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Message-ID: <20250513031316.2147548-3-shakeel.butt@linux.dev>
Date: Mon, 12 May 2025 20:13:11 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Johannes Weiner <hannes@...xchg.org>,
Michal Hocko <mhocko@...nel.org>,
Roman Gushchin <roman.gushchin@...ux.dev>,
Muchun Song <muchun.song@...ux.dev>,
Vlastimil Babka <vbabka@...e.cz>,
Alexei Starovoitov <ast@...nel.org>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Harry Yoo <harry.yoo@...cle.com>,
Yosry Ahmed <yosry.ahmed@...ux.dev>,
bpf@...r.kernel.org,
linux-mm@...ck.org,
cgroups@...r.kernel.org,
linux-kernel@...r.kernel.org,
Meta kernel team <kernel-team@...a.com>
Subject: [RFC PATCH 2/7] memcg: move preempt disable to callers of memcg_rstat_updated
Let's move the explicit preempt disable code to the callers of
memcg_rstat_updated and also remove the memcg_stats_lock and related
functions which ensures the callers of stats update functions have
disabled preemption because now the stats update functions are
explicitly disabling preemption.
Signed-off-by: Shakeel Butt <shakeel.butt@...ux.dev>
---
mm/memcontrol.c | 74 +++++++++++++------------------------------------
1 file changed, 19 insertions(+), 55 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2c4c095bf26c..62450e7991d8 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -558,47 +558,21 @@ static u64 flush_last_time;
#define FLUSH_TIME (2UL*HZ)
-/*
- * Accessors to ensure that preemption is disabled on PREEMPT_RT because it can
- * not rely on this as part of an acquired spinlock_t lock. These functions are
- * never used in hardirq context on PREEMPT_RT and therefore disabling preemtion
- * is sufficient.
- */
-static void memcg_stats_lock(void)
-{
- preempt_disable_nested();
- VM_WARN_ON_IRQS_ENABLED();
-}
-
-static void __memcg_stats_lock(void)
-{
- preempt_disable_nested();
-}
-
-static void memcg_stats_unlock(void)
-{
- preempt_enable_nested();
-}
-
-
static bool memcg_vmstats_needs_flush(struct memcg_vmstats *vmstats)
{
return atomic64_read(&vmstats->stats_updates) >
MEMCG_CHARGE_BATCH * num_online_cpus();
}
-static inline void memcg_rstat_updated(struct mem_cgroup *memcg, int val)
+static inline void memcg_rstat_updated(struct mem_cgroup *memcg, int val,
+ int cpu)
{
struct memcg_vmstats_percpu *statc;
- int cpu;
int stats_updates;
if (!val)
return;
- /* Don't assume callers have preemption disabled. */
- cpu = get_cpu();
-
cgroup_rstat_updated(memcg->css.cgroup, cpu);
statc = this_cpu_ptr(memcg->vmstats_percpu);
for (; statc; statc = statc->parent) {
@@ -619,7 +593,6 @@ static inline void memcg_rstat_updated(struct mem_cgroup *memcg, int val)
atomic64_add(stats_updates,
&statc->vmstats->stats_updates);
}
- put_cpu();
}
static void __mem_cgroup_flush_stats(struct mem_cgroup *memcg, bool force)
@@ -717,6 +690,7 @@ void __mod_memcg_state(struct mem_cgroup *memcg, enum memcg_stat_item idx,
int val)
{
int i = memcg_stats_index(idx);
+ int cpu;
if (mem_cgroup_disabled())
return;
@@ -724,12 +698,14 @@ void __mod_memcg_state(struct mem_cgroup *memcg, enum memcg_stat_item idx,
if (WARN_ONCE(BAD_STAT_IDX(i), "%s: missing stat item %d\n", __func__, idx))
return;
- memcg_stats_lock();
+ cpu = get_cpu();
+
__this_cpu_add(memcg->vmstats_percpu->state[i], val);
val = memcg_state_val_in_pages(idx, val);
- memcg_rstat_updated(memcg, val);
+ memcg_rstat_updated(memcg, val, cpu);
trace_mod_memcg_state(memcg, idx, val);
- memcg_stats_unlock();
+
+ put_cpu();
}
#ifdef CONFIG_MEMCG_V1
@@ -758,6 +734,7 @@ static void __mod_memcg_lruvec_state(struct lruvec *lruvec,
struct mem_cgroup_per_node *pn;
struct mem_cgroup *memcg;
int i = memcg_stats_index(idx);
+ int cpu;
if (WARN_ONCE(BAD_STAT_IDX(i), "%s: missing stat item %d\n", __func__, idx))
return;
@@ -765,24 +742,7 @@ static void __mod_memcg_lruvec_state(struct lruvec *lruvec,
pn = container_of(lruvec, struct mem_cgroup_per_node, lruvec);
memcg = pn->memcg;
- /*
- * The caller from rmap relies on disabled preemption because they never
- * update their counter from in-interrupt context. For these two
- * counters we check that the update is never performed from an
- * interrupt context while other caller need to have disabled interrupt.
- */
- __memcg_stats_lock();
- if (IS_ENABLED(CONFIG_DEBUG_VM)) {
- switch (idx) {
- case NR_ANON_MAPPED:
- case NR_FILE_MAPPED:
- case NR_ANON_THPS:
- WARN_ON_ONCE(!in_task());
- break;
- default:
- VM_WARN_ON_IRQS_ENABLED();
- }
- }
+ cpu = get_cpu();
/* Update memcg */
__this_cpu_add(memcg->vmstats_percpu->state[i], val);
@@ -791,9 +751,10 @@ static void __mod_memcg_lruvec_state(struct lruvec *lruvec,
__this_cpu_add(pn->lruvec_stats_percpu->state[i], val);
val = memcg_state_val_in_pages(idx, val);
- memcg_rstat_updated(memcg, val);
+ memcg_rstat_updated(memcg, val, cpu);
trace_mod_memcg_lruvec_state(memcg, idx, val);
- memcg_stats_unlock();
+
+ put_cpu();
}
/**
@@ -873,6 +834,7 @@ void __count_memcg_events(struct mem_cgroup *memcg, enum vm_event_item idx,
unsigned long count)
{
int i = memcg_events_index(idx);
+ int cpu;
if (mem_cgroup_disabled())
return;
@@ -880,11 +842,13 @@ void __count_memcg_events(struct mem_cgroup *memcg, enum vm_event_item idx,
if (WARN_ONCE(BAD_STAT_IDX(i), "%s: missing stat item %d\n", __func__, idx))
return;
- memcg_stats_lock();
+ cpu = get_cpu();
+
__this_cpu_add(memcg->vmstats_percpu->events[i], count);
- memcg_rstat_updated(memcg, count);
+ memcg_rstat_updated(memcg, count, cpu);
trace_count_memcg_events(memcg, idx, count);
- memcg_stats_unlock();
+
+ put_cpu();
}
unsigned long memcg_events(struct mem_cgroup *memcg, int event)
--
2.47.1
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