Multi-objective Workflow Scheduling: An Analysis of the Energy Efficiency and Makespan Tradeoff

While in the past scheduling algorithms were almost exclusively targeted at optimizing applications´ make span, today they must simultaneously optimise several goals. Among these goals, energy efficiency is receiving increasing attention for environmental and financial reasons. In contrast to related work that optimises energy consumption as a single objective function, we reformulate in this paper the problem as a bi-objective optimisation by considering both make span and energy as goals. We study the potential benefits of using a Pareto-based workflow scheduling algorithm called MOHEFT using realistic energy consumption and performance models for task executions. We analyse the tradeoff solutions computed by MOHET for different workflows (different in shapes and sizes) in different execution scenarios (different resources in terms of energy consumption). The obtained results show that our bi-objective approach found in some cases schedules that reduce the energy consumption up to 85% with only 3.3% of make span concessions.