert(_markBitMap.covers(start), "Out of bounds"); | |
| 1089 // See comment in direct_allocated() about when objects should | |
| 1090 // be allocated live. | |
| 1091 if (_collectorState >= Marking) { | |
| 1092 // we already hold the marking bit map lock, taken in | |
| 1093 // the prologue | |
| 1094 if (par) { | |
| 1095 _markBitMap.par_mark(start); | |
| 1096 } else { | |
| 1097 _markBitMap.mark(start); | |
| 1098 } | |
| 1099 // We don't need to mark the object as uninitialized (as | |
| 1100 // in direct_allocated above) because this is being done with the | |
| 1101 // world stopped and the object will be initialized by the | |
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1102 // time the marking, precleaning or sweeping get to look at it. |
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1103 // But see the code for copying objects into the CMS generation, |
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1104 // where we need to ensure that concurrent readers of the |
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1105 // block offset table are able to safely navigate a block that |
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1106 // is in flux from being free to being allocated (and in |
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1107 // transition while being copied into) and subsequently |
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1108 // becoming a bona-fide object when the copy/promotion is complete. |
| 0 | 1109 assert(SafepointSynchronize::is_at_safepoint(), |
| 1110 "expect promotion only at safepoints"); | |
| 1111 | |
| 1112 if (_collectorState < Sweeping) { | |
| 1113 // Mark the appropriate cards in the modUnionTable, so that | |
| 1114 // this object gets scanned before the sweep. If this is | |
| 1115 // not done, CMS generation references in the object might | |
| 1116 // not get marked. | |
| 1117 // For the case of arrays, which are otherwise precisely | |
| 1118 // marked, we need to dirty the entire array, not just its head. | |
| 1119 if (is_obj_array) { | |
| 1120 // The [par_]mark_range() method expects mr.end() below to | |
| 1121 // be aligned to the granularity of a bit's representation | |
| 1122 // in the heap. In the case of the MUT below, that's a | |
| 1123 // card size. | |
| 1124 MemRegion mr(start, | |
| 1125 (HeapWord*)round_to((intptr_t)(start + obj_size), | |
| 1126 CardTableModRefBS::card_size /* bytes */)); | |
| 1127 if (par) { | |
| 1128 _modUnionTable.par_mark_range(mr); | |
| 1129 } else { | |
| 1130 _modUnionTable.mark_range(mr); | |
| 1131 } | |
| 1132 } else { // not an obj array; we can just mark the head | |
| 1133 if (par) { | |
| 1134 _modUnionTable.par_mark(start); | |
| 1135 } else { | |
| 1136 _modUnionTable.mark(start); | |
| 1137 } | |
| 1138 } | |
| 1139 } | |
| 1140 } | |
| 1141 } | |
| 1142 | |
| 1143 static inline size_t percent_of_space(Space* space, HeapWord* addr) | |
| 1144 { | |
| 1145 size_t delta = pointer_delta(addr, space->bottom()); | |
| 1146 return (size_t)(delta * 100.0 / (space->capacity() / HeapWordSize)); | |
| 1147 } | |
| 1148 | |
| 1149 void CMSCollector::icms_update_allocation_limits() | |
| 1150 { | |
| 1151 Generation* gen0 = GenCollectedHeap::heap()->get_gen(0); | |
| 1152 EdenSpace* eden = gen0->as_DefNewGeneration()->eden(); | |
| 1153 | |
| 1154 const unsigned int duty_cycle = stats().icms_update_duty_cycle(); | |
| 1155 if (CMSTraceIncrementalPacing) { | |
| 1156 stats().print(); | |
| 1157 } | |
| 1158 | |
| 1159 assert(duty_cycle <= 100, "invalid duty cycle"); | |
| 1160 if (duty_cycle != 0) { | |
| 1161 // The duty_cycle is a percentage between 0 and 100; convert to words and | |
| 1162 // then compute the offset from the endpoints of the space. | |
| 1163 size_t free_words = eden->free() / HeapWordSize; | |
| 1164 double free_words_dbl = (double)free_words; | |
| 1165 size_t duty_cycle_words = (size_t)(free_words_dbl * duty_cycle / 100.0); | |
| 1166 size_t offset_words = (free_words - duty_cycle_words) / 2; | |
| 1167 | |
| 1168 _icms_start_limit = eden->top() + offset_words; | |
| 1169 _icms_stop_limit = eden->end() - offset_words; | |
| 1170 | |
| 1171 // The limits may be adjusted (shifted to the right) by | |
| 1172 // CMSIncrementalOffset, to allow the application more mutator time after a | |
| 1173 // young gen gc (when all mutators were stopped) and before CMS starts and | |
| 1174 // takes away one or more cpus. | |
| 1175 if (CMSIncrementalOffset != 0) { | |
| 1176 double adjustment_dbl = free_words_dbl * CMSIncrementalOffset / 100.0; | |
| 1177 size_t adjustment = (size_t)adjustment_dbl; | |
| 1178 HeapWord* tmp_stop = _icms_stop_limit + adjustment; | |
| 1179 if (tmp_stop > _icms_stop_limit && tmp_stop < eden->end()) { | |
| 1180 _icms_start_limit += adjustment; | |
| 1181 _icms_stop_limit = tmp_stop; | |
| 1182 } | |
| 1183 } | |
| 1184 } | |
| 1185 if (duty_cycle == 0 || (_icms_start_limit == _icms_stop_limit)) { | |
| 1186 _icms_start_limit = _icms_stop_limit = eden->end(); | |
| 1187 } | |
| 1188 | |
| 1189 // Install the new start limit. | |
| 1190 eden->set_soft_end(_icms_start_limit); | |
| 1191 | |
| 1192 if (CMSTraceIncrementalMode) { | |
| 1193 gclog_or_tty->print(" icms alloc limits: " | |
| 1194 PTR_FORMAT "," PTR_FORMAT | |
| 1195 " (" SIZE_FORMAT "%%," SIZE_FORMAT "%%) ", | |
| 1196 _icms_start_limit, _icms_stop_limit, | |
| 1197 percent_of_space(eden, _icms_start_limit), | |
| 1198 percent_of_space(eden, _icms_stop_limit)); | |
| 1199 if (Verbose) { | |
| 1200 gclog_or_tty->print("eden: "); | |
| 1201 eden->print_on(gclog_or_tty); | |
| 1202 } | |
| 1203 } | |
| 1204 } | |
| 1205 | |
| 1206 // Any changes here should try to maintain the invariant | |
| 1207 // that if this method is called with _icms_start_limit | |
| 1208 // and _icms_stop_limit both NULL, then it should return NULL | |
| 1209 // and not notify the icms thread. | |
| 1210 HeapWord* | |
| 1211 CMSCollector::allocation_limit_reached(Space* space, HeapWord* top, | |
| 1212 size_t word_size) | |
| 1213 { | |
| 1214 // A start_limit equal to end() means the duty cycle is 0, so treat that as a | |
| 1215 // nop. | |
| 1216 if (CMSIncrementalMode && _icms_start_limit != space->end()) { | |
| 1217 if (top <= _icms_start_limit) { | |
| 1218 if (CMSTraceIncrementalMode) { | |
| 1219 space->print_on(gclog_or_tty); | |
| 1220 gclog_or_tty->stamp(); | |
| 1221 gclog_or_tty->print_cr(" start limit top=" PTR_FORMAT | |
| 1222 ", new limit=" PTR_FORMAT | |
| 1223 " (" SIZE_FORMAT "%%)", | |
| 1224 top, _icms_stop_limit, | |
| 1225 percent_of_space(space, _icms_stop_limit)); | |
| 1226 } | |
| 1227 ConcurrentMarkSweepThread::start_icms(); | |
| 1228 assert(top < _icms_stop_limit, "Tautology"); | |
| 1229 if (word_size < pointer_delta(_icms_stop_limit, top)) { | |
| 1230 return _icms_stop_limit; | |
| 1231 } | |
| 1232 | |
| 1233 // The allocation will cross both the _start and _stop limits, so do the | |
| 1234 // stop notification also and return end(). | |
| 1235 if (CMSTraceIncrementalMode) { | |
| 1236 space->print_on(gclog_or_tty); | |
| 1237 gclog_or_tty->stamp(); | |
| 1238 gclog_or_tty->print_cr(" +stop limit top=" PTR_FORMAT | |
| 1239 ", new limit=" PTR_FORMAT | |
| 1240 " (" SIZE_FORMAT "%%)", | |
| 1241 top, space->end(), | |
| 1242 percent_of_space(space, space->end())); | |
| 1243 } | |
| 1244 ConcurrentMarkSweepThread::stop_icms(); | |
| 1245 return space->end(); | |
| 1246 } | |
| 1247 | |
| 1248 if (top <= _icms_stop_limit) { | |
| 1249 if (CMSTraceIncrementalMode) { | |
| 1250 space->print_on(gclog_or_tty); | |
| 1251 gclog_or_tty->stamp(); | |
| 1252 gclog_or_tty->print_cr(" stop limit top=" PTR_FORMAT | |
| 1253 ", new limit=" PTR_FORMAT | |
| 1254 " (" SIZE_FORMAT "%%)", | |
| 1255 top, space->end(), | |
| 1256 percent_of_space(space, space->end())); | |
| 1257 } | |
| 1258 ConcurrentMarkSweepThread::stop_icms(); | |
| 1259 return space->end(); | |
| 1260 } | |
| 1261 | |
| 1262 if (CMSTraceIncrementalMode) { | |
| 1263 space->print_on(gclog_or_tty); | |
| 1264 gclog_or_tty->stamp(); | |
| 1265 gclog_or_tty->print_cr(" end limit top=" PTR_FORMAT | |
| 1266 ", new limit=" PTR_FORMAT, | |
| 1267 top, NULL); | |
| 1268 } | |
| 1269 } | |
| 1270 | |
| 1271 return NULL; | |
| 1272 } | |
| 1273 | |
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1274 oop ConcurrentMarkSweepGeneration::promote(oop obj, size_t obj_size) { |
| 0 | 1275 assert(obj_size == (size_t)obj->size(), "bad obj_size passed in"); |
| 1276 // allocate, copy and if necessary update promoinfo -- | |
| 1277 // delegate to underlying space. | |
| 1278 assert_lock_strong(freelistLock()); | |
| 1279 | |
| 1280 #ifndef PRODUCT | |
| 1281 if (Universe::heap()->promotion_should_fail()) { | |
| 1282 return NULL; | |
| 1283 } | |
| 1284 #endif // #ifndef PRODUCT | |
| 1285 | |
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1286 oop res = _cmsSpace->promote(obj, obj_size); |
| 0 | 1287 if (res == NULL) { |
| 1288 // expand and retry | |
| 1289 size_t s = _cmsSpace->expansionSpaceRequired(obj_size); // HeapWords | |
| 1290 expand(s*HeapWordSize, MinHeapDeltaBytes, | |
| 1291 CMSExpansionCause::_satisfy_promotion); | |
| 1292 // Since there's currently no next generation, we don't try to promote | |
| 1293 // into a more senior generation. | |
| 1294 assert(next_gen() == NULL, "assumption, based upon which no attempt " | |
| 1295 "is made to pass on a possibly failing " | |
| 1296 "promotion to next generation"); | |
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1297 res = _cmsSpace->promote(obj, obj_size); |
| 0 | 1298 } |
| 1299 if (res != NULL) { | |
| 1300 // See comment in allocate() about when objects should | |
| 1301 // be allocated live. | |
| 1302 assert(obj->is_oop(), "Will dereference klass pointer below"); | |
| 1303 collector()->promoted(false, // Not parallel | |
| 1304 (HeapWord*)res, obj->is_objArray(), obj_size); | |
| 1305 // promotion counters | |
| 1306 NOT_PRODUCT( | |
| 1307 _numObjectsPromoted++; | |
| 1308 _numWordsPromoted += | |
| 1309 (int)(CompactibleFreeListSpace::adjustObjectSize(obj->size())); | |
| 1310 ) | |
| 1311 } | |
| 1312 return res; | |
| 1313 } | |
| 1314 | |
| 1315 | |
| 1316 HeapWord* | |
| 1317 ConcurrentMarkSweepGeneration::allocation_limit_reached(Space* space, | |
| 1318 HeapWord* top, | |
| 1319 size_t word_sz) | |
| 1320 { | |
| 1321 return collector()->allocation_limit_reached(space, top, word_sz); | |
| 1322 } | |
| 1323 | |
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1324 // IMPORTANT: Notes on object size recognition in CMS. |
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1325 // --------------------------------------------------- |
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1326 // A block of storage in the CMS generation is always in |
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1327 // one of three states. A free block (FREE), an allocated |
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1328 // object (OBJECT) whose size() method reports the correct size, |
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1329 // and an intermediate state (TRANSIENT) in which its size cannot |
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1330 // be accurately determined. |
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1331 // STATE IDENTIFICATION: (32 bit and 64 bit w/o COOPS) |
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1332 // ----------------------------------------------------- |
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1333 // FREE: klass_word & 1 == 1; mark_word holds block size |
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1334 // |
|
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1335 // OBJECT: klass_word installed; klass_word != 0 && klass_word & 1 == 0; |
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1336 // obj->size() computes correct size |
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1337 // [Perm Gen objects needs to be "parsable" before they can be navigated] |
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1338 // |
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1339 // TRANSIENT: klass_word == 0; size is indeterminate until we become an OBJECT |
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1340 // |
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1341 // STATE IDENTIFICATION: (64 bit+COOPS) |
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1342 // ------------------------------------ |
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1343 // FREE: mark_word & CMS_FREE_BIT == 1; mark_word & ~CMS_FREE_BIT gives block_size |
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1344 // |
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1345 // OBJECT: klass_word installed; klass_word != 0; |
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1346 // obj->size() computes correct size |
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1347 // [Perm Gen comment above continues to hold] |
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1348 // |
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1349 // TRANSIENT: klass_word == 0; size is indeterminate until we become an OBJECT |
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1350 // |
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1351 // |
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1352 // STATE TRANSITION DIAGRAM |
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1353 // |
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1354 // mut / parnew mut / parnew |
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1355 // FREE --------------------> TRANSIENT ---------------------> OBJECT --| |
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1356 // ^ | |
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1357 // |------------------------ DEAD <------------------------------------| |
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1358 // sweep mut |
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1359 // |
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1360 // While a block is in TRANSIENT state its size cannot be determined |
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1361 // so readers will either need to come back later or stall until |
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1362 // the size can be determined. Note that for the case of direct |
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1363 // allocation, P-bits, when available, may be used to determine the |
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1364 // size of an object that may not yet have been initialized. |
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1365 |
| 0 | 1366 // Things to support parallel young-gen collection. |
| 1367 oop | |
| 1368 ConcurrentMarkSweepGeneration::par_promote(int thread_num, | |
| 1369 oop old, markOop m, | |
| 1370 size_t word_sz) { | |
| 1371 #ifndef PRODUCT | |
| 1372 if (Universe::heap()->promotion_should_fail()) { | |
| 1373 return NULL; | |
| 1374 } | |
| 1375 #endif // #ifndef PRODUCT | |
| 1376 | |
| 1377 CMSParGCThreadState* ps = _par_gc_thread_states[thread_num]; | |
| 1378 PromotionInfo* promoInfo = &ps->promo; | |
| 1379 // if we are tracking promotions, then first ensure space for | |
| 1380 // promotion (including spooling space for saving header if necessary). | |
| 1381 // then allocate and copy, then track promoted info if needed. | |
| 1382 // When tracking (see PromotionInfo::track()), the mark word may | |
| 1383 // be displaced and in this case restoration of the mark word | |
| 1384 // occurs in the (oop_since_save_marks_)iterate phase. | |
| 1385 if (promoInfo->tracking() && !promoInfo->ensure_spooling_space()) { | |
| 1386 // Out of space for allocating spooling buffers; | |
| 1387 // try expanding and allocating spooling buffers. | |
| 1388 if (!expand_and_ensure_spooling_space(promoInfo)) { | |
| 1389 return NULL; | |
| 1390 } | |
| 1391 } | |
| 1392 assert(promoInfo->has_spooling_space(), "Control point invariant"); | |
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1393 const size_t alloc_sz = CompactibleFreeListSpace::adjustObjectSize(word_sz); |
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1394 HeapWord* obj_ptr = ps->lab.alloc(alloc_sz); |
| 0 | 1395 if (obj_ptr == NULL) { |
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1396 obj_ptr = expand_and_par_lab_allocate(ps, alloc_sz); |
| 0 | 1397 if (obj_ptr == NULL) { |
| 1398 return NULL; | |
| 1399 } | |
| 1400 } | |
| 1401 oop obj = oop(obj_ptr); | |
|
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1402 OrderAccess::storestore(); |
| 187 | 1403 assert(obj->klass_or_null() == NULL, "Object should be uninitialized here."); |
|
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1404 assert(!((FreeChunk*)obj_ptr)->isFree(), "Error, block will look free but show wrong size"); |
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1405 // IMPORTANT: See note on object initialization for CMS above. |
| 0 | 1406 // Otherwise, copy the object. Here we must be careful to insert the |
| 1407 // klass pointer last, since this marks the block as an allocated object. | |
| 187 | 1408 // Except with compressed oops it's the mark word. |
| 0 | 1409 HeapWord* old_ptr = (HeapWord*)old; |
|
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1410 // Restore the mark word copied above. |
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1411 obj->set_mark(m); |
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1412 assert(obj->klass_or_null() == NULL, "Object should be uninitialized here."); |
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1413 assert(!((FreeChunk*)obj_ptr)->isFree(), "Error, block will look free but show wrong size"); |
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1414 OrderAccess::storestore(); |
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1415 |
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1416 if (UseCompressedOops) { |
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1417 // Copy gap missed by (aligned) header size calculation below |
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1418 obj->set_klass_gap(old->klass_gap()); |
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1419 } |
| 0 | 1420 if (word_sz > (size_t)oopDesc::header_size()) { |
| 1421 Copy::aligned_disjoint_words(old_ptr + oopDesc::header_size(), | |
| 1422 obj_ptr + oopDesc::header_size(), | |
| 1423 word_sz - oopDesc::header_size()); | |
| 1424 } | |
| 187 | 1425 |
| 0 | 1426 // Now we can track the promoted object, if necessary. We take care |
| 1521 | 1427 // to delay the transition from uninitialized to full object |
| 0 | 1428 // (i.e., insertion of klass pointer) until after, so that it |
| 1429 // atomically becomes a promoted object. | |
| 1430 if (promoInfo->tracking()) { | |
| 1431 promoInfo->track((PromotedObject*)obj, old->klass()); | |
| 1432 } | |
|
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1433 assert(obj->klass_or_null() == NULL, "Object should be uninitialized here."); |
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1434 assert(!((FreeChunk*)obj_ptr)->isFree(), "Error, block will look free but show wrong size"); |
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1435 assert(old->is_oop(), "Will use and dereference old klass ptr below"); |
| 187 | 1436 |
| 1437 // Finally, install the klass pointer (this should be volatile). | |
|
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1438 OrderAccess::storestore(); |
| 0 | 1439 obj->set_klass(old->klass()); |
|
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1440 // We should now be able to calculate the right size for this object |
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1441 assert(obj->is_oop() && obj->size() == (int)word_sz, "Error, incorrect size computed for promoted object"); |
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1442 |
| 0 | 1443 collector()->promoted(true, // parallel |
| 1444 obj_ptr, old->is_objArray(), word_sz); | |
| 1445 | |
| 1446 NOT_PRODUCT( | |
|
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1447 Atomic::inc_ptr(&_numObjectsPromoted); |
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1448 Atomic::add_ptr(alloc_sz, &_numWordsPromoted); |
| 0 | 1449 ) |
| 1450 | |
| 1451 return obj; | |
| 1452 } | |
| 1453 | |
| 1454 void | |
| 1455 ConcurrentMarkSweepGeneration:: | |
| 1456 par_promote_alloc_undo(int thread_num, | |
| 1457 HeapWord* obj, size_t word_sz) { | |
| 1458 // CMS does not support promotion undo. | |
| 1459 ShouldNotReachHere(); | |
| 1460 } | |
| 1461 | |
| 1462 void | |
| 1463 ConcurrentMarkSweepGeneration:: | |
| 1464 par_promote_alloc_done(int thread_num) { | |
| 1465 CMSParGCThreadState* ps = _par_gc_thread_states[thread_num]; | |
|
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|
1466 ps->lab.retire(thread_num); |
| 0 | 1467 } |
| 1468 | |
| 1469 void | |
| 1470 ConcurrentMarkSweepGeneration:: | |
| 1471 par_oop_since_save_marks_iterate_done(int thread_num) { | |
| 1472 CMSParGCThreadState* ps = _par_gc_thread_states[thread_num]; | |
| 1473 ParScanWithoutBarrierClosure* dummy_cl = NULL; | |
| 1474 ps->promo.promoted_oops_iterate_nv(dummy_cl); | |
| 1475 } | |
| 1476 | |
| 1477 // XXXPERM | |
| 1478 bool ConcurrentMarkSweepGeneration::should_collect(bool full, | |
| 1479 size_t size, | |
| 1480 bool tlab) | |
| 1481 { | |
| 1482 // We allow a STW collection only if a full | |
| 1483 // collection was requested. | |
| 1484 return full || should_allocate(size, tlab); // FIX ME !!! | |
| 1485 // This and promotion failure handling are connected at the | |
| 1486 // hip and should be fixed by untying them. | |
| 1487 } | |
| 1488 | |
| 1489 bool CMSCollector::shouldConcurrentCollect() { | |
| 1490 if (_full_gc_requested) { | |
| 1491 if (Verbose && PrintGCDetails) { | |
| 1492 gclog_or_tty->print_cr("CMSCollector: collect because of explicit " | |
|
1520
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|
1493 " gc request (or gc_locker)"); |
| 0 | 1494 } |
| 1495 return true; | |
| 1496 } | |
| 1497 | |
| 1498 // For debugging purposes, change the type of collection. | |
| 1499 // If the rotation is not on the concurrent collection | |
| 1500 // type, don't start a concurrent collection. | |
| 1501 NOT_PRODUCT( | |
| 1502 if (RotateCMSCollectionTypes && | |
| 1503 (_cmsGen->debug_collection_type() != | |
| 1504 ConcurrentMarkSweepGeneration::Concurrent_collection_type)) { | |
| 1505 assert(_cmsGen->debug_collection_type() != | |
| 1506 ConcurrentMarkSweepGeneration::Unknown_collection_type, | |
| 1507 "Bad cms collection type"); | |
| 1508 return false; | |
| 1509 } | |
| 1510 ) | |
| 1511 | |
| 1512 FreelistLocker x(this); | |
| 1513 // ------------------------------------------------------------------ | |
| 1514 // Print out lots of information which affects the initiation of | |
| 1515 // a collection. | |
| 1516 if (PrintCMSInitiationStatistics && stats().valid()) { | |
| 1517 gclog_or_tty->print("CMSCollector shouldConcurrentCollect: "); | |
| 1518 gclog_or_tty->stamp(); | |
| 1519 gclog_or_tty->print_cr(""); | |
| 1520 stats().print_on(gclog_or_tty); | |
| 1521 gclog_or_tty->print_cr("time_until_cms_gen_full %3.7f", | |
| 1522 stats().time_until_cms_gen_full()); | |
| 1523 gclog_or_tty->print_cr("free="SIZE_FORMAT, _cmsGen->free()); | |
| 1524 gclog_or_tty->print_cr("contiguous_available="SIZE_FORMAT, | |
| 1525 _cmsGen->contiguous_available()); | |
| 1526 gclog_or_tty->print_cr("promotion_rate=%g", stats().promotion_rate()); | |
| 1527 gclog_or_tty->print_cr("cms_allocation_rate=%g", stats().cms_allocation_rate()); | |
| 1528 gclog_or_tty->print_cr("occupancy=%3.7f", _cmsGen->occupancy()); | |
|
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|
1529 gclog_or_tty->print_cr("initiatingOccupancy=%3.7f", _cmsGen->initiating_occupancy()); |
|
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1530 gclog_or_tty->print_cr("initiatingPermOccupancy=%3.7f", _permGen->initiating_occupancy()); |
| 0 | 1531 } |
| 1532 // ------------------------------------------------------------------ | |
| 1533 | |
| 1534 // If the estimated time to complete a cms collection (cms_duration()) | |
| 1535 // is less than the estimated time remaining until the cms generation | |
| 1536 // is full, start a collection. | |
| 1537 if (!UseCMSInitiatingOccupancyOnly) { | |
| 1538 if (stats().valid()) { | |
| 1539 if (stats().time_until_cms_start() == 0.0) { | |
| 1540 return true; | |
| 1541 } | |
| 1542 } else { | |
| 1543 // We want to conservatively collect somewhat early in order | |
| 1544 // to try and "bootstrap" our CMS/promotion statistics; | |
| 1545 // this branch will not fire after the first successful CMS | |
| 1546 // collection because the stats should then be valid. | |
| 1547 if (_cmsGen->occupancy() >= _bootstrap_occupancy) { | |
| 1548 if (Verbose && PrintGCDetails) { | |
| 1549 gclog_or_tty->print_cr( | |
| 1550 " CMSCollector: collect for bootstrapping statistics:" | |
| 1551 " occupancy = %f, boot occupancy = %f", _cmsGen->occupancy(), | |
| 1552 _bootstrap_occupancy); | |
| 1553 } | |
| 1554 return true; | |
| 1555 } | |
| 1556 } | |
| 1557 } | |
| 1558 | |
| 1559 // Otherwise, we start a collection cycle if either the perm gen or | |
| 1560 // old gen want a collection cycle started. Each may use | |
| 1561 // an appropriate criterion for making this decision. | |
| 1562 // XXX We need to make sure that the gen expansion | |
|
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1563 // criterion dovetails well with this. XXX NEED TO FIX THIS |
|
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|
1564 if (_cmsGen->should_concurrent_collect()) { |
| 0 | 1565 if (Verbose && PrintGCDetails) { |
| 1566 gclog_or_tty->print_cr("CMS old gen initiated"); | |
| 1567 } | |
| 1568 return true; | |
| 1569 } | |
| 1570 | |
|
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1571 // We start a collection if we believe an incremental collection may fail; |
|
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1572 // this is not likely to be productive in practice because it's probably too |
|
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|
1573 // late anyway. |
|
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|
1574 GenCollectedHeap* gch = GenCollectedHeap::heap(); |
|
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1575 assert(gch->collector_policy()->is_two_generation_policy(), |
|
0834225a7916
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1576 "You may want to check the correctness of the following"); |
|
0834225a7916
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|
1577 if (gch->incremental_collection_will_fail()) { |
|
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1578 if (PrintGCDetails && Verbose) { |
|
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|
1579 gclog_or_tty->print("CMSCollector: collect because incremental collection will fail "); |
| 0 | 1580 } |
| 1581 return true; | |
| 1582 } | |
| 1583 | |
|
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1584 if (CMSClassUnloadingEnabled && _permGen->should_concurrent_collect()) { |
|
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|
1585 bool res = update_should_unload_classes(); |
|
0834225a7916
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|
1586 if (res) { |
|
0834225a7916
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|
1587 if (Verbose && PrintGCDetails) { |
|
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|
1588 gclog_or_tty->print_cr("CMS perm gen initiated"); |
|
0834225a7916
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|
1589 } |
|
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1590 return true; |
|
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|
1591 } |
|
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|
1592 } |
| 0 | 1593 return false; |
| 1594 } | |
| 1595 | |
| 1596 // Clear _expansion_cause fields of constituent generations | |
| 1597 void CMSCollector::clear_expansion_cause() { | |
| 1598 _cmsGen->clear_expansion_cause(); | |
| 1599 _permGen->clear_expansion_cause(); | |
| 1600 } | |
| 1601 | |
|
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1602 // We should be conservative in starting a collection cycle. To |
|
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|
1603 // start too eagerly runs the risk of collecting too often in the |
|
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|
1604 // extreme. To collect too rarely falls back on full collections, |
|
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|
1605 // which works, even if not optimum in terms of concurrent work. |
|
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|
1606 // As a work around for too eagerly collecting, use the flag |
|
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|
1607 // UseCMSInitiatingOccupancyOnly. This also has the advantage of |
|
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|
1608 // giving the user an easily understandable way of controlling the |
|
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1609 // collections. |
|
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1610 // We want to start a new collection cycle if any of the following |
|
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|
1611 // conditions hold: |
|
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1612 // . our current occupancy exceeds the configured initiating occupancy |
|
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1613 // for this generation, or |
|
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1614 // . we recently needed to expand this space and have not, since that |
|
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1615 // expansion, done a collection of this generation, or |
|
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1616 // . the underlying space believes that it may be a good idea to initiate |
|
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1617 // a concurrent collection (this may be based on criteria such as the |
|
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1618 // following: the space uses linear allocation and linear allocation is |
|
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1619 // going to fail, or there is believed to be excessive fragmentation in |
|
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1620 // the generation, etc... or ... |
|
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1621 // [.(currently done by CMSCollector::shouldConcurrentCollect() only for |
|
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1622 // the case of the old generation, not the perm generation; see CR 6543076): |
|
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|
1623 // we may be approaching a point at which allocation requests may fail because |
|
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1624 // we will be out of sufficient free space given allocation rate estimates.] |
|
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1625 bool ConcurrentMarkSweepGeneration::should_concurrent_collect() const { |
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1626 |
| 0 | 1627 assert_lock_strong(freelistLock()); |
|
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1628 if (occupancy() > initiating_occupancy()) { |
| 0 | 1629 if (PrintGCDetails && Verbose) { |
| 1630 gclog_or_tty->print(" %s: collect because of occupancy %f / %f ", | |
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1631 short_name(), occupancy(), initiating_occupancy()); |
| 0 | 1632 } |
| 1633 return true; | |
| 1634 } | |
| 1635 if (UseCMSInitiatingOccupancyOnly) { | |
| 1636 return false; | |
| 1637 } | |
| 1638 if (expansion_cause() == CMSExpansionCause::_satisfy_allocation) { | |
| 1639 if (PrintGCDetails && Verbose) { | |
| 1640 gclog_or_tty->print(" %s: collect because expanded for allocation ", | |
| 1641 short_name()); | |
| 1642 } | |
| 1643 return true; | |
| 1644 } | |
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1645 if (_cmsSpace->should_concurrent_collect()) { |
| 0 | 1646 if (PrintGCDetails && Verbose) { |
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1647 gclog_or_tty->print(" %s: collect because cmsSpace says so ", |
| 0 | 1648 short_name()); |
| 1649 } | |
| 1650 return true; | |
| 1651 } | |
| 1652 return false; | |
| 1653 } | |
| 1654 | |
| 1655 void ConcurrentMarkSweepGeneration::collect(bool full, | |
| 1656 bool clear_all_soft_refs, | |
| 1657 size_t size, | |
| 1658 bool tlab) | |
| 1659 { | |
| 1660 collector()->collect(full, clear_all_soft_refs, size, tlab); | |
| 1661 } | |
| 1662 | |
| 1663 void CMSCollector::collect(bool full, | |
| 1664 bool clear_all_soft_refs, | |
| 1665 size_t size, | |
| 1666 bool tlab) | |
| 1667 { | |
| 1668 if (!UseCMSCollectionPassing && _collectorState > Idling) { | |
| 1669 // For debugging purposes skip the collection if the state | |
| 1670 // is not currently idle | |
| 1671 if (TraceCMSState) { | |
| 1672 gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " skipped full:%d CMS state %d", | |
| 1673 Thread::current(), full, _collectorState); | |
| 1674 } | |
| 1675 return; | |
| 1676 } | |
| 1677 | |
| 1678 // The following "if" branch is present for defensive reasons. | |
| 1679 // In the current uses of this interface, it can be replaced with: | |
| 1680 // assert(!GC_locker.is_active(), "Can't be called otherwise"); | |
| 1681 // But I am not placing that assert here to allow future | |
| 1682 // generality in invoking this interface. | |
| 1683 if (GC_locker::is_active()) { | |
| 1684 // A consistency test for GC_locker | |
| 1685 assert(GC_locker::needs_gc(), "Should have been set already"); | |
| 1686 // Skip this foreground collection, instead | |
| 1687 // expanding the heap if necessary. | |
| 1688 // Need the free list locks for the call to free() in compute_new_size() | |
| 1689 compute_new_size(); | |
| 1690 return; | |
| 1691 } | |
| 1692 acquire_control_and_collect(full, clear_all_soft_refs); | |
| 1693 _full_gcs_since_conc_gc++; | |
| 1694 | |
| 1695 } | |
| 1696 | |
| 1697 void CMSCollector::request_full_gc(unsigned int full_gc_count) { | |
| 1698 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 1699 unsigned int gc_count = gch->total_full_collections(); | |
| 1700 if (gc_count == full_gc_count) { | |
| 1701 MutexLockerEx y(CGC_lock, Mutex::_no_safepoint_check_flag); | |
| 1702 _full_gc_requested = true; | |
| 1703 CGC_lock->notify(); // nudge CMS thread | |
| 1704 } | |
| 1705 } | |
| 1706 | |
| 1707 | |
| 1708 // The foreground and background collectors need to coordinate in order | |
| 1709 // to make sure that they do not mutually interfere with CMS collections. | |
| 1710 // When a background collection is active, | |
| 1711 // the foreground collector may need to take over (preempt) and | |
| 1712 // synchronously complete an ongoing collection. Depending on the | |
| 1713 // frequency of the background collections and the heap usage | |
| 1714 // of the application, this preemption can be seldom or frequent. | |
| 1715 // There are only certain | |
| 1716 // points in the background collection that the "collection-baton" | |
| 1717 // can be passed to the foreground collector. | |
| 1718 // | |
| 1719 // The foreground collector will wait for the baton before | |
| 1720 // starting any part of the collection. The foreground collector | |
| 1721 // will only wait at one location. | |
| 1722 // | |
| 1723 // The background collector will yield the baton before starting a new | |
| 1724 // phase of the collection (e.g., before initial marking, marking from roots, | |
| 1725 // precleaning, final re-mark, sweep etc.) This is normally done at the head | |
| 1726 // of the loop which switches the phases. The background collector does some | |
| 1727 // of the phases (initial mark, final re-mark) with the world stopped. | |
| 1728 // Because of locking involved in stopping the world, | |
| 1729 // the foreground collector should not block waiting for the background | |
| 1730 // collector when it is doing a stop-the-world phase. The background | |
| 1731 // collector will yield the baton at an additional point just before | |
| 1732 // it enters a stop-the-world phase. Once the world is stopped, the | |
| 1733 // background collector checks the phase of the collection. If the | |
| 1734 // phase has not changed, it proceeds with the collection. If the | |
| 1735 // phase has changed, it skips that phase of the collection. See | |
| 1736 // the comments on the use of the Heap_lock in collect_in_background(). | |
| 1737 // | |
| 1738 // Variable used in baton passing. | |
| 1739 // _foregroundGCIsActive - Set to true by the foreground collector when | |
| 1740 // it wants the baton. The foreground clears it when it has finished | |
| 1741 // the collection. | |
| 1742 // _foregroundGCShouldWait - Set to true by the background collector | |
| 1743 // when it is running. The foreground collector waits while | |
| 1744 // _foregroundGCShouldWait is true. | |
| 1745 // CGC_lock - monitor used to protect access to the above variables | |
| 1746 // and to notify the foreground and background collectors. | |
| 1747 // _collectorState - current state of the CMS collection. | |
| 1748 // | |
| 1749 // The foreground collector | |
| 1750 // acquires the CGC_lock | |
| 1751 // sets _foregroundGCIsActive | |
| 1752 // waits on the CGC_lock for _foregroundGCShouldWait to be false | |
| 1753 // various locks acquired in preparation for the collection | |
| 1754 // are released so as not to block the background collector | |
| 1755 // that is in the midst of a collection | |
| 1756 // proceeds with the collection | |
| 1757 // clears _foregroundGCIsActive | |
| 1758 // returns | |
| 1759 // | |
| 1760 // The background collector in a loop iterating on the phases of the | |
| 1761 // collection | |
| 1762 // acquires the CGC_lock | |
| 1763 // sets _foregroundGCShouldWait | |
| 1764 // if _foregroundGCIsActive is set | |
| 1765 // clears _foregroundGCShouldWait, notifies _CGC_lock | |
| 1766 // waits on _CGC_lock for _foregroundGCIsActive to become false | |
| 1767 // and exits the loop. | |
| 1768 // otherwise | |
| 1769 // proceed with that phase of the collection | |
| 1770 // if the phase is a stop-the-world phase, | |
| 1771 // yield the baton once more just before enqueueing | |
| 1772 // the stop-world CMS operation (executed by the VM thread). | |
| 1773 // returns after all phases of the collection are done | |
| 1774 // | |
| 1775 | |
| 1776 void CMSCollector::acquire_control_and_collect(bool full, | |
| 1777 bool clear_all_soft_refs) { | |
| 1778 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint"); | |
| 1779 assert(!Thread::current()->is_ConcurrentGC_thread(), | |
| 1780 "shouldn't try to acquire control from self!"); | |
| 1781 | |
| 1782 // Start the protocol for acquiring control of the | |
| 1783 // collection from the background collector (aka CMS thread). | |
| 1784 assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(), | |
| 1785 "VM thread should have CMS token"); | |
| 1786 // Remember the possibly interrupted state of an ongoing | |
| 1787 // concurrent collection | |
| 1788 CollectorState first_state = _collectorState; | |
| 1789 | |
| 1790 // Signal to a possibly ongoing concurrent collection that | |
| 1791 // we want to do a foreground collection. | |
| 1792 _foregroundGCIsActive = true; | |
| 1793 | |
| 1794 // Disable incremental mode during a foreground collection. | |
| 1795 ICMSDisabler icms_disabler; | |
| 1796 | |
| 1797 // release locks and wait for a notify from the background collector | |
| 1798 // releasing the locks in only necessary for phases which | |
| 1799 // do yields to improve the granularity of the collection. | |
| 1800 assert_lock_strong(bitMapLock()); | |
| 1801 // We need to lock the Free list lock for the space that we are | |
| 1802 // currently collecting. | |
| 1803 assert(haveFreelistLocks(), "Must be holding free list locks"); | |
| 1804 bitMapLock()->unlock(); | |
| 1805 releaseFreelistLocks(); | |
| 1806 { | |
| 1807 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
| 1808 if (_foregroundGCShouldWait) { | |
| 1809 // We are going to be waiting for action for the CMS thread; | |
| 1810 // it had better not be gone (for instance at shutdown)! | |
| 1811 assert(ConcurrentMarkSweepThread::cmst() != NULL, | |
| 1812 "CMS thread must be running"); | |
| 1813 // Wait here until the background collector gives us the go-ahead | |
| 1814 ConcurrentMarkSweepThread::clear_CMS_flag( | |
| 1815 ConcurrentMarkSweepThread::CMS_vm_has_token); // release token | |
| 1816 // Get a possibly blocked CMS thread going: | |
| 1817 // Note that we set _foregroundGCIsActive true above, | |
| 1818 // without protection of the CGC_lock. | |
| 1819 CGC_lock->notify(); | |
| 1820 assert(!ConcurrentMarkSweepThread::vm_thread_wants_cms_token(), | |
| 1821 "Possible deadlock"); | |
| 1822 while (_foregroundGCShouldWait) { | |
| 1823 // wait for notification | |
| 1824 CGC_lock->wait(Mutex::_no_safepoint_check_flag); | |
| 1825 // Possibility of delay/starvation here, since CMS token does | |
| 1826 // not know to give priority to VM thread? Actually, i think | |
| 1827 // there wouldn't be any delay/starvation, but the proof of | |
| 1828 // that "fact" (?) appears non-trivial. XXX 20011219YSR | |
| 1829 } | |
| 1830 ConcurrentMarkSweepThread::set_CMS_flag( | |
| 1831 ConcurrentMarkSweepThread::CMS_vm_has_token); | |
| 1832 } | |
| 1833 } | |
| 1834 // The CMS_token is already held. Get back the other locks. | |
| 1835 assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(), | |
| 1836 "VM thread should have CMS token"); | |
| 1837 getFreelistLocks(); | |
| 1838 bitMapLock()->lock_without_safepoint_check(); | |
| 1839 if (TraceCMSState) { | |
| 1840 gclog_or_tty->print_cr("CMS foreground collector has asked for control " | |
| 1841 INTPTR_FORMAT " with first state %d", Thread::current(), first_state); | |
| 1842 gclog_or_tty->print_cr(" gets control with state %d", _collectorState); | |
| 1843 } | |
| 1844 | |
| 1845 // Check if we need to do a compaction, or if not, whether | |
| 1846 // we need to start the mark-sweep from scratch. | |
| 1847 bool should_compact = false; | |
| 1848 bool should_start_over = false; | |
| 1849 decide_foreground_collection_type(clear_all_soft_refs, | |
| 1850 &should_compact, &should_start_over); | |
| 1851 | |
| 1852 NOT_PRODUCT( | |
| 1853 if (RotateCMSCollectionTypes) { | |
| 1854 if (_cmsGen->debug_collection_type() == | |
| 1855 ConcurrentMarkSweepGeneration::MSC_foreground_collection_type) { | |
| 1856 should_compact = true; | |
| 1857 } else if (_cmsGen->debug_collection_type() == | |
| 1858 ConcurrentMarkSweepGeneration::MS_foreground_collection_type) { | |
| 1859 should_compact = false; | |
| 1860 } | |
| 1861 } | |
| 1862 ) | |
| 1863 | |
| 1864 if (PrintGCDetails && first_state > Idling) { | |
| 1865 GCCause::Cause cause = GenCollectedHeap::heap()->gc_cause(); | |
| 1866 if (GCCause::is_user_requested_gc(cause) || | |
| 1867 GCCause::is_serviceability_requested_gc(cause)) { | |
| 1868 gclog_or_tty->print(" (concurrent mode interrupted)"); | |
| 1869 } else { | |
| 1870 gclog_or_tty->print(" (concurrent mode failure)"); | |
| 1871 } | |
| 1872 } | |
| 1873 | |
| 1874 if (should_compact) { | |
| 1875 // If the collection is being acquired from the background | |
| 1876 // collector, there may be references on the discovered | |
| 1877 // references lists that have NULL referents (being those | |
| 1878 // that were concurrently cleared by a mutator) or | |
| 1879 // that are no longer active (having been enqueued concurrently | |
| 1880 // by the mutator). | |
| 1881 // Scrub the list of those references because Mark-Sweep-Compact | |
| 1882 // code assumes referents are not NULL and that all discovered | |
| 1883 // Reference objects are active. | |
| 1884 ref_processor()->clean_up_discovered_references(); | |
| 1885 | |
| 1886 do_compaction_work(clear_all_soft_refs); | |
| 1887 | |
| 1888 // Has the GC time limit been exceeded? | |
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1889 DefNewGeneration* young_gen = _young_gen->as_DefNewGeneration(); |
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1890 size_t max_eden_size = young_gen->max_capacity() - |
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1891 young_gen->to()->capacity() - |
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1892 young_gen->from()->capacity(); |
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1893 GenCollectedHeap* gch = GenCollectedHeap::heap(); |
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1894 GCCause::Cause gc_cause = gch->gc_cause(); |
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1895 size_policy()->check_gc_overhead_limit(_young_gen->used(), |
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1896 young_gen->eden()->used(), |
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1897 _cmsGen->max_capacity(), |
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1898 max_eden_size, |
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1899 full, |
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1900 gc_cause, |
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1901 gch->collector_policy()); |
| 0 | 1902 } else { |
| 1903 do_mark_sweep_work(clear_all_soft_refs, first_state, | |
| 1904 should_start_over); | |
| 1905 } | |
| 1906 // Reset the expansion cause, now that we just completed | |
| 1907 // a collection cycle. | |
| 1908 clear_expansion_cause(); | |
| 1909 _foregroundGCIsActive = false; | |
| 1910 return; | |
| 1911 } | |
| 1912 | |
| 1913 // Resize the perm generation and the tenured generation | |
| 1914 // after obtaining the free list locks for the | |
| 1915 // two generations. | |
| 1916 void CMSCollector::compute_new_size() { | |
| 1917 assert_locked_or_safepoint(Heap_lock); | |
| 1918 FreelistLocker z(this); | |
| 1919 _permGen->compute_new_size(); | |
| 1920 _cmsGen->compute_new_size(); | |
| 1921 } | |
| 1922 | |
| 1923 // A work method used by foreground collection to determine | |
| 1924 // what type of collection (compacting or not, continuing or fresh) | |
| 1925 // it should do. | |
| 1926 // NOTE: the intent is to make UseCMSCompactAtFullCollection | |
| 1927 // and CMSCompactWhenClearAllSoftRefs the default in the future | |
| 1928 // and do away with the flags after a suitable period. | |
| 1929 void CMSCollector::decide_foreground_collection_type( | |
| 1930 bool clear_all_soft_refs, bool* should_compact, | |
| 1931 bool* should_start_over) { | |
| 1932 // Normally, we'll compact only if the UseCMSCompactAtFullCollection | |
| 1933 // flag is set, and we have either requested a System.gc() or | |
| 1934 // the number of full gc's since the last concurrent cycle | |
| 1935 // has exceeded the threshold set by CMSFullGCsBeforeCompaction, | |
| 1936 // or if an incremental collection has failed | |
| 1937 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 1938 assert(gch->collector_policy()->is_two_generation_policy(), | |
| 1939 "You may want to check the correctness of the following"); | |
| 1940 // Inform cms gen if this was due to partial collection failing. | |
| 1941 // The CMS gen may use this fact to determine its expansion policy. | |
| 1942 if (gch->incremental_collection_will_fail()) { | |
| 1943 assert(!_cmsGen->incremental_collection_failed(), | |
| 1944 "Should have been noticed, reacted to and cleared"); | |
| 1945 _cmsGen->set_incremental_collection_failed(); | |
| 1946 } | |
| 1947 *should_compact = | |
| 1948 UseCMSCompactAtFullCollection && | |
| 1949 ((_full_gcs_since_conc_gc >= CMSFullGCsBeforeCompaction) || | |
| 1950 GCCause::is_user_requested_gc(gch->gc_cause()) || | |
| 1951 gch->incremental_collection_will_fail()); | |
| 1952 *should_start_over = false; | |
| 1953 if (clear_all_soft_refs && !*should_compact) { | |
| 1954 // We are about to do a last ditch collection attempt | |
| 1955 // so it would normally make sense to do a compaction | |
| 1956 // to reclaim as much space as possible. | |
| 1957 if (CMSCompactWhenClearAllSoftRefs) { | |
| 1958 // Default: The rationale is that in this case either | |
| 1959 // we are past the final marking phase, in which case | |
| 1960 // we'd have to start over, or so little has been done | |
| 1961 // that there's little point in saving that work. Compaction | |
| 1962 // appears to be the sensible choice in either case. | |
| 1963 *should_compact = true; | |
| 1964 } else { | |
| 1965 // We have been asked to clear all soft refs, but not to | |
| 1966 // compact. Make sure that we aren't past the final checkpoint | |
| 1967 // phase, for that is where we process soft refs. If we are already | |
| 1968 // past that phase, we'll need to redo the refs discovery phase and | |
| 1969 // if necessary clear soft refs that weren't previously | |
| 1970 // cleared. We do so by remembering the phase in which | |
| 1971 // we came in, and if we are past the refs processing | |
| 1972 // phase, we'll choose to just redo the mark-sweep | |
| 1973 // collection from scratch. | |
| 1974 if (_collectorState > FinalMarking) { | |
| 1975 // We are past the refs processing phase; | |
| 1976 // start over and do a fresh synchronous CMS cycle | |
| 1977 _collectorState = Resetting; // skip to reset to start new cycle | |
| 1978 reset(false /* == !asynch */); | |
| 1979 *should_start_over = true; | |
| 1980 } // else we can continue a possibly ongoing current cycle | |
| 1981 } | |
| 1982 } | |
| 1983 } | |
| 1984 | |
| 1985 // A work method used by the foreground collector to do | |
| 1986 // a mark-sweep-compact. | |
| 1987 void CMSCollector::do_compaction_work(bool clear_all_soft_refs) { | |
| 1988 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 1989 TraceTime t("CMS:MSC ", PrintGCDetails && Verbose, true, gclog_or_tty); | |
| 1990 if (PrintGC && Verbose && !(GCCause::is_user_requested_gc(gch->gc_cause()))) { | |
| 1991 gclog_or_tty->print_cr("Compact ConcurrentMarkSweepGeneration after %d " | |
| 1992 "collections passed to foreground collector", _full_gcs_since_conc_gc); | |
| 1993 } | |
| 1994 | |
| 1995 // Sample collection interval time and reset for collection pause. | |
| 1996 if (UseAdaptiveSizePolicy) { | |
| 1997 size_policy()->msc_collection_begin(); | |
| 1998 } | |
| 1999 | |
| 2000 // Temporarily widen the span of the weak reference processing to | |
| 2001 // the entire heap. | |
| 2002 MemRegion new_span(GenCollectedHeap::heap()->reserved_region()); | |
| 2003 ReferenceProcessorSpanMutator x(ref_processor(), new_span); | |
| 2004 | |
| 2005 // Temporarily, clear the "is_alive_non_header" field of the | |
| 2006 // reference processor. | |
| 2007 ReferenceProcessorIsAliveMutator y(ref_processor(), NULL); | |
| 2008 | |
| 2009 // Temporarily make reference _processing_ single threaded (non-MT). | |
| 2010 ReferenceProcessorMTProcMutator z(ref_processor(), false); | |
| 2011 | |
| 2012 // Temporarily make refs discovery atomic | |
| 2013 ReferenceProcessorAtomicMutator w(ref_processor(), true); | |
| 2014 | |
| 2015 ref_processor()->set_enqueuing_is_done(false); | |
| 2016 ref_processor()->enable_discovery(); | |
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2017 ref_processor()->setup_policy(clear_all_soft_refs); |
| 0 | 2018 // If an asynchronous collection finishes, the _modUnionTable is |
| 2019 // all clear. If we are assuming the collection from an asynchronous | |
| 2020 // collection, clear the _modUnionTable. | |
| 2021 assert(_collectorState != Idling || _modUnionTable.isAllClear(), | |
| 2022 "_modUnionTable should be clear if the baton was not passed"); | |
| 2023 _modUnionTable.clear_all(); | |
| 2024 | |
| 2025 // We must adjust the allocation statistics being maintained | |
| 2026 // in the free list space. We do so by reading and clearing | |
| 2027 // the sweep timer and updating the block flux rate estimates below. | |
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2028 assert(!_intra_sweep_timer.is_active(), "_intra_sweep_timer should be inactive"); |
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2029 if (_inter_sweep_timer.is_active()) { |
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2030 _inter_sweep_timer.stop(); |
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2031 // Note that we do not use this sample to update the _inter_sweep_estimate. |
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2032 _cmsGen->cmsSpace()->beginSweepFLCensus((float)(_inter_sweep_timer.seconds()), |
