1 /* 2 * Copyright (c) 2002, 2011, 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 "gc_implementation/parallelScavenge/cardTableExtension.hpp" 28 #include "gc_implementation/parallelScavenge/gcTaskManager.hpp" 29 #include "gc_implementation/parallelScavenge/generationSizer.hpp" 30 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.hpp" 31 #include "gc_implementation/parallelScavenge/psAdaptiveSizePolicy.hpp" 32 #include "gc_implementation/parallelScavenge/psMarkSweep.hpp" 33 #include "gc_implementation/parallelScavenge/psParallelCompact.hpp" 34 #include "gc_implementation/parallelScavenge/psScavenge.inline.hpp" 35 #include "gc_implementation/parallelScavenge/psTasks.hpp" 36 #include "gc_implementation/shared/isGCActiveMark.hpp" 37 #include "gc_implementation/shared/spaceDecorator.hpp" 38 #include "gc_interface/gcCause.hpp" 39 #include "memory/collectorPolicy.hpp" 40 #include "memory/gcLocker.inline.hpp" 41 #include "memory/referencePolicy.hpp" 42 #include "memory/referenceProcessor.hpp" 43 #include "memory/resourceArea.hpp" 44 #include "oops/oop.inline.hpp" 45 #include "oops/oop.psgc.inline.hpp" 46 #include "runtime/biasedLocking.hpp" 47 #include "runtime/fprofiler.hpp" 48 #include "runtime/handles.inline.hpp" 49 #include "runtime/threadCritical.hpp" 50 #include "runtime/vmThread.hpp" 51 #include "runtime/vm_operations.hpp" 52 #include "services/memoryService.hpp" 53 #include "utilities/stack.inline.hpp" 54 55 56 HeapWord* PSScavenge::_to_space_top_before_gc = NULL; 57 int PSScavenge::_consecutive_skipped_scavenges = 0; 58 ReferenceProcessor* PSScavenge::_ref_processor = NULL; 59 CardTableExtension* PSScavenge::_card_table = NULL; 60 bool PSScavenge::_survivor_overflow = false; 61 int PSScavenge::_tenuring_threshold = 0; 62 HeapWord* PSScavenge::_young_generation_boundary = NULL; 63 elapsedTimer PSScavenge::_accumulated_time; 64 Stack<markOop> PSScavenge::_preserved_mark_stack; 65 Stack<oop> PSScavenge::_preserved_oop_stack; 66 CollectorCounters* PSScavenge::_counters = NULL; 67 bool PSScavenge::_promotion_failed = false; 68 69 // Define before use 70 class PSIsAliveClosure: public BoolObjectClosure { 71 public: 72 void do_object(oop p) { 73 assert(false, "Do not call."); 74 } 75 bool do_object_b(oop p) { 76 return (!PSScavenge::is_obj_in_young((HeapWord*) p)) || p->is_forwarded(); 77 } 78 }; 79 80 PSIsAliveClosure PSScavenge::_is_alive_closure; 81 82 class PSKeepAliveClosure: public OopClosure { 83 protected: 84 MutableSpace* _to_space; 85 PSPromotionManager* _promotion_manager; 86 87 public: 88 PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) { 89 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 90 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 91 _to_space = heap->young_gen()->to_space(); 92 93 assert(_promotion_manager != NULL, "Sanity"); 94 } 95 96 template <class T> void do_oop_work(T* p) { 97 assert (!oopDesc::is_null(*p), "expected non-null ref"); 98 assert ((oopDesc::load_decode_heap_oop_not_null(p))->is_oop(), 99 "expected an oop while scanning weak refs"); 100 101 // Weak refs may be visited more than once. 102 if (PSScavenge::should_scavenge(p, _to_space)) { 103 PSScavenge::copy_and_push_safe_barrier(_promotion_manager, p); 104 } 105 } 106 virtual void do_oop(oop* p) { PSKeepAliveClosure::do_oop_work(p); } 107 virtual void do_oop(narrowOop* p) { PSKeepAliveClosure::do_oop_work(p); } 108 }; 109 110 class PSEvacuateFollowersClosure: public VoidClosure { 111 private: 112 PSPromotionManager* _promotion_manager; 113 public: 114 PSEvacuateFollowersClosure(PSPromotionManager* pm) : _promotion_manager(pm) {} 115 116 virtual void do_void() { 117 assert(_promotion_manager != NULL, "Sanity"); 118 _promotion_manager->drain_stacks(true); 119 guarantee(_promotion_manager->stacks_empty(), 120 "stacks should be empty at this point"); 121 } 122 }; 123 124 class PSPromotionFailedClosure : public ObjectClosure { 125 virtual void do_object(oop obj) { 126 if (obj->is_forwarded()) { 127 