// 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/objects-visiting.h"
#include "src/heap/objects-visiting-inl.h"
#include "src/v8.h"
namespace v8 {
namespace internal {
IncrementalMarking::StepActions IncrementalMarking::IdleStepActions() {
return StepActions(IncrementalMarking::NO_GC_VIA_STACK_GUARD,
IncrementalMarking::FORCE_MARKING,
IncrementalMarking::DO_NOT_FORCE_COMPLETION);
}
IncrementalMarking::IncrementalMarking(Heap* heap)
: heap_(heap),
observer_(*this, kAllocatedThreshold),
state_(STOPPED),
is_compacting_(false),
steps_count_(0),
old_generation_space_available_at_start_of_incremental_(0),
old_generation_space_used_at_start_of_incremental_(0),
bytes_rescanned_(0),
should_hurry_(false),
marking_speed_(0),
bytes_scanned_(0),
allocated_(0),
write_barriers_invoked_since_last_step_(0),
idle_marking_delay_counter_(0),
no_marking_scope_depth_(0),
unscanned_bytes_of_large_object_(0),
was_activated_(false),
finalize_marking_completed_(false),
incremental_marking_finalization_rounds_(0),
request_type_(COMPLETE_MARKING) {}
bool IncrementalMarking::BaseRecordWrite(HeapObject* obj, Object* value) {
HeapObject* value_heap_obj = HeapObject::cast(value);
MarkBit value_bit = Marking::MarkBitFrom(value_heap_obj);
DCHECK(!Marking::IsImpossible(value_bit));
MarkBit obj_bit = Marking::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());
IncrementalMarking* marking = isolate->heap()->incremental_marking();
MemoryChunk* chunk = MemoryChunk::FromAddress(obj->address());
int counter = chunk->write_barrier_counter();
if (counter < (MemoryChunk::kWriteBarrierCounterGranularity / 2)) {
marking->write_barriers_invoked_since_last_step_ +=
MemoryChunk::kWriteBarrierCounterGranularity -
chunk->write_barrier_counter();
chunk->set_write_barrier_counter(
MemoryChunk::kWriteBarrierCounterGranularity);
}
marking->RecordWrite(obj, slot, *slot);
}
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
(slot), value);
}
}
void IncrementalMarking::RecordWriteIntoCodeSlow(HeapObject* obj,
RelocInfo* rinfo,
Object* value) {
if (BaseRecordWrite(obj, value)) {
// Object is not going to be rescanned. We need to record the slot.
heap_->mark_compact_collector()->RecordRelocSlot(rinfo,
Code::cast(value));
}
}
void IncrementalMarking::RecordWrites(HeapObject* obj) {
if (IsMarking()) {
MarkBit obj_bit = Marking::MarkBitFrom(obj);
if (Marking::IsBlack(obj_bit)) {
MemoryChunk* chunk = MemoryChunk::FromAddress(obj->address());
if (chunk->IsFlagSet(MemoryChunk::HAS_PROGRESS_BAR)) {
chunk->set_progress_bar(0);
}
BlackToGreyAndUnshift(obj, obj_bit);
RestartIfNotMarking();
}
}
}
void IncrementalMarking::BlackToGreyAndUnshift(HeapObject* obj,
MarkBit mark_bit) {
DCHECK(Marking::MarkBitFrom(obj) == mark_bit);
DCHECK(obj->Size() >= 2 * kPointerSize);
DCHECK(IsMarking());
Marking::BlackToGrey(mark_bit);
int obj_size = obj->Size();
MemoryChunk::IncrementLiveBytesFromGC(obj, -obj_size);
bytes_scanned_ -= obj_size;
int64_t old_bytes_rescanned = bytes_rescanned_;
bytes_rescanned_ = old_bytes_rescanned + obj_size;
if ((bytes_rescanned_ >> 20) != (old_bytes_rescanned >> 20)) {
if (bytes_rescanned_ > 2 * heap_->PromotedSpaceSizeOfObjects()) {
// If we have queued twice the heap size for rescanning then we are
// going around in circles, scanning the same objects again and again
// as the program mutates the heap faster than we can incrementally
// trace it. In this case we switch to non-incremental marking in
// order to finish off this marking phase.
