Thèses sur le sujet « REAL-TIME TASKS »
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1
Singh, Abhishek Jeffay Kevin. « Co-scheduling real-time tasks and non real-time tasks using empirical probability distribution of execution time requirements ». Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2009. http://dc.lib.unc.edu/u?/etd,2724.
Texte intégralRésumé :
Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2009.Title from electronic title page (viewed Mar. 10, 2010). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Computer Science." Discipline: Computer Science; Department/School: Computer Science.
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Zhu, Wenjing. « Adaptive threshhold-based scheduling for real-time and non-real-time tasks ». Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/29913.
Texte intégralRésumé :
This thesis documents our study on scheduling mixed real-time and non-real-time tasks with different performance metrics. The work is motivated by the need to provide satisfactory performance trade-offs in a dynamic environment where the arrival rates and proportions of the real-time and non-real-time tasks vary with time. We first examine two threshold-based schemes, Queue Length Threshold and Minimum Laxity Threshold, and propose the corresponding
adaptive schemes based on our results from approximate analysis and simulation. The idea is to improve performance by adjusting trade-off points adaptively as the arrival rates change. We further discuss the idea of integrating the two thresholds. The new algorithm, ADP, is evaluated by simulation under various load conditions and compared with other common
scheduling disciplines as well as an optimal algorithm. Some implementation issues are also discussed. We conclude that by setting appropriate threshold functions in accordance to the requirements of applications, we can achieve satisfactory bounded loss ratio for real-time tasks and acceptably low average delay for non-real-time tasks in a wide range of workload conditions.Science, Faculty of
Computer Science, Department of
Graduate
3
DI, FRISCHIA STEFANO. « Real-Time Algorithms for Spectral Classification Tasks ». Doctoral thesis, Università degli Studi dell'Aquila, 2021. http://hdl.handle.net/11697/177860.
Texte intégralRésumé :
The present PhD thesis covers a research about real-time spectral classification
exploiting machine learning tools and in particular deep learning with neural networks.
Spectroscopy is the study of the interaction between matter and electromagnetic
radiation. In particular, we focused on Raman spectroscopy because it allows a
chemical compound identification that has many fields of application. Our approach
to solve spectral classification is a combination of signal processing methods and
machine learning tools. First, it has been analysed the most important spectrum
feature that could affect classification accuracy: signal-to-noise ratio. Since the
level of noise must be reduced both at acquisition time and at processing time, an
investigation of the noise sources in a CCD device has been carried on in order to
identify the main parameters that concur to generate noise. Once that the best
acquisition strategy has been demonstrated, we focused on a Cultural Heritage case
of study about pigment spectra classification, exploiting machine learning tools
to overcome the problem of a limited reference database. A hierarchical pipeline
of signal processing methods has been designed to implement the necessary Data
Augmentation. In addition, these methods have been enhanced with the use of
Generative Adversarial Networks (GANs). Once that an augmented dataset has
been generated, we tested it on 3 different neural network architectures, finding
that the Convolutional Neural Networks (CNN) with GAN enhancement is the
best approach for classification. The implemented technique of the present thesis is
potentially applicable in every spectroscopic analysis that lacks a sufficient number
of training reference examples.
4
Nemati, Farhang. « Partitioned Scheduling of Real-Time Tasks on Multi-core Platforms ». Licentiate thesis, Mälardalen University, School of Innovation, Design and Engineering, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-9595.
Texte intégralRésumé :
In recent years multiprocessor architectures have become mainstream, and multi-core processors are found in products ranging from small portable cell phones to large computer servers. In parallel, research on real-time systems has mainly focused on traditional single-core processors. Hence, in order for real-time systems to fully leverage on the extra capacity offered by new multi-core processors, new design techniques, scheduling approaches, and real-time analysis methods have to be developed.
In the multi-core and multiprocessor domain there are mainly two scheduling approaches, global and partitioned scheduling. Under global scheduling each task can execute on any processor at any time while under partitioned scheduling tasks are statically allocated to processors and migration of tasks among processors is not allowed. Besides simplicity and efficiency of partitioned scheduling protocols, existing scheduling and synchronization methods developed for single-core processor platforms can more easily be extended to partitioned scheduling. This also simplifies migration of existing systems to multi-cores. An important issue related to partitioned scheduling is distribution of tasks among processors which is a bin-packing problem.
In this thesis we propose a partitioning framework for distributing tasks on the processors of multi-core platforms. Depending on the type of performance we desire to achieve, the framework may distribute a task set differently, e.g., in an application in which tasks process huge amounts of data the goal of the framework may be to decrease cache misses.Furthermore, we propose a blocking-aware partitioning heuristic algorithm to distribute tasks onto the processors of a multi-core architecture. The objective of the proposed algorithm is to decrease blocking overhead of tasks which reduces the total utilization and has the potential to reduce the number of required processors.Finally, we have implemented a tool to facilitate evaluation and comparison of different multiprocessor scheduling and synchronization approaches, as well as different partitioning heuristics. We have applied the tool in the evaluation of several partitioning heuristic algorithms, and the tool is flexible to which any new scheduling or synchronization protocol as well as any new partitioning heuristic can easily be added.
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Chang, Tzu-Chiang. « Static scheduler for hard real-time tasks on multiprocessor systems ». Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/24043.
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Han, Kai. « Scheduling Distributed Real-Time Tasks in Unreliable and Untrustworthy Systems ». Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/26917.
Texte intégralRésumé :
In this dissertation, we consider scheduling distributed soft real-time tasks in unreliable
(e.g., those with arbitrary node and network failures) and untrustworthy systems (e.g., those
with Byzantine node behaviors). We present a distributed real-time scheduling algorithm
called Gamma. Gamma considers a distributed (i.e., multi-node) task model where tasks are
subject to Time/Utility Function (or TUF) end-to-end time constraints, and the scheduling
optimality criterion of maximizing the total accrued utility. The algorithm makes three novel
contributions. First, Gamma uses gossip for reliably propagating task scheduling parameters
and for discovering task execution nodes. Second, Gamma achieves distributed real-time
mutual exclusion in unreliable environments. Third, the algorithm guards against potential
disruption of message propagation due to Byzantine attacks using a mechanism called
Launcher-Attacker-Infective-Susceptible-Immunized-Removed-Consumer (or LAISIRC). By
doing so, the algorithm schedules tasks with probabilistic termination-time satisfactions,
despite system unreliability and untrustworthiness.
We analytically establish several timeliness and non-timeliness properties of the algorithm
including probabilistic end-to-end task termination time satisfactions, optimality
of message overheads, mutual exclusion guarantees, and the mathematical model of the
LAISIRC mechanism. We conducted simulation-based experimental studies and compared
Gamma with its competitors. Our experimental studies reveal that Gammaâ s scheduling algorithm
accrues greater utility and satisfies a greater number of deadlines than do competitor
algorithms (e.g., HVDF) by as much as 47% and 45%, respectively. LAISIRC is more tolerant
to Byzantine attacks than competitor protocols (e.g., Path Verification) by obtaining as much as 28% higher correctness ratio. Gammaâ s mutual exclusion algorithm accrues greater
utility than do competitor algorithms (e.g., EDF-Sigma) by as much as 25%. Further, we
implemented the basic Gamma algorithm in the Emulab/ChronOS 250-node testbed, and
measured the algorithmâ s performance. Our implementation measurements validate our
theoretical analysis and the algorithm's effectiveness and robustness.Ph. D.
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Qamhieh, Manar. « Scheduling of parallel real-time DAG tasks on multiprocessor systems ». Thesis, Paris Est, 2015. http://www.theses.fr/2015PEST1030/document.