obj->init_mark(); 128 } 129 } 130 }; 131 132 class PSRefProcTaskProxy: public GCTask { 133 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 134 ProcessTask & _rp_task; 135 uint _work_id; 136 public: 137 PSRefProcTaskProxy(ProcessTask & rp_task, uint work_id) 138 : _rp_task(rp_task), 139 _work_id(work_id) 140 { } 141 142 private: 143 virtual char* name() { return (char *)"Process referents by policy in parallel"; } 144 virtual void do_it(GCTaskManager* manager, uint which); 145 }; 146 147 void PSRefProcTaskProxy::do_it(GCTaskManager* manager, uint which) 148 { 149 PSPromotionManager* promotion_manager = 150 PSPromotionManager::gc_thread_promotion_manager(which); 151 assert(promotion_manager != NULL, "sanity check"); 152 PSKeepAliveClosure keep_alive(promotion_manager); 153 PSEvacuateFollowersClosure evac_followers(promotion_manager); 154 PSIsAliveClosure is_alive; 155 _rp_task.work(_work_id, is_alive, keep_alive, evac_followers); 156 } 157 158 class PSRefEnqueueTaskProxy: public GCTask { 159 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 160 EnqueueTask& _enq_task; 161 uint _work_id; 162 163 public: 164 PSRefEnqueueTaskProxy(EnqueueTask& enq_task, uint work_id) 165 : _enq_task(enq_task), 166 _work_id(work_id) 167 { } 168 169 virtual char* name() { return (char *)"Enqueue reference objects in parallel"; } 170 virtual void do_it(GCTaskManager* manager, uint which) 171 { 172 _enq_task.work(_work_id); 173 } 174 }; 175 176 class PSRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 177 virtual void execute(ProcessTask& task); 178 virtual void execute(EnqueueTask& task); 179 }; 180 181 void PSRefProcTaskExecutor::execute(ProcessTask& task) 182 { 183 GCTaskQueue* q = GCTaskQueue::create(); 184 for(uint i=0; i<ParallelGCThreads; i++) { 185 q->enqueue(new PSRefProcTaskProxy(task, i)); 186 } 187 ParallelTaskTerminator terminator( 188 ParallelScavengeHeap::gc_task_manager()->workers(), 189 (TaskQueueSetSuper*) PSPromotionManager::stack_array_depth()); 190 if (task.marks_oops_alive() && ParallelGCThreads > 1) { 191 for (uint j=0; j<ParallelGCThreads; j++) { 192 q->enqueue(new StealTask(&terminator)); 193 } 194 } 195 ParallelScavengeHeap::gc_task_manager()->execute_and_wait(q); 196 } 197 198 199 void PSRefProcTaskExecutor::execute(EnqueueTask& task) 200 { 201 GCTaskQueue* q = GCTaskQueue::create(); 202 for(uint i=0; i<ParallelGCThreads; i++) { 203 q->enqueue(new PSRefEnqueueTaskProxy(task, i)); 204 } 205 ParallelScavengeHeap::gc_task_manager()->execute_and_wait(q); 206 } 207 208 // This method contains all heap specific policy for invoking scavenge. 209 // PSScavenge::invoke_no_policy() will do nothing but attempt to 210 // scavenge. It will not clean up after failed promotions, bail out if 211 // we've exceeded policy time limits, or any other special behavior. 212 // All such policy should be placed here. 213 // 214 // Note that this method should only be called from the vm_thread while 215 // at a safepoint! 216 void PSScavenge::invoke() { 217 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint"); 218 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread"); 219 assert(!Universe::heap()->is_gc_active(), "not reentrant"); 220 221 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 222 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 223 224 PSAdaptiveSizePolicy* policy = heap->size_policy(); 225 IsGCActiveMark mark; 226 227 bool scavenge_was_done = PSScavenge::invoke_no_policy(); 228 229 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters(); 230 if (UsePerfData) 231 counters->update_full_follows_scavenge(0); 232 if (!scavenge_was_done || 233 policy->should_full_GC(heap->old_gen()->free_in_bytes())) { 234 if (UsePerfData) 235 counters->update_full_follows_scavenge(full_follows_scavenge); 236 GCCauseSetter gccs(heap, GCCause::_adaptive_size_policy); 237 CollectorPolicy* cp = heap->collector_policy(); 238 const bool clear_all_softrefs = cp->should_clear_all_soft_refs(); 239 240 if (UseParallelOldGC) { 241 PSParallelCompact::invoke_no_policy(clear_all_softrefs); 242 } else { 243 PSMarkSweep::invoke_no_policy(clear_all_softrefs); 244 } 245 } 246 } 247 248 // This method contains no policy. You should probably 249 // be calling invoke() instead. 