1 /* 2 * Copyright (c) 2001, 2015, 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/stringTable.hpp" 27 #include "classfile/systemDictionary.hpp" 28 #include "code/codeCache.hpp" 29 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.hpp" 30 #include "gc_implementation/parallelScavenge/psAdaptiveSizePolicy.hpp" 31 #include "gc_implementation/parallelScavenge/psMarkSweep.hpp" 32 #include "gc_implementation/parallelScavenge/psMarkSweepDecorator.hpp" 33 #include "gc_implementation/parallelScavenge/psOldGen.hpp" 34 #include "gc_implementation/parallelScavenge/psScavenge.hpp" 35 #include "gc_implementation/parallelScavenge/psYoungGen.hpp" 36 #include "gc_implementation/shared/gcHeapSummary.hpp" 37 #include "gc_implementation/shared/gcTimer.hpp" 38 #include "gc_implementation/shared/gcTrace.hpp" 39 #include "gc_implementation/shared/gcTraceTime.hpp" 40 #include "gc_implementation/shared/isGCActiveMark.hpp" 41 #include "gc_implementation/shared/markSweep.hpp" 42 #include "gc_implementation/shared/spaceDecorator.hpp" 43 #include "gc_interface/gcCause.hpp" 44 #include "memory/gcLocker.inline.hpp" 45 #include "memory/referencePolicy.hpp" 46 #include "memory/referenceProcessor.hpp" 47 #include "oops/oop.inline.hpp" 48 #include "runtime/biasedLocking.hpp" 49 #include "runtime/fprofiler.hpp" 50 #include "runtime/safepoint.hpp" 51 #include "runtime/vmThread.hpp" 52 #include "services/management.hpp" 53 #include "services/memoryService.hpp" 54 #include "utilities/events.hpp" 55 #include "utilities/stack.inline.hpp" 56 57 elapsedTimer PSMarkSweep::_accumulated_time; 58 jlong PSMarkSweep::_time_of_last_gc = 0; 59 CollectorCounters* PSMarkSweep::_counters = NULL; 60 61 void PSMarkSweep::initialize() { 62 MemRegion mr = Universe::heap()->reserved_region(); 63 _ref_processor = new ReferenceProcessor(mr); // a vanilla ref proc 64 _counters = new CollectorCounters("PSMarkSweep", 1); 65 } 66 67 // This method contains all heap specific policy for invoking mark sweep. 68 // PSMarkSweep::invoke_no_policy() will only attempt to mark-sweep-compact 69 // the heap. It will do nothing further. If we need to bail out for policy 70 // reasons, scavenge before full gc, or any other specialized behavior, it 71 // needs to be added here. 72 // 73 // Note that this method should only be called from the vm_thread while 74 // at a safepoint! 75 // 76 // Note that the all_soft_refs_clear flag in the collector policy 77 // may be true because this method can be called without intervening 78 // activity. For example when the heap space is tight and full measure 79 // are being taken to free space. 80 81 void PSMarkSweep::invoke(bool maximum_heap_compaction) { 82 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint"); 83 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread"); 84 assert(!Universe::heap()->is_gc_active(), "not reentrant"); 85 86 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 87 GCCause::Cause gc_cause = heap->gc_cause(); 88 PSAdaptiveSizePolicy* policy = heap->size_policy(); 89 IsGCActiveMark mark; 90 91 if (ScavengeBeforeFullGC) { 92 PSScavenge::invoke_no_policy(); 93 } 94 95 const bool clear_all_soft_refs = 96 heap->collector_policy()->should_clear_all_soft_refs(); 97 98 uint count = maximum_heap_compaction ? 1 : MarkSweepAlwaysCompactCount; 99 UIntFlagSetting flag_setting(MarkSweepAlwaysCompactCount, count); 100 PSMarkSweep::invoke_no_policy(clear_all_soft_refs || maximum_heap_compaction); 101 } 102 103 // This method contains no policy. You should probably 104 // be calling invoke() instead. 