This routine provides a means to find out in what areas your program spends most
of its time. The argument buf points to bufsiz bytes of core.
Every virtual 10 milliseconds, the user's program counter (PC) is examined:
offset is subtracted and the result is multiplied by scale and
divided by 65536. If the resulting value is less than bufsiz, then the
corresponding entry in buf is incremented. If buf is NULL,
profiling is disabled.