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Re: [Hurd-alpha-devel] Re: L4 instead of gnumach?

From: Ron Farrer
Subject: Re: [Hurd-alpha-devel] Re: L4 instead of gnumach?
Date: Sun, 29 Oct 2000 13:43:21 -0800
User-agent: Mutt/1.0.1i

OKUJI Yoshinori ( wrote:

>   To understand why Mach emulation is bad, you need to know how L4
> improved IPC performance. They have improved the performance in
> various aspects, but in simple words, they made IPC semantics more
> lean. If you add the extra flesh again, the performance would be the
> same as Mach. In fact, they demonstrated this in the paper on
> Unix/L3. Anyway, read articles/papers on L3/L4 as many as
> possible. You should be able to realize how difficult getting good
> perfomance is. Very careful optimizations are necessary (e.g. see the
> paper on L4-Linux).
>   However, I think Mach emulation would be a good thing as the first
> step, because you will be able to investigate how different L4 is from
> Mach and what would be necessary to be done in details. But I'd like
> to point out that Mach emulation should be temporary but not a
> permanent solution.

NO - a Mach emulation would only be a _step_ in porting. Eventually it
would be ideal to do away with all the Mach dependencies, but FIRST we
need to get hurd to actually work on L4. 

>   Isn't your (ultimate) goal to remove Mach-things from Hurd? cthreads
> is a Mach-only multithreading method, while pthreads is designed for a
> platform-independent manner. In addition, obviously, much more
> programmers know pthreads than cthreads.

Yes, again this would only be a temporary step. pthreads is the
ultimate goal. 

>   That's a very, very good thing. It is certain that big projects such
> as Hurd cannot be cooperatively developed without clear goals. I'm
> quite glad to hear that you make an effort. Please call me out when
> you begin the work. I'd like to participate. :)

Great! Let's see what everyone thinks. If the majory think this is
worthwile (I do, and hope everyone else does) then we'll see how we can 
organize specific tasks for people... 


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