Energy Management for Periodic Real-Time Tasks with Variable Assurance Requirements

Reliability-aware power management (RAPM) schemes, which consider the negative effects of voltage scaling on system reliability, were recently studied to save energy while preserving system reliability. The existing RAPM schemes for periodic tasks may be, however, inherently unfair in that they can manage only some tasks at the expense of the other remaining tasks. In this work, we propose the flexible reliability-aware power management framework, which allows the management of all the tasks in the system, according to their assurance requirements. Optimally solving this problem is shown to be NP-hard in the strong sense and upper bounds on energy savings are derived. Then, by extending the processor demand analysis, a pseudo-polynomial-time static scheme is proposed for the "deeply red" recovery patterns. On-line schemes that manage dynamic slack for better energy savings and reliability enhancement are also discussed. The schemes are evaluated extensively through simulations. The results show that, compared to the previous RAPM schemes, the new flexible RAPM schemes can guarantee the assurance requirements for all the tasks, but at the cost of slightly decreased energy savings. However, when combined with dynamic reclaiming, the new schemes become as competitive as the previous ones on the energy dimension, while improving overall reliability.