The present disclosure provides a computer program product and activity recording system for identifying idleness in a processor via a concurrent software environment. A thread state indicator records an indication of a synchronization state of a software thread that is associated with an identification of the software thread. A time profiler identifies a processor of the computer system being idle and records an indication that the processor is idle. A dispatch monitor identifies a dispatch of the software thread to the processor. In response to the dispatch monitor determining the indication identifies that the processor is idle and the indication of a synchronization state of the software thread indicating the software thread ceases to execute in the processor, the dispatch monitor generates a record attributing the idleness of the processor to the software thread and the indicated synchronization state.