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=-5.3 required=3.0 tests=BAYES_00, 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 B0466C433ED for ; Fri, 9 Apr 2021 10:14:10 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 393D26103E for ; Fri, 9 Apr 2021 10:14:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 393D26103E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id C77DD6B006C; Fri, 9 Apr 2021 06:14:09 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C4E286B006E; Fri, 9 Apr 2021 06:14:09 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B18976B0070; Fri, 9 Apr 2021 06:14:09 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0069.hostedemail.com [216.40.44.69]) by kanga.kvack.org (Postfix) with ESMTP id 956F46B006C for ; Fri, 9 Apr 2021 06:14:09 -0400 (EDT) Received: from smtpin31.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 43F6F8248047 for ; Fri, 9 Apr 2021 10:14:09 +0000 (UTC) X-FDA: 78012418218.31.67BCA6D Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf18.hostedemail.com (Postfix) with ESMTP id F18382000242 for ; Fri, 9 Apr 2021 10:14:08 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 65BF4AF03; Fri, 9 Apr 2021 10:14:07 +0000 (UTC) Date: Fri, 9 Apr 2021 12:14:04 +0200 From: Oscar Salvador To: Dave Hansen Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, shy828301@gmail.com, weixugc@google.com, rientjes@google.com, ying.huang@intel.com, dan.j.williams@intel.com, david@redhat.com Subject: Re: [PATCH 03/10] mm/migrate: update node demotion order during on hotplug events Message-ID: <20210409101400.GA32159@linux> References: <20210401183216.443C4443@viggo.jf.intel.com> <20210401183221.977831DE@viggo.jf.intel.com> 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-Stat-Signature: 3zzqbxzo9km36ckcqk17ssafzj4tkskb X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: F18382000242 Received-SPF: none (suse.de>: No applicable sender policy available) receiver=imf18; identity=mailfrom; envelope-from=""; helo=mx2.suse.de; client-ip=195.135.220.15 X-HE-DKIM-Result: none/none X-HE-Tag: 1617963248-21947 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 Thu, Apr 08, 2021 at 11:52:51AM +0200, Oscar Salvador wrote: > I am not really into PMEM, and I ignore whether we need > CONFIG_MEMORY_HOTPLUG in order to have such memory on the system. > If so, the following can be partly ignored. Ok, I refreshed by memory with [1]. >From that, it seems that in order to use PMEM as RAM we need CONFIG_MEMORY_HOTPLUG. But is that always the case? Can happen that in some scenario PMEM comes ready to use and we do not need the hotplug trick? Anyway, I would still like to clarify the state of the HOTPLUG_CPU. On x86_64, HOTPLUG_CPU and MEMORY_HOTPLUG are tied by SPM means, but on arm64 one can have MEMORY_HOTPLUG while not having picked HOTPLUG_CPU. My point is that we might want to put the callback functions and the callback registration for cpu-hotplug guarded by its own HOTPLUG_CPU instead of guarding it in the same MEMORY_HOTPLUG block to make it more clear? -- Oscar Salvador SUSE L3