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chromium / v8 / v8 / a007dfc18e95a79cba33cd2e850ddf650853752d / . / src / heap / incremental-marking.cc
blob: 1de248be56d9b7a45bda48f332bcd4ff6a9d9fe8 [file] [log] [blame]
// Copyright 2012 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "src/heap/incremental-marking.h"
#include "src/code-stubs.h"
#include "src/compilation-cache.h"
#include "src/conversions.h"
#include "src/heap/gc-idle-time-handler.h"
#include "src/heap/gc-tracer.h"
#include "src/heap/mark-compact-inl.h"
#include "src/heap/object-stats.h"
#include "src/heap/objects-visiting-inl.h"
#include "src/heap/objects-visiting.h"
#include "src/tracing/trace-event.h"
#include "src/v8.h"
namespace v8 {
namespace internal {
IncrementalMarking::IncrementalMarking(Heap* heap)
: heap_(heap),
state_(STOPPED),
initial_old_generation_size_(0),
bytes_marked_ahead_of_schedule_(0),
unscanned_bytes_of_large_object_(0),
idle_marking_delay_counter_(0),
incremental_marking_finalization_rounds_(0),
is_compacting_(false),
should_hurry_(false),
was_activated_(false),
black_allocation_(false),
finalize_marking_completed_(false),
request_type_(NONE),
new_generation_observer_(*this, kAllocatedThreshold),
old_generation_observer_(*this, kAllocatedThreshold) {}
bool IncrementalMarking::BaseRecordWrite(HeapObject* obj, Object* value) {
HeapObject* value_heap_obj = HeapObject::cast(value);
MarkBit value_bit = ObjectMarking::MarkBitFrom(value_heap_obj);
DCHECK(!Marking::IsImpossible(value_bit));
MarkBit obj_bit = ObjectMarking::MarkBitFrom(obj);
DCHECK(!Marking::IsImpossible(obj_bit));
bool is_black = Marking::IsBlack(obj_bit);
if (is_black && Marking::IsWhite(value_bit)) {
WhiteToGreyAndPush(value_heap_obj, value_bit);
RestartIfNotMarking();
}
return is_compacting_ && is_black;
}
void IncrementalMarking::RecordWriteSlow(HeapObject* obj, Object** slot,
Object* value) {
if (BaseRecordWrite(obj, value) && slot != NULL) {
// Object is not going to be rescanned we need to record the slot.
heap_->mark_compact_collector()->RecordSlot(obj, slot, value);
}
}
void IncrementalMarking::RecordWriteFromCode(HeapObject* obj, Object** slot,
Isolate* isolate) {
DCHECK(obj->IsHeapObject());
isolate->heap()->incremental_marking()->RecordWrite(obj, slot, *slot);
}
// static
void IncrementalMarking::RecordWriteOfCodeEntryFromCode(JSFunction* host,
Object** slot,
Isolate* isolate) {
DCHECK(host->IsJSFunction());
IncrementalMarking* marking = isolate->heap()->incremental_marking();
Code* value = Code::cast(
Code::GetObjectFromEntryAddress(reinterpret_cast<Address>(slot)));
marking->RecordWriteOfCodeEntry(host, slot, value);
}
void IncrementalMarking::RecordCodeTargetPatch(Code* host, Address pc,
HeapObject* value) {
if (IsMarking()) {
RelocInfo rinfo(heap_->isolate(), pc, RelocInfo::CODE_TARGET, 0, host);
RecordWriteIntoCode(host, &rinfo, value);
}
}
void IncrementalMarking::RecordCodeTargetPatch(Address pc, HeapObject* value) {
if (IsMarking()) {
Code* host = heap_->isolate()
->inner_pointer_to_code_cache()
->GcSafeFindCodeForInnerPointer(pc);
RelocInfo rinfo(heap_->isolate(), pc, RelocInfo::CODE_TARGET, 0, host);
RecordWriteIntoCode(host, &rinfo, value);
}
}
void IncrementalMarking::RecordWriteOfCodeEntrySlow(JSFunction* host,
Object** slot,
Code* value) {
if (BaseRecordWrite(host, value)) {
DCHECK(slot != NULL);
heap_->mark_compact_collector()->RecordCodeEntrySlot(
host, reinterpret_cast<Address>(slot), value);
}
}
void IncrementalMarking::RecordWriteIntoCodeSlow(Code* host, RelocInfo* rinfo,
Object* value) {
if (BaseRecordWrite(host, value)) {
// Object is not going to be rescanned. We need to record the slot.
heap_->mark_compact_collector()->RecordRelocSlot(host, rinfo, value);
}
}
void IncrementalMarking::WhiteToGreyAndPush(HeapObject* obj, MarkBit mark_bit) {
Marking::WhiteToGrey(mark_bit);
heap_->mark_compact_collector()->marking_deque()->Push(obj);
}
static void MarkObjectGreyDoNotEnqueue(Object* obj) {
if (obj->IsHeapObject()) {
HeapObject* heap_obj = HeapObject::cast(obj);
MarkBit mark_bit = ObjectMarking::MarkBitFrom(HeapObject::cast(obj));
if (Marking::IsBlack(mark_bit)) {
MemoryChunk::IncrementLiveBytesFromGC(heap_obj, -heap_obj->Size());
}
Marking::AnyToGrey(mark_bit);
}
}
void IncrementalMarking::TransferMark(Heap* heap, Address old_start,
Address new_start) {
// This is only used when resizing an object.
DCHECK(MemoryChunk::FromAddress(old_start) ==
MemoryChunk::FromAddress(new_start));
if (!heap->incremental_marking()->IsMarking()) return;
// If the mark doesn't move, we don't check the color of the object.
