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SubjectRe: [CFS Bandwidth Control v4 6/7] sched: hierarchical task accounting for SCHED_OTHER
* Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com> [2011-02-23 11:02:40]:

> (2011/02/16 12:18), Paul Turner wrote:
> > @@ -1428,6 +1464,7 @@ enqueue_task_fair(struct rq *rq, struct
> > update_cfs_shares(cfs_rq);
> > }
> >
> > + account_hier_tasks(&p->se, 1);
> > hrtick_update(rq);
> > }
> >
> > @@ -1461,6 +1498,7 @@ static void dequeue_task_fair(struct rq
> > update_cfs_shares(cfs_rq);
> > }
> >
> > + account_hier_tasks(&p->se, -1);
> > hrtick_update(rq);
> > }
> >
>
> Why hrtick_update() is need to be delayed after modifying nr_running?
> You should not impact current hrtick logic without once mentioning.
>
> > Index: tip/kernel/sched_rt.c
> > ===================================================================
> > --- tip.orig/kernel/sched_rt.c
> > +++ tip/kernel/sched_rt.c
> > @@ -906,6 +906,8 @@ enqueue_task_rt(struct rq *rq, struct ta
> >
> > 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)
> > @@ -916,6 +918,8 @@ static void dequeue_task_rt(struct rq *r
> > dequeue_rt_entity(rt_se);
> >
> > dequeue_pushable_task(rq, p);
> > +
> > + dec_nr_running(rq);
> > }
> >
> > /*
>
> I think similar change for sched_stoptask.c is required.
>
> In fact I could not boot tip/master with this v4 patchset.
> It reports rcu stall warns without applying following tweak:
>
> --- a/kernel/sched_stoptask.c
> +++ b/kernel/sched_stoptask.c
> @@ -35,11 +35,13 @@ 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);
> }
>

Good catch!

Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>


--
Three Cheers,
Balbir


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