Date: Wed, 14 Feb 1996 09:58:16 -0500 (EST) From: "Ron G. Minnich" <rminnich@Sarnoff.COM> To: hackers@FreeBSD.org Subject: Re: VM question Message-ID: <Pine.SUN.3.91.960214095357.10107B-100000@terra> In-Reply-To: <3121D613.C680.001@pmail.tepco.co.jp>
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> Actually, I'd like to implement a sort of DSM that provides
> page-in/out over the network transparently to the user process.
well, having done some of these myself I can tell you: the freebsd signal
handling code is not quite there and so won't tell you what you need to
know when a sigsegv/sigbus happens, to wit: you can't tell what type of
fault occurred (read or write). It is now giving you the faulting virtual
address, which is an improvement.
also, the vm does not quite work right in terms of communicating needed
information to the lower-level layers so that information is not
available there also. For a view of how to do this right, check out the
sunos vm (just look in the include files for protos of getpage/putpage
etc.). No bsd unix has done this right for DSM, and neither has linux,
which is a shame.
IF you want to write a DSM to learn how to do it, go for it. If you just
want one you have a couple choices:
1) basic DSM with no coherency support: use NFS shared mapped files over
the net
2) Add simple coherency support: many options:
1) use my MNFS, except due to aforementioned VM/VFS problems it does
not work completely
2) add a tcp connection to support coherency traffic
ron
ron
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