Re: [PATCH 2/2] sched/rt: Move sched_rt_entity::back to under the CONFIG_RT_GROUP_SCHED block

[Yajun Deng]

On 2023/10/9 18:16, Ingo Molnar wrote:
> * Yajun Deng <yajun.deng@xxxxxxxxx> wrote:
>
> > The member back in struct sched_rt_entity only related to RT_GROUP_SCHED,
> > So move sched_rt_entity::back to under the CONFIG_RT_GROUP_SCHED block. It
> > will save a few bytes.
> >
> > Also, init child when parent isn't NULL in init_tg_rt_entry().
> >
> > Signed-off-by: Yajun Deng <yajun.deng@xxxxxxxxx>
> > ---
> >   include/linux/sched.h |  2 +-
> >   kernel/sched/rt.c     | 18 +++++++++---------
> >   2 files changed, 10 insertions(+), 10 deletions(-)
> >
> > diff --git a/include/linux/sched.h b/include/linux/sched.h
> > index 292c31697248..d0fe56603e60 100644
> > --- a/include/linux/sched.h
> > +++ b/include/linux/sched.h
> > @@ -597,8 +597,8 @@ struct sched_rt_entity {
> >   	unsigned short			on_rq;
> >   	unsigned short			on_list;
> >   
> > -	struct sched_rt_entity		*back;
> >   #ifdef CONFIG_RT_GROUP_SCHED
> > +	struct sched_rt_entity		*back;
> >   	struct sched_rt_entity		*parent;
> >   	/* rq on which this entity is (to be) queued: */
> >   	struct rt_rq			*rt_rq;
> Title claims this change - the rest of the changes should be in a separate
> patch:


Okay. I will send v2.

> > diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> > index 642edbd24ffb..7b3105b875f1 100644
> > --- a/kernel/sched/rt.c
> > +++ b/kernel/sched/rt.c
> > @@ -233,8 +233,10 @@ void init_tg_rt_entry(struct task_group *tg, struct rt_rq *rt_rq,
> >   
> >   	if (!parent)
> >   		rt_se->rt_rq = &rq->rt;
> > -	else
> > +	else {
> >   		rt_se->rt_rq = parent->my_q;
> > +		parent->back = rt_se;
> > +	}
> >   
> >   	rt_se->my_q = rt_rq;
> >   	rt_se->parent = parent;
> > @@ -1441,23 +1443,21 @@ static void __dequeue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flag
> >    */
> >   static void dequeue_rt_stack(struct sched_rt_entity *rt_se, unsigned int flags)
> >   {
> > -	struct sched_rt_entity *back = NULL;
> > +	struct sched_rt_entity *root = NULL;
> >   	unsigned int rt_nr_running;
> >   
> > -	for_each_sched_rt_entity(rt_se) {
> > -		rt_se->back = back;
> > -		back = rt_se;
> > -	}
> > +	for_each_sched_rt_entity(rt_se)
> > +		root = rt_se;
> >   
> > -	rt_nr_running = rt_rq_of_se(back)->rt_nr_running;
> > +	rt_nr_running = rt_rq_of_se(root)->rt_nr_running;
> >   
> > -	rt_se = back;
> > +	rt_se = root;
> >   	for_each_sched_rt_entity_back(rt_se) {
> >   		if (on_rt_rq(rt_se))
> >   			__dequeue_rt_entity(rt_se, flags);
> >   	}
> >   
> > -	dequeue_top_rt_rq(rt_rq_of_se(back), rt_nr_running);
> > +	dequeue_top_rt_rq(rt_rq_of_se(root), rt_nr_running);
> >   }
> >   
> >   static void enqueue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags)
> > --
> > 2.25.1
> Thanks,
>
> 	Ingo