Communication based proactive link power management

As the number of cores in CMPs increases, NoC is projected to be the dominant communication fabric. Increase in the number of cores brings an important issue to the forefront, the issue of chip power consumption, which is projected to increase rapidly with the increase in number of cores. Since NoC infrastructure contributes significantly to the total chip power consumption, reducing NoC power is crucial. While circuit level techniques are important in reducing NoC power, architectural and software level approaches can be very effective in optimizing power consumption. Any such technique power saving technique should be scalable and have minimal adverse impact on performance. We propose a dynamic, communication link usage based, proactive link power management scheme. This scheme, using a Markov model, proactively manages communication link turn-ons and turn-offs, which results in negligible performance degradation and significant power savings. We show that our prediction scheme is about 98% accurate for the SPEC OMP benchmarks and about 93% over all applications experimented. This accuracy helps us achieve link power savings of up to 44% and an average link power savings of 23.5%. More importantly, it incurs performance penalties as low as 0.3% on average.