blob: 2628898c8622e4753b4707e5ed07c1d5e1e367db [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.
#ifndef V8_HEAP_HEAP_H_
#define V8_HEAP_HEAP_H_
#include <cmath>
#include <map>
// Clients of this interface shouldn't depend on lots of heap internals.
// Do not include anything from src/heap here!
#include "include/v8.h"
#include "src/allocation.h"
#include "src/assert-scope.h"
#include "src/atomic-utils.h"
#include "src/globals.h"
#include "src/heap-symbols.h"
// TODO(mstarzinger): Two more includes to kill!
#include "src/heap/spaces.h"
#include "src/heap/store-buffer.h"
#include "src/list.h"
namespace v8 {
namespace internal {
using v8::MemoryPressureLevel;
// Defines all the roots in Heap.
V(Map, byte_array_map, ByteArrayMap) \
V(Map, free_space_map, FreeSpaceMap) \
V(Map, one_pointer_filler_map, OnePointerFillerMap) \
V(Map, two_pointer_filler_map, TwoPointerFillerMap) \
/* Cluster the most popular ones in a few cache lines here at the top. */ \
V(Oddball, undefined_value, UndefinedValue) \
V(Oddball, the_hole_value, TheHoleValue) \
V(Oddball, null_value, NullValue) \
V(Oddball, true_value, TrueValue) \
V(Oddball, false_value, FalseValue) \
V(String, empty_string, empty_string) \
V(Oddball, uninitialized_value, UninitializedValue) \
V(Map, cell_map, CellMap) \
V(Map, global_property_cell_map, GlobalPropertyCellMap) \
V(Map, shared_function_info_map, SharedFunctionInfoMap) \
V(Map, meta_map, MetaMap) \
V(Map, heap_number_map, HeapNumberMap) \
V(Map, mutable_heap_number_map, MutableHeapNumberMap) \
V(Map, float32x4_map, Float32x4Map) \
V(Map, int32x4_map, Int32x4Map) \
V(Map, uint32x4_map, Uint32x4Map) \
V(Map, bool32x4_map, Bool32x4Map) \
V(Map, int16x8_map, Int16x8Map) \
V(Map, uint16x8_map, Uint16x8Map) \
V(Map, bool16x8_map, Bool16x8Map) \
V(Map, int8x16_map, Int8x16Map) \
V(Map, uint8x16_map, Uint8x16Map) \
V(Map, bool8x16_map, Bool8x16Map) \
V(Map, native_context_map, NativeContextMap) \
V(Map, fixed_array_map, FixedArrayMap) \
V(Map, code_map, CodeMap) \
V(Map, scope_info_map, ScopeInfoMap) \
V(Map, fixed_cow_array_map, FixedCOWArrayMap) \
V(Map, fixed_double_array_map, FixedDoubleArrayMap) \
V(Map, weak_cell_map, WeakCellMap) \
V(Map, transition_array_map, TransitionArrayMap) \
V(Map, one_byte_string_map, OneByteStringMap) \
V(Map, one_byte_internalized_string_map, OneByteInternalizedStringMap) \
V(Map, function_context_map, FunctionContextMap) \
V(FixedArray, empty_fixed_array, EmptyFixedArray) \
V(ByteArray, empty_byte_array, EmptyByteArray) \
V(DescriptorArray, empty_descriptor_array, EmptyDescriptorArray) \
/* The roots above this line should be boring from a GC point of view. */ \
/* This means they are never in new space and never on a page that is */ \
/* being compacted. */ \
V(Oddball, no_interceptor_result_sentinel, NoInterceptorResultSentinel) \
V(Oddball, arguments_marker, ArgumentsMarker) \
V(Oddball, exception, Exception) \
V(Oddball, termination_exception, TerminationException) \
V(Oddball, optimized_out, OptimizedOut) \
V(FixedArray, number_string_cache, NumberStringCache) \
V(Object, instanceof_cache_function, InstanceofCacheFunction) \
V(Object, instanceof_cache_map, InstanceofCacheMap) \
V(Object, instanceof_cache_answer, InstanceofCacheAnswer) \
V(FixedArray, single_character_string_cache, SingleCharacterStringCache) \
V(FixedArray, string_split_cache, StringSplitCache) \
V(FixedArray, regexp_multiple_cache, RegExpMultipleCache) \
V(Smi, hash_seed, HashSeed) \
V(Map, hash_table_map, HashTableMap) \
V(Map, ordered_hash_table_map, OrderedHashTableMap) \
V(Map, symbol_map, SymbolMap) \
V(Map, string_map, StringMap) \
V(Map, cons_one_byte_string_map, ConsOneByteStringMap) \
V(Map, cons_string_map, ConsStringMap) \
V(Map, sliced_string_map, SlicedStringMap) \
V(Map, sliced_one_byte_string_map, SlicedOneByteStringMap) \
V(Map, external_string_map, ExternalStringMap) \
V(Map, external_string_with_one_byte_data_map, \
ExternalStringWithOneByteDataMap) \
V(Map, external_one_byte_string_map, ExternalOneByteStringMap) \
V(Map, native_source_string_map, NativeSourceStringMap) \
V(Map, short_external_string_map, ShortExternalStringMap) \
V(Map, short_external_string_with_one_byte_data_map, \
ShortExternalStringWithOneByteDataMap) \
V(Map, internalized_string_map, InternalizedStringMap) \
V(Map, external_internalized_string_map, ExternalInternalizedStringMap) \
V(Map, external_internalized_string_with_one_byte_data_map, \
ExternalInternalizedStringWithOneByteDataMap) \
V(Map, external_one_byte_internalized_string_map, \
ExternalOneByteInternalizedStringMap) \
V(Map, short_external_internalized_string_map, \
ShortExternalInternalizedStringMap) \
V(Map, short_external_internalized_string_with_one_byte_data_map, \
ShortExternalInternalizedStringWithOneByteDataMap) \
V(Map, short_external_one_byte_internalized_string_map, \
ShortExternalOneByteInternalizedStringMap) \
V(Map, short_external_one_byte_string_map, ShortExternalOneByteStringMap) \
V(Map, fixed_uint8_array_map, FixedUint8ArrayMap) \
V(Map, fixed_int8_array_map, FixedInt8ArrayMap) \
V(Map, fixed_uint16_array_map, FixedUint16ArrayMap) \
V(Map, fixed_int16_array_map, FixedInt16ArrayMap) \
V(Map, fixed_uint32_array_map, FixedUint32ArrayMap) \
V(Map, fixed_int32_array_map, FixedInt32ArrayMap) \
V(Map, fixed_float32_array_map, FixedFloat32ArrayMap) \
V(Map, fixed_float64_array_map, FixedFloat64ArrayMap) \
V(Map, fixed_uint8_clamped_array_map, FixedUint8ClampedArrayMap) \
V(FixedTypedArrayBase, empty_fixed_uint8_array, EmptyFixedUint8Array) \
V(FixedTypedArrayBase, empty_fixed_int8_array, EmptyFixedInt8Array) \
V(FixedTypedArrayBase, empty_fixed_uint16_array, EmptyFixedUint16Array) \
V(FixedTypedArrayBase, empty_fixed_int16_array, EmptyFixedInt16Array) \
V(FixedTypedArrayBase, empty_fixed_uint32_array, EmptyFixedUint32Array) \
V(FixedTypedArrayBase, empty_fixed_int32_array, EmptyFixedInt32Array) \
V(FixedTypedArrayBase, empty_fixed_float32_array, EmptyFixedFloat32Array) \
V(FixedTypedArrayBase, empty_fixed_float64_array, EmptyFixedFloat64Array) \
V(FixedTypedArrayBase, empty_fixed_uint8_clamped_array, \
EmptyFixedUint8ClampedArray) \
V(Map, sloppy_arguments_elements_map, SloppyArgumentsElementsMap) \
V(Map, catch_context_map, CatchContextMap) \
V(Map, with_context_map, WithContextMap) \
V(Map, debug_evaluate_context_map, DebugEvaluateContextMap) \
V(Map, block_context_map, BlockContextMap) \
V(Map, module_context_map, ModuleContextMap) \
V(Map, script_context_map, ScriptContextMap) \
V(Map, script_context_table_map, ScriptContextTableMap) \
V(Map, undefined_map, UndefinedMap) \
V(Map, the_hole_map, TheHoleMap) \
V(Map, null_map, NullMap) \
V(Map, boolean_map, BooleanMap) \
V(Map, uninitialized_map, UninitializedMap) \
V(Map, arguments_marker_map, ArgumentsMarkerMap) \
V(Map, no_interceptor_result_sentinel_map, NoInterceptorResultSentinelMap) \
V(Map, exception_map, ExceptionMap) \
V(Map, termination_exception_map, TerminationExceptionMap) \
V(Map, optimized_out_map, OptimizedOutMap) \
V(Map, message_object_map, JSMessageObjectMap) \
V(Map, foreign_map, ForeignMap) \
V(Map, neander_map, NeanderMap) \
V(Map, external_map, ExternalMap) \
V(HeapNumber, nan_value, NanValue) \
V(HeapNumber, infinity_value, InfinityValue) \
V(HeapNumber, minus_zero_value, MinusZeroValue) \
V(HeapNumber, minus_infinity_value, MinusInfinityValue) \
V(JSObject, message_listeners, MessageListeners) \
V(UnseededNumberDictionary, code_stubs, CodeStubs) \
V(Code, js_entry_code, JsEntryCode) \
V(Code, js_construct_entry_code, JsConstructEntryCode) \
V(FixedArray, natives_source_cache, NativesSourceCache) \
V(FixedArray, experimental_natives_source_cache, \
ExperimentalNativesSourceCache) \
V(FixedArray, extra_natives_source_cache, ExtraNativesSourceCache) \
V(FixedArray, experimental_extra_natives_source_cache, \
ExperimentalExtraNativesSourceCache) \
V(Script, empty_script, EmptyScript) \
V(NameDictionary, intrinsic_function_names, IntrinsicFunctionNames) \
V(NameDictionary, empty_properties_dictionary, EmptyPropertiesDictionary) \
V(Cell, undefined_cell, UndefinedCell) \
V(Object, symbol_registry, SymbolRegistry) \
V(Object, script_list, ScriptList) \
V(SeededNumberDictionary, empty_slow_element_dictionary, \
EmptySlowElementDictionary) \
V(FixedArray, materialized_objects, MaterializedObjects) \
V(FixedArray, microtask_queue, MicrotaskQueue) \
V(TypeFeedbackVector, dummy_vector, DummyVector) \
V(FixedArray, cleared_optimized_code_map, ClearedOptimizedCodeMap) \
V(FixedArray, detached_contexts, DetachedContexts) \
V(ArrayList, retained_maps, RetainedMaps) \
V(WeakHashTable, weak_object_to_code_table, WeakObjectToCodeTable) \
V(PropertyCell, array_protector, ArrayProtector) \
V(PropertyCell, empty_property_cell, EmptyPropertyCell) \
V(Object, weak_stack_trace_list, WeakStackTraceList) \
V(Object, noscript_shared_function_infos, NoScriptSharedFunctionInfos) \
V(Map, bytecode_array_map, BytecodeArrayMap) \
V(WeakCell, empty_weak_cell, EmptyWeakCell) \
V(PropertyCell, species_protector, SpeciesProtector)
// Entries in this list are limited to Smis and are not visited during GC.