105 bool PSMarkSweep::invoke_no_policy(bool clear_all_softrefs) { 106 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); 107 assert(ref_processor() != NULL, "Sanity"); 108 109 if (GC_locker::check_active_before_gc()) { 110 return false; 111 } 112 113 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 114 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 115 GCCause::Cause gc_cause = heap->gc_cause(); 116 117 _gc_timer->register_gc_start(); 118 _gc_tracer->report_gc_start(gc_cause, _gc_timer->gc_start()); 119 120 PSAdaptiveSizePolicy* size_policy = heap->size_policy(); 121 122 // The scope of casr should end after code that can change 123 // CollectorPolicy::_should_clear_all_soft_refs. 124 ClearedAllSoftRefs casr(clear_all_softrefs, heap->collector_policy()); 125 126 PSYoungGen* young_gen = heap->young_gen(); 127 PSOldGen* old_gen = heap->old_gen(); 128 129 // Increment the invocation count 130 heap->increment_total_collections(true /* full */); 131 132 // Save information needed to minimize mangling 133 heap->record_gen_tops_before_GC(); 134 135 // We need to track unique mark sweep invocations as well. 136 _total_invocations++; 137 138 AdaptiveSizePolicyOutput(size_policy, heap->total_collections()); 139 140 heap->print_heap_before_gc(); 141 heap->trace_heap_before_gc(_gc_tracer); 142 143 // Fill in TLABs 144 heap->accumulate_statistics_all_tlabs(); 145 heap->ensure_parsability(true); // retire TLABs 146 147 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) { 148 HandleMark hm; // Discard invalid handles created during verification 149 Universe::verify(" VerifyBeforeGC:"); 150 } 151 152 // Verify object start arrays 153 if (VerifyObjectStartArray && 154 VerifyBeforeGC) { 155 old_gen->verify_object_start_array(); 156 } 157 158 heap->pre_full_gc_dump(_gc_timer); 159 160 // Filled in below to track the state of the young gen after the collection. 161 bool eden_empty; 162 bool survivors_empty; 163 bool young_gen_empty; 164 165 { 166 HandleMark hm; 167 168 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); 169 GCTraceTime t1(GCCauseString("Full GC", gc_cause), PrintGC, !PrintGCDetails, NULL, _gc_tracer->gc_id()); 170 TraceCollectorStats tcs(counters()); 171 TraceMemoryManagerStats tms(true /* Full GC */,gc_cause); 172 173 if (TraceOldGenTime) accumulated_time()->start(); 174 175 // Let the size policy know we're starting 176 size_policy->major_collection_begin(); 177 178 CodeCache::gc_prologue(); 179 BiasedLocking::preserve_marks(); 180 181 // Capture heap size before collection for printing. 182 size_t prev_used = heap->used(); 183 184 // Capture metadata size before collection for sizing. 185 size_t metadata_prev_used = MetaspaceAux::used_bytes(); 186 187 // For PrintGCDetails 188 size_t old_gen_prev_used = old_gen->used_in_bytes(); 189 size_t young_gen_prev_used = young_gen->used_in_bytes(); 190 191 allocate_stacks(); 192 193 COMPILER2_PRESENT(DerivedPointerTable::clear()); 194 195 ref_processor()->enable_discovery(); 196 ref_processor()->setup_policy(clear_all_softrefs); 197 198 mark_sweep_phase1(clear_all_softrefs); 199 200 mark_sweep_phase2(); 201 202 // Don't add any more derived pointers during phase3 203 COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity")); 204 COMPILER2_PRESENT(DerivedPointerTable::set_active(false)); 205 206 mark_sweep_phase3(); 207 208 mark_sweep_phase4(); 209 210 restore_marks(); 211 212 deallocate_stacks(); 213 214 if (ZapUnusedHeapArea) { 215 // Do a complete mangle (top to end) because the usage for 216 // scratch does not maintain a top pointer. 217 young_gen->to_space()->mangle_unused_area_complete(); 218 } 219 220 eden_empty = young_gen->eden_space()->is_empty(); 221 if (!eden_empty) { 222 eden_empty = absorb_live_data_from_eden(size_policy, young_gen, old_gen); 223 } 224 225 // Update heap occupancy information which is used as 226 // input to soft ref clearing policy at the next gc. 227 Universe::update_heap_info_at_gc(); 228 229 survivors_empty = young_gen->from_space()->is_empty() && 230 young_gen->to_space()->is_empty(); 231 young_gen_empty = eden_empty && survivors_empty; 232 233 ModRefBarrierSet* modBS = barrier_set_cast<ModRefBarrierSet>(heap->barrier_set()); 234 MemRegion old_mr = heap->old_gen()->reserved(); 235 if (young_gen_empty) { 236 modBS->clear(MemRegion(old_mr.start(), old_mr.end())); 237 } else { 238 modBS->invalidate(MemRegion(old_mr.start(), old_mr.end())); 239 } 240 241 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 242 ClassLoaderDataGraph::purge(); 243 