Probabilistic-WCET reliability: Statistical testing of EVT hypotheses

Reghenzani, Federico; Massari, Giuseppe; Fornaciari, William

doi:10.1016/j.micpro.2020.103135

Cited by 17 publications

(20 citation statements)

References 41 publications

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“…The possible applications of the probabilistic theory, shown in the previous section, rely on the fact that the pWCET is correctly computed. The EVT produces reliable results only if three assumptions are satisfied: the input representativity, the independent and identically distributed condition, and the maximum domain of attraction hypotheses [53]. Such conditions are analyzed in detail in the following paragraphs.…”

Section: Applicabilitymentioning

confidence: 99%

“…This condition is almost always true if the time measurements are considered as continuous samples, while in the discrete case (e.g., number of clocks), this cannot be assumed true and must be verified. In any case, to check the validity of the MDA hypothesis, a goodness-of-fit statistical test is usually performed [53] a posteriori of the pWCET analysis. This goodness-of-fit test also helps to identify any error in the estimation phase due to its ability to detect the discrepancies between the estimated pWCET distribution and the real measured data.…”

Section: Maximum Domain Of Attraction Hypothesismentioning

confidence: 99%

“…Applying the statistical theory to real-world scenarios is, in fact, not trivial and requires methods and procedures designed to fit the specific problem domain. In a previous work [52], we investigated the adherence of such hypotheses for embedded systems by running WCET benchmarks on different platforms, from a simple microprocessor to a complex embedded Linux system. A detailed description of the estimation process and statistical tests is available in the paper by Santinelli et al [57] and by Lima et al [41].…”

Section: B Probabilistic Real-time In Cpsmentioning

confidence: 99%

“…Finally, the Kolmogorov-Smirnov (KS) and the Anderson-Darling (AD) tests were used to check the MDA hypothesis. The choice of these tests was made based on previous stateof-the-art works [53].…”

Section: Compliance With Evt Hypothesesmentioning

confidence: 99%

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Timing Predictability in High-Performance Computing With Probabilistic Real-Time

2020

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Application requirements in High-Performance Computing (HPC) are becoming increasingly exacting, and the demand for computational resources is rising. In parallel, new application domains are emerging, as well as additional requirements, such as meeting real-time constraints. This requirement, typical of embedded systems, is difficult to guarantee when dealing with HPC infrastructures, due to the intrinsic complexity of the system. Traditional embedded systems static analyses to estimate the Worst-Case Execution Time (WCET) are not applicable to HPC, because modeling and analyzing all the system's hardware and software components is not practical. Measurement-based probabilistic analyses for the WCET emerged in the last decade to overcome these issues, but it requires the system to satisfy certain conditions to estimate a correct and safe WCET. In this work, we show the emerging application timing requirements, and we propose to exploit the probabilistic real-time theory to achieve the required time predictability. After a brief recap of the fundamentals of this methodology, we focus on its applicability to HPC systems, to check their ability to satisfy such conditions. In particular, we studied the advantages of having heterogeneous processors in HPC nodes and how resource management affects the applicability of the proposed technique.

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Section: Applicabilitymentioning

confidence: 99%

Section: Maximum Domain Of Attraction Hypothesismentioning

confidence: 99%

Section: B Probabilistic Real-time In Cpsmentioning

confidence: 99%

Section: Compliance With Evt Hypothesesmentioning

confidence: 99%

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Timing Predictability in High-Performance Computing With Probabilistic Real-Time

2020

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“…Most of these approaches are based on the estimation of the distribution tail by exploiting the Extreme Value Theory, a statistical theory to model the probability of extreme events, that in the real-time case it is used for the WCET of the tasks. Unfortunately, the theory is still immature and several challenges yet to be addressed before considering its results reliable [31], [43], [45]. Hence, in this work, we propose to exploit the probabilistic information not to directly estimate the WCET for scheduling analysis purposes, but to use them for the optimization of the system energy consumption.…”

Section: Introductionmentioning

confidence: 99%

Optimizing Energy in Non-Preemptive Mixed-Criticality Scheduling by Exploiting Probabilistic Information

Bhuiyan

Reghenzani

Fornaciari

et al. 2020

IEEE Trans. Comput.-Aided Des. Integr. Circuits Syst.

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The strict requirements on the timing correctness biased the modeling and analysis of real-time systems towards the worst-case performances. Such focus on the worst-case, however, does not provide enough information to effectively steer the resource/energy optimization. In this paper, we integrate a probabilistic-based energy prediction strategy with the precise scheduling of mixed-criticality tasks, where the timing correctness must be met for all tasks at all scenarios. The Dynamic Voltage and Frequency Scaling (DVFS) is applied to this precise scheduling policy to enable energy minimization. We propose a probabilistic technique to derive an energy-efficient speed (for the processor) that minimizes the average energy consumption, while guaranteeing the (worst-case) timing correctness for all tasks, including lo-criticality ones, under any execution condition. We present a response time analysis for such systems under the nonpreemptive fixed-priority scheduling policy. Finally, we conduct an extensive simulation campaign based on randomly generated task sets to verify the effectiveness of our algorithm (w.r.t. energy savings) and it reports up to 46% energy-saving.

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Beyond the Traditional Analyses and Resource Management in Real-Time Systems

Reghenzani

2022

Special Topics in Information Technology

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The difficulties in estimating the Worst-Case Execution Time (WCET) of applications make the use of modern computing architectures limited in real-time systems. Critical embedded systems require the tasks of hard real-time applications to meet their deadlines, and formal proofs on the validity of this condition are usually required by certification authorities. In the last decade, researchers proposed the use of probabilistic measurement-based methods to estimate the WCET instead of traditional static methods. In this chapter, we summarize recent theoretical and quantitative results on the use of probabilistic approaches to estimate the WCET presented in the PhD thesis of the author, including possible exploitation scenarios, open challenges, and future directions.

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Probabilistic-WCET reliability: Statistical testing of EVT hypotheses

Cited by 17 publications

References 41 publications

Timing Predictability in High-Performance Computing With Probabilistic Real-Time

Timing Predictability in High-Performance Computing With Probabilistic Real-Time

Optimizing Energy in Non-Preemptive Mixed-Criticality Scheduling by Exploiting Probabilistic Information

Beyond the Traditional Analyses and Resource Management in Real-Time Systems

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