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annotate src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp @ 993:54b3b351d6f9
Merge
| author | jrose |
|---|---|
| date | Wed, 23 Sep 2009 23:56:15 -0700 |
| parents | 148e5441d916 8b46c4d82093 |
| children | 753cf9794df9 |
| rev | line source |
|---|---|
| 0 | 1 /* |
| 579 | 2 * Copyright 2001-2009 Sun Microsystems, Inc. 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 * | |
| 19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, | |
| 20 * CA 95054 USA or visit www.sun.com if you need additional information or | |
| 21 * have any questions. | |
| 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), | |
| 162 _dilatation_factor(((double)MinChunkSize)/((double)(oopDesc::header_size()))), | |
| 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 ) | |
| 198 if (ParallelGCThreads > 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. | |
| 225 assert(MinChunkSize >= oopDesc::header_size(), "just checking"); | |
| 226 assert(_dilatation_factor >= 1.0, "from previous assert"); | |
| 227 } | |
| 228 | |
|
94
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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 |
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256 |
| 0 | 257 void ConcurrentMarkSweepGeneration::ref_processor_init() { |
| 258 assert(collector() != NULL, "no collector"); | |
| 259 collector()->ref_processor_init(); | |
| 260 } | |
| 261 | |
| 262 void CMSCollector::ref_processor_init() { | |
| 263 if (_ref_processor == NULL) { | |
| 264 // Allocate and initialize a reference processor | |
| 265 _ref_processor = ReferenceProcessor::create_ref_processor( | |
| 266 _span, // span | |
| 267 _cmsGen->refs_discovery_is_atomic(), // atomic_discovery | |
| 268 _cmsGen->refs_discovery_is_mt(), // mt_discovery | |
| 269 &_is_alive_closure, | |
| 270 ParallelGCThreads, | |
| 271 ParallelRefProcEnabled); | |
| 272 // Initialize the _ref_processor field of CMSGen | |
| 273 _cmsGen->set_ref_processor(_ref_processor); | |
| 274 | |
| 275 // Allocate a dummy ref processor for perm gen. | |
| 276 ReferenceProcessor* rp2 = new ReferenceProcessor(); | |
| 277 if (rp2 == NULL) { | |
| 278 vm_exit_during_initialization("Could not allocate ReferenceProcessor object"); | |
| 279 } | |
| 280 _permGen->set_ref_processor(rp2); | |
| 281 } | |
| 282 } | |
| 283 | |
| 284 CMSAdaptiveSizePolicy* CMSCollector::size_policy() { | |
| 285 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 286 assert(gch->kind() == CollectedHeap::GenCollectedHeap, | |
| 287 "Wrong type of heap"); | |
| 288 CMSAdaptiveSizePolicy* sp = (CMSAdaptiveSizePolicy*) | |
| 289 gch->gen_policy()->size_policy(); | |
| 290 assert(sp->is_gc_cms_adaptive_size_policy(), | |
| 291 "Wrong type of size policy"); | |
| 292 return sp; | |
| 293 } | |
| 294 | |
| 295 CMSGCAdaptivePolicyCounters* CMSCollector::gc_adaptive_policy_counters() { | |
| 296 CMSGCAdaptivePolicyCounters* results = | |
| 297 (CMSGCAdaptivePolicyCounters*) collector_policy()->counters(); | |
| 298 assert( | |
| 299 results->kind() == GCPolicyCounters::CMSGCAdaptivePolicyCountersKind, | |
| 300 "Wrong gc policy counter kind"); | |
| 301 return results; | |
| 302 } | |
| 303 | |
| 304 | |
| 305 void ConcurrentMarkSweepGeneration::initialize_performance_counters() { | |
| 306 | |
| 307 const char* gen_name = "old"; | |
| 308 | |
| 309 // Generation Counters - generation 1, 1 subspace | |
| 310 _gen_counters = new GenerationCounters(gen_name, 1, 1, &_virtual_space); | |
| 311 | |
| 312 _space_counters = new GSpaceCounters(gen_name, 0, | |
| 313 _virtual_space.reserved_size(), | |
| 314 this, _gen_counters); | |
| 315 } | |
| 316 | |
| 317 CMSStats::CMSStats(ConcurrentMarkSweepGeneration* cms_gen, unsigned int alpha): | |
| 318 _cms_gen(cms_gen) | |
| 319 { | |
| 320 assert(alpha <= 100, "bad value"); | |
| 321 _saved_alpha = alpha; | |
| 322 | |
| 323 // Initialize the alphas to the bootstrap value of 100. | |
| 324 _gc0_alpha = _cms_alpha = 100; | |
| 325 | |
| 326 _cms_begin_time.update(); | |
| 327 _cms_end_time.update(); | |
| 328 | |
| 329 _gc0_duration = 0.0; | |
| 330 _gc0_period = 0.0; | |
| 331 _gc0_promoted = 0; | |
| 332 | |
| 333 _cms_duration = 0.0; | |
| 334 _cms_period = 0.0; | |
| 335 _cms_allocated = 0; | |
| 336 | |
| 337 _cms_used_at_gc0_begin = 0; | |
| 338 _cms_used_at_gc0_end = 0; | |
| 339 _allow_duty_cycle_reduction = false; | |
| 340 _valid_bits = 0; | |
| 341 _icms_duty_cycle = CMSIncrementalDutyCycle; | |
| 342 } | |
| 343 | |
| 344 // If promotion failure handling is on use | |
| 345 // the padded average size of the promotion for each | |
| 346 // young generation collection. | |
| 347 double CMSStats::time_until_cms_gen_full() const { | |
| 348 size_t cms_free = _cms_gen->cmsSpace()->free(); | |
| 349 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 350 size_t expected_promotion = gch->get_gen(0)->capacity(); | |
| 351 if (HandlePromotionFailure) { | |
| 352 expected_promotion = MIN2( | |
| 353 (size_t) _cms_gen->gc_stats()->avg_promoted()->padded_average(), | |
| 354 expected_promotion); | |
| 355 } | |
| 356 if (cms_free > expected_promotion) { | |
| 357 // Start a cms collection if there isn't enough space to promote | |
| 358 // for the next minor collection. Use the padded average as | |
| 359 // a safety factor. | |
| 360 cms_free -= expected_promotion; | |
| 361 | |
| 362 // Adjust by the safety factor. | |
| 363 double cms_free_dbl = (double)cms_free; | |
| 364 cms_free_dbl = cms_free_dbl * (100.0 - CMSIncrementalSafetyFactor) / 100.0; | |
| 365 | |
| 366 if (PrintGCDetails && Verbose) { | |
| 367 gclog_or_tty->print_cr("CMSStats::time_until_cms_gen_full: cms_free " | |
| 368 SIZE_FORMAT " expected_promotion " SIZE_FORMAT, | |
| 369 cms_free, expected_promotion); | |
| 370 gclog_or_tty->print_cr(" cms_free_dbl %f cms_consumption_rate %f", | |
| 371 cms_free_dbl, cms_consumption_rate() + 1.0); | |
| 372 } | |
| 373 // Add 1 in case the consumption rate goes to zero. | |
| 374 return cms_free_dbl / (cms_consumption_rate() + 1.0); | |
| 375 } | |
| 376 return 0.0; | |
| 377 } | |
| 378 | |
| 379 // Compare the duration of the cms collection to the | |
| 380 // time remaining before the cms generation is empty. | |
| 381 // Note that the time from the start of the cms collection | |
| 382 // to the start of the cms sweep (less than the total | |
| 383 // duration of the cms collection) can be used. This | |
| 384 // has been tried and some applications experienced | |
| 385 // promotion failures early in execution. This was | |
| 386 // possibly because the averages were not accurate | |
| 387 // enough at the beginning. | |
| 388 double CMSStats::time_until_cms_start() const { | |
| 389 // We add "gc0_period" to the "work" calculation | |
| 390 // below because this query is done (mostly) at the | |
| 391 // end of a scavenge, so we need to conservatively | |
| 392 // account for that much possible delay | |
| 393 // in the query so as to avoid concurrent mode failures | |
| 394 // due to starting the collection just a wee bit too | |
| 395 // late. | |
| 396 double work = cms_duration() + gc0_period(); | |
| 397 double deadline = time_until_cms_gen_full(); | |
| 398 if (work > deadline) { | |
| 399 if (Verbose && PrintGCDetails) { | |
| 400 gclog_or_tty->print( | |
| 401 " CMSCollector: collect because of anticipated promotion " | |
| 402 "before full %3.7f + %3.7f > %3.7f ", cms_duration(), | |
| 403 gc0_period(), time_until_cms_gen_full()); | |
| 404 } | |
| 405 return 0.0; | |
| 406 } | |
| 407 return work - deadline; | |
| 408 } | |
| 409 | |
| 410 // Return a duty cycle based on old_duty_cycle and new_duty_cycle, limiting the | |
| 411 // amount of change to prevent wild oscillation. | |
| 412 unsigned int CMSStats::icms_damped_duty_cycle(unsigned int old_duty_cycle, | |
| 413 unsigned int new_duty_cycle) { | |
| 414 assert(old_duty_cycle <= 100, "bad input value"); | |
| 415 assert(new_duty_cycle <= 100, "bad input value"); | |
| 416 | |
| 417 // Note: use subtraction with caution since it may underflow (values are | |
| 418 // unsigned). Addition is safe since we're in the range 0-100. | |
| 419 unsigned int damped_duty_cycle = new_duty_cycle; | |
| 420 if (new_duty_cycle < old_duty_cycle) { | |
| 421 const unsigned int largest_delta = MAX2(old_duty_cycle / 4, 5U); | |
| 422 if (new_duty_cycle + largest_delta < old_duty_cycle) { | |
| 423 damped_duty_cycle = old_duty_cycle - largest_delta; | |
| 424 } | |
| 425 } else if (new_duty_cycle > old_duty_cycle) { | |
| 426 const unsigned int largest_delta = MAX2(old_duty_cycle / 4, 15U); | |
| 427 if (new_duty_cycle > old_duty_cycle + largest_delta) { | |
| 428 damped_duty_cycle = MIN2(old_duty_cycle + largest_delta, 100U); | |
| 429 } | |
| 430 } | |
| 431 assert(damped_duty_cycle <= 100, "invalid duty cycle computed"); | |
| 432 | |
| 433 if (CMSTraceIncrementalPacing) { | |
| 434 gclog_or_tty->print(" [icms_damped_duty_cycle(%d,%d) = %d] ", | |
| 435 old_duty_cycle, new_duty_cycle, damped_duty_cycle); | |
| 436 } | |
| 437 return damped_duty_cycle; | |
| 438 } | |
| 439 | |
| 440 unsigned int CMSStats::icms_update_duty_cycle_impl() { | |
| 441 assert(CMSIncrementalPacing && valid(), | |
| 442 "should be handled in icms_update_duty_cycle()"); | |
| 443 | |
| 444 double cms_time_so_far = cms_timer().seconds(); | |
| 445 double scaled_duration = cms_duration_per_mb() * _cms_used_at_gc0_end / M; | |
| 446 double scaled_duration_remaining = fabsd(scaled_duration - cms_time_so_far); | |
| 447 | |
| 448 // Avoid division by 0. | |
| 449 double time_until_full = MAX2(time_until_cms_gen_full(), 0.01); | |
| 450 double duty_cycle_dbl = 100.0 * scaled_duration_remaining / time_until_full; | |
| 451 | |
| 452 unsigned int new_duty_cycle = MIN2((unsigned int)duty_cycle_dbl, 100U); | |
| 453 if (new_duty_cycle > _icms_duty_cycle) { | |
| 454 // Avoid very small duty cycles (1 or 2); 0 is allowed. | |
| 455 if (new_duty_cycle > 2) { | |
| 456 _icms_duty_cycle = icms_damped_duty_cycle(_icms_duty_cycle, | |
| 457 new_duty_cycle); | |
| 458 } | |
| 459 } else if (_allow_duty_cycle_reduction) { | |
| 460 // The duty cycle is reduced only once per cms cycle (see record_cms_end()). | |
| 461 new_duty_cycle = icms_damped_duty_cycle(_icms_duty_cycle, new_duty_cycle); | |
| 462 // Respect the minimum duty cycle. | |
| 463 unsigned int min_duty_cycle = (unsigned int)CMSIncrementalDutyCycleMin; | |
| 464 _icms_duty_cycle = MAX2(new_duty_cycle, min_duty_cycle); | |
| 465 } | |
| 466 | |
| 467 if (PrintGCDetails || CMSTraceIncrementalPacing) { | |
| 468 gclog_or_tty->print(" icms_dc=%d ", _icms_duty_cycle); | |
| 469 } | |
| 470 | |
| 471 _allow_duty_cycle_reduction = false; | |
| 472 return _icms_duty_cycle; | |
| 473 } | |
| 474 | |
| 475 #ifndef PRODUCT | |
| 476 void CMSStats::print_on(outputStream *st) const { | |
| 477 st->print(" gc0_alpha=%d,cms_alpha=%d", _gc0_alpha, _cms_alpha); | |
| 478 st->print(",gc0_dur=%g,gc0_per=%g,gc0_promo=" SIZE_FORMAT, | |
| 479 gc0_duration(), gc0_period(), gc0_promoted()); | |
| 480 st->print(",cms_dur=%g,cms_dur_per_mb=%g,cms_per=%g,cms_alloc=" SIZE_FORMAT, | |
| 481 cms_duration(), cms_duration_per_mb(), | |
| 482 cms_period(), cms_allocated()); | |
| 483 st->print(",cms_since_beg=%g,cms_since_end=%g", | |
| 484 cms_time_since_begin(), cms_time_since_end()); | |
| 485 st->print(",cms_used_beg=" SIZE_FORMAT ",cms_used_end=" SIZE_FORMAT, | |
| 486 _cms_used_at_gc0_begin, _cms_used_at_gc0_end); | |
| 487 if (CMSIncrementalMode) { | |
| 488 st->print(",dc=%d", icms_duty_cycle()); | |
| 489 } | |
| 490 | |
| 491 if (valid()) { | |
| 492 st->print(",promo_rate=%g,cms_alloc_rate=%g", | |
| 493 promotion_rate(), cms_allocation_rate()); | |
| 494 st->print(",cms_consumption_rate=%g,time_until_full=%g", | |
| 495 cms_consumption_rate(), time_until_cms_gen_full()); | |
| 496 } | |
| 497 st->print(" "); | |
| 498 } | |
| 499 #endif // #ifndef PRODUCT | |
| 500 | |
| 501 CMSCollector::CollectorState CMSCollector::_collectorState = | |
| 502 CMSCollector::Idling; | |
| 503 bool CMSCollector::_foregroundGCIsActive = false; | |
| 504 bool CMSCollector::_foregroundGCShouldWait = false; | |
| 505 | |
| 506 CMSCollector::CMSCollector(ConcurrentMarkSweepGeneration* cmsGen, | |
| 507 ConcurrentMarkSweepGeneration* permGen, | |
| 508 CardTableRS* ct, | |
| 509 ConcurrentMarkSweepPolicy* cp): | |
| 510 _cmsGen(cmsGen), | |
| 511 _permGen(permGen), | |
| 512 _ct(ct), | |
| 513 _ref_processor(NULL), // will be set later | |
| 514 _conc_workers(NULL), // may be set later | |
| 515 _abort_preclean(false), | |
| 516 _start_sampling(false), | |
| 517 _between_prologue_and_epilogue(false), | |
| 518 _markBitMap(0, Mutex::leaf + 1, "CMS_markBitMap_lock"), | |
| 519 _perm_gen_verify_bit_map(0, -1 /* no mutex */, "No_lock"), | |
| 520 _modUnionTable((CardTableModRefBS::card_shift - LogHeapWordSize), | |
| 521 -1 /* lock-free */, "No_lock" /* dummy */), | |
| 522 _modUnionClosure(&_modUnionTable), | |
| 523 _modUnionClosurePar(&_modUnionTable), | |
|
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524 // Adjust my span to cover old (cms) gen and perm gen |
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525 _span(cmsGen->reserved()._union(permGen->reserved())), |
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526 // Construct the is_alive_closure with _span & markBitMap |
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527 _is_alive_closure(_span, &_markBitMap), |
| 0 | 528 _restart_addr(NULL), |
| 529 _overflow_list(NULL), | |
| 530 _preserved_oop_stack(NULL), | |
| 531 _preserved_mark_stack(NULL), | |
| 532 _stats(cmsGen), | |
| 533 _eden_chunk_array(NULL), // may be set in ctor body | |
| 534 _eden_chunk_capacity(0), // -- ditto -- | |
| 535 _eden_chunk_index(0), // -- ditto -- | |
| 536 _survivor_plab_array(NULL), // -- ditto -- | |
| 537 _survivor_chunk_array(NULL), // -- ditto -- | |
| 538 _survivor_chunk_capacity(0), // -- ditto -- | |
| 539 _survivor_chunk_index(0), // -- ditto -- | |
| 540 _ser_pmc_preclean_ovflw(0), | |
|
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541 _ser_kac_preclean_ovflw(0), |
| 0 | 542 _ser_pmc_remark_ovflw(0), |
| 543 _par_pmc_remark_ovflw(0), | |
| 544 _ser_kac_ovflw(0), | |
| 545 _par_kac_ovflw(0), | |
| 546 #ifndef PRODUCT | |
| 547 _num_par_pushes(0), | |
| 548 #endif | |
| 549 _collection_count_start(0), | |
| 550 _verifying(false), | |
| 551 _icms_start_limit(NULL), | |
| 552 _icms_stop_limit(NULL), | |
| 553 _verification_mark_bm(0, Mutex::leaf + 1, "CMS_verification_mark_bm_lock"), | |
| 554 _completed_initialization(false), | |
| 555 _collector_policy(cp), | |
|
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556 _should_unload_classes(false), |
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557 _concurrent_cycles_since_last_unload(0), |
|
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558 _roots_scanning_options(0), |
| 0 | 559 _sweep_estimate(CMS_SweepWeight, CMS_SweepPadding) |
| 560 { | |
| 561 if (ExplicitGCInvokesConcurrentAndUnloadsClasses) { | |
| 562 ExplicitGCInvokesConcurrent = true; | |
| 563 } | |
| 564 // Now expand the span and allocate the collection support structures | |
| 565 // (MUT, marking bit map etc.) to cover both generations subject to | |
| 566 // collection. | |
| 567 | |
| 568 // First check that _permGen is adjacent to _cmsGen and above it. | |
| 569 assert( _cmsGen->reserved().word_size() > 0 | |
| 570 && _permGen->reserved().word_size() > 0, | |
| 571 "generations should not be of zero size"); | |
| 572 assert(_cmsGen->reserved().intersection(_permGen->reserved()).is_empty(), | |
| 573 "_cmsGen and _permGen should not overlap"); | |
| 574 assert(_cmsGen->reserved().end() == _permGen->reserved().start(), | |
| 575 "_cmsGen->end() different from _permGen->start()"); | |
| 576 | |
| 577 // For use by dirty card to oop closures. | |
| 578 _cmsGen->cmsSpace()->set_collector(this); | |
| 579 _permGen->cmsSpace()->set_collector(this); | |
| 580 | |
| 581 // Allocate MUT and marking bit map | |
| 582 { | |
| 583 MutexLockerEx x(_markBitMap.lock(), Mutex::_no_safepoint_check_flag); | |
| 584 if (!_markBitMap.allocate(_span)) { | |
| 585 warning("Failed to allocate CMS Bit Map"); | |
| 586 return; | |
| 587 } | |
| 588 assert(_markBitMap.covers(_span), "_markBitMap inconsistency?"); | |
| 589 } | |
| 590 { | |
| 591 _modUnionTable.allocate(_span); | |
| 592 assert(_modUnionTable.covers(_span), "_modUnionTable inconsistency?"); | |
| 593 } | |
| 594 | |
| 595 if (!_markStack.allocate(CMSMarkStackSize)) { | |
| 596 warning("Failed to allocate CMS Marking Stack"); | |
| 597 return; | |
| 598 } | |
| 599 if (!_revisitStack.allocate(CMSRevisitStackSize)) { | |
| 600 warning("Failed to allocate CMS Revisit Stack"); | |
| 601 return; | |
| 602 } | |
| 603 | |
| 604 // Support for multi-threaded concurrent phases | |
| 605 if (ParallelGCThreads > 0 && CMSConcurrentMTEnabled) { | |
| 606 if (FLAG_IS_DEFAULT(ParallelCMSThreads)) { | |
| 607 // just for now | |
| 608 FLAG_SET_DEFAULT(ParallelCMSThreads, (ParallelGCThreads + 3)/4); | |
| 609 } | |
| 610 if (ParallelCMSThreads > 1) { | |
| 611 _conc_workers = new YieldingFlexibleWorkGang("Parallel CMS Threads", | |
| 612 ParallelCMSThreads, true); | |
| 613 if (_conc_workers == NULL) { | |
| 614 warning("GC/CMS: _conc_workers allocation failure: " | |
| 615 "forcing -CMSConcurrentMTEnabled"); | |
| 616 CMSConcurrentMTEnabled = false; | |
| 617 } | |
| 618 } else { | |
| 619 CMSConcurrentMTEnabled = false; | |
| 620 } | |
| 621 } | |
| 622 if (!CMSConcurrentMTEnabled) { | |
| 623 ParallelCMSThreads = 0; | |
| 624 } else { | |
| 625 // Turn off CMSCleanOnEnter optimization temporarily for | |
| 626 // the MT case where it's not fixed yet; see 6178663. | |
| 627 CMSCleanOnEnter = false; | |
| 628 } | |
| 629 assert((_conc_workers != NULL) == (ParallelCMSThreads > 1), | |
| 630 "Inconsistency"); | |
| 631 | |
| 632 // Parallel task queues; these are shared for the | |
| 633 // concurrent and stop-world phases of CMS, but | |
| 634 // are not shared with parallel scavenge (ParNew). | |
| 635 { | |
| 636 uint i; | |
| 637 uint num_queues = (uint) MAX2(ParallelGCThreads, ParallelCMSThreads); | |
| 638 | |
| 639 if ((CMSParallelRemarkEnabled || CMSConcurrentMTEnabled | |
| 640 || ParallelRefProcEnabled) | |
| 641 && num_queues > 0) { | |
| 642 _task_queues = new OopTaskQueueSet(num_queues); | |
| 643 if (_task_queues == NULL) { | |
| 644 warning("task_queues allocation failure."); | |
| 645 return; | |
| 646 } | |
| 647 _hash_seed = NEW_C_HEAP_ARRAY(int, num_queues); | |
| 648 if (_hash_seed == NULL) { | |
| 649 warning("_hash_seed array allocation failure"); | |
| 650 return; | |
| 651 } | |
| 652 | |
| 653 // XXX use a global constant instead of 64! | |
| 654 typedef struct OopTaskQueuePadded { | |
| 655 OopTaskQueue work_queue; | |
| 656 char pad[64 - sizeof(OopTaskQueue)]; // prevent false sharing | |
| 657 } OopTaskQueuePadded; | |
| 658 | |
| 659 for (i = 0; i < num_queues; i++) { | |
| 660 OopTaskQueuePadded *q_padded = new OopTaskQueuePadded(); | |
| 661 if (q_padded == NULL) { | |
| 662 warning("work_queue allocation failure."); | |
| 663 return; | |
| 664 } | |
| 665 _task_queues->register_queue(i, &q_padded->work_queue); | |
| 666 } | |
| 667 for (i = 0; i < num_queues; i++) { | |
| 668 _task_queues->queue(i)->initialize(); | |
| 669 _hash_seed[i] = 17; // copied from ParNew | |
| 670 } | |
| 671 } | |
| 672 } | |
| 673 | |
|
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674 _cmsGen ->init_initiating_occupancy(CMSInitiatingOccupancyFraction, CMSTriggerRatio); |
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675 _permGen->init_initiating_occupancy(CMSInitiatingPermOccupancyFraction, CMSTriggerPermRatio); |
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676 |
| 0 | 677 // Clip CMSBootstrapOccupancy between 0 and 100. |
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678 _bootstrap_occupancy = ((double)MIN2((uintx)100, MAX2((uintx)0, CMSBootstrapOccupancy))) |
| 0 | 679 /(double)100; |
| 680 | |
| 681 _full_gcs_since_conc_gc = 0; | |
| 682 | |
| 683 // Now tell CMS generations the identity of their collector | |
| 684 ConcurrentMarkSweepGeneration::set_collector(this); | |
| 685 | |
| 686 // Create & start a CMS thread for this CMS collector | |
| 687 _cmsThread = ConcurrentMarkSweepThread::start(this); | |
| 688 assert(cmsThread() != NULL, "CMS Thread should have been created"); | |
| 689 assert(cmsThread()->collector() == this, | |
| 690 "CMS Thread should refer to this gen"); | |
| 691 assert(CGC_lock != NULL, "Where's the CGC_lock?"); | |
| 692 | |
| 693 // Support for parallelizing young gen rescan | |
| 694 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 695 _young_gen = gch->prev_gen(_cmsGen); | |
| 696 if (gch->supports_inline_contig_alloc()) { | |
| 697 _top_addr = gch->top_addr(); | |
| 698 _end_addr = gch->end_addr(); | |
| 699 assert(_young_gen != NULL, "no _young_gen"); | |
| 700 _eden_chunk_index = 0; | |
| 701 _eden_chunk_capacity = (_young_gen->max_capacity()+CMSSamplingGrain)/CMSSamplingGrain; | |
| 702 _eden_chunk_array = NEW_C_HEAP_ARRAY(HeapWord*, _eden_chunk_capacity); | |
| 703 if (_eden_chunk_array == NULL) { | |
| 704 _eden_chunk_capacity = 0; | |
| 705 warning("GC/CMS: _eden_chunk_array allocation failure"); | |
| 706 } | |
| 707 } | |
| 708 assert(_eden_chunk_array != NULL || _eden_chunk_capacity == 0, "Error"); | |
| 709 | |
| 710 // Support for parallelizing survivor space rescan | |
| 711 if (CMSParallelRemarkEnabled && CMSParallelSurvivorRemarkEnabled) { | |
| 712 size_t max_plab_samples = MaxNewSize/((SurvivorRatio+2)*MinTLABSize); | |
| 713 _survivor_plab_array = NEW_C_HEAP_ARRAY(ChunkArray, ParallelGCThreads); | |
| 714 _survivor_chunk_array = NEW_C_HEAP_ARRAY(HeapWord*, 2*max_plab_samples); | |
| 715 _cursor = NEW_C_HEAP_ARRAY(size_t, ParallelGCThreads); | |
| 716 if (_survivor_plab_array == NULL || _survivor_chunk_array == NULL | |
| 717 || _cursor == NULL) { | |
| 718 warning("Failed to allocate survivor plab/chunk array"); | |
| 719 if (_survivor_plab_array != NULL) { | |
| 720 FREE_C_HEAP_ARRAY(ChunkArray, _survivor_plab_array); | |
| 721 _survivor_plab_array = NULL; | |
| 722 } | |
| 723 if (_survivor_chunk_array != NULL) { | |
| 724 FREE_C_HEAP_ARRAY(HeapWord*, _survivor_chunk_array); | |
| 725 _survivor_chunk_array = NULL; | |
| 726 } | |
| 727 if (_cursor != NULL) { | |
| 728 FREE_C_HEAP_ARRAY(size_t, _cursor); | |
| 729 _cursor = NULL; | |
| 730 } | |
| 731 } else { | |
| 732 _survivor_chunk_capacity = 2*max_plab_samples; | |
| 733 for (uint i = 0; i < ParallelGCThreads; i++) { | |
| 734 HeapWord** vec = NEW_C_HEAP_ARRAY(HeapWord*, max_plab_samples); | |
| 735 if (vec == NULL) { | |
| 736 warning("Failed to allocate survivor plab array"); | |
| 737 for (int j = i; j > 0; j--) { | |
| 738 FREE_C_HEAP_ARRAY(HeapWord*, _survivor_plab_array[j-1].array()); | |
| 739 } | |
| 740 FREE_C_HEAP_ARRAY(ChunkArray, _survivor_plab_array); | |
| 741 FREE_C_HEAP_ARRAY(HeapWord*, _survivor_chunk_array); | |
| 742 _survivor_plab_array = NULL; | |
| 743 _survivor_chunk_array = NULL; | |
| 744 _survivor_chunk_capacity = 0; | |
| 745 break; | |
| 746 } else { | |
| 747 ChunkArray* cur = | |
| 748 ::new (&_survivor_plab_array[i]) ChunkArray(vec, | |
| 749 max_plab_samples); | |
| 750 assert(cur->end() == 0, "Should be 0"); | |
| 751 assert(cur->array() == vec, "Should be vec"); | |
| 752 assert(cur->capacity() == max_plab_samples, "Error"); | |
| 753 } | |
| 754 } | |
| 755 } | |
| 756 } | |
| 757 assert( ( _survivor_plab_array != NULL | |
| 758 && _survivor_chunk_array != NULL) | |
| 759 || ( _survivor_chunk_capacity == 0 | |
| 760 && _survivor_chunk_index == 0), | |
| 761 "Error"); | |
| 762 | |
| 763 // Choose what strong roots should be scanned depending on verification options | |
| 764 // and perm gen collection mode. | |
| 765 if (!CMSClassUnloadingEnabled) { | |
| 766 // If class unloading is disabled we want to include all classes into the root set. | |
| 767 add_root_scanning_option(SharedHeap::SO_AllClasses); | |
| 768 } else { | |
| 769 add_root_scanning_option(SharedHeap::SO_SystemClasses); | |
| 770 } | |
| 771 | |
| 772 NOT_PRODUCT(_overflow_counter = CMSMarkStackOverflowInterval;) | |
| 773 _gc_counters = new CollectorCounters("CMS", 1); | |
| 774 _completed_initialization = true; | |
| 775 _sweep_timer.start(); // start of time | |
| 776 } | |
| 777 | |
| 778 const char* ConcurrentMarkSweepGeneration::name() const { | |
| 779 return "concurrent mark-sweep generation"; | |
| 780 } | |
| 781 void ConcurrentMarkSweepGeneration::update_counters() { | |
| 782 if (UsePerfData) { | |
| 783 _space_counters->update_all(); | |
| 784 _gen_counters->update_all(); | |
| 785 } | |
| 786 } | |
| 787 | |
| 788 // this is an optimized version of update_counters(). it takes the | |
| 789 // used value as a parameter rather than computing it. | |
| 790 // | |
| 791 void ConcurrentMarkSweepGeneration::update_counters(size_t used) { | |
| 792 if (UsePerfData) { | |
| 793 _space_counters->update_used(used); | |
| 794 _space_counters->update_capacity(); | |
| 795 _gen_counters->update_all(); | |
| 796 } | |
| 797 } | |
| 798 | |
| 799 void ConcurrentMarkSweepGeneration::print() const { | |
| 800 Generation::print(); | |
| 801 cmsSpace()->print(); | |
| 802 } | |
| 803 | |
| 804 #ifndef PRODUCT | |
| 805 void ConcurrentMarkSweepGeneration::print_statistics() { | |
| 806 cmsSpace()->printFLCensus(0); | |
| 807 } | |
| 808 #endif | |
| 809 | |
| 810 void ConcurrentMarkSweepGeneration::printOccupancy(const char *s) { | |
| 811 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 812 if (PrintGCDetails) { | |
| 813 if (Verbose) { | |
| 814 gclog_or_tty->print(" [%d %s-%s: "SIZE_FORMAT"("SIZE_FORMAT")]", | |
| 815 level(), short_name(), s, used(), capacity()); | |
| 816 } else { | |
| 817 gclog_or_tty->print(" [%d %s-%s: "SIZE_FORMAT"K("SIZE_FORMAT"K)]", | |
| 818 level(), short_name(), s, used() / K, capacity() / K); | |
| 819 } | |
| 820 } | |
| 821 if (Verbose) { | |
| 822 gclog_or_tty->print(" "SIZE_FORMAT"("SIZE_FORMAT")", | |
| 823 gch->used(), gch->capacity()); | |
| 824 } else { | |
| 825 gclog_or_tty->print(" "SIZE_FORMAT"K("SIZE_FORMAT"K)", | |
| 826 gch->used() / K, gch->capacity() / K); | |
| 827 } | |
| 828 } | |
| 829 | |
| 830 size_t | |
| 831 ConcurrentMarkSweepGeneration::contiguous_available() const { | |
| 832 // dld proposes an improvement in precision here. If the committed | |
| 833 // part of the space ends in a free block we should add that to | |
| 834 // uncommitted size in the calculation below. Will make this | |
| 835 // change later, staying with the approximation below for the | |
| 836 // time being. -- ysr. | |
| 837 return MAX2(_virtual_space.uncommitted_size(), unsafe_max_alloc_nogc()); | |
| 838 } | |
| 839 | |
| 840 size_t | |
| 841 ConcurrentMarkSweepGeneration::unsafe_max_alloc_nogc() const { | |
| 842 return _cmsSpace->max_alloc_in_words() * HeapWordSize; | |
| 843 } | |
| 844 | |
| 845 size_t ConcurrentMarkSweepGeneration::max_available() const { | |
| 846 return free() + _virtual_space.uncommitted_size(); | |
| 847 } | |
| 848 | |
| 849 bool ConcurrentMarkSweepGeneration::promotion_attempt_is_safe( | |
| 850 size_t max_promotion_in_bytes, | |
| 851 bool younger_handles_promotion_failure) const { | |
| 852 | |
| 853 // This is the most conservative test. Full promotion is | |
| 854 // guaranteed if this is used. The multiplicative factor is to | |
| 855 // account for the worst case "dilatation". | |
| 856 double adjusted_max_promo_bytes = _dilatation_factor * max_promotion_in_bytes; | |
| 857 if (adjusted_max_promo_bytes > (double)max_uintx) { // larger than size_t | |
| 858 adjusted_max_promo_bytes = (double)max_uintx; | |
| 859 } | |
| 860 bool result = (max_contiguous_available() >= (size_t)adjusted_max_promo_bytes); | |
| 861 | |
| 862 if (younger_handles_promotion_failure && !result) { | |
| 863 // Full promotion is not guaranteed because fragmentation | |
| 864 // of the cms generation can prevent the full promotion. | |
| 865 result = (max_available() >= (size_t)adjusted_max_promo_bytes); | |
| 866 | |
| 867 if (!result) { | |
| 868 // With promotion failure handling the test for the ability | |
| 869 // to support the promotion does not have to be guaranteed. | |
| 870 // Use an average of the amount promoted. | |
| 871 result = max_available() >= (size_t) | |
| 872 gc_stats()->avg_promoted()->padded_average(); | |
| 873 if (PrintGC && Verbose && result) { | |
| 874 gclog_or_tty->print_cr( | |
| 875 "\nConcurrentMarkSweepGeneration::promotion_attempt_is_safe" | |
| 876 " max_available: " SIZE_FORMAT | |
| 877 " avg_promoted: " SIZE_FORMAT, | |
| 878 max_available(), (size_t) | |
| 879 gc_stats()->avg_promoted()->padded_average()); | |
| 880 } | |
| 881 } else { | |
| 882 if (PrintGC && Verbose) { | |
| 883 gclog_or_tty->print_cr( | |
| 884 "\nConcurrentMarkSweepGeneration::promotion_attempt_is_safe" | |
| 885 " max_available: " SIZE_FORMAT | |
| 886 " adj_max_promo_bytes: " SIZE_FORMAT, | |
| 887 max_available(), (size_t)adjusted_max_promo_bytes); | |
| 888 } | |
| 889 } | |
| 890 } else { | |
| 891 if (PrintGC && Verbose) { | |
| 892 gclog_or_tty->print_cr( | |
| 893 "\nConcurrentMarkSweepGeneration::promotion_attempt_is_safe" | |
| 894 " contiguous_available: " SIZE_FORMAT | |
| 895 " adj_max_promo_bytes: " SIZE_FORMAT, | |
| 896 max_contiguous_available(), (size_t)adjusted_max_promo_bytes); | |
| 897 } | |
| 898 } | |
| 899 return result; | |
| 900 } | |
| 901 | |
| 902 CompactibleSpace* | |
| 903 ConcurrentMarkSweepGeneration::first_compaction_space() const { | |
| 904 return _cmsSpace; | |
| 905 } | |
| 906 | |
| 907 void ConcurrentMarkSweepGeneration::reset_after_compaction() { | |
| 908 // Clear the promotion information. These pointers can be adjusted | |
| 909 // along with all the other pointers into the heap but | |
| 910 // compaction is expected to be a rare event with | |
| 911 // a heap using cms so don't do it without seeing the need. | |
| 912 if (ParallelGCThreads > 0) { | |
| 913 for (uint i = 0; i < ParallelGCThreads; i++) { | |
| 914 _par_gc_thread_states[i]->promo.reset(); | |
| 915 } | |
| 916 } | |
| 917 } | |
| 918 | |
| 919 void ConcurrentMarkSweepGeneration::space_iterate(SpaceClosure* blk, bool usedOnly) { | |
| 920 blk->do_space(_cmsSpace); | |
| 921 } | |
| 922 | |
| 923 void ConcurrentMarkSweepGeneration::compute_new_size() { | |
| 924 assert_locked_or_safepoint(Heap_lock); | |
| 925 | |
| 926 // If incremental collection failed, we just want to expand | |
| 927 // to the limit. | |
| 928 if (incremental_collection_failed()) { | |
| 929 clear_incremental_collection_failed(); | |
| 930 grow_to_reserved(); | |
| 931 return; | |
| 932 } | |
| 933 | |
| 934 size_t expand_bytes = 0; | |
| 935 double free_percentage = ((double) free()) / capacity(); | |
| 936 double desired_free_percentage = (double) MinHeapFreeRatio / 100; | |
| 937 double maximum_free_percentage = (double) MaxHeapFreeRatio / 100; | |
| 938 | |
| 939 // compute expansion delta needed for reaching desired free percentage | |
| 940 if (free_percentage < desired_free_percentage) { | |
| 941 size_t desired_capacity = (size_t)(used() / ((double) 1 - desired_free_percentage)); | |
| 942 assert(desired_capacity >= capacity(), "invalid expansion size"); | |
| 943 expand_bytes = MAX2(desired_capacity - capacity(), MinHeapDeltaBytes); | |
| 944 } | |
| 945 if (expand_bytes > 0) { | |
| 946 if (PrintGCDetails && Verbose) { | |
| 947 size_t desired_capacity = (size_t)(used() / ((double) 1 - desired_free_percentage)); | |
| 948 gclog_or_tty->print_cr("\nFrom compute_new_size: "); | |
| 949 gclog_or_tty->print_cr(" Free fraction %f", free_percentage); | |
| 950 gclog_or_tty->print_cr(" Desired free fraction %f", | |
| 951 desired_free_percentage); | |
| 952 gclog_or_tty->print_cr(" Maximum free fraction %f", | |
| 953 maximum_free_percentage); | |
| 954 gclog_or_tty->print_cr(" Capactiy "SIZE_FORMAT, capacity()/1000); | |
| 955 gclog_or_tty->print_cr(" Desired capacity "SIZE_FORMAT, | |
| 956 desired_capacity/1000); | |
| 957 int prev_level = level() - 1; | |
| 958 if (prev_level >= 0) { | |
| 959 size_t prev_size = 0; | |
| 960 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 961 Generation* prev_gen = gch->_gens[prev_level]; | |
| 962 prev_size = prev_gen->capacity(); | |
| 963 gclog_or_tty->print_cr(" Younger gen size "SIZE_FORMAT, | |
| 964 prev_size/1000); | |
| 965 } | |
| 966 gclog_or_tty->print_cr(" unsafe_max_alloc_nogc "SIZE_FORMAT, | |
| 967 unsafe_max_alloc_nogc()/1000); | |
| 968 gclog_or_tty->print_cr(" contiguous available "SIZE_FORMAT, | |
| 969 contiguous_available()/1000); | |
| 970 gclog_or_tty->print_cr(" Expand by "SIZE_FORMAT" (bytes)", | |
| 971 expand_bytes); | |
| 972 } | |
| 973 // safe if expansion fails | |
| 974 expand(expand_bytes, 0, CMSExpansionCause::_satisfy_free_ratio); | |
| 975 if (PrintGCDetails && Verbose) { | |
| 976 gclog_or_tty->print_cr(" Expanded free fraction %f", | |
| 977 ((double) free()) / capacity()); | |
| 978 } | |
| 979 } | |
| 980 } | |
| 981 | |
| 982 Mutex* ConcurrentMarkSweepGeneration::freelistLock() const { | |
| 983 return cmsSpace()->freelistLock(); | |
| 984 } | |
| 985 | |
| 986 HeapWord* ConcurrentMarkSweepGeneration::allocate(size_t size, | |
| 987 bool tlab) { | |
| 988 CMSSynchronousYieldRequest yr; | |
| 989 MutexLockerEx x(freelistLock(), | |
| 990 Mutex::_no_safepoint_check_flag); | |
| 991 return have_lock_and_allocate(size, tlab); | |
| 992 } | |
| 993 | |
| 994 HeapWord* ConcurrentMarkSweepGeneration::have_lock_and_allocate(size_t size, | |
| 995 bool tlab) { | |
| 996 assert_lock_strong(freelistLock()); | |
| 997 size_t adjustedSize = CompactibleFreeListSpace::adjustObjectSize(size); | |
| 998 HeapWord* res = cmsSpace()->allocate(adjustedSize); | |
| 999 // Allocate the object live (grey) if the background collector has | |
| 1000 // started marking. This is necessary because the marker may | |
| 1001 // have passed this address and consequently this object will | |
| 1002 // not otherwise be greyed and would be incorrectly swept up. | |
| 1003 // Note that if this object contains references, the writing | |
| 1004 // of those references will dirty the card containing this object | |
| 1005 // allowing the object to be blackened (and its references scanned) | |
| 1006 // either during a preclean phase or at the final checkpoint. | |
| 1007 if (res != NULL) { | |
| 1008 collector()->direct_allocated(res, adjustedSize); | |
| 1009 _direct_allocated_words += adjustedSize; | |
| 1010 // allocation counters | |
| 1011 NOT_PRODUCT( | |
| 1012 _numObjectsAllocated++; | |
| 1013 _numWordsAllocated += (int)adjustedSize; | |
| 1014 ) | |
| 1015 } | |
| 1016 return res; | |
| 1017 } | |
| 1018 | |
| 1019 // In the case of direct allocation by mutators in a generation that | |
| 1020 // is being concurrently collected, the object must be allocated | |
| 1021 // live (grey) if the background collector has started marking. | |
| 1022 // This is necessary because the marker may | |
| 1023 // have passed this address and consequently this object will | |
| 1024 // not otherwise be greyed and would be incorrectly swept up. | |
| 1025 // Note that if this object contains references, the writing | |
| 1026 // of those references will dirty the card containing this object | |
| 1027 // allowing the object to be blackened (and its references scanned) | |
| 1028 // either during a preclean phase or at the final checkpoint. | |
| 1029 void CMSCollector::direct_allocated(HeapWord* start, size_t size) { | |
| 1030 assert(_markBitMap.covers(start, size), "Out of bounds"); | |
| 1031 if (_collectorState >= Marking) { | |
| 1032 MutexLockerEx y(_markBitMap.lock(), | |
| 1033 Mutex::_no_safepoint_check_flag); | |
| 1034 // [see comments preceding SweepClosure::do_blk() below for details] | |
| 1035 // 1. need to mark the object as live so it isn't collected | |
| 1036 // 2. need to mark the 2nd bit to indicate the object may be uninitialized | |
| 1037 // 3. need to mark the end of the object so sweeper can skip over it | |
| 1038 // if it's uninitialized when the sweeper reaches it. | |
| 1039 _markBitMap.mark(start); // object is live | |
| 1040 _markBitMap.mark(start + 1); // object is potentially uninitialized? | |
| 1041 _markBitMap.mark(start + size - 1); | |
| 1042 // mark end of object | |
| 1043 } | |
| 1044 // check that oop looks uninitialized | |
| 187 | 1045 assert(oop(start)->klass_or_null() == NULL, "_klass should be NULL"); |
| 0 | 1046 } |
| 1047 | |
| 1048 void CMSCollector::promoted(bool par, HeapWord* start, | |
| 1049 bool is_obj_array, size_t obj_size) { | |
| 1050 assert(_markBitMap.covers(start), "Out of bounds"); | |
| 1051 // See comment in direct_allocated() about when objects should | |
| 1052 // be allocated live. | |
| 1053 if (_collectorState >= Marking) { | |
| 1054 // we already hold the marking bit map lock, taken in | |
| 1055 // the prologue | |
| 1056 if (par) { | |
| 1057 _markBitMap.par_mark(start); | |
| 1058 } else { | |
| 1059 _markBitMap.mark(start); | |
| 1060 } | |
| 1061 // We don't need to mark the object as uninitialized (as | |
| 1062 // in direct_allocated above) because this is being done with the | |
| 1063 // world stopped and the object will be initialized by the | |
| 1064 // time the sweeper gets to look at it. | |
| 1065 assert(SafepointSynchronize::is_at_safepoint(), | |
| 1066 "expect promotion only at safepoints"); | |
| 1067 | |
| 1068 if (_collectorState < Sweeping) { | |
| 1069 // Mark the appropriate cards in the modUnionTable, so that | |
| 1070 // this object gets scanned before the sweep. If this is | |
| 1071 // not done, CMS generation references in the object might | |
| 1072 // not get marked. | |
| 1073 // For the case of arrays, which are otherwise precisely | |
| 1074 // marked, we need to dirty the entire array, not just its head. | |
| 1075 if (is_obj_array) { | |
| 1076 // The [par_]mark_range() method expects mr.end() below to | |
| 1077 // be aligned to the granularity of a bit's representation | |
| 1078 // in the heap. In the case of the MUT below, that's a | |
| 1079 // card size. | |
| 1080 MemRegion mr(start, | |
| 1081 (HeapWord*)round_to((intptr_t)(start + obj_size), | |
| 1082 CardTableModRefBS::card_size /* bytes */)); | |
| 1083 if (par) { | |
| 1084 _modUnionTable.par_mark_range(mr); | |
| 1085 } else { | |
| 1086 _modUnionTable.mark_range(mr); | |
| 1087 } | |
| 1088 } else { // not an obj array; we can just mark the head | |
| 1089 if (par) { | |
| 1090 _modUnionTable.par_mark(start); | |
| 1091 } else { | |
| 1092 _modUnionTable.mark(start); | |
| 1093 } | |
| 1094 } | |
| 1095 } | |
| 1096 } | |
| 1097 } | |
| 1098 | |
| 1099 static inline size_t percent_of_space(Space* space, HeapWord* addr) | |
| 1100 { | |
| 1101 size_t delta = pointer_delta(addr, space->bottom()); | |
| 1102 return (size_t)(delta * 100.0 / (space->capacity() / HeapWordSize)); | |
| 1103 } | |
| 1104 | |
| 1105 void CMSCollector::icms_update_allocation_limits() | |
| 1106 { | |
| 1107 Generation* gen0 = GenCollectedHeap::heap()->get_gen(0); | |
| 1108 EdenSpace* eden = gen0->as_DefNewGeneration()->eden(); | |
| 1109 | |
| 1110 const unsigned int duty_cycle = stats().icms_update_duty_cycle(); | |
| 1111 if (CMSTraceIncrementalPacing) { | |
| 1112 stats().print(); | |
| 1113 } | |
| 1114 | |
| 1115 assert(duty_cycle <= 100, "invalid duty cycle"); | |
| 1116 if (duty_cycle != 0) { | |
| 1117 // The duty_cycle is a percentage between 0 and 100; convert to words and | |
| 1118 // then compute the offset from the endpoints of the space. | |
| 1119 size_t free_words = eden->free() / HeapWordSize; | |
| 1120 double free_words_dbl = (double)free_words; | |
| 1121 size_t duty_cycle_words = (size_t)(free_words_dbl * duty_cycle / 100.0); | |
| 1122 size_t offset_words = (free_words - duty_cycle_words) / 2; | |
| 1123 | |
| 1124 _icms_start_limit = eden->top() + offset_words; | |
| 1125 _icms_stop_limit = eden->end() - offset_words; | |
| 1126 | |
| 1127 // The limits may be adjusted (shifted to the right) by | |
| 1128 // CMSIncrementalOffset, to allow the application more mutator time after a | |
| 1129 // young gen gc (when all mutators were stopped) and before CMS starts and | |
| 1130 // takes away one or more cpus. | |
| 1131 if (CMSIncrementalOffset != 0) { | |
| 1132 double adjustment_dbl = free_words_dbl * CMSIncrementalOffset / 100.0; | |
| 1133 size_t adjustment = (size_t)adjustment_dbl; | |
| 1134 HeapWord* tmp_stop = _icms_stop_limit + adjustment; | |
| 1135 if (tmp_stop > _icms_stop_limit && tmp_stop < eden->end()) { | |
| 1136 _icms_start_limit += adjustment; | |
| 1137 _icms_stop_limit = tmp_stop; | |
| 1138 } | |
| 1139 } | |
| 1140 } | |
| 1141 if (duty_cycle == 0 || (_icms_start_limit == _icms_stop_limit)) { | |
| 1142 _icms_start_limit = _icms_stop_limit = eden->end(); | |
| 1143 } | |
| 1144 | |
| 1145 // Install the new start limit. | |
| 1146 eden->set_soft_end(_icms_start_limit); | |
| 1147 | |
| 1148 if (CMSTraceIncrementalMode) { | |
| 1149 gclog_or_tty->print(" icms alloc limits: " | |
| 1150 PTR_FORMAT "," PTR_FORMAT | |
| 1151 " (" SIZE_FORMAT "%%," SIZE_FORMAT "%%) ", | |
| 1152 _icms_start_limit, _icms_stop_limit, | |
| 1153 percent_of_space(eden, _icms_start_limit), | |
| 1154 percent_of_space(eden, _icms_stop_limit)); | |
| 1155 if (Verbose) { | |
| 1156 gclog_or_tty->print("eden: "); | |
| 1157 eden->print_on(gclog_or_tty); | |
| 1158 } | |
| 1159 } | |
| 1160 } | |
| 1161 | |
| 1162 // Any changes here should try to maintain the invariant | |
| 1163 // that if this method is called with _icms_start_limit | |
| 1164 // and _icms_stop_limit both NULL, then it should return NULL | |
| 1165 // and not notify the icms thread. | |
| 1166 HeapWord* | |
| 1167 CMSCollector::allocation_limit_reached(Space* space, HeapWord* top, | |
| 1168 size_t word_size) | |
| 1169 { | |
| 1170 // A start_limit equal to end() means the duty cycle is 0, so treat that as a | |
| 1171 // nop. | |
| 1172 if (CMSIncrementalMode && _icms_start_limit != space->end()) { | |
| 1173 if (top <= _icms_start_limit) { | |
| 1174 if (CMSTraceIncrementalMode) { | |
| 1175 space->print_on(gclog_or_tty); | |
| 1176 gclog_or_tty->stamp(); | |
| 1177 gclog_or_tty->print_cr(" start limit top=" PTR_FORMAT | |
| 1178 ", new limit=" PTR_FORMAT | |
| 1179 " (" SIZE_FORMAT "%%)", | |
| 1180 top, _icms_stop_limit, | |
| 1181 percent_of_space(space, _icms_stop_limit)); | |
| 1182 } | |
| 1183 ConcurrentMarkSweepThread::start_icms(); | |
| 1184 assert(top < _icms_stop_limit, "Tautology"); | |
| 1185 if (word_size < pointer_delta(_icms_stop_limit, top)) { | |
| 1186 return _icms_stop_limit; | |
| 1187 } | |
| 1188 | |
| 1189 // The allocation will cross both the _start and _stop limits, so do the | |
| 1190 // stop notification also and return end(). | |
| 1191 if (CMSTraceIncrementalMode) { | |
| 1192 space->print_on(gclog_or_tty); | |
| 1193 gclog_or_tty->stamp(); | |
| 1194 gclog_or_tty->print_cr(" +stop limit top=" PTR_FORMAT | |
| 1195 ", new limit=" PTR_FORMAT | |
| 1196 " (" SIZE_FORMAT "%%)", | |
| 1197 top, space->end(), | |
| 1198 percent_of_space(space, space->end())); | |
| 1199 } | |
| 1200 ConcurrentMarkSweepThread::stop_icms(); | |
| 1201 return space->end(); | |
| 1202 } | |
| 1203 | |
| 1204 if (top <= _icms_stop_limit) { | |
| 1205 if (CMSTraceIncrementalMode) { | |
| 1206 space->print_on(gclog_or_tty); | |
| 1207 gclog_or_tty->stamp(); | |
| 1208 gclog_or_tty->print_cr(" stop limit top=" PTR_FORMAT | |
| 1209 ", new limit=" PTR_FORMAT | |
| 1210 " (" SIZE_FORMAT "%%)", | |
| 1211 top, space->end(), | |
| 1212 percent_of_space(space, space->end())); | |
| 1213 } | |
| 1214 ConcurrentMarkSweepThread::stop_icms(); | |
| 1215 return space->end(); | |
| 1216 } | |
| 1217 | |
| 1218 if (CMSTraceIncrementalMode) { | |
| 1219 space->print_on(gclog_or_tty); | |
| 1220 gclog_or_tty->stamp(); | |
| 1221 gclog_or_tty->print_cr(" end limit top=" PTR_FORMAT | |
| 1222 ", new limit=" PTR_FORMAT, | |
| 1223 top, NULL); | |
| 1224 } | |
| 1225 } | |
| 1226 | |
| 1227 return NULL; | |
| 1228 } | |
| 1229 | |
|
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1230 oop ConcurrentMarkSweepGeneration::promote(oop obj, size_t obj_size) { |
| 0 | 1231 assert(obj_size == (size_t)obj->size(), "bad obj_size passed in"); |
| 1232 // allocate, copy and if necessary update promoinfo -- | |
| 1233 // delegate to underlying space. | |
| 1234 assert_lock_strong(freelistLock()); | |
| 1235 | |
| 1236 #ifndef PRODUCT | |
| 1237 if (Universe::heap()->promotion_should_fail()) { | |
| 1238 return NULL; | |
| 1239 } | |
| 1240 #endif // #ifndef PRODUCT | |
| 1241 | |
|
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1242 oop res = _cmsSpace->promote(obj, obj_size); |
| 0 | 1243 if (res == NULL) { |
| 1244 // expand and retry | |
| 1245 size_t s = _cmsSpace->expansionSpaceRequired(obj_size); // HeapWords | |
| 1246 expand(s*HeapWordSize, MinHeapDeltaBytes, | |
| 1247 CMSExpansionCause::_satisfy_promotion); | |
| 1248 // Since there's currently no next generation, we don't try to promote | |
| 1249 // into a more senior generation. | |
| 1250 assert(next_gen() == NULL, "assumption, based upon which no attempt " | |
| 1251 "is made to pass on a possibly failing " | |
| 1252 "promotion to next generation"); | |
|
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1253 res = _cmsSpace->promote(obj, obj_size); |
| 0 | 1254 } |
| 1255 if (res != NULL) { | |
| 1256 // See comment in allocate() about when objects should | |
| 1257 // be allocated live. | |
| 1258 assert(obj->is_oop(), "Will dereference klass pointer below"); | |
| 1259 collector()->promoted(false, // Not parallel | |
| 1260 (HeapWord*)res, obj->is_objArray(), obj_size); | |
| 1261 // promotion counters | |
| 1262 NOT_PRODUCT( | |
| 1263 _numObjectsPromoted++; | |
| 1264 _numWordsPromoted += | |
| 1265 (int)(CompactibleFreeListSpace::adjustObjectSize(obj->size())); | |
| 1266 ) | |
| 1267 } | |
| 1268 return res; | |
| 1269 } | |
| 1270 | |
| 1271 | |
| 1272 HeapWord* | |
| 1273 ConcurrentMarkSweepGeneration::allocation_limit_reached(Space* space, | |
| 1274 HeapWord* top, | |
| 1275 size_t word_sz) | |
| 1276 { | |
| 1277 return collector()->allocation_limit_reached(space, top, word_sz); | |
| 1278 } | |
| 1279 | |
| 1280 // Things to support parallel young-gen collection. | |
| 1281 oop | |
| 1282 ConcurrentMarkSweepGeneration::par_promote(int thread_num, | |
| 1283 oop old, markOop m, | |
| 1284 size_t word_sz) { | |
| 1285 #ifndef PRODUCT | |
| 1286 if (Universe::heap()->promotion_should_fail()) { | |
| 1287 return NULL; | |
| 1288 } | |
| 1289 #endif // #ifndef PRODUCT | |
| 1290 | |
| 1291 CMSParGCThreadState* ps = _par_gc_thread_states[thread_num]; | |
| 1292 PromotionInfo* promoInfo = &ps->promo; | |
| 1293 // if we are tracking promotions, then first ensure space for | |
| 1294 // promotion (including spooling space for saving header if necessary). | |
| 1295 // then allocate and copy, then track promoted info if needed. | |
| 1296 // When tracking (see PromotionInfo::track()), the mark word may | |
| 1297 // be displaced and in this case restoration of the mark word | |
| 1298 // occurs in the (oop_since_save_marks_)iterate phase. | |
| 1299 if (promoInfo->tracking() && !promoInfo->ensure_spooling_space()) { | |
| 1300 // Out of space for allocating spooling buffers; | |
| 1301 // try expanding and allocating spooling buffers. | |
| 1302 if (!expand_and_ensure_spooling_space(promoInfo)) { | |
| 1303 return NULL; | |
| 1304 } | |
| 1305 } | |
| 1306 assert(promoInfo->has_spooling_space(), "Control point invariant"); | |
| 1307 HeapWord* obj_ptr = ps->lab.alloc(word_sz); | |
| 1308 if (obj_ptr == NULL) { | |
| 1309 obj_ptr = expand_and_par_lab_allocate(ps, word_sz); | |
| 1310 if (obj_ptr == NULL) { | |
| 1311 return NULL; | |
| 1312 } | |
| 1313 } | |
| 1314 oop obj = oop(obj_ptr); | |
| 187 | 1315 assert(obj->klass_or_null() == NULL, "Object should be uninitialized here."); |
| 0 | 1316 // Otherwise, copy the object. Here we must be careful to insert the |
| 1317 // klass pointer last, since this marks the block as an allocated object. | |
| 187 | 1318 // Except with compressed oops it's the mark word. |
| 0 | 1319 HeapWord* old_ptr = (HeapWord*)old; |
| 1320 if (word_sz > (size_t)oopDesc::header_size()) { | |
| 1321 Copy::aligned_disjoint_words(old_ptr + oopDesc::header_size(), | |
| 1322 obj_ptr + oopDesc::header_size(), | |
| 1323 word_sz - oopDesc::header_size()); | |
| 1324 } | |
| 187 | 1325 |
| 1326 if (UseCompressedOops) { | |
| 1327 // Copy gap missed by (aligned) header size calculation above | |
| 1328 obj->set_klass_gap(old->klass_gap()); | |
| 1329 } | |
| 1330 | |
| 0 | 1331 // Restore the mark word copied above. |
| 1332 obj->set_mark(m); | |
| 187 | 1333 |
| 0 | 1334 // Now we can track the promoted object, if necessary. We take care |
| 1335 // To delay the transition from uninitialized to full object | |
| 1336 // (i.e., insertion of klass pointer) until after, so that it | |
| 1337 // atomically becomes a promoted object. | |
| 1338 if (promoInfo->tracking()) { | |
| 1339 promoInfo->track((PromotedObject*)obj, old->klass()); | |
| 1340 } | |
| 187 | 1341 |
| 1342 // Finally, install the klass pointer (this should be volatile). | |
| 0 | 1343 obj->set_klass(old->klass()); |
| 1344 | |
| 1345 assert(old->is_oop(), "Will dereference klass ptr below"); | |
| 1346 collector()->promoted(true, // parallel | |
| 1347 obj_ptr, old->is_objArray(), word_sz); | |
| 1348 | |
| 1349 NOT_PRODUCT( | |
| 1350 Atomic::inc(&_numObjectsPromoted); | |
| 1351 Atomic::add((jint)CompactibleFreeListSpace::adjustObjectSize(obj->size()), | |
| 1352 &_numWordsPromoted); | |
| 1353 ) | |
| 1354 | |
| 1355 return obj; | |
| 1356 } | |
| 1357 | |
| 1358 void | |
| 1359 ConcurrentMarkSweepGeneration:: | |
| 1360 par_promote_alloc_undo(int thread_num, | |
| 1361 HeapWord* obj, size_t word_sz) { | |
| 1362 // CMS does not support promotion undo. | |
| 1363 ShouldNotReachHere(); | |
| 1364 } | |
| 1365 | |
| 1366 void | |
| 1367 ConcurrentMarkSweepGeneration:: | |
| 1368 par_promote_alloc_done(int thread_num) { | |
| 1369 CMSParGCThreadState* ps = _par_gc_thread_states[thread_num]; | |
| 1370 ps->lab.retire(); | |
| 1371 #if CFLS_LAB_REFILL_STATS | |
| 1372 if (thread_num == 0) { | |
| 1373 _cmsSpace->print_par_alloc_stats(); | |
| 1374 } | |
| 1375 #endif | |
| 1376 } | |
| 1377 | |
| 1378 void | |
| 1379 ConcurrentMarkSweepGeneration:: | |
| 1380 par_oop_since_save_marks_iterate_done(int thread_num) { | |
| 1381 CMSParGCThreadState* ps = _par_gc_thread_states[thread_num]; | |
| 1382 ParScanWithoutBarrierClosure* dummy_cl = NULL; | |
| 1383 ps->promo.promoted_oops_iterate_nv(dummy_cl); | |
| 1384 } | |
| 1385 | |
| 1386 // XXXPERM | |
| 1387 bool ConcurrentMarkSweepGeneration::should_collect(bool full, | |
| 1388 size_t size, | |
| 1389 bool tlab) | |
| 1390 { | |
| 1391 // We allow a STW collection only if a full | |
| 1392 // collection was requested. | |
| 1393 return full || should_allocate(size, tlab); // FIX ME !!! | |
| 1394 // This and promotion failure handling are connected at the | |
| 1395 // hip and should be fixed by untying them. | |
| 1396 } | |
| 1397 | |
| 1398 bool CMSCollector::shouldConcurrentCollect() { | |
| 1399 if (_full_gc_requested) { | |
| 1400 assert(ExplicitGCInvokesConcurrent, "Unexpected state"); | |
| 1401 if (Verbose && PrintGCDetails) { | |
| 1402 gclog_or_tty->print_cr("CMSCollector: collect because of explicit " | |
| 1403 " gc request"); | |
| 1404 } | |
| 1405 return true; | |
| 1406 } | |
| 1407 | |
| 1408 // For debugging purposes, change the type of collection. | |
| 1409 // If the rotation is not on the concurrent collection | |
| 1410 // type, don't start a concurrent collection. | |
| 1411 NOT_PRODUCT( | |
| 1412 if (RotateCMSCollectionTypes && | |
| 1413 (_cmsGen->debug_collection_type() != | |
| 1414 ConcurrentMarkSweepGeneration::Concurrent_collection_type)) { | |
| 1415 assert(_cmsGen->debug_collection_type() != | |
| 1416 ConcurrentMarkSweepGeneration::Unknown_collection_type, | |
| 1417 "Bad cms collection type"); | |
| 1418 return false; | |
| 1419 } | |
| 1420 ) | |
| 1421 | |
| 1422 FreelistLocker x(this); | |
| 1423 // ------------------------------------------------------------------ | |
| 1424 // Print out lots of information which affects the initiation of | |
| 1425 // a collection. | |
| 1426 if (PrintCMSInitiationStatistics && stats().valid()) { | |
| 1427 gclog_or_tty->print("CMSCollector shouldConcurrentCollect: "); | |
| 1428 gclog_or_tty->stamp(); | |
| 1429 gclog_or_tty->print_cr(""); | |
| 1430 stats().print_on(gclog_or_tty); | |
| 1431 gclog_or_tty->print_cr("time_until_cms_gen_full %3.7f", | |
| 1432 stats().time_until_cms_gen_full()); | |
| 1433 gclog_or_tty->print_cr("free="SIZE_FORMAT, _cmsGen->free()); | |
| 1434 gclog_or_tty->print_cr("contiguous_available="SIZE_FORMAT, | |
| 1435 _cmsGen->contiguous_available()); | |
| 1436 gclog_or_tty->print_cr("promotion_rate=%g", stats().promotion_rate()); | |
| 1437 gclog_or_tty->print_cr("cms_allocation_rate=%g", stats().cms_allocation_rate()); | |
| 1438 gclog_or_tty->print_cr("occupancy=%3.7f", _cmsGen->occupancy()); | |
|
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1439 gclog_or_tty->print_cr("initiatingOccupancy=%3.7f", _cmsGen->initiating_occupancy()); |
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1440 gclog_or_tty->print_cr("initiatingPermOccupancy=%3.7f", _permGen->initiating_occupancy()); |
| 0 | 1441 } |
| 1442 // ------------------------------------------------------------------ | |
| 1443 | |
| 1444 // If the estimated time to complete a cms collection (cms_duration()) | |
| 1445 // is less than the estimated time remaining until the cms generation | |
| 1446 // is full, start a collection. | |
| 1447 if (!UseCMSInitiatingOccupancyOnly) { | |
| 1448 if (stats().valid()) { | |
| 1449 if (stats().time_until_cms_start() == 0.0) { | |
| 1450 return true; | |
| 1451 } | |
| 1452 } else { | |
| 1453 // We want to conservatively collect somewhat early in order | |
