On Mon, Oct 19, 2020 at 09:43:16PM -0400, Joel Fernandes (Google) wrote:
> + /*
> + * If this sibling doesn't yet have a suitable task to
> + * run; ask for the most elegible task, given the
> + * highest priority task already selected for this
> + * core.
> + */
> + p = pick_task(rq_i, class, max);
> + if (!p) {
> + /*
> + * If there weren't no cookies; we don't need to
> + * bother with the other siblings.
> + * If the rest of the core is not running a
> tagged
> + * task, i.e. need_sync == 0, and the current
> CPU
> + * which called into the schedule() loop does
> not
> + * have any tasks for this class, skip
> selecting for
> + * other siblings since there's no point. We
> don't skip
> + * for RT/DL because that could make CFS
> force-idle RT.
> + */
> + if (i == cpu && !need_sync && class ==
> &fair_sched_class)
> + goto next_class;
> +
> + continue;
> + }
I'm failing to understand the class == &fair_sched_class bit.
IIRC the condition is such that the core doesn't have a cookie (we don't
need to sync the threads) so we'll only do a pick for our local CPU.
That should be invariant of class.
