/*

 * 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.

 *

 */

#include "precompiled.hpp"

#include "gc/serial/defNewGeneration.inline.hpp"

#include "gc/serial/serialHeap.inline.hpp"

#include "gc/serial/tenuredGeneration.hpp"

#include "gc/shared/adaptiveSizePolicy.hpp"

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

#include "gc/shared/cardTableRS.hpp"

#include "gc/shared/collectorCounters.hpp"

#include "gc/shared/gcArguments.hpp"

#include "gc/shared/gcHeapSummary.hpp"

#include "gc/shared/gcLocker.hpp"

#include "gc/shared/gcPolicyCounters.hpp"

#include "gc/shared/gcTimer.hpp"

#include "gc/shared/gcTrace.hpp"

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

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

#include "gc/shared/generationSpec.hpp"

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

#include "gc/shared/referencePolicy.hpp"

#include "gc/shared/referenceProcessorPhaseTimes.hpp"

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

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

#include "gc/shared/strongRootsScope.hpp"

#include "gc/shared/weakProcessor.hpp"

#include "logging/log.hpp"

#include "memory/iterator.inline.hpp"

#include "memory/resourceArea.hpp"

#include "oops/instanceRefKlass.hpp"

#include "oops/oop.inline.hpp"

#include "runtime/java.hpp"

#include "runtime/prefetch.inline.hpp"

#include "runtime/thread.inline.hpp"

#include "utilities/align.hpp"

#include "utilities/copy.hpp"

#include "utilities/globalDefinitions.hpp"

#include "utilities/stack.inline.hpp"

//

// DefNewGeneration functions.

// Methods of protected closure types.

DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) {

  assert(_young_gen->kind() == Generation::DefNew, "Expected the young generation here");

}

bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {

  return (HeapWord*)p >= _young_gen->reserved().end() || p->is_forwarded();

}

DefNewGeneration::KeepAliveClosure::

KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {

  _rs = GenCollectedHeap::heap()->rem_set();

}

void DefNewGeneration::KeepAliveClosure::do_oop(oop* p)       { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }

void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }

DefNewGeneration::FastKeepAliveClosure::

FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :

  DefNewGeneration::KeepAliveClosure(cl) {

  _boundary = g->reserved().end();

}

void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p)       { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }

void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }

DefNewGeneration::FastEvacuateFollowersClosure::

FastEvacuateFollowersClosure(SerialHeap* heap,

                             FastScanClosure* cur,

                             FastScanClosure* older) :

  _heap(heap), _scan_cur_or_nonheap(cur), _scan_older(older)

{

}

void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {

  do {

    _heap->oop_since_save_marks_iterate(_scan_cur_or_nonheap, _scan_older);

  } while (!_heap->no_allocs_since_save_marks());

  guarantee(_heap->young_gen()->promo_failure_scan_is_complete(), "Failed to finish scan");

}

ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :

    OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)

{

  _boundary = _g->reserved().end();

}

FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :

    OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)

{

  _boundary = _g->reserved().end();

}

void CLDScanClosure::do_cld(ClassLoaderData* cld) {

  NOT_PRODUCT(ResourceMark rm);

  log_develop_trace(gc, scavenge)("CLDScanClosure::do_cld " PTR_FORMAT ", %s, dirty: %s",

                                  p2i(cld),

                                  cld->loader_name_and_id(),

                                  cld->has_modified_oops() ? "true" : "false");

  // If the cld has not been dirtied we know that there's

  // no references into  the young gen and we can skip it.

  if (cld->has_modified_oops()) {

    if (_accumulate_modified_oops) {

      cld->accumulate_modified_oops();

    }

    // Tell the closure which CLD is being scanned so that it can be dirtied

    // if oops are left pointing into the young gen.

