https://bugs.kde.org/show_bug.cgi?id=522757
Bug ID: 522757
Summary: Icons-Only Task Manager tooltip causes excessive
plasmashell CPU spike on hover
Classification: Plasma
Product: plasmashell
Version First 6.7.2
Reported In:
Platform: KDE Linux
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: Task Manager and Icons-Only Task Manager widgets
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Target Milestone: 1.0
DESCRIPTION
Hovering over icons in the Icons-Only Task Manager causes plasmashell to spike
to ~60-75% CPU. The spike occurs on tooltip appear and disappear. The issue
scales significantly with display scaling — at 200% scale spikes reached ~75%
plasmashell CPU, at 100% scale ~60%.
Issue only occurs when an icon represents multiple grouped windows (tooltip
shows multi-window grid). Single window icons do not trigger the spike.
Suggests the per-hover cost scales with the number of windows being rendered in
the tooltip grid, consistent with dynamic QML delegate instantiation rather
than cached layout.
STEPS TO REPRODUCE
1. Have Icons-Only Task Manager on panel with "Show small window prewiews when
hovering over tasks" enabled
2. Have 2+ windows of the same application open (e.g. 7 Firefox windows)
3. Hover over the grouped icon
4. Observe CPU spike
OBSERVED RESULT
plasmashell CPU spikes to ~60-75% on hover. Spike is shorter/faster at 100%
scale than 200%.
EXPECTED RESULT
Minimal CPU usage on hover.
SOFTWARE/OS VERSIONS
Operating System: Fedora Linux 44
KDE Plasma Version: 6.7.2
KDE Frameworks Version: 6.27.0
Qt Version: 6.11.1
Kernel Version: 7.0.14-201.fc44.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 20 × 13th Gen Intel® Core™ i5-13600K
Memory: 32 GB of RAM (31.1 GB usable)
Graphics Processor 1: Intel® Arc A770
ADDITIONAL INFORMATION
* perf top during spike shows JIT-hot addresses in plasmashell (Qt V4 JIT
engine — QML/JavaScript execution)
* KWin-side thumbnails (Alt+Tab, Overview) are unaffected and cause no spike
* Disabling the Blur desktop effect reduced spike duration but did not
eliminate it
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