Re: [PATCH v2 1/4] block/mq-deadline: Improve request accounting further

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On 9/28/21 12:03 AM, 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")
Reviewed-by: Damien Le Moal <damien.lemoal@xxxxxxx>
Reviewed-by: Niklas Cassel <Niklas.Cassel@xxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxx>
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
  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 47f042fa6a68..c27b4347ca91 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: Hannes Reinecke <hare@xxxxxxx>

Cheers,

Hannes
--
Dr. Hannes Reinecke                Kernel Storage Architect
hare@xxxxxxx                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer



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