Instructions Retired per Cycle, or IPC shows average number of retired instructions per cycle. Modern superscalar processors issue up to four instructions per cycle, suggesting a theoretical best IPC of 4. But various effects (long-latency memory, floating-point, or SIMD operations; non-retired instructions due to branch mispredictions; instruction starvation in the front-end) tend to pull the observed IPC down. A IPC of 1 is generally considered acceptable for HPC applications but different application domains will have very different expected values. Nonetheless, IPC is an excellent metric for judging an overall potential for application performance tuning.

The IPC may be too low. This could be caused by issues such as memory stalls, instruction starvation, branch misprediction or long latency instructions. Explore the other hardware-related metrics to identify what is causing low IPC.