+ mm-mglru-run-aging-when-one-type-has-no-populatable-folios.patch added to mm-new branch

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

The patch titled
     Subject: mm/mglru: run aging when one type has no populatable folios
has been added to the -mm mm-new branch.  Its filename is
     mm-mglru-run-aging-when-one-type-has-no-populatable-folios.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-one-type-has-no-populatable-folios.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: "Barry Song (Xiaomi)" <baohua@kernel.org>
Subject: mm/mglru: run aging when one type has no populatable folios
Date: Sat, 14 Nov 2026 02:55:36 +0800

We may have scan budget remaining for anon or file but no folios in
populatable generations to scan.  In this case, `scan_folios()` may waste
time scanning that type while the other type still has populatable folios.

Run aging in this case to make more folios populatable.  This also helps
respect the scan budget distribution determined by swappiness.

To avoid excessive aging, allow no-populatable aging only once per
`try_to_shrink_lruvec()` invocation.

With extreme swappiness values such as 1 and 200, reclaim initially
focuses exclusively on the preferred type.  In this case, defer aging the
lagging type until `sc->priority` reaches `DEF_PRIORITY / 2`.  This avoids
unnecessary aging and has shown better performance in testing.

Link: https://lore.kernel.org/20261113185541.70203-12-baohua@kernel.org
Signed-off-by: Barry Song (Xiaomi) <baohua@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.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: <lyugaofei@xiaomi.com>
Cc: Michal Hocko <mhocko@kernel.org>
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>
Cc: Bo Zhang <zhangbo0325@gmail.com>
---

 mm/vmscan.c |   49 ++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 38 insertions(+), 11 deletions(-)

--- a/mm/vmscan.c~mm-mglru-run-aging-when-one-type-has-no-populatable-folios
+++ a/mm/vmscan.c
@@ -5109,7 +5109,8 @@ static bool lru_gen_imbalanced(struct lr
 }
 
 static bool should_run_aging(struct lruvec *lruvec, unsigned long max_seq,
-			     struct scan_control *sc, int swappiness)
+			     struct scan_control *sc, int swappiness,
+			     bool no_populatable)
 {
 	DEFINE_MIN_SEQ(lruvec);
 
@@ -5121,6 +5122,13 @@ static bool should_run_aging(struct lruv
 	if (sc->priority == DEF_PRIORITY)
 		return false;
 
+	/*
+	 * Run aging if scan budget remains but no folios
+	 * in populatable generations are available to scan.
+	 */
+	if (no_populatable)
+		return true;
+
 	/* better to run aging even though eviction is still possible */
 	if (evictable_min_seq(min_seq, swappiness) + MIN_NR_GENS == max_seq)
 		return true;
@@ -5208,6 +5216,13 @@ static bool try_to_shrink_lruvec(struct
 	bool need_rotate = false, should_age = false;
 	int swappiness = get_swappiness(lruvec, sc);
 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
+	/*
+	 * Avoid aging the lagging type under extreme swappiness,
+	 * as reclaim of the unpreferred type is disabled until
+	 * DEF_PRIORITY / 2.
+	 */
+	bool allow_no_populatable_age = (sc->priority <= DEF_PRIORITY / 2) ||
+		(swappiness > MIN_SWAPPINESS + 1 && swappiness < MAX_SWAPPINESS);
 
 	/*
 	 * Proactive reclaim initiated by userspace for anonymous memory only.
@@ -5225,22 +5240,19 @@ static bool try_to_shrink_lruvec(struct
 	lru_gen_prepare_scan(lruvec, sc, memcg, swappiness, nr);
 
 	while (nr[LRU_GEN_ANON] > 0 || nr[LRU_GEN_FILE] > 0) {
-		DEFINE_MAX_SEQ(lruvec);
+		unsigned long orig_file, orig_anon;
+		unsigned long max_seq;
+		bool no_populatable;
+		long scanned;
 
 		if (mem_cgroup_below_min(sc->target_mem_cgroup, memcg)) {
 			need_rotate = true;
 			break;
 		}
 
-		if (should_run_aging(lruvec, max_seq, sc, swappiness)) {
-			trace_mm_mglru_aging(lruvec, sc, swappiness);
-			if (try_to_inc_max_seq(lruvec, max_seq, swappiness, false))
-				need_rotate = true;
-			should_age = true;
-		}
-
-		if (!evict_folio_lists(nr, lruvec, sc, swappiness, MIN_LRU_BATCH))
-			break;
+		orig_anon = nr[LRU_GEN_ANON];
+		orig_file = nr[LRU_GEN_FILE];
+		scanned = evict_folio_lists(nr, lruvec, sc, swappiness, MIN_LRU_BATCH);
 
 		if (should_abort_scan(lruvec, sc))
 			break;
@@ -5252,6 +5264,21 @@ static bool try_to_shrink_lruvec(struct
 		if (root_reclaim(sc) && should_age)
 			break;
 
+		/* Limit no_populatable aging to once per try_to_shrink_lruvec() */
+		no_populatable = allow_no_populatable_age &&
+			((nr[LRU_GEN_ANON] && nr[LRU_GEN_ANON] == orig_anon) ||
+			(nr[LRU_GEN_FILE] && nr[LRU_GEN_FILE] == orig_file));
+		allow_no_populatable_age &= !no_populatable;
+		max_seq = READ_ONCE((lruvec)->lrugen.max_seq);
+		if (should_run_aging(lruvec, max_seq, sc, swappiness, no_populatable)) {
+			trace_mm_mglru_aging(lruvec, sc, swappiness);
+			if (try_to_inc_max_seq(lruvec, max_seq, swappiness, false))
+				need_rotate = true;
+			should_age = true;
+		}
+		if (!scanned)
+			break;
+
 		cond_resched();
 	}
 
_

Patches currently in -mm which might be from baohua@kernel.org are

arm64-vmalloc-allow-arch_vmap_pte_range_map_size-to-batch-multiple-cont_pte.patch
mm-vmalloc-extend-page-table-walk-to-support-larger-page_shift-sizes-and-eliminate-page-table-rewalk.patch
mm-vmalloc-map-contiguous-pages-in-batches-for-vmap-if-possible.patch
mm-vmalloc-align-vm_area-so-vmap-can-batch-mappings.patch
mm-mglru-avoid-placing-rejected-folios-below-populated-gen.patch
mm-mglru-run-aging-when-one-type-has-no-populatable-folios.patch
mm-mglru-restrict-eviction-accounting-to-eligible-zones.patch
mm-mglru-reduce-lru-lock-contention-by-shrinking-folio-batches-in-inc_min_seq.patch
mm-mglru-make-swappiness=1-file-reclaim-more-aggressive.patch