Add a sysctl to enable/disable memory recharging for offline memcgs. Add
a config option to control whether or not it is enabled by default.
Signed-off-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
---
include/linux/memcontrol.h | 2 ++
kernel/sysctl.c | 11 +++++++++++
mm/Kconfig | 12 ++++++++++++
mm/memcontrol.c | 9 ++++++++-
4 files changed, 33 insertions(+), 1 deletion(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 59b653d4a76e..ae9f09ee90cb 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -60,6 +60,8 @@ struct mem_cgroup_reclaim_cookie {
#ifdef CONFIG_MEMCG
+extern int sysctl_recharge_offline_memcgs;
+
#define MEM_CGROUP_ID_SHIFT 16
#define MEM_CGROUP_ID_MAX USHRT_MAX
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 354a2d294f52..1735d1d95652 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2249,6 +2249,17 @@ static struct ctl_table vm_table[] = {
.extra2 = (void *)&mmap_rnd_compat_bits_max,
},
#endif
+#ifdef CONFIG_MEMCG
+ {
+ .procname = "recharge_offline_memcgs",
+ .data = &sysctl_recharge_offline_memcgs,
+ .maxlen = sizeof(sysctl_recharge_offline_memcgs),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = SYSCTL_ZERO,
+ .extra2 = SYSCTL_ONE,
+ },
+#endif /* CONFIG_MEMCG */
{ }
};
diff --git a/mm/Kconfig b/mm/Kconfig
index 09130434e30d..9462c4b598d9 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -1236,6 +1236,18 @@ config LOCK_MM_AND_FIND_VMA
bool
depends on !STACK_GROWSUP
+config MEMCG_RECHARGE_OFFLINE_ENABLED
+ bool "Recharge memory charged to offline memcgs"
+ depends on MEMCG
+ help
+ When a memory cgroup is removed by userspace, try to recharge any
+ memory still charged to it to avoid having it live on as an offline
+ memcg. Offline memcgs potentially consume memory and limit scalability
+ of some operations.
+
+ This option enables the above behavior by default. It can be override
+ at runtime through /proc/sys/vm/recharge_offline_memcgs.
+
source "mm/damon/Kconfig"
endmenu
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2fe9c6f1be80..25cdb17eaaa3 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -96,6 +96,9 @@ static bool cgroup_memory_nobpf __ro_after_init;
static DECLARE_WAIT_QUEUE_HEAD(memcg_cgwb_frn_waitq);
#endif
+int sysctl_recharge_offline_memcgs __read_mostly = IS_ENABLED(
+ CONFIG_MEMCG_RECHARGE_OFFLINE_ENABLED);
+
static struct workqueue_struct *memcg_recharge_wq;
/* Whether legacy memory+swap accounting is active */
@@ -6592,7 +6595,8 @@ static void memcg_recharge_mapped_folios(struct mem_cgroup *memcg)
INIT_DELAYED_WORK(&memcg->recharge_mapped_work.dwork,
memcg_do_recharge_mapped_folios);
- if (memcg_recharge_wq && memcg_nr_local_mapped_pages(memcg)) {
+ if (sysctl_recharge_offline_memcgs &&
+ memcg_recharge_wq && memcg_nr_local_mapped_pages(memcg)) {
memcg->recharge_mapped_work.retries = 0;
queue_delayed_work(memcg_recharge_wq,
&memcg->recharge_mapped_work.dwork, 0);
@@ -6605,6 +6609,9 @@ static bool should_do_deferred_recharge(struct folio *folio)
struct mem_cgroup *memcg;
bool ret;
+ if (!sysctl_recharge_offline_memcgs)
+ return false;
+
rcu_read_lock();
memcg = folio_memcg_rcu(folio);
ret = memcg && !!(memcg->css.flags & CSS_DYING);
--
2.41.0.255.g8b1d071c50-goog
