Java example source code file (psMarkSweep.cpp)

This example Java source code file (psMarkSweep.cpp) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

collectedheap\:\:parallelscavengeheap, compiler2_present, gctracetime, null, parallelscavengeheap, parallelscavengeheap*, printgcdetails, psoldgen, psyounggen, sanity, size_format, verbose

The psMarkSweep.cpp Java example source code

/*
 * Copyright (c) 2001, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#include "precompiled.hpp"
#include "classfile/symbolTable.hpp"
#include "classfile/systemDictionary.hpp"
#include "code/codeCache.hpp"
#include "gc_implementation/parallelScavenge/parallelScavengeHeap.hpp"
#include "gc_implementation/parallelScavenge/psAdaptiveSizePolicy.hpp"
#include "gc_implementation/parallelScavenge/psMarkSweep.hpp"
#include "gc_implementation/parallelScavenge/psMarkSweepDecorator.hpp"
#include "gc_implementation/parallelScavenge/psOldGen.hpp"
#include "gc_implementation/parallelScavenge/psScavenge.hpp"
#include "gc_implementation/parallelScavenge/psYoungGen.hpp"
#include "gc_implementation/shared/gcHeapSummary.hpp"
#include "gc_implementation/shared/gcTimer.hpp"
#include "gc_implementation/shared/gcTrace.hpp"
#include "gc_implementation/shared/gcTraceTime.hpp"
#include "gc_implementation/shared/isGCActiveMark.hpp"
#include "gc_implementation/shared/markSweep.hpp"
#include "gc_implementation/shared/spaceDecorator.hpp"
#include "gc_interface/gcCause.hpp"
#include "memory/gcLocker.inline.hpp"
#include "memory/referencePolicy.hpp"
#include "memory/referenceProcessor.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/biasedLocking.hpp"
#include "runtime/fprofiler.hpp"
#include "runtime/safepoint.hpp"
#include "runtime/vmThread.hpp"
#include "services/management.hpp"
#include "services/memoryService.hpp"
#include "utilities/events.hpp"
#include "utilities/stack.inline.hpp"

elapsedTimer        PSMarkSweep::_accumulated_time;
jlong               PSMarkSweep::_time_of_last_gc   = 0;
CollectorCounters*  PSMarkSweep::_counters = NULL;

void PSMarkSweep::initialize() {
  MemRegion mr = Universe::heap()->reserved_region();
  _ref_processor = new ReferenceProcessor(mr);     // a vanilla ref proc
  _counters = new CollectorCounters("PSMarkSweep", 1);
}

// This method contains all heap specific policy for invoking mark sweep.
// PSMarkSweep::invoke_no_policy() will only attempt to mark-sweep-compact
// the heap. It will do nothing further. If we need to bail out for policy
// reasons, scavenge before full gc, or any other specialized behavior, it
// needs to be added here.
//
// Note that this method should only be called from the vm_thread while
// at a safepoint!
//
// Note that the all_soft_refs_clear flag in the collector policy
// may be true because this method can be called without intervening
// activity.  For example when the heap space is tight and full measure
// are being taken to free space.

void PSMarkSweep::invoke(bool maximum_heap_compaction) {
  assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
  assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
  assert(!Universe::heap()->is_gc_active(), "not reentrant");

  ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
  GCCause::Cause gc_cause = heap->gc_cause();
  PSAdaptiveSizePolicy* policy = heap->size_policy();
  IsGCActiveMark mark;

  if (ScavengeBeforeFullGC) {
    PSScavenge::invoke_no_policy();
  }

  const bool clear_all_soft_refs =
    heap->collector_policy()->should_clear_all_soft_refs();

  uint count = maximum_heap_compaction ? 1 : MarkSweepAlwaysCompactCount;
  UIntFlagSetting flag_setting(MarkSweepAlwaysCompactCount, count);
  PSMarkSweep::invoke_no_policy(clear_all_soft_refs || maximum_heap_compaction);
}

