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Re: question about cpu usage

From: zhu chao <>
Date: Sat, 23 Oct 2004 16:52:05 +0800
Message-ID: <>

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 <> 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 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.
> \--

Zhu Chao

Received on Sat Oct 23 2004 - 03:47:44 CDT

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