Power management in the EPOS system

Power management strategies for embedded systems typi-cally rely on static, application driven deactivation of com-ponents (e.g. sleep, suspend), or on dynamic voltage and frequency scaling. However, the design and implementation of these strategies in embedded operating system often fail to deal with real-time and quality-of-service (QoS) require-ments. The EPOS system implements an infra-structure that sup-ports both static (application-driven) and dynamic (system-driven) power management. In this work, this infrastructure is used to explore energy as a parameter for QoS in em-bedded systems, with the goal of guaranteeing energy con-sumption metrics, while preserving the deadlines of essen-tial (hard real-time) tasks. Given a set of real-time tasks and their associated energy consumption, we provide equa-tions to check schedulability in project-time. At runtime, a preemptive scheduler for imprecise tasks prevents the exe-cution of optional subtasks whenever there is the possibil-ity of deadline loss or depletion of the energy source. We show that this mechanism is effective in controlling energy consumption and ensuring “best-effort ” computation with-out deadline loss