On Tue, Sep 04, 2007 at 07:38:24PM +0200, Alfred M. Szmidt wrote:
> Both L4 and Coyotos use synchrony message passing, while Mach uses
> asynchronous message passing. The Hurd servers depend on the
> functionality of async. message passing so just rewriting them to
> become synchronous would be quite a big problem. There are many other
> differences between Mach, L4, Coyotos, ... So it is not at all
> trivial, and will require huge changes.
Well, Shapiro abandoned the attempt to implement a partially-async IPC
mechanism in Coyotos; but Neal and Marcus are sticking with the idea,
and it is part of Marucs' prototype kernel.
The thread model of the Hurd servers will probably need to change sooner
or later for better performance; but this is pretty orthogonal to a
possible microkernel change. The advantage of writing our own kernel is
that we can implement the features that *we* think most useful, instead
of building a system around some existing kernel.
So, async vs. sync IPC is not really an issue. How much the existing
code will need to be adapted depends on different questions.