Adds runtimeStatsTotalMetric to collect v8 metrics and bucket them based on UE.

tracing/tracing/metrics/v8/runtime_stats_metric.html

Index: tracing/tracing/metrics/v8/runtime_stats_metric.html
diff --git a/tracing/tracing/metrics/v8/runtime_stats_metric.html b/tracing/tracing/metrics/v8/runtime_stats_metric.html
index 1e319353ebea4273f60b559f162342ed06d5df65..25d42a4e2d176ae733bffb3a4e8b5e7d88a3896f 100644
--- a/tracing/tracing/metrics/v8/runtime_stats_metric.html
+++ b/tracing/tracing/metrics/v8/runtime_stats_metric.html
@@ -81,10 +81,9 @@ tr.exportTo('tr.metrics.v8', function() {
       tr.b.UnitPrefixScale.METRIC.MICRO, tr.b.UnitPrefixScale.METRIC.MILLI);
   }
 
-  function computeRuntimeStats(values, model, endTime) {
-    var slices = [...model.getDescendantEvents()].filter(event =>
-        event instanceof tr.e.v8.V8ThreadSlice &&
-        event.start <= endTime);
+  // TODO(crbug.com/688342): Remove this function when runtimeStatsMetric is
+  // removed.
+  function computeRuntimeStats(histograms, slices) {
 
     var runtimeGroupCollection = new tr.e.v8.RuntimeStatsGroupCollection();
     runtimeGroupCollection.addSlices(slices);
@@ -96,12 +95,12 @@ tr.exportTo('tr.metrics.v8', function() {
         var durationSampleHistogram = createDurationHistogram_(entry.name);
         durationSampleHistogram.addSample(convertMicroToMilli_(entry.time));
         durationSamples.set(entry.name + ':duration', durationSampleHistogram);
-        values.addHistogram(durationSampleHistogram);
+        histograms.addHistogram(durationSampleHistogram);
 
         var countSampleHistogram = createCountHistogram_(entry.name);
         countSampleHistogram.addSample(entry.count);
         countSamples.set(entry.name + ':count', countSampleHistogram);
-        values.addHistogram(countSampleHistogram);
+        histograms.addHistogram(countSampleHistogram);
       }
 
       var durationHistogram = createDurationHistogram_(runtimeGroup.name);
@@ -113,22 +112,87 @@ tr.exportTo('tr.metrics.v8', function() {
         samples: countSamples
       });
 
-      values.addHistogram(durationHistogram);
-      values.addHistogram(countHistogram);
+      histograms.addHistogram(durationHistogram);
+      histograms.addHistogram(countHistogram);
     }
   }
 
-  function runtimeStatsMetric(values, model) {
+  // TODO(crbug.com/688342): Remove this metric and use runtimeStatsTotalMetric
+  // instead when the runtimeStatsTotalMetric is stable.
+  function runtimeStatsMetric(histograms, model) {
     var interactiveTime = computeInteractiveTime_(model);
     var domContentLoadedTime = computeDomContentLoadedTime_(model);
     var endTime = Math.max(interactiveTime, domContentLoadedTime);
-    computeRuntimeStats(values, model, endTime);
+    var slices = [...model.getDescendantEvents()].filter(event =>
+          event instanceof tr.e.v8.V8ThreadSlice && event.start <= endTime);
+    computeRuntimeStats(histograms, slices);
+  }
+
+  function computeRuntimeStatsBucketOnUE(histograms, slices,
+               histogramNamePrefix) {
+    var runtimeGroupCollection = new tr.e.v8.RuntimeStatsGroupCollection();
+    runtimeGroupCollection.addSlices(slices);
+
+    for (var runtimeGroup of runtimeGroupCollection.runtimeGroups) {
+      var histogramName = histogramNamePrefix + '_' + runtimeGroup.name;
+      var durationHistogram = createDurationHistogram_(histogramName);
+      durationHistogram.addSample(convertMicroToMilli_(runtimeGroup.time));
+      histograms.addHistogram(durationHistogram);
+
+      var countHistogram = createCountHistogram_(histogramName);
+      countHistogram.addSample(runtimeGroup.count);
+      histograms.addHistogram(countHistogram);
+    }
+  }
+
+  function runtimeStatsTotalMetric(histograms, model) {
+    var v8ThreadSlices = [...model.getDescendantEvents()].filter(event =>
+          event instanceof tr.e.v8.V8ThreadSlice).sort((e1, e2) =>
+          e1.start - e2.start);
+    var v8SlicesBucketOnUEMap = {};

[benjhayden, 2017/02/10 17:59:25]

Please use ES6 Maps instead of dictionaries.

