[PATCH] mm: batch updating mm_counters

tlb_finish_mmu used to batch zap_pte_range's update of mm rss, which may be
worthwhile if the mm is contended, and would reduce atomic operations if the
counts were atomic.  Let zap_pte_range now batch its updates to file_rss and
anon_rss, per page-table in case we drop the lock outside; and copy_pte_range
batch them too.

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, 32 insertions, 15 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 59d42e50fa53..da642b5528fa 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -332,6 +332,16 @@ out:
         return pte_offset_kernel(pmd, address);
 }
 
+static inline void add_mm_rss(struct mm_struct *mm, int file_rss, int anon_rss)
+{
+        if (file_rss)
+                add_mm_counter(mm, file_rss, file_rss);
+        if (anon_rss)
+                add_mm_counter(mm, anon_rss, anon_rss);
+}
+
+#define NO_RSS 2        /* Increment neither file_rss nor anon_rss */
+
 /*
  * copy one vm_area from one task to the other. Assumes the page tables
  * already present in the new task to be cleared in the whole range
@@ -341,7 +351,7 @@ out:
  * but may be dropped within p[mg]d_alloc() and pte_alloc_map().
  */
 
-static inline void
+static inline int
 copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
                 pte_t *dst_pte, pte_t *src_pte, unsigned long vm_flags,
                 unsigned long addr)
@@ -349,6 +359,7 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
         pte_t pte = *src_pte;
         struct page *page;
         unsigned long pfn;
+        int anon = NO_RSS;
 
         /* pte contains position in swap or file, so copy. */
         if (unlikely(!pte_present(pte))) {
@@ -361,8 +372,7 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
                                 spin_unlock(&mmlist_lock);
                         }
                 }
-                set_pte_at(dst_mm, addr, dst_pte, pte);
-                return;
+                goto out_set_pte;
         }
 
         pfn = pte_pfn(pte);
@@ -375,10 +385,8 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
         if (pfn_valid(pfn))
                 page = pfn_to_page(pfn);
 
-        if (!page || PageReserved(page)) {
-                set_pte_at(dst_mm, addr, dst_pte, pte);
-                return;
-        }
+        if (!page || PageReserved(page))
+                goto out_set_pte;
 
         /*
          * If it's a COW mapping, write protect it both
@@ -397,12 +405,12 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
                 pte = pte_mkclean(pte);
         pte = pte_mkold(pte);
         get_page(page);
-        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);
+        anon = !!PageAnon(page);
+
+out_set_pte:
+        set_pte_at(dst_mm, addr, dst_pte, pte);
+        return anon;
 }
 
 static int copy_pte_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
@@ -412,8 +420,10 @@ static int copy_pte_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
         pte_t *src_pte, *dst_pte;
         unsigned long vm_flags = vma->vm_flags;
         int progress = 0;
+        int rss[NO_RSS+1], anon;
 
 again:
+        rss[1] = rss[0] = 0;
         dst_pte = pte_alloc_map(dst_mm, dst_pmd, addr);
         if (!dst_pte)
                 return -ENOMEM;
@@ -436,13 +446,16 @@ again:
                         progress++;
                         continue;
                 }
-                copy_one_pte(dst_mm, src_mm, dst_pte, src_pte, vm_flags, addr);
+                anon = copy_one_pte(dst_mm, src_mm, dst_pte, src_pte,
+                                                        vm_flags, addr);
+                rss[anon]++;
                 progress += 8;
         } while (dst_pte++, src_pte++, addr += PAGE_SIZE, addr != end);
         spin_unlock(&src_mm->page_table_lock);
 
         pte_unmap_nested(src_pte - 1);
         pte_unmap(dst_pte - 1);
+        add_mm_rss(dst_mm, rss[0], rss[1]);
         cond_resched_lock(&dst_mm->page_table_lock);
         if (addr != end)
                 goto again;
@@ -533,6 +546,8 @@ static void zap_pte_range(struct mmu_gather *tlb, pmd_t *pmd,
                                 struct zap_details *details)
 {
         pte_t *pte;
+        int file_rss = 0;
+        int anon_rss = 0;
 
         pte = pte_offset_map(pmd, addr);
         do {
@@ -576,13 +591,13 @@ static void zap_pte_range(struct mmu_gather *tlb, pmd_t *pmd,
                                 set_pte_at(tlb->mm, addr, pte,
                                            pgoff_to_pte(page->index));
                         if (PageAnon(page))
-                                dec_mm_counter(tlb->mm, anon_rss);
+                                anon_rss++;
                         else {
                                 if (pte_dirty(ptent))
                                         set_page_dirty(page);
                                 if (pte_young(ptent))
                                         mark_page_accessed(page);
-                                dec_mm_counter(tlb->mm, file_rss);
+                                file_rss++;
                         }
                         page_remove_rmap(page);
                         tlb_remove_page(tlb, page);
@@ -598,6 +613,8 @@ static void zap_pte_range(struct mmu_gather *tlb, pmd_t *pmd,
                         free_swap_and_cache(pte_to_swp_entry(ptent));
                 pte_clear_full(tlb->mm, addr, pte, tlb->fullmm);
         } while (pte++, addr += PAGE_SIZE, addr != end);
+
+        add_mm_rss(tlb->mm, -file_rss, -anon_rss);
         pte_unmap(pte - 1);
 }