From owner-freebsd-current Tue Mar 21 1:12:31 2000 Delivered-To: freebsd-current@freebsd.org Received: from popserver-02.iinet.net.au (popserver-02.iinet.net.au [203.59.24.148]) by hub.freebsd.org (Postfix) with ESMTP id 600E537BA4E for ; Tue, 21 Mar 2000 01:12:01 -0800 (PST) (envelope-from julian@elischer.org) Received: from jules.elischer.org (reggae-01-126.nv.iinet.net.au [203.59.62.126]) by popserver-02.iinet.net.au (8.9.3/8.9.3) with SMTP id RAA12690; Tue, 21 Mar 2000 17:11:06 +0800 Message-ID: <38D73C75.15FB7483@elischer.org> Date: Tue, 21 Mar 2000 01:10:13 -0800 From: Julian Elischer X-Mailer: Mozilla 3.04Gold (X11; I; FreeBSD 5.0-CURRENT i386) MIME-Version: 1.0 To: Poul-Henning Kamp Cc: Matthew Dillon , current@FreeBSD.ORG Subject: Re: B_WRITE cleanup patch, please test! References: <21290.953589428@critter.freebsd.dk> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Poul-Henning Kamp wrote: > > In message <200003202129.NAA71883@apollo.backplane.com>, Matthew Dillon writes: > > I think the biggest win in regards to being able to arbitrarily stack > > devices is to NOT attempt to forward struct buf's between devices when > > non-trivial manipulation is required, and instead to make struct buf's > > cheap enough that a device can simply allocate a new one and copy the > > appropriate fields. > > > > In particular I really hate all the various b_*blkno fields. b_lblkno, > > b_blkno, and b_pblkno. It is precisely due to the existance of these > > hacks that arbitrary device stacking is difficult. > > This is basically what the stuff I'm doing addresses. I have been advocating since 1991 that the memory involved with IO should be referenced as a vector of page/offset/length triplets (physical addresses), and that all drivers should take that as input. IF he driver needs to do programmed IO only then should it map the page into KV space. > > -- > Poul-Henning Kamp FreeBSD coreteam member > phk@FreeBSD.ORG "Real hackers run -current on their laptop." > FreeBSD -- It will take a long time before progress goes too far! -- __--_|\ Julian Elischer / \ julian@elischer.org ( OZ ) World tour 2000 ---> X_.---._/ presently in: Perth v To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message