lkml.org 
[lkml]   [2020]   [Feb]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2 6/6] sched/rt: Remove unnecessary assignment in inc/dec_rt_migration
On 02/24/20 13:03, Dietmar Eggemann wrote:
> On 24.02.20 12:31, Qais Yousef wrote:
> > On 02/24/20 00:16, Dietmar Eggemann wrote:
> >> On 23.02.20 19:40, Qais Yousef wrote:
>
> [...]
>
> >>> - rt_rq = &rq_of_rt_rq(rt_rq)->rt;
> >>
> >> IMHO, this is here to get the root rt_rq from any rt_rq (task_groups).
> >> Looks like that e.g rt_nr_total is only maintained on root rt_rq's.
> >>
> >> Similar to CFS' &rq_of(cfs_rq)->cfs (cfs_rq_util_change()) to get root
> >> cfs_rq.
> >>
> >> Not sure where CONFIG_RT_GROUP_SCHED=y is used but it's part of the rt
> >> class implementation.
> >
> > Ah I see. That was obvious.. How about the below comment?
> >
> > This code is executed only if rt_entity_is_task(), I don't think this grantees
> > that the rt_rq isn't for a group?
>
> No, an rt task can run in this taskgroup (e.g. "/tg/tg1"), i.e. in
> tg1->rt_rq[cpu].
>
> The taskgroup skeleton rt_se of e.g. "/tg/tg1/tg11" would also run in
> tg1->rt_rq[cpu] but for those rt_se's we bail out of [inc/dec]_rt_migration.
>
> >
> > I need to go and unravel the layers maybe.
> >
> > Thanks!
> >
> > --
> > Qais Yousef
> >
> > -->8--
> >
> > diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> > index b35e49cdafcc..f929867215c4 100644
> > --- a/kernel/sched/rt.c
> > +++ b/kernel/sched/rt.c
> > @@ -343,6 +343,8 @@ static void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
> > return;
> >
> > p = rt_task_of(rt_se);
> > +
> > + /* get the root rt_rq if this is the rt_rq of a group */
>
> Not sure if a comment like this will help since:
>
> (a) the definition of rq_of_rt_rq() for the !CONFIG_RT_GROUP_SCHED case
>
> (b) rt_rq might already be the root rt_rq in case the task runs in "/"

I thought the comment explains that.

FWIW I don't think someone looking at the code need to look at rq_of_rt_rq() to
get the dependency, but if the above doesn't help I have no better suggestion.
So I'll drop it.

Thanks

--
Qais Yousef

\
 
 \ /
  Last update: 2020-02-24 14:48    [W:0.048 / U:0.040 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site