I run an old desktop mainboard as my homelab server. It runs Ubuntu smoothly at loads between 0.2 and 3 (whatever unit that is).
Problem:
Occasionally, the CPU load skyrockets above 400 (yes really), making the machine totally unresponsive. The only solution is the reset button.
Solution:
- I haven’t found what the cause might be, but I think that a reboot every few days would prevent it from ever happening. That could be done easily with a crontab line.
- alternatively, I would like to have some dead-simple script running in the background that simply looks at the CPU load and executes a reboot when the load climbs over a given threshold.
–> How could such a cpu-load-triggered reboot be implemented?
edit: I asked ChatGPT to help me create a script that is started by crontab every X minutes. The script has a kill-threshold that does a kill-9 on the top process, and a higher reboot-threshold that … reboots the machine. before doing either, or none of these, it will write a log line. I hope this will keep my system running, and I will review the log file to see how it fares. Or, it might inexplicable break my system. Fun!
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Here’s a better suggestion. Why don’t you see if you can find out what’s causing the issue? It sounds a like a problem occurring in userspace. Try running htop
You know you are right, and I’ve tried. I can manually monitor but it doesn’t happen just then. I don’t know yet what causes it, I can only assume it’s one of the Docker containers because the machine is doing nothing else.
I am doing this to find out how often it happens, how quickly it happens, and what’s at the top when it happens.
I can manually monitor but it doesn’t happen just then
Setup proper monitoring with history. That way yo don’t have to babysit the server, you can just look at the charts after a crash. I usually go with netdata
Just as a side note, the load factor can also mean that processes are limited by IO:
Unix systems traditionally just counted processes waiting for the CPU, but Linux also counts processes waiting for other resources – for example, processes waiting to read from or write to the disk.
I would assume that wouldn’t cause so much contention that the system is unusable, though, right? Unless they’re busy waiting.
Have you tried turning your swap off?
Nope, haven’t. It says I have 2 GB of swap on a 16 GB RAM system, and that seems reasonable.
Why would you recommend turning swap off?
To check if your problem is caused by excessive memory usage requiring constant swapping. If it is, turning swap off will make some process be killed instead of slowing the computer down.
