Subject: About paging Date: Thu, 14 Nov 1991 10:02:06 +0100 From: kw@dde.dk (Kurt Wachmann)
One tiny question first:
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* Any pointers to a working ftp mailserver?? I can't ftp!! *
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About swapping/paging:
I think demand paged virtual memory is a requirement for a
real OS. No more crammed "just a bit better than DOS" OS'es,
please! After all, disk memory is still cheaper than RAM.
Peter MacDonald asks if it's possible to demand pages from the
load-module: yes in deed. This is done in lots of commercial
systems; one reason being the startup time for large applica --
tions; e.g. emacs :-). You only need a few pages of 4kb to
start the monster. The system will seem much faster.
For this to work properly, a few things are needed. For in --
stance, the code segment of the load module must start at a
block boundary in the file system, eg. offset 2kb from the
start.
The file system must also be fast - pointers to physical disk
locations should be kept in RAM - in this way, it will not be
(much) slower than reading from a swap-disk.
Of course the load module must be locked while it's being
executed.
I still think we need to be able to swap out data - think
about running X-applications, with tons of data almost never
being used.
Kind regards
Kurt \/\/achmann, M.Sc. EE/SE