The Case for Fair Multiprocessor Scheduling
نویسندگان
چکیده
Partitioning and global scheduling are two approaches for scheduling real-time tasks on multiprocessors. Though partitioning is sub-optimal, it has traditionally been preferred; this is mainly due to the fact that well-understood uniprocessor scheduling algorithms can be used on each processor. In recent years, global-scheduling algorithms based on the concept of “proportionate fairness” (Pfairness) have received considerable attention. Pfair algorithms are of interest because they are currently the only known method for optimally scheduling periodic, sporadic, and “rate-based” task systems on multiprocessors. In addition, there has been growing practical interest in scheduling with fairness guarantees. However, the frequency of context switching and migration in Pfair-scheduled systems has led to some questions concerning the practicality of Pfair scheduling. In this paper, we investigate this issue by comparing the PD Pfair algorithm to the EDF-FF partitioning scheme, which uses “first fit” (FF) as a partitioning heuristic and the earliest-deadlinefirst (EDF) algorithm for per-processor scheduling. We present experimental results that show that PD is competitive with, and in some cases outperforms, EDF-FF. These results suggest that Pfair scheduling is a viable alternative to partitioning. Furthermore, as discussed herein, Pfair scheduling provides many additional benefits, such as simple and efficient synchronization, temporal isolation, fault tolerance, and support for dynamic tasks.
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