A model of hierarchical real-time virtual resources

A real-time virtual resource is an abstraction for resource sharing where application task groups must meet timing constraints and knowledge of all the timing requirements may not be available for a global schedulability analysis, such as is the case in the open system environment. In a 2001 paper, we introduced the notion of a real-time virtual resource which operates at a fraction of the rate of the shared physical resource and whose rate of service provision varies with time but is bounded. The shared resource is partitioned into real-time virtual resources by a resource-level scheduler such that each real-time virtual resource is accessible only by an individual application task group; tasks within the same task group are scheduled by an application-task-level scheduler that is specialized to the real-time requirements of the tasks in the group. In this paper we propose a hierarchical real-time virtual resource model that permits resource partitioning to be extended to multiple levels. Through this model, partitions on each level are scheduled as if they had access to a dedicated resource and there is minimal interference between neighboring partition levels. We also investigate the partitioning of real-time virtual resources subject to scheduling quantum requirements.