2040320 - 17.54% jetstream3 source-map-wtb-Geometric (OSX) regression on Tue May 12 2026

Status: RESOLVED WONTFIX

(Core :: JavaScript: GC, defect, P1)

Description

[Treeherder Bug Filer]

Perfherder has detected a browsertime performance regression from push 22d0beae1255e59e0bf588a0ed407d991c29aedd. 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]
18%	jetstream3 source-map-wtb-Geometric (doc)	macosx1500-aarch64-shippable	fission webrender	639.21 -> 527.06

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 50277 (See documentation link for details).
• Profiling jobs: Trigger jobs from Treeherder job view or request them from [e-mail].

Comment 1

[Jon Coppeard (:jonco)]

Investigating.

Comment 2

[BugBot [:suhaib / :marco]]

Set release status flags based on info from the regressing bug 2004011

Comment 3

[Ryan VanderMeulen [:RyanVM]]

Bug 2004011 was reverted for 152.0b2.

Comment 4

[Jon Coppeard (:jonco)]

Profiles indicate that this was caused by GC timing differences with a GC now happening during this test rather than the previous one. Other platforms are not affected. Closing as WONTFIX.