Messages in this thread | | | Date | Mon, 24 Feb 2020 13:47:25 +0000 | From | Qais Yousef <> | Subject | Re: [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
| |