NAME

       migrate_pages - move all pages in a process to another set of nodes

LIBRARY

       NUMA (Non-Uniform Memory Access) policy library (libnuma, -lnuma)

SYNOPSIS

       #include <numaif.h>

       long migrate_pages(int pid, unsigned long maxnode,
                          const unsigned long *old_nodes,
                          const unsigned long *new_nodes);

DESCRIPTION

       migrate_pages()  attempts  to  move  all pages of the process pid that are in memory nodes
       old_nodes to the memory nodes in new_nodes.  Pages not located in any  node  in  old_nodes
       will  not  be  migrated.   As  far as possible, the kernel maintains the relative topology
       relationship inside old_nodes during the migration to new_nodes.

       The old_nodes and new_nodes arguments are pointers to bit masks of node numbers,  with  up
       to  maxnode  bits  in  each  mask.   These masks are maintained as arrays of unsigned long
       integers (in the last long integer,  the  bits  beyond  those  specified  by  maxnode  are
       ignored).   The maxnode argument is the maximum node number in the bit mask plus one (this
       is the same as in mbind(2), but different from select(2)).

       The pid argument is the ID of the process whose pages are to be moved.  To move  pages  in
       another  process,  the  caller  must be privileged (CAP_SYS_NICE) or the real or effective
       user ID of the calling process must match the real or saved-set  user  ID  of  the  target
       process.  If pid is 0, then migrate_pages() moves pages of the calling process.

       Pages  shared  with  another  process will be moved only if the initiating process has the
       CAP_SYS_NICE privilege.

RETURN VALUE

       On success migrate_pages() returns the number of pages that could not be  moved  (i.e.,  a
       return  of  zero  means that all pages were successfully moved).  On error, it returns -1,
       and sets errno to indicate the error.

ERRORS

       EFAULT Part or all of the memory range specified by old_nodes/new_nodes and maxnode points
              outside your accessible address space.

       EINVAL The  value  specified  by maxnode exceeds a kernel-imposed limit.  Or, old_nodes or
              new_nodes specifies one or  more  node  IDs  that  are  greater  than  the  maximum
              supported node ID.  Or, none of the node IDs specified by new_nodes are on-line and
              allowed by the process's current cpuset context, or none  of  the  specified  nodes
              contain memory.

       EPERM  Insufficient  privilege  (CAP_SYS_NICE)  to  move pages of the process specified by
              pid, or insufficient privilege (CAP_SYS_NICE) to access the specified target nodes.

       ESRCH  No process matching pid could be found.

STANDARDS

       Linux.

HISTORY

       Linux 2.6.16.

NOTES

       For information on library support, see numa(7).

       Use get_mempolicy(2) with the MPOL_F_MEMS_ALLOWED flag to obtain the set of nodes that are
       allowed  by the calling process's cpuset.  Note that this information is subject to change
       at any time by manual or automatic reconfiguration of the cpuset.

       Use of migrate_pages() may result in pages  whose  location  (node)  violates  the  memory
       policy established for the specified addresses (see mbind(2)) and/or the specified process
       (see set_mempolicy(2)).  That is, memory policy does not constrain the  destination  nodes
       used by migrate_pages().

       The <numaif.h> header is not included with glibc, but requires installing libnuma-devel or
       a similar package.

SEE ALSO

       get_mempolicy(2), mbind(2), set_mempolicy(2), numa(3), numa_maps(5),  cpuset(7),  numa(7),
       migratepages(8), numastat(8)

       Documentation/vm/page_migration.rst in the Linux kernel source tree