Rising energy consumption is of growing concern for cloud data center providers. Modern processors try to counteract this problem through low-power idle states that save energy in phases with little demand for compute resources. Making proper use of this feature, however, requires knowledge about the properties of these states for the very processors used in a specific setup; most importantly, the energy consumed in each idle state and the latency for resuming normal operation. Unfortunately, hardware vendors usually do not
provide this critical information.

In this paper, we propose a scheme for automatically analyzing the idle states of modern Intel processors. Our open-source implementation uses an extensible Linux kernel module to measure the energy and latency implications of a system’s processor without any manual intervention or external equipment. We demonstrate the practical applicability of our approach by analyzing two Intel processors from the Haswell and Skylake generation — an Intel Core i7-4790 and an Intel Core i7-6700K, respectively. The results show that our implementation yields reliable, precise, and reproducible measurements for the energy and latency implications of each processor’s various idle states.