TCP loopback connection vs Unix Domain Socket performance

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.

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 usUDS average latency: 2 usPIPE average latency: 2 usTCP average throughput: 0.253702 million msg/sUDS average throughput: 1.733874 million msg/sPIPE 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.

Redis benchmark shows unix domain socket can be significant faster than TCP loopback.

When the server and client benchmark programs run on the same box, both the TCP/IP loopback and unix domain sockets can be used. Depending on the platform, unix domain sockets can achieve around 50% more throughput than the TCP/IP loopback (on Linux for instance). The default behavior of redis-benchmark is to use the TCP/IP loopback.

However, this difference only matters when throughput is high.