[mythria, 2017/02/13 15:54:49]

Done.

+    // User expectations can sometime overlap. So, certain v8 slices can be
+    // included in more than one expectation. We count such slices in each
+    // of the expectations. This is done so as to minimize the noise due to
+    // the differences in the extent of overlap between the runs.
+    for (var expectation of model.userModel.expectations) {
+      var slices = expectation.range.filterArray(v8ThreadSlices,
+          event => event.start);
+      if (slices.length === 0) continue;
+      // filterArray filters the array that intersects the range inclusively.
+      // Expectations are not inclusive i.e. expectations are like [0, 1),
+      // [1, 2). v8ThreadSlices that start at 1 should be counted only in [1,2)
+      // bucket. Filter out sample at the boundary so that they are not counted
+      // twice.
+      var lastSlice = slices[slices.length - 1];
+      if (!expectation.range.intersectsRangeExclusive(lastSlice.range))

[benjhayden, 2017/02/10 17:59:25]

Please use curly braces here.
https://github.com/catapult-project/catapult/blob/master/docs/style-guide.md#...

[mythria, 2017/02/13 15:54:49]

Thanks. Done.

+        slices.pop();
+
+      if (v8SlicesBucketOnUEMap[expectation.stageTitle] === undefined) {
+        v8SlicesBucketOnUEMap[expectation.stageTitle] = slices;
+      } else {
+        var totalSlices = v8SlicesBucketOnUEMap[expectation.stageTitle].concat(
+                          slices);
+        v8SlicesBucketOnUEMap[expectation.stageTitle] = totalSlices;
+      }
+    }
+
+    // Add histograms for each UE.
+    for (var name in v8SlicesBucketOnUEMap) {
+      computeRuntimeStatsBucketOnUE(histograms, v8SlicesBucketOnUEMap[name],
+           name);

[mythria, 2017/02/09 17:21:39]

We just want to add one sample per each UE, basically the sum of all slices for
that UE. I am sorry, I did not realize that what I did earlier will add multiple
samples to the histogram and hence the metrics we may track would not be the sum
of all samples in each UE, but would be the average of the UEs in each bucket.

[benjhayden, 2017/02/10 17:59:25]

Just to clarify, this doesn't add one sample per UserExpectation object, this
code adds one sample per unique *stageTitle* (R/A/I/L).
Both can be valid metric formulations, and it can also be valid to add one
histogram sample per v8 sample.
Which formulation you want is up to you, the metric designer. If you're not
sure, you can try the metric this way, see how it works out, and then revisit
this design decision.
Histograms can compute both average and sum statistics, so the differences
between the 3 formulations are basically only relevant when you consider how
Histograms will be merged across story repetitions and stories. This merging
currently only happens in results.html, but it will be happening in the
Histogram Pipeline soon, which will affect the data on the dashboard. Once
historic data is on the dashboard, you can't easily recompute it, so if you need
to reformulate a metric down the road, you might lose historical continuity in
the charts on the dashboard.

This is all just FYI, and an apology for not knowing how to explain it very well
on how-to-write-metrics.md. :-)

[mythria, 2017/02/13 15:54:49]

Thanks for the detailed explanation.

+    }
+    // Also compute the metric that includes all of the samples. The values
+    // in UE buckets do not add up to the total of all samples, since we
+    // duplicate some of the samples in multiple buckets when the UEs overlap.
+    computeRuntimeStatsBucketOnUE(histograms, v8ThreadSlices, 'Any');
   }
 
+  tr.metrics.MetricRegistry.register(runtimeStatsTotalMetric);
   tr.metrics.MetricRegistry.register(runtimeStatsMetric);
 
   return {
     runtimeStatsMetric,
+    runtimeStatsTotalMetric,
   };
 });
 </script>