1682722 - scrolling becomes janky while content is being loaded

Status: NEW

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

Description

[Karl Dubost💡 :karlcow]

Not sure which component where it should go

I don't think this is an emergency. This is happening on chrome too, but the feeling is slightly jankier in Firefox. Initially reported on https://webcompat.com/issues/61395

The janky scrolling is happening when content is being loaded.
So this is probably a performance issue.

Performance profile https://share.firefox.dev/37rT5d7

1. Go to https://thenextweb.com/insider/2015/07/02/am-i-crazy-for-watching-youtube-videos-at-1-5x-speed/
2. scroll quickly

Expected: smooth scroll

Actual: scroll is becoming janky and jumping sometimes.

Comment 1

[Mike Conley (:mconley) (:⚙️)]

I'm seeing some really long composites on the Renderer thread which I think is where the jank is probably coming from? I also see long hangs in the main thread of the content process caused by the DevTools (presumably what's powering the profile being gathered?) but I suspect those are a red herring.

So given the long composites, dropping this into Graphics :: WebRender (since I believe WebRender is enabled here).

Comment 2

[Jamie Nicol [:jnicol]]

This is another page with a diagonal svg spritesheet. Causing us to upload 3381x3381 textures, which janks.