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From: Minchan Kim <minchan@kernel.org>
To: Shakeel Butt <shakeelb@google.com>
Cc: Michal Hocko <mhocko@kernel.org>,
	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?
Date: Wed, 11 Mar 2020 17:18:49 -0700
Message-ID: <20200312001849.GA96953@google.com> (raw)
In-Reply-To: <CALvZod6b73_ay_kxph143Aj+XBq04Np0z2bK4Rfn8qppihrmTw@mail.gmail.com>

On Wed, Mar 11, 2020 at 04:53:17PM -0700, Shakeel Butt wrote:
> On Wed, Mar 11, 2020 at 1:45 AM Michal Hocko <mhocko@kernel.org> 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.
> >
> 
> What about the remote_madvise(MADV_PAGEOUT)? Will your patch disable
> the pageout from that code path as well for pages with mapcount > 1?

Maybe, not because process_madvise syscall needs more previliedge(ie,
PTRACE_MODE_ATTACH_FSCREDS) so I guess it would be more secure.
So in that case, I want to rely on the LRU chance for shared pages.

With that, the manager process could give a hint to several processes
and finally makes them paging out.

What do you think?


  reply index

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-10 18:08 Jann Horn
2020-03-10 18:48 ` Michal Hocko
2020-03-10 19:11   ` Jann Horn
2020-03-10 21:09     ` Michal Hocko
2020-03-10 22:48       ` Dave Hansen
2020-03-11  8:45         ` Michal Hocko
2020-03-11 22:02           ` Minchan Kim
2020-03-11 23:53           ` Shakeel Butt
2020-03-12  0:18             ` Minchan Kim [this message]
2020-03-12  2:03               ` Daniel Colascione
2020-03-12 15:15                 ` Shakeel Butt
2020-03-10 20:19   ` Daniel Colascione
2020-03-10 21:40     ` Jann Horn
2020-03-10 21:52       ` Daniel Colascione
2020-03-10 22:14 ` Minchan Kim
2020-03-12  8:22 ` Michal Hocko
2020-03-12 15:40   ` Vlastimil Babka
2020-03-12 20:16   ` Minchan Kim
2020-03-12 20:26     ` Dave Hansen
2020-03-12 20:41     ` Michal Hocko
2020-03-13  2:08       ` Minchan Kim
2020-03-13  8:05         ` Michal Hocko
2020-03-13 20:59           ` Minchan Kim
2020-03-16  9:20             ` Michal Hocko
2020-03-17  1:43               ` Minchan Kim
2020-03-17  7:12                 ` Michal Hocko
2020-03-17 15:00                   ` Minchan Kim
2020-03-17 15:58                     ` Michal Hocko
2020-03-17 17:20                       ` Minchan Kim
2020-03-12 21:41     ` Dave Hansen
2020-03-13  2:00       ` Minchan Kim
2020-03-13 16:59         ` Dave Hansen
2020-03-13 21:13           ` Minchan Kim
2020-03-12 23:29     ` Jann Horn

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