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Date: Fri, 9 Dec 2005 16:16:41 -0800
From: Keith Mannthey <kmannth@gmail.com>
To: Andi Kleen <ak@muc.de>
Subject: Re: [patch 3/3] add x86-64 support for memory hot-add
Cc: Matt Tolentino <metolent@cs.vt.edu>, akpm@osdl.org, discuss@x86-64.org,
       linux-kernel@vger.kernel.org, matthew.e.tolentino@intel.com
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> These should be all __cpuinit.
>
> In general SRAT has a hotplug memory bit so it's possible
> to predict how much memory there will be in advance. Since
> the overhead of the kernel page tables should be very
> low I would prefer if you just used instead.

How much overhead would there be?

> (i.e. instead of extending the kernel mapping preallocate
> the direct mapping and just clear the P bits)

On my box the SRAT for hot-add areas exposed are from the end
installed memory to way out in outerspace.
SRAT: hot plug zone found 280000000 - 2300000000
I can't hot add that sort of range on my box but the bios didn't want
to limit or is planing for really really big dimms.

I wouldn't want to waste resource for areas that will never be added.

Thanks,
 Keith