6.4. Impact of the CPU speed on UDP traffic throughput

Due to missing packet aggregation, UDP is less efficient than TCP for bulk transfers. The CPU frequency can limit throughput on high-speed links because Generic Receive Offload (GRO) and UDP Segmentation Offload (USO) are disabled by default.

For example, on a tuned host with a high Maximum Transmission Unit (MTU) and large socket buffers, a 3 GHz CPU can process the traffic of a 10 GBit NIC that sends or receives UDP traffic at full speed. However, you can expect about 1-2 Gbps speed loss for every 100 MHz CPU speed under 3 GHz when you transmit UDP traffic. Also, if a CPU speed of 3 GHz can closely achieve 10 Gbps, the same CPU restricts UDP traffic on a 40 GBit NIC to roughly 20-25 Gbps.