Donald Bren School of Information and Computer Sciences

Frequency scaling of a processor based on slowdown factor, gives considerable power savings. The slowdown factors are computed from the task set executing on the processor. These factors are non-trivial for periodic tasks with deadlines not equal to their period. This paper describes how to compute static slowdown factors for a task set with an underlying earliest dealine first (EDF) schedule. We give a density slowdown method, which eficiently computes a slowdown factor. The constant slowdown factor not being optimal, we compute the optimal slowdown factors by looking at all the jobs up to the hyper-period of the task set. This is based on Yao's optimal algorithm for non-periodic tasks. Dynamic slowdown techniques further enhance the power savings. We show that dynamic slowdown factors can be easily incorporated over these static slowdown factors, thereby increasing the total energy savings.