// It doesn't matter whether the object is black, since it hasn't changed
// size, so the adjustment to the live data count will be zero anyway.
if (old_start == new_start) return;
MarkBit new_mark_bit = ObjectMarking::MarkBitFrom(new_start);
MarkBit old_mark_bit = ObjectMarking::MarkBitFrom(old_start);
#ifdef DEBUG
Marking::ObjectColor old_color = Marking::Color(old_mark_bit);
#endif
if (Marking::IsBlack(old_mark_bit)) {
Marking::BlackToWhite(old_mark_bit);
Marking::MarkBlack(new_mark_bit);
return;
} else if (Marking::IsGrey(old_mark_bit)) {
Marking::GreyToWhite(old_mark_bit);
heap->incremental_marking()->WhiteToGreyAndPush(
HeapObject::FromAddress(new_start), new_mark_bit);
heap->incremental_marking()->RestartIfNotMarking();
}
#ifdef DEBUG
Marking::ObjectColor new_color = Marking::Color(new_mark_bit);
DCHECK(new_color == old_color);
#endif
}
class IncrementalMarkingMarkingVisitor
: public StaticMarkingVisitor<IncrementalMarkingMarkingVisitor> {
public:
static void Initialize() {
StaticMarkingVisitor<IncrementalMarkingMarkingVisitor>::Initialize();
table_.Register(kVisitFixedArray, &VisitFixedArrayIncremental);
table_.Register(kVisitNativeContext, &VisitNativeContextIncremental);
}
static const int kProgressBarScanningChunk = 32 * 1024;
static void VisitFixedArrayIncremental(Map* map, HeapObject* object) {
MemoryChunk* chunk = MemoryChunk::FromAddress(object->address());
if (chunk->IsFlagSet(MemoryChunk::HAS_PROGRESS_BAR)) {
DCHECK(!FLAG_use_marking_progress_bar ||
chunk->owner()->identity() == LO_SPACE);
Heap* heap = map->GetHeap();
// When using a progress bar for large fixed arrays, scan only a chunk of
// the array and try to push it onto the marking deque again until it is
// fully scanned. Fall back to scanning it through to the end in case this
// fails because of a full deque.
int object_size = FixedArray::BodyDescriptor::SizeOf(map, object);
int start_offset =
Max(FixedArray::BodyDescriptor::kStartOffset, chunk->progress_bar());
int end_offset =
Min(object_size, start_offset + kProgressBarScanningChunk);
int already_scanned_offset = start_offset;
bool scan_until_end = false;
do {
VisitPointers(heap, object, HeapObject::RawField(object, start_offset),
HeapObject::RawField(object, end_offset));
start_offset = end_offset;
end_offset = Min(object_size, end_offset + kProgressBarScanningChunk);
scan_until_end =
heap->mark_compact_collector()->marking_deque()->IsFull();
} while (scan_until_end && start_offset < object_size);
chunk->set_progress_bar(start_offset);
if (start_offset < object_size) {
if (Marking::IsGrey(ObjectMarking::MarkBitFrom(object))) {
heap->mark_compact_collector()->marking_deque()->Unshift(object);
} else {
DCHECK(Marking::IsBlack(ObjectMarking::MarkBitFrom(object)));
heap->mark_compact_collector()->UnshiftBlack(object);
}
heap->incremental_marking()->NotifyIncompleteScanOfObject(
object_size - (start_offset - already_scanned_offset));
}
} else {
FixedArrayVisitor::Visit(map, object);
}
}
static void VisitNativeContextIncremental(Map* map, HeapObject* object) {
Context* context = Context::cast(object);
// We will mark cache black with a separate pass when we finish marking.
// Note that GC can happen when the context is not fully initialized,
// so the cache can be undefined.
Object* cache = context->get(Context::NORMALIZED_MAP_CACHE_INDEX);
if (!cache->IsUndefined(map->GetIsolate())) {
MarkObjectGreyDoNotEnqueue(cache);
}
VisitNativeContext(map, context);
}
INLINE(static void VisitPointer(Heap* heap, HeapObject* object, Object** p)) {
Object* target = *p;
if (target->IsHeapObject()) {
heap->mark_compact_collector()->RecordSlot(object, p, target);
MarkObject(heap, target);
}
}
INLINE(static void VisitPointers(Heap* heap, HeapObject* object,
Object** start, Object** end)) {
for (Object** p = start; p < end; p++) {
Object* target = *p;
if (target->IsHeapObject()) {
heap->mark_compact_collector()->RecordSlot(object, p, target);
MarkObject(heap, target);
}
}
}
// Marks the object grey and pushes it on the marking stack.
INLINE(static void MarkObject(Heap* heap, Object* obj)) {
IncrementalMarking::MarkGrey(heap, HeapObject::cast(obj));
}
// Marks the object black without pushing it on the marking stack.
// Returns true if object needed marking and false otherwise.
INLINE(static bool MarkObjectWithoutPush(Heap* heap, Object* obj)) {
HeapObject* heap_object = HeapObject::cast(obj);
MarkBit mark_bit = ObjectMarking::MarkBitFrom(heap_object);
if (Marking::IsWhite(mark_bit)) {
Marking::MarkBlack(mark_bit);
MemoryChunk::IncrementLiveBytesFromGC(heap_object, heap_object->Size());
return true;
}
return false;
}
};
void IncrementalMarking::IterateBlackObject(HeapObject* object) {
if (IsMarking() && Marking::IsBlack(ObjectMarking::MarkBitFrom(object))) {
Page* page = Page::FromAddress(object->address());
if ((page->owner() != nullptr) && (page->owner()->identity() == LO_SPACE)) {
// IterateBlackObject requires us to visit the whole object.
