Received: from maia.hub.org (maia-2.hub.org [200.46.204.251]) by mail.postgresql.org (Postfix) with ESMTP id 388841337B63 for ; Wed, 27 Oct 2010 19:45:12 -0300 (ADT) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.204.251]) (amavisd-maia, port 10024) with ESMTP id 83974-05 for ; Wed, 27 Oct 2010 22:45:05 +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 CC3A01337B5C for ; Wed, 27 Oct 2010 19:45:04 -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 o9RMixEB029869; Wed, 27 Oct 2010 18:44:59 -0400 (EDT) To: Brad Nicholson cc: Greg Smith , =?ISO-8859-1?Q?Andr=E9_Volpato?= , pgsql-performance@postgresql.org Subject: Re: AIX slow buffer reads In-reply-to: <4CC8A9A3.7060901@ca.afilias.info> References: <1141414014.10692.1288199109474.JavaMail.root@zimbra01a> <4CC87C69.5070301@2ndquadrant.com> <26542.1288210215@sss.pgh.pa.us> <4CC8A9A3.7060901@ca.afilias.info> Comments: In-reply-to Brad Nicholson message dated "Wed, 27 Oct 2010 18:37:23 -0400" Date: Wed, 27 Oct 2010 18:44:59 -0400 Message-ID: <29868.1288219499@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=-1.91 tagged_above=-10 required=5 tests=BAYES_00=-1.9, T_RP_MATCHES_RCVD=-0.01 X-Spam-Level: X-Archive-Number: 201010/521 X-Sequence-Number: 40939 Brad Nicholson writes: > On 10/27/2010 4:10 PM, Tom Lane wrote: >> AFAICT from googling, AIX does have posix_fadvise, though maybe it >> doesn't do anything useful ... > If there is an easy way to check if it does do anything useful? If so, > I can check it out. If you don't see any performance change in bitmap scans between effective_io_concurrency = 0 and effective_io_concurrency = maybe 4 or so, then you could probably conclude it's a no-op. regards, tom lane