#define SMI_ROOT_LIST(V) \
V(Smi, stack_limit, StackLimit) \
V(Smi, real_stack_limit, RealStackLimit) \
V(Smi, last_script_id, LastScriptId) \
V(Smi, arguments_adaptor_deopt_pc_offset, ArgumentsAdaptorDeoptPCOffset) \
V(Smi, construct_stub_deopt_pc_offset, ConstructStubDeoptPCOffset) \
V(Smi, getter_stub_deopt_pc_offset, GetterStubDeoptPCOffset) \
V(Smi, setter_stub_deopt_pc_offset, SetterStubDeoptPCOffset)
#define ROOT_LIST(V) \
V(StringTable, string_table, StringTable)
// Heap roots that are known to be immortal immovable, for which we can safely
// skip write barriers. This list is not complete and has omissions.
V(ByteArrayMap) \
V(BytecodeArrayMap) \
V(FreeSpaceMap) \
V(OnePointerFillerMap) \
V(TwoPointerFillerMap) \
V(UndefinedValue) \
V(TheHoleValue) \
V(NullValue) \
V(TrueValue) \
V(FalseValue) \
V(UninitializedValue) \
V(CellMap) \
V(GlobalPropertyCellMap) \
V(SharedFunctionInfoMap) \
V(MetaMap) \
V(HeapNumberMap) \
V(MutableHeapNumberMap) \
V(Float32x4Map) \
V(Int32x4Map) \
V(Uint32x4Map) \
V(Bool32x4Map) \
V(Int16x8Map) \
V(Uint16x8Map) \
V(Bool16x8Map) \
V(Int8x16Map) \
V(Uint8x16Map) \
V(Bool8x16Map) \
V(NativeContextMap) \
V(FixedArrayMap) \
V(CodeMap) \
V(ScopeInfoMap) \
V(FixedCOWArrayMap) \
V(FixedDoubleArrayMap) \
V(WeakCellMap) \
V(TransitionArrayMap) \
V(NoInterceptorResultSentinel) \
V(HashTableMap) \
V(OrderedHashTableMap) \
V(EmptyFixedArray) \
V(EmptyByteArray) \
V(EmptyDescriptorArray) \
V(ArgumentsMarker) \
V(SymbolMap) \
V(SloppyArgumentsElementsMap) \
V(FunctionContextMap) \
V(CatchContextMap) \
V(WithContextMap) \
V(BlockContextMap) \
V(ModuleContextMap) \
V(ScriptContextMap) \
V(UndefinedMap) \
V(TheHoleMap) \
V(NullMap) \
V(BooleanMap) \
V(UninitializedMap) \
V(ArgumentsMarkerMap) \
V(JSMessageObjectMap) \
V(ForeignMap) \
V(NeanderMap) \
V(NanValue) \
V(InfinityValue) \
V(MinusZeroValue) \
V(MinusInfinityValue) \
V(EmptyWeakCell) \
V(empty_string) \
// Forward declarations.
class AllocationObserver;
class ArrayBufferTracker;
class GCIdleTimeAction;
class GCIdleTimeHandler;
class GCIdleTimeHeapState;
class GCTracer;
class HeapObjectsFilter;
class HeapStats;
class HistogramTimer;
class Isolate;
class MemoryReducer;
class ObjectStats;
class Scavenger;
class ScavengeJob;
class WeakObjectRetainer;
typedef void (*ObjectSlotCallback)(HeapObject** from, HeapObject* to);
// A queue of objects promoted during scavenge. Each object is accompanied
// by it's size to avoid dereferencing a map pointer for scanning.
// The last page in to-space is used for the promotion queue. On conflict
// during scavenge, the promotion queue is allocated externally and all
// entries are copied to the external queue.
class PromotionQueue {
explicit PromotionQueue(Heap* heap)
: front_(NULL),
heap_(heap) {}
void Initialize();
void Destroy() {
delete emergency_stack_;
emergency_stack_ = NULL;
Page* GetHeadPage() {
return Page::FromAllocationAreaAddress(reinterpret_cast<Address>(rear_));
void SetNewLimit(Address limit) {
// If we are already using an emergency stack, we can ignore it.
if (emergency_stack_) return;
// If the limit is not on the same page, we can ignore it.
if (Page::FromAllocationAreaAddress(limit) != GetHeadPage()) return;
limit_ = reinterpret_cast<struct Entry*>(limit);
if (limit_ <= rear_) {
bool IsBelowPromotionQueue(Address to_space_top) {
// If an emergency stack is used, the to-space address cannot interfere
// with the promotion queue.
if (emergency_stack_) return true;
// If the given to-space top pointer and the head of the promotion queue
// are not on the same page, then the to-space objects are below the
// promotion queue.
if (GetHeadPage() != Page::FromAddress(to_space_top)) {
return true;
// If the to space top pointer is smaller or equal than the promotion
// queue head, then the to-space objects are below the promotion queue.
return reinterpret_cast<struct Entry*>(to_space_top) <= rear_;
bool is_empty() {
return (front_ == rear_) &&
(emergency_stack_ == NULL || emergency_stack_->length() == 0);
inline void insert(HeapObject* target, int32_t size, bool was_marked_black);
void remove(HeapObject** target, int32_t* size, bool* was_marked_black) {
if (front_ == rear_) {
Entry e = emergency_stack_->RemoveLast();
*target = e.obj_;
*size = e.size_;
*was_marked_black = e.was_marked_black_;
struct Entry* entry = reinterpret_cast<struct Entry*>(--front_);
*target = entry->obj_;
*size = entry->size_;
*was_marked_black = entry->was_marked_black_;
// Assert no underflow.
struct Entry {
Entry(HeapObject* obj, int32_t size, bool was_marked_black)
: obj_(obj), size_(size), was_marked_black_(was_marked_black) {}
HeapObject* obj_;
int32_t size_ : 31;
bool was_marked_black_ : 1;
void RelocateQueueHead();
// The front of the queue is higher in the memory page chain than the rear.
struct Entry* front_;
struct Entry* rear_;
struct Entry* limit_;
List<Entry>* emergency_stack_;
Heap* heap_;
enum ArrayStorageAllocationMode {
enum class ClearRecordedSlots { kYes, kNo };
class Heap {
// Declare all the root indices. This defines the root list order.
enum RootListIndex {
#define ROOT_INDEX_DECLARATION(type, name, camel_name) k##camel_name##RootIndex,
#define STRING_INDEX_DECLARATION(name, str) k##name##RootIndex,
#define SYMBOL_INDEX_DECLARATION(name) k##name##RootIndex,
#define SYMBOL_INDEX_DECLARATION(name, description) k##name##RootIndex,
// Utility type maps
#define DECLARE_STRUCT_MAP(NAME, Name, name) k##Name##MapRootIndex,
#define ROOT_INDEX_DECLARATION(type, name, camel_name) k##camel_name##RootIndex,
kStrongRootListLength = kStringTableRootIndex,
kSmiRootsStart = kStringTableRootIndex + 1
enum FindMementoMode { kForRuntime, kForGC };
// Indicates whether live bytes adjustment is triggered
// - from within the GC code before sweeping started (SEQUENTIAL_TO_SWEEPER),
// - or from within GC (CONCURRENT_TO_SWEEPER),
// - or mutator code (CONCURRENT_TO_SWEEPER).
enum UpdateAllocationSiteMode { kGlobal, kCached };
// Taking this lock prevents the GC from entering a phase that relocates
// object references.
class RelocationLock {
explicit RelocationLock(Heap* heap) : heap_(heap) {
~RelocationLock() { heap_->relocation_mutex_.Unlock(); }
Heap* heap_;
// Support for partial snapshots. After calling this we have a linear
// space to write objects in each space.
struct Chunk {
uint32_t size;
Address start;
Address end;
typedef List<Chunk> Reservation;
static const intptr_t kMinimumOldGenerationAllocationLimit =
8 * (Page::kPageSize > MB ? Page::kPageSize : MB);
static const int kInitalOldGenerationLimitFactor = 2;
// Don't apply pointer multiplier on Android since it has no swap space and
// should instead adapt it's heap size based on available physical memory.
static const int kPointerMultiplier = 1;
static const int kPointerMultiplier = i::kPointerSize / 4;
// The new space size has to be a power of 2. Sizes are in MB.
static const int kMaxSemiSpaceSizeLowMemoryDevice = 1 * kPointerMultiplier;
static const int kMaxSemiSpaceSizeMediumMemoryDevice = 4 * kPointerMultiplier;
static const int kMaxSemiSpaceSizeHighMemoryDevice = 8 * kPointerMultiplier;
static const int kMaxSemiSpaceSizeHugeMemoryDevice = 8 * kPointerMultiplier;
// The old space size has to be a multiple of Page::kPageSize.
// Sizes are in MB.
static const int kMaxOldSpaceSizeLowMemoryDevice = 128 * kPointerMultiplier;
static const int kMaxOldSpaceSizeMediumMemoryDevice =
256 * kPointerMultiplier;
static const int kMaxOldSpaceSizeHighMemoryDevice = 512 * kPointerMultiplier;
static const int kMaxOldSpaceSizeHugeMemoryDevice = 700 * kPointerMultiplier;
// The executable size has to be a multiple of Page::kPageSize.
