Message-ID: <4C77F4F4.4020900@2ndquadrant.com>
Date: Fri, 27 Aug 2010 13:25:08 -0400
From: Greg Smith <greg@2ndquadrant.com>
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To: Scott Carey <scott@richrelevance.com>
CC: Philippe Rimbault <primbault@edd.fr>,
	"pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
Subject: Re: Performance on new 64bit server compared to my 32bit
 desktop
References: <4C6CE64D.6070104@edd.fr> <4C6D76FE.9010407@2ndquadrant.com>
	<E613263E-09D5-4562-BBAF-C72B09883E26@richrelevance.com>
In-Reply-To: <E613263E-09D5-4562-BBAF-C72B09883E26@richrelevance.com>
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Scott Carey wrote:
> But the select count(*) query, cached in RAM is 3x faster in one system than the other.  The CPUs aren't 3x different performance wise.  Something else may be wrong here.
>
> An individual Core2 Duo 2.93Ghz should be at most 50% faster than a 2.2Ghz Opteron for such a query.   Unless there are some compile options that are set wrong.   I would check the compile options.
>   

Sure, it might be.  But I've seen RAM on an Intel chip like the E7500 
here (DDR3-1066 or better, around 10GB/s possible) run almost 3X as fast 
as what you'll find paired with an Opteron 2427 (DDR2-800, closer to 
3.5GB/s).  Throw in the clock differences and there you go.

I've been wandering around for years warning that the older Opterons on 
DDR2 running a single PostgreSQL process are dog slow compared to the 
same thing on Intel.  So that alone might actually be enough to account 
for the difference.  Ultimately the multi-processor stuff is what's more 
important to most apps, though, which is why I was hinting to properly 
run that instead.

-- 
Greg Smith  2ndQuadrant US  Baltimore, MD
PostgreSQL Training, Services and Support
greg@2ndQuadrant.com   www.2ndQuadrant.us