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From: Johannes Weiner <hannes@cmpxchg.org>
To: Michal Hocko <mhocko@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>,
	akpm@linux-foundation.org, rientjes@google.com,
	willy@infradead.org, yuzhoujian@didichuxing.com,
	jrdr.linux@gmail.com, guro@fb.com,
	penguin-kernel@i-love.sakura.ne.jp, ebiederm@xmission.com,
	shakeelb@google.com, christian@brauner.io, minchan@kernel.org,
	timmurray@google.com, dancol@google.com, joel@joelfernandes.org,
	jannh@google.com, linux-mm@kvack.org,
	lsf-pc@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
	kernel-team@android.com
Subject: Re: [RFC 0/2] opportunistic memory reclaim of a killed process
Date: Thu, 11 Apr 2019 13:19:09 -0400	[thread overview]
Message-ID: <20190411171909.GB5136@cmpxchg.org> (raw)
In-Reply-To: <20190411105111.GR10383@dhcp22.suse.cz>

On Thu, Apr 11, 2019 at 12:51:11PM +0200, Michal Hocko wrote:
> I would question whether we really need this at all? Relying on the exit
> speed sounds like a fundamental design problem of anything that relies
> on it. Sure task exit might be slow, but async mm tear down is just a
> mere optimization this is not guaranteed to really help in speading
> things up. OOM killer uses it as a guarantee for a forward progress in a
> finite time rather than as soon as possible.

I don't think it's flawed, it's just optimizing the user experience as
best as it can. You don't want to kill things prematurely, but once
there is pressure you want to rectify it quickly. That's valid.

We have a tool that does this, side effect or not, so I think it's
fair to try to make use of it when oom killing from userspace (which
we explictily support with oom_control in cgroup1 and memory.high in
cgroup2, and it's not just an Android thing).

The question is how explicit a contract we want to make with
userspace, and I would much prefer to not overpromise on a best-effort
thing like this, or even making the oom reaper ABI.

If unconditionally reaping killed tasks is too expensive, I'd much
prefer a simple kill hint over an explicit task reclaim interface.

  parent reply	other threads:[~2019-04-11 17:19 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-11  1:43 [RFC 0/2] opportunistic memory reclaim of a killed process Suren Baghdasaryan
2019-04-11  1:43 ` [RFC 1/2] mm: oom: expose expedite_reclaim to use oom_reaper outside of oom_kill.c Suren Baghdasaryan
2019-04-25 21:12   ` Tetsuo Handa
2019-04-25 21:56     ` Suren Baghdasaryan
2019-04-11  1:43 ` [RFC 2/2] signal: extend pidfd_send_signal() to allow expedited process killing Suren Baghdasaryan
2019-04-11 10:30   ` Christian Brauner
2019-04-11 10:34     ` Christian Brauner
2019-04-11 15:18     ` Suren Baghdasaryan
2019-04-11 15:23       ` Suren Baghdasaryan
2019-04-11 16:25         ` Daniel Colascione
2019-04-11 15:33   ` Matthew Wilcox
2019-04-11 17:05     ` Johannes Weiner
2019-04-11 17:09     ` Suren Baghdasaryan
2019-04-11 17:33       ` Daniel Colascione
2019-04-11 17:36         ` Matthew Wilcox
2019-04-11 17:47           ` Daniel Colascione
2019-04-12  6:49             ` Michal Hocko
2019-04-12 14:15               ` Suren Baghdasaryan
2019-04-12 14:20                 ` Daniel Colascione
2019-04-12 21:03             ` Matthew Wilcox
2019-04-11 17:52           ` Suren Baghdasaryan
2019-04-11 21:45       ` Roman Gushchin
2019-04-11 21:59         ` Suren Baghdasaryan
2019-04-12  6:53     ` Michal Hocko
2019-04-12 14:10       ` Suren Baghdasaryan
2019-04-12 14:14       ` Daniel Colascione
2019-04-12 15:30         ` Daniel Colascione
2019-04-25 16:09         ` Suren Baghdasaryan
2019-04-11 10:51 ` [RFC 0/2] opportunistic memory reclaim of a killed process Michal Hocko
2019-04-11 16:18   ` Joel Fernandes
2019-04-11 18:12     ` Michal Hocko
2019-04-11 19:14       ` Joel Fernandes
2019-04-11 20:11         ` Michal Hocko
2019-04-11 21:11           ` Joel Fernandes
2019-04-11 16:20   ` Sandeep Patil
2019-04-11 16:47   ` Suren Baghdasaryan
2019-04-11 18:19     ` Michal Hocko
2019-04-11 19:56       ` Suren Baghdasaryan
2019-04-11 20:17         ` Michal Hocko
2019-04-11 17:19   ` Johannes Weiner [this message]
2019-04-11 11:51 ` [Lsf-pc] " Rik van Riel
2019-04-11 12:16   ` Michal Hocko
2019-04-11 16:54     ` Suren Baghdasaryan

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