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RTOS support for mixed time-triggered and event-triggered task sets

Authors:

Martijn van den Heuvel , Damir Isovic, Reinder Bril , Johan Lukkien , Gowri Sankar Ramachandran

Publication Type:

Conference/Workshop Paper

Venue:

10th EUC


Abstract

Many embedded systems have complex timing constraints and, at the same time, have flexibility requirements which prohibit offline planning of the entire system. To support a mixture of time-triggered and event-triggered tasks, some industrial systems deploy an RTOS with a table-driven dispatcher complemented with a preemptive scheduler to allocate the free time slots to event-driven tasks. Rather than allocating dedicated time-slots to time-triggered tasks, in this work we provide RTOS support to dynamically re-allocate time-slots of time triggered tasks within a pre-computed time range to maximize the available processing capacity for event-triggered tasks. Although the concept - called slotshifting - is not new, we are the first to extend a commercial RTOS with such support.In addition, we extend slot shifting with a run-time mechanism to reclaim resources of time-triggered tasks when their reserved capacities are unused. This mechanism eliminates over-provisioning of capacities to (event-triggered) tasks that have been converted to periodic tasks to resolve interdependencies during off-line synthesis, e.g. allowing for a resource-efficient implementation of a polling task.After implementing our unique RTOS extensions, we investigate the run-time overheads for the corresponding scheduling mechanisms. Measurements show that the increase in terms of absolute run-time overhead is minor compared to an off-the-shelf micro-kernel with a fixed-priority scheduler

Bibtex

@inproceedings{van den Heuvel2633,
author = {Martijn van den Heuvel and Damir Isovic and Reinder Bril and Johan Lukkien and Gowri Sankar Ramachandran},
title = {RTOS support for mixed time-triggered and event-triggered task sets},
month = {December},
year = {2012},
booktitle = {10th IEEE/IFIP International Conference on Embedded and Ubiquitous Computing},
url = {http://www.es.mdh.se/publications/2633-}
}