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From: blarson@skat.usc.edu.UUCP
Newsgroups: comp.arch,comp.os.misc
Subject: Re: Shared libraries (Was: Re: Big Programs Hurt Performance)
Message-ID: <4578@oberon.USC.EDU>
Date: Wed, 30-Sep-87 02:39:18 EDT
Article-I.D.: oberon.4578
Posted: Wed Sep 30 02:39:18 1987
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In article <2971@psuvax1.psu.edu> schwartz@gondor.psu.edu (Scott E. Schwartz) writes:
[some misinformation about Primos shared libraries]

Primos has had shared libraries for > 5 years.  Prior to Primos 19.4,
they only could be installed from the console, at a fixed address
determined by the system administrator.  Primos shared libraries are
implemented via an indirect call through a pointer to the routine name
with the fault bit set.  (Hardware support) The pointer is replaced by
one to the actual address, so future calls to the same function just
go through an additional level of inderection.  (The pointer must be
in the data section rather than the code section for EPFs.)

At Primos 19.4, an additional mechinism was added so additional
libraries could be searched, via a per-user library search list.  The
system administrator can modify the system wide default search rules.

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.

I seriously doubt any performance hit at Primos 20.0 can be attributed
to shared libraries, unless the system administrator made a serious
mistake in the default search rules.  It's hard to do a remote
diagnosis on limited information, but it sounds like the system has
inadiquate memory and/or problems related to the new disk format.
(Possibly due to improper installation of 20.0.)

Ps:  We went to Primos 21.0 for improved performance on one of our
large systems.
--
Bob Larson		Arpa: Blarson@Ecla.Usc.Edu
Uucp: {sdcrdcf,cit-vax}!oberon!skat!blarson		blarson@skat.usc.edu
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