Having trouble achieving 1Gbit UDP throughput

Question

For UDP packets with a payload less then 1470, is it possible to achieve 1Gbit throughput? Due to the small packet size, there should be some bottlenecks in achieving such t

Answer 1

Check the documentation for the switch you're using. Switches are constrained in the number of packets per second (pps) they can deliver and often can't sustain 1GBps if you're sending packets with significantly smaller than the maximum payload size.

Another thing to check is whether your network card is doing interrupt coalescing, and what is the maximum number of send/receive descriptors it can support. At that level of throughput the interrupt service time and context switching time can become a big overhead on the host system even with a modern CPU and memory system.

Also if you're using gigabit over copper, the smallest ethernet frame the card will emit is 512 bytes, so smaller messages will be padded to that size. This is because of requirements for carrier sense/collision detection.