linux-kernel - Re: [PATCH RESEND 0/1] AHCI: Optimize interrupt processing

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Date:	Thu, 11 Jul 2013 12:26:30 +0200
From:	Alexander Gordeev <agordeev@...hat.com>
To:	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>
Cc:	Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org,
	linux-ide@...r.kernel.org, Jeff Garzik <jgarzik@...ox.com>,
	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>,
	Jens Axboe <axboe@...nel.dk>
Subject: Re: [PATCH RESEND 0/1] AHCI: Optimize interrupt processing

On Wed, May 22, 2013 at 07:03:05PM +0200, Jens Axboe wrote:
> On Wed, May 22 2013, Alexander Gordeev wrote:
> > On Wed, May 22, 2013 at 08:50:03AM +0900, Tejun Heo wrote:
> > > Hmmmmmm..... I'd normally apply this patch but block layer is just
> > > growing multi-queue support and libata is likely to be converted to mq
> > > in foreseeable future, so I'm a bit hesitant to make irq handling more
> > > sophiscated right now.  Would you be interested in looking into
> > > converting libata to blk mq support?  I'm pretty sure it'd yield far
> > > better outcome if done properly.
> > 
> > I am not committing, but will look into it, sure.
> 
> Would be most awesome, I'm sure Nic would not mind a bit of help on the
> SCSI/libata side :-)

Hi Nicholas,

Could you please clarify the status of SCSI MQ support? Is it usable now?

I tried git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending.git,
but it does not appear working without (at least) changes below to SCSI lib:

Thanks!

diff --git a/drivers/scsi/scsi-mq.c b/drivers/scsi/scsi-mq.c
index ca6ff67..d8cc7a4 100644
--- a/drivers/scsi/scsi-mq.c
+++ b/drivers/scsi/scsi-mq.c
@@ -155,6 +155,7 @@ void scsi_mq_done(struct scsi_cmnd *sc)
 static struct blk_mq_ops scsi_mq_ops = {
 	.queue_rq	= scsi_mq_queue_rq,
 	.map_queue	= blk_mq_map_queue,
+	.timeout	= scsi_times_out,
 	.alloc_hctx	= blk_mq_alloc_single_hw_queue,
 	.free_hctx	= blk_mq_free_single_hw_queue,
 };
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 65360db..33aa373 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -283,7 +283,10 @@ int scsi_execute(struct scsi_device *sdev, const unsigned char *cmd,
 	/*
 	 * head injection *required* here otherwise quiesce won't work
 	 */
-	blk_execute_rq(req->q, NULL, req, 1);
+	if (q->mq_ops)
+		blk_mq_execute_rq(req->q, req);
+	else
+		blk_execute_rq(req->q, NULL, req, 1);
 
 	/*
 	 * Some devices (USB mass-storage in particular) may transfer
@@ -298,12 +301,8 @@ int scsi_execute(struct scsi_device *sdev, const unsigned char *cmd,
 		*resid = req->resid_len;
 	ret = req->errors;
  out:
-	if (q->mq_ops) {
-		printk("scsi_execute(): Calling blk_mq_free_request >>>\n");
-		blk_mq_free_request(req);
-	} else {
+	if (!q->mq_ops)
 		blk_put_request(req);
-	}
 
 	return ret;
 }


> And personally, can't wait to run it on the laptop! That's right, I
> alpha test on the laptop.
> 
> -- 
> Jens Axboe
> 

-- 
Regards,
Alexander Gordeev
agordeev@...hat.com
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