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From:   Suren Baghdasaryan <surenb@google.com>
Date:   Mon, 2 Aug 2021 12:53:51 -0700
Message-ID: <CAJuCfpHObuK7jOcqdme9fU5=zFoteaY+5f2_uKdW0VQJa6H7OQ@mail.gmail.com>
Subject: Re: [PATCH v3 1/2] mm: introduce process_mrelease system call
To:     Shakeel Butt <shakeelb@google.com>
Cc:     Michal Hocko <mhocko@suse.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        David Rientjes <rientjes@google.com>,
        Matthew Wilcox <willy@infradead.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Roman Gushchin <guro@fb.com>, Rik van Riel <riel@surriel.com>,
        Minchan Kim <minchan@kernel.org>,
        Christian Brauner <christian@brauner.io>,
        Christoph Hellwig <hch@infradead.org>,
        Oleg Nesterov <oleg@redhat.com>,
        David Hildenbrand <david@redhat.com>,
        Jann Horn <jannh@google.com>,
        Andy Lutomirski <luto@kernel.org>,
        Christian Brauner <christian.brauner@ubuntu.com>,
        Florian Weimer <fweimer@redhat.com>,
        Jan Engelhardt <jengelh@inai.de>,
        Tim Murray <timmurray@google.com>,
        Linux API <linux-api@vger.kernel.org>,
        Linux MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        kernel-team <kernel-team@android.com>
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On Mon, Jul 26, 2021 at 6:44 AM Shakeel Butt <shakeelb@google.com> wrote:
>
> On Mon, Jul 26, 2021 at 12:27 AM Michal Hocko <mhocko@suse.com> wrote:
> >
> [...]
> >
> > Is process_mrelease on all of them really necessary? I thought that the
> > primary reason for the call is to guarantee a forward progress in cases
> > where the userspace OOM victim cannot die on SIGKILL. That should be
> > more an exception than a normal case, no?
> >
>
> I am thinking of using this API in this way: On user-defined OOM
> condition, kill a job/cgroup and unconditionally reap all of its
> processes. Keep monitoring the situation and if it does not improve go
> for another kill and reap.
>
> I can add additional logic in between kill and reap to see if reap is
> necessary but unconditionally reaping is more simple.
>
> >
> > > An alternative would be to have a cgroup specific interface for
> > > reaping similar to cgroup.kill.
> >
> > Could you elaborate?
> >
>
> I mentioned this in [1] where I was thinking if it makes sense to
> overload cgroup.kill to also add the SIGKILLed processes in
> oom_reaper_list. The downside would be that there will be one thread
> doing the reaping and the syscall approach allows userspace to reap in
> multiple threads. I think for now, I would go with whatever Suren is
> proposing and we can always add more stuff if need arises.
>
> [1] https://lore.kernel.org/containers/CALvZod4jsb6bFzTOS4ZRAJGAzBru0oWanAhezToprjACfGm+ew@mail.gmail.com/

Hi Folks,
So far I don't think there was any request for further changes.
Anything else you would want me to address or are we in a good shape
wrt this feature?
If so, would people who had a chance to review this patchset be
willing to endorse it with their Reviewed-by or Acked-by?
Thanks,
Suren.