scholarly journals Reducing WCET Overestimations in Multi-Thread Loops with Critical Section Usage

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1747
Author(s):  
Simona Ramanauskaite ◽  
Asta Slotkiene ◽  
Kornelija Tunaityte ◽  
Ivan Suzdalev ◽  
Andrius Stankevicius ◽  
...  
Keyword(s):  
Execution Time ◽  
Timing Analysis ◽  
Time Estimation ◽  
Calculation Model ◽  
Critical Section ◽  
Worst Case ◽  
Worst Case Execution Time ◽  
Time Calculation ◽  
Multiple Threads ◽  
Time Systems

Worst-case execution time (WCET) is an important metric in real-time systems that helps in energy usage modeling and predefined execution time requirement evaluation. While basic timing analysis relies on execution path identification and its length evaluation, multi-thread code with critical section usage brings additional complications and requires analysis of resource-waiting time estimation. In this paper, we solve a problem of worst-case execution time overestimation reduction in situations when multiple threads are executing loops with the same critical section usage in each iteration. The experiment showed the worst-case execution time does not take into account the proportion between computational and critical sections; therefore, we proposed a new worst-case execution time calculation model to reduce the overestimation. The proposed model results prove to reduce the overestimation on average by half in comparison to the theoretical model. Therefore, this leads to more accurate execution time and energy consumption estimation.

Use of Measurements in Worst-Case Execution Time Estimation for Real-Time Systems

2021 ◽  
Author(s):  
Jessica Junia Santillo Costa ◽  
Romulo Silva de Oliveira ◽  
Luis Fernando Arcaro
Keyword(s):  
Real Time ◽  
Execution Time ◽  
Time Estimation ◽  
Real Time Systems ◽  
Worst Case ◽  
Worst Case Execution Time ◽  
Time Systems

An Overview of Worst-Case Execution Time Estimation for Embedded Programs

2014 ◽  
Vol 651-653 ◽  
pp. 624-629
Author(s):  
Liang Liang Kong ◽  
Lin Xiang Shi ◽  
Lin Chen
Keyword(s):  
Embedded Systems ◽  
Real Time ◽  
Execution Time ◽  
Time Estimation ◽  
Worst Case ◽  
Performance Metric ◽  
Worst Case Execution Time ◽  
Hard Real Time ◽  
Time Systems

Most embedded systems are real-time systems, so real-time is an important performance metric for embedded systems. The worst-case execution time (WCET) estimation for embedded programs could satisfy the requirement of hard real-time evaluation, so it is widely used in embedded systems evaluation. Based on sufficient survey on the progress of WCET estimation around the world, it proposes a new classification of WCET estimation. After introducing the principle of WCET estimation, it mainly demonstrates various types of technologies to estimate WCET and classifies them into two main streams, namely, static and dynamic WCET estimations. Finally, it shows the development of WCET analysis tools.

scholarly journals Worst-case Execution Time Calculation for Query-based Monitors by Witness Generation

2021 ◽  
Vol 20 (6) ◽  
pp. 1-36
Author(s):  
Márton Búr ◽  
Kristóf Marussy ◽  
Brett H. Meyer ◽  
Dániel Varró
Keyword(s):  
Real Time ◽  
Execution Time ◽  
Timing Analysis ◽  
Runtime Monitoring ◽  
Worst Case ◽  
Data Intensive ◽  
Monitoring Programs ◽  
Worst Case Execution Time ◽  
Time Calculation ◽  
Graph Queries

Runtime monitoring plays a key role in the assurance of modern intelligent cyber-physical systems, which are frequently data-intensive and safety-critical. While graph queries can serve as an expressive yet formally precise specification language to capture the safety properties of interest, there are no timeliness guarantees for such auto-generated runtime monitoring programs, which prevents their use in a real-time setting. While worst-case execution time (WCET) bounds derived by existing static WCET estimation techniques are safe, they may not be tight as they are unable to exploit domain-specific (semantic) information about the input models. This article presents a semantic-aware WCET analysis method for data-driven monitoring programs derived from graph queries. The method incorporates results obtained from low-level timing analysis into the objective function of a modern graph solver. This allows the systematic generation of input graph models up to a specified size (referred to as witness models ) for which the monitor is expected to take the most time to complete. Hence, the estimated execution time of the monitors on these graphs can be considered as safe and tight WCET. Additionally, we perform a set of experiments with query-based programs running on a real-time platform over a set of generated models to investigate the relationship between execution times and their estimates, and we compare WCET estimates produced by our approach with results from two well-known timing analyzers, aiT and OTAWA.

