1869528 - 48.55 - 10.46% reddit-billgates-post-1.posts FirstVisualChange / reddit-billgates-post-1.posts LastVisualChange + 3 more (Windows) regression on Thu December 7 2023

Status: RESOLVED WONTFIX

(Core :: DOM: Core & HTML, defect)

Description

[Acasandrei Beatrice (needinfo me)]

Perfherder has detected a browsertime performance regression from push 6767f1605049012cccf15d42c103b63d8efd8313. As author of one of the patches included in that push, we need your help to address this regression.

Regressions:

Ratio	Test	Platform	Options	Absolute values (old vs new)	Performance Profiles
49%	reddit-billgates-post-1.posts FirstVisualChange	windows10-64-shippable-qr	cold fission webrender	55.92 -> 83.08
34%	reddit-billgates-post-1.posts SpeedIndex	windows10-64-shippable-qr	cold fission webrender	102.78 -> 137.37
33%	reddit-billgates-post-1.posts ContentfulSpeedIndex	windows10-64-shippable-qr	cold fission webrender	199.82 -> 264.97
26%	reddit-billgates-post-1.posts PerceptualSpeedIndex	windows10-64-shippable-qr	cold fission webrender	183.94 -> 231.07
10%	reddit-billgates-post-1.posts LastVisualChange	windows10-64-shippable-qr	cold fission webrender	519.17 -> 573.47

Improvements:

Ratio	Test	Platform	Options	Absolute values (old vs new)	Performance Profiles
30%	reddit-billgates-post-1.comments FirstVisualChange	windows10-64-shippable-qr	cold fission webrender	80.99 -> 56.92
19%	reddit-billgates-post-1.comments PerceptualSpeedIndex	windows10-64-shippable-qr	cold fission webrender	211.67 -> 170.46
18%	reddit-billgates-post-1.comments SpeedIndex	windows10-64-shippable-qr	cold fission webrender	287.23 -> 236.82
13%	reddit-billgates-post-1.comments LastVisualChange	windows10-64-shippable-qr	cold fission webrender	503.15 -> 440.03
12%	reddit-billgates-post-1.comments PerceptualSpeedIndex	linux1804-64-shippable-qr	cold fission webrender	179.54 -> 157.20
...	...	...	...	...	...
2%	linkedin SpeedIndex	windows10-64-shippable-qr	fission warm webrender	691.43 -> 676.08	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. Please follow our guide to handling regression bugs and let us know your plans within 3 business days, or the patch(es) may be backed out in accordance with our regression policy.

If you need the profiling jobs you can trigger them yourself from treeherder job view or ask a sheriff to do that for you.

For more information on performance sheriffing please see our FAQ.

Comment 1

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

Set release status flags based on info from the regressing bug 1868744

Comment 2

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

Thanks to sparky I got the comparison videos, and looks like a tiny pause just moved around. *.comments is now faster but *.posts slower.
Exactly the kind of thing which could happen when changing GC scheduling. But neither of those interactions has higher priority, so I think we can live with this change.