Exact schedulability test for sporadic mixed-criticality real-time systems using antichains and oracles

TL;DR

This paper presents an exact schedulability test for mixed-criticality real-time systems using automata, oracles, and simulation techniques, significantly reducing computational complexity and enabling practical analysis of complex task sets.

Contribution

It introduces a generic algorithm with oracle-based techniques for efficient exact schedulability testing, addressing state explosion issues in mixed-criticality systems.

Findings

Achieves up to 99.998% reduction in search space

Supports task sets with up to 8 tasks or maximum periods of 350

Enables derivation of a new dynamic-priority scheduler

Abstract

This work addresses the problem of exact schedulability assessment in uniprocessor mixed-criticality real-time systems with sporadic task sets. We model the problem by means of a finite automaton that has to be explored in order to check for schedulability. To mitigate the state explosion problem, we provide a generic algorithm which is parameterised by several techniques called oracles and simulation relations. These techniques leverage results from the scheduling literature as "plug-ins" that make the algorithm more efficient in practice. Our approach achieves up to a 99.998% reduction in the search space required for exact schedulability testing, making it practical for a range of task sets, up to 8 tasks or maximum periods of 350. This method enables to challenge the pessimism of an existing schedulability test and to derive a new dynamic-priority scheduler, demonstrating its good performance. This is the full version of an RTNS 2024 paper.