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 bool do_object_b(oop p) { 74 return (!PSScavenge::is_obj_in_young((HeapWord*) p)) || p->is_forwarded(); 75 } 76 }; 77 78 PSIsAliveClosure PSScavenge::_is_alive_closure; 79 80 class PSKeepAliveClosure: public OopClosure { 81 protected: 82 MutableSpace* _to_space; 83 PSPromotionManager* _promotion_manager; 84 85 public: 86 PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) { 87 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 88 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 89 _to_space = heap->young_gen()->to_space(); 90 91 assert(_promotion_manager != NULL, "Sanity"); 92 } 93 94 template <class T> void do_oop_work(T* p) { 95 assert (!oopDesc::is_null(*p), "expected non-null ref"); 96 assert ((oopDesc::load_decode_heap_oop_not_null(p))->is_oop(), 97 "expected an oop while scanning weak refs"); 98 99 // Weak refs may be visited more than once. 100 if (PSScavenge::should_scavenge(p, _to_space)) { 101 PSScavenge::copy_and_push_safe_barrier<T, /*promote_immediately=*/false>(_promotion_manager, p); 102 } 103 } 104 virtual void do_oop(oop* p) { PSKeepAliveClosure::do_oop_work(p); } 105 virtual void do_oop(narrowOop* p) { PSKeepAliveClosure::do_oop_work(p); } 106 }; 107 108 class PSEvacuateFollowersClosure: public VoidClosure { 109 private: 110 PSPromotionManager* _promotion_manager; 111 public: 112 PSEvacuateFollowersClosure(PSPromotionManager* pm) : _promotion_manager(pm) {} 113 114 virtual void do_void() { 115 assert(_promotion_manager != NULL, "Sanity"); 116 _promotion_manager->drain_stacks(true); 117 guarantee(_promotion_manager->stacks_empty(), 118 "stacks should be empty at this point"); 119 } 120 }; 121 122 class PSPromotionFailedClosure : public ObjectClosure { 123 virtual void do_object(oop obj) { 124 if (obj->is_forwarded()) { 125 obj->init_mark(); 126 } 127 } 128 }; 129 130 class PSRefProcTaskProxy: public GCTask { 131 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 132 ProcessTask & _rp_task; 133 uint _work_id; 134 public: 135 PSRefProcTaskProxy(ProcessTask & rp_task, uint work_id) 136 : _rp_task(rp_task), 137 _work_id(work_id) 138 { } 139 140 private: 141 virtual char* name() { return (char *)"Process referents by policy in parallel"; } 142 virtual void do_it(GCTaskManager* manager, uint which); 143 }; 144 145 void PSRefProcTaskProxy::do_it(GCTaskManager* manager, uint which) 146 { 147 PSPromotionManager* promotion_manager = 148 PSPromotionManager::gc_thread_promotion_manager(which); 149 assert(promotion_manager != NULL, "sanity check"); 150 PSKeepAliveClosure keep_alive(promotion_manager); 151 PSEvacuateFollowersClosure evac_followers(promotion_manager); 152 PSIsAliveClosure is_alive; 153 _rp_task.work(_work_id, is_alive, keep_alive, evac_followers); 154 } 155 156 class PSRefEnqueueTaskProxy: public GCTask { 157 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 158 EnqueueTask& _enq_task; 159 uint _work_id; 160 161 public: 162 PSRefEnqueueTaskProxy(EnqueueTask& enq_task, uint work_id) 163 : _enq_task(enq_task), 164 _work_id(work_id) 165 { } 166 167 virtual char* name() { return (char *)"Enqueue reference objects in parallel"; } 168 virtual void do_it(GCTaskManager* manager, uint which) 169 { 170 _enq_task.work(_work_id); 171 } 172 }; 173 174 class PSRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 175 virtual void execute(ProcessTask& task); 176 virtual void execute(EnqueueTask& task); 177 }; 178 179 void PSRefProcTaskExecutor::execute(ProcessTask& task) 180 { 181 GCTaskQueue* q = GCTaskQueue::create(); 182 GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager(); 183 for(uint i=0; i < manager->active_workers(); i++) { 184 q->enqueue(new PSRefProcTaskProxy(task, i)); 185 } 186 ParallelTaskTerminator terminator(manager->active_workers(), 187 (TaskQueueSetSuper*) PSPromotionManager::stack_array_depth()); 