memcg: show real limit under hierarchy mode

Show "real" limit of memcg.  This helps my debugging and maybe useful for
users.

While testing hierarchy like this

	mount -t cgroup none /cgroup -t memory
	mkdir /cgroup/A
	set use_hierarchy==1 to "A"
	mkdir /cgroup/A/01
	mkdir /cgroup/A/01/02
	mkdir /cgroup/A/01/03
	mkdir /cgroup/A/01/03/04
	mkdir /cgroup/A/08
	mkdir /cgroup/A/08/01
	....
and set each own limit to them, "real" limit of each memcg is unclear.
This patch shows real limit by checking all ancestors.

Changelog: (v1) -> (v2)
	- remove "if" and use "min(a,b)"

Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index c7d78ec..8d2e5c8 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1782,6 +1782,34 @@ static int mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
        return ret;
 }
 
+static void memcg_get_hierarchical_limit(struct mem_cgroup *memcg,
+               unsigned long long *mem_limit, unsigned long long *memsw_limit)
+{
+       struct cgroup *cgroup;
+       unsigned long long min_limit, min_memsw_limit, tmp;
+
+       min_limit = res_counter_read_u64(&memcg->res, RES_LIMIT);
+       min_memsw_limit = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
+       cgroup = memcg->css.cgroup;
+       if (!memcg->use_hierarchy)
+               goto out;
+
+       while (cgroup->parent) {
+               cgroup = cgroup->parent;
+               memcg = mem_cgroup_from_cont(cgroup);
+               if (!memcg->use_hierarchy)
+                       break;
+               tmp = res_counter_read_u64(&memcg->res, RES_LIMIT);
+               min_limit = min(min_limit, tmp);
+               tmp = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
+               min_memsw_limit = min(min_memsw_limit, tmp);
+       }
+out:
+       *mem_limit = min_limit;
+       *memsw_limit = min_memsw_limit;
+       return;
+}
+
 static int mem_cgroup_reset(struct cgroup *cont, unsigned int event)
 {
        struct mem_cgroup *mem;
@@ -1855,6 +1883,13 @@ static int mem_control_stat_show(struct cgroup *cont, struct cftype *cft,
                cb->fill(cb, "unevictable", unevictable * PAGE_SIZE);
 
        }
+       {
+               unsigned long long limit, memsw_limit;
+               memcg_get_hierarchical_limit(mem_cont, &limit, &memsw_limit);
+               cb->fill(cb, "hierarchical_memory_limit", limit);
+               if (do_swap_account)
+                       cb->fill(cb, "hierarchical_memsw_limit", memsw_limit);
+       }
 
 #ifdef CONFIG_DEBUG_VM
        cb->fill(cb, "inactive_ratio", calc_inactive_ratio(mem_cont, NULL));