Re: hyperthreadin low performance

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