[ofa-general] Very high CPU load during RDMA communication

[Diego Guella]

----- Original Message ----- 
>A newbie question about  InfiniBand: while running an RDMA bandwidth
> test I noticed that the RDMA communication occupied 99% CPU time,
> which is much more than I expected for InfiniBand. Is this normal or
> should I check my setup ?
>
> How the test was run:
> (host 1) ib_rdma_bw -s 104857600
> (host 2) time ib_rdma_bw -s 104857600 192.168.64.7

I think it's normal, I see the same behavior here.
If you take a look at ib_rdma_bw code, you can see that the program waits in 
a while() loop, polling the CQ for the WC to appear.
I think it's coded that way to get the WC as soon as possible and report a 
more precise time (that is used after to compute BW).

If you don't want that behavior in your application you could use event 
notification for the CQ.



Regards,

Diego