Reinder J Bril r j briltue nl TUe

Reinder J. Bril, r. j. bril@tue. nl TU/e Informatica, System Architecture and Networking Real-Time Architectures 2003/2004 Construction of time lines for FPPS Reinder J. Bril 29 -04 -2004 1

Reinder J. Bril, r. j. bril@tue. nl TU/e Informatica, System Architecture and Networking Worst-case response times • Simultaneous release of i with all higher priority tasks at time a (critical instant). – Draw a time line with releases of the highest priority task 1 with a first release at time a. For every release, task 1 can start immediately upon every release and execute its worst-case computation time to completion. – Given the responses of tasks 1 till i– 1, draw releases of task i with a first release at time a. For each release, the execution of task i fills the “gaps” left by the higher priority tasks till i has executed its worst-case computation time. The procedure is stopped when either the response time of task j with j < i exceeds its deadline Dj, in which case the set of tasks is not schedulable, or when i completes. In the latter case, the worst-case response time WRi is found. 2

Reinder J. Bril, r. j. bril@tue. nl TU/e Informatica, System Architecture and Networking Best-case response times • Simultaneous release of all higher priority tasks with a completion of i at time f (optimal instant). – Draw a time line with releases of the highest priority task 1 with a last release at time f – T 1. For every release, task 1 can start immediately upon every release and execute its best-case computation time to completion. – Given the responses of tasks 1 till i– 2, draw releases of task i– 1 with a last release at time f – Ti– 1. For each release, the execution of task i– 1 fills the “gaps” left by the higher priority tasks till i– 1 has executed its best-case computation time. – The execution of task i fills the “gaps” left by the higher priority tasks from time f backwards in time till i has executed its best-case computation time. The procedure is stopped when i completes, in which case the bestcase response time BRi is found. 3