Perf analysis tools

How to analyse Servo HTML traces (--profiler-trace-path)

Use the servo command:

servo$ servo --profiler-trace-path=trace.html --print-pwm <url>
analyse$ RUST_LOG=analyse=info cargo run -r servo <trace.html> [trace.html ...]

--print-pwm tells you in the terminal running Servo when you’ve waited long enough for the Time To Interactive metric to appear in your trace.

How to analyse Chromium Perfetto traces (--trace-startup --trace-startup-file)

Use the chromium command, where <url> is the same URL as the page you loaded:

analyse$ google-chrome-stable --trace-startup --trace-startup-file=chrome.pftrace <url>
analyse$ python traceconv json chrome.pftrace chrome.json
analyse$ RUST_LOG=analyse=info cargo run -r chromium <url> <chrome.json> [chrome.json ...]

How to generate a combined Chrome JSON trace

Use the combined command, where each <command> is a servo or chromium command from above:

analyse$ RUST_LOG=analyse=info cargo run -r combined <command> [[-- <command>] ...]

These traces can be opened in the Perfetto UI.