Irregular frame rate in some fullscreen games

For lunar, please try MUTTER_DEBUG_TRIPLE_BUFFERING=never although I don't expect that's the issue. Assuming that's not the issue, please also try MUTTER_DEBUG=kms and then monitor the posting method with:

  journalctl -f /usr/bin/gnome-shell | grep Posting

or collect it afterwards:

  journalctl -b0 /usr/bin/gnome-shell | grep Posting > journal.txt

and attach the results here.

Separately, another setting to try is: CLUTTER_PAINT=disable-dynamic-max-render-time

If all of those fail to improve the situation then having "vsync on" in the game might be triggering https://gitlab.gnome.org/GNOME/mutter/-/issues/2646 which is fixed in Mesa 23.0.2. Though you should have that fixed version already, unless you're using a proprietary AMD driver?

If I set CLUTTER_PAINT=disable-dynamic-max-render-time it fixes the issue! I only had that variable set during the test.

Thanks. Does that mean MUTTER_DEBUG_TRIPLE_BUFFERING=never made no difference?

Please report the bug upstream at https://gitlab.gnome.org/GNOME/mutter/-/issues and mention:

 * GPU model
 * graphics driver in use (lspci -k)
 * The version of libmutter installed (should be 44.0)
 * That CLUTTER_PAINT=disable-dynamic-max-render-time fixes it

The other upstream issue currently open that requires CLUTTER_PAINT=disable-dynamic-max-render-time is https://gitlab.gnome.org/GNOME/mutter/-/issues/2334 but that seems to be different enough that you should log a new bug.

I tested MUTTER_DEBUG_TRIPLE_BUFFERING=never first and it made no difference.

This bug might be another cousin of bug 2017137 and bug 2017097 (both fixed as part of the 44.1 update). It would happen on either Wayland or Xorg if the graphics driver doesn't support timestamp queries.

According to upstream, the fix for this bug can't safely be applied to releases before 44.0 (https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3080#note_1772454) so I just *hope* nobody encounters this bug on jammy.

Debian fix proposed in https://salsa.debian.org/gnome-team/mutter/-/merge_requests/95

Actually if we did need to fix jammy then we could just enforce the workaround there:
CLUTTER_PAINT=disable-dynamic-max-render-time

This bug was fixed in the package mutter - 44.2-3ubuntu1

---------------
mutter (44.2-3ubuntu1) mantic; urgency=medium

  * Merge with Debian. Remaining changes:
    - Add x11-Add-support-for-fractional-scaling-using-Randr.patch
    - Add window-Add-ability-to-override-the-edge-constraints.patch
      + Make possible for extensions (such as Tiling Assistant) to override
        window constraints

mutter (44.2-3) experimental; urgency=medium

  * Cherry-pick patch to fix build test with mesa 23.1 (LP: #2025287)

mutter (44.2-2ubuntu1) mantic; urgency=medium

  * Merge with Debian. Remaining changes:
    - Add x11-Add-support-for-fractional-scaling-using-Randr.patch
    - Add window-Add-ability-to-override-the-edge-constraints.patch
      + Make possible for extensions (such as Tiling Assistant) to override
        window constraints

mutter (44.2-2) experimental; urgency=medium

  [ Daniel van Vugt ]
  * Cherry-pick 2 patches for stuttering fixes
    * Avoid cursor stuttering over some windows (LP: #2023766). This will also
      improve best-case input latency by roughly half a frame.
    * Avoid render stuttering in some fullscreen games (LP: #2016990).
  * Update Support-Dynamic-triple-double-buffering.patch
    * Fix a failure to resume from sleep (frozen black screen), which seems
      to be an old bug but only became likely in 44.1.
    * Fix a crash on resume from sleep (LP: #2020049).

 -- Jeremy Bícha <email address hidden> Wed, 28 Jun 2023 15:31:07 -0400