Secondary GPU frame rates are held back by dynamic-max-render-time

[Daniel van Vugt]

[ Impact ]

Secondary GPU frame rates are held back by dynamic-max-render-time as shown on this amdgpu setup connected to a 60 Hz monitor:

main: 30 FPS
main + CLUTTER_PAINT=disable-dynamic-max-render-time: 60 FPS

https://gitlab.gnome.org/GNOME/mutter/-/issues/3070

[ Test Plan ]

This is imprecise because many machines won't exhibit a measurable difference...

1. Set up a dual GPU machine with dual monitors using an open source driver such as amdgpu or nouveau. If you are using Mutter 46 or later then the closed source Nvidia driver may also be used in theory.

2. In a Wayland session, check that the frame rate being achieved on the monitor connected to the secondary GPU is at least that of the refresh rate.

3. Add CLUTTER_PAINT=disable-dynamic-max-render-time to /etc/environment and reboot.

4. In a Wayland session, check that the frame rate on the monitor connected to the secondary GPU has not changed (didn't get better) after the environment change.

5. Remove the change from /etc/environment.

[ Where problems could occur ]

Anywhere in frame scheduling and frame rate performance, since that is what changed.

[ Other Info ]

[Timo Aaltonen (tjaalton)]

Hello Daniel, or anyone else affected,

Accepted mutter into noble-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/mutter/46.2-1ubuntu0.24.04.1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, what testing has been performed on the package and change the tag from verification-needed-noble to verification-done-noble. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-noble. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance for helping!

N.B. The updated package will be released to -updates after the bug(s) fixed by this package have been verified and the package has been in -proposed for a minimum of 7 days.

[Daniel van Vugt (vanvugt)]

Verified fixed in 46.2-1ubuntu0.24.04.1 using the test plan in the bug description.