X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (av.hub.org [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 4BFE4DA3A5 for ; Thu, 6 Oct 2005 10:23:49 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 95401-05 for ; Thu, 6 Oct 2005 13:23:40 +0000 (GMT) Received: from mx1.surnet.cl (mx2.surnet.cl [216.155.73.181]) by svr1.postgresql.org (Postfix) with ESMTP id 4CDB0DA394 for ; Thu, 6 Oct 2005 10:23:41 -0300 (ADT) Received: from unknown (HELO cluster.surnet.cl) ([216.155.73.165]) by mx1.surnet.cl with ESMTP; 06 Oct 2005 09:23:17 -0400 Received: from alvh.no-ip.org (200.85.218.5) by cluster.surnet.cl (7.0.043) (authenticated as alvherre@surnet.cl) id 433A601F001FA325; Thu, 6 Oct 2005 09:23:45 -0400 Received: by alvh.no-ip.org (Postfix, from userid 1000) id 7BBD6C2DC18; Thu, 6 Oct 2005 09:23:45 -0400 (CLT) Date: Thu, 6 Oct 2005 09:23:45 -0400 From: Alvaro Herrera To: Ian Westmacott Cc: "Thomas F. O'Connell" , pgsql-performance@postgresql.org Subject: Re: wal_buffers Message-ID: <20051006132345.GI5373@surnet.cl> Mail-Followup-To: Ian Westmacott , "Thomas F. O'Connell" , pgsql-performance@postgresql.org References: <1128518624.15795.28.camel@spectre.intellivid.com> <1128603390.18319.16.camel@spectre.intellivid.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1128603390.18319.16.camel@spectre.intellivid.com> User-Agent: Mutt/1.5.10i X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=1.999 required=5 tests=[AWL=-0.827, DNS_FROM_RFC_ABUSE=0.374, DNS_FROM_RFC_POST=1.376, FORGED_RCVD_HELO=0.05, RCVD_IN_NJABL_PROXY=1.026] X-Spam-Level: * X-Archive-Number: 200510/125 X-Sequence-Number: 14893 On Thu, Oct 06, 2005 at 08:56:31AM -0400, Ian Westmacott wrote: > On Thu, 2005-10-06 at 02:39, Thomas F. O'Connell wrote: > > The WAL Configuration chapter (25.2) has a pretty good discussion of > > how wal_buffers is used: > > > > http://www.postgresql.org/docs/8.0/static/wal-configuration.html > > > > You might also take a look at Josh Berkus' recent testing on this > > setting: > > > > http://www.powerpostgresql.com/ > > Thanks; I'd seen the documentation, but not Josh Berkus' > testing. > > For my part, I don't have a large number of concurrent > connections, only one. But it is doing large writes, > and XLogInsert is number 2 on the profile (with > LWLockAcquire and LWLockRelease close behind). I suppose > that is expected, but lead by the documentation I wanted > to make sure XLogInsert always had some buffer space to > play with. If you are using a single connection, you are wasting lots of cycles just waiting for the disk to spin. Were you to use multiple connections, some transactions could be doing some useful work while others are waiting for their transaction to be committed. -- Alvaro Herrera http://www.amazon.com/gp/registry/5ZYLFMCVHXC "I suspect most samba developers are already technically insane... Of course, since many of them are Australians, you can't tell." (L. Torvalds)