Re: hyperthreadin low performance

From: domenico febbo <mimmopasticcio(at)gmail(dot)com>
To: Mark Kirkwood <mark(dot)kirkwood(at)catalyst(dot)net(dot)nz>
Cc: David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, Jeison Bedoya Delgado <jeisonb(at)audifarma(dot)com(dot)co>, "pgsql-performance(at)postgresql(dot)org list" <pgsql-performance(at)postgresql(dot)org>
Subject: Re: hyperthreadin low performance
Date: 2015-07-23 11:37:29
Message-ID: CALqvQ1ND4YWvNBvgQ9g5PqC1GMvwbcGWjPgiFPP61rQDffA4dw@mail.gmail.com
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is the problem also in PostgreSQL 9.4.x?
I'm going to buy a production's server with 4 sockets E7-4850 12 cores
so 12*4 = 48 cores (and 96 threads using HT).

What do you suggest?
Using or not HT?

BR
Domenico

2015-07-21 11:07 GMT+02:00 Mark Kirkwood <mark(dot)kirkwood(at)catalyst(dot)net(dot)nz>:
> On 21/07/15 20:04, David Rowley wrote:
>>
>> On 21 July 2015 at 14:59, Jeison Bedoya Delgado
>> <jeisonb(at)audifarma(dot)com(dot)co <mailto:jeisonb(at)audifarma(dot)com(dot)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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