Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

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

sched/debug: Optimize sched_domain sysctl generation 



Currently we unconditionally destroy all sysctl bits and regenerate
them after we've rebuild the domains (even if that rebuild is a
no-op).

And since we unconditionally (re)build the sysctl for all possible
CPUs, onlining all CPUs gets us O(n^2) time. Instead change this to
only rebuild the bits for CPUs we've actually installed new domains
on.

Reported-by: default avatarOfer Levi(SW) <oferle@mellanox.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 09e0dd8e

kernel/sched/debug.c

+54 −14
Original line number Diff line number Diff line
@@ -327,38 +327,78 @@ static struct ctl_table *sd_alloc_ctl_cpu_table(int cpu) 
	return table;

}



static cpumask_var_t sd_sysctl_cpus;

static struct ctl_table_header *sd_sysctl_header;



void register_sched_domain_sysctl(void)

{

	int i, cpu_num = num_possible_cpus();

	struct ctl_table *entry = sd_alloc_ctl_entry(cpu_num + 1);

	static struct ctl_table *cpu_entries;

	static struct ctl_table **cpu_idx;

	char buf[32];

	int i;



	if (!cpu_entries) {

		cpu_entries = sd_alloc_ctl_entry(num_possible_cpus() + 1);

		if (!cpu_entries)

			return;



		WARN_ON(sd_ctl_dir[0].child);

	sd_ctl_dir[0].child = entry;

		sd_ctl_dir[0].child = cpu_entries;

	}



	if (!cpu_idx) {

		struct ctl_table *e = cpu_entries;



	if (entry == NULL)

		cpu_idx = kcalloc(nr_cpu_ids, sizeof(struct ctl_table*), GFP_KERNEL);

		if (!cpu_idx)

			return;



		/* deal with sparse possible map */

		for_each_possible_cpu(i) {

			cpu_idx[i] = e;

			e++;

		}

	}



	if (!cpumask_available(sd_sysctl_cpus)) {

		if (!alloc_cpumask_var(&sd_sysctl_cpus, GFP_KERNEL))

			return;



		/* init to possible to not have holes in @cpu_entries */

		cpumask_copy(sd_sysctl_cpus, cpu_possible_mask);

	}



	for_each_cpu(i, sd_sysctl_cpus) {

		struct ctl_table *e = cpu_idx[i];



		if (e->child)

			sd_free_ctl_entry(&e->child);



		if (!e->procname) {

			snprintf(buf, 32, "cpu%d", i);

		entry->procname = kstrdup(buf, GFP_KERNEL);

		entry->mode = 0555;

		entry->child = sd_alloc_ctl_cpu_table(i);

		entry++;

			e->procname = kstrdup(buf, GFP_KERNEL);

		}

		e->mode = 0555;

		e->child = sd_alloc_ctl_cpu_table(i);



		__cpumask_clear_cpu(i, sd_sysctl_cpus);

	}



	WARN_ON(sd_sysctl_header);

	sd_sysctl_header = register_sysctl_table(sd_ctl_root);

}



void dirty_sched_domain_sysctl(int cpu)

{

	if (cpumask_available(sd_sysctl_cpus))

		__cpumask_set_cpu(cpu, sd_sysctl_cpus);

}



/* may be called multiple times per register */

void unregister_sched_domain_sysctl(void)

{

	unregister_sysctl_table(sd_sysctl_header);

	sd_sysctl_header = NULL;

	if (sd_ctl_dir[0].child)

		sd_free_ctl_entry(&sd_ctl_dir[0].child);

}

#endif /* CONFIG_SYSCTL */

#endif /* CONFIG_SMP */

kernel/sched/sched.h

+4 −0
Original line number Diff line number Diff line
@@ -1120,11 +1120,15 @@ extern int group_balance_cpu(struct sched_group *sg); 


#if defined(CONFIG_SCHED_DEBUG) && defined(CONFIG_SYSCTL)

void register_sched_domain_sysctl(void);

void dirty_sched_domain_sysctl(int cpu);

void unregister_sched_domain_sysctl(void);

#else

static inline void register_sched_domain_sysctl(void)

{

}

static inline void dirty_sched_domain_sysctl(int cpu)

{

}

static inline void unregister_sched_domain_sysctl(void)

{

}

kernel/sched/topology.c

+1 −0
Original line number Diff line number Diff line
@@ -459,6 +459,7 @@ cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu) 
	rq_attach_root(rq, rd);

	tmp = rq->sd;

	rcu_assign_pointer(rq->sd, sd);

	dirty_sched_domain_sysctl(cpu);

	destroy_sched_domains(tmp);



	update_top_cache_domain(cpu);