// This method contains no policy. You should probably
// be calling invoke() instead.
bool PSMarkSweep::invoke_no_policy(bool clear_all_softrefs) {
  assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
  assert(ref_processor() != NULL, "Sanity");

  if (GC_locker::check_active_before_gc()) {
    return false;
  }

  ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
  assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
  GCCause::Cause gc_cause = heap->gc_cause();

  _gc_timer->register_gc_start();
  _gc_tracer->report_gc_start(gc_cause, _gc_timer->gc_start());

  PSAdaptiveSizePolicy* size_policy = heap->size_policy();

  // The scope of casr should end after code that can change
  // CollectorPolicy::_should_clear_all_soft_refs.
  ClearedAllSoftRefs casr(clear_all_softrefs, heap->collector_policy());

  PSYoungGen* young_gen = heap->young_gen();
  PSOldGen* old_gen = heap->old_gen();

  // Increment the invocation count
  heap->increment_total_collections(true /* full */);

  // Save information needed to minimize mangling
  heap->record_gen_tops_before_GC();

  // We need to track unique mark sweep invocations as well.
  _total_invocations++;

  AdaptiveSizePolicyOutput(size_policy, heap->total_collections());

  heap->print_heap_before_gc();
  heap->trace_heap_before_gc(_gc_tracer);

  // Fill in TLABs
  heap->accumulate_statistics_all_tlabs();
  heap->ensure_parsability(true);  // retire TLABs

  if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
    HandleMark hm;  // Discard invalid handles created during verification
    Universe::verify(" VerifyBeforeGC:");
  }

  // Verify object start arrays
  if (VerifyObjectStartArray &&
      VerifyBeforeGC) {
    old_gen->verify_object_start_array();
  }

  heap->pre_full_gc_dump(_gc_timer);

  // Filled in below to track the state of the young gen after the collection.
  bool eden_empty;
  bool survivors_empty;
  bool young_gen_empty;

  {
    HandleMark hm;

    gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
    TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
    GCTraceTime t1(GCCauseString("Full GC", gc_cause), PrintGC, !PrintGCDetails, NULL);
    TraceCollectorStats tcs(counters());
    TraceMemoryManagerStats tms(true /* Full GC */,gc_cause);

    if (TraceGen1Time) accumulated_time()->start();

    // Let the size policy know we're starting
    size_policy->major_collection_begin();

    CodeCache::gc_prologue();
    Threads::gc_prologue();
    BiasedLocking::preserve_marks();

    // Capture heap size before collection for printing.
    size_t prev_used = heap->used();

    // Capture metadata size before collection for sizing.
    size_t metadata_prev_used = MetaspaceAux::allocated_used_bytes();

    // For PrintGCDetails
    size_t old_gen_prev_used = old_gen->used_in_bytes();
    size_t young_gen_prev_used = young_gen->used_in_bytes();

    allocate_stacks();

    COMPILER2_PRESENT(DerivedPointerTable::clear());

    ref_processor()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
    ref_processor()->setup_policy(clear_all_softrefs);

    mark_sweep_phase1(clear_all_softrefs);

    mark_sweep_phase2();

    // Don't add any more derived pointers during phase3
    COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
    COMPILER2_PRESENT(DerivedPointerTable::set_active(false));

    mark_sweep_phase3();

    mark_sweep_phase4();

    restore_marks();

    deallocate_stacks();

    if (ZapUnusedHeapArea) {
      // Do a complete mangle (top to end) because the usage for
      // scratch does not maintain a top pointer.
      young_gen->to_space()->mangle_unused_area_complete();
    }

    eden_empty = young_gen->eden_space()->is_empty();
    if (!eden_empty) {
      eden_empty = absorb_live_data_from_eden(size_policy, young_gen, old_gen);
    }

    // Update heap occupancy information which is used as
    // input to soft ref clearing policy at the next gc.
    Universe::update_heap_info_at_gc();

    survivors_empty = young_gen->from_space()->is_empty() &&
                      young_gen->to_space()->is_empty();
    young_gen_empty = eden_empty && survivors_empty;

