src/v8/src/heap/concurrent-marking.h

// Copyright 2017 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_CONCURRENT_MARKING_
#define V8_HEAP_CONCURRENT_MARKING_

#include "src/allocation.h"
#include "src/cancelable-task.h"
#include "src/heap/spaces.h"
#include "src/heap/worklist.h"
#include "src/utils.h"
#include "src/v8.h"

namespace v8 {
namespace internal {

class Heap;
class Isolate;
class MajorNonAtomicMarkingState;
struct WeakObjects;

using LiveBytesMap =
    std::unordered_map<MemoryChunk*, intptr_t, MemoryChunk::Hasher>;

class ConcurrentMarking {
 public:
  // When the scope is entered, the concurrent marking tasks
  // are paused and are not looking at the heap objects.
  class PauseScope {
   public:
    explicit PauseScope(ConcurrentMarking* concurrent_marking);
    ~PauseScope();

   private:
    ConcurrentMarking* concurrent_marking_;
  };

  static const int kMaxTasks = 4;
  using MarkingWorklist = Worklist<HeapObject*, 64 /* segment size */>;

  ConcurrentMarking(Heap* heap, MarkingWorklist* shared,
                    MarkingWorklist* bailout, MarkingWorklist* on_hold,
                    WeakObjects* weak_objects);

  void ScheduleTasks();
  void WaitForTasks();
  void EnsureCompleted();
  void RescheduleTasksIfNeeded();
  // Flushes the local live bytes into the given marking state.
  void FlushLiveBytes(MajorNonAtomicMarkingState* marking_state);
  // This function is called for a new space page that was cleared after
  // scavenge and is going to be re-used.
  void ClearLiveness(MemoryChunk* chunk);

  int TaskCount() { return task_count_; }

  size_t TotalMarkedBytes();

 private:
  struct TaskState {
    // When the concurrent marking task has this lock, then objects in the
    // heap are guaranteed to not move.
    base::Mutex lock;
    // The main thread sets this flag to true, when it wants the concurrent
    // maker to give up the lock.
    base::AtomicValue<bool> interrupt_request;
    // The concurrent marker waits on this condition until the request
    // flag is cleared by the main thread.
    base::ConditionVariable interrupt_condition;
    LiveBytesMap live_bytes;
    size_t marked_bytes;
    char cache_line_padding[64];
  };
  class Task;
  void Run(int task_id, TaskState* task_state);
  Heap* heap_;
  MarkingWorklist* shared_;
  MarkingWorklist* bailout_;
  MarkingWorklist* on_hold_;
  WeakObjects* weak_objects_;
  TaskState task_state_[kMaxTasks + 1];
  base::AtomicNumber<size_t> total_marked_bytes_;
  base::Mutex pending_lock_;
  base::ConditionVariable pending_condition_;
  int pending_task_count_;
  bool is_pending_[kMaxTasks + 1];
  CancelableTaskManager::Id cancelable_id_[kMaxTasks + 1];
  int task_count_;
};

}  // namespace internal
}  // namespace v8

#endif  // V8_HEAP_PAGE_PARALLEL_JOB_