[PATCH 1/3] block: Requeue req as head if driver touched it

[PATCH 1/3] block: Requeue req as head if driver touched it

[Christian Löhle]

In case the driver set RQF_DONTPREP flag, requeue the request as head as
it is likely that the backing storage already had a request to an
adjacent region, so getting the requeued request out as soon as possible
may give us some performance benefit.

Signed-off-by: Christian Loehle <cloehle@hyperstone.com>
---
 block/blk-mq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 33292c01875d..d863c826fb23 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1429,7 +1429,7 @@ static void blk_mq_requeue_work(struct work_struct *work)
 		 * merge.
 		 */
 		if (rq->rq_flags & RQF_DONTPREP)
-			blk_mq_request_bypass_insert(rq, false, false);
+			blk_mq_request_bypass_insert(rq, true, false);
 		else
 			blk_mq_sched_insert_request(rq, true, false, false);
 	}
-- 
2.37.3
Hyperstone GmbH | Reichenaustr. 39a  | 78467 Konstanz
Managing Director: Dr. Jan Peter Berns.
Commercial register of local courts: Freiburg HRB381782

Re: [PATCH 1/3] block: Requeue req as head if driver touched it

[Ulf Hansson]

On Wed, 26 Oct 2022 at 09:30, Christian Löhle <CLoehle@hyperstone.com> wrote:
>
> In case the driver set RQF_DONTPREP flag, requeue the request as head as
> it is likely that the backing storage already had a request to an
> adjacent region, so getting the requeued request out as soon as possible
> may give us some performance benefit.

This is a bit handwavy to me. Would you mind extending this with a
small concrete example, to better understand the benefit?

>
> Signed-off-by: Christian Loehle <cloehle@hyperstone.com>

Other than the above nitpick, I can't think of any obvious unwanted
side-effects this could have. So, feel free to add:

Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>

Kind regards
Uffe

> ---
>  block/blk-mq.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 33292c01875d..d863c826fb23 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -1429,7 +1429,7 @@ static void blk_mq_requeue_work(struct work_struct *work)
>                  * merge.
>                  */
>                 if (rq->rq_flags & RQF_DONTPREP)
> -                       blk_mq_request_bypass_insert(rq, false, false);
> +                       blk_mq_request_bypass_insert(rq, true, false);
>                 else
>                         blk_mq_sched_insert_request(rq, true, false, false);
>         }
> --
> 2.37.3
> Hyperstone GmbH | Reichenaustr. 39a  | 78467 Konstanz
> Managing Director: Dr. Jan Peter Berns.
> Commercial register of local courts: Freiburg HRB381782
>

RE: [PATCH 1/3] block: Requeue req as head if driver touched it

[Christian Löhle]

Jens could you consider this patch?
As far as I can see Barts series has not been merged in any form that would fix my problem and even if it does, requeuing RQF_DONTPREP as head seems on par at worst and a performance improvement at best.


-----Original Message-----
From: Christian Löhle 
Sent: Mittwoch, 26. Oktober 2022 09:29
To: axboe@kernel.dk; ulf.hansson@linaro.org; linux-mmc@vger.kernel.org; linux-kernel@vger.kernel.org; 'linux-block@vger.kernel.org' <linux-block@vger.kernel.org>
Cc: 'Avri Altman' <Avri.Altman@wdc.com>; adrian.hunter@intel.com; vincent.whitchurch@axis.com; 'Christian Löhle' <CLoehle@hyperstone.com>
Subject: [PATCH 1/3] block: Requeue req as head if driver touched it

In case the driver set RQF_DONTPREP flag, requeue the request as head as it is likely that the backing storage already had a request to an adjacent region, so getting the requeued request out as soon as possible may give us some performance benefit.

Signed-off-by: Christian Loehle <cloehle@hyperstone.com>
---
 block/blk-mq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c index 33292c01875d..d863c826fb23 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1429,7 +1429,7 @@ static void blk_mq_requeue_work(struct work_struct *work)
 		 * merge.
 		 */
 		if (rq->rq_flags & RQF_DONTPREP)
-			blk_mq_request_bypass_insert(rq, false, false);
+			blk_mq_request_bypass_insert(rq, true, false);
 		else
 			blk_mq_sched_insert_request(rq, true, false, false);
 	}
--
2.37.3

Hyperstone GmbH | Reichenaustr. 39a  | 78467 Konstanz
Managing Director: Dr. Jan Peter Berns.
Commercial register of local courts: Freiburg HRB381782