|
HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|
|
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | STANDARDS | HISTORY | NOTES | SEE ALSO |
|
|
|
move_pages(2) System Calls Manual move_pages(2)
move_pages - move individual pages of a process to another node
NUMA (Non-Uniform Memory Access) policy library (libnuma, -lnuma)
#include <numaif.h>
long move_pages(int pid, unsigned long count, void *pages[.count],
const int nodes[.count], int status[.count], int flags);
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:
• 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
process.
• 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 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.
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.
Linux.
Linux 2.6.18.
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)
Linux man-pages (unreleased) (date) move_pages(2)
Pages that refer to this page: syscalls(2), numa(3), capabilities(7), numa(7)
|
HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|