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| author | Hugh Dickins <hugh@veritas.com> | 2005-06-21 17:15:11 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-06-21 18:46:21 -0700 |
| commit | d296e9cd02c92e576ecce5344026a4df4353cdb2 (patch) | |
| tree | 76af62c5d2c16e89672f71f2f4c7a65aa36ff914 /mm/memory.c | |
| parent | 08ef472937e918875a82fd350d3de138aac50414 (diff) | |
| download | lwn-d296e9cd02c92e576ecce5344026a4df4353cdb2.tar.gz lwn-d296e9cd02c92e576ecce5344026a4df4353cdb2.zip | |
[PATCH] do_wp_page: cannot share file page
A small optimization to do_wp_page's check for whether to avoid copy by
reusing the page already mapped. It can never share a cached file page,
nor can it share a reserved page (often the empty zero page), so it's a
waste of time to lock and unlock in those cases. Which nowadays can both
be neatly excluded by a preliminary PageAnon test.
Christoph has reported that a preliminary page_count test proved valuable
for scalability here, but PageAnon covers more common cases all at once.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'mm/memory.c')
| -rw-r--r-- | mm/memory.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/memory.c b/mm/memory.c index b8846cf2358a..1c0a3db78a05 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1239,7 +1239,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct * vma, } old_page = pfn_to_page(pfn); - if (!TestSetPageLocked(old_page)) { + if (PageAnon(old_page) && !TestSetPageLocked(old_page)) { int reuse = can_share_swap_page(old_page); unlock_page(old_page); if (reuse) { |