[PATCH v4 2/2] memcg: add oom_kill_inherit event indicator

[chengkaitao <chengkaitao@didiglobal.com>]

From: chengkaitao <pilgrimtao@gmail.com>

Oom_kill_inherit can reflect the number of child cgroups selected by
the parent cgroup's OOM killer. We can refer to the proportion of the
indicator to adjust the value of oom_protect. The larger oom_protect,
the smaller oom_kill_inherit.

Signed-off-by: chengkaitao <pilgrimtao@gmail.com>
---
 Documentation/admin-guide/cgroup-v2.rst | 4 ++++
 include/linux/memcontrol.h              | 1 +
 mm/memcontrol.c                         | 6 ++++++
 3 files changed, 11 insertions(+)

diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index 51e9a84d508a..e6f56443d049 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -1358,6 +1358,10 @@ PAGE_SIZE multiple when read back.
 		The number of processes belonging to this cgroup
 		killed by any kind of OOM killer.
 
+	  oom_kill_inherit
+		The number of processes belonging to this cgroup
+		killed by all Ancestral memcg's OOM killer.
+
           oom_group_kill
                 The number of times a group OOM has occurred.
 
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 23ea28d98c0e..d7797f9a0605 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -46,6 +46,7 @@ enum memcg_memory_event {
 	MEMCG_MAX,
 	MEMCG_OOM,
 	MEMCG_OOM_KILL,
+	MEMCG_OOM_INHERIT,
 	MEMCG_OOM_GROUP_KILL,
 	MEMCG_SWAP_HIGH,
 	MEMCG_SWAP_MAX,
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 8ee67abb415f..cf3cacf26cec 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2129,6 +2129,10 @@ struct mem_cgroup *mem_cgroup_get_oom_group(struct task_struct *victim,
 
 		if (memcg == oom_domain)
 			break;
+		/* we use oom.group's logic to update the OOM_INHERIT indicator,
+		 * but OOM_INHERIT and oom.group are independent of each other.
+		 */
+		memcg_memory_event(memcg, MEMCG_OOM_INHERIT);
 	}
 
 	if (oom_group)
@@ -6622,6 +6626,8 @@ static void __memory_events_show(struct seq_file *m, atomic_long_t *events)
 	seq_printf(m, "oom %lu\n", atomic_long_read(&events[MEMCG_OOM]));
 	seq_printf(m, "oom_kill %lu\n",
 		   atomic_long_read(&events[MEMCG_OOM_KILL]));
+	seq_printf(m, "oom_kill_inherit %lu\n",
+		   atomic_long_read(&events[MEMCG_OOM_INHERIT]));
 	seq_printf(m, "oom_group_kill %lu\n",
 		   atomic_long_read(&events[MEMCG_OOM_GROUP_KILL]));
 }
-- 
2.14.1