Bug 513066

Summary:	Very high CPU usage in KWin::SubSurfaceInterface::parentApplyState
Product:	[Plasma] kwin	Reporter:	leo
Component:	wayland-generic	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED DUPLICATE
Severity:	normal
Priority:	NOR
Version First Reported In:	6.5.3
Target Milestone:	---
Platform:	NixOS
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description leo 2025-12-08 00:41:34 UTC

SUMMARY
Randomly, usually after kwin_wayland has been running for a few hours, kwin_wayland will spike up to 60-90% CPU usage. Based on `perf top`, this is almost entirely spent in KWin::SubSurfaceInterface::parentApplyState (specifically, in QHash<KWin::SubSurfaceInterface*, QPoint>::tryEmplace_impl).

STEPS TO REPRODUCE
1. Log in
2. Wait a few hours

OBSERVED RESULT
kwin_wayland spikes to high CPU usage, resulting in fans spinning up.

EXPECTED RESULT
kwin_wayland's resource usage remains reasonable.

SOFTWARE/OS VERSIONS
Operating System: NixOS 26.05
KDE Plasma Version: 6.5.3
KDE Frameworks Version: 6.20.0
Qt Version: 6.10.1
Kernel Version: 6.17.9 (64-bit)
Graphics Platform: Wayland

Comment 1 leo 2025-12-08 00:44:48 UTC

Oops, don't know how I didn't see this other issue before....

*** This bug has been marked as a duplicate of bug 509924 ***