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Commit d039ac60 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched: Validate assumptions in sched_init_numa() 



Add some code to validate assumptions we're making and output
warnings if they are not.

If this trigger we want to know about it.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Alex Shi <lkml.alex@gmail.com>
Link: http://lkml.kernel.org/n/tip-6uc3wk5s9udxtdl9cnku0vtt@git.kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent c3decf0d

kernel/sched/core.c

+80 −19
Original line number Diff line number Diff line
@@ -5556,15 +5556,20 @@ static cpumask_var_t sched_domains_tmpmask; /* sched_domains_mutex */ 


#ifdef CONFIG_SCHED_DEBUG



static __read_mostly int sched_domain_debug_enabled;

static __read_mostly int sched_debug_enabled;



static int __init sched_domain_debug_setup(char *str)

static int __init sched_debug_setup(char *str)

{

	sched_domain_debug_enabled = 1;

	sched_debug_enabled = 1;



	return 0;

}

early_param("sched_debug", sched_domain_debug_setup);

early_param("sched_debug", sched_debug_setup);



static inline bool sched_debug(void)

{

	return sched_debug_enabled;

}



static int sched_domain_debug_one(struct sched_domain *sd, int cpu, int level,

				  struct cpumask *groupmask)
@@ -5657,7 +5662,7 @@ static void sched_domain_debug(struct sched_domain *sd, int cpu) 
{

	int level = 0;



	if (!sched_domain_debug_enabled)

	if (!sched_debug_enabled)

		return;



	if (!sd) {
@@ -5678,6 +5683,10 @@ static void sched_domain_debug(struct sched_domain *sd, int cpu) 
}

#else /* !CONFIG_SCHED_DEBUG */

# define sched_domain_debug(sd, cpu) do { } while (0)

static inline bool sched_debug(void)

{

	return false;

}

#endif /* CONFIG_SCHED_DEBUG */



static int sd_degenerate(struct sched_domain *sd)
@@ -6373,7 +6382,6 @@ static struct sched_domain_topology_level *sched_domain_topology = default_topol 
#ifdef CONFIG_NUMA



static int sched_domains_numa_levels;

static int sched_domains_numa_scale;

static int *sched_domains_numa_distance;

static struct cpumask ***sched_domains_numa_masks;

static int sched_domains_curr_level;
@@ -6438,6 +6446,42 @@ static const struct cpumask *sd_numa_mask(int cpu) 
	return sched_domains_numa_masks[sched_domains_curr_level][cpu_to_node(cpu)];

}



static void sched_numa_warn(const char *str)

{

	static int done = false;

	int i,j;



	if (done)

		return;



	done = true;



	printk(KERN_WARNING "ERROR: %s\n\n", str);



	for (i = 0; i < nr_node_ids; i++) {

		printk(KERN_WARNING "  ");

		for (j = 0; j < nr_node_ids; j++)

			printk(KERN_CONT "%02d ", node_distance(i,j));

		printk(KERN_CONT "\n");

	}

	printk(KERN_WARNING "\n");

}



static bool find_numa_distance(int distance)

{

	int i;



	if (distance == node_distance(0, 0))

		return true;



	for (i = 0; i < sched_domains_numa_levels; i++) {

		if (sched_domains_numa_distance[i] == distance)

			return true;

	}



	return false;

}



static void sched_init_numa(void)

{

	int next_distance, curr_distance = node_distance(0, 0);
@@ -6445,7 +6489,6 @@ static void sched_init_numa(void) 
	int level = 0;

	int i, j, k;



	sched_domains_numa_scale = curr_distance;

	sched_domains_numa_distance = kzalloc(sizeof(int) * nr_node_ids, GFP_KERNEL);

	if (!sched_domains_numa_distance)

		return;
@@ -6456,17 +6499,28 @@ static void sched_init_numa(void) 
	 *

	 * Assumes node_distance(0,j) includes all distances in

	 * node_distance(i,j) in order to avoid cubic time.

	 *

	 * XXX: could be optimized to O(n log n) by using sort()

	 */

	next_distance = curr_distance;

	for (i = 0; i < nr_node_ids; i++) {

		for (j = 0; j < nr_node_ids; j++) {

			int distance = node_distance(0, j);

			for (k = 0; k < nr_node_ids; k++) {

				int distance = node_distance(i, k);



				if (distance > curr_distance &&

				    (distance < next_distance ||

				     next_distance == curr_distance))

					next_distance = distance;



				/*

				 * While not a strong assumption it would be nice to know

				 * about cases where if node A is connected to B, B is not

				 * equally connected to A.

				 */

				if (sched_debug() && node_distance(k, i) != distance)

					sched_numa_warn("Node-distance not symmetric");



				if (sched_debug() && i && !find_numa_distance(distance))

					sched_numa_warn("Node-0 not representative");

			}

			if (next_distance != curr_distance) {

				sched_domains_numa_distance[level++] = next_distance;
@@ -6474,6 +6528,13 @@ static void sched_init_numa(void) 
				curr_distance = next_distance;

			} else break;

		}



		/*

		 * In case of sched_debug() we verify the above assumption.

		 */

		if (!sched_debug())

			break;

	}

	/*

	 * 'level' contains the number of unique distances, excluding the

	 * identity distance node_distance(i,i).