topic System CPU Usage in Operating System - HP-UX

System CPU Usage

Simon Hargrave — Tue, 03 Dec 2002 15:49:45 GMT

Hi, I have an L2000 (single CPU, 2Gb RAM) which is having performance problems. It is running OmniBack, VPO and an Oracle scheduling system.

CPU usage is fairly consistently 100%, with %sys varying from 30-50%, and %usr consuming the remainder (there's 0% wio).

Disk usage is low, no large IO queuing, but runq regularly 6-10 (which for a single CPU I think is excessive!)

Highest system call CPU time user is read() (eg used cum. 15 sec CPU in 70second sample period, is this excessive?) so I assume this is partially what's causing the problem, but since I've ascertained that disk I/O isn't the issue, what's the best way of finding out what's doing so much read()ing?

If it's not this, any other general pointers would be good? If I have to ask for money for new CPU I'd at least like to be able to quantify the reasons.

Cheers Sy

Re: System CPU Usage

Martin Johnson — Tue, 03 Dec 2002 15:52:54 GMT

Check the kernel parameter "timeslice". If it is set to 1, increase it to 10. That should reduce some of your system CPU overhead.

HTH
Marty

Re: System CPU Usage

Simon Hargrave — Tue, 03 Dec 2002 16:14:27 GMT

The timeslice parameter is already at the default 10ms.

Re: System CPU Usage

Leif Halvarsson_2 — Tue, 03 Dec 2002 16:30:58 GMT

Hi,
If you use the top command, can you see which processes uses most cpu time ?

Re: System CPU Usage

Simon Hargrave — Tue, 03 Dec 2002 16:39:55 GMT

Yes, but like I say it's the System CPU% that worries me, there's no one CPU hogging process.

However I've just shut down one of our applications (a scheduling system that sits on oracle) and the CPU has gone down to 20% usage, so I think I've found the culprit!

I'll do some digging with Glance on the particular processes for that app and see what that digs up.