Mercurial > hg > graal-compiler
annotate src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp @ 7:2faf283ce688
6621144: CMS: assertion failure "is_cms_thread == Thread::current()->is_ConcurrentGC_thread()"
Summary: Take lock conditionally (in asynchronous mode only) when updating the dead-object map.
Reviewed-by: jmasa
| author | ysr |
|---|---|
| date | Sat, 16 Feb 2008 22:41:20 -0800 |
| parents | a61af66fc99e |
| children | 173195ff483a |
| rev | line source |
|---|---|
| 0 | 1 /* |
| 2 * Copyright 2001-2007 Sun Microsystems, Inc. All Rights Reserved. | |
| 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; | |
| 193 assert(junk->prev_addr() == (void*)(oop(junk)->klass_addr()), | |
| 194 "Offset of FreeChunk::_prev within FreeChunk must match" | |
| 195 " that of OopDesc::_klass within OopDesc"); | |
| 196 ) | |
| 197 if (ParallelGCThreads > 0) { | |
| 198 typedef CMSParGCThreadState* CMSParGCThreadStatePtr; | |
| 199 _par_gc_thread_states = | |
| 200 NEW_C_HEAP_ARRAY(CMSParGCThreadStatePtr, ParallelGCThreads); | |
| 201 if (_par_gc_thread_states == NULL) { | |
| 202 vm_exit_during_initialization("Could not allocate par gc structs"); | |
| 203 } | |
| 204 for (uint i = 0; i < ParallelGCThreads; i++) { | |
| 205 _par_gc_thread_states[i] = new CMSParGCThreadState(cmsSpace()); | |
| 206 if (_par_gc_thread_states[i] == NULL) { | |
| 207 vm_exit_during_initialization("Could not allocate par gc structs"); | |
| 208 } | |
| 209 } | |
| 210 } else { | |
| 211 _par_gc_thread_states = NULL; | |
| 212 } | |
| 213 _incremental_collection_failed = false; | |
| 214 // The "dilatation_factor" is the expansion that can occur on | |
| 215 // account of the fact that the minimum object size in the CMS | |
| 216 // generation may be larger than that in, say, a contiguous young | |
| 217 // generation. | |
| 218 // Ideally, in the calculation below, we'd compute the dilatation | |
| 219 // factor as: MinChunkSize/(promoting_gen's min object size) | |
| 220 // Since we do not have such a general query interface for the | |
| 221 // promoting generation, we'll instead just use the mimimum | |
| 222 // object size (which today is a header's worth of space); | |
| 223 // note that all arithmetic is in units of HeapWords. | |
| 224 assert(MinChunkSize >= oopDesc::header_size(), "just checking"); | |
| 225 assert(_dilatation_factor >= 1.0, "from previous assert"); | |
| 226 } | |
| 227 | |
| 228 void ConcurrentMarkSweepGeneration::ref_processor_init() { | |
| 229 assert(collector() != NULL, "no collector"); | |
| 230 collector()->ref_processor_init(); | |
| 231 } | |
| 232 | |
| 233 void CMSCollector::ref_processor_init() { | |
| 234 if (_ref_processor == NULL) { | |
| 235 // Allocate and initialize a reference processor | |
| 236 _ref_processor = ReferenceProcessor::create_ref_processor( | |
| 237 _span, // span | |
| 238 _cmsGen->refs_discovery_is_atomic(), // atomic_discovery | |
| 239 _cmsGen->refs_discovery_is_mt(), // mt_discovery | |
| 240 &_is_alive_closure, | |
| 241 ParallelGCThreads, | |
| 242 ParallelRefProcEnabled); | |
| 243 // Initialize the _ref_processor field of CMSGen | |
| 244 _cmsGen->set_ref_processor(_ref_processor); | |
| 245 | |
| 246 // Allocate a dummy ref processor for perm gen. | |
| 247 ReferenceProcessor* rp2 = new ReferenceProcessor(); | |
| 248 if (rp2 == NULL) { | |
| 249 vm_exit_during_initialization("Could not allocate ReferenceProcessor object"); | |
| 250 } | |
| 251 _permGen->set_ref_processor(rp2); | |
| 252 } | |
| 253 } | |
| 254 | |
| 255 CMSAdaptiveSizePolicy* CMSCollector::size_policy() { | |
| 256 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 257 assert(gch->kind() == CollectedHeap::GenCollectedHeap, | |
| 258 "Wrong type of heap"); | |
| 259 CMSAdaptiveSizePolicy* sp = (CMSAdaptiveSizePolicy*) | |
| 260 gch->gen_policy()->size_policy(); | |
| 261 assert(sp->is_gc_cms_adaptive_size_policy(), | |
| 262 "Wrong type of size policy"); | |
| 263 return sp; | |
| 264 } | |
| 265 | |
| 266 CMSGCAdaptivePolicyCounters* CMSCollector::gc_adaptive_policy_counters() { | |
| 267 CMSGCAdaptivePolicyCounters* results = | |
| 268 (CMSGCAdaptivePolicyCounters*) collector_policy()->counters(); | |
| 269 assert( | |
| 270 results->kind() == GCPolicyCounters::CMSGCAdaptivePolicyCountersKind, | |
| 271 "Wrong gc policy counter kind"); | |
| 272 return results; | |
| 273 } | |
| 274 | |
| 275 | |
| 276 void ConcurrentMarkSweepGeneration::initialize_performance_counters() { | |
| 277 | |
| 278 const char* gen_name = "old"; | |
| 279 | |
| 280 // Generation Counters - generation 1, 1 subspace | |
| 281 _gen_counters = new GenerationCounters(gen_name, 1, 1, &_virtual_space); | |
| 282 | |
| 283 _space_counters = new GSpaceCounters(gen_name, 0, | |
| 284 _virtual_space.reserved_size(), | |
| 285 this, _gen_counters); | |
| 286 } | |
| 287 | |
| 288 CMSStats::CMSStats(ConcurrentMarkSweepGeneration* cms_gen, unsigned int alpha): | |
| 289 _cms_gen(cms_gen) | |
| 290 { | |
| 291 assert(alpha <= 100, "bad value"); | |
| 292 _saved_alpha = alpha; | |
| 293 | |
| 294 // Initialize the alphas to the bootstrap value of 100. | |
| 295 _gc0_alpha = _cms_alpha = 100; | |
| 296 | |
| 297 _cms_begin_time.update(); | |
| 298 _cms_end_time.update(); | |
| 299 | |
| 300 _gc0_duration = 0.0; | |
| 301 _gc0_period = 0.0; | |
| 302 _gc0_promoted = 0; | |
| 303 | |
| 304 _cms_duration = 0.0; | |
| 305 _cms_period = 0.0; | |
| 306 _cms_allocated = 0; | |
| 307 | |
| 308 _cms_used_at_gc0_begin = 0; | |
| 309 _cms_used_at_gc0_end = 0; | |
| 310 _allow_duty_cycle_reduction = false; | |
| 311 _valid_bits = 0; | |
| 312 _icms_duty_cycle = CMSIncrementalDutyCycle; | |
| 313 } | |
| 314 | |
| 315 // If promotion failure handling is on use | |
| 316 // the padded average size of the promotion for each | |
| 317 // young generation collection. | |
| 318 double CMSStats::time_until_cms_gen_full() const { | |
| 319 size_t cms_free = _cms_gen->cmsSpace()->free(); | |
| 320 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 321 size_t expected_promotion = gch->get_gen(0)->capacity(); | |
| 322 if (HandlePromotionFailure) { | |
| 323 expected_promotion = MIN2( | |
| 324 (size_t) _cms_gen->gc_stats()->avg_promoted()->padded_average(), | |
| 325 expected_promotion); | |
| 326 } | |
| 327 if (cms_free > expected_promotion) { | |
| 328 // Start a cms collection if there isn't enough space to promote | |
| 329 // for the next minor collection. Use the padded average as | |
| 330 // a safety factor. | |
| 331 cms_free -= expected_promotion; | |
| 332 | |
| 333 // Adjust by the safety factor. | |
| 334 double cms_free_dbl = (double)cms_free; | |
| 335 cms_free_dbl = cms_free_dbl * (100.0 - CMSIncrementalSafetyFactor) / 100.0; | |
| 336 | |
| 337 if (PrintGCDetails && Verbose) { | |
| 338 gclog_or_tty->print_cr("CMSStats::time_until_cms_gen_full: cms_free " | |
| 339 SIZE_FORMAT " expected_promotion " SIZE_FORMAT, | |
| 340 cms_free, expected_promotion); | |
| 341 gclog_or_tty->print_cr(" cms_free_dbl %f cms_consumption_rate %f", | |
| 342 cms_free_dbl, cms_consumption_rate() + 1.0); | |
| 343 } | |
| 344 // Add 1 in case the consumption rate goes to zero. | |
| 345 return cms_free_dbl / (cms_consumption_rate() + 1.0); | |
| 346 } | |
| 347 return 0.0; | |
| 348 } | |
| 349 | |
| 350 // Compare the duration of the cms collection to the | |
| 351 // time remaining before the cms generation is empty. | |
| 352 // Note that the time from the start of the cms collection | |
| 353 // to the start of the cms sweep (less than the total | |
| 354 // duration of the cms collection) can be used. This | |
| 355 // has been tried and some applications experienced | |
| 356 // promotion failures early in execution. This was | |
| 357 // possibly because the averages were not accurate | |
| 358 // enough at the beginning. | |
| 359 double CMSStats::time_until_cms_start() const { | |
| 360 // We add "gc0_period" to the "work" calculation | |
| 361 // below because this query is done (mostly) at the | |
| 362 // end of a scavenge, so we need to conservatively | |
| 363 // account for that much possible delay | |
| 364 // in the query so as to avoid concurrent mode failures | |
| 365 // due to starting the collection just a wee bit too | |
| 366 // late. | |
| 367 double work = cms_duration() + gc0_period(); | |
| 368 double deadline = time_until_cms_gen_full(); | |
| 369 if (work > deadline) { | |
| 370 if (Verbose && PrintGCDetails) { | |
| 371 gclog_or_tty->print( | |
| 372 " CMSCollector: collect because of anticipated promotion " | |
| 373 "before full %3.7f + %3.7f > %3.7f ", cms_duration(), | |
| 374 gc0_period(), time_until_cms_gen_full()); | |
| 375 } | |
| 376 return 0.0; | |
| 377 } | |
| 378 return work - deadline; | |
| 379 } | |
| 380 | |
| 381 // Return a duty cycle based on old_duty_cycle and new_duty_cycle, limiting the | |
| 382 // amount of change to prevent wild oscillation. | |
| 383 unsigned int CMSStats::icms_damped_duty_cycle(unsigned int old_duty_cycle, | |
| 384 unsigned int new_duty_cycle) { | |
| 385 assert(old_duty_cycle <= 100, "bad input value"); | |
| 386 assert(new_duty_cycle <= 100, "bad input value"); | |
| 387 | |
| 388 // Note: use subtraction with caution since it may underflow (values are | |
| 389 // unsigned). Addition is safe since we're in the range 0-100. | |
| 390 unsigned int damped_duty_cycle = new_duty_cycle; | |
| 391 if (new_duty_cycle < old_duty_cycle) { | |
| 392 const unsigned int largest_delta = MAX2(old_duty_cycle / 4, 5U); | |
| 393 if (new_duty_cycle + largest_delta < old_duty_cycle) { | |
| 394 damped_duty_cycle = old_duty_cycle - largest_delta; | |
| 395 } | |
| 396 } else if (new_duty_cycle > old_duty_cycle) { | |
| 397 const unsigned int largest_delta = MAX2(old_duty_cycle / 4, 15U); | |
| 398 if (new_duty_cycle > old_duty_cycle + largest_delta) { | |
| 399 damped_duty_cycle = MIN2(old_duty_cycle + largest_delta, 100U); | |
| 400 } | |
| 401 } | |
| 402 assert(damped_duty_cycle <= 100, "invalid duty cycle computed"); | |
| 403 | |
| 404 if (CMSTraceIncrementalPacing) { | |
| 405 gclog_or_tty->print(" [icms_damped_duty_cycle(%d,%d) = %d] ", | |
| 406 old_duty_cycle, new_duty_cycle, damped_duty_cycle); | |
| 407 } | |
| 408 return damped_duty_cycle; | |
| 409 } | |
| 410 | |
| 411 unsigned int CMSStats::icms_update_duty_cycle_impl() { | |
| 412 assert(CMSIncrementalPacing && valid(), | |
| 413 "should be handled in icms_update_duty_cycle()"); | |
| 414 | |
| 415 double cms_time_so_far = cms_timer().seconds(); | |
| 416 double scaled_duration = cms_duration_per_mb() * _cms_used_at_gc0_end / M; | |
| 417 double scaled_duration_remaining = fabsd(scaled_duration - cms_time_so_far); | |
| 418 | |
| 419 // Avoid division by 0. | |
| 420 double time_until_full = MAX2(time_until_cms_gen_full(), 0.01); | |
| 421 double duty_cycle_dbl = 100.0 * scaled_duration_remaining / time_until_full; | |
| 422 | |
| 423 unsigned int new_duty_cycle = MIN2((unsigned int)duty_cycle_dbl, 100U); | |
| 424 if (new_duty_cycle > _icms_duty_cycle) { | |
| 425 // Avoid very small duty cycles (1 or 2); 0 is allowed. | |
| 426 if (new_duty_cycle > 2) { | |
| 427 _icms_duty_cycle = icms_damped_duty_cycle(_icms_duty_cycle, | |
| 428 new_duty_cycle); | |
| 429 } | |
| 430 } else if (_allow_duty_cycle_reduction) { | |
| 431 // The duty cycle is reduced only once per cms cycle (see record_cms_end()). | |
| 432 new_duty_cycle = icms_damped_duty_cycle(_icms_duty_cycle, new_duty_cycle); | |
| 433 // Respect the minimum duty cycle. | |
| 434 unsigned int min_duty_cycle = (unsigned int)CMSIncrementalDutyCycleMin; | |
| 435 _icms_duty_cycle = MAX2(new_duty_cycle, min_duty_cycle); | |
| 436 } | |
| 437 | |
| 438 if (PrintGCDetails || CMSTraceIncrementalPacing) { | |
| 439 gclog_or_tty->print(" icms_dc=%d ", _icms_duty_cycle); | |
| 440 } | |
| 441 | |
| 442 _allow_duty_cycle_reduction = false; | |
| 443 return _icms_duty_cycle; | |
| 444 } | |
| 445 | |
| 446 #ifndef PRODUCT | |
| 447 void CMSStats::print_on(outputStream *st) const { | |
| 448 st->print(" gc0_alpha=%d,cms_alpha=%d", _gc0_alpha, _cms_alpha); | |
| 449 st->print(",gc0_dur=%g,gc0_per=%g,gc0_promo=" SIZE_FORMAT, | |
| 450 gc0_duration(), gc0_period(), gc0_promoted()); | |
| 451 st->print(",cms_dur=%g,cms_dur_per_mb=%g,cms_per=%g,cms_alloc=" SIZE_FORMAT, | |
| 452 cms_duration(), cms_duration_per_mb(), | |
| 453 cms_period(), cms_allocated()); | |
| 454 st->print(",cms_since_beg=%g,cms_since_end=%g", | |
| 455 cms_time_since_begin(), cms_time_since_end()); | |
| 456 st->print(",cms_used_beg=" SIZE_FORMAT ",cms_used_end=" SIZE_FORMAT, | |
| 457 _cms_used_at_gc0_begin, _cms_used_at_gc0_end); | |
| 458 if (CMSIncrementalMode) { | |
| 459 st->print(",dc=%d", icms_duty_cycle()); | |
| 460 } | |
| 461 | |
| 462 if (valid()) { | |
| 463 st->print(",promo_rate=%g,cms_alloc_rate=%g", | |
| 464 promotion_rate(), cms_allocation_rate()); | |
| 465 st->print(",cms_consumption_rate=%g,time_until_full=%g", | |
| 466 cms_consumption_rate(), time_until_cms_gen_full()); | |
| 467 } | |
| 468 st->print(" "); | |
| 469 } | |
| 470 #endif // #ifndef PRODUCT | |
| 471 | |
| 472 CMSCollector::CollectorState CMSCollector::_collectorState = | |
| 473 CMSCollector::Idling; | |
| 474 bool CMSCollector::_foregroundGCIsActive = false; | |
| 475 bool CMSCollector::_foregroundGCShouldWait = false; | |
| 476 | |
| 477 CMSCollector::CMSCollector(ConcurrentMarkSweepGeneration* cmsGen, | |
| 478 ConcurrentMarkSweepGeneration* permGen, | |
| 479 CardTableRS* ct, | |
| 480 ConcurrentMarkSweepPolicy* cp): | |
| 481 _cmsGen(cmsGen), | |
| 482 _permGen(permGen), | |
| 483 _ct(ct), | |
| 484 _ref_processor(NULL), // will be set later | |
| 485 _conc_workers(NULL), // may be set later | |
| 486 _abort_preclean(false), | |
| 487 _start_sampling(false), | |
| 488 _between_prologue_and_epilogue(false), | |
| 489 _markBitMap(0, Mutex::leaf + 1, "CMS_markBitMap_lock"), | |
| 490 _perm_gen_verify_bit_map(0, -1 /* no mutex */, "No_lock"), | |
| 491 _modUnionTable((CardTableModRefBS::card_shift - LogHeapWordSize), | |
| 492 -1 /* lock-free */, "No_lock" /* dummy */), | |
| 493 _modUnionClosure(&_modUnionTable), | |
| 494 _modUnionClosurePar(&_modUnionTable), | |
| 495 _is_alive_closure(&_markBitMap), | |
| 496 _restart_addr(NULL), | |
| 497 _overflow_list(NULL), | |
| 498 _preserved_oop_stack(NULL), | |
| 499 _preserved_mark_stack(NULL), | |
| 500 _stats(cmsGen), | |
| 501 _eden_chunk_array(NULL), // may be set in ctor body | |
| 502 _eden_chunk_capacity(0), // -- ditto -- | |
| 503 _eden_chunk_index(0), // -- ditto -- | |
| 504 _survivor_plab_array(NULL), // -- ditto -- | |
| 505 _survivor_chunk_array(NULL), // -- ditto -- | |
| 506 _survivor_chunk_capacity(0), // -- ditto -- | |
| 507 _survivor_chunk_index(0), // -- ditto -- | |
| 508 _ser_pmc_preclean_ovflw(0), | |
| 509 _ser_pmc_remark_ovflw(0), | |
| 510 _par_pmc_remark_ovflw(0), | |
| 511 _ser_kac_ovflw(0), | |
| 512 _par_kac_ovflw(0), | |
| 513 #ifndef PRODUCT | |
| 514 _num_par_pushes(0), | |
| 515 #endif | |
| 516 _collection_count_start(0), | |
| 517 _verifying(false), | |
| 518 _icms_start_limit(NULL), | |
| 519 _icms_stop_limit(NULL), | |
| 520 _verification_mark_bm(0, Mutex::leaf + 1, "CMS_verification_mark_bm_lock"), | |
| 521 _completed_initialization(false), | |
| 522 _collector_policy(cp), | |
| 523 _unload_classes(false), | |
| 524 _unloaded_classes_last_cycle(false), | |
| 525 _sweep_estimate(CMS_SweepWeight, CMS_SweepPadding) | |
| 526 { | |
| 527 if (ExplicitGCInvokesConcurrentAndUnloadsClasses) { | |
| 528 ExplicitGCInvokesConcurrent = true; | |
| 529 } | |
| 530 // Now expand the span and allocate the collection support structures | |
| 531 // (MUT, marking bit map etc.) to cover both generations subject to | |
| 532 // collection. | |
| 533 | |
| 534 // First check that _permGen is adjacent to _cmsGen and above it. | |
| 535 assert( _cmsGen->reserved().word_size() > 0 | |
| 536 && _permGen->reserved().word_size() > 0, | |
| 537 "generations should not be of zero size"); | |
| 538 assert(_cmsGen->reserved().intersection(_permGen->reserved()).is_empty(), | |
| 539 "_cmsGen and _permGen should not overlap"); | |
| 540 assert(_cmsGen->reserved().end() == _permGen->reserved().start(), | |
| 541 "_cmsGen->end() different from _permGen->start()"); | |
| 542 | |
| 543 // For use by dirty card to oop closures. | |
| 544 _cmsGen->cmsSpace()->set_collector(this); | |
| 545 _permGen->cmsSpace()->set_collector(this); | |
| 546 | |
| 547 // Adjust my span to cover old (cms) gen and perm gen | |
| 548 _span = _cmsGen->reserved()._union(_permGen->reserved()); | |
| 549 // Initialize the span of is_alive_closure | |
| 550 _is_alive_closure.set_span(_span); | |
| 551 | |
| 552 // Allocate MUT and marking bit map | |
| 553 { | |
| 554 MutexLockerEx x(_markBitMap.lock(), Mutex::_no_safepoint_check_flag); | |
| 555 if (!_markBitMap.allocate(_span)) { | |
| 556 warning("Failed to allocate CMS Bit Map"); | |
| 557 return; | |
| 558 } | |
| 559 assert(_markBitMap.covers(_span), "_markBitMap inconsistency?"); | |
| 560 } | |
| 561 { | |
| 562 _modUnionTable.allocate(_span); | |
| 563 assert(_modUnionTable.covers(_span), "_modUnionTable inconsistency?"); | |
| 564 } | |
| 565 | |
| 566 if (!_markStack.allocate(CMSMarkStackSize)) { | |
| 567 warning("Failed to allocate CMS Marking Stack"); | |
| 568 return; | |
| 569 } | |
| 570 if (!_revisitStack.allocate(CMSRevisitStackSize)) { | |
| 571 warning("Failed to allocate CMS Revisit Stack"); | |
| 572 return; | |
| 573 } | |
| 574 | |
| 575 // Support for multi-threaded concurrent phases | |
| 576 if (ParallelGCThreads > 0 && CMSConcurrentMTEnabled) { | |
| 577 if (FLAG_IS_DEFAULT(ParallelCMSThreads)) { | |
| 578 // just for now | |
| 579 FLAG_SET_DEFAULT(ParallelCMSThreads, (ParallelGCThreads + 3)/4); | |
| 580 } | |
| 581 if (ParallelCMSThreads > 1) { | |
| 582 _conc_workers = new YieldingFlexibleWorkGang("Parallel CMS Threads", | |
| 583 ParallelCMSThreads, true); | |
| 584 if (_conc_workers == NULL) { | |
| 585 warning("GC/CMS: _conc_workers allocation failure: " | |
| 586 "forcing -CMSConcurrentMTEnabled"); | |
| 587 CMSConcurrentMTEnabled = false; | |
| 588 } | |
| 589 } else { | |
| 590 CMSConcurrentMTEnabled = false; | |
| 591 } | |
| 592 } | |
| 593 if (!CMSConcurrentMTEnabled) { | |
| 594 ParallelCMSThreads = 0; | |
| 595 } else { | |
| 596 // Turn off CMSCleanOnEnter optimization temporarily for | |
| 597 // the MT case where it's not fixed yet; see 6178663. | |
| 598 CMSCleanOnEnter = false; | |
| 599 } | |
| 600 assert((_conc_workers != NULL) == (ParallelCMSThreads > 1), | |
| 601 "Inconsistency"); | |
| 602 | |
| 603 // Parallel task queues; these are shared for the | |
| 604 // concurrent and stop-world phases of CMS, but | |
| 605 // are not shared with parallel scavenge (ParNew). | |
| 606 { | |
| 607 uint i; | |
| 608 uint num_queues = (uint) MAX2(ParallelGCThreads, ParallelCMSThreads); | |
| 609 | |
| 610 if ((CMSParallelRemarkEnabled || CMSConcurrentMTEnabled | |
| 611 || ParallelRefProcEnabled) | |
| 612 && num_queues > 0) { | |
| 613 _task_queues = new OopTaskQueueSet(num_queues); | |
| 614 if (_task_queues == NULL) { | |
| 615 warning("task_queues allocation failure."); | |
| 616 return; | |
| 617 } | |
| 618 _hash_seed = NEW_C_HEAP_ARRAY(int, num_queues); | |
| 619 if (_hash_seed == NULL) { | |
| 620 warning("_hash_seed array allocation failure"); | |
| 621 return; | |
| 622 } | |
| 623 | |
| 624 // XXX use a global constant instead of 64! | |
| 625 typedef struct OopTaskQueuePadded { | |
| 626 OopTaskQueue work_queue; | |
| 627 char pad[64 - sizeof(OopTaskQueue)]; // prevent false sharing | |
| 628 } OopTaskQueuePadded; | |
| 629 | |
| 630 for (i = 0; i < num_queues; i++) { | |
| 631 OopTaskQueuePadded *q_padded = new OopTaskQueuePadded(); | |
| 632 if (q_padded == NULL) { | |
| 633 warning("work_queue allocation failure."); | |
| 634 return; | |
| 635 } | |
| 636 _task_queues->register_queue(i, &q_padded->work_queue); | |
| 637 } | |
| 638 for (i = 0; i < num_queues; i++) { | |
| 639 _task_queues->queue(i)->initialize(); | |
| 640 _hash_seed[i] = 17; // copied from ParNew | |
| 641 } | |
| 642 } | |
| 643 } | |
| 644 | |
| 645 // "initiatingOccupancy" is the occupancy ratio at which we trigger | |
| 646 // a new collection cycle. Unless explicitly specified via | |
| 647 // CMSTriggerRatio, it is calculated by: | |
| 648 // Let "f" be MinHeapFreeRatio in | |
| 649 // | |
| 650 // intiatingOccupancy = 100-f + | |
| 651 // f * (CMSTriggerRatio/100) | |
| 652 // That is, if we assume the heap is at its desired maximum occupancy at the | |
| 653 // end of a collection, we let CMSTriggerRatio of the (purported) free | |
| 654 // space be allocated before initiating a new collection cycle. | |
| 655 if (CMSInitiatingOccupancyFraction > 0) { | |
| 656 _initiatingOccupancy = (double)CMSInitiatingOccupancyFraction / 100.0; | |
| 657 } else { | |
| 658 _initiatingOccupancy = ((100 - MinHeapFreeRatio) + | |
| 659 (double)(CMSTriggerRatio * | |
| 660 MinHeapFreeRatio) / 100.0) | |
| 661 / 100.0; | |
| 662 } | |
| 663 // Clip CMSBootstrapOccupancy between 0 and 100. | |
| 664 _bootstrap_occupancy = ((double)MIN2((intx)100, MAX2((intx)0, CMSBootstrapOccupancy))) | |
| 665 /(double)100; | |
| 666 | |
| 667 _full_gcs_since_conc_gc = 0; | |
| 668 | |
| 669 // Now tell CMS generations the identity of their collector | |
| 670 ConcurrentMarkSweepGeneration::set_collector(this); | |
| 671 | |
| 672 // Create & start a CMS thread for this CMS collector | |
| 673 _cmsThread = ConcurrentMarkSweepThread::start(this); | |
| 674 assert(cmsThread() != NULL, "CMS Thread should have been created"); | |
| 675 assert(cmsThread()->collector() == this, | |
| 676 "CMS Thread should refer to this gen"); | |
| 677 assert(CGC_lock != NULL, "Where's the CGC_lock?"); | |
| 678 | |
| 679 // Support for parallelizing young gen rescan | |
| 680 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 681 _young_gen = gch->prev_gen(_cmsGen); | |
| 682 if (gch->supports_inline_contig_alloc()) { | |
| 683 _top_addr = gch->top_addr(); | |
| 684 _end_addr = gch->end_addr(); | |
| 685 assert(_young_gen != NULL, "no _young_gen"); | |
| 686 _eden_chunk_index = 0; | |
| 687 _eden_chunk_capacity = (_young_gen->max_capacity()+CMSSamplingGrain)/CMSSamplingGrain; | |
| 688 _eden_chunk_array = NEW_C_HEAP_ARRAY(HeapWord*, _eden_chunk_capacity); | |
| 689 if (_eden_chunk_array == NULL) { | |
| 690 _eden_chunk_capacity = 0; | |
| 691 warning("GC/CMS: _eden_chunk_array allocation failure"); | |
| 692 } | |
| 693 } | |
| 694 assert(_eden_chunk_array != NULL || _eden_chunk_capacity == 0, "Error"); | |
| 695 | |
| 696 // Support for parallelizing survivor space rescan | |
| 697 if (CMSParallelRemarkEnabled && CMSParallelSurvivorRemarkEnabled) { | |
| 698 size_t max_plab_samples = MaxNewSize/((SurvivorRatio+2)*MinTLABSize); | |
| 699 _survivor_plab_array = NEW_C_HEAP_ARRAY(ChunkArray, ParallelGCThreads); | |
| 700 _survivor_chunk_array = NEW_C_HEAP_ARRAY(HeapWord*, 2*max_plab_samples); | |
| 701 _cursor = NEW_C_HEAP_ARRAY(size_t, ParallelGCThreads); | |
| 702 if (_survivor_plab_array == NULL || _survivor_chunk_array == NULL | |
| 703 || _cursor == NULL) { | |
| 704 warning("Failed to allocate survivor plab/chunk array"); | |
| 705 if (_survivor_plab_array != NULL) { | |
| 706 FREE_C_HEAP_ARRAY(ChunkArray, _survivor_plab_array); | |
| 707 _survivor_plab_array = NULL; | |
| 708 } | |
| 709 if (_survivor_chunk_array != NULL) { | |
| 710 FREE_C_HEAP_ARRAY(HeapWord*, _survivor_chunk_array); | |
| 711 _survivor_chunk_array = NULL; | |
| 712 } | |
| 713 if (_cursor != NULL) { | |
| 714 FREE_C_HEAP_ARRAY(size_t, _cursor); | |
| 715 _cursor = NULL; | |
| 716 } | |
| 717 } else { | |
| 718 _survivor_chunk_capacity = 2*max_plab_samples; | |
| 719 for (uint i = 0; i < ParallelGCThreads; i++) { | |
| 720 HeapWord** vec = NEW_C_HEAP_ARRAY(HeapWord*, max_plab_samples); | |
| 721 if (vec == NULL) { | |
| 722 warning("Failed to allocate survivor plab array"); | |
| 723 for (int j = i; j > 0; j--) { | |
| 724 FREE_C_HEAP_ARRAY(HeapWord*, _survivor_plab_array[j-1].array()); | |
| 725 } | |
| 726 FREE_C_HEAP_ARRAY(ChunkArray, _survivor_plab_array); | |
| 727 FREE_C_HEAP_ARRAY(HeapWord*, _survivor_chunk_array); | |
| 728 _survivor_plab_array = NULL; | |
| 729 _survivor_chunk_array = NULL; | |
| 730 _survivor_chunk_capacity = 0; | |
| 731 break; | |
| 732 } else { | |
| 733 ChunkArray* cur = | |
| 734 ::new (&_survivor_plab_array[i]) ChunkArray(vec, | |
| 735 max_plab_samples); | |
| 736 assert(cur->end() == 0, "Should be 0"); | |
| 737 assert(cur->array() == vec, "Should be vec"); | |
| 738 assert(cur->capacity() == max_plab_samples, "Error"); | |
| 739 } | |
| 740 } | |
| 741 } | |
| 742 } | |
| 743 assert( ( _survivor_plab_array != NULL | |
| 744 && _survivor_chunk_array != NULL) | |
| 745 || ( _survivor_chunk_capacity == 0 | |
| 746 && _survivor_chunk_index == 0), | |
| 747 "Error"); | |
| 748 | |
| 749 // Choose what strong roots should be scanned depending on verification options | |
| 750 // and perm gen collection mode. | |
| 751 if (!CMSClassUnloadingEnabled) { | |
| 752 // If class unloading is disabled we want to include all classes into the root set. | |
| 753 add_root_scanning_option(SharedHeap::SO_AllClasses); | |
| 754 } else { | |
| 755 add_root_scanning_option(SharedHeap::SO_SystemClasses); | |
| 756 } | |
| 757 | |
| 758 NOT_PRODUCT(_overflow_counter = CMSMarkStackOverflowInterval;) | |
| 759 _gc_counters = new CollectorCounters("CMS", 1); | |
| 760 _completed_initialization = true; | |
| 761 _sweep_timer.start(); // start of time | |
| 762 } | |
| 763 | |
| 764 const char* ConcurrentMarkSweepGeneration::name() const { | |
| 765 return "concurrent mark-sweep generation"; | |
| 766 } | |
| 767 void ConcurrentMarkSweepGeneration::update_counters() { | |
| 768 if (UsePerfData) { | |
| 769 _space_counters->update_all(); | |
| 770 _gen_counters->update_all(); | |
| 771 } | |
| 772 } | |
| 773 | |
| 774 // this is an optimized version of update_counters(). it takes the | |
| 775 // used value as a parameter rather than computing it. | |
| 776 // | |
| 777 void ConcurrentMarkSweepGeneration::update_counters(size_t used) { | |
| 778 if (UsePerfData) { | |
| 779 _space_counters->update_used(used); | |
| 780 _space_counters->update_capacity(); | |
| 781 _gen_counters->update_all(); | |
| 782 } | |
| 783 } | |
| 784 | |
| 785 void ConcurrentMarkSweepGeneration::print() const { | |
| 786 Generation::print(); | |
| 787 cmsSpace()->print(); | |
| 788 } | |
| 789 | |
| 790 #ifndef PRODUCT | |
| 791 void ConcurrentMarkSweepGeneration::print_statistics() { | |
| 792 cmsSpace()->printFLCensus(0); | |
| 793 } | |
| 794 #endif | |
| 795 | |
| 796 void ConcurrentMarkSweepGeneration::printOccupancy(const char *s) { | |
| 797 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 798 if (PrintGCDetails) { | |
| 799 if (Verbose) { | |
| 800 gclog_or_tty->print(" [%d %s-%s: "SIZE_FORMAT"("SIZE_FORMAT")]", | |
| 801 level(), short_name(), s, used(), capacity()); | |
| 802 } else { | |
| 803 gclog_or_tty->print(" [%d %s-%s: "SIZE_FORMAT"K("SIZE_FORMAT"K)]", | |
| 804 level(), short_name(), s, used() / K, capacity() / K); | |
| 805 } | |
| 806 } | |
| 807 if (Verbose) { | |
| 808 gclog_or_tty->print(" "SIZE_FORMAT"("SIZE_FORMAT")", | |
| 809 gch->used(), gch->capacity()); | |
| 810 } else { | |
| 811 gclog_or_tty->print(" "SIZE_FORMAT"K("SIZE_FORMAT"K)", | |
| 812 gch->used() / K, gch->capacity() / K); | |
| 813 } | |
| 814 } | |
| 815 | |
| 816 size_t | |
| 817 ConcurrentMarkSweepGeneration::contiguous_available() const { | |
| 818 // dld proposes an improvement in precision here. If the committed | |
| 819 // part of the space ends in a free block we should add that to | |
| 820 // uncommitted size in the calculation below. Will make this | |
| 821 // change later, staying with the approximation below for the | |
| 822 // time being. -- ysr. | |
| 823 return MAX2(_virtual_space.uncommitted_size(), unsafe_max_alloc_nogc()); | |
| 824 } | |
| 825 | |
| 826 size_t | |
| 827 ConcurrentMarkSweepGeneration::unsafe_max_alloc_nogc() const { | |
| 828 return _cmsSpace->max_alloc_in_words() * HeapWordSize; | |
| 829 } | |
| 830 | |
| 831 size_t ConcurrentMarkSweepGeneration::max_available() const { | |
| 832 return free() + _virtual_space.uncommitted_size(); | |
| 833 } | |
| 834 | |
| 835 bool ConcurrentMarkSweepGeneration::promotion_attempt_is_safe( | |
| 836 size_t max_promotion_in_bytes, | |
| 837 bool younger_handles_promotion_failure) const { | |
| 838 | |
| 839 // This is the most conservative test. Full promotion is | |
| 840 // guaranteed if this is used. The multiplicative factor is to | |
| 841 // account for the worst case "dilatation". | |
| 842 double adjusted_max_promo_bytes = _dilatation_factor * max_promotion_in_bytes; | |
| 843 if (adjusted_max_promo_bytes > (double)max_uintx) { // larger than size_t | |
| 844 adjusted_max_promo_bytes = (double)max_uintx; | |
| 845 } | |
| 846 bool result = (max_contiguous_available() >= (size_t)adjusted_max_promo_bytes); | |
| 847 | |
| 848 if (younger_handles_promotion_failure && !result) { | |
| 849 // Full promotion is not guaranteed because fragmentation | |
| 850 // of the cms generation can prevent the full promotion. | |
| 851 result = (max_available() >= (size_t)adjusted_max_promo_bytes); | |
| 852 | |
| 853 if (!result) { | |
| 854 // With promotion failure handling the test for the ability | |
| 855 // to support the promotion does not have to be guaranteed. | |
| 856 // Use an average of the amount promoted. | |
| 857 result = max_available() >= (size_t) | |
| 858 gc_stats()->avg_promoted()->padded_average(); | |
| 859 if (PrintGC && Verbose && result) { | |
| 860 gclog_or_tty->print_cr( | |
| 861 "\nConcurrentMarkSweepGeneration::promotion_attempt_is_safe" | |
| 862 " max_available: " SIZE_FORMAT | |
| 863 " avg_promoted: " SIZE_FORMAT, | |
| 864 max_available(), (size_t) | |
| 865 gc_stats()->avg_promoted()->padded_average()); | |
| 866 } | |
| 867 } else { | |
| 868 if (PrintGC && Verbose) { | |
| 869 gclog_or_tty->print_cr( | |
| 870 "\nConcurrentMarkSweepGeneration::promotion_attempt_is_safe" | |
| 871 " max_available: " SIZE_FORMAT | |
| 872 " adj_max_promo_bytes: " SIZE_FORMAT, | |
| 873 max_available(), (size_t)adjusted_max_promo_bytes); | |
| 874 } | |
| 875 } | |
| 876 } else { | |
| 877 if (PrintGC && Verbose) { | |
| 878 gclog_or_tty->print_cr( | |
| 879 "\nConcurrentMarkSweepGeneration::promotion_attempt_is_safe" | |
| 880 " contiguous_available: " SIZE_FORMAT | |
| 881 " adj_max_promo_bytes: " SIZE_FORMAT, | |
| 882 max_contiguous_available(), (size_t)adjusted_max_promo_bytes); | |
| 883 } | |
| 884 } | |
| 885 return result; | |
| 886 } | |
| 887 | |
| 888 CompactibleSpace* | |
| 889 ConcurrentMarkSweepGeneration::first_compaction_space() const { | |
| 890 return _cmsSpace; | |
| 891 } | |
| 892 | |
| 893 void ConcurrentMarkSweepGeneration::reset_after_compaction() { | |
| 894 // Clear the promotion information. These pointers can be adjusted | |
| 895 // along with all the other pointers into the heap but | |
| 896 // compaction is expected to be a rare event with | |
| 897 // a heap using cms so don't do it without seeing the need. | |
| 898 if (ParallelGCThreads > 0) { | |
| 899 for (uint i = 0; i < ParallelGCThreads; i++) { | |
| 900 _par_gc_thread_states[i]->promo.reset(); | |
| 901 } | |
| 902 } | |
| 903 } | |
| 904 | |
| 905 void ConcurrentMarkSweepGeneration::space_iterate(SpaceClosure* blk, bool usedOnly) { | |
| 906 blk->do_space(_cmsSpace); | |
| 907 } | |
| 908 | |
| 909 void ConcurrentMarkSweepGeneration::compute_new_size() { | |
| 910 assert_locked_or_safepoint(Heap_lock); | |
| 911 | |
| 912 // If incremental collection failed, we just want to expand | |
| 913 // to the limit. | |
| 914 if (incremental_collection_failed()) { | |
| 915 clear_incremental_collection_failed(); | |
| 916 grow_to_reserved(); | |
| 917 return; | |
| 918 } | |
| 919 | |
| 920 size_t expand_bytes = 0; | |
| 921 double free_percentage = ((double) free()) / capacity(); | |
| 922 double desired_free_percentage = (double) MinHeapFreeRatio / 100; | |
| 923 double maximum_free_percentage = (double) MaxHeapFreeRatio / 100; | |
| 924 | |
| 925 // compute expansion delta needed for reaching desired free percentage | |
| 926 if (free_percentage < desired_free_percentage) { | |
| 927 size_t desired_capacity = (size_t)(used() / ((double) 1 - desired_free_percentage)); | |
| 928 assert(desired_capacity >= capacity(), "invalid expansion size"); | |
| 929 expand_bytes = MAX2(desired_capacity - capacity(), MinHeapDeltaBytes); | |
| 930 } | |
| 931 if (expand_bytes > 0) { | |
| 932 if (PrintGCDetails && Verbose) { | |
| 933 size_t desired_capacity = (size_t)(used() / ((double) 1 - desired_free_percentage)); | |
| 934 gclog_or_tty->print_cr("\nFrom compute_new_size: "); | |
| 935 gclog_or_tty->print_cr(" Free fraction %f", free_percentage); | |
| 936 gclog_or_tty->print_cr(" Desired free fraction %f", | |
| 937 desired_free_percentage); | |
| 938 gclog_or_tty->print_cr(" Maximum free fraction %f", | |
| 939 maximum_free_percentage); | |
| 940 gclog_or_tty->print_cr(" Capactiy "SIZE_FORMAT, capacity()/1000); | |
| 941 gclog_or_tty->print_cr(" Desired capacity "SIZE_FORMAT, | |
| 942 desired_capacity/1000); | |
| 943 int prev_level = level() - 1; | |
| 944 if (prev_level >= 0) { | |
| 945 size_t prev_size = 0; | |
| 946 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 947 Generation* prev_gen = gch->_gens[prev_level]; | |
| 948 prev_size = prev_gen->capacity(); | |
| 949 gclog_or_tty->print_cr(" Younger gen size "SIZE_FORMAT, | |
| 950 prev_size/1000); | |
| 951 } | |
| 952 gclog_or_tty->print_cr(" unsafe_max_alloc_nogc "SIZE_FORMAT, | |
| 953 unsafe_max_alloc_nogc()/1000); | |
| 954 gclog_or_tty->print_cr(" contiguous available "SIZE_FORMAT, | |
| 955 contiguous_available()/1000); | |
| 956 gclog_or_tty->print_cr(" Expand by "SIZE_FORMAT" (bytes)", | |
| 957 expand_bytes); | |
| 958 } | |
| 959 // safe if expansion fails | |
| 960 expand(expand_bytes, 0, CMSExpansionCause::_satisfy_free_ratio); | |
| 961 if (PrintGCDetails && Verbose) { | |
| 962 gclog_or_tty->print_cr(" Expanded free fraction %f", | |
| 963 ((double) free()) / capacity()); | |
| 964 } | |
| 965 } | |
| 966 } | |
| 967 | |
| 968 Mutex* ConcurrentMarkSweepGeneration::freelistLock() const { | |
| 969 return cmsSpace()->freelistLock(); | |
| 970 } | |
| 971 | |
| 972 HeapWord* ConcurrentMarkSweepGeneration::allocate(size_t size, | |
| 973 bool tlab) { | |
| 974 CMSSynchronousYieldRequest yr; | |
| 975 MutexLockerEx x(freelistLock(), | |
| 976 Mutex::_no_safepoint_check_flag); | |
| 977 return have_lock_and_allocate(size, tlab); | |
| 978 } | |
| 979 | |
| 980 HeapWord* ConcurrentMarkSweepGeneration::have_lock_and_allocate(size_t size, | |
| 981 bool tlab) { | |
| 982 assert_lock_strong(freelistLock()); | |
| 983 size_t adjustedSize = CompactibleFreeListSpace::adjustObjectSize(size); | |
| 984 HeapWord* res = cmsSpace()->allocate(adjustedSize); | |
| 985 // Allocate the object live (grey) if the background collector has | |
| 986 // started marking. This is necessary because the marker may | |
| 987 // have passed this address and consequently this object will | |
| 988 // not otherwise be greyed and would be incorrectly swept up. | |
| 989 // Note that if this object contains references, the writing | |
| 990 // of those references will dirty the card containing this object | |
| 991 // allowing the object to be blackened (and its references scanned) | |
| 992 // either during a preclean phase or at the final checkpoint. | |
| 993 if (res != NULL) { | |
| 994 collector()->direct_allocated(res, adjustedSize); | |
| 995 _direct_allocated_words += adjustedSize; | |
| 996 // allocation counters | |
| 997 NOT_PRODUCT( | |
| 998 _numObjectsAllocated++; | |
| 999 _numWordsAllocated += (int)adjustedSize; | |
| 1000 ) | |
| 1001 } | |
| 1002 return res; | |
| 1003 } | |
| 1004 | |
| 1005 // In the case of direct allocation by mutators in a generation that | |
| 1006 // is being concurrently collected, the object must be allocated | |
| 1007 // live (grey) if the background collector has started marking. | |
| 1008 // This is necessary because the marker may | |
| 1009 // have passed this address and consequently this object will | |
| 1010 // not otherwise be greyed and would be incorrectly swept up. | |
| 1011 // Note that if this object contains references, the writing | |
| 1012 // of those references will dirty the card containing this object | |
| 1013 // allowing the object to be blackened (and its references scanned) | |
| 1014 // either during a preclean phase or at the final checkpoint. | |
| 1015 void CMSCollector::direct_allocated(HeapWord* start, size_t size) { | |
| 1016 assert(_markBitMap.covers(start, size), "Out of bounds"); | |
| 1017 if (_collectorState >= Marking) { | |
| 1018 MutexLockerEx y(_markBitMap.lock(), | |
| 1019 Mutex::_no_safepoint_check_flag); | |
| 1020 // [see comments preceding SweepClosure::do_blk() below for details] | |
| 1021 // 1. need to mark the object as live so it isn't collected | |
| 1022 // 2. need to mark the 2nd bit to indicate the object may be uninitialized | |
| 1023 // 3. need to mark the end of the object so sweeper can skip over it | |
| 1024 // if it's uninitialized when the sweeper reaches it. | |
| 1025 _markBitMap.mark(start); // object is live | |
| 1026 _markBitMap.mark(start + 1); // object is potentially uninitialized? | |
| 1027 _markBitMap.mark(start + size - 1); | |
| 1028 // mark end of object | |
| 1029 } | |
| 1030 // check that oop looks uninitialized | |
| 1031 assert(oop(start)->klass() == NULL, "_klass should be NULL"); | |
| 1032 } | |
| 1033 | |
| 1034 void CMSCollector::promoted(bool par, HeapWord* start, | |
| 1035 bool is_obj_array, size_t obj_size) { | |
| 1036 assert(_markBitMap.covers(start), "Out of bounds"); | |
| 1037 // See comment in direct_allocated() about when objects should | |
| 1038 // be allocated live. | |
| 1039 if (_collectorState >= Marking) { | |
| 1040 // we already hold the marking bit map lock, taken in | |
| 1041 // the prologue | |
| 1042 if (par) { | |
| 1043 _markBitMap.par_mark(start); | |
| 1044 } else { | |
| 1045 _markBitMap.mark(start); | |
| 1046 } | |
| 1047 // We don't need to mark the object as uninitialized (as | |
| 1048 // in direct_allocated above) because this is being done with the | |
| 1049 // world stopped and the object will be initialized by the | |
| 1050 // time the sweeper gets to look at it. | |
| 1051 assert(SafepointSynchronize::is_at_safepoint(), | |
| 1052 "expect promotion only at safepoints"); | |
| 1053 | |
| 1054 if (_collectorState < Sweeping) { | |
| 1055 // Mark the appropriate cards in the modUnionTable, so that | |
| 1056 // this object gets scanned before the sweep. If this is | |
| 1057 // not done, CMS generation references in the object might | |
| 1058 // not get marked. | |
| 1059 // For the case of arrays, which are otherwise precisely | |
| 1060 // marked, we need to dirty the entire array, not just its head. | |
| 1061 if (is_obj_array) { | |
| 1062 // The [par_]mark_range() method expects mr.end() below to | |
| 1063 // be aligned to the granularity of a bit's representation | |
| 1064 // in the heap. In the case of the MUT below, that's a | |
| 1065 // card size. | |
| 1066 MemRegion mr(start, | |
| 1067 (HeapWord*)round_to((intptr_t)(start + obj_size), | |
| 1068 CardTableModRefBS::card_size /* bytes */)); | |
| 1069 if (par) { | |
| 1070 _modUnionTable.par_mark_range(mr); | |
| 1071 } else { | |
| 1072 _modUnionTable.mark_range(mr); | |
| 1073 } | |
| 1074 } else { // not an obj array; we can just mark the head | |
| 1075 if (par) { | |
| 1076 _modUnionTable.par_mark(start); | |
| 1077 } else { | |
| 1078 _modUnionTable.mark(start); | |
| 1079 } | |
| 1080 } | |
| 1081 } | |
| 1082 } | |
| 1083 } | |
| 1084 | |
| 1085 static inline size_t percent_of_space(Space* space, HeapWord* addr) | |
| 1086 { | |
| 1087 size_t delta = pointer_delta(addr, space->bottom()); | |
| 1088 return (size_t)(delta * 100.0 / (space->capacity() / HeapWordSize)); | |
| 1089 } | |
| 1090 | |
| 1091 void CMSCollector::icms_update_allocation_limits() | |
| 1092 { | |
| 1093 Generation* gen0 = GenCollectedHeap::heap()->get_gen(0); | |
| 1094 EdenSpace* eden = gen0->as_DefNewGeneration()->eden(); | |
| 1095 | |
| 1096 const unsigned int duty_cycle = stats().icms_update_duty_cycle(); | |
| 1097 if (CMSTraceIncrementalPacing) { | |
| 1098 stats().print(); | |
| 1099 } | |
| 1100 | |
| 1101 assert(duty_cycle <= 100, "invalid duty cycle"); | |
| 1102 if (duty_cycle != 0) { | |
| 1103 // The duty_cycle is a percentage between 0 and 100; convert to words and | |
| 1104 // then compute the offset from the endpoints of the space. | |
| 1105 size_t free_words = eden->free() / HeapWordSize; | |
| 1106 double free_words_dbl = (double)free_words; | |
| 1107 size_t duty_cycle_words = (size_t)(free_words_dbl * duty_cycle / 100.0); | |
| 1108 size_t offset_words = (free_words - duty_cycle_words) / 2; | |
| 1109 | |
| 1110 _icms_start_limit = eden->top() + offset_words; | |
| 1111 _icms_stop_limit = eden->end() - offset_words; | |
| 1112 | |
| 1113 // The limits may be adjusted (shifted to the right) by | |
| 1114 // CMSIncrementalOffset, to allow the application more mutator time after a | |
| 1115 // young gen gc (when all mutators were stopped) and before CMS starts and | |
| 1116 // takes away one or more cpus. | |
| 1117 if (CMSIncrementalOffset != 0) { | |
| 1118 double adjustment_dbl = free_words_dbl * CMSIncrementalOffset / 100.0; | |
| 1119 size_t adjustment = (size_t)adjustment_dbl; | |
| 1120 HeapWord* tmp_stop = _icms_stop_limit + adjustment; | |
| 1121 if (tmp_stop > _icms_stop_limit && tmp_stop < eden->end()) { | |
| 1122 _icms_start_limit += adjustment; | |
| 1123 _icms_stop_limit = tmp_stop; | |
| 1124 } | |
| 1125 } | |
| 1126 } | |
| 1127 if (duty_cycle == 0 || (_icms_start_limit == _icms_stop_limit)) { | |
| 1128 _icms_start_limit = _icms_stop_limit = eden->end(); | |
| 1129 } | |
| 1130 | |
| 1131 // Install the new start limit. | |
| 1132 eden->set_soft_end(_icms_start_limit); | |
| 1133 | |
| 1134 if (CMSTraceIncrementalMode) { | |
| 1135 gclog_or_tty->print(" icms alloc limits: " | |
| 1136 PTR_FORMAT "," PTR_FORMAT | |
| 1137 " (" SIZE_FORMAT "%%," SIZE_FORMAT "%%) ", | |
| 1138 _icms_start_limit, _icms_stop_limit, | |
| 1139 percent_of_space(eden, _icms_start_limit), | |
| 1140 percent_of_space(eden, _icms_stop_limit)); | |
| 1141 if (Verbose) { | |
| 1142 gclog_or_tty->print("eden: "); | |
| 1143 eden->print_on(gclog_or_tty); | |
| 1144 } | |
| 1145 } | |
| 1146 } | |
| 1147 | |
| 1148 // Any changes here should try to maintain the invariant | |
| 1149 // that if this method is called with _icms_start_limit | |
| 1150 // and _icms_stop_limit both NULL, then it should return NULL | |
| 1151 // and not notify the icms thread. | |
| 1152 HeapWord* | |
| 1153 CMSCollector::allocation_limit_reached(Space* space, HeapWord* top, | |
| 1154 size_t word_size) | |
| 1155 { | |
| 1156 // A start_limit equal to end() means the duty cycle is 0, so treat that as a | |
| 1157 // nop. | |
| 1158 if (CMSIncrementalMode && _icms_start_limit != space->end()) { | |
| 1159 if (top <= _icms_start_limit) { | |
| 1160 if (CMSTraceIncrementalMode) { | |
| 1161 space->print_on(gclog_or_tty); | |
| 1162 gclog_or_tty->stamp(); | |
| 1163 gclog_or_tty->print_cr(" start limit top=" PTR_FORMAT | |
| 1164 ", new limit=" PTR_FORMAT | |
| 1165 " (" SIZE_FORMAT "%%)", | |
| 1166 top, _icms_stop_limit, | |
| 1167 percent_of_space(space, _icms_stop_limit)); | |
| 1168 } | |
| 1169 ConcurrentMarkSweepThread::start_icms(); | |
| 1170 assert(top < _icms_stop_limit, "Tautology"); | |
| 1171 if (word_size < pointer_delta(_icms_stop_limit, top)) { | |
| 1172 return _icms_stop_limit; | |
| 1173 } | |
| 1174 | |
| 1175 // The allocation will cross both the _start and _stop limits, so do the | |
| 1176 // stop notification also and return end(). | |
| 1177 if (CMSTraceIncrementalMode) { | |
| 1178 space->print_on(gclog_or_tty); | |
| 1179 gclog_or_tty->stamp(); | |
| 1180 gclog_or_tty->print_cr(" +stop limit top=" PTR_FORMAT | |
| 1181 ", new limit=" PTR_FORMAT | |
| 1182 " (" SIZE_FORMAT "%%)", | |
| 1183 top, space->end(), | |
| 1184 percent_of_space(space, space->end())); | |
| 1185 } | |
| 1186 ConcurrentMarkSweepThread::stop_icms(); | |
| 1187 return space->end(); | |
| 1188 } | |
| 1189 | |
| 1190 if (top <= _icms_stop_limit) { | |
| 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 (CMSTraceIncrementalMode) { | |
| 1205 space->print_on(gclog_or_tty); | |
| 1206 gclog_or_tty->stamp(); | |
| 1207 gclog_or_tty->print_cr(" end limit top=" PTR_FORMAT | |
| 1208 ", new limit=" PTR_FORMAT, | |
| 1209 top, NULL); | |
| 1210 } | |
| 1211 } | |
| 1212 | |
| 1213 return NULL; | |
| 1214 } | |
| 1215 | |
| 1216 oop ConcurrentMarkSweepGeneration::promote(oop obj, size_t obj_size, oop* ref) { | |
| 1217 assert(obj_size == (size_t)obj->size(), "bad obj_size passed in"); | |
| 1218 // allocate, copy and if necessary update promoinfo -- | |
| 1219 // delegate to underlying space. | |
| 1220 assert_lock_strong(freelistLock()); | |
| 1221 | |
| 1222 #ifndef PRODUCT | |
| 1223 if (Universe::heap()->promotion_should_fail()) { | |
| 1224 return NULL; | |
| 1225 } | |
| 1226 #endif // #ifndef PRODUCT | |
| 1227 | |
| 1228 oop res = _cmsSpace->promote(obj, obj_size, ref); | |
| 1229 if (res == NULL) { | |
| 1230 // expand and retry | |
| 1231 size_t s = _cmsSpace->expansionSpaceRequired(obj_size); // HeapWords | |
| 1232 expand(s*HeapWordSize, MinHeapDeltaBytes, | |
| 1233 CMSExpansionCause::_satisfy_promotion); | |
| 1234 // Since there's currently no next generation, we don't try to promote | |
| 1235 // into a more senior generation. | |
| 1236 assert(next_gen() == NULL, "assumption, based upon which no attempt " | |
| 1237 "is made to pass on a possibly failing " | |
| 1238 "promotion to next generation"); | |
| 1239 res = _cmsSpace->promote(obj, obj_size, ref); | |
| 1240 } | |
| 1241 if (res != NULL) { | |
| 1242 // See comment in allocate() about when objects should | |
| 1243 // be allocated live. | |
| 1244 assert(obj->is_oop(), "Will dereference klass pointer below"); | |
| 1245 collector()->promoted(false, // Not parallel | |
| 1246 (HeapWord*)res, obj->is_objArray(), obj_size); | |
| 1247 // promotion counters | |
| 1248 NOT_PRODUCT( | |
| 1249 _numObjectsPromoted++; | |
| 1250 _numWordsPromoted += | |
| 1251 (int)(CompactibleFreeListSpace::adjustObjectSize(obj->size())); | |
| 1252 ) | |
| 1253 } | |
| 1254 return res; | |
| 1255 } | |
| 1256 | |
| 1257 | |
| 1258 HeapWord* | |
| 1259 ConcurrentMarkSweepGeneration::allocation_limit_reached(Space* space, | |
| 1260 HeapWord* top, | |
| 1261 size_t word_sz) | |
| 1262 { | |
| 1263 return collector()->allocation_limit_reached(space, top, word_sz); | |
| 1264 } | |
| 1265 | |
| 1266 // Things to support parallel young-gen collection. | |
| 1267 oop | |
| 1268 ConcurrentMarkSweepGeneration::par_promote(int thread_num, | |
| 1269 oop old, markOop m, | |
| 1270 size_t word_sz) { | |
| 1271 #ifndef PRODUCT | |
| 1272 if (Universe::heap()->promotion_should_fail()) { | |
| 1273 return NULL; | |
| 1274 } | |
| 1275 #endif // #ifndef PRODUCT | |
| 1276 | |
| 1277 CMSParGCThreadState* ps = _par_gc_thread_states[thread_num]; | |
| 1278 PromotionInfo* promoInfo = &ps->promo; | |
| 1279 // if we are tracking promotions, then first ensure space for | |
| 1280 // promotion (including spooling space for saving header if necessary). | |
| 1281 // then allocate and copy, then track promoted info if needed. | |
| 1282 // When tracking (see PromotionInfo::track()), the mark word may | |
| 1283 // be displaced and in this case restoration of the mark word | |
| 1284 // occurs in the (oop_since_save_marks_)iterate phase. | |
| 1285 if (promoInfo->tracking() && !promoInfo->ensure_spooling_space()) { | |
| 1286 // Out of space for allocating spooling buffers; | |
| 1287 // try expanding and allocating spooling buffers. | |
| 1288 if (!expand_and_ensure_spooling_space(promoInfo)) { | |
| 1289 return NULL; | |
| 1290 } | |
| 1291 } | |
| 1292 assert(promoInfo->has_spooling_space(), "Control point invariant"); | |
| 1293 HeapWord* obj_ptr = ps->lab.alloc(word_sz); | |
| 1294 if (obj_ptr == NULL) { | |
| 1295 obj_ptr = expand_and_par_lab_allocate(ps, word_sz); | |
| 1296 if (obj_ptr == NULL) { | |
| 1297 return NULL; | |
| 1298 } | |
| 1299 } | |
| 1300 oop obj = oop(obj_ptr); | |
| 1301 assert(obj->klass() == NULL, "Object should be uninitialized here."); | |
| 1302 // Otherwise, copy the object. Here we must be careful to insert the | |
| 1303 // klass pointer last, since this marks the block as an allocated object. | |
