{"title":"Independence Thresholds: Balancing Tractability and Practicality in Soft Real-Time Stochastic Analysis","authors":"R. Liu, A. Mills, James H. Anderson","doi":"10.1109/RTSS.2014.38","DOIUrl":"https://doi.org/10.1109/RTSS.2014.38","url":null,"abstract":"The issue of stochastic response-time analysis is considered in the context of soft real-time multiprocessor schedulers. For such analysis to yield tractable, closed-form results, it is inevitably necessary to assume that execution times are probabilistically independent. However, stochastic dependencies among tasks are often common in actual systems. To enable closed-form analysis results to be applied to such systems, the concept of an independence threshold is introduced. Such a threshold is a \"tunable\" per-task parameter that can be adjusted to control the extent of dependency in task execution times as assumed in analysis, such thresholds can even be applied in settings where explicit dependencies exist among tasks through resource sharing. A method is presented for setting independence thresholds in which measured task execution times are subjected to known statistical independence tests. This method is applied in a case study involving MPEG decoding. In this case study, the usage of independence thresholds enabled up to a 3.5-fold reduction in provisioned task execution times compared to a worst-case provisioning without compromising analysis assumptions.","PeriodicalId":353167,"journal":{"name":"2014 IEEE Real-Time Systems Symposium","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126754151","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Adaptive Mixed Criticality Scheduling with Deferred Preemption","authors":"A. Burns, Robert I. Davis","doi":"10.1109/RTSS.2014.12","DOIUrl":"https://doi.org/10.1109/RTSS.2014.12","url":null,"abstract":"Adaptive Mixed Criticality (AMC) scheduling has previously been shown to be the most effective fixed priority approach for scheduling mixed criticality systems, while the idea of final non-preemptive regions has been shown to improve the schedulability of systems with a single criticality level. In this paper, we combine AMC with the concept of non-preemptive regions by making the final part of each task's execution at each criticality level non-preemptive. We derive schedulability analysis for this approach, and provide an effective algorithm for choosing each task's priority and the durations of its non-preemptive regions. Evaluations illustrate the benefits of this approach in terms of increased schedulability.","PeriodicalId":353167,"journal":{"name":"2014 IEEE Real-Time Systems Symposium","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129219210","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
K. Chatterjee, Andreas Pavlogiannis, A. Kößler, U. Schmid
{"title":"A Framework for Automated Competitive Analysis of On-line Scheduling of Firm-Deadline Tasks","authors":"K. Chatterjee, Andreas Pavlogiannis, A. Kößler, U. Schmid","doi":"10.1109/RTSS.2014.9","DOIUrl":"https://doi.org/10.1109/RTSS.2014.9","url":null,"abstract":"We present a flexible framework for the automated competitive analysis of on-line scheduling algorithms for firm-deadline real-time tasks based on multi-objective graphs: Given a task set and an on-line scheduling algorithm specified as a labeled transition system, along with some optional safety, liveness, and/or limit-average constraints for the adversary, we automatically compute the competitive ratio of the algorithm w.r.t. A clairvoyant scheduler. We demonstrate the flexibility and power of our approach by comparing the competitive ratio of several on-line algorithms, including Dover, that have been proposed in the past, for various task sets. Our experimental results reveal that none of these algorithms is universally optimal, in the sense that there are task sets where other schedulers provide better performance. Our framework is hence a very useful design tool for selecting optimal algorithms for a given application.","PeriodicalId":353167,"journal":{"name":"2014 IEEE Real-Time Systems Symposium","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128707343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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