linux-kernel - [PATCH mm-unstable v1 2/5] mm/mglru: improve should_run

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Date: Wed, 14 Feb 2024 06:05:35 +0000
From: Kinsey Ho <kinseyho@...gle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, 
	Yu Zhao <yuzhao@...gle.com>, Donet Tom <donettom@...ux.vnet.ibm.com>, 
	"Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>, Kinsey Ho <kinseyho@...gle.com>
Subject: [PATCH mm-unstable v1 2/5] mm/mglru: improve should_run_aging()

scan_control *sc does not need to be passed into should_run_aging(), as
it provides only the reclaim priority. This can be moved to
get_nr_to_scan().

Refactor should_run_aging() and get_nr_to_scan() to improve code
readability. No functional changes.

Signed-off-by: Kinsey Ho <kinseyho@...gle.com>
---
 mm/vmscan.c | 25 +++++++++++--------------
 1 file changed, 11 insertions(+), 14 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 9d15648561ec..87de39e7410b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4602,14 +4602,13 @@ static int evict_folios(struct lruvec *lruvec, struct scan_control *sc, int swap
 }
 
 static bool should_run_aging(struct lruvec *lruvec, unsigned long max_seq,
-			     struct scan_control *sc, bool can_swap, unsigned long *nr_to_scan)
+			     bool can_swap, unsigned long *nr_to_scan)
 {
 	int gen, type, zone;
 	unsigned long old = 0;
 	unsigned long young = 0;
 	unsigned long total = 0;
 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
-	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
 	DEFINE_MIN_SEQ(lruvec);
 
 	/* whether this lruvec is completely out of cold folios */
@@ -4637,13 +4636,7 @@ static bool should_run_aging(struct lruvec *lruvec, unsigned long max_seq,
 		}
 	}
 
-	/* try to scrape all its memory if this memcg was deleted */
-	if (!mem_cgroup_online(memcg)) {
-		*nr_to_scan = total;
-		return false;
-	}
-
-	*nr_to_scan = total >> sc->priority;
+	*nr_to_scan = total;
 
 	/*
 	 * The aging tries to be lazy to reduce the overhead, while the eviction
@@ -4675,6 +4668,7 @@ static bool should_run_aging(struct lruvec *lruvec, unsigned long max_seq,
  */
 static long get_nr_to_scan(struct lruvec *lruvec, struct scan_control *sc, bool can_swap)
 {
+	bool success;
 	unsigned long nr_to_scan;
 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
 	DEFINE_MAX_SEQ(lruvec);
@@ -4682,14 +4676,17 @@ static long get_nr_to_scan(struct lruvec *lruvec, struct scan_control *sc, bool
 	if (mem_cgroup_below_min(sc->target_mem_cgroup, memcg))
 		return -1;
 
-	if (!should_run_aging(lruvec, max_seq, sc, can_swap, &nr_to_scan))
-		return nr_to_scan;
+	success = should_run_aging(lruvec, max_seq, can_swap, &nr_to_scan);
 
-	/* skip the aging path at the default priority */
-	if (sc->priority == DEF_PRIORITY)
+	/* try to scrape all its memory if this memcg was deleted */
+	if (nr_to_scan && !mem_cgroup_online(memcg))
 		return nr_to_scan;
 
-	/* skip this lruvec as it's low on cold folios */
+	/* try to get away with not aging at the default priority */
+	if (!success || sc->priority == DEF_PRIORITY)
+		return nr_to_scan >> sc->priority;
+
+	/* stop scanning this lruvec as it's low on cold folios */
 	return try_to_inc_max_seq(lruvec, max_seq, can_swap, false) ? -1 : 0;
 }
 
-- 
2.43.0.687.g38aa6559b0-goog