1. A multicore processor system comprising a core configured to: detect a change in a state of assignment of a multicore processor; obtain, upon detecting the change in the state of assignment, a number of accesses by processes, assigned to cores of the multicore processor, of a common resource shared by the multicore processor; calculate an access ratio based on the obtained number of accesses; and notify an arbitration circuit of the calculated access ratio, the arbitration circuit arbitrating accesses of the common resource by the multicore processor.