From: Johannes Weiner <hannes@cmpxchg.org>
To: Michal Hocko <mhocko@kernel.org>
Cc: Yafang Shao <laoar.shao@gmail.com>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linux MM <linux-mm@kvack.org>
Subject: Re: [PATCH] mm, memcg: clear page protection when memcg oom group happens
Date: Mon, 25 Nov 2019 09:42:13 -0500 [thread overview]
Message-ID: <20191125144213.GB602168@cmpxchg.org> (raw)
In-Reply-To: <20191125142150.GP31714@dhcp22.suse.cz>
On Mon, Nov 25, 2019 at 03:21:50PM +0100, Michal Hocko wrote:
> On Mon 25-11-19 22:11:15, Yafang Shao wrote:
> > When there're no processes, we don't need to protect the pages. You
> > can consider it as 'fault tolerance' .
>
> I have already tried to explain why this is a bold statement that
> doesn't really hold universally and that the kernel doesn't really have
> enough information to make an educated guess.
I agree, this is not obviously true. And the kernel shouldn't try to
guess whether the explicit userspace configuration is still desirable
to userspace or not. Should we also delete the cgroup when it becomes
empty for example?
It's better to implement these kinds of policy decisions from
userspace.
There is a cgroup.events file that can be polled, and its "populated"
field shows conveniently whether there are tasks in a subtree or
not. You can use that to clear protection settings.
next prev parent reply other threads:[~2019-11-25 14:42 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-25 10:14 Yafang Shao
2019-11-25 11:08 ` Michal Hocko
2019-11-25 11:37 ` Yafang Shao
2019-11-25 11:54 ` Michal Hocko
2019-11-25 12:17 ` Yafang Shao
2019-11-25 12:31 ` Michal Hocko
2019-11-25 12:37 ` Yafang Shao
2019-11-25 12:45 ` Michal Hocko
2019-11-25 14:11 ` Yafang Shao
2019-11-25 14:21 ` Michal Hocko
2019-11-25 14:42 ` Johannes Weiner [this message]
2019-11-25 14:45 ` Yafang Shao
2019-11-26 3:52 ` Yafang Shao
2019-11-26 7:31 ` Michal Hocko
2019-11-26 9:35 ` Yafang Shao
2019-11-26 9:50 ` Michal Hocko
2019-11-26 10:02 ` Yafang Shao
2019-11-26 10:22 ` Michal Hocko
2019-11-26 10:56 ` Yafang Shao
2019-11-25 14:44 ` Yafang Shao
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