an information processing device of the invention includes a measurement section which detects the changes in the uses of a built - in memory and an external memory , and a control section which monitors the measurement result from the measurement section , changes the configuration of the built - in memory , transfers the data stored in the built - in memory and the external memory , and changes the external memory area and the built - in memory area used by the cpu and other bus master devices , wherein it is possible to detect the changes in the memory utilization efficiency that cannot be predicted by static analysis , and to maintain an optimal memory configuration .