Performance testing is a challenging topic with many, many variables. Ranging from the # of threads you specify for iperf to how much memory is on the system and in what slots they are in and what slot your NIC is in (a x1 vs a x8 for example).
Having done a lot of tests with iperf and netperf, I can tell you that all of these factors and many more can come into play. I'd recommend doing some research, the 1st thing you might try is specify the number of cores and threads to use.
Lots of articles out there on different apsects of this topic. There is no single answer, lots of variables.
best of luck,
Thanks for the info. That's kinda what I've run into. I've already fiddled with the rmem buffer sizes and MTU. Didn't think to check the PCI speeds. They are both in PCIe x16 slots so that shouldn't be a problem.
Found a few decent articles to that have shed some light, but I haven't fixed it yet:
Still running at max of about 9.5Gbe when using a single port, and 4.8Gbe on each port when using both ports though . Will keep trying and post here if I find an answer.