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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_ParallelWork_h
#define gc_ParallelWork_h
#include "mozilla/Maybe.h"
#include <algorithm>
#include "gc/GCParallelTask.h"
#include "gc/GCRuntime.h"
#include "js/SliceBudget.h"
#include "vm/HelperThreads.h"
namespace js {
namespace gcstats {
enum class PhaseKind : uint8_t;
namespace gc {
template <typename WorkItem>
using ParallelWorkFunc = size_t (*)(GCRuntime*, const WorkItem&);
// A GCParallelTask task that executes WorkItems from a WorkItemIterator.
// The WorkItemIterator class must supply done(), next() and get() methods. The
// get() method must return WorkItems objects.
template <typename WorkItem, typename WorkItemIterator>
class ParallelWorker : public GCParallelTask {
using WorkFunc = ParallelWorkFunc<WorkItem>;
ParallelWorker(GCRuntime* gc, gcstats::PhaseKind phaseKind, GCUse use,
WorkFunc func, WorkItemIterator& work,
const JS::SliceBudget& budget, AutoLockHelperThreadState& lock)
: GCParallelTask(gc, phaseKind, use),
item_(work.get()) {
// Consume a work item on creation so that we can stop creating workers if
// the number of workers exceeds the number of work items.;
void run(AutoLockHelperThreadState& lock) {
AutoUnlockHelperThreadState unlock(lock);
for (;;) {
size_t steps = func_(gc, item_);
budget_.step(std::max(steps, size_t(1)));
if (budget_.isOverBudget()) {
AutoLockHelperThreadState lock;
if (work().done()) {
item_ = work().get();
WorkItemIterator& work() { return work_.ref(); }
// A function to execute work items on the helper thread.
WorkFunc func_;
// An iterator which produces work items to execute.
HelperThreadLockData<WorkItemIterator&> work_;
// The budget that determines how long to run for.
JS::SliceBudget budget_;
// The next work item to process.
WorkItem item_;
static constexpr size_t MaxParallelWorkers = 8;
// An RAII class that starts a number of ParallelWorkers and waits for them to
// finish.
template <typename WorkItem, typename WorkItemIterator>
class MOZ_RAII AutoRunParallelWork {
using Worker = ParallelWorker<WorkItem, WorkItemIterator>;
using WorkFunc = ParallelWorkFunc<WorkItem>;
AutoRunParallelWork(GCRuntime* gc, WorkFunc func,
gcstats::PhaseKind phaseKind, GCUse use,
WorkItemIterator& work, const JS::SliceBudget& budget,
AutoLockHelperThreadState& lock)
: gc(gc), phaseKind(phaseKind), lock(lock), tasksStarted(0) {
size_t workerCount = gc->parallelWorkerCount();
MOZ_ASSERT(workerCount <= MaxParallelWorkers);
MOZ_ASSERT_IF(workerCount == 0, work.done());
for (size_t i = 0; i < workerCount && !work.done(); i++) {
tasks[i].emplace(gc, phaseKind, use, func, work, budget, lock);
gc->startTask(*tasks[i], lock);
~AutoRunParallelWork() {
for (size_t i = 0; i < tasksStarted; i++) {
gc->joinTask(*tasks[i], lock);
for (size_t i = tasksStarted; i < MaxParallelWorkers; i++) {
GCRuntime* gc;
gcstats::PhaseKind phaseKind;
AutoLockHelperThreadState& lock;
size_t tasksStarted;
mozilla::Maybe<Worker> tasks[MaxParallelWorkers];
} /* namespace gc */
} /* namespace js */
#endif /* gc_ParallelWork_h */