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Commit 953bfcd1 authored by Paul Turner's avatar Paul Turner Committed by Ingo Molnar
Browse files

sched: Implement hierarchical task accounting for SCHED_OTHER 



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: default avatarPaul Turner <pjt@google.com>
Reviewed-by: default avatarHidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110721184756.878333391@google.com


Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 5710f15b

kernel/sched.c

+2 −4
Original line number Diff line number Diff line
@@ -311,7 +311,7 @@ struct task_group root_task_group; 
/* CFS-related fields in a runqueue */

struct cfs_rq {

	struct load_weight load;

	unsigned long nr_running;

	unsigned long nr_running, h_nr_running;



	u64 exec_clock;

	u64 min_vruntime;
@@ -1802,7 +1802,6 @@ static void activate_task(struct rq *rq, struct task_struct *p, int flags) 
		rq->nr_uninterruptible--;



	enqueue_task(rq, p, flags);

	inc_nr_running(rq);

}



/*
@@ -1814,7 +1813,6 @@ static void deactivate_task(struct rq *rq, struct task_struct *p, int flags) 
		rq->nr_uninterruptible++;



	dequeue_task(rq, p, flags);

	dec_nr_running(rq);

}



#ifdef CONFIG_IRQ_TIME_ACCOUNTING
@@ -4258,7 +4256,7 @@ pick_next_task(struct rq *rq) 
	 * Optimization: we know that if all tasks are in

	 * the fair class we can call that function directly:

	 */

	if (likely(rq->nr_running == rq->cfs.nr_running)) {

	if (likely(rq->nr_running == rq->cfs.h_nr_running)) {

		p = fair_sched_class.pick_next_task(rq);

		if (likely(p))

			return p;

kernel/sched_fair.c

+6 −0
Original line number Diff line number Diff line
@@ -1310,16 +1310,19 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) 
			break;

		cfs_rq = cfs_rq_of(se);

		enqueue_entity(cfs_rq, se, flags);

		cfs_rq->h_nr_running++;

		flags = ENQUEUE_WAKEUP;

	}



	for_each_sched_entity(se) {

		cfs_rq = cfs_rq_of(se);

		cfs_rq->h_nr_running++;



		update_cfs_load(cfs_rq, 0);

		update_cfs_shares(cfs_rq);

	}



	inc_nr_running(rq);

	hrtick_update(rq);

}
@@ -1339,6 +1342,7 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags) 
	for_each_sched_entity(se) {

		cfs_rq = cfs_rq_of(se);

		dequeue_entity(cfs_rq, se, flags);

		cfs_rq->h_nr_running--;



		/* Don't dequeue parent if it has other entities besides us */

		if (cfs_rq->load.weight) {
@@ -1358,11 +1362,13 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags) 


	for_each_sched_entity(se) {

		cfs_rq = cfs_rq_of(se);

		cfs_rq->h_nr_running--;



		update_cfs_load(cfs_rq, 0);

		update_cfs_shares(cfs_rq);

	}



	dec_nr_running(rq);

	hrtick_update(rq);

}

kernel/sched_rt.c

+4 −1
Original line number Diff line number Diff line
@@ -936,6 +936,8 @@ enqueue_task_rt(struct rq *rq, struct task_struct *p, int flags) 


	if (!task_current(rq, p) && p->rt.nr_cpus_allowed > 1)

		enqueue_pushable_task(rq, p);



	inc_nr_running(rq);

}



static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags)
@@ -946,6 +948,8 @@ static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags) 
	dequeue_rt_entity(rt_se);



	dequeue_pushable_task(rq, p);



	dec_nr_running(rq);

}



/*
@@ -1841,4 +1845,3 @@ static void print_rt_stats(struct seq_file *m, int cpu) 
	rcu_read_unlock();

}

#endif /* CONFIG_SCHED_DEBUG */

kernel/sched_stoptask.c

+2 −0
Original line number Diff line number Diff line
@@ -34,11 +34,13 @@ static struct task_struct *pick_next_task_stop(struct rq *rq) 
static void

enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags)

{

	inc_nr_running(rq);

}



static void

dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags)

{

	dec_nr_running(rq);

}



static void yield_task_stop(struct rq *rq)