2063983 - 11.78 - 10.59% perf_reftest_singletons insert-subtree-not-nth-edge-has-pseudo.html + 1 more (Linux) regression on Fri August 7 2026

Status: RESOLVED WONTFIX

(Firefox :: Sidebar, defect)

Description

[Performance Sheriff Bot]

Perfherder has detected a talos performance regression from push fea353a5dcf42c07b7dbc069808a27c29bb3dcb6. 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.

Regression	Test	Platform	Options	Absolute values [old vs new]
12%	perf_reftest_singletons insert-subtree-not-nth-edge-has-pseudo.html (doc)	linux2404-64-shippable	e10s fission stylo webrender	78.89 ms -> 88.19 ms
11%	perf_reftest_singletons insert-subtree-not-nth-edge-has-pseudo.html (doc)	linux2404-64-shippable	e10s fission stylo webrender	78.88 ms -> 87.24 ms

Support & Actionable Steps

For questions, please contact [e-mail]. You can also find help on Slack (#perf-help) or Matrix (#perftest).

Action guide details:

• See the guide to handling regression bugs for investigation steps.
• Review the alert summary for affected tests, graphs, and comparisons.
• Check the PerfCompare results.
• Tests on Try: Run all tests using ./mach try perf --alert 52135 (See documentation link for details).
• Test locally: To run the tests locally use ./mach perftest 52135
• Profiling jobs: Trigger jobs from Treeherder job view or request them from [e-mail].

Comment 1

[BugBot [:suhaib / :marco]]

Set release status flags based on info from the regressing bug 2054065

Comment 2

[Kelly Cochrane [:kcochrane]]

This was not caused by my css change to remove instances of :root:has()

Comment 3

[Bas Schouten (:bas.schouten)]

It seems like this has been steadily improving over time again. Looks like there might still be a very small regression left but I think I can live with that. It's historically frequently been on higher values.