page->ResetProgressBar();
}
Map* map = object->map();
MarkGrey(heap_, map);
IncrementalMarkingMarkingVisitor::IterateBody(map, object);
}
}
class IncrementalMarkingRootMarkingVisitor : public ObjectVisitor {
public:
explicit IncrementalMarkingRootMarkingVisitor(
IncrementalMarking* incremental_marking)
: heap_(incremental_marking->heap()) {}
void VisitPointer(Object** p) override { MarkObjectByPointer(p); }
void VisitPointers(Object** start, Object** end) override {
for (Object** p = start; p < end; p++) MarkObjectByPointer(p);
}
private:
void MarkObjectByPointer(Object** p) {
Object* obj = *p;
if (!obj->IsHeapObject()) return;
IncrementalMarking::MarkGrey(heap_, HeapObject::cast(obj));
}
Heap* heap_;
};
void IncrementalMarking::Initialize() {
IncrementalMarkingMarkingVisitor::Initialize();
}
void IncrementalMarking::SetOldSpacePageFlags(MemoryChunk* chunk,
bool is_marking,
bool is_compacting) {
if (is_marking) {
chunk->SetFlag(MemoryChunk::POINTERS_TO_HERE_ARE_INTERESTING);
chunk->SetFlag(MemoryChunk::POINTERS_FROM_HERE_ARE_INTERESTING);
} else {
chunk->ClearFlag(MemoryChunk::POINTERS_TO_HERE_ARE_INTERESTING);
chunk->SetFlag(MemoryChunk::POINTERS_FROM_HERE_ARE_INTERESTING);
}
}
void IncrementalMarking::SetNewSpacePageFlags(MemoryChunk* chunk,
bool is_marking) {
chunk->SetFlag(MemoryChunk::POINTERS_TO_HERE_ARE_INTERESTING);
if (is_marking) {
chunk->SetFlag(MemoryChunk::POINTERS_FROM_HERE_ARE_INTERESTING);
} else {
chunk->ClearFlag(MemoryChunk::POINTERS_FROM_HERE_ARE_INTERESTING);
}
}
void IncrementalMarking::DeactivateIncrementalWriteBarrierForSpace(
PagedSpace* space) {
for (Page* p : *space) {
SetOldSpacePageFlags(p, false, false);
}
}
void IncrementalMarking::DeactivateIncrementalWriteBarrierForSpace(
NewSpace* space) {
for (Page* p : *space) {
SetNewSpacePageFlags(p, false);
}
}
void IncrementalMarking::DeactivateIncrementalWriteBarrier() {
DeactivateIncrementalWriteBarrierForSpace(heap_->old_space());
DeactivateIncrementalWriteBarrierForSpace(heap_->map_space());
DeactivateIncrementalWriteBarrierForSpace(heap_->code_space());
DeactivateIncrementalWriteBarrierForSpace(heap_->new_space());
for (LargePage* lop : *heap_->lo_space()) {
SetOldSpacePageFlags(lop, false, false);
}
}
void IncrementalMarking::ActivateIncrementalWriteBarrier(PagedSpace* space) {
for (Page* p : *space) {
SetOldSpacePageFlags(p, true, is_compacting_);
}
}
void IncrementalMarking::ActivateIncrementalWriteBarrier(NewSpace* space) {
for (Page* p : *space) {
SetNewSpacePageFlags(p, true);
}
}
void IncrementalMarking::ActivateIncrementalWriteBarrier() {
ActivateIncrementalWriteBarrier(heap_->old_space());
ActivateIncrementalWriteBarrier(heap_->map_space());
ActivateIncrementalWriteBarrier(heap_->code_space());
ActivateIncrementalWriteBarrier(heap_->new_space());
for (LargePage* lop : *heap_->lo_space()) {
SetOldSpacePageFlags(lop, true, is_compacting_);
}
}
bool IncrementalMarking::WasActivated() { return was_activated_; }
bool IncrementalMarking::CanBeActivated() {
// Only start incremental marking in a safe state: 1) when incremental
// marking is turned on, 2) when we are currently not in a GC, and
// 3) when we are currently not serializing or deserializing the heap.
return FLAG_incremental_marking && heap_->gc_state() == Heap::NOT_IN_GC &&
heap_->deserialization_complete() &&
!heap_->isolate()->serializer_enabled();
}
void IncrementalMarking::ActivateGeneratedStub(Code* stub) {
DCHECK(RecordWriteStub::GetMode(stub) == RecordWriteStub::STORE_BUFFER_ONLY);
if (!IsMarking()) {
// Initially stub is generated in STORE_BUFFER_ONLY mode thus
// we don't need to do anything if incremental marking is
// not active.
