}
#endif
-static int
-move_one_task_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
- struct sched_domain *sd, enum cpu_idle_type idle)
+/*
+ * move_tasks tries to move up to max_load_move weighted load from busiest to
+ * this_rq, as part of a balancing operation within domain "sd".
+ * Returns 1 if successful and 0 otherwise.
+ *
+ * Called with both runqueues locked.
+ */
+static int move_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
+ unsigned long max_load_move,
+ struct sched_domain *sd, enum cpu_idle_type idle,
+ int *all_pinned)
{
- struct cfs_rq *busy_cfs_rq;
- struct rq_iterator cfs_rq_iterator;
+ unsigned long total_load_moved = 0, load_moved;
+ int this_best_prio = this_rq->curr->prio;
+
+ do {
+ load_moved = load_balance_fair(this_rq, this_cpu, busiest,
+ max_load_move - total_load_moved,
+ sd, idle, all_pinned, &this_best_prio);
- cfs_rq_iterator.start = load_balance_start_fair;
- cfs_rq_iterator.next = load_balance_next_fair;
+ total_load_moved += load_moved;
- for_each_leaf_cfs_rq(busiest, busy_cfs_rq) {
+#ifdef CONFIG_PREEMPT
/*
- * pass busy_cfs_rq argument into
- * load_balance_[start|next]_fair iterators
+ * NEWIDLE balancing is a source of latency, so preemptible
+ * kernels will stop after the first task is pulled to minimize
+ * the critical section.
*/
- cfs_rq_iterator.arg = busy_cfs_rq;
- if (iter_move_one_task(this_rq, this_cpu, busiest, sd, idle,
- &cfs_rq_iterator))
- return 1;
+ if (idle == CPU_NEWLY_IDLE && this_rq->nr_running)
+ break;
+
+ if (raw_spin_is_contended(&this_rq->lock) ||
+ raw_spin_is_contended(&busiest->lock))
+ break;
+#endif
+ } while (load_moved && max_load_move > total_load_moved);
+
+ return total_load_moved > 0;
+}
+
+/********** Helpers for find_busiest_group ************************/
+/*
+ * sd_lb_stats - Structure to store the statistics of a sched_domain
+ * during load balancing.
+ */
+struct sd_lb_stats {
+ struct sched_group *busiest; /* Busiest group in this sd */
+ struct sched_group *this; /* Local group in this sd */
+ unsigned long total_load; /* Total load of all groups in sd */
+ unsigned long total_pwr; /* Total power of all groups in sd */
+ unsigned long avg_load; /* Average load across all groups in sd */
+
+ /** Statistics of this group */
+ unsigned long this_load;
+ unsigned long this_load_per_task;
+ unsigned long this_nr_running;
+
+ /* Statistics of the busiest group */
+ unsigned long max_load;
+ unsigned long busiest_load_per_task;
+ unsigned long busiest_nr_running;
+
+ int group_imb; /* Is there imbalance in this sd */
+#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
+ int power_savings_balance; /* Is powersave balance needed for this sd */
+ struct sched_group *group_min; /* Least loaded group in sd */
+ struct sched_group *group_leader; /* Group which relieves group_min */
+ unsigned long min_load_per_task; /* load_per_task in group_min */
+ unsigned long leader_nr_running; /* Nr running of group_leader */
+ unsigned long min_nr_running; /* Nr running of group_min */
+#endif
+};
+
+/*
+ * sg_lb_stats - stats of a sched_group required for load_balancing
+ */
+struct sg_lb_stats {
+ unsigned long avg_load; /*Avg load across the CPUs of the group */
+ unsigned long group_load; /* Total load over the CPUs of the group */
+ unsigned long sum_nr_running; /* Nr tasks running in the group */
+ unsigned long sum_weighted_load; /* Weighted load of group's tasks */
+ unsigned long group_capacity;
+ int group_imb; /* Is there an imbalance in the group ? */
+};
+
+/**
+ * group_first_cpu - Returns the first cpu in the cpumask of a sched_group.
+ * @group: The group whose first cpu is to be returned.
+ */
+static inline unsigned int group_first_cpu(struct sched_group *group)
+{
+ return cpumask_first(sched_group_cpus(group));
+}
+
+/**
+ * get_sd_load_idx - Obtain the load index for a given sched domain.
+ * @sd: The sched_domain whose load_idx is to be obtained.
+ * @idle: The Idle status of the CPU for whose sd load_icx is obtained.
+ */
+static inline int get_sd_load_idx(struct sched_domain *sd,
+ enum cpu_idle_type idle)
+{
+ int load_idx;
+
+ switch (idle) {
+ case CPU_NOT_IDLE:
+ load_idx = sd->busy_idx;
+ break;
+
+ case CPU_NEWLY_IDLE:
+ load_idx = sd->newidle_idx;
+ break;
+ default:
+ load_idx = sd->idle_idx;
+ break;
+ }
+
+ return load_idx;
+}
+
+
+#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
+/**
+ * init_sd_power_savings_stats - Initialize power savings statistics for
+ * the given sched_domain, during load balancing.
+ *
+ * @sd: Sched domain whose power-savings statistics are to be initialized.
+ * @sds: Variable containing the statistics for sd.
+ * @idle: Idle status of the CPU at which we're performing load-balancing.
+ */
+static inline void init_sd_power_savings_stats(struct sched_domain *sd,
+ struct sd_lb_stats *sds, enum cpu_idle_type idle)
+{
+ /*
+ * Busy processors will not participate in power savings
+ * balance.
+ */
+ if (idle == CPU_NOT_IDLE || !(sd->flags & SD_POWERSAVINGS_BALANCE))
+ sds->power_savings_balance = 0;
+ else {
+ sds->power_savings_balance = 1;
+ sds->min_nr_running = ULONG_MAX;
+ sds->leader_nr_running = 0;
+ }
+}
+
+/**
+ * update_sd_power_savings_stats - Update the power saving stats for a
+ * sched_domain while performing load balancing.
+ *
+ * @group: sched_group belonging to the sched_domain under consideration.
+ * @sds: Variable containing the statistics of the sched_domain
+ * @local_group: Does group contain the CPU for which we're performing
+ * load balancing ?
+ * @sgs: Variable containing the statistics of the group.