if (FLAG_trace_incremental_marking) {
PrintIsolate(
heap()->isolate(),
"Hurrying incremental marking because of lack of progress\n");
}
marking_speed_ = kMaxMarkingSpeed;
}
}
heap_->mark_compact_collector()->marking_deque()->Unshift(obj);
}
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 = Marking::MarkBitFrom(HeapObject::cast(obj));
if (Marking::IsBlack(mark_bit)) {
MemoryChunk::IncrementLiveBytesFromGC(heap_obj, -heap_obj->Size());
}
Marking::AnyToGrey(mark_bit);
}
}
static inline void MarkBlackOrKeepBlack(HeapObject* heap_object,
MarkBit mark_bit, int size) {
DCHECK(!Marking::IsImpossible(mark_bit));
if (Marking::IsBlack(mark_bit)) return;
Marking::MarkBlack(mark_bit);
MemoryChunk::IncrementLiveBytesFromGC(heap_object, size);
}
class IncrementalMarkingMarkingVisitor
: public StaticMarkingVisitor {
public:
static void Initialize() {
StaticMarkingVisitor::Initialize();
table_.Register(kVisitFixedArray, &VisitFixedArrayIncremental);
table_.Register(kVisitNativeContext, &VisitNativeContextIncremental);
table_.Register(kVisitJSRegExp, &VisitJSRegExp);
}
static const int kProgressBarScanningChunk = 32 * 1024;
static void VisitFixedArrayIncremental(Map* map, HeapObject* object) {
MemoryChunk* chunk = MemoryChunk::FromAddress(object->address());
// TODO(mstarzinger): Move setting of the flag to the allocation site of
// the array. The visitor should just check the flag.
if (FLAG_use_marking_progress_bar &&
chunk->owner()->identity() == LO_SPACE) {
chunk->SetFlag(MemoryChunk::HAS_PROGRESS_BAR);
}
if (chunk->IsFlagSet(MemoryChunk::HAS_PROGRESS_BAR)) {
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(Marking::MarkBitFrom(object))) {
heap->mark_compact_collector()->marking_deque()->Unshift(object);
} else {
DCHECK(Marking::IsBlack(Marking::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()) {
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::MarkObject(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 = Marking::MarkBitFrom(heap_object);
if (Marking::IsWhite(mark_bit)) {
Marking::MarkBlack(mark_bit);
MemoryChunk::IncrementLiveBytesFromGC(heap_object, heap_object->Size());
return true;
}
return false;
}
};
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::MarkObject(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);
}
chunk->SetFlag(MemoryChunk::SCAN_ON_SCAVENGE);
}
void IncrementalMarking::DeactivateIncrementalWriteBarrierForSpace(
PagedSpace* space) {
PageIterator it(space);
while (it.has_next()) {
Page* p = it.next();
SetOldSpacePageFlags(p, false, false);
}
}
void IncrementalMarking::DeactivateIncrementalWriteBarrierForSpace(
NewSpace* space) {
NewSpacePageIterator it(space);
while (it.has_next()) {
NewSpacePage* p = it.next();
SetNewSpacePageFlags(p, false);
}
}
void IncrementalMarking::DeactivateIncrementalWriteBarrier() {
DeactivateIncrementalWriteBarrierForSpace(heap_->old_space());
DeactivateIncrementalWriteBarrierForSpace(heap_->map_space());
DeactivateIncrementalWriteBarrierForSpace(heap_->code_space());
DeactivateIncrementalWriteBarrierForSpace(heap_->new_space());
LargePage* lop = heap_->lo_space()->first_page();
while (lop->is_valid()) {
SetOldSpacePageFlags(lop, false, false);
lop = lop->next_page();
}
}
void IncrementalMarking::ActivateIncrementalWriteBarrier(PagedSpace* space) {
PageIterator it(space);
while (it.has_next()) {
Page* p = it.next();
SetOldSpacePageFlags(p, true, is_compacting_);
}
}
