Temperature-Aware Scheduling: When is System-Throttling Good Enough?

In computing centers, power-aware operating systems ensure that processor temperatures do not exceed a threshold by utilizing system-throttling. In this technique, the system load (or alternatively, the clock speed) is scaled when the temperature hits this threshold. At other times, the system operates at maximum load. In this paper, we show that such simple system-throttling rules are in fact the best one can achieve under certain assumptions. We show that maintaining a constant operating speed (and thus temperature) always does more work than operating in alternating periods of cooling and heating. As a result, for certain settings and for a reasonable temperature model, we prove that system-throttling is the most effective temperature-aware scheduling. Naturally, these assumptions do not always hold; we also discuss the scenario when some of our assumptions are relaxed, and argue why one needs more complex scheduling algorithms in this case.