Optimizing Distributed Real-Time Embedded System Handling Dependence and Several Strict Periodicity Constraints

Kermia, Omar

doi:10.1155/2011/561794

Cited by 4 publications

(7 citation statements)

References 6 publications

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“…• The proposed nonpolynomial sufficient schedulability condition noticed NP_SSC: if( 13) ∧ ( 14) else (15). • The proposed polynomial sufficient schedulability condition noticed P_SSC: if( 13) ∧ (14) else (16).…”

Section: Schedulability Conditions Evaluationmentioning

confidence: 99%

“…However, it turns out that strict periodicity is more constrained than the period constraint commonly taken into account which leads, generally, to an underutilization of the processor resources and an impractical schedulability analysis. 15 Therefore, it is quite conceivable to consider that only task input part necessitates the highest priority and, thus, is strictly periodic, while the remaining part of the task, including outputs, must rather run before a deadline. This way, as a strictly periodic part of the control task, input portion (shaded in red in Figure 1) is necessarily nonpreemptive whereas the remaining part of the task (shaded in blue in Figure 1) is a process that it may be preempted.…”

Section: Introductionmentioning

confidence: 99%

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Strictly periodic first: An optimal variant of LLF for scheduling tasks in a time‐critical cyber‐physical system

Kermia¹

2020

Concurrency and Computation

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Cyber-physical systems (CPSs) include time-critical embedded systems where strict timing constraints are considered. These specific CPSs are dealing with close loop control functions, they are interfacing to sensors and actuators and have to fulfill safety critical real-time constraints. To guarantee the timing correctness, a lot of work introduced the strict-periodicity constraint. The latter is of great importance since it concerns sensors/actuators periodic tasks for which the relevancy of information they use is linked to the accuracy of their repetition. Applied to real-time control systems, the strict-periodicity constraint ensures much more stability and robustness. Therefore, the problem of scheduling real-time strictly periodic tasks has been targeted by several works in the literature but all these works were interested in nonpreemptive systems. In this work, we consider as strictly periodic and nonpreemptive only the sensory subtask and the remaining portion of the task may be preempted. This way, input transaction of every task receives the highest priority when accessing processor resource which enhances system predictability. On the other hand, the preemption allows easing schedulability analysis and, most of the time, it leads to a better processor utilization. The article proposes an optimal such task scheduling algorithm, called SPF for Strictly Periodic First, based on the Least Laxity First (LLF) scheduler and an efficient schedulability analysis. Simulation experiments with randomly generated task sets allowed showing the effectiveness of the proposed approach.

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Section: Schedulability Conditions Evaluationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Strictly periodic first: An optimal variant of LLF for scheduling tasks in a time‐critical cyber‐physical system

Kermia¹

2020

Concurrency and Computation

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“…As periods are strict then

s_{i}^{{T T}_{j}}

, the start‐time of

μ_{i}^{{T T}_{j}}

, is given by

s_{i}^{{T T}_{j}} = s_{i}^{{T T}_{0}} + j \cdot T_{i}^{T T}

where

s_{i}^{{T T}_{0}}

is the start‐time of the first instance of

μ_{i}^{T T}

. More details on strict periodicity may be found in .…”

Section: Model and Problem Formulationmentioning

confidence: 99%

Schedulability analysis and efficient scheduling of rate constrained messages in the TTEthernet protocol

Kermia

2017

Softw Pract Exp

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Over time, cyber-physical systems are becoming mixed criticality systems. As the complexity and the size of these systems grow, computation/communication resources should be more efficient than with traditional systems. TTEthernet is a communication infrastructure that enables the use of a single physical communication infrastructure for distributed mixed criticality applications while providing timely determinism. TTEthernet distinguishes between two traffic categories: the standard event triggered and the time triggered. The latter, for which higher priority is granted, is subject to strong timing guarantees because of strict periodicity constraint that fixes start-time cycles of time-triggered messages. In addition, event-triggered traffic includes rate-constrained messages that are of lower priority and have a minimum time interval between their transmission. The paper proposes both an on-line efficient scheduling algorithm and a necessary and sufficient schedulability condition based on the worst case response time computation for rate-constrained messages while taking into account time-triggered messages transmission.

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“…Moreover, most of works cited before impose their own tasks scheduling, not necessarily, compliant with the one provided by the real-time operating system on which we aim to reduce the synchronization effects. Indeed, any scheduling algorithm applied on a real-time operating system can deal with one or several constraints [9] such temporal constraints, load balancing, , etc., and it is excluded to modify the resulting schedule otherwise constraints will not be met any more.…”

Section: Introductionmentioning

confidence: 99%

“…In a word, it automatically generates synchronized distributed executives from both application and target architecture description models. Some applications running under SynDEx are given in [9].…”

Section: Introductionmentioning

confidence: 99%

An Effective Synchronization Cost Reduction Approach

Kermia¹,

Kechad²

2013

2013 IEEE 10th International Conference on High Performance Computing and Communications &Amp; 2013 IEEE International Conferen

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In the area of distributed embedded systems, the literature includes a considerable number of works on synchronization tools or protocols but little ones on the non less important topic of synchronization cost. Synchronization operations impose temporal order on a software system by forcing some tasks to wait until other tasks complete their computations. However, synchronization costs can negatively affect embedded system performances. This paper proposes an effective approach for minimizing the synchronization cost by eliminating redundant synchronizations and describes tests performed under realistic conditions which have shown significant improvements.

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Optimizing Distributed Real-Time Embedded System Handling Dependence and Several Strict Periodicity Constraints

Cited by 4 publications

References 6 publications

Strictly periodic first: An optimal variant of LLF for scheduling tasks in a time‐critical cyber‐physical system

Strictly periodic first: An optimal variant of LLF for scheduling tasks in a time‐critical cyber‐physical system

Schedulability analysis and efficient scheduling of rate constrained messages in the TTEthernet protocol

An Effective Synchronization Cost Reduction Approach

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