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From: erics@sco.COM (eric smith)
Newsgroups: comp.sys.mac.system
Subject: Re: VM rule of thumb (sic)
Message-ID: <12384@scolex.sco.COM>
Date: 1 Jun 91 17:36:31 GMT
Article-I.D.: scolex.12384
References: <1991May30.132020.23146@xn.ll.mit.edu>
Sender: news@sco.COM
Organization: The Santa Cruz Operation, Inc.
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delaney@xn.ll.mit.edu (John R. Delaney) writes:

>And by the way, what we have on the Mac's right now strikes me as
>demand-paged memory, not virtual memory. But please, let's not start a
>"true virtual memory" thread to go along with the "true multi-tasking"
>thread.

Well since you started it .... :-)

From what I understand of VM on the Mac (I'm not running 7.0 yet)
it definitely is virtual memory and not demand paging. In demand paging,
an application's pages would not be read in from their original disk
location until they were accessed. Thus if a page was never used it would
never be read in at all. What I gather about the Mac's VM is that an
application is read in as before and also written to the special disk area
that contains the entire VM contents. Applications may then be swapped in
and out from there as needed, but I believe that the entire application
has to be in physical memory in order to run (correct me if I'm wrong).
In any case, the application must completely fit into the virtual space.
This is not demand paging.

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