MetaspaceAux::verify_metrics(); 244 245 BiasedLocking::restore_marks(); 246 CodeCache::gc_epilogue(); 247 JvmtiExport::gc_epilogue(); 248 249 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 250 251 ref_processor()->enqueue_discovered_references(NULL); 252 253 // Update time of last GC 254 reset_millis_since_last_gc(); 255 256 // Let the size policy know we're done 257 size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause); 258 259 if (UseAdaptiveSizePolicy) { 260 261 if (PrintAdaptiveSizePolicy) { 262 gclog_or_tty->print("AdaptiveSizeStart: "); 263 gclog_or_tty->stamp(); 264 gclog_or_tty->print_cr(" collection: %d ", 265 heap->total_collections()); 266 if (Verbose) { 267 gclog_or_tty->print("old_gen_capacity: " SIZE_FORMAT 268 " young_gen_capacity: " SIZE_FORMAT, 269 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes()); 270 } 271 } 272 273 // Don't check if the size_policy is ready here. Let 274 // the size_policy check that internally. 275 if (UseAdaptiveGenerationSizePolicyAtMajorCollection && 276 ((gc_cause != GCCause::_java_lang_system_gc) || 277 UseAdaptiveSizePolicyWithSystemGC)) { 278 // Swap the survivor spaces if from_space is empty. The 279 // resize_young_gen() called below is normally used after 280 // a successful young GC and swapping of survivor spaces; 281 // otherwise, it will fail to resize the young gen with 282 // the current implementation. 283 if (young_gen->from_space()->is_empty()) { 284 young_gen->from_space()->clear(SpaceDecorator::Mangle); 285 young_gen->swap_spaces(); 286 } 287 288 // Calculate optimal free space amounts 289 assert(young_gen->max_size() > 290 young_gen->from_space()->capacity_in_bytes() + 291 young_gen->to_space()->capacity_in_bytes(), 292 "Sizes of space in young gen are out-of-bounds"); 293 294 size_t young_live = young_gen->used_in_bytes(); 295 size_t eden_live = young_gen->eden_space()->used_in_bytes(); 296 size_t old_live = old_gen->used_in_bytes(); 297 size_t cur_eden = young_gen->eden_space()->capacity_in_bytes(); 298 size_t max_old_gen_size = old_gen->max_gen_size(); 299 size_t max_eden_size = young_gen->max_size() - 300 young_gen->from_space()->capacity_in_bytes() - 301 young_gen->to_space()->capacity_in_bytes(); 302 303 // Used for diagnostics 304 size_policy->clear_generation_free_space_flags(); 305 306 size_policy->compute_generations_free_space(young_live, 307 eden_live, 308 old_live, 309 cur_eden, 310 max_old_gen_size, 311 max_eden_size, 312 true /* full gc*/); 313 314 size_policy->check_gc_overhead_limit(young_live, 315 eden_live, 316 max_old_gen_size, 317 max_eden_size, 318 true /* full gc*/, 319 gc_cause, 320 heap->collector_policy()); 321 322 size_policy->decay_supplemental_growth(true /* full gc*/); 323 324 heap->resize_old_gen(size_policy->calculated_old_free_size_in_bytes()); 325 326 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(), 327 size_policy->calculated_survivor_size_in_bytes()); 328 } 329 if (PrintAdaptiveSizePolicy) { 330 gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ", 331 heap->total_collections()); 332 } 333 } 334 335 if (UsePerfData) { 336 heap->gc_policy_counters()->update_counters(); 337 heap->gc_policy_counters()->update_old_capacity( 338 old_gen->capacity_in_bytes()); 339 heap->gc_policy_counters()->update_young_capacity( 340 young_gen->capacity_in_bytes()); 341 } 342 343 heap->resize_all_tlabs(); 344 345 // We collected the heap, recalculate the metaspace capacity 346 MetaspaceGC::compute_new_size(); 347 348 if (TraceOldGenTime) accumulated_time()->stop(); 349 350 if (PrintGC) { 351 if (PrintGCDetails) { 352 // Don't print a GC timestamp here. This is after the GC so 353 // would be confusing. 