[PATCH 1/1] mmzone: code cleanup for LRU stats.

[PATCH 1/1] mmzone: code cleanup for LRU stats.

[Maninder Singh]

Replacing hardcoded values with enum lru_stats for LRU stats.

Signed-off-by: Maninder Singh <maninder1.s-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
Signed-off-by: Vaneet Narang <v.narang-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
---
 include/linux/mmzone.h |   12 ++++++++----
 mm/memcontrol.c        |   20 ++++++++++----------
 mm/vmscan.c            |   20 ++++++++++----------
 3 files changed, 28 insertions(+), 24 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 68cc063..fd993e4 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -198,17 +198,21 @@ static inline int is_active_lru(enum lru_list lru)
 	return (lru == LRU_ACTIVE_ANON || lru == LRU_ACTIVE_FILE);
 }
 
+enum lru_stats {
+	LRU_ANON_STAT, /* anon LRU stats */
+	LRU_FILE_STAT, /* file LRU stats */
+	LRU_MAX_STAT
+};
+
 struct zone_reclaim_stat {
 	/*
 	 * The pageout code in vmscan.c keeps track of how many of the
 	 * mem/swap backed and file backed pages are referenced.
 	 * The higher the rotated/scanned ratio, the more valuable
 	 * that cache is.
-	 *
-	 * The anon LRU stats live in [0], file LRU stats in [1]
 	 */
-	unsigned long		recent_rotated[2];
-	unsigned long		recent_scanned[2];
+	unsigned long		recent_rotated[LRU_MAX_STAT];
+	unsigned long		recent_scanned[LRU_MAX_STAT];
 };
 
 struct lruvec {
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 11e97e0..49c8e4d 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3373,23 +3373,23 @@ static int memcg_stat_show(struct seq_file *m, void *v)
 		int nid, zid;
 		struct mem_cgroup_per_zone *mz;
 		struct zone_reclaim_stat *rstat;
-		unsigned long recent_rotated[2] = {0, 0};
-		unsigned long recent_scanned[2] = {0, 0};
+		unsigned long recent_rotated[LRU_MAX_STAT] = {0, 0};
+		unsigned long recent_scanned[LRU_MAX_STAT] = {0, 0};
 
 		for_each_online_node(nid)
 			for (zid = 0; zid < MAX_NR_ZONES; zid++) {
 				mz = &memcg->nodeinfo[nid]->zoneinfo[zid];
 				rstat = &mz->lruvec.reclaim_stat;
 
-				recent_rotated[0] += rstat->recent_rotated[0];
-				recent_rotated[1] += rstat->recent_rotated[1];
-				recent_scanned[0] += rstat->recent_scanned[0];
-				recent_scanned[1] += rstat->recent_scanned[1];
+				recent_rotated[LRU_ANON_STAT] += rstat->recent_rotated[LRU_ANON_STAT];
+				recent_rotated[LRU_FILE_STAT] += rstat->recent_rotated[LRU_FILE_STAT];
+				recent_scanned[LRU_ANON_STAT] += rstat->recent_scanned[LRU_ANON_STAT];
+				recent_scanned[LRU_FILE_STAT] += rstat->recent_scanned[LRU_FILE_STAT];
 			}
-		seq_printf(m, "recent_rotated_anon %lu\n", recent_rotated[0]);
-		seq_printf(m, "recent_rotated_file %lu\n", recent_rotated[1]);
-		seq_printf(m, "recent_scanned_anon %lu\n", recent_scanned[0]);
-		seq_printf(m, "recent_scanned_file %lu\n", recent_scanned[1]);
+		seq_printf(m, "recent_rotated_anon %lu\n", recent_rotated[LRU_ANON_STAT]);
+		seq_printf(m, "recent_rotated_file %lu\n", recent_rotated[LRU_FILE_STAT]);
+		seq_printf(m, "recent_scanned_anon %lu\n", recent_scanned[LRU_ANON_STAT]);
+		seq_printf(m, "recent_scanned_file %lu\n", recent_scanned[LRU_FILE_STAT]);
 	}
 #endif
 
diff --git a/mm/vmscan.c b/mm/vmscan.c
index ee3bbd5..7a66554 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2176,14 +2176,14 @@ static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg,
 		get_lru_size(lruvec, LRU_INACTIVE_FILE);
 
 	spin_lock_irq(&zone->lru_lock);
-	if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
-		reclaim_stat->recent_scanned[0] /= 2;
-		reclaim_stat->recent_rotated[0] /= 2;
+	if (unlikely(reclaim_stat->recent_scanned[LRU_ANON_STAT] > anon / 4)) {
+		reclaim_stat->recent_scanned[LRU_ANON_STAT] /= 2;
+		reclaim_stat->recent_rotated[LRU_ANON_STAT] /= 2;
 	}
 
-	if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
-		reclaim_stat->recent_scanned[1] /= 2;
-		reclaim_stat->recent_rotated[1] /= 2;
+	if (unlikely(reclaim_stat->recent_scanned[LRU_FILE_STAT] > file / 4)) {
+		reclaim_stat->recent_scanned[LRU_FILE_STAT] /= 2;
+		reclaim_stat->recent_rotated[LRU_FILE_STAT] /= 2;
 	}
 
 	/*
@@ -2191,11 +2191,11 @@ static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg,
 	 * proportional to the fraction of recently scanned pages on
 	 * each list that were recently referenced and in active use.
 	 */
-	ap = anon_prio * (reclaim_stat->recent_scanned[0] + 1);
-	ap /= reclaim_stat->recent_rotated[0] + 1;
+	ap = anon_prio * (reclaim_stat->recent_scanned[LRU_ANON_STAT] + 1);
+	ap /= reclaim_stat->recent_rotated[LRU_ANON_STAT] + 1;
 
-	fp = file_prio * (reclaim_stat->recent_scanned[1] + 1);
-	fp /= reclaim_stat->recent_rotated[1] + 1;
+	fp = file_prio * (reclaim_stat->recent_scanned[LRU_FILE_STAT] + 1);
+	fp /= reclaim_stat->recent_rotated[LRU_FILE_STAT] + 1;
 	spin_unlock_irq(&zone->lru_lock);
 
 	fraction[0] = ap;
-- 
1.7.9.5

Re: [PATCH 1/1] mmzone: code cleanup for LRU stats.

[Johannes Weiner]

On Mon, Jan 18, 2016 at 12:48:12PM +0530, Maninder Singh wrote:
> Replacing hardcoded values with enum lru_stats for LRU stats.
> 
> Signed-off-by: Maninder Singh <maninder1.s-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
> Signed-off-by: Vaneet Narang <v.narang-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>

I don't think the code is hard to understand, it always says 'anon' or
'file' or similar for every context where it's important to understand
what the magic array index means.

And this patch makes the lines too long and unwieldy.