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Message-ID: <7ee856f6-ca13-67dc-d2db-d73ef31ffdd9@huawei.com>
Date: Thu, 2 Sep 2021 21:23:07 +0800
From: "yukuai (C)" <yukuai3@...wei.com>
To: Paolo Valente <paolo.valente@...aro.org>
CC: <axboe@...nel.dk>, <linux-block@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, <yi.zhang@...wei.com>
Subject: Re: [PATCH v2 1/4] block, bfq: add support to track if root_group
have any pending requests
On 2021/08/27 1:00, Paolo Valente wrote:
>
>
>> Il giorno 6 ago 2021, alle ore 04:08, Yu Kuai <yukuai3@...wei.com> ha scritto:
>>
>> Add a new member in bfq_data to track number of queues that are in
>> root_group with any pending requests.
>
> maybe modify the last part of the sentence as: ... and that have some pending request
>
>> This will be used in next patch
>> to optmize queue idle judgment when root_group doesn't have any
>> pending requests.
>>
>> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
>> ---
>> block/bfq-iosched.c | 8 +++++++-
>> block/bfq-iosched.h | 13 +++++++++++--
>> block/bfq-wf2q.c | 37 ++++++++++++++++++++++++-------------
>> 3 files changed, 42 insertions(+), 16 deletions(-)
>>
>> diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
>> index 727955918563..7c6b412f9a9c 100644
>> --- a/block/bfq-iosched.c
>> +++ b/block/bfq-iosched.c
>> @@ -859,8 +859,14 @@ void __bfq_weights_tree_remove(struct bfq_data *bfqd,
>> void bfq_weights_tree_remove(struct bfq_data *bfqd,
>> struct bfq_queue *bfqq)
>> {
>> - struct bfq_entity *entity = bfqq->entity.parent;
>> + struct bfq_entity *entity = &bfqq->entity;
>> +
>> + if (entity->in_groups_with_pending_reqs) {
>> + entity->in_groups_with_pending_reqs = false;
>> + bfqd->num_queues_with_pending_reqs_in_root--;
>
> Here you cross the comment "The decrement of
> num_groups_with_pending_reqs is not performed immediately upon ...".
>
> Find a way to
> - move that comment up, and to make it correct for this slightly
> different decrement
> - leave a correct comment (probably shorter) in the original position
>
>> + }
>>
>> + entity = entity->parent;
>> for_each_entity(entity) {
>> struct bfq_sched_data *sd = entity->my_sched_data;
>>
>> diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
>> index 99c2a3cb081e..610769214f72 100644
>> --- a/block/bfq-iosched.h
>> +++ b/block/bfq-iosched.h
>> @@ -195,7 +195,12 @@ struct bfq_entity {
>> /* flag, set to request a weight, ioprio or ioprio_class change */
>> int prio_changed;
>>
>> - /* flag, set if the entity is counted in groups_with_pending_reqs */
>> + /*
>> + * If entity represents bfq_group, this flag will set
>
> will be set?
>
>> if the group is
>> + * not root_group and have
>
> has
>
>> any pending requests; If entity represents
>
> one more nit: use lowercase after semicolon
>
>> + * bfq_queue, this flag will set
>
> will be set
>
>> if the queue is in root_group and have
>> + * any pending requests.
>> + */
>> bool in_groups_with_pending_reqs;
>>
>
> The name of the above field follows from the fact that entity is
> counted in groups_with_pending_reqs. You change this fact, because,
> in your patch, a queue is not counted in groups_with_pending_reqs.
> But you leave the same name. This creates confusion.
>
>
>> /* last child queue of entity created (for non-leaf entities) */
>> @@ -539,7 +544,11 @@ struct bfq_data {
>> * with no request waiting for completion.
>> */
>> unsigned int num_groups_with_pending_reqs;
>> -
>> + /*
>> + * number of queues that are in root_group with at least one request
>> + * waiting for completion.
>
> please link somehow this comment to the long comment that comes before it
>
>> + */
>> + unsigned int num_queues_with_pending_reqs_in_root;
>
> Why using two counters? I mean, couldn't you simply count also the
> root group in num_groups_with_pending_reqs?
Hi, Paolo
Thanks for taking time reviewing these patches
I was doing this too complicated, while counting root group into
num_groups_with_pending_reqs is much easier. I'll do this in next
iteration.
Thanks
Yu Kuai
>
>> /*
>> * Per-class (RT, BE, IDLE) number of bfq_queues containing
>> * requests (including the queue in service, even if it is
>> diff --git a/block/bfq-wf2q.c b/block/bfq-wf2q.c
>> index 7a462df71f68..188c8f907219 100644
>> --- a/block/bfq-wf2q.c
>> +++ b/block/bfq-wf2q.c
>> @@ -946,6 +946,29 @@ static void bfq_update_fin_time_enqueue(struct bfq_entity *entity,
>> bfq_active_insert(st, entity);
>> }
>>
>> +static void bfq_update_groups_with_pending_reqs(struct bfq_entity *entity)
>> +{
>> +#ifdef CONFIG_BFQ_GROUP_IOSCHED
>> + struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
>> +
>
> why do you introduce an extra variable bfqq, instead of doing as in
> the original version of the code? In addition, you remove the comment
> /* bfq_group */
>
> Thanks,
> Paolo
>
>> + if (bfqq) {
>> + if (!entity->parent && !entity->in_groups_with_pending_reqs) {
>> + entity->in_groups_with_pending_reqs = true;
>> + bfqq->bfqd->num_queues_with_pending_reqs_in_root++;
>> + }
>> + } else {
>> + if (!entity->in_groups_with_pending_reqs) {
>> + struct bfq_group *bfqg =
>> + container_of(entity, struct bfq_group, entity);
>> + struct bfq_data *bfqd = bfqg->bfqd;
>> +
>> + entity->in_groups_with_pending_reqs = true;
>> + bfqd->num_groups_with_pending_reqs++;
>> + }
>> + }
>> +#endif
>> +}
>> +
>> /**
>> * __bfq_activate_entity - handle activation of entity.
>> * @entity: the entity being activated.
>> @@ -999,19 +1022,7 @@ static void __bfq_activate_entity(struct bfq_entity *entity,
>> entity->on_st_or_in_serv = true;
>> }
>>
>> -#ifdef CONFIG_BFQ_GROUP_IOSCHED
>> - if (!bfq_entity_to_bfqq(entity)) { /* bfq_group */
>> - struct bfq_group *bfqg =
>> - container_of(entity, struct bfq_group, entity);
>> - struct bfq_data *bfqd = bfqg->bfqd;
>> -
>> - if (!entity->in_groups_with_pending_reqs) {
>> - entity->in_groups_with_pending_reqs = true;
>> - bfqd->num_groups_with_pending_reqs++;
>> - }
>> - }
>> -#endif
>> -
>> + bfq_update_groups_with_pending_reqs(entity);
>> bfq_update_fin_time_enqueue(entity, st, backshifted);
>> }
>>
>> --
>> 2.31.1
>>
>
> .
>
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