blob: 3d8234f392a49e7ae43212ec954ccfead6a9970c [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>
#include <unordered_map>
#include <vector>
// 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/accessors.h"
#include "src/allocation.h"
#include "src/assert-scope.h"
#include "src/base/atomic-utils.h"
#include "src/globals.h"
#include "src/heap-symbols.h"
#include "src/objects.h"
#include "src/objects/code.h"
#include "src/objects/hash-table.h"
#include "src/objects/string-table.h"
#include "src/visitors.h"
namespace v8 {
namespace debug {
typedef void (*OutOfMemoryCallback)(void* data);
} // namespace debug
namespace internal {
namespace heap {
class HeapTester;
class TestMemoryAllocatorScope;
} // namespace heap
class BytecodeArray;
class CodeDataContainer;
class DeoptimizationData;
class HandlerTable;
class IncrementalMarking;
class JSArrayBuffer;
using v8::MemoryPressureLevel;
// Defines all the roots in Heap.
/* Cluster the most popular ones in a few cache lines here at the top. */ \
/* The first 32 entries are most often used in the startup snapshot and */ \
/* can use a shorter representation in the serialization format. */ \
V(Map, free_space_map, FreeSpaceMap) \
V(Map, one_pointer_filler_map, OnePointerFillerMap) \
V(Map, two_pointer_filler_map, TwoPointerFillerMap) \
V(Oddball, uninitialized_value, UninitializedValue) \
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(Map, meta_map, MetaMap) \
V(Map, byte_array_map, ByteArrayMap) \
V(Map, fixed_array_map, FixedArrayMap) \
V(Map, fixed_cow_array_map, FixedCOWArrayMap) \
V(Map, hash_table_map, HashTableMap) \
V(Map, symbol_map, SymbolMap) \
V(Map, one_byte_string_map, OneByteStringMap) \
V(Map, one_byte_internalized_string_map, OneByteInternalizedStringMap) \
V(Map, scope_info_map, ScopeInfoMap) \
V(Map, shared_function_info_map, SharedFunctionInfoMap) \
V(Map, code_map, CodeMap) \
V(Map, function_context_map, FunctionContextMap) \
V(Map, cell_map, CellMap) \
V(Map, weak_cell_map, WeakCellMap) \
V(Map, global_property_cell_map, GlobalPropertyCellMap) \
V(Map, foreign_map, ForeignMap) \
V(Map, heap_number_map, HeapNumberMap) \
V(Map, transition_array_map, TransitionArrayMap) \
V(Map, feedback_vector_map, FeedbackVectorMap) \
V(ScopeInfo, empty_scope_info, EmptyScopeInfo) \
V(FixedArray, empty_fixed_array, EmptyFixedArray) \
V(DescriptorArray, empty_descriptor_array, EmptyDescriptorArray) \
/* Entries beyond the first 32 */ \
/* 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. */ \
/* Oddballs */ \
V(Oddball, arguments_marker, ArgumentsMarker) \
V(Oddball, exception, Exception) \
V(Oddball, termination_exception, TerminationException) \
V(Oddball, optimized_out, OptimizedOut) \
V(Oddball, stale_register, StaleRegister) \
/* Context maps */ \
V(Map, native_context_map, NativeContextMap) \
V(Map, module_context_map, ModuleContextMap) \
V(Map, eval_context_map, EvalContextMap) \
V(Map, script_context_map, ScriptContextMap) \
V(Map, block_context_map, BlockContextMap) \
V(Map, catch_context_map, CatchContextMap) \
V(Map, with_context_map, WithContextMap) \
V(Map, debug_evaluate_context_map, DebugEvaluateContextMap) \
V(Map, script_context_table_map, ScriptContextTableMap) \
/* Maps */ \
V(Map, descriptor_array_map, DescriptorArrayMap) \
V(Map, array_list_map, ArrayListMap) \
V(Map, fixed_double_array_map, FixedDoubleArrayMap) \
V(Map, mutable_heap_number_map, MutableHeapNumberMap) \
V(Map, ordered_hash_map_map, OrderedHashMapMap) \
V(Map, ordered_hash_set_map, OrderedHashSetMap) \
V(Map, name_dictionary_map, NameDictionaryMap) \
V(Map, global_dictionary_map, GlobalDictionaryMap) \
V(Map, number_dictionary_map, NumberDictionaryMap) \
V(Map, string_table_map, StringTableMap) \
V(Map, weak_hash_table_map, WeakHashTableMap) \
V(Map, sloppy_arguments_elements_map, SloppyArgumentsElementsMap) \
V(Map, small_ordered_hash_map_map, SmallOrderedHashMapMap) \
V(Map, small_ordered_hash_set_map, SmallOrderedHashSetMap) \
V(Map, code_data_container_map, CodeDataContainerMap) \
V(Map, message_object_map, JSMessageObjectMap) \
V(Map, external_map, ExternalMap) \
V(Map, bytecode_array_map, BytecodeArrayMap) \
V(Map, module_info_map, ModuleInfoMap) \
V(Map, no_closures_cell_map, NoClosuresCellMap) \
V(Map, one_closure_cell_map, OneClosureCellMap) \
V(Map, many_closures_cell_map, ManyClosuresCellMap) \
V(Map, property_array_map, PropertyArrayMap) \
V(Map, bigint_map, BigIntMap) \
/* String maps */ \
V(Map, native_source_string_map, NativeSourceStringMap) \
V(Map, string_map, StringMap) \
V(Map, cons_one_byte_string_map, ConsOneByteStringMap) \
V(Map, cons_string_map, ConsStringMap) \
V(Map, thin_one_byte_string_map, ThinOneByteStringMap) \
V(Map, thin_string_map, ThinStringMap) \
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, 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) \
/* Array element maps */ \
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) \
/* Oddball maps */ \
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, exception_map, ExceptionMap) \
V(Map, termination_exception_map, TerminationExceptionMap) \
V(Map, optimized_out_map, OptimizedOutMap) \
V(Map, stale_register_map, StaleRegisterMap) \
/* Canonical empty values */ \
V(EnumCache, empty_enum_cache, EmptyEnumCache) \
V(PropertyArray, empty_property_array, EmptyPropertyArray) \
V(ByteArray, empty_byte_array, EmptyByteArray) \
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(Script, empty_script, EmptyScript) \
V(Cell, undefined_cell, UndefinedCell) \
V(FixedArray, empty_sloppy_arguments_elements, EmptySloppyArgumentsElements) \
V(NumberDictionary, empty_slow_element_dictionary, \
EmptySlowElementDictionary) \
V(FixedArray, empty_ordered_hash_map, EmptyOrderedHashMap) \
V(FixedArray, empty_ordered_hash_set, EmptyOrderedHashSet) \
V(PropertyCell, empty_property_cell, EmptyPropertyCell) \
V(WeakCell, empty_weak_cell, EmptyWeakCell) \
V(InterceptorInfo, noop_interceptor_info, NoOpInterceptorInfo) \
/* Protectors */ \
V(Cell, array_constructor_protector, ArrayConstructorProtector) \
V(PropertyCell, no_elements_protector, NoElementsProtector) \
V(Cell, is_concat_spreadable_protector, IsConcatSpreadableProtector) \
V(PropertyCell, species_protector, SpeciesProtector) \
V(Cell, string_length_protector, StringLengthProtector) \
V(Cell, fast_array_iteration_protector, FastArrayIterationProtector) \
V(PropertyCell, array_iterator_protector, ArrayIteratorProtector) \
V(PropertyCell, array_buffer_neutering_protector, \
ArrayBufferNeuteringProtector) \
/* Special numbers */ \
V(HeapNumber, nan_value, NanValue) \
V(HeapNumber, hole_nan_value, HoleNanValue) \
V(HeapNumber, infinity_value, InfinityValue) \
V(HeapNumber, minus_zero_value, MinusZeroValue) \
V(HeapNumber, minus_infinity_value, MinusInfinityValue) \
/* Caches */ \
V(FixedArray, number_string_cache, NumberStringCache) \
