sched: rt-group: smp balancing
Currently the rt group scheduling does a per cpu runtime limit, however
the rt load balancer makes no guarantees about an equal spread of real-
time tasks, just that at any one time, the highest priority tasks run.
Solve this by making the runtime limit a global property by borrowing
excessive runtime from the other cpus once the local limit runs out.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/sched.c b/kernel/sched.c
index bb20323..313cd4f 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -164,6 +164,7 @@
struct rt_bandwidth {
ktime_t rt_period;
u64 rt_runtime;
+ spinlock_t rt_runtime_lock;
struct hrtimer rt_period_timer;
};
@@ -198,6 +199,8 @@
rt_b->rt_period = ns_to_ktime(period);
rt_b->rt_runtime = runtime;
+ spin_lock_init(&rt_b->rt_runtime_lock);
+
hrtimer_init(&rt_b->rt_period_timer,
CLOCK_MONOTONIC, HRTIMER_MODE_REL);
rt_b->rt_period_timer.function = sched_rt_period_timer;
@@ -414,6 +417,8 @@
#endif
int rt_throttled;
u64 rt_time;
+ u64 rt_runtime;
+ spinlock_t rt_runtime_lock;
#ifdef CONFIG_RT_GROUP_SCHED
unsigned long rt_nr_boosted;
@@ -7299,6 +7304,8 @@
rt_rq->rt_time = 0;
rt_rq->rt_throttled = 0;
+ rt_rq->rt_runtime = 0;
+ spin_lock_init(&rt_rq->rt_runtime_lock);
#ifdef CONFIG_RT_GROUP_SCHED
rt_rq->rt_nr_boosted = 0;
@@ -7335,6 +7342,7 @@
init_rt_rq(rt_rq, rq);
rt_rq->tg = tg;
rt_rq->rt_se = rt_se;
+ rt_rq->rt_runtime = tg->rt_bandwidth.rt_runtime;
if (add)
list_add(&rt_rq->leaf_rt_rq_list, &rq->leaf_rt_rq_list);
@@ -7391,6 +7399,8 @@
init_tg_rt_entry(rq, &init_task_group,
&per_cpu(init_rt_rq, i),
&per_cpu(init_sched_rt_entity, i), i, 1);
+#else
+ rq->rt.rt_runtime = def_rt_bandwidth.rt_runtime;
#endif
for (j = 0; j < CPU_LOAD_IDX_MAX; j++)
@@ -7974,11 +7984,11 @@
static int tg_set_bandwidth(struct task_group *tg,
u64 rt_period, u64 rt_runtime)
{
- int err = 0;
+ int i, err = 0;
mutex_lock(&rt_constraints_mutex);
read_lock(&tasklist_lock);
- if (rt_runtime_us == 0 && tg_has_rt_tasks(tg)) {
+ if (rt_runtime == 0 && tg_has_rt_tasks(tg)) {
err = -EBUSY;
goto unlock;
}
@@ -7986,8 +7996,19 @@
err = -EINVAL;
goto unlock;
}
+
+ spin_lock_irq(&tg->rt_bandwidth.rt_runtime_lock);
tg->rt_bandwidth.rt_period = ns_to_ktime(rt_period);
tg->rt_bandwidth.rt_runtime = rt_runtime;
+
+ for_each_possible_cpu(i) {
+ struct rt_rq *rt_rq = tg->rt_rq[i];
+
+ spin_lock(&rt_rq->rt_runtime_lock);
+ rt_rq->rt_runtime = rt_runtime;
+ spin_unlock(&rt_rq->rt_runtime_lock);
+ }
+ spin_unlock_irq(&tg->rt_bandwidth.rt_runtime_lock);
unlock:
read_unlock(&tasklist_lock);
mutex_unlock(&rt_constraints_mutex);
@@ -8052,6 +8073,19 @@
#else
static int sched_rt_global_constraints(void)
{
+ unsigned long flags;
+ int i;
+
+ spin_lock_irqsave(&def_rt_bandwidth.rt_runtime_lock, flags);
+ for_each_possible_cpu(i) {
+ struct rt_rq *rt_rq = &cpu_rq(i)->rt;
+
+ spin_lock(&rt_rq->rt_runtime_lock);
+ rt_rq->rt_runtime = global_rt_runtime();
+ spin_unlock(&rt_rq->rt_runtime_lock);
+ }
+ spin_unlock_irqrestore(&def_rt_bandwidth.rt_runtime_lock, flags);
+
return 0;
}
#endif
@@ -8168,7 +8202,7 @@
#endif
#ifdef CONFIG_RT_GROUP_SCHED
-static int cpu_rt_runtime_write(struct cgroup *cgrp, struct cftype *cft,
+static ssize_t cpu_rt_runtime_write(struct cgroup *cgrp, struct cftype *cft,
struct file *file,
const char __user *userbuf,
size_t nbytes, loff_t *unused_ppos)