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Re: [Xen-devel] [RFC PATCH] page_alloc: use first half of higher order chunks when halving

On Wed, Mar 26, 2014 at 11:08:01AM -0400, Konrad Rzeszutek Wilk wrote:
> Could you elaborate a bit more on the use-case please?
> My understanding is that most drivers use a scatter gather list - in which
> case it does not matter if the underlaying MFNs in the PFNs spare are
> not contingous.
> But I presume the issue you are hitting is with drivers doing dma_map_page
> and the page is not 4KB but rather large (compound page). Is that the
> problem you have observed?

Drivers are using very large size arguments to dma_alloc_coherent()
for things like RX and TX descriptor rings.


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