System for processing activation request of port by counting number of busy response for activation request and response of busy end association with another port

摘要

With respect to each of low speed and high speed input/output ports of an input/output control unit, an activation time from a time point when an end status in association with the end of transfer is responded to a time point when an activation request is received is measured and stored in a memory. When the high speed port receives an activation request from a high speed channel, the activation time in the memory measured with respect to the low speed port is read out and an input/output request for the low speed port is preferentially accepted for such an activation time. As an activation time of the low speed port, the minimum time, average time, and maximum time are obtained from the result of the measurement. Either one of the above three times is selected as an activation time so as to almost equalize busy ratios of the high speed port and low speed port.