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Fri, 9 Apr 2021 18:59:24 +0000 (UTC) Subject: Re: [PATCH 03/10] mm/migrate: update node demotion order during on hotplug events To: Oscar Salvador , 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 References: <20210401183216.443C4443@viggo.jf.intel.com> <20210401183221.977831DE@viggo.jf.intel.com> <20210409101400.GA32159@linux> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: Date: Fri, 9 Apr 2021 20:59:21 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210409101400.GA32159@linux> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Stat-Signature: 8hbwf3qifxjth4r6m4zd4nunq1mmh3jy X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 6DAB480192E8 Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf27; identity=mailfrom; envelope-from=""; helo=us-smtp-delivery-124.mimecast.com; client-ip=63.128.21.124 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1617994769-418696 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 09.04.21 12:14, Oscar Salvador wrote: > 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? The only way to add more System RAM is via add_memory() and friends like add_memory_driver_managed(). These all require CONFIG_MEMORY_HOTPLUG. Memory ballooning is a different case, but there we're only adjusting the managed page counters. -- Thanks, David / dhildenb