| 1304 HeapWord* old_ptr = (HeapWord*)old; | |
| 1305 if (word_sz > (size_t)oopDesc::header_size()) { | |
| 1306 Copy::aligned_disjoint_words(old_ptr + oopDesc::header_size(), | |
| 1307 obj_ptr + oopDesc::header_size(), | |
| 1308 word_sz - oopDesc::header_size()); | |
| 1309 } | |
| 1310 // Restore the mark word copied above. | |
| 1311 obj->set_mark(m); | |
| 1312 // Now we can track the promoted object, if necessary. We take care | |
| 1313 // To delay the transition from uninitialized to full object | |
| 1314 // (i.e., insertion of klass pointer) until after, so that it | |
| 1315 // atomically becomes a promoted object. | |
| 1316 if (promoInfo->tracking()) { | |
| 1317 promoInfo->track((PromotedObject*)obj, old->klass()); | |
| 1318 } | |
| 1319 // Finally, install the klass pointer. | |
| 1320 obj->set_klass(old->klass()); | |
| 1321 | |
| 1322 assert(old->is_oop(), "Will dereference klass ptr below"); | |
| 1323 collector()->promoted(true, // parallel | |
| 1324 obj_ptr, old->is_objArray(), word_sz); | |
| 1325 | |
| 1326 NOT_PRODUCT( | |
| 1327 Atomic::inc(&_numObjectsPromoted); | |
| 1328 Atomic::add((jint)CompactibleFreeListSpace::adjustObjectSize(obj->size()), | |
| 1329 &_numWordsPromoted); | |
| 1330 ) | |
| 1331 | |
| 1332 return obj; | |
| 1333 } | |
| 1334 | |
| 1335 void | |
| 1336 ConcurrentMarkSweepGeneration:: | |
| 1337 par_promote_alloc_undo(int thread_num, | |
| 1338 HeapWord* obj, size_t word_sz) { | |
| 1339 // CMS does not support promotion undo. | |
| 1340 ShouldNotReachHere(); | |
| 1341 } | |
| 1342 | |
| 1343 void | |
| 1344 ConcurrentMarkSweepGeneration:: | |
| 1345 par_promote_alloc_done(int thread_num) { | |
| 1346 CMSParGCThreadState* ps = _par_gc_thread_states[thread_num]; | |
| 1347 ps->lab.retire(); | |
| 1348 #if CFLS_LAB_REFILL_STATS | |
| 1349 if (thread_num == 0) { | |
| 1350 _cmsSpace->print_par_alloc_stats(); | |
| 1351 } | |
| 1352 #endif | |
| 1353 } | |
| 1354 | |
| 1355 void | |
| 1356 ConcurrentMarkSweepGeneration:: | |
| 1357 par_oop_since_save_marks_iterate_done(int thread_num) { | |
| 1358 CMSParGCThreadState* ps = _par_gc_thread_states[thread_num]; | |
| 1359 ParScanWithoutBarrierClosure* dummy_cl = NULL; | |
| 1360 ps->promo.promoted_oops_iterate_nv(dummy_cl); | |
| 1361 } | |
| 1362 | |
| 1363 // XXXPERM | |
| 1364 bool ConcurrentMarkSweepGeneration::should_collect(bool full, | |
| 1365 size_t size, | |
| 1366 bool tlab) | |
| 1367 { | |
| 1368 // We allow a STW collection only if a full | |
| 1369 // collection was requested. | |
| 1370 return full || should_allocate(size, tlab); // FIX ME !!! | |
| 1371 // This and promotion failure handling are connected at the | |
| 1372 // hip and should be fixed by untying them. | |
| 1373 } | |
| 1374 | |
| 1375 bool CMSCollector::shouldConcurrentCollect() { | |
| 1376 if (_full_gc_requested) { | |
| 1377 assert(ExplicitGCInvokesConcurrent, "Unexpected state"); | |
| 1378 if (Verbose && PrintGCDetails) { | |
| 1379 gclog_or_tty->print_cr("CMSCollector: collect because of explicit " | |
| 1380 " gc request"); | |
| 1381 } | |
| 1382 return true; | |
| 1383 } | |
| 1384 | |
| 1385 // For debugging purposes, change the type of collection. | |
| 1386 // If the rotation is not on the concurrent collection | |
| 1387 // type, don't start a concurrent collection. | |
| 1388 NOT_PRODUCT( | |
| 1389 if (RotateCMSCollectionTypes && | |
| 1390 (_cmsGen->debug_collection_type() != | |
| 1391 ConcurrentMarkSweepGeneration::Concurrent_collection_type)) { | |
| 1392 assert(_cmsGen->debug_collection_type() != | |
| 1393 ConcurrentMarkSweepGeneration::Unknown_collection_type, | |
| 1394 "Bad cms collection type"); | |
| 1395 return false; | |
| 1396 } | |
| 1397 ) | |
| 1398 | |
| 1399 FreelistLocker x(this); | |
| 1400 // ------------------------------------------------------------------ | |
| 1401 // Print out lots of information which affects the initiation of | |
| 1402 // a collection. | |
| 1403 if (PrintCMSInitiationStatistics && stats().valid()) { | |
| 1404 gclog_or_tty->print("CMSCollector shouldConcurrentCollect: "); | |
| 1405 gclog_or_tty->stamp(); | |
| 1406 gclog_or_tty->print_cr(""); | |
| 1407 stats().print_on(gclog_or_tty); | |
| 1408 gclog_or_tty->print_cr("time_until_cms_gen_full %3.7f", | |
| 1409 stats().time_until_cms_gen_full()); | |
| 1410 gclog_or_tty->print_cr("free="SIZE_FORMAT, _cmsGen->free()); | |
| 1411 gclog_or_tty->print_cr("contiguous_available="SIZE_FORMAT, | |
| 1412 _cmsGen->contiguous_available()); | |
| 1413 gclog_or_tty->print_cr("promotion_rate=%g", stats().promotion_rate()); | |
| 1414 gclog_or_tty->print_cr("cms_allocation_rate=%g", stats().cms_allocation_rate()); | |
| 1415 gclog_or_tty->print_cr("occupancy=%3.7f", _cmsGen->occupancy()); | |
| 1416 gclog_or_tty->print_cr("initiatingOccupancy=%3.7f", initiatingOccupancy()); | |
| 1417 } | |
| 1418 // ------------------------------------------------------------------ | |
| 1419 | |
| 1420 // If the estimated time to complete a cms collection (cms_duration()) | |
| 1421 // is less than the estimated time remaining until the cms generation | |
| 1422 // is full, start a collection. | |
| 1423 if (!UseCMSInitiatingOccupancyOnly) { | |
| 1424 if (stats().valid()) { | |
| 1425 if (stats().time_until_cms_start() == 0.0) { | |
| 1426 return true; | |
| 1427 } | |
| 1428 } else { | |
| 1429 // We want to conservatively collect somewhat early in order | |
| 1430 // to try and "bootstrap" our CMS/promotion statistics; | |
| 1431 // this branch will not fire after the first successful CMS | |
| 1432 // collection because the stats should then be valid. | |
| 1433 if (_cmsGen->occupancy() >= _bootstrap_occupancy) { | |
| 1434 if (Verbose && PrintGCDetails) { | |
| 1435 gclog_or_tty->print_cr( | |
| 1436 " CMSCollector: collect for bootstrapping statistics:" | |
| 1437 " occupancy = %f, boot occupancy = %f", _cmsGen->occupancy(), | |
| 1438 _bootstrap_occupancy); | |
| 1439 } | |
| 1440 return true; | |
| 1441 } | |
| 1442 } | |
| 1443 } | |
| 1444 | |
| 1445 // Otherwise, we start a collection cycle if either the perm gen or | |
| 1446 // old gen want a collection cycle started. Each may use | |
| 1447 // an appropriate criterion for making this decision. | |
| 1448 // XXX We need to make sure that the gen expansion | |
| 1449 // criterion dovetails well with this. | |
| 1450 if (_cmsGen->shouldConcurrentCollect(initiatingOccupancy())) { | |
| 1451 if (Verbose && PrintGCDetails) { | |
| 1452 gclog_or_tty->print_cr("CMS old gen initiated"); | |
| 1453 } | |
| 1454 return true; | |
| 1455 } | |
| 1456 | |
| 1457 if (cms_should_unload_classes() && | |
| 1458 _permGen->shouldConcurrentCollect(initiatingOccupancy())) { | |
| 1459 if (Verbose && PrintGCDetails) { | |
| 1460 gclog_or_tty->print_cr("CMS perm gen initiated"); | |
| 1461 } | |
| 1462 return true; | |
| 1463 } | |
| 1464 | |
| 1465 return false; | |
| 1466 } | |
| 1467 | |
| 1468 // Clear _expansion_cause fields of constituent generations | |
| 1469 void CMSCollector::clear_expansion_cause() { | |
| 1470 _cmsGen->clear_expansion_cause(); | |
| 1471 _permGen->clear_expansion_cause(); | |
| 1472 } | |
| 1473 | |
| 1474 bool ConcurrentMarkSweepGeneration::shouldConcurrentCollect( | |
| 1475 double initiatingOccupancy) { | |
| 1476 // We should be conservative in starting a collection cycle. To | |
| 1477 // start too eagerly runs the risk of collecting too often in the | |
| 1478 // extreme. To collect too rarely falls back on full collections, | |
| 1479 // which works, even if not optimum in terms of concurrent work. | |
| 1480 // As a work around for too eagerly collecting, use the flag | |
| 1481 // UseCMSInitiatingOccupancyOnly. This also has the advantage of | |
| 1482 // giving the user an easily understandable way of controlling the | |
| 1483 // collections. | |
| 1484 // We want to start a new collection cycle if any of the following | |
| 1485 // conditions hold: | |
| 1486 // . our current occupancy exceeds the initiating occupancy, or | |
| 1487 // . we recently needed to expand and have not since that expansion, | |
| 1488 // collected, or | |
| 1489 // . we are not using adaptive free lists and linear allocation is | |
| 1490 // going to fail, or | |
| 1491 // . (for old gen) incremental collection has already failed or | |
| 1492 // may soon fail in the near future as we may not be able to absorb | |
| 1493 // promotions. | |
| 1494 assert_lock_strong(freelistLock()); | |
| 1495 | |
| 1496 if (occupancy() > initiatingOccupancy) { | |
| 1497 if (PrintGCDetails && Verbose) { | |
| 1498 gclog_or_tty->print(" %s: collect because of occupancy %f / %f ", | |
| 1499 short_name(), occupancy(), initiatingOccupancy); | |
| 1500 } | |
| 1501 return true; | |
| 1502 } | |
| 1503 if (UseCMSInitiatingOccupancyOnly) { | |
| 1504 return false; | |
| 1505 } | |
| 1506 if (expansion_cause() == CMSExpansionCause::_satisfy_allocation) { | |
| 1507 if (PrintGCDetails && Verbose) { | |
| 1508 gclog_or_tty->print(" %s: collect because expanded for allocation ", | |
| 1509 short_name()); | |
| 1510 } | |
| 1511 return true; | |
| 1512 } | |
| 1513 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 1514 assert(gch->collector_policy()->is_two_generation_policy(), | |
| 1515 "You may want to check the correctness of the following"); | |
| 1516 if (gch->incremental_collection_will_fail()) { | |
| 1517 if (PrintGCDetails && Verbose) { | |
| 1518 gclog_or_tty->print(" %s: collect because incremental collection will fail ", | |
| 1519 short_name()); | |
| 1520 } | |
| 1521 return true; | |
| 1522 } | |
| 1523 if (!_cmsSpace->adaptive_freelists() && | |
| 1524 _cmsSpace->linearAllocationWouldFail()) { | |
| 1525 if (PrintGCDetails && Verbose) { | |
| 1526 gclog_or_tty->print(" %s: collect because of linAB ", | |
| 1527 short_name()); | |
| 1528 } | |
| 1529 return true; | |
| 1530 } | |
| 1531 return false; | |
| 1532 } | |
| 1533 | |
| 1534 void ConcurrentMarkSweepGeneration::collect(bool full, | |
| 1535 bool clear_all_soft_refs, | |
| 1536 size_t size, | |
| 1537 bool tlab) | |
| 1538 { | |
| 1539 collector()->collect(full, clear_all_soft_refs, size, tlab); | |
| 1540 } | |
| 1541 | |
| 1542 void CMSCollector::collect(bool full, | |
| 1543 bool clear_all_soft_refs, | |
| 1544 size_t size, | |
| 1545 bool tlab) | |
| 1546 { | |
| 1547 if (!UseCMSCollectionPassing && _collectorState > Idling) { | |
| 1548 // For debugging purposes skip the collection if the state | |
| 1549 // is not currently idle | |
| 1550 if (TraceCMSState) { | |
| 1551 gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " skipped full:%d CMS state %d", | |
| 1552 Thread::current(), full, _collectorState); | |
| 1553 } | |
| 1554 return; | |
| 1555 } | |
| 1556 | |
| 1557 // The following "if" branch is present for defensive reasons. | |
| 1558 // In the current uses of this interface, it can be replaced with: | |
| 1559 // assert(!GC_locker.is_active(), "Can't be called otherwise"); | |
| 1560 // But I am not placing that assert here to allow future | |
| 1561 // generality in invoking this interface. | |
| 1562 if (GC_locker::is_active()) { | |
| 1563 // A consistency test for GC_locker | |
| 1564 assert(GC_locker::needs_gc(), "Should have been set already"); | |
| 1565 // Skip this foreground collection, instead | |
| 1566 // expanding the heap if necessary. | |
| 1567 // Need the free list locks for the call to free() in compute_new_size() | |
| 1568 compute_new_size(); | |
| 1569 return; | |
| 1570 } | |
| 1571 acquire_control_and_collect(full, clear_all_soft_refs); | |
| 1572 _full_gcs_since_conc_gc++; | |
| 1573 | |
| 1574 } | |
| 1575 | |
| 1576 void CMSCollector::request_full_gc(unsigned int full_gc_count) { | |
| 1577 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 1578 unsigned int gc_count = gch->total_full_collections(); | |
| 1579 if (gc_count == full_gc_count) { | |
| 1580 MutexLockerEx y(CGC_lock, Mutex::_no_safepoint_check_flag); | |
| 1581 _full_gc_requested = true; | |
| 1582 CGC_lock->notify(); // nudge CMS thread | |
| 1583 } | |
| 1584 } | |
| 1585 | |
| 1586 | |
| 1587 // The foreground and background collectors need to coordinate in order | |
| 1588 // to make sure that they do not mutually interfere with CMS collections. | |
| 1589 // When a background collection is active, | |
| 1590 // the foreground collector may need to take over (preempt) and | |
| 1591 // synchronously complete an ongoing collection. Depending on the | |
| 1592 // frequency of the background collections and the heap usage | |
| 1593 // of the application, this preemption can be seldom or frequent. | |
| 1594 // There are only certain | |
| 1595 // points in the background collection that the "collection-baton" | |
| 1596 // can be passed to the foreground collector. | |
| 1597 // | |
| 1598 // The foreground collector will wait for the baton before | |
| 1599 // starting any part of the collection. The foreground collector | |
| 1600 // will only wait at one location. | |
| 1601 // | |
| 1602 // The background collector will yield the baton before starting a new | |
| 1603 // phase of the collection (e.g., before initial marking, marking from roots, | |
| 1604 // precleaning, final re-mark, sweep etc.) This is normally done at the head | |
| 1605 // of the loop which switches the phases. The background collector does some | |
| 1606 // of the phases (initial mark, final re-mark) with the world stopped. | |
| 1607 // Because of locking involved in stopping the world, | |
| 1608 // the foreground collector should not block waiting for the background | |
| 1609 // collector when it is doing a stop-the-world phase. The background | |
| 1610 // collector will yield the baton at an additional point just before | |
| 1611 // it enters a stop-the-world phase. Once the world is stopped, the | |
| 1612 // background collector checks the phase of the collection. If the | |
| 1613 // phase has not changed, it proceeds with the collection. If the | |
| 1614 // phase has changed, it skips that phase of the collection. See | |
| 1615 // the comments on the use of the Heap_lock in collect_in_background(). | |
| 1616 // | |
| 1617 // Variable used in baton passing. | |
| 1618 // _foregroundGCIsActive - Set to true by the foreground collector when | |
| 1619 // it wants the baton. The foreground clears it when it has finished | |
| 1620 // the collection. | |
| 1621 // _foregroundGCShouldWait - Set to true by the background collector | |
| 1622 // when it is running. The foreground collector waits while | |
| 1623 // _foregroundGCShouldWait is true. | |
| 1624 // CGC_lock - monitor used to protect access to the above variables | |
| 1625 // and to notify the foreground and background collectors. | |
| 1626 // _collectorState - current state of the CMS collection. | |
| 1627 // | |
| 1628 // The foreground collector | |
| 1629 // acquires the CGC_lock | |
| 1630 // sets _foregroundGCIsActive | |
| 1631 // waits on the CGC_lock for _foregroundGCShouldWait to be false | |
| 1632 // various locks acquired in preparation for the collection | |
| 1633 // are released so as not to block the background collector | |
| 1634 // that is in the midst of a collection | |
| 1635 // proceeds with the collection | |
| 1636 // clears _foregroundGCIsActive | |
| 1637 // returns | |
| 1638 // | |
| 1639 // The background collector in a loop iterating on the phases of the | |
| 1640 // collection | |
| 1641 // acquires the CGC_lock | |
| 1642 // sets _foregroundGCShouldWait | |
| 1643 // if _foregroundGCIsActive is set | |
| 1644 // clears _foregroundGCShouldWait, notifies _CGC_lock | |
| 1645 // waits on _CGC_lock for _foregroundGCIsActive to become false | |
| 1646 // and exits the loop. | |
| 1647 // otherwise | |
| 1648 // proceed with that phase of the collection | |
| 1649 // if the phase is a stop-the-world phase, | |
| 1650 // yield the baton once more just before enqueueing | |
| 1651 // the stop-world CMS operation (executed by the VM thread). | |
| 1652 // returns after all phases of the collection are done | |
| 1653 // | |
| 1654 | |
| 1655 void CMSCollector::acquire_control_and_collect(bool full, | |
| 1656 bool clear_all_soft_refs) { | |
| 1657 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint"); | |
| 1658 assert(!Thread::current()->is_ConcurrentGC_thread(), | |
| 1659 "shouldn't try to acquire control from self!"); | |
| 1660 | |
| 1661 // Start the protocol for acquiring control of the | |
| 1662 // collection from the background collector (aka CMS thread). | |
| 1663 assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(), | |
| 1664 "VM thread should have CMS token"); | |
| 1665 // Remember the possibly interrupted state of an ongoing | |
| 1666 // concurrent collection | |
| 1667 CollectorState first_state = _collectorState; | |
| 1668 | |
| 1669 // Signal to a possibly ongoing concurrent collection that | |
| 1670 // we want to do a foreground collection. | |
| 1671 _foregroundGCIsActive = true; | |
| 1672 | |
| 1673 // Disable incremental mode during a foreground collection. | |
| 1674 ICMSDisabler icms_disabler; | |
| 1675 | |
| 1676 // release locks and wait for a notify from the background collector | |
| 1677 // releasing the locks in only necessary for phases which | |
| 1678 // do yields to improve the granularity of the collection. | |
| 1679 assert_lock_strong(bitMapLock()); | |
| 1680 // We need to lock the Free list lock for the space that we are | |
| 1681 // currently collecting. | |
| 1682 assert(haveFreelistLocks(), "Must be holding free list locks"); | |
| 1683 bitMapLock()->unlock(); | |
| 1684 releaseFreelistLocks(); | |
| 1685 { | |
| 1686 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
| 1687 if (_foregroundGCShouldWait) { | |
| 1688 // We are going to be waiting for action for the CMS thread; | |
| 1689 // it had better not be gone (for instance at shutdown)! | |
| 1690 assert(ConcurrentMarkSweepThread::cmst() != NULL, | |
| 1691 "CMS thread must be running"); | |
| 1692 // Wait here until the background collector gives us the go-ahead | |
| 1693 ConcurrentMarkSweepThread::clear_CMS_flag( | |
| 1694 ConcurrentMarkSweepThread::CMS_vm_has_token); // release token | |
| 1695 // Get a possibly blocked CMS thread going: | |
| 1696 // Note that we set _foregroundGCIsActive true above, | |
| 1697 // without protection of the CGC_lock. | |
| 1698 CGC_lock->notify(); | |
| 1699 assert(!ConcurrentMarkSweepThread::vm_thread_wants_cms_token(), | |
| 1700 "Possible deadlock"); | |
| 1701 while (_foregroundGCShouldWait) { | |
| 1702 // wait for notification | |
| 1703 CGC_lock->wait(Mutex::_no_safepoint_check_flag); | |
| 1704 // Possibility of delay/starvation here, since CMS token does | |
| 1705 // not know to give priority to VM thread? Actually, i think | |
| 1706 // there wouldn't be any delay/starvation, but the proof of | |
| 1707 // that "fact" (?) appears non-trivial. XXX 20011219YSR | |
| 1708 } | |
| 1709 ConcurrentMarkSweepThread::set_CMS_flag( | |
| 1710 ConcurrentMarkSweepThread::CMS_vm_has_token); | |
| 1711 } | |
| 1712 } | |
| 1713 // The CMS_token is already held. Get back the other locks. | |
| 1714 assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(), | |
| 1715 "VM thread should have CMS token"); | |
| 1716 getFreelistLocks(); | |
| 1717 bitMapLock()->lock_without_safepoint_check(); | |
| 1718 if (TraceCMSState) { | |
| 1719 gclog_or_tty->print_cr("CMS foreground collector has asked for control " | |
| 1720 INTPTR_FORMAT " with first state %d", Thread::current(), first_state); | |
| 1721 gclog_or_tty->print_cr(" gets control with state %d", _collectorState); | |
| 1722 } | |
| 1723 | |
| 1724 // Check if we need to do a compaction, or if not, whether | |
| 1725 // we need to start the mark-sweep from scratch. | |
| 1726 bool should_compact = false; | |
| 1727 bool should_start_over = false; | |
| 1728 decide_foreground_collection_type(clear_all_soft_refs, | |
| 1729 &should_compact, &should_start_over); | |
| 1730 | |
| 1731 NOT_PRODUCT( | |
| 1732 if (RotateCMSCollectionTypes) { | |
| 1733 if (_cmsGen->debug_collection_type() == | |
| 1734 ConcurrentMarkSweepGeneration::MSC_foreground_collection_type) { | |
| 1735 should_compact = true; | |
| 1736 } else if (_cmsGen->debug_collection_type() == | |
| 1737 ConcurrentMarkSweepGeneration::MS_foreground_collection_type) { | |
| 1738 should_compact = false; | |
| 1739 } | |
| 1740 } | |
| 1741 ) | |
| 1742 | |
| 1743 if (PrintGCDetails && first_state > Idling) { | |
| 1744 GCCause::Cause cause = GenCollectedHeap::heap()->gc_cause(); | |
| 1745 if (GCCause::is_user_requested_gc(cause) || | |
| 1746 GCCause::is_serviceability_requested_gc(cause)) { | |
| 1747 gclog_or_tty->print(" (concurrent mode interrupted)"); | |
| 1748 } else { | |
| 1749 gclog_or_tty->print(" (concurrent mode failure)"); | |
| 1750 } | |
| 1751 } | |
| 1752 | |
| 1753 if (should_compact) { | |
| 1754 // If the collection is being acquired from the background | |
| 1755 // collector, there may be references on the discovered | |
| 1756 // references lists that have NULL referents (being those | |
| 1757 // that were concurrently cleared by a mutator) or | |
| 1758 // that are no longer active (having been enqueued concurrently | |
| 1759 // by the mutator). | |
| 1760 // Scrub the list of those references because Mark-Sweep-Compact | |
| 1761 // code assumes referents are not NULL and that all discovered | |
| 1762 // Reference objects are active. | |
| 1763 ref_processor()->clean_up_discovered_references(); | |
| 1764 | |
| 1765 do_compaction_work(clear_all_soft_refs); | |
| 1766 | |
| 1767 // Has the GC time limit been exceeded? | |
| 1768 check_gc_time_limit(); | |
| 1769 | |
| 1770 } else { | |
| 1771 do_mark_sweep_work(clear_all_soft_refs, first_state, | |
| 1772 should_start_over); | |
| 1773 } | |
| 1774 // Reset the expansion cause, now that we just completed | |
| 1775 // a collection cycle. | |
| 1776 clear_expansion_cause(); | |
| 1777 _foregroundGCIsActive = false; | |
| 1778 return; | |
| 1779 } | |
| 1780 | |
| 1781 void CMSCollector::check_gc_time_limit() { | |
| 1782 | |
| 1783 // Ignore explicit GC's. Exiting here does not set the flag and | |
| 1784 // does not reset the count. Updating of the averages for system | |
| 1785 // GC's is still controlled by UseAdaptiveSizePolicyWithSystemGC. | |
| 1786 GCCause::Cause gc_cause = GenCollectedHeap::heap()->gc_cause(); | |
| 1787 if (GCCause::is_user_requested_gc(gc_cause) || | |
| 1788 GCCause::is_serviceability_requested_gc(gc_cause)) { | |
| 1789 return; | |
| 1790 } | |
| 1791 | |
| 1792 // Calculate the fraction of the CMS generation was freed during | |
| 1793 // the last collection. | |
| 1794 // Only consider the STW compacting cost for now. | |
| 1795 // | |
| 1796 // Note that the gc time limit test only works for the collections | |
| 1797 // of the young gen + tenured gen and not for collections of the | |
| 1798 // permanent gen. That is because the calculation of the space | |
| 1799 // freed by the collection is the free space in the young gen + | |
| 1800 // tenured gen. | |
| 1801 | |
| 1802 double fraction_free = | |
| 1803 ((double)_cmsGen->free())/((double)_cmsGen->max_capacity()); | |
| 1804 if ((100.0 * size_policy()->compacting_gc_cost()) > | |
| 1805 ((double) GCTimeLimit) && | |
| 1806 ((fraction_free * 100) < GCHeapFreeLimit)) { | |
| 1807 size_policy()->inc_gc_time_limit_count(); | |
| 1808 if (UseGCOverheadLimit && | |
| 1809 (size_policy()->gc_time_limit_count() > | |
| 1810 AdaptiveSizePolicyGCTimeLimitThreshold)) { | |
| 1811 size_policy()->set_gc_time_limit_exceeded(true); | |
| 1812 // Avoid consecutive OOM due to the gc time limit by resetting | |
| 1813 // the counter. | |
| 1814 size_policy()->reset_gc_time_limit_count(); | |
| 1815 if (PrintGCDetails) { | |
| 1816 gclog_or_tty->print_cr(" GC is exceeding overhead limit " | |
| 1817 "of %d%%", GCTimeLimit); | |
| 1818 } | |
| 1819 } else { | |
| 1820 if (PrintGCDetails) { | |
| 1821 gclog_or_tty->print_cr(" GC would exceed overhead limit " | |
| 1822 "of %d%%", GCTimeLimit); | |
| 1823 } | |
| 1824 } | |
| 1825 } else { | |
| 1826 size_policy()->reset_gc_time_limit_count(); | |
| 1827 } | |
| 1828 } | |
| 1829 | |
| 1830 // Resize the perm generation and the tenured generation | |
| 1831 // after obtaining the free list locks for the | |
| 1832 // two generations. | |
| 1833 void CMSCollector::compute_new_size() { | |
| 1834 assert_locked_or_safepoint(Heap_lock); | |
| 1835 FreelistLocker z(this); | |
| 1836 _permGen->compute_new_size(); | |
| 1837 _cmsGen->compute_new_size(); | |
| 1838 } | |
| 1839 | |
| 1840 // A work method used by foreground collection to determine | |
| 1841 // what type of collection (compacting or not, continuing or fresh) | |
| 1842 // it should do. | |
| 1843 // NOTE: the intent is to make UseCMSCompactAtFullCollection | |
| 1844 // and CMSCompactWhenClearAllSoftRefs the default in the future | |
| 1845 // and do away with the flags after a suitable period. | |
| 1846 void CMSCollector::decide_foreground_collection_type( | |
| 1847 bool clear_all_soft_refs, bool* should_compact, | |
| 1848 bool* should_start_over) { | |
| 1849 // Normally, we'll compact only if the UseCMSCompactAtFullCollection | |
| 1850 // flag is set, and we have either requested a System.gc() or | |
| 1851 // the number of full gc's since the last concurrent cycle | |
| 1852 // has exceeded the threshold set by CMSFullGCsBeforeCompaction, | |
| 1853 // or if an incremental collection has failed | |
| 1854 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 1855 assert(gch->collector_policy()->is_two_generation_policy(), | |
| 1856 "You may want to check the correctness of the following"); | |
| 1857 // Inform cms gen if this was due to partial collection failing. | |
| 1858 // The CMS gen may use this fact to determine its expansion policy. | |
| 1859 if (gch->incremental_collection_will_fail()) { | |
| 1860 assert(!_cmsGen->incremental_collection_failed(), | |
| 1861 "Should have been noticed, reacted to and cleared"); | |
| 1862 _cmsGen->set_incremental_collection_failed(); | |
| 1863 } | |
| 1864 *should_compact = | |
| 1865 UseCMSCompactAtFullCollection && | |
| 1866 ((_full_gcs_since_conc_gc >= CMSFullGCsBeforeCompaction) || | |
| 1867 GCCause::is_user_requested_gc(gch->gc_cause()) || | |
| 1868 gch->incremental_collection_will_fail()); | |
| 1869 *should_start_over = false; | |
| 1870 if (clear_all_soft_refs && !*should_compact) { | |
| 1871 // We are about to do a last ditch collection attempt | |
| 1872 // so it would normally make sense to do a compaction | |
| 1873 // to reclaim as much space as possible. | |
| 1874 if (CMSCompactWhenClearAllSoftRefs) { | |
| 1875 // Default: The rationale is that in this case either | |
| 1876 // we are past the final marking phase, in which case | |
| 1877 // we'd have to start over, or so little has been done | |
| 1878 // that there's little point in saving that work. Compaction | |
| 1879 // appears to be the sensible choice in either case. | |
| 1880 *should_compact = true; | |
| 1881 } else { | |
| 1882 // We have been asked to clear all soft refs, but not to | |
| 1883 // compact. Make sure that we aren't past the final checkpoint | |
| 1884 // phase, for that is where we process soft refs. If we are already | |
| 1885 // past that phase, we'll need to redo the refs discovery phase and | |
| 1886 // if necessary clear soft refs that weren't previously | |
| 1887 // cleared. We do so by remembering the phase in which | |
| 1888 // we came in, and if we are past the refs processing | |
| 1889 // phase, we'll choose to just redo the mark-sweep | |
| 1890 // collection from scratch. | |
| 1891 if (_collectorState > FinalMarking) { | |
| 1892 // We are past the refs processing phase; | |
| 1893 // start over and do a fresh synchronous CMS cycle | |
| 1894 _collectorState = Resetting; // skip to reset to start new cycle | |
| 1895 reset(false /* == !asynch */); | |
| 1896 *should_start_over = true; | |
| 1897 } // else we can continue a possibly ongoing current cycle | |
| 1898 } | |
| 1899 } | |
| 1900 } | |
| 1901 | |
| 1902 // A work method used by the foreground collector to do | |
| 1903 // a mark-sweep-compact. | |
| 1904 void CMSCollector::do_compaction_work(bool clear_all_soft_refs) { | |
| 1905 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 1906 TraceTime t("CMS:MSC ", PrintGCDetails && Verbose, true, gclog_or_tty); | |
| 1907 if (PrintGC && Verbose && !(GCCause::is_user_requested_gc(gch->gc_cause()))) { | |
| 1908 gclog_or_tty->print_cr("Compact ConcurrentMarkSweepGeneration after %d " | |
| 1909 "collections passed to foreground collector", _full_gcs_since_conc_gc); | |
| 1910 } | |
| 1911 | |
| 1912 // Sample collection interval time and reset for collection pause. | |
| 1913 if (UseAdaptiveSizePolicy) { | |
| 1914 size_policy()->msc_collection_begin(); | |
| 1915 } | |
| 1916 | |
| 1917 // Temporarily widen the span of the weak reference processing to | |
| 1918 // the entire heap. | |
| 1919 MemRegion new_span(GenCollectedHeap::heap()->reserved_region()); | |
| 1920 ReferenceProcessorSpanMutator x(ref_processor(), new_span); | |
| 1921 | |
| 1922 // Temporarily, clear the "is_alive_non_header" field of the | |
| 1923 // reference processor. | |
| 1924 ReferenceProcessorIsAliveMutator y(ref_processor(), NULL); | |
| 1925 | |
| 1926 // Temporarily make reference _processing_ single threaded (non-MT). | |
| 1927 ReferenceProcessorMTProcMutator z(ref_processor(), false); | |
| 1928 | |
| 1929 // Temporarily make refs discovery atomic | |
| 1930 ReferenceProcessorAtomicMutator w(ref_processor(), true); | |
| 1931 | |
| 1932 ref_processor()->set_enqueuing_is_done(false); | |
| 1933 ref_processor()->enable_discovery(); | |
| 1934 // If an asynchronous collection finishes, the _modUnionTable is | |
| 1935 // all clear. If we are assuming the collection from an asynchronous | |
| 1936 // collection, clear the _modUnionTable. | |
| 1937 assert(_collectorState != Idling || _modUnionTable.isAllClear(), | |
| 1938 "_modUnionTable should be clear if the baton was not passed"); | |
| 1939 _modUnionTable.clear_all(); | |
| 1940 | |
| 1941 // We must adjust the allocation statistics being maintained | |
| 1942 // in the free list space. We do so by reading and clearing | |
| 1943 // the sweep timer and updating the block flux rate estimates below. | |
| 1944 assert(_sweep_timer.is_active(), "We should never see the timer inactive"); | |
| 1945 _sweep_timer.stop(); | |
| 1946 // Note that we do not use this sample to update the _sweep_estimate. | |
| 1947 _cmsGen->cmsSpace()->beginSweepFLCensus((float)(_sweep_timer.seconds()), | |
| 1948 _sweep_estimate.padded_average()); | |
| 1949 | |
| 1950 GenMarkSweep::invoke_at_safepoint(_cmsGen->level(), | |
| 1951 ref_processor(), clear_all_soft_refs); | |
| 1952 #ifdef ASSERT | |
| 1953 CompactibleFreeListSpace* cms_space = _cmsGen->cmsSpace(); | |
| 1954 size_t free_size = cms_space->free(); | |
| 1955 assert(free_size == | |
| 1956 pointer_delta(cms_space->end(), cms_space->compaction_top()) | |
| 1957 * HeapWordSize, | |
| 1958 "All the free space should be compacted into one chunk at top"); | |
| 1959 assert(cms_space->dictionary()->totalChunkSize( | |
| 1960 debug_only(cms_space->freelistLock())) == 0 || | |
| 1961 cms_space->totalSizeInIndexedFreeLists() == 0, | |
| 1962 "All the free space should be in a single chunk"); | |
| 1963 size_t num = cms_space->totalCount(); | |
| 1964 assert((free_size == 0 && num == 0) || | |
| 1965 (free_size > 0 && (num == 1 || num == 2)), | |
| 1966 "There should be at most 2 free chunks after compaction"); | |
| 1967 #endif // ASSERT | |
| 1968 _collectorState = Resetting; | |
| 1969 assert(_restart_addr == NULL, | |
| 1970 "Should have been NULL'd before baton was passed"); | |
| 1971 reset(false /* == !asynch */); | |
| 1972 _cmsGen->reset_after_compaction(); | |
| 1973 | |
| 1974 if (verifying() && !cms_should_unload_classes()) { | |
| 1975 perm_gen_verify_bit_map()->clear_all(); | |
| 1976 } | |
| 1977 | |
| 1978 // Clear any data recorded in the PLAB chunk arrays. | |
| 1979 if (_survivor_plab_array != NULL) { | |
| 1980 reset_survivor_plab_arrays(); | |
| 1981 } | |
| 1982 | |
| 1983 // Adjust the per-size allocation stats for the next epoch. | |
| 1984 _cmsGen->cmsSpace()->endSweepFLCensus(sweepCount() /* fake */); | |
| 1985 // Restart the "sweep timer" for next epoch. | |
| 1986 _sweep_timer.reset(); | |
| 1987 _sweep_timer.start(); | |
| 1988 | |
| 1989 // Sample collection pause time and reset for collection interval. | |
| 1990 if (UseAdaptiveSizePolicy) { | |
| 1991 size_policy()->msc_collection_end(gch->gc_cause()); | |
| 1992 } | |
| 1993 | |
| 1994 // For a mark-sweep-compact, compute_new_size() will be called | |
| 1995 // in the heap's do_collection() method. | |
| 1996 } | |
| 1997 | |
| 1998 // A work method used by the foreground collector to do | |
| 1999 // a mark-sweep, after taking over from a possibly on-going | |
| 2000 // concurrent mark-sweep collection. | |
| 2001 void CMSCollector::do_mark_sweep_work(bool clear_all_soft_refs, | |
| 2002 CollectorState first_state, bool should_start_over) { | |
| 2003 if (PrintGC && Verbose) { | |
| 2004 gclog_or_tty->print_cr("Pass concurrent collection to foreground " | |
| 2005 "collector with count %d", | |
| 2006 _full_gcs_since_conc_gc); | |
| 2007 } | |
| 2008 switch (_collectorState) { | |
| 2009 case Idling: | |
| 2010 if (first_state == Idling || should_start_over) { | |
| 2011 // The background GC was not active, or should | |
| 2012 // restarted from scratch; start the cycle. | |
| 2013 _collectorState = InitialMarking; | |
| 2014 } | |
| 2015 // If first_state was not Idling, then a background GC | |
| 2016 // was in progress and has now finished. No need to do it | |
| 2017 // again. Leave the state as Idling. | |
| 2018 break; | |
| 2019 case Precleaning: | |
| 2020 // In the foreground case don't do the precleaning since | |
| 2021 // it is not done concurrently and there is extra work | |
| 2022 // required. | |
| 2023 _collectorState = FinalMarking; | |
| 2024 } | |
| 2025 if (PrintGCDetails && | |
| 2026 (_collectorState > Idling || | |
| 2027 !GCCause::is_user_requested_gc(GenCollectedHeap::heap()->gc_cause()))) { | |
| 2028 gclog_or_tty->print(" (concurrent mode failure)"); | |
| 2029 } | |
| 2030 collect_in_foreground(clear_all_soft_refs); | |
| 2031 | |
| 2032 // For a mark-sweep, compute_new_size() will be called | |
| 2033 // in the heap's do_collection() method. | |
| 2034 } | |
| 2035 | |
| 2036 | |
| 2037 void CMSCollector::getFreelistLocks() const { | |
| 2038 // Get locks for all free lists in all generations that this | |
| 2039 // collector is responsible for | |
| 2040 _cmsGen->freelistLock()->lock_without_safepoint_check(); | |
| 2041 _permGen->freelistLock()->lock_without_safepoint_check(); | |
| 2042 } | |
| 2043 | |
| 2044 void CMSCollector::releaseFreelistLocks() const { | |
| 2045 // Release locks for all free lists in all generations that this | |
| 2046 // collector is responsible for | |
| 2047 _cmsGen->freelistLock()->unlock(); | |
| 2048 _permGen->freelistLock()->unlock(); | |
| 2049 } | |
| 2050 | |
| 2051 bool CMSCollector::haveFreelistLocks() const { | |
| 2052 // Check locks for all free lists in all generations that this | |
| 2053 // collector is responsible for | |
| 2054 assert_lock_strong(_cmsGen->freelistLock()); | |
| 2055 assert_lock_strong(_permGen->freelistLock()); | |
| 2056 PRODUCT_ONLY(ShouldNotReachHere()); | |
| 2057 return true; | |
| 2058 } | |
| 2059 | |
| 2060 // A utility class that is used by the CMS collector to | |
| 2061 // temporarily "release" the foreground collector from its | |
| 2062 // usual obligation to wait for the background collector to | |
| 2063 // complete an ongoing phase before proceeding. | |
| 2064 class ReleaseForegroundGC: public StackObj { | |
| 2065 private: | |
| 2066 CMSCollector* _c; | |
| 2067 public: | |
| 2068 ReleaseForegroundGC(CMSCollector* c) : _c(c) { | |
| 2069 assert(_c->_foregroundGCShouldWait, "Else should not need to call"); | |
| 2070 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
| 2071 // allow a potentially blocked foreground collector to proceed | |
| 2072 _c->_foregroundGCShouldWait = false; | |
| 2073 if (_c->_foregroundGCIsActive) { | |
| 2074 CGC_lock->notify(); | |
| 2075 } | |
| 2076 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 2077 "Possible deadlock"); | |
| 2078 } | |
| 2079 | |
| 2080 ~ReleaseForegroundGC() { | |
| 2081 assert(!_c->_foregroundGCShouldWait, "Usage protocol violation?"); | |
| 2082 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
| 2083 _c->_foregroundGCShouldWait = true; | |
| 2084 } | |
| 2085 }; | |
| 2086 | |
| 2087 // There are separate collect_in_background and collect_in_foreground because of | |
| 2088 // the different locking requirements of the background collector and the | |
| 2089 // foreground collector. There was originally an attempt to share | |
| 2090 // one "collect" method between the background collector and the foreground | |
| 2091 // collector but the if-then-else required made it cleaner to have | |
| 2092 // separate methods. | |
| 2093 void CMSCollector::collect_in_background(bool clear_all_soft_refs) { | |
| 2094 assert(Thread::current()->is_ConcurrentGC_thread(), | |
| 2095 "A CMS asynchronous collection is only allowed on a CMS thread."); | |
| 2096 | |
| 2097 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 2098 { | |
| 2099 bool safepoint_check = Mutex::_no_safepoint_check_flag; | |
| 2100 MutexLockerEx hl(Heap_lock, safepoint_check); | |
| 2101 MutexLockerEx x(CGC_lock, safepoint_check); | |
| 2102 if (_foregroundGCIsActive || !UseAsyncConcMarkSweepGC) { | |
| 2103 // The foreground collector is active or we're | |
| 2104 // not using asynchronous collections. Skip this | |
| 2105 // background collection. | |
| 2106 assert(!_foregroundGCShouldWait, "Should be clear"); | |
| 2107 return; | |
| 2108 } else { | |
| 2109 assert(_collectorState == Idling, "Should be idling before start."); | |
| 2110 _collectorState = InitialMarking; | |
| 2111 // Reset the expansion cause, now that we are about to begin | |
| 2112 // a new cycle. | |
| 2113 clear_expansion_cause(); | |
| 2114 } | |
| 2115 _unloaded_classes_last_cycle = cms_should_unload_classes(); // ... from last cycle | |
| 2116 // This controls class unloading in response to an explicit gc request. | |
| 2117 // If ExplicitGCInvokesConcurrentAndUnloadsClasses is set, then | |
| 2118 // we will unload classes even if CMSClassUnloadingEnabled is not set. | |
| 2119 // See CR 6541037 and related CRs. | |
| 2120 _unload_classes = _full_gc_requested // ... for this cycle | |
| 2121 && ExplicitGCInvokesConcurrentAndUnloadsClasses; | |
| 2122 _full_gc_requested = false; // acks all outstanding full gc requests | |
| 2123 // Signal that we are about to start a collection | |
| 2124 gch->increment_total_full_collections(); // ... starting a collection cycle | |
| 2125 _collection_count_start = gch->total_full_collections(); | |
| 2126 } | |
| 2127 | |
| 2128 // Used for PrintGC | |
| 2129 size_t prev_used; | |
| 2130 if (PrintGC && Verbose) { | |
| 2131 prev_used = _cmsGen->used(); // XXXPERM | |
| 2132 } | |
| 2133 | |
| 2134 // The change of the collection state is normally done at this level; | |
| 2135 // the exceptions are phases that are executed while the world is | |
| 2136 // stopped. For those phases the change of state is done while the | |
| 2137 // world is stopped. For baton passing purposes this allows the | |
| 2138 // background collector to finish the phase and change state atomically. | |
| 2139 // The foreground collector cannot wait on a phase that is done | |
| 2140 // while the world is stopped because the foreground collector already | |
| 2141 // has the world stopped and would deadlock. | |
| 2142 while (_collectorState != Idling) { | |
| 2143 if (TraceCMSState) { | |
| 2144 gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " in CMS state %d", | |
| 2145 Thread::current(), _collectorState); | |
| 2146 } | |
| 2147 // The foreground collector | |
| 2148 // holds the Heap_lock throughout its collection. | |
| 2149 // holds the CMS token (but not the lock) | |
| 2150 // except while it is waiting for the background collector to yield. | |
| 2151 // | |
| 2152 // The foreground collector should be blocked (not for long) | |
| 2153 // if the background collector is about to start a phase | |
| 2154 // executed with world stopped. If the background | |
| 2155 // collector has already started such a phase, the | |
| 2156 // foreground collector is blocked waiting for the | |
| 2157 // Heap_lock. The stop-world phases (InitialMarking and FinalMarking) | |
| 2158 // are executed in the VM thread. | |
| 2159 // | |
| 2160 // The locking order is | |
| 2161 // PendingListLock (PLL) -- if applicable (FinalMarking) | |
| 2162 // Heap_lock (both this & PLL locked in VM_CMS_Operation::prologue()) | |
| 2163 // CMS token (claimed in | |
| 2164 // stop_world_and_do() --> | |
| 2165 // safepoint_synchronize() --> | |
| 2166 // CMSThread::synchronize()) | |
| 2167 | |
| 2168 { | |
| 2169 // Check if the FG collector wants us to yield. | |
| 2170 CMSTokenSync x(true); // is cms thread | |
| 2171 if (waitForForegroundGC()) { | |
| 2172 // We yielded to a foreground GC, nothing more to be | |
| 2173 // done this round. | |
| 2174 assert(_foregroundGCShouldWait == false, "We set it to false in " | |
| 2175 "waitForForegroundGC()"); | |
| 2176 if (TraceCMSState) { | |
| 2177 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT | |
| 2178 " exiting collection CMS state %d", | |
| 2179 Thread::current(), _collectorState); | |
| 2180 } | |
| 2181 return; | |
| 2182 } else { | |
| 2183 // The background collector can run but check to see if the | |
| 2184 // foreground collector has done a collection while the | |
| 2185 // background collector was waiting to get the CGC_lock | |
| 2186 // above. If yes, break so that _foregroundGCShouldWait | |
| 2187 // is cleared before returning. | |
| 2188 if (_collectorState == Idling) { | |
| 2189 break; | |
| 2190 } | |
| 2191 } | |
| 2192 } | |
| 2193 | |
| 2194 assert(_foregroundGCShouldWait, "Foreground collector, if active, " | |
| 2195 "should be waiting"); | |
| 2196 | |
| 2197 switch (_collectorState) { | |
| 2198 case InitialMarking: | |
| 2199 { | |
| 2200 ReleaseForegroundGC x(this); | |
| 2201 stats().record_cms_begin(); | |
| 2202 | |
| 2203 VM_CMS_Initial_Mark initial_mark_op(this); | |
| 2204 VMThread::execute(&initial_mark_op); | |
| 2205 } | |
| 2206 // The collector state may be any legal state at this point | |
| 2207 // since the background collector may have yielded to the | |
| 2208 // foreground collector. | |
| 2209 break; | |
| 2210 case Marking: | |
| 2211 // initial marking in checkpointRootsInitialWork has been completed | |
| 2212 if (markFromRoots(true)) { // we were successful | |
| 2213 assert(_collectorState == Precleaning, "Collector state should " | |
| 2214 "have changed"); | |
| 2215 } else { | |
| 2216 assert(_foregroundGCIsActive, "Internal state inconsistency"); | |
| 2217 } | |
| 2218 break; | |
| 2219 case Precleaning: | |
| 2220 if (UseAdaptiveSizePolicy) { | |
| 2221 size_policy()->concurrent_precleaning_begin(); | |
| 2222 } | |
| 2223 // marking from roots in markFromRoots has been completed | |
| 2224 preclean(); | |
| 2225 if (UseAdaptiveSizePolicy) { | |
| 2226 size_policy()->concurrent_precleaning_end(); | |
| 2227 } | |
| 2228 assert(_collectorState == AbortablePreclean || | |
| 2229 _collectorState == FinalMarking, | |
| 2230 "Collector state should have changed"); | |
| 2231 break; | |
| 2232 case AbortablePreclean: | |
| 2233 if (UseAdaptiveSizePolicy) { | |
| 2234 size_policy()->concurrent_phases_resume(); | |
| 2235 } | |
| 2236 abortable_preclean(); | |
| 2237 if (UseAdaptiveSizePolicy) { | |
| 2238 size_policy()->concurrent_precleaning_end(); | |
| 2239 } | |
| 2240 assert(_collectorState == FinalMarking, "Collector state should " | |
| 2241 "have changed"); | |
| 2242 break; | |
| 2243 case FinalMarking: | |
| 2244 { | |
| 2245 ReleaseForegroundGC x(this); | |
| 2246 | |
| 2247 VM_CMS_Final_Remark final_remark_op(this); | |
| 2248 VMThread::execute(&final_remark_op); | |
| 2249 } | |
| 2250 assert(_foregroundGCShouldWait, "block post-condition"); | |
| 2251 break; | |
| 2252 case Sweeping: | |
| 2253 if (UseAdaptiveSizePolicy) { | |
| 2254 size_policy()->concurrent_sweeping_begin(); | |
| 2255 } | |
| 2256 // final marking in checkpointRootsFinal has been completed | |
| 2257 sweep(true); | |
| 2258 assert(_collectorState == Resizing, "Collector state change " | |
| 2259 "to Resizing must be done under the free_list_lock"); | |
| 2260 _full_gcs_since_conc_gc = 0; | |
| 2261 | |
| 2262 // Stop the timers for adaptive size policy for the concurrent phases | |
| 2263 if (UseAdaptiveSizePolicy) { | |
| 2264 size_policy()->concurrent_sweeping_end(); | |
| 2265 size_policy()->concurrent_phases_end(gch->gc_cause(), | |
| 2266 gch->prev_gen(_cmsGen)->capacity(), | |
| 2267 _cmsGen->free()); | |
| 2268 } | |
| 2269 | |
| 2270 case Resizing: { | |
| 2271 // Sweeping has been completed... | |
| 2272 // At this point the background collection has completed. | |
| 2273 // Don't move the call to compute_new_size() down | |
| 2274 // into code that might be executed if the background | |
| 2275 // collection was preempted. | |
| 2276 { | |
| 2277 ReleaseForegroundGC x(this); // unblock FG collection | |
| 2278 MutexLockerEx y(Heap_lock, Mutex::_no_safepoint_check_flag); | |
| 2279 CMSTokenSync z(true); // not strictly needed. | |
| 2280 if (_collectorState == Resizing) { | |
| 2281 compute_new_size(); | |
| 2282 _collectorState = Resetting; | |
| 2283 } else { | |
| 2284 assert(_collectorState == Idling, "The state should only change" | |
| 2285 " because the foreground collector has finished the collection"); | |
| 2286 } | |
| 2287 } | |
| 2288 break; | |
| 2289 } | |
| 2290 case Resetting: | |
| 2291 // CMS heap resizing has been completed | |
| 2292 reset(true); | |
| 2293 assert(_collectorState == Idling, "Collector state should " | |
| 2294 "have changed"); | |
| 2295 stats().record_cms_end(); | |
| 2296 // Don't move the concurrent_phases_end() and compute_new_size() | |
| 2297 // calls to here because a preempted background collection | |
| 2298 // has it's state set to "Resetting". | |
| 2299 break; | |
| 2300 case Idling: | |
| 2301 default: | |
| 2302 ShouldNotReachHere(); | |
| 2303 break; | |
| 2304 } | |
| 2305 if (TraceCMSState) { | |
| 2306 gclog_or_tty->print_cr(" Thread " INTPTR_FORMAT " done - next CMS state %d", | |
| 2307 Thread::current(), _collectorState); | |
| 2308 } | |
| 2309 assert(_foregroundGCShouldWait, "block post-condition"); | |
| 2310 } | |
| 2311 | |
| 2312 // Should this be in gc_epilogue? | |
| 2313 collector_policy()->counters()->update_counters(); | |
| 2314 | |
| 2315 { | |
| 2316 // Clear _foregroundGCShouldWait and, in the event that the | |
| 2317 // foreground collector is waiting, notify it, before | |
| 2318 // returning. | |
| 2319 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
| 2320 _foregroundGCShouldWait = false; | |
| 2321 if (_foregroundGCIsActive) { | |
| 2322 CGC_lock->notify(); | |
| 2323 } | |
| 2324 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 2325 "Possible deadlock"); | |
| 2326 } | |
| 2327 if (TraceCMSState) { | |
| 2328 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT | |
| 2329 " exiting collection CMS state %d", | |
| 2330 Thread::current(), _collectorState); | |
| 2331 } | |
| 2332 if (PrintGC && Verbose) { | |
| 2333 _cmsGen->print_heap_change(prev_used); | |
| 2334 } | |
| 2335 } | |
| 2336 | |
| 2337 void CMSCollector::collect_in_foreground(bool clear_all_soft_refs) { | |
| 2338 assert(_foregroundGCIsActive && !_foregroundGCShouldWait, | |
| 2339 "Foreground collector should be waiting, not executing"); | |
| 2340 assert(Thread::current()->is_VM_thread(), "A foreground collection" | |
| 2341 "may only be done by the VM Thread with the world stopped"); | |
| 2342 assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(), | |
| 2343 "VM thread should have CMS token"); | |
| 2344 | |
| 2345 NOT_PRODUCT(TraceTime t("CMS:MS (foreground) ", PrintGCDetails && Verbose, | |
| 2346 true, gclog_or_tty);) | |
| 2347 if (UseAdaptiveSizePolicy) { | |
| 2348 size_policy()->ms_collection_begin(); | |
| 2349 } | |
| 2350 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact); | |
| 2351 | |
| 2352 HandleMark hm; // Discard invalid handles created during verification | |
| 2353 | |
| 2354 if (VerifyBeforeGC && | |
| 2355 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
| 2356 Universe::verify(true); | |
| 2357 } | |
| 2358 | |
| 2359 bool init_mark_was_synchronous = false; // until proven otherwise | |
