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  • 1.
    Abdullah, Syed Md Jakaria
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Moghaddami Khalilzad, Nima
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Towards Implementation of Virtual-Clustered Multiprocessor Scheduling in Linux2013In: Proceedings of the 8th IEEE International Symposium on Industrial Embedded Systems, SIES 2013, 2013, p. 97-100Conference paper (Refereed)
    Abstract [en]

    Cluster based multiprocessor scheduling can be seen as a hybrid approach combining benefits of both partitioned and global scheduling. Virtual clustering further enhances it by providing dynamic cluster resource allocation and applying hierarchical scheduling techniques. Over the years, the study of virtual cluster scheduling has been limited to theoretical analysis. In this paper, we present our initial ideas about implementing virtual cluster scheduling in Linux. The purpose of this implementation is twofold: (i) we would like to demonstrate the feasibility of its implementation in an operating system, without modifying the kernel source code, (ii) we present practical insights on the overhead of implementing this framework.

  • 2.
    Afshar, Sara
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Khalilzad, Nima
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Bril, Reinder J.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. Universiteit Eindhoven, Eindhoven, Netherlands.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Intra-component Resource Sharing on a Virtual Multiprocessor Platform2016In: ACM SIGBED Review: Special Issue on 8th International Workshop on Compositional Theory and Technology for Real-Time Embedded Systems, 2016, p. 31-32Conference paper (Refereed)
    Abstract [en]

    Component-based software development facilitates the development process of large and complex software systems. By the advent of multiprocessors, the independently developed components can be integrated on a multi-core platform to achieve an efficient use of system hardware and a decrease in system power consumption and costs. In this paper, we consider a virtual multiprocessor platform where each component can be dynamically allocated to any set of processors of the platform with a maximum concurrency level. Global-EDF is used for intra-component scheduling. The existing analysis for such systems have assumed that tasks are independent. In this paper, we enable intra-component resource sharing for this platform. We investigate using a spin-based resource sharing protocol with the accompanying analysis that extends the existing analysis for independent tasks. We briefly illustrate and evaluate our initial results with an example.

  • 3.
    Afshar, Sara
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Moghaddami Khalilzad, Nima
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Nemati, Farhang
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    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.

  • 4.
    Ashjaei, Mohammad
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Khalilzad, Nima
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Mubeen, Saad
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. IS (Embedded Systems).
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Sander, Ingo
    Royal Institute of Technology, Sweden.
    Almeida, Luis
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Designing End-to-end Resource Reservations in Predictable Distributed Embedded Systems2017In: Real-time systems, ISSN 0922-6443, E-ISSN 1573-1383, Vol. 53, no 6, p. 916-956Article in journal (Refereed)
    Abstract [en]

    Contemporary distributed embedded systems in many domains have become highly complex due to ever-increasing demand on advanced computer controlled functionality. The resource reservation techniques can be effective in lowering the software complexity, ensuring predictability and allowing flexibility during the development and execution of these systems. This paper proposes a novel end-to-end resource reservation model for distributed embedded systems. In order to support the development of predictable systems using the proposed model, the paper provides a method to design resource reservations and an end-to-end timing analysis. The reservation design can be subjected to different optimization criteria with respect to runtime footprint, overhead or performance. The paper also presents and evaluates a case study to show the usability of the proposed model, reservation design method and end-to-end timing analysis. 

  • 5.
    Ashjaei, Seyed Mohammad Hossein
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Khalilzad, Nima
    Qamcom Research and Technology, Stockholm, Sweden.
    Mubeen, Saad
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Modeling, Designing and Analyzing Resource Reservations in Distributed Embedded Systems2018In: Real-Time Modelling and Processing for Communication Systems / [ed] Springer, Springer , 2018, p. 203-256Chapter in book (Other academic)
  • 6.
    Becker, Matthias
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Khalilzad, Nima
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Bril, Reinder J.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. Technische Universiteit Eindhoven, Eindhoven, Netherlands.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Extended support for limited preemption fixed priority scheduling for OSEK/AUTOSAR-compliant operating systems2015In: 2015 10th IEEE International Symposium on Industrial Embedded Systems, SIES 2015 - Proceedings, 2015, p. 207-217Conference paper (Refereed)
    Abstract [en]

