Re: Samba

[Neal H Walfield <neal@walfield.org>]

> Neal H Warfield wrote:
> > If we reimplement mach over an exokernel, it will only decrease
> > the microkernel's portability -- we now have a dependency on an
> > exokernel rather then a generic piece of hardware.
> 
> What's the difference?  Either you port the Mach microkernel or you port the
> exokernel.  In either case, you have localized machine dependent operations
> to a small portion of the overall system code.
> 
> The very goal of the exokernel design is to reduce the number of context
> switches required.
> 
> Check out the site at http://www.pdos.lcs.mit.edu/exo.html.  This gives a
> brief introduction.  They implemented a Web server on the kernel, called
> Cheetah, which ran eight times faster than NCSA.  You can also obtain
> volumes of information by going to www.mit.edu and doing a search on
> "exokernel."
> 

An exokernel is not a microkernel.  Although they both have similar
goals, minimize what the kernel has to do, they approach the problem
quite differently.  A microkernel attempts to manage the low level
resources and export an interface.  An exokernel, on the other hand,
merely wraps the resources in a security blanket and exports them to
the applications directly.  This would require a hurd library to provide
the current mach environment, which could increase context switches even
more.  This is, of course, all speculation; if you create a proof of
concept and prove me wrong, more power to you. It is my feelings that
to use an exokernel will require nearly all of the mach kernel to be
reimplemented over it, however, I am very interested in what your ideas
are.

Best regards,
-Neal

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Neal Walfield                                              neal@walfield.org
UMass Lowell - Fox 1512                                  Phone: 978-934-5347
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Love is the triumph of imagination over intelligence.
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