1 /*
   2  * Copyright (c) 2001, 2012, 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 "classfile/systemDictionary.hpp"
  28 #include "code/codeCache.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/psMarkSweepDecorator.hpp"
  34 #include "gc_implementation/parallelScavenge/psOldGen.hpp"
  35 #include "gc_implementation/parallelScavenge/psScavenge.hpp"
  36 #include "gc_implementation/parallelScavenge/psYoungGen.hpp"
  37 #include "gc_implementation/shared/isGCActiveMark.hpp"
  38 #include "gc_implementation/shared/markSweep.hpp"
  39 #include "gc_implementation/shared/spaceDecorator.hpp"
  40 #include "gc_interface/gcCause.hpp"
  41 #include "memory/gcLocker.inline.hpp"
  42 #include "memory/referencePolicy.hpp"
  43 #include "memory/referenceProcessor.hpp"
  44 #include "oops/oop.inline.hpp"
  45 #include "runtime/biasedLocking.hpp"
  46 #include "runtime/fprofiler.hpp"
  47 #include "runtime/safepoint.hpp"
  48 #include "runtime/vmThread.hpp"
  49 #include "services/management.hpp"
  50 #include "services/memoryService.hpp"
  51 #include "utilities/events.hpp"
  52 #include "utilities/stack.inline.hpp"
  53 
  54 elapsedTimer        PSMarkSweep::_accumulated_time;
  55 jlong               PSMarkSweep::_time_of_last_gc   = 0;
  56 CollectorCounters*  PSMarkSweep::_counters = NULL;
  57 
  58 void PSMarkSweep::initialize() {
  59   MemRegion mr = Universe::heap()->reserved_region();
  60   _ref_processor = new ReferenceProcessor(mr);     // a vanilla ref proc
  61   _counters = new CollectorCounters("PSMarkSweep", 1);
  62 }
  63 
  64 // This method contains all heap specific policy for invoking mark sweep.
  65 // PSMarkSweep::invoke_no_policy() will only attempt to mark-sweep-compact
  66 // the heap. It will do nothing further. If we need to bail out for policy
  67 // reasons, scavenge before full gc, or any other specialized behavior, it
  68 // needs to be added here.
  69 //
  70 // Note that this method should only be called from the vm_thread while
  71 // at a safepoint!
  72 //
  73 // Note that the all_soft_refs_clear flag in the collector policy
  74 // may be true because this method can be called without intervening
  75 // activity.  For example when the heap space is tight and full measure
  76 // are being taken to free space.
  77 
  78 void PSMarkSweep::invoke(bool maximum_heap_compaction) {
  79   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
  80   assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
  81   assert(!Universe::heap()->is_gc_active(), "not reentrant");
  82 
  83   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
  84   GCCause::Cause gc_cause = heap->gc_cause();
  85   PSAdaptiveSizePolicy* policy = heap->size_policy();
  86   IsGCActiveMark mark;
  87 
  88   if (ScavengeBeforeFullGC) {
  89     PSScavenge::invoke_no_policy();
  90   }
  91 
  92   const bool clear_all_soft_refs =
  93     heap->collector_policy()->should_clear_all_soft_refs();
  94 
  95   int count = (maximum_heap_compaction)?1:MarkSweepAlwaysCompactCount;
  96   IntFlagSetting flag_setting(MarkSweepAlwaysCompactCount, count);
  97   PSMarkSweep::invoke_no_policy(clear_all_soft_refs || maximum_heap_compaction);
  98 }
  99 
 100 // This method contains no policy. You should probably
 101 // be calling invoke() instead.
 102 bool PSMarkSweep::invoke_no_policy(bool clear_all_softrefs) {
 103   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
 104   assert(ref_processor() != NULL, "Sanity");
 105 
 106   if (GC_locker::check_active_before_gc()) {
 107     return false;
 108   }
 109 
 110   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
 111   GCCause::Cause gc_cause = heap->gc_cause();
 112   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 113   PSAdaptiveSizePolicy* size_policy = heap->size_policy();
 114 
 115   // The scope of casr should end after code that can change
 116   // CollectorPolicy::_should_clear_all_soft_refs.
