W91 USENIX in retrospect

[terri_watson at cis.ohio-state.edu]

Well, I won't really summarize any papers, but I might encourage some
discussion on the kernel panel session.  I found it interesting and
slightly entertaining.

The main theme was micro vs. monolithic kernel design <or the lack
thereof :>.

what should be in the kernel?  is it better to have "everything you
ever wanted + the kitchen sink" in there to minimize context switching
etc, or would you rather move it into user space for "clean structure"
and "modularity" but pay a penalty for messages etc, or what about
separate components that can be tested in user space, but moved into
kernel space for increased efficiency?

obviously, not all the pros & cons are listed above, but this is a
sample of the talk(/discussion/argument/<meta-del> -- argument?  did
_I_ say that?).

other phrases included importance of "glue" between the boxes -- how
do you connect the components together?  

large kernels:
are "large" kernels inherently bad?  or is it just that they weren't
designed properly?  could they be designed properly?  can they be made
to work on new architectures with parallelism & distributed environs
effectively?

micro kernels:
do you have to pay a severe penalty for message passing?  are they
easier to debug?  more flexible?  one argument is that such kernels
are more effective in providing mechanism, not policy

how many primitives should be in the kernel?  

One point that was made near the end of the discussion was that some
of the conflict seemed to arise from the style of computing that the
user preferred, single machine/board based, or more distributed.
Should a user want to share "his" machines resources with others?
(Personally, I would say emphatically YES in the general case, but
apparently some there were not of the same opinion.  For those of us
with no money to buy many machines of our own, the thought of stealing
idle cycles from hundreds of other machines is immensely appealing.
<grin>)

Terri Watson
The Ohio State University
elf at cis.ohio-state.edu