void IncrementalMarking::ActivateIncrementalWriteBarrier(NewSpace* space) {
NewSpacePageIterator it(space->ToSpaceStart(), space->ToSpaceEnd());
while (it.has_next()) {
NewSpacePage* p = it.next();
SetNewSpacePageFlags(p, true);
}
}
void IncrementalMarking::ActivateIncrementalWriteBarrier() {
ActivateIncrementalWriteBarrier(heap_->old_space());
ActivateIncrementalWriteBarrier(heap_->map_space());
ActivateIncrementalWriteBarrier(heap_->code_space());
ActivateIncrementalWriteBarrier(heap_->new_space());
LargePage* lop = heap_->lo_space()->first_page();
while (lop->is_valid()) {
SetOldSpacePageFlags(lop, true, is_compacting_);
lop = lop->next_page();
}
}
bool IncrementalMarking::ShouldActivateEvenWithoutIdleNotification() {
return CanBeActivated() &&
heap_->HeapIsFullEnoughToStartIncrementalMarking(
heap_->old_generation_allocation_limit());
}
bool IncrementalMarking::WasActivated() { return was_activated_; }
bool IncrementalMarking::CanBeActivated() {
#ifndef DEBUG
static const intptr_t kActivationThreshold = 8 * MB;
#else
// TODO(gc) consider setting this to some low level so that some
// debug tests run with incremental marking and some without.
static const intptr_t kActivationThreshold = 0;
#endif
// 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.
// Don't switch on for very small heaps.
return FLAG_incremental_marking && heap_->gc_state() == Heap::NOT_IN_GC &&
heap_->deserialization_complete() &&
!heap_->isolate()->serializer_enabled() &&
heap_->PromotedSpaceSizeOfObjects() > kActivationThreshold;
}
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);
}
}
void IncrementalMarking::NotifyOfHighPromotionRate() {
if (IsMarking()) {
if (marking_speed_ < kFastMarking) {
if (FLAG_trace_gc) {
PrintIsolate(heap()->isolate(),
"Increasing marking speed to %d "
"due to high promotion rate\n",
static_cast(kFastMarking));
}
marking_speed_ = kFastMarking;
}
}
}
static void PatchIncrementalMarkingRecordWriteStubs(
Heap* heap, RecordWriteStub::Mode mode) {
UnseededNumberDictionary* stubs = heap->code_stubs();
int capacity = stubs->Capacity();
for (int i = 0; i < capacity; i++) {
Object* k = stubs->KeyAt(i);
if (stubs->IsKey(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(const char* reason) {
if (FLAG_trace_incremental_marking) {
PrintF("[IncrementalMarking] Start (%s)\n",
(reason == nullptr) ? "unknown reason" : reason);
}
DCHECK(FLAG_incremental_marking);
DCHECK(state_ == STOPPED);
DCHECK(heap_->gc_state() == Heap::NOT_IN_GC);
DCHECK(!heap_->isolate()->serializer_enabled());
HistogramTimerScope incremental_marking_scope(
heap_->isolate()->counters()->gc_incremental_marking_start());
ResetStepCounters();
was_activated_ = true;
if (!heap_->mark_compact_collector()->sweeping_in_progress()) {
StartMarking();
} else {
if (FLAG_trace_incremental_marking) {
PrintF("[IncrementalMarking] Start sweeping.\n");
}
state_ = SWEEPING;
}
heap_->new_space()->AddInlineAllocationObserver(&observer_);
incremental_marking_job()->Start(heap_);
}
void IncrementalMarking::StartMarking() {
if (FLAG_trace_incremental_marking) {
PrintF("[IncrementalMarking] Start marking\n");
}
is_compacting_ = !FLAG_never_compact &&
heap_->mark_compact_collector()->StartCompaction(
MarkCompactCollector::INCREMENTAL_COMPACTION);
state_ = MARKING;
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();
if (FLAG_cleanup_code_caches_at_gc) {
// We will mark cache black with a separate pass
// when we finish marking.