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2033 _inter_sweep_estimate.padded_average(), |
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2034 _intra_sweep_estimate.padded_average()); |
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2035 } |
| 0 | 2036 |
|
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2037 { |
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2038 TraceCMSMemoryManagerStats(); |
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2039 } |
| 0 | 2040 GenMarkSweep::invoke_at_safepoint(_cmsGen->level(), |
| 2041 ref_processor(), clear_all_soft_refs); | |
| 2042 #ifdef ASSERT | |
| 2043 CompactibleFreeListSpace* cms_space = _cmsGen->cmsSpace(); | |
| 2044 size_t free_size = cms_space->free(); | |
| 2045 assert(free_size == | |
| 2046 pointer_delta(cms_space->end(), cms_space->compaction_top()) | |
| 2047 * HeapWordSize, | |
| 2048 "All the free space should be compacted into one chunk at top"); | |
| 2049 assert(cms_space->dictionary()->totalChunkSize( | |
| 2050 debug_only(cms_space->freelistLock())) == 0 || | |
| 2051 cms_space->totalSizeInIndexedFreeLists() == 0, | |
| 2052 "All the free space should be in a single chunk"); | |
| 2053 size_t num = cms_space->totalCount(); | |
| 2054 assert((free_size == 0 && num == 0) || | |
| 2055 (free_size > 0 && (num == 1 || num == 2)), | |
| 2056 "There should be at most 2 free chunks after compaction"); | |
| 2057 #endif // ASSERT | |
| 2058 _collectorState = Resetting; | |
| 2059 assert(_restart_addr == NULL, | |
| 2060 "Should have been NULL'd before baton was passed"); | |
| 2061 reset(false /* == !asynch */); | |
| 2062 _cmsGen->reset_after_compaction(); | |
|
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2063 _concurrent_cycles_since_last_unload = 0; |
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2064 |
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2065 if (verifying() && !should_unload_classes()) { |
| 0 | 2066 perm_gen_verify_bit_map()->clear_all(); |
| 2067 } | |
| 2068 | |
| 2069 // Clear any data recorded in the PLAB chunk arrays. | |
| 2070 if (_survivor_plab_array != NULL) { | |
| 2071 reset_survivor_plab_arrays(); | |
| 2072 } | |
| 2073 | |
| 2074 // Adjust the per-size allocation stats for the next epoch. | |
|
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2075 _cmsGen->cmsSpace()->endSweepFLCensus(sweep_count() /* fake */); |
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2076 // Restart the "inter sweep timer" for the next epoch. |
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2077 _inter_sweep_timer.reset(); |
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2078 _inter_sweep_timer.start(); |
| 0 | 2079 |
| 2080 // Sample collection pause time and reset for collection interval. | |
| 2081 if (UseAdaptiveSizePolicy) { | |
| 2082 size_policy()->msc_collection_end(gch->gc_cause()); | |
| 2083 } | |
| 2084 | |
| 2085 // For a mark-sweep-compact, compute_new_size() will be called | |
| 2086 // in the heap's do_collection() method. | |
| 2087 } | |
| 2088 | |
| 2089 // A work method used by the foreground collector to do | |
| 2090 // a mark-sweep, after taking over from a possibly on-going | |
| 2091 // concurrent mark-sweep collection. | |
| 2092 void CMSCollector::do_mark_sweep_work(bool clear_all_soft_refs, | |
| 2093 CollectorState first_state, bool should_start_over) { | |
| 2094 if (PrintGC && Verbose) { | |
| 2095 gclog_or_tty->print_cr("Pass concurrent collection to foreground " | |
| 2096 "collector with count %d", | |
| 2097 _full_gcs_since_conc_gc); | |
| 2098 } | |
| 2099 switch (_collectorState) { | |
| 2100 case Idling: | |
| 2101 if (first_state == Idling || should_start_over) { | |
| 2102 // The background GC was not active, or should | |
| 2103 // restarted from scratch; start the cycle. | |
| 2104 _collectorState = InitialMarking; | |
| 2105 } | |
| 2106 // If first_state was not Idling, then a background GC | |
| 2107 // was in progress and has now finished. No need to do it | |
| 2108 // again. Leave the state as Idling. | |
| 2109 break; | |
| 2110 case Precleaning: | |
| 2111 // In the foreground case don't do the precleaning since | |
| 2112 // it is not done concurrently and there is extra work | |
| 2113 // required. | |
| 2114 _collectorState = FinalMarking; | |
| 2115 } | |
| 2116 if (PrintGCDetails && | |
| 2117 (_collectorState > Idling || | |
| 2118 !GCCause::is_user_requested_gc(GenCollectedHeap::heap()->gc_cause()))) { | |
| 2119 gclog_or_tty->print(" (concurrent mode failure)"); | |
| 2120 } | |
| 2121 collect_in_foreground(clear_all_soft_refs); | |
| 2122 | |
| 2123 // For a mark-sweep, compute_new_size() will be called | |
| 2124 // in the heap's do_collection() method. | |
| 2125 } | |
| 2126 | |
| 2127 | |
| 2128 void CMSCollector::getFreelistLocks() const { | |
| 2129 // Get locks for all free lists in all generations that this | |
| 2130 // collector is responsible for | |
| 2131 _cmsGen->freelistLock()->lock_without_safepoint_check(); | |
| 2132 _permGen->freelistLock()->lock_without_safepoint_check(); | |
| 2133 } | |
| 2134 | |
| 2135 void CMSCollector::releaseFreelistLocks() const { | |
| 2136 // Release locks for all free lists in all generations that this | |
| 2137 // collector is responsible for | |
| 2138 _cmsGen->freelistLock()->unlock(); | |
| 2139 _permGen->freelistLock()->unlock(); | |
| 2140 } | |
| 2141 | |
| 2142 bool CMSCollector::haveFreelistLocks() const { | |
| 2143 // Check locks for all free lists in all generations that this | |
| 2144 // collector is responsible for | |
| 2145 assert_lock_strong(_cmsGen->freelistLock()); | |
| 2146 assert_lock_strong(_permGen->freelistLock()); | |
| 2147 PRODUCT_ONLY(ShouldNotReachHere()); | |
| 2148 return true; | |
| 2149 } | |
| 2150 | |
| 2151 // A utility class that is used by the CMS collector to | |
| 2152 // temporarily "release" the foreground collector from its | |
| 2153 // usual obligation to wait for the background collector to | |
| 2154 // complete an ongoing phase before proceeding. | |
| 2155 class ReleaseForegroundGC: public StackObj { | |
| 2156 private: | |
| 2157 CMSCollector* _c; | |
| 2158 public: | |
| 2159 ReleaseForegroundGC(CMSCollector* c) : _c(c) { | |
| 2160 assert(_c->_foregroundGCShouldWait, "Else should not need to call"); | |
| 2161 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
| 2162 // allow a potentially blocked foreground collector to proceed | |
| 2163 _c->_foregroundGCShouldWait = false; | |
| 2164 if (_c->_foregroundGCIsActive) { | |
| 2165 CGC_lock->notify(); | |
| 2166 } | |
| 2167 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 2168 "Possible deadlock"); | |
| 2169 } | |
| 2170 | |
| 2171 ~ReleaseForegroundGC() { | |
| 2172 assert(!_c->_foregroundGCShouldWait, "Usage protocol violation?"); | |
| 2173 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
| 2174 _c->_foregroundGCShouldWait = true; | |
| 2175 } | |
| 2176 }; | |
| 2177 | |
| 2178 // There are separate collect_in_background and collect_in_foreground because of | |
| 2179 // the different locking requirements of the background collector and the | |
| 2180 // foreground collector. There was originally an attempt to share | |
| 2181 // one "collect" method between the background collector and the foreground | |
| 2182 // collector but the if-then-else required made it cleaner to have | |
| 2183 // separate methods. | |
| 2184 void CMSCollector::collect_in_background(bool clear_all_soft_refs) { | |
| 2185 assert(Thread::current()->is_ConcurrentGC_thread(), | |
| 2186 "A CMS asynchronous collection is only allowed on a CMS thread."); | |
| 2187 | |
| 2188 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 2189 { | |
| 2190 bool safepoint_check = Mutex::_no_safepoint_check_flag; | |
| 2191 MutexLockerEx hl(Heap_lock, safepoint_check); | |
|
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2192 FreelistLocker fll(this); |
| 0 | 2193 MutexLockerEx x(CGC_lock, safepoint_check); |
| 2194 if (_foregroundGCIsActive || !UseAsyncConcMarkSweepGC) { | |
| 2195 // The foreground collector is active or we're | |
| 2196 // not using asynchronous collections. Skip this | |
| 2197 // background collection. | |
| 2198 assert(!_foregroundGCShouldWait, "Should be clear"); | |
| 2199 return; | |
| 2200 } else { | |
| 2201 assert(_collectorState == Idling, "Should be idling before start."); | |
| 2202 _collectorState = InitialMarking; | |
| 2203 // Reset the expansion cause, now that we are about to begin | |
| 2204 // a new cycle. | |
| 2205 clear_expansion_cause(); | |
| 2206 } | |
|
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2207 // Decide if we want to enable class unloading as part of the |
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2208 // ensuing concurrent GC cycle. |
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2209 update_should_unload_classes(); |
| 0 | 2210 _full_gc_requested = false; // acks all outstanding full gc requests |
| 2211 // Signal that we are about to start a collection | |
| 2212 gch->increment_total_full_collections(); // ... starting a collection cycle | |
| 2213 _collection_count_start = gch->total_full_collections(); | |
| 2214 } | |
| 2215 | |
| 2216 // Used for PrintGC | |
| 2217 size_t prev_used; | |
| 2218 if (PrintGC && Verbose) { | |
| 2219 prev_used = _cmsGen->used(); // XXXPERM | |
| 2220 } | |
| 2221 | |
| 2222 // The change of the collection state is normally done at this level; | |
| 2223 // the exceptions are phases that are executed while the world is | |
| 2224 // stopped. For those phases the change of state is done while the | |
| 2225 // world is stopped. For baton passing purposes this allows the | |
| 2226 // background collector to finish the phase and change state atomically. | |
| 2227 // The foreground collector cannot wait on a phase that is done | |
| 2228 // while the world is stopped because the foreground collector already | |
| 2229 // has the world stopped and would deadlock. | |
| 2230 while (_collectorState != Idling) { | |
| 2231 if (TraceCMSState) { | |
| 2232 gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " in CMS state %d", | |
| 2233 Thread::current(), _collectorState); | |
| 2234 } | |
| 2235 // The foreground collector | |
| 2236 // holds the Heap_lock throughout its collection. | |
| 2237 // holds the CMS token (but not the lock) | |
| 2238 // except while it is waiting for the background collector to yield. | |
| 2239 // | |
| 2240 // The foreground collector should be blocked (not for long) | |
| 2241 // if the background collector is about to start a phase | |
| 2242 // executed with world stopped. If the background | |
| 2243 // collector has already started such a phase, the | |
| 2244 // foreground collector is blocked waiting for the | |
| 2245 // Heap_lock. The stop-world phases (InitialMarking and FinalMarking) | |
| 2246 // are executed in the VM thread. | |
| 2247 // | |
| 2248 // The locking order is | |
| 2249 // PendingListLock (PLL) -- if applicable (FinalMarking) | |
| 2250 // Heap_lock (both this & PLL locked in VM_CMS_Operation::prologue()) | |
| 2251 // CMS token (claimed in | |
| 2252 // stop_world_and_do() --> | |
| 2253 // safepoint_synchronize() --> | |
| 2254 // CMSThread::synchronize()) | |
| 2255 | |
| 2256 { | |
| 2257 // Check if the FG collector wants us to yield. | |
| 2258 CMSTokenSync x(true); // is cms thread | |
| 2259 if (waitForForegroundGC()) { | |
| 2260 // We yielded to a foreground GC, nothing more to be | |
| 2261 // done this round. | |
| 2262 assert(_foregroundGCShouldWait == false, "We set it to false in " | |
| 2263 "waitForForegroundGC()"); | |
| 2264 if (TraceCMSState) { | |
| 2265 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT | |
| 2266 " exiting collection CMS state %d", | |
| 2267 Thread::current(), _collectorState); | |
| 2268 } | |
| 2269 return; | |
| 2270 } else { | |
| 2271 // The background collector can run but check to see if the | |
| 2272 // foreground collector has done a collection while the | |
| 2273 // background collector was waiting to get the CGC_lock | |
| 2274 // above. If yes, break so that _foregroundGCShouldWait | |
| 2275 // is cleared before returning. | |
| 2276 if (_collectorState == Idling) { | |
| 2277 break; | |
| 2278 } | |
| 2279 } | |
| 2280 } | |
| 2281 | |
| 2282 assert(_foregroundGCShouldWait, "Foreground collector, if active, " | |
| 2283 "should be waiting"); | |
| 2284 | |
| 2285 switch (_collectorState) { | |
| 2286 case InitialMarking: | |
| 2287 { | |
| 2288 ReleaseForegroundGC x(this); | |
| 2289 stats().record_cms_begin(); | |
| 2290 | |
| 2291 VM_CMS_Initial_Mark initial_mark_op(this); | |
| 2292 VMThread::execute(&initial_mark_op); | |
| 2293 } | |
| 2294 // The collector state may be any legal state at this point | |
| 2295 // since the background collector may have yielded to the | |
| 2296 // foreground collector. | |
| 2297 break; | |
| 2298 case Marking: | |
| 2299 // initial marking in checkpointRootsInitialWork has been completed | |
| 2300 if (markFromRoots(true)) { // we were successful | |
| 2301 assert(_collectorState == Precleaning, "Collector state should " | |
| 2302 "have changed"); | |
| 2303 } else { | |
| 2304 assert(_foregroundGCIsActive, "Internal state inconsistency"); | |
| 2305 } | |
| 2306 break; | |
| 2307 case Precleaning: | |
| 2308 if (UseAdaptiveSizePolicy) { | |
| 2309 size_policy()->concurrent_precleaning_begin(); | |
| 2310 } | |
| 2311 // marking from roots in markFromRoots has been completed | |
| 2312 preclean(); | |
| 2313 if (UseAdaptiveSizePolicy) { | |
| 2314 size_policy()->concurrent_precleaning_end(); | |
| 2315 } | |
| 2316 assert(_collectorState == AbortablePreclean || | |
| 2317 _collectorState == FinalMarking, | |
| 2318 "Collector state should have changed"); | |
| 2319 break; | |
| 2320 case AbortablePreclean: | |
| 2321 if (UseAdaptiveSizePolicy) { | |
| 2322 size_policy()->concurrent_phases_resume(); | |
| 2323 } | |
| 2324 abortable_preclean(); | |
| 2325 if (UseAdaptiveSizePolicy) { | |
| 2326 size_policy()->concurrent_precleaning_end(); | |
| 2327 } | |
| 2328 assert(_collectorState == FinalMarking, "Collector state should " | |
| 2329 "have changed"); | |
| 2330 break; | |
| 2331 case FinalMarking: | |
| 2332 { | |
| 2333 ReleaseForegroundGC x(this); | |
| 2334 | |
| 2335 VM_CMS_Final_Remark final_remark_op(this); | |
| 2336 VMThread::execute(&final_remark_op); | |
| 935 | 2337 } |
| 0 | 2338 assert(_foregroundGCShouldWait, "block post-condition"); |
| 2339 break; | |
| 2340 case Sweeping: | |
| 2341 if (UseAdaptiveSizePolicy) { | |
| 2342 size_policy()->concurrent_sweeping_begin(); | |
| 2343 } | |
| 2344 // final marking in checkpointRootsFinal has been completed | |
| 2345 sweep(true); | |
| 2346 assert(_collectorState == Resizing, "Collector state change " | |
| 2347 "to Resizing must be done under the free_list_lock"); | |
| 2348 _full_gcs_since_conc_gc = 0; | |
| 2349 | |
| 2350 // Stop the timers for adaptive size policy for the concurrent phases | |
| 2351 if (UseAdaptiveSizePolicy) { | |
| 2352 size_policy()->concurrent_sweeping_end(); | |
| 2353 size_policy()->concurrent_phases_end(gch->gc_cause(), | |
| 2354 gch->prev_gen(_cmsGen)->capacity(), | |
| 2355 _cmsGen->free()); | |
| 2356 } | |
| 2357 | |
| 2358 case Resizing: { | |
| 2359 // Sweeping has been completed... | |
| 2360 // At this point the background collection has completed. | |
| 2361 // Don't move the call to compute_new_size() down | |
| 2362 // into code that might be executed if the background | |
| 2363 // collection was preempted. | |
| 2364 { | |
| 2365 ReleaseForegroundGC x(this); // unblock FG collection | |
| 2366 MutexLockerEx y(Heap_lock, Mutex::_no_safepoint_check_flag); | |
| 2367 CMSTokenSync z(true); // not strictly needed. | |
| 2368 if (_collectorState == Resizing) { | |
| 2369 compute_new_size(); | |
| 2370 _collectorState = Resetting; | |
| 2371 } else { | |
| 2372 assert(_collectorState == Idling, "The state should only change" | |
| 2373 " because the foreground collector has finished the collection"); | |
| 2374 } | |
| 2375 } | |
| 2376 break; | |
| 2377 } | |
| 2378 case Resetting: | |
| 2379 // CMS heap resizing has been completed | |
| 2380 reset(true); | |
| 2381 assert(_collectorState == Idling, "Collector state should " | |
| 2382 "have changed"); | |
| 2383 stats().record_cms_end(); | |
| 2384 // Don't move the concurrent_phases_end() and compute_new_size() | |
| 2385 // calls to here because a preempted background collection | |
| 2386 // has it's state set to "Resetting". | |
| 2387 break; | |
| 2388 case Idling: | |
| 2389 default: | |
| 2390 ShouldNotReachHere(); | |
| 2391 break; | |
| 2392 } | |
| 2393 if (TraceCMSState) { | |
| 2394 gclog_or_tty->print_cr(" Thread " INTPTR_FORMAT " done - next CMS state %d", | |
| 2395 Thread::current(), _collectorState); | |
| 2396 } | |
| 2397 assert(_foregroundGCShouldWait, "block post-condition"); | |
| 2398 } | |
| 2399 | |
| 2400 // Should this be in gc_epilogue? | |
| 2401 collector_policy()->counters()->update_counters(); | |
| 2402 | |
| 2403 { | |
| 2404 // Clear _foregroundGCShouldWait and, in the event that the | |
| 2405 // foreground collector is waiting, notify it, before | |
| 2406 // returning. | |
| 2407 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
| 2408 _foregroundGCShouldWait = false; | |
| 2409 if (_foregroundGCIsActive) { | |
| 2410 CGC_lock->notify(); | |
| 2411 } | |
| 2412 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 2413 "Possible deadlock"); | |
| 2414 } | |
| 2415 if (TraceCMSState) { | |
| 2416 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT | |
| 2417 " exiting collection CMS state %d", | |
| 2418 Thread::current(), _collectorState); | |
| 2419 } | |
| 2420 if (PrintGC && Verbose) { | |
| 2421 _cmsGen->print_heap_change(prev_used); | |
| 2422 } | |
| 2423 } | |
| 2424 | |
| 2425 void CMSCollector::collect_in_foreground(bool clear_all_soft_refs) { | |
| 2426 assert(_foregroundGCIsActive && !_foregroundGCShouldWait, | |
| 2427 "Foreground collector should be waiting, not executing"); | |
| 2428 assert(Thread::current()->is_VM_thread(), "A foreground collection" | |
| 2429 "may only be done by the VM Thread with the world stopped"); | |
| 2430 assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(), | |
| 2431 "VM thread should have CMS token"); | |
| 2432 | |
| 2433 NOT_PRODUCT(TraceTime t("CMS:MS (foreground) ", PrintGCDetails && Verbose, | |
| 2434 true, gclog_or_tty);) | |
| 2435 if (UseAdaptiveSizePolicy) { | |
| 2436 size_policy()->ms_collection_begin(); | |
| 2437 } | |
| 2438 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact); | |
| 2439 | |
| 2440 HandleMark hm; // Discard invalid handles created during verification | |
| 2441 | |
| 2442 if (VerifyBeforeGC && | |
| 2443 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
| 2444 Universe::verify(true); | |
| 2445 } | |
| 2446 | |
|
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2447 // Snapshot the soft reference policy to be used in this collection cycle. |
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2448 ref_processor()->setup_policy(clear_all_soft_refs); |
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2449 |
| 0 | 2450 bool init_mark_was_synchronous = false; // until proven otherwise |
| 2451 while (_collectorState != Idling) { | |
| 2452 if (TraceCMSState) { | |
| 2453 gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " in CMS state %d", | |
| 2454 Thread::current(), _collectorState); | |
| 2455 } | |
| 2456 switch (_collectorState) { | |
| 2457 case InitialMarking: | |
| 2458 init_mark_was_synchronous = true; // fact to be exploited in re-mark | |
| 2459 checkpointRootsInitial(false); | |
| 2460 assert(_collectorState == Marking, "Collector state should have changed" | |
| 2461 " within checkpointRootsInitial()"); | |
| 2462 break; | |
| 2463 case Marking: | |
| 2464 // initial marking in checkpointRootsInitialWork has been completed | |
| 2465 if (VerifyDuringGC && | |
| 2466 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
| 2467 gclog_or_tty->print("Verify before initial mark: "); | |
| 2468 Universe::verify(true); | |
| 2469 } | |
| 2470 { | |
| 2471 bool res = markFromRoots(false); | |
| 2472 assert(res && _collectorState == FinalMarking, "Collector state should " | |
| 2473 "have changed"); | |
| 2474 break; | |
| 2475 } | |
| 2476 case FinalMarking: | |
| 2477 if (VerifyDuringGC && | |
| 2478 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
| 2479 gclog_or_tty->print("Verify before re-mark: "); | |
| 2480 Universe::verify(true); | |
| 2481 } | |
| 2482 checkpointRootsFinal(false, clear_all_soft_refs, | |
| 2483 init_mark_was_synchronous); | |
| 2484 assert(_collectorState == Sweeping, "Collector state should not " | |
| 2485 "have changed within checkpointRootsFinal()"); | |
| 2486 break; | |
| 2487 case Sweeping: | |
| 2488 // final marking in checkpointRootsFinal has been completed | |
| 2489 if (VerifyDuringGC && | |
| 2490 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
| 2491 gclog_or_tty->print("Verify before sweep: "); | |
| 2492 Universe::verify(true); | |
| 2493 } | |
| 2494 sweep(false); | |
| 2495 assert(_collectorState == Resizing, "Incorrect state"); | |
| 2496 break; | |
| 2497 case Resizing: { | |
| 2498 // Sweeping has been completed; the actual resize in this case | |
| 2499 // is done separately; nothing to be done in this state. | |
| 2500 _collectorState = Resetting; | |
| 2501 break; | |
| 2502 } | |
| 2503 case Resetting: | |
| 2504 // The heap has been resized. | |
| 2505 if (VerifyDuringGC && | |
| 2506 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
| 2507 gclog_or_tty->print("Verify before reset: "); | |
| 2508 Universe::verify(true); | |
| 2509 } | |
| 2510 reset(false); | |
| 2511 assert(_collectorState == Idling, "Collector state should " | |
| 2512 "have changed"); | |
| 2513 break; | |
| 2514 case Precleaning: | |
| 2515 case AbortablePreclean: | |
| 2516 // Elide the preclean phase | |
| 2517 _collectorState = FinalMarking; | |
| 2518 break; | |
| 2519 default: | |
| 2520 ShouldNotReachHere(); | |
| 2521 } | |
| 2522 if (TraceCMSState) { | |
| 2523 gclog_or_tty->print_cr(" Thread " INTPTR_FORMAT " done - next CMS state %d", | |
| 2524 Thread::current(), _collectorState); | |
| 2525 } | |
| 2526 } | |
| 2527 | |
| 2528 if (UseAdaptiveSizePolicy) { | |
| 2529 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 2530 size_policy()->ms_collection_end(gch->gc_cause()); | |
| 2531 } | |
| 2532 | |
| 2533 if (VerifyAfterGC && | |
| 2534 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
| 2535 Universe::verify(true); | |
| 2536 } | |
| 2537 if (TraceCMSState) { | |
| 2538 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT | |
| 2539 " exiting collection CMS state %d", | |
| 2540 Thread::current(), _collectorState); | |
| 2541 } | |
| 2542 } | |
| 2543 | |
| 2544 bool CMSCollector::waitForForegroundGC() { | |
| 2545 bool res = false; | |
| 2546 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 2547 "CMS thread should have CMS token"); | |
| 2548 // Block the foreground collector until the | |
| 2549 // background collectors decides whether to | |
| 2550 // yield. | |
| 2551 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
| 2552 _foregroundGCShouldWait = true; | |
| 2553 if (_foregroundGCIsActive) { | |
| 2554 // The background collector yields to the | |
| 2555 // foreground collector and returns a value | |
| 2556 // indicating that it has yielded. The foreground | |
| 2557 // collector can proceed. | |
| 2558 res = true; | |
| 2559 _foregroundGCShouldWait = false; | |
| 2560 ConcurrentMarkSweepThread::clear_CMS_flag( | |
| 2561 ConcurrentMarkSweepThread::CMS_cms_has_token); | |
| 2562 ConcurrentMarkSweepThread::set_CMS_flag( | |
| 2563 ConcurrentMarkSweepThread::CMS_cms_wants_token); | |
| 2564 // Get a possibly blocked foreground thread going | |
| 2565 CGC_lock->notify(); | |
| 2566 if (TraceCMSState) { | |
| 2567 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT " waiting at CMS state %d", | |
| 2568 Thread::current(), _collectorState); | |
| 2569 } | |
| 2570 while (_foregroundGCIsActive) { | |
| 2571 CGC_lock->wait(Mutex::_no_safepoint_check_flag); | |
| 2572 } | |
| 2573 ConcurrentMarkSweepThread::set_CMS_flag( | |
| 2574 ConcurrentMarkSweepThread::CMS_cms_has_token); | |
| 2575 ConcurrentMarkSweepThread::clear_CMS_flag( | |
| 2576 ConcurrentMarkSweepThread::CMS_cms_wants_token); | |
| 2577 } | |
| 2578 if (TraceCMSState) { | |
| 2579 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT " continuing at CMS state %d", | |
| 2580 Thread::current(), _collectorState); | |
| 2581 } | |
| 2582 return res; | |
| 2583 } | |
| 2584 | |
| 2585 // Because of the need to lock the free lists and other structures in | |
| 2586 // the collector, common to all the generations that the collector is | |
| 2587 // collecting, we need the gc_prologues of individual CMS generations | |
| 2588 // delegate to their collector. It may have been simpler had the | |
| 2589 // current infrastructure allowed one to call a prologue on a | |
| 2590 // collector. In the absence of that we have the generation's | |
| 2591 // prologue delegate to the collector, which delegates back | |
| 2592 // some "local" work to a worker method in the individual generations | |
| 2593 // that it's responsible for collecting, while itself doing any | |
| 2594 // work common to all generations it's responsible for. A similar | |
| 2595 // comment applies to the gc_epilogue()'s. | |
| 2596 // The role of the varaible _between_prologue_and_epilogue is to | |
| 2597 // enforce the invocation protocol. | |
| 2598 void CMSCollector::gc_prologue(bool full) { | |
| 2599 // Call gc_prologue_work() for each CMSGen and PermGen that | |
| 2600 // we are responsible for. | |
| 2601 | |
| 2602 // The following locking discipline assumes that we are only called | |
| 2603 // when the world is stopped. | |
| 2604 assert(SafepointSynchronize::is_at_safepoint(), "world is stopped assumption"); | |
| 2605 | |
| 2606 // The CMSCollector prologue must call the gc_prologues for the | |
| 2607 // "generations" (including PermGen if any) that it's responsible | |
| 2608 // for. | |
| 2609 | |
| 2610 assert( Thread::current()->is_VM_thread() | |
| 2611 || ( CMSScavengeBeforeRemark | |
| 2612 && Thread::current()->is_ConcurrentGC_thread()), | |
| 2613 "Incorrect thread type for prologue execution"); | |
| 2614 | |
| 2615 if (_between_prologue_and_epilogue) { | |
| 2616 // We have already been invoked; this is a gc_prologue delegation | |
| 2617 // from yet another CMS generation that we are responsible for, just | |
| 2618 // ignore it since all relevant work has already been done. | |
| 2619 return; | |
| 2620 } | |
| 2621 | |
| 2622 // set a bit saying prologue has been called; cleared in epilogue | |
| 2623 _between_prologue_and_epilogue = true; | |
| 2624 // Claim locks for common data structures, then call gc_prologue_work() | |
| 2625 // for each CMSGen and PermGen that we are responsible for. | |
| 2626 | |
| 2627 getFreelistLocks(); // gets free list locks on constituent spaces | |
| 2628 bitMapLock()->lock_without_safepoint_check(); | |
| 2629 | |
| 2630 // Should call gc_prologue_work() for all cms gens we are responsible for | |
| 2631 bool registerClosure = _collectorState >= Marking | |
| 2632 && _collectorState < Sweeping; | |
|
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2633 ModUnionClosure* muc = CollectedHeap::use_parallel_gc_threads() ? |
|
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2634 &_modUnionClosurePar |
| 0 | 2635 : &_modUnionClosure; |
| 2636 _cmsGen->gc_prologue_work(full, registerClosure, muc); | |
| 2637 _permGen->gc_prologue_work(full, registerClosure, muc); | |
| 2638 | |
| 2639 if (!full) { | |
| 2640 stats().record_gc0_begin(); | |
| 2641 } | |
| 2642 } | |
| 2643 | |
| 2644 void ConcurrentMarkSweepGeneration::gc_prologue(bool full) { | |
| 2645 // Delegate to CMScollector which knows how to coordinate between | |
| 2646 // this and any other CMS generations that it is responsible for | |
| 2647 // collecting. | |
| 2648 collector()->gc_prologue(full); | |
| 2649 } | |
| 2650 | |
| 2651 // This is a "private" interface for use by this generation's CMSCollector. | |
| 2652 // Not to be called directly by any other entity (for instance, | |
| 2653 // GenCollectedHeap, which calls the "public" gc_prologue method above). | |
| 2654 void ConcurrentMarkSweepGeneration::gc_prologue_work(bool full, | |
| 2655 bool registerClosure, ModUnionClosure* modUnionClosure) { | |
| 2656 assert(!incremental_collection_failed(), "Shouldn't be set yet"); | |
| 2657 assert(cmsSpace()->preconsumptionDirtyCardClosure() == NULL, | |
| 2658 "Should be NULL"); | |
| 2659 if (registerClosure) { | |
| 2660 cmsSpace()->setPreconsumptionDirtyCardClosure(modUnionClosure); | |
| 2661 } | |
| 2662 cmsSpace()->gc_prologue(); | |
| 2663 // Clear stat counters | |
| 2664 NOT_PRODUCT( | |
| 2665 assert(_numObjectsPromoted == 0, "check"); | |
| 2666 assert(_numWordsPromoted == 0, "check"); | |
| 2667 if (Verbose && PrintGC) { | |
| 2668 gclog_or_tty->print("Allocated "SIZE_FORMAT" objects, " | |
| 2669 SIZE_FORMAT" bytes concurrently", | |
| 2670 _numObjectsAllocated, _numWordsAllocated*sizeof(HeapWord)); | |
| 2671 } | |
| 2672 _numObjectsAllocated = 0; | |
| 2673 _numWordsAllocated = 0; | |
| 2674 ) | |
| 2675 } | |
| 2676 | |
| 2677 void CMSCollector::gc_epilogue(bool full) { | |
| 2678 // The following locking discipline assumes that we are only called | |
| 2679 // when the world is stopped. | |
| 2680 assert(SafepointSynchronize::is_at_safepoint(), | |
| 2681 "world is stopped assumption"); | |
| 2682 | |
| 2683 // Currently the CMS epilogue (see CompactibleFreeListSpace) merely checks | |
| 2684 // if linear allocation blocks need to be appropriately marked to allow the | |
| 2685 // the blocks to be parsable. We also check here whether we need to nudge the | |
| 2686 // CMS collector thread to start a new cycle (if it's not already active). | |
| 2687 assert( Thread::current()->is_VM_thread() | |
| 2688 || ( CMSScavengeBeforeRemark | |
| 2689 && Thread::current()->is_ConcurrentGC_thread()), | |
| 2690 "Incorrect thread type for epilogue execution"); | |
| 2691 | |
| 2692 if (!_between_prologue_and_epilogue) { | |
| 2693 // We have already been invoked; this is a gc_epilogue delegation | |
| 2694 // from yet another CMS generation that we are responsible for, just | |
| 2695 // ignore it since all relevant work has already been done. | |
| 2696 return; | |
| 2697 } | |
| 2698 assert(haveFreelistLocks(), "must have freelist locks"); | |
| 2699 assert_lock_strong(bitMapLock()); | |
| 2700 | |
| 2701 _cmsGen->gc_epilogue_work(full); | |
| 2702 _permGen->gc_epilogue_work(full); | |
| 2703 | |
| 2704 if (_collectorState == AbortablePreclean || _collectorState == Precleaning) { | |
| 2705 // in case sampling was not already enabled, enable it | |
| 2706 _start_sampling = true; | |
| 2707 } | |
| 2708 // reset _eden_chunk_array so sampling starts afresh | |
| 2709 _eden_chunk_index = 0; | |
| 2710 | |
| 2711 size_t cms_used = _cmsGen->cmsSpace()->used(); | |
| 2712 size_t perm_used = _permGen->cmsSpace()->used(); | |
| 2713 | |
| 2714 // update performance counters - this uses a special version of | |
| 2715 // update_counters() that allows the utilization to be passed as a | |
| 2716 // parameter, avoiding multiple calls to used(). | |
| 2717 // | |
| 2718 _cmsGen->update_counters(cms_used); | |
| 2719 _permGen->update_counters(perm_used); | |
| 2720 | |
| 2721 if (CMSIncrementalMode) { | |
| 2722 icms_update_allocation_limits(); | |
| 2723 } | |
| 2724 | |
| 2725 bitMapLock()->unlock(); | |
| 2726 releaseFreelistLocks(); | |
| 2727 | |
| 2728 _between_prologue_and_epilogue = false; // ready for next cycle | |
| 2729 } | |
| 2730 | |
| 2731 void ConcurrentMarkSweepGeneration::gc_epilogue(bool full) { | |
| 2732 collector()->gc_epilogue(full); | |
| 2733 | |
| 2734 // Also reset promotion tracking in par gc thread states. | |
|
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2735 if (CollectedHeap::use_parallel_gc_threads()) { |
| 0 | 2736 for (uint i = 0; i < ParallelGCThreads; i++) { |
|
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2737 _par_gc_thread_states[i]->promo.stopTrackingPromotions(i); |
| 0 | 2738 } |
| 2739 } | |
| 2740 } | |
| 2741 | |
| 2742 void ConcurrentMarkSweepGeneration::gc_epilogue_work(bool full) { | |
| 2743 assert(!incremental_collection_failed(), "Should have been cleared"); | |
| 2744 cmsSpace()->setPreconsumptionDirtyCardClosure(NULL); | |
| 2745 cmsSpace()->gc_epilogue(); | |
| 2746 // Print stat counters | |
| 2747 NOT_PRODUCT( | |
| 2748 assert(_numObjectsAllocated == 0, "check"); | |
| 2749 assert(_numWordsAllocated == 0, "check"); | |
| 2750 if (Verbose && PrintGC) { | |
| 2751 gclog_or_tty->print("Promoted "SIZE_FORMAT" objects, " | |
| 2752 SIZE_FORMAT" bytes", | |
| 2753 _numObjectsPromoted, _numWordsPromoted*sizeof(HeapWord)); | |
| 2754 } | |
| 2755 _numObjectsPromoted = 0; | |
| 2756 _numWordsPromoted = 0; | |
| 2757 ) | |
| 2758 | |
| 2759 if (PrintGC && Verbose) { | |
| 2760 // Call down the chain in contiguous_available needs the freelistLock | |
| 2761 // so print this out before releasing the freeListLock. | |
| 2762 gclog_or_tty->print(" Contiguous available "SIZE_FORMAT" bytes ", | |
| 2763 contiguous_available()); | |
| 2764 } | |
| 2765 } | |
| 2766 | |
| 2767 #ifndef PRODUCT | |
| 2768 bool CMSCollector::have_cms_token() { | |
| 2769 Thread* thr = Thread::current(); | |
| 2770 if (thr->is_VM_thread()) { | |
| 2771 return ConcurrentMarkSweepThread::vm_thread_has_cms_token(); | |
| 2772 } else if (thr->is_ConcurrentGC_thread()) { | |
| 2773 return ConcurrentMarkSweepThread::cms_thread_has_cms_token(); | |
| 2774 } else if (thr->is_GC_task_thread()) { | |
| 2775 return ConcurrentMarkSweepThread::vm_thread_has_cms_token() && | |
| 2776 ParGCRareEvent_lock->owned_by_self(); | |
| 2777 } | |
| 2778 return false; | |
| 2779 } | |
| 2780 #endif | |
| 2781 | |
| 2782 // Check reachability of the given heap address in CMS generation, | |
| 2783 // treating all other generations as roots. | |
| 2784 bool CMSCollector::is_cms_reachable(HeapWord* addr) { | |
| 2785 // We could "guarantee" below, rather than assert, but i'll | |
| 2786 // leave these as "asserts" so that an adventurous debugger | |
| 2787 // could try this in the product build provided some subset of | |
| 2788 // the conditions were met, provided they were intersted in the | |
| 2789 // results and knew that the computation below wouldn't interfere | |
| 2790 // with other concurrent computations mutating the structures | |
| 2791 // being read or written. | |
| 2792 assert(SafepointSynchronize::is_at_safepoint(), | |
| 2793 "Else mutations in object graph will make answer suspect"); | |
| 2794 assert(have_cms_token(), "Should hold cms token"); | |
| 2795 assert(haveFreelistLocks(), "must hold free list locks"); | |
| 2796 assert_lock_strong(bitMapLock()); | |
| 2797 | |
| 2798 // Clear the marking bit map array before starting, but, just | |
| 2799 // for kicks, first report if the given address is already marked | |
| 2800 gclog_or_tty->print_cr("Start: Address 0x%x is%s marked", addr, | |
| 2801 _markBitMap.isMarked(addr) ? "" : " not"); | |
| 2802 | |
| 2803 if (verify_after_remark()) { | |
| 2804 MutexLockerEx x(verification_mark_bm()->lock(), Mutex::_no_safepoint_check_flag); | |
| 2805 bool result = verification_mark_bm()->isMarked(addr); | |
| 2806 gclog_or_tty->print_cr("TransitiveMark: Address 0x%x %s marked", addr, | |
| 2807 result ? "IS" : "is NOT"); | |
| 2808 return result; | |
| 2809 } else { | |
| 2810 gclog_or_tty->print_cr("Could not compute result"); | |
| 2811 return false; | |
| 2812 } | |
| 2813 } | |
| 2814 | |
| 2815 //////////////////////////////////////////////////////// | |
| 2816 // CMS Verification Support | |
| 2817 //////////////////////////////////////////////////////// | |
| 2818 // Following the remark phase, the following invariant | |
| 2819 // should hold -- each object in the CMS heap which is | |
| 2820 // marked in markBitMap() should be marked in the verification_mark_bm(). | |
| 2821 | |
| 2822 class VerifyMarkedClosure: public BitMapClosure { | |
| 2823 CMSBitMap* _marks; | |
| 2824 bool _failed; | |
| 2825 | |
| 2826 public: | |
| 2827 VerifyMarkedClosure(CMSBitMap* bm): _marks(bm), _failed(false) {} | |
| 2828 | |
|
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2829 bool do_bit(size_t offset) { |
| 0 | 2830 HeapWord* addr = _marks->offsetToHeapWord(offset); |
| 2831 if (!_marks->isMarked(addr)) { | |
|
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2832 oop(addr)->print_on(gclog_or_tty); |
| 0 | 2833 gclog_or_tty->print_cr(" ("INTPTR_FORMAT" should have been marked)", addr); |
| 2834 _failed = true; | |
| 2835 } | |
|
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2836 return true; |
| 0 | 2837 } |
| 2838 | |
| 2839 bool failed() { return _failed; } | |
| 2840 }; | |
| 2841 | |
| 2842 bool CMSCollector::verify_after_remark() { | |
| 2843 gclog_or_tty->print(" [Verifying CMS Marking... "); | |
| 2844 MutexLockerEx ml(verification_mark_bm()->lock(), Mutex::_no_safepoint_check_flag); | |
| 2845 static bool init = false; | |
| 2846 | |
| 2847 assert(SafepointSynchronize::is_at_safepoint(), | |
| 2848 "Else mutations in object graph will make answer suspect"); | |
| 2849 assert(have_cms_token(), | |
| 2850 "Else there may be mutual interference in use of " | |
| 2851 " verification data structures"); | |
| 2852 assert(_collectorState > Marking && _collectorState <= Sweeping, | |
| 2853 "Else marking info checked here may be obsolete"); | |
| 2854 assert(haveFreelistLocks(), "must hold free list locks"); | |
| 2855 assert_lock_strong(bitMapLock()); | |
| 2856 | |
| 2857 | |
| 2858 // Allocate marking bit map if not already allocated | |
| 2859 if (!init) { // first time | |
| 2860 if (!verification_mark_bm()->allocate(_span)) { | |
| 2861 return false; | |
| 2862 } | |
| 2863 init = true; | |
| 2864 } | |
| 2865 | |
| 2866 assert(verification_mark_stack()->isEmpty(), "Should be empty"); | |
| 2867 | |
| 2868 // Turn off refs discovery -- so we will be tracing through refs. | |
| 2869 // This is as intended, because by this time | |
| 2870 // GC must already have cleared any refs that need to be cleared, | |
| 2871 // and traced those that need to be marked; moreover, | |
| 2872 // the marking done here is not going to intefere in any | |
| 2873 // way with the marking information used by GC. | |
| 2874 NoRefDiscovery no_discovery(ref_processor()); | |
| 2875 | |
| 2876 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;) | |
| 2877 | |
| 2878 // Clear any marks from a previous round | |
| 2879 verification_mark_bm()->clear_all(); | |
| 2880 assert(verification_mark_stack()->isEmpty(), "markStack should be empty"); | |
|
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2881 verify_work_stacks_empty(); |
| 0 | 2882 |
| 2883 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 2884 gch->ensure_parsability(false); // fill TLABs, but no need to retire them | |
| 2885 // Update the saved marks which may affect the root scans. | |
| 2886 gch->save_marks(); | |
| 2887 | |
| 2888 if (CMSRemarkVerifyVariant == 1) { | |
| 2889 // In this first variant of verification, we complete | |
| 2890 // all marking, then check if the new marks-verctor is | |
| 2891 // a subset of the CMS marks-vector. | |
| 2892 verify_after_remark_work_1(); | |
| 2893 } else if (CMSRemarkVerifyVariant == 2) { | |
| 2894 // In this second variant of verification, we flag an error | |
| 2895 // (i.e. an object reachable in the new marks-vector not reachable | |
| 2896 // in the CMS marks-vector) immediately, also indicating the | |
| 2897 // identify of an object (A) that references the unmarked object (B) -- | |
| 2898 // presumably, a mutation to A failed to be picked up by preclean/remark? | |
| 2899 verify_after_remark_work_2(); | |
| 2900 } else { | |
| 2901 warning("Unrecognized value %d for CMSRemarkVerifyVariant", | |
| 2902 CMSRemarkVerifyVariant); | |
| 2903 } | |
| 2904 gclog_or_tty->print(" done] "); | |
| 2905 return true; | |
| 2906 } | |
| 2907 | |
| 2908 void CMSCollector::verify_after_remark_work_1() { | |
| 2909 ResourceMark rm; | |
| 2910 HandleMark hm; | |
| 2911 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 2912 | |
| 2913 // Mark from roots one level into CMS | |
|
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2914 MarkRefsIntoClosure notOlder(_span, verification_mark_bm()); |
| 0 | 2915 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. |
| 2916 | |
| 2917 gch->gen_process_strong_roots(_cmsGen->level(), | |
| 2918 true, // younger gens are roots | |
|
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2919 true, // activate StrongRootsScope |
| 0 | 2920 true, // collecting perm gen |
| 2921 SharedHeap::ScanningOption(roots_scanning_options()), | |
|
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2922 ¬Older, |
|
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2923 true, // walk code active on stacks |
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2924 NULL); |
| 0 | 2925 |
| 2926 // Now mark from the roots | |
| 2927 assert(_revisitStack.isEmpty(), "Should be empty"); | |
| 2928 MarkFromRootsClosure markFromRootsClosure(this, _span, | |
| 2929 verification_mark_bm(), verification_mark_stack(), &_revisitStack, | |
| 2930 false /* don't yield */, true /* verifying */); | |
| 2931 assert(_restart_addr == NULL, "Expected pre-condition"); | |
| 2932 verification_mark_bm()->iterate(&markFromRootsClosure); | |
| 2933 while (_restart_addr != NULL) { | |
| 2934 // Deal with stack overflow: by restarting at the indicated | |
| 2935 // address. | |
| 2936 HeapWord* ra = _restart_addr; | |
| 2937 markFromRootsClosure.reset(ra); | |
| 2938 _restart_addr = NULL; | |
| 2939 verification_mark_bm()->iterate(&markFromRootsClosure, ra, _span.end()); | |
| 2940 } | |
| 2941 assert(verification_mark_stack()->isEmpty(), "Should have been drained"); | |
| 2942 verify_work_stacks_empty(); | |
| 2943 // Should reset the revisit stack above, since no class tree | |
| 2944 // surgery is forthcoming. | |
| 2945 _revisitStack.reset(); // throwing away all contents | |
| 2946 | |
| 2947 // Marking completed -- now verify that each bit marked in | |
| 2948 // verification_mark_bm() is also marked in markBitMap(); flag all | |
| 2949 // errors by printing corresponding objects. | |
| 2950 VerifyMarkedClosure vcl(markBitMap()); | |
| 2951 verification_mark_bm()->iterate(&vcl); | |
| 2952 if (vcl.failed()) { | |
| 2953 gclog_or_tty->print("Verification failed"); | |
|
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2954 Universe::heap()->print_on(gclog_or_tty); |
|
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2955 fatal("CMS: failed marking verification after remark"); |
| 0 | 2956 } |
| 2957 } | |
| 2958 | |
| 2959 void CMSCollector::verify_after_remark_work_2() { | |
| 2960 ResourceMark rm; | |
| 2961 HandleMark hm; | |
| 2962 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 2963 | |
| 2964 // Mark from roots one level into CMS | |
| 2965 MarkRefsIntoVerifyClosure notOlder(_span, verification_mark_bm(), | |
|
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2966 markBitMap()); |
| 0 | 2967 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. |
| 2968 gch->gen_process_strong_roots(_cmsGen->level(), | |
| 2969 true, // younger gens are roots | |
|
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2970 true, // activate StrongRootsScope |
| 0 | 2971 true, // collecting perm gen |
| 2972 SharedHeap::ScanningOption(roots_scanning_options()), | |
|
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2973 ¬Older, |
|
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2974 true, // walk code active on stacks |
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|
2975 NULL); |
| 0 | 2976 |
| 2977 // Now mark from the roots | |
| 2978 assert(_revisitStack.isEmpty(), "Should be empty"); | |
| 2979 MarkFromRootsVerifyClosure markFromRootsClosure(this, _span, | |
| 2980 verification_mark_bm(), markBitMap(), verification_mark_stack()); | |
| 2981 assert(_restart_addr == NULL, "Expected pre-condition"); | |
| 2982 verification_mark_bm()->iterate(&markFromRootsClosure); | |
| 2983 while (_restart_addr != NULL) { | |
| 2984 // Deal with stack overflow: by restarting at the indicated | |
| 2985 // address. | |
| 2986 HeapWord* ra = _restart_addr; | |
| 2987 markFromRootsClosure.reset(ra); | |
| 2988 _restart_addr = NULL; | |
| 2989 verification_mark_bm()->iterate(&markFromRootsClosure, ra, _span.end()); | |
| 2990 } | |
| 2991 assert(verification_mark_stack()->isEmpty(), "Should have been drained"); | |
| 2992 verify_work_stacks_empty(); | |
| 2993 // Should reset the revisit stack above, since no class tree | |
| 2994 // surgery is forthcoming. | |
| 2995 _revisitStack.reset(); // throwing away all contents | |
| 2996 | |
| 2997 // Marking completed -- now verify that each bit marked in | |
| 2998 // verification_mark_bm() is also marked in markBitMap(); flag all | |
| 2999 // errors by printing corresponding objects. | |
| 3000 VerifyMarkedClosure vcl(markBitMap()); | |
| 3001 verification_mark_bm()->iterate(&vcl); | |
| 3002 assert(!vcl.failed(), "Else verification above should not have succeeded"); | |
| 3003 } | |
| 3004 | |
| 3005 void ConcurrentMarkSweepGeneration::save_marks() { | |
| 3006 // delegate to CMS space | |
| 3007 cmsSpace()->save_marks(); | |
| 3008 for (uint i = 0; i < ParallelGCThreads; i++) { | |
| 3009 _par_gc_thread_states[i]->promo.startTrackingPromotions(); | |
| 3010 } | |
| 3011 } | |
| 3012 | |
| 3013 bool ConcurrentMarkSweepGeneration::no_allocs_since_save_marks() { | |
| 3014 return cmsSpace()->no_allocs_since_save_marks(); | |
| 3015 } | |
| 3016 | |
| 3017 #define CMS_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \ | |
| 3018 \ | |
| 3019 void ConcurrentMarkSweepGeneration:: \ | |
| 3020 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \ | |
| 3021 cl->set_generation(this); \ | |
| 3022 cmsSpace()->oop_since_save_marks_iterate##nv_suffix(cl); \ | |
| 3023 cl->reset_generation(); \ | |
| 3024 save_marks(); \ | |
| 3025 } | |
| 3026 | |
| 3027 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DEFN) | |
| 3028 | |
| 3029 void | |
| 3030 ConcurrentMarkSweepGeneration::object_iterate_since_last_GC(ObjectClosure* blk) | |
| 3031 { | |
| 3032 // Not currently implemented; need to do the following. -- ysr. | |
| 3033 // dld -- I think that is used for some sort of allocation profiler. So it | |
| 3034 // really means the objects allocated by the mutator since the last | |
| 3035 // GC. We could potentially implement this cheaply by recording only | |
| 3036 // the direct allocations in a side data structure. | |
| 3037 // | |
| 3038 // I think we probably ought not to be required to support these | |
| 3039 // iterations at any arbitrary point; I think there ought to be some | |
| 3040 // call to enable/disable allocation profiling in a generation/space, | |
| 3041 // and the iterator ought to return the objects allocated in the | |
| 3042 // gen/space since the enable call, or the last iterator call (which | |
| 3043 // will probably be at a GC.) That way, for gens like CM&S that would | |
| 3044 // require some extra data structure to support this, we only pay the | |
| 3045 // cost when it's in use... | |
| 3046 cmsSpace()->object_iterate_since_last_GC(blk); | |
| 3047 } | |
| 3048 | |
| 3049 void | |
| 3050 ConcurrentMarkSweepGeneration::younger_refs_iterate(OopsInGenClosure* cl) { | |
| 3051 cl->set_generation(this); | |
| 3052 younger_refs_in_space_iterate(_cmsSpace, cl); | |
| 3053 cl->reset_generation(); | |
| 3054 } | |
| 3055 | |
| 3056 void | |
| 3057 ConcurrentMarkSweepGeneration::oop_iterate(MemRegion mr, OopClosure* cl) { | |
| 3058 if (freelistLock()->owned_by_self()) { | |
| 3059 Generation::oop_iterate(mr, cl); | |
| 3060 } else { | |
| 3061 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
| 3062 Generation::oop_iterate(mr, cl); | |
| 3063 } | |
| 3064 } | |
| 3065 | |
| 3066 void | |
| 3067 ConcurrentMarkSweepGeneration::oop_iterate(OopClosure* cl) { | |
| 3068 if (freelistLock()->owned_by_self()) { | |
| 3069 Generation::oop_iterate(cl); | |
| 3070 } else { | |
| 3071 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
| 3072 Generation::oop_iterate(cl); | |
| 3073 } | |
| 3074 } | |
| 3075 | |
| 3076 void | |
| 3077 ConcurrentMarkSweepGeneration::object_iterate(ObjectClosure* cl) { | |
| 3078 if (freelistLock()->owned_by_self()) { | |
| 3079 Generation::object_iterate(cl); | |
| 3080 } else { | |
| 3081 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
| 3082 Generation::object_iterate(cl); | |
| 3083 } | |
| 3084 } | |
| 3085 | |
| 3086 void | |
|
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3087 ConcurrentMarkSweepGeneration::safe_object_iterate(ObjectClosure* cl) { |
|
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3088 if (freelistLock()->owned_by_self()) { |
|
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|
3089 Generation::safe_object_iterate(cl); |
|
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|
3090 } else { |
|
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|
3091 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); |
|
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|
3092 Generation::safe_object_iterate(cl); |
|
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|
3093 } |
|
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|
3094 } |
|
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|
3095 |
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|
3096 void |
| 0 | 3097 ConcurrentMarkSweepGeneration::pre_adjust_pointers() { |
| 3098 } | |
| 3099 | |
| 3100 void | |
| 3101 ConcurrentMarkSweepGeneration::post_compact() { | |
| 3102 } | |
| 3103 | |
| 3104 void | |
| 3105 ConcurrentMarkSweepGeneration::prepare_for_verify() { | |
| 3106 // Fix the linear allocation blocks to look like free blocks. | |
| 3107 | |
| 3108 // Locks are normally acquired/released in gc_prologue/gc_epilogue, but those | |
| 3109 // are not called when the heap is verified during universe initialization and | |
| 3110 // at vm shutdown. | |
| 3111 if (freelistLock()->owned_by_self()) { | |
| 3112 cmsSpace()->prepare_for_verify(); | |
| 3113 } else { | |
| 3114 MutexLockerEx fll(freelistLock(), Mutex::_no_safepoint_check_flag); | |
| 3115 cmsSpace()->prepare_for_verify(); | |
| 3116 } | |
| 3117 } | |
| 3118 | |
| 3119 void | |
| 3120 ConcurrentMarkSweepGeneration::verify(bool allow_dirty /* ignored */) { | |
| 3121 // Locks are normally acquired/released in gc_prologue/gc_epilogue, but those | |
| 3122 // are not called when the heap is verified during universe initialization and | |
| 3123 // at vm shutdown. | |
| 3124 if (freelistLock()->owned_by_self()) { | |
| 3125 cmsSpace()->verify(false /* ignored */); | |
| 3126 } else { | |
| 3127 MutexLockerEx fll(freelistLock(), Mutex::_no_safepoint_check_flag); | |
| 3128 cmsSpace()->verify(false /* ignored */); | |
| 3129 } | |
| 3130 } | |
| 3131 | |
| 3132 void CMSCollector::verify(bool allow_dirty /* ignored */) { | |
| 3133 _cmsGen->verify(allow_dirty); | |
| 3134 _permGen->verify(allow_dirty); | |
| 3135 } | |
| 3136 | |
| 3137 #ifndef PRODUCT | |
| 3138 bool CMSCollector::overflow_list_is_empty() const { | |
| 3139 assert(_num_par_pushes >= 0, "Inconsistency"); | |
| 3140 if (_overflow_list == NULL) { | |
| 3141 assert(_num_par_pushes == 0, "Inconsistency"); | |
| 3142 } | |
| 3143 return _overflow_list == NULL; | |
| 3144 } | |
| 3145 | |
| 3146 // The methods verify_work_stacks_empty() and verify_overflow_empty() | |
| 3147 // merely consolidate assertion checks that appear to occur together frequently. | |
| 3148 void CMSCollector::verify_work_stacks_empty() const { | |
| 3149 assert(_markStack.isEmpty(), "Marking stack should be empty"); | |
| 3150 assert(overflow_list_is_empty(), "Overflow list should be empty"); | |
| 3151 } | |
| 3152 | |
| 3153 void CMSCollector::verify_overflow_empty() const { | |
| 3154 assert(overflow_list_is_empty(), "Overflow list should be empty"); | |
| 3155 assert(no_preserved_marks(), "No preserved marks"); | |
| 3156 } | |
| 3157 #endif // PRODUCT | |
| 3158 | |
|
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3159 // Decide if we want to enable class unloading as part of the |