188 if (task.marks_oops_alive() && manager->active_workers() > 1) { 189 for (uint j = 0; j < manager->active_workers(); j++) { 190 q->enqueue(new StealTask(&terminator)); 191 } 192 } 193 manager->execute_and_wait(q); 194 } 195 196 197 void PSRefProcTaskExecutor::execute(EnqueueTask& task) 198 { 199 GCTaskQueue* q = GCTaskQueue::create(); 200 GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager(); 201 for(uint i=0; i < manager->active_workers(); i++) { 202 q->enqueue(new PSRefEnqueueTaskProxy(task, i)); 203 } 204 manager->execute_and_wait(q); 205 } 206 207 // This method contains all heap specific policy for invoking scavenge. 208 // PSScavenge::invoke_no_policy() will do nothing but attempt to 209 // scavenge. It will not clean up after failed promotions, bail out if 210 // we've exceeded policy time limits, or any other special behavior. 211 // All such policy should be placed here. 212 // 213 // Note that this method should only be called from the vm_thread while 214 // at a safepoint! 215 bool PSScavenge::invoke() { 216 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint"); 217 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread"); 218 assert(!Universe::heap()->is_gc_active(), "not reentrant"); 219 220 ParallelScavengeHeap* const heap = (ParallelScavengeHeap*)Universe::heap(); 221 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 222 223 PSAdaptiveSizePolicy* policy = heap->size_policy(); 224 IsGCActiveMark mark; 225 226 const bool scavenge_done = PSScavenge::invoke_no_policy(); 227 const bool need_full_gc = !scavenge_done || 228 policy->should_full_GC(heap->old_gen()->free_in_bytes()); 229 bool full_gc_done = false; 230 231 if (UsePerfData) { 232 PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters(); 233 const int ffs_val = need_full_gc ? full_follows_scavenge : not_skipped; 234 counters->update_full_follows_scavenge(ffs_val); 235 } 236 237 if (need_full_gc) { 238 GCCauseSetter gccs(heap, GCCause::_adaptive_size_policy); 239 CollectorPolicy* cp = heap->collector_policy(); 240 const bool clear_all_softrefs = cp->should_clear_all_soft_refs(); 241 242 if (UseParallelOldGC) { 243 full_gc_done = PSParallelCompact::invoke_no_policy(clear_all_softrefs); 244 } else { 245 full_gc_done = PSMarkSweep::invoke_no_policy(clear_all_softrefs); 246 } 247 } 248 249 return full_gc_done; 250 } 251 252 // This method contains no policy. You should probably 253 // be calling invoke() instead. 254 bool PSScavenge::invoke_no_policy() { 255 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint"); 256 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread"); 257 258 assert(_preserved_mark_stack.is_empty(), "should be empty"); 259 assert(_preserved_oop_stack.is_empty(), "should be empty"); 260 261 TimeStamp scavenge_entry; 262 TimeStamp scavenge_midpoint; 263 TimeStamp scavenge_exit; 264 265 scavenge_entry.update(); 266 267 if (GC_locker::check_active_before_gc()) { 268 return false; 269 } 270 271 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 272 GCCause::Cause gc_cause = heap->gc_cause(); 273 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 274 275 // Check for potential problems. 276 if (!should_attempt_scavenge()) { 277 return false; 278 } 279 280 bool promotion_failure_occurred = false; 281 282 PSYoungGen* young_gen = heap->young_gen(); 283 PSOldGen* old_gen = heap->old_gen(); 284 PSAdaptiveSizePolicy* size_policy = heap->size_policy(); 285 heap->increment_total_collections(); 286 287 AdaptiveSizePolicyOutput(size_policy, heap->total_collections()); 288 289 if ((gc_cause != GCCause::_java_lang_system_gc) || 290 UseAdaptiveSizePolicyWithSystemGC) { 291 // Gather the feedback data for eden occupancy. 