| 2360 while (_collectorState != Idling) { | |
| 2361 if (TraceCMSState) { | |
| 2362 gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " in CMS state %d", | |
| 2363 Thread::current(), _collectorState); | |
| 2364 } | |
| 2365 switch (_collectorState) { | |
| 2366 case InitialMarking: | |
| 2367 init_mark_was_synchronous = true; // fact to be exploited in re-mark | |
| 2368 checkpointRootsInitial(false); | |
| 2369 assert(_collectorState == Marking, "Collector state should have changed" | |
| 2370 " within checkpointRootsInitial()"); | |
| 2371 break; | |
| 2372 case Marking: | |
| 2373 // initial marking in checkpointRootsInitialWork has been completed | |
| 2374 if (VerifyDuringGC && | |
| 2375 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
| 2376 gclog_or_tty->print("Verify before initial mark: "); | |
| 2377 Universe::verify(true); | |
| 2378 } | |
| 2379 { | |
| 2380 bool res = markFromRoots(false); | |
| 2381 assert(res && _collectorState == FinalMarking, "Collector state should " | |
| 2382 "have changed"); | |
| 2383 break; | |
| 2384 } | |
| 2385 case FinalMarking: | |
| 2386 if (VerifyDuringGC && | |
| 2387 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
| 2388 gclog_or_tty->print("Verify before re-mark: "); | |
| 2389 Universe::verify(true); | |
| 2390 } | |
| 2391 checkpointRootsFinal(false, clear_all_soft_refs, | |
| 2392 init_mark_was_synchronous); | |
| 2393 assert(_collectorState == Sweeping, "Collector state should not " | |
| 2394 "have changed within checkpointRootsFinal()"); | |
| 2395 break; | |
| 2396 case Sweeping: | |
| 2397 // final marking in checkpointRootsFinal has been completed | |
| 2398 if (VerifyDuringGC && | |
| 2399 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
| 2400 gclog_or_tty->print("Verify before sweep: "); | |
| 2401 Universe::verify(true); | |
| 2402 } | |
| 2403 sweep(false); | |
| 2404 assert(_collectorState == Resizing, "Incorrect state"); | |
| 2405 break; | |
| 2406 case Resizing: { | |
| 2407 // Sweeping has been completed; the actual resize in this case | |
| 2408 // is done separately; nothing to be done in this state. | |
| 2409 _collectorState = Resetting; | |
| 2410 break; | |
| 2411 } | |
| 2412 case Resetting: | |
| 2413 // The heap has been resized. | |
| 2414 if (VerifyDuringGC && | |
| 2415 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
| 2416 gclog_or_tty->print("Verify before reset: "); | |
| 2417 Universe::verify(true); | |
| 2418 } | |
| 2419 reset(false); | |
| 2420 assert(_collectorState == Idling, "Collector state should " | |
| 2421 "have changed"); | |
| 2422 break; | |
| 2423 case Precleaning: | |
| 2424 case AbortablePreclean: | |
| 2425 // Elide the preclean phase | |
| 2426 _collectorState = FinalMarking; | |
| 2427 break; | |
| 2428 default: | |
| 2429 ShouldNotReachHere(); | |
| 2430 } | |
| 2431 if (TraceCMSState) { | |
| 2432 gclog_or_tty->print_cr(" Thread " INTPTR_FORMAT " done - next CMS state %d", | |
| 2433 Thread::current(), _collectorState); | |
| 2434 } | |
| 2435 } | |
| 2436 | |
| 2437 if (UseAdaptiveSizePolicy) { | |
| 2438 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 2439 size_policy()->ms_collection_end(gch->gc_cause()); | |
| 2440 } | |
| 2441 | |
| 2442 if (VerifyAfterGC && | |
| 2443 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
| 2444 Universe::verify(true); | |
| 2445 } | |
| 2446 if (TraceCMSState) { | |
| 2447 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT | |
| 2448 " exiting collection CMS state %d", | |
| 2449 Thread::current(), _collectorState); | |
| 2450 } | |
| 2451 } | |
| 2452 | |
| 2453 bool CMSCollector::waitForForegroundGC() { | |
| 2454 bool res = false; | |
| 2455 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 2456 "CMS thread should have CMS token"); | |
| 2457 // Block the foreground collector until the | |
| 2458 // background collectors decides whether to | |
| 2459 // yield. | |
| 2460 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); | |
| 2461 _foregroundGCShouldWait = true; | |
| 2462 if (_foregroundGCIsActive) { | |
| 2463 // The background collector yields to the | |
| 2464 // foreground collector and returns a value | |
| 2465 // indicating that it has yielded. The foreground | |
| 2466 // collector can proceed. | |
| 2467 res = true; | |
| 2468 _foregroundGCShouldWait = false; | |
| 2469 ConcurrentMarkSweepThread::clear_CMS_flag( | |
| 2470 ConcurrentMarkSweepThread::CMS_cms_has_token); | |
| 2471 ConcurrentMarkSweepThread::set_CMS_flag( | |
| 2472 ConcurrentMarkSweepThread::CMS_cms_wants_token); | |
| 2473 // Get a possibly blocked foreground thread going | |
| 2474 CGC_lock->notify(); | |
| 2475 if (TraceCMSState) { | |
| 2476 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT " waiting at CMS state %d", | |
| 2477 Thread::current(), _collectorState); | |
| 2478 } | |
| 2479 while (_foregroundGCIsActive) { | |
| 2480 CGC_lock->wait(Mutex::_no_safepoint_check_flag); | |
| 2481 } | |
| 2482 ConcurrentMarkSweepThread::set_CMS_flag( | |
| 2483 ConcurrentMarkSweepThread::CMS_cms_has_token); | |
| 2484 ConcurrentMarkSweepThread::clear_CMS_flag( | |
| 2485 ConcurrentMarkSweepThread::CMS_cms_wants_token); | |
| 2486 } | |
| 2487 if (TraceCMSState) { | |
| 2488 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT " continuing at CMS state %d", | |
| 2489 Thread::current(), _collectorState); | |
| 2490 } | |
| 2491 return res; | |
| 2492 } | |
| 2493 | |
| 2494 // Because of the need to lock the free lists and other structures in | |
| 2495 // the collector, common to all the generations that the collector is | |
| 2496 // collecting, we need the gc_prologues of individual CMS generations | |
| 2497 // delegate to their collector. It may have been simpler had the | |
| 2498 // current infrastructure allowed one to call a prologue on a | |
| 2499 // collector. In the absence of that we have the generation's | |
| 2500 // prologue delegate to the collector, which delegates back | |
| 2501 // some "local" work to a worker method in the individual generations | |
| 2502 // that it's responsible for collecting, while itself doing any | |
| 2503 // work common to all generations it's responsible for. A similar | |
| 2504 // comment applies to the gc_epilogue()'s. | |
| 2505 // The role of the varaible _between_prologue_and_epilogue is to | |
| 2506 // enforce the invocation protocol. | |
| 2507 void CMSCollector::gc_prologue(bool full) { | |
| 2508 // Call gc_prologue_work() for each CMSGen and PermGen that | |
| 2509 // we are responsible for. | |
| 2510 | |
| 2511 // The following locking discipline assumes that we are only called | |
| 2512 // when the world is stopped. | |
| 2513 assert(SafepointSynchronize::is_at_safepoint(), "world is stopped assumption"); | |
| 2514 | |
| 2515 // The CMSCollector prologue must call the gc_prologues for the | |
| 2516 // "generations" (including PermGen if any) that it's responsible | |
| 2517 // for. | |
| 2518 | |
| 2519 assert( Thread::current()->is_VM_thread() | |
| 2520 || ( CMSScavengeBeforeRemark | |
| 2521 && Thread::current()->is_ConcurrentGC_thread()), | |
| 2522 "Incorrect thread type for prologue execution"); | |
| 2523 | |
| 2524 if (_between_prologue_and_epilogue) { | |
| 2525 // We have already been invoked; this is a gc_prologue delegation | |
| 2526 // from yet another CMS generation that we are responsible for, just | |
| 2527 // ignore it since all relevant work has already been done. | |
| 2528 return; | |
| 2529 } | |
| 2530 | |
| 2531 // set a bit saying prologue has been called; cleared in epilogue | |
| 2532 _between_prologue_and_epilogue = true; | |
| 2533 // Claim locks for common data structures, then call gc_prologue_work() | |
| 2534 // for each CMSGen and PermGen that we are responsible for. | |
| 2535 | |
| 2536 getFreelistLocks(); // gets free list locks on constituent spaces | |
| 2537 bitMapLock()->lock_without_safepoint_check(); | |
| 2538 | |
| 2539 // Should call gc_prologue_work() for all cms gens we are responsible for | |
| 2540 bool registerClosure = _collectorState >= Marking | |
| 2541 && _collectorState < Sweeping; | |
| 2542 ModUnionClosure* muc = ParallelGCThreads > 0 ? &_modUnionClosurePar | |
| 2543 : &_modUnionClosure; | |
| 2544 _cmsGen->gc_prologue_work(full, registerClosure, muc); | |
| 2545 _permGen->gc_prologue_work(full, registerClosure, muc); | |
| 2546 | |
| 2547 if (!full) { | |
| 2548 stats().record_gc0_begin(); | |
| 2549 } | |
| 2550 } | |
| 2551 | |
| 2552 void ConcurrentMarkSweepGeneration::gc_prologue(bool full) { | |
| 2553 // Delegate to CMScollector which knows how to coordinate between | |
| 2554 // this and any other CMS generations that it is responsible for | |
| 2555 // collecting. | |
| 2556 collector()->gc_prologue(full); | |
| 2557 } | |
| 2558 | |
| 2559 // This is a "private" interface for use by this generation's CMSCollector. | |
| 2560 // Not to be called directly by any other entity (for instance, | |
| 2561 // GenCollectedHeap, which calls the "public" gc_prologue method above). | |
| 2562 void ConcurrentMarkSweepGeneration::gc_prologue_work(bool full, | |
| 2563 bool registerClosure, ModUnionClosure* modUnionClosure) { | |
| 2564 assert(!incremental_collection_failed(), "Shouldn't be set yet"); | |
| 2565 assert(cmsSpace()->preconsumptionDirtyCardClosure() == NULL, | |
| 2566 "Should be NULL"); | |
| 2567 if (registerClosure) { | |
| 2568 cmsSpace()->setPreconsumptionDirtyCardClosure(modUnionClosure); | |
| 2569 } | |
| 2570 cmsSpace()->gc_prologue(); | |
| 2571 // Clear stat counters | |
| 2572 NOT_PRODUCT( | |
| 2573 assert(_numObjectsPromoted == 0, "check"); | |
| 2574 assert(_numWordsPromoted == 0, "check"); | |
| 2575 if (Verbose && PrintGC) { | |
| 2576 gclog_or_tty->print("Allocated "SIZE_FORMAT" objects, " | |
| 2577 SIZE_FORMAT" bytes concurrently", | |
| 2578 _numObjectsAllocated, _numWordsAllocated*sizeof(HeapWord)); | |
| 2579 } | |
| 2580 _numObjectsAllocated = 0; | |
| 2581 _numWordsAllocated = 0; | |
| 2582 ) | |
| 2583 } | |
| 2584 | |
| 2585 void CMSCollector::gc_epilogue(bool full) { | |
| 2586 // The following locking discipline assumes that we are only called | |
| 2587 // when the world is stopped. | |
| 2588 assert(SafepointSynchronize::is_at_safepoint(), | |
| 2589 "world is stopped assumption"); | |
| 2590 | |
| 2591 // Currently the CMS epilogue (see CompactibleFreeListSpace) merely checks | |
| 2592 // if linear allocation blocks need to be appropriately marked to allow the | |
| 2593 // the blocks to be parsable. We also check here whether we need to nudge the | |
| 2594 // CMS collector thread to start a new cycle (if it's not already active). | |
| 2595 assert( Thread::current()->is_VM_thread() | |
| 2596 || ( CMSScavengeBeforeRemark | |
| 2597 && Thread::current()->is_ConcurrentGC_thread()), | |
| 2598 "Incorrect thread type for epilogue execution"); | |
| 2599 | |
| 2600 if (!_between_prologue_and_epilogue) { | |
| 2601 // We have already been invoked; this is a gc_epilogue delegation | |
| 2602 // from yet another CMS generation that we are responsible for, just | |
| 2603 // ignore it since all relevant work has already been done. | |
| 2604 return; | |
| 2605 } | |
| 2606 assert(haveFreelistLocks(), "must have freelist locks"); | |
| 2607 assert_lock_strong(bitMapLock()); | |
| 2608 | |
| 2609 _cmsGen->gc_epilogue_work(full); | |
| 2610 _permGen->gc_epilogue_work(full); | |
| 2611 | |
| 2612 if (_collectorState == AbortablePreclean || _collectorState == Precleaning) { | |
| 2613 // in case sampling was not already enabled, enable it | |
| 2614 _start_sampling = true; | |
| 2615 } | |
| 2616 // reset _eden_chunk_array so sampling starts afresh | |
| 2617 _eden_chunk_index = 0; | |
| 2618 | |
| 2619 size_t cms_used = _cmsGen->cmsSpace()->used(); | |
| 2620 size_t perm_used = _permGen->cmsSpace()->used(); | |
| 2621 | |
| 2622 // update performance counters - this uses a special version of | |
| 2623 // update_counters() that allows the utilization to be passed as a | |
| 2624 // parameter, avoiding multiple calls to used(). | |
| 2625 // | |
| 2626 _cmsGen->update_counters(cms_used); | |
| 2627 _permGen->update_counters(perm_used); | |
| 2628 | |
| 2629 if (CMSIncrementalMode) { | |
| 2630 icms_update_allocation_limits(); | |
| 2631 } | |
| 2632 | |
| 2633 bitMapLock()->unlock(); | |
| 2634 releaseFreelistLocks(); | |
| 2635 | |
| 2636 _between_prologue_and_epilogue = false; // ready for next cycle | |
| 2637 } | |
| 2638 | |
| 2639 void ConcurrentMarkSweepGeneration::gc_epilogue(bool full) { | |
| 2640 collector()->gc_epilogue(full); | |
| 2641 | |
| 2642 // Also reset promotion tracking in par gc thread states. | |
| 2643 if (ParallelGCThreads > 0) { | |
| 2644 for (uint i = 0; i < ParallelGCThreads; i++) { | |
| 2645 _par_gc_thread_states[i]->promo.stopTrackingPromotions(); | |
| 2646 } | |
| 2647 } | |
| 2648 } | |
| 2649 | |
| 2650 void ConcurrentMarkSweepGeneration::gc_epilogue_work(bool full) { | |
| 2651 assert(!incremental_collection_failed(), "Should have been cleared"); | |
| 2652 cmsSpace()->setPreconsumptionDirtyCardClosure(NULL); | |
| 2653 cmsSpace()->gc_epilogue(); | |
| 2654 // Print stat counters | |
| 2655 NOT_PRODUCT( | |
| 2656 assert(_numObjectsAllocated == 0, "check"); | |
| 2657 assert(_numWordsAllocated == 0, "check"); | |
| 2658 if (Verbose && PrintGC) { | |
| 2659 gclog_or_tty->print("Promoted "SIZE_FORMAT" objects, " | |
| 2660 SIZE_FORMAT" bytes", | |
| 2661 _numObjectsPromoted, _numWordsPromoted*sizeof(HeapWord)); | |
| 2662 } | |
| 2663 _numObjectsPromoted = 0; | |
| 2664 _numWordsPromoted = 0; | |
| 2665 ) | |
| 2666 | |
| 2667 if (PrintGC && Verbose) { | |
| 2668 // Call down the chain in contiguous_available needs the freelistLock | |
| 2669 // so print this out before releasing the freeListLock. | |
| 2670 gclog_or_tty->print(" Contiguous available "SIZE_FORMAT" bytes ", | |
| 2671 contiguous_available()); | |
| 2672 } | |
| 2673 } | |
| 2674 | |
| 2675 #ifndef PRODUCT | |
| 2676 bool CMSCollector::have_cms_token() { | |
| 2677 Thread* thr = Thread::current(); | |
| 2678 if (thr->is_VM_thread()) { | |
| 2679 return ConcurrentMarkSweepThread::vm_thread_has_cms_token(); | |
| 2680 } else if (thr->is_ConcurrentGC_thread()) { | |
| 2681 return ConcurrentMarkSweepThread::cms_thread_has_cms_token(); | |
| 2682 } else if (thr->is_GC_task_thread()) { | |
| 2683 return ConcurrentMarkSweepThread::vm_thread_has_cms_token() && | |
| 2684 ParGCRareEvent_lock->owned_by_self(); | |
| 2685 } | |
| 2686 return false; | |
| 2687 } | |
| 2688 #endif | |
| 2689 | |
| 2690 // Check reachability of the given heap address in CMS generation, | |
| 2691 // treating all other generations as roots. | |
| 2692 bool CMSCollector::is_cms_reachable(HeapWord* addr) { | |
| 2693 // We could "guarantee" below, rather than assert, but i'll | |
| 2694 // leave these as "asserts" so that an adventurous debugger | |
| 2695 // could try this in the product build provided some subset of | |
| 2696 // the conditions were met, provided they were intersted in the | |
| 2697 // results and knew that the computation below wouldn't interfere | |
| 2698 // with other concurrent computations mutating the structures | |
| 2699 // being read or written. | |
| 2700 assert(SafepointSynchronize::is_at_safepoint(), | |
| 2701 "Else mutations in object graph will make answer suspect"); | |
| 2702 assert(have_cms_token(), "Should hold cms token"); | |
| 2703 assert(haveFreelistLocks(), "must hold free list locks"); | |
| 2704 assert_lock_strong(bitMapLock()); | |
| 2705 | |
| 2706 // Clear the marking bit map array before starting, but, just | |
| 2707 // for kicks, first report if the given address is already marked | |
| 2708 gclog_or_tty->print_cr("Start: Address 0x%x is%s marked", addr, | |
| 2709 _markBitMap.isMarked(addr) ? "" : " not"); | |
| 2710 | |
| 2711 if (verify_after_remark()) { | |
| 2712 MutexLockerEx x(verification_mark_bm()->lock(), Mutex::_no_safepoint_check_flag); | |
| 2713 bool result = verification_mark_bm()->isMarked(addr); | |
| 2714 gclog_or_tty->print_cr("TransitiveMark: Address 0x%x %s marked", addr, | |
| 2715 result ? "IS" : "is NOT"); | |
| 2716 return result; | |
| 2717 } else { | |
| 2718 gclog_or_tty->print_cr("Could not compute result"); | |
| 2719 return false; | |
| 2720 } | |
| 2721 } | |
| 2722 | |
| 2723 //////////////////////////////////////////////////////// | |
| 2724 // CMS Verification Support | |
| 2725 //////////////////////////////////////////////////////// | |
| 2726 // Following the remark phase, the following invariant | |
| 2727 // should hold -- each object in the CMS heap which is | |
| 2728 // marked in markBitMap() should be marked in the verification_mark_bm(). | |
| 2729 | |
| 2730 class VerifyMarkedClosure: public BitMapClosure { | |
| 2731 CMSBitMap* _marks; | |
| 2732 bool _failed; | |
| 2733 | |
| 2734 public: | |
| 2735 VerifyMarkedClosure(CMSBitMap* bm): _marks(bm), _failed(false) {} | |
| 2736 | |
| 2737 void do_bit(size_t offset) { | |
| 2738 HeapWord* addr = _marks->offsetToHeapWord(offset); | |
| 2739 if (!_marks->isMarked(addr)) { | |
| 2740 oop(addr)->print(); | |
| 2741 gclog_or_tty->print_cr(" ("INTPTR_FORMAT" should have been marked)", addr); | |
| 2742 _failed = true; | |
| 2743 } | |
| 2744 } | |
| 2745 | |
| 2746 bool failed() { return _failed; } | |
| 2747 }; | |
| 2748 | |
| 2749 bool CMSCollector::verify_after_remark() { | |
| 2750 gclog_or_tty->print(" [Verifying CMS Marking... "); | |
| 2751 MutexLockerEx ml(verification_mark_bm()->lock(), Mutex::_no_safepoint_check_flag); | |
| 2752 static bool init = false; | |
| 2753 | |
| 2754 assert(SafepointSynchronize::is_at_safepoint(), | |
| 2755 "Else mutations in object graph will make answer suspect"); | |
| 2756 assert(have_cms_token(), | |
| 2757 "Else there may be mutual interference in use of " | |
| 2758 " verification data structures"); | |
| 2759 assert(_collectorState > Marking && _collectorState <= Sweeping, | |
| 2760 "Else marking info checked here may be obsolete"); | |
| 2761 assert(haveFreelistLocks(), "must hold free list locks"); | |
| 2762 assert_lock_strong(bitMapLock()); | |
| 2763 | |
| 2764 | |
| 2765 // Allocate marking bit map if not already allocated | |
| 2766 if (!init) { // first time | |
| 2767 if (!verification_mark_bm()->allocate(_span)) { | |
| 2768 return false; | |
| 2769 } | |
| 2770 init = true; | |
| 2771 } | |
| 2772 | |
| 2773 assert(verification_mark_stack()->isEmpty(), "Should be empty"); | |
| 2774 | |
| 2775 // Turn off refs discovery -- so we will be tracing through refs. | |
| 2776 // This is as intended, because by this time | |
| 2777 // GC must already have cleared any refs that need to be cleared, | |
| 2778 // and traced those that need to be marked; moreover, | |
| 2779 // the marking done here is not going to intefere in any | |
| 2780 // way with the marking information used by GC. | |
| 2781 NoRefDiscovery no_discovery(ref_processor()); | |
| 2782 | |
| 2783 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;) | |
| 2784 | |
| 2785 // Clear any marks from a previous round | |
| 2786 verification_mark_bm()->clear_all(); | |
| 2787 assert(verification_mark_stack()->isEmpty(), "markStack should be empty"); | |
| 2788 assert(overflow_list_is_empty(), "overflow list should be empty"); | |
| 2789 | |
| 2790 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 2791 gch->ensure_parsability(false); // fill TLABs, but no need to retire them | |
| 2792 // Update the saved marks which may affect the root scans. | |
| 2793 gch->save_marks(); | |
| 2794 | |
| 2795 if (CMSRemarkVerifyVariant == 1) { | |
| 2796 // In this first variant of verification, we complete | |
| 2797 // all marking, then check if the new marks-verctor is | |
| 2798 // a subset of the CMS marks-vector. | |
| 2799 verify_after_remark_work_1(); | |
| 2800 } else if (CMSRemarkVerifyVariant == 2) { | |
| 2801 // In this second variant of verification, we flag an error | |
| 2802 // (i.e. an object reachable in the new marks-vector not reachable | |
| 2803 // in the CMS marks-vector) immediately, also indicating the | |
| 2804 // identify of an object (A) that references the unmarked object (B) -- | |
| 2805 // presumably, a mutation to A failed to be picked up by preclean/remark? | |
| 2806 verify_after_remark_work_2(); | |
| 2807 } else { | |
| 2808 warning("Unrecognized value %d for CMSRemarkVerifyVariant", | |
| 2809 CMSRemarkVerifyVariant); | |
| 2810 } | |
| 2811 gclog_or_tty->print(" done] "); | |
| 2812 return true; | |
| 2813 } | |
| 2814 | |
| 2815 void CMSCollector::verify_after_remark_work_1() { | |
| 2816 ResourceMark rm; | |
| 2817 HandleMark hm; | |
| 2818 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 2819 | |
| 2820 // Mark from roots one level into CMS | |
| 2821 MarkRefsIntoClosure notOlder(_span, verification_mark_bm(), true /* nmethods */); | |
| 2822 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. | |
| 2823 | |
| 2824 gch->gen_process_strong_roots(_cmsGen->level(), | |
| 2825 true, // younger gens are roots | |
| 2826 true, // collecting perm gen | |
| 2827 SharedHeap::ScanningOption(roots_scanning_options()), | |
| 2828 NULL, ¬Older); | |
| 2829 | |
| 2830 // Now mark from the roots | |
| 2831 assert(_revisitStack.isEmpty(), "Should be empty"); | |
| 2832 MarkFromRootsClosure markFromRootsClosure(this, _span, | |
| 2833 verification_mark_bm(), verification_mark_stack(), &_revisitStack, | |
| 2834 false /* don't yield */, true /* verifying */); | |
| 2835 assert(_restart_addr == NULL, "Expected pre-condition"); | |
| 2836 verification_mark_bm()->iterate(&markFromRootsClosure); | |
| 2837 while (_restart_addr != NULL) { | |
| 2838 // Deal with stack overflow: by restarting at the indicated | |
| 2839 // address. | |
| 2840 HeapWord* ra = _restart_addr; | |
| 2841 markFromRootsClosure.reset(ra); | |
| 2842 _restart_addr = NULL; | |
| 2843 verification_mark_bm()->iterate(&markFromRootsClosure, ra, _span.end()); | |
| 2844 } | |
| 2845 assert(verification_mark_stack()->isEmpty(), "Should have been drained"); | |
| 2846 verify_work_stacks_empty(); | |
| 2847 // Should reset the revisit stack above, since no class tree | |
| 2848 // surgery is forthcoming. | |
| 2849 _revisitStack.reset(); // throwing away all contents | |
| 2850 | |
| 2851 // Marking completed -- now verify that each bit marked in | |
| 2852 // verification_mark_bm() is also marked in markBitMap(); flag all | |
| 2853 // errors by printing corresponding objects. | |
| 2854 VerifyMarkedClosure vcl(markBitMap()); | |
| 2855 verification_mark_bm()->iterate(&vcl); | |
| 2856 if (vcl.failed()) { | |
| 2857 gclog_or_tty->print("Verification failed"); | |
| 2858 Universe::heap()->print(); | |
| 2859 fatal(" ... aborting"); | |
| 2860 } | |
| 2861 } | |
| 2862 | |
| 2863 void CMSCollector::verify_after_remark_work_2() { | |
| 2864 ResourceMark rm; | |
| 2865 HandleMark hm; | |
| 2866 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 2867 | |
| 2868 // Mark from roots one level into CMS | |
| 2869 MarkRefsIntoVerifyClosure notOlder(_span, verification_mark_bm(), | |
| 2870 markBitMap(), true /* nmethods */); | |
| 2871 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. | |
| 2872 gch->gen_process_strong_roots(_cmsGen->level(), | |
| 2873 true, // younger gens are roots | |
| 2874 true, // collecting perm gen | |
| 2875 SharedHeap::ScanningOption(roots_scanning_options()), | |
| 2876 NULL, ¬Older); | |
| 2877 | |
| 2878 // Now mark from the roots | |
| 2879 assert(_revisitStack.isEmpty(), "Should be empty"); | |
| 2880 MarkFromRootsVerifyClosure markFromRootsClosure(this, _span, | |
| 2881 verification_mark_bm(), markBitMap(), verification_mark_stack()); | |
| 2882 assert(_restart_addr == NULL, "Expected pre-condition"); | |
| 2883 verification_mark_bm()->iterate(&markFromRootsClosure); | |
| 2884 while (_restart_addr != NULL) { | |
| 2885 // Deal with stack overflow: by restarting at the indicated | |
| 2886 // address. | |
| 2887 HeapWord* ra = _restart_addr; | |
| 2888 markFromRootsClosure.reset(ra); | |
| 2889 _restart_addr = NULL; | |
| 2890 verification_mark_bm()->iterate(&markFromRootsClosure, ra, _span.end()); | |
| 2891 } | |
| 2892 assert(verification_mark_stack()->isEmpty(), "Should have been drained"); | |
| 2893 verify_work_stacks_empty(); | |
| 2894 // Should reset the revisit stack above, since no class tree | |
| 2895 // surgery is forthcoming. | |
| 2896 _revisitStack.reset(); // throwing away all contents | |
| 2897 | |
| 2898 // Marking completed -- now verify that each bit marked in | |
| 2899 // verification_mark_bm() is also marked in markBitMap(); flag all | |
| 2900 // errors by printing corresponding objects. | |
| 2901 VerifyMarkedClosure vcl(markBitMap()); | |
| 2902 verification_mark_bm()->iterate(&vcl); | |
| 2903 assert(!vcl.failed(), "Else verification above should not have succeeded"); | |
| 2904 } | |
| 2905 | |
| 2906 void ConcurrentMarkSweepGeneration::save_marks() { | |
| 2907 // delegate to CMS space | |
| 2908 cmsSpace()->save_marks(); | |
| 2909 for (uint i = 0; i < ParallelGCThreads; i++) { | |
| 2910 _par_gc_thread_states[i]->promo.startTrackingPromotions(); | |
| 2911 } | |
| 2912 } | |
| 2913 | |
| 2914 bool ConcurrentMarkSweepGeneration::no_allocs_since_save_marks() { | |
| 2915 return cmsSpace()->no_allocs_since_save_marks(); | |
| 2916 } | |
| 2917 | |
| 2918 #define CMS_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \ | |
| 2919 \ | |
| 2920 void ConcurrentMarkSweepGeneration:: \ | |
| 2921 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \ | |
| 2922 cl->set_generation(this); \ | |
| 2923 cmsSpace()->oop_since_save_marks_iterate##nv_suffix(cl); \ | |
| 2924 cl->reset_generation(); \ | |
| 2925 save_marks(); \ | |
| 2926 } | |
| 2927 | |
| 2928 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DEFN) | |
| 2929 | |
| 2930 void | |
| 2931 ConcurrentMarkSweepGeneration::object_iterate_since_last_GC(ObjectClosure* blk) | |
| 2932 { | |
| 2933 // Not currently implemented; need to do the following. -- ysr. | |
| 2934 // dld -- I think that is used for some sort of allocation profiler. So it | |
| 2935 // really means the objects allocated by the mutator since the last | |
| 2936 // GC. We could potentially implement this cheaply by recording only | |
| 2937 // the direct allocations in a side data structure. | |
| 2938 // | |
| 2939 // I think we probably ought not to be required to support these | |
| 2940 // iterations at any arbitrary point; I think there ought to be some | |
| 2941 // call to enable/disable allocation profiling in a generation/space, | |
| 2942 // and the iterator ought to return the objects allocated in the | |
| 2943 // gen/space since the enable call, or the last iterator call (which | |
| 2944 // will probably be at a GC.) That way, for gens like CM&S that would | |
| 2945 // require some extra data structure to support this, we only pay the | |
| 2946 // cost when it's in use... | |
| 2947 cmsSpace()->object_iterate_since_last_GC(blk); | |
| 2948 } | |
| 2949 | |
| 2950 void | |
| 2951 ConcurrentMarkSweepGeneration::younger_refs_iterate(OopsInGenClosure* cl) { | |
| 2952 cl->set_generation(this); | |
| 2953 younger_refs_in_space_iterate(_cmsSpace, cl); | |
| 2954 cl->reset_generation(); | |
| 2955 } | |
| 2956 | |
| 2957 void | |
| 2958 ConcurrentMarkSweepGeneration::oop_iterate(MemRegion mr, OopClosure* cl) { | |
| 2959 if (freelistLock()->owned_by_self()) { | |
| 2960 Generation::oop_iterate(mr, cl); | |
| 2961 } else { | |
| 2962 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
| 2963 Generation::oop_iterate(mr, cl); | |
| 2964 } | |
| 2965 } | |
| 2966 | |
| 2967 void | |
| 2968 ConcurrentMarkSweepGeneration::oop_iterate(OopClosure* cl) { | |
| 2969 if (freelistLock()->owned_by_self()) { | |
| 2970 Generation::oop_iterate(cl); | |
| 2971 } else { | |
| 2972 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
| 2973 Generation::oop_iterate(cl); | |
| 2974 } | |
| 2975 } | |
| 2976 | |
| 2977 void | |
| 2978 ConcurrentMarkSweepGeneration::object_iterate(ObjectClosure* cl) { | |
| 2979 if (freelistLock()->owned_by_self()) { | |
| 2980 Generation::object_iterate(cl); | |
| 2981 } else { | |
| 2982 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
| 2983 Generation::object_iterate(cl); | |
| 2984 } | |
| 2985 } | |
| 2986 | |
| 2987 void | |
| 2988 ConcurrentMarkSweepGeneration::pre_adjust_pointers() { | |
| 2989 } | |
| 2990 | |
| 2991 void | |
| 2992 ConcurrentMarkSweepGeneration::post_compact() { | |
| 2993 } | |
| 2994 | |
| 2995 void | |
| 2996 ConcurrentMarkSweepGeneration::prepare_for_verify() { | |
| 2997 // Fix the linear allocation blocks to look like free blocks. | |
| 2998 | |
| 2999 // Locks are normally acquired/released in gc_prologue/gc_epilogue, but those | |
| 3000 // are not called when the heap is verified during universe initialization and | |
| 3001 // at vm shutdown. | |
| 3002 if (freelistLock()->owned_by_self()) { | |
| 3003 cmsSpace()->prepare_for_verify(); | |
| 3004 } else { | |
| 3005 MutexLockerEx fll(freelistLock(), Mutex::_no_safepoint_check_flag); | |
| 3006 cmsSpace()->prepare_for_verify(); | |
| 3007 } | |
| 3008 } | |
| 3009 | |
| 3010 void | |
| 3011 ConcurrentMarkSweepGeneration::verify(bool allow_dirty /* ignored */) { | |
| 3012 // Locks are normally acquired/released in gc_prologue/gc_epilogue, but those | |
| 3013 // are not called when the heap is verified during universe initialization and | |
| 3014 // at vm shutdown. | |
| 3015 if (freelistLock()->owned_by_self()) { | |
| 3016 cmsSpace()->verify(false /* ignored */); | |
| 3017 } else { | |
| 3018 MutexLockerEx fll(freelistLock(), Mutex::_no_safepoint_check_flag); | |
| 3019 cmsSpace()->verify(false /* ignored */); | |
| 3020 } | |
| 3021 } | |
| 3022 | |
| 3023 void CMSCollector::verify(bool allow_dirty /* ignored */) { | |
| 3024 _cmsGen->verify(allow_dirty); | |
| 3025 _permGen->verify(allow_dirty); | |
| 3026 } | |
| 3027 | |
| 3028 #ifndef PRODUCT | |
| 3029 bool CMSCollector::overflow_list_is_empty() const { | |
| 3030 assert(_num_par_pushes >= 0, "Inconsistency"); | |
| 3031 if (_overflow_list == NULL) { | |
| 3032 assert(_num_par_pushes == 0, "Inconsistency"); | |
| 3033 } | |
| 3034 return _overflow_list == NULL; | |
| 3035 } | |
| 3036 | |
| 3037 // The methods verify_work_stacks_empty() and verify_overflow_empty() | |
| 3038 // merely consolidate assertion checks that appear to occur together frequently. | |
| 3039 void CMSCollector::verify_work_stacks_empty() const { | |
| 3040 assert(_markStack.isEmpty(), "Marking stack should be empty"); | |
| 3041 assert(overflow_list_is_empty(), "Overflow list should be empty"); | |
| 3042 } | |
| 3043 | |
| 3044 void CMSCollector::verify_overflow_empty() const { | |
| 3045 assert(overflow_list_is_empty(), "Overflow list should be empty"); | |
| 3046 assert(no_preserved_marks(), "No preserved marks"); | |
| 3047 } | |
| 3048 #endif // PRODUCT | |
| 3049 | |
| 3050 void CMSCollector::setup_cms_unloading_and_verification_state() { | |
| 3051 const bool should_verify = VerifyBeforeGC || VerifyAfterGC || VerifyDuringGC | |
| 3052 || VerifyBeforeExit; | |
| 3053 const int rso = SharedHeap::SO_Symbols | SharedHeap::SO_Strings | |
| 3054 | SharedHeap::SO_CodeCache; | |
| 3055 | |
| 3056 if (cms_should_unload_classes()) { // Should unload classes this cycle | |
| 3057 remove_root_scanning_option(rso); // Shrink the root set appropriately | |
| 3058 set_verifying(should_verify); // Set verification state for this cycle | |
| 3059 return; // Nothing else needs to be done at this time | |
| 3060 } | |
| 3061 | |
| 3062 // Not unloading classes this cycle | |
| 3063 assert(!cms_should_unload_classes(), "Inconsitency!"); | |
| 3064 if ((!verifying() || cms_unloaded_classes_last_cycle()) && should_verify) { | |
| 3065 // We were not verifying, or we _were_ unloading classes in the last cycle, | |
| 3066 // AND some verification options are enabled this cycle; in this case, | |
| 3067 // we must make sure that the deadness map is allocated if not already so, | |
| 3068 // and cleared (if already allocated previously -- | |
| 3069 // CMSBitMap::sizeInBits() is used to determine if it's allocated). | |
| 3070 if (perm_gen_verify_bit_map()->sizeInBits() == 0) { | |
| 3071 if (!perm_gen_verify_bit_map()->allocate(_permGen->reserved())) { | |
| 3072 warning("Failed to allocate permanent generation verification CMS Bit Map;\n" | |
| 3073 "permanent generation verification disabled"); | |
| 3074 return; // Note that we leave verification disabled, so we'll retry this | |
| 3075 // allocation next cycle. We _could_ remember this failure | |
| 3076 // and skip further attempts and permanently disable verification | |
| 3077 // attempts if that is considered more desirable. | |
| 3078 } | |
| 3079 assert(perm_gen_verify_bit_map()->covers(_permGen->reserved()), | |
| 3080 "_perm_gen_ver_bit_map inconsistency?"); | |
| 3081 } else { | |
| 3082 perm_gen_verify_bit_map()->clear_all(); | |
| 3083 } | |
| 3084 // Include symbols, strings and code cache elements to prevent their resurrection. | |
| 3085 add_root_scanning_option(rso); | |
| 3086 set_verifying(true); | |
| 3087 } else if (verifying() && !should_verify) { | |
| 3088 // We were verifying, but some verification flags got disabled. | |
| 3089 set_verifying(false); | |
| 3090 // Exclude symbols, strings and code cache elements from root scanning to | |
| 3091 // reduce IM and RM pauses. | |
| 3092 remove_root_scanning_option(rso); | |
| 3093 } | |
| 3094 } | |
| 3095 | |
| 3096 | |
| 3097 #ifndef PRODUCT | |
| 3098 HeapWord* CMSCollector::block_start(const void* p) const { | |
| 3099 const HeapWord* addr = (HeapWord*)p; | |
| 3100 if (_span.contains(p)) { | |
| 3101 if (_cmsGen->cmsSpace()->is_in_reserved(addr)) { | |
| 3102 return _cmsGen->cmsSpace()->block_start(p); | |
| 3103 } else { | |
| 3104 assert(_permGen->cmsSpace()->is_in_reserved(addr), | |
| 3105 "Inconsistent _span?"); | |
| 3106 return _permGen->cmsSpace()->block_start(p); | |
| 3107 } | |
| 3108 } | |
| 3109 return NULL; | |
| 3110 } | |
| 3111 #endif | |
| 3112 | |
| 3113 HeapWord* | |
| 3114 ConcurrentMarkSweepGeneration::expand_and_allocate(size_t word_size, | |
| 3115 bool tlab, | |
| 3116 bool parallel) { | |
| 3117 assert(!tlab, "Can't deal with TLAB allocation"); | |
| 3118 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); | |
| 3119 expand(word_size*HeapWordSize, MinHeapDeltaBytes, | |
| 3120 CMSExpansionCause::_satisfy_allocation); | |
| 3121 if (GCExpandToAllocateDelayMillis > 0) { | |
| 3122 os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false); | |
| 3123 } | |
| 3124 size_t adj_word_sz = CompactibleFreeListSpace::adjustObjectSize(word_size); | |
| 3125 if (parallel) { | |
| 3126 return cmsSpace()->par_allocate(adj_word_sz); | |
| 3127 } else { | |
| 3128 return cmsSpace()->allocate(adj_word_sz); | |
| 3129 } | |
| 3130 } | |
| 3131 | |
| 3132 // YSR: All of this generation expansion/shrinking stuff is an exact copy of | |
| 3133 // OneContigSpaceCardGeneration, which makes me wonder if we should move this | |
| 3134 // to CardGeneration and share it... | |
| 3135 void ConcurrentMarkSweepGeneration::expand(size_t bytes, size_t expand_bytes, | |
| 3136 CMSExpansionCause::Cause cause) | |
| 3137 { | |
| 3138 assert_locked_or_safepoint(Heap_lock); | |
| 3139 | |
| 3140 size_t aligned_bytes = ReservedSpace::page_align_size_up(bytes); | |
| 3141 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); | |
| 3142 bool success = false; | |
| 3143 if (aligned_expand_bytes > aligned_bytes) { | |
| 3144 success = grow_by(aligned_expand_bytes); | |
| 3145 } | |
| 3146 if (!success) { | |
| 3147 success = grow_by(aligned_bytes); | |
| 3148 } | |
| 3149 if (!success) { | |
| 3150 size_t remaining_bytes = _virtual_space.uncommitted_size(); | |
| 3151 if (remaining_bytes > 0) { | |
| 3152 success = grow_by(remaining_bytes); | |
| 3153 } | |
| 3154 } | |
| 3155 if (GC_locker::is_active()) { | |
| 3156 if (PrintGC && Verbose) { | |
| 3157 gclog_or_tty->print_cr("Garbage collection disabled, expanded heap instead"); | |
| 3158 } | |
| 3159 } | |
| 3160 // remember why we expanded; this information is used | |
| 3161 // by shouldConcurrentCollect() when making decisions on whether to start | |
| 3162 // a new CMS cycle. | |
| 3163 if (success) { | |
| 3164 set_expansion_cause(cause); | |
| 3165 if (PrintGCDetails && Verbose) { | |
| 3166 gclog_or_tty->print_cr("Expanded CMS gen for %s", | |
| 3167 CMSExpansionCause::to_string(cause)); | |
| 3168 } | |
| 3169 } | |
| 3170 } | |
| 3171 | |
| 3172 HeapWord* ConcurrentMarkSweepGeneration::expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz) { | |
| 3173 HeapWord* res = NULL; | |
| 3174 MutexLocker x(ParGCRareEvent_lock); | |
| 3175 while (true) { | |
| 3176 // Expansion by some other thread might make alloc OK now: | |
| 3177 res = ps->lab.alloc(word_sz); | |
| 3178 if (res != NULL) return res; | |
| 3179 // If there's not enough expansion space available, give up. | |
| 3180 if (_virtual_space.uncommitted_size() < (word_sz * HeapWordSize)) { | |
| 3181 return NULL; | |
| 3182 } | |
| 3183 // Otherwise, we try expansion. | |
| 3184 expand(word_sz*HeapWordSize, MinHeapDeltaBytes, | |
| 3185 CMSExpansionCause::_allocate_par_lab); | |
| 3186 // Now go around the loop and try alloc again; | |
| 3187 // A competing par_promote might beat us to the expansion space, | |
| 3188 // so we may go around the loop again if promotion fails agaion. | |
| 3189 if (GCExpandToAllocateDelayMillis > 0) { | |
| 3190 os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false); | |
| 3191 } | |
| 3192 } | |
| 3193 } | |
| 3194 | |
| 3195 | |
| 3196 bool ConcurrentMarkSweepGeneration::expand_and_ensure_spooling_space( | |
| 3197 PromotionInfo* promo) { | |
| 3198 MutexLocker x(ParGCRareEvent_lock); | |
| 3199 size_t refill_size_bytes = promo->refillSize() * HeapWordSize; | |
| 3200 while (true) { | |
| 3201 // Expansion by some other thread might make alloc OK now: | |
| 3202 if (promo->ensure_spooling_space()) { | |
| 3203 assert(promo->has_spooling_space(), | |
| 3204 "Post-condition of successful ensure_spooling_space()"); | |
| 3205 return true; | |
| 3206 } | |
| 3207 // If there's not enough expansion space available, give up. | |
| 3208 if (_virtual_space.uncommitted_size() < refill_size_bytes) { | |
| 3209 return false; | |
| 3210 } | |
| 3211 // Otherwise, we try expansion. | |
| 3212 expand(refill_size_bytes, MinHeapDeltaBytes, | |
| 3213 CMSExpansionCause::_allocate_par_spooling_space); | |
| 3214 // Now go around the loop and try alloc again; | |
| 3215 // A competing allocation might beat us to the expansion space, | |
| 3216 // so we may go around the loop again if allocation fails again. | |
| 3217 if (GCExpandToAllocateDelayMillis > 0) { | |
| 3218 os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false); | |
| 3219 } | |
| 3220 } | |
| 3221 } | |
| 3222 | |
| 3223 | |
| 3224 | |
| 3225 void ConcurrentMarkSweepGeneration::shrink(size_t bytes) { | |
| 3226 assert_locked_or_safepoint(Heap_lock); | |
| 3227 size_t size = ReservedSpace::page_align_size_down(bytes); | |
| 3228 if (size > 0) { | |
| 3229 shrink_by(size); | |
| 3230 } | |
| 3231 } | |
| 3232 | |
| 3233 bool ConcurrentMarkSweepGeneration::grow_by(size_t bytes) { | |
| 3234 assert_locked_or_safepoint(Heap_lock); | |
| 3235 bool result = _virtual_space.expand_by(bytes); | |
| 3236 if (result) { | |
| 3237 HeapWord* old_end = _cmsSpace->end(); | |
| 3238 size_t new_word_size = | |
| 3239 heap_word_size(_virtual_space.committed_size()); | |
| 3240 MemRegion mr(_cmsSpace->bottom(), new_word_size); | |
| 3241 _bts->resize(new_word_size); // resize the block offset shared array | |
| 3242 Universe::heap()->barrier_set()->resize_covered_region(mr); | |
| 3243 // Hmmmm... why doesn't CFLS::set_end verify locking? | |
| 3244 // This is quite ugly; FIX ME XXX | |
| 3245 _cmsSpace->assert_locked(); | |
| 3246 _cmsSpace->set_end((HeapWord*)_virtual_space.high()); | |
| 3247 | |
| 3248 // update the space and generation capacity counters | |
| 3249 if (UsePerfData) { | |
| 3250 _space_counters->update_capacity(); | |
| 3251 _gen_counters->update_all(); | |
| 3252 } | |
| 3253 | |
| 3254 if (Verbose && PrintGC) { | |
| 3255 size_t new_mem_size = _virtual_space.committed_size(); | |
| 3256 size_t old_mem_size = new_mem_size - bytes; | |
| 3257 gclog_or_tty->print_cr("Expanding %s from %ldK by %ldK to %ldK", | |
| 3258 name(), old_mem_size/K, bytes/K, new_mem_size/K); | |
| 3259 } | |
| 3260 } | |
| 3261 return result; | |
| 3262 } | |
| 3263 | |
| 3264 bool ConcurrentMarkSweepGeneration::grow_to_reserved() { | |
| 3265 assert_locked_or_safepoint(Heap_lock); | |
| 3266 bool success = true; | |
| 3267 const size_t remaining_bytes = _virtual_space.uncommitted_size(); | |
| 3268 if (remaining_bytes > 0) { | |
| 3269 success = grow_by(remaining_bytes); | |
| 3270 DEBUG_ONLY(if (!success) warning("grow to reserved failed");) | |
| 3271 } | |
| 3272 return success; | |
| 3273 } | |
| 3274 | |
| 3275 void ConcurrentMarkSweepGeneration::shrink_by(size_t bytes) { | |
| 3276 assert_locked_or_safepoint(Heap_lock); | |
| 3277 assert_lock_strong(freelistLock()); | |
| 3278 // XXX Fix when compaction is implemented. | |
| 3279 warning("Shrinking of CMS not yet implemented"); | |
| 3280 return; | |
| 3281 } | |
| 3282 | |
| 3283 | |
| 3284 // Simple ctor/dtor wrapper for accounting & timer chores around concurrent | |
| 3285 // phases. | |
| 3286 class CMSPhaseAccounting: public StackObj { | |
| 3287 public: | |
| 3288 CMSPhaseAccounting(CMSCollector *collector, | |
| 3289 const char *phase, | |
| 3290 bool print_cr = true); | |
| 3291 ~CMSPhaseAccounting(); | |
| 3292 | |
| 3293 private: | |
| 3294 CMSCollector *_collector; | |
| 3295 const char *_phase; | |
| 3296 elapsedTimer _wallclock; | |
| 3297 bool _print_cr; | |
| 3298 | |
| 3299 public: | |
| 3300 // Not MT-safe; so do not pass around these StackObj's | |
| 3301 // where they may be accessed by other threads. | |
| 3302 jlong wallclock_millis() { | |
| 3303 assert(_wallclock.is_active(), "Wall clock should not stop"); | |
| 3304 _wallclock.stop(); // to record time | |
| 3305 jlong ret = _wallclock.milliseconds(); | |
| 3306 _wallclock.start(); // restart | |
| 3307 return ret; | |
| 3308 } | |
| 3309 }; | |
| 3310 | |
| 3311 CMSPhaseAccounting::CMSPhaseAccounting(CMSCollector *collector, | |
| 3312 const char *phase, | |
| 3313 bool print_cr) : | |
| 3314 _collector(collector), _phase(phase), _print_cr(print_cr) { | |
| 3315 | |
| 3316 if (PrintCMSStatistics != 0) { | |
| 3317 _collector->resetYields(); | |
| 3318 } | |
| 3319 if (PrintGCDetails && PrintGCTimeStamps) { | |
| 3320 gclog_or_tty->date_stamp(PrintGCDateStamps); | |
| 3321 gclog_or_tty->stamp(); | |
| 3322 gclog_or_tty->print_cr(": [%s-concurrent-%s-start]", | |
| 3323 _collector->cmsGen()->short_name(), _phase); | |
| 3324 } | |
| 3325 _collector->resetTimer(); | |
| 3326 _wallclock.start(); | |
| 3327 _collector->startTimer(); | |
| 3328 } | |
| 3329 | |
| 3330 CMSPhaseAccounting::~CMSPhaseAccounting() { | |
| 3331 assert(_wallclock.is_active(), "Wall clock should not have stopped"); | |
| 3332 _collector->stopTimer(); | |
| 3333 _wallclock.stop(); | |
| 3334 if (PrintGCDetails) { | |
| 3335 gclog_or_tty->date_stamp(PrintGCDateStamps); | |
| 3336 if (PrintGCTimeStamps) { | |
| 3337 gclog_or_tty->stamp(); | |
| 3338 gclog_or_tty->print(": "); | |
| 3339 } | |
| 3340 gclog_or_tty->print("[%s-concurrent-%s: %3.3f/%3.3f secs]", | |
| 3341 _collector->cmsGen()->short_name(), | |
| 3342 _phase, _collector->timerValue(), _wallclock.seconds()); | |
| 3343 if (_print_cr) { | |
| 3344 gclog_or_tty->print_cr(""); | |
| 3345 } | |
| 3346 if (PrintCMSStatistics != 0) { | |
| 3347 gclog_or_tty->print_cr(" (CMS-concurrent-%s yielded %d times)", _phase, | |
| 3348 _collector->yields()); | |
| 3349 } | |
| 3350 } | |
| 3351 } | |
| 3352 | |
| 3353 // CMS work | |
| 3354 | |
| 3355 // Checkpoint the roots into this generation from outside | |
| 3356 // this generation. [Note this initial checkpoint need only | |
| 3357 // be approximate -- we'll do a catch up phase subsequently.] | |
| 3358 void CMSCollector::checkpointRootsInitial(bool asynch) { | |
| 3359 assert(_collectorState == InitialMarking, "Wrong collector state"); | |
| 3360 check_correct_thread_executing(); | |
| 3361 ReferenceProcessor* rp = ref_processor(); | |
| 3362 SpecializationStats::clear(); | |
| 3363 assert(_restart_addr == NULL, "Control point invariant"); | |
| 3364 if (asynch) { | |
| 3365 // acquire locks for subsequent manipulations | |
| 3366 MutexLockerEx x(bitMapLock(), | |
| 3367 Mutex::_no_safepoint_check_flag); | |
| 3368 checkpointRootsInitialWork(asynch); | |
| 3369 rp->verify_no_references_recorded(); | |
| 3370 rp->enable_discovery(); // enable ("weak") refs discovery | |
| 3371 _collectorState = Marking; | |
| 3372 } else { | |
| 3373 // (Weak) Refs discovery: this is controlled from genCollectedHeap::do_collection | |
| 3374 // which recognizes if we are a CMS generation, and doesn't try to turn on | |
| 3375 // discovery; verify that they aren't meddling. | |
| 3376 assert(!rp->discovery_is_atomic(), | |
| 3377 "incorrect setting of discovery predicate"); | |
| 3378 assert(!rp->discovery_enabled(), "genCollectedHeap shouldn't control " | |
| 3379 "ref discovery for this generation kind"); | |
| 3380 // already have locks | |
| 3381 checkpointRootsInitialWork(asynch); | |
| 3382 rp->enable_discovery(); // now enable ("weak") refs discovery | |
| 3383 _collectorState = Marking; | |
| 3384 } | |
| 3385 SpecializationStats::print(); | |
| 3386 } | |
| 3387 | |
| 3388 void CMSCollector::checkpointRootsInitialWork(bool asynch) { | |
| 3389 assert(SafepointSynchronize::is_at_safepoint(), "world should be stopped"); | |
| 3390 assert(_collectorState == InitialMarking, "just checking"); | |
| 3391 | |
| 3392 // If there has not been a GC[n-1] since last GC[n] cycle completed, | |
| 3393 // precede our marking with a collection of all | |
| 3394 // younger generations to keep floating garbage to a minimum. | |
| 3395 // XXX: we won't do this for now -- it's an optimization to be done later. | |
| 3396 | |
| 3397 // already have locks | |
| 3398 assert_lock_strong(bitMapLock()); | |
| 3399 assert(_markBitMap.isAllClear(), "was reset at end of previous cycle"); | |
| 3400 | |
| 3401 // Setup the verification and class unloading state for this | |
| 3402 // CMS collection cycle. | |
| 3403 setup_cms_unloading_and_verification_state(); | |
| 3404 | |
| 3405 NOT_PRODUCT(TraceTime t("\ncheckpointRootsInitialWork", | |
| 3406 PrintGCDetails && Verbose, true, gclog_or_tty);) | |
| 3407 if (UseAdaptiveSizePolicy) { | |
| 3408 size_policy()->checkpoint_roots_initial_begin(); | |
| 3409 } | |
| 3410 | |
| 3411 // Reset all the PLAB chunk arrays if necessary. | |
| 3412 if (_survivor_plab_array != NULL && !CMSPLABRecordAlways) { | |
| 3413 reset_survivor_plab_arrays(); | |
| 3414 } | |
| 3415 | |
| 3416 ResourceMark rm; | |
| 3417 HandleMark hm; | |
| 3418 | |
| 3419 FalseClosure falseClosure; | |
| 3420 // In the case of a synchronous collection, we will elide the | |
| 3421 // remark step, so it's important to catch all the nmethod oops | |
| 3422 // in this step; hence the last argument to the constrcutor below. | |
| 3423 MarkRefsIntoClosure notOlder(_span, &_markBitMap, !asynch /* nmethods */); | |
| 3424 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 3425 | |
| 3426 verify_work_stacks_empty(); | |
| 3427 verify_overflow_empty(); | |
| 3428 | |
| 3429 gch->ensure_parsability(false); // fill TLABs, but no need to retire them | |
| 3430 // Update the saved marks which may affect the root scans. | |
| 3431 gch->save_marks(); | |
| 3432 | |
| 3433 // weak reference processing has not started yet. | |
| 3434 ref_processor()->set_enqueuing_is_done(false); | |
| 3435 | |
| 3436 { | |
| 3437 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;) | |
| 3438 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. | |
| 3439 gch->gen_process_strong_roots(_cmsGen->level(), | |
| 3440 true, // younger gens are roots | |
| 3441 true, // collecting perm gen | |
| 3442 SharedHeap::ScanningOption(roots_scanning_options()), | |
| 3443 NULL, ¬Older); | |
| 3444 } | |
| 3445 | |
| 3446 // Clear mod-union table; it will be dirtied in the prologue of | |
| 3447 // CMS generation per each younger generation collection. | |
| 3448 | |
| 3449 assert(_modUnionTable.isAllClear(), | |
| 3450 "Was cleared in most recent final checkpoint phase" | |
| 3451 " or no bits are set in the gc_prologue before the start of the next " | |
| 3452 "subsequent marking phase."); | |
| 3453 | |
| 3454 // Temporarily disabled, since pre/post-consumption closures don't | |
| 3455 // care about precleaned cards | |
