[scheduler] Monitor renderer load level.

third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc

Index: third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc
diff --git a/third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc b/third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc
index 9c5e33a261fef355db3ff3399cc626aa9141ce70..cd2f35e187456d9f85996d532aa4a9b27da594b2 100644
--- a/third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc
+++ b/third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc
@@ -36,6 +36,17 @@ const double kShortIdlePeriodDurationPercentile = 50;
 // Amount of idle time left in a frame (as a ratio of the vsync interval) above
 // which main thread compositing can be considered fast.
 const double kFastCompositingIdleTimeThreshold = .2;
+
+void ReportForegroundRendererTaskLoad(base::TimeTicks time, double load) {
+  UMA_HISTOGRAM_PERCENTAGE("RendererScheduler.ForegroundRendererLoad",
+                           static_cast<int>(load * 100));
+}
+
+void ReportBackgroundRendererTaskLoad(base::TimeTicks time, double load) {
+  UMA_HISTOGRAM_PERCENTAGE("RendererScheduler.BackgroundRendererLoad",
+                           static_cast<int>(load * 100));
+}
+
 }  // namespace
 
 RendererSchedulerImpl::RendererSchedulerImpl(
@@ -123,6 +134,12 @@ RendererSchedulerImpl::MainThreadOnly::MainThreadOnly(
                           time_source,
                           kShortIdlePeriodDurationSampleCount,
                           kShortIdlePeriodDurationPercentile),
+      background_renderer_load_tracker(
+          time_source->NowTicks(),

[Sami, 2016/08/22 14:33:16]

It'd be nice to pass in the same starting time to both trackers :P

[altimin, 2016/08/22 15:36:24]

Done.

+          base::Bind(&ReportBackgroundRendererTaskLoad)),
+      foreground_renderer_load_tracker(
+          time_source->NowTicks(),
+          base::Bind(&ReportForegroundRendererTaskLoad)),
       current_use_case(UseCase::NONE),
       timer_queue_suspend_count(0),
       navigation_task_expected_count(0),
@@ -163,6 +180,10 @@ RendererSchedulerImpl::CompositorThreadOnly::CompositorThreadOnly()
 RendererSchedulerImpl::CompositorThreadOnly::~CompositorThreadOnly() {}
 
 void RendererSchedulerImpl::Shutdown() {
+  base::TimeTicks now = tick_clock()->NowTicks();
+  MainThreadOnly().background_renderer_load_tracker.RecordIdle(now);
+  MainThreadOnly().foreground_renderer_load_tracker.RecordIdle(now);
+
   throttling_helper_.reset();
   helper_.Shutdown();
   MainThreadOnly().was_shutdown = true;
@@ -405,6 +426,11 @@ void RendererSchedulerImpl::OnRendererBackgrounded() {
     return;
 
   MainThreadOnly().renderer_backgrounded = true;
+
+  base::TimeTicks now = tick_clock()->NowTicks();
+  MainThreadOnly().foreground_renderer_load_tracker.Pause(now);
+  MainThreadOnly().background_renderer_load_tracker.Resume(now);
+
   if (!MainThreadOnly().timer_queue_suspension_when_backgrounded_enabled)
     return;
 
@@ -426,6 +452,11 @@ void RendererSchedulerImpl::OnRendererForegrounded() {
 
   MainThreadOnly().renderer_backgrounded = false;
   MainThreadOnly().renderer_suspended = false;
+
+  base::TimeTicks now = tick_clock()->NowTicks();
+  MainThreadOnly().foreground_renderer_load_tracker.Resume(now);
+  MainThreadOnly().background_renderer_load_tracker.Pause(now);
+
   suspend_timers_when_backgrounded_closure_.Cancel();
   ResumeTimerQueueWhenForegrounded();
 }
@@ -1413,6 +1444,10 @@ void RendererSchedulerImpl::ReportTaskTime(base::TimeTicks start_time,
                                                                    end_time);
   MainThreadOnly().long_task_tracker.RecordLongTask(
       start_time, end_time - start_time);
+  MainThreadOnly().foreground_renderer_load_tracker.RecordTaskTime(start_time,

[Sami, 2016/08/22 14:33:16]

Could we only do this for the one active one?

[altimin, 2016/08/22 15:36:24]

Started to bail out early from ThreadLoadTracker::Advance when thread is paused
instead.

+                                                                   end_time);
+  MainThreadOnly().background_renderer_load_tracker.RecordTaskTime(start_time,
+                                                                   end_time);

[Sami, 2016/08/22 14:33:16]

Maybe add a comment saying we'd really want to use thread time instead of wall
time but for efficiency reasons we're reusing the wall time measurement here?

[altimin, 2016/08/22 15:36:24]

Done.

   UMA_HISTOGRAM_CUSTOM_COUNTS("RendererScheduler.TaskTime",
                               (end_time - start_time).InMicroseconds(), 1,
                               1000000, 50);