[PATCH] More page migration: do not inc/dec rss counters

If we install a migration entry then the rss not really decreases since the
page is just moved somewhere else.  We can save ourselves the work of
decrementing and later incrementing which will just eventually cause cacheline
bouncing.
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

mm/migrate.c

@@ -164,7 +164,6 @@ static void remove_migration_pte(struct vm_area_struct *vma, unsigned long addr,
 	if (!is_migration_entry(entry) || migration_entry_to_page(entry) != old)
 		goto out;
 
-	inc_mm_counter(mm, anon_rss);
 	get_page(new);
 	pte = pte_mkold(mk_pte(new, vma->vm_page_prot));
 	if (is_write_migration_entry(entry))

mm/rmap.c

@@ -595,6 +595,7 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
 					list_add(&mm->mmlist, &init_mm.mmlist);
 				spin_unlock(&mmlist_lock);
 			}
+			dec_mm_counter(mm, anon_rss);
 		} else {
 			/*
 			 * Store the pfn of the page in a special migration
@@ -606,7 +607,6 @@ 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);