Force events to be non blocking if main thread is unresponsive.

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 25376e87f14eab36a4df8cfeac668a9928540ad9..9430977554e611ef4bdb6568464884859c6415fa 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
@@ -45,6 +45,9 @@ constexpr base::TimeDelta kThreadLoadTrackerWaitingPeriodBeforeReporting =
 // We do not throttle anything while audio is played and shortly after that.
 constexpr base::TimeDelta kThrottlingDelayAfterAudioIsPlayed =
     base::TimeDelta::FromSeconds(5);
+// Maximum task queueing time before the main thread is considered unresponsive.
+constexpr base::TimeDelta kMainThreadResponsivenessThreshold =
+    base::TimeDelta::FromMilliseconds(200);
 
 void ReportForegroundRendererTaskLoad(base::TimeTicks time, double load) {
   int load_percentage = static_cast<int>(load * 100);
@@ -64,8 +67,8 @@ void ReportBackgroundRendererTaskLoad(base::TimeTicks time, double load) {
 
 base::TimeTicks MonotonicTimeInSecondsToTimeTicks(
     double monotonicTimeInSeconds) {
-  return base::TimeTicks() + base::TimeDelta::FromSecondsD(
-      monotonicTimeInSeconds);
+  return base::TimeTicks() +
+         base::TimeDelta::FromSecondsD(monotonicTimeInSeconds);
 }
 }  // namespace
 
@@ -90,11 +93,15 @@ RendererSchedulerImpl::RendererSchedulerImpl(
           base::Bind(&RendererSchedulerImpl::UpdatePolicy,
                      base::Unretained(this)),
           helper_.ControlTaskRunner()),
+      seqlock_queueing_time_estimator_(
+          QueueingTimeEstimator(this, base::TimeDelta::FromSeconds(1))),
       main_thread_only_(this,
                         compositor_task_runner_,
                         helper_.scheduler_tqm_delegate().get(),
                         helper_.scheduler_tqm_delegate()->NowTicks()),
+      any_thread_(this),
       policy_may_need_update_(&any_thread_lock_),
+      main_thread_responsiveness_threshold_(kMainThreadResponsivenessThreshold),
       weak_factory_(this) {
   task_queue_throttler_.reset(
       new TaskQueueThrottler(this, "renderer.scheduler"));
@@ -156,8 +163,6 @@ RendererSchedulerImpl::MainThreadOnly::MainThreadOnly(
       timer_task_cost_estimator(time_source,
                                 kTimerTaskEstimationSampleCount,
                                 kTimerTaskEstimationPercentile),
-      queueing_time_estimator(renderer_scheduler_impl,
-                              base::TimeDelta::FromSeconds(1)),
       idle_time_estimator(compositor_task_runner,
                           time_source,
                           kShortIdlePeriodDurationSampleCount,
@@ -197,7 +202,8 @@ RendererSchedulerImpl::MainThreadOnly::MainThreadOnly(
 
 RendererSchedulerImpl::MainThreadOnly::~MainThreadOnly() {}
 
-RendererSchedulerImpl::AnyThread::AnyThread()
+RendererSchedulerImpl::AnyThread::AnyThread(
+    RendererSchedulerImpl* renderer_scheduler_impl)
     : awaiting_touch_start_response(false),
       in_idle_period(false),
       begin_main_frame_on_critical_path(false),
@@ -208,7 +214,8 @@ RendererSchedulerImpl::AnyThread::AnyThread()
 RendererSchedulerImpl::AnyThread::~AnyThread() {}
 
 RendererSchedulerImpl::CompositorThreadOnly::CompositorThreadOnly()
-    : last_input_type(blink::WebInputEvent::Undefined) {}
+    : last_input_type(blink::WebInputEvent::Undefined),
+      main_thread_seems_unresponsive(false) {}
 
 RendererSchedulerImpl::CompositorThreadOnly::~CompositorThreadOnly() {}
 
@@ -1510,6 +1517,43 @@ void RendererSchedulerImpl::SetRAILModeObserver(RAILModeObserver* observer) {
   MainThreadOnly().rail_mode_observer = observer;
 }
 
+bool RendererSchedulerImpl::MainThreadSeemsUnresponsive() {
+  base::TimeTicks now = tick_clock()->NowTicks();

[alex clarke (OOO till 29th), 2016/11/14 17:00:17]

Is it worth adding a TRACE_EVENT here?

[tdresser, 2016/12/15 13:17:00]

For when we're checking if the main thread is unresponsive?
What's the goal?

(Not saying we shouldn't, I'm just not clear on why we should.)

