+#ifdef CONFIG_SMP
+/*
+ * distribute shares of all task groups among their schedulable entities,
+ * to reflect load distribution across cpus.
+ */
+static int rebalance_shares(struct sched_domain *sd, int this_cpu)
+{
+ struct cfs_rq *cfs_rq;
+ struct rq *rq = cpu_rq(this_cpu);
+ cpumask_t sdspan = sd->span;
+ int balanced = 1;
+
+ /* Walk thr' all the task groups that we have */
+ for_each_leaf_cfs_rq(rq, cfs_rq) {
+ int i;
+ unsigned long total_load = 0, total_shares;
+ struct task_group *tg = cfs_rq->tg;
+
+ /* Gather total task load of this group across cpus */
+ for_each_cpu_mask(i, sdspan)
+ total_load += tg->cfs_rq[i]->load.weight;
+
+ /* Nothing to do if this group has no load */
+ if (!total_load)
+ continue;
+
+ /*
+ * tg->shares represents the number of cpu shares the task group
+ * is eligible to hold on a single cpu. On N cpus, it is
+ * eligible to hold (N * tg->shares) number of cpu shares.
+ */
+ total_shares = tg->shares * cpus_weight(sdspan);
+
+ /*
+ * redistribute total_shares across cpus as per the task load
+ * distribution.
+ */
+ for_each_cpu_mask(i, sdspan) {
+ unsigned long local_load, local_shares;
+
+ local_load = tg->cfs_rq[i]->load.weight;
+ local_shares = (local_load * total_shares) / total_load;
+ if (!local_shares)
+ local_shares = MIN_GROUP_SHARES;
+ if (local_shares == tg->se[i]->load.weight)
+ continue;
+
+ spin_lock_irq(&cpu_rq(i)->lock);
+ set_se_shares(tg->se[i], local_shares);
+ spin_unlock_irq(&cpu_rq(i)->lock);
+ balanced = 0;
+ }
+ }
+
+ return balanced;
+}
+
+/*
+ * How frequently should we rebalance_shares() across cpus?
+ *
+ * The more frequently we rebalance shares, the more accurate is the fairness
+ * of cpu bandwidth distribution between task groups. However higher frequency
+ * also implies increased scheduling overhead.
+ *
+ * sysctl_sched_min_bal_int_shares represents the minimum interval between
+ * consecutive calls to rebalance_shares() in the same sched domain.
+ *
+ * sysctl_sched_max_bal_int_shares represents the maximum interval between
+ * consecutive calls to rebalance_shares() in the same sched domain.
+ *
+ * These settings allows for the appropriate trade-off between accuracy of
+ * fairness and the associated overhead.
+ *
+ */
+
+/* default: 8ms, units: milliseconds */
+const_debug unsigned int sysctl_sched_min_bal_int_shares = 8;
+
+/* default: 128ms, units: milliseconds */
+const_debug unsigned int sysctl_sched_max_bal_int_shares = 128;
+
+/* kernel thread that runs rebalance_shares() periodically */
+static int load_balance_monitor(void *unused)
+{
+ unsigned int timeout = sysctl_sched_min_bal_int_shares;
+ struct sched_param schedparm;
+ int ret;
+
+ /*
+ * We don't want this thread's execution to be limited by the shares
+ * assigned to default group (init_task_group). Hence make it run
+ * as a SCHED_RR RT task at the lowest priority.
+ */
+ schedparm.sched_priority = 1;
+ ret = sched_setscheduler(current, SCHED_RR, &schedparm);
+ if (ret)
+ printk(KERN_ERR "Couldn't set SCHED_RR policy for load balance"
+ " monitor thread (error = %d) \n", ret);
+
+ while (!kthread_should_stop()) {
+ int i, cpu, balanced = 1;
+
+ /* Prevent cpus going down or coming up */
+ get_online_cpus();
+ /* lockout changes to doms_cur[] array */
+ lock_doms_cur();
+ /*
+ * Enter a rcu read-side critical section to safely walk rq->sd
+ * chain on various cpus and to walk task group list
+ * (rq->leaf_cfs_rq_list) in rebalance_shares().
+ */
+ rcu_read_lock();
+
+ for (i = 0; i < ndoms_cur; i++) {
+ cpumask_t cpumap = doms_cur[i];
+ struct sched_domain *sd = NULL, *sd_prev = NULL;
+
+ cpu = first_cpu(cpumap);
+
+ /* Find the highest domain at which to balance shares */
+ for_each_domain(cpu, sd) {
+ if (!(sd->flags & SD_LOAD_BALANCE))
+ continue;
+ sd_prev = sd;
+ }
+
+ sd = sd_prev;
+ /* sd == NULL? No load balance reqd in this domain */
+ if (!sd)
+ continue;
+
+ balanced &= rebalance_shares(sd, cpu);
+ }
+
+ rcu_read_unlock();
+
+ unlock_doms_cur();
+ put_online_cpus();
+
+ if (!balanced)
+ timeout = sysctl_sched_min_bal_int_shares;
+ else if (timeout < sysctl_sched_max_bal_int_shares)
+ timeout *= 2;
+
+ msleep_interruptible(timeout);
+ }
+
+ return 0;
+}
+#endif /* CONFIG_SMP */
+
+static void free_sched_group(struct task_group *tg)
+{
+ int i;
+
+ for_each_possible_cpu(i) {
+ if (tg->cfs_rq)
+ kfree(tg->cfs_rq[i]);
+ if (tg->se)
+ kfree(tg->se[i]);
+ if (tg->rt_rq)
+ kfree(tg->rt_rq[i]);
+ if (tg->rt_se)
+ kfree(tg->rt_se[i]);
+ }
+
+ kfree(tg->cfs_rq);
+ kfree(tg->se);
+ kfree(tg->rt_rq);
+ kfree(tg->rt_se);
+ kfree(tg);
+}
+