Re: [PATCH v3 4/4] sched/fair: Check the SD_ASYM_PACKING flag in sched_use_asym_prio()

[Ricardo Neri]

On Thu, Feb 01, 2024 at 07:54:47PM +0800, alexs@xxxxxxxxxx wrote:
> From: Alex Shi <alexs@xxxxxxxxxx>
> 
> 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"

s/places"/places./

> 
> Signed-off-by: Alex Shi <alexs@xxxxxxxxxx>
> To: Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx>
> To: Ben Segall <bsegall@xxxxxxxxxx>
> To: Steven Rostedt <rostedt@xxxxxxxxxxx>
> To: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
> To: Valentin Schneider <vschneid@xxxxxxxxxx>
> To: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
> To: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
> To: Juri Lelli <juri.lelli@xxxxxxxxxx>
> To: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> To: Ingo Molnar <mingo@xxxxxxxxxx>
> ---
>  kernel/sched/fair.c | 15 +++++++--------
>  1 file changed, 7 insertions(+), 8 deletions(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 44fd5e2ca642..bd32efbea688 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -9741,6 +9741,9 @@ 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;
>  
> @@ -9940,11 +9943,9 @@ 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))

You should align sched_group_asym() to !local_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))
> @@ -11040,9 +11041,7 @@ 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) {
> @@ -11138,7 +11137,7 @@ 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) &&
> +	return env->idle != CPU_NOT_IDLE &&
>  	       sched_use_asym_prio(env->sd, env->dst_cpu) &&
>  	       (sched_asym_prefer(env->dst_cpu, env->src_cpu) ||

Perhaps you can rearrange the spaghetti of conditions to make better use of
the full 80-column line.