Obstacles in Worst-Case Execution Time Analysis

Kirner, Raimund; Puschner, Peter

doi:10.1109/isorc.2008.65

Cited by 42 publications

(26 citation statements)

References 11 publications

(12 reference statements)

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“…Measurement-based timing analysis is a common practice for timing analysis on real processors in industrial domains that include space, automotive and elements of avionics [34], [17], [20]. End-to-end measurements are collected in controlled conditions and the ETB is derived by adding an engineering margin to the Longest Observed Execution Time (LOET) [20].…”

Section: Deriving Etb Under Different Contention Conditionsmentioning

confidence: 99%

Seeking Time-Composable Partitions of Tasks for COTS Multicore Processors

Fernández

Abella

Quiñones

et al. 2015

2015 IEEE 18th International Symposium on Real-Time Distributed Computing

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Abstract-The timing verification of real-time singlecore systems involves a timing analysis step that yields an Execution Time Bound (ETB) for each task, followed by a schedulability analysis step, where the scheduling attributes of the individual tasks, including the ETB, are studied from the system level perspective. The transition between those two steps involves accounting for the interference effects that arise when tasks contend for access to shared resource. The advent of multicore processors challenges the viability of this two-step approach because several complex contention effects at the processor level arise that cause tasks to be unable to make progress while actually holding the CPU, which are very difficult to tightly capture by simply inflating the tasks' ETB. In this paper we show how contention on access to hardware shared resources creates a circular dependence between the determination of tasks' ETB and their scheduling at run time. To help loosen this knot we present an approach that acknowledges different flavors of time composability, examining in detail the variant intended for partitioned scheduling, which we evaluate on two real processor boards used in the space domain.

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Section: Deriving Etb Under Different Contention Conditionsmentioning

confidence: 99%

Seeking Time-Composable Partitions of Tasks for COTS Multicore Processors

Fernández

Abella

Quiñones

et al. 2015

2015 IEEE 18th International Symposium on Real-Time Distributed Computing

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“…Modern hardware equipped with performance enhancement units have dramatically complicated the static modeling [3] leading to an interest in measurement-based techniques. As the larger values of execution time are often hard to create test cases for and in normal operation occur infrequently [4], the measurementbased approaches are combined with probabilistic models that quantify how likely an execution time is exceeded.…”

Section: Introductionmentioning

confidence: 99%

Open Challenges for Probabilistic Measurement-Based Worst-Case Execution Time

Gil

Bate

Lima

et al. 2017

IEEE Embedded Syst. Lett.

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Abstract-The Worst-Case Execution Time (WCET) is a critical parameter describing the largest value for the execution time of programs. Even though such a parameter is very hard to attain, it is essential as part of guaranteeing a real-time system meets its timing requirements. The complexity of modern hardware has increased the challenges of statically analysing the WCET and reduced the reliability of purely measured the WCET. This has led to the emergence of probabilistic WCETs (pWCETs) analysis as a viable technique. The low probability of appearance of large execution times of a program has motivated the utilization of rare events theory like Extreme Value Theory (EVT). As pWCET estimation based on EVT has matured as a discipline, a number of open challenges have become apparent when applying the existing approaches. Our paper enumerates key challenges while establishing a state of the art of EVT-based pWCET estimation methods.

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“…Analysis of the worst-case execution time (WCET) [1] for systems built from conventional components is relatively complicated [2,3]. On one hand it is very difficult to re-engineer the behavior of a processor in order to construct a model that reflects the timing of all operations of the processor correctly.…”

Section: Introductionmentioning

confidence: 99%

Time-Predictable Computing

Kirner

Puschner

2010

Software Technologies for Embedded and Ubiquitous Systems

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Abstract. Real-time systems need to be time-predictable in order to prove the timeliness of all their time-critical responses. While this is a well-known fact, recent efforts of the community on concretizing the predictability of task timing have shown that there is no common agreement about what the term timepredictability exactly means. In this paper we propose a universal definition of time-predictability that combines the essence of different discussions about this term. This definition is then instantiated to concrete types of time-predictability, like worst-case execution time (WCET) predictability. Finally, we introduce the concept of a timing barrier as a mechanism for constructing time-predictable systems.

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Obstacles in Worst-Case Execution Time Analysis

Cited by 42 publications

References 11 publications

Seeking Time-Composable Partitions of Tasks for COTS Multicore Processors

Seeking Time-Composable Partitions of Tasks for COTS Multicore Processors

Open Challenges for Probabilistic Measurement-Based Worst-Case Execution Time

Time-Predictable Computing

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