| 1454 // to try and "bootstrap" our CMS/promotion statistics; | |
| 1455 // this branch will not fire after the first successful CMS | |
| 1456 // collection because the stats should then be valid. | |
| 1457 if (_cmsGen->occupancy() >= _bootstrap_occupancy) { | |
| 1458 if (Verbose && PrintGCDetails) { | |
| 1459 gclog_or_tty->print_cr( | |
| 1460 " CMSCollector: collect for bootstrapping statistics:" | |
| 1461 " occupancy = %f, boot occupancy = %f", _cmsGen->occupancy(), | |
| 1462 _bootstrap_occupancy); | |
| 1463 } | |
| 1464 return true; | |
| 1465 } | |
| 1466 } | |
| 1467 } | |
| 1468 | |
| 1469 // Otherwise, we start a collection cycle if either the perm gen or | |
| 1470 // old gen want a collection cycle started. Each may use | |
| 1471 // an appropriate criterion for making this decision. | |
| 1472 // XXX We need to make sure that the gen expansion | |
|
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1473 // criterion dovetails well with this. XXX NEED TO FIX THIS |
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1474 if (_cmsGen->should_concurrent_collect()) { |
| 0 | 1475 if (Verbose && PrintGCDetails) { |
| 1476 gclog_or_tty->print_cr("CMS old gen initiated"); | |
| 1477 } | |
| 1478 return true; | |
| 1479 } | |
| 1480 | |
|
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1481 // We start a collection if we believe an incremental collection may fail; |
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1482 // this is not likely to be productive in practice because it's probably too |
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1483 // late anyway. |
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1484 GenCollectedHeap* gch = GenCollectedHeap::heap(); |
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1485 assert(gch->collector_policy()->is_two_generation_policy(), |
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1486 "You may want to check the correctness of the following"); |
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1487 if (gch->incremental_collection_will_fail()) { |
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1488 if (PrintGCDetails && Verbose) { |
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1489 gclog_or_tty->print("CMSCollector: collect because incremental collection will fail "); |
| 0 | 1490 } |
| 1491 return true; | |
| 1492 } | |
| 1493 | |
|
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1494 if (CMSClassUnloadingEnabled && _permGen->should_concurrent_collect()) { |
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1495 bool res = update_should_unload_classes(); |
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1496 if (res) { |
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1497 if (Verbose && PrintGCDetails) { |
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1498 gclog_or_tty->print_cr("CMS perm gen initiated"); |
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1499 } |
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1500 return true; |
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1501 } |
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1502 } |
| 0 | 1503 return false; |
| 1504 } | |
| 1505 | |
| 1506 // Clear _expansion_cause fields of constituent generations | |
| 1507 void CMSCollector::clear_expansion_cause() { | |
| 1508 _cmsGen->clear_expansion_cause(); | |
| 1509 _permGen->clear_expansion_cause(); | |
| 1510 } | |
| 1511 | |
|
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1512 // We should be conservative in starting a collection cycle. To |
|
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1513 // start too eagerly runs the risk of collecting too often in the |
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1514 // extreme. To collect too rarely falls back on full collections, |
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1515 // which works, even if not optimum in terms of concurrent work. |
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1516 // As a work around for too eagerly collecting, use the flag |
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1517 // UseCMSInitiatingOccupancyOnly. This also has the advantage of |
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1518 // giving the user an easily understandable way of controlling the |
|
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1519 // collections. |
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1520 // We want to start a new collection cycle if any of the following |
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1521 // conditions hold: |
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1522 // . our current occupancy exceeds the configured initiating occupancy |
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1523 // for this generation, or |
|
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1524 // . we recently needed to expand this space and have not, since that |
|
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1525 // expansion, done a collection of this generation, or |
|
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1526 // . the underlying space believes that it may be a good idea to initiate |
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1527 // a concurrent collection (this may be based on criteria such as the |
|
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1528 // following: the space uses linear allocation and linear allocation is |
|
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1529 // going to fail, or there is believed to be excessive fragmentation in |
|
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1530 // the generation, etc... or ... |
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1531 // [.(currently done by CMSCollector::shouldConcurrentCollect() only for |
|
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1532 // the case of the old generation, not the perm generation; see CR 6543076): |
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1533 // we may be approaching a point at which allocation requests may fail because |
|
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1534 // we will be out of sufficient free space given allocation rate estimates.] |
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1535 bool ConcurrentMarkSweepGeneration::should_concurrent_collect() const { |
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1536 |
| 0 | 1537 assert_lock_strong(freelistLock()); |
|
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1538 if (occupancy() > initiating_occupancy()) { |
| 0 | 1539 if (PrintGCDetails && Verbose) { |
| 1540 gclog_or_tty->print(" %s: collect because of occupancy %f / %f ", | |
|
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1541 short_name(), occupancy(), initiating_occupancy()); |
| 0 | 1542 } |
| 1543 return true; | |
| 1544 } | |
| 1545 if (UseCMSInitiatingOccupancyOnly) { | |
| 1546 return false; | |
| 1547 } | |
| 1548 if (expansion_cause() == CMSExpansionCause::_satisfy_allocation) { | |
| 1549 if (PrintGCDetails && Verbose) { | |
| 1550 gclog_or_tty->print(" %s: collect because expanded for allocation ", | |
| 1551 short_name()); | |
| 1552 } | |
| 1553 return true; | |
| 1554 } | |
|
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1555 if (_cmsSpace->should_concurrent_collect()) { |
| 0 | 1556 if (PrintGCDetails && Verbose) { |
|
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1557 gclog_or_tty->print(" %s: collect because cmsSpace says so ", |
| 0 | 1558 short_name()); |
| 1559 } | |
| 1560 return true; | |
| 1561 } | |
| 1562 return false; | |
| 1563 } | |
| 1564 | |
| 1565 void ConcurrentMarkSweepGeneration::collect(bool full, | |
| 1566 bool clear_all_soft_refs, | |
| 1567 size_t size, | |
| 1568 bool tlab) | |
| 1569 { | |
| 1570 collector()->collect(full, clear_all_soft_refs, size, tlab); | |
| 1571 } | |
| 1572 | |
| 1573 void CMSCollector::collect(bool full, | |
| 1574 bool clear_all_soft_refs, | |
| 1575 size_t size, | |
| 1576 bool tlab) | |
| 1577 { | |
| 1578 if (!UseCMSCollectionPassing && _collectorState > Idling) { | |
| 1579 // For debugging purposes skip the collection if the state | |
| 1580 // is not currently idle | |
| 1581 if (TraceCMSState) { | |
| 1582 gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " skipped full:%d CMS state %d", | |
| 1583 Thread::current(), full, _collectorState); | |
| 1584 } | |
| 1585 return; | |
| 1586 } | |
| 1587 | |
| 1588 // The following "if" branch is present for defensive reasons. | |
| 1589 // In the current uses of this interface, it can be replaced with: | |
| 1590 // assert(!GC_locker.is_active(), "Can't be called otherwise"); | |
| 1591 // But I am not placing that assert here to allow future | |
| 1592 // generality in invoking this interface. | |
| 1593 if (GC_locker::is_active()) { | |
| 1594 // A consistency test for GC_locker | |
| 1595 assert(GC_locker::needs_gc(), "Should have been set already"); | |
| 1596 // Skip this foreground collection, instead | |
| 1597 // expanding the heap if necessary. | |
| 1598 // Need the free list locks for the call to free() in compute_new_size() | |
| 1599 compute_new_size(); | |
| 1600 return; | |
| 1601 } | |
| 1602 acquire_control_and_collect(full, clear_all_soft_refs); | |
| 1603 _full_gcs_since_conc_gc++; | |
| 1604 | |
| 1605 } | |
| 1606 | |
| 1607 void CMSCollector::request_full_gc(unsigned int full_gc_count) { | |
| 1608 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 1609 unsigned int gc_count = gch->total_full_collections(); | |
| 1610 if (gc_count == full_gc_count) { | |
| 1611 MutexLockerEx y(CGC_lock, Mutex::_no_safepoint_check_flag); | |
| 1612 _full_gc_requested = true; | |
| 1613 CGC_lock->notify(); // nudge CMS thread | |
| 1614 } | |
| 1615 } | |
| 1616 | |
| 1617 | |
| 1618 // The foreground and background collectors need to coordinate in order | |
| 1619 // to make sure that they do not mutually interfere with CMS collections. | |
| 1620 // When a background collection is active, | |
| 1621 // the foreground collector may need to take over (preempt) and | |
| 1622 // synchronously complete an ongoing collection. Depending on the | |
| 1623 // frequency of the background collections and the heap usage | |
| 1624 // of the application, this preemption can be seldom or frequent. | |
| 1625 // There are only certain | |
| 1626 // points in the background collection that the "collection-baton" | |
| 1627 // can be passed to the foreground collector. | |
| 1628 // | |
| 1629 // The foreground collector will wait for the baton before | |
| 1630 // starting any part of the collection. The foreground collector | |
| 1631 // will only wait at one location. | |
| 1632 // | |
| 1633 // The background collector will yield the baton before starting a new | |
| 1634 // phase of the collection (e.g., before initial marking, marking from roots, | |
| 1635 // precleaning, final re-mark, sweep etc.) This is normally done at the head | |
| 1636 // of the loop which switches the phases. The background collector does some | |
| 1637 // of the phases (initial mark, final re-mark) with the world stopped. | |
| 1638 // Because of locking involved in stopping the world, | |
| 1639 // the foreground collector should not block waiting for the background | |
| 1640 // collector when it is doing a stop-the-world phase. The background | |
| 1641 // collector will yield the baton at an additional point just before | |
| 1642 // it enters a stop-the-world phase. Once the world is stopped, the | |
| 1643 // background collector checks the phase of the collection. If the | |
| 1644 // phase has not changed, it proceeds with the collection. If the | |
| 1645 // phase has changed, it skips that phase of the collection. See | |
| 1646 // the comments on the use of the Heap_lock in collect_in_background(). | |
| 1647 // | |
| 1648 // Variable used in baton passing. | |
| 1649 // _foregroundGCIsActive - Set to true by the foreground collector when | |
| 1650 // it wants the baton. The foreground clears it when it has finished | |
| 1651 // the collection. | |
| 1652 // _foregroundGCShouldWait - Set to true by the background collector | |
| 1653 // when it is running. The foreground collector waits while | |
| 1654 // _foregroundGCShouldWait is true. | |
| 1655 // CGC_lock - monitor used to protect access to the above variables | |
| 1656 // and to notify the foreground and background collectors. | |
| 1657 // _collectorState - current state of the CMS collection. | |
| 1658 // | |
| 1659 // The foreground collector | |
| 1660 // acquires the CGC_lock | |
| 1661 // sets _foregroundGCIsActive | |
| 1662 // waits on the CGC_lock for _foregroundGCShouldWait to be false | |
| 1663 // various locks acquired in preparation for the collection | |
| 1664 // are released so as not to block the background collector | |
| 1665 // that is in the midst of a collection | |
| 1666 // proceeds with the collection | |
| 1667 // clears _foregroundGCIsActive | |
| 1668 // returns | |
| 1669 // | |
| 1670 // The background collector in a loop iterating on the phases of the | |
| 1671 // collection | |
| 1672 // acquires the CGC_lock | |
| 1673 // sets _foregroundGCShouldWait | |
| 1674 // if _foregroundGCIsActive is set | |
| 1675 // clears _foregroundGCShouldWait, notifies _CGC_lock | |
| 1676 // waits on _CGC_lock for _foregroundGCIsActive to become false | |
| 1677 // and exits the loop. | |
| 1678 // otherwise | |
| 1679 // proceed with that phase of the collection | |
| 1680 // if the phase is a stop-the-world phase, | |
| 1681 // yield the baton once more just before enqueueing | |
| 1682 // the stop-world CMS operation (executed by the VM thread). | |
| 1683 // returns after all phases of the collection are done | |
| 1684 // | |
| 1685 | |
| 1686 void CMSCollector::acquire_control_and_collect(bool full, | |
| 1687 bool clear_all_soft_refs) { | |
| 1688 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint"); | |
| 1689 assert(!Thread::current()->is_ConcurrentGC_thread(), | |
| 1690 "shouldn't try to acquire control from self!"); | |
| 1691 | |
| 1692 // Start the protocol for acquiring control of the | |
| 1693 // collection from the background collector (aka CMS thread). | |
| 1694 assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(), | |
| 1695 "VM thread should have CMS token"); | |
| 1696 // Remember the possibly interrupted state of an ongoing | |
| 1697 // concurrent collection | |
| 1698 CollectorState first_state = _collectorState; | |
| 1699 | |
| 1700 // Signal to a possibly ongoing concurrent collection that | |
| 1701 // we want to do a foreground collection. | |
| 1702 _foregroundGCIsActive = true; | |
| 1703 | |
| 1704 // Disable incremental mode during a foreground collection. | |
| 1705 ICMSDisabler icms_disabler; | |
| 1706 | |
| 1707 // release locks and wait for a notify from the background collector | |
| 1708 // releasing the locks in only necessary for phases which | |
| 1709 // do yields to improve the granularity of the collection. | |
| 1710 assert_lock_strong(bitMapLock()); | |
| 1711 // We need to lock the Free list lock for the space that we are | |
| 1712 // currently collecting. | |
| 1713 assert(haveFreelistLocks(), "Must be holding free list locks"); | |
| 1714 bitMapLock()->unlock(); | |
| 1715 releaseFreelistLocks(); | |
| 1716 { | |
| 1717 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
| 1718 if (_foregroundGCShouldWait) { | |
| 1719 // We are going to be waiting for action for the CMS thread; | |
| 1720 // it had better not be gone (for instance at shutdown)! | |
| 1721 assert(ConcurrentMarkSweepThread::cmst() != NULL, | |
| 1722 "CMS thread must be running"); | |
| 1723 // Wait here until the background collector gives us the go-ahead | |
| 1724 ConcurrentMarkSweepThread::clear_CMS_flag( | |
| 1725 ConcurrentMarkSweepThread::CMS_vm_has_token); // release token | |
| 1726 // Get a possibly blocked CMS thread going: | |
| 1727 // Note that we set _foregroundGCIsActive true above, | |
| 1728 // without protection of the CGC_lock. | |
| 1729 CGC_lock->notify(); | |
| 1730 assert(!ConcurrentMarkSweepThread::vm_thread_wants_cms_token(), | |
| 1731 "Possible deadlock"); | |
| 1732 while (_foregroundGCShouldWait) { | |
| 1733 // wait for notification | |
| 1734 CGC_lock->wait(Mutex::_no_safepoint_check_flag); | |
| 1735 // Possibility of delay/starvation here, since CMS token does | |
| 1736 // not know to give priority to VM thread? Actually, i think | |
| 1737 // there wouldn't be any delay/starvation, but the proof of | |
| 1738 // that "fact" (?) appears non-trivial. XXX 20011219YSR | |
| 1739 } | |
| 1740 ConcurrentMarkSweepThread::set_CMS_flag( | |
| 1741 ConcurrentMarkSweepThread::CMS_vm_has_token); | |
| 1742 } | |
| 1743 } | |
| 1744 // The CMS_token is already held. Get back the other locks. | |
| 1745 assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(), | |
| 1746 "VM thread should have CMS token"); | |
| 1747 getFreelistLocks(); | |
| 1748 bitMapLock()->lock_without_safepoint_check(); | |
| 1749 if (TraceCMSState) { | |
| 1750 gclog_or_tty->print_cr("CMS foreground collector has asked for control " | |
| 1751 INTPTR_FORMAT " with first state %d", Thread::current(), first_state); | |
| 1752 gclog_or_tty->print_cr(" gets control with state %d", _collectorState); | |
| 1753 } | |
| 1754 | |
| 1755 // Check if we need to do a compaction, or if not, whether | |
| 1756 // we need to start the mark-sweep from scratch. | |
| 1757 bool should_compact = false; | |
| 1758 bool should_start_over = false; | |
| 1759 decide_foreground_collection_type(clear_all_soft_refs, | |
| 1760 &should_compact, &should_start_over); | |
| 1761 | |
| 1762 NOT_PRODUCT( | |
| 1763 if (RotateCMSCollectionTypes) { | |
| 1764 if (_cmsGen->debug_collection_type() == | |
| 1765 ConcurrentMarkSweepGeneration::MSC_foreground_collection_type) { | |
| 1766 should_compact = true; | |
| 1767 } else if (_cmsGen->debug_collection_type() == | |
| 1768 ConcurrentMarkSweepGeneration::MS_foreground_collection_type) { | |
| 1769 should_compact = false; | |
| 1770 } | |
| 1771 } | |
| 1772 ) | |
| 1773 | |
| 1774 if (PrintGCDetails && first_state > Idling) { | |
| 1775 GCCause::Cause cause = GenCollectedHeap::heap()->gc_cause(); | |
| 1776 if (GCCause::is_user_requested_gc(cause) || | |
| 1777 GCCause::is_serviceability_requested_gc(cause)) { | |
| 1778 gclog_or_tty->print(" (concurrent mode interrupted)"); | |
| 1779 } else { | |
| 1780 gclog_or_tty->print(" (concurrent mode failure)"); | |
| 1781 } | |
| 1782 } | |
| 1783 | |
| 1784 if (should_compact) { | |
| 1785 // If the collection is being acquired from the background | |
| 1786 // collector, there may be references on the discovered | |
| 1787 // references lists that have NULL referents (being those | |
| 1788 // that were concurrently cleared by a mutator) or | |
| 1789 // that are no longer active (having been enqueued concurrently | |
| 1790 // by the mutator). | |
| 1791 // Scrub the list of those references because Mark-Sweep-Compact | |
| 1792 // code assumes referents are not NULL and that all discovered | |
| 1793 // Reference objects are active. | |
| 1794 ref_processor()->clean_up_discovered_references(); | |
| 1795 | |
| 1796 do_compaction_work(clear_all_soft_refs); | |
| 1797 | |
| 1798 // Has the GC time limit been exceeded? | |
| 1799 check_gc_time_limit(); | |
| 1800 | |
| 1801 } else { | |
| 1802 do_mark_sweep_work(clear_all_soft_refs, first_state, | |
| 1803 should_start_over); | |
| 1804 } | |
| 1805 // Reset the expansion cause, now that we just completed | |
| 1806 // a collection cycle. | |
| 1807 clear_expansion_cause(); | |
| 1808 _foregroundGCIsActive = false; | |
| 1809 return; | |
| 1810 } | |
| 1811 | |
| 1812 void CMSCollector::check_gc_time_limit() { | |
| 1813 | |
| 1814 // Ignore explicit GC's. Exiting here does not set the flag and | |
| 1815 // does not reset the count. Updating of the averages for system | |
| 1816 // GC's is still controlled by UseAdaptiveSizePolicyWithSystemGC. | |
| 1817 GCCause::Cause gc_cause = GenCollectedHeap::heap()->gc_cause(); | |
| 1818 if (GCCause::is_user_requested_gc(gc_cause) || | |
| 1819 GCCause::is_serviceability_requested_gc(gc_cause)) { | |
| 1820 return; | |
| 1821 } | |
| 1822 | |
| 1823 // Calculate the fraction of the CMS generation was freed during | |
| 1824 // the last collection. | |
| 1825 // Only consider the STW compacting cost for now. | |
| 1826 // | |
| 1827 // Note that the gc time limit test only works for the collections | |
| 1828 // of the young gen + tenured gen and not for collections of the | |
| 1829 // permanent gen. That is because the calculation of the space | |
| 1830 // freed by the collection is the free space in the young gen + | |
| 1831 // tenured gen. | |
| 1832 | |
| 1833 double fraction_free = | |
| 1834 ((double)_cmsGen->free())/((double)_cmsGen->max_capacity()); | |
| 1835 if ((100.0 * size_policy()->compacting_gc_cost()) > | |
| 1836 ((double) GCTimeLimit) && | |
| 1837 ((fraction_free * 100) < GCHeapFreeLimit)) { | |
| 1838 size_policy()->inc_gc_time_limit_count(); | |
| 1839 if (UseGCOverheadLimit && | |
| 1840 (size_policy()->gc_time_limit_count() > | |
| 1841 AdaptiveSizePolicyGCTimeLimitThreshold)) { | |
| 1842 size_policy()->set_gc_time_limit_exceeded(true); | |
| 1843 // Avoid consecutive OOM due to the gc time limit by resetting | |
| 1844 // the counter. | |
| 1845 size_policy()->reset_gc_time_limit_count(); | |
| 1846 if (PrintGCDetails) { | |
| 1847 gclog_or_tty->print_cr(" GC is exceeding overhead limit " | |
| 1848 "of %d%%", GCTimeLimit); | |
| 1849 } | |
| 1850 } else { | |
| 1851 if (PrintGCDetails) { | |
| 1852 gclog_or_tty->print_cr(" GC would exceed overhead limit " | |
| 1853 "of %d%%", GCTimeLimit); | |
| 1854 } | |
| 1855 } | |
| 1856 } else { | |
| 1857 size_policy()->reset_gc_time_limit_count(); | |
| 1858 } | |
| 1859 } | |
| 1860 | |
| 1861 // Resize the perm generation and the tenured generation | |
| 1862 // after obtaining the free list locks for the | |
| 1863 // two generations. | |
| 1864 void CMSCollector::compute_new_size() { | |
| 1865 assert_locked_or_safepoint(Heap_lock); | |
| 1866 FreelistLocker z(this); | |
| 1867 _permGen->compute_new_size(); | |
| 1868 _cmsGen->compute_new_size(); | |
| 1869 } | |
| 1870 | |
| 1871 // A work method used by foreground collection to determine | |
| 1872 // what type of collection (compacting or not, continuing or fresh) | |
| 1873 // it should do. | |
| 1874 // NOTE: the intent is to make UseCMSCompactAtFullCollection | |
| 1875 // and CMSCompactWhenClearAllSoftRefs the default in the future | |
| 1876 // and do away with the flags after a suitable period. | |
| 1877 void CMSCollector::decide_foreground_collection_type( | |
| 1878 bool clear_all_soft_refs, bool* should_compact, | |
| 1879 bool* should_start_over) { | |
| 1880 // Normally, we'll compact only if the UseCMSCompactAtFullCollection | |
| 1881 // flag is set, and we have either requested a System.gc() or | |
| 1882 // the number of full gc's since the last concurrent cycle | |
| 1883 // has exceeded the threshold set by CMSFullGCsBeforeCompaction, | |
| 1884 // or if an incremental collection has failed | |
| 1885 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 1886 assert(gch->collector_policy()->is_two_generation_policy(), | |
| 1887 "You may want to check the correctness of the following"); | |
| 1888 // Inform cms gen if this was due to partial collection failing. | |
| 1889 // The CMS gen may use this fact to determine its expansion policy. | |
| 1890 if (gch->incremental_collection_will_fail()) { | |
| 1891 assert(!_cmsGen->incremental_collection_failed(), | |
| 1892 "Should have been noticed, reacted to and cleared"); | |
| 1893 _cmsGen->set_incremental_collection_failed(); | |
| 1894 } | |
| 1895 *should_compact = | |
| 1896 UseCMSCompactAtFullCollection && | |
| 1897 ((_full_gcs_since_conc_gc >= CMSFullGCsBeforeCompaction) || | |
| 1898 GCCause::is_user_requested_gc(gch->gc_cause()) || | |
| 1899 gch->incremental_collection_will_fail()); | |
| 1900 *should_start_over = false; | |
| 1901 if (clear_all_soft_refs && !*should_compact) { | |
| 1902 // We are about to do a last ditch collection attempt | |
| 1903 // so it would normally make sense to do a compaction | |
| 1904 // to reclaim as much space as possible. | |
| 1905 if (CMSCompactWhenClearAllSoftRefs) { | |
| 1906 // Default: The rationale is that in this case either | |
| 1907 // we are past the final marking phase, in which case | |
| 1908 // we'd have to start over, or so little has been done | |
| 1909 // that there's little point in saving that work. Compaction | |
| 1910 // appears to be the sensible choice in either case. | |
| 1911 *should_compact = true; | |
| 1912 } else { | |
| 1913 // We have been asked to clear all soft refs, but not to | |
| 1914 // compact. Make sure that we aren't past the final checkpoint | |
| 1915 // phase, for that is where we process soft refs. If we are already | |
| 1916 // past that phase, we'll need to redo the refs discovery phase and | |
| 1917 // if necessary clear soft refs that weren't previously | |
| 1918 // cleared. We do so by remembering the phase in which | |
| 1919 // we came in, and if we are past the refs processing | |
| 1920 // phase, we'll choose to just redo the mark-sweep | |
| 1921 // collection from scratch. | |
| 1922 if (_collectorState > FinalMarking) { | |
| 1923 // We are past the refs processing phase; | |
| 1924 // start over and do a fresh synchronous CMS cycle | |
| 1925 _collectorState = Resetting; // skip to reset to start new cycle | |
| 1926 reset(false /* == !asynch */); | |
| 1927 *should_start_over = true; | |
| 1928 } // else we can continue a possibly ongoing current cycle | |
| 1929 } | |
| 1930 } | |
| 1931 } | |
| 1932 | |
| 1933 // A work method used by the foreground collector to do | |
| 1934 // a mark-sweep-compact. | |
| 1935 void CMSCollector::do_compaction_work(bool clear_all_soft_refs) { | |
| 1936 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 1937 TraceTime t("CMS:MSC ", PrintGCDetails && Verbose, true, gclog_or_tty); | |
| 1938 if (PrintGC && Verbose && !(GCCause::is_user_requested_gc(gch->gc_cause()))) { | |
| 1939 gclog_or_tty->print_cr("Compact ConcurrentMarkSweepGeneration after %d " | |
| 1940 "collections passed to foreground collector", _full_gcs_since_conc_gc); | |
| 1941 } | |
| 1942 | |
| 1943 // Sample collection interval time and reset for collection pause. | |
| 1944 if (UseAdaptiveSizePolicy) { | |
| 1945 size_policy()->msc_collection_begin(); | |
| 1946 } | |
| 1947 | |
| 1948 // Temporarily widen the span of the weak reference processing to | |
| 1949 // the entire heap. | |
| 1950 MemRegion new_span(GenCollectedHeap::heap()->reserved_region()); | |
| 1951 ReferenceProcessorSpanMutator x(ref_processor(), new_span); | |
| 1952 | |
| 1953 // Temporarily, clear the "is_alive_non_header" field of the | |
| 1954 // reference processor. | |
| 1955 ReferenceProcessorIsAliveMutator y(ref_processor(), NULL); | |
| 1956 | |
| 1957 // Temporarily make reference _processing_ single threaded (non-MT). | |
| 1958 ReferenceProcessorMTProcMutator z(ref_processor(), false); | |
| 1959 | |
| 1960 // Temporarily make refs discovery atomic | |
| 1961 ReferenceProcessorAtomicMutator w(ref_processor(), true); | |
| 1962 | |
| 1963 ref_processor()->set_enqueuing_is_done(false); | |
| 1964 ref_processor()->enable_discovery(); | |
|
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1965 ref_processor()->setup_policy(clear_all_soft_refs); |
| 0 | 1966 // If an asynchronous collection finishes, the _modUnionTable is |
| 1967 // all clear. If we are assuming the collection from an asynchronous | |
| 1968 // collection, clear the _modUnionTable. | |
| 1969 assert(_collectorState != Idling || _modUnionTable.isAllClear(), | |
| 1970 "_modUnionTable should be clear if the baton was not passed"); | |
| 1971 _modUnionTable.clear_all(); | |
| 1972 | |
| 1973 // We must adjust the allocation statistics being maintained | |
| 1974 // in the free list space. We do so by reading and clearing | |
| 1975 // the sweep timer and updating the block flux rate estimates below. | |
| 1976 assert(_sweep_timer.is_active(), "We should never see the timer inactive"); | |
| 1977 _sweep_timer.stop(); | |
| 1978 // Note that we do not use this sample to update the _sweep_estimate. | |
| 1979 _cmsGen->cmsSpace()->beginSweepFLCensus((float)(_sweep_timer.seconds()), | |
| 1980 _sweep_estimate.padded_average()); | |
| 1981 | |
| 1982 GenMarkSweep::invoke_at_safepoint(_cmsGen->level(), | |
| 1983 ref_processor(), clear_all_soft_refs); | |
| 1984 #ifdef ASSERT | |
| 1985 CompactibleFreeListSpace* cms_space = _cmsGen->cmsSpace(); | |
| 1986 size_t free_size = cms_space->free(); | |
| 1987 assert(free_size == | |
| 1988 pointer_delta(cms_space->end(), cms_space->compaction_top()) | |
| 1989 * HeapWordSize, | |
| 1990 "All the free space should be compacted into one chunk at top"); | |
| 1991 assert(cms_space->dictionary()->totalChunkSize( | |
| 1992 debug_only(cms_space->freelistLock())) == 0 || | |
| 1993 cms_space->totalSizeInIndexedFreeLists() == 0, | |
| 1994 "All the free space should be in a single chunk"); | |
| 1995 size_t num = cms_space->totalCount(); | |
| 1996 assert((free_size == 0 && num == 0) || | |
| 1997 (free_size > 0 && (num == 1 || num == 2)), | |
| 1998 "There should be at most 2 free chunks after compaction"); | |
| 1999 #endif // ASSERT | |
| 2000 _collectorState = Resetting; | |
| 2001 assert(_restart_addr == NULL, | |
| 2002 "Should have been NULL'd before baton was passed"); | |
| 2003 reset(false /* == !asynch */); | |
| 2004 _cmsGen->reset_after_compaction(); | |
|
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2005 _concurrent_cycles_since_last_unload = 0; |
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2007 if (verifying() && !should_unload_classes()) { |
| 0 | 2008 perm_gen_verify_bit_map()->clear_all(); |
| 2009 } | |
| 2010 | |
| 2011 // Clear any data recorded in the PLAB chunk arrays. | |
| 2012 if (_survivor_plab_array != NULL) { | |
| 2013 reset_survivor_plab_arrays(); | |
| 2014 } | |
| 2015 | |
| 2016 // Adjust the per-size allocation stats for the next epoch. | |
| 2017 _cmsGen->cmsSpace()->endSweepFLCensus(sweepCount() /* fake */); | |
| 2018 // Restart the "sweep timer" for next epoch. | |
| 2019 _sweep_timer.reset(); | |
| 2020 _sweep_timer.start(); | |
| 2021 | |
| 2022 // Sample collection pause time and reset for collection interval. | |
| 2023 if (UseAdaptiveSizePolicy) { | |
| 2024 size_policy()->msc_collection_end(gch->gc_cause()); | |
| 2025 } | |
| 2026 | |
| 2027 // For a mark-sweep-compact, compute_new_size() will be called | |
| 2028 // in the heap's do_collection() method. | |
| 2029 } | |
| 2030 | |
| 2031 // A work method used by the foreground collector to do | |
| 2032 // a mark-sweep, after taking over from a possibly on-going | |
| 2033 // concurrent mark-sweep collection. | |
| 2034 void CMSCollector::do_mark_sweep_work(bool clear_all_soft_refs, | |
| 2035 CollectorState first_state, bool should_start_over) { | |
| 2036 if (PrintGC && Verbose) { | |
| 2037 gclog_or_tty->print_cr("Pass concurrent collection to foreground " | |
| 2038 "collector with count %d", | |
| 2039 _full_gcs_since_conc_gc); | |
| 2040 } | |
| 2041 switch (_collectorState) { | |
| 2042 case Idling: | |
| 2043 if (first_state == Idling || should_start_over) { | |
| 2044 // The background GC was not active, or should | |
| 2045 // restarted from scratch; start the cycle. | |
| 2046 _collectorState = InitialMarking; | |
| 2047 } | |
| 2048 // If first_state was not Idling, then a background GC | |
| 2049 // was in progress and has now finished. No need to do it | |
| 2050 // again. Leave the state as Idling. | |
| 2051 break; | |
| 2052 case Precleaning: | |
| 2053 // In the foreground case don't do the precleaning since | |
| 2054 // it is not done concurrently and there is extra work | |
| 2055 // required. | |
| 2056 _collectorState = FinalMarking; | |
| 2057 } | |
| 2058 if (PrintGCDetails && | |
| 2059 (_collectorState > Idling || | |
| 2060 !GCCause::is_user_requested_gc(GenCollectedHeap::heap()->gc_cause()))) { | |
| 2061 gclog_or_tty->print(" (concurrent mode failure)"); | |
| 2062 } | |
| 2063 collect_in_foreground(clear_all_soft_refs); | |
| 2064 | |
| 2065 // For a mark-sweep, compute_new_size() will be called | |
| 2066 // in the heap's do_collection() method. | |
| 2067 } | |
| 2068 | |
| 2069 | |
| 2070 void CMSCollector::getFreelistLocks() const { | |
| 2071 // Get locks for all free lists in all generations that this | |
| 2072 // collector is responsible for | |
| 2073 _cmsGen->freelistLock()->lock_without_safepoint_check(); | |
| 2074 _permGen->freelistLock()->lock_without_safepoint_check(); | |
| 2075 } | |
| 2076 | |
| 2077 void CMSCollector::releaseFreelistLocks() const { | |
| 2078 // Release locks for all free lists in all generations that this | |
| 2079 // collector is responsible for | |
| 2080 _cmsGen->freelistLock()->unlock(); | |
| 2081 _permGen->freelistLock()->unlock(); | |
| 2082 } | |
| 2083 | |
| 2084 bool CMSCollector::haveFreelistLocks() const { | |
| 2085 // Check locks for all free lists in all generations that this | |
| 2086 // collector is responsible for | |
| 2087 assert_lock_strong(_cmsGen->freelistLock()); | |
| 2088 assert_lock_strong(_permGen->freelistLock()); | |
| 2089 PRODUCT_ONLY(ShouldNotReachHere()); | |
| 2090 return true; | |
| 2091 } | |
| 2092 | |
| 2093 // A utility class that is used by the CMS collector to | |
| 2094 // temporarily "release" the foreground collector from its | |
| 2095 // usual obligation to wait for the background collector to | |
| 2096 // complete an ongoing phase before proceeding. | |
| 2097 class ReleaseForegroundGC: public StackObj { | |
| 2098 private: | |
| 2099 CMSCollector* _c; | |
| 2100 public: | |
| 2101 ReleaseForegroundGC(CMSCollector* c) : _c(c) { | |
| 2102 assert(_c->_foregroundGCShouldWait, "Else should not need to call"); | |
| 2103 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
| 2104 // allow a potentially blocked foreground collector to proceed | |
| 2105 _c->_foregroundGCShouldWait = false; | |
| 2106 if (_c->_foregroundGCIsActive) { | |
| 2107 CGC_lock->notify(); | |
| 2108 } | |
| 2109 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 2110 "Possible deadlock"); | |
| 2111 } | |
| 2112 | |
| 2113 ~ReleaseForegroundGC() { | |
| 2114 assert(!_c->_foregroundGCShouldWait, "Usage protocol violation?"); | |
| 2115 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
| 2116 _c->_foregroundGCShouldWait = true; | |
| 2117 } | |
| 2118 }; | |
| 2119 | |
| 2120 // There are separate collect_in_background and collect_in_foreground because of | |
| 2121 // the different locking requirements of the background collector and the | |
| 2122 // foreground collector. There was originally an attempt to share | |
| 2123 // one "collect" method between the background collector and the foreground | |
| 2124 // collector but the if-then-else required made it cleaner to have | |
| 2125 // separate methods. | |
| 2126 void CMSCollector::collect_in_background(bool clear_all_soft_refs) { | |
| 2127 assert(Thread::current()->is_ConcurrentGC_thread(), | |
| 2128 "A CMS asynchronous collection is only allowed on a CMS thread."); | |
| 2129 | |
| 2130 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 2131 { | |
| 2132 bool safepoint_check = Mutex::_no_safepoint_check_flag; | |
| 2133 MutexLockerEx hl(Heap_lock, safepoint_check); | |
|
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2134 FreelistLocker fll(this); |
| 0 | 2135 MutexLockerEx x(CGC_lock, safepoint_check); |
| 2136 if (_foregroundGCIsActive || !UseAsyncConcMarkSweepGC) { | |
| 2137 // The foreground collector is active or we're | |
| 2138 // not using asynchronous collections. Skip this | |
| 2139 // background collection. | |
| 2140 assert(!_foregroundGCShouldWait, "Should be clear"); | |
| 2141 return; | |
| 2142 } else { | |
| 2143 assert(_collectorState == Idling, "Should be idling before start."); | |
| 2144 _collectorState = InitialMarking; | |
| 2145 // Reset the expansion cause, now that we are about to begin | |
| 2146 // a new cycle. | |
| 2147 clear_expansion_cause(); | |
| 2148 } | |
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2149 // Decide if we want to enable class unloading as part of the |
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2150 // ensuing concurrent GC cycle. |
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2151 update_should_unload_classes(); |
| 0 | 2152 _full_gc_requested = false; // acks all outstanding full gc requests |
| 2153 // Signal that we are about to start a collection | |
| 2154 gch->increment_total_full_collections(); // ... starting a collection cycle | |
| 2155 _collection_count_start = gch->total_full_collections(); | |
| 2156 } | |
| 2157 | |
| 2158 // Used for PrintGC | |
| 2159 size_t prev_used; | |
| 2160 if (PrintGC && Verbose) { | |
| 2161 prev_used = _cmsGen->used(); // XXXPERM | |
| 2162 } | |
| 2163 | |
| 2164 // The change of the collection state is normally done at this level; | |
| 2165 // the exceptions are phases that are executed while the world is | |
| 2166 // stopped. For those phases the change of state is done while the | |
| 2167 // world is stopped. For baton passing purposes this allows the | |
| 2168 // background collector to finish the phase and change state atomically. | |
| 2169 // The foreground collector cannot wait on a phase that is done | |
| 2170 // while the world is stopped because the foreground collector already | |
| 2171 // has the world stopped and would deadlock. | |
| 2172 while (_collectorState != Idling) { | |
| 2173 if (TraceCMSState) { | |
| 2174 gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " in CMS state %d", | |
| 2175 Thread::current(), _collectorState); | |
| 2176 } | |
| 2177 // The foreground collector | |
| 2178 // holds the Heap_lock throughout its collection. | |
| 2179 // holds the CMS token (but not the lock) | |
| 2180 // except while it is waiting for the background collector to yield. | |
| 2181 // | |
| 2182 // The foreground collector should be blocked (not for long) | |
| 2183 // if the background collector is about to start a phase | |
| 2184 // executed with world stopped. If the background | |
| 2185 // collector has already started such a phase, the | |
| 2186 // foreground collector is blocked waiting for the | |
| 2187 // Heap_lock. The stop-world phases (InitialMarking and FinalMarking) | |
| 2188 // are executed in the VM thread. | |
| 2189 // | |
| 2190 // The locking order is | |
| 2191 // PendingListLock (PLL) -- if applicable (FinalMarking) | |
| 2192 // Heap_lock (both this & PLL locked in VM_CMS_Operation::prologue()) | |
| 2193 // CMS token (claimed in | |
| 2194 // stop_world_and_do() --> | |
| 2195 // safepoint_synchronize() --> | |
| 2196 // CMSThread::synchronize()) | |
| 2197 | |
| 2198 { | |
| 2199 // Check if the FG collector wants us to yield. | |
| 2200 CMSTokenSync x(true); // is cms thread | |
| 2201 if (waitForForegroundGC()) { | |
| 2202 // We yielded to a foreground GC, nothing more to be | |
| 2203 // done this round. | |
| 2204 assert(_foregroundGCShouldWait == false, "We set it to false in " | |
| 2205 "waitForForegroundGC()"); | |
| 2206 if (TraceCMSState) { | |
| 2207 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT | |
| 2208 " exiting collection CMS state %d", | |
| 2209 Thread::current(), _collectorState); | |
| 2210 } | |
| 2211 return; | |
| 2212 } else { | |
| 2213 // The background collector can run but check to see if the | |
| 2214 // foreground collector has done a collection while the | |
| 2215 // background collector was waiting to get the CGC_lock | |
| 2216 // above. If yes, break so that _foregroundGCShouldWait | |
| 2217 // is cleared before returning. | |
| 2218 if (_collectorState == Idling) { | |
| 2219 break; | |
| 2220 } | |
| 2221 } | |
| 2222 } | |
| 2223 | |
| 2224 assert(_foregroundGCShouldWait, "Foreground collector, if active, " | |
| 2225 "should be waiting"); | |
| 2226 | |
| 2227 switch (_collectorState) { | |
| 2228 case InitialMarking: | |
| 2229 { | |
| 2230 ReleaseForegroundGC x(this); | |
| 2231 stats().record_cms_begin(); | |
| 2232 | |
| 2233 VM_CMS_Initial_Mark initial_mark_op(this); | |
| 2234 VMThread::execute(&initial_mark_op); | |
| 2235 } | |
| 2236 // The collector state may be any legal state at this point | |
| 2237 // since the background collector may have yielded to the | |
| 2238 // foreground collector. | |
| 2239 break; | |
| 2240 case Marking: | |
| 2241 // initial marking in checkpointRootsInitialWork has been completed | |
| 2242 if (markFromRoots(true)) { // we were successful | |
| 2243 assert(_collectorState == Precleaning, "Collector state should " | |
| 2244 "have changed"); | |
| 2245 } else { | |
| 2246 assert(_foregroundGCIsActive, "Internal state inconsistency"); | |
| 2247 } | |
| 2248 break; | |
| 2249 case Precleaning: | |
| 2250 if (UseAdaptiveSizePolicy) { | |
| 2251 size_policy()->concurrent_precleaning_begin(); | |
| 2252 } | |
| 2253 // marking from roots in markFromRoots has been completed | |
| 2254 preclean(); | |
| 2255 if (UseAdaptiveSizePolicy) { | |
| 2256 size_policy()->concurrent_precleaning_end(); | |
| 2257 } | |
| 2258 assert(_collectorState == AbortablePreclean || | |
| 2259 _collectorState == FinalMarking, | |
| 2260 "Collector state should have changed"); | |
| 2261 break; | |
| 2262 case AbortablePreclean: | |
| 2263 if (UseAdaptiveSizePolicy) { | |
| 2264 size_policy()->concurrent_phases_resume(); | |
| 2265 } | |
| 2266 abortable_preclean(); | |
| 2267 if (UseAdaptiveSizePolicy) { | |
| 2268 size_policy()->concurrent_precleaning_end(); | |
| 2269 } | |
| 2270 assert(_collectorState == FinalMarking, "Collector state should " | |
| 2271 "have changed"); | |
| 2272 break; | |
| 2273 case FinalMarking: | |
| 2274 { | |
| 2275 ReleaseForegroundGC x(this); | |
| 2276 | |
| 2277 VM_CMS_Final_Remark final_remark_op(this); | |
| 2278 VMThread::execute(&final_remark_op); | |
| 935 | 2279 } |
| 0 | 2280 assert(_foregroundGCShouldWait, "block post-condition"); |
| 2281 break; | |
| 2282 case Sweeping: | |
| 2283 if (UseAdaptiveSizePolicy) { | |
| 2284 size_policy()->concurrent_sweeping_begin(); | |
| 2285 } | |
| 2286 // final marking in checkpointRootsFinal has been completed | |
| 2287 sweep(true); | |
| 2288 assert(_collectorState == Resizing, "Collector state change " | |
| 2289 "to Resizing must be done under the free_list_lock"); | |
| 2290 _full_gcs_since_conc_gc = 0; | |
| 2291 | |
| 2292 // Stop the timers for adaptive size policy for the concurrent phases | |
| 2293 if (UseAdaptiveSizePolicy) { | |
| 2294 size_policy()->concurrent_sweeping_end(); | |
| 2295 size_policy()->concurrent_phases_end(gch->gc_cause(), | |
| 2296 gch->prev_gen(_cmsGen)->capacity(), | |
| 2297 _cmsGen->free()); | |
| 2298 } | |
| 2299 | |
| 2300 case Resizing: { | |
| 2301 // Sweeping has been completed... | |
| 2302 // At this point the background collection has completed. | |
| 2303 // Don't move the call to compute_new_size() down | |
| 2304 // into code that might be executed if the background | |
| 2305 // collection was preempted. | |
| 2306 { | |
| 2307 ReleaseForegroundGC x(this); // unblock FG collection | |
| 2308 MutexLockerEx y(Heap_lock, Mutex::_no_safepoint_check_flag); | |
| 2309 CMSTokenSync z(true); // not strictly needed. | |
| 2310 if (_collectorState == Resizing) { | |
| 2311 compute_new_size(); | |
| 2312 _collectorState = Resetting; | |
| 2313 } else { | |
| 2314 assert(_collectorState == Idling, "The state should only change" | |
| 2315 " because the foreground collector has finished the collection"); | |
| 2316 } | |
| 2317 } | |
| 2318 break; | |
| 2319 } | |
| 2320 case Resetting: | |
| 2321 // CMS heap resizing has been completed | |
| 2322 reset(true); | |
| 2323 assert(_collectorState == Idling, "Collector state should " | |
| 2324 "have changed"); | |
| 2325 stats().record_cms_end(); | |
| 2326 // Don't move the concurrent_phases_end() and compute_new_size() | |
| 2327 // calls to here because a preempted background collection | |
| 2328 // has it's state set to "Resetting". | |
| 2329 break; | |
| 2330 case Idling: | |
| 2331 default: | |
| 2332 ShouldNotReachHere(); | |
| 2333 break; | |
| 2334 } | |
| 2335 if (TraceCMSState) { | |
| 2336 gclog_or_tty->print_cr(" Thread " INTPTR_FORMAT " done - next CMS state %d", | |
| 2337 Thread::current(), _collectorState); | |
| 2338 } | |
| 2339 assert(_foregroundGCShouldWait, "block post-condition"); | |
| 2340 } | |
| 2341 | |
| 2342 // Should this be in gc_epilogue? | |
| 2343 collector_policy()->counters()->update_counters(); | |
| 2344 | |
| 2345 { | |
| 2346 // Clear _foregroundGCShouldWait and, in the event that the | |
| 2347 // foreground collector is waiting, notify it, before | |
| 2348 // returning. | |
| 2349 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
| 2350 _foregroundGCShouldWait = false; | |
| 2351 if (_foregroundGCIsActive) { | |
| 2352 CGC_lock->notify(); | |
| 2353 } | |
| 2354 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 2355 "Possible deadlock"); | |
| 2356 } | |
| 2357 if (TraceCMSState) { | |
| 2358 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT | |
| 2359 " exiting collection CMS state %d", | |
| 2360 Thread::current(), _collectorState); | |
| 2361 } | |
| 2362 if (PrintGC && Verbose) { | |
| 2363 _cmsGen->print_heap_change(prev_used); | |
| 2364 } | |
| 2365 } | |
| 2366 | |
| 2367 void CMSCollector::collect_in_foreground(bool clear_all_soft_refs) { | |
| 2368 assert(_foregroundGCIsActive && !_foregroundGCShouldWait, | |
| 2369 "Foreground collector should be waiting, not executing"); | |
| 2370 assert(Thread::current()->is_VM_thread(), "A foreground collection" | |
| 2371 "may only be done by the VM Thread with the world stopped"); | |
| 2372 assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(), | |
| 2373 "VM thread should have CMS token"); | |
| 2374 | |
| 2375 NOT_PRODUCT(TraceTime t("CMS:MS (foreground) ", PrintGCDetails && Verbose, | |
| 2376 true, gclog_or_tty);) | |
| 2377 if (UseAdaptiveSizePolicy) { | |
| 2378 size_policy()->ms_collection_begin(); | |
| 2379 } | |
| 2380 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact); | |
| 2381 | |
| 2382 HandleMark hm; // Discard invalid handles created during verification | |
| 2383 | |
| 2384 if (VerifyBeforeGC && | |
| 2385 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
| 2386 Universe::verify(true); | |
| 2387 } | |
| 2388 | |
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2389 // Snapshot the soft reference policy to be used in this collection cycle. |
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2390 ref_processor()->setup_policy(clear_all_soft_refs); |
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2391 |
| 0 | 2392 bool init_mark_was_synchronous = false; // until proven otherwise |
| 2393 while (_collectorState != Idling) { | |
| 2394 if (TraceCMSState) { | |
| 2395 gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " in CMS state %d", | |
| 2396 Thread::current(), _collectorState); | |
| 2397 } | |
| 2398 switch (_collectorState) { | |
| 2399 case InitialMarking: | |
| 2400 init_mark_was_synchronous = true; // fact to be exploited in re-mark | |
| 2401 checkpointRootsInitial(false); | |
| 2402 assert(_collectorState == Marking, "Collector state should have changed" | |
| 2403 " within checkpointRootsInitial()"); | |
| 2404 break; | |
| 2405 case Marking: | |
| 2406 // initial marking in checkpointRootsInitialWork has been completed | |
| 2407 if (VerifyDuringGC && | |
| 2408 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
| 2409 gclog_or_tty->print("Verify before initial mark: "); | |
| 2410 Universe::verify(true); | |
| 2411 } | |
| 2412 { | |
| 2413 bool res = markFromRoots(false); | |
| 2414 assert(res && _collectorState == FinalMarking, "Collector state should " | |
| 2415 "have changed"); | |
| 2416 break; | |
| 2417 } | |
| 2418 case FinalMarking: | |
| 2419 if (VerifyDuringGC && | |
| 2420 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
| 2421 gclog_or_tty->print("Verify before re-mark: "); | |
| 2422 Universe::verify(true); | |
| 2423 } | |
| 2424 checkpointRootsFinal(false, clear_all_soft_refs, | |
| 2425 init_mark_was_synchronous); | |
| 2426 assert(_collectorState == Sweeping, "Collector state should not " | |
| 2427 "have changed within checkpointRootsFinal()"); | |
| 2428 break; | |
| 2429 case Sweeping: | |
| 2430 // final marking in checkpointRootsFinal has been completed | |
| 2431 if (VerifyDuringGC && | |
| 2432 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
| 2433 gclog_or_tty->print("Verify before sweep: "); | |
| 2434 Universe::verify(true); | |
| 2435 } | |
| 2436 sweep(false); | |
| 2437 assert(_collectorState == Resizing, "Incorrect state"); | |
| 2438 break; | |
| 2439 case Resizing: { | |
| 2440 // Sweeping has been completed; the actual resize in this case | |
| 2441 // is done separately; nothing to be done in this state. | |
| 2442 _collectorState = Resetting; | |
| 2443 break; | |
| 2444 } | |
| 2445 case Resetting: | |
| 2446 // The heap has been resized. | |
| 2447 if (VerifyDuringGC && | |
| 2448 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
| 2449 gclog_or_tty->print("Verify before reset: "); | |
| 2450 Universe::verify(true); | |
| 2451 } | |
| 2452 reset(false); | |
| 2453 assert(_collectorState == Idling, "Collector state should " | |
| 2454 "have changed"); | |
| 2455 break; | |
| 2456 case Precleaning: | |
| 2457 case AbortablePreclean: | |
| 2458 // Elide the preclean phase | |
| 2459 _collectorState = FinalMarking; | |
| 2460 break; | |
| 2461 default: | |
| 2462 ShouldNotReachHere(); | |
| 2463 } | |
| 2464 if (TraceCMSState) { | |
| 2465 gclog_or_tty->print_cr(" Thread " INTPTR_FORMAT " done - next CMS state %d", | |
| 2466 Thread::current(), _collectorState); | |
| 2467 } | |
| 2468 } | |
| 2469 | |
| 2470 if (UseAdaptiveSizePolicy) { | |
| 2471 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 2472 size_policy()->ms_collection_end(gch->gc_cause()); | |
| 2473 } | |
| 2474 | |
| 2475 if (VerifyAfterGC && | |
| 2476 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
| 2477 Universe::verify(true); | |
| 2478 } | |
| 2479 if (TraceCMSState) { | |
| 2480 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT | |
| 2481 " exiting collection CMS state %d", | |
| 2482 Thread::current(), _collectorState); | |
| 2483 } | |
| 2484 } | |
| 2485 | |
| 2486 bool CMSCollector::waitForForegroundGC() { | |
| 2487 bool res = false; | |
| 2488 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 2489 "CMS thread should have CMS token"); | |
| 2490 // Block the foreground collector until the | |
| 2491 // background collectors decides whether to | |
| 2492 // yield. | |
| 2493 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
| 2494 _foregroundGCShouldWait = true; | |
| 2495 if (_foregroundGCIsActive) { | |
| 2496 // The background collector yields to the | |
| 2497 // foreground collector and returns a value | |
| 2498 // indicating that it has yielded. The foreground | |
| 2499 // collector can proceed. | |
| 2500 res = true; | |
| 2501 _foregroundGCShouldWait = false; | |
| 2502 ConcurrentMarkSweepThread::clear_CMS_flag( | |
| 2503 ConcurrentMarkSweepThread::CMS_cms_has_token); | |
| 2504 ConcurrentMarkSweepThread::set_CMS_flag( | |
| 2505 ConcurrentMarkSweepThread::CMS_cms_wants_token); | |
| 2506 // Get a possibly blocked foreground thread going | |
| 2507 CGC_lock->notify(); | |
| 2508 if (TraceCMSState) { | |
| 2509 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT " waiting at CMS state %d", | |
| 2510 Thread::current(), _collectorState); | |
| 2511 } | |
| 2512 while (_foregroundGCIsActive) { | |
| 2513 CGC_lock->wait(Mutex::_no_safepoint_check_flag); | |
| 2514 } | |
| 2515 ConcurrentMarkSweepThread::set_CMS_flag( | |
| 2516 ConcurrentMarkSweepThread::CMS_cms_has_token); | |
| 2517 ConcurrentMarkSweepThread::clear_CMS_flag( | |
| 2518 ConcurrentMarkSweepThread::CMS_cms_wants_token); | |
| 2519 } | |
| 2520 if (TraceCMSState) { | |
| 2521 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT " continuing at CMS state %d", | |
| 2522 Thread::current(), _collectorState); | |
| 2523 } | |
| 2524 return res; | |
| 2525 } | |
| 2526 | |
| 2527 // Because of the need to lock the free lists and other structures in | |
| 2528 // the collector, common to all the generations that the collector is | |
| 2529 // collecting, we need the gc_prologues of individual CMS generations | |
| 2530 // delegate to their collector. It may have been simpler had the | |
| 2531 // current infrastructure allowed one to call a prologue on a | |
| 2532 // collector. In the absence of that we have the generation's | |
| 2533 // prologue delegate to the collector, which delegates back | |
| 2534 // some "local" work to a worker method in the individual generations | |
| 2535 // that it's responsible for collecting, while itself doing any | |
| 2536 // work common to all generations it's responsible for. A similar | |
| 2537 // comment applies to the gc_epilogue()'s. | |
| 2538 // The role of the varaible _between_prologue_and_epilogue is to | |
| 2539 // enforce the invocation protocol. | |
| 2540 void CMSCollector::gc_prologue(bool full) { | |
| 2541 // Call gc_prologue_work() for each CMSGen and PermGen that | |
| 2542 // we are responsible for. | |
| 2543 | |
| 2544 // The following locking discipline assumes that we are only called | |
| 2545 // when the world is stopped. | |
| 2546 assert(SafepointSynchronize::is_at_safepoint(), "world is stopped assumption"); | |
| 2547 | |
| 2548 // The CMSCollector prologue must call the gc_prologues for the | |
| 2549 // "generations" (including PermGen if any) that it's responsible | |
| 2550 // for. | |
| 2551 | |
| 2552 assert( Thread::current()->is_VM_thread() | |
| 2553 || ( CMSScavengeBeforeRemark | |
| 2554 && Thread::current()->is_ConcurrentGC_thread()), | |
