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|
// 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_MARK_COMPACT_H_
#define V8_HEAP_MARK_COMPACT_H_
#include <vector>
#include "src/heap/concurrent-marking.h"
#include "src/heap/marking.h"
#include "src/heap/objects-visiting.h"
#include "src/heap/spaces.h"
#include "src/heap/sweeper.h"
#include "src/heap/worklist.h"
namespace v8 {
namespace internal {
// Forward declarations.
class EvacuationJobTraits;
class HeapObjectVisitor;
class ItemParallelJob;
class MigrationObserver;
class RecordMigratedSlotVisitor;
class UpdatingItem;
class YoungGenerationMarkingVisitor;
template <typename ConcreteState, AccessMode access_mode>
class MarkingStateBase {
public:
V8_INLINE MarkBit MarkBitFrom(HeapObject* obj) {
return MarkBitFrom(MemoryChunk::FromAddress(obj->address()),
obj->address());
}
V8_INLINE MarkBit MarkBitFrom(MemoryChunk* p, Address addr) {
return static_cast<ConcreteState*>(this)->bitmap(p)->MarkBitFromIndex(
p->AddressToMarkbitIndex(addr));
}
Marking::ObjectColor Color(HeapObject* obj) {
return Marking::Color(MarkBitFrom(obj));
}
V8_INLINE bool IsImpossible(HeapObject* obj) {
return Marking::IsImpossible<access_mode>(MarkBitFrom(obj));
}
V8_INLINE bool IsBlack(HeapObject* obj) {
return Marking::IsBlack<access_mode>(MarkBitFrom(obj));
}
V8_INLINE bool IsWhite(HeapObject* obj) {
return Marking::IsWhite<access_mode>(MarkBitFrom(obj));
}
V8_INLINE bool IsGrey(HeapObject* obj) {
return Marking::IsGrey<access_mode>(MarkBitFrom(obj));
}
V8_INLINE bool IsBlackOrGrey(HeapObject* obj) {
return Marking::IsBlackOrGrey<access_mode>(MarkBitFrom(obj));
}
V8_INLINE bool WhiteToGrey(HeapObject* obj) {
return Marking::WhiteToGrey<access_mode>(MarkBitFrom(obj));
}
V8_INLINE bool WhiteToBlack(HeapObject* obj) {
return WhiteToGrey(obj) && GreyToBlack(obj);
}
V8_INLINE bool GreyToBlack(HeapObject* obj) {
MemoryChunk* p = MemoryChunk::FromAddress(obj->address());
MarkBit markbit = MarkBitFrom(p, obj->address());
if (!Marking::GreyToBlack<access_mode>(markbit)) return false;
static_cast<ConcreteState*>(this)->IncrementLiveBytes(p, obj->Size());
return true;
}
void ClearLiveness(MemoryChunk* chunk) {
static_cast<ConcreteState*>(this)->bitmap(chunk)->Clear();
static_cast<ConcreteState*>(this)->SetLiveBytes(chunk, 0);
}
};
class MarkBitCellIterator {
public:
MarkBitCellIterator(MemoryChunk* chunk, Bitmap* bitmap) : chunk_(chunk) {
DCHECK(Bitmap::IsCellAligned(
chunk_->AddressToMarkbitIndex(chunk_->area_start())));
DCHECK(Bitmap::IsCellAligned(
chunk_->AddressToMarkbitIndex(chunk_->area_end())));
last_cell_index_ =
Bitmap::IndexToCell(chunk_->AddressToMarkbitIndex(chunk_->area_end()));
cell_base_ = chunk_->area_start();
cell_index_ =
Bitmap::IndexToCell(chunk_->AddressToMarkbitIndex(cell_base_));
cells_ = bitmap->cells();
}
inline bool Done() { return cell_index_ >= last_cell_index_; }
inline bool HasNext() { return cell_index_ < last_cell_index_ - 1; }
inline MarkBit::CellType* CurrentCell() {
DCHECK_EQ(cell_index_, Bitmap::IndexToCell(Bitmap::CellAlignIndex(
chunk_->AddressToMarkbitIndex(cell_base_))));
return &cells_[cell_index_];
}
inline Address CurrentCellBase() {
DCHECK_EQ(cell_index_, Bitmap::IndexToCell(Bitmap::CellAlignIndex(
chunk_->AddressToMarkbitIndex(cell_base_))));
return cell_base_;
}
V8_WARN_UNUSED_RESULT inline bool Advance() {
cell_base_ += Bitmap::kBitsPerCell * kPointerSize;
return ++cell_index_ != last_cell_index_;
}
inline bool Advance(unsigned int new_cell_index) {
if (new_cell_index != cell_index_) {
DCHECK_GT(new_cell_index, cell_index_);
DCHECK_LE(new_cell_index, last_cell_index_);
unsigned int diff = new_cell_index - cell_index_;
cell_index_ = new_cell_index;
cell_base_ += diff * (Bitmap::kBitsPerCell * kPointerSize);