} else if (IsCompacting()) {
RecordWriteStub::Patch(stub, RecordWriteStub::INCREMENTAL_COMPACTION);
} else {
RecordWriteStub::Patch(stub, RecordWriteStub::INCREMENTAL);
}
}
static void PatchIncrementalMarkingRecordWriteStubs(
Heap* heap, RecordWriteStub::Mode mode) {
UnseededNumberDictionary* stubs = heap->code_stubs();
int capacity = stubs->Capacity();
Isolate* isolate = heap->isolate();
for (int i = 0; i < capacity; i++) {
Object* k = stubs->KeyAt(i);
if (stubs->IsKey(isolate, k)) {
uint32_t key = NumberToUint32(k);
if (CodeStub::MajorKeyFromKey(key) == CodeStub::RecordWrite) {
Object* e = stubs->ValueAt(i);
if (e->IsCode()) {
RecordWriteStub::Patch(Code::cast(e), mode);
}
}
}
}
}
void IncrementalMarking::Start(GarbageCollectionReason gc_reason) {
if (FLAG_trace_incremental_marking) {
int old_generation_size_mb =
static_cast<int>(heap()->PromotedSpaceSizeOfObjects() / MB);
int old_generation_limit_mb =
static_cast<int>(heap()->old_generation_allocation_limit() / MB);
heap()->isolate()->PrintWithTimestamp(
"[IncrementalMarking] Start (%s): old generation %dMB, limit %dMB, "
"slack %dMB\n",
Heap::GarbageCollectionReasonToString(gc_reason),
old_generation_size_mb, old_generation_limit_mb,
Max(0, old_generation_limit_mb - old_generation_size_mb));
}
DCHECK(FLAG_incremental_marking);
DCHECK(state_ == STOPPED);
DCHECK(heap_->gc_state() == Heap::NOT_IN_GC);
DCHECK(!heap_->isolate()->serializer_enabled());
Counters* counters = heap_->isolate()->counters();
counters->incremental_marking_reason()->AddSample(
static_cast<int>(gc_reason));
HistogramTimerScope incremental_marking_scope(
counters->gc_incremental_marking_start());
TRACE_EVENT0("v8", "V8.GCIncrementalMarkingStart");
heap_->tracer()->NotifyIncrementalMarkingStart();
start_time_ms_ = heap()->MonotonicallyIncreasingTimeInMs();
initial_old_generation_size_ = heap_->PromotedSpaceSizeOfObjects();
old_generation_allocation_counter_ = heap_->OldGenerationAllocationCounter();
bytes_allocated_ = 0;
bytes_marked_ahead_of_schedule_ = 0;
should_hurry_ = false;
was_activated_ = true;
if (!heap_->mark_compact_collector()->sweeping_in_progress()) {
StartMarking();
} else {
if (FLAG_trace_incremental_marking) {
heap()->isolate()->PrintWithTimestamp(
"[IncrementalMarking] Start sweeping.\n");
}
state_ = SWEEPING;
}
SpaceIterator it(heap_);
while (it.has_next()) {
Space* space = it.next();
if (space == heap_->new_space()) {
space->AddAllocationObserver(&new_generation_observer_);
} else {
space->AddAllocationObserver(&old_generation_observer_);
}
}
incremental_marking_job()->Start(heap_);
}
void IncrementalMarking::StartMarking() {
if (heap_->isolate()->serializer_enabled()) {
// Black allocation currently starts when we start incremental marking,
// but we cannot enable black allocation while deserializing. Hence, we
// have to delay the start of incremental marking in that case.
if (FLAG_trace_incremental_marking) {
heap()->isolate()->PrintWithTimestamp(
"[IncrementalMarking] Start delayed - serializer\n");
}
return;
}
if (FLAG_trace_incremental_marking) {
heap()->isolate()->PrintWithTimestamp(
"[IncrementalMarking] Start marking\n");
}
is_compacting_ = !FLAG_never_compact &&
heap_->mark_compact_collector()->StartCompaction(
MarkCompactCollector::INCREMENTAL_COMPACTION);
state_ = MARKING;
if (heap_->UsingEmbedderHeapTracer()) {
TRACE_GC(heap()->tracer(),
GCTracer::Scope::MC_INCREMENTAL_WRAPPER_PROLOGUE);
heap_->embedder_heap_tracer()->TracePrologue(
heap_->embedder_reachable_reference_reporter());
}
RecordWriteStub::Mode mode = is_compacting_
? RecordWriteStub::INCREMENTAL_COMPACTION
: RecordWriteStub::INCREMENTAL;
PatchIncrementalMarkingRecordWriteStubs(heap_, mode);
heap_->mark_compact_collector()->EnsureMarkingDequeIsCommittedAndInitialize(
MarkCompactCollector::kMaxMarkingDequeSize);
ActivateIncrementalWriteBarrier();
// Marking bits are cleared by the sweeper.
#ifdef VERIFY_HEAP
if (FLAG_verify_heap) {
heap_->mark_compact_collector()->VerifyMarkbitsAreClean();
}
#endif
heap_->CompletelyClearInstanceofCache();
heap_->isolate()->compilation_cache()->MarkCompactPrologue();
// Mark strong roots grey.
IncrementalMarkingRootMarkingVisitor visitor(this);
heap_->IterateStrongRoots(&visitor, VISIT_ONLY_STRONG);
// Ready to start incremental marking.
if (FLAG_trace_incremental_marking) {
heap()->isolate()->PrintWithTimestamp("[IncrementalMarking] Running\n");
}
}
void IncrementalMarking::StartBlackAllocation() {
DCHECK(FLAG_black_allocation);
DCHECK(IsMarking());
black_allocation_ = true;
heap()->old_space()->MarkAllocationInfoBlack();
heap()->map_space()->MarkAllocationInfoBlack();
heap()->code_space()->MarkAllocationInfoBlack();
if (FLAG_trace_incremental_marking) {
heap()->isolate()->PrintWithTimestamp(
"[IncrementalMarking] Black allocation started\n");
}
}
void IncrementalMarking::FinishBlackAllocation() {
if (black_allocation_) {
black_allocation_ = false;
if (FLAG_trace_incremental_marking) {
heap()->isolate()->PrintWithTimestamp(
"[IncrementalMarking] Black allocation finished\n");
}
}
}
void IncrementalMarking::AbortBlackAllocation() {
if (FLAG_trace_incremental_marking) {
heap()->isolate()->PrintWithTimestamp(
"[IncrementalMarking] Black allocation aborted\n");
}
}
void IncrementalMarking::MarkRoots() {
DCHECK(!finalize_marking_completed_);
DCHECK(IsMarking());
IncrementalMarkingRootMarkingVisitor visitor(this);
heap_->IterateStrongRoots(&visitor, VISIT_ONLY_STRONG);
}
void IncrementalMarking::MarkObjectGroups() {
TRACE_GC(heap_->tracer(),
GCTracer::Scope::MC_INCREMENTAL_FINALIZE_OBJECT_GROUPING);
DCHECK(!heap_->UsingEmbedderHeapTracer());
DCHECK(!finalize_marking_completed_);
DCHECK(IsMarking());
IncrementalMarkingRootMarkingVisitor visitor(this);
heap_->mark_compact_collector()->MarkImplicitRefGroups(&MarkGrey);
heap_->isolate()->global_handles()->IterateObjectGroups(
&visitor, &MarkCompactCollector::IsUnmarkedHeapObjectWithHeap);
heap_->isolate()->global_handles()->RemoveImplicitRefGroups();
heap_->isolate()->global_handles()->RemoveObjectGroups();
}
void IncrementalMarking::ProcessWeakCells() {
DCHECK(!finalize_marking_completed_);
DCHECK(IsMarking());
Object* the_hole_value = heap()->the_hole_value();
Object* weak_cell_obj = heap()->encountered_weak_cells();
Object* weak_cell_head = Smi::kZero;
WeakCell* prev_weak_cell_obj = NULL;
while (weak_cell_obj != Smi::kZero) {
WeakCell* weak_cell = reinterpret_cast<WeakCell*>(weak_cell_obj);
// We do not insert cleared weak cells into the list, so the value
// cannot be a Smi here.