Texte intégralRésumé :
Les applications temps réel durs sont celles qui doivent exécuter en respectant des contraintes temporelles. L'ordonnancement temps réel a bien été étudié sur mono-processeurs depuis plusieurs années. Récemment, l'utilisation d'architectures multiprocesseurs a augmenté dans les applications industrielles et des architectures parallèles sont proposées pour que le logiciel devienne compatible avec ces plateformes. L'ordonnancement multiprocesseurs de tâches parallèles dépendantes n'est pas une simple généralisation du cas mono-processeur et la problématique d'ordonnancement devient plus complexe et difficile. Dans cette thèse, nous étudions le problème d'ordonnancement temps réel de graphes de tâches parallèles acycliques sur des plateformes multiprocesseurs. Dans ce modèle, un graphe est composé d'un ensemble de sous-tâches dépendantes sous contraintes de précédence qui expriment les relations de précédences entre les sous-tâches. L'ordre d'exécution des sous-tâches est dynamique, c'est-à-dire que les sous-tâches peuvent s'exécuter en parallèle ou séquentiellement par rapport aux décisions de l'ordonnanceur temps réel. Pour traiter les contraintes de précédence, nous proposons deux méthodes pour l'ordonnancement des graphes : par transformation du modèle de graphe de sous tâches parallèles en un modèle de tâches séquentielles indépendantes, plus simple à ordonnancer et par ordonnancement direct des graphes en prenant en compte les relations de dépendance entre les sous-tâches. Nous proposons un ordonnancement des graphes en prenant directement en compte les paramètres temporels des graphes et un ordonnancement au niveau des sous-tâches, par rapport à des paramètres temporels attribués aux sous-tâches par un algorithme spécifique. Enfin, nous prouvons que les deux méthodes d'ordonnancement de graphes ne sont pas comparables. Nous fournissons alors des résultats de simulation pour comparer ces méthodes en utilisant les algorithmes d'ordonnancement globaux EDF et DM. Nous avons développé un logiciel nommé YARTISS pour générer des graphes aléatoires et réaliser les simulationsThe interest for multiprocessor systems has recently been increased in industrial applications, and parallel programming API's have been introduced to benefit from new processing capabilities. The use of multiprocessors for real-time systems, whose execution is performed based on certain temporal constraints is now investigated by the industry. Real-time scheduling problem becomes more complex and challenging in that context. In multiprocessor systems, a hard real-time scheduler is responsible for allocating ready jobs to available processors of the systems while respecting their timing parameters. In this thesis, we study the problem of real-time scheduling of parallel Directed Acyclic Graph (DAG) tasks on homogeneous multiprocessor systems. In this model, a DAG task consists of a set of subtasks that execute under precedence constraints. At all times, the real-time scheduler is responsible for determining how subtasks execute, either sequentially or in parallel, based on the available processors of the system. We propose two DAG scheduling approaches to determine the execution form of DAG tasks. The first approach is the DAG Stretching algorithm, from the Model Transformation approach, which forces DAG tasks to execute as sequentially as possible. The second approach is the Direct Scheduling, which aims at scheduling DAG tasks while respecting their internal dependencies. We provide real-time schedulability analyses for Direct Scheduling at DAG-Level and at Subtask-Level. Due to the incomparability of DAG scheduling approaches, we use extensive simulations to compare performance of global EDF with global DM scheduling using our simulation tool YARTISS
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Haugli, Fredrik Bakkevig. « Using online worst-case execution time analysis and alternative tasks in real time systems ». Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for teknisk kybernetikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-26100.
Texte intégralRésumé :
As embedded hardware becomes more powerful, it allows for more complex realtime systems running tasks with highly dynamic execution times. This dynamicitymakes the already formidable task of producing accurate WCET analysis evenmore di?cult. Since the variation in execution time depends on task input andthe state of the system, it is postulated that a more accurate estimate for theWCET can be found online with knowledge about the task parameters.This thesis will explore the concept of online execution time analysis and itspotential utilization. Line detection in images through Hough line transform isfound to be a relevant application whose execution time can be estimated bythe contrast of the input image. A system for scheduling tasks utilizing theironline WCET estimate is then discussed. It dynamically checks for potentialdeadline misses and degrades tasks, either by running a more e?cient alternativetask instead or by aborting the task, until timely execution is guaranteed. Anexperiment is presented, demonstrating a higher throughput of tasks with onlineWCET estimation. Finally, the work on a framework for more precise simulationsand experiments is presented.
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Huang, Chiao Ching Baskiyar Sanjeev. « Minimum power consumption for rate monotonic tasks ». Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/FALL/Computer_Science_and_Software_Engineering/Thesis/Huang_Chiao_10.pdf.
Texte intégral
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Rafiq, Salman. « Measuring Performance of Soft Real-Time Tasks on Multi-core Systems ». Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-37219.
Texte intégralRésumé :
Multi-core platforms are well established, and they are slowly moving into the area of embedded and real-time systems. Nowadays to take advantage of multi-core systems in terms of throughput, soft real-time applications are run together with general purpose applications under an operating system such as Linux. But due to shared hardware resources in multi-core architectures, it is likely that these applications will interfere and compete with each other. This can cause slower response times for soft real-time tasks. In order to investigate this problem, a number of memory intensive and computation intensive soft real-time tasks were co-scheduled with Linux SMP running a general purpose task on it. For performance measurement a test environment is created that uses hardware registers to count core, level-2 cache and memory bus events at run-time instead of having a simulator tool. In particular events related to L1 and L2 instruction and data cache, memory bus utilization and difference in response times of soft real-time tasks are measured. After completing this research, we can say that it is only possible for soft real-time applications to co-exist with Linux SMP cores running general purpose applications without major performance degradation, if the task on Linux is not much memory intensive. If it is memory intensive then there is a trade-off between number of cores running general purpose applications and the amount of tolerance an embedded system can have in response times.
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Liberg, Tim, et Per-Erik Måhl. « GPU-accelerated Model Checking of Periodic Self-Suspending Real-Time Tasks ». Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-14661.
Texte intégralRésumé :
Efficient model checking is important in order to make this type of software verification useful for systems that are complex in their structure. If a system is too large or complex then model checking does not simply scale, i.e., it could take too much time to verify the system. This is one strong argument for focusing on making model checking faster. Another interesting aim is to make model checking so fast that it can be used for predicting scheduling decisions for real-time schedulers at runtime. This of course requires the model checking to complete within a order of milliseconds or even microseconds. The aim is set very high but the results of this thesis will at least give a hint on whether this seems possible or not. The magic card for (maybe) making this possible is called Graphics Processing Unit (GPU). This thesis will investigate if and how a model checking algorithm can be ported and executed on a GPU. Modern GPU architectures offers a high degree of processing power since they are equipped with up to 1000 (NVIDIA GTX 590) or 3000 (NVIDIA Tesla K10) processor cores. The drawback is that they offer poor thread-communication possibilities and memory caches compared to CPU. This makes it very difficult to port CPU programs to GPUs.The example model (system) used in this thesis represents a real-time task scheduler that can schedule up to three periodic self-suspending tasks. The aim is to verify, i.e., find a feasible schedule for these tasks, and do it as fast as possible with the help of the GPU.
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Nie, Yonggao. « Limited-preemptive fixed priority scheduling of real-time tasks on multiprocessors ». Thesis, Mälardalens högskola, Inbyggda system, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-28265.
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AULUCK, NITIN. « REAL-TIME SCHEDULING ALGORITHMS FOR PRECEDENCE RELATED TASKS ON HETEROGENEOUS MULTIPROCESSORS ». University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1109288052.
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Katre, Kedar Maheshwar. « Policies for Migration of Real-Time tasks in Embedded Multicore Systems ». OpenSIUC, 2010. https://opensiuc.lib.siu.edu/theses/264.
Texte intégralRésumé :
There has been a lot of work that has been done on timing predictability of real-time tasks on embedded systems. The main assumption in these studies has been that the timing behavior has been based on single processor systems. The scenario has changed entirely when the single core systems have been replaced with the new Multicore systems. The timing predictability is controlled by the migrating tasks, the network topology connecting the cores and the number of cores on the system. In this thesis we come up with a feasibility analysis which depends on the characteristics of the tasks viz. number of cache lines, time of migration, available bandwith, number of tasks etc. We also test this analysis on novel mechanisms of migration which have been proposed recently and present its results.
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Motakpalli, Sankalpanand. « Aperiodic Job Handling in Cache-Based Real-Time Systems ». OpenSIUC, 2017. https://opensiuc.lib.siu.edu/dissertations/1474.
Texte intégralRésumé :
Real-time systems require a-priori temporal guarantees. While most of the normal operation in such a system is modeled using time-driven, hard-deadline sporadic tasks, event-driven behavior is modeled using aperiodic jobs with soft or no deadlines. To provide good Quality-of- Service for aperiodic jobs in the presence of sporadic tasks, aperiodic servers were introduced. Aperiodic servers act as a sporadic task and reserve a quota periodically to serve aperiodic jobs. The use of aperiodic servers in systems with caches is unsafe because aperiodic servers do not take into account, the indirect cache-related preemption delays that the execution of aperiodic jobs might impose on the lower-priority sporadic tasks, thus jeopardizing their safety. To solve this problem, we propose an enhancement to the aperiodic server that we call a Cache Delay Server. Here, each lower-priority sporadic task is assigned a delay quota to accommodate the cache-related preemption delay imposed by the execution of aperiodic jobs. Aperiodic jobs are allowed to execute at their assigned server priority only when all the active lower-priority sporadic tasks have a sufficient delay quota to accommodate it. Simulation results demonstrate that a Cache Delay Server ensures the safety of sporadic tasks while providing acceptable Quality-of-Service for aperiodic jobs. We propose a Integer Linear Program based approach to calculate delay quotas for sporadic tasks within a task set where Cache Delay Servers have been pre-assigned. We then propose algorithms to determine Cache Delay Server characteristics for a given sporadic task set. Finally, we extend the Cache Delay Server concept to multi-core architectures and propose approaches to schedule aperiodic jobs on appropriate Cache Delay Servers. Simulation results demonstrate the effectiveness of all our proposed algorithms in improving aperiodic job response times while maintaining the safety of sporadic task execution.
