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 <[EMAIL PROTECTED]>
---
kernel/sched.c | 38 ++++++++++++++++++++++-
kernel/sched_rt.c | 88 ++++++++++++++++++++++++++++++++++++++++++++++++++++--
2 files changed, 121 insertions(+), 5 deletions(-)
Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -169,6 +169,7 @@ static inline ktime_t ns_to_ktime(u64 ns
struct rt_bandwidth {
ktime_t rt_period;
u64 rt_runtime;
+ spinlock_t rt_runtime_lock;
struct hrtimer rt_period_timer;
};
@@ -203,6 +204,8 @@ void init_rt_bandwidth(struct rt_bandwid
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;
@@ -471,6 +474,8 @@ struct rt_rq {
#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;
@@ -7216,6 +7221,8 @@ static void init_rt_rq(struct rt_rq *rt_
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;
@@ -7252,6 +7259,7 @@ static void init_tg_rt_entry(struct rq *
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);
@@ -7307,6 +7315,8 @@ void __init sched_init(void)
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++)
@@ -8007,15 +8017,26 @@ static int __rt_schedulable(struct task_
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);
if (!__rt_schedulable(tg, rt_period, rt_runtime)) {
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:
mutex_unlock(&rt_constraints_mutex);
@@ -8079,6 +8100,19 @@ static int sched_rt_global_constraints(v
#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
@@ -8195,7 +8229,7 @@ static u64 cpu_shares_read_uint(struct c
#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)
Index: linux-2.6/kernel/sched_rt.c
===================================================================
--- linux-2.6.orig/kernel/sched_rt.c
+++ linux-2.6/kernel/sched_rt.c
@@ -62,7 +62,12 @@ static inline u64 sched_rt_runtime(struc
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 @@ struct rt_rq *sched_rt_period_rt_rq(stru
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 @@ struct rt_rq *sched_rt_period_rt_rq(stru
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 @@ static int do_sched_rt_period_timer(stru
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 @@ static int do_sched_rt_period_timer(stru
}
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 @@ static int do_sched_rt_period_timer(stru
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) {
+ 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 @@ static int sched_rt_runtime_exceeded(str
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 @@ static void update_curr_rt(struct rq *rq
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
--
--
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