292 young_gen->eden_space()->accumulate_statistics(); 293 } 294 295 if (ZapUnusedHeapArea) { 296 // Save information needed to minimize mangling 297 heap->record_gen_tops_before_GC(); 298 } 299 300 heap->print_heap_before_gc(); 301 302 assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity"); 303 assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity"); 304 305 size_t prev_used = heap->used(); 306 assert(promotion_failed() == false, "Sanity"); 307 308 // Fill in TLABs 309 heap->accumulate_statistics_all_tlabs(); 310 heap->ensure_parsability(true); // retire TLABs 311 312 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) { 313 HandleMark hm; // Discard invalid handles created during verification 314 Universe::verify(" VerifyBeforeGC:"); 315 } 316 317 { 318 ResourceMark rm; 319 HandleMark hm; 320 321 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps); 322 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); 323 TraceTime t1(GCCauseString("GC", gc_cause), PrintGC, !PrintGCDetails, gclog_or_tty); 324 TraceCollectorStats tcs(counters()); 325 TraceMemoryManagerStats tms(false /* not full GC */,gc_cause); 326 327 if (TraceGen0Time) accumulated_time()->start(); 328 329 // Let the size policy know we're starting 330 size_policy->minor_collection_begin(); 331 332 // Verify the object start arrays. 333 if (VerifyObjectStartArray && 334 VerifyBeforeGC) { 335 old_gen->verify_object_start_array(); 336 } 337 338 // Verify no unmarked old->young roots 339 if (VerifyRememberedSets) { 340 CardTableExtension::verify_all_young_refs_imprecise(); 341 } 342 343 if (!ScavengeWithObjectsInToSpace) { 344 assert(young_gen->to_space()->is_empty(), 345 "Attempt to scavenge with live objects in to_space"); 346 young_gen->to_space()->clear(SpaceDecorator::Mangle); 347 } else if (ZapUnusedHeapArea) { 348 young_gen->to_space()->mangle_unused_area(); 349 } 350 save_to_space_top_before_gc(); 351 352 COMPILER2_PRESENT(DerivedPointerTable::clear()); 353 354 reference_processor()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/); 355 reference_processor()->setup_policy(false); 356 357 // We track how much was promoted to the next generation for 358 // the AdaptiveSizePolicy. 359 size_t old_gen_used_before = old_gen->used_in_bytes(); 360 361 // For PrintGCDetails 362 size_t young_gen_used_before = young_gen->used_in_bytes(); 363 364 // Reset our survivor overflow. 365 set_survivor_overflow(false); 366 367 // We need to save the old top values before 368 // creating the promotion_manager. We pass the top 369 // values to the card_table, to prevent it from 370 // straying into the promotion labs. 371 HeapWord* old_top = old_gen->object_space()->top(); 372 373 // Release all previously held resources 374 gc_task_manager()->release_all_resources(); 375 376 // Set the number of GC threads to be used in this collection 377 gc_task_manager()->set_active_gang(); 378 gc_task_manager()->task_idle_workers(); 379 // Get the active number of workers here and use that value 380 // throughout the methods. 381 uint active_workers = gc_task_manager()->active_workers(); 382 heap->set_par_threads(active_workers); 383 384 PSPromotionManager::pre_scavenge(); 385 386 // We'll use the promotion manager again later. 387 PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager(); 388 { 389 // TraceTime("Roots"); 390 ParallelScavengeHeap::ParStrongRootsScope psrs; 391 392 GCTaskQueue* q = GCTaskQueue::create(); 393 394 if (!old_gen->object_space()->is_empty()) { 395 // There are only old-to-young pointers if there are objects 396 // in the old gen. 397 uint stripe_total = active_workers; 398 for(uint i=0; i < stripe_total; i++) { 399 q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i, stripe_total)); 400 } 401 } 402 403 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe)); 404 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles)); 405 // We scan the thread roots in parallel 406 Threads::create_thread_roots_tasks(q); 407 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer)); 