Hi Vincent,
On Wed, May 13, 2020 at 02:34:22PM +0200 Vincent Guittot wrote:
> Although not exactly identical, unthrottle_cfs_rq() and enqueue_task_fair()
> are quite close and follow the same sequence for enqueuing an entity in the
> cfs hierarchy. Modify unthrottle_cfs_rq() to use the same pattern as
> enqueue_task_fair(). This fixes a problem already faced with the latter and
> add an optimization in the last for_each_sched_entity loop.
>
> Reported-by Tao Zhou <[email protected]>
> Reviewed-by: Phil Auld <[email protected]>
> Signed-off-by: Vincent Guittot <[email protected]>
> ---
>
> v2 changes:
> - Remove useless if statement
>
> kernel/sched/fair.c | 41 ++++++++++++++++++++++++++++++-----------
> 1 file changed, 30 insertions(+), 11 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 4e12ba882663..a0c690d57430 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4816,26 +4816,44 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
> idle_task_delta = cfs_rq->idle_h_nr_running;
> for_each_sched_entity(se) {
> if (se->on_rq)
> - enqueue = 0;
Can probably drop the now-unused enqueue variable too.
Cheers,
Phil
> + break;
> + cfs_rq = cfs_rq_of(se);
> + enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
>
> + cfs_rq->h_nr_running += task_delta;
> + cfs_rq->idle_h_nr_running += idle_task_delta;
> +
> + /* end evaluation on encountering a throttled cfs_rq */
> + if (cfs_rq_throttled(cfs_rq))
> + goto unthrottle_throttle;
> + }
> +
> + for_each_sched_entity(se) {
> cfs_rq = cfs_rq_of(se);
> - if (enqueue) {
> - enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
> - } else {
> - update_load_avg(cfs_rq, se, 0);
> - se_update_runnable(se);
> - }
> +
> + update_load_avg(cfs_rq, se, UPDATE_TG);
> + se_update_runnable(se);
>
> cfs_rq->h_nr_running += task_delta;
> cfs_rq->idle_h_nr_running += idle_task_delta;
>
> +
> + /* end evaluation on encountering a throttled cfs_rq */
> if (cfs_rq_throttled(cfs_rq))
> - break;
> + goto unthrottle_throttle;
> +
> + /*
> + * One parent has been throttled and cfs_rq removed from the
> + * list. Add it back to not break the leaf list.
> + */
> + if (throttled_hierarchy(cfs_rq))
> + list_add_leaf_cfs_rq(cfs_rq);
> }
>
> - if (!se)
> - add_nr_running(rq, task_delta);
> + /* At this point se is NULL and we are at root level*/
> + add_nr_running(rq, task_delta);
>
> +unthrottle_throttle:
> /*
> * The cfs_rq_throttled() breaks in the above iteration can result in
> * incomplete leaf list maintenance, resulting in triggering the
> @@ -4844,7 +4862,8 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
> for_each_sched_entity(se) {
> cfs_rq = cfs_rq_of(se);
>
> - list_add_leaf_cfs_rq(cfs_rq);
> + if (list_add_leaf_cfs_rq(cfs_rq))
> + break;
> }
>
> assert_list_leaf_cfs_rq(rq);
> --
> 2.17.1
>
--
On Wed, 13 May 2020 at 14:56, Phil Auld <[email protected]> wrote:
>
> Hi Vincent,
>
> On Wed, May 13, 2020 at 02:34:22PM +0200 Vincent Guittot wrote:
> > Although not exactly identical, unthrottle_cfs_rq() and enqueue_task_fair()
> > are quite close and follow the same sequence for enqueuing an entity in the
> > cfs hierarchy. Modify unthrottle_cfs_rq() to use the same pattern as
> > enqueue_task_fair(). This fixes a problem already faced with the latter and
> > add an optimization in the last for_each_sched_entity loop.
> >
> > Reported-by Tao Zhou <[email protected]>
> > Reviewed-by: Phil Auld <[email protected]>
> > Signed-off-by: Vincent Guittot <[email protected]>
> > ---
> >
> > v2 changes:
> > - Remove useless if statement
> >
> > kernel/sched/fair.c | 41 ++++++++++++++++++++++++++++++-----------
> > 1 file changed, 30 insertions(+), 11 deletions(-)
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 4e12ba882663..a0c690d57430 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -4816,26 +4816,44 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
> > idle_task_delta = cfs_rq->idle_h_nr_running;
> > for_each_sched_entity(se) {
> > if (se->on_rq)
> > - enqueue = 0;
>
> Can probably drop the now-unused enqueue variable too.
argh, yes, it dropped during rebase.
preparing a v3
>
>
> Cheers,
> Phil
>
>
>
> > + break;
> > + cfs_rq = cfs_rq_of(se);
> > + enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
> >
> > + cfs_rq->h_nr_running += task_delta;
> > + cfs_rq->idle_h_nr_running += idle_task_delta;
> > +
> > + /* end evaluation on encountering a throttled cfs_rq */
> > + if (cfs_rq_throttled(cfs_rq))
> > + goto unthrottle_throttle;
> > + }
> > +
> > + for_each_sched_entity(se) {
> > cfs_rq = cfs_rq_of(se);
> > - if (enqueue) {
> > - enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
> > - } else {
> > - update_load_avg(cfs_rq, se, 0);
> > - se_update_runnable(se);
> > - }
> > +
> > + update_load_avg(cfs_rq, se, UPDATE_TG);
> > + se_update_runnable(se);
> >
> > cfs_rq->h_nr_running += task_delta;
> > cfs_rq->idle_h_nr_running += idle_task_delta;
> >
> > +
> > + /* end evaluation on encountering a throttled cfs_rq */
> > if (cfs_rq_throttled(cfs_rq))
> > - break;
> > + goto unthrottle_throttle;
> > +
> > + /*
> > + * One parent has been throttled and cfs_rq removed from the
> > + * list. Add it back to not break the leaf list.
> > + */
> > + if (throttled_hierarchy(cfs_rq))
> > + list_add_leaf_cfs_rq(cfs_rq);
> > }
> >
> > - if (!se)
> > - add_nr_running(rq, task_delta);
> > + /* At this point se is NULL and we are at root level*/
> > + add_nr_running(rq, task_delta);
> >
> > +unthrottle_throttle:
> > /*
> > * The cfs_rq_throttled() breaks in the above iteration can result in
> > * incomplete leaf list maintenance, resulting in triggering the
> > @@ -4844,7 +4862,8 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
> > for_each_sched_entity(se) {
> > cfs_rq = cfs_rq_of(se);
> >
> > - list_add_leaf_cfs_rq(cfs_rq);
> > + if (list_add_leaf_cfs_rq(cfs_rq))
> > + break;
> > }
> >
> > assert_list_leaf_cfs_rq(rq);
> > --
> > 2.17.1
> >
>
> --
>