return true;
}
return false;
}
// Return the next mark bit cell. If there is no next it returns 0;
inline MarkBit::CellType PeekNext() {
if (HasNext()) {
return cells_[cell_index_ + 1];
}
return 0;
}
private:
MemoryChunk* chunk_;
MarkBit::CellType* cells_;
unsigned int last_cell_index_;
unsigned int cell_index_;
Address cell_base_;
};
enum LiveObjectIterationMode {
kBlackObjects,
kGreyObjects,
kAllLiveObjects
};
template <LiveObjectIterationMode mode>
class LiveObjectRange {
public:
class iterator {
public:
using value_type = std::pair<HeapObject*, int /* size */>;
using pointer = const value_type*;
using reference = const value_type&;
using iterator_category = std::forward_iterator_tag;
inline iterator(MemoryChunk* chunk, Bitmap* bitmap, Address start);
inline iterator& operator++();
inline iterator operator++(int);
bool operator==(iterator other) const {
return current_object_ == other.current_object_;
}
bool operator!=(iterator other) const { return !(*this == other); }
value_type operator*() {
return std::make_pair(current_object_, current_size_);
}
private:
inline void AdvanceToNextValidObject();
MemoryChunk* const chunk_;
Map* const one_word_filler_map_;
Map* const two_word_filler_map_;
Map* const free_space_map_;
MarkBitCellIterator it_;
Address cell_base_;
MarkBit::CellType current_cell_;
HeapObject* current_object_;
int current_size_;
};
LiveObjectRange(MemoryChunk* chunk, Bitmap* bitmap)
: chunk_(chunk),
bitmap_(bitmap),
start_(chunk_->area_start()),
end_(chunk->area_end()) {}
inline iterator begin();
inline iterator end();
private:
MemoryChunk* const chunk_;
Bitmap* bitmap_;
Address start_;
Address end_;
};
class LiveObjectVisitor : AllStatic {
public:
enum IterationMode {
kKeepMarking,
kClearMarkbits,
};
// Visits black objects on a MemoryChunk until the Visitor returns |false| for
// an object. If IterationMode::kClearMarkbits is passed the markbits and
// slots for visited objects are cleared for each successfully visited object.
template <class Visitor, typename MarkingState>
static bool VisitBlackObjects(MemoryChunk* chunk, MarkingState* state,
Visitor* visitor, IterationMode iteration_mode,
HeapObject** failed_object);
// Visits black objects on a MemoryChunk. The visitor is not allowed to fail
// visitation for an object.
template <class Visitor, typename MarkingState>
static void VisitBlackObjectsNoFail(MemoryChunk* chunk, MarkingState* state,
Visitor* visitor,
IterationMode iteration_mode);
// Visits black objects on a MemoryChunk. The visitor is not allowed to fail
// visitation for an object.
template <class Visitor, typename MarkingState>
static void VisitGreyObjectsNoFail(MemoryChunk* chunk, MarkingState* state,
Visitor* visitor,
IterationMode iteration_mode);
template <typename MarkingState>
static void RecomputeLiveBytes(MemoryChunk* chunk, MarkingState* state);
};
enum PageEvacuationMode { NEW_TO_NEW, NEW_TO_OLD };
enum MarkingTreatmentMode { KEEP, CLEAR };
enum class RememberedSetUpdatingMode { ALL, OLD_TO_NEW_ONLY };
// Base class for minor and full MC collectors.
class MarkCompactCollectorBase {
public:
virtual ~MarkCompactCollectorBase() {}
virtual void SetUp() = 0;
virtual void TearDown() = 0;
virtual void CollectGarbage() = 0;
inline Heap* heap() const { return heap_; }
inline Isolate* isolate() { return heap()->isolate(); }
protected:
static const int kMainThread = 0;
explicit MarkCompactCollectorBase(Heap* heap)
: heap_(heap), old_to_new_slots_(0) {}
// Marking operations for objects reachable from roots.
virtual void MarkLiveObjects() = 0;
// Mark objects reachable (transitively) from objects in the marking
// work list.
virtual void ProcessMarkingWorklist() = 0;
// Clear non-live references held in side data structures.
