Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753247Ab3DWAF2 (ORCPT ); Mon, 22 Apr 2013 20:05:28 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:34614 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752511Ab3DWAFZ (ORCPT ); Mon, 22 Apr 2013 20:05:25 -0400 X-SecurityPolicyCheck: OK by SHieldMailChecker v1.7.4 Message-ID: <5175D01E.5000302@jp.fujitsu.com> Date: Tue, 23 Apr 2013 09:04:46 +0900 From: Yasuaki Ishimatsu User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:17.0) Gecko/20130328 Thunderbird/17.0.5 MIME-Version: 1.0 To: Andrew Morton CC: , , , , , , Subject: Re: [Bug fix PATCH v2] numa, cpu hotplug: Change links of CPU and node when changing node number by onlining CPU References: <5170D4CB.20900@jp.fujitsu.com> <20130422153541.04ba682f13910cfede0d2ff7@linux-foundation.org> In-Reply-To: <20130422153541.04ba682f13910cfede0d2ff7@linux-foundation.org> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1598 Lines: 40 2013/04/23 7:35, Andrew Morton wrote: > On Fri, 19 Apr 2013 14:23:23 +0900 Yasuaki Ishimatsu wrote: > >> When booting x86 system contains memoryless node, node numbers of CPUs >> on memoryless node were changed to nearest online node number by >> init_cpu_to_node() because the node is not online. >> >> ... >> >> If we hot add memory to memoryless node and offine/online all CPUs on >> the node, node numbers of these CPUs are changed to correct node numbers >> by srat_detect_node() because the node become online. > > OK, here's a dumb question. > > At boot time the CPUs are assigned to the "nearest online node" rather > than to their real memoryless node. The patch arranges for those CPUs > to still be assigned to the "nearest online node" _after_ some memory > is hot-added to their real node. Correct? Yes. For changing node number of CPUs safely, we should offline CPUs. > > Would it not be better to fix this by assigning those CPUs to their real, > memoryless node right at the initial boot? Or is there something in > the kernel which makes cpus-on-a-memoryless-node not work correctly? > I think assigning CPUs to real node is better. But current Linux's node strongly depend on memory. Thus if we just create cpus-on-a-memoryless-node, the kernel cannot work correctly. Thanks, Yasuaki Ishimatsu -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/