Pfair scheduling improvement to reduce interprocessor migrations

Abstract : Proportionate-fair (Pfair) scheduling is a particulary promising global scheduling technique for multiprocessor systems. Actually three Pfair scheduling algorithms have been proved optimal for scheduling periodic, sporadic and rate-based tasks on a real-time multiprocessor. However, task migration is unrestricted under Pfair scheduling. In the worst case, a task may be migrated each time it is scheduled. To correct this problem, we propose to complement initial Pfair scheduling algorithm by some heuristics that strive to minimize the total number of migrations. Experimental simulations are presented to evaluate and compare the proposed heuristics and we show that the number of migrations can be substantially reduced by adding these simple rules.