1. A method of controlling an information processing apparatus including a memory for storing data, an I/O controller connected to an I/O unit for issuing a plurality of requests corresponding to the data, and a processor connected to the memory and the I/O controller, the method comprising: determining, by a determining unit included in the I/O controller, whether a guarantee order control of the plurality of requests including precedent requests and subsequent requests, is to be executed by either of the processor and the I/O controller in reference to request types of the precedent requests and the subsequent requests being subsequent to the precedent requests, the guarantee order control being used for preventing the subsequent requests from skipping the precedent requests; transmitting, by a transmitting unit included in the I/O controller, a subsequent request to the processor after transmitting a precedent request to the processor when the determining unit determines that the guarantee order control is executed by the processor; transmitting, by a transmitting unit included in the processor, the subsequent request to the memory when the determining unit determines that the guarantee order control is executed by the processor; and transmitting, by a control unit included in the processor, the subsequent request to the memory upon completion of execution of the precedent request at the memory.