    Fixed Priority Scheduling (FPS) is the de facto standard in industry and it is the scheduling algorithm used in OSEK/AUTOSAR. Applications in such systems are compositions of so called runnables, the functional entities of the system. Runnables are mapped to operating system tasks during system synthesis. In order to improve system performance it is proposed to execute runnables non-preemptively while varying the tasks threshold between runnables. This allows simpler resource access, can reduce the stack usage of the system, and improve the schedulability of the task sets. FPDS , as a special case of fixed-priority scheduling with deferred preemptions, executes subjobs non-preemptively and preemption points have preemption thresholds, providing exactly the proposed behavior. However OSEK/AUTOSAR-conform systems cannot execute such schedules. In this paper we present an approach allowing the execution of FPDS schedules. In our approach we exploit pseudo resources in order to implement FPDS . It is further shown that our optimal algorithm produces a minimum number of resource accesses. In addition, a simulation based evaluation is presented in which the number of resource accesses as well as the number of required pseudo-resources by the proposed algorithms are investigated. Finally, we report the overhead of resource access primitives using our measurements performed on an AUTOSARcompliant operating system.

  • 7.
    Khalilzad, Nima
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Adaptive and Flexible Scheduling Frameworks for Component-Based Real-Time Systems2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Modern computer systems are often designed to play a multipurpose role. Therefore, they are capable of running a number of software components (software programs) simultaneously in parallel. These software components should share the system resources (e.g. processor and network) such that all of them run and finish their computations as expected. On the other hand, a number of software components have timing requirements meaning that they should not only access the resources, but this access should also be in a timely manner. Thus, there is a need to timely share the resources among different software components. The time-sharing is often realized by reserving a time-portion of resources for each component. Such a reservation should be adequate and resource-efficient. It should be sufficient to preserve the timing properties of the components. Also, the reservations should be resource-efficient to reduce the components' footprint on the resources which in turn allows integration of more software components on a given hardware resource. In this thesis, we mainly focus on the resource-efficiency of the reservations. We consider two cases. (I) Components which can tolerate occasional timing violations (soft real-time components): in this case we adjust the reservations during run-time to match the reservation sizes based on the instantaneous requirements of the components. (II) Components which cannot tolerate any timing violations (hard real-time components): in this case we use flexible approaches which allow us to improve the resource-efficiency at the design time.

  • 8.
    Khalilzad, Nima
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Ashjaei, Mohammad
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Almeida, Luis
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. IT/DEEC/University of Porto, Portugal.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Adaptive Multi-Resource End-to-End Reservations for Component-Based Distributed Real-Time Systems2015In: ESTIMedia 2015 - 13th IEEE Symposium on Embedded Systems for Real-Time Multimedia, 2015, p. Article number 7351772-Conference paper (Refereed)
    Abstract [en]

    Complexity in the real-time embedded softwaredomain has been growing rapidly. The component-based softwaredevelopment approach facilitates the development process of suchsoftware systems by dividing a complex system into a numberof simpler components. Resource reservation techniques havebeen widely used for providing resources to real-time softwarecomponents. In this paper we target real-time components operatingon a distributed resource infrastructure. Furthermore,we target a class of software components which demonstratedynamic resource consumption behavior. A prime example ofsuch components is a multimedia software component. In thepaper, we present a framework supporting multi-resource endto-end resource reservations. We reserve resource bandwidths onboth processor resources as well as on the network resources. Theproposed framework utilizes a Multiple Input Multiple Output(MIMO) controller which adjusts the sizes of reservations trackingthe dynamic resource demands of the software components. Finally, we present a case study using a multimedia component todemonstrate the performance and efficiency of our framework.

