linux-kernel - Re: [PATCH] x86-64: improve e820_search

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Message-ID: <4A03BC1A.9060605@zytor.com>
Date:	Thu, 07 May 2009 21:59:06 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jan Beulich <jbeulich@...ell.com>
CC:	mingo@...e.hu, tglx@...utronix.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86-64: improve e820_search_gap()

Jan Beulich wrote:
> Impact: bug fix
> 
> Blindly putting the gap close after max_pfn is in conflict with that
> same memory range potentially being used by hotplugged memory.
> 
> Also, make the function static to ensure there are no other users that
> could depend on the previous behavior regarding the way start_addr gets
> specified.
> 
> Signed-off-by: Jan Beulich <jbeulich@...ell.com>
> 

So blindly locate it somewhere else?  How is that inherently better?
Wouldn't a machine with hotplug memory (which doesn't bother advertising
that fact so we can reserve the address space) be just as likely to use
a sparse memory space, since one can hardly expect the hardware to pack
the space (packing in hardware is why PCs generally have a
mostly-contiguous RAM space) when the memory is hotplugged?

I think I'm missing something fundamental...

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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