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[195.135.221.2]) by mx.google.com with ESMTP id b47si124521ede.153.2019.04.03.01.01.17 for ; Wed, 03 Apr 2019 01:01:17 -0700 (PDT) Received-SPF: pass (google.com: domain of osalvador@suse.de designates 195.135.221.2 as permitted sender) client-ip=195.135.221.2; Authentication-Results: mx.google.com; spf=pass (google.com: domain of osalvador@suse.de designates 195.135.221.2 as permitted sender) smtp.mailfrom=osalvador@suse.de Received: by suse.de (Postfix, from userid 1000) id A8CEC47E0; Wed, 3 Apr 2019 10:01:16 +0200 (CEST) Date: Wed, 3 Apr 2019 10:01:16 +0200 From: Oscar Salvador To: Michal Hocko Cc: David Hildenbrand , akpm@linux-foundation.org, dan.j.williams@intel.com, Jonathan.Cameron@huawei.com, anshuman.khandual@arm.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 0/4] mm,memory_hotplug: allocate memmap from hotadded memory Message-ID: <20190403080113.adj2m3szhhnvzu56@d104.suse.de> References: <20190328134320.13232-1-osalvador@suse.de> <20190329084547.5k37xjwvkgffwajo@d104.suse.de> <20190329134243.GA30026@dhcp22.suse.cz> <20190401075936.bjt2qsrhw77rib77@d104.suse.de> <20190401115306.GF28293@dhcp22.suse.cz> <20190402082812.fefamf7qlzulb7t2@d104.suse.de> <20190402124845.GD28293@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190402124845.GD28293@dhcp22.suse.cz> User-Agent: NeoMutt/20170421 (1.8.2) 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 Tue, Apr 02, 2019 at 02:48:45PM +0200, Michal Hocko wrote: > So what is going to happen when you hotadd two memblocks. The first one > holds memmaps and then you want to hotremove (not just offline) it? If you hot-add two memblocks, this means that either: a) you hot-add a 256MB-memory-device (128MB per memblock) b) you hot-add two 128MB-memory-device Either way, hot-removing only works for memory-device as a whole, so there is no problem. Vmemmaps are created per hot-added operations, this means that vmemmaps will be created for the hot-added range. And since hot-add/hot-remove operations works with the same granularity, there is no problem. E.g: # (qemu) object_add memory-backend-ram,id=ram0,size=128M # (qemu) device_add pc-dimm,id=dimm0,memdev=ram0,node=1 # (qemu) object_add memory-backend-ram,id=ram1,size=512M # (qemu) device_add pc-dimm,id=dimm1,memdev=ram1,node=1 # (qemu) object_add memory-backend-ram,id=ram2,size=1G # (qemu) device_add pc-dimm,id=dimm2,memdev=ram2,node=1 These are three hot-add operations. Each hot-add operation will create use vmemmaps to hold the memmap for its hot-added sections. -- Oscar Salvador SUSE L3