[openib-general] heads-up - ipoib NAPI

[Eli cohen]

On Tue, 2006-09-26 at 21:34 -0700, Shirley Ma wrote:

> NAPI patch moves ipoib poll from hardware interrupt context to softirq
> context. It would reduce the hardware interrupts, reduce hardware
> latency and induce some network latency. It might reduce cpu
> utilization. But I still question about the BW improvement. I did see
> various performance with the same test under the same condition.
> 
When you open just one connection you can see around 10% of variations
in BW measure. But then you don't utilize all the CPU power you have and
you don't get to the threshold where NAPI becomes effective.
Using multiple connections utilizes all CPUs in the system, increases
send rate, and increases the chances of the receiver to poll CQEs up to
its quota and be scheduled again without re-enabling interrupts.


> Have you tested this patch with different message sizes, different
> socket sizes? Are these results consistent better?
> 
I used large socket sizes but I think with that with multiple
connections this parameter does not have significant effect.