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Re: Microkernels (was Re: Sparc port?)

On Wed, Mar 10, 1999 at 10:36:58AM +1100, David McDonald wrote:
> "M.C. Vernon" wrote:
> > I (and some other Cambridge people) am of the opinion that the current
> > hurd doesn't get the maximum benefit out of it's microkernel design, and
> > one of the reasons is that its microkernel is not very micro. Sure, Mach
> > is smaller than linux, but it's still pretty big. I think this is because
> > it tries to do too much: things like IDE, SCSI and so on should IMHO be
> > servers: the microkernel should do as little as possible
> Not that my opinion should count for much, but I am inclined to agree with the
> above.
> QNX, a commercial/proprietary microkernel O/S does very little else other than
> message passing. Whilst it aims to service a different market (it is a real-time
> O/S), it is an excellent MK design (In my opinion at least). Hurd has the
> potential to go beyond QNX in terms of overall usefulness but a large
> MK does not seem to do anything of value towards achieving this.

The job of a microkernel is extremely simple: process accounting, resource
management, and DMA delegation to direct device drivers. DMA isn't really
the right term here, though, but something more along the lines of direct
register access to hardware.

This would make, say, the Ne2k (or other) network driver (or any other
device driver) run in userland, with direct access to the card's registers
and memory addresses. This driver, in turn, would adhere to an API spec, so
protocol translators (from userland) could be applied.

This is basic MK design philosophy. Even quota management for resources
moves to userland.

Now, you create three levels of processing: the kernel, the Hurd, and
userland. This affords extreme flexibility.

But, nobody can really claim there is enough interest in Hurd at this point
to chase after such an idealistic design philosophy.

..Aaron Van Couwenberghe... ..vanco@sonic.net.. ..aaronv@debian.org....
	Berlin:			http://www.berlin-consortium.org
	Debian GNU/Linux:	http://www.debian.org

"...Nothing astonishes men so much as common sense and plain dealing..."
	-- Ralph Waldo Emerson

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