mm: multi-gen LRU: shuffle should_run_aging()

Move should_run_aging() next to its only caller left.

Link: https://lkml.kernel.org/r/20221222041905.2431096-6-yuzhao@google.com
Signed-off-by: Yu Zhao <yuzhao@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Michael Larabel <Michael@MichaelLarabel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/vmscan.c

@@ -4467,68 +4467,6 @@ static bool try_to_inc_max_seq(struct lruvec *lruvec, unsigned long max_seq,
 	return true;
 }
 
-static bool should_run_aging(struct lruvec *lruvec, unsigned long max_seq,
-			     struct scan_control *sc, 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 */
-	if (min_seq[!can_swap] + MIN_NR_GENS > max_seq) {
-		*nr_to_scan = 0;
-		return true;
-	}
-
-	for (type = !can_swap; type < ANON_AND_FILE; type++) {
-		unsigned long seq;
-
-		for (seq = min_seq[type]; seq <= max_seq; seq++) {
-			unsigned long size = 0;
-
-			gen = lru_gen_from_seq(seq);
-
-			for (zone = 0; zone < MAX_NR_ZONES; zone++)
-				size += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L);
-
-			total += size;
-			if (seq == max_seq)
-				young += size;
-			else if (seq + MIN_NR_GENS == max_seq)
-				old += size;
-		}
-	}
-
-	/* try to scrape all its memory if this memcg was deleted */
-	*nr_to_scan = mem_cgroup_online(memcg) ? (total >> sc->priority) : total;
-
-	/*
-	 * The aging tries to be lazy to reduce the overhead, while the eviction
-	 * stalls when the number of generations reaches MIN_NR_GENS. Hence, the
-	 * ideal number of generations is MIN_NR_GENS+1.
-	 */
-	if (min_seq[!can_swap] + MIN_NR_GENS < max_seq)
-		return false;
-
-	/*
-	 * It's also ideal to spread pages out evenly, i.e., 1/(MIN_NR_GENS+1)
-	 * of the total number of pages for each generation. A reasonable range
-	 * for this average portion is [1/MIN_NR_GENS, 1/(MIN_NR_GENS+2)]. The
-	 * aging cares about the upper bound of hot pages, while the eviction
-	 * cares about the lower bound of cold pages.
-	 */
-	if (young * MIN_NR_GENS > total)
-		return true;
-	if (old * (MIN_NR_GENS + 2) < total)
-		return true;
-
-	return false;
-}
-
 static bool lruvec_is_sizable(struct lruvec *lruvec, struct scan_control *sc)
 {
 	int gen, type, zone;
@@ -5112,6 +5050,68 @@ static int evict_folios(struct lruvec *lruvec, struct scan_control *sc, int swap
 	return scanned;
 }
 
+static bool should_run_aging(struct lruvec *lruvec, unsigned long max_seq,
+			     struct scan_control *sc, 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 */
+	if (min_seq[!can_swap] + MIN_NR_GENS > max_seq) {
+		*nr_to_scan = 0;
+		return true;
+	}
+
+	for (type = !can_swap; type < ANON_AND_FILE; type++) {
+		unsigned long seq;
+
+		for (seq = min_seq[type]; seq <= max_seq; seq++) {
+			unsigned long size = 0;
+
+			gen = lru_gen_from_seq(seq);
+
+			for (zone = 0; zone < MAX_NR_ZONES; zone++)
+				size += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L);
+
+			total += size;
+			if (seq == max_seq)
+				young += size;
+			else if (seq + MIN_NR_GENS == max_seq)
+				old += size;
+		}
+	}
+
+	/* try to scrape all its memory if this memcg was deleted */
+	*nr_to_scan = mem_cgroup_online(memcg) ? (total >> sc->priority) : total;
+
+	/*
+	 * The aging tries to be lazy to reduce the overhead, while the eviction
+	 * stalls when the number of generations reaches MIN_NR_GENS. Hence, the
+	 * ideal number of generations is MIN_NR_GENS+1.
+	 */
+	if (min_seq[!can_swap] + MIN_NR_GENS < max_seq)
+		return false;
+
+	/*
+	 * It's also ideal to spread pages out evenly, i.e., 1/(MIN_NR_GENS+1)
+	 * of the total number of pages for each generation. A reasonable range
+	 * for this average portion is [1/MIN_NR_GENS, 1/(MIN_NR_GENS+2)]. The
+	 * aging cares about the upper bound of hot pages, while the eviction
+	 * cares about the lower bound of cold pages.
+	 */
+	if (young * MIN_NR_GENS > total)
+		return true;
+	if (old * (MIN_NR_GENS + 2) < total)
+		return true;
+
+	return false;
+}
+
 /*
  * For future optimizations:
  * 1. Defer try_to_inc_max_seq() to workqueues to reduce latency for memcg