From: Joel Fernandes <joel@joelfernandes.org>
To: Suren Baghdasaryan <surenb@google.com>
Cc: "Christian Brauner" <christian@brauner.io>,
"Sultan Alsawaf" <sultan@kerneltoast.com>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"open list:ANDROID DRIVERS" <devel@driverdev.osuosl.org>,
"Daniel Colascione" <dancol@google.com>,
"Todd Kjos" <tkjos@android.com>,
"Kees Cook" <keescook@chromium.org>,
"Peter Zijlstra" <peterz@infradead.org>,
"Martijn Coenen" <maco@android.com>,
LKML <linux-kernel@vger.kernel.org>,
"Tim Murray" <timmurray@google.com>,
"Michal Hocko" <mhocko@kernel.org>, linux-mm <linux-mm@kvack.org>,
"Arve Hjønnevåg" <arve@android.com>,
"Ingo Molnar" <mingo@redhat.com>,
"Steven Rostedt" <rostedt@goodmis.org>,
"Oleg Nesterov" <oleg@redhat.com>,
"Andy Lutomirski" <luto@amacapital.net>,
kernel-team <kernel-team@android.com>
Subject: Re: [RFC] simple_lmk: Introduce Simple Low Memory Killer for Android
Date: Tue, 7 May 2019 14:46:50 -0400 [thread overview]
Message-ID: <20190507184650.GA139364@google.com> (raw)
In-Reply-To: <CAJuCfpFeOVzDUq5O_cVgVGjonWDWjVVR192On6eB5gf==_uPKw@mail.gmail.com>
On Tue, May 07, 2019 at 09:28:47AM -0700, Suren Baghdasaryan wrote:
> From: Christian Brauner <christian@brauner.io>
> Date: Tue, May 7, 2019 at 3:58 AM
> To: Sultan Alsawaf
> Cc: Greg Kroah-Hartman, open list:ANDROID DRIVERS, Daniel Colascione,
> Todd Kjos, Kees Cook, Peter Zijlstra, Martijn Coenen, LKML, Tim
> Murray, Michal Hocko, Suren Baghdasaryan, linux-mm, Arve Hjønnevåg,
> Ingo Molnar, Steven Rostedt, Oleg Nesterov, Joel Fernandes, Andy
> Lutomirski, kernel-team
>
> > On Tue, May 07, 2019 at 01:12:36AM -0700, Sultan Alsawaf wrote:
> > > On Tue, May 07, 2019 at 09:43:34AM +0200, Greg Kroah-Hartman wrote:
> > > > Given that any "new" android device that gets shipped "soon" should be
> > > > using 4.9.y or newer, is this a real issue?
> > >
> > > It's certainly a real issue for those who can't buy brand new Android devices
> > > without software bugs every six months :)
> > >
>
> Hi Sultan,
> Looks like you are posting this patch for devices that do not use
> userspace LMKD solution due to them using older kernels or due to
> their vendors sticking to in-kernel solution. If so, I see couple
> logistical issues with this patch. I don't see it being adopted in
> upstream kernel 5.x since it re-implements a deprecated mechanism even
> though vendors still use it. Vendors on the other hand, will not adopt
> it until you show evidence that it works way better than what
> lowmemorykilled driver does now. You would have to provide measurable
> data and explain your tests before they would consider spending time
> on this.
> On the implementation side I'm not convinced at all that this would
> work better on all devices and in all circumstances. We had cases when
> a new mechanism would show very good results until one usecase
> completely broke it. Bulk killing of processes that you are doing in
> your patch was a very good example of such a decision which later on
> we had to rethink. That's why baking these policies into kernel is
> very problematic. Another problem I see with the implementation that
> it ties process killing with the reclaim scan depth. It's very similar
> to how vmpressure works and vmpressure in my experience is very
> unpredictable.
Yeah it does seem conceptually similar, good point.
> > > Regardless, even if PSI were backported, a full-fledged LMKD using it has yet to
> > > be made, so it wouldn't be of much use now.
> >
> > This is work that is ongoing and requires kernel changes to make it
> > feasible. One of the things that I have been working on for quite a
> > while is the whole file descriptor for processes thing that is important
> > for LMKD (Even though I never thought about this use-case when I started
> > pitching this.). Joel and Daniel have joined in and are working on
> > making LMKD possible.
> > What I find odd is that every couple of weeks different solutions to the
> > low memory problem are pitched. There is simple_lkml, there is LMKD, and
> > there was a patchset that wanted to speed up memory reclaim at process
> > kill-time by adding a new flag to the new pidfd_send_signal() syscall.
> > That all seems - though related - rather uncoordinated.
>
> I'm not sure why pidfd_wait and expedited reclaim is seen as
> uncoordinated effort. All of them are done to improve userspace LMKD.
Christian, pidfd_wait and expedited reclaim are both coordinated efforts and
solve different problems related to LMK. simple_lmk is entirely different
effort that we already hesitated about when it was first posted, now we
hesitate again due to the issues Suren and others mentioned.
