From: Li Zefan <lizefan@huawei.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Tejun Heo <tj@kernel.org>, Glauber Costa <glommer@parallels.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Johannes Weiner <hannes@cmpxchg.org>,
LKML <linux-kernel@vger.kernel.org>,
Cgroups <cgroups@vger.kernel.org>,
linux-mm@kvack.org
Subject: [PATCH 7/9] memcg: don't need to get a reference to the parent
Date: Fri, 17 May 2013 15:04:42 +0800 [thread overview]
Message-ID: <5195D68A.8000205@huawei.com> (raw)
In-Reply-To: <5195D5F8.7000609@huawei.com>
The cgroup core guarantees it's always safe to access the parent.
v2:
- added a comment in mem_cgroup_put() as suggested by Michal
- removed mem_cgroup_get(), otherwise gcc will warn that it's not used
Signed-off-by: Li Zefan <lizefan@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
mm/memcontrol.c | 19 +++----------------
1 file changed, 3 insertions(+), 16 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index b11ea88..c6d267a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -508,7 +508,6 @@ enum res_type {
*/
static DEFINE_MUTEX(memcg_create_mutex);
-static void mem_cgroup_get(struct mem_cgroup *memcg);
static void mem_cgroup_put(struct mem_cgroup *memcg);
static inline
@@ -6171,19 +6170,10 @@ static void free_rcu(struct rcu_head *rcu_head)
schedule_work(&memcg->work_freeing);
}
-static void mem_cgroup_get(struct mem_cgroup *memcg)
-{
- atomic_inc(&memcg->refcnt);
-}
-
static void __mem_cgroup_put(struct mem_cgroup *memcg, int count)
{
- if (atomic_sub_and_test(count, &memcg->refcnt)) {
- struct mem_cgroup *parent = parent_mem_cgroup(memcg);
+ if (atomic_sub_and_test(count, &memcg->refcnt))
call_rcu(&memcg->rcu_freeing, free_rcu);
- if (parent)
- mem_cgroup_put(parent);
- }
}
static void mem_cgroup_put(struct mem_cgroup *memcg)
@@ -6286,12 +6276,9 @@ mem_cgroup_css_online(struct cgroup *cont)
res_counter_init(&memcg->kmem, &parent->kmem);
/*
- * We increment refcnt of the parent to ensure that we can
- * safely access it on res_counter_charge/uncharge.
- * This refcnt will be decremented when freeing this
- * mem_cgroup(see mem_cgroup_put).
+ * No need to take a reference to the parent because cgroup
+ * core guarantees its existence.
*/
- mem_cgroup_get(parent);
} else {
res_counter_init(&memcg->res, NULL);
res_counter_init(&memcg->memsw, NULL);
--
1.8.0.2
--
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next prev parent reply other threads:[~2013-05-17 7:05 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-17 7:02 [PATCH 0/12][V3] memcg: make memcg's life cycle the same as cgroup Li Zefan
2013-05-17 7:03 ` [PATCH 1/9] Revert "memcg: avoid dangling reference count in creation failure." Li Zefan
2013-05-17 7:03 ` [PATCH 2/9] memcg, kmem: fix reference count handling on the error path Li Zefan
2013-05-17 7:03 ` [PATCH 3/9] memcg: use css_get() in sock_update_memcg() Li Zefan
2013-05-17 7:03 ` [PATCH 4/9] memcg: don't use mem_cgroup_get() when creating a kmemcg cache Li Zefan
2013-05-17 7:04 ` [PATCH 5/9] memcg: use css_get/put when charging/uncharging kmem Li Zefan
2013-05-17 18:08 ` Tejun Heo
2013-05-22 8:36 ` Li Zefan
2013-05-24 7:54 ` Michal Hocko
2013-05-30 5:48 ` Tejun Heo
2013-05-30 15:12 ` Michal Hocko
2013-05-17 7:04 ` [PATCH 6/9] memcg: use css_get/put for swap memcg Li Zefan
2013-05-17 7:04 ` Li Zefan [this message]
2013-05-17 7:05 ` [PATCH 8/9] memcg: kill memcg refcnt Li Zefan
2013-05-17 7:05 ` [PATCH 9/9] memcg: don't need to free memcg via RCU or workqueue Li Zefan
2013-05-17 7:06 ` [PATCH 0/12][V3] memcg: make memcg's life cycle the same as cgroup Li Zefan
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