1 /* 2 * Copyright (c) 2002, 2013, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "classfile/symbolTable.hpp" 27 #include "code/codeCache.hpp" 28 #include "gc_implementation/parallelScavenge/cardTableExtension.hpp" 29 #include "gc_implementation/parallelScavenge/gcTaskManager.hpp" 30 #include "gc_implementation/parallelScavenge/generationSizer.hpp" 31 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.hpp" 32 #include "gc_implementation/parallelScavenge/psAdaptiveSizePolicy.hpp" 33 #include "gc_implementation/parallelScavenge/psMarkSweep.hpp" 34 #include "gc_implementation/parallelScavenge/psParallelCompact.hpp" 35 #include "gc_implementation/parallelScavenge/psScavenge.inline.hpp" 36 #include "gc_implementation/parallelScavenge/psTasks.hpp" 37 #include "gc_implementation/shared/isGCActiveMark.hpp" 38 #include "gc_implementation/shared/spaceDecorator.hpp" 39 #include "gc_interface/gcCause.hpp" 40 #include "memory/collectorPolicy.hpp" 41 #include "memory/gcLocker.inline.hpp" 42 #include "memory/referencePolicy.hpp" 43 #include "memory/referenceProcessor.hpp" 44 #include "memory/resourceArea.hpp" 45 #include "oops/oop.inline.hpp" 46 #include "oops/oop.psgc.inline.hpp" 47 #include "runtime/biasedLocking.hpp" 48 #include "runtime/fprofiler.hpp" 49 #include "runtime/handles.inline.hpp" 50 #include "runtime/threadCritical.hpp" 51 #include "runtime/vmThread.hpp" 52 #include "runtime/vm_operations.hpp" 53 #include "services/memoryService.hpp" 54 #include "utilities/stack.inline.hpp" 55 56 57 HeapWord* PSScavenge::_to_space_top_before_gc = NULL; 58 int PSScavenge::_consecutive_skipped_scavenges = 0; 59 ReferenceProcessor* PSScavenge::_ref_processor = NULL; 60 CardTableExtension* PSScavenge::_card_table = NULL; 61 bool PSScavenge::_survivor_overflow = false; 62 uint PSScavenge::_tenuring_threshold = 0; 63 HeapWord* PSScavenge::_young_generation_boundary = NULL; 64 elapsedTimer PSScavenge::_accumulated_time; 65 Stack<markOop, mtGC> PSScavenge::_preserved_mark_stack; 66 Stack<oop, mtGC> PSScavenge::_preserved_oop_stack; 67 CollectorCounters* PSScavenge::_counters = NULL; 68 bool PSScavenge::_promotion_failed = false; 69 70 // Define before use 71 class PSIsAliveClosure: public BoolObjectClosure { 72 public: 73 void do_object(oop p) { 74 assert(false, "Do not call."); 75 } 76 bool do_object_b(oop p) { 77 return (!PSScavenge::is_obj_in_young((HeapWord*) p)) || p->is_forwarded(); 78 } 79 }; 80 81 PSIsAliveClosure PSScavenge::_is_alive_closure; 82 83 class PSKeepAliveClosure: public OopClosure { 84 protected: 85 MutableSpace* _to_space; 86 PSPromotionManager* _promotion_manager; 87 88 public: 89 PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) { 90 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 91 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 92 _to_space = heap->young_gen()->to_space(); 93 94 assert(_promotion_manager != NULL, "Sanity"); 95 } 96 97 template <class T> void do_oop_work(T* p) { 98 assert (!oopDesc::is_null(*p), "expected non-null ref"); 99 assert ((oopDesc::load_decode_heap_oop_not_null(p))->is_oop(), 100 "expected an oop while scanning weak refs"); 101 102 // Weak refs may be visited more than once. 103 if (PSScavenge::should_scavenge(p, _to_space)) { 104 PSScavenge::copy_and_push_safe_barrier<T, /*promote_immediately=*/false>(_promotion_manager, p); 105 } 106 } 107 virtual void do_oop(oop* p) { PSKeepAliveClosure::do_oop_work(p); } 108 virtual void do_oop(narrowOop* p) { PSKeepAliveClosure::do_oop_work(p); } 109 }; 110 111 class PSEvacuateFollowersClosure: public VoidClosure { 112 private: 113 PSPromotionManager* _promotion_manager; 114 public: 115 PSEvacuateFollowersClosure(PSPromotionManager* pm) : _promotion_manager(pm) {} 116 117 virtual void do_void() { 118 assert(_promotion_manager != NULL, "Sanity"); 119 _promotion_manager->drain_stacks(true); 120 guarantee(_promotion_manager->stacks_empty(), 121 "stacks should be empty at this point"); 122 } 123 }; 124 125 class PSPromotionFailedClosure : public ObjectClosure { 126 virtual void do_object(oop obj) { 127 if (obj->is_forwarded()) { 128 obj->init_mark(); 