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[213.151.95.130]) by smtp.gmail.com with ESMTPSA id l10sm19891393wrg.90.2019.11.27.00.50.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 27 Nov 2019 00:50:09 -0800 (PST) Date: Wed, 27 Nov 2019 09:50:08 +0100 From: Michal Hocko To: Qian Cai Cc: Pengfei Li , "lixinhai.lxh@gmail.com" , akpm , mgorman , Vlastimil Babka , cl , "iamjoonsoo.kim" , guro , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" Subject: Re: [RFC v1 00/19] Modify zonelist to nodelist v1 Message-ID: <20191127085008.GM20912@dhcp22.suse.cz> References: <20191125083948.GC31714@dhcp22.suse.cz> <828BAB69-4B46-418F-A5E2-35B0756340D0@lca.pw> <20191126154101.GJ20912@dhcp22.suse.cz> <8B426079-6091-4898-8D77-609915C273E8@lca.pw> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <8B426079-6091-4898-8D77-609915C273E8@lca.pw> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 26-11-19 14:04:06, Qian Cai wrote: > > > > On Nov 26, 2019, at 10:41 AM, Michal Hocko wrote: > > > > On Tue 26-11-19 10:30:56, Qian Cai wrote: > >> > >> > >>> On Nov 25, 2019, at 3:39 AM, Michal Hocko wrote: > >>> > >>> People do care about ZONE_MOVABLE and if there is a non-movable memory > >>> sitting there then it is a bug. Please report that. > >> > >> It is trivial to test yourself if you ever care. Just pass kernelcore= > >> to as many NUMA machines you could find, an then test if ever possible > >> to offline those memory. > > > > I definitely do care if you can provide more details (ideally in a > > separate email thread). I am using movable memory for memory hotplug > > usecases and so far I do not remember any kernel/non-movable allocations > > would make it in - modulo bugs when somebody might use __GFP_MOVABLE > > when it is not appropriate. > > > > I don’t think it is anything to do with __GFP_MOVABLE. It is about booting a kernel > with either passing kernelcore= or movablecore=. Then, those ZONE_MOVABLE will > have non-movable pages which looks like those from vmemmap_populate(). OK, I see. This looks like a bug in kernelcore/movablecore. And honestly I wouldn't be surprised because these are hacks that should have been removed. I have even attempted to do that because their main usecase is mostly gone. There were some objections though... > How do you create ZONE_MOVALBLE in this first place? The most common usecase I work with is to use movable_node parameter which makes whole nodes marked as hotplugable to be moved to ZONE_MOVABLE. -- Michal Hocko SUSE Labs