[PATCH] mm, vmscan: cleanup up inactive_list_is_low

[Michal Hocko]

inactive_list_is_low is effectively duplicating logic implemented by
lruvec_lru_size_eligibe_zones. Let's use the dedicated function to
get the number of eligible pages on the lru list and ask use
lruvec_lru_size to get the total LRU lize only when the tracing is
really requested. We are still iterating over all LRUs two times in that
case but a) inactive_list_is_low is not a hot path and b) this can be
addressed at the tracing layer and only evaluate arguments only when the
tracing is enabled in future if that ever matters.

Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
---
 mm/vmscan.c | 38 ++++++++++----------------------------
 1 file changed, 10 insertions(+), 28 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 137bc85067d3..a9c881f06c0e 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2054,11 +2054,10 @@ static bool inactive_list_is_low(struct lruvec *lruvec, bool file,
 						struct scan_control *sc, bool trace)
 {
 	unsigned long inactive_ratio;
-	unsigned long total_inactive, inactive;
-	unsigned long total_active, active;
+	unsigned long inactive, active;
+	enum lru_list inactive_lru = file * LRU_FILE;
+	enum lru_list active_lru = file * LRU_FILE + LRU_ACTIVE;
 	unsigned long gb;
-	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
-	int zid;
 
 	/*
 	 * If we don't have swap space, anonymous page deactivation
@@ -2067,27 +2066,8 @@ static bool inactive_list_is_low(struct lruvec *lruvec, bool file,
 	if (!file && !total_swap_pages)
 		return false;
 
-	total_inactive = inactive = lruvec_lru_size(lruvec, file * LRU_FILE);
-	total_active = active = lruvec_lru_size(lruvec, file * LRU_FILE + LRU_ACTIVE);
-
-	/*
-	 * For zone-constrained allocations, it is necessary to check if
-	 * deactivations are required for lowmem to be reclaimed. This
-	 * calculates the inactive/active pages available in eligible zones.
-	 */
-	for (zid = sc->reclaim_idx + 1; zid < MAX_NR_ZONES; zid++) {
-		struct zone *zone = &pgdat->node_zones[zid];
-		unsigned long inactive_zone, active_zone;
-
-		if (!managed_zone(zone))
-			continue;
-
-		inactive_zone = lruvec_zone_lru_size(lruvec, file * LRU_FILE, zid);
-		active_zone = lruvec_zone_lru_size(lruvec, (file * LRU_FILE) + LRU_ACTIVE, zid);
-
-		inactive -= min(inactive, inactive_zone);
-		active -= min(active, active_zone);
-	}
+	inactive = lruvec_lru_size_eligibe_zones(lruvec, inactive_lru, sc->reclaim_idx);
+	active = lruvec_lru_size_eligibe_zones(lruvec, active_lru, sc->reclaim_idx);
 
 	gb = (inactive + active) >> (30 - PAGE_SHIFT);
 	if (gb)
@@ -2096,10 +2076,12 @@ static bool inactive_list_is_low(struct lruvec *lruvec, bool file,
 		inactive_ratio = 1;
 
 	if (trace)
-		trace_mm_vmscan_inactive_list_is_low(pgdat->node_id,
+		trace_mm_vmscan_inactive_list_is_low(lruvec_pgdat(lruvec)->node_id,
 				sc->reclaim_idx,
-				total_inactive, inactive,
-				total_active, active, inactive_ratio, file);
+				lruvec_lru_size(lruvec, inactive_lru), inactive,
+				lruvec_lru_size(lruvec, active_lru), active,
+				inactive_ratio, file);
+
 	return inactive * inactive_ratio < active;
 }
 
-- 
2.10.2

-- 
Michal Hocko
SUSE Labs