From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx114.postini.com [74.125.245.114]) by kanga.kvack.org (Postfix) with SMTP id 037106B0072 for ; Fri, 11 Jan 2013 04:45:41 -0500 (EST) From: Glauber Costa Subject: [PATCH v2 3/7] memcg: provide online test for memcg Date: Fri, 11 Jan 2013 13:45:23 +0400 Message-Id: <1357897527-15479-4-git-send-email-glommer@parallels.com> In-Reply-To: <1357897527-15479-1-git-send-email-glommer@parallels.com> References: <1357897527-15479-1-git-send-email-glommer@parallels.com> Sender: owner-linux-mm@kvack.org List-ID: To: cgroups@vger.kernel.org Cc: linux-mm@kvack.org, Michal Hocko , kamezawa.hiroyu@jp.fujitsu.com, Johannes Weiner , Tejun Heo , Glauber Costa Since we are now splitting the memcg creation in two parts, following the cgroup standard, it would be helpful to be able to determine if a created memcg is already online. We can do this by initially forcing the refcnt to 0, and waiting until the last minute to flip it to 1. During memcg's lifetime, this value will vary. But if it ever reaches 0 again, memcg will be destructed. We can therefore be sure that any value different than 0 will mean that our group is online. Signed-off-by: Glauber Costa --- mm/memcontrol.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 2229945..2ac2808 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -475,6 +475,11 @@ enum res_type { static void mem_cgroup_get(struct mem_cgroup *memcg); static void mem_cgroup_put(struct mem_cgroup *memcg); +static inline bool mem_cgroup_online(struct mem_cgroup *memcg) +{ + return atomic_read(&memcg->refcnt) > 0; +} + static inline struct mem_cgroup *mem_cgroup_from_css(struct cgroup_subsys_state *s) { @@ -6098,7 +6103,7 @@ mem_cgroup_css_alloc(struct cgroup *cont) memcg->last_scanned_node = MAX_NUMNODES; INIT_LIST_HEAD(&memcg->oom_notify); - atomic_set(&memcg->refcnt, 1); + atomic_set(&memcg->refcnt, 0); memcg->move_charge_at_immigrate = 0; mutex_init(&memcg->thresholds_lock); spin_lock_init(&memcg->move_lock); @@ -6116,10 +6121,13 @@ mem_cgroup_css_online(struct cgroup *cont) struct mem_cgroup *memcg, *parent; int error = 0; - if (!cont->parent) + memcg = mem_cgroup_from_cont(cont); + if (!cont->parent) { + /* no need to lock, since this is the root cgroup */ + atomic_set(&memcg->refcnt, 1); return 0; + } - memcg = mem_cgroup_from_cont(cont); parent = mem_cgroup_from_cont(cont->parent); memcg->use_hierarchy = parent->use_hierarchy; @@ -6151,6 +6159,7 @@ mem_cgroup_css_online(struct cgroup *cont) } memcg->swappiness = mem_cgroup_swappiness(parent); + atomic_set(&memcg->refcnt, 1); error = memcg_init_kmem(memcg, &mem_cgroup_subsys); if (error) { -- 1.7.11.7 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org