Re: [PATCH v2] mm, memcg: skip killing processes under memcg protection at first scan

[Michal Hocko <mhocko@suse.com>]

On Tue 20-08-19 17:26:49, Yafang Shao wrote:
> On Tue, Aug 20, 2019 at 5:17 PM Michal Hocko <mhocko@suse.com> wrote:
[...]
> > > As there's a memory.oom.group option to select killing all processes
> > > in a memcg, why not introduce a memcg level memcg.oom.score_adj?
> >
> > Because the oom selection is process based as already mentioned. There
> > was a long discussion about memcg based oom victim selection last year
> > but no consensus has been achieved.
> >
> > > Then we can set different scores to different memcgs.
> > > Because we always deploy lots of containers on a single host, when OOM
> > > occurs it will better to prefer killing the low priority containers
> > > (with higher memcg.oom.score_adj) first.
> >
> > How would you define low priority container with score_adj?
> >
> 
> For example, Container-A is high priority and Container-B is low priority.
> When OOM killer happens we prefer to kill all processes in Container-B
> and prevent Container-A from being killed.
> So we set memroy.oom.score_adj  with -1000 to Container-A  and +1000
> to Container-B, both container with memory.oom.cgroup set.
> When we set memroy.oom.score_adj  to a container, all processes
> belonging to this container will be set this value to their own
> oom_score_adj.

I hope you can see that this on/off mechanism doesn't scale and thus it
is a dubious interface. Just think of mutlitple containers.

-- 
Michal Hocko
SUSE Labs