[$] NUMA nodes for persistent-memory management

While persistent memory is normally valued for its persistence, there isalso a subcurrent of interest in using it in settings where persistence isnot important. In particular, the fact that this memory is relativelyinexpensive makes it appealing to use instead of ordinary RAM inbudget-conscious settings. At the 2019 Linux Storage, Filesystem, andMemory-Management Summit, two sessions in the memory-management tracklooked at how the kernel's NUMA mechanism could be pressed into service tomanage non-persistent uses of persistent memory.