250 bool PSScavenge::invoke_no_policy() { 251 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint"); 252 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread"); 253 254 assert(_preserved_mark_stack.is_empty(), "should be empty"); 255 assert(_preserved_oop_stack.is_empty(), "should be empty"); 256 257 TimeStamp scavenge_entry; 258 TimeStamp scavenge_midpoint; 259 TimeStamp scavenge_exit; 260 261 scavenge_entry.update(); 262 263 if (GC_locker::check_active_before_gc()) { 264 return false; 265 } 266 267 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 268 GCCause::Cause gc_cause = heap->gc_cause(); 269 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 270 271 // Check for potential problems. 272 if (!should_attempt_scavenge()) { 273 return false; 274 } 275 276 bool promotion_failure_occurred = false; 277 278 PSYoungGen* young_gen = heap->young_gen(); 279 PSOldGen* old_gen = heap->old_gen(); 280 PSPermGen* perm_gen = heap->perm_gen(); 281 PSAdaptiveSizePolicy* size_policy = heap->size_policy(); 282 heap->increment_total_collections(); 283 284 AdaptiveSizePolicyOutput(size_policy, heap->total_collections()); 285 286 if ((gc_cause != GCCause::_java_lang_system_gc) || 287 UseAdaptiveSizePolicyWithSystemGC) { 288 // Gather the feedback data for eden occupancy. 289 young_gen->eden_space()->accumulate_statistics(); 290 } 291 292 if (ZapUnusedHeapArea) { 293 // Save information needed to minimize mangling 294 heap->record_gen_tops_before_GC(); 295 } 296 297 if (PrintHeapAtGC) { 298 Universe::print_heap_before_gc(); 299 } 300 301 assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity"); 302 assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity"); 303 304 size_t prev_used = heap->used(); 305 assert(promotion_failed() == false, "Sanity"); 306 307 // Fill in TLABs 308 heap->accumulate_statistics_all_tlabs(); 309 heap->ensure_parsability(true); // retire TLABs 310 311 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) { 312 HandleMark hm; // Discard invalid handles created during verification 313 gclog_or_tty->print(" VerifyBeforeGC:"); 314 Universe::verify(true); 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("GC", 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 perm_gen->verify_object_start_array(); 337 } 338 339 // Verify no unmarked old->young roots 340 if (VerifyRememberedSets) { 341 CardTableExtension::verify_all_young_refs_imprecise(); 342 } 343 344 if (!ScavengeWithObjectsInToSpace) { 345 assert(young_gen->to_space()->is_empty(), 346 "Attempt to scavenge with live objects in to_space"); 347 young_gen->to_space()->clear(SpaceDecorator::Mangle); 348 } else if (ZapUnusedHeapArea) { 349 young_gen->to_space()->mangle_unused_area(); 350 } 351 save_to_space_top_before_gc(); 352 353 NOT_PRODUCT(reference_processor()->verify_no_references_recorded()); 354 COMPILER2_PRESENT(DerivedPointerTable::clear()); 355 356 reference_processor()->enable_discovery(); 357 reference_processor()->setup_policy(false); 358 359 // We track how much was promoted to the next generation for 360 // the AdaptiveSizePolicy. 361 size_t old_gen_used_before = old_gen->used_in_bytes(); 362 363 // For PrintGCDetails 364 size_t young_gen_used_before = young_gen->used_in_bytes(); 365 366 // Reset our survivor overflow. 367 set_survivor_overflow(false); 368 369 // We need to save the old/perm top values before 370 // creating the promotion_manager. We pass the top 371 // values to the card_table, to prevent it from 372 // straying into the promotion labs. 373 HeapWord* old_top = old_gen->object_space()->top(); 374 HeapWord* perm_top = perm_gen->object_space()->top(); 375 376 // Release all previously held resources 377 gc_task_manager()->release_all_resources(); 378 379 PSPromotionManager::pre_scavenge(); 380 381 // We'll use the promotion manager again later. 