+ */
+static inline void update_sd_power_savings_stats(struct sched_group *group,
+ struct sd_lb_stats *sds, int local_group, struct sg_lb_stats *sgs)
+{
+
+ if (!sds->power_savings_balance)
+ return;
+
+ /*
+ * If the local group is idle or completely loaded
+ * no need to do power savings balance at this domain
+ */
+ if (local_group && (sds->this_nr_running >= sgs->group_capacity ||
+ !sds->this_nr_running))
+ sds->power_savings_balance = 0;
+
+ /*
+ * If a group is already running at full capacity or idle,
+ * don't include that group in power savings calculations
+ */
+ if (!sds->power_savings_balance ||
+ sgs->sum_nr_running >= sgs->group_capacity ||
+ !sgs->sum_nr_running)
+ return;
+
+ /*
+ * Calculate the group which has the least non-idle load.
+ * This is the group from where we need to pick up the load
+ * for saving power
+ */
+ if ((sgs->sum_nr_running < sds->min_nr_running) ||
+ (sgs->sum_nr_running == sds->min_nr_running &&
+ group_first_cpu(group) > group_first_cpu(sds->group_min))) {
+ sds->group_min = group;
+ sds->min_nr_running = sgs->sum_nr_running;
+ sds->min_load_per_task = sgs->sum_weighted_load /
+ sgs->sum_nr_running;
+ }
+
+ /*
+ * Calculate the group which is almost near its
+ * capacity but still has some space to pick up some load
+ * from other group and save more power
+ */
+ if (sgs->sum_nr_running + 1 > sgs->group_capacity)
+ return;
+
+ if (sgs->sum_nr_running > sds->leader_nr_running ||
+ (sgs->sum_nr_running == sds->leader_nr_running &&
+ group_first_cpu(group) < group_first_cpu(sds->group_leader))) {
+ sds->group_leader = group;
+ sds->leader_nr_running = sgs->sum_nr_running;
}
+}
+
+/**
+ * check_power_save_busiest_group - see if there is potential for some power-savings balance
+ * @sds: Variable containing the statistics of the sched_domain
+ * under consideration.
+ * @this_cpu: Cpu at which we're currently performing load-balancing.
+ * @imbalance: Variable to store the imbalance.
+ *
+ * Description:
+ * Check if we have potential to perform some power-savings balance.
+ * If yes, set the busiest group to be the least loaded group in the
+ * sched_domain, so that it's CPUs can be put to idle.
+ *
+ * Returns 1 if there is potential to perform power-savings balance.
+ * Else returns 0.
+ */
+static inline int check_power_save_busiest_group(struct sd_lb_stats *sds,
+ int this_cpu, unsigned long *imbalance)
+{
+ if (!sds->power_savings_balance)
+ return 0;
+
+ if (sds->this != sds->group_leader ||
+ sds->group_leader == sds->group_min)
+ return 0;
+
+ *imbalance = sds->min_load_per_task;
+ sds->busiest = sds->group_min;
+
+ return 1;
+
+}
+#else /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */
+static inline void init_sd_power_savings_stats(struct sched_domain *sd,
+ struct sd_lb_stats *sds, enum cpu_idle_type idle)
+{
+ return;
+}
+
+static inline void update_sd_power_savings_stats(struct sched_group *group,
+ struct sd_lb_stats *sds, int local_group, struct sg_lb_stats *sgs)
+{
+ return;
+}
+static inline int check_power_save_busiest_group(struct sd_lb_stats *sds,
+ int this_cpu, unsigned long *imbalance)
+{
return 0;
}
+#endif /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */
-static void rq_online_fair(struct rq *rq)
+
+unsigned long default_scale_freq_power(struct sched_domain *sd, int cpu)
{
- update_sysctl();
+ return SCHED_LOAD_SCALE;
}
-static void rq_offline_fair(struct rq *rq)
+unsigned long __weak arch_scale_freq_power(struct sched_domain *sd, int cpu)
+{
+ return default_scale_freq_power(sd, cpu);
+}
+
+unsigned long default_scale_smt_power(struct sched_domain *sd, int cpu)
+{
+ unsigned long weight = cpumask_weight(sched_domain_span(sd));
+ unsigned long smt_gain = sd->smt_gain;
+
+ smt_gain /= weight;
+
+ return smt_gain;
+}
+
+unsigned long __weak arch_scale_smt_power(struct sched_domain *sd, int cpu)
+{
+ return default_scale_smt_power(sd, cpu);
+}
+
+unsigned long scale_rt_power(int cpu)
+{
+ struct rq *rq = cpu_rq(cpu);
+ u64 total, available;
+
+ sched_avg_update(rq);
+
+ total = sched_avg_period() + (rq->clock - rq->age_stamp);
+ available = total - rq->rt_avg;
+
+ if (unlikely((s64)total < SCHED_LOAD_SCALE))
+ total = SCHED_LOAD_SCALE;
+
+ total >>= SCHED_LOAD_SHIFT;
+
+ return div_u64(available, total);
+}
+
+static void update_cpu_power(struct sched_domain *sd, int cpu)
+{
+ unsigned long weight = cpumask_weight(sched_domain_span(sd));
+ unsigned long power = SCHED_LOAD_SCALE;
+ struct sched_group *sdg = sd->groups;
+
+ if (sched_feat(ARCH_POWER))
+ power *= arch_scale_freq_power(sd, cpu);
+ else
+ power *= default_scale_freq_power(sd, cpu);
+
+ power >>= SCHED_LOAD_SHIFT;
+
+ if ((sd->flags & SD_SHARE_CPUPOWER) && weight > 1) {
+ if (sched_feat(ARCH_POWER))
+ power *= arch_scale_smt_power(sd, cpu);
+ else
+ power *= default_scale_smt_power(sd, cpu);
+
+ power >>= SCHED_LOAD_SHIFT;
+ }
+
+ power *= scale_rt_power(cpu);
+ power >>= SCHED_LOAD_SHIFT;
+
+ if (!power)
+ power = 1;
+
+ sdg->cpu_power = power;
+}
+
+static void update_group_power(struct sched_domain *sd, int cpu)
+{
+ struct sched_domain *child = sd->child;
+ struct sched_group *group, *sdg = sd->groups;
+ unsigned long power;
+
+ if (!child) {
+ update_cpu_power(sd, cpu);
+ return;
+ }
+
+ power = 0;
+
+ group = child->groups;
+ do {
+ power += group->cpu_power;
+ group = group->next;
+ } while (group != child->groups);
+
+ sdg->cpu_power = power;
+}
+
+/**
+ * update_sg_lb_stats - Update sched_group's statistics for load balancing.
+ * @sd: The sched_domain whose statistics are to be updated.
+ * @group: sched_group whose statistics are to be updated.
+ * @this_cpu: Cpu for which load balance is currently performed.
+ * @idle: Idle status of this_cpu
+ * @load_idx: Load index of sched_domain of this_cpu for load calc.
