Google Git
Sign in
cobalt / cobalt / f9bc0139df6e6eb149345ab9b6ffcc40603fc09f / . / third_party / v8 / src / heap / heap.cc
blob: 77d673af9a0ba57596f1301bd78cef367a98c212 [file] [log] [blame]
// Copyright 2012 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "src/heap/heap.h"
#include <atomic>
#include <cinttypes>
#include <iomanip>
#include <memory>
#include <unordered_map>
#include <unordered_set>
#include "src/api/api-inl.h"
#include "src/base/bits.h"
#include "src/base/flags.h"
#include "src/base/once.h"
#include "src/base/platform/mutex.h"
#include "src/base/utils/random-number-generator.h"
#include "src/builtins/accessors.h"
#include "src/codegen/assembler-inl.h"
#include "src/codegen/compilation-cache.h"
#include "src/common/assert-scope.h"
#include "src/common/globals.h"
#include "src/debug/debug.h"
#include "src/deoptimizer/deoptimizer.h"
#include "src/execution/isolate-utils-inl.h"
#include "src/execution/microtask-queue.h"
#include "src/execution/runtime-profiler.h"
#include "src/execution/v8threads.h"
#include "src/execution/vm-state-inl.h"
#include "src/handles/global-handles.h"
#include "src/heap/array-buffer-sweeper.h"
#include "src/heap/barrier.h"
#include "src/heap/base/stack.h"
#include "src/heap/code-object-registry.h"
#include "src/heap/code-stats.h"
#include "src/heap/collection-barrier.h"
#include "src/heap/combined-heap.h"
#include "src/heap/concurrent-allocator.h"
#include "src/heap/concurrent-marking.h"
#include "src/heap/embedder-tracing.h"
#include "src/heap/finalization-registry-cleanup-task.h"
#include "src/heap/gc-idle-time-handler.h"
#include "src/heap/gc-tracer.h"
#include "src/heap/heap-controller.h"
#include "src/heap/heap-write-barrier-inl.h"
#include "src/heap/incremental-marking-inl.h"
#include "src/heap/incremental-marking.h"
#include "src/heap/large-spaces.h"
#include "src/heap/local-heap.h"
#include "src/heap/mark-compact-inl.h"
#include "src/heap/mark-compact.h"
#include "src/heap/marking-barrier-inl.h"
#include "src/heap/marking-barrier.h"
#include "src/heap/memory-chunk-inl.h"
#include "src/heap/memory-measurement.h"
#include "src/heap/memory-reducer.h"
#include "src/heap/object-stats.h"
#include "src/heap/objects-visiting-inl.h"
#include "src/heap/objects-visiting.h"
#include "src/heap/paged-spaces-inl.h"
#include "src/heap/read-only-heap.h"
#include "src/heap/remembered-set.h"
#include "src/heap/safepoint.h"
#include "src/heap/scavenge-job.h"
#include "src/heap/scavenger-inl.h"
#include "src/heap/stress-marking-observer.h"
#include "src/heap/stress-scavenge-observer.h"
#include "src/heap/sweeper.h"
#include "src/init/bootstrapper.h"
#include "src/init/v8.h"
#include "src/interpreter/interpreter.h"
#include "src/logging/log.h"
#include "src/numbers/conversions.h"
#include "src/objects/data-handler.h"
#include "src/objects/feedback-vector.h"
#include "src/objects/free-space-inl.h"
#include "src/objects/hash-table-inl.h"
#include "src/objects/maybe-object.h"
#include "src/objects/shared-function-info.h"
#include "src/objects/slots-atomic-inl.h"
#include "src/objects/slots-inl.h"
#include "src/regexp/regexp.h"
#include "src/snapshot/embedded/embedded-data.h"
#include "src/snapshot/serializer-deserializer.h"
#include "src/snapshot/snapshot.h"
#include "src/strings/string-stream.h"
#include "src/strings/unicode-decoder.h"
#include "src/strings/unicode-inl.h"
#include "src/tracing/trace-event.h"
#include "src/utils/utils-inl.h"
#include "src/utils/utils.h"
#ifdef V8_ENABLE_CONSERVATIVE_STACK_SCANNING
#include "src/heap/conservative-stack-visitor.h"
#endif
#include "src/base/platform/wrappers.h"
// Has to be the last include (doesn't have include guards):
#include "src/objects/object-macros.h"
namespace v8 {
namespace internal {
#ifdef V8_ENABLE_THIRD_PARTY_HEAP
Isolate* Heap::GetIsolateFromWritableObject(HeapObject object) {
return reinterpret_cast<Isolate*>(
third_party_heap::Heap::GetIsolate(object.address()));
}
#endif
// These are outside the Heap class so they can be forward-declared
// in heap-write-barrier-inl.h.
bool Heap_PageFlagsAreConsistent(HeapObject object) {
return Heap::PageFlagsAreConsistent(object);
}
void Heap_GenerationalBarrierSlow(HeapObject object, Address slot,
HeapObject value) {
Heap::GenerationalBarrierSlow(object, slot, value);
}
void Heap_WriteBarrierForCodeSlow(Code host) {
Heap::WriteBarrierForCodeSlow(host);
}
void Heap_GenerationalBarrierForCodeSlow(Code host, RelocInfo* rinfo,
HeapObject object) {
Heap::GenerationalBarrierForCodeSlow(host, rinfo, object);
}
void Heap_GenerationalEphemeronKeyBarrierSlow(Heap* heap,
EphemeronHashTable table,
Address slot) {
heap->RecordEphemeronKeyWrite(table, slot);
}
void Heap::SetArgumentsAdaptorDeoptPCOffset(int pc_offset) {
DCHECK_EQ(Smi::zero(), arguments_adaptor_deopt_pc_offset());
set_arguments_adaptor_deopt_pc_offset(Smi::FromInt(pc_offset));
}
void Heap::SetConstructStubCreateDeoptPCOffset(int pc_offset) {
DCHECK_EQ(Smi::zero(), construct_stub_create_deopt_pc_offset());
set_construct_stub_create_deopt_pc_offset(Smi::FromInt(pc_offset));
}
void Heap::SetConstructStubInvokeDeoptPCOffset(int pc_offset) {
DCHECK_EQ(Smi::zero(), construct_stub_invoke_deopt_pc_offset());
set_construct_stub_invoke_deopt_pc_offset(Smi::FromInt(pc_offset));
}
void Heap::SetInterpreterEntryReturnPCOffset(int pc_offset) {
DCHECK_EQ(Smi::zero(), interpreter_entry_return_pc_offset());
set_interpreter_entry_return_pc_offset(Smi::FromInt(pc_offset));
}
void Heap::SetSerializedObjects(FixedArray objects) {
DCHECK(isolate()->serializer_enabled());
set_serialized_objects(objects);
}
void Heap::SetSerializedGlobalProxySizes(FixedArray sizes) {
DCHECK(isolate()->serializer_enabled());
set_serialized_global_proxy_sizes(sizes);
}
void Heap::SetBasicBlockProfilingData(Handle<ArrayList> list) {
set_basic_block_profiling_data(*list);
}
bool Heap::GCCallbackTuple::operator==(
const Heap::GCCallbackTuple& other) const {
return other.callback == callback && other.data == data;
}
Heap::GCCallbackTuple& Heap::GCCallbackTuple::operator=(
const Heap::GCCallbackTuple& other) V8_NOEXCEPT = default;
class ScavengeTaskObserver : public AllocationObserver {
public:
ScavengeTaskObserver(Heap* heap, intptr_t step_size)
: AllocationObserver(step_size), heap_(heap) {}
void Step(int bytes_allocated, Address, size_t) override {
heap_->ScheduleScavengeTaskIfNeeded();
}
private:
Heap* heap_;
};
Heap::Heap()
: isolate_(isolate()),
memory_pressure_level_(MemoryPressureLevel::kNone),
global_pretenuring_feedback_(kInitialFeedbackCapacity),
safepoint_(new GlobalSafepoint(this)),
external_string_table_(this),
collection_barrier_(new CollectionBarrier(this)) {
// Ensure old_generation_size_ is a multiple of kPageSize.
DCHECK_EQ(0, max_old_generation_size() & (Page::kPageSize - 1));
set_native_contexts_list(Smi::zero());
set_allocation_sites_list(Smi::zero());
set_dirty_js_finalization_registries_list(Smi::zero());
set_dirty_js_finalization_registries_list_tail(Smi::zero());
// Put a dummy entry in the remembered pages so we can find the list the
// minidump even if there are no real unmapped pages.
RememberUnmappedPage(kNullAddress, false);
}
Heap::~Heap() = default;
size_t Heap::MaxReserved() {
const size_t kMaxNewLargeObjectSpaceSize = max_semi_space_size_;
return static_cast<size_t>(2 * max_semi_space_size_ +
kMaxNewLargeObjectSpaceSize +
max_old_generation_size());
}
size_t Heap::YoungGenerationSizeFromOldGenerationSize(size_t old_generation) {
// Compute the semi space size and cap it.
size_t ratio = old_generation <= kOldGenerationLowMemory
? kOldGenerationToSemiSpaceRatioLowMemory
: kOldGenerationToSemiSpaceRatio;
size_t semi_space = old_generation / ratio;
semi_space = Min<size_t>(semi_space, kMaxSemiSpaceSize);
semi_space = Max<size_t>(semi_space, kMinSemiSpaceSize);
semi_space = RoundUp(semi_space, Page::kPageSize);
return YoungGenerationSizeFromSemiSpaceSize(semi_space);
}
size_t Heap::HeapSizeFromPhysicalMemory(uint64_t physical_memory) {
// Compute the old generation size and cap it.
uint64_t old_generation = physical_memory /
kPhysicalMemoryToOldGenerationRatio *
kHeapLimitMultiplier;
old_generation =
Min<uint64_t>(old_generation, MaxOldGenerationSize(physical_memory));
old_generation = Max<uint64_t>(old_generation, V8HeapTrait::kMinSize);
old_generation = RoundUp(old_generation, Page::kPageSize);
size_t young_generation = YoungGenerationSizeFromOldGenerationSize(
static_cast<size_t>(old_generation));
return static_cast<size_t>(old_generation) + young_generation;
}
void Heap::GenerationSizesFromHeapSize(size_t heap_size,
size_t* young_generation_size,
size_t* old_generation_size) {
// Initialize values for the case when the given heap size is too small.
*young_generation_size = 0;
*old_generation_size = 0;
// Binary search for the largest old generation size that fits to the given
// heap limit considering the correspondingly sized young generation.
size_t lower = 0, upper = heap_size;
while (lower + 1 < upper) {
size_t old_generation = lower + (upper - lower) / 2;
size_t young_generation =
YoungGenerationSizeFromOldGenerationSize(old_generation);
if (old_generation + young_generation <= heap_size) {
// This size configuration fits into the given heap limit.
*young_generation_size = young_generation;
*old_generation_size = old_generation;
lower = old_generation;
} else {
upper = old_generation;
}
}
}
size_t Heap::MinYoungGenerationSize() {
return YoungGenerationSizeFromSemiSpaceSize(kMinSemiSpaceSize);
}
size_t Heap::MinOldGenerationSize() {
size_t paged_space_count =
LAST_GROWABLE_PAGED_SPACE - FIRST_GROWABLE_PAGED_SPACE + 1;
return paged_space_count * Page::kPageSize;
}
size_t Heap::AllocatorLimitOnMaxOldGenerationSize() {
#ifdef V8_COMPRESS_POINTERS
// Isolate and the young generation are also allocated on the heap.
return kPtrComprHeapReservationSize -
YoungGenerationSizeFromSemiSpaceSize(kMaxSemiSpaceSize) -
RoundUp(sizeof(Isolate), size_t{1} << kPageSizeBits);
#endif
return std::numeric_limits<size_t>::max();
}
size_t Heap::MaxOldGenerationSize(uint64_t physical_memory) {
size_t max_size = V8HeapTrait::kMaxSize;
// Finch experiment: Increase the heap size from 2GB to 4GB for 64-bit
// systems with physical memory bigger than 16GB. The physical memory
// is rounded up to GB.
constexpr bool x64_bit = Heap::kHeapLimitMultiplier >= 2;
if (FLAG_huge_max_old_generation_size && x64_bit &&
(physical_memory + 512 * MB) / GB >= 16) {
DCHECK_EQ(max_size / GB, 2);
max_size *= 2;
}
return Min(max_size, AllocatorLimitOnMaxOldGenerationSize());
}
size_t Heap::YoungGenerationSizeFromSemiSpaceSize(size_t semi_space_size) {
return semi_space_size * (2 + kNewLargeObjectSpaceToSemiSpaceRatio);
}
size_t Heap::SemiSpaceSizeFromYoungGenerationSize(
size_t young_generation_size) {
return young_generation_size / (2 + kNewLargeObjectSpaceToSemiSpaceRatio);
}
size_t Heap::Capacity() {
if (!HasBeenSetUp()) return 0;
return new_space_->Capacity() + OldGenerationCapacity();
}
size_t Heap::OldGenerationCapacity() {
if (!HasBeenSetUp()) return 0;
PagedSpaceIterator spaces(this);
size_t total = 0;
for (PagedSpace* space = spaces.Next(); space != nullptr;
space = spaces.Next()) {
total += space->Capacity();
}
return total + lo_space_->SizeOfObjects() + code_lo_space_->SizeOfObjects();
}
size_t Heap::CommittedOldGenerationMemory() {
if (!HasBeenSetUp()) return 0;
PagedSpaceIterator spaces(this);
size_t total = 0;
for (PagedSpace* space = spaces.Next(); space != nullptr;
space = spaces.Next()) {
total += space->CommittedMemory();
}
return total + lo_space_->Size() + code_lo_space_->Size();
}
size_t Heap::CommittedMemoryOfUnmapper() {
if (!HasBeenSetUp()) return 0;
return memory_allocator()->unmapper()->CommittedBufferedMemory();
}
size_t Heap::CommittedMemory() {
if (!HasBeenSetUp()) return 0;
return new_space_->CommittedMemory() + new_lo_space_->Size() +
CommittedOldGenerationMemory();
}
size_t Heap::CommittedPhysicalMemory() {
if (!HasBeenSetUp()) return 0;
size_t total = 0;
for (SpaceIterator it(this); it.HasNext();) {
total += it.Next()->CommittedPhysicalMemory();
}
return total;
}
size_t Heap::CommittedMemoryExecutable() {
if (!HasBeenSetUp()) return 0;
return static_cast<size_t>(memory_allocator()->SizeExecutable());
}
void Heap::UpdateMaximumCommitted() {
if (!HasBeenSetUp()) return;
const size_t current_committed_memory = CommittedMemory();
if (current_committed_memory > maximum_committed_) {
maximum_committed_ = current_committed_memory;
}
}
size_t Heap::Available() {
if (!HasBeenSetUp()) return 0;
size_t total = 0;
for (SpaceIterator it(this); it.HasNext();) {
total += it.Next()->Available();
}
total += memory_allocator()->Available();
return total;
}
bool Heap::CanExpandOldGeneration(size_t size) {
if (force_oom_ || force_gc_on_next_allocation_) return false;
if (OldGenerationCapacity() + size > max_old_generation_size()) return false;
// The OldGenerationCapacity does not account compaction spaces used
// during evacuation. Ensure that expanding the old generation does push
// the total allocated memory size over the maximum heap size.
return memory_allocator()->Size() + size <= MaxReserved();
}
bool Heap::CanExpandOldGenerationBackground(size_t size) {
if (force_oom_) return false;
// When the heap is tearing down, then GC requests from background threads
// are not served and the threads are allowed to expand the heap to avoid OOM.
return gc_state() == TEAR_DOWN ||
memory_allocator()->Size() + size <= MaxReserved();
}
bool Heap::CanPromoteYoungAndExpandOldGeneration(size_t size) {
// Over-estimate the new space size using capacity to allow some slack.
return CanExpandOldGeneration(size + new_space_->Capacity() +
new_lo_space_->Size());
}
bool Heap::HasBeenSetUp() const {
// We will always have a new space when the heap is set up.
return new_space_ != nullptr;
}
GarbageCollector Heap::SelectGarbageCollector(AllocationSpace space,
const char** reason) {
// Is global GC requested?
if (space != NEW_SPACE && space != NEW_LO_SPACE) {
isolate_->counters()->gc_compactor_caused_by_request()->Increment();
*reason = "GC in old space requested";
return MARK_COMPACTOR;
}
if (FLAG_gc_global || ShouldStressCompaction()) {
*reason = "GC in old space forced by flags";
return MARK_COMPACTOR;
}
if (incremental_marking()->NeedsFinalization() &&
AllocationLimitOvershotByLargeMargin()) {
*reason = "Incremental marking needs finalization";
return MARK_COMPACTOR;
}
if (!CanPromoteYoungAndExpandOldGeneration(0)) {
isolate_->counters()
->gc_compactor_caused_by_oldspace_exhaustion()
->Increment();
*reason = "scavenge might not succeed";
return MARK_COMPACTOR;
}
// Default
*reason = nullptr;
return YoungGenerationCollector();
}
void Heap::SetGCState(HeapState state) {
gc_state_.store(state, std::memory_order_relaxed);
}
void Heap::PrintShortHeapStatistics() {
if (!FLAG_trace_gc_verbose) return;
PrintIsolate(isolate_,
"Memory allocator, used: %6zu KB,"
" available: %6zu KB\n",
memory_allocator()->Size() / KB,
memory_allocator()->Available() / KB);
PrintIsolate(isolate_,
"Read-only space, used: %6zu KB"
", available: %6zu KB"
", committed: %6zu KB\n",
read_only_space_->Size() / KB, size_t{0},
read_only_space_->CommittedMemory() / KB);
PrintIsolate(isolate_,
"New space, used: %6zu KB"
", available: %6zu KB"
", committed: %6zu KB\n",
new_space_->Size() / KB, new_space_->Available() / KB,
new_space_->CommittedMemory() / KB);
PrintIsolate(isolate_,
"New large object space, used: %6zu KB"
", available: %6zu KB"
", committed: %6zu KB\n",
new_lo_space_->SizeOfObjects() / KB,
new_lo_space_->Available() / KB,
new_lo_space_->CommittedMemory() / KB);
PrintIsolate(isolate_,
"Old space, used: %6zu KB"
", available: %6zu KB"
", committed: %6zu KB\n",
old_space_->SizeOfObjects() / KB, old_space_->Available() / KB,
old_space_->CommittedMemory() / KB);
PrintIsolate(isolate_,
"Code space, used: %6zu KB"
", available: %6zu KB"
", committed: %6zu KB\n",
code_space_->SizeOfObjects() / KB, code_space_->Available() / KB,
code_space_->CommittedMemory() / KB);
PrintIsolate(isolate_,
"Map space, used: %6zu KB"
", available: %6zu KB"
", committed: %6zu KB\n",
map_space_->SizeOfObjects() / KB, map_space_->Available() / KB,
map_space_->CommittedMemory() / KB);
PrintIsolate(isolate_,
"Large object space, used: %6zu KB"
", available: %6zu KB"
", committed: %6zu KB\n",
lo_space_->SizeOfObjects() / KB, lo_space_->Available() / KB,
lo_space_->CommittedMemory() / KB);
PrintIsolate(isolate_,
"Code large object space, used: %6zu KB"
", available: %6zu KB"
", committed: %6zu KB\n",
code_lo_space_->SizeOfObjects() / KB,
code_lo_space_->Available() / KB,
code_lo_space_->CommittedMemory() / KB);
ReadOnlySpace* const ro_space = read_only_space_;
PrintIsolate(isolate_,
"All spaces, used: %6zu KB"
", available: %6zu KB"
", committed: %6zu KB\n",
(this->SizeOfObjects() + ro_space->Size()) / KB,
(this->Available()) / KB,
(this->CommittedMemory() + ro_space->CommittedMemory()) / KB);
PrintIsolate(isolate_,
"Unmapper buffering %zu chunks of committed: %6zu KB\n",
memory_allocator()->unmapper()->NumberOfCommittedChunks(),
CommittedMemoryOfUnmapper() / KB);
PrintIsolate(isolate_, "External memory reported: %6" PRId64 " KB\n",
external_memory_.total() / KB);
PrintIsolate(isolate_, "Backing store memory: %6zu KB\n",
backing_store_bytes_ / KB);
PrintIsolate(isolate_, "External memory global %zu KB\n",
external_memory_callback_() / KB);
PrintIsolate(isolate_, "Total time spent in GC : %.1f ms\n",
total_gc_time_ms_);
}
void Heap::PrintFreeListsStats() {
DCHECK(FLAG_trace_gc_freelists);
if (FLAG_trace_gc_freelists_verbose) {
PrintIsolate(isolate_,
"Freelists statistics per Page: "
"[category: length || total free bytes]\n");
}
std::vector<int> categories_lengths(
old_space()->free_list()->number_of_categories(), 0);
std::vector<size_t> categories_sums(
old_space()->free_list()->number_of_categories(), 0);
unsigned int pageCnt = 0;
// This loops computes freelists lengths and sum.
// If FLAG_trace_gc_freelists_verbose is enabled, it also prints
// the stats of each FreeListCategory of each Page.
for (Page* page : *old_space()) {
std::ostringstream out_str;
if (FLAG_trace_gc_freelists_verbose) {
out_str << "Page " << std::setw(4) << pageCnt;
}
for (int cat = kFirstCategory;
cat <= old_space()->free_list()->last_category(); cat++) {
FreeListCategory* free_list =
page->free_list_category(static_cast<FreeListCategoryType>(cat));
int length = free_list->FreeListLength();
size_t sum = free_list->SumFreeList();
if (FLAG_trace_gc_freelists_verbose) {
out_str << "[" << cat << ": " << std::setw(4) << length << " || "
<< std::setw(6) << sum << " ]"
<< (cat == old_space()->free_list()->last_category() ? "\n"
: ", ");
}
categories_lengths[cat] += length;
categories_sums[cat] += sum;
}
if (FLAG_trace_gc_freelists_verbose) {
PrintIsolate(isolate_, "%s", out_str.str().c_str());
}
pageCnt++;
}
// Print statistics about old_space (pages, free/wasted/used memory...).
PrintIsolate(
isolate_,
"%d pages. Free space: %.1f MB (waste: %.2f). "
"Usage: %.1f/%.1f (MB) -> %.2f%%.\n",
pageCnt, static_cast<double>(old_space_->Available()) / MB,
static_cast<double>(old_space_->Waste()) / MB,
static_cast<double>(old_space_->Size()) / MB,
static_cast<double>(old_space_->Capacity()) / MB,
static_cast<double>(old_space_->Size()) / old_space_->Capacity() * 100);
// Print global statistics of each FreeListCategory (length & sum).
PrintIsolate(isolate_,
"FreeLists global statistics: "
"[category: length || total free KB]\n");
std::ostringstream out_str;
for (int cat = kFirstCategory;
cat <= old_space()->free_list()->last_category(); cat++) {
out_str << "[" << cat << ": " << categories_lengths[cat] << " || "
<< std::fixed << std::setprecision(2)
<< static_cast<double>(categories_sums[cat]) / KB << " KB]"
<< (cat == old_space()->free_list()->last_category() ? "\n" : ", ");
}
PrintIsolate(isolate_, "%s", out_str.str().c_str());
}
void Heap::DumpJSONHeapStatistics(std::stringstream& stream) {
HeapStatistics stats;
reinterpret_cast<v8::Isolate*>(isolate())->GetHeapStatistics(&stats);
// clang-format off
#define DICT(s) "{" << s << "}"
#define LIST(s) "[" << s << "]"
#define ESCAPE(s) "\"" << s << "\""
#define MEMBER(s) ESCAPE(s) << ":"
auto SpaceStatistics = [this](int space_index) {
HeapSpaceStatistics space_stats;
reinterpret_cast<v8::Isolate*>(isolate())->GetHeapSpaceStatistics(
&space_stats, space_index);
std::stringstream stream;
stream << DICT(
MEMBER("name")
<< ESCAPE(BaseSpace::GetSpaceName(
static_cast<AllocationSpace>(space_index)))
<< ","
MEMBER("size") << space_stats.space_size() << ","
MEMBER("used_size") << space_stats.space_used_size() << ","
MEMBER("available_size") << space_stats.space_available_size() << ","
MEMBER("physical_size") << space_stats.physical_space_size());
return stream.str();
};
stream << DICT(
MEMBER("isolate") << ESCAPE(reinterpret_cast<void*>(isolate())) << ","
MEMBER("id") << gc_count() << ","
MEMBER("time_ms") << isolate()->time_millis_since_init() << ","
MEMBER("total_heap_size") << stats.total_heap_size() << ","
MEMBER("total_heap_size_executable")
<< stats.total_heap_size_executable() << ","
MEMBER("total_physical_size") << stats.total_physical_size() << ","
MEMBER("total_available_size") << stats.total_available_size() << ","
MEMBER("used_heap_size") << stats.used_heap_size() << ","
MEMBER("heap_size_limit") << stats.heap_size_limit() << ","
MEMBER("malloced_memory") << stats.malloced_memory() << ","
MEMBER("external_memory") << stats.external_memory() << ","
MEMBER("peak_malloced_memory") << stats.peak_malloced_memory() << ","
MEMBER("spaces") << LIST(
SpaceStatistics(RO_SPACE) << "," <<
SpaceStatistics(NEW_SPACE) << "," <<
SpaceStatistics(OLD_SPACE) << "," <<
SpaceStatistics(CODE_SPACE) << "," <<
SpaceStatistics(MAP_SPACE) << "," <<
SpaceStatistics(LO_SPACE) << "," <<
SpaceStatistics(CODE_LO_SPACE) << "," <<
SpaceStatistics(NEW_LO_SPACE)));
#undef DICT
#undef LIST
#undef ESCAPE
#undef MEMBER
// clang-format on
}
void Heap::ReportStatisticsAfterGC() {
for (int i = 0; i < static_cast<int>(v8::Isolate::kUseCounterFeatureCount);
++i) {
int count = deferred_counters_[i];
deferred_counters_[i] = 0;
while (count > 0) {
count--;
isolate()->CountUsage(static_cast<v8::Isolate::UseCounterFeature>(i));
}
}
}
void Heap::AddHeapObjectAllocationTracker(
HeapObjectAllocationTracker* tracker) {
if (allocation_trackers_.empty() && FLAG_inline_new) {
DisableInlineAllocation();
}
allocation_trackers_.push_back(tracker);
}
void Heap::RemoveHeapObjectAllocationTracker(
HeapObjectAllocationTracker* tracker) {
allocation_trackers_.erase(std::remove(allocation_trackers_.begin(),
allocation_trackers_.end(), tracker),
allocation_trackers_.end());
if (allocation_trackers_.empty() && FLAG_inline_new) {
EnableInlineAllocation();
}
}
void Heap::AddRetainingPathTarget(Handle<HeapObject> object,
RetainingPathOption option) {
if (!FLAG_track_retaining_path) {
PrintF("Retaining path tracking requires --track-retaining-path\n");
} else {
Handle<WeakArrayList> array(retaining_path_targets(), isolate());
int index = array->length();
array = WeakArrayList::AddToEnd(isolate(), array,
MaybeObjectHandle::Weak(object));
set_retaining_path_targets(*array);
DCHECK_EQ(array->length(), index + 1);
retaining_path_target_option_[index] = option;
}
}
bool Heap::IsRetainingPathTarget(HeapObject object,
RetainingPathOption* option) {
WeakArrayList targets = retaining_path_targets();
int length = targets.length();
MaybeObject object_to_check = HeapObjectReference::Weak(object);
for (int i = 0; i < length; i++) {
MaybeObject target = targets.Get(i);
DCHECK(target->IsWeakOrCleared());
if (target == object_to_check) {
DCHECK(retaining_path_target_option_.count(i));
*option = retaining_path_target_option_[i];
return true;
}
}
return false;
}
void Heap::PrintRetainingPath(HeapObject target, RetainingPathOption option) {
PrintF("\n\n\n");
PrintF("#################################################\n");
PrintF("Retaining path for %p:\n", reinterpret_cast<void*>(target.ptr()));
HeapObject object = target;
std::vector<std::pair<HeapObject, bool>> retaining_path;
Root root = Root::kUnknown;
bool ephemeron = false;
while (true) {
retaining_path.push_back(std::make_pair(object, ephemeron));
if (option == RetainingPathOption::kTrackEphemeronPath &&
ephemeron_retainer_.count(object)) {
object = ephemeron_retainer_[object];
ephemeron = true;
} else if (retainer_.count(object)) {
object = retainer_[object];
ephemeron = false;
} else {
if (retaining_root_.count(object)) {
root = retaining_root_[object];
}
break;
}
}
int distance = static_cast<int>(retaining_path.size());
for (auto node : retaining_path) {
HeapObject object = node.first;
bool ephemeron = node.second;
PrintF("\n");
PrintF("^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n");
PrintF("Distance from root %d%s: ", distance,
ephemeron ? " (ephemeron)" : "");
object.ShortPrint();
PrintF("\n");
#ifdef OBJECT_PRINT
object.Print();
PrintF("\n");
#endif
--distance;
}
PrintF("\n");
PrintF("^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n");
PrintF("Root: %s\n", RootVisitor::RootName(root));
PrintF("-------------------------------------------------\n");
}
void Heap::AddRetainer(HeapObject retainer, HeapObject object) {
if (retainer_.count(object)) return;
retainer_[object] = retainer;
RetainingPathOption option = RetainingPathOption::kDefault;
if (IsRetainingPathTarget(object, &option)) {
// Check if the retaining path was already printed in
// AddEphemeronRetainer().
if (ephemeron_retainer_.count(object) == 0 ||
option == RetainingPathOption::kDefault) {
PrintRetainingPath(object, option);
}
}
}
void Heap::AddEphemeronRetainer(HeapObject retainer, HeapObject object) {
if (ephemeron_retainer_.count(object)) return;
ephemeron_retainer_[object] = retainer;
RetainingPathOption option = RetainingPathOption::kDefault;
if (IsRetainingPathTarget(object, &option) &&
option == RetainingPathOption::kTrackEphemeronPath) {
// Check if the retaining path was already printed in AddRetainer().
if (retainer_.count(object) == 0) {
PrintRetainingPath(object, option);
}
}
}
void Heap::AddRetainingRoot(Root root, HeapObject object) {
if (retaining_root_.count(object)) return;
retaining_root_[object] = root;
RetainingPathOption option = RetainingPathOption::kDefault;
if (IsRetainingPathTarget(object, &option)) {
PrintRetainingPath(object, option);
}
}
void Heap::IncrementDeferredCount(v8::Isolate::UseCounterFeature feature) {
deferred_counters_[feature]++;
}
bool Heap::UncommitFromSpace() { return new_space_->UncommitFromSpace(); }
void Heap::GarbageCollectionPrologue() {
TRACE_GC(tracer(), GCTracer::Scope::HEAP_PROLOGUE);
// Reset GC statistics.
promoted_objects_size_ = 0;
previous_semi_space_copied_object_size_ = semi_space_copied_object_size_;
semi_space_copied_object_size_ = 0;
nodes_died_in_new_space_ = 0;
nodes_copied_in_new_space_ = 0;
nodes_promoted_ = 0;
UpdateMaximumCommitted();
#ifdef DEBUG
DCHECK(!AllowHeapAllocation::IsAllowed() && gc_state() == NOT_IN_GC);
if (FLAG_gc_verbose) Print();
#endif // DEBUG
if (new_space_->IsAtMaximumCapacity()) {
maximum_size_scavenges_++;
} else {
maximum_size_scavenges_ = 0;
}
if (FLAG_track_retaining_path) {
retainer_.clear();
ephemeron_retainer_.clear();
retaining_root_.clear();
}
memory_allocator()->unmapper()->PrepareForGC();
}
void Heap::GarbageCollectionPrologueInSafepoint() {
TRACE_GC(tracer(), GCTracer::Scope::HEAP_PROLOGUE_SAFEPOINT);
gc_count_++;
UpdateNewSpaceAllocationCounter();
CheckNewSpaceExpansionCriteria();
}
size_t Heap::SizeOfObjects() {
size_t total = 0;
for (SpaceIterator it(this); it.HasNext();) {
total += it.Next()->SizeOfObjects();
}
return total;
}
size_t Heap::TotalGlobalHandlesSize() {
return isolate_->global_handles()->TotalSize();
}
size_t Heap::UsedGlobalHandlesSize() {
return isolate_->global_handles()->UsedSize();
}
void Heap::MergeAllocationSitePretenuringFeedback(
const PretenuringFeedbackMap& local_pretenuring_feedback) {
AllocationSite site;
for (auto& site_and_count : local_pretenuring_feedback) {
site = site_and_count.first;
MapWord map_word = site_and_count.first.map_word();
if (map_word.IsForwardingAddress()) {
site = AllocationSite::cast(map_word.ToForwardingAddress());
}
// We have not validated the allocation site yet, since we have not
// dereferenced the site during collecting information.
