linux-kernel - [PATCH 1/7] mm: workingset: don't drop refault information prematurely

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Date:   Mon,  7 May 2018 17:01:29 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-block@...r.kernel.org, cgroups@...r.kernel.org
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...uxfoundation.org>,
        Tejun Heo <tj@...nel.org>,
        Balbir Singh <bsingharora@...il.com>,
        Mike Galbraith <efault@....de>,
        Oliver Yang <yangoliver@...com>,
        Shakeel Butt <shakeelb@...gle.com>,
        xxx xxx <x.qendo@...il.com>,
        Taras Kondratiuk <takondra@...co.com>,
        Daniel Walker <danielwa@...co.com>,
        Vinayak Menon <vinmenon@...eaurora.org>,
        Ruslan Ruslichenko <rruslich@...co.com>, kernel-team@...com
Subject: [PATCH 1/7] mm: workingset: don't drop refault information prematurely

From: Johannes Weiner <jweiner@...com>

If we just keep enough refault information to match the CURRENT page
cache during reclaim time, we could lose a lot of events when there is
only a temporary spike in non-cache memory consumption that pushes out
all the cache. Once cache comes back, we won't see those refaults.
They might not be actionable for LRU aging, but we want to know about
them for measuring memory pressure.

Signed-off-by: Johannes Weiner <jweiner@...com>
---
 mm/workingset.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/mm/workingset.c b/mm/workingset.c
index 40ee02c83978..53759a3cf99a 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -364,7 +364,7 @@ static unsigned long count_shadow_nodes(struct shrinker *shrinker,
 {
 	unsigned long max_nodes;
 	unsigned long nodes;
-	unsigned long cache;
+	unsigned long pages;
 
 	/* list_lru lock nests inside the IRQ-safe i_pages lock */
 	local_irq_disable();
@@ -393,14 +393,14 @@ static unsigned long count_shadow_nodes(struct shrinker *shrinker,
 	 *
 	 * PAGE_SIZE / radix_tree_nodes / node_entries * 8 / PAGE_SIZE
 	 */
-	if (sc->memcg) {
-		cache = mem_cgroup_node_nr_lru_pages(sc->memcg, sc->nid,
-						     LRU_ALL_FILE);
-	} else {
-		cache = node_page_state(NODE_DATA(sc->nid), NR_ACTIVE_FILE) +
-			node_page_state(NODE_DATA(sc->nid), NR_INACTIVE_FILE);
-	}
-	max_nodes = cache >> (RADIX_TREE_MAP_SHIFT - 3);
+#ifdef CONFIG_MEMCG
+	if (sc->memcg)
+		pages = page_counter_read(&sc->memcg->memory);
+	else
+#endif
+		pages = node_present_pages(sc->nid);
+
+	max_nodes = pages >> (RADIX_TREE_MAP_SHIFT - 3);
 
 	if (nodes <= max_nodes)
 		return 0;
-- 
2.17.0