You're completely ignoring MAP_POPULATE being used to aggressively asynchronously read-ahead the data on the kernel side, which the read-based implementation is

You're completely ignoring MAP_POPULATE being used to aggressively asynchronously read-ahead the data on the kernel side, which the read-based implementation isn't attempting any equivalent of (posix_fadvise(2) and readahead(2) come to mind). Frankly TFA is relatively useless as an mmap vs. read comparison.