libnuma

libnuma is a userspace library for Linux that provides NUMA (non-uniform memory access) awareness to applications. It offers a C API that enables programs to discover the system's NUMA topology and to control memory allocation and thread or process placement with respect to NUMA nodes. libnuma is commonly used as part of the numactl package to improve locality and performance on systems with multiple memory nodes.

Key capabilities include querying the NUMA topology, allocating memory on specific nodes, and applying memory policies to execution contexts. Applications can allocate memory on a particular node, allocate memory interleaved across several nodes, or allocate without node constraints. The library supports setting and querying memory binding policies such as bind, interleave, preferred, and default, and it provides mechanisms to bind or migrate execution to a set of nodes as needed.

Internally, libnuma relies on the kernel-provided NUMA topology and uses representations such as node bitmasks to describe allowed or preferred node sets. It exposes functions to retrieve the allowed memory nodes for the current thread, to bind memory policy for memory regions, and to free memory when it is no longer needed. The API is designed for performance-critical applications, including databases and high-performance computing workloads that benefit from memory locality.

Platform and usage notes: libnuma runs on Linux on NUMA-enabled architectures and is distributed with the NUMA support tools. It is widely used by applications that require explicit control over memory placement and policy to optimize latency and bandwidth characteristics.