CPU usage suddenly started spiking

[papapenguin]

Starting this morning, my CPU usage began spiking -- completely bogging down my system and making every program almost unusable. Top shows plasma-systemo as the culprit...any ideas what is going on?

[toad]

Now that is a proper AI tip:


It looks like you’re investigating a CPU spike related to plasma-systemmonitor (often truncated as plasma-systemo in process lists). This is a common issue in KDE Plasma environments where the monitoring service itself begins consuming the very resources it's supposed to be tracking.

If you are following that forum thread, here is a breakdown of why this happens and how you can troubleshoot it: Why is plasma-systemmonitor Spiking?


The most frequent culprits for this specific process hanging or spiking are:

• Sensor Polling Overload: If you have custom "System Monitor" widgets on your desktop or dashboard with high refresh rates, the backend service can get overwhelmed.
• Broken Configuration Files: Corrupted local settings in the plasma-systemmonitorrc file.
• KDE Daemon (KSD) Sync Issues: Sometimes the process hangs while trying to fetch data from the hardware sensors (lm-sensors).

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Immediate Steps to Take

1. Kill the Process: If your UI is lagging, open your terminal (Konsole) and run: killall plasma-systemmonitor This is safe; it will just close the monitor app or stop the background data collection.
2. Reset the Configuration: If the spike returns immediately upon reopening the monitor, try clearing the local config: rm ~/.config/plasma-systemmonitorrc
3. Check for "Zombie" Sensors: Open the System Monitor application manually, go to "Edit Page," and see if any old or disconnected sensors (like an old GPU or a disconnected network drive) are still being tracked. Removing these often drops CPU usage instantly.

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Understanding the Resource Flow


When plasma-systemmonitor runs, it interacts with several layers of your OS. If one layer is slow, the monitor "spins" its wheels waiting for a response, causing the CPU spike. Is it actually ksysguard?


Depending on which version of Kubuntu you are running, you might be transitioning from the old ksysguard to the new plasma-systemmonitor. Having both running or having old widgets trying to call the new API can sometimes cause conflicts.