* [PATCH 1/2] memcg: move mem_cgroup_swappiness to memcontrol.h
2026-07-11 9:11 [PATCH 0/2] mm: fix node reclaim swappiness handling Ridong Chen
@ 2026-07-11 9:11 ` Ridong Chen
2026-07-11 9:11 ` [PATCH 2/2] mm: vmscan: fix node reclaim ignoring swappiness parameter Ridong Chen
1 sibling, 0 replies; 3+ messages in thread
From: Ridong Chen @ 2026-07-11 9:11 UTC (permalink / raw)
To: Andrew Morton, Johannes Weiner, Michal Hocko, Roman Gushchin,
Shakeel Butt, Muchun Song, Chris Li, Kairui Song,
David Hildenbrand, Barry Song, Yuanchu Xie
Cc: linux-mm, cgroups, linux-kernel, ridong.chen, Ridong Chen
From: Ridong Chen <chenridong@xiaomi.com>
The per-memcg swappiness knob is v1-only; v2 always uses global
vm_swappiness and ignores the per-cgroup field.
Guard memcg->swappiness with CONFIG_MEMCG_V1, and move the helper
to memcontrol.h where it belongs.
No functional change for v1; v2-only kernels drop the unused field.
Signed-off-by: Ridong Chen <chenridong@xiaomi.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
---
include/linux/memcontrol.h | 25 +++++++++++++++++++++++--
include/linux/swap.h | 19 -------------------
mm/memcontrol.c | 3 +--
3 files changed, 24 insertions(+), 23 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index e1f46a0016fc..f59614956f96 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -239,8 +239,6 @@ struct mem_cgroup {
*/
bool oom_group;
- int swappiness;
-
/* memory.events and memory.events.local */
struct cgroup_file events_file;
struct cgroup_file events_local_file;
@@ -318,6 +316,9 @@ struct mem_cgroup {
/* List of events which userspace want to receive */
struct list_head event_list;
spinlock_t event_list_lock;
+
+ int swappiness;
+
#endif /* CONFIG_MEMCG_V1 */
struct mem_cgroup_per_node *nodeinfo[];
@@ -365,6 +366,9 @@ enum objext_flags {
#define OBJEXTS_FLAGS_MASK (__NR_OBJEXTS_FLAGS - 1)
+/* Defined in mm/vmscan.c; used by mem_cgroup_swappiness(). */
+extern int vm_swappiness;
+
#ifdef CONFIG_MEMCG
/*
* After the initialization objcg->memcg is always pointing at
@@ -1440,6 +1444,23 @@ static inline void mem_cgroup_flush_workqueue(void) { }
static inline int mem_cgroup_init(void) { return 0; }
#endif /* CONFIG_MEMCG */
+static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg)
+{
+#ifdef CONFIG_MEMCG_V1
+ /* Cgroup2 doesn't have per-cgroup swappiness */
+ if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
+ return READ_ONCE(vm_swappiness);
+
+ /* root ? */
+ if (mem_cgroup_disabled() || mem_cgroup_is_root(memcg))
+ return READ_ONCE(vm_swappiness);
+
+ return READ_ONCE(memcg->swappiness);
+#else
+ return READ_ONCE(vm_swappiness);
+#endif
+}
+
/*
* Extended information for slab objects stored as an array in page->memcg_data
* if MEMCG_DATA_OBJEXTS is set.
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 8f0f68e245ba..2cfe364d66dc 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -372,7 +372,6 @@ extern unsigned long mem_cgroup_shrink_node(struct mem_cgroup *mem,
pg_data_t *pgdat,
unsigned long *nr_scanned);
extern unsigned long shrink_all_memory(unsigned long nr_pages);
-extern int vm_swappiness;
long remove_mapping(struct address_space *mapping, struct folio *folio);
#if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
@@ -537,25 +536,7 @@ static inline int add_swap_extent(struct swap_info_struct *sis,
}
#endif /* CONFIG_SWAP */
#ifdef CONFIG_MEMCG
-static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg)
-{
- /* Cgroup2 doesn't have per-cgroup swappiness */
- if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
- return READ_ONCE(vm_swappiness);
-
- /* root ? */
- if (mem_cgroup_disabled() || mem_cgroup_is_root(memcg))
- return READ_ONCE(vm_swappiness);
-
- return READ_ONCE(memcg->swappiness);
-}
-
void lru_reparent_memcg(struct mem_cgroup *memcg, struct mem_cgroup *parent, int nid);
-#else
-static inline int mem_cgroup_swappiness(struct mem_cgroup *mem)
-{
- return READ_ONCE(vm_swappiness);
-}
#endif
#if defined(CONFIG_SWAP) && defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6dc4888a90f3..b61def56c41a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4174,11 +4174,10 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
