2004692 - 4.04 - 3.83% speedometer Elm-TodoMVC/CompletingAllItems/Sync / speedometer Elm-TodoMVC/CompletingAllItems (Windows) regression on Mon November 24 2025

Status: RESOLVED WONTFIX

(Firefox :: Sidebar, defect)

Description

[Treeherder Bug Filer]

Perfherder has detected a browsertime performance regression from push 37f1c536fdb89cd69039774a87f3ad8a94b95328. As author of one of the patches included in that push, we need your help to address this regression.

Please acknowledge, and begin investigating this alert within 3 business days, or the patch(es) may be backed out in accordance with our regression policy. Our guide to handling regression bugs has information about how you can proceed with this investigation.

If you have any questions or need any help with the investigation, please reach out to [e-mail]. Alternatively, you can find help on Slack by joining #perf-help, and on Matrix you can find help by joining #perftest.

Regressions:

Ratio	Test	Platform	Options	Absolute values (old vs new)	Performance Profiles
4%	speedometer Elm-TodoMVC/CompletingAllItems/Sync	windows11-64-24h2-shippable	fission webrender	34.80 -> 36.21	Before/After
4%	speedometer Elm-TodoMVC/CompletingAllItems	windows11-64-24h2-shippable	fission webrender	36.59 -> 38.00	Before/After

Details of the alert can be found in the alert summary, including links to graphs and comparisons for each of the affected tests.

If you need the profiling jobs you can trigger them yourself from treeherder job view or ask [e-mail] to do that for you.

You can run all of these tests on try with ./mach try perf --alert 47737

The following documentation link provides more information about this command.

Comment 1

[BugBot [:suhaib / :marco]]

Set release status flags based on info from the regressing bug 1905212

Comment 2

[Ryan VanderMeulen [:RyanVM]]

Bug 543435 landed immediately after bug 1905212 seems a lot more likely to be the culprit looking at the graphs.

Comment 3

[BugBot [:suhaib / :marco]]

:vhilla, since you are the author of the regressor, bug 543435, could you take a look? Also, could you set the severity field?

For more information, please visit BugBot documentation.

Comment 4

[Vincent Hilla [:vhilla]]

https://bugzilla.mozilla.org/show_bug.cgi?id=2002544#c3 might apply here too.

Something interesting I see in the profile is that the number of DOMContentLoaded increased 83 -> 163. The number of CreateAboutBlankDocumentViewer stayed the same. Looking at benchmark-runner.js _appendFrame and prepareCurrentSuite, we first bind the test iframe and then navigate it. Bug 543435 means we'll now fully load the about:blank, have some additional IPC and a slight performance hit is expected.

Comment 5

[Vincent Hilla [:vhilla]]

:smaug I think we can close this one?

Comment 6

[Olli Pettay [:smaug][[e-mail]]]

yeah
(there are other perf regressions we are looking at)