    BarrierSet* bs = heap->barrier_set();
    if (bs->is_a(BarrierSet::ModRef)) {
      ModRefBarrierSet* modBS = (ModRefBarrierSet*)bs;
      MemRegion old_mr = heap->old_gen()->reserved();
      if (young_gen_empty) {
        modBS->clear(MemRegion(old_mr.start(), old_mr.end()));
      } else {
        modBS->invalidate(MemRegion(old_mr.start(), old_mr.end()));
      }
    }

    // Delete metaspaces for unloaded class loaders and clean up loader_data graph
    ClassLoaderDataGraph::purge();
    MetaspaceAux::verify_metrics();

    BiasedLocking::restore_marks();
    Threads::gc_epilogue();
    CodeCache::gc_epilogue();
    JvmtiExport::gc_epilogue();

    COMPILER2_PRESENT(DerivedPointerTable::update_pointers());

    ref_processor()->enqueue_discovered_references(NULL);

    // Update time of last GC
    reset_millis_since_last_gc();

    // Let the size policy know we're done
    size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);

    if (UseAdaptiveSizePolicy) {

      if (PrintAdaptiveSizePolicy) {
        gclog_or_tty->print("AdaptiveSizeStart: ");
        gclog_or_tty->stamp();
        gclog_or_tty->print_cr(" collection: %d ",
                       heap->total_collections());
        if (Verbose) {
          gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d",
            old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
        }
      }

      // Don't check if the size_policy is ready here.  Let
      // the size_policy check that internally.
      if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
          ((gc_cause != GCCause::_java_lang_system_gc) ||
            UseAdaptiveSizePolicyWithSystemGC)) {
        // Calculate optimal free space amounts
        assert(young_gen->max_size() >
          young_gen->from_space()->capacity_in_bytes() +
          young_gen->to_space()->capacity_in_bytes(),
          "Sizes of space in young gen are out-of-bounds");

        size_t young_live = young_gen->used_in_bytes();
        size_t eden_live = young_gen->eden_space()->used_in_bytes();
        size_t old_live = old_gen->used_in_bytes();
        size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
        size_t max_old_gen_size = old_gen->max_gen_size();
        size_t max_eden_size = young_gen->max_size() -
          young_gen->from_space()->capacity_in_bytes() -
          young_gen->to_space()->capacity_in_bytes();

        // Used for diagnostics
        size_policy->clear_generation_free_space_flags();

        size_policy->compute_generations_free_space(young_live,
                                                    eden_live,
                                                    old_live,
                                                    cur_eden,
                                                    max_old_gen_size,
                                                    max_eden_size,
                                                    true /* full gc*/);

        size_policy->check_gc_overhead_limit(young_live,
                                             eden_live,
                                             max_old_gen_size,
                                             max_eden_size,
                                             true /* full gc*/,
                                             gc_cause,
                                             heap->collector_policy());

        size_policy->decay_supplemental_growth(true /* full gc*/);

        heap->resize_old_gen(size_policy->calculated_old_free_size_in_bytes());

        // Don't resize the young generation at an major collection.  A
        // desired young generation size may have been calculated but
        // resizing the young generation complicates the code because the
        // resizing of the old generation may have moved the boundary
        // between the young generation and the old generation.  Let the
        // young generation resizing happen at the minor collections.
      }
      if (PrintAdaptiveSizePolicy) {
        gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
                       heap->total_collections());
      }
    }

    if (UsePerfData) {
      heap->gc_policy_counters()->update_counters();
      heap->gc_policy_counters()->update_old_capacity(
        old_gen->capacity_in_bytes());
      heap->gc_policy_counters()->update_young_capacity(
        young_gen->capacity_in_bytes());
    }

    heap->resize_all_tlabs();

    // We collected the heap, recalculate the metaspace capacity
    MetaspaceGC::compute_new_size();

    if (TraceGen1Time) accumulated_time()->stop();

    if (PrintGC) {
      if (PrintGCDetails) {
        // Don't print a GC timestamp here.  This is after the GC so
        // would be confusing.
        young_gen->print_used_change(young_gen_prev_used);
        old_gen->print_used_change(old_gen_prev_used);
      }
      heap->print_heap_change(prev_used);
      if (PrintGCDetails) {
        MetaspaceAux::print_metaspace_change(metadata_prev_used);
      }
    }