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Zhu, Kaiqian. « Limited Preemptive Earliest Deadline First Scheduling of Real-Time Tasks on Multiprocessors ». Thesis, Mälardalens högskola, Inbyggda system, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-28252.
Texte intégralRésumé :
Real-time systems are employed in many areas, such as aerospace and defenses. In real-time systems, especially in hard real-time systems, it is important to meet the associated time requirements. With the increasing demand for high speed processing capabilities, the requirement for high computing power is becoming more and more urgent. However, it is no longer possible to increase processor speeds because of thermal and power constraints. Consequently, industry has focused on providing more computing capabilities using more number of processors.As to the scheduling policies, they can be classified into two categories, preemptive and non-preemptive. Preemptive scheduling allows preemptions arbitrarily, whereas it implies prohibitively high preemption related overheads. On the contrary, the non-preemptive scheduling which do not allow preemption at all, will not have such overheads, but suffers due to the block time on high priority tasks. Limited preemptive scheduling, that builds on the best of preemptive and non-preemptive scheduling, benefits from the limited number of preemptions without a major effect on real-time properties. It is proved that limited preemptive scheduling dominates preemptive and non-preemptive scheduling on uniprocessors under fixed priority. However, less work has been done on multiprocessor limited preemptive scheduling, especially under Earliest Deadline First (EDF). On a multiprocessor, limited preemptively scheduling real-time tasks imply an additional challenge with respect to determining which of the running task to preempt. On one extreme, the scheduler can preempt the lowest priority running task and this is referred to as Adaptive Deferred Scheduling (ADS). On the other hand, the scheduler can preempt any lower priority running task that becomes pre-emptible. Such a scheduler is referred to as Regular Deferred Scheduling (RDS)In this work, we empirically investigate the performance of ADS and RDS, and compare it with the global preemptive and non-preemptive scheduling, in the context of an EDF based scheduler. Our empirical investigation revealed that the number of preemptions under ADS is less compared to RDS, at runtime. This is due to the fact that by delaying preemptions, the higher priority tasks that are released subsequently will run in priority order thereby avoiding the need for more preemptions. Also, by delaying preemptions, the possibility of one or more processors becoming available increases. Experiments investigating the schedulability ratio shows that ADS and RDS performs almost equally well, but better than fully non-preemptive scheduling.
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Zahaf, Houssam-Eddine. « Energy efficient scheduling of parallel real-time tasks on heterogeneous multicore systems ». Thesis, Lille 1, 2016. http://www.theses.fr/2016LIL10100/document.
Texte intégralRésumé :
Les systèmes cyber-physiques (CPS) et d’Internet des objets génèrent un volume et une variété des données sans précédant. Le temps que ces données parcourent le réseau dans son chemin vers le cloud, la possibilité de réagir à un événement critique pourrait être tardive. Pour résoudre ce problème, les traitements de données nécessitant une réponse rapide sont faits à proximité d’où les données sont collectées. Ainsi, seuls les résultats du pré-traitement sont envoyées au cloud et la réaction pourrai être déclenché suffisamment rapide pour préserver l’intégrité du système. Ce modèle de calcul est connu comme Fog Computing. Un large spectre d’applications de CPS ont des contraintes temporelle et peuvent être facilement parallélisées en distribuant les calculs sur différents sous-ensembles de données en même temps. Ceci peut permettre d’obtenir un temps de réponse plus court et un temps de creux plus large. Ainsi, on peut réduire la fréquence du processeur et/ou éteindre des parties du processeur afin de réduire la consommation d’énergie. Dans cette thèse, nous nous concentrons sur le problème d'ordonnancement d’un ensemble de taches temps-réels parallèles sur des architectures multi-coeurs dans l’objectif de réduire la consommation d’énergie en respectant toutes les contraintes temporelles. Nous proposons ainsi plusieurs modèles de tâches et des testes d'ordonnançabilité pour résoudre le problème d’allocation des threads aux processeurs. Nous proposons aussi des méthodes qui permettent de sélectionner les fréquences et les états des processeurs. Les modèles proposés peuvent être implantés comme des directives dans la même logique que OpenMPCyber physical systems (CPS) and Internet of Objects (IoT) are generating an unprecedented volume and variety of data that needs to be collected and stored on the cloud before being processed. By the time the data makes its way to the cloud for analysis, the opportunity to trigger a reply might be late. One approach to solve this problem is to analyze the most time-sensitive data at the network edge, close to where it is generated. Thus, only the pre-processed results are sent to the cloud. This computation model is know as *Fog Computing* or *Edge computing*. Critical CPS applications using the fog computing model may have real-time constraints because results must be delivered in a pre-determined time window. Furthermore, in many relevant applications of CPS, the processing can be parallelized by applying the same processing on different sub-sets of data at the same time by the mean parallel programming techniques. This allow to achieve a shorter response time, and then, a larger slack time, which can be used to reduce energy consumption. In this thesis we focus on the problem of scheduling a set of parallel tasks on multicore processors, with the goal of reducing the energy consumption while all deadlines are met. We propose several realistic task models on architectures with identical and heterogeneous cores, and we develop algorithms for allocating threads to processors, select the core frequencies, and perform schedulability analysis. The proposed task models can be realized by using OpenMP-like APIs
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Gaid, MEMB, AS Cela et Y. Hamam. « Optimal Real-Time Scheduling of Control Tasks with State Feedback Resource Allocation ». IEEE Transactions on Control Systems Technology, 2009. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1001370.
Texte intégralRésumé :
Abstract—This paper proposes a new approach for the optimal
integrated control and real-time scheduling of control tasks.
First, the problem of the optimal integrated control and nonpreemptive
off-line scheduling of control tasks in the sense of
the H2 performance criterion is addressed. It is shown that this
problem may be decomposed into two sub-problems. The first
sub-problem aims at finding the optimal non-preemptive off-line
schedule, and may be solved using the branch and bound method.
The second sub-problem uses the lifting technique to determine
the optimal control gains, based on the solution of the first
sub-problem. Second, an efficient on-line scheduling algorithm
is proposed. This algorithm, called Reactive Pointer Placement
(RPP) scheduling algorithm, uses the plant state information to
dispatch the computational resources in a way that improves
control performance. Control performance improvements as well
as stability guarantees are formally proven. Finally, simulations
as well as experimental results are presented in order to illustrate
the effectiveness of the proposed approach.
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Zuhily, Areej. « Scheduling analysis of fixed priority hard real-time systems with multiframe tasks ». Thesis, University of York, 2009. http://etheses.whiterose.ac.uk/11090/.
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Babbar, Davender. « On-line hard real-time scheduling of parallel tasks on partitionable multiprocessors / ». The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487858417983777.
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Craig, David W. (David William) Carleton University Dissertation Engineering Electrical. « Light traffic loss of random hard real-time tasks in a network ». Ottawa, 1988.
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Lennvall, Tomas. « Handling aperiodic tasks and overload in distributed off-line scheduled real-time systems / ». Västerås : Mälardalen University, 2003. http://www.mrtc.mdh.se/publications/0541.pdf.
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Devarasetty, Ravi Kiran. « Heuristic Algorithms for Adaptive Resource Management of Periodic Tasks in Soft Real-Time Distributed Systems ». Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/31219.
Texte intégralRésumé :
Dynamic real-time distributed systems are characterized by significant run-time uncertainties at the mission and system levels. Typically, processing and communication latencies in such systems do not have known upper bounds and event and task arrivals and failure occurrences are non-deterministically distributed. This thesis proposes adaptive resource management heuristic techniques for periodic tasks in dynamic real-time distributed systems with the (soft real-time) objective of minimizing missed deadline ratios. The proposed resource management techniques continuously monitor the application tasks at run-time for adherence to the desired real-time requirements, detects timing failures or trends for impending failures (due to workload fluctuations), and dynamically allocate resources by replicating subtasks of application tasks for load sharing. We present "predictive" resource allocation algorithms that determine the number of subtask replicas that are required for adapting the application to a given
workload situation using statistical regression theory. The algorithms use regression equations that forecast subtask timeliness as a function of external load parameters such as number of sensor reports and internal resource load parameters such as CPU utilization. The regression equations are determined off-line and on-line from application profiles that are collected off-line and on-line, respectively. To evaluate the performance of the predictive algorithms, we consider algorithms that determine the number of subtask replicas using empirically determined functions. The empirical functions compute the number of replicas as a function of the rate of change in the application workload during a "window" of past task periods. We implemented the resource management algorithms as part of a middleware infrastructure and measured the performance of the algorithms using a real-time benchmark. The experimental results indicate that the predictive, regression theory-based algorithms generally produce lower missed
deadline ratios than the empirical strategies under the workload conditions that were studied.Master of Science
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Satka, Zenepe, et Hena Hodžić. « Minimizing the unpredictability that real-time tasks suffer due to inter-core cache interference ». Thesis, Mälardalens högskola, Inbyggda system, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-48542.
