> Interrupt-based sampling introduces skids on modern processors. That means that the instruction pointer stored in each sample designates the place where the program was interrupted to process the PMU interrupt, not the place where the counter actually overflows, i.e., where it was at the end of the sampling period. In some case, the distance between those two points may be several dozen instructions or more if there were taken branches.

https://perf.wiki.kernel.org/index.php/Tutorial#Event-based_...