linux-kernel - Re: [PATCH v5 4/5] sched/fair: Check the SD_ASYM_PACKING flag in sched_use_asym

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Date: Tue, 13 Feb 2024 18:02:01 +0100
From: Vincent Guittot <vincent.guittot@...aro.org>
To: alexs@...nel.org
Cc: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>, 
	Juri Lelli <juri.lelli@...hat.com>, Dietmar Eggemann <dietmar.eggemann@....com>, 
	Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>, 
	Daniel Bristot de Oliveira <bristot@...hat.com>, Valentin Schneider <vschneid@...hat.com>, 
	"open list:SCHEDULER" <linux-kernel@...r.kernel.org>, 
	Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Subject: Re: [PATCH v5 4/5] sched/fair: Check the SD_ASYM_PACKING flag in sched_use_asym_prio()

On Sat, 10 Feb 2024 at 12:36, <alexs@...nel.org> wrote:
>
> From: Alex Shi <alexs@...nel.org>
>
> sched_use_asym_prio() checks whether CPU priorities should be used. It
> makes sense to check for the SD_ASYM_PACKING() inside the function.
> Since both sched_asym() and sched_group_asym() use sched_use_asym_prio(),
> remove the now superfluous checks for the flag in various places.
>
> Tested-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
> Signed-off-by: Alex Shi <alexs@...nel.org>
> Cc: linux-kernel@...r.kernel.org
> Cc: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
> Cc: Ben Segall <bsegall@...gle.com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Dietmar Eggemann <dietmar.eggemann@....com>
> Cc: Valentin Schneider <vschneid@...hat.com>
> Cc: Daniel Bristot de Oliveira <bristot@...hat.com>
> Cc: Vincent Guittot <vincent.guittot@...aro.org>
> Cc: Juri Lelli <juri.lelli@...hat.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Ingo Molnar <mingo@...hat.com>
> Reviewed-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>

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

> ---
>  kernel/sched/fair.c | 16 +++++++---------
>  1 file changed, 7 insertions(+), 9 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 426eda9eda57..cd1ec57c0b7b 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -9740,6 +9740,9 @@ group_type group_classify(unsigned int imbalance_pct,
>   */
>  static bool sched_use_asym_prio(struct sched_domain *sd, int cpu)
>  {
> +       if (!(sd->flags & SD_ASYM_PACKING))
> +               return false;
> +
>         if (!sched_smt_active())
>                 return true;
>
> @@ -9933,11 +9936,9 @@ static inline void update_sg_lb_stats(struct lb_env *env,
>         sgs->group_weight = group->group_weight;
>
>         /* Check if dst CPU is idle and preferred to this group */
> -       if (!local_group && env->sd->flags & SD_ASYM_PACKING &&
> -           env->idle != CPU_NOT_IDLE && sgs->sum_h_nr_running &&
> -           sched_group_asym(env, sgs, group)) {
> +       if (!local_group && env->idle != CPU_NOT_IDLE && sgs->sum_h_nr_running &&
> +           sched_group_asym(env, sgs, group))
>                 sgs->group_asym_packing = 1;
> -       }
>
>         /* Check for loaded SMT group to be balanced to dst CPU */
>         if (!local_group && smt_balance(env, sgs, group))
> @@ -11033,9 +11034,7 @@ static struct rq *find_busiest_queue(struct lb_env *env,
>                  * If balancing between cores, let lower priority CPUs help
>                  * SMT cores with more than one busy sibling.
>                  */
> -               if ((env->sd->flags & SD_ASYM_PACKING) &&
> -                   sched_asym(env->sd, i, env->dst_cpu) &&
> -                   nr_running == 1)
> +               if (sched_asym(env->sd, i, env->dst_cpu) && nr_running == 1)
>                         continue;
>
>                 switch (env->migration_type) {
> @@ -11131,8 +11130,7 @@ asym_active_balance(struct lb_env *env)
>          * the lower priority @env::dst_cpu help it. Do not follow
>          * CPU priority.
>          */
> -       return env->idle != CPU_NOT_IDLE && (env->sd->flags & SD_ASYM_PACKING) &&
> -              sched_use_asym_prio(env->sd, env->dst_cpu) &&
> +       return env->idle != CPU_NOT_IDLE && sched_use_asym_prio(env->sd, env->dst_cpu) &&
>                (sched_asym_prefer(env->dst_cpu, env->src_cpu) ||
>                 !sched_use_asym_prio(env->sd, env->src_cpu));
>  }
> --
> 2.43.0
>