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Re: Samba

>                                                             I also know
> that, in a multiserver environment, the number of IPC messages required
> decreases performance, because each message operation involves an expensive
> context switch.

Although this is true for Mach, this is not necessarily true for all
multiserver microkernel implementations; it is _theoretically_ possible
to create a kernel which does not suffer this problem.

>                   MIT developed an "exokernel" a few years back, which
> essentially provided only an abstraction of the underlying hardware, leaving
> most traditional operating system services left to execute in user space.
> Wouldn't it be theoretically possible to implement Mach's process
> management, memory management, and IPC mechanisms as some form of protected
> programs running in user space on top of this "exokernel?"  I'm not asking
> anyone to work on this, or even look into it.  I'm just curious if such an
> approach even sounds plausible.

What do you think using an exokernel will gain us?

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.

Additionally, it will not increase performance; the current killer
with the hurd/mach is the number of context switches to do any amount
of work (look in the archives for a discussion of this topic).  Will
an exokernel decrease the number of context switches?  Unlikely,
however, I am open to suggestions.

> By the way, I understand it is a Hurd convention to make /usr a symbolic
> link to /.  May I ask why?

May I answer with a question.  What does usr do?


Neal Walfield                                              neal@walfield.org
UMass Lowell - Fox 1512                                  Phone: 978-934-5347
                                                           Fax: 603-415-3645
Love is the triumph of imagination over intelligence.
                -- H. L. Mencken

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