* [PATCH -v3 1/2] memcg: move mem_cgroup_swappiness and vm_swappiness to mm/swap.h
2026-07-23 2:58 [PATCH -v3 0/2] mm: vmscan: fix node reclaim ignoring swappiness parameter Ridong
@ 2026-07-23 2:58 ` Ridong
2026-07-23 2:58 ` [PATCH -v3 2/2] mm: vmscan: fix node reclaim ignoring swappiness parameter Ridong
1 sibling, 0 replies; 3+ messages in thread
From: Ridong @ 2026-07-23 2:58 UTC (permalink / raw)
To: Johannes Weiner, Michal Hocko, Roman Gushchin, Shakeel Butt,
Andrew Morton, Chris Li, Kairui Song
Cc: Muchun Song, Kemeng Shi, Nhat Pham, Baoquan He, Barry Song,
Youngjun Park, David Hildenbrand, Qi Zheng, Lorenzo Stoakes,
Axel Rasmussen, Yuanchu Xie, Wei Xu, Davidlohr Bueso, cgroups,
linux-mm, linux-kernel, Song Hu, 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.
Both mem_cgroup_swappiness() and vm_swappiness are only used within
mm/ (memcontrol.c, memcontrol-v1.c, vmscan.c), so move them out of the
public include/linux/swap.h into the mm-private mm/swap.h. This keeps
unrelated declarations out of include/linux/swap.h.
Guard memcg->swappiness with CONFIG_MEMCG_V1 as well, so v2-only
kernels drop the unused field.
No functional change for v1; v2-only kernels drop the unused field.
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Barry Song <baohua@kernel.org>
Reviewed-by: Song Hu <husong@kylinos.cn>
Signed-off-by: Ridong Chen <chenridong@xiaomi.com>
---
include/linux/memcontrol.h | 4 ++--
include/linux/swap.h | 19 -------------------
mm/memcontrol.c | 4 ++--
mm/swap.h | 13 +++++++++++++
4 files changed, 17 insertions(+), 23 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 957260677678..e7a794dfb40e 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 +316,8 @@ 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[];
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 0544b2ec4c56..45f301d73e2a 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -309,7 +309,6 @@ static inline bool lru_cache_disabled(void)
}
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)
@@ -473,25 +472,7 @@ 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 *memcg)
-{
- 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 8319ad8c5c23..6864b76456fb 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -63,6 +63,7 @@
#include <linux/sched/isolation.h>
#include <linux/kmemleak.h>
#include "internal.h"
+#include "swap.h"
#include "swap_table.h"
#include <net/sock.h>
#include <net/ip.h>
@@ -4176,11 +4177,10 @@ 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);
diff --git a/mm/swap.h b/mm/swap.h
index abd26588abd2..b0488f7b68b5 100644
--- a/mm/swap.h
+++ b/mm/swap.h
@@ -4,6 +4,7 @@
#include <linux/atomic.h> /* for atomic_long_t */
#include <linux/mm.h> /* for PAGE_SHIFT */
+#include <linux/memcontrol.h> /* for mem_cgroup_swappiness() */
struct mempolicy;
struct swap_iocb;
@@ -99,6 +100,18 @@ struct swap_ops {
void (*submit_read)(struct swap_io_ctx *ctx);
};
+extern int vm_swappiness;
+
+static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg)
+{
+#ifdef CONFIG_MEMCG_V1
+ if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) &&
+ !mem_cgroup_disabled() && !mem_cgroup_is_root(memcg))
+ return memcg->swappiness;
+#endif
+ return READ_ONCE(vm_swappiness);
+}
+
#ifdef CONFIG_SWAP
#include <linux/swapops.h> /* for swp_offset */
#include <linux/blk_types.h> /* for bio_end_io_t */
--
2.34.1
^ permalink raw reply related [flat|nested] 3+ messages in thread* [PATCH -v3 2/2] mm: vmscan: fix node reclaim ignoring swappiness parameter
2026-07-23 2:58 [PATCH -v3 0/2] mm: vmscan: fix node reclaim ignoring swappiness parameter Ridong
2026-07-23 2:58 ` [PATCH -v3 1/2] memcg: move mem_cgroup_swappiness and vm_swappiness to mm/swap.h Ridong
@ 2026-07-23 2:58 ` Ridong
1 sibling, 0 replies; 3+ messages in thread
From: Ridong @ 2026-07-23 2:58 UTC (permalink / raw)
To: Johannes Weiner, Michal Hocko, Roman Gushchin, Shakeel Butt,
Andrew Morton, Chris Li, Kairui Song
Cc: Muchun Song, Kemeng Shi, Nhat Pham, Baoquan He, Barry Song,
Youngjun Park, David Hildenbrand, Qi Zheng, Lorenzo Stoakes,
Axel Rasmussen, Yuanchu Xie, Wei Xu, Davidlohr Bueso, cgroups,
linux-mm, linux-kernel, Song Hu, Ridong Chen, Ridong Chen, stable
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
Cc: stable@vger.kernel.org # 6.17+
Fixes: b980077899ea ("mm: introduce per-node proactive reclaim interface")
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Barry Song <baohua@kernel.org>
Acked-by: Qi Zheng <qi.zheng@linux.dev>
Tested-by: Song Hu <husong@kylinos.cn>
Reviewed-by: Song Hu <husong@kylinos.cn>
Signed-off-by: Ridong Chen <chenridong@xiaomi.com>
---
mm/vmscan.c | 19 +++++++------------
1 file changed, 7 insertions(+), 12 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 06e103f9781e..155167b3614b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -199,6 +199,13 @@ 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. */
@@ -239,13 +246,6 @@ static bool writeback_throttling_sane(struct scan_control *sc)
#endif
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)
{
@@ -261,11 +261,6 @@ 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,
--
2.34.1
^ permalink raw reply related [flat|nested] 3+ messages in thread