linux-kernel - Re: PS3: trouble with SPARSEMEM

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Date:	Tue, 04 Dec 2007 20:56:09 -0800
From:	Geoff Levand <geoffrey.levand@...sony.com>
To:	Geert Uytterhoeven <Geert.Uytterhoeven@...ycom.com>
CC:	Milton Miller <miltonm@....com>,
	Christoph Lameter <clameter@....com>,
	Andy Whitcroft <apw@...dowen.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Yasunori Goto <y-goto@...fujitsu.com>
Subject: Re: PS3: trouble with SPARSEMEM_VMEMMAP and kexec

Geert Uytterhoeven wrote:
> On Mon, 3 Dec 2007, Milton Miller wrote:
>> Chris, as you can see, PS3 needs to allocate 1/8th of total initial memory to
>> add any more memory.  Geoff, can you predict what linear address the
>> additional memory will occupy?  Judging from the attempted address toa add,
>> maybe not.   If not, my only thought is to pre-reserve an additional page and
>> consume it on the first add.   Additional adds will likely draw from the first
>> added region, pinning.
> 
> To me it sounds a bit strange that hotplug memory relies on having huge
> contiguous blocks of memory available. If this isn't done very early in the
> boot process, changes are high it will fail.
> 
> Would it be possible to allocate the memory from the newly added block, which
> is guaranteed to be unfragmented?


Yes, this sounds like a cleaner solution than pre-allocating, as the memory is
there and its properties are known.

-Geoff


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