Re: [PATCH 1/4] block/mq-deadline: Improve request accounting further

[Niklas Cassel <Niklas.Cassel@wdc.com>]

On Thu, Sep 23, 2021 at 04:26:52PM -0700, Bart Van Assche wrote:
> The scheduler .insert_requests() callback is called when a request is
> queued for the first time and also when it is requeued. Only count a
> request the first time it is queued. Additionally, since the mq-deadline
> scheduler only performs zone locking for requests that have been
> inserted, skip the zone unlock code for requests that have not been
> inserted into the mq-deadline scheduler.
> 
> Fixes: 38ba64d12d4c ("block/mq-deadline: Track I/O statistics")
> Cc: Damien Le Moal <damien.lemoal@wdc.com>
> Cc: Niklas Cassel <Niklas.Cassel@wdc.com>
> Cc: Hannes Reinecke <hare@suse.de>
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> ---
>  block/mq-deadline.c | 17 ++++++++++-------
>  1 file changed, 10 insertions(+), 7 deletions(-)
> 
> diff --git a/block/mq-deadline.c b/block/mq-deadline.c
> index 7f3c3932b723..b1175e4560ad 100644
> --- a/block/mq-deadline.c
> +++ b/block/mq-deadline.c
> @@ -677,8 +677,10 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
>  	blk_req_zone_write_unlock(rq);
>  
>  	prio = ioprio_class_to_prio[ioprio_class];
> -	dd_count(dd, inserted, prio);
> -	rq->elv.priv[0] = (void *)(uintptr_t)1;
> +	if (!rq->elv.priv[0]) {
> +		dd_count(dd, inserted, prio);
> +		rq->elv.priv[0] = (void *)(uintptr_t)1;
> +	}
>  
>  	if (blk_mq_sched_try_insert_merge(q, rq, &free)) {
>  		blk_mq_free_requests(&free);
> @@ -759,12 +761,13 @@ static void dd_finish_request(struct request *rq)
>  
>  	/*
>  	 * The block layer core may call dd_finish_request() without having
> -	 * called dd_insert_requests(). Hence only update statistics for
> -	 * requests for which dd_insert_requests() has been called. See also
> -	 * blk_mq_request_bypass_insert().
> +	 * called dd_insert_requests(). Skip requests that bypassed I/O
> +	 * scheduling. See also blk_mq_request_bypass_insert().
>  	 */
> -	if (rq->elv.priv[0])
> -		dd_count(dd, completed, prio);
> +	if (!rq->elv.priv[0])
> +		return;
> +
> +	dd_count(dd, completed, prio);
>  
>  	if (blk_queue_is_zoned(q)) {
>  		unsigned long flags;

Reviewed-by: Niklas Cassel <niklas.cassel@wdc.com>