From mboxrd@z Thu Jan 1 00:00:00 1970 From: Minchan Kim Subject: [PATCH v2 4/5] mm/madvise: allow KSM hints for remote API Date: Thu, 16 Jan 2020 15:59:52 -0800 Message-ID: <20200116235953.163318-5-minchan@kernel.org> References: <20200116235953.163318-1-minchan@kernel.org> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20200116235953.163318-1-minchan@kernel.org> Sender: linux-kernel-owner@vger.kernel.org To: Andrew Morton Cc: LKML , linux-mm , linux-api@vger.kernel.org, oleksandr@redhat.com, Suren Baghdasaryan , Tim Murray , Daniel Colascione , Sandeep Patil , Sonny Rao , Brian Geffon , Michal Hocko , Johannes Weiner , Shakeel Butt , John Dias , ktkhai@virtuozzo.com, christian.brauner@ubuntu.com, sjpark@amazon.de, Minchan Kim , Minchan Kim List-Id: linux-api@vger.kernel.org From: Oleksandr Natalenko 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 Signed-off-by: Minchan Kim --- 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; -- 2.25.0.rc1.283.g88dfdc4193-goog