1988709 - 11.87 - 4.98% damp source-map.SourceMapGenerator-toString.DAMP / damp jstracer.webconsole-performance.DAMP + 2 more (Windows) regression on Thu September 4 2025

Status: RESOLVED WORKSFORME

(Core :: Security: Process Sandboxing, defect)

Description

[Treeherder Bug Filer]

Perfherder has detected a devtools performance regression from push ad84e34ff5f704bc62a02b13002db49136fad08a. 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)
12%	damp source-map.SourceMapGenerator-toString.DAMP	windows11-64-24h2-shippable	e10s fission stylo webrender	112.27 -> 125.60
10%	damp jstracer.server-performance.DAMP	windows11-64-24h2-shippable	e10s fission stylo webrender	1,829.10 -> 2,017.94
5%	damp browser-toolbox.inspector-ready.DAMP	windows11-64-24h2-shippable	e10s fission stylo webrender	276.75 -> 291.33
5%	damp jstracer.webconsole-performance.DAMP	windows11-64-24h2-shippable	e10s fission stylo webrender	2,110.86 -> 2,216.09

Improvements:

Ratio	Test	Platform	Options	Absolute values (old vs new)
14%	damp custom.netmonitor.bigdatarequests.navigate.DAMP	windows11-64-24h2-shippable	e10s fission stylo webrender	642.90 -> 556.07
12%	damp screenshot.DAMP	windows11-64-24h2-shippable	e10s fission stylo webrender	464.37 -> 409.88
8%	damp custom.netmonitor.bigdatarequests.requestsFinished.DAMP	windows11-64-24h2-shippable	e10s fission stylo webrender	799.30 -> 734.63

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 46791

The following documentation link provides more information about this command.

Comment 1

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

Set release status flags based on info from the regressing bug 1966716

Comment 2

[Bob Owen (:bobowen)]

The graphs for the four regressions look a bit noisy and seem to have returned to normal afterwards, so I'm not sure there is a real issue here.
(This is only enabled on Nightly at the moment.)

Comment 3

[Acasandrei Beatrice (needinfo me)]

I can confirm that the graph returned to baseline following the spike observed in the culprit area.

Comment 4

[Bob Owen (:bobowen)]

I guess WORKSFORME is appropriate here then.