Response time analysis of multiframe mixed-criticality systems with arbitrary deadlines
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Response time analysis of multiframe mixed‑criticality systems with arbitrary deadlines Ishfaq Hussain, et al. [full author details at the end of the article] Accepted: 31 October 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The well-known model of Vestal aims to avoid excessive pessimism in the quantification of the processing requirements of mixed-criticality systems, while still guaranteeing the timeliness of higher-criticality functions. This can bring important savings in system costs, and indirectly help meet size, weight and power constraints. This efficiency is promoted via the use of multiple worst-case execution time (WCET) estimates for the same task, with each such estimate characterized by a confidence associated with a different criticality level. However, even this approach can be very pessimistic when the WCET of successive instances of the same task can vary greatly according to a known pattern, as in MP3 and MPEG codecs or the processing of ADVB video streams. In this paper, we present a schedulability analysis for the new multiframe mixed-criticality model, which allows tasks to have multiple, periodically repeating, WCETs in the same mode of operation. Our work extends both the analysis techniques for Static Mixed-Criticality scheduling (SMC) and Adaptive Mixed-Criticality scheduling (AMC), on one hand, and the schedulability analysis for multiframe task systems on the other. A constrained-deadline model is initially targeted, and then extended to the more general, but also more complex, arbitrary-deadline scenario. The corresponding optimal priority assignment for our schedulability analysis is also identified. Our proposed worst-case response time (WCRT) analysis for multiframe mixed-criticality systems is considerably less pessimistic than applying the static and adaptive mixed-criticality scheduling tests oblivious to the WCET variation patterns. Experimental evaluation with synthetic task sets demonstrates up to 20% and 31.4% higher scheduling success ratio (in absolute terms) for constrained-deadline analyses and arbitrary-deadline analyses, respectively, when compared to the best of their corresponding frameoblivious tests. Keywords Multiframe tasks · Arbitrary deadlines · Worst-case response time analysis · Mixed-criticality scheduling
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Real-Time Systems
1 Introduction Recent trends in many real-time embedded domains (e.g., automotive and avionics) favor mixed-criticality systems, where computing tasks of different criticalities co-exist on the same processor. A task’s criticality is a measure of the severity of the consequences of that task failing, in conjunction with the probability of such a failure. Accordingly, tasks of higher criticalities are developed according to stricter (and costlier) methodologies, and the same holds for the techniques for estimating their worst-case execution times (WCETs). Additionally, scheduling arrangements have to ensure that, even when sharing system resources, a misbehavior of a lower
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