 117   ClearedAllSoftRefs casr(clear_all_softrefs, heap->collector_policy());
 118 
 119   PSYoungGen* young_gen = heap->young_gen();
 120   PSOldGen* old_gen = heap->old_gen();
 121 
 122   // Increment the invocation count
 123   heap->increment_total_collections(true /* full */);
 124 
 125   // Save information needed to minimize mangling
 126   heap->record_gen_tops_before_GC();
 127 
 128   // We need to track unique mark sweep invocations as well.
 129   _total_invocations++;
 130 
 131   AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
 132 
 133   heap->print_heap_before_gc();
 134 
 135   // Fill in TLABs
 136   heap->accumulate_statistics_all_tlabs();
 137   heap->ensure_parsability(true);  // retire TLABs
 138 
 139   if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
 140     HandleMark hm;  // Discard invalid handles created during verification
 141     gclog_or_tty->print(" VerifyBeforeGC:");
 142     Universe::verify();
 143   }
 144 
 145   // Verify object start arrays
 146   if (VerifyObjectStartArray &&
 147       VerifyBeforeGC) {
 148     old_gen->verify_object_start_array();
 149   }
 150 
 151   heap->pre_full_gc_dump();
 152 
 153   // Filled in below to track the state of the young gen after the collection.
 154   bool eden_empty;
 155   bool survivors_empty;
 156   bool young_gen_empty;
 157 
 158   {
 159     HandleMark hm;
 160 
 161     gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
 162     TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
 163     TraceTime t1(GCCauseString("Full GC", gc_cause), PrintGC, !PrintGCDetails, gclog_or_tty);
 164     TraceCollectorStats tcs(counters());
 165     TraceMemoryManagerStats tms(true /* Full GC */,gc_cause);
 166 
 167     if (TraceGen1Time) accumulated_time()->start();
 168 
 169     // Let the size policy know we're starting
 170     size_policy->major_collection_begin();
 171 
 172     CodeCache::gc_prologue();
 173     Threads::gc_prologue();
 174     BiasedLocking::preserve_marks();
 175 
 176     // Capture heap size before collection for printing.
 177     size_t prev_used = heap->used();
 178 
 179     // Capture metadata size before collection for sizing.
 180     size_t metadata_prev_used = MetaspaceAux::used_in_bytes();
 181 
 182     // For PrintGCDetails
 183     size_t old_gen_prev_used = old_gen->used_in_bytes();
 184     size_t young_gen_prev_used = young_gen->used_in_bytes();
 185 
 186     allocate_stacks();
 187 
 188     COMPILER2_PRESENT(DerivedPointerTable::clear());
 189 
 190     ref_processor()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
 191     ref_processor()->setup_policy(clear_all_softrefs);
 192 
 193     mark_sweep_phase1(clear_all_softrefs);
 194 
 195     mark_sweep_phase2();
 196 
 197     // Don't add any more derived pointers during phase3
 198     COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
 199     COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
 200 
 201     mark_sweep_phase3();
 202 
 203     mark_sweep_phase4();
 204 
 205     restore_marks();
 206 
 207     deallocate_stacks();
 208 
 209     if (ZapUnusedHeapArea) {
 210       // Do a complete mangle (top to end) because the usage for
 211       // scratch does not maintain a top pointer.
 212       young_gen->to_space()->mangle_unused_area_complete();
 213     }
 214 
 215     eden_empty = young_gen->eden_space()->is_empty();
 216     if (!eden_empty) {
 217       eden_empty = absorb_live_data_from_eden(size_policy, young_gen, old_gen);
 218     }
 219 
 220     // Update heap occupancy information which is used as
 221     // input to soft ref clearing policy at the next gc.
