Each memory-controlled cgroup is assigned a unique ID and the total
number of memory cgroups is limited to MEM_CGROUP_ID_MAX.
This patch provides the ability to determine the number of
memory cgroups from the root memory cgroup, only.
A value of 1 (i.e. self count) is returned if there are no children.
For example, the number of memory cgroups can be established by
reading the /sys/fs/cgroup/memory/memory.total_cnt file.
Signed-off-by: Aaron Tomlin <atomlin@xxxxxxxxxx>
---
mm/memcontrol.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 29459a6ce1c7..a4f7cb40e233 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4535,6 +4535,19 @@ static int mem_cgroup_oom_control_write(struct cgroup_subsys_state *css,
return 0;
}
+static int mem_cgroup_total_count_read(struct cgroup_subsys_state *css,
+ struct cftype *cft)
+{
+ struct mem_cgroup *iter, *memcg = mem_cgroup_from_css(css);
+ int num = 0;
+
+ for_each_mem_cgroup_tree(iter, memcg)
+ num++;
+
+ /* Returns 1 (i.e. self count) if no children. */
+ return num;
+}
+
#ifdef CONFIG_CGROUP_WRITEBACK
#include <trace/events/writeback.h>
@@ -5050,6 +5063,11 @@ static struct cftype mem_cgroup_legacy_files[] = {
.write_u64 = mem_cgroup_oom_control_write,
.private = MEMFILE_PRIVATE(_OOM_TYPE, OOM_CONTROL),
},
+ {
+ .name = "total_cnt",
+ .flags = CFTYPE_ONLY_ON_ROOT,
+ .read_u64 = mem_cgroup_total_count_read,
+ },
{
.name = "pressure_level",
},
--
2.26.2
