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

Commit 786d6dc7 authored by Suresh Siddha's avatar Suresh Siddha Committed by Ingo Molnar
Browse files

sched, nohz: Clean up the find_new_ilb() using sched groups nr_busy_cpus 



nr_busy_cpus in the sched_group_power indicates whether the group
is semi idle or not. This helps remove the is_semi_idle_group() and simplify
the find_new_ilb() in the context of finding an optimal cpu that can do
idle load balancing.

Signed-off-by: default avatarSuresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20111202010832.656983582@sbsiddha-desk.sc.intel.com


Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 0b005cf5

kernel/sched/fair.c

+12 −36
Original line number Diff line number Diff line
@@ -4733,7 +4733,6 @@ out_unlock: 
 */

static struct {

	cpumask_var_t idle_cpus_mask;

	cpumask_var_t grp_idle_mask;

	atomic_t nr_cpus;

	unsigned long next_balance;     /* in jiffy units */

} nohz ____cacheline_aligned;
@@ -4773,33 +4772,6 @@ static inline struct sched_domain *lowest_flag_domain(int cpu, int flag) 
	for (sd = lowest_flag_domain(cpu, flag); \

		(sd && (sd->flags & flag)); sd = sd->parent)



/**

 * is_semi_idle_group - Checks if the given sched_group is semi-idle.

 * @ilb_group:	group to be checked for semi-idleness

 *

 * Returns:	1 if the group is semi-idle. 0 otherwise.

 *

 * We define a sched_group to be semi idle if it has atleast one idle-CPU

 * and atleast one non-idle CPU. This helper function checks if the given

 * sched_group is semi-idle or not.

 */

static inline int is_semi_idle_group(struct sched_group *ilb_group)

{

	cpumask_and(nohz.grp_idle_mask, nohz.idle_cpus_mask,

					sched_group_cpus(ilb_group));



	/*

	 * A sched_group is semi-idle when it has atleast one busy cpu

	 * and atleast one idle cpu.

	 */

	if (cpumask_empty(nohz.grp_idle_mask))

		return 0;



	if (cpumask_equal(nohz.grp_idle_mask, sched_group_cpus(ilb_group)))

		return 0;



	return 1;

}

/**

 * find_new_ilb - Finds the optimum idle load balancer for nomination.

 * @cpu:	The cpu which is nominating a new idle_load_balancer.
@@ -4815,8 +4787,8 @@ static inline int is_semi_idle_group(struct sched_group *ilb_group) 
static int find_new_ilb(int cpu)

{

	int ilb = cpumask_first(nohz.idle_cpus_mask);

	struct sched_group *ilbg;

	struct sched_domain *sd;

	struct sched_group *ilb_group;



	/*

	 * Have idle load balancer selection from semi-idle packages only
@@ -4834,23 +4806,28 @@ static int find_new_ilb(int cpu) 


	rcu_read_lock();

	for_each_flag_domain(cpu, sd, SD_POWERSAVINGS_BALANCE) {

		ilb_group = sd->groups;

		ilbg = sd->groups;



		do {

			if (is_semi_idle_group(ilb_group)) {

				ilb = cpumask_first(nohz.grp_idle_mask);

			if (ilbg->group_weight !=

				atomic_read(&ilbg->sgp->nr_busy_cpus)) {

				ilb = cpumask_first_and(nohz.idle_cpus_mask,

							sched_group_cpus(ilbg));

				goto unlock;

			}



			ilb_group = ilb_group->next;

			ilbg = ilbg->next;



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

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

	}

unlock:

	rcu_read_unlock();



out_done:

	if (ilb < nr_cpu_ids && idle_cpu(ilb))

		return ilb;



	return nr_cpu_ids;

}

#else /*  (CONFIG_SCHED_MC || CONFIG_SCHED_SMT) */

static inline int find_new_ilb(int call_cpu)
@@ -5588,7 +5565,6 @@ __init void init_sched_fair_class(void) 


#ifdef CONFIG_NO_HZ

	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);

	alloc_cpumask_var(&nohz.grp_idle_mask, GFP_NOWAIT);

#endif

#endif /* SMP */