From: Glyn Astill <glynastill@yahoo.co.uk>
To: Steve Clark <sclark@netwolves.com>
To: david@lang.hm
Cc: Scott Marlowe <scott.marlowe@gmail.com>
Cc: Joshua D. Drake <jd@commandprompt.com>
Cc: Kevin Grittner <Kevin.Grittner@wicourts.gov>
Cc: pgsql-performance@postgresql.org
Subject: Re: Linux: more cores = less concurrency.
Date: Mon, 11 Apr 2011 21:17:04 +0100 (BST)
Message-ID: <976931.36062.qm@web26004.mail.ukl.yahoo.com> (raw)
In-Reply-To: <alpine.DEB.2.00.1104111259350.32165@asgard.lang.hm>
--- On Mon, 11/4/11, david@lang.hm <david@lang.hm> wrote:
> From: david@lang.hm <david@lang.hm>
> Subject: Re: [PERFORM] Linux: more cores = less concurrency.
> To: "Steve Clark" <sclark@netwolves.com>
> Cc: "Scott Marlowe" <scott.marlowe@gmail.com>, "Joshua D. Drake" <jd@commandprompt.com>, "Kevin Grittner" <Kevin.Grittner@wicourts.gov>, pgsql-performance@postgresql.org, "Glyn Astill" <glynastill@yahoo.co.uk>
> Date: Monday, 11 April, 2011, 21:04
> On Mon, 11 Apr 2011, Steve Clark
> wrote:
>
> the limit isn't 8 cores, it's that the hyperthreaded cores
> don't work well with the postgres access patterns.
>
This has nothing to do with hyperthreading. I have a hyperthreaded benchmark purely for completion, but can we please forget about it.
The issue I'm seeing is that 8 real cores outperform 16 real cores, which outperform 32 real cores under high concurrency.
32 cores is much faster than 8 when I have relatively few clients, but as the number of clients is scaled up 8 cores wins outright.
I was hoping someone had seen this sort of behaviour before, and could offer some sort of explanation or advice.
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To: pgsql-performance@postgresql.org
Cc: glynastill@yahoo.co.uk, sclark@netwolves.com, david@lang.hm, scott.marlowe@gmail.com, jd@commandprompt.com, Kevin.Grittner@wicourts.gov
Subject: Re: Linux: more cores = less concurrency.
In-Reply-To: <976931.36062.qm@web26004.mail.ukl.yahoo.com>
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