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[192.55.52.88]) by mx.google.com with ESMTPS id q5si45176532pga.498.2019.04.16.14.22.34 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 16 Apr 2019 14:22:34 -0700 (PDT) Received-SPF: pass (google.com: domain of dave.hansen@intel.com designates 192.55.52.88 as permitted sender) client-ip=192.55.52.88; Authentication-Results: mx.google.com; spf=pass (google.com: domain of dave.hansen@intel.com designates 192.55.52.88 as permitted sender) smtp.mailfrom=dave.hansen@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 16 Apr 2019 14:22:34 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,359,1549958400"; d="scan'208";a="224124248" Received: from ray.jf.intel.com (HELO [10.7.201.126]) ([10.7.201.126]) by orsmga001.jf.intel.com with ESMTP; 16 Apr 2019 14:22:33 -0700 Subject: Re: [v2 RFC PATCH 0/9] Another Approach to Use PMEM as NUMA Node To: Yang Shi , Michal Hocko Cc: mgorman@techsingularity.net, riel@surriel.com, hannes@cmpxchg.org, akpm@linux-foundation.org, keith.busch@intel.com, 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 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> From: Dave Hansen Openpgp: preference=signencrypt Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <876768ad-a63a-99c3-59de-458403f008c4@linux.alibaba.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit 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 4/16/19 12:19 PM, Yang Shi wrote: > would we prefer to try all the nodes in the fallback order to find the > first less contended one (i.e. DRAM0 -> PMEM0 -> DRAM1 -> PMEM1 -> Swap)? Once a page went to DRAM1, how would we tell that it originated in DRAM0 and is following the DRAM0 path rather than the DRAM1 path? Memory on DRAM0's path would be: DRAM0 -> PMEM0 -> DRAM1 -> PMEM1 -> Swap Memory on DRAM1's path would be: DRAM1 -> PMEM1 -> DRAM0 -> PMEM0 -> Swap 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: 1. Pages keep no history of where they have been 2. Each node can only demote to one other node 3. The demotion path can not have cycles That ensures that we *can't* follow the paths you described above, if we follow those rules...