Re: [PATCH 1/3] block, bfq: do not idle if only one cgroup is activated

[yukuai (C)]

On 2021/07/24 15:12, Paolo Valente wrote:
> > Il giorno 14 lug 2021, alle ore 11:45, Yu Kuai <yukuai3@xxxxxxxxxx> ha scritto:
> >
> > If only one group is activated, specifically
> > 'bfqd->num_groups_with_pending_reqs == 1', there is no need to guarantee
> > the same share of the throughput of queues in the same group.
> >
> > Thus change the condition from '> 0' to '> 1' in
> > bfq_asymmetric_scenario().
>
> I see your point, and I agree with your goal.  Yet, your change seems
> not to suffer from the following problem.
>
> In addition to the groups that are created explicitly, there is the
> implicit root group.  So, when bfqd->num_groups_with_pending_reqs ==
> 1, there may be both active processes in the root group and active
> processes in the only group created explicitly.  In this case, idling
> is needed to preserve service guarantees.
>
> Probably your idea should be improved by making sure that there is
> pending I/O only from either the root group or the explicit group.
>
> Thanks,
> Paolo

Hi,

Thanks for you advice, will do this in the next iteration.

Best regards,
Kuai