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Commit e3589f6c authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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sched: Allow for overlapping sched_domain spans 



Allow for sched_domain spans that overlap by giving such domains their
own sched_group list instead of sharing the sched_groups amongst
each-other.

This is needed for machines with more than 16 nodes, because
sched_domain_node_span() will generate a node mask from the
16 nearest nodes without regard if these masks have any overlap.

Currently sched_domains have a sched_group that maps to their child
sched_domain span, and since there is no overlap we share the
sched_group between the sched_domains of the various CPUs. If however
there is overlap, we would need to link the sched_group list in
different ways for each cpu, and hence sharing isn't possible.

In order to solve this, allocate private sched_groups for each CPU's
sched_domain but have the sched_groups share a sched_group_power
structure such that we can uniquely track the power.

Reported-and-tested-by: default avatarAnton Blanchard <anton@samba.org>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-08bxqw9wis3qti9u5inifh3y@git.kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 9c3f75cb

include/linux/sched.h

+2 −0
Original line number Diff line number Diff line
@@ -844,6 +844,7 @@ enum cpu_idle_type { 
#define SD_SERIALIZE		0x0400	/* Only a single load balancing instance */

#define SD_ASYM_PACKING		0x0800  /* Place busy groups earlier in the domain */

#define SD_PREFER_SIBLING	0x1000	/* Prefer to place tasks in a sibling domain */

#define SD_OVERLAP		0x2000	/* sched_domains of this level overlap */



enum powersavings_balance_level {

	POWERSAVINGS_BALANCE_NONE = 0,  /* No power saving load balance */
@@ -894,6 +895,7 @@ static inline int sd_power_saving_flags(void) 
}



struct sched_group_power {

	atomic_t ref;

	/*

	 * CPU power of this group, SCHED_LOAD_SCALE being max power for a

	 * single CPU.

kernel/sched.c

+128 −29
Original line number Diff line number Diff line
@@ -6774,10 +6774,36 @@ static struct root_domain *alloc_rootdomain(void) 
	return rd;

}



static void free_sched_groups(struct sched_group *sg, int free_sgp)

{

	struct sched_group *tmp, *first;



	if (!sg)

		return;



	first = sg;

	do {

		tmp = sg->next;



		if (free_sgp && atomic_dec_and_test(&sg->sgp->ref))

			kfree(sg->sgp);



		kfree(sg);

		sg = tmp;

	} while (sg != first);

}



static void free_sched_domain(struct rcu_head *rcu)

{

	struct sched_domain *sd = container_of(rcu, struct sched_domain, rcu);

	if (atomic_dec_and_test(&sd->groups->ref)) {



	/*

	 * If its an overlapping domain it has private groups, iterate and

	 * nuke them all.

	 */

	if (sd->flags & SD_OVERLAP) {

		free_sched_groups(sd->groups, 1);

	} else if (atomic_dec_and_test(&sd->groups->ref)) {

		kfree(sd->groups->sgp);

		kfree(sd->groups);

	}
@@ -6967,15 +6993,73 @@ struct sched_domain_topology_level; 
typedef struct sched_domain *(*sched_domain_init_f)(struct sched_domain_topology_level *tl, int cpu);

typedef const struct cpumask *(*sched_domain_mask_f)(int cpu);



#define SDTL_OVERLAP	0x01



struct sched_domain_topology_level {

	sched_domain_init_f init;

	sched_domain_mask_f mask;

	int		    flags;

	struct sd_data      data;

};



/*

 * Assumes the sched_domain tree is fully constructed

 */

static int

build_overlap_sched_groups(struct sched_domain *sd, int cpu)

{

	struct sched_group *first = NULL, *last = NULL, *groups = NULL, *sg;

	const struct cpumask *span = sched_domain_span(sd);

	struct cpumask *covered = sched_domains_tmpmask;

	struct sd_data *sdd = sd->private;

	struct sched_domain *child;

	int i;



	cpumask_clear(covered);



	for_each_cpu(i, span) {

		struct cpumask *sg_span;



		if (cpumask_test_cpu(i, covered))

			continue;



		sg = kzalloc_node(sizeof(struct sched_group) + cpumask_size(),

				GFP_KERNEL, cpu_to_node(i));



		if (!sg)

			goto fail;



		sg_span = sched_group_cpus(sg);



		child = *per_cpu_ptr(sdd->sd, i);

		if (child->child) {

			child = child->child;

			cpumask_copy(sg_span, sched_domain_span(child));

		} else

			cpumask_set_cpu(i, sg_span);



		cpumask_or(covered, covered, sg_span);



		sg->sgp = *per_cpu_ptr(sdd->sgp, cpumask_first(sg_span));

		atomic_inc(&sg->sgp->ref);



		if (cpumask_test_cpu(cpu, sg_span))

			groups = sg;



		if (!first)

			first = sg;

		if (last)

			last->next = sg;

		last = sg;

		last->next = first;

	}

	sd->groups = groups;



	return 0;



fail:

	free_sched_groups(first, 0);



	return -ENOMEM;

}



static int get_group(int cpu, struct sd_data *sdd, struct sched_group **sg)

{

	struct sched_domain *sd = *per_cpu_ptr(sdd->sd, cpu);
@@ -6987,23 +7071,21 @@ static int get_group(int cpu, struct sd_data *sdd, struct sched_group **sg) 
	if (sg) {

		*sg = *per_cpu_ptr(sdd->sg, cpu);

		(*sg)->sgp = *per_cpu_ptr(sdd->sgp, cpu);

		atomic_set(&(*sg)->sgp->ref, 1); /* for claim_allocations */

	}



	return cpu;

}



/*

 * build_sched_groups takes the cpumask we wish to span, and a pointer

 * to a function which identifies what group(along with sched group) a CPU

 * belongs to. The return value of group_fn must be a >= 0 and < nr_cpu_ids

 * (due to the fact that we keep track of groups covered with a struct cpumask).