scholarly journals Worst-case execution-time analysis for embedded real-time systems

2003 ◽  
Vol 4 (4) ◽  
pp. 437-455 ◽  
Author(s):  
Jakob Engblom ◽  
Andreas Ermedahl ◽  
Mikael Sjödin ◽  
Jan Gustafsson ◽  
Hans Hansson
Keyword(s):  
Real Time ◽  
Execution Time ◽  
Real Time Systems ◽  
Time Analysis ◽  
Worst Case ◽  
Worst Case Execution Time ◽  
Time Systems

scholarly journals Analysing extreme value theory efficiency in probabilistic wcet estimation with block maxima

2021 ◽  
pp. 131-154
Author(s):  
Guilherme Isaias Debom Machado ◽  
Fabian Luis Vargas ◽  
Celso Maciel da Costa
Keyword(s):  
Extreme Value Theory ◽  
Execution Time ◽  
Value Theory ◽  
Extreme Value ◽  
System Delay ◽  
Worst Case ◽  
Worst Case Execution Time ◽  
Real Behavior ◽  
Block Maxima ◽  
Time Systems

The execution time is a requirement as much important as the computed result when designing real-time systems for critical applications. It is imperative to know the possible execution times, especially when some system delay may incur in equipment damages or even in crew injuries. With that in mind, the current work analyzes different techniques to define the Probabilistic Worst Case Execution Time (pWCET) using the Extreme Value Theory (EVT). Since probabilistic methodologies have been widely explored, this study aims to assure how accurate the pWCET estimations are when applying EVT knowledge. This analysis aims to compare system pWCET estimations to this real behavior, predicting the upper bound execution limits of two algorithms on MIPS processor. Further, this work regards the Block Maxima technique, which select the highest measured values to define a probabilistic distribution that represents the analyzed system. Based on the outcomes the Block Maxima technique points some limitations as requiring a large number of samples to get a reliable analysis. The obtained results have shown that EVT is a useful and trustworthy technique to define pWCET estimations.

Interactive WCET Prediction with Warning for Timeout Risk

2017 ◽  
Vol 31 (05) ◽  
pp. 1750012 ◽  
Author(s):  
Fanqi Meng ◽  
Xiaohong Su ◽  
Zhaoyang Qu
Keyword(s):  
Execution Time ◽  
Control Flow ◽  
Real Time Systems ◽  
Wcet Analysis ◽  
Running Speed ◽  
Worst Case ◽  
Worst Case Execution Time ◽  
Level Model ◽  
Hard Real Time ◽  
Time Systems

Worst case execution time (WCET) analysis is essential for exposing timeliness defects when developing hard real-time systems. However, it is too late to fix timeliness defects cheaply since developers generally perform WCET analysis in a final verification phase. To help developers quickly identify real timeliness defects in an early programming phase, a novel interactive WCET prediction with warning for timeout risk is proposed. The novelty is that the approach not only fast estimates WCET based on a control flow tree (CFT), but also assesses the estimated WCET with a trusted level by a lightweight false path analysis. According to the trusted levels, corresponding warnings will be triggered once the estimated WCET exceeds a preset safe threshold. Hence developers can identify real timeliness defects more timely and efficiently. To this end, we first analyze the reasons of the overestimation of CFT-based WCET calculation; then we propose a trusted level model of timeout risks; for recognizing the structural patterns of timeout risks, we develop a risk data counting algorithm; and we also give some tactics for applying our approach more effectively. Experimental results show that our approach has almost the same running speed compared with the fast and interactive WCET analysis, but it saves more time in identifying real timeliness defects.

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