1624030 - On macOS, kick off shader compilation of a certain set of shaders before the first draw

Status: REOPENED

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

Description

[Markus Stange [:mstange]]

Attachment: Insert shader warm-up here

Profile: https://perfht.ml/2WvDuUB

The first paint of a freshly-launched Firefox process takes an extra long time with WebRender on macOS because macOS doesn't let us cache OpenGL shaders.
Bug 1604615 aims at making shader compilation faster.

Another thing we can do is to trigger shader compilation ahead-of-time. During startup, there is a window of time before the first paint during which the Renderer thread is already alive but the main thread is still busy with other stuff. We can use that window to front-load some shader compilation, of a set of shaders that we expect to be used during the first paint.

Comment 1

[Jeff Muizelaar [:jrmuizel]]

It looks like we can accomplish this by starting shader compilation in webrender::shade::Shaders::new()

Comment 2

[Daniel Lu]

Attachment: Bug 1624030 - kicking off shader compilation of a certain set of shaders before the first draw. r=jrmuizel

Comment 3

[Daniel Lu]

Attachment: 2-second profile prior to addressing bug

Profile prior to bug patch: https://share.firefox.dev/2M5Vj6a

Comment 4

[Daniel Lu]

Attachment: 2-second profile after addressing bug

Profile following bug patch: https://share.firefox.dev/3enDHid

It seems the large chunk where the parent process gets blocked was reduced from about 235ms to 195ms (~20%) as a result of the precompilation.

Comment 5

[Markus Stange [:mstange]]

Looks great! Eliminating the remaining time would probably require bug 1624042, as a follow-up.

Comment 6

[Jeff Muizelaar [:jrmuizel]]

It would be interesting to time the individual shaders to see if the bulk of the time is being spent in some or if it's spread evenly.

Comment 7

[Daniel Lu]

(In reply to Jeff Muizelaar [:jrmuizel] from comment #6)

It would be interesting to time the individual shaders to see if the bulk of the time is being spent in some or if it's spread evenly.

I'll look into it soon!

Comment 8

[Jeff Muizelaar [:jrmuizel]]

It looks like this causes a major startup regression:
https://treeherder.mozilla.org/perf.html#/compare?originalProject=mozilla-central&newProject=try&newRevision=3fb282e4005a86db8532d78265418b0bf7ec448b&framework=1&selectedTimeRange=172800

Next steps might be to try to reduce the shaders that are precompiled. Because the list was chosen based on macOS perhaps we're compiling shaders that we wouldn't otherwise be.

Comment 9

[Daniel Lu]

Ah got it, thanks! I'll look into it

Comment 10

[BugBot [:suhaib / :marco]]

The bug assignee didn't login in Bugzilla in the last 7 months.
:bhood, could you have a look please?
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Comment 11

[Markus Stange [:mstange]]

This is still relevant. Shader compilation still causes an appreciable amount of delay during startup. Updated profile on a faster machine: https://share.firefox.dev/3TF63Lc