// Sizes are in MB.
static const int kMaxExecutableSizeLowMemoryDevice = 96 * kPointerMultiplier;
static const int kMaxExecutableSizeMediumMemoryDevice =
192 * kPointerMultiplier;
static const int kMaxExecutableSizeHighMemoryDevice =
256 * kPointerMultiplier;
static const int kMaxExecutableSizeHugeMemoryDevice =
256 * kPointerMultiplier;
static const int kTraceRingBufferSize = 512;
static const int kStacktraceBufferSize = 512;
static const double kMinHeapGrowingFactor;
static const double kMaxHeapGrowingFactor;
static const double kMaxHeapGrowingFactorMemoryConstrained;
static const double kMaxHeapGrowingFactorIdle;
static const double kTargetMutatorUtilization;
static const int kNoGCFlags = 0;
static const int kReduceMemoryFootprintMask = 1;
static const int kAbortIncrementalMarkingMask = 2;
static const int kFinalizeIncrementalMarkingMask = 4;
// Making the heap iterable requires us to abort incremental marking.
static const int kMakeHeapIterableMask = kAbortIncrementalMarkingMask;
// The roots that have an index less than this are always in old space.
static const int kOldSpaceRoots = 0x20;
// The minimum size of a HeapObject on the heap.
static const int kMinObjectSizeInWords = 2;
STATIC_ASSERT(kUndefinedValueRootIndex ==
STATIC_ASSERT(kTheHoleValueRootIndex == Internals::kTheHoleValueRootIndex);
STATIC_ASSERT(kNullValueRootIndex == Internals::kNullValueRootIndex);
STATIC_ASSERT(kTrueValueRootIndex == Internals::kTrueValueRootIndex);
STATIC_ASSERT(kFalseValueRootIndex == Internals::kFalseValueRootIndex);
STATIC_ASSERT(kempty_stringRootIndex == Internals::kEmptyStringRootIndex);
// Calculates the maximum amount of filler that could be required by the
// given alignment.
static int GetMaximumFillToAlign(AllocationAlignment alignment);
// Calculates the actual amount of filler required for a given address at the
// given alignment.
static int GetFillToAlign(Address address, AllocationAlignment alignment);
template <typename T>
static inline bool IsOneByte(T t, int chars);
static void FatalProcessOutOfMemory(const char* location,
bool is_heap_oom = false);
static bool RootIsImmortalImmovable(int root_index);
// Checks whether the space is valid.
static bool IsValidAllocationSpace(AllocationSpace space);
// Generated code can embed direct references to non-writable roots if
// they are in new space.
static bool RootCanBeWrittenAfterInitialization(RootListIndex root_index);
// Zapping is needed for verify heap, and always done in debug builds.
static inline bool ShouldZapGarbage() {
#ifdef DEBUG
return true;
return FLAG_verify_heap;
return false;
static double HeapGrowingFactor(double gc_speed, double mutator_speed);
// Copy block of memory from src to dst. Size of block should be aligned
// by pointer size.
static inline void CopyBlock(Address dst, Address src, int byte_size);
// Determines a static visitor id based on the given {map} that can then be
// stored on the map to facilitate fast dispatch for {StaticVisitorBase}.
static int GetStaticVisitorIdForMap(Map* map);
// Notifies the heap that is ok to start marking or other activities that
// should not happen during deserialization.
void NotifyDeserializationComplete();
intptr_t old_generation_allocation_limit() const {
return old_generation_allocation_limit_;
bool always_allocate() { return always_allocate_scope_count_.Value() != 0; }
Address* NewSpaceAllocationTopAddress() {
return new_space_.allocation_top_address();
Address* NewSpaceAllocationLimitAddress() {
return new_space_.allocation_limit_address();
Address* OldSpaceAllocationTopAddress() {
return old_space_->allocation_top_address();
Address* OldSpaceAllocationLimitAddress() {
return old_space_->allocation_limit_address();
bool CanExpandOldGeneration(int size) {
if (force_oom_) return false;
return (OldGenerationCapacity() + size) < MaxOldGenerationSize();
// Clear the Instanceof cache (used when a prototype changes).
inline void ClearInstanceofCache();
// FreeSpace objects have a null map after deserialization. Update the map.
void RepairFreeListsAfterDeserialization();
// Move len elements within a given array from src_index index to dst_index
// index.
void MoveElements(FixedArray* array, int dst_index, int src_index, int len);
// Initialize a filler object to keep the ability to iterate over the heap
// when introducing gaps within pages. If slots could have been recorded in
// the freed area, then pass ClearRecordedSlots::kYes as the mode. Otherwise,
// pass ClearRecordedSlots::kNo.
void CreateFillerObjectAt(Address addr, int size, ClearRecordedSlots mode);
bool CanMoveObjectStart(HeapObject* object);
// Maintain consistency of live bytes during incremental marking.
void AdjustLiveBytes(HeapObject* object, int by, InvocationMode mode);
// Trim the given array from the left. Note that this relocates the object
// start and hence is only valid if there is only a single reference to it.
FixedArrayBase* LeftTrimFixedArray(FixedArrayBase* obj, int elements_to_trim);
// Trim the given array from the right.
template<Heap::InvocationMode mode>
void RightTrimFixedArray(FixedArrayBase* obj, int elements_to_trim);
// Converts the given boolean condition to JavaScript boolean value.
inline Oddball* ToBoolean(bool condition);
// Check whether the heap is currently iterable.
bool IsHeapIterable();
// Notify the heap that a context has been disposed.
int NotifyContextDisposed(bool dependant_context);
void set_native_contexts_list(Object* object) {
native_contexts_list_ = object;
Object* native_contexts_list() const { return native_contexts_list_; }
void set_allocation_sites_list(Object* object) {
allocation_sites_list_ = object;
Object* allocation_sites_list() { return allocation_sites_list_; }
// Used in CreateAllocationSiteStub and the (de)serializer.
Object** allocation_sites_list_address() { return &allocation_sites_list_; }
void set_encountered_weak_collections(Object* weak_collection) {
encountered_weak_collections_ = weak_collection;
Object* encountered_weak_collections() const {
return encountered_weak_collections_;
void set_encountered_weak_cells(Object* weak_cell) {
encountered_weak_cells_ = weak_cell;
Object* encountered_weak_cells() const { return encountered_weak_cells_; }
void set_encountered_transition_arrays(Object* transition_array) {
encountered_transition_arrays_ = transition_array;
Object* encountered_transition_arrays() const {
return encountered_transition_arrays_;
// Number of mark-sweeps.
int ms_count() const { return ms_count_; }
// Checks whether the given object is allowed to be migrated from it's
// current space into the given destination space. Used for debugging.
inline bool AllowedToBeMigrated(HeapObject* object, AllocationSpace dest);
void CheckHandleCount();
// Number of "runtime allocations" done so far.
uint32_t allocations_count() { return allocations_count_; }
// Print short heap statistics.
void PrintShortHeapStatistics();
inline HeapState gc_state() { return gc_state_; }
inline bool IsInGCPostProcessing() { return gc_post_processing_depth_ > 0; }
// If an object has an AllocationMemento trailing it, return it, otherwise
// return NULL;
template <FindMementoMode mode>
inline AllocationMemento* FindAllocationMemento(HeapObject* object);
// Returns false if not able to reserve.
bool ReserveSpace(Reservation* reservations);
void SetEmbedderHeapTracer(EmbedderHeapTracer* tracer);
bool UsingEmbedderHeapTracer();
void TracePossibleWrapper(JSObject* js_object);
void RegisterExternallyReferencedObject(Object** object);
// Support for the API.
void CreateApiObjects();
// Implements the corresponding V8 API function.
bool IdleNotification(double deadline_in_seconds);
bool IdleNotification(int idle_time_in_ms);
void MemoryPressureNotification(MemoryPressureLevel level,
bool is_isolate_locked);
void CheckMemoryPressure();
double MonotonicallyIncreasingTimeInMs();
void RecordStats(HeapStats* stats, bool take_snapshot = false);
// Check new space expansion criteria and expand semispaces if it was hit.
void CheckNewSpaceExpansionCriteria();
inline bool HeapIsFullEnoughToStartIncrementalMarking(intptr_t limit) {
if (FLAG_stress_compaction && (gc_count_ & 1) != 0) return true;
intptr_t adjusted_allocation_limit = limit - new_space_.Capacity();
if (PromotedTotalSize() >= adjusted_allocation_limit) return true;
if (HighMemoryPressure()) return true;
return false;
void VisitExternalResources(v8::ExternalResourceVisitor* visitor);
// An object should be promoted if the object has survived a
// scavenge operation.
inline bool ShouldBePromoted(Address old_address, int object_size);
void ClearNormalizedMapCaches();
void IncrementDeferredCount(v8::Isolate::UseCounterFeature feature);
inline bool OldGenerationAllocationLimitReached();
void QueueMemoryChunkForFree(MemoryChunk* chunk);
void FreeQueuedChunks(MemoryChunk* list_head);
void FreeQueuedChunks();
void WaitUntilUnmappingOfFreeChunksCompleted();
// Completely clear the Instanceof cache (to stop it keeping objects alive
// around a GC).
inline void CompletelyClearInstanceofCache();
inline uint32_t HashSeed();
inline int NextScriptId();
inline void SetArgumentsAdaptorDeoptPCOffset(int pc_offset);
inline void SetConstructStubDeoptPCOffset(int pc_offset);
inline void SetGetterStubDeoptPCOffset(int pc_offset);
inline void SetSetterStubDeoptPCOffset(int pc_offset);
// For post mortem debugging.
void RememberUnmappedPage(Address page, bool compacted);
// Global inline caching age: it is incremented on some GCs after context
// disposal. We use it to flush inline caches.
int global_ic_age() { return global_ic_age_; }
void AgeInlineCaches() {
global_ic_age_ = (global_ic_age_ + 1) & SharedFunctionInfo::ICAgeBits::kMax;
int64_t amount_of_external_allocated_memory() {
return amount_of_external_allocated_memory_;
void update_amount_of_external_allocated_memory(int64_t delta) {
amount_of_external_allocated_memory_ += delta;
void DeoptMarkedAllocationSites();
bool DeoptMaybeTenuredAllocationSites() {
return new_space_.IsAtMaximumCapacity() && maximum_size_scavenges_ == 0;
void AddWeakObjectToCodeDependency(Handle<HeapObject> obj,
Handle<DependentCode> dep);
DependentCode* LookupWeakObjectToCodeDependency(Handle<HeapObject> obj);
void AddRetainedMap(Handle<Map> map);
// This event is triggered after successful allocation of a new object made
// by runtime. Allocations of target space for object evacuation do not
// trigger the event. In order to track ALL allocations one must turn off
// FLAG_inline_new and FLAG_use_allocation_folding.
inline void OnAllocationEvent(HeapObject* object, int size_in_bytes);
// This event is triggered after object is moved to a new place.
inline void OnMoveEvent(HeapObject* target, HeapObject* source,
int size_in_bytes);
bool deserialization_complete() const { return deserialization_complete_; }
bool HasLowAllocationRate();
bool HasHighFragmentation();
bool HasHighFragmentation(intptr_t used, intptr_t committed);
void SetOptimizeForLatency() { optimize_for_memory_usage_ = false; }
void SetOptimizeForMemoryUsage();
bool ShouldOptimizeForMemoryUsage() {
return optimize_for_memory_usage_ || HighMemoryPressure();
bool HighMemoryPressure() {
return memory_pressure_level_.Value() != MemoryPressureLevel::kNone;
// ===========================================================================
// Initialization. ===========================================================
// ===========================================================================
// Configure heap size in MB before setup. Return false if the heap has been
// set up already.
bool ConfigureHeap(int max_semi_space_size, int max_old_space_size,
int max_executable_size, size_t code_range_size);
bool ConfigureHeapDefault();
// Prepares the heap, setting up memory areas that are needed in the isolate
// without actually creating any objects.
bool SetUp();
// Bootstraps the object heap with the core set of objects required to run.
