The Cortex-A53 processor includes performance monitors that implement the ARM PMUv3 architecture. These enable you to gather various statistics on the operation of the processor and its memory system during runtime. These provide useful information about the behavior of the processor that you can use when debugging or profiling code.
The 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.