Monthly Archives: July 2012

Mozilla A-Team – How to compare talos numbers from try server to trunk

Have you ever been working on a change that you think will affect performance numbers and you were not sure how to verify the impact of your change?

I have had questions on how to do this and recently I needed to do it myself (as I introduced a change to Talos which caused a big old performance regression in everything).

The main use case I needed to do was run a change on Try server and verify that it did in fact fix my performance regression.  Normally I would go to tbpl, and click on each of my tests to see the reported number(s).  For each of those test:number sets, I would look on graph server (hint: you can get to graph server for a given test by clicking on the reported number) and verify that my numbers were inside the expected range for that test/platform/branch based on the history.  If only I was part of a software developers union I could complain that that boring time intensive work was not in my contract.

To simplify my life, I decided to automate this with a python script.  I wrote which will spit out a text based summary of what I described above.  Here is a sample output:

python --revision c094aeea5f73 --branch Try --masterbranch Firefox --test tp5n --platform Linux
    tp5n: 292.157 -> 400.444; 308.596

A quick explanation:

  • 292.157 is the lowest number reported in the last 7 days for tp5n,linux
  • 400.444 is the highest number reported in the last 7 days for tp5n,linux
  • 308.596 is the value reported from my test on try server for tp5n,linux

While this doesn’t do the previous 30 changesets and the next 5, it gives a pretty good indicator about what to expect.  I can run this on a different time range (to check the 7 days prior to my introduced regression) by adding –skipdays to the command line:

python --revision c094aeea5f73 --branch Try --masterbranch Firefox --test tp5n --platform Linux --skipdays 6
 **tp5n: 311.975 -> 398.571; 308.596

Here you will see a “**tp5n”, and that indicates that the Try server number is not in the range and should be looked at the old fashioned way.

Hope this helps in debugging.

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Filed under testdev

Mozilla A-Team – Unraveling the mystery of Talos – part 1 of a googol

Most people at Mozilla have heard of Talos, if you haven’t, Talos is the performance testing framework that runs for every checkin that occurs at Mozilla.

Over the course of the last year I have had the opportunity to extend, modify, retrofit, rewrite many parts of the harness and tests that make up Talos.

It seems that once or twice a month I get a question about Talos.  Wouldn’t it be nice if I documented Talos?  When Alice was the main owner of Talos, she had written up some great documentation and as of today I am announcing that it has gone through an update:

Stay tuned as there will be more updates to come as we make the documentation more useful.


Filed under general, testdev