A real-time system may have tasks with soft deadlines, as well as hard deadlines. While earliest deadline first scheduling is effective for hard deadline tasks, applying it to soft deadline tasks may waste schedulable processor capacity or sacrifice average reponse time. Better average response time may be obtained, while still guaranteeing hard deadlines, with an aperiodic server. In this paper, I propose a variable utilization server which schedules aperiodic tasks with controlable complexity, and gives better response time than constant utilization server in task set with the period of $k^i$.