V(FixedArray, single_character_string_cache, SingleCharacterStringCache) \
V(FixedArray, string_split_cache, StringSplitCache) \
V(FixedArray, regexp_multiple_cache, RegExpMultipleCache) \
/* Lists and dictionaries */ \
V(NameDictionary, empty_property_dictionary, EmptyPropertyDictionary) \
V(NameDictionary, public_symbol_table, PublicSymbolTable) \
V(NameDictionary, api_symbol_table, ApiSymbolTable) \
V(NameDictionary, api_private_symbol_table, ApiPrivateSymbolTable) \
V(Object, script_list, ScriptList) \
V(NumberDictionary, code_stubs, CodeStubs) \
V(FixedArray, materialized_objects, MaterializedObjects) \
V(FixedArray, microtask_queue, MicrotaskQueue) \
V(FixedArray, detached_contexts, DetachedContexts) \
V(HeapObject, retaining_path_targets, RetainingPathTargets) \
V(ArrayList, retained_maps, RetainedMaps) \
V(WeakHashTable, weak_object_to_code_table, WeakObjectToCodeTable) \
/* weak_new_space_object_to_code_list is an array of weak cells, where */ \
/* slots with even indices refer to the weak object, and the subsequent */ \
/* slots refer to the code with the reference to the weak object. */ \
V(ArrayList, weak_new_space_object_to_code_list, \
WeakNewSpaceObjectToCodeList) \
/* Feedback vectors that we need for code coverage or type profile */ \
V(Object, feedback_vectors_for_profiling_tools, \
FeedbackVectorsForProfilingTools) \
V(Object, weak_stack_trace_list, WeakStackTraceList) \
V(Object, noscript_shared_function_infos, NoScriptSharedFunctionInfos) \
V(FixedArray, serialized_objects, SerializedObjects) \
V(FixedArray, serialized_global_proxy_sizes, SerializedGlobalProxySizes) \
V(TemplateList, message_listeners, MessageListeners) \
/* DeserializeLazy handlers for lazy bytecode deserialization */ \
V(Object, deserialize_lazy_handler, DeserializeLazyHandler) \
V(Object, deserialize_lazy_handler_wide, DeserializeLazyHandlerWide) \
V(Object, deserialize_lazy_handler_extra_wide, \
DeserializeLazyHandlerExtraWide) \
/* JS Entries */ \
V(Code, js_entry_code, JsEntryCode) \
V(Code, js_construct_entry_code, JsConstructEntryCode) \
V(Code, js_run_microtasks_entry_code, JsRunMicrotasksEntryCode)
// 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, hash_seed, HashSeed) \
/* To distinguish the function templates, so that we can find them in the */ \
/* function cache of the native context. */ \
V(Smi, next_template_serial_number, NextTemplateSerialNumber) \
V(Smi, arguments_adaptor_deopt_pc_offset, ArgumentsAdaptorDeoptPCOffset) \
V(Smi, construct_stub_create_deopt_pc_offset, \
ConstructStubCreateDeoptPCOffset) \
V(Smi, construct_stub_invoke_deopt_pc_offset, \
ConstructStubInvokeDeoptPCOffset) \
V(Smi, interpreter_entry_return_pc_offset, InterpreterEntryReturnPCOffset)
#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(ArgumentsMarker) \
V(ArgumentsMarkerMap) \
V(ArrayBufferNeuteringProtector) \
V(ArrayIteratorProtector) \
V(NoElementsProtector) \
V(BigIntMap) \
V(BlockContextMap) \
V(BooleanMap) \
V(ByteArrayMap) \
V(BytecodeArrayMap) \
V(CatchContextMap) \
V(CellMap) \
V(CodeMap) \
V(DescriptorArrayMap) \
V(EmptyByteArray) \
V(EmptyDescriptorArray) \
V(EmptyFixedArray) \
V(EmptyFixedFloat32Array) \
V(EmptyFixedFloat64Array) \
V(EmptyFixedInt16Array) \
V(EmptyFixedInt32Array) \
V(EmptyFixedInt8Array) \
V(EmptyFixedUint16Array) \
V(EmptyFixedUint32Array) \
V(EmptyFixedUint8Array) \
V(EmptyFixedUint8ClampedArray) \
V(EmptyOrderedHashMap) \
V(EmptyOrderedHashSet) \
V(EmptyPropertyCell) \
V(EmptyScopeInfo) \
V(EmptyScript) \
V(EmptySloppyArgumentsElements) \
V(EmptySlowElementDictionary) \
V(empty_string) \
V(EmptyWeakCell) \
V(EvalContextMap) \
V(Exception) \
V(FalseValue) \
V(FastArrayIterationProtector) \
V(FixedArrayMap) \
V(FixedCOWArrayMap) \
V(FixedDoubleArrayMap) \
V(ForeignMap) \
V(FreeSpaceMap) \
V(FunctionContextMap) \
V(GlobalDictionaryMap) \
V(GlobalPropertyCellMap) \
V(HashTableMap) \
V(HeapNumberMap) \
V(HoleNanValue) \
V(InfinityValue) \
V(IsConcatSpreadableProtector) \
V(JsConstructEntryCode) \
V(JsEntryCode) \
V(JSMessageObjectMap) \
V(ManyClosuresCellMap) \
V(MetaMap) \
V(MinusInfinityValue) \
V(MinusZeroValue) \
V(ModuleContextMap) \
V(ModuleInfoMap) \
V(MutableHeapNumberMap) \
V(NameDictionaryMap) \
V(NanValue) \
V(NativeContextMap) \
V(NoClosuresCellMap) \
V(NullMap) \
V(NullValue) \
V(NumberDictionaryMap) \
V(OneClosureCellMap) \
V(OnePointerFillerMap) \
V(OptimizedOut) \
V(OrderedHashMapMap) \
V(OrderedHashSetMap) \
V(PropertyArrayMap) \
V(ScopeInfoMap) \
V(ScriptContextMap) \
V(SharedFunctionInfoMap) \
V(SloppyArgumentsElementsMap) \
V(SmallOrderedHashMapMap) \
V(SmallOrderedHashSetMap) \
V(SpeciesProtector) \
V(StaleRegister) \
V(StringLengthProtector) \
V(StringTableMap) \
V(SymbolMap) \
V(TerminationException) \
V(TheHoleMap) \
V(TheHoleValue) \
V(TransitionArrayMap) \
V(TrueValue) \
V(TwoPointerFillerMap) \
V(UndefinedCell) \
V(UndefinedMap) \
V(UndefinedValue) \
V(UninitializedMap) \
V(UninitializedValue) \
V(WeakCellMap) \
V(WeakHashTableMap) \
V(WithContextMap) \
#define FIXED_ARRAY_ELEMENTS_WRITE_BARRIER(heap, array, start, length) \
do { \
heap->RecordFixedArrayElements(array, start, length); \
heap->incremental_marking()->RecordWrites(array); \
} while (false)
class AllocationObserver;
class ArrayBufferCollector;
class ArrayBufferTracker;
class ConcurrentMarking;
class GCIdleTimeAction;
class GCIdleTimeHandler;
class GCIdleTimeHeapState;
class GCTracer;
class HeapObjectsFilter;
class HeapStats;
class HistogramTimer;
class Isolate;
class LocalEmbedderHeapTracer;
class MemoryAllocator;
class MemoryReducer;
class MinorMarkCompactCollector;
class ObjectIterator;
class ObjectStats;
class Page;
class PagedSpace;
class RootVisitor;
class ScavengeJob;
class Scavenger;
class Space;
class StoreBuffer;
class StressScavengeObserver;
class TracePossibleWrapperReporter;
class WeakObjectRetainer;
typedef void (*ObjectSlotCallback)(HeapObject** from, HeapObject* to);
enum ArrayStorageAllocationMode {
enum class ClearRecordedSlots { kYes, kNo };
enum class FixedArrayVisitationMode { kRegular, kIncremental };
enum class TraceRetainingPathMode { kEnabled, kDisabled };
enum class RetainingPathOption { kDefault, kTrackEphemeralPath };
enum class GarbageCollectionReason {
kUnknown = 0,
kAllocationFailure = 1,
kAllocationLimit = 2,
kContextDisposal = 3,
kCountersExtension = 4,
kDebugger = 5,
kDeserializer = 6,
kExternalMemoryPressure = 7,
kFinalizeMarkingViaStackGuard = 8,
kFinalizeMarkingViaTask = 9,
kFullHashtable = 10,
kHeapProfiler = 11,
kIdleTask = 12,
kLastResort = 13,
kLowMemoryNotification = 14,
kMakeHeapIterable = 15,
kMemoryPressure = 16,
kMemoryReducer = 17,
kRuntime = 18,
kSamplingProfiler = 19,
kSnapshotCreator = 20,
kTesting = 21
// If you add new items here, then update the incremental_marking_reason,
// mark_compact_reason, and scavenge_reason counters in counters.h.