MarkObjectGreyDoNotEnqueue(heap_->polymorphic_code_cache());
}
// Mark strong roots grey.
IncrementalMarkingRootMarkingVisitor visitor(this);
heap_->IterateStrongRoots(&visitor, VISIT_ONLY_STRONG);
// Ready to start incremental marking.
if (FLAG_trace_incremental_marking) {
PrintF("[IncrementalMarking] Running\n");
}
}
void IncrementalMarking::MarkRoots() {
DCHECK(!finalize_marking_completed_);
DCHECK(IsMarking());
IncrementalMarkingRootMarkingVisitor visitor(this);
heap_->IterateStrongRoots(&visitor, VISIT_ONLY_STRONG);
}
void IncrementalMarking::MarkObjectGroups() {
DCHECK(!finalize_marking_completed_);
DCHECK(IsMarking());
IncrementalMarkingRootMarkingVisitor visitor(this);
heap_->mark_compact_collector()->MarkImplicitRefGroups(&MarkObject);
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::FromInt(0);
WeakCell* prev_weak_cell_obj = NULL;
while (weak_cell_obj != Smi::FromInt(0)) {
WeakCell* weak_cell = reinterpret_cast(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::FromInt(0)) {
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(Marking::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 = Marking::MarkBitFrom(map);
if (i >= number_of_disposed_maps && !map_retaining_is_disabled &&
Marking::IsWhite(map_mark)) {
if (ShouldRetainMap(map, age)) {
MarkObject(heap(), map);
}
Object* prototype = map->prototype();
if (age > 0 && prototype->IsHeapObject() &&
Marking::IsWhite(Marking::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() {
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();
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());
double end = heap_->MonotonicallyIncreasingTimeInMs();
double delta = end - start;
heap_->tracer()->AddMarkingTime(delta);
heap_->tracer()->AddIncrementalMarkingFinalizationStep(delta);
if (FLAG_trace_incremental_marking) {
PrintF(
"[IncrementalMarking] Finalize incrementally round %d, "
"spent %d ms, marking progress %d.\n",
static_cast(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;
}
}
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);
if (heap_->InNewSpace(obj)) {
MapWord map_word = obj->map_word();
if (map_word.IsForwardingAddress()) {
HeapObject* dest = map_word.ToForwardingAddress();
array[new_top] = dest;
new_top = ((new_top + 1) & mask);
DCHECK(new_top != marking_deque->bottom());
#ifdef DEBUG
MarkBit mark_bit = Marking::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 = Marking::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) {
MarkObject(heap_, map);
IncrementalMarkingMarkingVisitor::IterateBody(map, obj);
MarkBit mark_bit = Marking::MarkBitFrom(obj);
#if ENABLE_SLOW_DCHECKS
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
MarkBlackOrKeepBlack(obj, mark_bit, size);
}
void IncrementalMarking::MarkObject(Heap* heap, HeapObject* obj) {
MarkBit mark_bit = Marking::MarkBitFrom(obj);
if (Marking::IsWhite(mark_bit)) {
heap->incremental_marking()->WhiteToGreyAndPush(obj, mark_bit);
}
}
intptr_t IncrementalMarking::ProcessMarkingDeque(intptr_t bytes_to_process) {
intptr_t bytes_processed = 0;
Map* filler_map = heap_->one_pointer_filler_map();
MarkingDeque* marking_deque =
heap_->mark_compact_collector()->marking_deque();
while (!marking_deque->IsEmpty() && bytes_processed < bytes_to_process) {
HeapObject* obj = marking_deque->Pop();
// Explicitly skip one word fillers. Incremental markbit patterns are
// correct only for objects that occupy at least two words.
