I am running some virtual machines with Oracle Virtualbox 4.3.10, and they have guest additions installed. I know that you can manually balloon (take away unused memory from the guest) RAM with
VBoxManage controlvm "[VM name]" guestmemoryballoon [amount in MB]
I heard there is a way to automatically do the ballooning with VBoxBalloonCtrl.exe. But what are the command-line options for it, and what does each one do? The official documentation is not clear.