// This is an inlined check of AllocationMemento::IsValid.
if (!site.IsAllocationSite() || site.IsZombie()) continue;
const int value = static_cast<int>(site_and_count.second);
DCHECK_LT(0, value);
if (site.IncrementMementoFoundCount(value)) {
// For sites in the global map the count is accessed through the site.
global_pretenuring_feedback_.insert(std::make_pair(site, 0));
}
}
}
void Heap::AddAllocationObserversToAllSpaces(
AllocationObserver* observer, AllocationObserver* new_space_observer) {
DCHECK(observer && new_space_observer);
SafepointScope scope(this);
for (SpaceIterator it(this); it.HasNext();) {
Space* space = it.Next();
if (space == new_space()) {
space->AddAllocationObserver(new_space_observer);
} else {
space->AddAllocationObserver(observer);
}
}
}
void Heap::RemoveAllocationObserversFromAllSpaces(
AllocationObserver* observer, AllocationObserver* new_space_observer) {
DCHECK(observer && new_space_observer);
SafepointScope scope(this);
for (SpaceIterator it(this); it.HasNext();) {
Space* space = it.Next();
if (space == new_space()) {
space->RemoveAllocationObserver(new_space_observer);
} else {
space->RemoveAllocationObserver(observer);
}
}
}
namespace {
inline bool MakePretenureDecision(
AllocationSite site, AllocationSite::PretenureDecision current_decision,
double ratio, bool maximum_size_scavenge) {
// Here we just allow state transitions from undecided or maybe tenure
// to don't tenure, maybe tenure, or tenure.
if ((current_decision == AllocationSite::kUndecided ||
current_decision == AllocationSite::kMaybeTenure)) {
if (ratio >= AllocationSite::kPretenureRatio) {
// We just transition into tenure state when the semi-space was at
// maximum capacity.
if (maximum_size_scavenge) {
site.set_deopt_dependent_code(true);
site.set_pretenure_decision(AllocationSite::kTenure);
// Currently we just need to deopt when we make a state transition to
// tenure.
return true;
}
site.set_pretenure_decision(AllocationSite::kMaybeTenure);
} else {
site.set_pretenure_decision(AllocationSite::kDontTenure);
}
}
return false;
}
inline bool DigestPretenuringFeedback(Isolate* isolate, AllocationSite site,
bool maximum_size_scavenge) {
bool deopt = false;
int create_count = site.memento_create_count();
int found_count = site.memento_found_count();
bool minimum_mementos_created =
create_count >= AllocationSite::kPretenureMinimumCreated;
double ratio = minimum_mementos_created || FLAG_trace_pretenuring_statistics
? static_cast<double>(found_count) / create_count
: 0.0;
AllocationSite::PretenureDecision current_decision =
site.pretenure_decision();
if (minimum_mementos_created) {
deopt = MakePretenureDecision(site, current_decision, ratio,
maximum_size_scavenge);
}
if (FLAG_trace_pretenuring_statistics) {
PrintIsolate(isolate,
"pretenuring: AllocationSite(%p): (created, found, ratio) "
"(%d, %d, %f) %s => %s\n",
reinterpret_cast<void*>(site.ptr()), create_count, found_count,
ratio, site.PretenureDecisionName(current_decision),
site.PretenureDecisionName(site.pretenure_decision()));
}
// Clear feedback calculation fields until the next gc.
site.set_memento_found_count(0);
site.set_memento_create_count(0);
return deopt;
}
} // namespace
void Heap::RemoveAllocationSitePretenuringFeedback(AllocationSite site) {
global_pretenuring_feedback_.erase(site);
}
bool Heap::DeoptMaybeTenuredAllocationSites() {
return new_space_->IsAtMaximumCapacity() && maximum_size_scavenges_ == 0;
}
void Heap::ProcessPretenuringFeedback() {
bool trigger_deoptimization = false;
if (FLAG_allocation_site_pretenuring) {
int tenure_decisions = 0;
int dont_tenure_decisions = 0;
int allocation_mementos_found = 0;
int allocation_sites = 0;
int active_allocation_sites = 0;
AllocationSite site;
// Step 1: Digest feedback for recorded allocation sites.
bool maximum_size_scavenge = MaximumSizeScavenge();
for (auto& site_and_count : global_pretenuring_feedback_) {
allocation_sites++;
site = site_and_count.first;
// Count is always access through the site.
DCHECK_EQ(0, site_and_count.second);
int found_count = site.memento_found_count();
// An entry in the storage does not imply that the count is > 0 because
// allocation sites might have been reset due to too many objects dying
// in old space.
if (found_count > 0) {
DCHECK(site.IsAllocationSite());
active_allocation_sites++;
allocation_mementos_found += found_count;
if (DigestPretenuringFeedback(isolate_, site, maximum_size_scavenge)) {
trigger_deoptimization = true;
}
if (site.GetAllocationType() == AllocationType::kOld) {
tenure_decisions++;
} else {
dont_tenure_decisions++;
}
}
}
// Step 2: Deopt maybe tenured allocation sites if necessary.
bool deopt_maybe_tenured = DeoptMaybeTenuredAllocationSites();
if (deopt_maybe_tenured) {
ForeachAllocationSite(
allocation_sites_list(),
[&allocation_sites, &trigger_deoptimization](AllocationSite site) {
DCHECK(site.IsAllocationSite());
allocation_sites++;
if (site.IsMaybeTenure()) {
site.set_deopt_dependent_code(true);
trigger_deoptimization = true;
}
});
}
if (trigger_deoptimization) {
isolate_->stack_guard()->RequestDeoptMarkedAllocationSites();
}
if (FLAG_trace_pretenuring_statistics &&
(allocation_mementos_found > 0 || tenure_decisions > 0 ||
dont_tenure_decisions > 0)) {
PrintIsolate(isolate(),
"pretenuring: deopt_maybe_tenured=%d visited_sites=%d "
"active_sites=%d "
"mementos=%d tenured=%d not_tenured=%d\n",
deopt_maybe_tenured ? 1 : 0, allocation_sites,
active_allocation_sites, allocation_mementos_found,
tenure_decisions, dont_tenure_decisions);
}
global_pretenuring_feedback_.clear();
global_pretenuring_feedback_.reserve(kInitialFeedbackCapacity);
}
}
void Heap::InvalidateCodeDeoptimizationData(Code code) {
CodePageMemoryModificationScope modification_scope(code);
code.set_deoptimization_data(ReadOnlyRoots(this).empty_fixed_array());
}
void Heap::DeoptMarkedAllocationSites() {
// TODO(hpayer): If iterating over the allocation sites list becomes a
// performance issue, use a cache data structure in heap instead.
ForeachAllocationSite(allocation_sites_list(), [](AllocationSite site) {
if (site.deopt_dependent_code()) {
site.dependent_code().MarkCodeForDeoptimization(
DependentCode::kAllocationSiteTenuringChangedGroup);
site.set_deopt_dependent_code(false);
}
});
Deoptimizer::DeoptimizeMarkedCode(isolate_);
}
void Heap::GarbageCollectionEpilogueInSafepoint(GarbageCollector collector) {
if (collector == MARK_COMPACTOR) {
memory_pressure_level_.store(MemoryPressureLevel::kNone,
std::memory_order_relaxed);
}
TRACE_GC(tracer(), GCTracer::Scope::HEAP_EPILOGUE_SAFEPOINT);
#define UPDATE_COUNTERS_FOR_SPACE(space) \
isolate_->counters()->space##_bytes_available()->Set( \
static_cast<int>(space()->Available())); \
isolate_->counters()->space##_bytes_committed()->Set( \
static_cast<int>(space()->CommittedMemory())); \
isolate_->counters()->space##_bytes_used()->Set( \
static_cast<int>(space()->SizeOfObjects()));
#define UPDATE_FRAGMENTATION_FOR_SPACE(space) \
if (space()->CommittedMemory() > 0) { \
isolate_->counters()->external_fragmentation_##space()->AddSample( \
static_cast<int>(100 - (space()->SizeOfObjects() * 100.0) / \
space()->CommittedMemory())); \
}
#define UPDATE_COUNTERS_AND_FRAGMENTATION_FOR_SPACE(space) \
UPDATE_COUNTERS_FOR_SPACE(space) \
UPDATE_FRAGMENTATION_FOR_SPACE(space)
UPDATE_COUNTERS_FOR_SPACE(new_space)
UPDATE_COUNTERS_AND_FRAGMENTATION_FOR_SPACE(old_space)
UPDATE_COUNTERS_AND_FRAGMENTATION_FOR_SPACE(code_space)
UPDATE_COUNTERS_AND_FRAGMENTATION_FOR_SPACE(map_space)
UPDATE_COUNTERS_AND_FRAGMENTATION_FOR_SPACE(lo_space)
#undef UPDATE_COUNTERS_FOR_SPACE
#undef UPDATE_FRAGMENTATION_FOR_SPACE
#undef UPDATE_COUNTERS_AND_FRAGMENTATION_FOR_SPACE
#ifdef DEBUG
// Old-to-new slot sets must be empty after each collection.
for (SpaceIterator it(this); it.HasNext();) {
Space* space = it.Next();
for (MemoryChunk* chunk = space->first_page(); chunk != space->last_page();
chunk = chunk->list_node().next())
DCHECK_NULL(chunk->invalidated_slots<OLD_TO_NEW>());
}
if (FLAG_print_global_handles) isolate_->global_handles()->Print();
if (FLAG_print_handles) PrintHandles();
if (FLAG_gc_verbose) Print();
if (FLAG_code_stats) ReportCodeStatistics("After GC");
if (FLAG_check_handle_count) CheckHandleCount();
#endif
if (Heap::ShouldZapGarbage() || FLAG_clear_free_memory) {
ZapFromSpace();
}
{
TRACE_GC(tracer(), GCTracer::Scope::HEAP_EPILOGUE_REDUCE_NEW_SPACE);
ReduceNewSpaceSize();
}
// Resume all threads waiting for the GC.
collection_barrier_->ResumeThreadsAwaitingCollection();
}
void Heap::GarbageCollectionEpilogue() {
TRACE_GC(tracer(), GCTracer::Scope::HEAP_EPILOGUE);
AllowHeapAllocation for_the_rest_of_the_epilogue;
UpdateMaximumCommitted();
isolate_->counters()->alive_after_last_gc()->Set(
static_cast<int>(SizeOfObjects()));
isolate_->counters()->string_table_capacity()->Set(
isolate()->string_table()->Capacity());
isolate_->counters()->number_of_symbols()->Set(
isolate()->string_table()->NumberOfElements());
if (CommittedMemory() > 0) {
isolate_->counters()->external_fragmentation_total()->AddSample(
static_cast<int>(100 - (SizeOfObjects() * 100.0) / CommittedMemory()));
isolate_->counters()->heap_sample_total_committed()->AddSample(
static_cast<int>(CommittedMemory() / KB));
isolate_->counters()->heap_sample_total_used()->AddSample(
static_cast<int>(SizeOfObjects() / KB));
isolate_->counters()->heap_sample_map_space_committed()->AddSample(
static_cast<int>(map_space()->CommittedMemory() / KB));
isolate_->counters()->heap_sample_code_space_committed()->AddSample(
static_cast<int>(code_space()->CommittedMemory() / KB));
isolate_->counters()->heap_sample_maximum_committed()->AddSample(
static_cast<int>(MaximumCommittedMemory() / KB));
}
#ifdef DEBUG
ReportStatisticsAfterGC();
#endif // DEBUG
last_gc_time_ = MonotonicallyIncreasingTimeInMs();
}
class GCCallbacksScope {
public:
explicit GCCallbacksScope(Heap* heap) : heap_(heap) {
heap_->gc_callbacks_depth_++;
}
~GCCallbacksScope() { heap_->gc_callbacks_depth_--; }
bool CheckReenter() { return heap_->gc_callbacks_depth_ == 1; }
private:
Heap* heap_;
};
void Heap::HandleGCRequest() {
if (FLAG_stress_scavenge > 0 && stress_scavenge_observer_->HasRequestedGC()) {
CollectAllGarbage(NEW_SPACE, GarbageCollectionReason::kTesting);
stress_scavenge_observer_->RequestedGCDone();
} else if (HighMemoryPressure()) {
incremental_marking()->reset_request_type();
CheckMemoryPressure();
} else if (CollectionRequested()) {
CheckCollectionRequested();
} else if (incremental_marking()->request_type() ==
IncrementalMarking::COMPLETE_MARKING) {
incremental_marking()->reset_request_type();
CollectAllGarbage(current_gc_flags_,
GarbageCollectionReason::kFinalizeMarkingViaStackGuard,
current_gc_callback_flags_);
} else if (incremental_marking()->request_type() ==
IncrementalMarking::FINALIZATION &&
incremental_marking()->IsMarking() &&
!incremental_marking()->finalize_marking_completed()) {
incremental_marking()->reset_request_type();
FinalizeIncrementalMarkingIncrementally(
GarbageCollectionReason::kFinalizeMarkingViaStackGuard);
}
}
void Heap::ScheduleScavengeTaskIfNeeded() {
DCHECK_NOT_NULL(scavenge_job_);
scavenge_job_->ScheduleTaskIfNeeded(this);
}
TimedHistogram* Heap::GCTypePriorityTimer(GarbageCollector collector) {
if (IsYoungGenerationCollector(collector)) {
if (isolate_->IsIsolateInBackground()) {
return isolate_->counters()->gc_scavenger_background();
}
return isolate_->counters()->gc_scavenger_foreground();
} else {
if (!incremental_marking()->IsStopped()) {
if (ShouldReduceMemory()) {
if (isolate_->IsIsolateInBackground()) {
return isolate_->counters()->gc_finalize_reduce_memory_background();
}
return isolate_->counters()->gc_finalize_reduce_memory_foreground();
} else {
if (isolate_->IsIsolateInBackground()) {
return isolate_->counters()->gc_finalize_background();
}
return isolate_->counters()->gc_finalize_foreground();
}
} else {
if (isolate_->IsIsolateInBackground()) {
return isolate_->counters()->gc_compactor_background();
}
return isolate_->counters()->gc_compactor_foreground();
}
}
}
TimedHistogram* Heap::GCTypeTimer(GarbageCollector collector) {
if (IsYoungGenerationCollector(collector)) {
return isolate_->counters()->gc_scavenger();
}
if (incremental_marking()->IsStopped()) {
return isolate_->counters()->gc_compactor();
}
if (ShouldReduceMemory()) {
return isolate_->counters()->gc_finalize_reduce_memory();
}
if (incremental_marking()->IsMarking() &&
incremental_marking()->local_marking_worklists()->IsPerContextMode()) {
return isolate_->counters()->gc_finalize_measure_memory();
}
return isolate_->counters()->gc_finalize();
}
void Heap::CollectAllGarbage(int flags, GarbageCollectionReason gc_reason,
const v8::GCCallbackFlags gc_callback_flags) {
// Since we are ignoring the return value, the exact choice of space does
// not matter, so long as we do not specify NEW_SPACE, which would not
// cause a full GC.
set_current_gc_flags(flags);
CollectGarbage(OLD_SPACE, gc_reason, gc_callback_flags);
set_current_gc_flags(kNoGCFlags);
}
namespace {
intptr_t CompareWords(int size, HeapObject a, HeapObject b) {
int slots = size / kTaggedSize;
DCHECK_EQ(a.Size(), size);
DCHECK_EQ(b.Size(), size);
Tagged_t* slot_a = reinterpret_cast<Tagged_t*>(a.address());
Tagged_t* slot_b = reinterpret_cast<Tagged_t*>(b.address());
for (int i = 0; i < slots; i++) {
if (*slot_a != *slot_b) {
return *slot_a - *slot_b;
}
slot_a++;
slot_b++;
}
return 0;
}
void ReportDuplicates(int size, std::vector<HeapObject>* objects) {
if (objects->size() == 0) return;
sort(objects->begin(), objects->end(), [size](HeapObject a, HeapObject b) {
intptr_t c = CompareWords(size, a, b);
if (c != 0) return c < 0;
return a < b;
});
std::vector<std::pair<int, HeapObject>> duplicates;
HeapObject current = (*objects)[0];
int count = 1;
for (size_t i = 1; i < objects->size(); i++) {
if (CompareWords(size, current, (*objects)[i]) == 0) {
count++;
} else {
if (count > 1) {
duplicates.push_back(std::make_pair(count - 1, current));
}
count = 1;
current = (*objects)[i];
}
}
if (count > 1) {
duplicates.push_back(std::make_pair(count - 1, current));
}
int threshold = FLAG_trace_duplicate_threshold_kb * KB;
sort(duplicates.begin(), duplicates.end());
for (auto it = duplicates.rbegin(); it != duplicates.rend(); ++it) {
int duplicate_bytes = it->first * size;
if (duplicate_bytes < threshold) break;
PrintF("%d duplicates of size %d each (%dKB)\n", it->first, size,
duplicate_bytes / KB);
PrintF("Sample object: ");
it->second.Print();
PrintF("============================\n");
}
}
} // anonymous namespace
void Heap::CollectAllAvailableGarbage(GarbageCollectionReason gc_reason) {
// Since we are ignoring the return value, the exact choice of space does
// not matter, so long as we do not specify NEW_SPACE, which would not
// cause a full GC.
// Major GC would invoke weak handle callbacks on weakly reachable
// handles, but won't collect weakly reachable objects until next
// major GC. Therefore if we collect aggressively and weak handle callback
// has been invoked, we rerun major GC to release objects which become
// garbage.
// Note: as weak callbacks can execute arbitrary code, we cannot
// hope that eventually there will be no weak callbacks invocations.
// Therefore stop recollecting after several attempts.
if (gc_reason == GarbageCollectionReason::kLastResort) {
InvokeNearHeapLimitCallback();
}
RuntimeCallTimerScope runtime_timer(
isolate(), RuntimeCallCounterId::kGC_Custom_AllAvailableGarbage);
// The optimizing compiler may be unnecessarily holding on to memory.
isolate()->AbortConcurrentOptimization(BlockingBehavior::kDontBlock);
isolate()->ClearSerializerData();
set_current_gc_flags(
kReduceMemoryFootprintMask |
(gc_reason == GarbageCollectionReason::kLowMemoryNotification ? kForcedGC
: 0));
isolate_->compilation_cache()->Clear();
const int kMaxNumberOfAttempts = 7;
const int kMinNumberOfAttempts = 2;
for (int attempt = 0; attempt < kMaxNumberOfAttempts; attempt++) {
if (!CollectGarbage(OLD_SPACE, gc_reason, kNoGCCallbackFlags) &&
attempt + 1 >= kMinNumberOfAttempts) {
break;
}
}
set_current_gc_flags(kNoGCFlags);
new_space_->Shrink();
new_lo_space_->SetCapacity(new_space_->Capacity() *
kNewLargeObjectSpaceToSemiSpaceRatio);
UncommitFromSpace();
EagerlyFreeExternalMemory();
if (FLAG_trace_duplicate_threshold_kb) {
std::map<int, std::vector<HeapObject>> objects_by_size;
PagedSpaceIterator spaces(this);
for (PagedSpace* space = spaces.Next(); space != nullptr;
space = spaces.Next()) {
PagedSpaceObjectIterator it(this, space);
for (HeapObject obj = it.Next(); !obj.is_null(); obj = it.Next()) {
objects_by_size[obj.Size()].push_back(obj);
}
}
{
LargeObjectSpaceObjectIterator it(lo_space());
for (HeapObject obj = it.Next(); !obj.is_null(); obj = it.Next()) {
objects_by_size[obj.Size()].push_back(obj);
}
}
for (auto it = objects_by_size.rbegin(); it != objects_by_size.rend();
++it) {
ReportDuplicates(it->first, &it->second);
}
}
}
void Heap::PreciseCollectAllGarbage(int flags,
GarbageCollectionReason gc_reason,
const GCCallbackFlags gc_callback_flags) {
if (!incremental_marking()->IsStopped()) {
FinalizeIncrementalMarkingAtomically(gc_reason);
}
CollectAllGarbage(flags, gc_reason, gc_callback_flags);
}
void Heap::ReportExternalMemoryPressure() {
const GCCallbackFlags kGCCallbackFlagsForExternalMemory =
static_cast<GCCallbackFlags>(
kGCCallbackFlagSynchronousPhantomCallbackProcessing |
kGCCallbackFlagCollectAllExternalMemory);
int64_t current = external_memory_.total();
int64_t baseline = external_memory_.low_since_mark_compact();
int64_t limit = external_memory_.limit();
TRACE_EVENT2(
"devtools.timeline,v8", "V8.ExternalMemoryPressure", "external_memory_mb",
static_cast<int>((current - baseline) / MB), "external_memory_limit_mb",
static_cast<int>((limit - baseline) / MB));
if (current > baseline + external_memory_hard_limit()) {
CollectAllGarbage(
kReduceMemoryFootprintMask,
GarbageCollectionReason::kExternalMemoryPressure,
static_cast<GCCallbackFlags>(kGCCallbackFlagCollectAllAvailableGarbage |
kGCCallbackFlagsForExternalMemory));
return;
}
if (incremental_marking()->IsStopped()) {
if (incremental_marking()->CanBeActivated()) {
StartIncrementalMarking(GCFlagsForIncrementalMarking(),
GarbageCollectionReason::kExternalMemoryPressure,
kGCCallbackFlagsForExternalMemory);
} else {
CollectAllGarbage(i::Heap::kNoGCFlags,
GarbageCollectionReason::kExternalMemoryPressure,
kGCCallbackFlagsForExternalMemory);
}
} else {
// Incremental marking is turned on an has already been started.
const double kMinStepSize = 5;
const double kMaxStepSize = 10;
const double ms_step = Min(
kMaxStepSize,
Max(kMinStepSize, static_cast<double>(current) / limit * kMinStepSize));
const double deadline = MonotonicallyIncreasingTimeInMs() + ms_step;
// Extend the gc callback flags with external memory flags.
current_gc_callback_flags_ = static_cast<GCCallbackFlags>(
current_gc_callback_flags_ | kGCCallbackFlagsForExternalMemory);
incremental_marking()->AdvanceWithDeadline(
deadline, IncrementalMarking::GC_VIA_STACK_GUARD, StepOrigin::kV8);
}
}
int64_t Heap::external_memory_limit() { return external_memory_.limit(); }
void Heap::EnsureFillerObjectAtTop() {
// There may be an allocation memento behind objects in new space. Upon
// evacuation of a non-full new space (or if we are on the last page) there
// may be uninitialized memory behind top. We fill the remainder of the page
// with a filler.
Address to_top = new_space_->top();
Page* page = Page::FromAddress(to_top - kTaggedSize);
if (page->Contains(to_top)) {
int remaining_in_page = static_cast<int>(page->area_end() - to_top);
CreateFillerObjectAt(to_top, remaining_in_page, ClearRecordedSlots::kNo);
}
}
Heap::DevToolsTraceEventScope::DevToolsTraceEventScope(Heap* heap,
const char* event_name,
const char* event_type)
: heap_(heap), event_name_(event_name) {
TRACE_EVENT_BEGIN2("devtools.timeline,v8", event_name_, "usedHeapSizeBefore",
heap_->SizeOfObjects(), "type", event_type);
}
Heap::DevToolsTraceEventScope::~DevToolsTraceEventScope() {
TRACE_EVENT_END1("devtools.timeline,v8", event_name_, "usedHeapSizeAfter",
heap_->SizeOfObjects());
}
bool Heap::CollectGarbage(AllocationSpace space,
GarbageCollectionReason gc_reason,
const v8::GCCallbackFlags gc_callback_flags) {
const char* collector_reason = nullptr;
GarbageCollector collector = SelectGarbageCollector(space, &collector_reason);
is_current_gc_forced_ = gc_callback_flags & v8::kGCCallbackFlagForced ||
current_gc_flags_ & kForcedGC ||
force_gc_on_next_allocation_;
if (force_gc_on_next_allocation_) force_gc_on_next_allocation_ = false;
DevToolsTraceEventScope devtools_trace_event_scope(
this, IsYoungGenerationCollector(collector) ? "MinorGC" : "MajorGC",
GarbageCollectionReasonToString(gc_reason));
// Filter on-stack reference below this method.
isolate()
->global_handles()
->CleanupOnStackReferencesBelowCurrentStackPosition();
// Ensure that all pending phantom callbacks are invoked.
isolate()->global_handles()->InvokeSecondPassPhantomCallbacks();
// The VM is in the GC state until exiting this function.
VMState<GC> state(isolate());
#ifdef V8_ENABLE_ALLOCATION_TIMEOUT
// Reset the allocation timeout, but make sure to allow at least a few
// allocations after a collection. The reason for this is that we have a lot
// of allocation sequences and we assume that a garbage collection will allow
// the subsequent allocation attempts to go through.
if (FLAG_random_gc_interval > 0 || FLAG_gc_interval >= 0) {
allocation_timeout_ = Max(6, NextAllocationTimeout(allocation_timeout_));
}
#endif
EnsureFillerObjectAtTop();
if (IsYoungGenerationCollector(collector) &&
!incremental_marking()->IsStopped()) {
if (FLAG_trace_incremental_marking) {
isolate()->PrintWithTimestamp(
"[IncrementalMarking] Scavenge during marking.\n");
}
}
size_t freed_global_handles = 0;
size_t committed_memory_before = 0;
if (collector == MARK_COMPACTOR) {
committed_memory_before = CommittedOldGenerationMemory();
}
{
tracer()->Start(collector, gc_reason, collector_reason);
DCHECK(AllowHeapAllocation::IsAllowed());
DCHECK(AllowGarbageCollection::IsAllowed());
DisallowHeapAllocation no_allocation_during_gc;
DisallowGarbageCollection no_gc_during_gc;
GarbageCollectionPrologue();
{
TimedHistogram* gc_type_timer = GCTypeTimer(collector);
TimedHistogramScope histogram_timer_scope(gc_type_timer, isolate_);
TRACE_EVENT0("v8", gc_type_timer->name());
TimedHistogram* gc_type_priority_timer = GCTypePriorityTimer(collector);
OptionalTimedHistogramScopeMode mode =
isolate_->IsMemorySavingsModeActive()
? OptionalTimedHistogramScopeMode::DONT_TAKE_TIME
: OptionalTimedHistogramScopeMode::TAKE_TIME;
OptionalTimedHistogramScope histogram_timer_priority_scope(
gc_type_priority_timer, isolate_, mode);
if (!IsYoungGenerationCollector(collector)) {
PROFILE(isolate_, CodeMovingGCEvent());
}
GCType gc_type = collector == MARK_COMPACTOR ? kGCTypeMarkSweepCompact
: kGCTypeScavenge;
{
GCCallbacksScope scope(this);
// Temporary override any embedder stack state as callbacks may create
// their own state on the stack and recursively trigger GC.
