1 files changed, 340 insertions, 0 deletions
diff --git a/image/DecodePool.cpp b/image/DecodePool.cpp
new file mode 100644
index 000000000..a8c4cbecc
--- /dev/null
+++ b/image/DecodePool.cpp
@@ -0,0 +1,340 @@
+/* -*- 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/Monitor.h"
+#include "nsCOMPtr.h"
+#include "nsIObserverService.h"
+#include "nsIThreadPool.h"
+#include "nsThreadManager.h"
+#include "nsThreadUtils.h"
+#include "nsXPCOMCIDInternal.h"
+#include "prsystem.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()
+    : mMonitor("DecodePoolImpl")
+    , mShuttingDown(false)
+  { }
+
+  /// Initialize the current thread for use by the decode pool.
+  void InitCurrentThread()
+  {
+    MOZ_ASSERT(!NS_IsMainThread());
+
+    mThreadNaming.SetThreadPoolName(NS_LITERAL_CSTRING("ImgDecoder"));
+  }
+
+  /// Shut down the provided decode pool thread.
+  static void ShutdownThread(nsIThread* aThisThread)
+  {
+    // Threads have to be shut down from another thread, so we'll ask the
+    // main thread to do it for us.
+    NS_DispatchToMainThread(NewRunnableMethod(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 RequestShutdown()
+  {
+    MonitorAutoLock lock(mMonitor);
+    mShuttingDown = true;
+    mMonitor.NotifyAll();
+  }
+
+  /// 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(Move(task));
+    } else {
+      mLowPriorityQueue.AppendElement(Move(task));
+    }
+
+    mMonitor.Notify();
+  }
+
+  /// Pops a new work item, blocking if necessary.
+  Work PopWork()
+  {
+    MonitorAutoLock lock(mMonitor);
+
+    do {
+      if (!mHighPriorityQueue.IsEmpty()) {
+        return PopWorkFromQueue(mHighPriorityQueue);
+      }
+
+      if (!mLowPriorityQueue.IsEmpty()) {
+        return PopWorkFromQueue(mLowPriorityQueue);
+      }
+
+      if (mShuttingDown) {
+        Work work;
+        work.mType = Work::Type::SHUTDOWN;
+        return work;
+      }
+
+      // Nothing to do; block until some work is available.
+      mMonitor.Wait();
+    } while (true);
+  }
+
+private:
+  ~DecodePoolImpl() { }
+
+  Work PopWorkFromQueue(nsTArray<RefPtr<IDecodingTask>>& aQueue)
+  {
+    Work work;
+    work.mType = Work::Type::TASK;
+    work.mTask = aQueue.LastElement().forget();
+    aQueue.RemoveElementAt(aQueue.Length() - 1);
+
+    return work;
+  }
+
+  nsThreadPoolNaming mThreadNaming;
+
+  // mMonitor guards the queues and mShuttingDown.
+  Monitor mMonitor;
+  nsTArray<RefPtr<IDecodingTask>> mHighPriorityQueue;
+  nsTArray<RefPtr<IDecodingTask>> mLowPriorityQueue;
+  bool mShuttingDown;
+};
+
+class DecodePoolWorker : public Runnable
+{
+public:
+  explicit DecodePoolWorker(DecodePoolImpl* aImpl) : mImpl(aImpl) { }
+
+  NS_IMETHOD Run() override
+  {
+    MOZ_ASSERT(!NS_IsMainThread());
+
+    mImpl->InitCurrentThread();
+
+    nsCOMPtr<nsIThread> thisThread;
+    nsThreadManager::get().GetCurrentThread(getter_AddRefs(thisThread));
+
+    do {
+      Work work = mImpl->PopWork();
+      switch (work.mType) {
+        case Work::Type::TASK:
+          work.mTask->Run();
+          break;
+
+        case Work::Type::SHUTDOWN:
+          DecodePoolImpl::ShutdownThread(thisThread);
+          return NS_OK;
+
+        default:
+          MOZ_ASSERT_UNREACHABLE("Unknown work type");
+      }
+    } while (true);
+
+    MOZ_ASSERT_UNREACHABLE("Exiting thread without Work::Type::SHUTDOWN");
+    return NS_OK;
+  }
+
+private:
+  RefPtr<DecodePoolImpl> mImpl;
+};
+
+/* 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()
+  : mImpl(new DecodePoolImpl)
+  , 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;
+  }
+
+  // Initialize the thread pool.
+  for (uint32_t i = 0 ; i < limit ; ++i) {
+    nsCOMPtr<nsIRunnable> worker = new DecodePoolWorker(mImpl);
+    nsCOMPtr<nsIThread> thread;
+    nsresult rv = NS_NewThread(getter_AddRefs(thread), worker);
+    MOZ_RELEASE_ASSERT(NS_SUCCEEDED(rv) && thread,
+                       "Should successfully create image decoding threads");
+    mThreads.AppendElement(Move(thread));
+  }
+
+  // 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");
+
+  nsTArray<nsCOMPtr<nsIThread>> threads;
+  nsCOMPtr<nsIThread> ioThread;
+
+  {
+    MutexAutoLock lock(mMutex);
+    threads.SwapElements(mThreads);
+    ioThread.swap(mIOThread);
+  }
+
+  mImpl->RequestShutdown();
+
+  for (uint32_t i = 0 ; i < threads.Length() ; ++i) {
+    threads[i]->Shutdown();
+  }
+
+  if (ioThread) {
+    ioThread->Shutdown();
+  }
+
+  return NS_OK;
+}
+
+void
+DecodePool::AsyncRun(IDecodingTask* aTask)
+{
+  MOZ_ASSERT(aTask);
+  mImpl->PushWork(aTask);
+}
+
+void
+DecodePool::SyncRunIfPreferred(IDecodingTask* aTask)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(aTask);
+
+  if (aTask->ShouldPreferSyncRun()) {
+    aTask->Run();
+    return;
+  }
+
+  AsyncRun(aTask);
+}
+
+void
+DecodePool::SyncRunIfPossible(IDecodingTask* aTask)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(aTask);
+  aTask->Run();
+}
+
+already_AddRefed<nsIEventTarget>
+DecodePool::GetIOEventTarget()
+{
+  MutexAutoLock threadPoolLock(mMutex);
+  nsCOMPtr<nsIEventTarget> target = do_QueryInterface(mIOThread);
+  return target.forget();
+}
+
+} // namespace image
+} // namespace mozilla