Bug 513066 - Very high CPU usage in KWin::SubSurfaceInterface::parentApplyState
Summary: Very high CPU usage in KWin::SubSurfaceInterface::parentApplyState
Status: RESOLVED DUPLICATE of bug 509924
Alias: None
Product: kwin
Classification: Plasma
Component: wayland-generic (other bugs)
Version First Reported In: 6.5.3
Platform: NixOS Linux
: NOR normal
Target Milestone: ---
Assignee: KWin default assignee
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2025-12-08 00:41 UTC by leo
Modified: 2025-12-08 00:44 UTC (History)
0 users

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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 ***