[$] NUMA policy and memory types

Non-uniform memory access (NUMA) systems have an architecture that attachesmemory to "nodes" within the system. CPUs, too, belong to nodes; memorythat is attached to the same node as a CPU will be faster to access (fromthat CPU) than memory on other nodes. This aspect of performance hasimportant implications for programs running on NUMA systems, and the kerneloffers a number of ways for user space to optimize their behavior. The NUMAabstraction is now being extended, though, and that is driving a need fornew ways of influencing memory allocation; the multi-preferencememory policy patch set is an attempt to meet that need.