Re: [PATCH v2 2/4] block, bfq: do not idle if only one cgroup is activated

[yukuai (C)]

On 2021/09/07 17:10, Paolo Valente wrote:
> > Il giorno 2 set 2021, alle ore 15:31, yukuai (C) <yukuai3@xxxxxxxxxx> ha scritto:
> >
> > On 2021/08/27 1:00, Paolo Valente wrote:
> > > Why do you make these extensive changes, while you can leave all the
> > > function unchanged and just modify the above condition to something
> > > like
> > > || bfqd->num_groups_with_pending_reqs > 1
> > > || (bfqd->num_groups_with_pending_reqs && bfqd->num_queues_with_pending_reqs_in_root)
> >
> > Hi, Paolo
> >
> > I was thinking that if CONFIG_BFQ_GROUP_IOSCHED is enabled, there is no
> > need to caculate smallest_weight, varied_queue_weights, and
> > multiple_classes_busy:
> >
> > If we count root group into num_groups_with_pending_reqs
> > - If num_groups_with_pending_reqs <= 1, idle is not needed
>
> Unfortunately, if active queues have different weights or belong to
> different classes, then idling is needed to preserve per-queue
> bandwidths.
>
> Thanks,
> Paolo

Hi, Paolo

It's right, if num_groups_with_pending_reqs == 1, multiple_classes_busy
should be checked, while smallest_weight and varied_queue_weights can
be skipped.

Thanks
Kuai

> .