/*

 * Copyright (c) 2001, 2019, 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.

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 */

#include "precompiled.hpp"

#include "aot/aotLoader.hpp"

#include "classfile/classLoaderDataGraph.hpp"

#include "classfile/stringTable.hpp"

#include "classfile/symbolTable.hpp"

#include "classfile/systemDictionary.hpp"

#include "code/codeCache.hpp"

#include "gc/parallel/parallelScavengeHeap.hpp"

#include "gc/parallel/psAdaptiveSizePolicy.hpp"

#include "gc/parallel/psMarkSweep.hpp"

#include "gc/parallel/psMarkSweepDecorator.hpp"

#include "gc/parallel/psOldGen.hpp"

#include "gc/parallel/psScavenge.hpp"

#include "gc/parallel/psYoungGen.hpp"

#include "gc/serial/markSweep.hpp"

#include "gc/shared/gcCause.hpp"

#include "gc/shared/gcHeapSummary.hpp"

#include "gc/shared/gcId.hpp"

#include "gc/shared/gcLocker.hpp"

#include "gc/shared/gcTimer.hpp"

#include "gc/shared/gcTrace.hpp"

#include "gc/shared/gcTraceTime.inline.hpp"

#include "gc/shared/isGCActiveMark.hpp"

#include "gc/shared/referencePolicy.hpp"

#include "gc/shared/referenceProcessor.hpp"

#include "gc/shared/referenceProcessorPhaseTimes.hpp"

#include "gc/shared/spaceDecorator.hpp"

#include "gc/shared/weakProcessor.hpp"

#include "logging/log.hpp"

#include "oops/oop.inline.hpp"

#include "runtime/biasedLocking.hpp"

#include "runtime/flags/flagSetting.hpp"

#include "runtime/handles.inline.hpp"

#include "runtime/safepoint.hpp"

#include "runtime/vmThread.hpp"

#include "services/management.hpp"

#include "services/memoryService.hpp"

#include "utilities/align.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;

SpanSubjectToDiscoveryClosure PSMarkSweep::_span_based_discoverer;

void PSMarkSweep::initialize() {

  _span_based_discoverer.set_span(ParallelScavengeHeap::heap()->reserved_region());

  set_ref_processor(new ReferenceProcessor(&_span_based_discoverer));     // a vanilla ref proc

  _counters = new CollectorCounters("Serial full collection pauses", 1);

  MarkSweep::initialize();

}

// 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(!ParallelScavengeHeap::heap()->is_gc_active(), "not reentrant");

  ParallelScavengeHeap* heap = ParallelScavengeHeap::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->soft_ref_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 (GCLocker::check_active_before_gc()) {

    return false;

  }

  ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();

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

  GCIdMark gc_id_mark;

  _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->soft_ref_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++;

  heap->print_heap_before_gc();

  heap->trace_heap_before_gc(_gc_tracer);

  // Fill in TLABs

  heap->ensure_parsability(true);  // retire TLABs

  if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {

    HandleMark hm;  // Discard invalid handles created during verification

    Universe::verify("Before GC");

  }

  // Verify object start arrays

  if (VerifyObjectStartArray &&

      VerifyBeforeGC) {

    old_gen->verify_object_start_array();

  }

  // 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;

    GCTraceCPUTime tcpu;

    GCTraceTime(Info, gc) t("Pause Full", NULL, gc_cause, true);

    heap->pre_full_gc_dump(_gc_timer);

    TraceCollectorStats tcs(counters());

    TraceMemoryManagerStats tms(heap->old_gc_manager(),gc_cause);

    if (log_is_enabled(Debug, gc, heap, exit)) {

      accumulated_time()->start();

    }

    // Let the size policy know we're starting

    size_policy->major_collection_begin();

    BiasedLocking::preserve_marks();

    // Capture metadata size before collection for sizing.

    size_t metadata_prev_used = MetaspaceUtils::used_bytes();

    size_t old_gen_prev_used = old_gen->used_in_bytes();

    size_t young_gen_prev_used = young_gen->used_in_bytes();

    allocate_stacks();

#if COMPILER2_OR_JVMCI

    DerivedPointerTable::clear();

#endif

    ref_processor()->enable_discovery();

    ref_processor()->setup_policy(clear_all_softrefs);

    mark_sweep_phase1(clear_all_softrefs);

    mark_sweep_phase2();

#if COMPILER2_OR_JVMCI

    // Don't add any more derived pointers during phase3

    assert(DerivedPointerTable::is_active(), "Sanity");

    DerivedPointerTable::set_active(false);

#endif

    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;

    PSCardTable* card_table = heap->card_table();

    MemRegion old_mr = heap->old_gen()->reserved();

    if (young_gen_empty) {

      card_table->clear(MemRegion(old_mr.start(), old_mr.end()));

    } else {

      card_table->invalidate(MemRegion(old_mr.start(), old_mr.end()));

    }

    // Delete metaspaces for unloaded class loaders and clean up loader_data graph

    ClassLoaderDataGraph::purge();

    MetaspaceUtils::verify_metrics();

    BiasedLocking::restore_marks();

    heap->prune_scavengable_nmethods();

    JvmtiExport::gc_epilogue();

#if COMPILER2_OR_JVMCI

    DerivedPointerTable::update_pointers();

#endif

    assert(!ref_processor()->discovery_enabled(), "Should have been disabled earlier");

    // 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) {

     log_debug(gc, ergo)("AdaptiveSizeStart: collection: %d ", heap->total_collections());

     log_trace(gc, ergo)("old_gen_capacity: " SIZE_FORMAT " young_gen_capacity: " SIZE_FORMAT,

                         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 &&

          AdaptiveSizePolicy::should_update_promo_stats(gc_cause)) {

        // Swap the survivor spaces if from_space is empty. The

        // resize_young_gen() called below is normally used after

        // a successful young GC and swapping of survivor spaces;

        // otherwise, it will fail to resize the young gen with

        // the current implementation.

        if (young_gen->from_space()->is_empty()) {

          young_gen->from_space()->clear(SpaceDecorator::Mangle);

          young_gen->swap_spaces();

        }

        // 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(eden_live,

                                             max_old_gen_size,

                                             max_eden_size,

                                             true /* full gc*/,

                                             gc_cause,

                                             heap->soft_ref_policy());

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

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

        heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),

                               size_policy->calculated_survivor_size_in_bytes());

      }

      log_debug(gc, ergo)("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 (log_is_enabled(Debug, gc, heap, exit)) {

      accumulated_time()->stop();

    }

    young_gen->print_used_change(young_gen_prev_used);

    old_gen->print_used_change(old_gen_prev_used);

    MetaspaceUtils::print_metaspace_change(metadata_prev_used);

    // Track memory usage and detect low memory

    MemoryService::track_memory_usage();

    heap->update_counters();

    heap->post_full_gc_dump(_gc_timer);

  }

  if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {

    HandleMark hm;  // Discard invalid handles created during verification

    Universe::verify("After GC");

  }

  // 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);

#ifdef TRACESPINNING

  ParallelTaskTerminator::print_termination_counts();

#endif

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

  _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_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.

  }

  log_trace(gc, ergo, heap)(" 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::heap();

  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);