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  • 1.
    Afshar, Sara
    et al.
    Mälardalens högskola, Inbyggda system.
    Moghaddami Khalilzad, Nima
    Mälardalens högskola, Inbyggda system.
    Nemati, Farhang
    Mälardalens högskola, Inbyggda system.
    Nolte, Thomas
    Mälardalens högskola, Inbyggda system.
    Resource Sharing among Prioritized Real-Time Applications on Multiprocessors2015In: ACM SIGBED Review - Special Issue on the 6th International Workshop on Compositional Theory and Technology for Real-Time Embedded Systems Homepage archiveVolume 12 Issue 1, 2015, p. 46-55Conference paper (Refereed)
    Abstract [en]

    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.

  • 2.
    Afshar, Sara
    et al.
    Mälardalen University, Västerås, Sweden.
    Nemati, Farhang
    Mälardalen University, Västerås, Sweden.
    Nolte, Thomas
    Mälardalen University, Västerås, Sweden.
    Resource Sharing under Multiprocessor Semi-Partitioned Scheduling2012In: 2012 IEEE International Conference on Embedded and Real-Time Computing Systems and Applications: Proceedings, IEEE, 2012, p. 290-299Conference paper (Refereed)
    Abstract [en]

    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.

  • 3.
    Afshar, Sara
    et al.
    Mälardalen University, Västerås, Sweden.
    Nemati, Farhang
    Mälardalen University, Västerås, Sweden.
    Nolte, Thomas
    Mälardalen University, Västerås, Sweden.
    Towards Resource Sharing under Multiprocessor Semi-Partitioned Scheduling2012In: 7th IEEE International Symposium on Industrial Embedded Systems (SIES'12): Conference Proceedings, IEEE, 2012, p. 315-318Conference paper (Refereed)
    Abstract [en]

    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.

  • 4.
    Behnam, Moris
    et al.
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås, Sweden.
    Nemati, Farhang
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås, Sweden.
    Nolte, Thomas
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås, Sweden.
    Grahn, Håkan
    School of Computing, Blekinge Institute of Technology, Karlskrona, Sweden.
    Towards an Efficient Approach for Resource Sharing in Real-Time Multiprocessor Systems2011In: 2011 6th IEEE International Symposium on Industrial and Embedded Systems: Conference Proceedings, IEEE , 2011, p. 99-102Conference paper (Refereed)
    Abstract [en]

    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.

  • 5.
    Nemati, Farhang
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Partitioned Scheduling of Real-Time Tasks on Multi-core Platforms2010Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    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.

  • 6.
    Nemati, Farhang
    Örebro University, School of Science and Technology. Mälardalens högskola, Akademin för innovation, design och teknik.
    Resource Sharing in Real-Time Systems on Multiprocessors2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    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 techniques 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 the distribution of tasks among the processors, which is a bin-packing problem.

    In this thesis 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 the blocking overhead of tasks, which reduces the total utilization and has the potential to reduce the number of required processors.

    In industrial embedded software systems, large and complex systems are usually divided into several components (applications) each of which is developed independently without knowledge of each other, and potentially in parallel. However, the applications may share mutually exclusive resources when they co-execute on a multi-core platform which introduce a challenge for the techniques needed to ensure predictability. In this thesis we have proposed a new synchronization protocol for handling mutually exclusive resources shared among real-time applications on a multi-core platform. The schedulability analysis of each application is performed in isolation and parallel and the requirements of each application with respect to the resources it may share are included in an interface. The protocol did not originally consider any priorities among the applications. We have proposed an additional version of the protocol which grants access to resources based on priorities assigned to the applications. We have also proposed an optimal priority assignment algorithm to assign unique priorities to the applications sharing resources. Our evaluations confirm that the protocol together with the priority assignment algorithm outperforms existing alternatives in most cases.

    In the proposed synchronization protocol each application is assumed to be allocated on one dedicated core. However, in this thesis we have further extended the synchronization protocol to be applicable for applications allocated on multiple dedicated cores of a multi-core platform. Furthermore, we have shown how to efficiently calculate the resource hold times of resources for applications. The resource hold time of a resource for an application is the maximum duration of time that the application may lock the resource whenever it requests the resource. Finally, the thesis discusses and proposes directions for future work.

