Chapter 11 - Cost-Efficient Mapping of Dynamic Concurrent Tasks in Embedded Real-Time Multimedia Systems

Abstract

This chapter presents a novel approach toward the management of concurrent tasks in dynamic real-time applications. The quality of the mapping can greatly affect both performance and energy consumption. It discusses a methodology to map the applications in a cost-efficient way onto a heterogeneous embedded multiprocessor platform. This approach is based on a design–time exploration, which results in a set of schedules and assignments for each task, represented by Pareto curves. At run time, a low-complexity scheduler selects an optimal combination of working points, exploiting the dynamic and nondeterministic behavior of the system. This approach leads to significant power saving compared with state-of-the art dynamic voltage scaling (DVS) techniques because of three major contributions. First, the effective combination of an intratask detailed design-time exploration and a low-overhead runtime scheduler. Second, the design–time scheduler provides a whole range of energy–time tradeoff points (Pareto curves) instead of a single fixed solution to use at run time. Third, by considering the information provided on run-time applications, and introducing a scenario approach to avoid the use of worst-case execution time (WCET) estimation, hard real-time constraints can still be met. In future, this work can be extended to provide automatic tool support for code synthesis and real-time operating system (RTOS) integration. A research is also underway on concurrency improving transformations to produce a better gray-box model as a starting point for the scheduler stage.