Scheduling issues in real-time systems
Chia-Mei Chen · University Libraries (University of Maryland) · 1995
System Model and Assumptions Our system model is a real-time system consisting of a set of processors and a set of periodic tasks. The system uses off-line scheduling to guarantee to meet the timing constraints of all tasks and adopts rollback or replication technique as fault-tolerance strategy. Let the elemental unit (EU) be the smallest non-preemptable execution unit [MA91]. Each EU is characterized by its release time, execution time, and deadline. Each task can be described by an elemental unit graph (EUG), where an EUG is a directed acyclic graph; each node is an EU and each directed edge represents the precedence relation and communication pattern. Since tasks are periodic, the window size for examining the execution behavior of the cyclic tasks can be the least common multiple (LCM) of the periods of all the tasks. We define such time interval as a frame. Let minframe of an EU be the time interval between its release time and its deadline. We adopt a fault model which permits ...