Message-ID: <4E3B13E8.7050002@peak6.com>
Date: Thu, 4 Aug 2011 16:49:28 -0500
From: Shaun Thomas <sthomas@peak6.com>
Reply-To: <sthomas@peak6.com>
Organization: Peak6
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To: Kevin Grittner <Kevin.Grittner@wicourts.gov>
CC: <pgsql-performance@postgresql.org>, Claire Chang <yenhsiac@yahoo.com>
Subject: Re: Postgres 8.4 memory related parameters
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	<4E3ABCFB020000250003FAF4@gw.wicourts.gov> <4E3B08D3.606@peak6.com>
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On 08/04/2011 04:36 PM, Kevin Grittner wrote:

> Anyway, I'm always willing to take advantage of the benchmarking
> work of others, so I'm very curious about where performance topped
> out for you with HT enabled, and whether disk waits were part of the
> mix.

Hah. Well, it peaked at 2x physical cores, where it ended up being 60% 
faster than true cores. It started to fall after that, until I hit 64 
concurrent connections and it dropped down to 36% faster. I should also 
note that this is with core turbo enabled and performance mode BIOS 
settings so it never goes into power saving mode. Without those, our 
results were inconsistent, with variance of up to 40% per run, on top of 
40% worse performance at concurrency past 2x core count.

I tested along a scale from 1 to 64 concurrent connections at a scale of 
100 so it would fit in memory. I was trying to test some new X5675s 
cores against our old E7450s. The scary part was that a dual X5675 ended 
up being 2.5x faster than a quad E7450 at 24-user concurrency. It's 
unreal. It's a great way to save on per-core licensing fees.

We're also on an 8.2 database. We're upgrading soon, I promise. :)

-- 
Shaun Thomas
OptionsHouse | 141 W. Jackson Blvd. | Suite 800 | Chicago IL, 60604
312-676-8870
sthomas@peak6.com

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