// Also update src/tools/metrics/histograms/histograms.xml in chromium.
enum class YoungGenerationHandling {
kRegularScavenge = 0,
kFastPromotionDuringScavenge = 1,
// Histogram::InspectConstructionArguments in chromium requires us to have at
// least three buckets.
kUnusedBucket = 2,
// If you add new items here, then update the young_generation_handling in
// counters.h.
// Also update src/tools/metrics/histograms/histograms.xml in chromium.
class AllocationResult {
static inline AllocationResult Retry(AllocationSpace space = NEW_SPACE) {
return AllocationResult(space);
// Implicit constructor from Object*.
AllocationResult(Object* object) // NOLINT
: object_(object) {
// AllocationResults can't return Smis, which are used to represent
// failure and the space to retry in.
AllocationResult() : object_(Smi::FromInt(NEW_SPACE)) {}
inline bool IsRetry() { return object_->IsSmi(); }
inline HeapObject* ToObjectChecked();
inline AllocationSpace RetrySpace();
template <typename T>
bool To(T** obj) {
if (IsRetry()) return false;
*obj = T::cast(object_);
return true;
explicit AllocationResult(AllocationSpace space)
: object_(Smi::FromInt(static_cast<int>(space))) {}
Object* object_;
STATIC_ASSERT(sizeof(AllocationResult) == kPointerSize);
#ifdef DEBUG
struct CommentStatistic {
const char* comment;
int size;
int count;
void Clear() {
comment = nullptr;
size = 0;
count = 0;
// Must be small, since an iteration is used for lookup.
static const int kMaxComments = 64;
class Heap {
// Declare all the root indices. This defines the root list order.
// clang-format off
enum RootListIndex {
#define DECL(type, name, camel_name) k##camel_name##RootIndex,
#undef DECL
#define DECL(name, str) k##name##RootIndex,
#undef DECL
#define DECL(name) k##name##RootIndex,
#undef DECL
#define DECL(name, description) k##name##RootIndex,
#undef DECL
#define DECL(accessor_name, AccessorName) k##AccessorName##AccessorRootIndex,
#undef DECL
#define DECL(NAME, Name, name) k##Name##MapRootIndex,
#undef DECL
#define DECL(NAME, Name, Size, name) k##Name##Size##MapRootIndex,
#undef DECL
#define DECL(type, name, camel_name) k##camel_name##RootIndex,
#undef DECL
kStrongRootListLength = kStringTableRootIndex,
kSmiRootsStart = kStringTableRootIndex + 1
// clang-format on
enum FindMementoMode { kForRuntime, kForGC };
using PretenuringFeedbackMap = std::unordered_map<AllocationSite*, size_t>;
// Taking this mutex prevents the GC from entering a phase that relocates
// object references.
base::Mutex* relocation_mutex() { return &relocation_mutex_; }
// 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 std::vector<Chunk> Reservation;
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;
// Semi-space size needs to be a multiple of page size.
static const int kMinSemiSpaceSizeInKB =
1 * kPointerMultiplier * ((1 << kPageSizeBits) / KB);
static const int kMaxSemiSpaceSizeInKB =
16 * kPointerMultiplier * ((1 << kPageSizeBits) / KB);
// The old space size has to be a multiple of Page::kPageSize.
// Sizes are in MB.
static const int kMinOldGenerationSize = 128 * kPointerMultiplier;
static const int kMaxOldGenerationSize = 1024 * kPointerMultiplier;
static const int kTraceRingBufferSize = 512;
static const int kStacktraceBufferSize = 512;
V8_EXPORT_PRIVATE static const double kMinHeapGrowingFactor;
V8_EXPORT_PRIVATE static const double kMaxHeapGrowingFactor;
static const double kMaxHeapGrowingFactorMemoryConstrained;
static const double kMaxHeapGrowingFactorIdle;
static const double kConservativeHeapGrowingFactor;
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 const int kMinPromotedPercentForFastPromotionMode = 90;
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);
V8_EXPORT_PRIVATE 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 inline bool IsYoungGenerationCollector(GarbageCollector collector) {
return collector == SCAVENGER || collector == MINOR_MARK_COMPACTOR;
static inline GarbageCollector YoungGenerationCollector() {
static inline const char* CollectorName(GarbageCollector collector) {
switch (collector) {
return "Scavenger";
return "Mark-Compact";
return "Minor Mark-Compact";
return "Unknown collector";
V8_EXPORT_PRIVATE static double MaxHeapGrowingFactor(
size_t max_old_generation_size);
V8_EXPORT_PRIVATE static double HeapGrowingFactor(double gc_speed,
double mutator_speed,
double max_factor);
// 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);
// Notifies the heap that is ok to start marking or other activities that
// should not happen during deserialization.
void NotifyDeserializationComplete();
inline Address* NewSpaceAllocationTopAddress();
inline Address* NewSpaceAllocationLimitAddress();
inline Address* OldSpaceAllocationTopAddress();
inline Address* OldSpaceAllocationLimitAddress();
// 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.
V8_EXPORT_PRIVATE HeapObject* CreateFillerObjectAt(Address addr, int size,
ClearRecordedSlots mode);
bool CanMoveObjectStart(HeapObject* object);
static bool IsImmovable(HeapObject* object);
// 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.
void RightTrimFixedArray(FixedArrayBase* obj, int elements_to_trim);
// Converts the given boolean condition to JavaScript boolean value.
inline Oddball* ToBoolean(bool condition);
// 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 IterateEncounteredWeakCollections(RootVisitor* visitor);
// 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.
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();
bool write_protect_code_memory() const { return write_protect_code_memory_; }
uintptr_t code_space_memory_modification_scope_depth() {
return code_space_memory_modification_scope_depth_;
void increment_code_space_memory_modification_scope_depth() {
void decrement_code_space_memory_modification_scope_depth() {
inline HeapState gc_state() { return gc_state_; }
void SetGCState(HeapState state);
inline bool IsInGCPostProcessing() { return gc_post_processing_depth_ > 0; }
// If an object has an AllocationMemento trailing it, return it, otherwise
// return nullptr;
template <FindMementoMode mode>
inline AllocationMemento* FindAllocationMemento(Map* map, HeapObject* object);
// Returns false if not able to reserve.
bool ReserveSpace(Reservation* reservations, std::vector<Address>* maps);
// 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();
void SetOutOfMemoryCallback(v8::debug::OutOfMemoryCallback callback,
void* data);
double MonotonicallyIncreasingTimeInMs();
void RecordStats(HeapStats* stats, bool take_snapshot = false);
// Check new space expansion criteria and expand semispaces if it was hit.
void CheckNewSpaceExpansionCriteria();
void VisitExternalResources(v8::ExternalResourceVisitor* visitor);
// An object should be promoted if the object has survived a
// scavenge operation.
inline bool ShouldBePromoted(Address old_address);
void IncrementDeferredCount(v8::Isolate::UseCounterFeature feature);
inline uint32_t HashSeed();
inline int NextScriptId();
inline int GetNextTemplateSerialNumber();
void SetSerializedObjects(FixedArray* objects);
void SetSerializedGlobalProxySizes(FixedArray* sizes);
// For post mortem debugging.
void RememberUnmappedPage(Address page, bool compacted);
int64_t external_memory_hard_limit() { return MaxOldGenerationSize() / 2; }
int64_t external_memory() { return external_memory_; }
void update_external_memory(int64_t delta) { external_memory_ += delta; }
void update_external_memory_concurrently_freed(intptr_t freed) {
void account_external_memory_concurrently_freed() {
external_memory_ -= external_memory_concurrently_freed_.Value();
void AddWeakNewSpaceObjectToCodeDependency(Handle<HeapObject> obj,
Handle<WeakCell> code);
void AddWeakObjectToCodeDependency(Handle<HeapObject> obj,
Handle<DependentCode> dep);
DependentCode* LookupWeakObjectToCodeDependency(Handle<HeapObject> obj);
void CompactWeakFixedArrays();
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.