// Returns whether it succeeded.
bool CreateHeapObjects();
// Destroys all memory allocated by the heap.
void TearDown();
// Returns whether SetUp has been called.
bool HasBeenSetUp();
// ===========================================================================
// Getters for spaces. =======================================================
// ===========================================================================
Address NewSpaceTop() { return; }
NewSpace* new_space() { return &new_space_; }
OldSpace* old_space() { return old_space_; }
OldSpace* code_space() { return code_space_; }
MapSpace* map_space() { return map_space_; }
LargeObjectSpace* lo_space() { return lo_space_; }
PagedSpace* paged_space(int idx) {
switch (idx) {
return old_space();
return map_space();
return code_space();
case LO_SPACE:
return NULL;
Space* space(int idx) {
switch (idx) {
return new_space();
case LO_SPACE:
return lo_space();
return paged_space(idx);
// Returns name of the space.
const char* GetSpaceName(int idx);
// ===========================================================================
// Getters to other components. ==============================================
// ===========================================================================
GCTracer* tracer() { return tracer_; }
MemoryAllocator* memory_allocator() { return memory_allocator_; }
PromotionQueue* promotion_queue() { return &promotion_queue_; }
inline Isolate* isolate();
MarkCompactCollector* mark_compact_collector() {
return mark_compact_collector_;
// ===========================================================================
// Root set access. ==========================================================
// ===========================================================================
// Heap root getters.
#define ROOT_ACCESSOR(type, name, camel_name) inline type* name();
// Utility type maps.
#define STRUCT_MAP_ACCESSOR(NAME, Name, name) inline Map* name##_map();
#define STRING_ACCESSOR(name, str) inline String* name();
#define SYMBOL_ACCESSOR(name) inline Symbol* name();
#define SYMBOL_ACCESSOR(name, description) inline Symbol* name();
Object* root(RootListIndex index) { return roots_[index]; }
Handle<Object> root_handle(RootListIndex index) {
return Handle<Object>(&roots_[index]);
// Generated code can embed this address to get access to the roots.
Object** roots_array_start() { return roots_; }
// Sets the stub_cache_ (only used when expanding the dictionary).
void SetRootCodeStubs(UnseededNumberDictionary* value) {
roots_[kCodeStubsRootIndex] = value;
void SetRootMaterializedObjects(FixedArray* objects) {
roots_[kMaterializedObjectsRootIndex] = objects;
void SetRootScriptList(Object* value) {
roots_[kScriptListRootIndex] = value;
void SetRootStringTable(StringTable* value) {
roots_[kStringTableRootIndex] = value;
void SetRootNoScriptSharedFunctionInfos(Object* value) {
roots_[kNoScriptSharedFunctionInfosRootIndex] = value;
// Set the stack limit in the roots_ array. Some architectures generate
// code that looks here, because it is faster than loading from the static
// jslimit_/real_jslimit_ variable in the StackGuard.
void SetStackLimits();
// The stack limit is thread-dependent. To be able to reproduce the same
// snapshot blob, we need to reset it before serializing.
void ClearStackLimits();
// Generated code can treat direct references to this root as constant.
bool RootCanBeTreatedAsConstant(RootListIndex root_index);
Map* MapForFixedTypedArray(ExternalArrayType array_type);
RootListIndex RootIndexForFixedTypedArray(ExternalArrayType array_type);
RootListIndex RootIndexForEmptyFixedTypedArray(ElementsKind kind);
FixedTypedArrayBase* EmptyFixedTypedArrayForMap(Map* map);
void RegisterStrongRoots(Object** start, Object** end);
void UnregisterStrongRoots(Object** start);
// ===========================================================================
// Inline allocation. ========================================================
// ===========================================================================
// Indicates whether inline bump-pointer allocation has been disabled.
bool inline_allocation_disabled() { return inline_allocation_disabled_; }
// Switch whether inline bump-pointer allocation should be used.
void EnableInlineAllocation();
void DisableInlineAllocation();
// ===========================================================================
// Methods triggering GCs. ===================================================
// ===========================================================================
// Performs garbage collection operation.
// Returns whether there is a chance that another major GC could
// collect more garbage.
inline bool CollectGarbage(
AllocationSpace space, const char* gc_reason = NULL,
const GCCallbackFlags gc_callback_flags = kNoGCCallbackFlags);
// Performs a full garbage collection. If (flags & kMakeHeapIterableMask) is
// non-zero, then the slower precise sweeper is used, which leaves the heap
// in a state where we can iterate over the heap visiting all objects.
void CollectAllGarbage(
int flags = kFinalizeIncrementalMarkingMask, const char* gc_reason = NULL,
const GCCallbackFlags gc_callback_flags = kNoGCCallbackFlags);
// Last hope GC, should try to squeeze as much as possible.
void CollectAllAvailableGarbage(const char* gc_reason = NULL);
// Reports and external memory pressure event, either performs a major GC or
// completes incremental marking in order to free external resources.
void ReportExternalMemoryPressure(const char* gc_reason = NULL);
// Invoked when GC was requested via the stack guard.
void HandleGCRequest();
// ===========================================================================
// Iterators. ================================================================
// ===========================================================================
// Iterates over all roots in the heap.
void IterateRoots(ObjectVisitor* v, VisitMode mode);
// Iterates over all strong roots in the heap.
void IterateStrongRoots(ObjectVisitor* v, VisitMode mode);
// Iterates over entries in the smi roots list. Only interesting to the
// serializer/deserializer, since GC does not care about smis.
void IterateSmiRoots(ObjectVisitor* v);
// Iterates over all the other roots in the heap.
void IterateWeakRoots(ObjectVisitor* v, VisitMode mode);
// Iterate pointers of promoted objects.
void IteratePromotedObject(HeapObject* target, int size,
bool was_marked_black,
ObjectSlotCallback callback);
void IteratePromotedObjectPointers(HeapObject* object, Address start,
Address end, bool record_slots,
ObjectSlotCallback callback);
// ===========================================================================
// Store buffer API. =========================================================
// ===========================================================================
// Write barrier support for object[offset] = o;
inline void RecordWrite(Object* object, int offset, Object* o);
inline void RecordFixedArrayElements(FixedArray* array, int offset,
int length);
Address* store_buffer_top_address() { return store_buffer()->top_address(); }
void ClearRecordedSlot(HeapObject* object, Object** slot);
void ClearRecordedSlotRange(Address start, Address end);
// ===========================================================================
// Incremental marking API. ==================================================
// ===========================================================================
// Start incremental marking and ensure that idle time handler can perform
// incremental steps.
void StartIdleIncrementalMarking();
// Starts incremental marking assuming incremental marking is currently
// stopped.
void StartIncrementalMarking(int gc_flags = kNoGCFlags,
const GCCallbackFlags gc_callback_flags =
const char* reason = nullptr);
void FinalizeIncrementalMarkingIfComplete(const char* comment);
bool TryFinalizeIdleIncrementalMarking(double idle_time_in_ms);
void RegisterReservationsForBlackAllocation(Reservation* reservations);
IncrementalMarking* incremental_marking() { return incremental_marking_; }
// ===========================================================================
// External string table API. ================================================
// ===========================================================================
// Registers an external string.
inline void RegisterExternalString(String* string);
// Finalizes an external string by deleting the associated external
// data and clearing the resource pointer.
inline void FinalizeExternalString(String* string);
// ===========================================================================
// Methods checking/returning the space of a given object/address. ===========
// ===========================================================================
// Returns whether the object resides in new space.
inline bool InNewSpace(Object* object);
inline bool InFromSpace(Object* object);
inline bool InToSpace(Object* object);
// Returns whether the object resides in old space.
inline bool InOldSpace(Object* object);
// Checks whether an address/object in the heap (including auxiliary
// area and unused area).
bool Contains(HeapObject* value);
// Checks whether an address/object in a space.
// Currently used by tests, serialization and heap verification only.
bool InSpace(HeapObject* value, AllocationSpace space);
// Slow methods that can be used for verification as they can also be used
// with off-heap Addresses.
bool ContainsSlow(Address addr);
bool InSpaceSlow(Address addr, AllocationSpace space);
inline bool InNewSpaceSlow(Address address);
inline bool InOldSpaceSlow(Address address);
// ===========================================================================
// Object statistics tracking. ===============================================
// ===========================================================================
// Returns the number of buckets used by object statistics tracking during a
// major GC. Note that the following methods fail gracefully when the bounds
// are exceeded though.
size_t NumberOfTrackedHeapObjectTypes();
// Returns object statistics about count and size at the last major GC.
// Objects are being grouped into buckets that roughly resemble existing
// instance types.
size_t ObjectCountAtLastGC(size_t index);
size_t ObjectSizeAtLastGC(size_t index);
// Retrieves names of buckets used by object statistics tracking.
bool GetObjectTypeName(size_t index, const char** object_type,
const char** object_sub_type);
// ===========================================================================
// GC statistics. ============================================================
// ===========================================================================
// Returns the maximum amount of memory reserved for the heap.
intptr_t MaxReserved() {
return 2 * max_semi_space_size_ + max_old_generation_size_;
int MaxSemiSpaceSize() { return max_semi_space_size_; }
int InitialSemiSpaceSize() { return initial_semispace_size_; }
intptr_t MaxOldGenerationSize() { return max_old_generation_size_; }
intptr_t MaxExecutableSize() { return max_executable_size_; }
// Returns the capacity of the heap in bytes w/o growing. Heap grows when
// more spaces are needed until it reaches the limit.
intptr_t Capacity();
// Returns the capacity of the old generation.
intptr_t OldGenerationCapacity();
// Returns the amount of memory currently committed for the heap.
intptr_t CommittedMemory();
// Returns the amount of memory currently committed for the old space.
intptr_t CommittedOldGenerationMemory();
// Returns the amount of executable memory currently committed for the heap.
intptr_t CommittedMemoryExecutable();
// Returns the amount of phyical memory currently committed for the heap.
size_t CommittedPhysicalMemory();
// Returns the maximum amount of memory ever committed for the heap.
intptr_t MaximumCommittedMemory() { return maximum_committed_; }
// Updates the maximum committed memory for the heap. Should be called
// whenever a space grows.
void UpdateMaximumCommitted();
// Returns the available bytes in space w/o growing.
