CPUSET

cpuset is a Linux kernel mechanism used to partition processor resources and memory locality for groups of tasks. It is implemented as part of the cgroup subsystem and allows administrators to designate which CPUs a group of processes may run on and from which NUMA memory nodes memory allocations may come. This helps improve cache locality and performance in multi-processor and NUMA systems.

A cpuset forms a hierarchical set within the cgroup filesystem. Each cpuset has attributes such as the CPUs and memory nodes assigned to it, and a tasks file that lists the PIDs belonging to the set. New processes typically inherit the cpuset membership of their parent. Child cpusets can narrow or extend the available CPUs or memory nodes, providing finer control over resource placement within the system.

Usage and applications include isolation and performance optimization for workloads. cpuset is commonly used by container runtimes and orchestration tools to bind containers or services to specific CPUs and NUMA nodes, reducing interference between workloads and improving locality. It can also be used to separate foreground work from background daemons or to enforce scheduling locality in NUMA-aware environments.

Notes and limitations: cpuset primarily controls where a task may execute and from which memory nodes it may allocate memory; it does not by itself enforce hard memory usage quotas. Operating on cpusets typically requires elevated privileges, such as root or appropriate capabilities. In modern systems, cpuset interacts with other cgroup controllers, and its interface appears in the cgroup hierarchy under sysfs, with exact paths depending on the system’s cgroup configuration.