Buildbot/Talos/Profiling

How to Run Talos in Profiling Mode

When profiling is enabled, we use the Gecko Profiler to capture profiles that can then be displayed by Cleopatra. When running in profiling mode, captured profiles are copied to the upload directory.

Locally

You need to set an upload directory and use the --spsProfile command line parameter with Talos to capture profiles and have them copied into the upload folder.

1. Set the upload folder (make sure it exists):

export MOZ_UPLOAD_DIR=/home/username/talos/upload

2. Run talos with --spsProfile

talos -n -d --develop --executablePath ~/work/gecko-dev/obj-x86_64-unknown-linux-gnu/dist/bin/firefox --activeTests ts --spsProfile

3. You will have one zip file per test in your upload folder. See this page for info about how to open profiles in cleopatra.

On TryServer

1. When you push to try, add "mozharness: --spsProfile" after "try: ..." to your commit message. Example:

try: -b do -u all -t chrome,nochrome mozharness: --spsProfile

2. When the tests finishes and you view the log, you will see something like

TinderboxPrint: Uploaded profile_tcanvasmark.zip to http://mozilla-releng-blobs.s3.amazonaws.com/blobs/...

3. Download the zip file from this URL, extract it and see this page for info about how to open profiles in cleopatra.

FAQ

The Talos results with profiling are always higher

Yes, profiling usually has non-trivial overhead. This is why you might want to try one of these two approaches:

• Do a Talos run with profiling on before and after your change and compare those numbers.
• Do a Talos run with profiling off to check if the issue still exists and at the same time do a run with profiling on to get the data from it.