| 1. |
- Afshar, Sara
(författare)
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Lock-Based Resource Sharing in Real-Time Multiprocessor Platforms
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Embedded systems are typically resource constrained, i.e., resources such as processors, I/O devices, shared buffers or shared memory can be limited for tasks in the system. Therefore, techniques that enable an efficient usage of such resources are of great importance.In the industry, typically large and complex software systems are divided into smaller parts (applications) where each part is developed independently. Migration towards multiprocessor platforms has become inevitable from an industrial perspective. Due to such migration and to efficient use of system resources, these applications eventually may be integrated on a shared multiprocessor platform. In order to facilitate the integration phase of the applications on a shared platform, the timing and resource requirements of each application can be provided in an interface when the application is developed. The system integrator can benefit from such provided information in the interface of each application to ease the integration process. In this thesis, we have provided the resource and timing requirements of each application in their interfaces for applications that may need several processors to be allocated on when they are developed.Although many scheduling techniques have been studied for multiprocessor systems, these techniques are usually based on the assumption that tasks are independent, i.e. do not share resources other than the processors. This assumption is typically not true. In this thesis, we provide an extension to such systems to handle sharing of resources other than processor among tasks. Two traditional approaches exist for multiprocessor systems to schedule tasks on processors. A recent scheduling approach for multiprocessors has combined the two traditional approaches and achieved a hybrid more efficient approach compared to the two previous one. Due to the complex nature of this scheduling approach the conventional approaches for resource sharing could not be used straight forwardly. In this thesis, we have modified resource sharing approaches such that they can be used in such hybrid scheduling systems. A second concern is that enabling resource sharing in the systems can cause unpredictable delays and variations in response time of tasks which can degrade system performance. Therefore, it is of great significance to improve the resource handling techniques to reduce the effect of imposed delays caused by resource sharing in a multiprocessor platform. In this thesis we have proposed alternative techniques for resource handling that can improve system performance for special setups.
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| 2. |
- Ashjaei, Mohammad, 1980-
(författare)
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Real-Time Communication over Switched Ethernet with Resource Reservation
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Due to the need for advanced computer-controlled functionality in distributed embedded systems the requirements on network communication are becoming overly intricate. This dissertation targets the requirements that are concerned with real-time guarantees, run-time adaptation, resource utilization and flexibility during the development. The Flexible Time-Triggered Switched Ethernet (FTT-SE) and Hard Real-Time Ethernet Switching (HaRTES) network architectures have emerged as two promising solutions that can cater for these requirements. However, these architectures do not support multi-hop communication as they are originally developed for single-switch networks. This dissertation presents a fundamental contribution in multi-hop real-time communication over the FTT-SE and HaRTES architectures targeting the above mentioned requirements. It proposes and evaluates various solutions for scheduling and forwarding the traffic through multiple switches in these architectures. These solutions preserve the ability of dynamic adaptation without jeopardizing real-time properties of the architectures. Moreover, the dissertation presents schedulability analyses for the timeliness verification and evaluation of the proposed solutions as well as several protocols to support run-time adaptation in the multi-hop communication. Finally, the work led to an end-to-end resource reservation framework, based on the proposed multi-hop architectures, to support flexibility during the development of the systems. The efficiency of the proposed solutions is evaluated on various case studies that are inspired from industrial systems.
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| 3. |
- Becker, Matthias, 1986-
(författare)
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Efficient Resource Management for Many-Core based Industrial Real-Time Systems
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The increased complexity of today’s industrial embedded systems stands inneed for more computational power while most systems must adhere to a restrictedenergy consumption, either to prolong the battery lifetime or to reduceoperational costs. The many-core processor is therefore a natural fit. Due tothe simple architecture of the compute cores, and therefore their good analyzability,such processors are additionally well suited for real-time applications.In our research, we focus on two particular problems which need to be addressedin order to pave the way into the many-core era. The first area is powerand thermal aware execution frameworks, where we present different energyaware extensions to well known load balancing algorithms, allowing them todynamically scale the number of active cores depending on their workload.In contrast, an additional framework is presented which balances workloadsto minimize temperature gradients on the die. The second line of works focuseson industrial standards in the face of massively parallel platforms, wherewe address the automotive and automation domain. We present an executionframework for IEC 61131-3 applications, allowing the consolidation of severalIEC 61131-3 applications on the same platform. Additionally, we discussseveral architectural options for the AUTOSAR software architecture on suchmassively parallel platforms.
