Scheduling aperiodic tasks in dynamic priority systems

Spuri, Marco; Buttazzo, Giorgio

doi:10.1007/bf00360340

Cited by 283 publications

(169 citation statements)

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“…The total bandwidth server (TBS) [79] provides soft CPU reservations: it guarantees that a minimum fraction of the total processor bandwidth will be available to entities that it schedules, but it can also take advantage of slack time in the schedule to provide extra CPU time. It is deadlinebased, and consequently can be scheduled using a USP.…”

Section: Schedulers From the Literaturementioning

confidence: 99%

Using Hierarchical Scheduling to Support Soft Real-Time Applications in General-Purpose Operating Systems

Stankovic¹,

Regehr²

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The CPU schedulers in general-purpose operating systems are designed to provide fast response time for interactive applications and high throughput for batch applications. The heuristics used to achieve these goals do not lend themselves to scheduling real-time applications, nor do they meet other scheduling requirements such as coordinating scheduling across several processors or machines, or enforcing isolation between applications, users, and administrative domains. Extending the scheduling subsystems of general-purpose operating systems in an ad hoc manner is time consuming and requires considerable expertise as well as source code to the operating system. Furthermore, once extended, the new scheduler may be as inflexible as the original.The thesis of this dissertation is that extending a general-purpose operating system with a general, heterogeneous scheduling hierarchy is feasible and useful. A hierarchy of schedulers generalizes the role of CPU schedulers by allowing them to schedule other schedulers in addition to scheduling threads. A general, heterogeneous scheduling hierarchy is one that allows arbitrary (or nearly arbitrary) scheduling algorithms throughout the hierarchy. In contrast, most of the previous work on hierarchical scheduling has imposed restrictions on the schedulers used in part or all of the hierarchy.This dissertation describes the Hierarchical Loadable Scheduler (HLS) architecture, which permits schedulers to be dynamically composed in the kernel of a general-purpose operating system. The most important characteristics of HLS, and the ones that distinguish it from previous work, are that it has demonstrated that a hierarchy of nearly arbitrary schedulers can be efficiently implemented in a general-purpose operating system, and that the behavior of a hierarchy of soft real-time schedulers can be reasoned about in order to provide guaranteed scheduling behavior to application threads. The flexibility afforded by HLS permits scheduling behavior to be tailored to meet complex requirements without encumbering users who have modest requirements with the performance and administrative costs of a complex scheduler.Contributions of this dissertation include the following.(1) The design, prototype implementation, and performance evaluation of HLS in Windows 2000. (2) A system of guarantees for scheduler composition that permits reasoning about the scheduling behavior of a hierarchy of soft real-time schedulers. Guarantees assure users that application requirements can be met throughout the lifetime of the application, and also provide application developers with a model of CPU allocation to which they can program. (3) The design, implementation, and evaluation of two augmented CPU reservation schedulers, which provide increase scheduling predictability when low-level operating system activity steals time from applications. iv AcknowledgmentsFirst of all, many thanks to my advisor Jack Stankovic for being supportive of me and my work, for giving me enough rope but not too much, for pushi...

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Section: Schedulers From the Literaturementioning

confidence: 99%

Using Hierarchical Scheduling to Support Soft Real-Time Applications in General-Purpose Operating Systems

Stankovic¹,

Regehr²

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“…An e cient method for assigning deadlines to soft aperiodic requests has been proposed by Spuri and Buttazzo in Ref. [23]. In this work the authors describe an algorithm, the Total Bandwidth Server (TBS) for enhancing the response time of soft aperiodic tasks in hard real-time environments.…”

Section: Sharing Resources Between Soft and Hard Tasksmentioning

confidence: 99%

“…[23], a set of periodic tasks with utilization factor p n i 1 g i a i and a TBS with a bandwidth s is schedulable by EDF (without resource constraints) if and only if p s T 1X 6…”

Section: Assigning Deadlines To Soft Tasksmentioning

confidence: 99%

“…Except for the TBS, dynamic aperiodic servers can mainly be divided into two classes: ®xed capacity servers (e.g., Polling, Deferrable [9] or Sporadic Server [23]), and slack stealing techniques (e.g., EDL and IPE [23]). …”

Section: Other Server Mechanismsmentioning

confidence: 99%

“…On the other hand, several aperiodic service mechanisms have been proposed under RM www.elsevier.com/locate/sysarc Journal of Systems Architecture 46 (2000) 327±338 [12,13,1,26] and under EDF [20,9,22,23], but no resource constraints have been taken into account. In Ref.…”

Section: Introductionmentioning

confidence: 99%

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Schedulability analysis of periodic and aperiodic tasks with resource constraints

Lipari

Buttazzo

2000

Journal of Systems Architecture

Self Cite

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In this paper, we address the problem of scheduling hybrid task sets consisting of hard periodic and soft aperiodic tasks that may share resources in exclusive mode in a dynamic environment, where tasks are scheduled based on their deadlines. Bounded blocking on exclusive resources is achieved by means of a dynamic resource access protocol which also prevents deadlocks and chained blocking. Aperiodic responsiveness is enhanced by an e cient servicing technique which assigns each aperiodic request a suitable deadline. Feasibility conditions are extended to handle tasks with deadlines di erent from periods and a reclaiming technique is presented to deal with early completions. Ó

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2013

Time‐Predictable Architectures

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Scheduling aperiodic tasks in dynamic priority systems

Cited by 283 publications

References 7 publications

Using Hierarchical Scheduling to Support Soft Real-Time Applications in General-Purpose Operating Systems

Using Hierarchical Scheduling to Support Soft Real-Time Applications in General-Purpose Operating Systems

Schedulability analysis of periodic and aperiodic tasks with resource constraints

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