linux.git/mm/migrate.c, branch v2.6.18

[PATCH] Allow migration of mlocked pages

2006-06-25T17:00:55+00:00

Hugh clarified the role of VM_LOCKED.  So we can now implement page
migration for mlocked pages.

Allow the migration of mlocked pages.  This means that try_to_unmap must
unmap mlocked pages in the migration case.

Signed-off-by: Christoph Lameter 
Acked-by: Hugh Dickins 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] page migration: Support a vma migration function

2006-06-25T17:00:55+00:00

Hooks for calling vma specific migration functions

With this patch a vma may define a vma->vm_ops->migrate function.  That
function may perform page migration on its own (some vmas may not contain page
structs and therefore cannot be handled by regular page migration.  Pages in a
vma may require special preparatory treatment before migration is possible
etc) .  Only mmap_sem is held when the migration function is called.  The
migrate() function gets passed two sets of nodemasks describing the source and
the target of the migration.  The flags parameter either contains

MPOL_MF_MOVE	which means that only pages used exclusively by
		the specified mm should be moved

or

MPOL_MF_MOVE_ALL which means that pages shared with other processes
		should also be moved.

The migration function returns 0 on success or an error condition.  An error
condition will prevent regular page migration from occurring.

On its own this patch cannot be included since there are no users for this
functionality.  But it seems that the uncached allocator will need this
functionality at some point.

Signed-off-by: Christoph Lameter 
Cc: Hugh Dickins 
Cc: Andi Kleen 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] SELinux: add security_task_movememory calls to mm code

2006-06-23T14:42:54+00:00

This patch inserts security_task_movememory hook calls into memory management
code to enable security modules to mediate this operation between tasks.

Since the last posting, the hook has been renamed following feedback from
Christoph Lameter.

Signed-off-by: David Quigley 
Acked-by:  Stephen Smalley 
Signed-off-by: James Morris 
Cc: Andi Kleen 
Acked-by: Christoph Lameter 
Acked-by: Chris Wright 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] page migration: sys_move_pages(): support moving of individual pages

2006-06-23T14:42:53+00:00

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 

  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: Christoph Lameter 
Cc: Hugh Dickins 
Cc: Jes Sorensen 
Cc: KAMEZAWA Hiroyuki 
Cc: Lee Schermerhorn 
Cc: Andi Kleen 
Cc: Michael Kerrisk 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] page migration: use allocator function for migrate_pages()

2006-06-23T14:42:53+00:00

Instead of passing a list of new pages, pass a function to allocate a new
page.  This allows the correct placement of MPOL_INTERLEAVE pages during page
migration.  It also further simplifies the callers of migrate pages.
migrate_pages() becomes similar to migrate_pages_to() so drop
migrate_pages_to().  The batching of new page allocations becomes unnecessary.

Signed-off-by: Christoph Lameter 
Cc: Hugh Dickins 
Cc: Jes Sorensen 
Cc: KAMEZAWA Hiroyuki 
Cc: Lee Schermerhorn 
Cc: Andi Kleen 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] page migration: handle freeing of pages in migrate_pages()

2006-06-23T14:42:53+00:00

Do not leave pages on the lists passed to migrate_pages().  Seems that we will
not need any postprocessing of pages.  This will simplify the handling of
pages by the callers of migrate_pages().

Signed-off-by: Christoph Lameter 
Cc: Hugh Dickins 
Cc: Jes Sorensen 
Cc: KAMEZAWA Hiroyuki 
Cc: Lee Schermerhorn 
Cc: Andi Kleen 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] page migration: simplify migrate_pages()

2006-06-23T14:42:52+00:00

Currently migrate_pages() is mess with lots of goto.  Extract two functions
from migrate_pages() and get rid of the gotos.

Plus we can just unconditionally set the locked bit on the new page since we
are the only one holding a reference.  Locking is to stop others from
accessing the page once we establish references to the new page.

Remove the list_del from move_to_lru in order to have finer control over list
processing.

[akpm@osdl.org: add debug check]
Signed-off-by: Christoph Lameter 
Cc: Hugh Dickins 
Cc: Jes Sorensen 
Cc: KAMEZAWA Hiroyuki 
Cc: Lee Schermerhorn 
Cc: Andi Kleen 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] More page migration: use migration entries for file pages

2006-06-23T14:42:51+00:00

This implements the use of migration entries to preserve ptes of file backed
pages during migration.  Processes can therefore be migrated back and forth
without loosing their connection to pagecache pages.

Note that we implement the migration entries only for linear mappings.
Nonlinear mappings still require the unmapping of the ptes for migration.

And another writepage() ugliness shows up.  writepage() can drop the page
lock.  Therefore we have to remove migration ptes before calling writepages()
in order to avoid having migration entries point to unlocked pages.

Signed-off-by: Christoph Lameter 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] More page migration: do not inc/dec rss counters

2006-06-23T14:42:51+00:00

If we install a migration entry then the rss not really decreases since the
page is just moved somewhere else.  We can save ourselves the work of
decrementing and later incrementing which will just eventually cause cacheline
bouncing.

Signed-off-by: Christoph Lameter 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] Swapless page migration: modify core logic

2006-06-23T14:42:50+00:00

Use the migration entries for page migration

This modifies the migration code to use the new migration entries.  It now
becomes possible to migrate anonymous pages without having to add a swap
entry.

We add a couple of new functions to replace migration entries with the proper
ptes.

We cannot take the tree_lock for migrating anonymous pages anymore.  However,
we know that we hold the only remaining reference to the page when the page
count reaches 1.

Signed-off-by: Christoph Lameter 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds