Tutorial/git's guide to c-state counters on Intel?

I am presently trying to tease-out why a "slight" change in kernel (4.4.7 to 4.4.11) might result in a large change in some VM to VM netperf TCP_RR performance. I've seen that if I set the system firmware to be in a static high performance mode rather than a dynamic power management (by the firmware) mode the gap narrows considerably.

I've come across:

  cstate_core/c3-residency/                          [Kernel PMU event]
  cstate_core/c6-residency/                          [Kernel PMU event]
  cstate_core/c7-residency/                          [Kernel PMU event]
  cstate_pkg/c2-residency/                           [Kernel PMU event]
  cstate_pkg/c3-residency/                           [Kernel PMU event]
  cstate_pkg/c6-residency/                           [Kernel PMU event]
  cstate_pkg/c7-residency/                           [Kernel PMU event]

and when I count those via perf comparing the two, back in the dynamic power managment mode, I can see more package c* residency on the slower setup (newer kernel). That fits with the hypothesis that the slower request/response performance is coming from going into and out of sleep states more - something which has been known to affect the likes of a netperf TCP_RR test for years. I don't see nearly as large a difference between the core c* counts though, which leaves me wondering why/how that might be.

The processors in question here are E5-2640:

model name : Intel(R) Xeon(R) CPU E5-2640 0 @ 2.50GHz

happy benchmarking,

rick jones