382 PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager(); 383 { 384 // TraceTime("Roots"); 385 ParallelScavengeHeap::ParStrongRootsScope psrs; 386 387 GCTaskQueue* q = GCTaskQueue::create(); 388 389 for(uint i=0; i<ParallelGCThreads; i++) { 390 q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i)); 391 } 392 393 q->enqueue(new SerialOldToYoungRootsTask(perm_gen, perm_top)); 394 395 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe)); 396 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles)); 397 // We scan the thread roots in parallel 398 Threads::create_thread_roots_tasks(q); 399 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer)); 400 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::flat_profiler)); 401 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management)); 402 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary)); 403 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmti)); 404 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::code_cache)); 405 406 ParallelTaskTerminator terminator( 407 gc_task_manager()->workers(), 408 (TaskQueueSetSuper*) promotion_manager->stack_array_depth()); 409 if (ParallelGCThreads>1) { 410 for (uint j=0; j<ParallelGCThreads; j++) { 411 q->enqueue(new StealTask(&terminator)); 412 } 413 } 414 415 gc_task_manager()->execute_and_wait(q); 416 } 417 418 scavenge_midpoint.update(); 419 420 // Process reference objects discovered during scavenge 421 { 422 reference_processor()->setup_policy(false); // not always_clear 423 PSKeepAliveClosure keep_alive(promotion_manager); 424 PSEvacuateFollowersClosure evac_followers(promotion_manager); 425 if (reference_processor()->processing_is_mt()) { 426 PSRefProcTaskExecutor task_executor; 427 reference_processor()->process_discovered_references( 428 &_is_alive_closure, &keep_alive, &evac_followers, &task_executor); 429 } else { 430 reference_processor()->process_discovered_references( 431 &_is_alive_closure, &keep_alive, &evac_followers, NULL); 432 } 433 } 434 435 // Enqueue reference objects discovered during scavenge. 436 if (reference_processor()->processing_is_mt()) { 437 PSRefProcTaskExecutor task_executor; 438 reference_processor()->enqueue_discovered_references(&task_executor); 439 } else { 440 reference_processor()->enqueue_discovered_references(NULL); 441 } 442 443 if (!JavaObjectsInPerm) { 444 // Unlink any dead interned Strings 445 StringTable::unlink(&_is_alive_closure); 446 // Process the remaining live ones 447 PSScavengeRootsClosure root_closure(promotion_manager); 448 StringTable::oops_do(&root_closure); 449 } 450 451 // Finally, flush the promotion_manager's labs, and deallocate its stacks. 452 PSPromotionManager::post_scavenge(); 453 454 promotion_failure_occurred = promotion_failed(); 455 if (promotion_failure_occurred) { 456 clean_up_failed_promotion(); 457 if (PrintGC) { 458 gclog_or_tty->print("--"); 459 } 460 } 461 462 // Let the size policy know we're done. Note that we count promotion 463 // failure cleanup time as part of the collection (otherwise, we're 464 // implicitly saying it's mutator time). 465 size_policy->minor_collection_end(gc_cause); 466 467 if (!promotion_failure_occurred) { 468 // Swap the survivor spaces. 469 470 471 young_gen->eden_space()->clear(SpaceDecorator::Mangle); 472 young_gen->from_space()->clear(SpaceDecorator::Mangle); 473 young_gen->swap_spaces(); 474 475 size_t survived = young_gen->from_space()->used_in_bytes(); 476 size_t promoted = old_gen->used_in_bytes() - old_gen_used_before; 477 size_policy->update_averages(_survivor_overflow, survived, promoted); 478 479 // A successful scavenge should restart the GC time limit count which is 480 // for full GC's. 481 size_policy->reset_gc_overhead_limit_count(); 482 if (UseAdaptiveSizePolicy) { 483 // Calculate the new survivor size and tenuring threshold 484 485 if (PrintAdaptiveSizePolicy) { 486 