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Re: VM Guest CPU/Core etc. Question

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Hi,

 

Performance is good. Look in your task manager of your windows machine and see how much CPU you normally use and how many cores.

You do not often run out of CPU and hardly ever more as a single core is being used.

Look at it this way, your host is scheduling the CPUs, your guest can use what is free.

 

To give a small example:

In the hypothetical case that your host is using 5 cores and your guest is configured for 4 cores then .. something is going to be slow, most likely all of them.

Now imagine having 2 guests with 4 cores and your host wants to use a core too...

 

This is a layman example as in that it isn't exactly how it works, depending on multiple factors the CPU scheduler and hypervisor can make smart decisions on how-to schedule the CPU, but it does paint the picture a bit.

Especially it highlights that it is more difficult for the hypervisor and CPU scheduler to schedule the CPU for a VM with 4 cores as it is for a VM with 2 cores.

VMs will end up waiting on each other and not be able to do anything even if there are 3 cores available.

 

So yes a VM with 4 cores might be able to use more CPU, but the more likely scenario is that you are adding extra lag.

 

Most VMs will not actually be able to use the more cores as normal desktop software isn't optimized for multi-core use.

Exceptions to that are things like SQL Server and Oracle, they actually know how-to use multiple cores.

So yes for them it might make sense to use 2 cores (I sure do)

Other examples are video rendering, that also is a process capable of using multiple cores at once.

 

--
Wil


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