Message-ID: <53F5FEE0.8040505@optionshouse.com>
Date: Thu, 21 Aug 2014 09:14:56 -0500
From: Shaun Thomas <sthomas@optionshouse.com>
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To: Mark Kirkwood <mark.kirkwood@catalyst.net.nz>, Josh Berkus
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CC: "Graeme B. Bell" <grb@skogoglandskap.no>
Subject: Re: Turn off Hyperthreading! WAS: 60 core performance with
 9.3
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On 08/20/2014 06:14 PM, Mark Kirkwood wrote:

> Notwithstanding the above results, my workmate Matt made an interesting
> observation: the scaling graph for (our) 60 core box (HT off), looks
> just like the one for our 32 core box with HT *on*.

Hmm. I know this sounds stupid and unlikely, but has anyone actually 
tested PostgreSQL on a system with more than 64 legitimate cores? The 
work Robert Haas did to fix the CPU locking way back when showed 
significant improvements up to 64, but so far as I know, nobody really 
tested beyond that.

I seem to remember similar choking effects when pre-9.2 systems 
encountered high CPU counts. I somehow doubt Intel would allow their HT 
architecture to regress so badly from Nehalem, which is almost 
3-generations old at this point. This smells like something in the 
software stack, up to and including the Linux kernel.

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

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