Re: [PATCH] drivers/scsi/qla1280.c; was Re: Buffered I/O to block device very slow and other SCSI issues...

[David Chinner <dgc@sgi.com>]

On Sun, May 11, 2008 at 11:17:03PM -0700, Jeremy Higdon wrote:
> On Thu, Mar 20, 2008 at 03:20:10AM -0700, Andrew Morton wrote:
> > > > I also suspect that CTQ has not been set up correctly on this
> > > > kernel, because:
> > > > 
> > > > $ cat /sys/block/sdb/device/queue_depth
> > > > 3
> > > > $ ls -l /sys/block/sdb/device/queue_depth
> > > > -r--r--r-- 1 root root 0 Mar 20 09:59 /sys/block/sdb/device/queue_depth
> > > > $
> > > > 
> > > > It appears to be hard coded to 3 and can't be changed....
> > > 
> > > That's a bug in the qla1280 driver.  I thought that had gotten fixed.
> > > It's looking at the wrong mailbox register after setting device parameters.
> > 
> > Was there a patch anywhere?
> 
> Promised patch...
....
> After the fix, I found that my disks were getting a queue depth of
> 255, which is far too many.  Most SCSI disks are limited to 32 or
> 64.  In any case, there's no point, queueing up a bunch of commands
> to the adapter that will just result in queue full or starve other
> targets from being issued commands due to running out of internal
> memory.  So I dropped default queue depth to 32 (from which 1 is
> subtracted elsewhere, giving net of 31).
> 
> I tested with a Seagate ST336753LC, and results look good, so
> I'm satisfied with this patch.
> 
> Signed-off-by: Jeremy Higdon <jeremy@sgi.com>

Works fine here.

Tested-by: Dave Chinner <dgc@sgi.com>

Cheers,

Dave.
-- 
Dave Chinner
Principal Engineer
SGI Australian Software Group