+ mm-mglru-run-aging-when-pages-are-rare-outside-the-youngest-gen.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/mglru: run aging when pages are rare outside the youngest gen
has been added to the -mm mm-new branch.  Its filename is
     mm-mglru-run-aging-when-pages-are-rare-outside-the-youngest-gen.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mglru-run-aging-when-pages-are-rare-outside-the-youngest-gen.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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------------------------------------------------------
From: lyugaofei <lyugaofei@xiaomi.com>
Subject: mm/mglru: run aging when pages are rare outside the youngest gen
Date: Thu, 12 Nov 2026 07:25:57 +0800

Run aging when the total number of pages outside the youngest
generation across both types falls below 1/MAX_NR_GENS of the number
of pages in the youngest generation. For extreme swappiness values
such as 1 and 200, also consider the balance of the corresponding
type.

This improves reclaim efficiency, especially at extreme swappiness
values, while reducing system time.

To avoid the overhead of aging, we only allow imbalance-based aging
when the reclaim priority is low enough that we might reclaim the
youngest generation.

Link: https://lore.kernel.org/20261111232603.9934-11-baohua@kernel.org
Signed-off-by: lyugaofei <lyugaofei@xiaomi.com>
Signed-off-by: Barry Song (Xiaomi) <baohua@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Co-developed-by: Barry Song (Xiaomi) <baohua@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <baoquan.he@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: <hui.zhu@linux.dev>
Cc: Kairui Song <kasong@tencent.com>
Cc: Kunwu Chan <kunwu.chan@gmail.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: wang lian <lianux.mm@gmail.com>
Cc: <liuxiang.277@bytedance.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Qi Zheng <qi.zheng@linux.dev>
Cc: Ridong Chen <ridong.chen@linux.dev>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: wangzicheng <wangzicheng@honor.com>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Cc: Bo Zhang <zhangbo56@xiaomi.com>
Cc: Hui Zhu <zhuhui@kylinos.cn>
Cc: Siddharth Chintamaneni <sidchintamaneni@gmail.com>
---

 mm/vmscan.c |   41 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 40 insertions(+), 1 deletion(-)

--- a/mm/vmscan.c~mm-mglru-run-aging-when-pages-are-rare-outside-the-youngest-gen
+++ a/mm/vmscan.c
@@ -5075,6 +5075,41 @@ retry:
 	return scanned;
 }
 
+static bool lru_gen_imbalanced(struct lruvec *lruvec, struct scan_control *sc,
+		int swappiness)
+{
+	unsigned long youngest[ANON_AND_FILE] = {0}, old[ANON_AND_FILE] = {0};
+	struct lru_gen_folio *lrugen = &lruvec->lrugen;
+	DEFINE_MAX_SEQ(lruvec);
+	DEFINE_MIN_SEQ(lruvec);
+	int type;
+
+	if (sc->priority > DEF_PRIORITY / 2)
+		return false;
+
+	for_each_evictable_type(type, swappiness) {
+		unsigned long seq;
+
+		youngest[type] = lruvec_gen_size(lrugen, type, max_seq);
+		for (seq = min_seq[type]; seq < max_seq; seq++)
+			old[type] += lruvec_gen_size(lrugen, type, seq);
+	}
+
+	/* the vast majority of pages sit in the youngest gen */
+	if (youngest[LRU_GEN_ANON] + youngest[LRU_GEN_FILE] >
+	    (old[LRU_GEN_ANON] + old[LRU_GEN_FILE]) * MAX_NR_GENS)
+		return true;
+
+	/* Swappiness extremes: the corresponding type matters */
+	if (swappiness == MIN_SWAPPINESS + 1)
+		return youngest[LRU_GEN_FILE] > old[LRU_GEN_FILE] * MAX_NR_GENS;
+
+	if (swappiness == MAX_SWAPPINESS)
+		return youngest[LRU_GEN_ANON] > old[LRU_GEN_ANON] * MAX_NR_GENS;
+
+	return false;
+}
+
 static bool should_run_aging(struct lruvec *lruvec, unsigned long max_seq,
 			     struct scan_control *sc, int swappiness)
 {
@@ -5089,7 +5124,11 @@ static bool should_run_aging(struct lruv
 		return false;
 
 	/* better to run aging even though eviction is still possible */
-	return evictable_min_seq(min_seq, swappiness) + MIN_NR_GENS == max_seq;
+	if (evictable_min_seq(min_seq, swappiness) + MIN_NR_GENS == max_seq)
+		return true;
+
+	/* run aging when folios outside the youngest gen are rare */
+	return lru_gen_imbalanced(lruvec, sc, swappiness);
 }
 
 static void lru_gen_prepare_scan(struct lruvec *lruvec, struct scan_control *sc,
_

Patches currently in -mm which might be from lyugaofei@xiaomi.com are

mm-mglru-run-aging-when-pages-are-rare-outside-the-youngest-gen.patch
mm-mglru-avoid-prolonged-anon-reclaim-with-swappiness=200.patch