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  • 251.
    Santos, Rui
    et al.
    Universidade de Aveiro.
    Vieria, A
    Universidade de Aveiro.
    Marau, Ricardo
    Universidade de Aveiro.
    Pedreiras, Paulo
    Universidade de Aveiro.
    Oliveira, A
    Universidade de Aveiro.
    Almeida, Luis
    University of Porto.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Implementing Server-Based Communication within Ethernet Switches2009In: Proceedings of the 2nd Workshop on Compositional Theory and Technology for Real-Time Embedded Systems (CRTS'09) in conjunction with the 30th IEEE International Real-Time Systems Symposium (RTSS'09), Washington, DC, USA, 2009Conference paper (Refereed)
  • 252.
    Santos, Rui
    et al.
    Universidade de Aveiro.
    Vieria, A
    Universidade de Aveiro.
    Marau, Ricardo
    Universidade de Aveiro.
    Pedreiras, Paulo
    Universidade de Aveiro.
    Oliveira, A
    Universidade de Aveiro.
    Almeida, Luis
    University of Porto.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Improving the efficiency of Ethernet switches for real-time communication2010Conference paper (Refereed)
    Abstract [en]

    The growth of connectivity in general, including in networked embedded systems, is continuously increasing the amount and diversity of information that needs being exchanged among nodes. The arrival pattern of such traffic is also frequently bursty and jittered, negatively impacting the system performance. In this paper we focus on switched Ethernet and we aim at providing flow-based dynamic scheduling that allows handling bursty and jittered traffic in a bandwidth efficient way. For that we use adaptive resource-reservation, associating servers to flows or groups of flows that contain the impact that a misbehaving flow can have. These servers can be adapted on-line to make a better use of the available bandwidth.

  • 253.
    Santos, Rui
    et al.
    University of Aveiro.
    Vieria, A
    University of Aveiro.
    Pedreiras, Paulo
    University of Aveiro.
    Oliveira, A
    University of Aveiro.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Almeida, Luis
    University of Porto.
    Marau, Ricardo
    University of Porto.
    Flexible, Efficient and Robust Real-Time Communication with Server-based Ethernet Switching2010In: IEEE International Workshop on Factory Communication Systems - Proceedings, WFCS 2010, 2010, p. 131-140Conference paper (Refereed)
    Abstract [en]

    The information exchanged in Networked Embedded Systems is steadily increasing in quantity, size, complexity and heterogeneity, with growing requirements for arbitrary arrival patterns and guaranteed QoS. One of the networking protocols that is becoming more common in such systems is Ethernet and its real-time Ethernet variants. However, they hardly support all the referred requirements in an efficient manner since they either favour determinism or throughput, but not both. A potential solution recently proposed by the authors is the Server-SE protocol that uses servers to confine traffic associated to specific applications or subsystems. Such an approach is dynamically reconfigurable and adaptive, being more bandwidth efficient while providing compos ability in the time domain. This paper proposes integrating the servers inside the Ethernet switch, boosting both the flexibility and the robustness of Server-SE, allowing, for example, the seamless connection of any Ethernet node. The switch is an FTT-enabled Ethernet Switch and the paper discusses two specific ways of integrating the servers, namely in software or in hardware. These options are described and compared analytically and experimentally. The former favours flexibility in the servers design and management while the latter provides lower latency.

  • 254.
    Sentilles, Séverine
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Pettersson, Anders
    Mälardalen University, School of Innovation, Design and Engineering.
    Nyström, Dag
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Pettersson, Paul
    Mälardalen University, School of Innovation, Design and Engineering.
    Crnkovic, Ivica
    Mälardalen University, School of Innovation, Design and Engineering.
    Save-IDE – A Tool for Design, Analysis andImplementation of Component-based Embedded Systems2009In: 2009 31ST INTERNATIONAL CONFERENCE ON SOFTWARE ENGINEERING, PROCEEDINGS, IEEE Computer Society , 2009, p. 607-610Conference paper (Refereed)
    Abstract [en]

    The paper presents Save-IDE, an Integrated Development Environment for thedevelopment of component-based embedded systems. Save-IDE supports efficient development of dependable embedded systems by providing tools for design of embedded software systems using a dedicated component model, formal specification and analysis of component and system behaviors already in early development phases, and a fully automated transformation of the system of components into an executable image.

