Re: [PATCH 9/9] memcg: simplify v1 event ratelimiting
From: Michal Hocko
Date: Thu Aug 13 2026 - 04:35:13 EST
On Tue 11-08-26 13:32:03, Shakeel Butt wrote:
> Thresholds are the only periodic v1 event left, so the target enum, the
> per-cpu target array and the switch in memcg1_event_ratelimit() all
> collapse to a single counter.
>
> memcg1_check_events() no longer needs a node id either, which lets
> memcg1_uncharge_batch() drop its nid argument and struct
> uncharge_gather drop the field feeding it.
>
> Signed-off-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Thanks!
> ---
> mm/memcontrol-v1.c | 43 +++++++++++--------------------------------
> mm/memcontrol-v1.h | 4 ++--
> mm/memcontrol.c | 4 +---
> 3 files changed, 14 insertions(+), 37 deletions(-)
>
> diff --git a/mm/memcontrol-v1.c b/mm/memcontrol-v1.c
> index 475f998b7643..bf2c7d53b01b 100644
> --- a/mm/memcontrol-v1.c
> +++ b/mm/memcontrol-v1.c
> @@ -200,15 +200,9 @@ static void mem_cgroup_threshold(struct mem_cgroup *memcg)
> * to trigger some periodic events. This is straightforward and better
> * than using jiffies etc. to handle periodic memcg event.
> */
> -enum mem_cgroup_events_target {
> - MEM_CGROUP_TARGET_THRESH,
> - MEM_CGROUP_TARGET_SOFTLIMIT,
> - MEM_CGROUP_NTARGETS,
> -};
> -
> struct memcg1_events_percpu {
> unsigned long nr_page_events;
> - unsigned long targets[MEM_CGROUP_NTARGETS];
> + unsigned long threshold_target;
> };
>
> static void memcg1_charge_statistics(struct mem_cgroup *memcg, int nr_pages)
> @@ -225,43 +219,28 @@ static void memcg1_charge_statistics(struct mem_cgroup *memcg, int nr_pages)
> }
>
> #define THRESHOLDS_EVENTS_TARGET 128
> -#define SOFTLIMIT_EVENTS_TARGET 1024
>
> -static bool memcg1_event_ratelimit(struct mem_cgroup *memcg,
> - enum mem_cgroup_events_target target)
> +static bool memcg1_event_ratelimit(struct mem_cgroup *memcg)
> {
> unsigned long val, next;
>
> val = __this_cpu_read(memcg->events_percpu->nr_page_events);
> - next = __this_cpu_read(memcg->events_percpu->targets[target]);
> + next = __this_cpu_read(memcg->events_percpu->threshold_target);
> /* from time_after() in jiffies.h */
> if ((long)(next - val) < 0) {
> - switch (target) {
> - case MEM_CGROUP_TARGET_THRESH:
> - next = val + THRESHOLDS_EVENTS_TARGET;
> - break;
> - case MEM_CGROUP_TARGET_SOFTLIMIT:
> - next = val + SOFTLIMIT_EVENTS_TARGET;
> - break;
> - default:
> - break;
> - }
> - __this_cpu_write(memcg->events_percpu->targets[target], next);
> + __this_cpu_write(memcg->events_percpu->threshold_target,
> + val + THRESHOLDS_EVENTS_TARGET);
> return true;
> }
> return false;
> }
>
> -/*
> - * Check events in order.