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(size_t used, size_t committed);
void ActivateMemoryReducerIfNeeded();
bool ShouldOptimizeForMemoryUsage();
bool HighMemoryPressure() {
return memory_pressure_level_.Value() != MemoryPressureLevel::kNone;
size_t HeapLimitForDebugging() {
const size_t kDebugHeapSizeFactor = 4;
size_t max_limit = std::numeric_limits<size_t>::max() / 4;
return Min(max_limit,
initial_max_old_generation_size_ * kDebugHeapSizeFactor);
void IncreaseHeapLimitForDebugging() {
max_old_generation_size_ =
Max(max_old_generation_size_, HeapLimitForDebugging());
void RestoreOriginalHeapLimit() {
// Do not set the limit lower than the live size + some slack.
size_t min_limit = SizeOfObjects() + SizeOfObjects() / 4;
max_old_generation_size_ =
Max(initial_max_old_generation_size_, min_limit));
bool IsHeapLimitIncreasedForDebugging() {
return max_old_generation_size_ == HeapLimitForDebugging();
// ===========================================================================
// Initialization. ===========================================================
// ===========================================================================
// Configure heap sizes
// max_semi_space_size_in_kb: maximum semi-space size in KB
// max_old_generation_size_in_mb: maximum old generation size in MB
// code_range_size_in_mb: code range size in MB
// Return false if the heap has been set up already.
bool ConfigureHeap(size_t max_semi_space_size_in_kb,
size_t max_old_generation_size_in_mb,
size_t code_range_size_in_mb);
bool ConfigureHeapDefault();
// Prepares the heap, setting up memory areas that are needed in the isolate
// without actually creating any objects.
bool SetUp();
// (Re-)Initialize hash seed from flag or RNG.
void InitializeHashSeed();
// Bootstraps the object heap with the core set of objects required to run.
// Returns whether it succeeded.
bool CreateHeapObjects();
// Create ObjectStats if live_object_stats_ or dead_object_stats_ are nullptr.
void CreateObjectStats();
// Destroys all memory allocated by the heap.
void TearDown();
// Returns whether SetUp has been called.
bool HasBeenSetUp();
bool use_tasks() const { return use_tasks_; }
// ===========================================================================
// Getters for spaces. =======================================================
// ===========================================================================
inline Address NewSpaceTop();
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_; }
inline PagedSpace* paged_space(int idx);
inline Space* space(int 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_; }
inline Isolate* isolate();
MarkCompactCollector* mark_compact_collector() {
return mark_compact_collector_;
MinorMarkCompactCollector* minor_mark_compact_collector() {
return minor_mark_compact_collector_;
ArrayBufferCollector* array_buffer_collector() {
return array_buffer_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 DATA_HANDLER_MAP_ACCESSOR(NAME, Name, Size, 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();
#define ACCESSOR_INFO_ACCESSOR(accessor_name, AccessorName) \
inline AccessorInfo* accessor_name##_accessor();
Object* root(RootListIndex index) { return roots_[index]; }
Handle<Object> root_handle(RootListIndex index) {
return Handle<Object>(&roots_[index]);
template <typename T>
bool IsRootHandle(Handle<T> handle, RootListIndex* index) const {
Object** const handle_location = bit_cast<Object**>(handle.address());
if (handle_location >= &roots_[kRootListLength]) return false;
if (handle_location < &roots_[0]) return false;
*index = static_cast<RootListIndex>(handle_location - &roots_[0]);
return true;
// 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(NumberDictionary* 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;
void SetMessageListeners(TemplateList* value) {
roots_[kMessageListenersRootIndex] = 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(const Map* map);
void RegisterStrongRoots(Object** start, Object** end);
void UnregisterStrongRoots(Object** start);
bool IsDeserializeLazyHandler(Code* code);
void SetDeserializeLazyHandler(Code* code);
void SetDeserializeLazyHandlerWide(Code* code);
void SetDeserializeLazyHandlerExtraWide(Code* code);
// ===========================================================================
// 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.
bool CollectGarbage(
AllocationSpace space, GarbageCollectionReason gc_reason,
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, GarbageCollectionReason gc_reason,
const GCCallbackFlags gc_callback_flags = kNoGCCallbackFlags);
// Last hope GC, should try to squeeze as much as possible.
void CollectAllAvailableGarbage(GarbageCollectionReason gc_reason);
// Reports and external memory pressure event, either performs a major GC or
// completes incremental marking in order to free external resources.
void ReportExternalMemoryPressure();
typedef v8::Isolate::GetExternallyAllocatedMemoryInBytesCallback
void SetGetExternallyAllocatedMemoryInBytesCallback(
GetExternallyAllocatedMemoryInBytesCallback callback) {
external_memory_callback_ = callback;
// Invoked when GC was requested via the stack guard.
void HandleGCRequest();
// ===========================================================================
// Iterators. ================================================================
// ===========================================================================
// Iterates over all roots in the heap.
void IterateRoots(RootVisitor* v, VisitMode mode);
// Iterates over all strong roots in the heap.
void IterateStrongRoots(RootVisitor* 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(RootVisitor* v);
// Iterates over all the other roots in the heap.
void IterateWeakRoots(RootVisitor* v, VisitMode mode);
// ===========================================================================
// Store buffer API. =========================================================
// ===========================================================================
// Write barrier support for object[offset] = o;
inline void RecordWrite(Object* object, Object** slot, Object* value);
inline void RecordWriteIntoCode(Code* host, RelocInfo* rinfo, Object* target);
void RecordWriteIntoCodeSlow(Code* host, RelocInfo* rinfo, Object* target);
void RecordWritesIntoCode(Code* code);
inline void RecordFixedArrayElements(FixedArray* array, int offset,
int length);
// Used for query incremental marking status in generated code.
Address* IsMarkingFlagAddress() {
return reinterpret_cast<Address*>(&is_marking_flag_);
void SetIsMarkingFlag(uint8_t flag) { is_marking_flag_ = flag; }
inline Address* store_buffer_top_address();
void ClearRecordedSlot(HeapObject* object, Object** slot);
void ClearRecordedSlotRange(Address start, Address end);
bool HasRecordedSlot(HeapObject* object, Object** slot);
// ===========================================================================
// Incremental marking API. ==================================================
// ===========================================================================
// Start incremental marking and ensure that idle time handler can perform
// incremental steps.
void StartIdleIncrementalMarking(
GarbageCollectionReason gc_reason,
GCCallbackFlags gc_callback_flags = GCCallbackFlags::kNoGCCallbackFlags);
// Starts incremental marking assuming incremental marking is currently
// stopped.
void StartIncrementalMarking(
int gc_flags, GarbageCollectionReason gc_reason,
GCCallbackFlags gc_callback_flags = GCCallbackFlags::kNoGCCallbackFlags);
void StartIncrementalMarkingIfAllocationLimitIsReached(
int gc_flags,
GCCallbackFlags gc_callback_flags = GCCallbackFlags::kNoGCCallbackFlags);
void FinalizeIncrementalMarkingIfComplete(GarbageCollectionReason gc_reason);
void RegisterDeserializedObjectsForBlackAllocation(
Reservation* reservations, const std::vector<HeapObject*>& large_objects,
const std::vector<Address>& maps);
IncrementalMarking* incremental_marking() { return incremental_marking_; }
// ===========================================================================
// Concurrent marking API. ===================================================
// ===========================================================================
ConcurrentMarking* concurrent_marking() { return concurrent_marking_; }
// The runtime uses this function to notify potentially unsafe object layout
// changes that require special synchronization with the concurrent marker.