HeapObject* value = HeapObject::cast(weak_cell->value());
// Remove weak cells with live objects from the list, they do not need
// clearing.
if (MarkCompactCollector::IsMarked(value)) {
// Record slot, if value is pointing to an evacuation candidate.
Object** slot = HeapObject::RawField(weak_cell, WeakCell::kValueOffset);
heap_->mark_compact_collector()->RecordSlot(weak_cell, slot, *slot);
// Remove entry somewhere after top.
if (prev_weak_cell_obj != NULL) {
prev_weak_cell_obj->set_next(weak_cell->next());
}
weak_cell_obj = weak_cell->next();
weak_cell->clear_next(the_hole_value);
} else {
if (weak_cell_head == Smi::kZero) {
weak_cell_head = weak_cell;
}
prev_weak_cell_obj = weak_cell;
weak_cell_obj = weak_cell->next();
}
}
// Top may have changed.
heap()->set_encountered_weak_cells(weak_cell_head);
}
bool ShouldRetainMap(Map* map, int age) {
if (age == 0) {
// The map has aged. Do not retain this map.
return false;
}
Object* constructor = map->GetConstructor();
if (!constructor->IsHeapObject() ||
Marking::IsWhite(
ObjectMarking::MarkBitFrom(HeapObject::cast(constructor)))) {
// The constructor is dead, no new objects with this map can
// be created. Do not retain this map.
return false;
}
return true;
}
void IncrementalMarking::RetainMaps() {
// Do not retain dead maps if flag disables it or there is
// - memory pressure (reduce_memory_footprint_),
// - GC is requested by tests or dev-tools (abort_incremental_marking_).
bool map_retaining_is_disabled = heap()->ShouldReduceMemory() ||
heap()->ShouldAbortIncrementalMarking() ||
FLAG_retain_maps_for_n_gc == 0;
ArrayList* retained_maps = heap()->retained_maps();
int length = retained_maps->Length();
// The number_of_disposed_maps separates maps in the retained_maps
// array that were created before and after context disposal.
// We do not age and retain disposed maps to avoid memory leaks.
int number_of_disposed_maps = heap()->number_of_disposed_maps_;
for (int i = 0; i < length; i += 2) {
DCHECK(retained_maps->Get(i)->IsWeakCell());
WeakCell* cell = WeakCell::cast(retained_maps->Get(i));
if (cell->cleared()) continue;
int age = Smi::cast(retained_maps->Get(i + 1))->value();
int new_age;
Map* map = Map::cast(cell->value());
MarkBit map_mark = ObjectMarking::MarkBitFrom(map);
if (i >= number_of_disposed_maps && !map_retaining_is_disabled &&
Marking::IsWhite(map_mark)) {
if (ShouldRetainMap(map, age)) {
MarkGrey(heap(), map);
}
Object* prototype = map->prototype();
if (age > 0 && prototype->IsHeapObject() &&
Marking::IsWhite(
ObjectMarking::MarkBitFrom(HeapObject::cast(prototype)))) {
// The prototype is not marked, age the map.
new_age = age - 1;
} else {
// The prototype and the constructor are marked, this map keeps only
// transition tree alive, not JSObjects. Do not age the map.
new_age = age;
}
} else {
new_age = FLAG_retain_maps_for_n_gc;
}
// Compact the array and update the age.
if (new_age != age) {
retained_maps->Set(i + 1, Smi::FromInt(new_age));
}
}
}
void IncrementalMarking::FinalizeIncrementally() {
TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_INCREMENTAL_FINALIZE_BODY);
DCHECK(!finalize_marking_completed_);
DCHECK(IsMarking());
double start = heap_->MonotonicallyIncreasingTimeInMs();
int old_marking_deque_top =
heap_->mark_compact_collector()->marking_deque()->top();
// After finishing incremental marking, we try to discover all unmarked
// objects to reduce the marking load in the final pause.
// 1) We scan and mark the roots again to find all changes to the root set.
// 2) We mark the object groups.
// 3) Age and retain maps embedded in optimized code.
// 4) Remove weak cell with live values from the list of weak cells, they
// do not need processing during GC.
MarkRoots();
if (!heap_->UsingEmbedderHeapTracer()) {
MarkObjectGroups();
}
if (incremental_marking_finalization_rounds_ == 0) {
// Map retaining is needed for perfromance, not correctness,
// so we can do it only once at the beginning of the finalization.
