[arch-general] High CPU on one core, but unable to find process responsible

[Jiachen Yang]

On 2018年03月12日 11:19, David Rosenstrauch wrote:
> My server's been exhibiting some very strange behavior lately.  Every
> couple of days I run into a situation where one core (core #0) on the
> quad core CPU starts continuously using around 34% of CPU, but I'm not
> able to see (using htop) any process that's responsible for using all
> that CPU.  Even when I tell htop to show me kernel threads too, I
> still am not able to see the offending process.  Every process remains
> under 1% CPU usage (except for occasional, small, short-lived spikes
> up) yet the CPU usage on that core remains permanently hovering at
> around 34%.  The problem goes away when I reboot, but then comes back
> with a day or so.
>
> I'm rather stumped as to how to fix this.  The server is a bit old,
> running an up-to-date installation of Arch on a Intel Core 2 Quad
> Q6600 CPU.  Any suggestions anyone might have as to either what might
> be going on here, or how to go about debugging it would be greatly
> appreciated.
>
> Thanks!
>
> DR

Can you check whether you have enabled "Detailed CPU time" option in
htop's setup (F2 -> Display options -> "Detailed CPU time")?
From my experience and understanging, htop's CPU meter is accounting
IO-wait/IRQ-response time by default but not showing them differently
unless you enabled the "Detailed CPU time" option.
And these waiting time is not accounted on each process or kernel
thread. Enabling that said option will revail more detailed CPU usage info.
High IO-wait or IRQ time is itself an indication of some misbehaving
hardware, but at least you can be sure that it is not by more
"dangerous" malwares or attacks.

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