Bug 1030487 - Don't report main-thread I/O to Telemetry unless it lasts more than 50ms; r=vladan

toolkit/components/telemetry/Telemetry.cpp

@@ -411,6 +411,9 @@ void TelemetryIOInterposeObserver::AddPath(const nsAString& aPath,
   mSafeDirs.AppendElement(SafeDir(aPath, aSubstName));
 }
 
+// Threshold for reporting slow main-thread I/O (50 milliseconds).
+const TimeDuration kTelemetryReportThreshold = TimeDuration::FromMilliseconds(50);
+
 void TelemetryIOInterposeObserver::Observe(Observation& aOb)
 {
   // We only report main-thread I/O
@@ -424,6 +427,10 @@ void TelemetryIOInterposeObserver::Observe(Observation& aOb)
     return;
   }
 
+  if (aOb.Duration() < kTelemetryReportThreshold) {
+    return;
+  }
+
   // Get the filename
   const char16_t* filename = aOb.Filename();
  

xpcom/build/IOInterposer.cpp

@@ -350,6 +350,7 @@ public:
                                        "IOInterposer", false)
   {
     mStart = TimeStamp::Now();
+    mEnd = mStart;
   }
 };