sched: rt-group: synchonised bandwidth period
Various SMP balancing algorithms require that the bandwidth period
run in sync.
Possible improvements are moving the rt_bandwidth thing into root_domain
and keeping a span per rt_bandwidth which marks throttled cpus.
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 e813e84..bb20323 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -115,6 +115,11 @@
*/
#define DEF_TIMESLICE (100 * HZ / 1000)
+/*
+ * single value that denotes runtime == period, ie unlimited time.
+ */
+#define RUNTIME_INF ((u64)~0ULL)
+
#ifdef CONFIG_SMP
/*
* Divide a load by a sched group cpu_power : (load / sg->__cpu_power)
@@ -156,6 +161,80 @@
struct list_head queue[MAX_RT_PRIO];
};
+struct rt_bandwidth {
+ ktime_t rt_period;
+ u64 rt_runtime;
+ struct hrtimer rt_period_timer;
+};
+
+static struct rt_bandwidth def_rt_bandwidth;
+
+static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun);
+
+static enum hrtimer_restart sched_rt_period_timer(struct hrtimer *timer)
+{
+ struct rt_bandwidth *rt_b =
+ container_of(timer, struct rt_bandwidth, rt_period_timer);
+ ktime_t now;
+ int overrun;
+ int idle = 0;
+
+ for (;;) {
+ now = hrtimer_cb_get_time(timer);
+ overrun = hrtimer_forward(timer, now, rt_b->rt_period);
+
+ if (!overrun)
+ break;
+
+ idle = do_sched_rt_period_timer(rt_b, overrun);
+ }
+
+ return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
+}
+
+static
+void init_rt_bandwidth(struct rt_bandwidth *rt_b, u64 period, u64 runtime)
+{
+ rt_b->rt_period = ns_to_ktime(period);
+ rt_b->rt_runtime = runtime;
+
+ hrtimer_init(&rt_b->rt_period_timer,
+ CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+ rt_b->rt_period_timer.function = sched_rt_period_timer;
+ rt_b->rt_period_timer.cb_mode = HRTIMER_CB_IRQSAFE_NO_SOFTIRQ;
+}
+
+static void start_rt_bandwidth(struct rt_bandwidth *rt_b)
+{
+ ktime_t now;
+
+ if (rt_b->rt_runtime == RUNTIME_INF)
+ return;
+
+ if (hrtimer_active(&rt_b->rt_period_timer))
+ return;
+
+ spin_lock(&rt_b->rt_runtime_lock);
+ for (;;) {
+ if (hrtimer_active(&rt_b->rt_period_timer))
+ break;
+
+ now = hrtimer_cb_get_time(&rt_b->rt_period_timer);
+ hrtimer_forward(&rt_b->rt_period_timer, now, rt_b->rt_period);
+ hrtimer_start(&rt_b->rt_period_timer,
+ rt_b->rt_period_timer.expires,
+ HRTIMER_MODE_ABS);
+ }
+ spin_unlock(&rt_b->rt_runtime_lock);
+}
+
+#ifdef CONFIG_RT_GROUP_SCHED
+static void destroy_rt_bandwidth(struct rt_bandwidth *rt_b)
+{
+ hrtimer_cancel(&rt_b->rt_period_timer);
+}
+#endif
+
#ifdef CONFIG_GROUP_SCHED
#include <linux/cgroup.h>
@@ -182,7 +261,7 @@
struct sched_rt_entity **rt_se;
struct rt_rq **rt_rq;
- u64 rt_runtime;
+ struct rt_bandwidth rt_bandwidth;
#endif
struct rcu_head rcu;
@@ -407,8 +486,6 @@
struct cfs_rq cfs;
struct rt_rq rt;
- u64 rt_period_expire;
- int rt_throttled;
#ifdef CONFIG_FAIR_GROUP_SCHED
/* list of leaf cfs_rq on this cpu: */
@@ -592,23 +669,6 @@
#define task_rq(p) cpu_rq(task_cpu(p))
#define cpu_curr(cpu) (cpu_rq(cpu)->curr)
-unsigned long rt_needs_cpu(int cpu)
-{
- struct rq *rq = cpu_rq(cpu);
- u64 delta;
-
- if (!rq->rt_throttled)
- return 0;
-
- if (rq->clock > rq->rt_period_expire)
- return 1;
-
- delta = rq->rt_period_expire - rq->clock;
- do_div(delta, NSEC_PER_SEC / HZ);
-
- return (unsigned long)delta;
-}
-
/*
* Tunables that become constants when CONFIG_SCHED_DEBUG is off:
*/
@@ -664,10 +724,18 @@
*/
int sysctl_sched_rt_runtime = 950000;
-/*
- * single value that denotes runtime == period, ie unlimited time.