EmbedderStackStateScope embedder_scope(
local_embedder_heap_tracer(),
EmbedderHeapTracer::EmbedderStackState::kMayContainHeapPointers);
if (scope.CheckReenter()) {
AllowHeapAllocation allow_allocation;
AllowGarbageCollection allow_gc;
AllowJavascriptExecution allow_js(isolate());
TRACE_GC(tracer(), GCTracer::Scope::HEAP_EXTERNAL_PROLOGUE);
VMState<EXTERNAL> state(isolate_);
HandleScope handle_scope(isolate_);
CallGCPrologueCallbacks(gc_type, kNoGCCallbackFlags);
}
}
if (V8_ENABLE_THIRD_PARTY_HEAP_BOOL) {
tp_heap_->CollectGarbage();
} else {
freed_global_handles +=
PerformGarbageCollection(collector, gc_callback_flags);
}
// Clear is_current_gc_forced now that the current GC is complete. Do this
// before GarbageCollectionEpilogue() since that could trigger another
// unforced GC.
is_current_gc_forced_ = false;
{
TRACE_GC(tracer(), GCTracer::Scope::HEAP_EXTERNAL_WEAK_GLOBAL_HANDLES);
gc_post_processing_depth_++;
{
AllowHeapAllocation allow_allocation;
AllowGarbageCollection allow_gc;
AllowJavascriptExecution allow_js(isolate());
freed_global_handles +=
isolate_->global_handles()->PostGarbageCollectionProcessing(
collector, gc_callback_flags);
}
gc_post_processing_depth_--;
}
{
GCCallbacksScope scope(this);
if (scope.CheckReenter()) {
AllowHeapAllocation allow_allocation;
AllowGarbageCollection allow_gc;
AllowJavascriptExecution allow_js(isolate());
TRACE_GC(tracer(), GCTracer::Scope::HEAP_EXTERNAL_EPILOGUE);
VMState<EXTERNAL> state(isolate_);
HandleScope handle_scope(isolate_);
CallGCEpilogueCallbacks(gc_type, gc_callback_flags);
}
}
if (collector == MARK_COMPACTOR || collector == SCAVENGER) {
tracer()->RecordGCPhasesHistograms(gc_type_timer);
}
}
GarbageCollectionEpilogue();
if (collector == MARK_COMPACTOR && FLAG_track_detached_contexts) {
isolate()->CheckDetachedContextsAfterGC();
}
if (collector == MARK_COMPACTOR) {
// Calculate used memory first, then committed memory. Following code
// assumes that committed >= used, which might not hold when this is
// calculated in the wrong order and background threads allocate
// in-between.
size_t used_memory_after = OldGenerationSizeOfObjects();
size_t committed_memory_after = CommittedOldGenerationMemory();
MemoryReducer::Event event;
event.type = MemoryReducer::kMarkCompact;
event.time_ms = MonotonicallyIncreasingTimeInMs();
// Trigger one more GC if
// - this GC decreased committed memory,
// - there is high fragmentation,
event.next_gc_likely_to_collect_more =
(committed_memory_before > committed_memory_after + MB) ||
HasHighFragmentation(used_memory_after, committed_memory_after);
event.committed_memory = committed_memory_after;
if (deserialization_complete_) {
memory_reducer_->NotifyMarkCompact(event);
}
if (initial_max_old_generation_size_ < max_old_generation_size() &&
used_memory_after < initial_max_old_generation_size_threshold_) {
set_max_old_generation_size(initial_max_old_generation_size_);
}
}
tracer()->Stop(collector);
}
if (collector == MARK_COMPACTOR &&
(gc_callback_flags & (kGCCallbackFlagForced |
kGCCallbackFlagCollectAllAvailableGarbage)) != 0) {
isolate()->CountUsage(v8::Isolate::kForcedGC);
}
// Start incremental marking for the next cycle. We do this only for scavenger
// to avoid a loop where mark-compact causes another mark-compact.
if (IsYoungGenerationCollector(collector)) {
StartIncrementalMarkingIfAllocationLimitIsReached(
GCFlagsForIncrementalMarking(),
kGCCallbackScheduleIdleGarbageCollection);
}
if (!CanExpandOldGeneration(0)) {
InvokeNearHeapLimitCallback();
if (!CanExpandOldGeneration(0)) {
FatalProcessOutOfMemory("Reached heap limit");
}
}
return freed_global_handles > 0;
}
int Heap::NotifyContextDisposed(bool dependant_context) {
if (!dependant_context) {
tracer()->ResetSurvivalEvents();
old_generation_size_configured_ = false;
set_old_generation_allocation_limit(initial_old_generation_size_);
MemoryReducer::Event event;
event.type = MemoryReducer::kPossibleGarbage;
event.time_ms = MonotonicallyIncreasingTimeInMs();
memory_reducer_->NotifyPossibleGarbage(event);
}
isolate()->AbortConcurrentOptimization(BlockingBehavior::kDontBlock);
if (!isolate()->context().is_null()) {
RemoveDirtyFinalizationRegistriesOnContext(isolate()->raw_native_context());
isolate()->raw_native_context().set_retained_maps(
ReadOnlyRoots(this).empty_weak_array_list());
}
tracer()->AddContextDisposalTime(MonotonicallyIncreasingTimeInMs());
return ++contexts_disposed_;
}
void Heap::StartIncrementalMarking(int gc_flags,
GarbageCollectionReason gc_reason,
GCCallbackFlags gc_callback_flags) {
DCHECK(incremental_marking()->IsStopped());
SafepointScope safepoint(this);
set_current_gc_flags(gc_flags);
current_gc_callback_flags_ = gc_callback_flags;
incremental_marking()->Start(gc_reason);
}
void Heap::StartIncrementalMarkingIfAllocationLimitIsReached(
int gc_flags, const GCCallbackFlags gc_callback_flags) {
if (incremental_marking()->IsStopped()) {
IncrementalMarkingLimit reached_limit = IncrementalMarkingLimitReached();
if (reached_limit == IncrementalMarkingLimit::kSoftLimit) {
incremental_marking()->incremental_marking_job()->ScheduleTask(this);
} else if (reached_limit == IncrementalMarkingLimit::kHardLimit) {
StartIncrementalMarking(
gc_flags,
OldGenerationSpaceAvailable() <= new_space_->Capacity()
? GarbageCollectionReason::kAllocationLimit
: GarbageCollectionReason::kGlobalAllocationLimit,
gc_callback_flags);
}
}
}
void Heap::StartIncrementalMarkingIfAllocationLimitIsReachedBackground() {
if (!incremental_marking()->IsStopped() ||
!incremental_marking()->CanBeActivated()) {
return;
}
const size_t old_generation_space_available = OldGenerationSpaceAvailable();
const base::Optional<size_t> global_memory_available =
GlobalMemoryAvailable();
if (old_generation_space_available < new_space_->Capacity() ||
(global_memory_available &&
*global_memory_available < new_space_->Capacity())) {
incremental_marking()->incremental_marking_job()->ScheduleTask(this);
}
}
void Heap::StartIdleIncrementalMarking(
GarbageCollectionReason gc_reason,
const GCCallbackFlags gc_callback_flags) {
StartIncrementalMarking(kReduceMemoryFootprintMask, gc_reason,
gc_callback_flags);
}
void Heap::MoveRange(HeapObject dst_object, const ObjectSlot dst_slot,
const ObjectSlot src_slot, int len,
WriteBarrierMode mode) {
DCHECK_NE(len, 0);
DCHECK_NE(dst_object.map(), ReadOnlyRoots(this).fixed_cow_array_map());
const ObjectSlot dst_end(dst_slot + len);
// Ensure no range overflow.
DCHECK(dst_slot < dst_end);
DCHECK(src_slot < src_slot + len);
if (FLAG_concurrent_marking && incremental_marking()->IsMarking()) {
if (dst_slot < src_slot) {
// Copy tagged values forward using relaxed load/stores that do not
// involve value decompression.
const AtomicSlot atomic_dst_end(dst_end);
AtomicSlot dst(dst_slot);
AtomicSlot src(src_slot);
while (dst < atomic_dst_end) {
*dst = *src;
++dst;
++src;
}
} else {
// Copy tagged values backwards using relaxed load/stores that do not
// involve value decompression.
const AtomicSlot atomic_dst_begin(dst_slot);
AtomicSlot dst(dst_slot + len - 1);
AtomicSlot src(src_slot + len - 1);
while (dst >= atomic_dst_begin) {
*dst = *src;
--dst;
--src;
}
}
} else {
MemMove(dst_slot.ToVoidPtr(), src_slot.ToVoidPtr(), len * kTaggedSize);
}
if (mode == SKIP_WRITE_BARRIER) return;
WriteBarrierForRange(dst_object, dst_slot, dst_end);
}
// Instantiate Heap::CopyRange() for ObjectSlot and MaybeObjectSlot.
template void Heap::CopyRange<ObjectSlot>(HeapObject dst_object,
ObjectSlot dst_slot,
ObjectSlot src_slot, int len,
WriteBarrierMode mode);
template void Heap::CopyRange<MaybeObjectSlot>(HeapObject dst_object,
MaybeObjectSlot dst_slot,
MaybeObjectSlot src_slot,
int len, WriteBarrierMode mode);
template <typename TSlot>
void Heap::CopyRange(HeapObject dst_object, const TSlot dst_slot,
const TSlot src_slot, int len, WriteBarrierMode mode) {
DCHECK_NE(len, 0);
DCHECK_NE(dst_object.map(), ReadOnlyRoots(this).fixed_cow_array_map());
const TSlot dst_end(dst_slot + len);
// Ensure ranges do not overlap.
DCHECK(dst_end <= src_slot || (src_slot + len) <= dst_slot);
if (FLAG_concurrent_marking && incremental_marking()->IsMarking()) {
// Copy tagged values using relaxed load/stores that do not involve value
// decompression.
const AtomicSlot atomic_dst_end(dst_end);
AtomicSlot dst(dst_slot);
AtomicSlot src(src_slot);
while (dst < atomic_dst_end) {
*dst = *src;
++dst;
++src;
}
} else {
MemCopy(dst_slot.ToVoidPtr(), src_slot.ToVoidPtr(), len * kTaggedSize);
}
if (mode == SKIP_WRITE_BARRIER) return;
WriteBarrierForRange(dst_object, dst_slot, dst_end);
}
#ifdef VERIFY_HEAP
// Helper class for verifying the string table.
class StringTableVerifier : public RootVisitor {
public:
explicit StringTableVerifier(Isolate* isolate) : isolate_(isolate) {}
void VisitRootPointers(Root root, const char* description,
FullObjectSlot start, FullObjectSlot end) override {
UNREACHABLE();
}
void VisitRootPointers(Root root, const char* description,
OffHeapObjectSlot start,
OffHeapObjectSlot end) override {
// Visit all HeapObject pointers in [start, end).
for (OffHeapObjectSlot p = start; p < end; ++p) {
Object o = p.load(isolate_);
DCHECK(!HasWeakHeapObjectTag(o));
if (o.IsHeapObject()) {
HeapObject object = HeapObject::cast(o);
// Check that the string is actually internalized.
CHECK(object.IsInternalizedString());
}
}
}
private:
Isolate* isolate_;
};
static void VerifyStringTable(Isolate* isolate) {
StringTableVerifier verifier(isolate);
isolate->string_table()->IterateElements(&verifier);
}
#endif // VERIFY_HEAP
void Heap::EnsureFromSpaceIsCommitted() {
if (new_space_->CommitFromSpaceIfNeeded()) return;
// Committing memory to from space failed.
// Memory is exhausted and we will die.
FatalProcessOutOfMemory("Committing semi space failed.");
}
bool Heap::CollectionRequested() {
return collection_barrier_->CollectionRequested();
}
void Heap::RequestCollectionBackground(LocalHeap* local_heap) {
if (local_heap->is_main_thread()) {
CollectAllGarbage(current_gc_flags_,
GarbageCollectionReason::kBackgroundAllocationFailure,
current_gc_callback_flags_);
} else {
collection_barrier_->AwaitCollectionBackground();
}
}
void Heap::CheckCollectionRequested() {
if (!collection_barrier_->CollectionRequested()) return;
CollectAllGarbage(current_gc_flags_,
GarbageCollectionReason::kBackgroundAllocationFailure,
current_gc_callback_flags_);
}
void Heap::UpdateSurvivalStatistics(int start_new_space_size) {
if (start_new_space_size == 0) return;
promotion_ratio_ = (static_cast<double>(promoted_objects_size_) /
static_cast<double>(start_new_space_size) * 100);
if (previous_semi_space_copied_object_size_ > 0) {
promotion_rate_ =
(static_cast<double>(promoted_objects_size_) /
static_cast<double>(previous_semi_space_copied_object_size_) * 100);
} else {
promotion_rate_ = 0;
}
semi_space_copied_rate_ =
(static_cast<double>(semi_space_copied_object_size_) /
static_cast<double>(start_new_space_size) * 100);
double survival_rate = promotion_ratio_ + semi_space_copied_rate_;
tracer()->AddSurvivalRatio(survival_rate);
}
size_t Heap::PerformGarbageCollection(
GarbageCollector collector, const v8::GCCallbackFlags gc_callback_flags) {
DisallowJavascriptExecution no_js(isolate());
base::Optional<SafepointScope> optional_safepoint_scope;
// Stop time-to-collection timer before safepoint - we do not want to measure
// time for safepointing.
collection_barrier_->StopTimeToCollectionTimer();
if (FLAG_local_heaps) {
optional_safepoint_scope.emplace(this);
}
#ifdef VERIFY_HEAP
if (FLAG_verify_heap) {
Verify();
}
#endif
tracer()->StartInSafepoint();
GarbageCollectionPrologueInSafepoint();
EnsureFromSpaceIsCommitted();
size_t start_young_generation_size =
Heap::new_space()->Size() + new_lo_space()->SizeOfObjects();
switch (collector) {
case MARK_COMPACTOR:
MarkCompact();
break;
case MINOR_MARK_COMPACTOR:
MinorMarkCompact();
break;
case SCAVENGER:
Scavenge();
break;
}
ProcessPretenuringFeedback();
UpdateSurvivalStatistics(static_cast<int>(start_young_generation_size));
ConfigureInitialOldGenerationSize();
if (collector != MARK_COMPACTOR) {
// Objects that died in the new space might have been accounted
// as bytes marked ahead of schedule by the incremental marker.
incremental_marking()->UpdateMarkedBytesAfterScavenge(
start_young_generation_size - SurvivedYoungObjectSize());
}
if (!fast_promotion_mode_ || collector == MARK_COMPACTOR) {
ComputeFastPromotionMode();
}
isolate_->counters()->objs_since_last_young()->Set(0);
isolate_->eternal_handles()->PostGarbageCollectionProcessing();
// Update relocatables.
Relocatable::PostGarbageCollectionProcessing(isolate_);
size_t freed_global_handles;
{
TRACE_GC(tracer(), GCTracer::Scope::HEAP_EXTERNAL_WEAK_GLOBAL_HANDLES);
// First round weak callbacks are not supposed to allocate and trigger
// nested GCs.
freed_global_handles =
isolate_->global_handles()->InvokeFirstPassWeakCallbacks();
}
if (collector == MARK_COMPACTOR) {
TRACE_GC(tracer(), GCTracer::Scope::HEAP_EMBEDDER_TRACING_EPILOGUE);
// TraceEpilogue may trigger operations that invalidate global handles. It
// has to be called *after* all other operations that potentially touch and
// reset global handles. It is also still part of the main garbage
// collection pause and thus needs to be called *before* any operation that
// can potentially trigger recursive garbage
local_embedder_heap_tracer()->TraceEpilogue();
}
#ifdef VERIFY_HEAP
if (FLAG_verify_heap) {
Verify();
}
#endif
RecomputeLimits(collector);
GarbageCollectionEpilogueInSafepoint(collector);
tracer()->StopInSafepoint();
return freed_global_handles;
}
void Heap::RecomputeLimits(GarbageCollector collector) {
if (!((collector == MARK_COMPACTOR) ||
(HasLowYoungGenerationAllocationRate() &&
old_generation_size_configured_))) {
return;
}
double v8_gc_speed =
tracer()->CombinedMarkCompactSpeedInBytesPerMillisecond();
double v8_mutator_speed =
tracer()->CurrentOldGenerationAllocationThroughputInBytesPerMillisecond();
double v8_growing_factor = MemoryController<V8HeapTrait>::GrowingFactor(
this, max_old_generation_size(), v8_gc_speed, v8_mutator_speed);
double global_growing_factor = 0;
if (UseGlobalMemoryScheduling()) {
DCHECK_NOT_NULL(local_embedder_heap_tracer());
double embedder_gc_speed = tracer()->EmbedderSpeedInBytesPerMillisecond();
double embedder_speed =
tracer()->CurrentEmbedderAllocationThroughputInBytesPerMillisecond();
double embedder_growing_factor =
(embedder_gc_speed > 0 && embedder_speed > 0)
? MemoryController<GlobalMemoryTrait>::GrowingFactor(
this, max_global_memory_size_, embedder_gc_speed,
embedder_speed)
: 0;
global_growing_factor = Max(v8_growing_factor, embedder_growing_factor);
}
size_t old_gen_size = OldGenerationSizeOfObjects();
size_t new_space_capacity = new_space()->Capacity();
HeapGrowingMode mode = CurrentHeapGrowingMode();
if (collector == MARK_COMPACTOR) {
external_memory_.ResetAfterGC();
set_old_generation_allocation_limit(
MemoryController<V8HeapTrait>::CalculateAllocationLimit(
this, old_gen_size, min_old_generation_size_,
max_old_generation_size(), new_space_capacity, v8_growing_factor,
mode));
if (UseGlobalMemoryScheduling()) {
DCHECK_GT(global_growing_factor, 0);
global_allocation_limit_ =
MemoryController<GlobalMemoryTrait>::CalculateAllocationLimit(
this, GlobalSizeOfObjects(), min_global_memory_size_,
max_global_memory_size_, new_space_capacity,
global_growing_factor, mode);
}
CheckIneffectiveMarkCompact(
old_gen_size, tracer()->AverageMarkCompactMutatorUtilization());
} else if (HasLowYoungGenerationAllocationRate() &&
old_generation_size_configured_) {
size_t new_old_generation_limit =
MemoryController<V8HeapTrait>::CalculateAllocationLimit(
this, old_gen_size, min_old_generation_size_,
max_old_generation_size(), new_space_capacity, v8_growing_factor,
mode);
if (new_old_generation_limit < old_generation_allocation_limit()) {
set_old_generation_allocation_limit(new_old_generation_limit);
}
if (UseGlobalMemoryScheduling()) {
DCHECK_GT(global_growing_factor, 0);
size_t new_global_limit =
MemoryController<GlobalMemoryTrait>::CalculateAllocationLimit(
this, GlobalSizeOfObjects(), min_global_memory_size_,
max_global_memory_size_, new_space_capacity,
global_growing_factor, mode);
if (new_global_limit < global_allocation_limit_) {
global_allocation_limit_ = new_global_limit;
}
}
}
}
void Heap::CallGCPrologueCallbacks(GCType gc_type, GCCallbackFlags flags) {
RuntimeCallTimerScope runtime_timer(
isolate(), RuntimeCallCounterId::kGCPrologueCallback);
for (const GCCallbackTuple& info : gc_prologue_callbacks_) {
if (gc_type & info.gc_type) {
v8::Isolate* isolate = reinterpret_cast<v8::Isolate*>(this->isolate());
info.callback(isolate, gc_type, flags, info.data);
}
}
}
void Heap::CallGCEpilogueCallbacks(GCType gc_type, GCCallbackFlags flags) {
RuntimeCallTimerScope runtime_timer(
isolate(), RuntimeCallCounterId::kGCEpilogueCallback);
for (const GCCallbackTuple& info : gc_epilogue_callbacks_) {
if (gc_type & info.gc_type) {
v8::Isolate* isolate = reinterpret_cast<v8::Isolate*>(this->isolate());
info.callback(isolate, gc_type, flags, info.data);
}
}
}
void Heap::MarkCompact() {
PauseAllocationObserversScope pause_observers(this);
SetGCState(MARK_COMPACT);
LOG(isolate_, ResourceEvent("markcompact", "begin"));
CodeSpaceMemoryModificationScope code_modifcation(this);
UpdateOldGenerationAllocationCounter();
uint64_t size_of_objects_before_gc = SizeOfObjects();
mark_compact_collector()->Prepare();
ms_count_++;
MarkCompactPrologue();
mark_compact_collector()->CollectGarbage();
LOG(isolate_, ResourceEvent("markcompact", "end"));
MarkCompactEpilogue();
if (FLAG_allocation_site_pretenuring) {
EvaluateOldSpaceLocalPretenuring(size_of_objects_before_gc);
}
old_generation_size_configured_ = true;
// This should be updated before PostGarbageCollectionProcessing, which
// can cause another GC. Take into account the objects promoted during
// GC.
old_generation_allocation_counter_at_last_gc_ +=
static_cast<size_t>(promoted_objects_size_);
old_generation_size_at_last_gc_ = OldGenerationSizeOfObjects();
global_memory_at_last_gc_ = GlobalSizeOfObjects();
}
void Heap::MinorMarkCompact() {
#ifdef ENABLE_MINOR_MC
DCHECK(FLAG_minor_mc);
PauseAllocationObserversScope pause_observers(this);
SetGCState(MINOR_MARK_COMPACT);
LOG(isolate_, ResourceEvent("MinorMarkCompact", "begin"));
TRACE_GC(tracer(), GCTracer::Scope::MINOR_MC);
AlwaysAllocateScope always_allocate(this);
IncrementalMarking::PauseBlackAllocationScope pause_black_allocation(
incremental_marking());
ConcurrentMarking::PauseScope pause_scope(concurrent_marking());
minor_mark_compact_collector()->CollectGarbage();
LOG(isolate_, ResourceEvent("MinorMarkCompact", "end"));
SetGCState(NOT_IN_GC);
#else
UNREACHABLE();
#endif // ENABLE_MINOR_MC
}
void Heap::MarkCompactEpilogue() {
TRACE_GC(tracer(), GCTracer::Scope::MC_EPILOGUE);
SetGCState(NOT_IN_GC);
isolate_->counters()->objs_since_last_full()->Set(0);
incremental_marking()->Epilogue();
DCHECK(incremental_marking()->IsStopped());
}
void Heap::MarkCompactPrologue() {
TRACE_GC(tracer(), GCTracer::Scope::MC_PROLOGUE);
isolate_->descriptor_lookup_cache()->Clear();
RegExpResultsCache::Clear(string_split_cache());
RegExpResultsCache::Clear(regexp_multiple_cache());
isolate_->compilation_cache()->MarkCompactPrologue();
FlushNumberStringCache();
}
void Heap::CheckNewSpaceExpansionCriteria() {
if (new_space_->TotalCapacity() < new_space_->MaximumCapacity() &&
survived_since_last_expansion_ > new_space_->TotalCapacity()) {
// Grow the size of new space if there is room to grow, and enough data
// has survived scavenge since the last expansion.
new_space_->Grow();
survived_since_last_expansion_ = 0;
}
new_lo_space()->SetCapacity(new_space()->Capacity());
}
void Heap::EvacuateYoungGeneration() {
TRACE_GC(tracer(), GCTracer::Scope::SCAVENGER_FAST_PROMOTE);
base::MutexGuard guard(relocation_mutex());
ConcurrentMarking::PauseScope pause_scope(concurrent_marking());
if (!FLAG_concurrent_marking) {
DCHECK(fast_promotion_mode_);
DCHECK(CanPromoteYoungAndExpandOldGeneration(0));
}
mark_compact_collector()->sweeper()->EnsureIterabilityCompleted();
SetGCState(SCAVENGE);
LOG(isolate_, ResourceEvent("scavenge", "begin"));
// Move pages from new->old generation.
PageRange range(new_space()->first_allocatable_address(), new_space()->top());
for (auto it = range.begin(); it != range.end();) {
Page* p = (*++it)->prev_page();
new_space()->from_space().RemovePage(p);
Page::ConvertNewToOld(p);
if (incremental_marking()->IsMarking())
mark_compact_collector()->RecordLiveSlotsOnPage(p);
}
// Reset new space.
if (!new_space()->Rebalance()) {
FatalProcessOutOfMemory("NewSpace::Rebalance");
}
new_space()->ResetLinearAllocationArea();
new_space()->set_age_mark(new_space()->top());
for (auto it = new_lo_space()->begin(); it != new_lo_space()->end();) {
LargePage* page = *it;
// Increment has to happen after we save the page, because it is going to
// be removed below.
it++;
lo_space()->PromoteNewLargeObject(page);
}
// Fix up special trackers.
external_string_table_.PromoteYoung();
// GlobalHandles are updated in PostGarbageCollectonProcessing
size_t promoted = new_space()->Size() + new_lo_space()->Size();
IncrementYoungSurvivorsCounter(promoted);
IncrementPromotedObjectsSize(promoted);
IncrementSemiSpaceCopiedObjectSize(0);
LOG(isolate_, ResourceEvent("scavenge", "end"));
SetGCState(NOT_IN_GC);
}
void Heap::Scavenge() {
if (fast_promotion_mode_ && CanPromoteYoungAndExpandOldGeneration(0)) {
tracer()->NotifyYoungGenerationHandling(
YoungGenerationHandling::kFastPromotionDuringScavenge);
EvacuateYoungGeneration();
return;
}
tracer()->NotifyYoungGenerationHandling(
YoungGenerationHandling::kRegularScavenge);
TRACE_GC(tracer(), GCTracer::Scope::SCAVENGER_SCAVENGE);
base::MutexGuard guard(relocation_mutex());
ConcurrentMarking::PauseScope pause_scope(concurrent_marking());
// There are soft limits in the allocation code, designed to trigger a mark
// sweep collection by failing allocations. There is no sense in trying to
// trigger one during scavenge: scavenges allocation should always succeed.
AlwaysAllocateScope scope(this);
// Bump-pointer allocations done during scavenge are not real allocations.
// Pause the inline allocation steps.
PauseAllocationObserversScope pause_observers(this);
IncrementalMarking::PauseBlackAllocationScope pause_black_allocation(
incremental_marking());
mark_compact_collector()->sweeper()->EnsureIterabilityCompleted();
SetGCState(SCAVENGE);
// Flip the semispaces. After flipping, to space is empty, from space has
// live objects.
new_space()->Flip();
new_space()->ResetLinearAllocationArea();
// We also flip the young generation large object space. All large objects
// will be in the from space.
new_lo_space()->Flip();
new_lo_space()->ResetPendingObject();
// Implements Cheney's copying algorithm
LOG(isolate_, ResourceEvent("scavenge", "begin"));
scavenger_collector_->CollectGarbage();
LOG(isolate_, ResourceEvent("scavenge", "end"));
SetGCState(NOT_IN_GC);
}
void Heap::ComputeFastPromotionMode() {
const size_t survived_in_new_space =
survived_last_scavenge_ * 100 / new_space_->Capacity();
fast_promotion_mode_ =
!FLAG_optimize_for_size && FLAG_fast_promotion_new_space &&
!ShouldReduceMemory() && new_space_->IsAtMaximumCapacity() &&
survived_in_new_space >= kMinPromotedPercentForFastPromotionMode;
if (FLAG_trace_gc_verbose && !FLAG_trace_gc_ignore_scavenger) {
PrintIsolate(isolate(), "Fast promotion mode: %s survival rate: %zu%%\n",
fast_promotion_mode_ ? "true" : "false",
survived_in_new_space);
}
}
void Heap::UnprotectAndRegisterMemoryChunk(MemoryChunk* chunk) {
if (unprotected_memory_chunks_registry_enabled_) {
base::MutexGuard guard(&unprotected_memory_chunks_mutex_);
if (unprotected_memory_chunks_.insert(chunk).second) {
chunk->SetReadAndWritable();
}
}
}
void Heap::UnprotectAndRegisterMemoryChunk(HeapObject object) {
UnprotectAndRegisterMemoryChunk(MemoryChunk::FromHeapObject(object));
}
void Heap::UnregisterUnprotectedMemoryChunk(MemoryChunk* chunk) {
unprotected_memory_chunks_.erase(chunk);
}
void Heap::ProtectUnprotectedMemoryChunks() {
DCHECK(unprotected_memory_chunks_registry_enabled_);
for (auto chunk = unprotected_memory_chunks_.begin();
chunk != unprotected_memory_chunks_.end(); chunk++) {
CHECK(memory_allocator()->IsMemoryChunkExecutable(*chunk));
(*chunk)->SetDefaultCodePermissions();
}
unprotected_memory_chunks_.clear();
}
bool Heap::ExternalStringTable::Contains(String string) {
for (size_t i = 0; i < young_strings_.size(); ++i) {
if (young_strings_[i] == string) return true;
}
for (size_t i = 0; i < old_strings_.size(); ++i) {
if (old_strings_[i] == string) return true;
}
return false;
}
void Heap::UpdateExternalString(String string, size_t old_payload,
size_t new_payload) {
DCHECK(string.IsExternalString());
Page* page = Page::FromHeapObject(string);
if (old_payload > new_payload) {
page->DecrementExternalBackingStoreBytes(
ExternalBackingStoreType::kExternalString, old_payload - new_payload);
} else {
page->IncrementExternalBackingStoreBytes(
ExternalBackingStoreType::kExternalString, new_payload - old_payload);
}
}
String Heap::UpdateYoungReferenceInExternalStringTableEntry(Heap* heap,
FullObjectSlot p) {
HeapObject obj = HeapObject::cast(*p);
MapWord first_word = obj.map_word();
String new_string;
if (InFromPage(obj)) {
if (!first_word.IsForwardingAddress()) {
// Unreachable external string can be finalized.
String string = String::cast(obj);
if (!string.IsExternalString()) {
// Original external string has been internalized.
DCHECK(string.IsThinString());
return String();
}
heap->FinalizeExternalString(string);
return String();
}
new_string = String::cast(first_word.ToForwardingAddress());
} else {
new_string = String::cast(obj);
}
// String is still reachable.
if (new_string.IsThinString()) {
// Filtering Thin strings out of the external string table.
return String();
} else if (new_string.IsExternalString()) {
MemoryChunk::MoveExternalBackingStoreBytes(
ExternalBackingStoreType::kExternalString,
Page::FromAddress((*p).ptr()), Page::FromHeapObject(new_string),
ExternalString::cast(new_string).ExternalPayloadSize());
return new_string;
}
// Internalization can replace external strings with non-external strings.
return new_string.IsExternalString() ? new_string : String();
}
void Heap::ExternalStringTable::VerifyYoung() {
#ifdef DEBUG
std::set<String> visited_map;
std::map<MemoryChunk*, size_t> size_map;
ExternalBackingStoreType type = ExternalBackingStoreType::kExternalString;
for (size_t i = 0; i < young_strings_.size(); ++i) {
String obj = String::cast(young_strings_[i]);
MemoryChunk* mc = MemoryChunk::FromHeapObject(obj);
DCHECK(mc->InYoungGeneration());
DCHECK(heap_->InYoungGeneration(obj));
DCHECK(!obj.IsTheHole(heap_->isolate()));
DCHECK(obj.IsExternalString());
// Note: we can have repeated elements in the table.
DCHECK_EQ(0, visited_map.count(obj));
visited_map.insert(obj);
size_map[mc] += ExternalString::cast(obj).ExternalPayloadSize();
}
for (std::map<MemoryChunk*, size_t>::iterator it = size_map.begin();
it != size_map.end(); it++)
DCHECK_EQ(it->first->ExternalBackingStoreBytes(type), it->second);
#endif
}
void Heap::ExternalStringTable::Verify() {
#ifdef DEBUG
std::set<String> visited_map;
std::map<MemoryChunk*, size_t> size_map;
ExternalBackingStoreType type = ExternalBackingStoreType::kExternalString;
VerifyYoung();
for (size_t i = 0; i < old_strings_.size(); ++i) {
String obj = String::cast(old_strings_[i]);
MemoryChunk* mc = MemoryChunk::FromHeapObject(obj);
DCHECK(!mc->InYoungGeneration());
DCHECK(!heap_->InYoungGeneration(obj));
DCHECK(!obj.IsTheHole(heap_->isolate()));
DCHECK(obj.IsExternalString());
// Note: we can have repeated elements in the table.
