[$] Improving access to physically contiguous memory

For years, kernel developers have been told to avoid allocating large chunks of
physically contiguous memory; as the system runs and memory becomes
fragmented, satisfying such allocations becomes increasingly difficult.
But, as Zi Yan pointed out in a memory-management track session at the 2019
Linux Storage, Filesystem, and Memory-Management Summit, there are times
when contiguous memory is useful. In this session, the memory-management
developers discussed ways to make such allocations more likely to succeed.