Integration of Cache Partitioning and Preemption Threshold Scheduling to Improve Schedulability of Hard Real-Time Systems

Abstract

For preemptive scheduling with shared cache, different tasks may cause interference in the shared cache, leading to Cache-Related Preemption Overhead (CRPD). Cache partitioning is a well-known technique for mitigating unpredictable cache interference in preemptive scheduling, but it reduces cache space available to each task, causing an increase in task execution time. Non-preemptive scheduling algorithms do not incur CRPD, but they generally have poor schedulability. Preemption Threshold Scheduling (PTS) is an effective approach to strike a balance between preemptive and non-preemptive scheduling. We propose integration of cache partitioning and PTS to optimize schedulability on a uniprocessor. We force each subset of tasks assigned the same cache partition to be a non-preemptive group, by assigning the same PT to all tasks in the subset that is equal to or higher than the highest priority of the tasks in that subset. This eliminates CRPD within each cache partition, and helps to improve schedulability. We present an ILP formulation as well as an efficient heuristic algorithm.