Re: Linus replies

[Leonardo Lopes Pereira]

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On Wed, 10 May 2006 22:10:47 -0400 (EDT)
Donnie Jones <address@hidden> wrote:

> Hello,
> 
> Rebuttal from Linus' post:
> ***
> "The fundamental result of access space separation is that you can't share 
> data structures. That means that you can't share locking, it means that 
> you must copy any shared data, and that in turn means that you have a much 
> harder time handling coherency. All your algorithms basically end up being 
> distributed algorithms.
> 
> And anybody who tells you that distributed algorithms are "simpler" is 
> just so full of sh*t that it's not even funny.
> 
> Microkernels are much harder to write and maintain exactly because of this 
> issue. You can do simple things easily - and in particular, you can do 
> things where the information only passes in one direction quite easily, 
> but anythign else is much much harder, because there is no "shared state" 
> (by design). And in the absense of shared state, you have a hell of a lot 
> of problems trying to make any decision that spans more than one entity in 
> the system.
> 
> And I'm not just saying that. This is a fact. It's a fact that has been 
> shown in practice over and over again, not just in kernels. But it's been 
> shown in operating systems too - and not just once. The whole 
> "microkernels are simpler" argument is just bull, and it is clearly shown 
> to be bull by the fact that whenever you compare the speed of development 
> of a microkernel and a traditional kernel, the traditional kernel wins. By 
> a huge amount, too.
> 
> The whole argument that microkernels are somehow "more secure" or "more 
> stable" is also total crap. The fact that each individual piece is simple 
> and secure does not make the aggregate either simple or secure."
> ***
> 
> Could someone refute these statements for me?  Or do you agree with Linus' 
> that microkernels are actually not easier to maintain?

I think that noone will refute the fact that THE MICROKERNEL itself it harder 
to maintain. That is why the number of microkernels on the world is so small 
compared to the number of monolithical kernels. This doesn't mean that 
microkernels are worse.
> 
> __
> Donnie
> 
> 
> On Wed, 10 May 2006, Tom Bachmann wrote:
> 
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> > Donnie Jones wrote:
> >> For my pure education, what is gained going the microkernel way?
> >>
> >
> > The system gets more reliable (one component should not be able to crash
> > the whole system, and a "component" here can be e.g. a driver), the
> > software becomes easier to maintain (as you can efficiently split it up
> > in multiple parts), I'm sure there is more. This is just for multiserver
> > OSes.
> >
> > I think much of linus' posting is about microkernels and not multiserver
> > OSes.
> > - --
> > - -ness-
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> >
> 
> 
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