virtual void ClearNonLiveReferences() = 0;
virtual void EvacuatePrologue() = 0;
virtual void EvacuateEpilogue() = 0;
virtual void Evacuate() = 0;
virtual void EvacuatePagesInParallel() = 0;
virtual void UpdatePointersAfterEvacuation() = 0;
virtual UpdatingItem* CreateToSpaceUpdatingItem(MemoryChunk* chunk,
Address start,
Address end) = 0;
virtual UpdatingItem* CreateRememberedSetUpdatingItem(
MemoryChunk* chunk, RememberedSetUpdatingMode updating_mode) = 0;
template <class Evacuator, class Collector>
void CreateAndExecuteEvacuationTasks(
Collector* collector, ItemParallelJob* job,
RecordMigratedSlotVisitor* record_visitor,
MigrationObserver* migration_observer, const intptr_t live_bytes);
// Returns whether this page should be moved according to heuristics.
bool ShouldMovePage(Page* p, intptr_t live_bytes);
int CollectToSpaceUpdatingItems(ItemParallelJob* job);
template <typename IterateableSpace>
int CollectRememberedSetUpdatingItems(ItemParallelJob* job,
IterateableSpace* space,
RememberedSetUpdatingMode mode);
int NumberOfParallelCompactionTasks(int pages);
int NumberOfParallelPointerUpdateTasks(int pages, int slots);
int NumberOfParallelToSpacePointerUpdateTasks(int pages);
Heap* heap_;
// Number of old to new slots. Should be computed during MarkLiveObjects.
// -1 indicates that the value couldn't be computed.
int old_to_new_slots_;
};
class MinorMarkingState final
: public MarkingStateBase<MinorMarkingState, AccessMode::ATOMIC> {
public:
Bitmap* bitmap(const MemoryChunk* chunk) const {
return chunk->young_generation_bitmap_;
}
void IncrementLiveBytes(MemoryChunk* chunk, intptr_t by) {
chunk->young_generation_live_byte_count_ += by;
}
intptr_t live_bytes(MemoryChunk* chunk) const {
return chunk->young_generation_live_byte_count_;
}
void SetLiveBytes(MemoryChunk* chunk, intptr_t value) {
chunk->young_generation_live_byte_count_ = value;
}
};
class MinorNonAtomicMarkingState final
: public MarkingStateBase<MinorNonAtomicMarkingState,
AccessMode::NON_ATOMIC> {
public:
Bitmap* bitmap(const MemoryChunk* chunk) const {
return chunk->young_generation_bitmap_;
}
void IncrementLiveBytes(MemoryChunk* chunk, intptr_t by) {
chunk->young_generation_live_byte_count_ += by;
}
intptr_t live_bytes(MemoryChunk* chunk) const {
return chunk->young_generation_live_byte_count_;
}
void SetLiveBytes(MemoryChunk* chunk, intptr_t value) {
chunk->young_generation_live_byte_count_ = value;
}
};
// This marking state is used when concurrent marking is running.
class IncrementalMarkingState final
: public MarkingStateBase<IncrementalMarkingState, AccessMode::ATOMIC> {
public:
Bitmap* bitmap(const MemoryChunk* chunk) const {
return Bitmap::FromAddress(chunk->address() + MemoryChunk::kHeaderSize);
}
// Concurrent marking uses local live bytes.
void IncrementLiveBytes(MemoryChunk* chunk, intptr_t by) {
chunk->live_byte_count_ += by;
}
intptr_t live_bytes(MemoryChunk* chunk) const {
return chunk->live_byte_count_;
}
void SetLiveBytes(MemoryChunk* chunk, intptr_t value) {
chunk->live_byte_count_ = value;
}
};
class MajorAtomicMarkingState final
: public MarkingStateBase<MajorAtomicMarkingState, AccessMode::ATOMIC> {
public:
Bitmap* bitmap(const MemoryChunk* chunk) const {
return Bitmap::FromAddress(chunk->address() + MemoryChunk::kHeaderSize);
}
void IncrementLiveBytes(MemoryChunk* chunk, intptr_t by) {
chunk->live_byte_count_ += by;
}
intptr_t live_bytes(MemoryChunk* chunk) const {
return chunk->live_byte_count_;
}
void SetLiveBytes(MemoryChunk* chunk, intptr_t value) {
chunk->live_byte_count_ = value;
}
};
class MajorNonAtomicMarkingState final
: public MarkingStateBase<MajorNonAtomicMarkingState,
AccessMode::NON_ATOMIC> {
public:
Bitmap* bitmap(const MemoryChunk* chunk) const {
return Bitmap::FromAddress(chunk->address() + MemoryChunk::kHeaderSize);
}
void IncrementLiveBytes(MemoryChunk* chunk, intptr_t by) {
chunk->live_byte_count_ += by;
}
intptr_t live_bytes(MemoryChunk* chunk) const {
return chunk->live_byte_count_;
}
void SetLiveBytes(MemoryChunk* chunk, intptr_t value) {
chunk->live_byte_count_ = value;
}
};
struct Ephemeron {
HeapObject* key;
HeapObject* value;
};
typedef Worklist<Ephemeron, 64> EphemeronWorklist;
// Weak objects encountered during marking.
