linux-kernel - [PATCH 33/50] sched: numa: increment numa_migrate

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Date:	Tue, 10 Sep 2013 10:32:13 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Rik van Riel <riel@...hat.com>
Cc:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...nel.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>, Mel Gorman <mgorman@...e.de>
Subject: [PATCH 33/50] sched: numa: increment numa_migrate_seq when task runs in correct location

From: Rik van Riel <riel@...hat.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@...e.de: Only increment migrate_seq if migration temporarily disabled]
Signed-off-by: Rik van Riel <riel@...hat.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 5b4d94e..fd724bc 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;
+	}
 
 	/* Otherwise, try migrate to a CPU on the preferred node */
 	if (task_numa_migrate(p) != 0)
-- 
1.8.1.4

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