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From: lamaster@pioneer.arpa (Hugh LaMaster)
Newsgroups: comp.arch,comp.os.misc
Subject: Re: Shared libraries (Was: Re: Big Programs Hurt Performance)
Message-ID: <2933@ames.arpa>
Date: Wed, 31-Dec-69 18:59:59 EDT
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Posted: Wed Dec 31 18:59:59 1969
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In article <4578@oberon.USC.EDU> blarson@skat.usc.edu (Bob Larson) writes:

>
>These new shared libararies are a special case of EPFs.  EPFs are
>programs that are dynamicly linked into the user's address space (at a
>segment boundary) and are shared between users.  EPFs have been around
>since Primos 19.0, but were not documented and fully supported till
>Primos 19.4.

(repetitive disclaimer: virtual memory segments are NOT the same as 8086 or
PDP-11 segments).

I would add that the two level page table hardware and two level virtual
memory structure, permitting shared virtual memory segments, works so well
that it is a disappointment to me that not everyone does it.  Another possible
implementation of shared libraries using shared segments: map library code
directly onto a shared virtual memory segment.  Shared pages of the same
dataset need only one copy; if a different, (older) version of the dataset is
specified as a library, its pages are used.  User programs can share pages
without intervention of a system manager; nothing needs to be "installed".
Compare to what VMS gives you with global sections...




  Hugh LaMaster, m/s 233-9,  UUCP {topaz,lll-crg,ucbvax}!
  NASA Ames Research Center                ames!pioneer!lamaster
  Moffett Field, CA 94035    ARPA lamaster@ames-pioneer.arpa
  Phone:  (415)694-6117      ARPA lamaster@pioneer.arc.nasa.gov

(Disclaimer: "All opinions solely the author's responsibility")