| 3456 #if 0 | |
| 3457 { | |
| 3458 MemRegion mr = MemRegion((HeapWord*)_virtual_space.low(), | |
| 3459 (HeapWord*)_virtual_space.high()); | |
| 3460 _ct->ct_bs()->preclean_dirty_cards(mr); | |
| 3461 } | |
| 3462 #endif | |
| 3463 | |
| 3464 // Save the end of the used_region of the constituent generations | |
| 3465 // to be used to limit the extent of sweep in each generation. | |
| 3466 save_sweep_limits(); | |
| 3467 if (UseAdaptiveSizePolicy) { | |
| 3468 size_policy()->checkpoint_roots_initial_end(gch->gc_cause()); | |
| 3469 } | |
| 3470 verify_overflow_empty(); | |
| 3471 } | |
| 3472 | |
| 3473 bool CMSCollector::markFromRoots(bool asynch) { | |
| 3474 // we might be tempted to assert that: | |
| 3475 // assert(asynch == !SafepointSynchronize::is_at_safepoint(), | |
| 3476 // "inconsistent argument?"); | |
| 3477 // However that wouldn't be right, because it's possible that | |
| 3478 // a safepoint is indeed in progress as a younger generation | |
| 3479 // stop-the-world GC happens even as we mark in this generation. | |
| 3480 assert(_collectorState == Marking, "inconsistent state?"); | |
| 3481 check_correct_thread_executing(); | |
| 3482 verify_overflow_empty(); | |
| 3483 | |
| 3484 bool res; | |
| 3485 if (asynch) { | |
| 3486 | |
| 3487 // Start the timers for adaptive size policy for the concurrent phases | |
| 3488 // Do it here so that the foreground MS can use the concurrent | |
| 3489 // timer since a foreground MS might has the sweep done concurrently | |
| 3490 // or STW. | |
| 3491 if (UseAdaptiveSizePolicy) { | |
| 3492 size_policy()->concurrent_marking_begin(); | |
| 3493 } | |
| 3494 | |
| 3495 // Weak ref discovery note: We may be discovering weak | |
| 3496 // refs in this generation concurrent (but interleaved) with | |
| 3497 // weak ref discovery by a younger generation collector. | |
| 3498 | |
| 3499 CMSTokenSyncWithLocks ts(true, bitMapLock()); | |
| 3500 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
| 3501 CMSPhaseAccounting pa(this, "mark", !PrintGCDetails); | |
| 3502 res = markFromRootsWork(asynch); | |
| 3503 if (res) { | |
| 3504 _collectorState = Precleaning; | |
| 3505 } else { // We failed and a foreground collection wants to take over | |
| 3506 assert(_foregroundGCIsActive, "internal state inconsistency"); | |
| 3507 assert(_restart_addr == NULL, "foreground will restart from scratch"); | |
| 3508 if (PrintGCDetails) { | |
| 3509 gclog_or_tty->print_cr("bailing out to foreground collection"); | |
| 3510 } | |
| 3511 } | |
| 3512 if (UseAdaptiveSizePolicy) { | |
| 3513 size_policy()->concurrent_marking_end(); | |
| 3514 } | |
| 3515 } else { | |
| 3516 assert(SafepointSynchronize::is_at_safepoint(), | |
| 3517 "inconsistent with asynch == false"); | |
| 3518 if (UseAdaptiveSizePolicy) { | |
| 3519 size_policy()->ms_collection_marking_begin(); | |
| 3520 } | |
| 3521 // already have locks | |
| 3522 res = markFromRootsWork(asynch); | |
| 3523 _collectorState = FinalMarking; | |
| 3524 if (UseAdaptiveSizePolicy) { | |
| 3525 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 3526 size_policy()->ms_collection_marking_end(gch->gc_cause()); | |
| 3527 } | |
| 3528 } | |
| 3529 verify_overflow_empty(); | |
| 3530 return res; | |
| 3531 } | |
| 3532 | |
| 3533 bool CMSCollector::markFromRootsWork(bool asynch) { | |
| 3534 // iterate over marked bits in bit map, doing a full scan and mark | |
| 3535 // from these roots using the following algorithm: | |
| 3536 // . if oop is to the right of the current scan pointer, | |
| 3537 // mark corresponding bit (we'll process it later) | |
| 3538 // . else (oop is to left of current scan pointer) | |
| 3539 // push oop on marking stack | |
| 3540 // . drain the marking stack | |
| 3541 | |
| 3542 // Note that when we do a marking step we need to hold the | |
| 3543 // bit map lock -- recall that direct allocation (by mutators) | |
| 3544 // and promotion (by younger generation collectors) is also | |
| 3545 // marking the bit map. [the so-called allocate live policy.] | |
| 3546 // Because the implementation of bit map marking is not | |
| 3547 // robust wrt simultaneous marking of bits in the same word, | |
| 3548 // we need to make sure that there is no such interference | |
| 3549 // between concurrent such updates. | |
| 3550 | |
| 3551 // already have locks | |
| 3552 assert_lock_strong(bitMapLock()); | |
| 3553 | |
| 3554 // Clear the revisit stack, just in case there are any | |
| 3555 // obsolete contents from a short-circuited previous CMS cycle. | |
| 3556 _revisitStack.reset(); | |
| 3557 verify_work_stacks_empty(); | |
| 3558 verify_overflow_empty(); | |
| 3559 assert(_revisitStack.isEmpty(), "tabula rasa"); | |
| 3560 | |
| 3561 bool result = false; | |
| 3562 if (CMSConcurrentMTEnabled && ParallelCMSThreads > 0) { | |
| 3563 result = do_marking_mt(asynch); | |
| 3564 } else { | |
| 3565 result = do_marking_st(asynch); | |
| 3566 } | |
| 3567 return result; | |
| 3568 } | |
| 3569 | |
| 3570 // Forward decl | |
| 3571 class CMSConcMarkingTask; | |
| 3572 | |
| 3573 class CMSConcMarkingTerminator: public ParallelTaskTerminator { | |
| 3574 CMSCollector* _collector; | |
| 3575 CMSConcMarkingTask* _task; | |
| 3576 bool _yield; | |
| 3577 protected: | |
| 3578 virtual void yield(); | |
| 3579 public: | |
| 3580 // "n_threads" is the number of threads to be terminated. | |
| 3581 // "queue_set" is a set of work queues of other threads. | |
| 3582 // "collector" is the CMS collector associated with this task terminator. | |
| 3583 // "yield" indicates whether we need the gang as a whole to yield. | |
| 3584 CMSConcMarkingTerminator(int n_threads, TaskQueueSetSuper* queue_set, | |
| 3585 CMSCollector* collector, bool yield) : | |
| 3586 ParallelTaskTerminator(n_threads, queue_set), | |
| 3587 _collector(collector), | |
| 3588 _yield(yield) { } | |
| 3589 | |
| 3590 void set_task(CMSConcMarkingTask* task) { | |
| 3591 _task = task; | |
| 3592 } | |
| 3593 }; | |
| 3594 | |
| 3595 // MT Concurrent Marking Task | |
| 3596 class CMSConcMarkingTask: public YieldingFlexibleGangTask { | |
| 3597 CMSCollector* _collector; | |
| 3598 YieldingFlexibleWorkGang* _workers; // the whole gang | |
| 3599 int _n_workers; // requested/desired # workers | |
| 3600 bool _asynch; | |
| 3601 bool _result; | |
| 3602 CompactibleFreeListSpace* _cms_space; | |
| 3603 CompactibleFreeListSpace* _perm_space; | |
| 3604 HeapWord* _global_finger; | |
| 3605 | |
| 3606 // Exposed here for yielding support | |
| 3607 Mutex* const _bit_map_lock; | |
| 3608 | |
| 3609 // The per thread work queues, available here for stealing | |
| 3610 OopTaskQueueSet* _task_queues; | |
| 3611 CMSConcMarkingTerminator _term; | |
| 3612 | |
| 3613 public: | |
| 3614 CMSConcMarkingTask(CMSCollector* collector, | |
| 3615 CompactibleFreeListSpace* cms_space, | |
| 3616 CompactibleFreeListSpace* perm_space, | |
| 3617 bool asynch, int n_workers, | |
| 3618 YieldingFlexibleWorkGang* workers, | |
| 3619 OopTaskQueueSet* task_queues): | |
| 3620 YieldingFlexibleGangTask("Concurrent marking done multi-threaded"), | |
| 3621 _collector(collector), | |
| 3622 _cms_space(cms_space), | |
| 3623 _perm_space(perm_space), | |
| 3624 _asynch(asynch), _n_workers(n_workers), _result(true), | |
| 3625 _workers(workers), _task_queues(task_queues), | |
| 3626 _term(n_workers, task_queues, _collector, asynch), | |
| 3627 _bit_map_lock(collector->bitMapLock()) | |
| 3628 { | |
| 3629 assert(n_workers <= workers->total_workers(), | |
| 3630 "Else termination won't work correctly today"); // XXX FIX ME! | |
| 3631 _requested_size = n_workers; | |
| 3632 _term.set_task(this); | |
| 3633 assert(_cms_space->bottom() < _perm_space->bottom(), | |
| 3634 "Finger incorrectly initialized below"); | |
| 3635 _global_finger = _cms_space->bottom(); | |
| 3636 } | |
| 3637 | |
| 3638 | |
| 3639 OopTaskQueueSet* task_queues() { return _task_queues; } | |
| 3640 | |
| 3641 OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); } | |
| 3642 | |
| 3643 HeapWord** global_finger_addr() { return &_global_finger; } | |
| 3644 | |
| 3645 CMSConcMarkingTerminator* terminator() { return &_term; } | |
| 3646 | |
| 3647 void work(int i); | |
| 3648 | |
| 3649 virtual void coordinator_yield(); // stuff done by coordinator | |
| 3650 bool result() { return _result; } | |
| 3651 | |
| 3652 void reset(HeapWord* ra) { | |
| 3653 _term.reset_for_reuse(); | |
| 3654 } | |
| 3655 | |
| 3656 static bool get_work_from_overflow_stack(CMSMarkStack* ovflw_stk, | |
| 3657 OopTaskQueue* work_q); | |
| 3658 | |
| 3659 private: | |
| 3660 void do_scan_and_mark(int i, CompactibleFreeListSpace* sp); | |
| 3661 void do_work_steal(int i); | |
| 3662 void bump_global_finger(HeapWord* f); | |
| 3663 }; | |
| 3664 | |
| 3665 void CMSConcMarkingTerminator::yield() { | |
| 3666 if (ConcurrentMarkSweepThread::should_yield() && | |
| 3667 !_collector->foregroundGCIsActive() && | |
| 3668 _yield) { | |
| 3669 _task->yield(); | |
| 3670 } else { | |
| 3671 ParallelTaskTerminator::yield(); | |
| 3672 } | |
| 3673 } | |
| 3674 | |
| 3675 //////////////////////////////////////////////////////////////// | |
| 3676 // Concurrent Marking Algorithm Sketch | |
| 3677 //////////////////////////////////////////////////////////////// | |
| 3678 // Until all tasks exhausted (both spaces): | |
| 3679 // -- claim next available chunk | |
| 3680 // -- bump global finger via CAS | |
| 3681 // -- find first object that starts in this chunk | |
| 3682 // and start scanning bitmap from that position | |
| 3683 // -- scan marked objects for oops | |
| 3684 // -- CAS-mark target, and if successful: | |
| 3685 // . if target oop is above global finger (volatile read) | |
| 3686 // nothing to do | |
| 3687 // . if target oop is in chunk and above local finger | |
| 3688 // then nothing to do | |
| 3689 // . else push on work-queue | |
| 3690 // -- Deal with possible overflow issues: | |
| 3691 // . local work-queue overflow causes stuff to be pushed on | |
| 3692 // global (common) overflow queue | |
| 3693 // . always first empty local work queue | |
| 3694 // . then get a batch of oops from global work queue if any | |
| 3695 // . then do work stealing | |
| 3696 // -- When all tasks claimed (both spaces) | |
| 3697 // and local work queue empty, | |
| 3698 // then in a loop do: | |
| 3699 // . check global overflow stack; steal a batch of oops and trace | |
| 3700 // . try to steal from other threads oif GOS is empty | |
| 3701 // . if neither is available, offer termination | |
| 3702 // -- Terminate and return result | |
| 3703 // | |
| 3704 void CMSConcMarkingTask::work(int i) { | |
| 3705 elapsedTimer _timer; | |
| 3706 ResourceMark rm; | |
| 3707 HandleMark hm; | |
| 3708 | |
| 3709 DEBUG_ONLY(_collector->verify_overflow_empty();) | |
| 3710 | |
| 3711 // Before we begin work, our work queue should be empty | |
| 3712 assert(work_queue(i)->size() == 0, "Expected to be empty"); | |
| 3713 // Scan the bitmap covering _cms_space, tracing through grey objects. | |
| 3714 _timer.start(); | |
| 3715 do_scan_and_mark(i, _cms_space); | |
| 3716 _timer.stop(); | |
| 3717 if (PrintCMSStatistics != 0) { | |
| 3718 gclog_or_tty->print_cr("Finished cms space scanning in %dth thread: %3.3f sec", | |
| 3719 i, _timer.seconds()); // XXX: need xxx/xxx type of notation, two timers | |
| 3720 } | |
| 3721 | |
| 3722 // ... do the same for the _perm_space | |
| 3723 _timer.reset(); | |
| 3724 _timer.start(); | |
| 3725 do_scan_and_mark(i, _perm_space); | |
| 3726 _timer.stop(); | |
| 3727 if (PrintCMSStatistics != 0) { | |
| 3728 gclog_or_tty->print_cr("Finished perm space scanning in %dth thread: %3.3f sec", | |
| 3729 i, _timer.seconds()); // XXX: need xxx/xxx type of notation, two timers | |
| 3730 } | |
| 3731 | |
| 3732 // ... do work stealing | |
| 3733 _timer.reset(); | |
| 3734 _timer.start(); | |
| 3735 do_work_steal(i); | |
| 3736 _timer.stop(); | |
| 3737 if (PrintCMSStatistics != 0) { | |
| 3738 gclog_or_tty->print_cr("Finished work stealing in %dth thread: %3.3f sec", | |
| 3739 i, _timer.seconds()); // XXX: need xxx/xxx type of notation, two timers | |
| 3740 } | |
| 3741 assert(_collector->_markStack.isEmpty(), "Should have been emptied"); | |
| 3742 assert(work_queue(i)->size() == 0, "Should have been emptied"); | |
| 3743 // Note that under the current task protocol, the | |
| 3744 // following assertion is true even of the spaces | |
| 3745 // expanded since the completion of the concurrent | |
| 3746 // marking. XXX This will likely change under a strict | |
| 3747 // ABORT semantics. | |
| 3748 assert(_global_finger > _cms_space->end() && | |
| 3749 _global_finger >= _perm_space->end(), | |
| 3750 "All tasks have been completed"); | |
| 3751 DEBUG_ONLY(_collector->verify_overflow_empty();) | |
| 3752 } | |
| 3753 | |
| 3754 void CMSConcMarkingTask::bump_global_finger(HeapWord* f) { | |
| 3755 HeapWord* read = _global_finger; | |
| 3756 HeapWord* cur = read; | |
| 3757 while (f > read) { | |
| 3758 cur = read; | |
| 3759 read = (HeapWord*) Atomic::cmpxchg_ptr(f, &_global_finger, cur); | |
| 3760 if (cur == read) { | |
| 3761 // our cas succeeded | |
| 3762 assert(_global_finger >= f, "protocol consistency"); | |
| 3763 break; | |
| 3764 } | |
| 3765 } | |
| 3766 } | |
| 3767 | |
| 3768 // This is really inefficient, and should be redone by | |
| 3769 // using (not yet available) block-read and -write interfaces to the | |
| 3770 // stack and the work_queue. XXX FIX ME !!! | |
| 3771 bool CMSConcMarkingTask::get_work_from_overflow_stack(CMSMarkStack* ovflw_stk, | |
| 3772 OopTaskQueue* work_q) { | |
| 3773 // Fast lock-free check | |
| 3774 if (ovflw_stk->length() == 0) { | |
| 3775 return false; | |
| 3776 } | |
| 3777 assert(work_q->size() == 0, "Shouldn't steal"); | |
| 3778 MutexLockerEx ml(ovflw_stk->par_lock(), | |
| 3779 Mutex::_no_safepoint_check_flag); | |
| 3780 // Grab up to 1/4 the size of the work queue | |
| 3781 size_t num = MIN2((size_t)work_q->max_elems()/4, | |
| 3782 (size_t)ParGCDesiredObjsFromOverflowList); | |
| 3783 num = MIN2(num, ovflw_stk->length()); | |
| 3784 for (int i = (int) num; i > 0; i--) { | |
| 3785 oop cur = ovflw_stk->pop(); | |
| 3786 assert(cur != NULL, "Counted wrong?"); | |
| 3787 work_q->push(cur); | |
| 3788 } | |
| 3789 return num > 0; | |
| 3790 } | |
| 3791 | |
| 3792 void CMSConcMarkingTask::do_scan_and_mark(int i, CompactibleFreeListSpace* sp) { | |
| 3793 SequentialSubTasksDone* pst = sp->conc_par_seq_tasks(); | |
| 3794 int n_tasks = pst->n_tasks(); | |
| 3795 // We allow that there may be no tasks to do here because | |
| 3796 // we are restarting after a stack overflow. | |
| 3797 assert(pst->valid() || n_tasks == 0, "Uninitializd use?"); | |
| 3798 int nth_task = 0; | |
| 3799 | |
| 3800 HeapWord* start = sp->bottom(); | |
| 3801 size_t chunk_size = sp->marking_task_size(); | |
| 3802 while (!pst->is_task_claimed(/* reference */ nth_task)) { | |
| 3803 // Having claimed the nth task in this space, | |
| 3804 // compute the chunk that it corresponds to: | |
| 3805 MemRegion span = MemRegion(start + nth_task*chunk_size, | |
| 3806 start + (nth_task+1)*chunk_size); | |
| 3807 // Try and bump the global finger via a CAS; | |
| 3808 // note that we need to do the global finger bump | |
| 3809 // _before_ taking the intersection below, because | |
| 3810 // the task corresponding to that region will be | |
| 3811 // deemed done even if the used_region() expands | |
| 3812 // because of allocation -- as it almost certainly will | |
| 3813 // during start-up while the threads yield in the | |
| 3814 // closure below. | |
| 3815 HeapWord* finger = span.end(); | |
| 3816 bump_global_finger(finger); // atomically | |
| 3817 // There are null tasks here corresponding to chunks | |
| 3818 // beyond the "top" address of the space. | |
| 3819 span = span.intersection(sp->used_region()); | |
| 3820 if (!span.is_empty()) { // Non-null task | |
| 3821 // We want to skip the first object because | |
| 3822 // the protocol is to scan any object in its entirety | |
| 3823 // that _starts_ in this span; a fortiori, any | |
| 3824 // object starting in an earlier span is scanned | |
| 3825 // as part of an earlier claimed task. | |
| 3826 // Below we use the "careful" version of block_start | |
| 3827 // so we do not try to navigate uninitialized objects. | |
| 3828 HeapWord* prev_obj = sp->block_start_careful(span.start()); | |
| 3829 // Below we use a variant of block_size that uses the | |
| 3830 // Printezis bits to avoid waiting for allocated | |
| 3831 // objects to become initialized/parsable. | |
| 3832 while (prev_obj < span.start()) { | |
| 3833 size_t sz = sp->block_size_no_stall(prev_obj, _collector); | |
| 3834 if (sz > 0) { | |
| 3835 prev_obj += sz; | |
| 3836 } else { | |
| 3837 // In this case we may end up doing a bit of redundant | |
| 3838 // scanning, but that appears unavoidable, short of | |
| 3839 // locking the free list locks; see bug 6324141. | |
| 3840 break; | |
| 3841 } | |
| 3842 } | |
| 3843 if (prev_obj < span.end()) { | |
| 3844 MemRegion my_span = MemRegion(prev_obj, span.end()); | |
| 3845 // Do the marking work within a non-empty span -- | |
| 3846 // the last argument to the constructor indicates whether the | |
| 3847 // iteration should be incremental with periodic yields. | |
| 3848 Par_MarkFromRootsClosure cl(this, _collector, my_span, | |
| 3849 &_collector->_markBitMap, | |
| 3850 work_queue(i), | |
| 3851 &_collector->_markStack, | |
| 3852 &_collector->_revisitStack, | |
| 3853 _asynch); | |
| 3854 _collector->_markBitMap.iterate(&cl, my_span.start(), my_span.end()); | |
| 3855 } // else nothing to do for this task | |
| 3856 } // else nothing to do for this task | |
| 3857 } | |
| 3858 // We'd be tempted to assert here that since there are no | |
| 3859 // more tasks left to claim in this space, the global_finger | |
| 3860 // must exceed space->top() and a fortiori space->end(). However, | |
| 3861 // that would not quite be correct because the bumping of | |
| 3862 // global_finger occurs strictly after the claiming of a task, | |
| 3863 // so by the time we reach here the global finger may not yet | |
| 3864 // have been bumped up by the thread that claimed the last | |
| 3865 // task. | |
| 3866 pst->all_tasks_completed(); | |
| 3867 } | |
| 3868 | |
| 3869 class Par_ConcMarkingClosure: public OopClosure { | |
| 3870 CMSCollector* _collector; | |
| 3871 MemRegion _span; | |
| 3872 CMSBitMap* _bit_map; | |
| 3873 CMSMarkStack* _overflow_stack; | |
| 3874 CMSMarkStack* _revisit_stack; // XXXXXX Check proper use | |
| 3875 OopTaskQueue* _work_queue; | |
| 3876 | |
| 3877 public: | |
| 3878 Par_ConcMarkingClosure(CMSCollector* collector, OopTaskQueue* work_queue, | |
| 3879 CMSBitMap* bit_map, CMSMarkStack* overflow_stack): | |
| 3880 _collector(collector), | |
| 3881 _span(_collector->_span), | |
| 3882 _work_queue(work_queue), | |
| 3883 _bit_map(bit_map), | |
| 3884 _overflow_stack(overflow_stack) { } // need to initialize revisit stack etc. | |
| 3885 | |
| 3886 void do_oop(oop* p); | |
| 3887 void trim_queue(size_t max); | |
| 3888 void handle_stack_overflow(HeapWord* lost); | |
| 3889 }; | |
| 3890 | |
| 3891 // Grey object rescan during work stealing phase -- | |
| 3892 // the salient assumption here is that stolen oops must | |
| 3893 // always be initialized, so we do not need to check for | |
| 3894 // uninitialized objects before scanning here. | |
| 3895 void Par_ConcMarkingClosure::do_oop(oop* p) { | |
| 3896 oop this_oop = *p; | |
| 3897 assert(this_oop->is_oop_or_null(), | |
| 3898 "expected an oop or NULL"); | |
| 3899 HeapWord* addr = (HeapWord*)this_oop; | |
| 3900 // Check if oop points into the CMS generation | |
| 3901 // and is not marked | |
| 3902 if (_span.contains(addr) && !_bit_map->isMarked(addr)) { | |
| 3903 // a white object ... | |
| 3904 // If we manage to "claim" the object, by being the | |
| 3905 // first thread to mark it, then we push it on our | |
| 3906 // marking stack | |
| 3907 if (_bit_map->par_mark(addr)) { // ... now grey | |
| 3908 // push on work queue (grey set) | |
| 3909 bool simulate_overflow = false; | |
| 3910 NOT_PRODUCT( | |
| 3911 if (CMSMarkStackOverflowALot && | |
| 3912 _collector->simulate_overflow()) { | |
| 3913 // simulate a stack overflow | |
| 3914 simulate_overflow = true; | |
| 3915 } | |
| 3916 ) | |
| 3917 if (simulate_overflow || | |
| 3918 !(_work_queue->push(this_oop) || _overflow_stack->par_push(this_oop))) { | |
| 3919 // stack overflow | |
| 3920 if (PrintCMSStatistics != 0) { | |
| 3921 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
| 3922 SIZE_FORMAT, _overflow_stack->capacity()); | |
| 3923 } | |
| 3924 // We cannot assert that the overflow stack is full because | |
| 3925 // it may have been emptied since. | |
| 3926 assert(simulate_overflow || | |
| 3927 _work_queue->size() == _work_queue->max_elems(), | |
| 3928 "Else push should have succeeded"); | |
| 3929 handle_stack_overflow(addr); | |
| 3930 } | |
| 3931 } // Else, some other thread got there first | |
| 3932 } | |
| 3933 } | |
| 3934 | |
| 3935 void Par_ConcMarkingClosure::trim_queue(size_t max) { | |
| 3936 while (_work_queue->size() > max) { | |
| 3937 oop new_oop; | |
| 3938 if (_work_queue->pop_local(new_oop)) { | |
| 3939 assert(new_oop->is_oop(), "Should be an oop"); | |
| 3940 assert(_bit_map->isMarked((HeapWord*)new_oop), "Grey object"); | |
| 3941 assert(_span.contains((HeapWord*)new_oop), "Not in span"); | |
| 3942 assert(new_oop->is_parsable(), "Should be parsable"); | |
| 3943 new_oop->oop_iterate(this); // do_oop() above | |
| 3944 } | |
| 3945 } | |
| 3946 } | |
| 3947 | |
| 3948 // Upon stack overflow, we discard (part of) the stack, | |
| 3949 // remembering the least address amongst those discarded | |
| 3950 // in CMSCollector's _restart_address. | |
| 3951 void Par_ConcMarkingClosure::handle_stack_overflow(HeapWord* lost) { | |
| 3952 // We need to do this under a mutex to prevent other | |
| 3953 // workers from interfering with the expansion below. | |
| 3954 MutexLockerEx ml(_overflow_stack->par_lock(), | |
| 3955 Mutex::_no_safepoint_check_flag); | |
| 3956 // Remember the least grey address discarded | |
| 3957 HeapWord* ra = (HeapWord*)_overflow_stack->least_value(lost); | |
| 3958 _collector->lower_restart_addr(ra); | |
| 3959 _overflow_stack->reset(); // discard stack contents | |
| 3960 _overflow_stack->expand(); // expand the stack if possible | |
| 3961 } | |
| 3962 | |
| 3963 | |
| 3964 void CMSConcMarkingTask::do_work_steal(int i) { | |
| 3965 OopTaskQueue* work_q = work_queue(i); | |
| 3966 oop obj_to_scan; | |
| 3967 CMSBitMap* bm = &(_collector->_markBitMap); | |
| 3968 CMSMarkStack* ovflw = &(_collector->_markStack); | |
| 3969 int* seed = _collector->hash_seed(i); | |
| 3970 Par_ConcMarkingClosure cl(_collector, work_q, bm, ovflw); | |
| 3971 while (true) { | |
| 3972 cl.trim_queue(0); | |
| 3973 assert(work_q->size() == 0, "Should have been emptied above"); | |
| 3974 if (get_work_from_overflow_stack(ovflw, work_q)) { | |
| 3975 // Can't assert below because the work obtained from the | |
| 3976 // overflow stack may already have been stolen from us. | |
| 3977 // assert(work_q->size() > 0, "Work from overflow stack"); | |
| 3978 continue; | |
| 3979 } else if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) { | |
| 3980 assert(obj_to_scan->is_oop(), "Should be an oop"); | |
| 3981 assert(bm->isMarked((HeapWord*)obj_to_scan), "Grey object"); | |
| 3982 obj_to_scan->oop_iterate(&cl); | |
| 3983 } else if (terminator()->offer_termination()) { | |
| 3984 assert(work_q->size() == 0, "Impossible!"); | |
| 3985 break; | |
| 3986 } | |
| 3987 } | |
| 3988 } | |
| 3989 | |
| 3990 // This is run by the CMS (coordinator) thread. | |
| 3991 void CMSConcMarkingTask::coordinator_yield() { | |
| 3992 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 3993 "CMS thread should hold CMS token"); | |
| 3994 | |
| 3995 // First give up the locks, then yield, then re-lock | |
| 3996 // We should probably use a constructor/destructor idiom to | |
| 3997 // do this unlock/lock or modify the MutexUnlocker class to | |
| 3998 // serve our purpose. XXX | |
| 3999 assert_lock_strong(_bit_map_lock); | |
| 4000 _bit_map_lock->unlock(); | |
| 4001 ConcurrentMarkSweepThread::desynchronize(true); | |
| 4002 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 4003 _collector->stopTimer(); | |
| 4004 if (PrintCMSStatistics != 0) { | |
| 4005 _collector->incrementYields(); | |
| 4006 } | |
| 4007 _collector->icms_wait(); | |
| 4008 | |
| 4009 // It is possible for whichever thread initiated the yield request | |
| 4010 // not to get a chance to wake up and take the bitmap lock between | |
| 4011 // this thread releasing it and reacquiring it. So, while the | |
| 4012 // should_yield() flag is on, let's sleep for a bit to give the | |
| 4013 // other thread a chance to wake up. The limit imposed on the number | |
| 4014 // of iterations is defensive, to avoid any unforseen circumstances | |
| 4015 // putting us into an infinite loop. Since it's always been this | |
| 4016 // (coordinator_yield()) method that was observed to cause the | |
| 4017 // problem, we are using a parameter (CMSCoordinatorYieldSleepCount) | |
| 4018 // which is by default non-zero. For the other seven methods that | |
| 4019 // also perform the yield operation, as are using a different | |
| 4020 // parameter (CMSYieldSleepCount) which is by default zero. This way we | |
| 4021 // can enable the sleeping for those methods too, if necessary. | |
| 4022 // See 6442774. | |
| 4023 // | |
| 4024 // We really need to reconsider the synchronization between the GC | |
| 4025 // thread and the yield-requesting threads in the future and we | |
| 4026 // should really use wait/notify, which is the recommended | |
| 4027 // way of doing this type of interaction. Additionally, we should | |
| 4028 // consolidate the eight methods that do the yield operation and they | |
| 4029 // are almost identical into one for better maintenability and | |
| 4030 // readability. See 6445193. | |
| 4031 // | |
| 4032 // Tony 2006.06.29 | |
| 4033 for (unsigned i = 0; i < CMSCoordinatorYieldSleepCount && | |
| 4034 ConcurrentMarkSweepThread::should_yield() && | |
| 4035 !CMSCollector::foregroundGCIsActive(); ++i) { | |
| 4036 os::sleep(Thread::current(), 1, false); | |
| 4037 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 4038 } | |
| 4039 | |
| 4040 ConcurrentMarkSweepThread::synchronize(true); | |
| 4041 _bit_map_lock->lock_without_safepoint_check(); | |
| 4042 _collector->startTimer(); | |
| 4043 } | |
| 4044 | |
| 4045 bool CMSCollector::do_marking_mt(bool asynch) { | |
| 4046 assert(ParallelCMSThreads > 0 && conc_workers() != NULL, "precondition"); | |
| 4047 // In the future this would be determined ergonomically, based | |
| 4048 // on #cpu's, # active mutator threads (and load), and mutation rate. | |
| 4049 int num_workers = ParallelCMSThreads; | |
| 4050 | |
| 4051 CompactibleFreeListSpace* cms_space = _cmsGen->cmsSpace(); | |
| 4052 CompactibleFreeListSpace* perm_space = _permGen->cmsSpace(); | |
| 4053 | |
| 4054 CMSConcMarkingTask tsk(this, cms_space, perm_space, | |
| 4055 asynch, num_workers /* number requested XXX */, | |
| 4056 conc_workers(), task_queues()); | |
| 4057 | |
| 4058 // Since the actual number of workers we get may be different | |
| 4059 // from the number we requested above, do we need to do anything different | |
| 4060 // below? In particular, may be we need to subclass the SequantialSubTasksDone | |
| 4061 // class?? XXX | |
| 4062 cms_space ->initialize_sequential_subtasks_for_marking(num_workers); | |
| 4063 perm_space->initialize_sequential_subtasks_for_marking(num_workers); | |
| 4064 | |
| 4065 // Refs discovery is already non-atomic. | |
| 4066 assert(!ref_processor()->discovery_is_atomic(), "Should be non-atomic"); | |
| 4067 // Mutate the Refs discovery so it is MT during the | |
| 4068 // multi-threaded marking phase. | |
| 4069 ReferenceProcessorMTMutator mt(ref_processor(), num_workers > 1); | |
| 4070 | |
| 4071 conc_workers()->start_task(&tsk); | |
| 4072 while (tsk.yielded()) { | |
| 4073 tsk.coordinator_yield(); | |
| 4074 conc_workers()->continue_task(&tsk); | |
| 4075 } | |
| 4076 // If the task was aborted, _restart_addr will be non-NULL | |
| 4077 assert(tsk.completed() || _restart_addr != NULL, "Inconsistency"); | |
| 4078 while (_restart_addr != NULL) { | |
| 4079 // XXX For now we do not make use of ABORTED state and have not | |
| 4080 // yet implemented the right abort semantics (even in the original | |
| 4081 // single-threaded CMS case). That needs some more investigation | |
| 4082 // and is deferred for now; see CR# TBF. 07252005YSR. XXX | |
| 4083 assert(!CMSAbortSemantics || tsk.aborted(), "Inconsistency"); | |
| 4084 // If _restart_addr is non-NULL, a marking stack overflow | |
| 4085 // occured; we need to do a fresh marking iteration from the | |
| 4086 // indicated restart address. | |
| 4087 if (_foregroundGCIsActive && asynch) { | |
| 4088 // We may be running into repeated stack overflows, having | |
| 4089 // reached the limit of the stack size, while making very | |
| 4090 // slow forward progress. It may be best to bail out and | |
| 4091 // let the foreground collector do its job. | |
| 4092 // Clear _restart_addr, so that foreground GC | |
| 4093 // works from scratch. This avoids the headache of | |
| 4094 // a "rescan" which would otherwise be needed because | |
| 4095 // of the dirty mod union table & card table. | |
| 4096 _restart_addr = NULL; | |
| 4097 return false; | |
| 4098 } | |
| 4099 // Adjust the task to restart from _restart_addr | |
| 4100 tsk.reset(_restart_addr); | |
| 4101 cms_space ->initialize_sequential_subtasks_for_marking(num_workers, | |
| 4102 _restart_addr); | |
| 4103 perm_space->initialize_sequential_subtasks_for_marking(num_workers, | |
| 4104 _restart_addr); | |
| 4105 _restart_addr = NULL; | |
| 4106 // Get the workers going again | |
| 4107 conc_workers()->start_task(&tsk); | |
| 4108 while (tsk.yielded()) { | |
| 4109 tsk.coordinator_yield(); | |
| 4110 conc_workers()->continue_task(&tsk); | |
| 4111 } | |
| 4112 } | |
| 4113 assert(tsk.completed(), "Inconsistency"); | |
| 4114 assert(tsk.result() == true, "Inconsistency"); | |
| 4115 return true; | |
| 4116 } | |
| 4117 | |
| 4118 bool CMSCollector::do_marking_st(bool asynch) { | |
| 4119 ResourceMark rm; | |
| 4120 HandleMark hm; | |
| 4121 | |
| 4122 MarkFromRootsClosure markFromRootsClosure(this, _span, &_markBitMap, | |
| 4123 &_markStack, &_revisitStack, CMSYield && asynch); | |
| 4124 // the last argument to iterate indicates whether the iteration | |
| 4125 // should be incremental with periodic yields. | |
| 4126 _markBitMap.iterate(&markFromRootsClosure); | |
| 4127 // If _restart_addr is non-NULL, a marking stack overflow | |
| 4128 // occured; we need to do a fresh iteration from the | |
| 4129 // indicated restart address. | |
| 4130 while (_restart_addr != NULL) { | |
| 4131 if (_foregroundGCIsActive && asynch) { | |
| 4132 // We may be running into repeated stack overflows, having | |
| 4133 // reached the limit of the stack size, while making very | |
| 4134 // slow forward progress. It may be best to bail out and | |
| 4135 // let the foreground collector do its job. | |
| 4136 // Clear _restart_addr, so that foreground GC | |
| 4137 // works from scratch. This avoids the headache of | |
| 4138 // a "rescan" which would otherwise be needed because | |
| 4139 // of the dirty mod union table & card table. | |
| 4140 _restart_addr = NULL; | |
| 4141 return false; // indicating failure to complete marking | |
| 4142 } | |
| 4143 // Deal with stack overflow: | |
| 4144 // we restart marking from _restart_addr | |
| 4145 HeapWord* ra = _restart_addr; | |
| 4146 markFromRootsClosure.reset(ra); | |
| 4147 _restart_addr = NULL; | |
| 4148 _markBitMap.iterate(&markFromRootsClosure, ra, _span.end()); | |
| 4149 } | |
| 4150 return true; | |
| 4151 } | |
| 4152 | |
| 4153 void CMSCollector::preclean() { | |
| 4154 check_correct_thread_executing(); | |
| 4155 assert(Thread::current()->is_ConcurrentGC_thread(), "Wrong thread"); | |
| 4156 verify_work_stacks_empty(); | |
| 4157 verify_overflow_empty(); | |
| 4158 _abort_preclean = false; | |
| 4159 if (CMSPrecleaningEnabled) { | |
| 4160 _eden_chunk_index = 0; | |
| 4161 size_t used = get_eden_used(); | |
| 4162 size_t capacity = get_eden_capacity(); | |
| 4163 // Don't start sampling unless we will get sufficiently | |
| 4164 // many samples. | |
| 4165 if (used < (capacity/(CMSScheduleRemarkSamplingRatio * 100) | |
| 4166 * CMSScheduleRemarkEdenPenetration)) { | |
| 4167 _start_sampling = true; | |
| 4168 } else { | |
| 4169 _start_sampling = false; | |
| 4170 } | |
| 4171 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
| 4172 CMSPhaseAccounting pa(this, "preclean", !PrintGCDetails); | |
| 4173 preclean_work(CMSPrecleanRefLists1, CMSPrecleanSurvivors1); | |
| 4174 } | |
| 4175 CMSTokenSync x(true); // is cms thread | |
| 4176 if (CMSPrecleaningEnabled) { | |
| 4177 sample_eden(); | |
| 4178 _collectorState = AbortablePreclean; | |
| 4179 } else { | |
| 4180 _collectorState = FinalMarking; | |
| 4181 } | |
| 4182 verify_work_stacks_empty(); | |
| 4183 verify_overflow_empty(); | |
| 4184 } | |
| 4185 | |
| 4186 // Try and schedule the remark such that young gen | |
| 4187 // occupancy is CMSScheduleRemarkEdenPenetration %. | |
| 4188 void CMSCollector::abortable_preclean() { | |
| 4189 check_correct_thread_executing(); | |
| 4190 assert(CMSPrecleaningEnabled, "Inconsistent control state"); | |
| 4191 assert(_collectorState == AbortablePreclean, "Inconsistent control state"); | |
| 4192 | |
| 4193 // If Eden's current occupancy is below this threshold, | |
| 4194 // immediately schedule the remark; else preclean | |
| 4195 // past the next scavenge in an effort to | |
| 4196 // schedule the pause as described avove. By choosing | |
| 4197 // CMSScheduleRemarkEdenSizeThreshold >= max eden size | |
| 4198 // we will never do an actual abortable preclean cycle. | |
| 4199 if (get_eden_used() > CMSScheduleRemarkEdenSizeThreshold) { | |
| 4200 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
| 4201 CMSPhaseAccounting pa(this, "abortable-preclean", !PrintGCDetails); | |
| 4202 // We need more smarts in the abortable preclean | |
| 4203 // loop below to deal with cases where allocation | |
| 4204 // in young gen is very very slow, and our precleaning | |
| 4205 // is running a losing race against a horde of | |
| 4206 // mutators intent on flooding us with CMS updates | |
| 4207 // (dirty cards). | |
| 4208 // One, admittedly dumb, strategy is to give up | |
| 4209 // after a certain number of abortable precleaning loops | |
| 4210 // or after a certain maximum time. We want to make | |
| 4211 // this smarter in the next iteration. | |
| 4212 // XXX FIX ME!!! YSR | |
| 4213 size_t loops = 0, workdone = 0, cumworkdone = 0, waited = 0; | |
| 4214 while (!(should_abort_preclean() || | |
| 4215 ConcurrentMarkSweepThread::should_terminate())) { | |
| 4216 workdone = preclean_work(CMSPrecleanRefLists2, CMSPrecleanSurvivors2); | |
| 4217 cumworkdone += workdone; | |
| 4218 loops++; | |
| 4219 // Voluntarily terminate abortable preclean phase if we have | |
| 4220 // been at it for too long. | |
| 4221 if ((CMSMaxAbortablePrecleanLoops != 0) && | |
| 4222 loops >= CMSMaxAbortablePrecleanLoops) { | |
| 4223 if (PrintGCDetails) { | |
| 4224 gclog_or_tty->print(" CMS: abort preclean due to loops "); | |
| 4225 } | |
| 4226 break; | |
| 4227 } | |
| 4228 if (pa.wallclock_millis() > CMSMaxAbortablePrecleanTime) { | |
| 4229 if (PrintGCDetails) { | |
| 4230 gclog_or_tty->print(" CMS: abort preclean due to time "); | |
| 4231 } | |
| 4232 break; | |
| 4233 } | |
| 4234 // If we are doing little work each iteration, we should | |
| 4235 // take a short break. | |
| 4236 if (workdone < CMSAbortablePrecleanMinWorkPerIteration) { | |
| 4237 // Sleep for some time, waiting for work to accumulate | |
| 4238 stopTimer(); | |
| 4239 cmsThread()->wait_on_cms_lock(CMSAbortablePrecleanWaitMillis); | |
| 4240 startTimer(); | |
| 4241 waited++; | |
| 4242 } | |
| 4243 } | |
| 4244 if (PrintCMSStatistics > 0) { | |
| 4245 gclog_or_tty->print(" [%d iterations, %d waits, %d cards)] ", | |
| 4246 loops, waited, cumworkdone); | |
| 4247 } | |
| 4248 } | |
| 4249 CMSTokenSync x(true); // is cms thread | |
| 4250 if (_collectorState != Idling) { | |
| 4251 assert(_collectorState == AbortablePreclean, | |
| 4252 "Spontaneous state transition?"); | |
| 4253 _collectorState = FinalMarking; | |
| 4254 } // Else, a foreground collection completed this CMS cycle. | |
| 4255 return; | |
| 4256 } | |
| 4257 | |
| 4258 // Respond to an Eden sampling opportunity | |
| 4259 void CMSCollector::sample_eden() { | |
| 4260 // Make sure a young gc cannot sneak in between our | |
| 4261 // reading and recording of a sample. | |
| 4262 assert(Thread::current()->is_ConcurrentGC_thread(), | |
| 4263 "Only the cms thread may collect Eden samples"); | |
| 4264 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 4265 "Should collect samples while holding CMS token"); | |
| 4266 if (!_start_sampling) { | |
| 4267 return; | |
| 4268 } | |
| 4269 if (_eden_chunk_array) { | |
| 4270 if (_eden_chunk_index < _eden_chunk_capacity) { | |
| 4271 _eden_chunk_array[_eden_chunk_index] = *_top_addr; // take sample | |
| 4272 assert(_eden_chunk_array[_eden_chunk_index] <= *_end_addr, | |
| 4273 "Unexpected state of Eden"); | |
| 4274 // We'd like to check that what we just sampled is an oop-start address; | |
| 4275 // however, we cannot do that here since the object may not yet have been | |
| 4276 // initialized. So we'll instead do the check when we _use_ this sample | |
| 4277 // later. | |
| 4278 if (_eden_chunk_index == 0 || | |
| 4279 (pointer_delta(_eden_chunk_array[_eden_chunk_index], | |
| 4280 _eden_chunk_array[_eden_chunk_index-1]) | |
| 4281 >= CMSSamplingGrain)) { | |
| 4282 _eden_chunk_index++; // commit sample | |
| 4283 } | |
| 4284 } | |
| 4285 } | |
| 4286 if ((_collectorState == AbortablePreclean) && !_abort_preclean) { | |
| 4287 size_t used = get_eden_used(); | |
| 4288 size_t capacity = get_eden_capacity(); | |
| 4289 assert(used <= capacity, "Unexpected state of Eden"); | |
| 4290 if (used > (capacity/100 * CMSScheduleRemarkEdenPenetration)) { | |
| 4291 _abort_preclean = true; | |
| 4292 } | |
| 4293 } | |
| 4294 } | |
| 4295 | |
| 4296 | |
| 4297 size_t CMSCollector::preclean_work(bool clean_refs, bool clean_survivor) { | |
| 4298 assert(_collectorState == Precleaning || | |
| 4299 _collectorState == AbortablePreclean, "incorrect state"); | |
| 4300 ResourceMark rm; | |
| 4301 HandleMark hm; | |
| 4302 // Do one pass of scrubbing the discovered reference lists | |
| 4303 // to remove any reference objects with strongly-reachable | |
| 4304 // referents. | |
| 4305 if (clean_refs) { | |
| 4306 ReferenceProcessor* rp = ref_processor(); | |
| 4307 CMSPrecleanRefsYieldClosure yield_cl(this); | |
| 4308 assert(rp->span().equals(_span), "Spans should be equal"); | |
| 4309 CMSKeepAliveClosure keep_alive(this, _span, &_markBitMap, | |
| 4310 &_markStack); | |
| 4311 CMSDrainMarkingStackClosure complete_trace(this, | |
| 4312 _span, &_markBitMap, &_markStack, | |
| 4313 &keep_alive); | |
| 4314 | |
| 4315 // We don't want this step to interfere with a young | |
| 4316 // collection because we don't want to take CPU | |
| 4317 // or memory bandwidth away from the young GC threads | |
| 4318 // (which may be as many as there are CPUs). | |
| 4319 // Note that we don't need to protect ourselves from | |
| 4320 // interference with mutators because they can't | |
| 4321 // manipulate the discovered reference lists nor affect | |
| 4322 // the computed reachability of the referents, the | |
| 4323 // only properties manipulated by the precleaning | |
| 4324 // of these reference lists. | |
| 4325 stopTimer(); | |
| 4326 CMSTokenSyncWithLocks x(true /* is cms thread */, | |
| 4327 bitMapLock()); | |
| 4328 startTimer(); | |
| 4329 sample_eden(); | |
| 4330 // The following will yield to allow foreground | |
| 4331 // collection to proceed promptly. XXX YSR: | |
| 4332 // The code in this method may need further | |
| 4333 // tweaking for better performance and some restructuring | |
| 4334 // for cleaner interfaces. | |
| 4335 rp->preclean_discovered_references( | |
| 4336 rp->is_alive_non_header(), &keep_alive, &complete_trace, | |
| 4337 &yield_cl); | |
| 4338 } | |
| 4339 | |
| 4340 if (clean_survivor) { // preclean the active survivor space(s) | |
| 4341 assert(_young_gen->kind() == Generation::DefNew || | |
| 4342 _young_gen->kind() == Generation::ParNew || | |
| 4343 _young_gen->kind() == Generation::ASParNew, | |
| 4344 "incorrect type for cast"); | |
| 4345 DefNewGeneration* dng = (DefNewGeneration*)_young_gen; | |
| 4346 PushAndMarkClosure pam_cl(this, _span, ref_processor(), | |
| 4347 &_markBitMap, &_modUnionTable, | |
| 4348 &_markStack, &_revisitStack, | |
| 4349 true /* precleaning phase */); | |
| 4350 stopTimer(); | |
| 4351 CMSTokenSyncWithLocks ts(true /* is cms thread */, | |
| 4352 bitMapLock()); | |
| 4353 startTimer(); | |
| 4354 unsigned int before_count = | |
| 4355 GenCollectedHeap::heap()->total_collections(); | |
| 4356 SurvivorSpacePrecleanClosure | |
| 4357 sss_cl(this, _span, &_markBitMap, &_markStack, | |
| 4358 &pam_cl, before_count, CMSYield); | |
| 4359 dng->from()->object_iterate_careful(&sss_cl); | |
| 4360 dng->to()->object_iterate_careful(&sss_cl); | |
| 4361 } | |
| 4362 MarkRefsIntoAndScanClosure | |
| 4363 mrias_cl(_span, ref_processor(), &_markBitMap, &_modUnionTable, | |
| 4364 &_markStack, &_revisitStack, this, CMSYield, | |
| 4365 true /* precleaning phase */); | |
| 4366 // CAUTION: The following closure has persistent state that may need to | |
| 4367 // be reset upon a decrease in the sequence of addresses it | |
| 4368 // processes. | |
| 4369 ScanMarkedObjectsAgainCarefullyClosure | |
| 4370 smoac_cl(this, _span, | |
| 4371 &_markBitMap, &_markStack, &_revisitStack, &mrias_cl, CMSYield); | |
| 4372 | |
| 4373 // Preclean dirty cards in ModUnionTable and CardTable using | |
| 4374 // appropriate convergence criterion; | |
| 4375 // repeat CMSPrecleanIter times unless we find that | |
| 4376 // we are losing. | |
| 4377 assert(CMSPrecleanIter < 10, "CMSPrecleanIter is too large"); | |
| 4378 assert(CMSPrecleanNumerator < CMSPrecleanDenominator, | |
| 4379 "Bad convergence multiplier"); | |
| 4380 assert(CMSPrecleanThreshold >= 100, | |
| 4381 "Unreasonably low CMSPrecleanThreshold"); | |
| 4382 | |
| 4383 size_t numIter, cumNumCards, lastNumCards, curNumCards; | |
| 4384 for (numIter = 0, cumNumCards = lastNumCards = curNumCards = 0; | |
| 4385 numIter < CMSPrecleanIter; | |
| 4386 numIter++, lastNumCards = curNumCards, cumNumCards += curNumCards) { | |
| 4387 curNumCards = preclean_mod_union_table(_cmsGen, &smoac_cl); | |
| 4388 if (CMSPermGenPrecleaningEnabled) { | |
| 4389 curNumCards += preclean_mod_union_table(_permGen, &smoac_cl); | |
| 4390 } | |
| 4391 if (Verbose && PrintGCDetails) { | |
| 4392 gclog_or_tty->print(" (modUnionTable: %d cards)", curNumCards); | |
| 4393 } | |
| 4394 // Either there are very few dirty cards, so re-mark | |
| 4395 // pause will be small anyway, or our pre-cleaning isn't | |
| 4396 // that much faster than the rate at which cards are being | |
| 4397 // dirtied, so we might as well stop and re-mark since | |
| 4398 // precleaning won't improve our re-mark time by much. | |
| 4399 if (curNumCards <= CMSPrecleanThreshold || | |
| 4400 (numIter > 0 && | |
| 4401 (curNumCards * CMSPrecleanDenominator > | |
| 4402 lastNumCards * CMSPrecleanNumerator))) { | |
| 4403 numIter++; | |
| 4404 cumNumCards += curNumCards; | |
| 4405 break; | |
| 4406 } | |
| 4407 } | |
| 4408 curNumCards = preclean_card_table(_cmsGen, &smoac_cl); | |
| 4409 if (CMSPermGenPrecleaningEnabled) { | |
| 4410 curNumCards += preclean_card_table(_permGen, &smoac_cl); | |
| 4411 } | |
| 4412 cumNumCards += curNumCards; | |
| 4413 if (PrintGCDetails && PrintCMSStatistics != 0) { | |
| 4414 gclog_or_tty->print_cr(" (cardTable: %d cards, re-scanned %d cards, %d iterations)", | |
| 4415 curNumCards, cumNumCards, numIter); | |
| 4416 } | |
| 4417 return cumNumCards; // as a measure of useful work done | |
| 4418 } | |
| 4419 | |
| 4420 // PRECLEANING NOTES: | |
| 4421 // Precleaning involves: | |
| 4422 // . reading the bits of the modUnionTable and clearing the set bits. | |
| 4423 // . For the cards corresponding to the set bits, we scan the | |
| 4424 // objects on those cards. This means we need the free_list_lock | |
| 4425 // so that we can safely iterate over the CMS space when scanning | |
| 4426 // for oops. | |
| 4427 // . When we scan the objects, we'll be both reading and setting | |
| 4428 // marks in the marking bit map, so we'll need the marking bit map. | |
| 4429 // . For protecting _collector_state transitions, we take the CGC_lock. | |
| 4430 // Note that any races in the reading of of card table entries by the | |
| 4431 // CMS thread on the one hand and the clearing of those entries by the | |
| 4432 // VM thread or the setting of those entries by the mutator threads on the | |
| 4433 // other are quite benign. However, for efficiency it makes sense to keep | |
| 4434 // the VM thread from racing with the CMS thread while the latter is | |
| 4435 // dirty card info to the modUnionTable. We therefore also use the | |
| 4436 // CGC_lock to protect the reading of the card table and the mod union | |
| 4437 // table by the CM thread. | |
| 4438 // . We run concurrently with mutator updates, so scanning | |
| 4439 // needs to be done carefully -- we should not try to scan | |
| 4440 // potentially uninitialized objects. | |
| 4441 // | |
| 4442 // Locking strategy: While holding the CGC_lock, we scan over and | |
| 4443 // reset a maximal dirty range of the mod union / card tables, then lock | |
| 4444 // the free_list_lock and bitmap lock to do a full marking, then | |
| 4445 // release these locks; and repeat the cycle. This allows for a | |
| 4446 // certain amount of fairness in the sharing of these locks between | |
| 4447 // the CMS collector on the one hand, and the VM thread and the | |
| 4448 // mutators on the other. | |
| 4449 | |
| 4450 // NOTE: preclean_mod_union_table() and preclean_card_table() | |
| 4451 // further below are largely identical; if you need to modify | |
| 4452 // one of these methods, please check the other method too. | |
| 4453 | |
| 4454 size_t CMSCollector::preclean_mod_union_table( | |
| 4455 ConcurrentMarkSweepGeneration* gen, | |
| 4456 ScanMarkedObjectsAgainCarefullyClosure* cl) { | |
| 4457 verify_work_stacks_empty(); | |
| 4458 verify_overflow_empty(); | |
| 4459 | |
| 4460 // strategy: starting with the first card, accumulate contiguous | |
| 4461 // ranges of dirty cards; clear these cards, then scan the region | |
| 4462 // covered by these cards. | |
| 4463 | |
| 4464 // Since all of the MUT is committed ahead, we can just use | |
| 4465 // that, in case the generations expand while we are precleaning. | |
| 4466 // It might also be fine to just use the committed part of the | |
| 4467 // generation, but we might potentially miss cards when the | |
| 4468 // generation is rapidly expanding while we are in the midst | |
| 4469 // of precleaning. | |
| 4470 HeapWord* startAddr = gen->reserved().start(); | |
| 4471 HeapWord* endAddr = gen->reserved().end(); | |
| 4472 | |
| 4473 cl->setFreelistLock(gen->freelistLock()); // needed for yielding | |
| 4474 | |
| 4475 size_t numDirtyCards, cumNumDirtyCards; | |
| 4476 HeapWord *nextAddr, *lastAddr; | |
| 4477 for (cumNumDirtyCards = numDirtyCards = 0, | |
| 4478 nextAddr = lastAddr = startAddr; | |
| 4479 nextAddr < endAddr; | |
| 4480 nextAddr = lastAddr, cumNumDirtyCards += numDirtyCards) { | |
| 4481 | |
| 4482 ResourceMark rm; | |
| 4483 HandleMark hm; | |
| 4484 | |
| 4485 MemRegion dirtyRegion; | |
| 4486 { | |
| 4487 stopTimer(); | |
| 4488 CMSTokenSync ts(true); | |
| 4489 startTimer(); | |
| 4490 sample_eden(); | |
| 4491 // Get dirty region starting at nextOffset (inclusive), | |
| 4492 // simultaneously clearing it. | |
| 4493 dirtyRegion = | |
| 4494 _modUnionTable.getAndClearMarkedRegion(nextAddr, endAddr); | |
| 4495 assert(dirtyRegion.start() >= nextAddr, | |
| 4496 "returned region inconsistent?"); | |
| 4497 } | |
| 4498 // Remember where the next search should begin. | |
| 4499 // The returned region (if non-empty) is a right open interval, | |
| 4500 // so lastOffset is obtained from the right end of that | |
| 4501 // interval. | |
| 4502 lastAddr = dirtyRegion.end(); | |
| 4503 // Should do something more transparent and less hacky XXX | |
| 4504 numDirtyCards = | |