129 } 130 } 131 }; 132 133 class PSRefProcTaskProxy: public GCTask { 134 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 135 ProcessTask & _rp_task; 136 uint _work_id; 137 public: 138 PSRefProcTaskProxy(ProcessTask & rp_task, uint work_id) 139 : _rp_task(rp_task), 140 _work_id(work_id) 141 { } 142 143 private: 144 virtual char* name() { return (char *)"Process referents by policy in parallel"; } 145 virtual void do_it(GCTaskManager* manager, uint which); 146 }; 147 148 void PSRefProcTaskProxy::do_it(GCTaskManager* manager, uint which) 149 { 150 PSPromotionManager* promotion_manager = 151 PSPromotionManager::gc_thread_promotion_manager(which); 152 assert(promotion_manager != NULL, "sanity check"); 153 PSKeepAliveClosure keep_alive(promotion_manager); 154 PSEvacuateFollowersClosure evac_followers(promotion_manager); 155 PSIsAliveClosure is_alive; 156 _rp_task.work(_work_id, is_alive, keep_alive, evac_followers); 157 } 158 159 class PSRefEnqueueTaskProxy: public GCTask { 160 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 161 EnqueueTask& _enq_task; 162 uint _work_id; 163 164 public: 165 PSRefEnqueueTaskProxy(EnqueueTask& enq_task, uint work_id) 166 : _enq_task(enq_task), 167 _work_id(work_id) 168 { } 169 170 virtual char* name() { return (char *)"Enqueue reference objects in parallel"; } 171 virtual void do_it(GCTaskManager* manager, uint which) 172 { 173 _enq_task.work(_work_id); 174 } 175 }; 176 177 class PSRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 178 virtual void execute(ProcessTask& task); 179 virtual void execute(EnqueueTask& task); 180 }; 181 182 void PSRefProcTaskExecutor::execute(ProcessTask& task) 183 { 184 GCTaskQueue* q = GCTaskQueue::create(); 185 GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager(); 186 for(uint i=0; i < manager->active_workers(); i++) { 187 q->enqueue(new PSRefProcTaskProxy(task, i)); 188 } 189 ParallelTaskTerminator terminator(manager->active_workers(), 190 (TaskQueueSetSuper*) PSPromotionManager::stack_array_depth()); 191 if (task.marks_oops_alive() && manager->active_workers() > 1) { 192 for (uint j = 0; j < manager->active_workers(); j++) { 193 q->enqueue(new StealTask(&terminator)); 194 } 195 } 196 manager->execute_and_wait(q); 197 } 198 199 200 void PSRefProcTaskExecutor::execute(EnqueueTask& task) 201 { 202 GCTaskQueue* q = GCTaskQueue::create(); 203 GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager(); 204 for(uint i=0; i < manager->active_workers(); i++) { 205 q->enqueue(new PSRefEnqueueTaskProxy(task, i)); 206 } 207 manager->execute_and_wait(q); 208 } 209 210 // This method contains all heap specific policy for invoking scavenge. 211 // PSScavenge::invoke_no_policy() will do nothing but attempt to 212 // scavenge. It will not clean up after failed promotions, bail out if 213 // we've exceeded policy time limits, or any other special behavior. 214 // All such policy should be placed here. 215 // 216 // Note that this method should only be called from the vm_thread while 217 // at a safepoint! 218 bool PSScavenge::invoke() { 219 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint"); 220 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread"); 221 assert(!Universe::heap()->is_gc_active(), "not reentrant"); 222 223 ParallelScavengeHeap* const heap = (ParallelScavengeHeap*)Universe::heap(); 224 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 225 226 PSAdaptiveSizePolicy* policy = heap->size_policy(); 227 IsGCActiveMark mark; 228 229 const bool scavenge_done = PSScavenge::invoke_no_policy(); 230 const bool need_full_gc = !scavenge_done || 231 policy->should_full_GC(heap->old_gen()->free_in_bytes()); 232 bool full_gc_done = false; 233 234 if (UsePerfData) { 235 PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters(); 236 const int ffs_val = need_full_gc ? full_follows_scavenge : not_skipped; 237 counters->update_full_follows_scavenge(ffs_val); 238 } 239 240 if (need_full_gc) { 241 GCCauseSetter gccs(heap, GCCause::_adaptive_size_policy); 242 CollectorPolicy* cp = heap->collector_policy(); 243 const bool clear_all_softrefs = cp->should_clear_all_soft_refs(); 244 245 if (UseParallelOldGC) { 246 full_gc_done = PSParallelCompact::invoke_no_policy(clear_all_softrefs); 247 } else { 248 full_gc_done = PSMarkSweep::invoke_no_policy(clear_all_softrefs); 249 } 250 } 251 252 return full_gc_done; 253 } 254 255 // This method contains no policy. You should probably 256 // be calling invoke() instead. 