+ * @sd_idle: Idle status of the sched_domain containing group.
+ * @local_group: Does group contain this_cpu.
+ * @cpus: Set of cpus considered for load balancing.
+ * @balance: Should we balance.
+ * @sgs: variable to hold the statistics for this group.
+ */
+static inline void update_sg_lb_stats(struct sched_domain *sd,
+ struct sched_group *group, int this_cpu,
+ enum cpu_idle_type idle, int load_idx, int *sd_idle,
+ int local_group, const struct cpumask *cpus,
+ int *balance, struct sg_lb_stats *sgs)
+{
+ unsigned long load, max_cpu_load, min_cpu_load;
+ int i;
+ unsigned int balance_cpu = -1, first_idle_cpu = 0;
+ unsigned long sum_avg_load_per_task;
+ unsigned long avg_load_per_task;
+
+ if (local_group)
+ balance_cpu = group_first_cpu(group);
+
+ /* Tally up the load of all CPUs in the group */
+ sum_avg_load_per_task = avg_load_per_task = 0;
+ max_cpu_load = 0;
+ min_cpu_load = ~0UL;
+
+ for_each_cpu_and(i, sched_group_cpus(group), cpus) {
+ struct rq *rq = cpu_rq(i);
+
+ if (*sd_idle && rq->nr_running)
+ *sd_idle = 0;
+
+ /* Bias balancing toward cpus of our domain */
+ if (local_group) {
+ if (idle_cpu(i) && !first_idle_cpu) {
+ first_idle_cpu = 1;
+ balance_cpu = i;
+ }
+
+ load = target_load(i, load_idx);
+ } else {
+ load = source_load(i, load_idx);
+ if (load > max_cpu_load)
+ max_cpu_load = load;
+ if (min_cpu_load > load)
+ min_cpu_load = load;
+ }
+
+ sgs->group_load += load;
+ sgs->sum_nr_running += rq->nr_running;
+ sgs->sum_weighted_load += weighted_cpuload(i);
+
+ sum_avg_load_per_task += cpu_avg_load_per_task(i);
+ }
+
+ /*
+ * First idle cpu or the first cpu(busiest) in this sched group
+ * is eligible for doing load balancing at this and above
+ * domains. In the newly idle case, we will allow all the cpu's
+ * to do the newly idle load balance.
+ */
+ if (idle != CPU_NEWLY_IDLE && local_group &&
+ balance_cpu != this_cpu) {
+ *balance = 0;
+ return;
+ }
+
+ update_group_power(sd, this_cpu);
+
+ /* Adjust by relative CPU power of the group */
+ sgs->avg_load = (sgs->group_load * SCHED_LOAD_SCALE) / group->cpu_power;
+
+
+ /*
+ * Consider the group unbalanced when the imbalance is larger
+ * than the average weight of two tasks.
+ *
+ * APZ: with cgroup the avg task weight can vary wildly and
+ * might not be a suitable number - should we keep a
+ * normalized nr_running number somewhere that negates
+ * the hierarchy?
+ */
+ avg_load_per_task = (sum_avg_load_per_task * SCHED_LOAD_SCALE) /
+ group->cpu_power;
+
+ if ((max_cpu_load - min_cpu_load) > 2*avg_load_per_task)
+ sgs->group_imb = 1;
+
+ sgs->group_capacity =
+ DIV_ROUND_CLOSEST(group->cpu_power, SCHED_LOAD_SCALE);
+}
+
+/**
+ * update_sd_lb_stats - Update sched_group's statistics for load balancing.
+ * @sd: sched_domain whose statistics are to be updated.
+ * @this_cpu: Cpu for which load balance is currently performed.
+ * @idle: Idle status of this_cpu
+ * @sd_idle: Idle status of the sched_domain containing group.
+ * @cpus: Set of cpus considered for load balancing.
+ * @balance: Should we balance.
+ * @sds: variable to hold the statistics for this sched_domain.
+ */
+static inline void update_sd_lb_stats(struct sched_domain *sd, int this_cpu,
+ enum cpu_idle_type idle, int *sd_idle,
+ const struct cpumask *cpus, int *balance,
+ struct sd_lb_stats *sds)
+{
+ struct sched_domain *child = sd->child;
+ struct sched_group *group = sd->groups;
+ struct sg_lb_stats sgs;
+ int load_idx, prefer_sibling = 0;
+
+ if (child && child->flags & SD_PREFER_SIBLING)
+ prefer_sibling = 1;
+
+ init_sd_power_savings_stats(sd, sds, idle);
+ load_idx = get_sd_load_idx(sd, idle);
+
+ do {
+ int local_group;
+
+ local_group = cpumask_test_cpu(this_cpu,
+ sched_group_cpus(group));
+ memset(&sgs, 0, sizeof(sgs));
+ update_sg_lb_stats(sd, group, this_cpu, idle, load_idx, sd_idle,
+ local_group, cpus, balance, &sgs);
+
+ if (local_group && !(*balance))
+ return;
+
+ sds->total_load += sgs.group_load;
+ sds->total_pwr += group->cpu_power;
+
+ /*
+ * In case the child domain prefers tasks go to siblings
+ * first, lower the group capacity to one so that we'll try
+ * and move all the excess tasks away.
+ */
+ if (prefer_sibling)
+ sgs.group_capacity = min(sgs.group_capacity, 1UL);
+
+ if (local_group) {
+ sds->this_load = sgs.avg_load;
+ sds->this = group;
+ sds->this_nr_running = sgs.sum_nr_running;
+ sds->this_load_per_task = sgs.sum_weighted_load;
+ } else if (sgs.avg_load > sds->max_load &&
+ (sgs.sum_nr_running > sgs.group_capacity ||
+ sgs.group_imb)) {
+ sds->max_load = sgs.avg_load;
+ sds->busiest = group;
+ sds->busiest_nr_running = sgs.sum_nr_running;
+ sds->busiest_load_per_task = sgs.sum_weighted_load;
+ sds->group_imb = sgs.group_imb;
+ }
+
+ update_sd_power_savings_stats(group, sds, local_group, &sgs);
+ group = group->next;
+ } while (group != sd->groups);
+}
+
+/**
+ * fix_small_imbalance - Calculate the minor imbalance that exists
+ * amongst the groups of a sched_domain, during
+ * load balancing.
+ * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
+ * @this_cpu: The cpu at whose sched_domain we're performing load-balance.
+ * @imbalance: Variable to store the imbalance.
