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_rt.c b/kernel/sched_rt.c
index 8bc1761..6928ded 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -62,7 +62,12 @@
if (!rt_rq->tg)
return RUNTIME_INF;
- return rt_rq->tg->rt_bandwidth.rt_runtime;
+ return rt_rq->rt_runtime;
+}
+
+static inline u64 sched_rt_period(struct rt_rq *rt_rq)
+{
+ return ktime_to_ns(rt_rq->tg->rt_bandwidth.rt_period);
}
#define for_each_leaf_rt_rq(rt_rq, rq) \
@@ -145,11 +150,21 @@
return container_of(rt_b, struct task_group, rt_bandwidth)->rt_rq[cpu];
}
+static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
+{
+ return &rt_rq->tg->rt_bandwidth;
+}
+
#else
static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
{
- return def_rt_bandwidth.rt_runtime;
+ return rt_rq->rt_runtime;
+}
+
+static inline u64 sched_rt_period(struct rt_rq *rt_rq)
+{
+ return ktime_to_ns(def_rt_bandwidth.rt_period);
}
#define for_each_leaf_rt_rq(rt_rq, rq) \
@@ -200,6 +215,11 @@
return &cpu_rq(cpu)->rt;
}
+static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
+{
+ return &def_rt_bandwidth;
+}
+
#endif
static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
@@ -218,8 +238,10 @@
spin_lock(&rq->lock);
if (rt_rq->rt_time) {
- u64 runtime = rt_b->rt_runtime;
+ u64 runtime;
+ spin_lock(&rt_rq->rt_runtime_lock);
+ runtime = rt_rq->rt_runtime;
rt_rq->rt_time -= min(rt_rq->rt_time, overrun*runtime);
if (rt_rq->rt_throttled && rt_rq->rt_time < runtime) {
rt_rq->rt_throttled = 0;
@@ -227,6 +249,7 @@
}
if (rt_rq->rt_time || rt_rq->rt_nr_running)
idle = 0;
+ spin_unlock(&rt_rq->rt_runtime_lock);
}
if (enqueue)
@@ -237,6 +260,47 @@
return idle;
}
+#ifdef CONFIG_SMP
+static int balance_runtime(struct rt_rq *rt_rq)
+{
+ struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
+ struct root_domain *rd = cpu_rq(smp_processor_id())->rd;
+ int i, weight, more = 0;
+ u64 rt_period;
+
+ weight = cpus_weight(rd->span);
+
+ spin_lock(&rt_b->rt_runtime_lock);
+ rt_period = ktime_to_ns(rt_b->rt_period);
+ for_each_cpu_mask(i, rd->span) {
+ struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
+ s64 diff;
+
+ if (iter == rt_rq)
+ continue;
+
+ spin_lock(&iter->rt_runtime_lock);
+ diff = iter->rt_runtime - iter->rt_time;
+ if (diff > 0) {
+ do_div(diff, weight);
+ if (rt_rq->rt_runtime + diff > rt_period)
+ diff = rt_period - rt_rq->rt_runtime;
+ iter->rt_runtime -= diff;
+ rt_rq->rt_runtime += diff;
+ more = 1;
+ if (rt_rq->rt_runtime == rt_period) {
+ spin_unlock(&iter->rt_runtime_lock);
+ break;
+ }
+ }
+ spin_unlock(&iter->rt_runtime_lock);
+ }
+ spin_unlock(&rt_b->rt_runtime_lock);
+
+ return more;
+}
+#endif
+
static inline int rt_se_prio(struct sched_rt_entity *rt_se)
{
#ifdef CONFIG_RT_GROUP_SCHED
@@ -259,6 +323,22 @@
if (rt_rq->rt_throttled)
return rt_rq_throttled(rt_rq);
+ if (sched_rt_runtime(rt_rq) >= sched_rt_period(rt_rq))
+ return 0;
+
+#ifdef CONFIG_SMP
+ if (rt_rq->rt_time > runtime) {
+ int more;
+
+ spin_unlock(&rt_rq->rt_runtime_lock);
+ more = balance_runtime(rt_rq);
+ spin_lock(&rt_rq->rt_runtime_lock);
+
+ if (more)
+ runtime = sched_rt_runtime(rt_rq);
+ }
+#endif
+
if (rt_rq->rt_time > runtime) {
rt_rq->rt_throttled = 1;
if (rt_rq_throttled(rt_rq)) {
@@ -294,9 +374,11 @@
curr->se.exec_start = rq->clock;
cpuacct_charge(curr, delta_exec);
+ spin_lock(&rt_rq->rt_runtime_lock);
rt_rq->rt_time += delta_exec;
if (sched_rt_runtime_exceeded(rt_rq))
resched_task(curr);
+ spin_unlock(&rt_rq->rt_runtime_lock);
}
static inline