Received: from localhost (unknown [200.46.204.183]) by developer.postgresql.org (Postfix) with ESMTP id EC13A2E006F for ; Wed, 28 May 2008 22:19:11 -0300 (ADT) Received: from developer.postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 52711-01-3 for ; Wed, 28 May 2008 22:18:51 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from westnet.com (westnet.com [216.187.52.2]) by developer.postgresql.org (Postfix) with ESMTP id 449F42E0084 for ; Wed, 28 May 2008 22:06:11 -0300 (ADT) Received: from westnet.com (localhost [127.0.0.1]) by westnet.com (8.14.0/8.14.0) with ESMTP id m4T167Rd005502; Wed, 28 May 2008 21:06:07 -0400 (EDT) Received: from localhost (gsmith@localhost) by westnet.com (8.14.0/8.13.2/Submit) with ESMTP id m4T1660Q005499; Wed, 28 May 2008 21:06:07 -0400 (EDT) X-Authentication-Warning: westnet.com: gsmith owned process doing -bs Date: Wed, 28 May 2008 21:06:06 -0400 (EDT) From: Greg Smith X-X-Sender: gsmith@westnet.com To: Josh Berkus cc: pgsql-performance@postgresql.org Subject: Re: 2GB or not 2GB In-Reply-To: <200805281659.26945.josh@agliodbs.com> Message-ID: References: <200805281659.26945.josh@agliodbs.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200805/363 X-Sequence-Number: 30331 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@gregsmith.com http://www.gregsmith.com Baltimore, MD