Bug 495397

Summary:	All screens stutter every 60 seconds when running KDE Plasma 5
Product:	[Plasma] kwin	Reporter:	Kryštof Jelínek <krystof186>
Component:	performance	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED NOT A BUG
Severity:	normal
Priority:	NOR
Version First Reported In:	5.27.5
Target Milestone:	---
Platform:	Debian testing
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Kryštof Jelínek 2024-10-26 20:50:36 UTC

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SUMMARY
The screen stutters every 60 seconds (freezes for a short period of time, then runs at 2-3 frames per second for about 1 second, afterwards returns to normal operation) when running Plasma 5.

I initially thought that this was a graphics card issue, but I have confirmed that the issue does not occur on other desktop environments such as XFCE, hence probably not a GPU issue.

STEPS TO REPRODUCE
1. Log-in to a Plasma session (both X11 and Wayland are affected).
2. Use the desktop.
3. Observe screen lag every 60 seconds.

OBSERVED RESULT
All screens lag every 60 seconds. I have tried single a monitor configuration as well but nothing changed, even after changing the refresh rate.

EXPECTED RESULT
Screen not to tear.

SOFTWARE/OS VERSIONS
Confirmed to happen on Debian stable (BookWorm, 12) as well as on Debian testing.

Operating System: Debian GNU/Linux 12
KDE Plasma Version: 5.27.11
KDE Frameworks Version: 5.115.0
Qt Version: 5.15.13
Kernel Version: 6.11.4-amd64 (64-bit)
Graphics Platform: Wayland
Processors: 24 × AMD Ryzen 9 5900X 12-Core Processor
Memory: 62.7 GiB of RAM
Graphics Processor: NVIDIA GeForce RTX 3090/PCIe/SSE2
Manufacturer: ASUS

Comment 1 Kryštof Jelínek 2024-10-27 11:15:39 UTC

I have just found out that this behavior was caused by ddcutil - a tool to manage the brightness of monitors - that was detecting monitors (ddcutil detect) every 60 seconds and causing horrible lag not only on the GPU but on the CPU as well.

Check if you either use this tool to control the brightness of your laptop or for your external monitors, or if you use any shell extensions that might execute this command if you are having similar issues.