1732144 - Janky scrolling on intab.io (dual core CPU)

Status: NEW

(Core :: Graphics: WebRender, defect)

Description

[Gregory Pappas [:gregp]]

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:92.0) Gecko/20100101 Firefox/92.0

Steps to reproduce:

Visit https://intab.io
Scroll fast

Actual results:

Jank and checkerboarding

Expected results:

Normal scrolling

Comment 1

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

The Bugbug bot thinks this bug should belong to the 'Core::Panning and Zooming' component, and is moving the bug to that component. Please revert this change in case you think the bot is wrong.

Comment 2

[Botond Ballo [:botond]]

Gregory, would you be able to share a profile taken using profiler.firefox.com?

For me, the page scrolls not perfectly, but not terribly either, so I'm not sure if I'm seeing the same issue (hence it's better if you take the profile).

Comment 3

[Gregory Pappas [:gregp]]

(In reply to Botond Ballo [:botond] from comment #2)

Gregory, would you be able to share a profile taken using profiler.firefox.com?

For me, the page scrolls not perfectly, but not terribly either, so I'm not sure if I'm seeing the same issue (hence it's better if you take the profile).

https://share.firefox.dev/3ovm88i

Comment 4

[Alex Thayer [:alexical] (she/her)]

Hey G, just to double check here, does this page exhibit similar behavior in Chrome (or any Chromium-based browser)?

Comment 5

[Daniel Holbert [:dholbert]]

As one extra data point: on my (fairly-beefy) linux laptop, I'm seeing similar behavior to botond, fwiw (page scrolls not perfectly, but not too terribly). Here's a profile of me scrolling from the top to the bottom and then back to the middle (dragging the scrollbar), and then to the bottom/middle a few more times: https://share.firefox.dev/3oJK9a3

Web Content 3/3 is the relevant content process, and it has quite a few jank bars, with a mix of restyling and painting. The parent renderer process is pretty busy, too.

Comment 6

[Gregory Pappas [:gregp]]

(In reply to Doug Thayer [:dthayer] (he/him) from comment #4)

Hey G, just to double check here, does this page exhibit similar behavior in Chrome (or any Chromium-based browser)?

In Chrome it is acceptable. There is very minor jank but only when the page is loading. It seems to jank a lot and forever in Firefox and does not get better.

Comment 7

[Markus Stange [:mstange]]

I'm not sure what to make of G's profile - lots of things are randomly slow and the profiler sampling rate is rather inconsistent.
In dholbert's profile I see slow composites and lots of texture upload.

On my machine I can reproduce 3-5MB of texture upload for every composite.

I think this might be an invalidation or texture upload problem. Moving to WebRender.

Comment 8

[Markus Stange [:mstange]]

Here's a profile from my machine: https://share.firefox.dev/3dc4q2I
No jank, but more upload than in dholbert's profile, I think.

Comment 9

[Nicolas Silva [:nical]]

G's profile is taken on a computer with two physical cores so I guess a lot of things are competing for limited CPU resources, it would explain what random things show up a slow in the profile. Increasing the priority of the renderer thread would probably help.

Comment 10

[Gregory Pappas [:gregp]]

Tried this again after bug 1763405 landed, it may be slightly better but it still feels kinda bad. https://share.firefox.dev/3JvU2Rn