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Date:      Tue, 30 Nov 1999 07:19:09 +1100
From:      Peter Jeremy <jeremyp@gsmx07.alcatel.com.au>
To:        Peter Wemm <peter@netplex.com.au>
Cc:        arch@freebsd.org
Subject:   Re: Threads stuff - reality check..
Message-ID:  <99Nov30.071153est.40325@border.alcanet.com.au>
In-Reply-To: <19991129144125.C7E121CC6@overcee.netplex.com.au>
References:  <19991129144125.C7E121CC6@overcee.netplex.com.au>

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On 1999-Nov-30 01:41:25 +1100, Peter Wemm wrote:
>I'd hate to ruin a good pie-in-the-sky session on the design of the
>killer threads system and all, but I kinda wonder if we're aiming too
>hight to start with?
Maybe...

>Wouldn't it be better to put the pieces that we already have together and
>make something in time for 4.0 that runs with better concurrency than we
>have now?

I _would_ like to see something make it into 4.0.  I would also like to
be reasonably sure that whatever we initially put into 4.0 can evolve
into the final design as visualised by Julian, Daniel et al.  As I
understand it, this means that we need to have an `interim' threads
implementation that has pretty much the same user API and kernel
interface as our target (since the interfaces can't change until 5.0).
I believe we're allowed to undertake a major re-work of the underlying
code as long as the interfaces don't change.

That suggests that our priorities need to be:
1) What user API do we want?  I think there is general concensus that
   we need to use the same API as "everyone else" (pthread aka IEEE
   POSIX 1003.1c-1995).
2) What kernel interface do we need?  This is still the subject of
   much discussion.  In particular, it's not clear whether the thread
   scheduler should be in the kernel, userland or split between them
   in some manner.  If we can agree on a suitably extensible kernel
   interface (which basically means that the copyin and copyout
   structures both begin with a version and size), we might be able to
   sneak through a substantial interface change without objections.
3) Do we have some interim code that can meet 1 and 2 and be committed
   before the feature freeze?  Peter suggested Richard's native
   linuxthreads port.  I can't somment on it's suitability.

Peter




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