257 bool PSScavenge::invoke_no_policy() { 258 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint"); 259 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread"); 260 261 assert(_preserved_mark_stack.is_empty(), "should be empty"); 262 assert(_preserved_oop_stack.is_empty(), "should be empty"); 263 264 TimeStamp scavenge_entry; 265 TimeStamp scavenge_midpoint; 266 TimeStamp scavenge_exit; 267 268 scavenge_entry.update(); 269 270 if (GC_locker::check_active_before_gc()) { 271 return false; 272 } 273 274 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 275 GCCause::Cause gc_cause = heap->gc_cause(); 276 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 277 278 // Check for potential problems. 279 if (!should_attempt_scavenge()) { 280 return false; 281 } 282 283 bool promotion_failure_occurred = false; 284 285 PSYoungGen* young_gen = heap->young_gen(); 286 PSOldGen* old_gen = heap->old_gen(); 287 PSAdaptiveSizePolicy* size_policy = heap->size_policy(); 288 heap->increment_total_collections(); 289 290 AdaptiveSizePolicyOutput(size_policy, heap->total_collections()); 291 292 if ((gc_cause != GCCause::_java_lang_system_gc) || 293 UseAdaptiveSizePolicyWithSystemGC) { 294 // Gather the feedback data for eden occupancy. 295 young_gen->eden_space()->accumulate_statistics(); 296 } 297 298 if (ZapUnusedHeapArea) { 299 // Save information needed to minimize mangling 300 heap->record_gen_tops_before_GC(); 301 } 302 303 heap->print_heap_before_gc(); 304 305 assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity"); 306 assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity"); 307 308 size_t prev_used = heap->used(); 309 assert(promotion_failed() == false, "Sanity"); 310 311 // Fill in TLABs 312 heap->accumulate_statistics_all_tlabs(); 313 heap->ensure_parsability(true); // retire TLABs 314 315 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) { 316 HandleMark hm; // Discard invalid handles created during verification 317 Universe::verify(" VerifyBeforeGC:"); 318 } 319 320 { 321 ResourceMark rm; 322 HandleMark hm; 323 324 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps); 325 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); 326 TraceTime t1(GCCauseString("GC", gc_cause), PrintGC, !PrintGCDetails, gclog_or_tty); 327 TraceCollectorStats tcs(counters()); 328 TraceMemoryManagerStats tms(false /* not full GC */,gc_cause); 329 330 if (TraceGen0Time) accumulated_time()->start(); 331 332 // Let the size policy know we're starting 333 size_policy->minor_collection_begin(); 334 335 // Verify the object start arrays. 336 if (VerifyObjectStartArray && 337 VerifyBeforeGC) { 338 old_gen->verify_object_start_array(); 339 } 340 341 // Verify no unmarked old->young roots 342 if (VerifyRememberedSets) { 343 CardTableExtension::verify_all_young_refs_imprecise(); 344 } 345 346 if (!ScavengeWithObjectsInToSpace) { 347 assert(young_gen->to_space()->is_empty(), 348 "Attempt to scavenge with live objects in to_space"); 349 young_gen->to_space()->clear(SpaceDecorator::Mangle); 350 } else if (ZapUnusedHeapArea) { 351 young_gen->to_space()->mangle_unused_area(); 352 } 353 save_to_space_top_before_gc(); 354 355 COMPILER2_PRESENT(DerivedPointerTable::clear()); 356 357 reference_processor()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/); 358 reference_processor()->setup_policy(false); 359 360 // We track how much was promoted to the next generation for 361 // the AdaptiveSizePolicy. 362 size_t old_gen_used_before = old_gen->used_in_bytes(); 363 364 // For PrintGCDetails 365 size_t young_gen_used_before = young_gen->used_in_bytes(); 366 367 // Reset our survivor overflow. 