KDE high CPU usage after screen disconnects

Ask Fedora
1

Hi there,
I have my computer connected to a TV, which seems to disconnect after it is turned off for a while. This, for whatever reason, causes KDE to use ~10% of the CPU until the user that KDE has decided for do this to has logged back in (i.e. the entire night/day). This is a problem because the computer’s cooling system is not the strongest, and because… it just shouldn’t do that.

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The plasmashell process (and 1 other process I don’t remember the exact name of) is responsible for this CPU usage between 19:00-22:00 (which is when I loginctl terminate-userd it).

This has been happening repeatedly and frequently recently. Other than the screen being turned off, there doesn’t seem to be any pattern to this.

I am using wayland with AMD integrated graphics. The computer is configured to never sleep.

I’m pretty new to linux so I’m not really sure where the logs are to look for more clues, but this is the only remotely interesting output from journalctl /usr/bin/plasmashell

Mar 10 18:10:23 * plasmashell[738024]: requesting unexisting screen available rect -1
Mar 10 18:10:23 * plasmashell[738024]: There are no outputs - creating placeholder screen
Mar 10 18:10:25 * plasmashell[738024]: error creating screencast "Could not find window id {...}"

inxi:

CPU:
  Info: 8-core model: AMD Ryzen 7 5800H with Radeon Graphics bits: 64 type: MT MCP cache:
    L2: 4 MiB
  Speed (MHz): avg: 1103 min/max: 403/4465 cores: 1: 1103 2: 1103 3: 1103 4: 1103 5: 1103
    6: 1103 7: 1103 8: 1103 9: 1103 10: 1103 11: 1103 12: 1103 13: 1103 14: 1103 15: 1103 16: 1103
Graphics:
  Device-1: Advanced Micro Devices [AMD/ATI] Cezanne [Radeon Vega Series / Radeon Mobile Series]
    driver: amdgpu v: kernel
  Display: unspecified server: Xwayland v: 24.1.9 driver: gpu: amdgpu tty: 238x56
    resolution: 3840x2160
  API: EGL v: 1.5 drivers: radeonsi,swrast platforms: surfaceless,device
  API: OpenGL v: 4.6 compat-v: 4.5 vendor: mesa v: 25.3.6 note: console (EGL sourced)
    renderer: AMD Radeon Graphics (radeonsi renoir ACO DRM 3.64 6.18.16-200.fc43.x86_64), llvmpipe
    (LLVM 21.1.8 256 bits)
  API: Vulkan v: 1.4.341 drivers: radv,llvmpipe surfaces: N/A
  Info: Tools: api: clinfo, eglinfo, glxinfo, vulkaninfo de: kscreen-console,kscreen-doctor
    gpu: amd-smi,radeontop wl: wayland-info x11: xdriinfo, xdpyinfo, xprop, xrandr
Audio:
  Device-1: Advanced Micro Devices [AMD/ATI] Renoir/Cezanne HDMI/DP Audio driver: snd_hda_intel
  Device-2: Advanced Micro Devices [AMD] Audio Coprocessor driver: snd_rn_pci_acp3x
  Device-3: Advanced Micro Devices [AMD] Ryzen HD Audio driver: snd_hda_intel
  API: ALSA v: k6.18.16-200.fc43.x86_64 status: kernel-api
2

I see kde plasma bug fixes around disconnection of displays.
Not sure if the update with the fix has been released and on Fedora.

You could ask over at https://discuss.kde.org/ if your issue is known.

3

Strange question from me: if you only have 2 things running and you switch off the monitor (TV) why don’t you switch off the computer.
You already wrote: it just shouldn't do that, it also should not consume energy when it is not used. Switch it off, reboot when needed. This also makes sure you start with empty memory, updates, which were installed before the shutdown, are in session. It’s a win-win situation.

4

There are actually some other processes on the machine, like an automatic youtube downloader, that I wish to keep running on there, hence I don’t really want to turn off the machine. The machine does not use much power when idle, IIRC ~20 metric watts or less.

This is happening frequently enough that I’m considering making a script to automatically kill KDE if it’s using too much CPU for too long.

Which bugs fixes were you seeing? I might make a post on kde forum too.

5

I read https://blogs.kde.org/ for news on plasma which includes bug fixe info.
Checkout the release blog post, this week in plasma