RE: question about cpu usage
- From: "Gogala, Mladen" <Mladen.Gogala@xxxxxxxx>
- To: "'ryan_gaffuri@xxxxxxxxxxx'" <ryan_gaffuri@xxxxxxxxxxx>, oracle-l@xxxxxxxxxxxxx
- Date: Fri, 22 Oct 2004 16:07:44 -0400
Question asked in such generality really doesn't make much sense and can
only have one
answer: it depends. Mostly, it depends on what is CPU doing. Well optimized
queries will
typically have a short burst or two of intense CPU activity and then will
finish. Using
100% of CPU power is, unfortunately, also characteristic for "well cached"
queries which
can perform a gazillion logical block gets with no phyisical disk reads. An
example of
such query is the following:
SELECT COUNT(*) FROM EMP,EMP,EMP,EMP,EMP,EMP,EMP,EMP,EMP,EMP;
Table emp normally has 14 rows so the number of rows to count is POW(14,10)
and
RDBMS process will be spinning using 100% of CPU for approximately 30
minutes.
What will you get? A worhless number which could have been computed in a
much, much
cheaper fashion. So, the answer to your question is: optimize your most
expensive
queries and only then try predicting scalability and growth of your
database.
--
Mladen Gogala
A & E TV Network
Ext. 1216
> -----Original Message-----
> From: ryan_gaffuri@xxxxxxxxxxx [mailto:ryan_gaffuri@xxxxxxxxxxx]
> Sent: Friday, October 22, 2004 3:56 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?
> --
> //www.freelists.org/webpage/oracle-l
>
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