354 young_gen->print_used_change(young_gen_prev_used); 355 old_gen->print_used_change(old_gen_prev_used); 356 } 357 heap->print_heap_change(prev_used); 358 if (PrintGCDetails) { 359 MetaspaceAux::print_metaspace_change(metadata_prev_used); 360 } 361 } 362 363 // Track memory usage and detect low memory 364 MemoryService::track_memory_usage(); 365 heap->update_counters(); 366 } 367 368 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) { 369 HandleMark hm; // Discard invalid handles created during verification 370 Universe::verify(" VerifyAfterGC:"); 371 } 372 373 // Re-verify object start arrays 374 if (VerifyObjectStartArray && 375 VerifyAfterGC) { 376 old_gen->verify_object_start_array(); 377 } 378 379 if (ZapUnusedHeapArea) { 380 old_gen->object_space()->check_mangled_unused_area_complete(); 381 } 382 383 NOT_PRODUCT(ref_processor()->verify_no_references_recorded()); 384 385 heap->print_heap_after_gc(); 386 heap->trace_heap_after_gc(_gc_tracer); 387 388 heap->post_full_gc_dump(_gc_timer); 389 390 #ifdef TRACESPINNING 391 ParallelTaskTerminator::print_termination_counts(); 392 #endif 393 394 _gc_timer->register_gc_end(); 395 396 _gc_tracer->report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions()); 397 398 return true; 399 } 400 401 bool PSMarkSweep::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy, 402 PSYoungGen* young_gen, 403 PSOldGen* old_gen) { 404 MutableSpace* const eden_space = young_gen->eden_space(); 405 assert(!eden_space->is_empty(), "eden must be non-empty"); 406 assert(young_gen->virtual_space()->alignment() == 407 old_gen->virtual_space()->alignment(), "alignments do not match"); 408 409 if (!(UseAdaptiveSizePolicy && UseAdaptiveGCBoundary)) { 410 return false; 411 } 412 413 // Both generations must be completely committed. 414 if (young_gen->virtual_space()->uncommitted_size() != 0) { 415 return false; 416 } 417 if (old_gen->virtual_space()->uncommitted_size() != 0) { 418 return false; 419 } 420 421 // Figure out how much to take from eden. Include the average amount promoted 422 // in the total; otherwise the next young gen GC will simply bail out to a 423 // full GC. 424 const size_t alignment = old_gen->virtual_space()->alignment(); 425 const size_t eden_used = eden_space->used_in_bytes(); 426 const size_t promoted = (size_t)size_policy->avg_promoted()->padded_average(); 427 const size_t absorb_size = align_size_up(eden_used + promoted, alignment); 428 const size_t eden_capacity = eden_space->capacity_in_bytes(); 429 430 if (absorb_size >= eden_capacity) { 431 return false; // Must leave some space in eden. 432 } 433 434 const size_t new_young_size = young_gen->capacity_in_bytes() - absorb_size; 435 if (new_young_size < young_gen->min_gen_size()) { 436 return false; // Respect young gen minimum size. 437 } 438 439 if (TraceAdaptiveGCBoundary && Verbose) { 440 gclog_or_tty->print(" absorbing " SIZE_FORMAT "K: " 441 "eden " SIZE_FORMAT "K->" SIZE_FORMAT "K " 442 "from " SIZE_FORMAT "K, to " SIZE_FORMAT "K " 443 "young_gen " SIZE_FORMAT "K->" SIZE_FORMAT "K ", 444 absorb_size / K, 445 eden_capacity / K, (eden_capacity - absorb_size) / K, 446 young_gen->from_space()->used_in_bytes() / K, 447 young_gen->to_space()->used_in_bytes() / K, 448 young_gen->capacity_in_bytes() / K, new_young_size / K); 449 } 450 451 // Fill the unused part of the old gen. 452 MutableSpace* const old_space = old_gen->object_space(); 453 HeapWord* const unused_start = old_space->top(); 454 size_t const unused_words = pointer_delta(old_space->end(), unused_start); 455 456 if (unused_words > 0) { 457 if (unused_words < CollectedHeap::min_fill_size()) { 458 return false; // If the old gen cannot be filled, must give up. 459 } 460 CollectedHeap::fill_with_objects(unused_start, unused_words); 461 } 462 463 // Take the live data from eden and set both top and end in the old gen to 464 // eden top. (Need to set end because reset_after_change() mangles the region 465 // from end to virtual_space->high() in debug builds). 