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Träfflista för sökning "WFRF:(Behnam Moris) ;pers:(Nemati Farhang);pers:(Nolte Thomas)"

Sökning: WFRF:(Behnam Moris) > Nemati Farhang > Nolte Thomas

  • Resultat 1-10 av 11
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1.
  • Behnam, Moris, et al. (författare)
  • Towards an Efficient Approach for Resource Sharing in Real-Time Multiprocessor Systems
  • 2011
  • Ingår i: SIES 2011 - 6th IEEE International Symposium on Industrial Embedded Systems, Conference Proceedings. - IEEE. - 9781612848204 - 978-161284820-4 ; s. 99-102
  • 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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2.
  • Nemati, Farhang, et al. (författare)
  • An Investigation of Synchronization under Multiprocessors Hierarchical Scheduling
  • 2009
  • Ingår i: Proceedings of the Work-In-Progress (WIP) session of the 21st Euromicro Conference on Real-Time Systems (ECRTS'09). - Dublin, Ireland.
  • 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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3.
  • Nemati, Farhang, et al. (författare)
  • Blocking-Aware Partitioning for Multiprocessors
  • 2010
  • 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.
4.
  • Nemati, Farhang, et al. (författare)
  • Efficiently Migrating Real-Time Systems to Multi-Cores
  • 2009
  • Ingår i: Proceedings of 14th IEEE International Conference on Emerging Techonologies and Factory (ETFA'09). - 9781424427284 ; s. 1205-1212
  • 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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5.
  • Nemati, Farhang, et al. (författare)
  • Independently-Developed Real-Time Systems on Multi-Cores with Shared Resources
  • 2011
  • Ingår i: 23rd EUROMICRO Conference on Real-Time Systems (ECRTS'11). - Porto, Portugal. - 978-076954442-7 ; s. 251-261
  • 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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6.
  • Nemati, Farhang, et al. (författare)
  • Independently-developed Systems on Multi-cores with Shared Resources
  • 2010
  • 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.
  • 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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7.
  • Nemati, Farhang, et al. (författare)
  • Investigation of Implementing a Synchronization Protocol under Multiprocessors Hierarchical Scheduling
  • 2009
  • Ingår i: Proceedings of the Work-In-Progress (WIP) session of 14th IEEE International Conference on Emerging Techonologies and Factory (ETFA'09). - 9781424427284
  • 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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8.
  • Nemati, Farhang, et al. (författare)
  • Multiprocessor Synchronization and Hierarchical Scheduling
  • 2009
  • Ingår i: Proceedings of the First IEEE International Workshop on Real-time Systems on Multicore Platforms: Theory and Practice (XRTS-2009) in conjunction with ICPP'09. - 978-1-4244-4923-1 ; s. 58-64
  • 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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9.
  • Nemati, Farhang, et al. (författare)
  • Partitioning Real-Time Systems on Multiprocessors with Shared Resources
  • 2010
  • Ingår i: Lecture Notes in Computer Science, vol. 6490. - Springer. - 978-364217652-4 ; s. 253-269
  • Bokkapitel (övrigt vetenskapligt)abstract
    • There are two main approaches to task scheduling on multiprocessor/multi-core platforms; 1) global scheduling, under which migration of tasks among processors is allowed, and 2) partitioned scheduling under which tasks are allocated onto processors and task migration is not allowed. Under global scheduling a higher utilization bound can be achieved, but in practice the overheads of migrating tasks is high. On the other hand under partitioned scheduling, besides simplicity and efficiency, existing scheduling and synchronization methods developed for uniprocessor platforms can more easily be extended to partitioned scheduling. However the partitioned scheduling protocols suffer from the problem of partitioning tasks among processors/cores which is a bin-packing problem. Therefore, several heuristic algorithms have been developed for partitioning a task set on multiprocessor platforms. However, these algorithms typically assume independent tasks while in practice real-time systems often contain tasks that share resources and hence may block each other.In this paper we propose a blocking-aware partitioning algorithm which allocates a task~set onto processors in a way that the overall amount of blocking times of tasks are decreased. The algorithm reduces the total utilization which, in turn, has the potential to decrease the total number of required processors (cores). In this paper we evaluate our algorithm and compare it with an existing similar algorithm. The comparison criteria includes both number of schedulable systems as well as processor reduction performance.
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10.
  • Nemati, Farhang, et al. (författare)
  • Sharing Resources among Independently-developed Systems on Multi-cores
  • 2011
  • Ingår i: ACM SIGBED Review. - 1551-3688. ; 8:1, s. 46-53
  • 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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