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[192.55.52.151]) by mx.google.com with ESMTPS id w12si37182026pgr.412.2019.04.30.22.20.46 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 30 Apr 2019 22:20:47 -0700 (PDT) Received-SPF: pass (google.com: domain of fengguang.wu@intel.com designates 192.55.52.151 as permitted sender) client-ip=192.55.52.151; Authentication-Results: mx.google.com; spf=pass (google.com: domain of fengguang.wu@intel.com designates 192.55.52.151 as permitted sender) smtp.mailfrom=fengguang.wu@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga107.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 30 Apr 2019 22:20:46 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,416,1549958400"; d="scan'208";a="153757165" Received: from wul-mobl.ccr.corp.intel.com (HELO wfg-t570.sh.intel.com) ([10.254.212.158]) by FMSMGA003.fm.intel.com with ESMTP; 30 Apr 2019 22:20:34 -0700 Received: from wfg by wfg-t570.sh.intel.com with local (Exim 4.89) (envelope-from ) id 1hLhfT-0005Vd-6o; Wed, 01 May 2019 13:20:31 +0800 Date: Wed, 1 May 2019 13:20:31 +0800 From: Fengguang Wu To: Michal Hocko Cc: Yang Shi , mgorman@techsingularity.net, riel@surriel.com, hannes@cmpxchg.org, akpm@linux-foundation.org, dave.hansen@intel.com, keith.busch@intel.com, dan.j.williams@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: <20190501052031.dt7zbkw5n5gzf2eg@wfg-t540p.sh.intel.com> 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> <20190418090227.GG6567@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20190418090227.GG6567@dhcp22.suse.cz> User-Agent: NeoMutt/20170609 (1.8.3) 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 Thu, Apr 18, 2019 at 11:02:27AM +0200, Michal Hocko wrote: >On Wed 17-04-19 13:43:44, Yang Shi wrote: >[...] >> And, I'm wondering whether this optimization is also suitable to general >> NUMA balancing or not. > >If there are convincing numbers then this should be a preferable way to >deal with it. Please note that the number of promotions is not the only >metric to watch. The overal performance/access latency would be another one. Good question. Shi and me aligned today. Also talked with Mel (but sorry I must missed some points due to poor English listening). It becomes clear that 1) PMEM/DRAM page promotion/demotion is a hard problem to attack. There will and should be multiple approaches for open discussion before settling down. The criteria might be balanced complexity, overheads, performance, etc. 2) We need a lot more data to lay solid foundation for effective discussions. Testing will be a rather time consuming part for contributor. We'll need to work together to create a number of benchmarks that can well exercise the kernel promotion/demotion paths and gather the necessary numbers. By collaborating on a common set of tests, we can not only amortize efforts, but also compare different approaches or compare v1/v2/... of the same approach conveniently. Ying has already created several LKP test cases for that purpose. Shi and me plan to join the efforts, too. Thanks, Fengguang