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author | Hugh Dickins <hughd@google.com> | 2013-02-23 00:35:13 (GMT) |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-02-24 01:50:19 (GMT) |
commit | b79bc0a0c79e06cc87e17530e9c1c56c6f297e17 (patch) | |
tree | 617d8e3b2d8be512373c3351a92630c28248ecee /mm/migrate.c | |
parent | 4146d2d673e8d6abf9b30a5b5dd8cd95f29632eb (diff) | |
download | linux-b79bc0a0c79e06cc87e17530e9c1c56c6f297e17.tar.xz |
ksm: enable KSM page migration
Migration of KSM pages is now safe: remove the PageKsm restrictions from
mempolicy.c and migrate.c.
But keep PageKsm out of __unmap_and_move()'s anon_vma contortions, which
are irrelevant to KSM: it looks as if that code was preventing hotremove
migration of KSM pages, unless they happened to be in swapcache.
There is some question as to whether enforcing a NUMA mempolicy migration
ought to migrate KSM pages, mapped into entirely unrelated processes; but
moving page_mapcount > 1 is only permitted with MPOL_MF_MOVE_ALL anyway,
and it seems reasonable to assume that you wouldn't set MADV_MERGEABLE on
any area where this is a worry.
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Petr Holasek <pholasek@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Izik Eidus <izik.eidus@ravellosystems.com>
Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/migrate.c')
-rw-r--r-- | mm/migrate.c | 21 |
1 files changed, 3 insertions, 18 deletions
diff --git a/mm/migrate.c b/mm/migrate.c index e545ce7..20a03eb 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -731,20 +731,6 @@ static int __unmap_and_move(struct page *page, struct page *newpage, lock_page(page); } - /* - * Only memory hotplug's offline_pages() caller has locked out KSM, - * and can safely migrate a KSM page. The other cases have skipped - * PageKsm along with PageReserved - but it is only now when we have - * the page lock that we can be certain it will not go KSM beneath us - * (KSM will not upgrade a page from PageAnon to PageKsm when it sees - * its pagecount raised, but only here do we take the page lock which - * serializes that). - */ - if (PageKsm(page) && !offlining) { - rc = -EBUSY; - goto unlock; - } - /* charge against new page */ mem_cgroup_prepare_migration(page, newpage, &mem); @@ -771,7 +757,7 @@ static int __unmap_and_move(struct page *page, struct page *newpage, * File Caches may use write_page() or lock_page() in migration, then, * just care Anon page here. */ - if (PageAnon(page)) { + if (PageAnon(page) && !PageKsm(page)) { /* * Only page_lock_anon_vma_read() understands the subtleties of * getting a hold on an anon_vma from outside one of its mms. @@ -851,7 +837,6 @@ uncharge: mem_cgroup_end_migration(mem, page, newpage, (rc == MIGRATEPAGE_SUCCESS || rc == MIGRATEPAGE_BALLOON_SUCCESS)); -unlock: unlock_page(page); out: return rc; @@ -1155,7 +1140,7 @@ static int do_move_page_to_node_array(struct mm_struct *mm, goto set_status; /* Use PageReserved to check for zero page */ - if (PageReserved(page) || PageKsm(page)) + if (PageReserved(page)) goto put_and_set; pp->page = page; @@ -1317,7 +1302,7 @@ static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages, err = -ENOENT; /* Use PageReserved to check for zero page */ - if (!page || PageReserved(page) || PageKsm(page)) + if (!page || PageReserved(page)) goto set_status; err = page_to_nid(page); |