![Peter Zijlstra](/assets/img/avatar_default.png)
Extend group scheduling to also cover the realtime classes. It uses the time limiting introduced by the previous patch to allow multiple realtime groups. The hard time limit is required to keep behaviour deterministic. The algorithms used make the realtime scheduler O(tg), linear scaling wrt the number of task groups. This is the worst case behaviour I can't seem to get out of, the avg. case of the algorithms can be improved, I focused on correctness and worst case. [ akpm@linux-foundation.org: move side-effects out of BUG_ON(). ] Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
1203 lines
28 KiB
C
1203 lines
28 KiB
C
/*
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* Real-Time Scheduling Class (mapped to the SCHED_FIFO and SCHED_RR
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* policies)
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*/
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#ifdef CONFIG_SMP
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static inline int rt_overloaded(struct rq *rq)
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{
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return atomic_read(&rq->rd->rto_count);
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}
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static inline void rt_set_overload(struct rq *rq)
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{
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cpu_set(rq->cpu, rq->rd->rto_mask);
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/*
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* Make sure the mask is visible before we set
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* the overload count. That is checked to determine
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* if we should look at the mask. It would be a shame
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* if we looked at the mask, but the mask was not
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* updated yet.
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*/
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wmb();
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atomic_inc(&rq->rd->rto_count);
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}
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static inline void rt_clear_overload(struct rq *rq)
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{
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/* the order here really doesn't matter */
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atomic_dec(&rq->rd->rto_count);
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cpu_clear(rq->cpu, rq->rd->rto_mask);
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}
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static void update_rt_migration(struct rq *rq)
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{
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if (rq->rt.rt_nr_migratory && (rq->rt.rt_nr_running > 1)) {
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if (!rq->rt.overloaded) {
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rt_set_overload(rq);
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rq->rt.overloaded = 1;
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}
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} else if (rq->rt.overloaded) {
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rt_clear_overload(rq);
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rq->rt.overloaded = 0;
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}
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}
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#endif /* CONFIG_SMP */
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static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
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{
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return container_of(rt_se, struct task_struct, rt);
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}
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static inline int on_rt_rq(struct sched_rt_entity *rt_se)
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{
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return !list_empty(&rt_se->run_list);
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}
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#ifdef CONFIG_FAIR_GROUP_SCHED
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static inline unsigned int sched_rt_ratio(struct rt_rq *rt_rq)
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{
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if (!rt_rq->tg)
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return SCHED_RT_FRAC;
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return rt_rq->tg->rt_ratio;
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}
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#define for_each_leaf_rt_rq(rt_rq, rq) \
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list_for_each_entry(rt_rq, &rq->leaf_rt_rq_list, leaf_rt_rq_list)
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static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
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{
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return rt_rq->rq;
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}
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static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
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{
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return rt_se->rt_rq;
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}
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#define for_each_sched_rt_entity(rt_se) \
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for (; rt_se; rt_se = rt_se->parent)
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static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
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{
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return rt_se->my_q;
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}
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static void enqueue_rt_entity(struct sched_rt_entity *rt_se);
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static void dequeue_rt_entity(struct sched_rt_entity *rt_se);
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static void sched_rt_ratio_enqueue(struct rt_rq *rt_rq)
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{
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struct sched_rt_entity *rt_se = rt_rq->rt_se;
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if (rt_se && !on_rt_rq(rt_se) && rt_rq->rt_nr_running) {
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enqueue_rt_entity(rt_se);
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resched_task(rq_of_rt_rq(rt_rq)->curr);
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}
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}
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static void sched_rt_ratio_dequeue(struct rt_rq *rt_rq)
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{
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struct sched_rt_entity *rt_se = rt_rq->rt_se;
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if (rt_se && on_rt_rq(rt_se))
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dequeue_rt_entity(rt_se);
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}
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#else
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static inline unsigned int sched_rt_ratio(struct rt_rq *rt_rq)
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{
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return sysctl_sched_rt_ratio;
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}
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#define for_each_leaf_rt_rq(rt_rq, rq) \
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for (rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
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static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
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{
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return container_of(rt_rq, struct rq, rt);
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}
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static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
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{
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struct task_struct *p = rt_task_of(rt_se);
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struct rq *rq = task_rq(p);
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return &rq->rt;
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}
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#define for_each_sched_rt_entity(rt_se) \
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for (; rt_se; rt_se = NULL)
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static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
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{
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return NULL;
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}
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static inline void sched_rt_ratio_enqueue(struct rt_rq *rt_rq)
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{
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}
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static inline void sched_rt_ratio_dequeue(struct rt_rq *rt_rq)
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{
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}
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#endif
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static inline int rt_se_prio(struct sched_rt_entity *rt_se)
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{
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#ifdef CONFIG_FAIR_GROUP_SCHED
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struct rt_rq *rt_rq = group_rt_rq(rt_se);
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if (rt_rq)
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return rt_rq->highest_prio;
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#endif
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return rt_task_of(rt_se)->prio;
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}
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static int sched_rt_ratio_exceeded(struct rt_rq *rt_rq)
