Constrained energy allocation for mixed hard and soft real-time tasks

Voltage-Clock Scaling (VCS) is an effective approach to reducing total energy consumption in low power microprocessor systems. To provide real-time guarantees, the delay penalty in VCS needs to be carefully considered in real-time scheduling. In addition to real-time requirements, the systems may contain non-real-time tasks whose response time should be minimized. Thus, a combination of optimization objectives should be addressed when we establish a scheduling policy under a power consumption constraint. In this paper, we propose a VCS approach which leads to proper allocations of energy budgets for mixed hard and soft real-time tasks. Based on the schedulability of VCSEDF, we investigate the characteristics of energy demand of hard periodic and soft aperiodic tasks. Using simulation and subject to a given energy budget, proper voltage settings can be chosen to attain an improved performance for aperiodic tasks while meeting the deadline requirements of periodic tasks.