From: Shakeel Butt <shakeelb@google.com>
To: Daniel Colascione <dancol@google.com>
Cc: Minchan Kim <minchan@kernel.org>,
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>,
"Joel Fernandes (Google)" <joel@joelfernandes.org>
Subject: Re: interaction of MADV_PAGEOUT with CoW anonymous mappings?
Date: Thu, 12 Mar 2020 08:15:42 -0700 [thread overview]
Message-ID: <CALvZod6y87aJxq90p=99orPajxN30jOf_RohSw7OSRdrXg6-Ag@mail.gmail.com> (raw)
In-Reply-To: <CAKOZuev1XzbsCPJtOA=v9QMuVpEBKc0_5ZE4Oc4tzmKdFHy2Dg@mail.gmail.com>
On Wed, Mar 11, 2020 at 7:04 PM Daniel Colascione <dancol@google.com> wrote:
>
> On Wed, Mar 11, 2020 at 5:18 PM Minchan Kim <minchan@kernel.org> wrote:
> >
> > 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.
>
> I don't want the behavior of an madvise command to change depending on
> *how* the command is invoked. MADV_PAGEOUT should do the same thing
> regardless. If you want to allow purging of shared pages as well,
> please add a new MADV_PAGEOUT_ALL or something and require a privilege
> to use it.
>
I would like to have a way to pageout the shared pages and
MADV_PAGEOUT_ALL approach looks fine to me.
next prev parent reply other threads:[~2020-03-12 15:15 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-10 18:08 interaction of MADV_PAGEOUT with CoW anonymous mappings? 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
2020-03-12 2:03 ` Daniel Colascione
2020-03-12 15:15 ` Shakeel Butt [this message]
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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