Calculating the amount of vCPUs inside a Xeon based machine.

[gpiepenb]

In side my company there is some confusion about how to calculate the amount of vCPUs inside a Xeon based server. Hopefully you can confirm that my calculations are right. The processor specs form Intel:

Processor: Xeon(R) CPU E5-2680 v2 @ 2.80GHz

# of Cores: 10

# of Threads 20 (= 2 hyper threads/core, right?)

Server related info:

Hyper Threading enabled: True

# Sockets: 2

----------------------------------------------------------------------------

# vCPUs = (# Sockets)*(# of Cores)*(# of hyper threads/core)

# vCPUs = 2 * 10 * 2 = 40 (right?)

And can it always being said that the amount of hyper threads/core can be calculated from the Intel processor specs by:

(# of Threads)/(# of Cores)

So in this case 2. Just out of curiosity is the number of hyper threads/core always 2 or can this be more?

Looking forward to the answer.

Kind regards,

Gerard Piepenbrink.

[Emeth_O_Intel]

Hello,

Thank you for contacting Intel Xeon Community Support.

I would like to clarify that Hyper-Threading does not give you extra cores, it just abstracts task switching away from the operating system and does it on-chip. This gives the appearance of multiple threads to the operating system so that it can allocate tasks based on thread requirements, but this does not double the capabilities of that core. It just speeds up certain tasks.

Before providing you more details about the numbers of vCPUs of your processor and how to calculate them, I would like to ask you which hypervisor are you going to use in order to virtualize and perform this configuration?

For instance, VMWare ESXi is hyperthreading aware, so it knows which "cores" are hyperthreading cores and which are "real". So forget about hyperthreading. Also, it is important to mention that there is a limitation in the assignation of vCPU which is related to the license of the vSphere you are using.

As an addition, I would like to share with you the following link:

• Virtual CPU Configuration

I will be waiting for your outcome in order to proceed with the next step.

Best regards,

Emeth O.

Intel Server Specialist.

[gpiepenb]

Hi Emeth,

Thanks you for the quick response!

Ok, clear, hyper treading does not increase the amount of cores, but does it increase the amount of vCPUs?

Interesting the statement you gave, to forget about hyper threading. I hope this will take away some of the confusion then.

The server will be deployed as a vSphere ESX host, the virtualization will be performed by a type I hypervisor.

Hopefully this provides you with necessary information you asked.

Thanks for pointing out that there are limitations regarding assignation of vCPUs. I'll take a close look into the current licensing.

The link clarifies some of the common terms, I'll share this information with my colleagues.

Kind regards,

Gerard Piepenbrink

[Emeth_O_Intel]

Hello Gerard,

No problem, I am glad to help you out with this information.

Correct, I was doing some researches and I found that Hyper-Threading does not give you extra cores.

So, this feature will not increase the total amount of vCPUs on your VMware ESXi.

If you do not mind Gerald, I would like to do more research about the formula you provided to me in order to verify if there is a specific calculation in order to get the total amount of vCPU using the hypervisor VMware ESXi.

As soon as I will have more information about those details, I will be contacting you back in order to provide you the most accurate information about this.

Best regards,

Emeth O.

Intel Server Specialist.

[gpiepenb]

Hello Emeth,

Thanks for the reply!

Comming back to me with information about the specific calculation, would be very appreciated. In the end that's what this call is all about!

Looking forward for this information soon, and thank you for your assistence so far.

Kind regards,

Gerard Piepenbrink

[Emeth_O_Intel]

Hello Gerard,

We do not provide a calculation since this depends on the hypervisor being used the provisioning and "over-commitment" capabilities of the hypervisor itself. You would need to get in touch with the hypervisor vendor to see if they have a document where it would state what calculation they can do. There is another factor that needs to take into account which is workload. This is why it is best to have the hypervisor vendor to provide a more accurate calculation of this.

Also, I was doing some research and I found the following article:

https://www.intel.com/content/www/us/en/support/articles/000036898/processors/intel-xeon-processors.html

Please verify this information with VMware in order to get more details about the information you are looking for.

Have a wonderful day.

Best regards,

Emeth O.

[gpiepenb]

Hello Emeth,

I guess it's not as straight forward as I originally anticipated, I'll will take a look at the links you provided, hopefully they can help me to get to definite answer to my question.

I really appreciate your effort to help me to come this far..

You can close call.

Kind regards,

Gerard Piepenbrink