|
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|
3160 // ensuing concurrent GC cycle. We will collect the perm gen and |
|
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|
3161 // unload classes if it's the case that: |
|
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|
3162 // (1) an explicit gc request has been made and the flag |
|
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|
3163 // ExplicitGCInvokesConcurrentAndUnloadsClasses is set, OR |
|
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|
3164 // (2) (a) class unloading is enabled at the command line, and |
|
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|
3165 // (b) (i) perm gen threshold has been crossed, or |
|
0834225a7916
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|
3166 // (ii) old gen is getting really full, or |
|
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diff
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|
3167 // (iii) the previous N CMS collections did not collect the |
|
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|
3168 // perm gen |
|
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diff
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|
3169 // NOTE: Provided there is no change in the state of the heap between |
|
0834225a7916
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diff
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|
3170 // calls to this method, it should have idempotent results. Moreover, |
|
0834225a7916
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diff
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|
3171 // its results should be monotonically increasing (i.e. going from 0 to 1, |
|
0834225a7916
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diff
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|
3172 // but not 1 to 0) between successive calls between which the heap was |
|
0834225a7916
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|
3173 // not collected. For the implementation below, it must thus rely on |
|
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|
3174 // the property that concurrent_cycles_since_last_unload() |
|
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|
3175 // will not decrease unless a collection cycle happened and that |
|
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|
3176 // _permGen->should_concurrent_collect() and _cmsGen->is_too_full() are |
|
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|
3177 // themselves also monotonic in that sense. See check_monotonicity() |
|
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|
3178 // below. |
|
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|
3179 bool CMSCollector::update_should_unload_classes() { |
|
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|
3180 _should_unload_classes = false; |
|
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|
3181 // Condition 1 above |
|
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|
3182 if (_full_gc_requested && ExplicitGCInvokesConcurrentAndUnloadsClasses) { |
|
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|
3183 _should_unload_classes = true; |
|
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|
3184 } else if (CMSClassUnloadingEnabled) { // Condition 2.a above |
|
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|
3185 // Disjuncts 2.b.(i,ii,iii) above |
|
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|
3186 _should_unload_classes = (concurrent_cycles_since_last_unload() >= |
|
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|
3187 CMSClassUnloadingMaxInterval) |
|
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|
3188 || _permGen->should_concurrent_collect() |
|
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|
3189 || _cmsGen->is_too_full(); |
|
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|
3190 } |
|
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|
3191 return _should_unload_classes; |
|
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|
3192 } |
|
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|
3193 |
|
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|
3194 bool ConcurrentMarkSweepGeneration::is_too_full() const { |
|
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|
3195 bool res = should_concurrent_collect(); |
|
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|
3196 res = res && (occupancy() > (double)CMSIsTooFullPercentage/100.0); |
|
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|
3197 return res; |
|
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|
3198 } |
|
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|
3199 |
| 0 | 3200 void CMSCollector::setup_cms_unloading_and_verification_state() { |
| 3201 const bool should_verify = VerifyBeforeGC || VerifyAfterGC || VerifyDuringGC | |
| 3202 || VerifyBeforeExit; | |
| 3203 const int rso = SharedHeap::SO_Symbols | SharedHeap::SO_Strings | |
| 3204 | SharedHeap::SO_CodeCache; | |
| 3205 | |
|
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9
diff
changeset
|
3206 if (should_unload_classes()) { // Should unload classes this cycle |
| 0 | 3207 remove_root_scanning_option(rso); // Shrink the root set appropriately |
| 3208 set_verifying(should_verify); // Set verification state for this cycle | |
| 3209 return; // Nothing else needs to be done at this time | |
| 3210 } | |
| 3211 | |
| 3212 // Not unloading classes this cycle | |
|
94
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|
3213 assert(!should_unload_classes(), "Inconsitency!"); |
|
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diff
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|
3214 if ((!verifying() || unloaded_classes_last_cycle()) && should_verify) { |
| 0 | 3215 // We were not verifying, or we _were_ unloading classes in the last cycle, |
| 3216 // AND some verification options are enabled this cycle; in this case, | |
| 3217 // we must make sure that the deadness map is allocated if not already so, | |
| 3218 // and cleared (if already allocated previously -- | |
| 3219 // CMSBitMap::sizeInBits() is used to determine if it's allocated). | |
| 3220 if (perm_gen_verify_bit_map()->sizeInBits() == 0) { | |
| 3221 if (!perm_gen_verify_bit_map()->allocate(_permGen->reserved())) { | |
| 3222 warning("Failed to allocate permanent generation verification CMS Bit Map;\n" | |
| 3223 "permanent generation verification disabled"); | |
| 3224 return; // Note that we leave verification disabled, so we'll retry this | |
| 3225 // allocation next cycle. We _could_ remember this failure | |
| 3226 // and skip further attempts and permanently disable verification | |
| 3227 // attempts if that is considered more desirable. | |
| 3228 } | |
| 3229 assert(perm_gen_verify_bit_map()->covers(_permGen->reserved()), | |
| 3230 "_perm_gen_ver_bit_map inconsistency?"); | |
| 3231 } else { | |
| 3232 perm_gen_verify_bit_map()->clear_all(); | |
| 3233 } | |
| 3234 // Include symbols, strings and code cache elements to prevent their resurrection. | |
| 3235 add_root_scanning_option(rso); | |
| 3236 set_verifying(true); | |
| 3237 } else if (verifying() && !should_verify) { | |
| 3238 // We were verifying, but some verification flags got disabled. | |
| 3239 set_verifying(false); | |
| 3240 // Exclude symbols, strings and code cache elements from root scanning to | |
| 3241 // reduce IM and RM pauses. | |
| 3242 remove_root_scanning_option(rso); | |
| 3243 } | |
| 3244 } | |
| 3245 | |
| 3246 | |
| 3247 #ifndef PRODUCT | |
| 3248 HeapWord* CMSCollector::block_start(const void* p) const { | |
| 3249 const HeapWord* addr = (HeapWord*)p; | |
| 3250 if (_span.contains(p)) { | |
| 3251 if (_cmsGen->cmsSpace()->is_in_reserved(addr)) { | |
| 3252 return _cmsGen->cmsSpace()->block_start(p); | |
| 3253 } else { | |
| 3254 assert(_permGen->cmsSpace()->is_in_reserved(addr), | |
| 3255 "Inconsistent _span?"); | |
| 3256 return _permGen->cmsSpace()->block_start(p); | |
| 3257 } | |
| 3258 } | |
| 3259 return NULL; | |
| 3260 } | |
| 3261 #endif | |
| 3262 | |
| 3263 HeapWord* | |
| 3264 ConcurrentMarkSweepGeneration::expand_and_allocate(size_t word_size, | |
| 3265 bool tlab, | |
| 3266 bool parallel) { | |
| 3267 assert(!tlab, "Can't deal with TLAB allocation"); | |
| 3268 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
| 3269 expand(word_size*HeapWordSize, MinHeapDeltaBytes, | |
| 3270 CMSExpansionCause::_satisfy_allocation); | |
| 3271 if (GCExpandToAllocateDelayMillis > 0) { | |
| 3272 os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false); | |
| 3273 } | |
|
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|
3274 return have_lock_and_allocate(word_size, tlab); |
| 0 | 3275 } |
| 3276 | |
| 3277 // YSR: All of this generation expansion/shrinking stuff is an exact copy of | |
| 3278 // OneContigSpaceCardGeneration, which makes me wonder if we should move this | |
| 3279 // to CardGeneration and share it... | |
|
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|
3280 bool ConcurrentMarkSweepGeneration::expand(size_t bytes, size_t expand_bytes) { |
|
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|
3281 return CardGeneration::expand(bytes, expand_bytes); |
|
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|
3282 } |
|
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|
3283 |
| 0 | 3284 void ConcurrentMarkSweepGeneration::expand(size_t bytes, size_t expand_bytes, |
| 3285 CMSExpansionCause::Cause cause) | |
| 3286 { | |
|
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|
3287 |
|
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|
3288 bool success = expand(bytes, expand_bytes); |
|
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|
3289 |
| 0 | 3290 // remember why we expanded; this information is used |
| 3291 // by shouldConcurrentCollect() when making decisions on whether to start | |
| 3292 // a new CMS cycle. | |
| 3293 if (success) { | |
| 3294 set_expansion_cause(cause); | |
| 3295 if (PrintGCDetails && Verbose) { | |
| 3296 gclog_or_tty->print_cr("Expanded CMS gen for %s", | |
| 3297 CMSExpansionCause::to_string(cause)); | |
| 3298 } | |
| 3299 } | |
| 3300 } | |
| 3301 | |
| 3302 HeapWord* ConcurrentMarkSweepGeneration::expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz) { | |
| 3303 HeapWord* res = NULL; | |
| 3304 MutexLocker x(ParGCRareEvent_lock); | |
| 3305 while (true) { | |
| 3306 // Expansion by some other thread might make alloc OK now: | |
| 3307 res = ps->lab.alloc(word_sz); | |
| 3308 if (res != NULL) return res; | |
| 3309 // If there's not enough expansion space available, give up. | |
| 3310 if (_virtual_space.uncommitted_size() < (word_sz * HeapWordSize)) { | |
| 3311 return NULL; | |
| 3312 } | |
| 3313 // Otherwise, we try expansion. | |
| 3314 expand(word_sz*HeapWordSize, MinHeapDeltaBytes, | |
| 3315 CMSExpansionCause::_allocate_par_lab); | |
| 3316 // Now go around the loop and try alloc again; | |
| 3317 // A competing par_promote might beat us to the expansion space, | |
| 3318 // so we may go around the loop again if promotion fails agaion. | |
| 3319 if (GCExpandToAllocateDelayMillis > 0) { | |
| 3320 os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false); | |
| 3321 } | |
| 3322 } | |
| 3323 } | |
| 3324 | |
| 3325 | |
| 3326 bool ConcurrentMarkSweepGeneration::expand_and_ensure_spooling_space( | |
| 3327 PromotionInfo* promo) { | |
| 3328 MutexLocker x(ParGCRareEvent_lock); | |
| 3329 size_t refill_size_bytes = promo->refillSize() * HeapWordSize; | |
| 3330 while (true) { | |
| 3331 // Expansion by some other thread might make alloc OK now: | |
| 3332 if (promo->ensure_spooling_space()) { | |
| 3333 assert(promo->has_spooling_space(), | |
| 3334 "Post-condition of successful ensure_spooling_space()"); | |
| 3335 return true; | |
| 3336 } | |
| 3337 // If there's not enough expansion space available, give up. | |
| 3338 if (_virtual_space.uncommitted_size() < refill_size_bytes) { | |
| 3339 return false; | |
| 3340 } | |
| 3341 // Otherwise, we try expansion. | |
| 3342 expand(refill_size_bytes, MinHeapDeltaBytes, | |
| 3343 CMSExpansionCause::_allocate_par_spooling_space); | |
| 3344 // Now go around the loop and try alloc again; | |
| 3345 // A competing allocation might beat us to the expansion space, | |
| 3346 // so we may go around the loop again if allocation fails again. | |
| 3347 if (GCExpandToAllocateDelayMillis > 0) { | |
| 3348 os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false); | |
| 3349 } | |
| 3350 } | |
| 3351 } | |
| 3352 | |
| 3353 | |
| 3354 | |
| 3355 void ConcurrentMarkSweepGeneration::shrink(size_t bytes) { | |
| 3356 assert_locked_or_safepoint(Heap_lock); | |
| 3357 size_t size = ReservedSpace::page_align_size_down(bytes); | |
| 3358 if (size > 0) { | |
| 3359 shrink_by(size); | |
| 3360 } | |
| 3361 } | |
| 3362 | |
| 3363 bool ConcurrentMarkSweepGeneration::grow_by(size_t bytes) { | |
| 3364 assert_locked_or_safepoint(Heap_lock); | |
| 3365 bool result = _virtual_space.expand_by(bytes); | |
| 3366 if (result) { | |
| 3367 HeapWord* old_end = _cmsSpace->end(); | |
| 3368 size_t new_word_size = | |
| 3369 heap_word_size(_virtual_space.committed_size()); | |
| 3370 MemRegion mr(_cmsSpace->bottom(), new_word_size); | |
| 3371 _bts->resize(new_word_size); // resize the block offset shared array | |
| 3372 Universe::heap()->barrier_set()->resize_covered_region(mr); | |
| 3373 // Hmmmm... why doesn't CFLS::set_end verify locking? | |
| 3374 // This is quite ugly; FIX ME XXX | |
|
1145
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diff
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|
3375 _cmsSpace->assert_locked(freelistLock()); |
| 0 | 3376 _cmsSpace->set_end((HeapWord*)_virtual_space.high()); |
| 3377 | |
| 3378 // update the space and generation capacity counters | |
| 3379 if (UsePerfData) { | |
| 3380 _space_counters->update_capacity(); | |
| 3381 _gen_counters->update_all(); | |
| 3382 } | |
| 3383 | |
| 3384 if (Verbose && PrintGC) { | |
| 3385 size_t new_mem_size = _virtual_space.committed_size(); | |
| 3386 size_t old_mem_size = new_mem_size - bytes; | |
| 3387 gclog_or_tty->print_cr("Expanding %s from %ldK by %ldK to %ldK", | |
| 3388 name(), old_mem_size/K, bytes/K, new_mem_size/K); | |
| 3389 } | |
| 3390 } | |
| 3391 return result; | |
| 3392 } | |
| 3393 | |
| 3394 bool ConcurrentMarkSweepGeneration::grow_to_reserved() { | |
| 3395 assert_locked_or_safepoint(Heap_lock); | |
| 3396 bool success = true; | |
| 3397 const size_t remaining_bytes = _virtual_space.uncommitted_size(); | |
| 3398 if (remaining_bytes > 0) { | |
| 3399 success = grow_by(remaining_bytes); | |
| 3400 DEBUG_ONLY(if (!success) warning("grow to reserved failed");) | |
| 3401 } | |
| 3402 return success; | |
| 3403 } | |
| 3404 | |
| 3405 void ConcurrentMarkSweepGeneration::shrink_by(size_t bytes) { | |
| 3406 assert_locked_or_safepoint(Heap_lock); | |
| 3407 assert_lock_strong(freelistLock()); | |
| 3408 // XXX Fix when compaction is implemented. | |
| 3409 warning("Shrinking of CMS not yet implemented"); | |
| 3410 return; | |
| 3411 } | |
| 3412 | |
| 3413 | |
| 3414 // Simple ctor/dtor wrapper for accounting & timer chores around concurrent | |
| 3415 // phases. | |
| 3416 class CMSPhaseAccounting: public StackObj { | |
| 3417 public: | |
| 3418 CMSPhaseAccounting(CMSCollector *collector, | |
| 3419 const char *phase, | |
| 3420 bool print_cr = true); | |
| 3421 ~CMSPhaseAccounting(); | |
| 3422 | |
| 3423 private: | |
| 3424 CMSCollector *_collector; | |
| 3425 const char *_phase; | |
| 3426 elapsedTimer _wallclock; | |
| 3427 bool _print_cr; | |
| 3428 | |
| 3429 public: | |
| 3430 // Not MT-safe; so do not pass around these StackObj's | |
| 3431 // where they may be accessed by other threads. | |
| 3432 jlong wallclock_millis() { | |
| 3433 assert(_wallclock.is_active(), "Wall clock should not stop"); | |
| 3434 _wallclock.stop(); // to record time | |
| 3435 jlong ret = _wallclock.milliseconds(); | |
| 3436 _wallclock.start(); // restart | |
| 3437 return ret; | |
| 3438 } | |
| 3439 }; | |
| 3440 | |
| 3441 CMSPhaseAccounting::CMSPhaseAccounting(CMSCollector *collector, | |
| 3442 const char *phase, | |
| 3443 bool print_cr) : | |
| 3444 _collector(collector), _phase(phase), _print_cr(print_cr) { | |
| 3445 | |
| 3446 if (PrintCMSStatistics != 0) { | |
| 3447 _collector->resetYields(); | |
| 3448 } | |
| 3449 if (PrintGCDetails && PrintGCTimeStamps) { | |
| 3450 gclog_or_tty->date_stamp(PrintGCDateStamps); | |
| 3451 gclog_or_tty->stamp(); | |
| 3452 gclog_or_tty->print_cr(": [%s-concurrent-%s-start]", | |
| 3453 _collector->cmsGen()->short_name(), _phase); | |
| 3454 } | |
| 3455 _collector->resetTimer(); | |
| 3456 _wallclock.start(); | |
| 3457 _collector->startTimer(); | |
| 3458 } | |
| 3459 | |
| 3460 CMSPhaseAccounting::~CMSPhaseAccounting() { | |
| 3461 assert(_wallclock.is_active(), "Wall clock should not have stopped"); | |
| 3462 _collector->stopTimer(); | |
| 3463 _wallclock.stop(); | |
| 3464 if (PrintGCDetails) { | |
| 3465 gclog_or_tty->date_stamp(PrintGCDateStamps); | |
| 3466 if (PrintGCTimeStamps) { | |
| 3467 gclog_or_tty->stamp(); | |
| 3468 gclog_or_tty->print(": "); | |
| 3469 } | |
| 3470 gclog_or_tty->print("[%s-concurrent-%s: %3.3f/%3.3f secs]", | |
| 3471 _collector->cmsGen()->short_name(), | |
| 3472 _phase, _collector->timerValue(), _wallclock.seconds()); | |
| 3473 if (_print_cr) { | |
| 3474 gclog_or_tty->print_cr(""); | |
| 3475 } | |
| 3476 if (PrintCMSStatistics != 0) { | |
| 3477 gclog_or_tty->print_cr(" (CMS-concurrent-%s yielded %d times)", _phase, | |
| 3478 _collector->yields()); | |
| 3479 } | |
| 3480 } | |
| 3481 } | |
| 3482 | |
| 3483 // CMS work | |
| 3484 | |
| 3485 // Checkpoint the roots into this generation from outside | |
| 3486 // this generation. [Note this initial checkpoint need only | |
| 3487 // be approximate -- we'll do a catch up phase subsequently.] | |
| 3488 void CMSCollector::checkpointRootsInitial(bool asynch) { | |
| 3489 assert(_collectorState == InitialMarking, "Wrong collector state"); | |
| 3490 check_correct_thread_executing(); | |
|
1703
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6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
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1579
diff
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|
3491 TraceCMSMemoryManagerStats tms(_collectorState); |
| 0 | 3492 ReferenceProcessor* rp = ref_processor(); |
| 3493 SpecializationStats::clear(); | |
| 3494 assert(_restart_addr == NULL, "Control point invariant"); | |
| 3495 if (asynch) { | |
| 3496 // acquire locks for subsequent manipulations | |
| 3497 MutexLockerEx x(bitMapLock(), | |
| 3498 Mutex::_no_safepoint_check_flag); | |
| 3499 checkpointRootsInitialWork(asynch); | |
| 3500 rp->verify_no_references_recorded(); | |
| 3501 rp->enable_discovery(); // enable ("weak") refs discovery | |
| 3502 _collectorState = Marking; | |
| 3503 } else { | |
| 3504 // (Weak) Refs discovery: this is controlled from genCollectedHeap::do_collection | |
| 3505 // which recognizes if we are a CMS generation, and doesn't try to turn on | |
| 3506 // discovery; verify that they aren't meddling. | |
| 3507 assert(!rp->discovery_is_atomic(), | |
| 3508 "incorrect setting of discovery predicate"); | |
| 3509 assert(!rp->discovery_enabled(), "genCollectedHeap shouldn't control " | |
| 3510 "ref discovery for this generation kind"); | |
| 3511 // already have locks | |
| 3512 checkpointRootsInitialWork(asynch); | |
| 3513 rp->enable_discovery(); // now enable ("weak") refs discovery | |
| 3514 _collectorState = Marking; | |
| 3515 } | |
| 3516 SpecializationStats::print(); | |
| 3517 } | |
| 3518 | |
| 3519 void CMSCollector::checkpointRootsInitialWork(bool asynch) { | |
| 3520 assert(SafepointSynchronize::is_at_safepoint(), "world should be stopped"); | |
| 3521 assert(_collectorState == InitialMarking, "just checking"); | |
| 3522 | |
| 3523 // If there has not been a GC[n-1] since last GC[n] cycle completed, | |
| 3524 // precede our marking with a collection of all | |
| 3525 // younger generations to keep floating garbage to a minimum. | |
| 3526 // XXX: we won't do this for now -- it's an optimization to be done later. | |
| 3527 | |
| 3528 // already have locks | |
| 3529 assert_lock_strong(bitMapLock()); | |
| 3530 assert(_markBitMap.isAllClear(), "was reset at end of previous cycle"); | |
| 3531 | |
| 3532 // Setup the verification and class unloading state for this | |
| 3533 // CMS collection cycle. | |
| 3534 setup_cms_unloading_and_verification_state(); | |
| 3535 | |
| 3536 NOT_PRODUCT(TraceTime t("\ncheckpointRootsInitialWork", | |
| 3537 PrintGCDetails && Verbose, true, gclog_or_tty);) | |
| 3538 if (UseAdaptiveSizePolicy) { | |
| 3539 size_policy()->checkpoint_roots_initial_begin(); | |
| 3540 } | |
| 3541 | |
| 3542 // Reset all the PLAB chunk arrays if necessary. | |
| 3543 if (_survivor_plab_array != NULL && !CMSPLABRecordAlways) { | |
| 3544 reset_survivor_plab_arrays(); | |
| 3545 } | |
| 3546 | |
| 3547 ResourceMark rm; | |
| 3548 HandleMark hm; | |
| 3549 | |
| 3550 FalseClosure falseClosure; | |
| 3551 // In the case of a synchronous collection, we will elide the | |
| 3552 // remark step, so it's important to catch all the nmethod oops | |
|
994
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|
3553 // in this step. |
|
753cf9794df9
6885169: merge of 4957990 and 6863023 causes conflict on do_nmethods
jrose
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diff
changeset
|
3554 // The final 'true' flag to gen_process_strong_roots will ensure this. |
|
753cf9794df9
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993
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|
3555 // If 'async' is true, we can relax the nmethod tracing. |
|
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|
3556 MarkRefsIntoClosure notOlder(_span, &_markBitMap); |
| 0 | 3557 GenCollectedHeap* gch = GenCollectedHeap::heap(); |
| 3558 | |
| 3559 verify_work_stacks_empty(); | |
| 3560 verify_overflow_empty(); | |
| 3561 | |
| 3562 gch->ensure_parsability(false); // fill TLABs, but no need to retire them | |
| 3563 // Update the saved marks which may affect the root scans. | |
| 3564 gch->save_marks(); | |
| 3565 | |
| 3566 // weak reference processing has not started yet. | |
| 3567 ref_processor()->set_enqueuing_is_done(false); | |
| 3568 | |
| 3569 { | |
| 935 | 3570 // This is not needed. DEBUG_ONLY(RememberKlassesChecker imx(true);) |
| 0 | 3571 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;) |
| 3572 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. | |
| 3573 gch->gen_process_strong_roots(_cmsGen->level(), | |
| 3574 true, // younger gens are roots | |
|
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diff
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|
3575 true, // activate StrongRootsScope |
| 0 | 3576 true, // collecting perm gen |
| 3577 SharedHeap::ScanningOption(roots_scanning_options()), | |
|
989
148e5441d916
6863023: need non-perm oops in code cache for JSR 292
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798
diff
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|
3578 ¬Older, |
|
148e5441d916
6863023: need non-perm oops in code cache for JSR 292
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diff
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|
3579 true, // walk all of code cache if (so & SO_CodeCache) |
|
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|
3580 NULL); |
| 0 | 3581 } |
| 3582 | |
| 3583 // Clear mod-union table; it will be dirtied in the prologue of | |
| 3584 // CMS generation per each younger generation collection. | |
| 3585 | |
| 3586 assert(_modUnionTable.isAllClear(), | |
| 3587 "Was cleared in most recent final checkpoint phase" | |
| 3588 " or no bits are set in the gc_prologue before the start of the next " | |
| 3589 "subsequent marking phase."); | |
| 3590 | |
| 3591 // Temporarily disabled, since pre/post-consumption closures don't | |
| 3592 // care about precleaned cards | |
| 3593 #if 0 | |
| 3594 { | |
| 3595 MemRegion mr = MemRegion((HeapWord*)_virtual_space.low(), | |
| 3596 (HeapWord*)_virtual_space.high()); | |
| 3597 _ct->ct_bs()->preclean_dirty_cards(mr); | |
| 3598 } | |
| 3599 #endif | |
| 3600 | |
| 3601 // Save the end of the used_region of the constituent generations | |
| 3602 // to be used to limit the extent of sweep in each generation. | |
| 3603 save_sweep_limits(); | |
| 3604 if (UseAdaptiveSizePolicy) { | |
| 3605 size_policy()->checkpoint_roots_initial_end(gch->gc_cause()); | |
| 3606 } | |
| 3607 verify_overflow_empty(); | |
| 3608 } | |
| 3609 | |
| 3610 bool CMSCollector::markFromRoots(bool asynch) { | |
| 3611 // we might be tempted to assert that: | |
| 3612 // assert(asynch == !SafepointSynchronize::is_at_safepoint(), | |
| 3613 // "inconsistent argument?"); | |
| 3614 // However that wouldn't be right, because it's possible that | |
| 3615 // a safepoint is indeed in progress as a younger generation | |
| 3616 // stop-the-world GC happens even as we mark in this generation. | |
| 3617 assert(_collectorState == Marking, "inconsistent state?"); | |
| 3618 check_correct_thread_executing(); | |
| 3619 verify_overflow_empty(); | |
| 3620 | |
| 3621 bool res; | |
| 3622 if (asynch) { | |
| 3623 | |
| 3624 // Start the timers for adaptive size policy for the concurrent phases | |
| 3625 // Do it here so that the foreground MS can use the concurrent | |
| 3626 // timer since a foreground MS might has the sweep done concurrently | |
| 3627 // or STW. | |
| 3628 if (UseAdaptiveSizePolicy) { | |
| 3629 size_policy()->concurrent_marking_begin(); | |
| 3630 } | |
| 3631 | |
| 3632 // Weak ref discovery note: We may be discovering weak | |
| 3633 // refs in this generation concurrent (but interleaved) with | |
| 3634 // weak ref discovery by a younger generation collector. | |
| 3635 | |
| 3636 CMSTokenSyncWithLocks ts(true, bitMapLock()); | |
| 3637 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
| 3638 CMSPhaseAccounting pa(this, "mark", !PrintGCDetails); | |
| 3639 res = markFromRootsWork(asynch); | |
| 3640 if (res) { | |
| 3641 _collectorState = Precleaning; | |
| 3642 } else { // We failed and a foreground collection wants to take over | |
| 3643 assert(_foregroundGCIsActive, "internal state inconsistency"); | |
| 3644 assert(_restart_addr == NULL, "foreground will restart from scratch"); | |
| 3645 if (PrintGCDetails) { | |
| 3646 gclog_or_tty->print_cr("bailing out to foreground collection"); | |
| 3647 } | |
| 3648 } | |
| 3649 if (UseAdaptiveSizePolicy) { | |
| 3650 size_policy()->concurrent_marking_end(); | |
| 3651 } | |
| 3652 } else { | |
| 3653 assert(SafepointSynchronize::is_at_safepoint(), | |
| 3654 "inconsistent with asynch == false"); | |
| 3655 if (UseAdaptiveSizePolicy) { | |
| 3656 size_policy()->ms_collection_marking_begin(); | |
| 3657 } | |
| 3658 // already have locks | |
| 3659 res = markFromRootsWork(asynch); | |
| 3660 _collectorState = FinalMarking; | |
| 3661 if (UseAdaptiveSizePolicy) { | |
| 3662 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 3663 size_policy()->ms_collection_marking_end(gch->gc_cause()); | |
| 3664 } | |
| 3665 } | |
| 3666 verify_overflow_empty(); | |
| 3667 return res; | |
| 3668 } | |
| 3669 | |
| 3670 bool CMSCollector::markFromRootsWork(bool asynch) { | |
| 3671 // iterate over marked bits in bit map, doing a full scan and mark | |
| 3672 // from these roots using the following algorithm: | |
| 3673 // . if oop is to the right of the current scan pointer, | |
| 3674 // mark corresponding bit (we'll process it later) | |
| 3675 // . else (oop is to left of current scan pointer) | |
| 3676 // push oop on marking stack | |
| 3677 // . drain the marking stack | |
| 3678 | |
| 3679 // Note that when we do a marking step we need to hold the | |
| 3680 // bit map lock -- recall that direct allocation (by mutators) | |
| 3681 // and promotion (by younger generation collectors) is also | |
| 3682 // marking the bit map. [the so-called allocate live policy.] | |
| 3683 // Because the implementation of bit map marking is not | |
| 3684 // robust wrt simultaneous marking of bits in the same word, | |
| 3685 // we need to make sure that there is no such interference | |
| 3686 // between concurrent such updates. | |
| 3687 | |
| 3688 // already have locks | |
| 3689 assert_lock_strong(bitMapLock()); | |
| 3690 | |
| 3691 // Clear the revisit stack, just in case there are any | |
| 3692 // obsolete contents from a short-circuited previous CMS cycle. | |
| 3693 _revisitStack.reset(); | |
| 3694 verify_work_stacks_empty(); | |
| 3695 verify_overflow_empty(); | |
| 3696 assert(_revisitStack.isEmpty(), "tabula rasa"); | |
|
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3697 DEBUG_ONLY(RememberKlassesChecker cmx(should_unload_classes());) |
| 0 | 3698 bool result = false; |
| 1284 | 3699 if (CMSConcurrentMTEnabled && ConcGCThreads > 0) { |
| 0 | 3700 result = do_marking_mt(asynch); |
| 3701 } else { | |
| 3702 result = do_marking_st(asynch); | |
| 3703 } | |
| 3704 return result; | |
| 3705 } | |
| 3706 | |
| 3707 // Forward decl | |
| 3708 class CMSConcMarkingTask; | |
| 3709 | |
| 3710 class CMSConcMarkingTerminator: public ParallelTaskTerminator { | |
| 3711 CMSCollector* _collector; | |
| 3712 CMSConcMarkingTask* _task; | |
| 3713 bool _yield; | |
| 3714 protected: | |
| 3715 virtual void yield(); | |
| 3716 public: | |
| 3717 // "n_threads" is the number of threads to be terminated. | |
| 3718 // "queue_set" is a set of work queues of other threads. | |
| 3719 // "collector" is the CMS collector associated with this task terminator. | |
| 3720 // "yield" indicates whether we need the gang as a whole to yield. | |
| 3721 CMSConcMarkingTerminator(int n_threads, TaskQueueSetSuper* queue_set, | |
| 3722 CMSCollector* collector, bool yield) : | |
| 3723 ParallelTaskTerminator(n_threads, queue_set), | |
| 3724 _collector(collector), | |
| 3725 _yield(yield) { } | |
| 3726 | |
| 3727 void set_task(CMSConcMarkingTask* task) { | |
| 3728 _task = task; | |
| 3729 } | |
| 3730 }; | |
| 3731 | |
| 3732 // MT Concurrent Marking Task | |
| 3733 class CMSConcMarkingTask: public YieldingFlexibleGangTask { | |
| 3734 CMSCollector* _collector; | |
| 3735 int _n_workers; // requested/desired # workers | |
| 3736 bool _asynch; | |
| 3737 bool _result; | |
| 3738 CompactibleFreeListSpace* _cms_space; | |
| 3739 CompactibleFreeListSpace* _perm_space; | |
| 3740 HeapWord* _global_finger; | |
|
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3741 HeapWord* _restart_addr; |
| 0 | 3742 |
| 3743 // Exposed here for yielding support | |
| 3744 Mutex* const _bit_map_lock; | |
| 3745 | |
| 3746 // The per thread work queues, available here for stealing | |
| 3747 OopTaskQueueSet* _task_queues; | |
| 3748 CMSConcMarkingTerminator _term; | |
| 3749 | |
| 3750 public: | |
| 3751 CMSConcMarkingTask(CMSCollector* collector, | |
| 3752 CompactibleFreeListSpace* cms_space, | |
| 3753 CompactibleFreeListSpace* perm_space, | |
|
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3754 bool asynch, |
| 0 | 3755 YieldingFlexibleWorkGang* workers, |
| 3756 OopTaskQueueSet* task_queues): | |
| 3757 YieldingFlexibleGangTask("Concurrent marking done multi-threaded"), | |
| 3758 _collector(collector), | |
| 3759 _cms_space(cms_space), | |
| 3760 _perm_space(perm_space), | |
|
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3761 _asynch(asynch), _n_workers(0), _result(true), |
|
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3762 _task_queues(task_queues), |
|
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3763 _term(_n_workers, task_queues, _collector, asynch), |
| 0 | 3764 _bit_map_lock(collector->bitMapLock()) |
| 3765 { | |
|
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3766 _requested_size = _n_workers; |
| 0 | 3767 _term.set_task(this); |
| 3768 assert(_cms_space->bottom() < _perm_space->bottom(), | |
| 3769 "Finger incorrectly initialized below"); | |
|
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3770 _restart_addr = _global_finger = _cms_space->bottom(); |
| 0 | 3771 } |
| 3772 | |
| 3773 | |
| 3774 OopTaskQueueSet* task_queues() { return _task_queues; } | |
| 3775 | |
| 3776 OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); } | |
| 3777 | |
| 3778 HeapWord** global_finger_addr() { return &_global_finger; } | |
| 3779 | |
| 3780 CMSConcMarkingTerminator* terminator() { return &_term; } | |
| 3781 | |
|
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3782 virtual void set_for_termination(int active_workers) { |
|
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3783 terminator()->reset_for_reuse(active_workers); |
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3784 } |
|
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3785 |
| 0 | 3786 void work(int i); |
| 3787 | |
| 3788 virtual void coordinator_yield(); // stuff done by coordinator | |
| 3789 bool result() { return _result; } | |
| 3790 | |
| 3791 void reset(HeapWord* ra) { | |
|
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3792 assert(_global_finger >= _cms_space->end(), "Postcondition of ::work(i)"); |
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3793 assert(_global_finger >= _perm_space->end(), "Postcondition of ::work(i)"); |
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3794 assert(ra < _perm_space->end(), "ra too large"); |
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3795 _restart_addr = _global_finger = ra; |
| 0 | 3796 _term.reset_for_reuse(); |
| 3797 } | |
| 3798 | |
| 3799 static bool get_work_from_overflow_stack(CMSMarkStack* ovflw_stk, | |
| 3800 OopTaskQueue* work_q); | |
| 3801 | |
| 3802 private: | |
| 3803 void do_scan_and_mark(int i, CompactibleFreeListSpace* sp); | |
| 3804 void do_work_steal(int i); | |
| 3805 void bump_global_finger(HeapWord* f); | |
| 3806 }; | |
| 3807 | |
| 3808 void CMSConcMarkingTerminator::yield() { | |
| 3809 if (ConcurrentMarkSweepThread::should_yield() && | |
| 3810 !_collector->foregroundGCIsActive() && | |
| 3811 _yield) { | |
| 3812 _task->yield(); | |
| 3813 } else { | |
| 3814 ParallelTaskTerminator::yield(); | |
| 3815 } | |
| 3816 } | |
| 3817 | |
| 3818 //////////////////////////////////////////////////////////////// | |
| 3819 // Concurrent Marking Algorithm Sketch | |
| 3820 //////////////////////////////////////////////////////////////// | |
| 3821 // Until all tasks exhausted (both spaces): | |
| 3822 // -- claim next available chunk | |
| 3823 // -- bump global finger via CAS | |
| 3824 // -- find first object that starts in this chunk | |
| 3825 // and start scanning bitmap from that position | |
| 3826 // -- scan marked objects for oops | |
| 3827 // -- CAS-mark target, and if successful: | |
| 3828 // . if target oop is above global finger (volatile read) | |
| 3829 // nothing to do | |
| 3830 // . if target oop is in chunk and above local finger | |
| 3831 // then nothing to do | |
| 3832 // . else push on work-queue | |
| 3833 // -- Deal with possible overflow issues: | |
| 3834 // . local work-queue overflow causes stuff to be pushed on | |
| 3835 // global (common) overflow queue | |
| 3836 // . always first empty local work queue | |
| 3837 // . then get a batch of oops from global work queue if any | |
| 3838 // . then do work stealing | |
| 3839 // -- When all tasks claimed (both spaces) | |
| 3840 // and local work queue empty, | |
| 3841 // then in a loop do: | |
| 3842 // . check global overflow stack; steal a batch of oops and trace | |
| 3843 // . try to steal from other threads oif GOS is empty | |
| 3844 // . if neither is available, offer termination | |
| 3845 // -- Terminate and return result | |
| 3846 // | |
| 3847 void CMSConcMarkingTask::work(int i) { | |
| 3848 elapsedTimer _timer; | |
| 3849 ResourceMark rm; | |
| 3850 HandleMark hm; | |
| 3851 | |
| 3852 DEBUG_ONLY(_collector->verify_overflow_empty();) | |
| 3853 | |
| 3854 // Before we begin work, our work queue should be empty | |
| 3855 assert(work_queue(i)->size() == 0, "Expected to be empty"); | |
| 3856 // Scan the bitmap covering _cms_space, tracing through grey objects. | |
| 3857 _timer.start(); | |
| 3858 do_scan_and_mark(i, _cms_space); | |
| 3859 _timer.stop(); | |
| 3860 if (PrintCMSStatistics != 0) { | |
| 3861 gclog_or_tty->print_cr("Finished cms space scanning in %dth thread: %3.3f sec", | |
| 3862 i, _timer.seconds()); // XXX: need xxx/xxx type of notation, two timers | |
| 3863 } | |
| 3864 | |
| 3865 // ... do the same for the _perm_space | |
| 3866 _timer.reset(); | |
| 3867 _timer.start(); | |
| 3868 do_scan_and_mark(i, _perm_space); | |
| 3869 _timer.stop(); | |
| 3870 if (PrintCMSStatistics != 0) { | |
| 3871 gclog_or_tty->print_cr("Finished perm space scanning in %dth thread: %3.3f sec", | |
| 3872 i, _timer.seconds()); // XXX: need xxx/xxx type of notation, two timers | |
| 3873 } | |
| 3874 | |
| 3875 // ... do work stealing | |
| 3876 _timer.reset(); | |
| 3877 _timer.start(); | |
| 3878 do_work_steal(i); | |
| 3879 _timer.stop(); | |
| 3880 if (PrintCMSStatistics != 0) { | |
| 3881 gclog_or_tty->print_cr("Finished work stealing in %dth thread: %3.3f sec", | |
| 3882 i, _timer.seconds()); // XXX: need xxx/xxx type of notation, two timers | |
| 3883 } | |
| 3884 assert(_collector->_markStack.isEmpty(), "Should have been emptied"); | |
| 3885 assert(work_queue(i)->size() == 0, "Should have been emptied"); | |
| 3886 // Note that under the current task protocol, the | |
| 3887 // following assertion is true even of the spaces | |
| 3888 // expanded since the completion of the concurrent | |
| 3889 // marking. XXX This will likely change under a strict | |
| 3890 // ABORT semantics. | |
| 3891 assert(_global_finger > _cms_space->end() && | |
| 3892 _global_finger >= _perm_space->end(), | |
| 3893 "All tasks have been completed"); | |
| 3894 DEBUG_ONLY(_collector->verify_overflow_empty();) | |
| 3895 } | |
| 3896 | |
| 3897 void CMSConcMarkingTask::bump_global_finger(HeapWord* f) { | |
| 3898 HeapWord* read = _global_finger; | |
| 3899 HeapWord* cur = read; | |
| 3900 while (f > read) { | |
| 3901 cur = read; | |
| 3902 read = (HeapWord*) Atomic::cmpxchg_ptr(f, &_global_finger, cur); | |
| 3903 if (cur == read) { | |
| 3904 // our cas succeeded | |
| 3905 assert(_global_finger >= f, "protocol consistency"); | |
| 3906 break; | |
| 3907 } | |
| 3908 } | |
| 3909 } | |
| 3910 | |
| 3911 // This is really inefficient, and should be redone by | |
| 3912 // using (not yet available) block-read and -write interfaces to the | |
| 3913 // stack and the work_queue. XXX FIX ME !!! | |
| 3914 bool CMSConcMarkingTask::get_work_from_overflow_stack(CMSMarkStack* ovflw_stk, | |
| 3915 OopTaskQueue* work_q) { | |
| 3916 // Fast lock-free check | |
| 3917 if (ovflw_stk->length() == 0) { | |
| 3918 return false; | |
| 3919 } | |
| 3920 assert(work_q->size() == 0, "Shouldn't steal"); | |
| 3921 MutexLockerEx ml(ovflw_stk->par_lock(), | |
| 3922 Mutex::_no_safepoint_check_flag); | |
| 3923 // Grab up to 1/4 the size of the work queue | |
|
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3924 size_t num = MIN2((size_t)(work_q->max_elems() - work_q->size())/4, |
| 0 | 3925 (size_t)ParGCDesiredObjsFromOverflowList); |
| 3926 num = MIN2(num, ovflw_stk->length()); | |
| 3927 for (int i = (int) num; i > 0; i--) { | |
| 3928 oop cur = ovflw_stk->pop(); | |
| 3929 assert(cur != NULL, "Counted wrong?"); | |
| 3930 work_q->push(cur); | |
| 3931 } | |
| 3932 return num > 0; | |
| 3933 } | |
| 3934 | |
| 3935 void CMSConcMarkingTask::do_scan_and_mark(int i, CompactibleFreeListSpace* sp) { | |
| 3936 SequentialSubTasksDone* pst = sp->conc_par_seq_tasks(); | |
| 3937 int n_tasks = pst->n_tasks(); | |
| 3938 // We allow that there may be no tasks to do here because | |
| 3939 // we are restarting after a stack overflow. | |
|
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3940 assert(pst->valid() || n_tasks == 0, "Uninitialized use?"); |
| 0 | 3941 int nth_task = 0; |
| 3942 | |
|
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3943 HeapWord* aligned_start = sp->bottom(); |
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3944 if (sp->used_region().contains(_restart_addr)) { |
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3945 // Align down to a card boundary for the start of 0th task |
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3946 // for this space. |
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3947 aligned_start = |
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3948 (HeapWord*)align_size_down((uintptr_t)_restart_addr, |
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3949 CardTableModRefBS::card_size); |
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3950 } |
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3951 |
| 0 | 3952 size_t chunk_size = sp->marking_task_size(); |
| 3953 while (!pst->is_task_claimed(/* reference */ nth_task)) { | |
| 3954 // Having claimed the nth task in this space, | |
| 3955 // compute the chunk that it corresponds to: | |
|
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3956 MemRegion span = MemRegion(aligned_start + nth_task*chunk_size, |
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3957 aligned_start + (nth_task+1)*chunk_size); |
| 0 | 3958 // Try and bump the global finger via a CAS; |
| 3959 // note that we need to do the global finger bump | |
| 3960 // _before_ taking the intersection below, because | |
| 3961 // the task corresponding to that region will be | |
| 3962 // deemed done even if the used_region() expands | |
| 3963 // because of allocation -- as it almost certainly will | |
| 3964 // during start-up while the threads yield in the | |
| 3965 // closure below. | |
| 3966 HeapWord* finger = span.end(); | |
| 3967 bump_global_finger(finger); // atomically | |
| 3968 // There are null tasks here corresponding to chunks | |
| 3969 // beyond the "top" address of the space. | |
| 3970 span = span.intersection(sp->used_region()); | |
| 3971 if (!span.is_empty()) { // Non-null task | |
|
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3972 HeapWord* prev_obj; |
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3973 assert(!span.contains(_restart_addr) || nth_task == 0, |
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3974 "Inconsistency"); |
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3975 if (nth_task == 0) { |
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3976 // For the 0th task, we'll not need to compute a block_start. |
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3977 if (span.contains(_restart_addr)) { |
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3978 // In the case of a restart because of stack overflow, |
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3979 // we might additionally skip a chunk prefix. |
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3980 prev_obj = _restart_addr; |
| 0 | 3981 } else { |
|
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3982 prev_obj = span.start(); |
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3983 } |
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3984 } else { |
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3985 // We want to skip the first object because |
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3986 // the protocol is to scan any object in its entirety |
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3987 // that _starts_ in this span; a fortiori, any |
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3988 // object starting in an earlier span is scanned |
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|
3989 // as part of an earlier claimed task. |
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3990 // Below we use the "careful" version of block_start |
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3991 // so we do not try to navigate uninitialized objects. |
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3992 prev_obj = sp->block_start_careful(span.start()); |
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3993 // Below we use a variant of block_size that uses the |
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3994 // Printezis bits to avoid waiting for allocated |
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3995 // objects to become initialized/parsable. |
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3996 while (prev_obj < span.start()) { |
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3997 size_t sz = sp->block_size_no_stall(prev_obj, _collector); |
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3998 if (sz > 0) { |
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3999 prev_obj += sz; |
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4000 } else { |
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4001 // In this case we may end up doing a bit of redundant |
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4002 // scanning, but that appears unavoidable, short of |
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4003 // locking the free list locks; see bug 6324141. |
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4004 break; |
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4005 } |
| 0 | 4006 } |
| 4007 } | |
| 4008 if (prev_obj < span.end()) { | |
| 4009 MemRegion my_span = MemRegion(prev_obj, span.end()); | |
| 4010 // Do the marking work within a non-empty span -- | |
| 4011 // the last argument to the constructor indicates whether the | |
| 4012 // iteration should be incremental with periodic yields. | |
| 4013 Par_MarkFromRootsClosure cl(this, _collector, my_span, | |
| 4014 &_collector->_markBitMap, | |
| 4015 work_queue(i), | |
| 4016 &_collector->_markStack, | |
| 4017 &_collector->_revisitStack, | |
| 4018 _asynch); | |
| 4019 _collector->_markBitMap.iterate(&cl, my_span.start(), my_span.end()); | |
| 4020 } // else nothing to do for this task | |
| 4021 } // else nothing to do for this task | |
| 4022 } | |
| 4023 // We'd be tempted to assert here that since there are no | |
| 4024 // more tasks left to claim in this space, the global_finger | |
| 4025 // must exceed space->top() and a fortiori space->end(). However, | |
| 4026 // that would not quite be correct because the bumping of | |
| 4027 // global_finger occurs strictly after the claiming of a task, | |
| 4028 // so by the time we reach here the global finger may not yet | |
| 4029 // have been bumped up by the thread that claimed the last | |
| 4030 // task. | |
| 4031 pst->all_tasks_completed(); | |
| 4032 } | |
| 4033 | |
| 935 | 4034 class Par_ConcMarkingClosure: public Par_KlassRememberingOopClosure { |
|
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4035 private: |
| 0 | 4036 MemRegion _span; |
| 4037 CMSBitMap* _bit_map; | |
| 4038 CMSMarkStack* _overflow_stack; | |
| 4039 OopTaskQueue* _work_queue; | |
|
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4040 protected: |
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4041 DO_OOP_WORK_DEFN |
| 0 | 4042 public: |
| 4043 Par_ConcMarkingClosure(CMSCollector* collector, OopTaskQueue* work_queue, | |
| 935 | 4044 CMSBitMap* bit_map, CMSMarkStack* overflow_stack, |
| 4045 CMSMarkStack* revisit_stack): | |
| 4046 Par_KlassRememberingOopClosure(collector, NULL, revisit_stack), | |
| 0 | 4047 _span(_collector->_span), |
| 4048 _work_queue(work_queue), | |
| 4049 _bit_map(bit_map), | |
| 935 | 4050 _overflow_stack(overflow_stack) |
| 4051 { } | |
|
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4052 virtual void do_oop(oop* p); |
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4053 virtual void do_oop(narrowOop* p); |
| 0 | 4054 void trim_queue(size_t max); |
| 4055 void handle_stack_overflow(HeapWord* lost); | |
| 4056 }; | |
| 4057 | |
|
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4058 // Grey object scanning during work stealing phase -- |
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4059 // the salient assumption here is that any references |
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4060 // that are in these stolen objects being scanned must |
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4061 // already have been initialized (else they would not have |
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4062 // been published), so we do not need to check for |
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4063 // uninitialized objects before pushing here. |
|
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4064 void Par_ConcMarkingClosure::do_oop(oop obj) { |
|
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4065 assert(obj->is_oop_or_null(true), "expected an oop or NULL"); |
|
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4066 HeapWord* addr = (HeapWord*)obj; |
| 0 | 4067 // Check if oop points into the CMS generation |
| 4068 // and is not marked | |
| 4069 if (_span.contains(addr) && !_bit_map->isMarked(addr)) { | |
| 4070 // a white object ... | |
| 4071 // If we manage to "claim" the object, by being the | |
| 4072 // first thread to mark it, then we push it on our | |
| 4073 // marking stack | |
| 4074 if (_bit_map->par_mark(addr)) { // ... now grey | |
| 4075 // push on work queue (grey set) | |
| 4076 bool simulate_overflow = false; | |
| 4077 NOT_PRODUCT( | |
| 4078 if (CMSMarkStackOverflowALot && | |
| 4079 _collector->simulate_overflow()) { | |
| 4080 // simulate a stack overflow | |
| 4081 simulate_overflow = true; | |
| 4082 } | |
| 4083 ) | |
| 4084 if (simulate_overflow || | |
|
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4085 !(_work_queue->push(obj) || _overflow_stack->par_push(obj))) { |
| 0 | 4086 // stack overflow |
| 4087 if (PrintCMSStatistics != 0) { | |
| 4088 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
| 4089 SIZE_FORMAT, _overflow_stack->capacity()); | |
| 4090 } | |
| 4091 // We cannot assert that the overflow stack is full because | |
| 4092 // it may have been emptied since. | |
| 4093 assert(simulate_overflow || | |
| 4094 _work_queue->size() == _work_queue->max_elems(), | |
| 4095 "Else push should have succeeded"); | |
| 4096 handle_stack_overflow(addr); | |
| 4097 } | |
| 4098 } // Else, some other thread got there first | |
| 4099 } | |
| 4100 } | |
| 4101 | |
|
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4102 void Par_ConcMarkingClosure::do_oop(oop* p) { Par_ConcMarkingClosure::do_oop_work(p); } |
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4103 void Par_ConcMarkingClosure::do_oop(narrowOop* p) { Par_ConcMarkingClosure::do_oop_work(p); } |
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4104 |
| 0 | 4105 void Par_ConcMarkingClosure::trim_queue(size_t max) { |
| 4106 while (_work_queue->size() > max) { | |
| 4107 oop new_oop; | |
| 4108 if (_work_queue->pop_local(new_oop)) { | |
| 4109 assert(new_oop->is_oop(), "Should be an oop"); | |
| 4110 assert(_bit_map->isMarked((HeapWord*)new_oop), "Grey object"); | |
| 4111 assert(_span.contains((HeapWord*)new_oop), "Not in span"); | |
| 4112 assert(new_oop->is_parsable(), "Should be parsable"); | |
| 4113 new_oop->oop_iterate(this); // do_oop() above | |
| 4114 } | |
| 4115 } | |
| 4116 } | |
| 4117 | |
| 4118 // Upon stack overflow, we discard (part of) the stack, | |
| 4119 // remembering the least address amongst those discarded | |
| 4120 // in CMSCollector's _restart_address. | |
| 4121 void Par_ConcMarkingClosure::handle_stack_overflow(HeapWord* lost) { | |
| 4122 // We need to do this under a mutex to prevent other | |
|
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4123 // workers from interfering with the work done below. |
| 0 | 4124 MutexLockerEx ml(_overflow_stack->par_lock(), |
| 4125 Mutex::_no_safepoint_check_flag); | |
| 4126 // Remember the least grey address discarded | |
| 4127 HeapWord* ra = (HeapWord*)_overflow_stack->least_value(lost); | |
| 4128 _collector->lower_restart_addr(ra); | |
| 4129 _overflow_stack->reset(); // discard stack contents | |
| 4130 _overflow_stack->expand(); // expand the stack if possible | |
| 4131 } | |
| 4132 | |
| 4133 | |
| 4134 void CMSConcMarkingTask::do_work_steal(int i) { | |
| 4135 OopTaskQueue* work_q = work_queue(i); | |
| 4136 oop obj_to_scan; | |
| 4137 CMSBitMap* bm = &(_collector->_markBitMap); | |
| 4138 CMSMarkStack* ovflw = &(_collector->_markStack); | |
| 935 | 4139 CMSMarkStack* revisit = &(_collector->_revisitStack); |
| 0 | 4140 int* seed = _collector->hash_seed(i); |
