Re: [PATCH v3 1/4] sched/fair: Check CPU capacity before comparing group types during load balance

[Chen, Yu C]

On 5/15/2026 2:34 AM, Ricardo Neri wrote:

[ ... ]

> @@ -10818,6 +10818,20 @@ static bool update_sd_pick_busiest(struct lb_env *env,
>   	     sds->local_stat.group_type != group_has_spare))
>   		return false;
>   
> +	/*
> +	 * Candidate sg has no more than one task per CPU and has higher
> +	 * per-CPU capacity. Migrating tasks to less capable CPUs may harm
> +	 * throughput. Maximize throughput, power/energy consequences are not
> +	 * considered.
> +	 *
> +	 * Systems with SMT are unaffected, as asymmetric capacity is not set
> +	 * in such cases.
> +	 */

Does "SMT" here imply that group_smt_balance is unaffected?
Regardless of whether we move the check earlier, this seems to
already be guaranteed by the fact that the check only applies
to sgs->group_type <= group_fully_busy, which does not include
group_smt_balance. In other words, SD_ASYM_CPUCAPACITY is not
the only gatekeeper.

Other than that, the change looks good to me,Reviewed-by: Chen Yu 
<yu.c.chen@xxxxxxxxx>

thanks,
Chenyu
> +	if ((env->sd->flags & SD_ASYM_CPUCAPACITY) &&
> +	    (sgs->group_type <= group_fully_busy) &&
> +	    (capacity_greater(sg->sgc->min_capacity, capacity_of(env->dst_cpu))))
> +		return false;
> +