/*

 * Copyright (c) 2000, 2018, 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 "aot/aotLoader.hpp"

#include "classfile/symbolTable.hpp"

#include "classfile/stringTable.hpp"

#include "classfile/systemDictionary.hpp"

#include "classfile/vmSymbols.hpp"

#include "code/codeCache.hpp"

#include "code/icBuffer.hpp"

#include "gc/serial/defNewGeneration.hpp"

#include "gc/shared/adaptiveSizePolicy.hpp"

#include "gc/shared/cardTableBarrierSet.hpp"

#include "gc/shared/cardTableRS.hpp"

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

#include "gc/shared/collectorCounters.hpp"

#include "gc/shared/gcId.hpp"

#include "gc/shared/gcLocker.hpp"

#include "gc/shared/gcPolicyCounters.hpp"

#include "gc/shared/gcTrace.hpp"

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

#include "gc/shared/genCollectedHeap.hpp"

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

#include "gc/shared/generationSpec.hpp"

#include "gc/shared/space.hpp"

#include "gc/shared/strongRootsScope.hpp"

#include "gc/shared/vmGCOperations.hpp"

#include "gc/shared/weakProcessor.hpp"

#include "gc/shared/workgroup.hpp"

#include "memory/filemap.hpp"

#include "memory/metaspaceCounters.hpp"

#include "memory/resourceArea.hpp"

#include "oops/oop.inline.hpp"

#include "runtime/biasedLocking.hpp"

#include "runtime/flags/flagSetting.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/debug.hpp"

#include "utilities/formatBuffer.hpp"

#include "utilities/macros.hpp"

#include "utilities/stack.inline.hpp"

#include "utilities/vmError.hpp"

GenCollectedHeap::GenCollectedHeap(GenCollectorPolicy *policy,

                                   Generation::Name young,

                                   Generation::Name old,

                                   const char* policy_counters_name) :

  CollectedHeap(),

  _rem_set(NULL),

  _young_gen_spec(new GenerationSpec(young,

                                     policy->initial_young_size(),

                                     policy->max_young_size(),

                                     policy->gen_alignment())),

  _old_gen_spec(new GenerationSpec(old,

                                   policy->initial_old_size(),

                                   policy->max_old_size(),

                                   policy->gen_alignment())),

  _gen_policy(policy),

  _soft_ref_gen_policy(),

  _gc_policy_counters(new GCPolicyCounters(policy_counters_name, 2, 2)),

  _process_strong_tasks(new SubTasksDone(GCH_PS_NumElements)),

  _full_collections_completed(0) {

}

jint GenCollectedHeap::initialize() {

  // 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 = create_rem_set(reserved_region());

  _rem_set->initialize();

  CardTableBarrierSet *bs = new CardTableBarrierSet(_rem_set);

  bs->initialize();

  BarrierSet::set_barrier_set(bs);

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

  _young_gen = _young_gen_spec->init(young_rs, rem_set());

  heap_rs = heap_rs.last_part(_young_gen_spec->max_size());

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

  _old_gen = _old_gen_spec->init(old_rs, rem_set());

  clear_incremental_collection_failed();

  return JNI_OK;

}

CardTableRS* GenCollectedHeap::create_rem_set(const MemRegion& reserved_region) {

  return new CardTableRS(reserved_region, false /* scan_concurrently */);

}

void GenCollectedHeap::initialize_size_policy(size_t init_eden_size,

                                              size_t init_promo_size,

                                              size_t init_survivor_size) {

  const double max_gc_pause_sec = ((double) MaxGCPauseMillis) / 1000.0;

  _size_policy = new AdaptiveSizePolicy(init_eden_size,

                                        init_promo_size,

                                        init_survivor_size,

                                        max_gc_pause_sec,

                                        GCTimeRatio);

}

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");

  // Check for overflow.

  size_t total_reserved = _young_gen_spec->max_size() + _old_gen_spec->max_size();

  if (total_reserved < _young_gen_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,

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

         SIZE_FORMAT, total_reserved, alignment);

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

  os::trace_page_sizes("Heap",

                       collector_policy()->min_heap_byte_size(),

                       total_reserved,

                       alignment,

                       heap_rs->base(),

                       heap_rs->size());

  return heap_rs->base();

}

void GenCollectedHeap::post_initialize() {

  CollectedHeap::post_initialize();

  ref_processing_init();

  DefNewGeneration* def_new_gen = (DefNewGeneration*)_young_gen;

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

                         _old_gen->capacity(),

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

}

void GenCollectedHeap::ref_processing_init() {

  _young_gen->ref_processor_init();

  _old_gen->ref_processor_init();

}

GenerationSpec* GenCollectedHeap::young_gen_spec() const {

  return _young_gen_spec;

}

GenerationSpec* GenCollectedHeap::old_gen_spec() const {

  return _old_gen_spec;

}

size_t GenCollectedHeap::capacity() const {

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

}

size_t GenCollectedHeap::used() const {

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

}

void GenCollectedHeap::save_used_regions() {

  _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;

}

// Return true if any of the following is true:

// . the allocation won't fit into the current young gen heap

// . gc locker is occupied (jni critical section)

// . heap memory is tight -- the most recent previous collection

//   was a full collection because a partial collection (would

//   have) failed and is likely to fail again

bool GenCollectedHeap::should_try_older_generation_allocation(size_t word_size) const {

  size_t young_capacity = _young_gen->capacity_before_gc();

  return    (word_size > heap_word_size(young_capacity))

         || GCLocker::is_active_and_needs_gc()

         || incremental_collection_failed();

}

HeapWord* GenCollectedHeap::expand_heap_and_allocate(size_t size, bool   is_tlab) {

  HeapWord* result = NULL;

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

    result = _old_gen->expand_and_allocate(size, is_tlab);

  }

  if (result == NULL) {

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

      result = _young_gen->expand_and_allocate(size, is_tlab);

    }

  }

  assert(result == NULL || is_in_reserved(result), "result not in heap");

  return result;

}

HeapWord* GenCollectedHeap::mem_allocate_work(size_t size,

                                              bool is_tlab,

                                              bool* gc_overhead_limit_was_exceeded) {

  debug_only(check_for_valid_allocation_state());

  assert(no_gc_in_progress(), "Allocation during gc not allowed");

  // In general gc_overhead_limit_was_exceeded should be false so

  // set it so here and reset it to true only if the gc time

  // limit is being exceeded as checked below.