struct WeakObjects {
Worklist<WeakCell*, 64> weak_cells;
Worklist<TransitionArray*, 64> transition_arrays;
// Keep track of all EphemeronHashTables in the heap to process
// them in the atomic pause.
Worklist<EphemeronHashTable*, 64> ephemeron_hash_tables;
// Keep track of all ephemerons for concurrent marking tasks. Only store
// ephemerons in these Worklists if both key and value are unreachable at the
// moment.
//
// MarkCompactCollector::ProcessEphemeronsUntilFixpoint drains and fills these
// worklists.
//
// current_ephemerons is used as draining worklist in the current fixpoint
// iteration.
EphemeronWorklist current_ephemerons;
// Stores ephemerons to visit in the next fixpoint iteration.
EphemeronWorklist next_ephemerons;
// When draining the marking worklist new discovered ephemerons are pushed
// into this worklist.
EphemeronWorklist discovered_ephemerons;
// TODO(marja): For old space, we only need the slot, not the host
// object. Optimize this by adding a different storage for old space.
Worklist<std::pair<HeapObject*, HeapObjectReference**>, 64> weak_references;
Worklist<std::pair<HeapObject*, Code*>, 64> weak_objects_in_code;
};
struct EphemeronMarking {
std::vector<HeapObject*> newly_discovered;
bool newly_discovered_overflowed;
size_t newly_discovered_limit;
};
// Collector for young and old generation.
class MarkCompactCollector final : public MarkCompactCollectorBase {
public:
#ifdef V8_CONCURRENT_MARKING
using MarkingState = IncrementalMarkingState;
#else
using MarkingState = MajorNonAtomicMarkingState;
#endif // V8_CONCURRENT_MARKING
using NonAtomicMarkingState = MajorNonAtomicMarkingState;
// Wrapper for the shared and bailout worklists.
class MarkingWorklist {
public:
using ConcurrentMarkingWorklist = Worklist<HeapObject*, 64>;
// The heap parameter is not used but needed to match the sequential case.
explicit MarkingWorklist(Heap* heap) {}
void Push(HeapObject* object) {
bool success = shared_.Push(kMainThread, object);
USE(success);
DCHECK(success);
}
void PushBailout(HeapObject* object) {
bool success = bailout_.Push(kMainThread, object);
USE(success);
DCHECK(success);
}
HeapObject* Pop() {
HeapObject* result;
#ifdef V8_CONCURRENT_MARKING
if (bailout_.Pop(kMainThread, &result)) return result;
#endif
if (shared_.Pop(kMainThread, &result)) return result;
#ifdef V8_CONCURRENT_MARKING
// The expectation is that this work list is empty almost all the time
// and we can thus avoid the emptiness checks by putting it last.
if (on_hold_.Pop(kMainThread, &result)) return result;
#endif
return nullptr;
}
HeapObject* PopBailout() {
HeapObject* result;
#ifdef V8_CONCURRENT_MARKING
if (bailout_.Pop(kMainThread, &result)) return result;
#endif
return nullptr;
}
void Clear() {
bailout_.Clear();
shared_.Clear();
on_hold_.Clear();
}
bool IsBailoutEmpty() { return bailout_.IsLocalEmpty(kMainThread); }
bool IsEmpty() {
return bailout_.IsLocalEmpty(kMainThread) &&
shared_.IsLocalEmpty(kMainThread) &&
on_hold_.IsLocalEmpty(kMainThread) &&
bailout_.IsGlobalPoolEmpty() && shared_.IsGlobalPoolEmpty() &&
on_hold_.IsGlobalPoolEmpty();
}
int Size() {
return static_cast<int>(bailout_.LocalSize(kMainThread) +
shared_.LocalSize(kMainThread) +
on_hold_.LocalSize(kMainThread));
}
// Calls the specified callback on each element of the deques and replaces
// the element with the result of the callback. If the callback returns
// nullptr then the element is removed from the deque.
