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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at */
#ifndef gc_ParallelMarking_h
#define gc_ParallelMarking_h
#include "mozilla/Atomics.h"
#include "mozilla/DoublyLinkedList.h"
#include "mozilla/TimeStamp.h"
#include "gc/GCMarker.h"
#include "gc/GCParallelTask.h"
#include "js/HeapAPI.h"
#include "js/SliceBudget.h"
#include "threading/ConditionVariable.h"
#include "threading/ProtectedData.h"
namespace js {
class AutoLockHelperThreadState;
namespace gc {
class ParallelMarkTask;
// Per-runtime parallel marking state.
// This class is used on the main thread and coordinates parallel marking using
// several helper threads running ParallelMarkTasks.
// This uses a work-requesting approach. Threads mark until they run out of
// work and then add themselves to a list of waiting tasks and block. Running
// tasks with enough work may donate work to a waiting task and resume it.
class MOZ_STACK_CLASS ParallelMarker {
explicit ParallelMarker(GCRuntime* gc);
bool mark(JS::SliceBudget& sliceBudget);
using AtomicCount = mozilla::Atomic<uint32_t, mozilla::Relaxed>;
AtomicCount& waitingTaskCountRef() { return waitingTaskCount; }
bool hasWaitingTasks() { return waitingTaskCount != 0; }
void donateWorkFrom(GCMarker* src);
bool markOneColor(MarkColor color, JS::SliceBudget& sliceBudget);
bool hasWork(MarkColor color) const;
void addTask(ParallelMarkTask* task, const AutoLockHelperThreadState& lock);
void addTaskToWaitingList(ParallelMarkTask* task,
const AutoLockHelperThreadState& lock);
#ifdef DEBUG
bool isTaskInWaitingList(const ParallelMarkTask* task,
const AutoLockHelperThreadState& lock) const;
bool hasActiveTasks(const AutoLockHelperThreadState& lock) const {
return activeTasks;
void incActiveTasks(ParallelMarkTask* task,
const AutoLockHelperThreadState& lock);
void decActiveTasks(ParallelMarkTask* task,
const AutoLockHelperThreadState& lock);
size_t workerCount() const;
friend class ParallelMarkTask;
GCRuntime* const gc;
using ParallelMarkTaskList = mozilla::DoublyLinkedList<ParallelMarkTask>;
HelperThreadLockData<ParallelMarkTaskList> waitingTasks;
AtomicCount waitingTaskCount;
HelperThreadLockData<size_t> activeTasks;
// A helper thread task that performs parallel marking.
class alignas(TypicalCacheLineSize) ParallelMarkTask
: public GCParallelTask,
public mozilla::DoublyLinkedListElement<ParallelMarkTask> {
friend class ParallelMarker;
ParallelMarkTask(ParallelMarker* pm, GCMarker* marker, MarkColor color,
const JS::SliceBudget& budget);
void run(AutoLockHelperThreadState& lock) override;
void recordDuration() override;
bool tryMarking(AutoLockHelperThreadState& lock);
bool requestWork(AutoLockHelperThreadState& lock);
void waitUntilResumed(AutoLockHelperThreadState& lock);
void resume();
void resumeOnFinish(const AutoLockHelperThreadState& lock);
bool hasWork() const;
// The following fields are only accessed by the marker thread:
ParallelMarker* const pm;
GCMarker* const marker;
AutoSetMarkColor color;
JS::SliceBudget budget;
ConditionVariable resumed;
HelperThreadLockData<bool> isWaiting;
// Length of time this task spent blocked waiting for work.
MainThreadOrGCTaskData<mozilla::TimeDuration> markTime;
MainThreadOrGCTaskData<mozilla::TimeDuration> waitTime;
} // namespace gc
} // namespace js
#endif /* gc_ParallelMarking_h */