NAME¶

migrate_pages - move all pages in a process to another set of nodes

LIBRARY¶

NUMA (Non-Uniform Memory Access) policy library (libnuma, -lnuma)

SYNOPSIS¶

#include <numaif.h>

long migrate_pages(int pid, unsigned long maxnode,
                   const unsigned long *old_nodes,
                   const unsigned long *new_nodes);

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¶

EFAULT

Part or all of the memory range specified by old_nodes/new_nodes and maxnode points outside your accessible address space.

EINVAL

The value specified by maxnode exceeds a kernel-imposed limit. Or, old_nodes or new_nodes specifies one or more node IDs that are greater than the maximum supported node ID. Or, none of the node IDs specified by new_nodes are on-line and allowed by the process's current cpuset context, or none of the specified nodes contain memory.

EPERM

Insufficient privilege (CAP_SYS_NICE) to move pages of the process specified by pid, or insufficient privilege (CAP_SYS_NICE) to access the specified target nodes.

ESRCH

No process matching pid could be found.

STANDARDS¶

Linux.

HISTORY¶

Linux 2.6.16.

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.rst in the Linux kernel source tree