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// 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_H_
#define V8_HEAP_CONCURRENT_MARKING_H_
#include "include/v8-platform.h"
#include "src/allocation.h"
#include "src/base/atomic-utils.h"
#include "src/base/platform/condition-variable.h"
#include "src/base/platform/mutex.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 preempted and are not looking at the heap objects, concurrent marking
// is resumed when the scope is exited.
class PauseScope {
public:
explicit PauseScope(ConcurrentMarking* concurrent_marking);
~PauseScope();
private:
ConcurrentMarking* const concurrent_marking_;
const bool resume_on_exit_;
};
enum class StopRequest {
// Preempt ongoing tasks ASAP (and cancel unstarted tasks).
PREEMPT_TASKS,
// Wait for ongoing tasks to complete (and cancels unstarted tasks).
COMPLETE_ONGOING_TASKS,
// Wait for all scheduled tasks to complete (only use this in tests that
// control the full stack -- otherwise tasks cancelled by the platform can
// make this call hang).
COMPLETE_TASKS_FOR_TESTING,
};
// TODO(gab): The only thing that prevents this being above 7 is
// Worklist::kMaxNumTasks being maxed at 8 (concurrent marking doesn't use
// task 0, reserved for the main thread).
static constexpr int kMaxTasks = 7;
using MarkingWorklist = Worklist<HeapObject*, 64 /* segment size */>;
ConcurrentMarking(Heap* heap, MarkingWorklist* shared,
MarkingWorklist* bailout, MarkingWorklist* on_hold,
WeakObjects* weak_objects);
// Schedules asynchronous tasks to perform concurrent marking. Objects in the
// heap should not be moved while these are active (can be stopped safely via
// Stop() or PauseScope).
void ScheduleTasks();
// Stops concurrent marking per |stop_request|'s semantics. Returns true
// if concurrent marking was in progress, false otherwise.
bool Stop(StopRequest stop_request);
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_; }
// Checks if all threads are stopped.
bool IsStopped();
size_t TotalMarkedBytes();
void set_ephemeron_marked(bool ephemeron_marked) {
ephemeron_marked_.store(ephemeron_marked);
}
bool ephemeron_marked() { return ephemeron_marked_.load(); }
private:
struct TaskState {
// The main thread sets this flag to true when it wants the concurrent
// marker to give up the worker thread.
std::atomic<bool> preemption_request;
LiveBytesMap live_bytes;
size_t marked_bytes = 0;
char cache_line_padding[64];
};
class Task;
void Run(int task_id, TaskState* task_state);
Heap* const heap_;
MarkingWorklist* const shared_;
MarkingWorklist* const bailout_;
MarkingWorklist* const on_hold_;
WeakObjects* const weak_objects_;
TaskState task_state_[kMaxTasks + 1];
std::atomic<size_t> total_marked_bytes_{0};
std::atomic<bool> ephemeron_marked_{false};
base::Mutex pending_lock_;
base::ConditionVariable pending_condition_;
int pending_task_count_ = 0;
bool is_pending_[kMaxTasks + 1] = {};
CancelableTaskManager::Id cancelable_id_[kMaxTasks + 1] = {};
int task_count_ = 0;
};
} // namespace internal
} // namespace v8
#endif // V8_HEAP_CONCURRENT_MARKING_H_