Subject: Re: [PATCH 1/5] v2 Split the memory_block structure
From: Dave Hansen <dave@linux.vnet.ibm.com>
To: Nathan Fontenot <nfont@austin.ibm.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@ozlabs.org,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
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Date: Fri, 16 Jul 2010 11:33:30 -0700
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On Fri, 2010-07-16 at 13:23 -0500, Nathan Fontenot wrote:
> > If the memory_block's state was inferred to be the same as each
> > memory_block_section, couldn't we just keep a start and end phys_index
> > in the memory_block, and get away from having memory_block_sections at
> > all?
> 
> Oooohhh... I like.  Looking at the code it appears this is possible.  I'll
> try this out and include it in the next version of the patch.
> 
> Do you think we need to add an additional file to each memory block directory
> to indicate the number of memory sections in the memory block that are actually
> present? 

I think it's easiest to just say that each 'memory_block' can only hold
contiguous 'memory_block_sections', and we give either the start/end or
start/length pairs.  It gets a lot more complicated if we have to deal
with lots of holes.

I can just see the hardware designers reading this thread, with their
Dr. Evil laughs trying to come up with a reason to give us a couple of
terabytes of RAM with only every-other 16MB area populated. :)  

-- Dave

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