/*

 * Copyright (c) 2000, 2015, 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

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 */

#include "precompiled.hpp"

#include "classfile/symbolTable.hpp"

#include "classfile/systemDictionary.hpp"

#include "classfile/vmSymbols.hpp"

#include "code/codeCache.hpp"

#include "code/icBuffer.hpp"

#include "gc_implementation/shared/collectorCounters.hpp"

#include "gc_implementation/shared/gcTrace.hpp"

#include "gc_implementation/shared/gcTraceTime.hpp"

#include "gc_implementation/shared/vmGCOperations.hpp"

#include "gc_interface/collectedHeap.inline.hpp"

#include "memory/filemap.hpp"

#include "memory/gcLocker.inline.hpp"

#include "memory/genCollectedHeap.hpp"

#include "memory/genOopClosures.inline.hpp"

#include "memory/generationSpec.hpp"

#include "memory/resourceArea.hpp"

#include "memory/strongRootsScope.hpp"

#include "memory/space.hpp"

#include "oops/oop.inline.hpp"

#include "runtime/biasedLocking.hpp"

#include "runtime/fprofiler.hpp"

#include "runtime/handles.hpp"

#include "runtime/handles.inline.hpp"

#include "runtime/java.hpp"

#include "runtime/vmThread.hpp"

#include "services/management.hpp"

#include "services/memoryService.hpp"

#include "utilities/vmError.hpp"

#include "utilities/workgroup.hpp"

#include "utilities/macros.hpp"

#if INCLUDE_ALL_GCS

#include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"

#include "gc_implementation/concurrentMarkSweep/vmCMSOperations.hpp"

#endif // INCLUDE_ALL_GCS

GenCollectedHeap* GenCollectedHeap::_gch;

NOT_PRODUCT(size_t GenCollectedHeap::_skip_header_HeapWords = 0;)

// The set of potentially parallel tasks in root scanning.

enum GCH_strong_roots_tasks {

  GCH_PS_Universe_oops_do,

  GCH_PS_JNIHandles_oops_do,

  GCH_PS_ObjectSynchronizer_oops_do,

  GCH_PS_FlatProfiler_oops_do,

  GCH_PS_Management_oops_do,

  GCH_PS_SystemDictionary_oops_do,

  GCH_PS_ClassLoaderDataGraph_oops_do,

  GCH_PS_jvmti_oops_do,

  GCH_PS_CodeCache_oops_do,

  GCH_PS_younger_gens,

  // Leave this one last.

  GCH_PS_NumElements

};

GenCollectedHeap::GenCollectedHeap(GenCollectorPolicy *policy) :

  _rem_set(NULL),

  _gen_policy(policy),

  _process_strong_tasks(new SubTasksDone(GCH_PS_NumElements)),

  _full_collections_completed(0)

{

  assert(policy != NULL, "Sanity check");

  if (UseConcMarkSweepGC) {

    _workers = new FlexibleWorkGang("GC Thread", ParallelGCThreads,

                            /* are_GC_task_threads */true,

                            /* are_ConcurrentGC_threads */false);

    _workers->initialize_workers();

  } else {

    // Serial GC does not use workers.

    _workers = NULL;

  }

}

jint GenCollectedHeap::initialize() {

  CollectedHeap::pre_initialize();

  _n_gens = gen_policy()->number_of_generations();

  assert(_n_gens == 2, "There is no support for more than two generations");

  // While there are no constraints in the GC code that HeapWordSize

  // be any particular value, there are multiple other areas in the

  // system which believe this to be true (e.g. oop->object_size in some

  // cases incorrectly returns the size in wordSize units rather than

  // HeapWordSize).

  guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");

  // Allocate space for the heap.

  char* heap_address;

  ReservedSpace heap_rs;

  size_t heap_alignment = collector_policy()->heap_alignment();

  heap_address = allocate(heap_alignment, &heap_rs);

  if (!heap_rs.is_reserved()) {

    vm_shutdown_during_initialization(

      "Could not reserve enough space for object heap");

    return JNI_ENOMEM;

  }

  initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));

  _rem_set = collector_policy()->create_rem_set(reserved_region());

  set_barrier_set(rem_set()->bs());

  _gch = this;

  ReservedSpace young_rs = heap_rs.first_part(gen_policy()->young_gen_spec()->max_size(), false, false);

  _young_gen = gen_policy()->young_gen_spec()->init(young_rs, 0, rem_set());

  heap_rs = heap_rs.last_part(gen_policy()->young_gen_spec()->max_size());

