| 1. |
- 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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| 2. |
- 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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| 3. |
- Van Den Heuvel, M. M. H. P., et al.
(författare)
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Optimal and fast composition of resource-sharing components in hierarchical real-time systems
- 2014
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Ingår i: RTCSA 2014 - 20th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications. - 9781479939534 ; , s. Article number 6910547-
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Konferensbidrag (refereegranskat)abstract
- In this paper we consider various flavors of the stack resource policy (SRP) for arbitrating access to shared resources in a hierarchical scheduling framework (HSF) upon a uni-processor. We propose algorithms for exploring and selecting the (local) resource ceilings within components, such that it results in an optimal composition of resource-sharing components in an HSF. Existing methods are non-optimal, because (i) they optimize just the length of global non-preemptive execution of tasks and (ii) they do not detect whether or not resources are shared globally (i.e., between tasks of different components). Lifting these limitations leads to an exponential growth of the design space. This paper contributes a fast three-step methodology which lifts these limitations, i.e., we apply the SRP at each level of the HSF to just the resources being shared. Our algorithm selects those component interfaces (i.e., by fixing the local resource ceilings of each component) that minimize the system load.
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| 4. |
- 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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| 5. |
- Afshar, Sara
(författare)
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Lock-Based Resource Sharing for Real-Time Multiprocessors
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Embedded systems are widely used in the industry and are typically resource constrained, i.e., resources such as processors, I/O devices, shared buffers or shared memory might be limited in the system. Hence, techniques that can enable an efficient usage of processor bandwidths in such systems are of great importance. Locked-based resource sharing protocols are proposed as a solution to overcome resource limitation by allowing the available resources in the system to be safely shared. In recent years, due to a dramatic enhancement in the functionality of systems, a shift from single-core processors to multi-core processors has become inevitable from an industrial perspective to tackle the raised challenges due to increased system complexity. However, the resource sharing protocols are not fully mature for multi-core processors. The two classical multi-core processor resource sharing protocols, spin-based and suspension-based protocols, although providing mutually exclusive access to resources, can introduce long blocking delays to tasks, which may be unacceptable for many industrial applications. In this thesis we enhance the performance of resource sharing protocols for partitioned scheduling, which is the de-facto scheduling standard for industrial real-time multi-core processor systems such as in AUTOSAR, in terms of timing and memory requirements. A new scheduling approach uses a resource efficient hybrid approach combining both partitioned and global scheduling where the partitioned scheduling is used to schedule the major number of tasks in the system. In such a scheduling approach applications with critical task sets use partitioned scheduling to achieve higher level of predictability. Then the unused bandwidth on each core that is remained from partitioning is used to schedule less critical task sets using global scheduling to achieve higher system utilization. These scheduling schema however lacks a proper resource sharing protocol since the existing protocols designed for partitioned and global scheduling cannot be directly applied due to the complex hybrid structure of these scheduling frameworks. In this thesis we propose a resource sharing solution for such a complex structure. Further, we provide the blocking bounds incurred to tasks under the proposed protocols and enhance the schedulability analysis, which is an essential requirement for real-time systems, with the provided blocking bounds.
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| 6. |
- 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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| 7. |
- 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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| 8. |
- 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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| 9. |
- 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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| 10. |
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