// The old size is the size of the object before layout change.
void NotifyObjectLayoutChange(HeapObject* object, int old_size,
const DisallowHeapAllocation&);
// This function checks that either
// - the map transition is safe,
// - or it was communicated to GC using NotifyObjectLayoutChange.
void VerifyObjectLayoutChange(HeapObject* object, Map* new_map);
// ===========================================================================
// Deoptimization support API. ===============================================
// ===========================================================================
// Setters for code offsets of well-known deoptimization targets.
void SetArgumentsAdaptorDeoptPCOffset(int pc_offset);
void SetConstructStubCreateDeoptPCOffset(int pc_offset);
void SetConstructStubInvokeDeoptPCOffset(int pc_offset);
void SetInterpreterEntryReturnPCOffset(int pc_offset);
// Invalidates references in the given {code} object that are directly
// embedded within the instruction stream. Mutates write-protected code.
void InvalidateCodeEmbeddedObjects(Code* code);
// Invalidates references in the given {code} object that are referenced
// transitively from the deoptimization data. Mutates write-protected code.
void InvalidateCodeDeoptimizationData(Code* code);
void DeoptMarkedAllocationSites();
bool DeoptMaybeTenuredAllocationSites();
// ===========================================================================
// Embedder heap tracer support. =============================================
// ===========================================================================
LocalEmbedderHeapTracer* local_embedder_heap_tracer() {
return local_embedder_heap_tracer_;
void SetEmbedderHeapTracer(EmbedderHeapTracer* tracer);
void TracePossibleWrapper(JSObject* js_object);
void RegisterExternallyReferencedObject(Object** object);
// ===========================================================================
// 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);
// The total number of native contexts object on the heap.
size_t NumberOfNativeContexts();
// The total number of native contexts that were detached but were not
// garbage collected yet.
size_t NumberOfDetachedContexts();
// ===========================================================================
// Code statistics. ==========================================================
// ===========================================================================
// Collect code (Code and BytecodeArray objects) statistics.
void CollectCodeStatistics();
// ===========================================================================
// GC statistics. ============================================================
// ===========================================================================
// Returns the maximum amount of memory reserved for the heap.
size_t MaxReserved() {
return 2 * max_semi_space_size_ + max_old_generation_size_;
size_t MaxSemiSpaceSize() { return max_semi_space_size_; }
size_t InitialSemiSpaceSize() { return initial_semispace_size_; }
size_t MaxOldGenerationSize() { return max_old_generation_size_; }
static size_t ComputeMaxOldGenerationSize(uint64_t physical_memory) {
const int old_space_physical_memory_factor = 4;
int computed_size =
static_cast<int>(physical_memory / i::MB /
old_space_physical_memory_factor * kPointerMultiplier);
return Max(Min(computed_size, kMaxOldGenerationSize),
static size_t ComputeMaxSemiSpaceSize(uint64_t physical_memory) {
const uint64_t min_physical_memory = 512 * MB;
const uint64_t max_physical_memory = 3 * static_cast<uint64_t>(GB);
uint64_t capped_physical_memory =
Max(Min(physical_memory, max_physical_memory), min_physical_memory);
// linearly scale max semi-space size: (X-A)/(B-A)*(D-C)+C
int semi_space_size_in_kb =
static_cast<int>(((capped_physical_memory - min_physical_memory) *
(kMaxSemiSpaceSizeInKB - kMinSemiSpaceSizeInKB)) /
(max_physical_memory - min_physical_memory) +
return RoundUp(semi_space_size_in_kb, (1 << kPageSizeBits) / KB);
// Returns the capacity of the heap in bytes w/o growing. Heap grows when
// more spaces are needed until it reaches the limit.
size_t Capacity();
// Returns the capacity of the old generation.
size_t OldGenerationCapacity();
// Returns the amount of memory currently committed for the heap.
size_t CommittedMemory();
// Returns the amount of memory currently committed for the old space.
size_t CommittedOldGenerationMemory();
// Returns the amount of executable memory currently committed for the heap.
size_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.
size_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.
size_t Available();
// Returns of size of all objects residing in the heap.
size_t SizeOfObjects();
void UpdateSurvivalStatistics(int start_new_space_size);
inline void IncrementPromotedObjectsSize(size_t object_size) {
promoted_objects_size_ += object_size;
inline size_t promoted_objects_size() { return promoted_objects_size_; }
inline void IncrementSemiSpaceCopiedObjectSize(size_t object_size) {
semi_space_copied_object_size_ += object_size;
inline size_t semi_space_copied_object_size() {
return semi_space_copied_object_size_;
inline size_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(size_t survived) {
survived_last_scavenge_ = survived;
survived_since_last_expansion_ += survived;
inline uint64_t PromotedTotalSize() {
return PromotedSpaceSizeOfObjects() + PromotedExternalMemorySize();
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_at_last_gc_ =
old_generation_size_at_last_gc_ = 0;
size_t OldGenerationAllocationCounter() {
return old_generation_allocation_counter_at_last_gc_ +
// This should be used only for testing.
void set_old_generation_allocation_counter_at_last_gc(size_t new_value) {
old_generation_allocation_counter_at_last_gc_ = new_value;
size_t PromotedSinceLastGC() {
size_t old_generation_size = PromotedSpaceSizeOfObjects();
DCHECK_GE(old_generation_size, old_generation_size_at_last_gc_);
return old_generation_size - old_generation_size_at_last_gc_;
// This is called by the sweeper when it discovers more free space
// as expected at the end of the last GC.
void NotifyRefinedOldGenerationSize(size_t decreased_bytes) {
if (old_generation_size_at_last_gc_ != 0) {
// PromotedSpaceSizeOfObjects() is now smaller by |decreased_bytes|.
// Adjust old_generation_size_at_last_gc_ too so that PromotedSinceLastGC
// stay monotonically non-decreasing function.
DCHECK_GE(old_generation_size_at_last_gc_, decreased_bytes);
old_generation_size_at_last_gc_ -= decreased_bytes;
int gc_count() const { return gc_count_; }
// Returns the size of objects residing in non new spaces.
size_t PromotedSpaceSizeOfObjects();
// ===========================================================================
// Prologue/epilogue callback methods.========================================
// ===========================================================================
void AddGCPrologueCallback(v8::Isolate::GCCallbackWithData callback,
GCType gc_type_filter, void* data);
void RemoveGCPrologueCallback(v8::Isolate::GCCallbackWithData callback,
void* data);
void AddGCEpilogueCallback(v8::Isolate::GCCallbackWithData callback,
GCType gc_type_filter, void* data);
void RemoveGCEpilogueCallback(v8::Isolate::GCCallbackWithData callback,
void* data);
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. =====================================================
// ===========================================================================
// TODO(gc): API usability: encapsulate mutation of JSArrayBuffer::is_external
// in the registration/unregistration APIs. Consider dropping the "New" from
// "RegisterNewArrayBuffer" because one can re-register a previously
// unregistered buffer, too, and the name is confusing.
void RegisterNewArrayBuffer(JSArrayBuffer* buffer);
void UnregisterArrayBuffer(JSArrayBuffer* buffer);
// ===========================================================================
// Allocation site tracking. =================================================
// ===========================================================================
// Updates the AllocationSite of a given {object}. The entry (including the
// count) is cached on the local pretenuring feedback.
inline void UpdateAllocationSite(
Map* map, HeapObject* object,
PretenuringFeedbackMap* pretenuring_feedback);
// 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 PretenuringFeedbackMap& local_pretenuring_feedback);
// ===========================================================================
// Allocation tracking. ======================================================
// ===========================================================================
// Adds {new_space_observer} to new space and {observer} to any other space.
void AddAllocationObserversToAllSpaces(
AllocationObserver* observer, AllocationObserver* new_space_observer);
// Removes {new_space_observer} from new space and {observer} from any other
// space.
void RemoveAllocationObserversFromAllSpaces(
AllocationObserver* observer, AllocationObserver* new_space_observer);
// ===========================================================================
// Retaining path tracking. ==================================================
// ===========================================================================
// Adds the given object to the weak table of retaining path targets.
