Date: Fri, 04 May 2007 08:45:39 -0400
From: Michael Stone <mstone+postgres@mathom.us>
Subject: Re: Feature Request --- was: PostgreSQL Performance Tuning
In-reply-to: <Pine.GSO.4.64.0705032351240.14661@westnet.com>
To: Greg Smith <gsmith@gregsmith.com>
Cc: pgsql-performance@postgresql.org
Mail-followup-to: Greg Smith <gsmith@gregsmith.com>,
	pgsql-performance@postgresql.org
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	<200705010923.47951.josh@agliodbs.com>
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On Fri, May 04, 2007 at 12:33:29AM -0400, Greg Smith wrote:
>-bash-3.00$ psql
>postgres=# \timing
>Timing is on.
>postgres=# select count(*) from generate_series(1,100000,1);
>  count
>--------
>  100000
>(1 row)
>
>Time: 106.535 ms
>
>There you go, a completely cross-platform answer.  You should run the 
>statement twice and only use the second result for better consistancy.  I 
>ran this on all the sytems I was around today and got these results:
>
>P4 2.4GHz	107ms
>Xeon 3GHz	100ms
>Opteron 275	65ms
>Athlon X2 4600	61ms

PIII 1GHz	265ms
Opteron 250	39ms

something seems inconsistent here.

>For comparison sake, these numbers are more useful at predicting actual 
>application performance than Linux's bogomips number, which completely 
>reverses the relative performance of the Intel vs. AMD chips in this set 
>from the reality of how well they run Postgres.

You misunderstand the purpose of bogomips; they have no absolute 
meaning, and a comparison between different type of cpus is not 
possible.

>While I'm ranting here, I should mention that I also sigh every time I see 
>people suggest we should ask the user how big their database is.  The kind 
>of newbie user people keep talking about helping has *no idea whatsoever* 
>how big the data actually is after it gets into the database and all the 
>indexes are built.  

100% agreed.

Mike Stone