| 2555 "Incorrect thread type for prologue execution"); | |
| 2556 | |
| 2557 if (_between_prologue_and_epilogue) { | |
| 2558 // We have already been invoked; this is a gc_prologue delegation | |
| 2559 // from yet another CMS generation that we are responsible for, just | |
| 2560 // ignore it since all relevant work has already been done. | |
| 2561 return; | |
| 2562 } | |
| 2563 | |
| 2564 // set a bit saying prologue has been called; cleared in epilogue | |
| 2565 _between_prologue_and_epilogue = true; | |
| 2566 // Claim locks for common data structures, then call gc_prologue_work() | |
| 2567 // for each CMSGen and PermGen that we are responsible for. | |
| 2568 | |
| 2569 getFreelistLocks(); // gets free list locks on constituent spaces | |
| 2570 bitMapLock()->lock_without_safepoint_check(); | |
| 2571 | |
| 2572 // Should call gc_prologue_work() for all cms gens we are responsible for | |
| 2573 bool registerClosure = _collectorState >= Marking | |
| 2574 && _collectorState < Sweeping; | |
| 2575 ModUnionClosure* muc = ParallelGCThreads > 0 ? &_modUnionClosurePar | |
| 2576 : &_modUnionClosure; | |
| 2577 _cmsGen->gc_prologue_work(full, registerClosure, muc); | |
| 2578 _permGen->gc_prologue_work(full, registerClosure, muc); | |
| 2579 | |
| 2580 if (!full) { | |
| 2581 stats().record_gc0_begin(); | |
| 2582 } | |
| 2583 } | |
| 2584 | |
| 2585 void ConcurrentMarkSweepGeneration::gc_prologue(bool full) { | |
| 2586 // Delegate to CMScollector which knows how to coordinate between | |
| 2587 // this and any other CMS generations that it is responsible for | |
| 2588 // collecting. | |
| 2589 collector()->gc_prologue(full); | |
| 2590 } | |
| 2591 | |
| 2592 // This is a "private" interface for use by this generation's CMSCollector. | |
| 2593 // Not to be called directly by any other entity (for instance, | |
| 2594 // GenCollectedHeap, which calls the "public" gc_prologue method above). | |
| 2595 void ConcurrentMarkSweepGeneration::gc_prologue_work(bool full, | |
| 2596 bool registerClosure, ModUnionClosure* modUnionClosure) { | |
| 2597 assert(!incremental_collection_failed(), "Shouldn't be set yet"); | |
| 2598 assert(cmsSpace()->preconsumptionDirtyCardClosure() == NULL, | |
| 2599 "Should be NULL"); | |
| 2600 if (registerClosure) { | |
| 2601 cmsSpace()->setPreconsumptionDirtyCardClosure(modUnionClosure); | |
| 2602 } | |
| 2603 cmsSpace()->gc_prologue(); | |
| 2604 // Clear stat counters | |
| 2605 NOT_PRODUCT( | |
| 2606 assert(_numObjectsPromoted == 0, "check"); | |
| 2607 assert(_numWordsPromoted == 0, "check"); | |
| 2608 if (Verbose && PrintGC) { | |
| 2609 gclog_or_tty->print("Allocated "SIZE_FORMAT" objects, " | |
| 2610 SIZE_FORMAT" bytes concurrently", | |
| 2611 _numObjectsAllocated, _numWordsAllocated*sizeof(HeapWord)); | |
| 2612 } | |
| 2613 _numObjectsAllocated = 0; | |
| 2614 _numWordsAllocated = 0; | |
| 2615 ) | |
| 2616 } | |
| 2617 | |
| 2618 void CMSCollector::gc_epilogue(bool full) { | |
| 2619 // The following locking discipline assumes that we are only called | |
| 2620 // when the world is stopped. | |
| 2621 assert(SafepointSynchronize::is_at_safepoint(), | |
| 2622 "world is stopped assumption"); | |
| 2623 | |
| 2624 // Currently the CMS epilogue (see CompactibleFreeListSpace) merely checks | |
| 2625 // if linear allocation blocks need to be appropriately marked to allow the | |
| 2626 // the blocks to be parsable. We also check here whether we need to nudge the | |
| 2627 // CMS collector thread to start a new cycle (if it's not already active). | |
| 2628 assert( Thread::current()->is_VM_thread() | |
| 2629 || ( CMSScavengeBeforeRemark | |
| 2630 && Thread::current()->is_ConcurrentGC_thread()), | |
| 2631 "Incorrect thread type for epilogue execution"); | |
| 2632 | |
| 2633 if (!_between_prologue_and_epilogue) { | |
| 2634 // We have already been invoked; this is a gc_epilogue delegation | |
| 2635 // from yet another CMS generation that we are responsible for, just | |
| 2636 // ignore it since all relevant work has already been done. | |
| 2637 return; | |
| 2638 } | |
| 2639 assert(haveFreelistLocks(), "must have freelist locks"); | |
| 2640 assert_lock_strong(bitMapLock()); | |
| 2641 | |
| 2642 _cmsGen->gc_epilogue_work(full); | |
| 2643 _permGen->gc_epilogue_work(full); | |
| 2644 | |
| 2645 if (_collectorState == AbortablePreclean || _collectorState == Precleaning) { | |
| 2646 // in case sampling was not already enabled, enable it | |
| 2647 _start_sampling = true; | |
| 2648 } | |
| 2649 // reset _eden_chunk_array so sampling starts afresh | |
| 2650 _eden_chunk_index = 0; | |
| 2651 | |
| 2652 size_t cms_used = _cmsGen->cmsSpace()->used(); | |
| 2653 size_t perm_used = _permGen->cmsSpace()->used(); | |
| 2654 | |
| 2655 // update performance counters - this uses a special version of | |
| 2656 // update_counters() that allows the utilization to be passed as a | |
| 2657 // parameter, avoiding multiple calls to used(). | |
| 2658 // | |
| 2659 _cmsGen->update_counters(cms_used); | |
| 2660 _permGen->update_counters(perm_used); | |
| 2661 | |
| 2662 if (CMSIncrementalMode) { | |
| 2663 icms_update_allocation_limits(); | |
| 2664 } | |
| 2665 | |
| 2666 bitMapLock()->unlock(); | |
| 2667 releaseFreelistLocks(); | |
| 2668 | |
| 2669 _between_prologue_and_epilogue = false; // ready for next cycle | |
| 2670 } | |
| 2671 | |
| 2672 void ConcurrentMarkSweepGeneration::gc_epilogue(bool full) { | |
| 2673 collector()->gc_epilogue(full); | |
| 2674 | |
| 2675 // Also reset promotion tracking in par gc thread states. | |
| 2676 if (ParallelGCThreads > 0) { | |
| 2677 for (uint i = 0; i < ParallelGCThreads; i++) { | |
| 2678 _par_gc_thread_states[i]->promo.stopTrackingPromotions(); | |
| 2679 } | |
| 2680 } | |
| 2681 } | |
| 2682 | |
| 2683 void ConcurrentMarkSweepGeneration::gc_epilogue_work(bool full) { | |
| 2684 assert(!incremental_collection_failed(), "Should have been cleared"); | |
| 2685 cmsSpace()->setPreconsumptionDirtyCardClosure(NULL); | |
| 2686 cmsSpace()->gc_epilogue(); | |
| 2687 // Print stat counters | |
| 2688 NOT_PRODUCT( | |
| 2689 assert(_numObjectsAllocated == 0, "check"); | |
| 2690 assert(_numWordsAllocated == 0, "check"); | |
| 2691 if (Verbose && PrintGC) { | |
| 2692 gclog_or_tty->print("Promoted "SIZE_FORMAT" objects, " | |
| 2693 SIZE_FORMAT" bytes", | |
| 2694 _numObjectsPromoted, _numWordsPromoted*sizeof(HeapWord)); | |
| 2695 } | |
| 2696 _numObjectsPromoted = 0; | |
| 2697 _numWordsPromoted = 0; | |
| 2698 ) | |
| 2699 | |
| 2700 if (PrintGC && Verbose) { | |
| 2701 // Call down the chain in contiguous_available needs the freelistLock | |
| 2702 // so print this out before releasing the freeListLock. | |
| 2703 gclog_or_tty->print(" Contiguous available "SIZE_FORMAT" bytes ", | |
| 2704 contiguous_available()); | |
| 2705 } | |
| 2706 } | |
| 2707 | |
| 2708 #ifndef PRODUCT | |
| 2709 bool CMSCollector::have_cms_token() { | |
| 2710 Thread* thr = Thread::current(); | |
| 2711 if (thr->is_VM_thread()) { | |
| 2712 return ConcurrentMarkSweepThread::vm_thread_has_cms_token(); | |
| 2713 } else if (thr->is_ConcurrentGC_thread()) { | |
| 2714 return ConcurrentMarkSweepThread::cms_thread_has_cms_token(); | |
| 2715 } else if (thr->is_GC_task_thread()) { | |
| 2716 return ConcurrentMarkSweepThread::vm_thread_has_cms_token() && | |
| 2717 ParGCRareEvent_lock->owned_by_self(); | |
| 2718 } | |
| 2719 return false; | |
| 2720 } | |
| 2721 #endif | |
| 2722 | |
| 2723 // Check reachability of the given heap address in CMS generation, | |
| 2724 // treating all other generations as roots. | |
| 2725 bool CMSCollector::is_cms_reachable(HeapWord* addr) { | |
| 2726 // We could "guarantee" below, rather than assert, but i'll | |
| 2727 // leave these as "asserts" so that an adventurous debugger | |
| 2728 // could try this in the product build provided some subset of | |
| 2729 // the conditions were met, provided they were intersted in the | |
| 2730 // results and knew that the computation below wouldn't interfere | |
| 2731 // with other concurrent computations mutating the structures | |
| 2732 // being read or written. | |
| 2733 assert(SafepointSynchronize::is_at_safepoint(), | |
| 2734 "Else mutations in object graph will make answer suspect"); | |
| 2735 assert(have_cms_token(), "Should hold cms token"); | |
| 2736 assert(haveFreelistLocks(), "must hold free list locks"); | |
| 2737 assert_lock_strong(bitMapLock()); | |
| 2738 | |
| 2739 // Clear the marking bit map array before starting, but, just | |
| 2740 // for kicks, first report if the given address is already marked | |
| 2741 gclog_or_tty->print_cr("Start: Address 0x%x is%s marked", addr, | |
| 2742 _markBitMap.isMarked(addr) ? "" : " not"); | |
| 2743 | |
| 2744 if (verify_after_remark()) { | |
| 2745 MutexLockerEx x(verification_mark_bm()->lock(), Mutex::_no_safepoint_check_flag); | |
| 2746 bool result = verification_mark_bm()->isMarked(addr); | |
| 2747 gclog_or_tty->print_cr("TransitiveMark: Address 0x%x %s marked", addr, | |
| 2748 result ? "IS" : "is NOT"); | |
| 2749 return result; | |
| 2750 } else { | |
| 2751 gclog_or_tty->print_cr("Could not compute result"); | |
| 2752 return false; | |
| 2753 } | |
| 2754 } | |
| 2755 | |
| 2756 //////////////////////////////////////////////////////// | |
| 2757 // CMS Verification Support | |
| 2758 //////////////////////////////////////////////////////// | |
| 2759 // Following the remark phase, the following invariant | |
| 2760 // should hold -- each object in the CMS heap which is | |
| 2761 // marked in markBitMap() should be marked in the verification_mark_bm(). | |
| 2762 | |
| 2763 class VerifyMarkedClosure: public BitMapClosure { | |
| 2764 CMSBitMap* _marks; | |
| 2765 bool _failed; | |
| 2766 | |
| 2767 public: | |
| 2768 VerifyMarkedClosure(CMSBitMap* bm): _marks(bm), _failed(false) {} | |
| 2769 | |
|
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2770 bool do_bit(size_t offset) { |
| 0 | 2771 HeapWord* addr = _marks->offsetToHeapWord(offset); |
| 2772 if (!_marks->isMarked(addr)) { | |
| 2773 oop(addr)->print(); | |
| 2774 gclog_or_tty->print_cr(" ("INTPTR_FORMAT" should have been marked)", addr); | |
| 2775 _failed = true; | |
| 2776 } | |
|
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2777 return true; |
| 0 | 2778 } |
| 2779 | |
| 2780 bool failed() { return _failed; } | |
| 2781 }; | |
| 2782 | |
| 2783 bool CMSCollector::verify_after_remark() { | |
| 2784 gclog_or_tty->print(" [Verifying CMS Marking... "); | |
| 2785 MutexLockerEx ml(verification_mark_bm()->lock(), Mutex::_no_safepoint_check_flag); | |
| 2786 static bool init = false; | |
| 2787 | |
| 2788 assert(SafepointSynchronize::is_at_safepoint(), | |
| 2789 "Else mutations in object graph will make answer suspect"); | |
| 2790 assert(have_cms_token(), | |
| 2791 "Else there may be mutual interference in use of " | |
| 2792 " verification data structures"); | |
| 2793 assert(_collectorState > Marking && _collectorState <= Sweeping, | |
| 2794 "Else marking info checked here may be obsolete"); | |
| 2795 assert(haveFreelistLocks(), "must hold free list locks"); | |
| 2796 assert_lock_strong(bitMapLock()); | |
| 2797 | |
| 2798 | |
| 2799 // Allocate marking bit map if not already allocated | |
| 2800 if (!init) { // first time | |
| 2801 if (!verification_mark_bm()->allocate(_span)) { | |
| 2802 return false; | |
| 2803 } | |
| 2804 init = true; | |
| 2805 } | |
| 2806 | |
| 2807 assert(verification_mark_stack()->isEmpty(), "Should be empty"); | |
| 2808 | |
| 2809 // Turn off refs discovery -- so we will be tracing through refs. | |
| 2810 // This is as intended, because by this time | |
| 2811 // GC must already have cleared any refs that need to be cleared, | |
| 2812 // and traced those that need to be marked; moreover, | |
| 2813 // the marking done here is not going to intefere in any | |
| 2814 // way with the marking information used by GC. | |
| 2815 NoRefDiscovery no_discovery(ref_processor()); | |
| 2816 | |
| 2817 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;) | |
| 2818 | |
| 2819 // Clear any marks from a previous round | |
| 2820 verification_mark_bm()->clear_all(); | |
| 2821 assert(verification_mark_stack()->isEmpty(), "markStack should be empty"); | |
| 2822 assert(overflow_list_is_empty(), "overflow list should be empty"); | |
| 2823 | |
| 2824 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 2825 gch->ensure_parsability(false); // fill TLABs, but no need to retire them | |
| 2826 // Update the saved marks which may affect the root scans. | |
| 2827 gch->save_marks(); | |
| 2828 | |
| 2829 if (CMSRemarkVerifyVariant == 1) { | |
| 2830 // In this first variant of verification, we complete | |
| 2831 // all marking, then check if the new marks-verctor is | |
| 2832 // a subset of the CMS marks-vector. | |
| 2833 verify_after_remark_work_1(); | |
| 2834 } else if (CMSRemarkVerifyVariant == 2) { | |
| 2835 // In this second variant of verification, we flag an error | |
| 2836 // (i.e. an object reachable in the new marks-vector not reachable | |
| 2837 // in the CMS marks-vector) immediately, also indicating the | |
| 2838 // identify of an object (A) that references the unmarked object (B) -- | |
| 2839 // presumably, a mutation to A failed to be picked up by preclean/remark? | |
| 2840 verify_after_remark_work_2(); | |
| 2841 } else { | |
| 2842 warning("Unrecognized value %d for CMSRemarkVerifyVariant", | |
| 2843 CMSRemarkVerifyVariant); | |
| 2844 } | |
| 2845 gclog_or_tty->print(" done] "); | |
| 2846 return true; | |
| 2847 } | |
| 2848 | |
| 2849 void CMSCollector::verify_after_remark_work_1() { | |
| 2850 ResourceMark rm; | |
| 2851 HandleMark hm; | |
| 2852 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 2853 | |
| 2854 // Mark from roots one level into CMS | |
| 2855 MarkRefsIntoClosure notOlder(_span, verification_mark_bm(), true /* nmethods */); | |
| 2856 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. | |
| 2857 | |
| 2858 gch->gen_process_strong_roots(_cmsGen->level(), | |
| 2859 true, // younger gens are roots | |
|
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|
2860 true, // activate StrongRootsScope |
| 0 | 2861 true, // collecting perm gen |
| 2862 SharedHeap::ScanningOption(roots_scanning_options()), | |
|
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|
2863 ¬Older, |
|
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|
2864 true, // walk code active on stacks |
|
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|
2865 NULL); |
| 0 | 2866 |
| 2867 // Now mark from the roots | |
| 2868 assert(_revisitStack.isEmpty(), "Should be empty"); | |
| 2869 MarkFromRootsClosure markFromRootsClosure(this, _span, | |
| 2870 verification_mark_bm(), verification_mark_stack(), &_revisitStack, | |
| 2871 false /* don't yield */, true /* verifying */); | |
| 2872 assert(_restart_addr == NULL, "Expected pre-condition"); | |
| 2873 verification_mark_bm()->iterate(&markFromRootsClosure); | |
| 2874 while (_restart_addr != NULL) { | |
| 2875 // Deal with stack overflow: by restarting at the indicated | |
| 2876 // address. | |
| 2877 HeapWord* ra = _restart_addr; | |
| 2878 markFromRootsClosure.reset(ra); | |
| 2879 _restart_addr = NULL; | |
| 2880 verification_mark_bm()->iterate(&markFromRootsClosure, ra, _span.end()); | |
| 2881 } | |
| 2882 assert(verification_mark_stack()->isEmpty(), "Should have been drained"); | |
| 2883 verify_work_stacks_empty(); | |
| 2884 // Should reset the revisit stack above, since no class tree | |
| 2885 // surgery is forthcoming. | |
| 2886 _revisitStack.reset(); // throwing away all contents | |
| 2887 | |
| 2888 // Marking completed -- now verify that each bit marked in | |
| 2889 // verification_mark_bm() is also marked in markBitMap(); flag all | |
| 2890 // errors by printing corresponding objects. | |
| 2891 VerifyMarkedClosure vcl(markBitMap()); | |
| 2892 verification_mark_bm()->iterate(&vcl); | |
| 2893 if (vcl.failed()) { | |
| 2894 gclog_or_tty->print("Verification failed"); | |
| 2895 Universe::heap()->print(); | |
| 2896 fatal(" ... aborting"); | |
| 2897 } | |
| 2898 } | |
| 2899 | |
| 2900 void CMSCollector::verify_after_remark_work_2() { | |
| 2901 ResourceMark rm; | |
| 2902 HandleMark hm; | |
| 2903 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 2904 | |
| 2905 // Mark from roots one level into CMS | |
| 2906 MarkRefsIntoVerifyClosure notOlder(_span, verification_mark_bm(), | |
| 2907 markBitMap(), true /* nmethods */); | |
| 2908 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. | |
| 2909 gch->gen_process_strong_roots(_cmsGen->level(), | |
| 2910 true, // younger gens are roots | |
|
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|
2911 true, // activate StrongRootsScope |
| 0 | 2912 true, // collecting perm gen |
| 2913 SharedHeap::ScanningOption(roots_scanning_options()), | |
|
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2914 ¬Older, |
|
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|
2915 true, // walk code active on stacks |
|
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|
2916 NULL); |
| 0 | 2917 |
| 2918 // Now mark from the roots | |
| 2919 assert(_revisitStack.isEmpty(), "Should be empty"); | |
| 2920 MarkFromRootsVerifyClosure markFromRootsClosure(this, _span, | |
| 2921 verification_mark_bm(), markBitMap(), verification_mark_stack()); | |
| 2922 assert(_restart_addr == NULL, "Expected pre-condition"); | |
| 2923 verification_mark_bm()->iterate(&markFromRootsClosure); | |
| 2924 while (_restart_addr != NULL) { | |
| 2925 // Deal with stack overflow: by restarting at the indicated | |
| 2926 // address. | |
| 2927 HeapWord* ra = _restart_addr; | |
| 2928 markFromRootsClosure.reset(ra); | |
| 2929 _restart_addr = NULL; | |
| 2930 verification_mark_bm()->iterate(&markFromRootsClosure, ra, _span.end()); | |
| 2931 } | |
| 2932 assert(verification_mark_stack()->isEmpty(), "Should have been drained"); | |
| 2933 verify_work_stacks_empty(); | |
| 2934 // Should reset the revisit stack above, since no class tree | |
| 2935 // surgery is forthcoming. | |
| 2936 _revisitStack.reset(); // throwing away all contents | |
| 2937 | |
| 2938 // Marking completed -- now verify that each bit marked in | |
| 2939 // verification_mark_bm() is also marked in markBitMap(); flag all | |
| 2940 // errors by printing corresponding objects. | |
| 2941 VerifyMarkedClosure vcl(markBitMap()); | |
| 2942 verification_mark_bm()->iterate(&vcl); | |
| 2943 assert(!vcl.failed(), "Else verification above should not have succeeded"); | |
| 2944 } | |
| 2945 | |
| 2946 void ConcurrentMarkSweepGeneration::save_marks() { | |
| 2947 // delegate to CMS space | |
| 2948 cmsSpace()->save_marks(); | |
| 2949 for (uint i = 0; i < ParallelGCThreads; i++) { | |
| 2950 _par_gc_thread_states[i]->promo.startTrackingPromotions(); | |
| 2951 } | |
| 2952 } | |
| 2953 | |
| 2954 bool ConcurrentMarkSweepGeneration::no_allocs_since_save_marks() { | |
| 2955 return cmsSpace()->no_allocs_since_save_marks(); | |
| 2956 } | |
| 2957 | |
| 2958 #define CMS_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \ | |
| 2959 \ | |
| 2960 void ConcurrentMarkSweepGeneration:: \ | |
| 2961 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \ | |
| 2962 cl->set_generation(this); \ | |
| 2963 cmsSpace()->oop_since_save_marks_iterate##nv_suffix(cl); \ | |
| 2964 cl->reset_generation(); \ | |
| 2965 save_marks(); \ | |
| 2966 } | |
| 2967 | |
| 2968 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DEFN) | |
| 2969 | |
| 2970 void | |
| 2971 ConcurrentMarkSweepGeneration::object_iterate_since_last_GC(ObjectClosure* blk) | |
| 2972 { | |
| 2973 // Not currently implemented; need to do the following. -- ysr. | |
| 2974 // dld -- I think that is used for some sort of allocation profiler. So it | |
| 2975 // really means the objects allocated by the mutator since the last | |
| 2976 // GC. We could potentially implement this cheaply by recording only | |
| 2977 // the direct allocations in a side data structure. | |
| 2978 // | |
| 2979 // I think we probably ought not to be required to support these | |
| 2980 // iterations at any arbitrary point; I think there ought to be some | |
| 2981 // call to enable/disable allocation profiling in a generation/space, | |
| 2982 // and the iterator ought to return the objects allocated in the | |
| 2983 // gen/space since the enable call, or the last iterator call (which | |
| 2984 // will probably be at a GC.) That way, for gens like CM&S that would | |
| 2985 // require some extra data structure to support this, we only pay the | |
| 2986 // cost when it's in use... | |
| 2987 cmsSpace()->object_iterate_since_last_GC(blk); | |
| 2988 } | |
| 2989 | |
| 2990 void | |
| 2991 ConcurrentMarkSweepGeneration::younger_refs_iterate(OopsInGenClosure* cl) { | |
| 2992 cl->set_generation(this); | |
| 2993 younger_refs_in_space_iterate(_cmsSpace, cl); | |
| 2994 cl->reset_generation(); | |
| 2995 } | |
| 2996 | |
| 2997 void | |
| 2998 ConcurrentMarkSweepGeneration::oop_iterate(MemRegion mr, OopClosure* cl) { | |
| 2999 if (freelistLock()->owned_by_self()) { | |
| 3000 Generation::oop_iterate(mr, cl); | |
| 3001 } else { | |
| 3002 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
| 3003 Generation::oop_iterate(mr, cl); | |
| 3004 } | |
| 3005 } | |
| 3006 | |
| 3007 void | |
| 3008 ConcurrentMarkSweepGeneration::oop_iterate(OopClosure* cl) { | |
| 3009 if (freelistLock()->owned_by_self()) { | |
| 3010 Generation::oop_iterate(cl); | |
| 3011 } else { | |
| 3012 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
| 3013 Generation::oop_iterate(cl); | |
| 3014 } | |
| 3015 } | |
| 3016 | |
| 3017 void | |
| 3018 ConcurrentMarkSweepGeneration::object_iterate(ObjectClosure* cl) { | |
| 3019 if (freelistLock()->owned_by_self()) { | |
| 3020 Generation::object_iterate(cl); | |
| 3021 } else { | |
| 3022 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
| 3023 Generation::object_iterate(cl); | |
| 3024 } | |
| 3025 } | |
| 3026 | |
| 3027 void | |
|
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3028 ConcurrentMarkSweepGeneration::safe_object_iterate(ObjectClosure* cl) { |
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3029 if (freelistLock()->owned_by_self()) { |
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3030 Generation::safe_object_iterate(cl); |
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3031 } else { |
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3032 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); |
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3033 Generation::safe_object_iterate(cl); |
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3034 } |
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3035 } |
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3036 |
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3037 void |
| 0 | 3038 ConcurrentMarkSweepGeneration::pre_adjust_pointers() { |
| 3039 } | |
| 3040 | |
| 3041 void | |
| 3042 ConcurrentMarkSweepGeneration::post_compact() { | |
| 3043 } | |
| 3044 | |
| 3045 void | |
| 3046 ConcurrentMarkSweepGeneration::prepare_for_verify() { | |
| 3047 // Fix the linear allocation blocks to look like free blocks. | |
| 3048 | |
| 3049 // Locks are normally acquired/released in gc_prologue/gc_epilogue, but those | |
| 3050 // are not called when the heap is verified during universe initialization and | |
| 3051 // at vm shutdown. | |
| 3052 if (freelistLock()->owned_by_self()) { | |
| 3053 cmsSpace()->prepare_for_verify(); | |
| 3054 } else { | |
| 3055 MutexLockerEx fll(freelistLock(), Mutex::_no_safepoint_check_flag); | |
| 3056 cmsSpace()->prepare_for_verify(); | |
| 3057 } | |
| 3058 } | |
| 3059 | |
| 3060 void | |
| 3061 ConcurrentMarkSweepGeneration::verify(bool allow_dirty /* ignored */) { | |
| 3062 // Locks are normally acquired/released in gc_prologue/gc_epilogue, but those | |
| 3063 // are not called when the heap is verified during universe initialization and | |
| 3064 // at vm shutdown. | |
| 3065 if (freelistLock()->owned_by_self()) { | |
| 3066 cmsSpace()->verify(false /* ignored */); | |
| 3067 } else { | |
| 3068 MutexLockerEx fll(freelistLock(), Mutex::_no_safepoint_check_flag); | |
| 3069 cmsSpace()->verify(false /* ignored */); | |
| 3070 } | |
| 3071 } | |
| 3072 | |
| 3073 void CMSCollector::verify(bool allow_dirty /* ignored */) { | |
| 3074 _cmsGen->verify(allow_dirty); | |
| 3075 _permGen->verify(allow_dirty); | |
| 3076 } | |
| 3077 | |
| 3078 #ifndef PRODUCT | |
| 3079 bool CMSCollector::overflow_list_is_empty() const { | |
| 3080 assert(_num_par_pushes >= 0, "Inconsistency"); | |
| 3081 if (_overflow_list == NULL) { | |
| 3082 assert(_num_par_pushes == 0, "Inconsistency"); | |
| 3083 } | |
| 3084 return _overflow_list == NULL; | |
| 3085 } | |
| 3086 | |
| 3087 // The methods verify_work_stacks_empty() and verify_overflow_empty() | |
| 3088 // merely consolidate assertion checks that appear to occur together frequently. | |
| 3089 void CMSCollector::verify_work_stacks_empty() const { | |
| 3090 assert(_markStack.isEmpty(), "Marking stack should be empty"); | |
| 3091 assert(overflow_list_is_empty(), "Overflow list should be empty"); | |
| 3092 } | |
| 3093 | |
| 3094 void CMSCollector::verify_overflow_empty() const { | |
| 3095 assert(overflow_list_is_empty(), "Overflow list should be empty"); | |
| 3096 assert(no_preserved_marks(), "No preserved marks"); | |
| 3097 } | |
| 3098 #endif // PRODUCT | |
| 3099 | |
|
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3100 // Decide if we want to enable class unloading as part of the |
|
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3101 // ensuing concurrent GC cycle. We will collect the perm gen and |
|
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3102 // unload classes if it's the case that: |
|
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3103 // (1) an explicit gc request has been made and the flag |
|
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3104 // ExplicitGCInvokesConcurrentAndUnloadsClasses is set, OR |
|
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3105 // (2) (a) class unloading is enabled at the command line, and |
|
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3106 // (b) (i) perm gen threshold has been crossed, or |
|
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3107 // (ii) old gen is getting really full, or |
|
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3108 // (iii) the previous N CMS collections did not collect the |
|
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3109 // perm gen |
|
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3110 // NOTE: Provided there is no change in the state of the heap between |
|
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3111 // calls to this method, it should have idempotent results. Moreover, |
|
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3112 // its results should be monotonically increasing (i.e. going from 0 to 1, |
|
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3113 // but not 1 to 0) between successive calls between which the heap was |
|
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3114 // not collected. For the implementation below, it must thus rely on |
|
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3115 // the property that concurrent_cycles_since_last_unload() |
|
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3116 // will not decrease unless a collection cycle happened and that |
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3117 // _permGen->should_concurrent_collect() and _cmsGen->is_too_full() are |
|
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3118 // themselves also monotonic in that sense. See check_monotonicity() |
|
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3119 // below. |
|
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3120 bool CMSCollector::update_should_unload_classes() { |
|
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3121 _should_unload_classes = false; |
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3122 // Condition 1 above |
|
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3123 if (_full_gc_requested && ExplicitGCInvokesConcurrentAndUnloadsClasses) { |
|
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3124 _should_unload_classes = true; |
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3125 } else if (CMSClassUnloadingEnabled) { // Condition 2.a above |
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3126 // Disjuncts 2.b.(i,ii,iii) above |
|
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3127 _should_unload_classes = (concurrent_cycles_since_last_unload() >= |
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3128 CMSClassUnloadingMaxInterval) |
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3129 || _permGen->should_concurrent_collect() |
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3130 || _cmsGen->is_too_full(); |
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3131 } |
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3132 return _should_unload_classes; |
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3133 } |
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|
3134 |
|
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3135 bool ConcurrentMarkSweepGeneration::is_too_full() const { |
|
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3136 bool res = should_concurrent_collect(); |
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3137 res = res && (occupancy() > (double)CMSIsTooFullPercentage/100.0); |
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3138 return res; |
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3139 } |
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3140 |
| 0 | 3141 void CMSCollector::setup_cms_unloading_and_verification_state() { |
| 3142 const bool should_verify = VerifyBeforeGC || VerifyAfterGC || VerifyDuringGC | |
| 3143 || VerifyBeforeExit; | |
| 3144 const int rso = SharedHeap::SO_Symbols | SharedHeap::SO_Strings | |
| 3145 | SharedHeap::SO_CodeCache; | |
| 3146 | |
|
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3147 if (should_unload_classes()) { // Should unload classes this cycle |
| 0 | 3148 remove_root_scanning_option(rso); // Shrink the root set appropriately |
| 3149 set_verifying(should_verify); // Set verification state for this cycle | |
| 3150 return; // Nothing else needs to be done at this time | |
| 3151 } | |
| 3152 | |
| 3153 // Not unloading classes this cycle | |
|
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3154 assert(!should_unload_classes(), "Inconsitency!"); |
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3155 if ((!verifying() || unloaded_classes_last_cycle()) && should_verify) { |
| 0 | 3156 // We were not verifying, or we _were_ unloading classes in the last cycle, |
| 3157 // AND some verification options are enabled this cycle; in this case, | |
| 3158 // we must make sure that the deadness map is allocated if not already so, | |
| 3159 // and cleared (if already allocated previously -- | |
| 3160 // CMSBitMap::sizeInBits() is used to determine if it's allocated). | |
| 3161 if (perm_gen_verify_bit_map()->sizeInBits() == 0) { | |
| 3162 if (!perm_gen_verify_bit_map()->allocate(_permGen->reserved())) { | |
| 3163 warning("Failed to allocate permanent generation verification CMS Bit Map;\n" | |
| 3164 "permanent generation verification disabled"); | |
| 3165 return; // Note that we leave verification disabled, so we'll retry this | |
| 3166 // allocation next cycle. We _could_ remember this failure | |
| 3167 // and skip further attempts and permanently disable verification | |
| 3168 // attempts if that is considered more desirable. | |
| 3169 } | |
| 3170 assert(perm_gen_verify_bit_map()->covers(_permGen->reserved()), | |
| 3171 "_perm_gen_ver_bit_map inconsistency?"); | |
| 3172 } else { | |
| 3173 perm_gen_verify_bit_map()->clear_all(); | |
| 3174 } | |
| 3175 // Include symbols, strings and code cache elements to prevent their resurrection. | |
| 3176 add_root_scanning_option(rso); | |
| 3177 set_verifying(true); | |
| 3178 } else if (verifying() && !should_verify) { | |
| 3179 // We were verifying, but some verification flags got disabled. | |
| 3180 set_verifying(false); | |
| 3181 // Exclude symbols, strings and code cache elements from root scanning to | |
| 3182 // reduce IM and RM pauses. | |
| 3183 remove_root_scanning_option(rso); | |
| 3184 } | |
| 3185 } | |
| 3186 | |
| 3187 | |
| 3188 #ifndef PRODUCT | |
| 3189 HeapWord* CMSCollector::block_start(const void* p) const { | |
| 3190 const HeapWord* addr = (HeapWord*)p; | |
| 3191 if (_span.contains(p)) { | |
| 3192 if (_cmsGen->cmsSpace()->is_in_reserved(addr)) { | |
| 3193 return _cmsGen->cmsSpace()->block_start(p); | |
| 3194 } else { | |
| 3195 assert(_permGen->cmsSpace()->is_in_reserved(addr), | |
| 3196 "Inconsistent _span?"); | |
| 3197 return _permGen->cmsSpace()->block_start(p); | |
| 3198 } | |
| 3199 } | |
| 3200 return NULL; | |
| 3201 } | |
| 3202 #endif | |
| 3203 | |
| 3204 HeapWord* | |
| 3205 ConcurrentMarkSweepGeneration::expand_and_allocate(size_t word_size, | |
| 3206 bool tlab, | |
| 3207 bool parallel) { | |
| 3208 assert(!tlab, "Can't deal with TLAB allocation"); | |
| 3209 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
| 3210 expand(word_size*HeapWordSize, MinHeapDeltaBytes, | |
| 3211 CMSExpansionCause::_satisfy_allocation); | |
| 3212 if (GCExpandToAllocateDelayMillis > 0) { | |
| 3213 os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false); | |
| 3214 } | |
|
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3215 return have_lock_and_allocate(word_size, tlab); |
| 0 | 3216 } |
| 3217 | |
| 3218 // YSR: All of this generation expansion/shrinking stuff is an exact copy of | |
| 3219 // OneContigSpaceCardGeneration, which makes me wonder if we should move this | |
| 3220 // to CardGeneration and share it... | |
|
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3221 bool ConcurrentMarkSweepGeneration::expand(size_t bytes, size_t expand_bytes) { |
|
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3222 return CardGeneration::expand(bytes, expand_bytes); |
|
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3223 } |
|
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3224 |
| 0 | 3225 void ConcurrentMarkSweepGeneration::expand(size_t bytes, size_t expand_bytes, |
| 3226 CMSExpansionCause::Cause cause) | |
| 3227 { | |
|
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3228 |
|
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3229 bool success = expand(bytes, expand_bytes); |
|
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3230 |
| 0 | 3231 // remember why we expanded; this information is used |
| 3232 // by shouldConcurrentCollect() when making decisions on whether to start | |
| 3233 // a new CMS cycle. | |
| 3234 if (success) { | |
| 3235 set_expansion_cause(cause); | |
| 3236 if (PrintGCDetails && Verbose) { | |
| 3237 gclog_or_tty->print_cr("Expanded CMS gen for %s", | |
| 3238 CMSExpansionCause::to_string(cause)); | |
| 3239 } | |
| 3240 } | |
| 3241 } | |
| 3242 | |
| 3243 HeapWord* ConcurrentMarkSweepGeneration::expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz) { | |
| 3244 HeapWord* res = NULL; | |
| 3245 MutexLocker x(ParGCRareEvent_lock); | |
| 3246 while (true) { | |
| 3247 // Expansion by some other thread might make alloc OK now: | |
| 3248 res = ps->lab.alloc(word_sz); | |
| 3249 if (res != NULL) return res; | |
| 3250 // If there's not enough expansion space available, give up. | |
| 3251 if (_virtual_space.uncommitted_size() < (word_sz * HeapWordSize)) { | |
| 3252 return NULL; | |
| 3253 } | |
| 3254 // Otherwise, we try expansion. | |
| 3255 expand(word_sz*HeapWordSize, MinHeapDeltaBytes, | |
| 3256 CMSExpansionCause::_allocate_par_lab); | |
| 3257 // Now go around the loop and try alloc again; | |
| 3258 // A competing par_promote might beat us to the expansion space, | |
| 3259 // so we may go around the loop again if promotion fails agaion. | |
| 3260 if (GCExpandToAllocateDelayMillis > 0) { | |
| 3261 os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false); | |
| 3262 } | |
| 3263 } | |
| 3264 } | |
| 3265 | |
| 3266 | |
| 3267 bool ConcurrentMarkSweepGeneration::expand_and_ensure_spooling_space( | |
| 3268 PromotionInfo* promo) { | |
| 3269 MutexLocker x(ParGCRareEvent_lock); | |
| 3270 size_t refill_size_bytes = promo->refillSize() * HeapWordSize; | |
| 3271 while (true) { | |
| 3272 // Expansion by some other thread might make alloc OK now: | |
| 3273 if (promo->ensure_spooling_space()) { | |
| 3274 assert(promo->has_spooling_space(), | |
| 3275 "Post-condition of successful ensure_spooling_space()"); | |
| 3276 return true; | |
| 3277 } | |
| 3278 // If there's not enough expansion space available, give up. | |
| 3279 if (_virtual_space.uncommitted_size() < refill_size_bytes) { | |
| 3280 return false; | |
| 3281 } | |
| 3282 // Otherwise, we try expansion. | |
| 3283 expand(refill_size_bytes, MinHeapDeltaBytes, | |
| 3284 CMSExpansionCause::_allocate_par_spooling_space); | |
| 3285 // Now go around the loop and try alloc again; | |
| 3286 // A competing allocation might beat us to the expansion space, | |
| 3287 // so we may go around the loop again if allocation fails again. | |
| 3288 if (GCExpandToAllocateDelayMillis > 0) { | |
| 3289 os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false); | |
| 3290 } | |
| 3291 } | |
| 3292 } | |
| 3293 | |
| 3294 | |
| 3295 | |
| 3296 void ConcurrentMarkSweepGeneration::shrink(size_t bytes) { | |
| 3297 assert_locked_or_safepoint(Heap_lock); | |
| 3298 size_t size = ReservedSpace::page_align_size_down(bytes); | |
| 3299 if (size > 0) { | |
| 3300 shrink_by(size); | |
| 3301 } | |
| 3302 } | |
| 3303 | |
| 3304 bool ConcurrentMarkSweepGeneration::grow_by(size_t bytes) { | |
| 3305 assert_locked_or_safepoint(Heap_lock); | |
| 3306 bool result = _virtual_space.expand_by(bytes); | |
| 3307 if (result) { | |
| 3308 HeapWord* old_end = _cmsSpace->end(); | |
| 3309 size_t new_word_size = | |
| 3310 heap_word_size(_virtual_space.committed_size()); | |
| 3311 MemRegion mr(_cmsSpace->bottom(), new_word_size); | |
| 3312 _bts->resize(new_word_size); // resize the block offset shared array | |
| 3313 Universe::heap()->barrier_set()->resize_covered_region(mr); | |
| 3314 // Hmmmm... why doesn't CFLS::set_end verify locking? | |
| 3315 // This is quite ugly; FIX ME XXX | |
| 3316 _cmsSpace->assert_locked(); | |
| 3317 _cmsSpace->set_end((HeapWord*)_virtual_space.high()); | |
| 3318 | |
| 3319 // update the space and generation capacity counters | |
| 3320 if (UsePerfData) { | |
| 3321 _space_counters->update_capacity(); | |
| 3322 _gen_counters->update_all(); | |
| 3323 } | |
| 3324 | |
| 3325 if (Verbose && PrintGC) { | |
| 3326 size_t new_mem_size = _virtual_space.committed_size(); | |
| 3327 size_t old_mem_size = new_mem_size - bytes; | |
| 3328 gclog_or_tty->print_cr("Expanding %s from %ldK by %ldK to %ldK", | |
| 3329 name(), old_mem_size/K, bytes/K, new_mem_size/K); | |
| 3330 } | |
| 3331 } | |
| 3332 return result; | |
| 3333 } | |
| 3334 | |
| 3335 bool ConcurrentMarkSweepGeneration::grow_to_reserved() { | |
| 3336 assert_locked_or_safepoint(Heap_lock); | |
| 3337 bool success = true; | |
| 3338 const size_t remaining_bytes = _virtual_space.uncommitted_size(); | |
| 3339 if (remaining_bytes > 0) { | |
| 3340 success = grow_by(remaining_bytes); | |
| 3341 DEBUG_ONLY(if (!success) warning("grow to reserved failed");) | |
| 3342 } | |
| 3343 return success; | |
| 3344 } | |
| 3345 | |
| 3346 void ConcurrentMarkSweepGeneration::shrink_by(size_t bytes) { | |
| 3347 assert_locked_or_safepoint(Heap_lock); | |
| 3348 assert_lock_strong(freelistLock()); | |
| 3349 // XXX Fix when compaction is implemented. | |
| 3350 warning("Shrinking of CMS not yet implemented"); | |
| 3351 return; | |
| 3352 } | |
| 3353 | |
| 3354 | |
| 3355 // Simple ctor/dtor wrapper for accounting & timer chores around concurrent | |
| 3356 // phases. | |
| 3357 class CMSPhaseAccounting: public StackObj { | |
| 3358 public: | |
| 3359 CMSPhaseAccounting(CMSCollector *collector, | |
| 3360 const char *phase, | |
| 3361 bool print_cr = true); | |
| 3362 ~CMSPhaseAccounting(); | |
| 3363 | |
| 3364 private: | |
| 3365 CMSCollector *_collector; | |
| 3366 const char *_phase; | |
| 3367 elapsedTimer _wallclock; | |
| 3368 bool _print_cr; | |
| 3369 | |
| 3370 public: | |
| 3371 // Not MT-safe; so do not pass around these StackObj's | |
| 3372 // where they may be accessed by other threads. | |
| 3373 jlong wallclock_millis() { | |
| 3374 assert(_wallclock.is_active(), "Wall clock should not stop"); | |
| 3375 _wallclock.stop(); // to record time | |
| 3376 jlong ret = _wallclock.milliseconds(); | |
| 3377 _wallclock.start(); // restart | |
| 3378 return ret; | |
| 3379 } | |
| 3380 }; | |
| 3381 | |
| 3382 CMSPhaseAccounting::CMSPhaseAccounting(CMSCollector *collector, | |
| 3383 const char *phase, | |
| 3384 bool print_cr) : | |
| 3385 _collector(collector), _phase(phase), _print_cr(print_cr) { | |
| 3386 | |
| 3387 if (PrintCMSStatistics != 0) { | |
| 3388 _collector->resetYields(); | |
| 3389 } | |
| 3390 if (PrintGCDetails && PrintGCTimeStamps) { | |
| 3391 gclog_or_tty->date_stamp(PrintGCDateStamps); | |
| 3392 gclog_or_tty->stamp(); | |
| 3393 gclog_or_tty->print_cr(": [%s-concurrent-%s-start]", | |
| 3394 _collector->cmsGen()->short_name(), _phase); | |
| 3395 } | |
| 3396 _collector->resetTimer(); | |
| 3397 _wallclock.start(); | |
| 3398 _collector->startTimer(); | |
| 3399 } | |
| 3400 | |
| 3401 CMSPhaseAccounting::~CMSPhaseAccounting() { | |
| 3402 assert(_wallclock.is_active(), "Wall clock should not have stopped"); | |
| 3403 _collector->stopTimer(); | |
| 3404 _wallclock.stop(); | |
| 3405 if (PrintGCDetails) { | |
| 3406 gclog_or_tty->date_stamp(PrintGCDateStamps); | |
| 3407 if (PrintGCTimeStamps) { | |
| 3408 gclog_or_tty->stamp(); | |
| 3409 gclog_or_tty->print(": "); | |
| 3410 } | |
| 3411 gclog_or_tty->print("[%s-concurrent-%s: %3.3f/%3.3f secs]", | |
| 3412 _collector->cmsGen()->short_name(), | |
| 3413 _phase, _collector->timerValue(), _wallclock.seconds()); | |
| 3414 if (_print_cr) { | |
| 3415 gclog_or_tty->print_cr(""); | |
| 3416 } | |
| 3417 if (PrintCMSStatistics != 0) { | |
| 3418 gclog_or_tty->print_cr(" (CMS-concurrent-%s yielded %d times)", _phase, | |
| 3419 _collector->yields()); | |
| 3420 } | |
| 3421 } | |
| 3422 } | |
| 3423 | |
| 3424 // CMS work | |
| 3425 | |
| 3426 // Checkpoint the roots into this generation from outside | |
| 3427 // this generation. [Note this initial checkpoint need only | |
| 3428 // be approximate -- we'll do a catch up phase subsequently.] | |
| 3429 void CMSCollector::checkpointRootsInitial(bool asynch) { | |
| 3430 assert(_collectorState == InitialMarking, "Wrong collector state"); | |
| 3431 check_correct_thread_executing(); | |
| 3432 ReferenceProcessor* rp = ref_processor(); | |
| 3433 SpecializationStats::clear(); | |
| 3434 assert(_restart_addr == NULL, "Control point invariant"); | |
| 3435 if (asynch) { | |
| 3436 // acquire locks for subsequent manipulations | |
| 3437 MutexLockerEx x(bitMapLock(), | |
| 3438 Mutex::_no_safepoint_check_flag); | |
| 3439 checkpointRootsInitialWork(asynch); | |
| 3440 rp->verify_no_references_recorded(); | |
| 3441 rp->enable_discovery(); // enable ("weak") refs discovery | |
| 3442 _collectorState = Marking; | |
| 3443 } else { | |
| 3444 // (Weak) Refs discovery: this is controlled from genCollectedHeap::do_collection | |
| 3445 // which recognizes if we are a CMS generation, and doesn't try to turn on | |
| 3446 // discovery; verify that they aren't meddling. | |
| 3447 assert(!rp->discovery_is_atomic(), | |
| 3448 "incorrect setting of discovery predicate"); | |
| 3449 assert(!rp->discovery_enabled(), "genCollectedHeap shouldn't control " | |
| 3450 "ref discovery for this generation kind"); | |
| 3451 // already have locks | |
| 3452 checkpointRootsInitialWork(asynch); | |
| 3453 rp->enable_discovery(); // now enable ("weak") refs discovery | |
| 3454 _collectorState = Marking; | |
| 3455 } | |
| 3456 SpecializationStats::print(); | |
| 3457 } | |
| 3458 | |
| 3459 void CMSCollector::checkpointRootsInitialWork(bool asynch) { | |
| 3460 assert(SafepointSynchronize::is_at_safepoint(), "world should be stopped"); | |
| 3461 assert(_collectorState == InitialMarking, "just checking"); | |
| 3462 | |
| 3463 // If there has not been a GC[n-1] since last GC[n] cycle completed, | |
| 3464 // precede our marking with a collection of all | |
| 3465 // younger generations to keep floating garbage to a minimum. | |
| 3466 // XXX: we won't do this for now -- it's an optimization to be done later. | |
| 3467 | |
| 3468 // already have locks | |
| 3469 assert_lock_strong(bitMapLock()); | |
| 3470 assert(_markBitMap.isAllClear(), "was reset at end of previous cycle"); | |
| 3471 | |
| 3472 // Setup the verification and class unloading state for this | |
| 3473 // CMS collection cycle. | |
| 3474 setup_cms_unloading_and_verification_state(); | |
| 3475 | |
| 3476 NOT_PRODUCT(TraceTime t("\ncheckpointRootsInitialWork", | |
| 3477 PrintGCDetails && Verbose, true, gclog_or_tty);) | |
| 3478 if (UseAdaptiveSizePolicy) { | |
| 3479 size_policy()->checkpoint_roots_initial_begin(); | |
| 3480 } | |
| 3481 | |
| 3482 // Reset all the PLAB chunk arrays if necessary. | |
| 3483 if (_survivor_plab_array != NULL && !CMSPLABRecordAlways) { | |
| 3484 reset_survivor_plab_arrays(); | |
| 3485 } | |
| 3486 | |
| 3487 ResourceMark rm; | |
| 3488 HandleMark hm; | |
| 3489 | |
| 3490 FalseClosure falseClosure; | |
| 3491 // In the case of a synchronous collection, we will elide the | |
| 3492 // remark step, so it's important to catch all the nmethod oops | |
| 3493 // in this step; hence the last argument to the constrcutor below. | |
| 3494 MarkRefsIntoClosure notOlder(_span, &_markBitMap, !asynch /* nmethods */); | |
| 3495 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 3496 | |
| 3497 verify_work_stacks_empty(); | |
| 3498 verify_overflow_empty(); | |
| 3499 | |
| 3500 gch->ensure_parsability(false); // fill TLABs, but no need to retire them | |
| 3501 // Update the saved marks which may affect the root scans. | |
| 3502 gch->save_marks(); | |
| 3503 | |
| 3504 // weak reference processing has not started yet. | |
| 3505 ref_processor()->set_enqueuing_is_done(false); | |
| 3506 | |
| 3507 { | |
| 935 | 3508 // This is not needed. DEBUG_ONLY(RememberKlassesChecker imx(true);) |
| 0 | 3509 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;) |
| 3510 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. | |
| 3511 gch->gen_process_strong_roots(_cmsGen->level(), | |
| 3512 true, // younger gens are roots | |
|
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diff
changeset
|
3513 true, // activate StrongRootsScope |
| 0 | 3514 true, // collecting perm gen |
| 3515 SharedHeap::ScanningOption(roots_scanning_options()), | |
|
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diff
changeset
|
3516 ¬Older, |
|
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diff
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|
3517 true, // walk all of code cache if (so & SO_CodeCache) |
|
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|
3518 NULL); |
| 0 | 3519 } |
| 3520 | |
| 3521 // Clear mod-union table; it will be dirtied in the prologue of | |
| 3522 // CMS generation per each younger generation collection. | |
| 3523 | |
| 3524 assert(_modUnionTable.isAllClear(), | |
| 3525 "Was cleared in most recent final checkpoint phase" | |
| 3526 " or no bits are set in the gc_prologue before the start of the next " | |
| 3527 "subsequent marking phase."); | |
| 3528 | |
| 3529 // Temporarily disabled, since pre/post-consumption closures don't | |
| 3530 // care about precleaned cards | |
| 3531 #if 0 | |
| 3532 { | |
| 3533 MemRegion mr = MemRegion((HeapWord*)_virtual_space.low(), | |
| 3534 (HeapWord*)_virtual_space.high()); | |
| 3535 _ct->ct_bs()->preclean_dirty_cards(mr); | |
| 3536 } | |
| 3537 #endif | |
| 3538 | |
| 3539 // Save the end of the used_region of the constituent generations | |
| 3540 // to be used to limit the extent of sweep in each generation. | |
| 3541 save_sweep_limits(); | |
| 3542 if (UseAdaptiveSizePolicy) { | |
| 3543 size_policy()->checkpoint_roots_initial_end(gch->gc_cause()); | |
| 3544 } | |
| 3545 verify_overflow_empty(); | |
| 3546 } | |
| 3547 | |
| 3548 bool CMSCollector::markFromRoots(bool asynch) { | |
| 3549 // we might be tempted to assert that: | |
| 3550 // assert(asynch == !SafepointSynchronize::is_at_safepoint(), | |
| 3551 // "inconsistent argument?"); | |
| 3552 // However that wouldn't be right, because it's possible that | |
| 3553 // a safepoint is indeed in progress as a younger generation | |
| 3554 // stop-the-world GC happens even as we mark in this generation. | |
| 3555 assert(_collectorState == Marking, "inconsistent state?"); | |
| 3556 check_correct_thread_executing(); | |
| 3557 verify_overflow_empty(); | |
| 3558 | |
| 3559 bool res; | |
| 3560 if (asynch) { | |
| 3561 | |
| 3562 // Start the timers for adaptive size policy for the concurrent phases | |
| 3563 // Do it here so that the foreground MS can use the concurrent | |
| 3564 // timer since a foreground MS might has the sweep done concurrently | |
| 3565 // or STW. | |
| 3566 if (UseAdaptiveSizePolicy) { | |
| 3567 size_policy()->concurrent_marking_begin(); | |
| 3568 } | |
| 3569 | |
| 3570 // Weak ref discovery note: We may be discovering weak | |
| 3571 // refs in this generation concurrent (but interleaved) with | |
| 3572 // weak ref discovery by a younger generation collector. | |
| 3573 | |
| 3574 CMSTokenSyncWithLocks ts(true, bitMapLock()); | |
| 3575 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
| 3576 CMSPhaseAccounting pa(this, "mark", !PrintGCDetails); | |
| 3577 res = markFromRootsWork(asynch); | |
| 3578 if (res) { | |
| 3579 _collectorState = Precleaning; | |
| 3580 } else { // We failed and a foreground collection wants to take over | |
| 3581 assert(_foregroundGCIsActive, "internal state inconsistency"); | |
| 3582 assert(_restart_addr == NULL, "foreground will restart from scratch"); | |
| 3583 if (PrintGCDetails) { | |
| 3584 gclog_or_tty->print_cr("bailing out to foreground collection"); | |
| 3585 } | |
| 3586 } | |
| 3587 if (UseAdaptiveSizePolicy) { | |
| 3588 size_policy()->concurrent_marking_end(); | |
| 3589 } | |
| 3590 } else { | |
| 3591 assert(SafepointSynchronize::is_at_safepoint(), | |
| 3592 "inconsistent with asynch == false"); | |
| 3593 if (UseAdaptiveSizePolicy) { | |
| 3594 size_policy()->ms_collection_marking_begin(); | |
| 3595 } | |
| 3596 // already have locks | |
| 3597 res = markFromRootsWork(asynch); | |
| 3598 _collectorState = FinalMarking; | |
| 3599 if (UseAdaptiveSizePolicy) { | |
| 3600 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 3601 size_policy()->ms_collection_marking_end(gch->gc_cause()); | |
| 3602 } | |
| 3603 } | |
| 3604 verify_overflow_empty(); | |
| 3605 return res; | |
| 3606 } | |
| 3607 | |
| 3608 bool CMSCollector::markFromRootsWork(bool asynch) { | |
| 3609 // iterate over marked bits in bit map, doing a full scan and mark | |
| 3610 // from these roots using the following algorithm: | |
| 3611 // . if oop is to the right of the current scan pointer, | |
| 3612 // mark corresponding bit (we'll process it later) | |
| 3613 // . else (oop is to left of current scan pointer) | |
| 3614 // push oop on marking stack | |
| 3615 // . drain the marking stack | |
| 3616 | |
| 3617 // Note that when we do a marking step we need to hold the | |
| 3618 // bit map lock -- recall that direct allocation (by mutators) | |
| 3619 // and promotion (by younger generation collectors) is also | |
| 3620 // marking the bit map. [the so-called allocate live policy.] | |
| 3621 // Because the implementation of bit map marking is not | |
| 3622 // robust wrt simultaneous marking of bits in the same word, | |
| 3623 // we need to make sure that there is no such interference | |
| 3624 // between concurrent such updates. | |
| 3625 | |
| 3626 // already have locks | |
| 3627 assert_lock_strong(bitMapLock()); | |
| 3628 | |
| 3629 // Clear the revisit stack, just in case there are any | |
| 3630 // obsolete contents from a short-circuited previous CMS cycle. | |
| 3631 _revisitStack.reset(); | |
| 3632 verify_work_stacks_empty(); | |
| 3633 verify_overflow_empty(); | |
| 3634 assert(_revisitStack.isEmpty(), "tabula rasa"); | |
| 3635 | |
| 935 | 3636 DEBUG_ONLY(RememberKlassesChecker cmx(CMSClassUnloadingEnabled);) |
| 3637 | |
| 0 | 3638 bool result = false; |
| 3639 if (CMSConcurrentMTEnabled && ParallelCMSThreads > 0) { | |
| 3640 result = do_marking_mt(asynch); | |
| 3641 } else { | |
| 3642 result = do_marking_st(asynch); | |
| 3643 } | |
| 3644 return result; | |
| 3645 } | |
| 3646 | |
| 3647 // Forward decl | |
| 3648 class CMSConcMarkingTask; | |
| 3649 | |
| 3650 class CMSConcMarkingTerminator: public ParallelTaskTerminator { | |
| 3651 CMSCollector* _collector; | |
| 3652 CMSConcMarkingTask* _task; | |
| 3653 bool _yield; | |
| 3654 protected: | |
| 3655 virtual void yield(); | |
| 3656 public: | |
| 3657 // "n_threads" is the number of threads to be terminated. | |
| 3658 // "queue_set" is a set of work queues of other threads. | |
| 3659 // "collector" is the CMS collector associated with this task terminator. | |
| 3660 // "yield" indicates whether we need the gang as a whole to yield. | |
| 3661 CMSConcMarkingTerminator(int n_threads, TaskQueueSetSuper* queue_set, | |
| 3662 CMSCollector* collector, bool yield) : | |
| 3663 ParallelTaskTerminator(n_threads, queue_set), | |
| 3664 _collector(collector), | |
| 3665 _yield(yield) { } | |
| 3666 | |
| 3667 void set_task(CMSConcMarkingTask* task) { | |
| 3668 _task = task; | |
| 3669 } | |
| 3670 }; | |
| 3671 | |
| 3672 // MT Concurrent Marking Task | |
| 3673 class CMSConcMarkingTask: public YieldingFlexibleGangTask { | |
| 3674 CMSCollector* _collector; | |
| 3675 YieldingFlexibleWorkGang* _workers; // the whole gang | |
