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[213.175.37.10]) by smtp.gmail.com with ESMTPSA id n3sm4655448wmc.27.2020.01.17.04.34.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 17 Jan 2020 04:34:01 -0800 (PST) Date: Fri, 17 Jan 2020 13:34:00 +0100 From: Oleksandr Natalenko To: Kirill Tkhai Cc: Minchan Kim , Andrew Morton , LKML , linux-mm , linux-api@vger.kernel.org, Suren Baghdasaryan , Tim Murray , Daniel Colascione , Sandeep Patil , Sonny Rao , Brian Geffon , Michal Hocko , Johannes Weiner , Shakeel Butt , John Dias , christian.brauner@ubuntu.com, sjpark@amazon.de, Minchan Kim Subject: Re: [PATCH v2 4/5] mm/madvise: allow KSM hints for remote API Message-ID: <20200117123400.o3ne6kazkovq4okd@butterfly.localdomain> References: <20200116235953.163318-1-minchan@kernel.org> <20200116235953.163318-5-minchan@kernel.org> <37338e14-5a55-1926-b6c1-5f98b6a6fdb5@virtuozzo.com> MIME-Version: 1.0 In-Reply-To: <37338e14-5a55-1926-b6c1-5f98b6a6fdb5@virtuozzo.com> X-MC-Unique: XOZfUUttOy-qXZG7RhX6Ug-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 > >=20 > > 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: > >=20 > > * use LD_PRELOAD; or > > * patch the kernel with something like UKSM or PKSM. > >=20 > > (i skip ptrace can of worms here intentionally) > >=20 > > To overcome this restriction, lets employ a new remote madvise API. Thi= s > > can be used by some small userspace helper daemon that will do auto-KSM > > job for us. > >=20 > > I think of two major consumers of remote KSM hints: > >=20 > > * hosts, that run containers, especially similar ones and especially = in > > a trusted environment, sharing the same runtime like Node.js; > >=20 > > * 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. > >=20 > > 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 instanc= e > > depending on the amount of tabs. > >=20 > > 1 FF instance with 15 tabs: > >=20 > > $ echo "$(cat /sys/kernel/mm/ksm/pages_sharing) * 4 / 1024" | bc > > 410 > >=20 > > 2 FF instances, second one has 12 tabs (all the tabs are different): > >=20 > > $ echo "$(cat /sys/kernel/mm/ksm/pages_sharing) * 4 / 1024" | bc > > 592 > >=20 > > 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. > >=20 > > [1] https://lore.kernel.org/patchwork/patch/1012142/ > >=20 > > Signed-off-by: Oleksandr Natalenko > > Signed-off-by: Minchan Kim > > --- > > mm/madvise.c | 2 ++ > > 1 file changed, 2 insertions(+) > >=20 > > 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) > > =09switch (behavior) { > > =09case MADV_COLD: > > =09case MADV_PAGEOUT: > > +=09case MADV_MERGEABLE: > > +=09case MADV_UNMERGEABLE: > > =09=09return true; > > =09default: > > =09=09return false; >=20 > Remote madvise on KSM parameters should be OK. >=20 > 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. >=20 Thanks for the suggestion. Minchan, shall you adopt it directly, or I should send a separate patch? --=20 Best regards, Oleksandr Natalenko (post-factum) Senior Software Maintenance Engineer