408 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::flat_profiler)); 409 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management)); 410 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary)); 411 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::class_loader_data)); 412 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmti)); 413 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::code_cache)); 414 415 ParallelTaskTerminator terminator( 416 active_workers, 417 (TaskQueueSetSuper*) promotion_manager->stack_array_depth()); 418 if (active_workers > 1) { 419 for (uint j = 0; j < active_workers; j++) { 420 q->enqueue(new StealTask(&terminator)); 421 } 422 } 423 424 gc_task_manager()->execute_and_wait(q); 425 } 426 427 scavenge_midpoint.update(); 428 429 // Process reference objects discovered during scavenge 430 { 431 reference_processor()->setup_policy(false); // not always_clear 432 reference_processor()->set_active_mt_degree(active_workers); 433 PSKeepAliveClosure keep_alive(promotion_manager); 434 PSEvacuateFollowersClosure evac_followers(promotion_manager); 435 if (reference_processor()->processing_is_mt()) { 436 PSRefProcTaskExecutor task_executor; 437 reference_processor()->process_discovered_references( 438 &_is_alive_closure, &keep_alive, &evac_followers, &task_executor); 439 } else { 440 reference_processor()->process_discovered_references( 441 &_is_alive_closure, &keep_alive, &evac_followers, NULL); 442 } 443 } 444 445 // Enqueue reference objects discovered during scavenge. 446 if (reference_processor()->processing_is_mt()) { 447 PSRefProcTaskExecutor task_executor; 448 reference_processor()->enqueue_discovered_references(&task_executor); 449 } else { 450 reference_processor()->enqueue_discovered_references(NULL); 451 } 452 453 // Unlink any dead interned Strings 454 StringTable::unlink(&_is_alive_closure); 455 // Process the remaining live ones 456 PSScavengeRootsClosure root_closure(promotion_manager); 457 StringTable::oops_do(&root_closure); 458 459 // Finally, flush the promotion_manager's labs, and deallocate its stacks. 460 PSPromotionManager::post_scavenge(); 461 462 promotion_failure_occurred = promotion_failed(); 463 if (promotion_failure_occurred) { 464 clean_up_failed_promotion(); 465 if (PrintGC) { 466 gclog_or_tty->print("--"); 467 } 468 } 469 470 // Let the size policy know we're done. Note that we count promotion 471 // failure cleanup time as part of the collection (otherwise, we're 472 // implicitly saying it's mutator time). 473 size_policy->minor_collection_end(gc_cause); 474 475 if (!promotion_failure_occurred) { 476 // Swap the survivor spaces. 477 478 479 young_gen->eden_space()->clear(SpaceDecorator::Mangle); 480 young_gen->from_space()->clear(SpaceDecorator::Mangle); 481 young_gen->swap_spaces(); 482 483 size_t survived = young_gen->from_space()->used_in_bytes(); 484 size_t promoted = old_gen->used_in_bytes() - old_gen_used_before; 485 size_policy->update_averages(_survivor_overflow, survived, promoted); 486 487 // A successful scavenge should restart the GC time limit count which is 488 // for full GC's. 489 size_policy->reset_gc_overhead_limit_count(); 490 if (UseAdaptiveSizePolicy) { 491 // Calculate the new survivor size and tenuring threshold 492 493 if (PrintAdaptiveSizePolicy) { 494 gclog_or_tty->print("AdaptiveSizeStart: "); 495 gclog_or_tty->stamp(); 496 gclog_or_tty->print_cr(" collection: %d ", 497 heap->total_collections()); 498 499 if (Verbose) { 500 gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d", 501 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes()); 502 } 503 } 504 505 506 if (UsePerfData) { 507 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters(); 508 counters->update_old_eden_size( 509 size_policy->calculated_eden_size_in_bytes()); 510 counters->update_old_promo_size( 511 