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{
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unsigned int rt_ratio = sched_rt_ratio(rt_rq);
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u64 period, ratio;
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if (rt_ratio == SCHED_RT_FRAC)
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return 0;
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if (rt_rq->rt_throttled)
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return 1;
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period = (u64)sysctl_sched_rt_period * NSEC_PER_MSEC;
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ratio = (period * rt_ratio) >> SCHED_RT_FRAC_SHIFT;
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if (rt_rq->rt_time > ratio) {
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rt_rq->rt_throttled = 1;
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sched_rt_ratio_dequeue(rt_rq);
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return 1;
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}
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return 0;
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}
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static void __update_sched_rt_period(struct rt_rq *rt_rq, u64 period)
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{
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unsigned long rt_ratio = sched_rt_ratio(rt_rq);
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u64 ratio = (period * rt_ratio) >> SCHED_RT_FRAC_SHIFT;
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rt_rq->rt_time -= min(rt_rq->rt_time, ratio);
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if (rt_rq->rt_throttled) {
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rt_rq->rt_throttled = 0;
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sched_rt_ratio_enqueue(rt_rq);
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}
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}
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static void update_sched_rt_period(struct rq *rq)
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{
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struct rt_rq *rt_rq;
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u64 period;
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while (rq->clock > rq->rt_period_expire) {
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period = (u64)sysctl_sched_rt_period * NSEC_PER_MSEC;
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rq->rt_period_expire += period;
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for_each_leaf_rt_rq(rt_rq, rq)
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__update_sched_rt_period(rt_rq, period);
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}
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}
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/*
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* Update the current task's runtime statistics. Skip current tasks that
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* are not in our scheduling class.
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*/
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static void update_curr_rt(struct rq *rq)
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{
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struct task_struct *curr = rq->curr;
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struct sched_rt_entity *rt_se = &curr->rt;
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struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
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u64 delta_exec;
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if (!task_has_rt_policy(curr))
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return;
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delta_exec = rq->clock - curr->se.exec_start;
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if (unlikely((s64)delta_exec < 0))
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delta_exec = 0;
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schedstat_set(curr->se.exec_max, max(curr->se.exec_max, delta_exec));
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curr->se.sum_exec_runtime += delta_exec;
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curr->se.exec_start = rq->clock;
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cpuacct_charge(curr, delta_exec);
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rt_rq->rt_time += delta_exec;
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/*
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* might make it a tad more accurate:
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*
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* update_sched_rt_period(rq);
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*/
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if (sched_rt_ratio_exceeded(rt_rq))
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resched_task(curr);
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}
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static inline
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void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
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{
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WARN_ON(!rt_prio(rt_se_prio(rt_se)));
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rt_rq->rt_nr_running++;
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#if defined CONFIG_SMP || defined CONFIG_FAIR_GROUP_SCHED
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if (rt_se_prio(rt_se) < rt_rq->highest_prio)
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rt_rq->highest_prio = rt_se_prio(rt_se);
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#endif
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#ifdef CONFIG_SMP
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if (rt_se->nr_cpus_allowed > 1) {
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struct rq *rq = rq_of_rt_rq(rt_rq);
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rq->rt.rt_nr_migratory++;
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}
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update_rt_migration(rq_of_rt_rq(rt_rq));
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#endif
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}
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static inline
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void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
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{
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WARN_ON(!rt_prio(rt_se_prio(rt_se)));
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WARN_ON(!rt_rq->rt_nr_running);
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rt_rq->rt_nr_running--;
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#if defined CONFIG_SMP || defined CONFIG_FAIR_GROUP_SCHED
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if (rt_rq->rt_nr_running) {
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struct rt_prio_array *array;
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WARN_ON(rt_se_prio(rt_se) < rt_rq->highest_prio);
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if (rt_se_prio(rt_se) == rt_rq->highest_prio) {
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/* recalculate */
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array = &rt_rq->active;
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rt_rq->highest_prio =
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sched_find_first_bit(array->bitmap);
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} /* otherwise leave rq->highest prio alone */
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} else
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rt_rq->highest_prio = MAX_RT_PRIO;
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#endif
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#ifdef CONFIG_SMP
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if (rt_se->nr_cpus_allowed > 1) {
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struct rq *rq = rq_of_rt_rq(rt_rq);
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rq->rt.rt_nr_migratory--;
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}
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update_rt_migration(rq_of_rt_rq(rt_rq));
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#endif /* CONFIG_SMP */
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}
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static void enqueue_rt_entity(struct sched_rt_entity *rt_se)
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{
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struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
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struct rt_prio_array *array = &rt_rq->active;
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struct rt_rq *group_rq = group_rt_rq(rt_se);
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if (group_rq && group_rq->rt_throttled)
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return;
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list_add_tail(&rt_se->run_list, array->queue + rt_se_prio(rt_se));
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__set_bit(rt_se_prio(rt_se), array->bitmap);
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inc_rt_tasks(rt_se, rt_rq);
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}
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static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
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{
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struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
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struct rt_prio_array *array = &rt_rq->active;
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list_del_init(&rt_se->run_list);
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if (list_empty(array->queue + rt_se_prio(rt_se)))
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__clear_bit(rt_se_prio(rt_se), array->bitmap);
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dec_rt_tasks(rt_se, rt_rq);
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}
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/*
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* Because the prio of an upper entry depends on the lower
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* entries, we must remove entries top - down.
