[openib-general] [PATCH/RFC] IB/ipoib: add selective tx signaling - performance measurements

[Michael S. Tsirkin]

> >>Tests with iperf and netperf for unicast and multicast destinations show
> >>an improvement in the ability of user applications to xmit packets. 
> >>
> >>Examples: Number of successful writes as reported by 30 seconds UDP_STREAM of 100 byte packets.
> >>Tested with netperf on Dual CPU (64bit Intel Xeon 3GHz) running linux-2.6.20-rc1 (sender) and
> >>OFED-1.1 (receiver)
> > 
> > 
> > IMO netperf reporting is actually not too informative without stats settings.
> > Try running with e.g. -i 10,2 -I 99,5 - you might discover that your numbers are
> > only accurate within 30%
> 
> I tried that and I am getting a warning about confidence level not being
> achieved.  I am still trying to learn about that and trying to understand why
> (any ideas?) but for the meantime can you explain why do I need statistics when
> I am only trying to count the number of successful writes?

Otherwise your results could be just noise.

> >>Note that the results below show improvement only for TX so we see an end to end packet loss.
> > 
> > 
> > Hmm, as long as packet drops increase, BW improvements in UDP don't sound
> > too convincing, do they? You can get infinite BW at 100% drop ...
> > 
> > 
> >>Improving the receiver (NAPI) will reduce the packet loss. 
> > 
> > 
> > Needs testing with NAPI patch then?
>
> I tried NAPI and I get better results for the receiver but my opinion is that
> the receiver side is less important here since all I'm trying to improve is
> the ability to send packets. Am I right?

Only if you are sure something else is not dropping the packets (e.g.
buffer overruns triggered).

-- 
MST