DCHECK_EQ(0, visited_map.count(obj));
visited_map.insert(obj);
size_map[mc] += ExternalString::cast(obj).ExternalPayloadSize();
}
for (std::map<MemoryChunk*, size_t>::iterator it = size_map.begin();
it != size_map.end(); it++)
DCHECK_EQ(it->first->ExternalBackingStoreBytes(type), it->second);
#endif
}
void Heap::ExternalStringTable::UpdateYoungReferences(
Heap::ExternalStringTableUpdaterCallback updater_func) {
if (young_strings_.empty()) return;
FullObjectSlot start(young_strings_.data());
FullObjectSlot end(young_strings_.data() + young_strings_.size());
FullObjectSlot last = start;
for (FullObjectSlot p = start; p < end; ++p) {
String target = updater_func(heap_, p);
if (target.is_null()) continue;
DCHECK(target.IsExternalString());
if (InYoungGeneration(target)) {
// String is still in new space. Update the table entry.
last.store(target);
++last;
} else {
// String got promoted. Move it to the old string list.
old_strings_.push_back(target);
}
}
DCHECK(last <= end);
young_strings_.resize(last - start);
#ifdef VERIFY_HEAP
if (FLAG_verify_heap) {
VerifyYoung();
}
#endif
}
void Heap::ExternalStringTable::PromoteYoung() {
old_strings_.reserve(old_strings_.size() + young_strings_.size());
std::move(std::begin(young_strings_), std::end(young_strings_),
std::back_inserter(old_strings_));
young_strings_.clear();
}
void Heap::ExternalStringTable::IterateYoung(RootVisitor* v) {
if (!young_strings_.empty()) {
v->VisitRootPointers(
Root::kExternalStringsTable, nullptr,
FullObjectSlot(young_strings_.data()),
FullObjectSlot(young_strings_.data() + young_strings_.size()));
}
}
void Heap::ExternalStringTable::IterateAll(RootVisitor* v) {
IterateYoung(v);
if (!old_strings_.empty()) {
v->VisitRootPointers(
Root::kExternalStringsTable, nullptr,
FullObjectSlot(old_strings_.data()),
FullObjectSlot(old_strings_.data() + old_strings_.size()));
}
}
void Heap::UpdateYoungReferencesInExternalStringTable(
ExternalStringTableUpdaterCallback updater_func) {
external_string_table_.UpdateYoungReferences(updater_func);
}
void Heap::ExternalStringTable::UpdateReferences(
Heap::ExternalStringTableUpdaterCallback updater_func) {
if (old_strings_.size() > 0) {
FullObjectSlot start(old_strings_.data());
FullObjectSlot end(old_strings_.data() + old_strings_.size());
for (FullObjectSlot p = start; p < end; ++p)
p.store(updater_func(heap_, p));
}
UpdateYoungReferences(updater_func);
}
void Heap::UpdateReferencesInExternalStringTable(
ExternalStringTableUpdaterCallback updater_func) {
external_string_table_.UpdateReferences(updater_func);
}
void Heap::ProcessAllWeakReferences(WeakObjectRetainer* retainer) {
ProcessNativeContexts(retainer);
ProcessAllocationSites(retainer);
ProcessDirtyJSFinalizationRegistries(retainer);
}
void Heap::ProcessYoungWeakReferences(WeakObjectRetainer* retainer) {
ProcessNativeContexts(retainer);
}
void Heap::ProcessNativeContexts(WeakObjectRetainer* retainer) {
Object head = VisitWeakList<Context>(this, native_contexts_list(), retainer);
// Update the head of the list of contexts.
set_native_contexts_list(head);
}
void Heap::ProcessAllocationSites(WeakObjectRetainer* retainer) {
Object allocation_site_obj =
VisitWeakList<AllocationSite>(this, allocation_sites_list(), retainer);
set_allocation_sites_list(allocation_site_obj);
}
void Heap::ProcessDirtyJSFinalizationRegistries(WeakObjectRetainer* retainer) {
Object head = VisitWeakList<JSFinalizationRegistry>(
this, dirty_js_finalization_registries_list(), retainer);
set_dirty_js_finalization_registries_list(head);
// If the list is empty, set the tail to undefined. Otherwise the tail is set
// by WeakListVisitor<JSFinalizationRegistry>::VisitLiveObject.
if (head.IsUndefined(isolate())) {
set_dirty_js_finalization_registries_list_tail(head);
}
}
void Heap::ProcessWeakListRoots(WeakObjectRetainer* retainer) {
set_native_contexts_list(retainer->RetainAs(native_contexts_list()));
set_allocation_sites_list(retainer->RetainAs(allocation_sites_list()));
set_dirty_js_finalization_registries_list(
retainer->RetainAs(dirty_js_finalization_registries_list()));
set_dirty_js_finalization_registries_list_tail(
retainer->RetainAs(dirty_js_finalization_registries_list_tail()));
}
void Heap::ForeachAllocationSite(
Object list, const std::function<void(AllocationSite)>& visitor) {
DisallowHeapAllocation disallow_heap_allocation;
Object current = list;
while (current.IsAllocationSite()) {
AllocationSite site = AllocationSite::cast(current);
visitor(site);
Object current_nested = site.nested_site();
while (current_nested.IsAllocationSite()) {
AllocationSite nested_site = AllocationSite::cast(current_nested);
visitor(nested_site);
current_nested = nested_site.nested_site();
}
current = site.weak_next();
}
}
void Heap::ResetAllAllocationSitesDependentCode(AllocationType allocation) {
DisallowHeapAllocation no_allocation_scope;
bool marked = false;
ForeachAllocationSite(allocation_sites_list(),
[&marked, allocation, this](AllocationSite site) {
if (site.GetAllocationType() == allocation) {
site.ResetPretenureDecision();
site.set_deopt_dependent_code(true);
marked = true;
RemoveAllocationSitePretenuringFeedback(site);
return;
}
});
if (marked) isolate_->stack_guard()->RequestDeoptMarkedAllocationSites();
}
void Heap::EvaluateOldSpaceLocalPretenuring(
uint64_t size_of_objects_before_gc) {
uint64_t size_of_objects_after_gc = SizeOfObjects();
double old_generation_survival_rate =
(static_cast<double>(size_of_objects_after_gc) * 100) /
static_cast<double>(size_of_objects_before_gc);
if (old_generation_survival_rate < kOldSurvivalRateLowThreshold) {
// Too many objects died in the old generation, pretenuring of wrong
// allocation sites may be the cause for that. We have to deopt all
// dependent code registered in the allocation sites to re-evaluate
// our pretenuring decisions.
ResetAllAllocationSitesDependentCode(AllocationType::kOld);
if (FLAG_trace_pretenuring) {
PrintF(
"Deopt all allocation sites dependent code due to low survival "
"rate in the old generation %f\n",
old_generation_survival_rate);
}
}
}
void Heap::VisitExternalResources(v8::ExternalResourceVisitor* visitor) {
DisallowHeapAllocation no_allocation;
// All external strings are listed in the external string table.
class ExternalStringTableVisitorAdapter : public RootVisitor {
public:
explicit ExternalStringTableVisitorAdapter(
Isolate* isolate, v8::ExternalResourceVisitor* visitor)
: isolate_(isolate), visitor_(visitor) {}
void VisitRootPointers(Root root, const char* description,
FullObjectSlot start, FullObjectSlot end) override {
for (FullObjectSlot p = start; p < end; ++p) {
DCHECK((*p).IsExternalString());
visitor_->VisitExternalString(
Utils::ToLocal(Handle<String>(String::cast(*p), isolate_)));
}
}
private:
Isolate* isolate_;
v8::ExternalResourceVisitor* visitor_;
} external_string_table_visitor(isolate(), visitor);
external_string_table_.IterateAll(&external_string_table_visitor);
}
STATIC_ASSERT(IsAligned(FixedDoubleArray::kHeaderSize, kDoubleAlignment));
#ifdef V8_COMPRESS_POINTERS
// TODO(ishell, v8:8875): When pointer compression is enabled the kHeaderSize
// is only kTaggedSize aligned but we can keep using unaligned access since
// both x64 and arm64 architectures (where pointer compression supported)
// allow unaligned access to doubles.
STATIC_ASSERT(IsAligned(ByteArray::kHeaderSize, kTaggedSize));
#else
STATIC_ASSERT(IsAligned(ByteArray::kHeaderSize, kDoubleAlignment));
#endif
#ifdef V8_HOST_ARCH_32_BIT
// NOLINTNEXTLINE(runtime/references) (false positive)
STATIC_ASSERT((HeapNumber::kValueOffset & kDoubleAlignmentMask) == kTaggedSize);
#endif
int Heap::GetMaximumFillToAlign(AllocationAlignment alignment) {
switch (alignment) {
case kWordAligned:
return 0;
case kDoubleAligned:
case kDoubleUnaligned:
return kDoubleSize - kTaggedSize;
default:
UNREACHABLE();
}
return 0;
}
// static
int Heap::GetFillToAlign(Address address, AllocationAlignment alignment) {
if (alignment == kDoubleAligned && (address & kDoubleAlignmentMask) != 0)
return kTaggedSize;
if (alignment == kDoubleUnaligned && (address & kDoubleAlignmentMask) == 0)
return kDoubleSize - kTaggedSize; // No fill if double is always aligned.
return 0;
}
size_t Heap::GetCodeRangeReservedAreaSize() {
return kReservedCodeRangePages * MemoryAllocator::GetCommitPageSize();
}
// static
HeapObject Heap::PrecedeWithFiller(ReadOnlyRoots roots, HeapObject object,
int filler_size) {
CreateFillerObjectAt(roots, object.address(), filler_size,
ClearFreedMemoryMode::kDontClearFreedMemory);
return HeapObject::FromAddress(object.address() + filler_size);
}
// static
HeapObject Heap::AlignWithFiller(ReadOnlyRoots roots, HeapObject object,
int object_size, int allocation_size,
AllocationAlignment alignment) {
int filler_size = allocation_size - object_size;
DCHECK_LT(0, filler_size);
int pre_filler = GetFillToAlign(object.address(), alignment);
if (pre_filler) {
object = PrecedeWithFiller(roots, object, pre_filler);
filler_size -= pre_filler;
}
if (filler_size) {
CreateFillerObjectAt(roots, object.address() + object_size, filler_size,
ClearFreedMemoryMode::kDontClearFreedMemory);
}
return object;
}
void* Heap::AllocateExternalBackingStore(
const std::function<void*(size_t)>& allocate, size_t byte_length) {
if (!always_allocate()) {
size_t new_space_backing_store_bytes =
new_space()->ExternalBackingStoreBytes();
if (new_space_backing_store_bytes >= 2 * kMaxSemiSpaceSize &&
new_space_backing_store_bytes >= byte_length) {
// Performing a young generation GC amortizes over the allocated backing
// store bytes and may free enough external bytes for this allocation.
CollectGarbage(NEW_SPACE,
GarbageCollectionReason::kExternalMemoryPressure);
}
}
// TODO(ulan): Perform GCs proactively based on the byte_length and
// the current external backing store counters.
void* result = allocate(byte_length);
if (result) return result;
if (!always_allocate()) {
for (int i = 0; i < 2; i++) {
CollectGarbage(OLD_SPACE,
GarbageCollectionReason::kExternalMemoryPressure);
result = allocate(byte_length);
if (result) return result;
}
isolate()->counters()->gc_last_resort_from_handles()->Increment();
CollectAllAvailableGarbage(
GarbageCollectionReason::kExternalMemoryPressure);
}
return allocate(byte_length);
}
void Heap::ConfigureInitialOldGenerationSize() {
if (!old_generation_size_configured_ && tracer()->SurvivalEventsRecorded()) {
const size_t minimum_growing_step =
MemoryController<V8HeapTrait>::MinimumAllocationLimitGrowingStep(
CurrentHeapGrowingMode());
const size_t new_old_generation_allocation_limit =
Max(OldGenerationSizeOfObjects() + minimum_growing_step,
static_cast<size_t>(
static_cast<double>(old_generation_allocation_limit()) *
(tracer()->AverageSurvivalRatio() / 100)));
if (new_old_generation_allocation_limit <
old_generation_allocation_limit()) {
set_old_generation_allocation_limit(new_old_generation_allocation_limit);
} else {
old_generation_size_configured_ = true;
}
if (UseGlobalMemoryScheduling()) {
const size_t new_global_memory_limit = Max(
GlobalSizeOfObjects() + minimum_growing_step,
static_cast<size_t>(static_cast<double>(global_allocation_limit_) *
(tracer()->AverageSurvivalRatio() / 100)));
if (new_global_memory_limit < global_allocation_limit_) {
global_allocation_limit_ = new_global_memory_limit;
}
}
}
}
void Heap::FlushNumberStringCache() {
// Flush the number to string cache.
int len = number_string_cache().length();
for (int i = 0; i < len; i++) {
number_string_cache().set_undefined(i);
}
}
namespace {
HeapObject CreateFillerObjectAtImpl(ReadOnlyRoots roots, Address addr, int size,
ClearFreedMemoryMode clear_memory_mode) {
if (size == 0) return HeapObject();
HeapObject filler = HeapObject::FromAddress(addr);
if (size == kTaggedSize) {
filler.set_map_after_allocation(roots.unchecked_one_pointer_filler_map(),
SKIP_WRITE_BARRIER);
} else if (size == 2 * kTaggedSize) {
filler.set_map_after_allocation(roots.unchecked_two_pointer_filler_map(),
SKIP_WRITE_BARRIER);
if (clear_memory_mode == ClearFreedMemoryMode::kClearFreedMemory) {
AtomicSlot slot(ObjectSlot(addr) + 1);
*slot = static_cast<Tagged_t>(kClearedFreeMemoryValue);
}
} else {
DCHECK_GT(size, 2 * kTaggedSize);
filler.set_map_after_allocation(roots.unchecked_free_space_map(),
SKIP_WRITE_BARRIER);
FreeSpace::cast(filler).relaxed_write_size(size);
if (clear_memory_mode == ClearFreedMemoryMode::kClearFreedMemory) {
MemsetTagged(ObjectSlot(addr) + 2, Object(kClearedFreeMemoryValue),
(size / kTaggedSize) - 2);
}
}
// At this point, we may be deserializing the heap from a snapshot, and
// none of the maps have been created yet and are nullptr.
DCHECK((filler.map_slot().contains_value(kNullAddress) &&
!Heap::FromWritableHeapObject(filler)->deserialization_complete()) ||
filler.map().IsMap());
return filler;
}
#ifdef DEBUG
void VerifyNoNeedToClearSlots(Address start, Address end) {
BasicMemoryChunk* basic_chunk = BasicMemoryChunk::FromAddress(start);
if (basic_chunk->InReadOnlySpace()) return;
MemoryChunk* chunk = static_cast<MemoryChunk*>(basic_chunk);
// TODO(ulan): Support verification of large pages.
if (chunk->InYoungGeneration() || chunk->IsLargePage()) return;
BaseSpace* space = chunk->owner();
space->heap()->VerifySlotRangeHasNoRecordedSlots(start, end);
}
#else
void VerifyNoNeedToClearSlots(Address start, Address end) {}
#endif // DEBUG
} // namespace
// static
HeapObject Heap::CreateFillerObjectAt(ReadOnlyRoots roots, Address addr,
int size,
ClearFreedMemoryMode clear_memory_mode) {
// TODO(leszeks): Verify that no slots need to be recorded.
HeapObject filler =
CreateFillerObjectAtImpl(roots, addr, size, clear_memory_mode);
VerifyNoNeedToClearSlots(addr, addr + size);
return filler;
}
void Heap::CreateFillerObjectAtBackground(
Address addr, int size, ClearFreedMemoryMode clear_memory_mode) {
CreateFillerObjectAtImpl(ReadOnlyRoots(this), addr, size, clear_memory_mode);
// Do not verify whether slots are cleared here: the concurrent sweeper is not
// allowed to access the main thread's remembered set.
}
HeapObject Heap::CreateFillerObjectAt(Address addr, int size,
ClearRecordedSlots clear_slots_mode) {
if (size == 0) return HeapObject();
HeapObject filler = CreateFillerObjectAtImpl(
ReadOnlyRoots(this), addr, size,
clear_slots_mode == ClearRecordedSlots::kYes
? ClearFreedMemoryMode::kClearFreedMemory
: ClearFreedMemoryMode::kDontClearFreedMemory);
if (!V8_ENABLE_THIRD_PARTY_HEAP_BOOL) {
if (clear_slots_mode == ClearRecordedSlots::kYes) {
ClearRecordedSlotRange(addr, addr + size);
} else {
VerifyNoNeedToClearSlots(addr, addr + size);
}
}
return filler;
}
bool Heap::CanMoveObjectStart(HeapObject object) {
if (!FLAG_move_object_start) return false;
// Sampling heap profiler may have a reference to the object.
if (isolate()->heap_profiler()->is_sampling_allocations()) return false;
if (IsLargeObject(object)) return false;
// We can move the object start if the page was already swept.
return Page::FromHeapObject(object)->SweepingDone();
}
bool Heap::IsImmovable(HeapObject object) {
if (V8_ENABLE_THIRD_PARTY_HEAP_BOOL) {
// TODO(steveblackburn): For now all objects are immovable.
// Will need to revisit once moving is supported.
return true;
}
BasicMemoryChunk* chunk = BasicMemoryChunk::FromHeapObject(object);
return chunk->NeverEvacuate() || IsLargeObject(object);
}
bool Heap::IsLargeObject(HeapObject object) {
return BasicMemoryChunk::FromHeapObject(object)->IsLargePage();
}
#ifdef ENABLE_SLOW_DCHECKS
namespace {
class LeftTrimmerVerifierRootVisitor : public RootVisitor {
public:
explicit LeftTrimmerVerifierRootVisitor(FixedArrayBase to_check)
: to_check_(to_check) {}
void VisitRootPointers(Root root, const char* description,
FullObjectSlot start, FullObjectSlot end) override {
for (FullObjectSlot p = start; p < end; ++p) {
DCHECK_NE(*p, to_check_);
}
}
void VisitRootPointers(Root root, const char* description,
OffHeapObjectSlot start,
OffHeapObjectSlot end) override {
DCHECK_EQ(root, Root::kStringTable);
// We can skip iterating the string table, it doesn't point to any fixed
// arrays.
}
private:
FixedArrayBase to_check_;
DISALLOW_COPY_AND_ASSIGN(LeftTrimmerVerifierRootVisitor);
};
} // namespace
#endif // ENABLE_SLOW_DCHECKS
namespace {
bool MayContainRecordedSlots(HeapObject object) {
if (V8_ENABLE_THIRD_PARTY_HEAP_BOOL) return false;
// New space object do not have recorded slots.
if (BasicMemoryChunk::FromHeapObject(object)->InYoungGeneration())
return false;
// Allowlist objects that definitely do not have pointers.
if (object.IsByteArray() || object.IsFixedDoubleArray()) return false;
// Conservatively return true for other objects.
return true;
}
} // namespace
void Heap::OnMoveEvent(HeapObject target, HeapObject source,
int size_in_bytes) {
HeapProfiler* heap_profiler = isolate_->heap_profiler();
if (heap_profiler->is_tracking_object_moves()) {
heap_profiler->ObjectMoveEvent(source.address(), target.address(),
size_in_bytes);
}
for (auto& tracker : allocation_trackers_) {
tracker->MoveEvent(source.address(), target.address(), size_in_bytes);
}
if (target.IsSharedFunctionInfo()) {
LOG_CODE_EVENT(isolate_, SharedFunctionInfoMoveEvent(source.address(),
target.address()));
}
if (FLAG_verify_predictable) {
++allocations_count_;
// Advance synthetic time by making a time request.
MonotonicallyIncreasingTimeInMs();
UpdateAllocationsHash(source);
UpdateAllocationsHash(target);
UpdateAllocationsHash(size_in_bytes);
if (allocations_count_ % FLAG_dump_allocations_digest_at_alloc == 0) {
PrintAllocationsHash();
}
} else if (FLAG_fuzzer_gc_analysis) {
++allocations_count_;
}
}
FixedArrayBase Heap::LeftTrimFixedArray(FixedArrayBase object,
int elements_to_trim) {
if (elements_to_trim == 0) {
// This simplifies reasoning in the rest of the function.
return object;
}
CHECK(!object.is_null());
DCHECK(CanMoveObjectStart(object));
// Add custom visitor to concurrent marker if new left-trimmable type
// is added.
DCHECK(object.IsFixedArray() || object.IsFixedDoubleArray());
const int element_size = object.IsFixedArray() ? kTaggedSize : kDoubleSize;
const int bytes_to_trim = elements_to_trim * element_size;
Map map = object.map();
// For now this trick is only applied to fixed arrays which may be in new
// space or old space. In a large object space the object's start must
// coincide with chunk and thus the trick is just not applicable.
DCHECK(!IsLargeObject(object));
DCHECK(object.map() != ReadOnlyRoots(this).fixed_cow_array_map());
STATIC_ASSERT(FixedArrayBase::kMapOffset == 0);
STATIC_ASSERT(FixedArrayBase::kLengthOffset == kTaggedSize);
STATIC_ASSERT(FixedArrayBase::kHeaderSize == 2 * kTaggedSize);
const int len = object.length();
DCHECK(elements_to_trim <= len);
// Calculate location of new array start.
Address old_start = object.address();
Address new_start = old_start + bytes_to_trim;
if (incremental_marking()->IsMarking()) {
incremental_marking()->NotifyLeftTrimming(
object, HeapObject::FromAddress(new_start));
}
#ifdef DEBUG
if (MayContainRecordedSlots(object)) {
MemoryChunk* chunk = MemoryChunk::FromHeapObject(object);
DCHECK(!chunk->RegisteredObjectWithInvalidatedSlots<OLD_TO_OLD>(object));
DCHECK(!chunk->RegisteredObjectWithInvalidatedSlots<OLD_TO_NEW>(object));
}
#endif
// Technically in new space this write might be omitted (except for
// debug mode which iterates through the heap), but to play safer
// we still do it.
CreateFillerObjectAt(old_start, bytes_to_trim,
MayContainRecordedSlots(object)
? ClearRecordedSlots::kYes
: ClearRecordedSlots::kNo);
// Initialize header of the trimmed array. Since left trimming is only
// performed on pages which are not concurrently swept creating a filler
// object does not require synchronization.
RELAXED_WRITE_FIELD(object, bytes_to_trim, map);
RELAXED_WRITE_FIELD(object, bytes_to_trim + kTaggedSize,
Smi::FromInt(len - elements_to_trim));
FixedArrayBase new_object =
FixedArrayBase::cast(HeapObject::FromAddress(new_start));
// Notify the heap profiler of change in object layout.
OnMoveEvent(new_object, object, new_object.Size());
#ifdef ENABLE_SLOW_DCHECKS
if (FLAG_enable_slow_asserts) {
// Make sure the stack or other roots (e.g., Handles) don't contain pointers
// to the original FixedArray (which is now the filler object).
SafepointScope scope(this);
LeftTrimmerVerifierRootVisitor root_visitor(object);
ReadOnlyRoots(this).Iterate(&root_visitor);
IterateRoots(&root_visitor, {});
}
#endif // ENABLE_SLOW_DCHECKS
return new_object;
}
void Heap::RightTrimFixedArray(FixedArrayBase object, int elements_to_trim) {
const int len = object.length();
DCHECK_LE(elements_to_trim, len);
DCHECK_GE(elements_to_trim, 0);
int bytes_to_trim;
if (object.IsByteArray()) {
int new_size = ByteArray::SizeFor(len - elements_to_trim);
bytes_to_trim = ByteArray::SizeFor(len) - new_size;
DCHECK_GE(bytes_to_trim, 0);
} else if (object.IsFixedArray()) {
CHECK_NE(elements_to_trim, len);
bytes_to_trim = elements_to_trim * kTaggedSize;
} else {
DCHECK(object.IsFixedDoubleArray());
CHECK_NE(elements_to_trim, len);
bytes_to_trim = elements_to_trim * kDoubleSize;
}
CreateFillerForArray<FixedArrayBase>(object, elements_to_trim, bytes_to_trim);
}
void Heap::RightTrimWeakFixedArray(WeakFixedArray object,
int elements_to_trim) {
// This function is safe to use only at the end of the mark compact
// collection: When marking, we record the weak slots, and shrinking
// invalidates them.
DCHECK_EQ(gc_state(), MARK_COMPACT);
CreateFillerForArray<WeakFixedArray>(object, elements_to_trim,
elements_to_trim * kTaggedSize);
}
template <typename T>
void Heap::CreateFillerForArray(T object, int elements_to_trim,
int bytes_to_trim) {
DCHECK(object.IsFixedArrayBase() || object.IsByteArray() ||
object.IsWeakFixedArray());
// For now this trick is only applied to objects in new and paged space.
DCHECK(object.map() != ReadOnlyRoots(this).fixed_cow_array_map());
if (bytes_to_trim == 0) {
DCHECK_EQ(elements_to_trim, 0);
// No need to create filler and update live bytes counters.
return;
}
// Calculate location of new array end.
int old_size = object.Size();
Address old_end = object.address() + old_size;
Address new_end = old_end - bytes_to_trim;
#ifdef DEBUG
if (MayContainRecordedSlots(object)) {
MemoryChunk* chunk = MemoryChunk::FromHeapObject(object);
DCHECK(!chunk->RegisteredObjectWithInvalidatedSlots<OLD_TO_NEW>(object));
DCHECK(!chunk->RegisteredObjectWithInvalidatedSlots<OLD_TO_OLD>(object));
}
#endif
bool clear_slots = MayContainRecordedSlots(object);
// Technically in new space this write might be omitted (except for
// debug mode which iterates through the heap), but to play safer
// we still do it.
// We do not create a filler for objects in a large object space.
if (!IsLargeObject(object)) {
HeapObject filler = CreateFillerObjectAt(
new_end, bytes_to_trim,
clear_slots ? ClearRecordedSlots::kYes : ClearRecordedSlots::kNo);
DCHECK(!filler.is_null());
// Clear the mark bits of the black area that belongs now to the filler.
// This is an optimization. The sweeper will release black fillers anyway.
if (incremental_marking()->black_allocation() &&
incremental_marking()->marking_state()->IsBlackOrGrey(filler)) {
Page* page = Page::FromAddress(new_end);
incremental_marking()->marking_state()->bitmap(page)->ClearRange(
page->AddressToMarkbitIndex(new_end),
page->AddressToMarkbitIndex(new_end + bytes_to_trim));
}
} else if (clear_slots) {
// Large objects are not swept, so it is not necessary to clear the
// recorded slot.
MemsetTagged(ObjectSlot(new_end), Object(kClearedFreeMemoryValue),
(old_end - new_end) / kTaggedSize);
}
// Initialize header of the trimmed array. We are storing the new length
// using release store after creating a filler for the left-over space to
// avoid races with the sweeper thread.
object.synchronized_set_length(object.length() - elements_to_trim);
// Notify the heap object allocation tracker of change in object layout. The
// array may not be moved during GC, and size has to be adjusted nevertheless.
for (auto& tracker : allocation_trackers_) {
tracker->UpdateObjectSizeEvent(object.address(), object.Size());
}
}
void Heap::MakeHeapIterable() {
mark_compact_collector()->EnsureSweepingCompleted();
MakeLocalHeapLabsIterable();
}
void Heap::MakeLocalHeapLabsIterable() {
if (!FLAG_local_heaps) return;
safepoint()->IterateLocalHeaps([](LocalHeap* local_heap) {
local_heap->MakeLinearAllocationAreaIterable();
});
}
namespace {
double ComputeMutatorUtilizationImpl(double mutator_speed, double gc_speed) {
constexpr double kMinMutatorUtilization = 0.0;
constexpr double kConservativeGcSpeedInBytesPerMillisecond = 200000;
if (mutator_speed == 0) return kMinMutatorUtilization;
if (gc_speed == 0) gc_speed = kConservativeGcSpeedInBytesPerMillisecond;
// Derivation:
// mutator_utilization = mutator_time / (mutator_time + gc_time)
// mutator_time = 1 / mutator_speed
// gc_time = 1 / gc_speed
// mutator_utilization = (1 / mutator_speed) /
// (1 / mutator_speed + 1 / gc_speed)
// mutator_utilization = gc_speed / (mutator_speed + gc_speed)
return gc_speed / (mutator_speed + gc_speed);
}
} // namespace
double Heap::ComputeMutatorUtilization(const char* tag, double mutator_speed,
double gc_speed) {
double result = ComputeMutatorUtilizationImpl(mutator_speed, gc_speed);
if (FLAG_trace_mutator_utilization) {
isolate()->PrintWithTimestamp(
"%s mutator utilization = %.3f ("
"mutator_speed=%.f, gc_speed=%.f)\n",
tag, result, mutator_speed, gc_speed);
}
return result;
}
bool Heap::HasLowYoungGenerationAllocationRate() {
double mu = ComputeMutatorUtilization(
"Young generation",
tracer()->NewSpaceAllocationThroughputInBytesPerMillisecond(),
tracer()->ScavengeSpeedInBytesPerMillisecond(kForSurvivedObjects));
constexpr double kHighMutatorUtilization = 0.993;
return mu > kHighMutatorUtilization;
}
bool Heap::HasLowOldGenerationAllocationRate() {
double mu = ComputeMutatorUtilization(
"Old generation",
tracer()->OldGenerationAllocationThroughputInBytesPerMillisecond(),
tracer()->CombinedMarkCompactSpeedInBytesPerMillisecond());
const double kHighMutatorUtilization = 0.993;
return mu > kHighMutatorUtilization;
}
bool Heap::HasLowEmbedderAllocationRate() {
if (!UseGlobalMemoryScheduling()) return true;
DCHECK_NOT_NULL(local_embedder_heap_tracer());
double mu = ComputeMutatorUtilization(
"Embedder",
tracer()->CurrentEmbedderAllocationThroughputInBytesPerMillisecond(),
tracer()->EmbedderSpeedInBytesPerMillisecond());
const double kHighMutatorUtilization = 0.993;
return mu > kHighMutatorUtilization;
}
bool Heap::HasLowAllocationRate() {
return HasLowYoungGenerationAllocationRate() &&
HasLowOldGenerationAllocationRate() && HasLowEmbedderAllocationRate();
}
bool Heap::IsIneffectiveMarkCompact(size_t old_generation_size,
double mutator_utilization) {
const double kHighHeapPercentage = 0.8;
const double kLowMutatorUtilization = 0.4;
return old_generation_size >=
kHighHeapPercentage * max_old_generation_size() &&
mutator_utilization < kLowMutatorUtilization;
}
void Heap::CheckIneffectiveMarkCompact(size_t old_generation_size,
double mutator_utilization) {
const int kMaxConsecutiveIneffectiveMarkCompacts = 4;
if (!FLAG_detect_ineffective_gcs_near_heap_limit) return;
if (!IsIneffectiveMarkCompact(old_generation_size, mutator_utilization)) {
consecutive_ineffective_mark_compacts_ = 0;
return;
}
++consecutive_ineffective_mark_compacts_;
if (consecutive_ineffective_mark_compacts_ ==
kMaxConsecutiveIneffectiveMarkCompacts) {
if (InvokeNearHeapLimitCallback()) {
// The callback increased the heap limit.
consecutive_ineffective_mark_compacts_ = 0;
return;
}
FatalProcessOutOfMemory("Ineffective mark-compacts near heap limit");
}
}
bool Heap::HasHighFragmentation() {
size_t used = OldGenerationSizeOfObjects();
size_t committed = CommittedOldGenerationMemory();
return HasHighFragmentation(used, committed);
}
bool Heap::HasHighFragmentation(size_t used, size_t committed) {
const size_t kSlack = 16 * MB;
// Fragmentation is high if committed > 2 * used + kSlack.
// Rewrite the exression to avoid overflow.
DCHECK_GE(committed, used);
return committed - used > used + kSlack;
}
bool Heap::ShouldOptimizeForMemoryUsage() {
const size_t kOldGenerationSlack = max_old_generation_size() / 8;
return FLAG_optimize_for_size || isolate()->IsIsolateInBackground() ||
isolate()->IsMemorySavingsModeActive() || HighMemoryPressure() ||
!CanExpandOldGeneration(kOldGenerationSlack);
}
void Heap::ActivateMemoryReducerIfNeeded() {
// Activate memory reducer when switching to background if
// - there was no mark compact since the start.