466 HeapWord* const new_top = eden_space->top(); 467 old_gen->virtual_space()->expand_into(young_gen->virtual_space(), 468 absorb_size); 469 young_gen->reset_after_change(); 470 old_space->set_top(new_top); 471 old_space->set_end(new_top); 472 old_gen->reset_after_change(); 473 474 // Update the object start array for the filler object and the data from eden. 475 ObjectStartArray* const start_array = old_gen->start_array(); 476 for (HeapWord* p = unused_start; p < new_top; p += oop(p)->size()) { 477 start_array->allocate_block(p); 478 } 479 480 // Could update the promoted average here, but it is not typically updated at 481 // full GCs and the value to use is unclear. Something like 482 // 483 // cur_promoted_avg + absorb_size / number_of_scavenges_since_last_full_gc. 484 485 size_policy->set_bytes_absorbed_from_eden(absorb_size); 486 return true; 487 } 488 489 void PSMarkSweep::allocate_stacks() { 490 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 491 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 492 493 PSYoungGen* young_gen = heap->young_gen(); 494 495 MutableSpace* to_space = young_gen->to_space(); 496 _preserved_marks = (PreservedMark*)to_space->top(); 497 _preserved_count = 0; 498 499 // We want to calculate the size in bytes first. 500 _preserved_count_max = pointer_delta(to_space->end(), to_space->top(), sizeof(jbyte)); 501 // Now divide by the size of a PreservedMark 502 _preserved_count_max /= sizeof(PreservedMark); 503 } 504 505 506 void PSMarkSweep::deallocate_stacks() { 507 _preserved_mark_stack.clear(true); 508 _preserved_oop_stack.clear(true); 509 _marking_stack.clear(); 510 _objarray_stack.clear(true); 511 } 512 513 void PSMarkSweep::mark_sweep_phase1(bool clear_all_softrefs) { 514 // Recursively traverse all live objects and mark them 515 GCTraceTime tm("phase 1", PrintGCDetails && Verbose, true, _gc_timer, _gc_tracer->gc_id()); 516 trace(" 1"); 517 518 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 519 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 520 521 // Need to clear claim bits before the tracing starts. 522 ClassLoaderDataGraph::clear_claimed_marks(); 523 524 // General strong roots. 525 { 526 ParallelScavengeHeap::ParStrongRootsScope psrs; 527 Universe::oops_do(mark_and_push_closure()); 528 JNIHandles::oops_do(mark_and_push_closure()); // Global (strong) JNI handles 529 CLDToOopClosure mark_and_push_from_cld(mark_and_push_closure()); 530 MarkingCodeBlobClosure each_active_code_blob(mark_and_push_closure(), !CodeBlobToOopClosure::FixRelocations); 531 Threads::oops_do(mark_and_push_closure(), &mark_and_push_from_cld, &each_active_code_blob); 532 ObjectSynchronizer::oops_do(mark_and_push_closure()); 533 FlatProfiler::oops_do(mark_and_push_closure()); 534 Management::oops_do(mark_and_push_closure()); 535 JvmtiExport::oops_do(mark_and_push_closure()); 536 SystemDictionary::always_strong_oops_do(mark_and_push_closure()); 537 ClassLoaderDataGraph::always_strong_cld_do(follow_cld_closure()); 538 // Do not treat nmethods as strong roots for mark/sweep, since we can unload them. 539 //CodeCache::scavenge_root_nmethods_do(CodeBlobToOopClosure(mark_and_push_closure())); 540 } 541 542 // Flush marking stack. 543 follow_stack(); 544 545 // Process reference objects found during marking 546 { 547 ref_processor()->setup_policy(clear_all_softrefs); 548 const ReferenceProcessorStats& stats = 549 ref_processor()->process_discovered_references( 550 is_alive_closure(), mark_and_push_closure(), follow_stack_closure(), NULL, _gc_timer, _gc_tracer->gc_id()); 551 gc_tracer()->report_gc_reference_stats(stats); 552 } 553 554 // This is the point where the entire marking should have completed. 555 assert(_marking_stack.is_empty(), "Marking should have completed"); 556 557 // Unload classes and purge the SystemDictionary. 558 bool purged_class = SystemDictionary::do_unloading(is_alive_closure()); 559 560 // Unload nmethods. 561 CodeCache::do_unloading(is_alive_closure(), purged_class); 562 563 // Prune dead klasses from subklass/sibling/implementor lists. 564 Klass::clean_weak_klass_links(is_alive_closure()); 565 566 // Delete entries for dead interned strings. 567 StringTable::unlink(is_alive_closure()); 568 569 // Clean up unreferenced symbols in symbol table. 570 SymbolTable::unlink(); 571 _gc_tracer->report_object_count_after_gc(is_alive_closure()); 572 } 573 574 575 void PSMarkSweep::mark_sweep_phase2() { 576 GCTraceTime tm("phase 2", PrintGCDetails && Verbose, true, _gc_timer, _gc_tracer->gc_id()); 577 trace("2"); 578 579 // Now all live objects are marked, compute the new object addresses. 