Upstream has implemented the page tracking component through
WL#11082 InnoDB: Persistent page tracking: Service Interface.
some details about it in blogpost https://mysqlserverteam.com/innodb-clone-and-page-tracking/
Incremental backup can use this feature to efficiently find out the modified pages after
last full backup.
Implement a new option in xtrabackup --page-tracking
If enabled Xtrabackup will install mysqlbackup component and and set page tracking request to the running server during the first full backup.
During increment, PXB generates a map of all modified page after last backup using the page tracking component. this map would be used to copy only the modified pages after the last backup.