Selective signalling vs WQE size - was Re: [ofa-general] mthca max_sge value... ugh.

[Talpey, Thomas]

At 05:02 PM 5/20/2008, Roland Dreier wrote:
>
> > The idea is that for selective
> > signaling QPs, before you stamp the WQE, you read the value of the DS
> > field which denotes the effective size of the descriptor as used in the
> > previous post, and stamp only that area, relying on the fact that the
> > rest of the descriptor is already stamped.
>
>Does it make a measurable difference?  If so then it seems like a good idea.

I'll be happy to try it, but I bet it'll be hard to measure the difference
with a storage workload. It sounds like a bit of a micro-optimization
at the HCA interface, avoiding a few DMA cycles?

I didn't see a URL so let me know if so.

Tom.