Say you're minding your own business and you discover that
this process called
vmmem is using up all your
memory and CPU.
What is this guy and how do you make him stop?
vmmem process is a virtual process that
the system synthesizes to represent the memory and CPU resources
consumed by your virtual machines.
In other words,
if you see
vmmem consuming a lot of memory and CPU resources,
then that means your virtual machines are consuming
a lot of memory and CPU resources.
If you want to make it stop, shut down your virtual machines.
Bonus chatter: Strictly speaking, what it actually represents is the resources of the other virtual machines, since Windows itself is running in a virtual machine under the hypervisor. You may not be explicitly using the hypervisor, but some other features are built on top of the hypervisor.