| 935 | 4141 Par_ConcMarkingClosure cl(_collector, work_q, bm, ovflw, revisit); |
| 0 | 4142 while (true) { |
| 4143 cl.trim_queue(0); | |
| 4144 assert(work_q->size() == 0, "Should have been emptied above"); | |
| 4145 if (get_work_from_overflow_stack(ovflw, work_q)) { | |
| 4146 // Can't assert below because the work obtained from the | |
| 4147 // overflow stack may already have been stolen from us. | |
| 4148 // assert(work_q->size() > 0, "Work from overflow stack"); | |
| 4149 continue; | |
| 4150 } else if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) { | |
| 4151 assert(obj_to_scan->is_oop(), "Should be an oop"); | |
| 4152 assert(bm->isMarked((HeapWord*)obj_to_scan), "Grey object"); | |
| 4153 obj_to_scan->oop_iterate(&cl); | |
| 4154 } else if (terminator()->offer_termination()) { | |
| 4155 assert(work_q->size() == 0, "Impossible!"); | |
| 4156 break; | |
| 4157 } | |
| 4158 } | |
| 4159 } | |
| 4160 | |
| 4161 // This is run by the CMS (coordinator) thread. | |
| 4162 void CMSConcMarkingTask::coordinator_yield() { | |
| 4163 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 4164 "CMS thread should hold CMS token"); | |
| 935 | 4165 DEBUG_ONLY(RememberKlassesChecker mux(false);) |
| 0 | 4166 // First give up the locks, then yield, then re-lock |
| 4167 // We should probably use a constructor/destructor idiom to | |
| 4168 // do this unlock/lock or modify the MutexUnlocker class to | |
| 4169 // serve our purpose. XXX | |
| 4170 assert_lock_strong(_bit_map_lock); | |
| 4171 _bit_map_lock->unlock(); | |
| 4172 ConcurrentMarkSweepThread::desynchronize(true); | |
| 4173 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 4174 _collector->stopTimer(); | |
| 4175 if (PrintCMSStatistics != 0) { | |
| 4176 _collector->incrementYields(); | |
| 4177 } | |
| 4178 _collector->icms_wait(); | |
| 4179 | |
| 4180 // It is possible for whichever thread initiated the yield request | |
| 4181 // not to get a chance to wake up and take the bitmap lock between | |
| 4182 // this thread releasing it and reacquiring it. So, while the | |
| 4183 // should_yield() flag is on, let's sleep for a bit to give the | |
| 4184 // other thread a chance to wake up. The limit imposed on the number | |
| 4185 // of iterations is defensive, to avoid any unforseen circumstances | |
| 4186 // putting us into an infinite loop. Since it's always been this | |
| 4187 // (coordinator_yield()) method that was observed to cause the | |
| 4188 // problem, we are using a parameter (CMSCoordinatorYieldSleepCount) | |
| 4189 // which is by default non-zero. For the other seven methods that | |
| 4190 // also perform the yield operation, as are using a different | |
| 4191 // parameter (CMSYieldSleepCount) which is by default zero. This way we | |
| 4192 // can enable the sleeping for those methods too, if necessary. | |
| 4193 // See 6442774. | |
| 4194 // | |
| 4195 // We really need to reconsider the synchronization between the GC | |
| 4196 // thread and the yield-requesting threads in the future and we | |
| 4197 // should really use wait/notify, which is the recommended | |
| 4198 // way of doing this type of interaction. Additionally, we should | |
| 4199 // consolidate the eight methods that do the yield operation and they | |
| 4200 // are almost identical into one for better maintenability and | |
| 4201 // readability. See 6445193. | |
| 4202 // | |
| 4203 // Tony 2006.06.29 | |
| 4204 for (unsigned i = 0; i < CMSCoordinatorYieldSleepCount && | |
|
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4205 ConcurrentMarkSweepThread::should_yield() && |
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4206 !CMSCollector::foregroundGCIsActive(); ++i) { |
| 0 | 4207 os::sleep(Thread::current(), 1, false); |
| 4208 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 4209 } | |
| 4210 | |
| 4211 ConcurrentMarkSweepThread::synchronize(true); | |
| 4212 _bit_map_lock->lock_without_safepoint_check(); | |
| 4213 _collector->startTimer(); | |
| 4214 } | |
| 4215 | |
| 4216 bool CMSCollector::do_marking_mt(bool asynch) { | |
| 1284 | 4217 assert(ConcGCThreads > 0 && conc_workers() != NULL, "precondition"); |
| 0 | 4218 // In the future this would be determined ergonomically, based |
| 4219 // on #cpu's, # active mutator threads (and load), and mutation rate. | |
| 1284 | 4220 int num_workers = ConcGCThreads; |
| 0 | 4221 |
| 4222 CompactibleFreeListSpace* cms_space = _cmsGen->cmsSpace(); | |
| 4223 CompactibleFreeListSpace* perm_space = _permGen->cmsSpace(); | |
| 4224 | |
|
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4225 CMSConcMarkingTask tsk(this, |
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4226 cms_space, |
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4227 perm_space, |
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4228 asynch, |
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4229 conc_workers(), |
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4230 task_queues()); |
| 0 | 4231 |
| 4232 // Since the actual number of workers we get may be different | |
| 4233 // from the number we requested above, do we need to do anything different | |
| 4234 // below? In particular, may be we need to subclass the SequantialSubTasksDone | |
| 4235 // class?? XXX | |
| 4236 cms_space ->initialize_sequential_subtasks_for_marking(num_workers); | |
| 4237 perm_space->initialize_sequential_subtasks_for_marking(num_workers); | |
| 4238 | |
| 4239 // Refs discovery is already non-atomic. | |
| 4240 assert(!ref_processor()->discovery_is_atomic(), "Should be non-atomic"); | |
| 4241 // Mutate the Refs discovery so it is MT during the | |
| 4242 // multi-threaded marking phase. | |
| 4243 ReferenceProcessorMTMutator mt(ref_processor(), num_workers > 1); | |
|
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4244 DEBUG_ONLY(RememberKlassesChecker cmx(should_unload_classes());) |
| 0 | 4245 conc_workers()->start_task(&tsk); |
| 4246 while (tsk.yielded()) { | |
| 4247 tsk.coordinator_yield(); | |
| 4248 conc_workers()->continue_task(&tsk); | |
| 4249 } | |
| 4250 // If the task was aborted, _restart_addr will be non-NULL | |
| 4251 assert(tsk.completed() || _restart_addr != NULL, "Inconsistency"); | |
| 4252 while (_restart_addr != NULL) { | |
| 4253 // XXX For now we do not make use of ABORTED state and have not | |
| 4254 // yet implemented the right abort semantics (even in the original | |
| 4255 // single-threaded CMS case). That needs some more investigation | |
| 4256 // and is deferred for now; see CR# TBF. 07252005YSR. XXX | |
| 4257 assert(!CMSAbortSemantics || tsk.aborted(), "Inconsistency"); | |
| 4258 // If _restart_addr is non-NULL, a marking stack overflow | |
| 605 | 4259 // occurred; we need to do a fresh marking iteration from the |
| 0 | 4260 // indicated restart address. |
| 4261 if (_foregroundGCIsActive && asynch) { | |
| 4262 // We may be running into repeated stack overflows, having | |
| 4263 // reached the limit of the stack size, while making very | |
| 4264 // slow forward progress. It may be best to bail out and | |
| 4265 // let the foreground collector do its job. | |
| 4266 // Clear _restart_addr, so that foreground GC | |
| 4267 // works from scratch. This avoids the headache of | |
| 4268 // a "rescan" which would otherwise be needed because | |
| 4269 // of the dirty mod union table & card table. | |
| 4270 _restart_addr = NULL; | |
| 4271 return false; | |
| 4272 } | |
| 4273 // Adjust the task to restart from _restart_addr | |
| 4274 tsk.reset(_restart_addr); | |
| 4275 cms_space ->initialize_sequential_subtasks_for_marking(num_workers, | |
| 4276 _restart_addr); | |
| 4277 perm_space->initialize_sequential_subtasks_for_marking(num_workers, | |
| 4278 _restart_addr); | |
| 4279 _restart_addr = NULL; | |
| 4280 // Get the workers going again | |
| 4281 conc_workers()->start_task(&tsk); | |
| 4282 while (tsk.yielded()) { | |
| 4283 tsk.coordinator_yield(); | |
| 4284 conc_workers()->continue_task(&tsk); | |
| 4285 } | |
| 4286 } | |
| 4287 assert(tsk.completed(), "Inconsistency"); | |
| 4288 assert(tsk.result() == true, "Inconsistency"); | |
| 4289 return true; | |
| 4290 } | |
| 4291 | |
| 4292 bool CMSCollector::do_marking_st(bool asynch) { | |
| 4293 ResourceMark rm; | |
| 4294 HandleMark hm; | |
| 4295 | |
| 4296 MarkFromRootsClosure markFromRootsClosure(this, _span, &_markBitMap, | |
| 4297 &_markStack, &_revisitStack, CMSYield && asynch); | |
| 4298 // the last argument to iterate indicates whether the iteration | |
| 4299 // should be incremental with periodic yields. | |
| 4300 _markBitMap.iterate(&markFromRootsClosure); | |
| 4301 // If _restart_addr is non-NULL, a marking stack overflow | |
| 605 | 4302 // occurred; we need to do a fresh iteration from the |
| 0 | 4303 // indicated restart address. |
| 4304 while (_restart_addr != NULL) { | |
| 4305 if (_foregroundGCIsActive && asynch) { | |
| 4306 // We may be running into repeated stack overflows, having | |
| 4307 // reached the limit of the stack size, while making very | |
| 4308 // slow forward progress. It may be best to bail out and | |
| 4309 // let the foreground collector do its job. | |
| 4310 // Clear _restart_addr, so that foreground GC | |
| 4311 // works from scratch. This avoids the headache of | |
| 4312 // a "rescan" which would otherwise be needed because | |
| 4313 // of the dirty mod union table & card table. | |
| 4314 _restart_addr = NULL; | |
| 4315 return false; // indicating failure to complete marking | |
| 4316 } | |
| 4317 // Deal with stack overflow: | |
| 4318 // we restart marking from _restart_addr | |
| 4319 HeapWord* ra = _restart_addr; | |
| 4320 markFromRootsClosure.reset(ra); | |
| 4321 _restart_addr = NULL; | |
| 4322 _markBitMap.iterate(&markFromRootsClosure, ra, _span.end()); | |
| 4323 } | |
| 4324 return true; | |
| 4325 } | |
| 4326 | |
| 4327 void CMSCollector::preclean() { | |
| 4328 check_correct_thread_executing(); | |
| 4329 assert(Thread::current()->is_ConcurrentGC_thread(), "Wrong thread"); | |
| 4330 verify_work_stacks_empty(); | |
| 4331 verify_overflow_empty(); | |
| 4332 _abort_preclean = false; | |
| 4333 if (CMSPrecleaningEnabled) { | |
|
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4334 // Precleaning is currently not MT but the reference processor |
|
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4335 // may be set for MT. Disable it temporarily here. |
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|
4336 ReferenceProcessor* rp = ref_processor(); |
|
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|
4337 ReferenceProcessorMTProcMutator z(rp, false); |
| 0 | 4338 _eden_chunk_index = 0; |
| 4339 size_t used = get_eden_used(); | |
| 4340 size_t capacity = get_eden_capacity(); | |
| 4341 // Don't start sampling unless we will get sufficiently | |
| 4342 // many samples. | |
| 4343 if (used < (capacity/(CMSScheduleRemarkSamplingRatio * 100) | |
| 4344 * CMSScheduleRemarkEdenPenetration)) { | |
| 4345 _start_sampling = true; | |
| 4346 } else { | |
| 4347 _start_sampling = false; | |
| 4348 } | |
| 4349 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
| 4350 CMSPhaseAccounting pa(this, "preclean", !PrintGCDetails); | |
| 4351 preclean_work(CMSPrecleanRefLists1, CMSPrecleanSurvivors1); | |
| 4352 } | |
| 4353 CMSTokenSync x(true); // is cms thread | |
| 4354 if (CMSPrecleaningEnabled) { | |
| 4355 sample_eden(); | |
| 4356 _collectorState = AbortablePreclean; | |
| 4357 } else { | |
| 4358 _collectorState = FinalMarking; | |
| 4359 } | |
| 4360 verify_work_stacks_empty(); | |
| 4361 verify_overflow_empty(); | |
| 4362 } | |
| 4363 | |
| 4364 // Try and schedule the remark such that young gen | |
| 4365 // occupancy is CMSScheduleRemarkEdenPenetration %. | |
| 4366 void CMSCollector::abortable_preclean() { | |
| 4367 check_correct_thread_executing(); | |
| 4368 assert(CMSPrecleaningEnabled, "Inconsistent control state"); | |
| 4369 assert(_collectorState == AbortablePreclean, "Inconsistent control state"); | |
| 4370 | |
| 4371 // If Eden's current occupancy is below this threshold, | |
| 4372 // immediately schedule the remark; else preclean | |
| 4373 // past the next scavenge in an effort to | |
| 4374 // schedule the pause as described avove. By choosing | |
| 4375 // CMSScheduleRemarkEdenSizeThreshold >= max eden size | |
| 4376 // we will never do an actual abortable preclean cycle. | |
| 4377 if (get_eden_used() > CMSScheduleRemarkEdenSizeThreshold) { | |
| 4378 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
| 4379 CMSPhaseAccounting pa(this, "abortable-preclean", !PrintGCDetails); | |
| 4380 // We need more smarts in the abortable preclean | |
| 4381 // loop below to deal with cases where allocation | |
| 4382 // in young gen is very very slow, and our precleaning | |
| 4383 // is running a losing race against a horde of | |
| 4384 // mutators intent on flooding us with CMS updates | |
| 4385 // (dirty cards). | |
| 4386 // One, admittedly dumb, strategy is to give up | |
| 4387 // after a certain number of abortable precleaning loops | |
| 4388 // or after a certain maximum time. We want to make | |
| 4389 // this smarter in the next iteration. | |
| 4390 // XXX FIX ME!!! YSR | |
| 4391 size_t loops = 0, workdone = 0, cumworkdone = 0, waited = 0; | |
| 4392 while (!(should_abort_preclean() || | |
| 4393 ConcurrentMarkSweepThread::should_terminate())) { | |
| 4394 workdone = preclean_work(CMSPrecleanRefLists2, CMSPrecleanSurvivors2); | |
| 4395 cumworkdone += workdone; | |
| 4396 loops++; | |
| 4397 // Voluntarily terminate abortable preclean phase if we have | |
| 4398 // been at it for too long. | |
| 4399 if ((CMSMaxAbortablePrecleanLoops != 0) && | |
| 4400 loops >= CMSMaxAbortablePrecleanLoops) { | |
| 4401 if (PrintGCDetails) { | |
| 4402 gclog_or_tty->print(" CMS: abort preclean due to loops "); | |
| 4403 } | |
| 4404 break; | |
| 4405 } | |
| 4406 if (pa.wallclock_millis() > CMSMaxAbortablePrecleanTime) { | |
| 4407 if (PrintGCDetails) { | |
| 4408 gclog_or_tty->print(" CMS: abort preclean due to time "); | |
| 4409 } | |
| 4410 break; | |
| 4411 } | |
| 4412 // If we are doing little work each iteration, we should | |
| 4413 // take a short break. | |
| 4414 if (workdone < CMSAbortablePrecleanMinWorkPerIteration) { | |
| 4415 // Sleep for some time, waiting for work to accumulate | |
| 4416 stopTimer(); | |
| 4417 cmsThread()->wait_on_cms_lock(CMSAbortablePrecleanWaitMillis); | |
| 4418 startTimer(); | |
| 4419 waited++; | |
| 4420 } | |
| 4421 } | |
| 4422 if (PrintCMSStatistics > 0) { | |
| 4423 gclog_or_tty->print(" [%d iterations, %d waits, %d cards)] ", | |
| 4424 loops, waited, cumworkdone); | |
| 4425 } | |
| 4426 } | |
| 4427 CMSTokenSync x(true); // is cms thread | |
| 4428 if (_collectorState != Idling) { | |
| 4429 assert(_collectorState == AbortablePreclean, | |
| 4430 "Spontaneous state transition?"); | |
| 4431 _collectorState = FinalMarking; | |
| 4432 } // Else, a foreground collection completed this CMS cycle. | |
| 4433 return; | |
| 4434 } | |
| 4435 | |
| 4436 // Respond to an Eden sampling opportunity | |
| 4437 void CMSCollector::sample_eden() { | |
| 4438 // Make sure a young gc cannot sneak in between our | |
| 4439 // reading and recording of a sample. | |
| 4440 assert(Thread::current()->is_ConcurrentGC_thread(), | |
| 4441 "Only the cms thread may collect Eden samples"); | |
| 4442 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 4443 "Should collect samples while holding CMS token"); | |
| 4444 if (!_start_sampling) { | |
| 4445 return; | |
| 4446 } | |
| 4447 if (_eden_chunk_array) { | |
| 4448 if (_eden_chunk_index < _eden_chunk_capacity) { | |
| 4449 _eden_chunk_array[_eden_chunk_index] = *_top_addr; // take sample | |
| 4450 assert(_eden_chunk_array[_eden_chunk_index] <= *_end_addr, | |
| 4451 "Unexpected state of Eden"); | |
| 4452 // We'd like to check that what we just sampled is an oop-start address; | |
| 4453 // however, we cannot do that here since the object may not yet have been | |
| 4454 // initialized. So we'll instead do the check when we _use_ this sample | |
| 4455 // later. | |
| 4456 if (_eden_chunk_index == 0 || | |
| 4457 (pointer_delta(_eden_chunk_array[_eden_chunk_index], | |
| 4458 _eden_chunk_array[_eden_chunk_index-1]) | |
| 4459 >= CMSSamplingGrain)) { | |
| 4460 _eden_chunk_index++; // commit sample | |
| 4461 } | |
| 4462 } | |
| 4463 } | |
| 4464 if ((_collectorState == AbortablePreclean) && !_abort_preclean) { | |
| 4465 size_t used = get_eden_used(); | |
| 4466 size_t capacity = get_eden_capacity(); | |
| 4467 assert(used <= capacity, "Unexpected state of Eden"); | |
| 4468 if (used > (capacity/100 * CMSScheduleRemarkEdenPenetration)) { | |
| 4469 _abort_preclean = true; | |
| 4470 } | |
| 4471 } | |
| 4472 } | |
| 4473 | |
| 4474 | |
| 4475 size_t CMSCollector::preclean_work(bool clean_refs, bool clean_survivor) { | |
| 4476 assert(_collectorState == Precleaning || | |
| 4477 _collectorState == AbortablePreclean, "incorrect state"); | |
| 4478 ResourceMark rm; | |
| 4479 HandleMark hm; | |
| 4480 // Do one pass of scrubbing the discovered reference lists | |
| 4481 // to remove any reference objects with strongly-reachable | |
| 4482 // referents. | |
| 4483 if (clean_refs) { | |
| 4484 ReferenceProcessor* rp = ref_processor(); | |
| 4485 CMSPrecleanRefsYieldClosure yield_cl(this); | |
| 4486 assert(rp->span().equals(_span), "Spans should be equal"); | |
| 4487 CMSKeepAliveClosure keep_alive(this, _span, &_markBitMap, | |
| 935 | 4488 &_markStack, &_revisitStack, |
| 4489 true /* preclean */); | |
| 0 | 4490 CMSDrainMarkingStackClosure complete_trace(this, |
|
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4491 _span, &_markBitMap, &_markStack, |
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|
4492 &keep_alive, true /* preclean */); |
| 0 | 4493 |
| 4494 // We don't want this step to interfere with a young | |
| 4495 // collection because we don't want to take CPU | |
| 4496 // or memory bandwidth away from the young GC threads | |
| 4497 // (which may be as many as there are CPUs). | |
| 4498 // Note that we don't need to protect ourselves from | |
| 4499 // interference with mutators because they can't | |
| 4500 // manipulate the discovered reference lists nor affect | |
| 4501 // the computed reachability of the referents, the | |
| 4502 // only properties manipulated by the precleaning | |
| 4503 // of these reference lists. | |
| 4504 stopTimer(); | |
| 4505 CMSTokenSyncWithLocks x(true /* is cms thread */, | |
| 4506 bitMapLock()); | |
| 4507 startTimer(); | |
| 4508 sample_eden(); | |
| 935 | 4509 |
| 0 | 4510 // The following will yield to allow foreground |
| 4511 // collection to proceed promptly. XXX YSR: | |
| 4512 // The code in this method may need further | |
| 4513 // tweaking for better performance and some restructuring | |
| 4514 // for cleaner interfaces. | |
| 4515 rp->preclean_discovered_references( | |
| 4516 rp->is_alive_non_header(), &keep_alive, &complete_trace, | |
|
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|
4517 &yield_cl, should_unload_classes()); |
| 0 | 4518 } |
| 4519 | |
| 4520 if (clean_survivor) { // preclean the active survivor space(s) | |
| 4521 assert(_young_gen->kind() == Generation::DefNew || | |
| 4522 _young_gen->kind() == Generation::ParNew || | |
| 4523 _young_gen->kind() == Generation::ASParNew, | |
| 4524 "incorrect type for cast"); | |
| 4525 DefNewGeneration* dng = (DefNewGeneration*)_young_gen; | |
| 4526 PushAndMarkClosure pam_cl(this, _span, ref_processor(), | |
| 4527 &_markBitMap, &_modUnionTable, | |
| 4528 &_markStack, &_revisitStack, | |
| 4529 true /* precleaning phase */); | |
| 4530 stopTimer(); | |
| 4531 CMSTokenSyncWithLocks ts(true /* is cms thread */, | |
| 4532 bitMapLock()); | |
| 4533 startTimer(); | |
| 4534 unsigned int before_count = | |
| 4535 GenCollectedHeap::heap()->total_collections(); | |
| 4536 SurvivorSpacePrecleanClosure | |
| 4537 sss_cl(this, _span, &_markBitMap, &_markStack, | |
| 4538 &pam_cl, before_count, CMSYield); | |
|
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|
4539 DEBUG_ONLY(RememberKlassesChecker mx(should_unload_classes());) |
| 0 | 4540 dng->from()->object_iterate_careful(&sss_cl); |
| 4541 dng->to()->object_iterate_careful(&sss_cl); | |
| 4542 } | |
| 4543 MarkRefsIntoAndScanClosure | |
| 4544 mrias_cl(_span, ref_processor(), &_markBitMap, &_modUnionTable, | |
| 4545 &_markStack, &_revisitStack, this, CMSYield, | |
| 4546 true /* precleaning phase */); | |
| 4547 // CAUTION: The following closure has persistent state that may need to | |
| 4548 // be reset upon a decrease in the sequence of addresses it | |
| 4549 // processes. | |
| 4550 ScanMarkedObjectsAgainCarefullyClosure | |
| 4551 smoac_cl(this, _span, | |
| 4552 &_markBitMap, &_markStack, &_revisitStack, &mrias_cl, CMSYield); | |
| 4553 | |
| 4554 // Preclean dirty cards in ModUnionTable and CardTable using | |
| 4555 // appropriate convergence criterion; | |
| 4556 // repeat CMSPrecleanIter times unless we find that | |
| 4557 // we are losing. | |
| 4558 assert(CMSPrecleanIter < 10, "CMSPrecleanIter is too large"); | |
| 4559 assert(CMSPrecleanNumerator < CMSPrecleanDenominator, | |
| 4560 "Bad convergence multiplier"); | |
| 4561 assert(CMSPrecleanThreshold >= 100, | |
| 4562 "Unreasonably low CMSPrecleanThreshold"); | |
| 4563 | |
| 4564 size_t numIter, cumNumCards, lastNumCards, curNumCards; | |
| 4565 for (numIter = 0, cumNumCards = lastNumCards = curNumCards = 0; | |
| 4566 numIter < CMSPrecleanIter; | |
| 4567 numIter++, lastNumCards = curNumCards, cumNumCards += curNumCards) { | |
| 4568 curNumCards = preclean_mod_union_table(_cmsGen, &smoac_cl); | |
| 4569 if (CMSPermGenPrecleaningEnabled) { | |
| 4570 curNumCards += preclean_mod_union_table(_permGen, &smoac_cl); | |
| 4571 } | |
| 4572 if (Verbose && PrintGCDetails) { | |
| 4573 gclog_or_tty->print(" (modUnionTable: %d cards)", curNumCards); | |
| 4574 } | |
| 4575 // Either there are very few dirty cards, so re-mark | |
| 4576 // pause will be small anyway, or our pre-cleaning isn't | |
| 4577 // that much faster than the rate at which cards are being | |
| 4578 // dirtied, so we might as well stop and re-mark since | |
| 4579 // precleaning won't improve our re-mark time by much. | |
| 4580 if (curNumCards <= CMSPrecleanThreshold || | |
| 4581 (numIter > 0 && | |
| 4582 (curNumCards * CMSPrecleanDenominator > | |
| 4583 lastNumCards * CMSPrecleanNumerator))) { | |
| 4584 numIter++; | |
| 4585 cumNumCards += curNumCards; | |
| 4586 break; | |
| 4587 } | |
| 4588 } | |
| 4589 curNumCards = preclean_card_table(_cmsGen, &smoac_cl); | |
| 4590 if (CMSPermGenPrecleaningEnabled) { | |
| 4591 curNumCards += preclean_card_table(_permGen, &smoac_cl); | |
| 4592 } | |
| 4593 cumNumCards += curNumCards; | |
| 4594 if (PrintGCDetails && PrintCMSStatistics != 0) { | |
| 4595 gclog_or_tty->print_cr(" (cardTable: %d cards, re-scanned %d cards, %d iterations)", | |
| 4596 curNumCards, cumNumCards, numIter); | |
| 4597 } | |
| 4598 return cumNumCards; // as a measure of useful work done | |
| 4599 } | |
| 4600 | |
| 4601 // PRECLEANING NOTES: | |
| 4602 // Precleaning involves: | |
| 4603 // . reading the bits of the modUnionTable and clearing the set bits. | |
| 4604 // . For the cards corresponding to the set bits, we scan the | |
| 4605 // objects on those cards. This means we need the free_list_lock | |
| 4606 // so that we can safely iterate over the CMS space when scanning | |
| 4607 // for oops. | |
| 4608 // . When we scan the objects, we'll be both reading and setting | |
| 4609 // marks in the marking bit map, so we'll need the marking bit map. | |
| 4610 // . For protecting _collector_state transitions, we take the CGC_lock. | |
| 4611 // Note that any races in the reading of of card table entries by the | |
| 4612 // CMS thread on the one hand and the clearing of those entries by the | |
| 4613 // VM thread or the setting of those entries by the mutator threads on the | |
| 4614 // other are quite benign. However, for efficiency it makes sense to keep | |
| 4615 // the VM thread from racing with the CMS thread while the latter is | |
| 4616 // dirty card info to the modUnionTable. We therefore also use the | |
| 4617 // CGC_lock to protect the reading of the card table and the mod union | |
| 4618 // table by the CM thread. | |
| 4619 // . We run concurrently with mutator updates, so scanning | |
| 4620 // needs to be done carefully -- we should not try to scan | |
| 4621 // potentially uninitialized objects. | |
| 4622 // | |
| 4623 // Locking strategy: While holding the CGC_lock, we scan over and | |
| 4624 // reset a maximal dirty range of the mod union / card tables, then lock | |
| 4625 // the free_list_lock and bitmap lock to do a full marking, then | |
| 4626 // release these locks; and repeat the cycle. This allows for a | |
| 4627 // certain amount of fairness in the sharing of these locks between | |
| 4628 // the CMS collector on the one hand, and the VM thread and the | |
| 4629 // mutators on the other. | |
| 4630 | |
| 4631 // NOTE: preclean_mod_union_table() and preclean_card_table() | |
| 4632 // further below are largely identical; if you need to modify | |
| 4633 // one of these methods, please check the other method too. | |
| 4634 | |
| 4635 size_t CMSCollector::preclean_mod_union_table( | |
| 4636 ConcurrentMarkSweepGeneration* gen, | |
| 4637 ScanMarkedObjectsAgainCarefullyClosure* cl) { | |
| 4638 verify_work_stacks_empty(); | |
| 4639 verify_overflow_empty(); | |
| 4640 | |
| 935 | 4641 // Turn off checking for this method but turn it back on |
| 4642 // selectively. There are yield points in this method | |
| 4643 // but it is difficult to turn the checking off just around | |
| 4644 // the yield points. It is simpler to selectively turn | |
| 4645 // it on. | |
| 4646 DEBUG_ONLY(RememberKlassesChecker mux(false);) | |
| 4647 | |
| 0 | 4648 // strategy: starting with the first card, accumulate contiguous |
| 4649 // ranges of dirty cards; clear these cards, then scan the region | |
| 4650 // covered by these cards. | |
| 4651 | |
| 4652 // Since all of the MUT is committed ahead, we can just use | |
| 4653 // that, in case the generations expand while we are precleaning. | |
| 4654 // It might also be fine to just use the committed part of the | |
| 4655 // generation, but we might potentially miss cards when the | |
| 4656 // generation is rapidly expanding while we are in the midst | |
| 4657 // of precleaning. | |
| 4658 HeapWord* startAddr = gen->reserved().start(); | |
| 4659 HeapWord* endAddr = gen->reserved().end(); | |
| 4660 | |
| 4661 cl->setFreelistLock(gen->freelistLock()); // needed for yielding | |
| 4662 | |
| 4663 size_t numDirtyCards, cumNumDirtyCards; | |
| 4664 HeapWord *nextAddr, *lastAddr; | |
| 4665 for (cumNumDirtyCards = numDirtyCards = 0, | |
| 4666 nextAddr = lastAddr = startAddr; | |
| 4667 nextAddr < endAddr; | |
| 4668 nextAddr = lastAddr, cumNumDirtyCards += numDirtyCards) { | |
| 4669 | |
| 4670 ResourceMark rm; | |
| 4671 HandleMark hm; | |
| 4672 | |
| 4673 MemRegion dirtyRegion; | |
| 4674 { | |
| 4675 stopTimer(); | |
| 935 | 4676 // Potential yield point |
| 0 | 4677 CMSTokenSync ts(true); |
| 4678 startTimer(); | |
| 4679 sample_eden(); | |
| 4680 // Get dirty region starting at nextOffset (inclusive), | |
| 4681 // simultaneously clearing it. | |
| 4682 dirtyRegion = | |
| 4683 _modUnionTable.getAndClearMarkedRegion(nextAddr, endAddr); | |
| 4684 assert(dirtyRegion.start() >= nextAddr, | |
| 4685 "returned region inconsistent?"); | |
| 4686 } | |
| 4687 // Remember where the next search should begin. | |
| 4688 // The returned region (if non-empty) is a right open interval, | |
| 4689 // so lastOffset is obtained from the right end of that | |
| 4690 // interval. | |
| 4691 lastAddr = dirtyRegion.end(); | |
| 4692 // Should do something more transparent and less hacky XXX | |
| 4693 numDirtyCards = | |
| 4694 _modUnionTable.heapWordDiffToOffsetDiff(dirtyRegion.word_size()); | |
| 4695 | |
| 4696 // We'll scan the cards in the dirty region (with periodic | |
| 4697 // yields for foreground GC as needed). | |
| 4698 if (!dirtyRegion.is_empty()) { | |
| 4699 assert(numDirtyCards > 0, "consistency check"); | |
| 4700 HeapWord* stop_point = NULL; | |
|
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4701 stopTimer(); |
| 935 | 4702 // Potential yield point |
|
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4703 CMSTokenSyncWithLocks ts(true, gen->freelistLock(), |
|
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|
4704 bitMapLock()); |
|
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|
4705 startTimer(); |
| 0 | 4706 { |
| 4707 verify_work_stacks_empty(); | |
| 4708 verify_overflow_empty(); | |
| 4709 sample_eden(); | |
|
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|
4710 DEBUG_ONLY(RememberKlassesChecker mx(should_unload_classes());) |
| 0 | 4711 stop_point = |
| 4712 gen->cmsSpace()->object_iterate_careful_m(dirtyRegion, cl); | |
| 4713 } | |
| 4714 if (stop_point != NULL) { | |
| 4715 // The careful iteration stopped early either because it found an | |
| 4716 // uninitialized object, or because we were in the midst of an | |
| 4717 // "abortable preclean", which should now be aborted. Redirty | |
| 4718 // the bits corresponding to the partially-scanned or unscanned | |
| 4719 // cards. We'll either restart at the next block boundary or | |
| 4720 // abort the preclean. | |
| 4721 assert((CMSPermGenPrecleaningEnabled && (gen == _permGen)) || | |
| 4722 (_collectorState == AbortablePreclean && should_abort_preclean()), | |
| 4723 "Unparsable objects should only be in perm gen."); | |
| 4724 _modUnionTable.mark_range(MemRegion(stop_point, dirtyRegion.end())); | |
| 4725 if (should_abort_preclean()) { | |
| 4726 break; // out of preclean loop | |
| 4727 } else { | |
| 4728 // Compute the next address at which preclean should pick up; | |
| 4729 // might need bitMapLock in order to read P-bits. | |
| 4730 lastAddr = next_card_start_after_block(stop_point); | |
| 4731 } | |
| 4732 } | |
| 4733 } else { | |
| 4734 assert(lastAddr == endAddr, "consistency check"); | |
| 4735 assert(numDirtyCards == 0, "consistency check"); | |
| 4736 break; | |
| 4737 } | |
| 4738 } | |
| 4739 verify_work_stacks_empty(); | |
| 4740 verify_overflow_empty(); | |
| 4741 return cumNumDirtyCards; | |
| 4742 } | |
| 4743 | |
| 4744 // NOTE: preclean_mod_union_table() above and preclean_card_table() | |
| 4745 // below are largely identical; if you need to modify | |
| 4746 // one of these methods, please check the other method too. | |
| 4747 | |
| 4748 size_t CMSCollector::preclean_card_table(ConcurrentMarkSweepGeneration* gen, | |
| 4749 ScanMarkedObjectsAgainCarefullyClosure* cl) { | |
| 4750 // strategy: it's similar to precleamModUnionTable above, in that | |
| 4751 // we accumulate contiguous ranges of dirty cards, mark these cards | |
| 4752 // precleaned, then scan the region covered by these cards. | |
| 4753 HeapWord* endAddr = (HeapWord*)(gen->_virtual_space.high()); | |
| 4754 HeapWord* startAddr = (HeapWord*)(gen->_virtual_space.low()); | |
| 4755 | |
| 4756 cl->setFreelistLock(gen->freelistLock()); // needed for yielding | |
| 4757 | |
| 4758 size_t numDirtyCards, cumNumDirtyCards; | |
| 4759 HeapWord *lastAddr, *nextAddr; | |
| 4760 | |
| 4761 for (cumNumDirtyCards = numDirtyCards = 0, | |
| 4762 nextAddr = lastAddr = startAddr; | |
| 4763 nextAddr < endAddr; | |
| 4764 nextAddr = lastAddr, cumNumDirtyCards += numDirtyCards) { | |
| 4765 | |
| 4766 ResourceMark rm; | |
| 4767 HandleMark hm; | |
| 4768 | |
| 4769 MemRegion dirtyRegion; | |
| 4770 { | |
| 4771 // See comments in "Precleaning notes" above on why we | |
| 4772 // do this locking. XXX Could the locking overheads be | |
| 4773 // too high when dirty cards are sparse? [I don't think so.] | |
| 4774 stopTimer(); | |
| 4775 CMSTokenSync x(true); // is cms thread | |
| 4776 startTimer(); | |
| 4777 sample_eden(); | |
| 4778 // Get and clear dirty region from card table | |
|
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4779 dirtyRegion = _ct->ct_bs()->dirty_card_range_after_reset( |
|
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|
4780 MemRegion(nextAddr, endAddr), |
|
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|
4781 true, |
|
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|
4782 CardTableModRefBS::precleaned_card_val()); |
|
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|
4783 |
| 0 | 4784 assert(dirtyRegion.start() >= nextAddr, |
| 4785 "returned region inconsistent?"); | |
| 4786 } | |
| 4787 lastAddr = dirtyRegion.end(); | |
| 4788 numDirtyCards = | |
| 4789 dirtyRegion.word_size()/CardTableModRefBS::card_size_in_words; | |
| 4790 | |
| 4791 if (!dirtyRegion.is_empty()) { | |
| 4792 stopTimer(); | |
| 4793 CMSTokenSyncWithLocks ts(true, gen->freelistLock(), bitMapLock()); | |
| 4794 startTimer(); | |
| 4795 sample_eden(); | |
| 4796 verify_work_stacks_empty(); | |
| 4797 verify_overflow_empty(); | |
|
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|
4798 DEBUG_ONLY(RememberKlassesChecker mx(should_unload_classes());) |
| 0 | 4799 HeapWord* stop_point = |
| 4800 gen->cmsSpace()->object_iterate_careful_m(dirtyRegion, cl); | |
| 4801 if (stop_point != NULL) { | |
| 4802 // The careful iteration stopped early because it found an | |
| 4803 // uninitialized object. Redirty the bits corresponding to the | |
| 4804 // partially-scanned or unscanned cards, and start again at the | |
| 4805 // next block boundary. | |
| 4806 assert(CMSPermGenPrecleaningEnabled || | |
| 4807 (_collectorState == AbortablePreclean && should_abort_preclean()), | |
| 4808 "Unparsable objects should only be in perm gen."); | |
| 4809 _ct->ct_bs()->invalidate(MemRegion(stop_point, dirtyRegion.end())); | |
| 4810 if (should_abort_preclean()) { | |
| 4811 break; // out of preclean loop | |
| 4812 } else { | |
| 4813 // Compute the next address at which preclean should pick up. | |
| 4814 lastAddr = next_card_start_after_block(stop_point); | |
| 4815 } | |
| 4816 } | |
| 4817 } else { | |
| 4818 break; | |
| 4819 } | |
| 4820 } | |
| 4821 verify_work_stacks_empty(); | |
| 4822 verify_overflow_empty(); | |
| 4823 return cumNumDirtyCards; | |
| 4824 } | |
| 4825 | |
| 4826 void CMSCollector::checkpointRootsFinal(bool asynch, | |
| 4827 bool clear_all_soft_refs, bool init_mark_was_synchronous) { | |
| 4828 assert(_collectorState == FinalMarking, "incorrect state transition?"); | |
| 4829 check_correct_thread_executing(); | |
| 4830 // world is stopped at this checkpoint | |
| 4831 assert(SafepointSynchronize::is_at_safepoint(), | |
| 4832 "world should be stopped"); | |
|
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|
4833 TraceCMSMemoryManagerStats tms(_collectorState); |
| 0 | 4834 verify_work_stacks_empty(); |
| 4835 verify_overflow_empty(); | |
| 4836 | |
| 4837 SpecializationStats::clear(); | |
| 4838 if (PrintGCDetails) { | |
| 4839 gclog_or_tty->print("[YG occupancy: "SIZE_FORMAT" K ("SIZE_FORMAT" K)]", | |
| 4840 _young_gen->used() / K, | |
| 4841 _young_gen->capacity() / K); | |
| 4842 } | |
| 4843 if (asynch) { | |
| 4844 if (CMSScavengeBeforeRemark) { | |
| 4845 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 4846 // Temporarily set flag to false, GCH->do_collection will | |
| 4847 // expect it to be false and set to true | |
| 4848 FlagSetting fl(gch->_is_gc_active, false); | |
| 4849 NOT_PRODUCT(TraceTime t("Scavenge-Before-Remark", | |
| 4850 PrintGCDetails && Verbose, true, gclog_or_tty);) | |
| 4851 int level = _cmsGen->level() - 1; | |
| 4852 if (level >= 0) { | |
| 4853 gch->do_collection(true, // full (i.e. force, see below) | |
| 4854 false, // !clear_all_soft_refs | |
| 4855 0, // size | |
| 4856 false, // is_tlab | |
| 4857 level // max_level | |
| 4858 ); | |
| 4859 } | |
| 4860 } | |
| 4861 FreelistLocker x(this); | |
| 4862 MutexLockerEx y(bitMapLock(), | |
| 4863 Mutex::_no_safepoint_check_flag); | |
| 4864 assert(!init_mark_was_synchronous, "but that's impossible!"); | |
| 4865 checkpointRootsFinalWork(asynch, clear_all_soft_refs, false); | |
| 4866 } else { | |
| 4867 // already have all the locks | |
| 4868 checkpointRootsFinalWork(asynch, clear_all_soft_refs, | |
| 4869 init_mark_was_synchronous); | |
| 4870 } | |
| 4871 verify_work_stacks_empty(); | |
| 4872 verify_overflow_empty(); | |
| 4873 SpecializationStats::print(); | |
| 4874 } | |
| 4875 | |
| 4876 void CMSCollector::checkpointRootsFinalWork(bool asynch, | |
| 4877 bool clear_all_soft_refs, bool init_mark_was_synchronous) { | |
| 4878 | |
| 4879 NOT_PRODUCT(TraceTime tr("checkpointRootsFinalWork", PrintGCDetails, false, gclog_or_tty);) | |
| 4880 | |
| 4881 assert(haveFreelistLocks(), "must have free list locks"); | |
| 4882 assert_lock_strong(bitMapLock()); | |
| 4883 | |
| 4884 if (UseAdaptiveSizePolicy) { | |
| 4885 size_policy()->checkpoint_roots_final_begin(); | |
| 4886 } | |
| 4887 | |
| 4888 ResourceMark rm; | |
| 4889 HandleMark hm; | |
| 4890 | |
| 4891 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 4892 | |
|
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|
4893 if (should_unload_classes()) { |
| 0 | 4894 CodeCache::gc_prologue(); |
| 4895 } | |
| 4896 assert(haveFreelistLocks(), "must have free list locks"); | |
| 4897 assert_lock_strong(bitMapLock()); | |
| 4898 | |
|
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|
4899 DEBUG_ONLY(RememberKlassesChecker fmx(should_unload_classes());) |
| 0 | 4900 if (!init_mark_was_synchronous) { |
| 4901 // We might assume that we need not fill TLAB's when | |
| 4902 // CMSScavengeBeforeRemark is set, because we may have just done | |
| 4903 // a scavenge which would have filled all TLAB's -- and besides | |
| 4904 // Eden would be empty. This however may not always be the case -- | |
| 4905 // for instance although we asked for a scavenge, it may not have | |
| 4906 // happened because of a JNI critical section. We probably need | |
| 4907 // a policy for deciding whether we can in that case wait until | |
| 4908 // the critical section releases and then do the remark following | |
| 4909 // the scavenge, and skip it here. In the absence of that policy, | |
| 4910 // or of an indication of whether the scavenge did indeed occur, | |
| 4911 // we cannot rely on TLAB's having been filled and must do | |
| 4912 // so here just in case a scavenge did not happen. | |
| 4913 gch->ensure_parsability(false); // fill TLAB's, but no need to retire them | |
| 4914 // Update the saved marks which may affect the root scans. | |
| 4915 gch->save_marks(); | |
| 4916 | |
| 4917 { | |
| 4918 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;) | |
| 4919 | |
| 4920 // Note on the role of the mod union table: | |
| 4921 // Since the marker in "markFromRoots" marks concurrently with | |
| 4922 // mutators, it is possible for some reachable objects not to have been | |
| 4923 // scanned. For instance, an only reference to an object A was | |
| 4924 // placed in object B after the marker scanned B. Unless B is rescanned, | |
| 4925 // A would be collected. Such updates to references in marked objects | |
| 4926 // are detected via the mod union table which is the set of all cards | |
| 4927 // dirtied since the first checkpoint in this GC cycle and prior to | |
| 4928 // the most recent young generation GC, minus those cleaned up by the | |
| 4929 // concurrent precleaning. | |
|
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|
4930 if (CMSParallelRemarkEnabled && CollectedHeap::use_parallel_gc_threads()) { |
| 0 | 4931 TraceTime t("Rescan (parallel) ", PrintGCDetails, false, gclog_or_tty); |
| 4932 do_remark_parallel(); | |
| 4933 } else { | |
| 4934 TraceTime t("Rescan (non-parallel) ", PrintGCDetails, false, | |
| 4935 gclog_or_tty); | |
| 4936 do_remark_non_parallel(); | |
| 4937 } | |
| 4938 } | |
| 4939 } else { | |
| 4940 assert(!asynch, "Can't have init_mark_was_synchronous in asynch mode"); | |
| 4941 // The initial mark was stop-world, so there's no rescanning to | |
| 4942 // do; go straight on to the next step below. | |
| 4943 } | |
| 4944 verify_work_stacks_empty(); | |
| 4945 verify_overflow_empty(); | |
| 4946 | |
| 4947 { | |
| 4948 NOT_PRODUCT(TraceTime ts("refProcessingWork", PrintGCDetails, false, gclog_or_tty);) | |
| 4949 refProcessingWork(asynch, clear_all_soft_refs); | |
| 4950 } | |
| 4951 verify_work_stacks_empty(); | |
| 4952 verify_overflow_empty(); | |
| 4953 | |
|
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|
4954 if (should_unload_classes()) { |
| 0 | 4955 CodeCache::gc_epilogue(); |
| 4956 } | |
| 4957 | |
| 4958 // If we encountered any (marking stack / work queue) overflow | |
| 4959 // events during the current CMS cycle, take appropriate | |
| 4960 // remedial measures, where possible, so as to try and avoid | |
| 4961 // recurrence of that condition. | |
| 4962 assert(_markStack.isEmpty(), "No grey objects"); | |
| 4963 size_t ser_ovflw = _ser_pmc_remark_ovflw + _ser_pmc_preclean_ovflw + | |
|
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|
4964 _ser_kac_ovflw + _ser_kac_preclean_ovflw; |
| 0 | 4965 if (ser_ovflw > 0) { |
| 4966 if (PrintCMSStatistics != 0) { | |
| 4967 gclog_or_tty->print_cr("Marking stack overflow (benign) " | |
|
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4968 "(pmc_pc="SIZE_FORMAT", pmc_rm="SIZE_FORMAT", kac="SIZE_FORMAT |
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|
4969 ", kac_preclean="SIZE_FORMAT")", |
| 0 | 4970 _ser_pmc_preclean_ovflw, _ser_pmc_remark_ovflw, |
|
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|
4971 _ser_kac_ovflw, _ser_kac_preclean_ovflw); |
| 0 | 4972 } |
| 4973 _markStack.expand(); | |
| 4974 _ser_pmc_remark_ovflw = 0; | |
| 4975 _ser_pmc_preclean_ovflw = 0; | |
|
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|
4976 _ser_kac_preclean_ovflw = 0; |
| 0 | 4977 _ser_kac_ovflw = 0; |
| 4978 } | |
| 4979 if (_par_pmc_remark_ovflw > 0 || _par_kac_ovflw > 0) { | |
| 4980 if (PrintCMSStatistics != 0) { | |
| 4981 gclog_or_tty->print_cr("Work queue overflow (benign) " | |
| 4982 "(pmc_rm="SIZE_FORMAT", kac="SIZE_FORMAT")", | |
| 4983 _par_pmc_remark_ovflw, _par_kac_ovflw); | |
| 4984 } | |
| 4985 _par_pmc_remark_ovflw = 0; | |
| 4986 _par_kac_ovflw = 0; | |
| 4987 } | |
| 4988 if (PrintCMSStatistics != 0) { | |
| 4989 if (_markStack._hit_limit > 0) { | |
| 4990 gclog_or_tty->print_cr(" (benign) Hit max stack size limit ("SIZE_FORMAT")", | |
| 4991 _markStack._hit_limit); | |
| 4992 } | |
| 4993 if (_markStack._failed_double > 0) { | |
| 4994 gclog_or_tty->print_cr(" (benign) Failed stack doubling ("SIZE_FORMAT")," | |
| 4995 " current capacity "SIZE_FORMAT, | |
| 4996 _markStack._failed_double, | |
| 4997 _markStack.capacity()); | |
| 4998 } | |
| 4999 } | |
| 5000 _markStack._hit_limit = 0; | |
| 5001 _markStack._failed_double = 0; | |
| 5002 | |
| 935 | 5003 // Check that all the klasses have been checked |
| 5004 assert(_revisitStack.isEmpty(), "Not all klasses revisited"); | |
| 5005 | |
| 0 | 5006 if ((VerifyAfterGC || VerifyDuringGC) && |
| 5007 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
| 5008 verify_after_remark(); | |
| 5009 } | |
| 5010 | |
| 5011 // Change under the freelistLocks. | |
| 5012 _collectorState = Sweeping; | |
| 5013 // Call isAllClear() under bitMapLock | |
| 5014 assert(_modUnionTable.isAllClear(), "Should be clear by end of the" | |
| 5015 " final marking"); | |
| 5016 if (UseAdaptiveSizePolicy) { | |
| 5017 size_policy()->checkpoint_roots_final_end(gch->gc_cause()); | |
| 5018 } | |
| 5019 } | |
| 5020 | |
| 5021 // Parallel remark task | |
| 5022 class CMSParRemarkTask: public AbstractGangTask { | |
| 5023 CMSCollector* _collector; | |
| 5024 int _n_workers; | |
| 5025 CompactibleFreeListSpace* _cms_space; | |
| 5026 CompactibleFreeListSpace* _perm_space; | |
| 5027 | |
| 5028 // The per-thread work queues, available here for stealing. | |
| 5029 OopTaskQueueSet* _task_queues; | |
| 5030 ParallelTaskTerminator _term; | |
| 5031 | |
| 5032 public: | |
| 5033 CMSParRemarkTask(CMSCollector* collector, | |
| 5034 CompactibleFreeListSpace* cms_space, | |
| 5035 CompactibleFreeListSpace* perm_space, | |
|
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|
5036 int n_workers, FlexibleWorkGang* workers, |
| 0 | 5037 OopTaskQueueSet* task_queues): |
| 5038 AbstractGangTask("Rescan roots and grey objects in parallel"), | |
| 5039 _collector(collector), | |
| 5040 _cms_space(cms_space), _perm_space(perm_space), | |
| 5041 _n_workers(n_workers), | |
| 5042 _task_queues(task_queues), | |
|
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|
5043 _term(n_workers, task_queues) { } |
| 0 | 5044 |
| 5045 OopTaskQueueSet* task_queues() { return _task_queues; } | |
| 5046 | |
| 5047 OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); } | |
| 5048 | |
| 5049 ParallelTaskTerminator* terminator() { return &_term; } | |
|
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|
5050 int n_workers() { return _n_workers; } |
| 0 | 5051 |
| 5052 void work(int i); | |
| 5053 | |
| 5054 private: | |
| 5055 // Work method in support of parallel rescan ... of young gen spaces | |
| 5056 void do_young_space_rescan(int i, Par_MarkRefsIntoAndScanClosure* cl, | |
| 5057 ContiguousSpace* space, | |
| 5058 HeapWord** chunk_array, size_t chunk_top); | |
| 5059 | |
| 5060 // ... of dirty cards in old space | |
| 5061 void do_dirty_card_rescan_tasks(CompactibleFreeListSpace* sp, int i, | |
| 5062 Par_MarkRefsIntoAndScanClosure* cl); | |
| 5063 | |
| 5064 // ... work stealing for the above | |
| 5065 void do_work_steal(int i, Par_MarkRefsIntoAndScanClosure* cl, int* seed); | |
| 5066 }; | |
| 5067 | |
|
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5068 // work_queue(i) is passed to the closure |
|
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5069 // Par_MarkRefsIntoAndScanClosure. The "i" parameter |
|
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|
5070 // also is passed to do_dirty_card_rescan_tasks() and to |
|
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|
5071 // do_work_steal() to select the i-th task_queue. |
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|
5072 |
| 0 | 5073 void CMSParRemarkTask::work(int i) { |
| 5074 elapsedTimer _timer; | |
| 5075 ResourceMark rm; | |
| 5076 HandleMark hm; | |
| 5077 | |
| 5078 // ---------- rescan from roots -------------- | |
| 5079 _timer.start(); | |
| 5080 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 5081 Par_MarkRefsIntoAndScanClosure par_mrias_cl(_collector, | |
| 5082 _collector->_span, _collector->ref_processor(), | |
| 5083 &(_collector->_markBitMap), | |
| 5084 work_queue(i), &(_collector->_revisitStack)); | |
| 5085 | |
| 5086 // Rescan young gen roots first since these are likely | |
| 5087 // coarsely partitioned and may, on that account, constitute | |
| 5088 // the critical path; thus, it's best to start off that | |
| 5089 // work first. | |
| 5090 // ---------- young gen roots -------------- | |
| 5091 { | |
| 5092 DefNewGeneration* dng = _collector->_young_gen->as_DefNewGeneration(); | |
| 5093 EdenSpace* eden_space = dng->eden(); | |
| 5094 ContiguousSpace* from_space = dng->from(); | |
| 5095 ContiguousSpace* to_space = dng->to(); | |
| 5096 | |
| 5097 HeapWord** eca = _collector->_eden_chunk_array; | |
| 5098 size_t ect = _collector->_eden_chunk_index; | |
| 5099 HeapWord** sca = _collector->_survivor_chunk_array; | |
| 5100 size_t sct = _collector->_survivor_chunk_index; | |
| 5101 | |
| 5102 assert(ect <= _collector->_eden_chunk_capacity, "out of bounds"); | |
| 5103 assert(sct <= _collector->_survivor_chunk_capacity, "out of bounds"); | |
| 5104 | |
| 5105 do_young_space_rescan(i, &par_mrias_cl, to_space, NULL, 0); | |
| 5106 do_young_space_rescan(i, &par_mrias_cl, from_space, sca, sct); | |
| 5107 do_young_space_rescan(i, &par_mrias_cl, eden_space, eca, ect); | |
| 5108 | |
| 5109 _timer.stop(); | |
| 5110 if (PrintCMSStatistics != 0) { | |
| 5111 gclog_or_tty->print_cr( | |
| 5112 "Finished young gen rescan work in %dth thread: %3.3f sec", | |
| 5113 i, _timer.seconds()); | |
| 5114 } | |
| 5115 } | |
| 5116 | |
| 5117 // ---------- remaining roots -------------- | |
| 5118 _timer.reset(); | |
| 5119 _timer.start(); | |
| 5120 gch->gen_process_strong_roots(_collector->_cmsGen->level(), | |
| 5121 false, // yg was scanned above | |
|
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|
5122 false, // this is parallel code |
| 0 | 5123 true, // collecting perm gen |
| 5124 SharedHeap::ScanningOption(_collector->CMSCollector::roots_scanning_options()), | |
|
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|
5125 &par_mrias_cl, |
|
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|
5126 true, // walk all of code cache if (so & SO_CodeCache) |
|
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|
5127 NULL); |
|
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|
5128 assert(_collector->should_unload_classes() |
|
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|
5129 || (_collector->CMSCollector::roots_scanning_options() & SharedHeap::SO_CodeCache), |
|
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|
5130 "if we didn't scan the code cache, we have to be ready to drop nmethods with expired weak oops"); |
| 0 | 5131 _timer.stop(); |
| 5132 if (PrintCMSStatistics != 0) { | |
| 5133 gclog_or_tty->print_cr( | |
| 5134 "Finished remaining root rescan work in %dth thread: %3.3f sec", | |
| 5135 i, _timer.seconds()); | |
| 5136 } | |
| 5137 | |
| 5138 // ---------- rescan dirty cards ------------ | |
| 5139 _timer.reset(); | |
| 5140 _timer.start(); | |
| 5141 | |
| 5142 // Do the rescan tasks for each of the two spaces | |
| 5143 // (cms_space and perm_space) in turn. | |
|
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5144 // "i" is passed to select the "i-th" task_queue |
| 0 | 5145 do_dirty_card_rescan_tasks(_cms_space, i, &par_mrias_cl); |
| 5146 do_dirty_card_rescan_tasks(_perm_space, i, &par_mrias_cl); | |
| 5147 _timer.stop(); | |
| 5148 if (PrintCMSStatistics != 0) { | |
| 5149 gclog_or_tty->print_cr( | |
| 5150 "Finished dirty card rescan work in %dth thread: %3.3f sec", | |
| 5151 i, _timer.seconds()); | |
| 5152 } | |
| 5153 | |
| 5154 // ---------- steal work from other threads ... | |
| 5155 // ---------- ... and drain overflow list. | |
| 5156 _timer.reset(); | |
| 5157 _timer.start(); | |
| 5158 do_work_steal(i, &par_mrias_cl, _collector->hash_seed(i)); | |
| 5159 _timer.stop(); | |
| 5160 if (PrintCMSStatistics != 0) { | |
| 5161 gclog_or_tty->print_cr( | |
| 5162 "Finished work stealing in %dth thread: %3.3f sec", | |
| 5163 i, _timer.seconds()); | |
| 5164 } | |
| 5165 } | |
| 5166 | |
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5167 // Note that parameter "i" is not used. |
| 0 | 5168 void |
| 5169 CMSParRemarkTask::do_young_space_rescan(int i, | |
| 5170 Par_MarkRefsIntoAndScanClosure* cl, ContiguousSpace* space, | |
| 5171 HeapWord** chunk_array, size_t chunk_top) { | |
| 5172 // Until all tasks completed: | |
| 5173 // . claim an unclaimed task | |
| 5174 // . compute region boundaries corresponding to task claimed | |
| 5175 // using chunk_array | |
| 5176 // . par_oop_iterate(cl) over that region | |
| 5177 | |
| 5178 ResourceMark rm; | |
| 5179 HandleMark hm; | |
| 5180 | |
| 5181 SequentialSubTasksDone* pst = space->par_seq_tasks(); | |
| 5182 assert(pst->valid(), "Uninitialized use?"); | |
| 5183 | |
| 5184 int nth_task = 0; | |
| 5185 int n_tasks = pst->n_tasks(); | |
| 5186 | |
| 5187 HeapWord *start, *end; | |
| 5188 while (!pst->is_task_claimed(/* reference */ nth_task)) { | |
| 5189 // We claimed task # nth_task; compute its boundaries. | |
| 5190 if (chunk_top == 0) { // no samples were taken | |
| 5191 assert(nth_task == 0 && n_tasks == 1, "Can have only 1 EdenSpace task"); | |
| 5192 start = space->bottom(); | |
| 5193 end = space->top(); | |
| 5194 } else if (nth_task == 0) { | |
| 5195 start = space->bottom(); | |
| 5196 end = chunk_array[nth_task]; | |
| 5197 } else if (nth_task < (jint)chunk_top) { | |
| 5198 assert(nth_task >= 1, "Control point invariant"); | |
| 5199 start = chunk_array[nth_task - 1]; | |
| 5200 end = chunk_array[nth_task]; | |
| 5201 } else { | |
| 5202 assert(nth_task == (jint)chunk_top, "Control point invariant"); | |
| 5203 start = chunk_array[chunk_top - 1]; | |
| 5204 end = space->top(); | |
| 5205 } | |
| 5206 MemRegion mr(start, end); | |
| 5207 // Verify that mr is in space | |
| 5208 assert(mr.is_empty() || space->used_region().contains(mr), | |
