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Logical and physical cores on virtual machine CPU

asked 2014-12-07 23:32:48 -0600

I noticed in virt-manager that VM can get up to 16 logical cores. But I noticed that after installation of Windows 7 in computer properties always 2 physical cores. I realize this is newbie question but can anybody provide piece of documentationthat explains how numbers of VCPU in Horizon dashboard and logical cores and hardware core are related to each other?

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answered 2014-12-08 04:33:32 -0600

Prateek K gravatar image


Cores are something which is related to Hypervisor being used in the openstack setup. If you are using a bare-metal hypervisor such as esxi or KVM(almost bare-metal) then the number of cores the hypervisor gets is equal to the number of cores the physical CPU has( can be checked via command "cat /proc/cpuinfo").

Now the flavor which is used to spawn a Virtual Machine contains a attribute CPU CORES. The number of cores given there in the flavor will be equal to the number of cores given to the Virtual machine.

In case of emulated hypervisors such as qemu, It is not matter of how much cores you give or how much core VM shows as it is all emulated and the VM is running under user-space(i.e just as a simple process )


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Thanks. You explained me emulated cores and I think logical cores (16 available in virt-manager per machine) are the same in user-space.

szemtsov gravatar imageszemtsov ( 2014-12-08 20:39:13 -0600 )edit

yes ... for better view check how much cores your physical CPU is having and which hypervisor is being used

Prateek K gravatar imagePrateek K ( 2014-12-08 22:54:32 -0600 )edit

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Asked: 2014-12-07 23:32:48 -0600

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Last updated: Dec 07 '14