// Heap doesn't guarantee that it can allocate an object that requires
// all available bytes. Check MaxHeapObjectSize() instead.
intptr_t Available();
// Returns of size of all objects residing in the heap.
intptr_t SizeOfObjects();
void UpdateSurvivalStatistics(int start_new_space_size);
inline void IncrementPromotedObjectsSize(intptr_t object_size) {
DCHECK_GE(object_size, 0);
promoted_objects_size_ += object_size;
inline intptr_t promoted_objects_size() { return promoted_objects_size_; }
inline void IncrementSemiSpaceCopiedObjectSize(intptr_t object_size) {
DCHECK_GE(object_size, 0);
semi_space_copied_object_size_ += object_size;
inline intptr_t semi_space_copied_object_size() {
return semi_space_copied_object_size_;
inline intptr_t SurvivedNewSpaceObjectSize() {
return promoted_objects_size_ + semi_space_copied_object_size_;
inline void IncrementNodesDiedInNewSpace() { nodes_died_in_new_space_++; }
inline void IncrementNodesCopiedInNewSpace() { nodes_copied_in_new_space_++; }
inline void IncrementNodesPromoted() { nodes_promoted_++; }
inline void IncrementYoungSurvivorsCounter(intptr_t survived) {
DCHECK_GE(survived, 0);
survived_last_scavenge_ = survived;
survived_since_last_expansion_ += survived;
inline intptr_t PromotedTotalSize() {
int64_t total = PromotedSpaceSizeOfObjects() + PromotedExternalMemorySize();
if (total > std::numeric_limits<intptr_t>::max()) {
// TODO(erikcorry): Use uintptr_t everywhere we do heap size calculations.
return std::numeric_limits<intptr_t>::max();
if (total < 0) return 0;
return static_cast<intptr_t>(total);
inline void UpdateNewSpaceAllocationCounter();
inline size_t NewSpaceAllocationCounter();
// This should be used only for testing.
void set_new_space_allocation_counter(size_t new_value) {
new_space_allocation_counter_ = new_value;
void UpdateOldGenerationAllocationCounter() {
old_generation_allocation_counter_ = OldGenerationAllocationCounter();
size_t OldGenerationAllocationCounter() {
return old_generation_allocation_counter_ + PromotedSinceLastGC();
// This should be used only for testing.
void set_old_generation_allocation_counter(size_t new_value) {
old_generation_allocation_counter_ = new_value;
size_t PromotedSinceLastGC() {
return PromotedSpaceSizeOfObjects() - old_generation_size_at_last_gc_;
int gc_count() const { return gc_count_; }
// Returns the size of objects residing in non new spaces.
intptr_t PromotedSpaceSizeOfObjects();
double total_regexp_code_generated() { return total_regexp_code_generated_; }
void IncreaseTotalRegexpCodeGenerated(int size) {
total_regexp_code_generated_ += size;
void IncrementCodeGeneratedBytes(bool is_crankshafted, int size) {
if (is_crankshafted) {
crankshaft_codegen_bytes_generated_ += size;
} else {
full_codegen_bytes_generated_ += size;
// ===========================================================================
// Prologue/epilogue callback methods.========================================
// ===========================================================================
void AddGCPrologueCallback(v8::Isolate::GCCallback callback,
GCType gc_type_filter, bool pass_isolate = true);
void RemoveGCPrologueCallback(v8::Isolate::GCCallback callback);
void AddGCEpilogueCallback(v8::Isolate::GCCallback callback,
GCType gc_type_filter, bool pass_isolate = true);
void RemoveGCEpilogueCallback(v8::Isolate::GCCallback callback);
void CallGCPrologueCallbacks(GCType gc_type, GCCallbackFlags flags);
void CallGCEpilogueCallbacks(GCType gc_type, GCCallbackFlags flags);
// ===========================================================================
// Allocation methods. =======================================================
// ===========================================================================
// Creates a filler object and returns a heap object immediately after it.
MUST_USE_RESULT HeapObject* PrecedeWithFiller(HeapObject* object,
int filler_size);
// Creates a filler object if needed for alignment and returns a heap object
// immediately after it. If any space is left after the returned object,
// another filler object is created so the over allocated memory is iterable.
MUST_USE_RESULT HeapObject* AlignWithFiller(HeapObject* object,
int object_size,
int allocation_size,
AllocationAlignment alignment);
// ===========================================================================
// ArrayBuffer tracking. =====================================================
// ===========================================================================
void RegisterNewArrayBuffer(JSArrayBuffer* buffer);
void UnregisterArrayBuffer(JSArrayBuffer* buffer);
inline ArrayBufferTracker* array_buffer_tracker() {
return array_buffer_tracker_;
// ===========================================================================
// Allocation site tracking. =================================================
// ===========================================================================
// Updates the AllocationSite of a given {object}. If the global prenuring
// storage is passed as {pretenuring_feedback} the memento found count on
// the corresponding allocation site is immediately updated and an entry
// in the hash map is created. Otherwise the entry (including a the count
// value) is cached on the local pretenuring feedback.
template <UpdateAllocationSiteMode mode>
inline void UpdateAllocationSite(HeapObject* object,
HashMap* pretenuring_feedback);
// Removes an entry from the global pretenuring storage.
inline void RemoveAllocationSitePretenuringFeedback(AllocationSite* site);
// Merges local pretenuring feedback into the global one. Note that this
// method needs to be called after evacuation, as allocation sites may be
// evacuated and this method resolves forward pointers accordingly.
void MergeAllocationSitePretenuringFeedback(
const HashMap& local_pretenuring_feedback);
// =============================================================================
// Verify the heap is in its normal state before or after a GC.
void Verify();
#ifdef DEBUG
void set_allocation_timeout(int timeout) { allocation_timeout_ = timeout; }
void TracePathToObjectFrom(Object* target, Object* root);
void TracePathToObject(Object* target);
void TracePathToGlobal();
void Print();
void PrintHandles();
// Report heap statistics.
void ReportHeapStatistics(const char* title);
void ReportCodeStatistics(const char* title);
int CountHandlesForObject(Object* object);
class PretenuringScope;
class UnmapFreeMemoryTask;
// External strings table is a place where all external strings are
// registered. We need to keep track of such strings to properly
// finalize them.
class ExternalStringTable {
// Registers an external string.
inline void AddString(String* string);
inline void Iterate(ObjectVisitor* v);
// Restores internal invariant and gets rid of collected strings.
// Must be called after each Iterate() that modified the strings.
void CleanUp();
// Destroys all allocated memory.
void TearDown();
explicit ExternalStringTable(Heap* heap) : heap_(heap) {}
inline void Verify();
inline void AddOldString(String* string);
// Notifies the table that only a prefix of the new list is valid.
inline void ShrinkNewStrings(int position);
// To speed up scavenge collections new space string are kept
// separate from old space strings.
List<Object*> new_space_strings_;
List<Object*> old_space_strings_;
Heap* heap_;
friend class Heap;
struct StrongRootsList;
struct StringTypeTable {
InstanceType type;
int size;
RootListIndex index;
struct ConstantStringTable {
const char* contents;
RootListIndex index;
struct StructTable {
InstanceType type;
int size;
RootListIndex index;
struct GCCallbackPair {
GCCallbackPair(v8::Isolate::GCCallback callback, GCType gc_type,
bool pass_isolate)
: callback(callback), gc_type(gc_type), pass_isolate(pass_isolate) {}
bool operator==(const GCCallbackPair& other) const {
return other.callback == callback;
v8::Isolate::GCCallback callback;
GCType gc_type;
bool pass_isolate;
typedef String* (*ExternalStringTableUpdaterCallback)(Heap* heap,
Object** pointer);
static const int kInitialStringTableSize = 2048;
static const int kInitialEvalCacheSize = 64;
static const int kInitialNumberStringCacheSize = 256;
static const int kRememberedUnmappedPages = 128;
static const StringTypeTable string_type_table[];
static const ConstantStringTable constant_string_table[];
static const StructTable struct_table[];
static const int kYoungSurvivalRateHighThreshold = 90;
static const int kYoungSurvivalRateAllowedDeviation = 15;
static const int kOldSurvivalRateLowThreshold = 10;
static const int kMaxMarkCompactsInIdleRound = 7;
static const int kIdleScavengeThreshold = 5;
static const int kInitialFeedbackCapacity = 256;
static String* UpdateNewSpaceReferenceInExternalStringTableEntry(
Heap* heap, Object** pointer);
// Selects the proper allocation space based on the pretenuring decision.
static AllocationSpace SelectSpace(PretenureFlag pretenure) {
return (pretenure == TENURED) ? OLD_SPACE : NEW_SPACE;
#define ROOT_ACCESSOR(type, name, camel_name) \
inline void set_##name(type* value);
StoreBuffer* store_buffer() { return &store_buffer_; }
void set_current_gc_flags(int flags) {
current_gc_flags_ = flags;
DCHECK(!ShouldFinalizeIncrementalMarking() ||
inline bool ShouldReduceMemory() const {
return current_gc_flags_ & kReduceMemoryFootprintMask;
inline bool ShouldAbortIncrementalMarking() const {
return current_gc_flags_ & kAbortIncrementalMarkingMask;
inline bool ShouldFinalizeIncrementalMarking() const {
return current_gc_flags_ & kFinalizeIncrementalMarkingMask;
void PreprocessStackTraces();
// Checks whether a global GC is necessary
GarbageCollector SelectGarbageCollector(AllocationSpace space,
const char** reason);
// Make sure there is a filler value behind the top of the new space
// so that the GC does not confuse some unintialized/stale memory
// with the allocation memento of the object at the top
void EnsureFillerObjectAtTop();
// Ensure that we have swept all spaces in such a way that we can iterate
// over all objects. May cause a GC.
void MakeHeapIterable();
// Performs garbage collection operation.
// Returns whether there is a chance that another major GC could
// collect more garbage.
bool CollectGarbage(
GarbageCollector collector, const char* gc_reason,
const char* collector_reason,
const GCCallbackFlags gc_callback_flags = kNoGCCallbackFlags);
// Performs garbage collection
// Returns whether there is a chance another major GC could
// collect more garbage.
bool PerformGarbageCollection(
GarbageCollector collector,
const GCCallbackFlags gc_callback_flags = kNoGCCallbackFlags);
inline void UpdateOldSpaceLimits();
// Initializes a JSObject based on its map.
void InitializeJSObjectFromMap(JSObject* obj, FixedArray* properties,
Map* map);
// Initializes JSObject body starting at given offset.
void InitializeJSObjectBody(JSObject* obj, Map* map, int start_offset);
void InitializeAllocationMemento(AllocationMemento* memento,
AllocationSite* allocation_site);
bool CreateInitialMaps();
void CreateInitialObjects();
// These five Create*EntryStub functions are here and forced to not be inlined
// because of a gcc-4.4 bug that assigns wrong vtable entries.
NO_INLINE(void CreateJSEntryStub());
NO_INLINE(void CreateJSConstructEntryStub());
void CreateFixedStubs();
HeapObject* DoubleAlignForDeserialization(HeapObject* object, int size);
// Commits from space if it is uncommitted.
void EnsureFromSpaceIsCommitted();
// Uncommit unused semi space.
bool UncommitFromSpace() { return new_space_.UncommitFromSpace(); }
// Fill in bogus values in from space
void ZapFromSpace();
// Deopts all code that contains allocation instruction which are tenured or
// not tenured. Moreover it clears the pretenuring allocation site statistics.
void ResetAllAllocationSitesDependentCode(PretenureFlag flag);
// Evaluates local pretenuring for the old space and calls
// ResetAllTenuredAllocationSitesDependentCode if too many objects died in
// the old space.
void EvaluateOldSpaceLocalPretenuring(uint64_t size_of_objects_before_gc);
// Record statistics before and after garbage collection.
void ReportStatisticsBeforeGC();
void ReportStatisticsAfterGC();
// Creates and installs the full-sized number string cache.
int FullSizeNumberStringCacheLength();
// Flush the number to string cache.
void FlushNumberStringCache();
// TODO(hpayer): Allocation site pretenuring may make this method obsolete.
