2023900 - 8.66 - 2.51% speedometer3 TodoMVC-JavaScript-ES6-Webpack-Complex-DOM/DeletingAllItems/Async + 5 more (Linux) regression on Mon March 9 2026

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, defect)

Description

[Treeherder Bug Filer]

Perfherder has detected a browsertime performance regression from push 399801f5e270aefd936ab342512d1991487d4585. 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]	Performance Profiles
9%	speedometer3 TodoMVC-JavaScript-ES6-Webpack-Complex-DOM/DeletingAllItems/Async (doc)	linux1804-64-shippable-qr	fission webrender	2.44 ms -> 2.65 ms	Before/After
7%	speedometer3 TodoMVC-Angular-Complex-DOM/DeletingAllItems/Async (doc)	linux1804-64-shippable-qr	fission webrender	2.50 -> 2.68	Before/After
5%	speedometer3 TodoMVC-React-Complex-DOM/DeletingAllItems/Async (doc)	linux1804-64-shippable-qr	fission webrender	2.50 ms -> 2.64 ms	Before/After
3%	speedometer3 TodoMVC-React-Complex-DOM/Adding100Items/Async (doc)	linux1804-64-shippable-qr	fission webrender	5.51 -> 5.70	Before/After
3%	speedometer3 TodoMVC-Angular-Complex-DOM/CompletingAllItems/Async (doc)	linux1804-64-shippable-qr	fission webrender	5.40 ms -> 5.56 ms	Before/After
3%	speedometer3 TodoMVC-React-Complex-DOM/CompletingAllItems/Async (doc)	linux1804-64-shippable-qr	fission webrender	5.39 ms -> 5.52 ms	Before/After

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 49063 (See documentation link for details).
• Profiling jobs: Trigger jobs from Treeherder job view or request them from [e-mail].

Comment 1

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

Set release status flags based on info from the regressing bug 2021812

Comment 2

[Glenn Watson [:gw]]

Attachment: Bug 2023900 - Pool ClipManager clip cache maps to avoid alloc/free churn

The SC origin reference frame change (bug 2021812) caused a Speedometer 3
regression because each new reference frame triggers PushOverrideForASR,
which allocates a fresh std::unordered_map for the clip cache and destroys
it on pop. Profile analysis showed 90% of the BeginList overhead was in
malloc/free from this HashMap churn.

Replace the std::stack<ClipIdMap> with a std::vector<ClipIdMap> + index,
reusing cleared maps instead of allocating new ones. unordered_map::clear()
preserves the bucket array, so subsequent inserts don't allocate either.

Comment 3

[Glenn Watson [:gw]]

The attached patch should resolve (most of) the regression, any remaining can be resolved with ongoing work over the next month or so in this area.

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/ffcf0482a1d7
https://hg.mozilla.org/integration/autoland/rev/173224712dcc
Pool ClipManager clip cache maps to avoid alloc/free churn r=gfx-reviewers,nical

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/87f130aeb7ad
https://hg.mozilla.org/integration/autoland/rev/756771847c19
Revert "Bug 2023900 - Pool ClipManager clip cache maps to avoid alloc/free churn r=gfx-reviewers,nical" for causing failures at test_mousescroll.xhtml.

Comment 6

[Atila Butkovits]

Backed out for causing failures at test_mousescroll.xhtml.

Backout link: https://hg.mozilla.org/integration/autoland/rev/756771847c19

Push with failures: https://treeherder.mozilla.org/jobs?repo=autoland&resultStatus=testfailed%2Cbusted%2Cexception%2Cretry%2Cusercancel&searchStr=macos%2C14.70%2Cdebug%2Cmochitests%2Cwith%2Ce10s%2Cdisabled%2Ctest-macosx1470-64%2Fdebug-mochitest-chrome-1proc%2Cc&revision=173224712dcc4138495d5a42c40841980a4f7d96&selectedTaskRun=aUZTrq7CSvm1MqSzltnxWQ.0

Failure log: https://treeherder.mozilla.org/logviewer?job_id=554486177&repo=autoland&task=aUZTrq7CSvm1MqSzltnxWQ.0&lineNumber=16872

Comment 7

[Cristian Tuns]

This was caused by something else, relanding.(In reply to Atila Butkovits from comment #6)

Backed out for causing failures at test_mousescroll.xhtml.

Backout link: https://hg.mozilla.org/integration/autoland/rev/756771847c19

Push with failures: https://treeherder.mozilla.org/jobs?repo=autoland&resultStatus=testfailed%2Cbusted%2Cexception%2Cretry%2Cusercancel&searchStr=macos%2C14.70%2Cdebug%2Cmochitests%2Cwith%2Ce10s%2Cdisabled%2Ctest-macosx1470-64%2Fdebug-mochitest-chrome-1proc%2Cc&revision=173224712dcc4138495d5a42c40841980a4f7d96&selectedTaskRun=aUZTrq7CSvm1MqSzltnxWQ.0

Failure log: https://treeherder.mozilla.org/logviewer?job_id=554486177&repo=autoland&task=aUZTrq7CSvm1MqSzltnxWQ.0&lineNumber=16872

Comment 8

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/ec4b440098d2
https://hg.mozilla.org/integration/autoland/rev/bb8411db5b14
Pool ClipManager clip cache maps to avoid alloc/free churn r=gfx-reviewers,nical

Comment 9

[amarc]

https://hg.mozilla.org/mozilla-central/rev/bb8411db5b14