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tomf
Asked: 2021-10-18 10:41:46 +0800 CST

100% CPU usage reported, but no processes using the CPU

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I am running Debian 10 (kernel 4.19.0-18-amd64) on bare metal and I have recently noticed strange CPU usage.

Screenshot of htop, sorted by CPU%

Screenshot of top, sorted by CPU%

As you can see, 100% CPU usage is reported over all of the cores but the reported usage for each individual process does not seem to back this up.

I have looked at iotop

iotop, sorted in ascending order

Where else can I look to try and hunt down this resource hog?

Thanks.

linux debian top cpu-usage htop

2 Answers

  1. One thing I noticed is that according to top, 98.5% CPU is used by "niced" processes (note 98.5 ni). Niced processes are those having positive "nice" value, i.e. lower priority. As the next step, open "top" again, sort by "NI" value, and look for the higher values (from 1 to 19).

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  2. In general, even on 100% CPU activities without 100%RAM activities simultaneously , We consider it is just ok until it can get done when tasks list finishes.

    It is more important con consider LoadAvg vs RAM vs CPU in a big set of data. until all of them are about 100% and LoadAvg around 5 per physical core + 2 per virtualcpu (hyperthreading) , just survey , over start investigating & managing processes priorities & Affect any new tasks to dedicated (v)cpu with taskset until all goes back to lower consumption of resources.

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