Re: [RFC][PATCH 1/3] sched: Detect per-class runqueue changes

[Juri Lelli <juri.lelli@redhat.com>]

Hi Peter,

On 06/10/25 12:46, Peter Zijlstra wrote:
> Have enqueue/dequeue set a per-class bit in rq->queue_mask. This then
> enables easy tracking of which runqueues are modified over a
> lock-break.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> ---

Nice.

> @@ -12887,8 +12888,8 @@ static int sched_balance_newidle(struct
>  	if (this_rq->cfs.h_nr_queued && !pulled_task)
>  		pulled_task = 1;
>  
> -	/* Is there a task of a high priority class? */
> -	if (this_rq->nr_running != this_rq->cfs.h_nr_queued)
> +	/* If a higher prio class was modified, restart the pick */
> +	if (this_rq->queue_mask & ~((fair_sched_class.queue_mask << 1)-1))
>  		pulled_task = -1;

Does this however want a self-documenting inline helper or macro to make
it even more clear? If this is always going to be the only caller maybe
not so much.

Thanks,
Juri