368 set_survivor_overflow(false); 369 370 // We need to save the old top values before 371 // creating the promotion_manager. We pass the top 372 // values to the card_table, to prevent it from 373 // straying into the promotion labs. 374 HeapWord* old_top = old_gen->object_space()->top(); 375 376 // Release all previously held resources 377 gc_task_manager()->release_all_resources(); 378 379 // Set the number of GC threads to be used in this collection 380 gc_task_manager()->set_active_gang(); 381 gc_task_manager()->task_idle_workers(); 382 // Get the active number of workers here and use that value 383 // throughout the methods. 384 uint active_workers = gc_task_manager()->active_workers(); 385 heap->set_par_threads(active_workers); 386 387 PSPromotionManager::pre_scavenge(); 388 389 // We'll use the promotion manager again later. 390 PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager(); 391 { 392 // TraceTime("Roots"); 393 ParallelScavengeHeap::ParStrongRootsScope psrs; 394 395 GCTaskQueue* q = GCTaskQueue::create(); 396 397 if (!old_gen->object_space()->is_empty()) { 398 // There are only old-to-young pointers if there are objects 399 // in the old gen. 400 uint stripe_total = active_workers; 401 for(uint i=0; i < stripe_total; i++) { 402 q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i, stripe_total)); 403 } 404 } 405 406 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe)); 407 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles)); 408 // We scan the thread roots in parallel 409 Threads::create_thread_roots_tasks(q); 410 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer)); 411 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::flat_profiler)); 412 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management)); 413 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary)); 414 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmti)); 415 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::code_cache)); 416 417 ParallelTaskTerminator terminator( 418 active_workers, 419 (TaskQueueSetSuper*) promotion_manager->stack_array_depth()); 420 if (active_workers > 1) { 421 for (uint j = 0; j < active_workers; j++) { 422 q->enqueue(new StealTask(&terminator)); 423 } 424 } 425 426 gc_task_manager()->execute_and_wait(q); 427 } 428 429 scavenge_midpoint.update(); 430 431 // Process reference objects discovered during scavenge 432 { 433 reference_processor()->setup_policy(false); // not always_clear 434 reference_processor()->set_active_mt_degree(active_workers); 435 PSKeepAliveClosure keep_alive(promotion_manager); 436 PSEvacuateFollowersClosure evac_followers(promotion_manager); 437 if (reference_processor()->processing_is_mt()) { 438 PSRefProcTaskExecutor task_executor; 439 reference_processor()->process_discovered_references( 440 &_is_alive_closure, &keep_alive, &evac_followers, &task_executor); 441 } else { 442 reference_processor()->process_discovered_references( 443 &_is_alive_closure, &keep_alive, &evac_followers, NULL); 444 } 445 } 446 447 // Enqueue reference objects discovered during scavenge. 448 if (reference_processor()->processing_is_mt()) { 449 PSRefProcTaskExecutor task_executor; 450 reference_processor()->enqueue_discovered_references(&task_executor); 451 } else { 452 reference_processor()->enqueue_discovered_references(NULL); 453 } 454 455 // Unlink any dead interned Strings 456 StringTable::unlink(&_is_alive_closure); 457 // Process the remaining live ones 458 PSScavengeRootsClosure root_closure(promotion_manager); 459 StringTable::oops_do(&root_closure); 460 461 // Finally, flush the promotion_manager's labs, and deallocate its stacks. 462 PSPromotionManager::post_scavenge(); 463 464 promotion_failure_occurred = promotion_failed(); 465 if (promotion_failure_occurred) { 466 clean_up_failed_promotion(); 467 if (PrintGC) { 468 gclog_or_tty->print("--"); 469 } 470 } 471 472 // Let the size policy know we're done. Note that we count promotion 473 // failure cleanup time as part of the collection (otherwise, we're 474 // implicitly saying it's mutator time). 475 size_policy->minor_collection_end(gc_cause); 476 477 if (!promotion_failure_occurred) { 478 // Swap the survivor spaces. 