1625420 - 6.9% raptor-tp6-fandom-firefox-cold fcp (linux64-shippable-qr) regression on push 93cf130f59f97acc6ebb84c3505880cdcaca36c0 (Tue March 24 2020)

Status: RESOLVED WONTFIX

(Core :: Graphics: WebRender, defect, P3)

Description

[Marian Raiciof [:marauder]]

Raptor has detected a Firefox performance regression from push:

https://hg.mozilla.org/integration/autoland/pushloghtml?changeset=93cf130f59f97acc6ebb84c3505880cdcaca36c0

As author of one of the patches included in that push, we need your help to address this regression.

Regressions:

8% raptor-tp6-fandom-firefox-cold fcp linux64-shippable-qr opt 707.50 -> 764.75
7% raptor-tp6-fandom-firefox-cold fcp linux64-shippable-qr opt 712.71 -> 761.92

You can find links to graphs and comparison views for each of the above tests at: https://treeherder.mozilla.org/perf.html#/alerts?id=25502

On the page above you can see an alert for each affected platform as well as a link to a graph showing the history of scores for this test. There is also a link to a Treeherder page showing the Raptor jobs in a pushlog format.

To learn more about the regressing test(s) or reproducing them, please see: https://wiki.mozilla.org/TestEngineering/Performance/Raptor

*** Please let us know your plans within 3 business days, or the offending patch(es) will be backed out! ***

Our wiki page outlines the common responses and expectations: https://wiki.mozilla.org/TestEngineering/Performance/Talos/RegressionBugsHandling

Comment 1

[Andrew Osmond [:aosmond] (he/him)]

That's certainly interesting. I know the comparison is a little more expensive, but hard to believe it would cause an issue. The tiling need may have caused some machinery underneath to change. There are no other nearby changes which seem relevant so I'm confident it is indeed my change that triggered it (but unlikely to be directly responsible for the regression).

Comment 2

[Firefox Bug Husbandry Bot]

Because this bug's Severity has not been changed from the default since it was filed, and it's Priority is P3 (Backlog,) indicating it has been triaged, the bug's Severity is being updated to S3 (normal.)

Comment 3

[Glenn Watson [:gw]]

Too old to fix now.