creates a memory mapping to the file and then reads the mapping in an unrolled
loop similar to that used in bw_mem_rd(8).
The benchmark is intended to be used on a file
that is in memory, i.e., the benchmark is a reread benchmark. Other
file benchmarking can be done with
specification may end with ``k'' or ``m'' to mean
kilobytes (* 1024) or megabytes (* 1024 * 1024).