[tip:sched/core] sched/numa: Increment numa_migrate_seq when task runs in correct location

[tip-bot for Rik van Riel]

Commit-ID:  06ea5e035b4e66cc77790457a89fc7e368060c4b
Gitweb:     http://git.kernel.org/tip/06ea5e035b4e66cc77790457a89fc7e368060c4b
Author:     Rik van Riel <riel@xxxxxxxxxx>
AuthorDate: Mon, 7 Oct 2013 11:29:12 +0100
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 9 Oct 2013 12:40:41 +0200

sched/numa: Increment numa_migrate_seq when task runs in correct location

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.

Signed-off-by: Rik van Riel <riel@xxxxxxxxxx>
[ Only increment migrate_seq if migration temporarily disabled. ]
Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1381141781-10992-35-git-send-email-mgorman@xxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 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 f84ac3f..de9b4d8 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))
--
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