Re: [PATCH 10/19] sched/fair: Prioritize tasks preferring destination LLC during balancing

[K Prateek Nayak]

Hello Tim,

On 10/11/2025 11:54 PM, Tim Chen wrote:
> +/*
> + * Do LLC balance on sched group that contains LLC, and have tasks preferring
> + * to run on LLC in idle dst_cpu.
> + */
> +static inline bool llc_balance(struct lb_env *env, struct sg_lb_stats *sgs,
> +			       struct sched_group *group)
> +{
> +	struct sched_domain *child = env->sd->child;
> +	int llc;
> +
> +	if (!sched_cache_enabled())
> +		return false;
> +
> +	if (env->sd->flags & SD_SHARE_LLC)
> +		return false;
> +
> +	/* only care about task migration among LLCs */
> +	if (child && !(child->flags & SD_SHARE_LLC))

nit. You can just check group->flags here.

> +		return false;
> +
> +	llc = llc_idx(env->dst_cpu);
> +	if (sgs->nr_pref_llc[llc] > 0 &&
> +	    can_migrate_llc(env->src_cpu, env->dst_cpu, 0, true) == mig_llc)
> +		return true;
> +
> +	return false;
> +}
>  #else
>  static inline void record_sg_llc_stats(struct lb_env *env, struct sg_lb_stats *sgs,
>  				       struct sched_group *group)
>  {
>  }
> +
> +static inline bool llc_balance(struct lb_env *env, struct sg_lb_stats *sgs,
> +			       struct sched_group *group)
> +{
> +	return false;
> +}
>  #endif
>  
>  /**
> @@ -10954,6 +10988,11 @@ static inline void update_sg_lb_stats(struct lb_env *env,
>  	sgs->group_type = group_classify(env->sd->imbalance_pct, group, sgs);
>  
>  	record_sg_llc_stats(env, sgs, group);

Okay, I see the intention of recording this based on group stats.
Sorry for the noise on Patch 2.

> +
> +	/* Check for tasks in this group can be moved to their preferred LLC */
> +	if (!local_group && llc_balance(env, sgs, group))
> +		sgs->group_llc_balance = 1;
> +
>  	/* Computing avg_load makes sense only when group is overloaded */
>  	if (sgs->group_type == group_overloaded)
>  		sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) /

-- 
Thanks and Regards,
Prateek