// 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 <unordered_map>
#include <unordered_set>
#include "src/accessors.h"
#include "src/api-inl.h"
#include "src/assembler-inl.h"
#include "src/ast/context-slot-cache.h"
#include "src/base/bits.h"
#include "src/base/once.h"
#include "src/base/utils/random-number-generator.h"
#include "src/bootstrapper.h"
#include "src/code-stubs.h"
#include "src/compilation-cache.h"
#include "src/conversions.h"
#include "src/debug/debug.h"
#include "src/deoptimizer.h"
#include "src/feedback-vector.h"
#include "src/global-handles.h"
#include "src/heap/array-buffer-collector.h"
#include "src/heap/array-buffer-tracker-inl.h"
#include "src/heap/barrier.h"
#include "src/heap/code-stats.h"
#include "src/heap/concurrent-marking.h"
#include "src/heap/embedder-tracing.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.h"
#include "src/heap/item-parallel-job.h"
#include "src/heap/mark-compact-inl.h"
#include "src/heap/mark-compact.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/remembered-set.h"
#include "src/heap/scavenge-job.h"
#include "src/heap/scavenger-inl.h"
#include "src/heap/store-buffer.h"
#include "src/heap/stress-marking-observer.h"
#include "src/heap/stress-scavenge-observer.h"
#include "src/heap/sweeper.h"
#include "src/instruction-stream.h"
#include "src/interpreter/interpreter.h"
#include "src/objects/data-handler.h"
#include "src/objects/hash-table-inl.h"
#include "src/objects/maybe-object.h"
#include "src/objects/shared-function-info.h"
#include "src/regexp/jsregexp.h"
#include "src/runtime-profiler.h"
#include "src/snapshot/natives.h"
#include "src/snapshot/serializer-common.h"
#include "src/snapshot/snapshot.h"
#include "src/tracing/trace-event.h"
#include "src/unicode-decoder.h"
#include "src/unicode-inl.h"
#include "src/utils-inl.h"
#include "src/utils.h"
#include "src/v8.h"
#include "src/vm-state-inl.h"
// Has to be the last include (doesn't have include guards):
#include "src/objects/object-macros.h"
namespace v8 {
namespace internal {
void Heap::SetArgumentsAdaptorDeoptPCOffset(int pc_offset) {
DCHECK_EQ(Smi::kZero, arguments_adaptor_deopt_pc_offset());
set_arguments_adaptor_deopt_pc_offset(Smi::FromInt(pc_offset));
}
void Heap::SetConstructStubCreateDeoptPCOffset(int pc_offset) {
DCHECK(construct_stub_create_deopt_pc_offset() == Smi::kZero);
set_construct_stub_create_deopt_pc_offset(Smi::FromInt(pc_offset));
}
void Heap::SetConstructStubInvokeDeoptPCOffset(int pc_offset) {
DCHECK(construct_stub_invoke_deopt_pc_offset() == Smi::kZero);
set_construct_stub_invoke_deopt_pc_offset(Smi::FromInt(pc_offset));
}
void Heap::SetInterpreterEntryReturnPCOffset(int pc_offset) {
DCHECK_EQ(Smi::kZero, 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);
}
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) {
callback = other.callback;
gc_type = other.gc_type;
data = other.data;
return *this;
}
struct Heap::StrongRootsList {
Object** start;
Object** end;
StrongRootsList* next;
};
class IdleScavengeObserver : public AllocationObserver {
public:
IdleScavengeObserver(Heap& heap, intptr_t step_size)
: AllocationObserver(step_size), heap_(heap) {}
void Step(int bytes_allocated, Address, size_t) override {
heap_.ScheduleIdleScavengeIfNeeded(bytes_allocated);
}
private:
Heap& heap_;
};
Heap::Heap()
: external_memory_(0),
external_memory_limit_(kExternalAllocationSoftLimit),
external_memory_at_last_mark_compact_(0),
external_memory_concurrently_freed_(0),
isolate_(nullptr),
code_range_size_(0),
// semispace_size_ should be a power of 2 and old_generation_size_ should
// be a multiple of Page::kPageSize.
max_semi_space_size_(8 * (kPointerSize / 4) * MB),
initial_semispace_size_(kMinSemiSpaceSizeInKB * KB),
max_old_generation_size_(700ul * (kPointerSize / 4) * MB),
initial_max_old_generation_size_(max_old_generation_size_),
initial_old_generation_size_(max_old_generation_size_ /
kInitalOldGenerationLimitFactor),
old_generation_size_configured_(false),
// Variables set based on semispace_size_ and old_generation_size_ in
// ConfigureHeap.
// Will be 4 * reserved_semispace_size_ to ensure that young
// generation can be aligned to its size.
maximum_committed_(0),
survived_since_last_expansion_(0),
survived_last_scavenge_(0),
always_allocate_scope_count_(0),
memory_pressure_level_(MemoryPressureLevel::kNone),
contexts_disposed_(0),
number_of_disposed_maps_(0),
new_space_(nullptr),
old_space_(nullptr),
code_space_(nullptr),
map_space_(nullptr),
lo_space_(nullptr),
new_lo_space_(nullptr),
read_only_space_(nullptr),
write_protect_code_memory_(false),
code_space_memory_modification_scope_depth_(0),
gc_state_(NOT_IN_GC),
gc_post_processing_depth_(0),
allocations_count_(0),
raw_allocations_hash_(0),
stress_marking_observer_(nullptr),
stress_scavenge_observer_(nullptr),
allocation_step_in_progress_(false),
max_marking_limit_reached_(0.0),
ms_count_(0),
gc_count_(0),
consecutive_ineffective_mark_compacts_(0),
mmap_region_base_(0),
remembered_unmapped_pages_index_(0),
old_generation_allocation_limit_(initial_old_generation_size_),
inline_allocation_disabled_(false),
tracer_(nullptr),
promoted_objects_size_(0),
promotion_ratio_(0),
semi_space_copied_object_size_(0),
previous_semi_space_copied_object_size_(0),
semi_space_copied_rate_(0),
nodes_died_in_new_space_(0),
nodes_copied_in_new_space_(0),
nodes_promoted_(0),
maximum_size_scavenges_(0),
last_idle_notification_time_(0.0),
last_gc_time_(0.0),
mark_compact_collector_(nullptr),
minor_mark_compact_collector_(nullptr),
array_buffer_collector_(nullptr),
memory_allocator_(nullptr),
store_buffer_(nullptr),
incremental_marking_(nullptr),
concurrent_marking_(nullptr),
gc_idle_time_handler_(nullptr),
memory_reducer_(nullptr),
live_object_stats_(nullptr),
dead_object_stats_(nullptr),
scavenge_job_(nullptr),
parallel_scavenge_semaphore_(0),
idle_scavenge_observer_(nullptr),
new_space_allocation_counter_(0),
old_generation_allocation_counter_at_last_gc_(0),
old_generation_size_at_last_gc_(0),
global_pretenuring_feedback_(kInitialFeedbackCapacity),
is_marking_flag_(false),
ring_buffer_full_(false),
ring_buffer_end_(0),
configured_(false),
current_gc_flags_(Heap::kNoGCFlags),
current_gc_callback_flags_(GCCallbackFlags::kNoGCCallbackFlags),
external_string_table_(this),
gc_callbacks_depth_(0),
deserialization_complete_(false),
strong_roots_list_(nullptr),
heap_iterator_depth_(0),
local_embedder_heap_tracer_(nullptr),
fast_promotion_mode_(false),
force_oom_(false),
delay_sweeper_tasks_for_testing_(false),
pending_layout_change_object_(nullptr),
unprotected_memory_chunks_registry_enabled_(false)
#ifdef V8_ENABLE_ALLOCATION_TIMEOUT
,
allocation_timeout_(0)
#endif // V8_ENABLE_ALLOCATION_TIMEOUT
{
// Ensure old_generation_size_ is a multiple of kPageSize.
DCHECK_EQ(0, max_old_generation_size_ & (Page::kPageSize - 1));
memset(roots_, 0, sizeof(roots_[0]) * kRootListLength);
set_native_contexts_list(nullptr);
set_allocation_sites_list(Smi::kZero);
// 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);
}
size_t Heap::MaxReserved() {
const double kFactor = Page::kPageSize * 1.0 / Page::kAllocatableMemory;
return static_cast<size_t>(
(2 * max_semi_space_size_ + max_old_generation_size_) * kFactor);
}
size_t Heap::ComputeMaxOldGenerationSize(uint64_t physical_memory) {
const size_t old_space_physical_memory_factor = 4;
size_t computed_size = static_cast<size_t>(physical_memory / i::MB /
old_space_physical_memory_factor *
kPointerMultiplier);
return Max(Min(computed_size, HeapController::kMaxHeapSize),
HeapController::kMinHeapSize);
}
size_t Heap::Capacity() {
if (!HasBeenSetUp()) return 0;
return new_space_->Capacity() + OldGenerationCapacity();
}
size_t Heap::OldGenerationCapacity() {
if (!HasBeenSetUp()) return 0;
PagedSpaces spaces(this, PagedSpaces::SpacesSpecifier::kAllPagedSpaces);
size_t total = 0;
for (PagedSpace* space = spaces.next(); space != nullptr;
space = spaces.next()) {
total += space->Capacity();
}
return total + lo_space_->SizeOfObjects();
}
size_t Heap::CommittedOldGenerationMemory() {
if (!HasBeenSetUp()) return 0;
PagedSpaces spaces(this, PagedSpaces::SpacesSpecifier::kAllPagedSpaces);
size_t total = 0;
for (PagedSpace* space = spaces.next(); space != nullptr;
space = spaces.next()) {
total += space->CommittedMemory();
}
return total + lo_space_->Size();
}
size_t Heap::CommittedMemoryOfHeapAndUnmapper() {
if (!HasBeenSetUp()) return 0;
return CommittedMemory() +
memory_allocator()->unmapper()->CommittedBufferedMemory();
}
size_t Heap::CommittedMemory() {
if (!HasBeenSetUp()) return 0;
return new_space_->CommittedMemory() + CommittedOldGenerationMemory();
}
size_t Heap::CommittedPhysicalMemory() {
if (!HasBeenSetUp()) return 0;
size_t total = 0;
for (SpaceIterator it(this); it.has_next();) {
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.has_next();) {
total += it.next()->Available();
}
return total;
}
bool Heap::CanExpandOldGeneration(size_t size) {
if (force_oom_) return false;
if (OldGenerationCapacity() + size > MaxOldGenerationSize()) 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::HasBeenSetUp() {
// 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) {
isolate_->counters()->gc_compactor_caused_by_request()->Increment();
*reason = "GC in old space requested";
return MARK_COMPACTOR;
}
if (FLAG_gc_global || (FLAG_stress_compaction && (gc_count_ & 1) != 0)) {
*reason = "GC in old space forced by flags";
return MARK_COMPACTOR;
}
if (incremental_marking()->NeedsFinalization() &&
AllocationLimitOvershotByLargeMargin()) {
*reason = "Incremental marking needs finalization";
return MARK_COMPACTOR;
}
// Over-estimate the new space size using capacity to allow some slack.
if (!CanExpandOldGeneration(new_space_->TotalCapacity())) {
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_ = state;
}
void Heap::PrintShortHeapStatistics() {
if (!FLAG_trace_gc_verbose) return;
PrintIsolate(isolate_,
"Memory allocator, used: %6" PRIuS
" KB,"
" available: %6" PRIuS " KB\n",
memory_allocator()->Size() / KB,
memory_allocator()->Available() / KB);
PrintIsolate(isolate_,
"Read-only space, used: %6" PRIuS
" KB"
", available: %6" PRIuS
" KB"
", committed: %6" PRIuS " KB\n",
read_only_space_->Size() / KB,
read_only_space_->Available() / KB,
read_only_space_->CommittedMemory() / KB);
PrintIsolate(isolate_,
"New space, used: %6" PRIuS
" KB"
", available: %6" PRIuS
" KB"
", committed: %6" PRIuS " KB\n",
new_space_->Size() / KB, new_space_->Available() / KB,
new_space_->CommittedMemory() / KB);
PrintIsolate(isolate_,
"New large object space, used: %6" PRIuS
" KB"
", available: %6" PRIuS
" KB"
", committed: %6" PRIuS " KB\n",
new_lo_space_->SizeOfObjects() / KB,
new_lo_space_->Available() / KB,
new_lo_space_->CommittedMemory() / KB);
PrintIsolate(isolate_,
"Old space, used: %6" PRIuS
" KB"
", available: %6" PRIuS
" KB"
", committed: %6" PRIuS " KB\n",
old_space_->SizeOfObjects() / KB, old_space_->Available() / KB,
old_space_->CommittedMemory() / KB);
PrintIsolate(isolate_,
"Code space, used: %6" PRIuS
" KB"
", available: %6" PRIuS
" KB"
", committed: %6" PRIuS "KB\n",
code_space_->SizeOfObjects() / KB, code_space_->Available() / KB,
code_space_->CommittedMemory() / KB);
PrintIsolate(isolate_,
"Map space, used: %6" PRIuS
" KB"
", available: %6" PRIuS
" KB"
", committed: %6" PRIuS " KB\n",
map_space_->SizeOfObjects() / KB, map_space_->Available() / KB,
map_space_->CommittedMemory() / KB);
PrintIsolate(isolate_,
"Large object space, used: %6" PRIuS
" KB"
", available: %6" PRIuS
" KB"
", committed: %6" PRIuS " KB\n",
lo_space_->SizeOfObjects() / KB, lo_space_->Available() / KB,
lo_space_->CommittedMemory() / KB);
PrintIsolate(isolate_,
"All spaces, used: %6" PRIuS
" KB"
", available: %6" PRIuS
" KB"
", committed: %6" PRIuS "KB\n",
this->SizeOfObjects() / KB, this->Available() / KB,
this->CommittedMemory() / KB);
PrintIsolate(isolate_,
"Unmapper buffering %d chunks of committed: %6" PRIuS " KB\n",
memory_allocator()->unmapper()->NumberOfChunks(),
CommittedMemoryOfHeapAndUnmapper() / KB);
PrintIsolate(isolate_, "External memory reported: %6" PRId64 " KB\n",
external_memory_ / 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::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()) 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()) 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->IsWeakOrClearedHeapObject());
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", static_cast<void*>(target));
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);
{
AllowHeapAllocation for_the_first_part_of_prologue;
gc_count_++;
#ifdef VERIFY_HEAP
if (FLAG_verify_heap) {
Verify();
}
#endif
}
// 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;
}
CheckNewSpaceExpansionCriteria();
UpdateNewSpaceAllocationCounter();
if (FLAG_track_retaining_path) {
retainer_.clear();
ephemeron_retainer_.clear();
retaining_root_.clear();
}
}
size_t Heap::SizeOfObjects() {
size_t total = 0;
for (SpaceIterator it(this); it.has_next();) {
total += it.next()->SizeOfObjects();
}
return total;
}
const char* Heap::GetSpaceName(int idx) {
switch (idx) {
case NEW_SPACE:
return "new_space";
case OLD_SPACE:
return "old_space";
case MAP_SPACE:
return "map_space";
case CODE_SPACE:
return "code_space";
case LO_SPACE:
return "large_object_space";
case NEW_LO_SPACE:
return "new_large_object_space";
case RO_SPACE:
return "read_only_space";
default:
UNREACHABLE();
}
return nullptr;
}
void Heap::SetRootCodeStubs(SimpleNumberDictionary* value) {
roots_[kCodeStubsRootIndex] = value;
}
void Heap::RepairFreeListsAfterDeserialization() {
PagedSpaces spaces(this);
for (PagedSpace* space = spaces.next(); space != nullptr;
space = spaces.next()) {
space->RepairFreeListsAfterDeserialization();
}
}
void Heap::MergeAllocationSitePretenuringFeedback(
const PretenuringFeedbackMap& local_pretenuring_feedback) {
AllocationSite* site = nullptr;
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);
for (SpaceIterator it(this); it.has_next();) {
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);
for (SpaceIterator it(this); it.has_next();) {
Space* space = it.next();
if (space == new_space()) {
space->RemoveAllocationObserver(new_space_observer);
} else {
space->RemoveAllocationObserver(observer);
}
}
}
class Heap::SkipStoreBufferScope {
public:
explicit SkipStoreBufferScope(StoreBuffer* store_buffer)
: store_buffer_(store_buffer) {
store_buffer_->MoveAllEntriesToRememberedSet();
store_buffer_->SetMode(StoreBuffer::IN_GC);
}
