From: Greg Smith <gsmith@gregsmith.com>
To: Guillaume Smet <guillaume.smet@gmail.com>
Cc: pgsql-performance <pgsql-performance@postgresql.org>
Subject: Re: More shared buffers causes lower performances
Date: Wed, 26 Dec 2007 13:23:58 -0500 (EST)
Message-ID: <Pine.GSO.4.64.0712261316580.11546@westnet.com> (raw)
In-Reply-To: <1d4e0c10712260741w1f141fd6x2f482143d526ad48@mail.gmail.com>
References: <1d4e0c10712251606q6f9503deye3da4b68c51bf5e@mail.gmail.com>
<1198668065.4221.288.camel@ebony.site>
<1d4e0c10712260741w1f141fd6x2f482143d526ad48@mail.gmail.com>
On Wed, 26 Dec 2007, Guillaume Smet wrote:
> It's not checkpointing either as using pgbench-tools, I can see that
> tps and latency are quite stable during the entire run. Btw, thanks
> Greg for these nice tools.
I stole the graph idea from Mark Wong's DBT2 code and one of these days
I'll credit him appropriately.
> Then I decided to perform read-only tests using -S option (pgbench -S
> -s 100 -c 16 -t 30000 -U postgres bench). And still the same
> behaviour:
> shared_buffers=64MB : 20k tps
> shared_buffers=1024MB : 8k tps
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.
--
* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD
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To: pgsql-performance@postgresql.org
Cc: gsmith@gregsmith.com, guillaume.smet@gmail.com
Subject: Re: More shared buffers causes lower performances
In-Reply-To: <Pine.GSO.4.64.0712261316580.11546@westnet.com>
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