https://bugs.kde.org/show_bug.cgi?id=493741
Bug ID: 493741
Summary: Random lag spike on external screen of Nvidia hybrid
laptop
Classification: Plasma
Product: kwin
Version: 6.1.5
Platform: Arch Linux
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: performance
Assignee: kwin-bugs-n...@kde.org
Reporter: martelt...@gmail.com
Target Milestone: ---
Created attachment 174146
--> https://bugs.kde.org/attachment.cgi?id=174146&action=edit
Quick plot of the two frametime traces
SUMMARY
When using an external screen with my laptop, I see random lag spikes on the
image of this external screen, roughly once per minute. During these lag
spikes, the frame time goes from ~16 ms to 150-300 ms for a few frames, before
going back to normal.
While testing, I saw that this specific problem does not appear with a Windows
install, nor with latest Mutter (47.0). So it seems it is coming from something
Plasma specific, and not from a problem with my hardware or with Nvidia linux
drivers in general.
SOFTWARE/OS VERSIONS
KDE Plasma Version: 6.1.5
KDE Frameworks Version: 6.6.0
Qt Version: 6.7.2
Kernel Version: 6.10.10.arch1-1 (64-bit)
Processors: 16 × 11th Gen Intel® Core™ i7-11850H @ 2.50GHz
Memory: 14.8 Gio of RAM
Graphics Processor: Mesa Intel® UHD Graphics / NVIDIA RTX A3000 Laptop
GPU/PCIe/SSE2
Nvidia driver version : nvidia-open 560.35.03
ADDITIONAL INFORMATION
I used mangohud with vkcube (using Nvidia GPU) running maximized on the
external screen to capture the frametimes traces attached
I have tried multiple configurations in order to better determine the source of
these lags:
- X11/Wayland : I see the same type of lag spikes. Wayland has more problems
still with Nvidia, so I continued to investigate only with X11
- Hybrid graphics/Nvidia only (BIOS configuration) : this specific problem
disappears in Nvidia only configuration (but the frametime is more chaotic ...)
- Output resolution 1080p/4K : no change
- Laptop output DP/HDMI : no change
- I tried multiple screen configurations with different external screens, with
no impact on the lag spikes
- KWin/Mutter : Lag spikes disappear in Mutter
I don't have any ideas on where/how to investigate further, so I'm reporting
the issue here
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