// On each GC if the marker discovers the object, it will print the retaining
// path. This requires --track-retaining-path flag.
void AddRetainingPathTarget(Handle<HeapObject> object,
RetainingPathOption option);
// ===========================================================================
// Stack frame support. ======================================================
// ===========================================================================
// Returns the Code object for a given interior pointer. Returns nullptr if
// {inner_pointer} is not contained within a Code object.
Code* GcSafeFindCodeForInnerPointer(Address inner_pointer);
// Returns true if {addr} is contained within {code} and false otherwise.
// Mostly useful for debugging.
bool GcSafeCodeContains(HeapObject* code, Address addr);
// =============================================================================
// Verify the heap is in its normal state before or after a GC.
void Verify();
void VerifyRememberedSetFor(HeapObject* object);
void set_allocation_timeout(int timeout) { allocation_timeout_ = timeout; }
#ifdef DEBUG
void VerifyCountersAfterSweeping();
void VerifyCountersBeforeConcurrentSweeping();
void Print();
void PrintHandles();
// Report code statistics.
void ReportCodeStatistics(const char* title);
void* GetRandomMmapAddr() {
void* result = v8::internal::GetRandomMmapAddr();
// The Darwin kernel [as of macOS 10.12.5] does not clean up page
// directory entries [PDE] created from mmap or mach_vm_allocate, even
// after the region is destroyed. Using a virtual address space that is
// too large causes a leak of about 1 wired [can never be paged out] page
// per call to mmap(). The page is only reclaimed when the process is
// killed. Confine the hint to a 32-bit section of the virtual address
// space. See
uintptr_t offset =
reinterpret_cast<uintptr_t>(v8::internal::GetRandomMmapAddr()) &
result = reinterpret_cast<void*>(mmap_region_base_ + offset);
#endif // V8_OS_MACOSX
#endif // V8_TARGET_ARCH_X64
return result;
static const char* GarbageCollectionReasonToString(
GarbageCollectionReason gc_reason);
class SkipStoreBufferScope;
typedef String* (*ExternalStringTableUpdaterCallback)(Heap* heap,
Object** pointer);
// 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 {
explicit ExternalStringTable(Heap* heap) : heap_(heap) {}
// Registers an external string.
inline void AddString(String* string);
void IterateAll(RootVisitor* v);
void IterateNewSpaceStrings(RootVisitor* v);
void PromoteAllNewSpaceStrings();
// Restores internal invariant and gets rid of collected strings. Must be
// called after each Iterate*() that modified the strings.
void CleanUpAll();
void CleanUpNewSpaceStrings();
// Finalize all registered external strings and clear tables.
void TearDown();
void UpdateNewSpaceReferences(
Heap::ExternalStringTableUpdaterCallback updater_func);
void UpdateReferences(
Heap::ExternalStringTableUpdaterCallback updater_func);
void Verify();
Heap* const heap_;
// To speed up scavenge collections new space string are kept
// separate from old space strings.
std::vector<Object*> new_space_strings_;
std::vector<Object*> old_space_strings_;
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 GCCallbackTuple {
GCCallbackTuple(v8::Isolate::GCCallbackWithData callback, GCType gc_type,
void* data)
: callback(callback), gc_type(gc_type), data(data) {}
bool operator==(const GCCallbackTuple& other) const;
GCCallbackTuple& operator=(const GCCallbackTuple& other);
v8::Isolate::GCCallbackWithData callback;
GCType gc_type;
void* data;
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 const int kMaxScavengerTasks = 8;
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;
static size_t DefaultGetExternallyAllocatedMemoryInBytesCallback() {
return 0;
#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) != 0;
inline bool ShouldAbortIncrementalMarking() const {
return (current_gc_flags_ & kAbortIncrementalMarkingMask) != 0;
inline bool ShouldFinalizeIncrementalMarking() const {
return (current_gc_flags_ & kFinalizeIncrementalMarkingMask) != 0;
int NumberOfScavengeTasks();
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
// 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, Object* 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 CreateInternalAccessorInfoObjects();
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());
NO_INLINE(void CreateJSRunMicrotasksEntryStub());
void CreateFixedStubs();
// Commits from space if it is uncommitted.
void EnsureFromSpaceIsCommitted();
// Uncommit unused semi space.
bool 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 after garbage collection.
void ReportStatisticsAfterGC();
// Creates and installs the full-sized number string cache.
int FullSizeNumberStringCacheLength();
// Flush the number to string cache.
void FlushNumberStringCache();
void ConfigureInitialOldGenerationSize();
bool HasLowYoungGenerationAllocationRate();
bool HasLowOldGenerationAllocationRate();
double YoungGenerationMutatorUtilization();
double OldGenerationMutatorUtilization();
void ReduceNewSpaceSize();
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);
int NextAllocationTimeout(int current_timeout = 0);
inline void UpdateAllocationsHash(HeapObject* object);
inline void UpdateAllocationsHash(uint32_t value);
void PrintAllocationsHash();
void PrintMaxMarkingLimitReached();
void PrintMaxNewSpaceSizeReached();
int NextStressMarkingLimit();
void AddToRingBuffer(const char* string);
void GetFromRingBuffer(char* buffer);
void CompactRetainedMaps(ArrayList* retained_maps);
void CollectGarbageOnMemoryPressure();
void InvokeOutOfMemoryCallback();
void ComputeFastPromotionMode(double survival_rate);
// 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(GarbageCollectionReason 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();
// Removes an entry from the global pretenuring storage.
void RemoveAllocationSitePretenuringFeedback(AllocationSite* site);
// ===========================================================================
// 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();
// Performs a minor collection of just the young generation.
void MinorMarkCompact();
// Code to be run before and after mark-compact.
void MarkCompactPrologue();
void MarkCompactEpilogue();
// Performs a minor collection in new generation.
void Scavenge();
void EvacuateYoungGeneration();
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 size_t OldGenerationSpaceAvailable() {
if (old_generation_allocation_limit_ <= PromotedTotalSize()) return 0;
return old_generation_allocation_limit_ -
// We allow incremental marking to overshoot the allocation limit for
// performace reasons. If the overshoot is too large then we are more
// eager to finalize incremental marking.
inline bool AllocationLimitOvershotByLargeMargin() {
// This guards against too eager finalization in small heaps.
// The number is chosen based on v8.browsing_mobile on Nexus 7v2.
size_t kMarginForSmallHeaps = 32u * MB;
if (old_generation_allocation_limit_ >= PromotedTotalSize()) return false;
uint64_t overshoot = PromotedTotalSize() - old_generation_allocation_limit_;
// Overshoot margin is 50% of allocation limit or half-way to the max heap
// with special handling of small heaps.
uint64_t margin =
Min(Max(old_generation_allocation_limit_ / 2, kMarginForSmallHeaps),
(max_old_generation_size_ - old_generation_allocation_limit_) / 2);
return overshoot >= margin;
void UpdateTotalGCTime(double duration);
bool MaximumSizeScavenge() { return maximum_size_scavenges_ > 0; }
// ===========================================================================
// Growing strategy. =========================================================
// ===========================================================================
// For some webpages RAIL mode does not switch from PERFORMANCE_LOAD.
