Doors

The illumos and Solaris operating systems feature a novel interprocess communication (IPC) mechanism called "Doors".

Doors are like UNIX Domain Sockets, but much faster: the client process lends its current CPU timeslice to the server, allowing for communication at the speed of a context switch. This technique pays off when the system is under heavy load, because the two communicating processes do not need to wait on the scheduler.

I have developed a moderately popular tutorial on Doors, which is available on my GitHub profile: robertdfrench/revolving-doors. I also maintain the doors crate for the Rust language: https://crates.io/crates/doors.