This article is nonsensical. If you're reading this please don't start mmap'ing files just to read from them. It proposes an incredibly unrealistic scenario where the program is making thousands of random incredibly small unbuffered reads from a file. In reality 99 percent of programs will sequentially reading bytes into a buffer which makes orders of magnitude less syscalls.
Mmap is useful in niche scenarios, it's not magic.
Mmap is useful in niche scenarios, it's not magic.