1889792 - Scrolling Slack mesage history is very laggy when using SWGL and the quad conic gradient shader

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, defect, P3)

Description

[Chris Peterson [:cpeterson]]

I see a serious performance regression when trying to scroll Slack message history when using SWGL in Nightly 126.0a1 build 2024-04-04 on Windows. (I voluntarily use 32-bit Firefox builds and enable gfx.webrender.software = true to help dogfood SWGL, since I figure few other Nightly users will use 32-bit or SWGL.)

I tried bisecting the regression using mozregression, but the performance difference is not as obvious in a clean profile (still using SWGL), but a Firefox profile of my main profile (https://share.firefox.dev/3U5CfZN) shows a lot of CPU time spent in ps_quad_conic_gradient functions, so I'm guessing this is a regression from your fix for "Port conic gradients to the quad shaders" bug 1887837.

Comment 1

[Nicolas Silva [:nical]]

Ah, snap. I forgot to re-add the swgl fast path for radial gradients before landing.

Comment 2

[Nicolas Silva [:nical]]

Edit: Nevermind, radial gradients have a fast path but conic gradients dont. The regression comes from them not being cached anymore.

Comment 3

[Donal Meehan [:dmeehan]]

Setting Fx126 to Fixed sicne the regressor was backed out of central
https://bugzilla.mozilla.org/show_bug.cgi?id=1887837#c6

Comment 4

[Nicolas Silva [:nical]]

Slack uses the following full -screen conic gradient:

{ 
  prim_rect: Box2D((0.0, 0.0), (3840.0, 1927.0))
  center PointKey { x: 1920.0, y: 963.00024 },
  ConicGradientParams  { angle: 0.7853982, start_offset: 0.0, end_offset: 1.0 },
  stops: [
    GradientStop { offset: 0.0, color: ColorF { r: 0.79607844, g: 0.8, b: 0.8117647, a: 1.0 } },
    GradientStop { offset: 0.25, color: ColorF { r: 0.91764706, g: 0.91764706, b: 0.91764706, a: 1.0 } },
    GradientStop { offset: 0.5, color: ColorF { r: 0.79607844, g: 0.8, b: 0.8117647, a: 1.0 } },
    GradientStop { offset: 0.75, color: ColorF { r: 0.91764706, g: 0.91764706, b: 0.91764706, a: 1.0 } },
    GradientStop { offset: 1.0, color: ColorF { r: 0.79607844, g: 0.8, b: 0.8117647, a: 1.0 } }
  ]
}

Picture caching does not help as the scrollable part is not promoted to its own layer for some reason.

Pretty sad. Maximized on a 4k screen, We get to chose between a terribly expensive but barely visible (if at all, I can't see it) primitive drawn every frame or wasting 29MB of RAM (and memory bandwidth each frame) on said primitive.

Comment 5

[Nicolas Silva [:nical]]

Bug 1891543 helps quite a bit by making sure all of the conic gradient pixels we can occlude are occluded. However a lot of the backgrounds in slack aren't fully opaque so there is still a pretty large amount of conic gradient pixels and does not make perf good enough without caching.

Comment 6

[Nicolas Silva [:nical]]

Attachment: Bug 1889792 - Approximate atan2 in conic gradients. r=#gfx-reviewers

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/88bfb8f16975
Approximate atan2 in conic gradients. r=gfx-reviewers,lsalzman

Comment 8

[Aron Cseh]

• Backout link
• Push with failures
• Failure Log
• Failure Log 2

[task 2024-04-23T08:57:24.036Z] 08:57:24    ERROR -  error: unused variable: `data_handle`
[task 2024-04-23T08:57:24.036Z] 08:57:24     INFO -     --> gfx/wr/webrender/src/prepare.rs:233:52
[task 2024-04-23T08:57:24.036Z] 08:57:24     INFO -      |
[task 2024-04-23T08:57:24.037Z] 08:57:24     INFO -  233 |             PrimitiveInstanceKind::ConicGradient { data_handle, .. } => {

Comment 9

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/432931b16b1e
Approximate atan2 in conic gradients. r=gfx-reviewers,lsalzman

Comment 10

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/432931b16b1e

Comment 11

[Jeff Muizelaar [:jrmuizel]]

FWIW, here's Skia implementation: https://source.chromium.org/chromium/chromium/src/+/main:third_party/skia/src/opts/SkRasterPipeline_opts.h;l=3472;drc=a0bbf72581f07fafa9705a88a34d5eab8db53148