vmscan: Use an indexed array for LRU variables

Currently we are defining explicit variables for the inactive and active
list.  An indexed array can be more generic and avoid repeating similar
code in several places in the reclaim code.

We are saving a few bytes in terms of code size:

Before:

   text    data     bss     dec     hex filename
4097753  573120 4092484 8763357  85b7dd vmlinux

After:

   text    data     bss     dec     hex filename
4097729  573120 4092484 8763333  85b7c5 vmlinux

Having an easy way to add new lru lists may ease future work on the
reclaim code.

Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 63 insertions, 29 deletions

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index fdf3967e139..a6ac0d491fe 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -69,10 +69,8 @@ extern void mem_cgroup_note_reclaim_priority(struct mem_cgroup *mem,
 extern void mem_cgroup_record_reclaim_priority(struct mem_cgroup *mem,
 							int priority);
 
-extern long mem_cgroup_calc_reclaim_active(struct mem_cgroup *mem,
-				struct zone *zone, int priority);
-extern long mem_cgroup_calc_reclaim_inactive(struct mem_cgroup *mem,
-				struct zone *zone, int priority);
+extern long mem_cgroup_calc_reclaim(struct mem_cgroup *mem, struct zone *zone,
+					int priority, enum lru_list lru);
 
 #else /* CONFIG_CGROUP_MEM_RES_CTLR */
 static inline void page_reset_bad_cgroup(struct page *page)
@@ -159,14 +157,9 @@ static inline void mem_cgroup_record_reclaim_priority(struct mem_cgroup *mem,
 {
 }
 
-static inline long mem_cgroup_calc_reclaim_active(struct mem_cgroup *mem,
-					struct zone *zone, int priority)
-{
-	return 0;
-}
-
-static inline long mem_cgroup_calc_reclaim_inactive(struct mem_cgroup *mem,
-					struct zone *zone, int priority)
+static inline long mem_cgroup_calc_reclaim(struct mem_cgroup *mem,
+					struct zone *zone, int priority,
+					enum lru_list lru)
 {
 	return 0;
 }
diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
index 895bc4e9303..2704729777e 100644
--- a/include/linux/mm_inline.h
+++ b/include/linux/mm_inline.h
@@ -1,40 +1,67 @@
 static inline void
+add_page_to_lru_list(struct zone *zone, struct page *page, enum lru_list l)
+{
+	list_add(&page->lru, &zone->lru[l].list);
+	__inc_zone_state(zone, NR_LRU_BASE + l);
+}
+
+static inline void
+del_page_from_lru_list(struct zone *zone, struct page *page, enum lru_list l)
+{
+	list_del(&page->lru);
+	__dec_zone_state(zone, NR_LRU_BASE + l);
+}
+
+static inline void
 add_page_to_active_list(struct zone *zone, struct page *page)
 {
-	list_add(&page->lru, &zone->active_list);
-	__inc_zone_state(zone, NR_ACTIVE);
+	add_page_to_lru_list(zone, page, LRU_ACTIVE);
 }
 
 static inline void
 add_page_to_inactive_list(struct zone *zone, struct page *page)
 {
-	list_add(&page->lru, &zone->inactive_list);
-	__inc_zone_state(zone, NR_INACTIVE);
+	add_page_to_lru_list(zone, page, LRU_INACTIVE);
 }
 
 static inline void
 del_page_from_active_list(struct zone *zone, struct page *page)
 {
-	list_del(&page->lru);
-	__dec_zone_state(zone, NR_ACTIVE);
+	del_page_from_lru_list(zone, page, LRU_ACTIVE);
 }
 
 static inline void
 del_page_from_inactive_list(struct zone *zone, struct page *page)
 {
-	list_del(&page->lru);
-	__dec_zone_state(zone, NR_INACTIVE);
+	del_page_from_lru_list(zone, page, LRU_INACTIVE);
 }
 
 static inline void
 del_page_from_lru(struct zone *zone, struct page *page)
 {
+	enum lru_list l = LRU_INACTIVE;
+
 	list_del(&page->lru);
 	if (PageActive(page)) {
 		__ClearPageActive(page);
-		__dec_zone_state(zone, NR_ACTIVE);
-	} else {
-		__dec_zone_state(zone, NR_INACTIVE);
+		l = LRU_ACTIVE;
 	}
+	__dec_zone_state(zone, NR_LRU_BASE + l);
 }
 
+/**
+ * page_lru - which LRU list should a page be on?
+ * @page: the page to test
+ *
+ * Returns the LRU list a page should be on, as an index
+ * into the array of LRU lists.
+ */
+static inline enum lru_list page_lru(struct page *page)
+{
+	enum lru_list lru = LRU_BASE;
+
+	if (PageActive(page))
+		lru += LRU_ACTIVE;
+
+	return lru;
+}
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 428328a05fa..156e18f3919 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -81,8 +81,9 @@ struct zone_padding {
 enum zone_stat_item {
 	/* First 128 byte cacheline (assuming 64 bit words) */
 	NR_FREE_PAGES,
-	NR_INACTIVE,
-	NR_ACTIVE,
+	NR_LRU_BASE,
+	NR_INACTIVE = NR_LRU_BASE, /* must match order of LRU_[IN]ACTIVE */
+	NR_ACTIVE,	/*  "     "     "   "       "         */
 	NR_ANON_PAGES,	/* Mapped anonymous pages */
 	NR_FILE_MAPPED,	/* pagecache pages mapped into pagetables.
 			   only modified from process context */
@@ -107,6 +108,19 @@ enum zone_stat_item {
 #endif
 	NR_VM_ZONE_STAT_ITEMS };
 
+enum lru_list {
+	LRU_BASE,
+	LRU_INACTIVE=LRU_BASE,	/* must match order of NR_[IN]ACTIVE */
+	LRU_ACTIVE,		/*  "     "     "   "       "        */
+	NR_LRU_LISTS };
+
+#define for_each_lru(l) for (l = 0; l < NR_LRU_LISTS; l++)
+
+static inline int is_active_lru(enum lru_list l)
+{
+	return (l == LRU_ACTIVE);
+}
+
 struct per_cpu_pages {
 	int count;		/* number of pages in the list */
 	int high;		/* high watermark, emptying needed */
@@ -251,10 +265,10 @@ struct zone {
 
 	/* Fields commonly accessed by the page reclaim scanner */
 	spinlock_t		lru_lock;	
-	struct list_head	active_list;
-	struct list_head	inactive_list;
-	unsigned long		nr_scan_active;
-	unsigned long		nr_scan_inactive;
+	struct {
+		struct list_head list;
+		unsigned long nr_scan;
+	} lru[NR_LRU_LISTS];
 	unsigned long		pages_scanned;	   /* since last reclaim */
 	unsigned long		flags;		   /* zone flags, see below */