RetainMaps();
}
ProcessWeakCells();
int marking_progress =
abs(old_marking_deque_top -
heap_->mark_compact_collector()->marking_deque()->top());
marking_progress += static_cast<int>(heap_->wrappers_to_trace());
double end = heap_->MonotonicallyIncreasingTimeInMs();
double delta = end - start;
if (FLAG_trace_incremental_marking) {
heap()->isolate()->PrintWithTimestamp(
"[IncrementalMarking] Finalize incrementally round %d, "
"spent %d ms, marking progress %d.\n",
static_cast<int>(delta), incremental_marking_finalization_rounds_,
marking_progress);
}
++incremental_marking_finalization_rounds_;
if ((incremental_marking_finalization_rounds_ >=
FLAG_max_incremental_marking_finalization_rounds) ||
(marking_progress <
FLAG_min_progress_during_incremental_marking_finalization)) {
finalize_marking_completed_ = true;
}
if (FLAG_black_allocation && !heap()->ShouldReduceMemory() &&
!black_allocation_) {
// TODO(hpayer): Move to an earlier point as soon as we make faster marking
// progress.
StartBlackAllocation();
}
}
void IncrementalMarking::UpdateMarkingDequeAfterScavenge() {
if (!IsMarking()) return;
MarkingDeque* marking_deque =
heap_->mark_compact_collector()->marking_deque();
int current = marking_deque->bottom();
int mask = marking_deque->mask();
int limit = marking_deque->top();
HeapObject** array = marking_deque->array();
int new_top = current;
Map* filler_map = heap_->one_pointer_filler_map();
while (current != limit) {
HeapObject* obj = array[current];
DCHECK(obj->IsHeapObject());
current = ((current + 1) & mask);
// Only pointers to from space have to be updated.
if (heap_->InFromSpace(obj)) {
MapWord map_word = obj->map_word();
// There may be objects on the marking deque that do not exist anymore,
// e.g. left trimmed objects or objects from the root set (frames).
// If these object are dead at scavenging time, their marking deque
// entries will not point to forwarding addresses. Hence, we can discard
// them.
if (map_word.IsForwardingAddress()) {
HeapObject* dest = map_word.ToForwardingAddress();
if (Marking::IsBlack(ObjectMarking::MarkBitFrom(dest->address())))
continue;
array[new_top] = dest;
new_top = ((new_top + 1) & mask);
DCHECK(new_top != marking_deque->bottom());
#ifdef DEBUG
MarkBit mark_bit = ObjectMarking::MarkBitFrom(obj);
DCHECK(Marking::IsGrey(mark_bit) ||
(obj->IsFiller() && Marking::IsWhite(mark_bit)));
#endif
}
} else if (obj->map() != filler_map) {
// Skip one word filler objects that appear on the
// stack when we perform in place array shift.
array[new_top] = obj;
new_top = ((new_top + 1) & mask);
DCHECK(new_top != marking_deque->bottom());
#ifdef DEBUG
MarkBit mark_bit = ObjectMarking::MarkBitFrom(obj);
MemoryChunk* chunk = MemoryChunk::FromAddress(obj->address());
DCHECK(Marking::IsGrey(mark_bit) ||
(obj->IsFiller() && Marking::IsWhite(mark_bit)) ||
(chunk->IsFlagSet(MemoryChunk::HAS_PROGRESS_BAR) &&
Marking::IsBlack(mark_bit)));
#endif
}
}
marking_deque->set_top(new_top);
}
void IncrementalMarking::VisitObject(Map* map, HeapObject* obj, int size) {
MarkGrey(heap_, map);
IncrementalMarkingMarkingVisitor::IterateBody(map, obj);
#if ENABLE_SLOW_DCHECKS
MarkBit mark_bit = ObjectMarking::MarkBitFrom(obj);
MemoryChunk* chunk = MemoryChunk::FromAddress(obj->address());
SLOW_DCHECK(Marking::IsGrey(mark_bit) ||
(obj->IsFiller() && Marking::IsWhite(mark_bit)) ||
(chunk->IsFlagSet(MemoryChunk::HAS_PROGRESS_BAR) &&
Marking::IsBlack(mark_bit)));
#endif
MarkBlack(obj, size);
}
void IncrementalMarking::MarkGrey(Heap* heap, HeapObject* object) {
MarkBit mark_bit = ObjectMarking::MarkBitFrom(object);
if (Marking::IsWhite(mark_bit)) {
heap->incremental_marking()->WhiteToGreyAndPush(object, mark_bit);
}
}
void IncrementalMarking::MarkBlack(HeapObject* obj, int size) {
MarkBit mark_bit = ObjectMarking::MarkBitFrom(obj);
if (Marking::IsBlack(mark_bit)) return;
Marking::GreyToBlack(mark_bit);
MemoryChunk::IncrementLiveBytesFromGC(obj, size);
}
intptr_t IncrementalMarking::ProcessMarkingDeque(
intptr_t bytes_to_process, ForceCompletionAction completion) {
intptr_t bytes_processed = 0;
MarkingDeque* marking_deque =
heap_->mark_compact_collector()->marking_deque();
while (!marking_deque->IsEmpty() && (bytes_processed < bytes_to_process ||
completion == FORCE_COMPLETION)) {
HeapObject* obj = marking_deque->Pop();
// Left trimming may result in white filler objects on the marking deque.
// Ignore these objects.
if (obj->IsFiller()) {
DCHECK(Marking::IsImpossible(ObjectMarking::MarkBitFrom(obj)) ||
Marking::IsWhite(ObjectMarking::MarkBitFrom(obj)));
continue;
}
Map* map = obj->map();
int size = obj->SizeFromMap(map);
unscanned_bytes_of_large_object_ = 0;
VisitObject(map, obj, size);
bytes_processed += size - unscanned_bytes_of_large_object_;
}
return bytes_processed;
}
void IncrementalMarking::Hurry() {
// A scavenge may have pushed new objects on the marking deque (due to black
// allocation) even in COMPLETE state. This may happen if scavenges are
// forced e.g. in tests. It should not happen when COMPLETE was set when
// incremental marking finished and a regular GC was triggered after that
// because should_hurry_ will force a full GC.
if (!heap_->mark_compact_collector()->marking_deque()->IsEmpty()) {
double start = 0.0;
if (FLAG_trace_incremental_marking) {
start = heap_->MonotonicallyIncreasingTimeInMs();
if (FLAG_trace_incremental_marking) {
heap()->isolate()->PrintWithTimestamp("[IncrementalMarking] Hurry\n");
}
}
// TODO(gc) hurry can mark objects it encounters black as mutator
// was stopped.
