https://bugs.kde.org/show_bug.cgi?id=443254
Bug ID: 443254
Summary: Observable frame drop while the MangoHUD shows no
frame drop at all
Product: kwin
Version: 5.22.4
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: compositing
Assignee: kwin-bugs-n...@kde.org
Reporter: quwenruo.bt...@gmx.com
Target Milestone: ---
SUMMARY
In fact it's a long long time problem.
Whenever a game is running, mostly DXVK games using proton, and has MangoHUD
running with frametime and 90 FPS limit (display refreshrate 60Hz), no matter
how low the game setting I'm using, I can always feel some shuttering here and
there.
While MangoHUD reports a flat line for its frametime, and always have 90FPS, no
frame drop from the game.
Thus it seems KWin is doing something causing the frame drop/shuttering.
The CPU and GPU (Ryzen 3800X + RX6700XT) is definitely enough for the games I
play (for example, outer wilds with medium settings).
I want to try with compositing turned off or Vsync turned off, but
unfortunately there is no such option there.
Tried both OpenGL 2.0 and OpenGL3.1 as backend, no difference.
The other thing to mention is, I'm using two monitors, both 1920x1080 60hz, in
expanded mode (a large 3840x1080 area across those two displays).
Not sure if such xrandr setup is involved.
STEPS TO REPRODUCE
1. Setup KDE with default compositing using above hardware and xrandr setup
2. Run Steam games with proton, and using MangoHUD to record the frametime
3. Turn down the game settings to make sure the game can maintain whatever high
fps
4. Run the game for a while to expose any frame drop
OBSERVED RESULT
Frame drop here and there, which is definitely not acceptable for such
hardware.
EXPECTED RESULT
No frame drop observed as long as the machine can keep the FPS over 60 fps.
SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Archlinux
(available in About System)
KDE Plasma Version: 5.22.5
KDE Frameworks Version: 5.86.0
Qt Version: 5.12.2
ADDITIONAL INFORMATION
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