[PATCH] mm: rss = file_rss + anon_rss

I was lazy when we added anon_rss, and chose to change as few places as
possible.  So currently each anonymous page has to be counted twice, in rss
and in anon_rss.  Which won't be so good if those are atomic counts in some
configurations.

Change that around: keep file_rss and anon_rss separately, and add them
together (with get_mm_rss macro) when the total is needed - reading two
atomics is much cheaper than updating two atomics.  And update anon_rss
upfront, typically in memory.c, not tucked away in page_add_anon_rmap.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 3 insertions, 5 deletions

diff --git a/mm/rmap.c b/mm/rmap.c
index 1fc559e09ca8..504757624cce 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -445,8 +445,6 @@ void page_add_anon_rmap(struct page *page,
 {
         BUG_ON(PageReserved(page));
 
-        inc_mm_counter(vma->vm_mm, anon_rss);
-
         if (atomic_inc_and_test(&page->_mapcount)) {
                 struct anon_vma *anon_vma = vma->anon_vma;
 
@@ -561,9 +559,9 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma)
                 set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
                 BUG_ON(pte_file(*pte));
                 dec_mm_counter(mm, anon_rss);
-        }
+        } else
+                dec_mm_counter(mm, file_rss);
 
-        dec_mm_counter(mm, rss);
         page_remove_rmap(page);
         page_cache_release(page);
 
@@ -667,7 +665,7 @@ static void try_to_unmap_cluster(unsigned long cursor,
 
                 page_remove_rmap(page);
                 page_cache_release(page);
-                dec_mm_counter(mm, rss);
+                dec_mm_counter(mm, file_rss);
                 (*mapcount)--;
         }