  *gc_overhead_limit_was_exceeded = false;

  HeapWord* result = NULL;

  // Loop until the allocation is satisfied, or unsatisfied after GC.

  for (uint try_count = 1, gclocker_stalled_count = 0; /* return or throw */; try_count += 1) {

    HandleMark hm; // Discard any handles allocated in each iteration.

    // First allocation attempt is lock-free.

    Generation *young = _young_gen;

    assert(young->supports_inline_contig_alloc(),

      "Otherwise, must do alloc within heap lock");

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

      result = young->par_allocate(size, is_tlab);

      if (result != NULL) {

        assert(is_in_reserved(result), "result not in heap");

        return result;

      }

    }

    uint gc_count_before;  // Read inside the Heap_lock locked region.

    {

      MutexLocker ml(Heap_lock);

      log_trace(gc, alloc)("GenCollectedHeap::mem_allocate_work: attempting locked slow path allocation");

      // Note that only large objects get a shot at being

      // allocated in later generations.

      bool first_only = !should_try_older_generation_allocation(size);

      result = attempt_allocation(size, is_tlab, first_only);

      if (result != NULL) {

        assert(is_in_reserved(result), "result not in heap");

        return result;

      }

      if (GCLocker::is_active_and_needs_gc()) {

        if (is_tlab) {

          return NULL;  // Caller will retry allocating individual object.

        }

        if (!is_maximal_no_gc()) {

          // Try and expand heap to satisfy request.

          result = expand_heap_and_allocate(size, is_tlab);

          // Result could be null if we are out of space.

          if (result != NULL) {

            return result;

          }

        }

        if (gclocker_stalled_count > GCLockerRetryAllocationCount) {

          return NULL; // We didn't get to do a GC and we didn't get any memory.

        }

        // If this thread is not in a jni critical section, we stall

        // the requestor until the critical section has cleared and

        // GC allowed. When the critical section clears, a GC is

        // initiated by the last thread exiting the critical section; so

        // we retry the allocation sequence from the beginning of the loop,

        // rather than causing more, now probably unnecessary, GC attempts.

        JavaThread* jthr = JavaThread::current();

        if (!jthr->in_critical()) {

          MutexUnlocker mul(Heap_lock);

          // Wait for JNI critical section to be exited

          GCLocker::stall_until_clear();

          gclocker_stalled_count += 1;

          continue;

        } else {

          if (CheckJNICalls) {

            fatal("Possible deadlock due to allocating while"

                  " in jni critical section");

          }

          return NULL;

        }

      }

      // Read the gc count while the heap lock is held.

      gc_count_before = total_collections();

    }

    VM_GenCollectForAllocation op(size, is_tlab, gc_count_before);

    VMThread::execute(&op);

    if (op.prologue_succeeded()) {

      result = op.result();

      if (op.gc_locked()) {

         assert(result == NULL, "must be NULL if gc_locked() is true");

         continue;  // Retry and/or stall as necessary.

      }

      // Allocation has failed and a collection

      // has been done.  If the gc time limit was exceeded the

      // this time, return NULL so that an out-of-memory

      // will be thrown.  Clear gc_overhead_limit_exceeded

      // so that the overhead exceeded does not persist.

      const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();

      const bool softrefs_clear = soft_ref_policy()->all_soft_refs_clear();

      if (limit_exceeded && softrefs_clear) {

        *gc_overhead_limit_was_exceeded = true;

        size_policy()->set_gc_overhead_limit_exceeded(false);

        if (op.result() != NULL) {

          CollectedHeap::fill_with_object(op.result(), size);

        }

        return NULL;

      }

      assert(result == NULL || is_in_reserved(result),

             "result not in heap");

      return result;

    }

    // Give a warning if we seem to be looping forever.

    if ((QueuedAllocationWarningCount > 0) &&

        (try_count % QueuedAllocationWarningCount == 0)) {

          log_warning(gc, ergo)("GenCollectedHeap::mem_allocate_work retries %d times,"

                                " size=" SIZE_FORMAT " %s", try_count, size, is_tlab ? "(TLAB)" : "");

    }

  }

}

#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 mem_allocate_work(size,

                           false /* is_tlab */,

                           gc_overhead_limit_was_exceeded);

}

bool GenCollectedHeap::must_clear_all_soft_refs() {

  return _gc_cause == GCCause::_metadata_GC_clear_soft_refs ||

         _gc_cause == GCCause::_wb_full_gc;

}

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) {

  FormatBuffer<> title("Collect gen: %s", gen->short_name());

  GCTraceTime(Trace, gc, phases) t1(title);

  TraceCollectorStats tcs(gen->counters());

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

  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();

  log_trace(gc)("%s invoke=%d size=" SIZE_FORMAT, heap()->is_young_gen(gen) ? "Young" : "Old", gen->stat_record()->invocations, size * HeapWordSize);

  if (run_verification && VerifyBeforeGC) {

    HandleMark hm;  // Discard invalid handles created during verification

    Universe::verify("Before GC");

  }

  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