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From: Bart Van Assche <bvanassche@acm.org>
To: Damien Le Moal <Damien.LeMoal@wdc.com>, Jens Axboe <axboe@kernel.dk>
Cc: "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	Christoph Hellwig <hch@lst.de>, Jaegeuk Kim <jaegeuk@kernel.org>,
	Hannes Reinecke <hare@suse.de>, Ming Lei <ming.lei@redhat.com>,
	Johannes Thumshirn <Johannes.Thumshirn@wdc.com>,
	Himanshu Madhani <himanshu.madhani@oracle.com>
Subject: Re: [PATCH 12/14] block/mq-deadline: Add I/O priority support
Date: Wed, 9 Jun 2021 10:25:44 -0700	[thread overview]
Message-ID: <7fa81169-6c94-f7b1-f086-6f2caa775d41@acm.org> (raw)
In-Reply-To: <DM6PR04MB70818D0058A0B1249AC7EBFCE7369@DM6PR04MB7081.namprd04.prod.outlook.com>

On 6/8/21 10:03 PM, Damien Le Moal wrote:
> On 2021/06/09 8:07, Bart Van Assche wrote:
>>  struct deadline_data {
>>  	/*
>>  	 * run time data
>>  	 */
>>  
>>  	/*
>> -	 * requests (deadline_rq s) are present on both sort_list and fifo_list
>> +	 * Requests are present on both sort_list[] and fifo_list[][]. The
>> +	 * first index of fifo_list[][] is the I/O priority class (DD_*_PRIO).
>> +	 * The second index is the data direction (rq_data_dir(rq)).
>>  	 */
>>  	struct rb_root sort_list[DD_DIR_COUNT];
>> -	struct list_head fifo_list[DD_DIR_COUNT];
>> +	struct list_head fifo_list[DD_PRIO_COUNT][DD_DIR_COUNT];
> 
> Would it make sense to pack these 2 into a sub structure ? e.g.:
> 
> struct deadline_lists {
> 	struct rb_root sort_list;
> 	struct list_head fifo_list[DD_PRIO_COUNT];
> };
> 
> struct deadline_data {
> 	...
> 	/*
> 	 * Requests are present on both sort_list[] and fifo_list[][]. The
> 	 * first index of fifo_list[][] is the I/O priority class (DD_*_PRIO).
> 	 * The second index is the data direction (rq_data_dir(rq)).
>  	 */
> 	struct deadline_lists	lists[DD_DIR_COUNT];
 The deadline_fifo_request() function and several other functions
examine both directions so I think that grouping per direction would
complicate these functions. Grouping per I/O priority might help to make
these functions easier to read. Do you want me to look further into this?

>> +	struct deadline_data *dd = q->elevator->elevator_data;
>> +	const u8 ioprio_class = dd_rq_ioclass(next);
>> +	const enum dd_prio prio = ioprio_class_to_prio[ioprio_class];
>> +
>> +	if (next->elv.priv[0]) {
>> +		dd_count(dd, merged, prio);
>> +	} else {
>> +		WARN_ON_ONCE(true);
>> +	}
> 
> No need for the curly brackets I think.

I can leave these out but you may want to know that leaving the curly
brackets out from this patch will make it necessary to introduce these
in the next patch in this series.

>> +/* Number of requests queued for a given priority level. */
>> +static u32 dd_queued(struct deadline_data *dd, enum dd_prio prio)
>> +{
>> +	return dd_sum(dd, inserted, prio) - dd_sum(dd, completed, prio);
> 
> This also includes requests that are being executed on the device. Is that OK ?

Yes, and that's on purpose. Please note that this function is only used
to export statistics to user space.

Thanks,

Bart.

  reply	other threads:[~2021-06-09 17:25 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-08 23:06 [PATCH 00/14] Improve " Bart Van Assche
2021-06-08 23:06 ` [PATCH 01/14] block/Kconfig: Make the BLK_WBT and BLK_WBT_MQ entries consecutive Bart Van Assche
2021-06-09  4:14   ` Damien Le Moal
2021-06-09  7:03   ` Johannes Thumshirn
2021-06-10  6:02   ` Hannes Reinecke
2021-06-08 23:06 ` [PATCH 02/14] block/blk-cgroup: Swap the blk_throtl_init() and blk_iolatency_init() calls Bart Van Assche
2021-06-09  4:19   ` Damien Le Moal
2021-06-09  7:05   ` Johannes Thumshirn
2021-06-10  6:02   ` Hannes Reinecke
2021-06-08 23:06 ` [PATCH 03/14] block/blk-rq-qos: Move a function from a header file into a C file Bart Van Assche
2021-06-09  4:22   ` Damien Le Moal
2021-06-10  6:03   ` Hannes Reinecke
2021-06-08 23:06 ` [PATCH 04/14] block: Introduce the ioprio rq-qos policy Bart Van Assche
2021-06-09  4:40   ` Damien Le Moal
2021-06-09 16:48     ` Bart Van Assche
2021-06-10  0:29       ` Damien Le Moal
2021-06-10  6:20   ` Hannes Reinecke
2021-06-10 17:14     ` Bart Van Assche
2021-06-08 23:06 ` [PATCH 05/14] block/mq-deadline: Add several comments Bart Van Assche
2021-06-10  6:21   ` Hannes Reinecke
2021-06-08 23:06 ` [PATCH 06/14] block/mq-deadline: Add two lockdep_assert_held() statements Bart Van Assche
2021-06-10  6:21   ` Hannes Reinecke
2021-06-08 23:06 ` [PATCH 07/14] block/mq-deadline: Remove two local variables Bart Van Assche
2021-06-10  6:22   ` Hannes Reinecke
2021-06-08 23:06 ` [PATCH 08/14] block/mq-deadline: Rename dd_init_queue() and dd_exit_queue() Bart Van Assche
2021-06-08 23:06 ` [PATCH 09/14] block/mq-deadline: Improve compile-time argument checking Bart Van Assche
2021-06-08 23:06 ` [PATCH 10/14] block/mq-deadline: Improve the sysfs show and store macros Bart Van Assche
2021-06-09  4:46   ` Damien Le Moal
2021-06-09 16:54     ` Bart Van Assche
2021-06-10  0:31       ` Damien Le Moal
2021-06-09  7:11   ` Johannes Thumshirn
2021-06-09 16:59     ` Bart Van Assche
2021-06-10  6:23   ` Hannes Reinecke
2021-06-08 23:07 ` [PATCH 11/14] block/mq-deadline: Reserve 25% of scheduler tags for synchronous requests Bart Van Assche
2021-06-10  6:26   ` Hannes Reinecke
2021-06-08 23:07 ` [PATCH 12/14] block/mq-deadline: Add I/O priority support Bart Van Assche
2021-06-09  5:03   ` Damien Le Moal
2021-06-09 17:25     ` Bart Van Assche [this message]
2021-06-10  0:39       ` Damien Le Moal
2021-06-10  6:35   ` Hannes Reinecke
2021-06-08 23:07 ` [PATCH 13/14] block/mq-deadline: Add cgroup support Bart Van Assche
2021-06-10  6:37   ` Hannes Reinecke
2021-06-08 23:07 ` [PATCH 14/14] block/mq-deadline: Prioritize high-priority requests Bart Van Assche
2021-06-09  5:10   ` Damien Le Moal
2021-06-10  6:43   ` Hannes Reinecke

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