EQT: Record the max queueing time from navigation start to navigation away

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 fa6a06c86d0821630db268290ca2b6f145301b08..1eef3fb22bdac4188e023d3f024301fa361bca65 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
@@ -14,6 +14,7 @@
 #include "base/trace_event/trace_event.h"
 #include "base/trace_event/trace_event_argument.h"
 #include "cc/output/begin_frame_args.h"
+#include "components/metrics/single_sample_metrics_factory_impl.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/scheduler/base/real_time_domain.h"
 #include "platform/scheduler/base/task_queue_impl.h"
@@ -219,6 +220,7 @@ RendererSchedulerImpl::MainThreadOnly::MainThreadOnly(
       in_idle_period_for_testing(false),
       use_virtual_time(false),
       is_audio_playing(false),
+      has_navigated(false),
       rail_mode_observer(nullptr),
       wake_up_budget_pool(nullptr),
       task_duration_per_queue_type_histogram(base::Histogram::FactoryGet(
@@ -1631,6 +1633,25 @@ void RendererSchedulerImpl::RemovePendingNavigation(NavigatingFrameType type) {
   }
 }
 
+void RendererSchedulerImpl::OnCommitProvisionalLoad() {
+  // Initialize |max_queueing_time_metric| lazily so that
+  // |SingleSampleMetricsFactory::SetFactory()| is called before
+  // |SingleSampleMetricsFactory::Get()|
+  if (!GetMainThreadOnly().max_queueing_time_metric) {
+    GetMainThreadOnly().max_queueing_time_metric =
+        GetOrCreateMaxQueueingTimeMetric();
+  }
+  GetMainThreadOnly().max_queueing_time_metric.reset();
+  GetMainThreadOnly().max_queueing_time = base::TimeDelta();
+  GetMainThreadOnly().has_navigated = true;
+}
+
+std::unique_ptr<base::SingleSampleMetric>
+RendererSchedulerImpl::GetOrCreateMaxQueueingTimeMetric() {
+  return base::SingleSampleMetricsFactory::Get()->CreateCustomCountsMetric(

[Sami, 2017/05/31 10:30:34]

Based on the method name I would expect this to cache the result in
max_queueing_time_metric. Or do we need the second level cache at all if the
metrics factory handles everything for us?

[Liquan (Max) Gu, 2017/06/01 14:39:39]

There is a difference between caching it in max_queueing_time_metric or not. If
not caching, the single sample metric will destruct every time when we create or
get the metric to set value or reset the pointer. If caching, the metric won't
destruct when we want to set value only, and this is a necessary property for
the implementation. That's why we need this caching.

The singe sample metric is designed in a way that it inserts a sample to the
histogram when it destructs, so destruction should be used only when necessary.

[Sami, 2017/06/01 18:29:40]

I see. This function seems to create a new metric every time it's called so I
think the name GetOrCreate... is a little confusing, right?

[Liquan (Max) Gu, 2017/06/01 18:36:05]

Whoops, you are right. 

+      "RendererScheduler.MaxQueueingTime", 1, 10000, 50);
+}
+
 void RendererSchedulerImpl::OnNavigationStarted() {
   TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("renderer.scheduler"),
                "RendererSchedulerImpl::OnNavigationStarted");
@@ -1907,6 +1928,18 @@ void RendererSchedulerImpl::RemoveTaskTimeObserver(
 void RendererSchedulerImpl::OnQueueingTimeForWindowEstimated(
     base::TimeDelta queueing_time,
     base::TimeTicks window_start_time) {
+  if (GetMainThreadOnly().has_navigated) {
+    if (GetMainThreadOnly().max_queueing_time < queueing_time) {
+      if (!GetMainThreadOnly().max_queueing_time_metric) {
+        GetMainThreadOnly().max_queueing_time_metric =
+            GetOrCreateMaxQueueingTimeMetric();
+      }
+      GetMainThreadOnly().max_queueing_time_metric->SetSample(
+          queueing_time.InMilliseconds());
+      GetMainThreadOnly().max_queueing_time = queueing_time;
+    }
+  }
+
   // RendererScheduler reports the queueing time once per window's duration.
   //          |stepEQT|stepEQT|stepEQT|stepEQT|stepEQT|stepEQT|
   // Report:  |-------window EQT------|