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[195.135.220.15]) by mx.google.com with ESMTPS id n44si668786edn.69.2019.04.16.11.34.07 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 16 Apr 2019 11:34:07 -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 919C9AC58; Tue, 16 Apr 2019 18:34:06 +0000 (UTC) Date: Tue, 16 Apr 2019 20:34:04 +0200 From: Michal Hocko To: Dave Hansen Cc: Yang Shi , 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 Subject: Re: [v2 RFC PATCH 0/9] Another Approach to Use PMEM as NUMA Node Message-ID: <20190416183404.GA655@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> <20190416143958.GI11561@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Tue 16-04-19 08:46:56, Dave Hansen wrote: > On 4/16/19 7:39 AM, Michal Hocko wrote: > >> Strict binding also doesn't keep another app from moving the > >> memory. > > I would consider that a bug. > > A bug where, though? Certainly not in the kernel. Kernel should refrain from moving explicitly bound memory nilly willy. I certainly agree that there are corner cases. E.g. memory hotplug. We do break CPU affinity for CPU offline as well. So this is something user should expect. But the kernel shouldn't move explicitly bound pages to a different node implicitly. I am not sure whether we even do that during compaction if we do then I would consider _this_ to be a bug. And NUMA rebalancing under memory pressure falls into the same category IMO. -- Michal Hocko SUSE Labs