move_pages.2

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.\"                               Christoph Lameter
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.TH MOVE_PAGES 2 2006-10-31 "Linux 2.6.18" "Linux Programmer's Manual"
.SH NAME
move_pages \- Move individual pages of a process to another node
.SH SYNOPSIS
.B #include <numaif.h>
.sp
.BI "long move_pages(int " pid ", unsigned long count, void ** " pages ", const int * " nodes ", int * " status ", int " flags );
.SH DESCRIPTION
.BR move_pages ()
moves
.I count
pages to the
.I nodes.
The result of the move is reflected in
.I status.
The
.I flags
indicate constraints on the pages to be moved.

.I pid
is the process id in which pages are to be moved. Sufficient rights
must exist to move pages of another process. This means the moving
process either has root priviledges, has SYS_NICE administrative rights or
the same owner. If pid is 0 then we move pages of the current process.

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

.I 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
.I pid.

.I nodes
is either an array of integers that specify the desired location for each
page or it is NULL. Each integer is a node number. If NULL is specified then
move_pages will not move any pages but return the node of each page in
the
.I status
array. Having the status of each page may be necessary to determine
pages that need to be moved.

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

.I flags
specify what types of pages to move.
.B MPOL_MF_MOVE
means that only pages that are in exclusive use by the process
are to be moved.
.B MPOL_MF_MOVE_ALL
means that pages shared between multiple processes can also be moved.
The process must have root priviledges or SYS_NICE priviledges.

.SH Page states in the status array

.TP
.B 0..MAX_NUMNODES
Indicates that the location of the page is on this node.
.TP
.B -ENOENT
The page is not present.
.TP
.B -EACCES
The page is mapped by multiple processes and can only be moved
if
.I MPOL_MF_MOVE_ALL
is specified.
.TP
.B -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.
.TP
.B -EFAULT
This is a zero page or the memory area is not mapped by the process.
.TP
.B -ENOMEM
Unable to allocate memory on target node.
.TP
.B -EIO
Unable to write back a page. The page has to be written back
in order to move ti since the page is dirty and the filesystem
has not provide a migration function that would allow the move
of dirty pages.
.TP
.B -EINVAL
A dirty page cannot be moved. The filesystem does not
provide a migration function and has no ability to write back pages.

.SH "RETURN VALUE"
On success
.B move_pages
returns zero.
.SH ERRORS
.TP
.B -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.
.TP
.B -EINVAL
Flags other than
.I MPOL_MF_MOVE
and
.I MPOL_MF_MOVE_ALL
was specified or an attempt was made to migrate pages of a kernel thread.
.TP
.B -EPERM
.I MPOL_MF_MOVE_ALL
specified without sufficient privileges or an attempt to move a process
belonging to another user.
.TP
.B -EACCESS
On of the target nodes is not allowed by the current cpuset.
.TP
.B -ENODEV
On of the target nodes is not online.
.TP
.B -ESRCH
Process does not exist.
.TP
.B -E2BIG
Too many pages to move.
.TP
.B -EFAULT
Parameter array could not be accessed.
.SH "SEE ALSO"
.BR numa_maps (5),
.BR migratepages (8),
.BR numa_stat (8),
.BR numa (3)