== fmlock -- map a file into memory and lock it to RAM ==

fmlock is a small tool intended to load a file into the
block I/O cache and lock it there. This is done by mmap-ing
the whole file and calling mlock on the address space
occupied by the file. Then the program puts itself to sleep
until a signal arrives. The purpose of this is that (large)
files can be preloaded into RAM, specifically the block I/O
cache for other processes to read from. This is for example
required to measure the RAM bandwidth and CPU limited
throughput of data processing code, working on real data
without getting effected by I/O bottlenecks.