    _scavenge_closure->set_scanned_cld(cld);

    // Clean the cld since we're going to scavenge all the metadata.

    cld->oops_do(_scavenge_closure, ClassLoaderData::_claim_none, /*clear_modified_oops*/true);

    _scavenge_closure->set_scanned_cld(NULL);

  }

}

ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :

  _g(g)

{

  _boundary = _g->reserved().end();

}

DefNewGeneration::DefNewGeneration(ReservedSpace rs,

                                   size_t initial_size,

                                   size_t min_size,

                                   size_t max_size,

                                   const char* policy)

  : Generation(rs, initial_size),

    _preserved_marks_set(false /* in_c_heap */),

    _promo_failure_drain_in_progress(false),

    _should_allocate_from_space(false)

{

  MemRegion cmr((HeapWord*)_virtual_space.low(),

                (HeapWord*)_virtual_space.high());

  GenCollectedHeap* gch = GenCollectedHeap::heap();

  gch->rem_set()->resize_covered_region(cmr);

  _eden_space = new ContiguousSpace();

  _from_space = new ContiguousSpace();

  _to_space   = new ContiguousSpace();

  if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) {

    vm_exit_during_initialization("Could not allocate a new gen space");

  }

  // Compute the maximum eden and survivor space sizes. These sizes

  // are computed assuming the entire reserved space is committed.

  // These values are exported as performance counters.

  uintx size = _virtual_space.reserved_size();

  _max_survivor_size = compute_survivor_size(size, SpaceAlignment);

  _max_eden_size = size - (2*_max_survivor_size);

  // allocate the performance counters

  // Generation counters -- generation 0, 3 subspaces

  _gen_counters = new GenerationCounters("new", 0, 3,

      min_size, max_size, &_virtual_space);

  _gc_counters = new CollectorCounters(policy, 0);

  _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,

                                      _gen_counters);

  _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,

                                      _gen_counters);

  _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,

                                    _gen_counters);

  compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);

  update_counters();

  _old_gen = NULL;

  _tenuring_threshold = MaxTenuringThreshold;

  _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;

  _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();

}

void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,

                                                bool clear_space,

                                                bool mangle_space) {

  // If the spaces are being cleared (only done at heap initialization

  // currently), the survivor spaces need not be empty.

  // Otherwise, no care is taken for used areas in the survivor spaces

  // so check.

  assert(clear_space || (to()->is_empty() && from()->is_empty()),

    "Initialization of the survivor spaces assumes these are empty");

  // Compute sizes

  uintx size = _virtual_space.committed_size();

  uintx survivor_size = compute_survivor_size(size, SpaceAlignment);

  uintx eden_size = size - (2*survivor_size);

  assert(eden_size > 0 && survivor_size <= eden_size, "just checking");

  if (eden_size < minimum_eden_size) {

    // May happen due to 64Kb rounding, if so adjust eden size back up

    minimum_eden_size = align_up(minimum_eden_size, SpaceAlignment);

    uintx maximum_survivor_size = (size - minimum_eden_size) / 2;

    uintx unaligned_survivor_size =

      align_down(maximum_survivor_size, SpaceAlignment);

    survivor_size = MAX2(unaligned_survivor_size, SpaceAlignment);

    eden_size = size - (2*survivor_size);

    assert(eden_size > 0 && survivor_size <= eden_size, "just checking");

    assert(eden_size >= minimum_eden_size, "just checking");

  }

  char *eden_start = _virtual_space.low();

  char *from_start = eden_start + eden_size;

  char *to_start   = from_start + survivor_size;

  char *to_end     = to_start   + survivor_size;

  assert(to_end == _virtual_space.high(), "just checking");

  assert(Space::is_aligned(eden_start), "checking alignment");

  assert(Space::is_aligned(from_start), "checking alignment");

  assert(Space::is_aligned(to_start),   "checking alignment");

  MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);

  MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);

  MemRegion toMR  ((HeapWord*)to_start, (HeapWord*)to_end);

  // A minimum eden size implies that there is a part of eden that

  // is being used and that affects the initialization of any

  // newly formed eden.

  bool live_in_eden = minimum_eden_size > 0;

  // If not clearing the spaces, do some checking to verify that

  // the space are already mangled.

