Message-ID: <55B30C36.1090607@catalyst.net.nz>
Date: Sat, 25 Jul 2015 16:10:30 +1200
From: Mark Kirkwood <mark.kirkwood@catalyst.net.nz>
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To: domenico febbo <mimmopasticcio@gmail.com>
CC: David Rowley <david.rowley@2ndquadrant.com>,
 Jeison Bedoya Delgado <jeisonb@audifarma.com.co>,
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Subject: Re: hyperthreadin low performance
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On 23/07/15 23:37, domenico febbo wrote:
> 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?
>

 From my experience 9.4 is considerably better (we are using it on the 
60 core box mentioned prev).

48 cores should be fine, enabling HT and asking Postgres to effectively 
handle 96 could provoke issues. However it is reasonably easy to test - 
tune shared_buffers and checkpoint segments sensibly and run pgbench for 
a steadily increasing number of clients. With 48 cores you should 
(hopefully) see a tps curve that increases and then gently flattens off 
somewhere. If 96 cores are "too many" then you will see a tps curve that 
initially increases then sharply drops.

Cheers

Mark


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