Energy-Aware Successor Tree Consistent EDF Scheduling for PCTGs on MPSoCs

Abstract

Multiprocessor System-on-Chips (MPSoCs) computing architectures are gaining popularity due to their high-performance capabilities and exceptional Quality-of-Service (QoS), making them a particularly well-suited computing platform for computationally intensive workloads and applications. Nonetheless, The scheduling and allocation of a single task set with precedence restrictions on MPSoCs have presented a persistent research challenge in acquiring energy-efficient solutions. The complexity of this scheduling problem escalates when subject to conditional precedence constraints between the tasks, creating what is known as a Conditional Task Graph (CTG). Scheduling sets of Periodic Conditional Task Graphs (PCTGs) on MPSoC platforms poses even more challenges. This paper focuses on tackling the scheduling challenge for a group of PCTGs on MPSoCs equipped with shared memory. The primary goal is to minimize the overall anticipated energy usage, considering two distinct power models: dynamic and static power models. To address this challenge, this paper introduces an innovative scheduling method named Energy Efficient Successor Tree Consistent Earliest Deadline First (EESEDF). The EESEDF approach is primarily designed to maximize the worst-case processor utilization. Once the tasks are assigned to processors, it leverages the earliest successor tree consistent deadline-first strategy to arrange tasks on each processor. To minimize the overall expected energy consumption, EESEDF solves a convex Non-Linear Program (NLP) to determine the optimal speed for each task. Additionally, the paper presents a highly efficient online Dynamic Voltage Scaling (DVS) heuristic, which operates in O(1) time complexity and dynamically adjusts the task speeds in real-time. We achieved the average improvement, maximum improvement, and minimum improvement of EESEDF+Online-DVS 15%, 17%, and 12%, respectively compared to EESEDF alone. Furthermore, in the second set of experiments, we compared EESEDF against state-of-the-art techniques LESA and NCM. The results showed that EESEDF+Online-DVS outperformed these existing approaches, achieving notable energy efficiency improvements of 25% and 20% over LESA and NCM, respectively. Our proposed scheduler, EESEDF+Online-DVS, also achieves significant energy efficiency gains compared to existing methods. It outperforms IOETCS-Heuristic by approximately 13% while surpassing BESS and CAP-Online by impressive margins of 25% and 35%, respectively.

Keywords

• PCTGs
• scheduling
• shared memory
• MPSoCs
• conditional precedence constraints
• DVS