  • 9.
    Khalilzad, Nima
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Ashjaei, Mohammad
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Almeida, Luis
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. University of Porto, Portugal.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Towards Adaptive Resource Reservations for Component-Based Distributed Real-Time Systems2015In: ACM SIGBED Review - Special Issue on the 7th Workshop on Adaptive and Reconfigurable Embedded Systems (APRES 2015), 2015, p. 24-27Conference paper (Refereed)
    Abstract [en]

    —In this paper we present our ongoing work on developing a framework supporting adaptive resource reservations targeting component-based distributed real-time systems. The components may be spread over different resources in a distributed system. The proposed framework utilizes a reservationbased scheduling technique in which the sizes of reservations are adjusted during run-time to deal with dynamic resource demands of the software components. We present our modeling approach, we describe design options made and we present corresponding challenges.

  • 10.
    Khalilzad, Nima
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    An Adaptive Scheduling Framework for Component-Based Real-Time Systems2015Report (Other academic)
  • 11.
    Khalilzad, Nima
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    On Component-Based Software Development for Multiprocessor Real-Time Systems2015In: Proceedings - IEEE 21st International Conference on Embedded and Real-Time Computing Systems and Applications, RTCSA 2015, 2015, p. 132-140Conference paper (Refereed)
    Abstract [en]

    Component-based software development providesa modular approach to develop complex software systems. In the context of real-time systems, it is desirable to abstract the timing properties of software components using an interface foreach component. The timing properties of the whole system, composed of multiple components, is studied using the component interfaces. In this paper we focus on periodic interface models. In the case of components developed for single processor platforms, for examining the system schedulability, the interfaces can be regarded as periodic tasks. Thus, making it possible to use the conventional schedulability analyses for the system level schedulability test. In the case of components developed formultiprocessors, since interfaces may have utilization larger than 100 % of a single processor, it is not possible to directly use the component interfaces for the system schedulability test. There-fore, the interfaces have to be decomposed before performing thesystem level schedulability test. In this paper, we target the special case of partitioned EDF for scheduling the components integrated on a multiprocessor. Therefore, the system level schedulability test is equivalent to finding a feasible allocation of component interfaces on the multiprocessor. We propose two algorithms for allocating the multiprocessor periodic interfaces. In addition, we propose anorthogonal approach for developing component-based real-timesystems on multiprocessors in which components with utilizationmore than 100 % of a single processor are divided into smaller subcomponents before abstracting their interfaces. We show, through extensive evaluations, that our alternative approach significantly reduces the interface overhead.

  • 12.
    Khalilzad, Nima
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Faragardi, Hamid Reza
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Towards Energy-Aware Placement of Real-Time Virtual Machines in a Cloud Data Center2015In: Proceedings - 2015 IEEE 17th International Conference on High Performance Computing and Communications, 2015 IEEE 7th International Symposium on Cyberspace Safety and Security and 2015 IEEE 12th International Conference on Embedded Software and Systems, HPCC-CSS-ICESS 2015, 2015, p. 1657-1662Conference paper (Refereed)
    Abstract [en]

    Cloud computing is an evolving paradigm which is becoming an adoptable technology for a variety of applications. However, cloud infrastructures must be able to fulfill application requirements before adopting cloud solutions. Cloud infrastructure providers communicate the characteristics of their services to their customers through Service Level Agreements (SLA). In order for a real-time application to be able to use cloud technology, cloud infrastructure providers have to be able to provide timing guarantees in the SLAs. In this paper, we present our ongoing work regarding a cloud solution in which periodic tasks are provided as a service in the Software as a Service (SaS) model. Tasks belonging to a certain application are mapped in a Virtual Machine (VM). We also study the problem of VMplacement on a cloud infrastructure. We propose a placement mechanism which minimizes the energy consumption of the data center by consolidating VMs in a minimum number of servers while respecting the timing requirement of virtual machines.

