Estimate draw duration in SchedulerClient

cc/trees/thread_proxy.cc

Index: cc/trees/thread_proxy.cc
diff --git a/cc/trees/thread_proxy.cc b/cc/trees/thread_proxy.cc
index f61e7feb73e826b4b2ae6067c29a6ffd0b6a41fa..c58137268e53150b5220bc4306847c85a9d46a12 100644
--- a/cc/trees/thread_proxy.cc
+++ b/cc/trees/thread_proxy.cc
@@ -28,6 +28,10 @@ const double kContextRecreationTickRate = 0.03;
 // Measured in seconds.
 const double kSmoothnessTakesPriorityExpirationDelay = 0.25;
 
+const size_t kDrawDurationHistorySize = 60;

[ajuma, 2013/06/06 18:00:35]

We might actually want something smaller than this since we sometimes have brief
bursts of really expensive draws (e.g. 15ms rather than 1 or 2 ms), and we
wouldn't want the effects of these expensive draws to linger in our estimates
for too long.

+const double kDrawDurationEstimationPercentile = 100.0;
+const int kDrawDurationEstimatePaddingInMicroseconds = 0;

[ajuma, 2013/06/06 18:00:35]

The padding serves 2 purposes: First, by using appropriate padding, we might be
able to use percentile smaller than 100 (without causing us to underestimate too
often), which would avoid having a single expensive outlier frame bias our
estimates. Second, we can incorporate an estimate for GPU execution time into
the padding (if we'll be using a hard-coded value of GPU latency for the first
version of this).

+
 }  // namespace
 
 namespace cc {
@@ -67,7 +71,8 @@ ThreadProxy::ThreadProxy(LayerTreeHost* layer_tree_host,
       vsync_client_(NULL),
       inside_draw_(false),
       defer_commits_(false),
-      renew_tree_priority_on_impl_thread_pending_(false) {
+      renew_tree_priority_on_impl_thread_pending_(false),
+      draw_duration_history_(kDrawDurationHistorySize) {
   TRACE_EVENT0("cc", "ThreadProxy::ThreadProxy");
   DCHECK(IsMainThread());
   DCHECK(layer_tree_host_);
@@ -892,6 +897,7 @@ ScheduledActionDrawAndSwapResult
 ThreadProxy::ScheduledActionDrawAndSwapInternal(bool forced_draw) {
   TRACE_EVENT0("cc", "ThreadProxy::ScheduledActionDrawAndSwap");
 
+  base::TimeTicks start_time = base::TimeTicks::Now();
   base::AutoReset<bool> mark_inside(&inside_draw_, true);
 
   ScheduledActionDrawAndSwapResult result;
@@ -983,8 +989,11 @@ ThreadProxy::ScheduledActionDrawAndSwapInternal(bool forced_draw) {
         base::Bind(&ThreadProxy::DidCommitAndDrawFrame, main_thread_weak_ptr_));
   }
 
-  if (draw_frame)
+  if (draw_frame) {
     CheckOutputSurfaceStatusOnImplThread();
+    base::TimeTicks end_time = base::TimeTicks::Now();
+    draw_duration_history_.InsertSample(end_time - start_time);
+  }
 
   return result;
 }
@@ -1045,6 +1054,14 @@ void ThreadProxy::DidAnticipatedDrawTimeChange(base::TimeTicks time) {
   layer_tree_host_impl_->ResetCurrentFrameTimeForNextFrame();
 }
 
+base::TimeDelta ThreadProxy::DrawDurationEstimate() {
+  base::TimeDelta historical_estimate =
+      draw_duration_history_.Percentile(kDrawDurationEstimationPercentile);
+  base::TimeDelta padding = base::TimeDelta::FromMicroseconds(
+      kDrawDurationEstimatePaddingInMicroseconds);
+  return historical_estimate + padding;
+}
+
 void ThreadProxy::ReadyToFinalizeTextureUpdates() {
   DCHECK(IsImplThread());
   scheduler_on_impl_thread_->FinishCommit();