1// Copyright 2020 the V8 project authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef V8_HEAP_ARRAY_BUFFER_SWEEPER_H_
6#define V8_HEAP_ARRAY_BUFFER_SWEEPER_H_
7
8#include <memory>
9
10#include "src/base/logging.h"
11#include "src/base/platform/mutex.h"
12#include "src/objects/js-array-buffer.h"
13#include "src/tasks/cancelable-task.h"
14
15namespace v8 {
16namespace internal {
17
18class ArrayBufferExtension;
19class Heap;
20
21// Singly linked-list of ArrayBufferExtensions that stores head and tail of the
22// list to allow for concatenation of lists.
23struct ArrayBufferList final {
24  bool IsEmpty() const;
25  size_t ApproximateBytes() const { return bytes_; }
26  size_t BytesSlow() const;
27
28  void Append(ArrayBufferExtension* extension);
29  void Append(ArrayBufferList* list);
30
31  V8_EXPORT_PRIVATE bool ContainsSlow(ArrayBufferExtension* extension) const;
32
33 private:
34  ArrayBufferExtension* head_ = nullptr;
35  ArrayBufferExtension* tail_ = nullptr;
36  // Bytes are approximate as they may be subtracted eagerly, while the
37  // `ArrayBufferExtension` is still in the list. The extension will only be
38  // dropped on next sweep.
39  size_t bytes_ = 0;
40
41  friend class ArrayBufferSweeper;
42};
43
44// The ArrayBufferSweeper iterates and deletes ArrayBufferExtensions
45// concurrently to the application.
46class ArrayBufferSweeper final {
47 public:
48  enum class SweepingType { kYoung, kFull };
49
50  explicit ArrayBufferSweeper(Heap* heap);
51  ~ArrayBufferSweeper();
52
53  void RequestSweep(SweepingType sweeping_type);
54  void EnsureFinished();
55
56  // Track the given ArrayBufferExtension for the given JSArrayBuffer.
57  void Append(JSArrayBuffer object, ArrayBufferExtension* extension);
58
59  // Detaches an ArrayBufferExtension from a JSArrayBuffer.
60  void Detach(JSArrayBuffer object, ArrayBufferExtension* extension);
61
62  const ArrayBufferList& young() const { return young_; }
63  const ArrayBufferList& old() const { return old_; }
64
65  // Bytes accounted in the young generation. Rebuilt during sweeping.
66  size_t YoungBytes() const { return young().ApproximateBytes(); }
67  // Bytes accounted in the old generation. Rebuilt during sweeping.
68  size_t OldBytes() const { return old().ApproximateBytes(); }
69
70 private:
71  struct SweepingJob;
72
73  enum class SweepingState { kInProgress, kDone };
74
75  bool sweeping_in_progress() const { return job_.get(); }
76
77  // Finishes sweeping if it is already done.
78  void FinishIfDone();
79
80  // Increments external memory counters outside of ArrayBufferSweeper.
81  // Increment may trigger GC.
82  void IncrementExternalMemoryCounters(size_t bytes);
83  void DecrementExternalMemoryCounters(size_t bytes);
84
85  void Prepare(SweepingType type);
86  void Finalize();
87
88  void ReleaseAll(ArrayBufferList* extension);
89
90  Heap* const heap_;
91  std::unique_ptr<SweepingJob> job_;
92  base::Mutex sweeping_mutex_;
93  base::ConditionVariable job_finished_;
94  ArrayBufferList young_;
95  ArrayBufferList old_;
96};
97
98}  // namespace internal
99}  // namespace v8
100
101#endif  // V8_HEAP_ARRAY_BUFFER_SWEEPER_H_
102