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Unequal CPU-usage across all cores

Question asked by StefanKlotz on Feb 7, 2019
Latest reply on Apr 2, 2019 by StefanKlotz

When using the "top"-command and then pressing "1" you can see the CPU-usage of each individual CPU core.
We see the following result:
top - 17:11:31 up 6 days, 18:02,  1 user,  load average: 2.80, 4.14, 4.48
Tasks: 299 total,   1 running, 298 sleeping,   0 stopped,   0 zombie
Cpu0  : 80.0%us,  1.7%sy,  0.0%ni,  9.7%id,  0.0%wa,  0.0%hi,  8.7%si,  0.0%st
Cpu1  : 37.5%us, 12.6%sy,  0.0%ni, 49.2%id,  0.3%wa,  0.0%hi,  0.3%si,  0.0%st
Cpu2  : 39.9%us,  1.3%sy,  0.0%ni, 58.8%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu3  : 41.3%us,  2.0%sy,  0.0%ni, 56.0%id,  0.7%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu4  : 34.8%us,  1.3%sy,  0.0%ni, 63.5%id,  0.3%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu5  : 36.7%us,  1.7%sy,  0.0%ni, 61.3%id,  0.0%wa,  0.0%hi,  0.3%si,  0.0%st
Cpu6  : 37.2%us,  3.3%sy,  0.0%ni, 59.1%id,  0.3%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu7  : 40.7%us,  6.0%sy,  0.0%ni, 50.3%id,  3.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu8  : 32.1%us,  3.6%sy,  0.0%ni, 63.6%id,  0.3%wa,  0.0%hi,  0.3%si,  0.0%st
Cpu9  : 30.8%us,  9.4%sy,  0.0%ni, 59.9%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu10 : 40.3%us,  1.7%sy,  0.0%ni, 58.1%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu11 : 27.7%us,  4.7%sy,  0.0%ni, 67.7%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st


As you can see, we have currently 12 cores assigned to this VM, but the first core has a much higher load than all other cores.
The remaining 11 cores are using approx. the same load, so that's fine.
So what's the reason, why the first core has that much more load?
Is this some OS or administrative overhead?
Is this related to the ESX configuration and if yes, how can this be optimized?
Are there any commands or configurations we should check to get further details here?
What is this "si"-value? This is between 7-11% just for the first CPU.
Thank you!


Ciao Stefan