- */
-#define RUNTIME_INF ((u64)~0ULL)
+static inline u64 global_rt_period(void)
+{
+ return (u64)sysctl_sched_rt_period * NSEC_PER_USEC;
+}
+
+static inline u64 global_rt_runtime(void)
+{
+ if (sysctl_sched_rt_period < 0)
+ return RUNTIME_INF;
+
+ return (u64)sysctl_sched_rt_runtime * NSEC_PER_USEC;
+}
static const unsigned long long time_sync_thresh = 100000;
@@ -3854,7 +3922,6 @@
update_last_tick_seen(rq);
update_cpu_load(rq);
curr->sched_class->task_tick(rq, curr, 0);
- update_sched_rt_period(rq);
spin_unlock(&rq->lock);
#ifdef CONFIG_SMP
@@ -4689,7 +4756,7 @@
* Do not allow realtime tasks into groups that have no runtime
* assigned.
*/
- if (rt_policy(policy) && task_group(p)->rt_runtime == 0)
+ if (rt_policy(policy) && task_group(p)->rt_bandwidth.rt_runtime == 0)
return -EPERM;
#endif
@@ -7288,6 +7355,14 @@
init_defrootdomain();
#endif
+ init_rt_bandwidth(&def_rt_bandwidth,
+ global_rt_period(), global_rt_runtime());
+
+#ifdef CONFIG_RT_GROUP_SCHED
+ init_rt_bandwidth(&init_task_group.rt_bandwidth,
+ global_rt_period(), global_rt_runtime());
+#endif
+
#ifdef CONFIG_GROUP_SCHED
list_add(&init_task_group.list, &task_groups);
#endif
@@ -7312,15 +7387,11 @@
#endif
#ifdef CONFIG_RT_GROUP_SCHED
- init_task_group.rt_runtime =
- sysctl_sched_rt_runtime * NSEC_PER_USEC;
INIT_LIST_HEAD(&rq->leaf_rt_rq_list);
init_tg_rt_entry(rq, &init_task_group,
&per_cpu(init_rt_rq, i),
&per_cpu(init_sched_rt_entity, i), i, 1);
#endif
- rq->rt_period_expire = 0;
- rq->rt_throttled = 0;
for (j = 0; j < CPU_LOAD_IDX_MAX; j++)
rq->cpu_load[j] = 0;
@@ -7506,8 +7577,6 @@
#endif
-#ifdef CONFIG_GROUP_SCHED
-
#ifdef CONFIG_FAIR_GROUP_SCHED
static void free_fair_sched_group(struct task_group *tg)
{
@@ -7596,6 +7665,8 @@
{
int i;
+ destroy_rt_bandwidth(&tg->rt_bandwidth);
+
for_each_possible_cpu(i) {
if (tg->rt_rq)
kfree(tg->rt_rq[i]);
@@ -7621,7 +7692,8 @@
if (!tg->rt_se)
goto err;
- tg->rt_runtime = 0;
+ init_rt_bandwidth(&tg->rt_bandwidth,
+ ktime_to_ns(def_rt_bandwidth.rt_period), 0);
for_each_possible_cpu(i) {
rq = cpu_rq(i);
@@ -7674,6 +7746,7 @@
}
#endif
+#ifdef CONFIG_GROUP_SCHED
static void free_sched_group(struct task_group *tg)
{
free_fair_sched_group(tg);
@@ -7775,6 +7848,7 @@
task_rq_unlock(rq, &flags);
}
+#endif
#ifdef CONFIG_FAIR_GROUP_SCHED
static void set_se_shares(struct sched_entity *se, unsigned long shares)
@@ -7871,16 +7945,15 @@
struct task_group *tgi;
unsigned long total = 0;
unsigned long global_ratio =
- to_ratio(sysctl_sched_rt_period,
- sysctl_sched_rt_runtime < 0 ?