 222     Universe::update_heap_info_at_gc();
 223 
 224     survivors_empty = young_gen->from_space()->is_empty() &&
 225                       young_gen->to_space()->is_empty();
 226     young_gen_empty = eden_empty && survivors_empty;
 227 
 228     BarrierSet* bs = heap->barrier_set();
 229     if (bs->is_a(BarrierSet::ModRef)) {
 230       ModRefBarrierSet* modBS = (ModRefBarrierSet*)bs;
 231       MemRegion old_mr = heap->old_gen()->reserved();
 232       if (young_gen_empty) {
 233         modBS->clear(MemRegion(old_mr.start(), old_mr.end()));
 234       } else {
 235         modBS->invalidate(MemRegion(old_mr.start(), old_mr.end()));
 236       }
 237     }
 238 
 239     // Delete metaspaces for unloaded class loaders and clean up loader_data graph
 240     ClassLoaderDataGraph::purge();
 241 
 242     BiasedLocking::restore_marks();
 243     Threads::gc_epilogue();
 244     CodeCache::gc_epilogue();
 245     JvmtiExport::gc_epilogue();
 246 
 247     COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
 248 
 249     ref_processor()->enqueue_discovered_references(NULL);
 250 
 251     // Update time of last GC
 252     reset_millis_since_last_gc();
 253 
 254     // Let the size policy know we're done
 255     size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
 256 
 257     if (UseAdaptiveSizePolicy) {
 258 
 259       if (PrintAdaptiveSizePolicy) {
 260         gclog_or_tty->print("AdaptiveSizeStart: ");
 261         gclog_or_tty->stamp();
 262         gclog_or_tty->print_cr(" collection: %d ",
 263                        heap->total_collections());
 264         if (Verbose) {
 265           gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d",
 266             old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
 267         }
 268       }
 269 
 270       // Don't check if the size_policy is ready here.  Let
 271       // the size_policy check that internally.
 272       if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
 273           ((gc_cause != GCCause::_java_lang_system_gc) ||
 274             UseAdaptiveSizePolicyWithSystemGC)) {
 275         // Calculate optimal free space amounts
 276         assert(young_gen->max_size() >
 277           young_gen->from_space()->capacity_in_bytes() +
 278           young_gen->to_space()->capacity_in_bytes(),
 279           "Sizes of space in young gen are out-of-bounds");
 280         size_t max_eden_size = young_gen->max_size() -
 281           young_gen->from_space()->capacity_in_bytes() -
 282           young_gen->to_space()->capacity_in_bytes();
 283         size_policy->compute_generations_free_space(young_gen->used_in_bytes(),
 284                                  young_gen->eden_space()->used_in_bytes(),
 285                                  old_gen->used_in_bytes(),
 286                                  young_gen->eden_space()->capacity_in_bytes(),
 287                                  old_gen->max_gen_size(),
 288                                  max_eden_size,
 289                                  true /* full gc*/,
 290                                  gc_cause,
 291                                  heap->collector_policy());
 292 
 293         heap->resize_old_gen(size_policy->calculated_old_free_size_in_bytes());
 294 
 295         // Don't resize the young generation at an major collection.  A
 296         // desired young generation size may have been calculated but
 297         // resizing the young generation complicates the code because the
 298         // resizing of the old generation may have moved the boundary
 299         // between the young generation and the old generation.  Let the
 300         // young generation resizing happen at the minor collections.
 301       }
 302       if (PrintAdaptiveSizePolicy) {
 303         gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
 304                        heap->total_collections());
 305       }
 306     }
 307 
 308     if (UsePerfData) {
 309       heap->gc_policy_counters()->update_counters();
 310       heap->gc_policy_counters()->update_old_capacity(
 311         old_gen->capacity_in_bytes());
 312       heap->gc_policy_counters()->update_young_capacity(
 313         young_gen->capacity_in_bytes());
 314     }
 315 
 316     heap->resize_all_tlabs();
 317 
 318     // We collected the heap, recalculate the metaspace capacity
 319     MetaspaceGC::compute_new_size();
 320 
 321     if (TraceGen1Time) accumulated_time()->stop();
 322 
 323     if (PrintGC) {
 324       if (PrintGCDetails) {
 325         // Don't print a GC timestamp here.  This is after the GC so
 326         // would be confusing.
 327         young_gen->print_used_change(young_gen_prev_used);
 328         old_gen->print_used_change(old_gen_prev_used);
 329       }
 330       heap->print_heap_change(prev_used);
 331       if (PrintGCDetails) {
 332         MetaspaceAux::print_metaspace_change(metadata_prev_used);
 333       }
 334     }
 335 
 336     // Track memory usage and detect low memory
 337     MemoryService::track_memory_usage();
 338     heap->update_counters();
 339   }
 340 
 341   if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
 342     HandleMark hm;  // Discard invalid handles created during verification
 343     gclog_or_tty->print(" VerifyAfterGC:");
 344     Universe::verify();
 345   }
 346 
 347   // Re-verify object start arrays
 348   if (VerifyObjectStartArray &&
 349       VerifyAfterGC) {
 350     old_gen->verify_object_start_array();
 351   }
 352 
 353   if (ZapUnusedHeapArea) {
 354     old_gen->object_space()->check_mangled_unused_area_complete();
 355   }
 356 
 357   NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
 358 
 359   heap->print_heap_after_gc();
 360 
 361   heap->post_full_gc_dump();
 362 
 363 #ifdef TRACESPINNING
 364   ParallelTaskTerminator::print_termination_counts();
 365 #endif
 366 
 367   return true;
 368 }
 369 
 370 bool PSMarkSweep::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy,
 371                                              PSYoungGen* young_gen,
 372                                              PSOldGen* old_gen) {
 373   MutableSpace* const eden_space = young_gen->eden_space();
 374   assert(!eden_space->is_empty(), "eden must be non-empty");
 375   assert(young_gen->virtual_space()->alignment() ==
 376          old_gen->virtual_space()->alignment(), "alignments do not match");
 377 
 378   if (!(UseAdaptiveSizePolicy && UseAdaptiveGCBoundary)) {
 379     return false;
 380   }
 381 
 382   // Both generations must be completely committed.