  • 255.
    Shin, Insik
    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.
    Sjödin, Mikael
    Mälardalen University, School of Innovation, Design and Engineering.
    On Optimal Hierarchical Resource Sharing in Open Environments2008Report (Other academic)
    Abstract [en]

    This paper presents a new perspective in the context of supporting logical resource sharing under hierarchical scheduling. Our work is motivated from a tradeoff between reducing resource holding times and reducing system load (i.e., the collective processor requirements to guarantee the schedulability of hierarchical scheduling frameworks). We formulate an optimization problem that determines the resource holding times of each individual tasks (and therefore those of subsystems) with the goal of minimizing the system load subject to the system's schedulability. We present efficient algorithms to find an optimal solution to the problem, and we prove their correctness. 

  • 256. Shin, Insik
    et al.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Sjödin, Mikael
    Mälardalen University, School of Innovation, Design and Engineering.
    Synthesis of Optimal Interfaces for Hierarchical Scheduling with Resources 2008In: Proceedings of the 29th IEEE International Real-Time Systems Symposium (RTSS08)., 2008, p. 209-220Conference paper (Refereed)
    Abstract [en]

     

    This paper presents algorithms that (1) facilitate system independent synthesis of timing-interfaces for subsystems and (2) system-level selection of interfaces to minimize CPU load. The results presented are developed for hierarchical fixed-priority scheduling of subsystems that may share logical recourses (i.e., semaphores). We show that the use of shared resources results in a tradeoff problem, where resource locking times can be traded for CPU allocation, complicating the problem of finding the optimal interface configuration subject to schedulability. This paper presents a methodology where such a tradeoff can be effectively explored. It first synthesizes a bounded set of interface-candidates for each subsystem, independently of the final system, such that the set contains the interface that minimizes system load for any given  system. Then, integrating subsystems into a system, it finds the optimal selection of interfaces. Our algorithms have linear complexity to the number of tasks involved. Thus, our approach is highly suitable for adaptable and reconfigurable systems.

     

  • 257.
    Shin, Insik
    et al.
    Mälardalen University, Department of Computer Science and Electronics.
    Behnam, Moris
    Mälardalen University, Department of Computer Science and Electronics.
    Nolte, Thomas
    Mälardalen University, Department of Computer Science and Electronics.
    Sjödin, Mikael
    Mälardalen University, Department of Computer Science and Electronics.
    Towards Optimal Hierarchical Resource Sharing in Open Environments2007In: Proceedings of the Work-In-Progress (WIP) session of the 28th IEEE Real-Time Systems Symposium (RTSS'07), Tucson, AZ, USA, 2007, p. 57-60Conference paper (Refereed)
  • 258.
    Silva, Pedro
    et al.
    Universidade de Aveiro.
    Almeida, Luis
    Universidade do Porto.
    Caprini, Daniele
    University of Pavia.
    Facchinetti, Tullio
    University of Pavia.
    Benzi, Francesco
    University of Pavia.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Experiments on timing aspects of DC-Powerline communications2009In: Proceedings of the Work-In-Progress (WIP) session of 14th IEEE International Conference on Emerging Techonologies and Factory (ETFA'09), 2009Conference paper (Refereed)
    Abstract [en]

    The Power Line technology has received an increasing attention in the last decades due to its inherent benefits, mainly related to the reduction of cabling and associated costs. Power Line Communication (PLC) was first employed in power utilities, and since the 80s in home automation, too. However, its use in the automotive field received relatively little attention. This paper extends previous works towards assessing PLC technology forcommunications within the automotive domain. In particular, it focuses on the real-time behavior of such technology, namely the DCB500 adaptors supplied by the Yamar company, showing experimental results of transmission delays, communication overheads and effectiveness of the medium access control policies.

  • 259.
    Thörn, Jonathan
    et al.
    Mälardalen University.
    Vidimlic, Najda
    Mälardalen University.
    Friebe, Anna
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Papadopoulos, Alessandro
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Probabilistic Timing Analysis of a Periodic Task on a Microcontroller2019In: The 24th IEEE Conference on Emerging Technologies and Factory Automation ETFA2019, 2019, p. 1419-1422Conference paper (Refereed)
    Abstract [en]

    In this paper we present our ongoing work towards a realistic probabilistic timing analysis of embedded software systems subject to timing requirements. In order to provide such an analysis that captures necessary and important behavioural features of the software system under analysis, including the underlying platform, we have implemented a real-time system running on a Rasberry Pi microcontroller on which we have performed a series of experiments and measurements. The results so far suggest a new model for analysis that captures more detailed behaviour and consequently provides a more accurate and correct probabilistic analysis.

