Towards Compositionality in Real-Time Resource Partitioning Based on Regularity Bounds

• Authors: Aloysius K. Mok;Xiang (Alex) Feng
• Venue: RTSS '01 Proceedings of the 22nd IEEE Real-Time Systems Symposium
• Year: 2001

In real-time resource partitioning, a shared resource ispartitioned by a resource-level scheduler such that eachpartition is accessible only by an individual applicationtask group.Tasks within the same task group are scheduledby an application-task-level scheduler that is specializedto the real-time requirements of the tasks in the group.Anideal goal for resource partitioning in real-time systemsis to achieve a complete separation of concerns so that:(1) each task group may be executed as if it had accessto its own dedicated resource, and (2) there is minimalinteraction between the resource-level scheduler and theapplication-task-level scheduler.In [15], we introducedthe notion of a real-time virtual resource which operates ata fraction of the rate of the shared physical resource andwhose rate of operation varies with time but is bounded.Inthis paper, we discuss an approach to bound the variationof the rate of operation of a real-time virtual resourceby characterizing the rate variation from both temporaland supply dimensions and by expanding on the conceptof regularity that was first introduced in [19].For thecase of regular resource partitioning, we show that theutilization bounds of both fixed-priority scheduling anddynamic-priority scheduling remain unchanged from thosefor dedicated resources.We determine the utilizationbounds for the more general case of irregular partitioning.In particular, both types of partitions can be efficientlyconstructed by exploiting compositionally propertiesvis-a-vis the regularity measure.