// Re-visit incremental marking heuristics.
bool IsHighSurvivalRate() { return high_survival_rate_period_length_ > 0; }
void ConfigureInitialOldGenerationSize();
bool HasLowYoungGenerationAllocationRate();
bool HasLowOldGenerationAllocationRate();
double YoungGenerationMutatorUtilization();
double OldGenerationMutatorUtilization();
void ReduceNewSpaceSize();
bool TryFinalizeIdleIncrementalMarking(
double idle_time_in_ms, size_t size_of_objects,
size_t mark_compact_speed_in_bytes_per_ms);
GCIdleTimeHeapState ComputeHeapState();
bool PerformIdleTimeAction(GCIdleTimeAction action,
GCIdleTimeHeapState heap_state,
double deadline_in_ms);
void IdleNotificationEpilogue(GCIdleTimeAction action,
GCIdleTimeHeapState heap_state, double start_ms,
double deadline_in_ms);
inline void UpdateAllocationsHash(HeapObject* object);
inline void UpdateAllocationsHash(uint32_t value);
void PrintAlloctionsHash();
void AddToRingBuffer(const char* string);
void GetFromRingBuffer(char* buffer);
void CompactRetainedMaps(ArrayList* retained_maps);
void CollectGarbageOnMemoryPressure(const char* source);
// Attempt to over-approximate the weak closure by marking object groups and
// implicit references from global handles, but don't atomically complete
// marking. If we continue to mark incrementally, we might have marked
// objects that die later.
void FinalizeIncrementalMarking(const char* gc_reason);
// Returns the timer used for a given GC type.
// - GCScavenger: young generation GC
// - GCCompactor: full GC
// - GCFinalzeMC: finalization of incremental full GC
// - GCFinalizeMCReduceMemory: finalization of incremental full GC with
// memory reduction
HistogramTimer* GCTypeTimer(GarbageCollector collector);
// ===========================================================================
// Pretenuring. ==============================================================
// ===========================================================================
// Pretenuring decisions are made based on feedback collected during new space
// evacuation. Note that between feedback collection and calling this method
// object in old space must not move.
void ProcessPretenuringFeedback();
// ===========================================================================
// Actual GC. ================================================================
// ===========================================================================
// Code that should be run before and after each GC. Includes some
// reporting/verification activities when compiled with DEBUG set.
void GarbageCollectionPrologue();
void GarbageCollectionEpilogue();
// Performs a major collection in the whole heap.
void MarkCompact();
// Code to be run before and after mark-compact.
void MarkCompactPrologue();
void MarkCompactEpilogue();
// Performs a minor collection in new generation.
void Scavenge();
Address DoScavenge(ObjectVisitor* scavenge_visitor, Address new_space_front);
void UpdateNewSpaceReferencesInExternalStringTable(
ExternalStringTableUpdaterCallback updater_func);
void UpdateReferencesInExternalStringTable(
ExternalStringTableUpdaterCallback updater_func);
void ProcessAllWeakReferences(WeakObjectRetainer* retainer);
void ProcessYoungWeakReferences(WeakObjectRetainer* retainer);
void ProcessNativeContexts(WeakObjectRetainer* retainer);
void ProcessAllocationSites(WeakObjectRetainer* retainer);
void ProcessWeakListRoots(WeakObjectRetainer* retainer);
// ===========================================================================
// GC statistics. ============================================================
// ===========================================================================
inline intptr_t OldGenerationSpaceAvailable() {
return old_generation_allocation_limit_ - PromotedTotalSize();
// Returns maximum GC pause.
double get_max_gc_pause() { return max_gc_pause_; }
// Returns maximum size of objects alive after GC.
intptr_t get_max_alive_after_gc() { return max_alive_after_gc_; }
// Returns minimal interval between two subsequent collections.
double get_min_in_mutator() { return min_in_mutator_; }
// Update GC statistics that are tracked on the Heap.
void UpdateCumulativeGCStatistics(double duration, double spent_in_mutator,
double marking_time);
bool MaximumSizeScavenge() { return maximum_size_scavenges_ > 0; }
// ===========================================================================
// Growing strategy. =========================================================
// ===========================================================================
// Decrease the allocation limit if the new limit based on the given
// parameters is lower than the current limit.
void DampenOldGenerationAllocationLimit(intptr_t old_gen_size,
double gc_speed,
double mutator_speed);
// Calculates the allocation limit based on a given growing factor and a
// given old generation size.
intptr_t CalculateOldGenerationAllocationLimit(double factor,
intptr_t old_gen_size);
// Sets the allocation limit to trigger the next full garbage collection.
void SetOldGenerationAllocationLimit(intptr_t old_gen_size, double gc_speed,
double mutator_speed);
// ===========================================================================
// Idle notification. ========================================================
// ===========================================================================
bool RecentIdleNotificationHappened();
void ScheduleIdleScavengeIfNeeded(int bytes_allocated);
// ===========================================================================
// HeapIterator helpers. =====================================================
// ===========================================================================
void heap_iterator_start() { heap_iterator_depth_++; }
void heap_iterator_end() { heap_iterator_depth_--; }
bool in_heap_iterator() { return heap_iterator_depth_ > 0; }
// ===========================================================================
// Allocation methods. =======================================================
// ===========================================================================
// Returns a deep copy of the JavaScript object.
// Properties and elements are copied too.
// Optionally takes an AllocationSite to be appended in an AllocationMemento.
MUST_USE_RESULT AllocationResult CopyJSObject(JSObject* source,
AllocationSite* site = NULL);
// Allocates a JS Map in the heap.
MUST_USE_RESULT AllocationResult
AllocateMap(InstanceType instance_type, int instance_size,
ElementsKind elements_kind = TERMINAL_FAST_ELEMENTS_KIND);
// Allocates and initializes a new JavaScript object based on a
// constructor.
// If allocation_site is non-null, then a memento is emitted after the object
// that points to the site.
MUST_USE_RESULT AllocationResult AllocateJSObject(
JSFunction* constructor, PretenureFlag pretenure = NOT_TENURED,
AllocationSite* allocation_site = NULL);
// Allocates and initializes a new JavaScript object based on a map.
// Passing an allocation site means that a memento will be created that
// points to the site.
MUST_USE_RESULT AllocationResult
AllocateJSObjectFromMap(Map* map, PretenureFlag pretenure = NOT_TENURED,
AllocationSite* allocation_site = NULL);
// Allocates a HeapNumber from value.
MUST_USE_RESULT AllocationResult
AllocateHeapNumber(double value, MutableMode mode = IMMUTABLE,
PretenureFlag pretenure = NOT_TENURED);
// Allocates SIMD values from the given lane values.
#define SIMD_ALLOCATE_DECLARATION(TYPE, Type, type, lane_count, lane_type) \
AllocationResult Allocate##Type(lane_type lanes[lane_count], \
PretenureFlag pretenure = NOT_TENURED);
// Allocates a byte array of the specified length
MUST_USE_RESULT AllocationResult
AllocateByteArray(int length, PretenureFlag pretenure = NOT_TENURED);
// Allocates a bytecode array with given contents.
MUST_USE_RESULT AllocationResult
AllocateBytecodeArray(int length, const byte* raw_bytecodes, int frame_size,
int parameter_count, FixedArray* constant_pool);
// Copy the code and scope info part of the code object, but insert
// the provided data as the relocation information.
MUST_USE_RESULT AllocationResult CopyCode(Code* code,
Vector<byte> reloc_info);
MUST_USE_RESULT AllocationResult CopyCode(Code* code);
MUST_USE_RESULT AllocationResult
CopyBytecodeArray(BytecodeArray* bytecode_array);
// Allocates a fixed array initialized with undefined values
MUST_USE_RESULT AllocationResult
AllocateFixedArray(int length, PretenureFlag pretenure = NOT_TENURED);
// Allocate an uninitialized object. The memory is non-executable if the
// hardware and OS allow. This is the single choke-point for allocations
// performed by the runtime and should not be bypassed (to extend this to
// inlined allocations, use the Heap::DisableInlineAllocation() support).
MUST_USE_RESULT inline AllocationResult AllocateRaw(
int size_in_bytes, AllocationSpace space,
AllocationAlignment aligment = kWordAligned);
// Allocates a heap object based on the map.
MUST_USE_RESULT AllocationResult
Allocate(Map* map, AllocationSpace space,
AllocationSite* allocation_site = NULL);
// Allocates a partial map for bootstrapping.
MUST_USE_RESULT AllocationResult
AllocatePartialMap(InstanceType instance_type, int instance_size);
// Allocate a block of memory in the given space (filled with a filler).
// Used as a fall-back for generated code when the space is full.
MUST_USE_RESULT AllocationResult
AllocateFillerObject(int size, bool double_align, AllocationSpace space);
// Allocate an uninitialized fixed array.
MUST_USE_RESULT AllocationResult
AllocateRawFixedArray(int length, PretenureFlag pretenure);
// Allocate an uninitialized fixed double array.
MUST_USE_RESULT AllocationResult
AllocateRawFixedDoubleArray(int length, PretenureFlag pretenure);
// Allocate an initialized fixed array with the given filler value.
MUST_USE_RESULT AllocationResult
AllocateFixedArrayWithFiller(int length, PretenureFlag pretenure,
Object* filler);
// Allocate and partially initializes a String. There are two String
// encodings: one-byte and two-byte. These functions allocate a string of
// the given length and set its map and length fields. The characters of
// the string are uninitialized.
MUST_USE_RESULT AllocationResult
AllocateRawOneByteString(int length, PretenureFlag pretenure);
MUST_USE_RESULT AllocationResult
AllocateRawTwoByteString(int length, PretenureFlag pretenure);
// Allocates an internalized string in old space based on the character
// stream.
MUST_USE_RESULT inline AllocationResult AllocateInternalizedStringFromUtf8(
Vector<const char> str, int chars, uint32_t hash_field);
MUST_USE_RESULT inline AllocationResult AllocateOneByteInternalizedString(
Vector<const uint8_t> str, uint32_t hash_field);
MUST_USE_RESULT inline AllocationResult AllocateTwoByteInternalizedString(
Vector<const uc16> str, uint32_t hash_field);
template <bool is_one_byte, typename T>
MUST_USE_RESULT AllocationResult
AllocateInternalizedStringImpl(T t, int chars, uint32_t hash_field);
template <typename T>
MUST_USE_RESULT inline AllocationResult AllocateInternalizedStringImpl(
T t, int chars, uint32_t hash_field);
// Allocates an uninitialized fixed array. It must be filled by the caller.
MUST_USE_RESULT AllocationResult AllocateUninitializedFixedArray(int length);
// Make a copy of src and return it.
MUST_USE_RESULT inline AllocationResult CopyFixedArray(FixedArray* src);
// Make a copy of src, also grow the copy, and return the copy.
MUST_USE_RESULT AllocationResult
CopyFixedArrayAndGrow(FixedArray* src, int grow_by, PretenureFlag pretenure);
// Make a copy of src, also grow the copy, and return the copy.
MUST_USE_RESULT AllocationResult CopyFixedArrayUpTo(FixedArray* src,
int new_len,
PretenureFlag pretenure);
// Make a copy of src, set the map, and return the copy.
MUST_USE_RESULT AllocationResult
CopyFixedArrayWithMap(FixedArray* src, Map* map);
// Make a copy of src and return it.
