cc: Check for completed raster tasks at interval.

cc/worker_pool.cc

Index: cc/worker_pool.cc
diff --git a/cc/worker_pool.cc b/cc/worker_pool.cc
index 7d3428aa74d2f8bde286b73cb418549fb1504a70..c1a70ce8a655821a20eed4ae708e79a5f0a84269 100644
--- a/cc/worker_pool.cc
+++ b/cc/worker_pool.cc
@@ -28,6 +28,7 @@ class WorkerPoolTaskImpl : public internal::WorkerPoolTask {
 
   virtual void Run(RenderingStats* rendering_stats) OVERRIDE {
     task_.Run(rendering_stats);
+    base::subtle::NoBarrier_Store(&completed_, 1);

[brianderson, 2013/02/12 01:44:31]

I think you need a barrier before this store (or a release store).

[reveman, 2013/02/12 02:29:52]

Done.

   }
 
  private:
@@ -36,22 +37,24 @@ class WorkerPoolTaskImpl : public internal::WorkerPoolTask {
 
 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;
-
 }  // namespace
 
 namespace internal {
 
 WorkerPoolTask::WorkerPoolTask(const base::Closure& reply)
     : reply_(reply) {
+  base::subtle::NoBarrier_Store(&completed_, 0);

[brianderson, 2013/02/12 01:44:31]

I think you need a barrier after this store (or an acquire store).

[reveman, 2013/02/12 02:29:52]

Done.

 }
 
 WorkerPoolTask::~WorkerPoolTask() {
 }
 
+bool WorkerPoolTask::IsPending() {
+  return base::subtle::NoBarrier_Load(&completed_) == 0;
+}
+
 void WorkerPoolTask::Completed() {
+  DCHECK_EQ(base::subtle::NoBarrier_Load(&completed_), 1);
   reply_.Run();
 }
 
@@ -60,7 +63,6 @@ void WorkerPoolTask::Completed() {
 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();
@@ -80,23 +82,17 @@ void WorkerPool::Worker::StopAfterCompletingAllPendingTasks() {
   // 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(
+  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(stats)));
 
   pending_tasks_.push_back(task.Pass());
 
@@ -126,6 +122,15 @@ void WorkerPool::Worker::OnTaskCompleted() {
   worker_pool_->DidNumPendingTasksChange();
 }
 
+void WorkerPool::Worker::CheckForCompletedTasks() {
+  while (!pending_tasks_.empty()) {
+    if (pending_tasks_.front()->IsPending())
+      return;
+
+    OnTaskCompleted();
+  }
+}
+
 WorkerPool::WorkerPool(size_t num_threads)
     : workers_need_sorting_(false),
       shutdown_(false) {
@@ -164,10 +169,12 @@ void WorkerPool::PostTaskAndReply(
                           reply)).PassAs<internal::WorkerPoolTask>());
 }
 
-bool WorkerPool::IsBusy() {
-  Worker* worker = GetWorkerForNextTask();
-
-  return worker->num_pending_tasks() >= kNumPendingTasksPerWorker;
+void WorkerPool::CheckForCompletedTasks() {
+  for (WorkerVector::iterator it = workers_.begin();
+       it != workers_.end(); it++) {
+    Worker* worker = *it;
+    worker->CheckForCompletedTasks();
+  }
 }
 
 void WorkerPool::SetRecordRenderingStats(bool record_rendering_stats) {