From owner-freebsd-smp  Wed Aug 27 07:08:24 1997
Return-Path: <owner-freebsd-smp>
Received: (from root@localhost)
          by hub.freebsd.org (8.8.7/8.8.7) id HAA05309
          for smp-outgoing; Wed, 27 Aug 1997 07:08:24 -0700 (PDT)
Received: from chaos.amber.org (root@chaos.amber.org [205.231.232.12])
          by hub.freebsd.org (8.8.7/8.8.7) with ESMTP id HAA05302
          for <smp@FreeBSD.ORG>; Wed, 27 Aug 1997 07:08:20 -0700 (PDT)
Received: from chaos.amber.org (petrilli@chaos.amber.org [205.231.232.12]) by chaos.amber.org (8.7.5/8.6.12) with SMTP id KAA20509; Wed, 27 Aug 1997 10:07:23 -0400 (EDT)
Date: Wed, 27 Aug 1997 10:07:20 -0400 (EDT)
From: Christopher Petrilli <petrilli@amber.org>
To: Kyle Mestery <mestery@winternet.com>
cc: Peter Stubbs <peters@gil.com.au>, smp@FreeBSD.ORG
Subject: Re: A how does it work question.
In-Reply-To: <Pine.GSO.3.96.970827080051.7005C-100000@tundra.winternet.com>
Message-ID: <Pine.BSF.3.95q.970827100635.20292A-100000@chaos.amber.org>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Sender: owner-freebsd-smp@FreeBSD.ORG
X-Loop: FreeBSD.org
Precedence: bulk

Because of this, wouldn't it be appropriate to say that FreeBSD is an
Assymetric MP, not Symmetric?  Symmetric means that the kernel runs on
each processor, and there is no "one processor" which controls exclusivity
to the hardware.

Chris

On Wed, 27 Aug 1997, Kyle Mestery wrote:

> On Wed, 27 Aug 1997, Peter Stubbs wrote:
> 
> > I've been forced to sell my soul lately by doing a couple of MS Win
> > NT courses ( mouths to feed etc.. ). It seems that NT runs a
> > seperate instance of the kernel on each CPU present to provide it's
> > SMP support.
> > 
> > Is this the way FBSD smp does it?
> 
> As far as I know, no.  There is only one copy of the kernel running.  At
> present, access to the kernel is only allowed for one CPU (except for a
> few areas), Steve has been working on making it reentrant.
> 
> > Is this the only way to do it?
> 
> No.  Having the kernel be reentrant is another way.  This requires the
> correct lock "pushdown" into the kernel.  Instead of one giant lock,
> subsystems can each have their own lock, allowing multiple processors to
> be in different sections of the kernel.  This allows for increased
> parallelism.
> 
> > Doesn't this mean that lots more memory would be used keeping data 
> > for 2 kernels?
> > 
> I would assume so, but I dont know for sure.
> 
> Kyle Mestery
> StorageTek's Network Systems Group
> 7600 Boone Ave. N., Brooklyn Park, MN 55428
> mesteka@anubis.network.com, mestery@winternet.com
> 
> 
>