[CentOS] Find reason for heavy load
John R Pierce
pierce at hogranch.com
Wed Dec 30 06:21:03 UTC 2009
Noob Centos Admin wrote:
> However, iostat reports much lower %user and $system compared to top
> running at the same time so I'm not quite sure if I can rely on its
> figures.
> ...
> iostat
> Linux 2.6.18-128.1.16.el5xen 12/30/2009
> avg-cpu: %user %nice %system %iowait %steal %idle
> 3.28 0.20 1.16 2.38 0.01 92.97
>
iostat, if run with no parameters shows the average since reboot or
statistics reset.
run `iostat -x 5` to a) show details on all devices, and B) show 5
second samples. ignore the first output as thats average. the 2nd
and beyond outputs represent 5 second samples.
note, btw, 'load average' isn't CPU usage, its the number of processes
that are waiting to run. a load average of 8 means there are 8
processes waiting to use system resources. this does include processes
in iowait, but doesn't include processes that are sleeping on semaphores
and such, so it can be quite a lot higher than the cpu workload.
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