Map* map = obj->map();
if (map == filler_map) continue;
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::ProcessMarkingDeque() {
Map* filler_map = heap_->one_pointer_filler_map();
MarkingDeque* marking_deque =
heap_->mark_compact_collector()->marking_deque();
while (!marking_deque->IsEmpty()) {
HeapObject* obj = marking_deque->Pop();
// Explicitly skip one word fillers. Incremental markbit patterns are
// correct only for objects that occupy at least two words.
Map* map = obj->map();
if (map == filler_map) continue;
VisitObject(map, obj, obj->SizeFromMap(map));
}
}
void IncrementalMarking::Hurry() {
if (state() == MARKING) {
double start = 0.0;
if (FLAG_trace_incremental_marking || FLAG_print_cumulative_gc_stat) {
start = heap_->MonotonicallyIncreasingTimeInMs();
if (FLAG_trace_incremental_marking) {
PrintF("[IncrementalMarking] Hurry\n");
}
}
// TODO(gc) hurry can mark objects it encounters black as mutator
// was stopped.
ProcessMarkingDeque();
state_ = COMPLETE;
if (FLAG_trace_incremental_marking || FLAG_print_cumulative_gc_stat) {
double end = heap_->MonotonicallyIncreasingTimeInMs();
double delta = end - start;
heap_->tracer()->AddMarkingTime(delta);
if (FLAG_trace_incremental_marking) {
PrintF("[IncrementalMarking] Complete (hurry), spent %d ms.\n",
static_cast(delta));
}
}
}
if (FLAG_cleanup_code_caches_at_gc) {
PolymorphicCodeCache* poly_cache = heap_->polymorphic_code_cache();
Marking::GreyToBlack(Marking::MarkBitFrom(poly_cache));
MemoryChunk::IncrementLiveBytesFromGC(poly_cache,
PolymorphicCodeCache::kSize);
}
Object* context = heap_->native_contexts_list();
while (!context->IsUndefined()) {
// 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()) {
MarkBit mark_bit = Marking::MarkBitFrom(cache);
if (Marking::IsGrey(mark_bit)) {
Marking::GreyToBlack(mark_bit);
MemoryChunk::IncrementLiveBytesFromGC(cache, cache->Size());
}
}
context = Context::cast(context)->get(Context::NEXT_CONTEXT_LINK);
}
}
void IncrementalMarking::Stop() {
if (IsStopped()) return;
if (FLAG_trace_incremental_marking) {
PrintF("[IncrementalMarking] Stopping.\n");
}
heap_->new_space()->RemoveInlineAllocationObserver(&observer_);
IncrementalMarking::set_should_hurry(false);
ResetStepCounters();
if (IsMarking()) {
PatchIncrementalMarkingRecordWriteStubs(heap_,
RecordWriteStub::STORE_BUFFER_ONLY);
DeactivateIncrementalWriteBarrier();
if (is_compacting_) {
LargeObjectIterator it(heap_->lo_space());
for (HeapObject* obj = it.Next(); obj != NULL; obj = it.Next()) {
Page* p = Page::FromAddress(obj->address());
if (p->IsFlagSet(Page::RESCAN_ON_EVACUATION)) {
p->ClearFlag(Page::RESCAN_ON_EVACUATION);
}
}
}
}
heap_->isolate()->stack_guard()->ClearGC();
state_ = STOPPED;
is_compacting_ = false;
}
void IncrementalMarking::Finalize() {
Hurry();
state_ = STOPPED;
is_compacting_ = false;
heap_->new_space()->RemoveInlineAllocationObserver(&observer_);
IncrementalMarking::set_should_hurry(false);
ResetStepCounters();
PatchIncrementalMarkingRecordWriteStubs(heap_,
