From: | Greg Smith <gsmith(at)gregsmith(dot)com> |
---|---|
To: | Guillaume Smet <guillaume(dot)smet(at)gmail(dot)com> |
Cc: | pgsql-performance <pgsql-performance(at)postgresql(dot)org> |
Subject: | Re: More shared buffers causes lower performances |
Date: | 2007-12-26 18:23:58 |
Message-ID: | Pine.GSO.4.64.0712261316580.11546@westnet.com |
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Thread: | |
Lists: | pgsql-performance |
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(at)gregsmith(dot)com http://www.gregsmith.com Baltimore, MD
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