- Before adding any CPU's, check for contention%, co-stop, and ready times. If they are excessive (you can share if you want an assessment), then adding vCPU's will only make things worse.
- Since you are account for spikes and peaks (as well you should), how regular are the spikes above 18GHz (20GHz - 2GHz buffer). I see the average is 15GHz, which is within your limits.
- Can you also share the a screenshot of the Stress badge for this VM?
- What is the cores per socket count of the host on which this VM resides?
Once we have these things, I can help you make a judgment call.
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