I think it is a better idea for Sultan to spend his time on using/improving
PSI/LMKd than spending it on the simple_lmk. It could also be a good topic to
discuss in the Android track of the Linux plumbers conference.
thanks,
- Joel
next prev parent reply other threads:[~2019-05-07 18:46 UTC|newest]
Thread overview: 105+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-10 20:34 [RFC] simple_lmk: Introduce Simple Low Memory Killer for Android Sultan Alsawaf
2019-03-10 21:03 ` Greg Kroah-Hartman
2019-03-10 21:26 ` Sultan Alsawaf
2019-03-11 16:32 ` Joel Fernandes
2019-03-11 16:37 ` Joel Fernandes
2019-03-11 17:43 ` Michal Hocko
2019-03-11 17:58 ` Sultan Alsawaf
2019-03-11 20:10 ` Suren Baghdasaryan
2019-03-11 20:46 ` Sultan Alsawaf
2019-03-11 21:11 ` Joel Fernandes
2019-03-11 21:46 ` Sultan Alsawaf
2019-03-11 22:15 ` Suren Baghdasaryan
2019-03-11 22:36 ` Sultan Alsawaf
2019-03-12 8:05 ` Michal Hocko
2019-03-12 14:36 ` Suren Baghdasaryan
2019-03-12 15:25 ` Matthew Wilcox
2019-03-12 15:33 ` Michal Hocko
2019-03-12 15:39 ` Michal Hocko
2019-03-12 16:37 ` Sultan Alsawaf
2019-03-12 16:48 ` Michal Hocko
2019-03-12 16:58 ` Michal Hocko
2019-03-12 17:15 ` Suren Baghdasaryan
2019-03-12 17:17 ` Tim Murray
2019-03-12 17:45 ` Sultan Alsawaf
2019-03-12 18:43 ` Tim Murray
2019-03-12 18:50 ` Christian Brauner
2019-03-14 17:47 ` Joel Fernandes
2019-03-14 20:49 ` Sultan Alsawaf
2019-03-15 2:54 ` Joel Fernandes
2019-03-15 3:43 ` Sultan Alsawaf
2019-03-15 3:16 ` Steven Rostedt
2019-03-15 3:45 ` Sultan Alsawaf
2019-03-15 4:36 ` Daniel Colascione
2019-03-15 13:36 ` Joel Fernandes
2019-03-15 15:56 ` Suren Baghdasaryan
2019-03-15 16:12 ` Daniel Colascione
2019-03-15 16:43 ` Steven Rostedt
2019-03-15 17:17 ` Daniel Colascione
2019-03-15 18:03 ` Christian Brauner
2019-03-15 18:13 ` Joel Fernandes
2019-03-15 18:24 ` Christian Brauner
2019-03-15 18:49 ` Joel Fernandes
2019-03-16 17:31 ` Suren Baghdasaryan
2019-03-16 18:00 ` Daniel Colascione
2019-03-16 18:57 ` Christian Brauner
2019-03-16 19:37 ` Suren Baghdasaryan
2019-03-17 1:53 ` Joel Fernandes
2019-03-17 11:42 ` Christian Brauner
2019-03-17 15:40 ` Daniel Colascione
2019-03-18 0:29 ` Christian Brauner
2019-03-18 23:50 ` Joel Fernandes
2019-03-19 22:14 ` Christian Brauner
2019-03-19 22:26 ` Joel Fernandes
2019-03-19 22:48 ` Daniel Colascione
2019-03-19 23:10 ` Christian Brauner
2019-03-20 1:52 ` Joel Fernandes
2019-03-20 2:42 ` pidfd design Daniel Colascione
2019-03-20 3:59 ` Christian Brauner
2019-03-20 7:02 ` Daniel Colascione
2019-03-20 11:33 ` Joel Fernandes
2019-03-20 18:26 ` Christian Brauner
2019-03-20 18:38 ` Daniel Colascione
2019-03-20 18:51 ` Christian Brauner
2019-03-20 18:58 ` Andy Lutomirski
2019-03-20 19:14 ` Christian Brauner
2019-03-20 19:40 ` Daniel Colascione
2019-03-21 17:02 ` Andy Lutomirski
2019-03-20 19:19 ` Joel Fernandes
2019-03-20 19:29 ` Daniel Colascione
2019-03-24 14:44 ` Serge E. Hallyn
2019-03-24 18:48 ` Joel Fernandes
2019-03-20 19:11 ` Joel Fernandes
2019-05-07 2:16 ` [RFC] simple_lmk: Introduce Simple Low Memory Killer for Android Sultan Alsawaf
2019-05-07 7:04 ` Greg Kroah-Hartman
2019-05-07 7:27 ` Sultan Alsawaf
2019-05-07 7:43 ` Greg Kroah-Hartman
2019-05-07 8:12 ` Sultan Alsawaf
2019-05-07 10:58 ` Christian Brauner
2019-05-07 16:28 ` Suren Baghdasaryan
2019-05-07 16:38 ` Christian Brauner
2019-05-07 16:53 ` Sultan Alsawaf
2019-05-07 20:01 ` Suren Baghdasaryan
2019-05-07 18:46 ` Joel Fernandes [this message]
2019-05-07 17:17 ` Sultan Alsawaf
2019-05-07 17:29 ` Greg Kroah-Hartman
2019-05-07 11:09 ` Greg Kroah-Hartman
2019-05-07 12:26 ` Michal Hocko
2019-05-07 15:31 ` Oleg Nesterov
2019-05-07 16:35 ` Sultan Alsawaf
2019-05-09 15:56 ` Oleg Nesterov
2019-05-09 18:33 ` Sultan Alsawaf
2019-05-10 15:10 ` Oleg Nesterov
2019-05-13 16:45 ` Sultan Alsawaf
2019-05-14 16:44 ` Steven Rostedt
2019-05-14 17:31 ` Sultan Alsawaf
2019-05-15 14:58 ` Oleg Nesterov
2019-05-15 17:27 ` Sultan Alsawaf
2019-05-15 18:32 ` Steven Rostedt
2019-05-15 18:52 ` Sultan Alsawaf
2019-05-15 20:09 ` Steven Rostedt
2019-05-16 13:54 ` Oleg Nesterov
2019-03-17 16:35 ` Serge E. Hallyn
2019-03-17 17:11 ` Daniel Colascione
2019-03-17 17:16 ` Serge E. Hallyn
2019-03-17 22:02 ` Suren Baghdasaryan
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