~SkipStoreBufferScope() {
DCHECK(store_buffer_->Empty());
store_buffer_->SetMode(StoreBuffer::NOT_IN_GC);
}
private:
StoreBuffer* store_buffer_;
};
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",
static_cast<void*>(site), 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 = nullptr;
// 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->GetPretenureMode() == TENURED) {
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::InvalidateCodeEmbeddedObjects(Code* code) {
MemoryChunk* chunk = MemoryChunk::FromAddress(code->address());
CodePageMemoryModificationScope modification_scope(chunk);
code->InvalidateEmbeddedObjects(this);
}
void Heap::InvalidateCodeDeoptimizationData(Code* code) {
MemoryChunk* chunk = MemoryChunk::FromAddress(code->address());
CodePageMemoryModificationScope modification_scope(chunk);
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(), [this](AllocationSite* site) {
if (site->deopt_dependent_code()) {
site->dependent_code()->MarkCodeForDeoptimization(
isolate_, DependentCode::kAllocationSiteTenuringChangedGroup);
site->set_deopt_dependent_code(false);
}
});
Deoptimizer::DeoptimizeMarkedCode(isolate_);
}
void Heap::GarbageCollectionEpilogue() {
TRACE_GC(tracer(), GCTracer::Scope::HEAP_EPILOGUE);
if (Heap::ShouldZapGarbage() || FLAG_clear_free_memory) {
ZapFromSpace();
}
#ifdef VERIFY_HEAP
if (FLAG_verify_heap) {
Verify();
}
#endif
AllowHeapAllocation for_the_rest_of_the_epilogue;
#ifdef DEBUG
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
UpdateMaximumCommitted();
isolate_->counters()->alive_after_last_gc()->Set(
static_cast<int>(SizeOfObjects()));
isolate_->counters()->string_table_capacity()->Set(
string_table()->Capacity());
isolate_->counters()->number_of_symbols()->Set(
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));
}
#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
ReportStatisticsAfterGC();
#endif // DEBUG
last_gc_time_ = MonotonicallyIncreasingTimeInMs();
{
TRACE_GC(tracer(), GCTracer::Scope::HEAP_EPILOGUE_REDUCE_NEW_SPACE);
ReduceNewSpaceSize();
}
}
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 (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::ScheduleIdleScavengeIfNeeded(int bytes_allocated) {
scavenge_job_->ScheduleIdleTaskIfNeeded(this, bytes_allocated);
}
HistogramTimer* 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();
}
}
}
HistogramTimer* Heap::GCTypeTimer(GarbageCollector collector) {
if (IsYoungGenerationCollector(collector)) {
return isolate_->counters()->gc_scavenger();
} else {
if (!incremental_marking()->IsStopped()) {
if (ShouldReduceMemory()) {
return isolate_->counters()->gc_finalize_reduce_memory();
} else {
return isolate_->counters()->gc_finalize();
}
} else {
return isolate_->counters()->gc_compactor();
}
}
}
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 words = size / kPointerSize;
DCHECK_EQ(a->Size(), size);
DCHECK_EQ(b->Size(), size);
intptr_t* slot_a = reinterpret_cast<intptr_t*>(a->address());
intptr_t* slot_b = reinterpret_cast<intptr_t*>(b->address());
for (int i = 0; i < words; 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(kMakeHeapIterableMask | kReduceMemoryFootprintMask);
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,
v8::kGCCallbackFlagCollectAllAvailableGarbage) &&
attempt + 1 >= kMinNumberOfAttempts) {
break;
}
}
set_current_gc_flags(kNoGCFlags);
new_space_->Shrink();
UncommitFromSpace();
memory_allocator()->unmapper()->EnsureUnmappingCompleted();
if (FLAG_trace_duplicate_threshold_kb) {
std::map<int, std::vector<HeapObject*>> objects_by_size;
PagedSpaces spaces(this);
for (PagedSpace* space = spaces.next(); space != nullptr;
space = spaces.next()) {
HeapObjectIterator it(space);
for (HeapObject* obj = it.Next(); obj != nullptr; obj = it.Next()) {
objects_by_size[obj->Size()].push_back(obj);
}
}
{
LargeObjectIterator it(lo_space());
for (HeapObject* obj = it.Next(); obj != nullptr; 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::ReportExternalMemoryPressure() {
const GCCallbackFlags kGCCallbackFlagsForExternalMemory =
static_cast<GCCallbackFlags>(
kGCCallbackFlagSynchronousPhantomCallbackProcessing |
kGCCallbackFlagCollectAllExternalMemory);
if (external_memory_ >
(external_memory_at_last_mark_compact_ + external_memory_hard_limit())) {
CollectAllGarbage(
kReduceMemoryFootprintMask | kFinalizeIncrementalMarkingMask,
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>(external_memory_) /
external_memory_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()->AdvanceIncrementalMarking(
deadline, IncrementalMarking::GC_VIA_STACK_GUARD, StepOrigin::kV8);
}
}
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 - kPointerSize);
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);
}
}
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);
if (!CanExpandOldGeneration(new_space()->Capacity())) {
InvokeNearHeapLimitCallback();
}
// 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");
}
}
bool next_gc_likely_to_collect_more = false;
size_t committed_memory_before = 0;
if (collector == MARK_COMPACTOR) {
committed_memory_before = CommittedOldGenerationMemory();
}
{
tracer()->Start(collector, gc_reason, collector_reason);
DCHECK(AllowHeapAllocation::IsAllowed());
DisallowHeapAllocation no_allocation_during_gc;
GarbageCollectionPrologue();
{
HistogramTimer* gc_type_timer = GCTypeTimer(collector);
HistogramTimerScope histogram_timer_scope(gc_type_timer);
TRACE_EVENT0("v8", gc_type_timer->name());
HistogramTimer* gc_type_priority_timer = GCTypePriorityTimer(collector);
OptionalHistogramTimerScopeMode mode =
isolate_->IsMemorySavingsModeActive()
? OptionalHistogramTimerScopeMode::DONT_TAKE_TIME
: OptionalHistogramTimerScopeMode::TAKE_TIME;
OptionalHistogramTimerScope histogram_timer_priority_scope(
gc_type_priority_timer, mode);
next_gc_likely_to_collect_more =
PerformGarbageCollection(collector, gc_callback_flags);
if (collector == MARK_COMPACTOR) {
tracer()->RecordMarkCompactHistograms(gc_type_timer);
}
}
GarbageCollectionEpilogue();
if (collector == MARK_COMPACTOR && FLAG_track_detached_contexts) {
isolate()->CheckDetachedContextsAfterGC();
}
if (collector == MARK_COMPACTOR) {
size_t committed_memory_after = CommittedOldGenerationMemory();
size_t used_memory_after = OldGenerationSizeOfObjects();
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,
// - there are live detached contexts.
event.next_gc_likely_to_collect_more =
(committed_memory_before > committed_memory_after + MB) ||
HasHighFragmentation(used_memory_after, committed_memory_after) ||
(detached_contexts()->length() > 0);
event.committed_memory = committed_memory_after;
if (deserialization_complete_) {
memory_reducer_->NotifyMarkCompact(event);
}
}
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. The heap snapshot
// generator needs incremental marking to stay off after it aborted.
// We do this only for scavenger to avoid a loop where mark-compact
// causes another mark-compact.
if (IsYoungGenerationCollector(collector) &&
!ShouldAbortIncrementalMarking()) {
StartIncrementalMarkingIfAllocationLimitIsReached(
GCFlagsForIncrementalMarking(),
kGCCallbackScheduleIdleGarbageCollection);
}
return next_gc_likely_to_collect_more;
}
int Heap::NotifyContextDisposed(bool dependant_context) {
if (!dependant_context) {
tracer()->ResetSurvivalEvents();
old_generation_size_configured_ = false;
MemoryReducer::Event event;
event.type = MemoryReducer::kPossibleGarbage;
event.time_ms = MonotonicallyIncreasingTimeInMs();
memory_reducer_->NotifyPossibleGarbage(event);
}
isolate()->AbortConcurrentOptimization(BlockingBehavior::kDontBlock);
number_of_disposed_maps_ = retained_maps()->length();
tracer()->AddContextDisposalTime(MonotonicallyIncreasingTimeInMs());
return ++contexts_disposed_;
}
void Heap::StartIncrementalMarking(int gc_flags,
GarbageCollectionReason gc_reason,
GCCallbackFlags gc_callback_flags) {
DCHECK(incremental_marking()->IsStopped());
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,
GarbageCollectionReason::kAllocationLimit,
gc_callback_flags);
}
}
}
void Heap::StartIdleIncrementalMarking(
GarbageCollectionReason gc_reason,
const GCCallbackFlags gc_callback_flags) {
gc_idle_time_handler_->ResetNoProgressCounter();
StartIncrementalMarking(kReduceMemoryFootprintMask, gc_reason,
gc_callback_flags);
}
void Heap::MoveElements(FixedArray* array, int dst_index, int src_index,
int len, WriteBarrierMode mode) {
if (len == 0) return;
DCHECK(array->map() != ReadOnlyRoots(this).fixed_cow_array_map());
Object** dst = array->data_start() + dst_index;
Object** src = array->data_start() + src_index;
if (FLAG_concurrent_marking && incremental_marking()->IsMarking()) {
if (dst < src) {
for (int i = 0; i < len; i++) {
base::AsAtomicPointer::Relaxed_Store(
dst + i, base::AsAtomicPointer::Relaxed_Load(src + i));
}
} else {
for (int i = len - 1; i >= 0; i--) {
base::AsAtomicPointer::Relaxed_Store(
dst + i, base::AsAtomicPointer::Relaxed_Load(src + i));
}
}
} else {
MemMove(dst, src, len * kPointerSize);
}
if (mode == SKIP_WRITE_BARRIER) return;
FIXED_ARRAY_ELEMENTS_WRITE_BARRIER(this, array, dst_index, len);
}
#ifdef VERIFY_HEAP
// Helper class for verifying the string table.
class StringTableVerifier : public ObjectVisitor {
public:
explicit StringTableVerifier(Isolate* isolate) : isolate_(isolate) {}
void VisitPointers(HeapObject* host, Object** start, Object** end) override {
// Visit all HeapObject pointers in [start, end).
for (Object** p = start; p < end; p++) {
DCHECK(!HasWeakHeapObjectTag(*p));
if ((*p)->IsHeapObject()) {
HeapObject* object = HeapObject::cast(*p);
// Check that the string is actually internalized.
CHECK(object->IsTheHole(isolate_) || object->IsUndefined(isolate_) ||
object->IsInternalizedString());
}
}
}
void VisitPointers(HeapObject* host, MaybeObject** start,
MaybeObject** end) override {
UNREACHABLE();
}
private:
Isolate* isolate_;
};
static void VerifyStringTable(Isolate* isolate) {
StringTableVerifier verifier(isolate);
isolate->heap()->string_table()->IterateElements(&verifier);
}
#endif // VERIFY_HEAP
bool Heap::ReserveSpace(Reservation* reservations, std::vector<Address>* maps) {
bool gc_performed = true;
int counter = 0;
static const int kThreshold = 20;
while (gc_performed && counter++ < kThreshold) {
gc_performed = false;
for (int space = FIRST_SPACE;
space < SerializerDeserializer::kNumberOfSpaces; space++) {
Reservation* reservation = &reservations[space];
DCHECK_LE(1, reservation->size());
if (reservation->at(0).size == 0) {
DCHECK_EQ(1, reservation->size());
continue;
}
bool perform_gc = false;
if (space == MAP_SPACE) {
// We allocate each map individually to avoid fragmentation.
maps->clear();
DCHECK_LE(reservation->size(), 2);
int reserved_size = 0;
for (const Chunk& c : *reservation) reserved_size += c.size;
DCHECK_EQ(0, reserved_size % Map::kSize);
int num_maps = reserved_size / Map::kSize;
for (int i = 0; i < num_maps; i++) {
// The deserializer will update the skip list.
AllocationResult allocation = map_space()->AllocateRawUnaligned(
Map::kSize, PagedSpace::IGNORE_SKIP_LIST);
HeapObject* free_space = nullptr;
if (allocation.To(&free_space)) {
// Mark with a free list node, in case we have a GC before
// deserializing.
Address free_space_address = free_space->address();
CreateFillerObjectAt(free_space_address, Map::kSize,
ClearRecordedSlots::kNo);
maps->push_back(free_space_address);
} else {
perform_gc = true;
break;
}
}
} else if (space == LO_SPACE) {
// Just check that we can allocate during deserialization.
DCHECK_LE(reservation->size(), 2);
int reserved_size = 0;
for (const Chunk& c : *reservation) reserved_size += c.size;
perform_gc = !CanExpandOldGeneration(reserved_size);
} else {
for (auto& chunk : *reservation) {
AllocationResult allocation;
int size = chunk.size;
DCHECK_LE(static_cast<size_t>(size),
MemoryAllocator::PageAreaSize(
static_cast<AllocationSpace>(space)));
if (space == NEW_SPACE) {
allocation = new_space()->AllocateRawUnaligned(size);
} else {
// The deserializer will update the skip list.
allocation = paged_space(space)->AllocateRawUnaligned(
size, PagedSpace::IGNORE_SKIP_LIST);
}
HeapObject* free_space = nullptr;
if (allocation.To(&free_space)) {
// Mark with a free list node, in case we have a GC before
// deserializing.
Address free_space_address = free_space->address();
CreateFillerObjectAt(free_space_address, size,
ClearRecordedSlots::kNo);
DCHECK_GT(SerializerDeserializer::kNumberOfPreallocatedSpaces,
space);
chunk.start = free_space_address;
chunk.end = free_space_address + size;
} else {
perform_gc = true;
break;
}
}
}
if (perform_gc) {
// We cannot perfom a GC with an uninitialized isolate. This check
// fails for example if the max old space size is chosen unwisely,
// so that we cannot allocate space to deserialize the initial heap.
if (!deserialization_complete_) {
V8::FatalProcessOutOfMemory(
isolate(), "insufficient memory to create an Isolate");
}
if (space == NEW_SPACE) {
CollectGarbage(NEW_SPACE, GarbageCollectionReason::kDeserializer);
} else {
if (counter > 1) {
CollectAllGarbage(
kReduceMemoryFootprintMask | kAbortIncrementalMarkingMask,
GarbageCollectionReason::kDeserializer);
} else {
CollectAllGarbage(kAbortIncrementalMarkingMask,
GarbageCollectionReason::kDeserializer);
}
}
gc_performed = true;
break; // Abort for-loop over spaces and retry.
}
}
}
return !gc_performed;
}
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.");
}
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);
}
bool Heap::PerformGarbageCollection(
GarbageCollector collector, const v8::GCCallbackFlags gc_callback_flags) {
int freed_global_handles = 0;
if (!IsYoungGenerationCollector(collector)) {
PROFILE(isolate_, CodeMovingGCEvent());
}
#ifdef VERIFY_HEAP
if (FLAG_verify_heap) {
VerifyStringTable(this->isolate());
}
#endif
GCType gc_type =
collector == MARK_COMPACTOR ? kGCTypeMarkSweepCompact : kGCTypeScavenge;
{
GCCallbacksScope scope(this);
if (scope.CheckReenter()) {
AllowHeapAllocation allow_allocation;
TRACE_GC(tracer(), GCTracer::Scope::HEAP_EXTERNAL_PROLOGUE);
VMState<EXTERNAL> state(isolate_);
HandleScope handle_scope(isolate_);
CallGCPrologueCallbacks(gc_type, kNoGCCallbackFlags);
}
}
EnsureFromSpaceIsCommitted();
size_t start_new_space_size = Heap::new_space()->Size();
{
Heap::SkipStoreBufferScope skip_store_buffer_scope(store_buffer_);
switch (collector) {
case MARK_COMPACTOR:
UpdateOldGenerationAllocationCounter();
// Perform mark-sweep with optional compaction.
