Utilization bounds on allocating rate-monotonic scheduled multi-mode tasks on multiprocessor systems

Abstract

Formal models used for representing recurrent real-time processes have traditionally been characterized by a collection of jobs that are released periodically. However, such a modeling may result in resource under-utilization in systems whose behaviors are not entirely periodic. For instance, tasks in cyber-physical system (CPS) may change their service levels, e.g., periods and/or execution times, to adapt to the changes of environments. In this work, we study a model that is a generalization of the periodic task model, called multi-mode task model: a task has several modes specified with different execution times and periods to switch during runtime, independent of other tasks. Moreover, we study the problem of allocating a set of multi-mode tasks on a homogeneous multiprocessor system. We present a scheduling algorithm using any reasonable allocation decreasing (RAD) algorithm for task allocations for scheduling multi-mode tasks on multiprocessor systems. We prove that this algorithm achieves 38% utilization for implicit-deadline rate-monotonic (RM) scheduled multi-mode tasks on multiprocessor systems.