MUST_USE_RESULT inline AllocationResult CopyFixedDoubleArray(
FixedDoubleArray* src);
// Computes a single character string where the character has code.
// A cache is used for one-byte (Latin1) codes.
MUST_USE_RESULT AllocationResult
LookupSingleCharacterStringFromCode(uint16_t code);
// Allocate a symbol in old space.
MUST_USE_RESULT AllocationResult AllocateSymbol();
// Allocates an external array of the specified length and type.
MUST_USE_RESULT AllocationResult AllocateFixedTypedArrayWithExternalPointer(
int length, ExternalArrayType array_type, void* external_pointer,
PretenureFlag pretenure);
// Allocates a fixed typed array of the specified length and type.
MUST_USE_RESULT AllocationResult
AllocateFixedTypedArray(int length, ExternalArrayType array_type,
bool initialize, PretenureFlag pretenure);
// Make a copy of src and return it.
MUST_USE_RESULT AllocationResult CopyAndTenureFixedCOWArray(FixedArray* src);
// Make a copy of src, set the map, and return the copy.
MUST_USE_RESULT AllocationResult
CopyFixedDoubleArrayWithMap(FixedDoubleArray* src, Map* map);
// Allocates a fixed double array with uninitialized values. Returns
MUST_USE_RESULT AllocationResult AllocateUninitializedFixedDoubleArray(
int length, PretenureFlag pretenure = NOT_TENURED);
// Allocate empty fixed array.
MUST_USE_RESULT AllocationResult AllocateEmptyFixedArray();
// Allocate empty fixed typed array of given type.
MUST_USE_RESULT AllocationResult
AllocateEmptyFixedTypedArray(ExternalArrayType array_type);
// Allocate a tenured simple cell.
MUST_USE_RESULT AllocationResult AllocateCell(Object* value);
// Allocate a tenured JS global property cell initialized with the hole.
MUST_USE_RESULT AllocationResult AllocatePropertyCell();
MUST_USE_RESULT AllocationResult AllocateWeakCell(HeapObject* value);
MUST_USE_RESULT AllocationResult AllocateTransitionArray(int capacity);
// Allocates a new utility object in the old generation.
MUST_USE_RESULT AllocationResult AllocateStruct(InstanceType type);
// Allocates a new foreign object.
MUST_USE_RESULT AllocationResult
AllocateForeign(Address address, PretenureFlag pretenure = NOT_TENURED);
MUST_USE_RESULT AllocationResult
AllocateCode(int object_size, bool immovable);
MUST_USE_RESULT AllocationResult InternalizeStringWithKey(HashTableKey* key);
MUST_USE_RESULT AllocationResult InternalizeString(String* str);
// ===========================================================================
void set_force_oom(bool value) { force_oom_ = value; }
// The amount of external memory registered through the API kept alive
// by global handles
int64_t amount_of_external_allocated_memory_;
// Caches the amount of external memory registered at the last global gc.
int64_t amount_of_external_allocated_memory_at_last_global_gc_;
// This can be calculated directly from a pointer to the heap; however, it is
// more expedient to get at the isolate directly from within Heap methods.
Isolate* isolate_;
Object* roots_[kRootListLength];
size_t code_range_size_;
int max_semi_space_size_;
int initial_semispace_size_;
intptr_t max_old_generation_size_;
intptr_t initial_old_generation_size_;
bool old_generation_size_configured_;
intptr_t max_executable_size_;
intptr_t maximum_committed_;
// For keeping track of how much data has survived
// scavenge since last new space expansion.
intptr_t survived_since_last_expansion_;
// ... and since the last scavenge.
intptr_t survived_last_scavenge_;
// This is not the depth of nested AlwaysAllocateScope's but rather a single
// count, as scopes can be acquired from multiple tasks (read: threads).
AtomicNumber<size_t> always_allocate_scope_count_;
// Stores the memory pressure level that set by MemoryPressureNotification
// and reset by a mark-compact garbage collection.
AtomicValue<MemoryPressureLevel> memory_pressure_level_;
// For keeping track of context disposals.
int contexts_disposed_;
// The length of the retained_maps array at the time of context disposal.
// This separates maps in the retained_maps array that were created before
// and after context disposal.
int number_of_disposed_maps_;
int global_ic_age_;
NewSpace new_space_;
OldSpace* old_space_;
OldSpace* code_space_;
MapSpace* map_space_;
LargeObjectSpace* lo_space_;
HeapState gc_state_;
int gc_post_processing_depth_;
Address new_space_top_after_last_gc_;
// Returns the amount of external memory registered since last global gc.
int64_t PromotedExternalMemorySize();
// How many "runtime allocations" happened.
uint32_t allocations_count_;
// Running hash over allocations performed.
uint32_t raw_allocations_hash_;
// How many mark-sweep collections happened.
unsigned int ms_count_;
// How many gc happened.
unsigned int gc_count_;
// For post mortem debugging.
int remembered_unmapped_pages_index_;
Address remembered_unmapped_pages_[kRememberedUnmappedPages];
#ifdef DEBUG
// If the --gc-interval flag is set to a positive value, this
// variable holds the value indicating the number of allocations
// remain until the next failure and garbage collection.
int allocation_timeout_;
#endif // DEBUG
// Limit that triggers a global GC on the next (normally caused) GC. This
// is checked when we have already decided to do a GC to help determine
// which collector to invoke, before expanding a paged space in the old
// generation and on every allocation in large object space.
intptr_t old_generation_allocation_limit_;
// Indicates that an allocation has failed in the old generation since the
// last GC.
bool old_gen_exhausted_;
// Indicates that memory usage is more important than latency.
// TODO(ulan): Merge it with memory reducer once chromium:490559 is fixed.
bool optimize_for_memory_usage_;
// Indicates that inline bump-pointer allocation has been globally disabled
// for all spaces. This is used to disable allocations in generated code.
bool inline_allocation_disabled_;
// Weak list heads, threaded through the objects.
// List heads are initialized lazily and contain the undefined_value at start.
Object* native_contexts_list_;
Object* allocation_sites_list_;
// List of encountered weak collections (JSWeakMap and JSWeakSet) during
// marking. It is initialized during marking, destroyed after marking and
// contains Smi(0) while marking is not active.
Object* encountered_weak_collections_;
Object* encountered_weak_cells_;
Object* encountered_transition_arrays_;
List<GCCallbackPair> gc_epilogue_callbacks_;
List<GCCallbackPair> gc_prologue_callbacks_;
// Total RegExp code ever generated
double total_regexp_code_generated_;
int deferred_counters_[v8::Isolate::kUseCounterFeatureCount];
GCTracer* tracer_;
int high_survival_rate_period_length_;
intptr_t promoted_objects_size_;
double promotion_ratio_;
double promotion_rate_;
intptr_t semi_space_copied_object_size_;
intptr_t previous_semi_space_copied_object_size_;
double semi_space_copied_rate_;
int nodes_died_in_new_space_;
int nodes_copied_in_new_space_;
int nodes_promoted_;
// This is the pretenuring trigger for allocation sites that are in maybe
// tenure state. When we switched to the maximum new space size we deoptimize
// the code that belongs to the allocation site and derive the lifetime
// of the allocation site.
unsigned int maximum_size_scavenges_;
// Maximum GC pause.
double max_gc_pause_;
// Total time spent in GC.
double total_gc_time_ms_;
// Maximum size of objects alive after GC.
intptr_t max_alive_after_gc_;
// Minimal interval between two subsequent collections.
double min_in_mutator_;
// Cumulative GC time spent in marking.
double marking_time_;
// Cumulative GC time spent in sweeping.
double sweeping_time_;
// Last time an idle notification happened.
double last_idle_notification_time_;
// Last time a garbage collection happened.
double last_gc_time_;
Scavenger* scavenge_collector_;
MarkCompactCollector* mark_compact_collector_;
MemoryAllocator* memory_allocator_;
StoreBuffer store_buffer_;
IncrementalMarking* incremental_marking_;
GCIdleTimeHandler* gc_idle_time_handler_;
MemoryReducer* memory_reducer_;
ObjectStats* object_stats_;
ScavengeJob* scavenge_job_;
AllocationObserver* idle_scavenge_observer_;
// These two counters are monotomically increasing and never reset.
size_t full_codegen_bytes_generated_;
size_t crankshaft_codegen_bytes_generated_;
// This counter is increased before each GC and never reset.
// To account for the bytes allocated since the last GC, use the
// NewSpaceAllocationCounter() function.
size_t new_space_allocation_counter_;
// This counter is increased before each GC and never reset. To
// account for the bytes allocated since the last GC, use the
// OldGenerationAllocationCounter() function.
size_t old_generation_allocation_counter_;
// The size of objects in old generation after the last MarkCompact GC.
size_t old_generation_size_at_last_gc_;
// If the --deopt_every_n_garbage_collections flag is set to a positive value,
// this variable holds the number of garbage collections since the last
// deoptimization triggered by garbage collection.
int gcs_since_last_deopt_;
// The feedback storage is used to store allocation sites (keys) and how often
// they have been visited (values) by finding a memento behind an object. The
// storage is only alive temporary during a GC. The invariant is that all
// pointers in this map are already fixed, i.e., they do not point to
// forwarding pointers.
HashMap* global_pretenuring_feedback_;
char trace_ring_buffer_[kTraceRingBufferSize];
// If it's not full then the data is from 0 to ring_buffer_end_. If it's
// full then the data is from ring_buffer_end_ to the end of the buffer and
// from 0 to ring_buffer_end_.
bool ring_buffer_full_;
size_t ring_buffer_end_;
// Shared state read by the scavenge collector and set by ScavengeObject.
PromotionQueue promotion_queue_;
// Flag is set when the heap has been configured. The heap can be repeatedly
// configured through the API until it is set up.
bool configured_;
// Currently set GC flags that are respected by all GC components.
int current_gc_flags_;
// Currently set GC callback flags that are used to pass information between
// the embedder and V8's GC.
