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

       move_pages - move individual pages of a process to another node

       #include <numaif.h>

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

       Link with -lnuma.

       Note: There is no glibc wrapper for this system call; see NOTES.

       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.  If pid is
       0, then move_pages() moves pages of the calling process.

       To move pages in another process requires the following privileges:

       *  In kernels up to and including Linux 4.12: 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

       *  The older rules allowed the caller to discover various virtual address
          choices made by the kernel that could lead to the defeat of address-
          space-layout randomization for a process owned by the same UID as the
          caller, the rules were changed starting with Linux 4.13.  Since Linux
          4.13, permission is governed by a ptrace access mode
          PTRACE_MODE_READ_REALCREDS check with respect to the target process;
          see ptrace(2).

       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.
       Preinitialization of the array to a value which cannot represent a real
       numa node or valid error of status array could help to identify pages
       that have been migrated.

       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

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

              Identifies the node on which the page resides.

              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.

              This is a zero page or the memory area is not mapped by the

       -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.

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

              The page is not present.

              Unable to allocate memory on target node.

       On success move_pages() returns zero.  On error, it returns -1, and sets
       errno to indicate the error.  If positive value is returned, it is the
       number of nonmigrated pages.

       Positive value
              The number of nonmigrated pages if they were the result of
              nonfatal reasons (since Linux 4.17).

       E2BIG  Too many pages to move.  Since Linux 2.6.29, the kernel no longer
              generates this error.

       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.

       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.

       move_pages() first appeared on Linux in version 2.6.18.

       This system call is Linux-specific.

       Glibc does not provide a wrapper for this system call.  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.

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

       This page is part of release 5.13 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

Linux                              2021-03-22                      MOVE_PAGES(2)