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Date: Fri, 26 Jan 2007 07:56:09 -0800 (PST)
From: Christoph Lameter <clameter@sgi.com>
To: Andrew Morton <akpm@osdl.org>
cc: Mel Gorman <mel@csn.ul.ie>, linux-mm@kvack.org,
       linux-kernel@vger.kernel.org, Christoph Lameter <clameter@engr.sgi.com>
Subject: Re: [PATCH 0/8] Create ZONE_MOVABLE to partition memory between
 movable and non-movable pages
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 <20070126030753.03529e7a.akpm@osdl.org>
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On Fri, 26 Jan 2007, Andrew Morton wrote:

> - They add zillions of ifdefs

They just add a few for ZONE_DMA where we alreaday have similar ifdefs for 
ZONE_DMA32 and ZONE_HIGHMEM.

> - They make the VM's behaviour diverge between different platforms and
>   between differen configs on the same platforms, and hence degrade
>   maintainability and increase complexity.

They avoid unecessary complexity on platforms. They could be made to work 
on more platforms with measures to deal with what ZONE_DMA 
provides in different ways. There are 6 or so platforms that do not need 
ZONE_DMA at all.

> - We kicked around some quite different ways of implementing the same
>   things, but nothing came of it.  iirc, one was to remove the hard-coded
>   zones altogether and rework all the MM to operate in terms of
> 
> 	for (idx = 0; idx < NUMBER_OF_ZONES; idx++)
> 		...

Hmmm.. How would that be simpler?

> - I haven't seen any hard numbers to justify the change.

I have send you numbers showing significant reductions in code size.