+ */
+static inline void fix_small_imbalance(struct sd_lb_stats *sds,
+ int this_cpu, unsigned long *imbalance)
+{
+ unsigned long tmp, pwr_now = 0, pwr_move = 0;
+ unsigned int imbn = 2;
+
+ if (sds->this_nr_running) {
+ sds->this_load_per_task /= sds->this_nr_running;
+ if (sds->busiest_load_per_task >
+ sds->this_load_per_task)
+ imbn = 1;
+ } else
+ sds->this_load_per_task =
+ cpu_avg_load_per_task(this_cpu);
+
+ if (sds->max_load - sds->this_load + sds->busiest_load_per_task >=
+ sds->busiest_load_per_task * imbn) {
+ *imbalance = sds->busiest_load_per_task;
+ return;
+ }
+
+ /*
+ * OK, we don't have enough imbalance to justify moving tasks,
+ * however we may be able to increase total CPU power used by
+ * moving them.
+ */
+
+ pwr_now += sds->busiest->cpu_power *
+ min(sds->busiest_load_per_task, sds->max_load);
+ pwr_now += sds->this->cpu_power *
+ min(sds->this_load_per_task, sds->this_load);
+ pwr_now /= SCHED_LOAD_SCALE;
+
+ /* Amount of load we'd subtract */
+ tmp = (sds->busiest_load_per_task * SCHED_LOAD_SCALE) /
+ sds->busiest->cpu_power;
+ if (sds->max_load > tmp)
+ pwr_move += sds->busiest->cpu_power *
+ min(sds->busiest_load_per_task, sds->max_load - tmp);
+
+ /* Amount of load we'd add */
+ if (sds->max_load * sds->busiest->cpu_power <
+ sds->busiest_load_per_task * SCHED_LOAD_SCALE)
+ tmp = (sds->max_load * sds->busiest->cpu_power) /
+ sds->this->cpu_power;
+ else
+ tmp = (sds->busiest_load_per_task * SCHED_LOAD_SCALE) /
+ sds->this->cpu_power;
+ pwr_move += sds->this->cpu_power *
+ min(sds->this_load_per_task, sds->this_load + tmp);
+ pwr_move /= SCHED_LOAD_SCALE;
+
+ /* Move if we gain throughput */
+ if (pwr_move > pwr_now)
+ *imbalance = sds->busiest_load_per_task;
+}
+
+/**
+ * calculate_imbalance - Calculate the amount of imbalance present within the
+ * groups of a given sched_domain during load balance.
+ * @sds: statistics of the sched_domain whose imbalance is to be calculated.
+ * @this_cpu: Cpu for which currently load balance is being performed.
+ * @imbalance: The variable to store the imbalance.
+ */
+static inline void calculate_imbalance(struct sd_lb_stats *sds, int this_cpu,
+ unsigned long *imbalance)
+{
+ unsigned long max_pull;
+ /*
+ * In the presence of smp nice balancing, certain scenarios can have
+ * max load less than avg load(as we skip the groups at or below
+ * its cpu_power, while calculating max_load..)
+ */
+ if (sds->max_load < sds->avg_load) {
+ *imbalance = 0;
+ return fix_small_imbalance(sds, this_cpu, imbalance);
+ }
+
+ /* Don't want to pull so many tasks that a group would go idle */
+ max_pull = min(sds->max_load - sds->avg_load,
+ sds->max_load - sds->busiest_load_per_task);
+
+ /* How much load to actually move to equalise the imbalance */
+ *imbalance = min(max_pull * sds->busiest->cpu_power,
+ (sds->avg_load - sds->this_load) * sds->this->cpu_power)
+ / SCHED_LOAD_SCALE;
+
+ /*
+ * if *imbalance is less than the average load per runnable task
+ * there is no gaurantee that any tasks will be moved so we'll have
+ * a think about bumping its value to force at least one task to be
+ * moved
+ */
+ if (*imbalance < sds->busiest_load_per_task)
+ return fix_small_imbalance(sds, this_cpu, imbalance);
+
+}
+/******* find_busiest_group() helpers end here *********************/
+
+/**
+ * find_busiest_group - Returns the busiest group within the sched_domain
+ * if there is an imbalance. If there isn't an imbalance, and
+ * the user has opted for power-savings, it returns a group whose
+ * CPUs can be put to idle by rebalancing those tasks elsewhere, if
+ * such a group exists.
+ *
+ * Also calculates the amount of weighted load which should be moved
+ * to restore balance.
+ *
+ * @sd: The sched_domain whose busiest group is to be returned.
+ * @this_cpu: The cpu for which load balancing is currently being performed.
+ * @imbalance: Variable which stores amount of weighted load which should
+ * be moved to restore balance/put a group to idle.
+ * @idle: The idle status of this_cpu.
+ * @sd_idle: The idleness of sd
+ * @cpus: The set of CPUs under consideration for load-balancing.
+ * @balance: Pointer to a variable indicating if this_cpu
+ * is the appropriate cpu to perform load balancing at this_level.
+ *
+ * Returns: - the busiest group if imbalance exists.
+ * - If no imbalance and user has opted for power-savings balance,
+ * return the least loaded group whose CPUs can be
+ * put to idle by rebalancing its tasks onto our group.
+ */
+static struct sched_group *
+find_busiest_group(struct sched_domain *sd, int this_cpu,
+ unsigned long *imbalance, enum cpu_idle_type idle,
+ int *sd_idle, const struct cpumask *cpus, int *balance)
+{
+ struct sd_lb_stats sds;
+
+ memset(&sds, 0, sizeof(sds));
+
+ /*
+ * Compute the various statistics relavent for load balancing at
+ * this level.
+ */
+ update_sd_lb_stats(sd, this_cpu, idle, sd_idle, cpus,
+ balance, &sds);
+
+ /* Cases where imbalance does not exist from POV of this_cpu */
+ /* 1) this_cpu is not the appropriate cpu to perform load balancing
+ * at this level.
+ * 2) There is no busy sibling group to pull from.
+ * 3) This group is the busiest group.
+ * 4) This group is more busy than the avg busieness at this
+ * sched_domain.
+ * 5) The imbalance is within the specified limit.
+ * 6) Any rebalance would lead to ping-pong
+ */
+ if (!(*balance))
+ goto ret;
+
+ if (!sds.busiest || sds.busiest_nr_running == 0)
+ goto out_balanced;
+
+ if (sds.this_load >= sds.max_load)
+ goto out_balanced;
+
+ sds.avg_load = (SCHED_LOAD_SCALE * sds.total_load) / sds.total_pwr;
+
+ if (sds.this_load >= sds.avg_load)
+ goto out_balanced;
+
+ if (100 * sds.max_load <= sd->imbalance_pct * sds.this_load)
+ goto out_balanced;
+
+ sds.busiest_load_per_task /= sds.busiest_nr_running;
+ if (sds.group_imb)
+ sds.busiest_load_per_task =
+ min(sds.busiest_load_per_task, sds.avg_load);
+
+ /*
+ * We're trying to get all the cpus to the average_load, so we don't
+ * want to push ourselves above the average load, nor do we wish to
+ * reduce the max loaded cpu below the average load, as either of these
+ * actions would just result in more rebalancing later, and ping-pong
+ * tasks around. Thus we look for the minimum possible imbalance.
