From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758526AbaJIV2H (ORCPT ); Thu, 9 Oct 2014 17:28:07 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41600 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757978AbaJIV2D (ORCPT ); Thu, 9 Oct 2014 17:28:03 -0400 Date: Thu, 9 Oct 2014 17:27:47 -0400 From: Rik van Riel To: linux-kernel@vger.kernel.org Cc: "Vinod, Chegu" , Peter Zijlstra , Ingo Molnar , mgorman@suse.de Subject: [PATCH] sched,numa: check all nodes when placing a pseudo-interleaved group Message-ID: <20141009172747.0d97c38c@annuminas.surriel.com> Organization: Red Hat, Inc. MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In pseudo-interleaved numa_groups, all tasks try to relocate to the group's preferred_nid. When a group is spread across multiple NUMA nodes, this can lead to tasks swapping their location with other tasks inside the same group, instead of swapping location with tasks from other NUMA groups. This can keep NUMA groups from converging. Examining all nodes, when dealing with a task in a pseudo-interleaved NUMA group, avoids this problem. Note that only CPUs in nodes that improve the task or group score are examined, so the loop isn't too bad. Tested-by: Vinod Chegu Signed-off-by: Rik van Riel --- This patch allows the complex NUMA placement patch series to work, but it also fixes issues on normal NUMA systems, so this is an independent bugfix that can go in independently. kernel/sched/fair.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 17ebf41..78f1ade 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1419,8 +1419,15 @@ static int task_numa_migrate(struct task_struct *p) /* Try to find a spot on the preferred nid. */ task_numa_find_cpu(&env, taskimp, groupimp); - /* No space available on the preferred nid. Look elsewhere. */ - if (env.best_cpu == -1) { + /* + * Look at other nodes in these cases: + * - there is no space available on the preferred_nid + * - the task is part of a numa_group that is interleaved across + * multiple NUMA nodes; in order to better consolidate the group, + * we need to check other locations. + */ + if (env.best_cpu == -1 || (p->numa_group && + nodes_weight(p->numa_group->active_nodes) > 1)) { for_each_online_node(nid) { if (nid == env.src_nid || nid == p->numa_preferred_nid) continue;