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| 4. |
- Behnam, Moris, et al.
(författare)
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Towards an efficient approach for resource sharing in real-time multiprocessor systems
- 2011
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Ingår i: 2011 6th IEEE International Symposium on Industrial and Embedded Systems. - Västerås : IEEE. - 9781612848181 - 9781612848198 ; , s. 99-102, s. 99-102
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Konferensbidrag (refereegranskat)abstract
- Supporting resource sharing in multiprocessor architectures is one of the major problems that limit the potential performance benefits of using such architectures for real-time systems. Many approaches and algorithms have been proposed to support resource sharing, however, most of them impose either high blocking times on tasks or require a large memory allocation. In this paper we investigate the possibility of combining the lock-based approaches and wait-free approaches (using multiple buffers) in order to decrease both the blocking times that may affect the schedulability of tasks and the required memory. To achieve this, we propose a solution based on evaluating the maximum allowed blocking time on each task according to the schedulability analysis, and then find the minimum memory allocation for each resource that limits the blocking times on tasks to be less than the maximum allowed blocking times.
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| 5. |
- Nemati, Farhang, Senior Lecturer, 1975-, et al.
(författare)
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An Investigation of Synchronization under Multiprocessors Hierarchical Scheduling
- 2009
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Ingår i: Proceedings of the Work-In-Progress (WIP) session of the 21st Euromicro Conference on Real-Time Systems (ECRTS'09).
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Konferensbidrag (refereegranskat)abstract
- In the multi-core and multiprocessor research community, considerable work has been done on real-time multiprocessor scheduling algorithms where it is assumed the tasks are independent. However in practice a typical real-time system includes tasks that share resources. On the other hand, synchronization in the multiprocessor context has not received enough attention.In this paper we propose an extension to multiprocessor hierarchical scheduling to support resource sharing. We extend the scheduling framework with an existing synchronization protocol for global scheduling in multi-core systems.
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| 6. |
- Nemati, Farhang, Senior Lecturer, 1975-, et al.
(författare)
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Efficiently Migrating Real-Time Systems to Multi-Cores
- 2009
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Ingår i: 2009 IEEE Conference on Emerging Technologies & Factory Automation. - : IEEE. - 9781424427284 - 9781424427277 ; , s. 1205-1212
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Konferensbidrag (refereegranskat)abstract
- Power consumption and thermal problems limit a further increase of speed in single-core processors. Multi-core architectures have therefore received significant interest. However, a shift to multi-core processors is a big challenge for developers of embedded real-time systems, especially considering existing “legacy” systems which have been developed with uniprocessor assumptions. These systems have been developed and maintained by many developers over many years, and cannot easily be replaced due to the huge development investments they represent. An important issue while migrating to multi-cores is how to distribute tasks among cores to increase performance offered by the multi-core platform. In this paper we propose a partitioning algorithm to efficiently distribute legacy system tasks along with newly developed ones onto different cores. The target of the partitioning is increasing system performance while ensuring correctness.
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| 7. |
- Nemati, Farhang, Senior Lecturer, 1975-, et al.
