From owner-freebsd-hackers Tue Jan 5 15:09:49 1999 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id PAA27473 for freebsd-hackers-outgoing; Tue, 5 Jan 1999 15:09:49 -0800 (PST) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from apollo.backplane.com (apollo.backplane.com [209.157.86.2]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id PAA27463 for ; Tue, 5 Jan 1999 15:09:45 -0800 (PST) (envelope-from dillon@apollo.backplane.com) Received: (from dillon@localhost) by apollo.backplane.com (8.9.1/8.9.1) id PAA98255; Tue, 5 Jan 1999 15:08:57 -0800 (PST) (envelope-from dillon) Date: Tue, 5 Jan 1999 15:08:57 -0800 (PST) From: Matthew Dillon Message-Id: <199901052308.PAA98255@apollo.backplane.com> To: Terry Lambert Cc: dyson@iquest.net, tlambert@primenet.com, pfgiffun@bachue.usc.unal.edu.co, freebsd-hackers@FreeBSD.ORG Subject: Re: questions/problems with vm_fault() in Stable References: <199901051847.LAA10199@usr02.primenet.com> Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG :> had historically been split between VFS and VM, and the interfaces were :> defined without both parties understanding the needs. Since that is :> understood now, things should be reworked. : :Hmmm. : :I don't really buy this for the general case, which I believe is :still stacking layers that don't access local media. : :For local media FS's, things which actially do I/O through a page :fault, this is probably correct. Ouch.. no, get away from the 'local media' concept - it's a big time bust. If you make the distinction between hard media and soft media (or local media verses remote media), all you do is screw up the layering model. Even now, traditional hard-media-backed VFS layers such as UFS can be stacked on top of soft media layers such as MFS, which in turn is stacked on top of SWAP (which may be a hard or soft media layer itself). If you throw NFS into the fray it gets worse. It just doesn't work. Also, these sorts of schemes require both interacting VFS layers to have knowledge about each other that goes far beyond what two layers ought to know about each other. -Matt : Terry Lambert : terry@lambert.org :--- Matthew Dillon Engineering, HiWay Technologies, Inc. & BEST Internet Communications & God knows what else. (Please include original email in any response) To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message