Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Wed, 11 Mar 2020 15:02:41 -0700
From:   Minchan Kim <minchan@kernel.org>
To:     Michal Hocko <mhocko@kernel.org>
Cc:     Dave Hansen <dave.hansen@intel.com>, Jann Horn <jannh@google.com>,
        Linux-MM <linux-mm@kvack.org>,
        kernel list <linux-kernel@vger.kernel.org>,
        Daniel Colascione <dancol@google.com>,
        "Joel Fernandes (Google)" <joel@joelfernandes.org>
Subject: Re: interaction of MADV_PAGEOUT with CoW anonymous mappings?
Message-ID: <20200311220241.GA252592@google.com>
References: <CAG48ez0G3JkMq61gUmyQAaCq=_TwHbi1XKzWRooxZkv08PQKuw@mail.gmail.com>
 <20200310184814.GA8447@dhcp22.suse.cz>
 <CAG48ez2pNSKL9ZTH-PQ93+Kc6ObH6Pa1vVg3OS85WT0TB8m3=A@mail.gmail.com>
 <20200310210906.GD8447@dhcp22.suse.cz>
 <cf95db88-968d-fee5-1c15-10d024c09d8a@intel.com>
 <20200311084513.GD23944@dhcp22.suse.cz>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20200311084513.GD23944@dhcp22.suse.cz>
User-Agent: Mutt/1.12.2 (2019-09-21)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, Mar 11, 2020 at 09:45:13AM +0100, Michal Hocko wrote:
> On Tue 10-03-20 15:48:31, Dave Hansen wrote:
> > Maybe instead of just punting on MADV_PAGEOUT for map_count>1 we should
> > only let it affect the *local* process.  We could still put the page in
> > the swap cache, we just wouldn't go do the rmap walk.
> 
> Is it really worth medling with the reclaim code and special case
> MADV_PAGEOUT there? I mean it is quite reasonable to have an initial
> implementation that doesn't really touch shared pages because that can
> lead to all sorts of hard to debug and unexpected problems. So I would
> much rather go with a simple patch to check map count first and see
> whether somebody actually cares about those shared pages and go from
> there.
> 
> Minchan, do you want to take my diff and turn it into the proper patch
> or should I do it.

Hey Michal,

It would be great if you could send it.
Thanks.