[Devel] [PATCH vz8 07/15] mm: vmscan: move inactive_list_is_low() swap check to the caller

[Andrey Ryabinin]

From: Johannes Weiner <hannes at cmpxchg.org>

inactive_list_is_low() should be about one thing: checking the ratio
between inactive and active list.  Kitchensink checks like the one for
swap space makes the function hard to use and modify its callsites.
Luckly, most callers already have an understanding of the swap situation,
so it's easy to clean up.

get_scan_count() has its own, memcg-aware swap check, and doesn't even get
to the inactive_list_is_low() check on the anon list when there is no swap
space available.

shrink_list() is called on the results of get_scan_count(), so that check
is redundant too.

age_active_anon() has its own totalswap_pages check right before it checks
the list proportions.

The shrink_node_memcg() site is the only one that doesn't do its own swap
check.  Add it there.

Then delete the swap check from inactive_list_is_low().

Link: http://lkml.kernel.org/r/20191022144803.302233-4-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes at cmpxchg.org>
Reviewed-by: Roman Gushchin <guro at fb.com>
Reviewed-by: Shakeel Butt <shakeelb at google.com>
Acked-by: Michal Hocko <mhocko at suse.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>

(cherry picked from commit a108629149cc63cfb6fd446184e3e578e04bcfd1)
Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
---
 mm/vmscan.c | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 97f2d297d4a1..7be29b8b4811 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2032,13 +2032,6 @@ static bool inactive_list_is_low(struct lruvec *lruvec, bool file,
 	unsigned long refaults;
 	unsigned long gb;
 
-	/*
-	 * If we don't have swap space, anonymous page deactivation
-	 * is pointless.
-	 */
-	if (!file && !total_swap_pages)
-		return false;
-
 	inactive = lruvec_lru_size(lruvec, inactive_lru, sc->reclaim_idx);
 	active = lruvec_lru_size(lruvec, active_lru, sc->reclaim_idx);
 
@@ -2404,7 +2397,7 @@ static void shrink_node_memcg(struct pglist_data *pgdat, struct mem_cgroup *memc
 	 * Even if we did not try to evict anon pages at all, we want to
 	 * rebalance the anon lru active/inactive ratio.
 	 */
-	if (inactive_list_is_low(lruvec, false, sc, true))
+	if (total_swap_pages && inactive_list_is_low(lruvec, false, sc, true))
 		shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
 				   sc, LRU_ACTIVE_ANON);
 }
-- 
2.24.1