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SubjectRe: [PATCH v4 1/2] block, bfq: counted root group into 'num_groups_with_pending_reqs'
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> Il giorno 20 ott 2021, alle ore 11:38, yukuai (C) <yukuai3@huawei.com> ha scritto:
>
> On 2021/10/20 17:29, Paolo Valente wrote:
>>> Il giorno 20 ott 2021, alle ore 11:20, yukuai (C) <yukuai3@huawei.com> ha scritto:
>>>
>>> On 2021/10/20 16:51, Paolo Valente wrote:
>>>
>>>>> @@ -860,9 +870,25 @@ void bfq_weights_tree_remove(struct bfq_data *bfqd,
>>>>> struct bfq_queue *bfqq)
>>>>> {
>>>>> struct bfq_entity *entity = bfqq->entity.parent;
>>>>> + struct bfq_sched_data *sd;
>>>>> +
>>>>> + /*
>>>>> + * If the bfq queue is in root group, the decrement of
>>>>> + * num_groups_with_pending_reqs is performed immediately upon the
>>>>> + * deactivation of entity.
>>>>> + */
>>>>> + if (!entity) {
>>>>> + entity = &bfqd->root_group->entity;
>>>>> + sd = entity->my_sched_data;
>>>>> +
>>>>> + if (!sd->in_service_entity)
>>>>> + bfq_clear_group_with_pending_reqs(bfqd, entity);
>>>>> +
>>>>> + return;
>>>>> + }
>>>>>
>>>>> for_each_entity(entity) {
>>>>> - struct bfq_sched_data *sd = entity->my_sched_data;
>>>>> + sd = entity->my_sched_data;
>>>>>
>>>>> if (sd->next_in_service || sd->in_service_entity) {
>>>>> /*
>>>>> @@ -880,7 +906,8 @@ void bfq_weights_tree_remove(struct bfq_data *bfqd,
>>>>> }
>>>>>
>>>>> /*
>>>>> - * The decrement of num_groups_with_pending_reqs is
>>>>> + * If the bfq queue is not in root group,
>>>>> + * the decrement of num_groups_with_pending_reqs is
>>>> I'm sorry if I didn't notice this before, but why do you postpone the
>>>> decrement only for queues not in root group? If I'm not missing
>>>> anything, the active (i.e., with pending reqs) state of the root group
>>>> is to be computed as that of ay other group.
>>>
>>> Hi, Paolo
>>>
>>> I thought if queue is in root group, then bfqq->entity.parent is NULL,
>>> and such case is handled above, which is separate from previous
>>> implementation for queues that are not in root group.
>>>
>>> Is this the wrong way to handle root group?
>>>
>> I think that, if we want to count also the root group among the active
>> ones, then the logic for tagging the root group as active must be the
>> same as the other groups. Or am I missing something?
>
> Hi, Paolo
>
> Currently, if queue is in root group, bfqq->entity.parent is NULL, and
> this makes it hard to keep the same logic.
>
> Can we store root_group->my_entity to bfqq->entity.parent if the queue
> is in root group?
>

Any sensible implementation is ok for me. Usually, stuff for root
group is in the bfqd.

Thanks,
Paolo

> Thanks,
> Kuai

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