From owner-freebsd-hackers Sun Feb 23 2:35:44 2003 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 14D2737B407 for ; Sun, 23 Feb 2003 02:35:43 -0800 (PST) Received: from phoenix.infradead.org (phoenix.infradead.org [195.224.96.167]) by mx1.FreeBSD.org (Postfix) with ESMTP id E5F6D43FCB for ; Sun, 23 Feb 2003 02:35:41 -0800 (PST) (envelope-from hch@infradead.org) Received: from hch by phoenix.infradead.org with local (Exim 4.10) id 18mtTt-0004Aq-00; Sun, 23 Feb 2003 10:35:37 +0000 Date: Sun, 23 Feb 2003 10:35:37 +0000 From: Christoph Hellwig To: Terry Lambert Cc: Byunghyun Oh , freebsd-hackers@freebsd.org Subject: Re: Replacement for get_user_pages() of Linux Message-ID: <20030223103537.A16012@infradead.org> References: <20030223163746.A19421@shell.postech.ac.kr> <3E588B1B.484C4D61@mindspring.com> <20030223094958.A15347@infradead.org> <3E589FB3.46C1AAB2@mindspring.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5.1i In-Reply-To: <3E589FB3.46C1AAB2@mindspring.com>; from tlambert2@mindspring.com on Sun, Feb 23, 2003 at 02:17:23AM -0800 Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On Sun, Feb 23, 2003 at 02:17:23AM -0800, Terry Lambert wrote: > OK, you mean "make non-pageable". Well, I didn't write the initial mail :) > The question, I guess, is "why?". Are you trying to do a delayed > operation that will complete when the process has otherwise been > swapped out? well, I don't plan to do anything. The usual way get_user_pages is used on linux is: get_user_pages() perform scatter gatter dma to some device on the pages unping pages as linux VM scanning is fully mutithreaded pages could get paged out during the dma if you didn't pin them so this is needed. > > get_user_pages() does not establish a mapping, in Linux you don't need > > a kernel mapping to perform DMA on memory. > > In FreeBSD, you generally do. First off, the VM and buffer cache is > unified. That means that's there's no such thing as a buffer that > exists seperately from the VM system. Who talks about buffers? And yes, in Linux you can have buffers that have pages attached to it that aren't mapped into kernel virtual space, in fact that's usual for pages used for actual filesystem data if you have enough memory. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message