Texte intégralRésumé :
Since different companies are introducing new capabilities and features on their products, the demand for computing power and performance in real-time systems is increasing. To achieve higher performance, processor's manufactures have introduced multi-core platforms. These platforms provide the possibility of executing different tasks in parallel on multiple cores. Since tasks share the same cache level, they face some interference that affects their timing predictability. This thesis is divided into two parts. The first part presents a survey on the existing solutions that others have introduced to solve the problem of cache interference that tasks face on multi-core platforms. The second part's focus is on one of the hardware-based techniques introduced by Intel Cooperation to achieve timing predictability of real-time tasks. This technique is called Cache Allocation Technology (CAT) and the main idea of it is to divide last level cache on some partitions called classes of services that will be reserved to specific cores. Since tasks of one core can only access the assigned partition of it, cache interference will be decreased and a better real-time tasks' performance will be achieved. In the end to evaluate CAT efficiency an experiment is conducted with different test cases and the obtained results show a significant difference on real-time tasks' performance when CAT is applied.
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Courbin, Pierre. « Scheduling sequential or parallel hard real-time pre-emptive tasks upon identical multiprocessor platforms ». Thesis, Paris Est, 2013. http://www.theses.fr/2013PEST1081/document.
Texte intégralRésumé :
L'ordonnancement de tâches sur un système temps réel dur correspond à trouver une façon de choisir, à chaque instant, quelle tâche doit être exécutée sur le processeur pour que chacune ait le temps de terminer son travail avant son échéance. Ce problème, dans le contexte monoprocesseur, est déjà bien étudié et permet des applications sur des systèmes en production (aérospatiale, bourse etc.). Aujourd'hui, les plateformes multiprocesseur se sont généralisées et ont amené de nombreuses questions telles que l'utilisation efficace de tous les processeurs. Dans cette thèse, nous explorons les approches existantes pour résoudre ce problème. Nous étudions tout d'abord l'approche par partitionnement qui consiste à utiliser les recherches existantes en ramenant ce problème à plusieurs systèmes monoprocesseur. Ici, nous proposons un algorithme générique dont les paramètres sont adaptables en fonction de l'objectif à atteindre. Nous étudions ensuite l'approche par semi-partitionnement qui permet la migration d'un nombre restreint de tâches. Nous proposons une solution avec des migrations restreintes qui pourrait être assez simplement implémentée sur des systèmes concrets. Nous proposons ensuite une solution avec des migrations non restreintes qui offre de meilleurs résultats mais est plus difficile à implémenter. Enfin, les programmeurs utilisent de plus en plus le concept de tâches parallèles qui peuvent utiliser plusieurs processeurs en même temps. Ces tâches sont encore peu étudiées et nous proposons donc un nouveau modèle pour les représenter. Nous étudions les ordonnanceurs possibles et nous définissons une façon de garantir l'ordonnançabilité de ces tâches pour deux d'entre euxThe scheduling of tasks on a hard real-time system consists in finding a way to choose, at each time instant, which task should be executed on the processor so that each succeed to complete its work before its deadline. In the uniprocessor case, this problem is already well studied and enables us to do practical applications on real systems (aerospace, stock exchange etc.). Today, multiprocessor platforms are widespread and led to many issues such as the effective use of all processors. In this thesis, we explore the existing approaches to solve this problem. We first study the partitioning approach that reduces this problem to several uniprocessor systems and leverage existing research. For this one, we propose a generic partitioning algorithm whose parameters can be adapted according to different goals. We then study the semi-partitioning approach that allows migrations for a limited number of tasks. We propose a solution with restricted migration that could be implemented rather simply on real systems. We then propose a solution with unrestricted migration which provides better results but is more difficult to implement. Finally, programmers use more and more the concept of parallel tasks that can use multiple processors simultaneously. These tasks are still little studied and we propose a new model to represent them. We study the possible schedulers and define a way to ensure the schedulability of such tasks for two of them
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Varghese, B., M. Alamgir Hossain et Keshav P. Dahal. « Scheduling of tasks in multiprocessor system using hybrid genetic algorithms ». Springer Verlag, 2007. http://hdl.handle.net/10454/2552.
Texte intégralRésumé :
This paper presents an investigation into the optimal scheduling of realtime
tasks of a multiprocessor system using hybrid genetic algorithms (GAs). A comparative
study of heuristic approaches such as `Earliest Deadline First (EDF)¿ and
`Shortest Computation Time First (SCTF)¿ and genetic algorithm is explored and
demonstrated. The results of the simulation study using MATLAB is presented and
discussed. Finally, conclusions are drawn from the results obtained that genetic algorithm
can be used for scheduling of real-time tasks to meet deadlines, in turn to obtain
high processor utilization.
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Valentin, Eduardo Bezerra, et 92-36710870. « Scheduling hard real-time tasks in heterogeneous multiprocessor platforms subject to energy and temperature constraints ». Universidade Federal do Amazonas, 2017. http://tede.ufam.edu.br/handle/tede/6148.
Texte intégralRésumé :
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The power wall is a barrier to improvement in the processor design process due to the power consumption of components. The production of energy optimum systems demands knowledge of different disciplines. The usage of heterogeneous multicore platforms is appealing for recent applications, e.g., hard real-time systems. The motivation is the potential reduced energy consumption offered by such platforms. Hard real-time systems are present in life critical environments. Reducing the energy consumption on such systems is an onerous process. Scheduling becomes particularly challenging to improve system utilization and minimize system energy consumption and peak temperature on such platforms, specially subject to hard real-time constraints. Therefore, we propose a study to effectively answer the pertinent research question: “How to offer users timing correctness and guarantees of hard real-time systems executed on heterogeneous multicore systems with energy and temperature constraints?”. Finding optimal solutions for such question has still several open research questions. The main aim of this thesis is to propose an energy optimization method for hard realtime system on heterogeneous multicore platform demonstrating that it is possible to timely compute timing correctness and guarantees using a sufficient and necessary condition; accounting for energy, temperature, preemption, precedence, shared resources constraints, and architectural interference. The proposal is a two fold approach. First, we investigate the process of finding the optimal task to core and frequency to task processes by means of applying exact schedulability tests for heterogeneous multicore platforms. Second, the outcome of the optimization analysis shall be used as reference to the on-line scheduler. We believe that we have achieved the main objective of this research by combining: (a) schedulability analysis from hard real-time systems, (b) representative mathematical formulations, based on integer linear programming, covering modern processors technological characteristics and using a classical combinatorial mathematical formulation (Multilevel Generalized Assignment Problem), and (c) robust exact implicit enumeration algorithmic strategies from combinatorial optimization, such as branch-and-cut and branch-and-price. The systematic literature review in the research subject reveals that the field has open questions to be answered. For instance, to the knowledge of the author only five works in the state-of-the-art literature deal with the problem by providing optimal solutions. Typically, the existing approaches focus on either heuristics or approximation algorithms. Also, only one work has a proposal to evaluate the schedulability in this scenario with an exact test. The typical formulation in the specialized literature is a 0/1 integer linear programming model which considers a continuous processor frequency domain and determines a single operating frequency per processor. One of the hypotheses tested in this research is: stronger feasibility analysis offers tighter bounds for the problem. We believe that this can be observed, for example, in the results produced by solvers for fixed priority schedulers, by means of an analysis based on a comparative study. By applying less accurate schedulability tests, such as utilization based, the solvers take longer to converge to optimal solutions, when compared to solvers that apply exact schedulability tests based on response time analysis. Another hypothesis tested in this research is: practical instances of the problem are timely solvable to optimal. We have experimented, by means of a comparative study, on finding feasible solutions for workload for fixed priority schedulers with up to 50 tasks distributed on four processors with seven different available frequencies. On independent hard real-time tasks scheduled using EDF policy, we found optimal distribution of up to 90 tasks on four processors with seven different available frequencies. In both cases, the solutions were found within 30 min of execution time. Similarly, on dependent tasks workload, we have optimally distributed 22 tasks, from an automotive control hard real-time application, on four processors with seven different available frequencies, with two shared resources and 23 precedence constraints within 1.5 h. We consider a few hours in the design phase a price worth paying in this context.
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Stanhope, Austin. « A control architecture for dynamic execution of robot tasks trained in real-time using particle filters ». abstract and full text PDF (UNR users only), 2009. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1472980.
