Static-Priority Periodic Scheduling on Multiprocessors

We present a new sufficient condition for the schedulability of preemptable, periodic, hard-real-time task sets using the very simple static-priority weight-monotonic scheduling scheme. Like a previous condition due to Baruah et al., our condition actually determines pfair schedulability. Pfairness requires that the schedule, in addition to being periodic, schedules each task at an approximately even rate. Our condition improves on the previous one in two important ways. First, it can determine that task sets with high utilization and many tasks are schedulable, while the previous condition cannot. Second, our condition applies to both uniprocessors and multiprocessors, while the previous condition applies only to uniprocessors. We present simulations that show that our condition is highly accurate for many cases of interest.