1979285 - 43.56 - 20.05% tumblr loadtime / tumblr largestContentfulPaint + 1 more (Windows) regression on Fri July 11 2025

Status: RESOLVED WONTFIX

(Core :: Audio/Video: Playback, defect)

Description

[Treeherder Bug Filer]

Perfherder has detected a browsertime performance regression from push 8fc81b7f0d2a67a7021b11c174769eb71b91346d. 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
46%	tumblr loadtime	windows11-64-24h2-shippable	fission warm webrender	264.08 -> 386.67	Before/After
44%	tumblr loadtime	windows11-64-24h2-shippable	fission warm webrender	332.66 -> 477.57	Before/After
28%	tumblr SpeedIndex	windows11-64-24h2-shippable	fission warm webrender	126.73 -> 162.06	Before/After
21%	tumblr PerceptualSpeedIndex	windows11-64-24h2-shippable	fission warm webrender	106.39 -> 128.26	Before/After
20%	tumblr largestContentfulPaint	windows11-64-24h2-shippable	fission warm webrender	331.32 -> 397.73	Before/After

Improvements:

Ratio	Test	Platform	Options	Absolute values (old vs new)	Performance Profiles
5%	twitch loadtime	windows11-64-24h2-shippable	cold fission webrender	515.25 -> 488.34	Before/After
4%	twitch loadtime	windows11-64-24h2-shippable	fission warm webrender	484.25 -> 465.27	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 45997

The following documentation link provides more information about this command.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

Set release status flags based on info from the regressing bug 1976591

Comment 2

[Alastor Wu [:alwu][PTO 11/1-11/9]]

This is the expected change when using the hardware decoder again.