linux-kernel - Re: Does Linux have plan to support memory hole remapping?

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Message-ID: <kjmk5j7xrij.fsf@pelargir.dolphinics.no>
Date:	Wed, 09 Apr 2008 12:16:20 +0200
From:	Arne Georg Gleditsch <arne.gleditsch@...phinics.no>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Zhao Forrest <forrest.zhao@...il.com>, discuss@...-64.org,
	linux-kernel@...r.kernel.org, yhlu.kernel@...il.com, mingo@...e.hu
Subject: Re: Does Linux have plan to support memory hole remapping?

Andi Kleen <andi@...stfloor.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.
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