MarkCompact();
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();
break;
case MINOR_MARK_COMPACTOR:
MinorMarkCompact();
break;
case SCAVENGER:
if ((fast_promotion_mode_ &&
CanExpandOldGeneration(new_space()->Size()))) {
tracer()->NotifyYoungGenerationHandling(
YoungGenerationHandling::kFastPromotionDuringScavenge);
EvacuateYoungGeneration();
} else {
tracer()->NotifyYoungGenerationHandling(
YoungGenerationHandling::kRegularScavenge);
Scavenge();
}
break;
}
ProcessPretenuringFeedback();
}
UpdateSurvivalStatistics(static_cast<int>(start_new_space_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_new_space_size - SurvivedNewSpaceObjectSize());
}
if (!fast_promotion_mode_ || collector == MARK_COMPACTOR) {
ComputeFastPromotionMode();
}
isolate_->counters()->objs_since_last_young()->Set(0);
gc_post_processing_depth_++;
{
AllowHeapAllocation allow_allocation;
TRACE_GC(tracer(), GCTracer::Scope::HEAP_EXTERNAL_WEAK_GLOBAL_HANDLES);
freed_global_handles =
isolate_->global_handles()->PostGarbageCollectionProcessing(
collector, gc_callback_flags);
}
gc_post_processing_depth_--;
isolate_->eternal_handles()->PostGarbageCollectionProcessing();
// Update relocatables.
Relocatable::PostGarbageCollectionProcessing(isolate_);
double gc_speed = tracer()->CombinedMarkCompactSpeedInBytesPerMillisecond();
double mutator_speed =
tracer()->CurrentOldGenerationAllocationThroughputInBytesPerMillisecond();
size_t old_gen_size = OldGenerationSizeOfObjects();
if (collector == MARK_COMPACTOR) {
// Register the amount of external allocated memory.
external_memory_at_last_mark_compact_ = external_memory_;
external_memory_limit_ = external_memory_ + kExternalAllocationSoftLimit;
size_t new_limit = heap_controller()->CalculateAllocationLimit(
old_gen_size, max_old_generation_size_, gc_speed, mutator_speed,
new_space()->Capacity(), CurrentHeapGrowingMode());
old_generation_allocation_limit_ = new_limit;
CheckIneffectiveMarkCompact(
old_gen_size, tracer()->AverageMarkCompactMutatorUtilization());
} else if (HasLowYoungGenerationAllocationRate() &&
old_generation_size_configured_) {
size_t new_limit = heap_controller()->CalculateAllocationLimit(
old_gen_size, max_old_generation_size_, gc_speed, mutator_speed,
new_space()->Capacity(), CurrentHeapGrowingMode());
if (new_limit < old_generation_allocation_limit_) {
old_generation_allocation_limit_ = new_limit;
}
}
{
GCCallbacksScope scope(this);
if (scope.CheckReenter()) {
AllowHeapAllocation allow_allocation;
TRACE_GC(tracer(), GCTracer::Scope::HEAP_EXTERNAL_EPILOGUE);
VMState<EXTERNAL> state(isolate_);
HandleScope handle_scope(isolate_);
CallGCEpilogueCallbacks(gc_type, gc_callback_flags);
}
}
#ifdef VERIFY_HEAP
if (FLAG_verify_heap) {
VerifyStringTable(this->isolate());
}
#endif
return freed_global_handles > 0;
}
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"));
uint64_t size_of_objects_before_gc = SizeOfObjects();
CodeSpaceMemoryModificationScope code_modifcation(this);
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);
}
}
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(isolate());
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_->context_slot_cache()->Clear();
isolate_->descriptor_lookup_cache()->Clear();
RegExpResultsCache::Clear(string_split_cache());
RegExpResultsCache::Clear(regexp_multiple_cache());
isolate_->compilation_cache()->MarkCompactPrologue();
FlushNumberStringCache();
}
void Heap::CheckNewSpaceExpansionCriteria() {
if (FLAG_experimental_new_space_growth_heuristic) {
if (new_space_->TotalCapacity() < new_space_->MaximumCapacity() &&
survived_last_scavenge_ * 100 / new_space_->TotalCapacity() >= 10) {
// Grow the size of new space if there is room to grow, and more than 10%
// have survived the last scavenge.
new_space_->Grow();
survived_since_last_expansion_ = 0;
}
} else 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;
}
}
static bool IsUnscavengedHeapObject(Heap* heap, Object** p) {
return Heap::InFromSpace(*p) &&
!HeapObject::cast(*p)->map_word().IsForwardingAddress();
}
class ScavengeWeakObjectRetainer : public WeakObjectRetainer {
public:
virtual Object* RetainAs(Object* object) {
if (!Heap::InFromSpace(object)) {
return object;
}
MapWord map_word = HeapObject::cast(object)->map_word();
if (map_word.IsForwardingAddress()) {
return map_word.ToForwardingAddress();
}
return nullptr;
}
};
void Heap::EvacuateYoungGeneration() {
TRACE_GC(tracer(), GCTracer::Scope::SCAVENGER_FAST_PROMOTE);
base::LockGuard<base::Mutex> guard(relocation_mutex());
ConcurrentMarking::PauseScope pause_scope(concurrent_marking());
if (!FLAG_concurrent_marking) {
DCHECK(fast_promotion_mode_);
DCHECK(CanExpandOldGeneration(new_space()->Size()));
}
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());
// Fix up special trackers.
external_string_table_.PromoteAllNewSpaceStrings();
// GlobalHandles are updated in PostGarbageCollectonProcessing
IncrementYoungSurvivorsCounter(new_space()->Size());
IncrementPromotedObjectsSize(new_space()->Size());
IncrementSemiSpaceCopiedObjectSize(0);
LOG(isolate_, ResourceEvent("scavenge", "end"));
SetGCState(NOT_IN_GC);
}
static bool IsLogging(Isolate* isolate) {
return FLAG_verify_predictable || isolate->logger()->is_logging() ||
isolate->is_profiling() ||
(isolate->heap_profiler() != nullptr &&
isolate->heap_profiler()->is_tracking_object_moves()) ||
isolate->heap()->has_heap_object_allocation_tracker();
}
class PageScavengingItem final : public ItemParallelJob::Item {
public:
explicit PageScavengingItem(MemoryChunk* chunk) : chunk_(chunk) {}
virtual ~PageScavengingItem() {}
void Process(Scavenger* scavenger) { scavenger->ScavengePage(chunk_); }
private:
MemoryChunk* const chunk_;
};
class ScavengingTask final : public ItemParallelJob::Task {
public:
ScavengingTask(Heap* heap, Scavenger* scavenger, OneshotBarrier* barrier)
: ItemParallelJob::Task(heap->isolate()),
heap_(heap),
scavenger_(scavenger),
barrier_(barrier) {}
void RunInParallel() final {
TRACE_BACKGROUND_GC(
heap_->tracer(),
GCTracer::BackgroundScope::SCAVENGER_BACKGROUND_SCAVENGE_PARALLEL);
double scavenging_time = 0.0;
{
barrier_->Start();
TimedScope scope(&scavenging_time);
PageScavengingItem* item = nullptr;
while ((item = GetItem<PageScavengingItem>()) != nullptr) {
item->Process(scavenger_);
item->MarkFinished();
}
do {
scavenger_->Process(barrier_);
} while (!barrier_->Wait());
scavenger_->Process();
}
if (FLAG_trace_parallel_scavenge) {
PrintIsolate(heap_->isolate(),
"scavenge[%p]: time=%.2f copied=%zu promoted=%zu\n",
static_cast<void*>(this), scavenging_time,
scavenger_->bytes_copied(), scavenger_->bytes_promoted());
}
};
private:
Heap* const heap_;
Scavenger* const scavenger_;
OneshotBarrier* const barrier_;
};
int Heap::NumberOfScavengeTasks() {
if (!FLAG_parallel_scavenge) return 1;
const int num_scavenge_tasks =
static_cast<int>(new_space()->TotalCapacity()) / MB;
static int num_cores = V8::GetCurrentPlatform()->NumberOfWorkerThreads() + 1;
int tasks =
Max(1, Min(Min(num_scavenge_tasks, kMaxScavengerTasks), num_cores));
if (!CanExpandOldGeneration(static_cast<size_t>(tasks * Page::kPageSize))) {
// Optimize for memory usage near the heap limit.
tasks = 1;
}
return tasks;
}
void Heap::Scavenge() {
TRACE_GC(tracer(), GCTracer::Scope::SCAVENGER_SCAVENGE);
base::LockGuard<base::Mutex> 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(isolate());
// 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);
// Implements Cheney's copying algorithm
LOG(isolate_, ResourceEvent("scavenge", "begin"));
// Flip the semispaces. After flipping, to space is empty, from space has
// live objects.
new_space_->Flip();
new_space_->ResetLinearAllocationArea();
ItemParallelJob job(isolate()->cancelable_task_manager(),
¶llel_scavenge_semaphore_);
const int kMainThreadId = 0;
Scavenger* scavengers[kMaxScavengerTasks];
const bool is_logging = IsLogging(isolate());
const int num_scavenge_tasks = NumberOfScavengeTasks();
OneshotBarrier barrier;
Scavenger::CopiedList copied_list(num_scavenge_tasks);
Scavenger::PromotionList promotion_list(num_scavenge_tasks);
for (int i = 0; i < num_scavenge_tasks; i++) {
scavengers[i] =
new Scavenger(this, is_logging, &copied_list, &promotion_list, i);
job.AddTask(new ScavengingTask(this, scavengers[i], &barrier));
}
{
Sweeper* sweeper = mark_compact_collector()->sweeper();
// Pause the concurrent sweeper.
Sweeper::PauseOrCompleteScope pause_scope(sweeper);
// Filter out pages from the sweeper that need to be processed for old to
// new slots by the Scavenger. After processing, the Scavenger adds back
// pages that are still unsweeped. This way the Scavenger has exclusive
// access to the slots of a page and can completely avoid any locks on
// the page itself.
Sweeper::FilterSweepingPagesScope filter_scope(sweeper, pause_scope);
filter_scope.FilterOldSpaceSweepingPages(
[](Page* page) { return !page->ContainsSlots<OLD_TO_NEW>(); });
RememberedSet<OLD_TO_NEW>::IterateMemoryChunks(
this, [&job](MemoryChunk* chunk) {
job.AddItem(new PageScavengingItem(chunk));
});
RootScavengeVisitor root_scavenge_visitor(scavengers[kMainThreadId]);
{
// Identify weak unmodified handles. Requires an unmodified graph.
TRACE_GC(
tracer(),
GCTracer::Scope::SCAVENGER_SCAVENGE_WEAK_GLOBAL_HANDLES_IDENTIFY);
isolate()->global_handles()->IdentifyWeakUnmodifiedObjects(
&JSObject::IsUnmodifiedApiObject);
}
{
// Copy roots.
TRACE_GC(tracer(), GCTracer::Scope::SCAVENGER_SCAVENGE_ROOTS);
IterateRoots(&root_scavenge_visitor, VISIT_ALL_IN_SCAVENGE);
}
{
// Parallel phase scavenging all copied and promoted objects.
TRACE_GC(tracer(), GCTracer::Scope::SCAVENGER_SCAVENGE_PARALLEL);
job.Run(isolate()->async_counters());
DCHECK(copied_list.IsEmpty());
DCHECK(promotion_list.IsEmpty());
}
{
// Scavenge weak global handles.
TRACE_GC(tracer(),
GCTracer::Scope::SCAVENGER_SCAVENGE_WEAK_GLOBAL_HANDLES_PROCESS);
isolate()->global_handles()->MarkNewSpaceWeakUnmodifiedObjectsPending(
&IsUnscavengedHeapObject);
isolate()
->global_handles()
->IterateNewSpaceWeakUnmodifiedRootsForFinalizers(
&root_scavenge_visitor);
scavengers[kMainThreadId]->Process();
DCHECK(copied_list.IsEmpty());
DCHECK(promotion_list.IsEmpty());
isolate()
->global_handles()
->IterateNewSpaceWeakUnmodifiedRootsForPhantomHandles(
&root_scavenge_visitor, &IsUnscavengedHeapObject);
}
for (int i = 0; i < num_scavenge_tasks; i++) {
scavengers[i]->Finalize();
delete scavengers[i];
}
}
{
// Update references into new space
TRACE_GC(tracer(), GCTracer::Scope::SCAVENGER_SCAVENGE_UPDATE_REFS);
UpdateNewSpaceReferencesInExternalStringTable(
&UpdateNewSpaceReferenceInExternalStringTableEntry);
incremental_marking()->UpdateMarkingWorklistAfterScavenge();
}
if (FLAG_concurrent_marking) {
// Ensure that concurrent marker does not track pages that are
// going to be unmapped.
for (Page* p : PageRange(new_space()->from_space().first_page(), nullptr)) {
concurrent_marking()->ClearLiveness(p);
}
}
ScavengeWeakObjectRetainer weak_object_retainer;
ProcessYoungWeakReferences(&weak_object_retainer);
// Set age mark.
new_space_->set_age_mark(new_space_->top());
{
TRACE_GC(tracer(), GCTracer::Scope::SCAVENGER_PROCESS_ARRAY_BUFFERS);
ArrayBufferTracker::PrepareToFreeDeadInNewSpace(this);
}
array_buffer_collector()->FreeAllocationsOnBackgroundThread();
RememberedSet<OLD_TO_NEW>::IterateMemoryChunks(this, [](MemoryChunk* chunk) {
if (chunk->SweepingDone()) {
RememberedSet<OLD_TO_NEW>::FreeEmptyBuckets(chunk);
} else {
RememberedSet<OLD_TO_NEW>::PreFreeEmptyBuckets(chunk);
}
});
// Update how much has survived scavenge.
IncrementYoungSurvivorsCounter(SurvivedNewSpaceObjectSize());
// Scavenger may find new wrappers by iterating objects promoted onto a black
// page.
local_embedder_heap_tracer()->RegisterWrappersWithRemoteTracer();
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: %" PRIuS "%%\n",
fast_promotion_mode_ ? "true" : "false", survived_in_new_space);
}
}
void Heap::UnprotectAndRegisterMemoryChunk(MemoryChunk* chunk) {
if (unprotected_memory_chunks_registry_enabled_) {
base::LockGuard<base::Mutex> guard(&unprotected_memory_chunks_mutex_);
if (unprotected_memory_chunks_.insert(chunk).second) {
chunk->SetReadAndWritable();
}
}
}
void Heap::UnprotectAndRegisterMemoryChunk(HeapObject* object) {
UnprotectAndRegisterMemoryChunk(MemoryChunk::FromAddress(object->address()));
}
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)->SetReadAndExecutable();
}
unprotected_memory_chunks_.clear();
}
bool Heap::ExternalStringTable::Contains(HeapObject* obj) {
for (size_t i = 0; i < new_space_strings_.size(); ++i) {
if (new_space_strings_[i] == obj) return true;
}
for (size_t i = 0; i < old_space_strings_.size(); ++i) {
if (old_space_strings_[i] == obj) return true;
}
return false;
}
void Heap::ProcessMovedExternalString(Page* old_page, Page* new_page,
ExternalString* string) {
size_t size = string->ExternalPayloadSize();
new_page->IncrementExternalBackingStoreBytes(
ExternalBackingStoreType::kExternalString, size);
old_page->DecrementExternalBackingStoreBytes(
ExternalBackingStoreType::kExternalString, size);
}
String* Heap::UpdateNewSpaceReferenceInExternalStringTableEntry(Heap* heap,
Object** p) {
MapWord first_word = HeapObject::cast(*p)->map_word();
if (!first_word.IsForwardingAddress()) {
// Unreachable external string can be finalized.