// - the committed memory can be potentially reduced.
// 2 pages for the old, code, and map space + 1 page for new space.
const int kMinCommittedMemory = 7 * Page::kPageSize;
if (ms_count_ == 0 && CommittedMemory() > kMinCommittedMemory &&
isolate()->IsIsolateInBackground()) {
MemoryReducer::Event event;
event.type = MemoryReducer::kPossibleGarbage;
event.time_ms = MonotonicallyIncreasingTimeInMs();
memory_reducer_->NotifyPossibleGarbage(event);
}
}
void Heap::ReduceNewSpaceSize() {
// TODO(ulan): Unify this constant with the similar constant in
// GCIdleTimeHandler once the change is merged to 4.5.
static const size_t kLowAllocationThroughput = 1000;
const double allocation_throughput =
tracer()->CurrentAllocationThroughputInBytesPerMillisecond();
if (FLAG_predictable) return;
if (ShouldReduceMemory() ||
((allocation_throughput != 0) &&
(allocation_throughput < kLowAllocationThroughput))) {
new_space_->Shrink();
new_lo_space_->SetCapacity(new_space_->Capacity());
UncommitFromSpace();
}
}
void Heap::FinalizeIncrementalMarkingIfComplete(
GarbageCollectionReason gc_reason) {
if (incremental_marking()->IsMarking() &&
(incremental_marking()->IsReadyToOverApproximateWeakClosure() ||
(!incremental_marking()->finalize_marking_completed() &&
mark_compact_collector()->local_marking_worklists()->IsEmpty() &&
local_embedder_heap_tracer()->ShouldFinalizeIncrementalMarking()))) {
FinalizeIncrementalMarkingIncrementally(gc_reason);
} else if (incremental_marking()->IsComplete() ||
(incremental_marking()->IsMarking() &&
mark_compact_collector()->local_marking_worklists()->IsEmpty() &&
local_embedder_heap_tracer()
->ShouldFinalizeIncrementalMarking())) {
CollectAllGarbage(current_gc_flags_, gc_reason, current_gc_callback_flags_);
}
}
void Heap::FinalizeIncrementalMarkingAtomically(
GarbageCollectionReason gc_reason) {
DCHECK(!incremental_marking()->IsStopped());
CollectAllGarbage(current_gc_flags_, gc_reason, current_gc_callback_flags_);
}
void Heap::InvokeIncrementalMarkingPrologueCallbacks() {
GCCallbacksScope scope(this);
if (scope.CheckReenter()) {
AllowHeapAllocation allow_allocation;
TRACE_GC(tracer(), GCTracer::Scope::MC_INCREMENTAL_EXTERNAL_PROLOGUE);
VMState<EXTERNAL> state(isolate_);
HandleScope handle_scope(isolate_);
CallGCPrologueCallbacks(kGCTypeIncrementalMarking, kNoGCCallbackFlags);
}
}
void Heap::InvokeIncrementalMarkingEpilogueCallbacks() {
GCCallbacksScope scope(this);
if (scope.CheckReenter()) {
AllowHeapAllocation allow_allocation;
TRACE_GC(tracer(), GCTracer::Scope::MC_INCREMENTAL_EXTERNAL_EPILOGUE);
VMState<EXTERNAL> state(isolate_);
HandleScope handle_scope(isolate_);
CallGCEpilogueCallbacks(kGCTypeIncrementalMarking, kNoGCCallbackFlags);
}
}
void Heap::FinalizeIncrementalMarkingIncrementally(
GarbageCollectionReason gc_reason) {
if (FLAG_trace_incremental_marking) {
isolate()->PrintWithTimestamp(
"[IncrementalMarking] (%s).\n",
Heap::GarbageCollectionReasonToString(gc_reason));
}
DevToolsTraceEventScope devtools_trace_event_scope(
this, "MajorGC", "incremental finalization step");
HistogramTimerScope incremental_marking_scope(
isolate()->counters()->gc_incremental_marking_finalize());
TRACE_EVENT0("v8", "V8.GCIncrementalMarkingFinalize");
TRACE_GC(tracer(), GCTracer::Scope::MC_INCREMENTAL_FINALIZE);
SafepointScope safepoint(this);
InvokeIncrementalMarkingPrologueCallbacks();
incremental_marking()->FinalizeIncrementally();
InvokeIncrementalMarkingEpilogueCallbacks();
}
void Heap::NotifyObjectLayoutChange(
HeapObject object, const DisallowHeapAllocation&,
InvalidateRecordedSlots invalidate_recorded_slots) {
if (incremental_marking()->IsMarking()) {
incremental_marking()->MarkBlackAndVisitObjectDueToLayoutChange(object);
if (incremental_marking()->IsCompacting() &&
invalidate_recorded_slots == InvalidateRecordedSlots::kYes &&
MayContainRecordedSlots(object)) {
MemoryChunk::FromHeapObject(object)
->RegisterObjectWithInvalidatedSlots<OLD_TO_OLD>(object);
}
}
if (invalidate_recorded_slots == InvalidateRecordedSlots::kYes &&
MayContainRecordedSlots(object)) {
MemoryChunk::FromHeapObject(object)
->RegisterObjectWithInvalidatedSlots<OLD_TO_NEW>(object);
}
#ifdef VERIFY_HEAP
if (FLAG_verify_heap) {
DCHECK(pending_layout_change_object_.is_null());
pending_layout_change_object_ = object;
}
#endif
}
#ifdef VERIFY_HEAP
// Helper class for collecting slot addresses.
class SlotCollectingVisitor final : public ObjectVisitor {
public:
void VisitPointers(HeapObject host, ObjectSlot start,
ObjectSlot end) override {
VisitPointers(host, MaybeObjectSlot(start), MaybeObjectSlot(end));
}
void VisitPointers(HeapObject host, MaybeObjectSlot start,
MaybeObjectSlot end) final {
for (MaybeObjectSlot p = start; p < end; ++p) {
slots_.push_back(p);
}
}
void VisitCodeTarget(Code host, RelocInfo* rinfo) final { UNREACHABLE(); }
void VisitEmbeddedPointer(Code host, RelocInfo* rinfo) override {
UNREACHABLE();
}
int number_of_slots() { return static_cast<int>(slots_.size()); }
MaybeObjectSlot slot(int i) { return slots_[i]; }
private:
std::vector<MaybeObjectSlot> slots_;
};
void Heap::VerifyObjectLayoutChange(HeapObject object, Map new_map) {
if (!FLAG_verify_heap) return;
// Check that Heap::NotifyObjectLayoutChange was called for object transitions
// that are not safe for concurrent marking.
// If you see this check triggering for a freshly allocated object,
// use object->set_map_after_allocation() to initialize its map.
if (pending_layout_change_object_.is_null()) {
if (object.IsJSObject()) {
DCHECK(!object.map().TransitionRequiresSynchronizationWithGC(new_map));
} else if (object.IsString() &&
(new_map == ReadOnlyRoots(this).thin_string_map() ||
new_map == ReadOnlyRoots(this).thin_one_byte_string_map())) {
// When transitioning a string to ThinString,
// Heap::NotifyObjectLayoutChange doesn't need to be invoked because only
// tagged fields are introduced.
} else {
// Check that the set of slots before and after the transition match.
SlotCollectingVisitor old_visitor;
object.IterateFast(&old_visitor);
MapWord old_map_word = object.map_word();
// Temporarily set the new map to iterate new slots.
object.set_map_word(MapWord::FromMap(new_map));
SlotCollectingVisitor new_visitor;
object.IterateFast(&new_visitor);
// Restore the old map.
object.set_map_word(old_map_word);
DCHECK_EQ(new_visitor.number_of_slots(), old_visitor.number_of_slots());
for (int i = 0; i < new_visitor.number_of_slots(); i++) {
DCHECK(new_visitor.slot(i) == old_visitor.slot(i));
}
}
} else {
DCHECK_EQ(pending_layout_change_object_, object);
pending_layout_change_object_ = HeapObject();
}
}
#endif
GCIdleTimeHeapState Heap::ComputeHeapState() {
GCIdleTimeHeapState heap_state;
heap_state.contexts_disposed = contexts_disposed_;
heap_state.contexts_disposal_rate =
tracer()->ContextDisposalRateInMilliseconds();
heap_state.size_of_objects = static_cast<size_t>(SizeOfObjects());
heap_state.incremental_marking_stopped = incremental_marking()->IsStopped();
return heap_state;
}
bool Heap::PerformIdleTimeAction(GCIdleTimeAction action,
GCIdleTimeHeapState heap_state,
double deadline_in_ms) {
bool result = false;
switch (action) {
case GCIdleTimeAction::kDone:
result = true;
break;
case GCIdleTimeAction::kIncrementalStep: {
incremental_marking()->AdvanceWithDeadline(
deadline_in_ms, IncrementalMarking::NO_GC_VIA_STACK_GUARD,
StepOrigin::kTask);
FinalizeIncrementalMarkingIfComplete(
GarbageCollectionReason::kFinalizeMarkingViaTask);
result = incremental_marking()->IsStopped();
break;
}
case GCIdleTimeAction::kFullGC: {
DCHECK_LT(0, contexts_disposed_);
HistogramTimerScope scope(isolate_->counters()->gc_context());
TRACE_EVENT0("v8", "V8.GCContext");
CollectAllGarbage(kNoGCFlags, GarbageCollectionReason::kContextDisposal);
break;
}
}
return result;
}
void Heap::IdleNotificationEpilogue(GCIdleTimeAction action,
GCIdleTimeHeapState heap_state,
double start_ms, double deadline_in_ms) {
double idle_time_in_ms = deadline_in_ms - start_ms;
double current_time = MonotonicallyIncreasingTimeInMs();
last_idle_notification_time_ = current_time;
double deadline_difference = deadline_in_ms - current_time;
contexts_disposed_ = 0;
if (FLAG_trace_idle_notification) {
isolate_->PrintWithTimestamp(
"Idle notification: requested idle time %.2f ms, used idle time %.2f "
"ms, deadline usage %.2f ms [",
idle_time_in_ms, idle_time_in_ms - deadline_difference,
deadline_difference);
switch (action) {
case GCIdleTimeAction::kDone:
PrintF("done");
break;
case GCIdleTimeAction::kIncrementalStep:
PrintF("incremental step");
break;
case GCIdleTimeAction::kFullGC:
PrintF("full GC");
break;
}
PrintF("]");
if (FLAG_trace_idle_notification_verbose) {
PrintF("[");
heap_state.Print();
PrintF("]");
}
PrintF("\n");
}
}
double Heap::MonotonicallyIncreasingTimeInMs() {
return V8::GetCurrentPlatform()->MonotonicallyIncreasingTime() *
static_cast<double>(base::Time::kMillisecondsPerSecond);
}
void Heap::VerifyNewSpaceTop() { new_space()->VerifyTop(); }
bool Heap::IdleNotification(int idle_time_in_ms) {
return IdleNotification(
V8::GetCurrentPlatform()->MonotonicallyIncreasingTime() +
(static_cast<double>(idle_time_in_ms) /
static_cast<double>(base::Time::kMillisecondsPerSecond)));
}
bool Heap::IdleNotification(double deadline_in_seconds) {
CHECK(HasBeenSetUp());
double deadline_in_ms =
deadline_in_seconds *
static_cast<double>(base::Time::kMillisecondsPerSecond);
HistogramTimerScope idle_notification_scope(
isolate_->counters()->gc_idle_notification());
TRACE_EVENT0("v8", "V8.GCIdleNotification");
double start_ms = MonotonicallyIncreasingTimeInMs();
double idle_time_in_ms = deadline_in_ms - start_ms;
tracer()->SampleAllocation(start_ms, NewSpaceAllocationCounter(),
OldGenerationAllocationCounter(),
EmbedderAllocationCounter());
GCIdleTimeHeapState heap_state = ComputeHeapState();
GCIdleTimeAction action =
gc_idle_time_handler_->Compute(idle_time_in_ms, heap_state);
bool result = PerformIdleTimeAction(action, heap_state, deadline_in_ms);
IdleNotificationEpilogue(action, heap_state, start_ms, deadline_in_ms);
return result;
}
bool Heap::RecentIdleNotificationHappened() {
return (last_idle_notification_time_ +
GCIdleTimeHandler::kMaxScheduledIdleTime) >
MonotonicallyIncreasingTimeInMs();
}
class MemoryPressureInterruptTask : public CancelableTask {
public:
explicit MemoryPressureInterruptTask(Heap* heap)
: CancelableTask(heap->isolate()), heap_(heap) {}
~MemoryPressureInterruptTask() override = default;
private:
// v8::internal::CancelableTask overrides.
void RunInternal() override { heap_->CheckMemoryPressure(); }
Heap* heap_;
DISALLOW_COPY_AND_ASSIGN(MemoryPressureInterruptTask);
};
void Heap::CheckMemoryPressure() {
if (HighMemoryPressure()) {
// The optimizing compiler may be unnecessarily holding on to memory.
isolate()->AbortConcurrentOptimization(BlockingBehavior::kDontBlock);
}
// Reset the memory pressure level to avoid recursive GCs triggered by
// CheckMemoryPressure from AdjustAmountOfExternalMemory called by
// the finalizers.
MemoryPressureLevel memory_pressure_level = memory_pressure_level_.exchange(
MemoryPressureLevel::kNone, std::memory_order_relaxed);
if (memory_pressure_level == MemoryPressureLevel::kCritical) {
TRACE_EVENT0("devtools.timeline,v8", "V8.CheckMemoryPressure");
CollectGarbageOnMemoryPressure();
} else if (memory_pressure_level == MemoryPressureLevel::kModerate) {
if (FLAG_incremental_marking && incremental_marking()->IsStopped()) {
TRACE_EVENT0("devtools.timeline,v8", "V8.CheckMemoryPressure");
StartIncrementalMarking(kReduceMemoryFootprintMask,
GarbageCollectionReason::kMemoryPressure);
}
}
}
void Heap::CollectGarbageOnMemoryPressure() {
const int kGarbageThresholdInBytes = 8 * MB;
const double kGarbageThresholdAsFractionOfTotalMemory = 0.1;
// This constant is the maximum response time in RAIL performance model.
const double kMaxMemoryPressurePauseMs = 100;
double start = MonotonicallyIncreasingTimeInMs();
CollectAllGarbage(kReduceMemoryFootprintMask,
GarbageCollectionReason::kMemoryPressure,
kGCCallbackFlagCollectAllAvailableGarbage);
EagerlyFreeExternalMemory();
double end = MonotonicallyIncreasingTimeInMs();
// Estimate how much memory we can free.
int64_t potential_garbage =
(CommittedMemory() - SizeOfObjects()) + external_memory_.total();
// If we can potentially free large amount of memory, then start GC right
// away instead of waiting for memory reducer.
if (potential_garbage >= kGarbageThresholdInBytes &&
potential_garbage >=
CommittedMemory() * kGarbageThresholdAsFractionOfTotalMemory) {
// If we spent less than half of the time budget, then perform full GC
// Otherwise, start incremental marking.
if (end - start < kMaxMemoryPressurePauseMs / 2) {
CollectAllGarbage(kReduceMemoryFootprintMask,
GarbageCollectionReason::kMemoryPressure,
kGCCallbackFlagCollectAllAvailableGarbage);
} else {
if (FLAG_incremental_marking && incremental_marking()->IsStopped()) {
StartIncrementalMarking(kReduceMemoryFootprintMask,
GarbageCollectionReason::kMemoryPressure);
}
}
}
}
void Heap::MemoryPressureNotification(MemoryPressureLevel level,
bool is_isolate_locked) {
TRACE_EVENT1("devtools.timeline,v8", "V8.MemoryPressureNotification", "level",
static_cast<int>(level));
MemoryPressureLevel previous =
memory_pressure_level_.exchange(level, std::memory_order_relaxed);
if ((previous != MemoryPressureLevel::kCritical &&
level == MemoryPressureLevel::kCritical) ||
(previous == MemoryPressureLevel::kNone &&
level == MemoryPressureLevel::kModerate)) {
if (is_isolate_locked) {
CheckMemoryPressure();
} else {
ExecutionAccess access(isolate());
isolate()->stack_guard()->RequestGC();
auto taskrunner = V8::GetCurrentPlatform()->GetForegroundTaskRunner(
reinterpret_cast<v8::Isolate*>(isolate()));
taskrunner->PostTask(std::make_unique<MemoryPressureInterruptTask>(this));
}
}
}
void Heap::EagerlyFreeExternalMemory() {
array_buffer_sweeper()->EnsureFinished();
memory_allocator()->unmapper()->EnsureUnmappingCompleted();
}
void Heap::AddNearHeapLimitCallback(v8::NearHeapLimitCallback callback,
void* data) {
const size_t kMaxCallbacks = 100;
CHECK_LT(near_heap_limit_callbacks_.size(), kMaxCallbacks);
for (auto callback_data : near_heap_limit_callbacks_) {
CHECK_NE(callback_data.first, callback);
}
near_heap_limit_callbacks_.push_back(std::make_pair(callback, data));
}
void Heap::RemoveNearHeapLimitCallback(v8::NearHeapLimitCallback callback,
size_t heap_limit) {
for (size_t i = 0; i < near_heap_limit_callbacks_.size(); i++) {
if (near_heap_limit_callbacks_[i].first == callback) {
near_heap_limit_callbacks_.erase(near_heap_limit_callbacks_.begin() + i);
if (heap_limit) {
RestoreHeapLimit(heap_limit);
}
return;
}
}
UNREACHABLE();
}
void Heap::AppendArrayBufferExtension(JSArrayBuffer object,
ArrayBufferExtension* extension) {
array_buffer_sweeper_->Append(object, extension);
}
void Heap::AutomaticallyRestoreInitialHeapLimit(double threshold_percent) {
initial_max_old_generation_size_threshold_ =
initial_max_old_generation_size_ * threshold_percent;
}
bool Heap::InvokeNearHeapLimitCallback() {
if (near_heap_limit_callbacks_.size() > 0) {
HandleScope scope(isolate());
v8::NearHeapLimitCallback callback =
near_heap_limit_callbacks_.back().first;
void* data = near_heap_limit_callbacks_.back().second;
size_t heap_limit = callback(data, max_old_generation_size(),
initial_max_old_generation_size_);
if (heap_limit > max_old_generation_size()) {
set_max_old_generation_size(
Min(heap_limit, AllocatorLimitOnMaxOldGenerationSize()));
return true;
}
}
return false;
}
bool Heap::MeasureMemory(std::unique_ptr<v8::MeasureMemoryDelegate> delegate,
v8::MeasureMemoryExecution execution) {
HandleScope handle_scope(isolate());
std::vector<Handle<NativeContext>> contexts = FindAllNativeContexts();
std::vector<Handle<NativeContext>> to_measure;
for (auto& current : contexts) {
if (delegate->ShouldMeasure(
v8::Utils::ToLocal(Handle<Context>::cast(current)))) {
to_measure.push_back(current);
}
}
return memory_measurement_->EnqueueRequest(std::move(delegate), execution,
to_measure);
}
std::unique_ptr<v8::MeasureMemoryDelegate> Heap::MeasureMemoryDelegate(
Handle<NativeContext> context, Handle<JSPromise> promise,
v8::MeasureMemoryMode mode) {
return i::MemoryMeasurement::DefaultDelegate(isolate_, context, promise,
mode);
}
void Heap::CollectCodeStatistics() {
TRACE_EVENT0("v8", "Heap::CollectCodeStatistics");
CodeStatistics::ResetCodeAndMetadataStatistics(isolate());
// We do not look for code in new space, or map space. If code
// somehow ends up in those spaces, we would miss it here.
CodeStatistics::CollectCodeStatistics(code_space_, isolate());
CodeStatistics::CollectCodeStatistics(old_space_, isolate());
CodeStatistics::CollectCodeStatistics(code_lo_space_, isolate());
}
#ifdef DEBUG
void Heap::Print() {
if (!HasBeenSetUp()) return;
isolate()->PrintStack(stdout);
for (SpaceIterator it(this); it.HasNext();) {
it.Next()->Print();
}
}
void Heap::ReportCodeStatistics(const char* title) {
PrintF(">>>>>> Code Stats (%s) >>>>>>\n", title);
CollectCodeStatistics();
CodeStatistics::ReportCodeStatistics(isolate());
}
#endif // DEBUG
const char* Heap::GarbageCollectionReasonToString(
GarbageCollectionReason gc_reason) {
switch (gc_reason) {
case GarbageCollectionReason::kAllocationFailure:
return "allocation failure";
case GarbageCollectionReason::kAllocationLimit:
return "allocation limit";
case GarbageCollectionReason::kContextDisposal:
return "context disposal";
case GarbageCollectionReason::kCountersExtension:
return "counters extension";
case GarbageCollectionReason::kDebugger:
return "debugger";
case GarbageCollectionReason::kDeserializer:
return "deserialize";
case GarbageCollectionReason::kExternalMemoryPressure:
return "external memory pressure";
case GarbageCollectionReason::kFinalizeMarkingViaStackGuard:
return "finalize incremental marking via stack guard";
case GarbageCollectionReason::kFinalizeMarkingViaTask:
return "finalize incremental marking via task";
case GarbageCollectionReason::kFullHashtable:
return "full hash-table";
case GarbageCollectionReason::kHeapProfiler:
return "heap profiler";
case GarbageCollectionReason::kTask:
return "task";
case GarbageCollectionReason::kLastResort:
return "last resort";
case GarbageCollectionReason::kLowMemoryNotification:
return "low memory notification";
case GarbageCollectionReason::kMakeHeapIterable:
return "make heap iterable";
case GarbageCollectionReason::kMemoryPressure:
return "memory pressure";
case GarbageCollectionReason::kMemoryReducer:
return "memory reducer";
case GarbageCollectionReason::kRuntime:
return "runtime";
case GarbageCollectionReason::kSamplingProfiler:
return "sampling profiler";
case GarbageCollectionReason::kSnapshotCreator:
return "snapshot creator";
case GarbageCollectionReason::kTesting:
return "testing";
case GarbageCollectionReason::kExternalFinalize:
return "external finalize";
case GarbageCollectionReason::kGlobalAllocationLimit:
return "global allocation limit";
case GarbageCollectionReason::kMeasureMemory:
return "measure memory";
case GarbageCollectionReason::kUnknown:
return "unknown";
case GarbageCollectionReason::kBackgroundAllocationFailure:
return "background allocation failure";
}
UNREACHABLE();
}
bool Heap::Contains(HeapObject value) const {
if (V8_ENABLE_THIRD_PARTY_HEAP_BOOL) {
return true;
}
if (ReadOnlyHeap::Contains(value)) {
return false;
}
if (memory_allocator()->IsOutsideAllocatedSpace(value.address())) {
return false;
}
return HasBeenSetUp() &&
(new_space_->ToSpaceContains(value) || old_space_->Contains(value) ||
code_space_->Contains(value) || map_space_->Contains(value) ||
lo_space_->Contains(value) || code_lo_space_->Contains(value) ||
new_lo_space_->Contains(value));
}
bool Heap::InSpace(HeapObject value, AllocationSpace space) const {
if (memory_allocator()->IsOutsideAllocatedSpace(value.address())) {
return false;
}
if (!HasBeenSetUp()) return false;
switch (space) {
case NEW_SPACE:
return new_space_->ToSpaceContains(value);
case OLD_SPACE:
return old_space_->Contains(value);
case CODE_SPACE:
return code_space_->Contains(value);
case MAP_SPACE:
return map_space_->Contains(value);
case LO_SPACE:
return lo_space_->Contains(value);
case CODE_LO_SPACE:
return code_lo_space_->Contains(value);
case NEW_LO_SPACE:
return new_lo_space_->Contains(value);
case RO_SPACE:
return ReadOnlyHeap::Contains(value);
}
UNREACHABLE();
}
bool Heap::InSpaceSlow(Address addr, AllocationSpace space) const {
if (memory_allocator()->IsOutsideAllocatedSpace(addr)) {
return false;
}
if (!HasBeenSetUp()) return false;
switch (space) {
case NEW_SPACE:
return new_space_->ToSpaceContainsSlow(addr);
case OLD_SPACE:
return old_space_->ContainsSlow(addr);
case CODE_SPACE:
return code_space_->ContainsSlow(addr);
case MAP_SPACE:
return map_space_->ContainsSlow(addr);
case LO_SPACE:
return lo_space_->ContainsSlow(addr);
case CODE_LO_SPACE:
return code_lo_space_->ContainsSlow(addr);
case NEW_LO_SPACE:
return new_lo_space_->ContainsSlow(addr);
case RO_SPACE:
return read_only_space_->ContainsSlow(addr);
}
UNREACHABLE();
}
bool Heap::IsValidAllocationSpace(AllocationSpace space) {
switch (space) {
case NEW_SPACE:
case OLD_SPACE:
case CODE_SPACE:
case MAP_SPACE:
case LO_SPACE:
case NEW_LO_SPACE:
case CODE_LO_SPACE:
case RO_SPACE:
return true;
default:
return false;
}
}
#ifdef VERIFY_HEAP
void Heap::Verify() {
CHECK(HasBeenSetUp());
SafepointScope safepoint_scope(this);
HandleScope scope(isolate());
MakeLocalHeapLabsIterable();
// We have to wait here for the sweeper threads to have an iterable heap.
mark_compact_collector()->EnsureSweepingCompleted();
array_buffer_sweeper()->EnsureFinished();
VerifyPointersVisitor visitor(this);
IterateRoots(&visitor, {});
if (!isolate()->context().is_null() &&
!isolate()->normalized_map_cache()->IsUndefined(isolate())) {
NormalizedMapCache::cast(*isolate()->normalized_map_cache())
.NormalizedMapCacheVerify(isolate());
}
// The heap verifier can't deal with partially deserialized objects, so
// disable it if a deserializer is active.
// TODO(leszeks): Enable verification during deserialization, e.g. by only
// blocklisting objects that are in a partially deserialized state.
if (isolate()->has_active_deserializer()) return;
VerifySmisVisitor smis_visitor;
IterateSmiRoots(&smis_visitor);
new_space_->Verify(isolate());
old_space_->Verify(isolate(), &visitor);
map_space_->Verify(isolate(), &visitor);
VerifyPointersVisitor no_dirty_regions_visitor(this);
code_space_->Verify(isolate(), &no_dirty_regions_visitor);
lo_space_->Verify(isolate());
code_lo_space_->Verify(isolate());
new_lo_space_->Verify(isolate());
VerifyStringTable(isolate());
}
void Heap::VerifyReadOnlyHeap() {
CHECK(!read_only_space_->writable());
read_only_space_->Verify(isolate());
}
class SlotVerifyingVisitor : public ObjectVisitor {
public:
SlotVerifyingVisitor(std::set<Address>* untyped,
std::set<std::pair<SlotType, Address> >* typed)
: untyped_(untyped), typed_(typed) {}
virtual bool ShouldHaveBeenRecorded(HeapObject host, MaybeObject target) = 0;
void VisitPointers(HeapObject host, ObjectSlot start,
ObjectSlot end) override {
#ifdef DEBUG
for (ObjectSlot slot = start; slot < end; ++slot) {
DCHECK(!HasWeakHeapObjectTag(*slot));
}
#endif // DEBUG
VisitPointers(host, MaybeObjectSlot(start), MaybeObjectSlot(end));
}
void VisitPointers(HeapObject host, MaybeObjectSlot start,
MaybeObjectSlot end) final {
for (MaybeObjectSlot slot = start; slot < end; ++slot) {
if (ShouldHaveBeenRecorded(host, *slot)) {
CHECK_GT(untyped_->count(slot.address()), 0);
}
}
}
void VisitCodeTarget(Code host, RelocInfo* rinfo) override {
Object target = Code::GetCodeFromTargetAddress(rinfo->target_address());
if (ShouldHaveBeenRecorded(host, MaybeObject::FromObject(target))) {
CHECK(
InTypedSet(CODE_TARGET_SLOT, rinfo->pc()) ||
(rinfo->IsInConstantPool() &&
InTypedSet(CODE_ENTRY_SLOT, rinfo->constant_pool_entry_address())));
}
}
void VisitEmbeddedPointer(Code host, RelocInfo* rinfo) override {
Object target = rinfo->target_object();
if (ShouldHaveBeenRecorded(host, MaybeObject::FromObject(target))) {
CHECK(
InTypedSet(FULL_EMBEDDED_OBJECT_SLOT, rinfo->pc()) ||
InTypedSet(COMPRESSED_EMBEDDED_OBJECT_SLOT, rinfo->pc()) ||
(rinfo->IsInConstantPool() &&
InTypedSet(COMPRESSED_OBJECT_SLOT,
rinfo->constant_pool_entry_address())) ||
(rinfo->IsInConstantPool() &&
InTypedSet(FULL_OBJECT_SLOT, rinfo->constant_pool_entry_address())));
}
}
protected:
bool InUntypedSet(ObjectSlot slot) {
return untyped_->count(slot.address()) > 0;
}
private:
bool InTypedSet(SlotType type, Address slot) {
return typed_->count(std::make_pair(type, slot)) > 0;
}
std::set<Address>* untyped_;
std::set<std::pair<SlotType, Address> >* typed_;
};
class OldToNewSlotVerifyingVisitor : public SlotVerifyingVisitor {
public:
OldToNewSlotVerifyingVisitor(std::set<Address>* untyped,
std::set<std::pair<SlotType, Address>>* typed,
EphemeronRememberedSet* ephemeron_remembered_set)
: SlotVerifyingVisitor(untyped, typed),
ephemeron_remembered_set_(ephemeron_remembered_set) {}
bool ShouldHaveBeenRecorded(HeapObject host, MaybeObject target) override {
DCHECK_IMPLIES(target->IsStrongOrWeak() && Heap::InYoungGeneration(target),
Heap::InToPage(target));
return target->IsStrongOrWeak() && Heap::InYoungGeneration(target) &&
!Heap::InYoungGeneration(host);
}
void VisitEphemeron(HeapObject host, int index, ObjectSlot key,
ObjectSlot target) override {
VisitPointer(host, target);
#ifdef ENABLE_MINOR_MC
if (FLAG_minor_mc) return VisitPointer(host, target);
#endif
// Keys are handled separately and should never appear in this set.
