Received: from localhost (unknown [200.46.204.191]) by postgresql.org (Postfix) with ESMTP id 3DD0D2E00F0 for ; Fri, 14 Dec 2007 03:42:46 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.191]) (amavisd-maia, port 10024) with ESMTP id 31983-03 for ; Fri, 14 Dec 2007 03:42:46 -0400 (AST) Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by postgresql.org (Postfix) with ESMTP id 9C2732E30FF for ; Fri, 14 Dec 2007 03:42:43 -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 lBE7ggCC029186; Fri, 14 Dec 2007 02:42:42 -0500 (EST) To: Russell Smith cc: Simon Riggs , Kevin Grittner , pgsql-performance@postgresql.org Subject: Re: Heavy write activity on first vacuum of fresh TOAST data In-reply-to: <47623103.7030700@pws.com.au> References: <4760FF69.EE98.0025.0@wicourts.gov> <1197562283.4255.1829.camel@ebony.site> <47611B9D.EE98.0025.0@wicourts.gov> <1197569564.4255.1855.camel@ebony.site> <47614D86.EE98.0025.0@wicourts.gov> <1197582010.4255.1912.camel@ebony.site> <47623103.7030700@pws.com.au> Comments: In-reply-to Russell Smith message dated "Fri, 14 Dec 2007 18:30:11 +1100" Date: Fri, 14 Dec 2007 02:42:42 -0500 Message-ID: <29185.1197618162@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200712/207 X-Sequence-Number: 28023 Russell Smith writes: > Given vacuum must then touch every page, is there a win in only setting > hint bits on pages where vacuum has to do some other work on the page? > As vacuum is causing significant IO load for data that may not be > accessed for some time. Well, if vacuum doesn't do it then some other poor sod will have to. My feeling is that vacuum's purpose in life is to offload maintenance cycles from foreground queries, so we should be happy to have it setting all the hint bits. If Kevin doesn't like the resultant I/O load then he should use the vacuum_cost_delay parameters to dial down vacuum speed. regards, tom lane