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Date: Fri, 13 Jul 2018 16:16:31 -0700
From: Roman Gushchin <guro@fb.com>
Subject: Re: cgroup-aware OOM killer, how to move forward
Message-ID: <20180713231630.GB17467@castle.DHCP.thefacebook.com>
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To: David Rientjes <rientjes@google.com>
Cc: linux-mm@kvack.org, akpm@linux-foundation.org, mhocko@kernel.org, hannes@cmpxchg.org, tj@kernel.org, gthelen@google.com

On Fri, Jul 13, 2018 at 04:11:51PM -0700, David Rientjes wrote:
> On Fri, 13 Jul 2018, Roman Gushchin wrote:
> 
> > > All cgroup v2 files do not need to be boolean and the only way you can add 
> > > a subtree oom kill is to introduce yet another file later.  Please make it 
> > > tristate so that you can define a mechanism of default (process only), 
> > > local cgroup, or subtree, and so we can avoid adding another option later 
> > > that conflicts with the proposed one.  This should be easy.
> > 
> > David, we're adding a cgroup v2 knob, and in cgroup v2 a memory cgroup
> > either has a sub-tree, either attached processes. So, there is no difference
> > between local cgroup and subtree.
> > 
> 
> Uhm, what?  We're talking about a common ancestor reaching its limit, so 
> it's oom, and it has multiple immediate children with their own processes 
> attached.  The difference is killing all processes attached to the 
> victim's cgroup or all processes under the oom mem cgroup's subtree.
> 

But it's a binary decision, no?
If memory.group_oom set, the whole sub-tree will be killed. Otherwise not.