An information processing system performs a real-time operation periodically at specific time intervals. The system includes a unit for performing a scheduling operation of assigning the real-time operation to a processor to perform the real-time operation periodically at the specific time intervals by the processor, a unit for computing a ratio of an execution time of the real-time operation to be performed by the processor at a first operating speed, based on the specific time intervals and cost information concerning a time required to perform the real-time operation by the processor at the first operating speed, and a unit for performing an operating speed control operation to operate the processor at a second operating speed that is lower than the first operating speed, the second operating speed being determined based on the computed ratio.