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[62.201.165.239]) by smtp.gmail.com with ESMTPSA id m2-v6sm4082119wrw.76.2018.08.08.00.56.14 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 08 Aug 2018 00:56:15 -0700 (PDT) Received: by techadventures.net (Postfix, from userid 1000) id 690E312476D; Wed, 8 Aug 2018 09:56:14 +0200 (CEST) Date: Wed, 8 Aug 2018 09:56:14 +0200 From: Oscar Salvador To: David Hildenbrand Cc: Jerome Glisse , akpm@linux-foundation.org, mhocko@suse.com, dan.j.williams@intel.com, yasu.isimatu@gmail.com, logang@deltatee.com, dave.jiang@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Oscar Salvador Subject: Re: [RFC PATCH 2/3] mm/memory_hotplug: Create __shrink_pages and move it to offline_pages Message-ID: <20180808075614.GB9568@techadventures.net> References: <20180807133757.18352-1-osalvador@techadventures.net> <20180807133757.18352-3-osalvador@techadventures.net> <20180807135221.GA3301@redhat.com> <20180807204834.GA6844@techadventures.net> <20180807221345.GD3301@redhat.com> <20180808073835.GA9568@techadventures.net> <44f74b58-aae0-a44c-3b98-7b1aac186f8e@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <44f74b58-aae0-a44c-3b98-7b1aac186f8e@redhat.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 08, 2018 at 09:45:37AM +0200, David Hildenbrand wrote: > On 08.08.2018 09:38, Oscar Salvador wrote: > > On Tue, Aug 07, 2018 at 06:13:45PM -0400, Jerome Glisse wrote: > >>> And since we know for sure that memhotplug-code cannot call it with ZONE_DEVICE, > >>> I think this can be done easily. > >> > >> This might change down road but for now this is correct. They are > >> talks to enumerate device memory through standard platform mechanisms > >> and thus the kernel might see new types of resources down the road and > >> maybe we will want to hotplug them directly from regular hotplug path > >> as ZONE_DEVICE (lot of hypothetical at this point ;)). > > > > Well, I think that if that happens this whole thing will become > > much easier, since we will not have several paths for doing the same thing. > > > > Another thing that I realized is that while we want to move all operation-pages > > from remove_memory() path to offline_pages(), this can get tricky. > > > > Unless I am missing something, the devices from HMM and devm are not being registered > > against "memory_subsys" struct, and so, they never get to call memory_subsys_offline() > > and so offline_pages(). > > > > Which means that we would have to call __remove_zone() from those paths. > > But this alone will not work. > > I mean, they move it to the zone ("replacing online/offlining code"), so > they should take of removing it again. Yeah, I guess so. I mean, of course we can make this work by placing __remove_zone in devm_memremap_pages_release and hmm_devmem_release functions and make sure to call offline_mem_sections first. But sounds a bit "hacky".. Thanks -- Oscar Salvador SUSE L3