| 1. |
- Afshar, Sara, et al.
(author)
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Resource Sharing among Prioritized Real-Time Applications on Multiprocessors
- 2015
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In: ACM SIGBED Review - Special Issue on the 6th International Workshop on Compositional Theory and Technology for Real-Time Embedded Systems. - : Association for Computing Machinery (ACM). ; , s. 46-55
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Conference paper (peer-reviewed)abstract
- In this paper, we propose a new protocol for handling resource sharing among prioritized real-time applications composed on a multiprocessor platform. We propose an optimal priority assignment algorithm which assigns unique priorities to the applications based on information in their interfaces. We have performed experimental evaluations to compare the proposed protocol (called MSOS-Priority) to the current state of the art locking protocols under multiprocessor partitioned scheduling, i.e., MPCP, MSRP, FMLP, MSOS, and OMLP. The valuations show that MSOS-Priority mostly performs significantly better than alternative approaches.
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| 2. |
- Afshar, Sara, et al.
(author)
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Resource Sharing under Multiprocessor Semi-Partitioned Scheduling
- 2012
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In: 18th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA'12). - : IEEE. - 9781467330176 - 9780769548241 ; , s. 290-299
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Conference paper (peer-reviewed)abstract
- Semi-partitioned scheduling has become the subject of recent interest for multiprocessors due to better utilization results, compared to conventional global and partitioned scheduling algorithms. Under semi-partitioned scheduling, a major group of tasks are assigned to fixed processors while a low number of tasks are allocated to more than one processor. Various task assigning techniques have recently been proposed in a semi-partitioned environment. However, a synchronization mechanism for resource sharing among tasks in semi-partitioned scheduling has not yet been investigated. In this paper we propose and evaluate two methods for handling resource sharing under semi-partitioned scheduling in multiprocessor platforms. The main challenge addressed in this paper is to serve the resource requests of tasks that are assigned to different processors.
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| 3. |
- Afshar, Sara, et al.
(author)
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Towards Resource Sharing under Multiprocessor Semi-Partitioned Scheduling
- 2012
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In: 7th IEEE International Symposium on Industrial Embedded Systems (SIES'12). - : IEEE. - 9781467326834 - 9781467326858 ; , s. 315-318
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Conference paper (peer-reviewed)abstract
- Semi-partitioned scheduling has been the subject of recent interest, compared with conventional global and partitioned scheduling algorithms for multiprocessors, due to better utilization results. In semi-partitioned scheduling most tasks are assigned to fixed processors while a low number of tasks are split up and allocated to different processors. Various techniques have recently been proposed to assign tasks in a semi-partitioned environment. However, an appropriate resource sharing mechanism for handling the resource requests between tasks in semi-partitioned scheduling has not yet been investigated. In this paper we propose two methods for handling resource sharing under semi-partitioned scheduling in multiprocessor platforms. The main challenge is to handle the resource requests of tasks that are split over multiple processors.
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| 4. |
- Behnam, Moris, et al.
(author)
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Towards an efficient approach for resource sharing in real-time multiprocessor systems
- 2011
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In: 2011 6th IEEE International Symposium on Industrial and Embedded Systems. - Västerås : IEEE. - 9781612848181 - 9781612848198 ; , s. 99-102, s. 99-102
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Conference paper (peer-reviewed)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.
(author)
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An Investigation of Synchronization under Multiprocessors Hierarchical Scheduling
- 2009
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In: Proceedings of the Work-In-Progress (WIP) session of the 21st Euromicro Conference on Real-Time Systems (ECRTS'09).
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Conference paper (peer-reviewed)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.
(author)
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Efficiently Migrating Real-Time Systems to Multi-Cores
- 2009
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In: 2009 IEEE Conference on Emerging Technologies & Factory Automation. - : IEEE. - 9781424427284 - 9781424427277 ; , s. 1205-1212
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Conference paper (peer-reviewed)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.
(author)
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Independently-Developed Real-Time Systems on Multi-Cores with Shared Resources
- 2011
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In: 2011 23rd Euromicro Conference on Real-Time Systems. - Porto, Portugal : IEEE. - 9781457706431 ; , s. 251-261, s. 251-261
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Conference paper (peer-reviewed)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.
(author)
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Investigation of Implementing a Synchronization Protocol under Multiprocessors Hierarchical Scheduling
- 2009
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In: 2009 IEEE Conference on Emerging Technologies & Factory Automation. - : IEEE. - 9781424427277 - 9781424427284
-
Conference paper (peer-reviewed)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.
(author)
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Multiprocessor Synchronization and Hierarchical Scheduling
- 2009
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In: 2009 International Conference on Parallel Processing Workshops. - : IEEE. - 9781424449231 - 9780769538037 ; , s. 58-64
-
Conference paper (peer-reviewed)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-
(author)
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Partitioned Scheduling of Real-Time Tasks on Multi-core Platforms
- 2010
-
Licentiate thesis (other academic/artistic)abstract
- In recent years multiprocessor architectures have become mainstream, and multi-core processors are found in products ranging from small portable cell phones to large computer servers. In parallel, research on real-time systems has mainly focused on traditional single-core processors. Hence, in order for real-time systems to fully leverage on the extra capacity offered by new multi-core processors, new design techniques, scheduling approaches, and real-time analysis methods have to be developed.In the multi-core and multiprocessor domain there are mainly two scheduling approaches, global and partitioned scheduling. Under global scheduling each task can execute on any processor at any time while under partitioned scheduling tasks are statically allocated to processors and migration of tasks among processors is not allowed. Besides simplicity and efficiency of partitioned scheduling protocols, existing scheduling and synchronization methods developed for single-core processor platforms can more easily be extended to partitioned scheduling. This also simplifies migration of existing systems to multi-cores. An important issue related to partitioned scheduling is distribution of tasks among processors which is a bin-packing problem.In this thesis we propose a partitioning framework for distributing tasks on the processors of multi-core platforms. Depending on the type of performance we desire to achieve, the framework may distribute a task set differently, e.g., in an application in which tasks process huge amounts of data the goal of the framework may be to decrease cache misses.Furthermore, we propose a blocking-aware partitioning heuristic algorithm to distribute tasks onto the processors of a multi-core architecture. The objective of the proposed algorithm is to decrease blocking overhead of tasks which reduces the total utilization and has the potential to reduce the number of required processors.Finally, we have implemented a tool to facilitate evaluation and comparison of different multiprocessor scheduling and synchronization approaches, as well as different partitioning heuristics. We have applied the tool in the evaluation of several partitioning heuristic algorithms, and the tool is flexible to which any new scheduling or synchronization protocol as well as any new partitioning heuristic can easily be added.
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