ProcessMarkingDeque(0, FORCE_COMPLETION);
state_ = COMPLETE;
if (FLAG_trace_incremental_marking) {
double end = heap_->MonotonicallyIncreasingTimeInMs();
double delta = end - start;
if (FLAG_trace_incremental_marking) {
heap()->isolate()->PrintWithTimestamp(
"[IncrementalMarking] Complete (hurry), spent %d ms.\n",
static_cast<int>(delta));
}
}
}
Object* context = heap_->native_contexts_list();
while (!context->IsUndefined(heap_->isolate())) {
// GC can happen when the context is not fully initialized,
// so the cache can be undefined.
HeapObject* cache = HeapObject::cast(
Context::cast(context)->get(Context::NORMALIZED_MAP_CACHE_INDEX));
if (!cache->IsUndefined(heap_->isolate())) {
MarkBit mark_bit = ObjectMarking::MarkBitFrom(cache);
if (Marking::IsGrey(mark_bit)) {
Marking::GreyToBlack(mark_bit);
MemoryChunk::IncrementLiveBytesFromGC(cache, cache->Size());
}
}
context = Context::cast(context)->next_context_link();
}
}
void IncrementalMarking::Stop() {
if (IsStopped()) return;
if (FLAG_trace_incremental_marking) {
int old_generation_size_mb =
static_cast<int>(heap()->PromotedSpaceSizeOfObjects() / MB);
int old_generation_limit_mb =
static_cast<int>(heap()->old_generation_allocation_limit() / MB);
heap()->isolate()->PrintWithTimestamp(
"[IncrementalMarking] Stopping: old generation %dMB, limit %dMB, "
"overshoot %dMB\n",
old_generation_size_mb, old_generation_limit_mb,
Max(0, old_generation_size_mb - old_generation_limit_mb));
}
SpaceIterator it(heap_);
while (it.has_next()) {
Space* space = it.next();
if (space == heap_->new_space()) {
space->RemoveAllocationObserver(&new_generation_observer_);
} else {
space->RemoveAllocationObserver(&old_generation_observer_);
}
}
IncrementalMarking::set_should_hurry(false);
if (IsMarking()) {
PatchIncrementalMarkingRecordWriteStubs(heap_,
RecordWriteStub::STORE_BUFFER_ONLY);
DeactivateIncrementalWriteBarrier();
}
heap_->isolate()->stack_guard()->ClearGC();
state_ = STOPPED;
is_compacting_ = false;
FinishBlackAllocation();
}
void IncrementalMarking::Finalize() {
Hurry();
Stop();
}
void IncrementalMarking::FinalizeMarking(CompletionAction action) {
DCHECK(!finalize_marking_completed_);
if (FLAG_trace_incremental_marking) {
heap()->isolate()->PrintWithTimestamp(
"[IncrementalMarking] requesting finalization of incremental "
"marking.\n");
}
request_type_ = FINALIZATION;
if (action == GC_VIA_STACK_GUARD) {
heap_->isolate()->stack_guard()->RequestGC();
}
}
void IncrementalMarking::MarkingComplete(CompletionAction action) {
state_ = COMPLETE;
// We will set the stack guard to request a GC now. This will mean the rest
// of the GC gets performed as soon as possible (we can't do a GC here in a
// record-write context). If a few things get allocated between now and then
// that shouldn't make us do a scavenge and keep being incremental, so we set
// the should-hurry flag to indicate that there can't be much work left to do.
set_should_hurry(true);
if (FLAG_trace_incremental_marking) {
heap()->isolate()->PrintWithTimestamp(
"[IncrementalMarking] Complete (normal).\n");
}
request_type_ = COMPLETE_MARKING;
if (action == GC_VIA_STACK_GUARD) {
heap_->isolate()->stack_guard()->RequestGC();
}
}
void IncrementalMarking::Epilogue() {
was_activated_ = false;
finalize_marking_completed_ = false;
incremental_marking_finalization_rounds_ = 0;
}
double IncrementalMarking::AdvanceIncrementalMarking(
double deadline_in_ms, CompletionAction completion_action,
ForceCompletionAction force_completion, StepOrigin step_origin) {
DCHECK(!IsStopped());
double remaining_time_in_ms = 0.0;
intptr_t step_size_in_bytes = GCIdleTimeHandler::EstimateMarkingStepSize(
kStepSizeInMs,
heap()->tracer()->IncrementalMarkingSpeedInBytesPerMillisecond());
do {
Step(step_size_in_bytes, completion_action, force_completion, step_origin);
remaining_time_in_ms =
deadline_in_ms - heap()->MonotonicallyIncreasingTimeInMs();
} while (remaining_time_in_ms >= kStepSizeInMs && !IsComplete() &&
!heap()->mark_compact_collector()->marking_deque()->IsEmpty());
return remaining_time_in_ms;
}
void IncrementalMarking::FinalizeSweeping() {
DCHECK(state_ == SWEEPING);
if (heap_->mark_compact_collector()->sweeping_in_progress() &&
(!FLAG_concurrent_sweeping ||
!heap_->mark_compact_collector()->sweeper().AreSweeperTasksRunning())) {
heap_->mark_compact_collector()->EnsureSweepingCompleted();
}
if (!heap_->mark_compact_collector()->sweeping_in_progress()) {
StartMarking();
}
}
size_t IncrementalMarking::StepSizeToKeepUpWithAllocations() {
// Update bytes_allocated_ based on the allocation counter.