    // Track memory usage and detect low memory
    MemoryService::track_memory_usage();
    heap->update_counters();
  }

  if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
    HandleMark hm;  // Discard invalid handles created during verification
    Universe::verify(" VerifyAfterGC:");
  }

  // Re-verify object start arrays
  if (VerifyObjectStartArray &&
      VerifyAfterGC) {
    old_gen->verify_object_start_array();
  }

  if (ZapUnusedHeapArea) {
    old_gen->object_space()->check_mangled_unused_area_complete();
  }

  NOT_PRODUCT(ref_processor()->verify_no_references_recorded());

  heap->print_heap_after_gc();
  heap->trace_heap_after_gc(_gc_tracer);

  heap->post_full_gc_dump(_gc_timer);

#ifdef TRACESPINNING
  ParallelTaskTerminator::print_termination_counts();
#endif

  _gc_timer->register_gc_end();

  _gc_tracer->report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());

  return true;
}

bool PSMarkSweep::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy,
                                             PSYoungGen* young_gen,
                                             PSOldGen* old_gen) {
  MutableSpace* const eden_space = young_gen->eden_space();
  assert(!eden_space->is_empty(), "eden must be non-empty");
  assert(young_gen->virtual_space()->alignment() ==
         old_gen->virtual_space()->alignment(), "alignments do not match");

  if (!(UseAdaptiveSizePolicy && UseAdaptiveGCBoundary)) {
    return false;
  }

  // Both generations must be completely committed.
  if (young_gen->virtual_space()->uncommitted_size() != 0) {
    return false;
  }
  if (old_gen->virtual_space()->uncommitted_size() != 0) {
    return false;
  }

  // Figure out how much to take from eden.  Include the average amount promoted
  // in the total; otherwise the next young gen GC will simply bail out to a
  // full GC.
  const size_t alignment = old_gen->virtual_space()->alignment();
  const size_t eden_used = eden_space->used_in_bytes();
  const size_t promoted = (size_t)size_policy->avg_promoted()->padded_average();
  const size_t absorb_size = align_size_up(eden_used + promoted, alignment);
  const size_t eden_capacity = eden_space->capacity_in_bytes();

  if (absorb_size >= eden_capacity) {
    return false; // Must leave some space in eden.
  }

  const size_t new_young_size = young_gen->capacity_in_bytes() - absorb_size;
  if (new_young_size < young_gen->min_gen_size()) {
    return false; // Respect young gen minimum size.
  }

  if (TraceAdaptiveGCBoundary && Verbose) {
    gclog_or_tty->print(" absorbing " SIZE_FORMAT "K:  "
                        "eden " SIZE_FORMAT "K->" SIZE_FORMAT "K "
                        "from " SIZE_FORMAT "K, to " SIZE_FORMAT "K "
                        "young_gen " SIZE_FORMAT "K->" SIZE_FORMAT "K ",
                        absorb_size / K,
                        eden_capacity / K, (eden_capacity - absorb_size) / K,
                        young_gen->from_space()->used_in_bytes() / K,
                        young_gen->to_space()->used_in_bytes() / K,
                        young_gen->capacity_in_bytes() / K, new_young_size / K);
  }

  // Fill the unused part of the old gen.
  MutableSpace* const old_space = old_gen->object_space();
  HeapWord* const unused_start = old_space->top();
  size_t const unused_words = pointer_delta(old_space->end(), unused_start);

  if (unused_words > 0) {
    if (unused_words < CollectedHeap::min_fill_size()) {
      return false;  // If the old gen cannot be filled, must give up.
    }
    CollectedHeap::fill_with_objects(unused_start, unused_words);
  }

  // Take the live data from eden and set both top and end in the old gen to
  // eden top.  (Need to set end because reset_after_change() mangles the region
  // from end to virtual_space->high() in debug builds).
  HeapWord* const new_top = eden_space->top();
  old_gen->virtual_space()->expand_into(young_gen->virtual_space(),
                                        absorb_size);
  young_gen->reset_after_change();
  old_space->set_top(new_top);
  old_space->set_end(new_top);
  old_gen->reset_after_change();

