TCP loopback connection vs Unix Domain Socket performance

This benchmark: https://github.com/rigtorp/ipc-bench provides latency and throughput tests for TCP sockets, Unix Domain Sockets (UDS), and PIPEs.

Here you have the results on a single CPU 3.3GHz Linux machine :

TCP average latency: 6 us

UDS average latency: 2 us

PIPE average latency: 2 us

TCP average throughput: 0.253702 million msg/s

UDS average throughput: 1.733874 million msg/s

PIPE average throughput: 1.682796 million msg/s

66% latency reduction and almost 7X more throughput explain why most performance-critical software has their own IPC custom protocol.

Yes, local interprocess communication by unix domain sockets should be faster than communication by loopback localhost connections because you have less TCP overhead, see here.