CHECK(!InUntypedSet(key));
Object k = *key;
if (!ObjectInYoungGeneration(host) && ObjectInYoungGeneration(k)) {
EphemeronHashTable table = EphemeronHashTable::cast(host);
auto it = ephemeron_remembered_set_->find(table);
CHECK(it != ephemeron_remembered_set_->end());
int slot_index =
EphemeronHashTable::SlotToIndex(table.address(), key.address());
InternalIndex entry = EphemeronHashTable::IndexToEntry(slot_index);
CHECK(it->second.find(entry.as_int()) != it->second.end());
}
}
private:
EphemeronRememberedSet* ephemeron_remembered_set_;
};
template <RememberedSetType direction>
void CollectSlots(MemoryChunk* chunk, Address start, Address end,
std::set<Address>* untyped,
std::set<std::pair<SlotType, Address> >* typed) {
RememberedSet<direction>::Iterate(
chunk,
[start, end, untyped](MaybeObjectSlot slot) {
if (start <= slot.address() && slot.address() < end) {
untyped->insert(slot.address());
}
return KEEP_SLOT;
},
SlotSet::FREE_EMPTY_BUCKETS);
if (direction == OLD_TO_NEW) {
CHECK(chunk->SweepingDone());
RememberedSetSweeping::Iterate(
chunk,
[start, end, untyped](MaybeObjectSlot slot) {
if (start <= slot.address() && slot.address() < end) {
untyped->insert(slot.address());
}
return KEEP_SLOT;
},
SlotSet::FREE_EMPTY_BUCKETS);
}
RememberedSet<direction>::IterateTyped(
chunk, [=](SlotType type, Address slot) {
if (start <= slot && slot < end) {
typed->insert(std::make_pair(type, slot));
}
return KEEP_SLOT;
});
}
void Heap::VerifyRememberedSetFor(HeapObject object) {
MemoryChunk* chunk = MemoryChunk::FromHeapObject(object);
DCHECK_IMPLIES(chunk->mutex() == nullptr, ReadOnlyHeap::Contains(object));
// In RO_SPACE chunk->mutex() may be nullptr, so just ignore it.
base::LockGuard<base::Mutex, base::NullBehavior::kIgnoreIfNull> lock_guard(
chunk->mutex());
Address start = object.address();
Address end = start + object.Size();
std::set<Address> old_to_new;
std::set<std::pair<SlotType, Address> > typed_old_to_new;
if (!InYoungGeneration(object)) {
CollectSlots<OLD_TO_NEW>(chunk, start, end, &old_to_new, &typed_old_to_new);
OldToNewSlotVerifyingVisitor visitor(&old_to_new, &typed_old_to_new,
&this->ephemeron_remembered_set_);
object.IterateBody(&visitor);
}
// TODO(ulan): Add old to old slot set verification once all weak objects
// have their own instance types and slots are recorded for all weal fields.
}
#endif
#ifdef DEBUG
void Heap::VerifyCountersAfterSweeping() {
MakeLocalHeapLabsIterable();
PagedSpaceIterator spaces(this);
for (PagedSpace* space = spaces.Next(); space != nullptr;
space = spaces.Next()) {
space->VerifyCountersAfterSweeping(this);
}
}
void Heap::VerifyCountersBeforeConcurrentSweeping() {
PagedSpaceIterator spaces(this);
for (PagedSpace* space = spaces.Next(); space != nullptr;
space = spaces.Next()) {
space->VerifyCountersBeforeConcurrentSweeping();
}
}
#endif
void Heap::ZapFromSpace() {
if (!new_space_->IsFromSpaceCommitted()) return;
for (Page* page : PageRange(new_space_->from_space().first_page(), nullptr)) {
memory_allocator()->ZapBlock(page->area_start(),
page->HighWaterMark() - page->area_start(),
ZapValue());
}
}
void Heap::ZapCodeObject(Address start_address, int size_in_bytes) {
#ifdef DEBUG
DCHECK(IsAligned(start_address, kIntSize));
for (int i = 0; i < size_in_bytes / kIntSize; i++) {
Memory<int>(start_address + i * kIntSize) = kCodeZapValue;
}
#endif
}
// TODO(ishell): move builtin accessors out from Heap.
Code Heap::builtin(int index) {
DCHECK(Builtins::IsBuiltinId(index));
return Code::cast(Object(isolate()->builtins_table()[index]));
}
Address Heap::builtin_address(int index) {
DCHECK(Builtins::IsBuiltinId(index) || index == Builtins::builtin_count);
return reinterpret_cast<Address>(&isolate()->builtins_table()[index]);
}
void Heap::set_builtin(int index, Code builtin) {
DCHECK(Builtins::IsBuiltinId(index));
DCHECK(Internals::HasHeapObjectTag(builtin.ptr()));
// The given builtin may be completely uninitialized thus we cannot check its
// type here.
isolate()->builtins_table()[index] = builtin.ptr();
}
void Heap::IterateWeakRoots(RootVisitor* v, base::EnumSet<SkipRoot> options) {
DCHECK(!options.contains(SkipRoot::kWeak));
if (!options.contains(SkipRoot::kOldGeneration) &&
!options.contains(SkipRoot::kUnserializable)) {
// Do not visit for serialization, since the string table is custom
// serialized. Also do not visit if we are skipping old generation.
isolate()->string_table()->IterateElements(v);
}
v->Synchronize(VisitorSynchronization::kStringTable);
if (!options.contains(SkipRoot::kExternalStringTable) &&
!options.contains(SkipRoot::kUnserializable)) {
// Scavenge collections have special processing for this.
// Do not visit for serialization, since the external string table will
// be populated from scratch upon deserialization.
external_string_table_.IterateAll(v);
}
v->Synchronize(VisitorSynchronization::kExternalStringsTable);
}
void Heap::IterateSmiRoots(RootVisitor* v) {
// Acquire execution access since we are going to read stack limit values.
ExecutionAccess access(isolate());
v->VisitRootPointers(Root::kSmiRootList, nullptr,
roots_table().smi_roots_begin(),
roots_table().smi_roots_end());
v->Synchronize(VisitorSynchronization::kSmiRootList);
}
// We cannot avoid stale handles to left-trimmed objects, but can only make
// sure all handles still needed are updated. Filter out a stale pointer
// and clear the slot to allow post processing of handles (needed because
// the sweeper might actually free the underlying page).
class FixStaleLeftTrimmedHandlesVisitor : public RootVisitor {
public:
explicit FixStaleLeftTrimmedHandlesVisitor(Heap* heap) : heap_(heap) {
USE(heap_);
}
void VisitRootPointer(Root root, const char* description,
FullObjectSlot p) override {
FixHandle(p);
}
void VisitRootPointers(Root root, const char* description,
FullObjectSlot start, FullObjectSlot end) override {
for (FullObjectSlot p = start; p < end; ++p) FixHandle(p);
}
private:
inline void FixHandle(FullObjectSlot p) {
if (!(*p).IsHeapObject()) return;
HeapObject current = HeapObject::cast(*p);
if (!current.map_word().IsForwardingAddress() &&
current.IsFreeSpaceOrFiller()) {
#ifdef DEBUG
// We need to find a FixedArrayBase map after walking the fillers.
while (!current.map_word().IsForwardingAddress() &&
current.IsFreeSpaceOrFiller()) {
Address next = current.ptr();
if (current.map() == ReadOnlyRoots(heap_).one_pointer_filler_map()) {
next += kTaggedSize;
} else if (current.map() ==
ReadOnlyRoots(heap_).two_pointer_filler_map()) {
next += 2 * kTaggedSize;
} else {
next += current.Size();
}
current = HeapObject::cast(Object(next));
}
DCHECK(current.map_word().IsForwardingAddress() ||
current.IsFixedArrayBase());
#endif // DEBUG
p.store(Smi::zero());
}
}
Heap* heap_;
};
void Heap::IterateRoots(RootVisitor* v, base::EnumSet<SkipRoot> options) {
v->VisitRootPointers(Root::kStrongRootList, nullptr,
roots_table().strong_roots_begin(),
roots_table().strong_roots_end());
v->Synchronize(VisitorSynchronization::kStrongRootList);
isolate_->bootstrapper()->Iterate(v);
v->Synchronize(VisitorSynchronization::kBootstrapper);
Relocatable::Iterate(isolate_, v);
v->Synchronize(VisitorSynchronization::kRelocatable);
isolate_->debug()->Iterate(v);
v->Synchronize(VisitorSynchronization::kDebug);
isolate_->compilation_cache()->Iterate(v);
v->Synchronize(VisitorSynchronization::kCompilationCache);
if (!options.contains(SkipRoot::kOldGeneration)) {
IterateBuiltins(v);
v->Synchronize(VisitorSynchronization::kBuiltins);
}
// Iterate over pointers being held by inactive threads.
isolate_->thread_manager()->Iterate(v);
v->Synchronize(VisitorSynchronization::kThreadManager);
// Visitors in this block only run when not serializing. These include:
//
// - Thread-local and stack.
// - Handles.
// - Microtasks.
// - The startup object cache.
//
// When creating real startup snapshot, these areas are expected to be empty.
// It is also possible to create a snapshot of a *running* isolate for testing
// purposes. In this case, these areas are likely not empty and will simply be
// skipped.
//
// The general guideline for adding visitors to this section vs. adding them
// above is that non-transient heap state is always visited, transient heap
// state is visited only when not serializing.
if (!options.contains(SkipRoot::kUnserializable)) {
if (!options.contains(SkipRoot::kGlobalHandles)) {
if (options.contains(SkipRoot::kWeak)) {
if (options.contains(SkipRoot::kOldGeneration)) {
// Skip handles that are either weak or old.
isolate_->global_handles()->IterateYoungStrongAndDependentRoots(v);
} else {
// Skip handles that are weak.
isolate_->global_handles()->IterateStrongRoots(v);
}
} else {
// Do not skip weak handles.
if (options.contains(SkipRoot::kOldGeneration)) {
// Skip handles that are old.
isolate_->global_handles()->IterateAllYoungRoots(v);
} else {
// Do not skip any handles.
isolate_->global_handles()->IterateAllRoots(v);
}
}
}
v->Synchronize(VisitorSynchronization::kGlobalHandles);
if (!options.contains(SkipRoot::kStack)) {
IterateStackRoots(v);
v->Synchronize(VisitorSynchronization::kTop);
}
// Iterate over local handles in handle scopes.
FixStaleLeftTrimmedHandlesVisitor left_trim_visitor(this);
#ifndef V8_ENABLE_CONSERVATIVE_STACK_SCANNING
isolate_->handle_scope_implementer()->Iterate(&left_trim_visitor);
isolate_->handle_scope_implementer()->Iterate(v);
#endif
if (FLAG_local_heaps) {
safepoint_->Iterate(&left_trim_visitor);
safepoint_->Iterate(v);
}
isolate_->persistent_handles_list()->Iterate(&left_trim_visitor, isolate_);
isolate_->persistent_handles_list()->Iterate(v, isolate_);
v->Synchronize(VisitorSynchronization::kHandleScope);
if (options.contains(SkipRoot::kOldGeneration)) {
isolate_->eternal_handles()->IterateYoungRoots(v);
} else {
isolate_->eternal_handles()->IterateAllRoots(v);
}
v->Synchronize(VisitorSynchronization::kEternalHandles);
// Iterate over pending Microtasks stored in MicrotaskQueues.
MicrotaskQueue* default_microtask_queue =
isolate_->default_microtask_queue();
if (default_microtask_queue) {
MicrotaskQueue* microtask_queue = default_microtask_queue;
do {
microtask_queue->IterateMicrotasks(v);
microtask_queue = microtask_queue->next();
} while (microtask_queue != default_microtask_queue);
}
// Iterate over other strong roots (currently only identity maps and
// deoptimization entries).
for (StrongRootsEntry* current = strong_roots_head_; current;
current = current->next) {
v->VisitRootPointers(Root::kStrongRoots, nullptr, current->start,
current->end);
}
v->Synchronize(VisitorSynchronization::kStrongRoots);
// Iterate over the startup object cache unless serializing or
// deserializing.
SerializerDeserializer::Iterate(isolate_, v);
v->Synchronize(VisitorSynchronization::kStartupObjectCache);
}
if (!options.contains(SkipRoot::kWeak)) {
IterateWeakRoots(v, options);
}
}
void Heap::IterateWeakGlobalHandles(RootVisitor* v) {
isolate_->global_handles()->IterateWeakRoots(v);
}
void Heap::IterateBuiltins(RootVisitor* v) {
for (int i = 0; i < Builtins::builtin_count; i++) {
v->VisitRootPointer(Root::kBuiltins, Builtins::name(i),
FullObjectSlot(builtin_address(i)));
}
// The entry table doesn't need to be updated since all builtins are embedded.
STATIC_ASSERT(Builtins::AllBuiltinsAreIsolateIndependent());
}
void Heap::IterateStackRoots(RootVisitor* v) {
isolate_->Iterate(v);
isolate_->global_handles()->IterateStrongStackRoots(v);
}
namespace {
size_t GlobalMemorySizeFromV8Size(size_t v8_size) {
const size_t kGlobalMemoryToV8Ratio = 2;
return Min(static_cast<uint64_t>(std::numeric_limits<size_t>::max()),
static_cast<uint64_t>(v8_size) * kGlobalMemoryToV8Ratio);
}
} // anonymous namespace
void Heap::ConfigureHeap(const v8::ResourceConstraints& constraints) {
// Initialize max_semi_space_size_.
{
max_semi_space_size_ = 8 * (kSystemPointerSize / 4) * MB;
if (constraints.max_young_generation_size_in_bytes() > 0) {
max_semi_space_size_ = SemiSpaceSizeFromYoungGenerationSize(
constraints.max_young_generation_size_in_bytes());
}
if (FLAG_max_semi_space_size > 0) {
max_semi_space_size_ = static_cast<size_t>(FLAG_max_semi_space_size) * MB;
} else if (FLAG_max_heap_size > 0) {
size_t max_heap_size = static_cast<size_t>(FLAG_max_heap_size) * MB;
size_t young_generation_size, old_generation_size;
if (FLAG_max_old_space_size > 0) {
old_generation_size = static_cast<size_t>(FLAG_max_old_space_size) * MB;
young_generation_size = max_heap_size > old_generation_size
? max_heap_size - old_generation_size
: 0;
} else {
GenerationSizesFromHeapSize(max_heap_size, &young_generation_size,
&old_generation_size);
}
max_semi_space_size_ =
SemiSpaceSizeFromYoungGenerationSize(young_generation_size);
}
if (FLAG_stress_compaction) {
// This will cause more frequent GCs when stressing.
max_semi_space_size_ = MB;
}
// TODO(dinfuehr): Rounding to a power of 2 is not longer needed. Remove it.
max_semi_space_size_ =
static_cast<size_t>(base::bits::RoundUpToPowerOfTwo64(
static_cast<uint64_t>(max_semi_space_size_)));
max_semi_space_size_ = Max(max_semi_space_size_, kMinSemiSpaceSize);
max_semi_space_size_ = RoundDown<Page::kPageSize>(max_semi_space_size_);
}
// Initialize max_old_generation_size_ and max_global_memory_.
{
size_t max_old_generation_size = 700ul * (kSystemPointerSize / 4) * MB;
if (constraints.max_old_generation_size_in_bytes() > 0) {
max_old_generation_size = constraints.max_old_generation_size_in_bytes();
}
if (FLAG_max_old_space_size > 0) {
max_old_generation_size =
static_cast<size_t>(FLAG_max_old_space_size) * MB;
} else if (FLAG_max_heap_size > 0) {
size_t max_heap_size = static_cast<size_t>(FLAG_max_heap_size) * MB;
size_t young_generation_size =
YoungGenerationSizeFromSemiSpaceSize(max_semi_space_size_);
max_old_generation_size = max_heap_size > young_generation_size
? max_heap_size - young_generation_size
: 0;
}
max_old_generation_size =
Max(max_old_generation_size, MinOldGenerationSize());
max_old_generation_size =
Min(max_old_generation_size, AllocatorLimitOnMaxOldGenerationSize());
max_old_generation_size =
RoundDown<Page::kPageSize>(max_old_generation_size);
max_global_memory_size_ =
GlobalMemorySizeFromV8Size(max_old_generation_size);
set_max_old_generation_size(max_old_generation_size);
}
CHECK_IMPLIES(FLAG_max_heap_size > 0,
FLAG_max_semi_space_size == 0 || FLAG_max_old_space_size == 0);
// Initialize initial_semispace_size_.
{
initial_semispace_size_ = kMinSemiSpaceSize;
if (max_semi_space_size_ == kMaxSemiSpaceSize) {
// Start with at least 1*MB semi-space on machines with a lot of memory.
initial_semispace_size_ =
Max(initial_semispace_size_, static_cast<size_t>(1 * MB));
}
if (constraints.initial_young_generation_size_in_bytes() > 0) {
initial_semispace_size_ = SemiSpaceSizeFromYoungGenerationSize(
constraints.initial_young_generation_size_in_bytes());
}
if (FLAG_initial_heap_size > 0) {
size_t young_generation, old_generation;
Heap::GenerationSizesFromHeapSize(
static_cast<size_t>(FLAG_initial_heap_size) * MB, &young_generation,
&old_generation);
initial_semispace_size_ =
SemiSpaceSizeFromYoungGenerationSize(young_generation);
}
if (FLAG_min_semi_space_size > 0) {
initial_semispace_size_ =
static_cast<size_t>(FLAG_min_semi_space_size) * MB;
}
initial_semispace_size_ =
Min(initial_semispace_size_, max_semi_space_size_);
initial_semispace_size_ =
RoundDown<Page::kPageSize>(initial_semispace_size_);
}
if (FLAG_lazy_new_space_shrinking) {
initial_semispace_size_ = max_semi_space_size_;
}
// Initialize initial_old_space_size_.
{
initial_old_generation_size_ = kMaxInitialOldGenerationSize;
if (constraints.initial_old_generation_size_in_bytes() > 0) {
initial_old_generation_size_ =
constraints.initial_old_generation_size_in_bytes();
old_generation_size_configured_ = true;
}
if (FLAG_initial_heap_size > 0) {
size_t initial_heap_size =
static_cast<size_t>(FLAG_initial_heap_size) * MB;
size_t young_generation_size =
YoungGenerationSizeFromSemiSpaceSize(initial_semispace_size_);
initial_old_generation_size_ =
initial_heap_size > young_generation_size
? initial_heap_size - young_generation_size
: 0;
old_generation_size_configured_ = true;
}
if (FLAG_initial_old_space_size > 0) {
initial_old_generation_size_ =
static_cast<size_t>(FLAG_initial_old_space_size) * MB;
old_generation_size_configured_ = true;
}
initial_old_generation_size_ =
Min(initial_old_generation_size_, max_old_generation_size() / 2);
initial_old_generation_size_ =
RoundDown<Page::kPageSize>(initial_old_generation_size_);
}
if (old_generation_size_configured_) {
// If the embedder pre-configures the initial old generation size,
// then allow V8 to skip full GCs below that threshold.
min_old_generation_size_ = initial_old_generation_size_;
min_global_memory_size_ =
GlobalMemorySizeFromV8Size(min_old_generation_size_);
}
if (FLAG_semi_space_growth_factor < 2) {
FLAG_semi_space_growth_factor = 2;
}
set_old_generation_allocation_limit(initial_old_generation_size_);
global_allocation_limit_ =
GlobalMemorySizeFromV8Size(old_generation_allocation_limit());
initial_max_old_generation_size_ = max_old_generation_size();
// We rely on being able to allocate new arrays in paged spaces.
DCHECK(kMaxRegularHeapObjectSize >=
(JSArray::kHeaderSize +
FixedArray::SizeFor(JSArray::kInitialMaxFastElementArray) +
AllocationMemento::kSize));
code_range_size_ = constraints.code_range_size_in_bytes();
configured_ = true;
}
void Heap::AddToRingBuffer(const char* string) {
size_t first_part =
Min(strlen(string), kTraceRingBufferSize - ring_buffer_end_);
memcpy(trace_ring_buffer_ + ring_buffer_end_, string, first_part);
ring_buffer_end_ += first_part;
if (first_part < strlen(string)) {
ring_buffer_full_ = true;
size_t second_part = strlen(string) - first_part;
memcpy(trace_ring_buffer_, string + first_part, second_part);
ring_buffer_end_ = second_part;
}
}
void Heap::GetFromRingBuffer(char* buffer) {
size_t copied = 0;
if (ring_buffer_full_) {
copied = kTraceRingBufferSize - ring_buffer_end_;
memcpy(buffer, trace_ring_buffer_ + ring_buffer_end_, copied);
}
memcpy(buffer + copied, trace_ring_buffer_, ring_buffer_end_);
}
void Heap::ConfigureHeapDefault() {
v8::ResourceConstraints constraints;
ConfigureHeap(constraints);
}
void Heap::RecordStats(HeapStats* stats, bool take_snapshot) {
*stats->start_marker = HeapStats::kStartMarker;
*stats->end_marker = HeapStats::kEndMarker;
*stats->ro_space_size = read_only_space_->Size();
*stats->ro_space_capacity = read_only_space_->Capacity();
*stats->new_space_size = new_space_->Size();
*stats->new_space_capacity = new_space_->Capacity();
*stats->old_space_size = old_space_->SizeOfObjects();
*stats->old_space_capacity = old_space_->Capacity();
*stats->code_space_size = code_space_->SizeOfObjects();
*stats->code_space_capacity = code_space_->Capacity();
*stats->map_space_size = map_space_->SizeOfObjects();
*stats->map_space_capacity = map_space_->Capacity();
*stats->lo_space_size = lo_space_->Size();
*stats->code_lo_space_size = code_lo_space_->Size();
isolate_->global_handles()->RecordStats(stats);
*stats->memory_allocator_size = memory_allocator()->Size();
*stats->memory_allocator_capacity =
memory_allocator()->Size() + memory_allocator()->Available();
*stats->os_error = base::OS::GetLastError();
// TODO(leszeks): Include the string table in both current and peak usage.
*stats->malloced_memory = isolate_->allocator()->GetCurrentMemoryUsage();
*stats->malloced_peak_memory = isolate_->allocator()->GetMaxMemoryUsage();
if (take_snapshot) {
HeapObjectIterator iterator(this);
for (HeapObject obj = iterator.Next(); !obj.is_null();
obj = iterator.Next()) {
InstanceType type = obj.map().instance_type();
DCHECK(0 <= type && type <= LAST_TYPE);
stats->objects_per_type[type]++;
stats->size_per_type[type] += obj.Size();
}
}
if (stats->last_few_messages != nullptr)
GetFromRingBuffer(stats->last_few_messages);
}
size_t Heap::OldGenerationSizeOfObjects() {
PagedSpaceIterator spaces(this);
size_t total = 0;
for (PagedSpace* space = spaces.Next(); space != nullptr;
space = spaces.Next()) {
total += space->SizeOfObjects();
}
return total + lo_space_->SizeOfObjects() + code_lo_space_->SizeOfObjects();
}
size_t Heap::GlobalSizeOfObjects() {
const size_t on_heap_size = OldGenerationSizeOfObjects();
const size_t embedder_size = local_embedder_heap_tracer()
? local_embedder_heap_tracer()->used_size()
: 0;
return on_heap_size + embedder_size;
}
uint64_t Heap::AllocatedExternalMemorySinceMarkCompact() {
return external_memory_.AllocatedSinceMarkCompact();
}
bool Heap::AllocationLimitOvershotByLargeMargin() {
// This guards against too eager finalization in small heaps.
// The number is chosen based on v8.browsing_mobile on Nexus 7v2.
constexpr size_t kMarginForSmallHeaps = 32u * MB;
uint64_t size_now =
OldGenerationSizeOfObjects() + AllocatedExternalMemorySinceMarkCompact();
const size_t v8_overshoot = old_generation_allocation_limit() < size_now
? size_now - old_generation_allocation_limit()
: 0;
const size_t global_overshoot =
global_allocation_limit_ < GlobalSizeOfObjects()
? GlobalSizeOfObjects() - global_allocation_limit_
: 0;
// Bail out if the V8 and global sizes are still below their respective
// limits.
if (v8_overshoot == 0 && global_overshoot == 0) {
return false;
}
// Overshoot margin is 50% of allocation limit or half-way to the max heap
// with special handling of small heaps.
const size_t v8_margin =
Min(Max(old_generation_allocation_limit() / 2, kMarginForSmallHeaps),
(max_old_generation_size() - old_generation_allocation_limit()) / 2);
const size_t global_margin =
Min(Max(global_allocation_limit_ / 2, kMarginForSmallHeaps),
(max_global_memory_size_ - global_allocation_limit_) / 2);
return v8_overshoot >= v8_margin || global_overshoot >= global_margin;
}
// static
int Heap::MaxRegularHeapObjectSize(AllocationType allocation) {
if (!V8_ENABLE_THIRD_PARTY_HEAP_BOOL &&
(allocation == AllocationType::kCode)) {
return MemoryChunkLayout::MaxRegularCodeObjectSize();
}
return kMaxRegularHeapObjectSize;
}
bool Heap::ShouldOptimizeForLoadTime() {
return isolate()->rail_mode() == PERFORMANCE_LOAD &&
!AllocationLimitOvershotByLargeMargin() &&
MonotonicallyIncreasingTimeInMs() <
isolate()->LoadStartTimeMs() + kMaxLoadTimeMs;
}
// This predicate is called when an old generation space cannot allocated from
// the free list and is about to add a new page. Returning false will cause a
// major GC. It happens when the old generation allocation limit is reached and
// - either we need to optimize for memory usage,
// - or the incremental marking is not in progress and we cannot start it.
bool Heap::ShouldExpandOldGenerationOnSlowAllocation(LocalHeap* local_heap) {
if (always_allocate() || OldGenerationSpaceAvailable() > 0) return true;
// We reached the old generation allocation limit.
// Background threads need to be allowed to allocate without GC after teardown
// was initiated.
if (gc_state() == TEAR_DOWN) return true;
// Ensure that retry of allocation on background thread succeeds
if (IsRetryOfFailedAllocation(local_heap)) return true;
// Background thread requested GC, allocation should fail
if (CollectionRequested()) return false;
if (ShouldOptimizeForMemoryUsage()) return false;
if (ShouldOptimizeForLoadTime()) return true;
if (incremental_marking()->NeedsFinalization()) {
return !AllocationLimitOvershotByLargeMargin();
}
if (incremental_marking()->IsStopped() &&
IncrementalMarkingLimitReached() == IncrementalMarkingLimit::kNoLimit) {
// We cannot start incremental marking.
return false;
}
return true;
}
bool Heap::IsRetryOfFailedAllocation(LocalHeap* local_heap) {
if (!local_heap) return false;
return local_heap->allocation_failed_;
}
Heap::HeapGrowingMode Heap::CurrentHeapGrowingMode() {
if (ShouldReduceMemory() || FLAG_stress_compaction) {
return Heap::HeapGrowingMode::kMinimal;
}
if (ShouldOptimizeForMemoryUsage()) {
return Heap::HeapGrowingMode::kConservative;
}
if (memory_reducer()->ShouldGrowHeapSlowly()) {
return Heap::HeapGrowingMode::kSlow;
}
return Heap::HeapGrowingMode::kDefault;
}
base::Optional<size_t> Heap::GlobalMemoryAvailable() {
if (!UseGlobalMemoryScheduling()) return {};
size_t global_size = GlobalSizeOfObjects();
if (global_size < global_allocation_limit_)
return global_allocation_limit_ - global_size;
return 0;
}
double Heap::PercentToOldGenerationLimit() {
double size_at_gc = old_generation_size_at_last_gc_;
double size_now =
OldGenerationSizeOfObjects() + AllocatedExternalMemorySinceMarkCompact();
double current_bytes = size_now - size_at_gc;
double total_bytes = old_generation_allocation_limit() - size_at_gc;
return total_bytes > 0 ? (current_bytes / total_bytes) * 100.0 : 0;
}
double Heap::PercentToGlobalMemoryLimit() {
double size_at_gc = old_generation_size_at_last_gc_;
double size_now =
OldGenerationSizeOfObjects() + AllocatedExternalMemorySinceMarkCompact();
double current_bytes = size_now - size_at_gc;
double total_bytes = old_generation_allocation_limit() - size_at_gc;
return total_bytes > 0 ? (current_bytes / total_bytes) * 100.0 : 0;
}
// This function returns either kNoLimit, kSoftLimit, or kHardLimit.
// The kNoLimit means that either incremental marking is disabled or it is too
// early to start incremental marking.
// The kSoftLimit means that incremental marking should be started soon.
// The kHardLimit means that incremental marking should be started immediately.
Heap::IncrementalMarkingLimit Heap::IncrementalMarkingLimitReached() {
// Code using an AlwaysAllocateScope assumes that the GC state does not
// change; that implies that no marking steps must be performed.
if (!incremental_marking()->CanBeActivated() || always_allocate()) {
// Incremental marking is disabled or it is too early to start.
return IncrementalMarkingLimit::kNoLimit;
}
if (FLAG_stress_incremental_marking) {
return IncrementalMarkingLimit::kHardLimit;
}
if (incremental_marking()->IsBelowActivationThresholds()) {
// Incremental marking is disabled or it is too early to start.
return IncrementalMarkingLimit::kNoLimit;
}
if (ShouldStressCompaction() || HighMemoryPressure()) {
// If there is high memory pressure or stress testing is enabled, then
// start marking immediately.
return IncrementalMarkingLimit::kHardLimit;
}
if (FLAG_stress_marking > 0) {
int current_percent = static_cast<int>(
std::max(PercentToOldGenerationLimit(), PercentToGlobalMemoryLimit()));
if (current_percent > 0) {
if (FLAG_trace_stress_marking) {
isolate()->PrintWithTimestamp(
"[IncrementalMarking] %d%% of the memory limit reached\n",
current_percent);
}
if (FLAG_fuzzer_gc_analysis) {
// Skips values >=100% since they already trigger marking.
if (current_percent < 100) {
max_marking_limit_reached_ =
std::max<double>(max_marking_limit_reached_, current_percent);
}
} else if (current_percent >= stress_marking_percentage_) {
stress_marking_percentage_ = NextStressMarkingLimit();
return IncrementalMarkingLimit::kHardLimit;
}
}
}
if (FLAG_incremental_marking_soft_trigger > 0 ||
FLAG_incremental_marking_hard_trigger > 0) {
int current_percent = static_cast<int>(
std::max(PercentToOldGenerationLimit(), PercentToGlobalMemoryLimit()));
if (current_percent > FLAG_incremental_marking_hard_trigger &&
FLAG_incremental_marking_hard_trigger > 0) {
return IncrementalMarkingLimit::kHardLimit;
}
if (current_percent > FLAG_incremental_marking_soft_trigger &&
FLAG_incremental_marking_soft_trigger > 0) {
return IncrementalMarkingLimit::kSoftLimit;
}
return IncrementalMarkingLimit::kNoLimit;
}
size_t old_generation_space_available = OldGenerationSpaceAvailable();
const base::Optional<size_t> global_memory_available =
GlobalMemoryAvailable();
if (old_generation_space_available > new_space_->Capacity() &&
(!global_memory_available ||
global_memory_available > new_space_->Capacity())) {
return IncrementalMarkingLimit::kNoLimit;
}
if (ShouldOptimizeForMemoryUsage()) {
return IncrementalMarkingLimit::kHardLimit;
}
if (ShouldOptimizeForLoadTime()) {
return IncrementalMarkingLimit::kNoLimit;
}
if (old_generation_space_available == 0) {
return IncrementalMarkingLimit::kHardLimit;
}
if (global_memory_available && *global_memory_available == 0) {
return IncrementalMarkingLimit::kHardLimit;
}
return IncrementalMarkingLimit::kSoftLimit;
}
bool Heap::ShouldStressCompaction() const {
return FLAG_stress_compaction && (gc_count_ & 1) != 0;
}
void Heap::EnableInlineAllocation() {
if (!inline_allocation_disabled_) return;
inline_allocation_disabled_ = false;
// Update inline allocation limit for new space.
new_space()->AdvanceAllocationObservers();
new_space()->UpdateInlineAllocationLimit(0);
}
void Heap::DisableInlineAllocation() {
if (inline_allocation_disabled_) return;
inline_allocation_disabled_ = true;
// Update inline allocation limit for new space.
new_space()->UpdateInlineAllocationLimit(0);
// Update inline allocation limit for old spaces.
