Power-Aware Parametric Dispatching in Distributed Real-Time Systems

S.M. Elsharkawy, M.F. Younis, and C. Moulds (USA)

Keywords

Realtime Scheduling, Power Management, Digital Voltage Scaling, Distributed Systems, Parametric Dispatching.

Abstract

The majority of battery operated computing devices have the capability to employ Dynamic Voltage Scaling (DVS) as an effective method to minimize the power used by their processors. Algorithms employing DVS in real time systems must guarantee the satisfaction of all tasks’ timing constraints while minimizing power consumption. In this paper, we present a framework for scheduling and dis patching a distributed set of hard real-time tasks with relative timing constraints. In our approach, the scheduler employs the parametric real-time scheduling methodology to provide on-time completion guarantees for periodic hard real-time tasks. Moreover, the scheduler associates with each hard real-time task a feasibility range parameterized by timing parameters generated at run-time. The run-time dispatcher uses this information to calculate the system’s dynamic slack time. It uses the slack time to set the CPU speed using DVS in the time interval till the next scheduling point. The dis patcher reclaims the additional slack generated when a job uses fewer execution cycles than its worst-case estimate to further reduce power consumption. The proposed power aware dispatching method has running-time of O(1) with no need for off-line computations. Our simulation results show significant improvement in power savings over previously presented DVS-based scheduling methods.

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