  • 260.
    Uhlemann, Elisabeth
    et al.
    Halmstad University.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Scheduling Relay Nodes for Reliable Wireless Real-Time Communications2009In: Proceedings of the Work-In-Progress (WIP) session of 14th IEEE International Conference on Emerging Techonologies and Factory (ETFA'09), 2009Conference paper (Refereed)
    Abstract [en]

    We consider wireless relay networks for use in industrial applications with strict requirements on both timely and reliable communications. Frequently, more than one suitable relay node is available for retransmitting an erroneous packet. However, if commercially available transceivers are to be used; concurrent transmissions will result in collisions. Further, in a typical industrial network, there may be several data packets that need to travel from source to destination during the same timeperiod. Consequently, relay nodes need to be scheduled to data packets and time instances such that as many packets as possible can be received at their destinations with as high reliability as possible before their respective deadlines. Our goal is thus to increase the data reliability in industrial wireless networks, while respecting real-time deadlines.

  • 261.
    Van Den Heuvel, M. M. H. P.
    et al.
    Technische Universiteit Eindhoven, Netherlands .
    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.
    Lukkien, Johan J.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Optimal and fast composition of resource-sharing components in hierarchical real-time systems2014In: RTCSA 2014 - 20th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications, 2014, p. Article number 6910547-Conference paper (Refereed)
    Abstract [en]

    In this paper we consider various flavors of the stack resource policy (SRP) for arbitrating access to shared resources in a hierarchical scheduling framework (HSF) upon a uni-processor. We propose algorithms for exploring and selecting the (local) resource ceilings within components, such that it results in an optimal composition of resource-sharing components in an HSF. Existing methods are non-optimal, because (i) they optimize just the length of global non-preemptive execution of tasks and (ii) they do not detect whether or not resources are shared globally (i.e., between tasks of different components). Lifting these limitations leads to an exponential growth of the design space. This paper contributes a fast three-step methodology which lifts these limitations, i.e., we apply the SRP at each level of the HSF to just the resources being shared. Our algorithm selects those component interfaces (i.e., by fixing the local resource ceilings of each component) that minimize the system load.

  • 262.
    Van Den Heuvel, M. M. H. P.
    et al.
    Technische Universiteit Eindhoven,Netherlands .
    Bril, R. J.
    Technische Universiteit Eindhoven,Netherlands .
    Lukkien, J. J.
    Technische Universiteit Eindhoven,Netherlands .
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Performance evaluation of analysis methods for arbitrating non-preemptive resource access in compositional real-time systems2014In: 19th IEEE International Conference on Emerging Technologies and Factory Automation, ETFA 2014, 2014, p. Article number 7005065-Conference paper (Refereed)
    Abstract [en]

    In this paper, we compare and survey different ways to model the scheduling delays corresponding to non-preemptive critical sections being executed by the tasks of different components that ultimately need to share one processor. We focus on the performance of compositional timing analyses for systems and we compare different protocols for the arbitration of tasks that wish to execute critical sections. Such analysis methods support timing predictable composition of independently validated components. This validation consists of analyzing the worst-case impact of critical sections on the schedules of the component's tasks. Finally, we evaluate the performance of the analysis methods by means of a simulation study.

