RE: question about cpu usage (fwd)

dont see any harm in putting this on oracle-l. cary probably just didnt do a 
reply to all. 
the chart is very useful. 

-------------- Forwarded Message: -------------- 
From: "Cary Millsap" <cary.millsap@xxxxxxxxxx> 
To: <ryan_gaffuri@xxxxxxxxxxx> 
Subject: RE: question about cpu usage 
Date: Fri, 22 Oct 2004 20:06:54 +0000 

Ryan, 

Good question actually. It depends on how many CPUs are in there. If you 
have a copy of "Optimizing Oracle Performance" handy, check out table 9-3 on 
page 260. What it says is that you can expect performance to vary 
unpredictably on a 1-CPU machine when CPU utilization exceeds 50%. On a 
2-CPU machine, the magic number is about 57.7%. On a 4-CPU machine, it's 
66.5%. The table lists "knee in the curve" numbers for CPU counts ranging 
from 1 to 128. 

The whole section called "Behavior of M/M/m Systems" (pp254-266) should be 
of interest to you. 


Cary Millsap 
Hotsos Enterprises, Ltd. 
http://www.hotsos.com 
* Nullius in verba * 

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-----Original Message----- 
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] 
On Behalf Of ryan_gaffuri@xxxxxxxxxxx 
Sent: Friday, October 22, 2004 2:56 PM 
To: oracle-l@xxxxxxxxxxxxx 
Subject: question about cpu usage 

I'm not a hardware guy or sys admin person so forgive me if this is a stupid 
question. Leaving out all other variables(such as IO), should I expect 
performance to be the same in a databse if the server it is riding at is at 
90% cpu usages as opposed to 10%? since there would still be spare cycles? 
Or is there a declining returns as you get closing to the maximum available 
cpu usage? 
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