Subject: Re: [PATCH] Allow flatmem to be disabled when only sparsemem is
	implemented
From: Magnus Damm <magnus@valinux.co.jp>
To: Andy Whitcroft <apw@shadowen.org>
Cc: Anton Blanchard <anton@samba.org>, akpm@osdl.org,
       linux-kernel@vger.kernel.org
In-Reply-To: <4374F3EB.6040103@shadowen.org>
References: <20051111160341.GK14770@krispykreme>
	 <4374DA3D.6050704@shadowen.org>  <4374F3EB.6040103@shadowen.org>
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Date: Mon, 14 Nov 2005 09:53:06 +0900
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On Fri, 2005-11-11 at 19:41 +0000, Andy Whitcroft wrote:
> Andy Whitcroft wrote:
> > Anton Blanchard wrote:
> > 
> >>On architectures that implement sparsemem but not discontigmem we want
> >>to be able to hide the flatmem option in some cases. On ppc64 for
> >>example, when we select NUMA we must not select flatmem.
> > 
> > First reaction is that this is very reasonable.  I can see why you need
> > to do this as you don't have DISCONTIGMEM.  I will just go check the
> > major architectures and make sure they arn't relying on being able to
> > enable SPARSEMEM and getting FLATMEM too behaviour.  I don't think they
> > can be as they all have DISCONTIGMEM and so should be insulated.
> 
> Ok.  I've reviewed the usage of the memory model selectors in the
> architectures in 2.6.14-mm2.  It appears that only i386 is affected by
> this change, the others that use the selector have explicit enablement
> of FLATMEM.  This patch will interact badly with the current code to
> enable SPARSEMEM on non-numa systems.  However, this code is under
> review at this moment, and the proposed replacement (Message-ID:
> <4370BC30.40100@shadowen.org>) is compatible with this change.
> 
> In short as long as they go in together this change looks good.
> 
> Magnus, any feedback on the replacement SPARSEMEM enabler on non-NUMA
> i386 systems??

I tested your patch in QEMU on top of 2.6.15-rc1-git1 and it seems to
work well. Many thanks!

/ magnus

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