Bug 501055

Summary:	Display Configuration widget constantly using CPU time
Product:	[Plasma] KScreen	Reporter:	Avraham Hollander <anhollander516>
Component:	OSD and Plasma applet	Assignee:	kscreen-bugs-null <kscreen-bugs-null>
Status:	RESOLVED WORKSFORME
Severity:	normal	CC:	anhollander516, nate
Priority:	NOR
Version First Reported In:	6.3.3
Target Milestone:	1.0
Platform:	Gentoo Packages
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Avraham Hollander 2025-03-04 13:56:08 UTC

SUMMARY
plasmashell is using CPU time even when it's not being interacted with. It's not actually that high (<1%, not even enough to cause the CPU to come out of idle), but it happens on one system and not on the other.

STEPS TO REPRODUCE
It just happens all the time.

OBSERVED RESULT
I observed it initially with htop. Using strace shows that it is calling ppoll() many times per second, with exactly the same parameters. I know of lsfd, but I'm not sure exactly how to determine exactly what file descriptors are being referenced.

EXPECTED RESULT
On my other system, plasmashell stays idle, only occasionally making futex() syscalls.

SOFTWARE/OS VERSIONS
Operating System: Gentoo Linux 2.17
KDE Plasma Version: 6.3.2
KDE Frameworks Version: 6.11.0
Qt Version: 6.8.2
Kernel Version: 6.13.5-20R5-sched-ext (64-bit)
Graphics Platform: Wayland
Processors: 8 × Intel® Core™ i5-10310U CPU @ 1.70GHz
Memory: 7.5 GiB of RAM
Graphics Processor: Intel® UHD Graphics

ADDITIONAL INFORMATION
If I knew how to use profiling tools, I'd go straight to them. But I don't :(

Comment 1 Avraham Hollander 2025-03-04 14:00:09 UTC

Ok so I just tested a clean user account and the problem doesn't happen. Time to trial-and-error the problematic widget.

Comment 2 Avraham Hollander 2025-03-04 14:18:47 UTC

It was the Display Configuration widget in the System Tray. Disabling it and setting it back to "Shown when relevant" solved the problem, until logging out and logging back in. Disabling it entirely solved the problem for good. 

Looking on my other system, the Display Configuration widget was already disabled. Setting it to "Shown when relevant" on there did not cause the issue.

So the Display Configuration widget is still bugged, only on one of my systems.

Comment 3 Nate Graham 2025-03-19 21:51:59 UTC

Does that widget exhibit the same issue in a new clean user account on the same system, with the same display arrangement?

Comment 4 Avraham Hollander 2025-03-19 22:21:51 UTC

(In reply to Nate Graham from comment #3)
> Does that widget exhibit the same issue in a new clean user account on the
> same system, with the same display arrangement?

No it does not, I said in a previous comment that I first tested a clean user account before I narrowed it down to the Display Configuration widget.

I personally don't really care about it because I never plug any other displays into this system and don't need the widget, but it is a bug nonetheless and someone else may be experiencing it. Most people probably wouldn't even notice it because the CPU time used is so minor that it won't have a significant impact on performance or power consumption.

Comment 5 Nate Graham 2025-03-19 22:34:33 UTC

Thanks If this only happens on your main user account, it seems related to user configuration somehow. Unless you can profile it and tell us exactly what's wrong, I'm afraid there's likely no way to make this actionable, sorry!