From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1163571AbdEXLXh (ORCPT ); Wed, 24 May 2017 07:23:37 -0400 Received: from ozlabs.org ([103.22.144.67]:39163 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752094AbdEXLTr (ORCPT ); Wed, 24 May 2017 07:19:47 -0400 From: Michael Ellerman To: Michael Bringmann , Reza Arbab Cc: linux-kernel@vger.kernel.org, Paul Mackerras , "Aneesh Kumar K.V" , Bharata B Rao , Shailendra Singh , Thomas Gleixner , linuxppc-dev@lists.ozlabs.org, Sebastian Andrzej Siewior Subject: Re: [Patch 2/2]: powerpc/hotplug/mm: Fix hot-add memory node assoc In-Reply-To: References: <3bb44d92-b2ff-e197-4bdf-ec6d588d6dab@linux.vnet.ibm.com> <20170523155251.bqwc5mc4jpgzkqlm@arbab-laptop.localdomain> <1c1d70e3-4e45-b035-0e75-1b0f531c111b@linux.vnet.ibm.com> <20170523214922.bns675oqzqj4pkhc@arbab-laptop.localdomain> User-Agent: Notmuch/0.21 (https://notmuchmail.org) Date: Wed, 24 May 2017 21:19:42 +1000 Message-ID: <87poeya4dt.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Michael Bringmann writes: > On 05/23/2017 04:49 PM, Reza Arbab wrote: >> On Tue, May 23, 2017 at 03:05:08PM -0500, Michael Bringmann wrote: >>> On 05/23/2017 10:52 AM, Reza Arbab wrote: >>>> On Tue, May 23, 2017 at 10:15:44AM -0500, Michael Bringmann wrote: >>>>> +static void setup_nodes(void) >>>>> +{ >>>>> + int i, l = 32 /* MAX_NUMNODES */; >>>>> + >>>>> + for (i = 0; i < l; i++) { >>>>> + if (!node_possible(i)) { >>>>> + setup_node_data(i, 0, 0); >>>>> + node_set(i, node_possible_map); >>>>> + } >>>>> + } >>>>> +} >>>> >>>> This seems to be a workaround for 3af229f2071f ("powerpc/numa: Reset node_possible_map to only node_online_map"). >>> >>> They may be related, but that commit is not a replacement. The above patch ensures that >>> there are enough of the nodes initialized at startup to allow for memory hot-add into a >>> node that was not used at boot. (See 'setup_node_data' function in 'numa.c'.) That and >>> recording that the node was initialized. >> >> Is it really necessary to preinitialize these empty nodes using setup_node_data()? When you do memory hotadd into a node that was not used at boot, the node data already gets set up by >> >> add_memory >> add_memory_resource >> hotadd_new_pgdat >> arch_alloc_nodedata <-- allocs the pg_data_t >> ... >> free_area_init_node <-- sets NODE_DATA(nid)->node_id, etc. >> >> Removing setup_node_data() from that loop leaves only the call to node_set(). If 3af229f2071f (which reduces node_possible_map) was reverted, you wouldn't need to do that either. > > With or without 3af229f2071f, we would still need to add something, somewhere to add new > bits to the 'node_possible_map'. That is not being done. You mustn't add bits to the possible map after boot. That's its purpose, to tell you what nodes could ever *possibly* exist. cheers