From mboxrd@z Thu Jan 1 00:00:00 1970 From: Li Zefan Subject: [PATCH 4/9] memcg: don't use mem_cgroup_get() when creating a kmemcg cache Date: Fri, 17 May 2013 15:03:52 +0800 Message-ID: <5195D658.5000301@huawei.com> References: <5195D5F8.7000609@huawei.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5195D5F8.7000609@huawei.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Andrew Morton Cc: Tejun Heo , Glauber Costa , KAMEZAWA Hiroyuki , Johannes Weiner , LKML , Cgroups , linux-mm@kvack.org Use css_get()/css_put() instead of mem_cgroup_get()/mem_cgroup_put(). There are two things being done in the current code: First, we acquired a css_ref to make sure that the underlying cgroup would not go away. That is a short lived reference, and it is put as soon as the cache is created. At this point, we acquire a long-lived per-cache memcg reference count to guarantee that the memcg will still be alive. so it is: enqueue: css_get create : memcg_get, css_put destroy: memcg_put So we only need to get rid of the memcg_get, change the memcg_put to css_put, and get rid of the now extra css_put. (This changelog is mostly written by Glauber) Signed-off-by: Li Zefan Acked-by: Michal Hocko Acked-by: KAMEZAWA Hiroyuki --- mm/memcontrol.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index f1320d3..63526f9 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3227,7 +3227,7 @@ void memcg_release_cache(struct kmem_cache *s) list_del(&s->memcg_params->list); mutex_unlock(&memcg->slab_caches_mutex); - mem_cgroup_put(memcg); + css_put(&memcg->css); out: kfree(s->memcg_params); } @@ -3387,16 +3387,18 @@ static struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *memcg, mutex_lock(&memcg_cache_mutex); new_cachep = cachep->memcg_params->memcg_caches[idx]; - if (new_cachep) + if (new_cachep) { + css_put(&memcg->css); goto out; + } new_cachep = kmem_cache_dup(memcg, cachep); if (new_cachep == NULL) { new_cachep = cachep; + css_put(&memcg->css); goto out; } - mem_cgroup_get(memcg); atomic_set(&new_cachep->memcg_params->nr_pages , 0); cachep->memcg_params->memcg_caches[idx] = new_cachep; @@ -3484,8 +3486,6 @@ static void memcg_create_cache_work_func(struct work_struct *w) cw = container_of(w, struct create_work, work); memcg_create_kmem_cache(cw->memcg, cw->cachep); - /* Drop the reference gotten when we enqueued. */ - css_put(&cw->memcg->css); kfree(cw); } -- 1.8.0.2