On 10/8/07, Eric Van Hensbergen <ericvh@gmail.com> wrote:
>
> On 10/8/07, erik quanstrom <quanstro@coraid.com> wrote:
> > > His original Kernel, L3, was written in pure assembly for x86, using
> every
> > > trick possible.
> > >
> >
> > there's nothing wrong with assembly per ce, but i don't follow this
> logic.
> > generally speaking, compilers are better than humans at doing
> instruction
> > scrabble.
>
> Depends on the compiler ;)
>
> Ignoring the C++ (or all-assembly) nonsense, the general point of
> L3/L4 seemed to be "do IPC really, really well on whatever platform we
> are running on and then build a microkernel around it".  That's an
> oversimplification, and perhaps at that level of abstraction -- that
> was the goal of every microkernel (its just many/any didn't succeed at
> that goal).


Yep, L4 has a high level and low level spec for different architectures.  I
think there's like up to 255 virtual registers, which I think can actually
be realized in real hardware on the Itanium port.

IPC is just register swapping then.  IPC is also synchronous only.

I've been thinking a lot about this, particularly as we've been diving
> deep into tracing performance of our network paths as part of the Blue
> Gene work.  As of our preliminary results, it would seem that Plan 9
> attempts to take the most general approach to things with an emphasis
> on keeping everything simple.  Unfortunately we end up paying a heavy
> price in raw performance (at least in the networking case).  It may
> well be that "benchmark" performance is irrelevant, but I think its at
> least worth reviewing other-OS research from the last 20 years to see
> what we can learn.  It may be the case that we have cut our
> abstractions too high to take advantage of some architectural features
> present in modern microprocessors -- it may be that we want to allow
> for optimized locking and IPC/queues on particular architectures.
>
> I've heard mention the idea of turning the Plan 9 kernel into a a pure
> 9p mux and building the system around that -- one wonders how
> different we would look from a microkernel environment like L4 then.
> I know the Japanese folks talked about their efforts of "porting" Plan
> 9 on top of L4 at last years IWP9 -- I wonder if they've made any
> further progress...


I'd be very curious to know how that went...



        -eric
>