[RFC,3/5] libsas: dynamic queue depth

Good Stuff, 'cept I am worried about the host max queue depth of 128 on
the pm8001 driver resulting in starvation. I defer to Jack Wang's
judgement on that point (and will explore separately how we can increase
the host queue depth reliably on the pm8001).

Consider this an Ack from me that has an interlock on Jack Wang's Ack
... 

Sincerely -- Mark Salyzyn

-----Original Message-----
From: Dan Williams [mailto:dan.j.williams@intel.com] 
Sent: Tuesday, September 20, 2011 6:11 PM
To: linux-ide@vger.kernel.org; linux-scsi@vger.kernel.org
Cc: Dave Jiang; Luben Tuikov; jgarzik@pobox.com;
JBottomley@parallels.com; Jack Wang; Xiangliang Yu; Mark Salyzyn;
Christoph Hellwig
Subject: [RFC PATCH 3/5] libsas: dynamic queue depth

The queue-depth for libsas-attached devices initializes to 32 and can
only be increased manually via sysfs to a max of 64, while mpt2sas
attached devices initialize to 254 and dynamically float via the
midlayer ->change_queue_depth interface.

No performance regression was observed with this change on the isci
driver.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Mark Salyzyn <msalyzyn@us.xyratex.com>
Cc: Xiangliang Yu <yuxiangl@marvell.com>
Cc: Jack Wang <jack_wang@usish.com>
Cc: Mark Salyzyn <msalyzyn@us.xyratex.com>
Cc: Luben Tuikov <ltuikov@yahoo.com>
Tested-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/scsi/libsas/sas_scsi_host.c |   39
++++++++++++++++-------------------
 1 files changed, 18 insertions(+), 21 deletions(-)

Thanks Mark, I 'll post a patch to raise the default host can queue value,
I'm OK with his change!
--Jack
RE: [RFC PATCH 3/5] libsas: dynamic queue depth
> 
> Good Stuff, 'cept I am worried about the host max queue depth of 128 on
> the pm8001 driver resulting in starvation. I defer to Jack Wang's
> judgement on that point (and will explore separately how we can increase
> the host queue depth reliably on the pm8001).
> 
> Consider this an Ack from me that has an interlock on Jack Wang's Ack
> ...
> 
> Sincerely -- Mark Salyzyn
> 
> -----Original Message-----
> From: Dan Williams [mailto:dan.j.williams@intel.com]
> Sent: Tuesday, September 20, 2011 6:11 PM
> To: linux-ide@vger.kernel.org; linux-scsi@vger.kernel.org
> Cc: Dave Jiang; Luben Tuikov; jgarzik@pobox.com;
> JBottomley@parallels.com; Jack Wang; Xiangliang Yu; Mark Salyzyn;
> Christoph Hellwig
> Subject: [RFC PATCH 3/5] libsas: dynamic queue depth
> 
> The queue-depth for libsas-attached devices initializes to 32 and can
> only be increased manually via sysfs to a max of 64, while mpt2sas
> attached devices initialize to 254 and dynamically float via the
> midlayer ->change_queue_depth interface.
> 
> No performance regression was observed with this change on the isci
> driver.
> 
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Mark Salyzyn <msalyzyn@us.xyratex.com>
> Cc: Xiangliang Yu <yuxiangl@marvell.com>
> Cc: Jack Wang <jack_wang@usish.com>
> Cc: Mark Salyzyn <msalyzyn@us.xyratex.com>
> Cc: Luben Tuikov <ltuikov@yahoo.com>
> Tested-by: Dave Jiang <dave.jiang@intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  drivers/scsi/libsas/sas_scsi_host.c |   39
> ++++++++++++++++-------------------
>  1 files changed, 18 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/scsi/libsas/sas_scsi_host.c
> b/drivers/scsi/libsas/sas_scsi_host.c
> index 4c6923c..fe08ef0 100644
> --- a/drivers/scsi/libsas/sas_scsi_host.c
> +++ b/drivers/scsi/libsas/sas_scsi_host.c
> @@ -784,8 +784,7 @@ int sas_target_alloc(struct scsi_target *starget)
>  	return 0;
>  }
> 
> -#define SAS_DEF_QD 32
> -#define SAS_MAX_QD 64
> +#define SAS_DEF_QD 256
> 
>  int sas_slave_configure(struct scsi_device *scsi_dev)
>  {
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