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*
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* XXX: O(1/2 h^2) because we can only walk up, not down the chain.
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* doesn't matter much for now, as h=2 for GROUP_SCHED.
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*/
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static void dequeue_rt_stack(struct task_struct *p)
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{
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struct sched_rt_entity *rt_se, *top_se;
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/*
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* dequeue all, top - down.
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*/
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do {
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rt_se = &p->rt;
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top_se = NULL;
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for_each_sched_rt_entity(rt_se) {
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if (on_rt_rq(rt_se))
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top_se = rt_se;
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}
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if (top_se)
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dequeue_rt_entity(top_se);
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} while (top_se);
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}
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/*
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* Adding/removing a task to/from a priority array:
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*/
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static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup)
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{
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struct sched_rt_entity *rt_se = &p->rt;
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if (wakeup)
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rt_se->timeout = 0;
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dequeue_rt_stack(p);
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/*
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* enqueue everybody, bottom - up.
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*/
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for_each_sched_rt_entity(rt_se)
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enqueue_rt_entity(rt_se);
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inc_cpu_load(rq, p->se.load.weight);
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}
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static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int sleep)
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{
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struct sched_rt_entity *rt_se = &p->rt;
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struct rt_rq *rt_rq;
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update_curr_rt(rq);
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dequeue_rt_stack(p);
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/*
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* re-enqueue all non-empty rt_rq entities.
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*/
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for_each_sched_rt_entity(rt_se) {
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rt_rq = group_rt_rq(rt_se);
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if (rt_rq && rt_rq->rt_nr_running)
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enqueue_rt_entity(rt_se);
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}
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dec_cpu_load(rq, p->se.load.weight);
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}
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/*
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* Put task to the end of the run list without the overhead of dequeue
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* followed by enqueue.
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*/
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static
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void requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se)
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{
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struct rt_prio_array *array = &rt_rq->active;
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list_move_tail(&rt_se->run_list, array->queue + rt_se_prio(rt_se));
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}
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static void requeue_task_rt(struct rq *rq, struct task_struct *p)
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{
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struct sched_rt_entity *rt_se = &p->rt;
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struct rt_rq *rt_rq;
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for_each_sched_rt_entity(rt_se) {
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rt_rq = rt_rq_of_se(rt_se);
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requeue_rt_entity(rt_rq, rt_se);
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}
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}
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static void yield_task_rt(struct rq *rq)
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{
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requeue_task_rt(rq, rq->curr);
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}
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#ifdef CONFIG_SMP
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static int find_lowest_rq(struct task_struct *task);
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static int select_task_rq_rt(struct task_struct *p, int sync)
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{
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struct rq *rq = task_rq(p);
|
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/*
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* If the current task is an RT task, then
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* try to see if we can wake this RT task up on another
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* runqueue. Otherwise simply start this RT task
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* on its current runqueue.
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*
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* We want to avoid overloading runqueues. Even if
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* the RT task is of higher priority than the current RT task.
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* RT tasks behave differently than other tasks. If
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* one gets preempted, we try to push it off to another queue.
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* So trying to keep a preempting RT task on the same
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* cache hot CPU will force the running RT task to
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* a cold CPU. So we waste all the cache for the lower
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* RT task in hopes of saving some of a RT task
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* that is just being woken and probably will have
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* cold cache anyway.
