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>

1 files changed, 20 insertions, 6 deletions

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 428328a..156e18f 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 */