svn commit: r254520 - in head/sys: kern sys

[Peter Grehan]

Hi Andre,

> On 21.08.2013 17:03, Peter Grehan wrote:
>>> The way to go should be 4K clusters as they are native to the
>>> architecture.
>>> IIRC a PCIe DMA can't cross a 4K boundary anyway
>>
>>   That's a 4G boundary, for some devices.
>
> I meant a single PCIe DMA transaction can be at most 4K before it has to
> set up another one?

  4K is the maximum TLP size but that's rarely (ever?) used - 128 or 256 
bytes is more common. A DMA operation is just a sequence of TLPs 
originating from the endpoint.

later,

Peter.