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*/
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if (unlikely(rt_task(rq->curr)) &&
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(p->rt.nr_cpus_allowed > 1)) {
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int cpu = find_lowest_rq(p);
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return (cpu == -1) ? task_cpu(p) : cpu;
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}
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|
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/*
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* Otherwise, just let it ride on the affined RQ and the
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* post-schedule router will push the preempted task away
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*/
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return task_cpu(p);
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}
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#endif /* CONFIG_SMP */
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|
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/*
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* Preempt the current task with a newly woken task if needed:
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*/
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static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p)
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{
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if (p->prio < rq->curr->prio)
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resched_task(rq->curr);
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}
|
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|
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static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
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struct rt_rq *rt_rq)
|
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{
|
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struct rt_prio_array *array = &rt_rq->active;
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struct sched_rt_entity *next = NULL;
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struct list_head *queue;
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int idx;
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|
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if (sched_rt_ratio_exceeded(rt_rq))
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goto out;
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idx = sched_find_first_bit(array->bitmap);
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BUG_ON(idx >= MAX_RT_PRIO);
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queue = array->queue + idx;
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next = list_entry(queue->next, struct sched_rt_entity, run_list);
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out:
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return next;
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}
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|
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static struct task_struct *pick_next_task_rt(struct rq *rq)
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{
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struct sched_rt_entity *rt_se;
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struct task_struct *p;
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struct rt_rq *rt_rq;
|
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|
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retry:
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rt_rq = &rq->rt;
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|
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if (unlikely(!rt_rq->rt_nr_running))
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return NULL;
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|
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if (sched_rt_ratio_exceeded(rt_rq))
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return NULL;
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|
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do {
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rt_se = pick_next_rt_entity(rq, rt_rq);
|
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if (unlikely(!rt_se))
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goto retry;
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rt_rq = group_rt_rq(rt_se);
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|
} while (rt_rq);
|
|
|
|
p = rt_task_of(rt_se);
|
|
p->se.exec_start = rq->clock;
|
|
return p;
|
|
}
|
|
|
|
static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
|
|
{
|
|
update_curr_rt(rq);
|
|
p->se.exec_start = 0;
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
|
|
/* Only try algorithms three times */
|
|
#define RT_MAX_TRIES 3
|
|
|
|
static int double_lock_balance(struct rq *this_rq, struct rq *busiest);
|
|
static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep);
|
|
|
|
static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
|
|
{
|
|
if (!task_running(rq, p) &&
|
|
(cpu < 0 || cpu_isset(cpu, p->cpus_allowed)) &&
|
|
(p->rt.nr_cpus_allowed > 1))
|
|
return 1;
|
|
return 0;
|
|
}
|
|
|
|
/* Return the second highest RT task, NULL otherwise */
|
|
static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu)
|
|
{
|
|
struct task_struct *next = NULL;
|
|
struct sched_rt_entity *rt_se;
|
|
struct rt_prio_array *array;
|
|
struct rt_rq *rt_rq;
|
|
int idx;
|
|
|
|
for_each_leaf_rt_rq(rt_rq, rq) {
|
|
array = &rt_rq->active;
|
|
idx = sched_find_first_bit(array->bitmap);
|
|
next_idx:
|
|
if (idx >= MAX_RT_PRIO)
|
|
continue;
|
|
if (next && next->prio < idx)
|
|
continue;
|
|
list_for_each_entry(rt_se, array->queue + idx, run_list) {
|
|
struct task_struct *p = rt_task_of(rt_se);
|
|
if (pick_rt_task(rq, p, cpu)) {
|
|
next = p;
|
|
break;
|
|
}
|
|
}
|
|
if (!next) {
|
|
idx = find_next_bit(array->bitmap, MAX_RT_PRIO, idx+1);
|
|
goto next_idx;
|
|
}
|
|
}
|
|
|
|
return next;
|
|
}
|
|
|
|
static DEFINE_PER_CPU(cpumask_t, local_cpu_mask);
|
|
|
|
static int find_lowest_cpus(struct task_struct *task, cpumask_t *lowest_mask)
|
|
{
|
|
int lowest_prio = -1;
|
|
int lowest_cpu = -1;
|
|
int count = 0;
|
|
int cpu;
|
|
|
|
cpus_and(*lowest_mask, task_rq(task)->rd->online, task->cpus_allowed);
|
|
|
|
/*
|
|
* Scan each rq for the lowest prio.
|
|
*/
|
|
for_each_cpu_mask(cpu, *lowest_mask) {
|
|
struct rq *rq = cpu_rq(cpu);
|
|
|
|
/* We look for lowest RT prio or non-rt CPU */
|
|
if (rq->rt.highest_prio >= MAX_RT_PRIO) {
|
|
/*
|
|
* if we already found a low RT queue
|
|
* and now we found this non-rt queue
|
|
* clear the mask and set our bit.
|
|
* Otherwise just return the queue as is
|
|
* and the count==1 will cause the algorithm
|
|
* to use the first bit found.
|
|
*/
|
|
if (lowest_cpu != -1) {
|
|
cpus_clear(*lowest_mask);
|
|
cpu_set(rq->cpu, *lowest_mask);
|
|
}
|
|
return 1;
|
|
}
|
|
|
|
/* no locking for now */
|
|
if ((rq->rt.highest_prio > task->prio)
|
|
&& (rq->rt.highest_prio >= lowest_prio)) {
|
|
if (rq->rt.highest_prio > lowest_prio) {
|
|
/* new low - clear old data */
|
|
lowest_prio = rq->rt.highest_prio;
|
|
lowest_cpu = cpu;
|
|
count = 0;
|
|
}
|
|
count++;
|
|
} else
|
|
cpu_clear(cpu, *lowest_mask);
|
|
}
|
|
|
|
/*
|
|
* Clear out all the set bits that represent
|
|
* runqueues that were of higher prio than
|
|
* the lowest_prio.
|
|
*/
|
|
if (lowest_cpu > 0) {
|
|
/*
|
|
* Perhaps we could add another cpumask op to
|
|
* zero out bits. Like cpu_zero_bits(cpumask, nrbits);
|
|
* Then that could be optimized to use memset and such.