// The callback must accept HeapObject* and return HeapObject*.
template <typename Callback>
void Update(Callback callback) {
bailout_.Update(callback);
shared_.Update(callback);
on_hold_.Update(callback);
}
ConcurrentMarkingWorklist* shared() { return &shared_; }
ConcurrentMarkingWorklist* bailout() { return &bailout_; }
ConcurrentMarkingWorklist* on_hold() { return &on_hold_; }
void Print() {
PrintWorklist("shared", &shared_);
PrintWorklist("bailout", &bailout_);
PrintWorklist("on_hold", &on_hold_);
}
private:
// Prints the stats about the global pool of the worklist.
void PrintWorklist(const char* worklist_name,
ConcurrentMarkingWorklist* worklist);
// Worklist used for most objects.
ConcurrentMarkingWorklist shared_;
// Concurrent marking uses this worklist to bail out of concurrently
// marking certain object types. These objects are handled later in a STW
// pause after concurrent marking has finished.
ConcurrentMarkingWorklist bailout_;
// Concurrent marking uses this worklist to bail out of marking objects
// in new space's linear allocation area. Used to avoid black allocation
// for new space. This allow the compiler to remove write barriers
// for freshly allocatd objects.
ConcurrentMarkingWorklist on_hold_;
};
class RootMarkingVisitor;
class CustomRootBodyMarkingVisitor;
enum IterationMode {
kKeepMarking,
kClearMarkbits,
};
MarkingState* marking_state() { return &marking_state_; }
NonAtomicMarkingState* non_atomic_marking_state() {
return &non_atomic_marking_state_;
}
void SetUp() override;
void TearDown() override;
// Performs a global garbage collection.
void CollectGarbage() override;
void CollectEvacuationCandidates(PagedSpace* space);
void AddEvacuationCandidate(Page* p);
// Prepares for GC by resetting relocation info in old and map spaces and
// choosing spaces to compact.
void Prepare();
// Stop concurrent marking (either by preempting it right away or waiting for
// it to complete as requested by |stop_request|).
void FinishConcurrentMarking(ConcurrentMarking::StopRequest stop_request);
bool StartCompaction();
void AbortCompaction();
static inline bool IsOnEvacuationCandidate(Object* obj) {
return Page::FromAddress(reinterpret_cast<Address>(obj))
->IsEvacuationCandidate();
}
static inline bool IsOnEvacuationCandidate(MaybeObject* obj) {
return Page::FromAddress(reinterpret_cast<Address>(obj))
->IsEvacuationCandidate();
}
void RecordRelocSlot(Code* host, RelocInfo* rinfo, Object* target);
V8_INLINE static void RecordSlot(HeapObject* object, Object** slot,
HeapObject* target);
V8_INLINE static void RecordSlot(HeapObject* object,
HeapObjectReference** slot,
HeapObject* target);
void RecordLiveSlotsOnPage(Page* page);
void UpdateSlots(SlotsBuffer* buffer);
void UpdateSlotsRecordedIn(SlotsBuffer* buffer);
void ClearMarkbits();
bool is_compacting() const { return compacting_; }
// Ensures that sweeping is finished.
//
// Note: Can only be called safely from main thread.
void EnsureSweepingCompleted();
// Checks if sweeping is in progress right now on any space.
bool sweeping_in_progress() const { return sweeper_->sweeping_in_progress(); }
void set_evacuation(bool evacuation) { evacuation_ = evacuation; }
bool evacuation() const { return evacuation_; }
MarkingWorklist* marking_worklist() { return &marking_worklist_; }
WeakObjects* weak_objects() { return &weak_objects_; }
void AddWeakCell(WeakCell* weak_cell) {
weak_objects_.weak_cells.Push(kMainThread, weak_cell);
}
void AddTransitionArray(TransitionArray* array) {
weak_objects_.transition_arrays.Push(kMainThread, array);
}
void AddEphemeronHashTable(EphemeronHashTable* table) {
weak_objects_.ephemeron_hash_tables.Push(kMainThread, table);
}
void AddEphemeron(HeapObject* key, HeapObject* value) {
weak_objects_.discovered_ephemerons.Push(kMainThread,
Ephemeron{key, value});
}
void AddWeakReference(HeapObject* host, HeapObjectReference** slot) {
weak_objects_.weak_references.Push(kMainThread, std::make_pair(host, slot));
}
void AddWeakObjectInCode(HeapObject* object, Code* code) {
weak_objects_.weak_objects_in_code.Push(kMainThread,
std::make_pair(object, code));
}
void AddNewlyDiscovered(HeapObject* object) {
if (ephemeron_marking_.newly_discovered_overflowed) return;
if (ephemeron_marking_.newly_discovered.size() <
ephemeron_marking_.newly_discovered_limit) {
ephemeron_marking_.newly_discovered.push_back(object);
} else {
ephemeron_marking_.newly_discovered_overflowed = true;
}
}
void ResetNewlyDiscovered() {
ephemeron_marking_.newly_discovered_overflowed = false;
ephemeron_marking_.newly_discovered.clear();
}
Sweeper* sweeper() { return sweeper_; }
#ifdef DEBUG
// Checks whether performing mark-compact collection.
bool in_use() { return state_ > PREPARE_GC; }
bool are_map_pointers_encoded() { return state_ == UPDATE_POINTERS; }
#endif
void VerifyMarking();
#ifdef VERIFY_HEAP
void VerifyValidStoreAndSlotsBufferEntries();
void VerifyMarkbitsAreClean();
void VerifyMarkbitsAreDirty(PagedSpace* space);
void VerifyMarkbitsAreClean(PagedSpace* space);
void VerifyMarkbitsAreClean(NewSpace* space);
#endif
private:
explicit MarkCompactCollector(Heap* heap);
~MarkCompactCollector();
bool WillBeDeoptimized(Code* code);
void ComputeEvacuationHeuristics(size_t area_size,
int* target_fragmentation_percent,
size_t* max_evacuated_bytes);
void RecordObjectStats();
// Finishes GC, performs heap verification if enabled.
void Finish();
void MarkLiveObjects() override;
// Marks the object black and adds it to the marking work list.
// This is for non-incremental marking only.
V8_INLINE void MarkObject(HeapObject* host, HeapObject* obj);
// Marks the object black and adds it to the marking work list.
// This is for non-incremental marking only.
V8_INLINE void MarkRootObject(Root root, HeapObject* obj);
// Used by wrapper tracing.
V8_INLINE void MarkExternallyReferencedObject(HeapObject* obj);
// Mark the heap roots and all objects reachable from them.
void MarkRoots(RootVisitor* root_visitor,
ObjectVisitor* custom_root_body_visitor);
// Mark the string table specially. References to internalized strings from
// the string table are weak.
void MarkStringTable(ObjectVisitor* visitor);
// Marks object reachable from harmony weak maps and wrapper tracing.
void ProcessEphemeronMarking();
// If the call-site of the top optimized code was not prepared for
// deoptimization, then treat embedded pointers in the code as strong as
// otherwise they can die and try to deoptimize the underlying code.
void ProcessTopOptimizedFrame(ObjectVisitor* visitor);
// Collects a list of dependent code from maps embedded in optimize code.
DependentCode* DependentCodeListFromNonLiveMaps();
// Drains the main thread marking work list. Will mark all pending objects
// if no concurrent threads are running.
void ProcessMarkingWorklist() override;
enum class MarkingWorklistProcessingMode {
kDefault,
kTrackNewlyDiscoveredObjects
};
template <MarkingWorklistProcessingMode mode>
void ProcessMarkingWorklistInternal();
// Implements ephemeron semantics: Marks value if key is already reachable.
// Returns true if value was actually marked.
bool VisitEphemeron(HeapObject* key, HeapObject* value);
// Marks ephemerons and drains marking worklist iteratively
// until a fixpoint is reached.
void ProcessEphemeronsUntilFixpoint();
// Drains ephemeron and marking worklists. Single iteration of the
// fixpoint iteration.
bool ProcessEphemerons();
// Mark ephemerons and drain marking worklist with a linear algorithm.
// Only used if fixpoint iteration doesn't finish within a few iterations.
void ProcessEphemeronsLinear();
// Perform Wrapper Tracing if in use.
void PerformWrapperTracing();
// Callback function for telling whether the object *p is an unmarked
// heap object.
static bool IsUnmarkedHeapObject(Heap* heap, Object** p);
// Clear non-live references in weak cells, transition and descriptor arrays,
// and deoptimize dependent code of non-live maps.
void ClearNonLiveReferences() override;
void MarkDependentCodeForDeoptimization();
// Checks if the given weak cell is a simple transition from the parent map
// of the given dead target. If so it clears the transition and trims
// the descriptor array of the parent if needed.
void ClearPotentialSimpleMapTransition(Map* dead_target);
void ClearPotentialSimpleMapTransition(Map* map, Map* dead_target);
// Compact every array in the global list of transition arrays and
// trim the corresponding descriptor array if a transition target is non-live.
void ClearFullMapTransitions();
bool CompactTransitionArray(Map* map, TransitionArray* transitions,
DescriptorArray* descriptors);
void TrimDescriptorArray(Map* map, DescriptorArray* descriptors);
void TrimEnumCache(Map* map, DescriptorArray* descriptors);
// After all reachable objects have been marked those weak map entries
// with an unreachable key are removed from all encountered weak maps.
// The linked list of all encountered weak maps is destroyed.
void ClearWeakCollections();
// Goes through the list of encountered weak cells and clears those with
// dead values. If the value is a dead map and the parent map transitions to
// the dead map via weak cell, then this function also clears the map
// transition.
void ClearWeakCells();
void ClearWeakReferences();
void AbortWeakObjects();
// Starts sweeping of spaces by contributing on the main thread and setting
// up other pages for sweeping. Does not start sweeper tasks.
void StartSweepSpaces();
void StartSweepSpace(PagedSpace* space);
void EvacuatePrologue() override;
void EvacuateEpilogue() override;
void Evacuate() override;
void EvacuatePagesInParallel() override;
void UpdatePointersAfterEvacuation() override;
UpdatingItem* CreateToSpaceUpdatingItem(MemoryChunk* chunk, Address start,
Address end) override;
UpdatingItem* CreateRememberedSetUpdatingItem(
MemoryChunk* chunk, RememberedSetUpdatingMode updating_mode) override;
int CollectNewSpaceArrayBufferTrackerItems(ItemParallelJob* job);
int CollectOldSpaceArrayBufferTrackerItems(ItemParallelJob* job);
void ReleaseEvacuationCandidates();
void PostProcessEvacuationCandidates();
void ReportAbortedEvacuationCandidate(HeapObject* failed_object, Page* page);
void ClearMarkbitsInPagedSpace(PagedSpace* space);
void ClearMarkbitsInNewSpace(NewSpace* space);
static const int kEphemeronChunkSize = 8 * KB;
int NumberOfParallelEphemeronVisitingTasks(size_t elements);
base::Mutex mutex_;
base::Semaphore page_parallel_job_semaphore_;
#ifdef DEBUG
enum CollectorState {
IDLE,
PREPARE_GC,
MARK_LIVE_OBJECTS,
SWEEP_SPACES,
ENCODE_FORWARDING_ADDRESSES,
UPDATE_POINTERS,
RELOCATE_OBJECTS
};
// The current stage of the collector.
CollectorState state_;
#endif
bool was_marked_incrementally_;
bool evacuation_;
// True if we are collecting slots to perform evacuation from evacuation
// candidates.
bool compacting_;
bool black_allocation_;
bool have_code_to_deoptimize_;
MarkingWorklist marking_worklist_;
WeakObjects weak_objects_;
EphemeronMarking ephemeron_marking_;
// Candidates for pages that should be evacuated.
std::vector<Page*> evacuation_candidates_;
// Pages that are actually processed during evacuation.
std::vector<Page*> old_space_evacuation_pages_;
std::vector<Page*> new_space_evacuation_pages_;
std::vector<std::pair<HeapObject*, Page*>> aborted_evacuation_candidates_;
Sweeper* sweeper_;
MarkingState marking_state_;
NonAtomicMarkingState non_atomic_marking_state_;
friend class EphemeronHashTableMarkingTask;
friend class FullEvacuator;
friend class Heap;
friend class RecordMigratedSlotVisitor;
};
template <FixedArrayVisitationMode fixed_array_mode,
TraceRetainingPathMode retaining_path_mode, typename MarkingState>
class MarkingVisitor final
: public HeapVisitor<
int,
MarkingVisitor<fixed_array_mode, retaining_path_mode, MarkingState>> {
public:
typedef HeapVisitor<
int, MarkingVisitor<fixed_array_mode, retaining_path_mode, MarkingState>>
Parent;
V8_INLINE MarkingVisitor(MarkCompactCollector* collector,
MarkingState* marking_state);
V8_INLINE bool ShouldVisitMapPointer() { return false; }
V8_INLINE int VisitAllocationSite(Map* map, AllocationSite* object);
V8_INLINE int VisitBytecodeArray(Map* map, BytecodeArray* object);
V8_INLINE int VisitCodeDataContainer(Map* map, CodeDataContainer* object);
V8_INLINE int VisitEphemeronHashTable(Map* map, EphemeronHashTable* object);
V8_INLINE int VisitFixedArray(Map* map, FixedArray* object);
V8_INLINE int VisitJSApiObject(Map* map, JSObject* object);
V8_INLINE int VisitJSFunction(Map* map, JSFunction* object);
V8_INLINE int VisitMap(Map* map, Map* object);
V8_INLINE int VisitNativeContext(Map* map, Context* object);
V8_INLINE int VisitTransitionArray(Map* map, TransitionArray* object);
V8_INLINE int VisitWeakCell(Map* map, WeakCell* object);
// ObjectVisitor implementation.
