Tvrtko Ursulin of Igalia who led the fair scheduler work for DRM has decided to revert it for Linux 7.2. A set of 20 patches were sent out on Tuesday for reverting this change as a result of a user regression report. With Linux 7.2 stable hopefully releasing on Sunday, with less than one week to go Ursulin decided to play it safe and just revert the change for Linux 7.2 to allow proper time to investigate and fix the regression.
The report that was sent to the mailing list this past weekend indicated that the fair policy was causing "serious" performance degradation for the AMD Raddeon RX 9070 XT. Luke Wildhardt noted in his bug/regression report:
"Since the DRM scheduler default policy was switched to FAIR in 7.2, sustained 100% GPU load in-game on my RX 9070 XT causes severe performance degradation. In the example title running through Proton, Project Silverfish, the foreground application degrades to roughly 10 fps or freezes outright while audio continues, and the KDE Plasma Wayland session can lock up entirely, requiring a reboot or killing the compositor to recover. The problem is not limited to games. Running the game in the background + alt tabbing, then playing a YouTube video can also cause the entire desktop to freeze.
Then, if the game starts to stutter, either alt-tabbing, or opening up a menu in game (which reduced the load on the GPU) immediately stops the stuttering.
The issue is reliably reproducible under sustained GPU saturation, although the time-to-failure varies. Increasing shadow load (which decreases in-game frame rate) substantially shortens the time-to-failure."
Thus these 20 patches are working their way to the mainline Linux Git kernel tree this week as part of the DRM fixes to revert the fair policy for Linux 7.2.