size_t current_counter = heap_->OldGenerationAllocationCounter();
bytes_allocated_ += current_counter - old_generation_allocation_counter_;
old_generation_allocation_counter_ = current_counter;
return bytes_allocated_;
}
size_t IncrementalMarking::StepSizeToMakeProgress() {
// We increase step size gradually based on the time passed in order to
// leave marking work to standalone tasks. The ramp up duration and the
// target step count are chosen based on benchmarks.
const int kRampUpIntervalMs = 300;
const size_t kTargetStepCount = 128;
size_t step_size = Max(initial_old_generation_size_ / kTargetStepCount,
IncrementalMarking::kAllocatedThreshold);
double time_passed_ms =
heap_->MonotonicallyIncreasingTimeInMs() - start_time_ms_;
double factor = Min(time_passed_ms / kRampUpIntervalMs, 1.0);
return static_cast<size_t>(factor * step_size);
}
void IncrementalMarking::AdvanceIncrementalMarkingOnAllocation() {
if (heap_->gc_state() != Heap::NOT_IN_GC || !FLAG_incremental_marking ||
(state_ != SWEEPING && state_ != MARKING)) {
return;
}
size_t bytes_to_process =
StepSizeToKeepUpWithAllocations() + StepSizeToMakeProgress();
if (bytes_to_process >= IncrementalMarking::kAllocatedThreshold) {
// The first step after Scavenge will see many allocated bytes.
// Cap the step size to distribute the marking work more uniformly.
size_t max_step_size = GCIdleTimeHandler::EstimateMarkingStepSize(
kMaxStepSizeInMs,
heap()->tracer()->IncrementalMarkingSpeedInBytesPerMillisecond());
bytes_to_process = Min(bytes_to_process, max_step_size);
size_t bytes_processed = 0;
if (bytes_marked_ahead_of_schedule_ >= bytes_to_process) {
// Steps performed in tasks have put us ahead of schedule.
// We skip processing of marking dequeue here and thus
// shift marking time from inside V8 to standalone tasks.
bytes_marked_ahead_of_schedule_ -= bytes_to_process;
bytes_processed = bytes_to_process;
} else {
bytes_processed = Step(bytes_to_process, GC_VIA_STACK_GUARD,
FORCE_COMPLETION, StepOrigin::kV8);
}
bytes_allocated_ -= Min(bytes_allocated_, bytes_processed);
}
}
size_t IncrementalMarking::Step(size_t bytes_to_process,
CompletionAction action,
ForceCompletionAction completion,
StepOrigin step_origin) {
HistogramTimerScope incremental_marking_scope(
heap_->isolate()->counters()->gc_incremental_marking());
TRACE_EVENT0("v8", "V8.GCIncrementalMarking");
TRACE_GC(heap_->tracer(), GCTracer::Scope::MC_INCREMENTAL);
double start = heap_->MonotonicallyIncreasingTimeInMs();
if (state_ == SWEEPING) {
TRACE_GC(heap_->tracer(), GCTracer::Scope::MC_INCREMENTAL_SWEEPING);
FinalizeSweeping();
}
size_t bytes_processed = 0;
if (state_ == MARKING) {
const bool incremental_wrapper_tracing =
FLAG_incremental_marking_wrappers && heap_->UsingEmbedderHeapTracer();
const bool process_wrappers =
incremental_wrapper_tracing &&
(heap_->RequiresImmediateWrapperProcessing() ||
heap_->mark_compact_collector()->marking_deque()->IsEmpty());
bool wrapper_work_left = incremental_wrapper_tracing;
if (!process_wrappers) {
bytes_processed = ProcessMarkingDeque(bytes_to_process);
if (step_origin == StepOrigin::kTask) {
bytes_marked_ahead_of_schedule_ += bytes_processed;
}
} else {
const double wrapper_deadline =
heap_->MonotonicallyIncreasingTimeInMs() + kStepSizeInMs;
TRACE_GC(heap()->tracer(),
GCTracer::Scope::MC_INCREMENTAL_WRAPPER_TRACING);
heap_->RegisterWrappersWithEmbedderHeapTracer();
wrapper_work_left = heap_->embedder_heap_tracer()->AdvanceTracing(
wrapper_deadline, EmbedderHeapTracer::AdvanceTracingActions(
EmbedderHeapTracer::ForceCompletionAction::
DO_NOT_FORCE_COMPLETION));
}
if (heap_->mark_compact_collector()->marking_deque()->IsEmpty() &&
!wrapper_work_left) {
if (completion == FORCE_COMPLETION ||
IsIdleMarkingDelayCounterLimitReached()) {
if (!finalize_marking_completed_) {
FinalizeMarking(action);
} else {
MarkingComplete(action);
}
} else {
IncrementIdleMarkingDelayCounter();
}
}
}
double end = heap_->MonotonicallyIncreasingTimeInMs();
double duration = (end - start);
// Note that we report zero bytes here when sweeping was in progress or
// when we just started incremental marking. In these cases we did not
// process the marking deque.
heap_->tracer()->AddIncrementalMarkingStep(duration, bytes_processed);
if (FLAG_trace_incremental_marking) {
heap_->isolate()->PrintWithTimestamp(
"[IncrementalMarking] Step %s %zu bytes (%zu) in %.1f\n",
step_origin == StepOrigin::kV8 ? "in v8" : "in task", bytes_processed,
bytes_to_process, duration);
}
return bytes_processed;
}
bool IncrementalMarking::IsIdleMarkingDelayCounterLimitReached() {
return idle_marking_delay_counter_ > kMaxIdleMarkingDelayCounter;
}
void IncrementalMarking::IncrementIdleMarkingDelayCounter() {
idle_marking_delay_counter_++;
}
void IncrementalMarking::ClearIdleMarkingDelayCounter() {
idle_marking_delay_counter_ = 0;
}
} // namespace internal
} // namespace v8