 383   if (young_gen->virtual_space()->uncommitted_size() != 0) {
 384     return false;
 385   }
 386   if (old_gen->virtual_space()->uncommitted_size() != 0) {
 387     return false;
 388   }
 389 
 390   // Figure out how much to take from eden.  Include the average amount promoted
 391   // in the total; otherwise the next young gen GC will simply bail out to a
 392   // full GC.
 393   const size_t alignment = old_gen->virtual_space()->alignment();
 394   const size_t eden_used = eden_space->used_in_bytes();
 395   const size_t promoted = (size_t)size_policy->avg_promoted()->padded_average();
 396   const size_t absorb_size = align_size_up(eden_used + promoted, alignment);
 397   const size_t eden_capacity = eden_space->capacity_in_bytes();
 398 
 399   if (absorb_size >= eden_capacity) {
 400     return false; // Must leave some space in eden.
 401   }
 402 
 403   const size_t new_young_size = young_gen->capacity_in_bytes() - absorb_size;
 404   if (new_young_size < young_gen->min_gen_size()) {
 405     return false; // Respect young gen minimum size.
 406   }
 407 
 408   if (TraceAdaptiveGCBoundary && Verbose) {
 409     gclog_or_tty->print(" absorbing " SIZE_FORMAT "K:  "
 410                         "eden " SIZE_FORMAT "K->" SIZE_FORMAT "K "
 411                         "from " SIZE_FORMAT "K, to " SIZE_FORMAT "K "
 412                         "young_gen " SIZE_FORMAT "K->" SIZE_FORMAT "K ",
 413                         absorb_size / K,
 414                         eden_capacity / K, (eden_capacity - absorb_size) / K,
 415                         young_gen->from_space()->used_in_bytes() / K,
 416                         young_gen->to_space()->used_in_bytes() / K,
 417                         young_gen->capacity_in_bytes() / K, new_young_size / K);
 418   }
 419 
 420   // Fill the unused part of the old gen.
 421   MutableSpace* const old_space = old_gen->object_space();
 422   HeapWord* const unused_start = old_space->top();
 423   size_t const unused_words = pointer_delta(old_space->end(), unused_start);
 424 
 425   if (unused_words > 0) {
 426     if (unused_words < CollectedHeap::min_fill_size()) {
 427       return false;  // If the old gen cannot be filled, must give up.
 428     }
 429     CollectedHeap::fill_with_objects(unused_start, unused_words);
 430   }
 431 
 432   // Take the live data from eden and set both top and end in the old gen to
 433   // eden top.  (Need to set end because reset_after_change() mangles the region
 434   // from end to virtual_space->high() in debug builds).
 435   HeapWord* const new_top = eden_space->top();
 436   old_gen->virtual_space()->expand_into(young_gen->virtual_space(),
 437                                         absorb_size);
 438   young_gen->reset_after_change();
 439   old_space->set_top(new_top);
 440   old_space->set_end(new_top);
 441   old_gen->reset_after_change();
 442 
 443   // Update the object start array for the filler object and the data from eden.
 444   ObjectStartArray* const start_array = old_gen->start_array();
 445   for (HeapWord* p = unused_start; p < new_top; p += oop(p)->size()) {
 446     start_array->allocate_block(p);
 447   }
 448 
 449   // Could update the promoted average here, but it is not typically updated at
 450   // full GCs and the value to use is unclear.  Something like
 451   //
 452   // cur_promoted_avg + absorb_size / number_of_scavenges_since_last_full_gc.
