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authorShakeel Butt <shakeelb@google.com>2019-07-11 20:55:55 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-07-12 11:05:43 -0700
commit1e577f970f66a53d429cbee37b36177c9712f488 (patch)
tree3d167c4fff9e1b88a1e9c4727ab8d8e0128ded12 /Documentation
parentec165450968b26298bd1c373de37b0ab6d826b33 (diff)
mm, memcg: introduce memory.events.local
The memory controller in cgroup v2 exposes memory.events file for each memcg which shows the number of times events like low, high, max, oom and oom_kill have happened for the whole tree rooted at that memcg. Users can also poll or register notification to monitor the changes in that file. Any event at any level of the tree rooted at memcg will notify all the listeners along the path till root_mem_cgroup. There are existing users which depend on this behavior. However there are users which are only interested in the events happening at a specific level of the memcg tree and not in the events in the underlying tree rooted at that memcg. One such use-case is a centralized resource monitor which can dynamically adjust the limits of the jobs running on a system. The jobs can create their sub-hierarchy for their own sub-tasks. The centralized monitor is only interested in the events at the top level memcgs of the jobs as it can then act and adjust the limits of the jobs. Using the current memory.events for such centralized monitor is very inconvenient. The monitor will keep receiving events which it is not interested and to find if the received event is interesting, it has to read memory.event files of the next level and compare it with the top level one. So, let's introduce memory.events.local to the memcg which shows and notify for the events at the memcg level. Now, does memory.stat and memory.pressure need their local versions. IMHO no due to the no internal process contraint of the cgroup v2. The memory.stat file of the top level memcg of a job shows the stats and vmevents of the whole tree. The local stats or vmevents of the top level memcg will only change if there is a process running in that memcg but v2 does not allow that. Similarly for memory.pressure there will not be any process in the internal nodes and thus no chance of local pressure. Link: http://lkml.kernel.org/r/20190527174643.209172-1-shakeelb@google.com Signed-off-by: Shakeel Butt <shakeelb@google.com> Reviewed-by: Roman Gushchin <guro@fb.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Cc: Chris Down <chris@chrisdown.name> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/admin-guide/cgroup-v2.rst10
1 files changed, 10 insertions, 0 deletions
diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index a5c845338d6d..a9548de56ac9 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -1146,6 +1146,11 @@ PAGE_SIZE multiple when read back.
otherwise, a value change in this file generates a file
modified event.
+ Note that all fields in this file are hierarchical and the
+ file modified event can be generated due to an event down the
+ hierarchy. For for the local events at the cgroup level see
+ memory.events.local.
+
low
The number of times the cgroup is reclaimed due to
high memory pressure even though its usage is under
@@ -1185,6 +1190,11 @@ PAGE_SIZE multiple when read back.
The number of processes belonging to this cgroup
killed by any kind of OOM killer.
+ memory.events.local
+ Similar to memory.events but the fields in the file are local
+ to the cgroup i.e. not hierarchical. The file modified event
+ generated on this file reflects only the local events.
+
memory.stat
A read-only flat-keyed file which exists on non-root cgroups.