| 1. |
- Afshar, Sara, et al.
(författare)
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Intra-component Resource Sharing on a Virtual Multiprocessor Platform
- 2016
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Ingår i: ACM SIGBED Review. - : Association for Computing Machinery (ACM). - 1551-3688. ; , s. 31-32
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Konferensbidrag (refereegranskat)abstract
- Component-based software development facilitates the development process of large and complex software systems. By the advent of multiprocessors, the independently developed components can be integrated on a multi-core platform to achieve an efficient use of system hardware and a decrease in system power consumption and costs. In this paper, we consider a virtual multiprocessor platform where each component can be dynamically allocated to any set of processors of the platform with a maximum concurrency level. Global-EDF is used for intra-component scheduling. The existing analysis for such systems have assumed that tasks are independent. In this paper, we enable intra-component resource sharing for this platform. We investigate using a spin-based resource sharing protocol with the accompanying analysis that extends the existing analysis for independent tasks. We briefly illustrate and evaluate our initial results with an example.
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| 2. |
- Afshar, Sara, et al.
(författare)
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Resource sharing in a hybrid partitioned/global scheduling framework for multiprocessors
- 2015
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Ingår i: IEEE International Conference on Emerging Technologies and Factory Automation, ETFA. - 9781467379298
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Konferensbidrag (refereegranskat)abstract
- For resource-constrained embedded real-time systems, resource-efficient approaches are very important. Such an approach is presented in this paper, targeting systems where a critical application is partitioned on a multi-core platform and the remaining capacity on each core is provided to a noncritical application using resource reservation techniques. To exploit the potential parallelism of the non-critical application, global scheduling is used for its constituent tasks. Previously, we enabled intra-application resource sharing for such a framework, i.e. each application has its own dedicated set of resources. In this paper, we enable inter-application resource sharing, in particular between the critical application and the non-critical application. This effectively enables resource sharing in a hybrid partitioned/global scheduling framework on multiprocessors. For resource sharing, we use a spin-based synchronization protocol. We derive blocking bounds and extend existing schedulability analysis for such a system.
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| 3. |
- Afshar, Sara, et al.
(författare)
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Resource Sharing Under Global Scheduling with Partial Processor Bandwidth
- 2015
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Ingår i: 2015 10th IEEE International Symposium on Industrial Embedded Systems, SIES 2015 - Proceedings. - 9781467377119 ; , s. 195-206
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Konferensbidrag (refereegranskat)abstract
- Resource efficient approaches are of great importance for resource constrained embedded systems. In this paper, we present an approach targeting systems where tasks of a critical application are partitioned on a multi-core platform and by using resource reservation techniques, the remaining bandwidth capacity on each core is utilized for one or a set of non-critical application(s). To provide a resource efficient solution and to exploit the potential parallelism of the extra applications on the multi-core processor, global scheduling is used to schedule the tasks of the non-critical applications. Recently a specific instantiation of such a system has been studied where tasks do not share resources other than the processor. In this paper, we enable semaphore-based resource sharing among tasks within critical and non-critical applications using a suspension-based synchronization protocol. Tasks of non-critical applications have partial access to the processor bandwidth. The paper provides the systems schedulability analysis where blocking due to resource sharing is bounded. Further, we perform experimental evaluations under balanced and unbalanced allocation of tasks of a critical application to cores.
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| 4. |
- Afshar, Sara Zargari, et al.
(författare)
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An optimal spin-lock priority assignment algorithm for real-time multi-core systems
- 2017
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Ingår i: The 23th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications RTCSA'17.