  • 13.
    Khalilzad, Nima
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Kong, Fanxin
    McGill University, Canada.
    Liu, Xue
    McGill University, Canada.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    A Feedback Scheduling Framework for Component-Based Soft Real-Time Systems2015In: 21th IEEE Real-Time and Embedded Technology and Applications Symposium RTAS'15, 2015, p. 182-193Conference paper (Refereed)
    Abstract [en]

    Component-based software systems with real-time requirements are often scheduled using processor reservation techniques. Such techniques have mainly evolved around hard real-time systems in which worst-case resource demands are considered for the reservations. In soft real-time systems, reserv- ing the processors based on the worst-case demands results in unnecessary over-allocations. In this paper, targeting soft real-time systems running on multiprocessor platforms, we focus on components for which processor demand varies during run-time. We propose a feedback scheduling frameworkwhere processor reservations are used for scheduling components. The reservation bandwidths as well as the reservation periods are adapted using MIMO LQR controllers. We provide an allocation mechanism for distributing components over processors. The proposed framework is implemented in the TrueTime simulation tool for system identification. We use a case study to investigate the performance of our framework in the simulation tool. Finally, the framework is implemented in the Linux kernel for practical evaluations. The evaluation results suggest that the framework can efficiently adapt the reservation parameters during run-time by imposing negligible overhead.

  • 14.
    Khalilzad, Nima Moghaddami
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering.
    Towards adaptive hierarchical scheduling of overloaded real-time systems2011In: SIES 2011 - 6th IEEE International Symposium on Industrial Embedded Systems, Conference Proceedings, 2011, p. 39-42Conference paper (Refereed)
    Abstract [en]

    In a hierarchical scheduling framework, a resource can be shared among modules with different criticality levels. In our recently introduced adaptive hierarchical scheduling framework, modules receive a dynamic portion of the CPU during run-time. While providing temporal isolation is one of the main advantages of hierarchical scheduling, in an adaptive framework, for example when the CPU is overloaded, the higher priority modules can violate timing guarantees of the lower priority modules. However, the priorities of modules are assigned based on parameters other than the module criticality levels. For example the priority is often assigned according to periods and deadlines of tasks to increase the CPU utilization assuming static systems, i.e. modules parameters do not change during runtime. In an overload situation the high criticality modules should be superior to the low criticality modules in receiving resources. In this paper, extending our adaptive framework, we propose two techniques for controlling the CPU distribution among modules in an overload situation. We are taking another step towards having a complete adaptive hierarchical scheduling framework by incorporating an overload controller into our framework.

  • 15.
    Khalilzad, Nima Moghaddami
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Yekeh, Farahnaz
    Mälardalen University, School of Innovation, Design and Engineering.
    Asplund, Lars
    Mälardalen University, School of Innovation, Design and Engineering.
    Pordel, M.
    Umeå University.
    FPGA implementation of real-time Ethernet communication using RMII interface2011In: 2011 IEEE 3rd International Conference on Communication Software and Networks, ICCSN 2011, 2011, p. 35-39Conference paper (Refereed)
    Abstract [en]

    FPGA-based solutions have become more common in embedded systems these days. These systems need to communicate with external world. Considering high-speed and popularity of Ethernet communication, a reliable real-time Ethernet component inside FPGA is of special value. To that end, this paper presents a new solution for 100 Mb/s FPGA-based Ethernet communications with timing analysis. The solution deals with "Reduced Media-Independent Interface" in its physical layer. UDP is the network protocol which is implemented from physical to transport layer. For getting used in real-time applications, timing analysis is done in the communication system. Component based software engineering is used in the design and development processes. In order to test the components inside FPGA, two different approaches are utilized. Signal measurement in combination with introduced windows based application contributes much in testing and validation phases.

  • 16.
    Moghaddami Khalilzad, Nima
    Mälardalen University, School of Innovation, Design and Engineering.
    Adaptive Hierarchical Scheduling Framework for Real-Time Systems2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Modern computer systems are often designed to play a multipurpose role. Therefore, they are capable of running a number of software tasks (software programs) simultaneously in parallel. These software tasks should share the processor such that all of them run and finish their computations as expected. On the other hand, a number of software tasks have timing requirements meaning that they should not only access the processing unit, but this access should also be in a timely manner. Thus, there is a need to timely share the processor among different software programs (applications). The time-sharing often is realized by assigning a fixed and predefined processor time-portion to each application. However, there exists a group of applications where, i) their processor demand is changing in a wide range during run-time, and/or ii) their occasional timing violations can be tolerated. For systems that contain applications with the two aforementioned properties, it is not efficient to assign the applications with fixed processor time-portions. Because, if we allocate the processor resource based on the maximum resource demand of the applications, then the processor's computing capacity will be wasted during the time intervals where the applications will require a smaller portion than maximum resource demand. To this end, in this thesis we propose adaptive processor time-portion assignments. In our adaptive scheme, at each point in time, we monitor the actual demand of the applications, and we provide sufficient processor time-portions for each application. In doing so, we are able to integrate more applications on a shared and resource constrained system, while at the same time providing the applications with timing guarantees.

