gecko-dev/gfx/2d/JobScheduler.cpp

289 lines
7.0 KiB
C++

/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* 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 http://mozilla.org/MPL/2.0/. */
#include "JobScheduler.h"
#include "Logging.h"
namespace mozilla {
namespace gfx {
JobScheduler* JobScheduler::sSingleton = nullptr;
bool JobScheduler::Init(uint32_t aNumThreads, uint32_t aNumQueues)
{
MOZ_ASSERT(!sSingleton);
MOZ_ASSERT(aNumThreads >= aNumQueues);
sSingleton = new JobScheduler();
sSingleton->mNextQueue = 0;
for (uint32_t i = 0; i < aNumQueues; ++i) {
sSingleton->mDrawingQueues.push_back(new MultiThreadedJobQueue());
}
for (uint32_t i = 0; i < aNumThreads; ++i) {
sSingleton->mWorkerThreads.push_back(WorkerThread::Create(sSingleton->mDrawingQueues[i%aNumQueues]));
}
return true;
}
void JobScheduler::ShutDown()
{
MOZ_ASSERT(IsEnabled());
if (!IsEnabled()) {
return;
}
for (auto queue : sSingleton->mDrawingQueues) {
queue->ShutDown();
delete queue;
}
for (WorkerThread* thread : sSingleton->mWorkerThreads) {
// this will block until the thread is joined.
delete thread;
}
sSingleton->mWorkerThreads.clear();
delete sSingleton;
sSingleton = nullptr;
}
JobStatus
JobScheduler::ProcessJob(Job* aJob)
{
MOZ_ASSERT(aJob);
auto status = aJob->Run();
if (status == JobStatus::Error || status == JobStatus::Complete) {
delete aJob;
}
return status;
}
void
JobScheduler::SubmitJob(Job* aJob)
{
MOZ_ASSERT(aJob);
RefPtr<SyncObject> start = aJob->GetStartSync();
if (start && start->Register(aJob)) {
// The Job buffer starts with a non-signaled sync object, it
// is now registered in the list of task buffers waiting on the
// sync object, so we should not place it in the queue.
return;
}
GetQueueForJob(aJob)->SubmitJob(aJob);
}
void
JobScheduler::Join(SyncObject* aCompletion)
{
RefPtr<EventObject> waitForCompletion = new EventObject();
JobScheduler::SubmitJob(new SetEventJob(waitForCompletion, aCompletion));
waitForCompletion->Wait();
}
MultiThreadedJobQueue*
JobScheduler::GetQueueForJob(Job* aJob)
{
return aJob->IsPinnedToAThread() ? aJob->GetWorkerThread()->GetJobQueue()
: GetDrawingQueue();
}
Job::Job(SyncObject* aStart, SyncObject* aCompletion, WorkerThread* aThread)
: mNextWaitingJob(nullptr)
, mStartSync(aStart)
, mCompletionSync(aCompletion)
, mPinToThread(aThread)
{
if (mStartSync) {
mStartSync->AddSubsequent(this);
}
if (mCompletionSync) {
mCompletionSync->AddPrerequisite(this);
}
}
Job::~Job()
{
if (mCompletionSync) {
//printf(" -- Job %p dtor completion %p\n", this, mCompletionSync);
mCompletionSync->Signal();
mCompletionSync = nullptr;
}
}
JobStatus
SetEventJob::Run()
{
mEvent->Set();
return JobStatus::Complete;
}
SetEventJob::SetEventJob(EventObject* aEvent,
SyncObject* aStart, SyncObject* aCompletion,
WorkerThread* aWorker)
: Job(aStart, aCompletion, aWorker)
, mEvent(aEvent)
{}
SetEventJob::~SetEventJob()
{}
SyncObject::SyncObject(uint32_t aNumPrerequisites)
: mSignals(aNumPrerequisites)
, mFirstWaitingJob(nullptr)
#ifdef DEBUG
, mNumPrerequisites(aNumPrerequisites)
, mAddedPrerequisites(0)
#endif
{}
SyncObject::~SyncObject()
{
MOZ_ASSERT(mFirstWaitingJob == nullptr);
}
bool
SyncObject::Register(Job* aJob)
{
MOZ_ASSERT(aJob);
// For now, ensure that when we schedule the first subsequent, we have already
// created all of the prerequisites. This is an arbitrary restriction because
// we specify the number of prerequisites in the constructor, but in the typical
// scenario, if the assertion FreezePrerequisite blows up here it probably means
// we got the initial nmber of prerequisites wrong. We can decide to remove
// this restriction if needed.
