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From: Minchan Kim <minchan@kernel.org>
To: Oleksandr Natalenko <oleksandr@redhat.com>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>,
	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>,
	christian.brauner@ubuntu.com, sjpark@amazon.de
Subject: Re: [PATCH v2 4/5] mm/madvise: allow KSM hints for remote API
Date: Tue, 21 Jan 2020 09:45:01 -0800	[thread overview]
Message-ID: <20200121174501.GD140922@google.com> (raw)
In-Reply-To: <20200117123400.o3ne6kazkovq4okd@butterfly.localdomain>

On Fri, Jan 17, 2020 at 01:34:00PM +0100, Oleksandr Natalenko wrote:
> Hi.
> 
> On Fri, Jan 17, 2020 at 01:13:14PM +0300, Kirill Tkhai wrote:
> > On 17.01.2020 02:59, 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/
> > > 
> > > Signed-off-by: Oleksandr Natalenko <oleksandr@redhat.com>
> > > Signed-off-by: Minchan Kim <minchan@google.com>
> > > ---
> > >  mm/madvise.c | 2 ++
> > >  1 file changed, 2 insertions(+)
> > > 
> > > diff --git a/mm/madvise.c b/mm/madvise.c
> > > index 84cffd0900f1..89557998d287 100644
> > > --- a/mm/madvise.c
> > > +++ b/mm/madvise.c
> > > @@ -1000,6 +1000,8 @@ process_madvise_behavior_valid(int behavior)
> > >  	switch (behavior) {
> > >  	case MADV_COLD:
> > >  	case MADV_PAGEOUT:
> > > +	case MADV_MERGEABLE:
> > > +	case MADV_UNMERGEABLE:
> > >  		return true;
> > >  	default:
> > >  		return false;
> > 
> > Remote madvise on KSM parameters should be OK.
> > 
> > One thing is madvise_behavior_valid() places MADV_MERGEABLE/UNMERGEABLE
> > in #ifdef brackes, so -EINVAL is returned by madvise() syscall if KSM
> > is not enabled. Here we should follow the same way for symmetry.
> > 
> 
> Thanks for the suggestion.
> 
> Minchan, shall you adopt it directly, or I should send a separate patch?

I will handle it in next spin.

  reply	other threads:[~2020-01-21 17:45 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-16 23:59 [PATCH v2 0/5] introduce memory hinting API for external process Minchan Kim
2020-01-16 23:59 ` [PATCH v2 1/5] mm: factor out madvise's core functionality Minchan Kim
2020-01-17 10:02   ` Kirill Tkhai
2020-01-17 18:14     ` Minchan Kim
2020-01-16 23:59 ` [PATCH v2 2/5] mm: introduce external memory hinting API Minchan Kim
2020-01-17 11:52   ` Michal Hocko
2020-01-17 15:58     ` Kirill A. Shutemov
2020-01-17 17:32       ` Minchan Kim
2020-01-17 21:26         ` Kirill A. Shutemov
2020-01-18  9:40           ` SeongJae Park
2020-01-19 16:14           ` sspatil
2020-01-20  7:58             ` Michal Hocko
2020-01-20 10:39               ` Kirill Tkhai
2020-01-21 18:32               ` Minchan Kim
2020-01-22  8:28                 ` Michal Hocko
2020-01-22  9:36                   ` SeongJae Park
2020-01-22 10:02                     ` Michal Hocko
2020-01-22 13:28                       ` SeongJae Park
2020-01-23  1:41                   ` Minchan Kim
2020-01-23  9:13                     ` Michal Hocko
2020-01-21 18:11           ` Minchan Kim
2020-01-22 10:44             ` Oleksandr Natalenko
2020-01-23  1:43               ` Minchan Kim
2020-01-23  7:29                 ` Oleksandr Natalenko
2020-01-17 17:25     ` Minchan Kim
2020-01-20  8:03       ` Michal Hocko
2020-01-20 10:24     ` Kirill Tkhai
2020-01-20 11:27       ` Michal Hocko
2020-01-20 12:39         ` Kirill A. Shutemov
2020-01-20 13:24           ` Michal Hocko
2020-01-20 14:21             ` Kirill A. Shutemov
2020-01-20 15:44               ` Michal Hocko
2020-01-21 18:43             ` Minchan Kim
2020-01-16 23:59 ` [PATCH v2 3/5] mm/madvise: employ mmget_still_valid for write lock Minchan Kim
2020-01-16 23:59 ` [PATCH v2 4/5] mm/madvise: allow KSM hints for remote API Minchan Kim
2020-01-17 10:13   ` Kirill Tkhai
2020-01-17 12:34     ` Oleksandr Natalenko
2020-01-21 17:45       ` Minchan Kim [this message]
2020-01-16 23:59 ` [PATCH v2 5/5] mm: support both pid and pidfd for process_madvise Minchan Kim

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