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A Feedback Scheduling Framework for Component-Based Soft Real-Time Systems
Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.ORCID iD: 0000-0003-2670-3022
McGill University, Canada.
McGill University, Canada.
Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.ORCID iD: 0000-0002-1687-930X
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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.

Place, publisher, year, edition, pages
2015. 182-193 p.
National Category
Computer and Information Science
Identifiers
URN: urn:nbn:se:mdh:diva-28130DOI: 10.1109/RTAS.2015.7108441ISI: 000380616700016Scopus ID: 2-s2.0-84944682349ISBN: 978-1-4799-8603-3 (print)OAI: oai:DiVA.org:mdh-28130DiVA: diva2:819856
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
In thesis
1. Adaptive and Flexible Scheduling Frameworks for Component-Based Real-Time Systems
Open this publication in new window or tab >>Adaptive and Flexible Scheduling Frameworks for Component-Based Real-Time Systems
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:nbn:se:mdh:diva-29110 (URN)978-91-7485-235-6 (ISBN)
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

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