Received: from maia.hub.org (unknown [200.46.204.183]) by mail.postgresql.org (Postfix) with ESMTP id 908566402FA for ; Tue, 16 Mar 2010 11:31:03 -0300 (ADT) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 22785-09 for ; Tue, 16 Mar 2010 14:30:52 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by mail.postgresql.org (Postfix) with ESMTP id DF4E96388A4 for ; Tue, 16 Mar 2010 11:30:52 -0300 (ADT) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.14.2/8.14.2) with ESMTP id o2GEUWIG008286; Tue, 16 Mar 2010 10:30:32 -0400 (EDT) To: "Pierre C" cc: "Greg Smith" , "Dave Crooke" , "Paul McGarry" , pgsql-performance@postgresql.org Subject: Re: shared_buffers advice In-reply-to: References: <4B9F3302.4020900@2ndquadrant.com> Comments: In-reply-to "Pierre C" message dated "Tue, 16 Mar 2010 12:24:40 +0100" Date: Tue, 16 Mar 2010 10:30:32 -0400 Message-ID: <8285.1268749832@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=-2.599 tagged_above=-10 required=5 tests=BAYES_00=-2.599 X-Spam-Level: X-Archive-Number: 201003/167 X-Sequence-Number: 37992 "Pierre C" writes: > Does PG issue checkpoint writes in "sorted" order ? No. IIRC, a patch for that was submitted, and rejected because no significant performance improvement could be demonstrated. We don't have enough information about the actual on-disk layout to be very intelligent about this, so it's better to just issue the writes and let the OS sort them. regards, tom lane