479 480 481 young_gen->eden_space()->clear(SpaceDecorator::Mangle); 482 young_gen->from_space()->clear(SpaceDecorator::Mangle); 483 young_gen->swap_spaces(); 484 485 size_t survived = young_gen->from_space()->used_in_bytes(); 486 size_t promoted = old_gen->used_in_bytes() - old_gen_used_before; 487 size_policy->update_averages(_survivor_overflow, survived, promoted); 488 489 // A successful scavenge should restart the GC time limit count which is 490 // for full GC's. 491 size_policy->reset_gc_overhead_limit_count(); 492 if (UseAdaptiveSizePolicy) { 493 // Calculate the new survivor size and tenuring threshold 494 495 if (PrintAdaptiveSizePolicy) { 496 gclog_or_tty->print("AdaptiveSizeStart: "); 497 gclog_or_tty->stamp(); 498 gclog_or_tty->print_cr(" collection: %d ", 499 heap->total_collections()); 500 501 if (Verbose) { 502 gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d", 503 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes()); 504 } 505 } 506 507 508 if (UsePerfData) { 509 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters(); 510 counters->update_old_eden_size( 511 size_policy->calculated_eden_size_in_bytes()); 512 counters->update_old_promo_size( 513 size_policy->calculated_promo_size_in_bytes()); 514 counters->update_old_capacity(old_gen->capacity_in_bytes()); 515 counters->update_young_capacity(young_gen->capacity_in_bytes()); 516 counters->update_survived(survived); 517 counters->update_promoted(promoted); 518 counters->update_survivor_overflowed(_survivor_overflow); 519 } 520 521 size_t survivor_limit = 522 size_policy->max_survivor_size(young_gen->max_size()); 523 _tenuring_threshold = 524 size_policy->compute_survivor_space_size_and_threshold( 525 _survivor_overflow, 526 _tenuring_threshold, 527 survivor_limit); 528 529 if (PrintTenuringDistribution) { 530 gclog_or_tty->cr(); 531 gclog_or_tty->print_cr("Desired survivor size " SIZE_FORMAT " bytes, new threshold %u (max %u)", 532 size_policy->calculated_survivor_size_in_bytes(), 533 _tenuring_threshold, MaxTenuringThreshold); 534 } 535 536 if (UsePerfData) { 537 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters(); 538 counters->update_tenuring_threshold(_tenuring_threshold); 539 counters->update_survivor_size_counters(); 540 } 541 542 // Do call at minor collections? 543 // Don't check if the size_policy is ready at this 544 // level. Let the size_policy check that internally. 545 if (UseAdaptiveSizePolicy && 546 UseAdaptiveGenerationSizePolicyAtMinorCollection && 547 ((gc_cause != GCCause::_java_lang_system_gc) || 548 UseAdaptiveSizePolicyWithSystemGC)) { 549 550 // Calculate optimial free space amounts 551 assert(young_gen->max_size() > 552 young_gen->from_space()->capacity_in_bytes() + 553 young_gen->to_space()->capacity_in_bytes(), 554 "Sizes of space in young gen are out-of-bounds"); 555 size_t max_eden_size = young_gen->max_size() - 556 young_gen->from_space()->capacity_in_bytes() - 557 young_gen->to_space()->capacity_in_bytes(); 558 size_policy->compute_generation_free_space(young_gen->used_in_bytes(), 559 young_gen->eden_space()->used_in_bytes(), 560 old_gen->used_in_bytes(), 561 young_gen->eden_space()->capacity_in_bytes(), 562 old_gen->max_gen_size(), 563 max_eden_size, 564 false /* full gc*/, 565 gc_cause, 566 heap->collector_policy()); 567 568 } 569 // Resize the young generation at every collection 570 // even if new sizes have not been calculated. This is 571 // to allow resizes that may have been inhibited by the 572 // relative location of the "to" and "from" spaces. 573 574 // Resizing the old gen at minor collects can cause increases 575 // that don't feed back to the generation sizing policy until 576 // a major collection. Don't resize the old gen here. 577 578 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(), 579 size_policy->calculated_survivor_size_in_bytes()); 580 581 if (PrintAdaptiveSizePolicy) { 582 gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ", 583 heap->total_collections()); 584 } 585 } 586 587 // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can 588 // cause the change of the heap layout. Make sure eden is reshaped if that's the case. 589 // Also update() will case adaptive NUMA chunk resizing. 