 453 
 454   size_policy->set_bytes_absorbed_from_eden(absorb_size);
 455   return true;
 456 }
 457 
 458 void PSMarkSweep::allocate_stacks() {
 459   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
 460   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 461 
 462   PSYoungGen* young_gen = heap->young_gen();
 463 
 464   MutableSpace* to_space = young_gen->to_space();
 465   _preserved_marks = (PreservedMark*)to_space->top();
 466   _preserved_count = 0;
 467 
 468   // We want to calculate the size in bytes first.
 469   _preserved_count_max  = pointer_delta(to_space->end(), to_space->top(), sizeof(jbyte));
 470   // Now divide by the size of a PreservedMark
 471   _preserved_count_max /= sizeof(PreservedMark);
 472 }
 473 
 474 
 475 void PSMarkSweep::deallocate_stacks() {
 476   _preserved_mark_stack.clear(true);
 477   _preserved_oop_stack.clear(true);
 478   _marking_stack.clear();
 479   _objarray_stack.clear(true);
 480 }
 481 
 482 void PSMarkSweep::mark_sweep_phase1(bool clear_all_softrefs) {
 483   // Recursively traverse all live objects and mark them
 484   TraceTime tm("phase 1", PrintGCDetails && Verbose, true, gclog_or_tty);
 485   trace(" 1");
 486 
 487   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
 488   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 489 
 490   // Need to clear claim bits before the tracing starts.
 491   ClassLoaderDataGraph::clear_claimed_marks();
 492 
 493   // General strong roots.
 494   {
 495     ParallelScavengeHeap::ParStrongRootsScope psrs;
 496     Universe::oops_do(mark_and_push_closure());
 497     JNIHandles::oops_do(mark_and_push_closure());   // Global (strong) JNI handles
 498     CLDToOopClosure mark_and_push_from_cld(mark_and_push_closure());
 499     CodeBlobToOopClosure each_active_code_blob(mark_and_push_closure(), /*do_marking=*/ true);
 500     Threads::oops_do(mark_and_push_closure(), &mark_and_push_from_cld, &each_active_code_blob);
 501     ObjectSynchronizer::oops_do(mark_and_push_closure());
 502     FlatProfiler::oops_do(mark_and_push_closure());
 503     Management::oops_do(mark_and_push_closure());
 504     JvmtiExport::oops_do(mark_and_push_closure());
 505     SystemDictionary::always_strong_oops_do(mark_and_push_closure());
 506     ClassLoaderDataGraph::always_strong_oops_do(mark_and_push_closure(), follow_klass_closure(), true);
 507     // Do not treat nmethods as strong roots for mark/sweep, since we can unload them.
 508     //CodeCache::scavenge_root_nmethods_do(CodeBlobToOopClosure(mark_and_push_closure()));
 509   }
 510 
 511   // Flush marking stack.
 512   follow_stack();
 513 
 514   // Process reference objects found during marking
 515   {
 516     ref_processor()->setup_policy(clear_all_softrefs);
 517     ref_processor()->process_discovered_references(
 518       is_alive_closure(), mark_and_push_closure(), follow_stack_closure(), NULL);
 519   }
 520 
 521   // Follow system dictionary roots and unload classes
 522   bool purged_class = SystemDictionary::do_unloading(is_alive_closure());
 523 
 524   // Follow code cache roots
 525   CodeCache::do_unloading(is_alive_closure(), purged_class);
 526   follow_stack(); // Flush marking stack
 527 
 528   // Update subklass/sibling/implementor links of live klasses
 529   Klass::clean_weak_klass_links(&is_alive);
 530   assert(_marking_stack.is_empty(), "just drained");
 531 
 532   // Visit interned string tables and delete unmarked oops
 533   StringTable::unlink(is_alive_closure());
 534   // Clean up unreferenced symbols in symbol table.
 535   SymbolTable::unlink();
 536 
 537   assert(_marking_stack.is_empty(), "stack should be empty by now");
 538 }
 539 
 540 
 541 void PSMarkSweep::mark_sweep_phase2() {
 542   TraceTime tm("phase 2", PrintGCDetails && Verbose, true, gclog_or_tty);
 543   trace("2");
 544 
 545   // Now all live objects are marked, compute the new object addresses.
 546 
 547   // It is not required that we traverse spaces in the same order in
 548   // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
 549   // tracking expects us to do so. See comment under phase4.
