[sgtnoodle]

I've been doing some latency measurements like this, but between two processes using unix domain sockets. I'm measuring more on the order of 50uS on average, when using FIFO RT scheduling. I suspect the kernel is either letting processes linger for a little bit, or perhaps the "idle" threads tend to call into the kernel and let it do some non-preemptable book keeping.

If I crank up the amount of traffic going through the sockets, the average latency drops, presumably due to the processes being able to batch together multiple packets rather than having to block on each one.

[Const-me]

I only use AF_UNIX sockets when I need to pass open file handles between processes. I generally prefer message queues: https://linux.die.net/man/7/mq_overview

I haven’t measured myself, but other people did, and they found the latency of message queues is substantially lower: https://github.com/goldsborough/ipc-bench

[ambrosio]

You might want to measure yourself, because the table of results there doesn't make a lot of sense to me. 4-5 of those methods should be dominated by context switch latency and thus clustered together tightly.

I looked at the sources. The pipe and fifo benchmarks also send a signal on every message, so they're not measuring what you'd expect.