| 1. |
- Afshar, Sara, et al.
(författare)
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Resource Sharing under Multiprocessor Semi-Partitioned Scheduling
- 2012
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Ingår i: 18th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA'12). - 978-1-4673-3017-6 ; s. 290-299
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Konferensbidrag (refereegranskat)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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| 2. |
- Afshar, Sara, et al.
(författare)
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Towards Resource Sharing under Multiprocessor Semi-Partitioned Scheduling
- 2012
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Ingår i: 7th IEEE International Symposium on Industrial Embedded Systems (SIES'12) : Conference Proceedings. - 978-1-4673-2683-4 ; s. 315-318
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Konferensbidrag (refereegranskat)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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| 3. |
- 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: SIES 2011 - 6th IEEE International Symposium on Industrial Embedded Systems, Conference Proceedings. - IEEE. - 9781612848204 - 978-161284820-4 ; s. 99-102
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Konferensbidrag (refereegranskat)abstract
- Supporting resource sharing in multiprocessor architectures is one of the problems which may limit the benefits that can be archived using this type of architecture. 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 size. 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 time 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 requirement for each resource such that it limits the blocking times on tasks to be less than the maximum allowed blocking times.
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| 4. |
- Nemati, Farhang, et al.
(författare)
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A Flexible Tool for Evaluating Scheduling, Synchronization and Partitioning Algorithms on Multiprocessors
- 2010
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Ingår i: 15th IEEE International Conference on Emerging Techonologies and Factory (ETFA'10).
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Konferensbidrag (refereegranskat)abstract
- Multi-core platforms seem to be the way towards increasing performance of processors. Single-chip multiprocessors (multi-cores) are today the dominating technology for desktop computing. As the multi-cores are becoming the defacto processors, the need for new scheduling and resource sharing protocols has arisen.There are two major types of scheduling under multiprocessor/multi-core platforms. Global scheduling, under which migration of tasks among processors is allowed, and partitioned scheduling under which tasks are allocated onto processors and task migration is not allowed. The partitioned scheduling protocols suffer from the problem of partitioning tasks among processors/cores, which is a bin-packing problem. Heuristic algorithms have been developed for partitioning a task set on multiprocessor platforms.However, taking such technology to an industrial setting, it needs to be evaluated such that appropriate scheduling, synchronization and partitioning algorithms are selected.In this paper we present our work on a tool for investigation and evaluation of different approaches to scheduling, synchronization and partitioning on multi-core platforms. Our tool allows for comparison of different approaches with respect to a number of parameters such as number of schedulable systems and number of processors required for scheduling.The output of the tool includes a set of information and graphs to facilitate evaluation and comparison of different approaches.
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| 5. |
- Nemati, Farhang, et al.
(författare)
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A Framework for Real-Time Systems Migration to Multi-Cores
- 2009
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Rapport (övrigt vetenskapligt)abstract
- Power consumption and thermal problems limit afurther increase of speed in single-core processors.Processor architects are therefore moving toward multicoreprocessors. However, a shift to multi-core processorsis a big challenge for developers of embedded real-timesystems, especially considering existing “legacy†systemswhich have been developed with single-core processorassumptions. These systems have been developed andmaintained by many developers over many years, andcannot easily be replaced due to the huge developmentinvestments they represent. In this paper we investigatechallenges of migrating complex legacy real-time systemsto multi-core architectures. We propose a partitioningalgorithm to prepare the migration. Partitioning groupstask and maps them to the different cores on the multicoreprocessor, increasing system performance whileensuring correctness. We have run experiments thatcompare outputs of the algorithm to the outputs of anexhaustive search. Based on a cost function, the algorithmproduces systems very close to optimal partitioning withrespect to the cost function.
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| 6. |
- Nemati, Farhang, 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). - Dublin, Ireland.
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Konferensbidrag (refereegranskat)abstract
- community, considerable work has been done on real-timemultiprocessor scheduling algorithms where it is assumedthe tasks are independent. However in practice a typicalreal-time system includes tasks that share resources. On theother hand, synchronization in the multiprocessor contexthas not received enough attention.In this paper we propose an extension to multiprocessorhierarchical scheduling to support resource sharing. Weextend the scheduling framework with an existingsynchronization protocol for global scheduling in multi-coresystems.
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| 7. |
- Nemati, Farhang, et al.
(författare)
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Blocking-Aware Partitioning for Multiprocessors
- 2010
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Rapport (övrigt vetenskapligt)abstract
- In the multi-core and multiprocessor domain there are two scheduling approaches, global and partitioned scheduling. Under global scheduling each task can execute on any processor while under partitioned scheduling tasks are allocated to processors and migration of tasks among processors is not allowed. Under global scheduling the higher utilization bound can be achieved, but in practice the overheads of migrating tasks is high. On the other hand, besides simplicity and efficiency of partitioned scheduling protocols, existing scheduling and synchronization methods developed for uniprocessor 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 how to distribute tasks among processors/cores to increase performance offered by the platform. However, existing methods mostly assume independent tasks while in practice a typical real-time system contains tasks that share resources and they may block each other. In this paper we propose a blocking-aware partitioning algorithm to distribute tasks onto different processors. The proposed algorithm allocates a task set onto processors in a way that blocking times of tasks are decreased. This reduces the total utilization which has the potential to decrease the total number of needed processors/cores.
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| 8. |
- Nemati, Farhang, et al.
(författare)
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Efficiently Migrating Real-Time Systems to Multi-Cores
- 2009
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Ingår i: Proceedings of 14th IEEE International Conference on Emerging Techonologies and Factory (ETFA'09). ; 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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| 9. |
- Nemati, Farhang, 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: 23rd EUROMICRO Conference on Real-Time Systems (ECRTS'11). - Porto, Portugal. - 978-076954442-7 ; 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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| 10. |
- Nemati, Farhang, et al.
(författare)
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Independently-developed Systems on Multi-cores with Shared Resources
- 2010
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Ingår i: 3rd Workshop on Compositional Theory and Technology for Real-Time Embedded Systems (CRTS'10) in conjunction with the 31th IEEE International Real-Time Systems Symposium (RTSS'10). - San Diego, CA, USA.
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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-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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