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areid2
New Contributor I
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Power management monitoring on KNL

Does anyone have experience monitoring the power management states on the KNL processors or know where the Linux kernel support is at for this? I'm working with a 7210 processor and noticed that the cpupower command (and data under /sys) is showing strange results. When the processor is under full load with 256 threads it is showing that the processor is in a CX state almost 100% of the time. For example here is the data for 4 CPUs, the other 252 are about the same:

    |Nehalem                    || Mperf              || Idle_Stats         
CPU | C3   | C6   | PC3  | PC6  || C0   | Cx   | Freq || POLL | C1   | C2   
   0| 99.49|  0.00|  0.00|  0.00||  0.09| 99.91|  1299||  0.00|  0.00|  0.00
  64| 100.1|  0.00|  0.00|  0.00||  0.09| 99.91|  1299||  0.00|  0.00|  0.00
 128| 100.8|  0.00|  0.00|  0.00||  0.09| 99.91|  1299||  0.00|  0.00|  0.00
 192| 102.1|  0.00|  0.00|  0.00||  0.09| 99.91|  1299||  0.00|  0.00|  0.00

The application seems to be performing well, so I'm not sure whether the driver is just returning bad data, or if I'm just interpreting it wrong. I believe this data is coming from the intel_pstate driver. The frequency data above seems reasonable since the base frequency for that chip is 1.3 GHz, but there is some other info that seems a bit suspect. cpupower says that boost state isn't supported, but the processor specs say it can boost to 1.5GHz.

I'd be interested if anyone knows whether the kernel is reading useful power management data from the KNL chips, or if that is in the works.

Adam

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