String* string = String::cast(*p);
if (!string->IsExternalString()) {
// Original external string has been internalized.
DCHECK(string->IsThinString());
return nullptr;
}
heap->FinalizeExternalString(string);
return nullptr;
}
// String is still reachable.
String* new_string = String::cast(first_word.ToForwardingAddress());
String* original_string = reinterpret_cast<String*>(*p);
// The length of the original string is used to disambiguate the scenario
// of a ThingString being forwarded to an ExternalString (which already exists
// in the OLD space), and an ExternalString being forwarded to its promoted
// copy. See Scavenger::EvacuateThinString.
if (new_string->IsThinString() || original_string->length() == 0) {
// Filtering Thin strings out of the external string table.
return nullptr;
} else if (new_string->IsExternalString()) {
heap->ProcessMovedExternalString(
Page::FromAddress(reinterpret_cast<Address>(*p)),
Page::FromHeapObject(new_string), ExternalString::cast(new_string));
return new_string;
}
// Internalization can replace external strings with non-external strings.
return new_string->IsExternalString() ? new_string : nullptr;
}
void Heap::ExternalStringTable::VerifyNewSpace() {
#ifdef DEBUG
std::set<String*> visited_map;
std::map<MemoryChunk*, size_t> size_map;
ExternalBackingStoreType type = ExternalBackingStoreType::kExternalString;
for (size_t i = 0; i < new_space_strings_.size(); ++i) {
String* obj = String::cast(new_space_strings_[i]);
MemoryChunk* mc = MemoryChunk::FromHeapObject(obj);
DCHECK(mc->InNewSpace());
DCHECK(heap_->InNewSpace(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;
VerifyNewSpace();
for (size_t i = 0; i < old_space_strings_.size(); ++i) {
String* obj = String::cast(old_space_strings_[i]);
MemoryChunk* mc = MemoryChunk::FromHeapObject(obj);
DCHECK(!mc->InNewSpace());
DCHECK(!heap_->InNewSpace(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::UpdateNewSpaceReferences(
Heap::ExternalStringTableUpdaterCallback updater_func) {
if (new_space_strings_.empty()) return;
Object** start = new_space_strings_.data();
Object** end = start + new_space_strings_.size();
Object** last = start;
for (Object** p = start; p < end; ++p) {
String* target = updater_func(heap_, p);
if (target == nullptr) continue;
DCHECK(target->IsExternalString());
if (InNewSpace(target)) {
// String is still in new space. Update the table entry.
*last = target;
++last;
} else {
// String got promoted. Move it to the old string list.
old_space_strings_.push_back(target);
}
}
DCHECK_LE(last, end);
new_space_strings_.resize(static_cast<size_t>(last - start));
#ifdef VERIFY_HEAP
if (FLAG_verify_heap) {
VerifyNewSpace();
}
#endif
}
void Heap::ExternalStringTable::PromoteAllNewSpaceStrings() {
old_space_strings_.reserve(old_space_strings_.size() +
new_space_strings_.size());
std::move(std::begin(new_space_strings_), std::end(new_space_strings_),
std::back_inserter(old_space_strings_));
new_space_strings_.clear();
}
void Heap::ExternalStringTable::IterateNewSpaceStrings(RootVisitor* v) {
if (!new_space_strings_.empty()) {
v->VisitRootPointers(Root::kExternalStringsTable, nullptr,
new_space_strings_.data(),
new_space_strings_.data() + new_space_strings_.size());
}
}
void Heap::ExternalStringTable::IterateAll(RootVisitor* v) {
IterateNewSpaceStrings(v);
if (!old_space_strings_.empty()) {
v->VisitRootPointers(Root::kExternalStringsTable, nullptr,
old_space_strings_.data(),
old_space_strings_.data() + old_space_strings_.size());
}
}
void Heap::UpdateNewSpaceReferencesInExternalStringTable(
ExternalStringTableUpdaterCallback updater_func) {
external_string_table_.UpdateNewSpaceReferences(updater_func);
}
void Heap::ExternalStringTable::UpdateReferences(
Heap::ExternalStringTableUpdaterCallback updater_func) {
if (old_space_strings_.size() > 0) {
Object** start = old_space_strings_.data();
Object** end = start + old_space_strings_.size();
for (Object** p = start; p < end; ++p) *p = updater_func(heap_, p);
}
UpdateNewSpaceReferences(updater_func);
}
void Heap::UpdateReferencesInExternalStringTable(
ExternalStringTableUpdaterCallback updater_func) {
external_string_table_.UpdateReferences(updater_func);
}
void Heap::ProcessAllWeakReferences(WeakObjectRetainer* retainer) {
ProcessNativeContexts(retainer);
ProcessAllocationSites(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::ProcessWeakListRoots(WeakObjectRetainer* retainer) {
set_native_contexts_list(retainer->RetainAs(native_contexts_list()));
set_allocation_sites_list(retainer->RetainAs(allocation_sites_list()));
}
void Heap::ForeachAllocationSite(Object* list,
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(PretenureFlag flag) {
DisallowHeapAllocation no_allocation_scope;
bool marked = false;
ForeachAllocationSite(allocation_sites_list(),
[&marked, flag, this](AllocationSite* site) {
if (site->GetPretenureMode() == flag) {
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(TENURED);
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) {}
virtual void VisitRootPointers(Root root, const char* description,
Object** start, Object** end) {
for (Object** 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((FixedDoubleArray::kHeaderSize & kDoubleAlignmentMask) ==
0); // NOLINT
STATIC_ASSERT((FixedTypedArrayBase::kDataOffset & kDoubleAlignmentMask) ==
0); // NOLINT
#ifdef V8_HOST_ARCH_32_BIT
STATIC_ASSERT((HeapNumber::kValueOffset & kDoubleAlignmentMask) !=
0); // NOLINT
#endif
int Heap::GetMaximumFillToAlign(AllocationAlignment alignment) {
switch (alignment) {
case kWordAligned:
return 0;
case kDoubleAligned:
case kDoubleUnaligned:
return kDoubleSize - kPointerSize;
default:
UNREACHABLE();
}
return 0;
}
int Heap::GetFillToAlign(Address address, AllocationAlignment alignment) {
intptr_t offset = OffsetFrom(address);
if (alignment == kDoubleAligned && (offset & kDoubleAlignmentMask) != 0)
return kPointerSize;
if (alignment == kDoubleUnaligned && (offset & kDoubleAlignmentMask) == 0)
return kDoubleSize - kPointerSize; // No fill if double is always aligned.
return 0;
}
HeapObject* Heap::PrecedeWithFiller(HeapObject* object, int filler_size) {
CreateFillerObjectAt(object->address(), filler_size, ClearRecordedSlots::kNo);
return HeapObject::FromAddress(object->address() + filler_size);
}
HeapObject* Heap::AlignWithFiller(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(object, pre_filler);
filler_size -= pre_filler;
}
if (filler_size)
CreateFillerObjectAt(object->address() + object_size, filler_size,
ClearRecordedSlots::kNo);
return object;
}
void Heap::RegisterNewArrayBuffer(JSArrayBuffer* buffer) {
ArrayBufferTracker::RegisterNew(this, buffer);
}
void Heap::UnregisterArrayBuffer(JSArrayBuffer* buffer) {
ArrayBufferTracker::Unregister(this, buffer);
}
void Heap::ConfigureInitialOldGenerationSize() {
if (!old_generation_size_configured_ && tracer()->SurvivalEventsRecorded()) {
old_generation_allocation_limit_ =
Max(heap_controller()->MinimumAllocationLimitGrowingStep(
CurrentHeapGrowingMode()),
static_cast<size_t>(
static_cast<double>(old_generation_allocation_limit_) *
(tracer()->AverageSurvivalRatio() / 100)));
}
}
void Heap::CreateJSEntryStub() {
JSEntryStub stub(isolate(), StackFrame::ENTRY);
set_js_entry_code(*stub.GetCode());
}
void Heap::CreateJSConstructEntryStub() {
JSEntryStub stub(isolate(), StackFrame::CONSTRUCT_ENTRY);
set_js_construct_entry_code(*stub.GetCode());
}
void Heap::CreateJSRunMicrotasksEntryStub() {
JSEntryStub stub(isolate(), JSEntryStub::SpecialTarget::kRunMicrotasks);
set_js_run_microtasks_entry_code(*stub.GetCode());
}
void Heap::CreateFixedStubs() {
// Here we create roots for fixed stubs. They are needed at GC
// for cooking and uncooking (check out frames.cc).
// The eliminates the need for doing dictionary lookup in the
// stub cache for these stubs.
HandleScope scope(isolate());
// Canonicalize handles, so that we can share constant pool entries pointing
// to code targets without dereferencing their handles.
CanonicalHandleScope canonical(isolate());
// Create stubs that should be there, so we don't unexpectedly have to
// create them if we need them during the creation of another stub.
// Stub creation mixes raw pointers and handles in an unsafe manner so
// we cannot create stubs while we are creating stubs.
CodeStub::GenerateStubsAheadOfTime(isolate());
// gcc-4.4 has problem generating correct code of following snippet:
// { JSEntryStub stub;
// js_entry_code_ = *stub.GetCode();
// }
// { JSConstructEntryStub stub;
// js_construct_entry_code_ = *stub.GetCode();
// }
// To workaround the problem, make separate functions without inlining.
Heap::CreateJSEntryStub();
Heap::CreateJSConstructEntryStub();
Heap::CreateJSRunMicrotasksEntryStub();
}
bool Heap::RootCanBeWrittenAfterInitialization(Heap::RootListIndex root_index) {
switch (root_index) {
case kNumberStringCacheRootIndex:
case kCodeStubsRootIndex:
case kScriptListRootIndex:
case kMaterializedObjectsRootIndex:
case kMicrotaskQueueRootIndex:
case kDetachedContextsRootIndex:
case kRetainedMapsRootIndex:
case kRetainingPathTargetsRootIndex:
case kFeedbackVectorsForProfilingToolsRootIndex:
case kNoScriptSharedFunctionInfosRootIndex:
case kSerializedObjectsRootIndex:
case kSerializedGlobalProxySizesRootIndex:
case kPublicSymbolTableRootIndex:
case kApiSymbolTableRootIndex:
case kApiPrivateSymbolTableRootIndex:
case kMessageListenersRootIndex:
case kDeserializeLazyHandlerRootIndex:
case kDeserializeLazyHandlerWideRootIndex:
case kDeserializeLazyHandlerExtraWideRootIndex:
// Smi values
#define SMI_ENTRY(type, name, Name) case k##Name##RootIndex:
SMI_ROOT_LIST(SMI_ENTRY)
#undef SMI_ENTRY
// String table
case kStringTableRootIndex:
return true;
default:
return false;
}
}
bool Heap::RootCanBeTreatedAsConstant(RootListIndex root_index) {
bool can_be = !RootCanBeWrittenAfterInitialization(root_index) &&
!InNewSpace(root(root_index));
DCHECK_IMPLIES(can_be, IsImmovable(HeapObject::cast(root(root_index))));
return can_be;
}
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 {
Heap::RootListIndex RootIndexForFixedTypedArray(ExternalArrayType array_type) {
switch (array_type) {
#define ARRAY_TYPE_TO_ROOT_INDEX(Type, type, TYPE, ctype) \
case kExternal##Type##Array: \
return Heap::kFixed##Type##ArrayMapRootIndex;
TYPED_ARRAYS(ARRAY_TYPE_TO_ROOT_INDEX)
#undef ARRAY_TYPE_TO_ROOT_INDEX
}
UNREACHABLE();
}
Heap::RootListIndex RootIndexForFixedTypedArray(ElementsKind elements_kind) {
switch (elements_kind) {
#define TYPED_ARRAY_CASE(Type, type, TYPE, ctype) \
case TYPE##_ELEMENTS: \
return Heap::kFixed##Type##ArrayMapRootIndex;
TYPED_ARRAYS(TYPED_ARRAY_CASE)
default:
UNREACHABLE();
#undef TYPED_ARRAY_CASE
}
}
Heap::RootListIndex RootIndexForEmptyFixedTypedArray(
ElementsKind elements_kind) {
switch (elements_kind) {
#define ELEMENT_KIND_TO_ROOT_INDEX(Type, type, TYPE, ctype) \
case TYPE##_ELEMENTS: \
return Heap::kEmptyFixed##Type##ArrayRootIndex;
TYPED_ARRAYS(ELEMENT_KIND_TO_ROOT_INDEX)
#undef ELEMENT_KIND_TO_ROOT_INDEX
default:
UNREACHABLE();
}
}
} // namespace
Map* Heap::MapForFixedTypedArray(ExternalArrayType array_type) {
return Map::cast(roots_[RootIndexForFixedTypedArray(array_type)]);
}
Map* Heap::MapForFixedTypedArray(ElementsKind elements_kind) {
return Map::cast(roots_[RootIndexForFixedTypedArray(elements_kind)]);
}
FixedTypedArrayBase* Heap::EmptyFixedTypedArrayForMap(const Map* map) {
return FixedTypedArrayBase::cast(
roots_[RootIndexForEmptyFixedTypedArray(map->elements_kind())]);
}
HeapObject* Heap::CreateFillerObjectAt(Address addr, int size,
ClearRecordedSlots clear_slots_mode,
ClearFreedMemoryMode clear_memory_mode) {
if (size == 0) return nullptr;
HeapObject* filler = HeapObject::FromAddress(addr);
if (size == kPointerSize) {
filler->set_map_after_allocation(
reinterpret_cast<Map*>(root(kOnePointerFillerMapRootIndex)),
SKIP_WRITE_BARRIER);
} else if (size == 2 * kPointerSize) {
filler->set_map_after_allocation(
reinterpret_cast<Map*>(root(kTwoPointerFillerMapRootIndex)),
SKIP_WRITE_BARRIER);
if (clear_memory_mode == ClearFreedMemoryMode::kClearFreedMemory) {
Memory<Address>(addr + kPointerSize) =
static_cast<Address>(kClearedFreeMemoryValue);
}
} else {
DCHECK_GT(size, 2 * kPointerSize);
filler->set_map_after_allocation(
reinterpret_cast<Map*>(root(kFreeSpaceMapRootIndex)),
SKIP_WRITE_BARRIER);
FreeSpace::cast(filler)->relaxed_write_size(size);
if (clear_memory_mode == ClearFreedMemoryMode::kClearFreedMemory) {
memset(reinterpret_cast<void*>(addr + 2 * kPointerSize),
kClearedFreeMemoryValue, size - 2 * kPointerSize);
}
}
if (clear_slots_mode == ClearRecordedSlots::kYes) {
ClearRecordedSlotRange(addr, addr + size);
}
// 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() == nullptr && !deserialization_complete_) ||
filler->map()->IsMap());
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;
Address address = object->address();
if (lo_space()->Contains(object)) return false;
// We can move the object start if the page was already swept.
return Page::FromAddress(address)->SweepingDone();
}
bool Heap::IsImmovable(HeapObject* object) {
MemoryChunk* chunk = MemoryChunk::FromAddress(object->address());
return chunk->NeverEvacuate() || chunk->owner()->identity() == LO_SPACE;
}
#ifdef ENABLE_SLOW_DCHECKS
namespace {
class LeftTrimmerVerifierRootVisitor : public RootVisitor {
public:
explicit LeftTrimmerVerifierRootVisitor(FixedArrayBase* to_check)
: to_check_(to_check) {}
virtual void VisitRootPointers(Root root, const char* description,
Object** start, Object** end) {
for (Object** p = start; p < end; ++p) {
DCHECK_NE(*p, to_check_);
}
}
private:
FixedArrayBase* to_check_;
DISALLOW_COPY_AND_ASSIGN(LeftTrimmerVerifierRootVisitor);
};
} // namespace
#endif // ENABLE_SLOW_DCHECKS
namespace {
bool MayContainRecordedSlots(HeapObject* object) {
// New space object do not have recorded slots.
if (MemoryChunk::FromHeapObject(object)->InNewSpace()) return false;
// Whitelist objects that definitely do not have pointers.
if (object->IsByteArray() || object->IsFixedDoubleArray()) return false;
// Conservatively return true for other objects.
return true;
}
} // namespace
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_NOT_NULL(object);
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() ? kPointerSize : kDoubleSize;
const int bytes_to_trim = elements_to_trim * element_size;
Map* map = object->map();
// For now this trick is only applied to objects in new and paged space.
