The patch titled
Subject: mm, oom, docs: describe the cgroup-aware OOM killer
has been removed from the -mm tree. Its filename was
mm-oom-docs-describe-the-cgroup-aware-oom-killer.patch
This patch was dropped because an alternative patch was merged
------------------------------------------------------
From: Roman Gushchin <guro@xxxxxx>
Subject: mm, oom, docs: describe the cgroup-aware OOM killer
Document the cgroup-aware OOM killer.
[guro@xxxxxx: cgroup-aware OOM logic is disabled by default]
Link: http://lkml.kernel.org/r/20171201170149.GB27436@xxxxxxxxxxxxxxxxxxxxxxxxxxx
[mhocko@xxxxxxxx: clarify root memcg oom accounting]
Link: http://lkml.kernel.org/r/20180130122011.GB21609@xxxxxxxxxxxxxx
[akpm@xxxxxxxxxxxxxxxxxxxx: tweak text, fix typo]
Link: http://lkml.kernel.org/r/20171130152824.1591-7-guro@xxxxxx
Signed-off-by: Roman Gushchin <guro@xxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/admin-guide/cgroup-v2.rst | 74 ++++++++++++++++++++++
1 file changed, 74 insertions(+)
--- a/Documentation/admin-guide/cgroup-v2.rst~mm-oom-docs-describe-the-cgroup-aware-oom-killer
+++ a/Documentation/admin-guide/cgroup-v2.rst
@@ -48,6 +48,7 @@ v1 is available under Documentation/cgro
5-2-1. Memory Interface Files
5-2-2. Usage Guidelines
5-2-3. Memory Ownership
+ 5-2-4. OOM Killer
5-3. IO
5-3-1. IO Interface Files
5-3-2. Writeback
@@ -1069,6 +1070,31 @@ PAGE_SIZE multiple when read back.
high limit is used and monitored properly, this limit's
utility is limited to providing the final safety net.
+ memory.oom_group
+
+ A read-write single value file which exists on non-root
+ cgroups. The default is "0".
+
+ If set, OOM killer will consider the memory cgroup as an
+ indivisible memory consumers and compare it with other memory
+ consumers by it's memory footprint.
+ If such memory cgroup is selected as an OOM victim, all
+ processes belonging to it or it's descendants will be killed.
+
+ This applies to system-wide OOM conditions and reaching
+ the hard memory limit of the cgroup and their ancestor.
+ If OOM condition happens in a descendant cgroup with it's own
+ memory limit, the memory cgroup can't be considered
+ as an OOM victim, and OOM killer will not kill all belonging
+ tasks.
+
+ Also, OOM killer respects the /proc/pid/oom_score_adj value -1000,
+ and will never kill the unkillable task, even if memory.oom_group
+ is set.
+
+ If cgroup-aware OOM killer is not enabled, ENOTSUPP error
+ is returned on attempt to access the file.
+
memory.events
A read-only flat-keyed file which exists on non-root cgroups.
The following entries are defined. Unless specified
@@ -1293,6 +1319,54 @@ to be accessed repeatedly by other cgrou
POSIX_FADV_DONTNEED to relinquish the ownership of memory areas
belonging to the affected files to ensure correct memory ownership.
+OOM Killer
+~~~~~~~~~~
+
+Cgroup v2 memory controller implements a cgroup-aware OOM killer.
+It means that it treats cgroups as first class OOM entities.
+
+Cgroup-aware OOM logic is turned off by default and requires
+passing the "groupoom" option on mounting cgroupfs. It can also
+by remounting cgroupfs with the following command::
+
+ # mount -o remount,groupoom $MOUNT_POINT
+
+Under OOM conditions the memory controller tries to make the best
+choice of a victim, looking for a memory cgroup with the largest
+memory footprint, considering leaf cgroups and cgroups with the
+memory.oom_group option set, which are considered to be an indivisible
+memory consumers.
+
+By default, OOM killer will kill the biggest task in the selected
+memory cgroup. A user can change this behavior by enabling
+the per-cgroup memory.oom_group option. If set, it causes
+the OOM killer to kill all processes attached to the cgroup,
+except processes with oom_score_adj set to -1000.
+
+This affects both system- and cgroup-wide OOMs. For a cgroup-wide OOM
+the memory controller considers only cgroups belonging to the sub-tree
+of the OOM'ing cgroup.
+
+Leaf cgroups and cgroups with oom_group option set are compared based
+on their cumulative memory usage. The root cgroup is treated as a
+leaf memory cgroup as well, so it is compared with other leaf memory
+cgroups. Due to internal implementation restrictions the size of
+the root cgroup is the cumulative sum of oom_badness of all its tasks
+(in other words oom_score_adj of each task is obeyed). Relying on
+oom_score_adj (apart from OOM_SCORE_ADJ_MIN) can lead to over- or
+underestimation of the root cgroup consumption and it is therefore
+discouraged. This might change in the future, however.
+
+If there are no cgroups with the enabled memory controller,
+the OOM killer is using the "traditional" process-based approach.
+
+Please, note that memory charges are not migrating if tasks
+are moved between different memory cgroups. Moving tasks with
+significant memory footprint may affect OOM victim selection logic.
+If it's a case, please, consider creating a common ancestor for
+the source and destination memory cgroups and enabling oom_group
+on ancestor layer.
+
IO
--
_
Patches currently in -mm which might be from guro@xxxxxx are
mm-introduce-mem_cgroup_put-helper.patch
cgroup-list-groupoom-in-cgroup-features.patch
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