FreezePrerequisites();
int32_t signals = mSignals;
if (signals > 0) {
AddWaitingJob(aJob);
// Since Register and Signal can be called concurrently, it can happen that
// reading mSignals in Register happens before decrementing mSignals in Signal,
// but SubmitWaitingJobs happens before AddWaitingJob. This ordering means
// the SyncObject ends up in the signaled state with a task sitting in the
// waiting list. To prevent that we check mSignals a second time and submit
// again if signals reached zero in the mean time.
// We do this instead of holding a mutex around mSignals+mJobs to reduce
// lock contention.
int32_t signals2 = mSignals;
if (signals2 == 0) {
SubmitWaitingJobs();
}
return true;
}
return false;
}
void
SyncObject::Signal()
{
int32_t signals = --mSignals;
MOZ_ASSERT(signals >= 0);
if (signals == 0) {
SubmitWaitingJobs();
}
}
void
SyncObject::AddWaitingJob(Job* aJob)
{
// Push (using atomics) the task into the list of waiting tasks.
for (;;) {
Job* first = mFirstWaitingJob;
aJob->mNextWaitingJob = first;
if (mFirstWaitingJob.compareExchange(first, aJob)) {
break;
}
}
}
void SyncObject::SubmitWaitingJobs()
{
// Scheduling the tasks can cause code that modifies <this>'s reference
// count to run concurrently, and cause the caller of this function to
// be owned by another thread. We need to make sure the reference count
// does not reach 0 on another thread before the end of this method, so
// hold a strong ref to prevent that!
RefPtr<SyncObject> kungFuDeathGrip(this);
// First atomically swap mFirstWaitingJob and waitingJobs...
Job* waitingJobs = nullptr;
for (;;) {
waitingJobs = mFirstWaitingJob;
if (mFirstWaitingJob.compareExchange(waitingJobs, nullptr)) {
break;
}
}
// ... and submit all of the waiting tasks in waitingJob now that they belong
// to this thread.
while (waitingJobs) {
Job* next = waitingJobs->mNextWaitingJob;
waitingJobs->mNextWaitingJob = nullptr;
JobScheduler::GetQueueForJob(waitingJobs)->SubmitJob(waitingJobs);
waitingJobs = next;
}
}
bool
SyncObject::IsSignaled()
{
return mSignals == 0;
}
void
SyncObject::FreezePrerequisites()
{
MOZ_ASSERT(mAddedPrerequisites == mNumPrerequisites);
}
void
SyncObject::AddPrerequisite(Job* aJob)
{
MOZ_ASSERT(++mAddedPrerequisites <= mNumPrerequisites);
}
void
SyncObject::AddSubsequent(Job* aJob)
{
}
WorkerThread::WorkerThread(MultiThreadedJobQueue* aJobQueue)
: mQueue(aJobQueue)
{
aJobQueue->RegisterThread();
}
void
WorkerThread::Run()
{
SetName("gfx worker");
for (;;) {
Job* commands = nullptr;
if (!mQueue->WaitForJob(commands)) {
mQueue->UnregisterThread();
return;
}
JobStatus status = JobScheduler::ProcessJob(commands);
if (status == JobStatus::Error) {
// Don't try to handle errors for now, but that's open to discussions.
// I expect errors to be mostly OOM issues.
gfxDevCrash(LogReason::JobStatusError) << "Invalid job status " << (int)status;
}
}
}
} //namespace
} //namespace