Re: [PATCH] change global zonelist order on NUMA v3

[Lee Schermerhorn <Lee.Schermerhorn@hp.com>]

On Thu, 2007-04-26 at 09:06 -0700, Christoph Lameter wrote:
> Hmmmm... One additional easy way to fix this would be to create a DMA 
> node and place it very distant to other nodes. This would make it a 
> precious system resource that is only used for
> 
> 1. GFP_DMA allocations
> 
> 2. If the memory on the other nodes is exhausted.
> 

This would solve the problem for "100% CLM" configurations where the
only thing in the interleaved pseudo-node is DMA zone.  However, we can
configure any %-age of CLM between 0% [fully interleaved, pseudo-SMP]
and "100%" [which is not really, as I've mentioned].  Interestingly,
older revs of our firmware set the SLIT distance for the interleaved
pseudo-node to 255 [or such], so it was always last.  Then someone
decided that the interleaved node was effectively closer than other
nodes...

I have been considering an HP-platform-specific boot option [handled by
a new ia64 machine vec op] to re-distance the interleaved node, but for
other platforms, such as Kame's, I think we still need the ability to
move the DMA zones last in the Normal zone lists.  Or, exclude them
altogether?

Lee