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Sökning: WFRF:(Behnam Moris) > Övrigt vetenskapligt

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1.
  • Afshar, Sara, et al. (författare)
  • Per Processor Spin-Lock Priority for Partitioned Multiprocessor Real-Time Systems
  • 2014
  • Rapport (övrigt vetenskapligt)abstract
    • Two traditional approaches exist for a task that is blocked on a global resource; a task either performs a non-preemptive busy wait, i.e., spins, or suspends and releases the processor. Previously, we have shown that both approaches can be viewed as spinning either at the highest priority HP or at the lowest priority on the processor LP, respectively. Based on this view, previously we have generalized a task's blocking behavioral model, as spinning at any arbitrary priority level. In this paper, we focus on a particular class of spin-lock protocols from the introduced flexible spin-lock model where spinning is performed at a priority equal to or higher than the highest local ceiling of the global resources accessed on a processor referred to as CP spin-lock approach. In this paper, we assume that all tasks of a specific processor are spinning on the same priority level. Given this class and assumption, we show that there exists a spin-lock protocol in this range that dominates the classic spin-lock protocol which tasks spin on highest priority level (HP). However we show that this new approach is incomparable with the CP spin-lock approach. Moreover, we show that there may exist an intermediate spin-lock approach between the priority used by CP spin-lock approach and the new introduced spin-lock approach that can make a task set schedulable when those two cannot. We provide an extensive evaluation results comparing the HP, CP and the new proposed approach.
2.
  • Ashjaei, Mohammad, et al. (författare)
  • SEtSim: A Modular Simulation Tool for Switched Ethernet Networks
  • 2014
  • Rapport (övrigt vetenskapligt)abstract
    • Using high bandwidth network technologies in real-time applications, for example in automotive systems, is rapidly increasing. In this context, switched Ethernet-based protocols are becoming more popular due to their features such as providing a collision-free domain for transmission of messages. Moreover, switched Ethernet is a mature technology. Several protocols based on switched Ethernet have been proposed over the years, tuned for time critical applications. However, research for improving the features and performance of these protocols is still on-going. In order to evaluate the performance of early stage proposed protocols, the mathematical analysis and/or experiments are required. However, performing an experiment for complex network topologies with a large set of messages is not effortless. Therefore, using a simulation based approach for evaluating a protocol's performance and/or properties is highly useful. As a response to this we have, based on Simulink, developed a simulator, called SEtSim, for switched Ethernet networks. SEtSim currently supports different network topologies of the FTT-SE protocol, a master-slave protocol designed for standard Ethernet switches, as well as Ethernet AVB protocol. However, the kernel of SEtSim is designed such that it is possible to add and integrate other switched Ethernet-based protocols. In this paper, we describe the design of SEtSim and we show its scalability.
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3.
  • Behnam, Moris (författare)
  • Hierarchical Real Time Scheduling and Synchronization
  • 2008
  • Licentiatavhandling (övrigt vetenskapligt)abstract
    •  The Hierarchical Scheduling Framework (HSF) has been introduced to enable compositional schedulability analysis and execution of embedded software systems with real-time constraints. In this thesis, we consider a system consisting of a number of semi-independent components called subsystems, and these subsystems are allowed to share logical resources. The HSF provides CPU-time to the subsystems and it guarantees that the individual subsystems respect their allocated CPU budgets. However, if subsystems are allowed to share logical resources, extra complexity with respect to analysis and run-time mechanisms is introduced. In this thesis we address three issues related to hierarchical scheduling of semi-independent subsystems. In the first part, we investigate the feasibility of implementing the hierarchical scheduling framework in a commercial operating system, and we present the detailed figures of various key properties with respect to the overhead of the implementation.In the second part, we studied the problem of supporting shared resources in a hierarchical scheduling framework and we propose two different solutions to support resource sharing. The first proposed solution is called SIRAP, a synchronization protocol for resource sharing in hierarchically scheduled open real-time systems, and the second solution is an enhanced overrun mechanism.In the third part, we present a resource efficient approach to minimize system load (i.e., the collective CPU requirements to guarantee the schedulability of hierarchically scheduled subsystems). Our work is motivated from a tradeoff between reducing resource locking times and reducing system load. We formulate an optimization problem that determines the resource locking times of each individual subsystem with the goal of minimizing the system load subject to system schedulability. We present linear complexity algorithms to find an optimal solution to the problem, and we prove their correctness       
4.
