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

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);

       Link with -lnuma.

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 sta-
       tus 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 subsys-
	      tem 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().

       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), numa_stat(8)

COLOPHON

       This  page is part of release 3.44 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/.

Linux								    2010-06-11							     MOVE_PAGES(2)