Re: [PATCH 0/8] Optional ZONE_DMA V1

[Christoph Lameter <clameter@xxxxxxx>]

On Wed, 13 Sep 2006, Jack Steiner wrote:

> 	- will any IA64 platform require that ZONE_DMA be enabled (I think
> 	  the answer is "yes")

I think that still remains to be discussed. Today there are various means
to get around address restrictions.

> 	- if ZONE_DMA is enabled, ALTIX will still use only 1 zone. In your
> 	  statement above, you say that disabling ZONE_DMA save 1M cpu
> 	  structures. If ZONE_DMA is enabled, will these 1M structure be allocated
> 	  on SN even though they are not needed?

That has always been the case. In SLES9 and SLES10 we are using 1/4th of the pagesets.

Having no ZONE_DMA provides additional benefits besides saving memory. The 
VM balancing of allocations within a node becomes not necessary and 
various VM optimization can be performed. Loops are unrolled. Less zones 
have to be processed for draining / vm counter updates etc etc.


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