  ReservedSpace old_rs = heap_rs.first_part(gen_policy()->old_gen_spec()->max_size(), false, false);

  _old_gen = gen_policy()->old_gen_spec()->init(old_rs, 1, rem_set());

  clear_incremental_collection_failed();

#if INCLUDE_ALL_GCS

  // If we are running CMS, create the collector responsible

  // for collecting the CMS generations.

  if (collector_policy()->is_concurrent_mark_sweep_policy()) {

    bool success = create_cms_collector();

    if (!success) return JNI_ENOMEM;

  }

#endif // INCLUDE_ALL_GCS

  return JNI_OK;

}

char* GenCollectedHeap::allocate(size_t alignment,

                                 ReservedSpace* heap_rs){

  // Now figure out the total size.

  const size_t pageSize = UseLargePages ? os::large_page_size() : os::vm_page_size();

  assert(alignment % pageSize == 0, "Must be");

  GenerationSpec* young_spec = gen_policy()->young_gen_spec();

  GenerationSpec* old_spec = gen_policy()->old_gen_spec();

  // Check for overflow.

  size_t total_reserved = young_spec->max_size() + old_spec->max_size();

  if (total_reserved < young_spec->max_size()) {

    vm_exit_during_initialization("The size of the object heap + VM data exceeds "

                                  "the maximum representable size");

  }

  assert(total_reserved % alignment == 0,

         err_msg("Gen size; total_reserved=" SIZE_FORMAT ", alignment="

                 SIZE_FORMAT, total_reserved, alignment));

  *heap_rs = Universe::reserve_heap(total_reserved, alignment);

  return heap_rs->base();

}

void GenCollectedHeap::post_initialize() {

  CollectedHeap::post_initialize();

  ref_processing_init();

  GenCollectorPolicy *policy = (GenCollectorPolicy *)collector_policy();

  guarantee(policy->is_generation_policy(), "Illegal policy type");

  assert((_young_gen->kind() == Generation::DefNew) ||

         (_young_gen->kind() == Generation::ParNew),

    "Wrong youngest generation type");

  DefNewGeneration* def_new_gen = (DefNewGeneration*)_young_gen;

  assert(_old_gen->kind() == Generation::ConcurrentMarkSweep ||

         _old_gen->kind() == Generation::MarkSweepCompact,

    "Wrong generation kind");

  policy->initialize_size_policy(def_new_gen->eden()->capacity(),

                                 _old_gen->capacity(),

                                 def_new_gen->from()->capacity());

  policy->initialize_gc_policy_counters();

}

void GenCollectedHeap::ref_processing_init() {

  _young_gen->ref_processor_init();

  _old_gen->ref_processor_init();

}

size_t GenCollectedHeap::capacity() const {

  return _young_gen->capacity() + _old_gen->capacity();

}

size_t GenCollectedHeap::used() const {

  return _young_gen->used() + _old_gen->used();

}

// Save the "used_region" for generations level and lower.

void GenCollectedHeap::save_used_regions(int level) {

  assert(level >= 0, "Illegal level parameter");

  assert(level < _n_gens, "Illegal level parameter");

  if (level == 1) {

    _old_gen->save_used_region();

  }

  _young_gen->save_used_region();

}

size_t GenCollectedHeap::max_capacity() const {

  return _young_gen->max_capacity() + _old_gen->max_capacity();

}

// Update the _full_collections_completed counter

// at the end of a stop-world full GC.

unsigned int GenCollectedHeap::update_full_collections_completed() {

  MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);

  assert(_full_collections_completed <= _total_full_collections,

         "Can't complete more collections than were started");

  _full_collections_completed = _total_full_collections;

  ml.notify_all();

  return _full_collections_completed;

}

// Update the _full_collections_completed counter, as appropriate,

// at the end of a concurrent GC cycle. Note the conditional update

// below to allow this method to be called by a concurrent collector

// without synchronizing in any manner with the VM thread (which

// may already have initiated a STW full collection "concurrently").

unsigned int GenCollectedHeap::update_full_collections_completed(unsigned int count) {

  MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);

  assert((_full_collections_completed <= _total_full_collections) &&

         (count <= _total_full_collections),

         "Can't complete more collections than were started");

  if (count > _full_collections_completed) {

    _full_collections_completed = count;

    ml.notify_all();

  }

  return _full_collections_completed;

}

#ifndef PRODUCT

// Override of memory state checking method in CollectedHeap:

// Some collectors (CMS for example) can't have badHeapWordVal written

// in the first two words of an object. (For instance , in the case of

// CMS these words hold state used to synchronize between certain

// (concurrent) GC steps and direct allocating mutators.)

