Received: from localhost (unknown [200.46.204.183]) by postgresql.org (Postfix) with ESMTP id AE1032E3770 for ; Thu, 13 Dec 2007 14:52:30 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 89751-10 for ; Thu, 13 Dec 2007 14:52:28 -0400 (AST) Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by postgresql.org (Postfix) with ESMTP id F38572E3769 for ; Thu, 13 Dec 2007 14:52:27 -0400 (AST) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.14.1/8.14.1) with ESMTP id lBDIqM7k017874; Thu, 13 Dec 2007 13:52:22 -0500 (EST) To: Alvaro Herrera cc: Simon Riggs , Kevin Grittner , pgsql-performance@postgresql.org Subject: Re: Heavy write activity on first vacuum of fresh TOAST data In-reply-to: <20071213172656.GL6262@alvh.no-ip.org> References: <4760FF69.EE98.0025.0@wicourts.gov> <1197562283.4255.1829.camel@ebony.site> <476108F2.EE98.0025.0@wicourts.gov> <476108F2.EE98.0025.0@wicourts.gov> <13267.1197563721@sss.pgh.pa.us> <47610BF3.EE98.0025.0@wicourts.gov> <1197565242.4255.1853.camel@ebony.site> <20071213172656.GL6262@alvh.no-ip.org> Comments: In-reply-to Alvaro Herrera message dated "Thu, 13 Dec 2007 14:26:56 -0300" Date: Thu, 13 Dec 2007 13:52:22 -0500 Message-ID: <17873.1197571942@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200712/195 X-Sequence-Number: 28011 Alvaro Herrera writes: > Simon Riggs wrote: >> We might be able to have bgwriter set hint bits on dirty blocks, > I don't think that works, because the bgwriter has no access to the > catalogs, therefore it cannot examine the page contents. To bgwriter, > pages are opaque. Another issue is that this'd require bgwriter to access the clog SLRU area. I seem to remember worrying that that could lead to low-level deadlocks, though I cannot recall the exact case at the moment. Even without that, it would increase contention for SLRU, which we probably don't want. regards, tom lane