linux-kernel - Re: [PATCH 02/20] io-controller: Common flat fair queuing code in elevaotor layer

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Message-ID: <4A4B2B5E.3080309@cn.fujitsu.com>
Date:	Wed, 01 Jul 2009 17:24:46 +0800
From:	Gui Jianfeng <guijianfeng@...fujitsu.com>
To:	Vivek Goyal <vgoyal@...hat.com>
CC:	linux-kernel@...r.kernel.org,
	containers@...ts.linux-foundation.org, dm-devel@...hat.com,
	jens.axboe@...cle.com, nauman@...gle.com, dpshah@...gle.com,
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	paolo.valente@...more.it, ryov@...inux.co.jp,
	fernando@....ntt.co.jp, s-uchida@...jp.nec.com, taka@...inux.co.jp,
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	snitzer@...hat.com, akpm@...ux-foundation.org, peterz@...radead.org
Subject: Re: [PATCH 02/20] io-controller: Common flat fair queuing code in
 elevaotor layer

Vivek Goyal wrote:
...
> + * If ioscheduler has functionality of keeping track of close cooperator, check
> + * with it if it has got a closely co-operating queue.
> + */
> +static inline struct io_queue *elv_close_cooperator(struct request_queue *q,
> +					struct io_queue *ioq, int probe)
> +{
> +	struct elevator_queue *e = q->elevator;
> +	struct io_queue *new_ioq = NULL;
> +
> +	/*
> +	 * Currently this feature is supported only for flat hierarchy or
> +	 * root group queues so that default cfq behavior is not changed.
> +	 */
> +	if (!is_root_group_ioq(q, ioq))
> +		return NULL;
> +
> +	if (q->elevator->ops->elevator_close_cooperator_fn)
> +		new_ioq = e->ops->elevator_close_cooperator_fn(q,
> +						ioq->sched_queue, probe);
> +
> +	/* Only select co-operating queue if it belongs to root group */
> +	if (new_ioq && !is_root_group_ioq(q, new_ioq))
> +		return NULL;
> +
> +	return new_ioq;
> +}

  Hi Vivek,

  Currently, whether we can let this feature be supported if current queue 
  and found queue are in the same group? I guess this change won't break 
  the default cfq behavior. Am i missing something?

-- 
Regards
Gui Jianfeng

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