Re: [PATCH 07/19] sched/fair: Track LLC-preferred tasks per runqueue

[K Prateek Nayak]

Hello Tim,

On 10/11/2025 11:54 PM, Tim Chen wrote:
> @@ -3999,6 +4038,7 @@ account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
>  		struct rq *rq = rq_of(cfs_rq);
>  
>  		account_numa_enqueue(rq, task_of(se));
> +		account_llc_enqueue(rq, task_of(se));
>  		list_add(&se->group_node, &rq->cfs_tasks);
>  	}
>  	cfs_rq->nr_queued++;
> @@ -4010,9 +4050,14 @@ account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
>  	update_load_sub(&cfs_rq->load, se->load.weight);
>  	if (entity_is_task(se)) {
>  		account_numa_dequeue(rq_of(cfs_rq), task_of(se));
> +		account_llc_dequeue(rq_of(cfs_rq), task_of(se));
>  		list_del_init(&se->group_node);
>  	}
>  	cfs_rq->nr_queued--;
> +
> +	/* safeguard to clear the cache aware data */
> +	if (!parent_entity(se) && !cfs_rq->nr_queued)
> +		reset_llc_stats(rq_of(cfs_rq));

Instead of relying on reset_llc_stats() hack, I think a better approach
would be to have a "p->se.llc_sched_active" flag similar to how uclamp
has "uc_se->active" and we set this in account_llc_enqueue() which will
still check for sched_cache_enabled() but account_llc_dequeue() would
only check for "p->se.llc_sched_active" to decrement the stats and then
unset the flag.

That way, we cannot have an imbalanced accounting. Thoughts?

>  }
>  

-- 
Thanks and Regards,
Prateek