sched: rt time limit
Very simple time limit on the realtime scheduling classes.
Allow the rq's realtime class to consume sched_rt_ratio of every
sched_rt_period slice. If the class exceeds this quota the fair class
will preempt the realtime class.
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 83fbbcb..fd10d96 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -45,6 +45,50 @@
}
#endif /* CONFIG_SMP */
+static int sched_rt_ratio_exceeded(struct rq *rq, struct rt_rq *rt_rq)
+{
+ u64 period, ratio;
+
+ if (sysctl_sched_rt_ratio == SCHED_RT_FRAC)
+ return 0;
+
+ if (rt_rq->rt_throttled)
+ return 1;
+
+ period = (u64)sysctl_sched_rt_period * NSEC_PER_MSEC;
+ ratio = (period * sysctl_sched_rt_ratio) >> SCHED_RT_FRAC_SHIFT;
+
+ if (rt_rq->rt_time > ratio) {
+ rt_rq->rt_throttled = rq->clock + period - rt_rq->rt_time;
+ return 1;
+ }
+
+ return 0;
+}
+
+static void update_sched_rt_period(struct rq *rq)
+{
+ while (rq->clock > rq->rt_period_expire) {
+ u64 period, ratio;
+
+ period = (u64)sysctl_sched_rt_period * NSEC_PER_MSEC;
+ ratio = (period * sysctl_sched_rt_ratio) >> SCHED_RT_FRAC_SHIFT;
+
+ rq->rt.rt_time -= min(rq->rt.rt_time, ratio);
+ rq->rt_period_expire += period;
+ }
+
+ /*
+ * When the rt throttle is expired, let them rip.
+ * (XXX: use hrtick when available)
+ */
+ if (rq->rt.rt_throttled && rq->clock > rq->rt.rt_throttled) {
+ rq->rt.rt_throttled = 0;
+ if (!sched_rt_ratio_exceeded(rq, &rq->rt))
+ resched_task(rq->curr);
+ }
+}
+
/*
* Update the current task's runtime statistics. Skip current tasks that
* are not in our scheduling class.
@@ -66,6 +110,11 @@
curr->se.sum_exec_runtime += delta_exec;
curr->se.exec_start = rq->clock;
cpuacct_charge(curr, delta_exec);
+
+ rq->rt.rt_time += delta_exec;
+ update_sched_rt_period(rq);
+ if (sched_rt_ratio_exceeded(rq, &rq->rt))
+ resched_task(curr);
}
static inline void inc_rt_tasks(struct task_struct *p, struct rq *rq)
@@ -208,8 +257,12 @@
struct rt_prio_array *array = &rq->rt.active;
struct task_struct *next;
struct list_head *queue;
+ struct rt_rq *rt_rq = &rq->rt;
int idx;
+ if (sched_rt_ratio_exceeded(rq, rt_rq))
+ return NULL;
+
idx = sched_find_first_bit(array->bitmap);
if (idx >= MAX_RT_PRIO)
return NULL;
