Re: [v9 3/5] mm, oom: cgroup-aware OOM killer

From: Roman Gushchin
Date: Wed Oct 04 2017 - 11:05:31 EST

On Tue, Oct 03, 2017 at 04:22:46PM +0200, Michal Hocko wrote:
> On Tue 03-10-17 15:08:41, Roman Gushchin wrote:
> > On Tue, Oct 03, 2017 at 03:36:23PM +0200, Michal Hocko wrote:
> [...]
> > > I guess we want to inherit the value on the memcg creation but I agree
> > > that enforcing parent setting is weird. I will think about it some more
> > > but I agree that it is saner to only enforce per memcg value.
> >
> > I'm not against, but we should come up with a good explanation, why we're
> > inheriting it; or not inherit.
> Inheriting sounds like a less surprising behavior. Once you opt in for
> oom_group you can expect that descendants are going to assume the same
> unless they explicitly state otherwise.

Not sure I understand why. Setting memory.oom_group on a child memcg
has absolutely no meaning until memory.max is also set. In case of OOM
scoped to the parent memcg or above, parent's value defines the behavior.

If a user decides to create a separate OOM domain (be setting the hard
memory limit), he/she can also make a decision on how OOM event should
be handled.