DESCRIPTION

migrate_pages() attempts to move all pages of the process pid that are in memory nodes old_nodes to the memory nodes in new_nodes. Pages not located in any node in old_nodes will not be migrated. As far as possible, the kernel maintains the relative topology relationship inside old_nodes during the migration to new_nodes.

The old_nodes and new_nodes arguments are pointers to bit masks of node numbers, with up to maxnode bits in each mask. These masks are maintained as arrays of unsigned long integers (in the last long integer, the bits beyond those specified by maxnode are ignored). The maxnode argument is the maximum node number in the bit mask plus one (this is the same as in mbind(2), but different from select(2)).

The pid argument is the ID of the process whose 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 migrate_pages() moves pages of the calling process.

Pages shared with another process will be moved only if the initiating process has the CAP_SYS_NICE privilege.

RETURN VALUE

On success migrate_pages() returns the number of pages that could not be moved (i.e., a return of zero means that all pages were successfully moved). On error, it returns −1, and sets errno to indicate the error.

ERRORS

VERSIONS

The migrate_pages() system call first appeared on Linux in version 2.6.16.

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 calling process's cpuset. Note that this information is subject to change at any time by manual or automatic reconfiguration of the cpuset.

Use of migrate_pages() 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 migrate_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)

Documentation/vm/page_migration in the Linux kernel source tree