PURPOSE: To measure an occupation time ratio of each job from the total CPU time, which the operating system obtains on a basis of identifiers stored in a trace buffer, by providing a hardware tracer in the CPU.

CONSTITUTION: A hardware tracer 13 is provided in a CPU 1, and identifiers (address space discriminating information) 33 stored in a main storage device MSU 3 are sampled each time when an operating system OS 31 switches a job JOB 32. That is, the tracer 13 performs sampling at a specific period independently of the software operation and stores identifiers in a trace buffer 34 which the OS 31 prepares on the MSU 3. The OS 31 reads identifiers 33 stored in the buffer 34 to measure the total CPU time. Thus, since identifiers of jobs 32 which are operated in the interrupt inhibiting state can be sampled, the occupation time ratio of each job 32 is measured with a high precision.