*BSD News Article 27940


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From: tinguely@plains.NoDak.edu (Mark Tinguely)
Subject: Re: Notes on the *new* FreeBSD V1.1 VM system
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Date: Sat, 26 Feb 1994 05:09:48 GMT
References: <2khcvv$han@u.cc.utah.edu> <CLqK5I.IzH@ns1.nodak.edu> <wimlCLrCxo.Fvx@netcom.com>
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In article <wimlCLrCxo.Fvx@netcom.com> wiml@netcom.com (William Lewis) writes:
>Why can't demand-paged executables act like any other open file? It might

 this was talked about a long time ago. major problem is in writing to
 executable files (there are no problems in removing or moving a running
 process). to fix the problems changes would have to be done to write,
 the pagers and the vnodes and still this would not solve the NFS problem.

 There was even talk about the need for VM and file buffer consistancy
 where copy-on-writes could be used to take care of some problems on a per
 page level not on a per file level.

 in the end, we took the minimum solution rationalizing the decision by saying
 that this situation does not happen too often, and we have bigger fires in the
 VM to fix. real-soon-now, the time would be available to fix this right.

 to solve it, going back to the traditional swap model of all running
 applications have their text in backstore, would fix all of these problems,
 but at an expense (note: a comment of bias).

 using the filesystem to hold the text of the running processes will require
 something more encompassing that the current text busy flag. there are a
 few connecting concerns to fix all these problems connecting filesystems and
 VM.

 I am glad that Terry does the evangelical work on this and many other topics.

--mark.