Millicores

Millicore, or millicores, is a unit of CPU resource measurement used in modern container orchestration platforms. One millicore equals one thousandth of a single CPU core, i.e., 0.001 CPU. The term is commonly used in Kubernetes and similar systems to express CPU requests and limits for containers in a fine-grained way. In Kubernetes manifests, CPU resources are specified in cores, with the suffix m indicating millicores. For example, 1000m equals 1 core; 500m is 0.5 core; 250m is 0.25 core.

When scheduling, the Kubernetes scheduler considers requests.cpu to decide which node can accommodate a pod. At runtime, the container runtime enforces limits.cpu through the Linux cgroups mechanism, throttling the container if it attempts to exceed its limit. If no limit is set, a container may use more CPU up to the node's total capacity, potentially affecting other workloads.

Millicores are a scheduling abstraction and do not guarantee a fixed amount of wall-clock time; actual performance depends on many factors including CPU contention, I/O, and system load. The concept is distinct from CPUs expressed in hardware cores, which are fixed; millicores are a relative unit for allocation and accounting in multi-tenant environments.

Usage considerations include ensuring requests reflect anticipated workloads, while limits protect other workloads and enable predictable fairness; some platforms also support burstable configurations or overcommitting policies.