Can the number of CPU cores be reduced for a CentOS virtual machine?

Will asked:

Our VMware admins tell me that we can add additional virtual CPU cores to our VM’s, but they tell me that we can’t reduce the number of virtual CPU cores.

One recently stated, “CPU on the other hand is a bigger problem because while you can add CPU cores, you cannot take them away once done.” After asking a few why’s, he stated, “To the CPU add / subtract problem, that is a limitation of pretty much all OS versions and has nothing to do with the VMware version.”

My question is, can we reduce the number of CPU cores for a CentOS 6.8 virtual machine without having to reinstall or reconfigure the OS.

Web searches have turned up very little for me. Most search results are about adding virtual CPU cores or disabling CPU’s within the OS.

My motivation… Sometimes, we run into performance issues with our VM’s (e.g. this one is running Jenkins) and we need to resolve our performance issues quickly. Asking for more VMware resources (at least temporarily) turns into a slow, painful process because the admins say that once they give it to us, they can’t take it back.

Thank you for any help you can provide!

My answer:

Reducing the number of CPU cores merely requires that the VM be stopped. It can’t be done while the VM is running. Perhaps that is what they meant? I suppose it’s also possible that they don’t know this…

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