  • Behnam, Moris, et al. (författare)
  • Overrun Methods for Semi-Independent Real-Time Hierarchical Scheduling
  • 2009
  • Rapport (övrigt vetenskapligt)abstract
    • The Hierarchical Scheduling Framework (HSF) has been introduced as a design-time framework to enable compositional schedulability analysis of embedded software systems with real-time properties. In this paper a software system consists of a number of semi-independent components called subsystems. Subsystems are developed independently and later integrated to form a system. To support this design process, in the paper, the proposed methods allow non-intrusive configuration and tuning of subsystem timing-behaviour via subsystem interfaces for selecting scheduling parameters. This paper considers three methods to handle overruns due to resource sharing between subsystems in the HSF. For each one of these three overrun methods corresponding scheduling algorithms The work in this paper is supported by the Swedish Foundation for Strategic Research (SSF), via the research programme PROGRESS. and associated schedulability analysis are presented together with analysis that shows under what circumstances one or the other is preferred. The analysis is generalized to allow for both Fixed Priority Scheduling (FPS) and Earliest Deadline First (EDF) scheduling. Also, a further contribution of the paper is the technique of calculating resource-holding times within the framework under different scheduling algorithms. The resource holding times being an important parameter in the global schedulability analysis.
5.
  • Behnam, Moris, et al. (författare)
  • Real-Time Control Design for Flexible Scheduling using Jitter Margin
  • 2007
  • Rapport (övrigt vetenskapligt)abstract
    • Real-time control algorithms are designed based on thecharacteristics of the controlled plants and they require goodperformance without delays. However, digital control implementationtypically introduces delays and jitters due to insufficient CPUprocessing power and the limitations of the real-time schedulingmethod used. This can degrade the system performance or even make itunstable.In this paper we propose an integrated approach for control designand real-time scheduling, suitable for both discrete-time andcontinuous-time controllers. It guarantees system performance byaccepting a certain minimum value of jitter for control tasks andfeasibly schedules them together with other tasks in the system.Results from comparison with other approaches from real-time andcontrol theory domains underline the effectiveness of our method.
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6.
  • Behnam, Moris, 1973-, et al. (författare)
  • Schedulability analysis of synchronization protocols based on overrun without payback for hierarchical scheduling frameworks revisited
  • 2010
  • Rapport (övrigt vetenskapligt)abstract
    • In this paper, we show that both global as well as local schedulability analysis of synchronization protocols based on the stack resource protocol (SRP) and overrun without payback for hierarchical scheduling frameworks based on fixed-priority pre-emptive scheduling (FPPS) are pessimistic.We present improved global and local schedulability analysis,illustrate the improvements by means of examples, and show that the improved global analysis is both uniform and sustainable.We evaluate the improved global and local schedulabilityanalysis based on an extensive simulation study and comparethe results with the existing analysis.
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7.
  • Behnam, Moris, et al. (författare)
  • SIRAP: A Global Resource Sharing Protocol Facilitating Integration of Semi-independent Real-Time Systems
  • 2007
  • Rapport (övrigt vetenskapligt)abstract
    • This paper presents a protocol for resource sharing in a hierarchical real-time scheduling framework. Together, the protocol and the scheduling framework significantly reduce the efforts and errors associated with integrating multiple semi-independent subsystems on a single processor. Thus, our proposed techniques facilitate modern software development processes, where subsystems are developed by independent teams (or subcontractors) and at a later stage integrated into a single product. Using our solution, a subsystem need not know, and is not dependent on, the timing behaviour of other subsystems; even though they share mutually exclusive resources. In this paper we also prove the correctness of our approach and evaluate its efficiency.
