samples/cgroup: introduce memcg memory.events listener

This is a simple listener for memory events that handles counter changes
in runtime.  It can be set up for a specific memory cgroup v2.

The output example:
=====
$ /tmp/memcg_event_listener test
Initialized MEMCG events with counters:
MEMCG events:
	low: 0
	high: 0
	max: 0
	oom: 0
	oom_kill: 0
	oom_group_kill: 0
Started monitoring memory events from '/sys/fs/cgroup/test/memory.events'...
Received event in /sys/fs/cgroup/test/memory.events:
*** 1 MEMCG oom_kill event, change counter 0 => 1
Received event in /sys/fs/cgroup/test/memory.events:
*** 1 MEMCG oom_kill event, change counter 1 => 2
Received event in /sys/fs/cgroup/test/memory.events:
*** 1 MEMCG oom_kill event, change counter 2 => 3
Received event in /sys/fs/cgroup/test/memory.events:
*** 1 MEMCG oom_kill event, change counter 3 => 4
Received event in /sys/fs/cgroup/test/memory.events:
*** 2 MEMCG max events, change counter 0 => 2
Received event in /sys/fs/cgroup/test/memory.events:
*** 8 MEMCG max events, change counter 2 => 10
*** 1 MEMCG oom event, change counter 0 => 1
Received event in /sys/fs/cgroup/test/memory.events:
*** 1 MEMCG oom_kill event, change counter 4 => 5
^CExiting memcg event listener...
=====

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Dmitry Rokosov <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Shakeel Butt <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions