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// Copyright 2015 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_SCAVENGER_H_
#define V8_HEAP_SCAVENGER_H_
#include "src/base/platform/condition-variable.h"
#include "src/heap/local-allocator.h"
#include "src/heap/objects-visiting.h"
#include "src/heap/slot-set.h"
#include "src/heap/worklist.h"
namespace v8 {
namespace internal {
class OneshotBarrier;
class Scavenger {
public:
static const int kCopiedListSegmentSize = 256;
static const int kPromotionListSegmentSize = 256;
using ObjectAndSize = std::pair<HeapObject*, int>;
using CopiedList = Worklist<ObjectAndSize, kCopiedListSegmentSize>;
using PromotionList = Worklist<ObjectAndSize, kPromotionListSegmentSize>;
Scavenger(Heap* heap, bool is_logging, CopiedList* copied_list,
PromotionList* promotion_list, int task_id);
// Entry point for scavenging an old generation page. For scavenging single
// objects see RootScavengingVisitor and ScavengeVisitor below.
void ScavengePage(MemoryChunk* page);
// Processes remaining work (=objects) after single objects have been
// manually scavenged using ScavengeObject or CheckAndScavengeObject.
void Process(OneshotBarrier* barrier = nullptr);
// Finalize the Scavenger. Needs to be called from the main thread.
void Finalize();
size_t bytes_copied() const { return copied_size_; }
size_t bytes_promoted() const { return promoted_size_; }
private:
// Number of objects to process before interrupting for potentially waking
// up other tasks.
static const int kInterruptThreshold = 128;
static const int kInitialLocalPretenuringFeedbackCapacity = 256;
inline Heap* heap() { return heap_; }
inline void PageMemoryFence(MaybeObject* object);
void AddPageToSweeperIfNecessary(MemoryChunk* page);
// Potentially scavenges an object referenced from |slot_address| if it is
// indeed a HeapObject and resides in from space.
inline SlotCallbackResult CheckAndScavengeObject(Heap* heap,
Address slot_address);
// Scavenges an object |object| referenced from slot |p|. |object| is required
// to be in from space.
inline void ScavengeObject(HeapObjectReference** p, HeapObject* object);
// Copies |source| to |target| and sets the forwarding pointer in |source|.
V8_INLINE bool MigrateObject(Map* map, HeapObject* source, HeapObject* target,
int size);
V8_INLINE bool SemiSpaceCopyObject(Map* map, HeapObjectReference** slot,
HeapObject* object, int object_size);
V8_INLINE bool PromoteObject(Map* map, HeapObjectReference** slot,
HeapObject* object, int object_size);
V8_INLINE void EvacuateObject(HeapObjectReference** slot, Map* map,
HeapObject* source);
// Different cases for object evacuation.
V8_INLINE void EvacuateObjectDefault(Map* map, HeapObjectReference** slot,
HeapObject* object, int object_size);
V8_INLINE void EvacuateJSFunction(Map* map, HeapObject** slot,
JSFunction* object, int object_size);
inline void EvacuateThinString(Map* map, HeapObject** slot,
ThinString* object, int object_size);
inline void EvacuateShortcutCandidate(Map* map, HeapObject** slot,
ConsString* object, int object_size);
void IterateAndScavengePromotedObject(HeapObject* target, int size);
static inline bool ContainsOnlyData(VisitorId visitor_id);
Heap* const heap_;
PromotionList::View promotion_list_;
CopiedList::View copied_list_;
Heap::PretenuringFeedbackMap local_pretenuring_feedback_;
size_t copied_size_;
size_t promoted_size_;
LocalAllocator allocator_;
const bool is_logging_;
const bool is_incremental_marking_;
const bool is_compacting_;
friend class IterateAndScavengePromotedObjectsVisitor;
friend class RootScavengeVisitor;
friend class ScavengeVisitor;
};
// Helper class for turning the scavenger into an object visitor that is also
// filtering out non-HeapObjects and objects which do not reside in new space.
class RootScavengeVisitor final : public RootVisitor {
public:
explicit RootScavengeVisitor(Scavenger* scavenger);
void VisitRootPointer(Root root, const char* description, Object** p) final;
void VisitRootPointers(Root root, const char* description, Object** start,
Object** end) final;
private:
void ScavengePointer(Object** p);
Scavenger* const scavenger_;
};
class ScavengeVisitor final : public NewSpaceVisitor<ScavengeVisitor> {
public:
explicit ScavengeVisitor(Scavenger* scavenger);
V8_INLINE void VisitPointers(HeapObject* host, Object** start,
Object** end) final;
V8_INLINE void VisitPointers(HeapObject* host, MaybeObject** start,
MaybeObject** end) final;
private:
Scavenger* const scavenger_;
};
} // namespace internal
} // namespace v8
#endif // V8_HEAP_SCAVENGER_H_