RecordWriteStub::STORE_BUFFER_ONLY);
DeactivateIncrementalWriteBarrier();
DCHECK(heap_->mark_compact_collector()->marking_deque()->IsEmpty());
heap_->isolate()->stack_guard()->ClearGC();
}
void IncrementalMarking::FinalizeMarking(CompletionAction action) {
DCHECK(!finalize_marking_completed_);
if (FLAG_trace_incremental_marking) {
PrintF(
"[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) {
PrintF("[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(
intptr_t step_size_in_bytes, double deadline_in_ms,
IncrementalMarking::StepActions step_actions) {
DCHECK(!IsStopped());
if (step_size_in_bytes == 0) {
step_size_in_bytes = GCIdleTimeHandler::EstimateMarkingStepSize(
static_cast(GCIdleTimeHandler::kIncrementalMarkingStepTimeInMs),
static_cast(
heap()
->tracer()
->FinalIncrementalMarkCompactSpeedInBytesPerMillisecond()));
}
double remaining_time_in_ms = 0.0;
do {
Step(step_size_in_bytes, step_actions.completion_action,
step_actions.force_marking, step_actions.force_completion);
remaining_time_in_ms =
deadline_in_ms - heap()->MonotonicallyIncreasingTimeInMs();
} while (remaining_time_in_ms >=
2.0 * GCIdleTimeHandler::kIncrementalMarkingStepTimeInMs &&
!IsComplete() &&
!heap()->mark_compact_collector()->marking_deque()->IsEmpty());
return remaining_time_in_ms;
}
void IncrementalMarking::OldSpaceStep(intptr_t allocated) {
if (IsStopped() && ShouldActivateEvenWithoutIdleNotification()) {
heap()->StartIncrementalMarking(Heap::kNoGCFlags, kNoGCCallbackFlags,
"old space step");
} else {
Step(allocated * kFastMarking / kInitialMarkingSpeed, GC_VIA_STACK_GUARD);
}
}
void IncrementalMarking::SpeedUp() {
bool speed_up = false;
if ((steps_count_ % kMarkingSpeedAccellerationInterval) == 0) {
if (FLAG_trace_incremental_marking) {
PrintIsolate(heap()->isolate(), "Speed up marking after %d steps\n",
static_cast(kMarkingSpeedAccellerationInterval));
}
speed_up = true;
}
bool space_left_is_very_small =
(old_generation_space_available_at_start_of_incremental_ < 10 * MB);
bool only_1_nth_of_space_that_was_available_still_left =
(SpaceLeftInOldSpace() * (marking_speed_ + 1) <
old_generation_space_available_at_start_of_incremental_);
if (space_left_is_very_small ||
only_1_nth_of_space_that_was_available_still_left) {
if (FLAG_trace_incremental_marking)
PrintIsolate(heap()->isolate(),
"Speed up marking because of low space left\n");
speed_up = true;
}
bool size_of_old_space_multiplied_by_n_during_marking =
(heap_->PromotedTotalSize() >
(marking_speed_ + 1) *
old_generation_space_used_at_start_of_incremental_);
if (size_of_old_space_multiplied_by_n_during_marking) {
speed_up = true;
if (FLAG_trace_incremental_marking) {
PrintIsolate(heap()->isolate(),
"Speed up marking because of heap size increase\n");
}
}
int64_t promoted_during_marking =
heap_->PromotedTotalSize() -
old_generation_space_used_at_start_of_incremental_;
intptr_t delay = marking_speed_ * MB;
intptr_t scavenge_slack = heap_->MaxSemiSpaceSize();
// We try to scan at at least twice the speed that we are allocating.
