Influence of Discretization of Frequencies and Processor Allocation on Static Scheduling of Parallelizable Tasks with Deadlines

Models for energy-efficient static scheduling of parallelizable tasks with deadlines onfrequency-scalable parallel machines comprise moldable vs. malleable tasks and continuous vs. discrete frequency levels. We investigate the tradeoff between scheduling time and energy efficiency when going from continuous to discrete processor allocation and frequency levels. To this end, we present a tool to convert a schedule computed for malleable tasks on machines with continuous frequency scaling (P. Sanders, J. Speck, Euro-Par 2012) into one for moldable tasks on a machine with discrete frequency levels. We compare the energy efficiency of the converted schedule to the energy consumed by a schedule produced by the integrated crown scheduler (N. Melot et al., ACM TACO 2015) for moldable tasks and a machine with discrete frequency levels. Our experiments indicate that the converted Sanders Speck schedules, while computed faster, consume more energy on average than crown schedules. Surprisingly, it is not the step from malleable to moldable tasks that is responsible, but the step from continuous to discrete frequency levels.