  • 7.
    Nemati, Farhang
    et al.
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås, Sweden.
    Behnam, Moris
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås, Sweden.
    Nolte, Thomas
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås, Sweden.
    An Investigation of Synchronization under Multiprocessors Hierarchical Scheduling2009In: Proceedings of the Work-In-Progress (WIP) session of the 21st Euromicro Conference on Real-Time Systems (ECRTS'09), 2009Conference paper (Refereed)
    Abstract [en]

    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.

  • 8.
    Nemati, Farhang
    et al.
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås, Sweden.
    Behnam, Moris
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås, Sweden.
    Nolte, Thomas
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås, Sweden.
    Efficiently Migrating Real-Time Systems to Multi-Cores2009In: 2009 IEEE Conference on Emerging Technologies & Factory Automation, IEEE, 2009, p. 1205-1212Conference paper (Refereed)
    Abstract [en]

    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.

  • 9.
    Nemati, Farhang
    et al.
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås, Sweden.
    Behnam, Moris
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås, Sweden.
    Nolte, Thomas
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås, Sweden.
    Independently-Developed Real-Time Systems on Multi-Cores with Shared Resources2011In: 2011 23rd Euromicro Conference on Real-Time Systems: Proceedings, IEEE, 2011, p. 251-261Conference paper (Refereed)
    Abstract [en]

    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.

  • 10.
    Nemati, Farhang
    et al.
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås, Sweden.
    Behnam, Moris
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås, Sweden.
    Nolte, Thomas
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås, Sweden.
    Multiprocessor Synchronization and Hierarchical Scheduling2009In: 2009 International Conference on Parallel Processing Workshops: Proceedings / [ed] Barolli, L; Feng, WC, IEEE, 2009, p. 58-64Conference paper (Refereed)
    Abstract [en]

    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.

  • 11.
    Nemati, Farhang
    et al.
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås, Sweden.
    Behnam, Moris
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås, Sweden.
    Nolte, Thomas
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås, Sweden.
    Sharing Resources among Independently-developed Systems on Multi-cores2011In: ACM SIGBED Review, ISSN 1551-3688, Vol. 8, no 1, p. 46-53Article in journal (Refereed)
    Abstract [en]

    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.

  • 12.
    Nemati, Farhang
    et al.
    Mälardalen Real-Time Research Centre, Mälardalen University, Sweden.
    Behnam, Moris
    Mälardalen Real-Time Research Centre, Mälardalen University, Sweden.
    Nolte, Thomas
    Mälardalen Real-Time Research Centre, Mälardalen University, Sweden.
    J. Bril, Reinder
    Eindhoven University of Technology (TU/e), The Netherlands .
    Investigation of Implementing a Synchronization Protocol under Multiprocessors Hierarchical Scheduling2009In: 2009 IEEE Conference on Emerging Technologies & Factory Automation, IEEE, 2009Conference paper (Refereed)
    Abstract [en]

    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.

  • 13.
    Nemati, Farhang
    et al.
    Mälardalen Real-Time Research Centre, Mälardalen University, Sweden.
    Inam, Rafia
    Mälardalen Real-Time Research Centre, Mälardalen University, Sweden.
    Nolte, Thomas
    Mälardalen Real-Time Research Centre, Mälardalen University, Sweden.
    Sjödin, Mikael
    M ̈alardalen Real-Time Research Centre, Mälardalen University, Sweden.
    Towards Resource Sharing by Message Passing among Real-Time Components on Multi-cores2011In: IEEE International Conference on Emerging Technologies and Factory Automation, ETFA 2011 / [ed] Mammeri, Z, IEEE, 2011Conference paper (Refereed)
    Abstract [en]

    In this paper we propose a message passing synchronization protocol for resource sharing among real-time applications on multi-core platforms where each application is allocated on a cluster of cores. In this protocol the resources that are only used within an application (local resources) are handled by shared memory synchronization while the resources shared cross applications (global resources) are accessed by means of message passing. In our protocol the global resources are safely accessed without requiring to lock the resources explicitly. The goal is to avoid resource locking using shared memory, since accessing shared memory in multi-cores is very time consuming, whereas message passing has the potential to be much more efficient in systems with deep memory hierarchies.

