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Commit 2c8a50aa authored by Mel Gorman's avatar Mel Gorman Committed by Ingo Molnar
Browse files

sched/numa: Favor placing a task on the preferred node 



A tasks preferred node is selected based on the number of faults
recorded for a node but the actual task_numa_migate() conducts a global
search regardless of the preferred nid. This patch checks if the
preferred nid has capacity and if so, searches for a CPU within that
node. This avoids a global search when the preferred node is not
overloaded.

Signed-off-by: default avatarMel Gorman <mgorman@suse.de>
Reviewed-by: default avatarRik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1381141781-10992-41-git-send-email-mgorman@suse.de


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent fb13c7ee

kernel/sched/fair.c

+35 −19
Original line number Diff line number Diff line
@@ -1052,6 +1052,20 @@ unlock: 
	rcu_read_unlock();

}



static void task_numa_find_cpu(struct task_numa_env *env, long imp)

{

	int cpu;



	for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {

		/* Skip this CPU if the source task cannot migrate */

		if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p)))

			continue;



		env->dst_cpu = cpu;

		task_numa_compare(env, imp);

	}

}



static int task_numa_migrate(struct task_struct *p)

{

	struct task_numa_env env = {
@@ -1068,7 +1082,8 @@ static int task_numa_migrate(struct task_struct *p) 
	};

	struct sched_domain *sd;

	unsigned long faults;

	int nid, cpu, ret;

	int nid, ret;

	long imp;



	/*

	 * Pick the lowest SD_NUMA domain, as that would have the smallest
@@ -1085,28 +1100,29 @@ static int task_numa_migrate(struct task_struct *p) 


	faults = task_faults(p, env.src_nid);

	update_numa_stats(&env.src_stats, env.src_nid);

	env.dst_nid = p->numa_preferred_nid;

	imp = task_faults(env.p, env.dst_nid) - faults;

	update_numa_stats(&env.dst_stats, env.dst_nid);



	/* Find an alternative node with relatively better statistics */

	/*

	 * If the preferred nid has capacity then use it. Otherwise find an

	 * alternative node with relatively better statistics.

	 */

	if (env.dst_stats.has_capacity) {

		task_numa_find_cpu(&env, imp);

	} else {

		for_each_online_node(nid) {

		long imp;



		if (nid == env.src_nid)

			if (nid == env.src_nid || nid == p->numa_preferred_nid)

				continue;



			/* Only consider nodes that recorded more faults */

		imp = task_faults(p, nid) - faults;

			imp = task_faults(env.p, nid) - faults;

			if (imp < 0)

				continue;



			env.dst_nid = nid;

			update_numa_stats(&env.dst_stats, env.dst_nid);

		for_each_cpu(cpu, cpumask_of_node(nid)) {

			/* Skip this CPU if the source task cannot migrate */

			if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))

				continue;



			env.dst_cpu = cpu;

			task_numa_compare(&env, imp);

			task_numa_find_cpu(&env, imp);

		}

	}