  // Update the object start array for the filler object and the data from eden.
  ObjectStartArray* const start_array = old_gen->start_array();
  for (HeapWord* p = unused_start; p < new_top; p += oop(p)->size()) {
    start_array->allocate_block(p);
  }

  // Could update the promoted average here, but it is not typically updated at
  // full GCs and the value to use is unclear.  Something like
  //
  // cur_promoted_avg + absorb_size / number_of_scavenges_since_last_full_gc.

  size_policy->set_bytes_absorbed_from_eden(absorb_size);
  return true;
}

void PSMarkSweep::allocate_stacks() {
  ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
  assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

  PSYoungGen* young_gen = heap->young_gen();

  MutableSpace* to_space = young_gen->to_space();
  _preserved_marks = (PreservedMark*)to_space->top();
  _preserved_count = 0;

  // We want to calculate the size in bytes first.
  _preserved_count_max  = pointer_delta(to_space->end(), to_space->top(), sizeof(jbyte));
  // Now divide by the size of a PreservedMark
  _preserved_count_max /= sizeof(PreservedMark);
}


void PSMarkSweep::deallocate_stacks() {
  _preserved_mark_stack.clear(true);
  _preserved_oop_stack.clear(true);
  _marking_stack.clear();
  _objarray_stack.clear(true);
}

void PSMarkSweep::mark_sweep_phase1(bool clear_all_softrefs) {
  // Recursively traverse all live objects and mark them
  GCTraceTime tm("phase 1", PrintGCDetails && Verbose, true, _gc_timer);
  trace(" 1");

  ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
  assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

  // Need to clear claim bits before the tracing starts.
  ClassLoaderDataGraph::clear_claimed_marks();

  // General strong roots.
  {
    ParallelScavengeHeap::ParStrongRootsScope psrs;
    Universe::oops_do(mark_and_push_closure());
    JNIHandles::oops_do(mark_and_push_closure());   // Global (strong) JNI handles
    CLDToOopClosure mark_and_push_from_cld(mark_and_push_closure());
    CodeBlobToOopClosure each_active_code_blob(mark_and_push_closure(), /*do_marking=*/ true);
    Threads::oops_do(mark_and_push_closure(), &mark_and_push_from_cld, &each_active_code_blob);
    ObjectSynchronizer::oops_do(mark_and_push_closure());
    FlatProfiler::oops_do(mark_and_push_closure());
    Management::oops_do(mark_and_push_closure());
    JvmtiExport::oops_do(mark_and_push_closure());
    SystemDictionary::always_strong_oops_do(mark_and_push_closure());
    ClassLoaderDataGraph::always_strong_oops_do(mark_and_push_closure(), follow_klass_closure(), true);
    // Do not treat nmethods as strong roots for mark/sweep, since we can unload them.
    //CodeCache::scavenge_root_nmethods_do(CodeBlobToOopClosure(mark_and_push_closure()));
  }

  // Flush marking stack.
  follow_stack();

  // Process reference objects found during marking
  {
    ref_processor()->setup_policy(clear_all_softrefs);
    const ReferenceProcessorStats& stats =
      ref_processor()->process_discovered_references(
        is_alive_closure(), mark_and_push_closure(), follow_stack_closure(), NULL, _gc_timer);
    gc_tracer()->report_gc_reference_stats(stats);
  }

  // This is the point where the entire marking should have completed.
  assert(_marking_stack.is_empty(), "Marking should have completed");

  // Unload classes and purge the SystemDictionary.
  bool purged_class = SystemDictionary::do_unloading(is_alive_closure());

  // Unload nmethods.
  CodeCache::do_unloading(is_alive_closure(), purged_class);

  // Prune dead klasses from subklass/sibling/implementor lists.
  Klass::clean_weak_klass_links(is_alive_closure());

  // Delete entries for dead interned strings.
  StringTable::unlink(is_alive_closure());

  // Clean up unreferenced symbols in symbol table.
  SymbolTable::unlink();
  _gc_tracer->report_object_count_after_gc(is_alive_closure());
}


void PSMarkSweep::mark_sweep_phase2() {
  GCTraceTime tm("phase 2", PrintGCDetails && Verbose, true, _gc_timer);
  trace("2");

  // Now all live objects are marked, compute the new object addresses.

