Strange CPU clock discrepancy between host and guest


tpruszin

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Im lost with what else to try 

My VM's seem to be unable to run at the same Clock Speed as the host In VM's 

 

Unraid Host: $lscpu | grep MHz 

CPU MHz: 4300.040

 

Ubuntu Guest Q35 3.1 Lscpu | grep MHz 

CPU MHz: 3190.244

 

MacOS Guest Q35 3.1 MacCPUID

TSC Frequency 3,199,999 (Hz)

 

Windows 10 Guest PC-i440fx 3.1 CPUID

Core Speed 3192.00 MHz

 

Host is Intel i7-8700 Unraid 6.7.0 

 

All machines are using 

 <cpu mode='host-passthrough' check='none'>

with the exception of the extra -cpu flags for macOS 

 

virus capabilities shows host as Skylake-client-IBRS rather then CoffeeLake which is what happens if setting VM to mode=host-model

The VM also acknowledged both changes in the CPU architecture but clock speeds stay the same

 

Hopefully that's enough information for someone to help.

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@tpruszin Open a shell to unraid and run the following

watch grep \"cpu MHz\" /proc/cpuinfo

Now watch the cores you have assigned to the VM when you do some heavy load in the VM. In most cases you won't see the correct frequencies in the VM jumping up and down like on a real system. I have a Windows VM always reporting 4GHz no matter if idling or on heavy load, Aida and other software inside the VM reports 217MHz all the time. A Mint VM always reports 400MHz where on onraid itself you will see the exact frequencies jumping around depending on the load. Don't trust the numbers you see inside the VM.

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17 hours ago, bastl said:

@tpruszin Open a shell to unraid and run the following


watch grep \"cpu MHz\" /proc/cpuinfo

Now watch the cores you have assigned to the VM when you do some heavy load in the VM. In most cases you won't see the correct frequencies in the VM jumping up and down like on a real system. I have a Windows VM always reporting 4GHz no matter if idling or on heavy load, Aida and other software inside the VM reports 217MHz all the time. A Mint VM always reports 400MHz where on onraid itself you will see the exact frequencies jumping around depending on the load. Don't trust the numbers you see inside the VM.

Interesting thank you had to remove the \\ but UNRaid is showing the cores correctly but only with topology passed through without windows VM stuck and only shows 4 cores rather than 12 but the Host does still turbo boost and show all cores working when running benchmark in the guest 

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