  if (!clear_space) {

    // Must check mangling before the spaces are reshaped.  Otherwise,

    // the bottom or end of one space may have moved into another

    // a failure of the check may not correctly indicate which space

    // is not properly mangled.

    if (ZapUnusedHeapArea) {

      HeapWord* limit = (HeapWord*) _virtual_space.high();

      eden()->check_mangled_unused_area(limit);

      from()->check_mangled_unused_area(limit);

        to()->check_mangled_unused_area(limit);

    }

  }

  // Reset the spaces for their new regions.

  eden()->initialize(edenMR,

                     clear_space && !live_in_eden,

                     SpaceDecorator::Mangle);

  // If clear_space and live_in_eden, we will not have cleared any

  // portion of eden above its top. This can cause newly

  // expanded space not to be mangled if using ZapUnusedHeapArea.

  // We explicitly do such mangling here.

  if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {

    eden()->mangle_unused_area();

  }

  from()->initialize(fromMR, clear_space, mangle_space);

  to()->initialize(toMR, clear_space, mangle_space);

  // Set next compaction spaces.

  eden()->set_next_compaction_space(from());

  // The to-space is normally empty before a compaction so need

  // not be considered.  The exception is during promotion

  // failure handling when to-space can contain live objects.

  from()->set_next_compaction_space(NULL);

}

void DefNewGeneration::swap_spaces() {

  ContiguousSpace* s = from();

  _from_space        = to();

  _to_space          = s;

  eden()->set_next_compaction_space(from());

  // The to-space is normally empty before a compaction so need

  // not be considered.  The exception is during promotion

  // failure handling when to-space can contain live objects.

  from()->set_next_compaction_space(NULL);

  if (UsePerfData) {

    CSpaceCounters* c = _from_counters;

    _from_counters = _to_counters;

    _to_counters = c;

  }

}

bool DefNewGeneration::expand(size_t bytes) {

  MutexLocker x(ExpandHeap_lock);

  HeapWord* prev_high = (HeapWord*) _virtual_space.high();

  bool success = _virtual_space.expand_by(bytes);

  if (success && ZapUnusedHeapArea) {

    // Mangle newly committed space immediately because it

    // can be done here more simply that after the new

    // spaces have been computed.

    HeapWord* new_high = (HeapWord*) _virtual_space.high();

    MemRegion mangle_region(prev_high, new_high);

    SpaceMangler::mangle_region(mangle_region);

  }

  // Do not attempt an expand-to-the reserve size.  The

  // request should properly observe the maximum size of

  // the generation so an expand-to-reserve should be

  // unnecessary.  Also a second call to expand-to-reserve

  // value potentially can cause an undue expansion.

  // For example if the first expand fail for unknown reasons,

  // but the second succeeds and expands the heap to its maximum

  // value.

  if (GCLocker::is_active()) {

    log_debug(gc)("Garbage collection disabled, expanded heap instead");

  }

  return success;

}

size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate,

                                                    size_t new_size_before,

                                                    size_t alignment) const {

  size_t desired_new_size = new_size_before;

  if (NewSizeThreadIncrease > 0) {

    int threads_count;

    size_t thread_increase_size = 0;

    // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'.

    threads_count = Threads::number_of_non_daemon_threads();

    if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) {

      thread_increase_size = threads_count * NewSizeThreadIncrease;

      // 2. Check an overflow at 'new_size_candidate + thread_increase_size'.

      if (new_size_candidate <= max_uintx - thread_increase_size) {

        new_size_candidate += thread_increase_size;

        // 3. Check an overflow at 'align_up'.

        size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1));

        if (new_size_candidate <= aligned_max) {

          desired_new_size = align_up(new_size_candidate, alignment);

        }

      }

    }

  }

  return desired_new_size;

}

void DefNewGeneration::compute_new_size() {

  // This is called after a GC that includes the old generation, so from-space

  // will normally be empty.

  // Note that we check both spaces, since if scavenge failed they revert roles.