GCCallbackFlags current_gc_callback_flags_;
ExternalStringTable external_string_table_;
MemoryChunk* chunks_queued_for_free_;
size_t concurrent_unmapping_tasks_active_;
base::Semaphore pending_unmapping_tasks_semaphore_;
base::Mutex relocation_mutex_;
int gc_callbacks_depth_;
bool deserialization_complete_;
StrongRootsList* strong_roots_list_;
ArrayBufferTracker* array_buffer_tracker_;
// The depth of HeapIterator nestings.
int heap_iterator_depth_;
// Used for testing purposes.
bool force_oom_;
// Classes in "heap" can be friends.
friend class AlwaysAllocateScope;
friend class GCCallbacksScope;
friend class GCTracer;
friend class HeapIterator;
friend class IdleScavengeObserver;
friend class IncrementalMarking;
friend class IteratePromotedObjectsVisitor;
friend class MarkCompactCollector;
friend class MarkCompactMarkingVisitor;
friend class NewSpace;
friend class ObjectStatsVisitor;
friend class Page;
friend class Scavenger;
friend class StoreBuffer;
friend class TestMemoryAllocatorScope;
// The allocator interface.
friend class Factory;
// The Isolate constructs us.
friend class Isolate;
// Used in cctest.
friend class HeapTester;
class HeapStats {
static const int kStartMarker = 0xDECADE00;
static const int kEndMarker = 0xDECADE01;
int* start_marker; // 0
int* new_space_size; // 1
int* new_space_capacity; // 2
intptr_t* old_space_size; // 3
intptr_t* old_space_capacity; // 4
intptr_t* code_space_size; // 5
intptr_t* code_space_capacity; // 6
intptr_t* map_space_size; // 7
intptr_t* map_space_capacity; // 8
intptr_t* lo_space_size; // 9
int* global_handle_count; // 10
int* weak_global_handle_count; // 11
int* pending_global_handle_count; // 12
int* near_death_global_handle_count; // 13
int* free_global_handle_count; // 14
intptr_t* memory_allocator_size; // 15
intptr_t* memory_allocator_capacity; // 16
int* objects_per_type; // 17
int* size_per_type; // 18
int* os_error; // 19
char* last_few_messages; // 20
char* js_stacktrace; // 21
int* end_marker; // 22
class AlwaysAllocateScope {
explicit inline AlwaysAllocateScope(Isolate* isolate);
inline ~AlwaysAllocateScope();
Heap* heap_;
// Visitor class to verify interior pointers in spaces that do not contain
// or care about intergenerational references. All heap object pointers have to
// point into the heap to a location that has a map pointer at its first word.
// Caveat: Heap::Contains is an approximation because it can return true for
// objects in a heap space but above the allocation pointer.
class VerifyPointersVisitor : public ObjectVisitor {
inline void VisitPointers(Object** start, Object** end) override;
// Verify that all objects are Smis.
class VerifySmisVisitor : public ObjectVisitor {
inline void VisitPointers(Object** start, Object** end) override;
// Space iterator for iterating over all spaces of the heap. Returns each space
// in turn, and null when it is done.
class AllSpaces BASE_EMBEDDED {
explicit AllSpaces(Heap* heap) : heap_(heap), counter_(FIRST_SPACE) {}
Space* next();
Heap* heap_;
int counter_;
// Space iterator for iterating over all old spaces of the heap: Old space
// and code space. Returns each space in turn, and null when it is done.
class OldSpaces BASE_EMBEDDED {
explicit OldSpaces(Heap* heap) : heap_(heap), counter_(OLD_SPACE) {}
OldSpace* next();
Heap* heap_;
int counter_;
// Space iterator for iterating over all the paged spaces of the heap: Map
// space, old space, code space and cell space. Returns
// each space in turn, and null when it is done.
class PagedSpaces BASE_EMBEDDED {
explicit PagedSpaces(Heap* heap) : heap_(heap), counter_(OLD_SPACE) {}
PagedSpace* next();
Heap* heap_;
int counter_;
// Space iterator for iterating over all spaces of the heap.
// For each space an object iterator is provided. The deallocation of the
// returned object iterators is handled by the space iterator.
class SpaceIterator : public Malloced {
explicit SpaceIterator(Heap* heap);
virtual ~SpaceIterator();
bool has_next();
ObjectIterator* next();
ObjectIterator* CreateIterator();
Heap* heap_;
int current_space_; // from enum AllocationSpace.
ObjectIterator* iterator_; // object iterator for the current space.
// A HeapIterator provides iteration over the whole heap. It
// aggregates the specific iterators for the different spaces as
// these can only iterate over one space only.
// HeapIterator ensures there is no allocation during its lifetime
// (using an embedded DisallowHeapAllocation instance).
// HeapIterator can skip free list nodes (that is, de-allocated heap
// objects that still remain in the heap). As implementation of free
// nodes filtering uses GC marks, it can't be used during MS/MC GC
// phases. Also, it is forbidden to interrupt iteration in this mode,
// as this will leave heap objects marked (and thus, unusable).
class HeapIterator BASE_EMBEDDED {
enum HeapObjectsFiltering { kNoFiltering, kFilterUnreachable };
explicit HeapIterator(Heap* heap,
HeapObjectsFiltering filtering = kNoFiltering);
HeapObject* next();
struct MakeHeapIterableHelper {
explicit MakeHeapIterableHelper(Heap* heap) { heap->MakeHeapIterable(); }
HeapObject* NextObject();
// The following two fields need to be declared in this order. Initialization
// order guarantees that we first make the heap iterable (which may involve
// allocations) and only then lock it down by not allowing further
// allocations.
MakeHeapIterableHelper make_heap_iterable_helper_;
DisallowHeapAllocation no_heap_allocation_;
Heap* heap_;
HeapObjectsFiltering filtering_;
HeapObjectsFilter* filter_;
// Space iterator for iterating all the spaces.
SpaceIterator* space_iterator_;
// Object iterator for the space currently being iterated.
ObjectIterator* object_iterator_;
// Cache for mapping (map, property name) into field offset.
// Cleared at startup and prior to mark sweep collection.
class KeyedLookupCache {
// Lookup field offset for (map, name). If absent, -1 is returned.
int Lookup(Handle<Map> map, Handle<Name> name);
// Update an element in the cache.
void Update(Handle<Map> map, Handle<Name> name, int field_offset);
// Clear the cache.
void Clear();
static const int kLength = 256;
static const int kCapacityMask = kLength - 1;
static const int kMapHashShift = 5;
static const int kHashMask = -4; // Zero the last two bits.
static const int kEntriesPerBucket = 4;
static const int kEntryLength = 2;
static const int kMapIndex = 0;
static const int kKeyIndex = 1;
static const int kNotFound = -1;
// kEntriesPerBucket should be a power of 2.
STATIC_ASSERT((kEntriesPerBucket & (kEntriesPerBucket - 1)) == 0);
STATIC_ASSERT(kEntriesPerBucket == -kHashMask);
KeyedLookupCache() {
for (int i = 0; i < kLength; ++i) {
keys_[i].map = NULL;
keys_[i].name = NULL;
field_offsets_[i] = kNotFound;
static inline int Hash(Handle<Map> map, Handle<Name> name);
// Get the address of the keys and field_offsets arrays. Used in
// generated code to perform cache lookups.
Address keys_address() { return reinterpret_cast<Address>(&keys_); }
Address field_offsets_address() {
return reinterpret_cast<Address>(&field_offsets_);
struct Key {
Map* map;
Name* name;
Key keys_[kLength];
int field_offsets_[kLength];
friend class ExternalReference;
friend class Isolate;
// Cache for mapping (map, property name) into descriptor index.
// The cache contains both positive and negative results.
// Descriptor index equals kNotFound means the property is absent.
// Cleared at startup and prior to any gc.
class DescriptorLookupCache {
// Lookup descriptor index for (map, name).
// If absent, kAbsent is returned.
inline int Lookup(Map* source, Name* name);
// Update an element in the cache.
inline void Update(Map* source, Name* name, int result);
// Clear the cache.
void Clear();
static const int kAbsent = -2;
DescriptorLookupCache() {
for (int i = 0; i < kLength; ++i) {
keys_[i].source = NULL;
keys_[i].name = NULL;
results_[i] = kAbsent;
static inline int Hash(Object* source, Name* name);
static const int kLength = 64;
struct Key {
Map* source;
Name* name;
Key keys_[kLength];
int results_[kLength];
friend class Isolate;
// Abstract base class for checking whether a weak object should be retained.
class WeakObjectRetainer {
virtual ~WeakObjectRetainer() {}
// Return whether this object should be retained. If NULL is returned the
// object has no references. Otherwise the address of the retained object
// should be returned as in some GC situations the object has been moved.
virtual Object* RetainAs(Object* object) = 0;
#ifdef DEBUG
// Helper class for tracing paths to a search target Object from all roots.
// The TracePathFrom() method can be used to trace paths from a specific
// object to the search target object.
class PathTracer : public ObjectVisitor {
enum WhatToFind {
FIND_ALL, // Will find all matches.
FIND_FIRST // Will stop the search after first match.
// Tags 0, 1, and 3 are used. Use 2 for marking visited HeapObject.
static const int kMarkTag = 2;
// For the WhatToFind arg, if FIND_FIRST is specified, tracing will stop
// after the first match. If FIND_ALL is specified, then tracing will be
// done for all matches.
PathTracer(Object* search_target, WhatToFind what_to_find,
VisitMode visit_mode)
: search_target_(search_target),
no_allocation() {}
void VisitPointers(Object** start, Object** end) override;
void Reset();
void TracePathFrom(Object** root);
bool found() const { return found_target_; }
static Object* const kAnyGlobalObject;
class MarkVisitor;
class UnmarkVisitor;
void MarkRecursively(Object** p, MarkVisitor* mark_visitor);
void UnmarkRecursively(Object** p, UnmarkVisitor* unmark_visitor);
virtual void ProcessResults();
Object* search_target_;
bool found_target_;
bool found_target_in_trace_;
WhatToFind what_to_find_;
VisitMode visit_mode_;
List<Object*> object_stack_;
DisallowHeapAllocation no_allocation; // i.e. no gc allowed.
#endif // DEBUG
// -----------------------------------------------------------------------------
// Allows observation of allocations.
class AllocationObserver {
explicit AllocationObserver(intptr_t step_size)
: step_size_(step_size), bytes_to_next_step_(step_size) {
DCHECK(step_size >= kPointerSize);
virtual ~AllocationObserver() {}
// Called each time the observed space does an allocation step. This may be
// more frequently than the step_size we are monitoring (e.g. when there are
// multiple observers, or when page or space boundary is encountered.)
void AllocationStep(int bytes_allocated, Address soon_object, size_t size) {
bytes_to_next_step_ -= bytes_allocated;
if (bytes_to_next_step_ <= 0) {
Step(static_cast<int>(step_size_ - bytes_to_next_step_), soon_object,
step_size_ = GetNextStepSize();
bytes_to_next_step_ = step_size_;
intptr_t step_size() const { return step_size_; }
intptr_t bytes_to_next_step() const { return bytes_to_next_step_; }
// Pure virtual method provided by the subclasses that gets called when at
// least step_size bytes have been allocated. soon_object is the address just
// allocated (but not yet initialized.) size is the size of the object as
// requested (i.e. w/o the alignment fillers). Some complexities to be aware
// of:
// 1) soon_object will be nullptr in cases where we end up observing an
// allocation that happens to be a filler space (e.g. page boundaries.)
// 2) size is the requested size at the time of allocation. Right-trimming
// may change the object size dynamically.
// 3) soon_object may actually be the first object in an allocation-folding
// group. In such a case size is the size of the group rather than the
// first object.
virtual void Step(int bytes_allocated, Address soon_object, size_t size) = 0;
// Subclasses can override this method to make step size dynamic.
virtual intptr_t GetNextStepSize() { return step_size_; }
intptr_t step_size_;
intptr_t bytes_to_next_step_;
friend class LargeObjectSpace;
friend class NewSpace;
friend class PagedSpace;
} // namespace internal
} // namespace v8
#endif // V8_HEAP_HEAP_H_