2044901 - 82.09 - 11.49% tscrollx + 5 more (Linux, OSX) regression on Thu May 28 2026

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, defect)

Description

[Treeherder Bug Filer]

Perfherder has detected a talos performance regression from push cd6f7923ddaeca342e64f1e450152dbc3a4ea80c. 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]
82%	tscrollx (doc)	macosx1470-64-shippable	e10s fission stylo webrender-sw	0.48 -> 0.88
37%	tp5o_scroll (doc)	macosx1470-64-shippable	e10s fission stylo webrender-sw	1.05 -> 1.43
30%	tscrollx (doc)	linux2404-64-shippable	e10s fission stylo webrender-sw	0.65 -> 0.84
27%	tscrollx (doc)	linux2404-64-shippable	e10s fission stylo webrender	2.05 -> 2.59
13%	tscrollx (doc)	macosx1470-64-shippable	e10s fission stylo webrender	0.46 -> 0.52
11%	tp5o_scroll (doc)	linux2404-64-shippable	e10s fission stylo webrender-sw	1.37 -> 1.52

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 50527 (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 2042044

Comment 2

[Glenn Watson [:gw]]

I'll investigate this week.

Comment 3

[Glenn Watson [:gw]]

It looks like all six tscrollx/tp5o_scroll signatures have returned to their pre-regression baselines as of bug 2044211 ("Refactor text runs to store glyphs with device offsets"), which removed the per-frame text-run snapping cost introduced here.

https://bugzilla.mozilla.org/show_bug.cgi?id=2044211

Comment 4

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

It has been over 7 days with no activity on this performance regression.

:gw, since you are the author of the regressor, bug 2042044, which triggered this performance alert, could you please provide a progress update?

If this regression is something that fixes a bug, changes the baseline of the regression metrics, or otherwise will not be fixed, please consider closing it as WONTFIX. See this documentation for more information on how to handle regressions.

For additional information/help, please needinfo the performance sheriff who filed this alert (they can be found in comment #0), or reach out in #perftest, or #perfsheriffs on Element.

For more information, please visit BugBot documentation.

Comment 5

[Glenn Watson [:gw]]

Confirmed on perfherder that these returned back to normal values after the linked bug in comment 3 landed.