+ * Negative imbalances (*we* are more loaded than anyone else) will
+ * be counted as no imbalance for these purposes -- we can't fix that
+ * by pulling tasks to us. Be careful of negative numbers as they'll
+ * appear as very large values with unsigned longs.
+ */
+ if (sds.max_load <= sds.busiest_load_per_task)
+ goto out_balanced;
+
+ /* Looks like there is an imbalance. Compute it */
+ calculate_imbalance(&sds, this_cpu, imbalance);
+ return sds.busiest;
+
+out_balanced:
+ /*
+ * There is no obvious imbalance. But check if we can do some balancing
+ * to save power.
+ */
+ if (check_power_save_busiest_group(&sds, this_cpu, imbalance))
+ return sds.busiest;
+ret:
+ *imbalance = 0;
+ return NULL;
+}
+
+/*
+ * find_busiest_queue - find the busiest runqueue among the cpus in group.
+ */
+static struct rq *
+find_busiest_queue(struct sched_group *group, enum cpu_idle_type idle,
+ unsigned long imbalance, const struct cpumask *cpus)
+{
+ struct rq *busiest = NULL, *rq;
+ unsigned long max_load = 0;
+ int i;
+
+ for_each_cpu(i, sched_group_cpus(group)) {
+ unsigned long power = power_of(i);
+ unsigned long capacity = DIV_ROUND_CLOSEST(power, SCHED_LOAD_SCALE);
+ unsigned long wl;
+
+ if (!cpumask_test_cpu(i, cpus))
+ continue;
+
+ rq = cpu_rq(i);
- wl = weighted_cpuload(i) * SCHED_LOAD_SCALE;
- wl /= power;
++ wl = weighted_cpuload(i);
+
++ /*
++ * When comparing with imbalance, use weighted_cpuload()
++ * which is not scaled with the cpu power.
++ */
+ if (capacity && rq->nr_running == 1 && wl > imbalance)
+ continue;
+
++ /*
++ * For the load comparisons with the other cpu's, consider
++ * the weighted_cpuload() scaled with the cpu power, so that
++ * the load can be moved away from the cpu that is potentially
++ * running at a lower capacity.
++ */
++ wl = (wl * SCHED_LOAD_SCALE) / power;
++
+ if (wl > max_load) {
+ max_load = wl;
+ busiest = rq;
+ }
+ }
+
+ return busiest;
+}
+
+/*
+ * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
+ * so long as it is large enough.
+ */
+#define MAX_PINNED_INTERVAL 512
+
+/* Working cpumask for load_balance and load_balance_newidle. */
+static DEFINE_PER_CPU(cpumask_var_t, load_balance_tmpmask);
+
+static int need_active_balance(struct sched_domain *sd, int sd_idle, int idle)
+{
+ if (idle == CPU_NEWLY_IDLE) {
+ /*
+ * The only task running in a non-idle cpu can be moved to this
+ * cpu in an attempt to completely freeup the other CPU
+ * package.
+ *
+ * The package power saving logic comes from
+ * find_busiest_group(). If there are no imbalance, then
+ * f_b_g() will return NULL. However when sched_mc={1,2} then
+ * f_b_g() will select a group from which a running task may be
+ * pulled to this cpu in order to make the other package idle.
+ * If there is no opportunity to make a package idle and if
+ * there are no imbalance, then f_b_g() will return NULL and no
+ * action will be taken in load_balance_newidle().
+ *
+ * Under normal task pull operation due to imbalance, there
+ * will be more than one task in the source run queue and
+ * move_tasks() will succeed. ld_moved will be true and this
+ * active balance code will not be triggered.
+ */
+ if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
+ !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
+ return 0;
+
+ if (sched_mc_power_savings < POWERSAVINGS_BALANCE_WAKEUP)
+ return 0;
+ }
+
+ return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
+}
+
+/*
+ * Check this_cpu to ensure it is balanced within domain. Attempt to move
+ * tasks if there is an imbalance.
+ */
+static int load_balance(int this_cpu, struct rq *this_rq,
+ struct sched_domain *sd, enum cpu_idle_type idle,
+ int *balance)
+{
+ int ld_moved, all_pinned = 0, active_balance = 0, sd_idle = 0;
+ struct sched_group *group;
+ unsigned long imbalance;
+ struct rq *busiest;
+ unsigned long flags;
+ struct cpumask *cpus = __get_cpu_var(load_balance_tmpmask);
+
+ cpumask_copy(cpus, cpu_active_mask);
+
+ /*
+ * When power savings policy is enabled for the parent domain, idle
+ * sibling can pick up load irrespective of busy siblings. In this case,
+ * let the state of idle sibling percolate up as CPU_IDLE, instead of
+ * portraying it as CPU_NOT_IDLE.
+ */
+ if (idle != CPU_NOT_IDLE && sd->flags & SD_SHARE_CPUPOWER &&
+ !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
+ sd_idle = 1;
+
+ schedstat_inc(sd, lb_count[idle]);
+
+redo:
+ update_shares(sd);
+ group = find_busiest_group(sd, this_cpu, &imbalance, idle, &sd_idle,
+ cpus, balance);
+
+ if (*balance == 0)
+ goto out_balanced;
+
+ if (!group) {
+ schedstat_inc(sd, lb_nobusyg[idle]);
+ goto out_balanced;
+ }
+
+ busiest = find_busiest_queue(group, idle, imbalance, cpus);
+ if (!busiest) {
+ schedstat_inc(sd, lb_nobusyq[idle]);
+ goto out_balanced;
+ }
+
+ BUG_ON(busiest == this_rq);
+
+ schedstat_add(sd, lb_imbalance[idle], imbalance);
+
+ ld_moved = 0;
+ if (busiest->nr_running > 1) {
+ /*
+ * Attempt to move tasks. If find_busiest_group has found
+ * an imbalance but busiest->nr_running <= 1, the group is
+ * still unbalanced. ld_moved simply stays zero, so it is
+ * correctly treated as an imbalance.
