1629443 - Stuttering scroll with WebRender on Pocket Trending page (LG G4, Adreno 418)

Status: NEW

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

Description

[Asif Youssuff]

Steps to reproduce:

1. Enable WebRender on Fenix
2. Navigate to https://getpocket.com/explore/trending?src=ff_android&cdn=0
3. Scroll down page

What happens:

Slight stutters at end of scroll completion.

Expected result:

Buttery smooth scroll.

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

Comment 1

[Asif Youssuff]

Attachment: about:support

Comment 2

[BugBot [:suhaib / :marco]]

:yoasif, if you think that's a regression, then could you try to find a regression range in using for example mozregression?

Comment 3

[Bert Peers [:bpeers]]

Thanks Asif. As per above comment -- is this a regression? If so would you able to provide a regression range? Thanks!

Comment 4

[Asif Youssuff]

Bert, I have no idea, honestly. This is a family member's device and they don't use WR (I enabled it on the "Firefox Preview for Nightly" app).

Comment 5

[Bert Peers [:bpeers]]

No worries, thanks for your help Asif!

Comment 6

[Jamie Nicol [:jnicol]]

Thanks for the information Asif. Would you be able to take another profile with screenshots disabled? They take up a non-insignificant amount of time. (You need to change the settings to "custom", ensure the Renderer thread is still selected, and unselect screenshots).

The page is super smooth on my OnePlus 6 (Adreno 630), but a bit laggy on my Pixel 2 (Adreno 540). And the report is on a 418. So my guess would be this is a general performance issue which more powerful hardware can paper over, rather than this being a hardware-specific bug.

Picture caching doesn't appear to be working too well on the page, which certainly won't help. But I would have thought we should render this smoothly even without.

Comment 7

[Jamie Nicol [:jnicol]]

Bug 1629835 should help somewhat, about 7% of that profile is GPU cache update. But the main culprit is draw_elements_instanced.

Comment 8

[Asif Youssuff]

Jamie, a NI would have helped - sorry, this completely slipped off of my radar!

Here's a new profile with the screenshots disabled: https://perfht.ml/2WC2Nmp

I wasn't sure if you wanted the RenderBackend, so I included that too - I hope that didn't slow it down too.

FWIW, I still see the issue on this device. Hope the new profile helps.