A judgment is made quickly about whether or not it is a memory or a chipset that is causing a performance bottleneck in an application program. A computer system of this invention includes at least one CPU, a controller that connects the CPU to a memory and to an I/O interface, in which the controller includes a response time measuring unit, which receives a request to access the memory and measures a response time taken to respond to the memory access request, a frequency counting unit, which measures an issue count of the memory access request, a measurement result storing unit, which stores a measurement result associating the response time with the corresponding issue count, and a measurement result control unit which outputs the measurement result stored in the measurement result storing unit when receiving a measurement result read request.