From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 68C35C433DF for ; Tue, 30 Jun 2020 18:51:44 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 36FAF2077D for ; Tue, 30 Jun 2020 18:51:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 36FAF2077D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 0C7226B0002; Tue, 30 Jun 2020 14:51:43 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0797E6B0003; 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Tue, 30 Jun 2020 18:51:39 +0000 (UTC) IronPort-SDR: OlHJjtnQpz+jH/z/LJbuyhAop/eHQ9lMx+l/cTQUt+Rtc//nKZwFOIfZwPDxKCnifNKTSNBxOQ Ad/9m7J24kBA== X-IronPort-AV: E=McAfee;i="6000,8403,9668"; a="147907664" X-IronPort-AV: E=Sophos;i="5.75,298,1589266800"; d="scan'208";a="147907664" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Jun 2020 11:51:37 -0700 IronPort-SDR: ZkYpj/mLUXbIPst+h4Nv36ush6kgRuICq8OnjtDynfAa3Bw9mWpB2GwnuT1iLFa2O2wdAg1fNy c2cGuFf3v/Lw== X-IronPort-AV: E=Sophos;i="5.75,298,1589266800"; d="scan'208";a="454711215" Received: from timfergu-mobl.amr.corp.intel.com (HELO [10.255.1.246]) ([10.255.1.246]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Jun 2020 11:51:36 -0700 Subject: Re: [RFC][PATCH 0/8] Migrate Pages in lieu of discard To: Shakeel Butt , Dave Hansen Cc: LKML , Linux MM , Yang Shi , David Rientjes , Huang Ying , Dan Williams References: <20200629234503.749E5340@viggo.jf.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: Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Rspamd-Queue-Id: CF9F76C3A X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 Content-Transfer-Encoding: quoted-printable 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 6/30/20 11:36 AM, Shakeel Butt wrote: >> This is part of a larger patch set. If you want to apply these or >> play with them, I'd suggest using the tree from here. It includes >> autonuma-based hot page promotion back to DRAM: >> >> http://lkml.kernel.org/r/c3d6de4d-f7c3-b505-2e64-8ee5f70b2118@= intel.com >> >> This is also all based on an upstream mechanism that allows >> persistent memory to be onlined and used as if it were volatile: >> >> http://lkml.kernel.org/r/20190124231441.37A4A305@viggo.jf.inte= l.com >> > I have a high level question. Given a reclaim request for a set of > nodes, if there is no demotion path out of that set, should the kernel > still consider the migrations within the set of nodes?=20 OK, to be specific, we're talking about a case where we've arrived at try_to_free_pages() and, say, all of the nodes on the system are set in sc->nodemask? Isn't the common case that all nodes are set in sc->nodemask? Since there is never a demotion path out of the set of all nodes, the common case would be that there is no demotion path out of a reclaim node set. If that's true, I'd say that the kernel still needs to consider migrations even within the set.