Re: Coyotos

[olafBuddenhagen]

Hi,

On Wed, Oct 28, 2009 at 09:36:12AM -0700, Jonathan S. Shapiro wrote:
> On Mon, Oct 26, 2009 at 7:22 PM, <address@hidden> wrote:

> > But it wasn't the only problem. Other issues were the fully
> > synchnonous IPC, which is unsuitable for certain use cases --
> > including situation common in a UNIX environment;
> 
> There is unchallenged evidence in the literature that Linux on top of
> L4 (which, note, uses a fully synchronous IPC model) is *faster* than
> Linux running native, I wonder if you can cite concrete examples and
> back them up with something better than assertions.

Running a single-server on top of a microkernel is a very different
thing than running a multiserver system...

Anyways, Neal and Marcus discussed this with you in all detail; and for
all I know, you agreed at some point: in fact, you even consented to
change the IPC mechanisms in Coyotos -- although you took that decision
back later on...

> > ...and the completely different resource management approach.
> >
> The Coyotos kernel does not *have* a resource management approach. It
> provides naming and primitive protection for atomic system resources
> at the level of pages, but does not define any policy over those
> resources. Resource management is performed entirely at user level.

It seems rather clear to me from reading the Viengoos papers, that
Neal's resource managment approach requires certain specific primitives
at the microkernel level.

> > I'm not sure whether the persistence mechanism was also a concern
> > already when this decision was made, or it was only later that
> > Marcus changed his mind on that...
> >
> Coyotos doesn't implement persistence,

I was under the impression that persistence also has an influence on
certain design decisions at the microkernel level... But I might be
wrong on this point.

> so if that was an issue, I have to conclude that people didn't look
> very seriously at Coyotos.

Indeed, *I* didn't look very closely. But Marcus and Neal did -- I'm
only trying to restate their conclusions as good as I can with my
limited understanding...

-antrik-