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NAME

       move_pages - move individual pages of a process to another node

SYNOPSIS

       #include <numaif.h>

       long move_pages(int pid, unsigned long count, void **pages,
                       const int *nodes, int *status, int flags);

DESCRIPTION

       move_pages() moves the specified pages of the process pid to the memory
       nodes specified by nodes.  The result  of  the  move  is  reflected  in
       status.  The flags indicate constraints on the pages to be moved.

       pid  is  the ID of the process in which 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
       move_pages() moves pages of the calling process.

       count is the number of pages to move.  It defines the size of the three
       arrays pages, nodes, and status.

       pages is an array of pointers to the pages that should be moved.  These
       are  pointers that should be aligned to page boundaries.  Addresses are
       specified as seen by the process specified by pid.

       nodes is an array of integers that specify  the  desired  location  for
       each page.  Each element in the array is a node number.  nodes can also
       be NULL, in which case move_pages() does not move any pages but instead
       will  return  the node where each page currently resides, in the status
       array.  Obtaining the status of each page may be necessary to determine
       pages that need to be moved.

       status  is  an  array  of integers that return the status of each page.
       The array only contains valid values if move_pages() did not return  an
       error.

       flags  specify  what  types  of pages to move.  MPOL_MF_MOVE means that
       only pages that are in exclusive use by the process are  to  be  moved.
       MPOL_MF_MOVE_ALL means that pages shared between multiple processes can
       also be moved.  The process must be privileged  (CAP_SYS_NICE)  to  use
       MPOL_MF_MOVE_ALL.

Page states in the status array

       The  following  values  can  be  returned in each element of the status
       array.

       0..MAX_NUMNODES
              Identifies the node on which the page resides.

       -EACCES
              The page is mapped by multiple processes and can only  be  moved
              if MPOL_MF_MOVE_ALL is specified.

       -EBUSY The  page  is  currently  busy  and  cannot be moved.  Try again
              later.  This occurs if a  page  is  undergoing  I/O  or  another
              kernel subsystem is holding a reference to the page.

       -EFAULT
              This  is  a  zero  page  or the memory area is not mapped by the
              process.

       -EIO   Unable to write back a page.  The page has to be written back in
              order  to  move  it  since the page is dirty and the file system
              does not provide a migration function that would allow the  move
              of dirty pages.

       -EINVAL
              A  dirty page cannot be moved.  The file system does not provide
              a migration function and has no ability to write back pages.

       -ENOENT
              The page is not present.

       -ENOMEM
              Unable to allocate memory on target node.

RETURN VALUE

       On success move_pages() returns zero.  On error,  it  returns  -1,  and
       sets errno to indicate the error.

ERRORS

       E2BIG  Too many pages to move.

       EACCES One of the target nodes is not allowed by the current cpuset.

       EFAULT Parameter array could not be accessed.

       EINVAL Flags other than MPOL_MF_MOVE and MPOL_MF_MOVE_ALL was specified
              or an attempt was made to migrate pages of a kernel thread.

       ENODEV One of the target nodes is not online.

       ENOENT No pages were found that require moving.  All pages  are  either
              already  on the target node, not present, had an invalid address
              or could not be moved  because  they  were  mapped  by  multiple
              processes.

       EPERM  The   caller   specified   MPOL_MF_MOVE_ALL  without  sufficient
              privileges (CAP_SYS_NICE).  Or, the  caller  attempted  to  move
              pages  of  a  process belonging to another user but did not have
              privilege to do so (CAP_SYS_NICE).

       ESRCH  Process does not exist.

VERSIONS

       move_pages() first appeared on Linux in version 2.6.18.

CONFORMING TO

       This system call is Linux-specific.

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 current cpuset.  Note that this
       information is subject to change at any time  by  manual  or  automatic
       reconfiguration of the cpuset.

       Use of this function 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
       move_pages().

SEE ALSO

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

COLOPHON

       This page is part of release 3.24 of the Linux  man-pages  project.   A
       description  of  the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.