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From: guy%gorodish@Sun.COM (Guy Harris)
Newsgroups: comp.arch,comp.unix.wizards,comp.os.misc
Subject: Re: Shared libraries (Was: Re: Big Programs Hurt Performance)
Message-ID: <29052@sun.uucp>
Date: Thu, 24-Sep-87 17:42:24 EDT
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Posted: Thu Sep 24 17:42:24 1987
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> How is COPYING the old shared libraries into executables which need 
> them ANY savings in disk usage?

If the sum of the disk size differences between the executables in question as
linked with the shared library and the executables in question as linked with
the unshared library is less than the size of the old shared library, it's
obviously going to save you disk space not to keep the old library around.  I
will not rule out this possibility out of hand.

> It seems it will be a DEAD LOSS: core (bigger executable images);

What do you mean by "core" here?  Do you mean "physical memory"?  Yes, shared
libraries will share physical memory better, but that has nothing to do with
the size of the executable image *per se*.  The smaller size of the image is,
in part, misleading; in order for the image to *run* it still needs to have the
shared libraries added in.

> virtual memory (it gets used up even if paged out);

Umm, images built without shared libraries will usually require *less* virtual
memory than ones built with shared libraries; the one built without shared
libraries doesn't include a whole pile of routines that it doesn't use.  That
stuff may be paged out, but you said "virtual memory", not "physical memory"
here.

> Why EVER have unsharable libraries???  

So that you can have a program with which to to back up to an old version of a
shared library if a new minor version has a bug in it (or if the file
containing the shared library got trashed, or if it got unlinked, or....)?
	Guy Harris
	{ihnp4, decvax, seismo, decwrl, ...}!sun!guy
	guy@sun.com