lkml.org 
[lkml]   [2019]   [Jun]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 5/8] sched,cfs: use explicit cfs_rq of parent se helper
From
Date
On Thu, 2019-06-20 at 18:23 +0200, Dietmar Eggemann wrote:
> On 6/12/19 9:32 PM, Rik van Riel wrote:
> > Use an explicit "cfs_rq of parent sched_entity" helper in a few
> > strategic places, where cfs_rq_of(se) may no longer point at the
> > right runqueue once we flatten the hierarchical cgroup runqueues.
> >
> > No functional change.
> >
> > Signed-off-by: Rik van Riel <riel@surriel.com>
> > ---
> > kernel/sched/fair.c | 17 +++++++++++++----
> > 1 file changed, 13 insertions(+), 4 deletions(-)
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index dcc521d251e3..c6ede2ecc935 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -275,6 +275,15 @@ static inline struct cfs_rq
> > *group_cfs_rq(struct sched_entity *grp)
> > return grp->my_q;
> > }
> >
> > +/* runqueue owned by the parent entity */
> > +static inline struct cfs_rq *group_cfs_rq_of_parent(struct
> > sched_entity *se)
> > +{
> > + if (se->parent)
> > + return group_cfs_rq(se->parent);
> > +
> > + return &cfs_rq_of(se)->rq->cfs;
> > +}
> > +
> > static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
> > {
> > struct rq *rq = rq_of(cfs_rq);
> > @@ -3298,7 +3307,7 @@ static inline int
> > propagate_entity_load_avg(struct sched_entity *se)
> >
> > gcfs_rq->propagate = 0;
> >
> > - cfs_rq = cfs_rq_of(se);
> > + cfs_rq = group_cfs_rq_of_parent(se);
> >
> > add_tg_cfs_propagate(cfs_rq, gcfs_rq->prop_runnable_sum);
> >
> > @@ -7779,7 +7788,7 @@ static void update_cfs_rq_h_load(struct
> > cfs_rq *cfs_rq)
> >
> > WRITE_ONCE(cfs_rq->h_load_next, NULL);
> > for_each_sched_entity(se) {
> > - cfs_rq = cfs_rq_of(se);
> > + cfs_rq = group_cfs_rq_of_parent(se);
>
> Why do you change this here? task_se_h_load() calls
> update_cfs_rq_h_load() with cfs_rq = group_cfs_rq_of_parent(se)
> because
> the task might not be on the cfs_rq yet.

Because patch 6 points cfs_rq_of(se) at the CPU's top level
cfs_rq for every task se ...

... but I guess since I have not changed where the cfs_rq_of
points for cgroup sched_entities, this change is not necessary
at this time, and I should be able to go without it, in this
function.

> But inside update_cfs_rq_h_load() the first se is derived from
> cfs_rq->tg->se[cpu_of(rq)] so in the first for_each_sched_entity()
> loop
> we should still start with group_cfs_rq() (se->my_q) ?
>
> The system doesn't barf with these two WARN_ON's in.
>
> @@ -7663,12 +7673,17 @@ static void update_cfs_rq_h_load(struct
> cfs_rq
> *cfs_rq)
> unsigned long now = jiffies;
> unsigned long load;
>
> + WARN_ON(se && (se != group_cfs_rq(se)->tg->se[cpu_of(rq)]));
> +
> if (cfs_rq->last_h_load_update == now)
> return;
>
> WRITE_ONCE(cfs_rq->h_load_next, NULL);
> for_each_sched_entity(se) {
> cfs_rq = group_cfs_rq_of_parent(se);
> +
> + WARN_ON(se != group_cfs_rq(se)->tg->se[cpu_of(rq)]);
> +
> WRITE_ONCE(cfs_rq->h_load_next, se);
> if (cfs_rq->last_h_load_update == now)
> break;
>
>
> [...]
>
>
--
All Rights Reversed.
[unhandled content-type:application/pgp-signature]
\
 
 \ /
  Last update: 2019-06-20 18:30    [W:0.098 / U:7.240 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site