From owner-freebsd-amd64@FreeBSD.ORG Mon May 23 23:30:03 2005 Return-Path: X-Original-To: freebsd-amd64@freebsd.org Delivered-To: freebsd-amd64@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id E919516A41C for ; Mon, 23 May 2005 23:30:03 +0000 (GMT) (envelope-from jmg@hydrogen.funkthat.com) Received: from mail24.sea5.speakeasy.net (mail24.sea5.speakeasy.net [69.17.117.26]) by mx1.FreeBSD.org (Postfix) with ESMTP id 48B3A43D53 for ; Mon, 23 May 2005 23:30:03 +0000 (GMT) (envelope-from jmg@hydrogen.funkthat.com) Received: (qmail 23690 invoked from network); 23 May 2005 23:30:03 -0000 Received: by simscan 1.1.0 ppid: 23670, pid: 23684, t: 0.1334s scanners: clamav: 0.84/m:31/d:888 Received: from gate.funkthat.com (HELO hydrogen.funkthat.com) ([69.17.45.168]) (envelope-sender ) by mail24.sea5.speakeasy.net (qmail-ldap-1.03) with SMTP for ; 23 May 2005 23:30:02 -0000 Received: from hydrogen.funkthat.com (yrozoh@localhost.funkthat.com [127.0.0.1]) by hydrogen.funkthat.com (8.12.10/8.11.6) with ESMTP id j4NNU22g086135; Mon, 23 May 2005 16:30:02 -0700 (PDT) (envelope-from jmg@hydrogen.funkthat.com) Received: (from jmg@localhost) by hydrogen.funkthat.com (8.12.10/8.12.10/Submit) id j4NNTngu086116; Mon, 23 May 2005 16:29:49 -0700 (PDT) Date: Mon, 23 May 2005 16:29:49 -0700 From: John-Mark Gurney To: Vivek Khera Message-ID: <20050523232948.GJ959@funkthat.com> Mail-Followup-To: Vivek Khera , freebsd-amd64@freebsd.org, freebsd-stable@freebsd.org References: <1116860293.10083.43.camel@lanshark.dmv.com> <20050523174415.GI959@funkthat.com> <1F46458B-2524-42AB-8B3D-0F54F485241B@khera.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1F46458B-2524-42AB-8B3D-0F54F485241B@khera.org> User-Agent: Mutt/1.4.1i X-Operating-System: FreeBSD 4.2-RELEASE i386 X-PGP-Fingerprint: B7 EC EF F8 AE ED A7 31 96 7A 22 B3 D8 56 36 F4 X-Files: The truth is out there X-URL: http://resnet.uoregon.edu/~gurney_j/ X-Resume: http://resnet.uoregon.edu/~gurney_j/resume.html Cc: freebsd-stable@freebsd.org, freebsd-amd64@freebsd.org Subject: Re: Manipulating disk cache (buf) settings X-BeenThere: freebsd-amd64@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: John-Mark Gurney List-Id: Porting FreeBSD to the AMD64 platform List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 23 May 2005 23:30:04 -0000 Vivek Khera wrote this message on Mon, May 23, 2005 at 17:17 -0400: > On May 23, 2005, at 1:44 PM, John-Mark Gurney wrote: > > >This is incorrect... FreeBSD merged the vm and buf systems a while > >back, > >so all of memory is used as a disk cache.. The buf cache is still > >used > >for filesystem meta data (and for pending writes of files, but > >those buf's > >reference the original page, not local storage)... > > > > Cool... So what would you recommend telling an application like > Postgres what the cache size is? All of RAM? That seems unlikely > given much of the ram is used for other things. Is there no upper > bound in how much RAM will be used for the cache? I'm not familar host Postgres uses the cache number to change it's behavior, but I would say choose a responable amount of memory that you expect to regularly have available on the system... If you are only using it for db, and a few other small processes, 512meg less than ram is probably reasonable... The other way is to try a few different values and see how it impacts performance.. -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."