Re: [PATCH v3 07/11] sched_ext: Add an event, SCX_EV_BYPASS_DISPATCH

[Tejun Heo]

Hello,

On Fri, Jan 31, 2025 at 04:09:34PM +0900, Changwoo Min wrote:
...
> @@ -2869,11 +2874,17 @@ static int balance_one(struct rq *rq, struct task_struct *prev)
>  	}
>  
>  	/* if there already are tasks to run, nothing to do */
> -	if (rq->scx.local_dsq.nr)
> +	if (rq->scx.local_dsq.nr) {
> +		if (scx_rq_bypassing(rq))
> +			__scx_add_event(SCX_EV_BYPASS_DISPATCH, 1);
>  		goto has_tasks;
> +	}
>  
> -	if (consume_global_dsq(rq))
> +	if (consume_global_dsq(rq)) {
> +		if (scx_rq_bypassing(rq))
> +			__scx_add_event(SCX_EV_BYPASS_DISPATCH, 1);

Hmm... Wouldn't it be easier to count it from select_task_rq_scx() and
do_enqueue_task()? The latter already has scx_rq_bypassing() condition and
the former one can easily cache bypassing test result and use that in the
else block.

> @@ -2899,10 +2910,16 @@ static int balance_one(struct rq *rq, struct task_struct *prev)
>  			rq->scx.flags |= SCX_RQ_BAL_KEEP;
>  			goto has_tasks;
>  		}
> -		if (rq->scx.local_dsq.nr)
> +		if (rq->scx.local_dsq.nr) {
> +			if (scx_rq_bypassing(rq))
> +				__scx_add_event(SCX_EV_BYPASS_DISPATCH, 1);
>  			goto has_tasks;
> -		if (consume_global_dsq(rq))
> +		}
> +		if (consume_global_dsq(rq)) {
> +			if (scx_rq_bypassing(rq))
> +				__scx_add_event(SCX_EV_BYPASS_DISPATCH, 1);
>  			goto has_tasks;
> +		}

The above can happen while bypass mode is being turned on but once on
control doesn't even reach here, right?

Thanks.

-- 
tejun