Dynamic frequency scaling with buffer insertion for mixed workloads

This paper presents a method to reduce the energy of interactive systems for mixed workloads: multimedia applications that require constant output rates and sporadic jobs that need prompt responses. The authors´ method divides multimedia programs into stages and inserts data buffers between them. Data buffering has three purposes: (1) to support constant output rates; (2) to allow frequency scaling for energy reduction; and (3) to shorten the response times of sporadic jobs. The authors construct frequency-assignment graphs. Each vertex represents the current state of the buffers and the frequencies of the processor. The authors develop an efficient graph-walk algorithm that assigns frequencies to reduce energy. The same method. can be applied to perform voltage scaling and the combination of frequency and voltage scaling. The authors´ experimental results on a Strong-ARM-based computer show that four discrete frequencies are sufficient to achieve nearly maximum energy saving. The method reduces the power consumption of an MPEG program by 46%. The authors also demonstrate a case that shortens the response time of a sporadic job by 55%.