https://bugs.kde.org/show_bug.cgi?id=511396
Bug ID: 511396
Summary: framerate stutter/lag in osu lazer on AMD
Classification: Plasma
Product: kwin
Version First 6.5.0
Reported In:
Platform: NixOS
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: performance
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
SUMMARY
After updating from Plasma 6.4.5 to Plasma 6.5.0, I noticed that my osu! lazer
is stuttering. The game is barely playable.
osu-lazer uses SDL2, or optionally SDL3 under-the-hood (setting environment
variable OSU_SDL3=true). It's rendering using an OpenGL renderer, or an
experimental Vulkan renderer. No matter the combination of SDL and renderer,
the game stutters when playing a song. The Vulkan renderer is even glitching
out with flickering, black frames whenever the stutters occur. Changing FPS
limit also does not change anything. Switching from multithreaded rendering to
singlethreaded rendering does not change anything. SDL has an environment
variable called SDL_VIDEODRIVER. Setting it to "wayland" enables native Wayland
support. Setting or not setting this also does not change anything.
The game does not stutter in song select or the main menu. Only when playing a
song. It also does not stutter in window mode, only in borderless window and
fullscreen. The stutters do not occur when the song has an "idle" part and
you're not clicking any objects. So it could also be related to sound or
keyboard/mouse input.
I ruled out updates of other programs that I use. I bisected the nixpkgs repo
and built my NixOS installation against the individual commits while iterating
through them. The first bad commit with stutters is
https://github.com/NixOS/nixpkgs/commit/15729ec4e1b90abbcec33b75c68d35dd5b968453,
which is the update from Plasma 6.4.5 to 6.5.0 in NixOS.
I am using an AMD Radeon RX 7900 XTX with mesa 25.2.5.
I have not tried osu on Arch, so I can't rule out that it is NixOS specific.
Furthermore, I have a friend who is using CachyOS on Nvidia, and he is not
experiencing these stutters.
Here's a video of it. It's hard to see on the video, but you can clearly see
the lag spikes in the "draw" section of the debug overlay.
https://youtu.be/ehJCY15L4ww
STEPS TO REPRODUCE
1. Open osu! lazer
2. Select and start a song
3. Play
OBSERVED RESULT
Experience stutters whenever hitting circles/sliders
EXPECTED RESULT
No stutters whenever hitting circles/sliders
SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Linux 6.17.2-zen, NixOS 25.11 (nixos-unstable, commit
08dacfca559e1d7da38f3cf05f1f45ee9bfd213c)
KDE Plasma Version: 6.5.0
KDE Frameworks Version: 6.19.0
Qt Version: 6.10.0
GPU: AMD Radeon RX 7900 XTX
Mesa: 25.2.5
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