From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx137.postini.com [74.125.245.137]) by kanga.kvack.org (Postfix) with SMTP id F0BF06B0002 for ; Mon, 22 Apr 2013 21:24:59 -0400 (EDT) Received: from m4.gw.fujitsu.co.jp (unknown [10.0.50.74]) by fgwmail6.fujitsu.co.jp (Postfix) with ESMTP id 4E79F3EE0C0 for ; Tue, 23 Apr 2013 10:24:58 +0900 (JST) Received: from smail (m4 [127.0.0.1]) by outgoing.m4.gw.fujitsu.co.jp (Postfix) with ESMTP id 3579E45DE50 for ; Tue, 23 Apr 2013 10:24:58 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (s4.gw.fujitsu.co.jp [10.0.50.94]) by m4.gw.fujitsu.co.jp (Postfix) with ESMTP id 1D9C645DE4D for ; Tue, 23 Apr 2013 10:24:58 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id 0BE37E08003 for ; Tue, 23 Apr 2013 10:24:58 +0900 (JST) Received: from G01JPEXCHYT16.g01.fujitsu.local (G01JPEXCHYT16.g01.fujitsu.local [10.128.194.55]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id ACD8A1DB802F for ; Tue, 23 Apr 2013 10:24:57 +0900 (JST) Message-ID: <5175E2D4.5030004@jp.fujitsu.com> Date: Tue, 23 Apr 2013 10:24:36 +0900 From: Yasuaki Ishimatsu MIME-Version: 1.0 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> <5175D01E.5000302@jp.fujitsu.com> <20130422173459.487fa3e6.akpm@linux-foundation.org> In-Reply-To: <20130422173459.487fa3e6.akpm@linux-foundation.org> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: kosaki.motohiro@gmail.com, mingo@kernel.org, hpa@zytor.com, srivatsa.bhat@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, x86@kernel.org, linux-mm@kvack.org 2013/04/23 9:34, Andrew Morton wrote: > On Tue, 23 Apr 2013 09:04:46 +0900 Yasuaki Ishimatsu wrote: > >> 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. > > hm, why. I'd have thought that if we tell the kernel something like > "this node has one zone, the size of which is zero bytes" then a > surprising amount of the existing code will Just Work. > > What goes wrong? Sorry I forgot detailed issue. When I saw following issue, I tried to fix it and found that current Linux's node strongly depend on memory. https://lkml.org/lkml/2012/9/12/20 I'll try to fix it again. 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/ > -- 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