  • 17.
    Moghaddami Khalilzad, Nima
    Mälardalen University, School of Innovation, Design and Engineering.
    Implementation of the Multi-Level Adaptive Hierarchical Scheduling Framework2013Report (Other academic)
  • 18. Moghaddami Khalilzad, Nima
    Multi-Level Adaptive Hierarchical Scheduling Framework for Composing Real-Time Systems2013Report (Other academic)
  • 19.
    Moghaddami Khalilzad, Nima
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Ashjaei, Seyed Mohammad Hossein
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Mubeen, Saad
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Sander, Ingo
    Royal Institute of Technology (KTH), Sweden.
    Towards Designing Efficient End-to-end Resource Reservations for Distributed Embedded Systems2016In: Forum on specification & Design Languages FDL'16, Bremen, Germany, 2016Conference paper (Refereed)
  • 20.
    Moghaddami Khalilzad, Nima
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Adaptive Hierarchical Scheduling Framework: Configuration and Evaluation2013Report (Other academic)
    Abstract [en]

    We have introduced an adaptive hierarchicalscheduling framework as a solution for composing dynamic realtime systems, i.e., systems where the CPU demand of its tasks aresubjected to unknown and potentially drastic changes during runtime. The framework consists of a controller which periodicallyadapts the system to the current load situation. In this paper,we unveil and explore the detailed behavior and performanceof such an adaptive framework. Specifically, we investigate thecontroller configurations enabling efficient control parameterswhich maximizes performance, and we evaluate the adaptiveframework against a traditional static one.

  • 21.
    Moghaddami Khalilzad, Nima
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Adaptive Hierarchical Scheduling Framework: Configuration and Evaluation2013Conference paper (Refereed)
    Abstract [en]

    We have introduced an adaptive hierarchical scheduling framework as a solution for composing dynamic real-time systems, i.e., systems where the CPU demand of its tasks are subjected to unknown and potentially drastic changes during run-time. The framework consists of a controller which periodically adapts the system to the current load situation. In this paper, we unveil and explore the detailed behavior and performance of such an adaptive framework. Specifically, we investigate the controller configurations enabling efficient control parameters which maximizes performance, and we evaluate the adaptive framework against a traditional static one. Furthermore, we demonstrate the results of our investigation using a practical multimedia case study in which we simulate the timing behavior of video decoding tasks running on our proposed framework. In addition, we compare the results of using our framework with the results of using static resource allocation approach.

  • 22.
    Moghaddami Khalilzad, Nima
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Exact and Approximate Supply Bound Function for Multiprocessor Periodic Resource Model: Unsynchronized Servers2012Conference paper (Refereed)
    Abstract [en]

    The Multi Processor Periodic Resource (MPR) model has been proposed for modeling compositional real-time systems which run on a shared multi processor hardware. In this paper we extend the MPR model such that the execution of virtual processors (servers) is not assumed to be synchronized i.e., the servers can have different phases. We believe that relaxing the server synchronization requirement provides greater deal of compatibility for implementing such a compositional method on various hardware platforms. We derive the resource supply bound function of the extended MPR model using an algorithm. Furthermore, we suggest an approach to calculate an approximate supply bound function with lower computational complexity for systems where calculating their supply bound function is computationally expensive.

  • 23.
    Moghaddami Khalilzad, Nima
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Implementation of the Multi-Level Adaptive Hierarchical Scheduling Framework2013In: Proceedings of OSPERT 2013, 2013, p. 11-19Conference paper (Refereed)
    Abstract [en]

    We have presented a multi-level adaptive hierarchical scheduling framework in our previous work. The framework targets compositional real-time systems which are composed of both hard and soft real-time systems. While static CPU portions are reserved for hard real-time components, the CPU portions of soft real-time components are adjusted during run-time. In this paper, we present the implementation details of our framework which is implemented as a Linux kernel loadable module. In addition, we present a case-study to evaluate the performance and the overhead of our framework.

