gecko-dev/image/DecodePool.cpp

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C++

/* -*- Mode: C++; tab-width: 2; 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 "DecodePool.h"
#include <algorithm>
#include "mozilla/ClearOnShutdown.h"
#include "mozilla/DebugOnly.h"
#include "mozilla/Monitor.h"
#include "mozilla/TimeStamp.h"
#include "nsCOMPtr.h"
#include "nsIObserverService.h"
#include "nsIThreadPool.h"
#include "nsThreadManager.h"
#include "nsThreadUtils.h"
#include "nsXPCOMCIDInternal.h"
#include "prsystem.h"
#include "nsIXULRuntime.h"
#include "gfxPrefs.h"
#include "Decoder.h"
#include "IDecodingTask.h"
#include "RasterImage.h"
using std::max;
using std::min;
namespace mozilla {
namespace image {
///////////////////////////////////////////////////////////////////////////////
// DecodePool implementation.
///////////////////////////////////////////////////////////////////////////////
/* static */ StaticRefPtr<DecodePool> DecodePool::sSingleton;
/* static */ uint32_t DecodePool::sNumCores = 0;
NS_IMPL_ISUPPORTS(DecodePool, nsIObserver)
struct Work {
enum class Type { TASK, SHUTDOWN } mType;
RefPtr<IDecodingTask> mTask;
};
class DecodePoolImpl {
public:
MOZ_DECLARE_REFCOUNTED_TYPENAME(DecodePoolImpl)
NS_INLINE_DECL_THREADSAFE_REFCOUNTING(DecodePoolImpl)
DecodePoolImpl(uint8_t aMaxThreads, uint8_t aMaxIdleThreads,
TimeDuration aIdleTimeout)
: mMonitor("DecodePoolImpl"),
mThreads(aMaxThreads),
mIdleTimeout(aIdleTimeout),
mMaxIdleThreads(aMaxIdleThreads),
mAvailableThreads(aMaxThreads),
mIdleThreads(0),
mShuttingDown(false) {
MonitorAutoLock lock(mMonitor);
bool success = CreateThread();
MOZ_RELEASE_ASSERT(success, "Must create first image decoder thread!");
}
/// Shut down the provided decode pool thread.
void ShutdownThread(nsIThread* aThisThread, bool aShutdownIdle) {
{
// If this is an idle thread shutdown, then we need to remove it from the
// worker array. Process shutdown will move the entire array.
MonitorAutoLock lock(mMonitor);
if (!mShuttingDown) {
++mAvailableThreads;
DebugOnly<bool> removed = mThreads.RemoveElement(aThisThread);
MOZ_ASSERT(aShutdownIdle);
MOZ_ASSERT(mAvailableThreads < mThreads.Capacity());
MOZ_ASSERT(removed);
}
}
// Threads have to be shut down from another thread, so we'll ask the
// main thread to do it for us.
SystemGroup::Dispatch(TaskCategory::Other,
NewRunnableMethod("DecodePoolImpl::ShutdownThread",
aThisThread, &nsIThread::Shutdown));
}
/**
* Requests shutdown. New work items will be dropped on the floor, and all
* decode pool threads will be shut down once existing work items have been
* processed.
*/
void Shutdown() {
nsTArray<nsCOMPtr<nsIThread>> threads;
{
MonitorAutoLock lock(mMonitor);
mShuttingDown = true;
mAvailableThreads = 0;
threads.SwapElements(mThreads);
mMonitor.NotifyAll();
}
for (uint32_t i = 0; i < threads.Length(); ++i) {
threads[i]->Shutdown();
}
}
bool IsShuttingDown() const {
MonitorAutoLock lock(mMonitor);
return mShuttingDown;
}
/// Pushes a new decode work item.
void PushWork(IDecodingTask* aTask) {
MOZ_ASSERT(aTask);
RefPtr<IDecodingTask> task(aTask);
MonitorAutoLock lock(mMonitor);
if (mShuttingDown) {
// Drop any new work on the floor if we're shutting down.
return;
}
if (task->Priority() == TaskPriority::eHigh) {
mHighPriorityQueue.AppendElement(std::move(task));
} else {
mLowPriorityQueue.AppendElement(std::move(task));
}
// If there are pending tasks, create more workers if and only if we have
// not exceeded the capacity, and any previously created workers are ready.
if (mAvailableThreads) {
size_t pending = mHighPriorityQueue.Length() + mLowPriorityQueue.Length();
if (pending > mIdleThreads) {
CreateThread();
}
}
mMonitor.Notify();
}
Work StartWork(bool aShutdownIdle) {
MonitorAutoLock lock(mMonitor);
// The thread was already marked as idle when it was created. Once it gets
// its first work item, it is assumed it is busy performing that work until
// it blocks on the monitor once again.
