Strange lags/refresh rate issues only on external display after sleep

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Hi all,

I am a software engineer and don’t know where to start investigating this issue. I am experiencing issues with my external 4K display connected through HDMI. I am on Arch, KDE Wayland session, not using a display manager. The issues started happening around the Kernel 6.14 release and/or Plasma 6.3.4. More system specs below.

The issue manifests itself as stuttery display which is especially apparent when scrolling webpages, opening plasmoids like the application launcher or moving windows around the screen. It feels like the screen is running only at half the refresh rate (which it isn’t since there are small amounts of time [fractions of a second] where the issue disappears). I think it is something global, because even the mouse cursor is stuttery.

From my own “experiments”, I can narrow down the issue as follows:

  • The issue only is with my external display. The internal display is always smooth and completely fine.
  • The issue only arises after considerable amounts of suspend time. If I leave the laptop asleep over lunch (30+ minutes), it happens. If I am on a call or on coffee break (5 minutes max.), the issue doesn’t happen.
  • Restarting the whole Plasma session doesn’t fix the issue. Changing display settings, re-plugging the cable and restarting the monitor don’t fix the issue. A reboot always fixes the issue on the spot.
  • Screen recording doesn’t show the issue in the recording itself but it is apparent on-screen whilst the recording is running.

A last very non-scientific observation:

  • The issue might (emphasis on might!) have something to do with Docker. When I have Docker compositions running, it happens more often.

The combination of issues lets me think that this should be an issue with the display driver or the graphics hardware itself especially because of the screen recording thing.

What I have investigated is the kernel logs which don’t show anything in particular.

Do you guys have some pointers for me where I should start looking for differences before / after sleep?

Thank you!

My specs
Operating System: Arch Linux
KDE Plasma Version: 6.3.5
KDE Frameworks Version: 6.14.0
Qt Version: 6.9.1
Kernel Version: 6.15.2-arch1-1 (64-bit)
Graphics Platform: Wayland
Processors: 14 × Intel® Core™ Ultra 7 155U
Memory: 30.8 GB of RAM
Graphics Processor: Intel® Graphics
Manufacturer: LENOVO
Product Name: 21LUCTO1WW
System Version: ThinkPad X13 Gen 5

External Monitor
BenQ PD2705U

2

Does

killall kwin_wayland

help?

If so, then, it just has to be issued once on session startup..

1 Like
3

Thanks for the suggestion. Restarting the whole session didn’t work.

Today, I updated to KDE frameworks 6.15 and left the laptop asleep over lunch and the problem didn’t arise again. I will investigate further and report back.

4

Make sure that your bios is up to date.

5

I don’t think restarting the whole session is the same as restarting kwin (killing kwin doesn’t wipe all state of the desktop while restarting the session does). But, it still may not work. Will be interested in your report..

6

Well.. I also tested around a bunch with running Docker and can report that on KDE Frameworks 6.15, for the second day in a row, no problems anymore.