linux-kernel - Re: [PATCH -next v9 2/4] block, bfq: record how many queues have pending requests

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Message-ID: <20220601131806.gs3txjgvhhbn5ign@quack3.lan>
Date:   Wed, 1 Jun 2022 15:18:06 +0200
From:   Jan Kara <jack@...e.cz>
To:     Yu Kuai <yukuai3@...wei.com>
Cc:     paolo.valente@...aro.org, jack@...e.cz, tj@...nel.org,
        axboe@...nel.dk, cgroups@...r.kernel.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        yi.zhang@...wei.com
Subject: Re: [PATCH -next v9 2/4] block, bfq: record how many queues have
 pending requests

On Wed 01-06-22 19:43:38, Yu Kuai wrote:
> Prepare to refactor the counting of 'num_groups_with_pending_reqs'.
> 
> Add a counter in bfq_group, update it while tracking if bfqq have pending
> requests and when bfq_bfqq_move() is called.
> 
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza


> ---
>  block/bfq-cgroup.c  | 10 ++++++++++
>  block/bfq-iosched.h |  1 +
>  block/bfq-wf2q.c    | 12 ++++++++++--
>  3 files changed, 21 insertions(+), 2 deletions(-)
> 
> diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
> index 09574af83566..88c0c320ddf3 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;
>  }
> @@ -646,6 +647,7 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
>  {
>  	struct bfq_entity *entity = &bfqq->entity;
>  	struct bfq_group *old_parent = bfqq_group(bfqq);
> +	bool has_pending_reqs = false;
>  
>  	/*
>  	 * No point to move bfqq to the same group, which can happen when
> @@ -666,6 +668,11 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
>  	 */
>  	bfqq->ref++;
>  
> +	if (entity->in_groups_with_pending_reqs) {
> +		has_pending_reqs = true;
> +		bfq_del_bfqq_in_groups_with_pending_reqs(bfqq);
> +	}
> +
>  	/* If bfqq is empty, then bfq_bfqq_expire also invokes
>  	 * bfq_del_bfqq_busy, thereby removing bfqq and its entity
>  	 * from data structures related to current group. Otherwise we
> @@ -693,6 +700,9 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
>  	/* pin down bfqg and its associated blkg  */
>  	bfqg_and_blkg_get(bfqg);
>  
> +	if (has_pending_reqs)
> +		bfq_add_bfqq_in_groups_with_pending_reqs(bfqq);
> +
>  	if (bfq_bfqq_busy(bfqq)) {
>  		if (unlikely(!bfqd->nonrot_with_queueing))
>  			bfq_pos_tree_add_move(bfqd, bfqq);
> diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
> index 69c7d15417e5..de2446a9b7ab 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 5704a0315cf2..6f36f3fe5cc8 100644
> --- a/block/bfq-wf2q.c
> +++ b/block/bfq-wf2q.c
> @@ -1651,16 +1651,24 @@ 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