Real-time system need to meet deadline. In this point of view, the system is required two functions to have determinism. One is interruptlatency stabilization and the other one is processing time reservation. The SCHED_DEADLINE has a feature to reserve CPU time in advance to ensure predictable behavior. In our evaluation, the granularity of CPU reservation is millisecond order.In this presentation, we show the evaluation results of current implementation to make clear the issue. Then we explain how to overcome this issue and its results.