// This constant limits the effect of load RAIL mode on GC.
// The value is arbitrary and chosen as the largest load time observed in
// v8 browsing benchmarks.
static const int kMaxLoadTimeMs = 7000;
bool ShouldOptimizeForLoadTime();
// Decrease the allocation limit if the new limit based on the given
// parameters is lower than the current limit.
void DampenOldGenerationAllocationLimit(size_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.
size_t CalculateOldGenerationAllocationLimit(double factor,
size_t old_gen_size);
// Sets the allocation limit to trigger the next full garbage collection.
void SetOldGenerationAllocationLimit(size_t old_gen_size, double gc_speed,
double mutator_speed);
size_t MinimumAllocationLimitGrowingStep();
size_t old_generation_allocation_limit() const {
return old_generation_allocation_limit_;
bool always_allocate() { return always_allocate_scope_count_.Value() != 0; }
bool CanExpandOldGeneration(size_t size);
bool IsCloseToOutOfMemory(size_t slack) {
return OldGenerationCapacity() + slack >= MaxOldGenerationSize();
bool ShouldExpandOldGenerationOnSlowAllocation();
enum class IncrementalMarkingLimit { kNoLimit, kSoftLimit, kHardLimit };
IncrementalMarkingLimit IncrementalMarkingLimitReached();
// ===========================================================================
// 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 = nullptr);
// 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,
int inobject_properties = 0);
// 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 = nullptr);
// 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 = nullptr);
// Allocates a HeapNumber from value.
MUST_USE_RESULT AllocationResult AllocateHeapNumber(
MutableMode mode = IMMUTABLE, PretenureFlag pretenure = NOT_TENURED);
MUST_USE_RESULT AllocationResult AllocateBigInt(int length);
// 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);
MUST_USE_RESULT AllocationResult CopyCode(Code* code,
CodeDataContainer* data_container);
MUST_USE_RESULT AllocationResult
CopyBytecodeArray(BytecodeArray* bytecode_array);
// Allocates a fixed array-like object with given map and initialized with
// undefined values.
MUST_USE_RESULT inline AllocationResult AllocateFixedArrayWithMap(
RootListIndex map_root_index, int length,
PretenureFlag pretenure = NOT_TENURED);
// Allocates a fixed array initialized with undefined values
MUST_USE_RESULT inline AllocationResult AllocateFixedArray(
int length, PretenureFlag pretenure = NOT_TENURED);
// Allocates a property array initialized with undefined values
MUST_USE_RESULT AllocationResult
AllocatePropertyArray(int length, PretenureFlag pretenure = NOT_TENURED);
// Allocate a feedback vector for the given shared function info. The slots
// are pre-filled with undefined.
MUST_USE_RESULT AllocationResult
AllocateFeedbackVector(SharedFunctionInfo* shared, PretenureFlag pretenure);
// Allocate an uninitialized feedback vector.
MUST_USE_RESULT AllocationResult
AllocateRawFeedbackVector(int length, PretenureFlag pretenure);
MUST_USE_RESULT AllocationResult AllocateSmallOrderedHashSet(
int length, PretenureFlag pretenure = NOT_TENURED);
MUST_USE_RESULT AllocationResult AllocateSmallOrderedHashMap(
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 = nullptr);
// 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(RootListIndex map_root_index, 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, PretenureFlag pretenure = NOT_TENURED);
// 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.
template <typename T>
MUST_USE_RESULT AllocationResult CopyArrayAndGrow(T* src, int grow_by,
PretenureFlag pretenure);
// Make a copy of src, also grow the copy, and return the copy.
MUST_USE_RESULT AllocationResult CopyPropertyArrayAndGrow(
PropertyArray* 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.
template <typename T>
MUST_USE_RESULT AllocationResult CopyArrayWithMap(T* src, Map* map);
// 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, set the map, and return the copy.
MUST_USE_RESULT AllocationResult CopyPropertyArray(PropertyArray* src);
// Make a copy of src and return it.
MUST_USE_RESULT inline AllocationResult CopyFixedDoubleArray(
FixedDoubleArray* src);
// Make a copy of src and return it.
MUST_USE_RESULT AllocationResult CopyFeedbackVector(FeedbackVector* 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 scope info.
MUST_USE_RESULT AllocationResult AllocateEmptyScopeInfo();
// 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(Name* name);
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, PretenureFlag pretenure = NOT_TENURED);
// Allocates a new foreign object.
MUST_USE_RESULT AllocationResult
AllocateForeign(Address address, PretenureFlag pretenure = NOT_TENURED);
// Allocates a new code object (mostly uninitialized). Can only be used when
// code space is unprotected and requires manual initialization by the caller.
MUST_USE_RESULT AllocationResult AllocateCode(int object_size,
Movability movability);
// Allocates a new code object (fully initialized). All header fields of the
// returned object are immutable and the code object is write protected.
MUST_USE_RESULT AllocationResult
AllocateCode(const CodeDesc& desc, Code::Kind kind, Handle<Object> self_ref,
int32_t builtin_index, ByteArray* reloc_info,
CodeDataContainer* data_container, HandlerTable* handler_table,
ByteArray* source_position_table, DeoptimizationData* deopt_data,
Movability movability, uint32_t stub_key, bool is_turbofanned,
int stack_slots, int safepoint_table_offset);
void set_force_oom(bool value) { force_oom_ = value; }
// ===========================================================================
// Retaining path tracing ====================================================
// ===========================================================================
void AddRetainer(HeapObject* retainer, HeapObject* object);
void AddEphemeralRetainer(HeapObject* retainer, HeapObject* object);
void AddRetainingRoot(Root root, HeapObject* object);
// Returns true if the given object is a target of retaining path tracking.
// Stores the option corresponding to the object in the provided *option.
bool IsRetainingPathTarget(HeapObject* object, RetainingPathOption* option);
void PrintRetainingPath(HeapObject* object, RetainingPathOption option);
// The amount of external memory registered through the API.
int64_t external_memory_;
// The limit when to trigger memory pressure from the API.
int64_t external_memory_limit_;
// Caches the amount of external memory registered at the last MC.
int64_t external_memory_at_last_mark_compact_;
// The amount of memory that has been freed concurrently.
base::AtomicNumber<intptr_t> external_memory_concurrently_freed_;
// 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_;
size_t max_semi_space_size_;
size_t initial_semispace_size_;
size_t max_old_generation_size_;
size_t initial_max_old_generation_size_;
size_t initial_old_generation_size_;
bool old_generation_size_configured_;
size_t maximum_committed_;
// For keeping track of how much data has survived
// scavenge since last new space expansion.
size_t survived_since_last_expansion_;
// ... and since the last scavenge.
size_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).
base::AtomicNumber<size_t> always_allocate_scope_count_;
// Stores the memory pressure level that set by MemoryPressureNotification
// and reset by a mark-compact garbage collection.
base::AtomicValue<MemoryPressureLevel> memory_pressure_level_;
v8::debug::OutOfMemoryCallback out_of_memory_callback_;
void* out_of_memory_callback_data_;
// 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_;
NewSpace* new_space_;
OldSpace* old_space_;
OldSpace* code_space_;
MapSpace* map_space_;
LargeObjectSpace* lo_space_;
// Map from the space id to the space.
Space* space_[LAST_SPACE + 1];
// Determines whether code space is write-protected. This is essentially a
// race-free copy of the {FLAG_write_protect_code_memory} flag.
bool write_protect_code_memory_;
// Holds the number of open CodeSpaceMemoryModificationScopes.
uintptr_t code_space_memory_modification_scope_depth_;
HeapState gc_state_;
int gc_post_processing_depth_;
// Returns the amount of external memory registered since last global gc.
uint64_t PromotedExternalMemorySize();
// How many "runtime allocations" happened.
uint32_t allocations_count_;
// Running hash over allocations performed.
uint32_t raw_allocations_hash_;
// Starts marking when stress_marking_percentage_% of the marking start limit
// is reached.
int stress_marking_percentage_;
// Observer that causes more frequent checks for reached incremental marking
// limit.