 *

 * build_sched_groups will build a circular linked list of the groups

 * covered by the given span, and will set each group's ->cpumask correctly,

 * and ->cpu_power to 0.

 *

 * Assumes the sched_domain tree is fully constructed

 */

static void

build_sched_groups(struct sched_domain *sd)

static int

build_sched_groups(struct sched_domain *sd, int cpu)

{

	struct sched_group *first = NULL, *last = NULL;

	struct sd_data *sdd = sd->private;
@@ -7011,6 +7093,12 @@ build_sched_groups(struct sched_domain *sd) 
	struct cpumask *covered;

	int i;



	get_group(cpu, sdd, &sd->groups);

	atomic_inc(&sd->groups->ref);



	if (cpu != cpumask_first(sched_domain_span(sd)))

		return 0;



	lockdep_assert_held(&sched_domains_mutex);

	covered = sched_domains_tmpmask;
@@ -7042,6 +7130,8 @@ build_sched_groups(struct sched_domain *sd) 
		last = sg;

	}

	last->next = first;



	return 0;

}



/*
@@ -7056,12 +7146,17 @@ build_sched_groups(struct sched_domain *sd) 
 */

static void init_sched_groups_power(int cpu, struct sched_domain *sd)

{

	WARN_ON(!sd || !sd->groups);

	struct sched_group *sg = sd->groups;



	if (cpu != group_first_cpu(sd->groups))

		return;

	WARN_ON(!sd || !sg);



	sd->groups->group_weight = cpumask_weight(sched_group_cpus(sd->groups));

	do {

		sg->group_weight = cpumask_weight(sched_group_cpus(sg));

		sg = sg->next;

	} while (sg != sd->groups);



	if (cpu != group_first_cpu(sg))

		return;



	update_group_power(sd, cpu);

}
@@ -7182,17 +7277,16 @@ static enum s_alloc __visit_domain_allocation_hell(struct s_data *d, 
static void claim_allocations(int cpu, struct sched_domain *sd)

{

	struct sd_data *sdd = sd->private;

	struct sched_group *sg = sd->groups;



	WARN_ON_ONCE(*per_cpu_ptr(sdd->sd, cpu) != sd);

	*per_cpu_ptr(sdd->sd, cpu) = NULL;



	if (cpu == cpumask_first(sched_group_cpus(sg))) {

		WARN_ON_ONCE(*per_cpu_ptr(sdd->sg, cpu) != sg);

	if (atomic_read(&(*per_cpu_ptr(sdd->sg, cpu))->ref))

		*per_cpu_ptr(sdd->sg, cpu) = NULL;



	if (atomic_read(&(*per_cpu_ptr(sdd->sgp, cpu))->ref))

		*per_cpu_ptr(sdd->sgp, cpu) = NULL;

}

}



#ifdef CONFIG_SCHED_SMT

static const struct cpumask *cpu_smt_mask(int cpu)
@@ -7216,7 +7310,7 @@ static struct sched_domain_topology_level default_topology[] = { 
#endif

	{ sd_init_CPU, cpu_cpu_mask, },

#ifdef CONFIG_NUMA

	{ sd_init_NODE, cpu_node_mask, },

	{ sd_init_NODE, cpu_node_mask, SDTL_OVERLAP, },

	{ sd_init_ALLNODES, cpu_allnodes_mask, },

#endif

	{ NULL, },
@@ -7284,7 +7378,9 @@ static void __sdt_free(const struct cpumask *cpu_map) 
		struct sd_data *sdd = &tl->data;



		for_each_cpu(j, cpu_map) {

			kfree(*per_cpu_ptr(sdd->sd, j));

			struct sched_domain *sd = *per_cpu_ptr(sdd->sd, j);

			if (sd && (sd->flags & SD_OVERLAP))

				free_sched_groups(sd->groups, 0);

			kfree(*per_cpu_ptr(sdd->sg, j));

			kfree(*per_cpu_ptr(sdd->sgp, j));

		}
@@ -7336,8 +7432,11 @@ static int build_sched_domains(const struct cpumask *cpu_map, 
		struct sched_domain_topology_level *tl;



		sd = NULL;

		for (tl = sched_domain_topology; tl->init; tl++)

		for (tl = sched_domain_topology; tl->init; tl++) {

			sd = build_sched_domain(tl, &d, cpu_map, attr, sd, i);

			if (tl->flags & SDTL_OVERLAP || sched_feat(FORCE_SD_OVERLAP))

				sd->flags |= SD_OVERLAP;

		}



		while (sd->child)

			sd = sd->child;
@@ -7349,13 +7448,13 @@ static int build_sched_domains(const struct cpumask *cpu_map, 
	for_each_cpu(i, cpu_map) {

		for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) {

			sd->span_weight = cpumask_weight(sched_domain_span(sd));

			get_group(i, sd->private, &sd->groups);

			atomic_inc(&sd->groups->ref);



			if (i != cpumask_first(sched_domain_span(sd)))

				continue;



			build_sched_groups(sd);

			if (sd->flags & SD_OVERLAP) {

				if (build_overlap_sched_groups(sd, i))

					goto error;

			} else {

				if (build_sched_groups(sd, i))

					goto error;

			}

		}

	}

kernel/sched_features.h

+2 −0
Original line number Diff line number Diff line
@@ -70,3 +70,5 @@ SCHED_FEAT(NONIRQ_POWER, 1) 
 * using the scheduler IPI. Reduces rq->lock contention/bounces.

 */

SCHED_FEAT(TTWU_QUEUE, 1)



SCHED_FEAT(FORCE_SD_OVERLAP, 0)