Here is a good use case for mmap - a process-a performs data processing and writes results to a disk (or tmpfs), next you need to repeatedly read in a process-b

Here is a good use case for mmap - a process-a performs data processing and writes results to a disk (or tmpfs), next you need to repeatedly read in a process-b (or read once but not sequentially). If you'll use read() you will: 1. double RAM usage - the file will be in a VM cache anyway (unless you'll use O_DIRECT which would make this pipeline slower) and without mmap() you'll have to create 2nd copy inside the process-b 2. add unnecessary kernel->userspace copy while reading data in process-b. But for saving data from process-a I would still use write() using MAXPHYS sized blocks: I'm not sure mmap would use optimal write block size, and with write it is easier detect errors (like ENOSPC).