580 581 // It is not required that we traverse spaces in the same order in 582 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops 583 // tracking expects us to do so. See comment under phase4. 584 585 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 586 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 587 588 PSOldGen* old_gen = heap->old_gen(); 589 590 // Begin compacting into the old gen 591 PSMarkSweepDecorator::set_destination_decorator_tenured(); 592 593 // This will also compact the young gen spaces. 594 old_gen->precompact(); 595 } 596 597 // This should be moved to the shared markSweep code! 598 class PSAlwaysTrueClosure: public BoolObjectClosure { 599 public: 600 bool do_object_b(oop p) { return true; } 601 }; 602 static PSAlwaysTrueClosure always_true; 603 604 void PSMarkSweep::mark_sweep_phase3() { 605 // Adjust the pointers to reflect the new locations 606 GCTraceTime tm("phase 3", PrintGCDetails && Verbose, true, _gc_timer, _gc_tracer->gc_id()); 607 trace("3"); 608 609 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 610 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 611 612 PSYoungGen* young_gen = heap->young_gen(); 613 PSOldGen* old_gen = heap->old_gen(); 614 615 // Need to clear claim bits before the tracing starts. 616 ClassLoaderDataGraph::clear_claimed_marks(); 617 618 // General strong roots. 619 Universe::oops_do(adjust_pointer_closure()); 620 JNIHandles::oops_do(adjust_pointer_closure()); // Global (strong) JNI handles 621 CLDToOopClosure adjust_from_cld(adjust_pointer_closure()); 622 Threads::oops_do(adjust_pointer_closure(), &adjust_from_cld, NULL); 623 ObjectSynchronizer::oops_do(adjust_pointer_closure()); 624 FlatProfiler::oops_do(adjust_pointer_closure()); 625 Management::oops_do(adjust_pointer_closure()); 626 JvmtiExport::oops_do(adjust_pointer_closure()); 627 SystemDictionary::oops_do(adjust_pointer_closure()); 628 ClassLoaderDataGraph::cld_do(adjust_cld_closure()); 629 630 // Now adjust pointers in remaining weak roots. (All of which should 631 // have been cleared if they pointed to non-surviving objects.) 632 // Global (weak) JNI handles 633 JNIHandles::weak_oops_do(&always_true, adjust_pointer_closure()); 634 635 CodeBlobToOopClosure adjust_from_blobs(adjust_pointer_closure(), CodeBlobToOopClosure::FixRelocations); 636 CodeCache::blobs_do(&adjust_from_blobs); 637 StringTable::oops_do(adjust_pointer_closure()); 638 ref_processor()->weak_oops_do(adjust_pointer_closure()); 639 PSScavenge::reference_processor()->weak_oops_do(adjust_pointer_closure()); 640 641 adjust_marks(); 642 643 young_gen->adjust_pointers(); 644 old_gen->adjust_pointers(); 645 } 646 647 void PSMarkSweep::mark_sweep_phase4() { 648 EventMark m("4 compact heap"); 649 GCTraceTime tm("phase 4", PrintGCDetails && Verbose, true, _gc_timer, _gc_tracer->gc_id()); 650 trace("4"); 651 652 // All pointers are now adjusted, move objects accordingly 653 654 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 655 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 656 657 PSYoungGen* young_gen = heap->young_gen(); 658 PSOldGen* old_gen = heap->old_gen(); 659 660 old_gen->compact(); 661 young_gen->compact(); 662 } 663 664 jlong PSMarkSweep::millis_since_last_gc() { 665 // We need a monotonically non-decreasing time in ms but 666 // os::javaTimeMillis() does not guarantee monotonicity. 667 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 668 jlong ret_val = now - _time_of_last_gc; 669 // XXX See note in genCollectedHeap::millis_since_last_gc(). 670 if (ret_val < 0) { 671 NOT_PRODUCT(warning("time warp: " JLONG_FORMAT, ret_val);) 672 return 0; 673 } 674 return ret_val; 675 } 676 677 void PSMarkSweep::reset_millis_since_last_gc() { 678 // We need a monotonically non-decreasing time in ms but 679 // os::javaTimeMillis() does not guarantee monotonicity. 680 _time_of_last_gc = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 681 }