| 5209 "Should be in space"); | |
| 5210 // Verify that "start" is an object boundary | |
| 5211 assert(mr.is_empty() || oop(mr.start())->is_oop(), | |
| 5212 "Should be an oop"); | |
| 5213 space->par_oop_iterate(mr, cl); | |
| 5214 } | |
| 5215 pst->all_tasks_completed(); | |
| 5216 } | |
| 5217 | |
| 5218 void | |
| 5219 CMSParRemarkTask::do_dirty_card_rescan_tasks( | |
| 5220 CompactibleFreeListSpace* sp, int i, | |
| 5221 Par_MarkRefsIntoAndScanClosure* cl) { | |
| 5222 // Until all tasks completed: | |
| 5223 // . claim an unclaimed task | |
| 5224 // . compute region boundaries corresponding to task claimed | |
| 5225 // . transfer dirty bits ct->mut for that region | |
| 5226 // . apply rescanclosure to dirty mut bits for that region | |
| 5227 | |
| 5228 ResourceMark rm; | |
| 5229 HandleMark hm; | |
| 5230 | |
| 5231 OopTaskQueue* work_q = work_queue(i); | |
| 5232 ModUnionClosure modUnionClosure(&(_collector->_modUnionTable)); | |
| 5233 // CAUTION! CAUTION! CAUTION! CAUTION! CAUTION! CAUTION! CAUTION! | |
| 5234 // CAUTION: This closure has state that persists across calls to | |
| 5235 // the work method dirty_range_iterate_clear() in that it has | |
| 5236 // imbedded in it a (subtype of) UpwardsObjectClosure. The | |
| 5237 // use of that state in the imbedded UpwardsObjectClosure instance | |
| 5238 // assumes that the cards are always iterated (even if in parallel | |
| 5239 // by several threads) in monotonically increasing order per each | |
| 5240 // thread. This is true of the implementation below which picks | |
| 5241 // card ranges (chunks) in monotonically increasing order globally | |
| 5242 // and, a-fortiori, in monotonically increasing order per thread | |
| 5243 // (the latter order being a subsequence of the former). | |
| 5244 // If the work code below is ever reorganized into a more chaotic | |
| 5245 // work-partitioning form than the current "sequential tasks" | |
| 5246 // paradigm, the use of that persistent state will have to be | |
| 5247 // revisited and modified appropriately. See also related | |
| 5248 // bug 4756801 work on which should examine this code to make | |
| 5249 // sure that the changes there do not run counter to the | |
| 5250 // assumptions made here and necessary for correctness and | |
| 5251 // efficiency. Note also that this code might yield inefficient | |
| 5252 // behaviour in the case of very large objects that span one or | |
| 5253 // more work chunks. Such objects would potentially be scanned | |
| 5254 // several times redundantly. Work on 4756801 should try and | |
| 5255 // address that performance anomaly if at all possible. XXX | |
| 5256 MemRegion full_span = _collector->_span; | |
| 5257 CMSBitMap* bm = &(_collector->_markBitMap); // shared | |
| 5258 CMSMarkStack* rs = &(_collector->_revisitStack); // shared | |
| 5259 MarkFromDirtyCardsClosure | |
| 5260 greyRescanClosure(_collector, full_span, // entire span of interest | |
| 5261 sp, bm, work_q, rs, cl); | |
| 5262 | |
| 5263 SequentialSubTasksDone* pst = sp->conc_par_seq_tasks(); | |
| 5264 assert(pst->valid(), "Uninitialized use?"); | |
| 5265 int nth_task = 0; | |
| 5266 const int alignment = CardTableModRefBS::card_size * BitsPerWord; | |
| 5267 MemRegion span = sp->used_region(); | |
| 5268 HeapWord* start_addr = span.start(); | |
| 5269 HeapWord* end_addr = (HeapWord*)round_to((intptr_t)span.end(), | |
| 5270 alignment); | |
| 5271 const size_t chunk_size = sp->rescan_task_size(); // in HeapWord units | |
| 5272 assert((HeapWord*)round_to((intptr_t)start_addr, alignment) == | |
| 5273 start_addr, "Check alignment"); | |
| 5274 assert((size_t)round_to((intptr_t)chunk_size, alignment) == | |
| 5275 chunk_size, "Check alignment"); | |
| 5276 | |
| 5277 while (!pst->is_task_claimed(/* reference */ nth_task)) { | |
| 5278 // Having claimed the nth_task, compute corresponding mem-region, | |
| 5279 // which is a-fortiori aligned correctly (i.e. at a MUT bopundary). | |
| 5280 // The alignment restriction ensures that we do not need any | |
| 5281 // synchronization with other gang-workers while setting or | |
| 5282 // clearing bits in thus chunk of the MUT. | |
| 5283 MemRegion this_span = MemRegion(start_addr + nth_task*chunk_size, | |
| 5284 start_addr + (nth_task+1)*chunk_size); | |
| 5285 // The last chunk's end might be way beyond end of the | |
| 5286 // used region. In that case pull back appropriately. | |
| 5287 if (this_span.end() > end_addr) { | |
| 5288 this_span.set_end(end_addr); | |
| 5289 assert(!this_span.is_empty(), "Program logic (calculation of n_tasks)"); | |
| 5290 } | |
| 5291 // Iterate over the dirty cards covering this chunk, marking them | |
| 5292 // precleaned, and setting the corresponding bits in the mod union | |
| 5293 // table. Since we have been careful to partition at Card and MUT-word | |
| 5294 // boundaries no synchronization is needed between parallel threads. | |
| 5295 _collector->_ct->ct_bs()->dirty_card_iterate(this_span, | |
| 5296 &modUnionClosure); | |
| 5297 | |
| 5298 // Having transferred these marks into the modUnionTable, | |
| 5299 // rescan the marked objects on the dirty cards in the modUnionTable. | |
| 5300 // Even if this is at a synchronous collection, the initial marking | |
| 5301 // may have been done during an asynchronous collection so there | |
| 5302 // may be dirty bits in the mod-union table. | |
| 5303 _collector->_modUnionTable.dirty_range_iterate_clear( | |
| 5304 this_span, &greyRescanClosure); | |
| 5305 _collector->_modUnionTable.verifyNoOneBitsInRange( | |
| 5306 this_span.start(), | |
| 5307 this_span.end()); | |
| 5308 } | |
| 5309 pst->all_tasks_completed(); // declare that i am done | |
| 5310 } | |
| 5311 | |
| 5312 // . see if we can share work_queues with ParNew? XXX | |
| 5313 void | |
| 5314 CMSParRemarkTask::do_work_steal(int i, Par_MarkRefsIntoAndScanClosure* cl, | |
| 5315 int* seed) { | |
| 5316 OopTaskQueue* work_q = work_queue(i); | |
| 5317 NOT_PRODUCT(int num_steals = 0;) | |
| 5318 oop obj_to_scan; | |
| 5319 CMSBitMap* bm = &(_collector->_markBitMap); | |
| 5320 | |
| 5321 while (true) { | |
| 5322 // Completely finish any left over work from (an) earlier round(s) | |
| 5323 cl->trim_queue(0); | |
|
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5324 size_t num_from_overflow_list = MIN2((size_t)(work_q->max_elems() - work_q->size())/4, |
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5325 (size_t)ParGCDesiredObjsFromOverflowList); |
| 0 | 5326 // Now check if there's any work in the overflow list |
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5327 // Passing ParallelGCThreads as the third parameter, no_of_gc_threads, |
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5328 // only affects the number of attempts made to get work from the |
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5329 // overflow list and does not affect the number of workers. Just |
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5330 // pass ParallelGCThreads so this behavior is unchanged. |
| 0 | 5331 if (_collector->par_take_from_overflow_list(num_from_overflow_list, |
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5332 work_q, |
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5333 ParallelGCThreads)) { |
| 0 | 5334 // found something in global overflow list; |
| 5335 // not yet ready to go stealing work from others. | |
| 5336 // We'd like to assert(work_q->size() != 0, ...) | |
| 5337 // because we just took work from the overflow list, | |
| 5338 // but of course we can't since all of that could have | |
| 5339 // been already stolen from us. | |
| 5340 // "He giveth and He taketh away." | |
| 5341 continue; | |
| 5342 } | |
| 5343 // Verify that we have no work before we resort to stealing | |
| 5344 assert(work_q->size() == 0, "Have work, shouldn't steal"); | |
| 5345 // Try to steal from other queues that have work | |
| 5346 if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) { | |
| 5347 NOT_PRODUCT(num_steals++;) | |
| 5348 assert(obj_to_scan->is_oop(), "Oops, not an oop!"); | |
| 5349 assert(bm->isMarked((HeapWord*)obj_to_scan), "Stole an unmarked oop?"); | |
| 5350 // Do scanning work | |
| 5351 obj_to_scan->oop_iterate(cl); | |
| 5352 // Loop around, finish this work, and try to steal some more | |
| 5353 } else if (terminator()->offer_termination()) { | |
| 5354 break; // nirvana from the infinite cycle | |
| 5355 } | |
| 5356 } | |
| 5357 NOT_PRODUCT( | |
| 5358 if (PrintCMSStatistics != 0) { | |
| 5359 gclog_or_tty->print("\n\t(%d: stole %d oops)", i, num_steals); | |
| 5360 } | |
| 5361 ) | |
| 5362 assert(work_q->size() == 0 && _collector->overflow_list_is_empty(), | |
| 5363 "Else our work is not yet done"); | |
| 5364 } | |
| 5365 | |
| 5366 // Return a thread-local PLAB recording array, as appropriate. | |
| 5367 void* CMSCollector::get_data_recorder(int thr_num) { | |
| 5368 if (_survivor_plab_array != NULL && | |
| 5369 (CMSPLABRecordAlways || | |
| 5370 (_collectorState > Marking && _collectorState < FinalMarking))) { | |
| 5371 assert(thr_num < (int)ParallelGCThreads, "thr_num is out of bounds"); | |
| 5372 ChunkArray* ca = &_survivor_plab_array[thr_num]; | |
| 5373 ca->reset(); // clear it so that fresh data is recorded | |
| 5374 return (void*) ca; | |
| 5375 } else { | |
| 5376 return NULL; | |
| 5377 } | |
| 5378 } | |
| 5379 | |
| 5380 // Reset all the thread-local PLAB recording arrays | |
| 5381 void CMSCollector::reset_survivor_plab_arrays() { | |
| 5382 for (uint i = 0; i < ParallelGCThreads; i++) { | |
| 5383 _survivor_plab_array[i].reset(); | |
| 5384 } | |
| 5385 } | |
| 5386 | |
| 5387 // Merge the per-thread plab arrays into the global survivor chunk | |
| 5388 // array which will provide the partitioning of the survivor space | |
| 5389 // for CMS rescan. | |
|
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5390 void CMSCollector::merge_survivor_plab_arrays(ContiguousSpace* surv, |
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5391 int no_of_gc_threads) { |
| 0 | 5392 assert(_survivor_plab_array != NULL, "Error"); |
| 5393 assert(_survivor_chunk_array != NULL, "Error"); | |
| 5394 assert(_collectorState == FinalMarking, "Error"); | |
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5395 for (int j = 0; j < no_of_gc_threads; j++) { |
| 0 | 5396 _cursor[j] = 0; |
| 5397 } | |
| 5398 HeapWord* top = surv->top(); | |
| 5399 size_t i; | |
| 5400 for (i = 0; i < _survivor_chunk_capacity; i++) { // all sca entries | |
| 5401 HeapWord* min_val = top; // Higher than any PLAB address | |
| 5402 uint min_tid = 0; // position of min_val this round | |
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5403 for (int j = 0; j < no_of_gc_threads; j++) { |
| 0 | 5404 ChunkArray* cur_sca = &_survivor_plab_array[j]; |
| 5405 if (_cursor[j] == cur_sca->end()) { | |
| 5406 continue; | |
| 5407 } | |
| 5408 assert(_cursor[j] < cur_sca->end(), "ctl pt invariant"); | |
| 5409 HeapWord* cur_val = cur_sca->nth(_cursor[j]); | |
| 5410 assert(surv->used_region().contains(cur_val), "Out of bounds value"); | |
| 5411 if (cur_val < min_val) { | |
| 5412 min_tid = j; | |
| 5413 min_val = cur_val; | |
| 5414 } else { | |
| 5415 assert(cur_val < top, "All recorded addresses should be less"); | |
| 5416 } | |
| 5417 } | |
| 5418 // At this point min_val and min_tid are respectively | |
| 5419 // the least address in _survivor_plab_array[j]->nth(_cursor[j]) | |
| 5420 // and the thread (j) that witnesses that address. | |
| 5421 // We record this address in the _survivor_chunk_array[i] | |
| 5422 // and increment _cursor[min_tid] prior to the next round i. | |
| 5423 if (min_val == top) { | |
| 5424 break; | |
| 5425 } | |
| 5426 _survivor_chunk_array[i] = min_val; | |
| 5427 _cursor[min_tid]++; | |
| 5428 } | |
| 5429 // We are all done; record the size of the _survivor_chunk_array | |
| 5430 _survivor_chunk_index = i; // exclusive: [0, i) | |
| 5431 if (PrintCMSStatistics > 0) { | |
| 5432 gclog_or_tty->print(" (Survivor:" SIZE_FORMAT "chunks) ", i); | |
| 5433 } | |
| 5434 // Verify that we used up all the recorded entries | |
| 5435 #ifdef ASSERT | |
| 5436 size_t total = 0; | |
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5437 for (int j = 0; j < no_of_gc_threads; j++) { |
| 0 | 5438 assert(_cursor[j] == _survivor_plab_array[j].end(), "Ctl pt invariant"); |
| 5439 total += _cursor[j]; | |
| 5440 } | |
| 5441 assert(total == _survivor_chunk_index, "Ctl Pt Invariant"); | |
| 5442 // Check that the merged array is in sorted order | |
| 5443 if (total > 0) { | |
| 5444 for (size_t i = 0; i < total - 1; i++) { | |
| 5445 if (PrintCMSStatistics > 0) { | |
| 5446 gclog_or_tty->print(" (chunk" SIZE_FORMAT ":" INTPTR_FORMAT ") ", | |
| 5447 i, _survivor_chunk_array[i]); | |
| 5448 } | |
| 5449 assert(_survivor_chunk_array[i] < _survivor_chunk_array[i+1], | |
| 5450 "Not sorted"); | |
| 5451 } | |
| 5452 } | |
| 5453 #endif // ASSERT | |
| 5454 } | |
| 5455 | |
| 5456 // Set up the space's par_seq_tasks structure for work claiming | |
| 5457 // for parallel rescan of young gen. | |
| 5458 // See ParRescanTask where this is currently used. | |
| 5459 void | |
| 5460 CMSCollector:: | |
| 5461 initialize_sequential_subtasks_for_young_gen_rescan(int n_threads) { | |
| 5462 assert(n_threads > 0, "Unexpected n_threads argument"); | |
| 5463 DefNewGeneration* dng = (DefNewGeneration*)_young_gen; | |
| 5464 | |
| 5465 // Eden space | |
| 5466 { | |
| 5467 SequentialSubTasksDone* pst = dng->eden()->par_seq_tasks(); | |
| 5468 assert(!pst->valid(), "Clobbering existing data?"); | |
| 5469 // Each valid entry in [0, _eden_chunk_index) represents a task. | |
| 5470 size_t n_tasks = _eden_chunk_index + 1; | |
| 5471 assert(n_tasks == 1 || _eden_chunk_array != NULL, "Error"); | |
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5472 // Sets the condition for completion of the subtask (how many threads |
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5473 // need to finish in order to be done). |
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5474 pst->set_n_threads(n_threads); |
| 0 | 5475 pst->set_n_tasks((int)n_tasks); |
| 5476 } | |
| 5477 | |
| 5478 // Merge the survivor plab arrays into _survivor_chunk_array | |
| 5479 if (_survivor_plab_array != NULL) { | |
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5480 merge_survivor_plab_arrays(dng->from(), n_threads); |
| 0 | 5481 } else { |
| 5482 assert(_survivor_chunk_index == 0, "Error"); | |
| 5483 } | |
| 5484 | |
| 5485 // To space | |
| 5486 { | |
| 5487 SequentialSubTasksDone* pst = dng->to()->par_seq_tasks(); | |
| 5488 assert(!pst->valid(), "Clobbering existing data?"); | |
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5489 // Sets the condition for completion of the subtask (how many threads |
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5490 // need to finish in order to be done). |
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5491 pst->set_n_threads(n_threads); |
| 0 | 5492 pst->set_n_tasks(1); |
| 5493 assert(pst->valid(), "Error"); | |
| 5494 } | |
| 5495 | |
| 5496 // From space | |
| 5497 { | |
| 5498 SequentialSubTasksDone* pst = dng->from()->par_seq_tasks(); | |
| 5499 assert(!pst->valid(), "Clobbering existing data?"); | |
| 5500 size_t n_tasks = _survivor_chunk_index + 1; | |
| 5501 assert(n_tasks == 1 || _survivor_chunk_array != NULL, "Error"); | |
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5502 // Sets the condition for completion of the subtask (how many threads |
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5503 // need to finish in order to be done). |
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5504 pst->set_n_threads(n_threads); |
| 0 | 5505 pst->set_n_tasks((int)n_tasks); |
| 5506 assert(pst->valid(), "Error"); | |
| 5507 } | |
| 5508 } | |
| 5509 | |
| 5510 // Parallel version of remark | |
| 5511 void CMSCollector::do_remark_parallel() { | |
| 5512 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
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5513 FlexibleWorkGang* workers = gch->workers(); |
| 0 | 5514 assert(workers != NULL, "Need parallel worker threads."); |
| 5515 int n_workers = workers->total_workers(); | |
| 5516 CompactibleFreeListSpace* cms_space = _cmsGen->cmsSpace(); | |
| 5517 CompactibleFreeListSpace* perm_space = _permGen->cmsSpace(); | |
| 5518 | |
| 5519 CMSParRemarkTask tsk(this, | |
| 5520 cms_space, perm_space, | |
| 5521 n_workers, workers, task_queues()); | |
| 5522 | |
| 5523 // Set up for parallel process_strong_roots work. | |
| 5524 gch->set_par_threads(n_workers); | |
| 5525 // We won't be iterating over the cards in the card table updating | |
| 5526 // the younger_gen cards, so we shouldn't call the following else | |
| 5527 // the verification code as well as subsequent younger_refs_iterate | |
| 5528 // code would get confused. XXX | |
| 5529 // gch->rem_set()->prepare_for_younger_refs_iterate(true); // parallel | |
| 5530 | |
| 5531 // The young gen rescan work will not be done as part of | |
| 5532 // process_strong_roots (which currently doesn't knw how to | |
| 5533 // parallelize such a scan), but rather will be broken up into | |
| 5534 // a set of parallel tasks (via the sampling that the [abortable] | |
| 5535 // preclean phase did of EdenSpace, plus the [two] tasks of | |
| 5536 // scanning the [two] survivor spaces. Further fine-grain | |
| 5537 // parallelization of the scanning of the survivor spaces | |
| 5538 // themselves, and of precleaning of the younger gen itself | |
| 5539 // is deferred to the future. | |
| 5540 initialize_sequential_subtasks_for_young_gen_rescan(n_workers); | |
| 5541 | |
| 5542 // The dirty card rescan work is broken up into a "sequence" | |
| 5543 // of parallel tasks (per constituent space) that are dynamically | |
| 5544 // claimed by the parallel threads. | |
| 5545 cms_space->initialize_sequential_subtasks_for_rescan(n_workers); | |
| 5546 perm_space->initialize_sequential_subtasks_for_rescan(n_workers); | |
| 5547 | |
| 5548 // It turns out that even when we're using 1 thread, doing the work in a | |
| 5549 // separate thread causes wide variance in run times. We can't help this | |
| 5550 // in the multi-threaded case, but we special-case n=1 here to get | |
| 5551 // repeatable measurements of the 1-thread overhead of the parallel code. | |
| 5552 if (n_workers > 1) { | |
| 5553 // Make refs discovery MT-safe | |
| 5554 ReferenceProcessorMTMutator mt(ref_processor(), true); | |
|
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5555 GenCollectedHeap::StrongRootsScope srs(gch); |
| 0 | 5556 workers->run_task(&tsk); |
| 5557 } else { | |
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5558 GenCollectedHeap::StrongRootsScope srs(gch); |
| 0 | 5559 tsk.work(0); |
| 5560 } | |
| 5561 gch->set_par_threads(0); // 0 ==> non-parallel. | |
| 5562 // restore, single-threaded for now, any preserved marks | |
| 5563 // as a result of work_q overflow | |
| 5564 restore_preserved_marks_if_any(); | |
| 5565 } | |
| 5566 | |
| 5567 // Non-parallel version of remark | |
| 5568 void CMSCollector::do_remark_non_parallel() { | |
| 5569 ResourceMark rm; | |
| 5570 HandleMark hm; | |
| 5571 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 5572 MarkRefsIntoAndScanClosure | |
| 5573 mrias_cl(_span, ref_processor(), &_markBitMap, &_modUnionTable, | |
| 5574 &_markStack, &_revisitStack, this, | |
| 5575 false /* should_yield */, false /* not precleaning */); | |
| 5576 MarkFromDirtyCardsClosure | |
| 5577 markFromDirtyCardsClosure(this, _span, | |
| 5578 NULL, // space is set further below | |
| 5579 &_markBitMap, &_markStack, &_revisitStack, | |
| 5580 &mrias_cl); | |
| 5581 { | |
| 5582 TraceTime t("grey object rescan", PrintGCDetails, false, gclog_or_tty); | |
|
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5583 // Iterate over the dirty cards, setting the corresponding bits in the |
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5584 // mod union table. |
| 0 | 5585 { |
| 5586 ModUnionClosure modUnionClosure(&_modUnionTable); | |
| 5587 _ct->ct_bs()->dirty_card_iterate( | |
| 5588 _cmsGen->used_region(), | |
| 5589 &modUnionClosure); | |
| 5590 _ct->ct_bs()->dirty_card_iterate( | |
| 5591 _permGen->used_region(), | |
| 5592 &modUnionClosure); | |
| 5593 } | |
| 5594 // Having transferred these marks into the modUnionTable, we just need | |
| 5595 // to rescan the marked objects on the dirty cards in the modUnionTable. | |
| 5596 // The initial marking may have been done during an asynchronous | |
| 5597 // collection so there may be dirty bits in the mod-union table. | |
| 5598 const int alignment = | |
| 5599 CardTableModRefBS::card_size * BitsPerWord; | |
| 5600 { | |
| 5601 // ... First handle dirty cards in CMS gen | |
| 5602 markFromDirtyCardsClosure.set_space(_cmsGen->cmsSpace()); | |
| 5603 MemRegion ur = _cmsGen->used_region(); | |
| 5604 HeapWord* lb = ur.start(); | |
| 5605 HeapWord* ub = (HeapWord*)round_to((intptr_t)ur.end(), alignment); | |
| 5606 MemRegion cms_span(lb, ub); | |
| 5607 _modUnionTable.dirty_range_iterate_clear(cms_span, | |
| 5608 &markFromDirtyCardsClosure); | |
| 5609 verify_work_stacks_empty(); | |
| 5610 if (PrintCMSStatistics != 0) { | |
| 5611 gclog_or_tty->print(" (re-scanned "SIZE_FORMAT" dirty cards in cms gen) ", | |
| 5612 markFromDirtyCardsClosure.num_dirty_cards()); | |
| 5613 } | |
| 5614 } | |
| 5615 { | |
| 5616 // .. and then repeat for dirty cards in perm gen | |
| 5617 markFromDirtyCardsClosure.set_space(_permGen->cmsSpace()); | |
| 5618 MemRegion ur = _permGen->used_region(); | |
| 5619 HeapWord* lb = ur.start(); | |
| 5620 HeapWord* ub = (HeapWord*)round_to((intptr_t)ur.end(), alignment); | |
| 5621 MemRegion perm_span(lb, ub); | |
| 5622 _modUnionTable.dirty_range_iterate_clear(perm_span, | |
| 5623 &markFromDirtyCardsClosure); | |
| 5624 verify_work_stacks_empty(); | |
| 5625 if (PrintCMSStatistics != 0) { | |
| 5626 gclog_or_tty->print(" (re-scanned "SIZE_FORMAT" dirty cards in perm gen) ", | |
| 5627 markFromDirtyCardsClosure.num_dirty_cards()); | |
| 5628 } | |
| 5629 } | |
| 5630 } | |
| 5631 if (VerifyDuringGC && | |
| 5632 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
| 5633 HandleMark hm; // Discard invalid handles created during verification | |
| 5634 Universe::verify(true); | |
| 5635 } | |
| 5636 { | |
| 5637 TraceTime t("root rescan", PrintGCDetails, false, gclog_or_tty); | |
| 5638 | |
| 5639 verify_work_stacks_empty(); | |
| 5640 | |
| 5641 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. | |
|
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|
5642 GenCollectedHeap::StrongRootsScope srs(gch); |
| 0 | 5643 gch->gen_process_strong_roots(_cmsGen->level(), |
| 5644 true, // younger gens as roots | |
|
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5645 false, // use the local StrongRootsScope |
| 0 | 5646 true, // collecting perm gen |
| 5647 SharedHeap::ScanningOption(roots_scanning_options()), | |
|
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5648 &mrias_cl, |
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5649 true, // walk code active on stacks |
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|
5650 NULL); |
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5651 assert(should_unload_classes() |
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5652 || (roots_scanning_options() & SharedHeap::SO_CodeCache), |
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|
5653 "if we didn't scan the code cache, we have to be ready to drop nmethods with expired weak oops"); |
| 0 | 5654 } |
| 5655 verify_work_stacks_empty(); | |
| 5656 // Restore evacuated mark words, if any, used for overflow list links | |
| 5657 if (!CMSOverflowEarlyRestoration) { | |
| 5658 restore_preserved_marks_if_any(); | |
| 5659 } | |
| 5660 verify_overflow_empty(); | |
| 5661 } | |
| 5662 | |
| 5663 //////////////////////////////////////////////////////// | |
| 5664 // Parallel Reference Processing Task Proxy Class | |
| 5665 //////////////////////////////////////////////////////// | |
|
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5666 class CMSRefProcTaskProxy: public AbstractGangTaskWOopQueues { |
| 0 | 5667 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; |
| 5668 CMSCollector* _collector; | |
| 5669 CMSBitMap* _mark_bit_map; | |
|
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5670 const MemRegion _span; |
| 0 | 5671 ProcessTask& _task; |
| 5672 | |
| 5673 public: | |
| 5674 CMSRefProcTaskProxy(ProcessTask& task, | |
| 5675 CMSCollector* collector, | |
| 5676 const MemRegion& span, | |
| 5677 CMSBitMap* mark_bit_map, | |
|
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5678 AbstractWorkGang* workers, |
| 0 | 5679 OopTaskQueueSet* task_queues): |
|
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5680 AbstractGangTaskWOopQueues("Process referents by policy in parallel", |
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5681 task_queues), |
| 0 | 5682 _task(task), |
|
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5683 _collector(collector), _span(span), _mark_bit_map(mark_bit_map) |
|
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5684 { |
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5685 assert(_collector->_span.equals(_span) && !_span.is_empty(), |
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5686 "Inconsistency in _span"); |
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5687 } |
| 0 | 5688 |
|
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5689 OopTaskQueueSet* task_queues() { return queues(); } |
| 0 | 5690 |
| 5691 OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); } | |
| 5692 | |
| 5693 void do_work_steal(int i, | |
| 5694 CMSParDrainMarkingStackClosure* drain, | |
| 5695 CMSParKeepAliveClosure* keep_alive, | |
| 5696 int* seed); | |
| 5697 | |
| 5698 virtual void work(int i); | |
| 5699 }; | |
| 5700 | |
| 5701 void CMSRefProcTaskProxy::work(int i) { | |
|
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5702 assert(_collector->_span.equals(_span), "Inconsistency in _span"); |
| 0 | 5703 CMSParKeepAliveClosure par_keep_alive(_collector, _span, |
| 935 | 5704 _mark_bit_map, |
| 5705 &_collector->_revisitStack, | |
| 5706 work_queue(i)); | |
| 0 | 5707 CMSParDrainMarkingStackClosure par_drain_stack(_collector, _span, |
| 935 | 5708 _mark_bit_map, |
| 5709 &_collector->_revisitStack, | |
| 5710 work_queue(i)); | |
|
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5711 CMSIsAliveClosure is_alive_closure(_span, _mark_bit_map); |
| 0 | 5712 _task.work(i, is_alive_closure, par_keep_alive, par_drain_stack); |
| 5713 if (_task.marks_oops_alive()) { | |
| 5714 do_work_steal(i, &par_drain_stack, &par_keep_alive, | |
| 5715 _collector->hash_seed(i)); | |
| 5716 } | |
| 5717 assert(work_queue(i)->size() == 0, "work_queue should be empty"); | |
| 5718 assert(_collector->_overflow_list == NULL, "non-empty _overflow_list"); | |
| 5719 } | |
| 5720 | |
| 5721 class CMSRefEnqueueTaskProxy: public AbstractGangTask { | |
| 5722 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; | |
| 5723 EnqueueTask& _task; | |
| 5724 | |
| 5725 public: | |
| 5726 CMSRefEnqueueTaskProxy(EnqueueTask& task) | |
| 5727 : AbstractGangTask("Enqueue reference objects in parallel"), | |
| 5728 _task(task) | |
| 5729 { } | |
| 5730 | |
| 5731 virtual void work(int i) | |
| 5732 { | |
| 5733 _task.work(i); | |
| 5734 } | |
| 5735 }; | |
| 5736 | |
| 5737 CMSParKeepAliveClosure::CMSParKeepAliveClosure(CMSCollector* collector, | |
| 935 | 5738 MemRegion span, CMSBitMap* bit_map, CMSMarkStack* revisit_stack, |
| 5739 OopTaskQueue* work_queue): | |
| 5740 Par_KlassRememberingOopClosure(collector, NULL, revisit_stack), | |
| 0 | 5741 _span(span), |
| 5742 _bit_map(bit_map), | |
| 5743 _work_queue(work_queue), | |
| 935 | 5744 _mark_and_push(collector, span, bit_map, revisit_stack, work_queue), |
| 0 | 5745 _low_water_mark(MIN2((uint)(work_queue->max_elems()/4), |
| 5746 (uint)(CMSWorkQueueDrainThreshold * ParallelGCThreads))) | |
| 5747 { } | |
| 5748 | |
| 5749 // . see if we can share work_queues with ParNew? XXX | |
| 5750 void CMSRefProcTaskProxy::do_work_steal(int i, | |
| 5751 CMSParDrainMarkingStackClosure* drain, | |
| 5752 CMSParKeepAliveClosure* keep_alive, | |
| 5753 int* seed) { | |
| 5754 OopTaskQueue* work_q = work_queue(i); | |
| 5755 NOT_PRODUCT(int num_steals = 0;) | |
| 5756 oop obj_to_scan; | |
| 5757 | |
| 5758 while (true) { | |
| 5759 // Completely finish any left over work from (an) earlier round(s) | |
| 5760 drain->trim_queue(0); | |
|
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5761 size_t num_from_overflow_list = MIN2((size_t)(work_q->max_elems() - work_q->size())/4, |
|
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|
5762 (size_t)ParGCDesiredObjsFromOverflowList); |
| 0 | 5763 // Now check if there's any work in the overflow list |
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5764 // Passing ParallelGCThreads as the third parameter, no_of_gc_threads, |
|
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|
5765 // only affects the number of attempts made to get work from the |
|
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|
5766 // overflow list and does not affect the number of workers. Just |
|
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|
5767 // pass ParallelGCThreads so this behavior is unchanged. |
| 0 | 5768 if (_collector->par_take_from_overflow_list(num_from_overflow_list, |
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|
5769 work_q, |
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|
5770 ParallelGCThreads)) { |
| 0 | 5771 // Found something in global overflow list; |
| 5772 // not yet ready to go stealing work from others. | |
| 5773 // We'd like to assert(work_q->size() != 0, ...) | |
| 5774 // because we just took work from the overflow list, | |
| 5775 // but of course we can't, since all of that might have | |
| 5776 // been already stolen from us. | |
| 5777 continue; | |
| 5778 } | |
| 5779 // Verify that we have no work before we resort to stealing | |
| 5780 assert(work_q->size() == 0, "Have work, shouldn't steal"); | |
| 5781 // Try to steal from other queues that have work | |
| 5782 if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) { | |
| 5783 NOT_PRODUCT(num_steals++;) | |
| 5784 assert(obj_to_scan->is_oop(), "Oops, not an oop!"); | |
| 5785 assert(_mark_bit_map->isMarked((HeapWord*)obj_to_scan), "Stole an unmarked oop?"); | |
| 5786 // Do scanning work | |
| 5787 obj_to_scan->oop_iterate(keep_alive); | |
| 5788 // Loop around, finish this work, and try to steal some more | |
| 5789 } else if (terminator()->offer_termination()) { | |
| 5790 break; // nirvana from the infinite cycle | |
| 5791 } | |
| 5792 } | |
| 5793 NOT_PRODUCT( | |
| 5794 if (PrintCMSStatistics != 0) { | |
| 5795 gclog_or_tty->print("\n\t(%d: stole %d oops)", i, num_steals); | |
| 5796 } | |
| 5797 ) | |
| 5798 } | |
| 5799 | |
| 5800 void CMSRefProcTaskExecutor::execute(ProcessTask& task) | |
| 5801 { | |
| 5802 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
|
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|
5803 FlexibleWorkGang* workers = gch->workers(); |
| 0 | 5804 assert(workers != NULL, "Need parallel worker threads."); |
| 5805 CMSRefProcTaskProxy rp_task(task, &_collector, | |
| 5806 _collector.ref_processor()->span(), | |
| 5807 _collector.markBitMap(), | |
|
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5808 workers, _collector.task_queues()); |
| 0 | 5809 workers->run_task(&rp_task); |
| 5810 } | |
| 5811 | |
| 5812 void CMSRefProcTaskExecutor::execute(EnqueueTask& task) | |
| 5813 { | |
| 5814 | |
| 5815 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
|
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5816 FlexibleWorkGang* workers = gch->workers(); |
| 0 | 5817 assert(workers != NULL, "Need parallel worker threads."); |
| 5818 CMSRefEnqueueTaskProxy enq_task(task); | |
| 5819 workers->run_task(&enq_task); | |
| 5820 } | |
| 5821 | |
| 5822 void CMSCollector::refProcessingWork(bool asynch, bool clear_all_soft_refs) { | |
| 5823 | |
| 5824 ResourceMark rm; | |
| 5825 HandleMark hm; | |
| 5826 | |
| 5827 ReferenceProcessor* rp = ref_processor(); | |
| 5828 assert(rp->span().equals(_span), "Spans should be equal"); | |
|
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|
5829 assert(!rp->enqueuing_is_done(), "Enqueuing should not be complete"); |
|
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|
5830 // Process weak references. |
|
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|
5831 rp->setup_policy(clear_all_soft_refs); |
|
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|
5832 verify_work_stacks_empty(); |
|
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|
5833 |
| 0 | 5834 CMSKeepAliveClosure cmsKeepAliveClosure(this, _span, &_markBitMap, |
| 935 | 5835 &_markStack, &_revisitStack, |
| 5836 false /* !preclean */); | |
| 0 | 5837 CMSDrainMarkingStackClosure cmsDrainMarkingStackClosure(this, |
| 5838 _span, &_markBitMap, &_markStack, | |
|
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5839 &cmsKeepAliveClosure, false /* !preclean */); |
| 0 | 5840 { |
| 5841 TraceTime t("weak refs processing", PrintGCDetails, false, gclog_or_tty); | |
| 5842 if (rp->processing_is_mt()) { | |
|
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5843 // Set the degree of MT here. If the discovery is done MT, there |
|
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5844 // may have been a different number of threads doing the discovery |
|
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5845 // and a different number of discovered lists may have Ref objects. |
|
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5846 // That is OK as long as the Reference lists are balanced (see |
|
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5847 // balance_all_queues() and balance_queues()). |
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5848 |
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5849 |
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5850 rp->set_mt_degree(ParallelGCThreads); |
| 0 | 5851 CMSRefProcTaskExecutor task_executor(*this); |
|
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5852 rp->process_discovered_references(&_is_alive_closure, |
| 0 | 5853 &cmsKeepAliveClosure, |
| 5854 &cmsDrainMarkingStackClosure, | |
| 5855 &task_executor); | |
| 5856 } else { | |
|
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5857 rp->process_discovered_references(&_is_alive_closure, |
| 0 | 5858 &cmsKeepAliveClosure, |
| 5859 &cmsDrainMarkingStackClosure, | |
| 5860 NULL); | |
| 5861 } | |
| 5862 verify_work_stacks_empty(); | |
| 5863 } | |
| 5864 | |
|
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|
5865 if (should_unload_classes()) { |
| 0 | 5866 { |
| 5867 TraceTime t("class unloading", PrintGCDetails, false, gclog_or_tty); | |
| 5868 | |
| 5869 // Follow SystemDictionary roots and unload classes | |
| 5870 bool purged_class = SystemDictionary::do_unloading(&_is_alive_closure); | |
| 5871 | |
| 5872 // Follow CodeCache roots and unload any methods marked for unloading | |
| 5873 CodeCache::do_unloading(&_is_alive_closure, | |
| 5874 &cmsKeepAliveClosure, | |
| 5875 purged_class); | |
| 5876 | |
| 5877 cmsDrainMarkingStackClosure.do_void(); | |
| 5878 verify_work_stacks_empty(); | |
| 5879 | |
| 5880 // Update subklass/sibling/implementor links in KlassKlass descendants | |
| 5881 assert(!_revisitStack.isEmpty(), "revisit stack should not be empty"); | |
| 5882 oop k; | |
| 5883 while ((k = _revisitStack.pop()) != NULL) { | |
| 5884 ((Klass*)(oopDesc*)k)->follow_weak_klass_links( | |
| 5885 &_is_alive_closure, | |
| 5886 &cmsKeepAliveClosure); | |
| 5887 } | |
| 5888 assert(!ClassUnloading || | |
| 5889 (_markStack.isEmpty() && overflow_list_is_empty()), | |
| 5890 "Should not have found new reachable objects"); | |
| 5891 assert(_revisitStack.isEmpty(), "revisit stack should have been drained"); | |
| 5892 cmsDrainMarkingStackClosure.do_void(); | |
| 5893 verify_work_stacks_empty(); | |
| 5894 } | |
| 5895 | |
| 5896 { | |
| 5897 TraceTime t("scrub symbol & string tables", PrintGCDetails, false, gclog_or_tty); | |
| 5898 // Now clean up stale oops in SymbolTable and StringTable | |
| 5899 SymbolTable::unlink(&_is_alive_closure); | |
| 5900 StringTable::unlink(&_is_alive_closure); | |
| 5901 } | |
| 5902 } | |
| 5903 | |
| 5904 verify_work_stacks_empty(); | |
| 5905 // Restore any preserved marks as a result of mark stack or | |
| 5906 // work queue overflow | |
| 5907 restore_preserved_marks_if_any(); // done single-threaded for now | |
| 5908 | |
| 5909 rp->set_enqueuing_is_done(true); | |
| 5910 if (rp->processing_is_mt()) { | |
|
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5911 rp->balance_all_queues(); |
| 0 | 5912 CMSRefProcTaskExecutor task_executor(*this); |
| 5913 rp->enqueue_discovered_references(&task_executor); | |
| 5914 } else { | |
| 5915 rp->enqueue_discovered_references(NULL); | |
| 5916 } | |
| 5917 rp->verify_no_references_recorded(); | |
| 5918 assert(!rp->discovery_enabled(), "should have been disabled"); | |
| 5919 | |
| 5920 // JVMTI object tagging is based on JNI weak refs. If any of these | |
| 5921 // refs were cleared then JVMTI needs to update its maps and | |
| 5922 // maybe post ObjectFrees to agents. | |
| 5923 JvmtiExport::cms_ref_processing_epilogue(); | |
| 5924 } | |
| 5925 | |
| 5926 #ifndef PRODUCT | |
| 5927 void CMSCollector::check_correct_thread_executing() { | |
| 5928 Thread* t = Thread::current(); | |
| 5929 // Only the VM thread or the CMS thread should be here. | |
| 5930 assert(t->is_ConcurrentGC_thread() || t->is_VM_thread(), | |
| 5931 "Unexpected thread type"); | |
| 5932 // If this is the vm thread, the foreground process | |
| 5933 // should not be waiting. Note that _foregroundGCIsActive is | |
| 5934 // true while the foreground collector is waiting. | |
| 5935 if (_foregroundGCShouldWait) { | |
| 5936 // We cannot be the VM thread | |
| 5937 assert(t->is_ConcurrentGC_thread(), | |
| 5938 "Should be CMS thread"); | |
| 5939 } else { | |
| 5940 // We can be the CMS thread only if we are in a stop-world | |
| 5941 // phase of CMS collection. | |
| 5942 if (t->is_ConcurrentGC_thread()) { | |
| 5943 assert(_collectorState == InitialMarking || | |
| 5944 _collectorState == FinalMarking, | |
| 5945 "Should be a stop-world phase"); | |
| 5946 // The CMS thread should be holding the CMS_token. | |
| 5947 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 5948 "Potential interference with concurrently " | |
| 5949 "executing VM thread"); | |
| 5950 } | |
| 5951 } | |
| 5952 } | |
| 5953 #endif | |
| 5954 | |
| 5955 void CMSCollector::sweep(bool asynch) { | |
| 5956 assert(_collectorState == Sweeping, "just checking"); | |
| 5957 check_correct_thread_executing(); | |
| 5958 verify_work_stacks_empty(); | |
| 5959 verify_overflow_empty(); | |
|
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5960 increment_sweep_count(); |
|
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5961 TraceCMSMemoryManagerStats tms(_collectorState); |
|
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5962 |
|
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5963 _inter_sweep_timer.stop(); |
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|
5964 _inter_sweep_estimate.sample(_inter_sweep_timer.seconds()); |
| 0 | 5965 size_policy()->avg_cms_free_at_sweep()->sample(_cmsGen->free()); |
| 5966 | |
| 5967 // PermGen verification support: If perm gen sweeping is disabled in | |
| 5968 // this cycle, we preserve the perm gen object "deadness" information | |
| 5969 // in the perm_gen_verify_bit_map. In order to do that we traverse | |
| 5970 // all blocks in perm gen and mark all dead objects. | |
|
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|
5971 if (verifying() && !should_unload_classes()) { |
| 0 | 5972 assert(perm_gen_verify_bit_map()->sizeInBits() != 0, |
| 5973 "Should have already been allocated"); | |
| 5974 MarkDeadObjectsClosure mdo(this, _permGen->cmsSpace(), | |
| 5975 markBitMap(), perm_gen_verify_bit_map()); | |
|
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|
5976 if (asynch) { |
|
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|
5977 CMSTokenSyncWithLocks ts(true, _permGen->freelistLock(), |
|
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|
5978 bitMapLock()); |
|
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|
5979 _permGen->cmsSpace()->blk_iterate(&mdo); |
|
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|
5980 } else { |
|
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|
5981 // In the case of synchronous sweep, we already have |
|
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|
5982 // the requisite locks/tokens. |
|
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|
5983 _permGen->cmsSpace()->blk_iterate(&mdo); |
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|
5984 } |
| 0 | 5985 } |
| 5986 | |
|
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5987 assert(!_intra_sweep_timer.is_active(), "Should not be active"); |
|
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5988 _intra_sweep_timer.reset(); |
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|
5989 _intra_sweep_timer.start(); |
| 0 | 5990 if (asynch) { |
| 5991 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
| 5992 CMSPhaseAccounting pa(this, "sweep", !PrintGCDetails); | |
| 5993 // First sweep the old gen then the perm gen | |
| 5994 { | |
| 5995 CMSTokenSyncWithLocks ts(true, _cmsGen->freelistLock(), | |
| 5996 bitMapLock()); | |
| 5997 sweepWork(_cmsGen, asynch); | |
| 5998 } | |
| 5999 | |
| 6000 // Now repeat for perm gen | |
|
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|
6001 if (should_unload_classes()) { |
| 0 | 6002 CMSTokenSyncWithLocks ts(true, _permGen->freelistLock(), |
| 6003 bitMapLock()); | |
| 6004 sweepWork(_permGen, asynch); | |
| 6005 } | |
| 6006 | |
| 6007 // Update Universe::_heap_*_at_gc figures. | |
| 6008 // We need all the free list locks to make the abstract state | |
| 6009 // transition from Sweeping to Resetting. See detailed note | |
| 6010 // further below. | |
| 6011 { | |
| 6012 CMSTokenSyncWithLocks ts(true, _cmsGen->freelistLock(), | |
| 6013 _permGen->freelistLock()); | |
| 6014 // Update heap occupancy information which is used as | |
| 6015 // input to soft ref clearing policy at the next gc. | |
| 6016 Universe::update_heap_info_at_gc(); | |
| 6017 _collectorState = Resizing; | |
| 6018 } | |
| 6019 } else { | |
| 6020 // already have needed locks | |
| 6021 sweepWork(_cmsGen, asynch); | |
| 6022 | |
|
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|
6023 if (should_unload_classes()) { |
| 0 | 6024 sweepWork(_permGen, asynch); |
| 6025 } | |
| 6026 // Update heap occupancy information which is used as | |
| 6027 // input to soft ref clearing policy at the next gc. | |
| 6028 Universe::update_heap_info_at_gc(); | |
| 6029 _collectorState = Resizing; | |
| 6030 } | |
| 6031 verify_work_stacks_empty(); | |
| 6032 verify_overflow_empty(); | |
| 6033 | |
|
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|
6034 _intra_sweep_timer.stop(); |
|
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|
6035 _intra_sweep_estimate.sample(_intra_sweep_timer.seconds()); |
|
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|
6036 |
|
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|
6037 _inter_sweep_timer.reset(); |
|
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|
6038 _inter_sweep_timer.start(); |
| 0 | 6039 |
| 6040 update_time_of_last_gc(os::javaTimeMillis()); | |
| 6041 | |
| 6042 // NOTE on abstract state transitions: | |
| 6043 // Mutators allocate-live and/or mark the mod-union table dirty | |
| 6044 // based on the state of the collection. The former is done in | |
| 6045 // the interval [Marking, Sweeping] and the latter in the interval | |
| 6046 // [Marking, Sweeping). Thus the transitions into the Marking state | |
| 6047 // and out of the Sweeping state must be synchronously visible | |
| 6048 // globally to the mutators. | |
| 6049 // The transition into the Marking state happens with the world | |
| 6050 // stopped so the mutators will globally see it. Sweeping is | |
| 6051 // done asynchronously by the background collector so the transition | |
| 6052 // from the Sweeping state to the Resizing state must be done | |
| 6053 // under the freelistLock (as is the check for whether to | |
| 6054 // allocate-live and whether to dirty the mod-union table). | |
| 6055 assert(_collectorState == Resizing, "Change of collector state to" | |
| 6056 " Resizing must be done under the freelistLocks (plural)"); | |
| 6057 | |
| 6058 // Now that sweeping has been completed, if the GCH's | |
| 6059 // incremental_collection_will_fail flag is set, clear it, | |
| 6060 // thus inviting a younger gen collection to promote into | |
| 6061 // this generation. If such a promotion may still fail, | |
| 6062 // the flag will be set again when a young collection is | |
| 6063 // attempted. | |
| 6064 // I think the incremental_collection_will_fail flag's use | |
| 6065 // is specific to a 2 generation collection policy, so i'll | |
| 6066 // assert that that's the configuration we are operating within. | |
| 6067 // The use of the flag can and should be generalized appropriately | |
| 6068 // in the future to deal with a general n-generation system. | |
| 6069 | |
| 6070 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 6071 assert(gch->collector_policy()->is_two_generation_policy(), | |
| 6072 "Resetting of incremental_collection_will_fail flag" | |
| 6073 " may be incorrect otherwise"); | |
| 6074 gch->clear_incremental_collection_will_fail(); | |
| 6075 gch->update_full_collections_completed(_collection_count_start); | |
| 6076 } | |
| 6077 | |
| 6078 // FIX ME!!! Looks like this belongs in CFLSpace, with | |
| 6079 // CMSGen merely delegating to it. | |
| 6080 void ConcurrentMarkSweepGeneration::setNearLargestChunk() { | |
|
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|
6081 double nearLargestPercent = FLSLargestBlockCoalesceProximity; |
| 0 | 6082 HeapWord* minAddr = _cmsSpace->bottom(); |
| 6083 HeapWord* largestAddr = | |
| 6084 (HeapWord*) _cmsSpace->dictionary()->findLargestDict(); | |
|
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|
6085 if (largestAddr == NULL) { |
| 0 | 6086 // The dictionary appears to be empty. In this case |
| 6087 // try to coalesce at the end of the heap. | |
| 6088 largestAddr = _cmsSpace->end(); | |
| 6089 } | |
| 6090 size_t largestOffset = pointer_delta(largestAddr, minAddr); | |
| 6091 size_t nearLargestOffset = | |
| 6092 (size_t)((double)largestOffset * nearLargestPercent) - MinChunkSize; | |
|
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|
6093 if (PrintFLSStatistics != 0) { |
|
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|
6094 gclog_or_tty->print_cr( |
|
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|
6095 "CMS: Large Block: " PTR_FORMAT ";" |
|
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|
6096 " Proximity: " PTR_FORMAT " -> " PTR_FORMAT, |
|
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|
6097 largestAddr, |
|
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|
6098 _cmsSpace->nearLargestChunk(), minAddr + nearLargestOffset); |
|
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|
6099 } |
| 0 | 6100 _cmsSpace->set_nearLargestChunk(minAddr + nearLargestOffset); |
| 6101 } | |
| 6102 | |
| 6103 bool ConcurrentMarkSweepGeneration::isNearLargestChunk(HeapWord* addr) { | |
| 6104 return addr >= _cmsSpace->nearLargestChunk(); | |
| 6105 } | |
| 6106 | |
| 6107 FreeChunk* ConcurrentMarkSweepGeneration::find_chunk_at_end() { | |
| 6108 return _cmsSpace->find_chunk_at_end(); | |
| 6109 } | |
| 6110 | |
| 6111 void ConcurrentMarkSweepGeneration::update_gc_stats(int current_level, | |
| 6112 bool full) { | |
| 6113 // The next lower level has been collected. Gather any statistics | |
| 6114 // that are of interest at this point. | |
| 6115 if (!full && (current_level + 1) == level()) { | |
| 6116 // Gather statistics on the young generation collection. | |
| 6117 collector()->stats().record_gc0_end(used()); | |
| 6118 } | |
| 6119 } | |
| 6120 | |
| 6121 CMSAdaptiveSizePolicy* ConcurrentMarkSweepGeneration::size_policy() { | |
| 6122 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 6123 assert(gch->kind() == CollectedHeap::GenCollectedHeap, | |
| 6124 "Wrong type of heap"); | |
| 6125 CMSAdaptiveSizePolicy* sp = (CMSAdaptiveSizePolicy*) | |
| 6126 gch->gen_policy()->size_policy(); | |
| 6127 assert(sp->is_gc_cms_adaptive_size_policy(), | |
| 6128 "Wrong type of size policy"); | |
| 6129 return sp; | |
| 6130 } | |
| 6131 | |
| 6132 void ConcurrentMarkSweepGeneration::rotate_debug_collection_type() { | |
| 6133 if (PrintGCDetails && Verbose) { | |
| 6134 gclog_or_tty->print("Rotate from %d ", _debug_collection_type); | |
| 6135 } | |
| 6136 _debug_collection_type = (CollectionTypes) (_debug_collection_type + 1); | |
| 6137 _debug_collection_type = | |
| 6138 (CollectionTypes) (_debug_collection_type % Unknown_collection_type); | |
| 6139 if (PrintGCDetails && Verbose) { | |
| 6140 gclog_or_tty->print_cr("to %d ", _debug_collection_type); | |
| 6141 } | |
| 6142 } | |
| 6143 | |
| 6144 void CMSCollector::sweepWork(ConcurrentMarkSweepGeneration* gen, | |
| 6145 bool asynch) { | |
| 6146 // We iterate over the space(s) underlying this generation, | |
| 6147 // checking the mark bit map to see if the bits corresponding | |
| 6148 // to specific blocks are marked or not. Blocks that are | |
| 6149 // marked are live and are not swept up. All remaining blocks | |
| 6150 // are swept up, with coalescing on-the-fly as we sweep up | |
| 6151 // contiguous free and/or garbage blocks: | |
| 6152 // We need to ensure that the sweeper synchronizes with allocators | |
| 6153 // and stop-the-world collectors. In particular, the following | |
| 6154 // locks are used: | |
| 6155 // . CMS token: if this is held, a stop the world collection cannot occur | |
| 6156 // . freelistLock: if this is held no allocation can occur from this | |
| 6157 // generation by another thread | |
| 6158 // . bitMapLock: if this is held, no other thread can access or update | |
| 6159 // | |
| 6160 | |
| 6161 // Note that we need to hold the freelistLock if we use | |
| 6162 // block iterate below; else the iterator might go awry if | |
| 6163 // a mutator (or promotion) causes block contents to change | |
| 6164 // (for instance if the allocator divvies up a block). | |
| 6165 // If we hold the free list lock, for all practical purposes | |
| 6166 // young generation GC's can't occur (they'll usually need to | |
| 6167 // promote), so we might as well prevent all young generation | |
| 6168 // GC's while we do a sweeping step. For the same reason, we might | |
| 6169 // as well take the bit map lock for the entire duration | |
| 6170 | |
| 6171 // check that we hold the requisite locks | |
| 6172 assert(have_cms_token(), "Should hold cms token"); | |
| 6173 assert( (asynch && ConcurrentMarkSweepThread::cms_thread_has_cms_token()) | |
| 6174 || (!asynch && ConcurrentMarkSweepThread::vm_thread_has_cms_token()), | |
| 6175 "Should possess CMS token to sweep"); | |
| 6176 assert_lock_strong(gen->freelistLock()); | |
| 6177 assert_lock_strong(bitMapLock()); | |
| 6178 | |
|
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6179 assert(!_inter_sweep_timer.is_active(), "Was switched off in an outer context"); |
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6180 assert(_intra_sweep_timer.is_active(), "Was switched on in an outer context"); |
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6181 gen->cmsSpace()->beginSweepFLCensus((float)(_inter_sweep_timer.seconds()), |
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6182 _inter_sweep_estimate.padded_average(), |
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6183 _intra_sweep_estimate.padded_average()); |
| 0 | 6184 gen->setNearLargestChunk(); |
| 6185 | |
| 6186 { | |
| 6187 SweepClosure sweepClosure(this, gen, &_markBitMap, | |
| 6188 CMSYield && asynch); | |
| 6189 gen->cmsSpace()->blk_iterate_careful(&sweepClosure); | |
| 6190 // We need to free-up/coalesce garbage/blocks from a | |
| 6191 // co-terminal free run. This is done in the SweepClosure | |
| 6192 // destructor; so, do not remove this scope, else the | |