PagedSpaceIterator spaces(this);
CodeSpaceMemoryModificationScope modification_scope(this);
for (PagedSpace* space = spaces.Next(); space != nullptr;
space = spaces.Next()) {
base::MutexGuard guard(space->mutex());
space->FreeLinearAllocationArea();
}
}
HeapObject Heap::AllocateRawWithLightRetrySlowPath(
int size, AllocationType allocation, AllocationOrigin origin,
AllocationAlignment alignment) {
HeapObject result;
AllocationResult alloc = AllocateRaw(size, allocation, origin, alignment);
if (alloc.To(&result)) {
// DCHECK that the successful allocation is not "exception". The one
// exception to this is when allocating the "exception" object itself, in
// which case this must be an ROSpace allocation and the exception object
// in the roots has to be unset.
DCHECK((CanAllocateInReadOnlySpace() &&
allocation == AllocationType::kReadOnly &&
ReadOnlyRoots(this).unchecked_exception() == Smi::zero()) ||
result != ReadOnlyRoots(this).exception());
return result;
}
// Two GCs before panicking. In newspace will almost always succeed.
for (int i = 0; i < 2; i++) {
CollectGarbage(alloc.RetrySpace(),
GarbageCollectionReason::kAllocationFailure);
alloc = AllocateRaw(size, allocation, origin, alignment);
if (alloc.To(&result)) {
DCHECK(result != ReadOnlyRoots(this).exception());
return result;
}
}
return HeapObject();
}
HeapObject Heap::AllocateRawWithRetryOrFailSlowPath(
int size, AllocationType allocation, AllocationOrigin origin,
AllocationAlignment alignment) {
AllocationResult alloc;
HeapObject result =
AllocateRawWithLightRetrySlowPath(size, allocation, origin, alignment);
if (!result.is_null()) return result;
isolate()->counters()->gc_last_resort_from_handles()->Increment();
CollectAllAvailableGarbage(GarbageCollectionReason::kLastResort);
{
AlwaysAllocateScope scope(this);
alloc = AllocateRaw(size, allocation, origin, alignment);
}
if (alloc.To(&result)) {
DCHECK(result != ReadOnlyRoots(this).exception());
return result;
}
// TODO(1181417): Fix this.
FatalProcessOutOfMemory("CALL_AND_RETRY_LAST");
return HeapObject();
}
void Heap::SetUp() {
#ifdef V8_ENABLE_ALLOCATION_TIMEOUT
allocation_timeout_ = NextAllocationTimeout();
#endif
#ifdef V8_ENABLE_THIRD_PARTY_HEAP
tp_heap_ = third_party_heap::Heap::New(isolate());
#endif
// Initialize heap spaces and initial maps and objects.
//
// If the heap is not yet configured (e.g. through the API), configure it.
// Configuration is based on the flags new-space-size (really the semispace
// size) and old-space-size if set or the initial values of semispace_size_
// and old_generation_size_ otherwise.
if (!configured_) ConfigureHeapDefault();
mmap_region_base_ =
reinterpret_cast<uintptr_t>(v8::internal::GetRandomMmapAddr()) &
~kMmapRegionMask;
// Set up memory allocator.
memory_allocator_.reset(
new MemoryAllocator(isolate_, MaxReserved(), code_range_size_));
mark_compact_collector_.reset(new MarkCompactCollector(this));
scavenger_collector_.reset(new ScavengerCollector(this));
incremental_marking_.reset(
new IncrementalMarking(this, mark_compact_collector_->weak_objects()));
if (FLAG_concurrent_marking || FLAG_parallel_marking) {
concurrent_marking_.reset(new ConcurrentMarking(
this, mark_compact_collector_->marking_worklists(),
mark_compact_collector_->weak_objects()));
} else {
concurrent_marking_.reset(new ConcurrentMarking(this, nullptr, nullptr));
}
marking_barrier_.reset(new MarkingBarrier(this));
for (int i = FIRST_SPACE; i <= LAST_SPACE; i++) {
space_[i] = nullptr;
}
}
void Heap::SetUpFromReadOnlyHeap(ReadOnlyHeap* ro_heap) {
DCHECK_NOT_NULL(ro_heap);
DCHECK_IMPLIES(read_only_space_ != nullptr,
read_only_space_ == ro_heap->read_only_space());
space_[RO_SPACE] = nullptr;
read_only_space_ = ro_heap->read_only_space();
}
void Heap::ReplaceReadOnlySpace(SharedReadOnlySpace* space) {
CHECK(V8_SHARED_RO_HEAP_BOOL);
if (read_only_space_) {
read_only_space_->TearDown(memory_allocator());
delete read_only_space_;
}
read_only_space_ = space;
}
class StressConcurrentAllocationObserver : public AllocationObserver {
public:
explicit StressConcurrentAllocationObserver(Heap* heap)
: AllocationObserver(1024), heap_(heap) {}
void Step(int bytes_allocated, Address, size_t) override {
DCHECK(heap_->deserialization_complete());
if (FLAG_stress_concurrent_allocation) {
// Only schedule task if --stress-concurrent-allocation is enabled. This
// allows tests to disable flag even when Isolate was already initialized.
StressConcurrentAllocatorTask::Schedule(heap_->isolate());
}
heap_->RemoveAllocationObserversFromAllSpaces(this, this);
heap_->need_to_remove_stress_concurrent_allocation_observer_ = false;
}
private:
Heap* heap_;
};
void Heap::SetUpSpaces() {
// Ensure SetUpFromReadOnlySpace has been ran.
DCHECK_NOT_NULL(read_only_space_);
space_[NEW_SPACE] = new_space_ =
new NewSpace(this, memory_allocator_->data_page_allocator(),
initial_semispace_size_, max_semi_space_size_);
space_[OLD_SPACE] = old_space_ = new OldSpace(this);
space_[CODE_SPACE] = code_space_ = new CodeSpace(this);
space_[MAP_SPACE] = map_space_ = new MapSpace(this);
space_[LO_SPACE] = lo_space_ = new OldLargeObjectSpace(this);
space_[NEW_LO_SPACE] = new_lo_space_ =
new NewLargeObjectSpace(this, new_space_->Capacity());
space_[CODE_LO_SPACE] = code_lo_space_ = new CodeLargeObjectSpace(this);
for (int i = 0; i < static_cast<int>(v8::Isolate::kUseCounterFeatureCount);
i++) {
deferred_counters_[i] = 0;
}
tracer_.reset(new GCTracer(this));
#ifdef ENABLE_MINOR_MC
minor_mark_compact_collector_ = new MinorMarkCompactCollector(this);
#else
minor_mark_compact_collector_ = nullptr;
#endif // ENABLE_MINOR_MC
array_buffer_sweeper_.reset(new ArrayBufferSweeper(this));
gc_idle_time_handler_.reset(new GCIdleTimeHandler());
memory_measurement_.reset(new MemoryMeasurement(isolate()));
memory_reducer_.reset(new MemoryReducer(this));
if (V8_UNLIKELY(TracingFlags::is_gc_stats_enabled())) {
live_object_stats_.reset(new ObjectStats(this));
dead_object_stats_.reset(new ObjectStats(this));
}
local_embedder_heap_tracer_.reset(new LocalEmbedderHeapTracer(isolate()));
LOG(isolate_, IntPtrTEvent("heap-capacity", Capacity()));
LOG(isolate_, IntPtrTEvent("heap-available", Available()));
mark_compact_collector()->SetUp();
#ifdef ENABLE_MINOR_MC
if (minor_mark_compact_collector() != nullptr) {
minor_mark_compact_collector()->SetUp();
}
#endif // ENABLE_MINOR_MC
scavenge_job_.reset(new ScavengeJob());
scavenge_task_observer_.reset(new ScavengeTaskObserver(
this, ScavengeJob::YoungGenerationTaskTriggerSize(this)));
new_space()->AddAllocationObserver(scavenge_task_observer_.get());
SetGetExternallyAllocatedMemoryInBytesCallback(
DefaultGetExternallyAllocatedMemoryInBytesCallback);
if (FLAG_stress_marking > 0) {
stress_marking_percentage_ = NextStressMarkingLimit();
stress_marking_observer_ = new StressMarkingObserver(this);
AddAllocationObserversToAllSpaces(stress_marking_observer_,
stress_marking_observer_);
}
if (FLAG_stress_scavenge > 0) {
stress_scavenge_observer_ = new StressScavengeObserver(this);
new_space()->AddAllocationObserver(stress_scavenge_observer_);
}
write_protect_code_memory_ = FLAG_write_protect_code_memory;
}
void Heap::InitializeHashSeed() {
DCHECK(!deserialization_complete_);
uint64_t new_hash_seed;
if (FLAG_hash_seed == 0) {
int64_t rnd = isolate()->random_number_generator()->NextInt64();
new_hash_seed = static_cast<uint64_t>(rnd);
} else {
new_hash_seed = static_cast<uint64_t>(FLAG_hash_seed);
}
ReadOnlyRoots(this).hash_seed().copy_in(
0, reinterpret_cast<byte*>(&new_hash_seed), kInt64Size);
}
int Heap::NextAllocationTimeout(int current_timeout) {
if (FLAG_random_gc_interval > 0) {
// If current timeout hasn't reached 0 the GC was caused by something
// different than --stress-atomic-gc flag and we don't update the timeout.
if (current_timeout <= 0) {
return isolate()->fuzzer_rng()->NextInt(FLAG_random_gc_interval + 1);
} else {
return current_timeout;
}
}
return FLAG_gc_interval;
}
void Heap::PrintAllocationsHash() {
uint32_t hash = StringHasher::GetHashCore(raw_allocations_hash_);
PrintF("\n### Allocations = %u, hash = 0x%08x\n", allocations_count(), hash);
}
void Heap::PrintMaxMarkingLimitReached() {
PrintF("\n### Maximum marking limit reached = %.02lf\n",
max_marking_limit_reached_);
}
void Heap::PrintMaxNewSpaceSizeReached() {
PrintF("\n### Maximum new space size reached = %.02lf\n",
stress_scavenge_observer_->MaxNewSpaceSizeReached());
}
int Heap::NextStressMarkingLimit() {
return isolate()->fuzzer_rng()->NextInt(FLAG_stress_marking + 1);
}
void Heap::NotifyDeserializationComplete() {
PagedSpaceIterator spaces(this);
for (PagedSpace* s = spaces.Next(); s != nullptr; s = spaces.Next()) {
if (isolate()->snapshot_available()) s->ShrinkImmortalImmovablePages();
#ifdef DEBUG
// All pages right after bootstrapping must be marked as never-evacuate.
for (Page* p : *s) {
DCHECK(p->NeverEvacuate());
}
#endif // DEBUG
}
if (FLAG_stress_concurrent_allocation) {
stress_concurrent_allocation_observer_.reset(
new StressConcurrentAllocationObserver(this));
AddAllocationObserversToAllSpaces(
stress_concurrent_allocation_observer_.get(),
stress_concurrent_allocation_observer_.get());
need_to_remove_stress_concurrent_allocation_observer_ = true;
}
deserialization_complete_ = true;
}
void Heap::NotifyBootstrapComplete() {
// This function is invoked for each native context creation. We are
// interested only in the first native context.
if (old_generation_capacity_after_bootstrap_ == 0) {
old_generation_capacity_after_bootstrap_ = OldGenerationCapacity();
}
}
void Heap::NotifyOldGenerationExpansion(AllocationSpace space,
MemoryChunk* chunk) {
// Pages created during bootstrapping may contain immortal immovable objects.
if (!deserialization_complete()) {
chunk->MarkNeverEvacuate();
}
if (space == CODE_SPACE || space == CODE_LO_SPACE) {
isolate()->AddCodeMemoryChunk(chunk);
}
const size_t kMemoryReducerActivationThreshold = 1 * MB;
if (old_generation_capacity_after_bootstrap_ && ms_count_ == 0 &&
OldGenerationCapacity() >= old_generation_capacity_after_bootstrap_ +
kMemoryReducerActivationThreshold &&
FLAG_memory_reducer_for_small_heaps) {
MemoryReducer::Event event;
event.type = MemoryReducer::kPossibleGarbage;
event.time_ms = MonotonicallyIncreasingTimeInMs();
memory_reducer()->NotifyPossibleGarbage(event);
}
}
void Heap::SetEmbedderHeapTracer(EmbedderHeapTracer* tracer) {
DCHECK_EQ(gc_state(), HeapState::NOT_IN_GC);
local_embedder_heap_tracer()->SetRemoteTracer(tracer);
}
EmbedderHeapTracer* Heap::GetEmbedderHeapTracer() const {
return local_embedder_heap_tracer()->remote_tracer();
}
EmbedderHeapTracer::TraceFlags Heap::flags_for_embedder_tracer() const {
if (is_current_gc_forced()) {
return EmbedderHeapTracer::TraceFlags::kForced;
} else if (ShouldReduceMemory()) {
return EmbedderHeapTracer::TraceFlags::kReduceMemory;
}
return EmbedderHeapTracer::TraceFlags::kNoFlags;
}
void Heap::RegisterExternallyReferencedObject(Address* location) {
GlobalHandles::MarkTraced(location);
Object object(*location);
if (!object.IsHeapObject()) {
// The embedder is not aware of whether numbers are materialized as heap
// objects are just passed around as Smis.
return;
}
HeapObject heap_object = HeapObject::cast(object);
DCHECK(IsValidHeapObject(this, heap_object));
if (FLAG_incremental_marking_wrappers && incremental_marking()->IsMarking()) {
incremental_marking()->WhiteToGreyAndPush(heap_object);
} else {
DCHECK(mark_compact_collector()->in_use());
mark_compact_collector()->MarkExternallyReferencedObject(heap_object);
}
}
void Heap::StartTearDown() {
SetGCState(TEAR_DOWN);
// Background threads may allocate and block until GC is performed. However
// this might never happen when the main thread tries to quit and doesn't
// process the event queue anymore. Avoid this deadlock by allowing all
// allocations after tear down was requested to make sure all background
// threads finish.
collection_barrier_->ShutdownRequested();
#ifdef VERIFY_HEAP
// {StartTearDown} is called fairly early during Isolate teardown, so it's
// a good time to run heap verification (if requested), before starting to
// tear down parts of the Isolate.
if (FLAG_verify_heap) {
SafepointScope scope(this);
Verify();
}
#endif
}
void Heap::TearDown() {
DCHECK_EQ(gc_state(), TEAR_DOWN);
if (FLAG_concurrent_marking || FLAG_parallel_marking)
concurrent_marking_->Pause();
// It's too late for Heap::Verify() here, as parts of the Isolate are
// already gone by the time this is called.
UpdateMaximumCommitted();
if (FLAG_verify_predictable || FLAG_fuzzer_gc_analysis) {
PrintAllocationsHash();
}
if (FLAG_fuzzer_gc_analysis) {
if (FLAG_stress_marking > 0) {
PrintMaxMarkingLimitReached();
}
if (FLAG_stress_scavenge > 0) {
PrintMaxNewSpaceSizeReached();
}
}
new_space()->RemoveAllocationObserver(scavenge_task_observer_.get());
scavenge_task_observer_.reset();
scavenge_job_.reset();
if (need_to_remove_stress_concurrent_allocation_observer_) {
RemoveAllocationObserversFromAllSpaces(
stress_concurrent_allocation_observer_.get(),
stress_concurrent_allocation_observer_.get());
}
stress_concurrent_allocation_observer_.reset();
if (FLAG_stress_marking > 0) {
RemoveAllocationObserversFromAllSpaces(stress_marking_observer_,
stress_marking_observer_);
delete stress_marking_observer_;
stress_marking_observer_ = nullptr;
}
if (FLAG_stress_scavenge > 0) {
new_space()->RemoveAllocationObserver(stress_scavenge_observer_);
delete stress_scavenge_observer_;
stress_scavenge_observer_ = nullptr;
}
if (mark_compact_collector_) {
mark_compact_collector_->TearDown();
mark_compact_collector_.reset();
}
#ifdef ENABLE_MINOR_MC
if (minor_mark_compact_collector_ != nullptr) {
minor_mark_compact_collector_->TearDown();
delete minor_mark_compact_collector_;
minor_mark_compact_collector_ = nullptr;
}
#endif // ENABLE_MINOR_MC
scavenger_collector_.reset();
array_buffer_sweeper_.reset();
incremental_marking_.reset();
concurrent_marking_.reset();
gc_idle_time_handler_.reset();
memory_measurement_.reset();
if (memory_reducer_ != nullptr) {
memory_reducer_->TearDown();
memory_reducer_.reset();
}
live_object_stats_.reset();
dead_object_stats_.reset();
local_embedder_heap_tracer_.reset();
external_string_table_.TearDown();
tracer_.reset();
for (int i = FIRST_MUTABLE_SPACE; i <= LAST_MUTABLE_SPACE; i++) {
delete space_[i];
space_[i] = nullptr;
}
isolate()->read_only_heap()->OnHeapTearDown(this);
read_only_space_ = nullptr;
memory_allocator()->TearDown();
StrongRootsEntry* next = nullptr;
for (StrongRootsEntry* current = strong_roots_head_; current;
current = next) {
next = current->next;
delete current;
}
strong_roots_head_ = nullptr;
memory_allocator_.reset();
}
void Heap::AddGCPrologueCallback(v8::Isolate::GCCallbackWithData callback,
GCType gc_type, void* data) {
DCHECK_NOT_NULL(callback);
DCHECK(gc_prologue_callbacks_.end() ==
std::find(gc_prologue_callbacks_.begin(), gc_prologue_callbacks_.end(),
GCCallbackTuple(callback, gc_type, data)));
gc_prologue_callbacks_.emplace_back(callback, gc_type, data);
}
void Heap::RemoveGCPrologueCallback(v8::Isolate::GCCallbackWithData callback,
void* data) {
DCHECK_NOT_NULL(callback);
for (size_t i = 0; i < gc_prologue_callbacks_.size(); i++) {
if (gc_prologue_callbacks_[i].callback == callback &&
gc_prologue_callbacks_[i].data == data) {
gc_prologue_callbacks_[i] = gc_prologue_callbacks_.back();
gc_prologue_callbacks_.pop_back();
return;
}
}
UNREACHABLE();
}
void Heap::AddGCEpilogueCallback(v8::Isolate::GCCallbackWithData callback,
GCType gc_type, void* data) {
DCHECK_NOT_NULL(callback);
DCHECK(gc_epilogue_callbacks_.end() ==
std::find(gc_epilogue_callbacks_.begin(), gc_epilogue_callbacks_.end(),
GCCallbackTuple(callback, gc_type, data)));
gc_epilogue_callbacks_.emplace_back(callback, gc_type, data);
}
void Heap::RemoveGCEpilogueCallback(v8::Isolate::GCCallbackWithData callback,
void* data) {
DCHECK_NOT_NULL(callback);
for (size_t i = 0; i < gc_epilogue_callbacks_.size(); i++) {
if (gc_epilogue_callbacks_[i].callback == callback &&
gc_epilogue_callbacks_[i].data == data) {
gc_epilogue_callbacks_[i] = gc_epilogue_callbacks_.back();
gc_epilogue_callbacks_.pop_back();
return;
}
}
UNREACHABLE();
}
namespace {
Handle<WeakArrayList> CompactWeakArrayList(Heap* heap,
Handle<WeakArrayList> array,
AllocationType allocation) {
if (array->length() == 0) {
return array;
}
int new_length = array->CountLiveWeakReferences();
if (new_length == array->length()) {
return array;
}
Handle<WeakArrayList> new_array = WeakArrayList::EnsureSpace(
heap->isolate(),
handle(ReadOnlyRoots(heap).empty_weak_array_list(), heap->isolate()),
new_length, allocation);
// Allocation might have caused GC and turned some of the elements into
// cleared weak heap objects. Count the number of live references again and
// fill in the new array.
int copy_to = 0;
for (int i = 0; i < array->length(); i++) {
MaybeObject element = array->Get(i);
if (element->IsCleared()) continue;
new_array->Set(copy_to++, element);
}
new_array->set_length(copy_to);
return new_array;
}
} // anonymous namespace
void Heap::CompactWeakArrayLists(AllocationType allocation) {
// Find known PrototypeUsers and compact them.
std::vector<Handle<PrototypeInfo>> prototype_infos;
{
HeapObjectIterator iterator(this);
for (HeapObject o = iterator.Next(); !o.is_null(); o = iterator.Next()) {
if (o.IsPrototypeInfo()) {
PrototypeInfo prototype_info = PrototypeInfo::cast(o);
if (prototype_info.prototype_users().IsWeakArrayList()) {
prototype_infos.emplace_back(handle(prototype_info, isolate()));
}
}
}
}
for (auto& prototype_info : prototype_infos) {
Handle<WeakArrayList> array(
WeakArrayList::cast(prototype_info->prototype_users()), isolate());
DCHECK_IMPLIES(allocation == AllocationType::kOld,
InOldSpace(*array) ||
*array == ReadOnlyRoots(this).empty_weak_array_list());
WeakArrayList new_array = PrototypeUsers::Compact(
array, this, JSObject::PrototypeRegistryCompactionCallback, allocation);
prototype_info->set_prototype_users(new_array);
}
// Find known WeakArrayLists and compact them.
Handle<WeakArrayList> scripts(script_list(), isolate());
DCHECK_IMPLIES(
!V8_ENABLE_THIRD_PARTY_HEAP_BOOL && allocation == AllocationType::kOld,
InOldSpace(*scripts));
scripts = CompactWeakArrayList(this, scripts, allocation);
set_script_list(*scripts);
}
void Heap::AddRetainedMap(Handle<NativeContext> context, Handle<Map> map) {
if (map->is_in_retained_map_list()) {
return;
}
Handle<WeakArrayList> array(context->retained_maps(), isolate());
if (array->IsFull()) {
CompactRetainedMaps(*array);
}
array =
WeakArrayList::AddToEnd(isolate(), array, MaybeObjectHandle::Weak(map));
array = WeakArrayList::AddToEnd(
isolate(), array,
MaybeObjectHandle(Smi::FromInt(FLAG_retain_maps_for_n_gc), isolate()));
if (*array != context->retained_maps()) {
context->set_retained_maps(*array);
}
map->set_is_in_retained_map_list(true);
}
void Heap::CompactRetainedMaps(WeakArrayList retained_maps) {
int length = retained_maps.length();
int new_length = 0;
// This loop compacts the array by removing cleared weak cells.
for (int i = 0; i < length; i += 2) {
MaybeObject maybe_object = retained_maps.Get(i);
if (maybe_object->IsCleared()) {
continue;
}
DCHECK(maybe_object->IsWeak());
MaybeObject age = retained_maps.Get(i + 1);
DCHECK(age->IsSmi());
if (i != new_length) {
retained_maps.Set(new_length, maybe_object);
retained_maps.Set(new_length + 1, age);
}
new_length += 2;
}
HeapObject undefined = ReadOnlyRoots(this).undefined_value();
for (int i = new_length; i < length; i++) {
retained_maps.Set(i, HeapObjectReference::Strong(undefined));
}
if (new_length != length) retained_maps.set_length(new_length);
}
void Heap::FatalProcessOutOfMemory(const char* location) {
v8::internal::V8::FatalProcessOutOfMemory(isolate(), location, true);
}
#ifdef DEBUG
class PrintHandleVisitor : public RootVisitor {
public:
void VisitRootPointers(Root root, const char* description,
FullObjectSlot start, FullObjectSlot end) override {
for (FullObjectSlot p = start; p < end; ++p)
PrintF(" handle %p to %p\n", p.ToVoidPtr(),
reinterpret_cast<void*>((*p).ptr()));
}
};
void Heap::PrintHandles() {
PrintF("Handles:\n");
PrintHandleVisitor v;
isolate_->handle_scope_implementer()->Iterate(&v);
}
#endif
class CheckHandleCountVisitor : public RootVisitor {
public:
CheckHandleCountVisitor() : handle_count_(0) {}
~CheckHandleCountVisitor() override {
CHECK_GT(HandleScope::kCheckHandleThreshold, handle_count_);
}
void VisitRootPointers(Root root, const char* description,
FullObjectSlot start, FullObjectSlot end) override {
handle_count_ += end - start;
}
private:
ptrdiff_t handle_count_;
};
void Heap::CheckHandleCount() {
CheckHandleCountVisitor v;
isolate_->handle_scope_implementer()->Iterate(&v);
}
void Heap::ClearRecordedSlot(HeapObject object, ObjectSlot slot) {
#ifndef V8_DISABLE_WRITE_BARRIERS
DCHECK(!IsLargeObject(object));
Page* page = Page::FromAddress(slot.address());
if (!page->InYoungGeneration()) {
DCHECK_EQ(page->owner_identity(), OLD_SPACE);
if (!page->SweepingDone()) {
RememberedSet<OLD_TO_NEW>::Remove(page, slot.address());
}
}
#endif
}
// static
int Heap::InsertIntoRememberedSetFromCode(MemoryChunk* chunk, Address slot) {
RememberedSet<OLD_TO_NEW>::Insert<AccessMode::NON_ATOMIC>(chunk, slot);
return 0;
}
#ifdef DEBUG
void Heap::VerifyClearedSlot(HeapObject object, ObjectSlot slot) {
#ifndef V8_DISABLE_WRITE_BARRIERS
DCHECK(!IsLargeObject(object));
if (InYoungGeneration(object)) return;
Page* page = Page::FromAddress(slot.address());
DCHECK_EQ(page->owner_identity(), OLD_SPACE);
// Slots are filtered with invalidated slots.
CHECK_IMPLIES(RememberedSet<OLD_TO_NEW>::Contains(page, slot.address()),
page->RegisteredObjectWithInvalidatedSlots<OLD_TO_NEW>(object));
CHECK_IMPLIES(RememberedSet<OLD_TO_OLD>::Contains(page, slot.address()),
page->RegisteredObjectWithInvalidatedSlots<OLD_TO_OLD>(object));
#endif
}
void Heap::VerifySlotRangeHasNoRecordedSlots(Address start, Address end) {
#ifndef V8_DISABLE_WRITE_BARRIERS
Page* page = Page::FromAddress(start);
DCHECK(!page->IsLargePage());
DCHECK(!page->InYoungGeneration());
RememberedSet<OLD_TO_NEW>::CheckNoneInRange(page, start, end);
#endif
}
#endif
void Heap::ClearRecordedSlotRange(Address start, Address end) {
#ifndef V8_DISABLE_WRITE_BARRIERS
Page* page = Page::FromAddress(start);
DCHECK(!page->IsLargePage());
if (!page->InYoungGeneration()) {
DCHECK_EQ(page->owner_identity(), OLD_SPACE);
if (!page->SweepingDone()) {
RememberedSet<OLD_TO_NEW>::RemoveRange(page, start, end,
SlotSet::KEEP_EMPTY_BUCKETS);
}
}
#endif
}
PagedSpace* PagedSpaceIterator::Next() {
int space = counter_++;
switch (space) {
case RO_SPACE:
UNREACHABLE();
case OLD_SPACE:
return heap_->old_space();
case CODE_SPACE:
return heap_->code_space();
case MAP_SPACE:
return heap_->map_space();
default:
DCHECK_GT(space, LAST_GROWABLE_PAGED_SPACE);
return nullptr;
}
}
SpaceIterator::SpaceIterator(Heap* heap)
: heap_(heap), current_space_(FIRST_MUTABLE_SPACE - 1) {}
SpaceIterator::~SpaceIterator() = default;
bool SpaceIterator::HasNext() {
// Iterate until no more spaces.
return current_space_ != LAST_SPACE;
}
Space* SpaceIterator::Next() {
DCHECK(HasNext());
return heap_->space(++current_space_);
}
class HeapObjectsFilter {
public:
virtual ~HeapObjectsFilter() = default;
virtual bool SkipObject(HeapObject object) = 0;
};
class UnreachableObjectsFilter : public HeapObjectsFilter {
public:
explicit UnreachableObjectsFilter(Heap* heap) : heap_(heap) {
MarkReachableObjects();
}
~UnreachableObjectsFilter() override {
for (auto it : reachable_) {
delete it.second;
it.second = nullptr;
}
}
bool SkipObject(HeapObject object) override {
if (object.IsFreeSpaceOrFiller()) return true;
BasicMemoryChunk* chunk = BasicMemoryChunk::FromHeapObject(object);
if (reachable_.count(chunk) == 0) return true;
return reachable_[chunk]->count(object) == 0;
}
private:
bool MarkAsReachable(HeapObject object) {
BasicMemoryChunk* chunk = BasicMemoryChunk::FromHeapObject(object);
if (reachable_.count(chunk) == 0) {
reachable_[chunk] = new std::unordered_set<HeapObject, Object::Hasher>();
}
if (reachable_[chunk]->count(object)) return false;
reachable_[chunk]->insert(object);
return true;
}
class MarkingVisitor : public ObjectVisitor, public RootVisitor {
public:
explicit MarkingVisitor(UnreachableObjectsFilter* filter)
: filter_(filter) {}
void VisitPointers(HeapObject host, ObjectSlot start,
ObjectSlot end) override {
MarkPointers(MaybeObjectSlot(start), MaybeObjectSlot(end));
}
void VisitPointers(HeapObject host, MaybeObjectSlot start,
MaybeObjectSlot end) final {
MarkPointers(start, end);
}
void VisitCodeTarget(Code host, RelocInfo* rinfo) final {
Code target = Code::GetCodeFromTargetAddress(rinfo->target_address());
MarkHeapObject(target);
}
void VisitEmbeddedPointer(Code host, RelocInfo* rinfo) final {
MarkHeapObject(rinfo->target_object());
}
void VisitRootPointers(Root root, const char* description,
FullObjectSlot start, FullObjectSlot end) override {
MarkPointersImpl(start, end);
}
void VisitRootPointers(Root root, const char* description,
OffHeapObjectSlot start,
OffHeapObjectSlot end) override {
MarkPointersImpl(start, end);
}
void TransitiveClosure() {
while (!marking_stack_.empty()) {
HeapObject obj = marking_stack_.back();
marking_stack_.pop_back();
obj.Iterate(this);
}
}
private:
void MarkPointers(MaybeObjectSlot start, MaybeObjectSlot end) {
MarkPointersImpl(start, end);
}
template <typename TSlot>
V8_INLINE void MarkPointersImpl(TSlot start, TSlot end) {
// Treat weak references as strong.