// In large object space the object's start must coincide with chunk
// and thus the trick is just not applicable.
DCHECK(!lo_space()->Contains(object));
DCHECK(object->map() != ReadOnlyRoots(this).fixed_cow_array_map());
STATIC_ASSERT(FixedArrayBase::kMapOffset == 0);
STATIC_ASSERT(FixedArrayBase::kLengthOffset == kPointerSize);
STATIC_ASSERT(FixedArrayBase::kHeaderSize == 2 * kPointerSize);
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));
}
// 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.
HeapObject* filler =
CreateFillerObjectAt(old_start, bytes_to_trim, ClearRecordedSlots::kYes);
// 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 + kPointerSize,
Smi::FromInt(len - elements_to_trim));
FixedArrayBase* new_object =
FixedArrayBase::cast(HeapObject::FromAddress(new_start));
// Remove recorded slots for the new map and length offset.
ClearRecordedSlot(new_object, HeapObject::RawField(new_object, 0));
ClearRecordedSlot(new_object, HeapObject::RawField(
new_object, FixedArrayBase::kLengthOffset));
// Handle invalidated old-to-old slots.
if (incremental_marking()->IsCompacting() &&
MayContainRecordedSlots(new_object)) {
// If the array was right-trimmed before, then it is registered in
// the invalidated_slots.
MemoryChunk::FromHeapObject(new_object)
->MoveObjectWithInvalidatedSlots(filler, new_object);
// We have to clear slots in the free space to avoid stale old-to-old slots.
// Note we cannot use ClearFreedMemoryMode of CreateFillerObjectAt because
// we need pointer granularity writes to avoid race with the concurrent
// marking.
if (filler->Size() > FreeSpace::kSize) {
MemsetPointer(HeapObject::RawField(filler, FreeSpace::kSize),
ReadOnlyRoots(this).undefined_value(),
(filler->Size() - FreeSpace::kSize) / kPointerSize);
}
}
// 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).
LeftTrimmerVerifierRootVisitor root_visitor(object);
IterateRoots(&root_visitor, VISIT_ALL);
}
#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;
DCHECK(!object->IsFixedTypedArrayBase());
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 * kPointerSize;
} 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 * kPointerSize);
}
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;
// Register the array as an object with invalidated old-to-old slots. We
// cannot use NotifyObjectLayoutChange as it would mark the array black,
// which is not safe for left-trimming because left-trimming re-pushes
// only grey arrays onto the marking worklist.
if (incremental_marking()->IsCompacting() &&
MayContainRecordedSlots(object)) {
// Ensure that the object survives because the InvalidatedSlotsFilter will
// compute its size from its map during pointers updating phase.
incremental_marking()->WhiteToGreyAndPush(object);
MemoryChunk::FromHeapObject(object)->RegisterObjectWithInvalidatedSlots(
object, old_size);
}
// 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 large object space.
// TODO(hpayer): We should shrink the large object page if the size
// of the object changed significantly.
if (!lo_space()->Contains(object)) {
HeapObject* filler =
CreateFillerObjectAt(new_end, bytes_to_trim, ClearRecordedSlots::kYes);
DCHECK_NOT_NULL(filler);
// 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));
}
}
// 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();
}
static double ComputeMutatorUtilization(double mutator_speed, double gc_speed) {
const double kMinMutatorUtilization = 0.0;
const 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);
}
double Heap::YoungGenerationMutatorUtilization() {
double mutator_speed = static_cast<double>(
tracer()->NewSpaceAllocationThroughputInBytesPerMillisecond());
double gc_speed =
tracer()->ScavengeSpeedInBytesPerMillisecond(kForSurvivedObjects);
double result = ComputeMutatorUtilization(mutator_speed, gc_speed);
if (FLAG_trace_mutator_utilization) {
isolate()->PrintWithTimestamp(
"Young generation mutator utilization = %.3f ("
"mutator_speed=%.f, gc_speed=%.f)\n",
result, mutator_speed, gc_speed);
}
return result;
}
double Heap::OldGenerationMutatorUtilization() {
double mutator_speed = static_cast<double>(
tracer()->OldGenerationAllocationThroughputInBytesPerMillisecond());
double gc_speed = static_cast<double>(
tracer()->CombinedMarkCompactSpeedInBytesPerMillisecond());
double result = ComputeMutatorUtilization(mutator_speed, gc_speed);
if (FLAG_trace_mutator_utilization) {
isolate()->PrintWithTimestamp(
"Old generation mutator utilization = %.3f ("
"mutator_speed=%.f, gc_speed=%.f)\n",
result, mutator_speed, gc_speed);
}
return result;
}
bool Heap::HasLowYoungGenerationAllocationRate() {
const double high_mutator_utilization = 0.993;
return YoungGenerationMutatorUtilization() > high_mutator_utilization;
}
bool Heap::HasLowOldGenerationAllocationRate() {
const double high_mutator_utilization = 0.993;
return OldGenerationMutatorUtilization() > high_mutator_utilization;
}
bool Heap::HasLowAllocationRate() {
return HasLowYoungGenerationAllocationRate() &&
HasLowOldGenerationAllocationRate();
}
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();
UncommitFromSpace();
}
}
void Heap::FinalizeIncrementalMarkingIfComplete(
GarbageCollectionReason gc_reason) {
if (incremental_marking()->IsMarking() &&
(incremental_marking()->IsReadyToOverApproximateWeakClosure() ||
(!incremental_marking()->finalize_marking_completed() &&
mark_compact_collector()->marking_worklist()->IsEmpty() &&
local_embedder_heap_tracer()->ShouldFinalizeIncrementalMarking()))) {
FinalizeIncrementalMarkingIncrementally(gc_reason);
} else if (incremental_marking()->IsComplete() ||
(mark_compact_collector()->marking_worklist()->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::FinalizeIncrementalMarkingIncrementally(
GarbageCollectionReason gc_reason) {
if (FLAG_trace_incremental_marking) {
isolate()->PrintWithTimestamp(
"[IncrementalMarking] (%s).\n",
Heap::GarbageCollectionReasonToString(gc_reason));
}
HistogramTimerScope incremental_marking_scope(
isolate()->counters()->gc_incremental_marking_finalize());
TRACE_EVENT0("v8", "V8.GCIncrementalMarkingFinalize");
TRACE_GC(tracer(), GCTracer::Scope::MC_INCREMENTAL_FINALIZE);
{
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);
}
}
incremental_marking()->FinalizeIncrementally();
{
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::RegisterDeserializedObjectsForBlackAllocation(
Reservation* reservations, const std::vector<HeapObject*>& large_objects,
const std::vector<Address>& maps) {
// TODO(ulan): pause black allocation during deserialization to avoid
// iterating all these objects in one go.
if (!incremental_marking()->black_allocation()) return;
// Iterate black objects in old space, code space, map space, and large
// object space for side effects.
IncrementalMarking::MarkingState* marking_state =
incremental_marking()->marking_state();
for (int i = OLD_SPACE; i < Serializer<>::kNumberOfSpaces; i++) {
const Heap::Reservation& res = reservations[i];
for (auto& chunk : res) {
Address addr = chunk.start;
while (addr < chunk.end) {
HeapObject* obj = HeapObject::FromAddress(addr);
// Objects can have any color because incremental marking can
// start in the middle of Heap::ReserveSpace().
if (marking_state->IsBlack(obj)) {
incremental_marking()->ProcessBlackAllocatedObject(obj);
}
addr += obj->Size();
}
}
}
// We potentially deserialized wrappers which require registering with the
// embedder as the marker will not find them.
local_embedder_heap_tracer()->RegisterWrappersWithRemoteTracer();
// Large object space doesn't use reservations, so it needs custom handling.
for (HeapObject* object : large_objects) {
incremental_marking()->ProcessBlackAllocatedObject(object);
}
// Map space doesn't use reservations, so it needs custom handling.
for (Address addr : maps) {
incremental_marking()->ProcessBlackAllocatedObject(
HeapObject::FromAddress(addr));
}
}
void Heap::NotifyObjectLayoutChange(HeapObject* object, int size,
const DisallowHeapAllocation&) {
if (incremental_marking()->IsMarking()) {
incremental_marking()->MarkBlackAndPush(object);
if (incremental_marking()->IsCompacting() &&
MayContainRecordedSlots(object)) {
MemoryChunk::FromHeapObject(object)->RegisterObjectWithInvalidatedSlots(
object, size);
}
}
#ifdef VERIFY_HEAP
if (FLAG_verify_heap) {
DCHECK_NULL(pending_layout_change_object_);
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, Object** start, Object** end) override {
VisitPointers(host, reinterpret_cast<MaybeObject**>(start),
reinterpret_cast<MaybeObject**>(end));
}
void VisitPointers(HeapObject* host, MaybeObject** start,
MaybeObject** end) final {
for (MaybeObject** p = start; p < end; p++) {
slots_.push_back(p);
}
}
int number_of_slots() { return static_cast<int>(slots_.size()); }
MaybeObject** slot(int i) { return slots_[i]; }
private:
std::vector<MaybeObject**> slots_;
};
void Heap::VerifyObjectLayoutChange(HeapObject* object, Map* new_map) {
if (!FLAG_verify_heap) return;
// Check that Heap::NotifyObjectLayout 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_ == nullptr) {
if (object->IsJSObject()) {
DCHECK(!object->map()->TransitionRequiresSynchronizationWithGC(new_map));
} 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_EQ(new_visitor.slot(i), old_visitor.slot(i));
}
}
} else {
DCHECK_EQ(pending_layout_change_object_, object);
pending_layout_change_object_ = nullptr;
}
}
#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.type) {
case DONE:
result = true;
break;
case DO_INCREMENTAL_STEP: {
const double remaining_idle_time_in_ms =
incremental_marking()->AdvanceIncrementalMarking(
deadline_in_ms, IncrementalMarking::NO_GC_VIA_STACK_GUARD,
StepOrigin::kTask);
if (remaining_idle_time_in_ms > 0.0) {
FinalizeIncrementalMarkingIfComplete(
GarbageCollectionReason::kFinalizeMarkingViaTask);
}
result = incremental_marking()->IsStopped();
break;
}
case DO_FULL_GC: {
DCHECK_LT(0, contexts_disposed_);
HistogramTimerScope scope(isolate_->counters()->gc_context());
TRACE_EVENT0("v8", "V8.GCContext");
CollectAllGarbage(kNoGCFlags, GarbageCollectionReason::kContextDisposal);
break;
}
case DO_NOTHING:
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 && action.type > DO_NOTHING) ||
FLAG_trace_idle_notification_verbose) {
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);
action.Print();
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);
}
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());
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) {}
virtual ~MemoryPressureInterruptTask() {}
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);
}
MemoryPressureLevel memory_pressure_level = memory_pressure_level_;
// Reset the memory pressure level to avoid recursive GCs triggered by
// CheckMemoryPressure from AdjustAmountOfExternalMemory called by
// the finalizers.
memory_pressure_level_ = MemoryPressureLevel::kNone;
if (memory_pressure_level == MemoryPressureLevel::kCritical) {
CollectGarbageOnMemoryPressure();
} else if (memory_pressure_level == MemoryPressureLevel::kModerate) {
if (FLAG_incremental_marking && incremental_marking()->IsStopped()) {
StartIncrementalMarking(kReduceMemoryFootprintMask,
GarbageCollectionReason::kMemoryPressure);
}
}
if (memory_reducer_) {
MemoryReducer::Event event;
event.type = MemoryReducer::kPossibleGarbage;
event.time_ms = MonotonicallyIncreasingTimeInMs();
memory_reducer_->NotifyPossibleGarbage(event);
}
}
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 | kAbortIncrementalMarkingMask,
GarbageCollectionReason::kMemoryPressure,
kGCCallbackFlagCollectAllAvailableGarbage);
double end = MonotonicallyIncreasingTimeInMs();
// Estimate how much memory we can free.
int64_t potential_garbage =
(CommittedMemory() - SizeOfObjects()) + external_memory_;
// 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 | kAbortIncrementalMarkingMask,
GarbageCollectionReason::kMemoryPressure,
kGCCallbackFlagCollectAllAvailableGarbage);
} else {
if (FLAG_incremental_marking && incremental_marking()->IsStopped()) {
StartIncrementalMarking(kReduceMemoryFootprintMask,
GarbageCollectionReason::kMemoryPressure);
}
}
}
}
void Heap::MemoryPressureNotification(MemoryPressureLevel level,
bool is_isolate_locked) {
MemoryPressureLevel previous = memory_pressure_level_;
memory_pressure_level_ = level;
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();
V8::GetCurrentPlatform()->CallOnForegroundThread(
reinterpret_cast<v8::Isolate*>(isolate()),
new MemoryPressureInterruptTask(this));
}
}
}
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();
}
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_) {
max_old_generation_size_ = heap_limit;
return true;
}
}
return false;
}
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(lo_space_, isolate());
}
#ifdef DEBUG
void Heap::Print() {
if (!HasBeenSetUp()) return;
isolate()->PrintStack(stdout);
for (SpaceIterator it(this); it.has_next();) {
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::kIdleTask:
return "idle 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::kUnknown:
return "unknown";
}
UNREACHABLE();
}
bool Heap::Contains(HeapObject* value) {
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) || read_only_space_->Contains(value));
}
bool Heap::ContainsSlow(Address addr) {
if (memory_allocator()->IsOutsideAllocatedSpace(addr)) {
return false;
}
return HasBeenSetUp() &&
(new_space_->ToSpaceContainsSlow(addr) ||
old_space_->ContainsSlow(addr) || code_space_->ContainsSlow(addr) ||
map_space_->ContainsSlow(addr) || lo_space_->ContainsSlow(addr) ||
read_only_space_->Contains(addr));
}
bool Heap::InSpace(HeapObject* value, AllocationSpace space) {
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 NEW_LO_SPACE:
return new_lo_space_->Contains(value);
case RO_SPACE:
return read_only_space_->Contains(value);
}
UNREACHABLE();
}
bool Heap::InSpaceSlow(Address addr, AllocationSpace space) {
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 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 RO_SPACE:
return true;
default:
return false;
}
}
bool Heap::RootIsImmortalImmovable(int root_index) {
switch (root_index) {
#define IMMORTAL_IMMOVABLE_ROOT(name) case Heap::k##name##RootIndex:
IMMORTAL_IMMOVABLE_ROOT_LIST(IMMORTAL_IMMOVABLE_ROOT)
#undef IMMORTAL_IMMOVABLE_ROOT
#define INTERNALIZED_STRING(name, value) case Heap::k##name##RootIndex:
INTERNALIZED_STRING_LIST(INTERNALIZED_STRING)
#undef INTERNALIZED_STRING
#define STRING_TYPE(NAME, size, name, Name) case Heap::k##Name##MapRootIndex:
STRING_TYPE_LIST(STRING_TYPE)
#undef STRING_TYPE
return true;
default:
return false;
}
}
#ifdef VERIFY_HEAP
class VerifyReadOnlyPointersVisitor : public VerifyPointersVisitor {
public:
explicit VerifyReadOnlyPointersVisitor(Heap* heap)
: VerifyPointersVisitor(heap) {}
protected:
void VerifyPointers(HeapObject* host, MaybeObject** start,
MaybeObject** end) override {
if (host != nullptr) {
CHECK(heap_->InReadOnlySpace(host->map()));
}
VerifyPointersVisitor::VerifyPointers(host, start, end);
for (MaybeObject** current = start; current < end; current++) {
HeapObject* object;
if ((*current)->ToStrongOrWeakHeapObject(&object)) {
CHECK(heap_->InReadOnlySpace(object));
}
}
}
};
void Heap::Verify() {
CHECK(HasBeenSetUp());
HandleScope scope(isolate());
// We have to wait here for the sweeper threads to have an iterable heap.
