From: Michal Hocko <mhocko@kernel.org>
To: Roman Gushchin <guro@fb.com>
Cc: Andrew Morton <akpm@linux-foundation.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: Wed, 18 Mar 2020 13:32:02 +0100 [thread overview]
Message-ID: <20200318123202.GL21362@dhcp22.suse.cz> (raw)
In-Reply-To: <20200316223510.3176148-1-guro@fb.com>
On Mon 16-03-20 15:35:10, 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>
After the follow up discussion I do agree that this should be sufficient
for now.
Acked-by: Michal Hocko <mhocko@suse.com>
> ---
> mm/memcontrol.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index daa399be4688..d8c4b7aa4e73 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1930,6 +1930,14 @@ struct mem_cgroup *mem_cgroup_get_oom_group(struct task_struct *victim,
> if (memcg == root_mem_cgroup)
> goto out;
>
> + /*
> + * If the victim task has been asynchronously moved to a different
> + * memory cgroup, we might end up killing tasks outside oom_domain.
> + * In this case it's better to ignore memory.group.oom.
> + */
> + if (unlikely(!mem_cgroup_is_descendant(memcg, oom_domain)))
> + goto out;
> +
> /*
> * Traverse the memory cgroup hierarchy from the victim task's
> * cgroup up to the OOMing cgroup (or root) to find the
> --
> 2.24.1
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2020-03-18 12:32 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 [this message]
2020-03-19 13:37 ` Johannes Weiner
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200318123202.GL21362@dhcp22.suse.cz \
--to=mhocko@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=guro@fb.com \
--cc=kernel-team@fb.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).