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a="160113102" X-IronPort-AV: E=Sophos;i="5.79,396,1602572400"; d="scan'208";a="160113102" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Feb 2021 14:56:51 -0800 IronPort-SDR: eUVBONpjJ3BLGgaOJimCxqbICfxzTT1G17bq/8EThov5LF0hViFILlP2d3gp0N8sHylxwcz49Q C3QgrPToZz+g== X-IronPort-AV: E=Sophos;i="5.79,396,1602572400"; d="scan'208";a="433105724" Received: from capeter1-mobl.amr.corp.intel.com (HELO [10.212.5.169]) ([10.212.5.169]) by orsmga001-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Feb 2021 14:56:50 -0800 Subject: Re: [RFC][PATCH 08/13] mm/migrate: demote pages during reclaim To: Yang Shi , Oscar Salvador Cc: Dave Hansen , Linux Kernel Mailing List , Linux MM , Yang Shi , David Rientjes , Huang Ying , Dan Williams References: <20210126003411.2AC51464@viggo.jf.intel.com> <20210126003427.73DFDD34@viggo.jf.intel.com> <20210202115516.GC12139@linux> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/2/21 2:45 PM, Yang Shi wrote: >> Should we keep it simple for now and only try to demote those pages that are >> free of cpusets and memory policies? >> Actually, demoting those pages to a CPU or a NUMA node that does not fall into >> their set, would violate those constraints right? > Yes, this has been discussed since the very beginning. There is not an > easy way to figure out the memory placement policy (cpuset and > mempolicy) from "page". I think this also prevents "demote those pages > that are free of cpusets and memory policies". > > The conclusion was the violation should be fine for now. And the > demotion feature is opt'ed in by a new node reclaim mode. This has come up a couple of times. I'll add a bit of changelog material about it in the last patch since that's where the opt-in is introduced.