Message-ID: <55AE0BE2.3040603@catalyst.net.nz>
Date: Tue, 21 Jul 2015 21:07:46 +1200
From: Mark Kirkwood <mark.kirkwood@catalyst.net.nz>
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To: David Rowley <david.rowley@2ndquadrant.com>,
 Jeison Bedoya Delgado <jeisonb@audifarma.com.co>
CC: pgsql-performance@postgresql.org
Subject: Re: hyperthreadin low performance
References: <55ADB586.2010406@audifarma.com.co>
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On 21/07/15 20:04, David Rowley wrote:
> On 21 July 2015 at 14:59, Jeison Bedoya Delgado
> <jeisonb@audifarma.com.co <mailto:jeisonb@audifarma.com.co>> wrote:
>
>     hi everyone,
>
>     Recently update a database to machine with RHEL7, but i see that the
>     performance is betther if the hyperthreading tecnology is
>     deactivated and use only 32 cores.
>
>     is normal that the machine performance is better with 32 cores that
>     64 cores?.
>
>
> You might be interested in
> http://www.postgresql.org/message-id/53F4F36E.6050003@agliodbs.com
>

However I do wonder if we have been misinterpreting these tests. We tend 
to assume the position of "see hyperthreading is bad, switch it off".

The linked post under the one above:

http://www.postgresql.org/message-id/53ED371D.109@catalyst.net.nz

shows that 60 core (no hyperthreading) performance is also pessimal, 
leading me to conclude that *perhaps* it is simply the number of cores 
that is the problem - particularly as benchmark results for single 
socket cpus clearly show hyperthreading helps performance...

Regards

Mark


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