Re: [Intel IOMMU 06/10] Avoid memory allocation failures in dma map api calls

Peter Zijlstra wrote:

What I'm saying is that if you do use the reserves, you should ensure
the use is bounded. I'm not seeing anything like that.

each mapping takes at most 3 pages

This is a generic API, who is to ensure some other non-swap device will
not deplete memory and deadlock the reclaim process?

that information is not available at this level ;(

Also, explain to me how an IOMMU is different from bounce buffers? They
both do the same thing, no? They both need memory in order to complete
DMA.

bounce buffers happen in a place where you can sleep.... that makes a lot of difference.

Is it just a broken API you're working against? If so, isn't the Linux
way to fix these things, that is why we have the source code after all.

well yes and no... the other iommu's snuck in as well... it's not entirely fair to hold this one back until a 2 year, 1400 driver project is completed ;(

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