> - *
> - */
> -static void memcg1_check_events(struct mem_cgroup *memcg, int nid)
> +static void memcg1_check_events(struct mem_cgroup *memcg)
> {
> if (IS_ENABLED(CONFIG_PREEMPT_RT))
> return;
>
> - if (unlikely(memcg1_event_ratelimit(memcg, MEM_CGROUP_TARGET_THRESH)))
> + if (unlikely(memcg1_event_ratelimit(memcg)))
> mem_cgroup_threshold(memcg);
> }
>
> @@ -271,7 +250,7 @@ void memcg1_commit_charge(struct folio *folio, struct mem_cgroup *memcg)
>
> local_irq_save(flags);
> memcg1_charge_statistics(memcg, folio_nr_pages(folio));
> - memcg1_check_events(memcg, folio_nid(folio));
> + memcg1_check_events(memcg);
> local_irq_restore(flags);
> }
>
> @@ -344,7 +323,7 @@ void __memcg1_swapout(struct folio *folio, struct swap_cluster_info *ci)
> VM_WARN_ON_IRQS_ENABLED();
> memcg1_charge_statistics(memcg, -folio_nr_pages(folio));
> preempt_enable_nested();
> - memcg1_check_events(memcg, folio_nid(folio));
> + memcg1_check_events(memcg);
>
> rcu_read_unlock();
> obj_cgroup_put(objcg);
> @@ -398,14 +377,14 @@ void memcg1_swapin(struct folio *folio)
> #endif
>
> void memcg1_uncharge_batch(struct mem_cgroup *memcg, unsigned long pgpgout,
> - unsigned long nr_memory, int nid)
> + unsigned long nr_memory)
> {
> unsigned long flags;
>
> local_irq_save(flags);
> count_memcg_events(memcg, PGPGOUT, pgpgout);
> __this_cpu_add(memcg->events_percpu->nr_page_events, nr_memory);
> - memcg1_check_events(memcg, nid);
> + memcg1_check_events(memcg);
> local_irq_restore(flags);
> }
>
> diff --git a/mm/memcontrol-v1.h b/mm/memcontrol-v1.h
> index f48d0e22e615..b9a21f0fd2c3 100644
> --- a/mm/memcontrol-v1.h
> +++ b/mm/memcontrol-v1.h
> @@ -59,7 +59,7 @@ void memcg1_oom_recover(struct mem_cgroup *memcg);
>
> void memcg1_commit_charge(struct folio *folio, struct mem_cgroup *memcg);
> void memcg1_uncharge_batch(struct mem_cgroup *memcg, unsigned long pgpgout,
> - unsigned long nr_memory, int nid);
> + unsigned long nr_memory);
>
> void memcg1_stat_format(struct mem_cgroup *memcg, struct seq_buf *s);
> void reparent_memcg1_state_local(struct mem_cgroup *memcg, struct mem_cgroup *parent);
> @@ -107,7 +107,7 @@ static inline void memcg1_commit_charge(struct folio *folio,
>
> static inline void memcg1_uncharge_batch(struct mem_cgroup *memcg,
> unsigned long pgpgout,
> - unsigned long nr_memory, int nid) {}
> + unsigned long nr_memory) {}
>
> static inline void memcg1_stat_format(struct mem_cgroup *memcg, struct seq_buf *s) {}
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index ba3ef821553d..44ef376d657b 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -5293,7 +5293,6 @@ struct uncharge_gather {
> unsigned long nr_memory;
> unsigned long pgpgout;
> unsigned long nr_kmem;
> - int nid;
> };
>
> static inline void uncharge_gather_clear(struct uncharge_gather *ug)
> @@ -5316,7 +5315,7 @@ static void uncharge_batch(const struct uncharge_gather *ug)
> memcg1_oom_recover(memcg);
> }
>
> - memcg1_uncharge_batch(memcg, ug->pgpgout, ug->nr_memory, ug->nid);
> + memcg1_uncharge_batch(memcg, ug->pgpgout, ug->nr_memory);
> rcu_read_unlock();
>
> /* drop reference from uncharge_folio */
> @@ -5345,7 +5344,6 @@ static void uncharge_folio(struct folio *folio, struct uncharge_gather *ug)
> uncharge_gather_clear(ug);
> }
> ug->objcg = objcg;
> - ug->nid = folio_nid(folio);
>
> /* pairs with obj_cgroup_put in uncharge_batch */
> obj_cgroup_get(objcg);
> --
> 2.53.0-Meta
--
Michal Hocko
SUSE Labs