mark_compact_collector()->EnsureSweepingCompleted();
VerifyPointersVisitor visitor(this);
IterateRoots(&visitor, VISIT_ONLY_STRONG);
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());
VerifyReadOnlyPointersVisitor read_only_visitor(this);
read_only_space_->Verify(isolate(), &read_only_visitor);
}
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, Object** start, Object** end) override {
#ifdef DEBUG
for (Object** slot = start; slot < end; slot++) {
DCHECK(!HasWeakHeapObjectTag(*slot));
}
#endif // DEBUG
VisitPointers(host, reinterpret_cast<MaybeObject**>(start),
reinterpret_cast<MaybeObject**>(end));
}
void VisitPointers(HeapObject* host, MaybeObject** start,
MaybeObject** end) final {
for (MaybeObject** slot = start; slot < end; slot++) {
if (ShouldHaveBeenRecorded(host, *slot)) {
CHECK_GT(untyped_->count(reinterpret_cast<Address>(slot)), 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(EMBEDDED_OBJECT_SLOT, rinfo->pc()) ||
(rinfo->IsInConstantPool() &&
InTypedSet(OBJECT_SLOT, rinfo->constant_pool_entry_address())));
}
}
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)
: SlotVerifyingVisitor(untyped, typed) {}
bool ShouldHaveBeenRecorded(HeapObject* host, MaybeObject* target) override {
DCHECK_IMPLIES(
target->IsStrongOrWeakHeapObject() && Heap::InNewSpace(target),
Heap::InToSpace(target));
return target->IsStrongOrWeakHeapObject() && Heap::InNewSpace(target) &&
!Heap::InNewSpace(host);
}
};
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](Address slot) {
if (start <= slot && slot < end) {
untyped->insert(slot);
}
return KEEP_SLOT;
},
SlotSet::PREFREE_EMPTY_BUCKETS);
RememberedSet<direction>::IterateTyped(
chunk, [start, end, typed](SlotType type, Address host, 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::FromAddress(object->address());
DCHECK_IMPLIES(chunk->mutex() == nullptr, InReadOnlySpace(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 (!InNewSpace(object)) {
store_buffer()->MoveAllEntriesToRememberedSet();
CollectSlots<OLD_TO_NEW>(chunk, start, end, &old_to_new, &typed_old_to_new);
OldToNewSlotVerifyingVisitor visitor(&old_to_new, &typed_old_to_new);
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() {
PagedSpaces spaces(this);
for (PagedSpace* space = spaces.next(); space != nullptr;
space = spaces.next()) {
space->VerifyCountersAfterSweeping();
}
}
void Heap::VerifyCountersBeforeConcurrentSweeping() {
PagedSpaces 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
for (int i = 0; i < size_in_bytes / kPointerSize; i++) {
reinterpret_cast<Object**>(start_address)[i] = Smi::FromInt(kCodeZapValue);
}
#endif
}
Code* Heap::builtin(int index) {
DCHECK(Builtins::IsBuiltinId(index));
// Code::cast cannot be used here since we access builtins
// during the marking phase of mark sweep. See IC::Clear.
return reinterpret_cast<Code*>(builtins_[index]);
}
Address Heap::builtin_address(int index) {
DCHECK(Builtins::IsBuiltinId(index) || index == Builtins::builtin_count);
return reinterpret_cast<Address>(&builtins_[index]);
}
void Heap::set_builtin(int index, HeapObject* builtin) {
DCHECK(Builtins::IsBuiltinId(index));
DCHECK(Internals::HasHeapObjectTag(builtin));
// The given builtin may be completely uninitialized thus we cannot check its
// type here.
builtins_[index] = builtin;
}
void Heap::IterateRoots(RootVisitor* v, VisitMode mode) {
IterateStrongRoots(v, mode);
IterateWeakRoots(v, mode);
}
void Heap::IterateWeakRoots(RootVisitor* v, VisitMode mode) {
const bool isMinorGC = mode == VISIT_ALL_IN_SCAVENGE ||
mode == VISIT_ALL_IN_MINOR_MC_MARK ||
mode == VISIT_ALL_IN_MINOR_MC_UPDATE;
v->VisitRootPointer(
Root::kStringTable, nullptr,
reinterpret_cast<Object**>(&roots_[kStringTableRootIndex]));
v->Synchronize(VisitorSynchronization::kStringTable);
if (!isMinorGC && mode != VISIT_ALL_IN_SWEEP_NEWSPACE &&
mode != VISIT_FOR_SERIALIZATION) {
// 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_[kSmiRootsStart],
&roots_[kRootListLength]);
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,
Object** p) override {
FixHandle(p);
}
void VisitRootPointers(Root root, const char* description, Object** start,
Object** end) override {
for (Object** p = start; p < end; p++) FixHandle(p);
}
private:
inline void FixHandle(Object** p) {
if (!(*p)->IsHeapObject()) return;
HeapObject* current = reinterpret_cast<HeapObject*>(*p);
const MapWord map_word = current->map_word();
if (!map_word.IsForwardingAddress() && current->IsFiller()) {
#ifdef DEBUG
// We need to find a FixedArrayBase map after walking the fillers.
while (current->IsFiller()) {
Address next = reinterpret_cast<Address>(current);
if (current->map() == ReadOnlyRoots(heap_).one_pointer_filler_map()) {
next += kPointerSize;
} else if (current->map() ==
ReadOnlyRoots(heap_).two_pointer_filler_map()) {
next += 2 * kPointerSize;
} else {
next += current->Size();
}
current = reinterpret_cast<HeapObject*>(next);
}
DCHECK(current->IsFixedArrayBase());
#endif // DEBUG
*p = nullptr;
}
}
Heap* heap_;
};
void Heap::IterateStrongRoots(RootVisitor* v, VisitMode mode) {
const bool isMinorGC = mode == VISIT_ALL_IN_SCAVENGE ||
mode == VISIT_ALL_IN_MINOR_MC_MARK ||
mode == VISIT_ALL_IN_MINOR_MC_UPDATE;
v->VisitRootPointers(Root::kStrongRootList, nullptr, &roots_[0],
&roots_[kStrongRootListLength]);
v->Synchronize(VisitorSynchronization::kStrongRootList);
isolate_->bootstrapper()->Iterate(v);
v->Synchronize(VisitorSynchronization::kBootstrapper);
isolate_->Iterate(v);
v->Synchronize(VisitorSynchronization::kTop);
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);
// Iterate over local handles in handle scopes.
FixStaleLeftTrimmedHandlesVisitor left_trim_visitor(this);
isolate_->handle_scope_implementer()->Iterate(&left_trim_visitor);
isolate_->handle_scope_implementer()->Iterate(v);
isolate_->IterateDeferredHandles(v);
v->Synchronize(VisitorSynchronization::kHandleScope);
// Iterate over the builtin code objects and code stubs in the
// heap. Note that it is not necessary to iterate over code objects
// on scavenge collections.
if (!isMinorGC) {
IterateBuiltins(v);
v->Synchronize(VisitorSynchronization::kBuiltins);
isolate_->interpreter()->IterateDispatchTable(v);
v->Synchronize(VisitorSynchronization::kDispatchTable);
}
// Iterate over global handles.
switch (mode) {
case VISIT_FOR_SERIALIZATION:
// Global handles are not iterated by the serializer. Values referenced by
// global handles need to be added manually.
break;
case VISIT_ONLY_STRONG:
isolate_->global_handles()->IterateStrongRoots(v);
break;
case VISIT_ALL_IN_SCAVENGE:
isolate_->global_handles()->IterateNewSpaceStrongAndDependentRoots(v);
break;
case VISIT_ALL_IN_MINOR_MC_MARK:
// Global handles are processed manually be the minor MC.
break;
case VISIT_ALL_IN_MINOR_MC_UPDATE:
// Global handles are processed manually be the minor MC.
break;
case VISIT_ALL_IN_SWEEP_NEWSPACE:
case VISIT_ALL:
isolate_->global_handles()->IterateAllRoots(v);
break;
}
v->Synchronize(VisitorSynchronization::kGlobalHandles);
// Iterate over eternal handles. Eternal handles are not iterated by the
// serializer. Values referenced by eternal handles need to be added manually.
if (mode != VISIT_FOR_SERIALIZATION) {
if (isMinorGC) {
isolate_->eternal_handles()->IterateNewSpaceRoots(v);
} else {
isolate_->eternal_handles()->IterateAllRoots(v);
}
}
v->Synchronize(VisitorSynchronization::kEternalHandles);
// Iterate over pointers being held by inactive threads.
isolate_->thread_manager()->Iterate(v);
v->Synchronize(VisitorSynchronization::kThreadManager);
// Iterate over other strong roots (currently only identity maps).
for (StrongRootsList* list = strong_roots_list_; list; list = list->next) {
v->VisitRootPointers(Root::kStrongRoots, nullptr, list->start, list->end);
}
v->Synchronize(VisitorSynchronization::kStrongRoots);
// Iterate over the partial snapshot cache unless serializing.
if (mode != VISIT_FOR_SERIALIZATION) {
SerializerDeserializer::Iterate(isolate_, v);
// We don't do a v->Synchronize call here because the serializer and the
// deserializer are deliberately out of sync here.
}
}
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), &builtins_[i]);
}
}
// TODO(1236194): Since the heap size is configurable on the command line
// and through the API, we should gracefully handle the case that the heap
// size is not big enough to fit all the initial objects.
void Heap::ConfigureHeap(size_t max_semi_space_size_in_kb,
size_t max_old_generation_size_in_mb,
size_t code_range_size_in_mb) {
// Overwrite default configuration.
if (max_semi_space_size_in_kb != 0) {
max_semi_space_size_ =
RoundUp<Page::kPageSize>(max_semi_space_size_in_kb * KB);
}
if (max_old_generation_size_in_mb != 0) {
max_old_generation_size_ = max_old_generation_size_in_mb * MB;
}
// If max space size flags are specified overwrite the configuration.
if (FLAG_max_semi_space_size > 0) {
max_semi_space_size_ = static_cast<size_t>(FLAG_max_semi_space_size) * MB;
}
if (FLAG_max_old_space_size > 0) {
max_old_generation_size_ =
static_cast<size_t>(FLAG_max_old_space_size) * MB;
}
if (Page::kPageSize > MB) {
max_semi_space_size_ = RoundUp<Page::kPageSize>(max_semi_space_size_);
max_old_generation_size_ =
RoundUp<Page::kPageSize>(max_old_generation_size_);
}
if (FLAG_stress_compaction) {
// This will cause more frequent GCs when stressing.
max_semi_space_size_ = MB;
}
// The new space size must be a power of two to support single-bit testing
// for containment.
max_semi_space_size_ = static_cast<size_t>(base::bits::RoundUpToPowerOfTwo64(
static_cast<uint64_t>(max_semi_space_size_)));
if (max_semi_space_size_ == kMaxSemiSpaceSizeInKB * KB) {
// 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 (FLAG_min_semi_space_size > 0) {
size_t initial_semispace_size =
static_cast<size_t>(FLAG_min_semi_space_size) * MB;
if (initial_semispace_size > max_semi_space_size_) {
initial_semispace_size_ = max_semi_space_size_;
if (FLAG_trace_gc) {
PrintIsolate(isolate_,
"Min semi-space size cannot be more than the maximum "
"semi-space size of %" PRIuS " MB\n",
max_semi_space_size_ / MB);
}
} else {
initial_semispace_size_ =
RoundUp<Page::kPageSize>(initial_semispace_size);
}
}
initial_semispace_size_ = Min(initial_semispace_size_, max_semi_space_size_);
if (FLAG_semi_space_growth_factor < 2) {
FLAG_semi_space_growth_factor = 2;
}
// The old generation is paged and needs at least one page for each space.
int paged_space_count =
LAST_GROWABLE_PAGED_SPACE - FIRST_GROWABLE_PAGED_SPACE + 1;
initial_max_old_generation_size_ = max_old_generation_size_ =
Max(static_cast<size_t>(paged_space_count * Page::kPageSize),
max_old_generation_size_);
if (FLAG_initial_old_space_size > 0) {
initial_old_generation_size_ = FLAG_initial_old_space_size * MB;
} else {
initial_old_generation_size_ =
max_old_generation_size_ / kInitalOldGenerationLimitFactor;
}
old_generation_allocation_limit_ = initial_old_generation_size_;
// We rely on being able to allocate new arrays in paged spaces.
DCHECK(kMaxRegularHeapObjectSize >=
(JSArray::kSize +
FixedArray::SizeFor(JSArray::kInitialMaxFastElementArray) +
AllocationMemento::kSize));
code_range_size_ = code_range_size_in_mb * MB;
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() { ConfigureHeap(0, 0, 0); }
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();
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();
*stats->malloced_memory = isolate_->allocator()->GetCurrentMemoryUsage();
*stats->malloced_peak_memory = isolate_->allocator()->GetMaxMemoryUsage();
if (take_snapshot) {
HeapIterator iterator(this);
for (HeapObject* obj = iterator.next(); obj != nullptr;
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);
if (stats->js_stacktrace != nullptr) {
FixedStringAllocator fixed(stats->js_stacktrace, kStacktraceBufferSize - 1);
StringStream accumulator(&fixed, StringStream::kPrintObjectConcise);
if (gc_state() == Heap::NOT_IN_GC) {
isolate()->PrintStack(&accumulator, Isolate::kPrintStackVerbose);
} else {
accumulator.Add("Cannot get stack trace in GC.");
}
}
}
size_t Heap::OldGenerationSizeOfObjects() {
PagedSpaces spaces(this, PagedSpaces::SpacesSpecifier::kAllPagedSpaces);
size_t total = 0;
for (PagedSpace* space = spaces.next(); space != nullptr;
space = spaces.next()) {
total += space->SizeOfObjects();
}
return total + lo_space_->SizeOfObjects();
}
uint64_t Heap::PromotedExternalMemorySize() {
if (external_memory_ <= external_memory_at_last_mark_compact_) return 0;
return static_cast<uint64_t>(external_memory_ -
external_memory_at_last_mark_compact_);
}
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() {
if (always_allocate() || OldGenerationSpaceAvailable() > 0) return true;
// We reached the old generation allocation limit.
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;
}
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;
}
// 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 (OldGenerationSizeOfObjects() <=
IncrementalMarking::kActivationThreshold) {
// Incremental marking is disabled or it is too early to start.
return IncrementalMarkingLimit::kNoLimit;
}
if ((FLAG_stress_compaction && (gc_count_ & 1) != 0) ||
HighMemoryPressure()) {
// If there is high memory pressure or stress testing is enabled, then
// start marking immediately.
return IncrementalMarkingLimit::kHardLimit;
}
if (FLAG_stress_marking > 0) {
double gained_since_last_gc =
PromotedSinceLastGC() +
(external_memory_ - external_memory_at_last_mark_compact_);
double size_before_gc =
OldGenerationObjectsAndPromotedExternalMemorySize() -
gained_since_last_gc;
double bytes_to_limit = old_generation_allocation_limit_ - size_before_gc;
if (bytes_to_limit > 0) {
double current_percent = (gained_since_last_gc / bytes_to_limit) * 100.0;
if (FLAG_trace_stress_marking) {
isolate()->PrintWithTimestamp(
"[IncrementalMarking] %.2lf%% of the memory limit reached\n",
current_percent);
}
if (FLAG_fuzzer_gc_analysis) {
// Skips values >=100% since they already trigger marking.
if (current_percent < 100.0) {
max_marking_limit_reached_ =
std::max(max_marking_limit_reached_, current_percent);
}
} else if (static_cast<int>(current_percent) >=
stress_marking_percentage_) {
stress_marking_percentage_ = NextStressMarkingLimit();
return IncrementalMarkingLimit::kHardLimit;
}
}
}
size_t old_generation_space_available = OldGenerationSpaceAvailable();
if (old_generation_space_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;
}
return IncrementalMarkingLimit::kSoftLimit;
}
void Heap::EnableInlineAllocation() {
if (!inline_allocation_disabled_) return;
inline_allocation_disabled_ = false;
// Update inline allocation limit for new space.