gclog_or_tty->print("AdaptiveSizeStart: "); 487 gclog_or_tty->stamp(); 488 gclog_or_tty->print_cr(" collection: %d ", 489 heap->total_collections()); 490 491 if (Verbose) { 492 gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d" 493 " perm_gen_capacity: %d ", 494 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes(), 495 perm_gen->capacity_in_bytes()); 496 } 497 } 498 499 500 if (UsePerfData) { 501 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters(); 502 counters->update_old_eden_size( 503 size_policy->calculated_eden_size_in_bytes()); 504 counters->update_old_promo_size( 505 size_policy->calculated_promo_size_in_bytes()); 506 counters->update_old_capacity(old_gen->capacity_in_bytes()); 507 counters->update_young_capacity(young_gen->capacity_in_bytes()); 508 counters->update_survived(survived); 509 counters->update_promoted(promoted); 510 counters->update_survivor_overflowed(_survivor_overflow); 511 } 512 513 size_t survivor_limit = 514 size_policy->max_survivor_size(young_gen->max_size()); 515 _tenuring_threshold = 516 size_policy->compute_survivor_space_size_and_threshold( 517 _survivor_overflow, 518 _tenuring_threshold, 519 survivor_limit); 520 521 if (PrintTenuringDistribution) { 522 gclog_or_tty->cr(); 523 gclog_or_tty->print_cr("Desired survivor size %ld bytes, new threshold %d (max %d)", 524 size_policy->calculated_survivor_size_in_bytes(), 525 _tenuring_threshold, MaxTenuringThreshold); 526 } 527 528 if (UsePerfData) { 529 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters(); 530 counters->update_tenuring_threshold(_tenuring_threshold); 531 counters->update_survivor_size_counters(); 532 } 533 534 // Do call at minor collections? 535 // Don't check if the size_policy is ready at this 536 // level. Let the size_policy check that internally. 537 if (UseAdaptiveSizePolicy && 538 UseAdaptiveGenerationSizePolicyAtMinorCollection && 539 ((gc_cause != GCCause::_java_lang_system_gc) || 540 UseAdaptiveSizePolicyWithSystemGC)) { 541 542 // Calculate optimial free space amounts 543 assert(young_gen->max_size() > 544 young_gen->from_space()->capacity_in_bytes() + 545 young_gen->to_space()->capacity_in_bytes(), 546 "Sizes of space in young gen are out-of-bounds"); 547 size_t max_eden_size = young_gen->max_size() - 548 young_gen->from_space()->capacity_in_bytes() - 549 young_gen->to_space()->capacity_in_bytes(); 550 size_policy->compute_generation_free_space(young_gen->used_in_bytes(), 551 young_gen->eden_space()->used_in_bytes(), 552 old_gen->used_in_bytes(), 553 perm_gen->used_in_bytes(), 554 young_gen->eden_space()->capacity_in_bytes(), 555 old_gen->max_gen_size(), 556 max_eden_size, 557 false /* full gc*/, 558 gc_cause, 559 heap->collector_policy()); 560 561 } 562 // Resize the young generation at every collection 563 // even if new sizes have not been calculated. This is 564 // to allow resizes that may have been inhibited by the 565 // relative location of the "to" and "from" spaces. 566 567 // Resizing the old gen at minor collects can cause increases 568 // that don't feed back to the generation sizing policy until 569 // a major collection. Don't resize the old gen here. 570 571 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(), 572 size_policy->calculated_survivor_size_in_bytes()); 573 574 if (PrintAdaptiveSizePolicy) { 575 gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ", 576 heap->total_collections()); 577 } 578 } 579 580 // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can 581 // cause the change of the heap layout. Make sure eden is reshaped if that's the case. 582 // Also update() will case adaptive NUMA chunk resizing. 