Re: [v8 0/4] cgroup-aware OOM killer

[Michal Hocko <mhocko@kernel.org>]

On Fri 15-09-17 12:55:55, David Rientjes wrote:
> On Fri, 15 Sep 2017, Roman Gushchin wrote:
> 
> > > But then you just enforce a structural restriction on your configuration
> > > because
> > > 	root
> > >         /  \
> > >        A    D
> > >       /\   
> > >      B  C
> > > 
> > > is a different thing than
> > > 	root
> > >         / | \
> > >        B  C  D
> > >
> > 
> > I actually don't have a strong argument against an approach to select
> > largest leaf or kill-all-set memcg. I think, in practice there will be
> > no much difference.
> > 
> > The only real concern I have is that then we have to do the same with
> > oom_priorities (select largest priority tree-wide), and this will limit
> > an ability to enforce the priority by parent cgroup.
> > 
> 
> Yes, oom_priority cannot select the largest priority tree-wide for exactly 
> that reason.  We need the ability to control from which subtree the kill 
> occurs in ancestor cgroups.  If multiple jobs are allocated their own 
> cgroups and they can own memory.oom_priority for their own subcontainers, 
> this becomes quite powerful so they can define their own oom priorities.   
> Otherwise, they can easily override the oom priorities of other cgroups.

Could you be more speicific about your usecase? What would be a
problem If we allow to only increase priority in children (like other
hierarchical controls).

-- 
Michal Hocko
SUSE Labs