[ofa-general] high latency results with qperf

[Or Gerlitz]

Hi Johann,

Using qperf I see unexplained high latancy of around 8-10us, where
if I use a different utility on the same setup (e.g ib_rdma_lat, mpi)
I get latency of about 1-2us, any idea? The setup is DDR based, connectx,
this test was done with qperf-0.4.0-1.ofed1.3.1 but it happens also with
later and probably also with the latest bits.

Or.

# qperf h2 -m 4 -t 20 rc_lat
rc_lat:
    latency  =  10.6 us

# qperf h2 -m 4 -t 20 ud_lat
ud_lat:
    latency  =  8.64 us

# ib_rdma_lat h2 -s 4
Latency typical: 1.49403 usec
Latency best   : 1.47152 usec
Latency worst  : 5.8651 usec