We consider the intra-sporadic task model, which is a generalization of the sporadic task model motivated by recent work on Pfair scheduling. The intra-sporadic model is essentially a quantum-based, multiprocessor variant of the uniprocessor rate-based execution model of Jeffay and Goddard. In the intra-sporadic model, a task is specified by an average rate of execution, and there is no restriction on instantaneous execution rates. Such exibility is useful in applications in which some processing steps may be highly jittered. In previous work, we showed that an intra-sporadic task system is feasible on M processors i its total utilization is at most M . We also gave an optimal algorithm for scheduling intra-sporadic tasks on two processors. In this paper, we show that the PD² Pfair algorithm can be used to schedule any intra-sporadic task system that is feasible on M processors. Because the sporadic model is a special case of the intrasporadic model, our work shows that PD² is also optimal for scheduling sporadic tasks on a multiprocessor. This paper is the first to show that sporadic or intra-sporadic tasks can be optimally scheduled on systems of more than two processors.

This paper describes how Dynamic WindowConstrained Scheduling (DWCS) can guarantee real-time service to packets from multiple streams with different performance objectives. We show that: (1) DWCS can guarantee that no more than x packets miss their deadlines for every y consecutive packets requiring service, as long as the minimum aggregate bandwidth requirement of all real-time packet streams does not exceed the available bandwidth, (2) using DWCS, the delay of service to realtime packet streams is bounded even when the scheduler is overloaded, (3) DWCS can ensure that the delay bound of any given stream is independent of other streams, and (4) a fast response time for best-effort packet streams, in the presence of real-time packet streams, is possible. Furthermore, if a feasible schedule exists, each stream is guaranteed a minimum fraction of available bandwidth over a finite window of time. 1. Introduction Many real-time, distributed applications, such as telemedicine, virtual env...

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This paper considers the scheduling of soft real-time sporadic task systems under global EDF on an iden-tical multiprocessor. Though Pfair scheduling is theoretically optimal for hard real-time task systems on multiprocessors, it can incur significant run-time overhead. Hence, other scheduling algorithms that are not optimal, including EDF, have continued to receive considerable attention. However, prior research on such algorithms has focussed mostly on hard real-time systems, where, to ensure that all deadlines are met, ap-proximately 50 % of the available processing capacity will have to be sacrificed in the worst case. This may be overkill for soft real-time systems that can tolerate deadline misses by bounded amounts (i.e., bounded tardiness). In this paper, we derive tardiness bounds under preemptive and non-preemptive global EDF on multiprocessors when the total utilization of a task system is not restricted and may equal the number of pro-cessors. Our tardiness bounds depend on per-task utilizations and execution costs — the lower these values, the lower the tardiness bounds. As a final remark, we note that global EDF may be superior to partitioned EDF for multiprocessor-based soft real-time systems in that the latter does not offer any scope to improve system utilization even if bounded tardiness can be tolerated.

This paper presents an architecture for quality of service (QoS) control of time-sensitive applications in multi-programmed embedded systems. In such systems, tasks must receive appropriate timeliness guarantees from the operating system independently from one another; otherwise, the QoS experienced by the users may decrease. Moreover, fluctuations in time of the workloads make a static partitioning of the central processing unit (CPU) that is neither appropriate nor convenient, whereas an adaptive allocation based on an on-line monitoring of the application behaviour leads to an optimum design. By combining a resource reservation scheduler and a feedback-based mechanism, we allow applications to meet their QoS requirements with the minimum possible impact on CPU occupation. We implemented the framework in AQuoSA (Adaptive Quality of Service Architecture (AQuoSA).

This paper describes an algorithm for scheduling packets in real-time multimedia data streams. Common to these classes of data streams are service constraints in terms of bandwidth and delay. However, it is typical for realtime multimedia streams to tolerate bounded delay variations and, in some cases, finite losses of packets. We have therefore developed a scheduling algorithm that assumes streams have window-constraints on groups of consecutive packet deadlines. A window-constraint defines the number of packet deadlines that can be missed in a window of deadlines for consecutive packets in a stream.

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Today, only very few techniques out of the host of work on formal performance and timing analysis have been adopted in MpSoC (multiprocessor system-on-chip) design. One of the key reasons is a mismatch between the scheduling models assumed in most formal approaches and the heterogenous world of MpSoC scheduling techniques and communication patterns. This heterogeneity results from IP reuse and a plug-and-play design style, required to effectively reach the necessary design productivity. A second problem is the model complexity. While complex, specialized models can find their way into industry niches, their broad acceptance is extremely doubtful. In this paper, we review the existing scheduling analysis techniques with respect to these key requirements and derive a good compromise between model simplicity on the one hand, and applicability to MpSoC design on the other hand. The approach represents system-level scheduling analysis as a flow-analysis problem for event streams that can be configured to reuse the existing local scheduling analysis techniques. We define transformations between few key event stream models to meet the interfacing requirements of the compositional design style. An example demonstrates the application of the approach, as well as the worthiness of the results.

1 This author was also supported by an IBM Ph.D. fellowship.

Formal methods are growing in importance for performance analysis of real-time systems, but embedded system heterogeneity limits the application of these methods to subsystems or special cases. One of the problems is the rich variety of interactions between embedded system processes, which cannot be directly expressed with the typical event models used in real-time analysis.