590 assert(young_gen->eden_space()->is_empty(), "eden space should be empty now"); 591 young_gen->eden_space()->update(); 592 593 heap->gc_policy_counters()->update_counters(); 594 595 heap->resize_all_tlabs(); 596 597 assert(young_gen->to_space()->is_empty(), "to space should be empty now"); 598 } 599 600 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 601 602 NOT_PRODUCT(reference_processor()->verify_no_references_recorded()); 603 604 CodeCache::prune_scavenge_root_nmethods(); 605 606 // Re-verify object start arrays 607 if (VerifyObjectStartArray && 608 VerifyAfterGC) { 609 old_gen->verify_object_start_array(); 610 } 611 612 // Verify all old -> young cards are now precise 613 if (VerifyRememberedSets) { 614 // Precise verification will give false positives. Until this is fixed, 615 // use imprecise verification. 616 // CardTableExtension::verify_all_young_refs_precise(); 617 CardTableExtension::verify_all_young_refs_imprecise(); 618 } 619 620 if (TraceGen0Time) accumulated_time()->stop(); 621 622 if (PrintGC) { 623 if (PrintGCDetails) { 624 // Don't print a GC timestamp here. This is after the GC so 625 // would be confusing. 626 young_gen->print_used_change(young_gen_used_before); 627 } 628 heap->print_heap_change(prev_used); 629 } 630 631 // Track memory usage and detect low memory 632 MemoryService::track_memory_usage(); 633 heap->update_counters(); 634 635 gc_task_manager()->release_idle_workers(); 636 } 637 638 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) { 639 HandleMark hm; // Discard invalid handles created during verification 640 Universe::verify(" VerifyAfterGC:"); 641 } 642 643 heap->print_heap_after_gc(); 644 645 if (ZapUnusedHeapArea) { 646 young_gen->eden_space()->check_mangled_unused_area_complete(); 647 young_gen->from_space()->check_mangled_unused_area_complete(); 648 young_gen->to_space()->check_mangled_unused_area_complete(); 649 } 650 651 scavenge_exit.update(); 652 653 if (PrintGCTaskTimeStamps) { 654 tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " " INT64_FORMAT, 655 scavenge_entry.ticks(), scavenge_midpoint.ticks(), 656 scavenge_exit.ticks()); 657 gc_task_manager()->print_task_time_stamps(); 658 } 659 660 #ifdef TRACESPINNING 661 ParallelTaskTerminator::print_termination_counts(); 662 #endif 663 664 return !promotion_failure_occurred; 665 } 666 667 // This method iterates over all objects in the young generation, 668 // unforwarding markOops. It then restores any preserved mark oops, 669 // and clears the _preserved_mark_stack. 670 void PSScavenge::clean_up_failed_promotion() { 671 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 672 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 673 assert(promotion_failed(), "Sanity"); 674 675 PSYoungGen* young_gen = heap->young_gen(); 676 677 { 678 ResourceMark rm; 679 680 // Unforward all pointers in the young gen. 681 PSPromotionFailedClosure unforward_closure; 682 young_gen->object_iterate(&unforward_closure); 683 684 if (PrintGC && Verbose) { 685 gclog_or_tty->print_cr("Restoring %d marks", _preserved_oop_stack.size()); 686 } 687 688 // Restore any saved marks. 689 while (!_preserved_oop_stack.is_empty()) { 690 oop obj = _preserved_oop_stack.pop(); 691 markOop mark = _preserved_mark_stack.pop(); 692 obj->set_mark(mark); 693 } 694 695 // Clear the preserved mark and oop stack caches. 696 _preserved_mark_stack.clear(true); 697 _preserved_oop_stack.clear(true); 698 _promotion_failed = false; 699 } 700 701 // Reset the PromotionFailureALot counters. 702 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();) 703 } 704 705 // This method is called whenever an attempt to promote an object 706 // fails. Some markOops will need preservation, some will not. Note 707 // that the entire eden is traversed after a failed promotion, with 708 // all forwarded headers replaced by the default markOop. This means 709 // it is not neccessary to preserve most markOops. 