From owner-freebsd-current Mon Dec 27 16:27: 7 1999 Delivered-To: freebsd-current@freebsd.org Received: from apollo.backplane.com (apollo.backplane.com [216.240.41.2]) by hub.freebsd.org (Postfix) with ESMTP id D99201529C for ; Mon, 27 Dec 1999 16:27:03 -0800 (PST) (envelope-from dillon@apollo.backplane.com) Received: (from dillon@localhost) by apollo.backplane.com (8.9.3/8.9.1) id QAA34572; Mon, 27 Dec 1999 16:26:59 -0800 (PST) (envelope-from dillon) Date: Mon, 27 Dec 1999 16:26:59 -0800 (PST) From: Matthew Dillon Message-Id: <199912280026.QAA34572@apollo.backplane.com> To: Poul-Henning Kamp Cc: freebsd-current@FreeBSD.ORG Subject: Re: Proposed patch to fix VN device (again) References: <7427.946340596@critter.freebsd.dk> Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG : :In message <199912280012.QAA34430@apollo.backplane.com>, Matthew Dillon writes: : :> Sigh. Ok, I've fixed the VN device. Again. It looks like the removal of :> /dev/drum removed a little too much. We need the device infrastructure :> to support the VN device's use of swap backing store. :> :> This patch below is a commit candidate. It could use a review, then I'll :> commit it. : :Could you please explain why you need this ? : :-- :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! VN calls vm_pager_strategy() which collects I/O in filesystem buffers (bp)'s in order to cluster the I/O, and you cannot initiate I/O on filesystem buffers without a valid b_dev. So, the jist of the problem is that in order to get reasonable performance out of the thing (i.e. not issue 4K I/O's to the disk), we have to use filesystem buffers which means the bp must be properly initialized. -Matt Matthew Dillon To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message