A Jitter-Free Kernel for Hard Real-Time Systems
Christo Angelov, Jesper Berthing
Abstract. The paper presents advanced task management techniques featuring Boolean vectors and bitwise vector operations on kernel data structures in the context of the HARTEXTM hard real-time kernel. These techniques have been consistently applied to all aspects of task management and interaction. Hence, the execution time of system functions no longer depends on the number of tasks involved, resulting in predictable, jitter-free kernel operation. This approach has been further extended to time management resulting in a new type of kernel component, which can be used to implement timed multitasking - a novel technique providing for jitter-free execution of hard real-time tasks.
predictable dynamic scheduling is more promising but it requires the development of a new generation of safe real-time kernels, which provide a secure and predictable environment for application tasks through predictable task scheduling and interaction, extensive timing and monitoring facilities, and last but not least - predictable behaviour of the kernel itself. Such functionality cannot be efficiently accomplished using conventional kernel algorithms and data structures, i.e. linked lists used to implement system queues. Extensive linked list processing introduces substantial and largely varying overhead known as kernel jitter [4].
highly deterministic (jitter-free)....
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The interrupts in the middle of execution of a Task or unexpected processing overhead which decreases the deterministic behaviour is called Jitter.
Christo Angelov, Jesper Berthing
Abstract. The paper presents advanced task management techniques featuring Boolean vectors and bitwise vector operations on kernel data structures in the context of the HARTEXTM hard real-time kernel. These techniques have been consistently applied to all aspects of task management and interaction. Hence, the execution time of system functions no longer depends on the number of tasks involved, resulting in predictable, jitter-free kernel operation. This approach has been further extended to time management resulting in a new type of kernel component, which can be used to implement timed multitasking - a novel technique providing for jitter-free execution of hard real-time tasks.
predictable dynamic scheduling is more promising but it requires the development of a new generation of safe real-time kernels, which provide a secure and predictable environment for application tasks through predictable task scheduling and interaction, extensive timing and monitoring facilities, and last but not least - predictable behaviour of the kernel itself. Such functionality cannot be efficiently accomplished using conventional kernel algorithms and data structures, i.e. linked lists used to implement system queues. Extensive linked list processing introduces substantial and largely varying overhead known as kernel jitter [4].
highly deterministic (jitter-free)....
------
The interrupts in the middle of execution of a Task or unexpected processing overhead which decreases the deterministic behaviour is called Jitter.
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