  • 14.
    Nemati, Farhang
    et al.
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås, Sweden.
    Kraft, Johan
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås, Sweden.
    Nolte, Thomas
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås, Sweden.
    Towards Migrating Legacy Real-Time Systems to Multi-Core Platforms2008In: 2008 IEEE International Conference on Emerging Technologies and Factory Automation / [ed] Fay, IA, IEEE, 2008, p. 717-720Conference paper (Refereed)
    Abstract [en]

    Power consumption and thermal problems limit the single-core processors to be faster. Processor architects are therefore moving toward multi-coreprocessors. Developers of embedded real-time systems however hesitates a shift to multi-core processors, especially for existing "legacy" systemswhich have been developed with single-core processor assumptions. These systems have been developed and maintained by many developers over many years, and can not easily be replaced due to the huge development investments they represent. In this paper we investigate challenges ofmigrating complex legacy real-time systems to multi-core architectures. We propose componentization and partitioning to prepare the migration. Componentization groups logically related tasks into components (or subsystems). This provides an abstraction layer from a scheduling perspective, which facilitates migration. Partitioning maps tasks to the different cores on the multi-core processor, maximizing system performance while ensuring correctness.

  • 15.
    Nemati, Farhang
    et al.
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås, Sweden.
    Kraft, Johan
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås, Sweden.
    Norström, Christer
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås, Sweden.
    Validation of Temporal Simulation Models of Complex Real-Time Systems2008In: 2008 32nd Annual IEEE International Computer Software and Applications Conference: Proceedings, IEEE, 2008, p. 1335-1340Conference paper (Refereed)
    Abstract [en]

    Model based analysis has the potential to facilitate maintenance of complex real-time systems, as it allows for impact analysis with respect to the systems' temporal behavior. Model based analysis of temporal behavior of a legacy real-time system has also the potential to support migration toward component based system. However, since most software systems today have been developed in a traditional, code oriented manner, sufficiently detailed models are typically not available. To apply model based analysis on these systems, models have to be extracted from their implementation and observed run-time behavior. This requires methods for model validation. The paper proposes a novel method for model validation and presents a framework for evaluation of model validation methods, which will be used to evaluate the proposed method. The method is targeting temporal models extracted from complex real-time systems.

  • 16.
    Nemati, Farhang
    et al.
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås, Sweden.
    Nolte, Thomas
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås, Sweden.
    Resource Hold Times under Multiprocessor Static-Priority Global Scheduling2011In: 2011 IEEE 17th International Conference on Embedded and Real-Time Computing Systems and Applications. Volume 1: Proceedings, IEEE Computer Society , 2011, p. 197-206Conference paper (Refereed)
    Abstract [en]

    Recently there has been a lot of interest in coexisting of multiple independently-developed real-time applications on a shared open platform. On the other hand, emerging of multi-core platforms and the performance and possibilities they offer has attracted a lot of attention in multiprocessor real-time analysis, protocols and techniques. Co-executing independently- developedreal-time applications on a shared multiprocessor system, where each application executes on a dedicated sub set of processors, requires to overcome the problem of handling mutually exclusive shared resources among those applications. To handle resource sharing, it is important to determine the Resource Hold Time (RHT), i.e., the maximum duration of time that an application locks a shared resource.

    In this paper, we study resource hold times under multiprocessor static-priority global scheduling. We present how to compute RHT's for each resource in an application. We also show how to decrease the RHT's without compromising the schedulability of the application. We show that decreasing all RHT's for all shared resources is a multiobjective optimization problem and there can exist multiple Paretooptimal solutions.

