1. A computer readable storage device, comprising: instructions for receiving notifications from within a guest operating system and configured to monitor activities of a guest operating system of a virtual machine, to determine an amount of guest physical addresses associated with the guest operating system, and to trigger the notifications, the virtual machine comprising the memory manager, the guest operating system of the virtual machine executing the memory manager to monitor the activities from within the guest operating system, determine the amount of guest physical addresses from within the guest operating system, and trigger the notifications from within the guest operating system, each notification from the notifications being triggered based on a comparison of the determined amount of guest physical addresses and a predefined amount; instructions for determining a memory status from the values associated with the triggered notifications, the memory status indicating a memory pressure in the memory assigned to the guest operating system; and instructions for adjusting, based on the determined memory status, the amount of guest physical addresses determined by the memory manager.