From: Jesper Krogh <jesper@krogh.cc>
To: James Cloos <cloos@jhcloos.com>
Cc: Glyn Astill <glynastill@yahoo.co.uk>
Cc: Steve Clark <sclark@netwolves.com>
Cc: david@lang.hm, 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: Tue, 12 Apr 2011 07:17:54 +0200
Message-ID: <4DA3E082.5040903@krogh.cc> (raw)
In-Reply-To: <m3k4f034k5.fsf@jhcloos.com>
References: <976931.36062.qm@web26004.mail.ukl.yahoo.com>
<m3k4f034k5.fsf@jhcloos.com>
On 2011-04-11 22:39, James Cloos wrote:
>>>>>> "GA" == Glyn Astill<glynastill@yahoo.co.uk> writes:
> GA> I was hoping someone had seen this sort of behaviour before,
> GA> and could offer some sort of explanation or advice.
>
> Jesper's reply is probably most on point as to the reason.
>
> I know that recent Opterons use some of their cache to better manage
> cache-coherency. I presum recent Xeons do so, too, but perhaps yours
> are not recent enough for that?
Better cache-coherence also benefits, but it does nothing to
the fact that remote DRAM fetches is way more expensive
than local ones. (Hard numbers to get excact nowadays).
--
Jesper
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To: pgsql-performance@postgresql.org
Cc: jesper@krogh.cc, cloos@jhcloos.com, glynastill@yahoo.co.uk, sclark@netwolves.com, scott.marlowe@gmail.com, jd@commandprompt.com, Kevin.Grittner@wicourts.gov
Subject: Re: Linux: more cores = less concurrency.
In-Reply-To: <4DA3E082.5040903@krogh.cc>
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