Energy Characterization of Embedded Real-Time Operating Systems

In this chapter we present a methodology to analyze the energy overhead due to the presence of an embedded operating system in a wearable device. Our objective is to determine the key parameters affecting the energy consumption of the RTOS allowing the development of more efficient OS-based power management policies. To achieve this target, we present a characterization strategy that stimulates the RTOS both at the kernel and at the UO driver level by analyzing various OS-related parameters. Our analysis focus in particular on the relationship between energy consumption and processor frequency characterizing the different functionalities of an RTOS, suggesting a way to develop effective OS-aware energy optimization policies based on variable voltage and frequency. Experimental results are presented for eCos, an open-source embedded OS ported and installed on a prototype of wearable device, the HP SmartBadgeIV.1