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Konferensbidrag (refereegranskat)abstract
- Support for exclusive access to shared (global) resources is instrumental in the context of embedded real-time multi-core systems, and mechanisms for achieving such access must be deterministic and efficient. There exist two traditional approaches for multiprocessors when a task requests a global resource that is locked by a task on a remote core: a spin-based approach, i.e. non-preemptive busy waiting for the resource to become available, and a suspension-based approach, i.e. the task relinquishes the processor. A suspension-based approach can be viewed as a spin-based approach where the lowest priority on a core is used during spinning, similar to a non-preemptive spin-based approach where the highest priority on a core is used. By taking such a view, we previously provided a general model for spinning, where any arbitrary priority can be used for spinning, i.e. from the lowest to the highest priority on a core. Targeting partitioned fixed-priority preemptive scheduled multiprocessors and spin-based approaches that use a fixed priority for spinning per core for all tasks, we aim at increasing the schedulability of multiprocessor systems by using the spin-lock priority per core as parameter. In this paper, we present (i) a generalization of the traditional worst-case response-time analysis for non-preemptive spin-based approaches addressing an arbitrary but fixed spin-lock priority per core, (ii) an optimal spin-lock priority assignment (OSPA) algorithm per core, i.e. an algorithm that will find a fixed spin-lock priority per core that will make the system schedulable, whenever such an assignment exists and, (iii) comparative evaluations of the OSPA algorithm with the spin-based and suspension-based approaches where OSPA showed up to 38% improvement compared to both approaches.
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| 5. |
- Ashjaei, Mohammad, et al.
(författare)
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Improved Message Forwarding for Multi-Hop HaRTES Real-Time Ethernet Networks
- 2016
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Ingår i: Journal of Signal Processing Systems. - : Springer Science and Business Media LLC. - 1939-8018 .- 1939-8115. ; 84:1, s. 47-67
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Tidskriftsartikel (refereegranskat)abstract
- Nowadays, switched Ethernet networks are used in complex systems that encompass tens to hundreds of nodes and thousands of signals. Such scenarios require multi-switch architectures where communications frequently occur in multiple hops. In this paper we investigate techniques to allow efficient multi-hop communication using HaRTES switches. These are modified Ethernet switches that provide real-time traffic scheduling, dynamic bandwidth management and temporal isolation between real-time and non-real-time traffic. This paper addresses the problem of forwarding traffic in HaRTES networks. Two methods have been recently proposed, namely Distributed Global Scheduling (DGS) that buffers traffic between switches, and Reduced Buffering Scheme (RBS), that uses immediate forwarding. In this paper, we discuss the design and implementation of RBS within HaRTES and we carry out an experimental validation with a prototype implementation. Then, we carry out a comparison between RBS and DGS using worst-case response time analysis and simulation. The comparison clearly establishes the superiority of RBS concerning end-to-end response times. In fact, with sample message sets, we achieved reductions in end-to-end delay that were as high as 80 %.
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| 6. |
- Ashjaei, Mohammad, et al.
(författare)
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Reduced Buffering Solution for Multi-Hop HaRTES Switched Ethernet Networks
- 2014
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Ingår i: The 20th IEEE International Conference on embedded and Real-Time Computing Systems and Applications RTCSA'14. - 9781479939534 ; , s. Article number 6910504-
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Konferensbidrag (refereegranskat)abstract
- In the context of switched Ethernet networks, multi-hop communication is essential as the networks in industrial applications comprise a high amount of nodes, that is far beyond the capability of a single switch. In this paper, we focus on multi-hop communication using HaRTES switches. The HaRTES switch is a modified Ethernet switch that provides real-time traffic scheduling, dynamic Quality-of-Service and temporal isolation between real-time and non-real-time traffic. Herein, we propose a method, called Reduced Buffering Scheme, to conduct the traffic through multiple HaRTES switches in a multi-hop HaRTES architecture. In order to enable the new scheduling method we propose to modify the HaRTES switch structure. Moreover, we develop a response time analysis for the new method. We also compare the proposed method with a method previously proposed, called Distributed Global Scheduling, based on their traffic response times. We show that, the new method forwards all types of traffic including the highest, the medium and the lowest priority, faster than the previous method in most of the cases. Furthermore, we show that the new method performs even better for larger networks compared with the previous one.
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| 7. |
- Ashjaei, Mohammad, et al.
