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

[PATCH] zoned vm counters: split NR_ANON_PAGES off from NR_FILE_MAPPED

2006-06-30T18:25:35+00:00

The current NR_FILE_MAPPED is used by zone reclaim and the dirty load
calculation as the number of mapped pagecache pages.  However, that is not
true.  NR_FILE_MAPPED includes the mapped anonymous pages.  This patch
separates those and therefore allows an accurate tracking of the anonymous
pages per zone.

It then becomes possible to determine the number of unmapped pages per zone
and we can avoid scanning for unmapped pages if there are none.

Also it may now be possible to determine the mapped/unmapped ratio in
get_dirty_limit.  Isnt the number of anonymous pages irrelevant in that
calculation?

Note that this will change the meaning of the number of mapped pages reported
in /proc/vmstat /proc/meminfo and in the per node statistics.  This may affect
user space tools that monitor these counters!  NR_FILE_MAPPED works like
NR_FILE_DIRTY.  It is only valid for pagecache pages.

Signed-off-by: Christoph Lameter 
Cc: Trond Myklebust 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] zoned vm counters: convert nr_mapped to per zone counter

2006-06-30T18:25:34+00:00

nr_mapped is important because it allows a determination of how many pages of
a zone are not mapped, which would allow a more efficient means of determining
when we need to reclaim memory in a zone.

We take the nr_mapped field out of the page state structure and define a new
per zone counter named NR_FILE_MAPPED (the anonymous pages will be split off
from NR_MAPPED in the next patch).

We replace the use of nr_mapped in various kernel locations.  This avoids the
looping over all processors in try_to_free_pages(), writeback, reclaim (swap +
zone reclaim).

[akpm@osdl.org: bugfix]
Signed-off-by: Christoph Lameter 
Cc: Trond Myklebust 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[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] 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: rip out swap based logic

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

Rip the page migration logic out.

Remove all code that has to do with swapping during page migration.

This also guts the ability to migrate pages to swap.  No one used that so lets
let it go for good.

Page migration should be a bit broken after this patch.

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

[PATCH] Swapless page migration: add R/W migration entries

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

Implement read/write migration ptes

We take the upper two swapfiles for the two types of migration ptes and define
a series of macros in swapops.h.

The VM is modified to handle the migration entries.  migration entries can
only be encountered when the page they are pointing to is locked.  This limits
the number of places one has to fix.  We also check in copy_pte_range and in
mprotect_pte_range() for migration ptes.

We check for migration ptes in do_swap_cache and call a function that will
then wait on the page lock.  This allows us to effectively stop all accesses
to apge.

Migration entries are created by try_to_unmap if called for migration and
removed by local functions in migrate.c

From: Hugh Dickins 

  Several times while testing swapless page migration (I've no NUMA, just
  hacking it up to migrate recklessly while running load), I've hit the
  BUG_ON(!PageLocked(p)) in migration_entry_to_page.

  This comes from an orphaned migration entry, unrelated to the current
  correctly locked migration, but hit by remove_anon_migration_ptes as it
  checks an address in each vma of the anon_vma list.

  Such an orphan may be left behind if an earlier migration raced with fork:
  copy_one_pte can duplicate a migration entry from parent to child, after
  remove_anon_migration_ptes has checked the child vma, but before it has
  removed it from the parent vma.  (If the process were later to fault on this
  orphaned entry, it would hit the same BUG from migration_entry_wait.)

  This could be fixed by locking anon_vma in copy_one_pte, but we'd rather
  not.  There's no such problem with file pages, because vma_prio_tree_add
  adds child vma after parent vma, and the page table locking at each end is
  enough to serialize.  Follow that example with anon_vma: add new vmas to the
  tail instead of the head.

  (There's no corresponding problem when inserting migration entries,
  because a missed pte will leave the page count and mapcount high, which is
  allowed for.  And there's no corresponding problem when migrating via swap,
  because a leftover swap entry will be correctly faulted.  But the swapless
  method has no refcounting of its entries.)

From: Ingo Molnar 

  pte_unmap_unlock() takes the pte pointer as an argument.

From: Hugh Dickins 

  Several times while testing swapless page migration, gcc has tried to exec
  a pointer instead of a string: smells like COW mappings are not being
  properly write-protected on fork.

  The protection in copy_one_pte looks very convincing, until at last you
  realize that the second arg to make_migration_entry is a boolean "write",
  and SWP_MIGRATION_READ is 30.

  Anyway, it's better done like in change_pte_range, using
  is_write_migration_entry and make_migration_entry_read.

From: Hugh Dickins 

  Remove unnecessary obfuscation from sys_swapon's range check on swap type,
  which blew up causing memory corruption once swapless migration made
  MAX_SWAPFILES no longer 2 ^ MAX_SWAPFILES_SHIFT.

Signed-off-by: Hugh Dickins 
Acked-by: Martin Schwidefsky 
Signed-off-by: Hugh Dickins 
Signed-off-by: Christoph Lameter 
Signed-off-by: Ingo Molnar 
From: Hugh Dickins 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] page migration cleanup: rename "ignrefs" to "migration"

2006-06-23T14:42:49+00:00

migrate is a better name since it is only used by page migration.

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

[PATCH] mm: more CONFIG_DEBUG_VM

2006-03-22T15:54:02+00:00

Put a few more checks under CONFIG_DEBUG_VM

Signed-off-by: Nick Piggin 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] mm: kill kmem_cache_t usage

2006-03-22T15:53:58+00:00

We have struct kmem_cache now so use it instead of the old typedef.

Signed-off-by: Pekka Enberg 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds