Sporadic Server revisited

Faggioli, Dario; Bertogna, Marko; Checconi, Fabio

doi:10.1145/1774088.1774160

Cited by 12 publications

(7 citation statements)

References 24 publications

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“…As discussed earlier, vehicles in a given lane that need to access the intersection are modeled as aperiodic tasks that are queued in a task queue (associated with that lane) until they are ready to be executed on the processor, i.e., until the vehicles are permitted to enter and cross an intersection. To serve these aperiodic tasks, we leverage the concept of sporadic servers [12]. In our setting, a sporadic server is responsible for executing the queued aperiodic requests.…”

Section: Sporadic Servers To Execute Aperiodic Tasksmentioning

confidence: 99%

A Real-Time Server Based Approach for Safe and Timely Intersection Crossings

Oza

Chantem

2019

2019 IEEE 25th International Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA)

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Safe and efficient traffic control remains a challenging task with the continued increase in the number of vehicles, especially in urban areas. This manuscript focuses on traffic control at intersections, since urban roads with closely spaced intersections are often prone to queue spillbacks, which disrupt traffic flows across the entire network and increase congestion.While various intelligent traffic control solutions exist for autonomous systems, they are not applicable to or ineffective against human-operated vehicles or mixed traffic. On the other hand, existing approaches to manage intersections with human-operated vehicles, cannot adequately adjust to dynamic traffic conditions. This manuscript presents a technologyagnostic adaptive real-time server based approach to dynamically determine signal timings at an intersection based on changing traffic conditions and queue lengths (i.e., wait times) to minimize, if not eliminate, spillbacks without unnecessarily increasing delays associated with intersection crossings. We also provide timeliness guarantee bounds by analyzing the travel time delays, hence making our approach more dependable and predictable. The proposed approach was validated in simulations and on a realistic hardware testbed with robots mimicking human driving behaviors. Compared to the pre-timed traffic control and an adaptive scheduling based traffic control, our algorithm is able to avoid spillbacks under highly dynamic traffic conditions and improve the average crossing delay in most cases by 10-50%. (GENERAL AUDIENCE ABSTRACT)Safe and efficient traffic control remains a challenging task with the continued increase in the number of vehicles, especially in urban areas. This manuscript focuses on traffic control at intersections, since urban roads with closely spaced intersections are often prone to congestion that blocks other intersection upstream, which disrupt traffic flows across the entire network. While various intelligent traffic control solutions exist for autonomous systems, they are not applicable to or ineffective against human-operated vehicles or mixed traffic. On the other hand, existing approaches to manage intersections with human-operated vehicles, cannot adequately adjust to dynamic traffic conditions. This work presents a technologyagnostic adaptive approach to dynamically determine signal timings at an intersection based on changing traffic conditions and queue lengths (i.e., wait times) to minimize, if not eliminate, spillbacks without unnecessarily increasing delays associated with intersection crossings. We also provide theoretical bounds to guarantee the performance of our approach in terms of the travel delays that may incur on the vehicles in the system, hence making our approach more dependable and predictable. The proposed approach was validated in simulations and on a realistic hardware testbed which uses robots to mimic human driving behaviour in an urban environment. Comparisons with widely deployed and state-of-the-art traffic control techniques show that our ...

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Section: Sporadic Servers To Execute Aperiodic Tasksmentioning

confidence: 99%

A Real-Time Server Based Approach for Safe and Timely Intersection Crossings

Oza

Chantem

2019

2019 IEEE 25th International Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA)

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“…For example, SS has been adapted and optimized to be effectively used in multi-processor systems [14]; DS has been shown to improve the performance of soft tasks when compared to BG in asymmetric multi-processor systems [9]; and both an optimal slack-based policy and DP have been used in order to globally allocate soft tasks among processors [3], [4], with DP outperforming the slack policy in heavy loaded systems.…”

Section: Ieee Transactions On Software Engineeringmentioning

confidence: 99%

Analyzing the Effect of Gain Time on Soft-Task Scheduling Policies in Real-Time Systems

Búrdalo¹,

Terrasa²,

Espinosa³

et al. 2012

IIEEE Trans. Software Eng.

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Abstract-In hard real-time systems, gain time is defined as the difference between the worst-case execution time of a hard task and its actual processor consumption at run time. This paper presents the results of an empirical study about how the presence of a significant amount of gain time in a hard real-time system questions the advantages of using the most representative scheduling algorithms or policies for aperiodic or soft tasks in fixed-priority preemptive systems. The work presented here refines and complements many other studies in this research area, in which such policies have been introduced and compared. This work has been performed by using the authors' testing framework for soft scheduling policies, which produces actual, synthetic, randomly-generated applications, executes them in an instrumented real-time operating system, and finally processes this information to obtain several statistical outcomes. The results show that, in general, the presence of a significant amount of gain time reduces the performance benefit of the scheduling policies under study when compared to serving the soft tasks in background, which is considered the theoretical worst case. In some cases, this performance benefit is so small that the use of a specific scheduling policy for soft tasks is questionable.

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“…In [8], the importance of handling overruns is addressed. The authors propose a 'payback' mechanism that limits the amount of time a server can accumulate when its budget is exceeded.…”

Section: Related Workmentioning

confidence: 99%

“…In addition, the authors of [8] introduce an optimization to reduce the number of timer events by only arming a replenishment timer when the server has work to perform. We have observed that one can further reduce the number of timers events by not only checking if the server has work to perform, but also checking whether the server has budget.…”

Section: Related Workmentioning

confidence: 99%

Defects of the POSIX Sporadic Server and How to Correct Them

Stanovich

Baker

Wang

et al. 2010

2010 16th IEEE Real-Time and Embedded Technology and Applications Symposium

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The specification of the sporadic server real-time scheduling policy in the IEEE POSIX standard is defective, and needs to be corrected. Via experiments using a POSIX sporadic server implementation under Linux, as well as simulations, we have shown and confirmed previously unreported defects. We propose and demonstrate a corrected sporadic server formulation that eliminates these defects without changes to the syntax of the API or any significant increase in implementation complexity.

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Sporadic Server revisited

Cited by 12 publications

References 24 publications

A Real-Time Server Based Approach for Safe and Timely Intersection Crossings

A Real-Time Server Based Approach for Safe and Timely Intersection Crossings

Analyzing the Effect of Gain Time on Soft-Task Scheduling Policies in Real-Time Systems

Defects of the POSIX Sporadic Server and How to Correct Them

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