|
|
*/
|
|
for_each_cpu_mask(cpu, *lowest_mask) {
|
|
if (cpu >= lowest_cpu)
|
|
break;
|
|
cpu_clear(cpu, *lowest_mask);
|
|
}
|
|
}
|
|
|
|
return count;
|
|
}
|
|
|
|
static inline int pick_optimal_cpu(int this_cpu, cpumask_t *mask)
|
|
{
|
|
int first;
|
|
|
|
/* "this_cpu" is cheaper to preempt than a remote processor */
|
|
if ((this_cpu != -1) && cpu_isset(this_cpu, *mask))
|
|
return this_cpu;
|
|
|
|
first = first_cpu(*mask);
|
|
if (first != NR_CPUS)
|
|
return first;
|
|
|
|
return -1;
|
|
}
|
|
|
|
static int find_lowest_rq(struct task_struct *task)
|
|
{
|
|
struct sched_domain *sd;
|
|
cpumask_t *lowest_mask = &__get_cpu_var(local_cpu_mask);
|
|
int this_cpu = smp_processor_id();
|
|
int cpu = task_cpu(task);
|
|
int count = find_lowest_cpus(task, lowest_mask);
|
|
|
|
if (!count)
|
|
return -1; /* No targets found */
|
|
|
|
/*
|
|
* There is no sense in performing an optimal search if only one
|
|
* target is found.
|
|
*/
|
|
if (count == 1)
|
|
return first_cpu(*lowest_mask);
|
|
|
|
/*
|
|
* At this point we have built a mask of cpus representing the
|
|
* lowest priority tasks in the system. Now we want to elect
|
|
* the best one based on our affinity and topology.
|
|
*
|
|
* We prioritize the last cpu that the task executed on since
|
|
* it is most likely cache-hot in that location.
|
|
*/
|
|
if (cpu_isset(cpu, *lowest_mask))
|
|
return cpu;
|
|
|
|
/*
|
|
* Otherwise, we consult the sched_domains span maps to figure
|
|
* out which cpu is logically closest to our hot cache data.
|
|
*/
|
|
if (this_cpu == cpu)
|
|
this_cpu = -1; /* Skip this_cpu opt if the same */
|
|
|
|
for_each_domain(cpu, sd) {
|
|
if (sd->flags & SD_WAKE_AFFINE) {
|
|
cpumask_t domain_mask;
|
|
int best_cpu;
|
|
|
|
cpus_and(domain_mask, sd->span, *lowest_mask);
|
|
|
|
best_cpu = pick_optimal_cpu(this_cpu,
|
|
&domain_mask);
|
|
if (best_cpu != -1)
|
|
return best_cpu;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* And finally, if there were no matches within the domains
|
|
* just give the caller *something* to work with from the compatible
|
|
* locations.
|
|
*/
|
|
return pick_optimal_cpu(this_cpu, lowest_mask);
|
|
}
|
|
|
|
/* Will lock the rq it finds */
|
|
static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
|
|
{
|
|
struct rq *lowest_rq = NULL;
|
|
int tries;
|
|
int cpu;
|
|
|
|
for (tries = 0; tries < RT_MAX_TRIES; tries++) {
|
|
cpu = find_lowest_rq(task);
|
|
|
|
if ((cpu == -1) || (cpu == rq->cpu))
|
|
break;
|
|
|
|
lowest_rq = cpu_rq(cpu);
|
|
|
|
/* if the prio of this runqueue changed, try again */
|
|
if (double_lock_balance(rq, lowest_rq)) {
|
|
/*
|
|
* We had to unlock the run queue. In
|
|
* the mean time, task could have
|
|
* migrated already or had its affinity changed.
|
|
* Also make sure that it wasn't scheduled on its rq.
|
|
*/
|
|
if (unlikely(task_rq(task) != rq ||
|
|
!cpu_isset(lowest_rq->cpu,
|
|
task->cpus_allowed) ||
|
|
task_running(rq, task) ||
|
|
!task->se.on_rq)) {
|
|
|
|
spin_unlock(&lowest_rq->lock);
|
|
lowest_rq = NULL;
|
|
break;
|
|
}
|
|
}
|
|
|
|
/* If this rq is still suitable use it. */
|
|
if (lowest_rq->rt.highest_prio > task->prio)
|
|
break;
|
|
|
|
/* try again */
|
|
spin_unlock(&lowest_rq->lock);
|
|
lowest_rq = NULL;
|
|
}
|
|
|
|
return lowest_rq;
|
|
}
|
|
|
|
/*
|
|
* If the current CPU has more than one RT task, see if the non
|
|
* running task can migrate over to a CPU that is running a task
|
|
* of lesser priority.
|
|
*/
|
|
static int push_rt_task(struct rq *rq)
|
|
{
|
|
struct task_struct *next_task;
|
|
struct rq *lowest_rq;
|
|
int ret = 0;
|
|
int paranoid = RT_MAX_TRIES;
|
|
|
|
if (!rq->rt.overloaded)
|
|
return 0;
|
|
|
|
next_task = pick_next_highest_task_rt(rq, -1);
|
|
if (!next_task)
|
|
return 0;
|
|
|
|
retry:
|
|
if (unlikely(next_task == rq->curr)) {
|
|
WARN_ON(1);
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* It's possible that the next_task slipped in of
|
|
* higher priority than current. If that's the case
|
|
* just reschedule current.
