## Sensitivity Analysis for Fixed-Priority RealTime Systems (2006)

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Venue: | BNB06] [CKT03] [FGB01] [HHJ |

Citations: | 30 - 10 self |

### BibTeX

@INPROCEEDINGS{Bini06sensitivityanalysis,

author = {Enrico Bini and Marco Di Natale and Giorgio Buttazzo and Scuola Superiore Sant’anna},

title = {Sensitivity Analysis for Fixed-Priority RealTime Systems},

booktitle = {BNB06] [CKT03] [FGB01] [HHJ},

year = {2006}

}

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### Abstract

At early stages in the design of real-time embedded applications, the timing attributes of the computational activities are often incompletely specified or subject to changes. Later in the development cycle, schedulability analysis can be used to check the feasibility of the task set. However, the knowledge of the worst-case response times of tasks is often not sufficient to precisely determine the actions that would correct a non-schedulable design. In these situations, sensitivity analysis provides useful information for changing the implementation, by giving a measure of those computation times that must be reduced to achieve feasibility, or those that can be increased in case of a product extension, or providing the range of feasible periods for selecting the proper task activation rates. In this work, we exploit the concept of feasibility region to propose a faster and more concise solution to the sensitivity analysis problem with respect to existing techniques based on binary search. Furthermore, we show how the formalization of other problems in the feasibility domain, such as managing overloads through elastic scheduling, can be extended to the exact analysis. 1.

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Citation Context ...mputation times or on the activation rates to make the system schedulable. For models that can be analyzed by a simple utilizationbased test, the feasibility region is defined by the well known bound =-=[13]-=- C · f ≤ U A lub where UA lub is the least upper bound of the algorithm A considered for scheduling the set of tasks. As it will be shown later, the feasibility region both in the C-space and in the f... |

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Citation Context ... a performance degradation. Being a generalization of feasibility analysis, sensitivity analysis heavily borrows from existing results. The most popular among them is the Response Time Analysis (RTA) =-=[11, 1]-=-. Although alternative efficient techniques have been proposed in the literature [4], RTA is currently the most adopted technique for deciding upon the schedulability of a task set, since it provides ... |

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Citation Context ...hniques for sensitivity analysis are based on binary search over the schedulability property defined by Lehoczky [12], or other formulations of the algorithm for computing the response time of a task =-=[18, 23]-=-. In the context of distributed scheduling, a system-level sensitivity analysis of the task computation times against end-to-end deadlines has been proposed [19]. The method is based on binary search ... |

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Citation Context ...ious work, our sensitivity analysis also applies to the domain of task periods, providing a theoretical support for those control systems that perform rate adaptation to cope with overload conditions =-=[7, 8]-=-. Moreover, it addresses very practical design issues, such as finding the fastest execution rate that can be assigned to one or more critical control loops. Alternatively, when fixing the defects of ... |

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Citation Context ...the multiframe task model proposed by Mok [16] allows the user to specify different execution times for different task instances, through a sequence of numbers. The generalized multi-frame task model =-=[3]-=- adds explicit deadlines to the multi-frame model and allows assigning distinct minimum separation values to the instances inside a multi-frame cycle. The recurring task model defined by Baruah [2] al... |

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Citation Context ...analysis heavily borrows from existing results. The most popular among them is the Response Time Analysis (RTA) [11, 1]. Although alternative efficient techniques have been proposed in the literature =-=[4]-=-, RTA is currently the most adopted technique for deciding upon the schedulability of a task set, since it provides a necessary and sufficient condition. Efforts have been devoted to reduce its averag... |

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Citation Context ...ah [2] allows modeling restricted forms of conditional real-time code and control flows. To relax the pessimistic assumptions typically made in the evaluation of the task set attributes, some authors =-=[6, 14]-=- proposed a probabilistic model for task execution times and activations, which can be used to analyze soft real-time applications. Feasibility tests for these models are derived by applying stochasti... |

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Citation Context ...ently the most adopted technique for deciding upon the schedulability of a task set, since it provides a necessary and sufficient condition. Efforts have been devoted to reduce its average complexity =-=[21]-=- and extend its applicability to more general task models [17]. Unfortunately, however, RTA is unfit for sensitivity analysis since it provides an aggregate value as the result of the application of a... |

17 | Optimal task rate selection in fixed priority systems
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Citation Context ...) and the analysis tool in MAST [15]. In this paper we present a new type of sensitivity analysis that exploits the concept of feasibility region in the domain of the task variables, as introduced in =-=[4, 5]-=-. By measuring the distance of a task configuration, expressed as a point in the space of the task variables, from the region delimiting the set of the feasible tasks, we can provide the variations th... |

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Citation Context ...ious work, our sensitivity analysis also applies to the domain of task periods, providing a theoretical support for those control systems that perform rate adaptation to cope with overload conditions =-=[7, 8]-=-. Moreover, it addresses very practical design issues, such as finding the fastest execution rate that can be assigned to one or more critical control loops. Alternatively, when fixing the defects of ... |

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Citation Context ...hniques for sensitivity analysis are based on binary search over the schedulability property defined by Lehoczky [12], or other formulations of the algorithm for computing the response time of a task =-=[18, 23]-=-. In the context of distributed scheduling, a system-level sensitivity analysis of the task computation times against end-to-end deadlines has been proposed [19]. The method is based on binary search ... |

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Citation Context ...ensitivity analysis of the task computation times against end-to-end deadlines has been proposed [19]. The method is based on binary search and has been implemented in commercial tools by SymTAVision =-=[10]-=-. A problem of this method is that it performs a feasibility test at each iteration of the binary search, making the resulting complexity considerably high. Our algorithm does not suffer from this dra... |

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Citation Context ...is greater simplicity comes at the price of a simpler task model. Other tools offering a built-in sensitivity analysis engine are RTA-OSEK by ETAS (formerly LiveDevices) and the analysis tool in MAST =-=[15]-=-. In this paper we present a new type of sensitivity analysis that exploits the concept of feasibility region in the domain of the task variables, as introduced in [4, 5]. By measuring the distance of... |