Energy Saving Scheduling for Embedded Real-Time Linux Applications

The problem of reducing energy consumption is becoming very important in the design of embedded real-time systems. Many of these systems, in fact, are powered by rechargeable batteries, and the goal is to extend, as much as it is possible, the autonomy of the system. To reduce energy consumption, one possible approach is to selectively slow down the processor frequency. In this paper we propose a modification of the Linux kernel to schedule aperiodic tasks in a soft realtime environment. The proposed solution consists in a new scheduling strategy based on the Resource Reservation Framework [9], which introduces very little modification to the Linux API. Our scheduler is based on Algorithm GRUB (Greedy Reclamation of Unused Bandwidth), presented by Baruah and Lipari [5]. After presenting the algorithm, we describe its implementation on a Intrinsyc CerfCube 250, which uses a Intel PXA250 processor. We show with an example of multimedia application that, by using our approach, we save up to 38% of energy with respect to an unmodified Linux.

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