PerfStats
PerfStats is a framework for the low-overhead selective collection of internal performance metrics. The results are accessible through ChromeUtils, Browsertime output, and in select performance tests.
Adding a new PerfStat
Define the new PerfStat by adding it to this list in PerfStats.h
.
Then, in C++ code, wrap execution in an RAII object, e.g.
PerfStats::AutoMetricRecording<PerfStats::Metric::MyMetric>()
or call the following function manually:
PerfStats::RecordMeasurement(PerfStats::Metric::MyMetric, Start, End)
For incrementing counters, use the following:
PerfStats::RecordMeasurementCount(PerfStats::Metric::MyMetric, incrementCount)
Here’s an example of a patch where a new PerfStat was added and used.
Enabling collection
To enable collection, use ChromeUtils.setPerfStatsFeatures(array<string> metrics)
, where passing an empty array disables all metrics. Pass an array of metric names corresponding to the Metric
enum values, e.g. ["LayerBuilding", "DisplayListBuilding"]
. To enable all metrics, you may use ChromeUtils.enableAllPerfStatsFeatures()
.
Accessing results
Results can be accessed with ChromeUtils.CollectPerfStats()
.
The Browsertime test framework will sum results across processes and report them in its output.
The raptor-browsertime Windows essential pageload tests also collect all PerfStats.