| 6193 // end-of-sweep-census below will be off by a little bit. | |
| 6194 } | |
| 6195 gen->cmsSpace()->sweep_completed(); | |
|
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6196 gen->cmsSpace()->endSweepFLCensus(sweep_count()); |
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6197 if (should_unload_classes()) { // unloaded classes this cycle, |
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6198 _concurrent_cycles_since_last_unload = 0; // ... reset count |
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6199 } else { // did not unload classes, |
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6200 _concurrent_cycles_since_last_unload++; // ... increment count |
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6201 } |
| 0 | 6202 } |
| 6203 | |
| 6204 // Reset CMS data structures (for now just the marking bit map) | |
| 6205 // preparatory for the next cycle. | |
| 6206 void CMSCollector::reset(bool asynch) { | |
| 6207 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 6208 CMSAdaptiveSizePolicy* sp = size_policy(); | |
| 6209 AdaptiveSizePolicyOutput(sp, gch->total_collections()); | |
| 6210 if (asynch) { | |
| 6211 CMSTokenSyncWithLocks ts(true, bitMapLock()); | |
| 6212 | |
| 6213 // If the state is not "Resetting", the foreground thread | |
| 6214 // has done a collection and the resetting. | |
| 6215 if (_collectorState != Resetting) { | |
| 6216 assert(_collectorState == Idling, "The state should only change" | |
| 6217 " because the foreground collector has finished the collection"); | |
| 6218 return; | |
| 6219 } | |
| 6220 | |
| 6221 // Clear the mark bitmap (no grey objects to start with) | |
| 6222 // for the next cycle. | |
| 6223 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
| 6224 CMSPhaseAccounting cmspa(this, "reset", !PrintGCDetails); | |
| 6225 | |
| 6226 HeapWord* curAddr = _markBitMap.startWord(); | |
| 6227 while (curAddr < _markBitMap.endWord()) { | |
| 6228 size_t remaining = pointer_delta(_markBitMap.endWord(), curAddr); | |
| 6229 MemRegion chunk(curAddr, MIN2(CMSBitMapYieldQuantum, remaining)); | |
| 6230 _markBitMap.clear_large_range(chunk); | |
| 6231 if (ConcurrentMarkSweepThread::should_yield() && | |
| 6232 !foregroundGCIsActive() && | |
| 6233 CMSYield) { | |
| 6234 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 6235 "CMS thread should hold CMS token"); | |
| 6236 assert_lock_strong(bitMapLock()); | |
| 6237 bitMapLock()->unlock(); | |
| 6238 ConcurrentMarkSweepThread::desynchronize(true); | |
| 6239 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 6240 stopTimer(); | |
| 6241 if (PrintCMSStatistics != 0) { | |
| 6242 incrementYields(); | |
| 6243 } | |
| 6244 icms_wait(); | |
| 6245 | |
| 6246 // See the comment in coordinator_yield() | |
| 6247 for (unsigned i = 0; i < CMSYieldSleepCount && | |
|
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6248 ConcurrentMarkSweepThread::should_yield() && |
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6249 !CMSCollector::foregroundGCIsActive(); ++i) { |
| 0 | 6250 os::sleep(Thread::current(), 1, false); |
| 6251 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 6252 } | |
| 6253 | |
| 6254 ConcurrentMarkSweepThread::synchronize(true); | |
| 6255 bitMapLock()->lock_without_safepoint_check(); | |
| 6256 startTimer(); | |
| 6257 } | |
| 6258 curAddr = chunk.end(); | |
| 6259 } | |
|
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6260 // A successful mostly concurrent collection has been done. |
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6261 // Because only the full (i.e., concurrent mode failure) collections |
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6262 // are being measured for gc overhead limits, clean the "near" flag |
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6263 // and count. |
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6264 sp->reset_gc_overhead_limit_count(); |
| 0 | 6265 _collectorState = Idling; |
| 6266 } else { | |
| 6267 // already have the lock | |
| 6268 assert(_collectorState == Resetting, "just checking"); | |
| 6269 assert_lock_strong(bitMapLock()); | |
| 6270 _markBitMap.clear_all(); | |
| 6271 _collectorState = Idling; | |
| 6272 } | |
| 6273 | |
| 6274 // Stop incremental mode after a cycle completes, so that any future cycles | |
| 6275 // are triggered by allocation. | |
| 6276 stop_icms(); | |
| 6277 | |
| 6278 NOT_PRODUCT( | |
| 6279 if (RotateCMSCollectionTypes) { | |
| 6280 _cmsGen->rotate_debug_collection_type(); | |
| 6281 } | |
| 6282 ) | |
| 6283 } | |
| 6284 | |
| 6285 void CMSCollector::do_CMS_operation(CMS_op_type op) { | |
| 6286 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps); | |
| 6287 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
| 6288 TraceTime t("GC", PrintGC, !PrintGCDetails, gclog_or_tty); | |
| 6289 TraceCollectorStats tcs(counters()); | |
| 6290 | |
| 6291 switch (op) { | |
| 6292 case CMS_op_checkpointRootsInitial: { | |
| 6293 checkpointRootsInitial(true); // asynch | |
| 6294 if (PrintGC) { | |
| 6295 _cmsGen->printOccupancy("initial-mark"); | |
| 6296 } | |
| 6297 break; | |
| 6298 } | |
| 6299 case CMS_op_checkpointRootsFinal: { | |
| 6300 checkpointRootsFinal(true, // asynch | |
| 6301 false, // !clear_all_soft_refs | |
| 6302 false); // !init_mark_was_synchronous | |
| 6303 if (PrintGC) { | |
| 6304 _cmsGen->printOccupancy("remark"); | |
| 6305 } | |
| 6306 break; | |
| 6307 } | |
| 6308 default: | |
| 6309 fatal("No such CMS_op"); | |
| 6310 } | |
| 6311 } | |
| 6312 | |
| 6313 #ifndef PRODUCT | |
| 6314 size_t const CMSCollector::skip_header_HeapWords() { | |
| 6315 return FreeChunk::header_size(); | |
| 6316 } | |
| 6317 | |
| 6318 // Try and collect here conditions that should hold when | |
| 6319 // CMS thread is exiting. The idea is that the foreground GC | |
| 6320 // thread should not be blocked if it wants to terminate | |
| 6321 // the CMS thread and yet continue to run the VM for a while | |
| 6322 // after that. | |
| 6323 void CMSCollector::verify_ok_to_terminate() const { | |
| 6324 assert(Thread::current()->is_ConcurrentGC_thread(), | |
| 6325 "should be called by CMS thread"); | |
| 6326 assert(!_foregroundGCShouldWait, "should be false"); | |
| 6327 // We could check here that all the various low-level locks | |
| 6328 // are not held by the CMS thread, but that is overkill; see | |
| 6329 // also CMSThread::verify_ok_to_terminate() where the CGC_lock | |
| 6330 // is checked. | |
| 6331 } | |
| 6332 #endif | |
| 6333 | |
| 6334 size_t CMSCollector::block_size_using_printezis_bits(HeapWord* addr) const { | |
|
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6335 assert(_markBitMap.isMarked(addr) && _markBitMap.isMarked(addr + 1), |
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6336 "missing Printezis mark?"); |
| 0 | 6337 HeapWord* nextOneAddr = _markBitMap.getNextMarkedWordAddress(addr + 2); |
| 6338 size_t size = pointer_delta(nextOneAddr + 1, addr); | |
| 6339 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
| 6340 "alignment problem"); | |
| 6341 assert(size >= 3, "Necessary for Printezis marks to work"); | |
| 6342 return size; | |
| 6343 } | |
| 6344 | |
| 6345 // A variant of the above (block_size_using_printezis_bits()) except | |
| 6346 // that we return 0 if the P-bits are not yet set. | |
| 6347 size_t CMSCollector::block_size_if_printezis_bits(HeapWord* addr) const { | |
| 6348 if (_markBitMap.isMarked(addr)) { | |
| 6349 assert(_markBitMap.isMarked(addr + 1), "Missing Printezis bit?"); | |
| 6350 HeapWord* nextOneAddr = _markBitMap.getNextMarkedWordAddress(addr + 2); | |
| 6351 size_t size = pointer_delta(nextOneAddr + 1, addr); | |
| 6352 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
| 6353 "alignment problem"); | |
| 6354 assert(size >= 3, "Necessary for Printezis marks to work"); | |
| 6355 return size; | |
| 6356 } else { | |
| 6357 assert(!_markBitMap.isMarked(addr + 1), "Bit map inconsistency?"); | |
| 6358 return 0; | |
| 6359 } | |
| 6360 } | |
| 6361 | |
| 6362 HeapWord* CMSCollector::next_card_start_after_block(HeapWord* addr) const { | |
| 6363 size_t sz = 0; | |
| 6364 oop p = (oop)addr; | |
| 187 | 6365 if (p->klass_or_null() != NULL && p->is_parsable()) { |
| 0 | 6366 sz = CompactibleFreeListSpace::adjustObjectSize(p->size()); |
| 6367 } else { | |
| 6368 sz = block_size_using_printezis_bits(addr); | |
| 6369 } | |
| 6370 assert(sz > 0, "size must be nonzero"); | |
| 6371 HeapWord* next_block = addr + sz; | |
| 6372 HeapWord* next_card = (HeapWord*)round_to((uintptr_t)next_block, | |
| 6373 CardTableModRefBS::card_size); | |
| 6374 assert(round_down((uintptr_t)addr, CardTableModRefBS::card_size) < | |
| 6375 round_down((uintptr_t)next_card, CardTableModRefBS::card_size), | |
| 6376 "must be different cards"); | |
| 6377 return next_card; | |
| 6378 } | |
| 6379 | |
| 6380 | |
| 6381 // CMS Bit Map Wrapper ///////////////////////////////////////// | |
| 6382 | |
| 6383 // Construct a CMS bit map infrastructure, but don't create the | |
| 6384 // bit vector itself. That is done by a separate call CMSBitMap::allocate() | |
| 6385 // further below. | |
| 6386 CMSBitMap::CMSBitMap(int shifter, int mutex_rank, const char* mutex_name): | |
|
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6387 _bm(), |
| 0 | 6388 _shifter(shifter), |
| 6389 _lock(mutex_rank >= 0 ? new Mutex(mutex_rank, mutex_name, true) : NULL) | |
| 6390 { | |
| 6391 _bmStartWord = 0; | |
| 6392 _bmWordSize = 0; | |
| 6393 } | |
| 6394 | |
| 6395 bool CMSBitMap::allocate(MemRegion mr) { | |
| 6396 _bmStartWord = mr.start(); | |
| 6397 _bmWordSize = mr.word_size(); | |
| 6398 ReservedSpace brs(ReservedSpace::allocation_align_size_up( | |
| 6399 (_bmWordSize >> (_shifter + LogBitsPerByte)) + 1)); | |
| 6400 if (!brs.is_reserved()) { | |
| 6401 warning("CMS bit map allocation failure"); | |
| 6402 return false; | |
| 6403 } | |
| 6404 // For now we'll just commit all of the bit map up fromt. | |
| 6405 // Later on we'll try to be more parsimonious with swap. | |
| 6406 if (!_virtual_space.initialize(brs, brs.size())) { | |
| 6407 warning("CMS bit map backing store failure"); | |
| 6408 return false; | |
| 6409 } | |
| 6410 assert(_virtual_space.committed_size() == brs.size(), | |
| 6411 "didn't reserve backing store for all of CMS bit map?"); | |
|
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6412 _bm.set_map((BitMap::bm_word_t*)_virtual_space.low()); |
| 0 | 6413 assert(_virtual_space.committed_size() << (_shifter + LogBitsPerByte) >= |
| 6414 _bmWordSize, "inconsistency in bit map sizing"); | |
| 6415 _bm.set_size(_bmWordSize >> _shifter); | |
| 6416 | |
| 6417 // bm.clear(); // can we rely on getting zero'd memory? verify below | |
| 6418 assert(isAllClear(), | |
| 6419 "Expected zero'd memory from ReservedSpace constructor"); | |
| 6420 assert(_bm.size() == heapWordDiffToOffsetDiff(sizeInWords()), | |
| 6421 "consistency check"); | |
| 6422 return true; | |
| 6423 } | |
| 6424 | |
| 6425 void CMSBitMap::dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl) { | |
| 6426 HeapWord *next_addr, *end_addr, *last_addr; | |
| 6427 assert_locked(); | |
| 6428 assert(covers(mr), "out-of-range error"); | |
| 6429 // XXX assert that start and end are appropriately aligned | |
| 6430 for (next_addr = mr.start(), end_addr = mr.end(); | |
| 6431 next_addr < end_addr; next_addr = last_addr) { | |
| 6432 MemRegion dirty_region = getAndClearMarkedRegion(next_addr, end_addr); | |
| 6433 last_addr = dirty_region.end(); | |
| 6434 if (!dirty_region.is_empty()) { | |
| 6435 cl->do_MemRegion(dirty_region); | |
| 6436 } else { | |
| 6437 assert(last_addr == end_addr, "program logic"); | |
| 6438 return; | |
| 6439 } | |
| 6440 } | |
| 6441 } | |
| 6442 | |
| 6443 #ifndef PRODUCT | |
| 6444 void CMSBitMap::assert_locked() const { | |
| 6445 CMSLockVerifier::assert_locked(lock()); | |
| 6446 } | |
| 6447 | |
| 6448 bool CMSBitMap::covers(MemRegion mr) const { | |
| 6449 // assert(_bm.map() == _virtual_space.low(), "map inconsistency"); | |
| 6450 assert((size_t)_bm.size() == (_bmWordSize >> _shifter), | |
| 6451 "size inconsistency"); | |
| 6452 return (mr.start() >= _bmStartWord) && | |
| 6453 (mr.end() <= endWord()); | |
| 6454 } | |
| 6455 | |
| 6456 bool CMSBitMap::covers(HeapWord* start, size_t size) const { | |
| 6457 return (start >= _bmStartWord && (start + size) <= endWord()); | |
| 6458 } | |
| 6459 | |
| 6460 void CMSBitMap::verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) { | |
| 6461 // verify that there are no 1 bits in the interval [left, right) | |
| 6462 FalseBitMapClosure falseBitMapClosure; | |
| 6463 iterate(&falseBitMapClosure, left, right); | |
| 6464 } | |
| 6465 | |
| 6466 void CMSBitMap::region_invariant(MemRegion mr) | |
| 6467 { | |
| 6468 assert_locked(); | |
| 6469 // mr = mr.intersection(MemRegion(_bmStartWord, _bmWordSize)); | |
| 6470 assert(!mr.is_empty(), "unexpected empty region"); | |
| 6471 assert(covers(mr), "mr should be covered by bit map"); | |
| 6472 // convert address range into offset range | |
| 6473 size_t start_ofs = heapWordToOffset(mr.start()); | |
| 6474 // Make sure that end() is appropriately aligned | |
| 6475 assert(mr.end() == (HeapWord*)round_to((intptr_t)mr.end(), | |
| 6476 (1 << (_shifter+LogHeapWordSize))), | |
| 6477 "Misaligned mr.end()"); | |
| 6478 size_t end_ofs = heapWordToOffset(mr.end()); | |
| 6479 assert(end_ofs > start_ofs, "Should mark at least one bit"); | |
| 6480 } | |
| 6481 | |
| 6482 #endif | |
| 6483 | |
| 6484 bool CMSMarkStack::allocate(size_t size) { | |
| 6485 // allocate a stack of the requisite depth | |
| 6486 ReservedSpace rs(ReservedSpace::allocation_align_size_up( | |
| 6487 size * sizeof(oop))); | |
| 6488 if (!rs.is_reserved()) { | |
| 6489 warning("CMSMarkStack allocation failure"); | |
| 6490 return false; | |
| 6491 } | |
| 6492 if (!_virtual_space.initialize(rs, rs.size())) { | |
| 6493 warning("CMSMarkStack backing store failure"); | |
| 6494 return false; | |
| 6495 } | |
| 6496 assert(_virtual_space.committed_size() == rs.size(), | |
| 6497 "didn't reserve backing store for all of CMS stack?"); | |
| 6498 _base = (oop*)(_virtual_space.low()); | |
| 6499 _index = 0; | |
| 6500 _capacity = size; | |
| 6501 NOT_PRODUCT(_max_depth = 0); | |
| 6502 return true; | |
| 6503 } | |
| 6504 | |
| 6505 // XXX FIX ME !!! In the MT case we come in here holding a | |
| 6506 // leaf lock. For printing we need to take a further lock | |
| 6507 // which has lower rank. We need to recallibrate the two | |
| 6508 // lock-ranks involved in order to be able to rpint the | |
| 6509 // messages below. (Or defer the printing to the caller. | |
| 6510 // For now we take the expedient path of just disabling the | |
| 6511 // messages for the problematic case.) | |
| 6512 void CMSMarkStack::expand() { | |
| 1284 | 6513 assert(_capacity <= MarkStackSizeMax, "stack bigger than permitted"); |
| 6514 if (_capacity == MarkStackSizeMax) { | |
| 0 | 6515 if (_hit_limit++ == 0 && !CMSConcurrentMTEnabled && PrintGCDetails) { |
| 6516 // We print a warning message only once per CMS cycle. | |
| 6517 gclog_or_tty->print_cr(" (benign) Hit CMSMarkStack max size limit"); | |
| 6518 } | |
| 6519 return; | |
| 6520 } | |
| 6521 // Double capacity if possible | |
| 1284 | 6522 size_t new_capacity = MIN2(_capacity*2, MarkStackSizeMax); |
| 0 | 6523 // Do not give up existing stack until we have managed to |
| 6524 // get the double capacity that we desired. | |
| 6525 ReservedSpace rs(ReservedSpace::allocation_align_size_up( | |
| 6526 new_capacity * sizeof(oop))); | |
| 6527 if (rs.is_reserved()) { | |
| 6528 // Release the backing store associated with old stack | |
| 6529 _virtual_space.release(); | |
| 6530 // Reinitialize virtual space for new stack | |
| 6531 if (!_virtual_space.initialize(rs, rs.size())) { | |
| 6532 fatal("Not enough swap for expanded marking stack"); | |
| 6533 } | |
| 6534 _base = (oop*)(_virtual_space.low()); | |
| 6535 _index = 0; | |
| 6536 _capacity = new_capacity; | |
| 6537 } else if (_failed_double++ == 0 && !CMSConcurrentMTEnabled && PrintGCDetails) { | |
| 6538 // Failed to double capacity, continue; | |
| 6539 // we print a detail message only once per CMS cycle. | |
| 6540 gclog_or_tty->print(" (benign) Failed to expand marking stack from "SIZE_FORMAT"K to " | |
| 6541 SIZE_FORMAT"K", | |
| 6542 _capacity / K, new_capacity / K); | |
| 6543 } | |
| 6544 } | |
| 6545 | |
| 6546 | |
| 6547 // Closures | |
| 6548 // XXX: there seems to be a lot of code duplication here; | |
| 6549 // should refactor and consolidate common code. | |
| 6550 | |
| 6551 // This closure is used to mark refs into the CMS generation in | |
| 6552 // the CMS bit map. Called at the first checkpoint. This closure | |
| 6553 // assumes that we do not need to re-mark dirty cards; if the CMS | |
| 6554 // generation on which this is used is not an oldest (modulo perm gen) | |
| 6555 // generation then this will lose younger_gen cards! | |
| 6556 | |
| 6557 MarkRefsIntoClosure::MarkRefsIntoClosure( | |
|
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6558 MemRegion span, CMSBitMap* bitMap): |
| 0 | 6559 _span(span), |
|
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6560 _bitMap(bitMap) |
| 0 | 6561 { |
| 6562 assert(_ref_processor == NULL, "deliberately left NULL"); | |
| 6563 assert(_bitMap->covers(_span), "_bitMap/_span mismatch"); | |
| 6564 } | |
| 6565 | |
|
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6566 void MarkRefsIntoClosure::do_oop(oop obj) { |
| 0 | 6567 // if p points into _span, then mark corresponding bit in _markBitMap |
|
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6568 assert(obj->is_oop(), "expected an oop"); |
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6569 HeapWord* addr = (HeapWord*)obj; |
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6570 if (_span.contains(addr)) { |
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6571 // this should be made more efficient |
|
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6572 _bitMap->mark(addr); |
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6573 } |
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6574 } |
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6575 |
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6576 void MarkRefsIntoClosure::do_oop(oop* p) { MarkRefsIntoClosure::do_oop_work(p); } |
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6577 void MarkRefsIntoClosure::do_oop(narrowOop* p) { MarkRefsIntoClosure::do_oop_work(p); } |
| 0 | 6578 |
| 6579 // A variant of the above, used for CMS marking verification. | |
| 6580 MarkRefsIntoVerifyClosure::MarkRefsIntoVerifyClosure( | |
|
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6581 MemRegion span, CMSBitMap* verification_bm, CMSBitMap* cms_bm): |
| 0 | 6582 _span(span), |
| 6583 _verification_bm(verification_bm), | |
|
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6584 _cms_bm(cms_bm) |
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6585 { |
| 0 | 6586 assert(_ref_processor == NULL, "deliberately left NULL"); |
| 6587 assert(_verification_bm->covers(_span), "_verification_bm/_span mismatch"); | |
| 6588 } | |
| 6589 | |
|
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6590 void MarkRefsIntoVerifyClosure::do_oop(oop obj) { |
| 0 | 6591 // if p points into _span, then mark corresponding bit in _markBitMap |
|
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6592 assert(obj->is_oop(), "expected an oop"); |
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6593 HeapWord* addr = (HeapWord*)obj; |
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6594 if (_span.contains(addr)) { |
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6595 _verification_bm->mark(addr); |
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6596 if (!_cms_bm->isMarked(addr)) { |
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6597 oop(addr)->print(); |
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6598 gclog_or_tty->print_cr(" (" INTPTR_FORMAT " should have been marked)", addr); |
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6599 fatal("... aborting"); |
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6600 } |
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6601 } |
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6602 } |
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6603 |
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6604 void MarkRefsIntoVerifyClosure::do_oop(oop* p) { MarkRefsIntoVerifyClosure::do_oop_work(p); } |
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6605 void MarkRefsIntoVerifyClosure::do_oop(narrowOop* p) { MarkRefsIntoVerifyClosure::do_oop_work(p); } |
| 0 | 6606 |
| 6607 ////////////////////////////////////////////////// | |
| 6608 // MarkRefsIntoAndScanClosure | |
| 6609 ////////////////////////////////////////////////// | |
| 6610 | |
| 6611 MarkRefsIntoAndScanClosure::MarkRefsIntoAndScanClosure(MemRegion span, | |
| 6612 ReferenceProcessor* rp, | |
| 6613 CMSBitMap* bit_map, | |
| 6614 CMSBitMap* mod_union_table, | |
| 6615 CMSMarkStack* mark_stack, | |
| 6616 CMSMarkStack* revisit_stack, | |
| 6617 CMSCollector* collector, | |
| 6618 bool should_yield, | |
| 6619 bool concurrent_precleaning): | |
| 6620 _collector(collector), | |
| 6621 _span(span), | |
| 6622 _bit_map(bit_map), | |
| 6623 _mark_stack(mark_stack), | |
| 6624 _pushAndMarkClosure(collector, span, rp, bit_map, mod_union_table, | |
| 6625 mark_stack, revisit_stack, concurrent_precleaning), | |
| 6626 _yield(should_yield), | |
| 6627 _concurrent_precleaning(concurrent_precleaning), | |
| 6628 _freelistLock(NULL) | |
| 6629 { | |
| 6630 _ref_processor = rp; | |
| 6631 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
| 6632 } | |
| 6633 | |
| 6634 // This closure is used to mark refs into the CMS generation at the | |
| 6635 // second (final) checkpoint, and to scan and transitively follow | |
| 6636 // the unmarked oops. It is also used during the concurrent precleaning | |
| 6637 // phase while scanning objects on dirty cards in the CMS generation. | |
| 6638 // The marks are made in the marking bit map and the marking stack is | |
| 6639 // used for keeping the (newly) grey objects during the scan. | |
| 6640 // The parallel version (Par_...) appears further below. | |
|
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6641 void MarkRefsIntoAndScanClosure::do_oop(oop obj) { |
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6642 if (obj != NULL) { |
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6643 assert(obj->is_oop(), "expected an oop"); |
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6644 HeapWord* addr = (HeapWord*)obj; |
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6645 assert(_mark_stack->isEmpty(), "pre-condition (eager drainage)"); |
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6646 assert(_collector->overflow_list_is_empty(), |
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6647 "overflow list should be empty"); |
| 0 | 6648 if (_span.contains(addr) && |
| 6649 !_bit_map->isMarked(addr)) { | |
| 6650 // mark bit map (object is now grey) | |
| 6651 _bit_map->mark(addr); | |
| 6652 // push on marking stack (stack should be empty), and drain the | |
| 6653 // stack by applying this closure to the oops in the oops popped | |
| 6654 // from the stack (i.e. blacken the grey objects) | |
|
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6655 bool res = _mark_stack->push(obj); |
| 0 | 6656 assert(res, "Should have space to push on empty stack"); |
| 6657 do { | |
| 6658 oop new_oop = _mark_stack->pop(); | |
| 6659 assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop"); | |
| 6660 assert(new_oop->is_parsable(), "Found unparsable oop"); | |
| 6661 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
| 6662 "only grey objects on this stack"); | |
| 6663 // iterate over the oops in this oop, marking and pushing | |
| 6664 // the ones in CMS heap (i.e. in _span). | |
| 6665 new_oop->oop_iterate(&_pushAndMarkClosure); | |
| 6666 // check if it's time to yield | |
| 6667 do_yield_check(); | |
| 6668 } while (!_mark_stack->isEmpty() || | |
| 6669 (!_concurrent_precleaning && take_from_overflow_list())); | |
| 6670 // if marking stack is empty, and we are not doing this | |
| 6671 // during precleaning, then check the overflow list | |
| 6672 } | |
| 6673 assert(_mark_stack->isEmpty(), "post-condition (eager drainage)"); | |
| 6674 assert(_collector->overflow_list_is_empty(), | |
| 6675 "overflow list was drained above"); | |
| 6676 // We could restore evacuated mark words, if any, used for | |
| 6677 // overflow list links here because the overflow list is | |
| 6678 // provably empty here. That would reduce the maximum | |
| 6679 // size requirements for preserved_{oop,mark}_stack. | |
| 6680 // But we'll just postpone it until we are all done | |
| 6681 // so we can just stream through. | |
| 6682 if (!_concurrent_precleaning && CMSOverflowEarlyRestoration) { | |
| 6683 _collector->restore_preserved_marks_if_any(); | |
| 6684 assert(_collector->no_preserved_marks(), "No preserved marks"); | |
| 6685 } | |
| 6686 assert(!CMSOverflowEarlyRestoration || _collector->no_preserved_marks(), | |
| 6687 "All preserved marks should have been restored above"); | |
| 6688 } | |
| 6689 } | |
| 6690 | |
|
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6691 void MarkRefsIntoAndScanClosure::do_oop(oop* p) { MarkRefsIntoAndScanClosure::do_oop_work(p); } |
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6692 void MarkRefsIntoAndScanClosure::do_oop(narrowOop* p) { MarkRefsIntoAndScanClosure::do_oop_work(p); } |
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6693 |
| 0 | 6694 void MarkRefsIntoAndScanClosure::do_yield_work() { |
| 6695 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 6696 "CMS thread should hold CMS token"); | |
| 6697 assert_lock_strong(_freelistLock); | |
| 6698 assert_lock_strong(_bit_map->lock()); | |
| 6699 // relinquish the free_list_lock and bitMaplock() | |
| 935 | 6700 DEBUG_ONLY(RememberKlassesChecker mux(false);) |
| 0 | 6701 _bit_map->lock()->unlock(); |
| 6702 _freelistLock->unlock(); | |
| 6703 ConcurrentMarkSweepThread::desynchronize(true); | |
| 6704 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 6705 _collector->stopTimer(); | |
| 6706 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
| 6707 if (PrintCMSStatistics != 0) { | |
| 6708 _collector->incrementYields(); | |
| 6709 } | |
| 6710 _collector->icms_wait(); | |
| 6711 | |
| 6712 // See the comment in coordinator_yield() | |
|
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6713 for (unsigned i = 0; |
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6714 i < CMSYieldSleepCount && |
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6715 ConcurrentMarkSweepThread::should_yield() && |
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6716 !CMSCollector::foregroundGCIsActive(); |
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6717 ++i) { |
| 0 | 6718 os::sleep(Thread::current(), 1, false); |
| 6719 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 6720 } | |
| 6721 | |
| 6722 ConcurrentMarkSweepThread::synchronize(true); | |
| 6723 _freelistLock->lock_without_safepoint_check(); | |
| 6724 _bit_map->lock()->lock_without_safepoint_check(); | |
| 6725 _collector->startTimer(); | |
| 6726 } | |
| 6727 | |
| 6728 /////////////////////////////////////////////////////////// | |
| 6729 // Par_MarkRefsIntoAndScanClosure: a parallel version of | |
| 6730 // MarkRefsIntoAndScanClosure | |
| 6731 /////////////////////////////////////////////////////////// | |
| 6732 Par_MarkRefsIntoAndScanClosure::Par_MarkRefsIntoAndScanClosure( | |
| 6733 CMSCollector* collector, MemRegion span, ReferenceProcessor* rp, | |
| 6734 CMSBitMap* bit_map, OopTaskQueue* work_queue, CMSMarkStack* revisit_stack): | |
| 6735 _span(span), | |
| 6736 _bit_map(bit_map), | |
| 6737 _work_queue(work_queue), | |
| 6738 _low_water_mark(MIN2((uint)(work_queue->max_elems()/4), | |
| 6739 (uint)(CMSWorkQueueDrainThreshold * ParallelGCThreads))), | |
| 6740 _par_pushAndMarkClosure(collector, span, rp, bit_map, work_queue, | |
| 6741 revisit_stack) | |
| 6742 { | |
| 6743 _ref_processor = rp; | |
| 6744 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
| 6745 } | |
| 6746 | |
| 6747 // This closure is used to mark refs into the CMS generation at the | |
| 6748 // second (final) checkpoint, and to scan and transitively follow | |
| 6749 // the unmarked oops. The marks are made in the marking bit map and | |
| 6750 // the work_queue is used for keeping the (newly) grey objects during | |
| 6751 // the scan phase whence they are also available for stealing by parallel | |
| 6752 // threads. Since the marking bit map is shared, updates are | |
| 6753 // synchronized (via CAS). | |
|
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6754 void Par_MarkRefsIntoAndScanClosure::do_oop(oop obj) { |
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6755 if (obj != NULL) { |
| 0 | 6756 // Ignore mark word because this could be an already marked oop |
| 6757 // that may be chained at the end of the overflow list. | |
|
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6758 assert(obj->is_oop(true), "expected an oop"); |
|
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6759 HeapWord* addr = (HeapWord*)obj; |
| 0 | 6760 if (_span.contains(addr) && |
| 6761 !_bit_map->isMarked(addr)) { | |
| 6762 // mark bit map (object will become grey): | |
| 6763 // It is possible for several threads to be | |
| 6764 // trying to "claim" this object concurrently; | |
| 6765 // the unique thread that succeeds in marking the | |
| 6766 // object first will do the subsequent push on | |
| 6767 // to the work queue (or overflow list). | |
| 6768 if (_bit_map->par_mark(addr)) { | |
| 6769 // push on work_queue (which may not be empty), and trim the | |
| 6770 // queue to an appropriate length by applying this closure to | |
| 6771 // the oops in the oops popped from the stack (i.e. blacken the | |
| 6772 // grey objects) | |
|
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6773 bool res = _work_queue->push(obj); |
| 0 | 6774 assert(res, "Low water mark should be less than capacity?"); |
| 6775 trim_queue(_low_water_mark); | |
| 6776 } // Else, another thread claimed the object | |
| 6777 } | |
| 6778 } | |
| 6779 } | |
| 6780 | |
|
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6781 void Par_MarkRefsIntoAndScanClosure::do_oop(oop* p) { Par_MarkRefsIntoAndScanClosure::do_oop_work(p); } |
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6782 void Par_MarkRefsIntoAndScanClosure::do_oop(narrowOop* p) { Par_MarkRefsIntoAndScanClosure::do_oop_work(p); } |
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6783 |
| 0 | 6784 // This closure is used to rescan the marked objects on the dirty cards |
| 6785 // in the mod union table and the card table proper. | |
| 6786 size_t ScanMarkedObjectsAgainCarefullyClosure::do_object_careful_m( | |
| 6787 oop p, MemRegion mr) { | |
| 6788 | |
| 6789 size_t size = 0; | |
| 6790 HeapWord* addr = (HeapWord*)p; | |
| 6791 DEBUG_ONLY(_collector->verify_work_stacks_empty();) | |
| 6792 assert(_span.contains(addr), "we are scanning the CMS generation"); | |
| 6793 // check if it's time to yield | |
| 6794 if (do_yield_check()) { | |
| 6795 // We yielded for some foreground stop-world work, | |
| 6796 // and we have been asked to abort this ongoing preclean cycle. | |
| 6797 return 0; | |
| 6798 } | |
| 6799 if (_bitMap->isMarked(addr)) { | |
| 6800 // it's marked; is it potentially uninitialized? | |
| 187 | 6801 if (p->klass_or_null() != NULL) { |
|
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6802 // If is_conc_safe is false, the object may be undergoing |
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6803 // change by the VM outside a safepoint. Don't try to |
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6804 // scan it, but rather leave it for the remark phase. |
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6805 if (CMSPermGenPrecleaningEnabled && |
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6806 (!p->is_conc_safe() || !p->is_parsable())) { |
| 0 | 6807 // Signal precleaning to redirty the card since |
| 6808 // the klass pointer is already installed. | |
| 6809 assert(size == 0, "Initial value"); | |
| 6810 } else { | |
| 6811 assert(p->is_parsable(), "must be parsable."); | |
| 6812 // an initialized object; ignore mark word in verification below | |
| 6813 // since we are running concurrent with mutators | |
| 6814 assert(p->is_oop(true), "should be an oop"); | |
| 6815 if (p->is_objArray()) { | |
| 6816 // objArrays are precisely marked; restrict scanning | |
| 6817 // to dirty cards only. | |
| 187 | 6818 size = CompactibleFreeListSpace::adjustObjectSize( |
| 6819 p->oop_iterate(_scanningClosure, mr)); | |
| 0 | 6820 } else { |
| 6821 // A non-array may have been imprecisely marked; we need | |
| 6822 // to scan object in its entirety. | |
| 6823 size = CompactibleFreeListSpace::adjustObjectSize( | |
| 6824 p->oop_iterate(_scanningClosure)); | |
| 6825 } | |
| 6826 #ifdef DEBUG | |
| 6827 size_t direct_size = | |
| 6828 CompactibleFreeListSpace::adjustObjectSize(p->size()); | |
| 6829 assert(size == direct_size, "Inconsistency in size"); | |
| 6830 assert(size >= 3, "Necessary for Printezis marks to work"); | |
| 6831 if (!_bitMap->isMarked(addr+1)) { | |
| 6832 _bitMap->verifyNoOneBitsInRange(addr+2, addr+size); | |
| 6833 } else { | |
| 6834 _bitMap->verifyNoOneBitsInRange(addr+2, addr+size-1); | |
| 6835 assert(_bitMap->isMarked(addr+size-1), | |
| 6836 "inconsistent Printezis mark"); | |
| 6837 } | |
| 6838 #endif // DEBUG | |
| 6839 } | |
| 6840 } else { | |
| 6841 // an unitialized object | |
| 6842 assert(_bitMap->isMarked(addr+1), "missing Printezis mark?"); | |
| 6843 HeapWord* nextOneAddr = _bitMap->getNextMarkedWordAddress(addr + 2); | |
| 6844 size = pointer_delta(nextOneAddr + 1, addr); | |
| 6845 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
| 6846 "alignment problem"); | |
| 6847 // Note that pre-cleaning needn't redirty the card. OopDesc::set_klass() | |
| 6848 // will dirty the card when the klass pointer is installed in the | |
| 6849 // object (signalling the completion of initialization). | |
| 6850 } | |
| 6851 } else { | |
| 6852 // Either a not yet marked object or an uninitialized object | |
| 187 | 6853 if (p->klass_or_null() == NULL || !p->is_parsable()) { |
| 0 | 6854 // An uninitialized object, skip to the next card, since |
| 6855 // we may not be able to read its P-bits yet. | |
| 6856 assert(size == 0, "Initial value"); | |
| 6857 } else { | |
| 6858 // An object not (yet) reached by marking: we merely need to | |
| 6859 // compute its size so as to go look at the next block. | |
| 6860 assert(p->is_oop(true), "should be an oop"); | |
| 6861 size = CompactibleFreeListSpace::adjustObjectSize(p->size()); | |
| 6862 } | |
| 6863 } | |
| 6864 DEBUG_ONLY(_collector->verify_work_stacks_empty();) | |
| 6865 return size; | |
| 6866 } | |
| 6867 | |
| 6868 void ScanMarkedObjectsAgainCarefullyClosure::do_yield_work() { | |
| 6869 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 6870 "CMS thread should hold CMS token"); | |
| 6871 assert_lock_strong(_freelistLock); | |
| 6872 assert_lock_strong(_bitMap->lock()); | |
| 935 | 6873 DEBUG_ONLY(RememberKlassesChecker mux(false);) |
| 0 | 6874 // relinquish the free_list_lock and bitMaplock() |
| 6875 _bitMap->lock()->unlock(); | |
| 6876 _freelistLock->unlock(); | |
| 6877 ConcurrentMarkSweepThread::desynchronize(true); | |
| 6878 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 6879 _collector->stopTimer(); | |
| 6880 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
| 6881 if (PrintCMSStatistics != 0) { | |
| 6882 _collector->incrementYields(); | |
| 6883 } | |
| 6884 _collector->icms_wait(); | |
| 6885 | |
| 6886 // See the comment in coordinator_yield() | |
| 6887 for (unsigned i = 0; i < CMSYieldSleepCount && | |
|
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6888 ConcurrentMarkSweepThread::should_yield() && |
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6889 !CMSCollector::foregroundGCIsActive(); ++i) { |
| 0 | 6890 os::sleep(Thread::current(), 1, false); |
| 6891 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 6892 } | |
| 6893 | |
| 6894 ConcurrentMarkSweepThread::synchronize(true); | |
| 6895 _freelistLock->lock_without_safepoint_check(); | |
| 6896 _bitMap->lock()->lock_without_safepoint_check(); | |
| 6897 _collector->startTimer(); | |
| 6898 } | |
| 6899 | |
| 6900 | |
| 6901 ////////////////////////////////////////////////////////////////// | |
| 6902 // SurvivorSpacePrecleanClosure | |
| 6903 ////////////////////////////////////////////////////////////////// | |
| 6904 // This (single-threaded) closure is used to preclean the oops in | |
| 6905 // the survivor spaces. | |
| 6906 size_t SurvivorSpacePrecleanClosure::do_object_careful(oop p) { | |
| 6907 | |
| 6908 HeapWord* addr = (HeapWord*)p; | |
| 6909 DEBUG_ONLY(_collector->verify_work_stacks_empty();) | |
| 6910 assert(!_span.contains(addr), "we are scanning the survivor spaces"); | |
| 187 | 6911 assert(p->klass_or_null() != NULL, "object should be initializd"); |
| 0 | 6912 assert(p->is_parsable(), "must be parsable."); |
| 6913 // an initialized object; ignore mark word in verification below | |
| 6914 // since we are running concurrent with mutators | |
| 6915 assert(p->is_oop(true), "should be an oop"); | |
| 6916 // Note that we do not yield while we iterate over | |
| 6917 // the interior oops of p, pushing the relevant ones | |
| 6918 // on our marking stack. | |
| 6919 size_t size = p->oop_iterate(_scanning_closure); | |
| 6920 do_yield_check(); | |
| 6921 // Observe that below, we do not abandon the preclean | |
| 6922 // phase as soon as we should; rather we empty the | |
| 6923 // marking stack before returning. This is to satisfy | |
| 6924 // some existing assertions. In general, it may be a | |
| 6925 // good idea to abort immediately and complete the marking | |
| 6926 // from the grey objects at a later time. | |
| 6927 while (!_mark_stack->isEmpty()) { | |
| 6928 oop new_oop = _mark_stack->pop(); | |
| 6929 assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop"); | |
| 6930 assert(new_oop->is_parsable(), "Found unparsable oop"); | |
| 6931 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
| 6932 "only grey objects on this stack"); | |
| 6933 // iterate over the oops in this oop, marking and pushing | |
| 6934 // the ones in CMS heap (i.e. in _span). | |
| 6935 new_oop->oop_iterate(_scanning_closure); | |
| 6936 // check if it's time to yield | |
| 6937 do_yield_check(); | |
| 6938 } | |
| 6939 unsigned int after_count = | |
| 6940 GenCollectedHeap::heap()->total_collections(); | |
| 6941 bool abort = (_before_count != after_count) || | |
| 6942 _collector->should_abort_preclean(); | |
| 6943 return abort ? 0 : size; | |
| 6944 } | |
| 6945 | |
| 6946 void SurvivorSpacePrecleanClosure::do_yield_work() { | |
| 6947 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 6948 "CMS thread should hold CMS token"); | |
| 6949 assert_lock_strong(_bit_map->lock()); | |
| 935 | 6950 DEBUG_ONLY(RememberKlassesChecker smx(false);) |
| 0 | 6951 // Relinquish the bit map lock |
| 6952 _bit_map->lock()->unlock(); | |
| 6953 ConcurrentMarkSweepThread::desynchronize(true); | |
| 6954 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 6955 _collector->stopTimer(); | |
| 6956 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
| 6957 if (PrintCMSStatistics != 0) { | |
| 6958 _collector->incrementYields(); | |
| 6959 } | |
| 6960 _collector->icms_wait(); | |
| 6961 | |
| 6962 // See the comment in coordinator_yield() | |
| 6963 for (unsigned i = 0; i < CMSYieldSleepCount && | |
| 6964 ConcurrentMarkSweepThread::should_yield() && | |
| 6965 !CMSCollector::foregroundGCIsActive(); ++i) { | |
| 6966 os::sleep(Thread::current(), 1, false); | |
| 6967 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 6968 } | |
| 6969 | |
| 6970 ConcurrentMarkSweepThread::synchronize(true); | |
| 6971 _bit_map->lock()->lock_without_safepoint_check(); | |
| 6972 _collector->startTimer(); | |
| 6973 } | |
| 6974 | |
| 6975 // This closure is used to rescan the marked objects on the dirty cards | |
| 6976 // in the mod union table and the card table proper. In the parallel | |
| 6977 // case, although the bitMap is shared, we do a single read so the | |
| 6978 // isMarked() query is "safe". | |
| 6979 bool ScanMarkedObjectsAgainClosure::do_object_bm(oop p, MemRegion mr) { | |
| 6980 // Ignore mark word because we are running concurrent with mutators | |
| 6981 assert(p->is_oop_or_null(true), "expected an oop or null"); | |
| 6982 HeapWord* addr = (HeapWord*)p; | |
| 6983 assert(_span.contains(addr), "we are scanning the CMS generation"); | |
| 6984 bool is_obj_array = false; | |
| 6985 #ifdef DEBUG | |
| 6986 if (!_parallel) { | |
| 6987 assert(_mark_stack->isEmpty(), "pre-condition (eager drainage)"); | |
| 6988 assert(_collector->overflow_list_is_empty(), | |
| 6989 "overflow list should be empty"); | |
| 6990 | |
| 6991 } | |
| 6992 #endif // DEBUG | |
| 6993 if (_bit_map->isMarked(addr)) { | |
| 6994 // Obj arrays are precisely marked, non-arrays are not; | |
| 6995 // so we scan objArrays precisely and non-arrays in their | |
| 6996 // entirety. | |
| 6997 if (p->is_objArray()) { | |
| 6998 is_obj_array = true; | |
| 6999 if (_parallel) { | |
| 7000 p->oop_iterate(_par_scan_closure, mr); | |
| 7001 } else { | |
| 7002 p->oop_iterate(_scan_closure, mr); | |
| 7003 } | |
| 7004 } else { | |
| 7005 if (_parallel) { | |
| 7006 p->oop_iterate(_par_scan_closure); | |
| 7007 } else { | |
| 7008 p->oop_iterate(_scan_closure); | |
| 7009 } | |
| 7010 } | |
| 7011 } | |
| 7012 #ifdef DEBUG | |
| 7013 if (!_parallel) { | |
| 7014 assert(_mark_stack->isEmpty(), "post-condition (eager drainage)"); | |
| 7015 assert(_collector->overflow_list_is_empty(), | |
| 7016 "overflow list should be empty"); | |
| 7017 | |
| 7018 } | |
| 7019 #endif // DEBUG | |
| 7020 return is_obj_array; | |
| 7021 } | |
| 7022 | |
| 7023 MarkFromRootsClosure::MarkFromRootsClosure(CMSCollector* collector, | |
| 7024 MemRegion span, | |
| 7025 CMSBitMap* bitMap, CMSMarkStack* markStack, | |
| 7026 CMSMarkStack* revisitStack, | |
| 7027 bool should_yield, bool verifying): | |
| 7028 _collector(collector), | |
| 7029 _span(span), | |
| 7030 _bitMap(bitMap), | |
| 7031 _mut(&collector->_modUnionTable), | |
| 7032 _markStack(markStack), | |
| 7033 _revisitStack(revisitStack), | |
| 7034 _yield(should_yield), | |
| 7035 _skipBits(0) | |
| 7036 { | |
| 7037 assert(_markStack->isEmpty(), "stack should be empty"); | |
| 7038 _finger = _bitMap->startWord(); | |
| 7039 _threshold = _finger; | |
| 7040 assert(_collector->_restart_addr == NULL, "Sanity check"); | |
| 7041 assert(_span.contains(_finger), "Out of bounds _finger?"); | |
| 7042 DEBUG_ONLY(_verifying = verifying;) | |
| 7043 } | |
| 7044 | |
| 7045 void MarkFromRootsClosure::reset(HeapWord* addr) { | |
| 7046 assert(_markStack->isEmpty(), "would cause duplicates on stack"); | |
| 7047 assert(_span.contains(addr), "Out of bounds _finger?"); | |
| 7048 _finger = addr; | |
| 7049 _threshold = (HeapWord*)round_to( | |
| 7050 (intptr_t)_finger, CardTableModRefBS::card_size); | |
| 7051 } | |
| 7052 | |
| 7053 // Should revisit to see if this should be restructured for | |
| 7054 // greater efficiency. | |
|
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7055 bool MarkFromRootsClosure::do_bit(size_t offset) { |
| 0 | 7056 if (_skipBits > 0) { |
| 7057 _skipBits--; | |
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7058 return true; |
| 0 | 7059 } |
| 7060 // convert offset into a HeapWord* | |
| 7061 HeapWord* addr = _bitMap->startWord() + offset; | |
| 7062 assert(_bitMap->endWord() && addr < _bitMap->endWord(), | |
| 7063 "address out of range"); | |
| 7064 assert(_bitMap->isMarked(addr), "tautology"); | |
| 7065 if (_bitMap->isMarked(addr+1)) { | |
| 7066 // this is an allocated but not yet initialized object | |
| 7067 assert(_skipBits == 0, "tautology"); | |
| 7068 _skipBits = 2; // skip next two marked bits ("Printezis-marks") | |
| 7069 oop p = oop(addr); | |
| 187 | 7070 if (p->klass_or_null() == NULL || !p->is_parsable()) { |
| 0 | 7071 DEBUG_ONLY(if (!_verifying) {) |
| 7072 // We re-dirty the cards on which this object lies and increase | |
| 7073 // the _threshold so that we'll come back to scan this object | |
| 7074 // during the preclean or remark phase. (CMSCleanOnEnter) | |
| 7075 if (CMSCleanOnEnter) { | |
| 7076 size_t sz = _collector->block_size_using_printezis_bits(addr); | |
| 7077 HeapWord* end_card_addr = (HeapWord*)round_to( | |
| 7078 (intptr_t)(addr+sz), CardTableModRefBS::card_size); | |
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7079 MemRegion redirty_range = MemRegion(addr, end_card_addr); |
| 0 | 7080 assert(!redirty_range.is_empty(), "Arithmetical tautology"); |
| 7081 // Bump _threshold to end_card_addr; note that | |
| 7082 // _threshold cannot possibly exceed end_card_addr, anyhow. | |
| 7083 // This prevents future clearing of the card as the scan proceeds | |
| 7084 // to the right. | |
| 7085 assert(_threshold <= end_card_addr, | |
| 7086 "Because we are just scanning into this object"); | |
| 7087 if (_threshold < end_card_addr) { | |
| 7088 _threshold = end_card_addr; | |
| 7089 } | |
| 187 | 7090 if (p->klass_or_null() != NULL) { |
| 0 | 7091 // Redirty the range of cards... |
| 7092 _mut->mark_range(redirty_range); | |
| 7093 } // ...else the setting of klass will dirty the card anyway. | |
| 7094 } | |
| 7095 DEBUG_ONLY(}) | |
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7096 return true; |
| 0 | 7097 } |
| 7098 } | |
| 7099 scanOopsInOop(addr); | |
|
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7100 return true; |
| 0 | 7101 } |
| 7102 | |
| 7103 // We take a break if we've been at this for a while, | |
| 7104 // so as to avoid monopolizing the locks involved. | |
| 7105 void MarkFromRootsClosure::do_yield_work() { | |
| 7106 // First give up the locks, then yield, then re-lock | |
| 7107 // We should probably use a constructor/destructor idiom to | |
| 7108 // do this unlock/lock or modify the MutexUnlocker class to | |
| 7109 // serve our purpose. XXX | |
| 7110 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 7111 "CMS thread should hold CMS token"); | |
| 7112 assert_lock_strong(_bitMap->lock()); | |
| 935 | 7113 DEBUG_ONLY(RememberKlassesChecker mux(false);) |
| 0 | 7114 _bitMap->lock()->unlock(); |
| 7115 ConcurrentMarkSweepThread::desynchronize(true); | |
| 7116 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 7117 _collector->stopTimer(); | |
| 7118 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
| 7119 if (PrintCMSStatistics != 0) { | |
| 7120 _collector->incrementYields(); | |
| 7121 } | |
| 7122 _collector->icms_wait(); | |
| 7123 | |
| 7124 // See the comment in coordinator_yield() | |
| 7125 for (unsigned i = 0; i < CMSYieldSleepCount && | |
| 7126 ConcurrentMarkSweepThread::should_yield() && | |
| 7127 !CMSCollector::foregroundGCIsActive(); ++i) { | |
| 7128 os::sleep(Thread::current(), 1, false); | |
| 7129 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 7130 } | |
| 7131 | |
| 7132 ConcurrentMarkSweepThread::synchronize(true); | |
| 7133 _bitMap->lock()->lock_without_safepoint_check(); | |
| 7134 _collector->startTimer(); | |
| 7135 } | |
| 7136 | |
| 7137 void MarkFromRootsClosure::scanOopsInOop(HeapWord* ptr) { | |
| 7138 assert(_bitMap->isMarked(ptr), "expected bit to be set"); | |
| 7139 assert(_markStack->isEmpty(), | |
| 7140 "should drain stack to limit stack usage"); | |
| 7141 // convert ptr to an oop preparatory to scanning | |
|
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7142 oop obj = oop(ptr); |
| 0 | 7143 // Ignore mark word in verification below, since we |
| 7144 // may be running concurrent with mutators. | |
|
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7145 assert(obj->is_oop(true), "should be an oop"); |
| 0 | 7146 assert(_finger <= ptr, "_finger runneth ahead"); |
| 7147 // advance the finger to right end of this object | |
|
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7148 _finger = ptr + obj->size(); |
| 0 | 7149 assert(_finger > ptr, "we just incremented it above"); |
| 7150 // On large heaps, it may take us some time to get through | |
| 7151 // the marking phase (especially if running iCMS). During | |
| 7152 // this time it's possible that a lot of mutations have | |
| 7153 // accumulated in the card table and the mod union table -- | |
| 7154 // these mutation records are redundant until we have | |
| 7155 // actually traced into the corresponding card. | |
| 7156 // Here, we check whether advancing the finger would make | |
| 7157 // us cross into a new card, and if so clear corresponding | |
| 7158 // cards in the MUT (preclean them in the card-table in the | |
| 7159 // future). | |
| 7160 | |
| 7161 DEBUG_ONLY(if (!_verifying) {) | |
| 7162 // The clean-on-enter optimization is disabled by default, | |
| 7163 // until we fix 6178663. | |
| 7164 if (CMSCleanOnEnter && (_finger > _threshold)) { | |
| 7165 // [_threshold, _finger) represents the interval | |
| 7166 // of cards to be cleared in MUT (or precleaned in card table). | |
| 7167 // The set of cards to be cleared is all those that overlap | |
| 7168 // with the interval [_threshold, _finger); note that | |
| 7169 // _threshold is always kept card-aligned but _finger isn't | |
| 7170 // always card-aligned. | |
| 7171 HeapWord* old_threshold = _threshold; | |
| 7172 assert(old_threshold == (HeapWord*)round_to( | |
| 7173 (intptr_t)old_threshold, CardTableModRefBS::card_size), | |
| 7174 "_threshold should always be card-aligned"); | |
| 7175 _threshold = (HeapWord*)round_to( | |
| 7176 (intptr_t)_finger, CardTableModRefBS::card_size); | |
| 7177 MemRegion mr(old_threshold, _threshold); | |
| 7178 assert(!mr.is_empty(), "Control point invariant"); | |
| 7179 assert(_span.contains(mr), "Should clear within span"); | |
| 7180 // XXX When _finger crosses from old gen into perm gen | |
| 7181 // we may be doing unnecessary cleaning; do better in the | |
| 7182 // future by detecting that condition and clearing fewer | |
| 7183 // MUT/CT entries. | |
| 7184 _mut->clear_range(mr); | |
| 7185 } | |
| 7186 DEBUG_ONLY(}) | |
| 7187 // Note: the finger doesn't advance while we drain | |
| 7188 // the stack below. | |
| 7189 PushOrMarkClosure pushOrMarkClosure(_collector, | |
| 7190 _span, _bitMap, _markStack, | |
| 7191 _revisitStack, | |
| 7192 _finger, this); | |
|
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7193 bool res = _markStack->push(obj); |
| 0 | 7194 assert(res, "Empty non-zero size stack should have space for single push"); |
| 7195 while (!_markStack->isEmpty()) { | |
| 7196 oop new_oop = _markStack->pop(); | |
| 7197 // Skip verifying header mark word below because we are | |
| 7198 // running concurrent with mutators. | |
| 7199 assert(new_oop->is_oop(true), "Oops! expected to pop an oop"); | |
| 7200 // now scan this oop's oops | |
| 7201 new_oop->oop_iterate(&pushOrMarkClosure); | |
| 7202 do_yield_check(); | |
| 7203 } | |
| 7204 assert(_markStack->isEmpty(), "tautology, emphasizing post-condition"); | |
| 7205 } | |
| 7206 | |
| 7207 Par_MarkFromRootsClosure::Par_MarkFromRootsClosure(CMSConcMarkingTask* task, | |
| 7208 CMSCollector* collector, MemRegion span, | |
| 7209 CMSBitMap* bit_map, | |
| 7210 OopTaskQueue* work_queue, | |
| 7211 CMSMarkStack* overflow_stack, | |
| 7212 CMSMarkStack* revisit_stack, | |
| 7213 bool should_yield): | |
| 7214 _collector(collector), | |
| 7215 _whole_span(collector->_span), | |
| 7216 _span(span), | |
| 7217 _bit_map(bit_map), | |
| 7218 _mut(&collector->_modUnionTable), | |
| 7219 _work_queue(work_queue), | |
| 7220 _overflow_stack(overflow_stack), | |
| 7221 _revisit_stack(revisit_stack), | |
| 7222 _yield(should_yield), | |
| 7223 _skip_bits(0), | |
| 7224 _task(task) | |
| 7225 { | |
| 7226 assert(_work_queue->size() == 0, "work_queue should be empty"); | |
| 7227 _finger = span.start(); | |
| 7228 _threshold = _finger; // XXX Defer clear-on-enter optimization for now | |
| 7229 assert(_span.contains(_finger), "Out of bounds _finger?"); | |
| 7230 } | |
| 7231 | |
| 7232 // Should revisit to see if this should be restructured for | |
