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Re: 2GB or not 2GB

From: Greg Smith <gsmith(at)gregsmith(dot)com>
To: Josh Berkus <josh(at)agliodbs(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: 2GB or not 2GB
Date: 2008-05-29 01:06:06
Message-ID: Pine.GSO.4.64.0805282042190.1115@westnet.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Wed, 28 May 2008, Josh Berkus wrote:

> shared_buffers:  according to witnesses, Greg Smith presented at East that
> based on PostgreSQL's buffer algorithms, buffers above 2GB would not
> really receive significant use.  However, Jignesh Shah has tested that on
> workloads with large numbers of connections, allocating up to 10GB
> improves performance.

Lies!  The only upper-limit for non-Windows platforms I mentioned was 
suggesting those recent tests at Sun showed a practical limit in the low 
multi-GB range.

I've run with 4GB usefully for one of the multi-TB systems I manage, the 
main index on the most frequently used table is 420GB and anything I can 
do to keep the most popular parts of that pegged in memory seems to help. 
I haven't tried to isolate the exact improvement going from 2GB to 4GB 
with benchmarks though.

--
* Greg Smith gsmith(at)gregsmith(dot)com http://www.gregsmith.com Baltimore, MD

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