[ILUG] It's illegal, according to the barrister in PC World

[Rick Moen]

Quoting Smelly Pooh (plop at redbrick.dcu.ie):

> And yet another was that they tried to implement too much (a lot of it
> being in kernel), had big delays, didn't have all the features they
> promised, and came out buggy.

That is true.  I'll point out, just for the sake of clarity, that this
likewise was not essential to the architecture, but basically a
management mistake concerning the ring-zero kernel feature set.  (One
can imagine an alternative Multics outcome where those features were
left to be omitted in userspace if at all.)

> Microkernels were always (in theory) going to be weaker on performance,
> but since microkernels like QNX could deliver good performance I imagine
> the problem lies more with Darwin's implementation (or that of Mach)

Implementation tends to hold lots of nasty surprises for people who
chose to believe the predictions of academic computing theory.  My point
was that performance and stability on the level of QNX's has turned out
to be possible _but difficult_.  In the end, it doesn't matter if your
OS could theoretically be superb _if and when_ you were able to work out 
the extremely thorny threading, semaphore, scheduling (etc.) problems.
What matters is how soon you can deliver a maintainable, stable codebase
with perforance in the target region.

Have you read this?  http://www.jwz.org/doc/worse-is-better.html
Interesting thoughts to contemplate, if you haven't already.

>> For starters, get written so that they work and perform well.
> 
> Well that's the advantage/disadvantage of microkernels isn't it?  

You sound (I figure) like you're thinking theory.  I'm thinking
implementation following theory.  But I tend to do that; I'm just a
lowly sysadmin, not a systems developer.

>> One infers that the success of the BeOS and QNX kernel developers in
>> this area (regardless of commercial scale) are testimony to their
>> sheer determination to make a difficult model work.
> 
> That's speculative... or  do you have references I can look at?

I'm inferring based on what I've seen, and read, and concluded after
talking to quite a lot of people, including some of the developers in
question (one of the few advantages, lately, of living in Silicon Gulch).  
But Those Views, They Do Differ<tm>.

-- 
Cheers,   "Why is the alphabet in that order?  Is it because of that song?"
Rick Moen                                              -- Steven Wright
rick at linuxmafia.com