| 3676 int _n_workers; // requested/desired # workers | |
| 3677 bool _asynch; | |
| 3678 bool _result; | |
| 3679 CompactibleFreeListSpace* _cms_space; | |
| 3680 CompactibleFreeListSpace* _perm_space; | |
| 3681 HeapWord* _global_finger; | |
|
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|
3682 HeapWord* _restart_addr; |
| 0 | 3683 |
| 3684 // Exposed here for yielding support | |
| 3685 Mutex* const _bit_map_lock; | |
| 3686 | |
| 3687 // The per thread work queues, available here for stealing | |
| 3688 OopTaskQueueSet* _task_queues; | |
| 3689 CMSConcMarkingTerminator _term; | |
| 3690 | |
| 3691 public: | |
| 3692 CMSConcMarkingTask(CMSCollector* collector, | |
| 3693 CompactibleFreeListSpace* cms_space, | |
| 3694 CompactibleFreeListSpace* perm_space, | |
| 3695 bool asynch, int n_workers, | |
| 3696 YieldingFlexibleWorkGang* workers, | |
| 3697 OopTaskQueueSet* task_queues): | |
| 3698 YieldingFlexibleGangTask("Concurrent marking done multi-threaded"), | |
| 3699 _collector(collector), | |
| 3700 _cms_space(cms_space), | |
| 3701 _perm_space(perm_space), | |
| 3702 _asynch(asynch), _n_workers(n_workers), _result(true), | |
| 3703 _workers(workers), _task_queues(task_queues), | |
| 3704 _term(n_workers, task_queues, _collector, asynch), | |
| 3705 _bit_map_lock(collector->bitMapLock()) | |
| 3706 { | |
| 3707 assert(n_workers <= workers->total_workers(), | |
| 3708 "Else termination won't work correctly today"); // XXX FIX ME! | |
| 3709 _requested_size = n_workers; | |
| 3710 _term.set_task(this); | |
| 3711 assert(_cms_space->bottom() < _perm_space->bottom(), | |
| 3712 "Finger incorrectly initialized below"); | |
|
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3713 _restart_addr = _global_finger = _cms_space->bottom(); |
| 0 | 3714 } |
| 3715 | |
| 3716 | |
| 3717 OopTaskQueueSet* task_queues() { return _task_queues; } | |
| 3718 | |
| 3719 OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); } | |
| 3720 | |
| 3721 HeapWord** global_finger_addr() { return &_global_finger; } | |
| 3722 | |
| 3723 CMSConcMarkingTerminator* terminator() { return &_term; } | |
| 3724 | |
| 3725 void work(int i); | |
| 3726 | |
| 3727 virtual void coordinator_yield(); // stuff done by coordinator | |
| 3728 bool result() { return _result; } | |
| 3729 | |
| 3730 void reset(HeapWord* ra) { | |
|
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3731 assert(_global_finger >= _cms_space->end(), "Postcondition of ::work(i)"); |
|
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|
3732 assert(_global_finger >= _perm_space->end(), "Postcondition of ::work(i)"); |
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3733 assert(ra < _perm_space->end(), "ra too large"); |
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3734 _restart_addr = _global_finger = ra; |
| 0 | 3735 _term.reset_for_reuse(); |
| 3736 } | |
| 3737 | |
| 3738 static bool get_work_from_overflow_stack(CMSMarkStack* ovflw_stk, | |
| 3739 OopTaskQueue* work_q); | |
| 3740 | |
| 3741 private: | |
| 3742 void do_scan_and_mark(int i, CompactibleFreeListSpace* sp); | |
| 3743 void do_work_steal(int i); | |
| 3744 void bump_global_finger(HeapWord* f); | |
| 3745 }; | |
| 3746 | |
| 3747 void CMSConcMarkingTerminator::yield() { | |
| 3748 if (ConcurrentMarkSweepThread::should_yield() && | |
| 3749 !_collector->foregroundGCIsActive() && | |
| 3750 _yield) { | |
| 3751 _task->yield(); | |
| 3752 } else { | |
| 3753 ParallelTaskTerminator::yield(); | |
| 3754 } | |
| 3755 } | |
| 3756 | |
| 3757 //////////////////////////////////////////////////////////////// | |
| 3758 // Concurrent Marking Algorithm Sketch | |
| 3759 //////////////////////////////////////////////////////////////// | |
| 3760 // Until all tasks exhausted (both spaces): | |
| 3761 // -- claim next available chunk | |
| 3762 // -- bump global finger via CAS | |
| 3763 // -- find first object that starts in this chunk | |
| 3764 // and start scanning bitmap from that position | |
| 3765 // -- scan marked objects for oops | |
| 3766 // -- CAS-mark target, and if successful: | |
| 3767 // . if target oop is above global finger (volatile read) | |
| 3768 // nothing to do | |
| 3769 // . if target oop is in chunk and above local finger | |
| 3770 // then nothing to do | |
| 3771 // . else push on work-queue | |
| 3772 // -- Deal with possible overflow issues: | |
| 3773 // . local work-queue overflow causes stuff to be pushed on | |
| 3774 // global (common) overflow queue | |
| 3775 // . always first empty local work queue | |
| 3776 // . then get a batch of oops from global work queue if any | |
| 3777 // . then do work stealing | |
| 3778 // -- When all tasks claimed (both spaces) | |
| 3779 // and local work queue empty, | |
| 3780 // then in a loop do: | |
| 3781 // . check global overflow stack; steal a batch of oops and trace | |
| 3782 // . try to steal from other threads oif GOS is empty | |
| 3783 // . if neither is available, offer termination | |
| 3784 // -- Terminate and return result | |
| 3785 // | |
| 3786 void CMSConcMarkingTask::work(int i) { | |
| 3787 elapsedTimer _timer; | |
| 3788 ResourceMark rm; | |
| 3789 HandleMark hm; | |
| 3790 | |
| 3791 DEBUG_ONLY(_collector->verify_overflow_empty();) | |
| 3792 | |
| 3793 // Before we begin work, our work queue should be empty | |
| 3794 assert(work_queue(i)->size() == 0, "Expected to be empty"); | |
| 3795 // Scan the bitmap covering _cms_space, tracing through grey objects. | |
| 3796 _timer.start(); | |
| 3797 do_scan_and_mark(i, _cms_space); | |
| 3798 _timer.stop(); | |
| 3799 if (PrintCMSStatistics != 0) { | |
| 3800 gclog_or_tty->print_cr("Finished cms space scanning in %dth thread: %3.3f sec", | |
| 3801 i, _timer.seconds()); // XXX: need xxx/xxx type of notation, two timers | |
| 3802 } | |
| 3803 | |
| 3804 // ... do the same for the _perm_space | |
| 3805 _timer.reset(); | |
| 3806 _timer.start(); | |
| 3807 do_scan_and_mark(i, _perm_space); | |
| 3808 _timer.stop(); | |
| 3809 if (PrintCMSStatistics != 0) { | |
| 3810 gclog_or_tty->print_cr("Finished perm space scanning in %dth thread: %3.3f sec", | |
| 3811 i, _timer.seconds()); // XXX: need xxx/xxx type of notation, two timers | |
| 3812 } | |
| 3813 | |
| 3814 // ... do work stealing | |
| 3815 _timer.reset(); | |
| 3816 _timer.start(); | |
| 3817 do_work_steal(i); | |
| 3818 _timer.stop(); | |
| 3819 if (PrintCMSStatistics != 0) { | |
| 3820 gclog_or_tty->print_cr("Finished work stealing in %dth thread: %3.3f sec", | |
| 3821 i, _timer.seconds()); // XXX: need xxx/xxx type of notation, two timers | |
| 3822 } | |
| 3823 assert(_collector->_markStack.isEmpty(), "Should have been emptied"); | |
| 3824 assert(work_queue(i)->size() == 0, "Should have been emptied"); | |
| 3825 // Note that under the current task protocol, the | |
| 3826 // following assertion is true even of the spaces | |
| 3827 // expanded since the completion of the concurrent | |
| 3828 // marking. XXX This will likely change under a strict | |
| 3829 // ABORT semantics. | |
| 3830 assert(_global_finger > _cms_space->end() && | |
| 3831 _global_finger >= _perm_space->end(), | |
| 3832 "All tasks have been completed"); | |
| 3833 DEBUG_ONLY(_collector->verify_overflow_empty();) | |
| 3834 } | |
| 3835 | |
| 3836 void CMSConcMarkingTask::bump_global_finger(HeapWord* f) { | |
| 3837 HeapWord* read = _global_finger; | |
| 3838 HeapWord* cur = read; | |
| 3839 while (f > read) { | |
| 3840 cur = read; | |
| 3841 read = (HeapWord*) Atomic::cmpxchg_ptr(f, &_global_finger, cur); | |
| 3842 if (cur == read) { | |
| 3843 // our cas succeeded | |
| 3844 assert(_global_finger >= f, "protocol consistency"); | |
| 3845 break; | |
| 3846 } | |
| 3847 } | |
| 3848 } | |
| 3849 | |
| 3850 // This is really inefficient, and should be redone by | |
| 3851 // using (not yet available) block-read and -write interfaces to the | |
| 3852 // stack and the work_queue. XXX FIX ME !!! | |
| 3853 bool CMSConcMarkingTask::get_work_from_overflow_stack(CMSMarkStack* ovflw_stk, | |
| 3854 OopTaskQueue* work_q) { | |
| 3855 // Fast lock-free check | |
| 3856 if (ovflw_stk->length() == 0) { | |
| 3857 return false; | |
| 3858 } | |
| 3859 assert(work_q->size() == 0, "Shouldn't steal"); | |
| 3860 MutexLockerEx ml(ovflw_stk->par_lock(), | |
| 3861 Mutex::_no_safepoint_check_flag); | |
| 3862 // Grab up to 1/4 the size of the work queue | |
|
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3863 size_t num = MIN2((size_t)(work_q->max_elems() - work_q->size())/4, |
| 0 | 3864 (size_t)ParGCDesiredObjsFromOverflowList); |
| 3865 num = MIN2(num, ovflw_stk->length()); | |
| 3866 for (int i = (int) num; i > 0; i--) { | |
| 3867 oop cur = ovflw_stk->pop(); | |
| 3868 assert(cur != NULL, "Counted wrong?"); | |
| 3869 work_q->push(cur); | |
| 3870 } | |
| 3871 return num > 0; | |
| 3872 } | |
| 3873 | |
| 3874 void CMSConcMarkingTask::do_scan_and_mark(int i, CompactibleFreeListSpace* sp) { | |
| 3875 SequentialSubTasksDone* pst = sp->conc_par_seq_tasks(); | |
| 3876 int n_tasks = pst->n_tasks(); | |
| 3877 // We allow that there may be no tasks to do here because | |
| 3878 // we are restarting after a stack overflow. | |
|
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3879 assert(pst->valid() || n_tasks == 0, "Uninitialized use?"); |
| 0 | 3880 int nth_task = 0; |
| 3881 | |
|
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3882 HeapWord* aligned_start = sp->bottom(); |
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3883 if (sp->used_region().contains(_restart_addr)) { |
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3884 // Align down to a card boundary for the start of 0th task |
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3885 // for this space. |
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3886 aligned_start = |
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3887 (HeapWord*)align_size_down((uintptr_t)_restart_addr, |
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3888 CardTableModRefBS::card_size); |
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3889 } |
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3890 |
| 0 | 3891 size_t chunk_size = sp->marking_task_size(); |
| 3892 while (!pst->is_task_claimed(/* reference */ nth_task)) { | |
| 3893 // Having claimed the nth task in this space, | |
| 3894 // compute the chunk that it corresponds to: | |
|
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3895 MemRegion span = MemRegion(aligned_start + nth_task*chunk_size, |
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3896 aligned_start + (nth_task+1)*chunk_size); |
| 0 | 3897 // Try and bump the global finger via a CAS; |
| 3898 // note that we need to do the global finger bump | |
| 3899 // _before_ taking the intersection below, because | |
| 3900 // the task corresponding to that region will be | |
| 3901 // deemed done even if the used_region() expands | |
| 3902 // because of allocation -- as it almost certainly will | |
| 3903 // during start-up while the threads yield in the | |
| 3904 // closure below. | |
| 3905 HeapWord* finger = span.end(); | |
| 3906 bump_global_finger(finger); // atomically | |
| 3907 // There are null tasks here corresponding to chunks | |
| 3908 // beyond the "top" address of the space. | |
| 3909 span = span.intersection(sp->used_region()); | |
| 3910 if (!span.is_empty()) { // Non-null task | |
|
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3911 HeapWord* prev_obj; |
|
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3912 assert(!span.contains(_restart_addr) || nth_task == 0, |
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3913 "Inconsistency"); |
|
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3914 if (nth_task == 0) { |
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3915 // For the 0th task, we'll not need to compute a block_start. |
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3916 if (span.contains(_restart_addr)) { |
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3917 // In the case of a restart because of stack overflow, |
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3918 // we might additionally skip a chunk prefix. |
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3919 prev_obj = _restart_addr; |
| 0 | 3920 } else { |
|
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3921 prev_obj = span.start(); |
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3922 } |
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3923 } else { |
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3924 // We want to skip the first object because |
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3925 // the protocol is to scan any object in its entirety |
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3926 // that _starts_ in this span; a fortiori, any |
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3927 // object starting in an earlier span is scanned |
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3928 // as part of an earlier claimed task. |
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3929 // Below we use the "careful" version of block_start |
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3930 // so we do not try to navigate uninitialized objects. |
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3931 prev_obj = sp->block_start_careful(span.start()); |
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3932 // Below we use a variant of block_size that uses the |
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3933 // Printezis bits to avoid waiting for allocated |
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3934 // objects to become initialized/parsable. |
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3935 while (prev_obj < span.start()) { |
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3936 size_t sz = sp->block_size_no_stall(prev_obj, _collector); |
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3937 if (sz > 0) { |
|
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3938 prev_obj += sz; |
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3939 } else { |
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3940 // In this case we may end up doing a bit of redundant |
|
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3941 // scanning, but that appears unavoidable, short of |
|
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3942 // locking the free list locks; see bug 6324141. |
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3943 break; |
|
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|
3944 } |
| 0 | 3945 } |
| 3946 } | |
| 3947 if (prev_obj < span.end()) { | |
| 3948 MemRegion my_span = MemRegion(prev_obj, span.end()); | |
| 3949 // Do the marking work within a non-empty span -- | |
| 3950 // the last argument to the constructor indicates whether the | |
| 3951 // iteration should be incremental with periodic yields. | |
| 3952 Par_MarkFromRootsClosure cl(this, _collector, my_span, | |
| 3953 &_collector->_markBitMap, | |
| 3954 work_queue(i), | |
| 3955 &_collector->_markStack, | |
| 3956 &_collector->_revisitStack, | |
| 3957 _asynch); | |
| 3958 _collector->_markBitMap.iterate(&cl, my_span.start(), my_span.end()); | |
| 3959 } // else nothing to do for this task | |
| 3960 } // else nothing to do for this task | |
| 3961 } | |
| 3962 // We'd be tempted to assert here that since there are no | |
| 3963 // more tasks left to claim in this space, the global_finger | |
| 3964 // must exceed space->top() and a fortiori space->end(). However, | |
| 3965 // that would not quite be correct because the bumping of | |
| 3966 // global_finger occurs strictly after the claiming of a task, | |
| 3967 // so by the time we reach here the global finger may not yet | |
| 3968 // have been bumped up by the thread that claimed the last | |
| 3969 // task. | |
| 3970 pst->all_tasks_completed(); | |
| 3971 } | |
| 3972 | |
| 935 | 3973 class Par_ConcMarkingClosure: public Par_KlassRememberingOopClosure { |
|
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3974 private: |
| 0 | 3975 MemRegion _span; |
| 3976 CMSBitMap* _bit_map; | |
| 3977 CMSMarkStack* _overflow_stack; | |
| 3978 OopTaskQueue* _work_queue; | |
|
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3979 protected: |
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3980 DO_OOP_WORK_DEFN |
| 0 | 3981 public: |
| 3982 Par_ConcMarkingClosure(CMSCollector* collector, OopTaskQueue* work_queue, | |
| 935 | 3983 CMSBitMap* bit_map, CMSMarkStack* overflow_stack, |
| 3984 CMSMarkStack* revisit_stack): | |
| 3985 Par_KlassRememberingOopClosure(collector, NULL, revisit_stack), | |
| 0 | 3986 _span(_collector->_span), |
| 3987 _work_queue(work_queue), | |
| 3988 _bit_map(bit_map), | |
| 935 | 3989 _overflow_stack(overflow_stack) |
| 3990 { } | |
|
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3991 virtual void do_oop(oop* p); |
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3992 virtual void do_oop(narrowOop* p); |
| 0 | 3993 void trim_queue(size_t max); |
| 3994 void handle_stack_overflow(HeapWord* lost); | |
| 3995 }; | |
| 3996 | |
|
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3997 // Grey object scanning during work stealing phase -- |
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3998 // the salient assumption here is that any references |
|
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3999 // that are in these stolen objects being scanned must |
|
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4000 // already have been initialized (else they would not have |
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4001 // been published), so we do not need to check for |
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4002 // uninitialized objects before pushing here. |
|
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4003 void Par_ConcMarkingClosure::do_oop(oop obj) { |
|
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4004 assert(obj->is_oop_or_null(true), "expected an oop or NULL"); |
|
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4005 HeapWord* addr = (HeapWord*)obj; |
| 0 | 4006 // Check if oop points into the CMS generation |
| 4007 // and is not marked | |
| 4008 if (_span.contains(addr) && !_bit_map->isMarked(addr)) { | |
| 4009 // a white object ... | |
| 4010 // If we manage to "claim" the object, by being the | |
| 4011 // first thread to mark it, then we push it on our | |
| 4012 // marking stack | |
| 4013 if (_bit_map->par_mark(addr)) { // ... now grey | |
| 4014 // push on work queue (grey set) | |
| 4015 bool simulate_overflow = false; | |
| 4016 NOT_PRODUCT( | |
| 4017 if (CMSMarkStackOverflowALot && | |
| 4018 _collector->simulate_overflow()) { | |
| 4019 // simulate a stack overflow | |
| 4020 simulate_overflow = true; | |
| 4021 } | |
| 4022 ) | |
| 4023 if (simulate_overflow || | |
|
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4024 !(_work_queue->push(obj) || _overflow_stack->par_push(obj))) { |
| 0 | 4025 // stack overflow |
| 4026 if (PrintCMSStatistics != 0) { | |
| 4027 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
| 4028 SIZE_FORMAT, _overflow_stack->capacity()); | |
| 4029 } | |
| 4030 // We cannot assert that the overflow stack is full because | |
| 4031 // it may have been emptied since. | |
| 4032 assert(simulate_overflow || | |
| 4033 _work_queue->size() == _work_queue->max_elems(), | |
| 4034 "Else push should have succeeded"); | |
| 4035 handle_stack_overflow(addr); | |
| 4036 } | |
| 4037 } // Else, some other thread got there first | |
| 4038 } | |
| 4039 } | |
| 4040 | |
|
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4041 void Par_ConcMarkingClosure::do_oop(oop* p) { Par_ConcMarkingClosure::do_oop_work(p); } |
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4042 void Par_ConcMarkingClosure::do_oop(narrowOop* p) { Par_ConcMarkingClosure::do_oop_work(p); } |
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4043 |
| 0 | 4044 void Par_ConcMarkingClosure::trim_queue(size_t max) { |
| 4045 while (_work_queue->size() > max) { | |
| 4046 oop new_oop; | |
| 4047 if (_work_queue->pop_local(new_oop)) { | |
| 4048 assert(new_oop->is_oop(), "Should be an oop"); | |
| 4049 assert(_bit_map->isMarked((HeapWord*)new_oop), "Grey object"); | |
| 4050 assert(_span.contains((HeapWord*)new_oop), "Not in span"); | |
| 4051 assert(new_oop->is_parsable(), "Should be parsable"); | |
| 4052 new_oop->oop_iterate(this); // do_oop() above | |
| 4053 } | |
| 4054 } | |
| 4055 } | |
| 4056 | |
| 4057 // Upon stack overflow, we discard (part of) the stack, | |
| 4058 // remembering the least address amongst those discarded | |
| 4059 // in CMSCollector's _restart_address. | |
| 4060 void Par_ConcMarkingClosure::handle_stack_overflow(HeapWord* lost) { | |
| 4061 // We need to do this under a mutex to prevent other | |
|
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4062 // workers from interfering with the work done below. |
| 0 | 4063 MutexLockerEx ml(_overflow_stack->par_lock(), |
| 4064 Mutex::_no_safepoint_check_flag); | |
| 4065 // Remember the least grey address discarded | |
| 4066 HeapWord* ra = (HeapWord*)_overflow_stack->least_value(lost); | |
| 4067 _collector->lower_restart_addr(ra); | |
| 4068 _overflow_stack->reset(); // discard stack contents | |
| 4069 _overflow_stack->expand(); // expand the stack if possible | |
| 4070 } | |
| 4071 | |
| 4072 | |
| 4073 void CMSConcMarkingTask::do_work_steal(int i) { | |
| 4074 OopTaskQueue* work_q = work_queue(i); | |
| 4075 oop obj_to_scan; | |
| 4076 CMSBitMap* bm = &(_collector->_markBitMap); | |
| 4077 CMSMarkStack* ovflw = &(_collector->_markStack); | |
| 935 | 4078 CMSMarkStack* revisit = &(_collector->_revisitStack); |
| 0 | 4079 int* seed = _collector->hash_seed(i); |
| 935 | 4080 Par_ConcMarkingClosure cl(_collector, work_q, bm, ovflw, revisit); |
| 0 | 4081 while (true) { |
| 4082 cl.trim_queue(0); | |
| 4083 assert(work_q->size() == 0, "Should have been emptied above"); | |
| 4084 if (get_work_from_overflow_stack(ovflw, work_q)) { | |
| 4085 // Can't assert below because the work obtained from the | |
| 4086 // overflow stack may already have been stolen from us. | |
| 4087 // assert(work_q->size() > 0, "Work from overflow stack"); | |
| 4088 continue; | |
| 4089 } else if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) { | |
| 4090 assert(obj_to_scan->is_oop(), "Should be an oop"); | |
| 4091 assert(bm->isMarked((HeapWord*)obj_to_scan), "Grey object"); | |
| 4092 obj_to_scan->oop_iterate(&cl); | |
| 4093 } else if (terminator()->offer_termination()) { | |
| 4094 assert(work_q->size() == 0, "Impossible!"); | |
| 4095 break; | |
| 4096 } | |
| 4097 } | |
| 4098 } | |
| 4099 | |
| 4100 // This is run by the CMS (coordinator) thread. | |
| 4101 void CMSConcMarkingTask::coordinator_yield() { | |
| 4102 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 4103 "CMS thread should hold CMS token"); | |
| 4104 | |
| 935 | 4105 DEBUG_ONLY(RememberKlassesChecker mux(false);) |
| 0 | 4106 // First give up the locks, then yield, then re-lock |
| 4107 // We should probably use a constructor/destructor idiom to | |
| 4108 // do this unlock/lock or modify the MutexUnlocker class to | |
| 4109 // serve our purpose. XXX | |
| 4110 assert_lock_strong(_bit_map_lock); | |
| 4111 _bit_map_lock->unlock(); | |
| 4112 ConcurrentMarkSweepThread::desynchronize(true); | |
| 4113 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 4114 _collector->stopTimer(); | |
| 4115 if (PrintCMSStatistics != 0) { | |
| 4116 _collector->incrementYields(); | |
| 4117 } | |
| 4118 _collector->icms_wait(); | |
| 4119 | |
| 4120 // It is possible for whichever thread initiated the yield request | |
| 4121 // not to get a chance to wake up and take the bitmap lock between | |
| 4122 // this thread releasing it and reacquiring it. So, while the | |
| 4123 // should_yield() flag is on, let's sleep for a bit to give the | |
| 4124 // other thread a chance to wake up. The limit imposed on the number | |
| 4125 // of iterations is defensive, to avoid any unforseen circumstances | |
| 4126 // putting us into an infinite loop. Since it's always been this | |
| 4127 // (coordinator_yield()) method that was observed to cause the | |
| 4128 // problem, we are using a parameter (CMSCoordinatorYieldSleepCount) | |
| 4129 // which is by default non-zero. For the other seven methods that | |
| 4130 // also perform the yield operation, as are using a different | |
| 4131 // parameter (CMSYieldSleepCount) which is by default zero. This way we | |
| 4132 // can enable the sleeping for those methods too, if necessary. | |
| 4133 // See 6442774. | |
| 4134 // | |
| 4135 // We really need to reconsider the synchronization between the GC | |
| 4136 // thread and the yield-requesting threads in the future and we | |
| 4137 // should really use wait/notify, which is the recommended | |
| 4138 // way of doing this type of interaction. Additionally, we should | |
| 4139 // consolidate the eight methods that do the yield operation and they | |
| 4140 // are almost identical into one for better maintenability and | |
| 4141 // readability. See 6445193. | |
| 4142 // | |
| 4143 // Tony 2006.06.29 | |
| 4144 for (unsigned i = 0; i < CMSCoordinatorYieldSleepCount && | |
|
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4145 ConcurrentMarkSweepThread::should_yield() && |
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4146 !CMSCollector::foregroundGCIsActive(); ++i) { |
| 0 | 4147 os::sleep(Thread::current(), 1, false); |
| 4148 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 4149 } | |
| 4150 | |
| 4151 ConcurrentMarkSweepThread::synchronize(true); | |
| 4152 _bit_map_lock->lock_without_safepoint_check(); | |
| 4153 _collector->startTimer(); | |
| 4154 } | |
| 4155 | |
| 4156 bool CMSCollector::do_marking_mt(bool asynch) { | |
| 4157 assert(ParallelCMSThreads > 0 && conc_workers() != NULL, "precondition"); | |
| 4158 // In the future this would be determined ergonomically, based | |
| 4159 // on #cpu's, # active mutator threads (and load), and mutation rate. | |
| 4160 int num_workers = ParallelCMSThreads; | |
| 4161 | |
| 4162 CompactibleFreeListSpace* cms_space = _cmsGen->cmsSpace(); | |
| 4163 CompactibleFreeListSpace* perm_space = _permGen->cmsSpace(); | |
| 4164 | |
| 4165 CMSConcMarkingTask tsk(this, cms_space, perm_space, | |
| 4166 asynch, num_workers /* number requested XXX */, | |
| 4167 conc_workers(), task_queues()); | |
| 4168 | |
| 4169 // Since the actual number of workers we get may be different | |
| 4170 // from the number we requested above, do we need to do anything different | |
| 4171 // below? In particular, may be we need to subclass the SequantialSubTasksDone | |
| 4172 // class?? XXX | |
| 4173 cms_space ->initialize_sequential_subtasks_for_marking(num_workers); | |
| 4174 perm_space->initialize_sequential_subtasks_for_marking(num_workers); | |
| 4175 | |
| 4176 // Refs discovery is already non-atomic. | |
| 4177 assert(!ref_processor()->discovery_is_atomic(), "Should be non-atomic"); | |
| 4178 // Mutate the Refs discovery so it is MT during the | |
| 4179 // multi-threaded marking phase. | |
| 4180 ReferenceProcessorMTMutator mt(ref_processor(), num_workers > 1); | |
| 4181 | |
| 935 | 4182 DEBUG_ONLY(RememberKlassesChecker cmx(CMSClassUnloadingEnabled);) |
| 4183 | |
| 0 | 4184 conc_workers()->start_task(&tsk); |
| 4185 while (tsk.yielded()) { | |
| 4186 tsk.coordinator_yield(); | |
| 4187 conc_workers()->continue_task(&tsk); | |
| 4188 } | |
| 4189 // If the task was aborted, _restart_addr will be non-NULL | |
| 4190 assert(tsk.completed() || _restart_addr != NULL, "Inconsistency"); | |
| 4191 while (_restart_addr != NULL) { | |
| 4192 // XXX For now we do not make use of ABORTED state and have not | |
| 4193 // yet implemented the right abort semantics (even in the original | |
| 4194 // single-threaded CMS case). That needs some more investigation | |
| 4195 // and is deferred for now; see CR# TBF. 07252005YSR. XXX | |
| 4196 assert(!CMSAbortSemantics || tsk.aborted(), "Inconsistency"); | |
| 4197 // If _restart_addr is non-NULL, a marking stack overflow | |
| 605 | 4198 // occurred; we need to do a fresh marking iteration from the |
| 0 | 4199 // indicated restart address. |
| 4200 if (_foregroundGCIsActive && asynch) { | |
| 4201 // We may be running into repeated stack overflows, having | |
| 4202 // reached the limit of the stack size, while making very | |
| 4203 // slow forward progress. It may be best to bail out and | |
| 4204 // let the foreground collector do its job. | |
| 4205 // Clear _restart_addr, so that foreground GC | |
| 4206 // works from scratch. This avoids the headache of | |
| 4207 // a "rescan" which would otherwise be needed because | |
| 4208 // of the dirty mod union table & card table. | |
| 4209 _restart_addr = NULL; | |
| 4210 return false; | |
| 4211 } | |
| 4212 // Adjust the task to restart from _restart_addr | |
| 4213 tsk.reset(_restart_addr); | |
| 4214 cms_space ->initialize_sequential_subtasks_for_marking(num_workers, | |
| 4215 _restart_addr); | |
| 4216 perm_space->initialize_sequential_subtasks_for_marking(num_workers, | |
| 4217 _restart_addr); | |
| 4218 _restart_addr = NULL; | |
| 4219 // Get the workers going again | |
| 4220 conc_workers()->start_task(&tsk); | |
| 4221 while (tsk.yielded()) { | |
| 4222 tsk.coordinator_yield(); | |
| 4223 conc_workers()->continue_task(&tsk); | |
| 4224 } | |
| 4225 } | |
| 4226 assert(tsk.completed(), "Inconsistency"); | |
| 4227 assert(tsk.result() == true, "Inconsistency"); | |
| 4228 return true; | |
| 4229 } | |
| 4230 | |
| 4231 bool CMSCollector::do_marking_st(bool asynch) { | |
| 4232 ResourceMark rm; | |
| 4233 HandleMark hm; | |
| 4234 | |
| 4235 MarkFromRootsClosure markFromRootsClosure(this, _span, &_markBitMap, | |
| 4236 &_markStack, &_revisitStack, CMSYield && asynch); | |
| 4237 // the last argument to iterate indicates whether the iteration | |
| 4238 // should be incremental with periodic yields. | |
| 4239 _markBitMap.iterate(&markFromRootsClosure); | |
| 4240 // If _restart_addr is non-NULL, a marking stack overflow | |
| 605 | 4241 // occurred; we need to do a fresh iteration from the |
| 0 | 4242 // indicated restart address. |
| 4243 while (_restart_addr != NULL) { | |
| 4244 if (_foregroundGCIsActive && asynch) { | |
| 4245 // We may be running into repeated stack overflows, having | |
| 4246 // reached the limit of the stack size, while making very | |
| 4247 // slow forward progress. It may be best to bail out and | |
| 4248 // let the foreground collector do its job. | |
| 4249 // Clear _restart_addr, so that foreground GC | |
| 4250 // works from scratch. This avoids the headache of | |
| 4251 // a "rescan" which would otherwise be needed because | |
| 4252 // of the dirty mod union table & card table. | |
| 4253 _restart_addr = NULL; | |
| 4254 return false; // indicating failure to complete marking | |
| 4255 } | |
| 4256 // Deal with stack overflow: | |
| 4257 // we restart marking from _restart_addr | |
| 4258 HeapWord* ra = _restart_addr; | |
| 4259 markFromRootsClosure.reset(ra); | |
| 4260 _restart_addr = NULL; | |
| 4261 _markBitMap.iterate(&markFromRootsClosure, ra, _span.end()); | |
| 4262 } | |
| 4263 return true; | |
| 4264 } | |
| 4265 | |
| 4266 void CMSCollector::preclean() { | |
| 4267 check_correct_thread_executing(); | |
| 4268 assert(Thread::current()->is_ConcurrentGC_thread(), "Wrong thread"); | |
| 4269 verify_work_stacks_empty(); | |
| 4270 verify_overflow_empty(); | |
| 4271 _abort_preclean = false; | |
| 4272 if (CMSPrecleaningEnabled) { | |
| 4273 _eden_chunk_index = 0; | |
| 4274 size_t used = get_eden_used(); | |
| 4275 size_t capacity = get_eden_capacity(); | |
| 4276 // Don't start sampling unless we will get sufficiently | |
| 4277 // many samples. | |
| 4278 if (used < (capacity/(CMSScheduleRemarkSamplingRatio * 100) | |
| 4279 * CMSScheduleRemarkEdenPenetration)) { | |
| 4280 _start_sampling = true; | |
| 4281 } else { | |
| 4282 _start_sampling = false; | |
| 4283 } | |
| 4284 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
| 4285 CMSPhaseAccounting pa(this, "preclean", !PrintGCDetails); | |
| 4286 preclean_work(CMSPrecleanRefLists1, CMSPrecleanSurvivors1); | |
| 4287 } | |
| 4288 CMSTokenSync x(true); // is cms thread | |
| 4289 if (CMSPrecleaningEnabled) { | |
| 4290 sample_eden(); | |
| 4291 _collectorState = AbortablePreclean; | |
| 4292 } else { | |
| 4293 _collectorState = FinalMarking; | |
| 4294 } | |
| 4295 verify_work_stacks_empty(); | |
| 4296 verify_overflow_empty(); | |
| 4297 } | |
| 4298 | |
| 4299 // Try and schedule the remark such that young gen | |
| 4300 // occupancy is CMSScheduleRemarkEdenPenetration %. | |
| 4301 void CMSCollector::abortable_preclean() { | |
| 4302 check_correct_thread_executing(); | |
| 4303 assert(CMSPrecleaningEnabled, "Inconsistent control state"); | |
| 4304 assert(_collectorState == AbortablePreclean, "Inconsistent control state"); | |
| 4305 | |
| 4306 // If Eden's current occupancy is below this threshold, | |
| 4307 // immediately schedule the remark; else preclean | |
| 4308 // past the next scavenge in an effort to | |
| 4309 // schedule the pause as described avove. By choosing | |
| 4310 // CMSScheduleRemarkEdenSizeThreshold >= max eden size | |
| 4311 // we will never do an actual abortable preclean cycle. | |
| 4312 if (get_eden_used() > CMSScheduleRemarkEdenSizeThreshold) { | |
| 4313 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
| 4314 CMSPhaseAccounting pa(this, "abortable-preclean", !PrintGCDetails); | |
| 4315 // We need more smarts in the abortable preclean | |
| 4316 // loop below to deal with cases where allocation | |
| 4317 // in young gen is very very slow, and our precleaning | |
| 4318 // is running a losing race against a horde of | |
| 4319 // mutators intent on flooding us with CMS updates | |
| 4320 // (dirty cards). | |
| 4321 // One, admittedly dumb, strategy is to give up | |
| 4322 // after a certain number of abortable precleaning loops | |
| 4323 // or after a certain maximum time. We want to make | |
| 4324 // this smarter in the next iteration. | |
| 4325 // XXX FIX ME!!! YSR | |
| 4326 size_t loops = 0, workdone = 0, cumworkdone = 0, waited = 0; | |
| 4327 while (!(should_abort_preclean() || | |
| 4328 ConcurrentMarkSweepThread::should_terminate())) { | |
| 4329 workdone = preclean_work(CMSPrecleanRefLists2, CMSPrecleanSurvivors2); | |
| 4330 cumworkdone += workdone; | |
| 4331 loops++; | |
| 4332 // Voluntarily terminate abortable preclean phase if we have | |
| 4333 // been at it for too long. | |
| 4334 if ((CMSMaxAbortablePrecleanLoops != 0) && | |
| 4335 loops >= CMSMaxAbortablePrecleanLoops) { | |
| 4336 if (PrintGCDetails) { | |
| 4337 gclog_or_tty->print(" CMS: abort preclean due to loops "); | |
| 4338 } | |
| 4339 break; | |
| 4340 } | |
| 4341 if (pa.wallclock_millis() > CMSMaxAbortablePrecleanTime) { | |
| 4342 if (PrintGCDetails) { | |
| 4343 gclog_or_tty->print(" CMS: abort preclean due to time "); | |
| 4344 } | |
| 4345 break; | |
| 4346 } | |
| 4347 // If we are doing little work each iteration, we should | |
| 4348 // take a short break. | |
| 4349 if (workdone < CMSAbortablePrecleanMinWorkPerIteration) { | |
| 4350 // Sleep for some time, waiting for work to accumulate | |
| 4351 stopTimer(); | |
| 4352 cmsThread()->wait_on_cms_lock(CMSAbortablePrecleanWaitMillis); | |
| 4353 startTimer(); | |
| 4354 waited++; | |
| 4355 } | |
| 4356 } | |
| 4357 if (PrintCMSStatistics > 0) { | |
| 4358 gclog_or_tty->print(" [%d iterations, %d waits, %d cards)] ", | |
| 4359 loops, waited, cumworkdone); | |
| 4360 } | |
| 4361 } | |
| 4362 CMSTokenSync x(true); // is cms thread | |
| 4363 if (_collectorState != Idling) { | |
| 4364 assert(_collectorState == AbortablePreclean, | |
| 4365 "Spontaneous state transition?"); | |
| 4366 _collectorState = FinalMarking; | |
| 4367 } // Else, a foreground collection completed this CMS cycle. | |
| 4368 return; | |
| 4369 } | |
| 4370 | |
| 4371 // Respond to an Eden sampling opportunity | |
| 4372 void CMSCollector::sample_eden() { | |
| 4373 // Make sure a young gc cannot sneak in between our | |
| 4374 // reading and recording of a sample. | |
| 4375 assert(Thread::current()->is_ConcurrentGC_thread(), | |
| 4376 "Only the cms thread may collect Eden samples"); | |
| 4377 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 4378 "Should collect samples while holding CMS token"); | |
| 4379 if (!_start_sampling) { | |
| 4380 return; | |
| 4381 } | |
| 4382 if (_eden_chunk_array) { | |
| 4383 if (_eden_chunk_index < _eden_chunk_capacity) { | |
| 4384 _eden_chunk_array[_eden_chunk_index] = *_top_addr; // take sample | |
| 4385 assert(_eden_chunk_array[_eden_chunk_index] <= *_end_addr, | |
| 4386 "Unexpected state of Eden"); | |
| 4387 // We'd like to check that what we just sampled is an oop-start address; | |
| 4388 // however, we cannot do that here since the object may not yet have been | |
| 4389 // initialized. So we'll instead do the check when we _use_ this sample | |
| 4390 // later. | |
| 4391 if (_eden_chunk_index == 0 || | |
| 4392 (pointer_delta(_eden_chunk_array[_eden_chunk_index], | |
| 4393 _eden_chunk_array[_eden_chunk_index-1]) | |
| 4394 >= CMSSamplingGrain)) { | |
| 4395 _eden_chunk_index++; // commit sample | |
| 4396 } | |
| 4397 } | |
| 4398 } | |
| 4399 if ((_collectorState == AbortablePreclean) && !_abort_preclean) { | |
| 4400 size_t used = get_eden_used(); | |
| 4401 size_t capacity = get_eden_capacity(); | |
| 4402 assert(used <= capacity, "Unexpected state of Eden"); | |
| 4403 if (used > (capacity/100 * CMSScheduleRemarkEdenPenetration)) { | |
| 4404 _abort_preclean = true; | |
| 4405 } | |
| 4406 } | |
| 4407 } | |
| 4408 | |
| 4409 | |
| 4410 size_t CMSCollector::preclean_work(bool clean_refs, bool clean_survivor) { | |
| 4411 assert(_collectorState == Precleaning || | |
| 4412 _collectorState == AbortablePreclean, "incorrect state"); | |
| 4413 ResourceMark rm; | |
| 4414 HandleMark hm; | |
| 4415 // Do one pass of scrubbing the discovered reference lists | |
| 4416 // to remove any reference objects with strongly-reachable | |
| 4417 // referents. | |
| 4418 if (clean_refs) { | |
| 4419 ReferenceProcessor* rp = ref_processor(); | |
| 4420 CMSPrecleanRefsYieldClosure yield_cl(this); | |
| 4421 assert(rp->span().equals(_span), "Spans should be equal"); | |
| 4422 CMSKeepAliveClosure keep_alive(this, _span, &_markBitMap, | |
| 935 | 4423 &_markStack, &_revisitStack, |
| 4424 true /* preclean */); | |
| 0 | 4425 CMSDrainMarkingStackClosure complete_trace(this, |
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4426 _span, &_markBitMap, &_markStack, |
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4427 &keep_alive, true /* preclean */); |
| 0 | 4428 |
| 4429 // We don't want this step to interfere with a young | |
| 4430 // collection because we don't want to take CPU | |
| 4431 // or memory bandwidth away from the young GC threads | |
| 4432 // (which may be as many as there are CPUs). | |
| 4433 // Note that we don't need to protect ourselves from | |
| 4434 // interference with mutators because they can't | |
| 4435 // manipulate the discovered reference lists nor affect | |
| 4436 // the computed reachability of the referents, the | |
| 4437 // only properties manipulated by the precleaning | |
| 4438 // of these reference lists. | |
| 4439 stopTimer(); | |
| 4440 CMSTokenSyncWithLocks x(true /* is cms thread */, | |
| 4441 bitMapLock()); | |
| 4442 startTimer(); | |
| 4443 sample_eden(); | |
| 935 | 4444 |
| 0 | 4445 // The following will yield to allow foreground |
| 4446 // collection to proceed promptly. XXX YSR: | |
| 4447 // The code in this method may need further | |
| 4448 // tweaking for better performance and some restructuring | |
| 4449 // for cleaner interfaces. | |
| 4450 rp->preclean_discovered_references( | |
| 4451 rp->is_alive_non_header(), &keep_alive, &complete_trace, | |
| 4452 &yield_cl); | |
| 4453 } | |
| 4454 | |
| 4455 if (clean_survivor) { // preclean the active survivor space(s) | |
| 4456 assert(_young_gen->kind() == Generation::DefNew || | |
| 4457 _young_gen->kind() == Generation::ParNew || | |
| 4458 _young_gen->kind() == Generation::ASParNew, | |
| 4459 "incorrect type for cast"); | |
| 4460 DefNewGeneration* dng = (DefNewGeneration*)_young_gen; | |
| 4461 PushAndMarkClosure pam_cl(this, _span, ref_processor(), | |
| 4462 &_markBitMap, &_modUnionTable, | |
| 4463 &_markStack, &_revisitStack, | |
| 4464 true /* precleaning phase */); | |
| 4465 stopTimer(); | |
| 4466 CMSTokenSyncWithLocks ts(true /* is cms thread */, | |
| 4467 bitMapLock()); | |
| 4468 startTimer(); | |
| 4469 unsigned int before_count = | |
| 4470 GenCollectedHeap::heap()->total_collections(); | |
| 4471 SurvivorSpacePrecleanClosure | |
| 4472 sss_cl(this, _span, &_markBitMap, &_markStack, | |
| 4473 &pam_cl, before_count, CMSYield); | |
| 935 | 4474 DEBUG_ONLY(RememberKlassesChecker mx(CMSClassUnloadingEnabled);) |
| 0 | 4475 dng->from()->object_iterate_careful(&sss_cl); |
| 4476 dng->to()->object_iterate_careful(&sss_cl); | |
| 4477 } | |
| 4478 MarkRefsIntoAndScanClosure | |
| 4479 mrias_cl(_span, ref_processor(), &_markBitMap, &_modUnionTable, | |
| 4480 &_markStack, &_revisitStack, this, CMSYield, | |
| 4481 true /* precleaning phase */); | |
| 4482 // CAUTION: The following closure has persistent state that may need to | |
| 4483 // be reset upon a decrease in the sequence of addresses it | |
| 4484 // processes. | |
| 4485 ScanMarkedObjectsAgainCarefullyClosure | |
| 4486 smoac_cl(this, _span, | |
| 4487 &_markBitMap, &_markStack, &_revisitStack, &mrias_cl, CMSYield); | |
| 4488 | |
| 4489 // Preclean dirty cards in ModUnionTable and CardTable using | |
| 4490 // appropriate convergence criterion; | |
| 4491 // repeat CMSPrecleanIter times unless we find that | |
| 4492 // we are losing. | |
| 4493 assert(CMSPrecleanIter < 10, "CMSPrecleanIter is too large"); | |
| 4494 assert(CMSPrecleanNumerator < CMSPrecleanDenominator, | |
| 4495 "Bad convergence multiplier"); | |
| 4496 assert(CMSPrecleanThreshold >= 100, | |
| 4497 "Unreasonably low CMSPrecleanThreshold"); | |
| 4498 | |
| 4499 size_t numIter, cumNumCards, lastNumCards, curNumCards; | |
| 4500 for (numIter = 0, cumNumCards = lastNumCards = curNumCards = 0; | |
| 4501 numIter < CMSPrecleanIter; | |
| 4502 numIter++, lastNumCards = curNumCards, cumNumCards += curNumCards) { | |
| 4503 curNumCards = preclean_mod_union_table(_cmsGen, &smoac_cl); | |
| 4504 if (CMSPermGenPrecleaningEnabled) { | |
| 4505 curNumCards += preclean_mod_union_table(_permGen, &smoac_cl); | |
| 4506 } | |
| 4507 if (Verbose && PrintGCDetails) { | |
| 4508 gclog_or_tty->print(" (modUnionTable: %d cards)", curNumCards); | |
| 4509 } | |
| 4510 // Either there are very few dirty cards, so re-mark | |
| 4511 // pause will be small anyway, or our pre-cleaning isn't | |
| 4512 // that much faster than the rate at which cards are being | |
| 4513 // dirtied, so we might as well stop and re-mark since | |
| 4514 // precleaning won't improve our re-mark time by much. | |
| 4515 if (curNumCards <= CMSPrecleanThreshold || | |
| 4516 (numIter > 0 && | |
| 4517 (curNumCards * CMSPrecleanDenominator > | |
| 4518 lastNumCards * CMSPrecleanNumerator))) { | |
| 4519 numIter++; | |
| 4520 cumNumCards += curNumCards; | |
| 4521 break; | |
| 4522 } | |
| 4523 } | |
| 4524 curNumCards = preclean_card_table(_cmsGen, &smoac_cl); | |
| 4525 if (CMSPermGenPrecleaningEnabled) { | |
| 4526 curNumCards += preclean_card_table(_permGen, &smoac_cl); | |
| 4527 } | |
| 4528 cumNumCards += curNumCards; | |
| 4529 if (PrintGCDetails && PrintCMSStatistics != 0) { | |
| 4530 gclog_or_tty->print_cr(" (cardTable: %d cards, re-scanned %d cards, %d iterations)", | |
| 4531 curNumCards, cumNumCards, numIter); | |
| 4532 } | |
| 4533 return cumNumCards; // as a measure of useful work done | |
| 4534 } | |
| 4535 | |
| 4536 // PRECLEANING NOTES: | |
| 4537 // Precleaning involves: | |
| 4538 // . reading the bits of the modUnionTable and clearing the set bits. | |
| 4539 // . For the cards corresponding to the set bits, we scan the | |
| 4540 // objects on those cards. This means we need the free_list_lock | |
| 4541 // so that we can safely iterate over the CMS space when scanning | |
| 4542 // for oops. | |
| 4543 // . When we scan the objects, we'll be both reading and setting | |
| 4544 // marks in the marking bit map, so we'll need the marking bit map. | |
| 4545 // . For protecting _collector_state transitions, we take the CGC_lock. | |
| 4546 // Note that any races in the reading of of card table entries by the | |
| 4547 // CMS thread on the one hand and the clearing of those entries by the | |
| 4548 // VM thread or the setting of those entries by the mutator threads on the | |
| 4549 // other are quite benign. However, for efficiency it makes sense to keep | |
| 4550 // the VM thread from racing with the CMS thread while the latter is | |
| 4551 // dirty card info to the modUnionTable. We therefore also use the | |
| 4552 // CGC_lock to protect the reading of the card table and the mod union | |
| 4553 // table by the CM thread. | |
| 4554 // . We run concurrently with mutator updates, so scanning | |
| 4555 // needs to be done carefully -- we should not try to scan | |
| 4556 // potentially uninitialized objects. | |
| 4557 // | |
| 4558 // Locking strategy: While holding the CGC_lock, we scan over and | |
| 4559 // reset a maximal dirty range of the mod union / card tables, then lock | |
| 4560 // the free_list_lock and bitmap lock to do a full marking, then | |
| 4561 // release these locks; and repeat the cycle. This allows for a | |
| 4562 // certain amount of fairness in the sharing of these locks between | |
| 4563 // the CMS collector on the one hand, and the VM thread and the | |
| 4564 // mutators on the other. | |
| 4565 | |
| 4566 // NOTE: preclean_mod_union_table() and preclean_card_table() | |
| 4567 // further below are largely identical; if you need to modify | |
| 4568 // one of these methods, please check the other method too. | |
| 4569 | |
| 4570 size_t CMSCollector::preclean_mod_union_table( | |
| 4571 ConcurrentMarkSweepGeneration* gen, | |
| 4572 ScanMarkedObjectsAgainCarefullyClosure* cl) { | |
| 4573 verify_work_stacks_empty(); | |
| 4574 verify_overflow_empty(); | |
| 4575 | |
| 935 | 4576 // Turn off checking for this method but turn it back on |
| 4577 // selectively. There are yield points in this method | |
| 4578 // but it is difficult to turn the checking off just around | |
| 4579 // the yield points. It is simpler to selectively turn | |
| 4580 // it on. | |
| 4581 DEBUG_ONLY(RememberKlassesChecker mux(false);) | |
| 4582 | |
| 0 | 4583 // strategy: starting with the first card, accumulate contiguous |
| 4584 // ranges of dirty cards; clear these cards, then scan the region | |
| 4585 // covered by these cards. | |
| 4586 | |
| 4587 // Since all of the MUT is committed ahead, we can just use | |
| 4588 // that, in case the generations expand while we are precleaning. | |
| 4589 // It might also be fine to just use the committed part of the | |
| 4590 // generation, but we might potentially miss cards when the | |
| 4591 // generation is rapidly expanding while we are in the midst | |
| 4592 // of precleaning. | |
| 4593 HeapWord* startAddr = gen->reserved().start(); | |
| 4594 HeapWord* endAddr = gen->reserved().end(); | |
| 4595 | |
| 4596 cl->setFreelistLock(gen->freelistLock()); // needed for yielding | |
| 4597 | |
| 4598 size_t numDirtyCards, cumNumDirtyCards; | |
| 4599 HeapWord *nextAddr, *lastAddr; | |
| 4600 for (cumNumDirtyCards = numDirtyCards = 0, | |
| 4601 nextAddr = lastAddr = startAddr; | |
| 4602 nextAddr < endAddr; | |
| 4603 nextAddr = lastAddr, cumNumDirtyCards += numDirtyCards) { | |
| 4604 | |
| 4605 ResourceMark rm; | |
| 4606 HandleMark hm; | |
| 4607 | |
| 4608 MemRegion dirtyRegion; | |
| 4609 { | |
| 4610 stopTimer(); | |
| 935 | 4611 // Potential yield point |
| 0 | 4612 CMSTokenSync ts(true); |
| 4613 startTimer(); | |
| 4614 sample_eden(); | |
| 4615 // Get dirty region starting at nextOffset (inclusive), | |
| 4616 // simultaneously clearing it. | |
| 4617 dirtyRegion = | |
| 4618 _modUnionTable.getAndClearMarkedRegion(nextAddr, endAddr); | |
| 4619 assert(dirtyRegion.start() >= nextAddr, | |
| 4620 "returned region inconsistent?"); | |
| 4621 } | |
| 4622 // Remember where the next search should begin. | |
| 4623 // The returned region (if non-empty) is a right open interval, | |
| 4624 // so lastOffset is obtained from the right end of that | |
| 4625 // interval. | |
| 4626 lastAddr = dirtyRegion.end(); | |
| 4627 // Should do something more transparent and less hacky XXX | |
| 4628 numDirtyCards = | |
| 4629 _modUnionTable.heapWordDiffToOffsetDiff(dirtyRegion.word_size()); | |
| 4630 | |
| 4631 // We'll scan the cards in the dirty region (with periodic | |
| 4632 // yields for foreground GC as needed). | |
| 4633 if (!dirtyRegion.is_empty()) { | |
| 4634 assert(numDirtyCards > 0, "consistency check"); | |
| 4635 HeapWord* stop_point = NULL; | |
|
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|
4636 stopTimer(); |
| 935 | 4637 // Potential yield point |
|
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4638 CMSTokenSyncWithLocks ts(true, gen->freelistLock(), |
|
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|
4639 bitMapLock()); |
|
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|
4640 startTimer(); |
| 0 | 4641 { |
| 4642 verify_work_stacks_empty(); | |
| 4643 verify_overflow_empty(); | |
| 4644 sample_eden(); | |
| 935 | 4645 DEBUG_ONLY(RememberKlassesChecker mx(CMSClassUnloadingEnabled);) |
| 0 | 4646 stop_point = |
| 4647 gen->cmsSpace()->object_iterate_careful_m(dirtyRegion, cl); | |
| 4648 } | |
| 4649 if (stop_point != NULL) { | |
| 4650 // The careful iteration stopped early either because it found an | |
| 4651 // uninitialized object, or because we were in the midst of an | |
| 4652 // "abortable preclean", which should now be aborted. Redirty | |
| 4653 // the bits corresponding to the partially-scanned or unscanned | |
| 4654 // cards. We'll either restart at the next block boundary or | |
| 4655 // abort the preclean. | |
| 4656 assert((CMSPermGenPrecleaningEnabled && (gen == _permGen)) || | |
| 4657 (_collectorState == AbortablePreclean && should_abort_preclean()), | |
| 4658 "Unparsable objects should only be in perm gen."); | |
| 4659 _modUnionTable.mark_range(MemRegion(stop_point, dirtyRegion.end())); | |
| 4660 if (should_abort_preclean()) { | |
| 4661 break; // out of preclean loop | |
| 4662 } else { | |
| 4663 // Compute the next address at which preclean should pick up; | |
| 4664 // might need bitMapLock in order to read P-bits. | |
| 4665 lastAddr = next_card_start_after_block(stop_point); | |
| 4666 } | |
| 4667 } | |
| 4668 } else { | |
| 4669 assert(lastAddr == endAddr, "consistency check"); | |
| 4670 assert(numDirtyCards == 0, "consistency check"); | |
| 4671 break; | |
| 4672 } | |
| 4673 } | |
| 4674 verify_work_stacks_empty(); | |
| 4675 verify_overflow_empty(); | |
| 4676 return cumNumDirtyCards; | |
| 4677 } | |
| 4678 | |
| 4679 // NOTE: preclean_mod_union_table() above and preclean_card_table() | |
| 4680 // below are largely identical; if you need to modify | |
| 4681 // one of these methods, please check the other method too. | |
| 4682 | |
| 4683 size_t CMSCollector::preclean_card_table(ConcurrentMarkSweepGeneration* gen, | |
| 4684 ScanMarkedObjectsAgainCarefullyClosure* cl) { | |
| 4685 // strategy: it's similar to precleamModUnionTable above, in that | |
| 4686 // we accumulate contiguous ranges of dirty cards, mark these cards | |
| 4687 // precleaned, then scan the region covered by these cards. | |
| 4688 HeapWord* endAddr = (HeapWord*)(gen->_virtual_space.high()); | |
| 4689 HeapWord* startAddr = (HeapWord*)(gen->_virtual_space.low()); | |
| 4690 | |
| 4691 cl->setFreelistLock(gen->freelistLock()); // needed for yielding | |
| 4692 | |
| 4693 size_t numDirtyCards, cumNumDirtyCards; | |
| 4694 HeapWord *lastAddr, *nextAddr; | |
| 4695 | |
| 4696 for (cumNumDirtyCards = numDirtyCards = 0, | |
| 4697 nextAddr = lastAddr = startAddr; | |
| 4698 nextAddr < endAddr; | |
| 4699 nextAddr = lastAddr, cumNumDirtyCards += numDirtyCards) { | |
| 4700 | |
| 4701 ResourceMark rm; | |
| 4702 HandleMark hm; | |
| 4703 | |
| 4704 MemRegion dirtyRegion; | |
| 4705 { | |
| 4706 // See comments in "Precleaning notes" above on why we | |
| 4707 // do this locking. XXX Could the locking overheads be | |
| 4708 // too high when dirty cards are sparse? [I don't think so.] | |
| 4709 stopTimer(); | |
| 4710 CMSTokenSync x(true); // is cms thread | |
| 4711 startTimer(); | |
| 4712 sample_eden(); | |
| 4713 // Get and clear dirty region from card table | |
|
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4714 dirtyRegion = _ct->ct_bs()->dirty_card_range_after_reset( |
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4715 MemRegion(nextAddr, endAddr), |
|
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4716 true, |
|
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4717 CardTableModRefBS::precleaned_card_val()); |
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4718 |
| 0 | 4719 assert(dirtyRegion.start() >= nextAddr, |
| 4720 "returned region inconsistent?"); | |
| 4721 } | |
| 4722 lastAddr = dirtyRegion.end(); | |
| 4723 numDirtyCards = | |
| 4724 dirtyRegion.word_size()/CardTableModRefBS::card_size_in_words; | |
| 4725 | |
| 4726 if (!dirtyRegion.is_empty()) { | |
| 4727 stopTimer(); | |
| 4728 CMSTokenSyncWithLocks ts(true, gen->freelistLock(), bitMapLock()); | |
| 4729 startTimer(); | |
| 4730 sample_eden(); | |
| 4731 verify_work_stacks_empty(); | |
| 4732 verify_overflow_empty(); | |
| 935 | 4733 DEBUG_ONLY(RememberKlassesChecker mx(CMSClassUnloadingEnabled);) |
| 0 | 4734 HeapWord* stop_point = |
| 4735 gen->cmsSpace()->object_iterate_careful_m(dirtyRegion, cl); | |
| 4736 if (stop_point != NULL) { | |
| 4737 // The careful iteration stopped early because it found an | |
