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From: Oleksandr Natalenko <oleksandr@redhat.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Minchan Kim <minchan@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>,
	linux-api@vger.kernel.org, Suren Baghdasaryan <surenb@google.com>,
	Tim Murray <timmurray@google.com>,
	Daniel Colascione <dancol@google.com>,
	Sandeep Patil <sspatil@google.com>,
	Sonny Rao <sonnyrao@google.com>,
	Brian Geffon <bgeffon@google.com>, Michal Hocko <mhocko@suse.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Shakeel Butt <shakeelb@google.com>,
	John Dias <joaodias@google.com>,
	Joel Fernandes <joel@joelfernandes.org>,
	Jann Horn <jannh@google.com>,
	alexander.h.duyck@linux.intel.com, sj38.park@gmail.com,
	SeongJae Park <sjpark@amazon.de>
Subject: Re: [PATCH v7 7/7] mm/madvise: allow KSM hints for remote API
Date: Fri, 6 Mar 2020 14:41:46 +0100	[thread overview]
Message-ID: <20200306134146.mqiyvsdnqty7so53@butterfly.localdomain> (raw)
In-Reply-To: <2a66abd8-4103-f11b-06d1-07762667eee6@suse.cz>

On Fri, Mar 06, 2020 at 02:13:49PM +0100, Vlastimil Babka wrote:
> On 3/2/20 8:36 PM, Minchan Kim wrote:
> > From: Oleksandr Natalenko <oleksandr@redhat.com>
> > 
> > It all began with the fact that KSM works only on memory that is marked
> > by madvise(). And the only way to get around that is to either:
> > 
> >   * use LD_PRELOAD; or
> >   * patch the kernel with something like UKSM or PKSM.
> > 
> > (i skip ptrace can of worms here intentionally)
> > 
> > To overcome this restriction, lets employ a new remote madvise API. This
> > can be used by some small userspace helper daemon that will do auto-KSM
> > job for us.
> > 
> > I think of two major consumers of remote KSM hints:
> > 
> >   * hosts, that run containers, especially similar ones and especially in
> >     a trusted environment, sharing the same runtime like Node.js;
> > 
> >   * heavy applications, that can be run in multiple instances, not
> >     limited to opensource ones like Firefox, but also those that cannot be
> >     modified since they are binary-only and, maybe, statically linked.
> > 
> > Speaking of statistics, more numbers can be found in the very first
> > submission, that is related to this one [1]. For my current setup with
> > two Firefox instances I get 100 to 200 MiB saved for the second instance
> > depending on the amount of tabs.
> > 
> > 1 FF instance with 15 tabs:
> > 
> >    $ echo "$(cat /sys/kernel/mm/ksm/pages_sharing) * 4 / 1024" | bc
> >    410
> > 
> > 2 FF instances, second one has 12 tabs (all the tabs are different):
> > 
> >    $ echo "$(cat /sys/kernel/mm/ksm/pages_sharing) * 4 / 1024" | bc
> >    592
> > 
> > At the very moment I do not have specific numbers for containerised
> > workload, but those should be comparable in case the containers share
> > similar/same runtime.
> > 
> > [1] https://lore.kernel.org/patchwork/patch/1012142/
> > 
> > Reviewed-by: SeongJae Park <sjpark@amazon.de>
> > Signed-off-by: Oleksandr Natalenko <oleksandr@redhat.com>
> > Signed-off-by: Minchan Kim <minchan@kernel.org>
> 
> This will lead to one process calling unmerge_ksm_pages() of another. There's a
> (signal_pending(current)) test there, should it check also the other task,
> analogically to task 3?

Do we care about current there then? Shall we just pass mm into unmerge_ksm_pages and check the signals of the target task only, be it current or something else?

> Then break_ksm() is fine as it is, as ksmd also calls it, right?

I think break_ksm() cares only about mmap_sem protection, so we should
be fine here.

