Comment 37 for bug 1953685

(In reply to Darkspirit from comment #30)
> Does the slowdown still occur with https://nightly.mozilla.org?
> Start it with env var, for example: `$ MOZ_ENABLE_WAYLAND=1 ~/Downloads/firefox/firefox`
>
> Can the problem be fixed by setting gfx.webrender.allow-partial-present-buffer-age to false, gfx.webrender.max-partial-present-rects to 0 on about:config and restarting Nightly?

While testing this I found something really strange about nightly:

When I start nightly with a brand new profile, at first run it only detects 120 fps (should be 180 on my system), but if I close nightly and reopen it, it now detects 180! This is without changing absolutely no setting at all.
I've reproduced this a second time by deleting the profile and recreating it.
What could be causing this? Shouldn't the first-run behavior be exactly the same as any other run?

Tested the same thing on FF stable with a new profile but the problem was still present after multiple FF startups.

When running at 180 fps it seems the issue is fixed in nightly, despite still getting some stutters here and there on TestUFO and VsyncTester. It's hard to say if it was smoother in FF 94 or not, but it seems like it was smoother before.

(In reply to Jon Voss from comment #31)
> Yes! Setting those two options in nightly resolves the issue.

Can you please test nightly again like I described above without changing any settings and see if you get the same behavior as me?
You probably fixed it by restarting nightly and not by changing the settings.