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[37.188.254.25]) by smtp.gmail.com with ESMTPSA id m17sm11793854wrw.3.2020.03.16.02.06.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 16 Mar 2020 02:06:54 -0700 (PDT) Date: Mon, 16 Mar 2020 10:06:52 +0100 From: Michal Hocko To: Vlastimil Babka Cc: Srikar Dronamraju , Sachin Sant , Linus Torvalds , LKML , linux-mm@kvack.org, Mel Gorman , "Kirill A. Shutemov" , Andrew Morton , linuxppc-dev@lists.ozlabs.org, Christopher Lameter , Joonsoo Kim , Kirill Tkhai Subject: Re: [PATCH 1/3] powerpc/numa: Set numa_node for all possible cpus Message-ID: <20200316090652.GC11482@dhcp22.suse.cz> References: <20200311110237.5731-1-srikar@linux.vnet.ibm.com> <20200311110237.5731-2-srikar@linux.vnet.ibm.com> <20200311115735.GM23944@dhcp22.suse.cz> <20200312052707.GA3277@linux.vnet.ibm.com> <5e5c736a-a88c-7c76-fc3d-7bc765e8dcba@suse.cz> <20200312131438.GB3277@linux.vnet.ibm.com> <61437352-8b54-38fa-4471-044a65c9d05a@suse.cz> <20200312161310.GC3277@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 12-03-20 17:41:58, Vlastimil Babka wrote: [...] > with nid present in: > N_POSSIBLE - pgdat might not exist, node_to_mem_node() must return some online I would rather have a dummy pgdat for those. Have a look at $ git grep "NODE_DATA.*->" | wc -l 63 Who knows how many else we have there. I haven't looked more closely. Besides that what is a real reason to not have pgdat ther and force all users of a $random node from those that the platform considers possible for special casing? Is that a memory overhead? Is that really a thing? Somebody has suggested to tweak some of the low level routines to do the special casing but I really have to say I do not like that. We shouldn't use the first online node or anything like that. We should simply always follow the topology presented by FW and of that we need to have a pgdat. -- Michal Hocko SUSE Labs