  • 263.
    van den Heuvel, Martijn
    et al.
    Technische Universiteit Eindhoven, the Netherlands.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering.
    J. Bril, Reinder
    Technische Universiteit Eindhoven, the Netherlands.
    Lukkien, Johan
    Technische Universiteit Eindhoven, the Netherlands.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Opaque Analysis for Resource Sharing in Compositional Real-Time Systems2011In: 4th Workshop on Compositional Theory and Technology for Real-Time Embedded Systems (CRTS'11), 2011Conference paper (Refereed)
    Abstract [en]

    In this paper we propose opaque analysis methods to integrate dependent real-time components into hierarchical fixed-priority scheduled systems. To arbitrate mutually exclusive resource access between components, we consider two existing protocols: HSRP - comprising overrun with and without payback - and SIRAP. An opaque analysis allows to postpone the choice of a synchronization protocol until component integration time. First, we identify the sources of pessimism in the existing analysis techniques and we conclude that both protocols assume different models in their local analysis. In particular, the compo- sitional analysis for overrun with payback (OWP) is not opaque and is pessimistic. The latter makes OWP expensive compared to its counter part without a payback mechanism (ONP). This paper presents an opaque and less pessimistic OWP analysis. Secondly, SIRAP requires more timing information to perform a task-level schedulability analysis. In many practical situations, however, detailed timing characteristics of tasks are hard to obtain. We introduce an opaque analysis for SIRAP using the analysis of ONP to reduce the required timing information during the local analysis. We show that the analysis for ONP cannot deem systems schedulable which are infeasible with SIRAP. The SIRAP analysis may therefore reduce the required system resources of a component by sacrificing the choice for an arbitrary synchronization protocol at system integration time.

  • 264.
    van den Heuvel, Martijn
    et al.
    TU/e, The Netherlands.
    J. Bril, Reinder
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Lukkien, Johan
    TU/e, The Netherlands.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Uniform Interfaces for Resource-Sharing Components in Hierarchically Scheduled Real-Time Systems2016In: Real-Time Systems, InTech , 2016Chapter in book (Other academic)
  • 265.
    Yang, Jinsong
    et al.
    ABB Corporate Research.
    Sandström, Kristian
    ABB Corporate Research.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering.
    Data Distribution Service for Industrial Automation2012In: IEEE Symposium on Emerging Technologies and Factory Automation, ETFA, 2012, p. Art.nr: 6489544-Conference paper (Refereed)
    Abstract [en]

    The IEC 61499 is an open standard for the next generation of distributed control and automation. Data Distribution Service for Real-Time Systems (DDS) is a specification of a publish/subscribe middleware for distributed systems, created by the Object Management Group (OMG) to standardize a data-centric publish-subscribe programming model for distributed systems. This paper evaluates the DDS communication performance based on a model built within the IEC 61499 standard and compares it with the traditional socket based solution for communication. According to the test results, the DDS communication has the potential to reduce the complexity and is suggested as a suitable solution for some classes of industrial control systems.

  • 266.
    Åkerholm, Mikael
    et al.
    Mälardalen University, Department of Computer Science and Electronics.
    Carlson, Jan
    Mälardalen University, Department of Computer Science and Electronics.
    Fredriksson, Johan
    Mälardalen University, Department of Computer Science and Electronics.
    Hansson, Hans
    Mälardalen University, Department of Computer Science and Electronics.
    Sjödin, Mikael
    Mälardalen University, Department of Computer Science and Electronics.
    Nolte, Thomas
    Mälardalen University, Department of Computer Science and Electronics.
    Håkansson, John
    Mälardalen University, Department of Computer Science and Electronics.
    Pettersson, Paul
    Mälardalen University, Department of Computer Science and Electronics.
    Handling Subsystems using the SaveComp Component Technology2006In: Workshop on Models and Analysis for Automotive Systems (WMAAS'06) in conjunction with the 27th IEEE Real-Time Systems Symposium (RTSS'06), Rio de Janeiro, Brazil, 2006Conference paper (Refereed)
  • 267.
    Åkerholm, Mikael
    et al.
    Mälardalen University, Department of Computer Science and Electronics.
    Carlson, Jan
    Mälardalen University, Department of Computer Science and Electronics.
    Håkansson, John
    Uppsala University, Uppsala, Sweden.
    Hansson, Hans
    Mälardalen University, Department of Computer Science and Electronics.
    Sjödin, Mikael
    Mälardalen University, Department of Computer Science and Electronics.
    Nolte, Thomas
    Mälardalen University, Department of Computer Science and Electronics.
    Pettersson, Paul
    Mälardalen University, Department of Computer Science and Electronics.
    The SaveCCM Language Reference Manual2007Report (Other academic)
    Abstract [en]

    This language reference describes the syntax and semantics of SaveCCM, a

    component modeling language for embedded systems designed with vehicle applications and safety concerns in focus. The SaveCCM component model was

    defined within the SAVE project. The SAVE components are influenced mainly

    by the Rubus component technology, with a switch concept similar to that

    in Koala. The semantics is defined by a transformation into timed automata

    with tasks, a formalism that explicitly models timing and real-time task scheduling.