583 assert(young_gen->eden_space()->is_empty(), "eden space should be empty now"); 584 young_gen->eden_space()->update(); 585 586 heap->gc_policy_counters()->update_counters(); 587 588 heap->resize_all_tlabs(); 589 590 assert(young_gen->to_space()->is_empty(), "to space should be empty now"); 591 } 592 593 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 594 595 NOT_PRODUCT(reference_processor()->verify_no_references_recorded()); 596 597 // Re-verify object start arrays 598 if (VerifyObjectStartArray && 599 VerifyAfterGC) { 600 old_gen->verify_object_start_array(); 601 perm_gen->verify_object_start_array(); 602 } 603 604 // Verify all old -> young cards are now precise 605 if (VerifyRememberedSets) { 606 // Precise verification will give false positives. Until this is fixed, 607 // use imprecise verification. 608 // CardTableExtension::verify_all_young_refs_precise(); 609 CardTableExtension::verify_all_young_refs_imprecise(); 610 } 611 612 if (TraceGen0Time) accumulated_time()->stop(); 613 614 if (PrintGC) { 615 if (PrintGCDetails) { 616 // Don't print a GC timestamp here. This is after the GC so 617 // would be confusing. 618 young_gen->print_used_change(young_gen_used_before); 619 } 620 heap->print_heap_change(prev_used); 621 } 622 623 // Track memory usage and detect low memory 624 MemoryService::track_memory_usage(); 625 heap->update_counters(); 626 } 627 628 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) { 629 HandleMark hm; // Discard invalid handles created during verification 630 gclog_or_tty->print(" VerifyAfterGC:"); 631 Universe::verify(false); 632 } 633 634 if (PrintHeapAtGC) { 635 Universe::print_heap_after_gc(); 636 } 637 638 if (ZapUnusedHeapArea) { 639 young_gen->eden_space()->check_mangled_unused_area_complete(); 640 young_gen->from_space()->check_mangled_unused_area_complete(); 641 young_gen->to_space()->check_mangled_unused_area_complete(); 642 } 643 644 scavenge_exit.update(); 645 646 if (PrintGCTaskTimeStamps) { 647 tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " " INT64_FORMAT, 648 scavenge_entry.ticks(), scavenge_midpoint.ticks(), 649 scavenge_exit.ticks()); 650 gc_task_manager()->print_task_time_stamps(); 651 } 652 653 #ifdef TRACESPINNING 654 ParallelTaskTerminator::print_termination_counts(); 655 #endif 656 657 return !promotion_failure_occurred; 658 } 659 660 // This method iterates over all objects in the young generation, 661 // unforwarding markOops. It then restores any preserved mark oops, 662 // and clears the _preserved_mark_stack. 663 void PSScavenge::clean_up_failed_promotion() { 664 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 665 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 666 assert(promotion_failed(), "Sanity"); 667 668 PSYoungGen* young_gen = heap->young_gen(); 669 670 { 671 ResourceMark rm; 672 673 // Unforward all pointers in the young gen. 674 PSPromotionFailedClosure unforward_closure; 675 young_gen->object_iterate(&unforward_closure); 676 677 if (PrintGC && Verbose) { 678 gclog_or_tty->print_cr("Restoring %d marks", _preserved_oop_stack.size()); 679 } 680 681 // Restore any saved marks. 682 while (!_preserved_oop_stack.is_empty()) { 683 oop obj = _preserved_oop_stack.pop(); 684 markOop mark = _preserved_mark_stack.pop(); 685 obj->set_mark(mark); 686 } 687 688 // Clear the preserved mark and oop stack caches. 689 _preserved_mark_stack.clear(true); 690 _preserved_oop_stack.clear(true); 691 _promotion_failed = false; 692 } 693 694 // Reset the PromotionFailureALot counters. 695 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();) 696 } 697 698 // This method is called whenever an attempt to promote an object 699 // fails. Some markOops will need preservation, some will not. Note 700 // that the entire eden is traversed after a failed promotion, with 701 // all forwarded headers replaced by the default markOop. This means 702 // it is not neccessary to preserve most markOops. 703 void PSScavenge::oop_promotion_failed(oop obj, markOop obj_mark) { 704 _promotion_failed = true; 705 if (obj_mark->must_be_preserved_for_promotion_failure(obj)) { 706 // Should use per-worker private stakcs hetre rather than 707 // locking a common pair of stacks. 