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From: Arne Georg Gleditsch <arne.gleditsch@dolphinics.no>
To: Andi Kleen <andi@firstfloor.org>
Cc: Zhao Forrest <forrest.zhao@gmail.com>, discuss@x86-64.org,
       linux-kernel@vger.kernel.org, yhlu.kernel@gmail.com, mingo@elte.hu
Subject: Re: Does Linux have plan to support memory hole remapping?
References: <ac8af0be0804090054w47f48ddel387d80a0331d16e1@mail.gmail.com>
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	<20080409100331.GH19010@one.firstfloor.org>
Date: Wed, 09 Apr 2008 12:16:20 +0200
In-Reply-To: <20080409100331.GH19010@one.firstfloor.org> (Andi Kleen's message
	of "Wed, 9 Apr 2008 12:03:31 +0200")
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Andi Kleen <andi@firstfloor.org> writes:
> On Wed, Apr 09, 2008 at 11:50:00AM +0200, Arne Georg Gleditsch wrote:
>> Hm, wouldn't the given e820 map and mtrr listing indicate that 512M were
>> actually remapped to 32G+ in this case?
>
> The way it usually works (if it is implemented correctly in the BIOS) 
> is that all memory starting at the hole moves up together 
> (often subject to DIMM boundaries etc.),
> not that the area below the hole is remapped individually.

Yes, bad choice of words on my part.

> BTW it is not actually 512MB that is lost. MemTotal does not 
> include mem_map and that alone is ~512MB (64 bytes for each 4K page)
>
> So as far as I can see there is no missing memory remapping in Zhao's case, 
> he's just confused by the MemTotal semantics.

...meaning that upgrading his BIOS isn't going to change anything for
him, which is what I suspected from the e820 readouts.

-- 
								Arne.