A job for which execution is requested is classified as one of classes. The amount of data to be written into a non-volatile storage device by execution of the job for which execution is requested is acquired. The efficiency index is calculated for each of the classes based on an execution evaluation value of the class and the amount of data to be written into the non-volatile storage device by execution of at least one job that has been already classified as the class. From among the classes, a class having an efficiency index of no greater than an efficiency threshold value is determined as the execution suspending class. When the job for which execution is requested belongs to the execution suspending class, execution of the job is suspended.