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

[Moni Shoua]

Michael S. Tsirkin wrote:
>>>>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).
> 
The number of sent packets reported by netperf is equal to the number of sent packets 
reported by netdev stats (from running ifconfig before and after netperf) and to the
number of sent packets reported by the port (perfquery)