- RUNTIME_INF : sysctl_sched_rt_runtime);
+ to_ratio(global_rt_period(), global_rt_runtime());
rcu_read_lock();
list_for_each_entry_rcu(tgi, &task_groups, list) {
if (tgi == tg)
continue;
- total += to_ratio(period, tgi->rt_runtime);
+ total += to_ratio(ktime_to_ns(tgi->rt_bandwidth.rt_period),
+ tgi->rt_bandwidth.rt_runtime);
}
rcu_read_unlock();
@@ -7898,16 +7971,11 @@
return 0;
}
-int sched_group_set_rt_runtime(struct task_group *tg, long rt_runtime_us)
+static int tg_set_bandwidth(struct task_group *tg,
+ u64 rt_period, u64 rt_runtime)
{
- u64 rt_runtime, rt_period;
int err = 0;
- rt_period = (u64)sysctl_sched_rt_period * NSEC_PER_USEC;
- rt_runtime = (u64)rt_runtime_us * NSEC_PER_USEC;
- if (rt_runtime_us == -1)
- rt_runtime = RUNTIME_INF;
-
mutex_lock(&rt_constraints_mutex);
read_lock(&tasklist_lock);
if (rt_runtime_us == 0 && tg_has_rt_tasks(tg)) {
@@ -7918,7 +7986,8 @@
err = -EINVAL;
goto unlock;
}
- tg->rt_runtime = rt_runtime;
+ tg->rt_bandwidth.rt_period = ns_to_ktime(rt_period);
+ tg->rt_bandwidth.rt_runtime = rt_runtime;
unlock:
read_unlock(&tasklist_lock);
mutex_unlock(&rt_constraints_mutex);
@@ -7926,19 +7995,96 @@
return err;
}
+int sched_group_set_rt_runtime(struct task_group *tg, long rt_runtime_us)
+{
+ u64 rt_runtime, rt_period;
+
+ rt_period = ktime_to_ns(tg->rt_bandwidth.rt_period);
+ rt_runtime = (u64)rt_runtime_us * NSEC_PER_USEC;
+ if (rt_runtime_us < 0)
+ rt_runtime = RUNTIME_INF;
+
+ return tg_set_bandwidth(tg, rt_period, rt_runtime);
+}
+
long sched_group_rt_runtime(struct task_group *tg)
{
u64 rt_runtime_us;
- if (tg->rt_runtime == RUNTIME_INF)
+ if (tg->rt_bandwidth.rt_runtime == RUNTIME_INF)
return -1;
- rt_runtime_us = tg->rt_runtime;
+ rt_runtime_us = tg->rt_bandwidth.rt_runtime;
do_div(rt_runtime_us, NSEC_PER_USEC);
return rt_runtime_us;
}
+
+int sched_group_set_rt_period(struct task_group *tg, long rt_period_us)
+{
+ u64 rt_runtime, rt_period;
+
+ rt_period = (u64)rt_period_us * NSEC_PER_USEC;
+ rt_runtime = tg->rt_bandwidth.rt_runtime;
+
+ return tg_set_bandwidth(tg, rt_period, rt_runtime);
+}
+
+long sched_group_rt_period(struct task_group *tg)
+{
+ u64 rt_period_us;
+
+ rt_period_us = ktime_to_ns(tg->rt_bandwidth.rt_period);
+ do_div(rt_period_us, NSEC_PER_USEC);
+ return rt_period_us;
+}
+
+static int sched_rt_global_constraints(void)
+{
+ int ret = 0;
+
+ mutex_lock(&rt_constraints_mutex);
+ if (!__rt_schedulable(NULL, 1, 0))
+ ret = -EINVAL;
+ mutex_unlock(&rt_constraints_mutex);
+
+ return ret;
+}
+#else
+static int sched_rt_global_constraints(void)
+{
+ return 0;
+}
#endif
-#endif /* CONFIG_GROUP_SCHED */
+
+int sched_rt_handler(struct ctl_table *table, int write,
+ struct file *filp, void __user *buffer, size_t *lenp,
+ loff_t *ppos)
+{
+ int ret;
+ int old_period, old_runtime;
+ static DEFINE_MUTEX(mutex);
+
+ mutex_lock(&mutex);
+ old_period = sysctl_sched_rt_period;
+ old_runtime = sysctl_sched_rt_runtime;
+
+ ret = proc_dointvec(table, write, filp, buffer, lenp, ppos);
+
+ if (!ret && write) {
+ ret = sched_rt_global_constraints();
+ if (ret) {
+ sysctl_sched_rt_period = old_period;
+ sysctl_sched_rt_runtime = old_runtime;
+ } else {
+ def_rt_bandwidth.rt_runtime = global_rt_runtime();
+ def_rt_bandwidth.rt_period =
+ ns_to_ktime(global_rt_period());
+ }
+ }
+ mutex_unlock(&mutex);
+
+ return ret;
+}
#ifdef CONFIG_CGROUP_SCHED
@@ -7988,7 +8134,7 @@
{
#ifdef CONFIG_RT_GROUP_SCHED
/* Don't accept realtime tasks when there is no way for them to run */
- if (rt_task(tsk) && cgroup_tg(cgrp)->rt_runtime == 0)
+ if (rt_task(tsk) && cgroup_tg(cgrp)->rt_bandwidth.rt_runtime == 0)
return -EINVAL;
#else
/* We don't support RT-tasks being in separate groups */
@@ -8066,6 +8212,17 @@
return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
}
+
+static int cpu_rt_period_write_uint(struct cgroup *cgrp, struct cftype *cftype,
+ u64 rt_period_us)
+{
+ return sched_group_set_rt_period(cgroup_tg(cgrp), rt_period_us);
+}
+
+static u64 cpu_rt_period_read_uint(struct cgroup *cgrp, struct cftype *cft)
+{
+ return sched_group_rt_period(cgroup_tg(cgrp));
+}
#endif
static struct cftype cpu_files[] = {
@@ -8082,6 +8239,11 @@
.read = cpu_rt_runtime_read,
.write = cpu_rt_runtime_write,
},
+ {
+ .name = "rt_period_us",
+ .read_uint = cpu_rt_period_read_uint,
+ .write_uint = cpu_rt_period_write_uint,
+ },
#endif
};