Re: [RFC PATCH 4/6] sched/fair: Restrict newidle balance to LLC domain

[Peter Zijlstra <peterz@infradead.org>]

On Tue, Oct 20, 2026 at 04:37:44PM +0800, Li kunyu wrote:

> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 6e2271484c86..f2bf4b53d8a9 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -14983,6 +14983,24 @@ static inline bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle
>  static inline void nohz_newidle_balance(struct rq *this_rq) { }
>  #endif /* !CONFIG_NO_HZ_COMMON */
>  
> +/*
> + * is_smt_buddy_newidle_constrain - After enabling the smt_buddy_assist
> + *                                  feature, check whether the current
> + *                                  scheduling domain meets the conditions
> + *                                  for skipping statistics.
> + * @sd: The current scheduling domain that is to be traversed.
> + */
> +static bool is_smt_buddy_newidle_constrain(struct sched_domain *sd)
> +{
> +	if (!sched_feat(SMT_BUDDY_ASSIST))
> +		return false;
> +
> +	if (sd->flags & SD_NUMA)
> +		return true;
> +
> +	return false;
> +}
> +
>  /*
>   * sched_balance_newidle is called by schedule() if this_cpu is about to become
>   * idle. Attempts to pull tasks from other CPUs.
> @@ -15080,7 +15098,8 @@ static int sched_balance_newidle(struct rq *this_rq, struct rq_flags *rf)
>  				weight = (1024 + weight/2) / weight;
>  			}
>  
> -			pulled_task = sched_balance_rq(this_cpu, this_rq,
> +			if (!is_smt_buddy_newidle_constrain(sd))
> +				pulled_task = sched_balance_rq(this_cpu, this_rq,
>  						   sd, CPU_NEWLY_IDLE,
>  						   &continue_balancing,
>  							false);

You could have just fiddled with SD_BALANCE_NEWIDLE, no? But instead you
went and did something inscrutable and violated coding style *again*.
Any multi-line block must have {} on.