Stop high CPU load with KDE & Plasmashell

This article is ideal for anyone who uses KDE and its so-called ‘Plasma’ interface as their desktop and suffers from consistently high processor (CPU) utilisation. It describes a way to reduce high system utilisation. I spent a long time searching the internet for the solution myself, so I would like to save my readers the trouble.

Symptoms

I didn’t notice the problem at first by regularly evaluating the system load, but rather by the suspiciously high activity of the computer at times when the load should not actually be high. The system generated a lot of heat even when idle, and the fans ran at full speed despite long periods of non-use. The noise from the fans gradually became annoying, so I had to look for the causes. In addition, I had only noticed this problem on one device: the only one I run with KDE and, of all things, my most powerful machine, which can handle the many decorative effects of the interface without any loss of performance.

Diagnosis

Whenever a device triggers suspiciously high activity when not in use, you should at least be curious and run the system monitor for a while. KSysGuard is available as a monitor under KDE. So we call it up from the start menu and look at the ‘System Load’ tab. A system should look something like this when not performing complex tasks.

CPU utilisation is in the single digits without computationally intensive tasks running in the background. In my opinion, the operating system should not burden the system so much that this value is permanently above this level.

If your value is significantly higher, take a look at the ‘Process Table’ tab and check for the processes with the highest CPU utilisation. Here, too, the CPU usage of individual processes should be in the single-digit percentage range when idle and only temporarily above that. If there are unexplained load peaks, the following processes are usually the culprits:

• plasmashell
• multiple processes beginning with “baloo”. i.e. baloo_file, baloo_extractor

During prolonged use of the computer, the aforementioned Baloo processes can use over 20% of the CPU and Plasmashell can permanently use up to 70% of the CPU. You then have a system that uses 90% of your CPU even when not in use!

To observe this further, you can restart Plasmashell while it is running by opening the console and entering the following command:

killall plasmashell; kstart plasmashell; exit

Once the desktop is restored, restart the system monitor and look at the process table. The utilisation of the above-mentioned processes is back to normal.

Disable Ballo desktop search

Now continue to use your system as usual and test the desktop search. To do this, simply open the Start menu and enter a search term. For example, a document you want to work on or an application that you open via the search function because there is no quick link on the desktop. The Baloo search service will open additional processes to routinely search and index all files on the system. The Plasma shell is closely integrated with the search service via a widget, and both gradually increase the load until values above 50% are reached.

This probably has to do with files that are constantly changing in the system, so that these processes never really come to a standstill. But a trivial background process that wastes so many system resources is clearly faulty in my opinion, which is why we should turn it off.

Troubleshooting

If your observations confirm my findings that the desktop search is causing the symptoms, it is best to disable it. If you use it frequently to index your files, I recommend finding an alternative and not using Baloo, or at least disabling it until a patch is available that permanently fixes the problem. Unfortunately, I have not found any clear indications that this is being actively worked on. You will surely find alternative search services quickly in the repository of your Linux distribution. I would not recommend ignoring the problem, if only for reasons of ergonomics if your device is constantly noisy. However, the unnecessary high load also affects the lifespan of your computer, as well as your electricity bill or battery if you are using a laptop.

You can easily disable it by going to Start menu / Computer / System settings / Search

or simply entering ‘file search’ in the Start menu.

There you can deactivate the Baloo search service.

Disable desktop search, click OK, and your settings will take effect after a restart.

Continue to monitor the system monitor. The load should now be noticeably lower and, with the removal of the Baloo search services, disappear completely. Uninstalling the associated package using apt would be another measure to completely remove the service from the system. However, I did not consider this necessary.