Using supertasks to improve processor utilization in multiprocessor real-time systems

Holman, Philip; Anderson, H. A.

doi:10.1109/emrts.2003.1212726

Cited by 10 publications

(14 citation statements)

References 9 publications

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“…To characterize scheduling guarantees, we use a four-parameter model, previously proposed by us in [Holman and Anderson 2003]. First, we let β − (≥ 1) and β + (≥ 1) denote (real-valued) lower and upper lag scalers.…”

Section: Pfair Variants Srinivasan and Andersonmentioning

confidence: 99%

Locking under Pfair scheduling

Holman

Anderson

2006

ACM Trans. Comput. Syst.

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We present several locking synchronization protocols for Pfair-scheduled multiprocessor systems. We focus on two classes of protocols. The first class is only applicable in systems in which all critical sections are short relative to the length of the scheduling quantum. In this case, efficient synchronization can be achieved by ensuring that all locks have been released before tasks are preempted. This is accomplished by exploiting the quantum-based nature of Pfair scheduling, which provides a priori knowledge of all possible preemption points. The second and more general protocol class is applicable to any system. For this class, we consider the use of a client-server model. We also discuss the viability of inheritance-based protocols in Pfair-scheduled systems.

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Section: Pfair Variants Srinivasan and Andersonmentioning

confidence: 99%

Locking under Pfair scheduling

Holman

Anderson

2006

ACM Trans. Comput. Syst.

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“…Whenever a supertask is scheduled, one of its component tasks is selected to execute according to an internal scheduling algorithm. In previous work, we presented algorithms for deriving supertask weights from component task sets using either quantum-based [6] or event-driven [9] scheduling. In addition to hierarchal-scheduling support, supertasks also provide a means to selectively restrict which tasks may execute in parallel.…”

Section: Extensionsmentioning

confidence: 99%

“…In [6,9], a supertask weight is cho- sen by comparing the least amount of processor time guaranteed to a supertask to the total processor-time requirement of all component tasks. Only the first of these two quantities requires adjustment due to staggering, and is independent of (E2).…”

Section: Impact On Analysismentioning

confidence: 99%

“…These extensions include task synchronization mechanisms [7,8], techniques for accounting for system overheads [14], and support for hierarchal scheduling [6,7,8,9]. To evaluate Pfair scheduling and its extensions, we have developed a Pfair prototype (from which we obtained some of the results presented later) that runs on a bus-based symmetric multiprocessor (SMP).…”

Section: Introductionmentioning

confidence: 99%

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Implementing pfairness on a symmetric multiprocessor

Holman

Anderson

Proceedings. RTAS 2004. 10th IEEE Real-Time and Embedded Technology and Applications Symposium, 2004.

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We consider the implementation of a Pfair scheduler on a symmetric multiprocessor (SMP). Although SMPs are in many ways well-suited for Pfair scheduling, experimental results presented herein suggest that bus contention resulting from the simultaneous scheduling of all processors can substantially degrade performance. To correct this problem, we propose a staggered model for Pfair scheduling that strives to improve performance by more evenly distributing bus traffic over time. Additional simulations and experiments with a scheduler prototype are presented to demonstrate the effectiveness of the staggering approach. In addition, we discuss other techniques for improving performance while maintaining worst-case predictability. Finally, we present an efficient scheduling algorithm to support the proposed model and briefly explain how existing Pfair results apply to staggered scheduling. *

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“…If some tasks read data from a device that is physically located in or connected to one of the machines, then that tasks must execute in their entirety in that particular machine and cannot be migrated to another processor. Moir and Ramamurthy [24] proposed the supertask approach [18,19,20]. In this approach, the non-migratory tasks bound to a specific processor are combined to be a single "supertask," which is then scheduled as an ordinary Pfair task; when a supertask is scheduled, one of its component tasks is selected for execution.…”

Section: Introductionmentioning

confidence: 99%

An efficient algorithm to reduce the inflations in multi- supertask environment by using a transient behavior prediction method

Hsu

Chen²

IEEE International Symposium on Communications and Information Technology, 2004. ISCIT 2004.

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Abstract:The supertask approach was proposed by Moir and Ramamthy as a means of supporting non-migratory tasks in Pfair-scheduled systems. In this approach, tasks bound to the same processor are combined into a single server task, called a supertask, which is scheduled as an ordinary Pfair task. When a supertask is scheduled, one of its component tasks is selected for execution. In previous work, Holman et al. showed that component-task deadlines can be guaranteed by inflating each supertask's utilization. In addition, their experimental results showed that the required inflation factors should be small in practice. Consequently, the average inflation produced by their rules is much greater than that actually required by the supertasks. In this paper, we first propose a notion of Transient Behavior Prediction for supertasks, which predicts the latest possible finish time of subtasks that belong to supertasks. On the basis of the notion, we present an efficient schedulability algorithm for Pfair supertasks in which the deadlines of all component tasks can be guaranteed. In addition, we propose a task merging process which combines the unschedulable supertasks with some Pfair tasks; hence, a newly supertask can be scheduled in the system. Finally, we propose the new reweighting functions that can be used when the previous two methods fail. Our reweighting functions produce smaller inflation factor than the previous work does. To demonstrate the efficacy of the supertasking approach, we present the experimental evaluations of our algorithm, which decreases substantially a number of reweights and the size of inflation when there are many supertasks in the Pfair-scheduled systems.

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Using supertasks to improve processor utilization in multiprocessor real-time systems

Cited by 10 publications

References 9 publications

Locking under Pfair scheduling

Locking under Pfair scheduling

Implementing pfairness on a symmetric multiprocessor

An efficient algorithm to reduce the inflations in multi- supertask environment by using a transient behavior prediction method

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