Implementation of Fluid Scheduling Using IPC Control Mechanism In realtime systems such as automobiles, correctness of processing tasks depends not only on its result, but also on time. Realtime scheduling is a basic approache to achieve realtime execution in realtime systems. Fluid scheduling is an optimal realtime scheduling model, which keeps the execution speed of each task proportional to its processor utilization. However, the speed of a task cannot be controlled arbitrarily on a general processor, making it impossible to implement fluid scheduling directly. Therefore, there have been many studies on pseudo fluid scheduling where the algorithm is based on repeat task execution which speed is constant in an interval. We apply the special mechanisms of Responsive MultiThreaded Processor (RMTP) to the novel control mechanism in order to implement fluid scheduling directly. RMTP is a prioritized SMT processor for realtime processing, which has 1. a thread speed control mechanism which controls execution speed of each thread and 2. a context cache enabling context switches in four clock cycles. In this paper, by adding a novel thread speed control mechanism, execution speeds of 40 threads are controlled to be constant over short time intervals, directly making fluid scheduling possible.

Fast Interrupt Handling Scheme by Using Interrupt WakeUp Mechanism In recent years, embedded realtime systems have grown in complexity and are required to be able to handle both periodic and aperiodic tasks. When an external interrupt occurs via an IO peripheral, the program counter jumps to the corresponding exception vector. This results in large overhead due to context switching. However, embedded realtime systems are required to execute tasks in realtime with high precision. The Responsive Multithreaded Processor (RMTP), a prioritized SMT CPU, consists of eight hardware contexts treated as eight logical processing cores and has various hardware mechanisms for finegrained realtime processing on the order of 10 xc2xb5s. One hardware mechanism implemented in RMTP is an interrupt wakeup mechanism that enables interrupttriggered thread wake ups. When a thread is designated to be an interrupt handling thread, it starts execution one clock cycle after an interrupt occurs. In this paper, we design and implement a software mechanism which reduces the interrupt response time by using this mechanism and demonstrate the effectiveness of our proposed method by RTL simulations. Evaluation results show that our proposed method achieves high realtime performance by reducing the interrupt response time by up to 82% compared to the baseline.