numactl − Control NUMA policy for processes or shared memory


numactl [ −−interleave nodes ] [ −−preferred node ] [ −−membind nodes ] [ −−cpunodebind nodes ] [ −−physcpubind cpus ] [ −−localalloc ] command {arguments ...}
numactl −−show
numactl −−hardware
[ −−huge ] [ −−offset offset ] [ −−shmmode shmmode ] [ −−length length ] [ −−strict ]
[ −−shmid id ] −−shm shmkeyfile | −−file tmpfsfile
[ −−touch ] [ −−dump ] memory policy


numactl runs processes with a specific NUMA scheduling or memory placement policy. The policy is set for command and inherited by all of its children. In addition it can set persistent policy for shared memory segments or files.

Policy settings are:

−−interleave=nodes, −i nodes

Set an memory interleave policy. Memory will be allocated using round robin on nodes. When memory cannot be allocated on the current interleave target fall back to other nodes.

−−membind=nodes, −m nodes

Only allocate memory from nodes. Allocation will fail when there is not enough memory available on these nodes.

−−cpunodebind=nodes, −N nodes

Only execute process on the CPUs of nodes. Note that nodes may consist of multiple CPUs.

−−physcpubind=cpus, −C cpus

Only execute process on cpus. This accepts physical cpu numbers as shown in the processor fields of /proc/cpuinfo.

−−localalloc, −l

Do always local allocation on the current node.


Preferably allocate memory on node, but if memory cannot be allocated there fall back to other nodes. This option takes only a single node number.

−−show, −s

Show NUMA policy settings of the current process.

−−hardware, −H

Show inventory of available nodes on the system.

Numactl can set up policy for a SYSV shared memory segment or a file in shmfs/hugetlbfs.

This policy is persistent and will be used by all mappings from that shared memory. The order of options matters here. The specification must at least include either of −−shm, −−shmid, −−file to specify the shared memory segment or file and a memory policy like described above ( −−interleave, −−localalloc, −−prefered, −−membind ).


When creating a SYSV shared memory segment use huge pages. Only valid before −−shmid or −−shm


Specify offset into the shared memory segment. Default 0. Valid units are m (for MB), g (for GB), k (for KB), otherwise it specifies bytes.


Give an error when a page in the policied area in the shared memory segment already was faulted in with a conflicting policy. Default is to silently ignore this.

−−shmmode shmmode

Only valid before −−shmid or −−shm When creating a shared memory segment set it to numeric mode shmmode.

−−length length

Apply policy to length range in the shared memory segment or make the segment length long Default is to use the remaining length Required when a shared memory segment is created and specifies the length of the new segment then. Valid units are m (for MB), g (for GB), k (for KB), otherwise it specifies bytes.

−−shmid id

Create or use an shared memory segment with numeric ID id

−−shm shmkeyfile

Create or use an shared memory segment, with the ID generated using ftok(3) from shmkeyfile

−−file tmpfsfile

Set policy for a file in tmpfs or hugetlbfs


Touch pages to enforce policy early. Default is to not touch them, the policy is applied when an applications maps and accesses a page.


Dump policy in the specified range.

Valid node specifiers


numactl −−interleave=all bigdatabase arguments Run big database with its memory interleaved on all CPUs.

numactl −−cpubind=0−−membind=0,1 process Run process on node 0 with memory allocated on node 0 and 1.

numactl −−preferred=1 numactl −−show Set preferred node 1 and show the resulting state.

numactl --interleave=all --shmkeyfile /tmp/shmkey Interleave all of the sysv shared memory regiion specified by /tmp/shmkey over all nodes.

numactl --offset=1G --length=1G --membind=1 --file /dev/shm/A --touch Bind the second gigabyte in the tmpfs file /dev/shm/A to node 1.

numactl --localalloc /dev/shm/file Reset the policy for the shared memory file file to the default localalloc policy.


Requires an NUMA policy aware kernel.

Command is not executed using a shell. If you want to use shell metacharacters in the child use sh -c as wrapper.

Setting policy for a hugetlbfs file does currently not work because it cannot be extended by truncate.

Shared memory segments larger than numactl’s address space cannot be completely policied. This could be a problem on 32bit architectures. Changing it piece by piece may work.

The old --cpubind which accepts node numbers, not cpu numbers, is deprecated and replaced with the new --cpunodebind and --physcpubind options.


/proc/cpuinfo for the listing of active CPUs. See proc(5) for details.

/sys/devices/system/node/node*/numastat for NUMA memory hit statistics.


Copyright 2002,2004 Andi Kleen, SuSE Labs. numactl and the demo programs are under the GNU General Public License, v.2


set_mempolicy(2) , get_mempolicy(2) , mbind(2) , sched_setaffinity(2) , sched_getaffinity(2) , proc(5) , ftok(3) , shmat(2) , migratepages(8)