| 7233 // greater efficiency. | |
|
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7234 bool Par_MarkFromRootsClosure::do_bit(size_t offset) { |
| 0 | 7235 if (_skip_bits > 0) { |
| 7236 _skip_bits--; | |
|
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7237 return true; |
| 0 | 7238 } |
| 7239 // convert offset into a HeapWord* | |
| 7240 HeapWord* addr = _bit_map->startWord() + offset; | |
| 7241 assert(_bit_map->endWord() && addr < _bit_map->endWord(), | |
| 7242 "address out of range"); | |
| 7243 assert(_bit_map->isMarked(addr), "tautology"); | |
| 7244 if (_bit_map->isMarked(addr+1)) { | |
| 7245 // this is an allocated object that might not yet be initialized | |
| 7246 assert(_skip_bits == 0, "tautology"); | |
| 7247 _skip_bits = 2; // skip next two marked bits ("Printezis-marks") | |
| 7248 oop p = oop(addr); | |
| 187 | 7249 if (p->klass_or_null() == NULL || !p->is_parsable()) { |
| 0 | 7250 // in the case of Clean-on-Enter optimization, redirty card |
| 7251 // and avoid clearing card by increasing the threshold. | |
|
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7252 return true; |
| 0 | 7253 } |
| 7254 } | |
| 7255 scan_oops_in_oop(addr); | |
|
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7256 return true; |
| 0 | 7257 } |
| 7258 | |
| 7259 void Par_MarkFromRootsClosure::scan_oops_in_oop(HeapWord* ptr) { | |
| 7260 assert(_bit_map->isMarked(ptr), "expected bit to be set"); | |
| 7261 // Should we assert that our work queue is empty or | |
| 7262 // below some drain limit? | |
| 7263 assert(_work_queue->size() == 0, | |
| 7264 "should drain stack to limit stack usage"); | |
| 7265 // convert ptr to an oop preparatory to scanning | |
|
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7266 oop obj = oop(ptr); |
| 0 | 7267 // Ignore mark word in verification below, since we |
| 7268 // may be running concurrent with mutators. | |
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7269 assert(obj->is_oop(true), "should be an oop"); |
| 0 | 7270 assert(_finger <= ptr, "_finger runneth ahead"); |
| 7271 // advance the finger to right end of this object | |
|
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7272 _finger = ptr + obj->size(); |
| 0 | 7273 assert(_finger > ptr, "we just incremented it above"); |
| 7274 // On large heaps, it may take us some time to get through | |
| 7275 // the marking phase (especially if running iCMS). During | |
| 7276 // this time it's possible that a lot of mutations have | |
| 7277 // accumulated in the card table and the mod union table -- | |
| 7278 // these mutation records are redundant until we have | |
| 7279 // actually traced into the corresponding card. | |
| 7280 // Here, we check whether advancing the finger would make | |
| 7281 // us cross into a new card, and if so clear corresponding | |
| 7282 // cards in the MUT (preclean them in the card-table in the | |
| 7283 // future). | |
| 7284 | |
| 7285 // The clean-on-enter optimization is disabled by default, | |
| 7286 // until we fix 6178663. | |
| 7287 if (CMSCleanOnEnter && (_finger > _threshold)) { | |
| 7288 // [_threshold, _finger) represents the interval | |
| 7289 // of cards to be cleared in MUT (or precleaned in card table). | |
| 7290 // The set of cards to be cleared is all those that overlap | |
| 7291 // with the interval [_threshold, _finger); note that | |
| 7292 // _threshold is always kept card-aligned but _finger isn't | |
| 7293 // always card-aligned. | |
| 7294 HeapWord* old_threshold = _threshold; | |
| 7295 assert(old_threshold == (HeapWord*)round_to( | |
| 7296 (intptr_t)old_threshold, CardTableModRefBS::card_size), | |
| 7297 "_threshold should always be card-aligned"); | |
| 7298 _threshold = (HeapWord*)round_to( | |
| 7299 (intptr_t)_finger, CardTableModRefBS::card_size); | |
| 7300 MemRegion mr(old_threshold, _threshold); | |
| 7301 assert(!mr.is_empty(), "Control point invariant"); | |
| 7302 assert(_span.contains(mr), "Should clear within span"); // _whole_span ?? | |
| 7303 // XXX When _finger crosses from old gen into perm gen | |
| 7304 // we may be doing unnecessary cleaning; do better in the | |
| 7305 // future by detecting that condition and clearing fewer | |
| 7306 // MUT/CT entries. | |
| 7307 _mut->clear_range(mr); | |
| 7308 } | |
| 7309 | |
| 7310 // Note: the local finger doesn't advance while we drain | |
| 7311 // the stack below, but the global finger sure can and will. | |
| 7312 HeapWord** gfa = _task->global_finger_addr(); | |
| 7313 Par_PushOrMarkClosure pushOrMarkClosure(_collector, | |
| 7314 _span, _bit_map, | |
| 7315 _work_queue, | |
| 7316 _overflow_stack, | |
| 7317 _revisit_stack, | |
| 7318 _finger, | |
| 7319 gfa, this); | |
|
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7320 bool res = _work_queue->push(obj); // overflow could occur here |
| 0 | 7321 assert(res, "Will hold once we use workqueues"); |
| 7322 while (true) { | |
| 7323 oop new_oop; | |
| 7324 if (!_work_queue->pop_local(new_oop)) { | |
| 7325 // We emptied our work_queue; check if there's stuff that can | |
| 7326 // be gotten from the overflow stack. | |
| 7327 if (CMSConcMarkingTask::get_work_from_overflow_stack( | |
| 7328 _overflow_stack, _work_queue)) { | |
| 7329 do_yield_check(); | |
| 7330 continue; | |
| 7331 } else { // done | |
| 7332 break; | |
| 7333 } | |
| 7334 } | |
| 7335 // Skip verifying header mark word below because we are | |
| 7336 // running concurrent with mutators. | |
| 7337 assert(new_oop->is_oop(true), "Oops! expected to pop an oop"); | |
| 7338 // now scan this oop's oops | |
| 7339 new_oop->oop_iterate(&pushOrMarkClosure); | |
| 7340 do_yield_check(); | |
| 7341 } | |
| 7342 assert(_work_queue->size() == 0, "tautology, emphasizing post-condition"); | |
| 7343 } | |
| 7344 | |
| 7345 // Yield in response to a request from VM Thread or | |
| 7346 // from mutators. | |
| 7347 void Par_MarkFromRootsClosure::do_yield_work() { | |
| 7348 assert(_task != NULL, "sanity"); | |
| 7349 _task->yield(); | |
| 7350 } | |
| 7351 | |
| 7352 // A variant of the above used for verifying CMS marking work. | |
| 7353 MarkFromRootsVerifyClosure::MarkFromRootsVerifyClosure(CMSCollector* collector, | |
| 7354 MemRegion span, | |
| 7355 CMSBitMap* verification_bm, CMSBitMap* cms_bm, | |
| 7356 CMSMarkStack* mark_stack): | |
| 7357 _collector(collector), | |
| 7358 _span(span), | |
| 7359 _verification_bm(verification_bm), | |
| 7360 _cms_bm(cms_bm), | |
| 7361 _mark_stack(mark_stack), | |
| 7362 _pam_verify_closure(collector, span, verification_bm, cms_bm, | |
| 7363 mark_stack) | |
| 7364 { | |
| 7365 assert(_mark_stack->isEmpty(), "stack should be empty"); | |
| 7366 _finger = _verification_bm->startWord(); | |
| 7367 assert(_collector->_restart_addr == NULL, "Sanity check"); | |
| 7368 assert(_span.contains(_finger), "Out of bounds _finger?"); | |
| 7369 } | |
| 7370 | |
| 7371 void MarkFromRootsVerifyClosure::reset(HeapWord* addr) { | |
| 7372 assert(_mark_stack->isEmpty(), "would cause duplicates on stack"); | |
| 7373 assert(_span.contains(addr), "Out of bounds _finger?"); | |
| 7374 _finger = addr; | |
| 7375 } | |
| 7376 | |
| 7377 // Should revisit to see if this should be restructured for | |
| 7378 // greater efficiency. | |
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7379 bool MarkFromRootsVerifyClosure::do_bit(size_t offset) { |
| 0 | 7380 // convert offset into a HeapWord* |
| 7381 HeapWord* addr = _verification_bm->startWord() + offset; | |
| 7382 assert(_verification_bm->endWord() && addr < _verification_bm->endWord(), | |
| 7383 "address out of range"); | |
| 7384 assert(_verification_bm->isMarked(addr), "tautology"); | |
| 7385 assert(_cms_bm->isMarked(addr), "tautology"); | |
| 7386 | |
| 7387 assert(_mark_stack->isEmpty(), | |
| 7388 "should drain stack to limit stack usage"); | |
| 7389 // convert addr to an oop preparatory to scanning | |
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7390 oop obj = oop(addr); |
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7391 assert(obj->is_oop(), "should be an oop"); |
| 0 | 7392 assert(_finger <= addr, "_finger runneth ahead"); |
| 7393 // advance the finger to right end of this object | |
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7394 _finger = addr + obj->size(); |
| 0 | 7395 assert(_finger > addr, "we just incremented it above"); |
| 7396 // Note: the finger doesn't advance while we drain | |
| 7397 // the stack below. | |
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7398 bool res = _mark_stack->push(obj); |
| 0 | 7399 assert(res, "Empty non-zero size stack should have space for single push"); |
| 7400 while (!_mark_stack->isEmpty()) { | |
| 7401 oop new_oop = _mark_stack->pop(); | |
| 7402 assert(new_oop->is_oop(), "Oops! expected to pop an oop"); | |
| 7403 // now scan this oop's oops | |
| 7404 new_oop->oop_iterate(&_pam_verify_closure); | |
| 7405 } | |
| 7406 assert(_mark_stack->isEmpty(), "tautology, emphasizing post-condition"); | |
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7407 return true; |
| 0 | 7408 } |
| 7409 | |
| 7410 PushAndMarkVerifyClosure::PushAndMarkVerifyClosure( | |
| 7411 CMSCollector* collector, MemRegion span, | |
| 7412 CMSBitMap* verification_bm, CMSBitMap* cms_bm, | |
| 7413 CMSMarkStack* mark_stack): | |
| 7414 OopClosure(collector->ref_processor()), | |
| 7415 _collector(collector), | |
| 7416 _span(span), | |
| 7417 _verification_bm(verification_bm), | |
| 7418 _cms_bm(cms_bm), | |
| 7419 _mark_stack(mark_stack) | |
| 7420 { } | |
| 7421 | |
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7422 void PushAndMarkVerifyClosure::do_oop(oop* p) { PushAndMarkVerifyClosure::do_oop_work(p); } |
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7423 void PushAndMarkVerifyClosure::do_oop(narrowOop* p) { PushAndMarkVerifyClosure::do_oop_work(p); } |
| 0 | 7424 |
| 7425 // Upon stack overflow, we discard (part of) the stack, | |
| 7426 // remembering the least address amongst those discarded | |
| 7427 // in CMSCollector's _restart_address. | |
| 7428 void PushAndMarkVerifyClosure::handle_stack_overflow(HeapWord* lost) { | |
| 7429 // Remember the least grey address discarded | |
| 7430 HeapWord* ra = (HeapWord*)_mark_stack->least_value(lost); | |
| 7431 _collector->lower_restart_addr(ra); | |
| 7432 _mark_stack->reset(); // discard stack contents | |
| 7433 _mark_stack->expand(); // expand the stack if possible | |
| 7434 } | |
| 7435 | |
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7436 void PushAndMarkVerifyClosure::do_oop(oop obj) { |
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7437 assert(obj->is_oop_or_null(), "expected an oop or NULL"); |
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7438 HeapWord* addr = (HeapWord*)obj; |
| 0 | 7439 if (_span.contains(addr) && !_verification_bm->isMarked(addr)) { |
| 7440 // Oop lies in _span and isn't yet grey or black | |
| 7441 _verification_bm->mark(addr); // now grey | |
| 7442 if (!_cms_bm->isMarked(addr)) { | |
| 7443 oop(addr)->print(); | |
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7444 gclog_or_tty->print_cr(" (" INTPTR_FORMAT " should have been marked)", |
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7445 addr); |
| 0 | 7446 fatal("... aborting"); |
| 7447 } | |
| 7448 | |
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7449 if (!_mark_stack->push(obj)) { // stack overflow |
| 0 | 7450 if (PrintCMSStatistics != 0) { |
| 7451 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
| 7452 SIZE_FORMAT, _mark_stack->capacity()); | |
| 7453 } | |
| 7454 assert(_mark_stack->isFull(), "Else push should have succeeded"); | |
| 7455 handle_stack_overflow(addr); | |
| 7456 } | |
| 7457 // anything including and to the right of _finger | |
| 7458 // will be scanned as we iterate over the remainder of the | |
| 7459 // bit map | |
| 7460 } | |
| 7461 } | |
| 7462 | |
| 7463 PushOrMarkClosure::PushOrMarkClosure(CMSCollector* collector, | |
| 7464 MemRegion span, | |
| 7465 CMSBitMap* bitMap, CMSMarkStack* markStack, | |
| 7466 CMSMarkStack* revisitStack, | |
| 7467 HeapWord* finger, MarkFromRootsClosure* parent) : | |
| 935 | 7468 KlassRememberingOopClosure(collector, collector->ref_processor(), revisitStack), |
| 0 | 7469 _span(span), |
| 7470 _bitMap(bitMap), | |
| 7471 _markStack(markStack), | |
| 7472 _finger(finger), | |
| 935 | 7473 _parent(parent) |
| 0 | 7474 { } |
| 7475 | |
| 7476 Par_PushOrMarkClosure::Par_PushOrMarkClosure(CMSCollector* collector, | |
| 7477 MemRegion span, | |
| 7478 CMSBitMap* bit_map, | |
| 7479 OopTaskQueue* work_queue, | |
| 7480 CMSMarkStack* overflow_stack, | |
| 7481 CMSMarkStack* revisit_stack, | |
| 7482 HeapWord* finger, | |
| 7483 HeapWord** global_finger_addr, | |
| 7484 Par_MarkFromRootsClosure* parent) : | |
| 935 | 7485 Par_KlassRememberingOopClosure(collector, |
| 7486 collector->ref_processor(), | |
| 7487 revisit_stack), | |
| 0 | 7488 _whole_span(collector->_span), |
| 7489 _span(span), | |
| 7490 _bit_map(bit_map), | |
| 7491 _work_queue(work_queue), | |
| 7492 _overflow_stack(overflow_stack), | |
| 7493 _finger(finger), | |
| 7494 _global_finger_addr(global_finger_addr), | |
| 935 | 7495 _parent(parent) |
| 0 | 7496 { } |
| 7497 | |
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7498 // Assumes thread-safe access by callers, who are |
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7499 // responsible for mutual exclusion. |
| 0 | 7500 void CMSCollector::lower_restart_addr(HeapWord* low) { |
| 7501 assert(_span.contains(low), "Out of bounds addr"); | |
| 7502 if (_restart_addr == NULL) { | |
| 7503 _restart_addr = low; | |
| 7504 } else { | |
| 7505 _restart_addr = MIN2(_restart_addr, low); | |
| 7506 } | |
| 7507 } | |
| 7508 | |
| 7509 // Upon stack overflow, we discard (part of) the stack, | |
| 7510 // remembering the least address amongst those discarded | |
| 7511 // in CMSCollector's _restart_address. | |
| 7512 void PushOrMarkClosure::handle_stack_overflow(HeapWord* lost) { | |
| 7513 // Remember the least grey address discarded | |
| 7514 HeapWord* ra = (HeapWord*)_markStack->least_value(lost); | |
| 7515 _collector->lower_restart_addr(ra); | |
| 7516 _markStack->reset(); // discard stack contents | |
| 7517 _markStack->expand(); // expand the stack if possible | |
| 7518 } | |
| 7519 | |
| 7520 // Upon stack overflow, we discard (part of) the stack, | |
| 7521 // remembering the least address amongst those discarded | |
| 7522 // in CMSCollector's _restart_address. | |
| 7523 void Par_PushOrMarkClosure::handle_stack_overflow(HeapWord* lost) { | |
| 7524 // We need to do this under a mutex to prevent other | |
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7525 // workers from interfering with the work done below. |
| 0 | 7526 MutexLockerEx ml(_overflow_stack->par_lock(), |
| 7527 Mutex::_no_safepoint_check_flag); | |
| 7528 // Remember the least grey address discarded | |
| 7529 HeapWord* ra = (HeapWord*)_overflow_stack->least_value(lost); | |
| 7530 _collector->lower_restart_addr(ra); | |
| 7531 _overflow_stack->reset(); // discard stack contents | |
| 7532 _overflow_stack->expand(); // expand the stack if possible | |
| 7533 } | |
| 7534 | |
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7535 void PushOrMarkClosure::do_oop(oop obj) { |
| 0 | 7536 // Ignore mark word because we are running concurrent with mutators. |
|
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7537 assert(obj->is_oop_or_null(true), "expected an oop or NULL"); |
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7538 HeapWord* addr = (HeapWord*)obj; |
| 0 | 7539 if (_span.contains(addr) && !_bitMap->isMarked(addr)) { |
| 7540 // Oop lies in _span and isn't yet grey or black | |
| 7541 _bitMap->mark(addr); // now grey | |
| 7542 if (addr < _finger) { | |
| 7543 // the bit map iteration has already either passed, or | |
| 7544 // sampled, this bit in the bit map; we'll need to | |
| 7545 // use the marking stack to scan this oop's oops. | |
| 7546 bool simulate_overflow = false; | |
| 7547 NOT_PRODUCT( | |
| 7548 if (CMSMarkStackOverflowALot && | |
| 7549 _collector->simulate_overflow()) { | |
| 7550 // simulate a stack overflow | |
| 7551 simulate_overflow = true; | |
| 7552 } | |
| 7553 ) | |
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7554 if (simulate_overflow || !_markStack->push(obj)) { // stack overflow |
| 0 | 7555 if (PrintCMSStatistics != 0) { |
| 7556 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
| 7557 SIZE_FORMAT, _markStack->capacity()); | |
| 7558 } | |
| 7559 assert(simulate_overflow || _markStack->isFull(), "Else push should have succeeded"); | |
| 7560 handle_stack_overflow(addr); | |
| 7561 } | |
| 7562 } | |
| 7563 // anything including and to the right of _finger | |
| 7564 // will be scanned as we iterate over the remainder of the | |
| 7565 // bit map | |
| 7566 do_yield_check(); | |
| 7567 } | |
| 7568 } | |
| 7569 | |
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7570 void PushOrMarkClosure::do_oop(oop* p) { PushOrMarkClosure::do_oop_work(p); } |
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7571 void PushOrMarkClosure::do_oop(narrowOop* p) { PushOrMarkClosure::do_oop_work(p); } |
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7572 |
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7573 void Par_PushOrMarkClosure::do_oop(oop obj) { |
| 0 | 7574 // Ignore mark word because we are running concurrent with mutators. |
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7575 assert(obj->is_oop_or_null(true), "expected an oop or NULL"); |
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7576 HeapWord* addr = (HeapWord*)obj; |
| 0 | 7577 if (_whole_span.contains(addr) && !_bit_map->isMarked(addr)) { |
| 7578 // Oop lies in _span and isn't yet grey or black | |
| 7579 // We read the global_finger (volatile read) strictly after marking oop | |
| 7580 bool res = _bit_map->par_mark(addr); // now grey | |
| 7581 volatile HeapWord** gfa = (volatile HeapWord**)_global_finger_addr; | |
| 7582 // Should we push this marked oop on our stack? | |
| 7583 // -- if someone else marked it, nothing to do | |
| 7584 // -- if target oop is above global finger nothing to do | |
| 7585 // -- if target oop is in chunk and above local finger | |
| 7586 // then nothing to do | |
| 7587 // -- else push on work queue | |
| 7588 if ( !res // someone else marked it, they will deal with it | |
| 7589 || (addr >= *gfa) // will be scanned in a later task | |
| 7590 || (_span.contains(addr) && addr >= _finger)) { // later in this chunk | |
| 7591 return; | |
| 7592 } | |
| 7593 // the bit map iteration has already either passed, or | |
| 7594 // sampled, this bit in the bit map; we'll need to | |
| 7595 // use the marking stack to scan this oop's oops. | |
| 7596 bool simulate_overflow = false; | |
| 7597 NOT_PRODUCT( | |
| 7598 if (CMSMarkStackOverflowALot && | |
| 7599 _collector->simulate_overflow()) { | |
| 7600 // simulate a stack overflow | |
| 7601 simulate_overflow = true; | |
| 7602 } | |
| 7603 ) | |
| 7604 if (simulate_overflow || | |
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7605 !(_work_queue->push(obj) || _overflow_stack->par_push(obj))) { |
| 0 | 7606 // stack overflow |
| 7607 if (PrintCMSStatistics != 0) { | |
| 7608 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
| 7609 SIZE_FORMAT, _overflow_stack->capacity()); | |
| 7610 } | |
| 7611 // We cannot assert that the overflow stack is full because | |
| 7612 // it may have been emptied since. | |
| 7613 assert(simulate_overflow || | |
| 7614 _work_queue->size() == _work_queue->max_elems(), | |
| 7615 "Else push should have succeeded"); | |
| 7616 handle_stack_overflow(addr); | |
| 7617 } | |
| 7618 do_yield_check(); | |
| 7619 } | |
| 7620 } | |
| 7621 | |
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7622 void Par_PushOrMarkClosure::do_oop(oop* p) { Par_PushOrMarkClosure::do_oop_work(p); } |
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7623 void Par_PushOrMarkClosure::do_oop(narrowOop* p) { Par_PushOrMarkClosure::do_oop_work(p); } |
| 0 | 7624 |
| 935 | 7625 KlassRememberingOopClosure::KlassRememberingOopClosure(CMSCollector* collector, |
| 7626 ReferenceProcessor* rp, | |
| 7627 CMSMarkStack* revisit_stack) : | |
| 7628 OopClosure(rp), | |
| 7629 _collector(collector), | |
| 7630 _revisit_stack(revisit_stack), | |
| 7631 _should_remember_klasses(collector->should_unload_classes()) {} | |
| 7632 | |
| 0 | 7633 PushAndMarkClosure::PushAndMarkClosure(CMSCollector* collector, |
| 7634 MemRegion span, | |
| 7635 ReferenceProcessor* rp, | |
| 7636 CMSBitMap* bit_map, | |
| 7637 CMSBitMap* mod_union_table, | |
| 7638 CMSMarkStack* mark_stack, | |
| 7639 CMSMarkStack* revisit_stack, | |
| 7640 bool concurrent_precleaning): | |
| 935 | 7641 KlassRememberingOopClosure(collector, rp, revisit_stack), |
| 0 | 7642 _span(span), |
| 7643 _bit_map(bit_map), | |
| 7644 _mod_union_table(mod_union_table), | |
| 7645 _mark_stack(mark_stack), | |
| 935 | 7646 _concurrent_precleaning(concurrent_precleaning) |
| 0 | 7647 { |
| 7648 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
| 7649 } | |
| 7650 | |
| 7651 // Grey object rescan during pre-cleaning and second checkpoint phases -- | |
| 7652 // the non-parallel version (the parallel version appears further below.) | |
|
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7653 void PushAndMarkClosure::do_oop(oop obj) { |
|
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7654 // Ignore mark word verification. If during concurrent precleaning, |
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7655 // the object monitor may be locked. If during the checkpoint |
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7656 // phases, the object may already have been reached by a different |
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7657 // path and may be at the end of the global overflow list (so |
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7658 // the mark word may be NULL). |
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7659 assert(obj->is_oop_or_null(true /* ignore mark word */), |
| 0 | 7660 "expected an oop or NULL"); |
|
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7661 HeapWord* addr = (HeapWord*)obj; |
| 0 | 7662 // Check if oop points into the CMS generation |
| 7663 // and is not marked | |
| 7664 if (_span.contains(addr) && !_bit_map->isMarked(addr)) { | |
| 7665 // a white object ... | |
| 7666 _bit_map->mark(addr); // ... now grey | |
| 7667 // push on the marking stack (grey set) | |
| 7668 bool simulate_overflow = false; | |
| 7669 NOT_PRODUCT( | |
| 7670 if (CMSMarkStackOverflowALot && | |
| 7671 _collector->simulate_overflow()) { | |
| 7672 // simulate a stack overflow | |
| 7673 simulate_overflow = true; | |
| 7674 } | |
| 7675 ) | |
|
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7676 if (simulate_overflow || !_mark_stack->push(obj)) { |
| 0 | 7677 if (_concurrent_precleaning) { |
|
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7678 // During precleaning we can just dirty the appropriate card(s) |
| 0 | 7679 // in the mod union table, thus ensuring that the object remains |
|
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7680 // in the grey set and continue. In the case of object arrays |
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7681 // we need to dirty all of the cards that the object spans, |
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7682 // since the rescan of object arrays will be limited to the |
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7683 // dirty cards. |
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7684 // Note that no one can be intefering with us in this action |
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7685 // of dirtying the mod union table, so no locking or atomics |
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7686 // are required. |
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7687 if (obj->is_objArray()) { |
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7688 size_t sz = obj->size(); |
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7689 HeapWord* end_card_addr = (HeapWord*)round_to( |
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7690 (intptr_t)(addr+sz), CardTableModRefBS::card_size); |
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7691 MemRegion redirty_range = MemRegion(addr, end_card_addr); |
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7692 assert(!redirty_range.is_empty(), "Arithmetical tautology"); |
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7693 _mod_union_table->mark_range(redirty_range); |
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7694 } else { |
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7695 _mod_union_table->mark(addr); |
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7696 } |
| 0 | 7697 _collector->_ser_pmc_preclean_ovflw++; |
| 7698 } else { | |
| 7699 // During the remark phase, we need to remember this oop | |
| 7700 // in the overflow list. | |
|
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7701 _collector->push_on_overflow_list(obj); |
| 0 | 7702 _collector->_ser_pmc_remark_ovflw++; |
| 7703 } | |
| 7704 } | |
| 7705 } | |
| 7706 } | |
| 7707 | |
| 7708 Par_PushAndMarkClosure::Par_PushAndMarkClosure(CMSCollector* collector, | |
| 7709 MemRegion span, | |
| 7710 ReferenceProcessor* rp, | |
| 7711 CMSBitMap* bit_map, | |
| 7712 OopTaskQueue* work_queue, | |
| 7713 CMSMarkStack* revisit_stack): | |
| 935 | 7714 Par_KlassRememberingOopClosure(collector, rp, revisit_stack), |
| 0 | 7715 _span(span), |
| 7716 _bit_map(bit_map), | |
| 935 | 7717 _work_queue(work_queue) |
| 0 | 7718 { |
| 7719 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
| 7720 } | |
| 7721 | |
|
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7722 void PushAndMarkClosure::do_oop(oop* p) { PushAndMarkClosure::do_oop_work(p); } |
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7723 void PushAndMarkClosure::do_oop(narrowOop* p) { PushAndMarkClosure::do_oop_work(p); } |
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7724 |
| 0 | 7725 // Grey object rescan during second checkpoint phase -- |
| 7726 // the parallel version. | |
|
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7727 void Par_PushAndMarkClosure::do_oop(oop obj) { |
| 0 | 7728 // In the assert below, we ignore the mark word because |
| 7729 // this oop may point to an already visited object that is | |
| 7730 // on the overflow stack (in which case the mark word has | |
| 7731 // been hijacked for chaining into the overflow stack -- | |
| 7732 // if this is the last object in the overflow stack then | |
| 7733 // its mark word will be NULL). Because this object may | |
| 7734 // have been subsequently popped off the global overflow | |
| 7735 // stack, and the mark word possibly restored to the prototypical | |
| 7736 // value, by the time we get to examined this failing assert in | |
| 7737 // the debugger, is_oop_or_null(false) may subsequently start | |
| 7738 // to hold. | |
|
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7739 assert(obj->is_oop_or_null(true), |
| 0 | 7740 "expected an oop or NULL"); |
|
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7741 HeapWord* addr = (HeapWord*)obj; |
| 0 | 7742 // Check if oop points into the CMS generation |
| 7743 // and is not marked | |
| 7744 if (_span.contains(addr) && !_bit_map->isMarked(addr)) { | |
| 7745 // a white object ... | |
| 7746 // If we manage to "claim" the object, by being the | |
| 7747 // first thread to mark it, then we push it on our | |
| 7748 // marking stack | |
| 7749 if (_bit_map->par_mark(addr)) { // ... now grey | |
| 7750 // push on work queue (grey set) | |
| 7751 bool simulate_overflow = false; | |
| 7752 NOT_PRODUCT( | |
| 7753 if (CMSMarkStackOverflowALot && | |
| 7754 _collector->par_simulate_overflow()) { | |
| 7755 // simulate a stack overflow | |
| 7756 simulate_overflow = true; | |
| 7757 } | |
| 7758 ) | |
|
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7759 if (simulate_overflow || !_work_queue->push(obj)) { |
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7760 _collector->par_push_on_overflow_list(obj); |
| 0 | 7761 _collector->_par_pmc_remark_ovflw++; // imprecise OK: no need to CAS |
| 7762 } | |
| 7763 } // Else, some other thread got there first | |
| 7764 } | |
| 7765 } | |
| 7766 | |
|
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7767 void Par_PushAndMarkClosure::do_oop(oop* p) { Par_PushAndMarkClosure::do_oop_work(p); } |
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7768 void Par_PushAndMarkClosure::do_oop(narrowOop* p) { Par_PushAndMarkClosure::do_oop_work(p); } |
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7769 |
| 941 | 7770 void PushAndMarkClosure::remember_mdo(DataLayout* v) { |
| 7771 // TBD | |
| 7772 } | |
| 7773 | |
| 7774 void Par_PushAndMarkClosure::remember_mdo(DataLayout* v) { | |
| 7775 // TBD | |
| 7776 } | |
| 7777 | |
| 0 | 7778 void CMSPrecleanRefsYieldClosure::do_yield_work() { |
| 935 | 7779 DEBUG_ONLY(RememberKlassesChecker mux(false);) |
| 0 | 7780 Mutex* bml = _collector->bitMapLock(); |
| 7781 assert_lock_strong(bml); | |
| 7782 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 7783 "CMS thread should hold CMS token"); | |
| 7784 | |
| 7785 bml->unlock(); | |
| 7786 ConcurrentMarkSweepThread::desynchronize(true); | |
| 7787 | |
| 7788 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 7789 | |
| 7790 _collector->stopTimer(); | |
| 7791 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
| 7792 if (PrintCMSStatistics != 0) { | |
| 7793 _collector->incrementYields(); | |
| 7794 } | |
| 7795 _collector->icms_wait(); | |
| 7796 | |
| 7797 // See the comment in coordinator_yield() | |
| 7798 for (unsigned i = 0; i < CMSYieldSleepCount && | |
| 7799 ConcurrentMarkSweepThread::should_yield() && | |
| 7800 !CMSCollector::foregroundGCIsActive(); ++i) { | |
| 7801 os::sleep(Thread::current(), 1, false); | |
| 7802 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 7803 } | |
| 7804 | |
| 7805 ConcurrentMarkSweepThread::synchronize(true); | |
| 7806 bml->lock(); | |
| 7807 | |
| 7808 _collector->startTimer(); | |
| 7809 } | |
| 7810 | |
| 7811 bool CMSPrecleanRefsYieldClosure::should_return() { | |
| 7812 if (ConcurrentMarkSweepThread::should_yield()) { | |
| 7813 do_yield_work(); | |
| 7814 } | |
| 7815 return _collector->foregroundGCIsActive(); | |
| 7816 } | |
| 7817 | |
| 7818 void MarkFromDirtyCardsClosure::do_MemRegion(MemRegion mr) { | |
| 7819 assert(((size_t)mr.start())%CardTableModRefBS::card_size_in_words == 0, | |
| 7820 "mr should be aligned to start at a card boundary"); | |
| 7821 // We'd like to assert: | |
| 7822 // assert(mr.word_size()%CardTableModRefBS::card_size_in_words == 0, | |
| 7823 // "mr should be a range of cards"); | |
| 7824 // However, that would be too strong in one case -- the last | |
| 7825 // partition ends at _unallocated_block which, in general, can be | |
| 7826 // an arbitrary boundary, not necessarily card aligned. | |
| 7827 if (PrintCMSStatistics != 0) { | |
| 7828 _num_dirty_cards += | |
| 7829 mr.word_size()/CardTableModRefBS::card_size_in_words; | |
| 7830 } | |
| 7831 _space->object_iterate_mem(mr, &_scan_cl); | |
| 7832 } | |
| 7833 | |
| 7834 SweepClosure::SweepClosure(CMSCollector* collector, | |
| 7835 ConcurrentMarkSweepGeneration* g, | |
| 7836 CMSBitMap* bitMap, bool should_yield) : | |
| 7837 _collector(collector), | |
| 7838 _g(g), | |
| 7839 _sp(g->cmsSpace()), | |
| 7840 _limit(_sp->sweep_limit()), | |
| 7841 _freelistLock(_sp->freelistLock()), | |
| 7842 _bitMap(bitMap), | |
| 7843 _yield(should_yield), | |
| 7844 _inFreeRange(false), // No free range at beginning of sweep | |
| 7845 _freeRangeInFreeLists(false), // No free range at beginning of sweep | |
| 7846 _lastFreeRangeCoalesced(false), | |
| 7847 _freeFinger(g->used_region().start()) | |
| 7848 { | |
| 7849 NOT_PRODUCT( | |
| 7850 _numObjectsFreed = 0; | |
| 7851 _numWordsFreed = 0; | |
| 7852 _numObjectsLive = 0; | |
| 7853 _numWordsLive = 0; | |
| 7854 _numObjectsAlreadyFree = 0; | |
| 7855 _numWordsAlreadyFree = 0; | |
| 7856 _last_fc = NULL; | |
| 7857 | |
| 7858 _sp->initializeIndexedFreeListArrayReturnedBytes(); | |
| 7859 _sp->dictionary()->initializeDictReturnedBytes(); | |
| 7860 ) | |
| 7861 assert(_limit >= _sp->bottom() && _limit <= _sp->end(), | |
| 7862 "sweep _limit out of bounds"); | |
| 7863 if (CMSTraceSweeper) { | |
| 7864 gclog_or_tty->print("\n====================\nStarting new sweep\n"); | |
| 7865 } | |
| 7866 } | |
| 7867 | |
| 7868 // We need this destructor to reclaim any space at the end | |
| 7869 // of the space, which do_blk below may not have added back to | |
| 7870 // the free lists. [basically dealing with the "fringe effect"] | |
| 7871 SweepClosure::~SweepClosure() { | |
| 7872 assert_lock_strong(_freelistLock); | |
| 7873 // this should be treated as the end of a free run if any | |
| 7874 // The current free range should be returned to the free lists | |
| 7875 // as one coalesced chunk. | |
| 7876 if (inFreeRange()) { | |
| 7877 flushCurFreeChunk(freeFinger(), | |
| 7878 pointer_delta(_limit, freeFinger())); | |
| 7879 assert(freeFinger() < _limit, "the finger pointeth off base"); | |
| 7880 if (CMSTraceSweeper) { | |
| 7881 gclog_or_tty->print("destructor:"); | |
| 7882 gclog_or_tty->print("Sweep:put_free_blk 0x%x ("SIZE_FORMAT") " | |
| 7883 "[coalesced:"SIZE_FORMAT"]\n", | |
| 7884 freeFinger(), pointer_delta(_limit, freeFinger()), | |
| 7885 lastFreeRangeCoalesced()); | |
| 7886 } | |
| 7887 } | |
| 7888 NOT_PRODUCT( | |
| 7889 if (Verbose && PrintGC) { | |
| 7890 gclog_or_tty->print("Collected "SIZE_FORMAT" objects, " | |
| 7891 SIZE_FORMAT " bytes", | |
| 7892 _numObjectsFreed, _numWordsFreed*sizeof(HeapWord)); | |
| 7893 gclog_or_tty->print_cr("\nLive "SIZE_FORMAT" objects, " | |
| 7894 SIZE_FORMAT" bytes " | |
| 7895 "Already free "SIZE_FORMAT" objects, "SIZE_FORMAT" bytes", | |
| 7896 _numObjectsLive, _numWordsLive*sizeof(HeapWord), | |
| 7897 _numObjectsAlreadyFree, _numWordsAlreadyFree*sizeof(HeapWord)); | |
| 7898 size_t totalBytes = (_numWordsFreed + _numWordsLive + _numWordsAlreadyFree) * | |
| 7899 sizeof(HeapWord); | |
| 7900 gclog_or_tty->print_cr("Total sweep: "SIZE_FORMAT" bytes", totalBytes); | |
| 7901 | |
| 7902 if (PrintCMSStatistics && CMSVerifyReturnedBytes) { | |
| 7903 size_t indexListReturnedBytes = _sp->sumIndexedFreeListArrayReturnedBytes(); | |
| 7904 size_t dictReturnedBytes = _sp->dictionary()->sumDictReturnedBytes(); | |
| 7905 size_t returnedBytes = indexListReturnedBytes + dictReturnedBytes; | |
| 7906 gclog_or_tty->print("Returned "SIZE_FORMAT" bytes", returnedBytes); | |
| 7907 gclog_or_tty->print(" Indexed List Returned "SIZE_FORMAT" bytes", | |
| 7908 indexListReturnedBytes); | |
| 7909 gclog_or_tty->print_cr(" Dictionary Returned "SIZE_FORMAT" bytes", | |
| 7910 dictReturnedBytes); | |
| 7911 } | |
| 7912 } | |
| 7913 ) | |
| 7914 // Now, in debug mode, just null out the sweep_limit | |
| 7915 NOT_PRODUCT(_sp->clear_sweep_limit();) | |
| 7916 if (CMSTraceSweeper) { | |
| 7917 gclog_or_tty->print("end of sweep\n================\n"); | |
| 7918 } | |
| 7919 } | |
| 7920 | |
| 7921 void SweepClosure::initialize_free_range(HeapWord* freeFinger, | |
| 7922 bool freeRangeInFreeLists) { | |
| 7923 if (CMSTraceSweeper) { | |
| 7924 gclog_or_tty->print("---- Start free range 0x%x with free block [%d] (%d)\n", | |
| 7925 freeFinger, _sp->block_size(freeFinger), | |
| 7926 freeRangeInFreeLists); | |
| 7927 } | |
| 7928 assert(!inFreeRange(), "Trampling existing free range"); | |
| 7929 set_inFreeRange(true); | |
| 7930 set_lastFreeRangeCoalesced(false); | |
| 7931 | |
| 7932 set_freeFinger(freeFinger); | |
| 7933 set_freeRangeInFreeLists(freeRangeInFreeLists); | |
| 7934 if (CMSTestInFreeList) { | |
| 7935 if (freeRangeInFreeLists) { | |
| 7936 FreeChunk* fc = (FreeChunk*) freeFinger; | |
| 7937 assert(fc->isFree(), "A chunk on the free list should be free."); | |
| 7938 assert(fc->size() > 0, "Free range should have a size"); | |
| 7939 assert(_sp->verifyChunkInFreeLists(fc), "Chunk is not in free lists"); | |
| 7940 } | |
| 7941 } | |
| 7942 } | |
| 7943 | |
| 7944 // Note that the sweeper runs concurrently with mutators. Thus, | |
| 7945 // it is possible for direct allocation in this generation to happen | |
| 7946 // in the middle of the sweep. Note that the sweeper also coalesces | |
| 7947 // contiguous free blocks. Thus, unless the sweeper and the allocator | |
| 7948 // synchronize appropriately freshly allocated blocks may get swept up. | |
| 7949 // This is accomplished by the sweeper locking the free lists while | |
| 7950 // it is sweeping. Thus blocks that are determined to be free are | |
| 7951 // indeed free. There is however one additional complication: | |
| 7952 // blocks that have been allocated since the final checkpoint and | |
| 7953 // mark, will not have been marked and so would be treated as | |
| 7954 // unreachable and swept up. To prevent this, the allocator marks | |
| 7955 // the bit map when allocating during the sweep phase. This leads, | |
| 7956 // however, to a further complication -- objects may have been allocated | |
| 7957 // but not yet initialized -- in the sense that the header isn't yet | |
| 7958 // installed. The sweeper can not then determine the size of the block | |
| 7959 // in order to skip over it. To deal with this case, we use a technique | |
| 7960 // (due to Printezis) to encode such uninitialized block sizes in the | |
| 7961 // bit map. Since the bit map uses a bit per every HeapWord, but the | |
| 7962 // CMS generation has a minimum object size of 3 HeapWords, it follows | |
| 7963 // that "normal marks" won't be adjacent in the bit map (there will | |
| 7964 // always be at least two 0 bits between successive 1 bits). We make use | |
| 7965 // of these "unused" bits to represent uninitialized blocks -- the bit | |
| 7966 // corresponding to the start of the uninitialized object and the next | |
| 7967 // bit are both set. Finally, a 1 bit marks the end of the object that | |
| 7968 // started with the two consecutive 1 bits to indicate its potentially | |
| 7969 // uninitialized state. | |
| 7970 | |
| 7971 size_t SweepClosure::do_blk_careful(HeapWord* addr) { | |
| 7972 FreeChunk* fc = (FreeChunk*)addr; | |
| 7973 size_t res; | |
| 7974 | |
|
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7975 // Check if we are done sweeping. Below we check "addr >= _limit" rather |
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|
7976 // than "addr == _limit" because although _limit was a block boundary when |
|
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|
7977 // we started the sweep, it may no longer be one because heap expansion |
|
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|
7978 // may have caused us to coalesce the block ending at the address _limit |
|
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|
7979 // with a newly expanded chunk (this happens when _limit was set to the |
|
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|
7980 // previous _end of the space), so we may have stepped past _limit; see CR 6977970. |
|
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|
7981 if (addr >= _limit) { // we have swept up to or past the limit, do nothing more |
| 0 | 7982 assert(_limit >= _sp->bottom() && _limit <= _sp->end(), |
| 7983 "sweep _limit out of bounds"); | |
|
1720
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7984 assert(addr < _sp->end(), "addr out of bounds"); |
| 0 | 7985 // help the closure application finish |
|
1720
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|
7986 return pointer_delta(_sp->end(), addr); |
|
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|
7987 } |
|
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|
7988 assert(addr < _limit, "sweep invariant"); |
| 0 | 7989 |
| 7990 // check if we should yield | |
| 7991 do_yield_check(addr); | |
| 7992 if (fc->isFree()) { | |
| 7993 // Chunk that is already free | |
| 7994 res = fc->size(); | |
| 7995 doAlreadyFreeChunk(fc); | |
| 7996 debug_only(_sp->verifyFreeLists()); | |
| 7997 assert(res == fc->size(), "Don't expect the size to change"); | |
| 7998 NOT_PRODUCT( | |
| 7999 _numObjectsAlreadyFree++; | |
| 8000 _numWordsAlreadyFree += res; | |
| 8001 ) | |
| 8002 NOT_PRODUCT(_last_fc = fc;) | |
| 8003 } else if (!_bitMap->isMarked(addr)) { | |
| 8004 // Chunk is fresh garbage | |
| 8005 res = doGarbageChunk(fc); | |
| 8006 debug_only(_sp->verifyFreeLists()); | |
| 8007 NOT_PRODUCT( | |
| 8008 _numObjectsFreed++; | |
| 8009 _numWordsFreed += res; | |
| 8010 ) | |
| 8011 } else { | |
| 8012 // Chunk that is alive. | |
| 8013 res = doLiveChunk(fc); | |
| 8014 debug_only(_sp->verifyFreeLists()); | |
| 8015 NOT_PRODUCT( | |
| 8016 _numObjectsLive++; | |
| 8017 _numWordsLive += res; | |
| 8018 ) | |
| 8019 } | |
| 8020 return res; | |
| 8021 } | |
| 8022 | |
| 8023 // For the smart allocation, record following | |
| 8024 // split deaths - a free chunk is removed from its free list because | |
| 8025 // it is being split into two or more chunks. | |
| 8026 // split birth - a free chunk is being added to its free list because | |
| 8027 // a larger free chunk has been split and resulted in this free chunk. | |
| 8028 // coal death - a free chunk is being removed from its free list because | |
| 8029 // it is being coalesced into a large free chunk. | |
| 8030 // coal birth - a free chunk is being added to its free list because | |
| 8031 // it was created when two or more free chunks where coalesced into | |
| 8032 // this free chunk. | |
| 8033 // | |
| 8034 // These statistics are used to determine the desired number of free | |
| 8035 // chunks of a given size. The desired number is chosen to be relative | |
| 8036 // to the end of a CMS sweep. The desired number at the end of a sweep | |
| 8037 // is the | |
| 8038 // count-at-end-of-previous-sweep (an amount that was enough) | |
| 8039 // - count-at-beginning-of-current-sweep (the excess) | |
| 8040 // + split-births (gains in this size during interval) | |
| 8041 // - split-deaths (demands on this size during interval) | |
| 8042 // where the interval is from the end of one sweep to the end of the | |
| 8043 // next. | |
| 8044 // | |
| 8045 // When sweeping the sweeper maintains an accumulated chunk which is | |
| 8046 // the chunk that is made up of chunks that have been coalesced. That | |
| 8047 // will be termed the left-hand chunk. A new chunk of garbage that | |
| 8048 // is being considered for coalescing will be referred to as the | |
| 8049 // right-hand chunk. | |
| 8050 // | |
| 8051 // When making a decision on whether to coalesce a right-hand chunk with | |
| 8052 // the current left-hand chunk, the current count vs. the desired count | |
| 8053 // of the left-hand chunk is considered. Also if the right-hand chunk | |
| 8054 // is near the large chunk at the end of the heap (see | |
| 8055 // ConcurrentMarkSweepGeneration::isNearLargestChunk()), then the | |
| 8056 // left-hand chunk is coalesced. | |
| 8057 // | |
| 8058 // When making a decision about whether to split a chunk, the desired count | |
| 8059 // vs. the current count of the candidate to be split is also considered. | |
| 8060 // If the candidate is underpopulated (currently fewer chunks than desired) | |
| 8061 // a chunk of an overpopulated (currently more chunks than desired) size may | |
| 8062 // be chosen. The "hint" associated with a free list, if non-null, points | |
| 8063 // to a free list which may be overpopulated. | |
| 8064 // | |
| 8065 | |
| 8066 void SweepClosure::doAlreadyFreeChunk(FreeChunk* fc) { | |
| 8067 size_t size = fc->size(); | |
| 8068 // Chunks that cannot be coalesced are not in the | |
| 8069 // free lists. | |
| 8070 if (CMSTestInFreeList && !fc->cantCoalesce()) { | |
| 8071 assert(_sp->verifyChunkInFreeLists(fc), | |
| 8072 "free chunk should be in free lists"); | |
| 8073 } | |
| 8074 // a chunk that is already free, should not have been | |
| 8075 // marked in the bit map | |
| 8076 HeapWord* addr = (HeapWord*) fc; | |
| 8077 assert(!_bitMap->isMarked(addr), "free chunk should be unmarked"); | |
| 8078 // Verify that the bit map has no bits marked between | |
| 8079 // addr and purported end of this block. | |
| 8080 _bitMap->verifyNoOneBitsInRange(addr + 1, addr + size); | |
| 8081 | |
| 8082 // Some chunks cannot be coalesced in under any circumstances. | |
| 8083 // See the definition of cantCoalesce(). | |
| 8084 if (!fc->cantCoalesce()) { | |
| 8085 // This chunk can potentially be coalesced. | |
| 8086 if (_sp->adaptive_freelists()) { | |
| 8087 // All the work is done in | |
| 8088 doPostIsFreeOrGarbageChunk(fc, size); | |
| 8089 } else { // Not adaptive free lists | |
| 8090 // this is a free chunk that can potentially be coalesced by the sweeper; | |
| 8091 if (!inFreeRange()) { | |
| 8092 // if the next chunk is a free block that can't be coalesced | |
| 8093 // it doesn't make sense to remove this chunk from the free lists | |
| 8094 FreeChunk* nextChunk = (FreeChunk*)(addr + size); | |
| 8095 assert((HeapWord*)nextChunk <= _limit, "sweep invariant"); | |
| 8096 if ((HeapWord*)nextChunk < _limit && // there's a next chunk... | |
| 8097 nextChunk->isFree() && // which is free... | |
| 8098 nextChunk->cantCoalesce()) { // ... but cant be coalesced | |
| 8099 // nothing to do | |
| 8100 } else { | |
| 8101 // Potentially the start of a new free range: | |
| 8102 // Don't eagerly remove it from the free lists. | |
| 8103 // No need to remove it if it will just be put | |
| 8104 // back again. (Also from a pragmatic point of view | |
| 8105 // if it is a free block in a region that is beyond | |
| 8106 // any allocated blocks, an assertion will fail) | |
| 8107 // Remember the start of a free run. | |
| 8108 initialize_free_range(addr, true); | |
| 8109 // end - can coalesce with next chunk | |
| 8110 } | |
| 8111 } else { | |
| 8112 // the midst of a free range, we are coalescing | |
| 8113 debug_only(record_free_block_coalesced(fc);) | |
| 8114 if (CMSTraceSweeper) { | |
| 8115 gclog_or_tty->print(" -- pick up free block 0x%x (%d)\n", fc, size); | |
| 8116 } | |
| 8117 // remove it from the free lists | |
| 8118 _sp->removeFreeChunkFromFreeLists(fc); | |
| 8119 set_lastFreeRangeCoalesced(true); | |
| 8120 // If the chunk is being coalesced and the current free range is | |
| 8121 // in the free lists, remove the current free range so that it | |
| 8122 // will be returned to the free lists in its entirety - all | |
| 8123 // the coalesced pieces included. | |
| 8124 if (freeRangeInFreeLists()) { | |
| 8125 FreeChunk* ffc = (FreeChunk*) freeFinger(); | |
| 8126 assert(ffc->size() == pointer_delta(addr, freeFinger()), | |
| 8127 "Size of free range is inconsistent with chunk size."); | |
| 8128 if (CMSTestInFreeList) { | |
| 8129 assert(_sp->verifyChunkInFreeLists(ffc), | |
| 8130 "free range is not in free lists"); | |
| 8131 } | |
| 8132 _sp->removeFreeChunkFromFreeLists(ffc); | |
| 8133 set_freeRangeInFreeLists(false); | |
| 8134 } | |
| 8135 } | |
| 8136 } | |
| 8137 } else { | |
| 8138 // Code path common to both original and adaptive free lists. | |
| 8139 | |
| 8140 // cant coalesce with previous block; this should be treated | |
| 8141 // as the end of a free run if any | |
| 8142 if (inFreeRange()) { | |
| 8143 // we kicked some butt; time to pick up the garbage | |
| 8144 assert(freeFinger() < addr, "the finger pointeth off base"); | |
| 8145 flushCurFreeChunk(freeFinger(), pointer_delta(addr, freeFinger())); | |
| 8146 } | |
| 8147 // else, nothing to do, just continue | |
| 8148 } | |
| 8149 } | |
| 8150 | |
| 8151 size_t SweepClosure::doGarbageChunk(FreeChunk* fc) { | |
| 8152 // This is a chunk of garbage. It is not in any free list. | |
| 8153 // Add it to a free list or let it possibly be coalesced into | |
| 8154 // a larger chunk. | |
| 8155 HeapWord* addr = (HeapWord*) fc; | |
| 8156 size_t size = CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size()); | |
| 8157 | |
| 8158 if (_sp->adaptive_freelists()) { | |
| 8159 // Verify that the bit map has no bits marked between | |
| 8160 // addr and purported end of just dead object. | |
| 8161 _bitMap->verifyNoOneBitsInRange(addr + 1, addr + size); | |
| 8162 | |
| 8163 doPostIsFreeOrGarbageChunk(fc, size); | |
| 8164 } else { | |
| 8165 if (!inFreeRange()) { | |
| 8166 // start of a new free range | |
| 8167 assert(size > 0, "A free range should have a size"); | |
| 8168 initialize_free_range(addr, false); | |
| 8169 | |
| 8170 } else { | |
| 8171 // this will be swept up when we hit the end of the | |
| 8172 // free range | |
| 8173 if (CMSTraceSweeper) { | |
| 8174 gclog_or_tty->print(" -- pick up garbage 0x%x (%d) \n", fc, size); | |
| 8175 } | |
| 8176 // If the chunk is being coalesced and the current free range is | |
| 8177 // in the free lists, remove the current free range so that it | |
| 8178 // will be returned to the free lists in its entirety - all | |
| 8179 // the coalesced pieces included. | |
| 8180 if (freeRangeInFreeLists()) { | |
| 8181 FreeChunk* ffc = (FreeChunk*)freeFinger(); | |
| 8182 assert(ffc->size() == pointer_delta(addr, freeFinger()), | |
| 8183 "Size of free range is inconsistent with chunk size."); | |
| 8184 if (CMSTestInFreeList) { | |
| 8185 assert(_sp->verifyChunkInFreeLists(ffc), | |
| 8186 "free range is not in free lists"); | |
| 8187 } | |
| 8188 _sp->removeFreeChunkFromFreeLists(ffc); | |
| 8189 set_freeRangeInFreeLists(false); | |
| 8190 } | |
| 8191 set_lastFreeRangeCoalesced(true); | |
| 8192 } | |
| 8193 // this will be swept up when we hit the end of the free range | |
| 8194 | |
| 8195 // Verify that the bit map has no bits marked between | |
| 8196 // addr and purported end of just dead object. | |
| 8197 _bitMap->verifyNoOneBitsInRange(addr + 1, addr + size); | |
| 8198 } | |
| 8199 return size; | |
| 8200 } | |
| 8201 | |
| 8202 size_t SweepClosure::doLiveChunk(FreeChunk* fc) { | |
| 8203 HeapWord* addr = (HeapWord*) fc; | |
| 8204 // The sweeper has just found a live object. Return any accumulated | |
| 8205 // left hand chunk to the free lists. | |
| 8206 if (inFreeRange()) { | |
| 8207 if (_sp->adaptive_freelists()) { | |
| 8208 flushCurFreeChunk(freeFinger(), | |
| 8209 pointer_delta(addr, freeFinger())); | |
| 8210 } else { // not adaptive freelists | |
| 8211 set_inFreeRange(false); | |
| 8212 // Add the free range back to the free list if it is not already | |
| 8213 // there. | |
| 8214 if (!freeRangeInFreeLists()) { | |
| 8215 assert(freeFinger() < addr, "the finger pointeth off base"); | |
| 8216 if (CMSTraceSweeper) { | |
| 8217 gclog_or_tty->print("Sweep:put_free_blk 0x%x (%d) " | |
| 8218 "[coalesced:%d]\n", | |
| 8219 freeFinger(), pointer_delta(addr, freeFinger()), | |
| 8220 lastFreeRangeCoalesced()); | |
| 8221 } | |
| 8222 _sp->addChunkAndRepairOffsetTable(freeFinger(), | |
| 8223 pointer_delta(addr, freeFinger()), lastFreeRangeCoalesced()); | |
| 8224 } | |
| 8225 } | |
| 8226 } | |
| 8227 | |
| 8228 // Common code path for original and adaptive free lists. | |
| 8229 | |
| 8230 // this object is live: we'd normally expect this to be | |
| 8231 // an oop, and like to assert the following: | |
| 8232 // assert(oop(addr)->is_oop(), "live block should be an oop"); | |
| 8233 // However, as we commented above, this may be an object whose | |
| 8234 // header hasn't yet been initialized. | |
| 8235 size_t size; | |
| 8236 assert(_bitMap->isMarked(addr), "Tautology for this control point"); | |
| 8237 if (_bitMap->isMarked(addr + 1)) { | |
| 8238 // Determine the size from the bit map, rather than trying to | |
| 8239 // compute it from the object header. | |
| 8240 HeapWord* nextOneAddr = _bitMap->getNextMarkedWordAddress(addr + 2); | |
| 8241 size = pointer_delta(nextOneAddr + 1, addr); | |
| 8242 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
| 8243 "alignment problem"); | |
| 8244 | |
| 8245 #ifdef DEBUG | |
| 187 | 8246 if (oop(addr)->klass_or_null() != NULL && |
|
94
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|
8247 ( !_collector->should_unload_classes() |
|
518
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|
8248 || (oop(addr)->is_parsable()) && |
|
0af8b0718fc9
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|
8249 oop(addr)->is_conc_safe())) { |
| 0 | 8250 // Ignore mark word because we are running concurrent with mutators |
| 8251 assert(oop(addr)->is_oop(true), "live block should be an oop"); | |
