1700005 - [RHEL8] Refreshes heavily stutter on Wayland since Firefox 86

Status: RESOLVED WONTFIX

(Core :: Widget: Gtk, defect, P3)

Description

[Alexey.Rusakov]

Attachment: about-support.txt

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:87.0) Gecko/20100101 Firefox/87.0

Steps to reproduce:

I used Firefox with MOZ_ENABLE_WAYLAND=1 through a few major versions by now without major issues; but after upgrading to Firefox 86 it became almost unusable on Wayland: repainting only happens about every 3 seconds. A visit to about:support revealed glxtest crashing - this was fixed in https://bugzilla.mozilla.org/show_bug.cgi?id=1689207; however, the problem reported here persists with the current Beta channel Flatpak as well. The about:support dump is attached. What's peculiar is that the problem subsided after a few minutes running on my primary profile and no more reproduces after an initial startup; the attached dump is from the secondary profile where I could still see it. CPU load etc. is normal. A similar case is described here: https://bbs.archlinux.org/viewtopic.php?id=263272.

According to mozregression:
6:57.88 INFO: Last good revision: 56716cbb41d729a6a11f7db3220eb734ae61f312
6:57.88 INFO: First bad revision: 9658708ceaea1c68abfac52cf15e34ca4fab1946

Comment 1

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

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

Comment 2

[Alexey.Rusakov]

...and after looking at the relevant changes, I just double-checked that switching off widget.wayland_vsync.enabled and restarting Firefox fixes the lagging.

Comment 3

[Robert Mader [:rmader]]

Hej Alexey, judging from the kernel you use you probably also use a older version of Gnome - mind sharing which version you use (and which OS)?

Comment 4

[Alexey.Rusakov]

This is Red Hat Enterprise Linux 8.3, and indeed some of its packages are older: Gnome Shell/Mutter 3.32, Wayland 1.17. Let me know if you need other versions.

Comment 5

[Robert Mader [:rmader]]

Thanks, that makes sense. The stuttering is caused by a Mutter bug (similar bugs exist in older versions Kwin and IIRC also Sway).

In Mutter the bug was fixed in 3.34[1] and was later backported to 3.28 (because it's used in Ubuntu 18.04 which Firefox uses for its CI). I now opened a backport request[2] for 3.32. Alternatively, Martin could make sure to disable widget.wayland_vsync.enabled in the RHEL build, if it's not already done (which of course doesn't fix official builds).

1: https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/839
2: https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1813

Comment 6

[Martin Stránský [:stransky] (ni? me)]

RHEL8 is not supposed to run Firefox with Wayland backend.