size_policy->calculated_promo_size_in_bytes()); 512 counters->update_old_capacity(old_gen->capacity_in_bytes()); 513 counters->update_young_capacity(young_gen->capacity_in_bytes()); 514 counters->update_survived(survived); 515 counters->update_promoted(promoted); 516 counters->update_survivor_overflowed(_survivor_overflow); 517 } 518 519 size_t survivor_limit = 520 size_policy->max_survivor_size(young_gen->max_size()); 521 _tenuring_threshold = 522 size_policy->compute_survivor_space_size_and_threshold( 523 _survivor_overflow, 524 _tenuring_threshold, 525 survivor_limit); 526 527 if (PrintTenuringDistribution) { 528 gclog_or_tty->cr(); 529 gclog_or_tty->print_cr("Desired survivor size " SIZE_FORMAT " bytes, new threshold %u (max %u)", 530 size_policy->calculated_survivor_size_in_bytes(), 531 _tenuring_threshold, MaxTenuringThreshold); 532 } 533 534 if (UsePerfData) { 535 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters(); 536 counters->update_tenuring_threshold(_tenuring_threshold); 537 counters->update_survivor_size_counters(); 538 } 539 540 // Do call at minor collections? 541 // Don't check if the size_policy is ready at this 542 // level. Let the size_policy check that internally. 543 if (UseAdaptiveSizePolicy && 544 UseAdaptiveGenerationSizePolicyAtMinorCollection && 545 ((gc_cause != GCCause::_java_lang_system_gc) || 546 UseAdaptiveSizePolicyWithSystemGC)) { 547 548 // Calculate optimial free space amounts 549 assert(young_gen->max_size() > 550 young_gen->from_space()->capacity_in_bytes() + 551 young_gen->to_space()->capacity_in_bytes(), 552 "Sizes of space in young gen are out-of-bounds"); 553 554 size_t young_live = young_gen->used_in_bytes(); 555 size_t eden_live = young_gen->eden_space()->used_in_bytes(); 556 size_t cur_eden = young_gen->eden_space()->capacity_in_bytes(); 557 size_t max_old_gen_size = old_gen->max_gen_size(); 558 size_t max_eden_size = young_gen->max_size() - 559 young_gen->from_space()->capacity_in_bytes() - 560 young_gen->to_space()->capacity_in_bytes(); 561 562 // Used for diagnostics 563 size_policy->clear_generation_free_space_flags(); 564 565 size_policy->compute_eden_space_size(young_live, 566 eden_live, 567 cur_eden, 568 max_eden_size, 569 false /* not full gc*/); 570 571 size_policy->check_gc_overhead_limit(young_live, 572 eden_live, 573 max_old_gen_size, 574 max_eden_size, 575 false /* not full gc*/, 576 gc_cause, 577 heap->collector_policy()); 578 579 size_policy->decay_supplemental_growth(false /* not full gc*/); 580 } 581 // Resize the young generation at every collection 582 // even if new sizes have not been calculated. This is 583 // to allow resizes that may have been inhibited by the 584 // relative location of the "to" and "from" spaces. 585 586 // Resizing the old gen at minor collects can cause increases 587 // that don't feed back to the generation sizing policy until 588 // a major collection. Don't resize the old gen here. 589 590 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(), 591 size_policy->calculated_survivor_size_in_bytes()); 592 593 if (PrintAdaptiveSizePolicy) { 594 gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ", 595 heap->total_collections()); 596 } 597 } 598 599 // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can 600 // cause the change of the heap layout. Make sure eden is reshaped if that's the case. 601 // Also update() will case adaptive NUMA chunk resizing. 602 assert(young_gen->eden_space()->is_empty(), "eden space should be empty now"); 603 young_gen->eden_space()->update(); 604 605 heap->gc_policy_counters()->update_counters(); 606 607 heap->resize_all_tlabs(); 608 609 assert(young_gen->to_space()->is_empty(), "to space should be empty now"); 610 } 611 612 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 613 614 NOT_PRODUCT(reference_processor()->verify_no_references_recorded()); 615 616 CodeCache::prune_scavenge_root_nmethods(); 617 618 // Re-verify object start arrays 619 if (VerifyObjectStartArray && 620 VerifyAfterGC) { 621 old_gen->verify_object_start_array(); 622 } 623 624 // Verify all old -> young cards are now precise 625 if (VerifyRememberedSets) { 626 // Precise verification will give false positives. Until this is fixed, 627 // use imprecise verification. 