• Christoph Lameter's avatar
    [PATCH] page migration: sys_move_pages(): support moving of individual pages · 742755a1
    Christoph Lameter authored
    move_pages() is used to move individual pages of a process. The function can
    be used to determine the location of pages and to move them onto the desired
    node. move_pages() returns status information for each page.
    
    long move_pages(pid, number_of_pages_to_move,
    		addresses_of_pages[],
    		nodes[] or NULL,
    		status[],
    		flags);
    
    The addresses of pages is an array of void * pointing to the
    pages to be moved.
    
    The nodes array contains the node numbers that the pages should be moved
    to. If a NULL is passed instead of an array then no pages are moved but
    the status array is updated. The status request may be used to determine
    the page state before issuing another move_pages() to move pages.
    
    The status array will contain the state of all individual page migration
    attempts when the function terminates. The status array is only valid if
    move_pages() completed successfullly.
    
    Possible page states in status[]:
    
    0..MAX_NUMNODES	The page is now on the indicated node.
    
    -ENOENT		Page is not present
    
    -EACCES		Page is mapped by multiple processes and can only
    		be moved if MPOL_MF_MOVE_ALL is specified.
    
    -EPERM		The page has been mlocked by a process/driver and
    		cannot be moved.
    
    -EBUSY		Page is busy and cannot be moved. Try again later.
    
    -EFAULT		Invalid address (no VMA or zero page).
    
    -ENOMEM		Unable to allocate memory on target node.
    
    -EIO		Unable to write back page. The page must 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 moving 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.
    
    The flags parameter indicates what types of pages to move:
    
    MPOL_MF_MOVE	Move pages that are only mapped by the process.
    
    MPOL_MF_MOVE_ALL Also move pages that are mapped by multiple processes.
    		Requires sufficient capabilities.
    
    Possible return codes from move_pages()
    
    -ENOENT		No pages found that would 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.
    
    -EINVAL		Flags other than MPOL_MF_MOVE(_ALL) specified or an attempt
    		to migrate pages in a kernel thread.
    
    -EPERM		MPOL_MF_MOVE_ALL specified without sufficient priviledges.
    		or an attempt to move a process belonging to another user.
    
    -EACCES		One of the target nodes is not allowed by the current cpuset.
    
    -ENODEV		One of the target nodes is not online.
    
    -ESRCH		Process does not exist.
    
    -E2BIG		Too many pages to move.
    
    -ENOMEM		Not enough memory to allocate control array.
    
    -EFAULT		Parameters could not be accessed.
    
    A test program for move_pages() may be found with the patches
    on ftp.kernel.org:/pub/linux/kernel/people/christoph/pmig/patches-2.6.17-rc4-mm3
    
    From: Christoph Lameter <clameter@sgi.com>
    
      Detailed results for sys_move_pages()
    
      Pass a pointer to an integer to get_new_page() that may be used to
      indicate where the completion status of a migration operation should be
      placed.  This allows sys_move_pags() to report back exactly what happened to
      each page.
    
      Wish there would be a better way to do this. Looks a bit hacky.
    Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
    Cc: Hugh Dickins <hugh@veritas.com>
    Cc: Jes Sorensen <jes@trained-monkey.org>
    Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
    Cc: Andi Kleen <ak@muc.de>
    Cc: Michael Kerrisk <mtk-manpages@gmx.net>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
    742755a1
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