  // It is not required that we traverse spaces in the same order in
  // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
  // tracking expects us to do so. See comment under phase4.

  ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
  assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

  PSOldGen* old_gen = heap->old_gen();

  // Begin compacting into the old gen
  PSMarkSweepDecorator::set_destination_decorator_tenured();

  // This will also compact the young gen spaces.
  old_gen->precompact();
}

// This should be moved to the shared markSweep code!
class PSAlwaysTrueClosure: public BoolObjectClosure {
public:
  bool do_object_b(oop p) { return true; }
};
static PSAlwaysTrueClosure always_true;

void PSMarkSweep::mark_sweep_phase3() {
  // Adjust the pointers to reflect the new locations
  GCTraceTime tm("phase 3", PrintGCDetails && Verbose, true, _gc_timer);
  trace("3");

  ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
  assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

  PSYoungGen* young_gen = heap->young_gen();
  PSOldGen* old_gen = heap->old_gen();

  // Need to clear claim bits before the tracing starts.
  ClassLoaderDataGraph::clear_claimed_marks();

  // General strong roots.
  Universe::oops_do(adjust_pointer_closure());
  JNIHandles::oops_do(adjust_pointer_closure());   // Global (strong) JNI handles
  CLDToOopClosure adjust_from_cld(adjust_pointer_closure());
  Threads::oops_do(adjust_pointer_closure(), &adjust_from_cld, NULL);
  ObjectSynchronizer::oops_do(adjust_pointer_closure());
  FlatProfiler::oops_do(adjust_pointer_closure());
  Management::oops_do(adjust_pointer_closure());
  JvmtiExport::oops_do(adjust_pointer_closure());
  // SO_AllClasses
  SystemDictionary::oops_do(adjust_pointer_closure());
  ClassLoaderDataGraph::oops_do(adjust_pointer_closure(), adjust_klass_closure(), true);

  // Now adjust pointers in remaining weak roots.  (All of which should
  // have been cleared if they pointed to non-surviving objects.)
  // Global (weak) JNI handles
  JNIHandles::weak_oops_do(&always_true, adjust_pointer_closure());

  CodeCache::oops_do(adjust_pointer_closure());
  StringTable::oops_do(adjust_pointer_closure());
  ref_processor()->weak_oops_do(adjust_pointer_closure());
  PSScavenge::reference_processor()->weak_oops_do(adjust_pointer_closure());

  adjust_marks();

  young_gen->adjust_pointers();
  old_gen->adjust_pointers();
}

void PSMarkSweep::mark_sweep_phase4() {
  EventMark m("4 compact heap");
  GCTraceTime tm("phase 4", PrintGCDetails && Verbose, true, _gc_timer);
  trace("4");

  // All pointers are now adjusted, move objects accordingly

  ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
  assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

  PSYoungGen* young_gen = heap->young_gen();
  PSOldGen* old_gen = heap->old_gen();

  old_gen->compact();
  young_gen->compact();
}

jlong PSMarkSweep::millis_since_last_gc() {
  // We need a monotonically non-deccreasing time in ms but
  // os::javaTimeMillis() does not guarantee monotonicity.
  jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
  jlong ret_val = now - _time_of_last_gc;
  // XXX See note in genCollectedHeap::millis_since_last_gc().
  if (ret_val < 0) {
    NOT_PRODUCT(warning("time warp: "INT64_FORMAT, ret_val);)
    return 0;
  }
  return ret_val;
}

void PSMarkSweep::reset_millis_since_last_gc() {
  // We need a monotonically non-deccreasing time in ms but
  // os::javaTimeMillis() does not guarantee monotonicity.
  _time_of_last_gc = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
}