SunOS vs. Ultrix comparison

[Marcus J. Ranum]

 yfcw14 at castle.ed.ac.uk (K P Donnelly) writes:

#define NONPARTISAN_MODE

>I have heard that SunOS has "shareable libraries".  I am not sure
>what these are, but they sound very like the dynamic linking of object
>files at load time which Edinburgh University's EMAS operating system
>(now disappearing) has had for over ten years, and the lack of which I
>find intensely frustrating as I try to move our program libraries to
>Unix.  Makefiles are a very poor substitute.  Can anyone tell me whether
>SunOS shareable libraries are really that good, or whether Ultrix is
>likely to aquire anything similar.

	Ultrix is not going to have shareable libraries in the near
future, but OSF/1 will eventually. I'm not sure of time frames. Right
now, though, SunOs has 'em and Ultrix doesn't.

	What does that mean? It means that the size of your executable
under SunOs is smaller than under Ultrix, but otherwise it doesn't make
a whole huge difference, depending on the way you run your applications.
If you are running the same application a great deal, Ultrix' not
having shared libraries doesn't make a difference, because there's a
good chance that application will already be at least partially in
memory [eg: the shell, or mail, or something like that]. SunOs' libraries
are useful for keeping disk space usage down for binaries, and you can
get some situations where parts of your shared library are already
in memory when an application starts, and don't need to be reloaded,
so shared libraries can be a win. SunOs' virtual memory subsystem is
different from Ultrix', too - the buffer cache and virtual memory are
sharing a common pool, which means that SunOs machines tend to be a
little better performers as single-user workstations, and can get
ground down a little faster in a timesharing envionment, depending
very much on the applications you are running. [IE: on a Sun, when
your buddy's on your machine running something memory intensive he
is effectively stealing *your* I/O bandwidth, and vice versa].

	As far as Makefiles go - SunOs' shared libraries *act* just like
compiling and linking a normal executable - you still have to link it
just about the same way as you would under any other UNIX. I can't
recall if you need to relink applications or not if the shared library
is updated. There are some slight constraints required in your code if
you want to write position-independent code for your own shared libraries,
I think [unless that has changed since SunOs4.0].

>Another thing which I find frustrating as we try to move to Unix is the
>way that many utilities strip the eighth bit at every opportunity.  Does
>Ultrix have better 8-bit character set support, perhaps carried over
>from the DEC multinational character set on VMS?

	Ultrix is well-behaved about 8-bit data, and has a lot of nice
internationalization tools for supporting various character sets. I never
played with that part on a Sun.

mjr.