In Section 55.3.4, we noted that, on Linux, the time required to add or check for the existence of a lock is a function of the position of the lock in the list of all locks on the file. Write two programs to verify this:
a) The first program should acquire (say) 40,001 write locks on a file. These locks are placed on alternating bytes of the file; that is, locks are placed on bytes 0, 2, 4, 6, and so on through to (say) byte 80,000. Having acquired these locks, the process then goes to sleep.
b) While the first program is sleeping, the second program loops (say) 10,000 times, using F_SETLK to try to lock one of the bytes locked by the previous program (these lock attempts always fail). In any particular execution, the program always tries to lock byte N * 2 of the file. Using the shell built-in time command, measure the time required by the second program for N equals 0, 10,000, 20,000, 30,000, and 40,000. Do the results match the expected linear behavior?