CPU Frequency Emulation Based on DVFS

Nowadays, virtualization is present in almost all computing infrastructures. Thanks to VM migration and server consolidation, virtualization helps in 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 observe that DVFS is mainly used, but still generates a waste of energy. In fact, the DVFS frequency scaling policies are based on advertised processor frequency. By default and thanks to the on demand governor, it scales up or down the processor frequency according to the current load and the different predefined threshold (up and down). However, the set of frequencies constitutes a discrete range of frequencies. In this case, the frequency required for a specific load will almost be scaled to a frequency more higher than expected, which leads to a non-efficient use of energy. In this paper, we analyze and address a way of emulating a precise CPU frequency thanks to the DVFS management in virtualized environments. We implemented and evaluated our prototype in the Xen hyper visor.