migrate_pages

MIGRATE_PAGES(2)            Linux Programmer's Manual           MIGRATE_PAGES(2)



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

SYNOPSIS
       #include <numaif.h>

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

       Note: There is no glibc wrapper for this system call; see NOTES.

       Link with -lnuma.

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.

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

CONFORMING TO
       This system call is Linux-specific.

NOTES
       Glibc does not provide a wrapper for this system call.  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

COLOPHON
       This page is part of release 5.13 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at
       https://www.kernel.org/doc/man-pages/.



Linux                              2021-03-22                   MIGRATE_PAGES(2)