linux-kernel - Re: [PATCH] x86 Boot NUMA kernels on non-NUMA hardware with DISCONTIG memory model

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Date:	Fri, 24 Aug 2007 19:38:16 +0200
From:	Andi Kleen <ak@...e.de>
To:	Mel Gorman <mel@...net.ie>
Cc:	Andi Kleen <ak@...e.de>, Andy Whitcroft <apw@...dowen.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86 Boot NUMA kernels on non-NUMA hardware with DISCONTIG memory model

> 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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