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

[Changwoo Min]

Hello,

On 25. 2. 3. 02:33, Tejun Heo wrote:
> 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.

That makes sense. I will change the code as you suggested.

> > @@ -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?

You are right. I will clean this up.

Regards,
Changwoo Min