Integrating finegrain application adaptation with global adaption for saving energy

Energy efficiency has become a primary design criterion for mobile multimedia devices. Prior work has proposed saving energy through coordinated adaptation in multiple system layers, in response to changing application demands and system resources. The scope and frequency of adaptation pose a fundamental conflict in such systems. The Illinois GRACE project addresses this conflict through a hierarchical solution which combines (1) infrequent (expensive) global adaptation that optimizes energy for all applications in the system and (2) frequent (cheap) per-application (or per-app) adaptation that optimizes for a single application at a time. This paper demonstrates the benefits of the hierarchical adaptation through a second-generation prototype, GRACE-2. Specifically, it shows that in a network bandwidth constrained environment, per-app application adaptation yields significant energy benefits over and above global adaptation.