Optimal deadline assignment for scheduling soft aperiodic tasks in hard real-time environments

Buttazzo, Giorgio; Sensini, F.

doi:10.1109/12.805154

Cited by 72 publications

(53 citation statements)

References 18 publications

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“…These results are not true for EDF, where otpimal algorithms have been found for minimizing aperiodic response times. In particular, the Improved Total Bandwith server (ITB) (Buttazzo and Sensini, 1999) assigns an initial deadline to an aperiodic request according to a TBS with a bandwidth U s = 1 − U p . Then, the algorithm tries to shorten this deadline as much as possible to enhance aperiodic responsiveness, still maintaining the periodic tasks schedulable.…”

Section: Aperiodic Task Handlingmentioning

confidence: 99%

Rate Monotonic vs. EDF: Judgment Day

Buttazzo

2003

Embedded Software

121

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Abstract. Since the first results published in 1973 by Liu and Layland on the Rate Monotonic (RM) and Earliest Deadline First (EDF) algorithms, a lot of progress has been made in the schedulability analysis of periodic task sets. Unfortunately, many misconceptions still exist about the properties of these two scheduling methods, which usually tend to favor RM more than EDF. Typical wrong statements often heard in technical conferences and even in research papers claim that RM is easier to analyze than EDF, it introduces less runtime overhead, it is more predictable in overload conditions, and causes less jitter in task execution.Since the above statements are either wrong, or not precise, it is time to clarify these issues in a systematic fashion, because the use of EDF allows a better exploitation of the available resources and significantly improves system's performance. This paper compares RM against EDF under several aspects, using existing theoretical results, specific simulation experiments, or simple counterexamples to show that many common beliefs are either false or only restricted to specific situations.

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Section: Aperiodic Task Handlingmentioning

confidence: 99%

Rate Monotonic vs. EDF: Judgment Day

Buttazzo

2003

Embedded Software

121

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“…Three aperiodic tasks servers are also provided to schedule the soft and hard aperiodic tasks together with the periodic ones: BG (Background Server ), EDL (Earliest Deadline as Late as possible) [29] and TBS (Total Bandwidth Server ) [30] . The two latter ones are optimal in the sense that they minimize the mean response time for the soft aperiodic tasks, and they maximize the acceptance ratio for the hard aperiodic tasks.…”

Section: Overviewmentioning

confidence: 99%

A concept of dynamically reconfigurable real-time vision system for autonomous mobile robotics

Cabrol

Garcia²,

Bonnin

et al. 2008

Int. J. Autom. Comput.

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Abstract:In this article, we describe specific constraints of vision systems that are dedicated to be embedded in mobile robots. If PC based hardware architecture is convenient in this field because of its versatility, its flexibility, its performance and its cost, current real-time operating systems are not completely adapted to long processings with varying duration, and it is often necessary to oversize the system to guarantee fail-safe functioning. Also, interactions with other robotic tasks having more priority are difficult to handle. To answer this problem, we have developed a dynamically reconfigurable vision processing system, based on the innovative features of Cléopatre real-time applicative layer concerning scheduling and fault tolerance. This framework allows to define emergency and optional tasks to ensure a minimal quality of service for the other subsystems of the robot, while allowing to adapt dynamically vision processing chain to an exceptional overlasting vision process or processor overload. Thus it allows a better cohabitation of several subsystems in a single hardware, and to develop less expensive but safe systems, as they will be designed for the regular case and not rare exceptional ones. At last, it brings a new way to think and develop vision systems, with pairs of complementary operators.

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“…Traditionally, hard and soft real-time systems have been scheduled using very different techniques [12]. However, many applications have both hard and soft timing constraints [3], and therefore researchers have proposed techniques for addressing mixed hard/soft real-time systems [3,5,4].…”

Section: Introductionmentioning

confidence: 99%