On Benchmarking the Predictability of Real-Time Mechanisms in User and Kernel Spaces for Real-Time Embedded Linux

Benchmarking the response time of real-time mechanisms is a good measure for predicting the performance of real-time systems. We report on analysis results obtained by comparing the response characteristics of real-time mechanisms in the kernel space to those in the user space for real-time embedded Linux: RTAI and Xenomai. Evaluations were performed on a semaphore, real-time FIFO, and Mailbox and Message queue. The periodicity of tasks was relatively consistent in the kernel space and Xenomai performed better than RTAI in the user space. For real-time mechanisms, the response times in the kernel space were better at low latencies. In Xenomai, the semaphore showed a good response time in both the kernel and user space, but real-time FIFO in RTAI showed a faster response. These results are promising for the estimation of deterministic real-time task execution to implement real-time systems using real-time embedded Linux.