A self-adaptable distributed DFS scheme for NoC-based MPSoCs

As processor count in MPSoCs increases, the use of NoCs becomes relevant, if not mandatory. However, power and energy restrictions, especially in mobile applications, may render the design of NoC-based MPSoCs over-constrained. The use of traditional dynamic voltage and frequency scaling (DVFS) techniques proved useful in several scenarios to save energy/power, but it presents scaling problems and slow response times. This work proposes a self-adaptable distributed dynamic frequency scaling (DFS) scheme for NoC-based MPSoCs. It takes into account the communication load and the utilization level of each processor to dynamically change its operating frequency. Frequency change decisions and clock generation are executed locally to each processor. Clock generation is simple, based on clock gating of a single global clock. The overhead of the scheme is minimum, the range of generated clocks is wide, and the response time is negligible. Experimental results with synthetic applications shows that the proposed scheme has an average execution time overhead below 7%, and may lead to considerable power and energy savings, since it allows an average reduction of 27% on the total number of executed instructions. Evaluating the proposed method with a real application, the execution time overhead reached 13%, while the total number of executed instructions was reduced by 64%.