[PATCH v3 2/5] mm/memcg: Introduce obj_cgroup_uncharge_mod_state()

Waiman Long
2021-04-14T01:21:01Z

In memcg_slab_free_hook()/pcpu_memcg_free_hook(), obj_cgroup_uncharge()
is followed by mod_objcg_state()/mod_memcg_state(). Each of these
function call goes through a separate irq_save/irq_restore cycle. That
is inefficient. Introduce a new function obj_cgroup_uncharge_mod_state()
that combines them with a single irq_save/irq_restore cycle.

Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Roman Gushchin <guro@fb.com>
---
include/linux/memcontrol.h | 2 ++
mm/memcontrol.c | 31 +++++++++++++++++++++++++++----
mm/percpu.c | 9 ++-------
mm/slab.h | 6 +++---
4 files changed, 34 insertions(+), 14 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 95f12996e66c..6890f999c1a3 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1592,6 +1592,8 @@ struct obj_cgroup *get_obj_cgroup_from_current(void);

int obj_cgroup_charge(struct obj_cgroup *objcg, gfp_t gfp, size_t size);
void obj_cgroup_uncharge(struct obj_cgroup *objcg, size_t size);
+void obj_cgroup_uncharge_mod_state(struct obj_cgroup *objcg, size_t size,
+ struct pglist_data *pgdat, int idx);

extern struct static_key_false memcg_kmem_enabled_key;

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index d66e1e38f8ac..b19100c68aa0 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3225,12 +3225,9 @@ static bool obj_stock_flush_required(struct memcg_stock_pcp *stock,
return false;
}

-static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes)
+static void __refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes)
{
struct memcg_stock_pcp *stock;
- unsigned long flags;
-
- local_irq_save(flags);

stock = this_cpu_ptr(&memcg_stock);
if (stock->cached_objcg != objcg) { /* reset if necessary */
@@ -3243,7 +3240,14 @@ static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes)

if (stock->nr_bytes > PAGE_SIZE)
drain_obj_stock(stock);
+}
+
+static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes)
+{
+ unsigned long flags;

+ local_irq_save(flags);
+ __refill_obj_stock(objcg, nr_bytes);
local_irq_restore(flags);
}

@@ -3292,6 +3296,25 @@ void obj_cgroup_uncharge(struct obj_cgroup *objcg, size_t size)
refill_obj_stock(objcg, size);
}

+void obj_cgroup_uncharge_mod_state(struct obj_cgroup *objcg, size_t size,
+ struct pglist_data *pgdat, int idx)
+{
+ unsigned long flags;
+ struct mem_cgroup *memcg;
+ struct lruvec *lruvec = NULL;
+
+ local_irq_save(flags);
+ __refill_obj_stock(objcg, size);
+
+ rcu_read_lock();
+ memcg = obj_cgroup_memcg(objcg);
+ if (pgdat)
+ lruvec = mem_cgroup_lruvec(memcg, pgdat);
+ __mod_memcg_lruvec_state(memcg, lruvec, idx, -(int)size);
+ rcu_read_unlock();
+ local_irq_restore(flags);
+}
+
#endif /* CONFIG_MEMCG_KMEM */

/*
diff --git a/mm/percpu.c b/mm/percpu.c
index 23308113a5ff..fd7aad6d7f90 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1631,13 +1631,8 @@ static void pcpu_memcg_free_hook(struct pcpu_chunk *chunk, int off, size_t size)
objcg = chunk->obj_cgroups[off >> PCPU_MIN_ALLOC_SHIFT];
chunk->obj_cgroups[off >> PCPU_MIN_ALLOC_SHIFT] = NULL;

- obj_cgroup_uncharge(objcg, size * num_possible_cpus());
-
- rcu_read_lock();
- mod_memcg_state(obj_cgroup_memcg(objcg), MEMCG_PERCPU_B,
- -(size * num_possible_cpus()));
- rcu_read_unlock();
-
+ obj_cgroup_uncharge_mod_state(objcg, size * num_possible_cpus(),
+ NULL, MEMCG_PERCPU_B);
obj_cgroup_put(objcg);
}

diff --git a/mm/slab.h b/mm/slab.h
index bc6c7545e487..677cdc52e641 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -366,9 +366,9 @@ static inline void memcg_slab_free_hook(struct kmem_cache *s_orig,
continue;

objcgs[off] = NULL;
- obj_cgroup_uncharge(objcg, obj_full_size(s));
- mod_objcg_state(objcg, page_pgdat(page), cache_vmstat_idx(s),
- -obj_full_size(s));
+ obj_cgroup_uncharge_mod_state(objcg, obj_full_size(s),
+ page_pgdat(page),
+ cache_vmstat_idx(s));
obj_cgroup_put(objcg);
}
}
--
2.18.1