And then, of course, we have to look at what kind of efficiency... cpu cycles, latency, memory usage, etc. You're absolutely correct in that raw cpu cycles are rarely the best optimization. In fact, on a multiuser system, a background task run through cron is often better implemented in samll chunks, i.e. shell script or Perl w/ system calls, just so the scheduler gets more chances to take back control to give to another user process. Woefully "inefficient" but far better for the health of the system.