linux-kernel - Re: [PATCH -next v8 4/4] block, bfq: do not idle if only one group is activated

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Date:   Wed, 1 Jun 2022 10:38:29 +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 4/4] block, bfq: do not idle if only one group
 is activated

On Tue 31-05-22 22:08:58, Yu Kuai wrote:
> Now that root group is counted into 'num_groups_with_pending_reqs',
> 'num_groups_with_pending_reqs > 0' is always true in
> bfq_asymmetric_scenario(). Thus change the condition to '> 1'.
> 
> On the other hand, this change can enable concurrent sync io if only
> one group is activated.
> 
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>

Looks good. Feel free to add:

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

Just one language fixup below:

> diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
> index 03b04892440c..d4aa8421968d 100644
> --- a/block/bfq-iosched.c
> +++ b/block/bfq-iosched.c
> @@ -820,7 +820,7 @@ bfq_pos_tree_add_move(struct bfq_data *bfqd, struct bfq_queue *bfqq)
>   * much easier to maintain the needed state:
>   * 1) all active queues have the same weight,
>   * 2) all active queues belong to the same I/O-priority class,
> - * 3) there are no active groups.
> + * 3) there are one active groups at most.
         ^^^ "there is at most one active group"

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR