gpu: Implement idle async pixel transfers.

content/common/gpu/gpu_command_buffer_stub.cc

Index: content/common/gpu/gpu_command_buffer_stub.cc
diff --git a/content/common/gpu/gpu_command_buffer_stub.cc b/content/common/gpu/gpu_command_buffer_stub.cc
index 7e539969cf33d195c377cdd21083c8369208a50a..306408f1d84e50c3716cafd2b4104d59763d06fe 100644
--- a/content/common/gpu/gpu_command_buffer_stub.cc
+++ b/content/common/gpu/gpu_command_buffer_stub.cc
@@ -88,8 +88,13 @@ void FastSetActiveURL(const GURL& url, size_t url_hash) {
 // The first time polling a fence, delay some extra time to allow other
 // stubs to process some work, or else the timing of the fences could
 // allow a pattern of alternating fast and slow frames to occur.
-const int64 kHandleMoreWorkPeriodMs = 2;
-const int64 kHandleMoreWorkPeriodBusyMs = 1;
+const int64 kHandleMoreWorkPeriodMicroseconds = 2000;
+const int64 kHandleMoreWorkPeriodBusyMicroseconds = 1000;
+
+// Use a shorter delay when there'ss idle work to be done.

[Sami, 2013/03/07 16:57:19]

Typo: there'ss

[reveman, 2013/03/07 20:21:04]

Done.

+const int64 kHandleMoreIdleWorkPeriodBusyMicroseconds = 100;
+// Prevents idle work from being starved.
+const int64 kMaxTimeSinceIdleMicroseconds = 10000;
 
 }  // namespace
 
@@ -126,6 +131,7 @@ GpuCommandBufferStub::GpuCommandBufferStub(
       watchdog_(watchdog),
       sync_point_wait_count_(0),
       delayed_work_scheduled_(false),
+      is_idle_(false),
       active_url_(active_url),
       total_gpu_memory_(0) {
   active_url_hash_ = base::Hash(active_url.possibly_invalid_spec());
@@ -166,6 +172,8 @@ bool GpuCommandBufferStub::OnMessageReceived(const IPC::Message& message) {
       return false;
   }
 
+  is_idle_ = false;
+
   // Always use IPC_MESSAGE_HANDLER_DELAY_REPLY for synchronous message handlers
   // here. This is so the reply can be delayed if the scheduler is unscheduled.
   bool handled = true;
@@ -211,7 +219,7 @@ bool GpuCommandBufferStub::OnMessageReceived(const IPC::Message& message) {
   IPC_END_MESSAGE_MAP()
 
   // Ensure that any delayed work that was created will be handled.
-  ScheduleDelayedWork(kHandleMoreWorkPeriodMs);
+  ScheduleDelayedWork(kHandleMoreWorkPeriodMicroseconds);
 
   DCHECK(handled);
   return handled;
@@ -235,9 +243,28 @@ void GpuCommandBufferStub::PollWork() {
   FastSetActiveURL(active_url_, active_url_hash_);
   if (decoder_.get() && !MakeCurrent())
     return;
-  if (scheduler_.get())
-    scheduler_->PollUnscheduleFences();
-  ScheduleDelayedWork(kHandleMoreWorkPeriodBusyMs);
+  int64 delay = kHandleMoreWorkPeriodBusyMicroseconds;
+  if (scheduler_.get()) {
+    bool fences_complete = scheduler_->PollUnscheduleFences();
+    // Perform idle work if all fences are complete.
+    if (fences_complete) {
+      DCHECK(!last_idle_time_.is_null());
+      base::TimeDelta time_since_idle = base::TimeTicks::Now() -
+          last_idle_time_;
+      base::TimeDelta max_time_since_idle =
+          base::TimeDelta::FromMicroseconds(kMaxTimeSinceIdleMicroseconds);
+
+      // Perform some idle work if idle or it's been too long since
+      // last time we were idle.
+      if (is_idle_ || time_since_idle > max_time_since_idle) {
+        last_idle_time_ = base::TimeTicks::Now();
+        // Use idle work period delay when there's more idle work pending.
+        if (scheduler_->PerformIdleWork())
+          delay = kHandleMoreIdleWorkPeriodBusyMicroseconds;
+      }
+    }
+  }
+  ScheduleDelayedWork(delay);
 }
 
 bool GpuCommandBufferStub::HasUnprocessedCommands() {
@@ -250,14 +277,26 @@ bool GpuCommandBufferStub::HasUnprocessedCommands() {
 }
 
 void GpuCommandBufferStub::ScheduleDelayedWork(int64 delay) {
-  if (HasMoreWork() && !delayed_work_scheduled_) {
-    delayed_work_scheduled_ = true;
-    MessageLoop::current()->PostDelayedTask(
-        FROM_HERE,
-        base::Bind(&GpuCommandBufferStub::PollWork,
-                   AsWeakPtr()),
-        base::TimeDelta::FromMilliseconds(delay));
+  if (!HasMoreWork()) {
+    last_idle_time_ = base::TimeTicks();
+    return;
   }
+
+  if (delayed_work_scheduled_)
+    return;
+  delayed_work_scheduled_ = true;
+
+  // Consider the command buffer idle if no messages are received between
+  // now and when PollWork is called.
+  is_idle_ = true;
+  if (last_idle_time_.is_null())
+    last_idle_time_ = base::TimeTicks::Now();
+
+  MessageLoop::current()->PostDelayedTask(
+      FROM_HERE,
+      base::Bind(&GpuCommandBufferStub::PollWork,
+                 AsWeakPtr()),
+      base::TimeDelta::FromMicroseconds(delay));
 }
 
 void GpuCommandBufferStub::OnEcho(const IPC::Message& message) {