Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Xunlei Pang <xlpang@linux.alibaba.com>
To:     Michal Hocko <mhocko@suse.com>, Roman Gushchin <guro@fb.com>,
        Johannes Weiner <hannes@cmpxchg.org>
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: [PATCH 2/3] mm/vmscan: Enable kswapd to reclaim low-protected memory
Date:   Mon,  3 Dec 2018 16:01:18 +0800
Message-Id: <20181203080119.18989-2-xlpang@linux.alibaba.com>
In-Reply-To: <20181203080119.18989-1-xlpang@linux.alibaba.com>
References: <20181203080119.18989-1-xlpang@linux.alibaba.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

There may be cgroup memory overcommitment, it will become
even common in the future.

Let's enable kswapd to reclaim low-protected memory in case
of memory pressure, to mitigate the global direct reclaim
pressures which could cause jitters to the response time of
lantency-sensitive groups.

Signed-off-by: Xunlei Pang <xlpang@linux.alibaba.com>
---
 mm/vmscan.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 62ac0c488624..3d412eb91f73 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3531,6 +3531,7 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx)
 
 	count_vm_event(PAGEOUTRUN);
 
+retry:
 	do {
 		unsigned long nr_reclaimed = sc.nr_reclaimed;
 		bool raise_priority = true;
@@ -3622,6 +3623,13 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx)
 			sc.priority--;
 	} while (sc.priority >= 1);
 
+	if (!sc.nr_reclaimed && sc.memcg_low_skipped) {
+		sc.priority = DEF_PRIORITY;
+		sc.memcg_low_reclaim = 1;
+		sc.memcg_low_skipped = 0;
+		goto retry;
+	}
+
 	if (!sc.nr_reclaimed)
 		pgdat->kswapd_failures++;
 
-- 
2.13.5 (Apple Git-94)