Systems and techniques are described for optimizing memory sharing. A described technique includes grouping virtual machines (VMs) into groups including a first group; initializing a first VM in the first group, wherein initializing the first VM includes identifying, for each of one or more first memory pages for the first VM, a respective base address for storing the first memory page using an address randomization technique, and storing, for each of the one or more first memory pages, data associating the first memory page with the respective base address for the first group, and initializing a second VM while the first VM is active, wherein initializing the second VM includes determining that the second VM is a member of the first group, and in response, storing one or more second memory pages for the second VM using the respective base addresses stored for the first group.