  • 17.
    Nemati, Farhang
    et al.
    Mälardalen Real-Time Research Centre, Västerås, Sweden.
    Nolte, Thomas
    Mälardalen Real-Time Research Centre, Västerås, Sweden.
    Resource Sharing among Prioritized Real-Time Applications on Multi-cores2012Report (Other academic)
    Abstract [en]

    MSOS (Multiprocessors Synchronization protocol for real-time Open Systems) is a synchronization protocol for handling resource sharing among independently-developed realtime applications (components) on multi-core platforms. MSOS does not consider any priority setting among applications. To handle resource sharing based on the priority of applications, in this paper we propose a new protocol that allows for resource sharing among prioritized real-time applications on a multi-core 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 existing MSOS as well as to the current state of the art locking protocols under multiprocessor partitioned scheduling, i.e., MPCP, MSRP, FMLP and OMLP. The evaluations show that MSOS-Priority mostly performs significantly better than alternative approaches.

  • 18.
    Nemati, Farhang
    et al.
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås,Sweden.
    Nolte, Thomas
    Mälardalen Real-Time Research Centre, Mälardalen University, Västerås,Sweden.
    Resource Sharing among Real-Time Components under Multiprocessor Clustered Scheduling2013In: Real-time systems, ISSN 0922-6443, E-ISSN 1573-1383, Vol. 49, no 5, p. 580-613Article in journal (Refereed)
    Abstract [en]

    In this paper we propose a general synchronization protocol for resource sharing among independently-developed real-time applications (components) on multi-core platforms. This protocol is a generalization of a previously proposed synchronization protocol (MSOS). In our proposed protocol, each component is statically allocated on a dedicated subset of processors (called cluster). A component has its own internal scheduler by which its tasks are scheduled. In this paper we focus on multiprocessor global fixed-priority preemptive scheduling algorithms to be used to schedule the tasks inside each component. Sharing the local resources is handled by the Priority Inheritance Protocol (PIP). For sharing the global resources (inter-component resource sharing) we have studied usage of FIFO and Round-Robin queues for access the resources across the components and usage of FIFO and prioritized queues inside the components. We have derived schedulability analysis for the different queue handling alternatives and compared their performance by using experimental evaluations. Finally, we have shown that the integration phase can be formulated in the form of a nonlinear integer programming problem where solution techniques in this domain can be used to minimize the total number of processors required to guarantee the schedulability of all components. As a proof of concept we have only provided the formulation for FIFO queues.

  • 19.
    Nemati, Farhang
    et al.
    Mälardalen Real-Time Research Centre, Västerås, Sweden.
    Nolte, Thomas
    Mälardalen Real-Time Research Centre, Västerås, Sweden.
    Behnam, Moris
    Mälardalen Real-Time Research Centre, Västerås, Sweden.
    Partitioning Real-Time Systems on Multiprocessors with Shared Resources2010In: Principles of Distributed Systems / [ed] Lu, CY; Masuzawa, T; Mosbah, M, Springer , 2010, Vol. 6490, p. 253-269Conference paper (Refereed)
    Abstract [en]

    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.

  • 20.
    Åsberg, Mikael
    et al.
    MRTC/Mälardalen University, Västerås, Sweden.
    Behnam, Moris
    MRTC/Mälardalen University, Västerås, Sweden.
    Nemati, Farhang
    MRTC/Mälardalen University, Västerås, Sweden.
    Nolte, Thomas
    MRTC/Mälardalen University, Västerås, Sweden.
    Towards Hierarchical Scheduling in AUTOSAR2009In: 2009 IEEE Conference on Emerging Technologies & Factory Automation, IEEE, 2009, article id 5347133Conference paper (Refereed)
    Abstract [en]

    AUTOSAR [17] is a partnership between automotive manufactures and suppliers. It aims at standardizing the automotive software architecture and separating software and hardware. This approach makes software more independent, maintainable, reuseable, etc. Still there is much work to do in order for this standard to be usable. This paper focus on automotive software integration in AUTOSAR, with the use of hierarchical scheduling as an enabling technology. At this point, AUTOSARcomponents do not have any timing relation with its tasks [19, 20]. This causes an unpredictive runtime behavior which can only be analyzed and verified after integration phase. We will discuss how integration can be done in AUTOSAR, with runtime temporal isolation of components. This will enable schedulability analysis at the level of components rather than at the level of tasks.

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