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

[Peter Zijlstra]

On Sat, Oct 11, 2025 at 11:24:47AM -0700, Tim Chen wrote:

> +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))
> +		return false;
> +
> +	llc = llc_idx(env->dst_cpu);
> +	if (sgs->nr_pref_llc[llc] > 0 &&

Robot says llc can be -1 here, and it don't like doing out of bound
array access.

> +	    can_migrate_llc(env->src_cpu, env->dst_cpu, 0, true) == mig_llc)
> +		return true;
> +
> +	return false;
> +}