研究発表

In this paper, we develop a kernel module that is able to boost the real-time capability of the Linux kernel in high-load situations. While the traditional Real-Time Linux requires a major ｍodification to　the kernel source code, the developed kernel module requires only a minor modification, for instance the Linux kernel 2.6.25 needs just one line modified, and thus it offers high scalability. The developed kernel　module overwrites a part of the Linux scheduler so that the pick next task member of the rt_sched_class　structure, which is a pointer to the function choosing a next scheduled task, refers to the original function　implemented in the module. The original function exploits such a scheduling algorithm that traces the remaining execution time of each task and dynamically assigns the highest priority to a job going to miss its deadline with the current priority. Using this framework, other scheduling algorithms can be also easily installed into the Linux kernel for improvement of real-time capability.

Extended T-N Plane Abstraction (E-TNPA) proposed in this paper realizes work-conserving and efficient optimal real-time scheduling on multiprocessors relative to the original T-N Plane Abstraction (TNPA). Additionally a scheduling algorithm named NVNLF (No Virtual Nodal Laxity First) is presented for E-TNPA. E-TNPA and NVNLF relax the restrictions of TNPA and the traditional algorithm LNREF, respectively. Arbitrary tasks can be preferentially executed by both tie-breaking rules and time apportionment policies in accordance with various system requirements with several restrictions. Simulation results show that E-TNPA significantly reduces the number of task preemptions as compared to TNPA.