About the PMU
The processor includes logic to gather various statistics on the operation of the processor and memory system during runtime, based on PMUv3 architecture.
These events provide useful information about the behavior of the processor that you can use when debugging or profiling code.
The processor PMU provides six counters. Each counter can count any of the events available in the processor. The absolute counts recorded might vary because of pipeline effects. This has negligible effect except in cases where the counters are enabled for a very short time.