A Practitioner’s Handbook for Real-Time Analysis

Klein, Mark; Ralya, Thomas; Pollak, Bill; Obenza, Ray; Harbour, Michael González

doi:10.1007/978-1-4615-2796-1

Cited by 344 publications

(73 citation statements)

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“…This is the basis for the traditional real-time theory [47,54]. In that theory, time constraints (which are largely limited to deadlines) are mapped to fixed priorities in algorithms such as Rate Monotonic Scheduling (RMS) [53] and Deadline Monotonic Scheduling (DMS) [53], or are mapped to dynamic priorities as in Least Laxity First (LLF) [59], or are directly used for scheduling as in Earliest Deadline First (EDF) [41].…”

Section: Timeliness Modelmentioning

confidence: 99%

On Best-Effort Utility Accrual Real-Time Scheduling on Multiprocessors

Garyali¹,

Dellinger²,

Ravindran³

2010

Lecture Notes in Computer Science

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We consider the problem of scheduling real-time tasks on a multiprocessor system. Our primary focus is scheduling on multiprocessor systems where the total task utilization demand, U , is greater than m, the number of processors on a multiprocessor system-i.e., the total available processing capacity of the system. When U > m, the system is said to be overloaded; otherwise, the system is said to be underloaded. While significant literature exists on multiprocessor real-time scheduling during underloads, little is known about scheduling during overloads, in particular, in the presence of task dependencies-e.g., due to synchronization constraints. We consider real-time tasks that are subject to time/utility function (or TUF) time constraints, which allow task urgency to be expressed independently of task importance-e.g., the most urgent task being the least important. The urgency/importance decoupling allowed by TUFs is especially important during overloads, when not all tasks can be optimally completed. We consider the timeliness optimization objective of maximizing the total accrued utility and the number of deadlines satisfied during overloads, while ensuring task mutual exclusion constraints and freedom from deadlocks. This problem is NP-hard. We develop a class of polynomial-time heuristic algorithms, called the Global Utility Accrual (or GUA) class of algorithms.The algorithms construct a directed acyclic graph representation of the task dependency relationship, and build a global multiprocessor schedule of the zero in-degree tasks to heuristically maximize the total accrued utility and ensure mutual exclusion. Potential deadlocks are detected through a cycle-detection algorithm, and resolved by aborting a task in the deadlock cycle. The GUA class of algorithms include two algorithms, namely, the Non-Greedy Global Utility Accrual (or NG-GUA) and Greedy Global Utility Accrual (or G-GUA) algorithms. NG-GUA and G-GUA differ in the way schedules are constructed towards meeting all task deadlines, when possible to do so. We establish several properties of the algorithms including conditions under which all task deadlines are met, satisfaction of mutual exclusion constraints, and deadlock-freedom.We create a Linux-based real-time kernel called ChronOS for multiprocessors. ChronOS is extended from the PREEMPT RT real-time Linux patch, which provides optimized interrupt service latencies and real-time locking primitives. ChronOS provides a scheduling framework for the implementation of a broad range of real-time scheduling algorithms, including utility accrual, non-utility accrual, global, and partitioned scheduling algorithms.We implement the GUA class of algorithms and their competitors in ChronOS and conduct experimental studies. The competitors include G-EDF, G-NP-EDF, G-FIFO, gMUA, P-EDF and P-DASA. Our study reveals that the GUA class of algorithms accrue higher utility and satisfy greater number of deadlines than the deadline-based scheduling algorithms by as much as 750% and 600%, respectively. In addition, ...

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Section: Timeliness Modelmentioning

confidence: 99%

On Best-Effort Utility Accrual Real-Time Scheduling on Multiprocessors

Garyali¹,

Dellinger²,

Ravindran³

2010

Lecture Notes in Computer Science

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“…Scheduling theory (Klein, et al, 1993) proposes two ways of analyzing response times of tasks with self-suspension: (i) treat suspension time as execution time or (ii) analyze separately each computation in worst case phasing and sum all partial results together with suspension times. Both of these methods are pessimistic however (Klein, et al, 1993).…”

Section: Response Time Analysismentioning

confidence: 99%

Timed Automata Model of Preemptive Multitasking Applications

Waszniowski

Hanzálek

2005

IFAC Proceedings Volumes

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The aim of this article is to show, how a multitasking application running under a real-time operating system compliant with the OSEK/VDX standard can be modeled by timed automata. The application under consideration consists of several tasks, it includes resource sharing and synchronization by events. For such system, model-checking theory based on timed automata and implemented in model-checking tools can be used to verify time and logical properties of the proposed model. It is shown that the proposed model is over-approximation in the case of preemptive scheduling policy. This methodology is demonstrated on automated gearbox case study.

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“…The motivation for ABASs comes from three different sources: l. architectural styles, such as those catalogued by Shaw and Garlan in (Shaw and Garlan, 1996) and by Buschmann et al in (Buschmann, et al, 1996) 2. analytic models of quality attributes, such as rate monotonic analysis for performance (Klein, et al, 1993) or Markov models for availability 3. architecture evaluation questionnaires, such as those used by AT&T (Maranzano, 1993) ABASs are a kind of architectural style, and hence they build squarely upon the foundational work of Shaw and Garlan, as well as the similar work of the design patterns community (Gamma, et al, 1994). However, in each of these cases, the kinds of reasoning that the architectural styles support is heuristic.…”

Section: Motivationsmentioning

confidence: 99%

Attribute-Based Architecture Styles

Klein

Kazman

Bass

et al. 1999

Software Architecture

Self Cite

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Abstract:Architectural styles have enjoyed widespread popularity in the past few years, and for good reason: they represent the distilled wisdom of many experienced architects and guide less experienced architects in designing their architectures. However, architectural styles employ qualitative reasoning to motivate when and under what conditions they should be used. In this paper we present the concept of an ABAS (Attribute-Based Architectural Style) which includes a set of components and connectors along with their topology, but which adds to this a quality attribute specific model that provides a method of reasoning about the behavior of component types that interact in the defined pattern. We will define ABASs in this paper, show how they are used, and argue for why this extension to the notion of architectural style is an important step toward creating a true engineering discipline of architectural design.

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A Practitioner’s Handbook for Real-Time Analysis

Cited by 344 publications

References 0 publications

On Best-Effort Utility Accrual Real-Time Scheduling on Multiprocessors

On Best-Effort Utility Accrual Real-Time Scheduling on Multiprocessors

Timed Automata Model of Preemptive Multitasking Applications

Attribute-Based Architecture Styles

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