Thought I’d report this here since it’s a fairly default setup:
I get some pretty severe video stuttering issues in certain videos in mpv when running the linux-cachyos-rc kernel (recompiled locally via kernel-manager, with the defaults left in place), alongside the default configuration of the sched-ext scx service (i.e., just sudo systemctl enable --now scx and sudo systemctl start scx), which I believe enabled the rusty scheduler.
The frame stuttering went away as soon as I disabled the scx service (which I believe switches back to the BORE scheduler).
Things I tried to get it working smoothly with the scx service running (which did not work):
- changing mpv settings like setting
video-sync=display-resampleandtscale=oversample, setting it to drop frames, toggling my shaders off, toggling nvdec hardware decoding on and off, various reloading etc. - overriding ananicy-cpp to start treating applications with the video type to nice -17, rather than just -4 (tangent-- the -4 default seems potentially insufficient for a lot of systems given how finicky smooth video playback can be)
- anaylzing the mkv files with the stuttering issues with ffmpeg (there were some issues with the encoding, but they only affected some portions at the beginning and end)
In the end, the thing that fixed it immediately was turning off the rusty scheduler.
My system is running an intel i9-13900k and an nvidia RTX 3090, outputting to 2x 4k screens at 120Hz, running on hdmi, using a KDE Plasma Wayland session.
The video in question was a 720p h.264 mkv file.
Anyway, as I said, I’m reporting this here because it’s a fairly standard setup, since I believe this scheduler setup is considered the default, and intended run mode that justifies the inclusion of sched-ext in the cachy kernel.
Could be an issue with new stuff in the 6.11 rc kernel interacting with rusty, but it could potentially be present with the non-rc. Hopefully this report will be useful if anyone else encounters this same issue while testing or debugging this setup, and happens upon this thread. (Since I’ve already resolved this issue by turning rusty off.)
Rusty can have some stutters, here and there.