linux-kernel - Re: [PATCH] cfq-iosched: Do not merge queues of BE and IDLE classes

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Date:	Wed, 24 Mar 2010 21:08:38 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Divyesh Shah <dpshah@...gle.com>
Cc:	jens.axboe@...cle.com, linux-kernel@...r.kernel.org,
	nauman@...gle.com
Subject: Re: [PATCH] cfq-iosched: Do not merge queues of BE and IDLE classes

On Wed, Mar 24, 2010 at 01:52:03PM -0700, Divyesh Shah wrote:
> even if they are found to be co-operating.
> 
> The prio_trees do not have any IDLE cfqqs on them. cfq_close_cooperator()
> is called from cfq_select_queue() and cfq_completed_request(). The latter
> ensures that the close cooperator code does not get invoked if the current
> cfqq is of class IDLE but the former doesn't seem to have any such checks.
> So an IDLE cfqq may get merged with a BE cfqq from the same group which
> should be avoided.
> 
> Signed-off-by: Divyesh Shah<dpshah@...gle.com>
> ---

Looks good to me.

Acked-by: Vivek Goyal <vgoyal@...hat.com>

Vivek

> 
>  block/cfq-iosched.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
> index dee9d93..e6910dc 100644
> --- a/block/cfq-iosched.c
> +++ b/block/cfq-iosched.c
> @@ -1721,6 +1721,8 @@ static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
>  {
>  	struct cfq_queue *cfqq;
>  
> +	if (cfq_class_idle(cur_cfqq))
> +		return NULL;
>  	if (!cfq_cfqq_sync(cur_cfqq))
>  		return NULL;
>  	if (CFQQ_SEEKY(cur_cfqq))
--
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