Re: [PATCH] sched/cache: Avoid publishing partial LLC utilization

[K Prateek Nayak]

Hello Jemmy,

On 10/10/2026 5:04 PM, Jemmy Wong wrote:
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -12121,6 +12121,13 @@ static void record_sg_llc_stats(struct lb_env *env,
>  	if (env->sd->child != rcu_dereference_all(per_cpu(sd_llc, env->dst_cpu)))
>  		return;
> 
> +	/*
> +	 * Affinity retries can remove CPUs from env->cpus. Do not publish
> +	 * partial utilization against the capacity of the whole group.
> +	 */
> +	if (!cpumask_subset(sched_group_span(group), env->cpus))
> +		return;
> +

nit.

When sched_balance_rq() does a "redo" and arrives here, env->flags
will always have LBF_ALL_PINNED set.

That would be a much cheaper check compared to cpumask_subset() to
ensure env->cpus covers all CPUs.

Thoughts?

>  	/*
>  	 * At this point we know this group spans a LLC domain.
>  	 * Record the statistic of this group in its corresponding
> --
> 2.25.1

-- 
Thanks and Regards,
Prateek