628 // CardTableExtension::verify_all_young_refs_precise(); 629 CardTableExtension::verify_all_young_refs_imprecise(); 630 } 631 632 if (TraceGen0Time) accumulated_time()->stop(); 633 634 if (PrintGC) { 635 if (PrintGCDetails) { 636 // Don't print a GC timestamp here. This is after the GC so 637 // would be confusing. 638 young_gen->print_used_change(young_gen_used_before); 639 } 640 heap->print_heap_change(prev_used); 641 } 642 643 // Track memory usage and detect low memory 644 MemoryService::track_memory_usage(); 645 heap->update_counters(); 646 647 gc_task_manager()->release_idle_workers(); 648 } 649 650 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) { 651 HandleMark hm; // Discard invalid handles created during verification 652 Universe::verify(" VerifyAfterGC:"); 653 } 654 655 heap->print_heap_after_gc(); 656 657 if (ZapUnusedHeapArea) { 658 young_gen->eden_space()->check_mangled_unused_area_complete(); 659 young_gen->from_space()->check_mangled_unused_area_complete(); 660 young_gen->to_space()->check_mangled_unused_area_complete(); 661 } 662 663 scavenge_exit.update(); 664 665 if (PrintGCTaskTimeStamps) { 666 tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " " INT64_FORMAT, 667 scavenge_entry.ticks(), scavenge_midpoint.ticks(), 668 scavenge_exit.ticks()); 669 gc_task_manager()->print_task_time_stamps(); 670 } 671 672 #ifdef TRACESPINNING 673 ParallelTaskTerminator::print_termination_counts(); 674 #endif 675 676 return !promotion_failure_occurred; 677 } 678 679 // This method iterates over all objects in the young generation, 680 // unforwarding markOops. It then restores any preserved mark oops, 681 // and clears the _preserved_mark_stack. 682 void PSScavenge::clean_up_failed_promotion() { 683 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 684 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 685 assert(promotion_failed(), "Sanity"); 686 687 PSYoungGen* young_gen = heap->young_gen(); 688 689 { 690 ResourceMark rm; 691 692 // Unforward all pointers in the young gen. 693 PSPromotionFailedClosure unforward_closure; 694 young_gen->object_iterate(&unforward_closure); 695 696 if (PrintGC && Verbose) { 697 gclog_or_tty->print_cr("Restoring %d marks", _preserved_oop_stack.size()); 698 } 699 700 // Restore any saved marks. 701 while (!_preserved_oop_stack.is_empty()) { 702 oop obj = _preserved_oop_stack.pop(); 703 markOop mark = _preserved_mark_stack.pop(); 704 obj->set_mark(mark); 705 } 706 707 // Clear the preserved mark and oop stack caches. 708 _preserved_mark_stack.clear(true); 709 _preserved_oop_stack.clear(true); 710 _promotion_failed = false; 711 } 712 713 // Reset the PromotionFailureALot counters. 714 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();) 715 } 716 717 // This method is called whenever an attempt to promote an object 718 // fails. Some markOops will need preservation, some will not. Note 719 // that the entire eden is traversed after a failed promotion, with 720 // all forwarded headers replaced by the default markOop. This means 721 // it is not neccessary to preserve most markOops. 722 void PSScavenge::oop_promotion_failed(oop obj, markOop obj_mark) { 723 _promotion_failed = true; 724 if (obj_mark->must_be_preserved_for_promotion_failure(obj)) { 725 // Should use per-worker private stakcs hetre rather than 726 // locking a common pair of stacks. 