AEQUITAS: Coordinated Energy Management Across Parallel Applications

A growing number of energy optimization solutions operate at the application runtime level. Despite delivering promising results, these application-scoped optimizations are fundamentally greedy: They assume to have an exclusive access to power management and often perform poorly when multiple power-managing applications co-exist, or different threads of the same application share power management hardware. In this paper, we introduce AEQUITAS, a first step to address this critical yet largely overlooked problem. The insight behind AEQUITAS is that co-existing applications may view power-managing hardware as a shared resource and coordinate power management decisions. As a concrete instance of this philosophy, we evaluated our ideas on top of a state-of-the-art energy-efficient work-stealing runtime. Experiments show that without AEQUITAS, multiple co-existing power-managing application runtimes suffer up to 32% performance loss and negate all power savings. With AEQUITAS, the beneficial energy-performance tradeoff reported in the single-application setting (12.9% energy savings and 2.5% performance loss) can be retained, but in a much more challenging setting where multiple power-managing runtimes co-exist on parallel architectures and multiple CPU cores share the same power domain.