710 void PSScavenge::oop_promotion_failed(oop obj, markOop obj_mark) { 711 _promotion_failed = true; 712 if (obj_mark->must_be_preserved_for_promotion_failure(obj)) { 713 // Should use per-worker private stakcs hetre rather than 714 // locking a common pair of stacks. 715 ThreadCritical tc; 716 _preserved_oop_stack.push(obj); 717 _preserved_mark_stack.push(obj_mark); 718 } 719 } 720 721 bool PSScavenge::should_attempt_scavenge() { 722 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 723 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 724 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters(); 725 726 if (UsePerfData) { 727 counters->update_scavenge_skipped(not_skipped); 728 } 729 730 PSYoungGen* young_gen = heap->young_gen(); 731 PSOldGen* old_gen = heap->old_gen(); 732 733 if (!ScavengeWithObjectsInToSpace) { 734 // Do not attempt to promote unless to_space is empty 735 if (!young_gen->to_space()->is_empty()) { 736 _consecutive_skipped_scavenges++; 737 if (UsePerfData) { 738 counters->update_scavenge_skipped(to_space_not_empty); 739 } 740 return false; 741 } 742 } 743 744 // Test to see if the scavenge will likely fail. 745 PSAdaptiveSizePolicy* policy = heap->size_policy(); 746 747 // A similar test is done in the policy's should_full_GC(). If this is 748 // changed, decide if that test should also be changed. 749 size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes(); 750 size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes()); 751 bool result = promotion_estimate < old_gen->free_in_bytes(); 752 753 if (PrintGCDetails && Verbose) { 754 gclog_or_tty->print(result ? " do scavenge: " : " skip scavenge: "); 755 gclog_or_tty->print_cr(" average_promoted " SIZE_FORMAT 756 " padded_average_promoted " SIZE_FORMAT 757 " free in old gen " SIZE_FORMAT, 758 (size_t) policy->average_promoted_in_bytes(), 759 (size_t) policy->padded_average_promoted_in_bytes(), 760 old_gen->free_in_bytes()); 761 if (young_gen->used_in_bytes() < 762 (size_t) policy->padded_average_promoted_in_bytes()) { 763 gclog_or_tty->print_cr(" padded_promoted_average is greater" 764 " than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes()); 765 } 766 } 767 768 if (result) { 769 _consecutive_skipped_scavenges = 0; 770 } else { 771 _consecutive_skipped_scavenges++; 772 if (UsePerfData) { 773 counters->update_scavenge_skipped(promoted_too_large); 774 } 775 } 776 return result; 777 } 778 779 // Used to add tasks 780 GCTaskManager* const PSScavenge::gc_task_manager() { 781 assert(ParallelScavengeHeap::gc_task_manager() != NULL, 782 "shouldn't return NULL"); 783 return ParallelScavengeHeap::gc_task_manager(); 784 } 785 786 void PSScavenge::initialize() { 787 // Arguments must have been parsed 788 789 if (AlwaysTenure) { 790 _tenuring_threshold = 0; 791 } else if (NeverTenure) { 792 _tenuring_threshold = markOopDesc::max_age + 1; 793 } else { 794 // We want to smooth out our startup times for the AdaptiveSizePolicy 795 _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold : 796 MaxTenuringThreshold; 797 } 798 799 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 800 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 801 802 PSYoungGen* young_gen = heap->young_gen(); 803 PSOldGen* old_gen = heap->old_gen(); 804 805 // Set boundary between young_gen and old_gen 806 assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(), 807 "old above young"); 808 _young_generation_boundary = young_gen->eden_space()->bottom(); 809 810 // Initialize ref handling object for scavenging. 811 MemRegion mr = young_gen->reserved(); 812 813 _ref_processor = 814 new ReferenceProcessor(mr, // span 815 ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing 816 (int) ParallelGCThreads, // mt processing degree 817 true, // mt discovery 818 (int) ParallelGCThreads, // mt discovery degree 819 true, // atomic_discovery 820 NULL, // header provides liveness info 821 false); // next field updates do not need write barrier 822 823 // Cache the cardtable 824 BarrierSet* bs = Universe::heap()->barrier_set(); 825 assert(bs->kind() == BarrierSet::CardTableModRef, "Wrong barrier set kind"); 826 _card_table = (CardTableExtension*)bs; 827 828 _counters = new CollectorCounters("PSScavenge", 0); 829 }