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

[fortin.pierre at bell.ca]

> We are migrating HP servers from RHAS3 to centos 4.8. Since, the load
> average is reaching really high values. Under usage we see loads of
> 15-20 instead of the 0.5-1.5 we were used to.
>
> I searched a lot for information on such an issue. Iostat, vmstat, top,
> ps. But I don't get significant hint.
>
> Cpu usage remains low, IO wait remains low, no disks are lagging, no
> swap usage.
>
> Are there some tool / other way to diagnose why the load average is
> high? Like which processes are waiting, where they are stuck. Are there
> calls to drivers or system process that are slow?

>I don't have an answer but out of curiosity, why would you move to a 4.x 
>instead of 5.x now?
>
>You might be able to do some ps snapshots to see the process in R state, 
>which is what the load average should be counting.  That might be 
>computed differently between the 2.4 and 2.6 kernels.

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.

-- 
   Les Mikesell
    lesmikesell at gmail.com
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