linux-kernel - Re: [PATCH] memcg: oom: ignore oom warnings from memory.max

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Date:   Thu, 30 Apr 2020 15:30:49 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Roman Gushchin <guro@...com>
Cc:     Shakeel Butt <shakeelb@...gle.com>,
        Michal Hocko <mhocko@...nel.org>,
        Greg Thelen <gthelen@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] memcg: oom: ignore oom warnings from memory.max

On Thu, Apr 30, 2020 at 12:06:10PM -0700, Roman Gushchin wrote:
> On Thu, Apr 30, 2020 at 11:27:12AM -0700, Shakeel Butt wrote:
> > @@ -6106,7 +6107,7 @@ static ssize_t memory_max_write(struct kernfs_open_file *of,
> >  		}
> >  
> >  		memcg_memory_event(memcg, MEMCG_OOM);
> > -		if (!mem_cgroup_out_of_memory(memcg, GFP_KERNEL, 0))
> > +		if (!mem_cgroup_out_of_memory(memcg, GFP_KERNEL, 0, true))
> 
> I wonder if we can handle it automatically from the oom_killer side?
> We can suppress warnings if oc->memcg is set and the cgroup scanning
> showed that there are no belonging processes?

Note that we do remote charging for certain consumers, where memory
gets charged from the outside of the cgroup.

We would want to know if these cause OOMs on an empty cgroup, rather
than force-charge the allocations quietly.