1685848 - [NSFW] Scrolling on reddit homepage is bad (WR vs non-WR). Possbily related to the ""Safe browsing mode" enabled on Reddit redesign

Status: RESOLVED WORKSFORME

(Core :: Graphics: WebRender, defect)

Description

[Mayank Bansal]

1. Create a new nightly profile
2. Go to reddit.com (no need to login)
3. Scroll a couple of pages down.

ER : Smooth while scrolling
AR: Very janky while scrolling

Profile : https://share.firefox.dev/2XrRQVc

Comment 1

[Mayank Bansal]

Attachment: about:support of my normal profile

Comment 2

[Henrik Skupin [:whimboo][⌚️UTC+1]]

Maybe a dupe of bug 1654087?

Comment 3

[Mayank Bansal]

Possibly. The profiles look different to me though.
I will link the two bugs for now.

Comment 4

[Markus Stange [:mstange]]

I agree, the two are unrelated.

Mayank, could you get another profile which includes the RenderBackend and WrWorker threads?

Looking at the "APZScroll Payload Presented" markers on the GPU process Compositor thread, things don't seem too terrible. I can see some extra long markers, during which it looks like the GPU process is starved of CPU resources. I'm not sure why - maybe we're rasterizing fonts or blobs in parallel. Example: https://share.firefox.dev/3shpTxD

Comment 5

[Mayank Bansal]

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

Comment 6

[Markus Stange [:mstange]]

Thanks! It looks like there is no activity on the WrWorker threads during those pauses. Example: https://share.firefox.dev/3qim6ON
So I'm still not sure what causes the GPU process to slow down while the parent and content processes are running fine.
Maybe we'll be able to get better insight into this once the profiler can get CPU usage of the entire process (not just of registered threads).

Comment 7

[Mike Conley (:mconley) (:⚙️)]

Maybe we'll be able to get better insight into this once the profiler can get CPU usage of the entire process (not just of registered threads).

Hey florian, is there anything special that the user needs to do to get CPU usage data for an entire process (and not just registered threads) right now?

Comment 8

[Mayank Bansal]

Profile with WR off (D3D11) : https://share.firefox.dev/2Ny7xJ1
Subjectively, it felt much more smooth than with WR.
Markus, would you be able to tell whats the difference between this profile, and the one in comment 5 which had WR enabled ?

Comment 9

[Markus Stange [:mstange]]

I wasn't able to see any specific reasons, other than "WebRender takes longer to process each frame". Moving this into the WebRender component, maybe others have better ideas.

Comment 10

[Mayank Bansal]

Ok, fairly certain STR. This is a combination of the "Safe browsing" enabled on reddit, and WR

STR:

1. Set the new design of Reddit as default
2. Enable the "Safe Browsing Mode" on Reddit. (On reddit, click on the username on top right->User Settings->Feed Settings->Safe Browsing Mode-> Enable)
3. Go to a NSFW page like this : https://www.reddit.com/user/eat_a_p3ach/
   3.5 Optional : Wait for 1 minute to let the GC/CC do its thing
4. Put the mouse cursor on one of the images/videos of the feed, an start scrolling down.

ER: Smooth scrolling
AR: Choppy scrolling

"Safe Browsing" on : https://share.firefox.dev/2ZAsF3T
"Safe Browsing" off : https://share.firefox.dev/3seIOIM

Comment 11

[Mayank Bansal]

FWIW: previously there were artifacts on the blurred image (as mentioned in https://bugzilla.mozilla.org/show_bug.cgi?id=1694017#c4). These artifacts have been fixed by bug 1749380

Comment 12

[Glenn Watson [:gw]]

Is this still a problem? It seems to run well on my local environment.

Comment 13

[Mayank Bansal]

With Hw-wr :
The page scrolls fine on my newer (and much faster) machine.
The page scrolls a little janky if I pinch-zoom on the page
There is also the comment on mix-blend surfaces here (https://bugzilla.mozilla.org/show_bug.cgi?id=1695273#c2)

With Sw-WR:
The page is still quite janky. But that is probably better tracked in bug 1695273

Given this, I am happy to close this bug as Worksforme.

Comment 14

[Frank Doty [:fdoty]]

Is this bug still reproducible? The perf team would like to triage this for performance impact, or close out as 'works for me' if that is the case. Can you advise?

Comment 15

[Benjamin De Kosnik [:bdekoz]]

I cannot reproduce this slowness/jank on reddit, on current linux (f39/frameworks-13) with current FF 124.0.1.

webrender.compositor.force-enabled false
webrender.compositor false
webrender.all false

Comment 16

[Mayank Bansal]

sure, lets close this. The perf issue is better tracked in bug 1695273.