From owner-freebsd-questions Mon Apr 3 1:14:15 2000 Delivered-To: freebsd-questions@freebsd.org Received: from dt051n0b.san.rr.com (dt051n0b.san.rr.com [204.210.32.11]) by hub.freebsd.org (Postfix) with ESMTP id C866437BC06 for ; Mon, 3 Apr 2000 01:14:12 -0700 (PDT) (envelope-from Doug@gorean.org) Received: from gorean.org (doug@master [10.0.0.2]) by dt051n0b.san.rr.com (8.9.3/8.9.3) with ESMTP id BAA96940; Mon, 3 Apr 2000 01:13:35 -0700 (PDT) (envelope-from Doug@gorean.org) Message-ID: <38E852AF.30CCEEE0@gorean.org> Date: Mon, 03 Apr 2000 01:13:35 -0700 From: Doug Barton Organization: Triborough Bridge & Tunnel Authority X-Mailer: Mozilla 4.72 [en] (X11; U; FreeBSD 5.0-CURRENT-0325 i386) X-Accept-Language: en MIME-Version: 1.0 To: nino@inode.at Cc: David Greenman , questions@freebsd.org Subject: Re: tuning the vm system / disk cache References: <20000403025556.S31173@TK147108.telekabel.at> <200004030209.TAA07259@implode.root.com> <20000403044319.V31173@TK147108.telekabel.at> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG "Marinos J . Yannikos" wrote: > > 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. This sounds like a textbook use of a memory filesystem. I've never set one up, but http://www.freebsd.org/handbook/disks-virtual.html looks promising. :) Good luck, Doug -- "So, the cows were part of a dream that dreamed itself into existence? Is that possible?" asked the student incredulously. The master simply replied, "Mu." To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message