Re: [RFC 0/8] Reduce MAX_NR_ZONES and remove useless zones.

[Christoph Lameter]

On Mon, 3 Jul 2006, Christoph Hellwig wrote:

> On Mon, Jul 03, 2006 at 02:55:34PM -0700, Christoph Lameter wrote:
> > I keep seeing zones on various platforms that are never used and wonder
> > why we compile support for them into the kernel.
> > 
> > IA64 on SGI for example only uses ZONE_DMA other IA64 platforms can
> > also use ZONE_NORMAL.
> 
> Which btw is utterly wrong.  It should have a 4GB ZONE_DMA32 and everything
> else in ZONE_NORMAL.

So we want to change the definition of ZONE_DMA to refer to the first 16MB 
only? ZONE_DMA32 is always a 4GB border? (Andy disagrees about DMA32 see 
his message!).

It seems to me that DMA can be run on ZONE_NORMAL. ZONE_DMAxx is used for 
situations in which DMA cannot be done to all of memory. ZONE_DMA allows 
an architecture to define a single exception zone that ends at 
MAX_DMA_ADDRESS (which is arch specific).

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