Stop looking at CPU usage; start looking at Linux PSI(parth21shah.substack.com)

parth21shah.substack.com

Stop looking at CPU usage; start looking at Linux PSI

https://parth21shah.substack.com/p/stop-looking-at-cpu-usage-start-looking

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I wrote this because alerting on CPU% / loadavg as machine health indicator has burned me a few times. The simple split I use now is: - CPU% = how busy the cores are - PSI = how much time tasks are stalled (CPU / memory / IO) In an eBPF agent I am working on (Linnix), I ended up looking at CPU and PSI together. High CPU + high PSI is interesting. High CPU + low PSI is usually just “busy”. This obviously doesn’t replace latency/SLO alerts at the app level.It’s only about which host metric to look at.