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SubjectRe: [PATCH v2 2/4] block, bfq: do not idle if only one cgroup is activated
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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
- If num_groups_with_pending_reqs > 1, idle is needed

Thus such changes can save some additional overhead.

Thanks
Yu Kuai

>
> In addition, I still wonder whether you can simply add also the root
> group to bfqd->num_groups_with_pending_reqs (when the root group is
> active). This would make the design much cleaner.
>
> Thanks,
> Paolo
>
>> -#endif
>> - ;
>> + return varied_queue_weights || multiple_classes_busy;
>> }
>>
>> /*
>> --
>> 2.31.1
>>
>
> .
>

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