Optimizing over FP/EDF Execution Times: Known Results and Open Problems

TL;DR

This paper reviews existing formulations of schedulability constraints for fixed priority and earliest deadline first scheduling, enabling optimization of execution times to minimize costs under real-time constraints.

Contribution

It provides a comprehensive review of linear constraint formulations for schedulability tests, facilitating optimization of execution times in real-time systems.

Findings

Formulations expressed by linear constraints enable optimization routines.

Schedulability tests accommodate unspecified execution times for design flexibility.

The review highlights open problems in optimizing execution times for real-time scheduling.

Abstract

In many use cases the execution time of tasks is unknown and can be chosen by the designer to increase or decrease the application features depending on the availability of processing capacity. If the application has real-time constraints, such as deadlines, then the necessary and sufficient schedulability test must allow the execution times to be left unspecified. By doing so, the designer can then perform optimization of the execution times by picking the schedulable values that minimize any given cost. In this paper, we review existing results on the formulation of both the Fixed Priority and Earliest Deadline First exact schedulability constraints. The reviewed formulations are expressed by a combination of linear constraints, which enables then optimization routines.