Profiling Chromium with V8

V8’s CPU & heap profilers are trivial to use from V8’s shells, but it may appear confusing how to use them with Chromium. This page should help you with it.

Why is using V8’s profilers with Chromium different from using them with V8 shells? #

Chromium is a complex application, unlike V8 shells. Below is the list of Chromium features that affect profiler usage:

How to run Chromium to get a CPU profile? #

Here is how to run Chromium in order to get a CPU profile from the start of the process:

./Chromium --no-sandbox --user-data-dir=`mktemp -d` --incognito --js-flags='--prof'

Please note that you wouldn’t see profiles in Developer Tools, because all the data is being logged to a file, not to Developer Tools.

Flags description #

--no-sandbox turns off the renderer sandbox so chrome can write to the log file.

--user-data-dir is used to create a fresh profile, use this to avoid caches and potential side-effects from installed extensions (optional).

--incognito is used to further prevent pollution of your results (optional).

--js-flags contains the flags passed to V8:

Android #

Chrome on Android has a number of unique points that make it a bit more complex to profile.

The following commands enable profiling on Android:

./build/android/adb_chrome_public_command_line --no-sandbox --single-process --js-flags='--logfile=/storage/emulated/0/Download/%t.log,--prof'
<Close and relaunch Chome on the Android device>
adb pull /storage/emulated/0/Download/<logfile>
./src/v8/tools/linux-tick-processor --apk-embedded-library=out/Release/lib.unstripped/ --preprocess <logfile>

Notes #

Under Windows, be sure to turn on .MAP file creation for chrome.dll, but not for chrome.exe.