Abstract Power-aware operating systems ensure that the system temperature does 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. 1 Introduction Energy and temperature management of processor systems is an increasingly important problem as the power consumption of these chips rises drastically with every new generation. At the same time, the rate of technological improvements in cooling systems has not been keeping pace [4]. Naturally, this has resulted in a large body of work that attempts to incorporate energy and temperature considerations into processor scheduling levels. Some of these are incorporated at the system level, where the on-chip architecture scales the speed of the processor if it is getting too hot. With advances in processor technology, this is also possible at the operating system level since most modern day processors have interfaces that allow the user to control its speed in real-time. The current processors by Intel, AMD, and IBM now allow a mechanism called dynamic voltage scaling (DVS) to control the clock speed of the processor [15] by varying the supply voltage. Most operating systems now also include commands which allow the user to access this interface (e.g., cpufreq in Linux).

Optical Networks (EPONs) has been an area of intense research in recent years. Most of the proposed solutions offer clever methods for fair grant sizing, traffic prediction, and prioritized, differentiated services. Barring some work by Kamal et al. and some elements in the scheme proposed by Ma et al., no work has been done on exploring the order of granting (i.e., ONU sequencing) in an EPON. In this paper, we propose an unexplored heuristic for improving the performance of the IPACT scheme with respect to the most important metric: packet delay. In this heuristic, the OLT always grants that ONU which has the Smallest (Available) Reported queue length, First (SARF). Our simulations indicate that our heuristic can improve the delay performance of IPACT by 10-20 % (when tested under the gated allocation policy). A. EPON I.