| 1. |
- Abdullah, Syed Md Jakaria, et al.
(author)
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Towards Implementation of Virtual-Clustered Multiprocessor Scheduling in Linux
- 2013
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In: Proceedings of the 8th IEEE International Symposium on Industrial Embedded Systems, SIES 2013. - 9781479906581 ; , s. 97-100
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Conference paper (peer-reviewed)abstract
- Cluster based multiprocessor scheduling can be seen as a hybrid approach combining benefits of both partitioned and global scheduling. Virtual clustering further enhances it by providing dynamic cluster resource allocation and applying hierarchical scheduling techniques. Over the years, the study of virtual cluster scheduling has been limited to theoretical analysis. In this paper, we present our initial ideas about implementing virtual cluster scheduling in Linux. The purpose of this implementation is twofold: (i) we would like to demonstrate the feasibility of its implementation in an operating system, without modifying the kernel source code, (ii) we present practical insights on the overhead of implementing this framework.
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| 2. |
- Afshar, Sara, et al.
(author)
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Integrating independently developed real-time applications on a shared multi-core architecture
- 2013
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In: ACM SIGBED Review, v. 10, n. 3. - : Association for Computing Machinery (ACM). ; , s. 49-56
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Conference paper (peer-reviewed)abstract
- The shift towards multi-core platforms has become inevitable from an industry perspective, therefore proper techniques are needed to deal with challenges related to this migration from single core architectures to a multi-core architecture. One of the main concerns for the system developers in this context is the migration of legacy real-time systems to multi-core architectures. To address this concern and to simplify migration, independently developed subsystems are abstracted with an interface, such that when working with multiple independently-developed subsystems to be integrated on a shared platform, one does not need to be aware of information or policies used in other subsystems in order to determine subsystem-level schedulability. Instead schedulability can be checked through their interfaces at the time of integration on a shared multi-core architecture. In this paper we propose a solution for the case where some of the independently-developed subsystems are distributed over more than one processor and we propose an approach to generate interfaces of subsystems that may share mutually exclusive resources.
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| 3. |
- Ashjaei, Mohammad, et al.
(author)
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A Compact Approach to Clustered Master-Slave Ethernet Networks
- 2012
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In: IEEE International Workshop on Factory Communication Systems - Proceedings, WFCS. - 9781467315739 ; , s. 157-160
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Conference paper (peer-reviewed)abstract
- Ethernet switches are increasingly used in real-time distributed systems as a technical solution to guarantee the timeliness in communications. However, there are still limitations related to real-time behavior caused by the limited number of priority levels and the possibility of memory overruns with consequent message losses. These limitations can be eliminated using a master/slave technique such as proposed by the FTT paradigm. This led to the FTT-SE protocol that schedules transmissions centrally in a master node. While this protocol has already been well studied and investigated for small networks with a single switch, its extension to larger networks is still an open issue. In this paper we propose a compact clustered solution to scale the FTT-SE protocol to networks of multiple switches by organizing the network in sub-networks composed of one master and one switch each and which can be connected directly, without bridges. This paper also shows how the timeliness of the traffic can still be enforced. The validation is currently on-going.
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| 4. |
- Ashjaei, Mohammad, et al.
(author)
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Implementing a Clock Synchronization Protocol on a Multi-Master Switched Ethernet Network
- 2013
-
Conference paper (peer-reviewed)abstract
- The interest to use Switched Ethernet technologies in real-time communication is increasing due to its absence of collisions when transmitting messages. Nevertheless, using COTS switches affect the timeliness guarantee inherent in potentially overflowing internal FIFO queues. In this paper we focus on a solution, called the FTT-SE protocol, which is developed based on a master-slave technique. Recently, an extension of the FTT-SE protocol has been proposed where the transmission of messages are controlled using multiple master nodes. In order to guarantee the correctness of the protocol, the masters should be timely synchronized. Therefore, in this paper we investigate using a clock synchronization protocol, based on the IEEE 1588 standard, among master nodes and we study the effects of this protocol on the network performance. In addition, we present a formal verification of this solution by means of model checking to prove the correctness of the FTT-SE protocol when the clock synchronization protocol is applied.
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| 5. |
- Ashjaei, Mohammad, et al.
(author)
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MTU Assignment in a Master-Slave Switched Ethernet Network
- 2013
-
Conference paper (peer-reviewed)abstract
- In this paper, we investigate the problem of selecting the Maximal Transmission Unit (MTU) size that maximizes the schedulability of real-time messages. We focus on a bandwidth-efficient master-slave switched Ethernet protocol, namely the FTT-SE protocol. We propose an algorithm to find the MTU for each message in order to maximize the schedulability of the messages. Moreover, we evaluate our proposed algorithm and we show that setting the MTU for messages using the algorithm increases the schedulability of messages compared with assigning the MTU to the maximum value that the protocol can support.
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| 6. |
- Ashjaei, Mohammad, et al.
