[edit] sorry, I've mistaken the concepts. The name is active memory deduplication, which sits on top on memory sharing.
http://www.redbooks.ibm.com/redpapers/pdfs/redp4827.pdf
[old]
It is called active memory sharing in the POWER world
https://www.ibm.com/docs/en/power9/9080-M9S?topic=sharing-ma...