Looking more closely at comment 0 here, it looks like this specifically regressed speedometer3 **for the "nightlyasrelease" build** (at least, that's what's highlighted in comment 0 here). If this is really limited to that configuration, that's kinda interesting (and relevant to the eventual Firefox 130 release.)
Bug 1908359 Comment 3 Edit History
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Looking more closely at comment 0 here, it looks like this specifically regressed speedometer3 **for the "nightlyasrelease" build** (at least, that's what's highlighted in comment 0 here). If this is really limited to that configuration, that's kinda interesting (and relevant to the eventual Firefox 130 release.) (EDIT: it looks like maybe that was the only sp3 task that was run for this revision, so that might be the trivial explanation for why this was found on that config in particular. I've triggered some more sp3 tasks for this revision and its parent.)