TestEngineering/Performance/FAQ
Sheriffing
Tree
Branch names and confusion
We have a variety of branches at Mozilla, here are the main ones that we see alerts on:
- Mozilla-Inbound (PGO, Non-PGO)
- Autoland (PGO, Non-PGO)
- Mozilla-Beta (all PGO)
Linux and Windows builds have PGO, OSX does not.
When investigating alerts, always look for the Non-PGO branch first. Usually expect to find changes on Mozilla-Inbound (about 50%) and Autoland (50%).
The volume on the branches is something to be aware of, we have higher volume on Mozilla-Inbound and Autoland, this means that alerts will be generated faster and it will be easier to track down the offending revision.
A final note, Mozilla-Beta is a branch where little development takes place. The volume is really low and alerts come 5 days (or more) later. It is important to address Mozilla-Beta alerts ASAP because that is what we are shipping to customers.
What is coalescing
Coalescing is a term we use for when we schedule jobs to run on a given machine. When the load is high these jobs are placed in a queue and the longer the queue we skip over some of the jobs. This allows us to get results on more recent changesets faster.
This affects talos numbers as we see regressions which show up over >1 changeset that is pushed. We have to manually fill in the coalesced jobs (including builds sometimes) to ensure we have the right changeset to blame for the regression.
Some things to be aware of:
- missing test jobs - This could be as easy as waiting for jobs to finish, or scheduling the missing job assuming it was coalesced, otherwise, it could be a missing build.
- missing builds - we would have to generate builds, which automatically schedules test jobs, sometimes these test jobs are coalesced and not run.
- results might not be possible due to build failures, or test failures
- pgo builds are not coalesced, they just run much less frequently. Most likely a pgo build isn't the root cause
Here is a view on treeherder of missing data (usually coalescing):
Note the two pushes that have no data (circled in red). If the regression happened around here, we might want to backfill those two jobs so we can ensure we are looking at the push which caused the regression instead of >1 push.
What is an uplift
Every 6 weeks we release a new version of Firefox. When we do that, our code which developers check into the nightly branch gets uplifted (thing of this as a large merge) to the Beta branch. Now all the code, features, and Talos regressions are on Beta.
This affects the Performance Sheriffs because we will get a big pile of alerts for Mozilla-Beta. These need to be addressed rapidly. Luckily almost all the regressions seen on Mozilla-Beta will already have been tracked on Mozilla-Inbound or Autoland.
Alert
See TestEngineering/Performance/Sheriffing/Alert_FAQ
Noise
See TestEngineering/Performance/Sheriffing/Noise_FAQ