| 4738 // uninitialized object. Redirty the bits corresponding to the | |
| 4739 // partially-scanned or unscanned cards, and start again at the | |
| 4740 // next block boundary. | |
| 4741 assert(CMSPermGenPrecleaningEnabled || | |
| 4742 (_collectorState == AbortablePreclean && should_abort_preclean()), | |
| 4743 "Unparsable objects should only be in perm gen."); | |
| 4744 _ct->ct_bs()->invalidate(MemRegion(stop_point, dirtyRegion.end())); | |
| 4745 if (should_abort_preclean()) { | |
| 4746 break; // out of preclean loop | |
| 4747 } else { | |
| 4748 // Compute the next address at which preclean should pick up. | |
| 4749 lastAddr = next_card_start_after_block(stop_point); | |
| 4750 } | |
| 4751 } | |
| 4752 } else { | |
| 4753 break; | |
| 4754 } | |
| 4755 } | |
| 4756 verify_work_stacks_empty(); | |
| 4757 verify_overflow_empty(); | |
| 4758 return cumNumDirtyCards; | |
| 4759 } | |
| 4760 | |
| 4761 void CMSCollector::checkpointRootsFinal(bool asynch, | |
| 4762 bool clear_all_soft_refs, bool init_mark_was_synchronous) { | |
| 4763 assert(_collectorState == FinalMarking, "incorrect state transition?"); | |
| 4764 check_correct_thread_executing(); | |
| 4765 // world is stopped at this checkpoint | |
| 4766 assert(SafepointSynchronize::is_at_safepoint(), | |
| 4767 "world should be stopped"); | |
| 4768 verify_work_stacks_empty(); | |
| 4769 verify_overflow_empty(); | |
| 4770 | |
| 4771 SpecializationStats::clear(); | |
| 4772 if (PrintGCDetails) { | |
| 4773 gclog_or_tty->print("[YG occupancy: "SIZE_FORMAT" K ("SIZE_FORMAT" K)]", | |
| 4774 _young_gen->used() / K, | |
| 4775 _young_gen->capacity() / K); | |
| 4776 } | |
| 4777 if (asynch) { | |
| 4778 if (CMSScavengeBeforeRemark) { | |
| 4779 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 4780 // Temporarily set flag to false, GCH->do_collection will | |
| 4781 // expect it to be false and set to true | |
| 4782 FlagSetting fl(gch->_is_gc_active, false); | |
| 4783 NOT_PRODUCT(TraceTime t("Scavenge-Before-Remark", | |
| 4784 PrintGCDetails && Verbose, true, gclog_or_tty);) | |
| 4785 int level = _cmsGen->level() - 1; | |
| 4786 if (level >= 0) { | |
| 4787 gch->do_collection(true, // full (i.e. force, see below) | |
| 4788 false, // !clear_all_soft_refs | |
| 4789 0, // size | |
| 4790 false, // is_tlab | |
| 4791 level // max_level | |
| 4792 ); | |
| 4793 } | |
| 4794 } | |
| 4795 FreelistLocker x(this); | |
| 4796 MutexLockerEx y(bitMapLock(), | |
| 4797 Mutex::_no_safepoint_check_flag); | |
| 4798 assert(!init_mark_was_synchronous, "but that's impossible!"); | |
| 4799 checkpointRootsFinalWork(asynch, clear_all_soft_refs, false); | |
| 4800 } else { | |
| 4801 // already have all the locks | |
| 4802 checkpointRootsFinalWork(asynch, clear_all_soft_refs, | |
| 4803 init_mark_was_synchronous); | |
| 4804 } | |
| 4805 verify_work_stacks_empty(); | |
| 4806 verify_overflow_empty(); | |
| 4807 SpecializationStats::print(); | |
| 4808 } | |
| 4809 | |
| 4810 void CMSCollector::checkpointRootsFinalWork(bool asynch, | |
| 4811 bool clear_all_soft_refs, bool init_mark_was_synchronous) { | |
| 4812 | |
| 4813 NOT_PRODUCT(TraceTime tr("checkpointRootsFinalWork", PrintGCDetails, false, gclog_or_tty);) | |
| 4814 | |
| 4815 assert(haveFreelistLocks(), "must have free list locks"); | |
| 4816 assert_lock_strong(bitMapLock()); | |
| 4817 | |
| 4818 if (UseAdaptiveSizePolicy) { | |
| 4819 size_policy()->checkpoint_roots_final_begin(); | |
| 4820 } | |
| 4821 | |
| 4822 ResourceMark rm; | |
| 4823 HandleMark hm; | |
| 4824 | |
| 4825 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 4826 | |
|
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4827 if (should_unload_classes()) { |
| 0 | 4828 CodeCache::gc_prologue(); |
| 4829 } | |
| 4830 assert(haveFreelistLocks(), "must have free list locks"); | |
| 4831 assert_lock_strong(bitMapLock()); | |
| 4832 | |
| 935 | 4833 DEBUG_ONLY(RememberKlassesChecker fmx(CMSClassUnloadingEnabled);) |
| 0 | 4834 if (!init_mark_was_synchronous) { |
| 4835 // We might assume that we need not fill TLAB's when | |
| 4836 // CMSScavengeBeforeRemark is set, because we may have just done | |
| 4837 // a scavenge which would have filled all TLAB's -- and besides | |
| 4838 // Eden would be empty. This however may not always be the case -- | |
| 4839 // for instance although we asked for a scavenge, it may not have | |
| 4840 // happened because of a JNI critical section. We probably need | |
| 4841 // a policy for deciding whether we can in that case wait until | |
| 4842 // the critical section releases and then do the remark following | |
| 4843 // the scavenge, and skip it here. In the absence of that policy, | |
| 4844 // or of an indication of whether the scavenge did indeed occur, | |
| 4845 // we cannot rely on TLAB's having been filled and must do | |
| 4846 // so here just in case a scavenge did not happen. | |
| 4847 gch->ensure_parsability(false); // fill TLAB's, but no need to retire them | |
| 4848 // Update the saved marks which may affect the root scans. | |
| 4849 gch->save_marks(); | |
| 4850 | |
| 4851 { | |
| 4852 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;) | |
| 4853 | |
| 4854 // Note on the role of the mod union table: | |
| 4855 // Since the marker in "markFromRoots" marks concurrently with | |
| 4856 // mutators, it is possible for some reachable objects not to have been | |
| 4857 // scanned. For instance, an only reference to an object A was | |
| 4858 // placed in object B after the marker scanned B. Unless B is rescanned, | |
| 4859 // A would be collected. Such updates to references in marked objects | |
| 4860 // are detected via the mod union table which is the set of all cards | |
| 4861 // dirtied since the first checkpoint in this GC cycle and prior to | |
| 4862 // the most recent young generation GC, minus those cleaned up by the | |
| 4863 // concurrent precleaning. | |
| 4864 if (CMSParallelRemarkEnabled && ParallelGCThreads > 0) { | |
| 4865 TraceTime t("Rescan (parallel) ", PrintGCDetails, false, gclog_or_tty); | |
| 4866 do_remark_parallel(); | |
| 4867 } else { | |
| 4868 TraceTime t("Rescan (non-parallel) ", PrintGCDetails, false, | |
| 4869 gclog_or_tty); | |
| 4870 do_remark_non_parallel(); | |
| 4871 } | |
| 4872 } | |
| 4873 } else { | |
| 4874 assert(!asynch, "Can't have init_mark_was_synchronous in asynch mode"); | |
| 4875 // The initial mark was stop-world, so there's no rescanning to | |
| 4876 // do; go straight on to the next step below. | |
| 4877 } | |
| 4878 verify_work_stacks_empty(); | |
| 4879 verify_overflow_empty(); | |
| 4880 | |
| 4881 { | |
| 4882 NOT_PRODUCT(TraceTime ts("refProcessingWork", PrintGCDetails, false, gclog_or_tty);) | |
| 4883 refProcessingWork(asynch, clear_all_soft_refs); | |
| 4884 } | |
| 4885 verify_work_stacks_empty(); | |
| 4886 verify_overflow_empty(); | |
| 4887 | |
|
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4888 if (should_unload_classes()) { |
| 0 | 4889 CodeCache::gc_epilogue(); |
| 4890 } | |
| 4891 | |
| 4892 // If we encountered any (marking stack / work queue) overflow | |
| 4893 // events during the current CMS cycle, take appropriate | |
| 4894 // remedial measures, where possible, so as to try and avoid | |
| 4895 // recurrence of that condition. | |
| 4896 assert(_markStack.isEmpty(), "No grey objects"); | |
| 4897 size_t ser_ovflw = _ser_pmc_remark_ovflw + _ser_pmc_preclean_ovflw + | |
|
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4898 _ser_kac_ovflw + _ser_kac_preclean_ovflw; |
| 0 | 4899 if (ser_ovflw > 0) { |
| 4900 if (PrintCMSStatistics != 0) { | |
| 4901 gclog_or_tty->print_cr("Marking stack overflow (benign) " | |
|
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4902 "(pmc_pc="SIZE_FORMAT", pmc_rm="SIZE_FORMAT", kac="SIZE_FORMAT |
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4903 ", kac_preclean="SIZE_FORMAT")", |
| 0 | 4904 _ser_pmc_preclean_ovflw, _ser_pmc_remark_ovflw, |
|
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4905 _ser_kac_ovflw, _ser_kac_preclean_ovflw); |
| 0 | 4906 } |
| 4907 _markStack.expand(); | |
| 4908 _ser_pmc_remark_ovflw = 0; | |
| 4909 _ser_pmc_preclean_ovflw = 0; | |
|
452
00b023ae2d78
6722113: CMS: Incorrect overflow handling during precleaning of Reference lists
ysr
parents:
360
diff
changeset
|
4910 _ser_kac_preclean_ovflw = 0; |
| 0 | 4911 _ser_kac_ovflw = 0; |
| 4912 } | |
| 4913 if (_par_pmc_remark_ovflw > 0 || _par_kac_ovflw > 0) { | |
| 4914 if (PrintCMSStatistics != 0) { | |
| 4915 gclog_or_tty->print_cr("Work queue overflow (benign) " | |
| 4916 "(pmc_rm="SIZE_FORMAT", kac="SIZE_FORMAT")", | |
| 4917 _par_pmc_remark_ovflw, _par_kac_ovflw); | |
| 4918 } | |
| 4919 _par_pmc_remark_ovflw = 0; | |
| 4920 _par_kac_ovflw = 0; | |
| 4921 } | |
| 4922 if (PrintCMSStatistics != 0) { | |
| 4923 if (_markStack._hit_limit > 0) { | |
| 4924 gclog_or_tty->print_cr(" (benign) Hit max stack size limit ("SIZE_FORMAT")", | |
| 4925 _markStack._hit_limit); | |
| 4926 } | |
| 4927 if (_markStack._failed_double > 0) { | |
| 4928 gclog_or_tty->print_cr(" (benign) Failed stack doubling ("SIZE_FORMAT")," | |
| 4929 " current capacity "SIZE_FORMAT, | |
| 4930 _markStack._failed_double, | |
| 4931 _markStack.capacity()); | |
| 4932 } | |
| 4933 } | |
| 4934 _markStack._hit_limit = 0; | |
| 4935 _markStack._failed_double = 0; | |
| 4936 | |
| 935 | 4937 // Check that all the klasses have been checked |
| 4938 assert(_revisitStack.isEmpty(), "Not all klasses revisited"); | |
| 4939 | |
| 0 | 4940 if ((VerifyAfterGC || VerifyDuringGC) && |
| 4941 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
| 4942 verify_after_remark(); | |
| 4943 } | |
| 4944 | |
| 4945 // Change under the freelistLocks. | |
| 4946 _collectorState = Sweeping; | |
| 4947 // Call isAllClear() under bitMapLock | |
| 4948 assert(_modUnionTable.isAllClear(), "Should be clear by end of the" | |
| 4949 " final marking"); | |
| 4950 if (UseAdaptiveSizePolicy) { | |
| 4951 size_policy()->checkpoint_roots_final_end(gch->gc_cause()); | |
| 4952 } | |
| 4953 } | |
| 4954 | |
| 4955 // Parallel remark task | |
| 4956 class CMSParRemarkTask: public AbstractGangTask { | |
| 4957 CMSCollector* _collector; | |
| 4958 WorkGang* _workers; | |
| 4959 int _n_workers; | |
| 4960 CompactibleFreeListSpace* _cms_space; | |
| 4961 CompactibleFreeListSpace* _perm_space; | |
| 4962 | |
| 4963 // The per-thread work queues, available here for stealing. | |
| 4964 OopTaskQueueSet* _task_queues; | |
| 4965 ParallelTaskTerminator _term; | |
| 4966 | |
| 4967 public: | |
| 4968 CMSParRemarkTask(CMSCollector* collector, | |
| 4969 CompactibleFreeListSpace* cms_space, | |
| 4970 CompactibleFreeListSpace* perm_space, | |
| 4971 int n_workers, WorkGang* workers, | |
| 4972 OopTaskQueueSet* task_queues): | |
| 4973 AbstractGangTask("Rescan roots and grey objects in parallel"), | |
| 4974 _collector(collector), | |
| 4975 _cms_space(cms_space), _perm_space(perm_space), | |
| 4976 _n_workers(n_workers), | |
| 4977 _workers(workers), | |
| 4978 _task_queues(task_queues), | |
| 4979 _term(workers->total_workers(), task_queues) { } | |
| 4980 | |
| 4981 OopTaskQueueSet* task_queues() { return _task_queues; } | |
| 4982 | |
| 4983 OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); } | |
| 4984 | |
| 4985 ParallelTaskTerminator* terminator() { return &_term; } | |
| 4986 | |
| 4987 void work(int i); | |
| 4988 | |
| 4989 private: | |
| 4990 // Work method in support of parallel rescan ... of young gen spaces | |
| 4991 void do_young_space_rescan(int i, Par_MarkRefsIntoAndScanClosure* cl, | |
| 4992 ContiguousSpace* space, | |
| 4993 HeapWord** chunk_array, size_t chunk_top); | |
| 4994 | |
| 4995 // ... of dirty cards in old space | |
| 4996 void do_dirty_card_rescan_tasks(CompactibleFreeListSpace* sp, int i, | |
| 4997 Par_MarkRefsIntoAndScanClosure* cl); | |
| 4998 | |
| 4999 // ... work stealing for the above | |
| 5000 void do_work_steal(int i, Par_MarkRefsIntoAndScanClosure* cl, int* seed); | |
| 5001 }; | |
| 5002 | |
| 5003 void CMSParRemarkTask::work(int i) { | |
| 5004 elapsedTimer _timer; | |
| 5005 ResourceMark rm; | |
| 5006 HandleMark hm; | |
| 5007 | |
| 5008 // ---------- rescan from roots -------------- | |
| 5009 _timer.start(); | |
| 5010 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 5011 Par_MarkRefsIntoAndScanClosure par_mrias_cl(_collector, | |
| 5012 _collector->_span, _collector->ref_processor(), | |
| 5013 &(_collector->_markBitMap), | |
| 5014 work_queue(i), &(_collector->_revisitStack)); | |
| 5015 | |
| 5016 // Rescan young gen roots first since these are likely | |
| 5017 // coarsely partitioned and may, on that account, constitute | |
| 5018 // the critical path; thus, it's best to start off that | |
| 5019 // work first. | |
| 5020 // ---------- young gen roots -------------- | |
| 5021 { | |
| 5022 DefNewGeneration* dng = _collector->_young_gen->as_DefNewGeneration(); | |
| 5023 EdenSpace* eden_space = dng->eden(); | |
| 5024 ContiguousSpace* from_space = dng->from(); | |
| 5025 ContiguousSpace* to_space = dng->to(); | |
| 5026 | |
| 5027 HeapWord** eca = _collector->_eden_chunk_array; | |
| 5028 size_t ect = _collector->_eden_chunk_index; | |
| 5029 HeapWord** sca = _collector->_survivor_chunk_array; | |
| 5030 size_t sct = _collector->_survivor_chunk_index; | |
| 5031 | |
| 5032 assert(ect <= _collector->_eden_chunk_capacity, "out of bounds"); | |
| 5033 assert(sct <= _collector->_survivor_chunk_capacity, "out of bounds"); | |
| 5034 | |
| 5035 do_young_space_rescan(i, &par_mrias_cl, to_space, NULL, 0); | |
| 5036 do_young_space_rescan(i, &par_mrias_cl, from_space, sca, sct); | |
| 5037 do_young_space_rescan(i, &par_mrias_cl, eden_space, eca, ect); | |
| 5038 | |
| 5039 _timer.stop(); | |
| 5040 if (PrintCMSStatistics != 0) { | |
| 5041 gclog_or_tty->print_cr( | |
| 5042 "Finished young gen rescan work in %dth thread: %3.3f sec", | |
| 5043 i, _timer.seconds()); | |
| 5044 } | |
| 5045 } | |
| 5046 | |
| 5047 // ---------- remaining roots -------------- | |
| 5048 _timer.reset(); | |
| 5049 _timer.start(); | |
| 5050 gch->gen_process_strong_roots(_collector->_cmsGen->level(), | |
| 5051 false, // yg was scanned above | |
|
989
148e5441d916
6863023: need non-perm oops in code cache for JSR 292
jrose
parents:
798
diff
changeset
|
5052 false, // this is parallel code |
| 0 | 5053 true, // collecting perm gen |
| 5054 SharedHeap::ScanningOption(_collector->CMSCollector::roots_scanning_options()), | |
|
989
148e5441d916
6863023: need non-perm oops in code cache for JSR 292
jrose
parents:
798
diff
changeset
|
5055 &par_mrias_cl, |
|
148e5441d916
6863023: need non-perm oops in code cache for JSR 292
jrose
parents:
798
diff
changeset
|
5056 true, // walk all of code cache if (so & SO_CodeCache) |
|
148e5441d916
6863023: need non-perm oops in code cache for JSR 292
jrose
parents:
798
diff
changeset
|
5057 NULL); |
|
148e5441d916
6863023: need non-perm oops in code cache for JSR 292
jrose
parents:
798
diff
changeset
|
5058 assert(_collector->should_unload_classes() |
|
148e5441d916
6863023: need non-perm oops in code cache for JSR 292
jrose
parents:
798
diff
changeset
|
5059 || (_collector->CMSCollector::roots_scanning_options() & SharedHeap::SO_CodeCache), |
|
148e5441d916
6863023: need non-perm oops in code cache for JSR 292
jrose
parents:
798
diff
changeset
|
5060 "if we didn't scan the code cache, we have to be ready to drop nmethods with expired weak oops"); |
| 0 | 5061 _timer.stop(); |
| 5062 if (PrintCMSStatistics != 0) { | |
| 5063 gclog_or_tty->print_cr( | |
| 5064 "Finished remaining root rescan work in %dth thread: %3.3f sec", | |
| 5065 i, _timer.seconds()); | |
| 5066 } | |
| 5067 | |
| 5068 // ---------- rescan dirty cards ------------ | |
| 5069 _timer.reset(); | |
| 5070 _timer.start(); | |
| 5071 | |
| 5072 // Do the rescan tasks for each of the two spaces | |
| 5073 // (cms_space and perm_space) in turn. | |
| 5074 do_dirty_card_rescan_tasks(_cms_space, i, &par_mrias_cl); | |
| 5075 do_dirty_card_rescan_tasks(_perm_space, i, &par_mrias_cl); | |
| 5076 _timer.stop(); | |
| 5077 if (PrintCMSStatistics != 0) { | |
| 5078 gclog_or_tty->print_cr( | |
| 5079 "Finished dirty card rescan work in %dth thread: %3.3f sec", | |
| 5080 i, _timer.seconds()); | |
| 5081 } | |
| 5082 | |
| 5083 // ---------- steal work from other threads ... | |
| 5084 // ---------- ... and drain overflow list. | |
| 5085 _timer.reset(); | |
| 5086 _timer.start(); | |
| 5087 do_work_steal(i, &par_mrias_cl, _collector->hash_seed(i)); | |
| 5088 _timer.stop(); | |
| 5089 if (PrintCMSStatistics != 0) { | |
| 5090 gclog_or_tty->print_cr( | |
| 5091 "Finished work stealing in %dth thread: %3.3f sec", | |
| 5092 i, _timer.seconds()); | |
| 5093 } | |
| 5094 } | |
| 5095 | |
| 5096 void | |
| 5097 CMSParRemarkTask::do_young_space_rescan(int i, | |
| 5098 Par_MarkRefsIntoAndScanClosure* cl, ContiguousSpace* space, | |
| 5099 HeapWord** chunk_array, size_t chunk_top) { | |
| 5100 // Until all tasks completed: | |
| 5101 // . claim an unclaimed task | |
| 5102 // . compute region boundaries corresponding to task claimed | |
| 5103 // using chunk_array | |
| 5104 // . par_oop_iterate(cl) over that region | |
| 5105 | |
| 5106 ResourceMark rm; | |
| 5107 HandleMark hm; | |
| 5108 | |
| 5109 SequentialSubTasksDone* pst = space->par_seq_tasks(); | |
| 5110 assert(pst->valid(), "Uninitialized use?"); | |
| 5111 | |
| 5112 int nth_task = 0; | |
| 5113 int n_tasks = pst->n_tasks(); | |
| 5114 | |
| 5115 HeapWord *start, *end; | |
| 5116 while (!pst->is_task_claimed(/* reference */ nth_task)) { | |
| 5117 // We claimed task # nth_task; compute its boundaries. | |
| 5118 if (chunk_top == 0) { // no samples were taken | |
| 5119 assert(nth_task == 0 && n_tasks == 1, "Can have only 1 EdenSpace task"); | |
| 5120 start = space->bottom(); | |
| 5121 end = space->top(); | |
| 5122 } else if (nth_task == 0) { | |
| 5123 start = space->bottom(); | |
| 5124 end = chunk_array[nth_task]; | |
| 5125 } else if (nth_task < (jint)chunk_top) { | |
| 5126 assert(nth_task >= 1, "Control point invariant"); | |
| 5127 start = chunk_array[nth_task - 1]; | |
| 5128 end = chunk_array[nth_task]; | |
| 5129 } else { | |
| 5130 assert(nth_task == (jint)chunk_top, "Control point invariant"); | |
| 5131 start = chunk_array[chunk_top - 1]; | |
| 5132 end = space->top(); | |
| 5133 } | |
| 5134 MemRegion mr(start, end); | |
| 5135 // Verify that mr is in space | |
| 5136 assert(mr.is_empty() || space->used_region().contains(mr), | |
| 5137 "Should be in space"); | |
| 5138 // Verify that "start" is an object boundary | |
| 5139 assert(mr.is_empty() || oop(mr.start())->is_oop(), | |
| 5140 "Should be an oop"); | |
| 5141 space->par_oop_iterate(mr, cl); | |
| 5142 } | |
| 5143 pst->all_tasks_completed(); | |
| 5144 } | |
| 5145 | |
| 5146 void | |
| 5147 CMSParRemarkTask::do_dirty_card_rescan_tasks( | |
| 5148 CompactibleFreeListSpace* sp, int i, | |
| 5149 Par_MarkRefsIntoAndScanClosure* cl) { | |
| 5150 // Until all tasks completed: | |
| 5151 // . claim an unclaimed task | |
| 5152 // . compute region boundaries corresponding to task claimed | |
| 5153 // . transfer dirty bits ct->mut for that region | |
| 5154 // . apply rescanclosure to dirty mut bits for that region | |
| 5155 | |
| 5156 ResourceMark rm; | |
| 5157 HandleMark hm; | |
| 5158 | |
| 5159 OopTaskQueue* work_q = work_queue(i); | |
| 5160 ModUnionClosure modUnionClosure(&(_collector->_modUnionTable)); | |
| 5161 // CAUTION! CAUTION! CAUTION! CAUTION! CAUTION! CAUTION! CAUTION! | |
| 5162 // CAUTION: This closure has state that persists across calls to | |
| 5163 // the work method dirty_range_iterate_clear() in that it has | |
| 5164 // imbedded in it a (subtype of) UpwardsObjectClosure. The | |
| 5165 // use of that state in the imbedded UpwardsObjectClosure instance | |
| 5166 // assumes that the cards are always iterated (even if in parallel | |
| 5167 // by several threads) in monotonically increasing order per each | |
| 5168 // thread. This is true of the implementation below which picks | |
| 5169 // card ranges (chunks) in monotonically increasing order globally | |
| 5170 // and, a-fortiori, in monotonically increasing order per thread | |
| 5171 // (the latter order being a subsequence of the former). | |
| 5172 // If the work code below is ever reorganized into a more chaotic | |
| 5173 // work-partitioning form than the current "sequential tasks" | |
| 5174 // paradigm, the use of that persistent state will have to be | |
| 5175 // revisited and modified appropriately. See also related | |
| 5176 // bug 4756801 work on which should examine this code to make | |
| 5177 // sure that the changes there do not run counter to the | |
| 5178 // assumptions made here and necessary for correctness and | |
| 5179 // efficiency. Note also that this code might yield inefficient | |
| 5180 // behaviour in the case of very large objects that span one or | |
| 5181 // more work chunks. Such objects would potentially be scanned | |
| 5182 // several times redundantly. Work on 4756801 should try and | |
| 5183 // address that performance anomaly if at all possible. XXX | |
| 5184 MemRegion full_span = _collector->_span; | |
| 5185 CMSBitMap* bm = &(_collector->_markBitMap); // shared | |
| 5186 CMSMarkStack* rs = &(_collector->_revisitStack); // shared | |
| 5187 MarkFromDirtyCardsClosure | |
| 5188 greyRescanClosure(_collector, full_span, // entire span of interest | |
| 5189 sp, bm, work_q, rs, cl); | |
| 5190 | |
| 5191 SequentialSubTasksDone* pst = sp->conc_par_seq_tasks(); | |
| 5192 assert(pst->valid(), "Uninitialized use?"); | |
| 5193 int nth_task = 0; | |
| 5194 const int alignment = CardTableModRefBS::card_size * BitsPerWord; | |
| 5195 MemRegion span = sp->used_region(); | |
| 5196 HeapWord* start_addr = span.start(); | |
| 5197 HeapWord* end_addr = (HeapWord*)round_to((intptr_t)span.end(), | |
| 5198 alignment); | |
| 5199 const size_t chunk_size = sp->rescan_task_size(); // in HeapWord units | |
| 5200 assert((HeapWord*)round_to((intptr_t)start_addr, alignment) == | |
| 5201 start_addr, "Check alignment"); | |
| 5202 assert((size_t)round_to((intptr_t)chunk_size, alignment) == | |
| 5203 chunk_size, "Check alignment"); | |
| 5204 | |
| 5205 while (!pst->is_task_claimed(/* reference */ nth_task)) { | |
| 5206 // Having claimed the nth_task, compute corresponding mem-region, | |
| 5207 // which is a-fortiori aligned correctly (i.e. at a MUT bopundary). | |
| 5208 // The alignment restriction ensures that we do not need any | |
| 5209 // synchronization with other gang-workers while setting or | |
| 5210 // clearing bits in thus chunk of the MUT. | |
| 5211 MemRegion this_span = MemRegion(start_addr + nth_task*chunk_size, | |
| 5212 start_addr + (nth_task+1)*chunk_size); | |
| 5213 // The last chunk's end might be way beyond end of the | |
| 5214 // used region. In that case pull back appropriately. | |
| 5215 if (this_span.end() > end_addr) { | |
| 5216 this_span.set_end(end_addr); | |
| 5217 assert(!this_span.is_empty(), "Program logic (calculation of n_tasks)"); | |
| 5218 } | |
| 5219 // Iterate over the dirty cards covering this chunk, marking them | |
| 5220 // precleaned, and setting the corresponding bits in the mod union | |
| 5221 // table. Since we have been careful to partition at Card and MUT-word | |
| 5222 // boundaries no synchronization is needed between parallel threads. | |
| 5223 _collector->_ct->ct_bs()->dirty_card_iterate(this_span, | |
| 5224 &modUnionClosure); | |
| 5225 | |
| 5226 // Having transferred these marks into the modUnionTable, | |
| 5227 // rescan the marked objects on the dirty cards in the modUnionTable. | |
| 5228 // Even if this is at a synchronous collection, the initial marking | |
| 5229 // may have been done during an asynchronous collection so there | |
| 5230 // may be dirty bits in the mod-union table. | |
| 5231 _collector->_modUnionTable.dirty_range_iterate_clear( | |
| 5232 this_span, &greyRescanClosure); | |
| 5233 _collector->_modUnionTable.verifyNoOneBitsInRange( | |
| 5234 this_span.start(), | |
| 5235 this_span.end()); | |
| 5236 } | |
| 5237 pst->all_tasks_completed(); // declare that i am done | |
| 5238 } | |
| 5239 | |
| 5240 // . see if we can share work_queues with ParNew? XXX | |
| 5241 void | |
| 5242 CMSParRemarkTask::do_work_steal(int i, Par_MarkRefsIntoAndScanClosure* cl, | |
| 5243 int* seed) { | |
| 5244 OopTaskQueue* work_q = work_queue(i); | |
| 5245 NOT_PRODUCT(int num_steals = 0;) | |
| 5246 oop obj_to_scan; | |
| 5247 CMSBitMap* bm = &(_collector->_markBitMap); | |
| 5248 | |
| 5249 while (true) { | |
| 5250 // Completely finish any left over work from (an) earlier round(s) | |
| 5251 cl->trim_queue(0); | |
|
679
cea947c8a988
6819891: ParNew: Fix work queue overflow code to deal correctly with +UseCompressedOops
ysr
parents:
628
diff
changeset
|
5252 size_t num_from_overflow_list = MIN2((size_t)(work_q->max_elems() - work_q->size())/4, |
|
cea947c8a988
6819891: ParNew: Fix work queue overflow code to deal correctly with +UseCompressedOops
ysr
parents:
628
diff
changeset
|
5253 (size_t)ParGCDesiredObjsFromOverflowList); |
| 0 | 5254 // Now check if there's any work in the overflow list |
| 5255 if (_collector->par_take_from_overflow_list(num_from_overflow_list, | |
| 5256 work_q)) { | |
| 5257 // found something in global overflow list; | |
| 5258 // not yet ready to go stealing work from others. | |
| 5259 // We'd like to assert(work_q->size() != 0, ...) | |
| 5260 // because we just took work from the overflow list, | |
| 5261 // but of course we can't since all of that could have | |
| 5262 // been already stolen from us. | |
| 5263 // "He giveth and He taketh away." | |
| 5264 continue; | |
| 5265 } | |
| 5266 // Verify that we have no work before we resort to stealing | |
| 5267 assert(work_q->size() == 0, "Have work, shouldn't steal"); | |
| 5268 // Try to steal from other queues that have work | |
| 5269 if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) { | |
| 5270 NOT_PRODUCT(num_steals++;) | |
| 5271 assert(obj_to_scan->is_oop(), "Oops, not an oop!"); | |
| 5272 assert(bm->isMarked((HeapWord*)obj_to_scan), "Stole an unmarked oop?"); | |
| 5273 // Do scanning work | |
| 5274 obj_to_scan->oop_iterate(cl); | |
| 5275 // Loop around, finish this work, and try to steal some more | |
| 5276 } else if (terminator()->offer_termination()) { | |
| 5277 break; // nirvana from the infinite cycle | |
| 5278 } | |
| 5279 } | |
| 5280 NOT_PRODUCT( | |
| 5281 if (PrintCMSStatistics != 0) { | |
| 5282 gclog_or_tty->print("\n\t(%d: stole %d oops)", i, num_steals); | |
| 5283 } | |
| 5284 ) | |
| 5285 assert(work_q->size() == 0 && _collector->overflow_list_is_empty(), | |
| 5286 "Else our work is not yet done"); | |
| 5287 } | |
| 5288 | |
| 5289 // Return a thread-local PLAB recording array, as appropriate. | |
| 5290 void* CMSCollector::get_data_recorder(int thr_num) { | |
| 5291 if (_survivor_plab_array != NULL && | |
| 5292 (CMSPLABRecordAlways || | |
| 5293 (_collectorState > Marking && _collectorState < FinalMarking))) { | |
| 5294 assert(thr_num < (int)ParallelGCThreads, "thr_num is out of bounds"); | |
| 5295 ChunkArray* ca = &_survivor_plab_array[thr_num]; | |
| 5296 ca->reset(); // clear it so that fresh data is recorded | |
| 5297 return (void*) ca; | |
| 5298 } else { | |
| 5299 return NULL; | |
| 5300 } | |
| 5301 } | |
| 5302 | |
| 5303 // Reset all the thread-local PLAB recording arrays | |
| 5304 void CMSCollector::reset_survivor_plab_arrays() { | |
| 5305 for (uint i = 0; i < ParallelGCThreads; i++) { | |
| 5306 _survivor_plab_array[i].reset(); | |
| 5307 } | |
| 5308 } | |
| 5309 | |
| 5310 // Merge the per-thread plab arrays into the global survivor chunk | |
| 5311 // array which will provide the partitioning of the survivor space | |
| 5312 // for CMS rescan. | |
| 5313 void CMSCollector::merge_survivor_plab_arrays(ContiguousSpace* surv) { | |
| 5314 assert(_survivor_plab_array != NULL, "Error"); | |
| 5315 assert(_survivor_chunk_array != NULL, "Error"); | |
| 5316 assert(_collectorState == FinalMarking, "Error"); | |
| 5317 for (uint j = 0; j < ParallelGCThreads; j++) { | |
| 5318 _cursor[j] = 0; | |
| 5319 } | |
| 5320 HeapWord* top = surv->top(); | |
| 5321 size_t i; | |
| 5322 for (i = 0; i < _survivor_chunk_capacity; i++) { // all sca entries | |
| 5323 HeapWord* min_val = top; // Higher than any PLAB address | |
| 5324 uint min_tid = 0; // position of min_val this round | |
| 5325 for (uint j = 0; j < ParallelGCThreads; j++) { | |
| 5326 ChunkArray* cur_sca = &_survivor_plab_array[j]; | |
| 5327 if (_cursor[j] == cur_sca->end()) { | |
| 5328 continue; | |
| 5329 } | |
| 5330 assert(_cursor[j] < cur_sca->end(), "ctl pt invariant"); | |
| 5331 HeapWord* cur_val = cur_sca->nth(_cursor[j]); | |
| 5332 assert(surv->used_region().contains(cur_val), "Out of bounds value"); | |
| 5333 if (cur_val < min_val) { | |
| 5334 min_tid = j; | |
| 5335 min_val = cur_val; | |
| 5336 } else { | |
| 5337 assert(cur_val < top, "All recorded addresses should be less"); | |
| 5338 } | |
| 5339 } | |
| 5340 // At this point min_val and min_tid are respectively | |
| 5341 // the least address in _survivor_plab_array[j]->nth(_cursor[j]) | |
| 5342 // and the thread (j) that witnesses that address. | |
| 5343 // We record this address in the _survivor_chunk_array[i] | |
| 5344 // and increment _cursor[min_tid] prior to the next round i. | |
| 5345 if (min_val == top) { | |
| 5346 break; | |
| 5347 } | |
| 5348 _survivor_chunk_array[i] = min_val; | |
| 5349 _cursor[min_tid]++; | |
| 5350 } | |
| 5351 // We are all done; record the size of the _survivor_chunk_array | |
| 5352 _survivor_chunk_index = i; // exclusive: [0, i) | |
| 5353 if (PrintCMSStatistics > 0) { | |
| 5354 gclog_or_tty->print(" (Survivor:" SIZE_FORMAT "chunks) ", i); | |
| 5355 } | |
| 5356 // Verify that we used up all the recorded entries | |
| 5357 #ifdef ASSERT | |
| 5358 size_t total = 0; | |
| 5359 for (uint j = 0; j < ParallelGCThreads; j++) { | |
| 5360 assert(_cursor[j] == _survivor_plab_array[j].end(), "Ctl pt invariant"); | |
| 5361 total += _cursor[j]; | |
| 5362 } | |
| 5363 assert(total == _survivor_chunk_index, "Ctl Pt Invariant"); | |
| 5364 // Check that the merged array is in sorted order | |
| 5365 if (total > 0) { | |
| 5366 for (size_t i = 0; i < total - 1; i++) { | |
| 5367 if (PrintCMSStatistics > 0) { | |
| 5368 gclog_or_tty->print(" (chunk" SIZE_FORMAT ":" INTPTR_FORMAT ") ", | |
| 5369 i, _survivor_chunk_array[i]); | |
| 5370 } | |
| 5371 assert(_survivor_chunk_array[i] < _survivor_chunk_array[i+1], | |
| 5372 "Not sorted"); | |
| 5373 } | |
| 5374 } | |
| 5375 #endif // ASSERT | |
| 5376 } | |
| 5377 | |
| 5378 // Set up the space's par_seq_tasks structure for work claiming | |
| 5379 // for parallel rescan of young gen. | |
| 5380 // See ParRescanTask where this is currently used. | |
| 5381 void | |
| 5382 CMSCollector:: | |
| 5383 initialize_sequential_subtasks_for_young_gen_rescan(int n_threads) { | |
| 5384 assert(n_threads > 0, "Unexpected n_threads argument"); | |
| 5385 DefNewGeneration* dng = (DefNewGeneration*)_young_gen; | |
| 5386 | |
| 5387 // Eden space | |
| 5388 { | |
| 5389 SequentialSubTasksDone* pst = dng->eden()->par_seq_tasks(); | |
| 5390 assert(!pst->valid(), "Clobbering existing data?"); | |
| 5391 // Each valid entry in [0, _eden_chunk_index) represents a task. | |
| 5392 size_t n_tasks = _eden_chunk_index + 1; | |
| 5393 assert(n_tasks == 1 || _eden_chunk_array != NULL, "Error"); | |
| 5394 pst->set_par_threads(n_threads); | |
| 5395 pst->set_n_tasks((int)n_tasks); | |
| 5396 } | |
| 5397 | |
| 5398 // Merge the survivor plab arrays into _survivor_chunk_array | |
| 5399 if (_survivor_plab_array != NULL) { | |
| 5400 merge_survivor_plab_arrays(dng->from()); | |
| 5401 } else { | |
| 5402 assert(_survivor_chunk_index == 0, "Error"); | |
| 5403 } | |
| 5404 | |
| 5405 // To space | |
| 5406 { | |
| 5407 SequentialSubTasksDone* pst = dng->to()->par_seq_tasks(); | |
| 5408 assert(!pst->valid(), "Clobbering existing data?"); | |
| 5409 pst->set_par_threads(n_threads); | |
| 5410 pst->set_n_tasks(1); | |
| 5411 assert(pst->valid(), "Error"); | |
| 5412 } | |
| 5413 | |
| 5414 // From space | |
| 5415 { | |
| 5416 SequentialSubTasksDone* pst = dng->from()->par_seq_tasks(); | |
| 5417 assert(!pst->valid(), "Clobbering existing data?"); | |
| 5418 size_t n_tasks = _survivor_chunk_index + 1; | |
| 5419 assert(n_tasks == 1 || _survivor_chunk_array != NULL, "Error"); | |
| 5420 pst->set_par_threads(n_threads); | |
| 5421 pst->set_n_tasks((int)n_tasks); | |
| 5422 assert(pst->valid(), "Error"); | |
| 5423 } | |
| 5424 } | |
| 5425 | |
| 5426 // Parallel version of remark | |
| 5427 void CMSCollector::do_remark_parallel() { | |
| 5428 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 5429 WorkGang* workers = gch->workers(); | |
| 5430 assert(workers != NULL, "Need parallel worker threads."); | |
| 5431 int n_workers = workers->total_workers(); | |
| 5432 CompactibleFreeListSpace* cms_space = _cmsGen->cmsSpace(); | |
| 5433 CompactibleFreeListSpace* perm_space = _permGen->cmsSpace(); | |
| 5434 | |
| 5435 CMSParRemarkTask tsk(this, | |
| 5436 cms_space, perm_space, | |
| 5437 n_workers, workers, task_queues()); | |
| 5438 | |
| 5439 // Set up for parallel process_strong_roots work. | |
| 5440 gch->set_par_threads(n_workers); | |
| 5441 // We won't be iterating over the cards in the card table updating | |
| 5442 // the younger_gen cards, so we shouldn't call the following else | |
| 5443 // the verification code as well as subsequent younger_refs_iterate | |
| 5444 // code would get confused. XXX | |
| 5445 // gch->rem_set()->prepare_for_younger_refs_iterate(true); // parallel | |
| 5446 | |
| 5447 // The young gen rescan work will not be done as part of | |
| 5448 // process_strong_roots (which currently doesn't knw how to | |
| 5449 // parallelize such a scan), but rather will be broken up into | |
| 5450 // a set of parallel tasks (via the sampling that the [abortable] | |
| 5451 // preclean phase did of EdenSpace, plus the [two] tasks of | |
| 5452 // scanning the [two] survivor spaces. Further fine-grain | |
| 5453 // parallelization of the scanning of the survivor spaces | |
| 5454 // themselves, and of precleaning of the younger gen itself | |
| 5455 // is deferred to the future. | |
| 5456 initialize_sequential_subtasks_for_young_gen_rescan(n_workers); | |
| 5457 | |
| 5458 // The dirty card rescan work is broken up into a "sequence" | |
| 5459 // of parallel tasks (per constituent space) that are dynamically | |
| 5460 // claimed by the parallel threads. | |
| 5461 cms_space->initialize_sequential_subtasks_for_rescan(n_workers); | |
| 5462 perm_space->initialize_sequential_subtasks_for_rescan(n_workers); | |
| 5463 | |
| 5464 // It turns out that even when we're using 1 thread, doing the work in a | |
| 5465 // separate thread causes wide variance in run times. We can't help this | |
| 5466 // in the multi-threaded case, but we special-case n=1 here to get | |
| 5467 // repeatable measurements of the 1-thread overhead of the parallel code. | |
| 5468 if (n_workers > 1) { | |
| 5469 // Make refs discovery MT-safe | |
| 5470 ReferenceProcessorMTMutator mt(ref_processor(), true); | |
|
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5471 GenCollectedHeap::StrongRootsScope srs(gch); |
| 0 | 5472 workers->run_task(&tsk); |
| 5473 } else { | |
|
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5474 GenCollectedHeap::StrongRootsScope srs(gch); |
| 0 | 5475 tsk.work(0); |
| 5476 } | |
| 5477 gch->set_par_threads(0); // 0 ==> non-parallel. | |
| 5478 // restore, single-threaded for now, any preserved marks | |
| 5479 // as a result of work_q overflow | |
| 5480 restore_preserved_marks_if_any(); | |
| 5481 } | |
| 5482 | |
| 5483 // Non-parallel version of remark | |
| 5484 void CMSCollector::do_remark_non_parallel() { | |
| 5485 ResourceMark rm; | |
| 5486 HandleMark hm; | |
| 5487 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 5488 MarkRefsIntoAndScanClosure | |
| 5489 mrias_cl(_span, ref_processor(), &_markBitMap, &_modUnionTable, | |
| 5490 &_markStack, &_revisitStack, this, | |
| 5491 false /* should_yield */, false /* not precleaning */); | |
| 5492 MarkFromDirtyCardsClosure | |
| 5493 markFromDirtyCardsClosure(this, _span, | |
| 5494 NULL, // space is set further below | |
| 5495 &_markBitMap, &_markStack, &_revisitStack, | |
| 5496 &mrias_cl); | |
| 5497 { | |
| 5498 TraceTime t("grey object rescan", PrintGCDetails, false, gclog_or_tty); | |
|
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5499 // Iterate over the dirty cards, setting the corresponding bits in the |
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5500 // mod union table. |
| 0 | 5501 { |
| 5502 ModUnionClosure modUnionClosure(&_modUnionTable); | |
| 5503 _ct->ct_bs()->dirty_card_iterate( | |
| 5504 _cmsGen->used_region(), | |
| 5505 &modUnionClosure); | |
| 5506 _ct->ct_bs()->dirty_card_iterate( | |
| 5507 _permGen->used_region(), | |
| 5508 &modUnionClosure); | |
| 5509 } | |
| 5510 // Having transferred these marks into the modUnionTable, we just need | |
| 5511 // to rescan the marked objects on the dirty cards in the modUnionTable. | |
| 5512 // The initial marking may have been done during an asynchronous | |
| 5513 // collection so there may be dirty bits in the mod-union table. | |
| 5514 const int alignment = | |
| 5515 CardTableModRefBS::card_size * BitsPerWord; | |
| 5516 { | |
| 5517 // ... First handle dirty cards in CMS gen | |
| 5518 markFromDirtyCardsClosure.set_space(_cmsGen->cmsSpace()); | |
| 5519 MemRegion ur = _cmsGen->used_region(); | |
| 5520 HeapWord* lb = ur.start(); | |
| 5521 HeapWord* ub = (HeapWord*)round_to((intptr_t)ur.end(), alignment); | |
| 5522 MemRegion cms_span(lb, ub); | |
| 5523 _modUnionTable.dirty_range_iterate_clear(cms_span, | |
| 5524 &markFromDirtyCardsClosure); | |
| 5525 verify_work_stacks_empty(); | |
| 5526 if (PrintCMSStatistics != 0) { | |
| 5527 gclog_or_tty->print(" (re-scanned "SIZE_FORMAT" dirty cards in cms gen) ", | |
| 5528 markFromDirtyCardsClosure.num_dirty_cards()); | |
| 5529 } | |
| 5530 } | |
| 5531 { | |
| 5532 // .. and then repeat for dirty cards in perm gen | |
| 5533 markFromDirtyCardsClosure.set_space(_permGen->cmsSpace()); | |
| 5534 MemRegion ur = _permGen->used_region(); | |
| 5535 HeapWord* lb = ur.start(); | |
| 5536 HeapWord* ub = (HeapWord*)round_to((intptr_t)ur.end(), alignment); | |
| 5537 MemRegion perm_span(lb, ub); | |
| 5538 _modUnionTable.dirty_range_iterate_clear(perm_span, | |
| 5539 &markFromDirtyCardsClosure); | |
| 5540 verify_work_stacks_empty(); | |
| 5541 if (PrintCMSStatistics != 0) { | |
| 5542 gclog_or_tty->print(" (re-scanned "SIZE_FORMAT" dirty cards in perm gen) ", | |
| 5543 markFromDirtyCardsClosure.num_dirty_cards()); | |
| 5544 } | |
| 5545 } | |
| 5546 } | |
| 5547 if (VerifyDuringGC && | |
| 5548 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
| 5549 HandleMark hm; // Discard invalid handles created during verification | |
| 5550 Universe::verify(true); | |
| 5551 } | |
| 5552 { | |
| 5553 TraceTime t("root rescan", PrintGCDetails, false, gclog_or_tty); | |
| 5554 | |
| 5555 verify_work_stacks_empty(); | |
| 5556 | |
| 5557 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. | |
|
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5558 GenCollectedHeap::StrongRootsScope srs(gch); |
| 0 | 5559 gch->gen_process_strong_roots(_cmsGen->level(), |
| 5560 true, // younger gens as roots | |
|
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5561 false, // use the local StrongRootsScope |
| 0 | 5562 true, // collecting perm gen |
| 5563 SharedHeap::ScanningOption(roots_scanning_options()), | |
|
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5564 &mrias_cl, |
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5565 true, // walk code active on stacks |
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5566 NULL); |
|
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5567 assert(should_unload_classes() |
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5568 || (roots_scanning_options() & SharedHeap::SO_CodeCache), |
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5569 "if we didn't scan the code cache, we have to be ready to drop nmethods with expired weak oops"); |
| 0 | 5570 } |
| 5571 verify_work_stacks_empty(); | |
| 5572 // Restore evacuated mark words, if any, used for overflow list links | |
| 5573 if (!CMSOverflowEarlyRestoration) { | |
| 5574 restore_preserved_marks_if_any(); | |
| 5575 } | |
| 5576 verify_overflow_empty(); | |
| 5577 } | |
| 5578 | |
| 5579 //////////////////////////////////////////////////////// | |
| 5580 // Parallel Reference Processing Task Proxy Class | |
| 5581 //////////////////////////////////////////////////////// | |
| 5582 class CMSRefProcTaskProxy: public AbstractGangTask { | |
| 5583 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; | |
| 5584 CMSCollector* _collector; | |
| 5585 CMSBitMap* _mark_bit_map; | |
|
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5586 const MemRegion _span; |
| 0 | 5587 OopTaskQueueSet* _task_queues; |
| 5588 ParallelTaskTerminator _term; | |
| 5589 ProcessTask& _task; | |
| 5590 | |
| 5591 public: | |
| 5592 CMSRefProcTaskProxy(ProcessTask& task, | |
| 5593 CMSCollector* collector, | |
| 5594 const MemRegion& span, | |
| 5595 CMSBitMap* mark_bit_map, | |
| 5596 int total_workers, | |
| 5597 OopTaskQueueSet* task_queues): | |
| 5598 AbstractGangTask("Process referents by policy in parallel"), | |
| 5599 _task(task), | |
| 5600 _collector(collector), _span(span), _mark_bit_map(mark_bit_map), | |
| 5601 _task_queues(task_queues), | |
| 5602 _term(total_workers, task_queues) | |
|
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5603 { |
|
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5604 assert(_collector->_span.equals(_span) && !_span.is_empty(), |
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5605 "Inconsistency in _span"); |
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5606 } |
| 0 | 5607 |
| 5608 OopTaskQueueSet* task_queues() { return _task_queues; } | |
| 5609 | |
| 5610 OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); } | |
| 5611 | |
| 5612 ParallelTaskTerminator* terminator() { return &_term; } | |
| 5613 | |
| 5614 void do_work_steal(int i, | |
| 5615 CMSParDrainMarkingStackClosure* drain, | |
| 5616 CMSParKeepAliveClosure* keep_alive, | |
| 5617 int* seed); | |
| 5618 | |
| 5619 virtual void work(int i); | |
| 5620 }; | |
| 5621 | |
| 5622 void CMSRefProcTaskProxy::work(int i) { | |
|
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5623 assert(_collector->_span.equals(_span), "Inconsistency in _span"); |
| 0 | 5624 CMSParKeepAliveClosure par_keep_alive(_collector, _span, |
| 935 | 5625 _mark_bit_map, |
| 5626 &_collector->_revisitStack, | |
| 5627 work_queue(i)); | |
| 0 | 5628 CMSParDrainMarkingStackClosure par_drain_stack(_collector, _span, |
| 935 | 5629 _mark_bit_map, |
| 5630 &_collector->_revisitStack, | |
| 5631 work_queue(i)); | |
|
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5632 CMSIsAliveClosure is_alive_closure(_span, _mark_bit_map); |
| 0 | 5633 _task.work(i, is_alive_closure, par_keep_alive, par_drain_stack); |
| 5634 if (_task.marks_oops_alive()) { | |
| 5635 do_work_steal(i, &par_drain_stack, &par_keep_alive, | |
| 5636 _collector->hash_seed(i)); | |
| 5637 } | |
| 5638 assert(work_queue(i)->size() == 0, "work_queue should be empty"); | |
| 5639 assert(_collector->_overflow_list == NULL, "non-empty _overflow_list"); | |
| 5640 } | |
| 5641 | |
| 5642 class CMSRefEnqueueTaskProxy: public AbstractGangTask { | |
| 5643 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; | |
| 5644 EnqueueTask& _task; | |
| 5645 | |
| 5646 public: | |
| 5647 CMSRefEnqueueTaskProxy(EnqueueTask& task) | |
| 5648 : AbstractGangTask("Enqueue reference objects in parallel"), | |
| 5649 _task(task) | |
| 5650 { } | |
| 5651 | |
| 5652 virtual void work(int i) | |
| 5653 { | |
| 5654 _task.work(i); | |
| 5655 } | |
| 5656 }; | |
| 5657 | |
| 5658 CMSParKeepAliveClosure::CMSParKeepAliveClosure(CMSCollector* collector, | |
| 935 | 5659 MemRegion span, CMSBitMap* bit_map, CMSMarkStack* revisit_stack, |
| 5660 OopTaskQueue* work_queue): | |
| 5661 Par_KlassRememberingOopClosure(collector, NULL, revisit_stack), | |
| 0 | 5662 _span(span), |
| 5663 _bit_map(bit_map), | |
| 5664 _work_queue(work_queue), | |
| 935 | 5665 _mark_and_push(collector, span, bit_map, revisit_stack, work_queue), |
| 0 | 5666 _low_water_mark(MIN2((uint)(work_queue->max_elems()/4), |
| 5667 (uint)(CMSWorkQueueDrainThreshold * ParallelGCThreads))) | |
| 5668 { } | |
| 5669 | |
| 5670 // . see if we can share work_queues with ParNew? XXX | |
| 5671 void CMSRefProcTaskProxy::do_work_steal(int i, | |
| 5672 CMSParDrainMarkingStackClosure* drain, | |
| 5673 CMSParKeepAliveClosure* keep_alive, | |
| 5674 int* seed) { | |
| 5675 OopTaskQueue* work_q = work_queue(i); | |
| 5676 NOT_PRODUCT(int num_steals = 0;) | |
| 5677 oop obj_to_scan; | |
| 5678 | |
| 5679 while (true) { | |
| 5680 // Completely finish any left over work from (an) earlier round(s) | |
| 5681 drain->trim_queue(0); | |
|
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5682 size_t num_from_overflow_list = MIN2((size_t)(work_q->max_elems() - work_q->size())/4, |
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5683 (size_t)ParGCDesiredObjsFromOverflowList); |
| 0 | 5684 // Now check if there's any work in the overflow list |
| 5685 if (_collector->par_take_from_overflow_list(num_from_overflow_list, | |
| 5686 work_q)) { | |
| 5687 // Found something in global overflow list; | |
| 5688 // not yet ready to go stealing work from others. | |
| 5689 // We'd like to assert(work_q->size() != 0, ...) | |
| 5690 // because we just took work from the overflow list, | |
| 5691 // but of course we can't, since all of that might have | |
| 5692 // been already stolen from us. | |
| 5693 continue; | |
| 5694 } | |
| 5695 // Verify that we have no work before we resort to stealing | |
| 5696 assert(work_q->size() == 0, "Have work, shouldn't steal"); | |
| 5697 // Try to steal from other queues that have work | |
| 5698 if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) { | |
| 5699 NOT_PRODUCT(num_steals++;) | |
| 5700 assert(obj_to_scan->is_oop(), "Oops, not an oop!"); | |
| 5701 assert(_mark_bit_map->isMarked((HeapWord*)obj_to_scan), "Stole an unmarked oop?"); | |
| 5702 // Do scanning work | |
| 5703 obj_to_scan->oop_iterate(keep_alive); | |
| 5704 // Loop around, finish this work, and try to steal some more | |
| 5705 } else if (terminator()->offer_termination()) { | |
| 5706 break; // nirvana from the infinite cycle | |
| 5707 } | |
| 5708 } | |
| 5709 NOT_PRODUCT( | |
| 5710 if (PrintCMSStatistics != 0) { | |
| 5711 gclog_or_tty->print("\n\t(%d: stole %d oops)", i, num_steals); | |
| 5712 } | |
| 5713 ) | |
| 5714 } | |
| 5715 | |
| 5716 void CMSRefProcTaskExecutor::execute(ProcessTask& task) | |
| 5717 { | |
| 5718 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 5719 WorkGang* workers = gch->workers(); | |
| 5720 assert(workers != NULL, "Need parallel worker threads."); | |
| 5721 int n_workers = workers->total_workers(); | |
| 5722 CMSRefProcTaskProxy rp_task(task, &_collector, | |
| 5723 _collector.ref_processor()->span(), | |
| 5724 _collector.markBitMap(), | |
| 5725 n_workers, _collector.task_queues()); | |
| 5726 workers->run_task(&rp_task); | |
| 5727 } | |
| 5728 | |
| 5729 void CMSRefProcTaskExecutor::execute(EnqueueTask& task) | |
| 5730 { | |
| 5731 | |
| 5732 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 5733 WorkGang* workers = gch->workers(); | |
| 5734 assert(workers != NULL, "Need parallel worker threads."); | |
| 5735 CMSRefEnqueueTaskProxy enq_task(task); | |
| 5736 workers->run_task(&enq_task); | |
| 5737 } | |
| 5738 | |
| 5739 void CMSCollector::refProcessingWork(bool asynch, bool clear_all_soft_refs) { | |
| 5740 | |
| 5741 ResourceMark rm; | |
| 5742 HandleMark hm; | |
| 5743 | |
| 5744 ReferenceProcessor* rp = ref_processor(); | |
| 5745 assert(rp->span().equals(_span), "Spans should be equal"); | |
|
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5746 assert(!rp->enqueuing_is_done(), "Enqueuing should not be complete"); |
|
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5747 // Process weak references. |
|
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5748 rp->setup_policy(clear_all_soft_refs); |
|
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5749 verify_work_stacks_empty(); |
|
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5750 |
| 0 | 5751 CMSKeepAliveClosure cmsKeepAliveClosure(this, _span, &_markBitMap, |
| 935 | 5752 &_markStack, &_revisitStack, |
| 5753 false /* !preclean */); | |
| 0 | 5754 CMSDrainMarkingStackClosure cmsDrainMarkingStackClosure(this, |
| 5755 _span, &_markBitMap, &_markStack, | |
|
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5756 &cmsKeepAliveClosure, false /* !preclean */); |
| 0 | 5757 { |
| 5758 TraceTime t("weak refs processing", PrintGCDetails, false, gclog_or_tty); | |
| 5759 if (rp->processing_is_mt()) { | |
| 5760 CMSRefProcTaskExecutor task_executor(*this); | |
|
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5761 rp->process_discovered_references(&_is_alive_closure, |
| 0 | 5762 &cmsKeepAliveClosure, |
| 5763 &cmsDrainMarkingStackClosure, | |
| 5764 &task_executor); | |
| 5765 } else { | |
|
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5766 rp->process_discovered_references(&_is_alive_closure, |
| 0 | 5767 &cmsKeepAliveClosure, |
| 5768 &cmsDrainMarkingStackClosure, | |
| 5769 NULL); | |
| 5770 } | |
| 5771 verify_work_stacks_empty(); | |
| 5772 } | |
| 5773 | |
|
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|
5774 if (should_unload_classes()) { |
| 0 | 5775 { |
| 5776 TraceTime t("class unloading", PrintGCDetails, false, gclog_or_tty); | |
| 5777 | |
| 5778 // Follow SystemDictionary roots and unload classes | |
| 5779 bool purged_class = SystemDictionary::do_unloading(&_is_alive_closure); | |
| 5780 | |
| 5781 // Follow CodeCache roots and unload any methods marked for unloading | |
| 5782 CodeCache::do_unloading(&_is_alive_closure, | |
| 5783 &cmsKeepAliveClosure, | |
| 5784 purged_class); | |
| 5785 | |
| 5786 cmsDrainMarkingStackClosure.do_void(); | |
| 5787 verify_work_stacks_empty(); | |
| 5788 | |
| 5789 // Update subklass/sibling/implementor links in KlassKlass descendants | |
| 5790 assert(!_revisitStack.isEmpty(), "revisit stack should not be empty"); | |
| 5791 oop k; | |
| 5792 while ((k = _revisitStack.pop()) != NULL) { | |
| 5793 ((Klass*)(oopDesc*)k)->follow_weak_klass_links( | |
| 5794 &_is_alive_closure, | |
| 5795 &cmsKeepAliveClosure); | |
| 5796 } | |
| 5797 assert(!ClassUnloading || | |
| 5798 (_markStack.isEmpty() && overflow_list_is_empty()), | |
| 5799 "Should not have found new reachable objects"); | |
| 5800 assert(_revisitStack.isEmpty(), "revisit stack should have been drained"); | |
| 5801 cmsDrainMarkingStackClosure.do_void(); | |
| 5802 verify_work_stacks_empty(); | |
| 5803 } | |
| 5804 | |
| 5805 { | |
| 5806 TraceTime t("scrub symbol & string tables", PrintGCDetails, false, gclog_or_tty); | |
| 5807 // Now clean up stale oops in SymbolTable and StringTable | |
| 5808 SymbolTable::unlink(&_is_alive_closure); | |
| 5809 StringTable::unlink(&_is_alive_closure); | |
| 5810 } | |
| 5811 } | |
| 5812 | |
| 5813 verify_work_stacks_empty(); | |
| 5814 // Restore any preserved marks as a result of mark stack or | |
| 5815 // work queue overflow | |
| 5816 restore_preserved_marks_if_any(); // done single-threaded for now | |
| 5817 | |
| 5818 rp->set_enqueuing_is_done(true); | |
| 5819 if (rp->processing_is_mt()) { | |
| 5820 CMSRefProcTaskExecutor task_executor(*this); | |
| 5821 rp->enqueue_discovered_references(&task_executor); | |
| 5822 } else { | |
| 5823 rp->enqueue_discovered_references(NULL); | |
| 5824 } | |
| 5825 rp->verify_no_references_recorded(); | |
| 5826 assert(!rp->discovery_enabled(), "should have been disabled"); | |
| 5827 | |
| 5828 // JVMTI object tagging is based on JNI weak refs. If any of these | |
| 5829 // refs were cleared then JVMTI needs to update its maps and | |
| 5830 // maybe post ObjectFrees to agents. | |
| 5831 JvmtiExport::cms_ref_processing_epilogue(); | |
| 5832 } | |
| 5833 | |
| 5834 #ifndef PRODUCT | |
| 5835 void CMSCollector::check_correct_thread_executing() { | |
| 5836 Thread* t = Thread::current(); | |
| 5837 // Only the VM thread or the CMS thread should be here. | |
| 5838 assert(t->is_ConcurrentGC_thread() || t->is_VM_thread(), | |
| 5839 "Unexpected thread type"); | |
| 5840 // If this is the vm thread, the foreground process | |
| 5841 // should not be waiting. Note that _foregroundGCIsActive is | |
| 5842 // true while the foreground collector is waiting. | |
| 5843 if (_foregroundGCShouldWait) { | |
| 5844 // We cannot be the VM thread | |
| 5845 assert(t->is_ConcurrentGC_thread(), | |
| 5846 "Should be CMS thread"); | |
| 5847 } else { | |
| 5848 // We can be the CMS thread only if we are in a stop-world | |
| 5849 // phase of CMS collection. | |
| 5850 if (t->is_ConcurrentGC_thread()) { | |
| 5851 assert(_collectorState == InitialMarking || | |
| 5852 _collectorState == FinalMarking, | |
| 5853 "Should be a stop-world phase"); | |
| 5854 // The CMS thread should be holding the CMS_token. | |
| 5855 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 5856 "Potential interference with concurrently " | |
| 5857 "executing VM thread"); | |
| 5858 } | |
| 5859 } | |
| 5860 } | |
| 5861 #endif | |
| 5862 | |
| 5863 void CMSCollector::sweep(bool asynch) { | |
| 5864 assert(_collectorState == Sweeping, "just checking"); | |
| 5865 check_correct_thread_executing(); | |
| 5866 verify_work_stacks_empty(); | |
| 5867 verify_overflow_empty(); | |
| 5868 incrementSweepCount(); | |
| 5869 _sweep_timer.stop(); | |
| 5870 _sweep_estimate.sample(_sweep_timer.seconds()); | |
| 5871 size_policy()->avg_cms_free_at_sweep()->sample(_cmsGen->free()); | |
| 5872 | |
| 5873 // PermGen verification support: If perm gen sweeping is disabled in | |
