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953bfcd10e
Introduce hierarchical task accounting for the group scheduling case in CFS, as well as promoting the responsibility for maintaining rq->nr_running to the scheduling classes. The primary motivation for this is that with scheduling classes supporting bandwidth throttling it is possible for entities participating in throttled sub-trees to not have root visible changes in rq->nr_running across activate and de-activate operations. This in turn leads to incorrect idle and weight-per-task load balance decisions. This also allows us to make a small fixlet to the fastpath in pick_next_task() under group scheduling. Note: this issue also exists with the existing sched_rt throttling mechanism. This patch does not address that. Signed-off-by: Paul Turner <pjt@google.com> Reviewed-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/20110721184756.878333391@google.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
106 lines
2.1 KiB
C
106 lines
2.1 KiB
C
/*
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* stop-task scheduling class.
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*
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* The stop task is the highest priority task in the system, it preempts
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* everything and will be preempted by nothing.
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*
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* See kernel/stop_machine.c
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*/
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#ifdef CONFIG_SMP
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static int
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select_task_rq_stop(struct task_struct *p, int sd_flag, int flags)
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{
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return task_cpu(p); /* stop tasks as never migrate */
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}
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#endif /* CONFIG_SMP */
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static void
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check_preempt_curr_stop(struct rq *rq, struct task_struct *p, int flags)
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{
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/* we're never preempted */
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}
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static struct task_struct *pick_next_task_stop(struct rq *rq)
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{
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struct task_struct *stop = rq->stop;
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if (stop && stop->on_rq)
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return stop;
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return NULL;
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}
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static void
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enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags)
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{
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inc_nr_running(rq);
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}
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static void
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dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags)
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{
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dec_nr_running(rq);
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}
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static void yield_task_stop(struct rq *rq)
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{
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BUG(); /* the stop task should never yield, its pointless. */
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}
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static void put_prev_task_stop(struct rq *rq, struct task_struct *prev)
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{
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}
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static void task_tick_stop(struct rq *rq, struct task_struct *curr, int queued)
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{
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}
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static void set_curr_task_stop(struct rq *rq)
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{
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}
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static void switched_to_stop(struct rq *rq, struct task_struct *p)
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{
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BUG(); /* its impossible to change to this class */
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}
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static void
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prio_changed_stop(struct rq *rq, struct task_struct *p, int oldprio)
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{
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BUG(); /* how!?, what priority? */
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}
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static unsigned int
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get_rr_interval_stop(struct rq *rq, struct task_struct *task)
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{
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return 0;
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}
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/*
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* Simple, special scheduling class for the per-CPU stop tasks:
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*/
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static const struct sched_class stop_sched_class = {
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.next = &rt_sched_class,
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.enqueue_task = enqueue_task_stop,
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.dequeue_task = dequeue_task_stop,
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.yield_task = yield_task_stop,
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.check_preempt_curr = check_preempt_curr_stop,
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.pick_next_task = pick_next_task_stop,
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.put_prev_task = put_prev_task_stop,
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#ifdef CONFIG_SMP
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.select_task_rq = select_task_rq_stop,
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#endif
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.set_curr_task = set_curr_task_stop,
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.task_tick = task_tick_stop,
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.get_rr_interval = get_rr_interval_stop,
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.prio_changed = prio_changed_stop,
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.switched_to = switched_to_stop,
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};
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