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[134.134.136.31]) by mx.google.com with ESMTPS id q64si18984689pga.492.2019.03.27.06.07.12 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 27 Mar 2019 06:07:12 -0700 (PDT) Received-SPF: softfail (google.com: domain of transitioning kbusch@kernel.org does not designate 134.134.136.31 as permitted sender) client-ip=134.134.136.31; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning kbusch@kernel.org does not designate 134.134.136.31 as permitted sender) smtp.mailfrom=kbusch@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 27 Mar 2019 06:07:11 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,276,1549958400"; d="scan'208";a="331140619" Received: from unknown (HELO localhost.localdomain) ([10.232.112.69]) by fmsmga006.fm.intel.com with ESMTP; 27 Mar 2019 06:07:10 -0700 Date: Wed, 27 Mar 2019 07:08:22 -0600 From: Keith Busch To: Yang Shi 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" Subject: Re: [PATCH 06/10] mm: vmscan: demote anon DRAM pages to PMEM node Message-ID: <20190327130822.GD7389@localhost.localdomain> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <39d8fb56-df60-9382-9b47-59081d823c3c@linux.alibaba.com> User-Agent: Mutt/1.9.1 (2017-09-22) 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 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.