[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, 17 insertions, 14 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 51eb38574830..59d42e50fa53 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -397,9 +397,10 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
                 pte = pte_mkclean(pte);
         pte = pte_mkold(pte);
         get_page(page);
-        inc_mm_counter(dst_mm, rss);
         if (PageAnon(page))
                 inc_mm_counter(dst_mm, anon_rss);
+        else
+                inc_mm_counter(dst_mm, file_rss);
         set_pte_at(dst_mm, addr, dst_pte, pte);
         page_dup_rmap(page);
 }
@@ -581,8 +582,8 @@ static void zap_pte_range(struct mmu_gather *tlb, pmd_t *pmd,
                                         set_page_dirty(page);
                                 if (pte_young(ptent))
                                         mark_page_accessed(page);
+                                dec_mm_counter(tlb->mm, file_rss);
                         }
-                        dec_mm_counter(tlb->mm, rss);
                         page_remove_rmap(page);
                         tlb_remove_page(tlb, page);
                         continue;
@@ -1290,13 +1291,15 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
         spin_lock(&mm->page_table_lock);
         page_table = pte_offset_map(pmd, address);
         if (likely(pte_same(*page_table, orig_pte))) {
-                if (PageAnon(old_page))
-                        dec_mm_counter(mm, anon_rss);
                 if (PageReserved(old_page))
-                        inc_mm_counter(mm, rss);
-                else
+                        inc_mm_counter(mm, anon_rss);
+                else {
                         page_remove_rmap(old_page);
-
+                        if (!PageAnon(old_page)) {
+                                inc_mm_counter(mm, anon_rss);
+                                dec_mm_counter(mm, file_rss);
+                        }
+                }
                 flush_cache_page(vma, address, pfn);
                 entry = mk_pte(new_page, vma->vm_page_prot);
                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
@@ -1701,7 +1704,7 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
 
         /* The page isn't present yet, go ahead with the fault. */
 
-        inc_mm_counter(mm, rss);
+        inc_mm_counter(mm, anon_rss);
         pte = mk_pte(page, vma->vm_page_prot);
         if (write_access && can_share_swap_page(page)) {
                 pte = maybe_mkwrite(pte_mkdirty(pte), vma);
@@ -1774,7 +1777,7 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
                         page_cache_release(page);
                         goto unlock;
                 }
-                inc_mm_counter(mm, rss);
+                inc_mm_counter(mm, anon_rss);
                 entry = mk_pte(page, vma->vm_page_prot);
                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
                 lru_cache_add_active(page);
@@ -1887,19 +1890,19 @@ retry:
          */
         /* Only go through if we didn't race with anybody else... */
         if (pte_none(*page_table)) {
-                if (!PageReserved(new_page))
-                        inc_mm_counter(mm, rss);
-
                 flush_icache_page(vma, new_page);
                 entry = mk_pte(new_page, vma->vm_page_prot);
                 if (write_access)
                         entry = maybe_mkwrite(pte_mkdirty(entry), vma);
                 set_pte_at(mm, address, page_table, entry);
                 if (anon) {
+                        inc_mm_counter(mm, anon_rss);
                         lru_cache_add_active(new_page);
                         page_add_anon_rmap(new_page, vma, address);
-                } else
+                } else if (!PageReserved(new_page)) {
+                        inc_mm_counter(mm, file_rss);
                         page_add_file_rmap(new_page);
+                }
         } else {
                 /* One of our sibling threads was faster, back out. */
                 page_cache_release(new_page);
@@ -2192,7 +2195,7 @@ EXPORT_SYMBOL(vmalloc_to_pfn);
 void update_mem_hiwater(struct task_struct *tsk)
 {
         if (tsk->mm) {
-                unsigned long rss = get_mm_counter(tsk->mm, rss);
+                unsigned long rss = get_mm_rss(tsk->mm);
 
                 if (tsk->mm->hiwater_rss < rss)
                         tsk->mm->hiwater_rss = rss;