From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932210Ab3JIRhd (ORCPT ); Wed, 9 Oct 2013 13:37:33 -0400 Received: from terminus.zytor.com ([198.137.202.10]:56482 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932399Ab3JIRdL (ORCPT ); Wed, 9 Oct 2013 13:33:11 -0400 Date: Wed, 9 Oct 2013 10:32:22 -0700 From: tip-bot for Mel Gorman Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org, peterz@infradead.org, hannes@cmpxchg.org, riel@redhat.com, aarcange@redhat.com, srikar@linux.vnet.ibm.com, mgorman@suse.de, tglx@linutronix.de Reply-To: mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, peterz@infradead.org, hannes@cmpxchg.org, riel@redhat.com, aarcange@redhat.com, srikar@linux.vnet.ibm.com, mgorman@suse.de, tglx@linutronix.de In-Reply-To: <1381141781-10992-52-git-send-email-mgorman@suse.de> References: <1381141781-10992-52-git-send-email-mgorman@suse.de> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sched/numa: Prevent parallel updates to group stats during placement Git-Commit-ID: 7dbd13ed06513b047216a7ffc718bad9df0660f1 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.7 (terminus.zytor.com [127.0.0.1]); Wed, 09 Oct 2013 10:32:29 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 7dbd13ed06513b047216a7ffc718bad9df0660f1 Gitweb: http://git.kernel.org/tip/7dbd13ed06513b047216a7ffc718bad9df0660f1 Author: Mel Gorman AuthorDate: Mon, 7 Oct 2013 11:29:29 +0100 Committer: Ingo Molnar CommitDate: Wed, 9 Oct 2013 14:48:02 +0200 sched/numa: Prevent parallel updates to group stats during placement Having multiple tasks in a group go through task_numa_placement simultaneously can lead to a task picking a wrong node to run on, because the group stats may be in the middle of an update. This patch avoids parallel updates by holding the numa_group lock during placement decisions. Signed-off-by: Mel Gorman Reviewed-by: Rik van Riel Cc: Andrea Arcangeli Cc: Johannes Weiner Cc: Srikar Dronamraju Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/1381141781-10992-52-git-send-email-mgorman@suse.de Signed-off-by: Ingo Molnar --- kernel/sched/fair.c | 35 +++++++++++++++++++++++------------ 1 file changed, 23 insertions(+), 12 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index c4df2de..1473499 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1233,6 +1233,7 @@ static void task_numa_placement(struct task_struct *p) { int seq, nid, max_nid = -1, max_group_nid = -1; unsigned long max_faults = 0, max_group_faults = 0; + spinlock_t *group_lock = NULL; seq = ACCESS_ONCE(p->mm->numa_scan_seq); if (p->numa_scan_seq == seq) @@ -1241,6 +1242,12 @@ static void task_numa_placement(struct task_struct *p) p->numa_migrate_seq++; p->numa_scan_period_max = task_scan_max(p); + /* If the task is part of a group prevent parallel updates to group stats */ + if (p->numa_group) { + group_lock = &p->numa_group->lock; + spin_lock(group_lock); + } + /* Find the node with the highest number of faults */ for_each_online_node(nid) { unsigned long faults = 0, group_faults = 0; @@ -1279,20 +1286,24 @@ static void task_numa_placement(struct task_struct *p) } } - /* - * If the preferred task and group nids are different, - * iterate over the nodes again to find the best place. - */ - if (p->numa_group && max_nid != max_group_nid) { - unsigned long weight, max_weight = 0; - - for_each_online_node(nid) { - weight = task_weight(p, nid) + group_weight(p, nid); - if (weight > max_weight) { - max_weight = weight; - max_nid = nid; + if (p->numa_group) { + /* + * If the preferred task and group nids are different, + * iterate over the nodes again to find the best place. + */ + if (max_nid != max_group_nid) { + unsigned long weight, max_weight = 0; + + for_each_online_node(nid) { + weight = task_weight(p, nid) + group_weight(p, nid); + if (weight > max_weight) { + max_weight = weight; + max_nid = nid; + } } } + + spin_unlock(group_lock); } /* Preferred node as the node with the most faults */