// The skip_header_HeapWords() method below, allows us to skip

// over the requisite number of HeapWord's. Note that (for

// generational collectors) this means that those many words are

// skipped in each object, irrespective of the generation in which

// that object lives. The resultant loss of precision seems to be

// harmless and the pain of avoiding that imprecision appears somewhat

// higher than we are prepared to pay for such rudimentary debugging

// support.

void GenCollectedHeap::check_for_non_bad_heap_word_value(HeapWord* addr,

                                                         size_t size) {

  if (CheckMemoryInitialization && ZapUnusedHeapArea) {

    // We are asked to check a size in HeapWords,

    // but the memory is mangled in juint words.

    juint* start = (juint*) (addr + skip_header_HeapWords());

    juint* end   = (juint*) (addr + size);

    for (juint* slot = start; slot < end; slot += 1) {

      assert(*slot == badHeapWordVal,

             "Found non badHeapWordValue in pre-allocation check");

    }

  }

}

#endif

HeapWord* GenCollectedHeap::attempt_allocation(size_t size,

                                               bool is_tlab,

                                               bool first_only) {

  HeapWord* res = NULL;

  if (_young_gen->should_allocate(size, is_tlab)) {

    res = _young_gen->allocate(size, is_tlab);

    if (res != NULL || first_only) {

      return res;

    }

  }

  if (_old_gen->should_allocate(size, is_tlab)) {

    res = _old_gen->allocate(size, is_tlab);

  }

  return res;

}

HeapWord* GenCollectedHeap::mem_allocate(size_t size,

                                         bool* gc_overhead_limit_was_exceeded) {

  return collector_policy()->mem_allocate_work(size,

                                               false /* is_tlab */,

                                               gc_overhead_limit_was_exceeded);

}

bool GenCollectedHeap::must_clear_all_soft_refs() {

  return _gc_cause == GCCause::_last_ditch_collection;

}

bool GenCollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {

  return UseConcMarkSweepGC &&

         ((cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) ||

          (cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent));

}

void GenCollectedHeap::collect_generation(Generation* gen, bool full, size_t size,

                                          bool is_tlab, bool run_verification, bool clear_soft_refs,

                                          bool restore_marks_for_biased_locking) {

  // Timer for individual generations. Last argument is false: no CR

  // FIXME: We should try to start the timing earlier to cover more of the GC pause

  // The PrintGCDetails logging starts before we have incremented the GC id. We will do that later

  // so we can assume here that the next GC id is what we want.

  GCTraceTime t1(gen->short_name(), PrintGCDetails, false, NULL, GCId::peek());

  TraceCollectorStats tcs(gen->counters());

  TraceMemoryManagerStats tmms(gen->kind(),gc_cause());

  size_t prev_used = gen->used();

  gen->stat_record()->invocations++;

  gen->stat_record()->accumulated_time.start();

  // Must be done anew before each collection because

  // a previous collection will do mangling and will

  // change top of some spaces.

  record_gen_tops_before_GC();

  if (PrintGC && Verbose) {

    gclog_or_tty->print("level=%d invoke=%d size=" SIZE_FORMAT,

                        gen->level(),

                        gen->stat_record()->invocations,

                        size * HeapWordSize);

  }

  if (run_verification && VerifyBeforeGC) {

    HandleMark hm;  // Discard invalid handles created during verification

    Universe::verify(" VerifyBeforeGC:");

  }

  COMPILER2_PRESENT(DerivedPointerTable::clear());

  if (restore_marks_for_biased_locking) {

    // We perform this mark word preservation work lazily

    // because it's only at this point that we know whether we

    // absolutely have to do it; we want to avoid doing it for

    // scavenge-only collections where it's unnecessary

    BiasedLocking::preserve_marks();

  }

  // Do collection work

  {

    // Note on ref discovery: For what appear to be historical reasons,

    // GCH enables and disabled (by enqueing) refs discovery.

    // In the future this should be moved into the generation's

    // collect method so that ref discovery and enqueueing concerns

    // are local to a generation. The collect method could return

    // an appropriate indication in the case that notification on

    // the ref lock was needed. This will make the treatment of

    // weak refs more uniform (and indeed remove such concerns

    // from GCH). XXX

    HandleMark hm;  // Discard invalid handles created during gc

    save_marks();   // save marks for all gens

    // We want to discover references, but not process them yet.