  • 24.
    Moghaddami Khalilzad, Nima
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Multi-Level Adaptive Hierarchical Scheduling Framework for Composing Real-Time Systems2013In: 2013 IEEE 19th International Conference on Embedded and Real-Time Computing Systems and Applications, RTCSA 2013, 2013, p. 320-329Conference paper (Refereed)
    Abstract [en]

    Processor partitioning and hierarchical scheduling have been widely used for composing hard real-time systems on a shared hardware platform while preserving the timing requirements of the systems. Due to the safety critical nature of the hard real-time systems for deriving the sufficient partition size often conservative analysis is used. Applying the exact same analysis for deriving the partition sizes for soft real-time systems result in unnecessary processors overallocation and consequently waste of the CPU resource. In this paper, to address the problem of composing soft and hard real-time systems on a resource constrained shared hardware, we present a multi-level adaptive hierarchical scheduling framework. In our framework, we adapt the processor partition sizes of soft real-time systems according to their need at each time point by on-line monitoring their processor demand. Furthermore, we implement our adaptive framework in the Linux kernel and show the performance of our framework using a case-study.

  • 25.
    Moghaddami Khalilzad, Nima
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Åsberg, Mikael
    Mälardalen University, School of Innovation, Design and Engineering.
    On Adaptive Hierarchical Scheduling of Real-time Systems Using a Feedback Controller2011In: 3rd Workshop on Adaptive and Reconfigurable Embedded Systems (APRES'11), 2011Conference paper (Refereed)
    Abstract [en]

    Hierarchical scheduling provides predictable timing and temporal isolation; two properties desirable in real-time embedded systems. In hierarchically scheduled systems, subsystems should receive a sufficient amount of CPU resources in order to be able to guarantee timing constraints of its internal parts (tasks). In static systems, an exact amount of CPU resource can be allocated to a subsystem. However, in dynamic systems, where execution times of tasks vary considerably during runtime, it is desirable to give a dynamic portion of the CPU given the current load situation. In this paper we present a feedback control approach for adapting the amount of CPU resource that is allocated to subsystems during run-time such that each subsystem receives sufficient resources while keeping the number of deadline violations to a minimum. We also show an example simulation where the controller adapts the budget of a subsystem.

  • 26.
    Moghaddami Khalilzad, Nima
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering.
    Spampinato, Giacomo
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Bandwidth Adaptation in Hierarchical Scheduling Using Fuzzy Controllers2012In: 7th IEEE International Symposium on Industrial Embedded Systems, SIES 2012 - Conference Proceedings, 2012, p. 148-157Conference paper (Refereed)
    Abstract [en]

    In our previous work, we have introduced an adaptive hierarchical scheduling framework as a solution for composing dynamic real-time systems, i.e., systems where the CPU demand of their tasks are subjected to unknown and potentially drastic changes during run-time. The framework uses the PI controller which periodically adapts the system to the current load situation. The conventional PI controller despite simplicity and low CPU overhead, provides acceptable performance. However, increasing the pressure on the controller e.g, with an application consisting of multiple tasks with drastically oscillating execution times, degrades the performance of the PI controller. Therefore, in this paper we modify the structure of our adaptive framework by replacing the PI controller with a fuzzy controller to achieve better performance. Furthermore, we conduct a simulation based case study in which we compose dynamic tasks such as video decoder tasks with a set of static tasks into a single system, and we show that the new fuzzy controller outperforms our previous PI controller.