> 
> > ---
> >  mm/madvise.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/mm/madvise.c b/mm/madvise.c
> > index e77c6c1fad34..f4fa962ee74d 100644
> > --- a/mm/madvise.c
> > +++ b/mm/madvise.c
> > @@ -1005,6 +1005,10 @@ process_madvise_behavior_valid(int behavior)
> >  	switch (behavior) {
> >  	case MADV_COLD:
> >  	case MADV_PAGEOUT:
> > +#ifdef CONFIG_KSM
> > +	case MADV_MERGEABLE:
> > +	case MADV_UNMERGEABLE:
> > +#endif
> >  		return true;
> >  	default:
> >  		return false;
> > 
> 

-- 
  Best regards,
    Oleksandr Natalenko (post-factum)
    Principal Software Maintenance Engineer



  reply	other threads:[~2020-03-06 13:41 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-02 19:36 [PATCH v7 0/7] introduce memory hinting API for external process Minchan Kim
2020-03-02 19:36 ` [PATCH v7 1/7] mm: pass task and mm to do_madvise Minchan Kim
2020-03-05 15:48   ` Vlastimil Babka
2020-05-08 18:21     ` Minchan Kim
2020-03-02 19:36 ` [PATCH v7 2/7] mm: introduce external memory hinting API Minchan Kim
2020-03-03 10:33   ` kbuild test robot
2020-03-03 14:57     ` Minchan Kim
2020-03-05 18:15   ` Vlastimil Babka
2020-03-10 22:20     ` Minchan Kim
2020-03-11  0:36       ` Minchan Kim
2020-03-12 12:40       ` Vlastimil Babka
2020-03-12 20:23         ` Minchan Kim
2020-05-08 18:33           ` Minchan Kim
2020-03-02 19:36 ` [PATCH v7 3/7] mm: check fatal signal pending of target process Minchan Kim
2020-03-06 10:22   ` Vlastimil Babka
2020-03-10 22:24     ` Minchan Kim
2020-03-02 19:36 ` [PATCH v7 4/7] pid: move pidfd_get_pid function to pid.c Minchan Kim
2020-03-06 10:57   ` Vlastimil Babka
2020-03-06 11:14   ` Christian Brauner
2020-03-02 19:36 ` [PATCH v7 5/7] mm: support both pid and pidfd for process_madvise Minchan Kim
2020-03-06 11:14   ` Vlastimil Babka
2020-03-11  0:42     ` Minchan Kim
2020-05-08 18:36       ` Minchan Kim
2020-05-08 23:04         ` Andrew Morton
2020-05-09 12:48           ` Christian Brauner
2020-05-09 23:14             ` Minchan Kim
2020-05-12 19:55               ` Suren Baghdasaryan
2020-03-02 19:36 ` [PATCH v7 6/7] mm/madvise: employ mmget_still_valid for write lock Minchan Kim
2020-03-06 12:52   ` Vlastimil Babka
2020-03-06 13:03     ` Oleksandr Natalenko
2020-03-06 16:03       ` Vlastimil Babka
2020-03-09 12:30         ` Oleksandr Natalenko
2020-03-10 22:28           ` Minchan Kim
2020-03-02 19:36 ` [PATCH v7 7/7] mm/madvise: allow KSM hints for remote API Minchan Kim
2020-03-06 13:13   ` Vlastimil Babka
2020-03-06 13:41     ` Oleksandr Natalenko [this message]
2020-03-06 16:08       ` Vlastimil Babka
2020-03-09 13:11         ` Oleksandr Natalenko
2020-03-09 15:08           ` Michal Hocko
2020-03-09 15:19             ` Oleksandr Natalenko
2020-03-09 15:42               ` Vlastimil Babka
2020-03-09 16:03                 ` Michal Hocko
2020-06-11  2:21   ` Jann Horn
2020-03-02 21:16 ` [PATCH v7 0/7] introduce memory hinting API for external process Andrew Morton
2020-03-02 21:42   ` Minchan Kim

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