I have two Linux machines, each equipped with a Solarflare SFN5122F 10GbE NIC. The two NICs are connected together with an SFP+ Direct Attach cable.
I am using netperf to measure TCP throughput between the two machines. On one box, I run:
and on the other:
netperf -t TCP_STREAM -H 192.168.x.x -- -m 32768
MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.x.x (192.168.x.x) port 0 AF_INET Recv Send Send Socket Socket Message Elapsed Size Size Size Time Throughput bytes bytes bytes secs. 10^6bits/sec 87380 16384 32768 10.02 1321.34
The measured throughput is 1.3Gb/s. This is 7.5x below the theoretical maximum, and only 30% faster than 1GbE.
What steps can I take to troubleshoot this?