| 5874 // this cycle, we preserve the perm gen object "deadness" information | |
| 5875 // in the perm_gen_verify_bit_map. In order to do that we traverse | |
| 5876 // all blocks in perm gen and mark all dead objects. | |
|
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5877 if (verifying() && !should_unload_classes()) { |
| 0 | 5878 assert(perm_gen_verify_bit_map()->sizeInBits() != 0, |
| 5879 "Should have already been allocated"); | |
| 5880 MarkDeadObjectsClosure mdo(this, _permGen->cmsSpace(), | |
| 5881 markBitMap(), perm_gen_verify_bit_map()); | |
|
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5882 if (asynch) { |
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5883 CMSTokenSyncWithLocks ts(true, _permGen->freelistLock(), |
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5884 bitMapLock()); |
|
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5885 _permGen->cmsSpace()->blk_iterate(&mdo); |
|
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5886 } else { |
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|
5887 // In the case of synchronous sweep, we already have |
|
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|
5888 // the requisite locks/tokens. |
|
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|
5889 _permGen->cmsSpace()->blk_iterate(&mdo); |
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|
5890 } |
| 0 | 5891 } |
| 5892 | |
| 5893 if (asynch) { | |
| 5894 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
| 5895 CMSPhaseAccounting pa(this, "sweep", !PrintGCDetails); | |
| 5896 // First sweep the old gen then the perm gen | |
| 5897 { | |
| 5898 CMSTokenSyncWithLocks ts(true, _cmsGen->freelistLock(), | |
| 5899 bitMapLock()); | |
| 5900 sweepWork(_cmsGen, asynch); | |
| 5901 } | |
| 5902 | |
| 5903 // Now repeat for perm gen | |
|
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|
5904 if (should_unload_classes()) { |
| 0 | 5905 CMSTokenSyncWithLocks ts(true, _permGen->freelistLock(), |
| 5906 bitMapLock()); | |
| 5907 sweepWork(_permGen, asynch); | |
| 5908 } | |
| 5909 | |
| 5910 // Update Universe::_heap_*_at_gc figures. | |
| 5911 // We need all the free list locks to make the abstract state | |
| 5912 // transition from Sweeping to Resetting. See detailed note | |
| 5913 // further below. | |
| 5914 { | |
| 5915 CMSTokenSyncWithLocks ts(true, _cmsGen->freelistLock(), | |
| 5916 _permGen->freelistLock()); | |
| 5917 // Update heap occupancy information which is used as | |
| 5918 // input to soft ref clearing policy at the next gc. | |
| 5919 Universe::update_heap_info_at_gc(); | |
| 5920 _collectorState = Resizing; | |
| 5921 } | |
| 5922 } else { | |
| 5923 // already have needed locks | |
| 5924 sweepWork(_cmsGen, asynch); | |
| 5925 | |
|
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|
5926 if (should_unload_classes()) { |
| 0 | 5927 sweepWork(_permGen, asynch); |
| 5928 } | |
| 5929 // Update heap occupancy information which is used as | |
| 5930 // input to soft ref clearing policy at the next gc. | |
| 5931 Universe::update_heap_info_at_gc(); | |
| 5932 _collectorState = Resizing; | |
| 5933 } | |
| 5934 verify_work_stacks_empty(); | |
| 5935 verify_overflow_empty(); | |
| 5936 | |
| 5937 _sweep_timer.reset(); | |
| 5938 _sweep_timer.start(); | |
| 5939 | |
| 5940 update_time_of_last_gc(os::javaTimeMillis()); | |
| 5941 | |
| 5942 // NOTE on abstract state transitions: | |
| 5943 // Mutators allocate-live and/or mark the mod-union table dirty | |
| 5944 // based on the state of the collection. The former is done in | |
| 5945 // the interval [Marking, Sweeping] and the latter in the interval | |
| 5946 // [Marking, Sweeping). Thus the transitions into the Marking state | |
| 5947 // and out of the Sweeping state must be synchronously visible | |
| 5948 // globally to the mutators. | |
| 5949 // The transition into the Marking state happens with the world | |
| 5950 // stopped so the mutators will globally see it. Sweeping is | |
| 5951 // done asynchronously by the background collector so the transition | |
| 5952 // from the Sweeping state to the Resizing state must be done | |
| 5953 // under the freelistLock (as is the check for whether to | |
| 5954 // allocate-live and whether to dirty the mod-union table). | |
| 5955 assert(_collectorState == Resizing, "Change of collector state to" | |
| 5956 " Resizing must be done under the freelistLocks (plural)"); | |
| 5957 | |
| 5958 // Now that sweeping has been completed, if the GCH's | |
| 5959 // incremental_collection_will_fail flag is set, clear it, | |
| 5960 // thus inviting a younger gen collection to promote into | |
| 5961 // this generation. If such a promotion may still fail, | |
| 5962 // the flag will be set again when a young collection is | |
| 5963 // attempted. | |
| 5964 // I think the incremental_collection_will_fail flag's use | |
| 5965 // is specific to a 2 generation collection policy, so i'll | |
| 5966 // assert that that's the configuration we are operating within. | |
| 5967 // The use of the flag can and should be generalized appropriately | |
| 5968 // in the future to deal with a general n-generation system. | |
| 5969 | |
| 5970 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 5971 assert(gch->collector_policy()->is_two_generation_policy(), | |
| 5972 "Resetting of incremental_collection_will_fail flag" | |
| 5973 " may be incorrect otherwise"); | |
| 5974 gch->clear_incremental_collection_will_fail(); | |
| 5975 gch->update_full_collections_completed(_collection_count_start); | |
| 5976 } | |
| 5977 | |
| 5978 // FIX ME!!! Looks like this belongs in CFLSpace, with | |
| 5979 // CMSGen merely delegating to it. | |
| 5980 void ConcurrentMarkSweepGeneration::setNearLargestChunk() { | |
| 5981 double nearLargestPercent = 0.999; | |
| 5982 HeapWord* minAddr = _cmsSpace->bottom(); | |
| 5983 HeapWord* largestAddr = | |
| 5984 (HeapWord*) _cmsSpace->dictionary()->findLargestDict(); | |
| 5985 if (largestAddr == 0) { | |
| 5986 // The dictionary appears to be empty. In this case | |
| 5987 // try to coalesce at the end of the heap. | |
| 5988 largestAddr = _cmsSpace->end(); | |
| 5989 } | |
| 5990 size_t largestOffset = pointer_delta(largestAddr, minAddr); | |
| 5991 size_t nearLargestOffset = | |
| 5992 (size_t)((double)largestOffset * nearLargestPercent) - MinChunkSize; | |
| 5993 _cmsSpace->set_nearLargestChunk(minAddr + nearLargestOffset); | |
| 5994 } | |
| 5995 | |
| 5996 bool ConcurrentMarkSweepGeneration::isNearLargestChunk(HeapWord* addr) { | |
| 5997 return addr >= _cmsSpace->nearLargestChunk(); | |
| 5998 } | |
| 5999 | |
| 6000 FreeChunk* ConcurrentMarkSweepGeneration::find_chunk_at_end() { | |
| 6001 return _cmsSpace->find_chunk_at_end(); | |
| 6002 } | |
| 6003 | |
| 6004 void ConcurrentMarkSweepGeneration::update_gc_stats(int current_level, | |
| 6005 bool full) { | |
| 6006 // The next lower level has been collected. Gather any statistics | |
| 6007 // that are of interest at this point. | |
| 6008 if (!full && (current_level + 1) == level()) { | |
| 6009 // Gather statistics on the young generation collection. | |
| 6010 collector()->stats().record_gc0_end(used()); | |
| 6011 } | |
| 6012 } | |
| 6013 | |
| 6014 CMSAdaptiveSizePolicy* ConcurrentMarkSweepGeneration::size_policy() { | |
| 6015 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 6016 assert(gch->kind() == CollectedHeap::GenCollectedHeap, | |
| 6017 "Wrong type of heap"); | |
| 6018 CMSAdaptiveSizePolicy* sp = (CMSAdaptiveSizePolicy*) | |
| 6019 gch->gen_policy()->size_policy(); | |
| 6020 assert(sp->is_gc_cms_adaptive_size_policy(), | |
| 6021 "Wrong type of size policy"); | |
| 6022 return sp; | |
| 6023 } | |
| 6024 | |
| 6025 void ConcurrentMarkSweepGeneration::rotate_debug_collection_type() { | |
| 6026 if (PrintGCDetails && Verbose) { | |
| 6027 gclog_or_tty->print("Rotate from %d ", _debug_collection_type); | |
| 6028 } | |
| 6029 _debug_collection_type = (CollectionTypes) (_debug_collection_type + 1); | |
| 6030 _debug_collection_type = | |
| 6031 (CollectionTypes) (_debug_collection_type % Unknown_collection_type); | |
| 6032 if (PrintGCDetails && Verbose) { | |
| 6033 gclog_or_tty->print_cr("to %d ", _debug_collection_type); | |
| 6034 } | |
| 6035 } | |
| 6036 | |
| 6037 void CMSCollector::sweepWork(ConcurrentMarkSweepGeneration* gen, | |
| 6038 bool asynch) { | |
| 6039 // We iterate over the space(s) underlying this generation, | |
| 6040 // checking the mark bit map to see if the bits corresponding | |
| 6041 // to specific blocks are marked or not. Blocks that are | |
| 6042 // marked are live and are not swept up. All remaining blocks | |
| 6043 // are swept up, with coalescing on-the-fly as we sweep up | |
| 6044 // contiguous free and/or garbage blocks: | |
| 6045 // We need to ensure that the sweeper synchronizes with allocators | |
| 6046 // and stop-the-world collectors. In particular, the following | |
| 6047 // locks are used: | |
| 6048 // . CMS token: if this is held, a stop the world collection cannot occur | |
| 6049 // . freelistLock: if this is held no allocation can occur from this | |
| 6050 // generation by another thread | |
| 6051 // . bitMapLock: if this is held, no other thread can access or update | |
| 6052 // | |
| 6053 | |
| 6054 // Note that we need to hold the freelistLock if we use | |
| 6055 // block iterate below; else the iterator might go awry if | |
| 6056 // a mutator (or promotion) causes block contents to change | |
| 6057 // (for instance if the allocator divvies up a block). | |
| 6058 // If we hold the free list lock, for all practical purposes | |
| 6059 // young generation GC's can't occur (they'll usually need to | |
| 6060 // promote), so we might as well prevent all young generation | |
| 6061 // GC's while we do a sweeping step. For the same reason, we might | |
| 6062 // as well take the bit map lock for the entire duration | |
| 6063 | |
| 6064 // check that we hold the requisite locks | |
| 6065 assert(have_cms_token(), "Should hold cms token"); | |
| 6066 assert( (asynch && ConcurrentMarkSweepThread::cms_thread_has_cms_token()) | |
| 6067 || (!asynch && ConcurrentMarkSweepThread::vm_thread_has_cms_token()), | |
| 6068 "Should possess CMS token to sweep"); | |
| 6069 assert_lock_strong(gen->freelistLock()); | |
| 6070 assert_lock_strong(bitMapLock()); | |
| 6071 | |
| 6072 assert(!_sweep_timer.is_active(), "Was switched off in an outer context"); | |
| 6073 gen->cmsSpace()->beginSweepFLCensus((float)(_sweep_timer.seconds()), | |
| 6074 _sweep_estimate.padded_average()); | |
| 6075 gen->setNearLargestChunk(); | |
| 6076 | |
| 6077 { | |
| 6078 SweepClosure sweepClosure(this, gen, &_markBitMap, | |
| 6079 CMSYield && asynch); | |
| 6080 gen->cmsSpace()->blk_iterate_careful(&sweepClosure); | |
| 6081 // We need to free-up/coalesce garbage/blocks from a | |
| 6082 // co-terminal free run. This is done in the SweepClosure | |
| 6083 // destructor; so, do not remove this scope, else the | |
| 6084 // end-of-sweep-census below will be off by a little bit. | |
| 6085 } | |
| 6086 gen->cmsSpace()->sweep_completed(); | |
| 6087 gen->cmsSpace()->endSweepFLCensus(sweepCount()); | |
|
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6088 if (should_unload_classes()) { // unloaded classes this cycle, |
|
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|
6089 _concurrent_cycles_since_last_unload = 0; // ... reset count |
|
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|
6090 } else { // did not unload classes, |
|
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|
6091 _concurrent_cycles_since_last_unload++; // ... increment count |
|
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|
6092 } |
| 0 | 6093 } |
| 6094 | |
| 6095 // Reset CMS data structures (for now just the marking bit map) | |
| 6096 // preparatory for the next cycle. | |
| 6097 void CMSCollector::reset(bool asynch) { | |
| 6098 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 6099 CMSAdaptiveSizePolicy* sp = size_policy(); | |
| 6100 AdaptiveSizePolicyOutput(sp, gch->total_collections()); | |
| 6101 if (asynch) { | |
| 6102 CMSTokenSyncWithLocks ts(true, bitMapLock()); | |
| 6103 | |
| 6104 // If the state is not "Resetting", the foreground thread | |
| 6105 // has done a collection and the resetting. | |
| 6106 if (_collectorState != Resetting) { | |
| 6107 assert(_collectorState == Idling, "The state should only change" | |
| 6108 " because the foreground collector has finished the collection"); | |
| 6109 return; | |
| 6110 } | |
| 6111 | |
| 6112 // Clear the mark bitmap (no grey objects to start with) | |
| 6113 // for the next cycle. | |
| 6114 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
| 6115 CMSPhaseAccounting cmspa(this, "reset", !PrintGCDetails); | |
| 6116 | |
| 6117 HeapWord* curAddr = _markBitMap.startWord(); | |
| 6118 while (curAddr < _markBitMap.endWord()) { | |
| 6119 size_t remaining = pointer_delta(_markBitMap.endWord(), curAddr); | |
| 6120 MemRegion chunk(curAddr, MIN2(CMSBitMapYieldQuantum, remaining)); | |
| 6121 _markBitMap.clear_large_range(chunk); | |
| 6122 if (ConcurrentMarkSweepThread::should_yield() && | |
| 6123 !foregroundGCIsActive() && | |
| 6124 CMSYield) { | |
| 6125 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 6126 "CMS thread should hold CMS token"); | |
| 6127 assert_lock_strong(bitMapLock()); | |
| 6128 bitMapLock()->unlock(); | |
| 6129 ConcurrentMarkSweepThread::desynchronize(true); | |
| 6130 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 6131 stopTimer(); | |
| 6132 if (PrintCMSStatistics != 0) { | |
| 6133 incrementYields(); | |
| 6134 } | |
| 6135 icms_wait(); | |
| 6136 | |
| 6137 // See the comment in coordinator_yield() | |
| 6138 for (unsigned i = 0; i < CMSYieldSleepCount && | |
|
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6139 ConcurrentMarkSweepThread::should_yield() && |
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6140 !CMSCollector::foregroundGCIsActive(); ++i) { |
| 0 | 6141 os::sleep(Thread::current(), 1, false); |
| 6142 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 6143 } | |
| 6144 | |
| 6145 ConcurrentMarkSweepThread::synchronize(true); | |
| 6146 bitMapLock()->lock_without_safepoint_check(); | |
| 6147 startTimer(); | |
| 6148 } | |
| 6149 curAddr = chunk.end(); | |
| 6150 } | |
| 6151 _collectorState = Idling; | |
| 6152 } else { | |
| 6153 // already have the lock | |
| 6154 assert(_collectorState == Resetting, "just checking"); | |
| 6155 assert_lock_strong(bitMapLock()); | |
| 6156 _markBitMap.clear_all(); | |
| 6157 _collectorState = Idling; | |
| 6158 } | |
| 6159 | |
| 6160 // Stop incremental mode after a cycle completes, so that any future cycles | |
| 6161 // are triggered by allocation. | |
| 6162 stop_icms(); | |
| 6163 | |
| 6164 NOT_PRODUCT( | |
| 6165 if (RotateCMSCollectionTypes) { | |
| 6166 _cmsGen->rotate_debug_collection_type(); | |
| 6167 } | |
| 6168 ) | |
| 6169 } | |
| 6170 | |
| 6171 void CMSCollector::do_CMS_operation(CMS_op_type op) { | |
| 6172 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps); | |
| 6173 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
| 6174 TraceTime t("GC", PrintGC, !PrintGCDetails, gclog_or_tty); | |
| 6175 TraceCollectorStats tcs(counters()); | |
| 6176 | |
| 6177 switch (op) { | |
| 6178 case CMS_op_checkpointRootsInitial: { | |
| 6179 checkpointRootsInitial(true); // asynch | |
| 6180 if (PrintGC) { | |
| 6181 _cmsGen->printOccupancy("initial-mark"); | |
| 6182 } | |
| 6183 break; | |
| 6184 } | |
| 6185 case CMS_op_checkpointRootsFinal: { | |
| 6186 checkpointRootsFinal(true, // asynch | |
| 6187 false, // !clear_all_soft_refs | |
| 6188 false); // !init_mark_was_synchronous | |
| 6189 if (PrintGC) { | |
| 6190 _cmsGen->printOccupancy("remark"); | |
| 6191 } | |
| 6192 break; | |
| 6193 } | |
| 6194 default: | |
| 6195 fatal("No such CMS_op"); | |
| 6196 } | |
| 6197 } | |
| 6198 | |
| 6199 #ifndef PRODUCT | |
| 6200 size_t const CMSCollector::skip_header_HeapWords() { | |
| 6201 return FreeChunk::header_size(); | |
| 6202 } | |
| 6203 | |
| 6204 // Try and collect here conditions that should hold when | |
| 6205 // CMS thread is exiting. The idea is that the foreground GC | |
| 6206 // thread should not be blocked if it wants to terminate | |
| 6207 // the CMS thread and yet continue to run the VM for a while | |
| 6208 // after that. | |
| 6209 void CMSCollector::verify_ok_to_terminate() const { | |
| 6210 assert(Thread::current()->is_ConcurrentGC_thread(), | |
| 6211 "should be called by CMS thread"); | |
| 6212 assert(!_foregroundGCShouldWait, "should be false"); | |
| 6213 // We could check here that all the various low-level locks | |
| 6214 // are not held by the CMS thread, but that is overkill; see | |
| 6215 // also CMSThread::verify_ok_to_terminate() where the CGC_lock | |
| 6216 // is checked. | |
| 6217 } | |
| 6218 #endif | |
| 6219 | |
| 6220 size_t CMSCollector::block_size_using_printezis_bits(HeapWord* addr) const { | |
|
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6221 assert(_markBitMap.isMarked(addr) && _markBitMap.isMarked(addr + 1), |
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6222 "missing Printezis mark?"); |
| 0 | 6223 HeapWord* nextOneAddr = _markBitMap.getNextMarkedWordAddress(addr + 2); |
| 6224 size_t size = pointer_delta(nextOneAddr + 1, addr); | |
| 6225 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
| 6226 "alignment problem"); | |
| 6227 assert(size >= 3, "Necessary for Printezis marks to work"); | |
| 6228 return size; | |
| 6229 } | |
| 6230 | |
| 6231 // A variant of the above (block_size_using_printezis_bits()) except | |
| 6232 // that we return 0 if the P-bits are not yet set. | |
| 6233 size_t CMSCollector::block_size_if_printezis_bits(HeapWord* addr) const { | |
| 6234 if (_markBitMap.isMarked(addr)) { | |
| 6235 assert(_markBitMap.isMarked(addr + 1), "Missing Printezis bit?"); | |
| 6236 HeapWord* nextOneAddr = _markBitMap.getNextMarkedWordAddress(addr + 2); | |
| 6237 size_t size = pointer_delta(nextOneAddr + 1, addr); | |
| 6238 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
| 6239 "alignment problem"); | |
| 6240 assert(size >= 3, "Necessary for Printezis marks to work"); | |
| 6241 return size; | |
| 6242 } else { | |
| 6243 assert(!_markBitMap.isMarked(addr + 1), "Bit map inconsistency?"); | |
| 6244 return 0; | |
| 6245 } | |
| 6246 } | |
| 6247 | |
| 6248 HeapWord* CMSCollector::next_card_start_after_block(HeapWord* addr) const { | |
| 6249 size_t sz = 0; | |
| 6250 oop p = (oop)addr; | |
| 187 | 6251 if (p->klass_or_null() != NULL && p->is_parsable()) { |
| 0 | 6252 sz = CompactibleFreeListSpace::adjustObjectSize(p->size()); |
| 6253 } else { | |
| 6254 sz = block_size_using_printezis_bits(addr); | |
| 6255 } | |
| 6256 assert(sz > 0, "size must be nonzero"); | |
| 6257 HeapWord* next_block = addr + sz; | |
| 6258 HeapWord* next_card = (HeapWord*)round_to((uintptr_t)next_block, | |
| 6259 CardTableModRefBS::card_size); | |
| 6260 assert(round_down((uintptr_t)addr, CardTableModRefBS::card_size) < | |
| 6261 round_down((uintptr_t)next_card, CardTableModRefBS::card_size), | |
| 6262 "must be different cards"); | |
| 6263 return next_card; | |
| 6264 } | |
| 6265 | |
| 6266 | |
| 6267 // CMS Bit Map Wrapper ///////////////////////////////////////// | |
| 6268 | |
| 6269 // Construct a CMS bit map infrastructure, but don't create the | |
| 6270 // bit vector itself. That is done by a separate call CMSBitMap::allocate() | |
| 6271 // further below. | |
| 6272 CMSBitMap::CMSBitMap(int shifter, int mutex_rank, const char* mutex_name): | |
|
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6273 _bm(), |
| 0 | 6274 _shifter(shifter), |
| 6275 _lock(mutex_rank >= 0 ? new Mutex(mutex_rank, mutex_name, true) : NULL) | |
| 6276 { | |
| 6277 _bmStartWord = 0; | |
| 6278 _bmWordSize = 0; | |
| 6279 } | |
| 6280 | |
| 6281 bool CMSBitMap::allocate(MemRegion mr) { | |
| 6282 _bmStartWord = mr.start(); | |
| 6283 _bmWordSize = mr.word_size(); | |
| 6284 ReservedSpace brs(ReservedSpace::allocation_align_size_up( | |
| 6285 (_bmWordSize >> (_shifter + LogBitsPerByte)) + 1)); | |
| 6286 if (!brs.is_reserved()) { | |
| 6287 warning("CMS bit map allocation failure"); | |
| 6288 return false; | |
| 6289 } | |
| 6290 // For now we'll just commit all of the bit map up fromt. | |
| 6291 // Later on we'll try to be more parsimonious with swap. | |
| 6292 if (!_virtual_space.initialize(brs, brs.size())) { | |
| 6293 warning("CMS bit map backing store failure"); | |
| 6294 return false; | |
| 6295 } | |
| 6296 assert(_virtual_space.committed_size() == brs.size(), | |
| 6297 "didn't reserve backing store for all of CMS bit map?"); | |
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6298 _bm.set_map((BitMap::bm_word_t*)_virtual_space.low()); |
| 0 | 6299 assert(_virtual_space.committed_size() << (_shifter + LogBitsPerByte) >= |
| 6300 _bmWordSize, "inconsistency in bit map sizing"); | |
| 6301 _bm.set_size(_bmWordSize >> _shifter); | |
| 6302 | |
| 6303 // bm.clear(); // can we rely on getting zero'd memory? verify below | |
| 6304 assert(isAllClear(), | |
| 6305 "Expected zero'd memory from ReservedSpace constructor"); | |
| 6306 assert(_bm.size() == heapWordDiffToOffsetDiff(sizeInWords()), | |
| 6307 "consistency check"); | |
| 6308 return true; | |
| 6309 } | |
| 6310 | |
| 6311 void CMSBitMap::dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl) { | |
| 6312 HeapWord *next_addr, *end_addr, *last_addr; | |
| 6313 assert_locked(); | |
| 6314 assert(covers(mr), "out-of-range error"); | |
| 6315 // XXX assert that start and end are appropriately aligned | |
| 6316 for (next_addr = mr.start(), end_addr = mr.end(); | |
| 6317 next_addr < end_addr; next_addr = last_addr) { | |
| 6318 MemRegion dirty_region = getAndClearMarkedRegion(next_addr, end_addr); | |
| 6319 last_addr = dirty_region.end(); | |
| 6320 if (!dirty_region.is_empty()) { | |
| 6321 cl->do_MemRegion(dirty_region); | |
| 6322 } else { | |
| 6323 assert(last_addr == end_addr, "program logic"); | |
| 6324 return; | |
| 6325 } | |
| 6326 } | |
| 6327 } | |
| 6328 | |
| 6329 #ifndef PRODUCT | |
| 6330 void CMSBitMap::assert_locked() const { | |
| 6331 CMSLockVerifier::assert_locked(lock()); | |
| 6332 } | |
| 6333 | |
| 6334 bool CMSBitMap::covers(MemRegion mr) const { | |
| 6335 // assert(_bm.map() == _virtual_space.low(), "map inconsistency"); | |
| 6336 assert((size_t)_bm.size() == (_bmWordSize >> _shifter), | |
| 6337 "size inconsistency"); | |
| 6338 return (mr.start() >= _bmStartWord) && | |
| 6339 (mr.end() <= endWord()); | |
| 6340 } | |
| 6341 | |
| 6342 bool CMSBitMap::covers(HeapWord* start, size_t size) const { | |
| 6343 return (start >= _bmStartWord && (start + size) <= endWord()); | |
| 6344 } | |
| 6345 | |
| 6346 void CMSBitMap::verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) { | |
| 6347 // verify that there are no 1 bits in the interval [left, right) | |
| 6348 FalseBitMapClosure falseBitMapClosure; | |
| 6349 iterate(&falseBitMapClosure, left, right); | |
| 6350 } | |
| 6351 | |
| 6352 void CMSBitMap::region_invariant(MemRegion mr) | |
| 6353 { | |
| 6354 assert_locked(); | |
| 6355 // mr = mr.intersection(MemRegion(_bmStartWord, _bmWordSize)); | |
| 6356 assert(!mr.is_empty(), "unexpected empty region"); | |
| 6357 assert(covers(mr), "mr should be covered by bit map"); | |
| 6358 // convert address range into offset range | |
| 6359 size_t start_ofs = heapWordToOffset(mr.start()); | |
| 6360 // Make sure that end() is appropriately aligned | |
| 6361 assert(mr.end() == (HeapWord*)round_to((intptr_t)mr.end(), | |
| 6362 (1 << (_shifter+LogHeapWordSize))), | |
| 6363 "Misaligned mr.end()"); | |
| 6364 size_t end_ofs = heapWordToOffset(mr.end()); | |
| 6365 assert(end_ofs > start_ofs, "Should mark at least one bit"); | |
| 6366 } | |
| 6367 | |
| 6368 #endif | |
| 6369 | |
| 6370 bool CMSMarkStack::allocate(size_t size) { | |
| 6371 // allocate a stack of the requisite depth | |
| 6372 ReservedSpace rs(ReservedSpace::allocation_align_size_up( | |
| 6373 size * sizeof(oop))); | |
| 6374 if (!rs.is_reserved()) { | |
| 6375 warning("CMSMarkStack allocation failure"); | |
| 6376 return false; | |
| 6377 } | |
| 6378 if (!_virtual_space.initialize(rs, rs.size())) { | |
| 6379 warning("CMSMarkStack backing store failure"); | |
| 6380 return false; | |
| 6381 } | |
| 6382 assert(_virtual_space.committed_size() == rs.size(), | |
| 6383 "didn't reserve backing store for all of CMS stack?"); | |
| 6384 _base = (oop*)(_virtual_space.low()); | |
| 6385 _index = 0; | |
| 6386 _capacity = size; | |
| 6387 NOT_PRODUCT(_max_depth = 0); | |
| 6388 return true; | |
| 6389 } | |
| 6390 | |
| 6391 // XXX FIX ME !!! In the MT case we come in here holding a | |
| 6392 // leaf lock. For printing we need to take a further lock | |
| 6393 // which has lower rank. We need to recallibrate the two | |
| 6394 // lock-ranks involved in order to be able to rpint the | |
| 6395 // messages below. (Or defer the printing to the caller. | |
| 6396 // For now we take the expedient path of just disabling the | |
| 6397 // messages for the problematic case.) | |
| 6398 void CMSMarkStack::expand() { | |
| 6399 assert(_capacity <= CMSMarkStackSizeMax, "stack bigger than permitted"); | |
| 6400 if (_capacity == CMSMarkStackSizeMax) { | |
| 6401 if (_hit_limit++ == 0 && !CMSConcurrentMTEnabled && PrintGCDetails) { | |
| 6402 // We print a warning message only once per CMS cycle. | |
| 6403 gclog_or_tty->print_cr(" (benign) Hit CMSMarkStack max size limit"); | |
| 6404 } | |
| 6405 return; | |
| 6406 } | |
| 6407 // Double capacity if possible | |
| 6408 size_t new_capacity = MIN2(_capacity*2, CMSMarkStackSizeMax); | |
| 6409 // Do not give up existing stack until we have managed to | |
| 6410 // get the double capacity that we desired. | |
| 6411 ReservedSpace rs(ReservedSpace::allocation_align_size_up( | |
| 6412 new_capacity * sizeof(oop))); | |
| 6413 if (rs.is_reserved()) { | |
| 6414 // Release the backing store associated with old stack | |
| 6415 _virtual_space.release(); | |
| 6416 // Reinitialize virtual space for new stack | |
| 6417 if (!_virtual_space.initialize(rs, rs.size())) { | |
| 6418 fatal("Not enough swap for expanded marking stack"); | |
| 6419 } | |
| 6420 _base = (oop*)(_virtual_space.low()); | |
| 6421 _index = 0; | |
| 6422 _capacity = new_capacity; | |
| 6423 } else if (_failed_double++ == 0 && !CMSConcurrentMTEnabled && PrintGCDetails) { | |
| 6424 // Failed to double capacity, continue; | |
| 6425 // we print a detail message only once per CMS cycle. | |
| 6426 gclog_or_tty->print(" (benign) Failed to expand marking stack from "SIZE_FORMAT"K to " | |
| 6427 SIZE_FORMAT"K", | |
| 6428 _capacity / K, new_capacity / K); | |
| 6429 } | |
| 6430 } | |
| 6431 | |
| 6432 | |
| 6433 // Closures | |
| 6434 // XXX: there seems to be a lot of code duplication here; | |
| 6435 // should refactor and consolidate common code. | |
| 6436 | |
| 6437 // This closure is used to mark refs into the CMS generation in | |
| 6438 // the CMS bit map. Called at the first checkpoint. This closure | |
| 6439 // assumes that we do not need to re-mark dirty cards; if the CMS | |
| 6440 // generation on which this is used is not an oldest (modulo perm gen) | |
| 6441 // generation then this will lose younger_gen cards! | |
| 6442 | |
| 6443 MarkRefsIntoClosure::MarkRefsIntoClosure( | |
| 6444 MemRegion span, CMSBitMap* bitMap, bool should_do_nmethods): | |
| 6445 _span(span), | |
| 6446 _bitMap(bitMap), | |
| 6447 _should_do_nmethods(should_do_nmethods) | |
| 6448 { | |
| 6449 assert(_ref_processor == NULL, "deliberately left NULL"); | |
| 6450 assert(_bitMap->covers(_span), "_bitMap/_span mismatch"); | |
| 6451 } | |
| 6452 | |
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6453 void MarkRefsIntoClosure::do_oop(oop obj) { |
| 0 | 6454 // if p points into _span, then mark corresponding bit in _markBitMap |
|
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6455 assert(obj->is_oop(), "expected an oop"); |
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6456 HeapWord* addr = (HeapWord*)obj; |
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6457 if (_span.contains(addr)) { |
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6458 // this should be made more efficient |
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6459 _bitMap->mark(addr); |
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6460 } |
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6461 } |
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6462 |
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6463 void MarkRefsIntoClosure::do_oop(oop* p) { MarkRefsIntoClosure::do_oop_work(p); } |
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6464 void MarkRefsIntoClosure::do_oop(narrowOop* p) { MarkRefsIntoClosure::do_oop_work(p); } |
| 0 | 6465 |
| 6466 // A variant of the above, used for CMS marking verification. | |
| 6467 MarkRefsIntoVerifyClosure::MarkRefsIntoVerifyClosure( | |
| 6468 MemRegion span, CMSBitMap* verification_bm, CMSBitMap* cms_bm, | |
| 6469 bool should_do_nmethods): | |
| 6470 _span(span), | |
| 6471 _verification_bm(verification_bm), | |
| 6472 _cms_bm(cms_bm), | |
| 6473 _should_do_nmethods(should_do_nmethods) { | |
| 6474 assert(_ref_processor == NULL, "deliberately left NULL"); | |
| 6475 assert(_verification_bm->covers(_span), "_verification_bm/_span mismatch"); | |
| 6476 } | |
| 6477 | |
|
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6478 void MarkRefsIntoVerifyClosure::do_oop(oop obj) { |
| 0 | 6479 // if p points into _span, then mark corresponding bit in _markBitMap |
|
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6480 assert(obj->is_oop(), "expected an oop"); |
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6481 HeapWord* addr = (HeapWord*)obj; |
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6482 if (_span.contains(addr)) { |
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6483 _verification_bm->mark(addr); |
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6484 if (!_cms_bm->isMarked(addr)) { |
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6485 oop(addr)->print(); |
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6486 gclog_or_tty->print_cr(" (" INTPTR_FORMAT " should have been marked)", addr); |
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6487 fatal("... aborting"); |
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6488 } |
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6489 } |
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6490 } |
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6491 |
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6492 void MarkRefsIntoVerifyClosure::do_oop(oop* p) { MarkRefsIntoVerifyClosure::do_oop_work(p); } |
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6493 void MarkRefsIntoVerifyClosure::do_oop(narrowOop* p) { MarkRefsIntoVerifyClosure::do_oop_work(p); } |
| 0 | 6494 |
| 6495 ////////////////////////////////////////////////// | |
| 6496 // MarkRefsIntoAndScanClosure | |
| 6497 ////////////////////////////////////////////////// | |
| 6498 | |
| 6499 MarkRefsIntoAndScanClosure::MarkRefsIntoAndScanClosure(MemRegion span, | |
| 6500 ReferenceProcessor* rp, | |
| 6501 CMSBitMap* bit_map, | |
| 6502 CMSBitMap* mod_union_table, | |
| 6503 CMSMarkStack* mark_stack, | |
| 6504 CMSMarkStack* revisit_stack, | |
| 6505 CMSCollector* collector, | |
| 6506 bool should_yield, | |
| 6507 bool concurrent_precleaning): | |
| 6508 _collector(collector), | |
| 6509 _span(span), | |
| 6510 _bit_map(bit_map), | |
| 6511 _mark_stack(mark_stack), | |
| 6512 _pushAndMarkClosure(collector, span, rp, bit_map, mod_union_table, | |
| 6513 mark_stack, revisit_stack, concurrent_precleaning), | |
| 6514 _yield(should_yield), | |
| 6515 _concurrent_precleaning(concurrent_precleaning), | |
| 6516 _freelistLock(NULL) | |
| 6517 { | |
| 6518 _ref_processor = rp; | |
| 6519 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
| 6520 } | |
| 6521 | |
| 6522 // This closure is used to mark refs into the CMS generation at the | |
| 6523 // second (final) checkpoint, and to scan and transitively follow | |
| 6524 // the unmarked oops. It is also used during the concurrent precleaning | |
| 6525 // phase while scanning objects on dirty cards in the CMS generation. | |
| 6526 // The marks are made in the marking bit map and the marking stack is | |
| 6527 // used for keeping the (newly) grey objects during the scan. | |
| 6528 // The parallel version (Par_...) appears further below. | |
|
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6529 void MarkRefsIntoAndScanClosure::do_oop(oop obj) { |
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6530 if (obj != NULL) { |
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6531 assert(obj->is_oop(), "expected an oop"); |
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6532 HeapWord* addr = (HeapWord*)obj; |
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6533 assert(_mark_stack->isEmpty(), "pre-condition (eager drainage)"); |
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6534 assert(_collector->overflow_list_is_empty(), |
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6535 "overflow list should be empty"); |
| 0 | 6536 if (_span.contains(addr) && |
| 6537 !_bit_map->isMarked(addr)) { | |
| 6538 // mark bit map (object is now grey) | |
| 6539 _bit_map->mark(addr); | |
| 6540 // push on marking stack (stack should be empty), and drain the | |
| 6541 // stack by applying this closure to the oops in the oops popped | |
| 6542 // from the stack (i.e. blacken the grey objects) | |
|
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6543 bool res = _mark_stack->push(obj); |
| 0 | 6544 assert(res, "Should have space to push on empty stack"); |
| 6545 do { | |
| 6546 oop new_oop = _mark_stack->pop(); | |
| 6547 assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop"); | |
| 6548 assert(new_oop->is_parsable(), "Found unparsable oop"); | |
| 6549 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
| 6550 "only grey objects on this stack"); | |
| 6551 // iterate over the oops in this oop, marking and pushing | |
| 6552 // the ones in CMS heap (i.e. in _span). | |
| 6553 new_oop->oop_iterate(&_pushAndMarkClosure); | |
| 6554 // check if it's time to yield | |
| 6555 do_yield_check(); | |
| 6556 } while (!_mark_stack->isEmpty() || | |
| 6557 (!_concurrent_precleaning && take_from_overflow_list())); | |
| 6558 // if marking stack is empty, and we are not doing this | |
| 6559 // during precleaning, then check the overflow list | |
| 6560 } | |
| 6561 assert(_mark_stack->isEmpty(), "post-condition (eager drainage)"); | |
| 6562 assert(_collector->overflow_list_is_empty(), | |
| 6563 "overflow list was drained above"); | |
| 6564 // We could restore evacuated mark words, if any, used for | |
| 6565 // overflow list links here because the overflow list is | |
| 6566 // provably empty here. That would reduce the maximum | |
| 6567 // size requirements for preserved_{oop,mark}_stack. | |
| 6568 // But we'll just postpone it until we are all done | |
| 6569 // so we can just stream through. | |
| 6570 if (!_concurrent_precleaning && CMSOverflowEarlyRestoration) { | |
| 6571 _collector->restore_preserved_marks_if_any(); | |
| 6572 assert(_collector->no_preserved_marks(), "No preserved marks"); | |
| 6573 } | |
| 6574 assert(!CMSOverflowEarlyRestoration || _collector->no_preserved_marks(), | |
| 6575 "All preserved marks should have been restored above"); | |
| 6576 } | |
| 6577 } | |
| 6578 | |
|
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6579 void MarkRefsIntoAndScanClosure::do_oop(oop* p) { MarkRefsIntoAndScanClosure::do_oop_work(p); } |
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6580 void MarkRefsIntoAndScanClosure::do_oop(narrowOop* p) { MarkRefsIntoAndScanClosure::do_oop_work(p); } |
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6581 |
| 0 | 6582 void MarkRefsIntoAndScanClosure::do_yield_work() { |
| 6583 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 6584 "CMS thread should hold CMS token"); | |
| 6585 assert_lock_strong(_freelistLock); | |
| 6586 assert_lock_strong(_bit_map->lock()); | |
| 6587 // relinquish the free_list_lock and bitMaplock() | |
| 935 | 6588 DEBUG_ONLY(RememberKlassesChecker mux(false);) |
| 0 | 6589 _bit_map->lock()->unlock(); |
| 6590 _freelistLock->unlock(); | |
| 6591 ConcurrentMarkSweepThread::desynchronize(true); | |
| 6592 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 6593 _collector->stopTimer(); | |
| 6594 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
| 6595 if (PrintCMSStatistics != 0) { | |
| 6596 _collector->incrementYields(); | |
| 6597 } | |
| 6598 _collector->icms_wait(); | |
| 6599 | |
| 6600 // See the comment in coordinator_yield() | |
|
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6601 for (unsigned i = 0; |
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6602 i < CMSYieldSleepCount && |
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6603 ConcurrentMarkSweepThread::should_yield() && |
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6604 !CMSCollector::foregroundGCIsActive(); |
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6605 ++i) { |
| 0 | 6606 os::sleep(Thread::current(), 1, false); |
| 6607 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 6608 } | |
| 6609 | |
| 6610 ConcurrentMarkSweepThread::synchronize(true); | |
| 6611 _freelistLock->lock_without_safepoint_check(); | |
| 6612 _bit_map->lock()->lock_without_safepoint_check(); | |
| 6613 _collector->startTimer(); | |
| 6614 } | |
| 6615 | |
| 6616 /////////////////////////////////////////////////////////// | |
| 6617 // Par_MarkRefsIntoAndScanClosure: a parallel version of | |
| 6618 // MarkRefsIntoAndScanClosure | |
| 6619 /////////////////////////////////////////////////////////// | |
| 6620 Par_MarkRefsIntoAndScanClosure::Par_MarkRefsIntoAndScanClosure( | |
| 6621 CMSCollector* collector, MemRegion span, ReferenceProcessor* rp, | |
| 6622 CMSBitMap* bit_map, OopTaskQueue* work_queue, CMSMarkStack* revisit_stack): | |
| 6623 _span(span), | |
| 6624 _bit_map(bit_map), | |
| 6625 _work_queue(work_queue), | |
| 6626 _low_water_mark(MIN2((uint)(work_queue->max_elems()/4), | |
| 6627 (uint)(CMSWorkQueueDrainThreshold * ParallelGCThreads))), | |
| 6628 _par_pushAndMarkClosure(collector, span, rp, bit_map, work_queue, | |
| 6629 revisit_stack) | |
| 6630 { | |
| 6631 _ref_processor = rp; | |
| 6632 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
| 6633 } | |
| 6634 | |
| 6635 // This closure is used to mark refs into the CMS generation at the | |
| 6636 // second (final) checkpoint, and to scan and transitively follow | |
| 6637 // the unmarked oops. The marks are made in the marking bit map and | |
| 6638 // the work_queue is used for keeping the (newly) grey objects during | |
| 6639 // the scan phase whence they are also available for stealing by parallel | |
| 6640 // threads. Since the marking bit map is shared, updates are | |
| 6641 // synchronized (via CAS). | |
|
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6642 void Par_MarkRefsIntoAndScanClosure::do_oop(oop obj) { |
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6643 if (obj != NULL) { |
| 0 | 6644 // Ignore mark word because this could be an already marked oop |
| 6645 // that may be chained at the end of the overflow list. | |
|
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6646 assert(obj->is_oop(true), "expected an oop"); |
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6647 HeapWord* addr = (HeapWord*)obj; |
| 0 | 6648 if (_span.contains(addr) && |
| 6649 !_bit_map->isMarked(addr)) { | |
| 6650 // mark bit map (object will become grey): | |
| 6651 // It is possible for several threads to be | |
| 6652 // trying to "claim" this object concurrently; | |
| 6653 // the unique thread that succeeds in marking the | |
| 6654 // object first will do the subsequent push on | |
| 6655 // to the work queue (or overflow list). | |
| 6656 if (_bit_map->par_mark(addr)) { | |
| 6657 // push on work_queue (which may not be empty), and trim the | |
| 6658 // queue to an appropriate length by applying this closure to | |
| 6659 // the oops in the oops popped from the stack (i.e. blacken the | |
| 6660 // grey objects) | |
|
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6661 bool res = _work_queue->push(obj); |
| 0 | 6662 assert(res, "Low water mark should be less than capacity?"); |
| 6663 trim_queue(_low_water_mark); | |
| 6664 } // Else, another thread claimed the object | |
| 6665 } | |
| 6666 } | |
| 6667 } | |
| 6668 | |
|
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6669 void Par_MarkRefsIntoAndScanClosure::do_oop(oop* p) { Par_MarkRefsIntoAndScanClosure::do_oop_work(p); } |
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6670 void Par_MarkRefsIntoAndScanClosure::do_oop(narrowOop* p) { Par_MarkRefsIntoAndScanClosure::do_oop_work(p); } |
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6671 |
| 0 | 6672 // This closure is used to rescan the marked objects on the dirty cards |
| 6673 // in the mod union table and the card table proper. | |
| 6674 size_t ScanMarkedObjectsAgainCarefullyClosure::do_object_careful_m( | |
| 6675 oop p, MemRegion mr) { | |
| 6676 | |
| 6677 size_t size = 0; | |
| 6678 HeapWord* addr = (HeapWord*)p; | |
| 6679 DEBUG_ONLY(_collector->verify_work_stacks_empty();) | |
| 6680 assert(_span.contains(addr), "we are scanning the CMS generation"); | |
| 6681 // check if it's time to yield | |
| 6682 if (do_yield_check()) { | |
| 6683 // We yielded for some foreground stop-world work, | |
| 6684 // and we have been asked to abort this ongoing preclean cycle. | |
| 6685 return 0; | |
| 6686 } | |
| 6687 if (_bitMap->isMarked(addr)) { | |
| 6688 // it's marked; is it potentially uninitialized? | |
| 187 | 6689 if (p->klass_or_null() != NULL) { |
|
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6690 // If is_conc_safe is false, the object may be undergoing |
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6691 // change by the VM outside a safepoint. Don't try to |
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6692 // scan it, but rather leave it for the remark phase. |
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6693 if (CMSPermGenPrecleaningEnabled && |
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6694 (!p->is_conc_safe() || !p->is_parsable())) { |
| 0 | 6695 // Signal precleaning to redirty the card since |
| 6696 // the klass pointer is already installed. | |
| 6697 assert(size == 0, "Initial value"); | |
| 6698 } else { | |
| 6699 assert(p->is_parsable(), "must be parsable."); | |
| 6700 // an initialized object; ignore mark word in verification below | |
| 6701 // since we are running concurrent with mutators | |
| 6702 assert(p->is_oop(true), "should be an oop"); | |
| 6703 if (p->is_objArray()) { | |
| 6704 // objArrays are precisely marked; restrict scanning | |
| 6705 // to dirty cards only. | |
| 187 | 6706 size = CompactibleFreeListSpace::adjustObjectSize( |
| 6707 p->oop_iterate(_scanningClosure, mr)); | |
| 0 | 6708 } else { |
| 6709 // A non-array may have been imprecisely marked; we need | |
| 6710 // to scan object in its entirety. | |
| 6711 size = CompactibleFreeListSpace::adjustObjectSize( | |
| 6712 p->oop_iterate(_scanningClosure)); | |
| 6713 } | |
| 6714 #ifdef DEBUG | |
| 6715 size_t direct_size = | |
| 6716 CompactibleFreeListSpace::adjustObjectSize(p->size()); | |
| 6717 assert(size == direct_size, "Inconsistency in size"); | |
| 6718 assert(size >= 3, "Necessary for Printezis marks to work"); | |
| 6719 if (!_bitMap->isMarked(addr+1)) { | |
| 6720 _bitMap->verifyNoOneBitsInRange(addr+2, addr+size); | |
| 6721 } else { | |
| 6722 _bitMap->verifyNoOneBitsInRange(addr+2, addr+size-1); | |
| 6723 assert(_bitMap->isMarked(addr+size-1), | |
| 6724 "inconsistent Printezis mark"); | |
| 6725 } | |
| 6726 #endif // DEBUG | |
| 6727 } | |
| 6728 } else { | |
| 6729 // an unitialized object | |
| 6730 assert(_bitMap->isMarked(addr+1), "missing Printezis mark?"); | |
| 6731 HeapWord* nextOneAddr = _bitMap->getNextMarkedWordAddress(addr + 2); | |
| 6732 size = pointer_delta(nextOneAddr + 1, addr); | |
| 6733 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
| 6734 "alignment problem"); | |
| 6735 // Note that pre-cleaning needn't redirty the card. OopDesc::set_klass() | |
| 6736 // will dirty the card when the klass pointer is installed in the | |
| 6737 // object (signalling the completion of initialization). | |
| 6738 } | |
| 6739 } else { | |
| 6740 // Either a not yet marked object or an uninitialized object | |
| 187 | 6741 if (p->klass_or_null() == NULL || !p->is_parsable()) { |
| 0 | 6742 // An uninitialized object, skip to the next card, since |
| 6743 // we may not be able to read its P-bits yet. | |
| 6744 assert(size == 0, "Initial value"); | |
| 6745 } else { | |
| 6746 // An object not (yet) reached by marking: we merely need to | |
| 6747 // compute its size so as to go look at the next block. | |
| 6748 assert(p->is_oop(true), "should be an oop"); | |
| 6749 size = CompactibleFreeListSpace::adjustObjectSize(p->size()); | |
| 6750 } | |
| 6751 } | |
| 6752 DEBUG_ONLY(_collector->verify_work_stacks_empty();) | |
| 6753 return size; | |
| 6754 } | |
| 6755 | |
| 6756 void ScanMarkedObjectsAgainCarefullyClosure::do_yield_work() { | |
| 6757 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 6758 "CMS thread should hold CMS token"); | |
| 6759 assert_lock_strong(_freelistLock); | |
| 6760 assert_lock_strong(_bitMap->lock()); | |
| 935 | 6761 DEBUG_ONLY(RememberKlassesChecker mux(false);) |
| 0 | 6762 // relinquish the free_list_lock and bitMaplock() |
| 6763 _bitMap->lock()->unlock(); | |
| 6764 _freelistLock->unlock(); | |
| 6765 ConcurrentMarkSweepThread::desynchronize(true); | |
| 6766 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 6767 _collector->stopTimer(); | |
| 6768 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
| 6769 if (PrintCMSStatistics != 0) { | |
| 6770 _collector->incrementYields(); | |
| 6771 } | |
| 6772 _collector->icms_wait(); | |
| 6773 | |
| 6774 // See the comment in coordinator_yield() | |
| 6775 for (unsigned i = 0; i < CMSYieldSleepCount && | |
|
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6776 ConcurrentMarkSweepThread::should_yield() && |
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6777 !CMSCollector::foregroundGCIsActive(); ++i) { |
| 0 | 6778 os::sleep(Thread::current(), 1, false); |
| 6779 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 6780 } | |
| 6781 | |
| 6782 ConcurrentMarkSweepThread::synchronize(true); | |
| 6783 _freelistLock->lock_without_safepoint_check(); | |
| 6784 _bitMap->lock()->lock_without_safepoint_check(); | |
| 6785 _collector->startTimer(); | |
| 6786 } | |
| 6787 | |
| 6788 | |
| 6789 ////////////////////////////////////////////////////////////////// | |
| 6790 // SurvivorSpacePrecleanClosure | |
| 6791 ////////////////////////////////////////////////////////////////// | |
| 6792 // This (single-threaded) closure is used to preclean the oops in | |
| 6793 // the survivor spaces. | |
| 6794 size_t SurvivorSpacePrecleanClosure::do_object_careful(oop p) { | |
| 6795 | |
| 6796 HeapWord* addr = (HeapWord*)p; | |
| 6797 DEBUG_ONLY(_collector->verify_work_stacks_empty();) | |
| 6798 assert(!_span.contains(addr), "we are scanning the survivor spaces"); | |
| 187 | 6799 assert(p->klass_or_null() != NULL, "object should be initializd"); |
| 0 | 6800 assert(p->is_parsable(), "must be parsable."); |
| 6801 // an initialized object; ignore mark word in verification below | |
| 6802 // since we are running concurrent with mutators | |
| 6803 assert(p->is_oop(true), "should be an oop"); | |
| 6804 // Note that we do not yield while we iterate over | |
| 6805 // the interior oops of p, pushing the relevant ones | |
| 6806 // on our marking stack. | |
| 6807 size_t size = p->oop_iterate(_scanning_closure); | |
| 6808 do_yield_check(); | |
| 6809 // Observe that below, we do not abandon the preclean | |
| 6810 // phase as soon as we should; rather we empty the | |
| 6811 // marking stack before returning. This is to satisfy | |
| 6812 // some existing assertions. In general, it may be a | |
| 6813 // good idea to abort immediately and complete the marking | |
| 6814 // from the grey objects at a later time. | |
| 6815 while (!_mark_stack->isEmpty()) { | |
| 6816 oop new_oop = _mark_stack->pop(); | |
| 6817 assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop"); | |
| 6818 assert(new_oop->is_parsable(), "Found unparsable oop"); | |
| 6819 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
| 6820 "only grey objects on this stack"); | |
| 6821 // iterate over the oops in this oop, marking and pushing | |
| 6822 // the ones in CMS heap (i.e. in _span). | |
| 6823 new_oop->oop_iterate(_scanning_closure); | |
| 6824 // check if it's time to yield | |
| 6825 do_yield_check(); | |
| 6826 } | |
| 6827 unsigned int after_count = | |
| 6828 GenCollectedHeap::heap()->total_collections(); | |
| 6829 bool abort = (_before_count != after_count) || | |
| 6830 _collector->should_abort_preclean(); | |
| 6831 return abort ? 0 : size; | |
| 6832 } | |
| 6833 | |
| 6834 void SurvivorSpacePrecleanClosure::do_yield_work() { | |
| 6835 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 6836 "CMS thread should hold CMS token"); | |
| 6837 assert_lock_strong(_bit_map->lock()); | |
| 935 | 6838 DEBUG_ONLY(RememberKlassesChecker smx(false);) |
| 0 | 6839 // Relinquish the bit map lock |
| 6840 _bit_map->lock()->unlock(); | |
| 6841 ConcurrentMarkSweepThread::desynchronize(true); | |
| 6842 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 6843 _collector->stopTimer(); | |
| 6844 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
| 6845 if (PrintCMSStatistics != 0) { | |
| 6846 _collector->incrementYields(); | |
| 6847 } | |
| 6848 _collector->icms_wait(); | |
| 6849 | |
| 6850 // See the comment in coordinator_yield() | |
| 6851 for (unsigned i = 0; i < CMSYieldSleepCount && | |
| 6852 ConcurrentMarkSweepThread::should_yield() && | |
| 6853 !CMSCollector::foregroundGCIsActive(); ++i) { | |
| 6854 os::sleep(Thread::current(), 1, false); | |
| 6855 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 6856 } | |
| 6857 | |
| 6858 ConcurrentMarkSweepThread::synchronize(true); | |
| 6859 _bit_map->lock()->lock_without_safepoint_check(); | |
| 6860 _collector->startTimer(); | |
| 6861 } | |
| 6862 | |
| 6863 // This closure is used to rescan the marked objects on the dirty cards | |
| 6864 // in the mod union table and the card table proper. In the parallel | |
| 6865 // case, although the bitMap is shared, we do a single read so the | |
| 6866 // isMarked() query is "safe". | |
| 6867 bool ScanMarkedObjectsAgainClosure::do_object_bm(oop p, MemRegion mr) { | |
| 6868 // Ignore mark word because we are running concurrent with mutators | |
| 6869 assert(p->is_oop_or_null(true), "expected an oop or null"); | |
| 6870 HeapWord* addr = (HeapWord*)p; | |
| 6871 assert(_span.contains(addr), "we are scanning the CMS generation"); | |
| 6872 bool is_obj_array = false; | |
| 6873 #ifdef DEBUG | |
| 6874 if (!_parallel) { | |
| 6875 assert(_mark_stack->isEmpty(), "pre-condition (eager drainage)"); | |
| 6876 assert(_collector->overflow_list_is_empty(), | |
| 6877 "overflow list should be empty"); | |
| 6878 | |
| 6879 } | |
| 6880 #endif // DEBUG | |
| 6881 if (_bit_map->isMarked(addr)) { | |
| 6882 // Obj arrays are precisely marked, non-arrays are not; | |
| 6883 // so we scan objArrays precisely and non-arrays in their | |
| 6884 // entirety. | |
| 6885 if (p->is_objArray()) { | |
| 6886 is_obj_array = true; | |
| 6887 if (_parallel) { | |
| 6888 p->oop_iterate(_par_scan_closure, mr); | |
| 6889 } else { | |
| 6890 p->oop_iterate(_scan_closure, mr); | |
| 6891 } | |
| 6892 } else { | |
| 6893 if (_parallel) { | |
| 6894 p->oop_iterate(_par_scan_closure); | |
| 6895 } else { | |
| 6896 p->oop_iterate(_scan_closure); | |
| 6897 } | |
| 6898 } | |
| 6899 } | |
| 6900 #ifdef DEBUG | |
| 6901 if (!_parallel) { | |
| 6902 assert(_mark_stack->isEmpty(), "post-condition (eager drainage)"); | |
| 6903 assert(_collector->overflow_list_is_empty(), | |
| 6904 "overflow list should be empty"); | |
| 6905 | |
| 6906 } | |
| 6907 #endif // DEBUG | |
| 6908 return is_obj_array; | |
| 6909 } | |
| 6910 | |
| 6911 MarkFromRootsClosure::MarkFromRootsClosure(CMSCollector* collector, | |
| 6912 MemRegion span, | |
| 6913 CMSBitMap* bitMap, CMSMarkStack* markStack, | |
| 6914 CMSMarkStack* revisitStack, | |
| 6915 bool should_yield, bool verifying): | |
| 6916 _collector(collector), | |
| 6917 _span(span), | |
| 6918 _bitMap(bitMap), | |
| 6919 _mut(&collector->_modUnionTable), | |
| 6920 _markStack(markStack), | |
| 6921 _revisitStack(revisitStack), | |
| 6922 _yield(should_yield), | |
| 6923 _skipBits(0) | |
| 6924 { | |
| 6925 assert(_markStack->isEmpty(), "stack should be empty"); | |
| 6926 _finger = _bitMap->startWord(); | |
| 6927 _threshold = _finger; | |
| 6928 assert(_collector->_restart_addr == NULL, "Sanity check"); | |
| 6929 assert(_span.contains(_finger), "Out of bounds _finger?"); | |
| 6930 DEBUG_ONLY(_verifying = verifying;) | |
| 6931 } | |
| 6932 | |
| 6933 void MarkFromRootsClosure::reset(HeapWord* addr) { | |
| 6934 assert(_markStack->isEmpty(), "would cause duplicates on stack"); | |
| 6935 assert(_span.contains(addr), "Out of bounds _finger?"); | |
| 6936 _finger = addr; | |
| 6937 _threshold = (HeapWord*)round_to( | |
| 6938 (intptr_t)_finger, CardTableModRefBS::card_size); | |
| 6939 } | |
| 6940 | |
| 6941 // Should revisit to see if this should be restructured for | |
| 6942 // greater efficiency. | |
|
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6943 bool MarkFromRootsClosure::do_bit(size_t offset) { |
| 0 | 6944 if (_skipBits > 0) { |
| 6945 _skipBits--; | |
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6946 return true; |
| 0 | 6947 } |
| 6948 // convert offset into a HeapWord* | |