(author)
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Performance Analysis of Master-Slave Multi-Hop Switched Ethernet Networks
- 2013
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In: Proceedings of the 8th IEEE International Symposium on Industrial Embedded Systems, SIES 2013. - 9781479906581 ; , s. 280-289
-
Conference paper (peer-reviewed)abstract
- There is an increasing trend towards using switched Ethernet in real-time distributed systems due to features like absence of collisions and high throughput. Nevertheless, a few problems persist, in particular related to priority inversion and limited length in queues. In this paper we focus on a protocol which uses a master-slave technique over standard switched Ethernet in order to overcome such problems, namely FTT-SE protocol. We present an improved response time analysis for such a network and we compare, analytically and with simulations, the results achieved with Network Calculus on a worst-case scenario. We show that our proposed response time analysis gives tighter bounds compared to Network Calculus. Moreover, we compare the performance of different solutions to scale the FTT-SE protocol with respect to the bandwidth utilization. Finally, we propose a new architecture to improve the average performance of master-slave switched Ethernet networks.
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| 7. |
- Ashjaei, Mohammad, et al.
(author)
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Supporting Multi-Hop Communications with HaRTES Ethernet Switches
- 2013
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Conference paper (peer-reviewed)abstract
- In this paper we identify the challenges of multi-hop communication when using a micro-segmented switched-Ethernet protocol with enhanced HaRTES switches. The HaRTES architecture has been explored in the scope of single-switch topology, and provides dynamic virtual channels that can be composed hierarchically and provide bounded latency together with temporal isolation. Herein we propose two different solutions regarding the traffic forwarding in multi-switch architectures, while maintaining the unique properties of the single HaRTES switch case. In the first approach, the traffic is buffered and scheduled sequentially in each hop. In the second solution the traffic is scheduled once and forwarded immediately through multiple switches without buffering. In this paper we present a brief comparison of both approaches and we report on the on-going work towards effective support to real-time communications in dynamic and complex Cyber-Physical Systems.
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| 8. |
- Ashjaei, Mohammad, et al.
(author)
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The Design and Implementation of a Simulator for Switched Ethernet Networks
- 2012
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In: 3rd International Workshop on Analysis Tools andMethodologies for Embeddedand Real-time Systems. ; , s. 57-62
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Conference paper (peer-reviewed)abstract
- In the context of Switched Ethernet, the Flexible Time-Triggered Switched Ethernet protocol (FTT-SE) was proposed to overcome the limitations and related problems of using COTS switches in real-time networks, such as overflow of switch queues due to uncontrolled arrival of packets. Although the FTT-SE protocol has been validated by several experiments on real applications, evaluation of different architectures as well as evaluation of large scale networks is not straightforward. Therefore, a simulator to evaluate different network architectures based on the FTT-SE protocol is useful. In this paper we present such a simulator. We address the extended FTT-SE protocol using multiple switches and we present a modular simulator based on Simulink/Matlab to visualize message transmissions and to evaluate end-to-end delay bounds of messages.
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| 9. |
- Ashjaei, Mohammad, et al.
(author)
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Worst-case delay analysis of master-slave switched ethernet networks
- 2012
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In: Proceeings of the 2nd International Workshop on Worst-Case Traversal Time. - New York, NY, USA : ACM. - 9781450316866 ; , s. 15-21
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Conference paper (peer-reviewed)abstract
- Switched Ethernet is increasingly used in real-time communication due to its intrinsic features such as micro segmentation and high throughput. However, COTS switches may impose long blocking times due to their FIFO queues and can also experience buffer overflow in outgoing queues due to uncontrolled packets arrival. The FTT-SE protocol uses a Master-Slave technique to overcome the COTS switch limitations in real-time applications. Recently, we extended the protocol for large scale networks and in this paper we present the worst-case delay analysis using the Network Calculus formalism for such a network. Moreover, we assess the end-to-end delay of traffic with simulation concluding that the obtained analytical results present a good match with the observed delays, providing uppers bounds that vary between 0% and 50% above the maximum measured values. © 2012 ACM.
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| 10. |
- Behnam, Moris, et al.
(author)
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Analysis and Optimization of the MTU in Real-Time Communications over Switched Ethernet
- 2011
-
In: IEEE Symposium on Emerging Technologies and Factory Automation, ETFA. ; , s. Art.nr. 6059021-
-
Conference paper (peer-reviewed)abstract
- The Flexible Time-Triggered communication over Switched Ethernet protocol (FTT-SE) was proposed to overcome the limitation of guaranteeing the real-time communication requirements of conventional switches, and at the same time to support reconfiguration of dynamic adaptive systems. The protocol fragments large messages into a sequence of packets that are individually scheduled. The maximum transmission unit (MTU), that restricts the packets size, has a significant effect on the schedulability of the packets. In this paper, we investigate the problem of selecting the optimal MTU size that maximizes the schedulability of real-time messages. We propose two algorithms to find optimal/sub-optimal values of MTU; the first one finds an optimal solution but exhibits high computational complexity, while the second one is sub-optimal but exhibits a lower computational complexity. Finally, we evaluate our proposed algorithms by means of simulation studies and compare their results with the results of assigning MTU to the maximum packet size that the protocol can allow.
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