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

["Nicholas A. Bellinger" <nab@linux-iscsi.org>]

On Thu, 2013-07-11 at 12:26 +0200, Alexander Gordeev wrote:
> 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?
> 

Hi Alexander,

Thanks for taking a look.  I've not made further progress in the last
weeks on scsi-mq, but am still using virtio-scsi + scsi-mq <->
vhost-scsi + per-cpu-ida for quite a bit for benchmarking purposes.

> 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:
> 

The only scsi-mq LLD conversions so far have been to virtio-scsi +
scsi_debug to nop REQ_TYPE_FS.

Just so I understand, your patch below is required in order to make what
LLD function with scsi-mq..?

Thanks!

--nab

> 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
> > 
>