DVFS Aware CPU Credit Enforcement in a Virtualized System

Nowadays, virtualization is present in almost all computing infrastructures. Thanks to VM migration and server consolidation, virtualization helps reducing power consumption in distributed environments. On another side, Dynamic Voltage and Frequency Scaling (DVFS) allows servers to dynamically modify the processor frequency (according to the CPU load) in order to achieve less energy consumption. We observed that these two techniques have several incompatibilities. For instance, if two virtual machines VM1 and VM2 are running on the same physical host (with their respective allocated credits), VM1 being overloaded and VM2 being underloaded, the host may be globally underloaded leading to a reduction of the processor frequency, which would penalize VM1 even if VM1’s owner booked a given CPU capacity. In this paper, we analyze the compatibility of available VM schedulers with DVFS management in virtualized environments, we identify key issues and finally propose a DVFS aware VM scheduler which addresses these issues. We implemented and evaluated our prototype in the Xen virtualized environment.