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Belaid, Ikbel. « On line-off line placement and scheduling of real time hardware tasks on dynamically reconfigurable platforms ». Nice, 2011. http://www.theses.fr/2011NICE4019.
Texte intégralRésumé :
Le placement et l’ordonnancement des tâches matérielles sont les éléments clés du système d’exploitation temps réel. Ces deux problèmes doivent être traités efficacement afin d’améliorer la qualité du placement exprimée par le taux de fragmentation de ressources et la latence de reconfiguration, et la qualité d’ordonnancement représentée par la durée d’exécution de l’application et la garantie des échéances. En utilisant les systèmes sur puce programmable, nous proposons d’exploiter les caractéristiques physiques de ces puces, en particulier la reconfiguration partielle dynamique. Nous traitons, dans premier temps, les tâches indépendantes. Nous suggérons une résolution analytique par des solveurs de programmation en nombres entiers mixtes qui se basent sur la méthode de séparation et évaluation pour réaliser le placement hors-ligne de ces tâches sur puce. La métaheuristique des abeilles est aussi proposer pour traiter ce problème. Nous proposons d’employer l’algorithme « Earliest deadline first » pour construire l’ordonnancement temps réel en ligne. Nous nous intéressons ensuite aux tâches dépendantes. En se basant également sur la programmation en nombres entiers mixtes, le placement et l’ordonnancement statiques des tâches matérielles périodiques, constituant un graphe acyclique orienté, sont élaborés. Quatre approches dynamiques sont proposées pour effectuer le placement et l’ordonnancement dynamique de plusieurs graphes sur différentes puces. Par les techniques de réutilisation et de prédiction, ces approches visent la réduction des temps d’exécution des graphes, la garantie des échéances et l’efficacité des ressourcesThe placement and scheduling of hardware tasks are the cores of the real-time operating system. Both problems must be solved efficiently to enhance the placement quality expressed by the rate of resource fragmentation and configuration overhead, and to improve the scheduling quality represented by the temporal spanning of the application and the guarantee of real-time constraints. In the context of the mixed architectures such as System on Programmable Chip (SoPC), we suggest exploiting the physical features of these architectures especially the partial run-time reconfiguration. The first part of the thesis deals with preemptive independents tasks. It suggests analytic resolution by means of mixed integer programming solver using the Branch and Bound method to achieve off-line placement of these tasks on a SoPC. The Bees metaheuristic is also proposed to handle this problem and we suggest employing dynamically the Earliest Deadline First algorithm to perform the real-time scheduling. The second part of the thesis focuses on dependent tasks where each one runs after the completion of all its proposed to resolve statically the placement and scheduling of periodic hardware tasks in a sole directed acyclic graph (DAG) on a SoPC. . Four dynamic approaches are also proposed to place and schedule dynamically multiple DAGs with unknown behavior on several SoPCs. Basing on prefetch and reuse techniques, these approaches aim to reduce the temporal spanning of DAGs, and to improve the guarantee of real-time constraints and resource efficiency
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Rajnoha, Peter. « Analýza jader real-time operačních systémů běžících na platformě FITkit ». Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2009. http://www.nusl.cz/ntk/nusl-236754.
Texte intégralRésumé :
The project is dedicated to the identification of the problems found while building RT operating systems for use in embedded devices. The project's main topic is the possibility of using RT system in the FITkit platform and it also discusses individual problems and their possible solutions. One of the problems is the way of acquiring the timing information for tasks to ensure their RT properties. We have extended existing simulator for given microcontroller that is also part of the FITkit. The simulator can be used for detailed monitoring of the execution of individual tasks in the system based on dynamic analysis, collecting timing statistics for given blocks of the program or it can be extended by new modules. The RM scheduling mechanism has been integrated into the FreeRTOS system as an example by considering the knowledge of the concrete operating system and acquired timing information.
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Poluri, Kaushik. « Bounding the Worst-Case Response Times of Hard-Real-Time Tasks under the Priority Ceiling Protocol in Cache-Based Architectures ». OpenSIUC, 2013. https://opensiuc.lib.siu.edu/theses/1213.
Texte intégralRésumé :
AN ABSTRACT OF THE THESIS OF KAUSHIK POLURI, for the Master of Science degree in Electrical and Computer Engineering, presented on 07/03/2013, at Southern Illinois University Carbondale. TITLE: Bounding the Worst-Case Response Times of Hard-Real-Time Tasks under the Priority Ceiling Protocol in Cache-Based Architectures MAJOR PROFESSOR: Dr. HARINI RAMAPRASAD Schedulability analysis of hard-real-time systems requires a-priori knowledge of the worst-case execution times (WCET) of all tasks. Static timing analysis is a safe technique used for calculating WCET that attempts to model program complexity, architectural complexity and complexity introduced by interference from other tasks. Modern architectural features such as caches make static timing analysis of a single task challenging due to unpredictability introduced by their reliance on the history of memory accesses and the analysis of a set of tasks even more challenging due to cache-related interference among tasks. Researchers have proposed several static timing analysis techniques that explicitly consider cache-eviction delays for independent hard-real-time tasks executing on cache-based architectures. However, there is little research in this area for resource-sharing tasks. Recently, an analysis technique was proposed for systems using the Priority Inheritance Protocol (PIP) to manage resource-arbitration among tasks. The Priority Ceiling Protocol (PCP) is a resource-arbitration protocol that offers distinct advantages over the PIP, including deadlock avoidance. However, to the best of our knowledge, there is currently no technique to bound the WCET of resource-sharing tasks under PCP with explicit consideration of cache-eviction delays. This thesis presents a technique to bound the WCETs and hence, the Worst-Case Response Times (WCRTs) of resource-sharing hard-real-time tasks executing on cache-based uniprocessor systems, specifically focusing on data cache analysis.
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Calafiore, Andrea. « Studio e sviluppo di un'infrastruttura di supporto alla schedulazione di hard/soft real-time tasks in ambiente QNX ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8312/.
Texte intégralRésumé :
La tesi tratta lo studio del sistema QNX e dello sviluppo di un simulatore di task hard/soft real-time, tramite uso di un meta-scheduler. Al termine dello sviluppo vengono valutate le prestazioni del sistema operativo QNX Neutrino.
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Nelissen, Geoffrey. « Efficient optimal multiprocessor scheduling algorithms for real-time systems ». Doctoral thesis, Universite Libre de Bruxelles, 2013. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209528.
Texte intégralRésumé :
Real-time systems are composed of a set of tasks that must respect some deadlines. We find them in applications as diversified as the telecommunications, medical devices, cars, planes, satellites, military applications, etc. Missing deadlines in a real-time system may cause various results such as a diminution of the quality of service provided by the system, the complete stop of the application or even the death of people. Being able to prove the correct operation of such systems is therefore primordial. This is the goal of the real-time scheduling theory.These last years, we have witnessed a paradigm shift in the computing platform architectures. Uniprocessor platforms have given place to multiprocessor architectures. While the real-time scheduling theory can be considered as being mature for uniprocessor systems, it is still an evolving research field for multiprocessor architectures. One of the main difficulties with multiprocessor platforms, is to provide an optimal scheduling algorithm (i.e. scheduling algorithm that constructs a schedule respecting all the task deadlines for any task set for which a solution exists). Although optimal multiprocessor real-time scheduling algorithms exist, they usually cause an excessive number of task preemptions and migrations during the schedule. These preemptions and migrations cause overheads that must be added to the task execution times. Therefore, task sets that would have been schedulable if preemptions and migrations had no cost, become unschedulable in practice. An efficient scheduling algorithm is therefore an algorithm that either minimize the number of preemptions and migrations, or reduce their cost.
In this dissertation, we expose the following results:
- We show that reducing the "fairness" in the schedule, advantageously impacts the number of preemptions and migrations. Hence, all the scheduling algorithms that will be proposed in this thesis, tend to reduce or even suppress the fairness in the computed schedule.
- We propose three new online scheduling algorithms. One of them --- namely, BF2 --- is optimal for the scheduling of sporadic tasks in discrete-time environments, and reduces the number of task preemptions and migrations in comparison with the state-of-the-art in discrete-time systems. The second one is optimal for the scheduling of periodic tasks in a continuous-time environment. Because this second algorithm is based on a semi-partitioned scheme, it should favorably impact the preemption overheads. The third algorithm --- named U-EDF --- is optimal for the scheduling of sporadic and dynamic task sets in a continuous-time environment. It is the first real-time scheduling algorithm which is not based on the notion of "fairness" and nevertheless remains optimal for the scheduling of sporadic (and dynamic) systems. This important result was achieved by extending the uniprocessor algorithm EDF to the multiprocessor scheduling problem.
- Because the coding techniques are also evolving as the degree of parallelism increases in computing platforms, we provide solutions enabling the scheduling of parallel tasks with the currently existing scheduling algorithms, which were initially designed for the scheduling of sequential independent tasks.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
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RAMACHANDRAN, GOWRI SANKAR. « Integration of enhanced slot-shifting in uc/os-II ». Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-12981.
