Memory counters at the Guest OS level
Memory rightsizing is best done with metrics from inside the Guest OS. You can use data from Linux or Windows for this. vRealize Operations 6.1 provides an agent that you can deploy on the Guest OS. We covered the deployment in this article: http://virtual-red-dot.info/vrealize-operations-6-1-end-point-operations/. With the agent, you can compare the data from inside the Guest and outside the Guest side by side.
We will cover Windows in this book as Windows memory management is not something that is well explained. Ed Bott sums it up the article at http://www.zdnet.com/article/windows-7-memory-usage-whats-the-best-way-to-measure/ by saying, "Windows memory management is rocket science." Like Ed has experienced, there is conflicting information, including that given by Microsoft. Mark Russinovich explains the situation in this TechNet post: https://blogs.technet.microsoft.com/markrussinovich/2008/11/17/pushing-the-limits-of-windows-virtual-memory...