Re: [PATCH 3/4] Embed zone_id information within the zonelist->zones pointer

Christoph Lameter
2007-08-14T19:56:11Z

On Tue, 14 Aug 2007, Andi Kleen wrote:

> > pci_set_consistent_dma_mask
> >
> > has that.
>
> While on x86 it is roughly identical (although the low level
> allocator is currently not very reliable) it makes a significant
> difference on some platforms. e.g. I was told on PA-RISC
> consistent memory is much more costly than non consistent ones.
> That's probably true on anything that's not full IO cache
> consistent.
>
> So while it would be reasonable semantics for x86 and IA64
> it's not for everybody else.

Right. That is the point of the function. It isolates these strange
platform dependencies. That is why there is no need for ZONE_DMA32 on any
other platform.