| 6949 HeapWord* addr = _bitMap->startWord() + offset; | |
| 6950 assert(_bitMap->endWord() && addr < _bitMap->endWord(), | |
| 6951 "address out of range"); | |
| 6952 assert(_bitMap->isMarked(addr), "tautology"); | |
| 6953 if (_bitMap->isMarked(addr+1)) { | |
| 6954 // this is an allocated but not yet initialized object | |
| 6955 assert(_skipBits == 0, "tautology"); | |
| 6956 _skipBits = 2; // skip next two marked bits ("Printezis-marks") | |
| 6957 oop p = oop(addr); | |
| 187 | 6958 if (p->klass_or_null() == NULL || !p->is_parsable()) { |
| 0 | 6959 DEBUG_ONLY(if (!_verifying) {) |
| 6960 // We re-dirty the cards on which this object lies and increase | |
| 6961 // the _threshold so that we'll come back to scan this object | |
| 6962 // during the preclean or remark phase. (CMSCleanOnEnter) | |
| 6963 if (CMSCleanOnEnter) { | |
| 6964 size_t sz = _collector->block_size_using_printezis_bits(addr); | |
| 6965 HeapWord* end_card_addr = (HeapWord*)round_to( | |
| 6966 (intptr_t)(addr+sz), CardTableModRefBS::card_size); | |
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6967 MemRegion redirty_range = MemRegion(addr, end_card_addr); |
| 0 | 6968 assert(!redirty_range.is_empty(), "Arithmetical tautology"); |
| 6969 // Bump _threshold to end_card_addr; note that | |
| 6970 // _threshold cannot possibly exceed end_card_addr, anyhow. | |
| 6971 // This prevents future clearing of the card as the scan proceeds | |
| 6972 // to the right. | |
| 6973 assert(_threshold <= end_card_addr, | |
| 6974 "Because we are just scanning into this object"); | |
| 6975 if (_threshold < end_card_addr) { | |
| 6976 _threshold = end_card_addr; | |
| 6977 } | |
| 187 | 6978 if (p->klass_or_null() != NULL) { |
| 0 | 6979 // Redirty the range of cards... |
| 6980 _mut->mark_range(redirty_range); | |
| 6981 } // ...else the setting of klass will dirty the card anyway. | |
| 6982 } | |
| 6983 DEBUG_ONLY(}) | |
|
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6984 return true; |
| 0 | 6985 } |
| 6986 } | |
| 6987 scanOopsInOop(addr); | |
|
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6988 return true; |
| 0 | 6989 } |
| 6990 | |
| 6991 // We take a break if we've been at this for a while, | |
| 6992 // so as to avoid monopolizing the locks involved. | |
| 6993 void MarkFromRootsClosure::do_yield_work() { | |
| 6994 // First give up the locks, then yield, then re-lock | |
| 6995 // We should probably use a constructor/destructor idiom to | |
| 6996 // do this unlock/lock or modify the MutexUnlocker class to | |
| 6997 // serve our purpose. XXX | |
| 6998 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 6999 "CMS thread should hold CMS token"); | |
| 7000 assert_lock_strong(_bitMap->lock()); | |
| 935 | 7001 DEBUG_ONLY(RememberKlassesChecker mux(false);) |
| 0 | 7002 _bitMap->lock()->unlock(); |
| 7003 ConcurrentMarkSweepThread::desynchronize(true); | |
| 7004 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 7005 _collector->stopTimer(); | |
| 7006 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
| 7007 if (PrintCMSStatistics != 0) { | |
| 7008 _collector->incrementYields(); | |
| 7009 } | |
| 7010 _collector->icms_wait(); | |
| 7011 | |
| 7012 // See the comment in coordinator_yield() | |
| 7013 for (unsigned i = 0; i < CMSYieldSleepCount && | |
| 7014 ConcurrentMarkSweepThread::should_yield() && | |
| 7015 !CMSCollector::foregroundGCIsActive(); ++i) { | |
| 7016 os::sleep(Thread::current(), 1, false); | |
| 7017 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 7018 } | |
| 7019 | |
| 7020 ConcurrentMarkSweepThread::synchronize(true); | |
| 7021 _bitMap->lock()->lock_without_safepoint_check(); | |
| 7022 _collector->startTimer(); | |
| 7023 } | |
| 7024 | |
| 7025 void MarkFromRootsClosure::scanOopsInOop(HeapWord* ptr) { | |
| 7026 assert(_bitMap->isMarked(ptr), "expected bit to be set"); | |
| 7027 assert(_markStack->isEmpty(), | |
| 7028 "should drain stack to limit stack usage"); | |
| 7029 // convert ptr to an oop preparatory to scanning | |
|
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7030 oop obj = oop(ptr); |
| 0 | 7031 // Ignore mark word in verification below, since we |
| 7032 // may be running concurrent with mutators. | |
|
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7033 assert(obj->is_oop(true), "should be an oop"); |
| 0 | 7034 assert(_finger <= ptr, "_finger runneth ahead"); |
| 7035 // advance the finger to right end of this object | |
|
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7036 _finger = ptr + obj->size(); |
| 0 | 7037 assert(_finger > ptr, "we just incremented it above"); |
| 7038 // On large heaps, it may take us some time to get through | |
| 7039 // the marking phase (especially if running iCMS). During | |
| 7040 // this time it's possible that a lot of mutations have | |
| 7041 // accumulated in the card table and the mod union table -- | |
| 7042 // these mutation records are redundant until we have | |
| 7043 // actually traced into the corresponding card. | |
| 7044 // Here, we check whether advancing the finger would make | |
| 7045 // us cross into a new card, and if so clear corresponding | |
| 7046 // cards in the MUT (preclean them in the card-table in the | |
| 7047 // future). | |
| 7048 | |
| 7049 DEBUG_ONLY(if (!_verifying) {) | |
| 7050 // The clean-on-enter optimization is disabled by default, | |
| 7051 // until we fix 6178663. | |
| 7052 if (CMSCleanOnEnter && (_finger > _threshold)) { | |
| 7053 // [_threshold, _finger) represents the interval | |
| 7054 // of cards to be cleared in MUT (or precleaned in card table). | |
| 7055 // The set of cards to be cleared is all those that overlap | |
| 7056 // with the interval [_threshold, _finger); note that | |
| 7057 // _threshold is always kept card-aligned but _finger isn't | |
| 7058 // always card-aligned. | |
| 7059 HeapWord* old_threshold = _threshold; | |
| 7060 assert(old_threshold == (HeapWord*)round_to( | |
| 7061 (intptr_t)old_threshold, CardTableModRefBS::card_size), | |
| 7062 "_threshold should always be card-aligned"); | |
| 7063 _threshold = (HeapWord*)round_to( | |
| 7064 (intptr_t)_finger, CardTableModRefBS::card_size); | |
| 7065 MemRegion mr(old_threshold, _threshold); | |
| 7066 assert(!mr.is_empty(), "Control point invariant"); | |
| 7067 assert(_span.contains(mr), "Should clear within span"); | |
| 7068 // XXX When _finger crosses from old gen into perm gen | |
| 7069 // we may be doing unnecessary cleaning; do better in the | |
| 7070 // future by detecting that condition and clearing fewer | |
| 7071 // MUT/CT entries. | |
| 7072 _mut->clear_range(mr); | |
| 7073 } | |
| 7074 DEBUG_ONLY(}) | |
| 7075 // Note: the finger doesn't advance while we drain | |
| 7076 // the stack below. | |
| 7077 PushOrMarkClosure pushOrMarkClosure(_collector, | |
| 7078 _span, _bitMap, _markStack, | |
| 7079 _revisitStack, | |
| 7080 _finger, this); | |
|
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7081 bool res = _markStack->push(obj); |
| 0 | 7082 assert(res, "Empty non-zero size stack should have space for single push"); |
| 7083 while (!_markStack->isEmpty()) { | |
| 7084 oop new_oop = _markStack->pop(); | |
| 7085 // Skip verifying header mark word below because we are | |
| 7086 // running concurrent with mutators. | |
| 7087 assert(new_oop->is_oop(true), "Oops! expected to pop an oop"); | |
| 7088 // now scan this oop's oops | |
| 7089 new_oop->oop_iterate(&pushOrMarkClosure); | |
| 7090 do_yield_check(); | |
| 7091 } | |
| 7092 assert(_markStack->isEmpty(), "tautology, emphasizing post-condition"); | |
| 7093 } | |
| 7094 | |
| 7095 Par_MarkFromRootsClosure::Par_MarkFromRootsClosure(CMSConcMarkingTask* task, | |
| 7096 CMSCollector* collector, MemRegion span, | |
| 7097 CMSBitMap* bit_map, | |
| 7098 OopTaskQueue* work_queue, | |
| 7099 CMSMarkStack* overflow_stack, | |
| 7100 CMSMarkStack* revisit_stack, | |
| 7101 bool should_yield): | |
| 7102 _collector(collector), | |
| 7103 _whole_span(collector->_span), | |
| 7104 _span(span), | |
| 7105 _bit_map(bit_map), | |
| 7106 _mut(&collector->_modUnionTable), | |
| 7107 _work_queue(work_queue), | |
| 7108 _overflow_stack(overflow_stack), | |
| 7109 _revisit_stack(revisit_stack), | |
| 7110 _yield(should_yield), | |
| 7111 _skip_bits(0), | |
| 7112 _task(task) | |
| 7113 { | |
| 7114 assert(_work_queue->size() == 0, "work_queue should be empty"); | |
| 7115 _finger = span.start(); | |
| 7116 _threshold = _finger; // XXX Defer clear-on-enter optimization for now | |
| 7117 assert(_span.contains(_finger), "Out of bounds _finger?"); | |
| 7118 } | |
| 7119 | |
| 7120 // Should revisit to see if this should be restructured for | |
| 7121 // greater efficiency. | |
|
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7122 bool Par_MarkFromRootsClosure::do_bit(size_t offset) { |
| 0 | 7123 if (_skip_bits > 0) { |
| 7124 _skip_bits--; | |
|
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7125 return true; |
| 0 | 7126 } |
| 7127 // convert offset into a HeapWord* | |
| 7128 HeapWord* addr = _bit_map->startWord() + offset; | |
| 7129 assert(_bit_map->endWord() && addr < _bit_map->endWord(), | |
| 7130 "address out of range"); | |
| 7131 assert(_bit_map->isMarked(addr), "tautology"); | |
| 7132 if (_bit_map->isMarked(addr+1)) { | |
| 7133 // this is an allocated object that might not yet be initialized | |
| 7134 assert(_skip_bits == 0, "tautology"); | |
| 7135 _skip_bits = 2; // skip next two marked bits ("Printezis-marks") | |
| 7136 oop p = oop(addr); | |
| 187 | 7137 if (p->klass_or_null() == NULL || !p->is_parsable()) { |
| 0 | 7138 // in the case of Clean-on-Enter optimization, redirty card |
| 7139 // and avoid clearing card by increasing the threshold. | |
|
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7140 return true; |
| 0 | 7141 } |
| 7142 } | |
| 7143 scan_oops_in_oop(addr); | |
|
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7144 return true; |
| 0 | 7145 } |
| 7146 | |
| 7147 void Par_MarkFromRootsClosure::scan_oops_in_oop(HeapWord* ptr) { | |
| 7148 assert(_bit_map->isMarked(ptr), "expected bit to be set"); | |
| 7149 // Should we assert that our work queue is empty or | |
| 7150 // below some drain limit? | |
| 7151 assert(_work_queue->size() == 0, | |
| 7152 "should drain stack to limit stack usage"); | |
| 7153 // convert ptr to an oop preparatory to scanning | |
|
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7154 oop obj = oop(ptr); |
| 0 | 7155 // Ignore mark word in verification below, since we |
| 7156 // may be running concurrent with mutators. | |
|
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7157 assert(obj->is_oop(true), "should be an oop"); |
| 0 | 7158 assert(_finger <= ptr, "_finger runneth ahead"); |
| 7159 // advance the finger to right end of this object | |
|
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7160 _finger = ptr + obj->size(); |
| 0 | 7161 assert(_finger > ptr, "we just incremented it above"); |
| 7162 // On large heaps, it may take us some time to get through | |
| 7163 // the marking phase (especially if running iCMS). During | |
| 7164 // this time it's possible that a lot of mutations have | |
| 7165 // accumulated in the card table and the mod union table -- | |
| 7166 // these mutation records are redundant until we have | |
| 7167 // actually traced into the corresponding card. | |
| 7168 // Here, we check whether advancing the finger would make | |
| 7169 // us cross into a new card, and if so clear corresponding | |
| 7170 // cards in the MUT (preclean them in the card-table in the | |
| 7171 // future). | |
| 7172 | |
| 7173 // The clean-on-enter optimization is disabled by default, | |
| 7174 // until we fix 6178663. | |
| 7175 if (CMSCleanOnEnter && (_finger > _threshold)) { | |
| 7176 // [_threshold, _finger) represents the interval | |
| 7177 // of cards to be cleared in MUT (or precleaned in card table). | |
| 7178 // The set of cards to be cleared is all those that overlap | |
| 7179 // with the interval [_threshold, _finger); note that | |
| 7180 // _threshold is always kept card-aligned but _finger isn't | |
| 7181 // always card-aligned. | |
| 7182 HeapWord* old_threshold = _threshold; | |
| 7183 assert(old_threshold == (HeapWord*)round_to( | |
| 7184 (intptr_t)old_threshold, CardTableModRefBS::card_size), | |
| 7185 "_threshold should always be card-aligned"); | |
| 7186 _threshold = (HeapWord*)round_to( | |
| 7187 (intptr_t)_finger, CardTableModRefBS::card_size); | |
| 7188 MemRegion mr(old_threshold, _threshold); | |
| 7189 assert(!mr.is_empty(), "Control point invariant"); | |
| 7190 assert(_span.contains(mr), "Should clear within span"); // _whole_span ?? | |
| 7191 // XXX When _finger crosses from old gen into perm gen | |
| 7192 // we may be doing unnecessary cleaning; do better in the | |
| 7193 // future by detecting that condition and clearing fewer | |
| 7194 // MUT/CT entries. | |
| 7195 _mut->clear_range(mr); | |
| 7196 } | |
| 7197 | |
| 7198 // Note: the local finger doesn't advance while we drain | |
| 7199 // the stack below, but the global finger sure can and will. | |
| 7200 HeapWord** gfa = _task->global_finger_addr(); | |
| 7201 Par_PushOrMarkClosure pushOrMarkClosure(_collector, | |
| 7202 _span, _bit_map, | |
| 7203 _work_queue, | |
| 7204 _overflow_stack, | |
| 7205 _revisit_stack, | |
| 7206 _finger, | |
| 7207 gfa, this); | |
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7208 bool res = _work_queue->push(obj); // overflow could occur here |
| 0 | 7209 assert(res, "Will hold once we use workqueues"); |
| 7210 while (true) { | |
| 7211 oop new_oop; | |
| 7212 if (!_work_queue->pop_local(new_oop)) { | |
| 7213 // We emptied our work_queue; check if there's stuff that can | |
| 7214 // be gotten from the overflow stack. | |
| 7215 if (CMSConcMarkingTask::get_work_from_overflow_stack( | |
| 7216 _overflow_stack, _work_queue)) { | |
| 7217 do_yield_check(); | |
| 7218 continue; | |
| 7219 } else { // done | |
| 7220 break; | |
| 7221 } | |
| 7222 } | |
| 7223 // Skip verifying header mark word below because we are | |
| 7224 // running concurrent with mutators. | |
| 7225 assert(new_oop->is_oop(true), "Oops! expected to pop an oop"); | |
| 7226 // now scan this oop's oops | |
| 7227 new_oop->oop_iterate(&pushOrMarkClosure); | |
| 7228 do_yield_check(); | |
| 7229 } | |
| 7230 assert(_work_queue->size() == 0, "tautology, emphasizing post-condition"); | |
| 7231 } | |
| 7232 | |
| 7233 // Yield in response to a request from VM Thread or | |
| 7234 // from mutators. | |
| 7235 void Par_MarkFromRootsClosure::do_yield_work() { | |
| 7236 assert(_task != NULL, "sanity"); | |
| 7237 _task->yield(); | |
| 7238 } | |
| 7239 | |
| 7240 // A variant of the above used for verifying CMS marking work. | |
| 7241 MarkFromRootsVerifyClosure::MarkFromRootsVerifyClosure(CMSCollector* collector, | |
| 7242 MemRegion span, | |
| 7243 CMSBitMap* verification_bm, CMSBitMap* cms_bm, | |
| 7244 CMSMarkStack* mark_stack): | |
| 7245 _collector(collector), | |
| 7246 _span(span), | |
| 7247 _verification_bm(verification_bm), | |
| 7248 _cms_bm(cms_bm), | |
| 7249 _mark_stack(mark_stack), | |
| 7250 _pam_verify_closure(collector, span, verification_bm, cms_bm, | |
| 7251 mark_stack) | |
| 7252 { | |
| 7253 assert(_mark_stack->isEmpty(), "stack should be empty"); | |
| 7254 _finger = _verification_bm->startWord(); | |
| 7255 assert(_collector->_restart_addr == NULL, "Sanity check"); | |
| 7256 assert(_span.contains(_finger), "Out of bounds _finger?"); | |
| 7257 } | |
| 7258 | |
| 7259 void MarkFromRootsVerifyClosure::reset(HeapWord* addr) { | |
| 7260 assert(_mark_stack->isEmpty(), "would cause duplicates on stack"); | |
| 7261 assert(_span.contains(addr), "Out of bounds _finger?"); | |
| 7262 _finger = addr; | |
| 7263 } | |
| 7264 | |
| 7265 // Should revisit to see if this should be restructured for | |
| 7266 // greater efficiency. | |
|
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7267 bool MarkFromRootsVerifyClosure::do_bit(size_t offset) { |
| 0 | 7268 // convert offset into a HeapWord* |
| 7269 HeapWord* addr = _verification_bm->startWord() + offset; | |
| 7270 assert(_verification_bm->endWord() && addr < _verification_bm->endWord(), | |
| 7271 "address out of range"); | |
| 7272 assert(_verification_bm->isMarked(addr), "tautology"); | |
| 7273 assert(_cms_bm->isMarked(addr), "tautology"); | |
| 7274 | |
| 7275 assert(_mark_stack->isEmpty(), | |
| 7276 "should drain stack to limit stack usage"); | |
| 7277 // convert addr to an oop preparatory to scanning | |
|
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7278 oop obj = oop(addr); |
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7279 assert(obj->is_oop(), "should be an oop"); |
| 0 | 7280 assert(_finger <= addr, "_finger runneth ahead"); |
| 7281 // advance the finger to right end of this object | |
|
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7282 _finger = addr + obj->size(); |
| 0 | 7283 assert(_finger > addr, "we just incremented it above"); |
| 7284 // Note: the finger doesn't advance while we drain | |
| 7285 // the stack below. | |
|
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7286 bool res = _mark_stack->push(obj); |
| 0 | 7287 assert(res, "Empty non-zero size stack should have space for single push"); |
| 7288 while (!_mark_stack->isEmpty()) { | |
| 7289 oop new_oop = _mark_stack->pop(); | |
| 7290 assert(new_oop->is_oop(), "Oops! expected to pop an oop"); | |
| 7291 // now scan this oop's oops | |
| 7292 new_oop->oop_iterate(&_pam_verify_closure); | |
| 7293 } | |
| 7294 assert(_mark_stack->isEmpty(), "tautology, emphasizing post-condition"); | |
|
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7295 return true; |
| 0 | 7296 } |
| 7297 | |
| 7298 PushAndMarkVerifyClosure::PushAndMarkVerifyClosure( | |
| 7299 CMSCollector* collector, MemRegion span, | |
| 7300 CMSBitMap* verification_bm, CMSBitMap* cms_bm, | |
| 7301 CMSMarkStack* mark_stack): | |
| 7302 OopClosure(collector->ref_processor()), | |
| 7303 _collector(collector), | |
| 7304 _span(span), | |
| 7305 _verification_bm(verification_bm), | |
| 7306 _cms_bm(cms_bm), | |
| 7307 _mark_stack(mark_stack) | |
| 7308 { } | |
| 7309 | |
|
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7310 void PushAndMarkVerifyClosure::do_oop(oop* p) { PushAndMarkVerifyClosure::do_oop_work(p); } |
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7311 void PushAndMarkVerifyClosure::do_oop(narrowOop* p) { PushAndMarkVerifyClosure::do_oop_work(p); } |
| 0 | 7312 |
| 7313 // Upon stack overflow, we discard (part of) the stack, | |
| 7314 // remembering the least address amongst those discarded | |
| 7315 // in CMSCollector's _restart_address. | |
| 7316 void PushAndMarkVerifyClosure::handle_stack_overflow(HeapWord* lost) { | |
| 7317 // Remember the least grey address discarded | |
| 7318 HeapWord* ra = (HeapWord*)_mark_stack->least_value(lost); | |
| 7319 _collector->lower_restart_addr(ra); | |
| 7320 _mark_stack->reset(); // discard stack contents | |
| 7321 _mark_stack->expand(); // expand the stack if possible | |
| 7322 } | |
| 7323 | |
|
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7324 void PushAndMarkVerifyClosure::do_oop(oop obj) { |
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7325 assert(obj->is_oop_or_null(), "expected an oop or NULL"); |
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7326 HeapWord* addr = (HeapWord*)obj; |
| 0 | 7327 if (_span.contains(addr) && !_verification_bm->isMarked(addr)) { |
| 7328 // Oop lies in _span and isn't yet grey or black | |
| 7329 _verification_bm->mark(addr); // now grey | |
| 7330 if (!_cms_bm->isMarked(addr)) { | |
| 7331 oop(addr)->print(); | |
|
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7332 gclog_or_tty->print_cr(" (" INTPTR_FORMAT " should have been marked)", |
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7333 addr); |
| 0 | 7334 fatal("... aborting"); |
| 7335 } | |
| 7336 | |
|
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7337 if (!_mark_stack->push(obj)) { // stack overflow |
| 0 | 7338 if (PrintCMSStatistics != 0) { |
| 7339 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
| 7340 SIZE_FORMAT, _mark_stack->capacity()); | |
| 7341 } | |
| 7342 assert(_mark_stack->isFull(), "Else push should have succeeded"); | |
| 7343 handle_stack_overflow(addr); | |
| 7344 } | |
| 7345 // anything including and to the right of _finger | |
| 7346 // will be scanned as we iterate over the remainder of the | |
| 7347 // bit map | |
| 7348 } | |
| 7349 } | |
| 7350 | |
| 7351 PushOrMarkClosure::PushOrMarkClosure(CMSCollector* collector, | |
| 7352 MemRegion span, | |
| 7353 CMSBitMap* bitMap, CMSMarkStack* markStack, | |
| 7354 CMSMarkStack* revisitStack, | |
| 7355 HeapWord* finger, MarkFromRootsClosure* parent) : | |
| 935 | 7356 KlassRememberingOopClosure(collector, collector->ref_processor(), revisitStack), |
| 0 | 7357 _span(span), |
| 7358 _bitMap(bitMap), | |
| 7359 _markStack(markStack), | |
| 7360 _finger(finger), | |
| 935 | 7361 _parent(parent) |
| 0 | 7362 { } |
| 7363 | |
| 7364 Par_PushOrMarkClosure::Par_PushOrMarkClosure(CMSCollector* collector, | |
| 7365 MemRegion span, | |
| 7366 CMSBitMap* bit_map, | |
| 7367 OopTaskQueue* work_queue, | |
| 7368 CMSMarkStack* overflow_stack, | |
| 7369 CMSMarkStack* revisit_stack, | |
| 7370 HeapWord* finger, | |
| 7371 HeapWord** global_finger_addr, | |
| 7372 Par_MarkFromRootsClosure* parent) : | |
| 935 | 7373 Par_KlassRememberingOopClosure(collector, |
| 7374 collector->ref_processor(), | |
| 7375 revisit_stack), | |
| 0 | 7376 _whole_span(collector->_span), |
| 7377 _span(span), | |
| 7378 _bit_map(bit_map), | |
| 7379 _work_queue(work_queue), | |
| 7380 _overflow_stack(overflow_stack), | |
| 7381 _finger(finger), | |
| 7382 _global_finger_addr(global_finger_addr), | |
| 935 | 7383 _parent(parent) |
| 0 | 7384 { } |
| 7385 | |
|
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7386 // Assumes thread-safe access by callers, who are |
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7387 // responsible for mutual exclusion. |
| 0 | 7388 void CMSCollector::lower_restart_addr(HeapWord* low) { |
| 7389 assert(_span.contains(low), "Out of bounds addr"); | |
| 7390 if (_restart_addr == NULL) { | |
| 7391 _restart_addr = low; | |
| 7392 } else { | |
| 7393 _restart_addr = MIN2(_restart_addr, low); | |
| 7394 } | |
| 7395 } | |
| 7396 | |
| 7397 // Upon stack overflow, we discard (part of) the stack, | |
| 7398 // remembering the least address amongst those discarded | |
| 7399 // in CMSCollector's _restart_address. | |
| 7400 void PushOrMarkClosure::handle_stack_overflow(HeapWord* lost) { | |
| 7401 // Remember the least grey address discarded | |
| 7402 HeapWord* ra = (HeapWord*)_markStack->least_value(lost); | |
| 7403 _collector->lower_restart_addr(ra); | |
| 7404 _markStack->reset(); // discard stack contents | |
| 7405 _markStack->expand(); // expand the stack if possible | |
| 7406 } | |
| 7407 | |
| 7408 // Upon stack overflow, we discard (part of) the stack, | |
| 7409 // remembering the least address amongst those discarded | |
| 7410 // in CMSCollector's _restart_address. | |
| 7411 void Par_PushOrMarkClosure::handle_stack_overflow(HeapWord* lost) { | |
| 7412 // We need to do this under a mutex to prevent other | |
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7413 // workers from interfering with the work done below. |
| 0 | 7414 MutexLockerEx ml(_overflow_stack->par_lock(), |
| 7415 Mutex::_no_safepoint_check_flag); | |
| 7416 // Remember the least grey address discarded | |
| 7417 HeapWord* ra = (HeapWord*)_overflow_stack->least_value(lost); | |
| 7418 _collector->lower_restart_addr(ra); | |
| 7419 _overflow_stack->reset(); // discard stack contents | |
| 7420 _overflow_stack->expand(); // expand the stack if possible | |
| 7421 } | |
| 7422 | |
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7423 void PushOrMarkClosure::do_oop(oop obj) { |
| 0 | 7424 // Ignore mark word because we are running concurrent with mutators. |
|
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7425 assert(obj->is_oop_or_null(true), "expected an oop or NULL"); |
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7426 HeapWord* addr = (HeapWord*)obj; |
| 0 | 7427 if (_span.contains(addr) && !_bitMap->isMarked(addr)) { |
| 7428 // Oop lies in _span and isn't yet grey or black | |
| 7429 _bitMap->mark(addr); // now grey | |
| 7430 if (addr < _finger) { | |
| 7431 // the bit map iteration has already either passed, or | |
| 7432 // sampled, this bit in the bit map; we'll need to | |
| 7433 // use the marking stack to scan this oop's oops. | |
| 7434 bool simulate_overflow = false; | |
| 7435 NOT_PRODUCT( | |
| 7436 if (CMSMarkStackOverflowALot && | |
| 7437 _collector->simulate_overflow()) { | |
| 7438 // simulate a stack overflow | |
| 7439 simulate_overflow = true; | |
| 7440 } | |
| 7441 ) | |
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7442 if (simulate_overflow || !_markStack->push(obj)) { // stack overflow |
| 0 | 7443 if (PrintCMSStatistics != 0) { |
| 7444 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
| 7445 SIZE_FORMAT, _markStack->capacity()); | |
| 7446 } | |
| 7447 assert(simulate_overflow || _markStack->isFull(), "Else push should have succeeded"); | |
| 7448 handle_stack_overflow(addr); | |
| 7449 } | |
| 7450 } | |
| 7451 // anything including and to the right of _finger | |
| 7452 // will be scanned as we iterate over the remainder of the | |
| 7453 // bit map | |
| 7454 do_yield_check(); | |
| 7455 } | |
| 7456 } | |
| 7457 | |
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7458 void PushOrMarkClosure::do_oop(oop* p) { PushOrMarkClosure::do_oop_work(p); } |
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7459 void PushOrMarkClosure::do_oop(narrowOop* p) { PushOrMarkClosure::do_oop_work(p); } |
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7460 |
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7461 void Par_PushOrMarkClosure::do_oop(oop obj) { |
| 0 | 7462 // Ignore mark word because we are running concurrent with mutators. |
|
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7463 assert(obj->is_oop_or_null(true), "expected an oop or NULL"); |
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7464 HeapWord* addr = (HeapWord*)obj; |
| 0 | 7465 if (_whole_span.contains(addr) && !_bit_map->isMarked(addr)) { |
| 7466 // Oop lies in _span and isn't yet grey or black | |
| 7467 // We read the global_finger (volatile read) strictly after marking oop | |
| 7468 bool res = _bit_map->par_mark(addr); // now grey | |
| 7469 volatile HeapWord** gfa = (volatile HeapWord**)_global_finger_addr; | |
| 7470 // Should we push this marked oop on our stack? | |
| 7471 // -- if someone else marked it, nothing to do | |
| 7472 // -- if target oop is above global finger nothing to do | |
| 7473 // -- if target oop is in chunk and above local finger | |
| 7474 // then nothing to do | |
| 7475 // -- else push on work queue | |
| 7476 if ( !res // someone else marked it, they will deal with it | |
| 7477 || (addr >= *gfa) // will be scanned in a later task | |
| 7478 || (_span.contains(addr) && addr >= _finger)) { // later in this chunk | |
| 7479 return; | |
| 7480 } | |
| 7481 // the bit map iteration has already either passed, or | |
| 7482 // sampled, this bit in the bit map; we'll need to | |
| 7483 // use the marking stack to scan this oop's oops. | |
| 7484 bool simulate_overflow = false; | |
| 7485 NOT_PRODUCT( | |
| 7486 if (CMSMarkStackOverflowALot && | |
| 7487 _collector->simulate_overflow()) { | |
| 7488 // simulate a stack overflow | |
| 7489 simulate_overflow = true; | |
| 7490 } | |
| 7491 ) | |
| 7492 if (simulate_overflow || | |
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7493 !(_work_queue->push(obj) || _overflow_stack->par_push(obj))) { |
| 0 | 7494 // stack overflow |
| 7495 if (PrintCMSStatistics != 0) { | |
| 7496 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
| 7497 SIZE_FORMAT, _overflow_stack->capacity()); | |
| 7498 } | |
| 7499 // We cannot assert that the overflow stack is full because | |
| 7500 // it may have been emptied since. | |
| 7501 assert(simulate_overflow || | |
| 7502 _work_queue->size() == _work_queue->max_elems(), | |
| 7503 "Else push should have succeeded"); | |
| 7504 handle_stack_overflow(addr); | |
| 7505 } | |
| 7506 do_yield_check(); | |
| 7507 } | |
| 7508 } | |
| 7509 | |
|
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7510 void Par_PushOrMarkClosure::do_oop(oop* p) { Par_PushOrMarkClosure::do_oop_work(p); } |
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7511 void Par_PushOrMarkClosure::do_oop(narrowOop* p) { Par_PushOrMarkClosure::do_oop_work(p); } |
| 0 | 7512 |
| 935 | 7513 KlassRememberingOopClosure::KlassRememberingOopClosure(CMSCollector* collector, |
| 7514 ReferenceProcessor* rp, | |
| 7515 CMSMarkStack* revisit_stack) : | |
| 7516 OopClosure(rp), | |
| 7517 _collector(collector), | |
| 7518 _revisit_stack(revisit_stack), | |
| 7519 _should_remember_klasses(collector->should_unload_classes()) {} | |
| 7520 | |
| 0 | 7521 PushAndMarkClosure::PushAndMarkClosure(CMSCollector* collector, |
| 7522 MemRegion span, | |
| 7523 ReferenceProcessor* rp, | |
| 7524 CMSBitMap* bit_map, | |
| 7525 CMSBitMap* mod_union_table, | |
| 7526 CMSMarkStack* mark_stack, | |
| 7527 CMSMarkStack* revisit_stack, | |
| 7528 bool concurrent_precleaning): | |
| 935 | 7529 KlassRememberingOopClosure(collector, rp, revisit_stack), |
| 0 | 7530 _span(span), |
| 7531 _bit_map(bit_map), | |
| 7532 _mod_union_table(mod_union_table), | |
| 7533 _mark_stack(mark_stack), | |
| 935 | 7534 _concurrent_precleaning(concurrent_precleaning) |
| 0 | 7535 { |
| 7536 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
| 7537 } | |
| 7538 | |
| 7539 // Grey object rescan during pre-cleaning and second checkpoint phases -- | |
| 7540 // the non-parallel version (the parallel version appears further below.) | |
|
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7541 void PushAndMarkClosure::do_oop(oop obj) { |
|
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7542 // Ignore mark word verification. If during concurrent precleaning, |
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7543 // the object monitor may be locked. If during the checkpoint |
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7544 // phases, the object may already have been reached by a different |
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7545 // path and may be at the end of the global overflow list (so |
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7546 // the mark word may be NULL). |
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7547 assert(obj->is_oop_or_null(true /* ignore mark word */), |
| 0 | 7548 "expected an oop or NULL"); |
|
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7549 HeapWord* addr = (HeapWord*)obj; |
| 0 | 7550 // Check if oop points into the CMS generation |
| 7551 // and is not marked | |
| 7552 if (_span.contains(addr) && !_bit_map->isMarked(addr)) { | |
| 7553 // a white object ... | |
| 7554 _bit_map->mark(addr); // ... now grey | |
| 7555 // push on the marking stack (grey set) | |
| 7556 bool simulate_overflow = false; | |
| 7557 NOT_PRODUCT( | |
| 7558 if (CMSMarkStackOverflowALot && | |
| 7559 _collector->simulate_overflow()) { | |
| 7560 // simulate a stack overflow | |
| 7561 simulate_overflow = true; | |
| 7562 } | |
| 7563 ) | |
|
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7564 if (simulate_overflow || !_mark_stack->push(obj)) { |
| 0 | 7565 if (_concurrent_precleaning) { |
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7566 // During precleaning we can just dirty the appropriate card(s) |
| 0 | 7567 // in the mod union table, thus ensuring that the object remains |
|
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7568 // in the grey set and continue. In the case of object arrays |
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7569 // we need to dirty all of the cards that the object spans, |
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7570 // since the rescan of object arrays will be limited to the |
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7571 // dirty cards. |
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7572 // Note that no one can be intefering with us in this action |
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7573 // of dirtying the mod union table, so no locking or atomics |
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7574 // are required. |
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7575 if (obj->is_objArray()) { |
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7576 size_t sz = obj->size(); |
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7577 HeapWord* end_card_addr = (HeapWord*)round_to( |
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7578 (intptr_t)(addr+sz), CardTableModRefBS::card_size); |
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7579 MemRegion redirty_range = MemRegion(addr, end_card_addr); |
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7580 assert(!redirty_range.is_empty(), "Arithmetical tautology"); |
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7581 _mod_union_table->mark_range(redirty_range); |
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7582 } else { |
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7583 _mod_union_table->mark(addr); |
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7584 } |
| 0 | 7585 _collector->_ser_pmc_preclean_ovflw++; |
| 7586 } else { | |
| 7587 // During the remark phase, we need to remember this oop | |
| 7588 // in the overflow list. | |
|
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7589 _collector->push_on_overflow_list(obj); |
| 0 | 7590 _collector->_ser_pmc_remark_ovflw++; |
| 7591 } | |
| 7592 } | |
| 7593 } | |
| 7594 } | |
| 7595 | |
| 7596 Par_PushAndMarkClosure::Par_PushAndMarkClosure(CMSCollector* collector, | |
| 7597 MemRegion span, | |
| 7598 ReferenceProcessor* rp, | |
| 7599 CMSBitMap* bit_map, | |
| 7600 OopTaskQueue* work_queue, | |
| 7601 CMSMarkStack* revisit_stack): | |
| 935 | 7602 Par_KlassRememberingOopClosure(collector, rp, revisit_stack), |
| 0 | 7603 _span(span), |
| 7604 _bit_map(bit_map), | |
| 935 | 7605 _work_queue(work_queue) |
| 0 | 7606 { |
| 7607 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
| 7608 } | |
| 7609 | |
|
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7610 void PushAndMarkClosure::do_oop(oop* p) { PushAndMarkClosure::do_oop_work(p); } |
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7611 void PushAndMarkClosure::do_oop(narrowOop* p) { PushAndMarkClosure::do_oop_work(p); } |
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7612 |
| 0 | 7613 // Grey object rescan during second checkpoint phase -- |
| 7614 // the parallel version. | |
|
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7615 void Par_PushAndMarkClosure::do_oop(oop obj) { |
| 0 | 7616 // In the assert below, we ignore the mark word because |
| 7617 // this oop may point to an already visited object that is | |
| 7618 // on the overflow stack (in which case the mark word has | |
| 7619 // been hijacked for chaining into the overflow stack -- | |
| 7620 // if this is the last object in the overflow stack then | |
| 7621 // its mark word will be NULL). Because this object may | |
| 7622 // have been subsequently popped off the global overflow | |
| 7623 // stack, and the mark word possibly restored to the prototypical | |
| 7624 // value, by the time we get to examined this failing assert in | |
| 7625 // the debugger, is_oop_or_null(false) may subsequently start | |
| 7626 // to hold. | |
|
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7627 assert(obj->is_oop_or_null(true), |
| 0 | 7628 "expected an oop or NULL"); |
|
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7629 HeapWord* addr = (HeapWord*)obj; |
| 0 | 7630 // Check if oop points into the CMS generation |
| 7631 // and is not marked | |
| 7632 if (_span.contains(addr) && !_bit_map->isMarked(addr)) { | |
| 7633 // a white object ... | |
| 7634 // If we manage to "claim" the object, by being the | |
| 7635 // first thread to mark it, then we push it on our | |
| 7636 // marking stack | |
| 7637 if (_bit_map->par_mark(addr)) { // ... now grey | |
| 7638 // push on work queue (grey set) | |
| 7639 bool simulate_overflow = false; | |
| 7640 NOT_PRODUCT( | |
| 7641 if (CMSMarkStackOverflowALot && | |
| 7642 _collector->par_simulate_overflow()) { | |
| 7643 // simulate a stack overflow | |
| 7644 simulate_overflow = true; | |
| 7645 } | |
| 7646 ) | |
|
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7647 if (simulate_overflow || !_work_queue->push(obj)) { |
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7648 _collector->par_push_on_overflow_list(obj); |
| 0 | 7649 _collector->_par_pmc_remark_ovflw++; // imprecise OK: no need to CAS |
| 7650 } | |
| 7651 } // Else, some other thread got there first | |
| 7652 } | |
| 7653 } | |
| 7654 | |
|
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7655 void Par_PushAndMarkClosure::do_oop(oop* p) { Par_PushAndMarkClosure::do_oop_work(p); } |
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7656 void Par_PushAndMarkClosure::do_oop(narrowOop* p) { Par_PushAndMarkClosure::do_oop_work(p); } |
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7657 |
| 941 | 7658 void PushAndMarkClosure::remember_mdo(DataLayout* v) { |
| 7659 // TBD | |
| 7660 } | |
| 7661 | |
| 7662 void Par_PushAndMarkClosure::remember_mdo(DataLayout* v) { | |
| 7663 // TBD | |
| 7664 } | |
| 7665 | |
| 0 | 7666 void CMSPrecleanRefsYieldClosure::do_yield_work() { |
| 935 | 7667 DEBUG_ONLY(RememberKlassesChecker mux(false);) |
| 0 | 7668 Mutex* bml = _collector->bitMapLock(); |
| 7669 assert_lock_strong(bml); | |
| 7670 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 7671 "CMS thread should hold CMS token"); | |
| 7672 | |
| 7673 bml->unlock(); | |
| 7674 ConcurrentMarkSweepThread::desynchronize(true); | |
| 7675 | |
| 7676 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 7677 | |
| 7678 _collector->stopTimer(); | |
| 7679 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
| 7680 if (PrintCMSStatistics != 0) { | |
| 7681 _collector->incrementYields(); | |
| 7682 } | |
| 7683 _collector->icms_wait(); | |
| 7684 | |
| 7685 // See the comment in coordinator_yield() | |
| 7686 for (unsigned i = 0; i < CMSYieldSleepCount && | |
| 7687 ConcurrentMarkSweepThread::should_yield() && | |
| 7688 !CMSCollector::foregroundGCIsActive(); ++i) { | |
| 7689 os::sleep(Thread::current(), 1, false); | |
| 7690 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 7691 } | |
| 7692 | |
| 7693 ConcurrentMarkSweepThread::synchronize(true); | |
| 7694 bml->lock(); | |
| 7695 | |
| 7696 _collector->startTimer(); | |
| 7697 } | |
| 7698 | |
| 7699 bool CMSPrecleanRefsYieldClosure::should_return() { | |
| 7700 if (ConcurrentMarkSweepThread::should_yield()) { | |
| 7701 do_yield_work(); | |
| 7702 } | |
| 7703 return _collector->foregroundGCIsActive(); | |
| 7704 } | |
| 7705 | |
| 7706 void MarkFromDirtyCardsClosure::do_MemRegion(MemRegion mr) { | |
| 7707 assert(((size_t)mr.start())%CardTableModRefBS::card_size_in_words == 0, | |
| 7708 "mr should be aligned to start at a card boundary"); | |
| 7709 // We'd like to assert: | |
| 7710 // assert(mr.word_size()%CardTableModRefBS::card_size_in_words == 0, | |
| 7711 // "mr should be a range of cards"); | |
| 7712 // However, that would be too strong in one case -- the last | |
| 7713 // partition ends at _unallocated_block which, in general, can be | |
| 7714 // an arbitrary boundary, not necessarily card aligned. | |
| 7715 if (PrintCMSStatistics != 0) { | |
| 7716 _num_dirty_cards += | |
| 7717 mr.word_size()/CardTableModRefBS::card_size_in_words; | |
| 7718 } | |
| 7719 _space->object_iterate_mem(mr, &_scan_cl); | |
| 7720 } | |
| 7721 | |
| 7722 SweepClosure::SweepClosure(CMSCollector* collector, | |
| 7723 ConcurrentMarkSweepGeneration* g, | |
| 7724 CMSBitMap* bitMap, bool should_yield) : | |
| 7725 _collector(collector), | |
| 7726 _g(g), | |
| 7727 _sp(g->cmsSpace()), | |
| 7728 _limit(_sp->sweep_limit()), | |
| 7729 _freelistLock(_sp->freelistLock()), | |
| 7730 _bitMap(bitMap), | |
| 7731 _yield(should_yield), | |
| 7732 _inFreeRange(false), // No free range at beginning of sweep | |
| 7733 _freeRangeInFreeLists(false), // No free range at beginning of sweep | |
| 7734 _lastFreeRangeCoalesced(false), | |
| 7735 _freeFinger(g->used_region().start()) | |
| 7736 { | |
| 7737 NOT_PRODUCT( | |
| 7738 _numObjectsFreed = 0; | |
| 7739 _numWordsFreed = 0; | |
| 7740 _numObjectsLive = 0; | |
| 7741 _numWordsLive = 0; | |
| 7742 _numObjectsAlreadyFree = 0; | |
| 7743 _numWordsAlreadyFree = 0; | |
| 7744 _last_fc = NULL; | |
| 7745 | |
| 7746 _sp->initializeIndexedFreeListArrayReturnedBytes(); | |
| 7747 _sp->dictionary()->initializeDictReturnedBytes(); | |
| 7748 ) | |
| 7749 assert(_limit >= _sp->bottom() && _limit <= _sp->end(), | |
| 7750 "sweep _limit out of bounds"); | |
| 7751 if (CMSTraceSweeper) { | |
| 7752 gclog_or_tty->print("\n====================\nStarting new sweep\n"); | |
| 7753 } | |
| 7754 } | |
| 7755 | |
| 7756 // We need this destructor to reclaim any space at the end | |
| 7757 // of the space, which do_blk below may not have added back to | |
| 7758 // the free lists. [basically dealing with the "fringe effect"] | |
| 7759 SweepClosure::~SweepClosure() { | |
| 7760 assert_lock_strong(_freelistLock); | |
| 7761 // this should be treated as the end of a free run if any | |
| 7762 // The current free range should be returned to the free lists | |
| 7763 // as one coalesced chunk. | |
| 7764 if (inFreeRange()) { | |
| 7765 flushCurFreeChunk(freeFinger(), | |
| 7766 pointer_delta(_limit, freeFinger())); | |
| 7767 assert(freeFinger() < _limit, "the finger pointeth off base"); | |
| 7768 if (CMSTraceSweeper) { | |
| 7769 gclog_or_tty->print("destructor:"); | |
| 7770 gclog_or_tty->print("Sweep:put_free_blk 0x%x ("SIZE_FORMAT") " | |
| 7771 "[coalesced:"SIZE_FORMAT"]\n", | |
| 7772 freeFinger(), pointer_delta(_limit, freeFinger()), | |
| 7773 lastFreeRangeCoalesced()); | |
| 7774 } | |
| 7775 } | |
| 7776 NOT_PRODUCT( | |
| 7777 if (Verbose && PrintGC) { | |
| 7778 gclog_or_tty->print("Collected "SIZE_FORMAT" objects, " | |
| 7779 SIZE_FORMAT " bytes", | |
| 7780 _numObjectsFreed, _numWordsFreed*sizeof(HeapWord)); | |
| 7781 gclog_or_tty->print_cr("\nLive "SIZE_FORMAT" objects, " | |
| 7782 SIZE_FORMAT" bytes " | |
| 7783 "Already free "SIZE_FORMAT" objects, "SIZE_FORMAT" bytes", | |
| 7784 _numObjectsLive, _numWordsLive*sizeof(HeapWord), | |
| 7785 _numObjectsAlreadyFree, _numWordsAlreadyFree*sizeof(HeapWord)); | |
| 7786 size_t totalBytes = (_numWordsFreed + _numWordsLive + _numWordsAlreadyFree) * | |
| 7787 sizeof(HeapWord); | |
| 7788 gclog_or_tty->print_cr("Total sweep: "SIZE_FORMAT" bytes", totalBytes); | |
| 7789 | |
| 7790 if (PrintCMSStatistics && CMSVerifyReturnedBytes) { | |
| 7791 size_t indexListReturnedBytes = _sp->sumIndexedFreeListArrayReturnedBytes(); | |
| 7792 size_t dictReturnedBytes = _sp->dictionary()->sumDictReturnedBytes(); | |
| 7793 size_t returnedBytes = indexListReturnedBytes + dictReturnedBytes; | |
| 7794 gclog_or_tty->print("Returned "SIZE_FORMAT" bytes", returnedBytes); | |
| 7795 gclog_or_tty->print(" Indexed List Returned "SIZE_FORMAT" bytes", | |
| 7796 indexListReturnedBytes); | |
| 7797 gclog_or_tty->print_cr(" Dictionary Returned "SIZE_FORMAT" bytes", | |
| 7798 dictReturnedBytes); | |
| 7799 } | |
| 7800 } | |
| 7801 ) | |
| 7802 // Now, in debug mode, just null out the sweep_limit | |
| 7803 NOT_PRODUCT(_sp->clear_sweep_limit();) | |
| 7804 if (CMSTraceSweeper) { | |
| 7805 gclog_or_tty->print("end of sweep\n================\n"); | |
| 7806 } | |
| 7807 } | |
| 7808 | |
| 7809 void SweepClosure::initialize_free_range(HeapWord* freeFinger, | |
| 7810 bool freeRangeInFreeLists) { | |
| 7811 if (CMSTraceSweeper) { | |
| 7812 gclog_or_tty->print("---- Start free range 0x%x with free block [%d] (%d)\n", | |
| 7813 freeFinger, _sp->block_size(freeFinger), | |
| 7814 freeRangeInFreeLists); | |
| 7815 } | |
| 7816 assert(!inFreeRange(), "Trampling existing free range"); | |
| 7817 set_inFreeRange(true); | |
| 7818 set_lastFreeRangeCoalesced(false); | |
| 7819 | |
| 7820 set_freeFinger(freeFinger); | |
| 7821 set_freeRangeInFreeLists(freeRangeInFreeLists); | |
| 7822 if (CMSTestInFreeList) { | |
| 7823 if (freeRangeInFreeLists) { | |
| 7824 FreeChunk* fc = (FreeChunk*) freeFinger; | |
| 7825 assert(fc->isFree(), "A chunk on the free list should be free."); | |
| 7826 assert(fc->size() > 0, "Free range should have a size"); | |
| 7827 assert(_sp->verifyChunkInFreeLists(fc), "Chunk is not in free lists"); | |
| 7828 } | |
| 7829 } | |
| 7830 } | |
| 7831 | |
| 7832 // Note that the sweeper runs concurrently with mutators. Thus, | |
| 7833 // it is possible for direct allocation in this generation to happen | |
| 7834 // in the middle of the sweep. Note that the sweeper also coalesces | |
| 7835 // contiguous free blocks. Thus, unless the sweeper and the allocator | |
| 7836 // synchronize appropriately freshly allocated blocks may get swept up. | |
| 7837 // This is accomplished by the sweeper locking the free lists while | |
| 7838 // it is sweeping. Thus blocks that are determined to be free are | |
| 7839 // indeed free. There is however one additional complication: | |
| 7840 // blocks that have been allocated since the final checkpoint and | |
| 7841 // mark, will not have been marked and so would be treated as | |
| 7842 // unreachable and swept up. To prevent this, the allocator marks | |
| 7843 // the bit map when allocating during the sweep phase. This leads, | |
| 7844 // however, to a further complication -- objects may have been allocated | |
| 7845 // but not yet initialized -- in the sense that the header isn't yet | |
| 7846 // installed. The sweeper can not then determine the size of the block | |
| 7847 // in order to skip over it. To deal with this case, we use a technique | |
| 7848 // (due to Printezis) to encode such uninitialized block sizes in the | |
| 7849 // bit map. Since the bit map uses a bit per every HeapWord, but the | |
| 7850 // CMS generation has a minimum object size of 3 HeapWords, it follows | |
| 7851 // that "normal marks" won't be adjacent in the bit map (there will | |
| 7852 // always be at least two 0 bits between successive 1 bits). We make use | |
| 7853 // of these "unused" bits to represent uninitialized blocks -- the bit | |
| 7854 // corresponding to the start of the uninitialized object and the next | |
| 7855 // bit are both set. Finally, a 1 bit marks the end of the object that | |
| 7856 // started with the two consecutive 1 bits to indicate its potentially | |
| 7857 // uninitialized state. | |
| 7858 | |
| 7859 size_t SweepClosure::do_blk_careful(HeapWord* addr) { | |
| 7860 FreeChunk* fc = (FreeChunk*)addr; | |
| 7861 size_t res; | |
| 7862 | |
| 7863 // check if we are done sweepinrg | |
| 7864 if (addr == _limit) { // we have swept up to the limit, do nothing more | |
| 7865 assert(_limit >= _sp->bottom() && _limit <= _sp->end(), | |
| 7866 "sweep _limit out of bounds"); | |
| 7867 // help the closure application finish | |
| 7868 return pointer_delta(_sp->end(), _limit); | |
| 7869 } | |
| 7870 assert(addr <= _limit, "sweep invariant"); | |
| 7871 | |
| 7872 // check if we should yield | |
| 7873 do_yield_check(addr); | |
| 7874 if (fc->isFree()) { | |
| 7875 // Chunk that is already free | |
| 7876 res = fc->size(); | |
| 7877 doAlreadyFreeChunk(fc); | |
| 7878 debug_only(_sp->verifyFreeLists()); | |
| 7879 assert(res == fc->size(), "Don't expect the size to change"); | |
| 7880 NOT_PRODUCT( | |
| 7881 _numObjectsAlreadyFree++; | |
| 7882 _numWordsAlreadyFree += res; | |
| 7883 ) | |
| 7884 NOT_PRODUCT(_last_fc = fc;) | |
| 7885 } else if (!_bitMap->isMarked(addr)) { | |
| 7886 // Chunk is fresh garbage | |
| 7887 res = doGarbageChunk(fc); | |
| 7888 debug_only(_sp->verifyFreeLists()); | |
| 7889 NOT_PRODUCT( | |
| 7890 _numObjectsFreed++; | |
| 7891 _numWordsFreed += res; | |
| 7892 ) | |
| 7893 } else { | |
| 7894 // Chunk that is alive. | |
| 7895 res = doLiveChunk(fc); | |
| 7896 debug_only(_sp->verifyFreeLists()); | |
| 7897 NOT_PRODUCT( | |
| 7898 _numObjectsLive++; | |
| 7899 _numWordsLive += res; | |
| 7900 ) | |
| 7901 } | |
| 7902 return res; | |
| 7903 } | |
| 7904 | |
| 7905 // For the smart allocation, record following | |
| 7906 // split deaths - a free chunk is removed from its free list because | |
| 7907 // it is being split into two or more chunks. | |
| 7908 // split birth - a free chunk is being added to its free list because | |
| 7909 // a larger free chunk has been split and resulted in this free chunk. | |
| 7910 // coal death - a free chunk is being removed from its free list because | |
| 7911 // it is being coalesced into a large free chunk. | |
| 7912 // coal birth - a free chunk is being added to its free list because | |
| 7913 // it was created when two or more free chunks where coalesced into | |
| 7914 // this free chunk. | |
| 7915 // | |
| 7916 // These statistics are used to determine the desired number of free | |
| 7917 // chunks of a given size. The desired number is chosen to be relative | |
| 7918 // to the end of a CMS sweep. The desired number at the end of a sweep | |
| 7919 // is the | |
| 7920 // count-at-end-of-previous-sweep (an amount that was enough) | |
| 7921 // - count-at-beginning-of-current-sweep (the excess) | |
| 7922 // + split-births (gains in this size during interval) | |
| 7923 // - split-deaths (demands on this size during interval) | |
| 7924 // where the interval is from the end of one sweep to the end of the | |
| 7925 // next. | |
| 7926 // | |
| 7927 // When sweeping the sweeper maintains an accumulated chunk which is | |
| 7928 // the chunk that is made up of chunks that have been coalesced. That | |
| 7929 // will be termed the left-hand chunk. A new chunk of garbage that | |
| 7930 // is being considered for coalescing will be referred to as the | |
| 7931 // right-hand chunk. | |
| 7932 // | |
| 7933 // When making a decision on whether to coalesce a right-hand chunk with | |
| 7934 // the current left-hand chunk, the current count vs. the desired count | |
| 7935 // of the left-hand chunk is considered. Also if the right-hand chunk | |
| 7936 // is near the large chunk at the end of the heap (see | |
| 7937 // ConcurrentMarkSweepGeneration::isNearLargestChunk()), then the | |
| 7938 // left-hand chunk is coalesced. | |
| 7939 // | |
| 7940 // When making a decision about whether to split a chunk, the desired count | |
| 7941 // vs. the current count of the candidate to be split is also considered. | |
| 7942 // If the candidate is underpopulated (currently fewer chunks than desired) | |
| 7943 // a chunk of an overpopulated (currently more chunks than desired) size may | |
| 7944 // be chosen. The "hint" associated with a free list, if non-null, points | |
| 7945 // to a free list which may be overpopulated. | |
| 7946 // | |
| 7947 | |
| 7948 void SweepClosure::doAlreadyFreeChunk(FreeChunk* fc) { | |
| 7949 size_t size = fc->size(); | |
| 7950 // Chunks that cannot be coalesced are not in the | |
| 7951 // free lists. | |
| 7952 if (CMSTestInFreeList && !fc->cantCoalesce()) { | |
| 7953 assert(_sp->verifyChunkInFreeLists(fc), | |
| 7954 "free chunk should be in free lists"); | |
| 7955 } | |
| 7956 // a chunk that is already free, should not have been | |
| 7957 // marked in the bit map | |
| 7958 HeapWord* addr = (HeapWord*) fc; | |
| 7959 assert(!_bitMap->isMarked(addr), "free chunk should be unmarked"); | |
| 7960 // Verify that the bit map has no bits marked between | |
| 7961 // addr and purported end of this block. | |
| 7962 _bitMap->verifyNoOneBitsInRange(addr + 1, addr + size); | |
| 7963 | |
| 7964 // Some chunks cannot be coalesced in under any circumstances. | |
| 7965 // See the definition of cantCoalesce(). | |
| 7966 if (!fc->cantCoalesce()) { | |
| 7967 // This chunk can potentially be coalesced. | |
| 7968 if (_sp->adaptive_freelists()) { | |
| 7969 // All the work is done in | |
| 7970 doPostIsFreeOrGarbageChunk(fc, size); | |
| 7971 } else { // Not adaptive free lists | |
| 7972 // this is a free chunk that can potentially be coalesced by the sweeper; | |
| 7973 if (!inFreeRange()) { | |
| 7974 // if the next chunk is a free block that can't be coalesced | |
| 7975 // it doesn't make sense to remove this chunk from the free lists | |
| 7976 FreeChunk* nextChunk = (FreeChunk*)(addr + size); | |
| 7977 assert((HeapWord*)nextChunk <= _limit, "sweep invariant"); | |
| 7978 if ((HeapWord*)nextChunk < _limit && // there's a next chunk... | |
| 7979 nextChunk->isFree() && // which is free... | |
| 7980 nextChunk->cantCoalesce()) { // ... but cant be coalesced | |
| 7981 // nothing to do | |
| 7982 } else { | |
| 7983 // Potentially the start of a new free range: | |
| 7984 // Don't eagerly remove it from the free lists. | |
| 7985 // No need to remove it if it will just be put | |
| 7986 // back again. (Also from a pragmatic point of view | |
| 7987 // if it is a free block in a region that is beyond | |
| 7988 // any allocated blocks, an assertion will fail) | |
| 7989 // Remember the start of a free run. | |
| 7990 initialize_free_range(addr, true); | |
| 7991 // end - can coalesce with next chunk | |
| 7992 } | |
| 7993 } else { | |
| 7994 // the midst of a free range, we are coalescing | |
| 7995 debug_only(record_free_block_coalesced(fc);) | |
| 7996 if (CMSTraceSweeper) { | |
| 7997 gclog_or_tty->print(" -- pick up free block 0x%x (%d)\n", fc, size); | |
| 7998 } | |
| 7999 // remove it from the free lists | |
| 8000 _sp->removeFreeChunkFromFreeLists(fc); | |
| 8001 set_lastFreeRangeCoalesced(true); | |
| 8002 // If the chunk is being coalesced and the current free range is | |
| 8003 // in the free lists, remove the current free range so that it | |
| 8004 // will be returned to the free lists in its entirety - all | |
