From: Johannes Weiner <hannes@cmpxchg.org>
To: Roman Gushchin <guro@fb.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@kernel.org>,
linux-mm@kvack.org, kernel-team@fb.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: memcg: make memory.oom.group tolerable to task migration
Date: Thu, 19 Mar 2020 09:37:46 -0400 [thread overview]
Message-ID: <20200319133746.GA187654@cmpxchg.org> (raw)
In-Reply-To: <20200316223510.3176148-1-guro@fb.com>
On Mon, Mar 16, 2020 at 03:35:10PM -0700, Roman Gushchin wrote:
> If a task is getting moved out of the OOMing cgroup, it might
> result in unexpected OOM killings if memory.oom.group is used
> anywhere in the cgroup tree.
>
> Imagine the following example:
>
> A (oom.group = 1)
> / \
> (OOM) B C
>
> Let's say B's memory.max is exceeded and it's OOMing. The OOM killer
> selects a task in B as a victim, but someone asynchronously moves
> the task into C. mem_cgroup_get_oom_group() will iterate over all
> ancestors of C up to the root cgroup. In theory it had to stop
> at the oom_domain level - the memory cgroup which is OOMing.
> But because B is not an ancestor of C, it's not happening.
> Instead it chooses A (because it's oom.group is set), and kills
> all tasks in A. This behavior is wrong because the OOM happened in B,
> so there is no reason to kill anything outside.
>
> Fix this by checking it the memory cgroup to which the task belongs
> is a descendant of the oom_domain. If not, memory.oom.group should
> be ignored, and the OOM killer should kill only the victim task.
>
> Signed-off-by: Roman Gushchin <guro@fb.com>
> Reported-by: Dan Schatzberg <dschatzberg@fb.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
prev parent reply other threads:[~2020-03-19 13:37 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-16 22:35 [PATCH] mm: memcg: make memory.oom.group tolerable to task migration Roman Gushchin
2020-03-17 7:52 ` Michal Hocko
2020-03-17 18:38 ` Roman Gushchin
2020-03-17 18:55 ` Michal Hocko
2020-03-17 20:36 ` Roman Gushchin
2020-03-18 12:31 ` Michal Hocko
2020-03-18 12:32 ` Michal Hocko
2020-03-19 13:37 ` Johannes Weiner [this message]
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