727 ThreadCritical tc; 728 _preserved_oop_stack.push(obj); 729 _preserved_mark_stack.push(obj_mark); 730 } 731 } 732 733 bool PSScavenge::should_attempt_scavenge() { 734 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 735 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 736 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters(); 737 738 if (UsePerfData) { 739 counters->update_scavenge_skipped(not_skipped); 740 } 741 742 PSYoungGen* young_gen = heap->young_gen(); 743 PSOldGen* old_gen = heap->old_gen(); 744 745 if (!ScavengeWithObjectsInToSpace) { 746 // Do not attempt to promote unless to_space is empty 747 if (!young_gen->to_space()->is_empty()) { 748 _consecutive_skipped_scavenges++; 749 if (UsePerfData) { 750 counters->update_scavenge_skipped(to_space_not_empty); 751 } 752 return false; 753 } 754 } 755 756 // Test to see if the scavenge will likely fail. 757 PSAdaptiveSizePolicy* policy = heap->size_policy(); 758 759 // A similar test is done in the policy's should_full_GC(). If this is 760 // changed, decide if that test should also be changed. 761 size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes(); 762 size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes()); 763 bool result = promotion_estimate < old_gen->free_in_bytes(); 764 765 if (PrintGCDetails && Verbose) { 766 gclog_or_tty->print(result ? " do scavenge: " : " skip scavenge: "); 767 gclog_or_tty->print_cr(" average_promoted " SIZE_FORMAT 768 " padded_average_promoted " SIZE_FORMAT 769 " free in old gen " SIZE_FORMAT, 770 (size_t) policy->average_promoted_in_bytes(), 771 (size_t) policy->padded_average_promoted_in_bytes(), 772 old_gen->free_in_bytes()); 773 if (young_gen->used_in_bytes() < 774 (size_t) policy->padded_average_promoted_in_bytes()) { 775 gclog_or_tty->print_cr(" padded_promoted_average is greater" 776 " than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes()); 777 } 778 } 779 780 if (result) { 781 _consecutive_skipped_scavenges = 0; 782 } else { 783 _consecutive_skipped_scavenges++; 784 if (UsePerfData) { 785 counters->update_scavenge_skipped(promoted_too_large); 786 } 787 } 788 return result; 789 } 790 791 // Used to add tasks 792 GCTaskManager* const PSScavenge::gc_task_manager() { 793 assert(ParallelScavengeHeap::gc_task_manager() != NULL, 794 "shouldn't return NULL"); 795 return ParallelScavengeHeap::gc_task_manager(); 796 } 797 798 void PSScavenge::initialize() { 799 // Arguments must have been parsed 800 801 if (AlwaysTenure) { 802 _tenuring_threshold = 0; 803 } else if (NeverTenure) { 804 _tenuring_threshold = markOopDesc::max_age + 1; 805 } else { 806 // We want to smooth out our startup times for the AdaptiveSizePolicy 807 _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold : 808 MaxTenuringThreshold; 809 } 810 811 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 812 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 813 814 PSYoungGen* young_gen = heap->young_gen(); 815 PSOldGen* old_gen = heap->old_gen(); 816 817 // Set boundary between young_gen and old_gen 818 assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(), 819 "old above young"); 820 _young_generation_boundary = young_gen->eden_space()->bottom(); 821 822 // Initialize ref handling object for scavenging. 823 MemRegion mr = young_gen->reserved(); 824 825 _ref_processor = 826 new ReferenceProcessor(mr, // span 827 ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing 828 (int) ParallelGCThreads, // mt processing degree 829 true, // mt discovery 830 (int) ParallelGCThreads, // mt discovery degree 831 true, // atomic_discovery 832 NULL, // header provides liveness info 833 false); // next field updates do not need write barrier 834 835 // Cache the cardtable 836 BarrierSet* bs = Universe::heap()->barrier_set(); 837 assert(bs->kind() == BarrierSet::CardTableModRef, "Wrong barrier set kind"); 838 _card_table = (CardTableExtension*)bs; 839 840 _counters = new CollectorCounters("PSScavenge", 0); 841 }