> 
> The big open question with the approach Yamamoto-san's patch uses (and
> blame me for that, as I was the one pestering about it about a year
> ago!) is that I don't know of any recent hard data on how much time
> our TCP spends handling hardware interrupts, versus the soft-interrupt
> (receive-side IP and TCP). It used to be a lot, but interrupt
> mitigation may change that.  And then, maybe transmit-side quickly
> becomes another bottleneck, which isn't helped much by this patch...
> 
During my tests a while ago, the receiving machine CPU were 

- 20% HW interrupt
- 30% SW interrupt
- 50% copyout()

when the receiving machine was at 100% load.  This varied a lot
depending of socket buffer sizes, MTU sizes etc.  

Note that the HW interrupts also includes transmit interrupt,
and that the transmitted ACKs are embedded in the SW stuff.

-- Ragge