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

From: Jan Kara <jack@suse.cz>
To: Yu Kuai <yukuai3@huawei.com>
Cc: paolo.valente@linaro.org, jack@suse.cz, axboe@kernel.dk,
	tj@kernel.org, linux-block@vger.kernel.org,
	cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
	yi.zhang@huawei.com
Subject: Re: [PATCH -next v8 4/4] block, bfq: do not idle if only one group is activated
Date: Wed, 1 Jun 2022 10:38:29 +0200	[thread overview]
Message-ID: <20220601083829.ywv4z5yfdmslcihv@quack3.lan> (raw)
In-Reply-To: <20220531140858.3324294-5-yukuai3@huawei.com>

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@huawei.com>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.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@suse.com>
SUSE Labs, CR