mmap is like tightly scoped, targeted swap. If the PoR is on disk, the OS is free to reclaim that memory for something else at anytime. It really is a beautiful

mmap is like tightly scoped, targeted swap. If the PoR is on disk, the OS is free to reclaim that memory for something else at anytime. It really is a beautiful hack, but if you turn on swap for the system in that way, it has to balance memory usage across all the running programs. In this use of mmap, there is nothing to swap out as the source of truth is always on disk. During general swap usage, memory has to travel in both directions.