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From: crowl@rochester.ARPA (Lawrence Crowl)
Newsgroups: comp.sys.intel
Subject: Re: comp.sys.intel
Message-ID: <22595@rochester.ARPA>
Date: Thu, 20-Nov-86 15:53:11 EST
Article-I.D.: rocheste.22595
Posted: Thu Nov 20 15:53:11 1986
Date-Received: Thu, 20-Nov-86 23:22:12 EST
References: <110@wldrdg.UUCP> <13772@amdcad.UUCP> <111@wldrdg.UUCP> <13801@amdcad.UUCP> <2971@rsch.WISC.EDU>
Reply-To: crowl@rochester.UUCP (Lawrence Crowl)
Distribution: na
Organization: U of Rochester, CS Dept, Rochester, NY
Lines: 24

In article <2971@rsch.WISC.EDU> mcvoy@rsch.WISC.EDU (Lawrence W. McVoy) writes:
>2) OK, a better question:  suppose my process forks (spawns a child) ...
>   In other words, I want to take the section of memory with virtual
>   addresses 0x01ffff to 0xffffff and have that shared.  Can this be
>   __easily__ done with the 386 memory management?  Seems like it 
>   would be a nice thing to support.  Don't forget, there may be 
>   valid data addresses both above and below the segment in question;
>   you can't split it into two, have to go to three chunks.

This is a biased question.  It askes "how do I use segments to share a portion
of my linear address space?"  The answer is that with segments you don't share
portions of your linear address space, you share collections of data contained
entirely within segments.  You would place the data you want to share in its
own segment and share the segment instead of carefully placing your data at a
known location in your linear address space and then sharing those locations.

Consider, suppose I want to share addresses 0x10010 through 0x10020, but MUST
NOT share 0x10000 through 0x1000F or 0x10021 through 0x20000.  How am I going
to do this in a paged virtual address space, assuming pages are 1 Kb large.
Don't scream "unfair", because it is the same question in a different guise.
-- 
  Lawrence Crowl		716-275-5766	University of Rochester
			crowl@rochester.arpa	Computer Science Department
 ...!{allegra,decvax,seismo}!rochester!crowl	Rochester, New York,  14627