https://bugs.kde.org/show_bug.cgi?id=513424
Bug ID: 513424
Summary: High plasmashell CPU usage after turning off screen
(only on laptops with external monitor)
Classification: Plasma
Product: plasmashell
Version First 6.5.4
Reported In:
Platform: Arch Linux
OS: Linux
Status: REPORTED
Severity: major
Priority: NOR
Component: Session Management
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Target Milestone: 1.0
SUMMARY
When a laptop connected to an external monitor (both screens in use) has "Turn
off screen when locked" enabled, abnormal high CPU usage (>60%) of plasmashell
is observed via `nvtop` over SSH after locking the screen and turning off the
display. Upon waking the screen and returning to the desktop, the desktop
background and panels disappear temporarily while application windows remain
visible. After a few seconds, the desktop background and panels recover, and
plasmashell CPU usage drops to low levels (<1%).
This issue occurs only on a laptop connected to an external monitor. The
problem disappears when the external monitor is disconnected.
Desktop computers connected to multiple monitors do not exhibit this issue.
STEPS TO REPRODUCE
1. Log into a Plasma Wayland session.
2. Connect the laptop to an external monitor and ensure both displays are
active.
3. In Power Management settings, set "When locked: Immediately" under "Turn off
screen".
4. Lock the screen and let the displays turn off.
5. Wait for a while.
6. SSH into the computer remotely and run `top` or `nvtop` to observe
plasmashell CPU usage.
OBSERVED RESULT
1. While the screen is off, plasmashell CPU usage exceeds 60%. After waking the
screen and logging into the desktop, plasmashell CPU usage drops below 1%.
2. When waking the screen and returning to the desktop, application windows
appear immediately, but the desktop background and panels take several seconds
to appear.
EXPECTED RESULT
1. The plasmashell process should maintain low CPU usage even when the screen
is turned off.
2. The desktop (background and panels) should appear immediately upon waking
the screen and logging into the desktop.
SOFTWARE/OS VERSIONS
Operating System: Arch Linux
KDE Plasma Version: 6.5.4
KDE Frameworks Version: 6.21.0
Qt Version: 6.10.1
Kernel Version: 6.17.9-zen1-1-zen (64-bit)
Graphics Platform: Wayland
Processors: 20 × AMD Ryzen AI 9 365 w/ Radeon 880M
Memory: 32 GiB of RAM (27.2 GiB usable)
Graphics Processor: AMD Radeon 890M Graphics
Manufacturer: LENOVO
System Version: ThinkBook 14 G7+ ASP
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