    The purpose of this document is to describe a semantics of the SAVE component modeling language, which can be used to describe timing and functional behavior of components. The model of a system is in some cases an over approximation of the actual system behavior. An implementation of a model can resolve non-determinism e.g. by merging tasks or assigning a scheduling policy (such as static scheduling or fixed priority, preemptive or not) that will resolve

    the non-determinism.

  • 268.
    Åsberg, Mikael
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering.
    Nemati, Farhang
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Towards Hierarchical Scheduling in AUTOSAR2009In: Proceedings of 14th IEEE International Conference on Emerging Techonologies and Factory (ETFA'09), 2009Conference 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.

  • 269.
    Åsberg, Mikael
    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.
    An Experimental Evaluation of Synchronization Protocol Mechanisms in the Domain of Hierarchical Fixed-Priority Scheduling2013In: ACM International Conference Proceeding Series, 2013, 2013, p. 77-85Conference paper (Refereed)
    Abstract [en]

    This paper presents an extensive implementation study where we evaluate and compare different synchronization protocol mechanisms within the domain of two-level hierarchical fixed-priority preemptive scheduling. These protocol mechanisms include HSRPnP (Hierarchical Stack Resource Policy no Payback), HSRPwP (Hierarchical Stack Resource Policy with Payback), SIRAP (Subsystem Integration and Resource Allocation Policy), RRP (Rollback Resource Policy) and SRPwD (Stack Resource Policy with Donation). In an attempt to shed new light to the research in this area, we focus on the actual software implementation of these protocols in a widely used real-time operating system (VxWorks). This study is not based on worst-case schedulability analysis which is the most common angle of work in this research field. All five protocols have been implemented, tested and executed for several months with many different parameters, for example; variant number of subsystems, number of resources, system utilization settings, resource allocation strategies etc. These tests generated a large amount of useful data, for example, protocol overhead, effective subsystem utilization, number of protocol mechanism invocations etc. Due to the large complexity and size of this data, we analyzed the data with state-of-the-art statistical methods and tools (Principal Component Analysis) in order to grasp the efficiency of the protocols with respect to a large number of different parameters.

  • 270.
    Åsberg, Mikael
    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.
    J. Bril, Reinder
    Technische Universiteit Eindhoven.
    Implementation of Overrun and Skipping in VxWorks2010In: Proceedings of the 6th International Workshop on Operating Systems Platforms for Embedded Real-Time Applications, Brussels, Belgium, 2010Conference paper (Refereed)
  • 271.
    Åsberg, Mikael
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Forsberg, Nils
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Kato, Shinpei
    Carnegie Mellon University, USA.
    Towards Real-Time Scheduling of Virtual Machines Without Kernel Modifications2011In: 16th IEEE International Conference on Emerging Technology and Factory Automation (ETFA'11), Work-in-Progress (WiP) session, Toulouse, France, 2011Conference paper (Refereed)
    Abstract [en]

    Virtualization is a well used technique in the area of internet server systems for managing several (legacy) applications on a single physical machine. These applications do not have strict time deadlines, which also reflects how these applications are scheduled. Using virtualization in an embedded real-time systems context is of course attractive, since we want to pack as much software as possible on a, as small as possible, hardware platform. The problem is that this kind of software does not easily cope well together, in the aspect of time related properties. Hence, we need a new mechanism, i.e., a scheduler, that can satisfy the timing requirements of each application. However, scheduler implementations typically require modifications to middleware or kernel and this is not acceptable in the area embedded systems, due to stability and reliability reasons. Hence, in this paper, we propose a framework for scheduling (soft real-time) applications residing in separate operating systems (virtual machines) using hierarchical fixed-priority preemptive scheduling, without the requirement of kernel modifications.

