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sched: rt time limit

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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>
This commit is contained in:
Peter Zijlstra
2008-01-25 21:08:29 +01:00
committed by Ingo Molnar
parent 8f4d37ec07
commit fa85ae2418
4 changed files with 122 additions and 21 deletions
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53
kernel/sched_rt.c
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@@ -45,6 +45,50 @@ static void update_rt_migration(struct rq *rq)
}
#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 @@ static void update_curr_rt(struct rq *rq)
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 @@ static struct task_struct *pick_next_task_rt(struct rq *rq)
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;