+ mm-mglru-enhance-cold-hot-inversion-handling-in-inc_min_seq.patch added to mm-new branch

+ mm-mglru-enhance-cold-hot-inversion-handling-in-inc_min_seq.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: mm/mglru: enhance cold/hot inversion handling in inc_min_seq()
has been added to the -mm mm-new branch.  Its filename is
     mm-mglru-enhance-cold-hot-inversion-handling-in-inc_min_seq.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mglru-enhance-cold-hot-inversion-handling-in-inc_min_seq.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: enhance cold/hot inversion handling in inc_min_seq()
Date: Wed, 2 Sep 2026 07:24:17 +0800

During aging, a folio's generation may already have been updated by
folio_update_gen(), even though it has not yet been moved to the
corresponding generation list.  Such folios are hotter than those already
in that generation.

It makes sense for inc_min_seq() to increment the generation of folios
that were never promoted during aging and move them to the tail of the new
oldest generation.  However, folios that were already promoted should
instead be moved to the head of their updated generation, just as
sort_folio() does in scan_folios().

Otherwise, promoted folios could end up behind folios that were never
promoted, effectively inverting their hot/cold ordering.

Link: https://lore.kernel.org/20260901232421.40157-4-baohua@kernel.org
Signed-off-by: Barry Song (Xiaomi) <baohua@kernel.org>
Reviewed-by: Kairui Song <kasong@tencent.com>
Tested-by: Xueyuan Chen <xueyuan.chen21@gmail.com>
Reviewed-by: Ridong Chen <ridong.chen@linux.dev>
Reviewed-by: Lian Wang <lianux.mm@gmail.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <baoquan.he@linux.dev>
Cc: David Hildenbrand <david@kernel.org>
Cc: David Stevens <stevensd@chromium.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kunwu Chan <kunwu.chan@gmail.com>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/vmscan.c |   12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

--- a/mm/vmscan.c~mm-mglru-enhance-cold-hot-inversion-handling-in-inc_min_seq
+++ a/mm/vmscan.c
@@ -3954,9 +3954,17 @@ static bool inc_min_seq(struct lruvec *l
 			VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio);
 
 			new_gen = __folio_inc_gen(folio, old_gen, &gen_increased);
-			list_move_tail(&folio->lru, &lrugen->folios[new_gen][type][zone]);
-			if (gen_increased)
+			/*
+			 * If gen_increased is false, this is a promotion. Put folios
+			 * at the head of the promoted gen. Otherwise, put them at
+			 * the tail of the second-oldest gen.
+			 */
+			if (gen_increased) {
 				delta += nr_pages;
+				list_move_tail(&folio->lru, &lrugen->folios[new_gen][type][zone]);
+			} else {
+				list_move(&folio->lru, &lrugen->folios[new_gen][type][zone]);
+			}
 			/* don't count the workingset being lazily promoted */
 			if (refs + workingset != BIT(LRU_REFS_WIDTH) + 1) {
 				int tier = lru_tier_from_refs(refs, workingset);
_

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

mm-mglru-make-retry-logic-explicit-in-isolate_folios.patch
mm-vmscan-avoid-pointless-large-folio-splits-without-swap.patch
mm-mglru-separate-folio-generation-update-from-lru-accounting.patch
mm-mglru-batch-update-lrugen-nr_pages-in-inc_min_seq.patch
mm-mglru-enhance-cold-hot-inversion-handling-in-inc_min_seq.patch
mm-mglru-exclude-folios-promoted-by-aging-from-protected-in-inc_min_seq.patch
mm-mglru-make-lru-folio-prefetch-helper-an-inline-function.patch
mm-mglru-move-folios-from-oldest-gen-to-second-oldest-gen-from-head-to-tail.patch
mm-mglru-batch-move-folios-to-the-second-oldest-gens-lru.patch