2020-11-10 02:14:19

by Peng Wang

Subject: [PATCH] sched/fair: Reorder throttle_cfs_rq() path

As commit 39f23ce07b93 ("sched/fair: Fix unthrottle_cfs_rq() for
leaf_cfs_rq list") does in unthrottle_cfs_rq(), throttle_cfs_rq()
can also use the same pattern as dequeue_task_fair().

There is no functional changes.

Signed-off-by: Peng Wang <[email protected]>
---
kernel/sched/fair.c | 34 +++++++++++++++++++++++-----------
1 file changed, 23 insertions(+), 11 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 290f9e3..27a69af 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4779,25 +4779,37 @@ static bool throttle_cfs_rq(struct cfs_rq *cfs_rq)
struct cfs_rq *qcfs_rq = cfs_rq_of(se);
/* throttled entity or throttle-on-deactivate */
if (!se->on_rq)
- break;
+ goto done;

- if (dequeue) {
- dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
- } else {
- update_load_avg(qcfs_rq, se, 0);
- se_update_runnable(se);
- }
+ dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);

qcfs_rq->h_nr_running -= task_delta;
qcfs_rq->idle_h_nr_running -= idle_task_delta;

- if (qcfs_rq->load.weight)
- dequeue = 0;
+ if (qcfs_rq->load.weight) {
+ /* Avoid re-evaluating load for this entity: */
+ se = parent_entity(se);
+ break;
+ }
}

- if (!se)
- sub_nr_running(rq, task_delta);
+ for_each_sched_entity(se) {
+ struct cfs_rq *qcfs_rq = cfs_rq_of(se);
+ /* throttled entity or throttle-on-deactivate */
+ if (!se->on_rq)
+ goto done;
+
+ update_load_avg(qcfs_rq, se, 0);
+ se_update_runnable(se);

+ qcfs_rq->h_nr_running -= task_delta;
+ qcfs_rq->idle_h_nr_running -= idle_task_delta;
+ }
+
+ /* At this point se is NULL and we are at root level*/
+ sub_nr_running(rq, task_delta);
+
+done:
/*
* Note: distribution will already see us throttled via the
* throttled-list. rq->lock protects completion.
--
2.9.5

2020-11-11 20:29:29

by Benjamin Segall

Subject: Re: [PATCH] sched/fair: Reorder throttle_cfs_rq() path

Peng Wang <[email protected]> writes:

> As commit 39f23ce07b93 ("sched/fair: Fix unthrottle_cfs_rq() for
> leaf_cfs_rq list") does in unthrottle_cfs_rq(), throttle_cfs_rq()
> can also use the same pattern as dequeue_task_fair().
>
> There is no functional changes.

It's generally a bit more hassle and less clear, but the parallel to
dequeue_task_fair probably makes up for it.

Reviewed-by: Ben Segall <[email protected]>

>
> Signed-off-by: Peng Wang <[email protected]>
> ---
> kernel/sched/fair.c | 34 +++++++++++++++++++++++-----------
> 1 file changed, 23 insertions(+), 11 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 290f9e3..27a69af 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4779,25 +4779,37 @@ static bool throttle_cfs_rq(struct cfs_rq *cfs_rq)
> struct cfs_rq *qcfs_rq = cfs_rq_of(se);
> /* throttled entity or throttle-on-deactivate */
> if (!se->on_rq)
> - break;
> + goto done;
>
> - if (dequeue) {
> - dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
> - } else {
> - update_load_avg(qcfs_rq, se, 0);
> - se_update_runnable(se);
> - }
> + dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
>
> qcfs_rq->h_nr_running -= task_delta;
> qcfs_rq->idle_h_nr_running -= idle_task_delta;
>
> - if (qcfs_rq->load.weight)
> - dequeue = 0;
> + if (qcfs_rq->load.weight) {
> + /* Avoid re-evaluating load for this entity: */
> + se = parent_entity(se);
> + break;
> + }
> }
>
> - if (!se)
> - sub_nr_running(rq, task_delta);
> + for_each_sched_entity(se) {
> + struct cfs_rq *qcfs_rq = cfs_rq_of(se);
> + /* throttled entity or throttle-on-deactivate */
> + if (!se->on_rq)
> + goto done;
> +
> + update_load_avg(qcfs_rq, se, 0);
> + se_update_runnable(se);
>
> + qcfs_rq->h_nr_running -= task_delta;
> + qcfs_rq->idle_h_nr_running -= idle_task_delta;
> + }
> +
> + /* At this point se is NULL and we are at root level*/
> + sub_nr_running(rq, task_delta);
> +
> +done:
> /*
> * Note: distribution will already see us throttled via the
> * throttled-list. rq->lock protects completion.