linux-kernel - Re: [PATCH -next v8 2/4] block, bfq: record how many queues have pending requests

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Date:   Wed, 1 Jun 2022 10:35:29 +0200
From:   Jan Kara <jack@...e.cz>
To:     Yu Kuai <yukuai3@...wei.com>
Cc:     paolo.valente@...aro.org, jack@...e.cz, axboe@...nel.dk,
        tj@...nel.org, linux-block@...r.kernel.org,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        yi.zhang@...wei.com
Subject: Re: [PATCH -next v8 2/4] block, bfq: record how many queues have
 pending requests

On Tue 31-05-22 22:08:56, Yu Kuai wrote:
> Prepare to refactor the counting of 'num_groups_with_pending_reqs'.
> 
> Add a counter in bfq_group, and update it while tracking if bfqq have
> pending requests.
> 
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>

Looks good, except I think that we also need to update the counters
'num_groups_with_pending_reqs' in bfq_move_bfqq()?

								Honza

> ---
>  block/bfq-cgroup.c  |  1 +
>  block/bfq-iosched.h |  1 +
>  block/bfq-wf2q.c    | 12 ++++++++++--
>  3 files changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
> index 09574af83566..0954a258a107 100644
> --- a/block/bfq-cgroup.c
> +++ b/block/bfq-cgroup.c
> @@ -557,6 +557,7 @@ static void bfq_pd_init(struct blkg_policy_data *pd)
>  				   */
>  	bfqg->bfqd = bfqd;
>  	bfqg->active_entities = 0;
> +	bfqg->num_queues_with_pending_reqs = 0;
>  	bfqg->online = true;
>  	bfqg->rq_pos_tree = RB_ROOT;
>  }
> diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
> index 3b9b1a0e7c1c..a5f7c0c1a3b3 100644
> --- a/block/bfq-iosched.h
> +++ b/block/bfq-iosched.h
> @@ -943,6 +943,7 @@ struct bfq_group {
>  	struct bfq_entity *my_entity;
>  
>  	int active_entities;
> +	int num_queues_with_pending_reqs;
>  
>  	struct rb_root rq_pos_tree;
>  
> diff --git a/block/bfq-wf2q.c b/block/bfq-wf2q.c
> index 12d20f26ad69..b533e17e9f0c 100644
> --- a/block/bfq-wf2q.c
> +++ b/block/bfq-wf2q.c
> @@ -1651,16 +1651,24 @@ static void bfq_add_bfqq_in_groups_with_pending_reqs(struct bfq_queue *bfqq)
>  {
>  	struct bfq_entity *entity = &bfqq->entity;
>  
> -	if (!entity->in_groups_with_pending_reqs)
> +	if (!entity->in_groups_with_pending_reqs) {
>  		entity->in_groups_with_pending_reqs = true;
> +#ifdef CONFIG_BFQ_GROUP_IOSCHED
> +		bfqq_group(bfqq)->num_queues_with_pending_reqs++;
> +#endif
> +	}
>  }
>  
>  void bfq_del_bfqq_in_groups_with_pending_reqs(struct bfq_queue *bfqq)
>  {
>  	struct bfq_entity *entity = &bfqq->entity;
>  
> -	if (entity->in_groups_with_pending_reqs)
> +	if (entity->in_groups_with_pending_reqs) {
>  		entity->in_groups_with_pending_reqs = false;
> +#ifdef CONFIG_BFQ_GROUP_IOSCHED
> +		bfqq_group(bfqq)->num_queues_with_pending_reqs--;
> +#endif
> +	}
>  }
>  
>  /*
> -- 
> 2.31.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR