Re: question about cpu usage
- From: zhu chao <zhuchao@xxxxxxxxx>
- To: anelson@xxxxxxxxxxx, Yong Huang <yong321@xxxxxxxxx>, bass chong <bchorng@xxxxxxxx>
- Date: Sat, 23 Oct 2004 16:52:05 +0800
I am not graduated from Computer Science major, so I only talk about
my own experience.
I have seen both cases,
1. CPU runs at 100% and application performance does not degrade. (We
run tuxedo middleware and I measured response time via txrpt). This
application use database heavily and SQL was not good.CPU number was 4
and load (uptime) was 8-10. The response time was same between CPU
usage at 60% and 100%. The bottleneck in the database was purely
Logical IO(no disk IO contention and lock contention etc).
2. CPU usage rise to 70% and we see a lot of application report error.
(Time out)This was because business grows and our server reached its
IO capacity. A lot of disk io wait event and also a lot of Enqueue
wait contention.
On Fri, 22 Oct 2004 19:41:22 -0500, Nelson, Allan <anelson@xxxxxxxxxxx> wrote:
> Response time for interactive users is non-linear with respect to cpu
> utilization. The curve looks like a hockey stick with the puck striking
> surface pointing up. If you are past the knee of the curve your
> interactive users are receiving unpredictable response times. If you
> are at 90% utilization and you have 4 CPU's or less you are probably
> driving your interactive users mad. Query response time for them will
> swing wildly between "normal" to 10 to 100 times normal. Your batch
> jobs and your total throughput on the other hand might be doing pretty
> well. You can get Cary Millsap and Jeff Holt's Optimizing Oracle
> Performance from O'Reilly. You can go to hotsos.com and register for a
> =66ree acount and get some white papers and an excel spreadsheet that will
> show you where the knee on the curve is relative to the number of CPU's.
> \--
Regards
Zhu Chao
www.cnoug.org
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