+ */
+ local_irq_save(flags);
+ double_rq_lock(this_rq, busiest);
+ ld_moved = move_tasks(this_rq, this_cpu, busiest,
+ imbalance, sd, idle, &all_pinned);
+ double_rq_unlock(this_rq, busiest);
+ local_irq_restore(flags);
+
+ /*
+ * some other cpu did the load balance for us.
+ */
+ if (ld_moved && this_cpu != smp_processor_id())
+ resched_cpu(this_cpu);
+
+ /* All tasks on this runqueue were pinned by CPU affinity */
+ if (unlikely(all_pinned)) {
+ cpumask_clear_cpu(cpu_of(busiest), cpus);
+ if (!cpumask_empty(cpus))
+ goto redo;
+ goto out_balanced;
+ }
+ }
+
+ if (!ld_moved) {
+ schedstat_inc(sd, lb_failed[idle]);
+ sd->nr_balance_failed++;
+
+ if (need_active_balance(sd, sd_idle, idle)) {
+ raw_spin_lock_irqsave(&busiest->lock, flags);
+
+ /* don't kick the migration_thread, if the curr
+ * task on busiest cpu can't be moved to this_cpu
+ */
+ if (!cpumask_test_cpu(this_cpu,
+ &busiest->curr->cpus_allowed)) {
+ raw_spin_unlock_irqrestore(&busiest->lock,
+ flags);
+ all_pinned = 1;
+ goto out_one_pinned;
+ }
+
+ if (!busiest->active_balance) {
+ busiest->active_balance = 1;
+ busiest->push_cpu = this_cpu;
+ active_balance = 1;
+ }
+ raw_spin_unlock_irqrestore(&busiest->lock, flags);
+ if (active_balance)
+ wake_up_process(busiest->migration_thread);
+
+ /*
+ * We've kicked active balancing, reset the failure
+ * counter.
+ */
+ sd->nr_balance_failed = sd->cache_nice_tries+1;
+ }
+ } else
+ sd->nr_balance_failed = 0;
+
+ if (likely(!active_balance)) {
+ /* We were unbalanced, so reset the balancing interval */
+ sd->balance_interval = sd->min_interval;
+ } else {
+ /*
+ * If we've begun active balancing, start to back off. This
+ * case may not be covered by the all_pinned logic if there
+ * is only 1 task on the busy runqueue (because we don't call
+ * move_tasks).
+ */
+ if (sd->balance_interval < sd->max_interval)
+ sd->balance_interval *= 2;
+ }
+
+ if (!ld_moved && !sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
+ !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
+ ld_moved = -1;
+
+ goto out;
+
+out_balanced:
+ schedstat_inc(sd, lb_balanced[idle]);
+
+ sd->nr_balance_failed = 0;
+
+out_one_pinned:
+ /* tune up the balancing interval */
+ if ((all_pinned && sd->balance_interval < MAX_PINNED_INTERVAL) ||
+ (sd->balance_interval < sd->max_interval))
+ sd->balance_interval *= 2;
+
+ if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
+ !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
+ ld_moved = -1;
+ else
+ ld_moved = 0;
+out:
+ if (ld_moved)
+ update_shares(sd);
+ return ld_moved;
+}
+
+/*
+ * idle_balance is called by schedule() if this_cpu is about to become
+ * idle. Attempts to pull tasks from other CPUs.
+ */
+static void idle_balance(int this_cpu, struct rq *this_rq)
+{
+ struct sched_domain *sd;
+ int pulled_task = 0;
+ unsigned long next_balance = jiffies + HZ;
+
+ this_rq->idle_stamp = this_rq->clock;
+
+ if (this_rq->avg_idle < sysctl_sched_migration_cost)
+ return;
+
+ /*
+ * Drop the rq->lock, but keep IRQ/preempt disabled.
+ */
+ raw_spin_unlock(&this_rq->lock);
+
+ for_each_domain(this_cpu, sd) {
+ unsigned long interval;
+ int balance = 1;
+
+ if (!(sd->flags & SD_LOAD_BALANCE))
+ continue;
+
+ if (sd->flags & SD_BALANCE_NEWIDLE) {
+ /* If we've pulled tasks over stop searching: */
+ pulled_task = load_balance(this_cpu, this_rq,
+ sd, CPU_NEWLY_IDLE, &balance);
+ }
+
+ interval = msecs_to_jiffies(sd->balance_interval);
+ if (time_after(next_balance, sd->last_balance + interval))
+ next_balance = sd->last_balance + interval;
+ if (pulled_task) {
+ this_rq->idle_stamp = 0;
+ break;
+ }
+ }
+
+ raw_spin_lock(&this_rq->lock);
+
+ if (pulled_task || time_after(jiffies, this_rq->next_balance)) {
+ /*
+ * We are going idle. next_balance may be set based on
+ * a busy processor. So reset next_balance.
+ */
+ this_rq->next_balance = next_balance;
+ }
+}
+
+/*
+ * active_load_balance is run by migration threads. It pushes running tasks
+ * off the busiest CPU onto idle CPUs. It requires at least 1 task to be
+ * running on each physical CPU where possible, and avoids physical /
+ * logical imbalances.
+ *
+ * Called with busiest_rq locked.
+ */
+static void active_load_balance(struct rq *busiest_rq, int busiest_cpu)
+{
+ int target_cpu = busiest_rq->push_cpu;
+ struct sched_domain *sd;
+ struct rq *target_rq;
+
+ /* Is there any task to move? */
+ if (busiest_rq->nr_running <= 1)
+ return;
+
+ target_rq = cpu_rq(target_cpu);
+
+ /*
+ * This condition is "impossible", if it occurs
+ * we need to fix it. Originally reported by
+ * Bjorn Helgaas on a 128-cpu setup.
+ */
+ BUG_ON(busiest_rq == target_rq);
+
+ /* move a task from busiest_rq to target_rq */
+ double_lock_balance(busiest_rq, target_rq);
+ update_rq_clock(busiest_rq);
+ update_rq_clock(target_rq);
+
+ /* Search for an sd spanning us and the target CPU. */
+ for_each_domain(target_cpu, sd) {
+ if ((sd->flags & SD_LOAD_BALANCE) &&
+ cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
+ break;
+ }
+
+ if (likely(sd)) {
+ schedstat_inc(sd, alb_count);
+
+ if (move_one_task(target_rq, target_cpu, busiest_rq,
+ sd, CPU_IDLE))
+ schedstat_inc(sd, alb_pushed);
+ else
+ schedstat_inc(sd, alb_failed);
+ }
+ double_unlock_balance(busiest_rq, target_rq);
+}
+
+#ifdef CONFIG_NO_HZ
+static struct {
+ atomic_t load_balancer;
+ cpumask_var_t cpu_mask;
+ cpumask_var_t ilb_grp_nohz_mask;
+} nohz ____cacheline_aligned = {
+ .load_balancer = ATOMIC_INIT(-1),
+};
+
+int get_nohz_load_balancer(void)
+{
+ return atomic_read(&nohz.load_balancer);
+}
+
+#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
+/**
+ * lowest_flag_domain - Return lowest sched_domain containing flag.