| 4505 _modUnionTable.heapWordDiffToOffsetDiff(dirtyRegion.word_size()); | |
| 4506 | |
| 4507 // We'll scan the cards in the dirty region (with periodic | |
| 4508 // yields for foreground GC as needed). | |
| 4509 if (!dirtyRegion.is_empty()) { | |
| 4510 assert(numDirtyCards > 0, "consistency check"); | |
| 4511 HeapWord* stop_point = NULL; | |
| 4512 { | |
| 4513 stopTimer(); | |
| 4514 CMSTokenSyncWithLocks ts(true, gen->freelistLock(), | |
| 4515 bitMapLock()); | |
| 4516 startTimer(); | |
| 4517 verify_work_stacks_empty(); | |
| 4518 verify_overflow_empty(); | |
| 4519 sample_eden(); | |
| 4520 stop_point = | |
| 4521 gen->cmsSpace()->object_iterate_careful_m(dirtyRegion, cl); | |
| 4522 } | |
| 4523 if (stop_point != NULL) { | |
| 4524 // The careful iteration stopped early either because it found an | |
| 4525 // uninitialized object, or because we were in the midst of an | |
| 4526 // "abortable preclean", which should now be aborted. Redirty | |
| 4527 // the bits corresponding to the partially-scanned or unscanned | |
| 4528 // cards. We'll either restart at the next block boundary or | |
| 4529 // abort the preclean. | |
| 4530 assert((CMSPermGenPrecleaningEnabled && (gen == _permGen)) || | |
| 4531 (_collectorState == AbortablePreclean && should_abort_preclean()), | |
| 4532 "Unparsable objects should only be in perm gen."); | |
| 4533 | |
| 4534 stopTimer(); | |
| 4535 CMSTokenSyncWithLocks ts(true, bitMapLock()); | |
| 4536 startTimer(); | |
| 4537 _modUnionTable.mark_range(MemRegion(stop_point, dirtyRegion.end())); | |
| 4538 if (should_abort_preclean()) { | |
| 4539 break; // out of preclean loop | |
| 4540 } else { | |
| 4541 // Compute the next address at which preclean should pick up; | |
| 4542 // might need bitMapLock in order to read P-bits. | |
| 4543 lastAddr = next_card_start_after_block(stop_point); | |
| 4544 } | |
| 4545 } | |
| 4546 } else { | |
| 4547 assert(lastAddr == endAddr, "consistency check"); | |
| 4548 assert(numDirtyCards == 0, "consistency check"); | |
| 4549 break; | |
| 4550 } | |
| 4551 } | |
| 4552 verify_work_stacks_empty(); | |
| 4553 verify_overflow_empty(); | |
| 4554 return cumNumDirtyCards; | |
| 4555 } | |
| 4556 | |
| 4557 // NOTE: preclean_mod_union_table() above and preclean_card_table() | |
| 4558 // below are largely identical; if you need to modify | |
| 4559 // one of these methods, please check the other method too. | |
| 4560 | |
| 4561 size_t CMSCollector::preclean_card_table(ConcurrentMarkSweepGeneration* gen, | |
| 4562 ScanMarkedObjectsAgainCarefullyClosure* cl) { | |
| 4563 // strategy: it's similar to precleamModUnionTable above, in that | |
| 4564 // we accumulate contiguous ranges of dirty cards, mark these cards | |
| 4565 // precleaned, then scan the region covered by these cards. | |
| 4566 HeapWord* endAddr = (HeapWord*)(gen->_virtual_space.high()); | |
| 4567 HeapWord* startAddr = (HeapWord*)(gen->_virtual_space.low()); | |
| 4568 | |
| 4569 cl->setFreelistLock(gen->freelistLock()); // needed for yielding | |
| 4570 | |
| 4571 size_t numDirtyCards, cumNumDirtyCards; | |
| 4572 HeapWord *lastAddr, *nextAddr; | |
| 4573 | |
| 4574 for (cumNumDirtyCards = numDirtyCards = 0, | |
| 4575 nextAddr = lastAddr = startAddr; | |
| 4576 nextAddr < endAddr; | |
| 4577 nextAddr = lastAddr, cumNumDirtyCards += numDirtyCards) { | |
| 4578 | |
| 4579 ResourceMark rm; | |
| 4580 HandleMark hm; | |
| 4581 | |
| 4582 MemRegion dirtyRegion; | |
| 4583 { | |
| 4584 // See comments in "Precleaning notes" above on why we | |
| 4585 // do this locking. XXX Could the locking overheads be | |
| 4586 // too high when dirty cards are sparse? [I don't think so.] | |
| 4587 stopTimer(); | |
| 4588 CMSTokenSync x(true); // is cms thread | |
| 4589 startTimer(); | |
| 4590 sample_eden(); | |
| 4591 // Get and clear dirty region from card table | |
| 4592 dirtyRegion = _ct->ct_bs()->dirty_card_range_after_preclean( | |
| 4593 MemRegion(nextAddr, endAddr)); | |
| 4594 assert(dirtyRegion.start() >= nextAddr, | |
| 4595 "returned region inconsistent?"); | |
| 4596 } | |
| 4597 lastAddr = dirtyRegion.end(); | |
| 4598 numDirtyCards = | |
| 4599 dirtyRegion.word_size()/CardTableModRefBS::card_size_in_words; | |
| 4600 | |
| 4601 if (!dirtyRegion.is_empty()) { | |
| 4602 stopTimer(); | |
| 4603 CMSTokenSyncWithLocks ts(true, gen->freelistLock(), bitMapLock()); | |
| 4604 startTimer(); | |
| 4605 sample_eden(); | |
| 4606 verify_work_stacks_empty(); | |
| 4607 verify_overflow_empty(); | |
| 4608 HeapWord* stop_point = | |
| 4609 gen->cmsSpace()->object_iterate_careful_m(dirtyRegion, cl); | |
| 4610 if (stop_point != NULL) { | |
| 4611 // The careful iteration stopped early because it found an | |
| 4612 // uninitialized object. Redirty the bits corresponding to the | |
| 4613 // partially-scanned or unscanned cards, and start again at the | |
| 4614 // next block boundary. | |
| 4615 assert(CMSPermGenPrecleaningEnabled || | |
| 4616 (_collectorState == AbortablePreclean && should_abort_preclean()), | |
| 4617 "Unparsable objects should only be in perm gen."); | |
| 4618 _ct->ct_bs()->invalidate(MemRegion(stop_point, dirtyRegion.end())); | |
| 4619 if (should_abort_preclean()) { | |
| 4620 break; // out of preclean loop | |
| 4621 } else { | |
| 4622 // Compute the next address at which preclean should pick up. | |
| 4623 lastAddr = next_card_start_after_block(stop_point); | |
| 4624 } | |
| 4625 } | |
| 4626 } else { | |
| 4627 break; | |
| 4628 } | |
| 4629 } | |
| 4630 verify_work_stacks_empty(); | |
| 4631 verify_overflow_empty(); | |
| 4632 return cumNumDirtyCards; | |
| 4633 } | |
| 4634 | |
| 4635 void CMSCollector::checkpointRootsFinal(bool asynch, | |
| 4636 bool clear_all_soft_refs, bool init_mark_was_synchronous) { | |
| 4637 assert(_collectorState == FinalMarking, "incorrect state transition?"); | |
| 4638 check_correct_thread_executing(); | |
| 4639 // world is stopped at this checkpoint | |
| 4640 assert(SafepointSynchronize::is_at_safepoint(), | |
| 4641 "world should be stopped"); | |
| 4642 verify_work_stacks_empty(); | |
| 4643 verify_overflow_empty(); | |
| 4644 | |
| 4645 SpecializationStats::clear(); | |
| 4646 if (PrintGCDetails) { | |
| 4647 gclog_or_tty->print("[YG occupancy: "SIZE_FORMAT" K ("SIZE_FORMAT" K)]", | |
| 4648 _young_gen->used() / K, | |
| 4649 _young_gen->capacity() / K); | |
| 4650 } | |
| 4651 if (asynch) { | |
| 4652 if (CMSScavengeBeforeRemark) { | |
| 4653 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 4654 // Temporarily set flag to false, GCH->do_collection will | |
| 4655 // expect it to be false and set to true | |
| 4656 FlagSetting fl(gch->_is_gc_active, false); | |
| 4657 NOT_PRODUCT(TraceTime t("Scavenge-Before-Remark", | |
| 4658 PrintGCDetails && Verbose, true, gclog_or_tty);) | |
| 4659 int level = _cmsGen->level() - 1; | |
| 4660 if (level >= 0) { | |
| 4661 gch->do_collection(true, // full (i.e. force, see below) | |
| 4662 false, // !clear_all_soft_refs | |
| 4663 0, // size | |
| 4664 false, // is_tlab | |
| 4665 level // max_level | |
| 4666 ); | |
| 4667 } | |
| 4668 } | |
| 4669 FreelistLocker x(this); | |
| 4670 MutexLockerEx y(bitMapLock(), | |
| 4671 Mutex::_no_safepoint_check_flag); | |
| 4672 assert(!init_mark_was_synchronous, "but that's impossible!"); | |
| 4673 checkpointRootsFinalWork(asynch, clear_all_soft_refs, false); | |
| 4674 } else { | |
| 4675 // already have all the locks | |
| 4676 checkpointRootsFinalWork(asynch, clear_all_soft_refs, | |
| 4677 init_mark_was_synchronous); | |
| 4678 } | |
| 4679 verify_work_stacks_empty(); | |
| 4680 verify_overflow_empty(); | |
| 4681 SpecializationStats::print(); | |
| 4682 } | |
| 4683 | |
| 4684 void CMSCollector::checkpointRootsFinalWork(bool asynch, | |
| 4685 bool clear_all_soft_refs, bool init_mark_was_synchronous) { | |
| 4686 | |
| 4687 NOT_PRODUCT(TraceTime tr("checkpointRootsFinalWork", PrintGCDetails, false, gclog_or_tty);) | |
| 4688 | |
| 4689 assert(haveFreelistLocks(), "must have free list locks"); | |
| 4690 assert_lock_strong(bitMapLock()); | |
| 4691 | |
| 4692 if (UseAdaptiveSizePolicy) { | |
| 4693 size_policy()->checkpoint_roots_final_begin(); | |
| 4694 } | |
| 4695 | |
| 4696 ResourceMark rm; | |
| 4697 HandleMark hm; | |
| 4698 | |
| 4699 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 4700 | |
| 4701 if (cms_should_unload_classes()) { | |
| 4702 CodeCache::gc_prologue(); | |
| 4703 } | |
| 4704 assert(haveFreelistLocks(), "must have free list locks"); | |
| 4705 assert_lock_strong(bitMapLock()); | |
| 4706 | |
| 4707 if (!init_mark_was_synchronous) { | |
| 4708 // We might assume that we need not fill TLAB's when | |
| 4709 // CMSScavengeBeforeRemark is set, because we may have just done | |
| 4710 // a scavenge which would have filled all TLAB's -- and besides | |
| 4711 // Eden would be empty. This however may not always be the case -- | |
| 4712 // for instance although we asked for a scavenge, it may not have | |
| 4713 // happened because of a JNI critical section. We probably need | |
| 4714 // a policy for deciding whether we can in that case wait until | |
| 4715 // the critical section releases and then do the remark following | |
| 4716 // the scavenge, and skip it here. In the absence of that policy, | |
| 4717 // or of an indication of whether the scavenge did indeed occur, | |
| 4718 // we cannot rely on TLAB's having been filled and must do | |
| 4719 // so here just in case a scavenge did not happen. | |
| 4720 gch->ensure_parsability(false); // fill TLAB's, but no need to retire them | |
| 4721 // Update the saved marks which may affect the root scans. | |
| 4722 gch->save_marks(); | |
| 4723 | |
| 4724 { | |
| 4725 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;) | |
| 4726 | |
| 4727 // Note on the role of the mod union table: | |
| 4728 // Since the marker in "markFromRoots" marks concurrently with | |
| 4729 // mutators, it is possible for some reachable objects not to have been | |
| 4730 // scanned. For instance, an only reference to an object A was | |
| 4731 // placed in object B after the marker scanned B. Unless B is rescanned, | |
| 4732 // A would be collected. Such updates to references in marked objects | |
| 4733 // are detected via the mod union table which is the set of all cards | |
| 4734 // dirtied since the first checkpoint in this GC cycle and prior to | |
| 4735 // the most recent young generation GC, minus those cleaned up by the | |
| 4736 // concurrent precleaning. | |
| 4737 if (CMSParallelRemarkEnabled && ParallelGCThreads > 0) { | |
| 4738 TraceTime t("Rescan (parallel) ", PrintGCDetails, false, gclog_or_tty); | |
| 4739 do_remark_parallel(); | |
| 4740 } else { | |
| 4741 TraceTime t("Rescan (non-parallel) ", PrintGCDetails, false, | |
| 4742 gclog_or_tty); | |
| 4743 do_remark_non_parallel(); | |
| 4744 } | |
| 4745 } | |
| 4746 } else { | |
| 4747 assert(!asynch, "Can't have init_mark_was_synchronous in asynch mode"); | |
| 4748 // The initial mark was stop-world, so there's no rescanning to | |
| 4749 // do; go straight on to the next step below. | |
| 4750 } | |
| 4751 verify_work_stacks_empty(); | |
| 4752 verify_overflow_empty(); | |
| 4753 | |
| 4754 { | |
| 4755 NOT_PRODUCT(TraceTime ts("refProcessingWork", PrintGCDetails, false, gclog_or_tty);) | |
| 4756 refProcessingWork(asynch, clear_all_soft_refs); | |
| 4757 } | |
| 4758 verify_work_stacks_empty(); | |
| 4759 verify_overflow_empty(); | |
| 4760 | |
| 4761 if (cms_should_unload_classes()) { | |
| 4762 CodeCache::gc_epilogue(); | |
| 4763 } | |
| 4764 | |
| 4765 // If we encountered any (marking stack / work queue) overflow | |
| 4766 // events during the current CMS cycle, take appropriate | |
| 4767 // remedial measures, where possible, so as to try and avoid | |
| 4768 // recurrence of that condition. | |
| 4769 assert(_markStack.isEmpty(), "No grey objects"); | |
| 4770 size_t ser_ovflw = _ser_pmc_remark_ovflw + _ser_pmc_preclean_ovflw + | |
| 4771 _ser_kac_ovflw; | |
| 4772 if (ser_ovflw > 0) { | |
| 4773 if (PrintCMSStatistics != 0) { | |
| 4774 gclog_or_tty->print_cr("Marking stack overflow (benign) " | |
| 4775 "(pmc_pc="SIZE_FORMAT", pmc_rm="SIZE_FORMAT", kac="SIZE_FORMAT")", | |
| 4776 _ser_pmc_preclean_ovflw, _ser_pmc_remark_ovflw, | |
| 4777 _ser_kac_ovflw); | |
| 4778 } | |
| 4779 _markStack.expand(); | |
| 4780 _ser_pmc_remark_ovflw = 0; | |
| 4781 _ser_pmc_preclean_ovflw = 0; | |
| 4782 _ser_kac_ovflw = 0; | |
| 4783 } | |
| 4784 if (_par_pmc_remark_ovflw > 0 || _par_kac_ovflw > 0) { | |
| 4785 if (PrintCMSStatistics != 0) { | |
| 4786 gclog_or_tty->print_cr("Work queue overflow (benign) " | |
| 4787 "(pmc_rm="SIZE_FORMAT", kac="SIZE_FORMAT")", | |
| 4788 _par_pmc_remark_ovflw, _par_kac_ovflw); | |
| 4789 } | |
| 4790 _par_pmc_remark_ovflw = 0; | |
| 4791 _par_kac_ovflw = 0; | |
| 4792 } | |
| 4793 if (PrintCMSStatistics != 0) { | |
| 4794 if (_markStack._hit_limit > 0) { | |
| 4795 gclog_or_tty->print_cr(" (benign) Hit max stack size limit ("SIZE_FORMAT")", | |
| 4796 _markStack._hit_limit); | |
| 4797 } | |
| 4798 if (_markStack._failed_double > 0) { | |
| 4799 gclog_or_tty->print_cr(" (benign) Failed stack doubling ("SIZE_FORMAT")," | |
| 4800 " current capacity "SIZE_FORMAT, | |
| 4801 _markStack._failed_double, | |
| 4802 _markStack.capacity()); | |
| 4803 } | |
| 4804 } | |
| 4805 _markStack._hit_limit = 0; | |
| 4806 _markStack._failed_double = 0; | |
| 4807 | |
| 4808 if ((VerifyAfterGC || VerifyDuringGC) && | |
| 4809 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
| 4810 verify_after_remark(); | |
| 4811 } | |
| 4812 | |
| 4813 // Change under the freelistLocks. | |
| 4814 _collectorState = Sweeping; | |
| 4815 // Call isAllClear() under bitMapLock | |
| 4816 assert(_modUnionTable.isAllClear(), "Should be clear by end of the" | |
| 4817 " final marking"); | |
| 4818 if (UseAdaptiveSizePolicy) { | |
| 4819 size_policy()->checkpoint_roots_final_end(gch->gc_cause()); | |
| 4820 } | |
| 4821 } | |
| 4822 | |
| 4823 // Parallel remark task | |
| 4824 class CMSParRemarkTask: public AbstractGangTask { | |
| 4825 CMSCollector* _collector; | |
| 4826 WorkGang* _workers; | |
| 4827 int _n_workers; | |
| 4828 CompactibleFreeListSpace* _cms_space; | |
| 4829 CompactibleFreeListSpace* _perm_space; | |
| 4830 | |
| 4831 // The per-thread work queues, available here for stealing. | |
| 4832 OopTaskQueueSet* _task_queues; | |
| 4833 ParallelTaskTerminator _term; | |
| 4834 | |
| 4835 public: | |
| 4836 CMSParRemarkTask(CMSCollector* collector, | |
| 4837 CompactibleFreeListSpace* cms_space, | |
| 4838 CompactibleFreeListSpace* perm_space, | |
| 4839 int n_workers, WorkGang* workers, | |
| 4840 OopTaskQueueSet* task_queues): | |
| 4841 AbstractGangTask("Rescan roots and grey objects in parallel"), | |
| 4842 _collector(collector), | |
| 4843 _cms_space(cms_space), _perm_space(perm_space), | |
| 4844 _n_workers(n_workers), | |
| 4845 _workers(workers), | |
| 4846 _task_queues(task_queues), | |
| 4847 _term(workers->total_workers(), task_queues) { } | |
| 4848 | |
| 4849 OopTaskQueueSet* task_queues() { return _task_queues; } | |
| 4850 | |
| 4851 OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); } | |
| 4852 | |
| 4853 ParallelTaskTerminator* terminator() { return &_term; } | |
| 4854 | |
| 4855 void work(int i); | |
| 4856 | |
| 4857 private: | |
| 4858 // Work method in support of parallel rescan ... of young gen spaces | |
| 4859 void do_young_space_rescan(int i, Par_MarkRefsIntoAndScanClosure* cl, | |
| 4860 ContiguousSpace* space, | |
| 4861 HeapWord** chunk_array, size_t chunk_top); | |
| 4862 | |
| 4863 // ... of dirty cards in old space | |
| 4864 void do_dirty_card_rescan_tasks(CompactibleFreeListSpace* sp, int i, | |
| 4865 Par_MarkRefsIntoAndScanClosure* cl); | |
| 4866 | |
| 4867 // ... work stealing for the above | |
| 4868 void do_work_steal(int i, Par_MarkRefsIntoAndScanClosure* cl, int* seed); | |
| 4869 }; | |
| 4870 | |
| 4871 void CMSParRemarkTask::work(int i) { | |
| 4872 elapsedTimer _timer; | |
| 4873 ResourceMark rm; | |
| 4874 HandleMark hm; | |
| 4875 | |
| 4876 // ---------- rescan from roots -------------- | |
| 4877 _timer.start(); | |
| 4878 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 4879 Par_MarkRefsIntoAndScanClosure par_mrias_cl(_collector, | |
| 4880 _collector->_span, _collector->ref_processor(), | |
| 4881 &(_collector->_markBitMap), | |
| 4882 work_queue(i), &(_collector->_revisitStack)); | |
| 4883 | |
| 4884 // Rescan young gen roots first since these are likely | |
| 4885 // coarsely partitioned and may, on that account, constitute | |
| 4886 // the critical path; thus, it's best to start off that | |
| 4887 // work first. | |
| 4888 // ---------- young gen roots -------------- | |
| 4889 { | |
| 4890 DefNewGeneration* dng = _collector->_young_gen->as_DefNewGeneration(); | |
| 4891 EdenSpace* eden_space = dng->eden(); | |
| 4892 ContiguousSpace* from_space = dng->from(); | |
| 4893 ContiguousSpace* to_space = dng->to(); | |
| 4894 | |
| 4895 HeapWord** eca = _collector->_eden_chunk_array; | |
| 4896 size_t ect = _collector->_eden_chunk_index; | |
| 4897 HeapWord** sca = _collector->_survivor_chunk_array; | |
| 4898 size_t sct = _collector->_survivor_chunk_index; | |
| 4899 | |
| 4900 assert(ect <= _collector->_eden_chunk_capacity, "out of bounds"); | |
| 4901 assert(sct <= _collector->_survivor_chunk_capacity, "out of bounds"); | |
| 4902 | |
| 4903 do_young_space_rescan(i, &par_mrias_cl, to_space, NULL, 0); | |
| 4904 do_young_space_rescan(i, &par_mrias_cl, from_space, sca, sct); | |
| 4905 do_young_space_rescan(i, &par_mrias_cl, eden_space, eca, ect); | |
| 4906 | |
| 4907 _timer.stop(); | |
| 4908 if (PrintCMSStatistics != 0) { | |
| 4909 gclog_or_tty->print_cr( | |
| 4910 "Finished young gen rescan work in %dth thread: %3.3f sec", | |
| 4911 i, _timer.seconds()); | |
| 4912 } | |
| 4913 } | |
| 4914 | |
| 4915 // ---------- remaining roots -------------- | |
| 4916 _timer.reset(); | |
| 4917 _timer.start(); | |
| 4918 gch->gen_process_strong_roots(_collector->_cmsGen->level(), | |
| 4919 false, // yg was scanned above | |
| 4920 true, // collecting perm gen | |
| 4921 SharedHeap::ScanningOption(_collector->CMSCollector::roots_scanning_options()), | |
| 4922 NULL, &par_mrias_cl); | |
| 4923 _timer.stop(); | |
| 4924 if (PrintCMSStatistics != 0) { | |
| 4925 gclog_or_tty->print_cr( | |
| 4926 "Finished remaining root rescan work in %dth thread: %3.3f sec", | |
| 4927 i, _timer.seconds()); | |
| 4928 } | |
| 4929 | |
| 4930 // ---------- rescan dirty cards ------------ | |
| 4931 _timer.reset(); | |
| 4932 _timer.start(); | |
| 4933 | |
| 4934 // Do the rescan tasks for each of the two spaces | |
| 4935 // (cms_space and perm_space) in turn. | |
| 4936 do_dirty_card_rescan_tasks(_cms_space, i, &par_mrias_cl); | |
| 4937 do_dirty_card_rescan_tasks(_perm_space, i, &par_mrias_cl); | |
| 4938 _timer.stop(); | |
| 4939 if (PrintCMSStatistics != 0) { | |
| 4940 gclog_or_tty->print_cr( | |
| 4941 "Finished dirty card rescan work in %dth thread: %3.3f sec", | |
| 4942 i, _timer.seconds()); | |
| 4943 } | |
| 4944 | |
| 4945 // ---------- steal work from other threads ... | |
| 4946 // ---------- ... and drain overflow list. | |
| 4947 _timer.reset(); | |
| 4948 _timer.start(); | |
| 4949 do_work_steal(i, &par_mrias_cl, _collector->hash_seed(i)); | |
| 4950 _timer.stop(); | |
| 4951 if (PrintCMSStatistics != 0) { | |
| 4952 gclog_or_tty->print_cr( | |
| 4953 "Finished work stealing in %dth thread: %3.3f sec", | |
| 4954 i, _timer.seconds()); | |
| 4955 } | |
| 4956 } | |
| 4957 | |
| 4958 void | |
| 4959 CMSParRemarkTask::do_young_space_rescan(int i, | |
| 4960 Par_MarkRefsIntoAndScanClosure* cl, ContiguousSpace* space, | |
| 4961 HeapWord** chunk_array, size_t chunk_top) { | |
| 4962 // Until all tasks completed: | |
| 4963 // . claim an unclaimed task | |
| 4964 // . compute region boundaries corresponding to task claimed | |
| 4965 // using chunk_array | |
| 4966 // . par_oop_iterate(cl) over that region | |
| 4967 | |
| 4968 ResourceMark rm; | |
| 4969 HandleMark hm; | |
| 4970 | |
| 4971 SequentialSubTasksDone* pst = space->par_seq_tasks(); | |
| 4972 assert(pst->valid(), "Uninitialized use?"); | |
| 4973 | |
| 4974 int nth_task = 0; | |
| 4975 int n_tasks = pst->n_tasks(); | |
| 4976 | |
| 4977 HeapWord *start, *end; | |
| 4978 while (!pst->is_task_claimed(/* reference */ nth_task)) { | |
| 4979 // We claimed task # nth_task; compute its boundaries. | |
| 4980 if (chunk_top == 0) { // no samples were taken | |
| 4981 assert(nth_task == 0 && n_tasks == 1, "Can have only 1 EdenSpace task"); | |
| 4982 start = space->bottom(); | |
| 4983 end = space->top(); | |
| 4984 } else if (nth_task == 0) { | |
| 4985 start = space->bottom(); | |
| 4986 end = chunk_array[nth_task]; | |
| 4987 } else if (nth_task < (jint)chunk_top) { | |
| 4988 assert(nth_task >= 1, "Control point invariant"); | |
| 4989 start = chunk_array[nth_task - 1]; | |
| 4990 end = chunk_array[nth_task]; | |
| 4991 } else { | |
| 4992 assert(nth_task == (jint)chunk_top, "Control point invariant"); | |
| 4993 start = chunk_array[chunk_top - 1]; | |
| 4994 end = space->top(); | |
| 4995 } | |
| 4996 MemRegion mr(start, end); | |
| 4997 // Verify that mr is in space | |
| 4998 assert(mr.is_empty() || space->used_region().contains(mr), | |
| 4999 "Should be in space"); | |
| 5000 // Verify that "start" is an object boundary | |
| 5001 assert(mr.is_empty() || oop(mr.start())->is_oop(), | |
| 5002 "Should be an oop"); | |
| 5003 space->par_oop_iterate(mr, cl); | |
| 5004 } | |
| 5005 pst->all_tasks_completed(); | |
| 5006 } | |
| 5007 | |
| 5008 void | |
| 5009 CMSParRemarkTask::do_dirty_card_rescan_tasks( | |
| 5010 CompactibleFreeListSpace* sp, int i, | |
| 5011 Par_MarkRefsIntoAndScanClosure* cl) { | |
| 5012 // Until all tasks completed: | |
| 5013 // . claim an unclaimed task | |
| 5014 // . compute region boundaries corresponding to task claimed | |
| 5015 // . transfer dirty bits ct->mut for that region | |
| 5016 // . apply rescanclosure to dirty mut bits for that region | |
| 5017 | |
| 5018 ResourceMark rm; | |
| 5019 HandleMark hm; | |
| 5020 | |
| 5021 OopTaskQueue* work_q = work_queue(i); | |
| 5022 ModUnionClosure modUnionClosure(&(_collector->_modUnionTable)); | |
| 5023 // CAUTION! CAUTION! CAUTION! CAUTION! CAUTION! CAUTION! CAUTION! | |
| 5024 // CAUTION: This closure has state that persists across calls to | |
| 5025 // the work method dirty_range_iterate_clear() in that it has | |
| 5026 // imbedded in it a (subtype of) UpwardsObjectClosure. The | |
| 5027 // use of that state in the imbedded UpwardsObjectClosure instance | |
| 5028 // assumes that the cards are always iterated (even if in parallel | |
| 5029 // by several threads) in monotonically increasing order per each | |
| 5030 // thread. This is true of the implementation below which picks | |
| 5031 // card ranges (chunks) in monotonically increasing order globally | |
| 5032 // and, a-fortiori, in monotonically increasing order per thread | |
| 5033 // (the latter order being a subsequence of the former). | |
| 5034 // If the work code below is ever reorganized into a more chaotic | |
| 5035 // work-partitioning form than the current "sequential tasks" | |
| 5036 // paradigm, the use of that persistent state will have to be | |
| 5037 // revisited and modified appropriately. See also related | |
| 5038 // bug 4756801 work on which should examine this code to make | |
| 5039 // sure that the changes there do not run counter to the | |
| 5040 // assumptions made here and necessary for correctness and | |
| 5041 // efficiency. Note also that this code might yield inefficient | |
| 5042 // behaviour in the case of very large objects that span one or | |
| 5043 // more work chunks. Such objects would potentially be scanned | |
| 5044 // several times redundantly. Work on 4756801 should try and | |
| 5045 // address that performance anomaly if at all possible. XXX | |
| 5046 MemRegion full_span = _collector->_span; | |
| 5047 CMSBitMap* bm = &(_collector->_markBitMap); // shared | |
| 5048 CMSMarkStack* rs = &(_collector->_revisitStack); // shared | |
| 5049 MarkFromDirtyCardsClosure | |
| 5050 greyRescanClosure(_collector, full_span, // entire span of interest | |
| 5051 sp, bm, work_q, rs, cl); | |
| 5052 | |
| 5053 SequentialSubTasksDone* pst = sp->conc_par_seq_tasks(); | |
| 5054 assert(pst->valid(), "Uninitialized use?"); | |
| 5055 int nth_task = 0; | |
| 5056 const int alignment = CardTableModRefBS::card_size * BitsPerWord; | |
| 5057 MemRegion span = sp->used_region(); | |
| 5058 HeapWord* start_addr = span.start(); | |
| 5059 HeapWord* end_addr = (HeapWord*)round_to((intptr_t)span.end(), | |
| 5060 alignment); | |
| 5061 const size_t chunk_size = sp->rescan_task_size(); // in HeapWord units | |
| 5062 assert((HeapWord*)round_to((intptr_t)start_addr, alignment) == | |
| 5063 start_addr, "Check alignment"); | |
| 5064 assert((size_t)round_to((intptr_t)chunk_size, alignment) == | |
| 5065 chunk_size, "Check alignment"); | |
| 5066 | |
| 5067 while (!pst->is_task_claimed(/* reference */ nth_task)) { | |
| 5068 // Having claimed the nth_task, compute corresponding mem-region, | |
| 5069 // which is a-fortiori aligned correctly (i.e. at a MUT bopundary). | |
| 5070 // The alignment restriction ensures that we do not need any | |
| 5071 // synchronization with other gang-workers while setting or | |
| 5072 // clearing bits in thus chunk of the MUT. | |
| 5073 MemRegion this_span = MemRegion(start_addr + nth_task*chunk_size, | |
| 5074 start_addr + (nth_task+1)*chunk_size); | |
| 5075 // The last chunk's end might be way beyond end of the | |
| 5076 // used region. In that case pull back appropriately. | |
| 5077 if (this_span.end() > end_addr) { | |
| 5078 this_span.set_end(end_addr); | |
| 5079 assert(!this_span.is_empty(), "Program logic (calculation of n_tasks)"); | |
| 5080 } | |
| 5081 // Iterate over the dirty cards covering this chunk, marking them | |
| 5082 // precleaned, and setting the corresponding bits in the mod union | |
| 5083 // table. Since we have been careful to partition at Card and MUT-word | |
| 5084 // boundaries no synchronization is needed between parallel threads. | |
| 5085 _collector->_ct->ct_bs()->dirty_card_iterate(this_span, | |
| 5086 &modUnionClosure); | |
| 5087 | |
| 5088 // Having transferred these marks into the modUnionTable, | |
| 5089 // rescan the marked objects on the dirty cards in the modUnionTable. | |
| 5090 // Even if this is at a synchronous collection, the initial marking | |
| 5091 // may have been done during an asynchronous collection so there | |
| 5092 // may be dirty bits in the mod-union table. | |
| 5093 _collector->_modUnionTable.dirty_range_iterate_clear( | |
| 5094 this_span, &greyRescanClosure); | |
| 5095 _collector->_modUnionTable.verifyNoOneBitsInRange( | |
| 5096 this_span.start(), | |
| 5097 this_span.end()); | |
| 5098 } | |
| 5099 pst->all_tasks_completed(); // declare that i am done | |
| 5100 } | |
| 5101 | |
| 5102 // . see if we can share work_queues with ParNew? XXX | |
| 5103 void | |
| 5104 CMSParRemarkTask::do_work_steal(int i, Par_MarkRefsIntoAndScanClosure* cl, | |
| 5105 int* seed) { | |
| 5106 OopTaskQueue* work_q = work_queue(i); | |
| 5107 NOT_PRODUCT(int num_steals = 0;) | |
| 5108 oop obj_to_scan; | |
| 5109 CMSBitMap* bm = &(_collector->_markBitMap); | |
| 5110 size_t num_from_overflow_list = | |
| 5111 MIN2((size_t)work_q->max_elems()/4, | |
| 5112 (size_t)ParGCDesiredObjsFromOverflowList); | |
| 5113 | |
| 5114 while (true) { | |
| 5115 // Completely finish any left over work from (an) earlier round(s) | |
| 5116 cl->trim_queue(0); | |
| 5117 // Now check if there's any work in the overflow list | |
| 5118 if (_collector->par_take_from_overflow_list(num_from_overflow_list, | |
| 5119 work_q)) { | |
| 5120 // found something in global overflow list; | |
| 5121 // not yet ready to go stealing work from others. | |
| 5122 // We'd like to assert(work_q->size() != 0, ...) | |
| 5123 // because we just took work from the overflow list, | |
| 5124 // but of course we can't since all of that could have | |
| 5125 // been already stolen from us. | |
| 5126 // "He giveth and He taketh away." | |
| 5127 continue; | |
| 5128 } | |
| 5129 // Verify that we have no work before we resort to stealing | |
| 5130 assert(work_q->size() == 0, "Have work, shouldn't steal"); | |
| 5131 // Try to steal from other queues that have work | |
| 5132 if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) { | |
| 5133 NOT_PRODUCT(num_steals++;) | |
| 5134 assert(obj_to_scan->is_oop(), "Oops, not an oop!"); | |
| 5135 assert(bm->isMarked((HeapWord*)obj_to_scan), "Stole an unmarked oop?"); | |
| 5136 // Do scanning work | |
| 5137 obj_to_scan->oop_iterate(cl); | |
| 5138 // Loop around, finish this work, and try to steal some more | |
| 5139 } else if (terminator()->offer_termination()) { | |
| 5140 break; // nirvana from the infinite cycle | |
| 5141 } | |
| 5142 } | |
| 5143 NOT_PRODUCT( | |
| 5144 if (PrintCMSStatistics != 0) { | |
| 5145 gclog_or_tty->print("\n\t(%d: stole %d oops)", i, num_steals); | |
| 5146 } | |
| 5147 ) | |
| 5148 assert(work_q->size() == 0 && _collector->overflow_list_is_empty(), | |
| 5149 "Else our work is not yet done"); | |
| 5150 } | |
| 5151 | |
| 5152 // Return a thread-local PLAB recording array, as appropriate. | |
| 5153 void* CMSCollector::get_data_recorder(int thr_num) { | |
| 5154 if (_survivor_plab_array != NULL && | |
| 5155 (CMSPLABRecordAlways || | |
| 5156 (_collectorState > Marking && _collectorState < FinalMarking))) { | |
| 5157 assert(thr_num < (int)ParallelGCThreads, "thr_num is out of bounds"); | |
| 5158 ChunkArray* ca = &_survivor_plab_array[thr_num]; | |
| 5159 ca->reset(); // clear it so that fresh data is recorded | |
| 5160 return (void*) ca; | |
| 5161 } else { | |
| 5162 return NULL; | |
| 5163 } | |
| 5164 } | |
| 5165 | |
| 5166 // Reset all the thread-local PLAB recording arrays | |
| 5167 void CMSCollector::reset_survivor_plab_arrays() { | |
| 5168 for (uint i = 0; i < ParallelGCThreads; i++) { | |
| 5169 _survivor_plab_array[i].reset(); | |
| 5170 } | |
| 5171 } | |
| 5172 | |
| 5173 // Merge the per-thread plab arrays into the global survivor chunk | |
| 5174 // array which will provide the partitioning of the survivor space | |
| 5175 // for CMS rescan. | |
| 5176 void CMSCollector::merge_survivor_plab_arrays(ContiguousSpace* surv) { | |
| 5177 assert(_survivor_plab_array != NULL, "Error"); | |
| 5178 assert(_survivor_chunk_array != NULL, "Error"); | |
| 5179 assert(_collectorState == FinalMarking, "Error"); | |
| 5180 for (uint j = 0; j < ParallelGCThreads; j++) { | |
| 5181 _cursor[j] = 0; | |
| 5182 } | |
| 5183 HeapWord* top = surv->top(); | |
| 5184 size_t i; | |
| 5185 for (i = 0; i < _survivor_chunk_capacity; i++) { // all sca entries | |
| 5186 HeapWord* min_val = top; // Higher than any PLAB address | |
| 5187 uint min_tid = 0; // position of min_val this round | |
| 5188 for (uint j = 0; j < ParallelGCThreads; j++) { | |
| 5189 ChunkArray* cur_sca = &_survivor_plab_array[j]; | |
| 5190 if (_cursor[j] == cur_sca->end()) { | |
| 5191 continue; | |
| 5192 } | |
| 5193 assert(_cursor[j] < cur_sca->end(), "ctl pt invariant"); | |
| 5194 HeapWord* cur_val = cur_sca->nth(_cursor[j]); | |
| 5195 assert(surv->used_region().contains(cur_val), "Out of bounds value"); | |
| 5196 if (cur_val < min_val) { | |
| 5197 min_tid = j; | |
| 5198 min_val = cur_val; | |
| 5199 } else { | |
| 5200 assert(cur_val < top, "All recorded addresses should be less"); | |
| 5201 } | |
| 5202 } | |
| 5203 // At this point min_val and min_tid are respectively | |
| 5204 // the least address in _survivor_plab_array[j]->nth(_cursor[j]) | |
| 5205 // and the thread (j) that witnesses that address. | |
| 5206 // We record this address in the _survivor_chunk_array[i] | |
| 5207 // and increment _cursor[min_tid] prior to the next round i. | |
| 5208 if (min_val == top) { | |
| 5209 break; | |
| 5210 } | |
| 5211 _survivor_chunk_array[i] = min_val; | |
| 5212 _cursor[min_tid]++; | |
| 5213 } | |
| 5214 // We are all done; record the size of the _survivor_chunk_array | |
| 5215 _survivor_chunk_index = i; // exclusive: [0, i) | |
| 5216 if (PrintCMSStatistics > 0) { | |
| 5217 gclog_or_tty->print(" (Survivor:" SIZE_FORMAT "chunks) ", i); | |
| 5218 } | |
| 5219 // Verify that we used up all the recorded entries | |
| 5220 #ifdef ASSERT | |
| 5221 size_t total = 0; | |
| 5222 for (uint j = 0; j < ParallelGCThreads; j++) { | |
| 5223 assert(_cursor[j] == _survivor_plab_array[j].end(), "Ctl pt invariant"); | |
| 5224 total += _cursor[j]; | |
| 5225 } | |
| 5226 assert(total == _survivor_chunk_index, "Ctl Pt Invariant"); | |
| 5227 // Check that the merged array is in sorted order | |
| 5228 if (total > 0) { | |
| 5229 for (size_t i = 0; i < total - 1; i++) { | |
| 5230 if (PrintCMSStatistics > 0) { | |
| 5231 gclog_or_tty->print(" (chunk" SIZE_FORMAT ":" INTPTR_FORMAT ") ", | |
| 5232 i, _survivor_chunk_array[i]); | |
| 5233 } | |
| 5234 assert(_survivor_chunk_array[i] < _survivor_chunk_array[i+1], | |
| 5235 "Not sorted"); | |
| 5236 } | |
| 5237 } | |
| 5238 #endif // ASSERT | |
| 5239 } | |
| 5240 | |
| 5241 // Set up the space's par_seq_tasks structure for work claiming | |
| 5242 // for parallel rescan of young gen. | |
| 5243 // See ParRescanTask where this is currently used. | |
| 5244 void | |
| 5245 CMSCollector:: | |
| 5246 initialize_sequential_subtasks_for_young_gen_rescan(int n_threads) { | |
| 5247 assert(n_threads > 0, "Unexpected n_threads argument"); | |
| 5248 DefNewGeneration* dng = (DefNewGeneration*)_young_gen; | |
| 5249 | |
| 5250 // Eden space | |
| 5251 { | |
| 5252 SequentialSubTasksDone* pst = dng->eden()->par_seq_tasks(); | |
| 5253 assert(!pst->valid(), "Clobbering existing data?"); | |
| 5254 // Each valid entry in [0, _eden_chunk_index) represents a task. | |
| 5255 size_t n_tasks = _eden_chunk_index + 1; | |
| 5256 assert(n_tasks == 1 || _eden_chunk_array != NULL, "Error"); | |
| 5257 pst->set_par_threads(n_threads); | |
| 5258 pst->set_n_tasks((int)n_tasks); | |
| 5259 } | |
| 5260 | |
| 5261 // Merge the survivor plab arrays into _survivor_chunk_array | |
| 5262 if (_survivor_plab_array != NULL) { | |
| 5263 merge_survivor_plab_arrays(dng->from()); | |
| 5264 } else { | |
| 5265 assert(_survivor_chunk_index == 0, "Error"); | |
| 5266 } | |
| 5267 | |
| 5268 // To space | |
| 5269 { | |
| 5270 SequentialSubTasksDone* pst = dng->to()->par_seq_tasks(); | |
| 5271 assert(!pst->valid(), "Clobbering existing data?"); | |
| 5272 pst->set_par_threads(n_threads); | |
| 5273 pst->set_n_tasks(1); | |
| 5274 assert(pst->valid(), "Error"); | |
| 5275 } | |
| 5276 | |
| 5277 // From space | |
| 5278 { | |
| 5279 SequentialSubTasksDone* pst = dng->from()->par_seq_tasks(); | |
| 5280 assert(!pst->valid(), "Clobbering existing data?"); | |
| 5281 size_t n_tasks = _survivor_chunk_index + 1; | |
| 5282 assert(n_tasks == 1 || _survivor_chunk_array != NULL, "Error"); | |
| 5283 pst->set_par_threads(n_threads); | |
| 5284 pst->set_n_tasks((int)n_tasks); | |
| 5285 assert(pst->valid(), "Error"); | |
| 5286 } | |
| 5287 } | |
| 5288 | |
| 5289 // Parallel version of remark | |
| 5290 void CMSCollector::do_remark_parallel() { | |
| 5291 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 5292 WorkGang* workers = gch->workers(); | |
| 5293 assert(workers != NULL, "Need parallel worker threads."); | |
| 5294 int n_workers = workers->total_workers(); | |
| 5295 CompactibleFreeListSpace* cms_space = _cmsGen->cmsSpace(); | |
| 5296 CompactibleFreeListSpace* perm_space = _permGen->cmsSpace(); | |
| 5297 | |
| 5298 CMSParRemarkTask tsk(this, | |
| 5299 cms_space, perm_space, | |
| 5300 n_workers, workers, task_queues()); | |
| 5301 | |
| 5302 // Set up for parallel process_strong_roots work. | |
| 5303 gch->set_par_threads(n_workers); | |
| 5304 gch->change_strong_roots_parity(); | |
| 5305 // We won't be iterating over the cards in the card table updating | |
| 5306 // the younger_gen cards, so we shouldn't call the following else | |
| 5307 // the verification code as well as subsequent younger_refs_iterate | |
| 5308 // code would get confused. XXX | |
| 5309 // gch->rem_set()->prepare_for_younger_refs_iterate(true); // parallel | |
| 5310 | |
| 5311 // The young gen rescan work will not be done as part of | |
| 5312 // process_strong_roots (which currently doesn't knw how to | |
| 5313 // parallelize such a scan), but rather will be broken up into | |
| 5314 // a set of parallel tasks (via the sampling that the [abortable] | |
| 5315 // preclean phase did of EdenSpace, plus the [two] tasks of | |
| 5316 // scanning the [two] survivor spaces. Further fine-grain | |
| 5317 // parallelization of the scanning of the survivor spaces | |
| 5318 // themselves, and of precleaning of the younger gen itself | |
| 5319 // is deferred to the future. | |
| 5320 initialize_sequential_subtasks_for_young_gen_rescan(n_workers); | |
| 5321 | |
| 5322 // The dirty card rescan work is broken up into a "sequence" | |
| 5323 // of parallel tasks (per constituent space) that are dynamically | |
| 5324 // claimed by the parallel threads. | |
| 5325 cms_space->initialize_sequential_subtasks_for_rescan(n_workers); | |
| 5326 perm_space->initialize_sequential_subtasks_for_rescan(n_workers); | |
| 5327 | |
| 5328 // It turns out that even when we're using 1 thread, doing the work in a | |
| 5329 // separate thread causes wide variance in run times. We can't help this | |
| 5330 // in the multi-threaded case, but we special-case n=1 here to get | |
| 5331 // repeatable measurements of the 1-thread overhead of the parallel code. | |
| 5332 if (n_workers > 1) { | |
| 5333 // Make refs discovery MT-safe | |
| 5334 ReferenceProcessorMTMutator mt(ref_processor(), true); | |
| 5335 workers->run_task(&tsk); | |
| 5336 } else { | |
| 5337 tsk.work(0); | |
| 5338 } | |
| 5339 gch->set_par_threads(0); // 0 ==> non-parallel. | |
| 5340 // restore, single-threaded for now, any preserved marks | |
| 5341 // as a result of work_q overflow | |
| 5342 restore_preserved_marks_if_any(); | |
| 5343 } | |
| 5344 | |
| 5345 // Non-parallel version of remark | |
| 5346 void CMSCollector::do_remark_non_parallel() { | |
| 5347 ResourceMark rm; | |
| 5348 HandleMark hm; | |
| 5349 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 5350 MarkRefsIntoAndScanClosure | |
| 5351 mrias_cl(_span, ref_processor(), &_markBitMap, &_modUnionTable, | |
| 5352 &_markStack, &_revisitStack, this, | |
| 5353 false /* should_yield */, false /* not precleaning */); | |
| 5354 MarkFromDirtyCardsClosure | |
| 5355 markFromDirtyCardsClosure(this, _span, | |
| 5356 NULL, // space is set further below | |
| 5357 &_markBitMap, &_markStack, &_revisitStack, | |
| 5358 &mrias_cl); | |
| 5359 { | |
| 5360 TraceTime t("grey object rescan", PrintGCDetails, false, gclog_or_tty); | |
| 5361 // Iterate over the dirty cards, marking them precleaned, and | |
| 5362 // setting the corresponding bits in the mod union table. | |
| 5363 { | |
| 5364 ModUnionClosure modUnionClosure(&_modUnionTable); | |
| 5365 _ct->ct_bs()->dirty_card_iterate( | |
| 5366 _cmsGen->used_region(), | |
| 5367 &modUnionClosure); | |
| 5368 _ct->ct_bs()->dirty_card_iterate( | |
| 5369 _permGen->used_region(), | |
| 5370 &modUnionClosure); | |
| 5371 } | |
| 5372 // Having transferred these marks into the modUnionTable, we just need | |
| 5373 // to rescan the marked objects on the dirty cards in the modUnionTable. | |
| 5374 // The initial marking may have been done during an asynchronous | |
| 5375 // collection so there may be dirty bits in the mod-union table. | |
| 5376 const int alignment = | |
| 5377 CardTableModRefBS::card_size * BitsPerWord; | |
| 5378 { | |
| 5379 // ... First handle dirty cards in CMS gen | |
| 5380 markFromDirtyCardsClosure.set_space(_cmsGen->cmsSpace()); | |
| 5381 MemRegion ur = _cmsGen->used_region(); | |
| 5382 HeapWord* lb = ur.start(); | |
| 5383 HeapWord* ub = (HeapWord*)round_to((intptr_t)ur.end(), alignment); | |
| 5384 MemRegion cms_span(lb, ub); | |
| 5385 _modUnionTable.dirty_range_iterate_clear(cms_span, | |
| 5386 &markFromDirtyCardsClosure); | |
| 5387 verify_work_stacks_empty(); | |
| 5388 if (PrintCMSStatistics != 0) { | |
| 5389 gclog_or_tty->print(" (re-scanned "SIZE_FORMAT" dirty cards in cms gen) ", | |
| 5390 markFromDirtyCardsClosure.num_dirty_cards()); | |
| 5391 } | |
| 5392 } | |
| 5393 { | |
| 5394 // .. and then repeat for dirty cards in perm gen | |
| 5395 markFromDirtyCardsClosure.set_space(_permGen->cmsSpace()); | |
| 5396 MemRegion ur = _permGen->used_region(); | |
| 5397 HeapWord* lb = ur.start(); | |
| 5398 HeapWord* ub = (HeapWord*)round_to((intptr_t)ur.end(), alignment); | |
| 5399 MemRegion perm_span(lb, ub); | |
| 5400 _modUnionTable.dirty_range_iterate_clear(perm_span, | |
| 5401 &markFromDirtyCardsClosure); | |
| 5402 verify_work_stacks_empty(); | |
| 5403 if (PrintCMSStatistics != 0) { | |
| 5404 gclog_or_tty->print(" (re-scanned "SIZE_FORMAT" dirty cards in perm gen) ", | |
| 5405 markFromDirtyCardsClosure.num_dirty_cards()); | |
| 5406 } | |
| 5407 } | |
| 5408 } | |
| 5409 if (VerifyDuringGC && | |
| 5410 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { | |
| 5411 HandleMark hm; // Discard invalid handles created during verification | |
| 5412 Universe::verify(true); | |
| 5413 } | |
| 5414 { | |
| 5415 TraceTime t("root rescan", PrintGCDetails, false, gclog_or_tty); | |
| 5416 | |
| 5417 verify_work_stacks_empty(); | |
| 5418 | |
| 5419 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel. | |
| 5420 gch->gen_process_strong_roots(_cmsGen->level(), | |
| 5421 true, // younger gens as roots | |
| 5422 true, // collecting perm gen | |
| 5423 SharedHeap::ScanningOption(roots_scanning_options()), | |
| 5424 NULL, &mrias_cl); | |
| 5425 } | |
| 5426 verify_work_stacks_empty(); | |
| 5427 // Restore evacuated mark words, if any, used for overflow list links | |
| 5428 if (!CMSOverflowEarlyRestoration) { | |
| 5429 restore_preserved_marks_if_any(); | |
| 5430 } | |
| 5431 verify_overflow_empty(); | |
| 5432 } | |
| 5433 | |
| 5434 //////////////////////////////////////////////////////// | |
| 5435 // Parallel Reference Processing Task Proxy Class | |
| 5436 //////////////////////////////////////////////////////// | |
| 5437 class CMSRefProcTaskProxy: public AbstractGangTask { | |
| 5438 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; | |
| 5439 CMSCollector* _collector; | |
| 5440 CMSBitMap* _mark_bit_map; | |
| 5441 MemRegion _span; | |
| 5442 OopTaskQueueSet* _task_queues; | |
| 5443 ParallelTaskTerminator _term; | |
| 5444 ProcessTask& _task; | |
| 5445 | |
| 5446 public: | |
| 5447 CMSRefProcTaskProxy(ProcessTask& task, | |
| 5448 CMSCollector* collector, | |
| 5449 const MemRegion& span, | |
| 5450 CMSBitMap* mark_bit_map, | |
| 5451 int total_workers, | |
| 5452 OopTaskQueueSet* task_queues): | |
| 5453 AbstractGangTask("Process referents by policy in parallel"), | |
| 5454 _task(task), | |
| 5455 _collector(collector), _span(span), _mark_bit_map(mark_bit_map), | |
| 5456 _task_queues(task_queues), | |
| 5457 _term(total_workers, task_queues) | |
| 5458 { } | |
| 5459 | |
| 5460 OopTaskQueueSet* task_queues() { return _task_queues; } | |
| 5461 | |
| 5462 OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); } | |
| 5463 | |
| 5464 ParallelTaskTerminator* terminator() { return &_term; } | |
| 5465 | |
| 5466 void do_work_steal(int i, | |
| 5467 CMSParDrainMarkingStackClosure* drain, | |
| 5468 CMSParKeepAliveClosure* keep_alive, | |
| 5469 int* seed); | |
| 5470 | |
| 5471 virtual void work(int i); | |
| 5472 }; | |
| 5473 | |
| 5474 void CMSRefProcTaskProxy::work(int i) { | |
| 5475 CMSParKeepAliveClosure par_keep_alive(_collector, _span, | |
| 5476 _mark_bit_map, work_queue(i)); | |
| 5477 CMSParDrainMarkingStackClosure par_drain_stack(_collector, _span, | |
| 5478 _mark_bit_map, work_queue(i)); | |
| 5479 CMSIsAliveClosure is_alive_closure(_mark_bit_map); | |
| 5480 _task.work(i, is_alive_closure, par_keep_alive, par_drain_stack); | |
| 5481 if (_task.marks_oops_alive()) { | |
| 5482 do_work_steal(i, &par_drain_stack, &par_keep_alive, | |
| 5483 _collector->hash_seed(i)); | |
| 5484 } | |
| 5485 assert(work_queue(i)->size() == 0, "work_queue should be empty"); | |
| 5486 assert(_collector->_overflow_list == NULL, "non-empty _overflow_list"); | |
| 5487 } | |
| 5488 | |
| 5489 class CMSRefEnqueueTaskProxy: public AbstractGangTask { | |
| 5490 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; | |
| 5491 EnqueueTask& _task; | |
| 5492 | |
| 5493 public: | |
| 5494 CMSRefEnqueueTaskProxy(EnqueueTask& task) | |
| 5495 : AbstractGangTask("Enqueue reference objects in parallel"), | |
| 5496 _task(task) | |
| 5497 { } | |
| 5498 | |
| 5499 virtual void work(int i) | |
| 5500 { | |
| 5501 _task.work(i); | |
| 5502 } | |
| 5503 }; | |
| 5504 | |
| 5505 CMSParKeepAliveClosure::CMSParKeepAliveClosure(CMSCollector* collector, | |
| 5506 MemRegion span, CMSBitMap* bit_map, OopTaskQueue* work_queue): | |
| 5507 _collector(collector), | |
| 5508 _span(span), | |
| 5509 _bit_map(bit_map), | |
| 5510 _work_queue(work_queue), | |
| 5511 _mark_and_push(collector, span, bit_map, work_queue), | |
| 5512 _low_water_mark(MIN2((uint)(work_queue->max_elems()/4), | |
| 5513 (uint)(CMSWorkQueueDrainThreshold * ParallelGCThreads))) | |
| 5514 { } | |
| 5515 | |
| 5516 // . see if we can share work_queues with ParNew? XXX | |
| 5517 void CMSRefProcTaskProxy::do_work_steal(int i, | |
| 5518 CMSParDrainMarkingStackClosure* drain, | |
| 5519 CMSParKeepAliveClosure* keep_alive, | |
| 5520 int* seed) { | |
| 5521 OopTaskQueue* work_q = work_queue(i); | |
| 5522 NOT_PRODUCT(int num_steals = 0;) | |
| 5523 oop obj_to_scan; | |
| 5524 size_t num_from_overflow_list = | |
| 5525 MIN2((size_t)work_q->max_elems()/4, | |
| 5526 (size_t)ParGCDesiredObjsFromOverflowList); | |
| 5527 | |
| 5528 while (true) { | |
| 5529 // Completely finish any left over work from (an) earlier round(s) | |
| 5530 drain->trim_queue(0); | |
| 5531 // Now check if there's any work in the overflow list | |
| 5532 if (_collector->par_take_from_overflow_list(num_from_overflow_list, | |
| 5533 work_q)) { | |
| 5534 // Found something in global overflow list; | |
| 5535 // not yet ready to go stealing work from others. | |
| 5536 // We'd like to assert(work_q->size() != 0, ...) | |
| 5537 // because we just took work from the overflow list, | |
| 5538 // but of course we can't, since all of that might have | |
| 5539 // been already stolen from us. | |
| 5540 continue; | |
| 5541 } | |
| 5542 // Verify that we have no work before we resort to stealing | |
| 5543 assert(work_q->size() == 0, "Have work, shouldn't steal"); | |
| 5544 // Try to steal from other queues that have work | |
| 5545 if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) { | |
| 5546 NOT_PRODUCT(num_steals++;) | |
| 5547 assert(obj_to_scan->is_oop(), "Oops, not an oop!"); | |
| 5548 assert(_mark_bit_map->isMarked((HeapWord*)obj_to_scan), "Stole an unmarked oop?"); | |
| 5549 // Do scanning work | |
| 5550 obj_to_scan->oop_iterate(keep_alive); | |
| 5551 // Loop around, finish this work, and try to steal some more | |
| 5552 } else if (terminator()->offer_termination()) { | |
| 5553 break; // nirvana from the infinite cycle | |
| 5554 } | |
| 5555 } | |
| 5556 NOT_PRODUCT( | |
| 5557 if (PrintCMSStatistics != 0) { | |
| 5558 gclog_or_tty->print("\n\t(%d: stole %d oops)", i, num_steals); | |
| 5559 } | |
| 5560 ) | |
| 5561 } | |
| 5562 | |
| 5563 void CMSRefProcTaskExecutor::execute(ProcessTask& task) | |
| 5564 { | |
| 5565 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 5566 WorkGang* workers = gch->workers(); | |
| 5567 assert(workers != NULL, "Need parallel worker threads."); | |
| 5568 int n_workers = workers->total_workers(); | |
| 5569 CMSRefProcTaskProxy rp_task(task, &_collector, | |
| 5570 _collector.ref_processor()->span(), | |
| 5571 _collector.markBitMap(), | |
| 5572 n_workers, _collector.task_queues()); | |
| 5573 workers->run_task(&rp_task); | |
| 5574 } | |
| 5575 | |
| 5576 void CMSRefProcTaskExecutor::execute(EnqueueTask& task) | |
| 5577 { | |
| 5578 | |
| 5579 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 5580 WorkGang* workers = gch->workers(); | |
| 5581 assert(workers != NULL, "Need parallel worker threads."); | |
| 5582 CMSRefEnqueueTaskProxy enq_task(task); | |
| 5583 workers->run_task(&enq_task); | |
| 5584 } | |
| 5585 | |
| 5586 void CMSCollector::refProcessingWork(bool asynch, bool clear_all_soft_refs) { | |
| 5587 | |
| 5588 ResourceMark rm; | |
| 5589 HandleMark hm; | |
| 5590 ReferencePolicy* soft_ref_policy; | |
| 5591 | |
| 5592 assert(!ref_processor()->enqueuing_is_done(), "Enqueuing should not be complete"); | |
