The numa block is used to configure how Nomad will assign CPU cores for a task while taking the NUMA hardware topology of a node into consideration. Workloads that are sensitive to memory latency can perform significantly better when pinned to CPU cores on the same NUMA node.

job "example" {  group "group" {    task "task" {      resources {        cores = 8        numa {          affinity = "require"        }      }    }  }}

In the example above, the task is requesting Nomad to reserve 8 CPU cores, all of which must be colocated on the same hardware NUMA node. The Nomad scheduler will ensure the task is placed on a Nomad node with sufficient unused CPU cores in a compatible configuration.

Configuring the numa block requires the task specifies CPU resources using the cores parameter.

numa Parameters

• affinity (string: "none") - Specifies the strategy Nomad will use when selecting CPU cores to assign to a task. Possible values are "none", "prefer", or "require".
  • none - Nomad is free to allocate CPU cores using any strategy. Nomad uses this freedom to allocate cores in such a way that minimizes the amount of fragmentation of core availability per NUMA node. It does so by bin-packing the chosen cores onto the NUMA nodes with the fewest number of cores available.
  • prefer - Nomad will select the set of CPU cores on a node that minimizes the total distance between those cores, but does not limit those CPU core selections to come from a single NUMA node.
  • require - Nomad will select a set of CPU cores that are strictly colocated on the same hardware NUMA node. If there are no Nomad nodes with a sufficient number of available cores in a compatible configuration, task placement will fail due to exhausted resources.