 550 
 551   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
 552   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 553 
 554   PSOldGen* old_gen = heap->old_gen();
 555 
 556   // Begin compacting into the old gen
 557   PSMarkSweepDecorator::set_destination_decorator_tenured();
 558 
 559   // This will also compact the young gen spaces.
 560   old_gen->precompact();
 561 }
 562 
 563 // This should be moved to the shared markSweep code!
 564 class PSAlwaysTrueClosure: public BoolObjectClosure {
 565 public:
 566   void do_object(oop p) { ShouldNotReachHere(); }
 567   bool do_object_b(oop p) { return true; }
 568 };
 569 static PSAlwaysTrueClosure always_true;
 570 
 571 void PSMarkSweep::mark_sweep_phase3() {
 572   // Adjust the pointers to reflect the new locations
 573   TraceTime tm("phase 3", PrintGCDetails && Verbose, true, gclog_or_tty);
 574   trace("3");
 575 
 576   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
 577   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 578 
 579   PSYoungGen* young_gen = heap->young_gen();
 580   PSOldGen* old_gen = heap->old_gen();
 581 
 582   // Need to clear claim bits before the tracing starts.
 583   ClassLoaderDataGraph::clear_claimed_marks();
 584 
 585   // General strong roots.
 586   Universe::oops_do(adjust_root_pointer_closure());
 587   JNIHandles::oops_do(adjust_root_pointer_closure());   // Global (strong) JNI handles
 588   CLDToOopClosure adjust_from_cld(adjust_root_pointer_closure());
 589   Threads::oops_do(adjust_root_pointer_closure(), &adjust_from_cld, NULL);
 590   ObjectSynchronizer::oops_do(adjust_root_pointer_closure());
 591   FlatProfiler::oops_do(adjust_root_pointer_closure());
 592   Management::oops_do(adjust_root_pointer_closure());
 593   JvmtiExport::oops_do(adjust_root_pointer_closure());
 594   // SO_AllClasses
 595   SystemDictionary::oops_do(adjust_root_pointer_closure());
 596   ClassLoaderDataGraph::oops_do(adjust_root_pointer_closure(), adjust_klass_closure(), true);
 597   //CodeCache::scavenge_root_nmethods_oops_do(adjust_root_pointer_closure());
 598 
 599   // Now adjust pointers in remaining weak roots.  (All of which should
 600   // have been cleared if they pointed to non-surviving objects.)
 601   // Global (weak) JNI handles
 602   JNIHandles::weak_oops_do(&always_true, adjust_root_pointer_closure());
 603 
 604   CodeCache::oops_do(adjust_pointer_closure());
 605   StringTable::oops_do(adjust_root_pointer_closure());
 606   ref_processor()->weak_oops_do(adjust_root_pointer_closure());
 607   PSScavenge::reference_processor()->weak_oops_do(adjust_root_pointer_closure());
 608 
 609   adjust_marks();
 610 
 611   young_gen->adjust_pointers();
 612   old_gen->adjust_pointers();
 613 }
 614 
 615 void PSMarkSweep::mark_sweep_phase4() {
 616   EventMark m("4 compact heap");
 617   TraceTime tm("phase 4", PrintGCDetails && Verbose, true, gclog_or_tty);
 618   trace("4");
 619 
 620   // All pointers are now adjusted, move objects accordingly
 621 
 622   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
 623   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 624 
 625   PSYoungGen* young_gen = heap->young_gen();
 626   PSOldGen* old_gen = heap->old_gen();
 627 
 628   old_gen->compact();
 629   young_gen->compact();
 630 }
 631 
 632 jlong PSMarkSweep::millis_since_last_gc() {
 633   // We need a monotonically non-deccreasing time in ms but
 634   // os::javaTimeMillis() does not guarantee monotonicity.
 635   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
 636   jlong ret_val = now - _time_of_last_gc;
 637   // XXX See note in genCollectedHeap::millis_since_last_gc().
 638   if (ret_val < 0) {
 639     NOT_PRODUCT(warning("time warp: "INT64_FORMAT, ret_val);)
 640     return 0;
 641   }
 642   return ret_val;
 643 }
 644 
 645 void PSMarkSweep::reset_millis_since_last_gc() {
 646   // We need a monotonically non-deccreasing time in ms but
 647   // os::javaTimeMillis() does not guarantee monotonicity.
 648   _time_of_last_gc = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
 649 }