Kim, Jin Hyun
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PublicationExtensible Energy Planning Framework for Preemptive Tasks(2017-05-01) Kim, Jin Hyun; Gangadharan, Deepak; Sokolsky, Oleg; Lee, Insup; Legay, AxelCyber-physical systems (CSPs) are demanding energy-efficient design not only of hardware (HW), but also of software (SW). Dynamic Voltage and and Frequency Scaling (DVFS) and Dynamic Power Manage (DPM) are most popular techniques to improve the energy efficiency. However, contemporary complicated HW and SW designs requires more elaborate and sophisticated energy management and efficiency evaluation techniques. This paper is concerned about energy supply planning for real-time scheduling systems (units) of which tasks need to meet deadlines. This paper presents a modelbased compositional energy planning technique that computes a minimal ratio of processor frequency that preserves schedulability of independent and preemptive tasks. The minimal ratio of processor frequency can be used to plan the energy supply of real-time components. Our model-based technique is extensible by refining our model with additional features so that energy management techniques and their energy efficiency can be evaluated by model checking techniques. We exploit the compositional framework for hierarchical scheduling systems and provide a new resource model for the frequency computation. As results, our use-case for avionics software components shows that our new method outperforms the classical real-time calculus (RTC) method, requiring 36.21% less frequency ratio on average for scheduling units under RM than the RTC method. PublicationTowards Overhead-Free Interface Theory for Compositional Hierarchical Real-Time Systems(2018-05-02) Kim, Jin Hyun; Kim, Kygong Hoon; Easwaran, Arvind; Lee, InsupMuch recent research has been conducted on compositional real-time scheduling framework as the framework becomes a useful fundamental theory for real-time OS-Hypervisor. Much recent research has been conducted on compositional real-time scheduling as the framework becomes a useful fundamental theory for real-time OS-Hypervisor. However, compositional frameworks suffer from abstraction overheads in composing components. In this paper, we classify the composition overheads into i) supply abstraction overhead associated with the supply from a resource provider, and ii) demand abstraction overhead associated with the component workload. Then, we provide sufficient conditions for each abstraction overhead to be eliminated. In addition, this paper provides a heuristic technique that transforms any component to satisfy the sufficient conditions so that the abstraction overheads are minimized. In our comparison, we showed our technique outperforms the prior overhead-reducing CF about 10% at average and other combination techniques about 8% in reducing the overhead.