move_pages — move individual pages of a process to another node
|unsigned long count,|
|const int *nodes,|
move_pages() moves the
the memory nodes specified by
nodes. The result of the move
is reflected in
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
count is the
number of pages to move. It defines the size of the three
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
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
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
The following values can be returned in each element of
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.
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 process.
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.
returns zero. On error, it returns −1, and sets
errno to indicate the error.
Too many pages to move.
One of the target nodes is not allowed by the current cpuset.
Parameter array could not be accessed.
Flags other than
MPOL_MF_MOVE_ALL was specified or an
attempt was made to migrate pages of a kernel
One of the target nodes is not online.
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.
The caller specified
MPOL_MF_MOVE_ALL without sufficient
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
Process does not exist.
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
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
header is not included with glibc, but requires installing
libnuma-devel or a
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FIXME Should programs normally be using move_pages() directly, or should
they rather be using interfaces in the numactl package?
(e.g., compare with recommendation in mbind(2)).
Does this page need to give advise on this topic?