|
|
*/
|
|
if (unlikely(next_task->prio < rq->curr->prio)) {
|
|
resched_task(rq->curr);
|
|
return 0;
|
|
}
|
|
|
|
/* We might release rq lock */
|
|
get_task_struct(next_task);
|
|
|
|
/* find_lock_lowest_rq locks the rq if found */
|
|
lowest_rq = find_lock_lowest_rq(next_task, rq);
|
|
if (!lowest_rq) {
|
|
struct task_struct *task;
|
|
/*
|
|
* find lock_lowest_rq releases rq->lock
|
|
* so it is possible that next_task has changed.
|
|
* If it has, then try again.
|
|
*/
|
|
task = pick_next_highest_task_rt(rq, -1);
|
|
if (unlikely(task != next_task) && task && paranoid--) {
|
|
put_task_struct(next_task);
|
|
next_task = task;
|
|
goto retry;
|
|
}
|
|
goto out;
|
|
}
|
|
|
|
deactivate_task(rq, next_task, 0);
|
|
set_task_cpu(next_task, lowest_rq->cpu);
|
|
activate_task(lowest_rq, next_task, 0);
|
|
|
|
resched_task(lowest_rq->curr);
|
|
|
|
spin_unlock(&lowest_rq->lock);
|
|
|
|
ret = 1;
|
|
out:
|
|
put_task_struct(next_task);
|
|
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* TODO: Currently we just use the second highest prio task on
|
|
* the queue, and stop when it can't migrate (or there's
|
|
* no more RT tasks). There may be a case where a lower
|
|
* priority RT task has a different affinity than the
|
|
* higher RT task. In this case the lower RT task could
|
|
* possibly be able to migrate where as the higher priority
|
|
* RT task could not. We currently ignore this issue.
|
|
* Enhancements are welcome!
|
|
*/
|
|
static void push_rt_tasks(struct rq *rq)
|
|
{
|
|
/* push_rt_task will return true if it moved an RT */
|
|
while (push_rt_task(rq))
|
|
;
|
|
}
|
|
|
|
static int pull_rt_task(struct rq *this_rq)
|
|
{
|
|
int this_cpu = this_rq->cpu, ret = 0, cpu;
|
|
struct task_struct *p, *next;
|
|
struct rq *src_rq;
|
|
|
|
if (likely(!rt_overloaded(this_rq)))
|
|
return 0;
|
|
|
|
next = pick_next_task_rt(this_rq);
|
|
|
|
for_each_cpu_mask(cpu, this_rq->rd->rto_mask) {
|
|
if (this_cpu == cpu)
|
|
continue;
|
|
|
|
src_rq = cpu_rq(cpu);
|
|
/*
|
|
* We can potentially drop this_rq's lock in
|
|
* double_lock_balance, and another CPU could
|
|
* steal our next task - hence we must cause
|
|
* the caller to recalculate the next task
|
|
* in that case:
|
|
*/
|
|
if (double_lock_balance(this_rq, src_rq)) {
|
|
struct task_struct *old_next = next;
|
|
|
|
next = pick_next_task_rt(this_rq);
|
|
if (next != old_next)
|
|
ret = 1;
|
|
}
|
|
|
|
/*
|
|
* Are there still pullable RT tasks?
|
|
*/
|
|
if (src_rq->rt.rt_nr_running <= 1) {
|
|
spin_unlock(&src_rq->lock);
|
|
continue;
|
|
}
|
|
|
|
p = pick_next_highest_task_rt(src_rq, this_cpu);
|
|
|
|
/*
|
|
* Do we have an RT task that preempts
|
|
* the to-be-scheduled task?
|
|
*/
|
|
if (p && (!next || (p->prio < next->prio))) {
|
|
WARN_ON(p == src_rq->curr);
|
|
WARN_ON(!p->se.on_rq);
|
|
|
|
/*
|
|
* There's a chance that p is higher in priority
|
|
* than what's currently running on its cpu.
|
|
* This is just that p is wakeing up and hasn't
|
|
* had a chance to schedule. We only pull
|
|
* p if it is lower in priority than the
|
|
* current task on the run queue or
|
|
* this_rq next task is lower in prio than
|
|
* the current task on that rq.
|
|
*/
|
|
if (p->prio < src_rq->curr->prio ||
|
|
(next && next->prio < src_rq->curr->prio))
|
|
goto out;
|
|
|
|
ret = 1;
|
|
|
|
deactivate_task(src_rq, p, 0);
|
|
set_task_cpu(p, this_cpu);
|
|
activate_task(this_rq, p, 0);
|
|
/*
|
|
* We continue with the search, just in
|
|
* case there's an even higher prio task
|
|
* in another runqueue. (low likelyhood
|
|
* but possible)
|
|
*
|
|
* Update next so that we won't pick a task
|
|
* on another cpu with a priority lower (or equal)
|
|
* than the one we just picked.
