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SubjectRe: [PATCH v4 1/2] block, bfq: counted root group into 'num_groups_with_pending_reqs'
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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?

Thanks,
Kuai

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