Worst-case Execution Time Prediction Research Articles

Interactive WCET Prediction with Warning for Timeout Risk

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.

Timing Analysis for Data and Wrap-Around Fill Caches

The contributions of this paper are twofold. First, an automatic tool-based approach is described to bound worst-case data cache performance. The approach works on fully optimized code, performs the analysis over the entire control flow of a program, detects and exploits both spatial and temporal locality within data references, and produces results typically within a few seconds. Results obtained by running the system on representative programs are presented and indicate that timing analysis of data cache behavior usually results in significantly tighter worst-case performance predictions. Second, a method to deal with realistic cache filling approaches, namely wrap-around-filling for cache misses, is presented as an extension to pipeline analysis. Results indicate that worst-case timing predictions become significantly tighter when wrap-around-fill analysis is performed. Overall, the contribution of this paper is a comprehensive report on methods and results of worst-case timing analysis for data caches and wrap-around caches. The approach taken is unique and provides a considerable step toward realistic worst-case execution time prediction of contemporary architectures and its use in schedulability analysis for hard real-time systems.