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

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Date:	Fri, 08 May 2009 07:40:54 +0100
From:	"Jan Beulich" <jbeulich@...ell.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	<mingo@...e.hu>, <tglx@...utronix.de>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86-64: improve e820_search_gap()

>>> "H. Peter Anvin" <hpa@...or.com> 08.05.09 06:59 >>>
>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?

Why blindly? Aren't hotpluggable memory ranges supposed to be reserved
in the E820 map?

Jan

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