1. One or more non-transitory computer-readable storage mediums storing one or more sequences of instructions, which when executed by one or more processors, cause: upon instantiating a particular virtual machine in which executes a guest operating system, causing one or more memory pages within a guest physical frame of the particular virtual machine to become unlikely or ineligible for selection as a candidate for eviction by the guest operating system by updating data structures maintained within the guest operating system to indicate that the one or more memory pages are a permanent part of a working set, wherein said working set is a static set of memory pages associated with a template used to instantiate said particular virtual machine, and wherein said one or more memory pages are currently shared or are intended to be shared with a different guest physical frame only accessible by a different operating system instance than said guest operating system.