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

[Michael S. Tsirkin]

> 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.

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MST