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From: Mel Gorman <mgorman@suse.de>
Subject: [PATCH 34/63] sched: numa: increment numa_migrate_seq when task runs in correct location
Date: Mon,  7 Oct 2013 11:29:12 +0100
Message-Id: <1381141781-10992-35-git-send-email-mgorman@suse.de>
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References: <1381141781-10992-1-git-send-email-mgorman@suse.de>
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To: Peter Zijlstra <a.p.zijlstra@chello.nl>, Rik van Riel <riel@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>, Ingo Molnar <mingo@kernel.org>, Andrea Arcangeli <aarcange@redhat.com>, Johannes Weiner <hannes@cmpxchg.org>, Linux-MM <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>, Mel Gorman <mgorman@suse.de>

From: Rik van Riel <riel@redhat.com>

When a task is already running on its preferred node, increment
numa_migrate_seq to indicate that the task is settled if migration is
temporarily disabled, and memory should migrate towards it.

[mgorman@suse.de: Only increment migrate_seq if migration temporarily disabled]
Signed-off-by: Rik van Riel <riel@redhat.com>
---
 kernel/sched/fair.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 559175b..9a2e68e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1016,8 +1016,16 @@ static void numa_migrate_preferred(struct task_struct *p)
 {
 	/* Success if task is already running on preferred CPU */
 	p->numa_migrate_retry = 0;
-	if (cpu_to_node(task_cpu(p)) == p->numa_preferred_nid)
+	if (cpu_to_node(task_cpu(p)) == p->numa_preferred_nid) {
+		/*
+		 * If migration is temporarily disabled due to a task migration
+		 * then re-enable it now as the task is running on its
+		 * preferred node and memory should migrate locally
+		 */
+		if (!p->numa_migrate_seq)
+			p->numa_migrate_seq++;
 		return;
+	}
 
 	/* This task has no NUMA fault statistics yet */
 	if (unlikely(p->numa_preferred_nid == -1))
-- 
1.8.4

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