From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f200.google.com (mail-pf0-f200.google.com [209.85.192.200]) by kanga.kvack.org (Postfix) with ESMTP id B1C126B0265 for ; Mon, 25 Jul 2016 23:59:49 -0400 (EDT) Received: by mail-pf0-f200.google.com with SMTP id h186so443546297pfg.3 for ; Mon, 25 Jul 2016 20:59:49 -0700 (PDT) Received: from heian.cn.fujitsu.com ([59.151.112.132]) by mx.google.com with ESMTP id zs5si36931596pab.226.2016.07.25.20.59.47 for ; Mon, 25 Jul 2016 20:59:48 -0700 (PDT) Subject: Re: [PATCH v9 0/7] Make cpuid <-> nodeid mapping persistent References: <1469435749-19582-1-git-send-email-douly.fnst@cn.fujitsu.com> <20160725162022.e90e9c6c74a5d147e39e5945@linux-foundation.org> From: Dou Liyang Message-ID: <34809745-7e48-29d3-f31b-826414ccdef3@cn.fujitsu.com> Date: Tue, 26 Jul 2016 11:59:38 +0800 MIME-Version: 1.0 In-Reply-To: <20160725162022.e90e9c6c74a5d147e39e5945@linux-foundation.org> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: cl@linux.com, tj@kernel.org, mika.j.penttila@gmail.com, mingo@redhat.com, rjw@rjwysocki.net, hpa@zytor.com, yasu.isimatu@gmail.com, isimatu.yasuaki@jp.fujitsu.com, kamezawa.hiroyu@jp.fujitsu.com, izumi.taku@jp.fujitsu.com, gongzhaogang@inspur.com, len.brown@intel.com, lenb@kernel.org, tglx@linutronix.de, chen.tang@easystack.cn, rafael@kernel.org, x86@kernel.org, linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org a?? 2016a1'07ae??26ae?JPY 07:20, Andrew Morton a??e??: > On Mon, 25 Jul 2016 16:35:42 +0800 Dou Liyang wrote: > >> [Problem] >> >> cpuid <-> nodeid mapping is firstly established at boot time. And workqueue caches >> the mapping in wq_numa_possible_cpumask in wq_numa_init() at boot time. >> >> When doing node online/offline, cpuid <-> nodeid mapping is established/destroyed, >> which means, cpuid <-> nodeid mapping will change if node hotplug happens. But >> workqueue does not update wq_numa_possible_cpumask. >> >> So here is the problem: >> >> Assume we have the following cpuid <-> nodeid in the beginning: >> >> Node | CPU >> ------------------------ >> node 0 | 0-14, 60-74 >> node 1 | 15-29, 75-89 >> node 2 | 30-44, 90-104 >> node 3 | 45-59, 105-119 >> >> and we hot-remove node2 and node3, it becomes: >> >> Node | CPU >> ------------------------ >> node 0 | 0-14, 60-74 >> node 1 | 15-29, 75-89 >> >> and we hot-add node4 and node5, it becomes: >> >> Node | CPU >> ------------------------ >> node 0 | 0-14, 60-74 >> node 1 | 15-29, 75-89 >> node 4 | 30-59 >> node 5 | 90-119 >> >> But in wq_numa_possible_cpumask, cpu30 is still mapped to node2, and the like. >> >> When a pool workqueue is initialized, if its cpumask belongs to a node, its >> pool->node will be mapped to that node. And memory used by this workqueue will >> also be allocated on that node. > > Plan B is to hunt down and fix up all the workqueue structures at > hotplug-time. Has that option been evaluated? > Yes, the option has been evaluate in this patch: http://www.gossamer-threads.com/lists/linux/kernel/2116748 > > Your fix is x86-only and this bug presumably affects other > architectures, yes?I think a "Plan B" would fix all architectures? > Yes, the bug may presumably affect few architectures which support CPU hotplug and NUMA. We have sent the "Plan B" in our community and got a lot of advice and ideas. Based on these suggestions, We carefully balance that two plan. Then we choice the first. > > Thirdly, what is the merge path for these patches? Is an x86 > or ACPI maintainer working with you on them? Yes, we get a lot of guidance and help from RJ who is an ACPI maintainer. Thanks, Dou -- 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