Date: Fri, 24 Aug 2007 19:38:16 +0200
From: Andi Kleen <ak@suse.de>
To: Mel Gorman <mel@skynet.ie>
Cc: Andi Kleen <ak@suse.de>, Andy Whitcroft <apw@shadowen.org>,
       linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86 Boot NUMA kernels on non-NUMA hardware with DISCONTIG memory model
Message-ID: <20070824173816.GC16227@bingen.suse.de>
References: <20070824162814.GD26374@skynet.ie> <20070824163521.GA16227@bingen.suse.de> <46CF0CCF.7010702@shadowen.org> <20070824170744.GB16227@bingen.suse.de> <20070824172626.GE26374@skynet.ie>
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> Other than the fact that the memmap must be PMD aligned to use hugepage
> entries for the memmap. 

Why is that so?  mem_map should be just part of lowmem anyways.

> It could be mapped with small pages in corner cases
> but the complexity worth it?

You don't need to map it with small pages in the normal case,
the only requirement is that c_p_a() is aware of it so it can
split it if needed.

> I can't see this type of lifting being done any time soon. As SPARSEMEM works
> and there is hope with the vmemmap work that DISCONTIG will finally go away,
> it may not be the best investment of time.

It's a trivial change, probably less code than your original patch.

-Andi
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