2007393 - 7.61 - 2.91% damp simple.styleeditor.open.DAMP / damp custom.jsdebugger.stepOut.DAMP + 2 more (Linux) regression on Thu December 18 2025

Status: RESOLVED FIXED

(Core :: DOM: Content Processes, defect)

Description

[Treeherder Bug Filer]

Perfherder has detected a devtools performance regression from push 114ef118363e700dd0b322eb3fad80b0868030cc. 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)
8%	damp simple.styleeditor.open.DAMP	linux1804-64-shippable-qr	e10s fission stylo webrender	141.81 -> 152.60
5%	damp custom.inspector.reload.DAMP	linux1804-64-shippable-qr	e10s fission stylo webrender	541.92 -> 569.39
4%	damp custom.inspector.manyrules.selectnode	linux1804-64-shippable-qr	e10s fission stylo webrender	779.53 -> 809.67
3%	damp custom.jsdebugger.stepOut.DAMP	linux1804-64-shippable-qr	e10s fission stylo webrender	709.70 -> 730.34

Improvements:

Ratio	Test	Platform	Options	Absolute values (old vs new)
8%	damp custom.jsdebugger.open-large-minified-file.DAMP	windows11-64-24h2-shippable	e10s fission stylo webrender	78.34 -> 71.90

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 48019

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 1999397

Comment 2

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

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

:mccr8, since you are the author of the regressor, bug 1999397, 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 3

[Andrew McCreight [:mccr8]]

Hmm that's unfortunate. The easiest workaround here is probably to opt out whatever devtools actor is sending a bunch of stuff.

Comment 4

[Andrew McCreight [:mccr8]]

The two actors I see being registered in devtools are BrowserToolboxDevToolsProcess and DevToolsProcess. They both have a message DevToolsProcessChild:packet that could be very big, I guess. There's also a DampLoad actor which could in theory be involved but it looks like it sends a trivial message. (It looks like I don't have a type for DampLoad yet so I guess I haven't run these perf tests yet. That's something to keep in mind...)

Comment 5

[Andrew McCreight [:mccr8]]

Attachment: Bug 2007393 - Don't use the new serializer for devtools.

Comment 6

[Andrew McCreight [:mccr8]]

Try:
https://treeherder.mozilla.org/jobs?repo=try&revision=aa4ae361a2fc5864b1582d609bf8facecc17db09
https://treeherder.mozilla.org/jobs?repo=try&revision=dd00693da78396474718cbb5ebd1461abbd2f532
https://perf.compare/compare-lando-results?baseLando=171108&newLando=171109&baseRepo=try&newRepo=try&framework=1

Comment 7

[Andrew McCreight [:mccr8]]

There are a ton of regressions, not just the few listed in comment 0. I guess I should have done a comparison to a build before I landed by pref flip, but I looked at a few of the subtest scores manually and things do seem to have more or less regressed to the original values.

Comment 8

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/a0670b7b8a56
https://hg.mozilla.org/integration/autoland/rev/48d6dd18a122
Don't use the new serializer for devtools. r=dom-core,smaug

Comment 9

[Norisz Fay [:noriszfay]]

https://hg.mozilla.org/mozilla-central/rev/48d6dd18a122