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.
PagedSpaces spaces(this);
CodeSpaceMemoryModificationScope modification_scope(this);
for (PagedSpace* space = spaces.next(); space != nullptr;
space = spaces.next()) {
space->FreeLinearAllocationArea();
}
}
HeapObject* Heap::EnsureImmovableCode(HeapObject* heap_object,
int object_size) {
// Code objects which should stay at a fixed address are allocated either
// in the first page of code space, in large object space, or (during
// snapshot creation) the containing page is marked as immovable.
DCHECK(heap_object);
DCHECK(code_space_->Contains(heap_object));
DCHECK_GE(object_size, 0);
if (!Heap::IsImmovable(heap_object)) {
if (isolate()->serializer_enabled() ||
code_space_->first_page()->Contains(heap_object->address())) {
MemoryChunk::FromAddress(heap_object->address())->MarkNeverEvacuate();
} else {
// Discard the first code allocation, which was on a page where it could
// be moved.
CreateFillerObjectAt(heap_object->address(), object_size,
ClearRecordedSlots::kNo);
heap_object = AllocateRawCodeInLargeObjectSpace(object_size);
UnprotectAndRegisterMemoryChunk(heap_object);
ZapCodeObject(heap_object->address(), object_size);
OnAllocationEvent(heap_object, object_size);
}
}
return heap_object;
}
HeapObject* Heap::AllocateRawWithLightRetry(int size, AllocationSpace space,
AllocationAlignment alignment) {
HeapObject* result;
AllocationResult alloc = AllocateRaw(size, space, alignment);
if (alloc.To(&result)) {
DCHECK(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, space, alignment);
if (alloc.To(&result)) {
DCHECK(result != ReadOnlyRoots(this).exception());
return result;
}
}
return nullptr;
}
HeapObject* Heap::AllocateRawWithRetryOrFail(int size, AllocationSpace space,
AllocationAlignment alignment) {
AllocationResult alloc;
HeapObject* result = AllocateRawWithLightRetry(size, space, alignment);
if (result) return result;
isolate()->counters()->gc_last_resort_from_handles()->Increment();
CollectAllAvailableGarbage(GarbageCollectionReason::kLastResort);
{
AlwaysAllocateScope scope(isolate());
alloc = AllocateRaw(size, space, alignment);
}
if (alloc.To(&result)) {
DCHECK(result != ReadOnlyRoots(this).exception());
return result;
}
// TODO(1181417): Fix this.
FatalProcessOutOfMemory("CALL_AND_RETRY_LAST");
return nullptr;
}
// TODO(jkummerow): Refactor this. AllocateRaw should take an "immovability"
// parameter and just do what's necessary.
HeapObject* Heap::AllocateRawCodeInLargeObjectSpace(int size) {
AllocationResult alloc = lo_space()->AllocateRaw(size, EXECUTABLE);
HeapObject* result;
if (alloc.To(&result)) {
DCHECK(result != ReadOnlyRoots(this).exception());
return result;
}
// Two GCs before panicking.
for (int i = 0; i < 2; i++) {
CollectGarbage(alloc.RetrySpace(),
GarbageCollectionReason::kAllocationFailure);
alloc = lo_space()->AllocateRaw(size, EXECUTABLE);
if (alloc.To(&result)) {
DCHECK(result != ReadOnlyRoots(this).exception());
return result;
}
}
isolate()->counters()->gc_last_resort_from_handles()->Increment();
CollectAllAvailableGarbage(GarbageCollectionReason::kLastResort);
{
AlwaysAllocateScope scope(isolate());
alloc = lo_space()->AllocateRaw(size, EXECUTABLE);
}
if (alloc.To(&result)) {
DCHECK(result != ReadOnlyRoots(this).exception());
return result;
}
// TODO(1181417): Fix this.
FatalProcessOutOfMemory("CALL_AND_RETRY_LAST");
return nullptr;
}
void Heap::SetUp() {
#ifdef V8_ENABLE_ALLOCATION_TIMEOUT
allocation_timeout_ = NextAllocationTimeout();
#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_ =
new MemoryAllocator(isolate_, MaxReserved(), code_range_size_);
store_buffer_ = new StoreBuffer(this);
heap_controller_ = new HeapController(this);
mark_compact_collector_ = new MarkCompactCollector(this);
incremental_marking_ =
new IncrementalMarking(this, mark_compact_collector_->marking_worklist(),
mark_compact_collector_->weak_objects());
if (FLAG_concurrent_marking) {
MarkCompactCollector::MarkingWorklist* marking_worklist =
mark_compact_collector_->marking_worklist();
concurrent_marking_ = new ConcurrentMarking(
this, marking_worklist->shared(), marking_worklist->bailout(),
marking_worklist->on_hold(), mark_compact_collector_->weak_objects());
} else {
concurrent_marking_ =
new ConcurrentMarking(this, nullptr, nullptr, nullptr, nullptr);
}
for (int i = FIRST_SPACE; i <= LAST_SPACE; i++) {
space_[i] = nullptr;
}
space_[RO_SPACE] = read_only_space_ = new ReadOnlySpace(this);
space_[NEW_SPACE] = new_space_ =
new NewSpace(this, 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 LargeObjectSpace(this);
space_[NEW_LO_SPACE] = new_lo_space_ = new NewLargeObjectSpace(this);
for (int i = 0; i < static_cast<int>(v8::Isolate::kUseCounterFeatureCount);
i++) {
deferred_counters_[i] = 0;
}
tracer_ = 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_collector_ = new ArrayBufferCollector(this);
gc_idle_time_handler_ = new GCIdleTimeHandler();
memory_reducer_ = new MemoryReducer(this);
if (V8_UNLIKELY(FLAG_gc_stats)) {
live_object_stats_ = new ObjectStats(this);
dead_object_stats_ = new ObjectStats(this);
}
scavenge_job_ = new ScavengeJob();
local_embedder_heap_tracer_ = new LocalEmbedderHeapTracer(isolate());
LOG(isolate_, IntPtrTEvent("heap-capacity", Capacity()));
LOG(isolate_, IntPtrTEvent("heap-available", Available()));
store_buffer()->SetUp();
mark_compact_collector()->SetUp();
#ifdef ENABLE_MINOR_MC
if (minor_mark_compact_collector() != nullptr) {
minor_mark_compact_collector()->SetUp();
}
#endif // ENABLE_MINOR_MC
idle_scavenge_observer_ = new IdleScavengeObserver(
*this, ScavengeJob::kBytesAllocatedBeforeNextIdleTask);
new_space()->AddAllocationObserver(idle_scavenge_observer_);
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;
external_reference_table_.Init(isolate_);
}
void Heap::InitializeHashSeed() {
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);
}
hash_seed()->copy_in(0, reinterpret_cast<byte*>(&new_hash_seed), kInt64Size);
}
void Heap::SetStackLimits() {
DCHECK_NOT_NULL(isolate_);
DCHECK(isolate_ == isolate());
// On 64 bit machines, pointers are generally out of range of Smis. We write
// something that looks like an out of range Smi to the GC.
// Set up the special root array entries containing the stack limits.
// These are actually addresses, but the tag makes the GC ignore it.
roots_[kStackLimitRootIndex] = reinterpret_cast<Object*>(
(isolate_->stack_guard()->jslimit() & ~kSmiTagMask) | kSmiTag);
roots_[kRealStackLimitRootIndex] = reinterpret_cast<Object*>(
(isolate_->stack_guard()->real_jslimit() & ~kSmiTagMask) | kSmiTag);
}
void Heap::ClearStackLimits() {
roots_[kStackLimitRootIndex] = Smi::kZero;
roots_[kRealStackLimitRootIndex] = Smi::kZero;
}
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() {
PagedSpaces 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
}
read_only_space()->MarkAsReadOnly();
deserialization_complete_ = true;
}
void Heap::SetEmbedderHeapTracer(EmbedderHeapTracer* tracer) {
DCHECK_EQ(gc_state_, HeapState::NOT_IN_GC);
local_embedder_heap_tracer()->SetRemoteTracer(tracer);
}
void Heap::TracePossibleWrapper(JSObject* js_object) {
DCHECK(js_object->IsApiWrapper());
if (js_object->GetEmbedderFieldCount() >= 2 &&
js_object->GetEmbedderField(0) &&
js_object->GetEmbedderField(0) != ReadOnlyRoots(this).undefined_value() &&
js_object->GetEmbedderField(1) != ReadOnlyRoots(this).undefined_value()) {
DCHECK_EQ(0,
reinterpret_cast<intptr_t>(js_object->GetEmbedderField(0)) % 2);
local_embedder_heap_tracer()->AddWrapperToTrace(std::pair<void*, void*>(
reinterpret_cast<void*>(js_object->GetEmbedderField(0)),
reinterpret_cast<void*>(js_object->GetEmbedderField(1))));
}
}
void Heap::RegisterExternallyReferencedObject(Object** object) {
// The embedder is not aware of whether numbers are materialized as heap
// objects are just passed around as Smis.
if (!(*object)->IsHeapObject()) return;
HeapObject* heap_object = HeapObject::cast(*object);
DCHECK(Contains(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); }
void Heap::TearDown() {
DCHECK_EQ(gc_state_, TEAR_DOWN);
#ifdef VERIFY_HEAP
if (FLAG_verify_heap) {
Verify();
}
#endif
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(idle_scavenge_observer_);
delete idle_scavenge_observer_;
idle_scavenge_observer_ = nullptr;
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 (heap_controller_ != nullptr) {
delete heap_controller_;
heap_controller_ = nullptr;
}
if (mark_compact_collector_ != nullptr) {
mark_compact_collector_->TearDown();
delete mark_compact_collector_;
mark_compact_collector_ = nullptr;
}
#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
if (array_buffer_collector_ != nullptr) {
delete array_buffer_collector_;
array_buffer_collector_ = nullptr;
}
delete incremental_marking_;
incremental_marking_ = nullptr;
delete concurrent_marking_;
concurrent_marking_ = nullptr;
delete gc_idle_time_handler_;
gc_idle_time_handler_ = nullptr;
if (memory_reducer_ != nullptr) {
memory_reducer_->TearDown();
delete memory_reducer_;
memory_reducer_ = nullptr;
}
if (live_object_stats_ != nullptr) {
delete live_object_stats_;
live_object_stats_ = nullptr;
}
if (dead_object_stats_ != nullptr) {
delete dead_object_stats_;
dead_object_stats_ = nullptr;
}
delete local_embedder_heap_tracer_;
local_embedder_heap_tracer_ = nullptr;
delete scavenge_job_;
scavenge_job_ = nullptr;
isolate_->global_handles()->TearDown();
external_string_table_.TearDown();
// Tear down all ArrayBuffers before tearing down the heap since their
// byte_length may be a HeapNumber which is required for freeing the backing
// store.
ArrayBufferTracker::TearDown(this);
delete tracer_;
tracer_ = nullptr;
for (int i = FIRST_SPACE; i <= LAST_SPACE; i++) {
delete space_[i];
space_[i] = nullptr;
}
store_buffer()->TearDown();
memory_allocator()->TearDown();
StrongRootsList* next = nullptr;
for (StrongRootsList* list = strong_roots_list_; list; list = next) {
next = list->next;
delete list;
}
strong_roots_list_ = nullptr;
delete store_buffer_;
store_buffer_ = nullptr;
delete memory_allocator_;
memory_allocator_ = nullptr;
}
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,
PretenureFlag pretenure) {
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, pretenure);
// 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->IsClearedWeakHeapObject()) continue;
new_array->Set(copy_to++, element);
}
new_array->set_length(copy_to);
return new_array;
}
} // anonymous namespace
void Heap::CompactWeakArrayLists(PretenureFlag pretenure) {
// Find known PrototypeUsers and compact them.
std::vector<Handle<PrototypeInfo>> prototype_infos;
{
HeapIterator iterator(this);
for (HeapObject* o = iterator.next(); o != nullptr; 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(pretenure == TENURED,
InOldSpace(*array) ||
*array == ReadOnlyRoots(this).empty_weak_array_list());
WeakArrayList* new_array = PrototypeUsers::Compact(
array, this, JSObject::PrototypeRegistryCompactionCallback, pretenure);
prototype_info->set_prototype_users(new_array);
}
// Find known WeakArrayLists and compact them.
Handle<WeakArrayList> scripts(script_list(), isolate());
DCHECK_IMPLIES(pretenure == TENURED, InOldSpace(*scripts));
scripts = CompactWeakArrayList(this, scripts, pretenure);
set_script_list(*scripts);
Handle<WeakArrayList> no_script_list(noscript_shared_function_infos(),
isolate());
DCHECK_IMPLIES(pretenure == TENURED, InOldSpace(*no_script_list));
no_script_list = CompactWeakArrayList(this, no_script_list, pretenure);
set_noscript_shared_function_infos(*no_script_list);
}
void Heap::AddRetainedMap(Handle<Map> map) {
if (map->is_in_retained_map_list()) {
return;
}
Handle<WeakArrayList> array(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 != retained_maps()) {
set_retained_maps(*array);
}
map->set_is_in_retained_map_list(true);
}
void Heap::CompactRetainedMaps(WeakArrayList* retained_maps) {
DCHECK_EQ(retained_maps, this->retained_maps());
int length = retained_maps->length();
int new_length = 0;
int new_number_of_disposed_maps = 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->IsClearedWeakHeapObject()) {
continue;
}
DCHECK(maybe_object->IsWeakHeapObject());
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);
}
if (i < number_of_disposed_maps_) {
new_number_of_disposed_maps += 2;
}
new_length += 2;
}
number_of_disposed_maps_ = new_number_of_disposed_maps;
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, Object** start,
Object** end) override {
for (Object** p = start; p < end; p++)
PrintF(" handle %p to %p\n", reinterpret_cast<void*>(p),
reinterpret_cast<void*>(*p));
}
};
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, Object** start,
Object** end) override {
handle_count_ += end - start;
}
private:
ptrdiff_t handle_count_;
};
void Heap::CheckHandleCount() {
CheckHandleCountVisitor v;
isolate_->handle_scope_implementer()->Iterate(&v);
}
Address* Heap::store_buffer_top_address() {
return store_buffer()->top_address();
}
// static
intptr_t Heap::store_buffer_mask_constant() {
return StoreBuffer::kStoreBufferMask;
}
// static
Address Heap::store_buffer_overflow_function_address() {
return FUNCTION_ADDR(StoreBuffer::StoreBufferOverflow);
}
void Heap::ClearRecordedSlot(HeapObject* object, Object** slot) {
Address slot_addr = reinterpret_cast<Address>(slot);
Page* page = Page::FromAddress(slot_addr);
if (!page->InNewSpace()) {
DCHECK_EQ(page->owner()->identity(), OLD_SPACE);
store_buffer()->DeleteEntry(slot_addr);
}
}
bool Heap::HasRecordedSlot(HeapObject* object, Object** slot) {
if (InNewSpace(object)) {
return false;
}
Address slot_addr = reinterpret_cast<Address>(slot);
Page* page = Page::FromAddress(slot_addr);
DCHECK_EQ(page->owner()->identity(), OLD_SPACE);
store_buffer()->MoveAllEntriesToRememberedSet();
return RememberedSet<OLD_TO_NEW>::Contains(page, slot_addr) ||
RememberedSet<OLD_TO_OLD>::Contains(page, slot_addr);
}
void Heap::ClearRecordedSlotRange(Address start, Address end) {
Page* page = Page::FromAddress(start);
if (!page->InNewSpace()) {
DCHECK_EQ(page->owner()->identity(), OLD_SPACE);
store_buffer()->DeleteEntry(start, end);
}
}
PagedSpace* PagedSpaces::next() {
switch (counter_++) {
case RO_SPACE:
// skip NEW_SPACE
counter_++;
return heap_->read_only_space();
case OLD_SPACE:
return heap_->old_space();
case CODE_SPACE:
return heap_->code_space();
case MAP_SPACE:
return heap_->map_space();
default:
return nullptr;
}
}
SpaceIterator::SpaceIterator(Heap* heap)
: heap_(heap), current_space_(FIRST_SPACE - 1) {}
SpaceIterator::~SpaceIterator() {
}
bool SpaceIterator::has_next() {
// Iterate until no more spaces.
