diff options
| author | Kirill A. Shutemov <kirill.shutemov@linux.intel.com> | 2016-07-27 00:25:26 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-07-27 01:19:19 +0200 |
| commit | dd78fedde4b99b322f2dc849d467d365a82e23ca (patch) | |
| tree | 5095c6e9fd2527a8636188059e35f7f45b9648a2 /mm/util.c | |
| parent | mm: postpone page table allocation until we have page to map (diff) | |
| download | linux-dd78fedde4b99b322f2dc849d467d365a82e23ca.tar.xz linux-dd78fedde4b99b322f2dc849d467d365a82e23ca.zip | |
rmap: support file thp
Naive approach: on mapping/unmapping the page as compound we update
->_mapcount on each 4k page. That's not efficient, but it's not obvious
how we can optimize this. We can look into optimization later.
PG_double_map optimization doesn't work for file pages since lifecycle
of file pages is different comparing to anon pages: file page can be
mapped again at any time.
Link: http://lkml.kernel.org/r/1466021202-61880-11-git-send-email-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/util.c')
| -rw-r--r-- | mm/util.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/mm/util.c b/mm/util.c index b756ee36f7f0..8d010ef2ce1c 100644 --- a/mm/util.c +++ b/mm/util.c @@ -412,6 +412,12 @@ int __page_mapcount(struct page *page) int ret; ret = atomic_read(&page->_mapcount) + 1; + /* + * For file THP page->_mapcount contains total number of mapping + * of the page: no need to look into compound_mapcount. + */ + if (!PageAnon(page) && !PageHuge(page)) + return ret; page = compound_head(page); ret += atomic_read(compound_mapcount_ptr(page)) + 1; if (PageDoubleMap(page)) |