NUMACTL(8)              Linux Administrator's Manual              NUMACTL(8)

NAME         top

       numactl - Control NUMA policy for processes or shared memory

SYNOPSIS         top

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

DESCRIPTION         top

       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.

       Use -- before command if using command options that could be confused
       with numactl options.

       nodes may be specified as N,N,N or  N-N or N,N-N or  N-N,N-N and so
       forth.  Relative nodes may be specifed as +N,N,N or  +N-N or +N,N-N
       and so forth. The + indicates that the node numbers are relative to
       the process' set of allowed nodes in its current cpuset.  A !N-N
       notation indicates the inverse of N-N, in other words all nodes
       except N-N.  If used with + notation, specify !+N-N. When same is
       specified the previous nodemask specified on the command line is
       used.  all means all nodes in the current cpuset.

       Instead of a number a node can also be:

       netdev:DEV                 The node connected to network device DEV.
       file:PATH                  The node the block device of PATH.
       ip:HOST                    The node of the network device of HOST
       block:PATH                 The node of block device PATH
       pci:[seg:]bus:dev[:func]   The node of a PCI device.

       Note that block resolves the kernel block device names only for udev
       names in /dev use file:

       Policy settings are:

       --all, -a
              Unset default cpuset awareness, so user can use all possible
              CPUs/nodes for following policy settings.

       --interleave=nodes, -i nodes
              Set a 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.  Multiple
              nodes may be specified on --interleave, --membind and

       --membind=nodes, -m nodes
              Only allocate memory from nodes.  Allocation will fail when
              there is not enough memory available on these nodes.  nodes
              may be specified as noted above.

       --cpunodebind=nodes, -N nodes
              Only execute command on the CPUs of nodes.  Note that nodes
              may consist of multiple CPUs.  nodes may be specified as noted

       --physcpubind=cpus, -C cpus
              Only execute process on cpus.  This accepts cpu numbers as
              shown in the processor fields of /proc/cpuinfo, or relative
              cpus as in relative to the current cpuset.  You may specify
              "all", which means all cpus in the current cpuset.  Physical
              cpus may be specified as N,N,N or  N-N or N,N-N or  N-N,N-N
              and so forth.  Relative cpus may be specifed as +N,N,N or  +N-
              N or +N,N-N and so forth. The + indicates that the cpu numbers
              are relative to the process' set of allowed cpus in its
              current cpuset.  A !N-N notation indicates the inverse of N-N,
              in other words all cpus except N-N.  If used with + notation,
              specify !+N-N.

       --localalloc, -l
              Always allocate 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.  Relative notation may be used.

       --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, --preferred, --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

       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.

       Dump all nodes of the specific range (very verbose!)

       Valid node specifiers

       all                 All nodes
       number              Node number
       number1{,number2}   Node number1 and Node number2
       number1-number2     Nodes from number1 to number2
       ! nodes             Invert selection of the following specification.

EXAMPLES         top

       numactl --physcpubind=+0-4,8-12 myapplic arguments Run myapplic on
       cpus 0-4 and 8-12 of the current cpuset.

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

       numactl --cpunodebind=0 --membind=0,1 process Run process on node 0
       with memory allocated on node 0 and 1.

       numactl --cpunodebind=0 --membind=0,1 -- process -l Run process as
       above, but with an option (-l) that would be confused with a numactl

       numactl --cpunodebind=netdev:eth0 --membind=netdev:eth0 network-
       server Run network-server on the node of network device eth0 with its
       memory also in the same node.

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

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

       Place a tmpfs file on 2 nodes:
         numactl --membind=2 dd if=/dev/zero of=/dev/shm/A bs=1M count=1024
         numactl --membind=3 dd if=/dev/zero of=/dev/shm/A seek=1024 bs=1M

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

NOTES         top

       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

FILES         top

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

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

COPYRIGHT         top

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

SEE ALSO         top

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

COLOPHON         top

       This page is part of the numactl (NUMA commands) project.
       Information about the project can be found at 
       ⟨⟩.  If you have a bug report for
       this manual page, send it to  This page
       was obtained from the project's upstream Git repository
       ⟨⟩ on 2019-11-19.  (At that
       time, the date of the most recent commit that was found in the repos‐
       itory was 2019-11-11.)  If you discover any rendering problems in
       this HTML version of the page, or you believe there is a better or
       more up-to-date source for the page, or you have corrections or
       improvements to the information in this COLOPHON (which is not part
       of the original manual page), send a mail to

SuSE Labs                         Mar 2004                        NUMACTL(8)

Pages that refer to this page: get_mempolicy(2)mbind(2)sched_setaffinity(2)set_mempolicy(2)numa(3)numa_maps(5)cpuset(7)numa(7)migratepages(8)migspeed(8)numastat(8)