MOZ_ASSERT(mIdleThreads > 0);
--mIdleThreads;
return PopWorkLocked(aShutdownIdle);
}
Work PopWork(bool aShutdownIdle) {
MonitorAutoLock lock(mMonitor);
return PopWorkLocked(aShutdownIdle);
}
private:
/// Pops a new work item, blocking if necessary.
Work PopWorkLocked(bool aShutdownIdle) {
mMonitor.AssertCurrentThreadOwns();
TimeDuration timeout = mIdleTimeout;
do {
if (!mHighPriorityQueue.IsEmpty()) {
return PopWorkFromQueue(mHighPriorityQueue);
}
if (!mLowPriorityQueue.IsEmpty()) {
return PopWorkFromQueue(mLowPriorityQueue);
}
if (mShuttingDown) {
return CreateShutdownWork();
}
// Nothing to do; block until some work is available.
AUTO_PROFILER_LABEL("DecodePoolImpl::PopWorkLocked::Wait", IDLE);
if (!aShutdownIdle) {
// This thread was created before we hit the idle thread maximum. It
// will never shutdown until the process itself is torn down.
++mIdleThreads;
MOZ_ASSERT(mIdleThreads <= mThreads.Capacity());
mMonitor.Wait();
} else {
// This thread should shutdown if it is idle. If we have waited longer
// than the timeout period without having done any work, then we should
// shutdown the thread.
if (timeout.IsZero()) {
return CreateShutdownWork();
}
++mIdleThreads;
MOZ_ASSERT(mIdleThreads <= mThreads.Capacity());
TimeStamp now = TimeStamp::Now();
mMonitor.Wait(timeout);
TimeDuration delta = TimeStamp::Now() - now;
if (delta > timeout) {
timeout = 0;
} else if (timeout != TimeDuration::Forever()) {
timeout -= delta;
}
}
MOZ_ASSERT(mIdleThreads > 0);
--mIdleThreads;
} while (true);
}
~DecodePoolImpl() {}
bool CreateThread();
Work PopWorkFromQueue(nsTArray<RefPtr<IDecodingTask>>& aQueue) {
Work work;
work.mType = Work::Type::TASK;
work.mTask = aQueue.PopLastElement();
return work;
}
Work CreateShutdownWork() const {
Work work;
work.mType = Work::Type::SHUTDOWN;
return work;
}
nsThreadPoolNaming mThreadNaming;
// mMonitor guards everything below.
mutable Monitor mMonitor;
nsTArray<RefPtr<IDecodingTask>> mHighPriorityQueue;
nsTArray<RefPtr<IDecodingTask>> mLowPriorityQueue;
nsTArray<nsCOMPtr<nsIThread>> mThreads;
TimeDuration mIdleTimeout;
uint8_t mMaxIdleThreads; // Maximum number of workers when idle.
uint8_t mAvailableThreads; // How many new threads can be created.
uint8_t mIdleThreads; // How many created threads are waiting.
bool mShuttingDown;
};
class DecodePoolWorker final : public Runnable {
public:
explicit DecodePoolWorker(DecodePoolImpl* aImpl, bool aShutdownIdle)
: Runnable("image::DecodePoolWorker"),
mImpl(aImpl),
mShutdownIdle(aShutdownIdle) {}
NS_IMETHOD Run() override {
MOZ_ASSERT(!NS_IsMainThread());
nsCOMPtr<nsIThread> thisThread;
nsThreadManager::get().GetCurrentThread(getter_AddRefs(thisThread));
Work work = mImpl->StartWork(mShutdownIdle);
do {
switch (work.mType) {
case Work::Type::TASK:
work.mTask->Run();
work.mTask = nullptr;
break;
case Work::Type::SHUTDOWN:
mImpl->ShutdownThread(thisThread, mShutdownIdle);
PROFILER_UNREGISTER_THREAD();
return NS_OK;
default:
MOZ_ASSERT_UNREACHABLE("Unknown work type");
}
work = mImpl->PopWork(mShutdownIdle);
} while (true);
MOZ_ASSERT_UNREACHABLE("Exiting thread without Work::Type::SHUTDOWN");
return NS_OK;
}
private:
RefPtr<DecodePoolImpl> mImpl;
bool mShutdownIdle;
};
bool DecodePoolImpl::CreateThread() {
mMonitor.AssertCurrentThreadOwns();
MOZ_ASSERT(mAvailableThreads > 0);
bool shutdownIdle = mThreads.Length() >= mMaxIdleThreads;
nsCOMPtr<nsIRunnable> worker = new DecodePoolWorker(this, shutdownIdle);
nsCOMPtr<nsIThread> thread;
nsresult rv = NS_NewNamedThread(mThreadNaming.GetNextThreadName("ImgDecoder"),
getter_AddRefs(thread), worker,
nsIThreadManager::kThreadPoolStackSize);
if (NS_FAILED(rv) || !thread) {
MOZ_ASSERT_UNREACHABLE("Should successfully create image decoding threads");
return false;
}
mThreads.AppendElement(std::move(thread));
--mAvailableThreads;
++mIdleThreads;
MOZ_ASSERT(mIdleThreads <= mThreads.Capacity());
return true;
}
/* static */ void DecodePool::Initialize() {
MOZ_ASSERT(NS_IsMainThread());
sNumCores = max<int32_t>(PR_GetNumberOfProcessors(), 1);
DecodePool::Singleton();
}
/* static */ DecodePool* DecodePool::Singleton() {
if (!sSingleton) {
MOZ_ASSERT(NS_IsMainThread());
sSingleton = new DecodePool();
ClearOnShutdown(&sSingleton);
}
return sSingleton;
}
/* static */ uint32_t DecodePool::NumberOfCores() { return sNumCores; }
DecodePool::DecodePool() : mMutex("image::DecodePool") {
// Determine the number of threads we want.
