From owner-freebsd-hackers@FreeBSD.ORG Fri Feb 13 17:44:30 2004 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 252B116A4CE for ; Fri, 13 Feb 2004 17:44:30 -0800 (PST) Received: from tx0.oucs.ox.ac.uk (tx0.oucs.ox.ac.uk [129.67.1.163]) by mx1.FreeBSD.org (Postfix) with ESMTP id F362943D2F for ; Fri, 13 Feb 2004 17:44:29 -0800 (PST) (envelope-from colin.percival@wadham.ox.ac.uk) Received: from scan0.oucs.ox.ac.uk ([129.67.1.162] helo=localhost) by tx0.oucs.ox.ac.uk with esmtp (Exim 4.24) id 1Aror6-0005Eh-Fe for FreeBSD-Hackers@freebsd.org; Sat, 14 Feb 2004 01:44:28 +0000 Received: from rx0.oucs.ox.ac.uk ([129.67.1.161]) by localhost (scan0.oucs.ox.ac.uk [129.67.1.162]) (amavisd-new, port 25) with ESMTP id 19971-04 for ; Sat, 14 Feb 2004 01:44:28 +0000 (GMT) Received: from gateway.wadham.ox.ac.uk ([163.1.161.253]) by rx0.oucs.ox.ac.uk with smtp (Exim 4.24) id 1Aror6-0005Ec-2E for FreeBSD-Hackers@freebsd.org; Sat, 14 Feb 2004 01:44:28 +0000 Received: (qmail 30957 invoked by uid 0); 14 Feb 2004 01:44:28 -0000 Received: from colin.percival@wadham.ox.ac.uk by gateway by uid 71 with qmail-scanner-1.16 (sweep: 2.14/3.71. spamassassin: 2.53. Clear:. Processed in 1.464256 secs); 14 Feb 2004 01:44:28 -0000 X-Qmail-Scanner-Mail-From: colin.percival@wadham.ox.ac.uk via gateway X-Qmail-Scanner: 1.16 (Clear:. Processed in 1.464256 secs) Received: from dhcp1131.wadham.ox.ac.uk (HELO piii600.wadham.ox.ac.uk) (163.1.161.131) by gateway.wadham.ox.ac.uk with SMTP; 14 Feb 2004 01:44:26 -0000 Message-Id: <6.0.1.1.1.20040214014043.040c9d40@imap.sfu.ca> X-Sender: cperciva@imap.sfu.ca (Unverified) X-Mailer: QUALCOMM Windows Eudora Version 6.0.1.1 Date: Sat, 14 Feb 2004 01:44:24 +0000 To: Robert Watson From: Colin Percival In-Reply-To: References: <20040213160451.GB13347@hal9000.halplant.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; format=flowed cc: FreeBSD Hackers Subject: Re: malloc backed md/mfs filesystem swapped? X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 14 Feb 2004 01:44:30 -0000 At 00:56 14/02/2004, Robert Watson wrote: >If you >have swap available, you pretty much always want to use swap-backing for >memory disks -- if there's room in memory they will run as fast as >malloc-backed, but you don't have to be as worried about the "Oh shoot, >I'm out of room" case. Actually, there is one consideration: swap-backed memory disks have a sector size equal to the machine page size. This will result in some inflation in memory usage, and can confuse program which expect a sector size of 512 bytes (for example, dd, which I plan on fixing but I haven't gotten around to yet). Colin Percival