From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Lukes To: 9fans@cse.psu.edu Subject: Re: [9fans] authorization schemes (was CORBA) Content-Type: text/plain References: <20010926173932.25052.qmail@g.bio.cse.psu.edu> <034801c14748$5925ee40$a2b9c6d4@SOMA> <3BB3722D.2D77B4BE@null.net> In-Reply-To: <3BB3722D.2D77B4BE@null.net> MIME-Version: 1.0 Message-Id: <01100112110900.00795@luchie-chowchows.demon.co.uk> Content-Transfer-Encoding: 8bit Date: Mon, 1 Oct 2001 11:35:14 +0100 Topicbox-Message-UUID: f83ab69e-eac9-11e9-9e20-41e7f4b1d025 > Boyd Roberts wrote: > > vfork()? was the v for vomit? or vegetative ... > According to some of the Berkeleyites, there was a flaw in > the VAX-11/750 memory management unit (microcode?) such > that they were unable to use copy-on-write. Ummm ... correct me if I'm wrong, but a) didn't vfork exist before the 11/750? I certainly remember having 4.1BSD on a 780 a *long* time before we could buy 750s ... b) If you can do demand paging correctly, then you *must* be able to do COW somehow, albeit possibly horibly inefficiently: if necessary, you could do a similar hack to the one they used to fake the page-referenced bit e.g. turn off page access entirely, take the fault, see what kind of fault it was, do what's necessary based on the page type etc. All that is required is that the h/w report the access fault type correctly, and if it doesn't do that, then COW is the least of your problems ... > When I > mentioned this to the AT&T UNIX System V developers, they > said it seemed to work fine for them.. Well, ain't that strange:-) ... Cheers, Dave.