From https://www.reddit.com/r/firefox/comments/ji6148/smooth_scrolling_not_working_with_webrender/

With Webrender enabled by defaut, the scrolling is laggy.

Page: https://g1.globo.com/
Profile: https://share.firefox.dev/3mUntBz

Can you ask for a new profile with the "Firefox Graphics" preset.

New profile here: https://share.firefox.dev/38kaNjv

That profile doesn't contain webrender threads. Could you include them as well, please?

Alright, here is the new profile https://share.firefox.dev/3lNhbUe.
I noticed that there is no smooth scrolling in different graphics cards, mine is Intel HD Graphics 4000, I tested on Intel UHD Graphics 520 and 620 and there is no smooth scrolling. Also, I believe that there is no smooth scrolling in direct3D 11.

Thank you! I'm not seeing anything particularly worrying in the profile. Somewhat surprising that GetLastCompletedFrameId shows up as much (~5% when zoomed into heavy part of Renderer thread). CompositorEndFrame shows as well, but that's more reasonable. Rendering-wise, there is just draw calls. Checking with profiler on my machine shows about 50 draw calls, which is perfectly fine. I suppose that could be the case of a memory bandwidth starvation if there was anything else going on in the system, but at least WR scene/frame building threads don't appear to be doing anything.

I don't believe this is related to Webrender because there is no smooth scrolling with webrender disabled (using Direct3D11). Something disabled smooth scrolling. I will show side by side, and old version of Firefox, in this case version 76 where the smooth scrolling is working and the latested version where there is no smooth scrolling. https://mega.nz/file/8KgVAYRQ#Jeonhl8U2I3AtxbMqfyuHEzgfQaNEFAIy2jB7hjGoEU

Oh, that's good to know, thank you! Would you be able to use MozRegression to narrow down the change that caused this?

Botond, I removed the wr-intel blocker and changed the component to APZ. Please feel free to correct!

I found out that the change happened from version 81 to 82 using mozregression.

Can you try going to about:config and setting the following prefs to see if it resolves your issue?

general.smoothScroll.mouseWheel.durationMinMS -> 200
general.smoothScroll.mouseWheel.durationMaxMS -> 400
general.smoothScroll.mouseWheel.migrationPercent -> 100

For new profiles in Firefox 82 we sped up the mousewheel scroll animation a little bit. From your video it does look like it's still doing smooth scrolling, just faster, so that's what I suspect you're seeing. If you set the prefs as I indicated above it should revert to the old behaviour.

(needinfo for comment 11)

That resolved the problem.

Thanks. I'm going to dupe this over to bug 1680077 then, where we are discussing the possibility of reverting the prefs to their previous defaults.