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SubjectRe: [PATCH 1/3] block, bfq: do not idle if only one cgroup is activated
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On 2021/07/24 15:12, Paolo Valente wrote:
>
>
>> Il giorno 14 lug 2021, alle ore 11:45, Yu Kuai <yukuai3@huawei.com> 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

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