Re: [PATCH 7/8] sched/fair: Do not compute overloaded status unnecessarily during lb

[Vincent Guittot]

On Wed, 11 Dec 2024 at 19:58, K Prateek Nayak <kprateek.nayak@xxxxxxx> wrote:
>
> Only set sg_overloaded when computing sg_lb_stats() at the highest sched
> domain since rd->overloaded status is updated only when load balancing
> at the highest domain. While at it, move setting of sg_overloaded below
> idle_cpu() check since an idle CPU can never be overloaded.
>
> Signed-off-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>
> ---
>  kernel/sched/fair.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index ec2a79c8d0e7..3f36805ecdca 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -10358,9 +10358,6 @@ static inline void update_sg_lb_stats(struct lb_env *env,
>                 nr_running = rq->nr_running;
>                 sgs->sum_nr_running += nr_running;
>
> -               if (nr_running > 1)
> -                       *sg_overloaded = 1;
> -
>                 if (cpu_overutilized(i))
>                         *sg_overutilized = 1;
>
> @@ -10373,6 +10370,10 @@ static inline void update_sg_lb_stats(struct lb_env *env,
>                         continue;
>                 }
>
> +               /* Overload indicator is only updated at root domain */
> +               if (!env->sd->parent && nr_running > 1)

nit: may be worth checking local variable 1st which should be cheaper
than env->sd->parent

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


> +                       *sg_overloaded = 1;
> +
>  #ifdef CONFIG_NUMA_BALANCING
>                 /* Only fbq_classify_group() uses this to classify NUMA groups */
>                 if (sd_flags & SD_NUMA) {
> --
> 2.34.1
>