From owner-freebsd-current  Tue Apr  6  8:49:24 1999
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From: "John S. Dyson" <toor@dyson.iquest.net>
Message-Id: <199904061547.KAA28401@dyson.iquest.net>
Subject: Re: SMP users (important)
In-Reply-To: <86wvzqm7pe.fsf@not.oeno.com> from Ville-Pertti Keinonen at "Apr 6, 99 12:14:37 pm"
To: will@iki.fi (Ville-Pertti Keinonen)
Date: Tue, 6 Apr 1999 10:47:21 -0500 (EST)
Cc: dyson@iquest.net, current@freebsd.org
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> 
> > per-processor registers that one could use (but loading a
> > general register with that per processor register would be
> > needed for access.)  Also, since the PPC has lots of registers,
> > one could? permanently reserve one of the general registers (r13?).
> 
> I really don't like the idea of breaking the normal language
> conventions for any processor.  For the i386, the use of segment
> registers is not relevant to C language conventions, but reserving a
> general register on any architecture should, IMHO, be avoided if at
> all possible.
>
I believe that SYSV might do it.

> 
> I believe that having meaningful values context-switched in segment
> registers can add context switch overhead.  It shouldn't be
> significant, though.
> 
It is probably *much* cheaper than the VM approaches.

John



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