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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 sta-
tus. 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 ker-
nel 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
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 pro-
cesses.
EPERM The caller specified MPOL_MF_MOVE_ALL without sufficient privi-
leges (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), numastat(8)
COLOPHON
This page is part of release 3.69 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
http://www.kernel.org/doc/man-pages/.
Linux 2010-06-11 MOVE_PAGES(2)
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