(författare)
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Response time analysis of multi-hop HaRTES Ethernet Switch networks
- 2014
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Ingår i: IEEE Int. Workshop Factory Commun. Syst. Proc. WFCS. - 9781479932351
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Konferensbidrag (refereegranskat)abstract
- In this paper we focus on micro-segmented switched-Ethernet networks with HaRTES switches. HaRTES switches provide synchronous and asynchronous real-time traffic scheduling, dynamic Quality-of-Service adaptation and transparent integration of real-time and non-real-time nodes. Herein we investigate the challenges of connecting multiple HaRTES switches in order to build multi-hop communication and we propose a method, named Distributed Global Scheduling, to handle the traffic forwarding in such an architecture while preserving the unique properties of the single HaRTES switch case. Moreover, we develop a response time analysis for the method. We also evaluate the level of pessimism embodied in the anal-ysis. Finally, we show the applicability of the proposed method in an industrial setting by applying it in an automotive case study.
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| 8. |
- Balasubramanian, S.M.N, et al.
(författare)
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A dual shared stack for FSLM in Erika enterprise
- 2017
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Ingår i: The 23rd IEEE International Conference on Embedded and Real-Time Computing Systems and Applications - WiP Session RTCSA'17.
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Konferensbidrag (refereegranskat)abstract
- Recently, the flexible spin-lock model (FSLM) has been introduced, unifying spin-based and suspension-based resource sharing protocols for real-time multi-core platforms. Unlike the multiprocessor stack resource policy (MSRP), FSLM doesn’t allow tasks on a core to share a single stack, however. In this paper, we present a hypothesis claiming that for a restricted range of spin-lock priorities, FSLM requires only two stacks. We briefly describe our implementation of a dual stack for FSLM in the Erika Enterprise RTOS as instantiated on an Altera Nios II platform using 4 soft-core processors.
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| 9. |
- Balasubramanian, S.M.N, et al.
(författare)
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Incorporating implementation overheads in the analysis for the flexible spin-lock model
- 2017
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Ingår i: IECON 2017 - 43RD ANNUAL CONFERENCE OF THE IEEE INDUSTRIAL ELECTRONICS SOCIETY. - 9781538611272 ; , s. 411-8418
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Konferensbidrag (refereegranskat)abstract
- The flexible spin-lock model (FSLM) unifies suspension-based and spin-based resource sharing protocols for partitioned fixed-priority preemptive scheduling based real-time multiprocessor platforms. Recent work has been done in defining the protocol for FSLM and providing a schedulability analysis without accounting for the implementation overheads. In this paper, we extend the analysis for FSLM with implementation overheads. Utilizing an initial implementation of FSLM in the OSEK/VDX-compliant Erika Enterprise RTOS on an Altera Nios II platform using 4 soft-core processors, we present an improved implementation. Given the design of the implementation, the overheads are characterized and incorporated in specific terms of the existing analysis. The paper also supplements the analysis with measurement results, enabling an analytical comparison of FSLM with the natively provided multiprocessor stack resource policy (MSRP), which may serve as a guideline for the choice of FSLM or MSRP for a specific application.
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| 10. |
- Balasubramanian, S. M. N., et al.
(författare)
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Practical challenges for FSLM
- 2018
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Ingår i: Proceedings - 2018 IEEE 24th International Conference on Embedded and Real-Time Computing Systems and Applications, RTCSA 2018. - : Institute of Electrical and Electronics Engineers Inc.. - 9781538677599 ; , s. 238-239
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Konferensbidrag (refereegranskat)abstract
- The flexible spin-lock model (FSLM) unifies suspension-based and spin-based resource access protocols for partitioned fixed-priority preemptive scheduling based real-time multi-core platforms. Recent work has been done in defining the protocol for FSLM, providing schedulability analysis, and investigating the practical consequences of the theoretical model. FSLM complies to the AUTOSAR standard for the automotive industry, and prototype implementations of FSLM in the OSEK/VDX-complaint Erika Enterprise Real-Time Operating System have been realized. In this paper, we briefly describe some practical challenges to improve efficiency and generality.
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