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Müller, Dirk, et Matthias Werner. « Improved Heuristics for Partitioned Multiprocessor Scheduling Based on Rate-Monotonic Small-Tasks ». Universitätsbibliothek Chemnitz, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-80762.
Texte intégralRésumé :
Partitioned preemptive EDF scheduling is very similar to bin packing, but there is a subtle difference. Estimating the probability of schedulability under a given total utilization has been studied empirically before. Here, we show an approach for closed-form formulae for the problem, starting with n = 3 tasks on m = 2 processors.
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Krappman, Alfred. « Identifying and alleviating shared cache contention : Achieving reliability of real-time tasks on a multi-OS and multi-core system ». Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-207857.
Texte intégralRésumé :
Current architecture trends results in processors being equipped with more cores and larger shared caches. Concurrent applications on multicore processors may interfere with each other when accessing shared resources. This is especially troublesome if deadline-bound real-time tasks are running. A tool illustrating contention was developed. The tool was used to confirm the contention problem and to evaluate the developed solution. This thesis surveyed state-of-the-art approaches concerned with mitigating contention. The approaches can be categorized as requiring modifications to the operating system, requiring modifications to hardware, requiring both or requiring neither. The approaches were also characterized by whether they focused on the source of contention or the contended for resource. An approach involving throttling of individual cores by clock modulation and toggling of hardware prefetchers was developed and tested. The solution was demonstrably effective in reducing contention. Contention effects were not eliminated. Possible further work include improving autonomous detection of contention and accounting for, and illustrating contention effects involving, additional contended for resources.
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Al, Sheikh Ahmad. « Resource allocation in hard real-time avionic systems : scheduling and routing problems ». Phd thesis, INSA de Toulouse, 2011. http://tel.archives-ouvertes.fr/tel-00631443.
Texte intégralRésumé :
Le domaine avionique a été transformé par l'apparition des architectures modulaires intégrées (IMA). Celles-ci définissent un support d'exécution et de communication standard et mutualisé afin de réduire la complexité de l'architecture physique. Cependant, du fait du partage des ressources, cette démarche introduit une plus grande complexité lors de la conception et de l'intégration des applications ce qui implique d'assister les concepteurs avec des outils dédiés. La présente thèse contribue à cet effort en se focalisant sur deux problèmes d'allocation de ressources : i) le problème de l'ordonnancement multiprocesseur de tâches strictement périodiques et ii) le problème du routage des messages échangés entre les fonctions avioniques. Le premier problème a été formalisé sous la forme d'un programme linéaire en nombres entiers afin de garantir un potentiel maximum d'évolution sur les durées d'exécutions des traitements. L'inefficacité d'une approche exacte pour des instances de grande taille, nous a conduit à développer une heuristique originale s'inspirant de la théorie des jeux couplée avec un algorithme multi-start. Le routage est formalisé sous la forme d'un problème d'optimisation sur la charge maximum des liens. Deux propositions sont faites pour le résoudre, l'une, exacte, est basée sur une formulation nœud-lien, et la seconde est une heuristique à deux niveaux basé sur une formulation lien-chemin. Mots-Clés en français : ordonnancement temps-réel, optimisation, systèmes avioniques, architectures modulaires intégrées, tâches strictement périodique, théorie de jeux, routage des liens virtuels
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Oliveira, Wilson Prates de. « Arquitetura de software para sistemas de tempo real ». Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/3/3152/tde-13012012-103355/.
Texte intégralRésumé :
O desenvolvimento de sistemas de controle em plataformas de tempo real é uma tarefa que envolve Engenharia de Controle e Ciência da Computação. Nas últimas décadas, estas áreas se desenvolveram como áreas independentes. Este trabalho busca diminuir distância entre as áreas propondo a utilização de métodos de Engenharia de Software em uma fase de modelagem do software de controle. Uma das propostas apresentadas no trabalho é a utilização de frameworks orientados a objetos no processo de Rapid Control Prototyping (RCP) para substituir a geração automática de código, eliminar os problemas de integração com código legado e tornar o processo RCP mais interativo. Outra proposta é a utilização de plataformas para RCP composta por uma camada de hardware real, uma camada SOTR e uma camada de aplicação formada pelo framework para análise e desenvolvimento de sistemas de controle centralizado ou distribuído.The development of real-time platform control systems is a task that involves Control Engineering and Computer Science. In the last decade, these areas have developed independent from each other. This paper seeks to decrease the distance between this areas, by proposing the use of Software Engineering methods in a software control modeling phase. One of the propositions in this paper is the use of object orientated frameworks in the Rapid Control Prototyping (RCP) process to substitute the automatic code generation, thus eliminating the problems with the legacy code and making the RCP process more interactive. Another proposition is the use of RCP directed platforms composed by a real hardware layer, a RTOS layer and an application layer formed by the framework for the analysis and development of the centralized or distributed control systems.
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Lam, Barbara. « LOW-COST MISSION SUPPORT CONCEPT ». International Foundation for Telemetering, 1996. http://hdl.handle.net/10150/607606.
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International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, CaliforniaThis paper presents a new architecture of the end-to-end ground system to reduce overall mission support costs. The present ground system of the Jet Propulsion Laboratory (JPL) is costly to operate, maintain, deploy, reproduce, and document. In the present climate of shrinking NASA budgets, this proposed architecture takes on added importance as it will dramatically reduce all of the above costs. Currently, the ground support functions (i.e., receiver, tracking, ranging, telemetry, command, monitor and control) are distributed among several subsystems that are housed in individual rack-mounted chassis. These subsystems can be integrated into one portable laptop system using established MultiChip Module (MCM) packaging technology. The large scale integration of subsystems into a small portable system will greatly reduce operations, maintenance and reproduction costs. Several of the subsystems can be implemented using Commercial Off-The-Shelf (COTS) products further decreasing non-recurring engineering costs. The inherent portability of the system will open up new ways for using the ground system at the “point-of-use” site as opposed to maintaining several large centralized stations. This eliminates the propagation delay of the data to the Principal Investigator (PI), enabling the capture of data in real-time and performing multiple tasks concurrently from any location in the world. Sample applications are to use the portable ground system in remote areas or mobile vessels for real-time correlation of satellite data with earth-bound instruments; thus, allowing near real-time feedback and control of scientific instruments. This end-to-end portable ground system will undoubtedly create opportunities for better scientific observation and data acquisition.
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Djokic, Jelena. « Investigation into Air Traffic Complexity as a Driver of a Controller‘s Workload ». Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-208110.