+  base::TimeDelta estimated_queueing_time;
+
+  bool can_read = false;
+  QueueingTimeEstimator::Data queueing_time_estimator_data;
+
+  base::subtle::Atomic32 version;
+  seqlock_queueing_time_estimator_.seqlock.ReadOrFail(&can_read, &version);
+
+  // If we fail to determine if the main thread is busy, assume whether or not
+  // it's busy hasn't change since the last time we asked.
+  if (!can_read)
+    return CompositorThreadOnly().main_thread_seems_unresponsive;
+
+  queueing_time_estimator_data = seqlock_queueing_time_estimator_.data.data();
+
+  // If we fail to determine if the main thread is busy, assume whether or not
+  // it's busy hasn't change since the last time we asked.
+  if (seqlock_queueing_time_estimator_.seqlock.ReadRetry(version))
+    return CompositorThreadOnly().main_thread_seems_unresponsive;
+
+  QueueingTimeEstimator queueing_time_estimator(queueing_time_estimator_data);
+
+  estimated_queueing_time =
+      queueing_time_estimator.EstimateQueueingTimeIncludingCurrentTask(now);
+
+  bool main_thread_seems_unresponsive =
+      estimated_queueing_time > main_thread_responsiveness_threshold_;
+  {

[Sami, 2016/11/14 21:16:45]

nit: any reason for these braces? We're not grabbing any locks here.

[tdresser, 2016/12/15 13:17:00]

Done.

+    CompositorThreadOnly().main_thread_seems_unresponsive =
+        main_thread_seems_unresponsive;
+  }
+
+  return main_thread_seems_unresponsive;
+}
+
 void RendererSchedulerImpl::RegisterTimeDomain(TimeDomain* time_domain) {
   helper_.RegisterTimeDomain(time_domain);
 }
@@ -1574,22 +1618,33 @@ void RendererSchedulerImpl::OnTriedToExecuteBlockedTask(
         "Blink deferred a task in order to make scrolling smoother. "
         "Your timer and network tasks should take less than 50ms to run "
         "to avoid this. Please see "
-        "https://developers.google.com/web/tools/chrome-devtools/profile/evaluate-performance/rail"
+        "https://developers.google.com/web/tools/chrome-devtools/profile/"
+        "evaluate-performance/rail"
         " and https://crbug.com/574343#c40 for more information.");
   }
 }
 
-void RendererSchedulerImpl::ReportTaskTime(TaskQueue* task_queue,
-                                           double start_time,
-                                           double end_time) {
+void RendererSchedulerImpl::ReportTaskStartTime(double start_time) {
+  base::TimeTicks start_time_ticks =
+      MonotonicTimeInSecondsToTimeTicks(start_time);
+  MainThreadOnly().current_task_start_time = start_time_ticks;
+  seqlock_queueing_time_estimator_.seqlock.WriteBegin();
+  seqlock_queueing_time_estimator_.data.OnTopLevelTaskStarted(start_time_ticks);
+  seqlock_queueing_time_estimator_.seqlock.WriteEnd();
+}
+
+void RendererSchedulerImpl::ReportTaskEndTime(TaskQueue* task_queue,
+                                              double start_time,
+                                              double end_time) {
   // TODO(scheduler-dev): Remove conversions when Blink starts using
   // base::TimeTicks instead of doubles for time.
   base::TimeTicks start_time_ticks =
       MonotonicTimeInSecondsToTimeTicks(start_time);
   base::TimeTicks end_time_ticks = MonotonicTimeInSecondsToTimeTicks(end_time);
 
-  MainThreadOnly().queueing_time_estimator.OnToplevelTaskCompleted(
-      start_time_ticks, end_time_ticks);
+  seqlock_queueing_time_estimator_.seqlock.WriteBegin();
+  seqlock_queueing_time_estimator_.data.OnTopLevelTaskCompleted(end_time_ticks);
+  seqlock_queueing_time_estimator_.seqlock.WriteEnd();
 
   task_queue_throttler()->OnTaskRunTimeReported(task_queue, start_time_ticks,
                                                 end_time_ticks);
@@ -1601,9 +1656,9 @@ void RendererSchedulerImpl::ReportTaskTime(TaskQueue* task_queue,
   MainThreadOnly().background_main_thread_load_tracker.RecordTaskTime(
       start_time_ticks, end_time_ticks);
   // TODO(altimin): Per-page metrics should also be considered.
-  UMA_HISTOGRAM_CUSTOM_COUNTS("RendererScheduler.TaskTime",
-                              (end_time_ticks - start_time_ticks).InMicroseconds(), 1,
-                              1000000, 50);
+  UMA_HISTOGRAM_CUSTOM_COUNTS(
+      "RendererScheduler.TaskTime",
+      (end_time_ticks - start_time_ticks).InMicroseconds(), 1, 1000000, 50);
   UMA_HISTOGRAM_ENUMERATION("RendererScheduler.NumberOfTasksPerQueueType",
                             static_cast<int>(task_queue->GetQueueType()),
                             static_cast<int>(TaskQueue::QueueType::COUNT));