  • 27.
    Moghaddami Khalilzad, Nima
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Lelli, Juri
    Scuola Superiore Sant’Anna, Italy.
    Lipari, Giuseppe
    Scuola Superiore Sant’Anna, Italy and LSV - ENS Cachan, France.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Towards Energy-aware Multiprocessor Hierarchical Scheduling of Real-time Systems2013Conference paper (Refereed)
    Abstract [en]

    Multiprocessor platforms are becoming increasingly more popular. Providing more computation capacity on a single hardware platform, multiprocessors make it possible to integrate previously federated real-time systems onto a single platform. Multiprocessor hierarchical scheduling techniques provide the ground for composing real-time components, while guaranteeing the timing correctness of the composed system. A considerable deal of compositional real-time systems are embedded systems that operate on battery power. In such systems, reducing the power consumption is of paramount importance to increase the system lifetime. In this paper, we present our idea on reducing the energy consumption when performing hierarchical scheduling on multiprocessors. We formulate the problem, present the model and sketch the outline of the solution. Finally, we present a number of challenges which will be addressed in our work.

  • 28.
    Moghaddami Khalilzad, Nima
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Liu, Meng
    Mälardalen University, School of Innovation, Design and Engineering.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering. Embedded Systems.
    Probabilistic Application Interfaces for Hierarchical Scheduling2013In: IEEE Real-Time Systems Symposium: IEEE Real-Time Systems Symposium Work-in-Progress (WiP) session, Vancouver, Canad, 2013Conference paper (Refereed)
  • 29.
    Moghaddami Khalilzad, Nima
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering.
    Åsberg, Mikael
    Mälardalen University, School of Innovation, Design and Engineering.
    Towards Adaptive Hierarchical Scheduling of Real-Time Systems2011In: IEEE Symposium on Emerging Technologies and Factory Automation, ETFA, 2011 / [ed] Mammeri, Z., New York: IEEE , 2011, p. 1-8Conference paper (Refereed)
    Abstract [en]

    Hierarchical scheduling provides a modular framework for integrating, scheduling and guaranteeing timing constraints of compositional real-time systems. In such a scheduling framework, all modules should receive a sufficient portion of the shared CPU to be able to guarantee timing constraints of their internal parts. In dynamic systems i.e., systems where the execution time of tasks are subjected to sudden and drastic changes during run-time, assigning fixed CPU portions to the modules is conducive to either low CPU utilization or numerous task deadline misses. In this paper, in order to address this problem, we propose an adaptive CPU allocation method which dynamically assigns CPU portions to the modules during run-time based on their current CPU demand. Besides, the presented approach is evaluated using a series of different simulations. In addition, we present a method for scheduling modules in situations when the CPU resource is not sufficient for scheduling all modules. We introduce the notion of module (subsystem) criticality, and in an overload situation we distribute the CPU resource based on the criticality of modules.

  • 30.
    Pordel, M.
    et al.
    Umeå University.
    Khalilzad, Nima Moghaddami
    Mälardalen University, School of Innovation, Design and Engineering.
    Yekeh, Farahnaz
    Mälardalen University, School of Innovation, Design and Engineering.
    Asplund, Lars
    Mälardalen University, School of Innovation, Design and Engineering.
    A component based architecture to improve testability, targeted FPGA-based vision systems2011In: 2011 IEEE 3rd International Conference on Communication Software and Networks, ICCSN 2011, 2011, p. 601-605Conference paper (Refereed)
    Abstract [en]

    FPGA has been used in many robotics projects for real-time image processing. It provides reliable systems with low execution time and simplified timing analysis. Many of these systems take a lot of time in development and testing phases. In some cases, it is not possible to test the system in real environments very often, due to accessibility, availability or cost problems. This paper is the result of a case study on vision systems for two robotics projects in which the vision team consisted of seven students working for six months fulltime on developing and implementing different image algorithms. While FPGA has been used for real-time image processing, some steps have been taken in order to reduce the development and testing phases. The main focus of the project is to integrate different testing methods with FPGA development. It includes a component based solution that uses a two-way communication with a PC controller for system evaluation and testing. Once the data is acquired from the vision board, the system stores it and simulates the same environment that has been captured earlier by feeding back the obtained data to FPGA. This approach addresses and implements a debugging methodology for FPGA based solutions which accelerate the development phase. In order to transfer massive information of images, RMII which is an interface for Ethernet communication, has been investigated and implemented. The provided solution makes changes easier, saves time and solves the problems mentioned earlier.

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