Driver Locked Memory on Hyper-V Guests

When monitoring the available memory on your Hyper-V guests, you may come across a curious issue where the available memory on the VM seems low given the memory usage of the processes currently running.  For example, the guest may have 12GB of memory with running processing consuming less than 2GB; yet, Task Manger shows only 1GB of available memory!

Task Manager Guest Memory Usage

Diagnosing the apparent problem further with a tool like RAMMap from Sysinternals, shows a huge chunk of memory being "used" as Driver Locked.