[PATCH 2/9] mm: fix check for reclaimable pages in PF_MEMALLOC reclaim throttling

From: Johannes Weiner <hannes@cmpxchg.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Jia He <hejianet@gmail.com>, Michal Hocko <mhocko@suse.cz>,
	Mel Gorman <mgorman@suse.de>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	kernel-team@fb.com
Subject: [PATCH 2/9] mm: fix check for reclaimable pages in PF_MEMALLOC reclaim throttling
Date: Tue, 28 Feb 2017 16:40:00 -0500	[thread overview]
Message-ID: <20170228214007.5621-3-hannes@cmpxchg.org> (raw)
In-Reply-To: <20170228214007.5621-1-hannes@cmpxchg.org>

PF_MEMALLOC direct reclaimers get throttled on a node when the sum of
all free pages in each zone fall below half the min watermark. During
the summation, we want to exclude zones that don't have reclaimables.
Checking the same pgdat over and over again doesn't make sense.

Fixes: 599d0c954f91 ("mm, vmscan: move LRU lists to node")
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
 mm/vmscan.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 407b27831ff7..f006140f58c6 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2838,8 +2838,10 @@ static bool pfmemalloc_watermark_ok(pg_data_t *pgdat)
 
 	for (i = 0; i <= ZONE_NORMAL; i++) {
 		zone = &pgdat->node_zones[i];
-		if (!managed_zone(zone) ||
-		    pgdat_reclaimable_pages(pgdat) == 0)
+		if (!managed_zone(zone))
+			continue;
+
+		if (!zone_reclaimable_pages(zone))
 			continue;
 
 		pfmemalloc_reserve += min_wmark_pages(zone);
-- 
2.11.1
