Bug 490693

Summary:	On X11, visible stutter when dragging objects while JetBrains Toolbox app is running
Product:	[Plasma] kwin	Reporter:	Karol Bryd <karolbe>
Component:	performance	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	REPORTED ---
Severity:	major	CC:	nate
Priority:	NOR
Version First Reported In:	6.1.3
Target Milestone:	---
Platform:	Fedora RPMs
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Karol Bryd 2024-07-23 10:18:37 UTC

SUMMARY

I am not sure if this is a bug in KWin, or Plasma etc - please reassign the product if I made a mistake.

Dragging icons and other objects with a mouse causes a lot of stutter and high CPU usage in Xorg process.
I think it started happening in Plasma 6.1.0.

STEPS TO REPRODUCE
1. Click and drag an icon from a task bar; it also happens when you drag e.g a clickable link in a browser.
2. Similar, although slightly less visible effect is when moving the mouse cursor over the task manager icons, mouse cursor kind of slows down and starts to stutter, when it is outside the toolbar it moves smoothly again. It also causes 98% CPU usage.

OBSERVED RESULT
Xorg process CPU usage jumps to 98%, there is a visible system slowdown, dragged icon or link moves with a visible stutter.


EXPECTED RESULT

There is no CPU usage hike, dragged object and cursor moves smoothly.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma:  Fedora 40
KDE Plasma Version: 6.1.3
KDE Frameworks Version:  6.4.0
Qt Version: 6.7.2
NVidia Driver: 550.67

ADDITIONAL INFORMATION

See attached video: https://photos.app.goo.gl/SGV5jbhbi5fdRgva8

Comment 1 Karol Bryd 2024-07-24 06:35:38 UTC

One more important detail: right after a reboot or clean login, the issue is gone. I resumed the system from sleep after the night and it stutters, but then I logged out and logged back in, and it was smooth again.

I also tested the latest NVIDIA driver, but it made no difference.

Comment 2 Karol Bryd 2024-07-24 14:07:26 UTC

I found the root cause - it is the Jetbrains Toolbox application (!!!).

As soon as I start it, the stutter starts. When I quit it, it system behaves normally.

Comment 3 Karol Bryd 2024-07-25 11:23:07 UTC

I have reported the problem in the Jetbrains Toolbox project:

https://youtrack.jetbrains.com/issue/TBX-12499/Starting-Jetbrains-Toolbox-causes-major-UI-slowdowns