Bug 499911

Summary:	Visual effects very slow with an external monitor
Product:	[Plasma] kwin	Reporter:	gus
Component:	multi-screen	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	REPORTED ---
Severity:	normal	CC:	nate
Priority:	NOR	Keywords:	multiscreen
Version First Reported In:	6.3.0
Target Milestone:	---
Platform:	Fedora RPMs
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description gus 2025-02-12 18:56:55 UTC

SUMMARY

When an external monitor (4k) is plugged-in with HDMI or usb dock, the desktop animations (e.g., shifting between virtual desktops, alt-tabe between windows, overview) can become very slow and choppy. Sometimes it is so slow has becoming difficult to use the desktop (say >1s to show overview).

When using Zoom on the browser (firefox), the slowness is even worse. No such slowness when using Zoom on the built-in screen.

STEPS TO REPRODUCE
1. Plug-in external monitor
2. Play around, open windows
3. Launch overview

OBSERVED RESULT

If overview has not been used in a while, it might be very slow (say take > 1s).

EXPECTED RESULT

No noticeable slow down should be observed, as in the case without an external monitor.

SOFTWARE/OS VERSIONS
Operating System: Fedora Linux 41
KDE Plasma Version: 6.2.5
KDE Frameworks Version: 6.10.0
Qt Version: 6.8.2
Kernel Version: 6.13.2-cachyos1.fc41.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 8 × 11th Gen Intel® Core™ i7-11390H @ 3.40GHz
Memory: 15.4 GiB of RAM
Graphics Processor: Mesa Intel® Iris® Xe Graphics

ADDITIONAL INFORMATION
Built-in screen: 1920x1080@60Hz, scale 100%
External monitor: Samsung U32J59x 3840x2160@60Hz, scale 120%

This slow behavior was also observed with Dell monitors (4k@30Hz).

Comment 1 gus 2025-02-19 16:13:10 UTC

Same issues with the recently released 6.3. 

Operating System: Fedora Linux 41
KDE Plasma Version: 6.3.0
KDE Frameworks Version: 6.11.0
Qt Version: 6.8.2
Kernel Version: 6.13.2-cachyos1.fc41.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 8 × 11th Gen Intel® Core™ i7-11390H @ 3.40GHz
Memory: 15.4 GiB of RAM
Graphics Processor: Intel® Iris® Xe Graphics

Comment 2 gus 2025-02-21 21:56:58 UTC

Could be related to https://bugs.kde.org/show_bug.cgi?id=500552. After a crash the animations are really sluggish.