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[195.135.220.15]) by mx.google.com with ESMTPS id i26si944905ejc.361.2019.05.15.01.33.23 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 15 May 2019 01:33:23 -0700 (PDT) Received-SPF: softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 92802AFA7; Wed, 15 May 2019 08:33:22 +0000 (UTC) Date: Wed, 15 May 2019 10:33:21 +0200 From: Michal Hocko To: Oleksandr Natalenko Cc: linux-kernel@vger.kernel.org, Kirill Tkhai , Vlastimil Babka , Matthew Wilcox , Pavel Tatashin , Timofey Titovets , Aaron Tomlin , Grzegorz Halat , linux-mm@kvack.org, linux-api@vger.kernel.org, Hugh Dickins Subject: Re: [PATCH RFC v2 0/4] mm/ksm: add option to automerge VMAs Message-ID: <20190515083321.GC16651@dhcp22.suse.cz> References: <20190514131654.25463-1-oleksandr@redhat.com> <20190514144105.GF4683@dhcp22.suse.cz> <20190514145122.GG4683@dhcp22.suse.cz> <20190515062523.5ndf7obzfgugilfs@butterfly.localdomain> <20190515065311.GB16651@dhcp22.suse.cz> <20190515073723.wbr522cpyjfelfav@butterfly.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190515073723.wbr522cpyjfelfav@butterfly.localdomain> User-Agent: Mutt/1.10.1 (2018-07-13) 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: On Wed 15-05-19 09:37:23, Oleksandr Natalenko wrote: [...] > > This is way too generic. Please provide something more specific. Ideally > > with numbers. Why those usecases cannot use an existing interfaces. > > Remember you are trying to add a new user interface which we will have > > to maintain for ever. > > For my current setup with 2 Firefox instances I get 100 to 200 MiB saved > for the second instance depending on the amount of tabs. What does prevent Firefox (an opensource project) to be updated to use the explicit merging? [...] > Answering your question regarding using existing interfaces, since > there's only one, madvise(2), this requires modifying all the > applications one wants to de-duplicate. In case of containers with > arbitrary content or in case of binary-only apps this is pretty hard if > not impossible to do properly. OK, this makes more sense. Please note that there are other people who would like to see certain madvise operations to be done on a remote process - e.g. to allow external memory management (Android would like to control memory aging so something like MADV_DONTNEED without loosing content and more probably) and potentially other madvise operations. Or maybe we need a completely new interface other than madvise. In general, having a more generic API that would cover more usecases is definitely much more preferable than one ad-hoc API that handles a very specific usecase. So please try to think about a more generic -- Michal Hocko SUSE Labs