Constraineddeadline

Constraineddeadline is a concept in real-time scheduling describing periodic tasks whose relative deadline D_i is no larger than their period T_i (D_i <= T_i). Each task is characterized by its execution time C_i, period T_i, and relative deadline D_i.

This category includes implicit-deadline tasks, where D_i = T_i, and distinguishes constraineddeadline from arbitrary-deadline tasks, where D_i > T_i.

Scheduling implications: Under fixed-priority scheduling, constrained deadlines enable specific schedulability analyses and often tighter worst-case response-time bounds. Under earliest-deadline-first scheduling, the feasibility tests reflect the constraint D_i <= T_i, which simplifies some analytic approaches.

In practice, the constraineddeadline model is used in academic studies and in real-time operating systems to design predictable systems where deadlines occur before the end of a task's period. For example, a task with C_i = 2 ms, T_i = 20 ms, and D_i = 15 ms is a constraineddeadline task.

See also real-time scheduling, rate-monotonic scheduling, earliest deadline first, implicit deadline, and arbitrary deadline.