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Modern computer systems are often designed to play a multipurpose role. Therefore, they are capable of running a number of software tasks (software programs) simultaneously in parallel. These software tasks should share the processor such that all of them run and finish their computations as expected. On the other hand, a number of software tasks have timing requirements meaning that they should not only access the processing unit, but this access should also be in a timely manner. Thus, there is a need to timely share the processor among different software programs (applications). The time-sharing often is realized by assigning a fixed and predefined processor time-portion to each application. However, there exists a group of applications where, i) their processor demand is changing in a wide range during run-time, and/or ii) their occasional timing violations can be tolerated. For systems that contain applications with the two aforementioned properties, it is not efficient to assign the applications with fixed processor time-portions. Because, if we allocate the processor resource based on the maximum resource demand of the applications, then the processor's computing capacity will be wasted during the time intervals where the applications will require a smaller portion than maximum resource demand. To this end, in this thesis we propose adaptive processor time-portion assignments. In our adaptive scheme, at each point in time, we monitor the actual demand of the applications, and we provide sufficient processor time-portions for each application. In doing so, we are able to integrate more applications on a shared and resource constrained system, while at the same time providing the applications with timing guarantees.

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.

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.