The performance of an executing computer program on a computer system is monitored using latency sampling. The program has object code instructions and is executing on the computer system. At intervals, the execution of the computer program is interrupted including delivering a first interrupt. In response to at least a subset of the first interrupts, a latency associated with a particular object code instruction is identified, and the latency is stored in a first database. The particular object code instruction is executed by the computer such that the program remains unmodified.