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: Suresh Siddha <suresh.b.siddha@intel.com> Signed-off-by: Peter 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: Ingo Molnar <mingo@elte.hu>
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@ -4733,7 +4733,6 @@ out_unlock:
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*/
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static struct {
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cpumask_var_t idle_cpus_mask;
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cpumask_var_t grp_idle_mask;
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atomic_t nr_cpus;
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unsigned long next_balance; /* in jiffy units */
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} nohz ____cacheline_aligned;
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@ -4773,33 +4772,6 @@ static inline struct sched_domain *lowest_flag_domain(int cpu, int flag)
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for (sd = lowest_flag_domain(cpu, flag); \
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(sd && (sd->flags & flag)); sd = sd->parent)
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/**
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* is_semi_idle_group - Checks if the given sched_group is semi-idle.
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* @ilb_group: group to be checked for semi-idleness
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*
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* Returns: 1 if the group is semi-idle. 0 otherwise.
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*
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* We define a sched_group to be semi idle if it has atleast one idle-CPU
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* and atleast one non-idle CPU. This helper function checks if the given
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* sched_group is semi-idle or not.
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*/
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static inline int is_semi_idle_group(struct sched_group *ilb_group)
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{
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cpumask_and(nohz.grp_idle_mask, nohz.idle_cpus_mask,
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sched_group_cpus(ilb_group));
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/*
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* A sched_group is semi-idle when it has atleast one busy cpu
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* and atleast one idle cpu.
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*/
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if (cpumask_empty(nohz.grp_idle_mask))
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return 0;
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if (cpumask_equal(nohz.grp_idle_mask, sched_group_cpus(ilb_group)))
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return 0;
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return 1;
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}
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/**
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* find_new_ilb - Finds the optimum idle load balancer for nomination.
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* @cpu: The cpu which is nominating a new idle_load_balancer.
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@ -4815,8 +4787,8 @@ static inline int is_semi_idle_group(struct sched_group *ilb_group)
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static int find_new_ilb(int cpu)
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{
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int ilb = cpumask_first(nohz.idle_cpus_mask);
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struct sched_group *ilbg;
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struct sched_domain *sd;
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struct sched_group *ilb_group;
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/*
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* Have idle load balancer selection from semi-idle packages only
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@ -4834,23 +4806,28 @@ static int find_new_ilb(int cpu)
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rcu_read_lock();
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for_each_flag_domain(cpu, sd, SD_POWERSAVINGS_BALANCE) {
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ilb_group = sd->groups;
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ilbg = sd->groups;
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do {
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if (is_semi_idle_group(ilb_group)) {
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ilb = cpumask_first(nohz.grp_idle_mask);
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if (ilbg->group_weight !=
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atomic_read(&ilbg->sgp->nr_busy_cpus)) {
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ilb = cpumask_first_and(nohz.idle_cpus_mask,
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sched_group_cpus(ilbg));
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goto unlock;
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}
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ilb_group = ilb_group->next;
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ilbg = ilbg->next;
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} while (ilb_group != sd->groups);
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} while (ilbg != sd->groups);
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}
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unlock:
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rcu_read_unlock();
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out_done:
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if (ilb < nr_cpu_ids && idle_cpu(ilb))
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return ilb;
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return nr_cpu_ids;
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}
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#else /* (CONFIG_SCHED_MC || CONFIG_SCHED_SMT) */
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static inline int find_new_ilb(int call_cpu)
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@ -5588,7 +5565,6 @@ __init void init_sched_fair_class(void)
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#ifdef CONFIG_NO_HZ
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zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
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alloc_cpumask_var(&nohz.grp_idle_mask, GFP_NOWAIT);
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#endif
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#endif /* SMP */
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