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Adaptive and Flexible Scheduling Frameworks for Component-Based Real-Time Systems
Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.ORCID iD: 0000-0003-2670-3022
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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

Abstract [sv]

Moderna datasystem är ofta utformade för att spela en mångsidig roll. De är därför kapabla till att köra flera mjukvarukomponenter (programvaror) samtidigt. Dessa mjukvarukomponenter delar systemresurser (t.ex. processorn och nätverket) under körning. Målet med mjukvarukomponentens körning är att avsluta sina beräkningar som förväntat. Vissa mjukvarukomponenter har även tidskrav vilket innebär att de inte bara kräver tillgång till systemresurser för att köra sina beräkningar, utan de har även krav på när denna tillgång sker för att mjukvarukomponenterna ska för rätt funktion kunna garantera att beräkningar utförs i rätt tid. Således finns det ett behov av att snabbt dela resurser mellan olika mjukvarukomponenter. Den tids-delning realiseras ofta genom att reservera en tidslucka för komponenten då denna är tänkt att och får använda resursen. Reservationen måste vara tillräcklig för att mjukvarukomponenten ska kunna köra som förväntat. Reservationen måste även tilldelas resurseffektivt dvs resurstid får inte slösas bort i onödan. Genom en resurseffektiv reservation av resurserminskar komponentens fotavtryck på resursen som i sin tur möjliggör integration av flera programvarukomponenter på samma resurs. Denna avhandling fokuserar främst på resurseffektivitet i samband med reservationerna. Två fall behandlas. (I) Komponenter som tål att missa vissa enstaka tidskrav (så kallade mjuka realtidskomponenter): i det här fallet anpassas reservationerna under körning enligt komponenternas ständigt föränderliga önskemål på reservationsstorlek. (II) Komponenter som inte kan hantera att tidskrav överträds (så kallade hårda realtidskomponenter): i det här fallet används flexibla strategier som möjliggör  förbättrad resurseffektiviteten redan vid design av systemet.

Place, publisher, year, edition, pages
Västerås: Mälardalen University , 2015.
Series
Mälardalen University Press Dissertations, ISSN 1651-4238 ; 191
National Category
Computer Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-29110ISBN: 978-91-7485-235-6 (print)OAI: oai:DiVA.org:mdh-29110DiVA: diva2:856215
Public defence
2015-11-05, Lambda, Mälardalens högskola, Västerås, 13:15 (English)
Opponent
Supervisors
Available from: 2015-09-24 Created: 2015-09-23 Last updated: 2015-10-15Bibliographically approved
List of papers
1. Bandwidth Adaptation in Hierarchical Scheduling Using Fuzzy Controllers
Open this publication in new window or tab >>Bandwidth Adaptation in Hierarchical Scheduling Using Fuzzy Controllers
2012 (English)In: 7th IEEE International Symposium on Industrial Embedded Systems, SIES 2012 - Conference Proceedings, 2012, 148-157 p.Conference paper, Published paper (Refereed)
Abstract [en]

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

National Category
Engineering and Technology
Identifiers
urn:nbn:se:mdh:diva-17266 (URN)10.1109/SIES.2012.6356580 (DOI)2-s2.0-84871577601 (Scopus ID)978-146732684-1 (ISBN)
Conference
7th IEEE International Symposium on Industrial Embedded Systems, SIES 2012; Karlsruhe; 20 June 2012 through 22 June 2012
Available from: 2012-12-20 Created: 2012-12-20 Last updated: 2015-09-24Bibliographically approved
2. An Adaptive Scheduling Framework for Component-Based Real-Time Systems
Open this publication in new window or tab >>An Adaptive Scheduling Framework for Component-Based Real-Time Systems
2015 (English)Report (Other academic)
National Category
Computer Engineering
Identifiers
urn:nbn:se:mdh:diva-29109 (URN)
Available from: 2015-09-23 Created: 2015-09-23 Last updated: 2015-09-24Bibliographically approved
3. A Feedback Scheduling Framework for Component-Based Soft Real-Time Systems
Open this publication in new window or tab >>A Feedback Scheduling Framework for Component-Based Soft Real-Time Systems
Show others...
2015 (English)In: 21th IEEE Real-Time and Embedded Technology and Applications Symposium RTAS'15, 2015, 182-193 p.Conference paper, Published paper (Refereed)
Abstract [en]

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

National Category
Computer and Information Science
Identifiers
urn:nbn:se:mdh:diva-28130 (URN)10.1109/RTAS.2015.7108441 (DOI)000380616700016 ()2-s2.0-84944682349 (Scopus ID)978-1-4799-8603-3 (ISBN)
External cooperation:
Conference
21th IEEE Real-Time and Embedded Technology and Applications Symposium RTAS'15, 13-16 Apr 2015, Seattle, United States
Projects
ARROWS - Design Techniques for Adaptive Embedded Systems
Available from: 2015-06-11 Created: 2015-06-08 Last updated: 2016-09-01Bibliographically approved
4. Adaptive Multi-Resource End-to-End Reservations for Component-Based Distributed Real-Time Systems
Open this publication in new window or tab >>Adaptive Multi-Resource End-to-End Reservations for Component-Based Distributed Real-Time Systems
Show others...
2015 (English)In: ESTIMedia 2015 - 13th IEEE Symposium on Embedded Systems for Real-Time Multimedia, 2015, Article number 7351772- p.Conference paper, Published paper (Refereed)
Abstract [en]

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

National Category
Computer Engineering
Identifiers
urn:nbn:se:mdh:diva-29106 (URN)10.1109/ESTIMedia.2015.7351772 (DOI)000377587200013 ()2-s2.0-84962285268 (Scopus ID)978-146738164-2 (ISBN)
Conference
IEEE Symposium on Embedded Systems for Real-Time Multimedia. October 8-9, 2015. Amsterdam, The Netherlands.
Available from: 2015-09-23 Created: 2015-09-23 Last updated: 2016-07-07Bibliographically approved
5. Exact and Approximate Supply Bound Function for Multiprocessor Periodic Resource Model: Unsynchronized Servers
Open this publication in new window or tab >>Exact and Approximate Supply Bound Function for Multiprocessor Periodic Resource Model: Unsynchronized Servers
2012 (English)Conference paper, Published paper (Refereed)
Abstract [en]

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

National Category
Engineering and Technology
Identifiers
urn:nbn:se:mdh:diva-17389 (URN)
Conference
5th Workshop on Compositional Theory and Technology for Real-Time Embedded Systems (CRTS 2012), San Juan, Puerto Rico, December 4, 2012
Available from: 2012-12-20 Created: 2012-12-20 Last updated: 2015-09-24Bibliographically approved
6. On Component-Based Software Development for Multiprocessor Real-Time Systems
Open this publication in new window or tab >>On Component-Based Software Development for Multiprocessor Real-Time Systems
2015 (English)In: Proceedings - IEEE 21st International Conference on Embedded and Real-Time Computing Systems and Applications, RTCSA 2015, 2015, 132-140 p.Conference paper, Published paper (Refereed)
Abstract [en]

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

National Category
Computer Engineering Computer Engineering
Identifiers
urn:nbn:se:mdh:diva-29108 (URN)10.1109/RTCSA.2015.27 (DOI)000378419800014 ()2-s2.0-84962803719 (Scopus ID)9781467378550 (ISBN)
Conference
21st IEEE International Conference on Embedded and Real-Time Computing Systems and Applications. August 19-21, 2015. Hong Kong, China.
Available from: 2015-09-23 Created: 2015-09-23 Last updated: 2016-10-31Bibliographically approved

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Output format
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