Comment by danceparty

You can get within a few percentage points, yes

I just tested this with two hosts with 4.14.127 upstream kernel and upstream mlx5 driver, and mellanox connectx-5 card. Using 16 iperf threads

[SUM] 0.0-10.0 sec 85.1 Gbits/sec

That's pretty close with no tuning, and well beyond 10gb/s we mentioned earlier