1682194 - (sw-wr-perf-clip-rect) cs_clip_rectangle shader is still slow in SW-WR

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, task)

Description

[Lee Salzman [:lsalzman]]

cs_clip_rectangle still shows up prominently in many profiles under SW-WR

Comment 1

[Jeff Muizelaar [:jrmuizel]]

See also bug 1674389 (https://searchfox.org/mozilla-central/rev/c7cf087b6e1384608ca3989f042f12f7cabd0a5f/mozglue/misc/PreXULSkeletonUI.cpp#538)

Comment 2

[Lee Salzman [:lsalzman]]

Attachment: Bug 1682194 - Accelerate cs_clip_rectangle in SWGL. r?jrmuizel

cs_clip_rectangle is slow because we evaluate distance AA for every fragment
the shader touches. With SWGL, we can do much better since we have control
over span. We calculate an inner opaque octagon which can just use a cheap
solid fill and an outer AA octagon within which we need to actually we do
AA and outside which we can just do another solid clear. This reduces most
of the cost of rounded-rectangles to just some setup work, a few fragments
of distance AA on the ends of a span, and large runs of solid color where
we don't have to do much work.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/8c6e26b7c280
Accelerate cs_clip_rectangle in SWGL. r=jrmuizel

Comment 4

[Alexandru Michis [:malexandru]]

https://hg.mozilla.org/mozilla-central/rev/8c6e26b7c280

Comment 5

[Lee Salzman [:lsalzman]]

Comment on attachment 9205774 [details]
Bug 1682194 - Accelerate cs_clip_rectangle in SWGL. r?jrmuizel

Beta/Release Uplift Approval Request

• User impact if declined: This resolves a major performance regression we identified with border-radius and box-shadows in Software Webrender and should affect a substantial portion of web pages.

Trying to do partial SW-WR rollout on Linux. Would like to avoid people reporting significant performance regressions months down the line.

• Is this code covered by automated tests?: Yes
• Has the fix been verified in Nightly?: Yes
• Needs manual test from QE?: No
• If yes, steps to reproduce:
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): Only impacts SW-WR/Linux. We can abort the rollout if unstable. Adequate time to deal with any bugs.
• String changes made/needed:

Comment 6

[Ryan VanderMeulen [:RyanVM]]

Comment on attachment 9205774 [details]
Bug 1682194 - Accelerate cs_clip_rectangle in SWGL. r?jrmuizel

Approved for 87.0b4.

Comment 7

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/releases/mozilla-beta/rev/6b3d93359c0b

Comment 8

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

== Change summary for alert #28966 (as of Mon, 01 Mar 2021 14:14:09 GMT) ==

Improvements:

Ratio	Suite	Test	Platform	Options	Absolute values (old vs new)
11%	tart		linux64-shippable-qr	e10s stylo webrender-sw	3.05 -> 2.73

For up to date results, see: https://treeherder.mozilla.org/perfherder/alerts?id=28966