#endif
page_counter_set_high(&memcg->swap, PAGE_COUNTER_MAX);
if (parent) {
- WRITE_ONCE(memcg->swappiness, mem_cgroup_swappiness(parent));
-
page_counter_init(&memcg->memory, &parent->memory, memcg_on_dfl);
page_counter_init(&memcg->swap, &parent->swap, false);
#ifdef CONFIG_MEMCG_V1
+ WRITE_ONCE(memcg->swappiness, mem_cgroup_swappiness(parent));
memcg->memory.track_failcnt = !memcg_on_dfl;
WRITE_ONCE(memcg->oom_kill_disable, READ_ONCE(parent->oom_kill_disable));
page_counter_init(&memcg->kmem, &parent->kmem, false);
--
2.43.0
^ permalink raw reply related [flat|nested] 3+ messages in thread* [PATCH 2/2] mm: vmscan: fix node reclaim ignoring swappiness parameter
2026-07-11 9:11 [PATCH 0/2] mm: fix node reclaim swappiness handling Ridong Chen
2026-07-11 9:11 ` [PATCH 1/2] memcg: move mem_cgroup_swappiness to memcontrol.h Ridong Chen
@ 2026-07-11 9:11 ` Ridong Chen
1 sibling, 0 replies; 3+ messages in thread
From: Ridong Chen @ 2026-07-11 9:11 UTC (permalink / raw)
To: Andrew Morton, Johannes Weiner, Michal Hocko, Roman Gushchin,
Shakeel Butt, Muchun Song, Chris Li, Kairui Song,
David Hildenbrand, Barry Song, Yuanchu Xie
Cc: linux-mm, cgroups, linux-kernel, ridong.chen, Ridong Chen
From: Ridong Chen <chenridong@xiaomi.com>
sc_swappiness() had two separate definitions depending on
CONFIG_MEMCG. The !CONFIG_MEMCG variant simply returned
vm_swappiness, ignoring the proactive_swappiness value passed
through scan_control. This caused the swappiness parameter
written to /sys/devices/system/node/nodeX/reclaim to have no
effect when CONFIG_MEMCG is disabled.
Fix this by consolidating sc_swappiness() into a single definition
that checks sc->proactive_swappiness first, then falls back to
mem_cgroup_swappiness() which already handles both CONFIG_MEMCG
and !CONFIG_MEMCG.
Before fix (swappiness=max ignored, mostly file pages reclaimed):
# cat /proc/sys/vm/swappiness
60
# cat /proc/vmstat | grep pgsteal
pgsteal_kswapd 0
pgsteal_direct 0
pgsteal_khugepaged 0
pgsteal_proactive 1840
pgsteal_anon 25
pgsteal_file 1815
# echo "64M swappiness=max" > /sys/devices/system/node/node0/reclaim
# cat /proc/vmstat | grep pgsteal
pgsteal_kswapd 0
pgsteal_direct 0
pgsteal_khugepaged 0
pgsteal_proactive 18013
pgsteal_anon 337
pgsteal_file 17676
After fix (swappiness=max honored, anon pages reclaimed as expected):
# cat /proc/vmstat | grep pgsteal
pgsteal_kswapd 0
pgsteal_direct 0
pgsteal_khugepaged 0
pgsteal_proactive 0
pgsteal_anon 0
pgsteal_file 0
# echo "64M swappiness=max" > /sys/devices/system/node/node0/reclaim
# cat /proc/vmstat | grep pgsteal
pgsteal_kswapd 0
pgsteal_direct 0
pgsteal_khugepaged 0
pgsteal_proactive 16283
pgsteal_anon 16283
pgsteal_file 0
Fixes: 68cd9050d871 ("mm: add swappiness= arg to memory.reclaim")
Signed-off-by: Ridong Chen <chenridong@xiaomi.com>
---
mm/vmscan.c | 17 +++++++----------
1 file changed, 7 insertions(+), 10 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 35c3bb15ae96..5271bd023c1d 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -198,6 +198,13 @@ struct scan_control {
*/
int vm_swappiness = 60;
+static int sc_swappiness(struct scan_control *sc, struct mem_cgroup *memcg)
+{
+ if (sc->proactive && sc->proactive_swappiness)
+ return *sc->proactive_swappiness;
+ return mem_cgroup_swappiness(memcg);
+}
+
#ifdef CONFIG_MEMCG
/* Returns true for reclaim through cgroup limits or cgroup interfaces. */
@@ -239,12 +246,6 @@ static bool writeback_throttling_sane(struct scan_control *sc)
return false;
}
-static int sc_swappiness(struct scan_control *sc, struct mem_cgroup *memcg)
-{
- if (sc->proactive && sc->proactive_swappiness)
- return *sc->proactive_swappiness;
- return mem_cgroup_swappiness(memcg);
-}
#else
static bool cgroup_reclaim(struct scan_control *sc)
{
@@ -261,10 +262,6 @@ static bool writeback_throttling_sane(struct scan_control *sc)
return true;
}
-static int sc_swappiness(struct scan_control *sc, struct mem_cgroup *memcg)
-{
- return READ_ONCE(vm_swappiness);
-}
#endif
static void set_task_reclaim_state(struct task_struct *task,
--
2.43.0
^ permalink raw reply related [flat|nested] 3+ messages in thread