|
|
*/
|
|
next = p;
|
|
|
|
}
|
|
out:
|
|
spin_unlock(&src_rq->lock);
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
|
|
static void pre_schedule_rt(struct rq *rq, struct task_struct *prev)
|
|
{
|
|
/* Try to pull RT tasks here if we lower this rq's prio */
|
|
if (unlikely(rt_task(prev)) && rq->rt.highest_prio > prev->prio)
|
|
pull_rt_task(rq);
|
|
}
|
|
|
|
static void post_schedule_rt(struct rq *rq)
|
|
{
|
|
/*
|
|
* If we have more than one rt_task queued, then
|
|
* see if we can push the other rt_tasks off to other CPUS.
|
|
* Note we may release the rq lock, and since
|
|
* the lock was owned by prev, we need to release it
|
|
* first via finish_lock_switch and then reaquire it here.
|
|
*/
|
|
if (unlikely(rq->rt.overloaded)) {
|
|
spin_lock_irq(&rq->lock);
|
|
push_rt_tasks(rq);
|
|
spin_unlock_irq(&rq->lock);
|
|
}
|
|
}
|
|
|
|
|
|
static void task_wake_up_rt(struct rq *rq, struct task_struct *p)
|
|
{
|
|
if (!task_running(rq, p) &&
|
|
(p->prio >= rq->rt.highest_prio) &&
|
|
rq->rt.overloaded)
|
|
push_rt_tasks(rq);
|
|
}
|
|
|
|
static unsigned long
|
|
load_balance_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
|
|
unsigned long max_load_move,
|
|
struct sched_domain *sd, enum cpu_idle_type idle,
|
|
int *all_pinned, int *this_best_prio)
|
|
{
|
|
/* don't touch RT tasks */
|
|
return 0;
|
|
}
|
|
|
|
static int
|
|
move_one_task_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
|
|
struct sched_domain *sd, enum cpu_idle_type idle)
|
|
{
|
|
/* don't touch RT tasks */
|
|
return 0;
|
|
}
|
|
|
|
static void set_cpus_allowed_rt(struct task_struct *p, cpumask_t *new_mask)
|
|
{
|
|
int weight = cpus_weight(*new_mask);
|
|
|
|
BUG_ON(!rt_task(p));
|
|
|
|
/*
|
|
* Update the migration status of the RQ if we have an RT task
|
|
* which is running AND changing its weight value.
|
|
*/
|
|
if (p->se.on_rq && (weight != p->rt.nr_cpus_allowed)) {
|
|
struct rq *rq = task_rq(p);
|
|
|
|
if ((p->rt.nr_cpus_allowed <= 1) && (weight > 1)) {
|
|
rq->rt.rt_nr_migratory++;
|
|
} else if ((p->rt.nr_cpus_allowed > 1) && (weight <= 1)) {
|
|
BUG_ON(!rq->rt.rt_nr_migratory);
|
|
rq->rt.rt_nr_migratory--;
|
|
}
|
|
|
|
update_rt_migration(rq);
|
|
}
|
|
|
|
p->cpus_allowed = *new_mask;
|
|
p->rt.nr_cpus_allowed = weight;
|
|
}
|
|
|
|
/* Assumes rq->lock is held */
|
|
static void join_domain_rt(struct rq *rq)
|
|
{
|
|
if (rq->rt.overloaded)
|
|
rt_set_overload(rq);
|
|
}
|
|
|
|
/* Assumes rq->lock is held */
|
|
static void leave_domain_rt(struct rq *rq)
|
|
{
|
|
if (rq->rt.overloaded)
|
|
rt_clear_overload(rq);
|
|
}
|
|
|
|
/*
|
|
* When switch from the rt queue, we bring ourselves to a position
|
|
* that we might want to pull RT tasks from other runqueues.
|
|
*/
|
|
static void switched_from_rt(struct rq *rq, struct task_struct *p,
|
|
int running)
|
|
{
|
|
/*
|
|
* If there are other RT tasks then we will reschedule
|
|
* and the scheduling of the other RT tasks will handle
|
|
* the balancing. But if we are the last RT task
|
|
* we may need to handle the pulling of RT tasks
|
|
* now.
|
|
*/
|
|
if (!rq->rt.rt_nr_running)
|
|
pull_rt_task(rq);
|
|
}
|
|
#endif /* CONFIG_SMP */
|
|
|
|
/*
|
|
* When switching a task to RT, we may overload the runqueue
|
|
* with RT tasks. In this case we try to push them off to
|
|
* other runqueues.
|
|
*/
|
|
static void switched_to_rt(struct rq *rq, struct task_struct *p,
|
|
int running)
|
|
{
|
|
int check_resched = 1;
|
|
|
|
/*
|
|
* If we are already running, then there's nothing
|
|
* that needs to be done. But if we are not running
|
|
* we may need to preempt the current running task.
|
|
* If that current running task is also an RT task
|
|
* then see if we can move to another run queue.
