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Find out why UX branch regressed when bug 918613 landed




Tabbed Browser
5 years ago
4 years ago


(Reporter: mconley, Assigned: mconley)


(Blocks: 1 bug, {perf})

Windows XP
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(Not tracked)


(Whiteboard: [Australis:M?][Australis:P5])

Looking at Datazilla this morning, I see a slight up-tick on several Windows XP TART subtests - specifically:

icon-open-DPI1.all.TART went from an average of 2.39 to 2.59
icon-open-DPI1.half.TART went from an average of 2.04 to 2.19
iconFade-open-DPI2.all.TART went from an average of 2.27 to 2.44
iconFade-open-DPI2.half.TART went from an average of 2.43 to 2.59
newtab-open-preload-no.all.TART went from an average of 2.97 to 3.09
newtab-open-preload-no.half.TART went from an average of 2.13 to 2.26
newtab-open-preload-yes.all.TART went from an average of 2.50 to 2.63
newtab-open-preload-yes.half.TART went from an average of 2.13 to 2.26
simple-open-DPI1.all.TART went from an average of 2.32 to 2.49
simple-open-DPI1.half.TART went from an average of 2.03 to 2.18

The spike is more obvious when looking at Datazilla graphs:


Here are the changesets in that range:


I'm immediately suspicious of:

3287d7bbdc14	Bas Schouten — Bug 918613: Convert cairo path code to use cairo_path_t. r=jrmuizel

Which just landed to fix bug 919656 (among other things).  I've pushed a patch to try that backs this out, and we'll see if these numbers go back down.

UX Baseline: https://tbpl.mozilla.org/?tree=Try&rev=647db2708384
UX + Backout: https://tbpl.mozilla.org/?tree=Try&rev=9a9e22855e71
Summary: Find out why UX branch regressed on TART between changeset cc1da159c811 (Sept 28) and e62689b72cc6 (Sept 29) → Find out why UX branch regressed when bug 918613 landed
(In reply to Mike Conley (:mconley) from comment #1)
> Backing out bug 918613 seems to result in a win:
> http://compare-talos.mattn.ca/breakdown.html?oldTestIds=30005317,30008601,
> 30008609,30008639,30008647,30008675,30008687,30008715&newTestIds=30005307,
> 30008593,30008617,30008625,30008695,30008707,
> 30008807&testName=tart&osName=Windows%20XP&server=graphs.mozilla.org
> So I conclude that something about bug 918613 slowed UX down on XP.
> Any idea what that might have been, Bas?

Not really, locally it strictly made things faster. However, there was a bug of something not drawing -without- 918613. Is it possible that this was -not- being drawn in TART? With the bug fixed, we'd now start drawing this (see bug 919656), where we previously weren't. Drawing stuff would certainly cause a performance 'regression' over not drawing stuff :P.
Flags: needinfo?(bas)
Bas has asked for TART profiles with and without this patch.

Builds are running, and I'll post links to profiles when they're done:

With 918613: https://tbpl.mozilla.org/?tree=Try&rev=c3f92a4a030b
Without: https://tbpl.mozilla.org/?tree=Try&rev=ea9679ef4356
As requested, here's a profile for a TART run on a build from just before the Azure merge happened:

It looks like bug 921038 + bug 764299 will be enough to neutralize the Windows XP regression, so I think we can dial back the priority on this one. I'd still like to know what happened, though...
Whiteboard: [Australis:M?][Australis:P1] → [Australis:M?][Australis:P5]
Both of the bugs mentioned in comment #6 have been fixed now, and XP has been neutralized.
Last Resolved: 4 years ago
Resolution: --- → WORKSFORME
Flags: needinfo?(bas)
I should still look into this a little more though, I too, would really like to know what happened here.
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