Something I ~never see mentioned in mmap discussions is that it completely bypasses the expensive syscall transition for read calls, which has only grown rapidly in cost thanks to all the speculative execution mitigations.

In benchmarking I found an mmap approach to be integral to achieving maximum performance in IO-heavy workloads on modern OSes [0]. (Note that it still is a win even with mitigations disabled.)

[0]: https://neosmart.net/blog/using-simd-acceleration-in-rust-to...