    // This mode is disabled in process_discovered_references if the

    // generation does some collection work, or in

    // enqueue_discovered_references if the generation returns

    // without doing any work.

    ReferenceProcessor* rp = gen->ref_processor();

    // If the discovery of ("weak") refs in this generation is

    // atomic wrt other collectors in this configuration, we

    // are guaranteed to have empty discovered ref lists.

    if (rp->discovery_is_atomic()) {

      rp->enable_discovery();

      rp->setup_policy(clear_soft_refs);

    } else {

      // collect() below will enable discovery as appropriate

    }

    gen->collect(full, clear_soft_refs, size, is_tlab);

    if (!rp->enqueuing_is_done()) {

      rp->enqueue_discovered_references();

    } else {

      rp->set_enqueuing_is_done(false);

    }

    rp->verify_no_references_recorded();

  }

  COMPILER2_PRESENT(DerivedPointerTable::update_pointers());

  gen->stat_record()->accumulated_time.stop();

  update_gc_stats(gen->level(), full);

  if (run_verification && VerifyAfterGC) {

    HandleMark hm;  // Discard invalid handles created during verification

    Universe::verify(" VerifyAfterGC:");

  }

  if (PrintGCDetails) {

    gclog_or_tty->print(":");

    gen->print_heap_change(prev_used);

  }

}

void GenCollectedHeap::do_collection(bool   full,

                                     bool   clear_all_soft_refs,

                                     size_t size,

                                     bool   is_tlab,

                                     int    max_level) {

  ResourceMark rm;

  DEBUG_ONLY(Thread* my_thread = Thread::current();)

  assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");

  assert(my_thread->is_VM_thread() ||

         my_thread->is_ConcurrentGC_thread(),

         "incorrect thread type capability");

  assert(Heap_lock->is_locked(),

         "the requesting thread should have the Heap_lock");

  guarantee(!is_gc_active(), "collection is not reentrant");

  assert(max_level < n_gens(), "sanity check");

  if (GC_locker::check_active_before_gc()) {

    return; // GC is disabled (e.g. JNI GetXXXCritical operation)

  }

  const bool do_clear_all_soft_refs = clear_all_soft_refs ||

                          collector_policy()->should_clear_all_soft_refs();

  ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());

  const size_t metadata_prev_used = MetaspaceAux::used_bytes();

  print_heap_before_gc();

  {

    FlagSetting fl(_is_gc_active, true);

    bool complete = full && (max_level == (n_gens()-1));

    const char* gc_cause_prefix = complete ? "Full GC" : "GC";

    TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);

    // The PrintGCDetails logging starts before we have incremented the GC id. We will do that later

    // so we can assume here that the next GC id is what we want.

    GCTraceTime t(GCCauseString(gc_cause_prefix, gc_cause()), PrintGCDetails, false, NULL, GCId::peek());

    gc_prologue(complete);

    increment_total_collections(complete);

    size_t gch_prev_used = used();

    bool run_verification = total_collections() >= VerifyGCStartAt;

    bool prepared_for_verification = false;

    int max_level_collected = 0;

    bool old_collects_young = (max_level == 1) &&

                              full &&

                              _old_gen->full_collects_younger_generations();

    if (!old_collects_young &&

        _young_gen->should_collect(full, size, is_tlab)) {

      if (run_verification && VerifyGCLevel <= 0 && VerifyBeforeGC) {

        prepare_for_verify();

        prepared_for_verification = true;

      }

      assert(!_young_gen->performs_in_place_marking(), "No young generation do in place marking");

      collect_generation(_young_gen,

                         full,

                         size,

                         is_tlab,

                         run_verification && VerifyGCLevel <= 0,

                         do_clear_all_soft_refs,

                         false);

      if (size > 0 && (!is_tlab || _young_gen->supports_tlab_allocation()) &&

          size * HeapWordSize <= _young_gen->unsafe_max_alloc_nogc()) {

        // Allocation request was met by young GC.

        size = 0;

      }

    }

    bool must_restore_marks_for_biased_locking = false;

    if (max_level == 1 && _old_gen->should_collect(full, size, is_tlab)) {

      if (!complete) {

        // The full_collections increment was missed above.

        increment_total_full_collections();

      }

      pre_full_gc_dump(NULL);    // do any pre full gc dumps

      if (!prepared_for_verification && run_verification &&

          VerifyGCLevel <= 1 && VerifyBeforeGC) {

        prepare_for_verify();

      }