|
|
*/
|
|
if (!running) {
|
|
#ifdef CONFIG_SMP
|
|
if (rq->rt.overloaded && push_rt_task(rq) &&
|
|
/* Don't resched if we changed runqueues */
|
|
rq != task_rq(p))
|
|
check_resched = 0;
|
|
#endif /* CONFIG_SMP */
|
|
if (check_resched && p->prio < rq->curr->prio)
|
|
resched_task(rq->curr);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Priority of the task has changed. This may cause
|
|
* us to initiate a push or pull.
|
|
*/
|
|
static void prio_changed_rt(struct rq *rq, struct task_struct *p,
|
|
int oldprio, int running)
|
|
{
|
|
if (running) {
|
|
#ifdef CONFIG_SMP
|
|
/*
|
|
* If our priority decreases while running, we
|
|
* may need to pull tasks to this runqueue.
|
|
*/
|
|
if (oldprio < p->prio)
|
|
pull_rt_task(rq);
|
|
/*
|
|
* If there's a higher priority task waiting to run
|
|
* then reschedule.
|
|
*/
|
|
if (p->prio > rq->rt.highest_prio)
|
|
resched_task(p);
|
|
#else
|
|
/* For UP simply resched on drop of prio */
|
|
if (oldprio < p->prio)
|
|
resched_task(p);
|
|
#endif /* CONFIG_SMP */
|
|
} else {
|
|
/*
|
|
* This task is not running, but if it is
|
|
* greater than the current running task
|
|
* then reschedule.
|
|
*/
|
|
if (p->prio < rq->curr->prio)
|
|
resched_task(rq->curr);
|
|
}
|
|
}
|
|
|
|
static void watchdog(struct rq *rq, struct task_struct *p)
|
|
{
|
|
unsigned long soft, hard;
|
|
|
|
if (!p->signal)
|
|
return;
|
|
|
|
soft = p->signal->rlim[RLIMIT_RTTIME].rlim_cur;
|
|
hard = p->signal->rlim[RLIMIT_RTTIME].rlim_max;
|
|
|
|
if (soft != RLIM_INFINITY) {
|
|
unsigned long next;
|
|
|
|
p->rt.timeout++;
|
|
next = DIV_ROUND_UP(min(soft, hard), USEC_PER_SEC/HZ);
|
|
if (next > p->rt.timeout) {
|
|
u64 next_time = p->se.sum_exec_runtime;
|
|
|
|
next_time += next * (NSEC_PER_SEC/HZ);
|
|
if (p->it_sched_expires > next_time)
|
|
p->it_sched_expires = next_time;
|
|
} else
|
|
p->it_sched_expires = p->se.sum_exec_runtime;
|
|
}
|
|
}
|
|
|
|
static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
|
|
{
|
|
update_curr_rt(rq);
|
|
|
|
watchdog(rq, p);
|
|
|
|
/*
|
|
* RR tasks need a special form of timeslice management.
|
|
* FIFO tasks have no timeslices.
|
|
*/
|
|
if (p->policy != SCHED_RR)
|
|
return;
|
|
|
|
if (--p->rt.time_slice)
|
|
return;
|
|
|
|
p->rt.time_slice = DEF_TIMESLICE;
|
|
|
|
/*
|
|
* Requeue to the end of queue if we are not the only element
|
|
* on the queue:
|
|
*/
|
|
if (p->rt.run_list.prev != p->rt.run_list.next) {
|
|
requeue_task_rt(rq, p);
|
|
set_tsk_need_resched(p);
|
|
}
|
|
}
|
|
|
|
static void set_curr_task_rt(struct rq *rq)
|
|
{
|
|
struct task_struct *p = rq->curr;
|
|
|
|
p->se.exec_start = rq->clock;
|
|
}
|
|
|
|
const struct sched_class rt_sched_class = {
|
|
.next = &fair_sched_class,
|
|
.enqueue_task = enqueue_task_rt,
|
|
.dequeue_task = dequeue_task_rt,
|
|
.yield_task = yield_task_rt,
|
|
#ifdef CONFIG_SMP
|
|
.select_task_rq = select_task_rq_rt,
|
|
#endif /* CONFIG_SMP */
|
|
|
|
.check_preempt_curr = check_preempt_curr_rt,
|
|
|
|
.pick_next_task = pick_next_task_rt,
|
|
.put_prev_task = put_prev_task_rt,
|
|
|
|
#ifdef CONFIG_SMP
|
|
.load_balance = load_balance_rt,
|
|
.move_one_task = move_one_task_rt,
|
|
.set_cpus_allowed = set_cpus_allowed_rt,
|
|
.join_domain = join_domain_rt,
|
|
.leave_domain = leave_domain_rt,
|
|
.pre_schedule = pre_schedule_rt,
|
|
.post_schedule = post_schedule_rt,
|
|
.task_wake_up = task_wake_up_rt,
|
|
.switched_from = switched_from_rt,
|
|
#endif
|
|
|
|
.set_curr_task = set_curr_task_rt,
|
|
.task_tick = task_tick_rt,
|
|
|
|
.prio_changed = prio_changed_rt,
|
|
.switched_to = switched_to_rt,
|
|
};
|