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8.
  • Behnam, Moris, 1973- (författare)
  • Synchronization Protocols for a Compositional Real-Time Scheduling Framework
  • 2010
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • In this thesis we propose techniques to simplify the integration of subsystems while minimizing the overall amount of CPU resources needed to guarantee the schedulability of real-time tasks. In addition, we provide solutions to the problem of allowing for the use of logical resources requiring mutual exclusion.The contribution of the thesis is presented in three parts. In the first part, we propose a synchronization protocol, called SIRAP, to facilitate sharing of logical resources in a hierarchical scheduling framework. In addition, we extend an existing synchronization protocol, called HSRP, such that each subsystem can be developed independently. The performance of the proposed protocols is evaluated by extensive simulations. In the second part, we present an efficient schedulability analysis that exploits the lower scheduling overhead introduced by each of the proposed protocols. Finally, in the third part, we propose new methods and algorithms that find the optimal system parameters (e.g., optimal resource ceiling), that minimize the amount of CPU resources required to ensure schedulability, when using the proposed synchronization protocols in a hierarchical scheduling framework.The motivation of this work comes from an emerging industrial trend in embedded software systems development to integrate multiple applications (subsystems) on a small number of processors. The purpose of this integration is to reduce the hardware related costs as well as the communication complexity between processors. In this setting a large number of industrial applications face the problem of preserving their real-time properties after their integration onto a single processor. In addition, temporal isolation between the applications during runtime may be required to prevent failure propagation between different applications.Specifically, we propose a hierarchical scheduling framework that allows for a simplified integration of subsystems. The framework preserves the essential temporal characteristics of the subsystems, both when running in isolation as well as when they are integrated with other subsystems. In this thesis, we assume a model where a system consists of a number of subsystems. The subsystems can interact with each other using shared logical resources. The framework ensures that the individual subsystem respects its allocated share of the processor. The difficulty lies in allowing two or more subsystems to share logical resources, which introduces an additional complexity in the schedulability analysis and also increases the system load.
9.
  • Inam, Rafia, 1974-, et al. (författare)
  • Compositional analysis for the multi-resource server - a technical report.
  • 2014
  • Rapport (övrigt vetenskapligt)abstract
    • The Multi-Resource Server (MRS) technique has been proposed toenable predictable execution of memory intensive real-time applicationson COTS multi-core platforms. It uses resource reservationapproaches in the context of CPU-bandwidth and memory-busbandwidth reservations to bound the interferences between the applicationsrunning on the same core as well as between the applicationsrunning on different cores. In this paper we present a completecompositional schedulability analysis for the Multi-ResourceServer technique. Based on the proposed analysis, we further providean experimental study that investigates the behaviour of theMRS and identify the factors that contribute mostly on the overallsystem performance.
10.
  • Inam, Rafia, 1974-, et al. (författare)
  • Support for Legacy Real-Time Applications in an HSF-Enabled FreeRTOS - a technical report
  • 2014
  • Rapport (övrigt vetenskapligt)abstract
    • This paper presents a runtime support to consolidate legacy together with other real-time applications, running a single instance of a real-time operating system (RTOS), and sharing system resources. In this context, we resort to the hierarchical scheduling framework (HSF) to provide tem- poral partitions for dierent applications, supporting their independent development and real-time analysis, thus resulting on a predictable inte- gration. In particular, the paper focuses on a constructive element, the legacy server that allows executing code that is unaware of the temporal partition within which it is deployed. Furthermore, we discuss the chal- lenges that need to be addressed to execute a legacy application in an HSF without modications to the original code. We focus on the chal- lenge of enabling sharing system resources, both hardware and software, as typically found in most industrial software systems. We propose a novel solution based on wrappers for the required RTOS system calls. We implement our ideas in a concrete implementation on FreeRTOS OS, taking advantage of a prior HSF implementation. The validation is performed by a proof-of-concept case study that shows a successful integration of a legacy application that uses shared resources in a system that executes other applications. 
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