Message-ID: <5099E094.9010703@catalyst.net.nz>
Date: Wed, 07 Nov 2012 17:16:20 +1300
From: Mark Kirkwood <mark.kirkwood@catalyst.net.nz>
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To: pgsql-performance@postgresql.org
Subject: Re: HT on or off for E5-26xx ?
References: <5099D5FA.90802@boreham.org>
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On 07/11/12 16:31, David Boreham wrote:
>
> I'm bringing up a new type of server using Intel E5-2620 (unisocket) 
> which was selected for good SpecIntRate performance vs cost/power (201 
> for $410 and 95W).
>
> Was assuming it was 6-core but I just noticed it has HT which is 
> currently enabled since I see 12 cores in /proc/cpuinfo
>
> Question for the performance experts : is it better to have HT enabled 
> or disabled for this generation of Xeon ?
> Workload will be moderately concurrent, small OLTP type transactions. 
> We'll also run a few low-load VMs (using KVM) and a big Java application.
>
>
>

I've been benchmarking a E5-4640 (4 socket) and hyperthreading off gave 
much better scaling behaviour in pgbench (gentle rise and flatten off), 
whereas with hyperthreading on there was a dramatic falloff after approx 
number clients = number of (hyperthreaded) cpus. The box is intended to 
be a pure db server, so we are running with hyperthreading off.

Cheers

Mark