NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON

MOVE_PAGES(2)             Linux Programmer's Manual            MOVE_PAGES(2)

NAME         top

       move_pages - move individual pages of a process to another node

SYNOPSIS         top

       #include <numaif.h>

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

       Link with -lnuma.

DESCRIPTION         top

       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 contains valid values only 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 be moved only
              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 filesystem
              does not provide a migration function that would allow the
              move of dirty pages.

       -EINVAL
              A dirty page cannot be moved.  The filesystem 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         top

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

ERRORS         top

       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         top

       move_pages() first appeared on Linux in version 2.6.18.

CONFORMING TO         top

       This system call is Linux-specific.

NOTES         top

       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().

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

SEE ALSO         top

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

COLOPHON         top

       This page is part of release 4.10 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at
       https://www.kernel.org/doc/man-pages/.

Linux                            2010-06-11                    MOVE_PAGES(2)