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Commit 20e07dea authored by Rik van Riel's avatar Rik van Riel Committed by Ingo Molnar
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sched/numa: Build per numa_group active node mask from numa_faults_cpu statistics 



The numa_faults_cpu statistics are used to maintain an active_nodes nodemask
per numa_group. This allows us to be smarter about when to do numa migrations.

Signed-off-by: default avatarRik van Riel <riel@redhat.com>
Acked-by: default avatarMel Gorman <mgorman@suse.de>
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Cc: Chegu Vinod <chegu_vinod@hp.com>
Link: http://lkml.kernel.org/r/1390860228-21539-5-git-send-email-riel@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 50ec8a40

kernel/sched/fair.c

+42 −0
Original line number Diff line number Diff line
@@ -885,6 +885,7 @@ struct numa_group { 
	struct list_head task_list;



	struct rcu_head rcu;

	nodemask_t active_nodes;

	unsigned long total_faults;

	unsigned long *faults_cpu;

	unsigned long faults[0];
@@ -918,6 +919,12 @@ static inline unsigned long group_faults(struct task_struct *p, int nid) 
		p->numa_group->faults[task_faults_idx(nid, 1)];

}



static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)

{

	return group->faults_cpu[task_faults_idx(nid, 0)] +

		group->faults_cpu[task_faults_idx(nid, 1)];

}



/*

 * These return the fraction of accesses done by a particular task, or

 * task group, on a particular numa node.  The group weight is given a
@@ -1270,6 +1277,38 @@ static void numa_migrate_preferred(struct task_struct *p) 
	task_numa_migrate(p);

}



/*

 * Find the nodes on which the workload is actively running. We do this by

 * tracking the nodes from which NUMA hinting faults are triggered. This can

 * be different from the set of nodes where the workload's memory is currently

 * located.

 *

 * The bitmask is used to make smarter decisions on when to do NUMA page

 * migrations, To prevent flip-flopping, and excessive page migrations, nodes

 * are added when they cause over 6/16 of the maximum number of faults, but

 * only removed when they drop below 3/16.

 */

static void update_numa_active_node_mask(struct numa_group *numa_group)

{

	unsigned long faults, max_faults = 0;

	int nid;



	for_each_online_node(nid) {

		faults = group_faults_cpu(numa_group, nid);

		if (faults > max_faults)

			max_faults = faults;

	}



	for_each_online_node(nid) {

		faults = group_faults_cpu(numa_group, nid);

		if (!node_isset(nid, numa_group->active_nodes)) {

			if (faults > max_faults * 6 / 16)

				node_set(nid, numa_group->active_nodes);

		} else if (faults < max_faults * 3 / 16)

			node_clear(nid, numa_group->active_nodes);

	}

}



/*

 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS

 * increments. The more local the fault statistics are, the higher the scan
@@ -1412,6 +1451,7 @@ static void task_numa_placement(struct task_struct *p) 
	update_task_scan_period(p, fault_types[0], fault_types[1]);



	if (p->numa_group) {

		update_numa_active_node_mask(p->numa_group);

		/*

		 * If the preferred task and group nids are different,

		 * iterate over the nodes again to find the best place.
@@ -1474,6 +1514,8 @@ static void task_numa_group(struct task_struct *p, int cpupid, int flags, 
		/* Second half of the array tracks nids where faults happen */

		grp->faults_cpu = grp->faults + 2 * nr_node_ids;



		node_set(task_node(current), grp->active_nodes);



		for (i = 0; i < 4*nr_node_ids; i++)

			grp->faults[i] = p->numa_faults_memory[i];