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SubjectRe: [PATCH v6 8/9] sched/fair: move task sched_avg attach to enqueue_task_fair()
On Thu, 18 Aug 2022 at 14:48, Chengming Zhou
<zhouchengming@bytedance.com> wrote:
>
> When wake_up_new_task(), we use post_init_entity_util_avg() to init
> util_avg/runnable_avg based on cpu's util_avg at that time, and
> attach task sched_avg to cfs_rq.
>
> Since enqueue_task_fair() -> enqueue_entity() -> update_load_avg()
> loop will do attach, we can move this work to update_load_avg().
>
> wake_up_new_task(p)
> post_init_entity_util_avg(p)
> attach_entity_cfs_rq() --> (1)
> activate_task(rq, p)
> enqueue_task() := enqueue_task_fair()
> enqueue_entity() loop
> update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH)
> if (!se->avg.last_update_time && (flags & DO_ATTACH))
> attach_entity_load_avg() --> (2)
>
> This patch move attach from (1) to (2), update related comments too.
>
> Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>

Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>

> ---
> kernel/sched/fair.c | 11 +++--------
> 1 file changed, 3 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index c319b0bd2bc1..93d7c7b110dd 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -799,8 +799,6 @@ void init_entity_runnable_average(struct sched_entity *se)
> /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
> }
>
> -static void attach_entity_cfs_rq(struct sched_entity *se);
> -
> /*
> * With new tasks being created, their initial util_avgs are extrapolated
> * based on the cfs_rq's current util_avg:
> @@ -863,8 +861,6 @@ void post_init_entity_util_avg(struct task_struct *p)
> se->avg.last_update_time = cfs_rq_clock_pelt(cfs_rq);
> return;
> }
> -
> - attach_entity_cfs_rq(se);
> }
>
> #else /* !CONFIG_SMP */
> @@ -4002,8 +3998,7 @@ static void migrate_se_pelt_lag(struct sched_entity *se) {}
> * @cfs_rq: cfs_rq to update
> *
> * The cfs_rq avg is the direct sum of all its entities (blocked and runnable)
> - * avg. The immediate corollary is that all (fair) tasks must be attached, see
> - * post_init_entity_util_avg().
> + * avg. The immediate corollary is that all (fair) tasks must be attached.
> *
> * cfs_rq->avg is used for task_h_load() and update_cfs_share() for example.
> *
> @@ -4236,8 +4231,8 @@ static void remove_entity_load_avg(struct sched_entity *se)
>
> /*
> * tasks cannot exit without having gone through wake_up_new_task() ->
> - * post_init_entity_util_avg() which will have added things to the
> - * cfs_rq, so we can remove unconditionally.
> + * enqueue_task_fair() which will have added things to the cfs_rq,
> + * so we can remove unconditionally.
> */
>
> sync_entity_load_avg(se);
> --
> 2.37.2
>

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