How does Hyper-V manage the core allocation with an Intel i9-13900(k)?

Question

Hi, I'm planning to build a new PC where I have to run multiple virtual machines at the same time.

I was thinking to use an i9-13900 (k or not) because of its 24 cores but I just realized that it has Performance Cores and Efficiency Cores so how does HyperV manage the core allocation with such architecture?

And another thing about the core allocation that I didn't understand very well is if I can allocate to a virtual machine only up to the maximum number of cores of the CPU, for example I actually have a CPU with 4 cores and 8 threads so I can allocate up to 4 cores or can I go beyond 4 until I reach 8 because it has 8 threads?

Thanks for the help.

Answer 1

Hello there,

A virtual machine’s vCPU count means the maximum number of threads that the VM can run at any given moment.

Generally, it's recommended to set 8 vCPUs per 1 physical core.

This article describes Hyper-V resource and isolation controls for virtual machines. These capabilities, which we'll refer to as Virtual Machine CPU Groups, or just "CPU groups", were introduced in Windows Server 2016. https://learn.microsoft.com/en-us/windows-server/virtualization/hyper-v/manage/manage-hyper-v-cpugroups

Hope this resolves your Query !!

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Answer 2

You can over-allocate up to a point. Read on here.

https://www.altaro.com/hyper-v/hyper-v-virtual-cpus-explained/

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Answer 3

If you try to allocate more cores than the host has you'll get something like below when you try to start it up.

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