V8_INLINE void VisitPointer(HeapObject* host, Object** p) final;
V8_INLINE void VisitPointer(HeapObject* host, MaybeObject** p) final;
V8_INLINE void VisitPointers(HeapObject* host, Object** start,
Object** end) final;
V8_INLINE void VisitPointers(HeapObject* host, MaybeObject** start,
MaybeObject** end) final;
V8_INLINE void VisitEmbeddedPointer(Code* host, RelocInfo* rinfo) final;
V8_INLINE void VisitCodeTarget(Code* host, RelocInfo* rinfo) final;
private:
// Granularity in which FixedArrays are scanned if |fixed_array_mode|
// is true.
static const int kProgressBarScanningChunk = 32 * 1024;
V8_INLINE int VisitFixedArrayIncremental(Map* map, FixedArray* object);
V8_INLINE void MarkMapContents(Map* map);
// Marks the object black without pushing it on the marking work list. Returns
// true if the object needed marking and false otherwise.
V8_INLINE bool MarkObjectWithoutPush(HeapObject* host, HeapObject* object);
// Marks the object grey and pushes it on the marking work list.
V8_INLINE void MarkObject(HeapObject* host, HeapObject* obj);
MarkingState* marking_state() { return marking_state_; }
MarkCompactCollector::MarkingWorklist* marking_worklist() const {
return collector_->marking_worklist();
}
Heap* const heap_;
MarkCompactCollector* const collector_;
MarkingState* const marking_state_;
};
class EvacuationScope {
public:
explicit EvacuationScope(MarkCompactCollector* collector)
: collector_(collector) {
collector_->set_evacuation(true);
}
~EvacuationScope() { collector_->set_evacuation(false); }
private:
MarkCompactCollector* collector_;
};
#ifdef ENABLE_MINOR_MC
// Collector for young-generation only.
class MinorMarkCompactCollector final : public MarkCompactCollectorBase {
public:
using MarkingState = MinorMarkingState;
using NonAtomicMarkingState = MinorNonAtomicMarkingState;
explicit MinorMarkCompactCollector(Heap* heap);
~MinorMarkCompactCollector();
MarkingState* marking_state() { return &marking_state_; }
NonAtomicMarkingState* non_atomic_marking_state() {
return &non_atomic_marking_state_;
}
void SetUp() override;
void TearDown() override;
void CollectGarbage() override;
void MakeIterable(Page* page, MarkingTreatmentMode marking_mode,
FreeSpaceTreatmentMode free_space_mode);
void CleanupSweepToIteratePages();
private:
using MarkingWorklist = Worklist<HeapObject*, 64 /* segment size */>;
class RootMarkingVisitor;
static const int kNumMarkers = 8;
static const int kMainMarker = 0;
inline MarkingWorklist* worklist() { return worklist_; }
inline YoungGenerationMarkingVisitor* main_marking_visitor() {
return main_marking_visitor_;
}
void MarkLiveObjects() override;
void MarkRootSetInParallel(RootMarkingVisitor* root_visitor);
V8_INLINE void MarkRootObject(HeapObject* obj);
void ProcessMarkingWorklist() override;
void ClearNonLiveReferences() override;
void EvacuatePrologue() override;
void EvacuateEpilogue() override;
void Evacuate() override;
void EvacuatePagesInParallel() override;
void UpdatePointersAfterEvacuation() override;
UpdatingItem* CreateToSpaceUpdatingItem(MemoryChunk* chunk, Address start,
Address end) override;
UpdatingItem* CreateRememberedSetUpdatingItem(
MemoryChunk* chunk, RememberedSetUpdatingMode updating_mode) override;
int CollectNewSpaceArrayBufferTrackerItems(ItemParallelJob* job);
int NumberOfParallelMarkingTasks(int pages);
MarkingWorklist* worklist_;
YoungGenerationMarkingVisitor* main_marking_visitor_;
base::Semaphore page_parallel_job_semaphore_;
std::vector<Page*> new_space_evacuation_pages_;
std::vector<Page*> sweep_to_iterate_pages_;
MarkingState marking_state_;
NonAtomicMarkingState non_atomic_marking_state_;
friend class YoungGenerationMarkingTask;
friend class YoungGenerationMarkingVisitor;
};
#endif // ENABLE_MINOR_MC
} // namespace internal
} // namespace v8
#endif // V8_HEAP_MARK_COMPACT_H_
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