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SubjectRe: [PATCH v6 9/9] sched/fair: don't init util/runnable_avg for !fair task
On Thu, 18 Aug 2022 at 14:48, Chengming Zhou
<zhouchengming@bytedance.com> wrote:
>
> post_init_entity_util_avg() init task util_avg according to the cpu util_avg
> at the time of fork, which will decay when switched_to_fair() some time later,
> we'd better to not set them at all in the case of !fair task.
>
> Suggested-by: Vincent Guittot <vincent.guittot@linaro.org>
> Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>

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

> ---
> kernel/sched/fair.c | 28 ++++++++++++++--------------
> 1 file changed, 14 insertions(+), 14 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 93d7c7b110dd..621bd19e10ae 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -833,20 +833,6 @@ void post_init_entity_util_avg(struct task_struct *p)
> long cpu_scale = arch_scale_cpu_capacity(cpu_of(rq_of(cfs_rq)));
> long cap = (long)(cpu_scale - cfs_rq->avg.util_avg) / 2;
>
> - if (cap > 0) {
> - if (cfs_rq->avg.util_avg != 0) {
> - sa->util_avg = cfs_rq->avg.util_avg * se->load.weight;
> - sa->util_avg /= (cfs_rq->avg.load_avg + 1);
> -
> - if (sa->util_avg > cap)
> - sa->util_avg = cap;
> - } else {
> - sa->util_avg = cap;
> - }
> - }
> -
> - sa->runnable_avg = sa->util_avg;
> -
> if (p->sched_class != &fair_sched_class) {
> /*
> * For !fair tasks do:
> @@ -861,6 +847,20 @@ void post_init_entity_util_avg(struct task_struct *p)
> se->avg.last_update_time = cfs_rq_clock_pelt(cfs_rq);
> return;
> }
> +
> + if (cap > 0) {
> + if (cfs_rq->avg.util_avg != 0) {
> + sa->util_avg = cfs_rq->avg.util_avg * se->load.weight;
> + sa->util_avg /= (cfs_rq->avg.load_avg + 1);
> +
> + if (sa->util_avg > cap)
> + sa->util_avg = cap;
> + } else {
> + sa->util_avg = cap;
> + }
> + }
> +
> + sa->runnable_avg = sa->util_avg;
> }
>
> #else /* !CONFIG_SMP */
> --
> 2.37.2
>

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