sGOV: Real energy savings for VMs with smart governors – sGOV

Governors are essential components of an operating system that manage energy consumption.
They are in charge of increasing or decreasing the frequency at which a CPU core operates to achieve energy savings while preserving performance.
Governors rely on the scheduler that keeps track of each thread running on each core and maintains metrics on the usage of each core.
The metrics maintained by the scheduler are periodically used by the governor to adjust the frequency.

We uncover a limitation of governors in the context of virtualization systems (angular stone to Cloud infrastructures).
Concretely, we discovered that since the scheduler incorrectly accounts virtual machine (VMs) idle times due to their black box nature.
Consequently, governors tend to decide to switch to an operating frequency higher than what should be, leading to energy waste.

The goal of sGov is to provide a generic and non-intrusive mechanism to improve governors in such scenarios so that
Cloud providers can directly benefit from it and achieve real energy savings.