  • 272.
    Åsberg, Mikael
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Kraft, Johan
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Kato, Shinpei
    Mälardalen University, School of Innovation, Design and Engineering.
    A loadable task execution recorder for Linux2010In: Proceedings of the 1st International Workshop on Analysis Tools and Methodologies for Embedded and Real-time Systems, Brussels, Belgium, 2010Conference paper (Refereed)
  • 273.
    Åsberg, Mikael
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Towards a User-Mode Approach to Partitioned Scheduling in the seL4 Microkernel2012Conference paper (Refereed)
    Abstract [en]

    This paper presents a preliminary study of applying partitioned scheduling in the seL4 microkernel. This microkernel is the first operating system kernel ever to be formally proven for its functional correctness. Even though the kernel is completely verified it still delivers high performance comparable to other L4 kernels. The seL4 kernel implements isolation of components in terms of the memory resource and security. However, there is still a missing part when it comes to isolation and that is time partitioning. Time partitioning can be implemented inside the kernel (privileged mode) or in user space (user mode). The latter is done using regular user-space thread(s) and can easily be modified while the other approach requires re-verification of the kernel whenever modifications to the time-partitioning policy is done. On the other hand, having the time-partitioning mechanism in privileged mode would yield better performance. We have implemented time partitioning (partitioned scheduling) in the seL4 user space and we elaborate on its performance in terms of overhead costs.

  • 274.
    Åsberg, Mikael
    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.
    Resource sharing using the rollback mechanism in hierarchically scheduled real-time open systems2013In: Real-Time Technology and Applications - Proceedings, 2013, p. 129-140Conference paper (Refereed)
    Abstract [en]

    In this paper we present a new synchronization protocol called RRP (Rollback Resource Policy) which is compatible with hierarchically scheduled open systems and specialized for resources that can be aborted and rolled back. We conduct an extensive event-based simulation and compare RRP against all equivalent existing protocols in hierarchical fixed priority preemptive scheduling; SIRAP (Subsystem Integration and Resource Allocation Policy), OPEN-HSRPnP (open systems version of Hierarchical Stack Resource Policy no Payback) and OPEN-HSRPwP (open systems version of Hierarchical Stack Resource Policy with Payback). Our simulation study shows that RRP has better average-case response-times than the state-of-the-art protocol in open systems, i.e., SIRAP, and that it performs better than OPEN-HSRPnP/OPEN-HSRPwP in terms of schedulability of randomly generated systems. The simulations consider both resources that are compatible with rollback as well as resources incompatible with rollback (only abort), such that the resource-rollback overhead can be evaluated. We also measure CPU overhead costs (in VxWorks) related to the rollback mechanism of tasks and resources. We use the eXtremeDB (embedded real-time) database to measure the resource-rollback overhead.

  • 275.
    Åsberg, Mikael
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Joki, Mikael
    Eskilstuna Elektronikpartner AB, Sverige.
    Hogbrink, Jimmy
    Eskilstuna Elektronikpartner AB, Sverige.
    Siwani, Saher
    Eskilstuna Elektronikpartner AB, Sverige.
    Fast Linux Bootup using Non-Intrusive Methods for Predictable Industrial Embedded Systems2013Conference paper (Refereed)
    Abstract [en]

    Fast kernel boot-time is one of the major concerns in industrial embedded systems. Application domains where boot time is relevant include (among others) automation, automotive, avionics etc. Linux is one of the big players among operating system solutions for general embedded systems, hence, a relevant question is how fast Linux can boot on typical hardware platforms (ARM9) used in such industrial systems. One important constraint is that this boot-time optimization should be as non-intrusive as possible. The reason for this comes from the fact that industrial embedded systems typically have high demands on reliability and stability. For example, adding, removing or changing critical source-code (such as kernel or initialization code) is impermissible. This paper shows the steps towards a fast-booting Linux kernel using non-intrusive methods. Moreover, targeting embedded systems with temporal constraints, the paper shows how fast the real-time scheduling framework ExSched can be loaded and started during bootup. This scheduling framework supports several real-time scheduling algorithms (user defined, multi-core, partitioned, fixed-priority periodic tasks etc.) and it does not modify the Linux kernel source code. Hence, the non-intrusive bootup optimization methods together with the unmodified Linux kernel and the non-patched real-time scheduler module offers both reliability and predictability.

