Virtual processor frequency emulation

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 while DVFS is widely used, it still generates a waste of energy. By default and thanks to the ondemand governor, it scales up or down the processor frequency according to the current load and the different predefined threshold (up and down). However, DVFS frequency scaling policies are based on advertised processor frequencies, i.e. the set of frequencies constitutes a discrete range of frequencies. The frequency required for a given load will be set to a frequency higher than necessary; which leads to an energy waste. In this paper, we propose a way to emulate a precise CPU frequency thanks to the DVFS management in virtualized environments. We implemented and evaluated our prototype in the Xen hypervisor