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[37.188.180.223]) by smtp.gmail.com with ESMTPSA id v21sm5906815wmh.26.2020.04.02.01.01.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Apr 2020 01:01:45 -0700 (PDT) Date: Thu, 2 Apr 2020 10:01:44 +0200 From: Michal Hocko To: Mike Rapoport Cc: Baoquan He , Hoan Tran , Catalin Marinas , Will Deacon , Andrew Morton , Vlastimil Babka , Oscar Salvador , Pavel Tatashin , Alexander Duyck , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , "David S. Miller" , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , "open list:MEMORY MANAGEMENT" , linux-arm-kernel@lists.infradead.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, x86@kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, lho@amperecomputing.com, mmorana@amperecomputing.com Subject: Re: [PATCH RFC] mm: remove CONFIG_HAVE_MEMBLOCK_NODE_MAP (was: Re: [PATCH v3 0/5] mm: Enable CONFIG_NODES_SPAN_OTHER_NODES by default for NUMA) Message-ID: <20200402080144.GK22681@dhcp22.suse.cz> References: <1585420282-25630-1-git-send-email-Hoan@os.amperecomputing.com> <20200330074246.GA14243@dhcp22.suse.cz> <20200330092127.GB30942@linux.ibm.com> <20200330095843.GF14243@dhcp22.suse.cz> <20200331215618.GG30942@linux.ibm.com> <20200401054227.GC2129@MiWiFi-R3L-srv> <20200401075155.GH30942@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200401075155.GH30942@linux.ibm.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 01-04-20 10:51:55, Mike Rapoport wrote: > Hi, > > On Wed, Apr 01, 2020 at 01:42:27PM +0800, Baoquan He wrote: [...] > > From above information, we can remove HAVE_MEMBLOCK_NODE_MAP, and > > replace it with CONFIG_NUMA. That sounds more sensible to store nid into > > memblock when NUMA support is enabled. > > Replacing CONFIG_HAVE_MEMBLOCK_NODE_MAP with CONFIG_NUMA will work, but > this will not help cleaning up the whole node/zone initialization mess and > we'll be stuck with two implementations. Yeah, this is far from optimal. > The overhead of enabling HAVE_MEMBLOCK_NODE_MAP is only for init time as > most architectures will anyway discard the entire memblock, so having it in > a UMA arch won't be a problem. The only exception is arm that uses > memblock for pfn_valid(), here we may also think about a solution to > compensate the addition of nid to the memblock structures. Well, we can make memblock_region->nid defined only for CONFIG_NUMA. memblock_get_region_node would then unconditionally return 0 on UMA. Essentially the same way we do NUMA for other MM code. I only see few direct usage of region->nid. -- Michal Hocko SUSE Labs