Nyman, Ulrik

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2015 - 20182
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  • Publication
    Optimizing the Resource Requirements of Hierarchical Scheduling Systems
    (2015-12-01) Kim, Jin Hyun; Legay, Axel; Traonouez, Louis-Marie; Boudjadar, Abdeldjalil; Nyman, Ulrik; Lee, Insup; Choi, Jin-Young; Larsen, Kim G.
    Compositional reasoning on hierarchical scheduling systems is a well-founded formal method that can construct schedulable and optimal system configurations in a compositional way. However, a compositional framework formulates the resource requirement of a component, called an interface, by assuming that a resource is always supplied by the parent components in the most pessimistic way. For this reason, the component interface demands more resources than the amount of resources that are really sufficient to satisfy sub-components. We provide two new supply bound functions which provides tighter bounds on the resource requirements of individual components. The tighter bounds are calculated by using more information about the scheduling system. We evaluate our new tighter bounds by using a model-based schedulability framework for hierarchical scheduling systems realized as Uppaal models. The timed models are checked using model checking tools Uppaal and Uppaal SMC, and we compare our results with the state of the art tool CARTS.
  • Publication
    Generic Formal Framework for Compositional Analysis of Hierarchical Scheduling Systems
    (2018-05-01) Boudjadar, Jalil; Kim, Jin Hyun; Phan, Linh Thi Xuan; Lee, Insup; Nyman, Ulrik; Larsen, Kim G.
    We present a compositional framework for the specification and analysis of hierarchical scheduling systems (HSS). Firstly we provide a generic formal model, which can be used to describe any type of scheduling system. The concept of Job automata is introduced in order to model job instantiation patterns. We model the interaction between different levels in the hierarchy through the use of state-based resource models. Our notion of resource model is general enough to capture multi-core architectures, preemptiveness and non-determinism.