|
518
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517
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|
8252 // is_conc_safe is checked before performing this assertion |
|
0af8b0718fc9
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|
8253 // because an object that is not is_conc_safe may yet have |
|
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|
8254 // the return from size() correct. |
| 0 | 8255 assert(size == |
| 8256 CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size()), | |
| 8257 "P-mark and computed size do not agree"); | |
| 8258 } | |
| 8259 #endif | |
| 8260 | |
| 8261 } else { | |
| 8262 // This should be an initialized object that's alive. | |
| 187 | 8263 assert(oop(addr)->klass_or_null() != NULL && |
|
94
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|
8264 (!_collector->should_unload_classes() |
| 0 | 8265 || oop(addr)->is_parsable()), |
| 8266 "Should be an initialized object"); | |
|
518
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|
8267 // Note that there are objects used during class redefinition |
|
0af8b0718fc9
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517
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|
8268 // (e.g., merge_cp in VM_RedefineClasses::merge_cp_and_rewrite() |
|
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|
8269 // which are discarded with their is_conc_safe state still |
|
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|
8270 // false. These object may be floating garbage so may be |
|
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|
8271 // seen here. If they are floating garbage their size |
|
0af8b0718fc9
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|
8272 // should be attainable from their klass. Do not that |
|
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|
8273 // is_conc_safe() is true for oop(addr). |
| 0 | 8274 // Ignore mark word because we are running concurrent with mutators |
| 8275 assert(oop(addr)->is_oop(true), "live block should be an oop"); | |
| 8276 // Verify that the bit map has no bits marked between | |
| 8277 // addr and purported end of this block. | |
| 8278 size = CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size()); | |
| 8279 assert(size >= 3, "Necessary for Printezis marks to work"); | |
| 8280 assert(!_bitMap->isMarked(addr+1), "Tautology for this control point"); | |
| 8281 DEBUG_ONLY(_bitMap->verifyNoOneBitsInRange(addr+2, addr+size);) | |
| 8282 } | |
| 8283 return size; | |
| 8284 } | |
| 8285 | |
| 8286 void SweepClosure::doPostIsFreeOrGarbageChunk(FreeChunk* fc, | |
| 8287 size_t chunkSize) { | |
| 8288 // doPostIsFreeOrGarbageChunk() should only be called in the smart allocation | |
| 8289 // scheme. | |
| 8290 bool fcInFreeLists = fc->isFree(); | |
| 8291 assert(_sp->adaptive_freelists(), "Should only be used in this case."); | |
| 8292 assert((HeapWord*)fc <= _limit, "sweep invariant"); | |
| 8293 if (CMSTestInFreeList && fcInFreeLists) { | |
| 8294 assert(_sp->verifyChunkInFreeLists(fc), | |
| 8295 "free chunk is not in free lists"); | |
| 8296 } | |
| 8297 | |
| 8298 | |
| 8299 if (CMSTraceSweeper) { | |
| 8300 gclog_or_tty->print_cr(" -- pick up another chunk at 0x%x (%d)", fc, chunkSize); | |
| 8301 } | |
| 8302 | |
| 8303 HeapWord* addr = (HeapWord*) fc; | |
| 8304 | |
| 8305 bool coalesce; | |
| 8306 size_t left = pointer_delta(addr, freeFinger()); | |
| 8307 size_t right = chunkSize; | |
| 8308 switch (FLSCoalescePolicy) { | |
| 8309 // numeric value forms a coalition aggressiveness metric | |
| 8310 case 0: { // never coalesce | |
| 8311 coalesce = false; | |
| 8312 break; | |
| 8313 } | |
| 8314 case 1: { // coalesce if left & right chunks on overpopulated lists | |
| 8315 coalesce = _sp->coalOverPopulated(left) && | |
| 8316 _sp->coalOverPopulated(right); | |
| 8317 break; | |
| 8318 } | |
| 8319 case 2: { // coalesce if left chunk on overpopulated list (default) | |
| 8320 coalesce = _sp->coalOverPopulated(left); | |
| 8321 break; | |
| 8322 } | |
| 8323 case 3: { // coalesce if left OR right chunk on overpopulated list | |
| 8324 coalesce = _sp->coalOverPopulated(left) || | |
| 8325 _sp->coalOverPopulated(right); | |
| 8326 break; | |
| 8327 } | |
| 8328 case 4: { // always coalesce | |
| 8329 coalesce = true; | |
| 8330 break; | |
| 8331 } | |
| 8332 default: | |
| 8333 ShouldNotReachHere(); | |
| 8334 } | |
| 8335 | |
| 8336 // Should the current free range be coalesced? | |
| 8337 // If the chunk is in a free range and either we decided to coalesce above | |
| 8338 // or the chunk is near the large block at the end of the heap | |
| 8339 // (isNearLargestChunk() returns true), then coalesce this chunk. | |
| 8340 bool doCoalesce = inFreeRange() && | |
| 8341 (coalesce || _g->isNearLargestChunk((HeapWord*)fc)); | |
| 8342 if (doCoalesce) { | |
| 8343 // Coalesce the current free range on the left with the new | |
| 8344 // chunk on the right. If either is on a free list, | |
| 8345 // it must be removed from the list and stashed in the closure. | |
| 8346 if (freeRangeInFreeLists()) { | |
| 8347 FreeChunk* ffc = (FreeChunk*)freeFinger(); | |
| 8348 assert(ffc->size() == pointer_delta(addr, freeFinger()), | |
| 8349 "Size of free range is inconsistent with chunk size."); | |
| 8350 if (CMSTestInFreeList) { | |
| 8351 assert(_sp->verifyChunkInFreeLists(ffc), | |
| 8352 "Chunk is not in free lists"); | |
| 8353 } | |
| 8354 _sp->coalDeath(ffc->size()); | |
| 8355 _sp->removeFreeChunkFromFreeLists(ffc); | |
| 8356 set_freeRangeInFreeLists(false); | |
| 8357 } | |
| 8358 if (fcInFreeLists) { | |
| 8359 _sp->coalDeath(chunkSize); | |
| 8360 assert(fc->size() == chunkSize, | |
| 8361 "The chunk has the wrong size or is not in the free lists"); | |
| 8362 _sp->removeFreeChunkFromFreeLists(fc); | |
| 8363 } | |
| 8364 set_lastFreeRangeCoalesced(true); | |
| 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. | |
| 8370 flushCurFreeChunk(freeFinger(), | |
| 8371 pointer_delta(addr, freeFinger())); | |
| 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 } | |
| 8378 void SweepClosure::flushCurFreeChunk(HeapWord* chunk, size_t size) { | |
| 8379 assert(inFreeRange(), "Should only be called if currently in a free range."); | |
| 8380 assert(size > 0, | |
| 8381 "A zero sized chunk cannot be added to the free lists."); | |
| 8382 if (!freeRangeInFreeLists()) { | |
| 8383 if(CMSTestInFreeList) { | |
| 8384 FreeChunk* fc = (FreeChunk*) chunk; | |
| 8385 fc->setSize(size); | |
| 8386 assert(!_sp->verifyChunkInFreeLists(fc), | |
| 8387 "chunk should not be in free lists yet"); | |
| 8388 } | |
| 8389 if (CMSTraceSweeper) { | |
| 8390 gclog_or_tty->print_cr(" -- add free block 0x%x (%d) to free lists", | |
| 8391 chunk, size); | |
| 8392 } | |
| 8393 // A new free range is going to be starting. The current | |
| 8394 // free range has not been added to the free lists yet or | |
| 8395 // was removed so add it back. | |
| 8396 // If the current free range was coalesced, then the death | |
| 8397 // of the free range was recorded. Record a birth now. | |
| 8398 if (lastFreeRangeCoalesced()) { | |
| 8399 _sp->coalBirth(size); | |
| 8400 } | |
| 8401 _sp->addChunkAndRepairOffsetTable(chunk, size, | |
| 8402 lastFreeRangeCoalesced()); | |
| 8403 } | |
| 8404 set_inFreeRange(false); | |
| 8405 set_freeRangeInFreeLists(false); | |
| 8406 } | |
| 8407 | |
| 8408 // We take a break if we've been at this for a while, | |
| 8409 // so as to avoid monopolizing the locks involved. | |
| 8410 void SweepClosure::do_yield_work(HeapWord* addr) { | |
| 8411 // Return current free chunk being used for coalescing (if any) | |
| 8412 // to the appropriate freelist. After yielding, the next | |
| 8413 // free block encountered will start a coalescing range of | |
| 8414 // free blocks. If the next free block is adjacent to the | |
| 8415 // chunk just flushed, they will need to wait for the next | |
| 8416 // sweep to be coalesced. | |
| 8417 if (inFreeRange()) { | |
| 8418 flushCurFreeChunk(freeFinger(), pointer_delta(addr, freeFinger())); | |
| 8419 } | |
| 8420 | |
| 8421 // First give up the locks, then yield, then re-lock. | |
| 8422 // We should probably use a constructor/destructor idiom to | |
| 8423 // do this unlock/lock or modify the MutexUnlocker class to | |
| 8424 // serve our purpose. XXX | |
| 8425 assert_lock_strong(_bitMap->lock()); | |
| 8426 assert_lock_strong(_freelistLock); | |
| 8427 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 8428 "CMS thread should hold CMS token"); | |
| 8429 _bitMap->lock()->unlock(); | |
| 8430 _freelistLock->unlock(); | |
| 8431 ConcurrentMarkSweepThread::desynchronize(true); | |
| 8432 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 8433 _collector->stopTimer(); | |
| 8434 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
| 8435 if (PrintCMSStatistics != 0) { | |
| 8436 _collector->incrementYields(); | |
| 8437 } | |
| 8438 _collector->icms_wait(); | |
| 8439 | |
| 8440 // See the comment in coordinator_yield() | |
| 8441 for (unsigned i = 0; i < CMSYieldSleepCount && | |
| 8442 ConcurrentMarkSweepThread::should_yield() && | |
| 8443 !CMSCollector::foregroundGCIsActive(); ++i) { | |
| 8444 os::sleep(Thread::current(), 1, false); | |
| 8445 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 8446 } | |
| 8447 | |
| 8448 ConcurrentMarkSweepThread::synchronize(true); | |
| 8449 _freelistLock->lock(); | |
| 8450 _bitMap->lock()->lock_without_safepoint_check(); | |
| 8451 _collector->startTimer(); | |
| 8452 } | |
| 8453 | |
| 8454 #ifndef PRODUCT | |
| 8455 // This is actually very useful in a product build if it can | |
| 8456 // be called from the debugger. Compile it into the product | |
| 8457 // as needed. | |
| 8458 bool debug_verifyChunkInFreeLists(FreeChunk* fc) { | |
| 8459 return debug_cms_space->verifyChunkInFreeLists(fc); | |
| 8460 } | |
| 8461 | |
| 8462 void SweepClosure::record_free_block_coalesced(FreeChunk* fc) const { | |
| 8463 if (CMSTraceSweeper) { | |
| 8464 gclog_or_tty->print("Sweep:coal_free_blk 0x%x (%d)\n", fc, fc->size()); | |
| 8465 } | |
| 8466 } | |
| 8467 #endif | |
| 8468 | |
| 8469 // CMSIsAliveClosure | |
| 8470 bool CMSIsAliveClosure::do_object_b(oop obj) { | |
| 8471 HeapWord* addr = (HeapWord*)obj; | |
| 8472 return addr != NULL && | |
| 8473 (!_span.contains(addr) || _bit_map->isMarked(addr)); | |
| 8474 } | |
| 8475 | |
| 935 | 8476 CMSKeepAliveClosure::CMSKeepAliveClosure( CMSCollector* collector, |
| 8477 MemRegion span, | |
| 8478 CMSBitMap* bit_map, CMSMarkStack* mark_stack, | |
| 8479 CMSMarkStack* revisit_stack, bool cpc): | |
| 8480 KlassRememberingOopClosure(collector, NULL, revisit_stack), | |
| 8481 _span(span), | |
| 8482 _bit_map(bit_map), | |
| 8483 _mark_stack(mark_stack), | |
| 8484 _concurrent_precleaning(cpc) { | |
| 8485 assert(!_span.is_empty(), "Empty span could spell trouble"); | |
| 8486 } | |
| 8487 | |
| 8488 | |
| 0 | 8489 // CMSKeepAliveClosure: the serial version |
|
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8490 void CMSKeepAliveClosure::do_oop(oop obj) { |
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8491 HeapWord* addr = (HeapWord*)obj; |
| 0 | 8492 if (_span.contains(addr) && |
| 8493 !_bit_map->isMarked(addr)) { | |
| 8494 _bit_map->mark(addr); | |
| 8495 bool simulate_overflow = false; | |
| 8496 NOT_PRODUCT( | |
| 8497 if (CMSMarkStackOverflowALot && | |
| 8498 _collector->simulate_overflow()) { | |
| 8499 // simulate a stack overflow | |
| 8500 simulate_overflow = true; | |
| 8501 } | |
| 8502 ) | |
|
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8503 if (simulate_overflow || !_mark_stack->push(obj)) { |
|
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8504 if (_concurrent_precleaning) { |
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8505 // We dirty the overflown object and let the remark |
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8506 // phase deal with it. |
|
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8507 assert(_collector->overflow_list_is_empty(), "Error"); |
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8508 // In the case of object arrays, we need to dirty all of |
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8509 // the cards that the object spans. No locking or atomics |
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8510 // are needed since no one else can be mutating the mod union |
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8511 // table. |
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8512 if (obj->is_objArray()) { |
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8513 size_t sz = obj->size(); |
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8514 HeapWord* end_card_addr = |
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8515 (HeapWord*)round_to((intptr_t)(addr+sz), CardTableModRefBS::card_size); |
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8516 MemRegion redirty_range = MemRegion(addr, end_card_addr); |
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8517 assert(!redirty_range.is_empty(), "Arithmetical tautology"); |
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8518 _collector->_modUnionTable.mark_range(redirty_range); |
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8519 } else { |
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8520 _collector->_modUnionTable.mark(addr); |
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8521 } |
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8522 _collector->_ser_kac_preclean_ovflw++; |
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8523 } else { |
|
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8524 _collector->push_on_overflow_list(obj); |
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8525 _collector->_ser_kac_ovflw++; |
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8526 } |
| 0 | 8527 } |
| 8528 } | |
| 8529 } | |
| 8530 | |
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8531 void CMSKeepAliveClosure::do_oop(oop* p) { CMSKeepAliveClosure::do_oop_work(p); } |
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8532 void CMSKeepAliveClosure::do_oop(narrowOop* p) { CMSKeepAliveClosure::do_oop_work(p); } |
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8533 |
| 0 | 8534 // CMSParKeepAliveClosure: a parallel version of the above. |
| 8535 // The work queues are private to each closure (thread), | |
| 8536 // but (may be) available for stealing by other threads. | |
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8537 void CMSParKeepAliveClosure::do_oop(oop obj) { |
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8538 HeapWord* addr = (HeapWord*)obj; |
| 0 | 8539 if (_span.contains(addr) && |
| 8540 !_bit_map->isMarked(addr)) { | |
| 8541 // In general, during recursive tracing, several threads | |
| 8542 // may be concurrently getting here; the first one to | |
| 8543 // "tag" it, claims it. | |
| 8544 if (_bit_map->par_mark(addr)) { | |
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8545 bool res = _work_queue->push(obj); |
| 0 | 8546 assert(res, "Low water mark should be much less than capacity"); |
| 8547 // Do a recursive trim in the hope that this will keep | |
| 8548 // stack usage lower, but leave some oops for potential stealers | |
| 8549 trim_queue(_low_water_mark); | |
| 8550 } // Else, another thread got there first | |
| 8551 } | |
| 8552 } | |
| 8553 | |
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8554 void CMSParKeepAliveClosure::do_oop(oop* p) { CMSParKeepAliveClosure::do_oop_work(p); } |
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8555 void CMSParKeepAliveClosure::do_oop(narrowOop* p) { CMSParKeepAliveClosure::do_oop_work(p); } |
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8556 |
| 0 | 8557 void CMSParKeepAliveClosure::trim_queue(uint max) { |
| 8558 while (_work_queue->size() > max) { | |
| 8559 oop new_oop; | |
| 8560 if (_work_queue->pop_local(new_oop)) { | |
| 8561 assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop"); | |
| 8562 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
| 8563 "no white objects on this stack!"); | |
| 8564 assert(_span.contains((HeapWord*)new_oop), "Out of bounds oop"); | |
| 8565 // iterate over the oops in this oop, marking and pushing | |
| 8566 // the ones in CMS heap (i.e. in _span). | |
| 8567 new_oop->oop_iterate(&_mark_and_push); | |
| 8568 } | |
| 8569 } | |
| 8570 } | |
| 8571 | |
| 935 | 8572 CMSInnerParMarkAndPushClosure::CMSInnerParMarkAndPushClosure( |
| 8573 CMSCollector* collector, | |
| 8574 MemRegion span, CMSBitMap* bit_map, | |
| 8575 CMSMarkStack* revisit_stack, | |
| 8576 OopTaskQueue* work_queue): | |
| 8577 Par_KlassRememberingOopClosure(collector, NULL, revisit_stack), | |
| 8578 _span(span), | |
| 8579 _bit_map(bit_map), | |
| 8580 _work_queue(work_queue) { } | |
| 8581 | |
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8582 void CMSInnerParMarkAndPushClosure::do_oop(oop obj) { |
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8583 HeapWord* addr = (HeapWord*)obj; |
| 0 | 8584 if (_span.contains(addr) && |
| 8585 !_bit_map->isMarked(addr)) { | |
| 8586 if (_bit_map->par_mark(addr)) { | |
| 8587 bool simulate_overflow = false; | |
| 8588 NOT_PRODUCT( | |
| 8589 if (CMSMarkStackOverflowALot && | |
| 8590 _collector->par_simulate_overflow()) { | |
| 8591 // simulate a stack overflow | |
| 8592 simulate_overflow = true; | |
| 8593 } | |
| 8594 ) | |
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8595 if (simulate_overflow || !_work_queue->push(obj)) { |
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8596 _collector->par_push_on_overflow_list(obj); |
| 0 | 8597 _collector->_par_kac_ovflw++; |
| 8598 } | |
| 8599 } // Else another thread got there already | |
| 8600 } | |
| 8601 } | |
| 8602 | |
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8603 void CMSInnerParMarkAndPushClosure::do_oop(oop* p) { CMSInnerParMarkAndPushClosure::do_oop_work(p); } |
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8604 void CMSInnerParMarkAndPushClosure::do_oop(narrowOop* p) { CMSInnerParMarkAndPushClosure::do_oop_work(p); } |
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8605 |
| 0 | 8606 ////////////////////////////////////////////////////////////////// |
| 8607 // CMSExpansionCause ///////////////////////////// | |
| 8608 ////////////////////////////////////////////////////////////////// | |
| 8609 const char* CMSExpansionCause::to_string(CMSExpansionCause::Cause cause) { | |
| 8610 switch (cause) { | |
| 8611 case _no_expansion: | |
| 8612 return "No expansion"; | |
| 8613 case _satisfy_free_ratio: | |
| 8614 return "Free ratio"; | |
| 8615 case _satisfy_promotion: | |
| 8616 return "Satisfy promotion"; | |
| 8617 case _satisfy_allocation: | |
| 8618 return "allocation"; | |
| 8619 case _allocate_par_lab: | |
| 8620 return "Par LAB"; | |
| 8621 case _allocate_par_spooling_space: | |
| 8622 return "Par Spooling Space"; | |
| 8623 case _adaptive_size_policy: | |
| 8624 return "Ergonomics"; | |
| 8625 default: | |
| 8626 return "unknown"; | |
| 8627 } | |
| 8628 } | |
| 8629 | |
| 8630 void CMSDrainMarkingStackClosure::do_void() { | |
| 8631 // the max number to take from overflow list at a time | |
| 8632 const size_t num = _mark_stack->capacity()/4; | |
|
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8633 assert(!_concurrent_precleaning || _collector->overflow_list_is_empty(), |
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8634 "Overflow list should be NULL during concurrent phases"); |
| 0 | 8635 while (!_mark_stack->isEmpty() || |
| 8636 // if stack is empty, check the overflow list | |
| 8637 _collector->take_from_overflow_list(num, _mark_stack)) { | |
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8638 oop obj = _mark_stack->pop(); |
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8639 HeapWord* addr = (HeapWord*)obj; |
| 0 | 8640 assert(_span.contains(addr), "Should be within span"); |
| 8641 assert(_bit_map->isMarked(addr), "Should be marked"); | |
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8642 assert(obj->is_oop(), "Should be an oop"); |
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8643 obj->oop_iterate(_keep_alive); |
| 0 | 8644 } |
| 8645 } | |
| 8646 | |
| 8647 void CMSParDrainMarkingStackClosure::do_void() { | |
| 8648 // drain queue | |
| 8649 trim_queue(0); | |
| 8650 } | |
| 8651 | |
| 8652 // Trim our work_queue so its length is below max at return | |
| 8653 void CMSParDrainMarkingStackClosure::trim_queue(uint max) { | |
| 8654 while (_work_queue->size() > max) { | |
| 8655 oop new_oop; | |
| 8656 if (_work_queue->pop_local(new_oop)) { | |
| 8657 assert(new_oop->is_oop(), "Expected an oop"); | |
| 8658 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
| 8659 "no white objects on this stack!"); | |
| 8660 assert(_span.contains((HeapWord*)new_oop), "Out of bounds oop"); | |
| 8661 // iterate over the oops in this oop, marking and pushing | |
| 8662 // the ones in CMS heap (i.e. in _span). | |
| 8663 new_oop->oop_iterate(&_mark_and_push); | |
| 8664 } | |
| 8665 } | |
| 8666 } | |
| 8667 | |
| 8668 //////////////////////////////////////////////////////////////////// | |
| 8669 // Support for Marking Stack Overflow list handling and related code | |
| 8670 //////////////////////////////////////////////////////////////////// | |
| 8671 // Much of the following code is similar in shape and spirit to the | |
| 8672 // code used in ParNewGC. We should try and share that code | |
| 8673 // as much as possible in the future. | |
| 8674 | |
| 8675 #ifndef PRODUCT | |
| 8676 // Debugging support for CMSStackOverflowALot | |
| 8677 | |
| 8678 // It's OK to call this multi-threaded; the worst thing | |
| 8679 // that can happen is that we'll get a bunch of closely | |
| 8680 // spaced simulated oveflows, but that's OK, in fact | |
| 8681 // probably good as it would exercise the overflow code | |
| 8682 // under contention. | |
| 8683 bool CMSCollector::simulate_overflow() { | |
| 8684 if (_overflow_counter-- <= 0) { // just being defensive | |
| 8685 _overflow_counter = CMSMarkStackOverflowInterval; | |
| 8686 return true; | |
| 8687 } else { | |
| 8688 return false; | |
| 8689 } | |
| 8690 } | |
| 8691 | |
| 8692 bool CMSCollector::par_simulate_overflow() { | |
| 8693 return simulate_overflow(); | |
| 8694 } | |
| 8695 #endif | |
| 8696 | |
| 8697 // Single-threaded | |
| 8698 bool CMSCollector::take_from_overflow_list(size_t num, CMSMarkStack* stack) { | |
| 8699 assert(stack->isEmpty(), "Expected precondition"); | |
| 8700 assert(stack->capacity() > num, "Shouldn't bite more than can chew"); | |
| 8701 size_t i = num; | |
| 8702 oop cur = _overflow_list; | |
| 8703 const markOop proto = markOopDesc::prototype(); | |
| 534 | 8704 NOT_PRODUCT(ssize_t n = 0;) |
| 0 | 8705 for (oop next; i > 0 && cur != NULL; cur = next, i--) { |
| 8706 next = oop(cur->mark()); | |
| 8707 cur->set_mark(proto); // until proven otherwise | |
| 8708 assert(cur->is_oop(), "Should be an oop"); | |
| 8709 bool res = stack->push(cur); | |
| 8710 assert(res, "Bit off more than can chew?"); | |
| 8711 NOT_PRODUCT(n++;) | |
| 8712 } | |
| 8713 _overflow_list = cur; | |
| 8714 #ifndef PRODUCT | |
| 8715 assert(_num_par_pushes >= n, "Too many pops?"); | |
| 8716 _num_par_pushes -=n; | |
| 8717 #endif | |
| 8718 return !stack->isEmpty(); | |
| 8719 } | |
| 8720 | |
| 534 | 8721 #define BUSY (oop(0x1aff1aff)) |
| 8722 // (MT-safe) Get a prefix of at most "num" from the list. | |
| 8723 // The overflow list is chained through the mark word of | |
| 8724 // each object in the list. We fetch the entire list, | |
| 8725 // break off a prefix of the right size and return the | |
| 8726 // remainder. If other threads try to take objects from | |
| 8727 // the overflow list at that time, they will wait for | |
| 8728 // some time to see if data becomes available. If (and | |
| 8729 // only if) another thread places one or more object(s) | |
| 8730 // on the global list before we have returned the suffix | |
| 8731 // to the global list, we will walk down our local list | |
| 8732 // to find its end and append the global list to | |
| 8733 // our suffix before returning it. This suffix walk can | |
| 8734 // prove to be expensive (quadratic in the amount of traffic) | |
| 8735 // when there are many objects in the overflow list and | |
| 8736 // there is much producer-consumer contention on the list. | |
| 8737 // *NOTE*: The overflow list manipulation code here and | |
| 8738 // in ParNewGeneration:: are very similar in shape, | |
| 8739 // except that in the ParNew case we use the old (from/eden) | |
| 8740 // copy of the object to thread the list via its klass word. | |
| 8741 // Because of the common code, if you make any changes in | |
| 8742 // the code below, please check the ParNew version to see if | |
| 8743 // similar changes might be needed. | |
| 8744 // CR 6797058 has been filed to consolidate the common code. | |
| 0 | 8745 bool CMSCollector::par_take_from_overflow_list(size_t num, |
|
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8746 OopTaskQueue* work_q, |
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8747 int no_of_gc_threads) { |
| 534 | 8748 assert(work_q->size() == 0, "First empty local work queue"); |
| 0 | 8749 assert(num < work_q->max_elems(), "Can't bite more than we can chew"); |
| 8750 if (_overflow_list == NULL) { | |
| 8751 return false; | |
| 8752 } | |
| 8753 // Grab the entire list; we'll put back a suffix | |
| 534 | 8754 oop prefix = (oop)Atomic::xchg_ptr(BUSY, &_overflow_list); |
| 8755 Thread* tid = Thread::current(); | |
|
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8756 // Before "no_of_gc_threads" was introduced CMSOverflowSpinCount was |
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8757 // set to ParallelGCThreads. |
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8758 size_t CMSOverflowSpinCount = (size_t) no_of_gc_threads; // was ParallelGCThreads; |
| 534 | 8759 size_t sleep_time_millis = MAX2((size_t)1, num/100); |
| 8760 // If the list is busy, we spin for a short while, | |
| 8761 // sleeping between attempts to get the list. | |
| 8762 for (size_t spin = 0; prefix == BUSY && spin < CMSOverflowSpinCount; spin++) { | |
| 8763 os::sleep(tid, sleep_time_millis, false); | |
| 8764 if (_overflow_list == NULL) { | |
| 8765 // Nothing left to take | |
| 8766 return false; | |
| 8767 } else if (_overflow_list != BUSY) { | |
| 8768 // Try and grab the prefix | |
| 8769 prefix = (oop)Atomic::xchg_ptr(BUSY, &_overflow_list); | |
| 8770 } | |
| 8771 } | |
| 8772 // If the list was found to be empty, or we spun long | |
| 8773 // enough, we give up and return empty-handed. If we leave | |
| 8774 // the list in the BUSY state below, it must be the case that | |
| 8775 // some other thread holds the overflow list and will set it | |
| 8776 // to a non-BUSY state in the future. | |
| 8777 if (prefix == NULL || prefix == BUSY) { | |
| 8778 // Nothing to take or waited long enough | |
| 8779 if (prefix == NULL) { | |
| 8780 // Write back the NULL in case we overwrote it with BUSY above | |
| 8781 // and it is still the same value. | |
| 8782 (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY); | |
| 8783 } | |
| 8784 return false; | |
| 8785 } | |
| 8786 assert(prefix != NULL && prefix != BUSY, "Error"); | |
| 0 | 8787 size_t i = num; |
| 8788 oop cur = prefix; | |
| 534 | 8789 // Walk down the first "num" objects, unless we reach the end. |
| 0 | 8790 for (; i > 1 && cur->mark() != NULL; cur = oop(cur->mark()), i--); |
| 534 | 8791 if (cur->mark() == NULL) { |
| 8792 // We have "num" or fewer elements in the list, so there | |
| 8793 // is nothing to return to the global list. | |
| 8794 // Write back the NULL in lieu of the BUSY we wrote | |
| 8795 // above, if it is still the same value. | |
| 8796 if (_overflow_list == BUSY) { | |
| 8797 (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY); | |
| 8798 } | |
| 8799 } else { | |
| 8800 // Chop off the suffix and rerturn it to the global list. | |
| 8801 assert(cur->mark() != BUSY, "Error"); | |
| 0 | 8802 oop suffix_head = cur->mark(); // suffix will be put back on global list |
| 8803 cur->set_mark(NULL); // break off suffix | |
| 534 | 8804 // It's possible that the list is still in the empty(busy) state |
| 8805 // we left it in a short while ago; in that case we may be | |
| 8806 // able to place back the suffix without incurring the cost | |
| 8807 // of a walk down the list. | |
| 0 | 8808 oop observed_overflow_list = _overflow_list; |
| 534 | 8809 oop cur_overflow_list = observed_overflow_list; |
| 8810 bool attached = false; | |
| 8811 while (observed_overflow_list == BUSY || observed_overflow_list == NULL) { | |
| 0 | 8812 observed_overflow_list = |
| 534 | 8813 (oop) Atomic::cmpxchg_ptr(suffix_head, &_overflow_list, cur_overflow_list); |
| 8814 if (cur_overflow_list == observed_overflow_list) { | |
| 8815 attached = true; | |
| 8816 break; | |
| 8817 } else cur_overflow_list = observed_overflow_list; | |
| 8818 } | |
| 8819 if (!attached) { | |
| 8820 // Too bad, someone else sneaked in (at least) an element; we'll need | |
| 8821 // to do a splice. Find tail of suffix so we can prepend suffix to global | |
| 8822 // list. | |
| 8823 for (cur = suffix_head; cur->mark() != NULL; cur = (oop)(cur->mark())); | |
| 8824 oop suffix_tail = cur; | |
| 8825 assert(suffix_tail != NULL && suffix_tail->mark() == NULL, | |
| 8826 "Tautology"); | |
| 8827 observed_overflow_list = _overflow_list; | |
| 8828 do { | |
| 8829 cur_overflow_list = observed_overflow_list; | |
| 8830 if (cur_overflow_list != BUSY) { | |
| 8831 // Do the splice ... | |
| 8832 suffix_tail->set_mark(markOop(cur_overflow_list)); | |
| 8833 } else { // cur_overflow_list == BUSY | |
| 8834 suffix_tail->set_mark(NULL); | |
| 8835 } | |
| 8836 // ... and try to place spliced list back on overflow_list ... | |
| 8837 observed_overflow_list = | |
| 8838 (oop) Atomic::cmpxchg_ptr(suffix_head, &_overflow_list, cur_overflow_list); | |
| 8839 } while (cur_overflow_list != observed_overflow_list); | |
| 8840 // ... until we have succeeded in doing so. | |
| 8841 } | |
| 0 | 8842 } |
| 8843 | |
| 8844 // Push the prefix elements on work_q | |
| 8845 assert(prefix != NULL, "control point invariant"); | |
| 8846 const markOop proto = markOopDesc::prototype(); | |
| 8847 oop next; | |
| 534 | 8848 NOT_PRODUCT(ssize_t n = 0;) |
| 0 | 8849 for (cur = prefix; cur != NULL; cur = next) { |
| 8850 next = oop(cur->mark()); | |
| 8851 cur->set_mark(proto); // until proven otherwise | |
| 8852 assert(cur->is_oop(), "Should be an oop"); | |
| 8853 bool res = work_q->push(cur); | |
| 8854 assert(res, "Bit off more than we can chew?"); | |
| 8855 NOT_PRODUCT(n++;) | |
| 8856 } | |
| 8857 #ifndef PRODUCT | |
| 8858 assert(_num_par_pushes >= n, "Too many pops?"); | |
| 8859 Atomic::add_ptr(-(intptr_t)n, &_num_par_pushes); | |
| 8860 #endif | |
| 8861 return true; | |
| 8862 } | |
| 8863 | |
| 8864 // Single-threaded | |
| 8865 void CMSCollector::push_on_overflow_list(oop p) { | |
| 8866 NOT_PRODUCT(_num_par_pushes++;) | |
| 8867 assert(p->is_oop(), "Not an oop"); | |
| 8868 preserve_mark_if_necessary(p); | |
| 8869 p->set_mark((markOop)_overflow_list); | |
| 8870 _overflow_list = p; | |
| 8871 } | |
| 8872 | |
| 8873 // Multi-threaded; use CAS to prepend to overflow list | |
| 8874 void CMSCollector::par_push_on_overflow_list(oop p) { | |
| 8875 NOT_PRODUCT(Atomic::inc_ptr(&_num_par_pushes);) | |
| 8876 assert(p->is_oop(), "Not an oop"); | |
| 8877 par_preserve_mark_if_necessary(p); | |
| 8878 oop observed_overflow_list = _overflow_list; | |
| 8879 oop cur_overflow_list; | |
| 8880 do { | |
| 8881 cur_overflow_list = observed_overflow_list; | |
| 534 | 8882 if (cur_overflow_list != BUSY) { |
| 8883 p->set_mark(markOop(cur_overflow_list)); | |
| 8884 } else { | |
| 8885 p->set_mark(NULL); | |
| 8886 } | |
| 0 | 8887 observed_overflow_list = |
| 8888 (oop) Atomic::cmpxchg_ptr(p, &_overflow_list, cur_overflow_list); | |
| 8889 } while (cur_overflow_list != observed_overflow_list); | |
| 8890 } | |
| 534 | 8891 #undef BUSY |
| 0 | 8892 |
| 8893 // Single threaded | |
| 8894 // General Note on GrowableArray: pushes may silently fail | |
| 8895 // because we are (temporarily) out of C-heap for expanding | |
| 8896 // the stack. The problem is quite ubiquitous and affects | |
| 8897 // a lot of code in the JVM. The prudent thing for GrowableArray | |
| 8898 // to do (for now) is to exit with an error. However, that may | |
| 8899 // be too draconian in some cases because the caller may be | |
| 534 | 8900 // able to recover without much harm. For such cases, we |
| 0 | 8901 // should probably introduce a "soft_push" method which returns |
| 8902 // an indication of success or failure with the assumption that | |
| 8903 // the caller may be able to recover from a failure; code in | |
| 8904 // the VM can then be changed, incrementally, to deal with such | |
| 8905 // failures where possible, thus, incrementally hardening the VM | |
| 8906 // in such low resource situations. | |
| 8907 void CMSCollector::preserve_mark_work(oop p, markOop m) { | |
|
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8908 _preserved_oop_stack.push(p); |
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8909 _preserved_mark_stack.push(m); |
| 0 | 8910 assert(m == p->mark(), "Mark word changed"); |
|
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8911 assert(_preserved_oop_stack.size() == _preserved_mark_stack.size(), |
| 0 | 8912 "bijection"); |
| 8913 } | |
| 8914 | |
| 8915 // Single threaded | |
| 8916 void CMSCollector::preserve_mark_if_necessary(oop p) { | |
| 8917 markOop m = p->mark(); | |
| 8918 if (m->must_be_preserved(p)) { | |
| 8919 preserve_mark_work(p, m); | |
| 8920 } | |
| 8921 } | |
| 8922 | |
| 8923 void CMSCollector::par_preserve_mark_if_necessary(oop p) { | |
| 8924 markOop m = p->mark(); | |
| 8925 if (m->must_be_preserved(p)) { | |
| 8926 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); | |
| 8927 // Even though we read the mark word without holding | |
| 8928 // the lock, we are assured that it will not change | |
| 8929 // because we "own" this oop, so no other thread can | |
| 8930 // be trying to push it on the overflow list; see | |
| 8931 // the assertion in preserve_mark_work() that checks | |
| 8932 // that m == p->mark(). | |
| 8933 preserve_mark_work(p, m); | |
| 8934 } | |
| 8935 } | |
| 8936 | |
| 8937 // We should be able to do this multi-threaded, | |
| 8938 // a chunk of stack being a task (this is | |
| 8939 // correct because each oop only ever appears | |
| 8940 // once in the overflow list. However, it's | |
| 8941 // not very easy to completely overlap this with | |
| 8942 // other operations, so will generally not be done | |
| 8943 // until all work's been completed. Because we | |
| 8944 // expect the preserved oop stack (set) to be small, | |
| 8945 // it's probably fine to do this single-threaded. | |
| 8946 // We can explore cleverer concurrent/overlapped/parallel | |
| 8947 // processing of preserved marks if we feel the | |
| 8948 // need for this in the future. Stack overflow should | |
| 8949 // be so rare in practice and, when it happens, its | |
| 8950 // effect on performance so great that this will | |
| 8951 // likely just be in the noise anyway. | |
| 8952 void CMSCollector::restore_preserved_marks_if_any() { | |
| 8953 assert(SafepointSynchronize::is_at_safepoint(), | |
| 8954 "world should be stopped"); | |
| 8955 assert(Thread::current()->is_ConcurrentGC_thread() || | |
| 8956 Thread::current()->is_VM_thread(), | |
| 8957 "should be single-threaded"); | |
|
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8958 assert(_preserved_oop_stack.size() == _preserved_mark_stack.size(), |
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8959 "bijection"); |
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8960 |
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8961 while (!_preserved_oop_stack.is_empty()) { |
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8962 oop p = _preserved_oop_stack.pop(); |
| 0 | 8963 assert(p->is_oop(), "Should be an oop"); |
| 8964 assert(_span.contains(p), "oop should be in _span"); | |
| 8965 assert(p->mark() == markOopDesc::prototype(), | |
| 8966 "Set when taken from overflow list"); | |
|
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8967 markOop m = _preserved_mark_stack.pop(); |
| 0 | 8968 p->set_mark(m); |
| 8969 } | |
|
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8970 assert(_preserved_mark_stack.is_empty() && _preserved_oop_stack.is_empty(), |
| 0 | 8971 "stacks were cleared above"); |
| 8972 } | |
| 8973 | |
| 8974 #ifndef PRODUCT | |
| 8975 bool CMSCollector::no_preserved_marks() const { | |
|
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8976 return _preserved_mark_stack.is_empty() && _preserved_oop_stack.is_empty(); |
| 0 | 8977 } |
| 8978 #endif | |
| 8979 | |
| 8980 CMSAdaptiveSizePolicy* ASConcurrentMarkSweepGeneration::cms_size_policy() const | |
| 8981 { | |
| 8982 GenCollectedHeap* gch = (GenCollectedHeap*) GenCollectedHeap::heap(); | |
| 8983 CMSAdaptiveSizePolicy* size_policy = | |
| 8984 (CMSAdaptiveSizePolicy*) gch->gen_policy()->size_policy(); | |
| 8985 assert(size_policy->is_gc_cms_adaptive_size_policy(), | |
| 8986 "Wrong type for size policy"); | |
| 8987 return size_policy; | |
| 8988 } | |
| 8989 | |
| 8990 void ASConcurrentMarkSweepGeneration::resize(size_t cur_promo_size, | |
| 8991 size_t desired_promo_size) { | |
| 8992 if (cur_promo_size < desired_promo_size) { | |
| 8993 size_t expand_bytes = desired_promo_size - cur_promo_size; | |
| 8994 if (PrintAdaptiveSizePolicy && Verbose) { | |
| 8995 gclog_or_tty->print_cr(" ASConcurrentMarkSweepGeneration::resize " | |
| 8996 "Expanding tenured generation by " SIZE_FORMAT " (bytes)", | |
| 8997 expand_bytes); | |
| 8998 } | |
| 8999 expand(expand_bytes, | |
| 9000 MinHeapDeltaBytes, | |
| 9001 CMSExpansionCause::_adaptive_size_policy); | |
| 9002 } else if (desired_promo_size < cur_promo_size) { | |
| 9003 size_t shrink_bytes = cur_promo_size - desired_promo_size; | |
| 9004 if (PrintAdaptiveSizePolicy && Verbose) { | |
| 9005 gclog_or_tty->print_cr(" ASConcurrentMarkSweepGeneration::resize " | |
| 9006 "Shrinking tenured generation by " SIZE_FORMAT " (bytes)", | |
| 9007 shrink_bytes); | |
| 9008 } | |
| 9009 shrink(shrink_bytes); | |
| 9010 } | |
| 9011 } | |
| 9012 | |
| 9013 CMSGCAdaptivePolicyCounters* ASConcurrentMarkSweepGeneration::gc_adaptive_policy_counters() { | |
| 9014 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 9015 CMSGCAdaptivePolicyCounters* counters = | |
| 9016 (CMSGCAdaptivePolicyCounters*) gch->collector_policy()->counters(); | |
| 9017 assert(counters->kind() == GCPolicyCounters::CMSGCAdaptivePolicyCountersKind, | |
| 9018 "Wrong kind of counters"); | |
| 9019 return counters; | |
| 9020 } | |
| 9021 | |
| 9022 | |
| 9023 void ASConcurrentMarkSweepGeneration::update_counters() { | |
| 9024 if (UsePerfData) { | |
| 9025 _space_counters->update_all(); | |
| 9026 _gen_counters->update_all(); | |
| 9027 CMSGCAdaptivePolicyCounters* counters = gc_adaptive_policy_counters(); | |
| 9028 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 9029 CMSGCStats* gc_stats_l = (CMSGCStats*) gc_stats(); | |
| 9030 assert(gc_stats_l->kind() == GCStats::CMSGCStatsKind, | |
| 9031 "Wrong gc statistics type"); | |
| 9032 counters->update_counters(gc_stats_l); | |
| 9033 } | |
| 9034 } | |
| 9035 | |
| 9036 void ASConcurrentMarkSweepGeneration::update_counters(size_t used) { | |
| 9037 if (UsePerfData) { | |
| 9038 _space_counters->update_used(used); | |
| 9039 _space_counters->update_capacity(); | |
| 9040 _gen_counters->update_all(); | |
| 9041 | |
| 9042 CMSGCAdaptivePolicyCounters* counters = gc_adaptive_policy_counters(); | |
| 9043 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 9044 CMSGCStats* gc_stats_l = (CMSGCStats*) gc_stats(); | |
| 9045 assert(gc_stats_l->kind() == GCStats::CMSGCStatsKind, | |
| 9046 "Wrong gc statistics type"); | |
| 9047 counters->update_counters(gc_stats_l); | |
| 9048 } | |
| 9049 } | |
| 9050 | |
| 9051 // The desired expansion delta is computed so that: | |
| 9052 // . desired free percentage or greater is used | |
| 9053 void ASConcurrentMarkSweepGeneration::compute_new_size() { | |
| 9054 assert_locked_or_safepoint(Heap_lock); | |
| 9055 | |
| 9056 GenCollectedHeap* gch = (GenCollectedHeap*) GenCollectedHeap::heap(); | |
| 9057 | |
| 9058 // If incremental collection failed, we just want to expand | |
| 9059 // to the limit. | |
| 9060 if (incremental_collection_failed()) { | |
| 9061 clear_incremental_collection_failed(); | |
| 9062 grow_to_reserved(); | |
| 9063 return; | |
| 9064 } | |
| 9065 | |
| 9066 assert(UseAdaptiveSizePolicy, "Should be using adaptive sizing"); | |
| 9067 | |
| 9068 assert(gch->kind() == CollectedHeap::GenCollectedHeap, | |
| 9069 "Wrong type of heap"); | |
| 9070 int prev_level = level() - 1; | |
| 9071 assert(prev_level >= 0, "The cms generation is the lowest generation"); | |
| 9072 Generation* prev_gen = gch->get_gen(prev_level); | |
| 9073 assert(prev_gen->kind() == Generation::ASParNew, | |
| 9074 "Wrong type of young generation"); | |
| 9075 ParNewGeneration* younger_gen = (ParNewGeneration*) prev_gen; | |
| 9076 size_t cur_eden = younger_gen->eden()->capacity(); | |
| 9077 CMSAdaptiveSizePolicy* size_policy = cms_size_policy(); | |
| 9078 size_t cur_promo = free(); | |
| 9079 size_policy->compute_tenured_generation_free_space(cur_promo, | |
| 9080 max_available(), | |
| 9081 cur_eden); | |
| 9082 resize(cur_promo, size_policy->promo_size()); | |
| 9083 | |
| 9084 // Record the new size of the space in the cms generation | |
| 9085 // that is available for promotions. This is temporary. | |
| 9086 // It should be the desired promo size. | |
| 9087 size_policy->avg_cms_promo()->sample(free()); | |
| 9088 size_policy->avg_old_live()->sample(used()); | |
| 9089 | |
| 9090 if (UsePerfData) { | |
| 9091 CMSGCAdaptivePolicyCounters* counters = gc_adaptive_policy_counters(); | |
| 9092 counters->update_cms_capacity_counter(capacity()); | |
| 9093 } | |
| 9094 } | |
| 9095 | |
| 9096 void ASConcurrentMarkSweepGeneration::shrink_by(size_t desired_bytes) { | |
| 9097 assert_locked_or_safepoint(Heap_lock); | |
| 9098 assert_lock_strong(freelistLock()); | |
| 9099 HeapWord* old_end = _cmsSpace->end(); | |
| 9100 HeapWord* unallocated_start = _cmsSpace->unallocated_block(); | |
| 9101 assert(old_end >= unallocated_start, "Miscalculation of unallocated_start"); | |
| 9102 FreeChunk* chunk_at_end = find_chunk_at_end(); | |
| 9103 if (chunk_at_end == NULL) { | |
| 9104 // No room to shrink | |
| 9105 if (PrintGCDetails && Verbose) { | |
| 9106 gclog_or_tty->print_cr("No room to shrink: old_end " | |
| 9107 PTR_FORMAT " unallocated_start " PTR_FORMAT | |
| 9108 " chunk_at_end " PTR_FORMAT, | |
| 9109 old_end, unallocated_start, chunk_at_end); | |
| 9110 } | |
| 9111 return; | |
| 9112 } else { | |
| 9113 | |
| 9114 // Find the chunk at the end of the space and determine | |
| 9115 // how much it can be shrunk. | |
| 9116 size_t shrinkable_size_in_bytes = chunk_at_end->size(); | |
| 9117 size_t aligned_shrinkable_size_in_bytes = | |
| 9118 align_size_down(shrinkable_size_in_bytes, os::vm_page_size()); | |
| 9119 assert(unallocated_start <= chunk_at_end->end(), | |
| 9120 "Inconsistent chunk at end of space"); | |
| 9121 size_t bytes = MIN2(desired_bytes, aligned_shrinkable_size_in_bytes); | |
| 9122 size_t word_size_before = heap_word_size(_virtual_space.committed_size()); | |
| 9123 | |
| 9124 // Shrink the underlying space | |
| 9125 _virtual_space.shrink_by(bytes); | |
| 9126 if (PrintGCDetails && Verbose) { | |
| 9127 gclog_or_tty->print_cr("ConcurrentMarkSweepGeneration::shrink_by:" | |
| 9128 " desired_bytes " SIZE_FORMAT | |
| 9129 " shrinkable_size_in_bytes " SIZE_FORMAT | |
| 9130 " aligned_shrinkable_size_in_bytes " SIZE_FORMAT | |
| 9131 " bytes " SIZE_FORMAT, | |
| 9132 desired_bytes, shrinkable_size_in_bytes, | |
| 9133 aligned_shrinkable_size_in_bytes, bytes); | |
| 9134 gclog_or_tty->print_cr(" old_end " SIZE_FORMAT | |
| 9135 " unallocated_start " SIZE_FORMAT, | |
| 9136 old_end, unallocated_start); | |
| 9137 } | |
| 9138 | |
| 9139 // If the space did shrink (shrinking is not guaranteed), | |
| 9140 // shrink the chunk at the end by the appropriate amount. | |
| 9141 if (((HeapWord*)_virtual_space.high()) < old_end) { | |
| 9142 size_t new_word_size = | |
| 9143 heap_word_size(_virtual_space.committed_size()); | |
| 9144 | |
| 9145 // Have to remove the chunk from the dictionary because it is changing | |
| 9146 // size and might be someplace elsewhere in the dictionary. | |
| 9147 | |
| 9148 // Get the chunk at end, shrink it, and put it | |
| 9149 // back. | |
| 9150 _cmsSpace->removeChunkFromDictionary(chunk_at_end); | |
| 9151 size_t word_size_change = word_size_before - new_word_size; | |
| 9152 size_t chunk_at_end_old_size = chunk_at_end->size(); | |
| 9153 assert(chunk_at_end_old_size >= word_size_change, | |
| 9154 "Shrink is too large"); | |
| 9155 chunk_at_end->setSize(chunk_at_end_old_size - | |
| 9156 word_size_change); | |
| 9157 _cmsSpace->freed((HeapWord*) chunk_at_end->end(), | |
| 9158 word_size_change); | |
| 9159 | |
| 9160 _cmsSpace->returnChunkToDictionary(chunk_at_end); | |
| 9161 | |
| 9162 MemRegion mr(_cmsSpace->bottom(), new_word_size); | |
| 9163 _bts->resize(new_word_size); // resize the block offset shared array | |
| 9164 Universe::heap()->barrier_set()->resize_covered_region(mr); | |
| 9165 _cmsSpace->assert_locked(); | |
| 9166 _cmsSpace->set_end((HeapWord*)_virtual_space.high()); | |
| 9167 | |
| 9168 NOT_PRODUCT(_cmsSpace->dictionary()->verify()); | |
| 9169 | |
| 9170 // update the space and generation capacity counters | |
| 9171 if (UsePerfData) { | |
| 9172 _space_counters->update_capacity(); | |
| 9173 _gen_counters->update_all(); | |
| 9174 } | |
| 9175 | |
| 9176 if (Verbose && PrintGCDetails) { | |
| 9177 size_t new_mem_size = _virtual_space.committed_size(); | |
| 9178 size_t old_mem_size = new_mem_size + bytes; | |
| 9179 gclog_or_tty->print_cr("Shrinking %s from %ldK by %ldK to %ldK", | |
| 9180 name(), old_mem_size/K, bytes/K, new_mem_size/K); | |
| 9181 } | |
| 9182 } | |
| 9183 | |
| 9184 assert(_cmsSpace->unallocated_block() <= _cmsSpace->end(), | |
| 9185 "Inconsistency at end of space"); | |
| 9186 assert(chunk_at_end->end() == _cmsSpace->end(), | |
| 9187 "Shrinking is inconsistent"); | |
| 9188 return; | |
| 9189 } | |
| 9190 } | |
| 9191 | |
| 9192 // Transfer some number of overflown objects to usual marking | |
| 9193 // stack. Return true if some objects were transferred. | |
| 9194 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
|
9195 size_t num = MIN2((size_t)(_mark_stack->capacity() - _mark_stack->length())/4, |
| 0 | 9196 (size_t)ParGCDesiredObjsFromOverflowList); |
| 9197 | |
| 9198 bool res = _collector->take_from_overflow_list(num, _mark_stack); | |
| 9199 assert(_collector->overflow_list_is_empty() || res, | |
| 9200 "If list is not empty, we should have taken something"); | |
| 9201 assert(!res || !_mark_stack->isEmpty(), | |
| 9202 "If we took something, it should now be on our stack"); | |
| 9203 return res; | |
| 9204 } | |
| 9205 | |
| 9206 size_t MarkDeadObjectsClosure::do_blk(HeapWord* addr) { | |
| 9207 size_t res = _sp->block_size_no_stall(addr, _collector); | |
| 9208 assert(res != 0, "Should always be able to compute a size"); | |
| 9209 if (_sp->block_is_obj(addr)) { | |
| 9210 if (_live_bit_map->isMarked(addr)) { | |
| 9211 // It can't have been dead in a previous cycle | |
| 9212 guarantee(!_dead_bit_map->isMarked(addr), "No resurrection!"); | |
| 9213 } else { | |
| 9214 _dead_bit_map->mark(addr); // mark the dead object | |
| 9215 } | |
| 9216 } | |
| 9217 return res; | |
| 9218 } | |
|
1703
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9219 |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9220 TraceCMSMemoryManagerStats::TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase): TraceMemoryManagerStats() { |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9221 |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9222 switch (phase) { |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9223 case CMSCollector::InitialMarking: |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9224 initialize(true /* fullGC */ , |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9225 true /* recordGCBeginTime */, |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9226 true /* recordPreGCUsage */, |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9227 false /* recordPeakUsage */, |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9228 false /* recordPostGCusage */, |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9229 true /* recordAccumulatedGCTime */, |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9230 false /* recordGCEndTime */, |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9231 false /* countCollection */ ); |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9232 break; |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9233 |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9234 case CMSCollector::FinalMarking: |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9235 initialize(true /* fullGC */ , |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9236 false /* recordGCBeginTime */, |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9237 false /* recordPreGCUsage */, |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9238 false /* recordPeakUsage */, |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9239 false /* recordPostGCusage */, |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9240 true /* recordAccumulatedGCTime */, |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9241 false /* recordGCEndTime */, |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9242 false /* countCollection */ ); |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9243 break; |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9244 |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9245 case CMSCollector::Sweeping: |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9246 initialize(true /* fullGC */ , |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9247 false /* recordGCBeginTime */, |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9248 false /* recordPreGCUsage */, |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9249 true /* recordPeakUsage */, |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9250 true /* recordPostGCusage */, |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9251 false /* recordAccumulatedGCTime */, |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9252 true /* recordGCEndTime */, |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9253 true /* countCollection */ ); |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9254 break; |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9255 |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9256 default: |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9257 ShouldNotReachHere(); |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9258 } |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9259 } |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9260 |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9261 // when bailing out of cms in concurrent mode failure |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9262 TraceCMSMemoryManagerStats::TraceCMSMemoryManagerStats(): TraceMemoryManagerStats() { |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9263 initialize(true /* fullGC */ , |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9264 true /* recordGCBeginTime */, |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9265 true /* recordPreGCUsage */, |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9266 true /* recordPeakUsage */, |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9267 true /* recordPostGCusage */, |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9268 true /* recordAccumulatedGCTime */, |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9269 true /* recordGCEndTime */, |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9270 true /* countCollection */ ); |
|
f6f3eef8a521
6581734: CMS Old Gen's collection usage is zero after GC which is incorrect
kevinw
parents:
1579
diff
changeset
|
9271 } |