[ofa-general] 20% latency increase between UD to RC latency

[Dror Goldenberg]

Or Gerlitz wrote:
> OK,its always good to start with facts on the ground... before
> commiting this test, my original thinking was that for messages
> whose size=X is less then the IB Link level MTU it holds that:
>
> 	latency(X,UD) <= latency(X,UC) <= latency(X,RC)
>
> Running the latency test provided with the perftest package on my systems (*)
> I get the below results. Does anyone has insight why the --minimal-- and typical
> UD latency is 1us ( = 20%) worse then the --minimal-- and typical RC latency???
>
> Or.
>
>   

In all devices that support the memfree architecture (InfiniHost III-Ex 
running at memfree mode, InfiniHost III Lx and ConnectX) you will find 
the performance of UD comparable to the RC/UC. With the introduction of 
the memfree architecture, we are focused on development and performance 
optimization for this architecture. That is the main reason for memfree 
to achieve better performance.

-Dror