From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752480AbcKHEpU (ORCPT ); Mon, 7 Nov 2016 23:45:20 -0500 Received: from szxga03-in.huawei.com ([119.145.14.66]:33996 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751234AbcKHEpS (ORCPT ); Mon, 7 Nov 2016 23:45:18 -0500 Message-ID: <582157E5.8000106@huawei.com> Date: Tue, 8 Nov 2016 12:43:17 +0800 From: Xishi Qiu User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:12.0) Gecko/20120428 Thunderbird/12.0.1 MIME-Version: 1.0 To: Vlastimil Babka , Andrew Morton , Tang Chen , Mel Gorman CC: Linux MM , LKML , "robert.liu@huawei.com" Subject: [RFC] mem-hotplug: shall we skip unmovable node when doing numa balance? Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.25.179] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On mem-hotplug system, there is a problem, please see the following case. memtester xxG, the memory will be alloced on a movable node. And after numa balancing, the memory may be migrated to the other node, it may be a unmovable node. This will reduce the free memory of the unmovable node, and may be oom later. My question is that shall we skip unmovable node when doing numa balance? or just let the manager set some numa policies? diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 057964d..f0954ac 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -2334,6 +2334,13 @@ int mpol_misplaced(struct page *page, struct vm_area_struct *vma, unsigned long out: mpol_cond_put(pol); + /* Skip unmovable nodes when do numa balancing */ + if (movable_node_enabled && ret != -1) { + zone = NODE_DATA(ret)->node_zones + MAX_NR_ZONES - 1; + if (!populated_zone(zone)) + ret = -1; + } + return ret; } Thanks, Xishi Qiu