Most modern systems use Non-Uniform Memory Access (NUMA) design for multiprocessing. In NUMA systems, memory and processors are organized in such a way that for a given processor, some parts of memory are closer to it (that is, connected by a more direct path) while other parts are farther from it. A processor can access memory that is closer to it much faster than the memory that is farther from it. The latency between the processors and different portions of the memory in a NUMA machine might be significantly different.
The new numatop(1M) command is an observability tool for runtime memory locality characterization and analysis of processes and threads running on a NUMA system. This tool helps to characterize the NUMA behavior of processes and threads and to identify where the NUMA-related performance bottlenecks reside.