Texte intégralRésumé :
The thesis describes an investigation into Air Traffic Control (ATC) complexity as a contributory factor in changes of controllers' workload. It is considered that ATC complexity, together with equipment interface and procedural demands comprise the task demands imposed on the en-route controller to perform certain activities, which mediated by performance shaping factors create workload. The data used to study this relationship came from ATC real-time simulations completed at EUROCONTROL CRDS in Budapest: recorded flown trajectories, communication performed by the controller (whether with other controllers or with the pilots), data entries related to flight data management, and instantaneous self-assessment ratings of workload provided by the controllers were used. The ATC complexity factors that have been consistently found to be important in the previous studies (related to aircraft density, flight attributes of each individual aircraft, aircraft conflicts and traffic disorder) and for which detailed calculation formula have been reported were selected for further analysis. Since the established set of factors resulted from multiple researches conducted in this field, it was assumed that some of these factors are correlated with one another, overlapping and possibly measuring similar concepts. Therefore, a reduction of the initial set of factors was performed by combining information contained within these factors into a smaller number of new artificial variables and by deleting statistically redundant portions of these factors prior to conducting further analysis. The Principal Component Analysis (PCA), which is the statistical method applied to achieve required reduction, resulted in the overall set of 6 complexity components, whose interpretations are driven by the factors that showed the strongest correlation with that component. In order to establish a link between ATC complexity and a controller's subjective workload, multiple regression analysis was performed, using the complexity components identified in the PCA as predictors of the workload ratings. In addition, some measures of controller’s activity (data entries made by the controllers related to flight data management, cumulative duration of radio calls, i.e. frequency occupancy time, and average duration of single calls) were added to the analysis to test whether information about the controller’s activity could be also useful for predicting workload, once the effect of complexity had been considered, and to verify whether the effect of complexity on workload could be mediated by the effect of complexity on the controller’s activity. The analysis revealed that both ATC complexity and the activities that the controller performs to deal with a demand imposed on him/her give a unique contribution to the prediction of workload ratings and therefore the workload of the controller is determined by both ATC complexity and controller’s activities. In addition, it was assumed that the workload is differently impacted by individual components of complexity, and further statistical analyses were performed to test this assumption. Understanding these differences could in fact facilitate comparison of the complexity levels of a single sector under different conditions, but also comparison of complexity levels of different sectors under same conditions. Firstly the changes in the workload and activities of the controllers under different conditions were investigated using analysis of variance. Subsequently, in order to be able to map these changes on the complexity components, it was necessary also to investigate into the changes that the complexity components undergo when observed under different conditions. The results revealed different behaviour of single complexity components when mapped on the changes recorded in the activities of the controller and workload, demonstrating that changes in controller’s activities and perceived workload are driven by different complexity components in different sectors and under different operational conditions. Shedding light on these contributors to the workload experienced by a controller can greatly facilitate the introduction of any change envisaged for the airspace under consideration. Namely, in the current structure, whenever new procedures or new working methods are subject to possible deployment, the identified complexity components could support the estimation of the impact that those changes would impose on the workload of the controller and further on decision making processes. Additionally, the complexity components are also applicable in the validation of the new concepts and new technologies to be introduced in the system when designing simulation scenarios against which new concepts would be assessed. As also demonstrated by the analysis, the comparison of different sectors, or even different sector designs within the same airspace, could be compared and contribute to the improvement of airspace designDie vorliegende Arbeit untersucht die Komplexität der Flugverkehrskontrolle (Air Traffic Control, ATC) als einen wesentlichen Einflussfaktor auf die Arbeitsbelastung des Radarlotsen. Die zentrale Annahme ist dabei, dass die Komplexität der ATC zusammen mit den Anforderungen aus den betrieblichen Rahmenbedingungen (technische Systemschnittstellen und Prozeduren) den Lotsen zu bestimmten Abläufen zwingen, welche die Arbeitsbelastung signifikant beeinflussen. Für die durchgeführten Untersuchungen standen Daten von ATC-Echtzeitsimulationen von EUROCONTROL CRDS Budapest zur Verfügung, die folgende Informationen umfassen: abgeflogene Flugtrajektorien, Kommunikationsprotokolle der Lotsen (untereinander oder zwischen Lotse und Pilot), Daten aus dem flight-data Management und Daten aus der regelmäßigen Selbstbewertung der Lotsen bezüglich ihrer aktuell gefühlten Arbeitsbelastung. Die bereits in früheren Studien identifizierten Komplexitätsvariablen (insbesondere die lokale Flugzeugdichte, spezifische Flugzeugeigenschaften, Konfliktsituationen zwischen Flugzeugen und die Verkehrslage betreffend) sowie hierzu erarbeitete mathematische Vorschriften bilden die Grundlage für die weiterführenden, detaillierten Untersuchungen. Aufgrund der Vielzahl an Komplexitätsvariablen aus diversen wissenschaftlichen Quellen war davon auszugehen, dass Korrelationen unter den Variablen vorliegen. Aus diesem Grund wurden zunächst statistisch redundante Informationen der ursprünglich vorliegenden Variablen reduziert, sodass als Ergebnis neue voneinander unabhängige Faktoren klassifiziert werden konnten. Die hierfür verwendete Hauptkomponentenanalyse (Principal Component Analysis - PCA) führte zu sechs statistisch signifikanten Komplexitätsfaktoren, die anhand der höchsten Korrelation zur zugeordneten Komponente interpretiert wurden. Um die Verbindung zwischen der ATC Komplexität und der subjektiv empfundenen Arbeitsbelastung herzustellen, wurde eine multiple Regressionsanalyse zwischen den Komplexitätsfaktoren und den abgeleiteten Arbeitsbelastungszuständen durchgeführt. Zusätzlich lagen für die Analyse der Arbeitsbelastung auch Daten über die Arbeitsaufgaben des Lotsen vor (bspw. Dateneinträge des Lotsen, Gesamtlänge der Funkanweisungen, durchschnittliche Länge der Funkanweisungen), um zu untersuchen, inwieweit sich aus den aktuell durchgeführten Arbeitsaufgaben bei gegebener Verkehrsnachfrage eine verlässliche Vorhersage über die Arbeitsbelastung ableiten lässt. Die Analyse zur Vorhersage der Arbeitsbelastung konnte zeigen, dass sowohl die ATC Komplexität als auch die aktuellen Arbeitsaufgaben einen individuellen und signifikanten Einfluss haben. Weiterhin wurde unterstellt, dass die spezifischen Komplexitätsfaktoren einen unterschiedlichen Effekt auf die Arbeitsbelastung ausüben. Die Überprüfung dieser Annahme war ebenfalls Bestandteil der umfangreichen statistischen Untersuchungen. Tatsächlich könnte ein fundamentales Verständnis der Komplexitätsgrade den Vergleich einzelner Luftraumsektoren unter verschiedenen operativen Randbedingungen, als auch den Vergleich unterschiedlicher Luftraumsektoren mit vergleichbaren operativen Randbedingungen wesentlich erleichtern. Zuerst wurden die Veränderungen der Arbeitsbelastung und -die Tätigkeiten der Lotsen unter Verwendung einer Varianzanalyse untersucht. Um eine valide Zuordnung zu den Komplexitätsfaktoren sicherzustellen, war es ebenfalls notwendig, die Veränderungen dieser Faktoren und Tätigkeiten unter wechselnden Randbedingungen zu analysieren. Die Analysen zeigen hierbei unterschiedliche Resultate bezüglich der jeweiligen Komplexitätsfaktoren. So beeinflussen die verschiedenen Komplexitätsfaktoren die Handlungsabläufe der Lotsen und die wahrgenommene Arbeitsbelastung, jedoch in Abhängigkeit von den ausgewählten Sektoren und den betrieblichen Randbedingungen. Unter Berücksichtigung dieser erarbeiteten Abhängigkeiten der Arbeitsbelastung des Lotsen können nun die Auswirkungen von Veränderungen im Luftraum zuverlässig bestimmt werden. Gerade in Bezug auf Veränderungen der gegenwärtigen Luftraumstruktur oder die Einführung neuer Prozeduren oder Arbeitsabläufe können die entwickelten Komplexitätsfaktoren bereits frühzeitig Aufschluss darüber geben, welche Konsequenzen solche Veränderungen auf die Arbeitsbelastung der Lotsen nach sich ziehen können und Entscheidungsprozesse unterstützen. Weiterhin sind die entwickelten Komplexitätsfaktoren als Grundlage für die Validierung neuer Konzepte und Technologien, gegebenenfalls unter Verwendung von entwickelten Simulationsszenarien, nutzbar. Darüber hinaus können die Komplexitätsfaktoren für die Gegenüberstellung von verschiedenen Luftraumsektoren genutzt werden und zur Abwägung bzw. Optimierung von Entwürfen eines Luftraumdesigns dienen
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Ndoye, Falou. « Ordonnancement temps réel préemptif multiprocesseur avec prise en compte du coût du système d’exploitation ». Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112056/document.
