> Coercing random access memory into a serial file just to go and emulate a random access over that file is... not a great way to deal with a high-performance primitive.

The file doesn't need to have an on-disk representation. I don't see why an mmap-ed file should behave any different from a SHM segment. They are basically the same thing, the SHM segment even has a file descriptor. It just doesn't have a name somewhere in the filesystem hierarchy. https://man7.org/linux/man-pages/man7/shm_overview.7.html