1975491 - 2.08 - 2.01% speedometer3 Perf-Dashboard/SelectingPoints/Sync / speedometer3 Perf-Dashboard/SelectingPoints/total (OSX) regression on Wed June 25 2025

Status: RESOLVED DUPLICATE of bug 1974493

(Core :: JavaScript Engine: JIT, defect, P1)

Description

[Treeherder Bug Filer]

Perfherder has detected a browsertime performance regression from push 29f18fab3ab5974f6426019d37a127816056c4e1. 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. Our guide to handling regression bugs has information about how you can proceed with this investigation.

If you have any questions or need any help with the investigation, please reach out to [e-mail]. Alternatively, you can find help on Slack by joining #perf-help, and on Matrix you can find help by joining #perftest.

Regressions:

Ratio	Test	Platform	Options	Absolute values (old vs new)	Performance Profiles
2%	speedometer3 Perf-Dashboard/SelectingPoints/Sync	macosx1500-aarch64-shippable	fission webrender	12.54 -> 12.80	Before/After
2%	speedometer3 Perf-Dashboard/SelectingPoints/total	macosx1500-aarch64-shippable	fission webrender	13.00 -> 13.27	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.

If you need the profiling jobs you can trigger them yourself from treeherder job view or ask [e-mail] to do that for you.

You can run all of these tests on try with ./mach try perf --alert 45776

The following documentation link provides more information about this command.

Comment 1

[BugBot [:suhaib / :marco]]

Set release status flags based on info from the regressing bug 1973117

Comment 2

[Mayank Bansal]

Windows does not seem to get this regression: https://treeherder.mozilla.org/perfherder/graphs?highlightAlerts=1&highlightChangelogData=1&highlightCommonAlerts=0&replicates=0&series=autoland,5257452,1,13&series=autoland,5248136,1,13&timerange=1209600&zoom=1750478398645,1751124298318,26.837624208886485,32.5815074738243

Comment 3

[Jan de Mooij [:jandem]]

Iain is on leave this month but this can wait until he's back. Bug 1973117 has some perf improvements from this change and comment 2 indicates this didn't affect Windows (thanks Mayank).

Comment 4

[BugBot [:suhaib / :marco]]

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

:iain, since you are the author of the regressor, bug 1973117, 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

[BugBot [:suhaib / :marco]]

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

:iain, since you are the author of the regressor, bug 1973117, 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 6

[BugBot [:suhaib / :marco]]

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

:iain, since you are the author of the regressor, bug 1973117, 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 7

[Iain Ireland [:iain]]

This seems similar to bug 1974493: it is reported as being regressed by bug 1973117 and bug 1971446, and it's a small architecture-specific regression that doesn't reproduce locally. As described in comment 6 on that bug, this seems likely to be a case where we are generating "better" code that happens to line up poorly with something micro-architectural in one particular loop.

I have one more thing I want to test to see if it improves things. If not, I will close this as WONTFIX.