Embedded Operating System Energy Analysis and Macro-Modeling

A large and increasing number of modern embedded systems are subject to tight power/energy constraints. It has been demonstrated that the operating system (OS) can havea significant impact on the energy efficiency of the embedded system. Hence, analysis of the energy effects of the OS is of great importance. Conventional approaches to energy analysis of the OS (and embedded software, in general) require the application software to be completely developed and integrated with the system software, and that either measurement on a hardware prototype or detailed simulation of the entire system be performed. Since this process requires significant design effort, unfortunately, it is typically too late in the design cycle to perform high-level or architectural optimizations on the embedded software, restrictingthe scope of power savings.Our work recognizes the need to provide embedded software designers with feedback about the effect of different OS services on energy consumption early in the design cycle. As a first step in that direction, this paper presents a systematic methodology to perform energy analysis and macro-modeling of an embedded OS. Our energy macro-models provide software architects and developers with an intuitive model for the OS energy effects, since they directly associate energy consumption with OS services and primitives that are visible to the application software. Our methodology consists of (i) an analysis stage, where we identify a set of energy components, called energy characteristics, which are useful to the designer in making OS-related design trade-offs, and (ii) a subsequent macro-modeling stage, where we collect data for the identified energy components and automatically derive macro-models for them. We validate our methodology by deriving energy macro-models for two state-of-the-art embedded OS's, µC/OS and Linux OS.