1688820 - 5.75 - 6.12% glterrain (windows10-64-shippable-qr) regression on push 1cbb897112bf1715857c6f7173c957f570cd2583 (Fri January 22 2021)

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, defect)

Description

[Alexandru Ionescu (needinfo me) [:alexandrui]]

Perfherder has detected a talos performance regression from push 1cbb897112bf1715857c6f7173c957f570cd2583. As author of one of the patches included in that push, we need your help to address this regression.

Regressions:

Ratio	Suite	Test	Platform	Options	Absolute values (old vs new)
6%	glterrain		windows10-64-shippable-qr	e10s stylo webrender-sw	2.16 -> 2.29
6%	glterrain		windows10-64-shippable-qr	e10s stylo webrender-sw	2.16 -> 2.29

Improvements:

Ratio	Suite	Test	Platform	Options	Absolute values (old vs new)
2%	tresize		linux64-shippable-qr	e10s stylo webrender-sw	13.63 -> 13.31

Details of the alert can be found in the alert summary, including links to graphs and comparisons for each of the affected tests. Please follow our guide to handling regression bugs and let us know your plans within 3 business days, or the offending patch(es) will be backed out in accordance with our regression policy.

For more information on performance sheriffing please see our FAQ.

Comment 1

[Lee Salzman [:lsalzman]]

Attachment: Bug 1688820 - force blend_pixels to inline more aggressively. r?jrmuizel

It appears that the slight refactoring of blend_pixels from the clip-mask
optimization in bug 1688104 caused clang-cl to inline blend_pixels more
pessimistically than it was doing before. Since this is an extremely hot
function that all alpha-pass rendering relies on, we generally just want
to inline this regardless of the slight increase in compile size since
a failure to aggressively optimize this can have noticeable performance
impacts.

Comment 2

[Lee Salzman [:lsalzman]]

Looks like bug 1688104 caused an inlining change that caused a noticeable slowdown. Forcing more things to inline seems to undo the regression.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/28c7fb5899c4
force blend_pixels to inline more aggressively. r=jrmuizel

Comment 4

[Bogdan Tara[:bogdan_tara | bogdant]]

https://hg.mozilla.org/mozilla-central/rev/28c7fb5899c4

Comment 5

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

Set release status flags based on info from the regressing bug 1688104

Comment 6

[Alexandru Ionescu (needinfo me) [:alexandrui]]

== Change summary for alert #28551 (as of Thu, 28 Jan 2021 03:19:38 GMT) ==

Improvements:

Ratio	Suite	Test	Platform	Options	Absolute values (old vs new)
6%	glterrain		windows10-64-shippable-qr	e10s stylo webrender-sw	2.29 -> 2.14

For up to date results, see: https://treeherder.mozilla.org/perfherder/alerts?id=28551

Comment 7

[Pascal Chevrel:pascalc]

Lee, would that perf fix be safe to uplift for beta or should it ride the 87 train? Thanks

Comment 8

[Lee Salzman [:lsalzman]]

(In reply to Pascal Chevrel:pascalc from comment #7)

Lee, would that perf fix be safe to uplift for beta or should it ride the 87 train? Thanks

There isn't really a need to uplift this. It was just a minor performance tweak and we haven't really shipped out to any substantial beta population for the moment.

Comment 9

[Pascal Chevrel:pascalc]

Thanks, marking as wontfix for 86 then.