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Identical memory pages can exist when multiple VMs run the same operating system. The hypervisor discovers redundancies by assigning hash values to pages and comparing them bit-by-bit when hash values match.
If the hypervisor identifies identical memory pages on multiple virtual machines (VMs) on a host, it shares them among virtual machines (VMs) with pointers. This frees up memory for new pages. If a VM's information on that shared page changes, the hypervisor writes the memory to a new page and readdresses a pointer.
Transparent page sharing is not available for large memory pages. Typically, only small memory pages are identical.