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Path: sserve!newshost.anu.edu.au!munnari.oz.au!bunyip.cc.uq.oz.au!harbinger.cc.monash.edu.au!msuinfo!agate!howland.reston.ans.net!noc.near.net!news.delphi.com!usenet From: John Dyson <dysonj@delphi.com> Newsgroups: comp.os.386bsd.questions Subject: Re: 16 MB RAM and Adaptec 1542C Date: Mon, 27 Jun 94 12:03:28 -0500 Organization: Delphi (info@delphi.com email, 800-695-4005 voice) Lines: 29 Message-ID: <ZSwyApw.dysonj@delphi.com> References: <2udhe3$ofk@toads.pgh.pa.us> <mldCrxqM7.7wp@netcom.com> <mldCrzoI2.BLw@netcom.com> <JKH.94Jun26140411@whisker.hubbard.ie> <Cs1oyv.Hzz@demon.co.uk> NNTP-Posting-Host: bos1d.delphi.com X-To: Ronald Khoo <ronald@demon.co.uk> Ronald Khoo <ronald@demon.co.uk> writes: >Is anyone going to retrofit this into NetBSD ? The FreeBSD bounce buffer code (that I wrote) has *very* low overhead and only requires the addition of 3-4 lines of code to the driver. Actually, it only *really* requires one line of code in the driver. The bouncing only happens on pages that need to be bounced -- and works by fooling the driver by leveraging the VM system against the problem. The bounce code is actually very simple and am suprised that it has not been added sooner. We did have some bugs in it (on FreeBSD-current), but mostly were a result of a brain-fart on my part. All of the VM/Bounce enhancements already reside in the FreeBSD 4.4-lite kernel tree (and they work very well.) Also, we have a running merged VM/buffer-cache vfs_io subsystem now (and it works very well.) It has some *very* interesting algorithms to minimize the thrashing problems associated with such merged VM/buffer cache systems. (The algorithms are interesting -- because they are simple.) Most all of such enhancements in FreeBSD are both architecture independent and (attempted) elegant. We are *really* trying to be innovative on the FreeBSD kernel development, and have been focusing on the i386 architecture otherwise it would defocus us on the kernel enhancements that *BSD desperately needs. V2.0 (4.4-lite) will have all of the old FreeBSD stuff (fully unencumbered and based directly on 4.4-lite and not Net/2) and a fully coherent VM/buffer-cache. John dyson@implode.root.com