[ofa-general] Re: why is CPU util/service demand so much higher with SDP than TCP?

[Rick Jones]

Michael S. Tsirkin wrote:
>>Quoting Rick Jones <rick.jones2 at hp.com>:
>>Subject: why is CPU util/service demand so much higher with SDP than TCP?
>>
>>So, while playing around with my new netperf SDP_RR test I've noticed that 
>>a single-byte _RR test over SDP has a much higher transactions per second 
>>(ie lower latency) than over TCP over the same HCA, but the CPU utilization 
>>is _very_ much higher and the service demand (cpu per transaction) as well. 
>>CPU util being higher makes sense with a higher transaction rate, but not 
>>the increased service demand - well at least not to my experience thusfar.
> 
> 
> That's expected.
> SDP by default uses polling aggressively to trade off service demand for latency.
> You can play with recv_poll module parameter to tune that.

Ah, so it is doing a sit and spin waiting for traffic.  I'll see about the 
recv_poll module parm - is it a binary or other?

rick jones