| 8005 // the coalesced pieces included. | |
| 8006 if (freeRangeInFreeLists()) { | |
| 8007 FreeChunk* ffc = (FreeChunk*) freeFinger(); | |
| 8008 assert(ffc->size() == pointer_delta(addr, freeFinger()), | |
| 8009 "Size of free range is inconsistent with chunk size."); | |
| 8010 if (CMSTestInFreeList) { | |
| 8011 assert(_sp->verifyChunkInFreeLists(ffc), | |
| 8012 "free range is not in free lists"); | |
| 8013 } | |
| 8014 _sp->removeFreeChunkFromFreeLists(ffc); | |
| 8015 set_freeRangeInFreeLists(false); | |
| 8016 } | |
| 8017 } | |
| 8018 } | |
| 8019 } else { | |
| 8020 // Code path common to both original and adaptive free lists. | |
| 8021 | |
| 8022 // cant coalesce with previous block; this should be treated | |
| 8023 // as the end of a free run if any | |
| 8024 if (inFreeRange()) { | |
| 8025 // we kicked some butt; time to pick up the garbage | |
| 8026 assert(freeFinger() < addr, "the finger pointeth off base"); | |
| 8027 flushCurFreeChunk(freeFinger(), pointer_delta(addr, freeFinger())); | |
| 8028 } | |
| 8029 // else, nothing to do, just continue | |
| 8030 } | |
| 8031 } | |
| 8032 | |
| 8033 size_t SweepClosure::doGarbageChunk(FreeChunk* fc) { | |
| 8034 // This is a chunk of garbage. It is not in any free list. | |
| 8035 // Add it to a free list or let it possibly be coalesced into | |
| 8036 // a larger chunk. | |
| 8037 HeapWord* addr = (HeapWord*) fc; | |
| 8038 size_t size = CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size()); | |
| 8039 | |
| 8040 if (_sp->adaptive_freelists()) { | |
| 8041 // Verify that the bit map has no bits marked between | |
| 8042 // addr and purported end of just dead object. | |
| 8043 _bitMap->verifyNoOneBitsInRange(addr + 1, addr + size); | |
| 8044 | |
| 8045 doPostIsFreeOrGarbageChunk(fc, size); | |
| 8046 } else { | |
| 8047 if (!inFreeRange()) { | |
| 8048 // start of a new free range | |
| 8049 assert(size > 0, "A free range should have a size"); | |
| 8050 initialize_free_range(addr, false); | |
| 8051 | |
| 8052 } else { | |
| 8053 // this will be swept up when we hit the end of the | |
| 8054 // free range | |
| 8055 if (CMSTraceSweeper) { | |
| 8056 gclog_or_tty->print(" -- pick up garbage 0x%x (%d) \n", fc, size); | |
| 8057 } | |
| 8058 // If the chunk is being coalesced and the current free range is | |
| 8059 // in the free lists, remove the current free range so that it | |
| 8060 // will be returned to the free lists in its entirety - all | |
| 8061 // the coalesced pieces included. | |
| 8062 if (freeRangeInFreeLists()) { | |
| 8063 FreeChunk* ffc = (FreeChunk*)freeFinger(); | |
| 8064 assert(ffc->size() == pointer_delta(addr, freeFinger()), | |
| 8065 "Size of free range is inconsistent with chunk size."); | |
| 8066 if (CMSTestInFreeList) { | |
| 8067 assert(_sp->verifyChunkInFreeLists(ffc), | |
| 8068 "free range is not in free lists"); | |
| 8069 } | |
| 8070 _sp->removeFreeChunkFromFreeLists(ffc); | |
| 8071 set_freeRangeInFreeLists(false); | |
| 8072 } | |
| 8073 set_lastFreeRangeCoalesced(true); | |
| 8074 } | |
| 8075 // this will be swept up when we hit the end of the free range | |
| 8076 | |
| 8077 // Verify that the bit map has no bits marked between | |
| 8078 // addr and purported end of just dead object. | |
| 8079 _bitMap->verifyNoOneBitsInRange(addr + 1, addr + size); | |
| 8080 } | |
| 8081 return size; | |
| 8082 } | |
| 8083 | |
| 8084 size_t SweepClosure::doLiveChunk(FreeChunk* fc) { | |
| 8085 HeapWord* addr = (HeapWord*) fc; | |
| 8086 // The sweeper has just found a live object. Return any accumulated | |
| 8087 // left hand chunk to the free lists. | |
| 8088 if (inFreeRange()) { | |
| 8089 if (_sp->adaptive_freelists()) { | |
| 8090 flushCurFreeChunk(freeFinger(), | |
| 8091 pointer_delta(addr, freeFinger())); | |
| 8092 } else { // not adaptive freelists | |
| 8093 set_inFreeRange(false); | |
| 8094 // Add the free range back to the free list if it is not already | |
| 8095 // there. | |
| 8096 if (!freeRangeInFreeLists()) { | |
| 8097 assert(freeFinger() < addr, "the finger pointeth off base"); | |
| 8098 if (CMSTraceSweeper) { | |
| 8099 gclog_or_tty->print("Sweep:put_free_blk 0x%x (%d) " | |
| 8100 "[coalesced:%d]\n", | |
| 8101 freeFinger(), pointer_delta(addr, freeFinger()), | |
| 8102 lastFreeRangeCoalesced()); | |
| 8103 } | |
| 8104 _sp->addChunkAndRepairOffsetTable(freeFinger(), | |
| 8105 pointer_delta(addr, freeFinger()), lastFreeRangeCoalesced()); | |
| 8106 } | |
| 8107 } | |
| 8108 } | |
| 8109 | |
| 8110 // Common code path for original and adaptive free lists. | |
| 8111 | |
| 8112 // this object is live: we'd normally expect this to be | |
| 8113 // an oop, and like to assert the following: | |
| 8114 // assert(oop(addr)->is_oop(), "live block should be an oop"); | |
| 8115 // However, as we commented above, this may be an object whose | |
| 8116 // header hasn't yet been initialized. | |
| 8117 size_t size; | |
| 8118 assert(_bitMap->isMarked(addr), "Tautology for this control point"); | |
| 8119 if (_bitMap->isMarked(addr + 1)) { | |
| 8120 // Determine the size from the bit map, rather than trying to | |
| 8121 // compute it from the object header. | |
| 8122 HeapWord* nextOneAddr = _bitMap->getNextMarkedWordAddress(addr + 2); | |
| 8123 size = pointer_delta(nextOneAddr + 1, addr); | |
| 8124 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
| 8125 "alignment problem"); | |
| 8126 | |
| 8127 #ifdef DEBUG | |
| 187 | 8128 if (oop(addr)->klass_or_null() != NULL && |
|
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8129 ( !_collector->should_unload_classes() |
|
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8130 || (oop(addr)->is_parsable()) && |
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8131 oop(addr)->is_conc_safe())) { |
| 0 | 8132 // Ignore mark word because we are running concurrent with mutators |
| 8133 assert(oop(addr)->is_oop(true), "live block should be an oop"); | |
|
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8134 // is_conc_safe is checked before performing this assertion |
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8135 // because an object that is not is_conc_safe may yet have |
|
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8136 // the return from size() correct. |
| 0 | 8137 assert(size == |
| 8138 CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size()), | |
| 8139 "P-mark and computed size do not agree"); | |
| 8140 } | |
| 8141 #endif | |
| 8142 | |
| 8143 } else { | |
| 8144 // This should be an initialized object that's alive. | |
| 187 | 8145 assert(oop(addr)->klass_or_null() != NULL && |
|
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8146 (!_collector->should_unload_classes() |
| 0 | 8147 || oop(addr)->is_parsable()), |
| 8148 "Should be an initialized object"); | |
|
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8149 // Note that there are objects used during class redefinition |
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8150 // (e.g., merge_cp in VM_RedefineClasses::merge_cp_and_rewrite() |
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8151 // which are discarded with their is_conc_safe state still |
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8152 // false. These object may be floating garbage so may be |
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8153 // seen here. If they are floating garbage their size |
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8154 // should be attainable from their klass. Do not that |
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8155 // is_conc_safe() is true for oop(addr). |
| 0 | 8156 // Ignore mark word because we are running concurrent with mutators |
| 8157 assert(oop(addr)->is_oop(true), "live block should be an oop"); | |
| 8158 // Verify that the bit map has no bits marked between | |
| 8159 // addr and purported end of this block. | |
| 8160 size = CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size()); | |
| 8161 assert(size >= 3, "Necessary for Printezis marks to work"); | |
| 8162 assert(!_bitMap->isMarked(addr+1), "Tautology for this control point"); | |
| 8163 DEBUG_ONLY(_bitMap->verifyNoOneBitsInRange(addr+2, addr+size);) | |
| 8164 } | |
| 8165 return size; | |
| 8166 } | |
| 8167 | |
| 8168 void SweepClosure::doPostIsFreeOrGarbageChunk(FreeChunk* fc, | |
| 8169 size_t chunkSize) { | |
| 8170 // doPostIsFreeOrGarbageChunk() should only be called in the smart allocation | |
| 8171 // scheme. | |
| 8172 bool fcInFreeLists = fc->isFree(); | |
| 8173 assert(_sp->adaptive_freelists(), "Should only be used in this case."); | |
| 8174 assert((HeapWord*)fc <= _limit, "sweep invariant"); | |
| 8175 if (CMSTestInFreeList && fcInFreeLists) { | |
| 8176 assert(_sp->verifyChunkInFreeLists(fc), | |
| 8177 "free chunk is not in free lists"); | |
| 8178 } | |
| 8179 | |
| 8180 | |
| 8181 if (CMSTraceSweeper) { | |
| 8182 gclog_or_tty->print_cr(" -- pick up another chunk at 0x%x (%d)", fc, chunkSize); | |
| 8183 } | |
| 8184 | |
| 8185 HeapWord* addr = (HeapWord*) fc; | |
| 8186 | |
| 8187 bool coalesce; | |
| 8188 size_t left = pointer_delta(addr, freeFinger()); | |
| 8189 size_t right = chunkSize; | |
| 8190 switch (FLSCoalescePolicy) { | |
| 8191 // numeric value forms a coalition aggressiveness metric | |
| 8192 case 0: { // never coalesce | |
| 8193 coalesce = false; | |
| 8194 break; | |
| 8195 } | |
| 8196 case 1: { // coalesce if left & right chunks on overpopulated lists | |
| 8197 coalesce = _sp->coalOverPopulated(left) && | |
| 8198 _sp->coalOverPopulated(right); | |
| 8199 break; | |
| 8200 } | |
| 8201 case 2: { // coalesce if left chunk on overpopulated list (default) | |
| 8202 coalesce = _sp->coalOverPopulated(left); | |
| 8203 break; | |
| 8204 } | |
| 8205 case 3: { // coalesce if left OR right chunk on overpopulated list | |
| 8206 coalesce = _sp->coalOverPopulated(left) || | |
| 8207 _sp->coalOverPopulated(right); | |
| 8208 break; | |
| 8209 } | |
| 8210 case 4: { // always coalesce | |
| 8211 coalesce = true; | |
| 8212 break; | |
| 8213 } | |
| 8214 default: | |
| 8215 ShouldNotReachHere(); | |
| 8216 } | |
| 8217 | |
| 8218 // Should the current free range be coalesced? | |
| 8219 // If the chunk is in a free range and either we decided to coalesce above | |
| 8220 // or the chunk is near the large block at the end of the heap | |
| 8221 // (isNearLargestChunk() returns true), then coalesce this chunk. | |
| 8222 bool doCoalesce = inFreeRange() && | |
| 8223 (coalesce || _g->isNearLargestChunk((HeapWord*)fc)); | |
| 8224 if (doCoalesce) { | |
| 8225 // Coalesce the current free range on the left with the new | |
| 8226 // chunk on the right. If either is on a free list, | |
| 8227 // it must be removed from the list and stashed in the closure. | |
| 8228 if (freeRangeInFreeLists()) { | |
| 8229 FreeChunk* ffc = (FreeChunk*)freeFinger(); | |
| 8230 assert(ffc->size() == pointer_delta(addr, freeFinger()), | |
| 8231 "Size of free range is inconsistent with chunk size."); | |
| 8232 if (CMSTestInFreeList) { | |
| 8233 assert(_sp->verifyChunkInFreeLists(ffc), | |
| 8234 "Chunk is not in free lists"); | |
| 8235 } | |
| 8236 _sp->coalDeath(ffc->size()); | |
| 8237 _sp->removeFreeChunkFromFreeLists(ffc); | |
| 8238 set_freeRangeInFreeLists(false); | |
| 8239 } | |
| 8240 if (fcInFreeLists) { | |
| 8241 _sp->coalDeath(chunkSize); | |
| 8242 assert(fc->size() == chunkSize, | |
| 8243 "The chunk has the wrong size or is not in the free lists"); | |
| 8244 _sp->removeFreeChunkFromFreeLists(fc); | |
| 8245 } | |
| 8246 set_lastFreeRangeCoalesced(true); | |
| 8247 } else { // not in a free range and/or should not coalesce | |
| 8248 // Return the current free range and start a new one. | |
| 8249 if (inFreeRange()) { | |
| 8250 // In a free range but cannot coalesce with the right hand chunk. | |
| 8251 // Put the current free range into the free lists. | |
| 8252 flushCurFreeChunk(freeFinger(), | |
| 8253 pointer_delta(addr, freeFinger())); | |
| 8254 } | |
| 8255 // Set up for new free range. Pass along whether the right hand | |
| 8256 // chunk is in the free lists. | |
| 8257 initialize_free_range((HeapWord*)fc, fcInFreeLists); | |
| 8258 } | |
| 8259 } | |
| 8260 void SweepClosure::flushCurFreeChunk(HeapWord* chunk, size_t size) { | |
| 8261 assert(inFreeRange(), "Should only be called if currently in a free range."); | |
| 8262 assert(size > 0, | |
| 8263 "A zero sized chunk cannot be added to the free lists."); | |
| 8264 if (!freeRangeInFreeLists()) { | |
| 8265 if(CMSTestInFreeList) { | |
| 8266 FreeChunk* fc = (FreeChunk*) chunk; | |
| 8267 fc->setSize(size); | |
| 8268 assert(!_sp->verifyChunkInFreeLists(fc), | |
| 8269 "chunk should not be in free lists yet"); | |
| 8270 } | |
| 8271 if (CMSTraceSweeper) { | |
| 8272 gclog_or_tty->print_cr(" -- add free block 0x%x (%d) to free lists", | |
| 8273 chunk, size); | |
| 8274 } | |
| 8275 // A new free range is going to be starting. The current | |
| 8276 // free range has not been added to the free lists yet or | |
| 8277 // was removed so add it back. | |
| 8278 // If the current free range was coalesced, then the death | |
| 8279 // of the free range was recorded. Record a birth now. | |
| 8280 if (lastFreeRangeCoalesced()) { | |
| 8281 _sp->coalBirth(size); | |
| 8282 } | |
| 8283 _sp->addChunkAndRepairOffsetTable(chunk, size, | |
| 8284 lastFreeRangeCoalesced()); | |
| 8285 } | |
| 8286 set_inFreeRange(false); | |
| 8287 set_freeRangeInFreeLists(false); | |
| 8288 } | |
| 8289 | |
| 8290 // We take a break if we've been at this for a while, | |
| 8291 // so as to avoid monopolizing the locks involved. | |
| 8292 void SweepClosure::do_yield_work(HeapWord* addr) { | |
| 8293 // Return current free chunk being used for coalescing (if any) | |
| 8294 // to the appropriate freelist. After yielding, the next | |
| 8295 // free block encountered will start a coalescing range of | |
| 8296 // free blocks. If the next free block is adjacent to the | |
| 8297 // chunk just flushed, they will need to wait for the next | |
| 8298 // sweep to be coalesced. | |
| 8299 if (inFreeRange()) { | |
| 8300 flushCurFreeChunk(freeFinger(), pointer_delta(addr, freeFinger())); | |
| 8301 } | |
| 8302 | |
| 8303 // First give up the locks, then yield, then re-lock. | |
| 8304 // We should probably use a constructor/destructor idiom to | |
| 8305 // do this unlock/lock or modify the MutexUnlocker class to | |
| 8306 // serve our purpose. XXX | |
| 8307 assert_lock_strong(_bitMap->lock()); | |
| 8308 assert_lock_strong(_freelistLock); | |
| 8309 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 8310 "CMS thread should hold CMS token"); | |
| 8311 _bitMap->lock()->unlock(); | |
| 8312 _freelistLock->unlock(); | |
| 8313 ConcurrentMarkSweepThread::desynchronize(true); | |
| 8314 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 8315 _collector->stopTimer(); | |
| 8316 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
| 8317 if (PrintCMSStatistics != 0) { | |
| 8318 _collector->incrementYields(); | |
| 8319 } | |
| 8320 _collector->icms_wait(); | |
| 8321 | |
| 8322 // See the comment in coordinator_yield() | |
| 8323 for (unsigned i = 0; i < CMSYieldSleepCount && | |
| 8324 ConcurrentMarkSweepThread::should_yield() && | |
| 8325 !CMSCollector::foregroundGCIsActive(); ++i) { | |
| 8326 os::sleep(Thread::current(), 1, false); | |
| 8327 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 8328 } | |
| 8329 | |
| 8330 ConcurrentMarkSweepThread::synchronize(true); | |
| 8331 _freelistLock->lock(); | |
| 8332 _bitMap->lock()->lock_without_safepoint_check(); | |
| 8333 _collector->startTimer(); | |
| 8334 } | |
| 8335 | |
| 8336 #ifndef PRODUCT | |
| 8337 // This is actually very useful in a product build if it can | |
| 8338 // be called from the debugger. Compile it into the product | |
| 8339 // as needed. | |
| 8340 bool debug_verifyChunkInFreeLists(FreeChunk* fc) { | |
| 8341 return debug_cms_space->verifyChunkInFreeLists(fc); | |
| 8342 } | |
| 8343 | |
| 8344 void SweepClosure::record_free_block_coalesced(FreeChunk* fc) const { | |
| 8345 if (CMSTraceSweeper) { | |
| 8346 gclog_or_tty->print("Sweep:coal_free_blk 0x%x (%d)\n", fc, fc->size()); | |
| 8347 } | |
| 8348 } | |
| 8349 #endif | |
| 8350 | |
| 8351 // CMSIsAliveClosure | |
| 8352 bool CMSIsAliveClosure::do_object_b(oop obj) { | |
| 8353 HeapWord* addr = (HeapWord*)obj; | |
| 8354 return addr != NULL && | |
| 8355 (!_span.contains(addr) || _bit_map->isMarked(addr)); | |
| 8356 } | |
| 8357 | |
| 935 | 8358 CMSKeepAliveClosure::CMSKeepAliveClosure( CMSCollector* collector, |
| 8359 MemRegion span, | |
| 8360 CMSBitMap* bit_map, CMSMarkStack* mark_stack, | |
| 8361 CMSMarkStack* revisit_stack, bool cpc): | |
| 8362 KlassRememberingOopClosure(collector, NULL, revisit_stack), | |
| 8363 _span(span), | |
| 8364 _bit_map(bit_map), | |
| 8365 _mark_stack(mark_stack), | |
| 8366 _concurrent_precleaning(cpc) { | |
| 8367 assert(!_span.is_empty(), "Empty span could spell trouble"); | |
| 8368 } | |
| 8369 | |
| 8370 | |
| 0 | 8371 // CMSKeepAliveClosure: the serial version |
|
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8372 void CMSKeepAliveClosure::do_oop(oop obj) { |
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8373 HeapWord* addr = (HeapWord*)obj; |
| 0 | 8374 if (_span.contains(addr) && |
| 8375 !_bit_map->isMarked(addr)) { | |
| 8376 _bit_map->mark(addr); | |
| 8377 bool simulate_overflow = false; | |
| 8378 NOT_PRODUCT( | |
| 8379 if (CMSMarkStackOverflowALot && | |
| 8380 _collector->simulate_overflow()) { | |
| 8381 // simulate a stack overflow | |
| 8382 simulate_overflow = true; | |
| 8383 } | |
| 8384 ) | |
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8385 if (simulate_overflow || !_mark_stack->push(obj)) { |
|
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8386 if (_concurrent_precleaning) { |
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8387 // We dirty the overflown object and let the remark |
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8388 // phase deal with it. |
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8389 assert(_collector->overflow_list_is_empty(), "Error"); |
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8390 // In the case of object arrays, we need to dirty all of |
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8391 // the cards that the object spans. No locking or atomics |
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8392 // are needed since no one else can be mutating the mod union |
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8393 // table. |
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8394 if (obj->is_objArray()) { |
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8395 size_t sz = obj->size(); |
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8396 HeapWord* end_card_addr = |
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8397 (HeapWord*)round_to((intptr_t)(addr+sz), CardTableModRefBS::card_size); |
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8398 MemRegion redirty_range = MemRegion(addr, end_card_addr); |
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8399 assert(!redirty_range.is_empty(), "Arithmetical tautology"); |
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8400 _collector->_modUnionTable.mark_range(redirty_range); |
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8401 } else { |
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8402 _collector->_modUnionTable.mark(addr); |
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8403 } |
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8404 _collector->_ser_kac_preclean_ovflw++; |
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8405 } else { |
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8406 _collector->push_on_overflow_list(obj); |
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8407 _collector->_ser_kac_ovflw++; |
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8408 } |
| 0 | 8409 } |
| 8410 } | |
| 8411 } | |
| 8412 | |
|
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8413 void CMSKeepAliveClosure::do_oop(oop* p) { CMSKeepAliveClosure::do_oop_work(p); } |
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8414 void CMSKeepAliveClosure::do_oop(narrowOop* p) { CMSKeepAliveClosure::do_oop_work(p); } |
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8415 |
| 0 | 8416 // CMSParKeepAliveClosure: a parallel version of the above. |
| 8417 // The work queues are private to each closure (thread), | |
| 8418 // but (may be) available for stealing by other threads. | |
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8419 void CMSParKeepAliveClosure::do_oop(oop obj) { |
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8420 HeapWord* addr = (HeapWord*)obj; |
| 0 | 8421 if (_span.contains(addr) && |
| 8422 !_bit_map->isMarked(addr)) { | |
| 8423 // In general, during recursive tracing, several threads | |
| 8424 // may be concurrently getting here; the first one to | |
| 8425 // "tag" it, claims it. | |
| 8426 if (_bit_map->par_mark(addr)) { | |
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8427 bool res = _work_queue->push(obj); |
| 0 | 8428 assert(res, "Low water mark should be much less than capacity"); |
| 8429 // Do a recursive trim in the hope that this will keep | |
| 8430 // stack usage lower, but leave some oops for potential stealers | |
| 8431 trim_queue(_low_water_mark); | |
| 8432 } // Else, another thread got there first | |
| 8433 } | |
| 8434 } | |
| 8435 | |
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8436 void CMSParKeepAliveClosure::do_oop(oop* p) { CMSParKeepAliveClosure::do_oop_work(p); } |
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8437 void CMSParKeepAliveClosure::do_oop(narrowOop* p) { CMSParKeepAliveClosure::do_oop_work(p); } |
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8438 |
| 0 | 8439 void CMSParKeepAliveClosure::trim_queue(uint max) { |
| 8440 while (_work_queue->size() > max) { | |
| 8441 oop new_oop; | |
| 8442 if (_work_queue->pop_local(new_oop)) { | |
| 8443 assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop"); | |
| 8444 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
| 8445 "no white objects on this stack!"); | |
| 8446 assert(_span.contains((HeapWord*)new_oop), "Out of bounds oop"); | |
| 8447 // iterate over the oops in this oop, marking and pushing | |
| 8448 // the ones in CMS heap (i.e. in _span). | |
| 8449 new_oop->oop_iterate(&_mark_and_push); | |
| 8450 } | |
| 8451 } | |
| 8452 } | |
| 8453 | |
| 935 | 8454 CMSInnerParMarkAndPushClosure::CMSInnerParMarkAndPushClosure( |
| 8455 CMSCollector* collector, | |
| 8456 MemRegion span, CMSBitMap* bit_map, | |
| 8457 CMSMarkStack* revisit_stack, | |
| 8458 OopTaskQueue* work_queue): | |
| 8459 Par_KlassRememberingOopClosure(collector, NULL, revisit_stack), | |
| 8460 _span(span), | |
| 8461 _bit_map(bit_map), | |
| 8462 _work_queue(work_queue) { } | |
| 8463 | |
|
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8464 void CMSInnerParMarkAndPushClosure::do_oop(oop obj) { |
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8465 HeapWord* addr = (HeapWord*)obj; |
| 0 | 8466 if (_span.contains(addr) && |
| 8467 !_bit_map->isMarked(addr)) { | |
| 8468 if (_bit_map->par_mark(addr)) { | |
| 8469 bool simulate_overflow = false; | |
| 8470 NOT_PRODUCT( | |
| 8471 if (CMSMarkStackOverflowALot && | |
| 8472 _collector->par_simulate_overflow()) { | |
| 8473 // simulate a stack overflow | |
| 8474 simulate_overflow = true; | |
| 8475 } | |
| 8476 ) | |
|
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8477 if (simulate_overflow || !_work_queue->push(obj)) { |
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8478 _collector->par_push_on_overflow_list(obj); |
| 0 | 8479 _collector->_par_kac_ovflw++; |
| 8480 } | |
| 8481 } // Else another thread got there already | |
| 8482 } | |
| 8483 } | |
| 8484 | |
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8485 void CMSInnerParMarkAndPushClosure::do_oop(oop* p) { CMSInnerParMarkAndPushClosure::do_oop_work(p); } |
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8486 void CMSInnerParMarkAndPushClosure::do_oop(narrowOop* p) { CMSInnerParMarkAndPushClosure::do_oop_work(p); } |
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8487 |
| 0 | 8488 ////////////////////////////////////////////////////////////////// |
| 8489 // CMSExpansionCause ///////////////////////////// | |
| 8490 ////////////////////////////////////////////////////////////////// | |
| 8491 const char* CMSExpansionCause::to_string(CMSExpansionCause::Cause cause) { | |
| 8492 switch (cause) { | |
| 8493 case _no_expansion: | |
| 8494 return "No expansion"; | |
| 8495 case _satisfy_free_ratio: | |
| 8496 return "Free ratio"; | |
| 8497 case _satisfy_promotion: | |
| 8498 return "Satisfy promotion"; | |
| 8499 case _satisfy_allocation: | |
| 8500 return "allocation"; | |
| 8501 case _allocate_par_lab: | |
| 8502 return "Par LAB"; | |
| 8503 case _allocate_par_spooling_space: | |
| 8504 return "Par Spooling Space"; | |
| 8505 case _adaptive_size_policy: | |
| 8506 return "Ergonomics"; | |
| 8507 default: | |
| 8508 return "unknown"; | |
| 8509 } | |
| 8510 } | |
| 8511 | |
| 8512 void CMSDrainMarkingStackClosure::do_void() { | |
| 8513 // the max number to take from overflow list at a time | |
| 8514 const size_t num = _mark_stack->capacity()/4; | |
|
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8515 assert(!_concurrent_precleaning || _collector->overflow_list_is_empty(), |
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8516 "Overflow list should be NULL during concurrent phases"); |
| 0 | 8517 while (!_mark_stack->isEmpty() || |
| 8518 // if stack is empty, check the overflow list | |
| 8519 _collector->take_from_overflow_list(num, _mark_stack)) { | |
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8520 oop obj = _mark_stack->pop(); |
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8521 HeapWord* addr = (HeapWord*)obj; |
| 0 | 8522 assert(_span.contains(addr), "Should be within span"); |
| 8523 assert(_bit_map->isMarked(addr), "Should be marked"); | |
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8524 assert(obj->is_oop(), "Should be an oop"); |
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8525 obj->oop_iterate(_keep_alive); |
| 0 | 8526 } |
| 8527 } | |
| 8528 | |
| 8529 void CMSParDrainMarkingStackClosure::do_void() { | |
| 8530 // drain queue | |
| 8531 trim_queue(0); | |
| 8532 } | |
| 8533 | |
| 8534 // Trim our work_queue so its length is below max at return | |
| 8535 void CMSParDrainMarkingStackClosure::trim_queue(uint max) { | |
| 8536 while (_work_queue->size() > max) { | |
| 8537 oop new_oop; | |
| 8538 if (_work_queue->pop_local(new_oop)) { | |
| 8539 assert(new_oop->is_oop(), "Expected an oop"); | |
| 8540 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
| 8541 "no white objects on this stack!"); | |
| 8542 assert(_span.contains((HeapWord*)new_oop), "Out of bounds oop"); | |
| 8543 // iterate over the oops in this oop, marking and pushing | |
| 8544 // the ones in CMS heap (i.e. in _span). | |
| 8545 new_oop->oop_iterate(&_mark_and_push); | |
| 8546 } | |
| 8547 } | |
| 8548 } | |
| 8549 | |
| 8550 //////////////////////////////////////////////////////////////////// | |
| 8551 // Support for Marking Stack Overflow list handling and related code | |
| 8552 //////////////////////////////////////////////////////////////////// | |
| 8553 // Much of the following code is similar in shape and spirit to the | |
| 8554 // code used in ParNewGC. We should try and share that code | |
| 8555 // as much as possible in the future. | |
| 8556 | |
| 8557 #ifndef PRODUCT | |
| 8558 // Debugging support for CMSStackOverflowALot | |
| 8559 | |
| 8560 // It's OK to call this multi-threaded; the worst thing | |
| 8561 // that can happen is that we'll get a bunch of closely | |
| 8562 // spaced simulated oveflows, but that's OK, in fact | |
| 8563 // probably good as it would exercise the overflow code | |
| 8564 // under contention. | |
| 8565 bool CMSCollector::simulate_overflow() { | |
| 8566 if (_overflow_counter-- <= 0) { // just being defensive | |
| 8567 _overflow_counter = CMSMarkStackOverflowInterval; | |
| 8568 return true; | |
| 8569 } else { | |
| 8570 return false; | |
| 8571 } | |
| 8572 } | |
| 8573 | |
| 8574 bool CMSCollector::par_simulate_overflow() { | |
| 8575 return simulate_overflow(); | |
| 8576 } | |
| 8577 #endif | |
| 8578 | |
| 8579 // Single-threaded | |
| 8580 bool CMSCollector::take_from_overflow_list(size_t num, CMSMarkStack* stack) { | |
| 8581 assert(stack->isEmpty(), "Expected precondition"); | |
| 8582 assert(stack->capacity() > num, "Shouldn't bite more than can chew"); | |
| 8583 size_t i = num; | |
| 8584 oop cur = _overflow_list; | |
| 8585 const markOop proto = markOopDesc::prototype(); | |
| 534 | 8586 NOT_PRODUCT(ssize_t n = 0;) |
| 0 | 8587 for (oop next; i > 0 && cur != NULL; cur = next, i--) { |
| 8588 next = oop(cur->mark()); | |
| 8589 cur->set_mark(proto); // until proven otherwise | |
| 8590 assert(cur->is_oop(), "Should be an oop"); | |
| 8591 bool res = stack->push(cur); | |
| 8592 assert(res, "Bit off more than can chew?"); | |
| 8593 NOT_PRODUCT(n++;) | |
| 8594 } | |
| 8595 _overflow_list = cur; | |
| 8596 #ifndef PRODUCT | |
| 8597 assert(_num_par_pushes >= n, "Too many pops?"); | |
| 8598 _num_par_pushes -=n; | |
| 8599 #endif | |
| 8600 return !stack->isEmpty(); | |
| 8601 } | |
| 8602 | |
| 534 | 8603 #define BUSY (oop(0x1aff1aff)) |
| 8604 // (MT-safe) Get a prefix of at most "num" from the list. | |
| 8605 // The overflow list is chained through the mark word of | |
| 8606 // each object in the list. We fetch the entire list, | |
| 8607 // break off a prefix of the right size and return the | |
| 8608 // remainder. If other threads try to take objects from | |
| 8609 // the overflow list at that time, they will wait for | |
| 8610 // some time to see if data becomes available. If (and | |
| 8611 // only if) another thread places one or more object(s) | |
| 8612 // on the global list before we have returned the suffix | |
| 8613 // to the global list, we will walk down our local list | |
| 8614 // to find its end and append the global list to | |
| 8615 // our suffix before returning it. This suffix walk can | |
| 8616 // prove to be expensive (quadratic in the amount of traffic) | |
| 8617 // when there are many objects in the overflow list and | |
| 8618 // there is much producer-consumer contention on the list. | |
| 8619 // *NOTE*: The overflow list manipulation code here and | |
| 8620 // in ParNewGeneration:: are very similar in shape, | |
| 8621 // except that in the ParNew case we use the old (from/eden) | |
| 8622 // copy of the object to thread the list via its klass word. | |
| 8623 // Because of the common code, if you make any changes in | |
| 8624 // the code below, please check the ParNew version to see if | |
| 8625 // similar changes might be needed. | |
| 8626 // CR 6797058 has been filed to consolidate the common code. | |
| 0 | 8627 bool CMSCollector::par_take_from_overflow_list(size_t num, |
| 8628 OopTaskQueue* work_q) { | |
| 534 | 8629 assert(work_q->size() == 0, "First empty local work queue"); |
| 0 | 8630 assert(num < work_q->max_elems(), "Can't bite more than we can chew"); |
| 8631 if (_overflow_list == NULL) { | |
| 8632 return false; | |
| 8633 } | |
| 8634 // Grab the entire list; we'll put back a suffix | |
| 534 | 8635 oop prefix = (oop)Atomic::xchg_ptr(BUSY, &_overflow_list); |
| 8636 Thread* tid = Thread::current(); | |
| 8637 size_t CMSOverflowSpinCount = (size_t)ParallelGCThreads; | |
| 8638 size_t sleep_time_millis = MAX2((size_t)1, num/100); | |
| 8639 // If the list is busy, we spin for a short while, | |
| 8640 // sleeping between attempts to get the list. | |
| 8641 for (size_t spin = 0; prefix == BUSY && spin < CMSOverflowSpinCount; spin++) { | |
| 8642 os::sleep(tid, sleep_time_millis, false); | |
| 8643 if (_overflow_list == NULL) { | |
| 8644 // Nothing left to take | |
| 8645 return false; | |
| 8646 } else if (_overflow_list != BUSY) { | |
| 8647 // Try and grab the prefix | |
| 8648 prefix = (oop)Atomic::xchg_ptr(BUSY, &_overflow_list); | |
| 8649 } | |
| 8650 } | |
| 8651 // If the list was found to be empty, or we spun long | |
| 8652 // enough, we give up and return empty-handed. If we leave | |
| 8653 // the list in the BUSY state below, it must be the case that | |
| 8654 // some other thread holds the overflow list and will set it | |
| 8655 // to a non-BUSY state in the future. | |
| 8656 if (prefix == NULL || prefix == BUSY) { | |
| 8657 // Nothing to take or waited long enough | |
| 8658 if (prefix == NULL) { | |
| 8659 // Write back the NULL in case we overwrote it with BUSY above | |
| 8660 // and it is still the same value. | |
| 8661 (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY); | |
| 8662 } | |
| 8663 return false; | |
| 8664 } | |
| 8665 assert(prefix != NULL && prefix != BUSY, "Error"); | |
| 0 | 8666 size_t i = num; |
| 8667 oop cur = prefix; | |
| 534 | 8668 // Walk down the first "num" objects, unless we reach the end. |
| 0 | 8669 for (; i > 1 && cur->mark() != NULL; cur = oop(cur->mark()), i--); |
| 534 | 8670 if (cur->mark() == NULL) { |
| 8671 // We have "num" or fewer elements in the list, so there | |
| 8672 // is nothing to return to the global list. | |
| 8673 // Write back the NULL in lieu of the BUSY we wrote | |
| 8674 // above, if it is still the same value. | |
| 8675 if (_overflow_list == BUSY) { | |
| 8676 (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY); | |
| 8677 } | |
| 8678 } else { | |
| 8679 // Chop off the suffix and rerturn it to the global list. | |
| 8680 assert(cur->mark() != BUSY, "Error"); | |
| 0 | 8681 oop suffix_head = cur->mark(); // suffix will be put back on global list |
| 8682 cur->set_mark(NULL); // break off suffix | |
| 534 | 8683 // It's possible that the list is still in the empty(busy) state |
| 8684 // we left it in a short while ago; in that case we may be | |
| 8685 // able to place back the suffix without incurring the cost | |
| 8686 // of a walk down the list. | |
| 0 | 8687 oop observed_overflow_list = _overflow_list; |
| 534 | 8688 oop cur_overflow_list = observed_overflow_list; |
| 8689 bool attached = false; | |
| 8690 while (observed_overflow_list == BUSY || observed_overflow_list == NULL) { | |
| 0 | 8691 observed_overflow_list = |
| 534 | 8692 (oop) Atomic::cmpxchg_ptr(suffix_head, &_overflow_list, cur_overflow_list); |
| 8693 if (cur_overflow_list == observed_overflow_list) { | |
| 8694 attached = true; | |
| 8695 break; | |
| 8696 } else cur_overflow_list = observed_overflow_list; | |
| 8697 } | |
| 8698 if (!attached) { | |
| 8699 // Too bad, someone else sneaked in (at least) an element; we'll need | |
| 8700 // to do a splice. Find tail of suffix so we can prepend suffix to global | |
| 8701 // list. | |
| 8702 for (cur = suffix_head; cur->mark() != NULL; cur = (oop)(cur->mark())); | |
| 8703 oop suffix_tail = cur; | |
| 8704 assert(suffix_tail != NULL && suffix_tail->mark() == NULL, | |
| 8705 "Tautology"); | |
| 8706 observed_overflow_list = _overflow_list; | |
| 8707 do { | |
| 8708 cur_overflow_list = observed_overflow_list; | |
| 8709 if (cur_overflow_list != BUSY) { | |
| 8710 // Do the splice ... | |
| 8711 suffix_tail->set_mark(markOop(cur_overflow_list)); | |
| 8712 } else { // cur_overflow_list == BUSY | |
| 8713 suffix_tail->set_mark(NULL); | |
| 8714 } | |
| 8715 // ... and try to place spliced list back on overflow_list ... | |
| 8716 observed_overflow_list = | |
| 8717 (oop) Atomic::cmpxchg_ptr(suffix_head, &_overflow_list, cur_overflow_list); | |
| 8718 } while (cur_overflow_list != observed_overflow_list); | |
| 8719 // ... until we have succeeded in doing so. | |
| 8720 } | |
| 0 | 8721 } |
| 8722 | |
| 8723 // Push the prefix elements on work_q | |
| 8724 assert(prefix != NULL, "control point invariant"); | |
| 8725 const markOop proto = markOopDesc::prototype(); | |
| 8726 oop next; | |
| 534 | 8727 NOT_PRODUCT(ssize_t n = 0;) |
| 0 | 8728 for (cur = prefix; cur != NULL; cur = next) { |
| 8729 next = oop(cur->mark()); | |
| 8730 cur->set_mark(proto); // until proven otherwise | |
| 8731 assert(cur->is_oop(), "Should be an oop"); | |
| 8732 bool res = work_q->push(cur); | |
| 8733 assert(res, "Bit off more than we can chew?"); | |
| 8734 NOT_PRODUCT(n++;) | |
| 8735 } | |
| 8736 #ifndef PRODUCT | |
| 8737 assert(_num_par_pushes >= n, "Too many pops?"); | |
| 8738 Atomic::add_ptr(-(intptr_t)n, &_num_par_pushes); | |
| 8739 #endif | |
| 8740 return true; | |
| 8741 } | |
| 8742 | |
| 8743 // Single-threaded | |
| 8744 void CMSCollector::push_on_overflow_list(oop p) { | |
| 8745 NOT_PRODUCT(_num_par_pushes++;) | |
| 8746 assert(p->is_oop(), "Not an oop"); | |
| 8747 preserve_mark_if_necessary(p); | |
| 8748 p->set_mark((markOop)_overflow_list); | |
| 8749 _overflow_list = p; | |
| 8750 } | |
| 8751 | |
| 8752 // Multi-threaded; use CAS to prepend to overflow list | |
| 8753 void CMSCollector::par_push_on_overflow_list(oop p) { | |
| 8754 NOT_PRODUCT(Atomic::inc_ptr(&_num_par_pushes);) | |
| 8755 assert(p->is_oop(), "Not an oop"); | |
| 8756 par_preserve_mark_if_necessary(p); | |
| 8757 oop observed_overflow_list = _overflow_list; | |
| 8758 oop cur_overflow_list; | |
| 8759 do { | |
| 8760 cur_overflow_list = observed_overflow_list; | |
| 534 | 8761 if (cur_overflow_list != BUSY) { |
| 8762 p->set_mark(markOop(cur_overflow_list)); | |
| 8763 } else { | |
| 8764 p->set_mark(NULL); | |
| 8765 } | |
| 0 | 8766 observed_overflow_list = |
| 8767 (oop) Atomic::cmpxchg_ptr(p, &_overflow_list, cur_overflow_list); | |
| 8768 } while (cur_overflow_list != observed_overflow_list); | |
| 8769 } | |
| 534 | 8770 #undef BUSY |
| 0 | 8771 |
| 8772 // Single threaded | |
| 8773 // General Note on GrowableArray: pushes may silently fail | |
| 8774 // because we are (temporarily) out of C-heap for expanding | |
| 8775 // the stack. The problem is quite ubiquitous and affects | |
| 8776 // a lot of code in the JVM. The prudent thing for GrowableArray | |
| 8777 // to do (for now) is to exit with an error. However, that may | |
| 8778 // be too draconian in some cases because the caller may be | |
| 534 | 8779 // able to recover without much harm. For such cases, we |
| 0 | 8780 // should probably introduce a "soft_push" method which returns |
| 8781 // an indication of success or failure with the assumption that | |
| 8782 // the caller may be able to recover from a failure; code in | |
| 8783 // the VM can then be changed, incrementally, to deal with such | |
| 8784 // failures where possible, thus, incrementally hardening the VM | |
| 8785 // in such low resource situations. | |
| 8786 void CMSCollector::preserve_mark_work(oop p, markOop m) { | |
| 8787 if (_preserved_oop_stack == NULL) { | |
| 8788 assert(_preserved_mark_stack == NULL, | |
| 8789 "bijection with preserved_oop_stack"); | |
| 8790 // Allocate the stacks | |
| 8791 _preserved_oop_stack = new (ResourceObj::C_HEAP) | |
| 8792 GrowableArray<oop>(PreserveMarkStackSize, true); | |
| 8793 _preserved_mark_stack = new (ResourceObj::C_HEAP) | |
| 8794 GrowableArray<markOop>(PreserveMarkStackSize, true); | |
| 8795 if (_preserved_oop_stack == NULL || _preserved_mark_stack == NULL) { | |
| 8796 vm_exit_out_of_memory(2* PreserveMarkStackSize * sizeof(oop) /* punt */, | |
| 8797 "Preserved Mark/Oop Stack for CMS (C-heap)"); | |
| 8798 } | |
| 8799 } | |
| 8800 _preserved_oop_stack->push(p); | |
| 8801 _preserved_mark_stack->push(m); | |
| 8802 assert(m == p->mark(), "Mark word changed"); | |
| 8803 assert(_preserved_oop_stack->length() == _preserved_mark_stack->length(), | |
| 8804 "bijection"); | |
| 8805 } | |
| 8806 | |
| 8807 // Single threaded | |
| 8808 void CMSCollector::preserve_mark_if_necessary(oop p) { | |
| 8809 markOop m = p->mark(); | |
| 8810 if (m->must_be_preserved(p)) { | |
| 8811 preserve_mark_work(p, m); | |
| 8812 } | |
| 8813 } | |
| 8814 | |
| 8815 void CMSCollector::par_preserve_mark_if_necessary(oop p) { | |
| 8816 markOop m = p->mark(); | |
| 8817 if (m->must_be_preserved(p)) { | |
| 8818 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); | |
| 8819 // Even though we read the mark word without holding | |
| 8820 // the lock, we are assured that it will not change | |
| 8821 // because we "own" this oop, so no other thread can | |
| 8822 // be trying to push it on the overflow list; see | |
| 8823 // the assertion in preserve_mark_work() that checks | |
| 8824 // that m == p->mark(). | |
| 8825 preserve_mark_work(p, m); | |
| 8826 } | |
| 8827 } | |
| 8828 | |
| 8829 // We should be able to do this multi-threaded, | |
| 8830 // a chunk of stack being a task (this is | |
| 8831 // correct because each oop only ever appears | |
| 8832 // once in the overflow list. However, it's | |
| 8833 // not very easy to completely overlap this with | |
| 8834 // other operations, so will generally not be done | |
| 8835 // until all work's been completed. Because we | |
| 8836 // expect the preserved oop stack (set) to be small, | |
| 8837 // it's probably fine to do this single-threaded. | |
| 8838 // We can explore cleverer concurrent/overlapped/parallel | |
| 8839 // processing of preserved marks if we feel the | |
| 8840 // need for this in the future. Stack overflow should | |
| 8841 // be so rare in practice and, when it happens, its | |
| 8842 // effect on performance so great that this will | |
| 8843 // likely just be in the noise anyway. | |
| 8844 void CMSCollector::restore_preserved_marks_if_any() { | |
| 8845 if (_preserved_oop_stack == NULL) { | |
| 8846 assert(_preserved_mark_stack == NULL, | |
| 8847 "bijection with preserved_oop_stack"); | |
| 8848 return; | |
| 8849 } | |
| 8850 | |
| 8851 assert(SafepointSynchronize::is_at_safepoint(), | |
| 8852 "world should be stopped"); | |
| 8853 assert(Thread::current()->is_ConcurrentGC_thread() || | |
| 8854 Thread::current()->is_VM_thread(), | |
| 8855 "should be single-threaded"); | |
| 8856 | |
| 8857 int length = _preserved_oop_stack->length(); | |
| 8858 assert(_preserved_mark_stack->length() == length, "bijection"); | |
| 8859 for (int i = 0; i < length; i++) { | |
| 8860 oop p = _preserved_oop_stack->at(i); | |
| 8861 assert(p->is_oop(), "Should be an oop"); | |
| 8862 assert(_span.contains(p), "oop should be in _span"); | |
| 8863 assert(p->mark() == markOopDesc::prototype(), | |
| 8864 "Set when taken from overflow list"); | |
| 8865 markOop m = _preserved_mark_stack->at(i); | |
| 8866 p->set_mark(m); | |
| 8867 } | |
| 8868 _preserved_mark_stack->clear(); | |
| 8869 _preserved_oop_stack->clear(); | |
| 8870 assert(_preserved_mark_stack->is_empty() && | |
| 8871 _preserved_oop_stack->is_empty(), | |
| 8872 "stacks were cleared above"); | |
| 8873 } | |
| 8874 | |
| 8875 #ifndef PRODUCT | |
| 8876 bool CMSCollector::no_preserved_marks() const { | |
| 8877 return ( ( _preserved_mark_stack == NULL | |
| 8878 && _preserved_oop_stack == NULL) | |
| 8879 || ( _preserved_mark_stack->is_empty() | |
| 8880 && _preserved_oop_stack->is_empty())); | |
| 8881 } | |
| 8882 #endif | |
| 8883 | |
| 8884 CMSAdaptiveSizePolicy* ASConcurrentMarkSweepGeneration::cms_size_policy() const | |
| 8885 { | |
| 8886 GenCollectedHeap* gch = (GenCollectedHeap*) GenCollectedHeap::heap(); | |
| 8887 CMSAdaptiveSizePolicy* size_policy = | |
| 8888 (CMSAdaptiveSizePolicy*) gch->gen_policy()->size_policy(); | |
| 8889 assert(size_policy->is_gc_cms_adaptive_size_policy(), | |
| 8890 "Wrong type for size policy"); | |
| 8891 return size_policy; | |
| 8892 } | |
| 8893 | |
| 8894 void ASConcurrentMarkSweepGeneration::resize(size_t cur_promo_size, | |
| 8895 size_t desired_promo_size) { | |
| 8896 if (cur_promo_size < desired_promo_size) { | |
| 8897 size_t expand_bytes = desired_promo_size - cur_promo_size; | |
| 8898 if (PrintAdaptiveSizePolicy && Verbose) { | |
| 8899 gclog_or_tty->print_cr(" ASConcurrentMarkSweepGeneration::resize " | |
| 8900 "Expanding tenured generation by " SIZE_FORMAT " (bytes)", | |
| 8901 expand_bytes); | |
| 8902 } | |
| 8903 expand(expand_bytes, | |
| 8904 MinHeapDeltaBytes, | |
| 8905 CMSExpansionCause::_adaptive_size_policy); | |
| 8906 } else if (desired_promo_size < cur_promo_size) { | |
| 8907 size_t shrink_bytes = cur_promo_size - desired_promo_size; | |
| 8908 if (PrintAdaptiveSizePolicy && Verbose) { | |
| 8909 gclog_or_tty->print_cr(" ASConcurrentMarkSweepGeneration::resize " | |
| 8910 "Shrinking tenured generation by " SIZE_FORMAT " (bytes)", | |
| 8911 shrink_bytes); | |
| 8912 } | |
| 8913 shrink(shrink_bytes); | |
| 8914 } | |
| 8915 } | |
| 8916 | |
| 8917 CMSGCAdaptivePolicyCounters* ASConcurrentMarkSweepGeneration::gc_adaptive_policy_counters() { | |
| 8918 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 8919 CMSGCAdaptivePolicyCounters* counters = | |
| 8920 (CMSGCAdaptivePolicyCounters*) gch->collector_policy()->counters(); | |
| 8921 assert(counters->kind() == GCPolicyCounters::CMSGCAdaptivePolicyCountersKind, | |
| 8922 "Wrong kind of counters"); | |
| 8923 return counters; | |
| 8924 } | |
| 8925 | |
| 8926 | |
| 8927 void ASConcurrentMarkSweepGeneration::update_counters() { | |
| 8928 if (UsePerfData) { | |
| 8929 _space_counters->update_all(); | |
| 8930 _gen_counters->update_all(); | |
| 8931 CMSGCAdaptivePolicyCounters* counters = gc_adaptive_policy_counters(); | |
| 8932 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 8933 CMSGCStats* gc_stats_l = (CMSGCStats*) gc_stats(); | |
| 8934 assert(gc_stats_l->kind() == GCStats::CMSGCStatsKind, | |
| 8935 "Wrong gc statistics type"); | |
| 8936 counters->update_counters(gc_stats_l); | |
| 8937 } | |
| 8938 } | |
| 8939 | |
| 8940 void ASConcurrentMarkSweepGeneration::update_counters(size_t used) { | |
| 8941 if (UsePerfData) { | |
| 8942 _space_counters->update_used(used); | |
| 8943 _space_counters->update_capacity(); | |
| 8944 _gen_counters->update_all(); | |
| 8945 | |
| 8946 CMSGCAdaptivePolicyCounters* counters = gc_adaptive_policy_counters(); | |
| 8947 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 8948 CMSGCStats* gc_stats_l = (CMSGCStats*) gc_stats(); | |
| 8949 assert(gc_stats_l->kind() == GCStats::CMSGCStatsKind, | |
| 8950 "Wrong gc statistics type"); | |
| 8951 counters->update_counters(gc_stats_l); | |
| 8952 } | |
| 8953 } | |
| 8954 | |
| 8955 // The desired expansion delta is computed so that: | |
| 8956 // . desired free percentage or greater is used | |
| 8957 void ASConcurrentMarkSweepGeneration::compute_new_size() { | |
| 8958 assert_locked_or_safepoint(Heap_lock); | |
| 8959 | |
| 8960 GenCollectedHeap* gch = (GenCollectedHeap*) GenCollectedHeap::heap(); | |
| 8961 | |
| 8962 // If incremental collection failed, we just want to expand | |
| 8963 // to the limit. | |
| 8964 if (incremental_collection_failed()) { | |
| 8965 clear_incremental_collection_failed(); | |
| 8966 grow_to_reserved(); | |
| 8967 return; | |
| 8968 } | |
| 8969 | |
| 8970 assert(UseAdaptiveSizePolicy, "Should be using adaptive sizing"); | |
| 8971 | |
| 8972 assert(gch->kind() == CollectedHeap::GenCollectedHeap, | |
| 8973 "Wrong type of heap"); | |
| 8974 int prev_level = level() - 1; | |
| 8975 assert(prev_level >= 0, "The cms generation is the lowest generation"); | |
| 8976 Generation* prev_gen = gch->get_gen(prev_level); | |
| 8977 assert(prev_gen->kind() == Generation::ASParNew, | |
| 8978 "Wrong type of young generation"); | |
| 8979 ParNewGeneration* younger_gen = (ParNewGeneration*) prev_gen; | |
| 8980 size_t cur_eden = younger_gen->eden()->capacity(); | |
| 8981 CMSAdaptiveSizePolicy* size_policy = cms_size_policy(); | |
| 8982 size_t cur_promo = free(); | |
| 8983 size_policy->compute_tenured_generation_free_space(cur_promo, | |
| 8984 max_available(), | |
| 8985 cur_eden); | |
| 8986 resize(cur_promo, size_policy->promo_size()); | |
| 8987 | |
| 8988 // Record the new size of the space in the cms generation | |
| 8989 // that is available for promotions. This is temporary. | |
| 8990 // It should be the desired promo size. | |
| 8991 size_policy->avg_cms_promo()->sample(free()); | |
| 8992 size_policy->avg_old_live()->sample(used()); | |
| 8993 | |
| 8994 if (UsePerfData) { | |
| 8995 CMSGCAdaptivePolicyCounters* counters = gc_adaptive_policy_counters(); | |
| 8996 counters->update_cms_capacity_counter(capacity()); | |
| 8997 } | |
| 8998 } | |
| 8999 | |
| 9000 void ASConcurrentMarkSweepGeneration::shrink_by(size_t desired_bytes) { | |
| 9001 assert_locked_or_safepoint(Heap_lock); | |
| 9002 assert_lock_strong(freelistLock()); | |
| 9003 HeapWord* old_end = _cmsSpace->end(); | |
| 9004 HeapWord* unallocated_start = _cmsSpace->unallocated_block(); | |
| 9005 assert(old_end >= unallocated_start, "Miscalculation of unallocated_start"); | |
| 9006 FreeChunk* chunk_at_end = find_chunk_at_end(); | |
| 9007 if (chunk_at_end == NULL) { | |
| 9008 // No room to shrink | |
| 9009 if (PrintGCDetails && Verbose) { | |
| 9010 gclog_or_tty->print_cr("No room to shrink: old_end " | |
| 9011 PTR_FORMAT " unallocated_start " PTR_FORMAT | |
| 9012 " chunk_at_end " PTR_FORMAT, | |
| 9013 old_end, unallocated_start, chunk_at_end); | |
| 9014 } | |
| 9015 return; | |
| 9016 } else { | |
| 9017 | |
| 9018 // Find the chunk at the end of the space and determine | |
| 9019 // how much it can be shrunk. | |
| 9020 size_t shrinkable_size_in_bytes = chunk_at_end->size(); | |
| 9021 size_t aligned_shrinkable_size_in_bytes = | |
| 9022 align_size_down(shrinkable_size_in_bytes, os::vm_page_size()); | |
| 9023 assert(unallocated_start <= chunk_at_end->end(), | |
| 9024 "Inconsistent chunk at end of space"); | |
| 9025 size_t bytes = MIN2(desired_bytes, aligned_shrinkable_size_in_bytes); | |
| 9026 size_t word_size_before = heap_word_size(_virtual_space.committed_size()); | |
| 9027 | |
| 9028 // Shrink the underlying space | |
| 9029 _virtual_space.shrink_by(bytes); | |
| 9030 if (PrintGCDetails && Verbose) { | |
| 9031 gclog_or_tty->print_cr("ConcurrentMarkSweepGeneration::shrink_by:" | |
| 9032 " desired_bytes " SIZE_FORMAT | |
| 9033 " shrinkable_size_in_bytes " SIZE_FORMAT | |
| 9034 " aligned_shrinkable_size_in_bytes " SIZE_FORMAT | |
| 9035 " bytes " SIZE_FORMAT, | |
| 9036 desired_bytes, shrinkable_size_in_bytes, | |
| 9037 aligned_shrinkable_size_in_bytes, bytes); | |
| 9038 gclog_or_tty->print_cr(" old_end " SIZE_FORMAT | |
| 9039 " unallocated_start " SIZE_FORMAT, | |
| 9040 old_end, unallocated_start); | |
| 9041 } | |
| 9042 | |
| 9043 // If the space did shrink (shrinking is not guaranteed), | |
| 9044 // shrink the chunk at the end by the appropriate amount. | |
| 9045 if (((HeapWord*)_virtual_space.high()) < old_end) { | |
| 9046 size_t new_word_size = | |
| 9047 heap_word_size(_virtual_space.committed_size()); | |
| 9048 | |
| 9049 // Have to remove the chunk from the dictionary because it is changing | |
| 9050 // size and might be someplace elsewhere in the dictionary. | |
| 9051 | |
| 9052 // Get the chunk at end, shrink it, and put it | |
| 9053 // back. | |
| 9054 _cmsSpace->removeChunkFromDictionary(chunk_at_end); | |
| 9055 size_t word_size_change = word_size_before - new_word_size; | |
| 9056 size_t chunk_at_end_old_size = chunk_at_end->size(); | |
| 9057 assert(chunk_at_end_old_size >= word_size_change, | |
| 9058 "Shrink is too large"); | |
| 9059 chunk_at_end->setSize(chunk_at_end_old_size - | |
| 9060 word_size_change); | |
| 9061 _cmsSpace->freed((HeapWord*) chunk_at_end->end(), | |
| 9062 word_size_change); | |
| 9063 | |
| 9064 _cmsSpace->returnChunkToDictionary(chunk_at_end); | |
| 9065 | |
| 9066 MemRegion mr(_cmsSpace->bottom(), new_word_size); | |
| 9067 _bts->resize(new_word_size); // resize the block offset shared array | |
| 9068 Universe::heap()->barrier_set()->resize_covered_region(mr); | |
| 9069 _cmsSpace->assert_locked(); | |
| 9070 _cmsSpace->set_end((HeapWord*)_virtual_space.high()); | |
| 9071 | |
| 9072 NOT_PRODUCT(_cmsSpace->dictionary()->verify()); | |
| 9073 | |
| 9074 // update the space and generation capacity counters | |
| 9075 if (UsePerfData) { | |
| 9076 _space_counters->update_capacity(); | |
| 9077 _gen_counters->update_all(); | |
| 9078 } | |
| 9079 | |
| 9080 if (Verbose && PrintGCDetails) { | |
| 9081 size_t new_mem_size = _virtual_space.committed_size(); | |
| 9082 size_t old_mem_size = new_mem_size + bytes; | |
| 9083 gclog_or_tty->print_cr("Shrinking %s from %ldK by %ldK to %ldK", | |
| 9084 name(), old_mem_size/K, bytes/K, new_mem_size/K); | |
| 9085 } | |
| 9086 } | |
| 9087 | |
| 9088 assert(_cmsSpace->unallocated_block() <= _cmsSpace->end(), | |
| 9089 "Inconsistency at end of space"); | |
| 9090 assert(chunk_at_end->end() == _cmsSpace->end(), | |
| 9091 "Shrinking is inconsistent"); | |
| 9092 return; | |
| 9093 } | |
| 9094 } | |
| 9095 | |
| 9096 // Transfer some number of overflown objects to usual marking | |
| 9097 // stack. Return true if some objects were transferred. | |
| 9098 bool MarkRefsIntoAndScanClosure::take_from_overflow_list() { | |
|
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|
9099 size_t num = MIN2((size_t)(_mark_stack->capacity() - _mark_stack->length())/4, |
| 0 | 9100 (size_t)ParGCDesiredObjsFromOverflowList); |
| 9101 | |
| 9102 bool res = _collector->take_from_overflow_list(num, _mark_stack); | |
| 9103 assert(_collector->overflow_list_is_empty() || res, | |
| 9104 "If list is not empty, we should have taken something"); | |
| 9105 assert(!res || !_mark_stack->isEmpty(), | |
| 9106 "If we took something, it should now be on our stack"); | |
| 9107 return res; | |
| 9108 } | |
| 9109 | |
| 9110 size_t MarkDeadObjectsClosure::do_blk(HeapWord* addr) { | |
| 9111 size_t res = _sp->block_size_no_stall(addr, _collector); | |
| 9112 assert(res != 0, "Should always be able to compute a size"); | |
| 9113 if (_sp->block_is_obj(addr)) { | |
| 9114 if (_live_bit_map->isMarked(addr)) { | |
| 9115 // It can't have been dead in a previous cycle | |
| 9116 guarantee(!_dead_bit_map->isMarked(addr), "No resurrection!"); | |
| 9117 } else { | |
| 9118 _dead_bit_map->mark(addr); // mark the dead object | |
| 9119 } | |
| 9120 } | |
| 9121 return res; | |
| 9122 } |