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 * This code is free software; you can redistribute it and/or modify it

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 * published by the Free Software Foundation.

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 * 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

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 */

#include "precompiled.hpp"

#include "classfile/symbolTable.hpp"

#include "classfile/systemDictionary.hpp"

#include "code/codeCache.hpp"

#include "gc_implementation/parallelScavenge/generationSizer.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/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();

  GCCause::Cause gc_cause = heap->gc_cause();

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

  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();

  // 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();

  // 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);

    TraceTime t1(GCCauseString("Full GC", gc_cause), PrintGC, !PrintGCDetails, gclog_or_tty);

    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 max_eden_size = young_gen->max_size() -

          young_gen->from_space()->capacity_in_bytes() -

          young_gen->to_space()->capacity_in_bytes();

        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->post_full_gc_dump();

#ifdef TRACESPINNING

  ParallelTaskTerminator::print_termination_counts();

#endif

  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

  TraceTime tm("phase 1", PrintGCDetails && Verbose, true, gclog_or_tty);

  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;