What does the API "getSystemConsumedEnergy" get?

[baihe-liu]

I'm trying to use pcm API to get energy consumption, my platform is Tiger Lake.
Could you please tell me what does system consumed energy means in the function "getSystemConsumedEnergy"?

template <class CounterStateType>
uint64 getSystemConsumedEnergy(const CounterStateType& before, const CounterStateType& after)
{
    return after.systemEnergyStatus - before.systemEnergyStatus;
}

I found SystemCounterState.systemEnergyStatus will only be updated by reading from MSR in function PCM::getALLCounterStates
And I got different result using SystemCounterState from 'getSystemCounterState' and 'getALLCounterStates'

================== Energy Consumption by getSystemCounterState  ==================  
[Energy_Monitor] getConsumedJoules: 14.5959 Joules
[Energy_Monitor] getConsumedJoules(0): 10.5076 Joules
[Energy_Monitor] getConsumedJoules(1): 0.000549316 Joules
[Energy_Monitor] getDRAMConsumedJoules: 0 Joules
[Energy_Monitor] getSystemConsumedJoules: 0 Joules
================== Energy Consumption by getALLCounterStates  ==================
[Energy_Monitor] getConsumedJoules: 14.5959 Joules
[Energy_Monitor] getConsumedJoules(0): 0 Joules
[Energy_Monitor] getConsumedJoules(1): 0 Joules
[Energy_Monitor] getDRAMConsumedJoules: 0 Joules
[Energy_Monitor] getSystemConsumedJoules: 7.3775 Joules

The system consumed joules is less that package consumed joules, what does the system consist of?
Thank you.

[rdementi]

Hi,

the value the system energy metric is retrieved from the MSR_PLATFORM_ENERGY_COUNTER register (Intel Software Developer Manual www.intel.com/sdm):

Platform vendor and BIOS communicate the system energy value to the CPU MSR register. Could you please also share the output of pcm utility? Here is a sample output from an HP laptop (the platform and BIOS vendor is HP):

The metrics of interest are "SYS energy", "CPU energy", "PP0 energy" and "PP1 energy"

[rdementi]

I checked that the "SYS energy" PCM value on my HP laptop is close to the power meter reading at the wall.