On Wednesday 28 March 2007 8:25 am, Alan Stern wrote:
> On Tue, 27 Mar 2007, David Brownell wrote:
> 
> > > Hmm... A CPU has to access all that data, and reading a cache line
> > > at a time surely as better. Although on the other hand, it's something
> > > streaming and thus just using the cache space for no good reason.
> > 
> > Right.  "Potentially".  Displacing hot cachelines for use-once data
> > will in various cases be a lose.
> 
> It would be nice to see somewhere a more explicit and detailed discussion 
> of the tradeoffs.  Under what conditions is it better to allocate DMA 
> memory rather than just using kmalloc() and calling dma_map_single()?

Ideally that discussion would already be in Documentation/DMA-mapping.txt
(or maybe Documentation/DMA-API.txt, but that's weak on such things).

- Dave

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