2060547 - 12.75% damp browser-toolbox.webconsole-ready.DAMP (Windows) regression on Mon July 27 2026

Status: RESOLVED WONTFIX

(DevTools :: General, defect, P3)

Description

[Performance Sheriff Bot]

Perfherder has detected a devtools performance regression from push c81c89c15dc7d2ce83e475bb4ca191a9dd577e82. 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]
13%	damp browser-toolbox.webconsole-ready.DAMP (doc)	windows11-64-24h2-shippable	e10s fission stylo webrender	359.24 ms -> 405.05 ms

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 51599 (See documentation link for details).
• Test locally: To run the tests locally use ./mach perftest 51599
• Profiling jobs: Trigger jobs from Treeherder job view or request them from [e-mail].

Comment 1

[BugBot [:suhaib / :marco]]

The Bugbug bot thinks this bug should belong to the 'DevTools::General' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Comment 2

[BugBot [:suhaib / :marco]]

Set release status flags based on info from the regressing bug 2056188

Comment 3

[Julian Descottes [:jdescottes]]

Might just be due to displaying more messages in the console when nova is enabled. Will check

Comment 4

[Sarah Clements [:sclements] | PTO until Sept 8th]

(In reply to Julian Descottes [:jdescottes] from comment #3)

Might just be due to displaying more messages in the console when nova is enabled. Will check

Thanks Julian, we're trying to resolve any suspected performance issues head of the release date and have enlisted the perf team to help. I saw you marked this as a P3 but if you're able to look sooner than later that'd be much appreciated.

Comment 5

[Julian Descottes [:jdescottes]]

After more investigations, the new figure is not directly related to the webconsole but to the inspector.

The test selects a few few panels one after the other, in particular it selects the inspector right before the webconsole.
With nova enabled, the element selected by default in the Browser Toolbox' inspector has a more styles applied than without nova.
Because of this, switching to the Console panel from the Inspector is slower.

Removing the inspector step from the test, I get the same performance with or without nova.
I also quickly built a "web toolbox" version of the browser toolbox test which regressed, and this one has the same performance with or without nova.

So this is not a performance regression, we just happen to select an element with more rules and the ruleview needs a bit more time to be destroyed.