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[195.135.220.15]) by mx.google.com with ESMTPS id h24si1781474edh.413.2019.04.17.09.39.13 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 17 Apr 2019 09:39:13 -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 A99A9B113; Wed, 17 Apr 2019 16:39:12 +0000 (UTC) Date: Wed, 17 Apr 2019 18:39:11 +0200 From: Michal Hocko To: Keith Busch Cc: Dave Hansen , Yang Shi , mgorman@techsingularity.net, riel@surriel.com, hannes@cmpxchg.org, akpm@linux-foundation.org, dan.j.williams@intel.com, fengguang.wu@intel.com, fan.du@intel.com, ying.huang@intel.com, ziy@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [v2 RFC PATCH 0/9] Another Approach to Use PMEM as NUMA Node Message-ID: <20190417163911.GA9523@dhcp22.suse.cz> References: <1554955019-29472-1-git-send-email-yang.shi@linux.alibaba.com> <20190412084702.GD13373@dhcp22.suse.cz> <20190416074714.GD11561@dhcp22.suse.cz> <876768ad-a63a-99c3-59de-458403f008c4@linux.alibaba.com> <20190417092318.GG655@dhcp22.suse.cz> <20190417152345.GB4786@localhost.localdomain> <20190417153923.GO5878@dhcp22.suse.cz> <20190417153739.GD4786@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190417153739.GD4786@localhost.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 17-04-19 09:37:39, Keith Busch wrote: > On Wed, Apr 17, 2019 at 05:39:23PM +0200, Michal Hocko wrote: > > On Wed 17-04-19 09:23:46, Keith Busch wrote: > > > On Wed, Apr 17, 2019 at 11:23:18AM +0200, Michal Hocko wrote: > > > > On Tue 16-04-19 14:22:33, Dave Hansen wrote: > > > > > Keith Busch had a set of patches to let you specify the demotion order > > > > > via sysfs for fun. The rules we came up with were: > > > > > > > > I am not a fan of any sysfs "fun" > > > > > > I'm hung up on the user facing interface, but there should be some way a > > > user decides if a memory node is or is not a migrate target, right? > > > > Why? Or to put it differently, why do we have to start with a user > > interface at this stage when we actually barely have any real usecases > > out there? > > The use case is an alternative to swap, right? The user has to decide > which storage is the swap target, so operating in the same spirit. I do not follow. If you use rebalancing you can still deplete the memory and end up in a swap storage. If you want to reclaim/swap rather than rebalance then you do not enable rebalancing (by node_reclaim or similar mechanism). -- Michal Hocko SUSE Labs