3. OProfile event counting mode

OProfile provides the ocount tool for collecting raw event counts on a per-application, per-process, per-cpu, or system-wide basis. Unlike the profiling tools, post-processing of the data collected is not necessary -- the data is displayed in the output of ocount. A common use case for event counting tools is when performance analysts want to determine the CPI (cycles per instruction) for an application. High CPI implies possible stalls, and many architectures provide events that give detailed information about the different types of stalls. The events provided are architecture-specific, so we refer the reader to the hardware manuals available for the processor type being used.