From owner-freebsd-questions Sun Apr 2 20: 2:31 2000 Delivered-To: freebsd-questions@freebsd.org Received: from implode.root.com (root.com [209.102.106.178]) by hub.freebsd.org (Postfix) with ESMTP id 0C22737BA6F for ; Sun, 2 Apr 2000 20:02:29 -0700 (PDT) (envelope-from dg@implode.root.com) Received: from implode.root.com (localhost [127.0.0.1]) by implode.root.com (8.8.8/8.8.5) with ESMTP id TAA07463; Sun, 2 Apr 2000 19:55:07 -0700 (PDT) Message-Id: <200004030255.TAA07463@implode.root.com> To: nino@inode.at Cc: questions@freebsd.org Subject: Re: tuning the vm system / disk cache In-reply-to: Your message of "Mon, 03 Apr 2000 04:43:19 +0200." <20000403044319.V31173@TK147108.telekabel.at> From: David Greenman Reply-To: dg@root.com Date: Sun, 02 Apr 2000 19:55:07 -0700 Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG >On Sun, Apr 02, 2000 at 07:09:52PM -0700, David Greenman wrote: >> I'm sure the system is already caching the entire file - evidence of this >> is the 438M of free memory, which the system would directly allocate from in >> order to cache the file. The only way I can explain the disk I/O is that there >> must be some writes taking place for some reason. > >You're right (of course). I checked Postgres' data directory and, >surprisingly, it writes temporary files for every query. Their filenames >begin with "pg_sorttemp", so the GROUP BY clause seems to be the culprit. > >Shouldn't it be possible to get rid of those disk accesses somehow? >These are very short-lived files, softupdates are enabled. -current/4.x-stable might behave better with the recent changes to reduce async write-behind. It all depends on the nature of the file writes and size of the file. This area is Matt Dillon's recent domain, so you may wish to discuss this with him. -DG David Greenman Co-founder/Principal Architect, The FreeBSD Project - http://www.freebsd.org Creator of high-performance Internet servers - http://www.terasolutions.com Pave the road of life with opportunities. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message