A multiprocessor system comprises: a plurality of processors; a counting, measuring and calculating (CMC) unit that determines a generating rate of sleep tasks and a time length of each of the sleep tasks based on an acceptable delay; a sleep task generator that generates the sleep tasks with the time length at the generating rate, and injects the generated sleep tasks into a traffic for original tasks; and a scheduler that assigns both the original tasks and the sleep tasks in the traffic to the plurality of processors, wherein each of the sleep tasks switches off one of the plurality of processors, on which the sleep task is assigned.