  • 276.
    Åsberg, Mikael
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Kato, Shinpei
    Carnegie Mellon University, Department of Electrical and Computer Engineering, United States.
    A Loadable Task Execution Recorder for Hierarchical Scheduling in Linux2011In: Proceedings - 17th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications, RTCSA 2011, 2011, p. 380-387Conference paper (Refereed)
    Abstract [en]

    This paper presents a Hierarchical Scheduling Framework (HSF) recorder for Linux-based operating systems. The HSF-recorder is a loadable kernel module that is capable of recording tasks and servers without requiring any kernel modifications. Hence, it complies with the reliability and stability requirements in the area of embedded systems where proven versions of Linux are preferred. The recorder is built upon the loadable real-time scheduler framework RESCH (REal-time SCHed- uler). We evaluate our recorder by comparing the overhead of this solu- tion against two other recorders. Also, the tracing accuracy of the HSF- recorder is tested by running a media-processing task together with periodic real-time Linux tasks in combination with servers. We experiment with different task parameters and scheduling strategies and measure the performance of the media-processing task. The tests are recorded with the HSF-recorder, and the Ftrace recorder, in order to show the correctness of the experiments and the HSF-recorder itself.

  • 277.
    Åsberg, Mikael
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Kato, Shinpei
    Towards Hierarchical Scheduling in Linux/Multi-core Platform2010In: 15th IEEE International Conference on Emerging Technologies and Factory Automation (ETFA 2010), 2010Conference paper (Refereed)
    Abstract [en]

    This paper proposes the implementation of 4 different scheduling strategies for combining multi-core scheduling with hierarchical scheduling. Three of the scheduling schemes are analyzable with state-of-the-art schedulability analysis theory, available in the real-time systems community. Our idea is to implement these hierarchical multi-core scheduling strategies in a Linux based operating system, without modifying the kernel, and evaluate them. As of now, we have developed/implemented a prototype two-level hierarchical scheduling framework (HSF) in Linux (uni-core), which supports fixed priority preemptive scheduling (FPPS) of periodic servers at the top level, and FPPS of periodic tasks at the second level. The HSF is based on the REal-time SCHeduler (RESCH) framework.(1)

  • 278.
    Åsberg, Mikael
    et al.
    Mälardalen University, School of Innovation, Design and Engineering. IS (Embedded Systems).
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Kato, Shinpei
    University of California, Santa Cruz, USA.
    Towards Partitioned Hierarchical Real-Time Scheduling on Multi-core Processors2013Conference paper (Refereed)
    Abstract [en]

    This paper extends previous work on hierarchical scheduling to multi-core systems. We have implemented partitioned multi-core scheduling of servers in the Linux kernel, using the scheduling framework ExSched. Neither ExSched nor the presented scheduler require any modifications to the Linux kernel. Hence, this makes the installation and kernel-version updates easier. We also present a user-space simulator which can be used when developing new multi-core hierarchical schedulers (plug-ins) for ExSched. We evaluate the overhead of our new multi-core hierarchical scheduler and compare it to a single-core hierarchical scheduler. Our results can be useful for developers that want to minimize the scheduler overhead when using partitioned hierarchical multi-core scheduling.

  • 279.
    Åsberg, Mikael
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Kato, Shinpei
    Nagoya University.
    Rajkumar, Ragunathan
    Carnegie Mellon University.
    ExSched: An External CPU Scheduler Framework for Real-Time Systems2012In: 18th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA'12), 2012, p. 240-249Conference paper (Refereed)
  • 280.
    Åsberg, Mikael
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Otero Perez, Clara M.
    NXP Semiconductors/Research, High Tech. Campus.
    Kato, Shinpei
    University of Tokyo.
    Execution Time Monitoring in Linux2009In: Proceedings of the Work-In-Progress (WIP) session of 14th IEEE International Conference on Emerging Techonologies and Factory (ETFA'09), 2009Conference paper (Refereed)
    Abstract [en]

    This paper presents an implementation of an Execution Time Monitor (ETM) which can be applied in a resource management framework, such as the one proposed in the Open Media Platform (OMP) [4]. OMP is a European project which aims at creating an open, flexible and resource efficient software architecture for mobile devices such as cell phones and handsets. One of its goals is to open up the possibility for software portability and fast integration of applications, in order to decrease development costs. The task of the ETM is to measure task execution time and provide this information to the scheduler which then can schedule tasks in a more efficient and dynamic way. This implementation is our first step towards a full resource management framework that later will include a hierarchical scheduler, for soft real-time systems.

