+ mm-add-max-swappiness-arg-to-lru_gen-for-anonymous-memory-only.patch added to mm-new branch

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

The patch titled
     Subject: mm: add max swappiness arg to lru_gen for anonymous memory only
has been added to the -mm mm-new branch.  Its filename is
     mm-add-max-swappiness-arg-to-lru_gen-for-anonymous-memory-only.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-add-max-swappiness-arg-to-lru_gen-for-anonymous-memory-only.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.

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------------------------------------------------------
From: Zhongkun He <hezhongkun.hzk@bytedance.com>
Subject: mm: add max swappiness arg to lru_gen for anonymous memory only
Date: Mon, 21 Apr 2025 17:13:30 +0800

MGLRU already supports reclaiming only from anonymous memory via the
/sys/kernel/debug/lru_gen interface.  Now, memory.reclaim also supports
the swappiness=max parameter to enable reclaiming solely from anonymous
memory.  To unify the semantics of proactive reclaiming from anonymous
folios, the max parameter is introduced.

Link: https://lkml.kernel.org/r/65181f7745d657d664d833c26d8a94cae40538b9.1745225696.git.hezhongkun.hzk@bytedance.com
Signed-off-by: Zhongkun He <hezhongkun.hzk@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Yosry Ahmed <yosry.ahmed@linux.dev>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 Documentation/admin-guide/mm/multigen_lru.rst |    5 +++--
 mm/vmscan.c                                   |   15 ++++++++++++---
 2 files changed, 15 insertions(+), 5 deletions(-)

--- a/Documentation/admin-guide/mm/multigen_lru.rst~mm-add-max-swappiness-arg-to-lru_gen-for-anonymous-memory-only
+++ a/Documentation/admin-guide/mm/multigen_lru.rst
@@ -151,8 +151,9 @@ generations less than or equal to ``min_
 ``min_gen_nr`` should be less than ``max_gen_nr-1``, since
 ``max_gen_nr`` and ``max_gen_nr-1`` are not fully aged (equivalent to
 the active list) and therefore cannot be evicted. ``swappiness``
-overrides the default value in ``/proc/sys/vm/swappiness``.
-``nr_to_reclaim`` limits the number of pages to evict.
+overrides the default value in ``/proc/sys/vm/swappiness`` and the valid
+range is [0-200, max], with max being exclusively used for the reclamation
+of anonymous memory. ``nr_to_reclaim`` limits the number of pages to evict.
 
 A typical use case is that a job scheduler runs this command before it
 tries to land a new job on a server. If it fails to materialize enough
--- a/mm/vmscan.c~mm-add-max-swappiness-arg-to-lru_gen-for-anonymous-memory-only
+++ a/mm/vmscan.c
@@ -5587,7 +5587,7 @@ static ssize_t lru_gen_seq_write(struct
 	while ((cur = strsep(&next, ",;\n"))) {
 		int n;
 		int end;
-		char cmd;
+		char cmd, swap_string[5];
 		unsigned int memcg_id;
 		unsigned int nid;
 		unsigned long seq;
@@ -5598,13 +5598,22 @@ static ssize_t lru_gen_seq_write(struct
 		if (!*cur)
 			continue;
 
-		n = sscanf(cur, "%c %u %u %lu %n %u %n %lu %n", &cmd, &memcg_id, &nid,
-			   &seq, &end, &swappiness, &end, &opt, &end);
+		n = sscanf(cur, "%c %u %u %lu %n %4s %n %lu %n", &cmd, &memcg_id, &nid,
+			   &seq, &end, swap_string, &end, &opt, &end);
 		if (n < 4 || cur[end]) {
 			err = -EINVAL;
 			break;
 		}
 
+		/* set by userspace for anonymous memory only */
+		if (!strncmp("max", swap_string, sizeof("max"))) {
+			swappiness = SWAPPINESS_ANON_ONLY;
+		} else {
+			err = kstrtouint(swap_string, 0, &swappiness);
+			if (err)
+				break;
+		}
+
 		err = run_cmd(cmd, memcg_id, nid, seq, &sc, swappiness, opt);
 		if (err)
 			break;
_

Patches currently in -mm which might be from hezhongkun.hzk@bytedance.com are

mm-add-swappiness=max-arg-to-memoryreclaim-for-only-anon-reclaim.patch
mm-vmscan-add-more-comments-about-cache_trim_mode.patch
mm-add-max-swappiness-arg-to-lru_gen-for-anonymous-memory-only.patch
mm-using-swappiness_anon_only-in-mglru.patch