/*

 * Copyright (c) 2000, 2014, 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/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/generation.inline.hpp"

#include "memory/generationSpec.hpp"

#include "memory/resourceArea.hpp"

#include "memory/sharedHeap.hpp"

#include "memory/space.hpp"

#include "oops/oop.inline.hpp"

#include "oops/oop.inline2.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/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 {

  // We probably want to parallelize both of these internally, but for now...

  GCH_PS_younger_gens,

  // Leave this one last.

  GCH_PS_NumElements

};

GenCollectedHeap::GenCollectedHeap(GenCollectorPolicy *policy) :

  SharedHeap(policy),

  _gen_policy(policy),

  _gen_process_roots_tasks(new SubTasksDone(GCH_PS_NumElements)),

  _full_collections_completed(0)

{

  if (_gen_process_roots_tasks == NULL ||

      !_gen_process_roots_tasks->valid()) {

    vm_exit_during_initialization("Failed necessary allocation.");

  }

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

}

jint GenCollectedHeap::initialize() {

  CollectedHeap::pre_initialize();

  int i;

  _n_gens = gen_policy()->number_of_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");

  // The heap must be at least as aligned as generations.

  size_t gen_alignment = Generation::GenGrain;

  _gen_specs = gen_policy()->generations();

  // Make sure the sizes are all aligned.

  for (i = 0; i < _n_gens; i++) {

    _gen_specs[i]->align(gen_alignment);

  }

  // Allocate space for the heap.

  char* heap_address;

  size_t total_reserved = 0;

  ReservedSpace heap_rs;

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

  heap_address = allocate(heap_alignment, &total_reserved, &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;

  for (i = 0; i < _n_gens; i++) {

    ReservedSpace this_rs = heap_rs.first_part(_gen_specs[i]->max_size(), false, false);

    _gens[i] = _gen_specs[i]->init(this_rs, i, rem_set());

    heap_rs = heap_rs.last_part(_gen_specs[i]->max_size());

  }

  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,

                                 size_t* _total_reserved,

                                 ReservedSpace* heap_rs){

  const char overflow_msg[] = "The size of the object heap + VM data exceeds "

    "the maximum representable size";

  // Now figure out the total size.

  size_t total_reserved = 0;

  const size_t pageSize = UseLargePages ?

      os::large_page_size() : os::vm_page_size();

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

  for (int i = 0; i < _n_gens; i++) {

    total_reserved += _gen_specs[i]->max_size();

    if (total_reserved < _gen_specs[i]->max_size()) {

      vm_exit_during_initialization(overflow_msg);

    }

  }

  assert(total_reserved % alignment == 0,

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

                 SIZE_FORMAT, total_reserved, alignment));

  *_total_reserved = total_reserved;

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

  return heap_rs->base();

}

void GenCollectedHeap::post_initialize() {

  SharedHeap::post_initialize();

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

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

  Generation* old_gen = get_gen(1);

  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() {

  SharedHeap::ref_processing_init();

  for (int i = 0; i < _n_gens; i++) {

    _gens[i]->ref_processor_init();

  }

}

size_t GenCollectedHeap::capacity() const {

  size_t res = 0;

  for (int i = 0; i < _n_gens; i++) {

    res += _gens[i]->capacity();

  }

  return res;

}

size_t GenCollectedHeap::used() const {

  size_t res = 0;

  for (int i = 0; i < _n_gens; i++) {

    res += _gens[i]->used();

  }

  return res;

}

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

void GenCollectedHeap::save_used_regions(int level) {

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

  for (int i = level; i >= 0; i--) {

    _gens[i]->save_used_region();

  }

}

size_t GenCollectedHeap::max_capacity() const {

  size_t res = 0;

  for (int i = 0; i < _n_gens; i++) {

    res += _gens[i]->max_capacity();

  }

  return res;

}

// 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;

  for (int i = 0; i < _n_gens; i++) {

    if (_gens[i]->should_allocate(size, is_tlab)) {

      res = _gens[i]->allocate(size, is_tlab);

      if (res != NULL) return res;

      else if (first_only) break;

    }

  }

  // Otherwise...

  return NULL;

}

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::do_collection(bool  full,

                                     bool   clear_all_soft_refs,

                                     size_t size,

                                     bool   is_tlab,

                                     int    max_level) {

  bool prepared_for_verification = false;

  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();

    int starting_level = 0;

    if (full) {

      // Search for the oldest generation which will collect all younger

      // generations, and start collection loop there.

      for (int i = max_level; i >= 0; i--) {

        if (_gens[i]->full_collects_younger_generations()) {

          starting_level = i;

          break;

        }

      }

    }

    bool must_restore_marks_for_biased_locking = false;

    int max_level_collected = starting_level;

    for (int i = starting_level; i <= max_level; i++) {

      if (_gens[i]->should_collect(full, size, is_tlab)) {

        if (i == n_gens() - 1) {  // a major collection is to happen

          if (!complete) {

            // The full_collections increment was missed above.

            increment_total_full_collections();

          }

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

        }

        // 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(_gens[i]->short_name(), PrintGCDetails, false, NULL, GCId::peek());

        TraceCollectorStats tcs(_gens[i]->counters());

        TraceMemoryManagerStats tmms(_gens[i]->kind(),gc_cause());

        size_t prev_used = _gens[i]->used();

        _gens[i]->stat_record()->invocations++;

        _gens[i]->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,

                     i,

                     _gens[i]->stat_record()->invocations,

                     size*HeapWordSize);

        }

        if (VerifyBeforeGC && i >= VerifyGCLevel &&

            total_collections() >= VerifyGCStartAt) {

          HandleMark hm;  // Discard invalid handles created during verification

          if (!prepared_for_verification) {

            prepare_for_verify();

            prepared_for_verification = true;

          }

          Universe::verify(" VerifyBeforeGC:");

        }

        COMPILER2_PRESENT(DerivedPointerTable::clear());

        if (!must_restore_marks_for_biased_locking &&

            _gens[i]->performs_in_place_marking()) {

          // 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

          must_restore_marks_for_biased_locking = true;

          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 = _gens[i]->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(true /*verify_disabled*/, true /*verify_no_refs*/);

            rp->setup_policy(do_clear_all_soft_refs);

          } else {

            // collect() below will enable discovery as appropriate

          }

          _gens[i]->collect(full, do_clear_all_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();

        }

        max_level_collected = i;

        // Determine if allocation request was met.

        if (size > 0) {

          if (!is_tlab || _gens[i]->supports_tlab_allocation()) {

            if (size*HeapWordSize <= _gens[i]->unsafe_max_alloc_nogc()) {

              size = 0;

            }

          }

        }

        COMPILER2_PRESENT(DerivedPointerTable::update_pointers());

        _gens[i]->stat_record()->accumulated_time.stop();

        update_gc_stats(i, full);

        if (VerifyAfterGC && i >= VerifyGCLevel &&

            total_collections() >= VerifyGCStartAt) {

          HandleMark hm;  // Discard invalid handles created during verification

          Universe::verify(" VerifyAfterGC:");

        }

        if (PrintGCDetails) {

          gclog_or_tty->print(":");

          _gens[i]->print_heap_change(prev_used);

        }