On Tue, 30 Jan 2018 13:20:11 +0100 Michal Hocko <mhocko@xxxxxxxxxx> wrote: > Subject: [PATCH] oom, memcg: clarify root memcg oom accounting > > David Rientjes has pointed out that the current way how the root memcg > is accounted for the cgroup aware OOM killer is undocumented. Unlike > regular cgroups there is no accounting going on in the root memcg > (mostly for performance reasons). Therefore we are suming up oom_badness > of its tasks. This might result in an over accounting because of the > oom_score_adj setting. Document this for now. Thanks. Some tweakage: --- a/Documentation/cgroup-v2.txt~mm-oom-docs-describe-the-cgroup-aware-oom-killer-fix-2-fix +++ a/Documentation/cgroup-v2.txt @@ -1292,13 +1292,13 @@ 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's compared with other leaf memory +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 a cumulative sum of oom_badness of all its tasks +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 (appart from OOM_SCORE_ADJ_MIN) can lead to over or -underestimating of the root cgroup consumption and it is therefore -discouraged. This might change in the future, though. +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. _ -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
