Re: Tasks list for GNU Mach

[Ashish Gokhale]

Hi All,
Is it possible to compare L4 and Mach side-by-side and
have list of features that are there in L4? Is the
design of Mach flawed or is it the implementation that
lacks the original vision? Or the focus is changing
too fast from one option to the other ? 

- Ashish

--- olafBuddenhagen@gmx.net wrote:

> Hi,
> 
> > please excuse my ignorance, but what's the Status
> of GNU Mach? I heard
> > the L4 microkernel is favored for the Hurd. Do you
> guys try to catch
> > up?
> 
> Well, the question is, favored by whom? It's
> actually quite a long
> story, and also I weren't around to get all of it
> first hand; but I'll
> try to sum up what I was able to gather.
> 
> A couple of years ago, Marcus (and some others),
> more and more exposed
> to the problems in Mach, made the claim that
> Hurd/Mach has no future,
> and further developement should be directed to a
> port to a modern
> microkernel like L4. This wasn't really surprising,
> as today it's widely
> known that Mach in it's existing form is severly
> flawed.
> 
> This, or maybe just unrelated loss of interest, made
> any work on GNUMach
> practically stop for the last few years. So
> additionally to the design
> flaws, it was also getting severly outdated.
> 
> After several years of design considerations (and
> waiting for L4
> Pistachio), a mostly complete design was in place,
> and work on Hurd/L4
> finally took off some 1 1/2 years ago. This spring
> it already looked
> quite promising.
> 
> At this point, Marcus' rising doubts about the
> originally planned
> capability system on top of L4 culiminated, and
> after learning about the
> upcoming L4ng and L4.sec, he decided to rework the
> capability part for
> these new L4 variants, while leaving the rest of the
> Hurd/L4 design
> intact. However, further discussions with the L4
> people and with
> Jonathan Shapiro triggered more and more doubts, and
> a couple of months
> ago, Marcus finally decided that the current
> half-implemented Hurd/L4
> design is fundamentally flawed as well, and work on
> it should stop, in
> favor of (another) complete redesign -- this time
> likely based on
> Shapiro's Coyotos instead of L4, and most certainly
> based on some
> EROS/Coyotos design ideas. (Whether this will still
> have *anything* to
> do with the Hurd -- except for Marcus being the
> leader -- is arguable;
> but that's another story...)
> 
> With all this confusion, and the future
> Hurd/whatever moving further and
> further away -- or maybe just by a plain coincidence
> -- interest in
> Hurd/Mach is on the rise again, and there is a
> remarkable revival in
> GNUMach hacking.
> 
> I don't think anyone actually believes a hacked up
> GNUMach should try to
> compete against L4. While it's certainly possible to
> turn Mach into
> something L4-like by incremental improvment, some of
> the necessary
> changes would be so fundamental, that it's likely
> easier to just move on
> to L4 at some point. The idea is probably rather
> that there is still
> *lots* of room for improvement with Hurd/Mach, and
> it's still a valuable
> project to work on -- the one that is actually
> likely to give us a
> useful and attractive Hurd in the forseeable future.
> Only once this room
> has been fathomed, and the Hurd has been proven to
> be actually able to
> deliver something useful not only visions, it's time
> to go for a further
> improved architecture.
> 
> So the current situation seems to be that while the
> existing Hurd/L4
> project is on ice probably for a long time, and
> Marcus' new
> Hurd/whatever is far into the future (and might end
> up not really having
> much to do with the Hurd), good old Hurd/Mach is on
> the rise again --
> which is a good thing. At least that's how I see it.
> 
> -antrik-
> 
> 
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