(författare)
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Independently-Developed Real-Time Systems on Multi-Cores with Shared Resources
- 2011
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Ingår i: 2011 23rd Euromicro Conference on Real-Time Systems. - Porto, Portugal : IEEE. - 9781457706431 ; , s. 251-261, s. 251-261
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Konferensbidrag (refereegranskat)abstract
- In this paper we propose a synchronization protocol for resource sharing among independently-developed real-time systems on multi-coreplatforms. The systems may use different scheduling policies and they may have their own local priority settings. Each system is allocated on a dedicated processor (core). In the proposed synchronization protocol, each system is abstracted by an interface which abstracts the information needed for supporting global resources. The protocol facilitates the composability of various real-time systems with different scheduling and priority settings on a multi-core platform. We have performed experimental evaluations and compared the performance of our proposed protocol (MSOS) against the two existing synchronization protocols MPCP and FMLP. The results show that the new synchronization protocol enables composability without any significant loss of performance. In fact, in most cases the new protocol performs better than at least one of the other two synchronization protocols. Hence, we believe that the proposed protocol is a viable solution for synchronization among independently-developedreal-time systems executing on a multi-core platform.
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| 8. |
- Nemati, Farhang, Senior Lecturer, 1975-, et al.
(författare)
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Investigation of Implementing a Synchronization Protocol under Multiprocessors Hierarchical Scheduling
- 2009
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Ingår i: 2009 IEEE Conference on Emerging Technologies & Factory Automation. - : IEEE. - 9781424427277 - 9781424427284
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Konferensbidrag (refereegranskat)abstract
- In the multi-core and multiprocessor domain, there has been considerable work done on scheduling techniques assuming that real-time tasks are independent. In practice a typical real-time system usually share logical resources among tasks. However, synchronization in the multiprocessor area has not received enough attention.In this paper we investigate the possibilities of extending multiprocessor hierarchical scheduling to support an existing synchronization protocol (FMLP) in multiprocessor systems. We discuss problems regarding implementation of the synchronization protocol under the multiprocessor hierarchical scheduling.
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| 9. |
- Nemati, Farhang, Senior Lecturer, 1975-, et al.
(författare)
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Multiprocessor Synchronization and Hierarchical Scheduling
- 2009
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Ingår i: 2009 International Conference on Parallel Processing Workshops. - : IEEE. - 9781424449231 - 9780769538037 ; , s. 58-64
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Konferensbidrag (refereegranskat)abstract
- Multi-core architectures have received significant interest as thermal and power consumption problems limit further increase of speed in single-cores. In the multi-core research community a considerable amount of work has been done on real-time multi-core scheduling algorithms where it is assumed tasks are independent. However, synchronization of dependent tasks executing on multi-cores has not received as much attention, even though typical real-time systems in practice include tasks that share resources.In this paper we propose a synchronization protocol for hierarchically scheduledmulti-core systems, and we present a comparison between the presented protocol and existing multi-core synchronization protocols. The presented protocol groups dependent tasks that directly or indirectly share mutually exclusive resources into independent components. Within a component dependent tasks use classical uniprocessor synchronization protocols, such as the Stack-based Resource allocation Protocol. The components are then scheduled on the cores by a global scheduler.There are two major approaches for scheduling multicore: partitioned and global scheduling. While most existing multi-core synchronization protocols support only one category, the protocol presented in this paper is developed to handle both scheduling approaches. The presented approach is developed to allow for co-execution of existing legacy real-time applications along with new applications, i.e., a legacy application is put into one or more components preserving its own (original) scheduling and synchronization protocols.
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| 10. |
- Nemati, Farhang, Senior Lecturer, 1975-, et al.
(författare)
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Sharing Resources among Independently-developed Systems on Multi-cores
- 2011
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Ingår i: ACM SIGBED Review. - New York : ACM SIGBED. - 1551-3688. ; 8:1, s. 46-53
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we propose a synchronization protocol for resource sharing among independently-developed real-time systems on multi-core platforms. The systems may use different scheduling policies and they may have arbitrary priority settings. When using this synchronization protocol each processor is abstracted by an interface which consists of a set of requirements. A requirement depends only on the worst-case time the processor may wait for resources, i.e., the maximum number of times that the resources can be blocked by other processors. We have derived schedulability conditions for each processor and based on the analysis we extract the interface of the processor. In this paper, we focus on the cases when each system is allocated on a dedicated processor.
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