+ * @cpu: The cpu whose lowest level of sched domain is to
+ * be returned.
+ * @flag: The flag to check for the lowest sched_domain
+ * for the given cpu.
+ *
+ * Returns the lowest sched_domain of a cpu which contains the given flag.
+ */
+static inline struct sched_domain *lowest_flag_domain(int cpu, int flag)
+{
+ struct sched_domain *sd;
+
+ for_each_domain(cpu, sd)
+ if (sd && (sd->flags & flag))
+ break;
+
+ return sd;
+}
+
+/**
+ * for_each_flag_domain - Iterates over sched_domains containing the flag.
+ * @cpu: The cpu whose domains we're iterating over.
+ * @sd: variable holding the value of the power_savings_sd
+ * for cpu.
+ * @flag: The flag to filter the sched_domains to be iterated.
+ *
+ * Iterates over all the scheduler domains for a given cpu that has the 'flag'
+ * set, starting from the lowest sched_domain to the highest.
+ */
+#define for_each_flag_domain(cpu, sd, 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.ilb_grp_nohz_mask, nohz.cpu_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.ilb_grp_nohz_mask))
+ return 0;
+
+ if (cpumask_equal(nohz.ilb_grp_nohz_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.
+ *
+ * Returns: Returns the id of the idle load balancer if it exists,
+ * Else, returns >= nr_cpu_ids.
+ *
+ * This algorithm picks the idle load balancer such that it belongs to a
+ * semi-idle powersavings sched_domain. The idea is to try and avoid
+ * completely idle packages/cores just for the purpose of idle load balancing
+ * when there are other idle cpu's which are better suited for that job.
+ */
+static int find_new_ilb(int cpu)
+{
+ struct sched_domain *sd;
+ struct sched_group *ilb_group;
+
+ /*
+ * Have idle load balancer selection from semi-idle packages only
+ * when power-aware load balancing is enabled
+ */
+ if (!(sched_smt_power_savings || sched_mc_power_savings))
+ goto out_done;
+
+ /*
+ * Optimize for the case when we have no idle CPUs or only one
+ * idle CPU. Don't walk the sched_domain hierarchy in such cases
+ */
+ if (cpumask_weight(nohz.cpu_mask) < 2)
+ goto out_done;
+
+ for_each_flag_domain(cpu, sd, SD_POWERSAVINGS_BALANCE) {
+ ilb_group = sd->groups;
+
+ do {
+ if (is_semi_idle_group(ilb_group))
+ return cpumask_first(nohz.ilb_grp_nohz_mask);
+
+ ilb_group = ilb_group->next;
+
+ } while (ilb_group != sd->groups);
+ }
+
+out_done:
+ return cpumask_first(nohz.cpu_mask);
+}
+#else /* (CONFIG_SCHED_MC || CONFIG_SCHED_SMT) */
+static inline int find_new_ilb(int call_cpu)
+{
+ return cpumask_first(nohz.cpu_mask);
+}
+#endif
+
+/*
+ * This routine will try to nominate the ilb (idle load balancing)
+ * owner among the cpus whose ticks are stopped. ilb owner will do the idle
+ * load balancing on behalf of all those cpus. If all the cpus in the system
+ * go into this tickless mode, then there will be no ilb owner (as there is
+ * no need for one) and all the cpus will sleep till the next wakeup event
+ * arrives...
+ *
+ * For the ilb owner, tick is not stopped. And this tick will be used
+ * for idle load balancing. ilb owner will still be part of
+ * nohz.cpu_mask..
+ *
+ * While stopping the tick, this cpu will become the ilb owner if there
+ * is no other owner. And will be the owner till that cpu becomes busy
+ * or if all cpus in the system stop their ticks at which point
+ * there is no need for ilb owner.
+ *
+ * When the ilb owner becomes busy, it nominates another owner, during the
+ * next busy scheduler_tick()
+ */
+int select_nohz_load_balancer(int stop_tick)
+{
+ int cpu = smp_processor_id();
+
+ if (stop_tick) {
+ cpu_rq(cpu)->in_nohz_recently = 1;
+
+ if (!cpu_active(cpu)) {
+ if (atomic_read(&nohz.load_balancer) != cpu)
+ return 0;
+
+ /*
+ * If we are going offline and still the leader,
+ * give up!
+ */
+ if (atomic_cmpxchg(&nohz.load_balancer, cpu, -1) != cpu)
+ BUG();
+
+ return 0;
+ }
+
+ cpumask_set_cpu(cpu, nohz.cpu_mask);
+
+ /* time for ilb owner also to sleep */
+ if (cpumask_weight(nohz.cpu_mask) == num_active_cpus()) {
+ if (atomic_read(&nohz.load_balancer) == cpu)
+ atomic_set(&nohz.load_balancer, -1);
+ return 0;
+ }
+
+ if (atomic_read(&nohz.load_balancer) == -1) {
+ /* make me the ilb owner */
+ if (atomic_cmpxchg(&nohz.load_balancer, -1, cpu) == -1)
+ return 1;
+ } else if (atomic_read(&nohz.load_balancer) == cpu) {
+ int new_ilb;
+
+ if (!(sched_smt_power_savings ||
+ sched_mc_power_savings))
+ return 1;
+ /*
+ * Check to see if there is a more power-efficient
+ * ilb.
+ */
+ new_ilb = find_new_ilb(cpu);
+ if (new_ilb < nr_cpu_ids && new_ilb != cpu) {
+ atomic_set(&nohz.load_balancer, -1);
+ resched_cpu(new_ilb);
+ return 0;
+ }
+ return 1;
+ }
+ } else {
+ if (!cpumask_test_cpu(cpu, nohz.cpu_mask))
+ return 0;
+
+ cpumask_clear_cpu(cpu, nohz.cpu_mask);
+
+ if (atomic_read(&nohz.load_balancer) == cpu)
+ if (atomic_cmpxchg(&nohz.load_balancer, cpu, -1) != cpu)
+ BUG();
+ }
+ return 0;
+}
+#endif
+
+static DEFINE_SPINLOCK(balancing);
+
+/*
+ * It checks each scheduling domain to see if it is due to be balanced,
+ * and initiates a balancing operation if so.
