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This letter presents partition-oriented ERfair scheduler (POES), a low-overhead proportional fair scheduler for hard real-time multiprocessor embedded systems. POES achieves lower overheads using an online partitioning/merging mechanism that retains the optimal schedulability of a fully global scheduler by merging processor groups as resources become critical while using partitioning for fast scheduling at other times. The principal objective is to remain only just as global at any given instant of time as is necessary to maintain ERfair schedulability of the system throughout the schedule length. Experimental results reveal that POES incurs almost no migrations at low workloads and achieves up to 32 times reduction in the number of migrations suffered with respect to the global ERfair scheduler on a set of two to 16 processors even when the average system load is as high as 85%. Theoretical analysis proves that POES typically has the same amortized complexity as that of the global ERfair algorithm.
Date of Publication: March 2011