vCap: Adaptive power capping for virtualized servers

Power capping on server nodes has become an essential feature in data centers for controlling energy costs and peak power consumption. More than half of the server nodes are virtualized in today's data centers; thus, providing a practical power capping technique for consolidated virtual environments is a significant research problem. This paper proposes a power capping technique, vCap, which makes resource allocation decisions to maximize the Quality-of-Service (QoS) while meeting the power constraints in virtualized servers that run multi-threaded applications. For a given set of applications, vCap first decides which applications to co-schedule based on application scalability and then optimizes the QoS in an application-aware manner for each VM by adaptively adjusting the CPU resources. Experiments on real-life multi-core servers show that vCap provides 12% higher energy efficiency in comparison to the state-of-the-art power capping techniques, while adhering to the power cap 92% of the time within a 2W error margin.