if (promoted_during_marking > bytes_scanned_ / 2 + scavenge_slack + delay) {
if (FLAG_trace_incremental_marking) {
PrintIsolate(heap()->isolate(),
"Speed up marking because marker was not keeping up\n");
}
speed_up = true;
}
if (speed_up) {
if (state_ != MARKING) {
if (FLAG_trace_incremental_marking) {
PrintIsolate(heap()->isolate(),
"Postponing speeding up marking until marking starts\n");
}
} else {
marking_speed_ += kMarkingSpeedAccelleration;
marking_speed_ = static_cast(
Min(kMaxMarkingSpeed, static_cast(marking_speed_ * 1.3)));
if (FLAG_trace_incremental_marking) {
PrintIsolate(heap()->isolate(), "Marking speed increased to %d\n",
marking_speed_);
}
}
}
}
intptr_t IncrementalMarking::Step(intptr_t allocated_bytes,
CompletionAction action,
ForceMarkingAction marking,
ForceCompletionAction completion) {
DCHECK(allocated_bytes >= 0);
if (heap_->gc_state() != Heap::NOT_IN_GC || !FLAG_incremental_marking ||
(state_ != SWEEPING && state_ != MARKING)) {
return 0;
}
allocated_ += allocated_bytes;
if (marking == DO_NOT_FORCE_MARKING && allocated_ < kAllocatedThreshold &&
write_barriers_invoked_since_last_step_ <
kWriteBarriersInvokedThreshold) {
return 0;
}
// If an idle notification happened recently, we delay marking steps.
if (marking == DO_NOT_FORCE_MARKING &&
heap_->RecentIdleNotificationHappened()) {
return 0;
}
if (state_ == MARKING && no_marking_scope_depth_ > 0) return 0;
intptr_t bytes_processed = 0;
{
HistogramTimerScope incremental_marking_scope(
heap_->isolate()->counters()->gc_incremental_marking());
double start = heap_->MonotonicallyIncreasingTimeInMs();
// The marking speed is driven either by the allocation rate or by the rate
// at which we are having to check the color of objects in the write
// barrier.
// It is possible for a tight non-allocating loop to run a lot of write
// barriers before we get here and check them (marking can only take place
// on
// allocation), so to reduce the lumpiness we don't use the write barriers
// invoked since last step directly to determine the amount of work to do.
intptr_t bytes_to_process =
marking_speed_ *
Max(allocated_, write_barriers_invoked_since_last_step_);
allocated_ = 0;
write_barriers_invoked_since_last_step_ = 0;
bytes_scanned_ += bytes_to_process;
if (state_ == SWEEPING) {
if (heap_->mark_compact_collector()->sweeping_in_progress() &&
(heap_->mark_compact_collector()->IsSweepingCompleted() ||
!FLAG_concurrent_sweeping)) {
heap_->mark_compact_collector()->EnsureSweepingCompleted();
}
if (!heap_->mark_compact_collector()->sweeping_in_progress()) {
bytes_scanned_ = 0;
StartMarking();
}
} else if (state_ == MARKING) {
bytes_processed = ProcessMarkingDeque(bytes_to_process);
if (heap_->mark_compact_collector()->marking_deque()->IsEmpty()) {
if (completion == FORCE_COMPLETION ||
IsIdleMarkingDelayCounterLimitReached()) {
if (!finalize_marking_completed_) {
FinalizeMarking(action);
} else {
MarkingComplete(action);
}
} else {
IncrementIdleMarkingDelayCounter();
}
}
}
steps_count_++;
// Speed up marking if we are marking too slow or if we are almost done
// with marking.
SpeedUp();
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);
}
return bytes_processed;
}
void IncrementalMarking::ResetStepCounters() {
steps_count_ = 0;
old_generation_space_available_at_start_of_incremental_ =
SpaceLeftInOldSpace();
old_generation_space_used_at_start_of_incremental_ =
heap_->PromotedTotalSize();
bytes_rescanned_ = 0;
marking_speed_ = kInitialMarkingSpeed;
bytes_scanned_ = 0;
write_barriers_invoked_since_last_step_ = 0;
}
int64_t IncrementalMarking::SpaceLeftInOldSpace() {
return heap_->MaxOldGenerationSize() - heap_->PromotedSpaceSizeOfObjects();
}
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