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Re: More shared buffers causes lower performances

From: "Guillaume Smet" <guillaume(dot)smet(at)gmail(dot)com>
To: "Greg Smith" <gsmith(at)gregsmith(dot)com>
Cc: pgsql-performance <pgsql-performance(at)postgresql(dot)org>
Subject: Re: More shared buffers causes lower performances
Date: 2007-12-26 21:52:04
Message-ID: 1d4e0c10712261352j2fbcd25ek1270331468d824b4@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Dec 26, 2007 7:23 PM, Greg Smith <gsmith(at)gregsmith(dot)com> wrote:
> Ah, now this is really interesting, as it rules out all the write
> components and should be easy to replicate even on a smaller server.  As
> you've already dumped a bunch of time into this the only other thing I
> would suggest checking is whether the same behavior also happens on 8.2 on
> your server.

Let's go with 8.2.5 on the same server (-s 100 / 16 clients / 50k
transactions per client / only read using -S option):
64MB: 33814 tps
512MB: 35833 tps
1024MB: 36986 tps
It's more consistent with what I expected.

I used PGDG RPMs compiled by Devrim for 8.2.5 and the ones I compiled
myself for 8.3b4 (based on the src.rpm of Devrim). I just asked Devrim
to build a set of x86_64 RPMs for 8.3b4 to see if it's not a
compilation problem (they were compiled on a brand new box freshly
installed so it would be a bit surprising but I want to be sure). He's
kindly uploading them right now so I'll work on new tests using his
RPMs.

I'll keep you informed of the results.

--
Guillaume

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