Re: [RFC PATCH 3/5] libsas: dynamic queue depth

Jack Wang
2011-09-22T01:38:54Z

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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