+ *
+ * Balancing parameters are set up in arch_init_sched_domains.
+ */
+static void rebalance_domains(int cpu, enum cpu_idle_type idle)
+{
+ int balance = 1;
+ struct rq *rq = cpu_rq(cpu);
+ unsigned long interval;
+ struct sched_domain *sd;
+ /* Earliest time when we have to do rebalance again */
+ unsigned long next_balance = jiffies + 60*HZ;
+ int update_next_balance = 0;
+ int need_serialize;
+
+ for_each_domain(cpu, sd) {
+ if (!(sd->flags & SD_LOAD_BALANCE))
+ continue;
+
+ interval = sd->balance_interval;
+ if (idle != CPU_IDLE)
+ interval *= sd->busy_factor;
+
+ /* scale ms to jiffies */
+ interval = msecs_to_jiffies(interval);
+ if (unlikely(!interval))
+ interval = 1;
+ if (interval > HZ*NR_CPUS/10)
+ interval = HZ*NR_CPUS/10;
+
+ need_serialize = sd->flags & SD_SERIALIZE;
+
+ if (need_serialize) {
+ if (!spin_trylock(&balancing))
+ goto out;
+ }
+
+ if (time_after_eq(jiffies, sd->last_balance + interval)) {
+ if (load_balance(cpu, rq, sd, idle, &balance)) {
+ /*
+ * We've pulled tasks over so either we're no
+ * longer idle, or one of our SMT siblings is
+ * not idle.
+ */
+ idle = CPU_NOT_IDLE;
+ }
+ sd->last_balance = jiffies;
+ }
+ if (need_serialize)
+ spin_unlock(&balancing);
+out:
+ if (time_after(next_balance, sd->last_balance + interval)) {
+ next_balance = sd->last_balance + interval;
+ update_next_balance = 1;
+ }
+
+ /*
+ * Stop the load balance at this level. There is another
+ * CPU in our sched group which is doing load balancing more
+ * actively.
+ */
+ if (!balance)
+ break;
+ }
+
+ /*
+ * next_balance will be updated only when there is a need.
+ * When the cpu is attached to null domain for ex, it will not be
+ * updated.
+ */
+ if (likely(update_next_balance))
+ rq->next_balance = next_balance;
+}
+
+/*
+ * run_rebalance_domains is triggered when needed from the scheduler tick.
+ * In CONFIG_NO_HZ case, the idle load balance owner will do the
+ * rebalancing for all the cpus for whom scheduler ticks are stopped.
+ */
+static void run_rebalance_domains(struct softirq_action *h)
+{
+ int this_cpu = smp_processor_id();
+ struct rq *this_rq = cpu_rq(this_cpu);
+ enum cpu_idle_type idle = this_rq->idle_at_tick ?
+ CPU_IDLE : CPU_NOT_IDLE;
+
+ rebalance_domains(this_cpu, idle);
+
+#ifdef CONFIG_NO_HZ
+ /*
+ * If this cpu is the owner for idle load balancing, then do the
+ * balancing on behalf of the other idle cpus whose ticks are
+ * stopped.
+ */
+ if (this_rq->idle_at_tick &&
+ atomic_read(&nohz.load_balancer) == this_cpu) {
+ struct rq *rq;
+ int balance_cpu;
+
+ for_each_cpu(balance_cpu, nohz.cpu_mask) {
+ if (balance_cpu == this_cpu)
+ continue;
+
+ /*
+ * If this cpu gets work to do, stop the load balancing
+ * work being done for other cpus. Next load
+ * balancing owner will pick it up.
+ */
+ if (need_resched())
+ break;
+
+ rebalance_domains(balance_cpu, CPU_IDLE);
+
+ rq = cpu_rq(balance_cpu);
+ if (time_after(this_rq->next_balance, rq->next_balance))
+ this_rq->next_balance = rq->next_balance;
+ }
+ }
+#endif
+}
+
+static inline int on_null_domain(int cpu)
+{
+ return !rcu_dereference(cpu_rq(cpu)->sd);
+}
+
+/*
+ * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
+ *
+ * In case of CONFIG_NO_HZ, this is the place where we nominate a new
+ * idle load balancing owner or decide to stop the periodic load balancing,
+ * if the whole system is idle.
+ */
+static inline void trigger_load_balance(struct rq *rq, int cpu)
+{
+#ifdef CONFIG_NO_HZ
+ /*
+ * If we were in the nohz mode recently and busy at the current
+ * scheduler tick, then check if we need to nominate new idle
+ * load balancer.
+ */
+ if (rq->in_nohz_recently && !rq->idle_at_tick) {
+ rq->in_nohz_recently = 0;
+
+ if (atomic_read(&nohz.load_balancer) == cpu) {
+ cpumask_clear_cpu(cpu, nohz.cpu_mask);
+ atomic_set(&nohz.load_balancer, -1);
+ }
+
+ if (atomic_read(&nohz.load_balancer) == -1) {
+ int ilb = find_new_ilb(cpu);
+
+ if (ilb < nr_cpu_ids)
+ resched_cpu(ilb);
+ }
+ }
+
+ /*
+ * If this cpu is idle and doing idle load balancing for all the
+ * cpus with ticks stopped, is it time for that to stop?
+ */
+ if (rq->idle_at_tick && atomic_read(&nohz.load_balancer) == cpu &&
+ cpumask_weight(nohz.cpu_mask) == num_online_cpus()) {
+ resched_cpu(cpu);
+ return;
+ }
+
+ /*
+ * If this cpu is idle and the idle load balancing is done by
+ * someone else, then no need raise the SCHED_SOFTIRQ
+ */
+ if (rq->idle_at_tick && atomic_read(&nohz.load_balancer) != cpu &&
+ cpumask_test_cpu(cpu, nohz.cpu_mask))
+ return;
+#endif
+ /* Don't need to rebalance while attached to NULL domain */
+ if (time_after_eq(jiffies, rq->next_balance) &&
+ likely(!on_null_domain(cpu)))
+ raise_softirq(SCHED_SOFTIRQ);
+}
+
+static void rq_online_fair(struct rq *rq)
+{
+ update_sysctl();
+}
+
+static void rq_offline_fair(struct rq *rq)
+{
+ update_sysctl();
+}
+
+#else /* CONFIG_SMP */
+
+/*
+ * on UP we do not need to balance between CPUs:
+ */
+static inline void idle_balance(int cpu, struct rq *rq)
{
- update_sysctl();
}
#endif /* CONFIG_SMP */
git://ftp.safe.ca / safe / jmp / linux-2.6 / commitdiff