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a="134120606" X-IronPort-AV: E=Sophos;i="5.75,301,1589266800"; d="scan'208";a="134120606" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Jul 2020 11:20:02 -0700 IronPort-SDR: 260PaXnd00p2Oc6hhqFTd5lSgLOi6PyDK01hUi0jLUnpl24Q6I59qA+u9kfX4UP1YGW6gSAuyO 0Jr7cyg8TeYQ== X-IronPort-AV: E=Sophos;i="5.75,301,1589266800"; d="scan'208";a="455201243" Received: from rapyeatx-mobl3.amr.corp.intel.com (HELO [10.255.2.31]) ([10.255.2.31]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Jul 2020 11:20:01 -0700 Subject: Re: [RFC][PATCH 3/8] mm/vmscan: Attempt to migrate page in lieu of discard To: "Huang, Ying" , David Rientjes Cc: Yang Shi , Dave Hansen , linux-kernel@vger.kernel.org, linux-mm@kvack.org, kbusch@kernel.org, dan.j.williams@intel.com References: <20200629234503.749E5340@viggo.jf.intel.com> <20200629234509.8F89C4EF@viggo.jf.intel.com> <039a5704-4468-f662-d660-668071842ca3@linux.alibaba.com> <87h7urlioe.fsf@yhuang-dev.intel.com> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <87h7urlioe.fsf@yhuang-dev.intel.com> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/1/20 1:54 AM, Huang, Ying wrote: > Why can not we just bind the memory of the application to node 0, 2, 3 > via mbind() or cpuset.mems? Then the application can allocate memory > directly from PMEM. And if we bind the memory of the application via > mbind() to node 0, we can only allocate memory directly from DRAM. Applications use cpuset.mems precisely because they don't want to allocate directly from PMEM. They want the good, deterministic, performance they get from DRAM. Even if they don't allocate directly from PMEM, is it OK for such an app to get its cold data migrated to PMEM? That's a much more subtle question and I suspect the kernel isn't going to have a single answer for it. I suspect we'll need a cpuset-level knob to turn auto-demotion on or off.