Re: [RFC 0/2] opportunistic memory reclaim of a killed process

From: Michal Hocko <mhocko@kernel.org>
To: Suren Baghdasaryan <surenb@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	David Rientjes <rientjes@google.com>,
	Matthew Wilcox <willy@infradead.org>,
	yuzhoujian@didichuxing.com,
	Souptick Joarder <jrdr.linux@gmail.com>,
	Roman Gushchin <guro@fb.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Shakeel Butt <shakeelb@google.com>,
	Christian Brauner <christian@brauner.io>,
	Minchan Kim <minchan@kernel.org>,
	Tim Murray <timmurray@google.com>,
	Daniel Colascione <dancol@google.com>,
	Joel Fernandes <joel@joelfernandes.org>,
	Jann Horn <jannh@google.com>, linux-mm <linux-mm@kvack.org>,
	lsf-pc@lists.linux-foundation.org,
	LKML <linux-kernel@vger.kernel.org>,
	kernel-team <kernel-team@android.com>
Subject: Re: [RFC 0/2] opportunistic memory reclaim of a killed process
Date: Thu, 11 Apr 2019 22:17:27 +0200	[thread overview]
Message-ID: <20190411201727.GB4743@dhcp22.suse.cz> (raw)
In-Reply-To: <CAJuCfpERmBzCpRTj5W1929OOiVEjcdBoSAsYXiYKoq0gsgRyhg@mail.gmail.com>

On Thu 11-04-19 12:56:32, Suren Baghdasaryan wrote:
> On Thu, Apr 11, 2019 at 11:19 AM Michal Hocko <mhocko@kernel.org> wrote:
> >
> > On Thu 11-04-19 09:47:31, Suren Baghdasaryan 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.
> > >
> > > Relying on it is wrong, I agree. There are protections like allocation
> > > throttling that we can fall back to stop memory depletion. However
> > > having a way to free up resources that are not needed by a dying
> > > process quickly would help to avoid throttling which hurts user
> > > experience.
> >
> > I am not opposing speeding up the exit time in general. That is a good
> > thing. Especially for a very large processes (e.g. a DB). But I do not
> > really think we want to expose an API to control this specific aspect.
> 
> Great! Thanks for confirming that the intent is not worthless.
> There were a number of ideas floating both internally and in the 2/2
> of this patchset. I would like to get some input on which
> implementation would be preferable. From your answer sounds like you
> think it should be a generic feature, should not require any new APIs
> or hints from the userspace and should be conducted for all kills
> unconditionally (irrespective of memory pressure, who is waiting for
> victim's death, etc.). Do I understand correctly that this would be
> the preferred solution?

Yes, I think the general tear down solution is much more preferable than
a questionable API. How that solution should look like is an open
question. I am not sure myself to be honest.
-- 
Michal Hocko
SUSE Labs