Texte intégralRésumé :
Dans cette thèse nous étudions le problème d'ordonnancement temps réel multiprocesseur préemptif avec prise en compte du coût exact du système d'exploitation. Ce coût est formé de deux parties : une partie facile à déterminer, correspondant au coût de l'ordonnanceur et une partie difficile à déterminer, correspondant au coût de la préemption. Cette difficulté est due au fait qu'une préemption peut en engendrer une autre, pouvant ainsi créer un phénomène d'avalanche. Dans un premier temps, nous avons étudié l'ordonnancement hors ligne multiprocesseur de tâches indépendantes avec prise en compte du coût exact de la préemption et proposé une analyse d'ordonnançabilité fondée sur une heuristique d'ordonnancement multiprocesseur. Cette heuristique utilise la stratégie d'ordonnancement multiprocesseur par partitionnement. Pour prendre en compte le coût exact de la préemption sur chaque processeur nous avons utilisé la condition d'ordonnançabilité proposée par Meumeu et Sorel. Cette condition d'ordonnançabilité pour des tâches à priorités fixes, est basée sur une opération binaire d'ordonnancement qui permet de compter le nombre exact de préemption et d'ajouter leur coût dans l'analyse d'ordonnançabilité des tâches. L'heuristique proposée permet de maximiser le facteur d'utilisation restant afin de répartir équitablement les tâches sur les processeurs et de réduire leur temps de réponse. Elle produit une table d'ordonnancement hors ligne. Dans un second temps, nous avons étudié l'ordonnancement hors ligne multiprocesseur de tâches dépendantes avec prise en compte du coût exact de la préemption. Puisque la condition d'ordonnançabilité utilisée pour ordonnancer les tâches indépendantes ne s'applique qu'à des tâches à priorités fixes, elle ne permet pas de gérer les inversions de priorités que peuvent entraîner les tâches dépendantes. Nous avons donc proposé une nouvelle condition d'ordonnançabilité pour des tâches à priorités dynamiques. Elle prend en compte le coût exact de la préemption et les dépendances sans aucune perte de données. Ensuite en utilisant toujours la stratégie d'ordonnancement par partitionnement, nous avons proposé pour des tâches dépendantes une heuristique d'ordonnancement multiprocesseur qui réutilise cette nouvelle condition d'ordonnançabilité au niveau de chaque processeur. Cette heuristique d'ordonnancement prend en compte les coûts de communication inter-processeurs. Elle permet aussi de minimiser sur chaque processeur le makespan (temps total d'exécution) des tâches. Cette heuristique produit pour chaque processeur une table d'ordonnancement hors ligne contenant les dates de début et de fin de chaque tâches et de chaque commmunication inter-processeur. En supposant que nous avons une architecture multiprocesseur de type dirigée par le temps (Time-Triggered) pour laquelle tous les processeurs ont une référence de temps unique, nous avons proposé pour chacun des processeurs un ordonnanceur en ligne qui utilise la table d'ordonnancement produite lors de l'ordonnancement hors ligne. Cet ordonnanceur en ligne a l'avantage d'avoir un coût constant qui de plus est facile à déterminer de manière exacte. En effet il correspond uniquement au temps de lecture dans la table d'ordonnancement pour obtenir la tâche sélectionnée lors de l'analyse d'ordonnançabilité hors ligne, alors que dans les ordonnanceurs classiques en ligne ce coût correspond à mettre à jour la liste des tâches qui sont dans l'état prêt à l'exécution puis à sélectionner une tâche selon un algorithme, par exemple RM, DM, EDF, etc. Il varie donc avec le nombre de tâches prêtes à s'exécuter qui change d'une invocation à l'autre de l'ordonnanceur. C'est ce coût qui est utilisé dans les analyses d'ordonnançabilités évoquées ci-dessus. Un autre avantage est qu'il n'est pas nécessaire de synchroniser l'accès aux mémoires de données partagées par plusieurs tâches, car cette synchronisation a été déjà effectuée lors de l'analyse d'ordonnançabilité hors ligneIn this thesis we studied the problem of multiprocessor preemptive real-time scheduling taking into account the exact cost of the operating system (OS). This cost is composed of two parts: a part easy to determine, corresponding to the scheduler cost and another part difficult to determine, corresponding to the preemption cost. This difficulty is due to the fact that a preemption can involve another one, being able to so create an avalanche phenomenon. First, we studied the off-line multiprocessor real-time scheduling of independent tasks taking into account the exact preemption cost. We proposed a schedulability analysis based on a multiprocessor scheduling heuristic. This heuristic uses the partitioned multiprocessor scheduling approach. In order to take into account the exact preemption cost on every processor we use the schedulability condition proposed by Meumeu and Sorel. This schedulability condition for fixed priorities tasks, is based on a binary scheduling operation which counts the exact number of preemptions and add their cost in the schedulability analysis. The proposed heuristic maximizes the remaining utilization factor to fairly distribute the tasks on processors and to reduce their response time. It produces an off-line scheduling table. Secondly, we studied the off-line multiprocessor real-time scheduling of dependent tasks taking into account the exact preemption cost. Because the schedulability condition used for scheduling independent tasks can be applied only to fixed priorities tasks, it does not allow to manage priorities inversions that are involved by dependent tasks. We proposed a new schedulability condition for dependent tasks which enables fixed and dynamic priorities. This schedulability condition takes into account the exact preemption cost and dependences between tasks without any loss of data. Always with the partitioned scheduling approach, we proposed for dependent tasks a multiprocessor scheduling heuristic which reuses, on every processor, the schedulability condition proposed previously. In addition, this scheduling heuristic takes into account the interprocessors communication costs. It also minimizes on every processor the makespan (total execution time of the tasks on all the processors). This heuristic produces for every processor an off-line scheduling table. Supposing that we have a time-triggered multiprocessor architecture such that all the processors have a unique time reference, we proposed for every processor an on-line scheduler which uses the scheduling table produced during the off-line schedulability analysis. This on-line scheduler has the advantage to have a constant cost that is easy to determine exactly.Indeed, this cost corresponds only to the time necessary to read in the scheduling table the task selected for execution. In the on-line classical scheduler, this cost corresponds to the time necessary to update the list of ready tasks in order to select a task, according to a given scheduling algorithm, for example RM, DM, EDF, etc. In this case, the cost for selecting a task varies with the number of ready tasks which changes from an invocation of the scheduler to another one. Another advantage of the proposed on-line scheduler is that it is not necessary to synchronize the access to the data shared by several tasks, because this synchronization was already done during the off-line schedulability analysis
42
Davis, Robert Ian. « On exploiting spare capacity in hard real-time systems ». Thesis, University of York, 1995. http://etheses.whiterose.ac.uk/10840/.
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Fisher, Nathan Wayne Baruah Sanjoy K. « The multiprocessor real-time scheduling of general task systems ». Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2007. http://dc.lib.unc.edu/u?/etd,1108.
Texte intégralRésumé :
Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2007.Title from electronic title page (viewed Mar. 27, 2008). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Computer Science." Discipline: Computer Science; Department/School: Computer Science.
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Zhou, Hongyi. « Task scheduling and synchronization for multiprocessor real-time systems ». Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/9178.
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Kivelevitch, Elad H. « Robust, Real Time, and Scalable Multi-Agent Task Allocation ». University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1337007279.
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Naedele, Martin. « On the modeling and evaluation of real-time systems ». [S.l.] : [s.n.], 2000. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=13564.
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Krauth, Elfriede Irene. « Real-time planning support : a task-technology fit perspective = Real-time planningsondersteuning : de afstemming tussen taak en technologie / ». Rotterdam : Erasmus Universiteit, 2008. http://opac.nebis.ch/cgi-bin/showAbstract.pl?u20=97890589221932.
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Sandnes, Frode Eika. « New approaches to static task graph scheduling for control ». Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362290.
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Ekberg, Pontus. « Models and Complexity Results in Real-Time Scheduling Theory ». Doctoral thesis, Uppsala universitet, Avdelningen för datorteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-267017.
Texte intégralRésumé :
When designing real-time systems, we want to prove that they will satisfy given timing constraints at run time. The main objective of real-time scheduling theory is to analyze properties of mathematical models that capture the temporal behaviors of such systems. These models typically consist of a collection of computational tasks, each of which generates an infinite sequence of task activations. In this thesis we study different classes of models and their corresponding analysis problems. First, we consider models of mixed-criticality systems. The timing constraints of these systems state that all tasks must meet their deadlines for the run-time scenarios fulfilling certain assumptions, for example on execution times. For the other scenarios, only the most important tasks must meet their deadlines. We study both tasks with sporadic activation patterns and tasks with complicated activation patterns described by arbitrary directed graphs. We present sufficient schedulability tests, i.e., methods used to prove that a given collection of tasks will meet their timing constraints under a particular scheduling algorithm. Second, we consider models where tasks can lock mutually exclusive resources and have activation patterns described by directed cycle graphs. We present an optimal scheduling algorithm and an exact schedulability test. Third, we address a pair of longstanding open problems in real-time scheduling theory. These concern the computational complexity of deciding whether a collection of sporadic tasks are schedulable on a uniprocessor. We show that this decision problem is strongly coNP-complete in the general case. In the case where the asymptotic resource utilization of the tasks is bounded by a constant smaller than 1, we show that it is weakly coNP-complete.
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hu, xiaoxiang. « Analysis of Time-related Properties in Real-time Data Aggregation Design ». Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-39046.
Texte intégralRésumé :
Data aggregation is extensively used in data management systems nowadays. Based on a data aggregation taxonomy named DAGGTAX, we propose an analytic process to evaluate the run-time platform and time-related parameters of Data Aggregation Processes (DAP) in a real-time system design, which can help designers to eliminate infeasible design decisions at early stage. The process for data aggregation design and analysis mainly includes the following outlined steps. Firstly, the user needs to specify the variation of the platform and DAP by figuring out the features of the system and time-related parameters respectively. Then, the user can choose one combination of the variations between the features of the platform and DAP, which forms the initial design of the system. Finally, apply the analytic method for feasibility analysis by schedulability analysis techniques. If there are no infeasibilities found in the process, then the design can be finished. Otherwise, the design must be altered from the run-time platform and DAP design stage, and the schedulability analysis will be applied again for the revised design until all the infeasibilities are fixed. In order to help designers to understand and describe the system and do feasibility analysis, we propose a new UML (Unified Modeling Language) profile that extends UML with concepts related to real-time data aggregation design. These extensions aim to accomplish the conceptual modeling of a real-time data aggregation. In addition, the transferring method based on UML profile to transfer the data aggregation design into a task model is proposed as well. In the end of the thesis, a case study, which applies the analytic process to analyze the architecture design of an environmental monitoring sensor network, is presented as a demonstration of our research.