From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f69.google.com (mail-pg0-f69.google.com [74.125.83.69]) by kanga.kvack.org (Postfix) with ESMTP id C10B36B0038 for ; Mon, 28 Nov 2016 19:09:33 -0500 (EST) Received: by mail-pg0-f69.google.com with SMTP id e9so391463480pgc.5 for ; Mon, 28 Nov 2016 16:09:33 -0800 (PST) Received: from mail-pg0-x244.google.com (mail-pg0-x244.google.com. [2607:f8b0:400e:c05::244]) by mx.google.com with ESMTPS id f5si57030297pgh.37.2016.11.28.16.09.32 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 28 Nov 2016 16:09:32 -0800 (PST) Received: by mail-pg0-x244.google.com with SMTP id p66so14477729pga.2 for ; Mon, 28 Nov 2016 16:09:32 -0800 (PST) Subject: Re: [mm v2 0/3] Support memory cgroup hotplug References: <1479875814-11938-1-git-send-email-bsingharora@gmail.com> <20161123072543.GD2864@dhcp22.suse.cz> <342ebcca-b54c-4bc6-906b-653042caae06@gmail.com> <20161123080744.GG2864@dhcp22.suse.cz> <61dc32fd-2802-6deb-24cf-fa11b5b31532@gmail.com> <20161123092830.GH2864@dhcp22.suse.cz> <962ac541-55c4-de09-59a3-4947c394eee6@gmail.com> <20161128211014.GB12143@htj.duckdns.org> From: Balbir Singh Message-ID: Date: Tue, 29 Nov 2016 11:09:26 +1100 MIME-Version: 1.0 In-Reply-To: <20161128211014.GB12143@htj.duckdns.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Tejun Heo Cc: Michal Hocko , linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, Andrew Morton , Johannes Weiner , Vladimir Davydov On 29/11/16 08:10, Tejun Heo wrote: > On Thu, Nov 24, 2016 at 12:05:12AM +1100, Balbir Singh wrote: >> On my desktop NODES_SHIFT is 6, many distro kernels have it a 9. I've known >> of solutions that use fake NUMA for partitioning and need as many nodes as >> possible. > > It was a crude kludge that people used before memcg. If people still > use it, that's fine but we don't want to optimize / make code > complicated for it, so let's please put away this part of > justification. Are you suggesting those use cases can be ignored now? > > It's understandable that some kernels want to have large NODES_SHIFT > to support wide range of configurations but if that makes wastage too > high, the simpler solution is updating the users to use the rumtime > detected possible number / mask instead of the compile time > NODES_SHIFT. Note that we do exactly the same thing for per-cpu > things - we configure high max but do all operations on what's > possible on the system. > > NUMA code already has possible detection. Why not simply make memcg > use those instead of MAX_NUMNODES like how we use nr_cpu_ids instead > of NR_CPUS? > nodes_possible_map is set to node_online_map at the moment for ppc64. Which becomes a problem when hotplugging a node that was not already online. I am not sure what you mean by possible detection. node_possible_map is set based on CONFIG_NODE_SHIFT and then can be adjusted by the architecture (if desired). Are you suggesting firmware populate it in? Thanks, Balbir Singh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org