From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: [PATCH v9 0/7] Make cpuid <-> nodeid mapping persistent Date: Mon, 25 Jul 2016 16:20:22 -0700 Message-ID: <20160725162022.e90e9c6c74a5d147e39e5945@linux-foundation.org> References: <1469435749-19582-1-git-send-email-douly.fnst@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1469435749-19582-1-git-send-email-douly.fnst@cn.fujitsu.com> Sender: owner-linux-mm@kvack.org To: Dou Liyang 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 List-Id: linux-acpi@vger.kernel.org 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? Your fix is x86-only and this bug presumably affects other architectures, yes? I think a "Plan B" would fix all architectures? Thirdly, what is the merge path for these patches? Is an x86 or ACPI maintainer working with you on them? -- 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