return current_space_ != LAST_SPACE;
}
Space* SpaceIterator::next() {
DCHECK(has_next());
return heap_->space(++current_space_);
}
class HeapObjectsFilter {
public:
virtual ~HeapObjectsFilter() {}
virtual bool SkipObject(HeapObject* object) = 0;
};
class UnreachableObjectsFilter : public HeapObjectsFilter {
public:
explicit UnreachableObjectsFilter(Heap* heap) : heap_(heap) {
MarkReachableObjects();
}
~UnreachableObjectsFilter() {
for (auto it : reachable_) {
delete it.second;
it.second = nullptr;
}
}
bool SkipObject(HeapObject* object) {
if (object->IsFiller()) return true;
MemoryChunk* chunk = MemoryChunk::FromAddress(object->address());
if (reachable_.count(chunk) == 0) return true;
return reachable_[chunk]->count(object) == 0;
}
private:
bool MarkAsReachable(HeapObject* object) {
MemoryChunk* chunk = MemoryChunk::FromAddress(object->address());
if (reachable_.count(chunk) == 0) {
reachable_[chunk] = new std::unordered_set<HeapObject*>();
}
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, Object** start,
Object** end) override {
MarkPointers(reinterpret_cast<MaybeObject**>(start),
reinterpret_cast<MaybeObject**>(end));
}
void VisitPointers(HeapObject* host, MaybeObject** start,
MaybeObject** end) final {
MarkPointers(start, end);
}
void VisitRootPointers(Root root, const char* description, Object** start,
Object** end) override {
MarkPointers(reinterpret_cast<MaybeObject**>(start),
reinterpret_cast<MaybeObject**>(end));
}
void TransitiveClosure() {
while (!marking_stack_.empty()) {
HeapObject* obj = marking_stack_.back();
marking_stack_.pop_back();
obj->Iterate(this);
}
}
private:
void MarkPointers(MaybeObject** start, MaybeObject** end) {
// Treat weak references as strong.
for (MaybeObject** p = start; p < end; p++) {
HeapObject* heap_object;
if ((*p)->ToStrongOrWeakHeapObject(&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, VISIT_ALL);
visitor.TransitiveClosure();
}
Heap* heap_;
DisallowHeapAllocation no_allocation_;
std::unordered_map<MemoryChunk*, std::unordered_set<HeapObject*>*> reachable_;
};
HeapIterator::HeapIterator(Heap* heap,
HeapIterator::HeapObjectsFiltering filtering)
: no_heap_allocation_(),
heap_(heap),
filtering_(filtering),
filter_(nullptr),
space_iterator_(nullptr),
object_iterator_(nullptr) {
heap_->MakeHeapIterable();
heap_->heap_iterator_start();
// 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();
}
HeapIterator::~HeapIterator() {
heap_->heap_iterator_end();
#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* HeapIterator::next() {
if (filter_ == nullptr) return NextObject();
HeapObject* obj = NextObject();
while ((obj != nullptr) && (filter_->SkipObject(obj))) obj = NextObject();
return obj;
}
HeapObject* HeapIterator::NextObject() {
// No iterator means we are done.
if (object_iterator_.get() == nullptr) return nullptr;
if (HeapObject* obj = object_iterator_.get()->Next()) {
// 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_->has_next()) {
object_iterator_ = space_iterator_->next()->GetObjectIterator();
if (HeapObject* obj = object_iterator_.get()->Next()) {
return obj;
}
}
}
// Done with the last space.
object_iterator_.reset(nullptr);
return nullptr;
}
void Heap::UpdateTotalGCTime(double duration) {
if (FLAG_trace_gc_verbose) {
total_gc_time_ms_ += duration;
}
}
void Heap::ExternalStringTable::CleanUpNewSpaceStrings() {
int last = 0;
Isolate* isolate = heap_->isolate();
for (size_t i = 0; i < new_space_strings_.size(); ++i) {
Object* o = new_space_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 (InNewSpace(o)) {
new_space_strings_[last++] = o;
} else {
old_space_strings_.push_back(o);
}
}
new_space_strings_.resize(last);
}
void Heap::ExternalStringTable::CleanUpAll() {
CleanUpNewSpaceStrings();
int last = 0;
Isolate* isolate = heap_->isolate();
for (size_t i = 0; i < old_space_strings_.size(); ++i) {
Object* o = old_space_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(!InNewSpace(o));
old_space_strings_[last++] = o;
}
old_space_strings_.resize(last);
#ifdef VERIFY_HEAP
if (FLAG_verify_heap) {
Verify();
}
#endif
}
void Heap::ExternalStringTable::TearDown() {
for (size_t i = 0; i < new_space_strings_.size(); ++i) {
Object* o = new_space_strings_[i];
// Dont finalize thin strings.
if (o->IsThinString()) continue;
heap_->FinalizeExternalString(ExternalString::cast(o));
}
new_space_strings_.clear();
for (size_t i = 0; i < old_space_strings_.size(); ++i) {
Object* o = old_space_strings_[i];
// Dont finalize thin strings.
if (o->IsThinString()) continue;
heap_->FinalizeExternalString(ExternalString::cast(o));
}
old_space_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;
}
void Heap::RegisterStrongRoots(Object** start, Object** end) {
StrongRootsList* list = new StrongRootsList();
list->next = strong_roots_list_;
list->start = start;
list->end = end;
strong_roots_list_ = list;
}
void Heap::UnregisterStrongRoots(Object** start) {
StrongRootsList* prev = nullptr;
StrongRootsList* list = strong_roots_list_;
while (list != nullptr) {
StrongRootsList* next = list->next;
if (list->start == start) {
if (prev) {
prev->next = next;
} else {
strong_roots_list_ = next;
}
delete list;
} else {
prev = list;
}
list = next;
}
}
bool Heap::IsDeserializeLazyHandler(Code* code) {
return (code == deserialize_lazy_handler() ||
code == deserialize_lazy_handler_wide() ||
code == deserialize_lazy_handler_extra_wide());
}
void Heap::SetDeserializeLazyHandler(Code* code) {
set_deserialize_lazy_handler(code);
}
void Heap::SetDeserializeLazyHandlerWide(Code* code) {
set_deserialize_lazy_handler_wide(code);
}
void Heap::SetDeserializeLazyHandlerExtraWide(Code* code) {
set_deserialize_lazy_handler_extra_wide(code);
}
void Heap::SetBuiltinsConstantsTable(FixedArray* cache) {
set_builtins_constants_table(cache);
}
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;
}
size_t Heap::NumberOfDetachedContexts() {
// The detached_contexts() array has two entries per detached context.
return detached_contexts()->length() / 2;
}
const char* AllocationSpaceName(AllocationSpace space) {
switch (space) {
case NEW_SPACE:
return "NEW_SPACE";
case OLD_SPACE:
return "OLD_SPACE";
case CODE_SPACE:
return "CODE_SPACE";
case MAP_SPACE:
return "MAP_SPACE";
case LO_SPACE:
return "LO_SPACE";
case NEW_LO_SPACE:
return "NEW_LO_SPACE";
case RO_SPACE:
return "RO_SPACE";
default:
UNREACHABLE();
}
return nullptr;
}
void VerifyPointersVisitor::VisitPointers(HeapObject* host, Object** start,
Object** end) {
VerifyPointers(host, reinterpret_cast<MaybeObject**>(start),
reinterpret_cast<MaybeObject**>(end));
}
void VerifyPointersVisitor::VisitPointers(HeapObject* host, MaybeObject** start,
MaybeObject** end) {
VerifyPointers(host, start, end);
}
void VerifyPointersVisitor::VisitRootPointers(Root root,
const char* description,
Object** start, Object** end) {
VerifyPointers(nullptr, reinterpret_cast<MaybeObject**>(start),
reinterpret_cast<MaybeObject**>(end));
}
void VerifyPointersVisitor::VerifyPointers(HeapObject* host,
MaybeObject** start,
MaybeObject** end) {
for (MaybeObject** current = start; current < end; current++) {
HeapObject* object;
if ((*current)->ToStrongOrWeakHeapObject(&object)) {
CHECK(heap_->Contains(object));
CHECK(object->map()->IsMap());
} else {
CHECK((*current)->IsSmi() || (*current)->IsClearedWeakHeapObject());
}
}
}
void VerifySmisVisitor::VisitRootPointers(Root root, const char* description,
Object** start, Object** end) {
for (Object** current = start; current < end; current++) {
CHECK((*current)->IsSmi());
}
}
bool Heap::AllowedToBeMigrated(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 (obj->map() == ReadOnlyRoots(this).one_pointer_filler_map()) return false;
InstanceType type = obj->map()->instance_type();
MemoryChunk* chunk = MemoryChunk::FromAddress(obj->address());
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 NEW_LO_SPACE:
case RO_SPACE:
return false;
}
UNREACHABLE();
}
void Heap::CreateObjectStats() {
if (V8_LIKELY(FLAG_gc_stats == 0)) return;
if (!live_object_stats_) {
live_object_stats_ = new ObjectStats(this);
}
if (!dead_object_stats_) {
dead_object_stats_ = new ObjectStats(this);
}
}
void AllocationObserver::AllocationStep(int bytes_allocated,
Address soon_object, size_t size) {
DCHECK_GE(bytes_allocated, 0);
bytes_to_next_step_ -= bytes_allocated;
if (bytes_to_next_step_ <= 0) {
Step(static_cast<int>(step_size_ - bytes_to_next_step_), soon_object, size);
step_size_ = GetNextStepSize();
bytes_to_next_step_ = step_size_;
}
DCHECK_GE(bytes_to_next_step_, 0);
}
namespace {
Map* GcSafeMapOfCodeSpaceObject(HeapObject* object) {
MapWord map_word = object->map_word();
return map_word.IsForwardingAddress() ? map_word.ToForwardingAddress()->map()
: map_word.ToMap();
}
int GcSafeSizeOfCodeSpaceObject(HeapObject* object) {
return object->SizeFromMap(GcSafeMapOfCodeSpaceObject(object));
}
Code* GcSafeCastToCode(Heap* heap, HeapObject* object, Address inner_pointer) {
Code* code = reinterpret_cast<Code*>(object);
DCHECK_NOT_NULL(code);
DCHECK(heap->GcSafeCodeContains(code, inner_pointer));
return code;
}
} // namespace
bool Heap::GcSafeCodeContains(HeapObject* 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 != nullptr) return code;
// Check if the inner pointer points into a large object chunk.
LargePage* large_page = lo_space()->FindPage(inner_pointer);
if (large_page != nullptr) {
return GcSafeCastToCode(this, large_page->GetObject(), inner_pointer);
}
DCHECK(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);
DCHECK_EQ(page->owner(), code_space());
mark_compact_collector()->sweeper()->EnsurePageIsIterable(page);
Address addr = page->skip_list()->StartFor(inner_pointer);
Address top = code_space()->top();
Address limit = code_space()->limit();
while (true) {
if (addr == top && addr != limit) {
addr = limit;
continue;
}
HeapObject* obj = HeapObject::FromAddress(addr);
int obj_size = GcSafeSizeOfCodeSpaceObject(obj);
Address next_addr = addr + obj_size;
if (next_addr > inner_pointer)
return GcSafeCastToCode(this, obj, inner_pointer);
addr = next_addr;
}
}
void Heap::WriteBarrierForCodeSlow(Code* code) {
for (RelocIterator it(code, RelocInfo::ModeMask(RelocInfo::EMBEDDED_OBJECT));
!it.done(); it.next()) {
GenerationalBarrierForCode(code, it.rinfo(), it.rinfo()->target_object());
MarkingBarrierForCode(code, it.rinfo(), it.rinfo()->target_object());
}
}
void Heap::GenerationalBarrierSlow(HeapObject* object, Address slot,
HeapObject* value) {
Heap* heap = Heap::FromWritableHeapObject(object);
heap->store_buffer()->InsertEntry(slot);
}
void Heap::GenerationalBarrierForElementsSlow(Heap* heap, FixedArray* array,
int offset, int length) {
for (int i = 0; i < length; i++) {
if (!InNewSpace(array->get(offset + i))) continue;
heap->store_buffer()->InsertEntry(
reinterpret_cast<Address>(array->RawFieldOfElementAt(offset + i)));
}
}
void Heap::GenerationalBarrierForCodeSlow(Code* host, RelocInfo* rinfo,
HeapObject* object) {
DCHECK(InNewSpace(object));
Page* source_page = Page::FromAddress(reinterpret_cast<Address>(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 {
DCHECK(RelocInfo::IsEmbeddedObject(rmode));
slot_type = OBJECT_SLOT;
}
}
RememberedSet<OLD_TO_NEW>::InsertTyped(
source_page, reinterpret_cast<Address>(host), slot_type, addr);
}
void Heap::MarkingBarrierSlow(HeapObject* object, Address slot,
HeapObject* value) {
Heap* heap = Heap::FromWritableHeapObject(object);
heap->incremental_marking()->RecordWriteSlow(
object, reinterpret_cast<HeapObjectReference**>(slot), value);
}
void Heap::MarkingBarrierForElementsSlow(Heap* heap, HeapObject* object) {
if (FLAG_concurrent_marking ||
heap->incremental_marking()->marking_state()->IsBlack(object)) {
heap->incremental_marking()->RevisitObject(object);
}
}
void Heap::MarkingBarrierForCodeSlow(Code* host, RelocInfo* rinfo,
HeapObject* object) {
Heap* heap = Heap::FromWritableHeapObject(host);
DCHECK(heap->incremental_marking()->IsMarking());
heap->incremental_marking()->RecordWriteIntoCode(host, rinfo, object);
}
bool Heap::PageFlagsAreConsistent(HeapObject* object) {
Heap* heap = Heap::FromWritableHeapObject(object);
MemoryChunk* chunk = MemoryChunk::FromHeapObject(object);
heap_internals::MemoryChunk* slim_chunk =
heap_internals::MemoryChunk::FromHeapObject(object);
const bool generation_consistency =
chunk->owner()->identity() != NEW_SPACE ||
(chunk->InNewSpace() && slim_chunk->InNewSpace());
const bool marking_consistency =
!heap->incremental_marking()->IsMarking() ||
(chunk->IsFlagSet(MemoryChunk::INCREMENTAL_MARKING) &&
slim_chunk->IsMarking());
return generation_consistency && marking_consistency;
}
static_assert(MemoryChunk::Flag::INCREMENTAL_MARKING ==
heap_internals::MemoryChunk::kMarkingBit,
"Incremental marking flag inconsistent");
static_assert(MemoryChunk::Flag::IN_FROM_SPACE ==
heap_internals::MemoryChunk::kFromSpaceBit,
"From space flag inconsistent");
static_assert(MemoryChunk::Flag::IN_TO_SPACE ==
heap_internals::MemoryChunk::kToSpaceBit,
"To space flag inconsistent");
static_assert(MemoryChunk::kFlagsOffset ==
heap_internals::MemoryChunk::kFlagsOffset,
"Flag offset inconsistent");
void Heap::SetEmbedderStackStateForNextFinalizaton(
EmbedderHeapTracer::EmbedderStackState stack_state) {
local_embedder_heap_tracer()->SetEmbedderStackStateForNextFinalization(
stack_state);
}
} // namespace internal
} // namespace v8