Fastest technique to pass messages between processes on Linux?

Question

What is the fastest technology to send messages between C++ application processes, on Linux? I am vaguely aware that the following techniques are on the table:

Answer 1

I would suggest looking at this also: How to use shared memory with Linux in C.

Basically, I'd drop network protocols such as TCP and UDP when doing IPC on a single machine. These have packeting overhead and are bound to even more resources (e.g. ports, loopback interface).