| 5593 // Process weak references. | |
| 5594 if (clear_all_soft_refs) { | |
| 5595 soft_ref_policy = new AlwaysClearPolicy(); | |
| 5596 } else { | |
| 5597 #ifdef COMPILER2 | |
| 5598 soft_ref_policy = new LRUMaxHeapPolicy(); | |
| 5599 #else | |
| 5600 soft_ref_policy = new LRUCurrentHeapPolicy(); | |
| 5601 #endif // COMPILER2 | |
| 5602 } | |
| 5603 verify_work_stacks_empty(); | |
| 5604 | |
| 5605 ReferenceProcessor* rp = ref_processor(); | |
| 5606 assert(rp->span().equals(_span), "Spans should be equal"); | |
| 5607 CMSKeepAliveClosure cmsKeepAliveClosure(this, _span, &_markBitMap, | |
| 5608 &_markStack); | |
| 5609 CMSDrainMarkingStackClosure cmsDrainMarkingStackClosure(this, | |
| 5610 _span, &_markBitMap, &_markStack, | |
| 5611 &cmsKeepAliveClosure); | |
| 5612 { | |
| 5613 TraceTime t("weak refs processing", PrintGCDetails, false, gclog_or_tty); | |
| 5614 if (rp->processing_is_mt()) { | |
| 5615 CMSRefProcTaskExecutor task_executor(*this); | |
| 5616 rp->process_discovered_references(soft_ref_policy, | |
| 5617 &_is_alive_closure, | |
| 5618 &cmsKeepAliveClosure, | |
| 5619 &cmsDrainMarkingStackClosure, | |
| 5620 &task_executor); | |
| 5621 } else { | |
| 5622 rp->process_discovered_references(soft_ref_policy, | |
| 5623 &_is_alive_closure, | |
| 5624 &cmsKeepAliveClosure, | |
| 5625 &cmsDrainMarkingStackClosure, | |
| 5626 NULL); | |
| 5627 } | |
| 5628 verify_work_stacks_empty(); | |
| 5629 } | |
| 5630 | |
| 5631 if (cms_should_unload_classes()) { | |
| 5632 { | |
| 5633 TraceTime t("class unloading", PrintGCDetails, false, gclog_or_tty); | |
| 5634 | |
| 5635 // Follow SystemDictionary roots and unload classes | |
| 5636 bool purged_class = SystemDictionary::do_unloading(&_is_alive_closure); | |
| 5637 | |
| 5638 // Follow CodeCache roots and unload any methods marked for unloading | |
| 5639 CodeCache::do_unloading(&_is_alive_closure, | |
| 5640 &cmsKeepAliveClosure, | |
| 5641 purged_class); | |
| 5642 | |
| 5643 cmsDrainMarkingStackClosure.do_void(); | |
| 5644 verify_work_stacks_empty(); | |
| 5645 | |
| 5646 // Update subklass/sibling/implementor links in KlassKlass descendants | |
| 5647 assert(!_revisitStack.isEmpty(), "revisit stack should not be empty"); | |
| 5648 oop k; | |
| 5649 while ((k = _revisitStack.pop()) != NULL) { | |
| 5650 ((Klass*)(oopDesc*)k)->follow_weak_klass_links( | |
| 5651 &_is_alive_closure, | |
| 5652 &cmsKeepAliveClosure); | |
| 5653 } | |
| 5654 assert(!ClassUnloading || | |
| 5655 (_markStack.isEmpty() && overflow_list_is_empty()), | |
| 5656 "Should not have found new reachable objects"); | |
| 5657 assert(_revisitStack.isEmpty(), "revisit stack should have been drained"); | |
| 5658 cmsDrainMarkingStackClosure.do_void(); | |
| 5659 verify_work_stacks_empty(); | |
| 5660 } | |
| 5661 | |
| 5662 { | |
| 5663 TraceTime t("scrub symbol & string tables", PrintGCDetails, false, gclog_or_tty); | |
| 5664 // Now clean up stale oops in SymbolTable and StringTable | |
| 5665 SymbolTable::unlink(&_is_alive_closure); | |
| 5666 StringTable::unlink(&_is_alive_closure); | |
| 5667 } | |
| 5668 } | |
| 5669 | |
| 5670 verify_work_stacks_empty(); | |
| 5671 // Restore any preserved marks as a result of mark stack or | |
| 5672 // work queue overflow | |
| 5673 restore_preserved_marks_if_any(); // done single-threaded for now | |
| 5674 | |
| 5675 rp->set_enqueuing_is_done(true); | |
| 5676 if (rp->processing_is_mt()) { | |
| 5677 CMSRefProcTaskExecutor task_executor(*this); | |
| 5678 rp->enqueue_discovered_references(&task_executor); | |
| 5679 } else { | |
| 5680 rp->enqueue_discovered_references(NULL); | |
| 5681 } | |
| 5682 rp->verify_no_references_recorded(); | |
| 5683 assert(!rp->discovery_enabled(), "should have been disabled"); | |
| 5684 | |
| 5685 // JVMTI object tagging is based on JNI weak refs. If any of these | |
| 5686 // refs were cleared then JVMTI needs to update its maps and | |
| 5687 // maybe post ObjectFrees to agents. | |
| 5688 JvmtiExport::cms_ref_processing_epilogue(); | |
| 5689 } | |
| 5690 | |
| 5691 #ifndef PRODUCT | |
| 5692 void CMSCollector::check_correct_thread_executing() { | |
| 5693 Thread* t = Thread::current(); | |
| 5694 // Only the VM thread or the CMS thread should be here. | |
| 5695 assert(t->is_ConcurrentGC_thread() || t->is_VM_thread(), | |
| 5696 "Unexpected thread type"); | |
| 5697 // If this is the vm thread, the foreground process | |
| 5698 // should not be waiting. Note that _foregroundGCIsActive is | |
| 5699 // true while the foreground collector is waiting. | |
| 5700 if (_foregroundGCShouldWait) { | |
| 5701 // We cannot be the VM thread | |
| 5702 assert(t->is_ConcurrentGC_thread(), | |
| 5703 "Should be CMS thread"); | |
| 5704 } else { | |
| 5705 // We can be the CMS thread only if we are in a stop-world | |
| 5706 // phase of CMS collection. | |
| 5707 if (t->is_ConcurrentGC_thread()) { | |
| 5708 assert(_collectorState == InitialMarking || | |
| 5709 _collectorState == FinalMarking, | |
| 5710 "Should be a stop-world phase"); | |
| 5711 // The CMS thread should be holding the CMS_token. | |
| 5712 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 5713 "Potential interference with concurrently " | |
| 5714 "executing VM thread"); | |
| 5715 } | |
| 5716 } | |
| 5717 } | |
| 5718 #endif | |
| 5719 | |
| 5720 void CMSCollector::sweep(bool asynch) { | |
| 5721 assert(_collectorState == Sweeping, "just checking"); | |
| 5722 check_correct_thread_executing(); | |
| 5723 verify_work_stacks_empty(); | |
| 5724 verify_overflow_empty(); | |
| 5725 incrementSweepCount(); | |
| 5726 _sweep_timer.stop(); | |
| 5727 _sweep_estimate.sample(_sweep_timer.seconds()); | |
| 5728 size_policy()->avg_cms_free_at_sweep()->sample(_cmsGen->free()); | |
| 5729 | |
| 5730 // PermGen verification support: If perm gen sweeping is disabled in | |
| 5731 // this cycle, we preserve the perm gen object "deadness" information | |
| 5732 // in the perm_gen_verify_bit_map. In order to do that we traverse | |
| 5733 // all blocks in perm gen and mark all dead objects. | |
| 5734 if (verifying() && !cms_should_unload_classes()) { | |
| 5735 assert(perm_gen_verify_bit_map()->sizeInBits() != 0, | |
| 5736 "Should have already been allocated"); | |
| 5737 MarkDeadObjectsClosure mdo(this, _permGen->cmsSpace(), | |
| 5738 markBitMap(), perm_gen_verify_bit_map()); | |
|
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5739 if (asynch) { |
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5740 CMSTokenSyncWithLocks ts(true, _permGen->freelistLock(), |
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5741 bitMapLock()); |
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5742 _permGen->cmsSpace()->blk_iterate(&mdo); |
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5743 } else { |
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5744 // In the case of synchronous sweep, we already have |
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5745 // the requisite locks/tokens. |
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5746 _permGen->cmsSpace()->blk_iterate(&mdo); |
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5747 } |
| 0 | 5748 } |
| 5749 | |
| 5750 if (asynch) { | |
| 5751 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
| 5752 CMSPhaseAccounting pa(this, "sweep", !PrintGCDetails); | |
| 5753 // First sweep the old gen then the perm gen | |
| 5754 { | |
| 5755 CMSTokenSyncWithLocks ts(true, _cmsGen->freelistLock(), | |
| 5756 bitMapLock()); | |
| 5757 sweepWork(_cmsGen, asynch); | |
| 5758 } | |
| 5759 | |
| 5760 // Now repeat for perm gen | |
| 5761 if (cms_should_unload_classes()) { | |
| 5762 CMSTokenSyncWithLocks ts(true, _permGen->freelistLock(), | |
| 5763 bitMapLock()); | |
| 5764 sweepWork(_permGen, asynch); | |
| 5765 } | |
| 5766 | |
| 5767 // Update Universe::_heap_*_at_gc figures. | |
| 5768 // We need all the free list locks to make the abstract state | |
| 5769 // transition from Sweeping to Resetting. See detailed note | |
| 5770 // further below. | |
| 5771 { | |
| 5772 CMSTokenSyncWithLocks ts(true, _cmsGen->freelistLock(), | |
| 5773 _permGen->freelistLock()); | |
| 5774 // Update heap occupancy information which is used as | |
| 5775 // input to soft ref clearing policy at the next gc. | |
| 5776 Universe::update_heap_info_at_gc(); | |
| 5777 _collectorState = Resizing; | |
| 5778 } | |
| 5779 } else { | |
| 5780 // already have needed locks | |
| 5781 sweepWork(_cmsGen, asynch); | |
| 5782 | |
| 5783 if (cms_should_unload_classes()) { | |
| 5784 sweepWork(_permGen, asynch); | |
| 5785 } | |
| 5786 // Update heap occupancy information which is used as | |
| 5787 // input to soft ref clearing policy at the next gc. | |
| 5788 Universe::update_heap_info_at_gc(); | |
| 5789 _collectorState = Resizing; | |
| 5790 } | |
| 5791 verify_work_stacks_empty(); | |
| 5792 verify_overflow_empty(); | |
| 5793 | |
| 5794 _sweep_timer.reset(); | |
| 5795 _sweep_timer.start(); | |
| 5796 | |
| 5797 update_time_of_last_gc(os::javaTimeMillis()); | |
| 5798 | |
| 5799 // NOTE on abstract state transitions: | |
| 5800 // Mutators allocate-live and/or mark the mod-union table dirty | |
| 5801 // based on the state of the collection. The former is done in | |
| 5802 // the interval [Marking, Sweeping] and the latter in the interval | |
| 5803 // [Marking, Sweeping). Thus the transitions into the Marking state | |
| 5804 // and out of the Sweeping state must be synchronously visible | |
| 5805 // globally to the mutators. | |
| 5806 // The transition into the Marking state happens with the world | |
| 5807 // stopped so the mutators will globally see it. Sweeping is | |
| 5808 // done asynchronously by the background collector so the transition | |
| 5809 // from the Sweeping state to the Resizing state must be done | |
| 5810 // under the freelistLock (as is the check for whether to | |
| 5811 // allocate-live and whether to dirty the mod-union table). | |
| 5812 assert(_collectorState == Resizing, "Change of collector state to" | |
| 5813 " Resizing must be done under the freelistLocks (plural)"); | |
| 5814 | |
| 5815 // Now that sweeping has been completed, if the GCH's | |
| 5816 // incremental_collection_will_fail flag is set, clear it, | |
| 5817 // thus inviting a younger gen collection to promote into | |
| 5818 // this generation. If such a promotion may still fail, | |
| 5819 // the flag will be set again when a young collection is | |
| 5820 // attempted. | |
| 5821 // I think the incremental_collection_will_fail flag's use | |
| 5822 // is specific to a 2 generation collection policy, so i'll | |
| 5823 // assert that that's the configuration we are operating within. | |
| 5824 // The use of the flag can and should be generalized appropriately | |
| 5825 // in the future to deal with a general n-generation system. | |
| 5826 | |
| 5827 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 5828 assert(gch->collector_policy()->is_two_generation_policy(), | |
| 5829 "Resetting of incremental_collection_will_fail flag" | |
| 5830 " may be incorrect otherwise"); | |
| 5831 gch->clear_incremental_collection_will_fail(); | |
| 5832 gch->update_full_collections_completed(_collection_count_start); | |
| 5833 } | |
| 5834 | |
| 5835 // FIX ME!!! Looks like this belongs in CFLSpace, with | |
| 5836 // CMSGen merely delegating to it. | |
| 5837 void ConcurrentMarkSweepGeneration::setNearLargestChunk() { | |
| 5838 double nearLargestPercent = 0.999; | |
| 5839 HeapWord* minAddr = _cmsSpace->bottom(); | |
| 5840 HeapWord* largestAddr = | |
| 5841 (HeapWord*) _cmsSpace->dictionary()->findLargestDict(); | |
| 5842 if (largestAddr == 0) { | |
| 5843 // The dictionary appears to be empty. In this case | |
| 5844 // try to coalesce at the end of the heap. | |
| 5845 largestAddr = _cmsSpace->end(); | |
| 5846 } | |
| 5847 size_t largestOffset = pointer_delta(largestAddr, minAddr); | |
| 5848 size_t nearLargestOffset = | |
| 5849 (size_t)((double)largestOffset * nearLargestPercent) - MinChunkSize; | |
| 5850 _cmsSpace->set_nearLargestChunk(minAddr + nearLargestOffset); | |
| 5851 } | |
| 5852 | |
| 5853 bool ConcurrentMarkSweepGeneration::isNearLargestChunk(HeapWord* addr) { | |
| 5854 return addr >= _cmsSpace->nearLargestChunk(); | |
| 5855 } | |
| 5856 | |
| 5857 FreeChunk* ConcurrentMarkSweepGeneration::find_chunk_at_end() { | |
| 5858 return _cmsSpace->find_chunk_at_end(); | |
| 5859 } | |
| 5860 | |
| 5861 void ConcurrentMarkSweepGeneration::update_gc_stats(int current_level, | |
| 5862 bool full) { | |
| 5863 // The next lower level has been collected. Gather any statistics | |
| 5864 // that are of interest at this point. | |
| 5865 if (!full && (current_level + 1) == level()) { | |
| 5866 // Gather statistics on the young generation collection. | |
| 5867 collector()->stats().record_gc0_end(used()); | |
| 5868 } | |
| 5869 } | |
| 5870 | |
| 5871 CMSAdaptiveSizePolicy* ConcurrentMarkSweepGeneration::size_policy() { | |
| 5872 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 5873 assert(gch->kind() == CollectedHeap::GenCollectedHeap, | |
| 5874 "Wrong type of heap"); | |
| 5875 CMSAdaptiveSizePolicy* sp = (CMSAdaptiveSizePolicy*) | |
| 5876 gch->gen_policy()->size_policy(); | |
| 5877 assert(sp->is_gc_cms_adaptive_size_policy(), | |
| 5878 "Wrong type of size policy"); | |
| 5879 return sp; | |
| 5880 } | |
| 5881 | |
| 5882 void ConcurrentMarkSweepGeneration::rotate_debug_collection_type() { | |
| 5883 if (PrintGCDetails && Verbose) { | |
| 5884 gclog_or_tty->print("Rotate from %d ", _debug_collection_type); | |
| 5885 } | |
| 5886 _debug_collection_type = (CollectionTypes) (_debug_collection_type + 1); | |
| 5887 _debug_collection_type = | |
| 5888 (CollectionTypes) (_debug_collection_type % Unknown_collection_type); | |
| 5889 if (PrintGCDetails && Verbose) { | |
| 5890 gclog_or_tty->print_cr("to %d ", _debug_collection_type); | |
| 5891 } | |
| 5892 } | |
| 5893 | |
| 5894 void CMSCollector::sweepWork(ConcurrentMarkSweepGeneration* gen, | |
| 5895 bool asynch) { | |
| 5896 // We iterate over the space(s) underlying this generation, | |
| 5897 // checking the mark bit map to see if the bits corresponding | |
| 5898 // to specific blocks are marked or not. Blocks that are | |
| 5899 // marked are live and are not swept up. All remaining blocks | |
| 5900 // are swept up, with coalescing on-the-fly as we sweep up | |
| 5901 // contiguous free and/or garbage blocks: | |
| 5902 // We need to ensure that the sweeper synchronizes with allocators | |
| 5903 // and stop-the-world collectors. In particular, the following | |
| 5904 // locks are used: | |
| 5905 // . CMS token: if this is held, a stop the world collection cannot occur | |
| 5906 // . freelistLock: if this is held no allocation can occur from this | |
| 5907 // generation by another thread | |
| 5908 // . bitMapLock: if this is held, no other thread can access or update | |
| 5909 // | |
| 5910 | |
| 5911 // Note that we need to hold the freelistLock if we use | |
| 5912 // block iterate below; else the iterator might go awry if | |
| 5913 // a mutator (or promotion) causes block contents to change | |
| 5914 // (for instance if the allocator divvies up a block). | |
| 5915 // If we hold the free list lock, for all practical purposes | |
| 5916 // young generation GC's can't occur (they'll usually need to | |
| 5917 // promote), so we might as well prevent all young generation | |
| 5918 // GC's while we do a sweeping step. For the same reason, we might | |
| 5919 // as well take the bit map lock for the entire duration | |
| 5920 | |
| 5921 // check that we hold the requisite locks | |
| 5922 assert(have_cms_token(), "Should hold cms token"); | |
| 5923 assert( (asynch && ConcurrentMarkSweepThread::cms_thread_has_cms_token()) | |
| 5924 || (!asynch && ConcurrentMarkSweepThread::vm_thread_has_cms_token()), | |
| 5925 "Should possess CMS token to sweep"); | |
| 5926 assert_lock_strong(gen->freelistLock()); | |
| 5927 assert_lock_strong(bitMapLock()); | |
| 5928 | |
| 5929 assert(!_sweep_timer.is_active(), "Was switched off in an outer context"); | |
| 5930 gen->cmsSpace()->beginSweepFLCensus((float)(_sweep_timer.seconds()), | |
| 5931 _sweep_estimate.padded_average()); | |
| 5932 gen->setNearLargestChunk(); | |
| 5933 | |
| 5934 { | |
| 5935 SweepClosure sweepClosure(this, gen, &_markBitMap, | |
| 5936 CMSYield && asynch); | |
| 5937 gen->cmsSpace()->blk_iterate_careful(&sweepClosure); | |
| 5938 // We need to free-up/coalesce garbage/blocks from a | |
| 5939 // co-terminal free run. This is done in the SweepClosure | |
| 5940 // destructor; so, do not remove this scope, else the | |
| 5941 // end-of-sweep-census below will be off by a little bit. | |
| 5942 } | |
| 5943 gen->cmsSpace()->sweep_completed(); | |
| 5944 gen->cmsSpace()->endSweepFLCensus(sweepCount()); | |
| 5945 } | |
| 5946 | |
| 5947 // Reset CMS data structures (for now just the marking bit map) | |
| 5948 // preparatory for the next cycle. | |
| 5949 void CMSCollector::reset(bool asynch) { | |
| 5950 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 5951 CMSAdaptiveSizePolicy* sp = size_policy(); | |
| 5952 AdaptiveSizePolicyOutput(sp, gch->total_collections()); | |
| 5953 if (asynch) { | |
| 5954 CMSTokenSyncWithLocks ts(true, bitMapLock()); | |
| 5955 | |
| 5956 // If the state is not "Resetting", the foreground thread | |
| 5957 // has done a collection and the resetting. | |
| 5958 if (_collectorState != Resetting) { | |
| 5959 assert(_collectorState == Idling, "The state should only change" | |
| 5960 " because the foreground collector has finished the collection"); | |
| 5961 return; | |
| 5962 } | |
| 5963 | |
| 5964 // Clear the mark bitmap (no grey objects to start with) | |
| 5965 // for the next cycle. | |
| 5966 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
| 5967 CMSPhaseAccounting cmspa(this, "reset", !PrintGCDetails); | |
| 5968 | |
| 5969 HeapWord* curAddr = _markBitMap.startWord(); | |
| 5970 while (curAddr < _markBitMap.endWord()) { | |
| 5971 size_t remaining = pointer_delta(_markBitMap.endWord(), curAddr); | |
| 5972 MemRegion chunk(curAddr, MIN2(CMSBitMapYieldQuantum, remaining)); | |
| 5973 _markBitMap.clear_large_range(chunk); | |
| 5974 if (ConcurrentMarkSweepThread::should_yield() && | |
| 5975 !foregroundGCIsActive() && | |
| 5976 CMSYield) { | |
| 5977 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 5978 "CMS thread should hold CMS token"); | |
| 5979 assert_lock_strong(bitMapLock()); | |
| 5980 bitMapLock()->unlock(); | |
| 5981 ConcurrentMarkSweepThread::desynchronize(true); | |
| 5982 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 5983 stopTimer(); | |
| 5984 if (PrintCMSStatistics != 0) { | |
| 5985 incrementYields(); | |
| 5986 } | |
| 5987 icms_wait(); | |
| 5988 | |
| 5989 // See the comment in coordinator_yield() | |
| 5990 for (unsigned i = 0; i < CMSYieldSleepCount && | |
| 5991 ConcurrentMarkSweepThread::should_yield() && | |
| 5992 !CMSCollector::foregroundGCIsActive(); ++i) { | |
| 5993 os::sleep(Thread::current(), 1, false); | |
| 5994 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 5995 } | |
| 5996 | |
| 5997 ConcurrentMarkSweepThread::synchronize(true); | |
| 5998 bitMapLock()->lock_without_safepoint_check(); | |
| 5999 startTimer(); | |
| 6000 } | |
| 6001 curAddr = chunk.end(); | |
| 6002 } | |
| 6003 _collectorState = Idling; | |
| 6004 } else { | |
| 6005 // already have the lock | |
| 6006 assert(_collectorState == Resetting, "just checking"); | |
| 6007 assert_lock_strong(bitMapLock()); | |
| 6008 _markBitMap.clear_all(); | |
| 6009 _collectorState = Idling; | |
| 6010 } | |
| 6011 | |
| 6012 // Stop incremental mode after a cycle completes, so that any future cycles | |
| 6013 // are triggered by allocation. | |
| 6014 stop_icms(); | |
| 6015 | |
| 6016 NOT_PRODUCT( | |
| 6017 if (RotateCMSCollectionTypes) { | |
| 6018 _cmsGen->rotate_debug_collection_type(); | |
| 6019 } | |
| 6020 ) | |
| 6021 } | |
| 6022 | |
| 6023 void CMSCollector::do_CMS_operation(CMS_op_type op) { | |
| 6024 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps); | |
| 6025 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); | |
| 6026 TraceTime t("GC", PrintGC, !PrintGCDetails, gclog_or_tty); | |
| 6027 TraceCollectorStats tcs(counters()); | |
| 6028 | |
| 6029 switch (op) { | |
| 6030 case CMS_op_checkpointRootsInitial: { | |
| 6031 checkpointRootsInitial(true); // asynch | |
| 6032 if (PrintGC) { | |
| 6033 _cmsGen->printOccupancy("initial-mark"); | |
| 6034 } | |
| 6035 break; | |
| 6036 } | |
| 6037 case CMS_op_checkpointRootsFinal: { | |
| 6038 checkpointRootsFinal(true, // asynch | |
| 6039 false, // !clear_all_soft_refs | |
| 6040 false); // !init_mark_was_synchronous | |
| 6041 if (PrintGC) { | |
| 6042 _cmsGen->printOccupancy("remark"); | |
| 6043 } | |
| 6044 break; | |
| 6045 } | |
| 6046 default: | |
| 6047 fatal("No such CMS_op"); | |
| 6048 } | |
| 6049 } | |
| 6050 | |
| 6051 #ifndef PRODUCT | |
| 6052 size_t const CMSCollector::skip_header_HeapWords() { | |
| 6053 return FreeChunk::header_size(); | |
| 6054 } | |
| 6055 | |
| 6056 // Try and collect here conditions that should hold when | |
| 6057 // CMS thread is exiting. The idea is that the foreground GC | |
| 6058 // thread should not be blocked if it wants to terminate | |
| 6059 // the CMS thread and yet continue to run the VM for a while | |
| 6060 // after that. | |
| 6061 void CMSCollector::verify_ok_to_terminate() const { | |
| 6062 assert(Thread::current()->is_ConcurrentGC_thread(), | |
| 6063 "should be called by CMS thread"); | |
| 6064 assert(!_foregroundGCShouldWait, "should be false"); | |
| 6065 // We could check here that all the various low-level locks | |
| 6066 // are not held by the CMS thread, but that is overkill; see | |
| 6067 // also CMSThread::verify_ok_to_terminate() where the CGC_lock | |
| 6068 // is checked. | |
| 6069 } | |
| 6070 #endif | |
| 6071 | |
| 6072 size_t CMSCollector::block_size_using_printezis_bits(HeapWord* addr) const { | |
| 6073 assert(_markBitMap.isMarked(addr) && _markBitMap.isMarked(addr + 1), | |
| 6074 "missing Printezis mark?"); | |
| 6075 HeapWord* nextOneAddr = _markBitMap.getNextMarkedWordAddress(addr + 2); | |
| 6076 size_t size = pointer_delta(nextOneAddr + 1, addr); | |
| 6077 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
| 6078 "alignment problem"); | |
| 6079 assert(size >= 3, "Necessary for Printezis marks to work"); | |
| 6080 return size; | |
| 6081 } | |
| 6082 | |
| 6083 // A variant of the above (block_size_using_printezis_bits()) except | |
| 6084 // that we return 0 if the P-bits are not yet set. | |
| 6085 size_t CMSCollector::block_size_if_printezis_bits(HeapWord* addr) const { | |
| 6086 if (_markBitMap.isMarked(addr)) { | |
| 6087 assert(_markBitMap.isMarked(addr + 1), "Missing Printezis bit?"); | |
| 6088 HeapWord* nextOneAddr = _markBitMap.getNextMarkedWordAddress(addr + 2); | |
| 6089 size_t size = pointer_delta(nextOneAddr + 1, addr); | |
| 6090 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
| 6091 "alignment problem"); | |
| 6092 assert(size >= 3, "Necessary for Printezis marks to work"); | |
| 6093 return size; | |
| 6094 } else { | |
| 6095 assert(!_markBitMap.isMarked(addr + 1), "Bit map inconsistency?"); | |
| 6096 return 0; | |
| 6097 } | |
| 6098 } | |
| 6099 | |
| 6100 HeapWord* CMSCollector::next_card_start_after_block(HeapWord* addr) const { | |
| 6101 size_t sz = 0; | |
| 6102 oop p = (oop)addr; | |
| 6103 if (p->klass() != NULL && p->is_parsable()) { | |
| 6104 sz = CompactibleFreeListSpace::adjustObjectSize(p->size()); | |
| 6105 } else { | |
| 6106 sz = block_size_using_printezis_bits(addr); | |
| 6107 } | |
| 6108 assert(sz > 0, "size must be nonzero"); | |
| 6109 HeapWord* next_block = addr + sz; | |
| 6110 HeapWord* next_card = (HeapWord*)round_to((uintptr_t)next_block, | |
| 6111 CardTableModRefBS::card_size); | |
| 6112 assert(round_down((uintptr_t)addr, CardTableModRefBS::card_size) < | |
| 6113 round_down((uintptr_t)next_card, CardTableModRefBS::card_size), | |
| 6114 "must be different cards"); | |
| 6115 return next_card; | |
| 6116 } | |
| 6117 | |
| 6118 | |
| 6119 // CMS Bit Map Wrapper ///////////////////////////////////////// | |
| 6120 | |
| 6121 // Construct a CMS bit map infrastructure, but don't create the | |
| 6122 // bit vector itself. That is done by a separate call CMSBitMap::allocate() | |
| 6123 // further below. | |
| 6124 CMSBitMap::CMSBitMap(int shifter, int mutex_rank, const char* mutex_name): | |
| 6125 _bm(NULL,0), | |
| 6126 _shifter(shifter), | |
| 6127 _lock(mutex_rank >= 0 ? new Mutex(mutex_rank, mutex_name, true) : NULL) | |
| 6128 { | |
| 6129 _bmStartWord = 0; | |
| 6130 _bmWordSize = 0; | |
| 6131 } | |
| 6132 | |
| 6133 bool CMSBitMap::allocate(MemRegion mr) { | |
| 6134 _bmStartWord = mr.start(); | |
| 6135 _bmWordSize = mr.word_size(); | |
| 6136 ReservedSpace brs(ReservedSpace::allocation_align_size_up( | |
| 6137 (_bmWordSize >> (_shifter + LogBitsPerByte)) + 1)); | |
| 6138 if (!brs.is_reserved()) { | |
| 6139 warning("CMS bit map allocation failure"); | |
| 6140 return false; | |
| 6141 } | |
| 6142 // For now we'll just commit all of the bit map up fromt. | |
| 6143 // Later on we'll try to be more parsimonious with swap. | |
| 6144 if (!_virtual_space.initialize(brs, brs.size())) { | |
| 6145 warning("CMS bit map backing store failure"); | |
| 6146 return false; | |
| 6147 } | |
| 6148 assert(_virtual_space.committed_size() == brs.size(), | |
| 6149 "didn't reserve backing store for all of CMS bit map?"); | |
| 6150 _bm.set_map((uintptr_t*)_virtual_space.low()); | |
| 6151 assert(_virtual_space.committed_size() << (_shifter + LogBitsPerByte) >= | |
| 6152 _bmWordSize, "inconsistency in bit map sizing"); | |
| 6153 _bm.set_size(_bmWordSize >> _shifter); | |
| 6154 | |
| 6155 // bm.clear(); // can we rely on getting zero'd memory? verify below | |
| 6156 assert(isAllClear(), | |
| 6157 "Expected zero'd memory from ReservedSpace constructor"); | |
| 6158 assert(_bm.size() == heapWordDiffToOffsetDiff(sizeInWords()), | |
| 6159 "consistency check"); | |
| 6160 return true; | |
| 6161 } | |
| 6162 | |
| 6163 void CMSBitMap::dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl) { | |
| 6164 HeapWord *next_addr, *end_addr, *last_addr; | |
| 6165 assert_locked(); | |
| 6166 assert(covers(mr), "out-of-range error"); | |
| 6167 // XXX assert that start and end are appropriately aligned | |
| 6168 for (next_addr = mr.start(), end_addr = mr.end(); | |
| 6169 next_addr < end_addr; next_addr = last_addr) { | |
| 6170 MemRegion dirty_region = getAndClearMarkedRegion(next_addr, end_addr); | |
| 6171 last_addr = dirty_region.end(); | |
| 6172 if (!dirty_region.is_empty()) { | |
| 6173 cl->do_MemRegion(dirty_region); | |
| 6174 } else { | |
| 6175 assert(last_addr == end_addr, "program logic"); | |
| 6176 return; | |
| 6177 } | |
| 6178 } | |
| 6179 } | |
| 6180 | |
| 6181 #ifndef PRODUCT | |
| 6182 void CMSBitMap::assert_locked() const { | |
| 6183 CMSLockVerifier::assert_locked(lock()); | |
| 6184 } | |
| 6185 | |
| 6186 bool CMSBitMap::covers(MemRegion mr) const { | |
| 6187 // assert(_bm.map() == _virtual_space.low(), "map inconsistency"); | |
| 6188 assert((size_t)_bm.size() == (_bmWordSize >> _shifter), | |
| 6189 "size inconsistency"); | |
| 6190 return (mr.start() >= _bmStartWord) && | |
| 6191 (mr.end() <= endWord()); | |
| 6192 } | |
| 6193 | |
| 6194 bool CMSBitMap::covers(HeapWord* start, size_t size) const { | |
| 6195 return (start >= _bmStartWord && (start + size) <= endWord()); | |
| 6196 } | |
| 6197 | |
| 6198 void CMSBitMap::verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) { | |
| 6199 // verify that there are no 1 bits in the interval [left, right) | |
| 6200 FalseBitMapClosure falseBitMapClosure; | |
| 6201 iterate(&falseBitMapClosure, left, right); | |
| 6202 } | |
| 6203 | |
| 6204 void CMSBitMap::region_invariant(MemRegion mr) | |
| 6205 { | |
| 6206 assert_locked(); | |
| 6207 // mr = mr.intersection(MemRegion(_bmStartWord, _bmWordSize)); | |
| 6208 assert(!mr.is_empty(), "unexpected empty region"); | |
| 6209 assert(covers(mr), "mr should be covered by bit map"); | |
| 6210 // convert address range into offset range | |
| 6211 size_t start_ofs = heapWordToOffset(mr.start()); | |
| 6212 // Make sure that end() is appropriately aligned | |
| 6213 assert(mr.end() == (HeapWord*)round_to((intptr_t)mr.end(), | |
| 6214 (1 << (_shifter+LogHeapWordSize))), | |
| 6215 "Misaligned mr.end()"); | |
| 6216 size_t end_ofs = heapWordToOffset(mr.end()); | |
| 6217 assert(end_ofs > start_ofs, "Should mark at least one bit"); | |
| 6218 } | |
| 6219 | |
| 6220 #endif | |
| 6221 | |
| 6222 bool CMSMarkStack::allocate(size_t size) { | |
| 6223 // allocate a stack of the requisite depth | |
| 6224 ReservedSpace rs(ReservedSpace::allocation_align_size_up( | |
| 6225 size * sizeof(oop))); | |
| 6226 if (!rs.is_reserved()) { | |
| 6227 warning("CMSMarkStack allocation failure"); | |
| 6228 return false; | |
| 6229 } | |
| 6230 if (!_virtual_space.initialize(rs, rs.size())) { | |
| 6231 warning("CMSMarkStack backing store failure"); | |
| 6232 return false; | |
| 6233 } | |
| 6234 assert(_virtual_space.committed_size() == rs.size(), | |
| 6235 "didn't reserve backing store for all of CMS stack?"); | |
| 6236 _base = (oop*)(_virtual_space.low()); | |
| 6237 _index = 0; | |
| 6238 _capacity = size; | |
| 6239 NOT_PRODUCT(_max_depth = 0); | |
| 6240 return true; | |
| 6241 } | |
| 6242 | |
| 6243 // XXX FIX ME !!! In the MT case we come in here holding a | |
| 6244 // leaf lock. For printing we need to take a further lock | |
| 6245 // which has lower rank. We need to recallibrate the two | |
| 6246 // lock-ranks involved in order to be able to rpint the | |
| 6247 // messages below. (Or defer the printing to the caller. | |
| 6248 // For now we take the expedient path of just disabling the | |
| 6249 // messages for the problematic case.) | |
| 6250 void CMSMarkStack::expand() { | |
| 6251 assert(_capacity <= CMSMarkStackSizeMax, "stack bigger than permitted"); | |
| 6252 if (_capacity == CMSMarkStackSizeMax) { | |
| 6253 if (_hit_limit++ == 0 && !CMSConcurrentMTEnabled && PrintGCDetails) { | |
| 6254 // We print a warning message only once per CMS cycle. | |
| 6255 gclog_or_tty->print_cr(" (benign) Hit CMSMarkStack max size limit"); | |
| 6256 } | |
| 6257 return; | |
| 6258 } | |
| 6259 // Double capacity if possible | |
| 6260 size_t new_capacity = MIN2(_capacity*2, CMSMarkStackSizeMax); | |
| 6261 // Do not give up existing stack until we have managed to | |
| 6262 // get the double capacity that we desired. | |
| 6263 ReservedSpace rs(ReservedSpace::allocation_align_size_up( | |
| 6264 new_capacity * sizeof(oop))); | |
| 6265 if (rs.is_reserved()) { | |
| 6266 // Release the backing store associated with old stack | |
| 6267 _virtual_space.release(); | |
| 6268 // Reinitialize virtual space for new stack | |
| 6269 if (!_virtual_space.initialize(rs, rs.size())) { | |
| 6270 fatal("Not enough swap for expanded marking stack"); | |
| 6271 } | |
| 6272 _base = (oop*)(_virtual_space.low()); | |
| 6273 _index = 0; | |
| 6274 _capacity = new_capacity; | |
| 6275 } else if (_failed_double++ == 0 && !CMSConcurrentMTEnabled && PrintGCDetails) { | |
| 6276 // Failed to double capacity, continue; | |
| 6277 // we print a detail message only once per CMS cycle. | |
| 6278 gclog_or_tty->print(" (benign) Failed to expand marking stack from "SIZE_FORMAT"K to " | |
| 6279 SIZE_FORMAT"K", | |
| 6280 _capacity / K, new_capacity / K); | |
| 6281 } | |
| 6282 } | |
| 6283 | |
| 6284 | |
| 6285 // Closures | |
| 6286 // XXX: there seems to be a lot of code duplication here; | |
| 6287 // should refactor and consolidate common code. | |
| 6288 | |
| 6289 // This closure is used to mark refs into the CMS generation in | |
| 6290 // the CMS bit map. Called at the first checkpoint. This closure | |
| 6291 // assumes that we do not need to re-mark dirty cards; if the CMS | |
| 6292 // generation on which this is used is not an oldest (modulo perm gen) | |
| 6293 // generation then this will lose younger_gen cards! | |
| 6294 | |
| 6295 MarkRefsIntoClosure::MarkRefsIntoClosure( | |
| 6296 MemRegion span, CMSBitMap* bitMap, bool should_do_nmethods): | |
| 6297 _span(span), | |
| 6298 _bitMap(bitMap), | |
| 6299 _should_do_nmethods(should_do_nmethods) | |
| 6300 { | |
| 6301 assert(_ref_processor == NULL, "deliberately left NULL"); | |
| 6302 assert(_bitMap->covers(_span), "_bitMap/_span mismatch"); | |
| 6303 } | |
| 6304 | |
| 6305 void MarkRefsIntoClosure::do_oop(oop* p) { | |
| 6306 // if p points into _span, then mark corresponding bit in _markBitMap | |
| 6307 oop thisOop = *p; | |
| 6308 if (thisOop != NULL) { | |
| 6309 assert(thisOop->is_oop(), "expected an oop"); | |
| 6310 HeapWord* addr = (HeapWord*)thisOop; | |
| 6311 if (_span.contains(addr)) { | |
| 6312 // this should be made more efficient | |
| 6313 _bitMap->mark(addr); | |
| 6314 } | |
| 6315 } | |
| 6316 } | |
| 6317 | |
| 6318 // A variant of the above, used for CMS marking verification. | |
| 6319 MarkRefsIntoVerifyClosure::MarkRefsIntoVerifyClosure( | |
| 6320 MemRegion span, CMSBitMap* verification_bm, CMSBitMap* cms_bm, | |
| 6321 bool should_do_nmethods): | |
| 6322 _span(span), | |
| 6323 _verification_bm(verification_bm), | |
| 6324 _cms_bm(cms_bm), | |
| 6325 _should_do_nmethods(should_do_nmethods) { | |
| 6326 assert(_ref_processor == NULL, "deliberately left NULL"); | |
| 6327 assert(_verification_bm->covers(_span), "_verification_bm/_span mismatch"); | |
| 6328 } | |
| 6329 | |
| 6330 void MarkRefsIntoVerifyClosure::do_oop(oop* p) { | |
| 6331 // if p points into _span, then mark corresponding bit in _markBitMap | |
| 6332 oop this_oop = *p; | |
| 6333 if (this_oop != NULL) { | |
| 6334 assert(this_oop->is_oop(), "expected an oop"); | |
| 6335 HeapWord* addr = (HeapWord*)this_oop; | |
| 6336 if (_span.contains(addr)) { | |
| 6337 _verification_bm->mark(addr); | |
| 6338 if (!_cms_bm->isMarked(addr)) { | |
| 6339 oop(addr)->print(); | |
| 6340 gclog_or_tty->print_cr(" ("INTPTR_FORMAT" should have been marked)", addr); | |
| 6341 fatal("... aborting"); | |
| 6342 } | |
| 6343 } | |
| 6344 } | |
| 6345 } | |
| 6346 | |
| 6347 ////////////////////////////////////////////////// | |
| 6348 // MarkRefsIntoAndScanClosure | |
| 6349 ////////////////////////////////////////////////// | |
| 6350 | |
| 6351 MarkRefsIntoAndScanClosure::MarkRefsIntoAndScanClosure(MemRegion span, | |
| 6352 ReferenceProcessor* rp, | |
| 6353 CMSBitMap* bit_map, | |
| 6354 CMSBitMap* mod_union_table, | |
| 6355 CMSMarkStack* mark_stack, | |
| 6356 CMSMarkStack* revisit_stack, | |
| 6357 CMSCollector* collector, | |
| 6358 bool should_yield, | |
| 6359 bool concurrent_precleaning): | |
| 6360 _collector(collector), | |
| 6361 _span(span), | |
| 6362 _bit_map(bit_map), | |
| 6363 _mark_stack(mark_stack), | |
| 6364 _pushAndMarkClosure(collector, span, rp, bit_map, mod_union_table, | |
| 6365 mark_stack, revisit_stack, concurrent_precleaning), | |
| 6366 _yield(should_yield), | |
| 6367 _concurrent_precleaning(concurrent_precleaning), | |
| 6368 _freelistLock(NULL) | |
| 6369 { | |
| 6370 _ref_processor = rp; | |
| 6371 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
| 6372 } | |
| 6373 | |
| 6374 // This closure is used to mark refs into the CMS generation at the | |
| 6375 // second (final) checkpoint, and to scan and transitively follow | |
| 6376 // the unmarked oops. It is also used during the concurrent precleaning | |
| 6377 // phase while scanning objects on dirty cards in the CMS generation. | |
| 6378 // The marks are made in the marking bit map and the marking stack is | |
| 6379 // used for keeping the (newly) grey objects during the scan. | |
| 6380 // The parallel version (Par_...) appears further below. | |
| 6381 void MarkRefsIntoAndScanClosure::do_oop(oop* p) { | |
| 6382 oop this_oop = *p; | |
| 6383 if (this_oop != NULL) { | |
| 6384 assert(this_oop->is_oop(), "expected an oop"); | |
| 6385 HeapWord* addr = (HeapWord*)this_oop; | |
| 6386 assert(_mark_stack->isEmpty(), "post-condition (eager drainage)"); | |
| 6387 assert(_collector->overflow_list_is_empty(), "should be empty"); | |
| 6388 if (_span.contains(addr) && | |
| 6389 !_bit_map->isMarked(addr)) { | |
| 6390 // mark bit map (object is now grey) | |
| 6391 _bit_map->mark(addr); | |
| 6392 // push on marking stack (stack should be empty), and drain the | |
| 6393 // stack by applying this closure to the oops in the oops popped | |
| 6394 // from the stack (i.e. blacken the grey objects) | |
| 6395 bool res = _mark_stack->push(this_oop); | |
| 6396 assert(res, "Should have space to push on empty stack"); | |
| 6397 do { | |
| 6398 oop new_oop = _mark_stack->pop(); | |
| 6399 assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop"); | |
| 6400 assert(new_oop->is_parsable(), "Found unparsable oop"); | |
| 6401 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
| 6402 "only grey objects on this stack"); | |
| 6403 // iterate over the oops in this oop, marking and pushing | |
| 6404 // the ones in CMS heap (i.e. in _span). | |
| 6405 new_oop->oop_iterate(&_pushAndMarkClosure); | |
| 6406 // check if it's time to yield | |
| 6407 do_yield_check(); | |
| 6408 } while (!_mark_stack->isEmpty() || | |
| 6409 (!_concurrent_precleaning && take_from_overflow_list())); | |
| 6410 // if marking stack is empty, and we are not doing this | |
| 6411 // during precleaning, then check the overflow list | |
| 6412 } | |
| 6413 assert(_mark_stack->isEmpty(), "post-condition (eager drainage)"); | |
| 6414 assert(_collector->overflow_list_is_empty(), | |
| 6415 "overflow list was drained above"); | |
| 6416 // We could restore evacuated mark words, if any, used for | |
| 6417 // overflow list links here because the overflow list is | |
| 6418 // provably empty here. That would reduce the maximum | |
| 6419 // size requirements for preserved_{oop,mark}_stack. | |
| 6420 // But we'll just postpone it until we are all done | |
| 6421 // so we can just stream through. | |
| 6422 if (!_concurrent_precleaning && CMSOverflowEarlyRestoration) { | |
| 6423 _collector->restore_preserved_marks_if_any(); | |
| 6424 assert(_collector->no_preserved_marks(), "No preserved marks"); | |
| 6425 } | |
| 6426 assert(!CMSOverflowEarlyRestoration || _collector->no_preserved_marks(), | |
| 6427 "All preserved marks should have been restored above"); | |
| 6428 } | |
| 6429 } | |
| 6430 | |
| 6431 void MarkRefsIntoAndScanClosure::do_yield_work() { | |
| 6432 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 6433 "CMS thread should hold CMS token"); | |
| 6434 assert_lock_strong(_freelistLock); | |
| 6435 assert_lock_strong(_bit_map->lock()); | |
| 6436 // relinquish the free_list_lock and bitMaplock() | |
| 6437 _bit_map->lock()->unlock(); | |
| 6438 _freelistLock->unlock(); | |
| 6439 ConcurrentMarkSweepThread::desynchronize(true); | |
| 6440 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 6441 _collector->stopTimer(); | |
| 6442 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
| 6443 if (PrintCMSStatistics != 0) { | |
| 6444 _collector->incrementYields(); | |
| 6445 } | |
| 6446 _collector->icms_wait(); | |
| 6447 | |
| 6448 // See the comment in coordinator_yield() | |
| 6449 for (unsigned i = 0; i < CMSYieldSleepCount && | |
| 6450 ConcurrentMarkSweepThread::should_yield() && | |
| 6451 !CMSCollector::foregroundGCIsActive(); ++i) { | |
| 6452 os::sleep(Thread::current(), 1, false); | |
| 6453 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 6454 } | |
| 6455 | |
| 6456 ConcurrentMarkSweepThread::synchronize(true); | |
| 6457 _freelistLock->lock_without_safepoint_check(); | |
| 6458 _bit_map->lock()->lock_without_safepoint_check(); | |
| 6459 _collector->startTimer(); | |
| 6460 } | |
| 6461 | |
| 6462 /////////////////////////////////////////////////////////// | |
| 6463 // Par_MarkRefsIntoAndScanClosure: a parallel version of | |
| 6464 // MarkRefsIntoAndScanClosure | |
| 6465 /////////////////////////////////////////////////////////// | |
| 6466 Par_MarkRefsIntoAndScanClosure::Par_MarkRefsIntoAndScanClosure( | |
| 6467 CMSCollector* collector, MemRegion span, ReferenceProcessor* rp, | |
| 6468 CMSBitMap* bit_map, OopTaskQueue* work_queue, CMSMarkStack* revisit_stack): | |
| 6469 _span(span), | |
| 6470 _bit_map(bit_map), | |
| 6471 _work_queue(work_queue), | |
| 6472 _low_water_mark(MIN2((uint)(work_queue->max_elems()/4), | |
| 6473 (uint)(CMSWorkQueueDrainThreshold * ParallelGCThreads))), | |
| 6474 _par_pushAndMarkClosure(collector, span, rp, bit_map, work_queue, | |
| 6475 revisit_stack) | |
| 6476 { | |
| 6477 _ref_processor = rp; | |
| 6478 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
| 6479 } | |
| 6480 | |
| 6481 // This closure is used to mark refs into the CMS generation at the | |
| 6482 // second (final) checkpoint, and to scan and transitively follow | |
| 6483 // the unmarked oops. The marks are made in the marking bit map and | |
| 6484 // the work_queue is used for keeping the (newly) grey objects during | |
| 6485 // the scan phase whence they are also available for stealing by parallel | |
| 6486 // threads. Since the marking bit map is shared, updates are | |
| 6487 // synchronized (via CAS). | |
| 6488 void Par_MarkRefsIntoAndScanClosure::do_oop(oop* p) { | |
| 6489 oop this_oop = *p; | |
| 6490 if (this_oop != NULL) { | |
| 6491 // Ignore mark word because this could be an already marked oop | |
| 6492 // that may be chained at the end of the overflow list. | |
| 6493 assert(this_oop->is_oop(true /* ignore mark word */), "expected an oop"); | |
| 6494 HeapWord* addr = (HeapWord*)this_oop; | |
| 6495 if (_span.contains(addr) && | |
| 6496 !_bit_map->isMarked(addr)) { | |
| 6497 // mark bit map (object will become grey): | |
| 6498 // It is possible for several threads to be | |
| 6499 // trying to "claim" this object concurrently; | |
| 6500 // the unique thread that succeeds in marking the | |
| 6501 // object first will do the subsequent push on | |
| 6502 // to the work queue (or overflow list). | |
| 6503 if (_bit_map->par_mark(addr)) { | |
| 6504 // push on work_queue (which may not be empty), and trim the | |
| 6505 // queue to an appropriate length by applying this closure to | |
| 6506 // the oops in the oops popped from the stack (i.e. blacken the | |
| 6507 // grey objects) | |
| 6508 bool res = _work_queue->push(this_oop); | |
| 6509 assert(res, "Low water mark should be less than capacity?"); | |
| 6510 trim_queue(_low_water_mark); | |
| 6511 } // Else, another thread claimed the object | |
| 6512 } | |
| 6513 } | |
| 6514 } | |
| 6515 | |
| 6516 // This closure is used to rescan the marked objects on the dirty cards | |
| 6517 // in the mod union table and the card table proper. | |
| 6518 size_t ScanMarkedObjectsAgainCarefullyClosure::do_object_careful_m( | |
| 6519 oop p, MemRegion mr) { | |
| 6520 | |
| 6521 size_t size = 0; | |
| 6522 HeapWord* addr = (HeapWord*)p; | |
| 6523 DEBUG_ONLY(_collector->verify_work_stacks_empty();) | |
| 6524 assert(_span.contains(addr), "we are scanning the CMS generation"); | |
| 6525 // check if it's time to yield | |
| 6526 if (do_yield_check()) { | |
| 6527 // We yielded for some foreground stop-world work, | |
| 6528 // and we have been asked to abort this ongoing preclean cycle. | |
| 6529 return 0; | |
| 6530 } | |
| 6531 if (_bitMap->isMarked(addr)) { | |
| 6532 // it's marked; is it potentially uninitialized? | |
| 6533 if (p->klass() != NULL) { | |
| 6534 if (CMSPermGenPrecleaningEnabled && !p->is_parsable()) { | |
| 6535 // Signal precleaning to redirty the card since | |
| 6536 // the klass pointer is already installed. | |
| 6537 assert(size == 0, "Initial value"); | |
| 6538 } else { | |
| 6539 assert(p->is_parsable(), "must be parsable."); | |
| 6540 // an initialized object; ignore mark word in verification below | |
| 6541 // since we are running concurrent with mutators | |
| 6542 assert(p->is_oop(true), "should be an oop"); | |
| 6543 if (p->is_objArray()) { | |
| 6544 // objArrays are precisely marked; restrict scanning | |
| 6545 // to dirty cards only. | |
| 6546 size = p->oop_iterate(_scanningClosure, mr); | |
| 6547 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
| 6548 "adjustObjectSize should be the identity for array sizes, " | |
| 6549 "which are necessarily larger than minimum object size of " | |
| 6550 "two heap words"); | |
| 6551 } else { | |
| 6552 // A non-array may have been imprecisely marked; we need | |
| 6553 // to scan object in its entirety. | |
| 6554 size = CompactibleFreeListSpace::adjustObjectSize( | |
| 6555 p->oop_iterate(_scanningClosure)); | |
| 6556 } | |
| 6557 #ifdef DEBUG | |
| 6558 size_t direct_size = | |
| 6559 CompactibleFreeListSpace::adjustObjectSize(p->size()); | |
| 6560 assert(size == direct_size, "Inconsistency in size"); | |
| 6561 assert(size >= 3, "Necessary for Printezis marks to work"); | |
| 6562 if (!_bitMap->isMarked(addr+1)) { | |
| 6563 _bitMap->verifyNoOneBitsInRange(addr+2, addr+size); | |
| 6564 } else { | |
| 6565 _bitMap->verifyNoOneBitsInRange(addr+2, addr+size-1); | |
| 6566 assert(_bitMap->isMarked(addr+size-1), | |
| 6567 "inconsistent Printezis mark"); | |
| 6568 } | |
| 6569 #endif // DEBUG | |
| 6570 } | |
| 6571 } else { | |
| 6572 // an unitialized object | |
| 6573 assert(_bitMap->isMarked(addr+1), "missing Printezis mark?"); | |
| 6574 HeapWord* nextOneAddr = _bitMap->getNextMarkedWordAddress(addr + 2); | |
| 6575 size = pointer_delta(nextOneAddr + 1, addr); | |
| 6576 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
| 6577 "alignment problem"); | |
| 6578 // Note that pre-cleaning needn't redirty the card. OopDesc::set_klass() | |
| 6579 // will dirty the card when the klass pointer is installed in the | |
| 6580 // object (signalling the completion of initialization). | |
| 6581 } | |
| 6582 } else { | |
| 6583 // Either a not yet marked object or an uninitialized object | |
| 6584 if (p->klass() == NULL || !p->is_parsable()) { | |
| 6585 // An uninitialized object, skip to the next card, since | |
| 6586 // we may not be able to read its P-bits yet. | |
| 6587 assert(size == 0, "Initial value"); | |
| 6588 } else { | |
| 6589 // An object not (yet) reached by marking: we merely need to | |
| 6590 // compute its size so as to go look at the next block. | |
| 6591 assert(p->is_oop(true), "should be an oop"); | |
| 6592 size = CompactibleFreeListSpace::adjustObjectSize(p->size()); | |
| 6593 } | |
| 6594 } | |
| 6595 DEBUG_ONLY(_collector->verify_work_stacks_empty();) | |
| 6596 return size; | |
| 6597 } | |
| 6598 | |
| 6599 void ScanMarkedObjectsAgainCarefullyClosure::do_yield_work() { | |
| 6600 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 6601 "CMS thread should hold CMS token"); | |
| 6602 assert_lock_strong(_freelistLock); | |
| 6603 assert_lock_strong(_bitMap->lock()); | |
| 6604 // relinquish the free_list_lock and bitMaplock() | |
| 6605 _bitMap->lock()->unlock(); | |
| 6606 _freelistLock->unlock(); | |
| 6607 ConcurrentMarkSweepThread::desynchronize(true); | |
| 6608 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 6609 _collector->stopTimer(); | |
| 6610 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
| 6611 if (PrintCMSStatistics != 0) { | |
| 6612 _collector->incrementYields(); | |
| 6613 } | |
| 6614 _collector->icms_wait(); | |
| 6615 | |
| 6616 // See the comment in coordinator_yield() | |
| 6617 for (unsigned i = 0; i < CMSYieldSleepCount && | |
| 6618 ConcurrentMarkSweepThread::should_yield() && | |
| 6619 !CMSCollector::foregroundGCIsActive(); ++i) { | |
| 6620 os::sleep(Thread::current(), 1, false); | |
| 6621 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 6622 } | |
| 6623 | |
| 6624 ConcurrentMarkSweepThread::synchronize(true); | |
| 6625 _freelistLock->lock_without_safepoint_check(); | |
| 6626 _bitMap->lock()->lock_without_safepoint_check(); | |
| 6627 _collector->startTimer(); | |
| 6628 } | |
| 6629 | |
| 6630 | |
| 6631 ////////////////////////////////////////////////////////////////// | |
| 6632 // SurvivorSpacePrecleanClosure | |
| 6633 ////////////////////////////////////////////////////////////////// | |
| 6634 // This (single-threaded) closure is used to preclean the oops in | |
| 6635 // the survivor spaces. | |
| 6636 size_t SurvivorSpacePrecleanClosure::do_object_careful(oop p) { | |
| 6637 | |
| 6638 HeapWord* addr = (HeapWord*)p; | |
| 6639 DEBUG_ONLY(_collector->verify_work_stacks_empty();) | |
| 6640 assert(!_span.contains(addr), "we are scanning the survivor spaces"); | |
| 6641 assert(p->klass() != NULL, "object should be initializd"); | |
| 6642 assert(p->is_parsable(), "must be parsable."); | |
| 6643 // an initialized object; ignore mark word in verification below | |
| 6644 // since we are running concurrent with mutators | |
