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SubjectRe: [PATCH 5/8] block: add code to track actual device queue depth
On Tue 01-11-16 15:08:48, Jens Axboe wrote:
> For blk-mq, ->nr_requests does track queue depth, at least at init
> time. But for the older queue paths, it's simply a soft setting.
> On top of that, it's generally larger than the hardware setting
> on purpose, to allow backup of requests for merging.
>
> Fill a hole in struct request with a 'queue_depth' member, that
> drivers can call to more closely inform the block layer of the
> real queue depth.
>
> Signed-off-by: Jens Axboe <axboe@fb.com>

The patch looks good to me. You can add:

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

Honza
> ---
> block/blk-settings.c | 12 ++++++++++++
> drivers/scsi/scsi.c | 3 +++
> include/linux/blkdev.h | 11 +++++++++++
> 3 files changed, 26 insertions(+)
>
> diff --git a/block/blk-settings.c b/block/blk-settings.c
> index 55369a65dea2..9cf053759363 100644
> --- a/block/blk-settings.c
> +++ b/block/blk-settings.c
> @@ -837,6 +837,18 @@ void blk_queue_flush_queueable(struct request_queue *q, bool queueable)
> EXPORT_SYMBOL_GPL(blk_queue_flush_queueable);
>
> /**
> + * blk_set_queue_depth - tell the block layer about the device queue depth
> + * @q: the request queue for the device
> + * @depth: queue depth
> + *
> + */
> +void blk_set_queue_depth(struct request_queue *q, unsigned int depth)
> +{
> + q->queue_depth = depth;
> +}
> +EXPORT_SYMBOL(blk_set_queue_depth);
> +
> +/**
> * blk_queue_write_cache - configure queue's write cache
> * @q: the request queue for the device
> * @wc: write back cache on or off
> diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
> index 1deb6adc411f..75455d4dab68 100644
> --- a/drivers/scsi/scsi.c
> +++ b/drivers/scsi/scsi.c
> @@ -621,6 +621,9 @@ int scsi_change_queue_depth(struct scsi_device *sdev, int depth)
> wmb();
> }
>
> + if (sdev->request_queue)
> + blk_set_queue_depth(sdev->request_queue, depth);
> +
> return sdev->queue_depth;
> }
> EXPORT_SYMBOL(scsi_change_queue_depth);
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 8396da2bb698..0c677fb35ce4 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -405,6 +405,8 @@ struct request_queue {
> struct blk_mq_ctx __percpu *queue_ctx;
> unsigned int nr_queues;
>
> + unsigned int queue_depth;
> +
> /* hw dispatch queues */
> struct blk_mq_hw_ctx **queue_hw_ctx;
> unsigned int nr_hw_queues;
> @@ -777,6 +779,14 @@ static inline bool blk_write_same_mergeable(struct bio *a, struct bio *b)
> return false;
> }
>
> +static inline unsigned int blk_queue_depth(struct request_queue *q)
> +{
> + if (q->queue_depth)
> + return q->queue_depth;
> +
> + return q->nr_requests;
> +}
> +
> /*
> * q->prep_rq_fn return values
> */
> @@ -1093,6 +1103,7 @@ extern void blk_limits_io_min(struct queue_limits *limits, unsigned int min);
> extern void blk_queue_io_min(struct request_queue *q, unsigned int min);
> extern void blk_limits_io_opt(struct queue_limits *limits, unsigned int opt);
> extern void blk_queue_io_opt(struct request_queue *q, unsigned int opt);
> +extern void blk_set_queue_depth(struct request_queue *q, unsigned int depth);
> extern void blk_set_default_limits(struct queue_limits *lim);
> extern void blk_set_stacking_limits(struct queue_limits *lim);
> extern int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
> --
> 2.7.4
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR

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