[PATCH 9/9] memcg: simplify v1 event ratelimiting

[Shakeel Butt <shakeel.butt@linux.dev>]

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@linux.dev>
---
 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