I had a network adaptor of speed 20Gbps. By stressing this adaptor using one of benchmarking tools (netperf is the tool which I used), I was able to get ~18Gbps which is well accepted.
Now, after installing one more adaptor of the same speed i.e. 20Gbps, and stressing both adaptors using the benchmarking tool, I was expecting ~36 to ~38Gbps. But still able to get the same ~18Gbps.
Does this mean, throughput gets calculated by considering average traffic on both physical adaptors and doesn't sum the values & always doesn't cross the boundary of a single adaptor link speed?
PS: The setup looks something like this. Total of 32 netperf sessions with sufficiently large socket buffer size and message sizes in send/receive calls which are 256K and 16K respectively. Each adaptor being used by 16 sessions simultaneously.