[CentOS] High load since passing from rhas3 to centos4.8

[Fernando Gleiser]

----- Original Message ----

> From: "fortin.pierre at bell.ca" <fortin.pierre at bell.ca>
> To: centos at centos.org
> Sent: Thu, January 14, 2010 5:47:43 PM
> Subject: Re: [CentOS] High load since passing from rhas3 to centos4.8
> 
> 
> 
> The purpose of the server is to run NMS Telephony cards. The only support is for 
> Centos 4.x on 32 bit systems. Anyway, since I have not found the trouble, it may 
> still be there with another centos version.
> 
> When I execute multiple ps during high load average period (above 10), here is 
> the kind of output I have:
> 
> ps aux | grep " R"
> USER       PID %CPU %MEM   VSZ  RSS TTY      STAT START   TIME COMMAND
> root     16295  0.0  0.0  3492  772 pts/1    R+   15:45   0:00 ps -aux
> root     16296  0.0  0.0  5400  648 pts/1    S+   15:45   0:00 grep  R
> 
> I see a lot of process in S, Sl, Ss+ and Ssl states.

first of all, if you have high load average with seemingly low utilization, it may be because of load imbalance between CPUs and/or short bursts of lots of short cpu-intensive processes.

Here's what I'd look at first:

run "vmstat 1 10" and look at the first column. if it's higher than 1/ncpu you're having cpu saturation.

rum "mpstat -P ALL 1 10", this gives you cpu utilisation per cpu (sar gives you the average among all processors)

Also take a look at "sar -q 1 10" to look at the CPU's queues sizes


Hope this helps


Fer