High CPU utilization at random times

[Guy B. Purcell]

On Oct 4, 2005, at 21:40, Dan Wilson wrote:

> I've been looking into a problem for quite some time now and have  
> come up stumped.  Every time I think I know what the problem is I  
> turn out to be wrong.
>
> PROBLEM:
> Randomly, and for no good reason, the CPU usage on this machine  
> will go up to anywhere from .7 to 1.5!?!?!?!?!?

I'm assuming these are load average numbers, not CPU utilization  
percentages or something else.  (This problem seems a tad off-topic  
for this list, since it really doesn't seem to be related to Nagios  
other than that Nagios is reporting seemingly unusual load.  Have you  
asked a Linux UG for suggestions?)

> HARDWARE:
> PIII 677
> 384MB ram
> Software RAID 1 with IDE(all partitions except swap, yes, I boot  
> from it too... I already took crap for booting from software raid,  
> but it works fine, really)
> extra drive for swap and nightly "snapshots" of /usr/local/ and / 
> etc and a few other things.


I don't see a problem at all (at least it wouldn't be on a Solaris  
box; not sure what the load avg. numbers under Mandrake mean):  on a  
box that's doing software RAID & running the Nagios server, you  
should expect to see some load, on average; and I wouldn't worry  
about loads up to twice the number of CPUs in the box for brief  
periods (again, at least not running Solaris, where "load average"  
means the number of processes in the run queue--including those on  
CPU, as well as those hanging out waiting on some I/O to complete).

However, if this box truly is doing nothing and you still see high  
loads--especially for prolonged periods--perhaps there is a problem.   
Try shutting down Nagios & any other daemons you don't need (eg.  
sendmail) for a while and checking the 'sar' logs for load bumps.  If  
you still see load when there shouldn't be any, you may have been  
hacked (although by someone not very competent if s/he allowed load  
from their hidden activities to show).

-Guy




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