| 6645 assert(p->is_oop(true), "should be an oop"); | |
| 6646 // Note that we do not yield while we iterate over | |
| 6647 // the interior oops of p, pushing the relevant ones | |
| 6648 // on our marking stack. | |
| 6649 size_t size = p->oop_iterate(_scanning_closure); | |
| 6650 do_yield_check(); | |
| 6651 // Observe that below, we do not abandon the preclean | |
| 6652 // phase as soon as we should; rather we empty the | |
| 6653 // marking stack before returning. This is to satisfy | |
| 6654 // some existing assertions. In general, it may be a | |
| 6655 // good idea to abort immediately and complete the marking | |
| 6656 // from the grey objects at a later time. | |
| 6657 while (!_mark_stack->isEmpty()) { | |
| 6658 oop new_oop = _mark_stack->pop(); | |
| 6659 assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop"); | |
| 6660 assert(new_oop->is_parsable(), "Found unparsable oop"); | |
| 6661 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
| 6662 "only grey objects on this stack"); | |
| 6663 // iterate over the oops in this oop, marking and pushing | |
| 6664 // the ones in CMS heap (i.e. in _span). | |
| 6665 new_oop->oop_iterate(_scanning_closure); | |
| 6666 // check if it's time to yield | |
| 6667 do_yield_check(); | |
| 6668 } | |
| 6669 unsigned int after_count = | |
| 6670 GenCollectedHeap::heap()->total_collections(); | |
| 6671 bool abort = (_before_count != after_count) || | |
| 6672 _collector->should_abort_preclean(); | |
| 6673 return abort ? 0 : size; | |
| 6674 } | |
| 6675 | |
| 6676 void SurvivorSpacePrecleanClosure::do_yield_work() { | |
| 6677 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 6678 "CMS thread should hold CMS token"); | |
| 6679 assert_lock_strong(_bit_map->lock()); | |
| 6680 // Relinquish the bit map lock | |
| 6681 _bit_map->lock()->unlock(); | |
| 6682 ConcurrentMarkSweepThread::desynchronize(true); | |
| 6683 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 6684 _collector->stopTimer(); | |
| 6685 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
| 6686 if (PrintCMSStatistics != 0) { | |
| 6687 _collector->incrementYields(); | |
| 6688 } | |
| 6689 _collector->icms_wait(); | |
| 6690 | |
| 6691 // See the comment in coordinator_yield() | |
| 6692 for (unsigned i = 0; i < CMSYieldSleepCount && | |
| 6693 ConcurrentMarkSweepThread::should_yield() && | |
| 6694 !CMSCollector::foregroundGCIsActive(); ++i) { | |
| 6695 os::sleep(Thread::current(), 1, false); | |
| 6696 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 6697 } | |
| 6698 | |
| 6699 ConcurrentMarkSweepThread::synchronize(true); | |
| 6700 _bit_map->lock()->lock_without_safepoint_check(); | |
| 6701 _collector->startTimer(); | |
| 6702 } | |
| 6703 | |
| 6704 // This closure is used to rescan the marked objects on the dirty cards | |
| 6705 // in the mod union table and the card table proper. In the parallel | |
| 6706 // case, although the bitMap is shared, we do a single read so the | |
| 6707 // isMarked() query is "safe". | |
| 6708 bool ScanMarkedObjectsAgainClosure::do_object_bm(oop p, MemRegion mr) { | |
| 6709 // Ignore mark word because we are running concurrent with mutators | |
| 6710 assert(p->is_oop_or_null(true), "expected an oop or null"); | |
| 6711 HeapWord* addr = (HeapWord*)p; | |
| 6712 assert(_span.contains(addr), "we are scanning the CMS generation"); | |
| 6713 bool is_obj_array = false; | |
| 6714 #ifdef DEBUG | |
| 6715 if (!_parallel) { | |
| 6716 assert(_mark_stack->isEmpty(), "pre-condition (eager drainage)"); | |
| 6717 assert(_collector->overflow_list_is_empty(), | |
| 6718 "overflow list should be empty"); | |
| 6719 | |
| 6720 } | |
| 6721 #endif // DEBUG | |
| 6722 if (_bit_map->isMarked(addr)) { | |
| 6723 // Obj arrays are precisely marked, non-arrays are not; | |
| 6724 // so we scan objArrays precisely and non-arrays in their | |
| 6725 // entirety. | |
| 6726 if (p->is_objArray()) { | |
| 6727 is_obj_array = true; | |
| 6728 if (_parallel) { | |
| 6729 p->oop_iterate(_par_scan_closure, mr); | |
| 6730 } else { | |
| 6731 p->oop_iterate(_scan_closure, mr); | |
| 6732 } | |
| 6733 } else { | |
| 6734 if (_parallel) { | |
| 6735 p->oop_iterate(_par_scan_closure); | |
| 6736 } else { | |
| 6737 p->oop_iterate(_scan_closure); | |
| 6738 } | |
| 6739 } | |
| 6740 } | |
| 6741 #ifdef DEBUG | |
| 6742 if (!_parallel) { | |
| 6743 assert(_mark_stack->isEmpty(), "post-condition (eager drainage)"); | |
| 6744 assert(_collector->overflow_list_is_empty(), | |
| 6745 "overflow list should be empty"); | |
| 6746 | |
| 6747 } | |
| 6748 #endif // DEBUG | |
| 6749 return is_obj_array; | |
| 6750 } | |
| 6751 | |
| 6752 MarkFromRootsClosure::MarkFromRootsClosure(CMSCollector* collector, | |
| 6753 MemRegion span, | |
| 6754 CMSBitMap* bitMap, CMSMarkStack* markStack, | |
| 6755 CMSMarkStack* revisitStack, | |
| 6756 bool should_yield, bool verifying): | |
| 6757 _collector(collector), | |
| 6758 _span(span), | |
| 6759 _bitMap(bitMap), | |
| 6760 _mut(&collector->_modUnionTable), | |
| 6761 _markStack(markStack), | |
| 6762 _revisitStack(revisitStack), | |
| 6763 _yield(should_yield), | |
| 6764 _skipBits(0) | |
| 6765 { | |
| 6766 assert(_markStack->isEmpty(), "stack should be empty"); | |
| 6767 _finger = _bitMap->startWord(); | |
| 6768 _threshold = _finger; | |
| 6769 assert(_collector->_restart_addr == NULL, "Sanity check"); | |
| 6770 assert(_span.contains(_finger), "Out of bounds _finger?"); | |
| 6771 DEBUG_ONLY(_verifying = verifying;) | |
| 6772 } | |
| 6773 | |
| 6774 void MarkFromRootsClosure::reset(HeapWord* addr) { | |
| 6775 assert(_markStack->isEmpty(), "would cause duplicates on stack"); | |
| 6776 assert(_span.contains(addr), "Out of bounds _finger?"); | |
| 6777 _finger = addr; | |
| 6778 _threshold = (HeapWord*)round_to( | |
| 6779 (intptr_t)_finger, CardTableModRefBS::card_size); | |
| 6780 } | |
| 6781 | |
| 6782 // Should revisit to see if this should be restructured for | |
| 6783 // greater efficiency. | |
| 6784 void MarkFromRootsClosure::do_bit(size_t offset) { | |
| 6785 if (_skipBits > 0) { | |
| 6786 _skipBits--; | |
| 6787 return; | |
| 6788 } | |
| 6789 // convert offset into a HeapWord* | |
| 6790 HeapWord* addr = _bitMap->startWord() + offset; | |
| 6791 assert(_bitMap->endWord() && addr < _bitMap->endWord(), | |
| 6792 "address out of range"); | |
| 6793 assert(_bitMap->isMarked(addr), "tautology"); | |
| 6794 if (_bitMap->isMarked(addr+1)) { | |
| 6795 // this is an allocated but not yet initialized object | |
| 6796 assert(_skipBits == 0, "tautology"); | |
| 6797 _skipBits = 2; // skip next two marked bits ("Printezis-marks") | |
| 6798 oop p = oop(addr); | |
| 6799 if (p->klass() == NULL || !p->is_parsable()) { | |
| 6800 DEBUG_ONLY(if (!_verifying) {) | |
| 6801 // We re-dirty the cards on which this object lies and increase | |
| 6802 // the _threshold so that we'll come back to scan this object | |
| 6803 // during the preclean or remark phase. (CMSCleanOnEnter) | |
| 6804 if (CMSCleanOnEnter) { | |
| 6805 size_t sz = _collector->block_size_using_printezis_bits(addr); | |
| 6806 HeapWord* start_card_addr = (HeapWord*)round_down( | |
| 6807 (intptr_t)addr, CardTableModRefBS::card_size); | |
| 6808 HeapWord* end_card_addr = (HeapWord*)round_to( | |
| 6809 (intptr_t)(addr+sz), CardTableModRefBS::card_size); | |
| 6810 MemRegion redirty_range = MemRegion(start_card_addr, end_card_addr); | |
| 6811 assert(!redirty_range.is_empty(), "Arithmetical tautology"); | |
| 6812 // Bump _threshold to end_card_addr; note that | |
| 6813 // _threshold cannot possibly exceed end_card_addr, anyhow. | |
| 6814 // This prevents future clearing of the card as the scan proceeds | |
| 6815 // to the right. | |
| 6816 assert(_threshold <= end_card_addr, | |
| 6817 "Because we are just scanning into this object"); | |
| 6818 if (_threshold < end_card_addr) { | |
| 6819 _threshold = end_card_addr; | |
| 6820 } | |
| 6821 if (p->klass() != NULL) { | |
| 6822 // Redirty the range of cards... | |
| 6823 _mut->mark_range(redirty_range); | |
| 6824 } // ...else the setting of klass will dirty the card anyway. | |
| 6825 } | |
| 6826 DEBUG_ONLY(}) | |
| 6827 return; | |
| 6828 } | |
| 6829 } | |
| 6830 scanOopsInOop(addr); | |
| 6831 } | |
| 6832 | |
| 6833 // We take a break if we've been at this for a while, | |
| 6834 // so as to avoid monopolizing the locks involved. | |
| 6835 void MarkFromRootsClosure::do_yield_work() { | |
| 6836 // First give up the locks, then yield, then re-lock | |
| 6837 // We should probably use a constructor/destructor idiom to | |
| 6838 // do this unlock/lock or modify the MutexUnlocker class to | |
| 6839 // serve our purpose. XXX | |
| 6840 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 6841 "CMS thread should hold CMS token"); | |
| 6842 assert_lock_strong(_bitMap->lock()); | |
| 6843 _bitMap->lock()->unlock(); | |
| 6844 ConcurrentMarkSweepThread::desynchronize(true); | |
| 6845 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 6846 _collector->stopTimer(); | |
| 6847 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
| 6848 if (PrintCMSStatistics != 0) { | |
| 6849 _collector->incrementYields(); | |
| 6850 } | |
| 6851 _collector->icms_wait(); | |
| 6852 | |
| 6853 // See the comment in coordinator_yield() | |
| 6854 for (unsigned i = 0; i < CMSYieldSleepCount && | |
| 6855 ConcurrentMarkSweepThread::should_yield() && | |
| 6856 !CMSCollector::foregroundGCIsActive(); ++i) { | |
| 6857 os::sleep(Thread::current(), 1, false); | |
| 6858 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 6859 } | |
| 6860 | |
| 6861 ConcurrentMarkSweepThread::synchronize(true); | |
| 6862 _bitMap->lock()->lock_without_safepoint_check(); | |
| 6863 _collector->startTimer(); | |
| 6864 } | |
| 6865 | |
| 6866 void MarkFromRootsClosure::scanOopsInOop(HeapWord* ptr) { | |
| 6867 assert(_bitMap->isMarked(ptr), "expected bit to be set"); | |
| 6868 assert(_markStack->isEmpty(), | |
| 6869 "should drain stack to limit stack usage"); | |
| 6870 // convert ptr to an oop preparatory to scanning | |
| 6871 oop this_oop = oop(ptr); | |
| 6872 // Ignore mark word in verification below, since we | |
| 6873 // may be running concurrent with mutators. | |
| 6874 assert(this_oop->is_oop(true), "should be an oop"); | |
| 6875 assert(_finger <= ptr, "_finger runneth ahead"); | |
| 6876 // advance the finger to right end of this object | |
| 6877 _finger = ptr + this_oop->size(); | |
| 6878 assert(_finger > ptr, "we just incremented it above"); | |
| 6879 // On large heaps, it may take us some time to get through | |
| 6880 // the marking phase (especially if running iCMS). During | |
| 6881 // this time it's possible that a lot of mutations have | |
| 6882 // accumulated in the card table and the mod union table -- | |
| 6883 // these mutation records are redundant until we have | |
| 6884 // actually traced into the corresponding card. | |
| 6885 // Here, we check whether advancing the finger would make | |
| 6886 // us cross into a new card, and if so clear corresponding | |
| 6887 // cards in the MUT (preclean them in the card-table in the | |
| 6888 // future). | |
| 6889 | |
| 6890 DEBUG_ONLY(if (!_verifying) {) | |
| 6891 // The clean-on-enter optimization is disabled by default, | |
| 6892 // until we fix 6178663. | |
| 6893 if (CMSCleanOnEnter && (_finger > _threshold)) { | |
| 6894 // [_threshold, _finger) represents the interval | |
| 6895 // of cards to be cleared in MUT (or precleaned in card table). | |
| 6896 // The set of cards to be cleared is all those that overlap | |
| 6897 // with the interval [_threshold, _finger); note that | |
| 6898 // _threshold is always kept card-aligned but _finger isn't | |
| 6899 // always card-aligned. | |
| 6900 HeapWord* old_threshold = _threshold; | |
| 6901 assert(old_threshold == (HeapWord*)round_to( | |
| 6902 (intptr_t)old_threshold, CardTableModRefBS::card_size), | |
| 6903 "_threshold should always be card-aligned"); | |
| 6904 _threshold = (HeapWord*)round_to( | |
| 6905 (intptr_t)_finger, CardTableModRefBS::card_size); | |
| 6906 MemRegion mr(old_threshold, _threshold); | |
| 6907 assert(!mr.is_empty(), "Control point invariant"); | |
| 6908 assert(_span.contains(mr), "Should clear within span"); | |
| 6909 // XXX When _finger crosses from old gen into perm gen | |
| 6910 // we may be doing unnecessary cleaning; do better in the | |
| 6911 // future by detecting that condition and clearing fewer | |
| 6912 // MUT/CT entries. | |
| 6913 _mut->clear_range(mr); | |
| 6914 } | |
| 6915 DEBUG_ONLY(}) | |
| 6916 | |
| 6917 // Note: the finger doesn't advance while we drain | |
| 6918 // the stack below. | |
| 6919 PushOrMarkClosure pushOrMarkClosure(_collector, | |
| 6920 _span, _bitMap, _markStack, | |
| 6921 _revisitStack, | |
| 6922 _finger, this); | |
| 6923 bool res = _markStack->push(this_oop); | |
| 6924 assert(res, "Empty non-zero size stack should have space for single push"); | |
| 6925 while (!_markStack->isEmpty()) { | |
| 6926 oop new_oop = _markStack->pop(); | |
| 6927 // Skip verifying header mark word below because we are | |
| 6928 // running concurrent with mutators. | |
| 6929 assert(new_oop->is_oop(true), "Oops! expected to pop an oop"); | |
| 6930 // now scan this oop's oops | |
| 6931 new_oop->oop_iterate(&pushOrMarkClosure); | |
| 6932 do_yield_check(); | |
| 6933 } | |
| 6934 assert(_markStack->isEmpty(), "tautology, emphasizing post-condition"); | |
| 6935 } | |
| 6936 | |
| 6937 Par_MarkFromRootsClosure::Par_MarkFromRootsClosure(CMSConcMarkingTask* task, | |
| 6938 CMSCollector* collector, MemRegion span, | |
| 6939 CMSBitMap* bit_map, | |
| 6940 OopTaskQueue* work_queue, | |
| 6941 CMSMarkStack* overflow_stack, | |
| 6942 CMSMarkStack* revisit_stack, | |
| 6943 bool should_yield): | |
| 6944 _collector(collector), | |
| 6945 _whole_span(collector->_span), | |
| 6946 _span(span), | |
| 6947 _bit_map(bit_map), | |
| 6948 _mut(&collector->_modUnionTable), | |
| 6949 _work_queue(work_queue), | |
| 6950 _overflow_stack(overflow_stack), | |
| 6951 _revisit_stack(revisit_stack), | |
| 6952 _yield(should_yield), | |
| 6953 _skip_bits(0), | |
| 6954 _task(task) | |
| 6955 { | |
| 6956 assert(_work_queue->size() == 0, "work_queue should be empty"); | |
| 6957 _finger = span.start(); | |
| 6958 _threshold = _finger; // XXX Defer clear-on-enter optimization for now | |
| 6959 assert(_span.contains(_finger), "Out of bounds _finger?"); | |
| 6960 } | |
| 6961 | |
| 6962 // Should revisit to see if this should be restructured for | |
| 6963 // greater efficiency. | |
| 6964 void Par_MarkFromRootsClosure::do_bit(size_t offset) { | |
| 6965 if (_skip_bits > 0) { | |
| 6966 _skip_bits--; | |
| 6967 return; | |
| 6968 } | |
| 6969 // convert offset into a HeapWord* | |
| 6970 HeapWord* addr = _bit_map->startWord() + offset; | |
| 6971 assert(_bit_map->endWord() && addr < _bit_map->endWord(), | |
| 6972 "address out of range"); | |
| 6973 assert(_bit_map->isMarked(addr), "tautology"); | |
| 6974 if (_bit_map->isMarked(addr+1)) { | |
| 6975 // this is an allocated object that might not yet be initialized | |
| 6976 assert(_skip_bits == 0, "tautology"); | |
| 6977 _skip_bits = 2; // skip next two marked bits ("Printezis-marks") | |
| 6978 oop p = oop(addr); | |
| 6979 if (p->klass() == NULL || !p->is_parsable()) { | |
| 6980 // in the case of Clean-on-Enter optimization, redirty card | |
| 6981 // and avoid clearing card by increasing the threshold. | |
| 6982 return; | |
| 6983 } | |
| 6984 } | |
| 6985 scan_oops_in_oop(addr); | |
| 6986 } | |
| 6987 | |
| 6988 void Par_MarkFromRootsClosure::scan_oops_in_oop(HeapWord* ptr) { | |
| 6989 assert(_bit_map->isMarked(ptr), "expected bit to be set"); | |
| 6990 // Should we assert that our work queue is empty or | |
| 6991 // below some drain limit? | |
| 6992 assert(_work_queue->size() == 0, | |
| 6993 "should drain stack to limit stack usage"); | |
| 6994 // convert ptr to an oop preparatory to scanning | |
| 6995 oop this_oop = oop(ptr); | |
| 6996 // Ignore mark word in verification below, since we | |
| 6997 // may be running concurrent with mutators. | |
| 6998 assert(this_oop->is_oop(true), "should be an oop"); | |
| 6999 assert(_finger <= ptr, "_finger runneth ahead"); | |
| 7000 // advance the finger to right end of this object | |
| 7001 _finger = ptr + this_oop->size(); | |
| 7002 assert(_finger > ptr, "we just incremented it above"); | |
| 7003 // On large heaps, it may take us some time to get through | |
| 7004 // the marking phase (especially if running iCMS). During | |
| 7005 // this time it's possible that a lot of mutations have | |
| 7006 // accumulated in the card table and the mod union table -- | |
| 7007 // these mutation records are redundant until we have | |
| 7008 // actually traced into the corresponding card. | |
| 7009 // Here, we check whether advancing the finger would make | |
| 7010 // us cross into a new card, and if so clear corresponding | |
| 7011 // cards in the MUT (preclean them in the card-table in the | |
| 7012 // future). | |
| 7013 | |
| 7014 // The clean-on-enter optimization is disabled by default, | |
| 7015 // until we fix 6178663. | |
| 7016 if (CMSCleanOnEnter && (_finger > _threshold)) { | |
| 7017 // [_threshold, _finger) represents the interval | |
| 7018 // of cards to be cleared in MUT (or precleaned in card table). | |
| 7019 // The set of cards to be cleared is all those that overlap | |
| 7020 // with the interval [_threshold, _finger); note that | |
| 7021 // _threshold is always kept card-aligned but _finger isn't | |
| 7022 // always card-aligned. | |
| 7023 HeapWord* old_threshold = _threshold; | |
| 7024 assert(old_threshold == (HeapWord*)round_to( | |
| 7025 (intptr_t)old_threshold, CardTableModRefBS::card_size), | |
| 7026 "_threshold should always be card-aligned"); | |
| 7027 _threshold = (HeapWord*)round_to( | |
| 7028 (intptr_t)_finger, CardTableModRefBS::card_size); | |
| 7029 MemRegion mr(old_threshold, _threshold); | |
| 7030 assert(!mr.is_empty(), "Control point invariant"); | |
| 7031 assert(_span.contains(mr), "Should clear within span"); // _whole_span ?? | |
| 7032 // XXX When _finger crosses from old gen into perm gen | |
| 7033 // we may be doing unnecessary cleaning; do better in the | |
| 7034 // future by detecting that condition and clearing fewer | |
| 7035 // MUT/CT entries. | |
| 7036 _mut->clear_range(mr); | |
| 7037 } | |
| 7038 | |
| 7039 // Note: the local finger doesn't advance while we drain | |
| 7040 // the stack below, but the global finger sure can and will. | |
| 7041 HeapWord** gfa = _task->global_finger_addr(); | |
| 7042 Par_PushOrMarkClosure pushOrMarkClosure(_collector, | |
| 7043 _span, _bit_map, | |
| 7044 _work_queue, | |
| 7045 _overflow_stack, | |
| 7046 _revisit_stack, | |
| 7047 _finger, | |
| 7048 gfa, this); | |
| 7049 bool res = _work_queue->push(this_oop); // overflow could occur here | |
| 7050 assert(res, "Will hold once we use workqueues"); | |
| 7051 while (true) { | |
| 7052 oop new_oop; | |
| 7053 if (!_work_queue->pop_local(new_oop)) { | |
| 7054 // We emptied our work_queue; check if there's stuff that can | |
| 7055 // be gotten from the overflow stack. | |
| 7056 if (CMSConcMarkingTask::get_work_from_overflow_stack( | |
| 7057 _overflow_stack, _work_queue)) { | |
| 7058 do_yield_check(); | |
| 7059 continue; | |
| 7060 } else { // done | |
| 7061 break; | |
| 7062 } | |
| 7063 } | |
| 7064 // Skip verifying header mark word below because we are | |
| 7065 // running concurrent with mutators. | |
| 7066 assert(new_oop->is_oop(true), "Oops! expected to pop an oop"); | |
| 7067 // now scan this oop's oops | |
| 7068 new_oop->oop_iterate(&pushOrMarkClosure); | |
| 7069 do_yield_check(); | |
| 7070 } | |
| 7071 assert(_work_queue->size() == 0, "tautology, emphasizing post-condition"); | |
| 7072 } | |
| 7073 | |
| 7074 // Yield in response to a request from VM Thread or | |
| 7075 // from mutators. | |
| 7076 void Par_MarkFromRootsClosure::do_yield_work() { | |
| 7077 assert(_task != NULL, "sanity"); | |
| 7078 _task->yield(); | |
| 7079 } | |
| 7080 | |
| 7081 // A variant of the above used for verifying CMS marking work. | |
| 7082 MarkFromRootsVerifyClosure::MarkFromRootsVerifyClosure(CMSCollector* collector, | |
| 7083 MemRegion span, | |
| 7084 CMSBitMap* verification_bm, CMSBitMap* cms_bm, | |
| 7085 CMSMarkStack* mark_stack): | |
| 7086 _collector(collector), | |
| 7087 _span(span), | |
| 7088 _verification_bm(verification_bm), | |
| 7089 _cms_bm(cms_bm), | |
| 7090 _mark_stack(mark_stack), | |
| 7091 _pam_verify_closure(collector, span, verification_bm, cms_bm, | |
| 7092 mark_stack) | |
| 7093 { | |
| 7094 assert(_mark_stack->isEmpty(), "stack should be empty"); | |
| 7095 _finger = _verification_bm->startWord(); | |
| 7096 assert(_collector->_restart_addr == NULL, "Sanity check"); | |
| 7097 assert(_span.contains(_finger), "Out of bounds _finger?"); | |
| 7098 } | |
| 7099 | |
| 7100 void MarkFromRootsVerifyClosure::reset(HeapWord* addr) { | |
| 7101 assert(_mark_stack->isEmpty(), "would cause duplicates on stack"); | |
| 7102 assert(_span.contains(addr), "Out of bounds _finger?"); | |
| 7103 _finger = addr; | |
| 7104 } | |
| 7105 | |
| 7106 // Should revisit to see if this should be restructured for | |
| 7107 // greater efficiency. | |
| 7108 void MarkFromRootsVerifyClosure::do_bit(size_t offset) { | |
| 7109 // convert offset into a HeapWord* | |
| 7110 HeapWord* addr = _verification_bm->startWord() + offset; | |
| 7111 assert(_verification_bm->endWord() && addr < _verification_bm->endWord(), | |
| 7112 "address out of range"); | |
| 7113 assert(_verification_bm->isMarked(addr), "tautology"); | |
| 7114 assert(_cms_bm->isMarked(addr), "tautology"); | |
| 7115 | |
| 7116 assert(_mark_stack->isEmpty(), | |
| 7117 "should drain stack to limit stack usage"); | |
| 7118 // convert addr to an oop preparatory to scanning | |
| 7119 oop this_oop = oop(addr); | |
| 7120 assert(this_oop->is_oop(), "should be an oop"); | |
| 7121 assert(_finger <= addr, "_finger runneth ahead"); | |
| 7122 // advance the finger to right end of this object | |
| 7123 _finger = addr + this_oop->size(); | |
| 7124 assert(_finger > addr, "we just incremented it above"); | |
| 7125 // Note: the finger doesn't advance while we drain | |
| 7126 // the stack below. | |
| 7127 bool res = _mark_stack->push(this_oop); | |
| 7128 assert(res, "Empty non-zero size stack should have space for single push"); | |
| 7129 while (!_mark_stack->isEmpty()) { | |
| 7130 oop new_oop = _mark_stack->pop(); | |
| 7131 assert(new_oop->is_oop(), "Oops! expected to pop an oop"); | |
| 7132 // now scan this oop's oops | |
| 7133 new_oop->oop_iterate(&_pam_verify_closure); | |
| 7134 } | |
| 7135 assert(_mark_stack->isEmpty(), "tautology, emphasizing post-condition"); | |
| 7136 } | |
| 7137 | |
| 7138 PushAndMarkVerifyClosure::PushAndMarkVerifyClosure( | |
| 7139 CMSCollector* collector, MemRegion span, | |
| 7140 CMSBitMap* verification_bm, CMSBitMap* cms_bm, | |
| 7141 CMSMarkStack* mark_stack): | |
| 7142 OopClosure(collector->ref_processor()), | |
| 7143 _collector(collector), | |
| 7144 _span(span), | |
| 7145 _verification_bm(verification_bm), | |
| 7146 _cms_bm(cms_bm), | |
| 7147 _mark_stack(mark_stack) | |
| 7148 { } | |
| 7149 | |
| 7150 | |
| 7151 // Upon stack overflow, we discard (part of) the stack, | |
| 7152 // remembering the least address amongst those discarded | |
| 7153 // in CMSCollector's _restart_address. | |
| 7154 void PushAndMarkVerifyClosure::handle_stack_overflow(HeapWord* lost) { | |
| 7155 // Remember the least grey address discarded | |
| 7156 HeapWord* ra = (HeapWord*)_mark_stack->least_value(lost); | |
| 7157 _collector->lower_restart_addr(ra); | |
| 7158 _mark_stack->reset(); // discard stack contents | |
| 7159 _mark_stack->expand(); // expand the stack if possible | |
| 7160 } | |
| 7161 | |
| 7162 void PushAndMarkVerifyClosure::do_oop(oop* p) { | |
| 7163 oop this_oop = *p; | |
| 7164 assert(this_oop->is_oop_or_null(), "expected an oop or NULL"); | |
| 7165 HeapWord* addr = (HeapWord*)this_oop; | |
| 7166 if (_span.contains(addr) && !_verification_bm->isMarked(addr)) { | |
| 7167 // Oop lies in _span and isn't yet grey or black | |
| 7168 _verification_bm->mark(addr); // now grey | |
| 7169 if (!_cms_bm->isMarked(addr)) { | |
| 7170 oop(addr)->print(); | |
| 7171 gclog_or_tty->print_cr(" ("INTPTR_FORMAT" should have been marked)", addr); | |
| 7172 fatal("... aborting"); | |
| 7173 } | |
| 7174 | |
| 7175 if (!_mark_stack->push(this_oop)) { // stack overflow | |
| 7176 if (PrintCMSStatistics != 0) { | |
| 7177 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
| 7178 SIZE_FORMAT, _mark_stack->capacity()); | |
| 7179 } | |
| 7180 assert(_mark_stack->isFull(), "Else push should have succeeded"); | |
| 7181 handle_stack_overflow(addr); | |
| 7182 } | |
| 7183 // anything including and to the right of _finger | |
| 7184 // will be scanned as we iterate over the remainder of the | |
| 7185 // bit map | |
| 7186 } | |
| 7187 } | |
| 7188 | |
| 7189 PushOrMarkClosure::PushOrMarkClosure(CMSCollector* collector, | |
| 7190 MemRegion span, | |
| 7191 CMSBitMap* bitMap, CMSMarkStack* markStack, | |
| 7192 CMSMarkStack* revisitStack, | |
| 7193 HeapWord* finger, MarkFromRootsClosure* parent) : | |
| 7194 OopClosure(collector->ref_processor()), | |
| 7195 _collector(collector), | |
| 7196 _span(span), | |
| 7197 _bitMap(bitMap), | |
| 7198 _markStack(markStack), | |
| 7199 _revisitStack(revisitStack), | |
| 7200 _finger(finger), | |
| 7201 _parent(parent), | |
| 7202 _should_remember_klasses(collector->cms_should_unload_classes()) | |
| 7203 { } | |
| 7204 | |
| 7205 Par_PushOrMarkClosure::Par_PushOrMarkClosure(CMSCollector* collector, | |
| 7206 MemRegion span, | |
| 7207 CMSBitMap* bit_map, | |
| 7208 OopTaskQueue* work_queue, | |
| 7209 CMSMarkStack* overflow_stack, | |
| 7210 CMSMarkStack* revisit_stack, | |
| 7211 HeapWord* finger, | |
| 7212 HeapWord** global_finger_addr, | |
| 7213 Par_MarkFromRootsClosure* parent) : | |
| 7214 OopClosure(collector->ref_processor()), | |
| 7215 _collector(collector), | |
| 7216 _whole_span(collector->_span), | |
| 7217 _span(span), | |
| 7218 _bit_map(bit_map), | |
| 7219 _work_queue(work_queue), | |
| 7220 _overflow_stack(overflow_stack), | |
| 7221 _revisit_stack(revisit_stack), | |
| 7222 _finger(finger), | |
| 7223 _global_finger_addr(global_finger_addr), | |
| 7224 _parent(parent), | |
| 7225 _should_remember_klasses(collector->cms_should_unload_classes()) | |
| 7226 { } | |
| 7227 | |
| 7228 | |
| 7229 void CMSCollector::lower_restart_addr(HeapWord* low) { | |
| 7230 assert(_span.contains(low), "Out of bounds addr"); | |
| 7231 if (_restart_addr == NULL) { | |
| 7232 _restart_addr = low; | |
| 7233 } else { | |
| 7234 _restart_addr = MIN2(_restart_addr, low); | |
| 7235 } | |
| 7236 } | |
| 7237 | |
| 7238 // Upon stack overflow, we discard (part of) the stack, | |
| 7239 // remembering the least address amongst those discarded | |
| 7240 // in CMSCollector's _restart_address. | |
| 7241 void PushOrMarkClosure::handle_stack_overflow(HeapWord* lost) { | |
| 7242 // Remember the least grey address discarded | |
| 7243 HeapWord* ra = (HeapWord*)_markStack->least_value(lost); | |
| 7244 _collector->lower_restart_addr(ra); | |
| 7245 _markStack->reset(); // discard stack contents | |
| 7246 _markStack->expand(); // expand the stack if possible | |
| 7247 } | |
| 7248 | |
| 7249 // Upon stack overflow, we discard (part of) the stack, | |
| 7250 // remembering the least address amongst those discarded | |
| 7251 // in CMSCollector's _restart_address. | |
| 7252 void Par_PushOrMarkClosure::handle_stack_overflow(HeapWord* lost) { | |
| 7253 // We need to do this under a mutex to prevent other | |
| 7254 // workers from interfering with the expansion below. | |
| 7255 MutexLockerEx ml(_overflow_stack->par_lock(), | |
| 7256 Mutex::_no_safepoint_check_flag); | |
| 7257 // Remember the least grey address discarded | |
| 7258 HeapWord* ra = (HeapWord*)_overflow_stack->least_value(lost); | |
| 7259 _collector->lower_restart_addr(ra); | |
| 7260 _overflow_stack->reset(); // discard stack contents | |
| 7261 _overflow_stack->expand(); // expand the stack if possible | |
| 7262 } | |
| 7263 | |
| 7264 | |
| 7265 void PushOrMarkClosure::do_oop(oop* p) { | |
| 7266 oop thisOop = *p; | |
| 7267 // Ignore mark word because we are running concurrent with mutators. | |
| 7268 assert(thisOop->is_oop_or_null(true), "expected an oop or NULL"); | |
| 7269 HeapWord* addr = (HeapWord*)thisOop; | |
| 7270 if (_span.contains(addr) && !_bitMap->isMarked(addr)) { | |
| 7271 // Oop lies in _span and isn't yet grey or black | |
| 7272 _bitMap->mark(addr); // now grey | |
| 7273 if (addr < _finger) { | |
| 7274 // the bit map iteration has already either passed, or | |
| 7275 // sampled, this bit in the bit map; we'll need to | |
| 7276 // use the marking stack to scan this oop's oops. | |
| 7277 bool simulate_overflow = false; | |
| 7278 NOT_PRODUCT( | |
| 7279 if (CMSMarkStackOverflowALot && | |
| 7280 _collector->simulate_overflow()) { | |
| 7281 // simulate a stack overflow | |
| 7282 simulate_overflow = true; | |
| 7283 } | |
| 7284 ) | |
| 7285 if (simulate_overflow || !_markStack->push(thisOop)) { // stack overflow | |
| 7286 if (PrintCMSStatistics != 0) { | |
| 7287 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
| 7288 SIZE_FORMAT, _markStack->capacity()); | |
| 7289 } | |
| 7290 assert(simulate_overflow || _markStack->isFull(), "Else push should have succeeded"); | |
| 7291 handle_stack_overflow(addr); | |
| 7292 } | |
| 7293 } | |
| 7294 // anything including and to the right of _finger | |
| 7295 // will be scanned as we iterate over the remainder of the | |
| 7296 // bit map | |
| 7297 do_yield_check(); | |
| 7298 } | |
| 7299 } | |
| 7300 | |
| 7301 void Par_PushOrMarkClosure::do_oop(oop* p) { | |
| 7302 oop this_oop = *p; | |
| 7303 // Ignore mark word because we are running concurrent with mutators. | |
| 7304 assert(this_oop->is_oop_or_null(true), "expected an oop or NULL"); | |
| 7305 HeapWord* addr = (HeapWord*)this_oop; | |
| 7306 if (_whole_span.contains(addr) && !_bit_map->isMarked(addr)) { | |
| 7307 // Oop lies in _span and isn't yet grey or black | |
| 7308 // We read the global_finger (volatile read) strictly after marking oop | |
| 7309 bool res = _bit_map->par_mark(addr); // now grey | |
| 7310 volatile HeapWord** gfa = (volatile HeapWord**)_global_finger_addr; | |
| 7311 // Should we push this marked oop on our stack? | |
| 7312 // -- if someone else marked it, nothing to do | |
| 7313 // -- if target oop is above global finger nothing to do | |
| 7314 // -- if target oop is in chunk and above local finger | |
| 7315 // then nothing to do | |
| 7316 // -- else push on work queue | |
| 7317 if ( !res // someone else marked it, they will deal with it | |
| 7318 || (addr >= *gfa) // will be scanned in a later task | |
| 7319 || (_span.contains(addr) && addr >= _finger)) { // later in this chunk | |
| 7320 return; | |
| 7321 } | |
| 7322 // the bit map iteration has already either passed, or | |
| 7323 // sampled, this bit in the bit map; we'll need to | |
| 7324 // use the marking stack to scan this oop's oops. | |
| 7325 bool simulate_overflow = false; | |
| 7326 NOT_PRODUCT( | |
| 7327 if (CMSMarkStackOverflowALot && | |
| 7328 _collector->simulate_overflow()) { | |
| 7329 // simulate a stack overflow | |
| 7330 simulate_overflow = true; | |
| 7331 } | |
| 7332 ) | |
| 7333 if (simulate_overflow || | |
| 7334 !(_work_queue->push(this_oop) || _overflow_stack->par_push(this_oop))) { | |
| 7335 // stack overflow | |
| 7336 if (PrintCMSStatistics != 0) { | |
| 7337 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at " | |
| 7338 SIZE_FORMAT, _overflow_stack->capacity()); | |
| 7339 } | |
| 7340 // We cannot assert that the overflow stack is full because | |
| 7341 // it may have been emptied since. | |
| 7342 assert(simulate_overflow || | |
| 7343 _work_queue->size() == _work_queue->max_elems(), | |
| 7344 "Else push should have succeeded"); | |
| 7345 handle_stack_overflow(addr); | |
| 7346 } | |
| 7347 do_yield_check(); | |
| 7348 } | |
| 7349 } | |
| 7350 | |
| 7351 | |
| 7352 PushAndMarkClosure::PushAndMarkClosure(CMSCollector* collector, | |
| 7353 MemRegion span, | |
| 7354 ReferenceProcessor* rp, | |
| 7355 CMSBitMap* bit_map, | |
| 7356 CMSBitMap* mod_union_table, | |
| 7357 CMSMarkStack* mark_stack, | |
| 7358 CMSMarkStack* revisit_stack, | |
| 7359 bool concurrent_precleaning): | |
| 7360 OopClosure(rp), | |
| 7361 _collector(collector), | |
| 7362 _span(span), | |
| 7363 _bit_map(bit_map), | |
| 7364 _mod_union_table(mod_union_table), | |
| 7365 _mark_stack(mark_stack), | |
| 7366 _revisit_stack(revisit_stack), | |
| 7367 _concurrent_precleaning(concurrent_precleaning), | |
| 7368 _should_remember_klasses(collector->cms_should_unload_classes()) | |
| 7369 { | |
| 7370 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
| 7371 } | |
| 7372 | |
| 7373 // Grey object rescan during pre-cleaning and second checkpoint phases -- | |
| 7374 // the non-parallel version (the parallel version appears further below.) | |
| 7375 void PushAndMarkClosure::do_oop(oop* p) { | |
| 7376 oop this_oop = *p; | |
| 7377 // Ignore mark word verification. If during concurrent precleaning | |
| 7378 // the object monitor may be locked. If during the checkpoint | |
| 7379 // phases, the object may already have been reached by a different | |
| 7380 // path and may be at the end of the global overflow list (so | |
| 7381 // the mark word may be NULL). | |
| 7382 assert(this_oop->is_oop_or_null(true/* ignore mark word */), | |
| 7383 "expected an oop or NULL"); | |
| 7384 HeapWord* addr = (HeapWord*)this_oop; | |
| 7385 // Check if oop points into the CMS generation | |
| 7386 // and is not marked | |
| 7387 if (_span.contains(addr) && !_bit_map->isMarked(addr)) { | |
| 7388 // a white object ... | |
| 7389 _bit_map->mark(addr); // ... now grey | |
| 7390 // push on the marking stack (grey set) | |
| 7391 bool simulate_overflow = false; | |
| 7392 NOT_PRODUCT( | |
| 7393 if (CMSMarkStackOverflowALot && | |
| 7394 _collector->simulate_overflow()) { | |
| 7395 // simulate a stack overflow | |
| 7396 simulate_overflow = true; | |
| 7397 } | |
| 7398 ) | |
| 7399 if (simulate_overflow || !_mark_stack->push(this_oop)) { | |
| 7400 if (_concurrent_precleaning) { | |
| 7401 // During precleaning we can just dirty the appropriate card | |
| 7402 // in the mod union table, thus ensuring that the object remains | |
| 7403 // in the grey set and continue. Note that no one can be intefering | |
| 7404 // with us in this action of dirtying the mod union table, so | |
| 7405 // no locking is required. | |
| 7406 _mod_union_table->mark(addr); | |
| 7407 _collector->_ser_pmc_preclean_ovflw++; | |
| 7408 } else { | |
| 7409 // During the remark phase, we need to remember this oop | |
| 7410 // in the overflow list. | |
| 7411 _collector->push_on_overflow_list(this_oop); | |
| 7412 _collector->_ser_pmc_remark_ovflw++; | |
| 7413 } | |
| 7414 } | |
| 7415 } | |
| 7416 } | |
| 7417 | |
| 7418 Par_PushAndMarkClosure::Par_PushAndMarkClosure(CMSCollector* collector, | |
| 7419 MemRegion span, | |
| 7420 ReferenceProcessor* rp, | |
| 7421 CMSBitMap* bit_map, | |
| 7422 OopTaskQueue* work_queue, | |
| 7423 CMSMarkStack* revisit_stack): | |
| 7424 OopClosure(rp), | |
| 7425 _collector(collector), | |
| 7426 _span(span), | |
| 7427 _bit_map(bit_map), | |
| 7428 _work_queue(work_queue), | |
| 7429 _revisit_stack(revisit_stack), | |
| 7430 _should_remember_klasses(collector->cms_should_unload_classes()) | |
| 7431 { | |
| 7432 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL"); | |
| 7433 } | |
| 7434 | |
| 7435 // Grey object rescan during second checkpoint phase -- | |
| 7436 // the parallel version. | |
| 7437 void Par_PushAndMarkClosure::do_oop(oop* p) { | |
| 7438 oop this_oop = *p; | |
| 7439 // In the assert below, we ignore the mark word because | |
| 7440 // this oop may point to an already visited object that is | |
| 7441 // on the overflow stack (in which case the mark word has | |
| 7442 // been hijacked for chaining into the overflow stack -- | |
| 7443 // if this is the last object in the overflow stack then | |
| 7444 // its mark word will be NULL). Because this object may | |
| 7445 // have been subsequently popped off the global overflow | |
| 7446 // stack, and the mark word possibly restored to the prototypical | |
| 7447 // value, by the time we get to examined this failing assert in | |
| 7448 // the debugger, is_oop_or_null(false) may subsequently start | |
| 7449 // to hold. | |
| 7450 assert(this_oop->is_oop_or_null(true), | |
| 7451 "expected an oop or NULL"); | |
| 7452 HeapWord* addr = (HeapWord*)this_oop; | |
| 7453 // Check if oop points into the CMS generation | |
| 7454 // and is not marked | |
| 7455 if (_span.contains(addr) && !_bit_map->isMarked(addr)) { | |
| 7456 // a white object ... | |
| 7457 // If we manage to "claim" the object, by being the | |
| 7458 // first thread to mark it, then we push it on our | |
| 7459 // marking stack | |
| 7460 if (_bit_map->par_mark(addr)) { // ... now grey | |
| 7461 // push on work queue (grey set) | |
| 7462 bool simulate_overflow = false; | |
| 7463 NOT_PRODUCT( | |
| 7464 if (CMSMarkStackOverflowALot && | |
| 7465 _collector->par_simulate_overflow()) { | |
| 7466 // simulate a stack overflow | |
| 7467 simulate_overflow = true; | |
| 7468 } | |
| 7469 ) | |
| 7470 if (simulate_overflow || !_work_queue->push(this_oop)) { | |
| 7471 _collector->par_push_on_overflow_list(this_oop); | |
| 7472 _collector->_par_pmc_remark_ovflw++; // imprecise OK: no need to CAS | |
| 7473 } | |
| 7474 } // Else, some other thread got there first | |
| 7475 } | |
| 7476 } | |
| 7477 | |
| 7478 void PushAndMarkClosure::remember_klass(Klass* k) { | |
| 7479 if (!_revisit_stack->push(oop(k))) { | |
| 7480 fatal("Revisit stack overflowed in PushAndMarkClosure"); | |
| 7481 } | |
| 7482 } | |
| 7483 | |
| 7484 void Par_PushAndMarkClosure::remember_klass(Klass* k) { | |
| 7485 if (!_revisit_stack->par_push(oop(k))) { | |
| 7486 fatal("Revist stack overflowed in Par_PushAndMarkClosure"); | |
| 7487 } | |
| 7488 } | |
| 7489 | |
| 7490 void CMSPrecleanRefsYieldClosure::do_yield_work() { | |
| 7491 Mutex* bml = _collector->bitMapLock(); | |
| 7492 assert_lock_strong(bml); | |
| 7493 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 7494 "CMS thread should hold CMS token"); | |
| 7495 | |
| 7496 bml->unlock(); | |
| 7497 ConcurrentMarkSweepThread::desynchronize(true); | |
| 7498 | |
| 7499 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 7500 | |
| 7501 _collector->stopTimer(); | |
| 7502 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
| 7503 if (PrintCMSStatistics != 0) { | |
| 7504 _collector->incrementYields(); | |
| 7505 } | |
| 7506 _collector->icms_wait(); | |
| 7507 | |
| 7508 // See the comment in coordinator_yield() | |
| 7509 for (unsigned i = 0; i < CMSYieldSleepCount && | |
| 7510 ConcurrentMarkSweepThread::should_yield() && | |
| 7511 !CMSCollector::foregroundGCIsActive(); ++i) { | |
| 7512 os::sleep(Thread::current(), 1, false); | |
| 7513 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 7514 } | |
| 7515 | |
| 7516 ConcurrentMarkSweepThread::synchronize(true); | |
| 7517 bml->lock(); | |
| 7518 | |
| 7519 _collector->startTimer(); | |
| 7520 } | |
| 7521 | |
| 7522 bool CMSPrecleanRefsYieldClosure::should_return() { | |
| 7523 if (ConcurrentMarkSweepThread::should_yield()) { | |
| 7524 do_yield_work(); | |
| 7525 } | |
| 7526 return _collector->foregroundGCIsActive(); | |
| 7527 } | |
| 7528 | |
| 7529 void MarkFromDirtyCardsClosure::do_MemRegion(MemRegion mr) { | |
| 7530 assert(((size_t)mr.start())%CardTableModRefBS::card_size_in_words == 0, | |
| 7531 "mr should be aligned to start at a card boundary"); | |
| 7532 // We'd like to assert: | |
| 7533 // assert(mr.word_size()%CardTableModRefBS::card_size_in_words == 0, | |
| 7534 // "mr should be a range of cards"); | |
| 7535 // However, that would be too strong in one case -- the last | |
| 7536 // partition ends at _unallocated_block which, in general, can be | |
| 7537 // an arbitrary boundary, not necessarily card aligned. | |
| 7538 if (PrintCMSStatistics != 0) { | |
| 7539 _num_dirty_cards += | |
| 7540 mr.word_size()/CardTableModRefBS::card_size_in_words; | |
| 7541 } | |
| 7542 _space->object_iterate_mem(mr, &_scan_cl); | |
| 7543 } | |
| 7544 | |
| 7545 SweepClosure::SweepClosure(CMSCollector* collector, | |
| 7546 ConcurrentMarkSweepGeneration* g, | |
| 7547 CMSBitMap* bitMap, bool should_yield) : | |
| 7548 _collector(collector), | |
| 7549 _g(g), | |
| 7550 _sp(g->cmsSpace()), | |
| 7551 _limit(_sp->sweep_limit()), | |
| 7552 _freelistLock(_sp->freelistLock()), | |
| 7553 _bitMap(bitMap), | |
| 7554 _yield(should_yield), | |
| 7555 _inFreeRange(false), // No free range at beginning of sweep | |
| 7556 _freeRangeInFreeLists(false), // No free range at beginning of sweep | |
| 7557 _lastFreeRangeCoalesced(false), | |
| 7558 _freeFinger(g->used_region().start()) | |
| 7559 { | |
| 7560 NOT_PRODUCT( | |
| 7561 _numObjectsFreed = 0; | |
| 7562 _numWordsFreed = 0; | |
| 7563 _numObjectsLive = 0; | |
| 7564 _numWordsLive = 0; | |
| 7565 _numObjectsAlreadyFree = 0; | |
| 7566 _numWordsAlreadyFree = 0; | |
| 7567 _last_fc = NULL; | |
| 7568 | |
| 7569 _sp->initializeIndexedFreeListArrayReturnedBytes(); | |
| 7570 _sp->dictionary()->initializeDictReturnedBytes(); | |
| 7571 ) | |
| 7572 assert(_limit >= _sp->bottom() && _limit <= _sp->end(), | |
| 7573 "sweep _limit out of bounds"); | |
| 7574 if (CMSTraceSweeper) { | |
| 7575 gclog_or_tty->print("\n====================\nStarting new sweep\n"); | |
| 7576 } | |
| 7577 } | |
| 7578 | |
| 7579 // We need this destructor to reclaim any space at the end | |
| 7580 // of the space, which do_blk below may not have added back to | |
| 7581 // the free lists. [basically dealing with the "fringe effect"] | |
| 7582 SweepClosure::~SweepClosure() { | |
| 7583 assert_lock_strong(_freelistLock); | |
| 7584 // this should be treated as the end of a free run if any | |
| 7585 // The current free range should be returned to the free lists | |
| 7586 // as one coalesced chunk. | |
| 7587 if (inFreeRange()) { | |
| 7588 flushCurFreeChunk(freeFinger(), | |
| 7589 pointer_delta(_limit, freeFinger())); | |
| 7590 assert(freeFinger() < _limit, "the finger pointeth off base"); | |
| 7591 if (CMSTraceSweeper) { | |
| 7592 gclog_or_tty->print("destructor:"); | |
| 7593 gclog_or_tty->print("Sweep:put_free_blk 0x%x ("SIZE_FORMAT") " | |
| 7594 "[coalesced:"SIZE_FORMAT"]\n", | |
| 7595 freeFinger(), pointer_delta(_limit, freeFinger()), | |
| 7596 lastFreeRangeCoalesced()); | |
| 7597 } | |
| 7598 } | |
| 7599 NOT_PRODUCT( | |
| 7600 if (Verbose && PrintGC) { | |
| 7601 gclog_or_tty->print("Collected "SIZE_FORMAT" objects, " | |
| 7602 SIZE_FORMAT " bytes", | |
| 7603 _numObjectsFreed, _numWordsFreed*sizeof(HeapWord)); | |
| 7604 gclog_or_tty->print_cr("\nLive "SIZE_FORMAT" objects, " | |
| 7605 SIZE_FORMAT" bytes " | |
| 7606 "Already free "SIZE_FORMAT" objects, "SIZE_FORMAT" bytes", | |
| 7607 _numObjectsLive, _numWordsLive*sizeof(HeapWord), | |
| 7608 _numObjectsAlreadyFree, _numWordsAlreadyFree*sizeof(HeapWord)); | |
| 7609 size_t totalBytes = (_numWordsFreed + _numWordsLive + _numWordsAlreadyFree) * | |
| 7610 sizeof(HeapWord); | |
| 7611 gclog_or_tty->print_cr("Total sweep: "SIZE_FORMAT" bytes", totalBytes); | |
| 7612 | |
| 7613 if (PrintCMSStatistics && CMSVerifyReturnedBytes) { | |
| 7614 size_t indexListReturnedBytes = _sp->sumIndexedFreeListArrayReturnedBytes(); | |
| 7615 size_t dictReturnedBytes = _sp->dictionary()->sumDictReturnedBytes(); | |
| 7616 size_t returnedBytes = indexListReturnedBytes + dictReturnedBytes; | |
| 7617 gclog_or_tty->print("Returned "SIZE_FORMAT" bytes", returnedBytes); | |
| 7618 gclog_or_tty->print(" Indexed List Returned "SIZE_FORMAT" bytes", | |
| 7619 indexListReturnedBytes); | |
| 7620 gclog_or_tty->print_cr(" Dictionary Returned "SIZE_FORMAT" bytes", | |
| 7621 dictReturnedBytes); | |
| 7622 } | |
| 7623 } | |
| 7624 ) | |
| 7625 // Now, in debug mode, just null out the sweep_limit | |
| 7626 NOT_PRODUCT(_sp->clear_sweep_limit();) | |
| 7627 if (CMSTraceSweeper) { | |
| 7628 gclog_or_tty->print("end of sweep\n================\n"); | |
| 7629 } | |
| 7630 } | |
| 7631 | |
| 7632 void SweepClosure::initialize_free_range(HeapWord* freeFinger, | |
| 7633 bool freeRangeInFreeLists) { | |
| 7634 if (CMSTraceSweeper) { | |
| 7635 gclog_or_tty->print("---- Start free range 0x%x with free block [%d] (%d)\n", | |
| 7636 freeFinger, _sp->block_size(freeFinger), | |
| 7637 freeRangeInFreeLists); | |
| 7638 } | |
| 7639 assert(!inFreeRange(), "Trampling existing free range"); | |
| 7640 set_inFreeRange(true); | |
| 7641 set_lastFreeRangeCoalesced(false); | |
| 7642 | |
| 7643 set_freeFinger(freeFinger); | |
| 7644 set_freeRangeInFreeLists(freeRangeInFreeLists); | |
| 7645 if (CMSTestInFreeList) { | |
| 7646 if (freeRangeInFreeLists) { | |
| 7647 FreeChunk* fc = (FreeChunk*) freeFinger; | |
| 7648 assert(fc->isFree(), "A chunk on the free list should be free."); | |
| 7649 assert(fc->size() > 0, "Free range should have a size"); | |
| 7650 assert(_sp->verifyChunkInFreeLists(fc), "Chunk is not in free lists"); | |
| 7651 } | |
| 7652 } | |
| 7653 } | |
| 7654 | |
| 7655 // Note that the sweeper runs concurrently with mutators. Thus, | |
| 7656 // it is possible for direct allocation in this generation to happen | |
| 7657 // in the middle of the sweep. Note that the sweeper also coalesces | |
| 7658 // contiguous free blocks. Thus, unless the sweeper and the allocator | |
| 7659 // synchronize appropriately freshly allocated blocks may get swept up. | |
| 7660 // This is accomplished by the sweeper locking the free lists while | |
| 7661 // it is sweeping. Thus blocks that are determined to be free are | |
| 7662 // indeed free. There is however one additional complication: | |
| 7663 // blocks that have been allocated since the final checkpoint and | |
| 7664 // mark, will not have been marked and so would be treated as | |
| 7665 // unreachable and swept up. To prevent this, the allocator marks | |
| 7666 // the bit map when allocating during the sweep phase. This leads, | |
| 7667 // however, to a further complication -- objects may have been allocated | |
| 7668 // but not yet initialized -- in the sense that the header isn't yet | |
| 7669 // installed. The sweeper can not then determine the size of the block | |
| 7670 // in order to skip over it. To deal with this case, we use a technique | |
| 7671 // (due to Printezis) to encode such uninitialized block sizes in the | |
| 7672 // bit map. Since the bit map uses a bit per every HeapWord, but the | |
| 7673 // CMS generation has a minimum object size of 3 HeapWords, it follows | |
| 7674 // that "normal marks" won't be adjacent in the bit map (there will | |
| 7675 // always be at least two 0 bits between successive 1 bits). We make use | |
| 7676 // of these "unused" bits to represent uninitialized blocks -- the bit | |
| 7677 // corresponding to the start of the uninitialized object and the next | |
| 7678 // bit are both set. Finally, a 1 bit marks the end of the object that | |
| 7679 // started with the two consecutive 1 bits to indicate its potentially | |
| 7680 // uninitialized state. | |
| 7681 | |
| 7682 size_t SweepClosure::do_blk_careful(HeapWord* addr) { | |
| 7683 FreeChunk* fc = (FreeChunk*)addr; | |
| 7684 size_t res; | |
| 7685 | |
| 7686 // check if we are done sweepinrg | |
| 7687 if (addr == _limit) { // we have swept up to the limit, do nothing more | |
| 7688 assert(_limit >= _sp->bottom() && _limit <= _sp->end(), | |
| 7689 "sweep _limit out of bounds"); | |
| 7690 // help the closure application finish | |
| 7691 return pointer_delta(_sp->end(), _limit); | |
| 7692 } | |
| 7693 assert(addr <= _limit, "sweep invariant"); | |
| 7694 | |
| 7695 // check if we should yield | |
| 7696 do_yield_check(addr); | |
| 7697 if (fc->isFree()) { | |
| 7698 // Chunk that is already free | |
| 7699 res = fc->size(); | |
| 7700 doAlreadyFreeChunk(fc); | |
| 7701 debug_only(_sp->verifyFreeLists()); | |
| 7702 assert(res == fc->size(), "Don't expect the size to change"); | |
| 7703 NOT_PRODUCT( | |
| 7704 _numObjectsAlreadyFree++; | |
| 7705 _numWordsAlreadyFree += res; | |
| 7706 ) | |
| 7707 NOT_PRODUCT(_last_fc = fc;) | |
| 7708 } else if (!_bitMap->isMarked(addr)) { | |
| 7709 // Chunk is fresh garbage | |
| 7710 res = doGarbageChunk(fc); | |
| 7711 debug_only(_sp->verifyFreeLists()); | |
| 7712 NOT_PRODUCT( | |
| 7713 _numObjectsFreed++; | |
| 7714 _numWordsFreed += res; | |
