cc: Heuristic for Renderer latency recovery

cc/trees/proxy_timing_history.cc

 // Copyright 2014 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/trees/proxy_timing_history.h"
 
 #include "base/metrics/histogram.h"
 
 const size_t kDurationHistorySize = 60;
 const double kCommitAndActivationDurationEstimationPercentile = 50.0;
 const double kDrawDurationEstimationPercentile = 100.0;
-const int kDrawDurationEstimatePaddingInMicroseconds = 0;
+const int kDrawDurationEstimatePaddingInMicroseconds = 1000;

[mithro-old, 2015/05/27 04:40:15]

Why this change?

This is also a magic number, why do we pad the DrawDurationEstimate with 1ms?

This also feels like the wrong place to be doing any padding?

[brianderson, 2015/05/27 23:22:32]

I'll move the padding to the scheduler so it's more obvious. I added the padding
to make races with the DisplayScheduler's deadline less likely. We don't account
for IPC propogation/descheduling delays anywhere else at the moment.

I can move this to a separate patch.

Before this patch, if we lost the race then we'd just go into a high latency
mode. If we lose the race with this patch though, we might try to recovery the
latency and lose the race over and over again.

I should probably add logic to make latency recovery less likely in the future
if it has failed in the past...

 
 namespace cc {
 
 ProxyTimingHistory::ProxyTimingHistory(
     RenderingStatsInstrumentation* rendering_stats_instrumentation)
     : draw_duration_history_(kDurationHistorySize),
       begin_main_frame_to_commit_duration_history_(kDurationHistorySize),
       commit_to_activate_duration_history_(kDurationHistorySize),
       rendering_stats_instrumentation_(rendering_stats_instrumentation) {
 }
@@ skipping 92 matching lines @@
                              base::TimeDelta::FromMilliseconds(100),
                              50);
   UMA_HISTOGRAM_CUSTOM_TIMES("Renderer.DrawDurationOverestimate",
                              draw_duration_overestimate,
                              base::TimeDelta::FromMilliseconds(1),
                              base::TimeDelta::FromMilliseconds(100),
                              50);
 }
 
 }  // namespace cc