[$] The next steps for userfaultfd()
The userfaultfd() system call
allows user space to intervene in the handling of page faults. As Andrea
Arcangeli and Mike Rapaport described in a 2017 Linux Storage, Filesystem,
and Memory-Management Summit session dedicated to the subject,
userfaultfd() was originally created to help with the live
migration of virtual machines between physical hosts. It allows pages to
be copied to the new host on demand, after the machine itself has been
moved, leading to faster, more predictable migrations. Work on
userfaultfd() is not finished, though; there are a number of other
features that developers would like to add.