int32_t prefLimit = gfxPrefs::ImageMTDecodingLimit();
uint32_t limit;
if (prefLimit <= 0) {
int32_t numCores = NumberOfCores();
if (numCores <= 1) {
limit = 1;
} else if (numCores == 2) {
// On an otherwise mostly idle system, having two image decoding threads
// doubles decoding performance, so it's worth doing on dual-core devices,
// even if under load we can't actually get that level of parallelism.
limit = 2;
} else {
limit = numCores - 1;
}
} else {
limit = static_cast<uint32_t>(prefLimit);
}
if (limit > 32) {
limit = 32;
}
// The parent process where there are content processes doesn't need as many
// threads for decoding images.
if (limit > 4 && XRE_IsE10sParentProcess()) {
limit = 4;
}
// The maximum number of idle threads allowed.
uint32_t idleLimit;
// The timeout period before shutting down idle threads.
int32_t prefIdleTimeout = gfxPrefs::ImageMTDecodingIdleTimeout();
TimeDuration idleTimeout;
if (prefIdleTimeout <= 0) {
idleTimeout = TimeDuration::Forever();
idleLimit = limit;
} else {
idleTimeout = TimeDuration::FromMilliseconds(prefIdleTimeout);
idleLimit = (limit + 1) / 2;
}
// Initialize the thread pool.
mImpl = new DecodePoolImpl(limit, idleLimit, idleTimeout);
// Initialize the I/O thread.
nsresult rv = NS_NewNamedThread("ImageIO", getter_AddRefs(mIOThread));
MOZ_RELEASE_ASSERT(NS_SUCCEEDED(rv) && mIOThread,
"Should successfully create image I/O thread");
nsCOMPtr<nsIObserverService> obsSvc = services::GetObserverService();
if (obsSvc) {
obsSvc->AddObserver(this, "xpcom-shutdown-threads", false);
}
}
DecodePool::~DecodePool() {
MOZ_ASSERT(NS_IsMainThread(), "Must shut down DecodePool on main thread!");
}
NS_IMETHODIMP
DecodePool::Observe(nsISupports*, const char* aTopic, const char16_t*) {
MOZ_ASSERT(strcmp(aTopic, "xpcom-shutdown-threads") == 0, "Unexpected topic");
nsCOMPtr<nsIThread> ioThread;
{
MutexAutoLock lock(mMutex);
ioThread.swap(mIOThread);
}
mImpl->Shutdown();
if (ioThread) {
ioThread->Shutdown();
}
return NS_OK;
}
bool DecodePool::IsShuttingDown() const { return mImpl->IsShuttingDown(); }
void DecodePool::AsyncRun(IDecodingTask* aTask) {
MOZ_ASSERT(aTask);
mImpl->PushWork(aTask);
}
bool DecodePool::SyncRunIfPreferred(IDecodingTask* aTask,
const nsCString& aURI) {
MOZ_ASSERT(NS_IsMainThread());
MOZ_ASSERT(aTask);
AUTO_PROFILER_LABEL_DYNAMIC_NSCSTRING("DecodePool::SyncRunIfPreferred",
GRAPHICS, aURI);
if (aTask->ShouldPreferSyncRun()) {
aTask->Run();
return true;
}
AsyncRun(aTask);
return false;
}
void DecodePool::SyncRunIfPossible(IDecodingTask* aTask,
const nsCString& aURI) {
MOZ_ASSERT(NS_IsMainThread());
MOZ_ASSERT(aTask);
AUTO_PROFILER_LABEL_DYNAMIC_NSCSTRING("DecodePool::SyncRunIfPossible",
GRAPHICS, aURI);
aTask->Run();
}
already_AddRefed<nsIEventTarget> DecodePool::GetIOEventTarget() {
MutexAutoLock threadPoolLock(mMutex);
nsCOMPtr<nsIEventTarget> target = mIOThread;
return target.forget();
}
} // namespace image
} // namespace mozilla