708 ThreadCritical tc; 709 _preserved_oop_stack.push(obj); 710 _preserved_mark_stack.push(obj_mark); 711 } 712 } 713 714 bool PSScavenge::should_attempt_scavenge() { 715 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 716 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 717 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters(); 718 719 if (UsePerfData) { 720 counters->update_scavenge_skipped(not_skipped); 721 } 722 723 PSYoungGen* young_gen = heap->young_gen(); 724 PSOldGen* old_gen = heap->old_gen(); 725 726 if (!ScavengeWithObjectsInToSpace) { 727 // Do not attempt to promote unless to_space is empty 728 if (!young_gen->to_space()->is_empty()) { 729 _consecutive_skipped_scavenges++; 730 if (UsePerfData) { 731 counters->update_scavenge_skipped(to_space_not_empty); 732 } 733 return false; 734 } 735 } 736 737 // Test to see if the scavenge will likely fail. 738 PSAdaptiveSizePolicy* policy = heap->size_policy(); 739 740 // A similar test is done in the policy's should_full_GC(). If this is 741 // changed, decide if that test should also be changed. 742 size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes(); 743 size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes()); 744 bool result = promotion_estimate < old_gen->free_in_bytes(); 745 746 if (PrintGCDetails && Verbose) { 747 gclog_or_tty->print(result ? " do scavenge: " : " skip scavenge: "); 748 gclog_or_tty->print_cr(" average_promoted " SIZE_FORMAT 749 " padded_average_promoted " SIZE_FORMAT 750 " free in old gen " SIZE_FORMAT, 751 (size_t) policy->average_promoted_in_bytes(), 752 (size_t) policy->padded_average_promoted_in_bytes(), 753 old_gen->free_in_bytes()); 754 if (young_gen->used_in_bytes() < 755 (size_t) policy->padded_average_promoted_in_bytes()) { 756 gclog_or_tty->print_cr(" padded_promoted_average is greater" 757 " than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes()); 758 } 759 } 760 761 if (result) { 762 _consecutive_skipped_scavenges = 0; 763 } else { 764 _consecutive_skipped_scavenges++; 765 if (UsePerfData) { 766 counters->update_scavenge_skipped(promoted_too_large); 767 } 768 } 769 return result; 770 } 771 772 // Used to add tasks 773 GCTaskManager* const PSScavenge::gc_task_manager() { 774 assert(ParallelScavengeHeap::gc_task_manager() != NULL, 775 "shouldn't return NULL"); 776 return ParallelScavengeHeap::gc_task_manager(); 777 } 778 779 void PSScavenge::initialize() { 780 // Arguments must have been parsed 781 782 if (AlwaysTenure) { 783 _tenuring_threshold = 0; 784 } else if (NeverTenure) { 785 _tenuring_threshold = markOopDesc::max_age + 1; 786 } else { 787 // We want to smooth out our startup times for the AdaptiveSizePolicy 788 _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold : 789 MaxTenuringThreshold; 790 } 791 792 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 793 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 794 795 PSYoungGen* young_gen = heap->young_gen(); 796 PSOldGen* old_gen = heap->old_gen(); 797 PSPermGen* perm_gen = heap->perm_gen(); 798 799 // Set boundary between young_gen and old_gen 800 assert(perm_gen->reserved().end() <= old_gen->object_space()->bottom(), 801 "perm above old"); 802 assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(), 803 "old above young"); 804 _young_generation_boundary = young_gen->eden_space()->bottom(); 805 806 // Initialize ref handling object for scavenging. 807 MemRegion mr = young_gen->reserved(); 808 _ref_processor = 809 new ReferenceProcessor(mr, // span 810 ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing 811 (int) ParallelGCThreads, // mt processing degree 812 true, // mt discovery 813 (int) ParallelGCThreads, // mt discovery degree 814 true, // atomic_discovery 815 NULL, // header provides liveness info 816 false); // next field updates do not need write barrier 817 818 // Cache the cardtable 819 BarrierSet* bs = Universe::heap()->barrier_set(); 820 assert(bs->kind() == BarrierSet::CardTableModRef, "Wrong barrier set kind"); 821 _card_table = (CardTableExtension*)bs; 822 823 _counters = new CollectorCounters("PSScavenge", 0); 824 }