Modelling and Analysing Conservative Governor of DVFS-enabled Processors
Robert Basmadjian, Hermann de Meer · 2018
Dynamic voltage and frequency scaling (DVFS) is a mechanism adopted by major hardware vendors to reduce power demand during times of low processor utilization. However, reducing processor frequency to decrease power demand usually results in degraded services' performance leading to service level agreement violations. Governors, which are a piece of software at kernel level, are devised to exploit the flexibility provided by DVFS technologies of the hardware. Utilization-based governors change frequency and voltage at discrete time instances based on workload's utilization without taking into account performance constraints of services. In this paper, a model for the utilization-based Conservative governor is proposed. The model allows us to predict both service performance (mean response time) and processor power demand. An M/M/1 simulator is presented which is used to validate the accuracy of the proposed model. For model accuracy validation, a second methodology based on the frequency probabilities of the processor is proposed. Both approaches confirm the derived DTMC model. We also carry out a comparison between On-demand and Conservative governors and show that the latter performs better for Markovian workloads.