  // If not we bail out (otherwise we would have to relocate the objects).

  if (!from()->is_empty() || !to()->is_empty()) {

    return;

  }

  GenCollectedHeap* gch = GenCollectedHeap::heap();

  size_t old_size = gch->old_gen()->capacity();

  size_t new_size_before = _virtual_space.committed_size();

  size_t min_new_size = initial_size();

  size_t max_new_size = reserved().byte_size();

  assert(min_new_size <= new_size_before &&

         new_size_before <= max_new_size,

         "just checking");

  // All space sizes must be multiples of Generation::GenGrain.

  size_t alignment = Generation::GenGrain;

  int threads_count = 0;

  size_t thread_increase_size = 0;

  size_t new_size_candidate = old_size / NewRatio;

  // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease

  // and reverts to previous value if any overflow happens

  size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment);

  // Adjust new generation size

  desired_new_size = clamp(desired_new_size, min_new_size, max_new_size);

  assert(desired_new_size <= max_new_size, "just checking");

  bool changed = false;

  if (desired_new_size > new_size_before) {

    size_t change = desired_new_size - new_size_before;

    assert(change % alignment == 0, "just checking");

    if (expand(change)) {

       changed = true;

    }

    // If the heap failed to expand to the desired size,

    // "changed" will be false.  If the expansion failed

    // (and at this point it was expected to succeed),

    // ignore the failure (leaving "changed" as false).

  }

  if (desired_new_size < new_size_before && eden()->is_empty()) {

    // bail out of shrinking if objects in eden

    size_t change = new_size_before - desired_new_size;

    assert(change % alignment == 0, "just checking");

    _virtual_space.shrink_by(change);

    changed = true;

  }

  if (changed) {

    // The spaces have already been mangled at this point but

    // may not have been cleared (set top = bottom) and should be.

    // Mangling was done when the heap was being expanded.

    compute_space_boundaries(eden()->used(),

                             SpaceDecorator::Clear,

                             SpaceDecorator::DontMangle);

    MemRegion cmr((HeapWord*)_virtual_space.low(),

                  (HeapWord*)_virtual_space.high());

    gch->rem_set()->resize_covered_region(cmr);

    log_debug(gc, ergo, heap)(

        "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",

        new_size_before/K, _virtual_space.committed_size()/K,

        eden()->capacity()/K, from()->capacity()/K);

    log_trace(gc, ergo, heap)(

        "  [allowed " SIZE_FORMAT "K extra for %d threads]",

          thread_increase_size/K, threads_count);

      }

}

void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) {

  assert(false, "NYI -- are you sure you want to call this?");

}

size_t DefNewGeneration::capacity() const {

  return eden()->capacity()

       + from()->capacity();  // to() is only used during scavenge

}

size_t DefNewGeneration::used() const {

  return eden()->used()

       + from()->used();      // to() is only used during scavenge

}

size_t DefNewGeneration::free() const {

  return eden()->free()

       + from()->free();      // to() is only used during scavenge

}

size_t DefNewGeneration::max_capacity() const {

  const size_t reserved_bytes = reserved().byte_size();

  return reserved_bytes - compute_survivor_size(reserved_bytes, SpaceAlignment);

}

size_t DefNewGeneration::unsafe_max_alloc_nogc() const {

  return eden()->free();

}

size_t DefNewGeneration::capacity_before_gc() const {

  return eden()->capacity();

}

size_t DefNewGeneration::contiguous_available() const {

  return eden()->free();

}

HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); }

HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }

void DefNewGeneration::object_iterate(ObjectClosure* blk) {

  eden()->object_iterate(blk);

  from()->object_iterate(blk);

}

void DefNewGeneration::space_iterate(SpaceClosure* blk,

                                     bool usedOnly) {

  blk->do_space(eden());

  blk->do_space(from());

  blk->do_space(to());

}

// The last collection bailed out, we are running out of heap space,

// so we try to allocate the from-space, too.

HeapWord* DefNewGeneration::allocate_from_space(size_t size) {

  bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc();

  // If the Heap_lock is not locked by this thread, this will be called

  // again later with the Heap_lock held.

  bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()));

  HeapWord* result = NULL;