From owner-freebsd-arch@FreeBSD.ORG  Wed Aug 10 20:57:49 2005
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From: John Baldwin <jhb@FreeBSD.org>
To: frank@exit.com
Date: Wed, 10 Aug 2005 16:38:25 -0400
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Cc: Andre Oppermann <andre@freebsd.org>, freebsd-arch@freebsd.org
Subject: Re: Special schedulers, one CPU only kernel, one only userland
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On Wednesday 10 August 2005 04:10 pm, Frank Mayhar wrote:
> On Wed, 2005-08-10 at 09:11 -0400, John Baldwin wrote:
> > I think this is the model that BSD/OS employed
> > for SMP in its 4.x series before they did their version of SMPng.
>
> I didn't grunge around in the scheduler (much), but as far as I'm aware
> BSD/OS 4.x used the Big Giant Lock mechanism just as FreeBSD did, and
> for the same reason.

I believe that at some point during the 4.x series they added a scheduler lock 
that covered just enough to allow threads that weren't asleep in the kernel 
to be switched to without require the big giant lock and that it was a pretty 
decent performance win over the earlier single BGL ala FreeBSD 4.x.

-- 
John Baldwin <jhb@FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org