| 7715 ) | |
| 7716 } else { | |
| 7717 // Chunk that is alive. | |
| 7718 res = doLiveChunk(fc); | |
| 7719 debug_only(_sp->verifyFreeLists()); | |
| 7720 NOT_PRODUCT( | |
| 7721 _numObjectsLive++; | |
| 7722 _numWordsLive += res; | |
| 7723 ) | |
| 7724 } | |
| 7725 return res; | |
| 7726 } | |
| 7727 | |
| 7728 // For the smart allocation, record following | |
| 7729 // split deaths - a free chunk is removed from its free list because | |
| 7730 // it is being split into two or more chunks. | |
| 7731 // split birth - a free chunk is being added to its free list because | |
| 7732 // a larger free chunk has been split and resulted in this free chunk. | |
| 7733 // coal death - a free chunk is being removed from its free list because | |
| 7734 // it is being coalesced into a large free chunk. | |
| 7735 // coal birth - a free chunk is being added to its free list because | |
| 7736 // it was created when two or more free chunks where coalesced into | |
| 7737 // this free chunk. | |
| 7738 // | |
| 7739 // These statistics are used to determine the desired number of free | |
| 7740 // chunks of a given size. The desired number is chosen to be relative | |
| 7741 // to the end of a CMS sweep. The desired number at the end of a sweep | |
| 7742 // is the | |
| 7743 // count-at-end-of-previous-sweep (an amount that was enough) | |
| 7744 // - count-at-beginning-of-current-sweep (the excess) | |
| 7745 // + split-births (gains in this size during interval) | |
| 7746 // - split-deaths (demands on this size during interval) | |
| 7747 // where the interval is from the end of one sweep to the end of the | |
| 7748 // next. | |
| 7749 // | |
| 7750 // When sweeping the sweeper maintains an accumulated chunk which is | |
| 7751 // the chunk that is made up of chunks that have been coalesced. That | |
| 7752 // will be termed the left-hand chunk. A new chunk of garbage that | |
| 7753 // is being considered for coalescing will be referred to as the | |
| 7754 // right-hand chunk. | |
| 7755 // | |
| 7756 // When making a decision on whether to coalesce a right-hand chunk with | |
| 7757 // the current left-hand chunk, the current count vs. the desired count | |
| 7758 // of the left-hand chunk is considered. Also if the right-hand chunk | |
| 7759 // is near the large chunk at the end of the heap (see | |
| 7760 // ConcurrentMarkSweepGeneration::isNearLargestChunk()), then the | |
| 7761 // left-hand chunk is coalesced. | |
| 7762 // | |
| 7763 // When making a decision about whether to split a chunk, the desired count | |
| 7764 // vs. the current count of the candidate to be split is also considered. | |
| 7765 // If the candidate is underpopulated (currently fewer chunks than desired) | |
| 7766 // a chunk of an overpopulated (currently more chunks than desired) size may | |
| 7767 // be chosen. The "hint" associated with a free list, if non-null, points | |
| 7768 // to a free list which may be overpopulated. | |
| 7769 // | |
| 7770 | |
| 7771 void SweepClosure::doAlreadyFreeChunk(FreeChunk* fc) { | |
| 7772 size_t size = fc->size(); | |
| 7773 // Chunks that cannot be coalesced are not in the | |
| 7774 // free lists. | |
| 7775 if (CMSTestInFreeList && !fc->cantCoalesce()) { | |
| 7776 assert(_sp->verifyChunkInFreeLists(fc), | |
| 7777 "free chunk should be in free lists"); | |
| 7778 } | |
| 7779 // a chunk that is already free, should not have been | |
| 7780 // marked in the bit map | |
| 7781 HeapWord* addr = (HeapWord*) fc; | |
| 7782 assert(!_bitMap->isMarked(addr), "free chunk should be unmarked"); | |
| 7783 // Verify that the bit map has no bits marked between | |
| 7784 // addr and purported end of this block. | |
| 7785 _bitMap->verifyNoOneBitsInRange(addr + 1, addr + size); | |
| 7786 | |
| 7787 // Some chunks cannot be coalesced in under any circumstances. | |
| 7788 // See the definition of cantCoalesce(). | |
| 7789 if (!fc->cantCoalesce()) { | |
| 7790 // This chunk can potentially be coalesced. | |
| 7791 if (_sp->adaptive_freelists()) { | |
| 7792 // All the work is done in | |
| 7793 doPostIsFreeOrGarbageChunk(fc, size); | |
| 7794 } else { // Not adaptive free lists | |
| 7795 // this is a free chunk that can potentially be coalesced by the sweeper; | |
| 7796 if (!inFreeRange()) { | |
| 7797 // if the next chunk is a free block that can't be coalesced | |
| 7798 // it doesn't make sense to remove this chunk from the free lists | |
| 7799 FreeChunk* nextChunk = (FreeChunk*)(addr + size); | |
| 7800 assert((HeapWord*)nextChunk <= _limit, "sweep invariant"); | |
| 7801 if ((HeapWord*)nextChunk < _limit && // there's a next chunk... | |
| 7802 nextChunk->isFree() && // which is free... | |
| 7803 nextChunk->cantCoalesce()) { // ... but cant be coalesced | |
| 7804 // nothing to do | |
| 7805 } else { | |
| 7806 // Potentially the start of a new free range: | |
| 7807 // Don't eagerly remove it from the free lists. | |
| 7808 // No need to remove it if it will just be put | |
| 7809 // back again. (Also from a pragmatic point of view | |
| 7810 // if it is a free block in a region that is beyond | |
| 7811 // any allocated blocks, an assertion will fail) | |
| 7812 // Remember the start of a free run. | |
| 7813 initialize_free_range(addr, true); | |
| 7814 // end - can coalesce with next chunk | |
| 7815 } | |
| 7816 } else { | |
| 7817 // the midst of a free range, we are coalescing | |
| 7818 debug_only(record_free_block_coalesced(fc);) | |
| 7819 if (CMSTraceSweeper) { | |
| 7820 gclog_or_tty->print(" -- pick up free block 0x%x (%d)\n", fc, size); | |
| 7821 } | |
| 7822 // remove it from the free lists | |
| 7823 _sp->removeFreeChunkFromFreeLists(fc); | |
| 7824 set_lastFreeRangeCoalesced(true); | |
| 7825 // If the chunk is being coalesced and the current free range is | |
| 7826 // in the free lists, remove the current free range so that it | |
| 7827 // will be returned to the free lists in its entirety - all | |
| 7828 // the coalesced pieces included. | |
| 7829 if (freeRangeInFreeLists()) { | |
| 7830 FreeChunk* ffc = (FreeChunk*) freeFinger(); | |
| 7831 assert(ffc->size() == pointer_delta(addr, freeFinger()), | |
| 7832 "Size of free range is inconsistent with chunk size."); | |
| 7833 if (CMSTestInFreeList) { | |
| 7834 assert(_sp->verifyChunkInFreeLists(ffc), | |
| 7835 "free range is not in free lists"); | |
| 7836 } | |
| 7837 _sp->removeFreeChunkFromFreeLists(ffc); | |
| 7838 set_freeRangeInFreeLists(false); | |
| 7839 } | |
| 7840 } | |
| 7841 } | |
| 7842 } else { | |
| 7843 // Code path common to both original and adaptive free lists. | |
| 7844 | |
| 7845 // cant coalesce with previous block; this should be treated | |
| 7846 // as the end of a free run if any | |
| 7847 if (inFreeRange()) { | |
| 7848 // we kicked some butt; time to pick up the garbage | |
| 7849 assert(freeFinger() < addr, "the finger pointeth off base"); | |
| 7850 flushCurFreeChunk(freeFinger(), pointer_delta(addr, freeFinger())); | |
| 7851 } | |
| 7852 // else, nothing to do, just continue | |
| 7853 } | |
| 7854 } | |
| 7855 | |
| 7856 size_t SweepClosure::doGarbageChunk(FreeChunk* fc) { | |
| 7857 // This is a chunk of garbage. It is not in any free list. | |
| 7858 // Add it to a free list or let it possibly be coalesced into | |
| 7859 // a larger chunk. | |
| 7860 HeapWord* addr = (HeapWord*) fc; | |
| 7861 size_t size = CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size()); | |
| 7862 | |
| 7863 if (_sp->adaptive_freelists()) { | |
| 7864 // Verify that the bit map has no bits marked between | |
| 7865 // addr and purported end of just dead object. | |
| 7866 _bitMap->verifyNoOneBitsInRange(addr + 1, addr + size); | |
| 7867 | |
| 7868 doPostIsFreeOrGarbageChunk(fc, size); | |
| 7869 } else { | |
| 7870 if (!inFreeRange()) { | |
| 7871 // start of a new free range | |
| 7872 assert(size > 0, "A free range should have a size"); | |
| 7873 initialize_free_range(addr, false); | |
| 7874 | |
| 7875 } else { | |
| 7876 // this will be swept up when we hit the end of the | |
| 7877 // free range | |
| 7878 if (CMSTraceSweeper) { | |
| 7879 gclog_or_tty->print(" -- pick up garbage 0x%x (%d) \n", fc, size); | |
| 7880 } | |
| 7881 // If the chunk is being coalesced and the current free range is | |
| 7882 // in the free lists, remove the current free range so that it | |
| 7883 // will be returned to the free lists in its entirety - all | |
| 7884 // the coalesced pieces included. | |
| 7885 if (freeRangeInFreeLists()) { | |
| 7886 FreeChunk* ffc = (FreeChunk*)freeFinger(); | |
| 7887 assert(ffc->size() == pointer_delta(addr, freeFinger()), | |
| 7888 "Size of free range is inconsistent with chunk size."); | |
| 7889 if (CMSTestInFreeList) { | |
| 7890 assert(_sp->verifyChunkInFreeLists(ffc), | |
| 7891 "free range is not in free lists"); | |
| 7892 } | |
| 7893 _sp->removeFreeChunkFromFreeLists(ffc); | |
| 7894 set_freeRangeInFreeLists(false); | |
| 7895 } | |
| 7896 set_lastFreeRangeCoalesced(true); | |
| 7897 } | |
| 7898 // this will be swept up when we hit the end of the free range | |
| 7899 | |
| 7900 // Verify that the bit map has no bits marked between | |
| 7901 // addr and purported end of just dead object. | |
| 7902 _bitMap->verifyNoOneBitsInRange(addr + 1, addr + size); | |
| 7903 } | |
| 7904 return size; | |
| 7905 } | |
| 7906 | |
| 7907 size_t SweepClosure::doLiveChunk(FreeChunk* fc) { | |
| 7908 HeapWord* addr = (HeapWord*) fc; | |
| 7909 // The sweeper has just found a live object. Return any accumulated | |
| 7910 // left hand chunk to the free lists. | |
| 7911 if (inFreeRange()) { | |
| 7912 if (_sp->adaptive_freelists()) { | |
| 7913 flushCurFreeChunk(freeFinger(), | |
| 7914 pointer_delta(addr, freeFinger())); | |
| 7915 } else { // not adaptive freelists | |
| 7916 set_inFreeRange(false); | |
| 7917 // Add the free range back to the free list if it is not already | |
| 7918 // there. | |
| 7919 if (!freeRangeInFreeLists()) { | |
| 7920 assert(freeFinger() < addr, "the finger pointeth off base"); | |
| 7921 if (CMSTraceSweeper) { | |
| 7922 gclog_or_tty->print("Sweep:put_free_blk 0x%x (%d) " | |
| 7923 "[coalesced:%d]\n", | |
| 7924 freeFinger(), pointer_delta(addr, freeFinger()), | |
| 7925 lastFreeRangeCoalesced()); | |
| 7926 } | |
| 7927 _sp->addChunkAndRepairOffsetTable(freeFinger(), | |
| 7928 pointer_delta(addr, freeFinger()), lastFreeRangeCoalesced()); | |
| 7929 } | |
| 7930 } | |
| 7931 } | |
| 7932 | |
| 7933 // Common code path for original and adaptive free lists. | |
| 7934 | |
| 7935 // this object is live: we'd normally expect this to be | |
| 7936 // an oop, and like to assert the following: | |
| 7937 // assert(oop(addr)->is_oop(), "live block should be an oop"); | |
| 7938 // However, as we commented above, this may be an object whose | |
| 7939 // header hasn't yet been initialized. | |
| 7940 size_t size; | |
| 7941 assert(_bitMap->isMarked(addr), "Tautology for this control point"); | |
| 7942 if (_bitMap->isMarked(addr + 1)) { | |
| 7943 // Determine the size from the bit map, rather than trying to | |
| 7944 // compute it from the object header. | |
| 7945 HeapWord* nextOneAddr = _bitMap->getNextMarkedWordAddress(addr + 2); | |
| 7946 size = pointer_delta(nextOneAddr + 1, addr); | |
| 7947 assert(size == CompactibleFreeListSpace::adjustObjectSize(size), | |
| 7948 "alignment problem"); | |
| 7949 | |
| 7950 #ifdef DEBUG | |
| 7951 if (oop(addr)->klass() != NULL && | |
| 7952 ( !_collector->cms_should_unload_classes() | |
| 7953 || oop(addr)->is_parsable())) { | |
| 7954 // Ignore mark word because we are running concurrent with mutators | |
| 7955 assert(oop(addr)->is_oop(true), "live block should be an oop"); | |
| 7956 assert(size == | |
| 7957 CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size()), | |
| 7958 "P-mark and computed size do not agree"); | |
| 7959 } | |
| 7960 #endif | |
| 7961 | |
| 7962 } else { | |
| 7963 // This should be an initialized object that's alive. | |
| 7964 assert(oop(addr)->klass() != NULL && | |
| 7965 (!_collector->cms_should_unload_classes() | |
| 7966 || oop(addr)->is_parsable()), | |
| 7967 "Should be an initialized object"); | |
| 7968 // Ignore mark word because we are running concurrent with mutators | |
| 7969 assert(oop(addr)->is_oop(true), "live block should be an oop"); | |
| 7970 // Verify that the bit map has no bits marked between | |
| 7971 // addr and purported end of this block. | |
| 7972 size = CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size()); | |
| 7973 assert(size >= 3, "Necessary for Printezis marks to work"); | |
| 7974 assert(!_bitMap->isMarked(addr+1), "Tautology for this control point"); | |
| 7975 DEBUG_ONLY(_bitMap->verifyNoOneBitsInRange(addr+2, addr+size);) | |
| 7976 } | |
| 7977 return size; | |
| 7978 } | |
| 7979 | |
| 7980 void SweepClosure::doPostIsFreeOrGarbageChunk(FreeChunk* fc, | |
| 7981 size_t chunkSize) { | |
| 7982 // doPostIsFreeOrGarbageChunk() should only be called in the smart allocation | |
| 7983 // scheme. | |
| 7984 bool fcInFreeLists = fc->isFree(); | |
| 7985 assert(_sp->adaptive_freelists(), "Should only be used in this case."); | |
| 7986 assert((HeapWord*)fc <= _limit, "sweep invariant"); | |
| 7987 if (CMSTestInFreeList && fcInFreeLists) { | |
| 7988 assert(_sp->verifyChunkInFreeLists(fc), | |
| 7989 "free chunk is not in free lists"); | |
| 7990 } | |
| 7991 | |
| 7992 | |
| 7993 if (CMSTraceSweeper) { | |
| 7994 gclog_or_tty->print_cr(" -- pick up another chunk at 0x%x (%d)", fc, chunkSize); | |
| 7995 } | |
| 7996 | |
| 7997 HeapWord* addr = (HeapWord*) fc; | |
| 7998 | |
| 7999 bool coalesce; | |
| 8000 size_t left = pointer_delta(addr, freeFinger()); | |
| 8001 size_t right = chunkSize; | |
| 8002 switch (FLSCoalescePolicy) { | |
| 8003 // numeric value forms a coalition aggressiveness metric | |
| 8004 case 0: { // never coalesce | |
| 8005 coalesce = false; | |
| 8006 break; | |
| 8007 } | |
| 8008 case 1: { // coalesce if left & right chunks on overpopulated lists | |
| 8009 coalesce = _sp->coalOverPopulated(left) && | |
| 8010 _sp->coalOverPopulated(right); | |
| 8011 break; | |
| 8012 } | |
| 8013 case 2: { // coalesce if left chunk on overpopulated list (default) | |
| 8014 coalesce = _sp->coalOverPopulated(left); | |
| 8015 break; | |
| 8016 } | |
| 8017 case 3: { // coalesce if left OR right chunk on overpopulated list | |
| 8018 coalesce = _sp->coalOverPopulated(left) || | |
| 8019 _sp->coalOverPopulated(right); | |
| 8020 break; | |
| 8021 } | |
| 8022 case 4: { // always coalesce | |
| 8023 coalesce = true; | |
| 8024 break; | |
| 8025 } | |
| 8026 default: | |
| 8027 ShouldNotReachHere(); | |
| 8028 } | |
| 8029 | |
| 8030 // Should the current free range be coalesced? | |
| 8031 // If the chunk is in a free range and either we decided to coalesce above | |
| 8032 // or the chunk is near the large block at the end of the heap | |
| 8033 // (isNearLargestChunk() returns true), then coalesce this chunk. | |
| 8034 bool doCoalesce = inFreeRange() && | |
| 8035 (coalesce || _g->isNearLargestChunk((HeapWord*)fc)); | |
| 8036 if (doCoalesce) { | |
| 8037 // Coalesce the current free range on the left with the new | |
| 8038 // chunk on the right. If either is on a free list, | |
| 8039 // it must be removed from the list and stashed in the closure. | |
| 8040 if (freeRangeInFreeLists()) { | |
| 8041 FreeChunk* ffc = (FreeChunk*)freeFinger(); | |
| 8042 assert(ffc->size() == pointer_delta(addr, freeFinger()), | |
| 8043 "Size of free range is inconsistent with chunk size."); | |
| 8044 if (CMSTestInFreeList) { | |
| 8045 assert(_sp->verifyChunkInFreeLists(ffc), | |
| 8046 "Chunk is not in free lists"); | |
| 8047 } | |
| 8048 _sp->coalDeath(ffc->size()); | |
| 8049 _sp->removeFreeChunkFromFreeLists(ffc); | |
| 8050 set_freeRangeInFreeLists(false); | |
| 8051 } | |
| 8052 if (fcInFreeLists) { | |
| 8053 _sp->coalDeath(chunkSize); | |
| 8054 assert(fc->size() == chunkSize, | |
| 8055 "The chunk has the wrong size or is not in the free lists"); | |
| 8056 _sp->removeFreeChunkFromFreeLists(fc); | |
| 8057 } | |
| 8058 set_lastFreeRangeCoalesced(true); | |
| 8059 } else { // not in a free range and/or should not coalesce | |
| 8060 // Return the current free range and start a new one. | |
| 8061 if (inFreeRange()) { | |
| 8062 // In a free range but cannot coalesce with the right hand chunk. | |
| 8063 // Put the current free range into the free lists. | |
| 8064 flushCurFreeChunk(freeFinger(), | |
| 8065 pointer_delta(addr, freeFinger())); | |
| 8066 } | |
| 8067 // Set up for new free range. Pass along whether the right hand | |
| 8068 // chunk is in the free lists. | |
| 8069 initialize_free_range((HeapWord*)fc, fcInFreeLists); | |
| 8070 } | |
| 8071 } | |
| 8072 void SweepClosure::flushCurFreeChunk(HeapWord* chunk, size_t size) { | |
| 8073 assert(inFreeRange(), "Should only be called if currently in a free range."); | |
| 8074 assert(size > 0, | |
| 8075 "A zero sized chunk cannot be added to the free lists."); | |
| 8076 if (!freeRangeInFreeLists()) { | |
| 8077 if(CMSTestInFreeList) { | |
| 8078 FreeChunk* fc = (FreeChunk*) chunk; | |
| 8079 fc->setSize(size); | |
| 8080 assert(!_sp->verifyChunkInFreeLists(fc), | |
| 8081 "chunk should not be in free lists yet"); | |
| 8082 } | |
| 8083 if (CMSTraceSweeper) { | |
| 8084 gclog_or_tty->print_cr(" -- add free block 0x%x (%d) to free lists", | |
| 8085 chunk, size); | |
| 8086 } | |
| 8087 // A new free range is going to be starting. The current | |
| 8088 // free range has not been added to the free lists yet or | |
| 8089 // was removed so add it back. | |
| 8090 // If the current free range was coalesced, then the death | |
| 8091 // of the free range was recorded. Record a birth now. | |
| 8092 if (lastFreeRangeCoalesced()) { | |
| 8093 _sp->coalBirth(size); | |
| 8094 } | |
| 8095 _sp->addChunkAndRepairOffsetTable(chunk, size, | |
| 8096 lastFreeRangeCoalesced()); | |
| 8097 } | |
| 8098 set_inFreeRange(false); | |
| 8099 set_freeRangeInFreeLists(false); | |
| 8100 } | |
| 8101 | |
| 8102 // We take a break if we've been at this for a while, | |
| 8103 // so as to avoid monopolizing the locks involved. | |
| 8104 void SweepClosure::do_yield_work(HeapWord* addr) { | |
| 8105 // Return current free chunk being used for coalescing (if any) | |
| 8106 // to the appropriate freelist. After yielding, the next | |
| 8107 // free block encountered will start a coalescing range of | |
| 8108 // free blocks. If the next free block is adjacent to the | |
| 8109 // chunk just flushed, they will need to wait for the next | |
| 8110 // sweep to be coalesced. | |
| 8111 if (inFreeRange()) { | |
| 8112 flushCurFreeChunk(freeFinger(), pointer_delta(addr, freeFinger())); | |
| 8113 } | |
| 8114 | |
| 8115 // First give up the locks, then yield, then re-lock. | |
| 8116 // We should probably use a constructor/destructor idiom to | |
| 8117 // do this unlock/lock or modify the MutexUnlocker class to | |
| 8118 // serve our purpose. XXX | |
| 8119 assert_lock_strong(_bitMap->lock()); | |
| 8120 assert_lock_strong(_freelistLock); | |
| 8121 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(), | |
| 8122 "CMS thread should hold CMS token"); | |
| 8123 _bitMap->lock()->unlock(); | |
| 8124 _freelistLock->unlock(); | |
| 8125 ConcurrentMarkSweepThread::desynchronize(true); | |
| 8126 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 8127 _collector->stopTimer(); | |
| 8128 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr()); | |
| 8129 if (PrintCMSStatistics != 0) { | |
| 8130 _collector->incrementYields(); | |
| 8131 } | |
| 8132 _collector->icms_wait(); | |
| 8133 | |
| 8134 // See the comment in coordinator_yield() | |
| 8135 for (unsigned i = 0; i < CMSYieldSleepCount && | |
| 8136 ConcurrentMarkSweepThread::should_yield() && | |
| 8137 !CMSCollector::foregroundGCIsActive(); ++i) { | |
| 8138 os::sleep(Thread::current(), 1, false); | |
| 8139 ConcurrentMarkSweepThread::acknowledge_yield_request(); | |
| 8140 } | |
| 8141 | |
| 8142 ConcurrentMarkSweepThread::synchronize(true); | |
| 8143 _freelistLock->lock(); | |
| 8144 _bitMap->lock()->lock_without_safepoint_check(); | |
| 8145 _collector->startTimer(); | |
| 8146 } | |
| 8147 | |
| 8148 #ifndef PRODUCT | |
| 8149 // This is actually very useful in a product build if it can | |
| 8150 // be called from the debugger. Compile it into the product | |
| 8151 // as needed. | |
| 8152 bool debug_verifyChunkInFreeLists(FreeChunk* fc) { | |
| 8153 return debug_cms_space->verifyChunkInFreeLists(fc); | |
| 8154 } | |
| 8155 | |
| 8156 void SweepClosure::record_free_block_coalesced(FreeChunk* fc) const { | |
| 8157 if (CMSTraceSweeper) { | |
| 8158 gclog_or_tty->print("Sweep:coal_free_blk 0x%x (%d)\n", fc, fc->size()); | |
| 8159 } | |
| 8160 } | |
| 8161 #endif | |
| 8162 | |
| 8163 // CMSIsAliveClosure | |
| 8164 bool CMSIsAliveClosure::do_object_b(oop obj) { | |
| 8165 HeapWord* addr = (HeapWord*)obj; | |
| 8166 return addr != NULL && | |
| 8167 (!_span.contains(addr) || _bit_map->isMarked(addr)); | |
| 8168 } | |
| 8169 | |
| 8170 // CMSKeepAliveClosure: the serial version | |
| 8171 void CMSKeepAliveClosure::do_oop(oop* p) { | |
| 8172 oop this_oop = *p; | |
| 8173 HeapWord* addr = (HeapWord*)this_oop; | |
| 8174 if (_span.contains(addr) && | |
| 8175 !_bit_map->isMarked(addr)) { | |
| 8176 _bit_map->mark(addr); | |
| 8177 bool simulate_overflow = false; | |
| 8178 NOT_PRODUCT( | |
| 8179 if (CMSMarkStackOverflowALot && | |
| 8180 _collector->simulate_overflow()) { | |
| 8181 // simulate a stack overflow | |
| 8182 simulate_overflow = true; | |
| 8183 } | |
| 8184 ) | |
| 8185 if (simulate_overflow || !_mark_stack->push(this_oop)) { | |
| 8186 _collector->push_on_overflow_list(this_oop); | |
| 8187 _collector->_ser_kac_ovflw++; | |
| 8188 } | |
| 8189 } | |
| 8190 } | |
| 8191 | |
| 8192 // CMSParKeepAliveClosure: a parallel version of the above. | |
| 8193 // The work queues are private to each closure (thread), | |
| 8194 // but (may be) available for stealing by other threads. | |
| 8195 void CMSParKeepAliveClosure::do_oop(oop* p) { | |
| 8196 oop this_oop = *p; | |
| 8197 HeapWord* addr = (HeapWord*)this_oop; | |
| 8198 if (_span.contains(addr) && | |
| 8199 !_bit_map->isMarked(addr)) { | |
| 8200 // In general, during recursive tracing, several threads | |
| 8201 // may be concurrently getting here; the first one to | |
| 8202 // "tag" it, claims it. | |
| 8203 if (_bit_map->par_mark(addr)) { | |
| 8204 bool res = _work_queue->push(this_oop); | |
| 8205 assert(res, "Low water mark should be much less than capacity"); | |
| 8206 // Do a recursive trim in the hope that this will keep | |
| 8207 // stack usage lower, but leave some oops for potential stealers | |
| 8208 trim_queue(_low_water_mark); | |
| 8209 } // Else, another thread got there first | |
| 8210 } | |
| 8211 } | |
| 8212 | |
| 8213 void CMSParKeepAliveClosure::trim_queue(uint max) { | |
| 8214 while (_work_queue->size() > max) { | |
| 8215 oop new_oop; | |
| 8216 if (_work_queue->pop_local(new_oop)) { | |
| 8217 assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop"); | |
| 8218 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
| 8219 "no white objects on this stack!"); | |
| 8220 assert(_span.contains((HeapWord*)new_oop), "Out of bounds oop"); | |
| 8221 // iterate over the oops in this oop, marking and pushing | |
| 8222 // the ones in CMS heap (i.e. in _span). | |
| 8223 new_oop->oop_iterate(&_mark_and_push); | |
| 8224 } | |
| 8225 } | |
| 8226 } | |
| 8227 | |
| 8228 void CMSInnerParMarkAndPushClosure::do_oop(oop* p) { | |
| 8229 oop this_oop = *p; | |
| 8230 HeapWord* addr = (HeapWord*)this_oop; | |
| 8231 if (_span.contains(addr) && | |
| 8232 !_bit_map->isMarked(addr)) { | |
| 8233 if (_bit_map->par_mark(addr)) { | |
| 8234 bool simulate_overflow = false; | |
| 8235 NOT_PRODUCT( | |
| 8236 if (CMSMarkStackOverflowALot && | |
| 8237 _collector->par_simulate_overflow()) { | |
| 8238 // simulate a stack overflow | |
| 8239 simulate_overflow = true; | |
| 8240 } | |
| 8241 ) | |
| 8242 if (simulate_overflow || !_work_queue->push(this_oop)) { | |
| 8243 _collector->par_push_on_overflow_list(this_oop); | |
| 8244 _collector->_par_kac_ovflw++; | |
| 8245 } | |
| 8246 } // Else another thread got there already | |
| 8247 } | |
| 8248 } | |
| 8249 | |
| 8250 ////////////////////////////////////////////////////////////////// | |
| 8251 // CMSExpansionCause ///////////////////////////// | |
| 8252 ////////////////////////////////////////////////////////////////// | |
| 8253 const char* CMSExpansionCause::to_string(CMSExpansionCause::Cause cause) { | |
| 8254 switch (cause) { | |
| 8255 case _no_expansion: | |
| 8256 return "No expansion"; | |
| 8257 case _satisfy_free_ratio: | |
| 8258 return "Free ratio"; | |
| 8259 case _satisfy_promotion: | |
| 8260 return "Satisfy promotion"; | |
| 8261 case _satisfy_allocation: | |
| 8262 return "allocation"; | |
| 8263 case _allocate_par_lab: | |
| 8264 return "Par LAB"; | |
| 8265 case _allocate_par_spooling_space: | |
| 8266 return "Par Spooling Space"; | |
| 8267 case _adaptive_size_policy: | |
| 8268 return "Ergonomics"; | |
| 8269 default: | |
| 8270 return "unknown"; | |
| 8271 } | |
| 8272 } | |
| 8273 | |
| 8274 void CMSDrainMarkingStackClosure::do_void() { | |
| 8275 // the max number to take from overflow list at a time | |
| 8276 const size_t num = _mark_stack->capacity()/4; | |
| 8277 while (!_mark_stack->isEmpty() || | |
| 8278 // if stack is empty, check the overflow list | |
| 8279 _collector->take_from_overflow_list(num, _mark_stack)) { | |
| 8280 oop this_oop = _mark_stack->pop(); | |
| 8281 HeapWord* addr = (HeapWord*)this_oop; | |
| 8282 assert(_span.contains(addr), "Should be within span"); | |
| 8283 assert(_bit_map->isMarked(addr), "Should be marked"); | |
| 8284 assert(this_oop->is_oop(), "Should be an oop"); | |
| 8285 this_oop->oop_iterate(_keep_alive); | |
| 8286 } | |
| 8287 } | |
| 8288 | |
| 8289 void CMSParDrainMarkingStackClosure::do_void() { | |
| 8290 // drain queue | |
| 8291 trim_queue(0); | |
| 8292 } | |
| 8293 | |
| 8294 // Trim our work_queue so its length is below max at return | |
| 8295 void CMSParDrainMarkingStackClosure::trim_queue(uint max) { | |
| 8296 while (_work_queue->size() > max) { | |
| 8297 oop new_oop; | |
| 8298 if (_work_queue->pop_local(new_oop)) { | |
| 8299 assert(new_oop->is_oop(), "Expected an oop"); | |
| 8300 assert(_bit_map->isMarked((HeapWord*)new_oop), | |
| 8301 "no white objects on this stack!"); | |
| 8302 assert(_span.contains((HeapWord*)new_oop), "Out of bounds oop"); | |
| 8303 // iterate over the oops in this oop, marking and pushing | |
| 8304 // the ones in CMS heap (i.e. in _span). | |
| 8305 new_oop->oop_iterate(&_mark_and_push); | |
| 8306 } | |
| 8307 } | |
| 8308 } | |
| 8309 | |
| 8310 //////////////////////////////////////////////////////////////////// | |
| 8311 // Support for Marking Stack Overflow list handling and related code | |
| 8312 //////////////////////////////////////////////////////////////////// | |
| 8313 // Much of the following code is similar in shape and spirit to the | |
| 8314 // code used in ParNewGC. We should try and share that code | |
| 8315 // as much as possible in the future. | |
| 8316 | |
| 8317 #ifndef PRODUCT | |
| 8318 // Debugging support for CMSStackOverflowALot | |
| 8319 | |
| 8320 // It's OK to call this multi-threaded; the worst thing | |
| 8321 // that can happen is that we'll get a bunch of closely | |
| 8322 // spaced simulated oveflows, but that's OK, in fact | |
| 8323 // probably good as it would exercise the overflow code | |
| 8324 // under contention. | |
| 8325 bool CMSCollector::simulate_overflow() { | |
| 8326 if (_overflow_counter-- <= 0) { // just being defensive | |
| 8327 _overflow_counter = CMSMarkStackOverflowInterval; | |
| 8328 return true; | |
| 8329 } else { | |
| 8330 return false; | |
| 8331 } | |
| 8332 } | |
| 8333 | |
| 8334 bool CMSCollector::par_simulate_overflow() { | |
| 8335 return simulate_overflow(); | |
| 8336 } | |
| 8337 #endif | |
| 8338 | |
| 8339 // Single-threaded | |
| 8340 bool CMSCollector::take_from_overflow_list(size_t num, CMSMarkStack* stack) { | |
| 8341 assert(stack->isEmpty(), "Expected precondition"); | |
| 8342 assert(stack->capacity() > num, "Shouldn't bite more than can chew"); | |
| 8343 size_t i = num; | |
| 8344 oop cur = _overflow_list; | |
| 8345 const markOop proto = markOopDesc::prototype(); | |
| 8346 NOT_PRODUCT(size_t n = 0;) | |
| 8347 for (oop next; i > 0 && cur != NULL; cur = next, i--) { | |
| 8348 next = oop(cur->mark()); | |
| 8349 cur->set_mark(proto); // until proven otherwise | |
| 8350 assert(cur->is_oop(), "Should be an oop"); | |
| 8351 bool res = stack->push(cur); | |
| 8352 assert(res, "Bit off more than can chew?"); | |
| 8353 NOT_PRODUCT(n++;) | |
| 8354 } | |
| 8355 _overflow_list = cur; | |
| 8356 #ifndef PRODUCT | |
| 8357 assert(_num_par_pushes >= n, "Too many pops?"); | |
| 8358 _num_par_pushes -=n; | |
| 8359 #endif | |
| 8360 return !stack->isEmpty(); | |
| 8361 } | |
| 8362 | |
| 8363 // Multi-threaded; use CAS to break off a prefix | |
| 8364 bool CMSCollector::par_take_from_overflow_list(size_t num, | |
| 8365 OopTaskQueue* work_q) { | |
| 8366 assert(work_q->size() == 0, "That's the current policy"); | |
| 8367 assert(num < work_q->max_elems(), "Can't bite more than we can chew"); | |
| 8368 if (_overflow_list == NULL) { | |
| 8369 return false; | |
| 8370 } | |
| 8371 // Grab the entire list; we'll put back a suffix | |
| 8372 oop prefix = (oop)Atomic::xchg_ptr(NULL, &_overflow_list); | |
| 8373 if (prefix == NULL) { // someone grabbed it before we did ... | |
| 8374 // ... we could spin for a short while, but for now we don't | |
| 8375 return false; | |
| 8376 } | |
| 8377 size_t i = num; | |
| 8378 oop cur = prefix; | |
| 8379 for (; i > 1 && cur->mark() != NULL; cur = oop(cur->mark()), i--); | |
| 8380 if (cur->mark() != NULL) { | |
| 8381 oop suffix_head = cur->mark(); // suffix will be put back on global list | |
| 8382 cur->set_mark(NULL); // break off suffix | |
| 8383 // Find tail of suffix so we can prepend suffix to global list | |
| 8384 for (cur = suffix_head; cur->mark() != NULL; cur = (oop)(cur->mark())); | |
| 8385 oop suffix_tail = cur; | |
| 8386 assert(suffix_tail != NULL && suffix_tail->mark() == NULL, | |
| 8387 "Tautology"); | |
| 8388 oop observed_overflow_list = _overflow_list; | |
| 8389 do { | |
| 8390 cur = observed_overflow_list; | |
| 8391 suffix_tail->set_mark(markOop(cur)); | |
| 8392 observed_overflow_list = | |
| 8393 (oop) Atomic::cmpxchg_ptr(suffix_head, &_overflow_list, cur); | |
| 8394 } while (cur != observed_overflow_list); | |
| 8395 } | |
| 8396 | |
| 8397 // Push the prefix elements on work_q | |
| 8398 assert(prefix != NULL, "control point invariant"); | |
| 8399 const markOop proto = markOopDesc::prototype(); | |
| 8400 oop next; | |
| 8401 NOT_PRODUCT(size_t n = 0;) | |
| 8402 for (cur = prefix; cur != NULL; cur = next) { | |
| 8403 next = oop(cur->mark()); | |
| 8404 cur->set_mark(proto); // until proven otherwise | |
| 8405 assert(cur->is_oop(), "Should be an oop"); | |
| 8406 bool res = work_q->push(cur); | |
| 8407 assert(res, "Bit off more than we can chew?"); | |
| 8408 NOT_PRODUCT(n++;) | |
| 8409 } | |
| 8410 #ifndef PRODUCT | |
| 8411 assert(_num_par_pushes >= n, "Too many pops?"); | |
| 8412 Atomic::add_ptr(-(intptr_t)n, &_num_par_pushes); | |
| 8413 #endif | |
| 8414 return true; | |
| 8415 } | |
| 8416 | |
| 8417 // Single-threaded | |
| 8418 void CMSCollector::push_on_overflow_list(oop p) { | |
| 8419 NOT_PRODUCT(_num_par_pushes++;) | |
| 8420 assert(p->is_oop(), "Not an oop"); | |
| 8421 preserve_mark_if_necessary(p); | |
| 8422 p->set_mark((markOop)_overflow_list); | |
| 8423 _overflow_list = p; | |
| 8424 } | |
| 8425 | |
| 8426 // Multi-threaded; use CAS to prepend to overflow list | |
| 8427 void CMSCollector::par_push_on_overflow_list(oop p) { | |
| 8428 NOT_PRODUCT(Atomic::inc_ptr(&_num_par_pushes);) | |
| 8429 assert(p->is_oop(), "Not an oop"); | |
| 8430 par_preserve_mark_if_necessary(p); | |
| 8431 oop observed_overflow_list = _overflow_list; | |
| 8432 oop cur_overflow_list; | |
| 8433 do { | |
| 8434 cur_overflow_list = observed_overflow_list; | |
| 8435 p->set_mark(markOop(cur_overflow_list)); | |
| 8436 observed_overflow_list = | |
| 8437 (oop) Atomic::cmpxchg_ptr(p, &_overflow_list, cur_overflow_list); | |
| 8438 } while (cur_overflow_list != observed_overflow_list); | |
| 8439 } | |
| 8440 | |
| 8441 // Single threaded | |
| 8442 // General Note on GrowableArray: pushes may silently fail | |
| 8443 // because we are (temporarily) out of C-heap for expanding | |
| 8444 // the stack. The problem is quite ubiquitous and affects | |
| 8445 // a lot of code in the JVM. The prudent thing for GrowableArray | |
| 8446 // to do (for now) is to exit with an error. However, that may | |
| 8447 // be too draconian in some cases because the caller may be | |
| 8448 // able to recover without much harm. For suych cases, we | |
| 8449 // should probably introduce a "soft_push" method which returns | |
| 8450 // an indication of success or failure with the assumption that | |
| 8451 // the caller may be able to recover from a failure; code in | |
| 8452 // the VM can then be changed, incrementally, to deal with such | |
| 8453 // failures where possible, thus, incrementally hardening the VM | |
| 8454 // in such low resource situations. | |
| 8455 void CMSCollector::preserve_mark_work(oop p, markOop m) { | |
| 8456 int PreserveMarkStackSize = 128; | |
| 8457 | |
| 8458 if (_preserved_oop_stack == NULL) { | |
| 8459 assert(_preserved_mark_stack == NULL, | |
| 8460 "bijection with preserved_oop_stack"); | |
| 8461 // Allocate the stacks | |
| 8462 _preserved_oop_stack = new (ResourceObj::C_HEAP) | |
| 8463 GrowableArray<oop>(PreserveMarkStackSize, true); | |
| 8464 _preserved_mark_stack = new (ResourceObj::C_HEAP) | |
| 8465 GrowableArray<markOop>(PreserveMarkStackSize, true); | |
| 8466 if (_preserved_oop_stack == NULL || _preserved_mark_stack == NULL) { | |
| 8467 vm_exit_out_of_memory(2* PreserveMarkStackSize * sizeof(oop) /* punt */, | |
| 8468 "Preserved Mark/Oop Stack for CMS (C-heap)"); | |
| 8469 } | |
| 8470 } | |
| 8471 _preserved_oop_stack->push(p); | |
| 8472 _preserved_mark_stack->push(m); | |
| 8473 assert(m == p->mark(), "Mark word changed"); | |
| 8474 assert(_preserved_oop_stack->length() == _preserved_mark_stack->length(), | |
| 8475 "bijection"); | |
| 8476 } | |
| 8477 | |
| 8478 // Single threaded | |
| 8479 void CMSCollector::preserve_mark_if_necessary(oop p) { | |
| 8480 markOop m = p->mark(); | |
| 8481 if (m->must_be_preserved(p)) { | |
| 8482 preserve_mark_work(p, m); | |
| 8483 } | |
| 8484 } | |
| 8485 | |
| 8486 void CMSCollector::par_preserve_mark_if_necessary(oop p) { | |
| 8487 markOop m = p->mark(); | |
| 8488 if (m->must_be_preserved(p)) { | |
| 8489 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); | |
| 8490 // Even though we read the mark word without holding | |
| 8491 // the lock, we are assured that it will not change | |
| 8492 // because we "own" this oop, so no other thread can | |
| 8493 // be trying to push it on the overflow list; see | |
| 8494 // the assertion in preserve_mark_work() that checks | |
| 8495 // that m == p->mark(). | |
| 8496 preserve_mark_work(p, m); | |
| 8497 } | |
| 8498 } | |
| 8499 | |
| 8500 // We should be able to do this multi-threaded, | |
| 8501 // a chunk of stack being a task (this is | |
| 8502 // correct because each oop only ever appears | |
| 8503 // once in the overflow list. However, it's | |
| 8504 // not very easy to completely overlap this with | |
| 8505 // other operations, so will generally not be done | |
| 8506 // until all work's been completed. Because we | |
| 8507 // expect the preserved oop stack (set) to be small, | |
| 8508 // it's probably fine to do this single-threaded. | |
| 8509 // We can explore cleverer concurrent/overlapped/parallel | |
| 8510 // processing of preserved marks if we feel the | |
| 8511 // need for this in the future. Stack overflow should | |
| 8512 // be so rare in practice and, when it happens, its | |
| 8513 // effect on performance so great that this will | |
| 8514 // likely just be in the noise anyway. | |
| 8515 void CMSCollector::restore_preserved_marks_if_any() { | |
| 8516 if (_preserved_oop_stack == NULL) { | |
| 8517 assert(_preserved_mark_stack == NULL, | |
| 8518 "bijection with preserved_oop_stack"); | |
| 8519 return; | |
| 8520 } | |
| 8521 | |
| 8522 assert(SafepointSynchronize::is_at_safepoint(), | |
| 8523 "world should be stopped"); | |
| 8524 assert(Thread::current()->is_ConcurrentGC_thread() || | |
| 8525 Thread::current()->is_VM_thread(), | |
| 8526 "should be single-threaded"); | |
| 8527 | |
| 8528 int length = _preserved_oop_stack->length(); | |
| 8529 assert(_preserved_mark_stack->length() == length, "bijection"); | |
| 8530 for (int i = 0; i < length; i++) { | |
| 8531 oop p = _preserved_oop_stack->at(i); | |
| 8532 assert(p->is_oop(), "Should be an oop"); | |
| 8533 assert(_span.contains(p), "oop should be in _span"); | |
| 8534 assert(p->mark() == markOopDesc::prototype(), | |
| 8535 "Set when taken from overflow list"); | |
| 8536 markOop m = _preserved_mark_stack->at(i); | |
| 8537 p->set_mark(m); | |
| 8538 } | |
| 8539 _preserved_mark_stack->clear(); | |
| 8540 _preserved_oop_stack->clear(); | |
| 8541 assert(_preserved_mark_stack->is_empty() && | |
| 8542 _preserved_oop_stack->is_empty(), | |
| 8543 "stacks were cleared above"); | |
| 8544 } | |
| 8545 | |
| 8546 #ifndef PRODUCT | |
| 8547 bool CMSCollector::no_preserved_marks() const { | |
| 8548 return ( ( _preserved_mark_stack == NULL | |
| 8549 && _preserved_oop_stack == NULL) | |
| 8550 || ( _preserved_mark_stack->is_empty() | |
| 8551 && _preserved_oop_stack->is_empty())); | |
| 8552 } | |
| 8553 #endif | |
| 8554 | |
| 8555 CMSAdaptiveSizePolicy* ASConcurrentMarkSweepGeneration::cms_size_policy() const | |
| 8556 { | |
| 8557 GenCollectedHeap* gch = (GenCollectedHeap*) GenCollectedHeap::heap(); | |
| 8558 CMSAdaptiveSizePolicy* size_policy = | |
| 8559 (CMSAdaptiveSizePolicy*) gch->gen_policy()->size_policy(); | |
| 8560 assert(size_policy->is_gc_cms_adaptive_size_policy(), | |
| 8561 "Wrong type for size policy"); | |
| 8562 return size_policy; | |
| 8563 } | |
| 8564 | |
| 8565 void ASConcurrentMarkSweepGeneration::resize(size_t cur_promo_size, | |
| 8566 size_t desired_promo_size) { | |
| 8567 if (cur_promo_size < desired_promo_size) { | |
| 8568 size_t expand_bytes = desired_promo_size - cur_promo_size; | |
| 8569 if (PrintAdaptiveSizePolicy && Verbose) { | |
| 8570 gclog_or_tty->print_cr(" ASConcurrentMarkSweepGeneration::resize " | |
| 8571 "Expanding tenured generation by " SIZE_FORMAT " (bytes)", | |
| 8572 expand_bytes); | |
| 8573 } | |
| 8574 expand(expand_bytes, | |
| 8575 MinHeapDeltaBytes, | |
| 8576 CMSExpansionCause::_adaptive_size_policy); | |
| 8577 } else if (desired_promo_size < cur_promo_size) { | |
| 8578 size_t shrink_bytes = cur_promo_size - desired_promo_size; | |
| 8579 if (PrintAdaptiveSizePolicy && Verbose) { | |
| 8580 gclog_or_tty->print_cr(" ASConcurrentMarkSweepGeneration::resize " | |
| 8581 "Shrinking tenured generation by " SIZE_FORMAT " (bytes)", | |
| 8582 shrink_bytes); | |
| 8583 } | |
| 8584 shrink(shrink_bytes); | |
| 8585 } | |
| 8586 } | |
| 8587 | |
| 8588 CMSGCAdaptivePolicyCounters* ASConcurrentMarkSweepGeneration::gc_adaptive_policy_counters() { | |
| 8589 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 8590 CMSGCAdaptivePolicyCounters* counters = | |
| 8591 (CMSGCAdaptivePolicyCounters*) gch->collector_policy()->counters(); | |
| 8592 assert(counters->kind() == GCPolicyCounters::CMSGCAdaptivePolicyCountersKind, | |
| 8593 "Wrong kind of counters"); | |
| 8594 return counters; | |
| 8595 } | |
| 8596 | |
| 8597 | |
| 8598 void ASConcurrentMarkSweepGeneration::update_counters() { | |
| 8599 if (UsePerfData) { | |
| 8600 _space_counters->update_all(); | |
| 8601 _gen_counters->update_all(); | |
| 8602 CMSGCAdaptivePolicyCounters* counters = gc_adaptive_policy_counters(); | |
| 8603 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 8604 CMSGCStats* gc_stats_l = (CMSGCStats*) gc_stats(); | |
| 8605 assert(gc_stats_l->kind() == GCStats::CMSGCStatsKind, | |
| 8606 "Wrong gc statistics type"); | |
| 8607 counters->update_counters(gc_stats_l); | |
| 8608 } | |
| 8609 } | |
| 8610 | |
| 8611 void ASConcurrentMarkSweepGeneration::update_counters(size_t used) { | |
| 8612 if (UsePerfData) { | |
| 8613 _space_counters->update_used(used); | |
| 8614 _space_counters->update_capacity(); | |
| 8615 _gen_counters->update_all(); | |
| 8616 | |
| 8617 CMSGCAdaptivePolicyCounters* counters = gc_adaptive_policy_counters(); | |
| 8618 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 8619 CMSGCStats* gc_stats_l = (CMSGCStats*) gc_stats(); | |
| 8620 assert(gc_stats_l->kind() == GCStats::CMSGCStatsKind, | |
| 8621 "Wrong gc statistics type"); | |
| 8622 counters->update_counters(gc_stats_l); | |
| 8623 } | |
| 8624 } | |
| 8625 | |
| 8626 // The desired expansion delta is computed so that: | |
| 8627 // . desired free percentage or greater is used | |
| 8628 void ASConcurrentMarkSweepGeneration::compute_new_size() { | |
| 8629 assert_locked_or_safepoint(Heap_lock); | |
| 8630 | |
| 8631 GenCollectedHeap* gch = (GenCollectedHeap*) GenCollectedHeap::heap(); | |
| 8632 | |
| 8633 // If incremental collection failed, we just want to expand | |
| 8634 // to the limit. | |
| 8635 if (incremental_collection_failed()) { | |
| 8636 clear_incremental_collection_failed(); | |
| 8637 grow_to_reserved(); | |
| 8638 return; | |
| 8639 } | |
| 8640 | |
| 8641 assert(UseAdaptiveSizePolicy, "Should be using adaptive sizing"); | |
| 8642 | |
| 8643 assert(gch->kind() == CollectedHeap::GenCollectedHeap, | |
| 8644 "Wrong type of heap"); | |
| 8645 int prev_level = level() - 1; | |
| 8646 assert(prev_level >= 0, "The cms generation is the lowest generation"); | |
| 8647 Generation* prev_gen = gch->get_gen(prev_level); | |
| 8648 assert(prev_gen->kind() == Generation::ASParNew, | |
| 8649 "Wrong type of young generation"); | |
| 8650 ParNewGeneration* younger_gen = (ParNewGeneration*) prev_gen; | |
| 8651 size_t cur_eden = younger_gen->eden()->capacity(); | |
| 8652 CMSAdaptiveSizePolicy* size_policy = cms_size_policy(); | |
| 8653 size_t cur_promo = free(); | |
| 8654 size_policy->compute_tenured_generation_free_space(cur_promo, | |
| 8655 max_available(), | |
| 8656 cur_eden); | |
| 8657 resize(cur_promo, size_policy->promo_size()); | |
| 8658 | |
| 8659 // Record the new size of the space in the cms generation | |
| 8660 // that is available for promotions. This is temporary. | |
| 8661 // It should be the desired promo size. | |
| 8662 size_policy->avg_cms_promo()->sample(free()); | |
| 8663 size_policy->avg_old_live()->sample(used()); | |
| 8664 | |
| 8665 if (UsePerfData) { | |
| 8666 CMSGCAdaptivePolicyCounters* counters = gc_adaptive_policy_counters(); | |
| 8667 counters->update_cms_capacity_counter(capacity()); | |
| 8668 } | |
| 8669 } | |
| 8670 | |
| 8671 void ASConcurrentMarkSweepGeneration::shrink_by(size_t desired_bytes) { | |
| 8672 assert_locked_or_safepoint(Heap_lock); | |
| 8673 assert_lock_strong(freelistLock()); | |
| 8674 HeapWord* old_end = _cmsSpace->end(); | |
| 8675 HeapWord* unallocated_start = _cmsSpace->unallocated_block(); | |
| 8676 assert(old_end >= unallocated_start, "Miscalculation of unallocated_start"); | |
| 8677 FreeChunk* chunk_at_end = find_chunk_at_end(); | |
| 8678 if (chunk_at_end == NULL) { | |
| 8679 // No room to shrink | |
| 8680 if (PrintGCDetails && Verbose) { | |
| 8681 gclog_or_tty->print_cr("No room to shrink: old_end " | |
| 8682 PTR_FORMAT " unallocated_start " PTR_FORMAT | |
| 8683 " chunk_at_end " PTR_FORMAT, | |
| 8684 old_end, unallocated_start, chunk_at_end); | |
| 8685 } | |
| 8686 return; | |
| 8687 } else { | |
| 8688 | |
| 8689 // Find the chunk at the end of the space and determine | |
| 8690 // how much it can be shrunk. | |
| 8691 size_t shrinkable_size_in_bytes = chunk_at_end->size(); | |
| 8692 size_t aligned_shrinkable_size_in_bytes = | |
| 8693 align_size_down(shrinkable_size_in_bytes, os::vm_page_size()); | |
| 8694 assert(unallocated_start <= chunk_at_end->end(), | |
| 8695 "Inconsistent chunk at end of space"); | |
| 8696 size_t bytes = MIN2(desired_bytes, aligned_shrinkable_size_in_bytes); | |
| 8697 size_t word_size_before = heap_word_size(_virtual_space.committed_size()); | |
| 8698 | |
| 8699 // Shrink the underlying space | |
| 8700 _virtual_space.shrink_by(bytes); | |
| 8701 if (PrintGCDetails && Verbose) { | |
| 8702 gclog_or_tty->print_cr("ConcurrentMarkSweepGeneration::shrink_by:" | |
| 8703 " desired_bytes " SIZE_FORMAT | |
| 8704 " shrinkable_size_in_bytes " SIZE_FORMAT | |
| 8705 " aligned_shrinkable_size_in_bytes " SIZE_FORMAT | |
| 8706 " bytes " SIZE_FORMAT, | |
| 8707 desired_bytes, shrinkable_size_in_bytes, | |
| 8708 aligned_shrinkable_size_in_bytes, bytes); | |
| 8709 gclog_or_tty->print_cr(" old_end " SIZE_FORMAT | |
| 8710 " unallocated_start " SIZE_FORMAT, | |
| 8711 old_end, unallocated_start); | |
| 8712 } | |
| 8713 | |
| 8714 // If the space did shrink (shrinking is not guaranteed), | |
| 8715 // shrink the chunk at the end by the appropriate amount. | |
| 8716 if (((HeapWord*)_virtual_space.high()) < old_end) { | |
| 8717 size_t new_word_size = | |
| 8718 heap_word_size(_virtual_space.committed_size()); | |
| 8719 | |
| 8720 // Have to remove the chunk from the dictionary because it is changing | |
| 8721 // size and might be someplace elsewhere in the dictionary. | |
| 8722 | |
| 8723 // Get the chunk at end, shrink it, and put it | |
| 8724 // back. | |
| 8725 _cmsSpace->removeChunkFromDictionary(chunk_at_end); | |
| 8726 size_t word_size_change = word_size_before - new_word_size; | |
| 8727 size_t chunk_at_end_old_size = chunk_at_end->size(); | |
| 8728 assert(chunk_at_end_old_size >= word_size_change, | |
| 8729 "Shrink is too large"); | |
| 8730 chunk_at_end->setSize(chunk_at_end_old_size - | |
| 8731 word_size_change); | |
| 8732 _cmsSpace->freed((HeapWord*) chunk_at_end->end(), | |
| 8733 word_size_change); | |
| 8734 | |
| 8735 _cmsSpace->returnChunkToDictionary(chunk_at_end); | |
| 8736 | |
| 8737 MemRegion mr(_cmsSpace->bottom(), new_word_size); | |
| 8738 _bts->resize(new_word_size); // resize the block offset shared array | |
| 8739 Universe::heap()->barrier_set()->resize_covered_region(mr); | |
| 8740 _cmsSpace->assert_locked(); | |
| 8741 _cmsSpace->set_end((HeapWord*)_virtual_space.high()); | |
| 8742 | |
| 8743 NOT_PRODUCT(_cmsSpace->dictionary()->verify()); | |
| 8744 | |
| 8745 // update the space and generation capacity counters | |
| 8746 if (UsePerfData) { | |
| 8747 _space_counters->update_capacity(); | |
| 8748 _gen_counters->update_all(); | |
| 8749 } | |
| 8750 | |
| 8751 if (Verbose && PrintGCDetails) { | |
| 8752 size_t new_mem_size = _virtual_space.committed_size(); | |
| 8753 size_t old_mem_size = new_mem_size + bytes; | |
| 8754 gclog_or_tty->print_cr("Shrinking %s from %ldK by %ldK to %ldK", | |
| 8755 name(), old_mem_size/K, bytes/K, new_mem_size/K); | |
| 8756 } | |
| 8757 } | |
| 8758 | |
| 8759 assert(_cmsSpace->unallocated_block() <= _cmsSpace->end(), | |
| 8760 "Inconsistency at end of space"); | |
| 8761 assert(chunk_at_end->end() == _cmsSpace->end(), | |
| 8762 "Shrinking is inconsistent"); | |
| 8763 return; | |
| 8764 } | |
| 8765 } | |
| 8766 | |
| 8767 // Transfer some number of overflown objects to usual marking | |
| 8768 // stack. Return true if some objects were transferred. | |
| 8769 bool MarkRefsIntoAndScanClosure::take_from_overflow_list() { | |
| 8770 size_t num = MIN2((size_t)_mark_stack->capacity()/4, | |
| 8771 (size_t)ParGCDesiredObjsFromOverflowList); | |
| 8772 | |
| 8773 bool res = _collector->take_from_overflow_list(num, _mark_stack); | |
| 8774 assert(_collector->overflow_list_is_empty() || res, | |
| 8775 "If list is not empty, we should have taken something"); | |
| 8776 assert(!res || !_mark_stack->isEmpty(), | |
| 8777 "If we took something, it should now be on our stack"); | |
| 8778 return res; | |
| 8779 } | |
| 8780 | |
| 8781 size_t MarkDeadObjectsClosure::do_blk(HeapWord* addr) { | |
| 8782 size_t res = _sp->block_size_no_stall(addr, _collector); | |
| 8783 assert(res != 0, "Should always be able to compute a size"); | |
| 8784 if (_sp->block_is_obj(addr)) { | |
| 8785 if (_live_bit_map->isMarked(addr)) { | |
| 8786 // It can't have been dead in a previous cycle | |
| 8787 guarantee(!_dead_bit_map->isMarked(addr), "No resurrection!"); | |
| 8788 } else { | |
| 8789 _dead_bit_map->mark(addr); // mark the dead object | |
| 8790 } | |
| 8791 } | |
| 8792 return res; | |
| 8793 } |