[$] Solutions for direct-map fragmentation

The kernel's "direct map" makes the entirety of a system's physical memoryavailable in the kernel's virtual address space. Normally, huge pages are used forthis mapping, making it relatively efficient to access. Increasingly,though, there is a need to carve some pages out of the direct map; thissplits up those huge pages and makes the system as a whole less efficient.During a memory-management session at the 2022Linux Storage, Filesystem, Memory-management and BPF Summit (LSFMM),Mike Rapoport led a session on direct-map fragmentation and how it might beavoided.