DragonFly BSD
DragonFly kernel List (threaded) for 2004-02
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Re: lkwt in DragonFly

To: Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx>
From: Julian Elischer <julian@xxxxxxxxxxxx>
Date: Wed, 11 Feb 2004 18:17:56 -0800

In-Reply-To: <200402101814.i1AIEItc046630@xxxxxxxxxxxxxxxxxxxx>
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Matthew Dillon wrote:
> :idem for linux, see: http://people.redhat.com/drepper/nptl-design.pdf
> :the short summary is that fixing your kernel to work nicely with 1:1
> :is easier then getting the hairy details of n:m properly working.

I would like to point out that FreeBSD 5 has its M:N implementation pretty 
worked out by now and it was:
1 persom part time for 2 year
2 people part time for 2 years

Considerrring that it was very "part time" at times,
that's not a lot, and given what we learned,
it would take DF a lot less time to implement something similar.
(especially with people working Full time (TM) on it :-)

> :
> :I'd like to know why for dragonfly n:m would be better.
> :
> :-- 
> :Sten Spans
>     n:m is always better then 1:1 because thread switches within each
>     virtual cpu (where the virtual cpu is represented by a single user 
>     process) require no context switch into the kernel at all.
>     n:m is definitely harder to do, but that doesn't mean it shouldn't be
>     done.  It's a great goal for DFly, IMHO.  The paper you are quoting is 
>     simply an opinion, like any paper.  It is not necessarily correct.
> 					-Matt
> 					Matthew Dillon 
> 					<dillon@xxxxxxxxxxxxx>

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