Isolate* isolate = filter_->heap_->isolate();
for (TSlot p = start; p < end; ++p) {
typename TSlot::TObject object = p.load(isolate);
HeapObject heap_object;
if (object.GetHeapObject(&heap_object)) {
MarkHeapObject(heap_object);
}
}
}
V8_INLINE void MarkHeapObject(HeapObject heap_object) {
if (filter_->MarkAsReachable(heap_object)) {
marking_stack_.push_back(heap_object);
}
}
UnreachableObjectsFilter* filter_;
std::vector<HeapObject> marking_stack_;
};
friend class MarkingVisitor;
void MarkReachableObjects() {
MarkingVisitor visitor(this);
heap_->IterateRoots(&visitor, {});
visitor.TransitiveClosure();
}
Heap* heap_;
DisallowHeapAllocation no_allocation_;
std::unordered_map<BasicMemoryChunk*,
std::unordered_set<HeapObject, Object::Hasher>*>
reachable_;
};
HeapObjectIterator::HeapObjectIterator(
Heap* heap, HeapObjectIterator::HeapObjectsFiltering filtering)
: heap_(heap),
safepoint_scope_(std::make_unique<SafepointScope>(heap)),
filtering_(filtering),
filter_(nullptr),
space_iterator_(nullptr),
object_iterator_(nullptr) {
heap_->MakeHeapIterable();
// Start the iteration.
space_iterator_ = new SpaceIterator(heap_);
switch (filtering_) {
case kFilterUnreachable:
filter_ = new UnreachableObjectsFilter(heap_);
break;
default:
break;
}
object_iterator_ = space_iterator_->Next()->GetObjectIterator(heap_);
}
HeapObjectIterator::~HeapObjectIterator() {
#ifdef DEBUG
// Assert that in filtering mode we have iterated through all
// objects. Otherwise, heap will be left in an inconsistent state.
if (filtering_ != kNoFiltering) {
DCHECK_NULL(object_iterator_);
}
#endif
delete space_iterator_;
delete filter_;
}
HeapObject HeapObjectIterator::Next() {
if (filter_ == nullptr) return NextObject();
HeapObject obj = NextObject();
while (!obj.is_null() && (filter_->SkipObject(obj))) obj = NextObject();
return obj;
}
HeapObject HeapObjectIterator::NextObject() {
// No iterator means we are done.
if (object_iterator_.get() == nullptr) return HeapObject();
HeapObject obj = object_iterator_.get()->Next();
if (!obj.is_null()) {
// If the current iterator has more objects we are fine.
return obj;
} else {
// Go though the spaces looking for one that has objects.
while (space_iterator_->HasNext()) {
object_iterator_ = space_iterator_->Next()->GetObjectIterator(heap_);
obj = object_iterator_.get()->Next();
if (!obj.is_null()) {
return obj;
}
}
}
// Done with the last space.
object_iterator_.reset(nullptr);
return HeapObject();
}
void Heap::UpdateTotalGCTime(double duration) {
if (FLAG_trace_gc_verbose) {
total_gc_time_ms_ += duration;
}
}
void Heap::ExternalStringTable::CleanUpYoung() {
int last = 0;
Isolate* isolate = heap_->isolate();
for (size_t i = 0; i < young_strings_.size(); ++i) {
Object o = young_strings_[i];
if (o.IsTheHole(isolate)) {
continue;
}
// The real external string is already in one of these vectors and was or
// will be processed. Re-processing it will add a duplicate to the vector.
if (o.IsThinString()) continue;
DCHECK(o.IsExternalString());
if (InYoungGeneration(o)) {
young_strings_[last++] = o;
} else {
old_strings_.push_back(o);
}
}
young_strings_.resize(last);
}
void Heap::ExternalStringTable::CleanUpAll() {
CleanUpYoung();
int last = 0;
Isolate* isolate = heap_->isolate();
for (size_t i = 0; i < old_strings_.size(); ++i) {
Object o = old_strings_[i];
if (o.IsTheHole(isolate)) {
continue;
}
// The real external string is already in one of these vectors and was or
// will be processed. Re-processing it will add a duplicate to the vector.
if (o.IsThinString()) continue;
DCHECK(o.IsExternalString());
DCHECK(!InYoungGeneration(o));
old_strings_[last++] = o;
}
old_strings_.resize(last);
#ifdef VERIFY_HEAP
if (FLAG_verify_heap) {
Verify();
}
#endif
}
void Heap::ExternalStringTable::TearDown() {
for (size_t i = 0; i < young_strings_.size(); ++i) {
Object o = young_strings_[i];
// Dont finalize thin strings.
if (o.IsThinString()) continue;
heap_->FinalizeExternalString(ExternalString::cast(o));
}
young_strings_.clear();
for (size_t i = 0; i < old_strings_.size(); ++i) {
Object o = old_strings_[i];
// Dont finalize thin strings.
if (o.IsThinString()) continue;
heap_->FinalizeExternalString(ExternalString::cast(o));
}
old_strings_.clear();
}
void Heap::RememberUnmappedPage(Address page, bool compacted) {
// Tag the page pointer to make it findable in the dump file.
if (compacted) {
page ^= 0xC1EAD & (Page::kPageSize - 1); // Cleared.
} else {
page ^= 0x1D1ED & (Page::kPageSize - 1); // I died.
}
remembered_unmapped_pages_[remembered_unmapped_pages_index_] = page;
remembered_unmapped_pages_index_++;
remembered_unmapped_pages_index_ %= kRememberedUnmappedPages;
}
size_t Heap::YoungArrayBufferBytes() {
return array_buffer_sweeper()->YoungBytes();
}
size_t Heap::OldArrayBufferBytes() {
return array_buffer_sweeper()->OldBytes();
}
StrongRootsEntry* Heap::RegisterStrongRoots(FullObjectSlot start,
FullObjectSlot end) {
base::MutexGuard guard(&strong_roots_mutex_);
StrongRootsEntry* entry = new StrongRootsEntry();
entry->start = start;
entry->end = end;
entry->prev = nullptr;
entry->next = strong_roots_head_;
if (strong_roots_head_) {
DCHECK_NULL(strong_roots_head_->prev);
strong_roots_head_->prev = entry;
}
strong_roots_head_ = entry;
return entry;
}
void Heap::UpdateStrongRoots(StrongRootsEntry* entry, FullObjectSlot start,
FullObjectSlot end) {
entry->start = start;
entry->end = end;
}
void Heap::UnregisterStrongRoots(StrongRootsEntry* entry) {
base::MutexGuard guard(&strong_roots_mutex_);
StrongRootsEntry* prev = entry->prev;
StrongRootsEntry* next = entry->next;
if (prev) prev->next = next;
if (next) next->prev = prev;
if (strong_roots_head_ == entry) {
DCHECK_NULL(prev);
strong_roots_head_ = next;
}
delete entry;
}
void Heap::SetBuiltinsConstantsTable(FixedArray cache) {
set_builtins_constants_table(cache);
}
void Heap::SetDetachedContexts(WeakArrayList detached_contexts) {
set_detached_contexts(detached_contexts);
}
void Heap::SetInterpreterEntryTrampolineForProfiling(Code code) {
DCHECK_EQ(Builtins::kInterpreterEntryTrampoline, code.builtin_index());
set_interpreter_entry_trampoline_for_profiling(code);
}
void Heap::PostFinalizationRegistryCleanupTaskIfNeeded() {
// Only one cleanup task is posted at a time.
if (!HasDirtyJSFinalizationRegistries() ||
is_finalization_registry_cleanup_task_posted_) {
return;
}
auto taskrunner = V8::GetCurrentPlatform()->GetForegroundTaskRunner(
reinterpret_cast<v8::Isolate*>(isolate()));
auto task = std::make_unique<FinalizationRegistryCleanupTask>(this);
taskrunner->PostNonNestableTask(std::move(task));
is_finalization_registry_cleanup_task_posted_ = true;
}
void Heap::EnqueueDirtyJSFinalizationRegistry(
JSFinalizationRegistry finalization_registry,
std::function<void(HeapObject object, ObjectSlot slot, Object target)>
gc_notify_updated_slot) {
// Add a FinalizationRegistry to the tail of the dirty list.
DCHECK(!HasDirtyJSFinalizationRegistries() ||
dirty_js_finalization_registries_list().IsJSFinalizationRegistry());
DCHECK(finalization_registry.next_dirty().IsUndefined(isolate()));
DCHECK(!finalization_registry.scheduled_for_cleanup());
finalization_registry.set_scheduled_for_cleanup(true);
if (dirty_js_finalization_registries_list_tail().IsUndefined(isolate())) {
DCHECK(dirty_js_finalization_registries_list().IsUndefined(isolate()));
set_dirty_js_finalization_registries_list(finalization_registry);
// dirty_js_finalization_registries_list_ is rescanned by
// ProcessWeakListRoots.
} else {
JSFinalizationRegistry tail = JSFinalizationRegistry::cast(
dirty_js_finalization_registries_list_tail());
tail.set_next_dirty(finalization_registry);
gc_notify_updated_slot(
tail, tail.RawField(JSFinalizationRegistry::kNextDirtyOffset),
finalization_registry);
}
set_dirty_js_finalization_registries_list_tail(finalization_registry);
// dirty_js_finalization_registries_list_tail_ is rescanned by
// ProcessWeakListRoots.
}
MaybeHandle<JSFinalizationRegistry> Heap::DequeueDirtyJSFinalizationRegistry() {
// Take a FinalizationRegistry from the head of the dirty list for fairness.
if (HasDirtyJSFinalizationRegistries()) {
Handle<JSFinalizationRegistry> head(
JSFinalizationRegistry::cast(dirty_js_finalization_registries_list()),
isolate());
set_dirty_js_finalization_registries_list(head->next_dirty());
head->set_next_dirty(ReadOnlyRoots(this).undefined_value());
if (*head == dirty_js_finalization_registries_list_tail()) {
set_dirty_js_finalization_registries_list_tail(
ReadOnlyRoots(this).undefined_value());
}
return head;
}
return {};
}
void Heap::RemoveDirtyFinalizationRegistriesOnContext(NativeContext context) {
if (!FLAG_harmony_weak_refs) return;
DisallowHeapAllocation no_gc;
Isolate* isolate = this->isolate();
Object prev = ReadOnlyRoots(isolate).undefined_value();
Object current = dirty_js_finalization_registries_list();
while (!current.IsUndefined(isolate)) {
JSFinalizationRegistry finalization_registry =
JSFinalizationRegistry::cast(current);
if (finalization_registry.native_context() == context) {
if (prev.IsUndefined(isolate)) {
set_dirty_js_finalization_registries_list(
finalization_registry.next_dirty());
} else {
JSFinalizationRegistry::cast(prev).set_next_dirty(
finalization_registry.next_dirty());
}
finalization_registry.set_scheduled_for_cleanup(false);
current = finalization_registry.next_dirty();
finalization_registry.set_next_dirty(
ReadOnlyRoots(isolate).undefined_value());
} else {
prev = current;
current = finalization_registry.next_dirty();
}
}
set_dirty_js_finalization_registries_list_tail(prev);
}
void Heap::KeepDuringJob(Handle<JSReceiver> target) {
DCHECK(FLAG_harmony_weak_refs);
DCHECK(weak_refs_keep_during_job().IsUndefined() ||
weak_refs_keep_during_job().IsOrderedHashSet());
Handle<OrderedHashSet> table;
if (weak_refs_keep_during_job().IsUndefined(isolate())) {
table = isolate()->factory()->NewOrderedHashSet();
} else {
table =
handle(OrderedHashSet::cast(weak_refs_keep_during_job()), isolate());
}
table = OrderedHashSet::Add(isolate(), table, target).ToHandleChecked();
set_weak_refs_keep_during_job(*table);
}
void Heap::ClearKeptObjects() {
set_weak_refs_keep_during_job(ReadOnlyRoots(isolate()).undefined_value());
}
size_t Heap::NumberOfTrackedHeapObjectTypes() {
return ObjectStats::OBJECT_STATS_COUNT;
}
size_t Heap::ObjectCountAtLastGC(size_t index) {
if (live_object_stats_ == nullptr || index >= ObjectStats::OBJECT_STATS_COUNT)
return 0;
return live_object_stats_->object_count_last_gc(index);
}
size_t Heap::ObjectSizeAtLastGC(size_t index) {
if (live_object_stats_ == nullptr || index >= ObjectStats::OBJECT_STATS_COUNT)
return 0;
return live_object_stats_->object_size_last_gc(index);
}
bool Heap::GetObjectTypeName(size_t index, const char** object_type,
const char** object_sub_type) {
if (index >= ObjectStats::OBJECT_STATS_COUNT) return false;
switch (static_cast<int>(index)) {
#define COMPARE_AND_RETURN_NAME(name) \
case name: \
*object_type = #name; \
*object_sub_type = ""; \
return true;
INSTANCE_TYPE_LIST(COMPARE_AND_RETURN_NAME)
#undef COMPARE_AND_RETURN_NAME
#define COMPARE_AND_RETURN_NAME(name) \
case ObjectStats::FIRST_VIRTUAL_TYPE + ObjectStats::name: \
*object_type = #name; \
*object_sub_type = ""; \
return true;
VIRTUAL_INSTANCE_TYPE_LIST(COMPARE_AND_RETURN_NAME)
#undef COMPARE_AND_RETURN_NAME
}
return false;
}
size_t Heap::NumberOfNativeContexts() {
int result = 0;
Object context = native_contexts_list();
while (!context.IsUndefined(isolate())) {
++result;
Context native_context = Context::cast(context);
context = native_context.next_context_link();
}
return result;
}
std::vector<Handle<NativeContext>> Heap::FindAllNativeContexts() {
std::vector<Handle<NativeContext>> result;
Object context = native_contexts_list();
while (!context.IsUndefined(isolate())) {
NativeContext native_context = NativeContext::cast(context);
result.push_back(handle(native_context, isolate()));
context = native_context.next_context_link();
}
return result;
}
std::vector<WeakArrayList> Heap::FindAllRetainedMaps() {
std::vector<WeakArrayList> result;
Object context = native_contexts_list();
while (!context.IsUndefined(isolate())) {
NativeContext native_context = NativeContext::cast(context);
result.push_back(native_context.retained_maps());
context = native_context.next_context_link();
}
return result;
}
size_t Heap::NumberOfDetachedContexts() {
// The detached_contexts() array has two entries per detached context.
return detached_contexts().length() / 2;
}
void VerifyPointersVisitor::VisitPointers(HeapObject host, ObjectSlot start,
ObjectSlot end) {
VerifyPointers(host, MaybeObjectSlot(start), MaybeObjectSlot(end));
}
void VerifyPointersVisitor::VisitPointers(HeapObject host,
MaybeObjectSlot start,
MaybeObjectSlot end) {
VerifyPointers(host, start, end);
}
void VerifyPointersVisitor::VisitRootPointers(Root root,
const char* description,
FullObjectSlot start,
FullObjectSlot end) {
VerifyPointersImpl(start, end);
}
void VerifyPointersVisitor::VisitRootPointers(Root root,
const char* description,
OffHeapObjectSlot start,
OffHeapObjectSlot end) {
VerifyPointersImpl(start, end);
}
void VerifyPointersVisitor::VerifyHeapObjectImpl(HeapObject heap_object) {
CHECK(IsValidHeapObject(heap_, heap_object));
CHECK(heap_object.map().IsMap());
}
template <typename TSlot>
void VerifyPointersVisitor::VerifyPointersImpl(TSlot start, TSlot end) {
Isolate* isolate = heap_->isolate();
for (TSlot slot = start; slot < end; ++slot) {
typename TSlot::TObject object = slot.load(isolate);
HeapObject heap_object;
if (object.GetHeapObject(&heap_object)) {
VerifyHeapObjectImpl(heap_object);
} else {
CHECK(object.IsSmi() || object.IsCleared());
}
}
}
void VerifyPointersVisitor::VerifyPointers(HeapObject host,
MaybeObjectSlot start,
MaybeObjectSlot end) {
// If this DCHECK fires then you probably added a pointer field
// to one of objects in DATA_ONLY_VISITOR_ID_LIST. You can fix
// this by moving that object to POINTER_VISITOR_ID_LIST.
DCHECK_EQ(ObjectFields::kMaybePointers,
Map::ObjectFieldsFrom(host.map().visitor_id()));
VerifyPointersImpl(start, end);
}
void VerifyPointersVisitor::VisitCodeTarget(Code host, RelocInfo* rinfo) {
Code target = Code::GetCodeFromTargetAddress(rinfo->target_address());
VerifyHeapObjectImpl(target);
}
void VerifyPointersVisitor::VisitEmbeddedPointer(Code host, RelocInfo* rinfo) {
VerifyHeapObjectImpl(rinfo->target_object());
}
void VerifySmisVisitor::VisitRootPointers(Root root, const char* description,
FullObjectSlot start,
FullObjectSlot end) {
for (FullObjectSlot current = start; current < end; ++current) {
CHECK((*current).IsSmi());
}
}
bool Heap::AllowedToBeMigrated(Map map, HeapObject obj, AllocationSpace dst) {
// Object migration is governed by the following rules:
//
// 1) Objects in new-space can be migrated to the old space
// that matches their target space or they stay in new-space.
// 2) Objects in old-space stay in the same space when migrating.
// 3) Fillers (two or more words) can migrate due to left-trimming of
// fixed arrays in new-space or old space.
// 4) Fillers (one word) can never migrate, they are skipped by
// incremental marking explicitly to prevent invalid pattern.
//
// Since this function is used for debugging only, we do not place
// asserts here, but check everything explicitly.
if (map == ReadOnlyRoots(this).one_pointer_filler_map()) return false;
InstanceType type = map.instance_type();
MemoryChunk* chunk = MemoryChunk::FromHeapObject(obj);
AllocationSpace src = chunk->owner_identity();
switch (src) {
case NEW_SPACE:
return dst == NEW_SPACE || dst == OLD_SPACE;
case OLD_SPACE:
return dst == OLD_SPACE;
case CODE_SPACE:
return dst == CODE_SPACE && type == CODE_TYPE;
case MAP_SPACE:
case LO_SPACE:
case CODE_LO_SPACE:
case NEW_LO_SPACE:
case RO_SPACE:
return false;
}
UNREACHABLE();
}
size_t Heap::EmbedderAllocationCounter() const {
return local_embedder_heap_tracer()
? local_embedder_heap_tracer()->allocated_size()
: 0;
}
void Heap::CreateObjectStats() {
if (V8_LIKELY(!TracingFlags::is_gc_stats_enabled())) return;
if (!live_object_stats_) {
live_object_stats_.reset(new ObjectStats(this));
}
if (!dead_object_stats_) {
dead_object_stats_.reset(new ObjectStats(this));
}
}
Map Heap::GcSafeMapOfCodeSpaceObject(HeapObject object) {
MapWord map_word = object.map_word();
return map_word.IsForwardingAddress() ? map_word.ToForwardingAddress().map()
: map_word.ToMap();
}
Code Heap::GcSafeCastToCode(HeapObject object, Address inner_pointer) {
Code code = Code::unchecked_cast(object);
DCHECK(!code.is_null());
DCHECK(GcSafeCodeContains(code, inner_pointer));
return code;
}
bool Heap::GcSafeCodeContains(Code code, Address addr) {
Map map = GcSafeMapOfCodeSpaceObject(code);
DCHECK(map == ReadOnlyRoots(this).code_map());
if (InstructionStream::TryLookupCode(isolate(), addr) == code) return true;
Address start = code.address();
Address end = code.address() + code.SizeFromMap(map);
return start <= addr && addr < end;
}
Code Heap::GcSafeFindCodeForInnerPointer(Address inner_pointer) {
Code code = InstructionStream::TryLookupCode(isolate(), inner_pointer);
if (!code.is_null()) return code;
if (V8_ENABLE_THIRD_PARTY_HEAP_BOOL) {
Address start = tp_heap_->GetObjectFromInnerPointer(inner_pointer);
return GcSafeCastToCode(HeapObject::FromAddress(start), inner_pointer);
}
// Check if the inner pointer points into a large object chunk.
LargePage* large_page = code_lo_space()->FindPage(inner_pointer);
if (large_page != nullptr) {
return GcSafeCastToCode(large_page->GetObject(), inner_pointer);
}
if (V8_LIKELY(code_space()->Contains(inner_pointer))) {
// Iterate through the page until we reach the end or find an object
// starting after the inner pointer.
Page* page = Page::FromAddress(inner_pointer);
Address start =
page->GetCodeObjectRegistry()->GetCodeObjectStartFromInnerAddress(
inner_pointer);
return GcSafeCastToCode(HeapObject::FromAddress(start), inner_pointer);
}
// It can only fall through to here during debugging, where for instance "jco"
// was called on an address within a RO_SPACE builtin. It cannot reach here
// during stack iteration as RO_SPACE memory is not executable so cannot
// appear on the stack as an instruction address.
DCHECK(ReadOnlyHeap::Contains(
HeapObject::FromAddress(inner_pointer & ~kHeapObjectTagMask)));
// TODO(delphick): Possibly optimize this as it iterates over all pages in
// RO_SPACE instead of just the one containing the address.
ReadOnlyHeapObjectIterator iterator(isolate()->read_only_heap());
for (HeapObject object = iterator.Next(); !object.is_null();
object = iterator.Next()) {
if (!object.IsCode()) continue;
Code code = Code::cast(object);
if (inner_pointer >= code.address() &&
inner_pointer < code.address() + code.Size()) {
return code;
}
}
UNREACHABLE();
}
void Heap::WriteBarrierForCodeSlow(Code code) {
for (RelocIterator it(code, RelocInfo::EmbeddedObjectModeMask()); !it.done();
it.next()) {
GenerationalBarrierForCode(code, it.rinfo(), it.rinfo()->target_object());
WriteBarrier::Marking(code, it.rinfo(), it.rinfo()->target_object());
}
}
void Heap::GenerationalBarrierSlow(HeapObject object, Address slot,
HeapObject value) {
MemoryChunk* chunk = MemoryChunk::FromHeapObject(object);
RememberedSet<OLD_TO_NEW>::Insert<AccessMode::NON_ATOMIC>(chunk, slot);
}
void Heap::RecordEphemeronKeyWrite(EphemeronHashTable table, Address slot) {
DCHECK(ObjectInYoungGeneration(HeapObjectSlot(slot).ToHeapObject()));
int slot_index = EphemeronHashTable::SlotToIndex(table.address(), slot);
InternalIndex entry = EphemeronHashTable::IndexToEntry(slot_index);
auto it =
ephemeron_remembered_set_.insert({table, std::unordered_set<int>()});
it.first->second.insert(entry.as_int());
}
void Heap::EphemeronKeyWriteBarrierFromCode(Address raw_object,
Address key_slot_address,
Isolate* isolate) {
EphemeronHashTable table = EphemeronHashTable::cast(Object(raw_object));
MaybeObjectSlot key_slot(key_slot_address);
MaybeObject maybe_key = *key_slot;
HeapObject key;
if (!maybe_key.GetHeapObject(&key)) return;
if (!ObjectInYoungGeneration(table) && ObjectInYoungGeneration(key)) {
isolate->heap()->RecordEphemeronKeyWrite(table, key_slot_address);
}
WriteBarrier::Marking(table, key_slot, maybe_key);
}
enum RangeWriteBarrierMode {
kDoGenerational = 1 << 0,
kDoMarking = 1 << 1,
kDoEvacuationSlotRecording = 1 << 2,
};
template <int kModeMask, typename TSlot>
void Heap::WriteBarrierForRangeImpl(MemoryChunk* source_page, HeapObject object,
TSlot start_slot, TSlot end_slot) {
// At least one of generational or marking write barrier should be requested.
STATIC_ASSERT(kModeMask & (kDoGenerational | kDoMarking));
// kDoEvacuationSlotRecording implies kDoMarking.
STATIC_ASSERT(!(kModeMask & kDoEvacuationSlotRecording) ||
(kModeMask & kDoMarking));
MarkingBarrier* marking_barrier = this->marking_barrier();
MarkCompactCollector* collector = this->mark_compact_collector();
for (TSlot slot = start_slot; slot < end_slot; ++slot) {
typename TSlot::TObject value = *slot;
HeapObject value_heap_object;
if (!value.GetHeapObject(&value_heap_object)) continue;
if ((kModeMask & kDoGenerational) &&
Heap::InYoungGeneration(value_heap_object)) {
RememberedSet<OLD_TO_NEW>::Insert<AccessMode::NON_ATOMIC>(source_page,
slot.address());
}
if ((kModeMask & kDoMarking) &&
marking_barrier->MarkValue(object, value_heap_object)) {
if (kModeMask & kDoEvacuationSlotRecording) {
collector->RecordSlot(source_page, HeapObjectSlot(slot),
value_heap_object);
}
}
}
}
// Instantiate Heap::WriteBarrierForRange() for ObjectSlot and MaybeObjectSlot.
template void Heap::WriteBarrierForRange<ObjectSlot>(HeapObject object,
ObjectSlot start_slot,
ObjectSlot end_slot);
template void Heap::WriteBarrierForRange<MaybeObjectSlot>(
HeapObject object, MaybeObjectSlot start_slot, MaybeObjectSlot end_slot);
template <typename TSlot>
void Heap::WriteBarrierForRange(HeapObject object, TSlot start_slot,
TSlot end_slot) {
MemoryChunk* source_page = MemoryChunk::FromHeapObject(object);
base::Flags<RangeWriteBarrierMode> mode;
if (!source_page->InYoungGeneration()) {
mode |= kDoGenerational;
}
if (incremental_marking()->IsMarking()) {
mode |= kDoMarking;
if (!source_page->ShouldSkipEvacuationSlotRecording<AccessMode::ATOMIC>()) {
mode |= kDoEvacuationSlotRecording;
}
}
switch (mode) {
// Nothing to be done.
case 0:
return;
// Generational only.
case kDoGenerational:
return WriteBarrierForRangeImpl<kDoGenerational>(source_page, object,
start_slot, end_slot);
// Marking, no evacuation slot recording.
case kDoMarking:
return WriteBarrierForRangeImpl<kDoMarking>(source_page, object,
start_slot, end_slot);
// Marking with evacuation slot recording.
case kDoMarking | kDoEvacuationSlotRecording:
return WriteBarrierForRangeImpl<kDoMarking | kDoEvacuationSlotRecording>(
source_page, object, start_slot, end_slot);
// Generational and marking, no evacuation slot recording.
case kDoGenerational | kDoMarking:
return WriteBarrierForRangeImpl<kDoGenerational | kDoMarking>(
source_page, object, start_slot, end_slot);
// Generational and marking with evacuation slot recording.
case kDoGenerational | kDoMarking | kDoEvacuationSlotRecording:
return WriteBarrierForRangeImpl<kDoGenerational | kDoMarking |
kDoEvacuationSlotRecording>(
source_page, object, start_slot, end_slot);
default:
UNREACHABLE();
}
}
void Heap::GenerationalBarrierForCodeSlow(Code host, RelocInfo* rinfo,
HeapObject object) {
DCHECK(InYoungGeneration(object));
Page* source_page = Page::FromHeapObject(host);
RelocInfo::Mode rmode = rinfo->rmode();
Address addr = rinfo->pc();
SlotType slot_type = SlotTypeForRelocInfoMode(rmode);
if (rinfo->IsInConstantPool()) {
addr = rinfo->constant_pool_entry_address();
if (RelocInfo::IsCodeTargetMode(rmode)) {
slot_type = CODE_ENTRY_SLOT;
} else if (RelocInfo::IsCompressedEmbeddedObject(rmode)) {
slot_type = COMPRESSED_OBJECT_SLOT;
} else {
DCHECK(RelocInfo::IsFullEmbeddedObject(rmode));
slot_type = FULL_OBJECT_SLOT;
}
}
uintptr_t offset = addr - source_page->address();
DCHECK_LT(offset, static_cast<uintptr_t>(TypedSlotSet::kMaxOffset));
RememberedSet<OLD_TO_NEW>::InsertTyped(source_page, slot_type,
static_cast<uint32_t>(offset));
}
bool Heap::PageFlagsAreConsistent(HeapObject object) {
if (V8_ENABLE_THIRD_PARTY_HEAP_BOOL) {
return true;
}
BasicMemoryChunk* chunk = BasicMemoryChunk::FromHeapObject(object);
heap_internals::MemoryChunk* slim_chunk =
heap_internals::MemoryChunk::FromHeapObject(object);
// Slim chunk flags consistency.
CHECK_EQ(chunk->InYoungGeneration(), slim_chunk->InYoungGeneration());
CHECK_EQ(chunk->IsFlagSet(MemoryChunk::INCREMENTAL_MARKING),
slim_chunk->IsMarking());
AllocationSpace identity = chunk->owner()->identity();
// Generation consistency.
CHECK_EQ(identity == NEW_SPACE || identity == NEW_LO_SPACE,
slim_chunk->InYoungGeneration());
// Read-only consistency.
CHECK_EQ(chunk->InReadOnlySpace(), slim_chunk->InReadOnlySpace());
// Marking consistency.
if (chunk->IsWritable()) {
// RO_SPACE can be shared between heaps, so we can't use RO_SPACE objects to
// find a heap. The exception is when the ReadOnlySpace is writeable, during
// bootstrapping, so explicitly allow this case.
Heap* heap = Heap::FromWritableHeapObject(object);
CHECK_EQ(slim_chunk->IsMarking(), heap->incremental_marking()->IsMarking());
} else {
// Non-writable RO_SPACE must never have marking flag set.
CHECK(!slim_chunk->IsMarking());
}
return true;
}
void Heap::SetEmbedderStackStateForNextFinalization(
EmbedderHeapTracer::EmbedderStackState stack_state) {
local_embedder_heap_tracer()->SetEmbedderStackStateForNextFinalization(
stack_state);
}
#ifdef DEBUG
void Heap::IncrementObjectCounters() {
isolate_->counters()->objs_since_last_full()->Increment();
isolate_->counters()->objs_since_last_young()->Increment();
}
#endif // DEBUG
// StrongRootBlocks are allocated as a block of addresses, prefixed with a
// StrongRootsEntry pointer:
//
// | StrongRootsEntry*
// | Address 1
// | ...
// | Address N
//
// The allocate method registers the range "Address 1" to "Address N" with the
// heap as a strong root array, saves that entry in StrongRootsEntry*, and
// returns a pointer to Address 1.
Address* StrongRootBlockAllocator::allocate(size_t n) {
void* block = base::Malloc(sizeof(StrongRootsEntry*) + n * sizeof(Address));
StrongRootsEntry** header = reinterpret_cast<StrongRootsEntry**>(block);
Address* ret = reinterpret_cast<Address*>(reinterpret_cast<char*>(block) +
sizeof(StrongRootsEntry*));
memset(ret, kNullAddress, n * sizeof(Address));
*header =
heap_->RegisterStrongRoots(FullObjectSlot(ret), FullObjectSlot(ret + n));
return ret;
}
void StrongRootBlockAllocator::deallocate(Address* p, size_t n) noexcept {
// The allocate method returns a pointer to Address 1, so the deallocate
// method has to offset that pointer back by sizeof(StrongRootsEntry*).
void* block = reinterpret_cast<char*>(p) - sizeof(StrongRootsEntry*);
StrongRootsEntry** header = reinterpret_cast<StrongRootsEntry**>(block);
heap_->UnregisterStrongRoots(*header);
base::Free(block);
}
} // namespace internal
} // namespace v8