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[195.135.220.15]) by mx.google.com with ESMTPS id w9si964303ejk.288.2019.07.19.04.36.49 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 19 Jul 2019 04:36:49 -0700 (PDT) Received-SPF: softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id A675DAB98; Fri, 19 Jul 2019 11:36:48 +0000 (UTC) Date: Fri, 19 Jul 2019 13:36:47 +0200 From: Michal Hocko To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Greg Kroah-Hartman , "Rafael J. Wysocki" , Andrew Morton , Stephen Rothwell , Pavel Tatashin , Oscar Salvador Subject: Re: [PATCH v1] drivers/base/node.c: Simplify unregister_memory_block_under_nodes() Message-ID: <20190719113647.GS30461@dhcp22.suse.cz> References: <20190718142239.7205-1-david@redhat.com> <20190719084239.GO30461@dhcp22.suse.cz> <20190719091313.GR30461@dhcp22.suse.cz> <48ea1d5d-ce40-aaad-b9fe-006488ed71dc@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <48ea1d5d-ce40-aaad-b9fe-006488ed71dc@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) 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 Fri 19-07-19 11:20:43, David Hildenbrand wrote: > On 19.07.19 11:13, Michal Hocko wrote: > > On Fri 19-07-19 11:05:51, David Hildenbrand wrote: > >> On 19.07.19 10:42, Michal Hocko wrote: > >>> On Thu 18-07-19 16:22:39, David Hildenbrand wrote: > >>>> We don't allow to offline memory block devices that belong to multiple > >>>> numa nodes. Therefore, such devices can never get removed. It is > >>>> sufficient to process a single node when removing the memory block. > >>>> > >>>> Remember for each memory block if it belongs to no, a single, or mixed > >>>> nodes, so we can use that information to skip unregistering or print a > >>>> warning (essentially a safety net to catch BUGs). > >>> > >>> I do not really like NUMA_NO_NODE - 1 thing. This is yet another invalid > >>> node that is magic. Why should we even care? In other words why is this > >>> patch an improvement? > >> > >> Oh, and to answer that part of the question: > >> > >> We no longer have to iterate over each pfn of a memory block to be removed. > > > > Is it possible that we are overzealous when unregistering syfs files and > > we should simply skip the pfn walk even without this change? > > > > I assume you mean something like v1 without the warning/"NUMA_NO_NODE -1"? > > See what I have right now below. Yes. I didn'g get to look closely but you caught the idea. Thanks! -- Michal Hocko SUSE Labs