AllocationObserver* stress_marking_observer_;
// Observer that can cause early scavenge start.
StressScavengeObserver* stress_scavenge_observer_;
// The maximum percent of the marking limit reached wihout causing marking.
// This is tracked when specyfing --fuzzer-gc-analysis.
double max_marking_limit_reached_;
// How many mark-sweep collections happened.
unsigned int ms_count_;
// How many gc happened.
unsigned int gc_count_;
static const uintptr_t kMmapRegionMask = 0xFFFFFFFFu;
uintptr_t mmap_region_base_;
// For post mortem debugging.
int remembered_unmapped_pages_index_;
Address remembered_unmapped_pages_[kRememberedUnmappedPages];
// 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.
size_t old_generation_allocation_limit_;
// 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_;
std::vector<GCCallbackTuple> gc_epilogue_callbacks_;
std::vector<GCCallbackTuple> gc_prologue_callbacks_;
GetExternallyAllocatedMemoryInBytesCallback external_memory_callback_;
int deferred_counters_[v8::Isolate::kUseCounterFeatureCount];
GCTracer* tracer_;
size_t promoted_objects_size_;
double promotion_ratio_;
double promotion_rate_;
size_t semi_space_copied_object_size_;
size_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_;
// Total time spent in GC.
double total_gc_time_ms_;
// Last time an idle notification happened.
double last_idle_notification_time_;
// Last time a garbage collection happened.
double last_gc_time_;
MarkCompactCollector* mark_compact_collector_;
MinorMarkCompactCollector* minor_mark_compact_collector_;
ArrayBufferCollector* array_buffer_collector_;
MemoryAllocator* memory_allocator_;
StoreBuffer* store_buffer_;
IncrementalMarking* incremental_marking_;
ConcurrentMarking* concurrent_marking_;
GCIdleTimeHandler* gc_idle_time_handler_;
MemoryReducer* memory_reducer_;
ObjectStats* live_object_stats_;
ObjectStats* dead_object_stats_;
ScavengeJob* scavenge_job_;
base::Semaphore parallel_scavenge_semaphore_;
AllocationObserver* idle_scavenge_observer_;
// 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_at_last_gc_;
// The size of objects in old generation after the last MarkCompact GC.
size_t old_generation_size_at_last_gc_;
// 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.
PretenuringFeedbackMap global_pretenuring_feedback_;
char trace_ring_buffer_[kTraceRingBufferSize];
// Used as boolean.
uint8_t is_marking_flag_;
// 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_;
// 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_;
base::Mutex relocation_mutex_;
int gc_callbacks_depth_;
bool deserialization_complete_;
StrongRootsList* strong_roots_list_;
// The depth of HeapIterator nestings.
int heap_iterator_depth_;
LocalEmbedderHeapTracer* local_embedder_heap_tracer_;
bool fast_promotion_mode_;
bool use_tasks_;
// Used for testing purposes.
bool force_oom_;
bool delay_sweeper_tasks_for_testing_;
HeapObject* pending_layout_change_object_;
// 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_;
std::map<HeapObject*, HeapObject*> retainer_;
std::map<HeapObject*, Root> retaining_root_;
// If an object is retained by an ephemeron, then the retaining key of the
// ephemeron is stored in this map.
std::map<HeapObject*, HeapObject*> ephemeral_retainer_;
// For each index inthe retaining_path_targets_ array this map
// stores the option of the corresponding target.
std::map<int, RetainingPathOption> retaining_path_target_option_;
// Classes in "heap" can be friends.
friend class AlwaysAllocateScope;
friend class ConcurrentMarking;
friend class GCCallbacksScope;
friend class GCTracer;
friend class HeapIterator;
friend class IdleScavengeObserver;
friend class IncrementalMarking;
friend class IncrementalMarkingJob;
friend class LargeObjectSpace;
template <FixedArrayVisitationMode fixed_array_mode,
TraceRetainingPathMode retaining_path_mode, typename MarkingState>
friend class MarkingVisitor;
friend class MarkCompactCollector;
friend class MarkCompactCollectorBase;
friend class MinorMarkCompactCollector;
friend class NewSpace;
friend class ObjectStatsCollector;
friend class Page;
friend class PagedSpace;
friend class Scavenger;
friend class StoreBuffer;
friend class Sweeper;
friend class heap::TestMemoryAllocatorScope;
// The allocator interface.
friend class Factory;
// The Isolate constructs us.
friend class Isolate;
// Used in cctest.
friend class heap::HeapTester;
class HeapStats {
static const int kStartMarker = 0xDECADE00;
static const int kEndMarker = 0xDECADE01;
intptr_t* start_marker; // 0
size_t* new_space_size; // 1
size_t* new_space_capacity; // 2
size_t* old_space_size; // 3
size_t* old_space_capacity; // 4
size_t* code_space_size; // 5
size_t* code_space_capacity; // 6
size_t* map_space_size; // 7
size_t* map_space_capacity; // 8
size_t* lo_space_size; // 9
size_t* global_handle_count; // 10
size_t* weak_global_handle_count; // 11
size_t* pending_global_handle_count; // 12
size_t* near_death_global_handle_count; // 13
size_t* free_global_handle_count; // 14
size_t* memory_allocator_size; // 15
size_t* memory_allocator_capacity; // 16
size_t* malloced_memory; // 17
size_t* malloced_peak_memory; // 18
size_t* objects_per_type; // 19
size_t* size_per_type; // 20
int* os_error; // 21
char* last_few_messages; // 22
char* js_stacktrace; // 23
intptr_t* end_marker; // 24
class AlwaysAllocateScope {
explicit inline AlwaysAllocateScope(Isolate* isolate);
inline ~AlwaysAllocateScope();
Heap* heap_;
class CodeSpaceMemoryModificationScope {
explicit inline CodeSpaceMemoryModificationScope(Heap* heap);
inline ~CodeSpaceMemoryModificationScope();
Heap* heap_;
class CodePageMemoryModificationScope {
explicit inline CodePageMemoryModificationScope(MemoryChunk* chunk);
inline ~CodePageMemoryModificationScope();
MemoryChunk* chunk_;
bool scope_active_;
// Disallow any GCs inside this scope, as a relocation of the underlying
// object would change the {MemoryChunk} that this scope targets.
DisallowHeapAllocation no_heap_allocation_;
// 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, public RootVisitor {
void VisitPointers(HeapObject* host, Object** start, Object** end) override;
void VisitRootPointers(Root root, Object** start, Object** end) override;
void VerifyPointers(Object** start, Object** end);
// Verify that all objects are Smis.
class VerifySmisVisitor : public RootVisitor {
void VisitRootPointers(Root root, Object** start, Object** end) override;
// 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.
explicit PagedSpaces(Heap* heap) : heap_(heap), counter_(OLD_SPACE) {}
PagedSpace* next();
Heap* heap_;
int counter_;
class SpaceIterator : public Malloced {
explicit SpaceIterator(Heap* heap);
virtual ~SpaceIterator();
bool has_next();
Space* next();
Heap* heap_;
int current_space_; // from enum AllocationSpace.
// 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();
HeapObject* NextObject();
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.
std::unique_ptr<ObjectIterator> object_iterator_;
// Abstract base class for checking whether a weak object should be retained.
class WeakObjectRetainer {
virtual ~WeakObjectRetainer() {}
// Return whether this object should be retained. If nullptr 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;
// -----------------------------------------------------------------------------
// Allows observation of allocations.
class AllocationObserver {
explicit AllocationObserver(intptr_t step_size)
: step_size_(step_size), bytes_to_next_step_(step_size) {
DCHECK_LE(kPointerSize, step_size);
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);
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 Space;
V8_EXPORT_PRIVATE const char* AllocationSpaceName(AllocationSpace space);
} // namespace internal
} // namespace v8
#endif // V8_HEAP_HEAP_H_