cc: Check for completed raster tasks at interval.

cc/worker_pool.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/worker_pool.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/stl_util.h"
@@ skipping 10 matching lines @@
 
 class WorkerPoolTaskImpl : public internal::WorkerPoolTask {
  public:
   WorkerPoolTaskImpl(const WorkerPool::Callback& task,
                      const base::Closure& reply)
       : internal::WorkerPoolTask(reply),
         task_(task) {}
 
   virtual void Run(RenderingStats* rendering_stats) OVERRIDE {
     task_.Run(rendering_stats);
+    base::subtle::Release_Store(&completed_, 1);
   }
 
  private:
   WorkerPool::Callback task_;
 };
 
 const char* kWorkerThreadNamePrefix = "Compositor";
 
-// Allow two pending tasks per worker. This keeps resource usage
-// low while making sure workers aren't unnecessarily idle.
-const int kNumPendingTasksPerWorker = 2;
+#if defined(OS_ANDROID)
+const int kNumPendingTasksPerWorker = 8;
+#else
+const int kNumPendingTasksPerWorker = 40;
+#endif
+
+const int kCheckForCompletedTasksDelayMs = 6;
 
 }  // namespace
 
 namespace internal {
 
-WorkerPoolTask::WorkerPoolTask(const base::Closure& reply)
-    : reply_(reply) {
+WorkerPoolTask::WorkerPoolTask(const base::Closure& reply) : reply_(reply) {
+  base::subtle::Acquire_Store(&completed_, 0);
 }
 
 WorkerPoolTask::~WorkerPoolTask() {
 }
 
-void WorkerPoolTask::Completed() {
+bool WorkerPoolTask::HasCompleted() {
+  return base::subtle::Acquire_Load(&completed_) == 1;
+}
+
+void WorkerPoolTask::DidComplete() {
+  DCHECK_EQ(base::subtle::Acquire_Load(&completed_), 1);
   reply_.Run();
 }
 
 }  // namespace internal
 
 WorkerPool::Worker::Worker(WorkerPool* worker_pool, const std::string name)
     : base::Thread(name.c_str()),
       worker_pool_(worker_pool),
-      weak_ptr_factory_(ALLOW_THIS_IN_INITIALIZER_LIST(this)),
       rendering_stats_(make_scoped_ptr(new RenderingStats)),
       record_rendering_stats_(false) {
   Start();
   DCHECK(IsRunning());
 }
 
 WorkerPool::Worker::~Worker() {
   DCHECK(!IsRunning());
   DCHECK_EQ(pending_tasks_.size(), 0);
 }
 
 void WorkerPool::Worker::StopAfterCompletingAllPendingTasks() {
   // Signals the thread to exit and returns once all pending tasks have run.
   Stop();
 
   // Complete all pending tasks. The Stop() call above guarantees that
   // all tasks have finished running.
   while (!pending_tasks_.empty())
     OnTaskCompleted();
-
-  // Cancel all pending replies.
-  weak_ptr_factory_.InvalidateWeakPtrs();
 }
 
 void WorkerPool::Worker::PostTask(scoped_ptr<internal::WorkerPoolTask> task) {
-  DCHECK_LT(num_pending_tasks(), kNumPendingTasksPerWorker);
-
   RenderingStats* stats =
       record_rendering_stats_ ? rendering_stats_.get() : NULL;
 
-  message_loop_proxy()->PostTaskAndReply(
+  worker_pool_->WillPostTask();
+
+  message_loop_proxy()->PostTask(
       FROM_HERE,
       base::Bind(&Worker::RunTask,
                  base::Unretained(task.get()),
-                 base::Unretained(stats)),
-      base::Bind(&Worker::OnTaskCompleted, weak_ptr_factory_.GetWeakPtr()));
+                 base::Unretained(worker_pool_),
+                 base::Unretained(stats)));
 
   pending_tasks_.push_back(task.Pass());
-
-  worker_pool_->DidNumPendingTasksChange();
 }
 
 void WorkerPool::Worker::Init() {
 #if defined(OS_ANDROID)
   // TODO(epenner): Move thread priorities to base. (crbug.com/170549)
   int nice_value = 10; // Idle priority.
   setpriority(PRIO_PROCESS, base::PlatformThread::CurrentId(), nice_value);
 #endif
 }
 
 // static
 void WorkerPool::Worker::RunTask(
-    internal::WorkerPoolTask* task, RenderingStats* rendering_stats) {
+    internal::WorkerPoolTask* task,
+    WorkerPool* worker_pool,
+    RenderingStats* rendering_stats) {
   task->Run(rendering_stats);
+  worker_pool->OnWorkCompletedOnWorkerThread();
 }
 
 void WorkerPool::Worker::OnTaskCompleted() {
   CHECK(!pending_tasks_.empty());
 
   scoped_ptr<internal::WorkerPoolTask> task = pending_tasks_.take_front();
-  task->Completed();
 
-  worker_pool_->DidNumPendingTasksChange();
+  // Notify worker pool of task completion.
+  worker_pool_->OnTaskCompleted();
+
+  task->DidComplete();
 }
 
-WorkerPool::WorkerPool(size_t num_threads)
-    : workers_need_sorting_(false),
-      shutdown_(false) {
+void WorkerPool::Worker::CheckForCompletedTasks() {
+  while (!pending_tasks_.empty()) {
+    if (!pending_tasks_.front()->HasCompleted())
+      return;
+
+    OnTaskCompleted();
+  }
+}
+
+WorkerPool::WorkerPool(WorkerPoolClient* client, size_t num_threads)
+    : client_(client),
+      origin_loop_(base::MessageLoopProxy::current()),
+      weak_ptr_factory_(ALLOW_THIS_IN_INITIALIZER_LIST(this)),
+      workers_need_sorting_(false),
+      pending_task_count_(0),
+      shutdown_(false),
+      check_for_completed_tasks_pending_(false),
+      idle_callback_(
+          base::Bind(&WorkerPool::OnIdle, weak_ptr_factory_.GetWeakPtr())) {
   const std::string thread_name_prefix = kWorkerThreadNamePrefix;
   while (workers_.size() < num_threads) {
     int thread_number = workers_.size() + 1;
     workers_.push_back(new Worker(
         this,
         thread_name_prefix + StringPrintf("Worker%d", thread_number).c_str()));
   }
+  base::subtle::Acquire_Store(&pending_task_count_, 0);
 }
 
 WorkerPool::~WorkerPool() {
   Shutdown();
   STLDeleteElements(&workers_);
+  // Cancel all pending callbacks.
+  weak_ptr_factory_.InvalidateWeakPtrs();
+  DCHECK_EQ(base::subtle::Acquire_Load(&pending_task_count_), 0);
 }
 
 void WorkerPool::Shutdown() {
   DCHECK(!shutdown_);
   shutdown_ = true;
 
   for (WorkerVector::iterator it = workers_.begin();
        it != workers_.end(); it++) {
     Worker* worker = *it;
     worker->StopAfterCompletingAllPendingTasks();
@@ skipping 43 matching lines @@
         worker->rendering_stats()->totalDeferredImageDecodeTime;
   }
 }
 
 WorkerPool::Worker* WorkerPool::GetWorkerForNextTask() {
   CHECK(!shutdown_);
   SortWorkersIfNeeded();
   return workers_.front();
 }
 
-void WorkerPool::DidNumPendingTasksChange() {
+void WorkerPool::ScheduleCheckForCompletedTasks() {
+  if (check_for_completed_tasks_pending_)
+    return;
+
+  check_for_completed_tasks_callback_.Reset(
+      base::Bind(&WorkerPool::CheckForCompletedTasks,
+                 weak_ptr_factory_.GetWeakPtr()));
+  origin_loop_->PostDelayedTask(
+      FROM_HERE,
+      check_for_completed_tasks_callback_.callback(),
+      base::TimeDelta::FromMilliseconds(kCheckForCompletedTasksDelayMs));
+  check_for_completed_tasks_pending_ = true;
+}
+
+void WorkerPool::WillPostTask() {
+  base::subtle::Barrier_AtomicIncrement(&pending_task_count_, 1);
+  ScheduleCheckForCompletedTasks();
   workers_need_sorting_ = true;
 }
 
+void WorkerPool::OnWorkCompletedOnWorkerThread() {
+  // Post idle handler task when pool work count reaches 0.
+  if (base::subtle::Barrier_AtomicIncrement(&pending_task_count_, -1) == 0) {
+    origin_loop_->PostTask(FROM_HERE, idle_callback_);
+  }
+}
+
+void WorkerPool::OnIdle() {
+  if (base::subtle::Acquire_Load(&pending_task_count_) == 0) {
+    check_for_completed_tasks_callback_.Cancel();
+    CheckForCompletedTasks();
+  }
+}
+
+void WorkerPool::CheckForCompletedTasks() {
+  check_for_completed_tasks_pending_ = false;
+
+  for (WorkerVector::iterator it = workers_.begin();
+       it != workers_.end(); it++) {
+    Worker* worker = *it;
+    worker->CheckForCompletedTasks();
+  }
+
+  client_->DidFinishDispatchingWorkerPoolCompletionCallbacks();
+
+  for (WorkerVector::iterator it = workers_.begin();
+       it != workers_.end(); it++) {
+    Worker* worker = *it;
+    if (worker->num_pending_tasks()) {

[brianderson, 2013/02/14 01:12:07]

No race condition and no unnecessary checks scheduled. Looks good!

+      ScheduleCheckForCompletedTasks();
+      break;
+    }
+  }
+}
+
+void WorkerPool::OnTaskCompleted() {
+  workers_need_sorting_ = true;
+}
+
 void WorkerPool::SortWorkersIfNeeded() {
   if (!workers_need_sorting_)
     return;
 
   std::sort(workers_.begin(), workers_.end(), NumPendingTasksComparator());
   workers_need_sorting_ = false;
 }
 
 }  // namespace cc