From owner-freebsd-hackers@FreeBSD.ORG Tue Mar 8 17:51:27 2005 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 4BC5616A4CF for ; Tue, 8 Mar 2005 17:51:27 +0000 (GMT) Received: from mail23.sea5.speakeasy.net (mail23.sea5.speakeasy.net [69.17.117.25]) by mx1.FreeBSD.org (Postfix) with ESMTP id EAEE543D64 for ; Tue, 8 Mar 2005 17:51:26 +0000 (GMT) (envelope-from jhb@FreeBSD.org) Received: (qmail 9285 invoked from network); 8 Mar 2005 17:51:26 -0000 Received: from server.baldwin.cx ([216.27.160.63]) (envelope-sender )AES256-SHA encrypted SMTP for ; 8 Mar 2005 17:51:25 -0000 Received: from [10.50.40.202] (gw1.twc.weather.com [216.133.140.1]) (authenticated bits=0) by server.baldwin.cx (8.13.1/8.13.1) with ESMTP id j28HpKHc030806; Tue, 8 Mar 2005 12:51:21 -0500 (EST) (envelope-from jhb@FreeBSD.org) From: John Baldwin To: freebsd-hackers@FreeBSD.org, kamalp@acm.org Date: Tue, 8 Mar 2005 11:28:34 -0500 User-Agent: KMail/1.6.2 References: <20050308162021.67813.qmail@web52702.mail.yahoo.com> In-Reply-To: <20050308162021.67813.qmail@web52702.mail.yahoo.com> MIME-Version: 1.0 Content-Disposition: inline Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <200503081128.34407.jhb@FreeBSD.org> X-Spam-Status: No, score=-102.8 required=4.2 tests=ALL_TRUSTED, USER_IN_WHITELIST autolearn=failed version=3.0.2 X-Spam-Checker-Version: SpamAssassin 3.0.2 (2004-11-16) on server.baldwin.cx cc: hackers@FreeBSD.org Subject: Re: using segmentation to manage memory in FreeBSD 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: Tue, 08 Mar 2005 17:51:27 -0000 On Tuesday 08 March 2005 11:20 am, Kamal R. Prasad wrote: > --- John Baldwin wrote: > > On Tuesday 08 March 2005 09:05 am, Ravi Krishna > > > > wrote: > > > Hi all! > > [snip] > > > Segments just provide a base + offset into the > > virtual address space that is > > backed by the TLB mappings, so to make this > > practically useful would be a lot > > more work than would first appear because your > > segments have to map virtually > > contiguous memory. > > If I had a processor with no MMU, but only memory > protection and a segment register, can I port freebsd > onto that architecture? I mean, use the segment > register to provide for non-conflicting process > spaces. Well, it is theoretically possible, yes, but practically speaking I'd think it would be a lot of work. The entire vm system assumes paging. If you had a way of emulating some rather large pages using segmentation then perhaps you could do that. -- John Baldwin <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve" = http://www.FreeBSD.org