[merged mm-stable] memcg-group-the-read-mostly-fields-of-struct-mem_cgroup.patch removed from -mm tree

[merged mm-stable] memcg-group-the-read-mostly-fields-of-struct-mem_cgroup.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: memcg: group the read-mostly fields of struct mem_cgroup
has been removed from the -mm tree.  Its filename was
     memcg-group-the-read-mostly-fields-of-struct-mem_cgroup.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Shakeel Butt <shakeel.butt@linux.dev>
Subject: memcg: group the read-mostly fields of struct mem_cgroup
Date: Fri, 4 Sep 2026 20:05:21 -0700

These fields are set when the memcg is created and only read after
that:

  vmstats_percpu   read on every stat update
  vmstats
  zswap_max, zswap_writeback
  private_id       read on every eviction and refault
  kmemcg_id        read on every list_lru lookup
  oom_group

Put them in one cache line group at the end of the struct, right before
nodeinfo[].  nodeinfo[] is read-mostly too but it is a flexible array, so
it cannot sit inside a group.  The group ends without padding so the two
share a line.

This also drops the ____cacheline_aligned_in_smp on vmstats_percpu added
by commit c1afbd5de131 ("mm/memcontrol: avoid false sharing between
vmstats and events").  That only aligned the start of the field. 
cgwb_domain followed it on the same line and is written on every writeout
completion.  A group boundary covers both sides.

No functional change.

Link: https://lore.kernel.org/20260905030522.1887837-6-shakeel.butt@linux.dev
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
---

 include/linux/memcontrol.h |   62 +++++++++++++++++++----------------
 mm/memcontrol.c            |   17 +++++++++
 2 files changed, 52 insertions(+), 27 deletions(-)

--- a/include/linux/memcontrol.h~memcg-group-the-read-mostly-fields-of-struct-mem_cgroup
+++ a/include/linux/memcontrol.h
@@ -183,9 +183,6 @@ struct obj_cgroup {
 struct mem_cgroup {
 	struct cgroup_subsys_state css;
 
-	/* Private memcg ID. Used to ID objects that outlive the cgroup */
-	int private_id;
-
 	/* Accounted resources */
 	struct page_counter memory;		/* Both v1 & v2 */
 
@@ -259,30 +256,6 @@ struct mem_cgroup {
 #endif
 	__cacheline_group_end_aligned(memcg_cold);
 
-#ifdef CONFIG_ZSWAP
-	unsigned long zswap_max;
-
-	/*
-	 * Prevent pages from this memcg from being written back from zswap to
-	 * swap, and from being swapped out on zswap store failures.
-	 */
-	bool zswap_writeback;
-#endif
-
-	/*
-	 * Should the OOM killer kill all belonging tasks, had it kill one?
-	 */
-	bool oom_group;
-
-	/* memory.stat */
-	struct memcg_vmstats	*vmstats;
-
-	int kmemcg_id;
-
-	/* Keep the hot per-CPU stats pointer away from memory event counters. */
-	struct memcg_vmstats_percpu __percpu *vmstats_percpu
-		____cacheline_aligned_in_smp;
-
 #ifdef CONFIG_MEMCG_V1
 	/* v1 only. Not grouped: v1 is legacy, sorting it is not worth it. */
 
@@ -322,6 +295,41 @@ struct mem_cgroup {
 	int swappiness;
 #endif /* CONFIG_MEMCG_V1 */
 
+	/*
+	 * Set when the memcg is created and cleared when it is offlined.
+	 * Never written on a hot path.
+	 */
+	__cacheline_group_begin_aligned(memcg_read_mostly);
+	/* Read on every stat update */
+	struct memcg_vmstats_percpu __percpu *vmstats_percpu;
+
+	/* memory.stat */
+	struct memcg_vmstats	*vmstats;
+
+#ifdef CONFIG_ZSWAP
+	unsigned long zswap_max;
+#endif
+
+	/* Private memcg ID. Used to ID objects that outlive the cgroup */
+	int private_id;
+
+	int kmemcg_id;
+
+	/*
+	 * Should the OOM killer kill all belonging tasks, had it kill one?
+	 */
+	bool oom_group;
+
+#ifdef CONFIG_ZSWAP
+	/*
+	 * Prevent pages from this memcg from being written back from zswap to
+	 * swap, and from being swapped out on zswap store failures.
+	 */
+	bool zswap_writeback;
+#endif
+	/* Not padded: nodeinfo[] is read-mostly too, let it share the line. */
+	__cacheline_group_end(memcg_read_mostly);
+
 	struct mem_cgroup_per_node *nodeinfo[];
 };
 
--- a/mm/memcontrol.c~memcg-group-the-read-mostly-fields-of-struct-mem_cgroup
+++ a/mm/memcontrol.c
@@ -5753,6 +5753,23 @@ static void __init memcg_struct_check(vo
 	CACHELINE_ASSERT_GROUP_MEMBER(struct mem_cgroup, memcg_cold,
 				      mm_list);
 #endif
+
+	CACHELINE_ASSERT_GROUP_MEMBER(struct mem_cgroup, memcg_read_mostly,
+				      vmstats_percpu);
+	CACHELINE_ASSERT_GROUP_MEMBER(struct mem_cgroup, memcg_read_mostly,
+				      vmstats);
+#ifdef CONFIG_ZSWAP
+	CACHELINE_ASSERT_GROUP_MEMBER(struct mem_cgroup, memcg_read_mostly,
+				      zswap_max);
+	CACHELINE_ASSERT_GROUP_MEMBER(struct mem_cgroup, memcg_read_mostly,
+				      zswap_writeback);
+#endif
+	CACHELINE_ASSERT_GROUP_MEMBER(struct mem_cgroup, memcg_read_mostly,
+				      private_id);
+	CACHELINE_ASSERT_GROUP_MEMBER(struct mem_cgroup, memcg_read_mostly,
+				      kmemcg_id);
+	CACHELINE_ASSERT_GROUP_MEMBER(struct mem_cgroup, memcg_read_mostly,
+				      oom_group);
 }
 
 int __init mem_cgroup_init(void)
_

Patches currently in -mm which might be from shakeel.butt@linux.dev are