blob: 933bc506b103830ed3baca3a956acf77958234ef [file] [log] [blame]
// Copyright 2012 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "src/heap/heap.h"
#include <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(),
&parallel_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::Verify() {
#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 (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) {
Verify();
}
#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()