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Cluster Telemetry

Run on Cluster Telemetry! (Google only, sorry)

Cluster Telemetry 101

Telemetry is Chrome's performance testing framework, using it you can perform arbitrary actions on a set of web pages and report metrics about it.

Cluster Telemetry allows you to run telemetry's benchmarks using multiple repository patches through Alexa's top 10k and top 100k web pages.
Developers can use the framework to:
  • Measure the performance of their patch against the top subset of the internet on both Desktop and Android using the perf page.
  • Gather metrics for analysis or for reports against 100k web pages on CT's VM farm using the analysis page.
  • Test visual impact of patches and prevent regressions affecting rendering pipeline using the pixel diff page.

Should I use CT?

If you would like to know how your patch impacts Chrome's performance/correctness or would like to do analysis against a very large repository of real world web pages then you should try out Cluster Telemetry.

CT has been used to gather perf data for the following projects:
  • Slimming paint
  • Performance data for layer squashing and compositing overlap map
  • SkPaint in Graphics Context
  • Culling
  • New paint dictionary
CT has been used to gather analysis data for the following projects:
  • UserCounter analysis
  • Gather data for a language detector
  • TTI variability study
  • Analysis of 5M SVGs
  • Stat rare usages
CT has been used for pixel diffing for the following projects:
  • SVG usage
  • Stacking context

Which telemetry benchmarks does CT support?

Currently the framework supports rasterize_and_record_micro, repaint, loading and usecounter benchmarks. It is likely the framework can support more benchmarks, but these are the ones which have been extensively tested.
CT also allows you to run against unlanded / modified benchmarks.

How accurate are CT's results?

For an empty patch repaint run on Desktop, these are the results:


The overall results from Cluster Telemetry runs are accurate within a percentage point.

The per webpage results (visible when you click on a field) do have some variance, but this has been greatly improved due to efforts detailed here.

Framework Code and Documentation

Cluster Telemetry is primarily written in Go with a few Python scripts. The frontend is written using Polymer. The framework lives in master/ct.
Here is more detailed documentation for the different pages:

Contact Us

If you have questions, please email rmistry@ or