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[115.124.30.130]) by mx.google.com with ESMTPS id az7si243901plb.21.2019.03.28.14.59.36 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 28 Mar 2019 14:59:37 -0700 (PDT) Received-SPF: pass (google.com: domain of yang.shi@linux.alibaba.com designates 115.124.30.130 as permitted sender) client-ip=115.124.30.130; Authentication-Results: mx.google.com; spf=pass (google.com: domain of yang.shi@linux.alibaba.com designates 115.124.30.130 as permitted sender) smtp.mailfrom=yang.shi@linux.alibaba.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=alibaba.com X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R611e4;CH=green;DM=||false|;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01f04452;MF=yang.shi@linux.alibaba.com;NM=1;PH=DS;RN=14;SR=0;TI=SMTPD_---0TNtCAaw_1553810371; Received: from US-143344MP.local(mailfrom:yang.shi@linux.alibaba.com fp:SMTPD_---0TNtCAaw_1553810371) by smtp.aliyun-inc.com(127.0.0.1); Fri, 29 Mar 2019 05:59:35 +0800 Subject: Re: [PATCH 06/10] mm: vmscan: demote anon DRAM pages to PMEM node To: Keith Busch Cc: "mhocko@suse.com" , "mgorman@techsingularity.net" , "riel@surriel.com" , "hannes@cmpxchg.org" , "akpm@linux-foundation.org" , "Hansen, Dave" , "Busch, Keith" , "Williams, Dan J" , "Wu, Fengguang" , "Du, Fan" , "Huang, Ying" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" References: <1553316275-21985-1-git-send-email-yang.shi@linux.alibaba.com> <1553316275-21985-7-git-send-email-yang.shi@linux.alibaba.com> <20190324222040.GE31194@localhost.localdomain> <20190327003541.GE4328@localhost.localdomain> <39d8fb56-df60-9382-9b47-59081d823c3c@linux.alibaba.com> <20190327130822.GD7389@localhost.localdomain> From: Yang Shi Message-ID: <599849e6-05b6-1e4d-7578-5cf8825963d2@linux.alibaba.com> Date: Thu, 28 Mar 2019 14:59:30 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20190327130822.GD7389@localhost.localdomain> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US 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 3/27/19 6:08 AM, Keith Busch wrote: > On Tue, Mar 26, 2019 at 08:41:15PM -0700, Yang Shi wrote: >> On 3/26/19 5:35 PM, Keith Busch wrote: >>> migration nodes have higher free capacity than source nodes. And since >>> your attempting THP's without ever splitting them, that also requires >>> lower fragmentation for a successful migration. >> Yes, it is possible. However, migrate_pages() already has logic to >> handle such case. If the target node has not enough space for migrating >> THP in a whole, it would split THP then retry with base pages. > Oh, you're right, my mistake on splitting. So you have a good best effort > migrate, but I still think it can fail for legitimate reasons that should > have a swap fallback. Yes, it still could fail. I can't tell which way is better for now. I just thought scanning another round then migrating should be still faster than swapping off the top of my head. Thanks, Yang