From: Josh Berkus <josh@agliodbs.com>
To: pgsql-performance@postgresql.org
Cc: Greg Smith <gsmith@gregsmith.com>
Cc: Peter Schuller <peter.schuller@infidyne.com>
Subject: Re: shared_buffers in 8.3 w/ lots of RAM on dedicated PG machine
Date: Fri, 15 Feb 2008 10:06:11 -0800
Message-ID: <200802151006.11858.josh@agliodbs.com> (raw)
In-Reply-To: <Pine.GSO.4.64.0802150916380.28161@westnet.com>
References: <20080215123528.GA16532@hyperion.scode.org>
<20080215135846.GA17327@hyperion.scode.org>
<Pine.GSO.4.64.0802150916380.28161@westnet.com>
On Friday 15 February 2008 06:29, Greg Smith wrote:
> PostgreSQL only uses direct I/O for writing to the WAL; everything else
> goes through the regular OS buffer cache unless you force it to do
> otherwise at the OS level (like some Solaris setups do with
> forcedirectio).
Also, note that even when direct I/O is available, most users and benchmark
tests have reported that having PostgreSQL "take over" the entire cache is
not a net performance gain. I believe this is mostly because our I/O and
caching code aren't designed for this kind of operation.
I believe that MyEmma had a different experience on their workload, though.
--
Josh Berkus
PostgreSQL @ Sun
San Francisco
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To: pgsql-performance@postgresql.org
Cc: josh@agliodbs.com, gsmith@gregsmith.com, peter.schuller@infidyne.com
Subject: Re: shared_buffers in 8.3 w/ lots of RAM on dedicated PG machine
In-Reply-To: <200802151006.11858.josh@agliodbs.com>
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