[$] A herd of migration discussions

Migration is the act of moving data from one location in physical
memory to another. The kernel may migrate pages for many reasons,
including defragmentation, improving NUMA locality, moving data to or from
memory hosted on a peripheral device, or freeing a range of
memory for other uses. Given the importance of migration to the
memory-management subsystem, there is a lot of interest in improving its
performance and removing impediments to its success. Several sessions in
the memory-management track of the 2025 Linux Storage, Filesystem,
Memory-Management, and BPF Summit were dedicated to this topic.