  • 281.
    Åsberg, Mikael
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Pettersson, Paul
    Mälardalen University, School of Innovation, Design and Engineering.
    Prototyping and Code Synthesis of Hierarchically Scheduled Systems using TIMES2010In: FTRA Journal of Convergence, ISSN 2093-7741, Vol. 1, no 1, p. 75-84Article in journal (Refereed)
    Abstract [en]

    In hierarchical scheduling a system is organized as a tree of nodes, where each node schedules its child nodes. A node contains tasks and/or subsystems, where a subsystem is typically developed by a development team. Given a system where each part is subcontracted to different developers, they can benefit from hierarchical scheduling by parallel development and simplified integration of subsystems. Each team should have the possibility to test their system before integration. Hence, we show how a node, in a hierarchical scheduling tree, can be analyzed in the Times tool by replacing all interference from nodes with a small set of higher priority tasks. We show an algorithm that can generate these tasks, including their parameters. Further, we use the Times code-generator, in combination with operating system extensions, to generate source code that emulates the scheduling environment for a subsystem, in an arbitrary level in the tree. Our experiments include two example systems. In the first case we generate source code for an industrial oriented platform (VxWorks) and conduct a performance evaluation. In the second example we generate source code that emulates the scheduling environment for a video application, running in Linux, and we perform a frame-rate evaluation.

  • 282.
    Åsberg, Mikael
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Pettersson, Paul
    Mälardalen University, School of Innovation, Design and Engineering.
    Prototyping Hierarchically Scheduled Systems using Task Automata and TIMES2010In: Proceedings of the 5th International Conference on Embedded and Multimedia Computing (EMC-10), 2010, p. article nr: 5575626-Conference paper (Refereed)
    Abstract [en]

    In hierarchical scheduling, a system is organized into multiple levels of individually scheduled subsystems (hierarchical scheduling tree), which provides several benefits for developers including possibilities for parallel development of subsystems. In this paper, we study how the model of task automata and the Times tool can be applied to provide support for rapid and early prototyping of hierarchically scheduled embedded systems. As a main result, we show how a single node, in an arbitrary level in a hierarchical scheduling tree (scheduled with fixed-priority preemptive scheduling), can easily be analyzed in Times by replacing all interfering nodes with a small set of higher priority (dummy) tasks. We show with an algorithm how these dummy tasks are generated (including task-parameters such as period, offset etc.). Further, we generate executable source code, with the Times code-generator, that emulates the scheduling environment (with our dummy tasks), i.e., the hierarchical scheduling tree and all of its preemptions, of a small example system. Yet another contribution is that we transform the generated (brickOS) source code to run on an industrial oriented platform (VxWorks), and conduct an performance evaluation.

  • 283.
    Åsberg, Mikael
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Pettersson, Paul
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Evaluating the Run-Time Performance of Synthesised Resource-Reservation Schedulers Using TAtoC, UPPAAL and Frama-C2013Report (Other academic)
  • 284.
    Åsberg, Mikael
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Pettersson, Paul
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Modelling, Verification and Synthesis of Two-Tier Hierarchical Fixed-Priority Preemptive Scheduling2011In: Proceedings - 23rd EUROMICRO Conference on Real-Time Systems (ECRTS'11), 2011, p. 172-181Conference paper (Refereed)
    Abstract [en]

    Hierarchical scheduling has major benefits when it comes to integrating hard real-time applications. One of those benefits is that it gives a clear runtime separation of applications in the time domain. This in turn gives a protection against timing error propagation in between applications. However, these benefits rely on the assumption that the scheduler itself schedules applications correctly according to the scheduling parameters and the chosen scheduling policy. A faulty scheduler can affect all applications in a negative way. Hence, being able to guarantee that the scheduler is correct is of great importance. Therefore, in this paper, we study how properties of hierarchical scheduling can be verified. We model a hierarchically scheduled system using task automata, and we conduct verification with model checking using the Times tool. Further, we generate C-code from the model and we execute the hierarchical scheduler in the Vx Works kernel. The CPU and memory overhead of the modelled scheduler is compared against an equivalent manually coded two-level hierarchical scheduler. We show that the worst-case memory consumption is similar and that there is a considerable difference in CPU overhead.

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